NC0024911_Facility Plan Update_20180215

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Metropolitan Sewerage District
OF BUNCOMBE COUNTY, NORTH CAROLINA
Dr. Bing Bai, Ph.D., EI, Environmental Engineer February 15, 2018
NPDES Complex Permitting
NC DEQ/ Division of Water Resources/ Water Quality Permitting wR
512 North Salisbury St.C�2Peg
1617 Mail Service Center o`v t\1W
Raleigh, NC 27699-1617
Dear Dr. Bai,
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The MSD WRF can presently meet the new ammonia limits during the winter
months (based on the application of EPA's updated criteria). For ultimate
compliance with new summer ammonia limits, all phases of the MSD facility
upgrade plan including biological, should be completed before the final limits are
applied. We expect that all of the steps needed to upgrade treatment will be
finished in approximately 12 years (by 2030). Twelve years is an aggressive
schedule of almost continuous construction and start-up testing to complete all
phases of plant improvements needed to accomplish MSD's ultimate treatment goal,
and to effectively and consistently meet the summer ammonia limits. Those steps to
upgrade the process need to follow a proper and methodical sequence so as to
assure best value and outcomes.
Attached is both a copy of the Ammonia Reduction Evaluation prepared by HDR and
a Memorandum from MSD's Engineer of Record regarding the considerations and
sequence of the above mentioned plant upgrades necessary to meet ammonia
reduction goals.
MSD invites you to come inspect the plant and the current construction, which we
believe is critical to your understanding what little room we have to juggle the
construction of major treatment facilities while keeping the plant in operation and
effectively treating wastewater.
It is not expected that the current Headworks Improvements project will
appreciably reduce the effluent ammonia. However, these improvements will
certainly provide for a more consistent treatment level from the RBC's. The Primary
Settling process construction, slated to begin in one year, will provide for some
moderate ammonia reduction. The construction of this project should be complete
along with operational testing by 2023. These two projects together may indeed
bring us closer to those limits calculated for 40 MGD, and should certainly provide
Protecting Our Natural Resources -
2028 Riverside Drive, Asheville, North Carolina 28804 Telephone [phone] Website -www msdbc.org

compliance with the 30 MGD calculated limits. Based upon recent engineering
projections MSD should not reach 30 MGD average annual flow until beyond 2050.
In addition to the technical and compliance importance of a step -wise upgrade
process for our facility, we believe the Division of Water Resources will want to
consider the sizeable scope of the improvements to be constructed and the financial
commitment ($90 - $100 million) required to complete these major improvements
and the associated impact to our customers.
Attached is an updated Figure 1 of the MSD WRF capital improvement sequence and
schedule. Also attached is a list/schedule of the projected yearly milestones toward
meeting that schedule as requested in your email of February 13, 2018.
If the Division plans to discuss this proposed renewal permit with the EPA, MSD
requests that we be included in these discussions.
Thank you for your extensive work and timely communications on this permit
renewal.
Sincerely,
Thomas E. Hartye, PE
General Manager
Cc: Forrest Westall
Peter Weed
Roger Edwards
Landon Davidson
Hunter Carson
Linda Wiggs

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Ammonia Reduction
Evaluation
FINAL DRAFT
Metropolitan Sewerage District of Buncombe County
April 8, 2015
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update 17NTABLE OF CONTENTS
TABLE OF CONTENTS
Listof Tables.......................................................................................................................ii
Tableof Figures..................................................................................................................11l
Appendices.........................................................................................................................
lil
1.0 INTRODUCTION.............................................................................................................
1
2.0 EXISTING TREATMENT FACILITIES.............................................................................
3
3.0 EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT
PERFORMANCE....................................................................................................................... 6
3.1. Existing National Pollutant Discharge Elimination System (NPDES) Discharge Limits.
6
3.2. Summary of Existing Treatment Performance..............................................................
7
3.3. Quarterly Chronic Toxicity Performance......................................................................11
3.4. Ammonia Water Quality Data......................................................................................11
4.0 EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE .........................13
4.1. Ammonia Study..........................................................................................................13
4.2. Supplemental Sampling..............................................................................................14
4.3. Evaluation of Nitrification Capacity of RBC Process....................................................22
4.4. Challenges in Achieving Additional Ammonia Reduction............................................22
4.4.1. Out of Service RBCs............................................................................................22
4.4.2. Poor Grit Removal...............................................................................................23
4.4.3. Wet Weather Flow...............................................................................................23
4.4.4. High Loads to RBC process.................................................................................24
4.4.5. Low Influent Alkalinity..........................................................................................25
4.4.6. Limited Ability to Predict and Control Nitrification.................................................25
4.5. Recommended Initial Improvements...........................................................................25
4.5.1. Replacement of Broken RBCs.............................................................................25
4.5.2. Grit Removal Improvements................................................................................25
4.5.3. Equalization for Wet Weather Flow Management................................................26
4.5.4. Primary Treatment...............................................................................................26
5.0 OPTIMIZATION OF EXISTING TREATMENT SYSTEM................................................27
5.1. RBC Replacement and Optimization Program............................................................27
5.2. Monitoring Program....................................................................................................29
6.0 EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL
AMMONIAREDUCTION TARGETS.........................................................................................30

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��'"�
TABLE OF CONTENTS c
6.1. Overview of Biological Treatment Upgrade Strategy...................................................30
6.2. Approach for Evaluating Biological Treatment Upgrades............................................30
6.2.1. Biological Treatment Influent Flows and Loads....................................................31
6.2.2. Effluent Objectives...............................................................................................34
6.2.3. Identification and Evaluation of Biological Treatment Alternatives ........................34
6.3. Conceptual Development of Biological Treatment Alternatives...................................38
6.4. Cost Estimates for Biological Treatment Upgrades.....................................................38
7.0 SUMMARY OF FINDINGS AND CONCLUSIONS..........................................................40
List of Tables
Table 3-1: Summary of French Broad River WRF Existing NPDES Discharge Limits (NC
0024911).................................................................................................................................... 6
Table 3-2: Summary of French Broad River WRF Quarterly Chronic Toxicity Results for 2011 —
Nov2014..................................................................................................................................11
Table 3-3: Summary of NH3-N Water Quality Data Collected For Ammonia Reduction
Evaluation.................................................................................................................................12
Table 4-1: Summary of Ammonia Study Data for Treatment Process Performance .................16
Table 4-2: Operational RBCs during Ammonia Study...............................................................16
Table 4-3: Summary of Supplemental Sampling Program Results (Averages of Five Samples
Collected 4/28/14 — 5/9/14).......................................................................................................17
Table 4-4: Summary of Supplemental Sampling Program Results (Averages of Five Samples
Collected 4/28/14 — 5/9/14, Excluding Outliers).........................................................................18
Table 5-1: Actual and Estimated Costs for RBC Optimization..................................................28
Table 5-2: Estimated Capital Costs (2014 dollars) for Phased Initial Improvements.................29
Table 6-1: Baseline Flows and Loads Based on Historic Data Review.....................................31
Table 6-2: Summary of Wastewater Loads and Concentrations at 40 mgd permitted Capacity
(Year 2042)...............................................................................................................................32
Table 6-3: Primary Effluent Estimates at 40 mgd Permitted Capacity (Year 2042) with
Chemically Enhanced High Rate Primary Clarifiers Optimized for TSS Removal ......................33
Table 6-4: Summary Biological Treatment Alternatives Considered.........................................35
Table 6-5: Feasible Alternatives for Meeting Ammonia Reduction Targets...............................37
Table 6-6: Estimated Capital Costs (2014 dollars) for Biological Alternatives ...........................39
Table A-1: Summary of Existing Unit Processes and Major Equipment at French Broad River
WRF.........................................................................................................................................43
Table A-2: Operational Status of RBCs as of April 2015..........................................................46

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
TABLE OF CONTENTS
Table of Figures
Figure 2-1:
French Broad River WRF - Existing Treatment Facility Process Flow Diagram.......
5
Figure 3-1:
30 -Day Running Average Effluent CBOD Performance for 2009 through 2014.......
8
Figure 3-2:
30 -Day Running Average Effluent TSS Performance for 2009 through 2014 ..........
8
Figure 3-3:
30 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to
Monthly Average Targets for Ammonia Reduction Evaluation....................................................
9
Figure 3-4:
7 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to
Targets for
Ammonia Reduction Evaluation..............................................................................10
Figure 4-1:
Ammonia Study Treatment Process Profile............................................................19
Figure 4-2:
Ammonia Study Intermediate Clarifier Effluent Nitrate + Nitrite- Nitrogen for Each
SamplingCampaign..................................................................................................................20
Figure 4-3:
Ammonia Study Treatment Process Alkalinity Profile.............................................20
Figure 4-4:
Ammonia Study Treatment Process Profile............................................................21
Figure 4-5:
2008 through 2013 Effluent Flows and Rainfall......................................................24
Appendices
APPENDIX A - SUMMARY OF EXISTING UNIT PROCESSES AND OPERATIONAL STATUS
OF RBCs
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��i
INTRODUCTION S
1.0 INTRODUCTION
The Metropolitan Sewerage District (MSD) of Buncombe County's French Broad River Water
Reclamation Facility (hereafter referred to as French Broad River WRF) was placed into service
in 1967 with a capacity of 25 million gallons per day (mgd). Originally an activated sludge
facility, the biological treatment process was converted to Rotating Biological Contactors (RBCs)
in 1988 as part of a federal government initiative to promote "innovative technology". The RBCs
were retrofitted into existing primary and secondary clarifier basins, and activated sludge
aeration tanks. In the same footprint, the 25 mgd activated sludge plant was expanded to 40
mgd using RBC technology.
Major treatment processes at the French Broad River WRF include Screening, Grit and Grease
Removal, Biological Treatment via seven -stage RBCs, Intermediate Clarification, Cloth Media
Filtration, Chlorine Disinfection, Dechlorination, Gravity Thickening, Belt Filter Press
Dewatering, and Fluidized Bed Sludge Incineration. Treated effluent is discharged to the French
Broad River.
The French Broad River WRF was designed based on meeting secondary treatment
requirements (monthly average CBOD5 and TSS concentrations of 25 and 30 mg/L,
respectively). The exiting French Broad River WRF NPDES permit (NC0024911) does not
include numerical discharge limits for ammonia -nitrogen (NH3-N). Compliance with NCDENR's
current ammonia policy is achieved through quarterly chronic toxicity monitoring.
As part of the French Broad River WRF 2011 NPDES permit renewal, Special Condition A. (7)
was added to the permit, which requires the French Broad River WRF to complete and submit
an Ammonia Reduction Evaluation to DWR within 4.5 years of the permit effective date of April
1, 2011. The evaluation shall consider the feasibility and cost for optimizing ammonia removal at
the current plant via operational improvements, and upgrading the plant to meet summer NH3-N
limits of 6.9 mg/L (monthly average) and 20.7 mg/L (weekly average), and winter limits of 17
mg/L (monthly average) and 35 mg/L (weekly average). Summer is defined as April 1 through
October 31. The study also includes monitoring of 36 monthly in -stream ammonia samples
collected approximately 3,000 feet downstream from the discharge.
This report documents findings from the Ammonia Reduction Evaluation completed to meet the
requirements of Special Condition A. (7) of the 2011 NPDES permit. This report presents an
evaluation of existing treatment plant performance data, including intensive intra -process data
collected by MSD specifically for the Ammonia Reduction Evaluation. In addition, this report
presents findings from an evaluation of the feasibility and cost of improvements for optimizing
ammonia removal via operational improvements and implementing upgrades to meet summer
NH3-N limits of 6.9 mg/L (monthly average) and 20.7 mg/L (weekly average), and winter limits of
17 mg/L (monthly average) and 35 mg/L (weekly average).

Metropolitan Sewerage District of Buncombe County I Facility Plan Update LMP
INTRODUCTION r
The main objectives for the Ammonia Reduction Evaluation include the following:
• Review existing data and prepare a summary of MSD's current regulatory compliance
status relative to the current NPDES effluent permit requirements, as well as ammonia
targets from Special Condition A. (7) in the NPDES permit.
• Present an evaluation of process sampling data collected to assess current nitrification
capabilities of existing RBCs.
• Evaluate feasibility and cost of optimizing ammonia removal through improvements to
the existing treatment system.
• Document optimization program that MSD has undertaken to improve RBC performance
and outline recommended sampling program to monitor performance improvements.
• Present initial upgrades needed to improve treatment performance and potentially
improve nitrification performance of the optimized RBC process.
• Present evaluation and cost of biological treatment system upgrades needed to achieve
proposed numerical ammonia reduction targets.

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EXISTING TREATMENT FACILITIES
2.0 EXISTING TREATMENT FACILITIES
The French Broad River WRF is permitted for a maximum month design flow of 40 mgd. A
process flow diagram of the existing French Broad River WRF is illustrated in Figure 2-1. Key
design criteria for the existing treatment processes and equipment are summarized in Table
A-1, located in the Appendix.
Influent wastewater is conveyed to the French Broad River WRF via a 66 -inch interceptor.
Septage, leachate, and incinerator recycle streams are also directed to the 66 -inch influent
interceptor upstream of the influent screens. The influent wastewater is conveyed to the Influent
Screening Facility. The influent screens consist of two traveling rake type screens with 3/4"
openings.
Screened wastewater is then directed to a wetwell and pumped via the Influent Pumping Station
to the Schreiber Grit and Grease Removal System. The Influent Pumping Station consists of
three vertical centrifugal wastewater pumps operating on variable frequency drives (VFDs).
Each pump is capable of pumping 40 mgd to the Grit and Grease Removal System providing a
total peak firm capacity of 80 mgd.
Following grit removal, the wastewater passes through the Primary Microscreens. The Primary
Microscreens were installed as part of the RBC conversion, but are no longer functional and this
process serves as "pass-through" for wastewater from the Grit and Grease facility to the RBC
process.
The RBC system was constructed in 1988 as part of an expansion project in which the French
Broad River WRF was converted from an activated sludge biological treatment process to the
RBC process and expanded from 25 mgd to 40 mgd.
An RBC process is a single pass, fixed film biological treatment process. An RBC process
consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is
supported just above the surface of the wastewater. Biological growth is attached to the surface
of the disc and forms a biofilm layer. The biological growth that becomes attached to the discs
assimilate the organic materials in the wastewater. The discs contact the wastewater with the
atmospheric air for oxidation as it rotates. The rotation also helps to slough off excess solids,
which are captured in a downstream clarification process. Unlike an activated sludge process,
an RBC process does not include return activated sludge (RAS) and the solids retention time
(SRT) of the biofilm is not a process controlled parameter. RBC processes can be designed to
achieve nitrification by providing additional RBC surface area to support nitrifier biofilm growth.
In an RBC process, nitrification does not typically occur until soluble BOD is reduced to 15 to 20
mg/L so RBC area needs to available to support nitrification biofilm growth. It is noted that the
French Broad River WRF RBC process was not designed based on CBOD removal.
The RBC units were installed within retrofitted primary clarifier, activated sludge, and secondary
clarifier tankage built as part of the original activated sludge plant. An air drive system is used to
rotate the RBCs. The air drive system consists of five 450 hp blowers and stainless steel air
diffusers installed under each RBC.

Metropolitan Sewerage District of Buncombe County I Facility Plan Update I,
EXISTING TREATMENT FACILITIES
The original RBC design includes seven stages of RBCs located in three RBC tanks. The three
basins are referred to as RBC Basins No. 1, 2, and 3. Each basin is divided into four parallel
channels. Stages 1-4 located in Basins No. 1 and No. 2 use standard density media. Stages 5-7
located in Basin No. 2 and Basin No. 3 use high density media. Aluminum slide gates were
installed as part of the RBC conversion to route flow through the RBC system and allow any
channel in any basin to be isolated and drained. MSD recently completed a project to repair and
replace inoperable gates.
There are a total of 152 RBCs. Many of the RBC units had previously failed, as the RBCs are
approaching the end of their useful life. In February 2014, at the start of this ammonia reduction
evaluation, 36 of the 152 units were inoperable, removed, or had broken shafts that were not
turning. By September 2014 two more units failed for a total of 38 units out of service. These 38
units were fairly equally divided between the three basins for a total of approximately 25% of the
RBCs out of service per basin. In November 2014, MSD replaced 20 failed RBCs with used
RBCs purchased from a wastewater treatment facility in Parkersburg, WV.
RBC effluent from Basin No. 3 is pumped to the Intermediate Clarifiers for settling and capture
of waste solids from the RBC process. The Intermediate Pump Station includes three variable
speed, submersible pumps. The Intermediate Clarifiers were installed in 1994 to settle out solids
from the RBC process prior to the Secondary Microscreens. The Secondary Microscreens were
originally intended to remove the RBC solids without intermediate clarification, but were often
overloaded and blinded by the TSS concentrations in the RBC effluent.
Like the Primary Microscreens, the Secondary Microscreens were approaching the end of their
useful life and were providing ineffective treatment. To improve treatment performance and
reliability following the intermediate clarifiers, MSD completed a project in 2012 in which the
Secondary Microscreens building was retrofitted to incorporate a Cloth Media Filtration System.
The Cloth Media Filtration System achieves additional TSS and BOD removal and typically
produces an average effluent TSS of less than 10 mg/L. The cloth media filters consist of 16
Aqua Aerobics Aqua Disk filters, arranged in 4 quads to allow use of common backwashing
equipment and controls.
Following filtration, the effluent is disinfected prior to discharge to the French Broad River.
Seven percent (7%) sodium hypochlorite solution is used to disinfect the filter effluent. The
disinfected effluent is dechlorinated using sodium bisulfite prior to discharge to the French
Broad River.
Solids handling at the French Broad River WRF includes gravity thickening of waste solids
captured in intermediate clarifiers and filter backwash waste, dewatering of thickened solids
using belt filter presses, and incineration of dewatered cake using a fluidized bed incinerator.
Incinerator ash is directed to a 13 acre ash lagoon. As shown in Figure 2-1, gravity thickener
overflow and ash lagoon overflow is directed to the head of the Primary Microscreens.
Incinerator returns (belt filter press filtrate and incinerator blowdowns) are directed to the 66 -
inch influent interceptor for recycle to the headworks. Filter backwash waste is typically directed
to the gravity thickeners but during wet -weather flows, approximately 60% of the filter backwash
waste is directed to the Primary Microscreens Effluent.
4

Aetropolitan Sewerage District of Buncombe County I Facility Plan Update
EXISTING TREATMENT FACILITIES
Figure 2-1: French Broad River WRF - Existing Treatment Facility Process Flow Diagram
r ■ ■ Leachate
0 . Septage
•Leachate Receiving
■ Manhole
. ■
" Influent
p , --- ;__ _ Influent PS
i r
Grit Removal , PMS
RBCS
Basin 1 Basin 2 Basin 3 ICL
Influent r
Intercept
■ 60% BW to PMS Effluent during rain events
:Influent .,■..■■■Y..■■Y..\■/■•\/......r.Y.■.■■...■■ .■...■..
" Manhole
' Ash Pond FBI : GTO
BFP • GT
...........
Ash
Y. • ■
Ash Lagoon
■ Overflow
■ ■
• Incinerator M BFP
• Returns Filtrate
r
•....................................................................r...........
Incinerator Return + BFP Filtrate
CMF CCT
FBR
. CMF
„/.■.; Backwash
100% BWto GT except during
rain events; 40% BW to GT
during rain events
5
Abbreviations
PS
Pump Station
PMS
Primary Microscreen
RBC
Rotating Biological Contactor
ICL
Intermediate Clarifiers
CMF
Cloth Media Filters
CCT
Chlorine Contact Tanks
BW
Filter backwash waste
GT
Gravity Thickener
GTO
Gravity Thickener Overflow
BFP
Belt Filter Press
FBI
Fluidized Bed Incinerator
FBR
French Broad River
5

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE I wO
3.0 EXISTING TREATMENT
REQUIREMENTS AND SUMMARY OF
CURRENT EFFLUENT PERFORMANCE
3.1. Existing National Pollutant Discharge Elimination
System (NPDES) Discharge Limits
The existing NPDES discharge limits for the French Broad River WRF, established under
NPDES Permit NC 0024911, are summarized in Table 3-1. The existing NPDES permit was
issued on February 25, 2011, became effective on April 1, 2011, and expires on December 31,
2015.
Table 3-1: Summary of French Broad River WRF Existing NPDES Discharge Limits (NC 0024911)
Parameter Monthly Average Weekly Average Daily Maximum
Limit Limit Limit
Flow
CBOD5'
TSS'
D.O.
Fecal ColiforM2
Total Residual Chlorine
pH
40.0 mgd
25.0 mg/L 40.0 mg/L
30.0 mg/L I 45.0 mg/L
Daily Average > 5.0 mg/L
200/100 ml 400/100 ml
Between 6.0 and 9.0 Standard Units
28 pg/L
Chronic Toxicity 1 Pass Quarterly Pass/Fail Chronic Toxicity test with Ceriodaphnia
at 12% waste concentration
'Monthly average removal of 85% of influent CBOD and TSS also required.
2Must also collect upstream and downstream in -stream fecal coliform grab samples three times per week during
June, July, August, and September, and once per week the remaining months of the year.
The current NPDES permit does not include discharge limits for ammonia -nitrogen (NH3-N),
total nitrogen (TN), and total phosphorus (TP) but does require daily monitoring for effluent NH3-
N and quarterly monitoring for effluent TN and TP. The current NPDES permit includes quarterly
chronic toxicity whole effluent toxicity monitoring using Ceriodaphnia as the test organism at
12% waste concentration. DWR's 1999 Ammonia Toxicity Policy allows permit holders for
existing flows to have the option to have ammonia limit(s) or to have quarterly chronic, WET
test, pass/fail at the instream waste concentration using Ceriodaphnia as the test organism.
The current NPDES permit also includes a new Special Condition, A.(7.), entitled "Ammonia
Reduction Evaluation". This Special Condition requires MSD to complete and submit an
Ammonia Reduction Evaluation to DWR within 4.5 years of the permit effective date of April 1,
2011, as described previously in Section 1.0.

Metropolitan Sewerage District of Buncombe County I Facility Plan Update 173EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
3.2. Summary of Existing Treatment Performance
The French Broad River WRF produces an effluent quality that routinely meets or performs
better than the current NPDES discharge limits. 30 -day running average and calendar month
average effluent CBOD concentration and percent removal results for 2009 through 2014 is
illustrated in Figure 3-1. Effluent CBOD is typically between 10 and 20 mg/L and removals
typically range from 85 to 95% with the lower removals occurring during wet -weather periods
when influent concentrations are diluted by wet -weather flows.
Similar data for effluent TSS is presented in Figure 3-2. Effluent TSS is typically 15 to 30 mg/L
through September 2012 when the Cloth Media Filters were put into service. Effluent TSS has
ranged from 8 to 10 mg/L since the filters were brought online. TSS removal was 80 to 93%
prior to the filters and has been 90 to 97% since the filters were brought online.
30 -day running average and calendar month average effluent NH3-N concentration results for
2009 through 2014 is illustrated in Figure 3-3. Seven-day running average and calendar week
average effluent NH3-N performance over the same time period is illustrated in Figure 3-4.
Effluent NH3-N averaged 15.7 mg/L over this time period. Average effluent NH3-N
concentrations were similar during summer (April — October) and winter (November — March)
operation.
As illustrated in Figure 3-3, between 2009 and 2014, the existing treatment process was not
achieving the summer (6.9 mg/L) or the winter (17 mg/L) monthly average effluent NH3-N
targets identified for the Ammonia Reduction Evaluation. Figure 3-4 illustrates that the existing
treatment process currently meets the winter weekly average NH3-N target (35 mg/L) identified
in the Ammonia Reduction Evaluation, but does not meet the summer weekly average NH3-N
target (20.7 mg/L).

Metropolitan Sewerage District of Buncombe County I Facility Plan Update L��
EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
100
100
90
1100%
•
90%
80
•
90%
80
80%
70
80%
70
70%
J
Co
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60
30 -Day Running Avg Effluent TSStO
p
50
X30 -Day Running Avg Effluent CBOD
60% —
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s Calendar Month Avg Effluent CBOD
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20
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20%
10AxAoi
30
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0
30%
0%
1/1/2009 1/1/2010 1/1/2011 1/1/2012 1/1/2013 1/1/2014 1/1/2015
Figure 3-1: 30 -Day Running Average Effluent CBOD Performance for 2009 through 2014
100
1100%
•
90
•
90%
80
80%
70
70%
60
30 -Day Running Avg Effluent TSStO
E
60% o
Calendar Month Avg Effluent TSS
Ln
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0
50°� E
• Calendar Month Avg TSS Removal
W
40
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W
30
30%
20
20%
10
10%
0
0%
1/1/2009 1/1/2010 1/1/2011 1/1/2012 1/1/2013 1/1/2014 1/1/2015
Figure 3-2: 30 -Day Running Average Effluent TSS Performance for 2009 through 2014

Metropolitan Sewerage District of Buncombe County I Facility Plan Update 17NEXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
Figure 3-3: 30 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to Monthly
Average Targets for Ammonia Reduction Evaluation
30
17.0 mg/L Monthly Ave Effluent NH3-N Winter
Target for Ammonia Reduction Evaluation
25
■
J
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20
Z
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Z
-
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■
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d
Q
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0
10
O
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6.9 mg/L Monthly Ave Effluent NH3 N Summer Target
for Ammonia Reduction Evaluation
5
• 30 -Day Running Avg -Winter ■ 30 -Day Running Avg - Summer ♦ Calendar Month Averages
0
1/1/2009 1/1/2010
1/1/2011 1/1/2012 1/1/2013 1/1/2014 1/1/2015
Figure 3-3: 30 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to Monthly
Average Targets for Ammonia Reduction Evaluation

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ���
EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
Figure 3-4: 7 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to Targets for
Ammonia Reduction Evaluation
10
35
35.0 mg/L Weekly Ave Effluent NH3 N Winter
Target for Ammonia Reduction Evaluation
30
■
25
!
Ammonia -N Summer Target for
■
EAmmonia
Reduction Evaluation
■20
--
— — — —
z
z
Y
�
�
EF
15
CU
�+
■
10
T
n
5
0
1/1/09
1/1/10 1/1/11
1/1/12 1/1/13 1/1/14 1/1/15
♦ 7 -Day Running Avg - Winter ■ 7 -Day Running Avg - Summer A Calendar Week Averages
Figure 3-4: 7 -Day Average Effluent NH3-N Performance for 2009 through 2014 Compared to Targets for
Ammonia Reduction Evaluation
10

IL
Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
3.3. Quarterly Chronic Toxicity Performance
Quarterly chronic toxicity test results for pass / fail tests completed with Ceriodaphnia from
February 2011 through May 2014 are summarized in Table 3-2. The NPDES permit requires a
passing value at 12% waste concentration. The French Broad River WRF effluent consistently
complied with the quarterly chronic toxicity requirement, with the exception of November 2011
which was attributed to residual chlorine concentration in the sample. In addition, the chronic
value is typically greater than 36%. Passing results for chronic toxicity indicates no ammonia
toxicity.
Table 3-2: Summary of French Broad River WRF Quarterly Chronic Toxicity Results for 2011 — Nov 2014
Sample Chronic LOEC NOEC
Collection Value
Date
Nov -14 Pass'
Sept -14 Pass'
May -14 >36% >36% >36%
Feb -14 >36% >36% >36%
Nov -13 29.4% 36% 24%
Aug -13 >36% >36% >36%
May -13 >36% >36% >36%
Feb -13 >36% >36% >36%
N.ov-12 >36% >36% ' >36%
Aug -12 >36% >36% ' >36%
May -12 >36% >36% >36%
Feb -12 >36% >36% >36%
Jan -12 >36% >36% >36%
Dec -11 >36% >36% >36%
Nov -112 10.4% 12% 9%
Aug -11 >36% >36% >36%
May -11 >36% >36% ' >36%
Feb -11 >36% >36% >36%
' MSD changed from a Phase II chronic Ceriodaphnia toxicity test to permit required chronic pass/fail test
in September 2014
2Toxicity for November 2011 sample was attributed to residual chlorine concentration in the sample.
3.4. Ammonia Water Quality Data
As part of the preparation for the Ammonia Reduction Evaluation, MSD collected monthly in -
stream ammonia samples between April 2011 and December 2014, as well as during three
week-long intensive sampling campaigns in November 2011, February 2012, and August 2012.
In addition to monthly samples, daily in -stream samples were also collected during the three
one-week intensive sample campaigns. Throughout the testing period, in -stream ammonia
samples were collected 3,000 feet down stream of the discharge, which is the monitoring point
required per the NPDES Permit Special Condition. The ammonia water quality data collected
between April 2011 and December 2014 is summarized in Table 3-3.
11

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EXISTING TREATMENT REQUIREMENTS AND SUMMARY OF CURRENT EFFLUENT PERFORMANCE
Table 3-3: Summary of NH3-N Water Quality Data Collected For Ammonia Reduction Evaluation
Date
Downstream River
Date
Downstream River
Sample (3,000 -ft
Sample (3,000 -ft
downstream)
downstream)
4/14/2011 i
0.69
8/10/2012
! 0.40
5/25/2011
0.65
8/11/2012
i 0.21
6/8/2011
0.65
8/12/2012
0.34
7/19/2011 !
0.46
9/14/2012
0.66
8/15/2011 I
0.40
10/12/2012
i 0.50
9/15/2011 i
1.30
11/8/2012 I
0.53
10/13/2011 i
0.48
12/13/2012
0.20
11/7/2011 i
2.60
1/8/2013 i
0.59
11/8/2011
0.72
2/13/2013 `
0.35
11/9/2011 i
0.80
3/18/2013
0.35
11/10/2011
0.83
4/11/2013
0.42
11/11/2011 i
0.74
5/14/2013
0.44
11/12/2011
0.53
6/19/2013
0.32
11/13/2011
0.49
7/19/2013 i
0.32
12/9/2011
0.45
8/9/2013 (
0.42
1/6/2012 j
0.43
9/10/2013 i
0.59
2/6/2012 ii
0.50
10/2/2013
1.10
2/7/2012 1
0.50
11/11/2013 ;
2.00
2/8/2012
0.43
12/4/2013
1.50
2/9/2012 ,i
0.47
1/16/2014 ;
0.22
2/10/2012 i
0.61
2/19/2014 i
0.44
2/11/2012
1.20
3/24/2014
1.00
2/12/2012
0.57
4/25/2014
0.53
3/12/2012
0.44
5/13/2014
0.53
4/17/2012 i
0.61
6/26/2014 ?
0.66
5/21/2012
0.29
7/22/2014 ;
0.44
6/8/2012
0.56
8/262014 j
0.73
7/6/2012 i
0.62
9/22/2014 I
0.60
8/6/2012 ,
0.61
10/9/2014
0.69
8/7/2012
0.39
11/4/2014 j
0.67
8/8/2012 ;
0.61
i
12/1/2014 j
0.78
8/9/2012
0.50
12

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
4.0 EVALUATION OF EXISTING AMMONIA
REMOVAL PERFORMANCE
MSD completed several intensive sampling campaigns between 2011 and 2014 to collect
additional wastewater characterization data and to estimate unit process treatment
performance. One of the primary goals was to document nitrification in the existing RBC
process. The following sections summarize findings from the supplemental sampling program.
4.1. Ammonia Study
The results of the intra -process sampling and the significant plant return streams (gravity
thickener overflow, incinerator return and ash lagoon overflow) are summarized in Table 4-1.
These are averages of all the data produced during the special sampling program.
The data shown in Figure 4-1 presents BOD, NH3-N and nitrite plus nitrate -nitrogen profiles
through the treatment process. The top panel shows the fate of total and soluble BOD. Total
BOD is reduced through the RBCs, intermediate clarifier and finally through the cloth media
filters. Soluble BOD is primarily removed in RBC Basins 1 and 2 (Stages 1 through 5) to below
20 mg/L. RBC's will nitrify once soluble BOD is reduced to 15 to 20 mg/L. The middle panel of
Figure 4-1 shows ammonia -nitrogen and TKN reductions occurring in RBC Basins 2 and 3
which occurs after soluble BOD is reduced to below 20 mg/L. The observed NH3-N reductions
are occurring because of nitrification in the latter RBC stages. This is confirmed in the bottom
panel of Figure 4-1 which shows the production of approximately 5 mg/L of nitrate plus nitrite
nitrogen. This low level of nitrification occurs in the three sampling campaigns as shown in
Figure 4-2; however consistent nitrification performance cannot be assumed because the RBCs
are not designed for nitrification in any kind of predictable way and the level of nitrification
achieved in the existing system is not readily controllable and expected to be inconsistent in the
existing treatment system.
A consequence of nitrification is a reduction in alkalinity which is shown in Figure 4-3. There is a
35 mg/L decrease in alkalinity in response to the production of 5.5 mg/L of nitrite plus nitrate
nitrogen. This translates to 6.4 mg of alkalinity consumed per mg of nitrite plus nitrate nitrogen
produced which is close to the stoichiometric requirement of 7.14 mg of alkalinity consumed per
mg of nitrite plus nitrate nitrogen produced. The influent alkalinity was more than sufficient to
accommodate nitrification achieved and was not limiting. The RBC pH was also within a
favorable range (between 7.3 and 7.5 su) for nitrification.
Based on process ammonia data collected within the treatment process as part of the intensive
sampling campaigns, it is estimated that approximately 5 mg/L of NH3-N was nitrified in the
existing RBC process during those sampling campaigns. An additional 11 to 13 mg/L of influent
nitrogen is removed through the treatment process. The additional nitrogen removal is primarily
attributed to biological assimilation of nutrients that occurs in the RBC process as a result of
biological oxidation of organics (i.e., removal of CBOD5). A small fraction of the nitrogen removal
is likely attributed to particulate nitrogen removal removed through sedimentation and/or
adsorption to biomass in the RBCs.
13

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE I wR
The intra -process sampling data was used to estimate BOD and ammonia removal rates in the
RBC process. Unit removal rates were estimated based on operational RBC surface area at the
time of sampling. At the time of sampling, a total of 36 of the 152 units were inoperable,
removed, or had broken shafts that were not turning. The number of RBCs operational during
the time of the testing is summarized in Table 4-2. The observed removal rates are in
agreement with removal rates published in Wastewater Engineering Treatment and Reuse
(Metcalf and Eddy, Inc., 4th Edition, 2004, Table 9-8, pg 933).
4.2. Supplemental Sampling
In addition to the Ammonia Study described above, additional supplemental sampling was
completed in 2014 to capture additional information needed to support the Ammonia Reduction
Evaluation. The supplemental sampling program provided the following:
Additional influent wastewater characterization data needed for process analysis.
Expanded parameter list including volatile suspended solids, filtered TKN,
phosphorus and COD including floc filtered COD (ff-COD).
Additional plant return sampling to characterize return loads.
Five sets of samples were collected between April 28, 2014 and May 9, 2014. The results of the
supplemental sampling data are summarized in Table 4-3. These are averages of all the data
produced during this sampling program. There were several abnormally high concentrations
noted during the sampling period. For example, on May 9, 2014, high recycle loads were noted
in the belt filter press filtrate and in the gravity thickener overflow. In addition, on April 28, 2014,
the influent TSS concentration was well above average. Averages were also estimated
excluding outlier data and are presented in Table 4-4. Considering variable conditions
encountered and limited time period for the supplemental sampling, prediction of future
performance cannot be made accurately.
The data shown in Figure 4-4 shows BOD, NH3-N and nitrite plus nitrate -nitrogen profiles
through the treatment process during the supplemental sampling. RBC performance during the
supplemental sampling was lower in comparison to during the Ammonia Study. The lower
treatment performance is likely attributed to the lower number of operational RBCs during the
Supplemental Sampling. MSD was completing gate replacement during the supplemental
sampling and had several basin trains out of service during the testing. On April 28, 2014,
Basins 2 and 3 of Train 3 were out of service. Between May 6 and May 9, 2014, Basins 2 and 3
of Train 4 were out of service. As a result, the operational surface area was approximately 20
percent lower in comparison to during the Ammonia Study.
As shown in the top panel of Figure 4-4, soluble BOD removal achieved in RBCs 1 and 2 is
lower in comparison to during Ammonia Study. This would be expected with the lower operating
RBC surface area. The observed SBOD removal rate based on the actual operating RBC was
slightly lower, but similar to the rate observed during the ammonia study.
As shown in the middle panel of Figure 4-1, lower ammonia -nitrogen and TKN reduction
occurred during the supplemental testing compared to the Ammonia Study. Nitrate plus nitrite
nitrogen production averaged approximately 2 mg/L during this testing. The observed
14

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
nitrification rate at the time of testing was lower in comparison to observed nitrification rates
during the Ammonia Study. The lower ammonia removal rates are likely attributed to higher
soluble BOD concentrations in Basins 2 and 3 and lower operating RBC surface area in Basin 3
with a train out of service during each of the testing days. The lower ammonia removal rates
may also be partially attributed to Train 3 being out of service just prior to the testing which
would have had an adverse impact on the population of nitrifiers there.
In summary, the differences in ammonia removal performance between the Ammonia Study and
the Supplemental Sampling illustrate how increasing the number of RBCs in service improves
treatment performance by achieving lower soluble BOD concentrations earlier in the RBC
process and provides additional surface area for nitrification to potentially occur in the
downstream RBCs. This conclusion makes technical sense and is consistent with the evaluation
of the data available. Improving ammonia reduction is something that will undoubtedly occur
with a higher level of RBCs in operation; however prediction of future reliable performance
cannot be made accurately.
15

Metropolitan Sewerage District of Buncombe County i Facility Plan Update ��
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
Table 4-1: Summary of Ammonia Study Data for Treatment Process Performance
Nitrogen Phosphorus
Process S -BOD
( C -BOD
TSS I NH3-N
TKN Nitrite +
Nitrate-
I Total
Organic
Total
Ortho Organic
I
MBAS
pH
Grab
pH
Com
Alkalinity
Headworks inf 66
168
200 1 22
40 I 0.18
40
17
5.5
2.6 !! 2.8
1.97
7.07
6.98
180
Plant Influent 51
163
199 22
37 0.19
+ 37
16
5.6
2.7 ! 2.9
1.84
7.10
7.16
180
Primary Microscreen 1 62
161
207 1 22
38 0.18
38
16
6.0
2.9 !j 3.1
1.77
7.06
7.09
183
Effluent I
�i
f
RBC1 Effluent 22
144
209 20
37 0.18
37
16
5.9
2.6 I 3.3
1.20
7.32
7.38
! 177
RBC2 Effluent 8
67
179 i 21
34 ! 1.33
35
13
6.1
3.6 2.5
0.30
7.36
7.48
i 149
RBCS Effluent ( 7
58
171. ; 17
30 5.49
35
13
6.0
3.3 2.6
0.26
7.36
7.51
142
Clarifier Effluent i 8
13
23 17
22 5.27
27
4
4.1
3.4 I 0.7
0.28
7.42
7.57
135
Filter Effluent 8
13
21 i 17
22 5.21
27
4
4.1
3.4 ; 0.6
0.24
7.47
7.69
j
116
Thickener Overflow 9
27
_66 18
27 0.45
27
9
5.2
3.9 1.2
0.25
7.24
7.41
I
j 160
Incinerator Return 66
165
210 24
40 3.66
43
16
12.5
7.5 i 5
0.31
7.23
6.75 f
135
Lagoon Overflow 3
3
6 i 27
I
29 0.17
29
2
6.1
6.2 -
0.26
7.39
7.45
138
Table 4-2: Operational RBCs during Ammonia Study
Basin No. RBC Number of Total Basin Surface
Stage units Area (ft 2)
1
1
16 i 4,335,000
1
2
18
2
3
12 7,717,500
2
j 4
23
2
5
21
3
6
14 4,030,000
3
7
12
Total All
116 j 16,082,500
Basins
16

Aetropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
Table 4-3: Summary of Supplemental Sampling Program Results (Averages of Five Samples Collected 4/28/14 - 5/9/14)
Process T -COD F -COD MOD SCOD TCBOD FCBOD TSS VSS TKN FTKN NH3-N NOX-N TP Ortho -P FP Alkalin
ity
Headworks inf j 421 187 (
46
160
69
206
225 1
30.7
24.4
19.1
5.4
3.0
134
Plant InfluentI 551 178 (
39
190
72
348
227
33.9 I
23.6
18.8
7.2
3.3
136
RBC1 Effluent*438 107
30
243
200
j
21.7
18.3
0.1
139
RBC2 Effluent* 428 75 {
13
297
226
23.7
20.1
0.2
147
RBC3 Effluent* j 300 66 j
i
13
I
198 i
152
30.2
20.6
18.1
1.7
6.2
2.9
137
Clarifier Effluent 126 71
1
19
24
30
25
24.3
22.6
19.1
1.3
3.6
3.1
137
Plant Effluent110 83
i
76
18
11
12
17
22.8
22.0
18.6
1.9
3.3
3.0
3.1
134
Thickener
Overflow 276 j 143
97
37
82
80
33.2
i 28.4
21.3
6.6
3.9
157
Filter Backwash i I i 880
j 273
693
696
� 64.3
0.0
6,8**
14.1
158**
Scrubber Water 1 95 83
+
22
18
153
17
22.6
22.7
19.4
13.5
4.9
66
Ash Clarifier 92 i 73
i
I
21
16
I
238
j 20
23.4
22.8
19.4
20.0
6.3
66
BFP Filtrate 544 419
90
50
318
77
47.9
I 47.8
31.9
32.9
19.7
128
Lagoon Overflow j 33 !
*-r;n R/ of DQr' P-;- ni., -H Q w am
i
ni f of
caniinp Hi
6
irinn 4/9R/14
0
camnlinn
j 13
and Train
( 6
III of Basins
29.8
No. 2
and 3 were
28.7
out of service
during
6.2
5/6/14
5.0
- 5/9/14
146
sampling.
**Filtered value.
17

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
Table 4-4: Summary of Supplemental Sampling Program Results (Averages of Five Samples Collected 4/28/14 - 5/9/14, Excluding Outliers)
Process T -COD F -COD ffCOD SCOD TCBOD FCBOD TSS VSS TKN FTKN NH3-N NO,,- "TP Ortho FP Alkalinity
N -P
Headworks inf
474 187
46
195
56
215 178
i 30.7
24.4
19.1
5.4
3.0
134
Plant InfluentI
480 I 178
49
190
48
224 189
31.2
23.6
18.8
6.6
3.3
136
RBC1 Effluent*
438 I 107
30
254 219
�
21.7
18.3
0.1
�
139
RBC2 Effluent*
428 75
13
272 ! 235
23.7
20.1
0.2
147
RBC3 Effluent*
300 66
13
207 176
i 30.2
20.6
18.1
1.7
6.2
i
2.9
137
Clarifier Effluent
126 71
19
8
31 28
24.3
22.6
19.1
1.3
3.6
3.1
137
Plant Effluent
110 72
69
18
11
14 13
e 21.3
22.0
18.6
1.9
3.3
3.0
i
3.1
134
Thickener
i
Overflow
256 129
65
28
82 80
33.2
28.4
21.3
6.6
3.9
157
Filter Backwash
880
273
664 595
64.3
0.0
6.8**
i 14.1
158**
Scrubber Water
95 83
22
18
153 j 17
22.6
22.7
19.4
13.5
4.9
!
66
Ash Clarifier
92 73
21
16
238 20
23.4
22.8
i 19.4
20.0
6.3 i
66
BFP Filtrate
90 76
13
13
277 18
21.9
22.5
I 19.2
25.6
I
7.3
60
Lagoon Overflow
41 I
6
0
13 6
29.8
j
28.7
6.2
5.0 ;
i
146
*Train rain IV of RBC: Basins No. 2 and 3 were out of service during 4/28/14 sampling and Train III of Basins No. 2 and 3 were out of service during 5/6/14 - 5/9/14
sampling.
**Filtered value.
-18

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
180
1—f—SBO
60
—6—TBO
140
120
J
100
O 80
60
40
20
0
40
35
J
30
z
25
20
O
z 15
+
p 10
z 5
0
�(>
�a
Qty
Figure 4-1: Ammonia Study Treatment Process Profile
19
40
Ammoni -nitrogen
35
TKN
30
J
25
E
z 20
15
c
z 10
=
5
z
0
40
35
J
30
z
25
20
O
z 15
+
p 10
z 5
0
�(>
�a
Qty
Figure 4-1: Ammonia Study Treatment Process Profile
19

Metropolitan Sewerage District of Buncombe County I Facility Plan Update (_�
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE I
II 1
sa.,
9.0
on
8.0
z
A 7.0
O
Z 6.0
N
z 5.0
c
4.0
3.0
L
2.0
Z) 1.0
M1
-4
N N
r-1
ri
.-i
r1
c -I
ci
c-1
c -I
e -I
c -I
ri
O
O
O
O
O
O
CN
CN
r4
rq
r14
rN
rn
m
Ln
r"
M
-i
m
Ln
1
N
N
N
1-i
i -i
r -I
ei
a --I
ri
N
N
N
a -i
Ln
00
N
a --I
00
Figure 4-2: Ammonia Study Intermediate Clarifier Effluent Nitrate + Nitrite- Nitrogen for Each Sampling
Campaign
rn 200
O 180
160
140
M
_, 120
own 100
80
Y_ 60
40
Y 20
a 0
�a
Qty
Figure 4-3: Ammonia Study Treatment Process Alkalinity Profile
20
♦
N
a -i
Ln
00
N
a --I
00
N
e -i
rn
00
N N
ci c -I
m
00 00
Figure 4-2: Ammonia Study Intermediate Clarifier Effluent Nitrate + Nitrite- Nitrogen for Each Sampling
Campaign
rn 200
O 180
160
140
M
_, 120
own 100
80
Y_ 60
40
Y 20
a 0
�a
Qty
Figure 4-3: Ammonia Study Treatment Process Alkalinity Profile
20

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ���
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
200
180
160
140
oc
120
100
O 80
m
60
40
20
0
40.0
—f—Ammonia-nitrogen
35.0 i tere
—�—TKN
30.0
ao
25.0
E
Z 20.0
,
m
= 15.0
z
10.0
5.0
0.0
40
35
wo
30
E 25
z
rn 20
z 15
z 10
5
0
�a
Figure 44: Ammonia Study Treatment Process Profile
21

Metropolitan Sewerage District of Buncombe County I Facility Plan Update 111—OP
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
4.3. Evaluation of Nitrification Capacity of RBC Process
The plant effluent monitoring data and results from the intensive sampling campaigns support
that the RBC process has been providing effective CBOD removal and achieves a low level of
nitrification at current loadings, even with 36 units out of service during the Ammonia Study. The
results of the 2014 Supplemental Sampling indicate that decreased RBC surface area
negatively impacted nitrification performance. The evaluation clearly shows that RBC
improvement alone cannot achieve the ammonia reduction targets and that even with additional
RBC's in service, it is impossible to predict with accuracy ammonia reduction that would be
achieved in the RBC process.
4.4. Challenges in Achieving Additional Ammonia Reduction
The French Broad River WRF has several existing treatment challenges that impact treatment
performance achieved in.the RBC process. These challenges need to be addressed for MSD to
recognize improved treatment and additional nitrification in the RBC process. These challenges
include the following:
• Number of RBCs out of service
• Poor grit removal and accumulation of solids in RBCs
• High loads to RBCs (need for primary treatment)
• Wet Weather Flows
• Low influent alkalinity
• Limited ability to predict and control nitrification
The following subsections provide a brief description of each of these challenges.
4.4.1. Out of Service RBCs
There are a total of 152 RBCs installed. Many of the original RBC units have failed as the RBCs
are approaching the end of their useful life. As of September 2014, a total of 38 of the 152 units
were inoperable, removed, or had broken shafts that were not turning. These 38 units were
fairly equally divided between the three basins for a total of approximately 25% of the RBCs out
of service per basin.
The number of operational RBCs impacts the total RBC surface area available for biological
treatment. As illustrated by differences in nitrification performance differences between the
Ammonia Study and Supplemental Sampling, treatment performance and nitrification
capabilities decrease with less RBCs in service. To maximize nitrification capabilities of the RBC
process, the failed RBCs should be replaced.
In late 2014, MSD replaced 20 of the out of service RBCs with replacement RBCs from other
decommissioned RBC facilities. MSD anticipates replacing most of the broken and damaged
RBCs. Restoration of the RBC process is a transitional upgrade strategy to increase the number
of RBCs in service and to achieve as much ammonia reduction as possible without establishing
a specific interim level of specific performance at the French Broad WRF.
22

� r
Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
4.4.2. Poor Grit Removal
Poor grit removal performance has been problematic at the French Broad River WRF,
particularly during wet -weather flow events. In 2008, MSD implemented a grit and grease
removal upgrade project which included the following improvements:
• Replacement of two existing grit classifier units with three smaller units.
• Replacement of existing grease skimmers with fixed air lance system.
• Installation of new air blowers.
• Replacement of existing grease screws.
Even with these improvements, pass through of grit continues to be an ongoing operational
issue. Grit performance testing was completed in 2011 by Grit Solutions. The girt performance
testing indicated that a significant portion of grit is not being removed by the Schreiber process
and also that a large portion of previously settled grit is being re -entrained in the wastewater
flow when the grit system is subjected to variable flows.
Poor grit removal and the lack of primary clarification results in collection of solids and grit
throughout the downstream processes. Grit and solids accumulation in the RBC process has
several negative impacts on the biological treatment process. First, the grit and solids
accumulation reduces retention time in the RBC process. Second, the additional solids increase
stress on the RBC equipment by increasing RBC operating weights and loads on the shafts.
This can be problematic in leading to shaft and bearing failures. Finally, the additional solids and
grit results in higher organic and solids loading rates to the RBC process. Because nitrification is
not typically achieved in an RBC process until most of the organic load has been oxidized, the
higher loading rates impacts nitrification performance.
Improved grit removal performance is a necessary step to improve existing RBC treatment
performance, as well as to provide an essential treatment step before adding enhanced
biological treatment.
4.4.3. Wet Weather Flow
Another challenge for the French Broad River WRF is high wet weather flow. Between 2009 and
2014, the French Broad River WRF experienced peak day / annual average flow peaking
factors of between 2.6 and 3.5. High peak day flows are attributed to Inflow and Infiltration (1/1)
during wet weather events. Historical effluent flow trends are presented in Figure 4-5. As
illustrated in Figure 4-5, higher peak flows events occurred during wetter years.
High wet weather flows create several challenges to biological treatment processes. One of the
biggest challenges is increased hydraulic loads to the secondary clarifiers and the potential for
reduced TSS removal efficiency during these periods. Elevated secondary clarifier effluent TSS
can results in a reduction in the biological mass and can result in a washout of the nitrification
process, particularly during winter operations when nitrification growth rates are low.
Fixed film processes, such as the RBC process, are typically more resilient to washout events in
comparison to suspended growth biological treatment processes since the largest portion of the
microorganisms are attached to the process. However, plant performance data does indicate
that French Broad River WRF performance is impacted during wet weather flows. Poorer
23

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE I wf
intermediate clarifier performance is noted during high flow events. In addition, grit removal
performance deteriorates during wet weather event, exacerbating grit accumulation challenges
previously discussed in Section 4.4.2.
MSD currently has an extensive and aggressive program for the improvement of its collection
system. The CIP for I&I reduction is as expansive as funding will allow and continues to provide
benefits. In addition to the ongoing collection system maintenance program, wet weather flow
management at French Broad River WRF would provide additional benefits in reducing
treatment performance impacts during wet weather events.
100 -
100
90
- 90
7 Day Average (IVIG D)
80
7 80
30 Day Average (MG D)
70
- 70
w
g 60
S
60
3
50
LL
50
c
„
c
3 40
40
M
�
3
W 30
30
a
20
Tip
- 20
10
10
0 ,
0
1/1/2008
1/1/2009
1/1/2010 1/1/2011
1/1/2012 1/1/2013 1/1/2014
Figure 4-5: 2008 through 2013 Effluent Flows and Rainfall
4.4.4. High Loads to RBC process
In an RBC process, nitrification does not occur until the majority of the organics have been
oxidized. One of the biggest challenges for the RBCs to achieve additional nitrification
performance is the high unit organic loads to the RBC process which limits potential for
improved nitrification achieved in Basin 2 as illustrated by the evaluation of the Ammonia Study
and Supplemental Sampling data.
The French Broad River WRF does not currently have a primary clarification process to reduce
influent loads to the RBC process. The lack of primary clarifiers has led to solids accumulation
in the RBCs which contributes to excessive biofilm growth and shaft failures. Any future
stabilization of the existing RBC process or upgrade to an alternative biological treatment
process should consider primary clarification to manage the loads to biological treatment.
24
I,
Figure 4-5: 2008 through 2013 Effluent Flows and Rainfall
4.4.4. High Loads to RBC process
In an RBC process, nitrification does not occur until the majority of the organics have been
oxidized. One of the biggest challenges for the RBCs to achieve additional nitrification
performance is the high unit organic loads to the RBC process which limits potential for
improved nitrification achieved in Basin 2 as illustrated by the evaluation of the Ammonia Study
and Supplemental Sampling data.
The French Broad River WRF does not currently have a primary clarification process to reduce
influent loads to the RBC process. The lack of primary clarifiers has led to solids accumulation
in the RBCs which contributes to excessive biofilm growth and shaft failures. Any future
stabilization of the existing RBC process or upgrade to an alternative biological treatment
process should consider primary clarification to manage the loads to biological treatment.
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
The current average influent total CBOD is approximately 180 mg/L while the soluble BOD is
approximately 55 mg/L. This indicates a high particulate CBOD component and suggests that
primary treatment could provide an effective means of load reduction to the biological treatment
process. Primary clarification will also extend the useful life of the RBCs and could potentially
improve their ability to nitrify.
4.4.5. Low Influent Alkalinity
The current influent alkalinity load is more than sufficient to support the current levels of
nitrification that are achieved in the RBC process. Alkalinity will potentially be deficient in the
future depending on the degree of nitrification. The optimum pH for nitrification is pH 7.5 to 8.
For these reasons, alkalinity addition may be needed to support ammonia removal reductions.
4.4.6. Limited Ability to Predict and Control Nitrification
The existing RBC process was not designed for nitrification, therefore the design RBC surface
area is based on organics removal and not nitrification. Unlike an activated sludge process, the
solids retention time (SRT) of an RBC process is not controlled. There are limited operational
process control parameters that can be made to improve nitrification performance in the existing
RBC process. The degree of nitrification performance achieved is a function of the organic load
to the RBC process and at what point within the RBC process the CBOD is sufficiently low to
support nitrification. The influent load to the RBC process is based on the influent load
variability, which is also not controllable. These factors make it difficult to predict and control the
level of nitrification in the existing RBC process.
4.5. Recommended Initial Improvements
Improvements are necessary at the French Broad River WRF to address existing treatment
challenges described in Section 4.4 to improve existing treatment performance and nitrification
capabilities. The following subsections describe the improvements and anticipated costs for the
short-term (within 10 years) improvement elements. The recommended initial improvements
are the "highest priority actions" based on the evaluations performed and the most effective way
to prepare the facility for the successful implementation of longer term improvements.
4.5.1. Replacement of Broken RBCs
Replacing out of service RBCs is recommended to increase operational surface area for the
biological treatment process to maximize nitrification capabilities of the existing RBC process.
MSD began implementing an RBC replacement program in 2014 as part of an optimization
strategy to improve existing RBC performance. MSD also completed several improvements
earlier in 2014 in preparation for replacing the RBCs. This included a project to repair and
replace inoperable gates. The gate replacement project was required to allow isolation of
individual RBC trains to conduct maintenance and allow RBC replacement. Another project
included cleanout of grit and solids that had accumulated in the RBC basins.
4.5.2. Grit Removal Improvements
Replacing the existing grit system with a better performing grit system is recommended in order
to reduce the wear and performance impacts on downstream processes and improve RBC
performance. In order to significantly improve grit removal which has been a proven problem at
25

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF EXISTING AMMONIA REMOVAL PERFORMANCE
the plant, it is recommended to replace the existing Schreiber process with a vortex -based grit
removal system. Proceeding with biological treatment improvements without these "headworks"
improvements is not an appropriate route to full facility upgrade.
4.5.3. Equalization for Wet Weather Flow Management
Surge / flow equalization is recommended as a strategy for the French Broad River WRF to trim
peak flows during wet -weather operations and reduce potential for adverse treatment process
impacts, such as nitrifier washout, associated with high flow events. The existing out of service
anaerobic sludge digester tanks should be considered for use as surge / flow equalization tanks.
The combined volume of these tanks is 4.2 MG which could be used to trim peak hourly and
daily flows. Peak flows that exceed 65 mgd can be routed to these tanks, and returned to the
plant at a controlled rate when flows drop below 65 mgd.
The goal of the surge / flow equalization system would be to mitigate peak flows such that the
maximum flow through the plant at any time is 65 mgd. Based on analysis of the last 4 years of
plant flow data the two existing digester tanks are sufficient to mitigate all the peak flows for
typical flow years. While not every wet weather event can be expected to be contained with this
volume, repurposing the anaerobic digesters to surge/equalization tanks will provide capacity to
manage peak flows during most wet weather periods. Wet weather flow management will
become an important aspect of plant operations. Relative to enhancing nitrification,
equalization, along with other wet weather operating strategies, would help to better promote
nitrification during wet weather periods.
4.5.4. Primary Treatment
Primary treatment at the French Broad River WRF would provide significant benefits in reducing
TSS and CBOD loads to the biological treatment process. This will offload the RBCs of a
significant CBOD load and enhance nitrification performance through the RBCs.
The primary challenge in considering primary treatment for the French Broad River WRF is
existing site constraints and space required for other improvements, such as grit removal
improvements. The most readily available area is the existing space in the Primary
Microscreens area.
Multiple primary treatment alternatives were reviewed to determine the best approach for MSD
subject to the site constraints and future requirements. Conventional primary clarification was
eliminated as a viable alternative because it would require more area than is available. Based
on evaluation of high rate primary treatment alternatives, chemically enhanced, high rate primary
treatment is recommended to accommodate French Broad River WRF site constraints.
Chemically enhanced high rate primary treatment systems typically achieve greater than 90%
TSS removal. For the French Broad River WRF, the goal of high rate primary treatment is to
balance TSS removal rates while maintaining sufficient primary effluent ortho-P and CBOD to
support downstream biological processes.
26

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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
OPTIMIZATION OF EXISTING TREATMENT SYSTEM
5.0 OPTIMIZATION OF EXISTING
TREATMENT SYSTEM
This section considers the feasibility and cost of optimizing the existing treatment system
through operational improvements.
Based on results from the Ammonia Study and Supplemental Sampling, there are limited
opportunities to recognize substantial additional ammonia reduction through operational
improvements alone. Capital improvements, as outlined in Section 4.4, identify the highest
priority objectives related to existing and future plant configurations and are important steps to
address existing treatment challenges and are expected to further improve nitrification
capabilities on the existing RBC process.
Several operational improvements have been identified to assist with maintaining operation and
life of the RBCs units. These operational improvements, combined with replacement of out of
service RBCs, provide the best opportunity for maximizing nitrification capabilities of the existing
RBC process through optimization. As such, this section focuses on the feasibility and cost of
optimizing the existing RBC process. A monitoring plan is then suggested to assess the benefits
of the RBC optimization program.
5.1. RBC Replacement and Optimization Program
Restoration of the RBC process is a transitional upgrade strategy for biological treatment as well
as improved nitrification performance at the French Broad River WRF. In 2014, MSD initiated an
RBC replacement and proactive maintenance program. The goal of this program is to replace
most of the out of service RBCs and to implement a proactive RBC maintenance program to
sustain a high percentage of operating RBCs. As discussed in Section 4.3, maximizing the
operating RBC surface area provides an opportunity for maximizing the nitrification capabilities
of the existing RBCs.
MSD recently completed an RBC gate replacement program which helps to manage flows
through the RBCs and allow segments of RBC trains to be taken out of service for preventative
maintenance, including biofilm growth control which is done by "starving" or in-situ chemical
treatment to strip excessive growth. The intent of this program is to prevent excessive biofilm
growth, control shaft weights and reduce the frequency of RBC failures. Following completion of
the gate replacement, MSD also completed cleanout of grit and solids that had accumulated in
the RBC basins. This proactive maintenance is one component of MSD's ongoing RBC
optimization program.
The second component of the RBC optimization program is restoring operation of out of service
RBCs. MSD has been working to locate used RBCs in good condition to restore operation of the
out of service RBCs. The first stage of this restoration program was to replace the out of service
RBCs in Basin 1 and the east half of Basin 2 RBCs back into service. This will be followed by
restoring RBCs in the west half of Basin 2 and most of Basin 3, substantially restoring the
remaining out of service RBCs.
27

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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
OPTIMIZATION OF EXISTING TREATMENT SYSTEM I�
The current location of in service and out of service RBCs is illustrated in Table A-2, located in
the Appendix.
Actual and future estimated costs for gate repair and replacement, RBC replacement, and grit
and solids removal are summarized in Table 5-1. Over $1.8 million will be spent by MSD on
RBC replacement and optimization.
Table 5-1: Actual and Estimated Costs for RBC Optimization
RBC Improvements
Cost
RBC Gate Repair and Replacement (2014)
$455,000
RBC Replacement — 20 RBCs in 2014
$674,000
RBC Replacement (for 95% Operational Target)
$400,000
Grit and Solids Removal (2014)
$136,000
Grit and Solids Removal (future)
$200,000
With all of the planned replacements, there would be a total of 147 operational RBCs, or
approximately 97% of the total RBCs. Under current loading conditions with no primary
treatment, this action will provide greater general treatment process flexibility and increase the
potential for additional nitrification. Nitrification performance diminishes when current maximum
month loadings are considered. The potential for nitrification will improve when additional RBCs
are replaced, but RBCs are not designed to nitrify, therefore actual ammonia effluent reduction
cannot be accurately projected. Results are variable depending on conditions, and are not
considered reliable for permit compliance for the levels identified in the ammonia reduction
evaluation targets or for establishing levels that may result from the planned RBC
improvements. Although necessary to extend the longevity of the RBCs, "starving" or in-situ
chemical treatment to strip excessive growth has a negative impact on nitrification.
Implementation of other recommended highest priority improvements outlined in Section 4.4 are
expected to further improve overall performance of the RBC process. For example,
implementation of effective primary treatment is anticipated to reduce organic load to the RBC
process which is expected to increase surface area available for nitrification by achieving a
soluble BOD of less than 20 mg/L earlier within the RBC train. Grit removal improvements are
also anticipated to reduce solids loads to the RBC process which will improve operating
conditions in the RBC basin and help to extend the life of the RBCs. Wet weather flow
attenuation will assist with maintaining nitrification during wet weather. The combination of these
improvements increases the potential for improved ammonia removal performance in the RBCs
in the future. It would be difficult to project additional ammonia removal that could be achieved
through these improvements. Therefore, an ongoing monitoring program to evaluate nitrification
changes that may result from improvements of the RBC system will be an effective way to track
potential improvement in effluent ammonia levels.
Cost estimates for initial improvements are summarized in Table 5-2. The upgrade of the facility
is a "stepwise" process and the initial highest priority actions are ones that are essential, and
required first, to an overall plant upgrade. The headworks and primary treatment improvements
28

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Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
OPTIMIZATION OF EXISTING TREATMENT SYSTEM
are a part of the overall fully upgraded facility. Over $15.5 million will be spent by MSD in the
next 5 to 7 years on upgrade projects to the treatment facility and for improvement of the RBC
process.
Table 5-2: Estimated Capital Costs (2014 dollars) for Phased Initial Improvements
Facility
Cost
Fine Screening and Grit Removal Improvements
$4,600,000
Surge Tank / Flow Equalization
$2,000,000
Primary Treatment
$9,000,000
5.2. Monitoring Program
This section outlines a proposed monitoring program for assessing the benefits of RBC
optimization alone and RBC optimization with implementation of initial upgrades. MSD
completed initial RBC replacement in November and December 2014. It is anticipated that
additional RBC replacement will be completed over the next year. In addition to the ongoing
RBC optimization program, MSD plans to move forward with design and construction of grit
removal and surge / flow equalization improvements to address the most critical treatment
challenges. Fine screening will also be installed as part of the grit removal project. It is
anticipated that these improvements could be complete and operational by 2018. Primary
treatment improvements are expected to be completed over the next 5 to 7 years.
Because some of the RBC replacements were just recently completed, it is too early to assess
benefits of increased RBC surface area. In addition, since the RBC replacement occurred
during winter operation, warmer operating temperatures will likely be required to allow time for
nitrification start-up in the replaced RBCs. It is recommended that sampling be initiated in
Summer 2015 to allow time for nitrification start-up.
An intra -process monitoring program could be conducted similar to the protocol used for the
Ammonia Study. If possible, the sampling program should be conducted to estimate nitrification
capacity of the most fully restored train. Process control of the RBCs is limited in relation to
nitrification. A reasonable approach is to continue monitoring and to do the very best possible
until a more reliable nitrification process can be implemented.
Following completion of baseline sampling for the RBC improvements alone, the intra -process
monitoring program could be repeated following completion of the grit removal improvements.
Based on timing for RBC and grit removal improvements, the baseline ammonia removal
improvements monitoring could be conducted between Summer 2015 and Winter 2017 prior to
completion of grit removal improvements. It is estimated that monitoring for additional ammonia
reduction improvements following completion of grit removal improvement project could begin in
Summer 2018. Similar monitoring can also be conducted following completion of high rate
primary treatment improvements. Sampling of intermediate clarifier NO,,- N could also be
conducted to provide additional data for monitoring nitrification improvements.
29

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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
6.0 EVALUATION OF BIOLOGICAL
TREATMENT UPGRADES TO MEET
NUMERICAL AMMONIA REDUCTION
TARGETS
6.1. Overview of Biological Treatment Upgrade Strategy
The existing RBC process in Basins 1, 2 and 3 is effective in removing CBOD, and under
current conditions and loads is able to provide a low level of nitrification. The existing treatment
plant maintains consistent compliance with existing permit limits, including consistent
compliance with chronic toxicity permit limits.
However, as discussed in Section 4.3, even with all RBCs in service, the existing RBC process
cannot be expected to provide a high degree of nitrification and cannot meet the monthly
average NH3-N targets for the Ammonia Reduction Evaluation. As discussed in Section 4.4, the
French Broad River WRF has several existing treatment challenges that limit the ability of the
existing RBC process to achieve additional nitrification and that must be addressed for overall
plant improvement. As described in Section 5, MSD has already initiated an RBC optimization
program to replace out of service RBCs and sustain the number of RBCs in operation through a
proactive RBC maintenance program. MSD plans to initiate a phased improvement program to
address the other existing treatment challenges. It is anticipated that grit removal and surge /
flow equalization improvements will be completed first with estimated completion in 2018.
Installation of high rate primary treatment is anticipated to be accomplished next over with
anticipated timing of 5 to 7 years.
MSD should continue with the option for quarterly chronic toxicity monitoring as the continued
option for compliance with DWR's existing ammonia toxicity policy. This will allow time needed
for MSD to complete the RBC optimization program and proposed initial improvements, conduct
a monitoring program to quantify additional ammonia removal achieved through optimization of
the RBCs alone, as well as with implementation of the initial improvements.
The following subsections present an evaluation of the feasibility and costs for biological
treatment upgrades to meet numerical ammonia targets for the Ammonia Reduction Evaluation.
As previously discussed, this is a phased transitional upgrade strategy, and the highest priority
improvements will be constructed first. The biological upgrade components can be completed
after these initial improvements are in operation. This phased approach is a logical, real-world
methodology for getting this large facility upgraded.
6.2. Approach for Evaluating Biological Treatment Upgrades
This section presents the overall approach for evaluating biological treatment upgrades required
to meet numerical ammonia targets fro the Ammonia Reduction Evaluation.
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
6.2.1. Biological Treatment Influent Flows and Loads
Flow and load projections at permitted flow conditions served as the basis for conceptual sizing
and evaluation of both highest priority improvements presented in Section 4.4 and biological
treatment alternatives.
Flow and load projections were based on the historic data analysis as well as domestic and
industrial growth rates provided by MSD. Current baseline flows, loads and peaking factors are
presented in Table 6-1.
Table 6-1: Baseline Flows and Loads Based on Historic Data Review
Parameter
Total
Average
Annual
Total
Industrial
Component
MM/AA
Peaking
Factor
Max 7 -
Day/AA
Peaking
Factor
Flow (mgd)
19
0.71
1.6
2.6
CBOD (Ib/d)
28,685
3,960
1.2
1.7
TSS (Ib/d)
41,165
1,502
1.4
2.3
i
NH3-N (Ib/d)
3,405
198(')
1.3
1.8
TKN (Ib/d)
5,618 (2)
I 327 (2)
1.3
1.8
(t) Based on 5% of CBOD load
(2) Based on TKN/NH3-N = 1.65 form ammonia study data.
No ammonia or TKN data was available for the industrial loads; therefore, the load was
assumed to be 5% of the industrial CBOD load. This was necessary because the growth rates
for domestic and industrial growth are different. The domestic flow and load growth rate is 1.0%
per year and the industrial growth rate is 1.2% per year.
Projected influent wastewater flows, loads, and concentrations at the maximum month permitted
flow of 40 mgd are summarized in Table 6-2. Flows and loads in Table 6-2 were used for
conceptual sizing of the biological treatment alternatives, taking into account any additional
treatment that would be achieved with high rate primary clarification. High rate primary clarifier
effluent loads are summarized in Table 6-3.
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update up
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
Table 6-2: Summary of Wastewater Loads and Concentrations at 40 mgd permitted Capacity (Year 2042)
Parameter Average Max Month Peak Week Max Day Peak Hour
Annual
Flow (mgd)
25.4
40
65.0
CBOD (Ib/d)
38,593
47,955 j
63,992
CBOD (mg/L)
182
144
118
TSS (Ib/d)
55,053
76,511
127,011
TSS (mg/L)
259
231
234
NH3-N (Ib/d)
4,560
i
5,856
8,082
NH3-N (mg/L)
21
18
15
TKN (Ib/d)
7,523
9,663
13,335
TKN (mg/L)
35
29
25
Total P (mg/L)
Average 5.8, Range 4.0 to 6.9
Ortho P (mg/L)
Range 2.4 to 2.9
pH (su)
6.5 to 7.5
Alkalinity (mg/L)
Average 180, Range 135 to 250
Temperature (°C)
Range 11 to 23
75
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
Table 6-3: Primary Effluent Estimates at 40 mgd Permitted Capacity (Year 2042) with Chemically Enhanced
High Rate Primary Clarifiers Optimized for TSS Removal
Parameter Average Max Month Peak Week Max Day Peak Hour
Annual
Flow (mgd)
25.4 I 40 65.0
75 80
CBOD (Ib/d)
21,221 33,192 54,174
CBOD (mg/L)Z
100 M 100 100
TSS (Ib/d)'
5,505 i 7,651 25,402
TSS (mg/L)
(
26 I 23 47
NH3-N (Ib/d)3
4,796 7,468 10,001
NH3-N (mg/L)
i
23 ! 23 18
TKN (Ib/d)4
6,395 9,663 13,335
TKN (mg/L)
30 30 25
Total P (mg/L)5
2 mg/L
Ortho P (mg/L)5
1 mg/L
pH (su)
6.5 to 7.5
Alkalinity (mg/L)
Average 180, Range 135 to 250
Temperature (°C)
Range 11 to 23
190% TSS removal assumed at annual average and maximum month; 80% TSS removal assumed at peak week.
2 Primary effluent CBOD was estimated assuming influent particulate CBOD/TSS ratio of 0.6 and a soluble CBOD of
55 mg/L. If resulting estimate was less than 100 mg/L, then the primary CBOD was rounded up 100 mg/L.
3 NI -13-N load estimated by
multiplying primary effluent TKN load by typical primary effluent NH3-N/TKN ratio of 0.75.
4 Primary effluent TKN calculated assumed that 15% of influent TKN load (particulate TKN) would be removed in the
primary clarifiers.
5Chemical addition to high
rate primary clarifiers would be dosed to maintain a primary effluent ortho-P concentration
of at least 1 mg/L.
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
6.2.2. Effluent Objectives
Biological upgrade alternatives were evaluated based on their ability to continue to meet
existing NPDES discharge requirements in addition to the ammonia reduction targets for the
Ammonia Reduction Evaluation.
The ammonia reduction targets include summer and winter effluent discharge targets; however,
it is important to note that summer is defined as between April 1 through October 31. Hence, it
is important that the biological treatment process be sized to achieve year-round nitrification so
that nitrification is sustained during the winter and the lower summer ammonia -N target can be
achieved at the on -set of the summer compliance period when operating temperatures are still
low. This also provides additional flexibility for the biological system to accommodate a more
stringent ammonia -N discharge limit should it be required in the future.
Flexibility for partial denitrification for alkalinity recovery and reduced aeration demands were
also considered when feasible.
6.2.3. Identification and Evaluation of Biological Treatment Alternatives
Preliminary screening of potential biological treatment alternative was completed to identify
feasible alternatives that could comply with the ammonia reduction targets. One of the
overarching goals was to work within the existing biological treatment tanks (Basins 1, 2 and 3)
because the plant site is underlain with hard rock. This constraint limited some of the secondary
treatment alternatives that were considered.
Table 6-4 presents a summary of the potentially feasible treatment alternatives that were
considered along with their advantages and disadvantages. These technologies were assessed
for their ability to comply with the ammonia reduction targets. Through this initial screening the
alternatives listed in Table 6-5 were identified as being feasible to meet the ammonia reduction
targets.
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update ���
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
Table 6-4: Summary Biological Treatment Alternatives Considered
Treatment Alternative Advantages Disadvantages
Rotating Biological Contactors • Familiarity of operation • Limited degree and
(RBC) • Most compatible with reliability of nitrification
existing facility • Availability of parts and
• Energy efficient replacement equipment
Conventional Activated
Sludge, BNR
Membrane Bioreactor (MBR)
• Reliable and well
demonstrated
• Can be retrofitted into
available tanks
• Can be configured to
recover alkalinity
• Reliable and well
demonstrated
• Can be retrofitted into
available tanks
• High biomass process
reduces tank volume
requirements
• Smallest footprint
• Eliminates need for
clarifiers
• Can be configured to
recover alkalinity
• Requires largest reactor
volume
• Increased clarification area
required
• Large footprint
• Construct deeper tanks for
reduced footprint and
energy efficiency
• Capital cost
• New operator skill set
needed
• Membrane maintenance
and eventual replacement
• More energy intensive
than other methods
• Fine screening required
(2to3mm)
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Metropolitan Sewerage District of Buncombe County I Facility Plan Update L��
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION I
TARGETS
Treatment Alternative Advantages Disadvantages
Integrated Fixed Film
Activated Sludge (IFAS) or
Moving Bed Biofilm reactor
(MBBR)
Step Feed BNR Process
A -Stage
• Reliable and well
demonstrated
• Can be retrofitted into
existing tanks
• High biomass process
reduces tank volume
requirements
• Media and support
equipment offered by
several vendors
• Smaller footprint than
conventional activated
sludge
• Can be configured to
recover alkalinity
• Capital cost
• Media can clog
• Fine screening required (6
mm with primary
clarification; 3 — 4 mm
without primary
clarification)
• Energy efficient . Increased clarification area
• Cost effective required
• Greatest ability to manage • Large footprint
peak wet weather flows • Construct deeper tanks for
• Proven to remove nitrogen reduced footprint and
• Most process flexibility. energy efficiency
• Can be configured to
recover alkalinity
• Can be retrofitted into
available tanks
• High biomass process
reduces tank volume
requirements
• Smaller footprint
• Enhances MLSS settling
characteristics and solids
capture
• Reduces clarifier area
requirements
• Can be configured to
recover alkalinity
• High rate CBOD removal
• Energy efficient
• Cost effective
• Small aeration tanks
• Relatively new process
with limited installations
• Proprietary process
• Must be coupled with
second stage nitrification
process
• Conventional clarification
area required
36

6 l j v
Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
Treatment Alternative Advantages Disadvantages
Mainstream
Deammonification
• Reduction in oxygen
demand (energy)
• Reduced alkalinity
requirements
• Reduction in biomass
production
• Reduction in carbon
demand for denitrification
• Can be part of an A/B
Stage process
• Emerging technology
• Ideal temperature is 30 to
35°C.
• Mainstream
deammonification is in the
investigative stage and
should not be considered
feasible at this time for full
scale application
Table 6-5: Feasible Alternatives for Meeting Ammonia Reduction Targets
Process Description
High Rate Primary Treatment and Full Conversion to Conventional
Activated Sludge Nitrification (Basin 1 and 2)
High Rate Primary Treatment and Full Conversion to Conventional
Activated Sludge Nitrification (Basin 2 only)
High Rate Primary Treatment with RBCs for CBOD Removal and Second
Stage Activated Sludge Nitrification
High Rate Primary Treatment with Parallel RBC and Nitrifying Activated
Sludge Processes
Full MBR Process
High Rate Primary Treatment with RBCs for CBOD Removal and Nitrifying
MBBR
High Rate Primary Treatment with full conversion to MBBRs
Full IFAS Process
37

vn }
Metropolitan Sewerage District of Buncombe County I Facility Plan Update
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
6.3. Conceptual Development of Biological Treatment
Alternatives
The feasible alternatives were considered in conceptual planning for upgrades to meet the
Ammonia Reduction Evaluation targets.
Pre -anoxic zones should be considered because of their ability to recover alkalinity and reduce
chemical consumption and O&M costs.
Construction sequencing and maintenance of plant operations for each of the biological options
is complicated because the existing structures must be modified and re -used inside their
existing footprint while the plant is kept sufficiently operational to continue to meet permit limits.
It was assumed based on the ongoing optimization program that the RBC process will be nearly
fully functional during the biological process upgrade. However, the plant will have very limited
or no ability to nitrify during construction, depending on high rate primary treatment
performance. Therefore, for construction sequencing, it was assumed that the plant would not
be required to comply with numerical ammonia limits until long term biological treatment
alternatives are constructed. This is a critical assumption for successful maintenance of plant
operations during construction and transition to a new biological treatment process.
All of the biological treatment alternatives incorporate the phased highest priority improvements
described in Section 4.4. It was assumed that new fine screening and grit removal, along with
high rate primary treatment would be constructed prior to upgrading the biological treatment
process. It is critical that the biological process conversion be completed after the high rate
primary treatment process in online and optimized to maximize TSS and particulate CBOD
removal. Additionally, at least three of the four existing biological trains must be kept operational
during construction to meet existing permit limits.
6.4. Cost Estimates for Biological Treatment Upgrades
New fine screening and grit removal, as well as high rate primary treatment, would need to be
constructed prior to upgrading the biological treatment process. High-level conceptual cost
ranges were prepared for the feasible biological treatment upgrade alternatives. Since the
biological upgrade cannot be completed first, it is assumed that the feasible alternatives may
change and other technologies may evolve. Costs were developed based on assumptions for
equipment, concrete, structures, infrastructure rehabilitation and demolition costs as well as
allowances as a percentage of construction for instrumentation and control, electrical and a 25%
overall contingency. Costs also include constructability and maintenance of plant operations
related items such as bypass pumping. Major equipment costs are based on vendor budgetary
estimates and are marked up by 40% as an allowance for installation. Unit costs for items such
as concrete and piping are installed cost estimates.
A summary of the estimated capital costs for the biological treatment upgrades are summarized
in Table 6-6.
38

Metropolitan Sewerage District of Buncombe County I Facility Plan Update ��
EVALUATION OF BIOLOGICAL TREATMENT UPGRADES TO MEET NUMERICAL AMMONIA REDUCTION
TARGETS
Table 6-6: Estimated Capital Costs (2014 dollars) for Biological Alternatives
Facility Cost
Activated Sludge
MBBR
IFAS
MBR
$35,000,000 - $50,000,000
$50,000,000 - $70,000,000
$35,000,000 - $50,000,000
>$250,000,000
39

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
SUMMARY OF FINDINGS AND CONCLUSIONS
7.0 SUMMARY OF FINDINGS AND
CONCLUSIONS
Below is a summary of key findings and conclusions for the Ammonia Reduction Evaluation:
• The French Broad River WRF maintains consistent compliance with existing permit
limits and complies with DWR's existing ammonia policy through consistent compliance
with chronic toxicity permit limits.
• The existing RBC process is effective in removing CBOD, and under current conditions
and loads is able to provide variable low level of nitrification.
• The existing RBC process, even with the improvements in RBC operations, cannot
currently meet targets for the Ammonia Reduction Evaluation, and RBC nitrification
cannot accurately be estimated.
• The results of the intensive sampling support that some additional improvement of
nitrification can be expected with increased RBC surface.
• Based on observed current nitrification rates from intensive sampling events, even with
all RBCs in service, the existing RBC process cannot provide a high degree of
predictable nitrification and cannot meet the monthly average NH3-N targets for the
Ammonia Reduction Evaluation.
• The French Broad River WRF has several existing treatment challenges that must be
addressed first in order to optimize the operation of the RBC system and provide an
appropriate treatment foundation for upgrading biological treatment at the facility. These
challenges include the following:
o Number of RBCs out of service
o Poor grit removal and accumulation of solids in RBCs
o High loads to RBCs
o Wet Weather Flows
o Limited influent alkalinity
o Limited ability to predict and control nitrification
• MSD has initiated an RBC optimization program to replace out of service RBCs and
sustain the number of RBCs in operation through a proactive RBC maintenance
program. By the end of this program, it is anticipated that 97% of the RBCs will be
operational.
• A monitoring program could quantify ammonia benefits of the RBC optimization.
• MSD intends to initiate a phased improvement program to address existing treatment
challenges, and to provide an overall upgrade of the WRF in accordance with an
appropriately scheduled and managed major treatment improvement project. It is
anticipated that grit removal and surge / flow equalization improvements will be
completed first with estimated completion in 2018. Installation of high rate primary
treatment is anticipated to be accomplished next over with anticipated timing of 5 to 7
years. It is anticipated that these improvements will further improve nitrification
capabilities of optimized RBC process.
40

Metropolitan Sewerage District of Buncombe County I Facility Plan Update
SUMMARY OF FINDINGS AND CONCLUSIONS
A monitoring program could quantify additional ammonia removal benefits with
implementation of each of the phased initial upgrades.
Significant and costly biological upgrades are required to achieve process control
managed year-round enhanced nitrification at the French Broad River WRF. The
addition of these improvements is planned and is a part of the overall upgrade program
for this facility.
Feasible biological alternatives were identified and conceptually developed.
o The identified initial improvements are required prior to implementation of all
biological treatment alternatives.
o Initial phases are costly, complex and require time to design and construct and
initiate operation.
o Implementation of the biological alternatives will be complicated and require an
extensive maintenance of operations plan to transition to an alternative
biological treatment process.
A phased biological implementation strategy is recommended. MSD should continue
with the option for quarterly chronic toxicity monitoring as the continued option for
compliance with the existing ammonia toxicity policy. This will allow time needed for
MSD to complete the RBC optimization program and proposed phased initial
improvements, as well as to conduct a monitoring program to quantify additional
nitrification achieved through optimization of the RBCs alone and with implementation of
the phased highest priority improvements.
41

-aluvlq;,dal dllvuoz;uayuz a2vd nqL
0 f ) .

Memorandum
To: Thomas Hartye, PE, General Manager
Peter Weed, Director of Water Reclamation Facility
From: Forrest R. Westall, PE, McGill Associates
Subject: MSD's WRF (Water Reclamation Facility) Upgrade Process and Schedule—Reference to
Proposed NPDES NH3-N Limitations
Copy: Ed Bradford, Roger Edwards, Hunter Carson, MSD
This memo provides a summary of the status of NPDES permit renewal for MSD's WRF and an
evaluation of the ongoing efforts that the MSD is making toward compliance with NH3-N Limitations
expected to be included in future permits for the facility. A schedule is provided for the completion of
the extensive overall upgrades underway at the MSD WRF.
Backeround and NPDES Permit Status
MSD holds an NPDES discharge permit for its WRF located adjacent to and discharging its treated
wastewater to the French Broad River. The current permit was issued February 25, 2011, with an
effective date of April 1, 2011 and an expiration date of December 31, 2015. In accordance with permit
requirements, MSD timely applied for its renewal of the permit. DWR received the request, but the
Division has not drafted a pre -notice renewal permit for MSD to review. Under established regulatory
procedures, authorization to discharge remains in effect under the conditions of the current permit and
remains so until the agency renews the permit.
The 2011 NPDES permit includes a requirement (Special Condition A. (7)) for MSD to develop an
Ammonia Reduction Study that would look at feasibility and cost to make operational changes and/or
plant upgrades to meet future ammonia limits of summer, 6.9 mg/L, monthly average and 20.7 mg/L,
weekly average, and winter, 17 mg/L, monthly average and 35 mg/L, weekly average.
This study was completed and submitted with the permit renewal application package sent to DWR on
May 5, 2015 (Ammonia Reduction Study attached). This report addressed in detail the current state of
nitrification in the Rotating Biological Contactor (RBC) process and noted limitations of the current
treatment process relative to NH3-N reduction, and describes a general path forward to secure
sufficient additional nitrification to meet the limitations noted. This path forward is built upon a
progressive, stepwise effort to improve the WRF from the head of the plant through the biological
treatment step.
MSD has consistently maintained contact with the Division both before and after submittal of the
renewal request in May of 2015. This has been done through numerous emails and phone contacts,
with MSD encouraging additional joint discussion and a site visit/meeting to review the conditions
planned for the renewal permit and, specifically, effluent NH3-N requirements DWR intends to

incorporate into the renewal. I believe a site visit and meeting would be helpful in understanding the
physical constraints of the site and the challenges of this comprehensive upgrade process. The renewal
permit is critical to MSD in establishing logical steps toward plant improvement and in making
appropriate WRF process changes that will result in consistent compliance with anticipated NH3-N
limitations.
DWR has previously communicated, including within the current permit, that the agency plans to
include specific ammonia (NH3-N) limits in the permit.
Current Facilities Plan and Construction
MSD is deeply engaged in and proceeding with a comprehensive facility upgrade process at the WRF.
These actions reflect a Board -approved facilities plan put in place for improvement of the facility and to
address several critical steps in its treatment process, including the biological treatment component.
This plan has been carefully developed to address treatment improvement beginning at the headworks
of the plant through its biological treatment step. This means that the effort begins by improving the
headworks and providing effective solids and grit removal, followed by the addition of a primary high -
rate clarification treatment process, and concludes with an appropriate upgrade of the biological
treatment step. This is a comprehensive, stepwise program that includes a financially sound funding
approach that is the keystone of MSD's WRF Capital Improvements Plan (CIP).
The headworks improvements (upgrading the bar screens, adding a fine screening facility, adding surge
tanks, and upgrading to a new grit removal system) will significantly reduce the grit and solids loading to
the RBC process, which has significantly affected the current biological treatment capacity.
The primary high -rate clarification technology yielded pilot tested removals between 60-80% CBCD, 70-
90% TSS , and 20-30% TKN which will result in an opportunity to better evaluate the nitrification
capability of the RBCS under lower solids (including organic material) levels. It is essential to evaluate
this process change before developing the appropriate biological treatment improvements.
The scope of this total effort requires careful consideration of funding, design constraints, permitting
steps, construction site limits, construction sequence, and the essential consideration of NPDES
compliance during each construction step. The cost of each component of this upgrade process requires
the allocation of significant financial resources. The MSD headworks project is currently contracted at
$9.01VI, the primary, high -rate clarification project is currently projected to cost $15.OM, and the
preliminary costs for full replacement of the biological step could be $55M. In addition to the
consideration of working from the head of the plant toward the effluent, the completion of this overall
effort is a tremendous commitment of resources and requires that MSD take a stepwise approach to
evaluating and financing these actions.
NH3-N Limitations, Scheduling Considerations, and Realities Related to NH3-N Reduction
The RBC biological treatment system employed by MSD was not specifically designed to meet proposed
NH3-N limitations. The French Broad River WRF site is severely limited due to a lack of area to expand,
challenges of doing major renovation while keeping the facility operational and in compliance, and
extensive subsurface bedrock. These constraints resulted in the use of the RBC technology for the

plant's biological treatment step. The relatively small footprint of this technology allowed the
installation of a 40 MGD capacity facility on the site.
However, MSD has for several years been carefully tracking plant performance, including nitrification
levels in the RBC system. Additionally, the District has implemented an aggressive program of restoring
full RBC capability at the facility. While data shows that there is some nitrification occurring within the
current system, MSD is not able to reliably depend on a specific nitrification level and cannot
consistently produce effluent NH3-N levels that can comply at all times with the projected limitations.
MSD's WRF NPDES permit has not previously included NH3-N limitations. While it is MSD's intention to
provide as much NH3-N reduction as possible with the current system, performance of the RBC process
cannot be reliably expected to comply with the expected limitations. As a result, setting an interim level
for effluent NH3-N prior to completion of the upgrade projects puts MSD in compliance jeopardy with
no real water quality benefit.
Because NH3-N, when included, will be a new limitation in the permit, a compliance schedule in the
permit is the appropriate mechanism for establishing a timeline for making the necessary improvements
in the treatment processes. There are several considerations that will assist in supporting and
establishing a workable schedule for NH3-N compliance, they include:
• The headworks improvements, currently under construction, must be completed (expected in
Spring 2019), placed in service and performance measured and demonstrated.
• The high rate primary treatment system, currently in design, must be completed (expected in
Spring 2021), placed in service and performance measured and demonstrated.
• The specific wastewater characteristics of the flow that is delivered to the biological treatment
step from the high rate primary treatment in MSD's WRF need to be established to have
accurate loading parameters for development of biological treatment improvements that can
consistently meet the proposed NH3-N limitations.
• Modification to the biological treatment component of the WRF will require a careful evaluation
of options, particularly since there are major site restrictions impacting the ability to construct
improvements while keeping the plant fully "on-line" and providing the best effluent quality
possible.
• Plant improvements should follow a stepwise installation process so that during plant upgrade
activities the facility will continue to comply with the parameters currently limited in the permit.
• Should the process to evaluate and determine the most appropriate actions for biological
treatment modifications result in a complete shift away from the RBCS, construction planning
will be extremely challenging and there may be a need to develop interim limits during the
biological treatment modification timeframe.
• Monitoring data upstream, effluent and downstream for NH3-N show that during actual stream
flow conditions concentrations do not represent a significant risk for water quality impact.
• WRF whole effluent toxicity data demonstrates consistent compliance.
• The overall upgrade project involves the allocation of a large amount of financial resources that
must be carefully planned over the period of the project.
3

Recommended Schedule
The WRF CIP calls for an extensive set of actions aimed at comprehensive rehabilitation and upgrade of
the plant. In the whole, it is a massive undertaking on a limited site. It is impossible to undertake all of
the needed improvements simultaneously. Because the effluent from the step upstream in the
treatment train to the next represents the design parameters for the downstream component, it is
essential to work from the head of the plant toward the final effluent when making comprehensive
plant upgrades. This is the sequence of installation/construction that MSD has planned for in order to
successfully complete its WRF upgrade.
MSD developed and is currently implementing a logical, stepwise approach for each phase of the WRF
upgrade process. It is essential to the success of the overall project that each treatment component be
upgraded in time sequence, upstream to downstream. Each phase must include preliminary planning,
identification of the most qualified design consultant, an evaluation of alternatives, design, permitting,
installation/construction, and an appropriate demonstration period to establish consistent performance.
Specific design of the downstream component requires the availability of demonstrated performance of
the upstream treatment step. This means that stable demonstration data from the new/upgraded
upstream component needs to be available to do effective design. This is particularly true when entirely
new treatment approaches are being used.
Based on this review of the actions needed to undertake and complete a comprehensive upgrade of the
MSD WRF, Figure 1 lays out the recommended schedule for this overall upgrade effort.
This schedule should be included in the permit. As we have discussed, it is important for MSD to
interact with DWR on the development of the renewal permit. Because of the scope and difficulty of
the WRF improvements needed to comply with the expected NH3-N limits, it is essential that MSD
secure a pre -notice draft of the NPDES renewal permit that can be reviewed and coordinated with DWR
before it goes to public notice. It will not be possible for MSD to comply with the NH3-N limits until the
extensive upgrade project is completed.
Attachments:
Ammonia Reduction Evaluation, April 10, 2015
Current NPDES Permit, February 25, 2011
MSD Facility Plan, available at http://www.msdbc.org/other/eng/MSD Facility Plan Update Final
Report April2015.zip
MSD Permit Renewal Application, Transmittal Letter, May 5, 2015
4

Figure 1. MSD Wastewater Reclamation Facility, Capital Improvements Plan Sequence and Schedule
d1D Task Description Duration Stan Finish 6 ! 2017 i 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 20Plant Headworks Construction 668 days Mon 4/3/17 Wed 1/30/19 !
_.
'lent Headworks Performance Testing
366 days
Thu 1/31/19
Fri 1/31/20
!
I
dant High Rate Primary Treatment Design & Permitting
915 days
Sat 7/30/16
Wed 1/30/19
Design I rre i
lent High Rate Primary Treatment Construction
732 days
Thu 1/31/19
Sun 1/3121
ructim
--_
'lent High Rate Primary Treatment Performance Testing
731 days
--- Mon 2/1/21
Wed 2/1/23
_
Perfbrmahce Teslin
iological Treatment Consultant Selection and Alternatives
550 days
—_—__
Mon 8/1/22
Thu 2/1/24,-
valuation
Evalu
iological Treatment Consultant Selection, Design and
731 days
Fn 2/2/24
Sun 211/26
'
ermitting
iological Treatment Construction
1097 days
Mon 2/2/26
Fri 2/229
'iological Treatment Pertormance Testing 366 days Sat 2/3/29 Sun 213/30
Report
Note: Projed durations are based on a 7 day week. I Design & Permitting � Performance Testing — Construction Evaluation Report
Created by Hunter Carson I ver I IMnrM 9f15/1a

Milestones Year Task Description
By one (1) year Complete Headworks construction
from effective 2019 Begin Headworks performance testing
date of the Complete High Rate Primary Treatment design & permitting
permit Begin High Rate Primary Treatment construction
By two (2) years
from effective
2020
Complete Headworks performance testing
date of the
2027
Continue High Rate Primary Treatment construction (50%)
permit
Continue Biological Treatment construction (66%)
2029
By three (3)
Begin Biological Treatment performance testing
years from
2021
Complete High Rate Primary Treatment construction
effective date of
Begin High Rate Primary Treatment performance testing
the permit
By four (4) years
from effective
2022
Continue High Rate Primary Treatment performance testing
date of the
Begin Biological Treatment Consultant Selection
permit
By five (5) years
from effective
2023
Complete High Rate Primary Treatment performance testing
date of the
Begin Biological Treatment Alternatives Evaluation Report
permit
By six (6) years
from effective
2024
Complete Biological Treatment Alternatives Evaluation Report
date of the
Begin Biological Treatment design
permit
2025 Continue Biological Treatment design and begin permitting
Complete Biological Treatment design and permitting
2026
Begin Biological Treatment construction
2027
Continue Biological Treatment construction (33%)
2028
Continue Biological Treatment construction (66%)
2029
Complete Biological Treatment construction
Begin Biological Treatment performance testing
2030
Complete Biological Treatment performance testing