NC0024937_Comments_20170405

CHARLOTTE
W6TER
April 5, 2017
NC Division of Water Resources
Mooresville Regional Office
610 East Center Avenue Suite 301
Mooresville, NC 28115
Re: Charlotte Water Comments on Sugar Creek WWTP pH Exceedance
NPDES Permit #NC0024937
Sugar Creek WWTP, Mecklenburg County
Dear Mr. Bell,
RECE(VEDINCDEQIDWR
APR 2 0 2017
Watewuality
PQrmittingSecti®n
Please let this letter serve as Charlotte Water's formal comments on the pH exceedance reported at the Sugar Creek
WWTP on February 3, 2017. Charlotte Water takes environmental compliance very seriously and has conducted a
thorough review of all data related to the Sugar Creek WWTP pH exceedance. Charlotte Water has reviewed and
considered the following information related to the exceedance:
1) Historical Sugar Creek WWTP effluent pH values
2) Field pH meter and facility pH meter calibration and maintenance information
3) Sample collection and analysis times
4) Field Measurement Records
5) Sugar Creek WWTP's Daily Operations Data including process control sample results
6) Effluent pH sample results for February 1-7, 2017.
7) Chain Of Custody's associated with this sample and other samples taken on this day
8) Employee training records and performance history
9) QA/QC quality checks and procedures for atypical results
Historical Effluent pH Values for Sugar Creek WWTP
Charlotte Water reviewed ten years of effluent pH data (2,534 results) and did not find any pH results that exceeded
8.0 s.u. Since late 2011, when Sugar Creek WWTP changed from the use of sodium hydroxide to magnesium
hydroxide for pH and alkalinity adjustment, effluent pH measurements have been more consistent. pH
measurements now exist in a much tighter range and are closer to neutral than before magnesium hydroxide was
utilized. Magnesium hydroxide has allowed our facilities to optimize pH and alkalinity adjustment without the pH
Charlotte Water 4222 Westmont Dr, Charlotte, NC 28217 charlottewater.org
Operated by the City of Charlotte

variability that we had previously experienced using sodium hydroxide in the process. The pH of the bulk
magnesium hydroxide used at Sugar WWTP is 9.9 s.u.
Process Control and Effluent Data for Sugar Creek WWTP
Sugar Creek WWTP collects daily process control data throughout the plant during all three shifts. All process
control pH data is measured with a pH probe that is calibrated daily with three standards: 4, 7, and 10. pH samples
at Sugar Creek WWTP are measured at the Aeration Tank Influent (ATI) and Final Clarifier Effluent (FCE) three
times a day (once per shift). Please see the chart below for a summary of the process control pH results measured
from February 1-7, 2017.
Date
Aeration Tank Influent (ATI) pH
. ,_ .
-Final Clarifier Effluent (FCE),
Final Effluent.
pH
1st
2nd
Shift
Shift
3rd Shift
1st Shift
2nd Shift
3rd Shift
8:00 -
2:30 -
12:00 -
8:00 -
2:30 - 3:00
12:00 -
(as reported
8:30
3:00
12:30 AM
8:30 AM
PM
12:30 AM
via eDMR)
AM
PM
02/01/17
7.2
7.5
7.1
7.0
6.5
7.0
6.9
02/02/17
7.3
7.2
7.1
7.2
7.0
6.8
6.7
02/03/17
7.3
7.2
7.3
6.5
6.9
6.8
9.8
Weekend -
02/04/17
7.1
7.0
7.3
7.0
7.0
6.5
N/A
Weekend -
02/05/17
7.3
6.9
7.0
6.9
6.8
6.9
N/A
02/06/17
7.1
7.6
7.3
7.1
6.6
6.7
6.7
02/07/17
7.4
7.5 1
7.5
7.1
6.7
7.1
7.3
As indicated in the table, on February 3, between 8:00 - 8:30 am, a process control pH sample was taken at the FCE
and yielded a pH result of 6.5 s.u. At 9:18 am the laboratory field services technician collected a pH sample at the
plant effluent. This pH sample was analyzed at 9:21 am and a result of 9.86 was recorded. Between 2:30 and 3:00
pm another process control sample was collected at the FCE and yielded a pH of 6.9 s.u. ,It is highly improbable that
the pH of such a large volume of water would dramatically rise (3.3 standard units) in approximately 1 hour, and then
return to a'near neutral' state within 5 hours.
All process control pH results for the entire week were typical results ranging from a pH of 6.5 to 7.5 s.u. All effluent
pH results for the week were also typical and ranged from a pH of 6.7 to 7.3 s.u., except the effluent pH result of 9.8
s.u. recorded by the lab tech on February 3, 2017. Furthermore, there is no point for introduction of magnesium
hydroxide between the FCE and the designated effluent monitoring location as indicated on the facility process flow
schematic (see attached facility process flow schematic).
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Additionally, all other process control parameters and data for the week were also within typical and expected
ranges. Charlotte Water would have expected other atypical process control results and noticeable biological
impacts to the treatment process if a significant pH increase to 9.8 s.u. had occurred in the treatment process. It is
also important to note that no upset conditions or other unusual observations or atypical lab results were noted during
this week.
Inexperienced Laboratory Field Services Technician
Charlotte Water would also like it to be known that the laboratory field services lab technician (lab tech) that collected
this pH had only been on the job for a few months and was still in training at the time of the pH sample collection and
analysis. Due to the lab tech's inexperience, coupled with the fact that the lab tech was unaccompanied by more
experienced personnel, the technician failed to recognize that this result was atypical and exceeded our NPDES
permitted pH limit. Technicians, as a part of their training, are required to review and have knowledge of Charlotte
Water's NPDES permit limits. Copies of these permits are kept in all vehicles used by Charlotte Water field services
staff.
In addition to not being familiar with the permit requirements, the lab tech also failed to take the appropriate actions
as required in Charlotte Water's QA/QC quality checks and procedures for atypical results. Lab tech's are trained to
resample to confirm all field measurements that are atypical or exceed Charlotte Water's permitted limits. They are
also required to call laboratory management while onsite and give notification of the atypical result so that this
information can be relayed to the operations staff at the treatment plant for further investigation. Regrettably, this lab
tech did not adhere to any of these procedures that were put in place to prevent these types of incidents. Charlotte
Water would also like to note that the lab tech that recorded this pH result has separated from employment with
Charlotte Water and is not available for further questions.
Charlotte Water's Conclusion
In conclusion, after thorough investigation and in consideration of the facts presented in this letter, Charlotte Water is
uncertain why this pH value was reported. Charlotte Water could speculate that this was simply a typo or that after
reading the last buffer, a pH 10 buffer, the lab tech failed to rinse the probe before measuring the effluent sample.
Instead, Charlotte Water prefers to adhere to the facts. In summary, the facts are as follows:
1. No effluent pH results at Sugar Creek WWTP in the last 10 years (2,534 results) have exceeded a pH of 8.0
S.U.
2. No pH results greater than 7.6 s.u. were measured at any location in the process from February 1 — 7.
3. All other effluent results and process control data was typical of normal operations from February 1— 7 and
no upset conditions were observed at Sugar Creek WWTP
4. The bulk chemical used at Sugar Creek WWTP for pH and alkalinity adjustment, magnesium hydroxide, has
a pH of 9.9 s.u.; almost the same as the recorded effluent pH of 9.86 s.u.
5. The lab tech who reported this result was in training, unaccompanied by more experienced personnel, failed
to follow procedures related to the reporting of atypical results including resampling, has since separated
from employment with Charlotte Water, and is not available for further questions.
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In light of the facts presented above, Charlotte Water is requesting that NCDWR take no action regarding the
reported pH exceedance that occurred at Sugar Creek WWTP on February 3, 2017. Again, Charlotte Water takes
environmental compliance very seriously and we appreciate the opportunity to comment on Sugar Creek WWTP's
reported pH exceedance. If you have any questions concerning the information contained in this response, or if you
need any additional information, please feel free to contact our Water Quality Program Administrator, Shannon
Sypolt, at 704-336-4581.
Respectfully,
c�q�L-'L -A --Q-Q
Jacqueline A. Jarrell, P. .
Operations Chief, Environmental Management Division
Charlotte Water
Cc: B. Allen (CLT Water)
S. Sypolt (CLT Water)
D. Denard (NCDWR Central Office)
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