NC0047384_Pretreatment_Corrective_Action_Plan_20190923

CITY OF GREENSBORO
WATER RESOURCES DEPARTMENT - WATER RECLAMATION DIVISION
T. Z. OSBORNE POTW - NPDES PERMIT #NC0047384
1,4-DIOXANE CORRECTIVE ACTION PLAN 9-23-2019
This document is in response to a DEQ letter dated July 22, 2019 which included: ... At this time
the Division is requesting the City provide their corrective action plan for locating and reducing
sources of 1, 4-dioxane. If you have already taken measures outline any past activities, the
outcomes from those activities and any future plan. Please submit your plan to the PERCS
Branch by September 23, 2019...
The following narrative timeline briefly outlines activities by the City of Greensboro Industrial
Waste Section (IWS) in relation to locating sources of and reducing discharges of 1,4-dioxane to
the Greensboro sanitary sewer system.
April 2014-October 2014:
- Greensboro initial meetings with DEQ staff (NPDES, lab, drinking water, basin coordinator)
- IWS initial meeting with Greensboro industrial users
- DEQ issues T. Z. Osborne (TZO) NPDES Permit with 1,4-dioxane reopener [June 2014]
- IWS 1,4-dioxane literature search: chemical structure, wastewater analytical methods, POTW
fate and transport, UCMR3, potential sources, and removal/pretreatment technologies
- DEQ & NCSU begin official 1,4-dioxane studies of Cape Fear River basin [Oct 2014]
March 2015-October 2015:
- DEQ and NCSU preliminary study results indicate Greensboro is a significant source of 1,4-
dioxane to the Cape Fear River (as well as 2 other cities)
- IWS develops Sampling Plan to address: Process control sampling and collection system
sampling including, 2 interconnected POTWs with daily flow and sludge transfer, 1600 miles
of sewer lines, 8000 commercial accounts, limited staff and resources
- Greensboro IWS organizes meeting/workshop for the 3 cities to share information and
hopefully discover a common source
o Detailed review of POTW processes, all treatment chemicals used, POTW
compliance history, bioassay test results, POTW upsets
o Detailed review of industrial dischargers (products, raw materials, SIC codes)
o Acceptance of. landfill leachate, septage, hauled industrial waste
o POTW and collection system sampling issues and potential strategies
City of Greensboro 1,4-Dioxane Corrective Action Plan 9-23-2019 page I

- [March 2015-May 2015] Initial Sampling at Greensboro's 2 POTWs
o 24-hour composite samples analyzed using Solid Waste method: from North Buffalo
influent, North Buffalo Sand Filter Effluent, TZO influent, TZO Sand Filter Effluent,
sludge cake, centrate, domestic sampling location, equipment blank
o Follow-up meeting with Greensboro industrial users to provide guidance for any of
their sampling and investigative activities (review of sampling, monitoring,
laboratories, and analytical procedures used by Greensboro)
o One-on-one conversations re: 1,4-dioxane during required industrial user inspections
- [May 2015-October 2015] TZO collection system Trunkline Monitoring
o 24-hour+ composite samples analyzed using Solid Waste method: various locations
in collection system with each location including at least 2 industrial users
o Domestic/background sampling also conducted to determine 1,4-dioxane baseline
October 2015:
- Trunkline monitoring results identify a significant source of 1,4-dioxane
- Meetings with significant source to request the following:
o Conduct internal facility/process investigation, perform internal sampling and
analyses, determine source of 1,4-dioxane discharge at their facility, research
processes for source reduction, develop reduction plan
o Industrial user voluntarily agreed to pursue source reductions
- TZO plant sampling suspended temporarily while industrial user conducted investigation
February 2016-March 2016:
- TZO plant sampling resumes w/split samples sent to 2 commercial labs (as IWS was still
concerned about no EPA approved wastewater analytical method)
- TZO hydraulically paired influent and effluent sample series to investigate 1,4-dioxane
POTW fate and transport
o Confirmed that conventional wastewater treatment processes cannot remove 1,4-
dioxane
- Sand Filter Effluent sampling indicates reductions of 1,4-dioxance discharged from TZO
o POTW discharge reductions achieved only due to voluntary efforts by the industrial
user
City of Greensboro 1,4-Dioxane Corrective Action Plan 9-23-2019 page 2

February 2016-November 2017:
- POTW Sand Filter Effluent monitoring voluntarily continues using non -EPA approved Solid
waste method
- September 7, 2019: EPA promulgates 40 CFR Part 136 method for 1,4-dioxane [Method
624.1]
- October 31, 2017: DEQ issues administrative letter that requires TZO monthly effluent
monitoring and eDMR reporting beginning December 2017 using new EPA approved
wastewater analytical method
- Over 80% reduction achieved comparing average Sand Filter Effluent value from Initial
Sampling Period (March 2015-October 2015) to average Sand Filter Effluent value from Post
Source Reduction period (February 2016 through November 2017)
RESULTS: Before and After Industrial User Reductions
1,4-Dioxane Data: (no EPA approved method)
Range
Avg.
Mar 2015 to Oct 2015
(µg/1)
(µg/1)
Prior to IUSource Reductions
T. Z. Osborne Influent
<3-1150
223
T. Z. Osborne Sand Filter Effluent
<3-659
126
1,4-Dioxane Data: (no EPA approved method)
Range
Avg.
Feb 2016 to Nov 2017
(µg/1)
(µg/1)
After IU Source Reductions
T. Z. Osborne Sand Filter Effluent
<3-350
22.4
December 2017- August 2019: eDMR effluent sampling
- December 2017: TZO Effluent sampling and eDMR reporting begins
- For the first few months of 2018, IWS had TZO effluent samples analyzed with both the
solid waste method and the newly approved wastewater method to confirm the 2 methods
had comparable results in order to confirm previous study period reductions
- June 2018 IWS begins TZO effluent split sampling with 3 commercial labs (Method 624.1):
Pace, Meritech, and R&A
- As with any new removal/reduction process, there have been a few glitches (4 months out of
this 21 month period did not reflect the historical removal efficiency, while the other 17
months did)
o Continued oversight of industrial user to maintain voluntary reductions
The City of Greensboro appreciates the support and guidance of DEQ during this process and
we look forward to working with DEQ and our peers in the future as we continue to further
reduce the discharge of 1, 4-dioxane to the Cape Fear River Basin.
City of Greensboro 1,4-Dioxane Corrective Action Plan 9-23-2019 page 3