Issues & Goals for Middleboro WWTP
High nitrogen levels are the primary issue in regard to Middleboro. Our goal should be to advocate for more stringent nitrogen limits in the next NPDES Permit.
WHY......? Because nitrogen is a nutrient which when present in excess causes eutrophication in the water. Eutrophication can reduce water oxygen levels and cause excessive weed and algae growth, both of which negatively impact the aquatic ecosystem.
HOW.....? By using available water quality data and nutrient guidelines established by EPA.
Learn more about nutrients HERE
The following is are excerpts from the Middleboro NPDES Permit.
NAME AND ADDRESS OF FACILITY WHERE DISCHARGE OCCURS:
Middleborough Water Pollution Control Facility
Middleborough, MA 02346
RECEIVING WATER:Nemasket River (Taunton River Basin, State Code - 62)
The Middleborough Water Pollution Control Facility is a 2.16 mgd advanced treatment facility
which discharges to the Nemasket River. The facility processes include primary clarification,
activated sludge treatment, secondary clarification, sand filters, seasonal chlorination and
dechlorination (using sodium bisulfite), and post aeration. The facility removes phosphorus
seasonally through chemical precipitation using ferric chloride. The facility maintains yearround
nitrification. Septage is received from the Towns of Middleborough and Lakeville.
Sludge is disposed in the Middleborough Town landfill (refer to Figure 1. for process details and
flow diagram and Figure 2. for geographical location).
7Q10 Data and Dilution Factor :
The United States Geological Survey (USGS) Gazetteer of Hydrologic Characteristics for the
Taunton River Basin (WRI Report 84-4283) lists a 7 day low flow with a recurrence interval of
10-years (7Q10) for the Nemasket River at Murdock Street (Gage Station No. 01107800) of 4.2
cfs with a drainage area of 69.4 square miles. The Town’s consulting engineer, Whitman and
Howard, estimated a drainage area of 67.1 square miles at the WWTF (see Whitman and
Howard letter dated October 29, 1993 in the permit file). Therefore, the 7Q10 at the WWTF will
be equal to 4.2 x 67.1 / 69.4 or 4.06 cfs. After subtracting plant flow of 1.06 cfs (the average
WWTF flow during the two year operating period of the gage), a 7Q10 of 3 cfs was used in the
existing permit. This is continued in the draft permit.
Summer limits have been established before based on dissolved oxygen from the previous Waste
Load Allocation (WLA). These limits will continue in the draft permit.
TKN, Nitrate and Nitrite :
Monitoring requirements for TKN, Nitrate and Nitrite will continue in order to have a long term
data base for evaluation of the effect of nitrogen compounds in the receiving water. A nitrogen
TMDL is currently being prepared for Mount Hope Bay, and information on point source
discharges of nitrogen are necessary to complete this strudy. The draft permit contains no limits
on the discharge of total nitrogen
Comment No. 4 :
"We also believe the EPA’s national guidance for nutrients and more specific ecoregion
recommendations provide compelling, scientifically and ecologically valid rationale for instituting
nitrogen concentration and loading limits for this facility and negate the line of reasoning to wait
until a TMDL/waste load allocation is completed before assigning limits. There are documented
problems in Mount Hope and Narragansett Bays and the Taunton River placing them on the list
of impaired waters for organic enrichment. An interim step of establishing at least conservative
nitrogen limits based on national guidance is warranted. Certainly many WWTP have nitrogen
limits despite the lack of a completed TMDL when there are waters downstream of discharges
with recognized problems associated with excess nutrient loads. While the information on TKN
and ammonia in the Fact Sheet shows a most months have reasonable monthly averages, the
concentrations, during this same period for nitrate-nitrogen had levels of 32 mg/lm (12/02)
despite year round nitrogen removal at this facility."
Due to the multiple sources of nitrogen and the far-field impacts relative to many of the areas,
EPA and MADEP believe that a comprehensive study is important before establishing limits.
Limits on nitrogen discharges are among the controls that may be included in future permits.
Any planning for additional wastewater abatement facilities done by the permittee should include
a consideration of abatement options that can either achieve higher levels of control of nitrogen
than are currently required or that can be most cost effectively retrofitted to provide higher
Middleboro WWTP NPDES Permit......... HERE
After following link click on fact sheet for basic overview and location of plant.