Final Project Report
Submitted by
Qizhong Guo,
Namsoo Suk, Hong-Chun Ahn, and Shan-Hui Ho
to
NJDEP Division of
Watershed Management
and
Delaware River
Basin Commission
October 1999
Executive
Summary
The objective of this modeling
study is to establish waste load allocations for the Millville Wastewater
Treatment Plant. The scope of study includes the development of the Maurice
River Estuary Model and the projection of impacts of various management
scenarios.
The study river reach
extends from downstream of Union Lake to Mauricetown with a total length of 13.2
miles. The Maurice River Estuary is classified as FW2-NT (Freshwater
2-Nontrout) from the downstream side of Union Dam to a point three miles
downstream of Millville Wastewater Treatment Plant, and is classified as SE
(Saline waters of estuaries) further downstream.
A widely used water quality model, USEPA’s WASP5 model, was adopted for this
modeling study. The field data collected in September 1992 were used for
calibration purposes, and the data collected in August and November 1992 were
used for verification purposes. The hydrodynamic component of the model was able
to reproduce the tidal elevations predicted by the National Ocean Service for
all the three months. It was also able to reproduce a set of tidal current data
collected in June 1998. The water
quality component of the model was able to reproduce measured concentrations of
salinity, chloride, dissolved oxygen, biochemical oxygen demand, chlorophyll-a,
ammonia, nitrate, organic nitrogen, orthophosphate, and organic phosphorus for
all three months. The model is believed to be calibrated and verified
sufficiently for its uses in wastewater allocations.
The current (year 1992) concentrations of dissolved oxygen
and total phosphorus in the estuary do not meet the established water quality
standards. The calibrated and verified model was used to project the impacts of
waste allocations and management scenarios on water quality in the estuary. The
major results of projections are:
1.
Concentration of dissolved oxygen concentration in the estuary
will not change significantly from the current conditions when the Millville
Wastewater Treatment Plant is operated at the design capacity (5MGD) and
freshwater inflows are at 7Q10 rates, but concentration of total phosphorus will
double.
2.
Concentration of dissolved oxygen in the estuary will not change
significantly with reductions of BOD and Ammonia concentrations in the effluent
from the Millville Wastewater Treatment Plant.
3.
The concentration of dissolved oxygen in the estuary is primarily
controlled by the low dissolved oxygen concentration at Mauricetown.
4.
The water quality standard of total phosphorus (0.1 mg/L) can be
achieved by reducing orthophosphate and organic phosphorus concentrations in the
effluent to 0.26 mg/L and 0.55 mg/L respectively in August, and to 0.35 mg/L and
0.76 mg/L, respectively in September.
5.
The water quality standard of total phosphorus (0.1 mg/L) can also
be achieved by increasing freshwater inflow rates (including discharge from
Union Dam) to 10 times the 7Q10 flow in the August month and to the 5 times the
7Q10 flow in the September month.
The current water quality
standards for dissolved oxygen and total phosphorus are recommended to be
re-examined in terms of the designated uses. If the current water quality
standards for dissolved oxygen are to be upheld, the cause of low dissolved
oxygen concentration at Mauricetown must be found in order to develop effective
management measures. If the current
water quality standards for total phosphorus are to be upheld, the relative
contributions of point- and non-point sources must be found.
In addition, it is recommended that the monitoring and modeling domain be
extended from the spillway of Union Lake Dam to a point within Delaware Bay in
future studies.
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