Narragansett Bay CommissionNEWEA, January 28th, 2013
Pamela Reitsma, Christine Comeau & Catherine Oliver
Narragansett Bay Commission Narragansett Bay Commission (NBC) is a quasi‐state agency which oversees the two largest WWTFs in Rhode Island: Bucklin Point in East Providence Field’s Point in Providence
Service Area: 10 municipalities 360,000 people served 8,000 commercial & industrial customers
Bucklin Point WWTF
Field’s Point WWTF
Field’s Point Bucklin Point Average dry weather flow of 45.5 MGD Installing biological nitrogen removal
(BNR) to meet seasonal 5 mg/L total nitrogen (TN) limit Expected to be completed in 2014 Largest IFAS system to meet 5 mg/L
2012 TN seasonal average: 7.6 mg/L and 2,608 lbs.
66 MG CSO tunnel, 38 CSOs & 80 miles of interceptors
Average dry weather flow of 23.9 MGD Comprehensive upgrade in 2006
UV disinfection BNR designed to 8 mg/L TN
Undergoing further construction to achieve 5 mg/L TN limit in 2014
2012 TN seasonal average: 6.4 mg/L and 954 lbs.
26 CSOs, North Diversion Structure & 30 miles of interceptors
Watershed Area: 1,853 mi2
60% in Massachusetts 40% in Rhode Island
Daily Freshwater Input (Rivers): 2.1 billion gallons
Daily Freshwater Input (All): 2.4 billion gallons
Largest Rivers Entering the Bay: Blackstone, Pawtuxet, Taunton
Population: Approximately 1.8 million 887,863 in Rhode Island 949,465 in Massachusetts
(http://www.savebay.org)
People living in the watershed contribute thousands of tons of nitrogen to the upper Bay annually by way of 35 WWTFs in Rhode Island and Massachusetts.
(http://www.nbep.org)
The Concerns about Nitrogen• Limiting nutrient in the Bay • Excess nitrogen can cause rapid growth
(blooms) of phytoplankton & algae• Blooms decompose, bacteria consumes
O2, reducing Dissolved Oxygen (DO)• Hypoxia (< 2.9 mg/L DO)• Anoxia (0.0 mg/L DO)
• Hypoxia tends to occur:• hot, calm summer periods• water is “stratified” or layered• DO prevented from reaching bottom
• Fish kill in Greenwich Bay 2003 accelerated plans by RIDEM to initiate N reductions at WWTF’s
Dissolved Inorganic Nitrogen (DIN)
* Most readily bio‐available form of N for use in primary production by plants & algae
Total Nitrogen (TN)
Total DissolvedNitrogen (TDN)
Dissolved Inorganic
Nitrogen (DIN)*
OrganicNitrogen
Nitrite(NO2
-)Nitrate(NO3
- )Ammonia
(NH4+)Diss. Organic
Nitrogen (DON)Particulate Organic
Nitrogen (PON)
A “Grand Experiment” “Some who work on the bay are fond of saying that we are beginning
a “grand experiment” to see how the bay will respond as it is weaned from almost a century of a high N diet. But in truth what we have embarked upon is an ecological adventure. We have no replicates, no controls, and many variables are changing simultaneously. We are also not testing any quantitative predications, except a general supposition that the concentrations of oxygen in the bottom water in the Upper bay will be less hypoxic for shorter periods and/or that hypoxia may be less frequent and cover a smaller area, and that less nuisance seaweed may accumulate on some of the beaches of the upper bay if N inputs are reduced”
“The various numerical models of the bay are not adequate to link changes in bottom water oxygen concentrations to N inputs in a rigorous way, so it appears that the approach will be to take out as much N from as many treatment facilities as the political, legal, economic, and engineering constraints will allow, and then see what happens to dissolved oxygen.”
‐Nixon, S.W. Nitrogen and Phosphorus Input into Narragansett Bay. Chapter 5. Science for Ecosystem‐Based Management. Narragansett Bay in the 21st Century. Desbonnet, A. and Costa‐Pierce, B. eds. 2008.
NBC Monitoring Initiatives Bay and River nutrients Bay and River Fecal and Enterococci
Continuous water quality monitoring at 2 sites
Water column profiles Water clarity (Secchi disk) Surface water quality mapping
Phytoplankton Population For more info, visit:
http://snapshot.narrabay.com/
River Nutrient Stations Nutrients measured bi‐monthly at 15 sites in RI & MA rivers
Total N loading – determined by using NBC nutrient results and USGS river flow data
Stations used in loading calculations based on where flow information is available: Blackstone River – Stateline Blackstone River – Slater Mill Moshassuck River – Mill Street Woonasquatucket River – Valley St Pawtuxet River Taunton River Ten Mile River Palmer River
DIN Loading Largest contributor –Blackstone River (5261 lbs/day)
Higher concentration at Stateline, but lower flow
Pawtuxet & Taunton Rivers are similar (2586 & 2448 lbs/day)
Ten Mile River ‐ highest DIN concentration, but low flow (1.49 mg/L & 80 MGD)
Remainder of rivers – low flow & concentration
Estimates of Percent Contribution DIN Load to Upper Bay
Data for these charts was collected between May 2006 and July 2012.
* After July 2011 Warren was included and Woonsocket was removed (because we started using more representative Slater Mill site on Blackstone rather than state line)
21%
12%
NBC 32%
10%15%
NBC 26% 24%
14%12%
11%
Fall River WWTFBP WWTFFP WWTFBlackstone RiverPawtuxet RiverTaunton RiverMoshassuck River
Woonasquatucket River
Ten Mile River
Palmer River
RI Point Sources = Bristol, EG, Blount, EP, Woonsocket
NBC 27%
23%
14%
11%12%
NBC Bay Sampling Locations – 7 Bay Locations Purpose: address and understand the impacts that facility operations have on receiving waters
Piloted in 2005, in earnest in 2007 Nutrients measured bi‐monthly Sampled: surface & bottom Collect at various stages of the tidal cycle
throughout the year Nutrient suite includes
Nitrite/nitrate Nitrite Total Dissolved Nitrogen Ammonia Orthophosphate Silicate Chlorophyll a Total Suspended Solids
More accurately determine the impact of NBC’s BNR systems & inform stakeholders
DIN 2012 Expected down Bay gradient, except…
Added new station –Pawtuxet Cove (0.57 mg/L)
Conimicut Point in GOOD category!!
Bullock’s Reach – very close to good category
What’s in store for Bay DIN after 2014??
DIN Concentrations – Field’s Point & Bay(M
ay –Octob
er) (M
ay –October)
DIN Concentrations – FP & Bay (no 2010 data)(M
ay –Octob
er)
DIN Concentrations at Field’s Point and sampling sites south of FP May – October 2007 – 2012 (no 2010 data) FUTURE PREDICTIONS
Bay Water Quality Only WQ criteria for the Bay is based on DO
Fixed site network monitors WQ in Bay
Northern half of the Bay is categorized as impaired for DO
Expanded area “At risk for DO impairment”
What else causes hypoxia? No direct link b/t nutrients & hypoxia
Many causes of hypoxia in the Bay Stratification Rainfall Reduced wind Hydrodynamics
Does NBC data support any of these factors???
Stratification
Weather
Hydrodynamics
Conclusions DIN concentrations reached GOOD category at Conimicut Point!!!
Field’s Point DIN strongly correlations with the DIN in Bay (Pomham Rocks, Edgewood Yacht Club, and Conimicut Point)
In 2014, reducing DIN from FP could result in DIN concentrations in the GOOD category at 3 Bay locations
NO correlation b/t DIN & hypoxia at Bullock’s Reach
Rainfall strongly correlated with hypoxia at Bullock’s Reach (could weather/stratification play a stronger role than DIN?)
Upgrades at WWTFs will decrease DIN in the future, but will this impact hypoxia?? Could it have unforeseen impacts on bay dynamics??
Thank you to EMDA & Laboratory staff!
For more info on NBC and it’s programs, please visit:
www.narrabay.com
http://snapshot.narrabay.com/
Questions??