The short version
In a March 2013 slide presentation, Amy Lowell, Falmouth's assistant wastewater manager, explained how the town's main wastewater treatment plant removes nitrogen and why the town is looking beyond that plant to protect its estuaries. The slides describe the plant's permit limits, how its bacteria-driven process works, and its results: nitrogen in the treated water averaged under 5 mg/L since start-up, and lower in 2011 and 2012. They also say the plant serves only about 3% of the town's developed properties, while most of the rest rely on septic systems or cesspools, which the slides name as the source of at least 75% of the controllable nitrogen reaching the estuaries. The town's plan pairs sewering of the lower Little Pond watershed with cheaper options such as widening the Bournes Pond inlet. This summary is based on the slides alone (text and figures). It is a town presentation, not a peer-reviewed paper.
What the report covers
The 25 slides move from how the town's main plant works to why the town's estuaries need more than that plant can offer.
- An overview of Falmouth's wastewater setup: the main plant (built in the 1980s, upgraded in 2005), a smaller plant at New Silver Beach, and some clusters and advanced individual systems.
- The main plant's groundwater discharge permit limits and its recent performance, including a chart of treated-water nitrogen from January 2011 to early 2013.
- A plain outline of biological nitrogen removal (bacteria turn ammonia into nitrate, then nitrate into nitrogen gas) and how the plant's batch reactors and filters do this.
- The plant manager's view on whether a strict 3 mg/L nitrogen limit could be enforced.
- Why Falmouth's 15 estuaries are in trouble, with a 1950 and 2009 aerial comparison of Little Pond.
- The town's Estuaries Restoration Plan, including the votes behind it, a list of its parts, and closer looks at widening the Bournes Pond inlet and sewering the lower Little Pond watershed.
What it found
- A small share of town is sewered. About 3% of Falmouth's developed properties (roughly 700) connect to the main plant's sewers, and a smaller plant at New Silver Beach serves about 200 more. Most other properties have septic systems or cesspools, and the main plant also treats the septage (pumped-out septic waste) they produce (Lowell, 2013).
- Permit limits. The plant may discharge up to 800,000 gallons a day, no more than 570,000 of it from outside the West Falmouth watershed. Nitrogen is capped at 10 mg/L as a daily maximum, with additional targets of 3 mg/L in the treated water and no more than 5,204 pounds a year to the West Falmouth Harbor watershed (Lowell, 2013).
- Under 5 mg/L on average. Flow ranges from 200,000 to 700,000 gallons a day with the seasons and the septage received. Treated-water nitrogen has averaged under 5 mg/L since start-up and was lower in 2011 and 2012. The chart for those years shows it mostly running a few mg/L, with brief spikes, the highest at roughly 7.5 mg/L (Lowell, 2013).
- A 3 mg/L enforceable limit worries the operators. The slides say 3 mg/L is generally achievable at the plant but call it the limit of the technology. They cite swings in what arrives at the plant, operator error, mechanical trouble, slow recovery of the bacteria in cold weather, and leftover hard-to-remove nitrogen that sometimes keeps the total above 3 mg/L (Lowell, 2013).
- Septic systems are the big source. The presentation calls excess nitrogen the main cause of the decline of Falmouth's estuaries and says at least 75% of the controllable nitrogen comes from septic systems. Falmouth has 15 estuaries, which the slides say is more than any other Massachusetts town. Little Pond is called the town's most degraded (Lowell, 2013).
- Voters backed a plan. In April 2011, Town Meeting unanimously appropriated $2.7 million for sewer design and demonstration projects, and a town-wide ballot supported it by 2 to 1 in every precinct. The plan lists eco-toilets, shellfish cultivation, permeable reactive barriers (underground walls that filter nitrogen from groundwater), denitrifying septic systems, road runoff fixes, widening the Bournes Pond inlet and sewering lower Little Pond (Lowell, 2013).
- Inlet widening versus sewers. The slides say a 90-foot opening at Bournes Pond could remove as much nitrogen as sewering over 350 homes at under 40% of the cost, with immediate benefits. For lower Little Pond, they point to very small lots, near build-out and many cesspools as reasons sewering is important and cost-effective (Lowell, 2013).
What it means for Waquoit Bay today
This presentation covers Falmouth as a whole. The plant it describes sits on the Buzzards Bay side, outside the Waquoit Bay watershed, and its permit is tied to the West Falmouth Harbor watershed. Waquoit Bay appears only on one map of estimated wastewater nitrogen cuts needed to meet state limits, where the slides note that the Waquoit figures were estimated by the town's consultant, GHD, from similar watersheds. So the numbers here should not be read as targets for the Bay.
It still gives useful background. Falmouth's plan was built on the same finding that drives CPWB's work: wastewater, mostly from septic systems, is the main nitrogen source we can control. The 2013 slides also show how the town weighed sewers against cheaper options, a question that is still open for Waquoit Bay, which Falmouth shares with Mashpee. For how the plan has fared since, see our summary of the town's 2019 progress report, and for one of the options listed here, see what a restored bog removed on the Coonamessett. Note too that a slide dated for the March 2013 talk refers to an August 2013 vote, so the deck was likely updated after it was first given.
See the presentation
Lowell, A. (2013, March 6). Nitrogen removal from municipal wastewater [Presentation slides]. Town of Falmouth, Massachusetts. https://web.whoi.edu/whstep/wp-content/uploads/sites/123/2018/07/Falmouth__Wastewater_presentation_Lowell_156684.pdf
License: The slides carry no license statement and include maps and graphics from other sources, so we link to the copy on the Woods Hole Oceanographic Institution website rather than host the PDF. This summary is based on the slides only, not on a spoken talk or a written report. The card image is a title card made from the citation.
Drafted with AI assistance from the linked source.
