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03/06/2018 03:54 PMIn a town without sewers, residents and businesses currently have two primary options for sewage treatment: If the lot is suitable, a relatively inexpensive, traditional septic system works, but on small lots or with higher-density uses, an expensive advanced technology system has been the solution. With a recent vote, Westbrook is exploring a third option.
Two proposed pilot studies of a passive nitrogen removal option for residential septic systems won support from the Board of Selectmen (BOS) at its Feb. 21 meeting. The BOS approved up to $30,600 for the design and field testing on two town-owned properties of a new conventional septic system design that adds a passive nitrogen reduction feature.
The goal is to demonstrate to regulators at the State Department of Energy & Environmental Protection (DEEP) and Department of Public Health (DOPH) that passive nitrogen removal is effective. If successful, the test-of-concept could provide a low-cost option for reducing nitrogen in septic system wastewater.
The new passive nitrogen removal option became possible for the first time on Jan. 11, 2018 when DOPH issued new technical standards for subsurface wastewater disposal.
“This is the best alternative so far to deal with the nitrogen. It allows us to go out to designated areas for AT [advanced technology] systems on the shoreline at risk of failure. This is a fairly inexpensive way to take the nitrogen out of the [septic] system and not have it go to the Sound,” Water Pollution Control Commission Chairman Lee McNamer told the selectmen.
Westbrook’s pilot projects testing the passive concept will be conducted on two town-owned properties, the John P. Riggio Building and the Town Beach and Concession Stand, each of which has aging septic systems in need of replacement.
The town’s consulting engineer, Nathan Jacobson of Jacobson and Associates, will be tapped to design and install two test pits at the Riggio Building in conjunction with a planned septic system replacement project. The pits will be located below the level of the conventional septic system’s leaching field where septic wastewater is distributed from the septic tank. This new layer below the septic leaching field will be comprised of a mixture of sand, sawdust, and wood chips; as the treated wastewater passes from the leaching field above into this lower layer by gravity, organic nitrogen, a pollutant that affects water quality, is removed.
When the treated wastewater reaches this new base layer mixture—referred to as a carbon source—a natural chemical reaction occurs. The organic nitrogen in the water interacts with the sawdust and wood chips through a chemical process that converts the wastewater’s organic nitrogen into nitrogen gas, a common gas. Earth’s atmosphere is comprised of 78 percent nitrogen gas and 21 percent oxygen.
According to McNamer, the average life of the wood chip and sand layer is about 75 years in this system.
As a result, the new passive process offers the promise of a cost effective long-term solution for reducing nitrogen pollution that would otherwise enter Long Island Sound and other waterways.
For now the new DOPH technical standards only permit use of passive nitrogen removal in new conventional septic systems located in areas subject to court-ordered pollution abatement, such as neighborhoods so designated in Old Saybrook, Westbrook, and Clinton.
Before the new standards, reducing nitrogen required adding an expensive advanced technology active nitrogen removal system in a septic system design. However, this active treatment option hasn’t proven to work well on residential properties that don’t have consistent year-round wastewater flow, such as the seasonal properties of beach communities. This new passive nitrogen treatment design could finally offer a promising cost effective solution.
Septic system designs and installations are regulated both locally through town health departments and at the state level through DOPH and DEEP. DOPH delegates to local health departments the authority to enforce health code rules for subsurface wastewater disposal for systems up to 2,000 gallons flow per day. Systems between 2,000 and 7,000 gallons flow per day are reviewed and approved by DOPH. Systems above 7,000 gallons per day are reviewed and approved by DEEP and typically include a third active nitrogen treatment stage for wastewater in the design.
For the two Westbrook pilot projects, DOPH and DEEP representatives are working closely with town Director of Health Sonia Marino and consulting engineer Nathan Jacobson to ensure the town’s pilot tests of the new design are effective and a good proof-of-concept.
“Both of these septic systems are antiquated anyway and need to be replaced. This funding is for engineering test pits,” Marino told the selectmen. “DEEP and DOPH will be holding our hands. They all have a keen interest in this. On March 1, [field] tests are scheduled.”
While these passive nitrogen treatment systems are not in use in Connecticut yet, they have been installed and proven effective in New York State (in Stony Brook), in Florida, and in Barnstable, Massachusetts.