MARSTONS MILLS — Two septic tanks may be better than one, at least when the second tank can do what the first won't.

The Sandy Shores neighborhood along the shore of Shubael Pond will help test for the next three years a wastewater system designed to remove nitrogen from septic tanks before it gets released into nature and wreaks havoc.

Fourteen cutting-edge alternative septic systems are being installed, thanks to money from the Barnstable Clean Water Coalition. The BCWC eventually hopes to install 50 systems in town to test their ability in the real world to reduce nitrogen to close to 10 milligrams per liter of wastewater.

Other agencies involved in the project include the Massachusetts Alternative Septic Systems Test Center at Joint Base Cape Cod, the Nature Conservancy, the Environmental Protection Agency and the town of Barnstable. 

"This is from money we raised as a non-profit," said Jennifer Loughran, of the BCWC. "We have installed 12 (innovative alternative) septic systems around a 56-acre kettle pond. We have scheduled two more for later this summer. This is primarily to help with nutrient pollution from the Marstons Mills River to the Three Bays Estuary."

Cape Cod will spend close to $4 billion treating wastewater to remove nitrogen over the next 50 years, according to the Cape Cod Commission.

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“Sewers are the right solution but it takes decades and billions of dollars so we need something to get results faster,” said Emma Gildesgame, climate adaption scientist with the Nature Conservancy. “We need to figure out a role for alternative systems which can be the most cost-effective solution.”

The Nature Conservancy believes alternative septic systems are more cost effective. According to their study, to remove a kilogram of nitrogen costs about $900 via a sewer as compared to $400 with a septic system upgrade and $150 with a cranberry bog wetland restoration project.

The Marstons Mills project is testing the "KleanTu nitROE" wastewater treatment system, a product that started on Martha's Vineyard.

Nitrogen from human waste is a fertilizer and can spark algal blooms in saltwater eventually leading to reduced light penetration, low dissolved oxygen levels in the water and less life and more muck along the sea floor. Shellfish and fish populations decline and water quality is poor.

“This is one of the alternative systems that does a better job removing nitrogen from wastewater than a traditional system,”  Gildesgame said. 

Bryan Horsley, of MASSTC, said the system — which is designed to remove the nitrogen that a typical septic tank misses — works well.

“One thing is they are easy to retrofit onto an existing system. It’s basically just a concrete box that is plugged in between the septic tank and the leach field," he explained. "The leach field is used to discharge the treated water out of the system. There are options that can be added to enhance phosphorus removal, as well.”

Loughran said the supplemental system costs about $25-35,000 for a home.

"The cost on the lower end is for a retrofit where it is added to an existing healthy Title 5 system," she said, adding it costs more if it's determined the home also needed a new septic system.

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Gildesgame said the KleanTu system comprises two chambers: one with limestone and one with wood chips.

"The only moving piece is an aerating pump,” she explained. “The limestone chamber converts the ammonia in the wastewater to a nitrate and then in the next chamber with the wood chips, the nitrate is converted to a gas.”

“IA (innovative alternative) systems typically work in a two-part process,” Horsley added. “The first step is aerobic, where an air pump puts air into the first section that supports microbial activity that nitrifies the wastewater. The wood chips are not aerated. They’re anoxic and that promotes different bacteria that do the denitrification and convert the nitrate to nitrogen gas. You need the chips to provide a carbon source.”

“In the absence of oxygen, there are all different processes. You’re tricking the system into using nitrogen instead of oxygen,” Gildesgame said.

Wood chips provide food in the form of carbon for bacteria that absorb the nitrates and convert them to gas. Normally the bacteria would absorb oxygen but in its absence, they utilize the nitrate instead, exhaling it as nitrogen gas. The lack of oxygen also prevents the chips from breaking down for decades.

“It’s a situation comparable to the bottom of the Great Lakes where you have logs that are preserved in great shape because they’re in the muck in anoxic conditions,” Horsley said. 

"This is next-generation nitrogen-removal technology,” Gldesgame declared. “This is now in the early stages of approval through the Mass. (Department of Environmental Protection). They are sitting in the ground for three years and we will be able to see how they work in the long term. Everything is super promising.”

The approval process commences as a pilot, just a test of a system, and proceeds to provisional approval, allowing the testing of up to 50 systems, which is the stage in which this project is. If the Department of Environmental Protection likes the results, the system can be approved for general use and potentially be funded through sources such as the Cape Cod and the Islands Water Protection Fund.

“They have some preliminary results already with 36 systems in the ground on Cape Cod and Martha’s Vineyard,” Gildesgame noted. “Ten milligrams per liter is the gold standard."

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In 19 KleanTu systems installed on Martha’s Vineyard, 14 of them reduced nitrogen to lower than 10 milligrams per liter. In all, nitrogen was greatly reduced in the wastewater.

"We had our first installation last August," Loughran recalled. "That one is getting 93% nitrogen reduction based on sampling by MASSTC. We had several installed in October and a couple in December. Some of those are seasonal residents, so it's too soon to tell. But two systems with full-time occupants are getting 93-96% total nitrogen reduction. That's a very limited sample but it's super-great performance."

This location in Marstons Mills was selected because the BCWC wanted to see if the systems would reduce nitrogen flowing into Shubael Pond. But closer study revealed groundwater was flowing out of the pond through the neighborhood towards the 6,739-acre Three Bays ecosystem (Cotuit Bay, West Bay and North Bay). The bays are also suffering from nutrient overload, according Barnstable Water Resources.

“The Barnstable Clean Water Consortium identified homeowners for the pilot study,” Gildesgame said. “They were all first contacted by the BCWC and there is no cost to the homeowner. It’s important to understand how the systems work together in a neighborhood.”

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“We’re working on finding a financing mechanism so the homeowner doesn’t pay the entire cost," she said. "We are just in the process of awarding a grant to MASSTC for finding sources of public and private funding.”

That grant will be for $100,000. The EPA is providing funds to monitor the performance of the systems for the next three years. The BCWC will fund two additional years of monitoring after that.

"The Barnstable Clean Water Coalition supports town sewering plans," Loughran pointed out. "What we're doing with the IA systems is not the only solution. It is a solution coupled with town sewering plans."

"The overall goal is to figure out how to expand the available technology and find options for septic systems and nature-based solutions such as wetland restoration quickly and cost effectively. This is just one piece of that. We are also doing cranberry bog restoration to a wetland to slow the flow of water through the marsh into the Three Bays Estuary. We’re looking at all these together to understand what solution will effectively reduce nitrogen.”

At MASSTC, there are many projects, including studying 20 different septic systems designs such as the one by KleanTu. 

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“Quite a few different IA systems are going through the (approval) process," Horsley said. "In addition to IA systems, I’m excited about ecological sanitation systems, things like composting toilets and urine-diverting toilets that look to not pollute in the first place. They reuse the nutrients. We’re also looking at pathogen-reducing technologies (with a $1.24 million grant in 2021 from EPA Science to Achieve Results program) focusing on virus removal by studying the spacing of the treatment system vs. the top level of the groundwater."

They're also studying drip dispersal to remove pharmaceuticals and other contaminants of emerging concern, saturated and unsaturated layered systems, groundwater separation, sand columns, leach field remediation, floating wetlands and more.