Distributed Nitrogen Removing I/A Septic Systems: A 2020 Primer for Cape Cod

by Bruce H. Walton
Innovation Council

Executive Summary

Have you ever wondered why there is an occasional not-so-nice smell at the beach, why there are beach closures, or why eel grass and scallops have disappeared from parts of the Cape coastline? It is primarily because of wastewater from our home toilets, and we can do something about it.

Nitrogen from home septic systems drives over 80% of the marine water quality problems on the Cape. Over 107,000 Cape homes (74%+) are not connected to a sewer system. Title 5 septic systems do not remove nearly enough nitrogen to meet the 2015 Section 208 Plan objective of reducing the Cape’s nitrogen load by more than 50%. Even with plans being developed to spend $4b+ over the next 30 years to sewer much of the Cape, there arguably will still be over 70,000 home septic systems in use in 20 years. New technologies (nitrogen removing Distributed Innovative/Alternative [I/A] Septic Systems) are being developed to remove nitrogen at the home level for costs equal to or less than sewering, creating a new paradigm for protecting our marine waters, ponds and streams from excess nitrogen loads. This article puts this complex environment into perspective and identifies the issues that will need attention for I/A systems to really make an impact. It is a primer for consumers and a call to self-educate, then act to protect our vital marine resources and home values.


Having spent four years talking with knowledgeable folks about marine water quality and nitrogen overloading on the Cape, it was very hard to find a high-level perspective on this extremely complex and evolving arena, so I decided to write a primer for Cape consumers.

High quality waters, both fresh and salt, are vital to the Cape & Islands lifestyle and economy, including home real estate values. However, we are now suffering from eutrophication, algae blooms, loss of eel grass, and other negative developments in our embayments, streams, and ponds. We are approaching crisis levels on multiple dimensions. The Association to Preserve Cape Cod (APCC) State of the Water report in 2019 noted, “More than two-thirds of coastal embayments and more than one-third of ponds are suffering from unacceptable water quality due to excess nutrients.” EPA notes that the biggest culprit is nitrogen coming from home septic systems.

Town-level planning and actions are underway to reach about 50% of Cape parcels (which may have multiple homes) with sewers over the next 30 years at a cost of about $4b. That may satisfy the Clean Water Act, but it is very expensive and is spread over a very long time. What about the homes at the end of the queue or that may never be connected because they are not in densely populated areas?


The Cape currently has 160,000 parcels, of which 145,000 are already developed and at least 107,000 (74%) are not connected to a sewer system. Non-connected homes utilize septic systems which discharge nitrogen into leaching fields. The nitrogen moves to our streams and ponds and eventually to the coast. While there are other associated chemicals (e.g. phosphorus – a big problem for ponds, and pharmaceuticals), septic nitrogen accounts for over 80% of the marine water quality problems on the Cape. The remaining 20% is caused by fertilizers (which often include more nitrogen) and storm water run-off.

Simply put, we are over-fertilizing our coastal waters with excess nitrogen.

To bring the Cape into sustainable nutrient balance, its total nitrogen load needs to be reduced by over 50% according to regional planning documents (EPA, Revised Plan 208, 2015). Sewering and central treatment plants to date have been the preferred approach. That approach is expensive and takes a long time to implement. New technologies are emerging that will enable a paradigm shift.

As of winter, 2020 eight of the Cape’s 15 towns had filed plans to sewer an additional 46,000 parcels by 2050. These plans, if fully funded and realized, would realistically reduce the load by one third, thus achieving about two thirds of the 50% target load reduction.

There are a broad range of approaches to reducing nitrogen on a particular site. Some deal with remediation of nitrogen already in the ecosystem (inlet widening, aquaculture, semi-permeable barriers, etc.). To explore the range of approaches, see the Technologies Matrix at https://www.capecodcommission.org/our-work/technologies-matrix/. They all have a role, but for this article I will focus on parcel-level septic systems that reduce nitrogen going into the ground in the first place.

It is critical that we create options for existing homes that will not get sewered under current plans. With 86% of the Cape’s 370,000 acres already developed or protected, new home construction will be limited. We can estimate that the Cape will still have close to 70,000 home septic systems in use in 2050. Today, about 90% of un-sewered Cape homes comply with Title 5, which is needed to sell a house. At nitrogen removal levels of 30-40%, Title 5 standards do not remove nearly enough nitrogen (see charts below).

Distributed Nitrogen Removing Innovative/Alternative (I/A) Septic Systems

The paradigm shift in domestic wastewater treatment comes in the form of distributed (i.e. located at the home) Innovative/Alternative (I/A) septic systems designed to remove substantial amounts of nitrogen. They represent an emerging option for many locations.

I/A septic systems improve Title 5 systems by adding effluent treatment that releases inert nitrogen gas back to the atmosphere instead of discharging it into a leaching field – and hence into groundwater. There are now over a half dozen I/A nitrogen removing systems approved by the state for general home use, and new systems are being tested each year. The Cape now has about 2300 installed I/A systems. Massachusetts requires maintenance contracts for them, and their performance must be reported to the local boards of health. On the Cape results are sent to the Barnstable County Innovative/Alternative Septic System Tracking Program and are posted to the Internet at https://septic.barnstablecountyhealth.org/.

State Approval Process for I/A Systems

A challenge for manufacturers is that the State approval process for a new system is expensive and time consuming. This thorough approval process ensures that systems coming to market will actually fulfil their promises or fail certification. There is a three-stage process, often starting with the Massachusetts Alternative Septic Systems Test Center (MASSTC) in Sandwich. After initially successful testing, a system goes into a Pilot Permit phase for a couple of years (up to 15 units), followed by Provisional Use permit for three years (50 units) with substantial monitoring and testing throughout. A successful outcome results in a General Use permit. Ultimately, the MA approval process can cost a manufacturer over $450,000 over six years. And this expenditure is just to get approved in Massachusetts.

U.S. EPA attempted to reduce this timeline and expense by coalescing MA piloting regulations with other New England states through a draft interstate agreement, but it was never signed. The five Chesapeake states have a successful interstate data sharing agreement to support analysis and approval of I/A systems.

Despite these challenges, new technical solutions are being developed and have significant additional promise. It is important to note the vital contribution of stakeholder organizations at local, regional, State and Federal levels for providing support and encouragement. See the website listing at the end of the article for a few of them. Without them, these innovative technologies would never see the light of day.

Nitrogen Load Reduction

How much of an impact can distributed I/A technologies make? One key metric is the nitrogen content of a system’s outflow, as expressed in parts per million (ppm) which is the same as milligrams per Liter (mg/L). We can do a back-of-the envelope estimate of the average summer load on the Cape by looking at a matrix of nitrogen contributors today. Here are some very rough numbers to scale the issue:

Cape Cod Nitrogen Load from Homes


System Nitrogen Outflow (mg/L)(1) Current Parcels % of Load
Untreated (cesspools) 45-65 10,700 14-15%
Title 5 26-42 94,000 78-81%
I/A Current Systems Target 19 2,300 1%
Best I/A Tech in Development 5-11
Sewer/Treatment Plants 5 38,000 4%
Totals 145,000

(1) Outflow performance is normally expressed as a range over time and is site specific. Some untreated flows have measured well above 100 mg/L. The Nitrogen Outflow ranges and Parcel counts above reflect conversations with MASSTC, CCC and MassDEP. The lower Nitrogen Outflow values associated with Untreated and Title 5 Systems have been used for past State and regional level modeling.

What really jumps out is that Untreated and Title 5 systems are by far the biggest contributors and the largest part of the problem, together contributing over 90% of the current load.

As noted, Cape towns have looked at sewering as the primary way to meet reduction goals. Below is a view in 2050 with the planned 46,000 new sewer hookups. It assumes that half of the 15,000 currently undeveloped parcels are developed (with current I/A systems level performance), and it keeps other ratios constant.

Cape Cod Nitrogen Load from Homes

System Nitrogen Outflow (mg/L) Future Parcels % of Load
Untreated (cesspools) 45-65 5,900 12%
Title 5 26-42 52,800 61-69%
I/A Current Systems Target 19 9,800 6-8%
Best I/A Tech in Development 5-11
Sewer/Treatment Plants 5 84,000 13-19%
Totals 152,500

A key in this comparison is that the total load in 2050 is reduced by about one third, achieving two thirds of the target load reduction. Additional load reduction will be achieved through remediation efforts. I/A systems may ultimately replace some sewering plans in lower-density-areas or later-installation plans.

The 2050 chart shows that Title 5 and Untreated systems will still comprise about three quarters of the total load. To achieve the mandated objective in less than 30 years I/A systems will have a valuable role. When targeted at the most sensitive areas, they can make an impact now, and there is time-value to starting now and becoming more aggressive as newer, even better technologies are approved.

Legislative and Regulatory Drivers

Beyond technology development, there will need to be both legislative and regulatory changes to drive homeowners to action. For instance, Title 5 today does not apply to homes that pass down generationally within a family. That means those homes will never contribute to improving water quality unless intra-family transfers are brought under Title 5 or better. Getting there will probably include both “carrots and sticks”. “Carrots” could include tax incentives, grants and State-supported financing. “Sticks” could include designation as a sensitive location or failing system and a five-year compliance window. By example, one regulation on Martha’s Vineyard requires that new construction utilize I/A.

Additionally, Title 5 loopholes need to be closed and State regulations need to be strengthened to incent or require significant additional nitrogen removal.

Cost Overview

The state of the art for I/A systems is improving, but cost is always an issue. It is hard to make apples-to-apples comparisons because of the differing combinations of performance, capital and operating costs. Generally, the centralized treatment approach requires significant up-front capital (for both the collection system [sewer pipes] and building new treatment facility capacity); but once installed, operating costs per parcel are low. I/A systems cost less per parcel to install but generally have somewhat higher annual operating costs than centralized treatment. There is a range of performance of differing I/A products, and not every parcel needs the equivalent of wastewater treatment plant performance. You will hear engineers and planners talk about Cost per Pound of Nitrogen Removed; that is an important measure but beyond this article’s scope. Finally, to make meaningful comparisons, one needs to account for financing over perhaps a 20-year period. One way or another, homeowners are going to pay more for wastewater handling in the future. Here is a bit more detail, based on a 2-3 bedroom house.

Capital Investment

For perspective, a new-house Title 5 system costs about $12,000 on the Cape. A current General Use Permitted I/A system will generally add $5,000-$15,000 in capital cost to that number yielding a total cost of $17,000-$27,000. Costs for retrofits are less predictable because you do not know what else you might have to fix when you start digging, but $25,000 capital cost is probably a reasonable assumption. Another variable is landscaping, not included in any of these numbers.

At a given point in time there is generally a trade-off between product cost and effectiveness. One of the new promising technologies is testing at performance levels close to sewage treatment plants and projects total capital costs of $30,000 for new construction, $20,000 for a retrofit. They also project requiring a somewhat smaller leaching field. They are early in an of-scale, heavily monitored test in Barnstable (see the Summer 2020 Newsletter at the Barnstable Clean Water Coalition (BCWC) website at the end of the article).

Operations and Maintenance (O&M)

The reality is that I/A systems require periodic attention and have a projected life of about 20-30 years (similar to Title 5 systems). At the end of that period, we might expect to refurbish or have better solutions available, but we cannot just install something and then forget about it, as many have done with Title 5 systems.

If an I/A system fails, who will know and how does it get fixed? Title 5 systems generally should be pumped every 2-3 years, yielding an O&M cost of $75-135/year, but many owners (especially for summer homes) do not bother until there is a problem or they want to sell the house. I/A systems generally require some power and need to be serviced 2-3 times per year at a total O&M cost of about $500-$700/year. In addition, there will be varying sampling requirements, depending on the permit level. For instance, the I/A system to be used in the BCWC test, which received a Provisional Use permit in May, 2020, projects total annual O&M costs of $1,400, dropping to about $700/year under a General Use permit. These numbers include maintenance, electricity and monitoring. This is where the State and other stakeholder organizations need to contribute early support and drive better ways to monitor/ensure system performance.

Total Cost Picture

Each town must develop its own Comprehensive Wastewater Management Plan (CWMP). I will use the Town of Barnstable as an example. The January, 2020 CWMP (see website listed at end of this article) notes the average direct capital cost for sewering almost 1000 homes and upgrading attendant treatment plants is $88,000/parcel. That is a gross number, and the homeowner does not pay that amount.

Homeowners with new sewer connections would pay real estate taxes of $660/year on the betterment (CWMP, Section 7), a System Development Charge of $2000 as a contribution to the backbone system and a hook-up fee, which might run $1-10,000 per home. Per the Barnstable CWMP, sewer bills average $400 annually, projected to grow at a 3% rate. Simplistically, that makes a total 20-year direct homeowner cost of $30,000-$39,000. But the total cost to the town, including financing, would be $108,000 per home for a total system cost of $1.06 billion. The plan would be financed through seven different sources including Rooms, Meals and other taxes, issuing bonds, rate increases, among others. Importantly, the homeowner has no say about when their neighborhood would be sewered; Barnstable has three 10-year phases to its plan. A September, 2020 Conservation Law Foundation (CLF) lawsuit against Barnstable, Mashpee and the MassDEP will bring added pressure to move more quickly.

Importantly, the CWMP looks to take an “adaptive management update” approach, reviewing the state of technology every five years to see if there are better ways forward; the first Barnstable review is due in 2025, so it is important to drive new approaches now to be prepared for that review.

A similar per parcel, 20-year calculation for BCWC’s I/A test would be $42,000 for a refit and $53,000 for new construction, including capital, financing (interest), O&M and monitoring. How these I/A costs might get divvied-up between the owner and the town’s tax base remains to be determined. These are very rough numbers and will vary depending upon site-specific issues.
This is quite a change from relative cost estimates done in 2014 as part of the 208 Plan Update where sewering was the clear price performance winner.

Performance Management

Ensuring proper care and ongoing performance is a huge issue, perhaps the elephant in the room. States hold wastewater treatment plants accountable for their performance and have a robust, mature infrastructure for doing so. How do you translate that requirement to an individual homeowner with an I/A system and share the cost fairly?

Here is a role, and a business opportunity, for the local wastewater utilities and others. There are already over three dozen vendors certified to monitor and maintain existing I/A systems on the Cape. An innovative program is being considered on Martha’s Vineyard where a homeowner buys and installs the system, then the local water utility would monitor and maintain it, billing the homeowner as part of the normal water and sewer billing cycle.

In support of I/A systems, the U.S. EPA is currently running a technology challenge to develop a nitrogen sensor that would monitor outflow in situ and send an alert to the maintenance provider and homeowner over the Internet when something fails. A Phase 2 winner was announced in May, 2020 (see U.S. EPA Sensor Challenge website listing at end). In addition to driving more consistent performance, this would reduce sampling requirements and could well reduce the need to do as much piloting for approvals, thus accelerating new solutions into the market.

Suffolk County, Long Island, NY

Long Island is a big sandbar on a Sole Source Aquifer, much like the Cape. It is also 74% unsewered with 360,000 residential parcels, of which 250,000 simply have cesspools (see Untreated in the above charts). They have 200,000 parcels where nitrogen is within 0-25 years of travel time to surface water (i.e. ponds and estuaries). They started late (2014), when the problem had reached crisis stage, but they are now aggressively exploring, certifying, installing, measuring and incenting I/A systems. They have provisionally approved I/A systems from eleven vendors. Their demonstration program now has 1000 I/A systems in place. Lessons learned include the need for consumer education, simple website support to guide homeowners, and streamlined sampling approaches that get more quickly to 90% confidence in the performance numbers. They have good granularity, definitions and prioritization techniques to drive actions where most needed on a watershed basis. Their conclusion is that distributed I/A systems are their most cost-effective approach. Their 50-year plan, including both I/A and sewering, should start showing groundwater improvements within a decade (see links to their websites at end).

Perhaps the biggest difference between the Cape and Long Island is their starting points. Title 5 forced the Cape to get better, starting back in 1995. Coming from cesspools, Long Island can see a bigger and more immediate improvement with current I/A performance. They are moving aggressively and expect to adjust along the way. We can learn from each other.


Like many environmental problems, there are common goals but no single answers, and the targets/solutions are ever evolving. Sewering/centralized treatment is the current Cape paradigm. We are now seeing confirmed development in I/A systems, to the point they are being rigorously tested and validated with lifecycle costs at or below that of sewering. These I/A systems might be the best bets for parts of a town where there are no plans to sewer, or where the sewers might not be built for 15-30 years. For I/A to reach maturity, business models for monitoring and maintenance will need concurrent development to effectively assure ongoing performance to spec.

We cannot wait for perfect science. We must be moving now with solutions that will get even better over time. And we need to rigorously study these new solutions in situ, both to validate them and to winnow out those that ultimately cannot make the grade. To quote Zee Crocker, Executive Director of the Barnstable Clean Water Coalition, at a recent presentation about I/A systems, “We cannot let perfection become the enemy of good.”

Fixing the Cape’s water problems will cost money. If we don’t aggressively work on the problem, we are going to pay anyway through reduced: fisheries, home values (see the Cape Cod Commission, 3bays link, at end), tourism and the quality of Cape life.
It will take multiple concurrent approaches to ensure quality waters for the Cape economy and for future generations. Distributed nitrogen removing I/A septic systems will be a valuable part of that future, and they are starting to make an impact now.

The State and other organizations are helping study new systems; soon they will need to focus more on implementing and financing. Consumers need to self-educate and assess what could work for them. The websites listed below are good places to start.

Bruce H. Walton, Innovation Council, New England Water Environment Association (NEWEA) bwalton@battliawinston.com. Bruce’s family has owned a Cape home for over 100 years. He was a board member of the NorthEast Water Innovation Network (NEWIN), whose mission has been to accelerate new technologies into the water industry. In January, 2020 NEWIN merged into NEWEA as part of its newly formed Innovation Council.

To learn more, see:

Association to Preserve Cape Cod (APCC)



Barnstable Clean Water Coalition (BCWC) www.bcleanwater.org

Barnstable County Septic Management Program (BCSMP) https://septic.barnstablecountyhealth.org/

Buzzards Bay Coalition https://www.savebuzzardsbay.org/current-issues/nitrogen-pollution/ – Excellent intro.

Cape Cod Commission (CCC)


https://www.capecodcommission.org/our-work/technologies-matrix/ – Technologies Matrix


https://capecodcommission.org/our-work/208-plan-implementation/ – 2017

https://ww2.capecodcommission.org/3bays/index.html – Effects on home prices.

https://sp.barnstablecounty.org/ccc/public/Documents/208%20Draft/Chapter%203%20Appendices/Appendix%203B.pdf – Cost Report 2014

Conservation Law Foundation Lawsuit 9.2020



Massachusetts Department of Environmental Protection (MassDEP)


Suffolk County, Long Island, NY



Revised Draft Subwatersheds Wastewater Plan, Executive Summary – 8/2019: https://suffolkcountyny.gov/Portals/0/formsdocs/planning/CEQ/2019/Appendix%20B%20-%20SWP%20Executive%20Summary%20August%202019.pdf?ver=2019-08-16-113254-687

Town of Barnstable Comprehensive Wastewater Management Plan (CWMP) – 1/2020


U.S. Environmental Protection Agency (EPA) in Massachusetts


U.S. EPA Nitrogen Sensor Challenge



West Falmouth I/A Demonstration Project – 2019 (excellent site with costed examples)



I am very grateful to the people in this arena who have contributed facts, leads and comment:

Brian Baumgaertel, MA Alternative Septic Systems Test Center (MASSTC)

Sara Burns, The Nature Conservancy (TNC)

Tom Cambareri, Water Resources Specialist,  formerly Cape Cod Commission (CCC)

Zee Crocker, Barnstable Clean Water Coalition (BCWC)

Rich Delaney, Center for Coastal Studies, Provincetown

Brian Dudley, MA Department of Environmental Protection (MassDEP)

Maggie Theroux Fieldsteel, U.S. Environmental Protection Agency (U.S. EPA)

George Heufelder, MASSTC

Justin Jobin, Suffolk County, Long Island, NY

Emily Michelle Olmsted, Barnstable County Septic Management Program (BCSMP)

Dan Ottenheimer, Yankee Onsite Wastewater Association (YOWA)

Tim Pasakarnis, CCC

Erin Perry, CCC

Daniel Santos, Barnstable Department of Public Works (DPW)

Chi Ho Sham, Eastern Research Group & President Elect of American Water Works Association (AWWA)

John Smith, KleanTu LLC, Edgartown, MA

Lauren Usilton, YOWA

Ivan Valiela, Marine Biological Laboratory (MBL), Woods Hole

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