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What Is an I/A OWTS? Suffolk County's Nitrogen-Reducing Septic Systems

Last reviewed October 17, 2026 · Official sources linked throughout

An I/A OWTS (Innovative and Alternative Onsite Wastewater Treatment System) is an advanced septic system that removes far more nitrogen than a cesspool or conventional septic system. It's the kind of system Suffolk County and New York State grants pay for. [source]

Why Suffolk County is replacing cesspools

The county says nearly 70% of Suffolk homes use cesspools and septic systems, a major source of nitrogen pollution that contaminates drinking water and fuels harmful algal blooms. [source] The average residential septic system discharges about 40 pounds of nitrogen a year. [source]

How an I/A system works

All approved I/A technologies in Suffolk use biological treatment. Aerobic bacteria convert nitrogen, then an anaerobic stage denitrifies it, releasing nitrogen gas into the atmosphere. [source] I/A systems also reduce biochemical oxygen demand and suspended solids before discharge to the leaching structure. [source]

Approved technologies and nitrogen performance

Suffolk standards limit I/A total nitrogen to an average of 19 mg/L. Technologies in the county's 2025 cost ranking: [cost ranking]

• Hydro-Action AN Series (plastic): 16.9 mg/L total nitrogen
• Hydro-Action AN Series (concrete): 16.9 mg/L total nitrogen
• Orenco Advantex AX-20: 16.7 mg/L total nitrogen
• Norweco Hydro-Kinetic (plastic): 13 mg/L total nitrogen
• Norweco Hydro-Kinetic (concrete): 13 mg/L total nitrogen
• SeptiTech STAAR (plastic): 15.8 mg/L total nitrogen
• SeptiTech STAAR (concrete): 15.8 mg/L total nitrogen
• Fuji Clean CEN Series: 12.7 mg/L total nitrogen

What you'll see in your yard

Most of the system is underground, but tank covers (which must stay accessible), a control panel with alarms, and air intake and vent piping will be visible. [source]

Living with an I/A system

• Annual professional maintenance is required, and grant-funded systems can't be removed without written approval from SCDHS. [source]
• Electric cost runs about $75–$250 a year. If the power goes out, the system works like a conventional septic system unless you have a backup generator. [source] [source]
• Components are replaceable; you may need a new pump or blower after about 10 years. [source]
• The county notes an I/A system could increase your property value. [source]

See what each technology costs.

Independent guide. Not affiliated with, endorsed by, or operated by Suffolk County, New York State, or any installer. This page is general information, not legal or financial advice.

Sources

• Suffolk County – Septic Grants Information Homepage — page accessed Oct 17, 2026
• Suffolk County – Septic Improvement Program FAQ (April 2026, PDF) — dated 4-2026
• Suffolk County DHS – What Homeowners Should Know About I/A OWTS (PDF) — dated 5-5-2026
• Suffolk County – SIP Vendor Cost Ranking, 4-bedroom home (PDF) — rev. 2025-11-06

Last reviewed October 17, 2026. Program rules change; always confirm with Suffolk County Department of Health Services (631-852-5811, [email protected]).