Suffolk officials on Monday presented a draft of a new code that would legalize new nitrogen-reducing septic systems for individual homes, and detailed a plan to identify where efforts targeting the pollutant should be directed.

The proposed new regulations would add a provision to the county’s sanitary code to allow property owners to install alternative septic systems, which, unlike traditional septic systems and cesspools, employ various technologies to reduce nitrogen.

About 360,000 homes in Suffolk County are unsewered, causing about 70 percent of the nitrogen pollution in the area’s waterways, according to the county.

Excess nitrogen leads to harmful algal blooms, a lack of oxygen in the water and a loss of vegetation in coastal marshes that buffer the area from the impacts of severe waves and flooding during storms, experts say.

The new systems, which reduce nitrogen to about 19 milligrams per liter — about half what is emitted from cesspools and traditional septic systems — have been installed in 19 homes in the county to test their effectiveness before they are approved, and a second round of installations is in the planning phase, said Peter Scully, deputy county executive for administration, at a meeting in Selden on Monday.

It is “the very first step of our sanitary-code change,” said Justin Jobin, the health department’s environmental projects coordinator.

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The code would require homeowners to register the systems with the county, enter into a contract with a maintenance provider to ensure the system is running and allow the county health department to inspect the system.

The new systems would have to be inspected and maintained regularly to ensure they still are treating the sewage for nitrogen, county officials said.

“It’s not a ‘set-and-forget’ mentality anymore,” Jobin said. “We have to change the way we think about these on-site systems.”

Jobin said he hoped the new code, which would require approval by the county legislature, would be in place by July.

Sarah Meyland, director of the Center for Water Resources Management at the New York Institute of Technology, said a future sticking point likely would be the limits of the new technology.

“They’re presenting it as a 50 percent improvement over the old system in terms of treatment quality,” she said. “I think a lot of people are going to want a higher degree of treatment. Now maybe that’s all these units can do at this point in time, but I just can’t imagine that that’s the best we can get looking into the future.”

The new code would allow the systems to be installed, but wouldn’t change the current practice of installing traditional septic systems or rebuilding broken cesspools. Still, Scully said, at issue would be how to help homeowners pay for the new alternative systems — estimated to cost between $10,000 and $24,000.

“Policymakers are going to have to wrestle with what to do about replacement” of old systems with the new ones, he said, adding that the replacement could be subsidized or covered by a fee on water usage that County Executive Steve Bellone proposed last month.

That fee — a $1 surcharge on every 1,000 gallons used — would bring in nearly $75 million that the county said would be directed to grants and loans to help homeowners replace cesspools, helping connect homes to sewer lines, and other projects related to sewage.

County officials are seeking state legislation to allow them to put the measure on the November ballot.

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While the county earlier had estimated a family of four would pay $73 a year — based on an estimated usage of 50 gallons per day per person — officials since have revised the estimated fee for a family to $96 a year.

Dorian Dale, the county’s director of sustainability, said the new figure takes into account differing estimates of how much water a person actually uses.

Monday’s meeting, held at Suffolk County Community College in Selden, also focused on identifying the boundaries of an estimated 200 microareas in the county that affect surface and groundwater to help direct efforts toward which areas need to be first targeted for nitrogen reduction.

The effort “will help guide county wastewater policy and give us an early indication of how best to tackle the problem,” said Ken Zegel, associate public health engineer with the county’s health department. “This will be the first time anybody’s looked at it on a countywide basis.”