East Hampton Town on Tuesday became the first in Suffolk County to require low-nitrogen septic systems be installed in all new buildings.

The town board approved legislation to mandate that the new systems, which emit half the amount of water-polluting nitrogen as standard systems, be required in new houses and commercial developments, and structures that have been significantly expanded starting Jan. 1, 2018.

Town officials also approved offering up to $16,000 in rebates to encourage property owners to replace their existing septic systems.

The mandate and rebates aim to cut down on nitrogen pollution, which causes algal blooms and bacterial contamination in bodies of water, officials said.

“Protecting water quality is our highest priority because our quality of life and economy depend on safe drinking water and pristine surface water,” Supervisor Larry Cantwell said in a statement.

East Hampton’s mandate is stricter than similar efforts in Brookhaven and Southampton Towns, which require that the systems approved by the Suffolk County Department of Health Services be placed in new residences only in environmentally sensitive areas.

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Town residents and environmental groups commended East Hampton Town officials for their septic system initiatives during recent public hearings, saying they have become frustrated by the worsening quality of water that has caused some bodies of water to be closed to bathing and shellfishing.

The mandate will “set in place the new norm for development and redevelopment” and “will have a tremendous impact,” said Sara Davison, executive director of the Friends of Georgica Pond Foundation, which seeks to protect the pond’s ecosystem.

But others questioned the impact of the new legislation.

“It adds quite a bit of construction cost,” said contractor Chris Tucci. “A $15,000 septic system on a $300,000 home is a significant update.”

About 6,000 properties that are near bodies of water are eligible for a rebate of 100 percent or up to $16,000. About 13,000 properties outside the Water Protection District are eligible for a rebate of up to $10,000.

The rebate program, which begins Sept. 1, will only be available to residents making less than $500,000 a year.

The rebates will be funded through the Community Preservation Fund, which is expected to receive about $150 million for town water quality improvement projects over the next 30 years. The fund is generated from a 2 percent tax on real estate transfers in the five East End towns of East Hampton, Southampton, Riverhead, Southold and Shelter Island.

Suffolk County also offers up to $11,000 in rebates to homeowners wishing to replace their sanitary systems.