The Suffolk legislature voted unanimously Tuesday to allow county health officials to approve new high-tech septic systems that could eventually replace the roughly 360,000 cesspools and septic systems that contribute nitrogen pollution to the county’s ground and surface water.

“This has been an extraordinary journey to this point,” Legis. Kara Hahn (D-Setauket) said. “But there are many more steps to come.”

The approval came after lawmakers and health officials emphasized that the new rules were not intended to allow developers to increase the amount of building they can do, but to protect the groundwater and bays from further degradation.

The new systems hold the promise of dramatically improving the removal of nitrogen from wastewater in the 70 percent of the county that is unsewered, health officials said.

But the widespread replacement of aging residential cesspools and septic systems still faces a substantial challenge because of cost.

Lawmakers earlier in the day held a lottery that picked 20 homeowners throughout Suffolk who will get the new high-tech systems — worth $19,000 apiece — for free to test whether the systems can reduce nitrogen enough to be certified by use in the county.

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The county is already testing the new systems from a similar lottery held last year, and expects to have enough data by September to certify the first of a half-dozen different kinds of systems undergoing the tests.

Walter Dawydiak, the health department’s director of the division of environmental quality, said the county expects to first allow use of the new systems for residential use for projects containing up to three new homes, with sewage flows of up to 1,000 gallons a day.

He said approval of the first commercial uses could come early next year.

Deputy County Executive Peter Scully said once the new systems are in use, the next step will be for the county to consider whether to require their use in new construction.

However, Suffolk’s Department of Health Services Commissioner Dr. James Tomarken emphasized that would be a “policy decision that is up to the county legislature.”

Suffolk County Executive Steve Bellone earlier this year sought state legislation to allow a November referendum to permit a $1 per 1,000 gallon surcharge on public water rates, but was stymied when Republican State Senate Majority Leader John Flanagan, through an aide, described the proposal “dead on arrival.”

At the time, Bellone said the surcharge could help homeowners install the new systems — estimated to cost between $15,000 to $25,000 — by providing grants and financing so it would be similar to the $5,000 cost of replacing a cesspool.

However, some critics also raised concerns that Bellone might look to use the fund to ease the county’s three-year budget shortfall, now estimated at $210 million heading into 2017.

Adrienne Esposito, executive director of Citizens Campaign for the Environment, cautioned the county to move slowly with approving the new systems and make all testing data public.

Lawmakers on Tuesday also approved Legis. Steve Stern’s (D-Huntington) proposal to bar the county from doing business with vendors and contractors who take part in a pro-Palestinian campaign to penalize Israel through boycotts, divestment and sanctions.

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The county would use a list of companies in the Boycotts, Divestment and Sanctions movement being compiled by the state under a ban Gov. Andrew M. Cuomo issued by executive order June 5.

“It’s sending a strong message we will not tolerate and not do business with those companies supportive of BDS,” Stern said.