New technology being developed at Stony Brook University could help reduce harmful nitrogen from septic systems that end up in Long Island's groundwater and waterways.

Experts say the underground filtering system known as a nitrogen-removing biofilter would be added on to existing residential septic systems. Supporters say it could possibly reduce 90 percent of the nitrogen that septic systems deposit into groundwater.

"It gets the nitrogen down to levels as good as some of the best sewage treatment plants out there," says Dr. Chris Gobler, of Stony Brook University.

It is yet to be determined if the biofilter systems will be required by the county at some point, or what they will cost.

Scientists say nitrogen has contributed to brown tides, mahogany tides, excess algae growth and major fish kill on the waters.