Suffolk County is promoting an eco-friendly water treatment device that replaces cesspools or septic tanks in an effort to help clean up Long Island's groundwater and save its bays. But the technology also comes with issues, including some that could affect your wallet.

There's something unusual going on under Tom Knipper's front yard, and environmentalists say it could be the key to cleaning up the troubled water in Long Island's bays. Instead of a cesspool or septic tank, Knipper has a state-of-the-art home wastewater treatment device. It uses a series of tanks and pumps to provide life support to bacteria, which feed on what's flushed down the toilet.

"They strip the oxygen from the molecule, which releases the nitrogen as a gas," says Joe Dansienski, of Hydro-Action.

With this process, at least half of the nitrogen in wastewater is removed. Nitrogen has been called the No. 1 threat to Long Island's environment.

COMPLETE COVERAGE: Water quality on Long Island

Most experts say nitrogen has been seeping from cesspools and septic tanks all over Suffolk and parts of Nassau, eventually finding its way into the bays, where it triggers brown tides and harms marine life.

"We could lose our shellfish industry, our finfish industry, our recreational value, our home values," says Adrienne Esposito, of the Citizens Campaign for the Environment. "We would lose what it is we love about living here on Long Island."

VIDEO: Extended interview with Adrienne Esposito

The technology is still being tested on the Island, but some Suffolk towns are already requiring such devices for new construction. Eventually, they may become mandatory for many thousands of existing homes in Suffolk.

A potential downside is cost. Installations average about $19,000 -- more than twice what a conventional septic tank costs. Suffolk is offering grants and low-interest loans to cover most of that price tag. But right now, there's not enough money to fund those grants for all homeowners who may need them. Officials haven't ruled out new water fees or taxes.

"I'm sure there's going to be a healthy discussion about which options make sense and which don't," says Suffolk Deputy County Executive Peter Scully. "There's going to be some tough decisions that need to be made by elected officials."

VIDEO: Extended interview with Peter Scully

Pat Molluso, of Patchogue, has mixed feelings about higher taxes for clean water.

"The environment needs clean water," he says. "But you have to evaluate what it's going to cost the homeowner."

Homeowners will also need to pony up hundreds of dollars for higher electric costs and a yearly maintenance contract, and they'll have to be careful. Baby wipes, too much bleach, flushing medicines and chemicals and even using a sink disposal could damage the system, requiring a costly pumpout.

"Try to think of this as if it's a very expensive appliance for your home," says Tom Montalbine, president of Roman Stone Construction.

As for reliability, data examined by Newsday and News 12 shows that many units currently under test by the county are failing to reduce nitrogen to the required limit. But county officials say the technology has been proven elsewhere and they're confident it will work on Long Island.

For their part, the Knippers say they're willing to do whatever it takes to make sure the water is kept pristine for future generations.

It will be up to Suffolk legislators to decide whether to require advanced home septic systems, who will be affected and how to pay for them.