Diagram showing a typical carbon filtration system. Contaminated water is extracted from the ground, pumped through carbon filters to remove the contamination, then returned to the aquifer. The carbon in the filters is replaced up to four times a year.

Water-treatment systems are designed to clean the groundwater, improve the quality of the aquifer  and help restore it to its natural state.

The remaining systems that are planned to be used by Brookhaven National Laboratory in projects outside the Lab's property are known as “carbon-filtration” systems. Suffolk County Water Authority uses these in more than 40 locations throughout its system to purify drinking water supplies. The system’s safety is well established. They are emissions-free and virtually noiseless.

Typically, a water-treatment system consists of extraction wells that are from 125 feet to more than 200 feet below ground. Submersible pumps are installed deep into the well. The water is pumped up through a pipe into a building that encloses two carbon filtration vessels to remove the contamination. The clean water is then pumped back into the ground and restored to the aquifer.

An aquifer is an underground layer of rock, sand, or gravel capable of storing water within cracks and pore spaces, or between grains. When water contained within an aquifer is of sufficient quantity and quality, it can be tapped and used for drinking or other purposes. The water contained in the aquifer is called groundwater.

Contaminants from the water pumped from the plume are collected on granules of carbon as the groundwater passes through the treatment system. Several times each year the used carbon is pumped into a tanker truck and taken to a recycling facility where it is heated to a high temperature to remove and destroy the chemicals. Then it is ready for reuse. Clean carbon is pumped into the empty vessel from the tanker to "recharge" the treatment system.

The pumping wells must be installed where they can most effectively remove the contamination. The filtering system, housed in a building about the size of a two-car garage and approximately one to one-and-a-half stories high, may be located near the pumping wells or some distance away, in which case the water is piped underground to the treatment system.

The systems to be installed by the Laboratory are expected to operate for eight to 15 years. The Laboratory will regularly monitor the groundwater and will turn off the systems when the environmental regulatory agencies overseeing the work agree that the systems have completed their work.