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Technology reduces pollution

By Lynn Nystrom

Spectrum Volume 17 Issue 14 - December 1, 1994

The Chesapeake Bay Program has identified nitrogen as a big polluter of water. But trying to control the nitrogen is difficult. About a third of this type of pollution entering the bay comes from air pollution, another third from sewage treatment plants, and the remainder is due to stormwater run-off, mostly from agricultural areas.

The "most controllable" of the three is the amount discharged by sewage treatment plants, says a veteran environmental engineer, Clifford Randall. But that doesn't mean the other two environmental menaces should be overlooked.

Randall and his colleagues have been working on restoring water quality for about two decades. They have targeted the Chesapeake Bay in their work, and as the remedial technologies show positive results, the bay is becoming a model for other localities.

Most recently, Randall has traveled to New York City to assist in reducing nitrogen pollution in Long Island Sound and to Ontario, Canada, to help modify wastewater treatment plants to lessen the amount of nitrogen emitted as an effluent.

When Randall, the Charles P. Lunsford professor of civil engineering, began his research on the Chesapeake Bay in the early 1970s, the focus was on phosphorus as a major polluter. The work of Randall and others has resulted in a greater than 40-percent reduction of the phosphorus inputs to the bay since 1985. The environmental engineers were able to meet the Chesapeake Bay Program reduction goals for phosphorus slated for the year 2000 by 1993, seven years ahead of deadline.

Their success with phosphorus meant that another chemical, nitrogen, became the water-quality controlling pollutant in the bay. Nitrogen was first identified as a major pollutant of the bay by Randall and other scientists in 1985. Since then the amount of nitrogen entering the bay has increased and the need for technology to reduce it has become critical.

To combat the nitrogen, Randall and his graduate students Dipankar Sen and Pramod Mitta have developed several concepts aimed at making nitrogen reduction easier and more economical. Called Integrated Fixed-film Activated Sludge (IFAS) technology, one approach is to use a product called Ringlace (TM), essentially a "nylon rope with curlicues," to maximize the amount of a bacterial population that can grow in a wastewater treatment plant. "They are installed in activated sludge tanks to accelerate the oxidation of ammonia to nitrates. The added benefit is that they simultaneously denitrify (remove nitrogen) nitrates," Randall explains, "It becomes nitrogen gas and enters the atmosphere as a non-pollutant."

The goal for the reduction of the nitrogen in the Chesapeake Bay is to eliminate 40 percent of the 1985 levels by the year 2000. "It is an attainable goal," Randall says, "if we can get the proper enforcement by the states. Right now, this enforcement is lagging because economical technology is needed. IFAS technology should substantially accelerate nitrogen reduction by treatment plants."