NTA Removal by Activated Sludge-Field Study

The chelating agent trisodium nitrilotriacetate (NTA) can be used effectively in combination with polyphosphates in the formulation of heavy-duty detergents. Laboratory investigations have shown that NTA is biodegraded to water, carbon dioxide, and inorganic nitrogen. In the field study at Heath, Ohio, NTA was shown to be removed by conventional activated sludge treatment. At influent NTA levels up to the maximum expected (∼8 mg/l) an average of 90 percent removal was found. At higher levels percent removal varied widely. The average removal was 75 percent. At no time during the 10-month study did the addition of NTA have any adverse effect on plant operation. Stream water taken downstream from the plant outfall degraded spiked NTA at a slightly faster rate than did water taken upstream from the plant outfall. Limited data from the field indicated that NTA degradation continued in the receiving stream.