The use of the carbon sources present in municipal wastewater to provide the energy required for nitrification-denitrification was evaluated on a pilot plant scale in a simulated plug flow reactor. Most of this report is devoted to the results from operation of a nine-pass activated sludge system receiving primary effluent. The first two passes and the last pass were aerated whereas the remaining passes were mechanically mixed. Nitrification occurred in the aerated passes and denitrification in the others. By maintaining a sufficiently low process loading, nearly all of the incoming ammonia was oxidized in the first two passes with most of the nitrate subsequently denitrified in the next six passes. Residual NH4(+)-N levels of 0.1 mg/l and (NO2(-) + NO3(-))-N levels of 1.0 mg/l were obtained with both steady state and diurnal flow. FeCl3 addition during a portion of the study increased the P removal to approximately 90% with no discernable impact on the nitrification-denitrification performance. Nitrification and denitrification kinetic rates measured during laboratory studies were found to correlate well with actual process rates. These rates were obtained under varying conditions of temperature, available COD, length of initial aeration period, etc.

Prepared by EPA-DC Pilot Plant, under contract no. 68-03-0349. Issued Nov. 1979. Includes bibliographical references (pages 93-94).