ABSTRACT
Pilot plant testing of the rotating contactor process on domestic wastewater has been conducted in the US since 1969. The rotating disc process appears to be especially suited to obtaining nitrification of domestic wastewater. One way of showing that the process is first order with respect to BOD removal is to plot percent BOD remaining as a function of retention time on semilog paper. Rotational disc velocity affects treatment in several ways. It increases the intensity of contact between the biomass and the wastewater; it increases the rate of aeration; and it more thoroughly mixes the contents of each stage of treatment. Several brief tests were conducted to determine if recycling settled secondary sludge to the first stage of discs would enhance treatment of the wastewater. The rotating contactor process is unaffected by wastewater temperatures above 55°F. The development and predominance of ammonia-oxidizing organisms in the process has been found to be primarily a function of BOD concentration.
