To aid in the further development of sewage treatment by activated sludge, a continuous flow automatically recording respirometer was used to study the response of aeration only and aeration with sludge return completely mixed activated sludge systems (CMAS) to step changes in the influent substrate. The experiments were conducted at 25 C with glucose; a mixture of glucose, glutamate, and acetate; and a mixture of sewage solids plus Metrecal. Influent substrate concentrations were doubled in the 3-hour and tripled in the 6-hour mean residence time aeration only experiments without increasing the soluble COD in the effluent. Decreases in the influent substrate concentrations produced rapid decreases in the rate of oxygen utilization. A procedure for calculating the rate of oxygen uptake by a CMAS system at any time during a step transient was developed.

A pilot scale field investigation of the effects of supplemental aeration on waste stabilization lagoons was conducted at Laramie, Wyoming, a low temperature, high altitude area. Both batch and complete mixed experiments were conducted using constant air flows. Loading rates, both hydraulic and process, were varied. The supplemental aeration provided both aeration and mixing, thereby increasing metabolic rates. BOD reductions varied from 72 to 85% under three different loadings, at temperatures of less than 12°C. No settleable solids were found in the effluent from the aerated system. Series operation was demonstrated to have the advantages of damping variations in quality parameters, providing for shock loading, and reducing coliform counts to minimum levels.

A prototype package plant incorporating the rotating disc wastewater treatment process was tested on municipal wastewater at the Village of Pewaukee, Wisconsin, to evaluate its treatment capabilities and establish guidelines for operation and testing of a full-scale rotating disc demonstration plant soon to be put into operation at Pewaukee. The package plant included a rotating bucket feed mechanism, ninety-one 1.75 meter diameter discs divided into two stages, and a secondary clarifier with a sludge-removal mechanism. Variables tested included hydraulic loading, rotational disc speed, sludge recycle, and wastewater treatment as it varied with climatic conditions.