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.

Two 100,000 gallon collapsible tanks were anchored under water in Lake Erie to demonstrate, on a pilot scale, the feasibility of storing combined sewer storm overflow in underwater flexible tanks. Site selection, model testing, system design, construction, and one year's operation were included in the investigation. During the year's operation, 988,000 gallons of storm overflow were contained and returned to the treatment plant for treatment. Construction, operation, and maintenance costs are discussed. It was determined that for larger installations, modular systems of 250,000 to 500,000 gallon basic unit tanks should be employed, with site characteristics determining both the overall feasibility of the system, and the optimum tank size should such a system be feasible. Life expectancy for tank materials can only be determined in full scale operation in the actual environment.

Research was conducted on experimental feedlots in Lubbock, Texas, to determine the characteristics of wastes from Southwestern cattle feedlots. The feedlots were generally operated in a manner conforming to normal commercial practice in the area. They were provided with collection pits that allowed the quantity of runoff to be measured accurately. Samples of runoff were collected routinely both during rainstorms and from the collection pits. Manure samples were also collected routinely for analysis. The quantity of runoff per unit area of concrete-surfaced lots is substantially greater than the quantity per unit area of dirt-surfaced lots. Concentrations of pollutants in concrete-lot runoff are substantially higher than corresponding concentrations in runoff from dirt-surfaced lots. Agronomic studies indicate that runoff can be used for irrigation of crops, but extreme caution is required in the application of runoff to crops to prevent damage to them.