Systems were developed to control the critical parameters of the activated sludge process to achieve reliable, high quality effluent. The waste water from a petrochemical plant contained ethylene glycol and was sometimes saline. An automated sampling system, sampling feed and homogenized mixed liquor, monitored the total carbon in both samples. Nutrients were added in proportion to the total carbon in the feed, thus maintaining low residual nutrients in the effluent. The sludge recycle flow rate was controlled by a food to microorganisms signal, measured as the ratio of total carbon in the feed to that in the mixed liquor. Toxic or inhibitory effects of the feed were measured by a Biological Inhibitor Detector, an instrument which measures the oxygen uptake of standard solutions before and after exposure of a bacteria sample to a feed sample and calculates an activity ratio. The use of the instrument as an upstream sensing device was demonstrated as toxic substances were added to the feed. The developed on-line control systems are applicable to municipal, industrial or combined treatment plants. A bibliography of 63 references is included.

"Grant No. S800 766; Program Element 1BBO36; ROAP/Task No. 21 AZP-36." "June 1975." Report prepared by The Dow Chemical Company, Texas Division, Freeport, Texas. Includes bibliographical references (pages 155-159).