Many of the country's wastewater treatment plants do not meet design expectations and NPDES permit standards. A research project was initiated to identify, quantify and rank the causes of this poor performance by comprehensive evaluations of 50 plants in nine western states. The identified highest ranking causes of limited plant performance reflect an inability of in-plant personnel to optimize process control and the performance of existing facilities. Deficiencies in design features also ranked high. The performance of each plant is typically limited by a unique combination of problems which require individual identification and elimination. The Composite Correction Program (CCP) was introduced and demonstrated. This approach to improving the performance of existing facilities was conducted at selected facilities. Areas of special evaluation include aerator and clarifier design, sludge production in activated sludge plants, aerobic digester operation, reference materials used in treatment plants, operator time and tasks before and after a CCP, and the effects of toxic substances on well-operated treatment facilities.

"M & I, Inc., Consulting Engineers." "August 1980." Includes bibliographical references. "Contract no. 68-03-2572."