Biological nutrient removal is needed at many municipal wastewater treatment facilities to control algae growth in receiving waters. This is of special concern in certain coastal areas, as well as the Great Lakes. An alternative to chemical treatment methods, which produce a residue for disposal, is a biological phosphorus removal treatment process. The success and reliability of the biological process depend on the ability to produce a fermentation product from the wastewater; namely acetate and propionate. Primary treatment sludge is fermented to provide additional acetate, but where this has been used, the acetate production has been below theoretical expectations. This may be due to the growth of other sulfate reducing and methane forming organisms that consume the acetate. A primary sludge fermentation system that uses intermittent oxygenation to inhibit the organisms and thus greatly increase the fermentation yield is being developed. Experiments designed to test this concept also investigate the use of oxidation-reduction potential measurements to control the process. A higher acetate and propionate production will greatly improve the reliability and performance of biological phosphorus removal systems. Experiments are designed to test this innovative concept using primary sludge at the City of Yakima WWTP. Oxygenation frequency, duration, and control methods are being studied and the effect on acetate and propionate yield followed.The potential commercial application as described by the awardee: An improved primary sludge fermentation process with a process control system using ORP measurements is expected. This involves process technology, equipment design, and a process control system that can be marketed. There is a significant need for improved technology for biological phosphorus removal economically competitive with chemical treatment systems.
