| Activated sludge has been used in the treatment of municipal and industrial wastewater since early this century. The growing interest in environmental quality has caused stricter water quality criteria for wastewater effluents discharge and this has led to a search for a simple activated sludge system which provides high treatment efficiency and a capacity for nutrient removal. The objective of this study was to evaluate the operational characteristics of a new activated sludge wastewater treatment system called a modified sequencing batch reactor, or MSBR.; A pilot-scale MSBR system consisting of two aeration cells and two alternating cells that exchanged their functions of solids separation and sequencing treatments of mixing only, aeration, and presettling was constructed, operated and evaluated. Carbonaceous organic metabolism and nitrification took place in the aeration cells while denitrification occurred during the mixing steps of sequencing treatments in the alternating cells. A high treatment efficiency consisting of 98 percent five day oxygen demand, or BOD5 removal, 97 percent total suspended solids, TSS removal, 96 percent ammonia nitrogen removal and 86 percent total nitrogen removal was achieved in this system treating a municipal wastewater.; By converting the first aeration cell to an anaerobic cell and a return sludge thickener, the MSBR system also removed phosphorus biologically using phosphorus removal bacteria, or Bio-P bacteria. The system had a minimum return sludge to the anaerobic cell and an optimized anaerobic detention time. Without the multiple recycling and the large reactor volume, 97 percent total phosphorus was removed in the system producing a final effluent total phosphorus of 0.2 mg/L.; The results obtained in this research demonstrated that the MSBR system was an efficient system producing a high quality effluent under a variety of operating conditions. The technology can be used for new wastewater treatment plants or for upgrading existing biological wastewater treatment systems such as aerated lagoons. |
