Simultaneous removal of phosphorus, nitrogen and organic substances by sequencing batch reactor activated sludge process.

Laboratory-scale sequencing batch reactor (SBR) activated sludge process was fed with synthetic wastewater to clarify the possibility on simultaneous removal of nitrogen, phosphorus, and organic substances by modifying operational schedule. Anoxic and/or anaerobic reactions in addition to aerobic reaction were introduced into a cycle of batch operation.The following conclusions can be made from this study : 1) Simultaneous removal of nitrogen, phosphorus and organic substances was shown to be possible by the modified operation of SBR in which an anoxic/anaerobic stage was introduced during the fill period.2) Oxidized nitrogen and activated sludge remained in the reactor at the end of the former cycle was removed by denitrification during the fill. Phosphorus was removed by the anaerobic release from the sludge during the fill followed by the luxury uptake by aeration.3) Both extension and reduction of the first anoxic/anaerobic stage damaged plant performance, thus an optimum length of time for these reactions must be chosen for successful operations. The best length of this stage coincided with that of the fill within the range of this study.4) The second anoxic/anaerobic and aerobic stage was not always necessary for successful nutrient removal. However, the introduction of these stages caused no detrimental effects on plant performance.