BIOLOGICAL REMOVAL OF NITROGEN AND PHOSPHORUS FROM WASTE-WATER BY A SINGLE SLUDGE REACTOR

A new biological process in a single sludge reactor containing the com bined anaerobic-anoxic-aerobic zones and a clarifier is tested to chec k continuous removal of organic substances, nitrogen and phosphorus fr om wastewater. Attempts have been made to delineate organic substances , nitrogen and phosphorus removal mechanisms and to evaluate the remov al efficiencies of these constituents with different internal recycle ratios and COD/TKN ratios. The removal efficiencies of TOC, BOD and CO D were observed to be higher than 95%, 95% and 90% in all runs, respec tively. In the case of aerobic recycle ratios, higher removal efficien cies were attained with the aerobic recycle ratio of 100% than with th at of 50% and 200%. The removal efficiencies are 88% for T-N(Total-Nit rogen) and 87% for PO4-P with the aerobic recycle ratio of 100%. Large differences in the removal of T-N and PO4-P with COD/TKN ratios were observed: at influent COD/TKN of 4.8, 6.6 and 9.8, removal efficiencie s for T-N are 69%, 80%, and 88% and those for PO4-P are 50%, 75% and 8 8%, respectively. The removal efficiencies decreased with the increase in nitrogen loading in wastewater.