EVALUATION OF NITROGEN REMOVAL BY STEP FEEDING IN LARGE TREATMENT PLANTS

Step feeding flow configuration is an attractive process alternative f or large treatment systems designed for nitrogen removal, eliminating the need for internal recycling and optimizing organic carbon utilizat ion for denitrification. Volume ratios of anoxic and aerobic volumes a nd wastewater fraction to be diverted from the inlet of the system are important parameters to be considered in the design of the step feedi ng process. Wastewater characterization and especially C/N ratio signi ficantly affect the design. The effect of wastewater characterization is illustrated for the Riva Plant in Istanbul, with a capacity of 4 mi llion population equivalent, designed as a two-stage step feeding syst em for biological nutrient removal. It is shown that the proposed desi gn cannot meet the effluent standard of 10 mgl(-1) total N for the rel evant sewage characterization assessed on the basis of an extensive ex perimental study, totally different from the one adopted for design. C opyright (C) 1996 IAWQ.