ENHANCED NUTRIENT REMOVAL BY LIMITING DISSOLVED-OXYGEN CONCENTRATION IN A CONTINUOUSLY FED, INTERMITTENTLY DECANTED, ACTIVATED-SLUDGE PLANT

A large scale pilot treatment system has been used to study the effect of limiting the dissolved oxygen concentration on phosphorus removal, and the effect of different solids retention time (SRT) on nitrogen r emoval in continuously fed and intermittently decanted (CFID) activate d sludge system. A basic operations schedule for biochemical oxygen de mand (BOD) removal was employed in the study. The objective of the stu dy was to develop operating data and to establish and verify that oper ational conditions conducive to enhanced nutrient removal can be maint ained. It was established that simultaneous nitrification, denitrifica tion and phosphorus uptake occur during the react phase. Nitrogen remo val was enhanced by increasing SRT under normal operating conditions, nearly complete nitrification with a total nitrogen removal of 70 perc ent took place in the reactor operating at an SRT of 20 days. Phosphor us removal was improved by limiting the dissolved oxygen (DO) concentr ation during the aeration phase. Total phosphorus content in the react or increases over time unless a phosphorus removal strategy is impleme nted.