Comparisons of Nutrients Removal Performance Between Two Types of Step Feed Processes From Municipal Wastewater

The anoxic/oxic(A/O) step feed process unit and operation parameters were adjusted to increase organics and nutrient removal by reconfiguring the process into a modified University of Cape town(UCT) step feed process treating municipal wastewater.The nutrients removal mechanisms in the modified UCT step feed process were discussed in detail.Results showed that the simultaneously highest removal efficiencies of chemical oxygen demanding(COD) of(83.9±3.3)%,total nitrogen(TN) of(83.5±1.4)% and phosphorus of(86.6±2.4)% were obtained in the modified UCT step feed process with the optimum operation parameters,which were the influent distribution ratio of 40%∶30%∶30%,the sludge retention time of 8~9 d,both the internal recycle ratio and the sludge recycle ratio of 75%,and the ratio of anaerobic/anoxic/oxic volumes of 1∶3∶6.In comparison with A/O step feed process,nitrogen and phosphorus removal performance was remarkablely improved.