Incorporating the Oxic-Settling-Anaerobic (OSA) Process into an Anoxic–Oxic System for Sewage Sludge Reduction and Nutrient Removal

Abstract

The production of sludge in biological wastewater treatments is a growing problem worldwide as it entails economic, environmental, and health problems. The oxicsettling- anaerobic (OSA) process is one of the techniques that have been developed to reduce the sludge produced in the activated sludge process (ASP). This article reports the feasibility of the application of the OSA process in a nutrient removal system, specifically, in an anoxic–oxic (A) process. The results reveal TN removal in the A1OSA system of 68.84% and 69.91% (for 7 and 11 h of sludge anaerobic exposure time, SAET, respectively) versus 38.02% and 32.47% in the OSA system with similar SAET. The percentage sludge reductions obtained were, respectively, 22.41% and 31.93% in the OSA system and 23.53% and 32.49% in the A1OSA system compared to the sludge produced in the conventional ASP. The study confirms the suitability of the application of the OSA process in a nutrient removal system, as nutrient removal performances are not affected, while at the same time achieving higher sludge reduction