Performance and kinetic modeling of modified attached-growth anoxic-oxic-anoxic reactor for onsite sanitation system treating septic tank effluent

Abstract

This paper investigated a combined process of a modified attached-growth anoxic-oxic-anoxic reactor (AG-AOAR) as a sustainable and effective post-treatment system for septic tank effluent was developed. The AG-AOAR was operated by varying hydraulic retention times (HRTs) from 24 to 72 h. The results showed that the AG-AOAR achieved highest removal efficiencies of 84, 66 and 91% of chemical oxygen demand (COD), total nitrogen (TN) and ammonium nitrogen (NH4-N), respectively, under the HRT of 72 h, resulting its effluent meeting the international and national discharge quality standards for non-sewered sanitation system. The Stover-Kincannon model was applicable to describe the kinetic constants of COD, TN, and NH4-N removal in the AG-AOAR (R2 > 0.85). Accordingly, the maximum utilization rates (μmax) were determined to be 41.1, 0.15 and 0.50 g/(L-d) for COD, TN and NH4-N removals, respectively, while the saturation constants (KB) were 57.7, 0.12 and 0.51 g/(L-d), respectively. These constant values could be applied for the design of the AG-AOAR to produce treated effluent meeting desired standards.