Up-concentration of wastewater to maximize biogas potential: A step towards positive energy wastewater treatment

Abstract

This study demonstrates a feasible and novel design of the up-concentration of domestic sewage through the Biosorption-Sedimentation Process (BSP). In this study, the system was operated at relatively shorter ratios of anoxic to anaerobic hydraulic retention times (Tano/Tan) with an infinite sludge retention time (SRT) to obtain an up-concentrated stream in terms of chemical oxygen demand (COD) and total phosphorous (TP) and ammonium-nitrogen removal in the effluent. Results indicate that the system has a potential of net energy yield up to 15.5 kW h/m3. Tano/Tan of 60 min/60 min was selected as an optimized run based on Carbon: Nitrogen: Phosphorous (C:N:P) ratio, ammonium-nitrogen concentration, and the maximum energy potential in terms of COD. For process optimization, Response Surface Methodology (RSM) was applied. The optimized run predicted by RSM against the required responses (COD, TP, NH4+-N and TKN) was almost the same as obtained from C:N:P ratio. To conclude, BSP system is not only capable of producing an up-concentrated effluent stream but also has a potential to yield biogas via anaerobic digestion (AD).