TREATING NUST DOMESTIC WASTEWATER USING DECENTRALIZED WASTEWATER TREATMENT SYSTEM

Abstract

Water security is a growing challenge for Pakistan as increased population growth, rapid urbanization and industrial development has increased the volumes of wastewater generated manifold. This is mainly because of improper water resource management in Pakistan. With more than 75% of Pakistan’s population residing in less dense semi-urban and rural areas, centralized wastewater treatment is not an option. In this regard, low cost, anaerobic, gravity-based and minimal energy-driven lab-scale plant of Decentralized Wastewater Treatment System (DWTS) was designed under this study. DWTS consisted of Storage Tank (ST), Anaerobic Baffled Reactor (ABR), Anaerobic Filter (AF) and Membrane Filter (MF) to treat real domestic wastewater of NUST. In order to evaluate the treatment performance for full scale DWTS, ABR and AF, combined system was operated at HRT of 24 hours with the use of locally available Polyvinyl Chloride (PVC) filter media and Granular Activated Carbon (GAC) filter media from coconut shell in different phases of the project. The system was inoculated with the combination of 70% of acclimatized sludge (COD:300 mg/L) and 30% of wetland’s sludge prior to system operation. The comparison between PVC media of two different lengths i.e. 20 mm and 25 mm revealed that PVC media of 20 mm length was more efficient because of its enhanced surface area with 61% removal of COD as compared to PVC media of 25 mm length with 52.5% removal of COD. However, in the next phase, the optimized PVC media length i.e. 20 mm was compared with the treatment performance of GAC, which revealed that GAC was even more efficient than PVC media of 20 mm length. The COD levels of NUST domestic wastewater using GAC filter media were reduced by 72% i.e. average COD of treated effluent was found to be 97 mg/L, significantly lower than the National Environmental Quality Standards (NEQS) (PAK-EPA, 2000) of 150 mg/L. Moreover, TSS, TKN and TP, were also reduced by 86.7%, 25.7% and 66% respectively, using the most optimum filter media i.e., GAC.