Performance evaluation of panelled anaerobic baffle-cum-filter reactor in treating municipal wastewater

• Startup period of PABFR −61 days with COD removal efficiency upto 90%.
• Appropriate HRT for operating PABFR is 8 h HRT.
• Recovery and reactivation(restart) of PABFR after hydraulic shock and shutdown were rapid.
• The reactor best suits rural decentralized wastewater treatment system.

A panelled anaerobic baffle-cum-filter reactor (PABFR) was developed to treat municipal wastewater in tropical climatic condition. The performance of the reactor was evaluated with respect to start-up mechanism, pollutant removal behaviour by varying hydraulic retention time (HRT) at different organic loading rates (OLR), resistance to shock loading, restart behaviour after a shutdown period and its potential to remove pathogen indicator. Acclimatization curve was plotted. It indicated a successful start-up period of 61 days with a COD removal efficiency of more than 90%. The alkalinity to volatile acid ratio was less than 0.5, which confirms reactor stability. Performance evaluation of the reactor was carried out for more than 682 days at 7 different HRTs ranging from 2 h to 40 h. The HRT of 8 h was found to be appropriate for PABFR configuration with removal efficiencies of 95%, 91% and 90% for suspended solids (SS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD), respectively. The recovery of the reactor after hydraulic shock (both transient and step) was two times better compared to conventional ABR because of the filter media present in the rear part of the PABFR. Reactivation after a short shutdown period was quick and yielded efficient treatment. The removal efficiency of the pathogen indicator was above 97.2% at a HRT of 8 h, but it is necessary to adopt appropriate post-treatment measures to guarantee reuse. Thus, with the above-mentioned properties, the PABFR is a suitable technology for decentralized municipal sewage treatment in suburban and rural areas of India.