Comparative study of septic tank, anaerobic filter, and anaerobic baffled reactor for treating domestic wastewater.

Since it is presently impossible to compare the performance of different anaerobic treatment systems under the same operating conditions, this study aims to provide a comprehensive performance analysis of septic tank (ST), anaerobic baffled reactor (ABR), and anaerobic filter (AF) with a further comparison of the performance among the systems limited to total suspended solids (TSS) and chemical oxygen demand (COD) removal efficiency under medium-strength wastewater condition. The experiment was conducted over 4 conditions with combined variations of hydraulic retention time (HRT) of 24 – 48 hr and sludge concentration of 10 – 20 g/L of MLSS, while sponge filter media (25 ppi) was selected for the AF system. ST provided overall COD and TSS removal efficiencies of approximately 71%±9% and 65%±20%, respectively. ABR achieved 83%±5% of COD and 73%±15% of TSS, whereas AF reactor attained 85%±4% and 76% ± 11%, respectively. Extended HRT from 24 hr to 48 hr provides significant removal efficiency enhancement to all three systems over COD removal but insignificant for TSS removal. AF proves to be the best system among the three options, followed by ABR and ST. Both AF and ABR provided considerably high treatment efficiency with HRT of 24 hr. In COD removal, ST follows far behind and still see an increase with prolonged HRT, a clear indication of HRT for 48 hr or longer is recommended or required. The concentration of approximately 10 g/L of MLSS in the system (first compartment) could probably be high enough for all three systems to provide satisfactory treatment efficiency in terms of COD, while higher concentration would increase TSS removal efficiency but not COD. [ABSTRACT FROM AUTHOR]