Effective treatment of night soil using anaerobic sequencing batch reactor (ASBR)

Abstract

Laboratory experiments were conducted to investigate the performance of the anaerobic sequencing batch reactor (ASBR) process for night soil treatment. The reactors were evaluated at an equivalent hydraulic retention time (HRT) of 10 days with an equivalent loading rate of 2.6 kgVS m-3day-1 (3.1 kgCOD m-3day,-1) at 35 ‡C. Digestion of night soil was possible using the ASBR at an HRT of 10 days in spite of high concentration of ammonia nitrogen and settleable solids. Solids were accumulated rapidly in the ASBRs, and their concentrations were 2.3-2.4 times higher than that in a completely mixed control reactor. Increases in gas production were observed in the ASBRs compared with the control reactor. Average increases in equivalent daily gas production from the ASBRs were 205-220% compared with that from the control run. The ASBR with reaction period/thickening period (R/T) ratio of 1 showed a little higher gas production and organic removal efficiency than that with R/T ratio of 3. Volatile solids removal based on supernatant of the ASBRs was 12–14% higher than that of control reactor. Thus, the ASBR was a stable and effective process for the treatment of night soil having high concentration of settleable organics and ammonia nitrogen.