Abstract
Treatment of low-strength soluble wastewater (CODz500 mg/L) was studied using an eight chambered anaerobic baffled reactor (ABR). At
pseudo steady-state (PSS), the average total and soluble COD values (CODT and CODS) at 8 h hydraulic retention time (HRT) were found to be
around 50 and 40 mg/L, respectively, while at 10 h HRT average CODT and CODS values were of the order of 47 and 37 mg/L, respectively.
COD and BOD (3 day, 27 C) removal averaged more than 90%. Effluent conformed to Indian standards laid down for BOD (less than 30 mg/L).
Reactor effluent characteristics exhibited very low values of standard deviation indicating excellent reactor stability at PSS in terms of effluent
characteristics. Based on mass balance calculations, more than 60% of raw wastewater COD was estimated to be recovered as CH4 in the gas
phase. Compartment-wise profiles indicated that most of the BOD and COD got reduced in the initial compartments only. Sudden drop in pH
(7.8e6.7) and formation of volatile fatty acids (VFA) (53e85 mg/L) were observed in the first compartment due to acidogenesis and acetogenesis.
The pH increased and VFA concentration decreased longitudinally down the reactor. Residence time distribution (RTD) studies revealed
that the flow pattern in the ABR was neither completely plug-flow nor perfectly mixed. Observations from scanning electron micrographs (SEM)
suggest that distinct phase separation takes place in an ABR.