Treatment of low-strength industrial wastewater using anaerobic baffled reactor

ABSTRACT

The performance of an anaerobic baffled reactor at the pilot scale, with a 100-L volume and six compartments, that is used to treat low-strength industrial wastewater [671.5 +/- 49.9 mg COD/L, 350.1 +/- 36.8 mg BOD[5]/L and 443.8 +/- 60.7 mg SO[4][-2]/L] was studied. The reactor was started with a hydraulic retention time [HRT] of 25 h at 35 °C, which was gradually reduced to 3.33 h. The best reactor performance was observed with an organic loading rate [OLR] and a sulfate loading rate [SLR] of 4.45 g COD/L.d and 3.32 g SO[4][-2]/L.d, which was obtained at a HRT of 4 h. The COD and SO4-2 removal efficiencies were 78.6% and 89.2%, respectively. Additionally, the majority of the COD and SO[4][-2] removal occurred in the first compartment, up to 51.2% and 69.1%, respectively. Moreover, the pH in the first compartment was also the lowest. Subsequently, when the temperature was reduced to 20 °C at a HRT of 4 h, the maximum removal efficiencies for COD and SO[4][-2] decreased to 59.4% and 66.1%, respectively. In this case, the highest COD and SO[4][-2] removal efficiencies were observed in the third and fourth compartments, respectively, and these compartments had lower pH values. This phenomenon indicates that decrease in temperature causes transference of the acidogenic phase toward subsequent reactor compartments. In addition, these findings further show the potential for sulfate removal of the acidogenic phase