Effects of different pre-treatment methods on anaerobic mixed microflora for hydrogen production and COD reduction from domestic effluent

Abstract

Effects of different pretreatment methods on sludge inoculum were evaluated concerning hydrogen (H2) production enhancement and COD (chemical oxygen demand) reduction, using domestic effluent in a batch system. The sludge was taken from a recycled line of the activated sludge reactor. Two types of pretreatment were investigated, heat treatment and chloroform treatment. The experiment was conducted at pH 4-6 and inoculum sizes of microbes were 10%, 20%, and 30% respectively; and experiment without sludge pretreatment was also conducted as control. The result showed that 30% COD reduction was achieved for chloroform pretreatment at pH 3 and 10% inoculum size. For heat treatment, a maximum COD removal of 60% was achieved in the experiment at pH 6 and 10% inoculum size. In chloroform pretreatment, a maximum volume of gas evolved was 3.6 mL, at pH 3 and 20% inoculum size. For heat pretreatment, maximum biogas evolved was 2.1 mL, at pH 3 and 10% inoculum size. The experimental results showed that the pretreatment methods (heat treatment and chloroform treatment) at 35 °C and initial pH 5.5 had a positive influence on H2 production yield and COD removal efficiency during the fermentative H2 production as compared to the control experiments (without pretreatment). Heat treatment method was shown to be a simple and useful method for enhancing both H2 producing and COD removal processes from domestic effluent with highest H2 yield and COD removal efficiency at 0.314 mmol H2/g COD and 86%, respectively.