Improvement of Anaerobic Digestion of Sewage Sludge, Using Combined Hydrogen Peroxide and Thermal PreTreatment

The present study investigates the influence of individual and combined hydrogen peroxide and thermal pretreatment of waste activated sludge on anaerobic digestion. For so doing, it employs anaerobic batch reactors in the mesophilic conditions. For comparison, soluble fractions of organic matter, biogas production, biochemical methane potential, removal of chemical oxygen demand (COD), and volatile solids (VS) have been measured during the anaerobic digestion process in systems with and without pretreatment. Hydrogen peroxide pretreatment has been tested in two concentrations of 30 g H2O2/kg VS and 60 g H2O2/kg VS and thermal pretreatment has been performed at two temperatures of 75℃ and 90℃. According to the results, the solubalisation of organic matter considerably improves, when combined hydrogen peroxide and thermal pretreatment is employed. As a result, in comparison to the control reactor, higher amounts of biogas (71%) and methane (81%) have been produced in the bioreactor, pretreated with combined hydrogen peroxide (30 g H2O2/kg VS) and heat (90 ℃). In addition, the removal efficiency of COD and VS from the digested sludge has been enhanced in the pretreated reactors (up to 39% and 92%, respectively) in comparison to the control reactor. The improved methane yield, COD, and VS are of paramount importance, not only because higher amounts of renewable energy are obtained from the anaerobic digestion process, but because sludge transport costs are reduced and the digested sludge obtains a higher potential application to agricultural lands.