Bioelectrochemical hydrogen peroxide production – an opportunity for sustainable mitigation of membrane bioreactor fouling
Paper in proceeding, 2010
Membranes in membrane bioreactors (MBR) are typically cleaned with sodium hypochlorite. The latter is a strong oxidant and of concern due to the possible formation of chlorinated hydrocarbons. Here, we propose a new concept for chemical membrane cleaning with hydrogen peroxide (H2O2), generated onsite in a bioelectrochemical system. The energy present in the wastewater organics can be used to power the production process. We investigated bioelectrochemical H2O2 production from a synthetic wastewater in an inclinedbed reactor and discuss the possibility of using H2O2 to replace sodium hypochlorite for membrane cleaning. Low current, the use of carbon fiber as opposed to graphite, and low pH in the cathode all benefited H2O2 production. It was also possible to generate H2O2 with a net energy output, i.e. by operating the reactor as a microbial fuel cell. The highest H2O2
concentration produced in this study was 176.3 mg/l, which was obtained at a production rate of 1.26 mg/h and an energy input of 0.32 kWh/kgH2O2. A concentration of 91.6 mg/l, a production rate of 0.54 mg/h and an energy output of 0.18 kWh/kgH2O2 was obtained when the reactor was operated as a microbial fuel cell. For application in a MBR, a relatively small portion (>3.8 mg/l BOD) of the influent organic compounds would have to be converted to
current by the electroactive bacteria living on the anode to produce sufficient amount of H2O2 for membrane cleaning. However, the produced H2O2 concentration must likely reach a concentration of 0.2-0.5%.