Biodegradation of Methanol Using Thiosulphate as an Electron Acceptor Under Anaerobic Conditions

BACKGROUND. Methanol is a volatile organic compound commonly found in the effluent of the pulp and paper industries. Because of its toxicity, methanol can cause metabolic acidosis, neurologic sequelae, and even death when ingested. Information on biokinetic activity such as biodegradation rate of methanol and thiosulphate, biomass growth rate and biomass yield coefficient is limited in the literature. OBJECTIVES. To study the biomass growth rate and biomass yield coefficients of methanol and thiosulphate biodegradation. This research aims to increase knowledge of how to reduce the emission of toxic gas to the environment. METHODS. The biodegradation trends of both methanol and thiosulphate were studied under anaerobic conditions using batch experiments at ambient temperature and alkaline conditions. Both supplement each other for their degradation. Methanol is an electron donor, whereas thiosulphate acts as an electron acceptor. A mixed culture from a previously used biomass in a biotrickling filter reactor from theUnited Nations Educational, Scientific and Cultural Organization (UNESCO), International Graduate Water Education Facility and fresh activated sludge from the Harnaschpolder wastewater treatment plant were used as a biomass source. RESULTS. A specific biomass growth rate of biomass ranging from 0.04 to 1.7g per day was observed. The thiosulphate is biologically degraded by the biomass grown inside the reactor. The biodegradation rate of thiosulphate in the reactor varied from 0.02 to 0.80g per unit gram of biomass per day. A biodegradation rate of methanol in the reactor was observed in the range between 0.04 to 3.9g per unit gram of biomass per day. Bacterial biomass was grown as per the amount of methanol present inside the reactor. A maximum biomass yield coefficient of 0.7g biomass per gram of methanol was recorded. Thiosulphate was converted to sulphate that indirectly served as an electron acceptor for methanol degradation. Both degradation of methanol and thiosulphate in this experiment were in the range of the degradation rate shown for sulphate and organic compounds in other studies. CONCLUSION. Simultaneous removal of thiosulphate and methanol using an anaerobic bioreactor is promising and can be applied on an industrial scale. This finding is an important contribution to public health as it reduces the emission of toxic gas to the environment.