The effect of combined cometabolism and gamma irradiation treatment on the biodegradability of diclofenac and sulfamethoxazole

Diclofenac and sulfamethoxazole are poorly degradable when using activated sludge or biofilm biomass in biological wastewater treatment. However, a biological phenomenon called cometabolism can improve the removal efficiency, especially in activated sludge treatment. In the case of cometabolism an easily degradable substrate is added to the wastewater under treatment. Such easily degradable molecules (e.g. methanol, acetic acid, ethylene glycol) also form in the anaerobic wastewater treatment steps and are utilized as substrates. The rate of oxidative biodegradation of pharmaceuticals (measured by using oxygen uptake rate) was shown to greatly increase in the presence of easily degradable substrates in activated sludge treatment. However, in biofilm treatment the rate of cometabolism remained low, because biofim biomass has much narrower bacterial diversity than activated sludge. The oxidation rate on biofilm was found to increase considerably by using an advanced oxidation process, ionizing radiation treatment, before cometabolism. This combined treatment, irradiation and cometabolism is recommended for the degradation of recalcitrant organic compounds on biofilm.