Treatment of simulated biomass gasification wastewater of varying strength in a three stage rotating biological contactor

Wastewater generated during wet scrubbing of producer gas formed in biomass gasifiers consist mainly of phenolics, heterocyclics, mono and polynuclear aromatic hydrocarbons (PAHs). The concentration of organics in such wastewater is reported to vary over a wide range depending on gasifier operating conditions and water recycling practices. Such variations may impact the performance of biological treatment processes due to the toxic nature of constituents. Treatment of simulated biomass gasification wastewater of varying strength in a rotating biological contactor (RBC), bioaugmented with a novel bacteria, Exiguobacterium aurantiacum, and operated at constant hydraulic retention time (HRT) of 24 h revealed consistently high removal efficiency in the range of 91-92% for organic loading rate (OLR) of 6.7-16.1 g-COD/m2/d. Increase in OLR to 39.5 g-COD/m2/d caused a marked drop in COD removal efficiency (83%). Greater than 74% removal was observed for all the components although the influent concentration of phenolics and heterocyclics were much higher compared to the PAHs. Abiotic loss in absence of the biofilm was consistently low (12-20% COD removal). Treatment was accompanied by significant reduction in acute toxicity. The biofilm consisting of E. aurantiacum and mixed microbial consortium thus have a good potential for removal of these toxic constituents.