New low-temperature applications of anaerobic wastewater treatment

Low-temperature or psychrophilic (<20 degrees C) anaerobic biological treatment of simple industrial wastewaters has recently been proven feasible as an alternative to more expensive mesophilic (ca. 37 degrees C) technology. We implemented novel expanded granular sludge bed (EGSB)-based bioreactor designs for 27 psychrophilic anaerobic digestion (PAD) trials for the treatment of a broad range of simple and complex synthetic wastewaters representing dairy, food-processing and pharmaceutical sector effluents. A variety of operating parameters, such as hydraulic retention time, organic and volumetric loading rates and upflow velocity, were tested. Chemical oxygen demand (COD) removal efficiencies were recorded, which were comparable to previous mesophilic trials. Specific methanogenic activity, toxicity and biodegradability batch assays were employed to monitor the metabolic capabilities of microbial consortia in anaerobic reactors. The prevalence of psychrotolerant communities was observed and psychrophilic populations were detected in two of the reactors. The potential of PAD with respect to global sustainable development is discussed.