Activated Anaerobic Digestion with a Membrane Filtration System

A novel process, activated anaerobic digestion, has been successfully demonstrated in a full scale facility. The process includes an anaerobic digester working with a screw press and a UF membrane system, and produces biogas from agricultural and industrial feedstocks. The system was operated at two temperature zones; thermophilic , at 55 degrees C in 2010 and at a startup temperature of 45 degrees C in 2011 at a daily biogas(methane) generation rate of 0.34 m3/kg COD.The feed materials included hog manure, corn silage, grains and other industrial organic material with high biogas potential. The membrane system is unique, with a vortex generator that resist fouling by physical and chemical components. The screw press cake separates non-active biosolids from active biomass, with the screw press cake shipped out as a nutrient rich fertilizer. The UF system captures and concentrates all microorganisms and returns them to the digester The UF membrane permeate is a high-quality water suitable for downstream treatment by reverse osmosis.GPS-X modeling software was utilized with the Mantis2 model. A model was calibrated and validated with two sets of data from full scale operation. The models were run for both steady state and dynamic operations. The results showed the impact of key variables including temperature and influent flow rate on the stability of the system. The model was also used to demonstrate the effects of selected disturbances, such as feed disruptions and step increase in feed. Both the full scale data and model predictions successfully established the stability of the new process and benefits from membrane filtration.