The BIOREK® concept: a hybrid membrane bioreactor concept for very strong wastewater

The BIOREK® manure and/or organic waste treatment process based on anaerobic digestion and subsequent treatment of the effluent with conventional and novel membrane technologies is presented. The process consists of a mesophilic anaerobic digester coupled to a cross-flow tubular ultrafiltration membrane (ADUF). The clear, sterile effluent, rich in ammonium (N), soluble phosphates (P) and potassium (K) is processed into saleable fertiliser products and potable, demineralised water. Compared to conventional solid-liquid treatment technologies available, the proposed technology not only alleviates organic waste-handling problems, but also retains biomass, thus enabling more complete conversion of the organic substances in the feed. The present work investigates the use of a thermophilic (50-55°C) as opposed to a mesophilic digester (30-37°C). It will be shown that the UF flux increases rapidly when increasing the feed temperature mainly due to a decrease in viscosity. Further the investigation will show that the removal of volatile ammonia with membrane contactor (CM) technology is far superior to that expected by conventional steam stripping. It is found that proper UF-permeate decarbonisation and pH adjustment lead to improved ammonia transfer rates. Ammonia removal efficiencies of up to 99.9% are reached at ambient feed temperatures.