Anaerobic digestion technologies for closing the domestic water, carbon and nutrient cycles

Sustainable wastewater treatment requires that household wastewater is coll ected and treated separately from industrial wastewater and rainwater run-o ffs. This separate treatment is, however, still inadequate, as more than 70 % of the nutrients and much of the chemical oxygen demand (COD) and potenti al pathogens of a domestic sewage system are confined to the few litres of black water (faeces, urine and toilet water). Whilst grey water can easily be filter treated and re-used for secondary household purposes, black water requires more intensive treatment due to its high COD and microbial (patho gens) content. Recently developed vacuum/dry toilets produce a nutrient ric h semi-solid waste stream, which. with proper treatment, offers the possibi lity of nutrient, carbon, water and energy recovery. This study investigate s the terrestrial applicability of Life Support System (LSS) concepts as a framework for future domestic waste management. The possibilities of treati ng black water together with other types of human-generated solid waste (bi owastes/mixed wastes) in an anaerobic reactor system at thermophilic condit ions, as well as some post treatment alternatives for product recovery and re-use, are considered. Energy can partially be recovered in the form of bi ogas produced during anaerobic digestion. The system is investigated in the form of theoretical mass balances, together with an assessment of the curr ent feasibility of this technology and other post-treatment alternatives.