Self-Sufficient Wastewater Reuse with Intermediate Dehydration and with Consideration of Product Recovery.

Sammanfattning: Municipal wastewater treatment has a long history of local handling with recovery of toilet wastes for use in agriculture and to some extent energy recovery from biogas by use of local handling. This may be seen as ―the first way‖ further developed by septic tanks and infiltration and recovery as in Ecological Sanitation and use of urine separation toilets. However, problems related to water borne diseases and odor problems successively gave rise to ―the second way‖ with central wastewater systems with large investments in water and sewer nets and increasingly better technologies for water treatment and wastewater treatment. This technology may treat municipal wastewater to a drinking water quality and recover part of energy and nutrients contents for eco-cycling. The problems noted and which are quite obvious are affordability in poor countries and the need for much energy supply and with negative effects of emission of greenhouse gases. Ways should be better evaluated to obtain both an effluent wastewater of drinking water quality and at the same time be self-sufficient with energy, obtain products with a commercial value and comply with methods to reduce the amounts of released greenhouse gases. It is suggested that an intermediate dehydration step should be used by dividing the main stream into two streams, one to which water has been transferred by methods as forward osmosis or freezing and one remaining concentrated stream that could be treated more efficiently. New technologies should be considered for electricity production as use of fuel cell technology and forward osmosis. Methods to diminish greenhouse gas emissions include avoidance of such redox potentials and process conditions that lead to greenhouse gas emissions and binding of carbon dioxide in algae and plants and in clatharates.