Forward osmosis for wastewater treatment and energy recovery: a techno-economic analysis

A novel wastewater treatment system was investigated using forward osmosis membranes to treat municipal wastewater. Treatment by forward osmosis was determined to cost $10 million per million gallons per day (MGD) of wastewater capacity over a 20-year lifetime, with an energy consumption of 870 kWh per million gallons. A case study at the Arcata Wastewater Treatment Plant was conducted to investigate a treatment system that combines energy recovery from algae biomass with forward osmosis membrane treatment using local seawater as a draw solution. Total system cost was calculated to be $29.7 million over a 20-year lifetime with a 2.3 MGD capacity. Energy recovery was found to offset the parasitic energy requirements of the system and produce an excess of 1,200 MWh annually. This research demonstrates a proof-of-concept study on the techno-economic feasibility of forward osmosis membranes to (1) treat municipal wastewater and (2) concentrate wastewater for energy recovery via anaerobic digestion of algae biomass