The Forward Osmosis Secondary Treatment (FOST) subsystem will be designed to treat the effluent of the primary treatment biological system. The FOST subsystem will be designed to remove suspended and dissolved solids in the processed wastewater effluent from the bioreactor. These contaminants have good rejection performance but high membrane fouling potential using conventional pressure-driven membrane techniques. The FOST approach addresses this issue through incorporation of FO pretreatment which allows conventional reverse osmosis (RO) to be used to reject these contaminants effectively without premature fouling due to micellar surfactant aggregates. ARC will complete design of the FOST during the first year of effort, and complete fabrication early in the second year. The FOST system will be tested to verify it meets design specifications before being delivered to Johnson Space Center for integration as part of the Alternative Water Processor.