Application of Membrane Distillation for Secondary Effluent Treatment towards Water Recovery

This paper presented the application of Direct Contact Membrane Distillation (DCMD) for the treatment of the secondary effluent of a municipal wastewater treatment plant (WWTP) to produce fresh water. The purification studies conducted at various feed temperatures demonstrated that the permeate water flux increased and that the water flux decreased quickly at the higher feed temperature. However, the electrical conductivity of permeate remained consistent at about 2.0 μS/cm. The majority of pollutants found in the secondary effluent, including SS, COD, nitrate, nitrite, phosphate, and total coliform, were entirely eliminated throughout the MD treatment process using a bi-composite membrane made of polytetrafluoroethylene and polypropylene at different feed stream temperatures. Ammonia had a limited rate of rejection, though. Protein and organic/inorganic aggregates made up the majority of the foulants were found on the membrane surface, not the inner pores. The long-term test, which involved an 18-day operation with a feed solution concentration of ten times, revealed that no wetness issue was seen despite a notable foulant deposit and reduction in water flux.