Primary‐effluent wastewater from the Allegheny County Sanitary Authority (Pennsylvania) was used as a surrogate for combined‐sewer‐overflow waters contained in the sewershed. Pathogens contained in combined‐primary‐effluent wastewaters or combined‐sewer overflows (CSOs) may pose a human‐health threat to those coming in contact with such receiving waters. Polymeric ultra‐ and nano‐membranes can be used to capture these microorganisms from CSOs. This research investigates the ability of polymeric hydrophobic and hydrophilic membranes, ranging in pore size from 0.2 to 0.8 μm, to remove pathogen‐indicator organisms (Escherichia coli, enterococcus, and fecal coliforms). Membranes, with pore size 0.45 μm and smaller, were able to reduce the bacteria levels to nondetectable levels, with the sole exception of one membrane with pore size 0.3 μm.
Dead-end microfiltration was used to evaluate the permeate flux and fouling mechanisms by primary sewage effluent from a local wastewater treatment plant for seven polymeric membranes ranging in pore size from 0.2 to 0.8 m. Permeate flux rates were evaluated during separate filtration runs at transmembrane pressures of 1.03 and 2.06 bar and during a periodic increase in filtration pressure from 1.03 to 4.14 bar in a single run. The steady-state permeate flux rates were very similar for all pressures and pore sizes, and there was little benefit from increasing the pressure during a microfiltration run. Hydrophobic membranes generally gave lower initial flux rates than hydrophilic membranes of the same pore size. This study suggests that the permeate flux reduction during a filtration run was mostly due to the cake buildup on the membrane surface, while the internal fouling of the membrane pores was limited.
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