Influence of phosphorus precipitation on permeability and soluble microbial product concentration in a membrane bioreactor.

Many articles have been published on coagulant dosing in membrane bioreactors, though few have been long-term studies examining the treatment of real wastewater. This study summarises the results of a membrane bioreactor pilot-plant (flat sheet membrane, nominal pore size 0.03 μm) that treated real municipal wastewater for two-years. Both influence of phosphorus precipitation by ferric sulphate on membrane permeability (flux decrease) and soluble microbial product concentration (especially on carbohydrates and proteins) were monitored. Flux decrease over work cycles lasting several months without phosphorus precipitation were compared to two periods with precipitation. X-ray elemental diffractometry of the filtration cake showed differences in the main contributors to inorganic fouling, with decreases in Ca and Si during operation with coagulant addition, and an increase in Fe.