Contribution of chemical precipitation to the membrane fouling in a high-solids type anaerobic membrane bioreactor treating OFMSW leachate

Anaerobic membrane bioreactors (AnMBR) were a promising technology to treat high-strength wastewater; however, inorganic precipitation trigged membrane fouling was an obstacle when treating leachate produced from the organic fraction of municipal solid waste. A flat sheet submerged AnMBR was therefore operated for 61 days to treat leachate with total solids in reactor reaching 57 g/L. The results obtained in this study found that approximately 95%, 74%, and 84% of the Ca, Mg, and P were removed through the formation of complex precipitates. Calcite was the dominant precipitation form. There were 17.4 mg-Ca/cm(2), 1.3 mg-P/cm(2), and 0.4 mg-Mg/cm2 residues attached to the membrane surface. Those materials were removed by immersing in a 2% citric acid solution and thus the membrane filtration ability was completely recovered. By the end, the concentration of inorganic materials inside the AnMBR accumulated to 42 g/L, accounting for 73% of the total solids. The trans-membrane pressure slightly increased from 3.1 kPa to 4.2 kPa indicating the sustainability of this high-solids type AnMBR. The chemical precipitation induced 91% removal of phosphors from leachate. Conclusively, this study may provide new insights into the formation of membrane fouling in a leachate treatment AnMBR.