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.

Automated summary

This study operated an AnMBR to treat high-strength leachate and successfully removed calcium, magnesium, and phosphorus through chemical precipitation. The membrane filtration ability was completely recovered by removing the residues attached to the membrane surface. The AnMBR showed good sustainability in treating high-strength wastewater.