A Tale of Two Winters: Operational Differences to Increase MBR Capacity in Cold Weather Months

Canton Water Reclamation Facility (Canton) has faced hardships meeting capacity during winter months since beginning operation as a membrane bioreactor (MBR) plant. In an attempt to resolve this issue, Canton collaborated with Kubota Membrane USA Corporation to identify technical causes of the MBR plant. Cold water temperatures created an environment that favored a high foulant concentration in the membrane tanks which prevented the membranes from filtering at design flows. Foulants were mainly quantified by tracking soluble chemical oxygen demand (sCOD) nearly every day 2019 to 2020, and tabulating historical data to develop a trend, relative to water temperature and membrane tank mixed liquor suspended solids concentration (MLSS). It was put forth that increasing the MLSS target value may reduce the sCOD; this was the case and it reduced the sCOD by approximately half in 2020, relative to 2019. In addition to an accumulation of foulants, MLSS and trans-membrane pressure (TMP) limits were causing operators to limit flow to individual treatment trains during high flow events. To this end, Kubota conducted tests at a pilot plant to validate increasing these operational upper limits. Fortunately, these tests were successful, and limits were increased from14,000 mg/L to 15,000 mg/L and 3.0 psi to 6.0 psi for MLSS and TMP, respectively. Nearing the end of the 2020 winter, two high flow events occurred with peak instantaneous flows exceeding 80 million gallons per day (mgd). During these events, the membranes were able to filter without issue.

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