AWWA WQTC65927

The efficacy of a combined AER/UF process for the polishing treatment of a high dissolved organic carbon (DOC) content surface water pretreated by coagulation/flocculation was investigated. In the first part of the study, the impact of resin dose, contact time and resin bead size on DOC removal was evaluated at lab-scale (batch experiments) using a strong base AER on a high DOC content surface water (> 8 mg DOC/L). Results showed a significant impact of resin dose and bead size on the kinetic removal of DOC for short contact times (i.e. <15 min). For resin dose higher than 700 mg/L and median bead size below 250 µm DOC removal remained constant after 30 minutes contact times with very high removal rates (80%). For the second part of the study, optimum AER treatment conditions were applied in combination with UF membrane filtration. Membrane filtration tests were conducted at pilot-scale with a "high DOC content" clarified water (3 mg DOC/L). They showed that a more severe fouling was observed for each filtration run in the presence of AER. This fouling was shown to be mainly reversible and caused by the progressive attrition of the AER through the centrifugal pump leading to the production of resin particles below 50 µm in diameter. Complementary experiments conducted in MilliQ water confirmed the strong reversible fouling potential of resin particles <50 µm. More important, results showed that irreversible fouling (loss of permeability recorded after backwash) was significantly lowered in the presence of AER (20 % of permeability loss in the presence of AER after 75 L of water filtered through the membrane as compared to 35 % in absence of resin). In addition, the DOC content of the clarified water was reduced to l.8 mg/L (40% removal rate), concentration that remained almost constant all along the experiment. Includes 15 references, tables, figures.