Study On MBR And Combined Process For Micro-polluted Surface Water Treatment

Freshwater resource is in short supply in China, and organic pollution widely exists in the source of drinking water, however the standard of drinking water quality is upgrading. To solve these problems and produce safe drinking water, a test of membrane bioreactor (MBR) for drinking water treatment was carried on. The micro-polluted surface water taken from a lake in Tianjin University campus was used as raw water in this test, quality of treated water before and after powdered activated carbon (PAC) dosing was examined.Whether dosing PAC or not, the aesthetic quality and NH3-N of treated water all could reach the requirement of Water Quality Standards for Urban Water Supply (CJ/T206-2005). PAC dosing ensured that CODMn in the treated met the requirement of the standard. It also reduced the cumulation of organic matter in the mixed liquor and relieved the membrane fouling.Trace-quantity phenol in raw water was removed rapidly and effectively by PAC absorption and bio-degradation. The absorption equilibrium could be reached within 2 hours, and the absorption capability was 0.6 mg/g. When the concentration of phenol in raw water was 149.4μg/L, it could be bio-degraded completely in 90 minutes. The average membrane rejection rate of bacteria, coliform and thermotolerant coliform was 98.42%, 95.99% and 98.78% respectively. The explanation of lower rejection rate was discussed. When the dosage of chlorine was 1.25-1.5mg/L, the concentration of residual chlorine and the micro-biological indexes in the treated water could meet the requirement of the standard.Organic and biological fouling were the main form of membrane fouling. Physical cleaning and NaOCl cleaning resumed the membrane flux effectively. The removal of the organic matter with molecular weight between 500 and 10 000 Dalton mostly depended on PAC absorption and bio-degradation, while the membrane separation was responsible for removing the organic mater with the molecular weight above 10 000 Dalton.The test results showed that using PAC-MBR combined process for micro-polluted surface water treatment, excellent quality of treated water could be abtained, the indexes such as turbidity, CODMn and NH3-N could reach the requirement of the standard entirely. The system run stably and also had strong ability against shock loading.