AWWA MTC64556

The combination of lime softening, chlorination, clarification and filtration have long been used as a treatment process in beverage plants because it provides consistent water quality. However, these processes require a very large plant area, generate a large volume of sludge that causes disposal problems, resulting in creating more problems than the benefits they offer. Chlorination produces trihalomethanes (THMs) and other byproducts which are detrimental to health and gives a taste to the final products. Using submerged spiral wound ultrafiltration membranes integrated with lime softening may replace the conventional lime softening, clarification and filtration processes. This research was conducted to demonstrate the feasibility of integrating immersed ultrafiltration (UF) membrane with lime softening. A pilot unit consisting of lime reactor and UF system treating municipal water supply was operated for a period of 1800 hours, at various pH levels ranging from 7.3 to 11.2, and at membrane flux rates of 15, 30 and 45 gfd. The filtrate from the pilot unit achieved alkalinity reduction to 20 to 30 mg/L preferred by carbonated soft drinks bottlers, with lime dosage close to the calculated value. The filtrate turbidity during the test was consistently 0.05 NTU. The TMP values obtained during the test ranged from 0.1 to 2.5 psi, while the permeability values ranged from 18.19 to 29.6 gfd/psi. The increase in flux resulted in a corresponding increase in TMP, and the increase in operating pH increases the rate of TMP. Permeability decreases with increasing operating pH. The total organic carbon (TOC) reduction ranges from 2.6 % to 15.8% with increasing operating pH. No scaling of the UF membranes was observed during the test. A thirty day UF membrane cleaning interval was predicted. The results from this study can be used as the basis of designing and operating a full scale Integrated Lime Softening UF Treatment Plant. Includes 12 references, tables, figures.