AWWA MTC50297

Three groups of challenge studies were conducted to evaluate the microbiocidal effectiveness of the NF membranes. In the first set of tests, the log removal of MS2 was investigated. In the second and third group of experiments, the membranes were challenged with Cryptosporidium parvum oocysts and Giardia muris cysts, respectively. The nanofiltration biological challenge studies demonstrated five to six log removals of G. muris cysts and C. parvum oocysts. Four or more logs of MS2 were removed with nanofiltration membranes. Maintenance of membrane integrity was critical to assuring process efficacy. When membrane element integrity was compromised, microorganisms were detected in the permeate. Changes in membrane element integrity were not necessarily reflected by changes in permeate water quality; however, and E. coli tracer study was an effective method for detecting compromised membrane vessels. Includes 4 references, tables.