Microbiological quality before and after nanofiltration

Abstract

A long‐term study identifies the benefits accrued when a distribution system fed with biologically treated water switches to a nanofiltered supply. The authors investigated microbiological behavior of a distribution system supplied initially with biologically treated water and then with nanofiltered water. Their purpose was to identify and evaluate the changes in microbiological water quality attributable to modifications in water treatment at the plant. During the course of the study, all data from various indicators of microbiological quality (i.e., heterotrophic plate counts, coliform enumeration, total direct counts, and fixed bacterial biomass) showed similar trends. Results indicated that the use of nanofiltration allows utilities to reduce chlorination of treated water and at least maintain or increase the microbiological quality of distributed water for areas with high residence times.

A comprehensive review of nanofiltration membranes:Treatment, pretreatment, modelling, and atomic force microscopy

“…Koyuncu and Yazgan [37] had good results in treating salty and polluted water from Kucukcekmece Lake in Istanbul using the TFC-S NF membrane. NF membranes were also found to be able to remove viruses and bacteria from surfaces quite successfully [11,[38][39][40][41]. Reiss et al [42] used an integrated membrane system of microfiltration with NF to remove Bacillus subillus spores from 5.4 to 10.7 log.…”

Understanding distribution system WATER QUALITY

“…Among water quality factors, water temperature is probably the most important one affecting coliform occurrences in a network (LeChevallier et al, 1996;Volk & Joret, 1994;LeChevallier, 1990). The level of biodegradable organic matter (BOM) has been shown to strongly affect the regrowth of heterotrophic bacteria in pilotand full-scale distribution systems (Laurent et al, 1999;Prévost et al, 1998;Laurent et al, 1997;Mathieu et al, 1992;Servais et al, 1992;Van der Kooij, 1992). The effect of BOM on coliform occurrences is not as clearly established, but some studies suggest its effect is significant (Laurent et al, 1999;LeChevallier et al, 1996;Volk & Joret, 1994).…”

“…The level of biodegradable organic matter (BOM) has been shown to strongly affect the regrowth of heterotrophic bacteria in pilotand full-scale distribution systems (Laurent et al, 1999;Prévost et al, 1998;Laurent et al, 1997;Mathieu et al, 1992;Servais et al, 1992;Van der Kooij, 1992). The effect of BOM on coliform occurrences is not as clearly established, but some studies suggest its effect is significant (Laurent et al, 1999;LeChevallier et al, 1996;Volk & Joret, 1994). The presence of a disinfectant residual such as chlorine may control the number of cultivable bacteria in the bulk phase but seems to have a more limited effect on biofilm and on sediment (Van der Kooij et al, 1999;Mathieu et al, 1992;LeChevallier et al, 1990).…”

Explaining the occurrence of coliforms in distribution systems

“…The benefits generated by reducing the biodegradable content of treated water through biological treatment have been demonstrated for the microbiological quality of water (Prévost et al, 1998) and for biofilm density (Volk & LeChevallier, 1999). Similarly, Laurent et al (1999) noted a reduction in the number of positive coliform samples in a distribution system following the installation of a nanofiltration treatment. Finally, certain lubricating oils were shown to release substantial levels of AOC into the water, which could in turn lead to increased bacterial growth (Sidorowicz, 1996; White & LeChevallier, 1993).…”