Chlorine requirement for biologically stable drinking water after nanofiltration

There is considerable interest in minimizing the chlorine residual in Japan's tap water because of increasing consumer complaints about the chlorinous odor of drinking water. However, minimization of the chlorine residual requires stricter control of biodegradable organics in finished water to...

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Bibliographic Details
Published in:Water science & technology. Water supply 2014-06, Vol.14 (3), p.405-413
Main Authors: OHKOUCHI, Y, YATA, Y, BUN, R, ITOH, S
Format: Article
Language:English
Subjects:
Applied sciences
Bacteria
Biodegradability
Biodegradation
Biofilms
Buildings. Public works
Chlorination
Chlorine
Control stability
Distribution
Drinking water
Exact sciences and technology
Filtration
Heterotrophic bacteria
Nanofiltration
Nanotechnology
Odor
Odors
Odour
Organic carbon
Regrowth
Removal
Seasonal variation
Seasonal variations
Water distribution
Water engineering
Water supply. Pipings. Water treatment
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Summary:There is considerable interest in minimizing the chlorine residual in Japan's tap water because of increasing consumer complaints about the chlorinous odor of drinking water. However, minimization of the chlorine residual requires stricter control of biodegradable organics in finished water to ensure biological stability during water distribution. In this context, we investigated the improvement of biological stability of drinking water by nanofiltration (NF). The removal of assimilable organic carbon (AOC) was 52% on average, but showed large seasonal variation. It was found to be difficult to maintain the acceptable AOC level for biologically stable water by NF. In addition, significant bacterial regrowth in NF permeates was still observed without chlorination, although 52% AOC was removed. Then, the chlorine concentration required to prevent bacterial regrowth during distribution of nanofiltrated water was determined using continuous-flow reactor systems. The heterotrophic plate counts (HPC) densities in biofilm were monitored at different chlorine conditions. The results indicated that the NF process could significantly reduce the chlorine requirement of the finished water. The relationship between free chlorine residual and HPC in biofilm formed from 1 μgC AOC showed that a trace level of chlorine residual,
ISSN:1606-9749
1607-0798
DOI:10.2166/ws.2013.214