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Inactivation of faecal indicator bacteria in a roof‐captured rainwater system under ambient meteorological conditions
Author(s) -
Ahmed W.,
Richardson K.,
Sidhu J.P.S.,
Jagals P.,
Toze S.
Publication year - 2014
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.12342
Subject(s) - rainwater harvesting , indicator bacteria , environmental science , bacteria , indicator organism , biology , microbiology and biotechnology , environmental chemistry , fecal coliform , ecology , environmental engineering , water quality , chemistry , genetics
Abstract Aims In this study, faecal indicator bacteria ( FIB ) namely E scherichia coli and E nterococcus spp. were seeded into slurries of possum faeces and placed on the roof and in the gutter of a roof‐captured rainwater ( RCR ) system. The persistence of FIB in these circumstances was determined under ambient climatic conditions. FIB persistence was also determined under in situ conditions in tank water using diffusion chambers. Methods and Results The numbers of surviving FIB at different time intervals were enumerated using culture‐based methods. Both FIB were rapidly inactivated on the roof under sunlight conditions ( T 90 = 2 h) compared with shade conditions ( T 90 = 9–53 h). Significant differences were observed between sunlight and shade conditions on the roof for both T 90 values of E . coli ( P < 0·001) and E nterococcus spp. ( P < 0·001). E. coli showed biphasic inactivation patterns under both clean and unclean gutter conditions. E nterococcus spp., however, showed rapid inactivation ( T 90 = 2 h for the clean gutter and T 90 = 6 h for the unclean gutter) compared with E. coli ( T 90 = 22 h for the clean gutter and T 90 = 20 h for the unclean gutter). Significant differences were also observed between the T 90 values of E . coli and E nterococcus spp. for both clean ( P < 0·001) and unclean ( P < 0·001) gutters. Both E . coli and E nterococcus spp. showed nonlinear biphasic inactivation in tank water. Significant difference was observed between the T 90 value of E . coli inactivation compared with E nterococcus spp. ( P < 0·001) in the tank water. Conclusions In this study, FIB were observed to survive longer ( T 90 = 9–53 h) on the roof under shade conditions compared with sunlight conditions ( T 90 = 2 h). If there is a rainfall event within two to three days after the deposition of faecal maters on the roof, it is highly likely that FIB would be transported to the tank water. When introduced into the tank, a relatively slow inactivation process may take place ( T 90 = 38–72 h). Significance and Impact of the Study The presence of FIB in water indicates faecal pollution and potential presence of enteric pathogens. Therefore, the information on the resilience of FIB , as obtained in this study, can be used for indirect assessment of health risks associated with using roof‐captured rainwater for potable and nonpotable purposes.