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Fate and Persistence of Pathogens Subjected to Disinfection (Paperback)
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Fate and Persistence of Pathogens Subjected to Disinfection (Paperback)
Series: WERF Research Report Series
Expected to ship within 12 - 17 working days
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Disinfection of wastewater is a necessary treatment process for
protecting the public from potential exposure to pathogenic
microorganisms because many wastewater effluents are discharged
into water bodies that may be used for recreation or as future
drinking water supplies. Two common forms of disinfection are
chlorine and ultraviolet (UV) light. However, microorganisms differ
in their susceptibility to UV and chlorine disinfectants. It is
necessary to understand how different classes of pathogens respond
to UV and chlorine disinfection processes in wastewater to better
develop strategies for optimizing the treatment of pathogens in
wastewater. It is also recognized that water quality may impact
disinfection effectiveness, such as protection of pathogen by
particles and disinfectant demand. This study investigated
bacteria, viruses and protozoan pathogens. All species of bacteria
tested were susceptible to both UV and chlorine, despite
differences in antibiotic resistance and tendency to aggregate.
Upon exposure to disinfection conditions that could indicate
viability of the bacteria tested, but not culturability using
common methods, it was found that UV and chlorine were effective in
eliminating the capability of viable but non-culturable bacteria to
resuscitate and become re-infective. Clostridium spores were
resistant to free chlorine and UV disinfection but found to be
susceptible to long exposure to monochloramine. Cryptosporidium was
resistant to all chlorine forms but very susceptible to UV
irradiation. Pathogenic and indicator viruses tested were very
susceptible to free chlorine and UV disinfection. UV radiation
throughout the 200 to 300 nm range was effective for inactivation
of viruses and C. parvum, but wavelengths between 260-270 nm and
below 220 nm appeared to be more effective for viruses, suggesting
a possible advantage for polychromatic UV sources. Sequential
disinfection strategies were proposed and tested to enhance
inactivation of various microorganisms. One scenario integrated UV
disinfection followed by dynamic chloramination through addition of
free chlorine and subsequent transformation to combined chlorine.
Further, disinfection of microorganisms in wastewater presents
challenges that are inherent to the water matrix, such as pathogens
associated with particles. UV and chlorine were both effective for
disinfection of coliform in wastewater but chlorine was found to be
more effective during long contact times for inactivation of
particle associated coliform. In addition to coliform, both
Cryptosporidium parvum and Salmonella typhimurium were identified
as being particle associated in wastewater using molecular
approaches developed to detect microbes in environmental samples
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