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

Recent scientific studies have indicated that industrial and pharmaceutical chemicals in our water environment at very low levels may have significant impacts on human and environmental health. Many of these contaminants are not removed using conventional water treatment processes. The use of ultraviolet (UV) light for disinfection of water is becoming increasingly common. The use of UV for photolysis and oxidation holds promise as a clean, effective technology for transforming environmental pollutants of concern.? The goal of this research was to assess, through use of bioassays and chemical analyses, the degradation, by-product formation, and subsequent toxicity of endocrine disrupting contaminants (EDCs) following UV and UV/H2O2 oxidation treatment of water. Known EDCs were investigated for treatability and subsequent formation of estrogenic by-products over a range of UV operating points. Evaluations of treatment were made by analytical chemistry and by assessing changes in estrogenic activity utilizing both in vitro and in vivo based assays. UV light alone either from LP or MP sources at low or high UV fluences will not be effective for degradation of the estrogenic chemicals studied, therefore, utilities should not expect any effects on estrogenic contaminants under UV disinfection conditions. For effective treatment of the EDCs studied, and likely others, UV can be used in combination with low levels of hydrogen peroxide to achieve advanced oxidation conditions for destroying parent compounds and residual estrogenic activity.? The use of an estrogen screening assay should complement any chemical analysis when studying treatment processes that result in transformation of an estrogenic parent contaminant to its known or unknown breakdown products. These assays can monitor residual estrogenic activity of any by-products, monitor estrogenic activity for mixtures of pollutants, and provide an end point marker, indicating effective treatment levels. ? ?

There is currently intense interest in the use of ultraviolet technology for helping to meet future regulations relating to improved microbial inactivation and decreased disinfection byproducts (DBPs).? Much of this interest has been fueled by recent research indicating the effectiveness of UV technologies for the inactivation of Cryptosporidium.? This scientific discovery, combined with proposed regulations concerning DBPs in the United States, has resulted in a need to evaluate the feasibility and effectiveness of UV irradiation for use as a disinfectant for drinking water.The objectives of this project were to:(1) develop and evaluate physical, chemical, and biological methods for calculating effective germicidal UV dose from medium-pressure (MP) and Pulsed-UV (P-UV) lamps;(2) establish a UV dose/log inactivation relationship for specific bacterial and viral indicators for MP and P-UV lamps;(3) determine the extent of photoreactivation and dark repair of heterotrophic bacteria after treatment by MP and P-UV lamps; and(4) compare the ability of MP and P-UV lamps to inactivate?Cryptosporidium.???Originally published by AwwaRF for its subscribers in 2003?This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

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

Recent scientific studies have indicated that industrial and pharmaceutical chemicals in our water environment at very low levels may have significant impacts on human and environmental health. Many of these contaminants are not removed using conventional water treatment processes. The use of ultraviolet (UV) light for disinfection of water is becoming increasingly common. The use of UV for photolysis and oxidation holds promise as a clean, effective technology for transforming environmental pollutants of concern.? The goal of this research was to assess, through use of bioassays and chemical analyses, the degradation, by-product formation, and subsequent toxicity of endocrine disrupting contaminants (EDCs) following UV and UV/H2O2 oxidation treatment of water. Known EDCs were investigated for treatability and subsequent formation of estrogenic by-products over a range of UV operating points. Evaluations of treatment were made by analytical chemistry and by assessing changes in estrogenic activity utilizing both in vitro and in vivo based assays. UV light alone either from LP or MP sources at low or high UV fluences will not be effective for degradation of the estrogenic chemicals studied, therefore, utilities should not expect any effects on estrogenic contaminants under UV disinfection conditions. For effective treatment of the EDCs studied, and likely others, UV can be used in combination with low levels of hydrogen peroxide to achieve advanced oxidation conditions for destroying parent compounds and residual estrogenic activity.? The use of an estrogen screening assay should complement any chemical analysis when studying treatment processes that result in transformation of an estrogenic parent contaminant to its known or unknown breakdown products. These assays can monitor residual estrogenic activity of any by-products, monitor estrogenic activity for mixtures of pollutants, and provide an end point marker, indicating effective treatment levels. ? ?

There is currently intense interest in the use of ultraviolet technology for helping to meet future regulations relating to improved microbial inactivation and decreased disinfection byproducts (DBPs).? Much of this interest has been fueled by recent research indicating the effectiveness of UV technologies for the inactivation of Cryptosporidium.? This scientific discovery, combined with proposed regulations concerning DBPs in the United States, has resulted in a need to evaluate the feasibility and effectiveness of UV irradiation for use as a disinfectant for drinking water.The objectives of this project were to:(1) develop and evaluate physical, chemical, and biological methods for calculating effective germicidal UV dose from medium-pressure (MP) and Pulsed-UV (P-UV) lamps;(2) establish a UV dose/log inactivation relationship for specific bacterial and viral indicators for MP and P-UV lamps;(3) determine the extent of photoreactivation and dark repair of heterotrophic bacteria after treatment by MP and P-UV lamps; and(4) compare the ability of MP and P-UV lamps to inactivate?Cryptosporidium.???Originally published by AwwaRF for its subscribers in 2003?This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below