WERF Research Report
2 total works
Disinfecting and Stabilizing Biosolids Using E-Beam and Chemical Oxidants
by Suresh D. Pillai and Robert S. Reimers
Published 13 June 2010
Available as an eBook only.
Municipal sewage and sludges can harbor a variety of infectious microorganisms as well as estrogenic compounds and their metabolites. Biosolids and other residuals generated from municipal wastewater treatment facilities need to be used for beneficial purposes such as land application. To reduce the potential for adverse environmental and human impacts, it is critical that novel approaches be investigated so that municipal biosolids can be disinfected and stabilized to reduce the pathogen loads and levels of estrogenic compounds.
The overall objective of this project was to demonstrate the disinfection and enhanced stabilization of municipal biosolids when high energy (10 MeV) Electron Beam (e-beam) technology is coupled with oxidants such as chlorine dioxide and ferrate. High energy E-Beam is effective as a disinfection technology. Significant reductions of all target organisms can be achieved in municipal biosolids depends on the dose that is employed. An e-beam treatment system utilizing 15 kGy e-beam dose has been designed and mathematically modeled and validated. Based on these engineering design considerations, e-beam treatment was shown to be cost-effective. There was synergistic disinfection of pathogens when e-beam is coupled with oxidants such as chlorine dioxide and ferrate. E-Beam at 8 kGy was unable to destroy estrogenic activity in the sludge samples. Ferrate (100 ppm) was capable of destroying estrogenic activity in the biosolid samples with or without the addition of e-beam irradiation. Chlorine dioxide (100 ppm) was not effective at destroying the estrogenic activity either by itself or in combination with e-beam. The combination of 100 ppm of ferrate with 8 kGy of e-beam promoted the stabilization of aerobic and anaerobic sludge samples as indicated by BOD, VSS and SOUR test results. The results demonstrate that 10 MeV e-beam is capable of cost-effectively inactivating a variety of bacterial and viral pathogens in aerobically and anaerobically digested biosolids. Overall, these results suggest that when e-beam is combined with ferrate significant reductions of microbial pathogens, estrogenic compounds and biosolid stabilization can be achieved.
Municipal sewage and sludges can harbor a variety of infectious microorganisms as well as estrogenic compounds and their metabolites. Biosolids and other residuals generated from municipal wastewater treatment facilities need to be used for beneficial purposes such as land application. To reduce the potential for adverse environmental and human impacts, it is critical that novel approaches be investigated so that municipal biosolids can be disinfected and stabilized to reduce the pathogen loads and levels of estrogenic compounds.
The overall objective of this project was to demonstrate the disinfection and enhanced stabilization of municipal biosolids when high energy (10 MeV) Electron Beam (e-beam) technology is coupled with oxidants such as chlorine dioxide and ferrate. High energy E-Beam is effective as a disinfection technology. Significant reductions of all target organisms can be achieved in municipal biosolids depends on the dose that is employed. An e-beam treatment system utilizing 15 kGy e-beam dose has been designed and mathematically modeled and validated. Based on these engineering design considerations, e-beam treatment was shown to be cost-effective. There was synergistic disinfection of pathogens when e-beam is coupled with oxidants such as chlorine dioxide and ferrate. E-Beam at 8 kGy was unable to destroy estrogenic activity in the sludge samples. Ferrate (100 ppm) was capable of destroying estrogenic activity in the biosolid samples with or without the addition of e-beam irradiation. Chlorine dioxide (100 ppm) was not effective at destroying the estrogenic activity either by itself or in combination with e-beam. The combination of 100 ppm of ferrate with 8 kGy of e-beam promoted the stabilization of aerobic and anaerobic sludge samples as indicated by BOD, VSS and SOUR test results. The results demonstrate that 10 MeV e-beam is capable of cost-effectively inactivating a variety of bacterial and viral pathogens in aerobically and anaerobically digested biosolids. Overall, these results suggest that when e-beam is combined with ferrate significant reductions of microbial pathogens, estrogenic compounds and biosolid stabilization can be achieved.
Developing Better Indicators for Pathogen Presence in Sewage Sludge
by Suresh D. Pillai
Published 15 December 2011
Available as an eBook only.
Today, more than eight million tons of biosolids are generated annually for land application nationwide. These biosolids contain beneficial plant nutrients, soil conditioners, and may also contain pathogenic bacteria, viruses, protozoa and parasites. The fate of pathogens is a concern for biosolids generators, applicators, and the general public. The ability to detect the presence of microbial pathogens and the resulting health risks in biosolids is a significant issue confronting the wastewater industry. Ideally, wastewater treatment plants should be able to monitor for specific pathogens in biosolids. Since it is almost impossible to detect and quantify the presence of all possible pathogens in waste matrices, there is a compelling need to identify a suite of indicators that can be used to predict the presence of pathogenic microorganisms in biosolids. The overall objective of this project was to identify those pathogens and surrogate indicator organisms that are at the highest density in raw sludge and determine their time-temperature-pH relationships in the laboratory under controlled conditions.
There were surprisingly low numbers of culturable enteric viruses (median values shown) ( 1 PFU/g), Salmonella spp ( 8 MPN/g), and helminth ova ( 1 ova/g) in the untreated sewage samples. Other pathogens, such as Shigella spp (25 MPN/g), Legionella spp (108 CFU/g), Aeromonas spp (108 CFU/g), MacConkey sorbitol-negative E.coli populations (104 MPN/g) were, however, present in larger numbers. When molecular PCR-based methods were used, the presence of gene sequences indicative of pathogens such as Adenovirus (107 gene copies/g), Giardia spp (105 gene copies/g) was evident. Other organisms such as aerobic spores (106 CFU/g), Cl. perfringens spores (106 CFU/g), fecal coliforms (108 MPN/g), E.coli (106 MPN/g), Enterococci (106 MPN/g), somatic coliphages (105 PFU/g) and male-specific coliphages (105 PFU/g) were present in large numbers. These results suggest that a suite of microorganisms which includes coliphages, enterococci, E.coli, fecal coliforms can be used to monitor the fate of microorganisms in sewage sludges.
Time-temperature studies were performed for a suite of organisms that included fecal coliforms, E. coli, Salmonella spp., somatic coliphages, male-specific coliphages, and poliovirus. The results indicate that of all organisms, coliphages are the most tolerant of all possible sewage-indicator organisms. They were able to withstand 60C for up to 120 minutes. Among bacteria, E.coli was the most conservative indicator organism, being able to at times withstand temperatures as high as 60C for up to 120 minutes. These results suggest that coliphages and E.coli are suitable as viral and bacterial indicators respectively to monitor the effectiveness of time and temperature treatments of municipal biosolids.
Today, more than eight million tons of biosolids are generated annually for land application nationwide. These biosolids contain beneficial plant nutrients, soil conditioners, and may also contain pathogenic bacteria, viruses, protozoa and parasites. The fate of pathogens is a concern for biosolids generators, applicators, and the general public. The ability to detect the presence of microbial pathogens and the resulting health risks in biosolids is a significant issue confronting the wastewater industry. Ideally, wastewater treatment plants should be able to monitor for specific pathogens in biosolids. Since it is almost impossible to detect and quantify the presence of all possible pathogens in waste matrices, there is a compelling need to identify a suite of indicators that can be used to predict the presence of pathogenic microorganisms in biosolids. The overall objective of this project was to identify those pathogens and surrogate indicator organisms that are at the highest density in raw sludge and determine their time-temperature-pH relationships in the laboratory under controlled conditions.
There were surprisingly low numbers of culturable enteric viruses (median values shown) ( 1 PFU/g), Salmonella spp ( 8 MPN/g), and helminth ova ( 1 ova/g) in the untreated sewage samples. Other pathogens, such as Shigella spp (25 MPN/g), Legionella spp (108 CFU/g), Aeromonas spp (108 CFU/g), MacConkey sorbitol-negative E.coli populations (104 MPN/g) were, however, present in larger numbers. When molecular PCR-based methods were used, the presence of gene sequences indicative of pathogens such as Adenovirus (107 gene copies/g), Giardia spp (105 gene copies/g) was evident. Other organisms such as aerobic spores (106 CFU/g), Cl. perfringens spores (106 CFU/g), fecal coliforms (108 MPN/g), E.coli (106 MPN/g), Enterococci (106 MPN/g), somatic coliphages (105 PFU/g) and male-specific coliphages (105 PFU/g) were present in large numbers. These results suggest that a suite of microorganisms which includes coliphages, enterococci, E.coli, fecal coliforms can be used to monitor the fate of microorganisms in sewage sludges.
Time-temperature studies were performed for a suite of organisms that included fecal coliforms, E. coli, Salmonella spp., somatic coliphages, male-specific coliphages, and poliovirus. The results indicate that of all organisms, coliphages are the most tolerant of all possible sewage-indicator organisms. They were able to withstand 60C for up to 120 minutes. Among bacteria, E.coli was the most conservative indicator organism, being able to at times withstand temperatures as high as 60C for up to 120 minutes. These results suggest that coliphages and E.coli are suitable as viral and bacterial indicators respectively to monitor the effectiveness of time and temperature treatments of municipal biosolids.