Water Reuse Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater (2012) / Chapter Skim
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Appendix A: Details in Support of the Risk Exemplar in Chapter 6
Appendix A: Details in Support of the Risk Exemplar in Chapter 6
Pages 233-248
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From page 233... ...
Human adenovirus occurrence data in the exemplar Pathogen Occurrence in Secondary Effluents were collected from peer-reviewed literature, which The information and assumptions used to estimate used molecular biology–based genome quantification pathogen occurrence in undisinfected secondary waste- methods (He and Jiang, 2005; Albinana-Gimenez et water effluent as a starting point for the risk exemplar is al., 2006; Bofill-Mas et al., 2006; Haramoto et al., 2007; discussed in this section and summarized in Table A-1. Katayama et al., 2008; Fong et al., 2010; Schlindwein Pathogen reduction from subsequent disinfection and et al., 2010)
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and tissue culture assays were performed on ade the dose-response model for this organism has been novirus isolated from secondary effluent, it is estimated developed previously based on epidemiological studies that the ratio between genome copies and infectious (Haas et al., 1999)
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for Salmonella spp. For adenovirus and norovirus, re- In the exemplar, excluding dilution, the overall moval was assumed to follow the removal credit for reduction in Cryptosporidium is assumed to correspond viruses in the surface water treatment rule, which was to the 4-log removal required by EPA, and the reducjudged to be negligible.
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. and partially denitrified secondary effluent, which has Findings from these field studies demonstrated that been subjected to granular media filtration, is applied infiltration into a relatively homogeneous sandy aquifer to surface spreading basins with subsequent soil aquifer can achieve up to 8-log virus removal over a distance of treatment (SAT)
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and groundwater wells. Given the usually low ies as well as a retention time of 6 months in the surface counts of Cryptosporidium in impaired source waters, spreading groundwater recharge case of the exemplar log removal studies under ambient conditions are not (much longer than is the case for any of the preceding practical.
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Pathogen Removal Assumed for Processes in Scenario 2 charged with reverse osmosis–treated reclaimed water will provide less favorable conditions for virus removal Process Adenovirus Norovirus Salmonella Cryptosporidium SAT + 6 mo 6 6 6 6 (99.9999%)
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Pathogen Chemical Occurrence in Secondary Effluents Removal Assumed for Processes in Scenario 3 Process Adenovirus Norovirus Salmonella Cryptosporidium For disinfection byproducts in secondary effluents, data were obtained from Krasner et al.
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240 TABLE A-5 Summary of Exemplar Calculations to Establish Pathogen Levels in Drinking Water for the Three Scenarios Scenario 1 De facto Reuse: Secondary effluent, disinfected with chlorine, diluted 95%, conventional water treatment Removal Removal in 2° Effluent through Discharge 95% Concentration in Die-off & WTP Influent Conventional Removal Drinking Water Concentration Disinfection Concentration dilution River Predation Concentration WTP by UV Concentration Norovirus 10,000 gc/L 0% 10,000 gc/l 95% 500 gc/L 0% 500 gc/L 99.99% 0.0% 0.050 gc/L Adenovirus 5,000 gc/L 0% 5,000 gc/L 95% 250 gc/L 0% 250 gc/L 99.99% 0.0% 0.025 gc/L Salmonella 500 CFU/L 99.80% 1.0 CFU/L 95% 0.1 CFU/L 0% 0.1 CFU/L 99.99% 96.8% 1.6E-07 CFU/L Cryptosporidium 17 oocyst/L 0% 17 oocyst/L 95% 0.85 oocyst/L 0% 0.85 oocyst/L 99.9% 90% 8.5E-05 oocysts/L Scenario 2 Secondary effluent, no disinfection, followed by SAT, 6 mo retention, no dilution, free chlorine disinfection 2° Effluent Concentration SAT Removal Concentration at Wellhead Removal by Chlorination Drinking Water Concentration Norovirus 10,000gc/L 99.9999% 1.0E-02 gc/L 99.99% 1.0E-06 gc/L Adenovirus 5,000 gc/L 99.9999% 5.0E-03 gc/L 99.99% 5.0E-07 gc/L Salmonella 500 CFU/L 99.9999% 5.0E-04 CFU/L 99.9999% 5.0E-10 CFU/L Cryptospoidium 17 oocyst/L 99.9999% 1.7E-05 oocysts/L 0.00% 1.7E-05 oocysts/L Scenario 3 Secondary effluent, MF, RO, UV/H202, groundwater injection, free chlorine disinfection Removal Removal through 2° Effluent Removal Removal through AWT Effluent Groundwater Wellhead Removal by Drinking Water Concentration through MF through RO UV/H2O2 Concentration Injection Concentration Free Chlorine Concentration Norovirus 10,000 gc/L 0% 97% 99.9999% 3.0E-04 gc/L 0% 3.0E-04 gc/L 99.99% 3.0E-08 gc/L Adenovirus 5,000 gc/L 0% 97% 99.9999% 1.5E-04 gc/L 0% 1.5E-04 gc/L 99.99% 1.5E-08 gc/L Salmonella 500 CFU/L 99.99% 99.99% 99.9999% 5.0E-12 CFU/L 0% 5.0E-12 CFU/L 99.9999% 5.0E-18 CFU/L Cryptosporidium 17 oocyst/L 99.99% 99.99% 99.9999% 1.7E-13 oocysts/L 0% 1.7E-13 oocysts/L 0% 1.70E-13 CFU/L
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Table A-8 lists the concentrations of the 24 chemicals in disinfected secondary effluent, and Table A-9 shows TABLE A-7 Summary of Quantitative Microbial Risk the concentrations for undisinfected secondary effluent. Assessment of Risk Exemplar Scenario 1 Scenario 2 Scenario 3 Assumptions Concerning Fate, Transport, and Organism De Facto Reuse SAT MF/RO/UV Removal A
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bRemaining after conventional surface water treatment (including coagulation/flocculation; filtration, free chlorine; residual chloramines) ; no transformation occurred in surface water.
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, a reclaimed water quality after microfil- and A-10 for the three scenarios for the source waters tration, reverse osmosis, and advanced oxidation (UV/ or the reclaimed water applied to the spreading or direct H2O2) is assumed.
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, and National Library of Medicine/National Institute of For each of the 24 chemicals identified in the Health maximum tolerated doses (MTDs) from which three water treatment scenarios, potential lifetime a drinking water action level can be derived (see also health risks were assessed by calculating margins of Chapter 5)
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<1 PFOS ng/L 12 54 <5 PFOA ng/L 11 21 dose metric is expressed as concentrations in drinking Risk Based Action Level (mg/L) = water.
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. Where of the risk exemplar.
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>0.4 >0.4 >0.4 NDMA Additional research to evaluate the effects of long-term, Disinfection Byproducts >2 Bromate N/A N/A low-level exposure to chemicals in reclaimed water >160 Bromoform 27 160 could provide additional insight on whether these areas Chloroform 16 80 16 >60 >60 >60 of uncertainty are biologically significant. DBCA >54 >140 DBAN N/A >80 >160 DBCM N/A >60 >60 DCAA 12 VERIFICATION >20 >20 DCAN N/A HAA5 6 12 12 The committee performed several levels of veriTHM 2.7 16 8 fication on this risk exemplar exercise to ensure that Pharmaceuticals the results are sound.
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