treatmenta Indicative Table A3.6 (continued) treatment processb Use Log reduction Indicative Water targetsa On-site exposure quality preventive Log reductions reduction criteria achievable by measures (log reductions) V 1.3 Option 1C: No treatment 0 Drip irrigation of Municipal use, plants P 0.8 with drip B 1.3 4.0 Not applicable irrigation and required including <10 NTU (95th Option 2: V 2.4 disinfection ongoing education percentile), <2 NTU Dual reticulation P 1.9 of householders and (target) with indoor and 12.5 cross- plumbers (for dual B 2.4 outdoor use OR E. coli reticulation) >>4.0 <1/100 mL Irrigation of >>4.0 commercial food Turbidity: <25 ion (if crops NTU (maximum), NTU = nephelometric turbidity units; UV = ultraviolet. a Given as where V = virus, represented by adenovirus type 41 for UV, which is more resistant and better characterised than rotavirus; P = protozoa, represented by ‘V’, ‘P’or ‘B’, spp. oocysts; B = bacteria, represented by which is more resistant and better characterised than Cryptosporidium E. coli, Campylobacter. b Indicative UV doses given are based on US EPA (2006) and refer to validated doses taking into consideration RED bias and other factors. 67 Appendix 3: Health risk assessment and management
Table A3.6 (continued) Use Log reduction targetsa Indicative treatment processb Log reductions achievable by treatmenta On-site preventive measures Indicative exposure reduction (log reductions) Water quality criteria Option 1C: Municipal use, with drip irrigation V 1.3 P 0.8 B 1.3 No treatment 0 Drip irrigation of plants 4.0 Not applicable Option 2: Dual reticulation with indoor and outdoor use OR Irrigation of commercial food crops V 2.4 P 1.9 B 2.4 (if and disinfection 12.5 >>4.0 >>4.0 cross- required including ongoing education of householders and plumbers (for dual reticulation) Turbidity: <25 NTU (maximum), <10 NTU (95th percentile), <2 NTU (target) E. coli <1/100 mL NTU = nephelometric turbidity units; UV = ultraviolet. a Given as ‘V’, ‘P’or ‘B’, where V = virus, represented by adenovirus type 41 for UV, which is more resistant and better characterised than rotavirus; P = protozoa, represented by Cryptosporidium spp. oocysts; B = bacteria, represented by E. coli, which is more resistant and better characterised than Campylobacter. b Indicative UV doses given are based on US EPA (2006) and refer to validated doses taking into consideration RED bias and other factors. Appendix 3: Health risk assessment and management 67 ion
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