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rai <br /> SEH <br /> Building a Better World MEMORANDUM <br /> for All of Us" <br /> TO: Chris Larson, PE <br /> FROM: Simon McCormack <br /> DATE: March 12, 2020 <br /> RE: Surface Water Treatment <br /> SEH No. 150732 14.00 <br /> The Surface Water Treatment Rule was established in 1989 to protect public health from the pathogens Giardia <br /> lamblia and viruses. Following the original rule, additional rules have been established to further protect public <br /> health by addressing the pathogen Cryptosporidium, addressing risk trade-offs with disinfection and disinfection <br /> byproducts, and enhancing water system processes. <br /> The rules apply to all water systems using surface water and together they act to limit the levels of pathogens <br /> (viruses, Giardia lamblia, and Cryptosporidium)and turbidity in the water, as well as ensure adequate disinfection <br /> of the water throughout the treatment process. Adequate disinfection throughout the treatment process is <br /> determined by conducting disinfection profiling where a system's microbial inactivation is calculated over 12 <br /> consecutive months. <br /> The three pathogens targeted by the surface water treatment rules are regulated by required removal efficiencies <br /> called log removal. Surface water treatment processes must remove 99.99% (4-log)of viruses, 99.9% (3-log)of <br /> Giardia lamblia, and 99% (2-log)of Cryptosporidium. Further Cryptosporidium removal may be required if high <br /> concentrations are found through source water monitoring. Source water monitoring, which can be waived if the <br /> treatment processes achieve 5.5-log removal, requires 24 months of Cryptosporidium monitoring where the <br /> average Cryptosporidium concentration determines the bin classification and the additional removal requirements <br /> (see Table 4-1). Additional Cryptosporidium removal can be achieved through additional disinfection (e.g. UV), <br /> improved treatment processes, and other measures. <br /> Along with those three pathogens, turbidity, a measure of the cloudiness of the water, is regulated as it serves as <br /> an indicator of the overall water quality and filter effectiveness, and because high turbidity levels are often <br /> associated with high pathogen levels. Turbidity must be reported each month from each individual filter's effluent <br /> (I FE), as well as the combined filter effluent(CFE). The CFE turbidity must be monitored and recorded every four <br /> hours and at least 95% of the turbidity measurements must be less than or equal to 0.3 NTU. MDH must be <br /> contacted if any measurement exceeds 1 NTU. The IFE turbidity must be monitored and recorded every 15 <br /> minutes and measurements exceeding 0.5 NTU must be investigated. <br /> Table 1.Surface Water Treatment Rule Bin Classification <br /> ClassificationBin •• for • • . <br /> < 0.075 No Additional Treatment <br /> From 0.075- < 1.0 1 log of Additional Treatment(90%) <br /> From 1.0- < 3.0 2 log of Additional Treatment(99%) <br /> >_ 3.0 2.5 log of Additional Treatment(99.7%) <br /> Engineers I Architects Planners I Scientists <br /> Short Elliott Hendrickson Inc.,3535 Vadnais Center Drive,St.Paul,MN 55110-3507 <br /> SEH is 100%employee-owned I sehinc.com 1 651.490.2000 1 800.325.2055 1 888.908.8166 fax <br />