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FROM : LRICHRISTINR FAX NO. : 650508%ee Jan. 2e 2003 o6:44PM PS entuic viruses may be estinlowd itochastically by numerical simulation such as Monte Carlo methods. The U S. EPA Sur&ce WaterTteatment Rule (SWTR) (U.S. EPA, 1989) defines an acceptable risk as less than or equal to one pathogen- derived infection per 10,000 population per year from use of a public water supply. Therefore, if a 10 annual risk of infection (leas than or equal to one infection per 10,000 population per year) is set as an acceptable risk for water reuse, the reliability can be calculated as the percent of time that infection risk due to exposure to amterie viruses in reclaimed water is less than the acceptable risk. Reliability cstimstiom for each exposure scenario are presented in Table I. FTOm the results of the analysis presented in Table 1, the reliability or relative safety of water rouse can be assessed in comparison to domestic water supplies that meet the SWTR. When the disinfected, filtered secondary effluent (tertiary troatmeut) is chlorinated az about 10 atg/L, there is virtually no difference in the probability of enteric virus infection whethgZadlimee water or domestic water is used for golf course / 1 4m b AIc,on, crop irrigation, and groundw%cr recharge. tlo� eniing on the water u!ality of the secondary effluent, them is a considerable difference in hWEh risks assse rated with ptposgrp aEonal impoundments when body contact its and �wim m�ing�may tatc�e fia�cce. Similar observations can be me& for the use of ch"ated spo secondary effluent reclahoed water from contact filtration with chorine doses of below 5 mg/L. Table 1. Reliability of various witter reuse applications meeting the criterion of one enteric virus infection per 10,000 population per year Adapted fivm Tssaka, et al., 19%. Secondary Reliability. % Treatment process cfrlu= Golf coupe Crop Reoreatims! Crointdwau r fromplaut Irrigation taigation impoundment recharge Full treaunant or onnnet A 100 IOD 77 100 lilirautm with 10 mglL B too 100 99 I(MI ohloriw dose achieving 5.2 C 100 LOO 98 100 log nnnovals of viruses D 99 LOD 62 Igo Chlnrmadnnofsecondary A 95 too 10 100 efflu.= with 7 mg/L B loo I W 81 100 chlorine achieving 3.9Ing C 99 100 93 100 m�vals of ADAM 0 a4 LOO 11 too :onset filtration with A 100 100 48 100 5mWLchlorineclose 3 1(a) IOD 96 100 achieving 4.7 log removals C 100 I00 97 100 arvituws D 97 100 39 100 Adapted fivm Tssaka, et al., 19%.