AWWA WQTC63971

The Washington State Department of Health (DOH) has been actively involved in the developmentof ultraviolet (UV) disinfection for regulatory credit since 2001. The City of Seattle's efforts to obtain LimitedAlternative to Filtration (LAF) designation for the Cedar River supply and efforts to use UVtechnology as a primary disinfectant prompted early involvement by DOH in reviewing validationprotocols, developing UV treatment technique violation (TTV) parameters, determining UVmonitoring and operating parameters, and developing monitoring and reporting forms. To date theDOH has granted regulatory disinfection credit to two surface water supplies in the State.DOH staff evaluated disinfection credit requirements for UV technology under three separate ruleapplications: the Surface Water Treatment Rule (SWTR) for Giardia lamblia inactivation; theLimited Alternative to Filtration (LAF) for Giardia lamblia and Cryptosporidium inactivation; and,the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) for Cryptosporidiuminactivation. Three separate regulatory approaches were developed since the regulatory basis forpathogen inactivation varies for each of these rule applications.For compliance with the SWTR, UV light can provide the primary Giardia lamblia inactivationbarrier. Water systems must calculate their minimum inactivation ratio (ratio of disinfectionprovided to disinfection required) on a daily basis. A water system incurs a TTV in any monthwhen the inactivation ratio is less than one on more than any day in that month. This inactivationrequirement served as the basis for evaluation of UV disinfection in accordance with the SWTR.Chemical disinfection is still required to inactivate viruses and provide a residual disinfectant asrequired by the SWTR.The UV disinfection requirements for a source that qualifies for a Limited Alternative to Filtrationwere developed based upon the criteria in the 1996 Safe Drinking Water Act Amendments. Theunderlying inactivation requirement is that treatment provides greater public health protection thanwould be provided by the combination of filtration and chlorination. Includes figures, extended abstract only.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

7

File Size:

1 file , 390 KB