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Few surface water supplies are immune to potential Cryptosporidium contamination. Concern for the protection of public health has motivated many utilities to implement ozonation for Cryptosporidium inactivation. The Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) will provide a new regulatory impetus to focus on advanced Cryptosporidium inactivation and/or removal for certain water supplies. Ozone remains one of the most practical and versatile technologies to achieve Cryptosporidium inactivation. A synergy of multiple benefits (reduction in disinfection by-products (DBPs), oxidation, microflocculation, and taste and odor treatment) make ozone the treatment technology of choice for many progressive utilities. Years before any regulatory direction had become known, many utilities adopted a proactive stance on planning, piloting, designing, and implementing ozone facilities for Cryptosporidium inactivation. A limited survey of selected recent water plants with ozone disinfection designed for Cryptosporidium inactivation is provided in this paper. Design inactivation targets have ranged from 1-log to 3-log. Of the water plants included in this selected survey, only Milwaukee exhibited positive detections of Cryptosporidium, during the highly publicized outbreak in 1993. The design criteria for the surveyed plants were generally based upon best-available research at the time of design. Many ozone system designers relied upon Gordon Finch's 1994 AWWARF-sponsored research, which has since been superseded by more recent work discussed in this paper. Currently, the USEPA offers no published guidelines on ozone disinfection requirements for Cryptosporidium inactivation. According to US Environmental Protection Agency sources, the development of inactivation criteria is still in progress, and publication of guidelines is anticipated in the fall of 2001. In the absence of any regulatory guidelines, ozone system designers have turned to the available research to develop defensible Cryptosporidium-based design criteria for ozone facilities. The inactivation model selected for design has a profound impact on ozone facility sizing and cost. A systematic approach for applying the latest research and inactivation models to develop basic ozone system design criteria is presented. Case studies for Gwinnett County, Georgia's new Shoal Creek Filter Plant treating high-quality Lake Lanier water, and the Philadelphia Water Department's (PWD's) multi-year ozone pilot studies at the Baxter Water Treatment Plant (WTP), treating the Delaware River and the Belmont WTP treating the Schuylkill River, provide illustrative and contrasting examples. Includes 10 references, tables, figures.

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Edition: Vol. - No. Published: 06/01/2001 Number of Pages: 20File Size: 1 file , 480 KB