AWWA MTC57571

The Long Term 2 Enhanced Surface Water Treatment Rule, developed to fulfill requirements set forth in the Safe Drinking Water Act (SDWA) Amendments of 1996, proposes new standards for the removal of Cryptosporidium in drinking water plants in an effort to provide increased public protection from acute illness. The rule proposes a minimum removal/inactivation requirement of 3 log, with additional removal required dependant upon the source water concentration of Cryptosporidium oocysts. The proposed rule includes a number of technologies, or "tool box", that may be applied to obtain the required level of removal/inactivation. Low-pressure membrane filtration, such as microfiltration and ultrafiltration, has been included as an appropriate technology for the removal of Cryptosporidium oocysts. US Environmental Protection Agency is proposing a distinct definition of what may constitute a membrane system, with particular emphasis on a requirement for a direct membrane integrity test. An acceptable direct membrane integrity test must have a resolution of 3 microns, and a sensitivity that is capable of verifying the log credit established for the system. This paper summarizes the proposed requirements for membrane technology and models integrity to demonstrate potential compliance issues for higher levels of Cryptosporidium removal/inactivation using membrane systems. The modeling indicates that typical configurations applied to the design of low-pressure membrane filtration may not, in some instances, provide adequate protection at higher Cryptosporidium removal/inactivation bins. Pre- and post-treatment may be applied with current design configurations to ensure compliance, or modifications may be made to improve the sensitivity of the testing. Includes 8 references, tables, figures.