Surface Water Treatment Rule (LT2) as part of its Retrospective Review Plan under Executive Order 13563 and the third Six-Year Review under the Safe Drinking Water Act. This meeting focused on binning requirements in the context of Round 1 monitoring results and analytical method changes, potential credits assigned to different risk mitigation tools and the use of E. coli as a screen to identify small PWSs that need to perform Cryptosporidium monitoring.
Perhaps the most significant focus of the most recent LT2 meeting (particularly for large systems) was the modeled predictions of potential impacts from the newly approvedCryptosporidium analysis method (Method 1623.1) on Round 2 monitoring results. While most utilities are not expected to see much impact from a change in analytical procedures, those with challenging water matrices could see significant improvements in recovery efficiency that could push Cryptosporidium results higher than those seen under Round 1 monitoring, and potentially into an action bin based on Round 2 monitoring. Based on EPA’s modeling, almost twice as many systems (85 total systems) are predicted to fall into an action bin using Method 1623.1 than if Method 1623 was used. Use of Method 1623.1 is not mandatory, but many labs are expected to convert to the method since it is endorsed by EPA, and it is generally not cost-effective for a lab to set up to run duplicative methods. Water utilities need to be aware of this potential issue as they plan for upcoming Round 2 monitoring and potential impacts.
For those utilities that have fallen (or may potentially fall) into an action bin, EPA also provided information on toolbox options being used in the field to achieve requiredCryptosporidium reductions. Based on information gathered from 96 water systems, optimized combined or individual filter performance is the most-used method for achieving required removal credits, followed by membrane filtration and ultraviolet light. EPA is compiling this information to inform its review of LT2 as well as to provide information to utilities that may be required to provide additional Cryptosporidium removal in the future.
EPA also provided information on the use of E. coli as a screen for Cryptosporidium by small drinking water systems. Based on analysis of data gathered during round 1 monitoring, EPA concludes that E. coli is an effective screening tool that can save small systems significant resources while remaining adequately protective of public health.
Due the length of time required to issue regulatory revisions, it is unclear what, if any, modifications EPA will be able to make to LT2 prior to round 2 monitoring for large systems. Rather, it is expected that much of the information EPA has provided during the recent public meetings and additional information collected will be used to inform longer term LT2 revisions under the Six-Year Review process. However, the information could be useful to utilities as they navigate the current LT2 monitoring and regulatory processes. Additional information, including meeting presentations from all of the LT2 public meetings, is available on EPA’s LT2 Public Meetings website. [Note: presentations from the December meeting are not yet posted, but should be posted in the near future.]