Stage 2 Disinfection By-Products (DBP)

The Stage 2 Disinfectants and Disinfection Byproducts Rule
The Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBPR) builds upon the Stage 1 DBPR to address higher risk public water systems for protection measures beyond those required for existing regulations.

The Stage 2 Disinfection Byproducts Rule will reduce potential cancer and reproductive and developmental health risks from disinfection byproducts (DBPs) in drinking water, which form when disinfectants are used to control microbial pathogens. Over 260 million individuals are exposed to DBPs.

The Stage 2 DBPR is being promulgated simultaneously with the Long Term 2 Enhanced Surface Water Treatment Rule to address concerns about risk tradeoffs between pathogens and DBPs.

Compliance monitoring for all systems subject to the Stage 2 DBP Rule will begin October 1, 2013.

Stage 2 Initial Distribution System Evaluation (IDSE)
Systems that did not qualify for a very small system waiver or a 40/30 waiver are required to complete an Initial Distribution System Evaluation (IDSE).
The requirements for systems required to complete an IDSE differ only slightly for systems designated as Schedule 3 (and their consecutives) serving 10,000 to 49,999 people and those with a Schedule 4 designation (serving fewer than 10,000 people). For both type systems data collection should be completed or nearly completed and IDSE reports will soon come due.

The IDSE report is due to the Vermont Water Supply Division by:

• January 1, 2010 - Schedule 3 Systems
• July 1, 2010 - Schedule 4 Systems

An IDSE Report for Standard Monitoring Template (Form 7) is available to use to prepare the IDSE Report: MSWord (299KB)

Quick Reference Guides for Stage 2 DBP Rule

• Schedule 3
• Schedule 4

EPA Stage 2 DBP Rule Site

Additional Information on Disinfection and DBPs

In 2007, The State of Vermont Water Supply Division hosted a symposium to examine recent research on the need for primary and secondary disinfection in the multi-barrier approach to providing safe water and the extent of primary disinfection procedures required to reduce the microbial threat to meet standards. The following links are the various Power Point presentations from the November Symposium.

• Waterborne Microorganisms and Disease: The Need for Disinfection

• Evaluating Disinfection By-Product Reduction Options Using Simultaneous Compliance Measures

• Primary Disinfectants In Drinking Water

• Alternative Secondary Disinfectants: Advantages and Disadvantages

• Risks from Disinfection By-Products Produced by Chlorine, Chloramine, and Chlorine Dioxide

• Reducing Disinfection By-Products: A Case Study

• Developments of the Stage 2 Disinfectants and Disinfection By-Products Rule