Surface Water TreaTment Rule
The original SWTR published in 1989 applies to all public water systems that use surface water or ground water under direct influence (GWUDI). It establishes a treatment technique that requires filtration unless certain criteria are met and it sets minimum disinfection requirements for Giardia lamblia and viruses.
Interim Enhanced SWTR and Stage 1 disinfectants/disinfection byproducts rule
The Interim Enhanced SWTR of December 1998 applies to public water systems that use surface water or groundwater under the direct influence of surface water (GWUDI) and serve at least 10,000 people. It requires states to conduct sanitary surveys for all surface water and GWUDI systems, including those that serve fewer than 10,000 people. The IESWTR amended the SWTR to strengthen microbial protection, including provisions specifically to address Cryptosporidium.
It was promulgated along with the Stage 1 Disinfectants/Disinfection Byproducts Rule, which reduced exposure to DBPs for customers of community water systems and non-transient noncommunity systems, including those serving fewer than 10,000 people, that add a disinfectant to the drinking water during any part of the treatment process.
Long-term 1 Enhanced SWTR
The Long-Term 1 ESWTR of January 2002 is a companion rule to the IESWTR and Stage 1 D/DBPR, providing parallel provisions for systems that serve fewer than 10,000 persons.
Long-term 2 ESWTR and stage 2 d/dbpr
The Long-Term 2 ESWTR of December 2005 applies to all public water systems that use surface water or GWUDI. In order to comply with the rule, water treatment plants that employ filtration must monitor their influent water and determine what Cryptosporidium occurrence “bin” the water treatment plant falls in. If classified in a higher bins, the plant must provide additional water treatment to further reduce Cryptosporidium levels by 1.0 - 2.5 log, depending on the bin.
It was promulgated along with the Stage 2 D/DBPR, which builds upon the Stage 1 D/DBPR by tightening compliance monitoring requirements for two groups of DBPs: total trihalomethanes (TTHM) and five haloacetic acids (HAA5). The rule targets systems with the greatest risk.
Most recently, EPA has begun reviewing the Long-Term 2 ESWTR under the SDWA's requirement to review rules every six years. The agency is assessing and analyzing information regarding occurrence, treatment, analytical methods, health effects and risk from all relevant waterborne pathogens to evaluate whether there are new or additional ways to manage risk while assuring equivalent or improved protection.
Through 2012, EPA has held three public meetings on the rule review, and AWWA has been at the table for all of them. The agency plans to complete this review no later than 2016. Look for more details here in the near future.
AWWA was actively involved as a stakeholder in all phases of the development of these regulations, including providing the following formal comments that helped to formulate the final rules and companion guidance.
Drinking Water Guidelines from Health Canada assert that, "Barring system specific exemptions, all public water systems, regardless of source water type, should be disinfected to produce microbiologically safe water and should maintain a disinfectant residual throughout the system at all times."
Treatment guidelines have been established for protozoa and enteric viruses as well as monitoring guidelines regarding occurrence of E. coli, total coliforms, heterotrophic plate count and current and emerging microbial contaminants of concern.
In addition, Health Canada has established a guideline for chlorine in drinking water.
One resource that can inform disinfectant selection is AWWA's guide for drinking water and wastewater systems titled, Selecting Disinfectants in a Security Conscious Environment.
This guide, published in 2009, describes a step-by-step process to evaluate disinfection options that meets the unique needs of each water, wastewater and reuse system. Available in the AWWA Store, the product builds on existing water sector engineering practices, manuals of practice, costing tools and public communication techniques to:
- address federal and local statutory and regulatory disinfection objectives;
- reflect local circumstances;
- compare disinfection options consistently;
- consider operational, process and supply-chain reliability as well as environmental, operator and community safety considerations;
- provide transparency in the decision-making process; and
- incorporate appropriate risk communication within the decision-making process and the community.
The guide details a 5-step process for selecting disinfectants:
- Assess Current Situation. Identify existing and future disinfection requirements and regulations and the ability of the existing disinfection process to meet them. Review past water quality and security assessments and recommendations and determine which recommendations have been or are planned to be implemented. Use the information gathered to establish system disinfection goals and objectives.
- Identify Options. Use a screening process to determine which disinfection options are feasible to carry forward for detailed evaluation.
- Evaluate Options. Evaluate each disinfection option identified as feasible in Step 2 by defining and then comparing and contrasting the attributes, costs, advantages and disadvantages of each option. This evaluation can reflect on design considerations such as reducing the quantity of hazardous substances stored on-site; the reliability and efficiency of potential disinfectant system options; and simplifying treatment processes where possible.
- Select Option. Use the results of the evaluation along with decision-making tools to select the preferred disinfection method.
- Implement Selected Option. Design, install, construct and start up the facilities and equipment required to implement the preferred disinfection method.
This resource also illustrates the use of two such tools: multi-attribute utility analysis (MAUA), and expanded social cost effectiveness analysis (ESCEA). CH2M Hill and Stratus Consulting prepared the following two spreadsheet tools that users can adapt to their own circumstances.