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Water Research Foundation has undertaken the Distribution System Water Quality Strategic Initiative to develop integrated projects focused on water quality changes that take place within drinking water distribution systems, including premise plumbing. The Foundation will commit up to $1 million in funding per year for the initiative, which is expected to be substantially leveraged with partner co-funding and researcher in-kind contributions. The initiative will be sustained until the objectives outlined below are achieved; the target timeframe for the initiative is 5-7 years.
Significant water quality changes that occur within water distribution systems have received increased attention, as these changes sometimes impact water quality. The impacts make it more challenging for water utilities to achieve expected levels of service and comply with regulatory requirements. Due to the complexity of the fate, transport, and transformation of contaminants, and their subsequent accumulation and release within the distribution system, the drinking water community has allocated significant resources to investigate the chemical, physical, and microbial mechanisms that cause distribution system water quality changes. Recent research activities have focused on characterizing these processes and their impacts on water quality.
Water Research Foundation has traditionally funded significant research on distribution system water quality. With the Distribution System Water Quality Strategic Initiative, the Foundation is now enhancing its efforts to solve distribution system water quality challenges by developing a sustained, multi-year, integrated research effort. The initiative is focusing on water quality degradation due to transformations that take place within the distribution system, such as pipes, tanks, and plumbing. Water quality can also be affected by loss of physical integrity (such as contaminant intrusion due to breaks or faulty repairs) and hydraulic integrity of pipes (such as contaminant intrusion due to low or negative pressures). Although physical and hydraulic integrity are not directly addressed in this initiative, they are important variables in maintaining distribution system water quality and are addressed through selected research projects under the Foundation’s other research programs.
Objectives
Each of the Foundation’s strategic initiatives is based on several specific objectives that represent problems to be solved or opportunities to be attained by the initiative. The following three objectives have been established for the Distribution System Water Quality Strategic Initiative. All projects funded under the initiative will contribute to meeting one or more of these objectives.
Goal 1: Understand Premise Plumbing Water Quality Changes
Although drinking water utilities do not generally assume direct responsibility for water quality changes caused by premise plumbing, these changes can reflect negatively on customer perception of tap water quality and utility performance, and thus are an important issue for utilities. The Distribution System Water Quality Strategic Initiative will achieve a substantial understanding of water quality changes caused by premise plumbing, and of methods to control the negative impacts of these changes. It will produce new and specific understanding of water quality impacts caused by premise plumbing, a new set of forensic tools to determine causes of premise plumbing water quality impacts, and an improved ability to positively impact water quality at the tap. This knowledge will enable drinking water utilities to take appropriate action in helping customers improve water quality at the tap.
Goal 2: Define and Measure Multiple Barriers to Ensure Distribution System Water Quality
Secondary disinfection (providing a disinfectant residual in the distribution system) has been a key component of drinking water treatment and distribution in the United States. While this practice provides a barrier to microbial contamination of finished water, it may also contribute to disinfection by-product formation, off-flavors, and other undesirable water quality changes. In some other countries, utilities focus on supplying biologically stable water without disinfectant residual as an alternative approach to controlling microbial contamination. This practice avoids water quality issues associated with disinfectant residual but provides no protection against pathogen intrusion into the distribution system through pipe breaks or negative pressure transients. Periodic flushing of distribution systems is also used to help mitigate distribution system water quality changes, but the level of protection afforded by this practice has not been quantified. Finally, many questions remain about the value of total coliform measurements as an indicator of distribution system integrity, as stipulated in the U.S. under the Total Coliform Rule. The Distribution System Water Quality Strategic Initiative will develop tools and approaches to thoroughly evaluate the benefits and costs of multiple barriers used to ensure distribution system water quality. New approaches for measuring distribution system integrity will be carefully evaluated. This work will enable water utilities to quantitatively evaluate the value of different barrier approaches, and institute measurement programs that will substantially increase the ability of utilities to measure the “health” of their system.
Goal 3: Chloramines – Filling in the Gaps
For a variety of reasons, the use of chloramines as a secondary disinfectant by U.S. drinking water utilities has been increasing, and this trend is expected to continue. Although the use of chloramines for secondary disinfection has already been studied extensively, considerable knowledge gaps remain. The Distribution System Water Quality Strategic Initiative will develop additional guidance and understanding to help address these gaps. Specific outcomes will include:
- Predictive models of lead and copper corrosion when switching from free chlorine to chloramines
- Improved understanding of customer acceptance issues such as claims of skin rashes associated with chloramines
- Improved understanding of disinfection by-product formation related to chloramines
- Tools to identify, control, and prevent nitrification episodes (in particular, recovery from nitrification episodes without the use of free chlorine)
- More precise quantification of nitrification impacts on distribution system water quality and materials, including impacts on premise plumbing
- More precise quantification of the disinfection and biofilm control efficacy of chloramines versus free chlorine
- Improved understanding of the fate of ammonia from flushing operations involving chloraminated systems
Water utilities will benefit from a more comprehensive understanding of chloramines and how to monitor and manage chloraminated systems, as well as an increased number of tools to prevent or control potential negative impacts from the use of chloramines.
Expert Panel
The expert panel is comprised of volunteers who provide direction and long-term stewardship for the strategic initiative.
Work Products
Expert Workshop Report (pdf, 1.59 mb)
As input to the expert panel in development of a Strategic Plan for the Distribution System Water Quality Strategic Initiative, an expert workshop was held May 30 and 31, 2007, in Englewood, Colorado. Twenty-one experts considered distribution system water quality concerns, and in breakout groups identified research projects to address high priority research needs. The workshop report includes a white paper on the state of knowledge in distribution system water quality that was prepared prior to the workshop to set the stage for productive discussions. Fourteen projects were identified by the workshop participants as particularly high priority, suitable for starting immediately. The workshop report was a primary input to the expert panel’s effort to develop strategic initiative objectives and the sequenced plan of projects to achieve those objectives.
Strategic Plan (pdf, 254 kb)
The Strategic Plan has been developed by the expert panel to set forth the objectives for the initiative and the sequenced plan of projects to achieve the objectives. The expert panel will evaluate the plan on an ongoing basis and revise it as necessary to respond to changing subscriber needs, results of ongoing relevant research, and input from subscribers, research partners, and other stakeholders.
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