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QUALIFICATIONS OF VERNON L. SNOEYINKMy name is Vernon L. Snoeyink. I am the Ivan Racheff Professor of Environmental Engineering at the University of Illinois where I have been a faculty member for 35 years.1 I am also Director of the Water CAMPWS, a National Science Foundation Science and Technology Center involving the University of Illinois, Stanford University and Clark Atlanta University, which has been established to develop advanced materials for use in water purification systems. I am the co-author of the textbook, Water Chemistry, and my research is focused on the chemistry of drinking water treatment and distribution. Recently I have done corrosion control research for cities such as Chicago and Boston. I have also consulted on corrosion control and distribution system projects for more than 25 cities, including Detroit, Cleveland, Austin TX, and Portland OR. Most recently I have lectured on control of distribution system problems in France, Seoul, and Beijing. I have received numerous awards for my research and I was elected to the National Academy of Engineering in 1998 in recognition of my research and education contributions. CH2M-HILL is the consultant for Washington Aqueduct on issues dealing with the lead problem here in Washington DC, and I have been engaged by CH2M-HILL as technical expert on this project. BACKGROUND INFORMATION CONCERNING THE LEAD PROBLEMIn July 2002, the District of Columbia Water and Sewer Authority's (WASA) routine tap samples for lead exceeded the action level of 15 parts per billion (ppb). The 90th percentile level of lead went from 8 ppb the monitoring period before, to 75 ppb, with more than 50-percent of the collected samples exceeding the action level. The two monitoring periods in 2003 resulted in 90t percentile lead levels of 40 ppb and 63 ppb respectively. The problem of excessive lead concentrations in tap water was first observed after the introduction of monochloramine to the system. Free chlorine was replaced by monochloramine in November 2000 in order to reduce the concentrations of disinfection byproducts. Disinfection byproducts include trihalomethanes and halogenated acetic acids that are suspected human carcinogens. While the evidence indicates that a potential cause of this problem is monochloramine, we unfortunately do not have a good explanation of why it did so. Investigation of the literature gives us promising research leads to follow, but a high priority area of research remains the determination of what happened here in Washington, and why it has not happened in other systems that use monochloramine, such as Dallas, TX, Denver, CO, Norfolk, VA and Portsmouth, VA. The differences in water chemistry and the scales that form on lead pipes in Washington, compared to those in other systems, must be carefully and thoroughly studied to determine this information. This research should be undertaken immediately, but it will require some time to complete and, unfortunately, will not be available to provide the basis of the solution to the problem. PLAN TO SOLVE THE PROBLEMThe Production Treatment Operations Team is lead by the Washington Aqueduct and its consultants. They will carry out the desktop studies that will lead to a recommended treatment approach as well as pipe loop studies to verify that approach and implement a partial, then full treatment process to reduce the corrosivity of the water. Desktop AnalysisWashington Aqueduct and its engineers will conduct a review of engineering reports and recent water quality changes in customers' distribution systems. The review will include evaluation of options that have worked successfully in other locations. The steps include:
The desktop study is not yet complete, but my opinion at this point is that the best alternative will be to add orthophosphate to the water at a pH of about 7.6. I have observed that this option has worked well in other systems and I believe that it will work here. The high pH option has the potential of generating problems with excessive calcium carbonate precipitation in the distribution system because of the nature of Potomac River water. The only uncertainty is that the situation here is not exactly the same as it is at other locations. Partial System Application
Full System Implementation
Pipe Loop Studies
Distribution System Operations TeamThe Distribution System Operations Team's plan is to develop an extensive distribution system monitoring program. The monitoring plan will be used to assess conditions before and after a revised treatment change. Either as a part of that plan, or as a separate monitoring plan, WASA will design a sampling plan for purposes of assessing extent of the lead levels in homes without lead service lines. The Production Treatment Operations Team will use these data as input into the effectiveness of the revised corrosion control treatment. 1. The opinions that I express here are my own, and not those of the University of Illinois or the National Science Foundation. |
