Lead Corrosion and Sequestering Case History
Midwestern University
A major Midwestern university failed lead in 1992. They contacted Water Solutions Unlimited the following spring to assist them with alleviating this problem and get them into compliance. They were also having discolored water problems, which resulted in having to flush their distribution system four times per year.
Background
The university has six well systems that are treated with only fluoride and chlorine prior to entry into the distribution system. There is approximately 0.4 - 1.0 mg/L of iron and 0.1 - 0.2 mg/L of manganese coming out of their aquifer. Prior to WSU, the school used sodium hexametaphosphate as a sequestrant to control the dirty water. The highest first-draw lead levels were 0.185 mg/L.
Solution
WSU wrote the university’s Optimal Corrosion Control Program (OCCP) for them and submitted required documents for the chemical feed permit. While these were being approved, we began working on improving the sequestering program. We recommended a sequestrant different from their current product which WSU had been using successfully for many years. The result was cutting flushing times in half, and eventually reducing the flushes to a normal spring-fall sequence. This saved valuable labor, water and money.
WSU ended up developing an entirely new product for the university. This also led to a series of new products later on. We tested the high sample sites used for first-draw testing and were not able to reduce the lead levels to below 0.015 mg/L with only the sequestering product. We improved the results, but not enough to get into compliance. We added another ingredient used for corrosion. This product reduced the previous high sample result to less than 0.0015 mg/L as lead. Today, all samples are less than 0.01 mg/L as Pb, the system is on reduced monitoring, and the system is clean.
Summary
This case points out several important distinctions about Water Solutions Unlimited:
We have an excellent understanding of:
1. Sequestering and polyphosphate ingredients.
2. Lead corrosion in ground water systems.
3. How to adapt to new corrosion challenges.