Lead Corrosion and Sequestering Case History
Northwestern Illinois Groundwater System
For over ten years this community was treated for “dirty water” problems by a competitor with mixed results, in our opinion. Finally, in the early 1990’s they failed lead. The competitor’s answer to solving this new additional problem was to continue using the same product, but only increase the feed rate. The result was the same as before- continued dirty water and they failed lead again.
WSU was finally allowed to treat the system. We approached the problem differently and had the system clean and in compliance within nine months.
Background
The treatment process consists only of chlorine and phosphate. The city is very hilly which causes system pressure problems and low areas that accumulate iron and manganese oxide sludge. The municipality had a history of not flushing often enough and not uni-directionally. The water from the aquifer contained 0.7 mg/L of iron and 0.15 mg/L of manganese.
Solution
WSU recommended a different ingredient to alleviate the “dirty water” problems. We always feel the need to get the system as clean as possible before attempting to apply a protective film to metal surfaces. Our feed rates were high enough to properly sequester the two metals, but still in the same range as the previous product. The difference was the ingredients.
We also emphasized the need to “properly” flush the system twice a year. The first year we had the operators flush a third time during the year to help us get the accumulated oxide out of the system. After that, we went to two flushes a year.
The result is 90th percentile lead readings of 0.009 mg/L and all results under 0.015 mg/L.
Summary
This case points out several important distinctions about Water Solutions Unlimited:
We have an excellent understanding of:
1. Sequestering and which polyphosphate ingredients to use. We live up to our motto- “Using the right product for the right application.”
2. Our tenacity to get plant personnel to flush the system properly.
3. We got the plant personnel to consistently feed the correct feed rate each day.