A Lead Corrosion/Sequestering/Chlorination Case History
South Central Wisconsin Application
A medium-size municipality in South Central Wisconsin had been failing lead for over five years. A major phosphate supplier attempted to get them into compliance using corrosion inhibitors during the five year period with no success. A corrosion coupon study was employed to compare inhibitors from four different phosphate manufacturers. The study was inconclusive after six months of operation. Shortly after this, Water Solutions Unlimited analyzed the system and presented a solution that was very unique. The representative from the Wisconsin DNR was at the presentation and felt that the recommendation at least deserved a try. WSU’s recommendation was quickly implemented and successful within six months.
Background
There are four distinct well systems that provide water to the city. The aquifer provides water with a small amount of hydrogen sulfide, as well as 0.3 mg/L of iron and 0.05 mg/L of manganese. Years ago the well systems were designed with aerators to strip out the hydrogen sulfide followed by a short detention pond. The problem was that there was no filtration following the aerators to remove the iron and manganese after it had been oxidized. The detention ponds collected a large portion of the two metal oxides, but not all of it. There were numerous discolored water complaints from time to time, but everyone got used to it over the years.
Solution
There were two important parts to the solution to this problem. A change had to be made to the chlorination system, as well as the feed location and type of phosphate chemical that needed to be fed.
The chlorination system was changed to allow for pre and post chlorination feed points. The amount fed at each location was controlled to allow the phosphate to do its job, yet allow sufficient free chlorine in the distribution system. Chemical Pump Sales & Service, Inc. (CPSS), an integral part of The Water Group, handled the chlorination work.
Water Solutions Unlimited, another part of The Water Group, approached the problem from the aspect that they had to first of all get the dirty water problems under control so that the distribution system metal surfaces could be as clean as possible. This allowed the corrosion inhibitor to apply a protective film to evenly coat the lines and inhibit the lead leaching.
Again, both the efforts of CPSS and WSU were necessary to solve this problem. Acting together as The Water Group, helped alleviate the municipality’s problem. Within nine months the municipality began passing their lead and copper testing. Another important aspect was that Public Notification was no longer required.
Summary
This case history points out several important distinctions about Water Solutions Unlimited:
Water Solutions Unlimited has a unique understanding of:
1. Solving lead corrosion problems in groundwater systems
2. Plant operation and the importance of feeding phosphate and chlorine in the correct
locations.
The Water Group (WSU and CPSS) can be an effective combination in solving water problems.