Copper Corrosion from Reverse Osmosis System
Central Illinois Groundwater Case History
A central Illinois groundwater system installed a reverse osmosis system in order to lower their radium levels coming from their wells. They started to get complaints from homeowners and plumbers about pinhole leaks in household copper plumbing. Water Solutions Unlimited analyzed the problem, reviewed past history of the system and provided treatment recommendations that minimized the problem within six months. The program included operational changes and a blended phosphate corrosion inhibitor.
Background
For over ten years the municipality operated the reverse osmosis system without problems. A year ago a new membrane was installed for the R.O. system. Pinhole leaks began appearing in household plumbing. Engineers recommended that the pH be elevated to over 8.5 with caustic soda from the original 7.8. The changes made very little difference as far as copper corrosion was concerned.
Solution
WSU researched water quality data for the past six to seven years. We noticed that prior to the membrane change for the R.O. system, calcium hardness levels were 50-65 mg/L as CaCO3. The current calcium levels were 20 mg/L. The municipality was able to process more water through the plant than before with the new membrane, so less water was by-passed to. They thought they were doing themselves a favor by taking advantage of the increased efficiency. They weren’t.
Water Solutions Unlimited recommended that they by-pass more water to bring the calcium hardness back up to the 50 mg/L level. We recommended that the pH be reduced back to the original 7.8 level. This reduced Caustic costs.
WSU also recommended a blended phosphate corrosion inhibitor. The reduction in caustic costs paid for the phosphate chemical. Within six months the copper corrosion complaints were cut in half. After two years the pinhole leaks have been reduced to zero. The municipality is happy for several reasons, but most importantly because the customers are happy again.
Summary
This case history points out several important distinctions about Water Solutions Unlimited:
We have an excellent understanding of:
1. How to analyze a corrosion problem.
2. How to provide the right corrosion inhibitor in conjunction with needed
adjustments for operating of the R.O. system.