September 2008 Press Release
Red/Yellow Water Discoloration
Davidson Water, Inc. provides water 365 days a year to over 130,000 people. We have provided exceptional quality for many years. We want to apologize to the customers of Davidson Water, Inc. who have been experiencing periodic red and yellow water conditions during the past several months. We deeply regret this condition has persisted and are working on a solution. We are working with several engineering firms, the North Carolina Department of Environmental Health and Natural Resources, and the EPA to resolve this situation. The water has been thoroughly tested and is safe for use but we realize it is esthetically unpleasing and an inconvenience.
Usually red and yellow water quality problems are a result of galvanized and unlined cast iron pipe in the distribution system. Most studies that have been conducted relating to red and yellow water conditions were done to understand why unlined cast iron and galvanized pipe creates red water, making it very perplexing as we do not have either in our distribution system.
New regulations passed by the EPA for total organic carbon (TOC) removal created the need to switch coagulants to stay in compliance. In 2002 we switched from aluminum sulfate to ferric chloride which greatly enhanced our removal of TOC and reduced disinfection byproduct levels. In 2006 testing showed that lead levels in water in homes that used lead solder in their plumbing or had fixtures that contained lead was on the rise. After talking with several experts and hiring an engineering firm specializing in water quality, we switched to ferric sulfate at their recommendation to prevent lead from leaching from home owners plumbing components while still having good TOC removal.
In 2007 and 2008 due to extreme drought conditions and low river flows, the normal flushing of water lines was halted by our regulating agency and governor. Ferric Sulfate contains iron and manganese properties that seem to be collecting in our distribution system. In the summer when water velocities in the pipe network increase because of increased demands and water temperatures rise the build up of ferric sulfate releases from piping causing red and yellow water conditions, which you, our customers, have experienced.
River flow has greatly improved in recent weeks which will allow for a thorough flushing of our distribution system this fall and winter. A method of oxidizing the ferric sulfate where it will not reappear in the distribution system as red and yellow water will be developed or a switch to another coagulant that will not produce red and yellow water and still keep us in compliance with all EPA regulations will be tested and proven before next summer when red and yellow water conditions can be more prominent.
Again, while red or yellow water discoloration is not a safety issue, we do apologize for the inconvenience and will diligently continue to make improvements.