By ESTEVAN MEDRANO
Port Isabel-South Padre Press
January 29, 2015
In response to an overexposure of THMs (trihalomethane) in the distributed water supply, The Laguna Madre Water District is conducting a pilot study over the use of chlorine dioxide to reduce the amount of total organic carbons (TOC) produced in the pretreatment of the water at the plant. Once followed with disinfectant, it should prevent harmful by-products from forming in the inner system. Ideally, the precise injection of chlorine dioxide into the water supply should improve the taste and overall quality of the water used every day by customers within the District.
The District received notice of the high levels THM levels from TCEQ (Texas Commission of Environmental Quality) on Dec. 17, obligating a distribution of public notice. The notice was mailed out January 13, but LMWD reassures residents that they are making efforts to quickly resolve the issue.
Trihalomethane is a harmful chemical compound formed as a by-product of chlorine when used to disinfect water to make it drinkable. Exposure can occur by ingestion or absorption through the skin. Long term effects include increased risks of multiple cancers, organ failure and reproduction issues, but it would take several years of heavy exposure for any major consequences to occur. The levels found in the District’s water supply was mere micrograms above government recommended levels —14 mcg per liter above regulation.
“Through the addition of chemicals and the filters we already have installed, we’re working on getting the right balance of various chlorine and chlorine dioxide to have a long term approach to preventing disinfectant by-product formation,” said Charles Ortiz, LMWD engineer. “We’re probably within 30 days of getting that finalized. We’ll continue the approval process with TCEQ to get our permanent condition placed,” he said.
This pilot study, which began Dec. 3 cost roughly $16,000. The addition of chlorine dioxide saves costs on chlorine gas and the District is seeking numerous additional monitoring points to find the best location to inject the chemical- whether it be the pipeline, rapid mix or after filtration.
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