Wednesday, June 4, 2014

City takes steps to resolve elevated THM in potable water supply

City's Water Treatment and Distribution Plant placed into service in 2001

Apalachicola city officials took steps at the regular scheduled meeting held last night after hearing a report from City Administrator Betty Webb to resolve the longstanding issue of elevated levels of trihalomethanes (THM) in the city’s drinking water supply.

To city purifies its raw drinking water by introducing chlorine as a disinfectant into the system.  When the chlorine combines with naturally-occurring materials in the water such as hydrogen sulfide, iron, and total organic carbon, which are all common in the Florida aquifer it forms the byproduct called trihalomethanes or THM.

When the hydrogen sulfide, iron, and total organic carbon levels are high they usually results in discolored water, laundry, and plumbing fixtures, this in turn results in increased complaints from the city’s water customers, thus the need for a disinfectant. In addition to the water chlorination the city uses aeration, filtering and sequestering.

However, several years ago the Environmental Protection Agency (EPA) and the Florida Department of Environmental Protection (FDEP) tighten the rules governing the level of THM acceptable in raw drinking water. The city is required to notify all of its water customers when the water system is tested and the results indicate the THM exceeds the new level set by the regulatory agencies, regardless of the amount.  Thus the notices you receive in the mail even if the tested levels are slightly elevated.

Only those with a compromised immure system who drink water with elevated THM over many, many years may be at risk of developing certain cancers.  To determine your risk factor if any, please consult with your doctor or healthcare provider.    

Webb told commissioners that the FDEP had approved a 90-day pilot study supported by the Florida Rural Water Association to treat the city’s water supply with an alternative disinfectant to determine if it improves water quality by decreasing the disinfection byproduct THM.

The FDEP is also requiring the city to conduct a Calgon Granular Activated Carbon (GAC) study along with the 90-day pilot study to determine the best water treatment objectives.

The commission voted to authorize Webb to proceed with the approved FDEP studies, which will start next Wednesday, June 11.