City changes disinfection process for drinking water
Returns to past method to improve quality and taste
Staff reporter
The City of Hillsboro is changing the disinfection process for the city's drinking water.
Traditionally, the city has used chlorine as a means to disinfect against bacteria. As of Feb. 2, the city will be using a method called combined chlorine or chloramination in the distribution system. This method had been used by the city in the past.
"We've been aiming toward doing this for quite some time," said Steve Garrett, city administrator.
Garrett said the city is meeting all of the requirements at the present time.
"This is a way to continue meeting those requirements," said Garrett.
Chloramination is a combination of chlorine and ammonia which form a new chemical complex called chloramines.
According to the Environmental Protection Agency (EPA) guidelines, chloramines are four times more stable than chlorine, and are valued for their residual effect in disinfecting drinking water. Although both are liquid gasses, chlorine evaporates at a faster rate than chloramines.
Although chloramines are not as potent as chlorine at killing bacteria, they will be enough to keep bacteria from growing in the pipes/distribution system, and will eliminate the need to add additional chlorine at the booster sites along the distribution pipes.
Local municipalities have been mandated by the EPA to eliminate or reduce Trihalomethanes (THMs) to .1 part per million or 100 parts per billion.
THMs are volatile organic chemicals which are produced when chlorine interacts with organic materials in the water. Some THMs have been associated with cancer.
Although chloramines are considered safer than chlorine for human consumption, the chemicals are deadly to fish, shellfish, reptiles, and amphibians.
Aquarists are encouraged by the city to check with pet stores for the proper method to neutralize the chemicals.
Chloramines also must be removed from water that is used for kidney dialysis units.
The chemicals cannot be removed by boiling or letting an open container of water stand to dissipate the chlorine gas. Only appropriate treatment of the water will remove both the chlorine and the ammonia.
Chloramination will reduce the possibility of future occurrences of THMs and will reduce the amount of chlorine used.
"A better water quality should be achieved," said Garrett, "better quality and better taste."
Costs are minimal and include some updating of equipment for injection into the system.
"This is nothing new," said Garrett, "these are standard operations from way back. This is a solution that has been around for a long time."
