Welsh Water switches to chloramine dosing

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Welsh Water has become the latest in a line of water authorities to switch to dosing with the disinfectant chloramine, rather than chlorine, and has just started adding the chemical to tapwater in the Anglesey area.

Welsh Water told Practical Fishkeeping: "Following a 500,000 upgrade of the Alaw and Cefni Water Treatment Works this year, new equipment has been installed at the plant to add chloramine to the treated water, a change from the traditional use of chlorine, to help maintain water quality throughout the distribution system. The system has now been fully commissioned."

"We produce top quality drinking water at our treatment works, and want to make sure that we maintain this excellent quality right to our customers' taps. Chlorine has been used to disinfect tapwater for many years, but it does not remain in the treated water for more than a few days. Chloramines, however, can remain in water for a longer period, ensuring quality is maintained in supply for a far greater period of time."

Tests have shown that chloramine, which is produced by adding ammonia to chlorine, can remain in the water for several weeks. This means that if you don't remove it completely it could go on harming both fish and filter bacteria.

Unlike chlorine, chloramine can't be removed by boiling, leaving the water to stand, aerating it, or spraying it into the aquarium or pond through a hose, and unless you take the appropriate steps to get rid of it, it will remain in the water.

When given a sufficiently long contact time (5-10 minutes) chloramine can be removed from water using a combination of activated carbon and zeolite. Some RO units will remove it, when equipped with carbon filters. However, the easiest way to remove it is to use a chemical water conditioner.

The majority of popular dechlorinators are based on an ingredient called sodium thiosulphate, in varying strengths. When added to water containing chlorine at the correct dosage, these water conditioners convert the chlorine to harmless chloride ions, making the water safe to use.

Several ingredients used in other dechlorinators, including sodium sulphite, sodium bisulphite and ascorbic acid, as well as sodium thiosulphate, can also remove monochloramine from tapwater.

However, many need to be used at double the normal dose for chlorinated water, and the vast majority of them also leave behind the ammonia part of the chloramine molecule, unless an additional ingredient has been added to take care of it. So, while you'll get rid of one toxin, you could potentially introduce another simply by treating the water.

Two products, Kent Ammonia Detox and API Ammo-Lock2 are capable of removing chloramine and the resulting ammonia. The vast majority of other dechlorinators do not do this.

Although many fishkeepers, and even aquatic retailers, may be unaware of it, over 10% of the UK's tapwater is now dosed with chloramine.