Water odour: PUB to study enhancement of treatment processes

National water agency PUB will look into enhancing treatment processes after some households in Pasir Ris, Yishun and Tampines reported on Wednesday that boiled tap water gave off a pandan smell.

PUB had said this issue was traced to water imported from Malaysia.

Screening technologies at present do not allow for the detection of trace amounts of the organic compound tetrahydrofuran (THF), which is responsible for the pandan-like odour, PUB said on Facebook yesterday. It added that it is working with the Malaysian authorities to identify the source of the THF.

Water from Malaysia is treated at PUB's waterworks in Johor before it arrives in Singapore, and similarly stringent water treatment and quality monitoring processes apply, the agency said.

It said that THF, which is highly soluble, has a low boiling point of 66 deg C. This causes it to vaporise upon boiling, giving off a distinctive floral scent.

PUB updated yesterday that it has completed flushing of service reservoirs, the transmission and distribution network and water tanks to remove THF traces from the system.

"The quality of water supply across the island remains consistently within normal and acceptable range. We have also been testing incoming water supply from Johor and are satisfied that it is now of good quality," it noted, adding that it will no longer provide water bags to affected households as the tap water is safe for consumption.

The full replacement of affected water in the network means there should no longer be any smell, although PUB noted that any "lingering" odours are "likely due to remnant water in house pipes". Customers are advised to run their taps for five minutes to eliminate this.