It said the Sungai Selangor water treatment plants (LRAs) Phase 1, 2 and 3 and the Rantau Panjang plant resumed operations in stages from 2.40am after reading zero TON (threshold odour number) three times in a row.

“As of 7 this morning, all four LRAs have completed their washing and pumping activities to ensure the quality of water supplied is clean and safe according to standards set by the health ministry,” it said in a statement.

“Air Selangor is working to stabilise the distribution system before water supply can be restored to users.”

The closure of the four plants saw 1,139,008 households in 1,279 areas in the Klang Valley going without water yesterday evening, after another case of odour pollution was detected in Sungai Selangor.

The solvent-like odour was detected around noon, recording a TON reading of eight.

Earlier this week, the state government passed amendments to the Selangor Water Management Authority enactment providing stiffer penalties to those polluting rivers used by treatment plants. This included a mandatory jail sentence and a RM1 million fine.

In September, pollution in Sungai Gong forced the closure of these same water treatment plants, disrupting supply to over five million users in the Klang Valley.

Last month, the same water treatment plants were again shutdown after odour pollution was detected in Sungai Selangor. The shutdown that lasted for nearly a week disrupted water supply to 1.19 million households.