The pollution caused Selangor water supply officials to suspend operations at the Sungai Semenyih water treatment plant for about 10 hours from 5pm yesterday.
Selangor executive councillor for the environment and consumer affairs, Hee Loy Sian, said the matter was detected by the Selangor water management board, Air Selangor, and the Environment Department while investigating the manhole system of the public sewer network in Bandar Bukit Mahkota, Bangi, near here.
“The foul smell emanated from a manhole within the vicinity of the residential area in Bandar Bukit Mahkota.
“It is likely to be the main location of pollutants entering the system, before they spread to Indah Water Consortium Sdn Bhd sewage plant.
“This waste cannot be treated by the sewage plant and caused a strong odour in the effluent discharge from the sewage plant when it flowed into Sungai Beranang and Sungai Semenyih, which provide the main source of raw water for the Sungai Semenyih water treatment plant.”
Following this, he said, activated carbon was used to reduce the foul smell in the river.
Heavy rain last night and early today further helped to reduce the odour and the treatment plant was back in operation by 4.30am today, he added.
Hee said the water board and the relevant agencies were now working to identify the culprit responsible for causing the odour pollution in the river.
Operations of the treatment plant were suspended because of the foul smell in the river, causing disruption in water supplies to more than 370,000 customers in the Petaling, Hulu Langat, Kuala Langat and Sepang districts.
Water supply had been restored to 81% of households in four affected districts of Selangor by 6pm today — 72% of the 132,953 customers in Petaling; 96% of 114,018 accounts in Hulu Langat; 61% of 49,180 accounts in Kuala Langat; and 85% of 75,880 accounts in Sepang.
“We are working to increase pressure and flow in the distribution system and accelerate the recovery process,” Air Selangor said in a statement today.
In other areas, water will be supplied through tanker lorries and 10 local service centres will continue to operate around the clock until the water supply is fully restored.