PETALING JAYA - River pollution is becoming a major cause of unscheduled water disruptions in the country.
Between 2008 and 2014, pollution shut down water treatment plants in rivers across Malaysia for 1,005.75 days or a total of 24,138 hours.
More than a third of these shutdowns were in Selangor.
Over the past seven years, closure of treatment plants caused by river pollution disrupted supply to hundreds of thousands in the state for at least 8,000 hours or 333 days.
National Water Services Commission (SPAN) chief executive Mohd Ridhuan Ismail said various types of river pollution, including wastewater, detergents, oil spills, muddied flow due to floods, deforestation and quarrying, caused treatment plants to be shut down.
He said treatment plants had limits in processing water and might not be able to filter out high levels of pollution.
"More than 90 per cent of the shutdowns in Johor between 2012 and 2015 was at the Skudai plant, caused by high amounts of ammonia in the river," he said.
In March, The Star highlighted the massive algae bloom pollution in the Sembrong Dam in Johor, a water source for some 120,000 people in the districts of Kluang and parts of Batu Pahat.
Mohd Ridhuan said treatment plant closures in states other than Malacca were due to murkiness, also known as turbidity in the raw water, caused by upstream activities.
He said the Merlimau plant in Malacca was shut down for eight months from June last year because of a sudden rise in the raw water's acidity and change in colour.
The full extent of these shut downs are not known, as SPAN does not have exact details on how many households were affected but if a plant ceases operating, even for an hour, households might be without water for several hours.
This is because it takes time for the emptied pipes to be refilled to the right amount of pressure to ensure regular water flow.
Mohd Ridhuan said it was vital for catchment areas to be kept safe, as they were water sources for millions of people.
He pointed out Sungai Selangor was one such area, adding that its four plants supplied water to 60 per cent of Selangor, Kuala Lumpur and Putrajaya, or more than four million people.
"When pollution in catchment areas cause shutdowns of treatment plants, the impact on consumers is huge," he said.
He said states needed to control development within water catchment areas and punish polluters harshly to serve as examples to others.
He said shutdowns in Perak were reduced "significantly" since 2011 when plants in the state were upgraded.
States which want to reduce the impacts caused by shutdowns can also relocate the plants in different catchment areas, he said, adding that the Langat 2 plant, which would pipe water from Pahang to Selangor, as an example of this.
The Langat 2 plant is set to be completed by 2017 and is designed to supply 1,130 million litres of water a day.