Treated wastewater from the proposed landfill in Bukit Tagar will be channelled into the Raja Musa peat swamp forest that feeds some of Selangor’s most important rivers.
Experts who have studied the project’s Environmental Impact Assessment are questioning the move as the wastewater could reach Sungai Selangor which supplies 60 per cent of the water Selangor, Kuala Lumpur and Putrajaya residents use.
They fear that man-made and natural channels in the swamp could carry wastewater into Sungai Ayer Hitam and from there, into Sungai Selangor, near water intake points. When discharged, the wastewater would be of a quality “close to Standard B but with elevated levels of the nutrient nitrate,” the report says.
However, the Environmental Quality (Sewage and Industrial Effluents) Regulations 1979 require wastewater discharged upstream of drinking-water intake points to meet Standard A.
The authors of the EIA also do not seem to be sure where the wastewater would flow once discharged into the swamp. They cite Sungai Selangor catchment, Sungai Tengi catchment and Sungai Ayer Hitam as possible options. In their assessment, the authors believe there would be little impact wherever the water flows.
However, an expert, who declined to be named, said because Sungai Selangor was a crucial source of drinking water, not a drop of wastewater should find its way there.
While the landfill (see map) had a 40-year lifespan, he warned that effects from the discharge of wastewater could linger for many more years. Peat swamps played a role in water supply and contamination of the peat might have an impact on water recipients, he said.
The 260ha landfill also sits within the Sungai Tengi catchment area, where its tributaries arise, says the report. Sungai Tengi provides water to Sekinchan, Tanjung Karang and the Tanjung Karang Irrigation Scheme — one of the country’s most productive padi growing areas.
According to the EIA, 700 cubic metres of treated wastewater will be discharged into the swamp daily in the initial stage. In later stages, at least 2,000 cubic metres will be discharged into the swamp which is rich with aquatic life and a favourite haunt for those fishing for ikan haruan or snakehead. The volume could fill two Olympic-sized pools. Concerns were also raised about possible effects of pumping wastewater into a peat swamp.
“While peat swamps have some ability to absorb pollutants, its threshold of tolerance is not known,” said Dr Zaini Ujang, professor of environmental engineering and director of the Institute of Environment and Water Resources Management at Universiti Teknologi Malaysia. He said a high content of inorganic substances and heavy metals in the wastewater could eventually destroy the swamp.
Faizal Parish, the director of Global Environment Centre, said there appeared to have been no study on the potential impact of the wastewater on the swamp, only an assertion that the effects would be positive.
He said the EIA stated that the wastewater would be contaminated with heavy metals and would be rich in nutrients which would significantly change the water and soil chemistry as well as affect vegetation and aquatic life. Faizal said the report had wrongly asserted that adding water to the swamp was positive as it might prevent it from drying out. He said pumping a lot of wastewater into the swamp during the wet season would flood it and likely kill the natural vegetation.
In subsequent dry seasons the dead vegetation would provide more fodder for forest fires that already occur frequently in the area. In its analysis of the impact on aquatic life in the swamp, the EIA acknowledges the possibility of accumulation of heavy metals — substances like mercury, chromium, cadmium, arsenic, and lead — that damage living things at low concentrations.
At least 18 species of fish and dozens of other species of animals have been sighted or trapped in the area. Although the report acknowledges that the substances can build up over time in the tissues of living organisms, it only recommends that this effect is monitored and treatment of wastewater be improved if serious problems develop.