ONCE polluted, there is little chance of rehabilitating a river back to its original pristine condition, a water quality specialist says.
More than that, it also has serious consequences on the ecosystem.
“We can take measures to reduce the impact (of the pollution) but it is near impossible to restore a polluted river back to the condition it was,” said Dr Zaki Zainudin.
StarMetro spoke to the expert to get his views on the pollution of two rivers in Kampung Orang Asli Sungai Buloh, Selangor, because of quarry activities.
Sungai Tolong and Sungai Kelebar have turned murky and the villagers are finding mud and sediment coming out of their taps.
Zaki said the murky appearance was due to the presence of suspended particulates in the water.
He pointed out that the presence of excess particulates in the river might prove fatal to the food chain in the river.
“Fish typically lay eggs in between small pebbles to protect them from being carried off by water current.
“Excessive particulates will close off the gaps between the pebbles, thus making it difficult for fish to lay eggs in those natural protected sites,” he said.
He further explained that sediments might also result in the river becoming more shallow and cause excess water to spill onto the riverbank thus dislodging more soil into it.
Zaki said approval from the Drainage and Irrigation Department (DID) was required before any diversion was made to an existing water body.
“Turbidity is a measure of water quality and measured in units known as NTU.
“A higher turbidity measure indicates a higher presence of suspended particulates.”
He noted that the National Water Quality Standards prescribed a maximum of 5NTU for drinking water or the equivalent of 25mg/L of suspended particulates.
The Forestry Department deployed temporary measures to mitigate the damage, by installing geotextiles to collect sediments and putting sandbags along the affected portion of the river to prevent more soil from being dislodged into the water.
When asked how effective geotextiles were in filtering polluted water, Zaki said it depended on the design.
“Soil erosion happens when rain is absorbed by an already weakened soil strength.
“Depending on rain frequency, more geotextiles may need to be installed,” he said.