In fact, the top five most polluted rivers in Malaysia are in Pasir Gudang and its adjacent areas.
The following is a graphic of the top 5 cleanest and polluted rivers in Malaysia based on the DoE's data.
Click on the Polluted and Cleanest buttons in the graphic for further details. Click on the dots representing each of the rivers for a closer look at their exact locations.
Why are the country’s dirtiest rivers concentrated in Pasir Gudang?
Water quality expert Dr Zaki Zainuddin testing a river's water quality.
Although under the Water Services Industry Act, all local authorities are required to hand over sewerage operations and management to the Indah Water Konsortium, in Pasir Gudang and Johor Baru, this continues to remain with the state government.
Because of this, water quality expert Dr Zaki Zainudin said the sewage system has not been upgraded.
Dr Zaki first visited Sungai Buluh in 2003, but even today, he can clearly recall the stink emanating from the water.
"It was so smelly I almost vomited," said the Johorean, who did his Master of Science (MSc) research paper on the rivers in Pasir Gudang.
Fast forward 16 years later - and little has changed.
Dr Zaki said there is a mixture of many different types of pollution which contributes to Pasir Gudang having such dirty rivers.
“There is a mix of so many sources (of pollution) - from industrial sources, sewage discharge due to some sewage plants being very old and not optimised, and oxidation ponds, sullage from restaurants and workshops, and direct discharge without treatment from squatters and villagers."
Sharing photos of rivers - Sg Rekoh, Sg Perembi and Sg Tengkorak - which water has turned black -, Dr Zaki said the development of the industrial area of Pasir Gudang is also very concentrated.
There are over an estimated 2,000 legal factories within 359.57 km2 area, with least 252 chemical factories.
“Even if the discharge (of effluents) from factories are within the legal limit, this is still very high because it’s jam packed."
In July, during an enforcement check on 90 chemical factories in Pasir Gudang, Johor state exco member Mohd Khuzzan Abu Bakar said 81 were found to have committed at least one offence under the Environmental Quality Act.
Dr Zaki said another reason for the bad river pollution in Pasir Gudang, Johor Baru and adjacent areas is that Johor Baru was an old town.
“(It was) one of the first, rapidly developing cities, since even pre-independence.
“Back in those days, there was a lack of or limited sewage and sullage management facilities,” he said.
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