IPOH: Preliminary water samples taken from Sungai Sitiawan, where dead fish and other aquatic life were recently found, showed elevated water temperatures.
Perak environment committee chairman Teh Kok Lim said readings taken at three locations — near the Wak Dol platform, D' Chalet homestay and Tanjung Uda River Resort — ranged from 31 to 32 degrees Celsius.
"At the first location, small fish were found dead, while larger aquatic life were found dead at the other two locations.
"The dissolved oxygen level at the first location was 5.86mg/L, 3.79mg/L at the second and 1.59mg/L at the third," he said in a statement on Thursday (Sept 3).
Teh said pH readings at the three locations ranged from 7.59 to 7.69.
Water temperatures of between 22 and 27 degrees Celsius are generally considered suitable for aquatic life, while higher temperatures can place aquatic organisms under stress.
Dissolved oxygen levels of about 5mg/L to 6mg/L are generally considered acceptable, while readings below 2mg/L can cause hypoxic conditions that may suffocate aquatic life.
Environmental groups had raised concerns over possible pollution in Sungai Sitiawan after dead aquatic life was discovered in late August.
Teh said the state Environment Department had also collected industrial effluent samples from a nearby factory to determine whether they matched samples taken from the river.
"The samples have been sent to the Chemistry Department for analysis.
"The investigation team also identified a damaged blower valve at the factory's sewage treatment plant," he said.
"Legal action will be taken pending the results of the analysis.
"The department will continue monitoring and conducting enforcement checks on premises suspected of causing river pollution," he added.
