H’ng, who is state local government, town and country planning committee chairman, told the Penang legislative assembly that the pollution was also caused by agricultural activities, waste disposal and other factors.

Bernama reported him as saying that enforcement action was being carried out in an integrated manner involving the environment department (DoE), local authorities, the Penang irrigation and drainage department, and technical agencies to identify the actual pollution source and implement corrective measures.

He was responding to a question from Sobri Saleh (PN-Permatang Berangan) who asked about the number of pollution complaints involving Sungai Kereh and the action taken by the state government.

“Among the measures being planned is transporting pig waste to the Ampang Jajar Transfer Station, where it would be processed as raw material through an anaerobic digestion system,” H’ng said.

“Through this process, organic waste is broken down in an oxygen-free environment to produce methane gas, which can be harnessed as a renewable energy source,” he added.

H’ng said the initiative would not only help reduce river pollution and environmental contamination risks, but also support sustainability efforts through more systemic waste management and the generation of environmentally friendly green energy.

In February 2025, then natural resources and environmental sustainability minister Nik Nazmi Nik Ahmad had said that waste from pig farms was believed to be polluting Sungai Kereh, with five readings from the river showing a high ammoniacal nitrogen sub-index, suggesting waste inflows, likely from animal sewage or fertilisers.

H’ng said that based on DoE’s records, seven complaints related to water pollution and foul odours in Sungai Kereh were received between 2024 and 2026.

He said field investigations, including site inspections, found drainage areas covered with aquatic weeds, which could slow water flow and contribute to the odour problem.