Two Guizhou-based liquor producers, Xijiu and Xiaohutuxian, have been forced by local authorities to make improvements to their wastewater discharge systems.

The rectification notices, issued by the provincial environmental protection department in Guizhou, also covered two coalmine enterprises and another liquor producer based in Zunyi in the province, the National Business Daily reported on Thursday.

Illegal operations identified among the liquor makers included discharging wastewater without any treatment, using substandard wastewater treatment facilities, and discharging excessive wastewater, the report said.

"The inspections and punishments are more severe and tougher this time.

"All those enterprises with illegal operations will not be allowed to start their production activities until their wastewater-processing facilities and procedures are up to standard during our check," an unnamed local official on environmental protection was quoted as saying by the report.

A plant owned by Kweichow Moutai Co Ltd was also exposed as having illegal operations during the latest large-scale water pollution inspection, the official said, without providing specific details.

"Since the plant is newly built, its procedures on wastewater treatment are very likely to become the norm in future. But we will take specific measures to deal with their illegal operations this time," the official said.

Earlier this month, a report in the National Business Daily exposed several liquor producers along the Chishui River, one of the tributaries of the Weihe River, as illegally discharging wastewater, which caused serious pollution to the river.