In lists published by the Ministry of Ecology and Environment over the past week, subsidiaries of state giants such as China Baowu Steel Group and the Aluminum Corporation of China were cited and fined for breaching emissions standards among other violations.
China has been stepping up its supervision capabilities and has plugged thousands of factories into a real-time emissions monitoring system, but enforcement remains one of its biggest challenges.
The ministry has continued to warn that China's slowing economy had given some regions an excuse to "loosen their grip" on environmental protection.
In the first quarter of this year, air quality in smog-prone northern regions fell compared to last year, and some regions also saw pollution readings in major lakes and rivers rise over the period.
A notice published last Friday said as many as 82 Chinese enterprises exceeded wastewater emissions standards in the fourth quarter of 2018, including 44 sewage treatment plants and six wastewater treatment facilities. A unit of the Aluminum Corporation of China in Shanxi province was named as one of five "serious offenders".
It said the unit had exceeded emissions restrictions for a total of 92 days during the period. The firm did not respond to requests for comment.
As well as being fined, the companies cited were told to restrict operations until problems were resolved. The biggest fine was meted out to a wastewater treatment plant in Liaoning province, which was ordered to pay 7.2 million yuan ($1.04 million).
In a separate review of monitoring standards in the Yangtze river delta and the Fenwei plain regions, the ministry identified more than 300 firms for equipment quality violations and exceeding wastewater discharge restrictions. It found only 22 percent of equipment was of the required standard.
The list included a special steel producing unit of Baosteel, China's biggest steelmaker. Baosteel did not respond to a request to comment.
($1 = 6.9085 yuan)
(Reporting by David Stanway, Muyu Xu and Tom Daly; Editing by Kenneth Maxwell)