China National Chemical Corp. (ChemChina), the nation's largest chemical maker, said Tuesday it was making headway in waste water treatment amid increased efforts to save energy and reduce emissions.

A pilot program in two chemical plants in the northern Chinese city of Tianjin could recycle more than 80 percent of the waste water generated by oil refining, the Beijing-based company said in a statement.

The recycling cost is just over 2 yuan (28 US cents) per tonne, compared with the city's water prices at 6.2 yuan per tonne, it said.

ChemChina president Ren Jianxin said last December that the company had set a target of "zero emissions" and would invest 700 million yuan this year to help its plants with technological transformation.

The state-owned company would reduce energy consumption for every 10,000 yuan of production value by 7 percent this year, with waste water discharges, chemical oxygen demand and sulphur dioxide emissions set to drop three percent, he said.

Chemical oxygen demand is a measure of water pollution, while sulphur dioxide is a cause of acid rain.

ChemChina, established in 2004, was ranked 35th among China's 500 top enterprises last year, with assets and annual sales both exceeding 100 billion yuan.