SHIJIAZHUANG - Water quality is back up to national standards in a reservoir which was contaminated after a chemical spill in Handan city in North China's Hebei province, said local authorities on Tuesday.

As of Monday, the overall quality of water in the Yuecheng Reservoir, source of Handan's tap water, has attained the national standard, said Hou Risheng, chief engineer with the city's environmental protection bureau.

On Dec 31, about 9 tonnes of aniline were leaked by a chemical plant owned by the Tianji Coal Chemical Industry Group into the Zhuozhang River in Changzhi city, Shanxi province.

The contamination has affected drinking water supplies of the Yuecheng Reservoir in downstream Handan, which has a population of more than 1 million people.

The Handan city government authorities cut water supply from the Yuecheng Reservoir on Saturday.

Hou said that, according to the water quality monitoring data, no aniline has been found in collected water samples.

And the detected volatile phenol indexes have reached the national standard for a drinking water source.

The official added that local authorities will strengthen water quality monitoring in the reservoir to ensure the safety of drinking water.

To date, tap water supply to the urban area has been resumed using water from the Yuecheng Reservoir and an underground water source.