HEFEI, Oct. 27 -- Water pollution in the Huaihe River remains serious after decades of anti-pollution treatment, with 22 percent of water not suitable for drinking, industrial or agricultural use, authorities said Monday.

Some 1,355 pollutant discharge outlets along the river released 5.17 billion tons of sewage water, 432,200 tons in chemical oxygen demand and 41,300 tons of ammonia nitrogen in 2013, far exceeding the 2030 target set by the government, according to the Huaihe Water Resources Commission under the Ministry of Water Resources.

China divides water quality into five grades. Grade I is drinkable and the least polluted, while grade V water can only be used for agriculture. Water worse than grade V accounted for 22 percent of the river and cannot even be used in agriculture, according to the commission.

The 1,000-km-long Huaihe River is one of China's major rivers, running through the east of the country between the Yangtze and Yellow rivers.

In 1994, China launched a campaign to clean the river, which has been heavily polluted since the 1980s, but the pollution still lingers despite expensive control efforts.