Sludge left by sewage causes sticky problem

BEIJING - About 80 percent of the sludge remaining after sewage treatment is not properly handled and has itself become a source of pollution, industry statistics has suggested.

Nearly 2,200 tons of sludge is produced each year in the country, but 80 percent is dumped or even piled up in the open air, according to the 2011 Market Analysis Report of Sludge Treatment in China issued by h2o-china.com, the website of China's water industry.

Sludge, the byproduct of sewage treatment plants, comes from organic matter in sewage. But dealing with the hazardous waste is far from safe, industry experts said.