Mystery of sewage treatment unveiled

CHINA has made rapid improvements in its sanitary services by building wastewater treatment plants. Yet its 4,000 sewage treatment plants could pose a risk of secondary contamination if they are unable to dispose excessive sludge properly.

Sludge accumulates as a result of the treatment of domestic sewage and industrial wastewater. Once created, sludge can be highly toxic and needs to be treated before disposal.

“Over 90 percent of municipal sewage and over 50 percent of industrial wastewater are treated using an activated sludge process in China. But challenges such as high energy consumption, frequent sludge bulking and foaming still remain, causing water contamination,” said Qiu Dongru, a researcher at the Institute of Hydrobiology of Chinese Academy of Sciences.

The activated sludge process was developed in England in 1914, and involves the production of an activated mass of microorganisms capable of aerobically stabilizing the organic content of waste water.

As a main wastewater treatment technology, the process has been adopted worldwide, yet the key factor in the technology had been unclear.

To unveil this mystery, a research group led by Qiu studied the microbiome of activated sludge and found that bacterial floc formation plays a central role in the process, allowing the sludge-and-effluent separation and recycling of activated sludge.

Their findings also provided the first direct experimental evidence that PEP-CTERM proteins are required for bacterial floc formation. The study was published online on Monday.