Sludge Watch ==> A Chinese way to transform sewage sludge into cement

[maureen.reilly at sympatico.ca]

Now, a Chinese way to transform sewage sludge into cement


Monday, September 11, 2006

http://www.dnaindia.com/report.asp?NewsID=1052334


BEIJING: As Chinese cities face mounting dumps of sewage sludge, an expert 
has found a new way to make use of the toxic material  by coverting it into 
bricks and cement at a low cost.

A professor with the Environmental and Biological Geochemistry Institute of 
the Zhejiang University in east China's Zhejiang Province Weng Huanxin has 
developed a method of transferring sludge into bricks and cement.

Sludge is threatening to besiege more than 700 cities in China. Beijing 
alone produces 1,000 tonnes of sludge a day, Shanghai 700 tonnes and 
Shenzhen 300 tonnes.

It is estimated that China's sludge amount will rise at an annual rate of 10 
to 15 per cent in the following years.

Beijing is expected to discharge over two million tonnes of sewage every day 
in 2008, which is likely to yield more than 2,000 tons of sludge if all the 
sewage is treated.

Most of the sludge is just piled up in open air or landfilled, which 
occupies too much land and may cause pollution. Direct burning will produce 
toxic fumes.

According to the new technology, sludge can be dried at a low temperature, 
under which toxic components are permanently fixed and won't volatilise any 
more. It is then made into hard bean-sized granules.

The granules, mixed with clays, can be burnt into light-weight bricks. Since 
each granule contains 1,500 kilocalories of heat, they themselves can 
contribute to burning and help save fuels.

Meanwhile, small holes emerging inside the granules after burning will 
reduce the weight of bricks and enhance their resistance against pressure.