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BIZCHINA> Review & Analysis
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Sludge solution
By Zhang Qi (China Daily)
Updated: 2008-03-31 14:05 Second, to make the heavy metals and bacteria passive, the sludge heap must be kept at a relatively high temperature for a week, preferably between 50 C to 60 C. So turning over the sludge isn't helpful. This being the case, to compost the sludge and remove pollutants is inherently contradictory in the traditional method. This is where ZB High-tech comes in. It keeps sludge in interior pools, with oxygen chambers built at the bottom of the pools to provide additional oxygen as needed. This is the world's first technology based on static oxygen consumption, as Han Yishun, the company's CEO, tells China Business Weekly. After the toxicity is removed, the sludge becomes an organic fertilizer. It can also be mixed with chemicals to suit the market in different regions, Han says. He also says the technology can be applied to other industries - such as paper mills, poultry farms and abattoirs - as their waste is highly organic. But the technology is not good for specialized industrial sewage plants, because the sludge produced tends to have too high a heavy metal content and is low on organic substances. Treatment plants The company is working with several partners to build sludge treatment plants. Most of them are small, and given the cost of moving sewage sludge, most are built next to sewage plants and paper mills. The company's largest project is a result of its partnership with Shandong-based Chenming Paper Co, completed in 2006, which can treat 300 tons of sludge a day. The largest in China, the project consists of 24 sludge pools and is equipped with an online oxygen monitoring system. Despite painstaking research and conclusive test results, Han says many people are still dubious about the quality of the end-product. "It is a prejudice," Zhao Bingqiang, a CAAS professor, says. "Actually, sludge is a very good material for fertilizer if it is treated properly." The right composting method can yield a highly nutritional fertilizer. "But landfills are clearly not the solution - rather, they're pollution," he says. "They infiltrate the soil and pollute groundwater. As for incineration, it's much more expensive than our composting solution. Our solution, as our philosophy says, is to recycle waste into a resource." (For more biz stories, please visit Industries)
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