March 18 is the final day of each fresh cassava-gathering season in Qiong Zhong county Hainan province. In the fresh cassava-processing workshop of Benlu, the starch production approaches to ending. Whereas, the UASB reactor of wastewater treatment system still kept producing a plenty of biogas. Because there is only one stove for flash dryer working short time every day, the quantity of biogas as fuel of the stove consumedly exceeds its requirement. Then they have to burn the remanent biogas. The operation engineer will start to force anaerobic bacterium in UASB reactor into temporary dormancy; it will be woken up when the new running season (September) comes.

Benlu Starch factory is the first factory adopts anaerobic and aerobic system to treat effluent water from cassava starch workshop in Hainan province. In 2000, they received ultimatum from the government, because the only river passing through Qiongzhong County was polluted by the effluent water from starch factory. They had to invest UASB to treat 3000m³/d wastewater, the draining water reached to national standard in 2001. The delightful thing is, they can get 2.5~2.8m³ biogas from each MT wastewater. And they adopted the biogas stage by stage to replace the heavy oil as the fuel of stove for starch drying. 5 years past, they have succeeded in replacing 80% of the heavy oil by biogas. Actually, till to 2005, they have already taken back all investment in the wastewater treatment by saving fuel. 

For commending their achievement in environment protection, the government of Hainan province provided 4,000,000RMB (equals 500,000USD) bounty to them as encouragement.

A new UASB reactor and two SBR tank constructed last year

Reported by: Mr. Zhao Bao Feng

May 8,2006