NKK to Develop Sewage Sludge Acid
Fermentation Technology
NKK has accepted a subcontract from the Japan Science
and Technology Corporation to develop a sewage sludge fermentation system
and has begun research aimed at full-scale commercialization of the
technology.
To accelerate and bring new efficiency to the sewage
sludge methane fermentation process, NKK will concentrate on the development
and verification of pre-processing technology. The technique involves
the addition of vitamins and other substances after sewage sludge has
been made soluble. These substances accelerate the speed of the acid
fermentation process.
NKK will build a pilot plant within its Keihin Works
during this fiscal year and, after testing the technology, will begin
onsite experiments at a sewage treatment plant during fiscal 2004. The
company expects the system to reduce sludge volume by at least 20% compared
to conventional methods, with a commensurate decrease in total processing
costs. NKK aims to commercialize the system in 2005, targeting mainly
sewage treatment plant operators nationwide.
The fermentation system will combine two techniques:
1) a pre-processing technique that makes sludge more soluble by adding
alkaline chemicals (caustic soda) and irradiating the sludge with ultrasonic
waves to destroy the bacteria in it; and 2) an acid fermentation process
that adds vitamins to the mixture to accelerate fermentation. Originally
developed by a Hiroshima University professor of advanced materials,
this technology is expected to reduce the processing time to 3-5 days
and eliminate roughly half of the solids in the sludge, thereby substantially
improving the efficiency of subsequent processes in methane fermentation
tanks. The new technology will also reduce space requirements and running
costs, while use of compact sludge concentration and dewatering equipment
will lower total costs.
NKK intends to move forward quickly on system development
and sees it as one of the key technologies in a range of comprehensive
system engineering services for better utilization of sewage resources.
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