2013 Volume 67 Issue 1 Pages 82-85
Lately methane fermentation technology is widely applied in many industries because of the recent development in this technology has made wastewater treatment highly effective. One of the advantages of this technology is to recover energy as biogas from organic compounds in wastewater. This paper describes application of methane fermentation technology to KP mill evaporate condensate at Nippon Paper’s two KP (kraft pulp) mills, the Yufutsu plant of Hokkaido mill and Iwakuni mill. Through the experience in actual operation of methane fermentation, it was recognized that there was a problem of overflowing granule from the reactor caused by upward flow in the reactor.
In order to look into the problem, we compared the properties of granule in Yufutsu plant with those in food mill which already established a stable process in methane fermentation treatment. As a result, filamentous acetic acid-degrading methanogens (Methanosaeta) was mainly observed in food mill’s granule, while spherical methanol-degrading methanogens (Metanosarsina) was mainly observed in Yufutsu plant’s granule. This difference of methanogen species, which was caused by methanol treatment, is presumed to weaken the cohesive force of granule, consequently making the granule remarkably fine. On the basis of the result of this investigation, we studied of method to prevent flocculated methanogens from becoming smaller by lab. -experiment. It was found that the addition of starchy wastewater was very effective. Trial at commercial plant showed that the addition of starchy wastewater increased Methanosaeta and granule became bigger and heavier.
