It is possible to freely adjust the moisture content of liquid sludge (moisture content 98%) or dewatered sludge (moisture content 85%) to the desired moisture content and dry it. The excess sludge generated by activated sludge wastewater treatment contains all the cells of bio-bacteria. If this sludge is fermented with the usual moisture adjustment, it will mature after 2 to 4 months and can be used as fermented fertilizer.If this sludge is boiled and dried with an Okadora cyclone dryer, the cell tissue is destroyed, and if the moisture is adjusted to 40 to 50% and then fermented, it can mature in just 6 to 8 days.Also, if sludge that has been dried to 10% moisture with a conventional hot air dryer is soaked in water, it will return to sludge again, and if used as fertilizer, it will cause the roots of food to rot.If it is boiled and dried with a cyclone dryer, the cells are completely destroyed, so it will not return to sludge even if it is submerged in water, and it can be used as an optimal fertilizer.