Decrease of sludge during the treatment process
Yokohama Environmental Planning Bureau. March 2016. Sewage Water Quality in Yokohama City. http://www.city.yokohama.lg.jp/kankyo/data/gesui/hakusho/swqinyc2016.pdf
Utilization of Resources Generated from Sludge Treatment
Sludge generated from wastewater treatment process is also recycled in Yokohama City. Sludge generated in eleven wastewater treatment plants is transported to two sludge treatment plants, and then subject to thickening, digestion, and dehydration processes. After the treatment, the weight of the sludge decreases by 400 times, and becomes an odorless, hygienic product. Gas generated during the digestion process is recovered as a source of energy and utilized for electricity generation and fuel for incineration in the treatment plants. In addition, the ash after incineration has been used as raw material for improved soil and cement.
- Technologies to utilize processed sludge
No small amount of sludge is generated from wastewater treatment plants, reaching about 20 % of the total industrial waste in Japan. Conventional landfilling of this by-product has been causing lack of space in disposal sites and environmental pollution. Local governments and sewage management bodies may decrease the significant volume of final disposal by cautiously processing the sludge and recycling it to fertilizer for farm land, construction materials, and a source of energy.