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Utilization of Sludge

Utilization as Fuel for Thermal Power Plant

Along with incinerating and reducing 100% of the sludge generated during the wastewater treatment process, we are diversifying the uses for recycled sludge and increasing our recycling ratio in order to extend the life of sanitary landfills.

FY2006 recycling rate 64%

Outline of Carbonization Project

In this project the carbonized material manufactured in the sludge carbonization facility constructed in the Tobu Sludge Plant is used as a substitute to the coal in coal thermal power plant. The design, construction, maintenance, management and operation of the sludge carbonization facility are collectively entrusted in a bulk package with a commissioned corporation. The operation started in November, 2007 and the operating term will be 20 years.
Since there is a clear knowledge about the customers over a long time period, this project ensures a stable recycling of resources. Thus, the project not only brings about vast improvement in recycling of sewage sludge (equivalent approximately to 9% of the annual sludge quantity), but also contributes to great reduction in the emission of greenhouse gas.

Carbonized material

Tobu Sludge Plant (Carbonized material production equipment)

  • Place of installation: Tobu Sludge Plant
  • Operation started: November 2007
  • Facility scale: Dewatered sludge-300 t/day

Scheme of Carbonization Project

Carbonized material production equipment

Various Materials

Super Ash (Size-controlled Ash)

By regulating the grains of incineration ash of sewage sludge to small size through classification and pulverization, the excellent characteristics of the incineration ash can be obtained for use as a substitute to the clay material (bentonite※) largely used in civil engineering works, etc.

Tobu Sludge Plant (Carbonized material production equipment)

※ Bentonite is a clay mineral produced by the transformation of volcanic ashes piled up at the bottom of sea or lake during volcanic eruptions, and is used as an admixture of cement.

Super-ash Facility

  • Place of installation: Kasai Water Reclamation Center
  • Operation commencement: March 2003
  • Facility scale: Manufacturing capacity-12,000 t

Lightweight Aggregate

The incineration ash of sewage sludge is used as a part of artificial lightweight aggregate, which itself is used as the material for lightweight concrete.

Lightweight Aggregate

Cement and Asphalt Material

Cement is mainly made up of the materials such as limestone, clay, siliceous material, iron material, etc. The sewage sludge incineration ash is generally composed of the aforesaid clay material, and therefore, can be used as a part of the cement material.
Further, its use as an asphalt admixture has also been started since the fiscal year 2002.

Cement and Asphalt Material

FY2006 recycling rate 64%

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