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Data Entry: June 2011
Name of Technology Phosphorus Recovery from Sewage Sludge Incinerator Ash
Technology Owner METAWATER Co., Ltd.
Waterworks & Sewerage Department, Gifu City Government
General Description This technology is to facilitate beneficial use of sewage incinerator ash by achieving the following.

(1)To recover phosphorus from incinerator ash for use as a high value-added raw material for fertilizers.
(2)To produce ash that meets the environmental quality standards for soil and the standards for soil contaminant levels and that also has a low phosphorus content and elution levels, for use as construction materials and the like.

Schematic diagram of phosphorus recovery technology for incinerator ash

Components of Technology The technology comprises the following:

(1)Phosphorus extractor
The phosphorus extractor removes phosphorus from incinerator ash as phosphate anions by adding an alkaline solution to high phosphorus concentration incinerator ash and maintaining a temperature of 50°C to 90°C for reaction. This is followed by solid-liquid separation of incinerator ash to separate low phosphorus-content incinerator ash (hereafter “dephosphorized ash E from a solution that contains a high level of phosphate anions (hereafter “phosphorus extract E.
In the case of recovery of raw material for liquid fertilizer, the phosphorus extract is the raw material.
Incidentally, ash after phosphorus extraction becomes dephosphorized ash meeting the environmental quality standards for soil and the standards for soil contaminant levels through rinsing with water followed by cleaning with wash water maintained at pH 5 by sulfuric acid.

(2) Phosphate precipitator
The phosphate precipitator adds slaked lime to the phosphorus extract to precipitate phosphorus in the form of calcium phosphate. The precipitate undergoes a solid-liquid separation process to separate recovered phosphate, whose main component is calcium phosphate, from an alkaline solution (hereafter “reclaimed reaction fluid E. Lacking chemicals are supplemented so that the reaction fluid can be used repeatedly.

Schematic diagram of technology used to recover phosphorus from incinerator ash
(phosphate recovery process)

Features of Technology This technology has the following features in contrast to the existing technologies used to recover phosphorus from sewage sludge or incinerator ash.

(1) Two types of product are obtained from incinerator ash recycling.
  • Dephosphorized ash: Easy to handle as a raw material for construction materials since it meets the environmental quality standards for soil and the standards for soil contaminant levels and has a low phosphorus content and elution levels.
  • Recovered phosphate or raw material for liquid fertilizer: Can be used as a raw material for phosphate or mixed fertilizer.
(2) Compact equipment
Since the newly developed technology recovers phosphorus from incinerator ash with high phosphorus concentration, it features more compact equipment than existing systems that recover phosphorus from sludge.

(3) Heating value requirements met by surplus heat of incinerator
The required heating value for heating at 50°C to 70°C is provided from the surplus heat of the incinerator.
Evaluation of Technology This technology was developed in the LOTUS Project (Lead to Outstanding technology for Utilization of Sludge Project) and evaluated and reviewed by the Sewerage Technology Development Project Committee under the Ministry of Land, Infrastructure and Transport in Japan in 2007.

[Link to the technology evaluation report]

Note: This technology was developed by NGK Insulators, Ltd. and Waterworks/Sewerage Department of Gifu City Government, and evaluated in 2007.  The water and environment business and services of NGK Insulators, Ltd were transferred and have been operated by METAWATER Co., Ltd since 2008.
Contact Information METAWATER Co., Ltd.

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