Sewage Works in Osaka, Japan

Respond to New Demands through Advanced-Technology R & D

(2) Implementing the joint research with private companies

Phosphorus recovery as MAP (magnesium ammonium phosphate) from digested sludge

In the centralized sludge treatment project implemented by Osaka city, sludge generated in sewage treatment plants is conveyed to Maishima Sludge Center through the sludge transportation pressure pipe network after thickening and anaerobic digestion (Thermophilic / High Concentration Digestion) process. Further sludge treatment processes such as dehydration and melting are implemented centralizedly at Maishima Sludge Center.
As the thermophilic / high concentration digested sludge that is conveyed through the pipe contains high concentration of ammonium nitrogen and phosphate ion, MAP scale may be generated and may seriously impact the sludge transportation pipe and sludge treatment process.
Currently soluble phosphorus in digested sludge is removed by making solid matters of phosphate and iron ion, which is supplied by inorganic coagulant added to digested sludge. However high concentration of iron will give harmful effect to sludge melting process.
Therefore, MAP Recovery Process has been developed by the joint research with private companies as an alternative countermeasure.

Facility for the Recovery of phosphorus of digested sludge as MAP (magnesium ammonium phosphate)

Research on effective removal of nitrogen contained in effluent from dewatering process of digested sludge

In the centralized sludge treatment project process, effluent which contains high concentration of nitrogen is generated from the sludge dehydration process. The aim of the research is development and practical use of nitrogen removal technology that causes less environmental loads and is easy to operate.
The ANAMMOX (Anaerobic Ammonium Oxidation) method is a new technology to remove nitrogen from dewatering effluent by the use of microorganisms that convert ammonia and nitrous acid into nitrogen gas and its joint research has been conducted since 2007.

Reaction route of Conventional Nitrification/Denitrification (left) and Denitrification using Anammox method

Adoption of Innovative Shield Tunneling Method

Since Osaka City has been densely urbanized, there is an increasing number of trunk sewer construction projects for which it is difficult to secure sufficient space. In addition, sewer construction requires lower noise/vibration, shorter construction period, and other measures for preserving the environment surrounding the construction site.
The Osaka City Government has dealt with these issues mainly by employing a vertical/horizontal continuous shield tunneling method, as well as by developing up-cut shield tunneling technology jointly with a private enterprise and putting it into practice. This up-cut shield tunneling system won the Technical Award for FY2001 from the Japan Society of Civil Engineers.

Vertical / horizontal continuous shield machine (model)	Up-cut shield tunneling machine

Tunneling Procedures of up-cut shield tunneling

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