Metawater Technology Selected for B-DASH Project
- “Energy Management System using an Intensive Solid-liquid Separation Technology” -
A project set up to demonstrate energy management systems using an intensive solid-liquid separation technology proposed by METAWATER (President: Tomoyasu Kida, Main Office at Minato ku, Tokyo) was selected for implementation in the B-DASH Project undertaken by MLIT.
The aim of the technology to be demonstrated is to establish a new sewage treatment flow from both the energy-conservation and energy–creation viewpoints based on the concepts of thorough solid-liquid separation and resource recovery during sewage sludge treatment. The goal is to develop sewage treatment plants capable of supplying their own power and of overall management of energy. (This was developed as a result of research conducted by a joint study team with the Japan Sewage Works Agency.)
Three innovative technologies will be demonstrated: "intensive solid-liquid separation"; "thermophilic digestion"; and "smart-power generation." When combined to function as a system, they achieve reduction of greenhouse gas emissions by 90% or more,* construction costs by 10% or more, and maintenance costs by 40% or more.
* Greenhouse gas emission includes emissions from sludge incineration.
Total annual greenhouse gas emissions from sewage treatment plants in Japan is estimated to be seven million tons or more. (See MLIT website for 2007 figures.) With Japan officially committed to the goal of reducing domestic greenhouse gas emissions to a level 25% below that of 1990, reducing power consumption and developing renewable energy recovery technologies for treatment plants have become urgent tasks.
It is against this background that MLIT has undertaken its B-DASH Project (Breakthrough by Dynamic Approach in Sewage High Technology Project). The objectives of this project are the acceleration of systematization and practical application of technologies used to convert sewage sludge into renewable energy and to promote the dissemination of the technologies inside and outside of Japan. The implementation of the B-DASH project has resulted in the construction of sewage treatment plants capable of supplying their own power, substantial reductions of costs and greenhouse gas emissions, international standardization of innovative technologies, and the provision of support for international development of water businesses through site sales at the demonstration facilities.
In line with this project strategy, METAWATER has developed innovative technologies for water treatment, sludge treatment, and energy management systems. In this latest project, the company is demonstrating a new sewage treatment plant in which these innovative technologies are systematized.
Project operator：Joint study team established by METAWATER and the Japan Sewage Works Agency (JS)
Demonstration field：Nakahama Sewage Treatment Plant, Osaka
The aim of this demonstration project is management of an entire sewage treatment plant by utilizing the three innovative technologies illustrated in the figure below. They are energy-conservation and energy–creation methods based on the concepts of thorough solid-liquid separation and resource recovery concepts. The target here is to raise electric power self-supply ratios while reducing greenhouse gas emissions and construction and maintenance costs.
This system performs intensive solid-liquid separation of sewage influent to separate sludge and treated water. This is done to achieve energy conservation by reducing inflow loads in the wastewater treatment system. Thermophilic digestion is used in the sludge treatment system, where the introduction of garbage will increase biogas recovery further to contribute to greater energy creation with a smart power generation system.
Individual innovative technologies
- 1. Intensive solid-liquid separation
Intensive solid-liquid separation with upflow filtration is used for primary treatment of sewage influent. This results in efficient elimination of SS and BOD in the filtered water, enabling significant energy savings in the water treatment process (with aeration power reduced by 20%). In addition, efficient primary sludge recovery (raw sludge increased by 40%) and reduction of excess sludge (by 40%) enables the establishment of a sludge treatment system in which energy is created.
Development of this technology began as part of CSO control technology developed in the MLIT's Sewerage Project, Integrated and Revolutionary Technology for 21st century (SPIRIT21: Sewerage Technology Development Project) in March, 2005. The system was then improved as a space-saving primary sludge alternative method in the MLIT's Next-generation Support New Technology Utilization Model Project undertaken in 2009 and 2010. Currently this technology is demonstrated as an ultra-high-efficiency technology that utilizes measures to improve removal ratios.
- 2. Thermophilic digestion
The system uses a carrier-filled type of thermophilic digestion technology capable of digesting within a short retention time (up to five days). Stable operation is ensured in a process in which the carrier effect offers resistance against load fluctuation, and ammonium concentration control and automatic controls to prevent hindrance to digestion are incorporated. The use of a steel plate tank provides design flexibility while making sediment dredging from the bottom of tank unnecessary. The addition of garbage to the raw sludge becomes possible, which in turn enables recovery of larger amount of biogas. Finally, downsizing of the digester makes steel plate tank manufacturing possible, which substantially reduces the cost of construction.
This technology has been demonstrated in a pilot plant (Yatsushiro Hokubu Sewage Treatment Plant, Kumamoto) since 2008, in a joint study conducted with JS ("Development of energy recovery utilization technology from sewage sludge appropriate for medium- and small-scale treatment plants"). After confirmation of stable operation (stable quality, record of continuous operation) and digestion performance, the demonstration this time is of a full-scale plant. (JS focuses on the study of this technology.)
- 3. Smart Power generation
Smart Power generation enables fuel-cell power generation with hybrid fuels, which ensures full utilization of recovered biogas. The system also offers extremely high power generation efficiency. Combining this system with plant operation optimization control enables reduction of power consumption. In addition, a high electric power self-supply ratio has been achieved due to energy management of the entire sewage treatment plant.
The system being demonstrated was developed using digestion-gas fuel-cell technology previously introduced at the Yamagata Sewage Treatment Plant and the Kumamoto Hokubu Sewage Treatment Plant. It is being demonstrated as a high-function modification system to control the flow (mixing ratio) compatible with two types of fuel, public gas and digestion gas.
Future Metawater efforts
This year, the company plans to set up and begin demonstrating a water treatment system (using intensive solid-liquid separation technology) with a capacity of 5,700 m3/day and a sludge treatment system (using thermophilic digestion and smart-power generation) with a daily capacity of 0.5 ton DS (including garbage) in Osaka's Nakahama Sewage Treatment Plant.