"Non-Aeration Recycled Water Treatment Demonstration Project" selected for B-DASH Project
- For Innovation of wastewater treatment in Tosa, a region of creation -
The project involves demonstrating technologies that contribute greatly to the sustainability of medium- and small-scale wastewater utilities facing financial and other difficulties.
In the Breakthrough by Dynamic Approach in Sewage High Technology Project (the B-DASH project) undertaken by MLIT*, the “Non-aeration Recycled Water Treatment Technology Demonstration Project” proposed by a joint study team was selected for implementation in 2014. The study team consists of four entities: Kochi City (Mayor: Seiya Okazaki ), Kochi University (President: Hiroshi Wakiguchi, Administrative Office in Kochi City ), Japan Sewage Works Agency (President: Yoshihiko Tanito, Main Office in Bunkyo- ku, Tokyo; hereinafter “JS”), and Metawater Co., Ltd. (President: Tomoyasu Kida, Main Office in Chiyoda -ku, Tokyo; “METAWATER” ).
The proposal includes technology contributing greatly to securing the sustainability of wastewater treatment utilities of medium- to -small municipalities facing such issues as population decrease, financial difficulties, and a shortage of engineer s . The technology are designed to (1) achieve substantial reduction of power consumption, (2) achieve stable treated water quality, and (3) avoid the need of substantial modification of existing facilities.
Compared with conventional activated sludge processes, this technology aims at dramatic cost reductions in construction and maintenance , and reduced power consumption . It contributes to stabilization of the management of sewerage service through energy conservation, while taking into account social demands to cope with such issues as tight energy supply -demand situations and global warning .
- *A demonstration project implemented by MLIT since 2011 to support the development of overseas water business by improving the efficiency of energy utilization in wastewater systems and reducing stock LCC by accelerating research and development work and practical implementation of new technologies. This project consists of demonstrating the effects of innovative technologies proposed by entities selected by public invitation and examined by experts. Plants of actual scale are used in the demonstrations.
Outline of the project
Kochi City, which provides the demonstration field, sets forth "Creation of a sustainable society based on recycling and coexistence with the environment" in its "Kochi City Sewerage Medium-term Vision" (developed in 2012). An important goal is to hand over a sound water environment to the next generation. A general engineering company in the field of water environment, METAWATER strives for creation of a water/resource/energy cycle by means of advanced core technologies. The four joint study team members, including Kochi University and JS, intend to work closely together to establish innovative technologies contributing to the further development of sewerage services and to a sustainable, sound water environment.
Project operators ：Joint study team including Kochi City, Kochi University, JS, and METAWATER
Demonstration field：Kochi City Simoji Sewage Treatment plant (Oguracho 5-25, Kochi City, Kochi Prefecture)
Existing treatment method：Conventional activated sludge process, etc.
Demonstration facilities will be constructed in the above field.
Features of this demonstration project
Japanese society is facing a rapidly decreasing and aging population. It is expected that management of sewerage facilities will be increasingly difficult in the future. Power consumption per unit treatment tends to be greater in the case of medium- to small-scale sewage treatment plants. Consequently, these plants face such tasks as upgrading operations to save electric power and reducing life cycle costs.
As an alternative to the conventional activated sludge process used to treats 75% of the wastewater in Japan, the demonstrated technology can reduce power consumption by about 70%. Along with power saving, it is expected to contribute to more efficient operation of treatment plants.
(1) Substantial reduction of power consumption
The conventional activated sludge process requires the fan to feed large amount of air into the bio reactor. This technology employs the air-liquid contact process to intake oxygen from air, reducing the power consumption of the fan equipment, a source of conventional high costs, and enabling oxygen supply with low power.
Treatment cost (per unit treatment) of water treatment system as a whole
(conventional activated sludge process)
|0.2kWh/m3||0.06kWh/m3 (target) 〔conventional rate▲70％〕|
(2) Securing stable treated water quality
In this technology, treated water from the second reactor (the conventional biological reactor) is recycled to the first reactor (the conventional primary settling tank) to enable biological treatment in the first tank. In this way, biological decomposition and removal of organics (BOD) is achieved in a stable manner by entirely using the first and second tanks.
The third tank (the conventional final settling tank) can remove fine suspended solids (SS) by means of physical filtration. This offers satisfactory treated-water quality.
This technology can also be operated under automated control. Stable treatment is ensured without the need for operators with high-levels of experience or technical knowledge.
(3) Applicability to the existing treatment plant
This technology is based on assumed utilization of existing civil works and tanks. With the innovative technology, the area required is about 50% of that required with conventional technology (activated sludge process). As for height, the system can be housed within the depth of existing tanks. This technology can therefore be applied to sewage treatment plants with double covers.
The innovative technology can eliminate the cost of building new structures even in sewage treatment plants which are expected to treat increased wastewater volumes in the future.
In the event of a future decrease in the population requiring service, the innovative technology allows for changes in the number of units according to the amount of water to be treated, which in turn enables further reduction of power consumption.