Masayoshi Kubota

Development of water re-use treatment system for municipal wastewater

Abstract The move for environmental protection and preservation of clean water sources has given rise to the latest tendency in Japan toward reuse of waste water after advanced treatment. As a means of saving water and securing water sources, water reuse systems are beginning to be installed to treat waste water for reuse as flushing water and cooling water for air conditioners. This study was conducted with the aim of developing a compact high-performance water treatment system that may meet the stated requirement. Most water reuse systems in practical use today are based on biological treatment. With this process, treatment is slow and equipment takes up much space. In addition, it involves a large amount of sludge. In an attempt to overcome these disadvantages, we developed a physico- chemical treatment technique that combines the three elementary techniques of dissolved air flotation, foaming separation, and activated carbon packed electrolyzer, and that permits multifunctional treatment with compact equipment. The activated carbon packed electrolyzer, which forms the core of the new system, is a newly developed technique. The purification mechanism was established, and conditions of application to actual waste water were determined. The electrolyzer was combined with the dissolved air flotation and foaming separation methods, to make up an optimum system. With a 10 m3/d trially manufactured apparatus, a demonstration test on reuse of sewage was performed to study the performance and economics of the system. The desired target was achieved and prospects were gained for commercialization.