CSO Disinfection in Tokyo, Japan: Confined Space Solutions Using a Small Footprint, Energy Efficient, High Rate Disinfection System Utilizing a Bromine Based Biocide
Operational success of a small footprint, low efficiency, high-rate, disinfection system for combined sewer overflows (CSO’s) has been demonstrated at six locations in Metropolitan Tokyo since 2001. An effective biocide, BCDMH (1-bromo-3-chloro-5, 5- dimethydantoin) is stored in a stable powdered form and can be dispatched at a high rate to raw water flows. Fast reaction times significantly reduce the size of mixing chambers by an order of magnitude over traditional NaOCl systems. Because of the small footprint, it has been possible to integrate such systems into existing water treatment, water recycling and pumping stations in land constrained Tokyo. Dosing systems are installed in areas as little as 25 feet by 25 feet. Disinfectant can be injected into raw water flows after screening. In the current systems, flow, during the length of the discharge pipe is sufficient to achieve disinfection. CSO events as large as 1,800 MGD have been successfully treated to Japanese government discharge standards of 3,000 CFU/ml. Similarity of CSO events and water quality in Japan, as well as operational data from a pilot unit in Northern Ohio confirms replicability and applicability of such systems in North America. Design and operational data from six Tokyo locations is presented in english and metric units. Poster addresses the following topics: 1) water quality of CSO events in Metropolitan Tokyo, 2) system design of a biocide disinfection system using BCDMH, 3) disinfection effectiveness of BCDMH to NaOCl, 4) power consumption & other design criteria.