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Completion of a Practical Automatically Controlled “Hot Spring Water Electrolysis Disinfection System

A safe and simple way to remove Legionella species from a chloride spring

March 30, 2010Takenaka Corporation

Takenaka Corporation (President: Toichi Takenaka) has, in cooperation with Tokyo Dome Resort Operations Corporation (President: Masanori Kanda) and Nakabohtec Corrosion Protecting Co., Ltd. (President: Masatoshi Eto), developed the “Hot Spring Water Electrolysis Disinfection System,” which performs electrolytic decomposition to disinfect Legionella species in hot spring water. It has been introduced as a working system at the Atami Korakuen Hotel, verifying its effectiveness
The Hot Spring Water Electrolysis Disinfection System consists of an electrolysis system installed inside hot spring pipes to electrolytically decompose chloride ions in hot spring water(chloride spring), producing chlorine which disinfects the hot spring water. Until now, Legionella species have generally been removed from circulating hot springs by chlorine agent injection. This system does not use a chlorine agent, enabling it to perform disinfection without harming the quality of the original hot spring water by, for example, preventing any chlorine odor.
The system automatically controls the residual chlorine concentration at a uniform level, simplifying operation and maintenance, and holding down the running costs, electricity charges, etc.

Chloride spring: A hot spring with NaCl (salt) as its principal constituent, formerly called a salt spring

【Merits of the System】

It is the perfect system for hot spring hotels and inns which desire the following features.

“We want to be able to easily control the residual chlorine concentration.”

Data obtained by a residual chlorine meter is fed back to the electrolytic cell, automatically adjusting the residual chlorine concentration according to the number of bathers, thereby simplifying the operation of the system.

“We want to be relieved of the daily task of injecting a chlorine agent.”

Under automatic control, the electrolysis system electrolytically decomposes hot spring water (chloride spring water), producing chlorine from the chloride ions in the hot spring water, so that the only required daily task is maintaining the residual chlorine meter.

“We want to reduce our electricity bills.”

The running cost, which is the cost of electricity, depends on the quantity and quality of the water processed, but it is low, at only a few thousand yen per year.

“We want to maintain the original quality of the hot spring water.”

The electrolyzed water obtained through electrolytic decomposition of the hot spring water (chloride spring water) has little chlorine odor and superior diffusibility, providing safety and good disinfection effects without harming the quality of hot spring water.

photo:External view of the electrolytic cell、Residual chlorine measurement、Control panel

<Electrolysis system>

【Verification of its Effectiveness】

The system began operating at the Atami Korakuen Hotel more than three years ago. This has confirmed that the system effectively disinfects the hot spring water while maintaining the residual chlorine concentration between 0.2 and 0.4 milligram per liter(mg/L), a level which satisfies the guidance standard of the Ministry of Health, Labor and Welfare.

Based on the successful operation of the system at the Atami Korakuen Hotel, the Takenaka Corporation plans to introduce it as an environment-friendly technology at inns and hotels equipped with circulating hot spring baths.

【Overview of the System】

1.Electrolysis System

The electrolysis system is a pipe type with electrodes, and its electrodes have a layered structure: titanium plated with noble metal. It can be easily installed anywhere, because it is installed inside a pipe without modification. Inside the pipe, it directly electrolytically decomposes the hot spring water, and the electrodes perform electrolysis with high efficiency. The system is sold by Nakabohtec Corrosion Protecting Co., Ltd.
*The system is suitable for application in hot springs where the concentration of chloride ions in the chloride spring water is 1,000 milligram per liter(mg/L) or higher. (A preliminary water quality survey must be performed before introducing the system.)

2.Residual chlorine meter

The residual chlorine meter monitors the residual chlorine concentration and constantly feeds the measured data back to the electrolysis system. It automatically controls the residual chlorine concentration between 0.2 and 0.4 milligram per liter(mg/L), which satisfies the guidance standard of the Ministry of Health, Labor and Welfare. The residual chlorine concentration is displayed digitally on the control panel, allowing the hot spring operator to check it at any time.