The aim of the project is to obtain detailed information on the sodium hypochlorite solutions available on the market and the chlorate content of the products supplied to water supply companies, as well as on the chlorate formation as a function of the storage conditions. The project process should generate the pre-requisites for revising the relevant standard for sodium hypochlorite.
The aim of the research project was to obtain further information about sodium chlorate content in sodium hypochlorite solutions on delivery routes from the manufacturer to the water supply company. In addition the chlorate formation as a function of the storage conditions was determined.
In order to record the production and storage conditions at manufactures and distributors, research was carried out on site. In addition laboratory tests were carried out to determine the formation of chlorate as a function of temperature and storage time.
As a result, DIN EN 901 should specify that the maximum permissible sodium chlorate content in relation to chlorine of 5.4% must be observed on delivery to the user (WU).
In order to improve the control of the storage time at the water supply company, DIN EN 901 should require stating the filling date of the charge by the loader of the delivery containers. In addition, the recording of the temperature during delivery or storage at the intermediary (at least the highest temperature) should be required by means of temperature-sensitive labelling.
If a sodium hypochlorite solution with a sodium chlorate content of 5.4 % is supplied, a storage temperature of 20°C at the water utility results in a storage time of more than 6 weeks without exceeding the maximum values for chlorate in drinking water for the addition of chlorine, which is used in Germany.