The sources and contamination sources of chromate in the raw water of drinking water suppliers were clarified in the southern area of the Upper Rhine Graben. Recommended actions were also suggested for its elimination.
For a few years now, the toxicity of hexavalent chromium (chromate) has been assessed as being more critical than was the case in the past. Therefore, since around 2013, consideration has been given to reducing the limit value for chromium in drinking water. However, in the last amendment to the German Drinking Water Ordinance on 3 January 2018, the limit value was not changed; it remains 50 µg/l for total chromium.
During the period when the authorities such as the Federal Ministry of Health and the German Environment Agency were also discussing a reduction in the drinking water limit value, several tests had been conducted on the presence of hexavalent chromium, in which chromium(VI) levels were determined in ground water, spring and surface water. Noticeably elevated concentrations of chromium(VI) were determined in the groundwater in the Upper Rhine Graben region. In this project, therefore, a more in-depth consideration of the chromium concentrations in groundwater and spring waters with high regional or local resolution was undertaken. A detailed examination of individual model areas and further investigations of groundwater measurement points also identified the causes of the chromate pollution.
In the analysed groundwater and spring water, chromium is primarily present as hexavalent chromate. Concentrations vary between < 0.02 µg/l and 3 µg/l. In relation to the retained limit value of 50 µg/l, these concentrations are therefore low.
The detailed investigations of a total of six model areas showed that increased chromium levels in groundwater and spring water are usually of geogenic origin.
