The rising nitrate contamination of ground water and higher costs of treatment of drinking water are receiving more and more public attention. Nitrate (NO3-) is a nitrogen compound. Nitrogen is an elementary component of all living organisms.
Nitrate is potentially hazardous to health and may cause methemoglobinemia in humans (especially children) through a chemical reaction. It can also produce precursors of potentially toxic and carcinogenic Nitrosamines.
This caused the establishment of a nitrate limit of 50 mg/l in drinking water in the German Drinking Water Ordinance of 2001. However, in 2016 the nitrate limit was exceeded at 28 % of the ground water testing sites in Germany.
The main source of nitrate in ground water is the nutrient contamination in agriculture, mainly organic fertilizer such as liquid manure and other animal excrement, produced by the steady increase of meat production, as well as digestate from biogas plants used for energy production. Since the surplus value of 70 kg/ha planned for 2030 was exceeded by almost 40 % in 2013 it is safe to assume that in the following years the nitrate limit for ground water wells will also be exceeded or in the worst case scenario the contamination increases even further.
There are several potential solutions to reduce the nitrate concentration in the ground water in a sustainable way. The most sustainable – though lengthy – would be in the reduction of nitrate levels through a reform of meat production as well as the reform and deconstruction of biogas plants as seen in Denmark.
As an alternative the contaminated ground water could be cleaned using several technologies such as electrodialysis or biological processes. A draw-back are the high operational costs.