Groundwater pollution

In the last two centuries, human pollution has been getting more and more dangerous to nature. We utilize the resources and flood the planet with chemicals, garbage, and plastic. Groundwater is no exception, moreover its vulnerability is even higher due to „invisibility” and it’s easy to forget about its protection. Although groundwater is naturally more protected than surface water, we can find in it lots of natural and artificial pollutants. It’s important to keep in mind that these two elements of water cycle are always in contact with one another and cannot be managed separately, as we will see in the following incidence from Miskolc. 2006 May was a very rainy month in the city with 215,8 mm precipitation just in 2 weeks on the 76 km2 drainage area of the city’s drinking water wells (as a comparison, the hungarian average is 500-750 mm per year). This enormous amount of water accumulated on the surface and transferred the bacteriological pollutants into the vulnerable karst aquifer, from where the pollution reached the drinking water supply wells. As a result, 3673 patients were registered.

Natural pollutants have no connection with human contamination. We can mention here pathogen organisms like protozoa, bacteria (e.g. Escherichia Coli, Salmonella typhi), and viruses (e.g. Hepatitis). These microbiological pollutants led to devastating epidemics through history but nowadays we have the technology to clear away these organisms from drinking water. There are also a lot of chemical pollutants in water that are dissolved due to water-rock interaction. In Hungary, arsenic may be the most generally known as it’s above the 10 microgram per liter limit value in drinking water in nearly 200 villages. Besides that, iron and manganese also often occur and cause a typical taste and brown colour in water. Methane is also a potential contaminant and very dangerous as it’s an explosive gas. In arid climate volcanic regions fluorine is also common. Several further pollutants could be listed, such as heavy metals, selenium or radioactive elements.

In water quality tests we can also count on many different anthropogenic contaminants. Because of agricultural landuse we can find high level of nitrate in shallow aquifers which can come from organic fertilizer or even from humans in case of no wastewater treatment. Concentration of toxic pesticides can also increase as a result of intensive agriculture. Due to industry, we can find hydrocarbon pollution in groundwater. It has two types: first one is LNAPL (e.g.: benzine) which has a lower density than water so it contaminates mainly the level of groundwater table and the unsaturated zone above; at the same time DNAPL hydrocarbons (e.g.: chlorobenzene) has a higher density, therefore these are concentrated in the bottom of the aquifers.

In the previous decades more and more researches have been dealing with emerging pollutants (EP) which are recognised in wastewater and unfortunately in natural water. One of them is microplastic which means plastic pieces with less than 5 mm diameter. According to the researches, an average 45 pieces were measured in every 1 m3 in the Danube near Budapest in 2018. Besides that, xenobiotics are also known as EPs. These are such components in biological systems that cannot be found under natural conditions. These are for example medicines (e.g.: ibuprofen), cosmetics, or food additives.

Source: https://ars.els-cdn.com/content/image/1-s2.0-S2352801X17302217-fx1_lrg.jpg

Maybe you can feel a little nervous after all these contaminants, but you shouldn’t forget that we have modern technologies to remove all pollution from water for having healthy and safe drinking water. In our next post, you can read about these water purification technologies.