Water Treatment "Part 3": Groundwater.

Safe water supply is a factor of economic growth. As that public health in Western Europe and North America has improved greatly since 1850, when safe drinking water began to be supplied.
In treatment plants, ground or surface water is treated to obtain potable water. Depending on the microbiological variables, the technical equipment is designed and the production plant is operated. Any small disturbance or contamination may cause it to exceed the standards recommended by the World Health Organization. Also, keeping water for long periods within the facilities may lead to the development of bacteria. Therefore, all of this must be taken into consideration during the process of producing potable water.

Sources of drinking water:

Only three percent of the Earth's water is fresh, and two-thirds of this fresh water is frozen, while the part that is not frozen is mostly underground. Potable water is made by treating fresh water. However, due to the high expense of salt extraction, saltwater is rarely chosen for treatment. Desalination of saltwater water is thus only employed to produce drinking water in areas where freshwater is in short supply, such as desert regions or tourist islands.

1- Groundwater:

Most of the time, groundwater needs very little treatment, as being underground for long periods of time makes it microbiologically stable.

Diagram of water well types

Groundwater is extracted in large quantities when a wide and easily porous aquifer is available, and to avoid pollution this aquifer must be almost isolated from the upper soil. The maximum values of the extracted groundwater are regulated and extraction permits are obtained in order to avoid agricultural and environmental damage, as the extraction of groundwater affects the water level in the soil and can cause the drying of that area.

The amount of undesired material that dissolves from the soil depends on the oxygen level of the water, which plays a significant role in defining the quality of groundwater. Most often, aerated groundwater is extracted from the free sandy aquifer, and this requires only minor treatment. As for groundwater, which is located under a continuous layer of mud underground, it contains undesirable components such as: iron, manganese, and ammonium, while it does not contain oxygen at all.

pH is the second important factor in determining groundwater quality. Carbon dioxide interacts with limestone in the earth and causes an increase in the pH. Rainwater always contains certain percentages of carbon dioxide and at a high concentration in industrialized countries, its presence (CO2) also leads to an increase in water hardness, a high concentration of bicarbonate, and the dissolution of unwanted minerals from the soil matrix.

It is worth noting that the groundwater is affected by the industrial pollution of the soil, as the use of fertilizer in agriculture increases the concentrations of nitrates in the groundwater, in addition to the fact that this water can be contaminated with pesticides.

Environmental contamination with pesticides

The basis of groundwater treatment are aeration and filtration. The mixing of anaerobic groundwater with aerobic surface water leads to iron sintering and clogging of groundwater wells. The maximum number of wells that can be constructed affects the pumping station's capacity. Pumping stations often have a limited dimension. The sites are typically not far from the distribution region, and compared to surface water projects, the investment and extraction costs are comparatively inexpensive due of the short transit distances and simple treatment facilities.

References:

• Unsafe water kills more people than war, Ban says on World Day". UN News. 22 March 2010. Retrieved 10 May 2018
• Raymond Desjardins- Livre: Le traitement des eaux- 2éme edition- Ecole Polytechnique de Montréal- 1997- ISBN 2-553-00643-8
• Drinking Water Treatment- EDX- Delft University of Technology.
• Book- Drinking Water: Principles and Practices- by Hans J C Van Dijk (Author), Jasper Q J C Verberk (Author), Peter J De Moel.