We all know that water is necessary for people to stay healthy and well. If you do not drink enough water, you can become dehydrated which can cause headaches and dizziness at moderate levels of dehydration. However, when one is severely dehydrated it can lead to low blood pressure, fever, increased heart rate, and can even cause you to pass out.
Given the fact that most people understand the importance of drinking water, it is also important that they know where the water they drink comes from. The majority of water on the planet is found in the ocean. Of the freshwater that is present, most of it is stored as ice. The freshwater that can be accessed is mostly stored as ground water. This means that it lays underneath the soil in a water table. This can be seen in the first figure on the Groundwater site. The water found in the water table can be accessed using wells.
Water found in water tables can, in many cases, be drunk without treatment once it comes out of the ground. The bacteria that is present at the top of the soil will filter out the organics. When the organics come into contact with the bacteria, they will break down. This makes it so they are unable to get into the water table. However, the water traveling through the soil will also have bacteria present. We do not want this bacteria to make it to the water table. There is an aerated portion of the soil which mean there is more space in the soil for water to pass through. In this area, the bacteria will be filtered out because it is too big to fit through the aerated zones. Therefore, minerals will be the only molecules found in the groundwater.
There are some chemicals that bacteria has a harder time breaking down. These include halogens and water soluble chemicals. The bacteria has a hard time breaking down halogens because they are highly unreactive. They will just make their way down through the soil into the water table. Once in the water, they will gather together near the bottom of the groundwater due to being denser than water. However, they will begin to dissolve in the groundwater and leak molecules into the water. The water soluble molecules will travel through the bacteria because there is a lot of water moving through the soil. When they reach the groundwater, they will form a group on the top of the water because they are less dense than water. Like the halogens, they will begin to dissolve and leak into the water.
The chemicals that are known to contaminate groundwater include: pesticides, nitrates, detergents, and methyl-t-butyl ether (MTBE). Pesticides might kill bacteria even if they are not fully halogenated which would allow them to get into the groundwater. Nitrates and detergents found in the groundwater tend to come from home septic tanks. MTBE was the most water soluble component in oil. However, it was found in groundwater too often so the use of it in oil has been banned. The Groundwater Foundation shows how multiple pollutant sources, including the ones discussed, get into the groundwater.
There are three ways to clean groundwater. The chemicals present can be trapped in one place to limit the exposure. The chemicals can be removed or they can be destroyed. To trap chemicals clay can be placed over the soil so that chemicals cannot get through. In water, a layer of clean sediment can be placed on top of the sediment to keep it from contamination the water. Also, the chemicals can be cast in either cement or glass. This process is used if there are inorganics present.
To remove the chemicals an Iron Wall can be placed into the water table. This will trap the chemicals but allow the water to flow through. Also, the soil can be dredged and sent to a landfill. Another removal method is pumping air out of the soil and the volatile chemicals will also leave with the air. Plants can also be used to remove chemicals. This is done through phytoremediation which allows the plats to remove the chemicals from the soil.
The methods used to destroy chemicals include using a pump with oxidation or reduction agents. This allows the chemicals to be destroyed by the addition of the agent. Organics can be destroyed by dredging and then incinerating the soil. Another way to destroy the chemicals is using microbials which can breakdown chemicals.
It is important to understand what ca contaminate groundwater and how to remove the contaminations. This is due to the fact that groundwater is one of the major sources of freshwater available for drinking.