Groundwater is an extremely precious resource. People all over the world depend it to satisfy a variety of needs. In the United States in 2000, total groundwater withdrawals, both fresh and saline, totaled approximately 408 billion gallons per day. The majority of water pumped from the ground is used for irrigating crops, but it is also used to satisfy public needs, industry/mining needs, domestic needs, and livestock needs. While some may think of groundwater as an everlasting resource, there are in fact problems that can threaten to turn the endless flow of water into a slow drip. One of the most serve problems that can threaten the supply of groundwater is contamination.
Groundwater Contamination
Humans tap into groundwater by digging wells in the land. Some of the more popular methods include dug wells, driven wells, and drilled wells. Through these wells, groundwater is pumped to the surface and then distributed to various locations to meet the needs of humans. Unfortunately, the very act of pumping groundwater itself is a threat to the resource. When groundwater is pumped, the water table near the well is lowered, resulting in a cone of depression. Overpumping groundwater can cause the slope of the cone of depression to increase, which creates a hydraulic gradient that causes the water in the aquifer to flow toward the well. If the well is located near an ocean, then the flow of groundwater toward a pumping well can bring seawater to the well. This process is known as saltwater intrusion, and it can make groundwater unusable for meeting the needs of humans.
Pesticides and other chemicals can also cause problems for groundwater. Chemicals that threaten groundwater include arsenic, carbofuran, cyanide, dioxin, lead, nitrates, and many others. Chemicals such as these are used for industrial, domestic, and agricultural purposes. These chemicals can and do get spilled onto the land. Rain that falls on the land then dissolves these chemicals and carries them down into the underlying aquifer. As was the case with saltwater intrusion, over pumping groundwater can cause the chemically tainted water to flow towards the well. When this water is brought to the surface, it is full of dangerous chemicals that can be harmful to humans.
Bacteria and microorganisms can also cause problems for groundwater. In fact, bacterial contamination is the most common water-quality problem in the groundwater supplies of rural areas. Two common microorganisms are Giardia and Cryptosporidium. Human and animal waste is a major source of these microorganisms. When waste comes into contact with groundwater, these organisms can move into the water. When humans consume the Giardia and Cryptosporidium in the water, they can experience severe digestive system problems, which can be life-threatening to the very young, very old, and those with damaged immune systems.
Preventing Contamination
Faced with so many elements that can contaminate groundwater, one might ask the question is there anything that can be done? Steps can be taken to prevent groundwater pollution from occurring in the first place. The condition of a well and its proximity to contamination sources determine the risk it poses groundwater. For example, a cracked well casing may allow fertilizer, nitrates, oil or pesticides to enter the well if these materials are spilled near the well. Feedlots, animal yards, septic systems and waste storage areas can also release large amounts of bacteria, nitrates and other contaminants that can pollute well water. Placing the well in the proper location to begin with and keeping it in good condition can prevent these problems from occurring.
Pesticide and chemical spills pose a risk to groundwater; however, steps can be taken to reduce this risk. First, improving the storage of these chemicals can cut down on groundwater contamination. If stored in a secure, properly constructed location, pesticides and other chemicals pose little danger to ground water. Second, cutting down on the use of pesticides and other chemicals lessens their impact on groundwater contamination. For example, if farmers use fewer pesticides on their crops, then the amount of pesticide that could possibly enter groundwater would also decrease.
Human waste also poses a risk to groundwater. Steps can be taken to reduce this risk. Making sure that septic tanks are not located near a well or a groundwater recharge site helps to reduce the risk to groundwater. In addition, properly caring for septic tanks can help lower the risk. Steps to maintain a safe and efficient septic tank include the following: installing multiple tanks or chambers in series to improve sludge and scum removal, installing gas deflectors and filter screens or inclined-plate settling units to help minimize solids entering the drain field, installing a tank that is large enough to accommodate at least 24 hours of wastewater flow, and pumping the tank every 3 to 5 years to maintain the functioning of the system.
Groundwater Clean-up
Once groundwater is contaminated, actions can sometimes be taken to clean the water up. These include physical, biological, and chemical treatment methods. Depending on the nature of the contamination, these treatment methods can be effective in returning groundwater to a usable form for humans.
One of the major physical water treatment methods is also one of the easiest to execute. In cases where certain bacteria have gotten into the groundwater, the water can be boiled. Boiling the water kills the bacteria, thus making the water suitable for drinking. A more complex physical treatment method involves building a new well. Depending on the location of the contaminated area and on the direction of flow of the groundwater, a new well can be constructed to pump out the contaminated water before it reaches a well that is used by humans.
Chemical water treatment methods can also be effective in combatting bacterial contamination. Urban water supplies in particular receive chemical treatment. One method of chemical treatment is chlorination. Chlorination involves adding chlorine to water in order to kill dangerous bacteria.
Finally, a relatively newer water treatment method is biological treatment. One biological treatment method is bioremediation. Biomremediation schemes reduce the amount of contaminants in groundwater, although often not to a low enough degree. It has recently been discovered that microorganisms play a role in removing metals such as zinc from groundwater. This discovery provides detailed insights into how metal removal occurs and, therefore, may be useful for improving bioremediation strategies.
Groundwater is clearly at risk of being contaminated. Exposure of groundwater to saltwater intrusion, pesticides, chemicals, and various bacteria can all render it unusable for human needs. With the increasing human population, any reduction in the supply of usable water is bound to have dramatic consequences for society as a whole. Therefore, it is in everyone’s best interest to take steps to help prevent the contamination of groundwater from occurring in the first place. Preventative measures may seem costly at first, but they will be worthwhile in the long run. Preventing contamination not only keeps the supply of groundwater intact, but it also eliminates the price people would have to pay in the future. While physical, chemical, and biological treatment methods do exist for cleaning up groundwater, many are very expensive and not always effective. It is worthwhile to spend money on preventative measures today so that money will not have to be spent to clean up groundwater in the future.
