8.22: Cleaning Up Groundwater

Would you drink this water?

Cleaning water is not easy. Cleaning groundwater is especially difficult. If you want to drink clean water, groundwater must not become polluted, or it must be cleaned.

Groundwater Pollution

Pollutants in surface water can filter into the ground and enter a groundwater aquifer. Irrigation water can bring pesticides and other chemicals. Water can seep through landfills. Tanks of gasoline stored underground can leak.

Pollutants can be filtered out of water that travels through rock and soil. Filtering is very effective, but it doesn't get out all of the pollutants.

Pollutants that enter an aquifer spread outward from the source. They spread in the direction the water is moving.

Cleaning Groundwater

It is a lot easier and cheaper not to pollute surface water than it is to clean it. That is even truer for groundwater. To clean groundwater, the water must be cleaned. Also, the rock and soil it travels through must be cleaned. Then the toxic rock and soil must be put somewhere. Cleaning polluted groundwater is expensive and can take years. Sometimes it can't even be done.

Stages of Groundwater Cleaning

To clean groundwater, you must:

• Eliminate the pollution source: An underground tank must be pumped dry and then dug out from the ground. A factory must be required to stop releasing toxic chemicals. Farms must be more careful about the chemicals they put on their fields.
• Monitor the extent of the pollutant: Scientists test water in wells. Sometimes they drill wells to test water. They learn how the groundwater is flowing: how fast and in what direction. They study the contaminants in the groundwater. Then they determine where the contaminant plume is going.

Test wells are drilled to monitor groundwater pollution.

• Engage in remediation: A barrier is constructed in the aquifer. This isolates the contaminated groundwater from the rest of the aquifer. The contaminated groundwater must be treated. Remediation is correcting a problem.
  • The cheapest and easiest way is to treat the water in the aquifer.
    • Bioremediation is one way of treating the water in the aquifer. Microorganisms are bioengineered to eat the pollutant. The organisms are injected into the contaminated region. They consume the pollutant. Bioremediation is short for biological remediation.
    • Chemical remediation can also treat water in the aquifer. A chemical is pumped into the aquifer. The chemical destroys the contaminant.
  • It is much more difficult and expensive to remove the water from the aquifer and then treat it. The water is pumped to the surface. It is then cleansed using chemical or biological methods. It is re-injected into the aquifer. The contaminated rock and soil must be dug up and the pollutant destroyed. Then it is returned to the ground. This is done only in extreme cases.

Summary

• To clean groundwater: remove the pollutant source, monitor the pollutant, and perform remediation.
• Scientists test the water in many wells to see where the contaminant is. They do this to tell where the contaminant is. Over time they can tell which direction the contaminant is moving.
• Cleaning groundwater in an aquifer requires bioremediation or chemical remediation. Bioremediation uses microorganisms to consume a pollutant. Chemical remediation destroys the contaminant.

Review

1. Why do contaminated soil or rock need to be cleaned in an aquifer?
2. What are the two types of remediation that can take place in an aquifer?
3. How do scientists monitor the contaminants in an aquifer?

Explore More

Use the resource below to answer the questions that follow.

1. What was the Hanford site used for?
2. What river needs to be protected? What is it used for?
3. By what routes did contamination get into the groundwater?
4. In the video, contamination decreased from 80 to 65 square miles. What was the main reason for that?
5. What is the goal at Hanford?
6. What is being done to clean the contaminated groundwater?
7. How are barriers used to clean groundwater?