cleaning up groundwater

cleaning groundwater

Preventing groundwater contamination is much easier and cheaper than cleaning it. To clean groundwater, the water, as well as the rock and soil through which it travels, must be cleansed. Thoroughly cleaning an aquifer would require cleansing each pore within the soil or rock unit. For this reason, cleaning polluted groundwater is very costly, takes years, and is sometimes not technically feasible. If the toxic materials can be removed from the aquifer, disposing of them is another challenge.

modeling the contaminant plume

Using the well data, the hydrologist uses a computer program with information on the permeability of the aquifer and the direction and rate of groundwater flow, then models the plume to predict the dispersal of the contaminant through the aquifer. Drilling test wells to monitor pollution is expensive.

monitoring the extent of the pollutant

Hydrologists must determine how far, in what direction, and how rapidly the plume is moving. They must determine the concentration of the contaminant to determine how much it is being diluted. The scientists will use existing wells and may drill test wells to check for concentrations and monitor the movement of the plume.

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elimination of the pollution source

If the source is an underground tank, the tank will be pumped dry and then dug out from the ground. If the source is a factory that is releasing toxic chemicals that are ending up in the groundwater, the factory may be required to stop the discharge.

stages of groundwater cleaning

remediation

First, an underground barrier is constructed to isolate the contaminated groundwater from the rest of the aquifer. Next, the contaminated groundwater may be treated in place. Bioremediation is relatively inexpensive. Bioengineered microorganisms are injected into the contaminant plume and allowed to consume the pollutant. Air may be pumped into the polluted region to encourage the growth and reproduction of the microbes. With chemical remediation, a chemical is pumped into the aquifer so the contaminant is destroyed. Acids or bases can neutralize contaminants or cause pollutants to precipitate from the water. The most difficult and expensive option is for reclamation teams to pump the water to the surface, cleanse it using chemical or biological methods, then re-inject it into the aquifer. The contaminated portions of the aquifer must be dug up and the pollutant destroyed by incinerating or chemically processing the soil, which is then returned to the ground. This technique is often prohibitively expensive and is done only in extreme cases. Click image to the left or use the URL below. URL:

instructional diagrams

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questions

it is easier and cheaper to clean up groundwater than to prevent it.

a) true

-->  b) false

cleaning an aquifer does no good if you do not also

-->  a) eliminate the pollution source.

b) stop using the groundwater as a water source.

c) drill test wells.

d) all of the above

to do chemical remediation of an acidic pollutant in an aquifer, introduce

a) a safe acidic compound.

-->  b) a safe basic compound.

c) a safe neutral compound.

d) none of the above

this form of remediation involves injecting microorganisms into the contaminant plume and allowing them to consume the pollutant.

a) chemical remediation

b) contaminant remediation

c) pollution remediation

-->  d) bioremediation

which form of remediation involves pumping a chemical into an aquifer to destroy a contaminant?

a) bioremediation

-->  b) chemical remediation

c) contaminant remediation

d) pollution remediation

a problem with having to bring toxic materials to the surface to cleanse them is

a) how to re-inject the cleansed rock and soil back into the aquifer.

b) where to do the bioremediation on the toxic materials.

-->  c) where to dispose of the toxic materials.

d) none of these.

if you pumped contaminated water from an aquifer, cleaned the water and pumped it back in what would happen?

a) the water would be clean and stay clean.

b) the water would clean the aquifer.

-->  c) the water would be re-contaminated by the aquifer.

d) its impossible to know what would happen.

the most dangerous contaminants in water are the ones that are visible.

a) true

-->  b) false

pumping water to the surface to clean the pollutant is more expensive than in situ cleaning methods because the soil and rock must be cleaned too.

-->  a) true

b) false

diagram questions

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