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<br />, <br />. <br /> <br />groundwater, such as nutrients, can cause algae blooms, weed problems, <br />and turbidity in surface waters. <br /> <br />CONCEPT 25: Sources of Qroundwater contamination may be continuous or <br />intermittent. <br /> <br />Action: A single addition of dye results in a single spot of dye to <br />follow. If you want a continuous color, you have to keep adding dye. <br /> <br />,Discussion: Some sources of contamination may occur as a single slug, <br />such as a spill. These will eventually move through and be flushed out <br />of the groundwater system. It may take days or years. Other <br />contamination sources may input contaminants continuously, such as a <br />wastewater treatment lagoon, septic tank, or landfill. <br /> <br />CONCEPT 26: Once Qroundwater becomes contaminated, the contamination may <br />oersist for 10nQ oeriods of time and over 10nQ distances. Groundwater can be <br />cleaned up but it takes time and money. <br /> <br />Action: Observe that the dye is eventually flushed out of the model or <br />removed through the pumping wells. <br /> <br />Discussion:, Unlike the model, the environment is not easily able to <br />eliminate pollutants. Contaminants may move only a few feet each year, <br />remaining in the groundwater for many years. Some contaminants may <br />adhere to the aquifer material, especially clayey portions. These <br />contaminants may not be flushed out by pumping. If pumping stops, the <br />contaminants may gradually be released into the ground water and <br />contamination will re-occur. <br /> <br />CONCEPT 27: Remediation. Physical, chemical, and biological processes can be <br />used to cleanup contaminated aquifers. <br /> <br />Action: Physical cleanup can be demonstrated by flushing water through <br />the model via the inlet or by adding water to the injection wells and <br />removing water through the pumping wells. <br /> <br />Action: Chemical cleanup can be demonstrated using the same method as <br />above only chlorox is added t~ represent a solvent or catalyst. <br /> <br />Discussion: There are three means of cleanup. <br />1. Physical cleanup <br />a. Excavation: remove the soil and clean the soil <br />b. Pump and treat or soil flushing: water is flushed through <br />the aquifer and removed via the pumping wells. The contaminated <br />water is treated (cleaned up) by surface processes such as in a <br />wastewater treatment plant. <br /> <br />2. Chemical cleanup. The pump and treat method is used but this time <br />a chemical (solvent, catalyst) is used to breakdown or mobilize the <br />contaminant. This is an in situ process and requires both injection and <br /> <br />9 <br />