The water resources of the Earth, which are composed mainly of ground water and surface water, are subject to pollution from a variety of sources. Anthropogenic activities are the primary causes of pollution. Accidental spills, old landfills and underground storage tanks, industrial facilities, septic tanks, agricultural practices, spent nuclear fuel repositories, and poor waste management and disposal practices are well-known sources of contamination caused by man. The quality of the Earth’s water resources has been declining since the middle of the 19th century, i.e., approximately since the beginning of the industrial revolution. However, the importance of this problem was recognized only after the mid-20th century, particularly in the case of the world’s increasingly utilized ground water resources. The delineation and subsequent cleanup of contaminated ground water in the world’s aquifers is a far more complex and expensive process when compared to a similar restoration of contaminated surface water. Therefore, it is very important to clean up currently degraded aquifers and protect the existing aquifers from further contamination to mitigate future cleanup costs and improve ground water quality for future generations.