purposes.The sources of organic compounds in oxidation ponds and the groundwater of the Pleistocene aquifer are mainly related to human and industrial activities.The most important overall of these compounds are aromatic hydrocarbons (mostly from gasoline, diesel and other fuels as benzene, toluene, ethylbenzene and xylene) and total oil and grease.The volatile organic compounds are detected in the three oxidation ponds with different concentrations, while the groundwater in the area of study is totally free from these compounds with few exceptions (wells Nos. 6, 7, 10, 12, 14 and 15).2.3.