Ground Water Pollution by Organic Solvents and their Microbial Degradation Products

Summary

Serious contamination of the ground water at a depth of about 30 m beneath a paint factory was found to have occurred as a result of the dispersion of organic solvents from a number of underground storage tanks. Samples of water in static and in dynamic conditions were taken from a well excavated to a depth of about 61 m close to the probable source of the pollution. Extraction with methylene chloride on a 100 ml water sample at various pH values yielded three fractions. The basic fraction was found to contain no significant traces of organic compounds, whilst the neutral fraction revealed considerable quantities (several tens of ppm) of various organic solvents commonly used in this kind of industry. These were hydrocarbons, prevalently aromatic, alcohols, glycol ethers, ketones, esters, alkyl halides. Other oxygenated compounds were also found to be present; these were alcoholic or ketonic, aliphatic or aromatic in nature, and their presence could hardly be ascribed to dispersions from the industry responsible for the pollution. Aliphatic and aromatic acids and alkyl phenols, which could not be explained by the products used in the factory, were also found in the acidic fraction. The presence of all these substances was attributed to oxidative microbial degradation of the hydrocarbon components present in the soil and water, which hypothesis was supported by the presence in the water samples of a large number of microorganisms capable of oxidizing aromatic hydrocarbons.