Abstract
Microbial status during a successful full-scale bioremediation by composting chlorophenol-contaminated soil was studied in three different ways: conventional enumeration of microbes on selective and general media, microbial activity assessed by soil respiration, and community structure studied by the utilization pattern of a large range of substrates using Biolog® microtitre plates. Utilization of ammonium, nitrate and soluble P was also followed. Chlorophenols were well removed in all compost piles which were mixtures of contaminated soil and bark chips or straw compost. The best indicator of the actual chlorophenol degradation efficiency was the number of microbes growing on plates with 2 mM pentachlorophenol (PCP) as the sole carbon source. Nutrient analyses showed that ammonium was rapidly used, and nitrification took place in some of the compost piles. The data from Biolog® microtitre plates was analyzed using the toolbox of Matlab® mathematical software. The areas under the substrate utilization curve were integrated for each substrate used, and they were used for principal component analysis. We were able to see pile-specific substrate usage for piles containing straw compost, but not for pile containing bark chips. All these characteristic substrates were either amino acids or amines. The results suggested that fast-growing microbes responsible for utilization of easily available substrates, measured by respiratory activity and substrate utilization patterns in Biolog, originated mainly from the added bulking agents, straw compost and bark chips. The chlorophenol-degraders originating from contaminated soil seemed not directly to contribute to the Biolog utilization pattern, but probably had benefited from the enhanced general microbial activity in the composts by cometabolism or synergism.
Published Version
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