MICROBIAL FUNCTIONAL-ACTIVITY DURING COMPOSTING OF CHLOROPHENOL-CONTAMINATED SAWMILL SOIL

Microbial status during a successful full-scale bioremediation by comp osting chlorophenol-contaminated soil was studied in three different w ays: conventional enumeration of microbes on selective and general med ia, microbial activity assessed by soil respiration, and community str ucture studied by the utilization pattern of a large range of substrat es using Biolog(R) microtitre plates. Utilization of ammonium, nitrate and soluble P was also followed. Chlorophenols were well removed in a ll compost piles which were mixtures of contaminated soil and bark chi ps or straw compost. The best indicator of the actual chlorophenol deg radation efficiency was the number of microbes growing on plates with 2 mM pentachlorophenol (PCP) as the sole carbon source. Nutrient analy ses showed that ammonium was rapidly used, and nitrification took plac e in some of the compost piles. The data from Biolog(R) microtitre pla tes was analyzed using the toolbox of Matlab(R) mathematical software. The areas under the substrate utilization curve were integrated for e ach substrate used, and they were used for principal component analysi s. We were able to see pile-specific substrate usage for piles contain ing straw compost, but not for pile containing bark chips. All these c haracteristic substrates were either amino acids or amines. The result s suggested that fast-growing microbes responsible for utilization of easily available substrates, measured by respiratory activity and subs trate utilization patterns in Biolog, originated mainly from the added bulking agents, straw compost and bark chips. The chlorophenol-degrad ers originating from contaminated soil seemed not directly to contribu te to the Biolog utilization pattern, but probably had benefited from the enhanced general microbial activity in the composts by cometabolis m or synergism. (C) 1997 Elsevier Science B.V.