Microbiological and Biochemical Activity in Soil Contaminated with Pyrene Subjected to Bioaugmentation

Abstract

The aim of the study was to determine the efficacy of bioaugmentation in pyrene-contaminated soil based on microbial counts, colony development index (CD), ecophysiological diversity index (EP), soil enzyme activity, and an assay of residual pyrene levels in the soil. The soil samples were contaminated with pyrene doses of 100 and 1000 mg kg−1 DM soil. Two bacterial consortia were used in the study: P1 (Bacillus frigoritolerans Z2B-19, Bacillus simplex 2–134, and Bacillus thuringiensis ex4) and P2 (Bacillus pumilus Bp-11, Bacillus safensis L22, and Bacillus aerophilus KUDC1741). The following parameters were determined: counts of organotrophic bacteria, actinobacteria, and fungi; CD; EP; and the activity of soil enzymes. The pyrene degradation efficacy of the bioaugmentation was also established. Microbiological activity was influenced by the level of soil contamination with pyrene, the test time, and the type of consortium. Pyrene had a stimulatory effect on the microbial counts and was a diversifier of CD values, EP values, and enzyme activity levels in the soil. Bioaugmentation initially promoted the growth of microorganisms, but ultimately diminished the ecophysiological diversity and the activity of soil enzymes. The microorganisms used for bioaugmentation accelerated pyrene removal from the soil, by 24.6% and 16.4% in the case of P1 and P2 consortium, respectively. The use of bioaugmentation provides favorable conditions for the effective elimination of pyrene from soil. As the microbiological and biochemical properties of the soil were improved in the initial phase of the study, this method can be recommended for the bioremediation of pyrene-contaminated soils.