Effects of sludge-amendment on mineralization of pyrene and microorganismsin sludge and soil

Hydrophobic contaminants sorb to sludge in wastewater treatment plants and enter the soil environment when the sludge is applied to agricultural field s. The mineralization of pyrene was examined in soil, in sludge mixed homog eneously into soil, and in sludge-soil systems containing a lump of sludge. Sludge-amendment enhanced the mineralization of pyrene in the soil compare d to soil without sludge, and the most extensive mineralization was observe d when the sludge was kept in a lump. The number of protozoa, heterotrophic bacteria and pyrene-mineralizing bacteria was much higher in the sludge co mpared to the soil. The amendment of sludge did not affect the number of pr otozoa and bacteria in the surrounding soil, which indicated that organic c ontaminants in the sludge had a little effect on the number of protozoa and bacteria in the surrounding soil. (C) 2001 Elsevier Science Ltd. All right s reserved.