Bioremediation of waters contaminated with crude oil and toxic heavy metals

In the Tulenovo oil deposit, Northeastern Bulgaria, waters contaminated wit h crude oil and toxic heavy metals (Cd, Cu, Ph, Mn, Fe) were treated by a p assive system of the type of the constructed wetlands. The waters had a pH of about 5.3-6.8 and contained about 2-10 mg/l oil. The concentrations of h eavy metals exceeded by two to eight times the relevant permissible levels for waters intended for use in the agriculture and/or industry. The flow ra te varied in the range of about 0.1-0.5 l/s. The wetland covered an area of about 200 m(2) and was about 35-40 cm deep. The wetland contained abundant water and emergent vegetation and a varied microflora. Typha latifolia, Ty pha angustifolia, Phragmites communis, Scirpus lacustris, Juncus spp. and d ifferent algae were the main plant species in the wetland. The microflora c onsisted of different hetero-trophic and autotrophic microorganisms. includ ing different oil-degrading bacteria and fungi, The oil content of the wate rs after treatment was decreased to less than 0.2 mg/l, and the concentrati ons of heavy metals were decreased below the relevant permissible levels. T he removal of the oil was connected with its degradation by the indigenous microflora. The removal of the toxic heavy metals was connected mainly with the processes of microbial dissimilatory sulphate reduction and biosorptio n, (C) 2001 Elsevier Science B.V. All rights reserved.