Bratkova S.Lavrova S.Angelov A.Nikolova K.Ivanov R.Koumanova B.2024-07-162024-07-162024-07-162024-07-162018-01-011314-79781314-7471SCOPUS_ID:85042088538https://rlib.uctm.edu/handle/123456789/1198Acid drainage wastewaters (pH 2.6 - 2.8) contaminated with Fe 200 mg/l, Cu 25 mg/l, Zn 25 mg/l, and As 15 mg/l were treated in a laboratory-scale installation. The installation design includes an anaerobic sulfidogenic bioreactor, a chemical reactor, an aerobic activated sludge reactor, an anaerobic biofilter and a vertical flow constructed wetland reactor, connected in series. Sulfate-reducing bacteria were adhered in biofilm, which is immobilized on zeolite particles in the anaerobic bioreactor. The bacteria were cultivated on a medium containing lactate as a source of carbon and energy. The influence of TOC/SO42- ratios 0.43, 0.54 0.64 on the rate of the microbial sulfate-reduction was determined. Pollutants removal was achieved in a chemical reactor by sedimentation with microbially produced H2S. SEM/EDS data and X-ray diffraction analyses proved that the precipitated heavy metals are mainly in forms of relevant insoluble sulfides. The design of the lab-scale installation makes possible efficient removal of the residual organic compounds and hydrogen sulfide as well as the processes of nitrification and denitrification to occur. The reported treating method allows the removal of heavy metals, COD, N and P from wastewaters below the permeable level for water intended for use in the agriculture and/or industry.enArticle