Combined strategy for the precipitation of heavy metals and biodegradation of petroleum in industrial wastewaters

The precipitation of chromium(III), copper(II), manganese(II) and zinc(II) by biogenic hydrogen sulfide generated by sulfate-reducing bacteria, Desulfovibrio sp., and the degradation of total petroleum hydrocarbons (TPH) in the presence of heavy metal by Pseudomonas aeruginosa AT18 have been carried out. An anaerobic stirred tank reactor was used to generate hydrogen sulfide with Desulfovibrio sp. culture and the precipitation of more than 95% of each metal was achieved in 24 h (metal solutions contained: 60, 49, 50 and 80 mg L-1 of chromium, copper, manganese and zinc sulfates). A stirred tank reactor with P. aeruginosa AT18, in the presence of the heavy metal solution and 2% (v/v) of petroleum, led to the degradation of 60% of the total petroleum hydrocarbons and the removal of Cr(III) 99%, Cu(II) 93%, Zn(II) 46% and Mn(II) 88% in the medium through biosorption phenomena. These results enabled the development of an integrated system in which the two processes were combined. The overall aim of the study was achieved, with 84% of TPH degraded and all of the metals completely removed. Work is currently underway aimed at improving this system (decrease in operation time, culture of P. aeruginosa in anaerobic conditions) in an effort to apply this process in the bioremediation of natural media contaminated with heavy metals and petroleum.