Bioleaching of cadmium(Cd) and zinc(Zn) from the contaminated soil using bacteria from wastewater sludge

The aim of this work was to determine the influence of various variants of bioleaching on the effectivity of releasing metal cadmium and zinc from contaminated soil using bacteria from activated sludge. The initial zinc and cadmium concentration in the soil was adequate - 957 and 252 mg kg(-1) dry-weight. The research was conducted in variants that considered different process factors such as mixing and aeration. The research was conducted in 3 variants of bioleaching - mixing and aerating, only mixing, only aerating and in 2 control variants - aerating and mixing. After the 7th and 14th day of the process the markings were made: the index of sulfur-oxidizing bacteria, metals content, sulfate concentration, pH. Determination of the elemental composition was performed by inductively coupled plasma - optical emission spectrometry. The best result of bioleaching for both metals was achieved in variants with mixing and aerating. For zinc, the efficiency of the bioleaching was 66% after 14 d of leading the process and cadmium was 99% after 7 d of leading the process. In the case of cadmium leading the process longer had a negative impact on bioleaching. The bacteria activity, sulfate concentration and pH measurement correspond to effectivity metals removal in bioleaching all variants.