Wpływ temperatury, intensywności mieszania oraz napowietrzania na efektywność procesu bioługowania metali z wybranych odpadów przemysłowych

In the research work the influence of temperature, mixing intensity and aeration on heavy metals release from two types of industrial heavy metal containing wastes - combustion ash and galvanic waste - was analyzed. The bioleaching process was carried out using the culture based on the activated sludge as a source of active, sulphur-oxidizing microflora. The presence of Acidithiobacillus thiooxidans bacteria was proved using PCR technique. The culture was initially adapted to the growth in presence of 1% sulphur, up to the moment it achieved pH 1-2. The experiment was carried out in four variants, with different process parameters: temperature 22 degrees C, mixing 125 rpm, without aeration; temperature 22 degrees C, mixing 50 rpm, without aeration; temperature 37 degrees C, mixing 125 rpm, without aeration; temperature 22 degrees C, mixed and aerated with compressed air. After 14 days the amount of heavy metals released from the wastes was determined using ASA method to evaluate the process effectiveness in different experimental conditions. Mean value, standard deviation and variation coefficient was calculated. The effectiveness of heavy metals removal from the ash was significantly higher than the galvanic sludge bioleaching, in which only cadmium and chromium was effectively released (with the average effectiveness of 14.8-47.8% of Cd and 12.5-90,6% of Cr, depending on the experimental variant). In case of the combustion ash, the average removal efficiencies were: 1.1-22% of Zn, 04-12.3% of Cu, 2.8-19.7% of Pb, 3.4-6.7% of Cd, 2.8-52.2% of Ni and 43.8-87.4% of Cr, depending on process parameters. The increase of temperature from 22 to 37 degrees C resulted in the increased effectiveness of almost all metals from both tested wastes. Cadmium was the only metal that was leached better in 22 degrees C. In case of galvanic waste, Cd was released more effectively in cultures with mixing intensity of 125 rpm, and in the culture without aeration, while the aeration was favorable to Cr release. For the ash the additional aeration increased the removal of Cu, Cd, Ni and Cr. Copper, lead, nickel and chromium were released effectively using the 50 rpm mixing but zinc - in 125 rpm. The influence of the mixing intensity on cadmium bioleaching from the ash was not observed. The research indicated that the influence of tested parameters depended on the type of the waste as well as the kind of the metal. It is probably influenced by the other factors like the form of the metal in the waste, that should be a subject of further investigations.