engleski

Zeolitized tuff as a carrier of bacteria

Three types of natural zeolite tuffs of particle size  0.125 mm, originating from Croatia, Turkey and Serbia were examined. The tuff from Croatia consisted of approximately 50% clinoptilolite, subordinate plagioclase feldspars and quartz (10-15% of each) and traces of K-feldspars and celadonite (app. 5% of each). The tuff from Turkey contained approximately 70% clinoptilolite, subordinate opal-CT and quartz (10– 15% of each) and traces of K-feldspars and biotite (app. 5% of each). The tuff from Serbia contained approximately 75% clinoptilolite and several minor constituents were analcime, calcite, plagioclase feldspars, biotite and quartz (app. 5% of each). The tuff from Serbia had the largest cation exchange capacity of 1.71 meq/g, followed by tuff from Croatia with 1.60 meq/g and tuff from Turkey with 1.35 meq/g. The main exchangeable cation in samples of tuffs from Turkey and Serbia was Ca, whereas Na was the main exchangeable cation in the sample of tuff from Croatia. The particles of the tuff from Croatia had the most negative zeta potential of -25.14 mV, followed by tuff from Turkey (-23.12 mV) and tuff form Serbia (-17.60 mV). The phosphate adsorption capacity varied from 22.5 mg P/kg for Serbian tuff, to 30.2 mg P/kg for Croatian tuff and 77.5 mg P/kg for Turkish tuff. The interaction of zeolite tuffs and phosphate-accumulating bacterium Acinetobacter junii in simulated wastewater was investigated. After 24h of contact with minerals, most of the bacterial population was immobilized onto minerals by adsorptive growth, while the rest of the bacteria remained as planktonic cells in supernatant. The highest number of immobilized cells was obtained on the tuff from Turkey (74.91x108 CFU/g), followed by tuff form Croatia (48.39x108 CFU/g), while the tuff from Serbia had the lowest number of immobilized cells (6.14x108 CFU/g). The zeta potential of A. junii (-18.4 mV) was negative, as well as the zeta potential of mineral particles and no correlation with the number of immobilized cells and zeta potential of minerals was obtained. The best bacterial activity measured as phosphate uptake rate per CFU was obtained with tuff from Croatia, followed by tuff from Turkey and tuff from Serbia. As the result of bacterial activity, the final percent of phosphate removal from wastewater decreased in the order: 50.23%, 46.32% and 40.21% for tuff from Croatia, Turkey and Serbia, respectively. It can be concluded that zeolite tuff can be a good carrier of phosphate-accumulating bacteria. The zeta potential of zeolite tuff was not a crucial factor which determined the immobilization of bacteria. The clinoptilolite content in the zeolite tuff was not the prevailing factor for the immobilization of bacteria. Bacterial immobilization on the zeolite tuff was defined by the original structure of material. The extent of bacterial immobilization on single zeolite tuff cannot be predicted by mineralogical and chemical analysis of mineral, its cation exchange capacity or its zeta potential. The phosphate- accumulating bacteria immobilized onto zeolite tuff as a biocarrier can find application in the bioaugmentation of activated sludge in order to achieve better phosphate removal from wastewater.

bacteria ; zeolite tuff ; wastewater ; immobilization

nije evidentirano