Ototrofik nitrat gidericilerin zenginleştirilmesi ve öğütülmüş lastiğin biyo-desülfürizasyonunda kullanımlarının araştırılması

Many new methods have been developed for the recycling of waste tires. Among these developed methods, bio-desulfurization takes attention with its low energy requirement, selectively breaking S bonds without damaging the rubber main chain and being an environmentally friendly application. This thesis aims to investigate the enrichment and use of sulfur-driven autotrophic denitrifiers for bio-desulphurization of ground tire rubber (GTR). In the first part of the study, sulfur-based autotrophic denitrifiers were enriched from seed sludges, taken from three different treatment plants. Elemental sulfur (S0) and thiosulfate (S2O32-) were selected as sulfur sources for the enrichment operation. Average nitrate removal efficiencies of the enrichment reactors (ERs), namely ER1, ER2, ER3 and ER4 were 96.0%, 96.9%, 97.6% and 87.2%, respectively. It was observed that ER4, the only one fed with S0, was more sensitive to shock loads and had relatively lower nitrate removal efficiency. In the second part of the study, bio-desulphurization of GTR was investigated using enriched autotrophic denitrifiers, namely, EC1, EC2, EC3 and EC4 obtained from ER1 to ER4, respectively. Thus the effects of seed sludge type in addition to electron donor were also investigated. An increase in the sulfate concentration was used as a bio-desulphurization indicator. Results revealed that abiotic nitrate removal via GTR was a significant process and zinc oxide content of GTR could react with the sulfate being produced through bio-desulfurization, as also stated in the literature. Bio-desulphurization was only obtained with EC3, enriched from biological nutrient removal sludge of the Leather Organized Industrial Zone Wastewater Treatment Plant, as 3.9%, when the possible zinc sulfate formation was not taken into account, which could cause an under-estimation of the desulfurization ratio. Considering the possible zinc sulfate formation, bio-desulphurization by EC2 (enriched from anaerobic digester) and EC3 were calculated as 3.6% and 8.2%, respectively, which are comparable to the literature data. Not considering the possible zinc sulfate formation could cause an underestimation of the desulfurization ratio. Electron donor effect on bio-desulfurization could not be detected because bio-desulfurization was not obtained by EC1 (S2O32--fed) and EC4 (S0-fed) cultures. It can be concluded that it is possible to achieve bio-desulfurization of GTR with autotrophic denitrifiers, when excess nitrate was fed.