Toxic and Biodegradation Potential of Waste Tires for Microorganisms Based on Two Experimental Designs

Abstract

Waste tires from traffic are a well-known environmental problem today. For this reason, the toxicity and potential biodegradation of crushed tires were tested in a respiration test with microorganisms. A non-specific soil microbial community was used. Two experimental designs and their effect on the results were compared—a test with the eluate from tires and a contact test, i.e., the solution containing tire particles during the test. The consumption of dissolved oxygen was measured in the assay over 28 days. The values obtained indicated zero biodegradation of all samples, but the toxicity of the eluates to microorganisms was different depending on whether the microorganisms were exposed only to the leachate or whether tire shred particles were still present in the leachate. In the presence of particles in solutions, the toxicity of the samples for microorganisms was higher. Additionally, the MTT (methyl tetrazolium test) viability assay was performed. The results indicated a 28% inhibition of the viability of microorganisms in samples with tire particles in comparison with eluate, where 9% inhibition was observed. The results confirmed that the contact assay (with the presence of particles) is a more natural and thorough method than the use of leachate.