Chem. Listy 99, 1234 – 2345 (2008) Chemistry and Life 2008 1 REMOVAL OF 2- MERCAPTOBENZOTHIAZOLE FROM SYNTHETIC WASTEWATER BEÁTA ALMÁSIOVÁ, JÁN DERCO, ANGELIKA KASSAI, EVA HÁSOVÁ Slovak University of Technology, Faculty of Chemical and Food Technology, Institute of Chemical and Environmental Engineering Radlinského 9, 812 37 Bratislava 1, Slovak Republic e-mail: beata.almasiova@stuba.sk; 1 Introduction 2-Mercaptobenzothiazole (MBT) is the most important member of the benzothiazole group of heterocyclic aromatic compounds. It is a pale yellow, crystalline substance with an unpleasant odor and a bitter taste . This xenobiotic compound is used mainly in the manufacture of rubber additive chemicals but also has other uses, notably as a corrosion inhibitor, antifreeze for automobiles. It is known as a toxic and poorly biodegradable pollutant. It is able to pass conventional treatment systems, widespread with surface and underground waters and enters into organisms [1]. Data concerning biodegradation of MBT are inconclusive. Some authors [2] have suggested it is recalcitrant to biodegradation. Genotoxicity investigations in bacterial and mammalian test systems provide some evidence indicating that MBT has the potential to induce mutations and chromosomal aberrations. Toxicity studies in rats and mice chronically exposed to MBT identified increases in various tumors [3]. Epidemiological investigations indicate that workers occupationally exposed to MBT have an increased risk of death from bladder cancer. MBT interfered with the nitrification processes and exhibited biocidal effects. MBT inhibits the degradation of easily degradable organics [4]. This work was aimed at study biodegradation of MBT and effect of this compound on activated sludge. Degradation of MBT by ozone was also studied. 2 Experimental 2.1 Biodegradability of MBT Adaptation of activated sludge to MBT was carried out in semicontinuos bioreactor. We were adapted MBT with maximal concentration 25 and 50 mg.l -1 on the activated sludge. Time of adaptation was 3 weeks. During the adaptation we measured inhibition effect of MBT on the activated sludge by respirometric measurements. Adsorption tests were performed both with adapted and nonadapted activated sludge to MBT. Adsorption of MBT on activated sludge was studied at various concentration values of MBT. We were measured the specific sorptive capacity of sludge at low (10, 20 and 60 mg.l -1 ) and high concentration of MBT (100, 200 and 500 mg.l -1 ). 2.2 Ozonation of MBT The feasibility of utilisation of ozone for degradation of MBT was investigated in laboratory scale equipment. The experiments were performed in bubble ozonation column. The ozonation equipment consists of two glass columns, 0.04 m diameter and 1.70 m height. The first column was filled with synthetic water with MBT, and the other one was filled with solution of potassium iodide to destroy residual ozone in the outlet of the first ozonation column. The system was operated in batch mode. Synthetic wastewater containing MBT was added into ozonation reactor at the beginning of trials. Continuous flow of oxygen 30 l.h -1 was applied for generation of ozone. The Lifetech ozone generator with the maximum ozone production 5 g.h -1 and Lifetech ozone UV detector were used. Ozonation trials were carried out at 70% of the power maximum of ozone generator. Initial concentration of MBT in synthetic water was 50 mg.l -1 . 3 Results MBT is not consumed by non adapted activated sludge. Decrease of respiration rate of non adapted activated sludge was observed with the increase of 2-MBTconcentration. Rapid decrease of respiration activity was observed for activated sludge after adaptation. The endogenous respirometric rate decreased by 6% at concentration 25 mg.l -1 MBT in comparison with reference model. The endogenous respirometric rate decreased by 39% at concentration 50 mg.l -1 MBT in comparison with reference model. The decrease of dissolved MBT concentration was observed at the low concentration levels. The value of COD and TOC increased after 10 days, which is caused by increase of concentration of MBT in solution. Table 1 shows the results of adsorption test carried out at lower concentration values of MBT. Negligible adsorption of MBT on activated sludge was observed at MBT concentration higher than 100 mg.l -1 . Table 1: Specific sorptive capacity of activated sludge cMBT at solution [mg.l -1 ] MBT decrease by adsorption [mg.l -1 ] MBT decrease by adsorption [mg.g -1 ] 10 4,2 42 20 5,9 59 60 6,8 68