Biodegradability of Syntans Using Ozonation as a Pretreatment Process: Fid-Bau Portal

Biodegradability of Syntans Using Ozonation as a Pretreatment Process

Dhivya Priya, N. / Sri Bala Kameswari, K. / Chitra, Kalyanaraman

Abstract Syntans are high molecular weight synthetic organic compounds that are used for rendering hides and skins into a non-putrifiable substance called leather. Biodegradability of syntans, phenol and sulfone based, used for tanning process was studied to arrive at their biodegradability index (BI). The BOD/COD ratio of 0.087 and 0.033 of these two syntans clearly indicates that they resist microbial attack and are recalcitrant to biodegradation. In order to increase the BI, as pretreatment, ozonation studies were carried out as one of the Advanced Oxidation Processes. These studies were carried out with a dosage of 0.54 g/L at pH 4.0 and 8.0 to see whether it was acting as molecular ozone or through release of ·OH radicals produced by decomposition; the contact time was optimized. An increase in BI to 0.1006 and 0.1088, respectively, was observed at acidic and alkaline pH for 15-min contact time for sulfone-based syntan. Whereas for the same contact time, in the case of phenol-based syntan, BI increased to 0.170 and 0.197, respectively, at acidic and alkaline pH. Further, efficacy of biological treatment of wastewater containing syntans was evaluated, with and without application of ozonation as pretreatment. During aerobic biological treatment, i.e., without pretreatment, only 25% of COD removal was observed whereas with application of ozone as pretreatment 50% removal of COD was observed for both the syntans for a residence time of 48 h. Even after application of ozonation, recalcitrant COD contributed by syntans was still persistent in the wastewater and the syntans can be classified as persistent organic pollutants.