Combination of Fenton and Biological Oxidation for Treatment of Heavily Polluted Fermentation Waste Broth

Andreja Žgajnar Gotvajn* and Jana Zagorc-Končan 
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, Ljubljana, Slovenia, 
E-mail: andreja.zgajnar@ki.si

 Abstract
The aim of our work was to study the biotreatability of heavily polluted pharmaceutical fermentation broth (COD value of 124,500 mg·L^–1) as well as application of Fenton oxidation for effective pretreatment. Because waste broth expressed biodegradability (BOD₅/COD ratio was 0.40), biological treatment was the first choice. At the same time, in preliminary ready biodegradability assessment test, diluted broth degraded 65% as well it was not toxic to mixed bacterial culture of activated sludge. Further experiments in pilot laboratory biological treatment plant confirm acceptable treatment efficiency up to 0.01 vol% of the broth added (76%). However, we had considered additional pretreatment method to be able to enhance biotreatability. Fenton procedure was optimised in batch reactor using different concentrations of Fe²⁺, H₂O₂, temperatures (40/45 °C), as well as different retention times (up to 30 minutes). The highest treatment efficiency reached only 44% according to COD, but ready biodegradability of the sample increased (82%). Fenton oxidation was confirmed as possible method for pretreatment of broth, because it slightly enhanced biodegradability, it reduced organic pollution and formed products were non-toxic. We have focused our future work into a study on optimisation of applied procedure for improving biotreatability of the investigated broth.

Key words: biodegradability, biological treatment, pharmaceutical waste broth, Fenton oxidation, toxicity