Cork boiling wastewater treatment at pilot plant scale: Comparison of solar photo-Fenton and ozone (O3, O3/H2O2). Toxicity and biodegradability assessment

Abstract

Remediation of cork boiling wastewater was studied as an example of complex industrial wastewater treatment by applying a protocol based on a combination of advanced technologies and chemical–biological assays. Solar photo-Fenton and ozone (alone or in combination with hydrogen peroxide at different pH conditions), at pilot plant scale have been used as chemical oxidation step. Additionally, the effect of a physic-chemical pre-treatment using different flocculants (FeSO4 and FeCl3) was evaluated. Although physic-chemical pre-treatment with Fe3+ provided good removals of COD, DOC and TSS, it was found that it did not enhance solar photo-Fenton post-treatment. On the contrary, ozone-based process was improved after physic-chemical pre-treatment with Fe3+, attaining higher degradation efficiencies with lower ozone consumptions for the combination with O3 at initial pH 7. Toxicity and biodegradability assays were performed to evaluate possible variations along the oxidation processes. After solar photo-Fenton treatment, toxicity and biodegradability remained constant at their initial values. Then, Zahn–Wellens test was carried out to study long term biodegradability and possible biomass adaptation to the partially photo-treated effluent. Decrease in toxicity values and short term biodegradability enhancement were observed for cork boiling wastewater treated by ozonation systems.