The treatment of veterinary antibiotics in swine wastewater by biodegradation and Fenton-like oxidation.

Elevated concentrations and potential toxicities of antibiotics in swine wastewater prompt the exploration of effective treatment methods to minimize the amount of antibiotics released to the environment. This study examined the technical and economic feasibility of using combined biodegradation and advanced oxidation processes for swine wastewater treatment. The up-flow anaerobic sludge blanket (UASB) reactor was mainly responsible for conventional organic pollutant removal (i.e., a COD removal rate of 75%). The subsequent sequencing batch reactor (SBR) under a short sludge retention time (SRT) of 3 days removed the biodegradable antibiotics by >95%, and hindered the nitrification process which retained NH4+-N and reduced operational cost (since the treated wastewater was intended to be used as a farm fertilizer). The subsequent Fenton-like oxidation (with the aid of citric acid) achieved an average antibiotic removal efficiency of 74% under optimal reaction conditions: H2O2 dosage of 2.9 mM, [Fe2+]: [H2O2] = 1:3, [CA]: [Fe2+] = 1:1, pH 6.0, reaction time of 120 min. The superior treatment efficiency of Fenton-like compared to the conventional Fenton (74% vs 5%) under nearly neutral conditions was attributed to the chelating role of citric acid with Fe2+/Fe3+, leading to the enhanced Fe2+/Fe3+ solubility and therefore the promotion of ∙OH formation. This hybrid process of anaerobic and aerobic biodegradation and Fenton-like oxidation should be suitable and cost-effective for the treatment of wastewater with abundant conventional pollutants and persistent emerging trace contaminants.