Coupling of acrylic dyeing wastewater treatment by heterogeneous Fenton oxidation in a continuous stirred tank reactor with biological degradation in a sequential batch reactor

• Published in: Journal of environmental management Vol. 166; pp. 193 - 203
• Main Authors: Esteves, Bruno M., Rodrigues, Carmen S.D., Boaventura, Rui A.R., Maldonado-Hódar, F.J., Madeira, Luís M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.01.2016; Academic Press Ltd
• Subjects: Biodegradation; Biodegradation, Environmental; Biological degradation; Bioreactors; Coloring Agents - chemistry; Coloring Agents - metabolism; Continuous stirred tank reactor; Dyes; Heterogeneous Fenton oxidation; Hydrogen Peroxide - chemistry; Iron; Oxidation; Oxidation-Reduction; Textile dyeing wastewater; Toxicity; Vibrio fischeri; Waste Water - chemistry; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - metabolism; Water treatment; Zeolites - chemistry; Textile dyeing wastewater; Heterogeneous Fenton oxidation; Biological degradation; Continuous stirred tank reactor
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2015.10.008

This work deals with the treatment of a recalcitrant effluent, from the dyeing stage of acrylic fibres, by combination of the heterogeneous Fenton's process in a continuous stirred tank reactor (CSTR) with biological degradation in a sequential batch reactor (SBR). Three different catalysts (a commercial Fe/ZSM-5 zeolite and two distinct Fe-containing activated carbons – ACs – prepared by wet impregnation of iron acetate and iron nitrate) were employed on the Fenton's process, and afterwards a parametric study was carried out to determine the effect of the main operating conditions, namely the hydrogen peroxide feed concentration, temperature and contact time. Under the best operating conditions found, using the activated carbon impregnated with iron nitrate, 62.7% of discolouration and 39.9% of total organic carbon (TOC) reduction were achieved, at steady-state. Furthermore, a considerable increase in the effluent's biodegradability was attained (BOD5:COD ratio increased from <0.001 to 0.27 and SOUR – specific oxygen uptake rate – from <0.2 to 11.1 mg O2/(gVSS·h)), alongside a major decrease in its toxicity (from 92.1 to 94.0% of Vibrio fischeri inhibition down to 6.9–9.9%). This allowed the application of the subsequent biological degradation stage. The combination of the two processes provided a treated effluent that clearly complies with the legislated discharge limits. It was also found that the iron leaching from the three catalysts tested was very small in all runs, a crucial factor for the stability and long-term use of such materials. •Acrylic dyeing wastewater is degraded by heterogeneous Fenton's oxidation.•Activated carbon impregnated with iron is used as a stable and active catalyst.•Fenton heterogeneous oxidation was carried out in a CSTR.•Fenton oxidation is complemented by biological degradation in a SBR.•Final effluent is non-toxic and accomplishes discharge limits.