AbstractsEarth & Environmental Science

Treatment of Textile Wastewater by Combining Biological Processes and Advanced Oxidation

by Marisa Punzi

Institution: University of Lund
Year: 2015
Keywords: textile wastewater; Azo dye; biological treatment; biofilm; microbial community; DGGE; green algae; photo-Fenton; ozone; toxicity; mutagenicity; LCA; cost analysis; Earth and Environmental Sciences; Biology and Life Sciences; Chemistry; Technology and Engineering
Record ID: 1358297
Full text PDF: http://lup.lub.lu.se/record/5367868



Treatment of textile wastewater is challenging because the water contains toxic compounds that have low biodegradability. Dyes, detergents, surfactants, biocides and more are used to improve the textile process and to make the clothes resistant to physical, chemical and biological agents. New technologies have been developed in the last decades and in particular Advanced Oxidation Processes (AOPs) have shown considerable potential for treatment of industrial effluents. These processes however are expensive and full scale applications are still scarce. In addition, the complex oxidation chemistry transforms the pollutants into a very large number of degradation intermediates which may be even more toxic than the original compounds. This thesis presents a novel treatment approach where two AOPs, photo-Fenton oxidation and ozonation, are used after an anaerobic biofilm process for treatment of textile wastewater, azo dyes degradation and removal of toxicity. The biological treatment cleaves the azo bonds of the dyes and consumes the biodegradable compounds whereas the following advanced oxidation degrades the aromatic amines and other by-products that are recalcitrant to biological degradation. The approach that includes photo-Fenton oxidation resulted in higher reduction of chemical oxygen demand (COD) than that with ozonation when treating real textile wastewater. The latter however resulted in higher reduction of toxicity towards the bacteria Vibrio fischeri and the shrimp Artemia salina. Mutagenic effects were detected in the untreated and biologically treated effluent, but not after photo-Fenton oxidation and ozonation. Environmental impact and costs of the two treatment strategies, at the operating conditions used in this study, are high compared with the full-scale biological process used in the Netherlands, where the wastewater is actually treated. Substitution of artificial light with sunlight and upscaling would result in great improvements in terms of electricity requirements and ozone consumption hence would bring down the environmental impact to values that are comparable to the biological process, suggesting that full scale implementation can be achieved. Further research should look into combining this treatment approach with technologies that allow water and salt recovery and reuse, to make the textile industry more sustainable. Colors have always been part of human life and culture. Today natural pigments have been substituted by synthetic dyes that usually end up threatening nature itself by polluting the environment. To what extent can we use chemistry and biology to minimize the environmental impact of the textile industry? During the dyeing process a certain amount of dye, 2 to 50 percent, does not bind to the fabric and is washed away. Companies are working on improving this process. Meanwhile something needs to be done to avoid the dye effluents ending up…