Effect of an azo dye on the performance of an aerobic granular sludge sequencing batch reactor treating a simulated textile wastewater.
This study analyzed the effect of an azo dye (Acid Red 14) on the performance of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) system operated with 6-h anaerobic-aerobic cycles for the treatment of a synthetic textile wastewater. In this sense, two SBRs inoculated with AGS from a domestic wastewater treatment plant were run in parallel, being one supplied with the dye and the other used as a dye-free control. The AGS successfully adapted to the new hydrodynamic conditions forming smaller, denser granules in both reactors, with optimal sludge volume index values of 19 and 17 mL g(-1) after 5-min and 30-min settling, respectively. As a result, high biomass concentration levels and sludge age values were registered, up to 13 gTSS L(-1) and 40 days, respectively, when deliberate biomass wastage was limited to the sampling needs. Stable dye removal yields above 90% were attained during the anaerobic reaction phase, confirmed by the formation of one of the aromatic amines arising from azo bond reduction. The control of the sludge retention time (SRT) to 15 days triggered a 30% reduction in the biodecolorization yield. However, the increase of the SRT values back to levels above 25 days reverted this effect and also promoted the complete bioconversion of the identified aromatic amine during the aerobic reaction phase. The dye and its breakdown products did not negatively affect the treatment performance, as organic load removal yields higher than 80% were attained in both reactors, up to 77% occurring in the anaerobic phase. These high anaerobic organic removal levels were correlated to an increase of Defluviicoccus-related glycogen accumulating organisms in the biomass. Also, the capacity of the system to deal with shocks of high dye concentration and organic load was successfully demonstrated. Granule breakup after long-term operation only occurred in the dye-free control SBR, suggesting that the azo dye plays an important role in improving granule stability. Fluorescence in situ hybridization (FISH) analysis confirmed the compact structure of the dye-fed granules, microbial activity being apparently maintained in the granule core, as opposed to the dye-free control. These findings support the potential application of the AGS technology for textile wastewater treatment.
iBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Electronic address: rita.franca@tecnico.ulisboa.pt.
Rita D G
RD
Franca
Microbiology of Man-Made Environments Laboratory, iBET - Instituto de Biologia Experimental e Tecnológica, Av. República, Qta. do Marquês, 2780-157 Oeiras, Portugal; ITQB - Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Quinta do Marquês, 2780-157 Oeiras, Portugal. Electronic address: avieira@itqb.unl.pt.
Anabela
A
Vieira
iBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Electronic address: ana.mata@estsetubal.ips.pt.
Ana M T
AM
Mata
UCIBIO, REQUIMTE, Department of Chemistry, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal. Electronic address: gs.carvalho@fct.unl.pt.
Gilda S
GS
Carvalho
iBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Electronic address: helena.pinheiro@tecnico.ulisboa.pt.
Helena M
HM
Pinheiro
iBB - Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Electronic address: nidia.lourenco@tecnico.ulisboa.pt.
Nídia D
ND
Lourenço
D001391:Azo Compounds / Q000378:metabolism*; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D012244:Rhodospirillaceae / Q000378:metabolism*; D012722:Sewage / Q000032:analysis*; D013783:Textile Industry; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D001391:Azo Compounds; D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical; C469409:Acid red 14
Aerobic granular sludge; Anaerobic-aerobic reaction; Aromatic amine biodegradation; Azo dye reduction; Sequencing batch reactor; Textile wastewater