Aerobic Granular Sludge for Dye Biodegradation in a Sequencing Batch Reactor With Anaerobic/Aerobic Cycles

• Published in: Clean : soil, air, water air, water, 2016-04, Vol.44 (4), p.438-443
• Main Authors: Sadri Moghaddam, Shabnam, Alavi Moghaddam, Mohammad Reza
• Format: Article
• Language: English
• Subjects: Acid Red 18; Biodegradation; Decolourization; Dye removal; Dyes; Extracellular polymeric substances; Reactors; Studies; Wastewater treatment
• ISSN: 1863-0650; 1863-0669
• DOI: 10.1002/clen.201400855

This study investigated the formation of aerobic granular sludge with the main objective of Acid Red 18 (AR18) biodegradation in an altering anaerobic–aerobic sequencing batch reactor. According to the obtained results, the cultivated granules showed a stable structure in the treatment of synthetic wastewater containing 50 mg/L AR18, while no considerable variety in their characteristics and no granule break up were observed. As reported by many researchers, decolourization of AR18 is due to the anaerobic biodegradation of the azo bond; however, monitoring of the dye biodegradation through UV‐Vis spectroscopy showed that the contribution of the aerobic phase in dye removal was significant. This indicates the penetration of AR18 into the inner layers of granules and the ability of anaerobic microorganisms within the granules to degrade the dye through the consumption of tightly bound extracellular polymeric substances (EPS) as a carbon and energy source. The aerobic granules were not able to decompose anaerobically formed AR18 intermediates under aerobic conditions. The increase of the initial dye concentration from 50 to 100 mg/L caused the production of excess loosely bound EPS, which led to instability of the granules and hampered the dye removal efficiency. The presence of azo dyes and their by‐products in aqueous ecosystems results in health problems. Aerobic granular sludge with the main objective of azo dye biodegradation was cultivated in an altering anaerobic–aerobic sequencing batch reactor. The obtained results showed that the cultivated aerobic granules were successfully applied for the biodegradation of 50 mg/L Acid Red 18 in both anaerobic and aerobic cycles.