Comparison of three combined sequencing batch reactor followed by enhanced Fenton process for an azo dye degradation: Bio-decolorization kinetics study.

The purpose of this research was to compare three combined sequencing batch reactor (SBR) - Fenton processes as post-treatment for the treatment of azo dye Acid Red 18 (AR18). Three combined treatment systems (CTS1, CTS2 and CTS3) were operated to investigate the biomass concentration, COD removal, AR18 dye decolorization and kinetics study. The MLSS concentration of CTS2 reached 7200 mg/L due to the use of external feeding in the SBR reactor of CTS2. The COD concentration remained 273 mg/L and 95 mg/L (initial COD=3270 mg/L) at the end of alternating anaerobic-aerobic SBR with external feeding (An-A MSBR) and CTS2, respectively, resulting in almost 65% of Fenton process efficiency. The dye concentration of 500 mg/L was finally reduced to less than 10mg/L in all systems indicating almost complete AR18 decolorization, which was also confirmed by UV-vis analysis. The dye was removed following two successive parts as parts 1 and 2 with pseudo zero-order and pseudo first-order kinetics, respectively, in all CTSs. Higher intermediate metabolites degradation was obtained using HPLC analysis in CTS2. Accordingly, a combined treatment system can be proposed as an appropriate and environmentally-friendly system for the treatment of the azo dye AR18 in wastewater.

Operation of integrated sequencing batch membrane bioreactor treating dye-containing wastewater at different SRTs: study of overall performance and fouling behavior.

The main aim of the present work was to study the overall performance and the fouling behavior of the integrated sequencing batch membrane bioreactor (SBMBR) treating synthetic dye-containing wastewater at different sludge retention times (SRTs) of 10, 40, and 160 days. For this reason, the removal efficiencies of color and chemical oxygen demand (COD) and the membrane fouling rates as well as the main sludge characteristics including extracellular polymeric substances (EPS), soluble microbial products (SMP), particle size distribution (PSD), and apparent viscosity were evaluated during the operation time of three SBMBRs. According to the obtained results, the decolorization efficiency was found to increase with increasing the SRT while the COD removal efficiency was similarly high (94-97%) in all SBMBRs regardless of SRT change. The rate of rise of transmembrane pressure (TMP) was much lower in the SBMBR operating at SRT of 160 days compared with the two other SBMBRs. Cake development on the membrane surface was recognized as the predominant fouling mechanism in three SBMBRs. Among the stated sludge properties, specific EPS and uniformity coefficient of the particle size distribution were suggested to be the controlling factors of the membrane fouling rate in three SBMBRs. During the operation at prolonged SRT (160 days in this study), better decolorization efficiency and lower biofouling rate were obtained in SBMBR system.