Integration of Fenton Oxidation and Biological Process with Sequencing Batch Reactor for the Treatment of Textile Wastewater
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Date
2020-02
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Addis Ababa University
Abstract
study was mainly aimed to investigate the treatment efficiency of the integrated system of
biological oxidation and homo catalytic advanced oxidation process for the treatment of textile
wastewater. Mineralization of a methyl orange dyes using artificial solar Fenton oxidation,
degradation of a Basic Blue 41 dyes and real textile waste water with conventional Fenton
oxidation were examined at laboratory scale in batch experiments using Box–Behnken statistical
experiment design. Dyestuff, hydrogen peroxide (H2O2) and ferrous ion dose (Fe2+)
concentrations were selected as potential independent factors for simulated dye aqueous solutions
while for real wastewater Fenton reagents (H2O2 and Fe2+ ) and pH were selected as independent
potential factors. Besides, color and total organic carbon (TOC) removal were measured as
desired response functions for artificial solar Fenton oxidation while color and chemical oxygen
demand (COD) were selected as desired response for conventional Fenton oxidation processes.
The total time of irradiation used in the case of artificial solar Fenton oxidation for all the
experimental runs were 20 minutes while the total reaction time for conventional Fenton
oxidation processes was 1hour. Perturbation plots showed that iron dosage was the key process
factor on the responses for both solar and conventional Fenton processes. At constant dye stuff
dose, color, TOC and COD removal increased with increasing H2O2 and Fe2+ concentrations up
to a certain level. High concentrations of H2O2 and Fe2+ for a constant dye stuff dose did not
result in better removal of color ,TOC and COD. The optimum ratio of Fe2+ / H2O2 /dyestuff
which gives a complete color removal and 96% TOC removal for the highest level of dye dose
for artificial solar Fenton was found to be 72 /1386 / 255 (mg/L). In this regard, Percent color
removal was higher than TOC removal. During degradation of Basic Blue 41 dye, the optimum ratio of H2O2/Fe2+/dyestuff which gives
a complete color removal and 95% COD removal was found to be 1195mg/L /90mg/L /255mg/L
while in the case of real wastewater degradation, the optimum ratio of that gives 87% color
removal and 79% COD removal were Fe2+/H2O2/pH (500.4mg/L/5187.6mg/L/2.9). In this regard,,
Fenton oxidation using optimum Fenton reagents at a pH of 2.9 is effective for the treatment of
acrylic fiber processing textile wastewater.
Subsequently, real textile wastewater was taken and treated with a sequencing batch reactor (SBR)
using a biomass taken from domestic wastewater treatment plant. Cycle period, air flowrate and
sludge retention time (SRT) were initially optimized using the response surface methodology
(RSM). The optimum ratio of cycle period/ air flowrate/SRT which indicated 57% COD removal
and 54% color removal was found to be 25 h /15L/h /16d. Two types of wastewater substrate
concentrations and various hydraulic retention time (HRT) were used at optimized conditions.
COD removal, color removal, sludge volume index (SVI) and mixed liquor suspended solid
(MLSS) were measured. The maximum COD removal (73%) and color removal (65.8%) were
obtained at an organic loading rate of 0.078 kg COD/m3d. SVI at the optimized condition was
found to be 90-92 mL/g. A first order kinetic model was used to represent the degradation of textile
wastewater.
Finally, the removal of COD and color studied on a real textile wastewater using a single
stage of Fenton oxidation, (SBR) and also with the combination of SBR with Fenton
oxidation. Optimum amount of chemical reagents and SBR process factors were used. The
effluent obtained from SBR at steady state conditions indicated a maximum COD and color
removal of 74.1% and 64.6% respectively. The effluent obtained from Fenton followed by
SBR (Fenton +SBR) at steady state conditions indicated a maximum COD and color removal efficiency of 86.3% and 84% respectively. while SBR followed by Fenton (SBR+ Fenton)
for three Fenton oxidation experimental runs indicated a maximum COD and color removal
of 80.2% and 73.6% respectively
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Keywords
Fenton oxidation, textile wastewater, sequencing batch reactor, biological process