Evaluation of anaerobic sludge volume for improving azo dye decolorization in a hybrid anaerobic reactor with built-in bioelectrochemical system

Abstract

A hybrid anaerobic reactor with built-in bioelectrochemical system (BES) has been verified for efficiently treating mixed azo dye wastewater, yet still facing many challenges, such as uncertain reactor construction and insufficient electron donors. In this study, an up-flow hybrid anaerobic reactor with built-in BES was developed for acid orange 7 (AO7) containing wastewater treatment. Cathode and real domestic wastewater both served as electron donor for driving azo dye decolorization. The decolorization efficiency (DE) of AO7 (200 mg/L) in the hybrid reactor was 80.34 ± 2.11% with volume ratio between anaerobic sludge and cathode (VR) of 0.5:1 and hydraulic retention time (HRT) of 6 h, which was 15.79% higher than that in BES without sludge zone. DE was improved to 86.02 ± 1.49% with VR increased to 1:1. Further increase in the VR to 1.5:1 and 2:1, chemical oxygen demand (COD) removal efficiency was continuously improved to 28.78 ± 1.96 and 32.19 ± 0.62%, but there was no obvious DE elevation (slightly increased to 87.62 ± 2.50 and 90.13 ± 3.10%). BES presented efficient electron utilization, the electron usage ratios (EURs) in which fluctuated between 11.02 and 13.06 mol e/mol AO7. It was less than half of that in sludge zone of 24.73-32.06 mol e/mol AO7. The present work optimized the volume ratio between anaerobic sludge and cathode that would be meaningful for the practical application of this hybrid system.

Magnetizing Calixarene: Azo Dye Removal from Aqueous Media by Fe3O4 Nanoparticles Fabricated with Carboxylic-Substituted Calix[4]arene

“…However, their manufacturing or processing operation releases large amounts of effluents directly into the aquatic environment which causes turbidity, eutrophication, and aggravation of aquatic life . Most of the azo dyes are carcinogenic, mutagenic, and nonbiodegradable, making them the main cause of water pollution. − For this, significant efforts have been made to detoxify the effects of contamination before the dye is discharged to main streams by using different methods, such as the Fenton process, in conjunction with ultrasound technology, flocculation/coagulation, oxidation–ozonation, , electrochemical process, − membrane filtration, , and photocatalysis, , solid phase extraction, − Among these, solid phase extraction has been very economical and is easy to model.…”

Azo dyes degradation by microorganisms – An efficient and sustainable approach

“…BERs are basically a combination of microorganisms with electrochemistry. It can degrade azo dyes, nitro compounds and antibiotics ( Cui et al, 2017 ). It works by electrical supply at anode which reduces the refractory substances (azo dyes having more than one – N N – bonds) at cathode ( Cao et al, 2018 ).…”

Joint Multi-Optimization of an Extremophilic Microbial Bioanode for Mitigation of Mixed Hazardous Azo Dyes in Textile Synthetic Wastewater

“…In terms of mechanical strength, chemical stability, electrical conductivity, and biocompatibility, the material must be suitable. Consequently, various WE materials have been tested in the BESs for textile effluent treatment, and the most adopted are carbon-based materials such as carbon cloth [19], carbon fiber brushes [20], carbon felt [21], carbon paper [22], carbon rod [23], graphite [24,25], and granular activated carbon [26]. However, the influence of the electrode surface on the bioelectrochemical treatment of azo dyes has not yet been well investigated.…”