Performance Evaluation of Pilot-scale Hybrid Anaerobic Baffled Reactor (HABR) to Process Dyeing Wastewater Based on Grey Relational Analysis

Performance and response of coupled microbial fuel cells for enhanced anaerobic treatment of azo dye wastewater with simultaneous recovery of electrical energy

The anaerobic baffled reactor (ABR) is an anaerobic bioreactor that uses baffles to separate the working area into multiple reaction zones. The ABR-microbial fuel cell (MFC) reactor was constructed by embedding MFC in each reaction zone of the ABR. Its degradation of azo dye type (acid mordant red) wastewater and microbial power generation performance were investigated. For different electrode area ratios, the best enhanced treatment and electrical energy output of the coupled system was achieved with an anode/cathode area ratio of 1:1. Compared with the electrode area ratio of 2:1 and 1:2, the power density increased by 82.5% and 80.6%, and the Coulomb efficiency increased by 133.3% and 64.7%. In addition, the best enhanced treatment of printing and dyeing wastewater was achieved by ABR-MFC at 1:1. At a dye concentration of 200 mg/L and a sucrose concentration of 1000 mg/L, the coupled system obtained a COD removal of 92.85% and a chromaticity removal of 96.2%, which achieved a relative COD and chromaticity removal improvement of 1.82% and 2.64%, respectively, relative to the ABR. Scanning electron microscopy (SEM) observation of the electrodes at 1:1 revealed that more microorganisms were attached to the anode surface of the coupled system, the particle size of the granular sludge within the system was larger, and the UV scanning pattern showed lower dye concentration in the water. In conclusion, the microbial fuel cell enhanced anaerobic treatment of dyeing wastewater was the most effective when the electrode area ratio was 1:1, and the best electrical energy output was obtained at the same time. ABR-MFC provides a new idea for the enhanced treatment of dyeing wastewater and electrical energy production.

Development and operation of immobilized cell plug flow bioreactor (PFR) for treatment of textile industry effluent and evaluation of its working efficiency

The release of untreated/partially treated effluent and solid waste from textile dyeing industries, having un-reacted dyes, their hydrolysed products and high total dissolved solids (TDS) over the period of time had led to the deterioration of ecological niches. In an endeavour to develop a sustainable and effective alternative to conventional approaches, a plug flow reactor (PFR) having immobilized cells of consortium of three indigenous bacterial isolates was developed. The reactor was fed with effluent collected from the equalization tank of a textile processing unit located near city of Amritsar, Punjab (India). The PFR over a period of 3 months achieved 97.98 %, 82.22 %, 87.36%, 77.71% and 68.75% lowering of colour, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS) and total suspended solids (TSS) respectively. The comparison of the phytotoxicity and genotoxicity of untreated and PFR-treated output samples using plant and animal models indicated significant lowering of respective toxicity potential. This is a first report, as per best of our knowledge, regarding direct treatment of textile industry effluent without any pre-treatment and with minimal nutritional inputs, which can be easily integrated into already existing treatment plant. The successful implementation of this system will lower the cost of coagulants/flocculants and also lowering the sludge generation.

Pilot-Scale Anaerobic Treatment of Printing and Dyeing Wastewater and Performance Prediction Based on Support Vector Regression

Printing and dyeing wastewater is characterized with complex water quality and poor biodegradability. In this study, a pilot-scale anaerobic baffled reactor (ABR) with packing was verified to effectively degrade the complex organic pollutants in the wastewater through the hydrolysis and acidification of anaerobic microorganisms. At a hydraulic retention time (HRT) of 12 h and an organic loading rate (OLR) of 2.0–2.5 kg COD/(m3·d), the ABR stabilized the fluctuation range of pH and achieved an average colority removal rate of 10.5%, which provided favorable conditions for subsequent aerobic treatment. During the early operation period, the reactor increased the alkalinity of the wastewater; after 97 days of operation, the volatile fatty acid (VFA) content in the wastewater decreased. To demonstrate the suitability of the support vector regression (SVR) technology in predicting the performance of the reactor, two SVR algorithms with three kernel functions were employed to relate the chemical oxygen demand (COD) removal rate to its influencing factors, and the predictions of both the training and validation groups agreed with the measurements. The results obtained from this study can contribute to the design and optimal operation of the anaerobic treatment project of the industrial wastewater treatment plant.

Decolourization of textile effluent using native microbial consortium enriched from textile industry effluent

A robust and efficient treatment process is required to address the problem of residual colour and avoid expensive post-treatment steps while dealing with textile effluents. In the present work, a novel microbial consortium enriched from textile effluent was used to optimize the process of decolourization under extreme conditions with minimum inputs. With PreTreatment Range (PTR) effluent as a carbon source and only 0.5 g/L yeast extract as external input, the process enabled 70-73% colour reduction (from 1910-1930 to 516-555 hazen) in dyeing unit wastewater. Unhindered performance at higher temperatures (30 °C-50 °C) and wide pH range (7-12) makes this process highly suitable for the treatment of warm and extremely alkaline textile effluents. No significant difference was observed in the decolourization efficiency for effluents from different batches (Colour: 1647-4307 hazen; pH-11.5-12.0) despite wide variation in nature and concentration of dyes employed. Long term (60 days) continuous mode performance monitoring at hydraulic retention time of 48 h in lab-scale bioreactor showed consistent colour (from 1734-1980 to 545-723 hazen) and chemical oxygen demand (1720-2170 to 669-844 mg/L) removal and consistently neutral pH of the treated water. Present study thus makes a significant contribution by uncovering the ability of native microbial consortium to reliably treat dye laden textile wastewater without any dilution or pre-treatment and with minimum external inputs. The results ensure easy applicability of this indigenously developed process at the industrial scale.

Performance of HABR + MSABP system for the treatment of dairy wastewater and analyses of microbial community structure and low excess sludge production

The potential of the system, a hybrid anaerobic baffled reactor (HABR) coupled with a multi-stage active biological process (MSABP) reactor, for simulated dairy wastewater at various temperature, hydraulic retention time (HRT), and pH was investigated. Percentage removals of chemical oxygen demand (COD) and NH₄⁺ were optimized using response surface methodology. Under optimized conditions (temperature, 33 °C; HRT, 24 h; pH, 7.35), the removal efficiencies of COD and NH₄⁺ were 99.89% and 97.83%, respectively. Miseq sequencing analysis exhibited that the anaerobic segment of the system was dominated by fermentation and acetogenic bacteria, and in the aerobic segment, microorganisms involved in the nitrogen cycle were significantly enriched. Meanwhile, it could be found that the excess sludge production of the process was much lower than that of other bio-processes. The average excess sludge production rate was 0.025-0.05 g SS/g COD removed under different organic loadings.

Carbon dot cross-linked polyvinylpyrrolidone hybrid hydrogel for simultaneous dye adsorption, photodegradation and bacterial elimination from waste water

The creation of a polymeric hydrogel from polyvinylpyrrolidone (PVP) cross-linked by Carbon Quantum Dots (CD) for the adsorption and photocatalytic degradation of both cationic and anionic dyes. PVP, an important biocompatible constituent and often surplus in cosmetic industry, was carboxylated through NaOH refluxing and covalently conjugated to surface amine functionality of CD derived from lemon juice and Cysteamine. The hybrid hydrogel was obtained from PVP-CD covalent conjugate by careful manipulation of pH and found to possess better rheological properties than only carboxylate-PVP. The monolayer physisorption of the dyes on the hydrogel was affected by hydrogen bonding, dispersion or inductive effect, and π-π interaction with the polymer backbone as well as the CD that followed pseudo-second-order kinetics. Degradation of the adsorbed dyes was instated by the unique Reactive Oxygen Species (ROS) generating ability of the CD embedded in the hydrogel matrix upon exposure to sunlight, the mechanism of which is also unveiled. The same CD-induced ROS was found to effectively annihilate both gram-positive and gram-negative bacteria in real polluted water in less than 10 min of photoexcitation of the hydrogel. The hydrogel was restored by mild acid wash that is able to perform dye adsorption and photo-degradation upto four cycles.