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This study explores the influence of ultrasonic pretreatment on the performance of a hybrid bioreactor treating synthetic textile wastewater. The study primarily focuses on assessing the decolorization and chemical oxygen demand (COD) reduction efficiency of a hybrid bioreactor. The hybrid bioreactor provided anaerobic-aerobic sequential treatment to the ultrasonically pretreated textile wastewater containing two new generation diazo dyes namely, reactive black 5 (RB5) and reactive red (RR120), along with other chemical constituents. Ultrasonic pretreatment produced approximately 52% color and 48% COD reduction efficiency at an optimized power of 200Wand 180 min sonication time. For the hybrid reactor treating ultrasonically pretreated textile wastewater, a maximum of 98% COD and 92% color removal efficiencies were obtained at an HRT of 32 h [organic loading rate (OLR) = 0.74 kgCODm-3d-1] and 24 h (OLR = 1.0 kgCODm-3 d-1), respectively. Significant levels of aromatic amines formation were observed in the anaerobic phase. However, those were effectively eliminated in the subsequent aerobic phase inside the hybrid bioreactor. Volatile fatty acids to bicarbonate alkalinity (VFA/B-alk.) ratios, one of the health indicators of the bioreactor operation, were found in the range of 0.23-0.32 at different hydraulic retention times (HRTs), thus indicating the adequate buffering capacity for stability of the bioreactor. The study demonstrates the importance of ultrasonic pretreatment for mineralizing organic and inorganic impurities present in textile wastewater, which significantly improves the performance of subsequent hybrid bioreactor. [ABSTRACT FROM AUTHOR]

The study explores the influence of physicochemical pretreatment on the performance of upflow anaerobic sludge blanket (UASB) reactors treating synthetic textile wastewater. Physicochemical pretreatment in this study utilized a new composite coagulant magnesium chloride added with aluminum chlorohydrate which produced nearly complete color removal and a partial chemical oxygen demand (COD) removal (~55%) efficiency. Various parameters such as volatile fatty acids (VFA), bicarbonate alkalinity (B-Alk.), gas production, total aromatic amines (TAAs) generation, COD, and color removal efficiency were monitored in the UASB reactors operated at different operating conditions. For the UASB reactor treating pretreated textile wastewater, a maximum of 99% COD removal was obtained at an organic loading rates (OLRs) of 1.2 kg COD m−3d−1and hydraulic retention time (HRT) of 20 h. Whereas in case of without pretreatment, a maximum of both 92% COD and color removal efficiency were achieved at an OLR of 2.4 kg COD m−3d−1and HRT of 20 h. However, in this case, highly toxic, carcinogenic, and mutagenic TAAs were observed to produce in the range of 6.9–8.1 mg L−1. VFA/B-Alk. ratios were found in the range of 0.05–0.15, indicating the sufficient buffering capacity for stability of the reactor. The study demonstrates the significance of physicochemical pretreatment on the performance of UASB reactor for the treatment of textile wastewater. Nevertheless, it also shows the importance of introducing pretreatment in order to avoid the production of harmful aromatic amines in the treated UASB effluent. [ABSTRACT FROM PUBLISHER]

In the present study, physico-chemically pre-treated textile wastewater with a residual chemical oxygen demand (COD) of 780 ± 10 mg L−1was treated using a lab-scale upflow anaerobic sludge blanket (UASB) reactor at variable HRTs of 30.8 to 8 h, and organic loading rates (OLRs) of 0.62–2.4 kg COD m−3 d−1. Using a new composite coagulant at dosage of 800 mg L−1for pre-treatment, more than 99% of colour was removed from the feeding influent to UASB reactor. The optimum OLR was found as 0.95 kg COD m−3 d−1at which maximum COD reduction (98%) was achieved. Modified Stover-Kincannon, Grau second-order, Monod, Haldane and Contois models were applied to evaluate the carbonaceous substrate removal kinetics inside the UASB reactor. The experimental results of this analysis revealed that modified Stover-Kincannon and Grau second-order kinetics were suitable for predicting the performance and to estimate the kinetic coefficients of UASB reactor. [ABSTRACT FROM PUBLISHER]

The aim of this work was to study the influence of the pre-treatment step, influent chemical oxygen demand (COD), and hydraulic retention time (HRT) on the decolourization and COD removal efficiency of the upflow anaerobic sludge blanket (UASB) reactors for treating textile wastewater. Statistical models were formulated based on these three variables to optimize the decolourization and COD removal efficiency in the UASB reactor using a full factorial central composite design. The high correlation coefficients (R2 = 0.99) and the low p-values (≤0.0001) reveal that the models and model terms are significant, which can be used to optimize the operational variables in an adequate way for the prediction of response variables. The COD removal efficiency of 70 % and decolourization efficiency of 81 % were observed for real textile wastewater treatment by UASB reactor without pre-treatment. Whereas for pre-treated real textile wastewater, these were 95 % and 100 %, respectively. The pre-treatment using a pre-investigated composite coagulant (MC + ACH) was vital in the overall treatment efficiency of the UASB reactor. Validation of model predictions for the treatment of synthetic and real textile wastewaters reveals the efficacy of these models for enhancing the decolourization and COD removal efficiency. [ABSTRACT FROM AUTHOR]

Textile industry is one of the most chemically intensive industries on the earth and the major polluter of potable water. It generates huge quantities of complex chemical substances as a part of unused materials including dyes in the form of wastewater during various stages of textile processing. The direct discharge of this wastewater into environment affects its ecological status by causing various undesirable changes. As environmental protection becomes a global concern, industries are finding novel solutions for developing technologies that can diminish the environmental damage. However, colour removal from textile wastewater by means of cheaper and environmental friendly technologies is still a major challenge. In this manuscript, several options of decolourisation of textile wastewater by chemical means have been reviewed. Based on the present review, some novel pre-hydrolysed coagulants such as Polyaluminium chloride (PACl), Polyaluminium ferric chloride (PAFCl), Polyferrous sulphate (PFS) and Polyferric chloride (PFCl) have been found to be more effective and suggested for decolourisation of the textile wastewater. Moreover, use of natural coagulants for textile wastewater treatment has also been emphasised and encouraged as the viable alternative because of their eco-friendly nature. [Copyright &y& Elsevier]

This study was conducted to assess the decolourisation and chemical oxygen demand (COD) reduction efficiency of a novel pre-hydrated aluminium salt as aluminium chlorohydrate (ACH) for the treatment of textile wastewater using coagulation/flocculation technology. Though, ACH belongs to the same group of polyaluminium salts, it is significantly different from polyaluminium chloride (PACl) in terms of the degree of hydration and alumina content and was used for the first time as a coagulant for the decolourisation of synthetic as well as real textile wastewater. The experimental results revealed that ACH is highly effective for the treatment of synthetic textile wastewater producing more than 99% of colour removal and 45% of COD reduction efficiency at a very low dosage of 200 mgL-1. The decolourisation of real textile wastewater was found to be very much in line with the results obtained for the treatment of synthetic textile wastewater. Superior decolourisation efficiency at a very low dosage as compared to that of the pre-established studies for real textile waste-water and least volume of easily dewatered sludge production makes ACH a novel and very promising coagulant for the treatment of industrial textile wastewater. [ABSTRACT FROM AUTHOR]