Akshaya Kumar Verma

A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters

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.

Supremacy of Magnesium Chloride for Decolourisation of Textile Wastewater: A Comparative Study on the Use of Different Coagulants

In this study, treatment efficiency of magnesium chloride (MgCl2.6H2O) was compared with respect to ferrous sulphate (FeSO4.7H2O), polyaluminium chloride (PACl), and aluminium chlorohydrate (ACH) for the treatment of textile wastewater. Treatment efficiency was assessed in terms of decolourisation and chemical oxygen demand (COD) reduction of synthetic textile wastewater containing reactive, direct and disperse dyes, along with the other chemical constituents that are normally released from different textile processing units. MgCl2.6H2O/Lime produced colour removal efficiency of 99.68% at a dosage 1200mg/L for the wastewater containing all the three dyes together. MgCl2.6H2O/Lime was also found to be the most effective coagulant system for treatment of textile wastewater containing only reactive dye, which produced 99.73% colour removal at a dosage of 1100 mg/L. For both the direct and disperse dyes, ACH was found to be superior over MgCl2.6H2O/Lime, FeSO4.7H2O/Lime, and PACl. Industrial grade ACH, which is normally used as polyelectrolyte, for the first time was used as coagulant in this study and was also appeared to be significant for decolourisation of textile wastewater containing all the three dyes together. From this study, MgCl2.6H2O/Lime was recommended as the best coagulant for the decolourisation of textile wastewater having very high original pH.

Applicability of a new pre-hydrated industrial grade polyaluminium salt for the decolourisation of textile wastewater

AbstractThis 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 mg L−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 ...

Carbonaceous organics removal kinetics in an upflow anaerobic sludge blanket (UASB) reactor treating physico-chemically pre-treated textile wastewater

In the present study, physico-chemically pre-treated textile wastewater with a residual chemical oxygen demand (COD) of 780 ± 10 mg L �1 was 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 �1 for 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 �1 at 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.