Investigation of the relation between COD fractions and the toxicity in a textile finishing industry wastewater: Effect of preozonation

Textile industry is one of the most common and essential sectors in the world. On the other hand, high volume of water consumption and varying wastewater characteristics due to many products such as dyes, biocides, carriers, detergents, etc. used in the process are the factors that have caused a continuous effort to find appropriate technologies to treat textile industry wastewater. In the last decade, the use of advanced oxidation processes (AOPs) has gained importance to degrade, decolorise and detoxicify the textile wastewater. However, the main mechanisms for AOPs for removing toxicity, thus, any contribution by the reduction of decreased inert factions in the effluent of textile wastewater are still to be studied. This study aimed to investigate the relation between inert COD fractions (which are characteristics in part of the influent wastewater, and in part generated in the biological treatment as the common used treatment process for textile industry) and effluent toxicity in the presence/absence of pre-ozonation. 18.5 mg/l of ozone dose was applied during 30 min oxidation on two wastewater samples taken from balancing tank of a textile industry localized in Istanbul, Turkey. A direct assessment method was used to determine inert COD fractions of the raw and ozonated wastewater samples. The toxicity of raw and treated was tested using newborn (24 h) samples of Daphnia magna for 24 h exposure time. The soluble inert COD (SI) decreased significantly while soluble residual microbial product (SP) increased slightly due to preozonation. The sum of soluble inert fractions were found in the order of 17-18% and 20% of total COD for raw and preozonated samples. Preozonation decreased the toxicity of raw wastewater. This phenomenon was evidenced also by testing the effluents of the inert COD determination reactors. © 2007

The effect of pre-ozone oxidation on acute toxicity and inert soluble COD fractions of a textile finishing industry wastewater

The present work evaluates pre-ozonation for removal of acute toxicity, color and COD as well as reduction of inert soluble COD fractions in two wastewater samples (S1 and S2) taken from a textile finishing industry, located in Istanbul (Turkey). The wastewater samples were oxidized at original pH of 8.6-8.8 under 18.5-24 mg/L of applied ozone doses. Acute toxicity was monitored using Daphnia magna. The results showed that pre-ozonation improved the biodegradability and reduced the acute toxicity. Acute toxicity in raw wastewaters was reduced by 80-90% using 129-200 mg/L transfered ozone (TrO3) concentrations. At this point, 86-96% of color, 33-39% of soluble COD and 57-64% of total COD were removed from wastewaters. Both color and COD parameters were found related to the acute toxicity of the wastewater. Pre-ozonation decreased the inert soluble COD fraction (SI) of raw wastewater while soluble product formation (SP) increased slightly (5-10 mg/L). However, residual COD (the sum of SI and SP) remained below discharge limit. © 2006 Elsevier B.V. All rights reserved

Evaluation of treatability for two textile mill effluents

The study emphasizes wastewater characteristics of two different textile plants as they apply to biological treatment. Although conventional characterization reveals no major differences, the effluents from the acrylic fiber and yarn dyeing plant exhibit all the properties of a non-biodegradable wastewater. Appropriate pretreatment consisting of partial chemical oxidation with H2O2 reduces its COD content to 700 mg l(-1), almost entirely biodegradable whereas COD fractionation indicates that the effluents of the cotton knit dyeing plant contain 9% residual fractions. Experimental investigation shows that most kinetic and stoichiometric properties of both wastewaters are compatible with that of domestic sewage with the exception of a much slower hydrolysis rate. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved

Advanced oxidation of commercial textile biocides in aqueous solution: effects on acute toxicity and biomass inhibition

In the present study, the decomposition of two biocides used in the textile finishing process with Advanced Oxidation Processes (AOPs) has been studied. Different AOPs, i.e O-3/OH-, TiO2/UV-A and Fe2+/H2O2 have been used representing mutually combined components of the chemically and photochemically driven advanced oxidation systems. The course of reaction was examined by changes in chemical oxygen demand (COD), total organic carbon (TOC) and acute toxicity towards the water flea Daphnia magna (assessed in terms of the effective dilution ratio LD50). Particular attention has been paid to determine the inhibitory effect of raw and ozonated biocides on biological activated sludge consortium at concentrations typically encountered in textile finishing effluents. Significant oxidation and mineralization of both biocides could be achieved employing ozonation at pH = 11.5 and heterogeneous photocatalysis (TiO2/UV-A) at pH = 5.0, whereas Fenton's reagent appeared to be less effective in COD and acute toxicity abatement