Treatment Of Dyehouse Effluents Research Articles

Application of a downflow microaerophilic fixed film (DFMFF) reactor for the treatment of dye house effluents using a developed bacterial consortium

The present study describes a downflow microaerophilic fixed film (DFMFF) reactor based treatment of dye house effluents. The major characteristics of the two effluents E-2 and E-5 under study were; chemical oxygen demand (COD) 4680-16,266 mg L−1, biological oxygen demand (BOD) 1575–3151 mg L−1 and American Dye Manufacturers' Institute (ADMI) color index of 10,794–21,413. DFMFF reactor was packed with ultra-high molecular weight polyethylene (UHMWPE) shredding. The developed consortium was allowed to grow and form bio-film on packed UHMWPE. Degradation of the effluents at a various hydraulic retention time (HRT) and organic loading rate (OLR) was studied. Batch mode studies in the reactor showed > 80% removal of BOD and COD at OLR of 4.3 kg L−1 day−1 of E-2 and 2.4 kg L−1 day−1 of E-5 at 48 h HRT. Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) analysis confirmed biodegradation and obtained results indicated significant induction of oxidoreductive enzyme activities of azoreductase, NADH–DCIP reductase and laccase enzymes. Reduction in phytotoxicity and microbial toxicity was observed after the treatment of both the effluents. The reactor was also operated on continuous mode for treatment of E-2 under sequential anaerobic–aerobic phase and charcoal treatment. Results of sequential effluent treatment resulted in a reduction of > 99% of COD, BOD and ADMI along with > 88% of solids removal from the effluent. The resulting effluent was clear and meets the discharge criteria so as to release into the sewers. .

Evaluation of a tannin-based coagulant on the decolorization of synthetic effluents

Natural-based coagulants have demonstrated significant advantages over conventional ones. In this work, the treatment of dyehouse effluents by coagulation-flocculation-sedimentation was studied using a commercial tannin-derived coagulant and compared with the common use of iron salt. Two aqueous solutions simulating textile dyehouse effluents were prepared using an azo dye (Direct Blue 85): E1, containing only dye and salts, and E2, with also three auxiliary dyeing chemicals. The treatment of E1 and E2 was optimized in batch mode (Jar tests) in terms of coagulant dosages and pH, in order to maximize color removal and find an acceptable settling velocity of flocs. Although the pH of the effluents is around 8, acidic conditions (pH 4–5) were experimentally found to be optimal for their total decolorization, at minimum coagulant dosages. In these conditions, iron sulfate provided decolorization using much lower dosages than those required for the tannin-coagulant. At pH 4, for instance, tannin-coagulant dosage required to find 100% color removal and easily settleable flocs was 3-times higher than that of iron(III) sulfate. However, at neutral and alkaline conditions, which are of major relevance in practical terms, the tannin-coagulant was much more efficient than the iron coagulant. At pH 8 (natural pH of E2), total decolorization was achieved using 180 mg L−1 of tannin-coagulant, while dosages up to 240 mg L−1 of iron sulfate were unable to provide more than 20% of decolorisation and settleable flocs. Continuous mode experiments, conducted in optimum conditions, confirmed the performance levels observed in jar tests.

Applicability and costs of nanofiltration in combination with photocatalysis for the treatment of dye house effluents.

Nanofiltration (NF) is a capable method for the separation of dyes, which can support and even improve the applicability of photocatalysis in effluent-treatment processes. The membrane process usually will need a special pre-treatment to avoid precipitation and fouling on the membrane surface. Conceptually NF can be applied in the pre-treatment prior to the catalytic reactor or in connection with the reactor to separate the liquid phase from the reaction system and to recycle finely suspended catalysts and/or organic compounds. When concerning such reaction systems on a bigger scale, cost figures will prove the usefulness of those concepts. Different applications of photocatalysis on the lab-scale have been published in recent years. Membrane technology is used almost in all those processes and an overview will be given of those recently published systems that have been reported to be potentially useful for a further scale-up. NF membranes are mostly used for the more sophisticated separation step of these processes and the additional costs of the NF treatment, without any associated equipments, will be described and illustrated. The total specific costs of industrial NF treatment processes in usefully adjusted and designed plants range from 1 to 6 US$/m3 treated effluent. Combination concepts will have a good precondition for further development and upscaling, if the NF costs discussed here in detail will be, together with the costs of photocatalysis, economically acceptable.

Treatment of dyehouse effluents using sequential combinations of electrochemical oxidation, membrane separation, and activated sludge

Reducing water demand in textile sector is one of the important environmental concerns. In this study, individual and combined effects of selected operational parameters on a full‐scale electrochemical oxidation (ECO) process treating dyehouse effluent were investigated experimentally. Combinations of variables including current density, wastewater pH, and conductivity resulting in maximum color removal efficiency were determined using the Box‐Behnken design method. In addition to color removal, variations in wastewater organic composition before and after ECO were also examined critically. Removal and/or generation of 22 polycyclic aromatic hydrocarbons (PAHs) before and after ECO were investigated under variable operational conditions. Treatability of ECO effluent using conventional activated sludge process was investigated by both full‐scale monitoring studies and batch‐scale nitrification tests. Toxicity impact of raw, ozonized, and electrochemically treated wastewaters on nitrifiers were also determined and compared. Water reuse and salt recovery alternatives were assessed by full‐scale tests in a pilot plant which is composed of nanofiltration (NF), reverse osmosis (RO), and activated sludge processes. Advantages and disadvantages of applying ECO process as a pretreatment prior to membrane‐based or biological methods were critically evaluated. The average flux values of NF and RO membranes without ECO were 39 ± 2 and 19.5 ± 1 L m−2 h−1, respectively. The average flux values of NF and RO membranes without ECO were 39 ± 2 and 19.5 ± 1 L m−2 h−1, respectively. The permeability of the membranes for raw dyehouse effluent (without ECO) were estimated to be 6.0 ± 11 and 0.73 ± 0.6 L m−2 h−1 bar−1 Another important observation was formation of some PAHs including naphthalene, acenaphtylene, anthracene, benzo(a)anthracene, and benzo(g,h,i)perylene as a function of operational conditions maintained in ECO process. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 472–481, 2014

Treatment of dyehouse effluents with a carbon-based adsorbent using anodic oxidation regeneration

Adsorption is an attractive route for the removal of coloured, toxic and non-biodegradable organics from wastewater as very low discharge standards can be achieved. This paper reports on the use of a novel carbon-based material, Nyex100, as an adsorbent material for the treatment of dyehouse effluent. The adsorbent has low porosity and high electrical conductivity and these factors have allowed the adsorbent to be electrochemically regenerated. This work has demonstrated that the adsorbent can be cycled through the process of adsorption and regeneration a number of times with little drop in adsorptive capacity. However regeneration appears to modify the preference for organic species adsorption. Electrochemical regeneration can be rapidly achieved (15-20 minutes) using low current densities (< 20 mA cm(-2)). However, the low adsorptive capacity of the adsorbent, because of its small surface area, means that large quantities of adsorbent would need to be cycled within the process to treat the effluent volume generated in even small dyehouses. Thus, it is believed that operating the process in this mode limits the practical application of this technology.

Advanced treatment of dyehouse effluents by Fe(II) and Mn(II)-catalyzed ozonation and the H2O2/O3 process

Treatment of synthetic dyehouse effluent containing six reactive dyestuffs and their assisting chemicals by O3/Fe(II), O3/Mn(II), and O3/H2O2 advanced oxidation processes was investigated. All oxidation processes were capable of completely decolourizing the wastewater within 30 min. Decolourization proceeded fastest by the O3/Mn(II) process, whereas the O3/H2O2 combination was more efficient in the removal of DOC (Dissolved Organic carbon) and UV254nm which were 11 and 53%, respectively, for one hour treatment time. Application of Fe(II)-catalyzed ozonation provided an effective means of removing colour and COD (Chemical Oxygen Demand) by a five- and nine-fold enhancement, respectively, compared with conventional coagulation applied at the same coagulant doses. Formation of toxic oxidation products was not observed during the course of treatment with all investigated advanced oxidation processes.