Enhancing laccase stability and activity for dyes decolorization using ZIF-8@MWCNT nanocomposite

The continuous use of chemical dyes in various industries, and their discharge into industrial effluents, results in severe problems to human life and water pollution. Laccases have the ability to decolorize dyes and toxic chemicals in industrial effluents as green biocatalysts. Their possible industrial applications have been limited by poor reusability, low stability, and loss of free laccase action. In this research, laccase was immobilized on zeolitic imidazolate framework coated multi-walled carbon nanotubes (Laccase@ZIF-8@MWCNTs) via metal affinity adsorption to develop an easy separable and stable enzyme. The optimum reaction conditions for immobilized laccase are at a pH of 3.0 and a temperature of 60?℃. The immobilized laccase was enhanced in storage and thermal stability. The results indicated that Laccase@ZIF-8@MWCNTs still maintained 68% of its original activity after 10 times of repeated use. Most importantly, the biocatalytic system was applied for decolorization of different dyes (20?mg·L^?1) without a mediator, and up to 97.4% for Eriochrome black T and 95.6% Acid red 88 was achieved in 25 min. Biocatalysts with these properties may be used in a variety of environmental and industrial applications.     

高效功能菌群RR的筛选及其群落分析

利用梯度浓度压力驯化法, 从厌氧反应器中筛选出对直接红28有具有良好脱色能力的混合菌群RR。在染料初始浓度为200mg/L, pH=7.0, 温度为35℃条件下, 经48h静止培养, 染料脱色率可达96.16%。进一步对其培养条件如pH值、温度、盐度、初始染料浓度等进行了脱色研究, 结果表明, 在pH=7、温度为45℃, 盐度为2mmol/L的情况下, 功能菌群脱色效果达到最佳。为了进一步适应工程无机条件, 筛选出以染料作为唯一氮源、碳源以及能量的功能菌群, 遂将培养基中葡萄糖去掉, 同样利用梯度浓度压力驯化法, 筛选出混合菌群RM, 并对其脱色性能及群落结构进行分析。混合菌群RM在染料初始浓度为50mg/L、温度为35℃、pH=7.0条件下, 48h后其脱色效率为20.05%。利用变性梯度凝胶电泳(DGGE)法, 对群落进行分析, 混合菌群RR主要为伯克霍尔德氏菌属(Burkholderia sp.)、链球菌属(Streptococcus)和克雷伯氏菌属(Klebsiella sp.), 菌群RM主要为伯克霍尔德氏菌属(Burkholderia sp.), 可见伯克霍尔德氏菌属菌株(Burkholderia sp.)可以适应工程无机环境, 并对直接红28存在一定的降解能力。     

Removal of Nickel and Boron from Plating Rinse Effluent by Electrochemical and Chemical Techniques

In this work, electrotreatment of nickel and boron containing plating rinse effluents was studied with mild steel and aluminum electrodes. Industrial effluent treatment directly by an electrochemical technique is capable of removing 80–85 % nickel. The residual nickel interfered with boron determination by curcumin method. The pH fall during electrotreatment in industrial effluent is due to electrodeposition of nickel at the cathode surface, evidenced by simulated effluent treatment. Nickel concentration can be reduced below the discharge limit from the industrial plating effluent by chemical precipitation and coagulation at pH above 8. Chemical precipitation showed maximum boron removal of about 50 %. Boron removal was 29.3–41.9 % and 20.6–33.1 % with ferric chloride and aluminum sulfate, respectively. A combination of chemical precipitation at pH 8.7 followed by electrotreatment reduces nickel to the discharge limit and also maximizes boron removal up to 59 %.     

Effect of HBT on the stability of laccase during the decolourization of textile wastewaters

BACKGROUND: This study concerns the assessment of laccase stability during textile industry effluent treatment by laccase in the presence of a mediator RESULTS: The effects of 1‐hydroxybenzotriazole (HBT) and textile wastewater on the stability of a crude laccase prepared from cultures of Trametes trogii during the process of textile industry effluent decolourization were determined. HBT was essential for decolourization of effluent by laccase. Decolourization efficiency decreased when effluent was repeatedly added to the reaction mixture, suggesting inhibition of laccase during the process. Stability of the laccase was not affected by different concentrations of effluent, but inactivation was proportional to HBT concentration. CONCLUSION: Experimental results showed that a redox mediator such as HBT was required for high decolourization rate of textile industry effluent; however free radicals generated from this compound inactivated the laccase used in the process. Copyright © 2009 Society of Chemical Industry     

Decolourization of the reconstituted dye bath effluent by commercial laccase treatment: Optimization through response surface methodology

This paper aims to study the effect of temperature, pH and enzyme concentration on decolourization of separately two reactive textile dyes (Black Novacron R and Blue Bezaktiv S-GLD 150) used in reconstituted dye bath effluent (textile dye and auxiliary components) and in aqueous dye solutions (dye dissolved in deionised water) by a commercial laccase formulation (DeniLite^® IIS). The central composite design (CCD) matrix and response surface methodology (RSM) have been applied to design experiments for the evaluation of the interactive effects of the three most important operating variables: temperature ‘T’ (25–45 °C), pH (3.0–7.0), and enzyme concentration ‘EC’ (80–240 U/L) on the enzymatic decolourization of the different synthetic dyes solutions at initial dye concentration of 40 mg/L. The RSM indicated that the optimum parameter values were respectively for the reconstituted Black Novacron R and the Blue Bezaktiv S-GLD 150 effluents: T = 43 °C and 41.44 °C, pH 6 and 6.29, EC = 222 and 226.43 U/L. The maximum colour removal was about 98.9% at 593 nm and 79.9% at 400 nm for reconstituted Black Novacron R effluent and about 98.9% at 620 nm for reconstituted Blue Bezaktiv S-GLD 150 effluent. For aqueous dye solutions, RSM has shown that colour removal obtained were quite similar. However, the optimum parameters were different. Hence, enzyme concentration depends on the effluent component.     

铝炭微电解处理刚果红废水的脱色动力学研究

采用铝炭微电解法处理刚果红废水。动力学研究结果表明,铝炭微电解降解刚果红的脱色过程符合表观二级动力学方程。刚果红脱色反应速率随着溶液初始p H、铝粉投加量、温度、摇床转速的增大而提高,随着铝炭质量比的降低先提高后降低。在温度为15~35℃范围内刚果红脱色反应活化能为17.75 k J/mol。采用铝炭微电解法处理某纺织印染公司实际印染废水,实验表明,在p H为11~12范围内,废水COD去除率不低于50%,反应后出水基本无颜色。     

Studies on coupled biological and photochemical treatment of soda pulp bleaching effluents from agro residue based pulp and paper mill

BACKGROUND: The effect of coupled biological and photochemical processes for treatment of bio‐recalcitrant effluents from chlorination (C) and first alkaline extraction (E₁) stages of soda pulp bleaching in an agro‐residue based pulp and paper mill has been investigated. RESULTS: The work aims to evaluate the coupled effect on the extent of degradation in terms of chemical oxygen demand (COD) reduction. Biological treatment of C and E₁ effluent resulted in 30% and 57% COD, respectively, after 1 day of treatment with acclimatized activated sludge. However, further increase in retention time did not show any significant change in degradation efficiency. Investigations on photocatalytic treatment (at 365 nm and 0.625 W) of C effluent resulted in 47% degradation under optimized conditions (3 g L^?1 TiO₂, pH 6.0 and 0.01 mol L^?1 NaOCl), and E₁ effluent showed 37% degradation under optimized conditions (2.5 g L^?1, pH 4.0 and 0.03 mol L^?1 NaOCl) after 6 h of UV irradiation. However, photocatalytic treatment of biotreated (1 day) effluents under similar optimized conditions significantly enhanced the degradation to 81% and 93% in C and E₁ effluent, respectively, after 2 h irradiation. CONCLUSION: Coupled biological treatment followed by photocatalysis is an effective method for the reduction of total organic carbon (TOC) of the test effluents and it would facilitate closed circuiting of water used for soda bleaching in an agro pulp and paper mill. Copyright © 2011 Society of Chemical Industry     

Biomass photochemistry-XXII: Combined photochemical and biological process for treatment of Kraft El effluent

The photocatalytic conditions for decontamination of Kraft effluents from Eucalyptus grandis (Brazil) and Pinus radiata (Chile) were studied. Irradiation in the presence of ZnO was similar for E. grandis and P. radiata effluents reaching a total decolorization after 2 h. This correlates with the mineralization process. When ZnO was immobilized on sand a two-fold faster decolorization was observed after 30 min of irradiation. The combined photochemical-biobleaching process was effective in the decolorization of Eucalyptus Kraft El effluent. By applying a short time of irradiation (10 min) the time necessary for 50% of biological colour reduction was decreased to half. The contribution of the photochemical process when applied as a post-treatment was least evident. In this case additional reduction of about 10% on the AOX content and almost completion of the decolorization process was observed for Pinus Kraft El effluent. Photochemistry applied to pulp and paper industry appeared as an important technique to remediate pollution problems.     

Removal of heavy metals using a brewer's yeast strain of Saccharomyces cerevisiae: application to the treatment of real electroplating effluents containing multielements

BACKGROUND: Yeast cells have been recognized as an effective type of biomass for the treatment of wastewaters containing heavy metals. However, its capability to treat efficiently complex effluents loaded with several metals ions (Cr, Cu, Ni and Zn) has never been reported. The aim of this work was to study the feasibility of a hybrid technology, which combines chemical precipitation at pH 6.0 with a subsequent biotechnological‐based process (using heat‐killed cells of a flocculent brewing strain of Saccharomyces cerevisiae), to remove simultaneously several metals from real electroplating effluents. RESULTS: Two effluents containing Cu, Ni and Zn (effluent A) or Cr, Cu and Ni (effluent B) were treated. In both effluents, pH was adjusted to 6.0; in effluent B, Cr(VI) was previously reduced to Cr(III). Chemical speciation studies allowed defining the amount of biomass to be employed with a minimum number of batches. Subsequently to pH adjustment to 6.0, effluents were fully treated with a serial batch of biomass. After the third batch, metal concentrations were lowered to below the legal limits of discharge; removals ≥ 89, 91, 92 and 94% were attained for Ni, Cu, Cr and Zn, respectively. CONCLUSIONS: In the present work, the usefulness of using flocculent brewing yeast cells to treat complex industrial effluents loaded with several heavy metals was demonstrated. The hybrid process developed was shown to be an efficient alternative for the treatment of real electroplating effluents. Copyright © 2010 Society of Chemical Industry     

A High Redox Potential Laccase from Pycnoporus sanguineus RP15: Potential Application for Dye Decolorization

Laccase production by Pycnoporus sanguineus RP15 grown in wheat bran and corncob under solid-state fermentation was optimized by response surface methodology using a Central Composite Rotational Design. A laccase (Lacps1) was purified and characterized and the potential of the pure Lacps1 and the crude culture extract for synthetic dye decolorization was evaluated. At optimal conditions (eight days, 26 °C, 18% (w/w) milled corncob, 0.8% (w/w) NH₄Cl and 50 mmol·L⁻¹ CuSO₄, initial moisture 4.1 mL·g⁻¹), the laccase activity reached 138.6 ± 13.2 U·g⁻¹. Lacps1 was a monomeric glycoprotein (67 kDa, 24% carbohydrate). Optimum pH and temperature for the oxidation of 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) were 4.4 and 74.4 °C, respectively. Lacps1 was stable at pH 3.0–8.0, and after two hours at 55–60 °C, presenting high redox potential (0.747 V vs. NHE). ABTS was oxidized with an apparent affinity constant of 147.0 ± 6.4 μmol·L⁻¹, maximum velocity of 413.4 ± 21.2 U·mg⁻¹ and catalytic efficiency of 3140.1 ± 149.6 L·mmol⁻¹·s⁻¹. The maximum decolorization percentages of bromophenol blue (BPB), remazol brilliant blue R and reactive blue 4 (RB4), at 25 or 40 °C without redox mediators, reached 90%, 80% and 60%, respectively, using either pure Lacps1 or the crude extract. This is the first study of the decolorization of BPB and RB4 by a P. sanguineus laccase. The data suggested good potential for treatment of industrial dye-containing effluents.     

Synthesis of Plantago Psyllium Mucilage Grafted Polyacrylamide and its Flocculation Efficiency in Tannery and Domestic Wastewater

A graft copolymer of P.psyllium mucilage and polyacrylamide has been synthesized in the presence of nitrogen using ceric ion-nitric acid redox initiator. This grafted copolymer was tested for its flocculation efficiency in Tannery and Domestic wastewater by the standard Jar Test method. The effects of polymer concentration, contact time and pH on percent removal of solid wastes from Tannery and Domestic effluents have been reported. The optimal dose was found to be 60 ppm, at which maximum solid removal from both the effluents took place. The maximum solid removal was seen after one hour at acidic pH in the case of the Domestic effluent and at alkaline pH in the case of Tannery effluent. X-ray analysis of the solid waste from effluents, grafted copolymer and flocs obtained after treatment of the effluents with the mucilage showed the interaction of the suspended solid wastes with the P. psyllium grafted polyacrylamide (Psy-g-PAM) copolymer. Psy-g-PAM has been proved to be a better flocculant than pure psyllium mucilage.     

Decolorisation of synthetic dyes by crude laccase from Rigidoporus lignosus W1

BACKGROUND: Effluents from the dyeing process containing dyes are difficult to degrade biologically. Therefore enzymatic dye decolorisation has received considerable attention recently. In this study the dye decolorisation potential of crude laccase from the white rot fungus Rigidoporus lignosus W1 was demonstrated on an anthraquinone dye, Remazol Brilliant Blue R (RBBR), and a triphenylmethane dye, malachite green (MG). Effects of pH, temperature and ionic strength on laccase activity and decolorisation efficiency were investigated. RESULTS: Native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate PAGE confirmed the decolorisation ability of the crude enzyme on RBBR and MG. A single laccase with a molecular mass of about 40 kDa appeared to be involved in the process. Efficient enzymatic decolorisation without redox mediator was achieved, with 39 mg L^?1 MG being removed within 2 h and 160 mg L^?1 RBBR within 1 h at 60 °C and pH 4.5. Although the laccase activity was inhibited in the presence of NaCl, it was renatured gradually in low concentrations of NaCl (<0.8 mol L^?1), resulting in unusual dye decolorisation kinetics. Surprisingly, unusual storage stability at alkaline pH was observed, with the laccase activity being enhanced 1.5–2‐fold after 3 h of incubation. CONCLUSION: Crude laccase with unusual storage stability from the fungus R. lignosus W1 showed excellent decolorisation ability on RBBR and MG without redox mediator. This laccase would seem to be a good candidate for application in dye decolorisation and textile effluent biotreatment. Copyright © 2008 Society of Chemical Industry     

Electrochemical treatment of pentachlorophenol in water and pulp bleaching effluent

Adsorbable organic halides (AOX) compounds produced during bleaching of pulp are recalcitrant and known to have eco-toxic effect. We have studied the removal of pentachlorophenol (PCP) as a model AOX compound in water as well as in pulp bleaching effluent of a bamboo based mill by electrochemical treatment in batch mode. It was found that 10 mg L⁻¹ of PCP in water was removed almost completely in <10 min at a current density of 6 mA cm⁻² in the presence of 1000 mg L⁻¹ NaCl serving as an electrolyte and source of chloride ions. The initial rate of PCP removal was found to decrease at alkaline pH (9.3) as compared to that at acidic pH (5.5). PCP removal in neutralized raw pulp bleach effluent (containing 1830 mg L⁻¹ of chloride) was very slow and incomplete even after 2 h of electrochemical treatment at a current density of 15 mA cm⁻². Various pretreatments of raw bleach effluent such as, alkaline sulfide using sodium sulfide, alkaline reduction using ferrous sulfate and coagulation using potash alum were evaluated. Electrochemical treatment of potash alum pretreated effluent (spiked with PCP) could achieve >90% removal of initial colour, COD and PCP in <1 h. The treatment scheme presented here may be a promising technology for removal of AOX, COD and colour from pulp bleaching effluent. The estimated cost of combined treatment (potash alum coagulation + electrochemical) is US$ 0.7–0.9 per cubic meter of the raw pulp bleach effluent.     

卡布龙红R4印染废水脱色菌的筛选及脱色条件的研究

从印染厂的活性污泥中筛选分离出了一株卡布龙红R4染料脱色优势菌X1,在30℃、200 r/min、染料质量浓度5 mg/L、接种量为6 mL、培养基为自然pH值的试验条件下进行脱色培养96 h,其脱色率最高,可达到68.4%。对COD、BOD5的质量浓度分别为85、21 mg/L,OD520值为0.23的印染排放废水在此工艺条件下进行脱色,脱色后出水COD、BOD5的质量浓度分别为5.8、2.90 mg/L,OD520值为0。     

Colour in textile effluents – sources,measurement, discharge consents and simulation: a review

This paper aims to review the problem of colour in textile effluents, the different classes of dyes available and their contribution to the problem. Through new regulations, pressure is being placed on water companies all over the world to reduce the amount of colour in sewage effluent. Dyes exhibit low toxicity to mammals and aquatic organisms and therefore colour consents are normally applied for aesthetic and industrial reasons rather than for prevention of toxicity. The absorbance, ADMI values and concentrations of dyes in effluent are examined here with particular reference to reactive azo dyes used in cotton processing. Colour consents, the problem of colour in textile wastewaters and the importance for research in this area are also discussed. Dye concentrations of 0.01 g dm⁻³ up to 0.25 g dm⁻³ have been cited as being present in dyehouse effluent, depending on the dyes and processes used. ADMI values ranged from 50 to 3890 units for the dyeing of cotton. It was concluded that 1500 ADMI units was a reasonable value to aim for when simulating coloured effluents. Simulated textile effluents may be used for research purposes. These should resemble real wastes as closely as possible, but it is often difficult to replicate the ADMI values, absorbance and spectra of real effluents. The concentrations of dye used in simulated effluents examined in literature varied from 0.01 g dm⁻³ to 7 g dm⁻³. As absorbance and ADMI values change with the types of dye used, it is difficult to relate these values to dye concentrations. A concentration of 0.18 g dm⁻³ of a Red or Yellow dye or 0.43 g dm⁻³ of a blue dye would provide an ADMI of approximately 1500 units and fits within the range of dye concentrations presented in literature. A dye mixture simulating colour in a real textile effluent is suggested and some limitations of simulating actual wastewaters discussed. © 1999 Society of Chemical Industry     

Effects of Dodecyl Trimethyl Ammonium Bromide Surfactant on Decolorization of Remazol Blue by a Living Aspergillus versicolor Strain

The effect of dodecyl trimethyl ammonium bromide (DTAB) cationic surfactant on Remazol Blue reactive dye bioremoval properties of a growing Aspergillus versicolor strain in a molasses medium was investigated in a batch system as a function of pH, dye and surfactant concentrations. To determine the optimal pH value in the presence of 0.5?mM DTAB pH 3 to 7 was examined and pH 6 was selected. The dye concentrations of 50, 100, 200, 400 and 800?mg/L were examined with 0.5?mM DTAB and maximum decolorization occurred in 100?mg/L dye (98.8?%). The surfactant concentration of 0.1, 0.5, 1 and 2?mM DTAB was performed in 100 and 800?mg/L dye. The effect of surfactant concentration (0.1 to 2?mM DTAB) in a fungal growth experiment has shown that DTAB inhibited fungal growth. The decolorization was increased from 53.6?% (dry weight: 1.31?g/L) to 100?% (dry weight:0.93?g/L) while the surfactant concentrations were increased from 0.1 to 1?mM. A. versicolor (dry weight: 0.93?g/L) showed its maximum dye removal activity, namely 100?% in 100?mg/L dye with 1?mM DTAB at pH 6 in 3?days. The use of surfactants in biological wastewater treatment process will save energy and lower energy costs (such as the required energy for treat techniques) by shortening the incubation period. The results showed that the A. versicolor strain, which produces laccase enzyme, can effectively decolorize reactive dyes by the enhancement of DTAB. Surfactant enhanced decolorization technology is one of the feasible approaches to remove textile dye from wastewater.     

Optimisation of reactive textile dyes degradation by laccase–mediator system

BACKGROUND: In the textile industry, large quantities of intensely coloured and toxic effluents are released, causing serious environmental pollution. Several biotechnological approaches have been suggested to eliminate this pollution source in an eco‐efficient manner. Laccase can be used to decolourise dyes and its substrate range can be extended by inclusion of a mediator. RESULTS: A screening using several laccase mediators (2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) (ABTS), 1‐hydroxybenzotriazole (HBT), N‐hydroxyacetanilide (NHA), polioxometalates, violuric acid (VA) and (2,2,6,6‐tetramethylpiperidin‐1‐yloxy) (TEMPO)) was performed on the degradation of six reactive textile dyes. ABTS was the most effective mediator leading to higher decolourisation. The efficiency of ABTS depends on the type of dye, pH, temperature and dye concentration. The optimum temperature and pH values were 35 °C and 5.0, respectively, for maximum decolourisation (above 70%) of reactive black 5, reactive blue 114 and reactive yellow 15. For reactive red 239 the optimum conditions were found to be a temperature of 40 °C and pH of 4.5 (above 56% decolourisation). ABTS has no effect at low concentrations, except for reactive blue 114, where it resulted in the best decolourisation (93%). A comparison of decolourisation based on the percentage absorbance reduction at the maximum absorbance wavelength of each dye and throughout the visible spectrum was made. CONCLUSIONS: These results suggest that the laccase mediator system could be used to treat textile dying wastewaters. Copyright © 2008 Society of Chemical Industry     

KnowVolution of a Fungal Laccase toward Alkaline pH

To date, commercial laccase preparations are used in the food, textile, and paper and pulp industries (mild pH). Laccases are attractive in the synthesis of dye molecules or oxidative lignin treatment, which take place at high pH (≥8.0). So far, one fungal laccase has been reported to be active at alkaline pH. Herein, engineering of the fungal laccase from Melanocarpus albomyces (MaL) for increased activity toward the substrate 2,6-dimethoxyphenol at pH (≥9.0) is reported. Through a knowledge-gaining directed evolution (KnowVolution) campaign, the key positions Leu365 and Leu513 were identified to increase alkaline tolerance. Both positions are located in close proximity of the T1Cu site. Molecular docking and simulations studies reveal that both substitutions act in a synergic way to stabilize and improve laccase activity at higher pH. Kinetic characterization of the final variant MaL-M1 (L365E/L513M) revealed at pH 9.8 a threefold improved k_cat (k_cat=(6.0±0.2) s⁻¹) compared with that of wild-type M. albomyces laccase (k_cat=(2.11±0.07) s⁻¹).     

云芝菌发酵产漆酶及其对靛蓝脱色的研究

采用云芝菌(Coriolus versicolor)摇瓶发酵生产漆酶,对主要的工艺参数进行了优化.研究结果表明:木质纤维废弃物木糖渣可用作云芝菌产酶的有效碳源,其适宜浓度为20.0 g·L-1;在培养基中添加10 0 g·L-1葡萄糖可以促进菌种的前期生长,有利于发酵后期漆酶的分泌合成;产酶培养基的最适C/N为20;适量的Cu2 和维生素C对漆酶的生成有明显促进作用,其适宜浓度分别为0.100 mmol·L-1和1.500 mmol·L-1.3.7 L自控式发酵罐中的产酶试验显示:最适通气量为100 L·h-1.在云芝菌的发酵进程中,前期主要为营养生长,产酶高峰期出现在发酵后期.在优化条件下发酵144 h,漆酶活力可高达2474.2 IU·mL-1.采用上述粗酶液处理靛蓝染料,当靛蓝浓度为50 mg·L-1,粗酶液用量为0.45%(Ⅴ∶Ⅴ)时,反应40 min,脱色率可达到94.8%.试验结果显示,漆酶在牛仔服生物整理及染整废水的脱色净化处理中具有良好的应用前景.     

The application of ozonation for the detoxification and biodegradability improvement of a textile auxiliary: Naphtalene sulphonic acid

From the environmental point of view, the textile industry dealing with operations such as fibre and fabric preparation, dyeing, finishing, printing etc. can be identified among the very chemical intensive sectors. Therefore the characterisation and management of textile auxiliaries within aqueous dyehouse effluents are becoming a challenging responsibility for the textile manufacturer. Although there is much speculation about the types and quantities of these chemicals released to the environment during textile manufacturing, there are only few data about the behaviour of these chemicals both in receiving water bodies and in wastewater treatment systems. Besides current understanding of industrial pollution control emphasizes the relevance of segregated stream management. This issue gains a further importance when segregated effluent streams containing auxiliaries with xenobiotic nature are considered.In this context the objective of the present study is to investigate the effect of ozonation on the toxicity and biodegradability of a naphthalene sulphonic acid derivative commonly applied in textile mills. The naphthalene sulphonic acid derivative prepared to simulate the actual situation in a dyebath discharge from a textile finishing industry has a COD of 1150 mg/l and a BOD of 10 mg/l, and pH of 5.5. Due to the highly soluble characteristic of the sulphonic groups the sample is completely soluble in nature. Ozonation experiments [conducted under the following conditions: 1200 mgO₃/h and 2400 mgO₃/h both at pH 5 and pH 11; 5325 mgO₃/h at both pH 12 and at the original pH (pH = 5.5)] show that the application of 5325 mgO₃/h ozone for 30 min at original pH can be considered as the optimum condition which is further evaluated in terms of inert COD fractions and acute toxicity. According to the experimental findings, raw naphtalene sulphonic acid derivative has an inert COD content of 1027 mg/l. With ozone application of 30 min 5325 mgO₃/h at original pH the inert COD concentration can be reduced down to 295 mg/l. The molecular weight cut-off experiments indicate that 58% of the COD originates from the 10 kDa-30 kDa fraction for the raw naphtalene sulphonic acid derivative. Due to chemical degradation under ozone, the fraction with the highest COD shifted to the < 1 kDa range for the ozonated naphtalene sulphonic acid derivative. Since the results related to the acute toxicity (in 50% v/v EC values) towards the marine algae Phaeodactylum tricornutum indicate that the toxicity of the formulation under investigation is increased considerably, it is recommended to run a further investigation by the use of another chemical oxidant instead of ozone.