Kinetics of phthalate reactions with ammonium hydroxide in aqueous matrix

Common phthalate pollutants, such as dimethyl phthalate and diethyl phthalate found in aqueous environmental matrices react with ammonium hydroxide at ordinary temperatures exhibiting an overall reaction order in the range 1.3-1.4. While the reaction is of first order with respect to the phthalate, the order of reaction is fractional in ammonium hydroxide. The rate constants for the reactions of these two phthalates in alkaline waters at ambient temperatures are in the range 1.3 x 10(-4) and 8.5 x 10(-5) Lx/mol s. Under these conditions the estimated half-lives for dimethyl phthalate and diethyl phthalate at a concentration of each at 20 mg/L is 4.5 and 14 h, respectively. Other phthalates are expected to exhibit similar kinetics in their base hydrolysis with NH4OH. Thus, the presence of both the phthalate esters and ammonia or ammonium salts in the water under alkaline conditions may result in their self-removal by hydrolysis.     

Fenton-like oxidation of 2,4,6-trinitrotoluene using different iron minerals

Degradation of 2,4,6-trinitrotoluene (TNT) was investigated in presence of different oxidants (Fenton's reagent, sodium persulfate, peroxymonosulfate and potassium permanganate) and different iron minerals (ferrihydrite, hematite, goethite, lepidocrocite, magnetite and pyrite) either in aqueous solution or in soil slurry systems. Fenton's reagent was the only oxidant able to degrade TNT in solution (k(app)=0.0348 min(-1)). When using iron oxide as heterogeneous catalyst at pH 3, specific reaction rate constants per surface area were k(surf)=1.47.10(-3) L min(-1) m(-2) and k(surf)=0.177 L min(-1) m(-2) for magnetite and pyrite, respectively while ferric iron minerals were inefficient for TNT degradation. The major asset of iron mineral catalyzed Fenton-like treatment has been the complete oxidation of the pollutant avoiding the accumulation of possible toxic by-products. In soil slurry systems, 38% abatement of the initial TNT concentration (2 g/kg) was reached after 24 h treatment time at neutral pH. Rate limiting steps were the availability of soluble iron at neutral pH together with desorption of the TNT fraction sorbed on the clay mineral surfaces.     

Ozonation kinetics of cork-processing water in a bubble column reactor

The oxidative degradation of organic pollutants present in cork-processing water at natural pH (6.45) was studied in a bubble column ozonation reactor. A steady reduction in both chemical oxygen demand (COD) and total organic carbon (TOC) was observed under the action of ozone alone and the feasibility of deep mineralisation (organic matter removal more than 90% in 120 min under the following experimental conditions: liquid volume 9L; superficial gas velocity 6.8x10(-3) m s(-1); ozone partial pressure 1.31 kPa; initial COD 328 mg L(-1); initial TOC 127 mg L(-1)) was demonstrated. The monitoring of pH, redox potential (ORP) and the mean oxidation number of carbon (MOC) was correlated with the oxidation and mineralisation of the organic species in the water. The ozonation of cork-processing water in the bubble column was analysed in terms of a mole balance coupled with ozonation kinetics modelled by the two-film theory of mass transfer and chemical reaction. Under the experimental conditions used, and in contrast with the literature, it was determined that the reaction follows a fast kinetic regime at the beginning of the oxidation process, shifting to the moderate and the slow kinetic regimes at later stages of the oxidation reaction. The dynamic change of the rate coefficient estimated by the model was correlated to changes in the water composition.     

Kinetics of triclosan oxidation by aqueous ozone and consequent loss of antibacterial activity: relevance to municipal wastewater ozonation

Oxidation of the antimicrobial agent triclosan by aqueous ozone (O(3)) was investigated to determine associated reaction kinetics, reaction site(s), and consequent changes in antibacterial activity of triclosan. Specific second-order rate constants, k(O(3)), were determined for reaction of O(3) with each of triclosan's acid-base species. The value of k(O(3)) determined for neutral triclosan was 1.3(+/-0.1)x10(3)M(-1)s(-1), while that measured for anionic triclosan was 5.1(+/-0.1)x10(8)M(-1)s(-1). Consequently, triclosan reacts very rapidly with O(3) at circumneutral pH (the pH-dependent, apparent second-order rate constant, K(app,O(3)) , is 3.8x10(7)M(-1)s(-1) at pH 7). The pH-dependence of K(app,O(3)) and comparison of triclosan reactivity toward O(3) with that of other phenolic compounds indicates that O(3) reacts initially with triclosan at the latter's phenol moiety. k(O(3)) values for neutral and anionic triclosan were successfully related to phenol ring substituent effects via Brown-Okamoto correlation with other substituted phenols, consistent with electrophilic attack of the triclosan phenol ring. Biological assay of O(3)-treated triclosan solutions indicates that reaction with O(3) yields efficient elimination of triclosan's antibacterial activity. In order to evaluate the applicability of these observations to actual wastewaters, triclosan oxidation was also investigated during ozonation of effluent samples from two conventional wastewater treatment plants. Nearly 100% triclosan depletion was achieved for a 4 mg/L(8.3x10(-5)mol/L)O(3) dose applied to a wastewater containing 7.5 mg/L of DOC, and approximately 58% triclosan depletion for dosage of 6 mg/L(1.3x10(-4)mol/L)O(3) to a wastewater containing 12.4 mg/L of DOC. At O(3) doses greater than 1mg/L(2.1x10(-5)mol/L), hydroxyl radical reactions accounted for <35% of observed triclosan losses in these wastewaters, indicating that triclosan oxidation was due primarily to the direct triclosan-O(3) reaction. Thus, ozonation appears to present an effective means of eliminating triclosan's antibacterial activity during wastewater treatment.     

Aqueous chlorination of the antibacterial agent trimethoprim: reaction kinetics and pathways

Trimethoprim (TMP), one of the antibacterials most frequently detected in municipal wastewaters and surface waters, reacts readily with free available chlorine (i.e., HOCl) at pH values between 3 and 9 (e.g., the pH-dependent apparent second-order rate constant, k'(app)=5.6 x 10(1)M(-1)s(-1), at pH 7). Solution pH significantly affects the rate of TMP reaction with HOCl. The reaction kinetics in reagent water systems can be well described by a second-order kinetic model incorporating speciation of both reactants and accounting for acid-mediated halogenation of TMP's 3,4,5-trimethoxybenzyl moiety. Studies with the substructure model compounds 2,4-diamino-5-methylpyrimidine and 3,4,5-trimethoxytoluene show that TMP reacts with HOCl primarily via its 3,4,5-trimethoxybenzyl moiety at acidic pH, and with its 2,4-diaminopyrimidinyl moiety at circumneutral and alkaline pH. LC/MS product analyses indicate that the TMP structure is not substantially degraded upon reactions with HOCl. Instead, a wide variety of (multi)chlorinated and hydroxylated products are formed. Experiments with real drinking water and wastewater matrixes confirmed that substantial TMP transformation can be expected for conditions typical of wastewater and drinking water chlorination.     

The hydroxide-assisted hydrolysis of cyanogen chloride in aqueous solution

The hydrolysis of cyanogen chloride (ClCN) was studied as a function of temperature and pH. Results were used to resolve discrepancies among previously reported kinetic constants. The pH dependence was studied over a range of 9.54-10.93 at a temperature of 21.0 degrees C. The effect of temperature was investigated over the range of 10-30 degrees C at a pH of approximately 10. Changes in the concentrations of ClCN and the reaction products cyanic acid and chloride ion were monitored with time. For the conditions corresponding to these experiments, the hydroxide-assisted hydrolysis pathway predominated. Collision frequency factor and activation energies recommended to represent the hydrolysis of ClCN in aqueous solution are A = 2.06 x 10(11) M-1 s-1 and Ea = 60,980 J mol-1 for the hydroxide-ion-assisted reaction, and A = 9.97 x 10(8) s-1 and Ea = 87,180 J mol-1 for the water-assisted reaction.     

Chlorine and ozone disinfection of Encephalitozoon intestinalis spores

Microsporidia are intracellular eukaryotic parasites which have the potential for zoonotic and environmental, including waterborne, transmission. Encephalitozoon intestinalis is a microsporidian pathogen of humans and animals and has been detected in surface water. It is also on the Contaminant Candidate List of potential emerging waterborne pathogens for the US EPA. We performed disinfection studies using chlorine and ozone on E. intestinalis spores with a cell-culture most-probable-number assay to determine infectivity. Chlorine experiments were performed at 5 degrees C at pH of 6, 7, and 8 with 1mg/L initial chlorine concentrations, while ozone experiments were performed at 5 degrees C and pH 7 with initial ozone doses of 1 and 0.5mg/L, both in buffered water. A derivation of Hom's model for disinfection kinetics under dynamic disinfectant concentrations was used to fit observed data and calculate concentration-time product (C*t) values. Chlorine C*t values varied with pH such that 99% (2-log(10)) C*t ranged from 12.8 at pH 6 to 68.8 at pH 8 (mg min/L). Ozone C*t values were approximately an order of magnitude less at 0.59--0.84 mg min/L, depending on initial concentration.     

Fenton oxidation of cork cooking wastewater--overall kinetic analysis

In the present work, the possibility of using chemical oxidation through Fenton's reagent for the pre-treatment of cork cooking wastewaters was exploited. Aiming both the selection of the best operating conditions (pH, Fe2+:H2O2 ratio and initial H2O2 concentration) and the evaluation of the overall reaction kinetics, trials were performed in a batch reactor. Operating at pH = 3.2, H2O2 concentration = 10.6 g/L and Fe2+:H2O2 ratio = 1:5 (by weight), about 66.4% of total organic carbon (TOC), 87.3% of chemical oxygen demand (COD) and 70.2% of biochemical oxygen demand (BOD5) were removed and an increase of the BOD5/COD ratio from 0.27 to 0.63 was achieved. In the temperature range 20-50 degrees C, the best performance was obtained at 30 degrees C. The kinetic study was undertaken at different initial TOC concentrations and temperatures. Overall kinetics can be described by a second-order followed by a zero-order rate equation and the apparent kinetic constants at 30 degrees C are k = 2.3 x 10(-4) L/mg min and k0 = 26.0 mg/L min, respectively. The experiments performed at different temperatures confirmed the global kinetic model and allowed to calculate the global activation energy for the second-order reaction (70.7 kJ/mol).     

Effects of water chemistry on arsenic removal from drinking water by electrocoagulation

Exposure to arsenic through drinking water poses a threat to human health. Electrocoagulation is a water treatment technology that involves electrolytic oxidation of anode materials and in-situ generation of coagulant. The electrochemical generation of coagulant is an alternative to using chemical coagulants, and the process can also oxidize As(III) to As(V). Batch electrocoagulation experiments were performed in the laboratory using iron electrodes. The experiments quantified the effects of pH, initial arsenic concentration and oxidation state, and concentrations of dissolved phosphate, silica and sulfate on the rate and extent of arsenic removal. The iron generated during electrocoagulation precipitated as lepidocrocite (γ-FeOOH), except when dissolved silica was present, and arsenic was removed by adsorption to the lepidocrocite. Arsenic removal was slower at higher pH. When solutions initially contained As(III), a portion of the As(III) was oxidized to As(V) during electrocoagulation. As(V) removal was faster than As(III) removal. The presence of 1 and 4 mg/L phosphate inhibited arsenic removal, while the presence of 5 and 20 mg/L silica or 10 and 50 mg/L sulfate had no significant effect on arsenic removal. For most conditions examined in this study, over 99.9% arsenic removal efficiency was achieved. Electrocoagulation was also highly effective at removing arsenic from drinking water in field trials conducted in a village in Eastern India. By using operation times long enough to produce sufficient iron oxide for removal of both phosphate and arsenate, the performance of the systems in field trials was not inhibited by high phosphate concentrations.     

Kinetics of the transformation of phenyl-urea herbicides during ozonation of natural waters: rate constants and model predictions

Oxidation of four phenyl-urea herbicides (isoproturon, chlortoluron, diuron, and linuron) was studied by ozone at pH=2, and by a combination of O3/H2O2 at pH=9. These experiments allowed the determination of the rate constants for their reactions with ozone and OH radicals. For reactions with ozone, the following rate constants were obtained: 1.9 +/- 0.2, 16.5 +/- 0.6, 393.5 +/- 8.4, and 2191 +/- 259 M(-1) s(-1) for linuron, diuron, chlortoluron, and isoproturon, respectively. The rate constants for the reaction with OH radicals were (7.9 +/- 0.1) x 10(9) M(-1) s(-1) for isoproturon, (6.9 +/- 0.2) x 10(9) M(-1) s(-1) for chlortoluron, (6.6 +/- 0.1) x 10(5) M(-1) s(-1) for diuron, and (5.9 +/- 0.1) x 10(9) M(-1) s(-1) for linuron. Furthermore, the simultaneous ozonation of these selected herbicides in some natural water systems (a commercial mineral water, a groundwater, and surface water from a reservoir) was studied. The influence of operating conditions (initial ozone dose, nature of herbicides, and type of water systems) on herbicide removal efficiency was established, and the parameter Rct (proposed by Elovitz, M.S., von Gunten, U., 1999. Hydroxyl radical/ozone ratios during ozonation processes. I. The Rct concept. Ozone Sci. Eng. 21, 239-260) was evaluated from simultaneous measurement of ozone and OH radicals. A kinetic model was proposed for the prediction of the elimination rate of herbicides in these natural waters, and application of this model revealed that experimental results and predicted values agreed fairly well. Finally, the partial contributions of direct ozone and radical pathways were evaluated, and the results showed that reaction with OH radicals was the major pathway for the oxidative transformation of diuron and linuron, even when conventional ozonation was applied, while for chlortoluron and isoproturon, direct ozonation was the major pathway.     

Rate constants of reactions of bromine with phenols in aqueous solution

The kinetics of bromination of six ortho- and para-substituted phenols was investigated between pH 5 and pH 12 in aqueous solution. Kinetics was followed with a continuous-flow reactor previously validated by studying the fast reaction between chlorine and ammonia. The overall reaction rate between bromine and phenols is controlled by the reaction of HOBr with the phenoxide ion between pH 6 and pH 10. The reaction of HOBr with the undissociated phenols and the reaction of BrO(-) with the phenoxide ions become only significant for pH<6 and pH>10, respectively. The second-order rate constants for the reaction of HOBr with phenoxide ions vary between 1.4(+/-0.1)x10(3) and 2.1(+/-0.5)x10(8)M(-1)s(-1) for 2,4,6-trichlorophenol and 4-methylphenol, respectively. Hammett-type correlation was obtained for the reaction of HOBr with the phenoxide ions (log(k)=8.0-3.33 x Sigmasigma) and was compared with Hammett-type correlations of HOCl and HOI. The reaction rate of bromine with phenol-like organic compounds was estimated to be about 10(3)-fold higher than with chlorine and 10(3)-fold lower than with ozone in drinking water treatment conditions.     

Ozonation of reverse osmosis concentrate: kinetics and efficiency of beta blocker oxidation

Reverse osmosis (RO) concentrate samples were obtained from a RO-membrane system that uses effluents of wastewater treatment plants (WWTP) as feed water for the production of drinking water. A number of different pharmaceuticals (e.g. antibiotics, contrast media, beta blockers) were found in the WWTP effluent as well as in the RO-concentrate. Overall, a concentration factor (feed:concentrate) of approximately 3-4 was measured. Beta blockers (acebutolol, atenolol, bisoprolol, celiprolol, metoprolol, propranolol, timolol) were found in the range of low ng/L to low microg/L. Because metoprolol and propranolol are classified as potentially toxic to aquatic organisms and all beta blocker molecules have moieties, which are reactive towards ozone (amine groups, activated aromatic rings), it was tested whether ozonation can be applied for their mitigation. Rate constants for the reaction of acebutolol, atenolol, metoprolol and propranolol with ozone and OH radicals were determined. At pH 7 acebutolol, atenolol and metoprolol react with ozone with an apparent second-order rate constant ( [Formula: see text] ) of about 2,000 M(-1)s(-1), whereas propranolol reacts with approximately 10(5)M(-1)s(-1). The rate constants for the reaction of the selected compounds with OH radicals were determined to be 0.5-1.0 x 10(10)M(-1)s(-1). Experiments with RO concentrate showed that an ozone dose of only 5mg/L resulted in a quantitative removal of propranolol in 0.8s and 10mg O(3)/L oxidized 70% of metoprolol in only 1.2s. Tests with chlorinated and non-chlorinated WWTP effluent showed an increase of ozone stability but a decrease of hydroxyl radical exposure in the samples after chlorination. This may shift the oxidation processes towards direct ozone reactions and favor the degradation of compounds with high [Formula: see text].     

Oxidative-coupling reaction of TNT reduction products by manganese oxide

Abiotic transformation of TNT reduction products via oxidative-coupling reaction was investigated using Mn oxide. In batch experiments, all the reduction products tested were completely transformed by birnessite, one of natural Mn oxides present in soil. Oxidative-coupling was the major transformation pathway, as confirmed by mass spectrometric analysis. Using observed pseudo-first-order rate constants with respect to birnessite loadings, surface area-normalized specific rate constants, ksurf, were determined. As expected, ksurf of diaminonitrotoluenes (DATs) (1.49-1.91L/m2 d) are greater about 2 orders than that of dinitroaminotoluenes (DNTs) (1.15 x 10(-2)-2.09 x 10(-2)L/m2d) due to the increased number of amine group. In addition, by comparing the value of ksurf between DNTs or DATs, amine group on ortho position is likely to be more preferred for the oxidation by birnessite. Although cross-coupling of TNT in the presence of various mediator compounds was found not to be feasible, transformation of TNT by reduction using Fe0 followed by oxidative-coupling using Mn oxide was efficient, as evaluated by UV-visible spectrometry.     

pH值和碱度对厌氧折流板反应器运行的影响

为考察pH值和碱度对厌氧折流板反应器(ABR)高效、稳定运行的影响,采用一个有效容积为28 L的4格室ABR反应器处理豆制品废水。ABR反应器运行72 d的结果表明:在启动阶段的前期外加碱液调节进水pH值,使pH值和碱度分别基本稳定在6.0～7.0和1 000～1 300mg/L,运行效果良好。启动45 d时,停止外加碱液对进水pH值进行调节,系统仍稳定运行,但启动阶段出现丙酸浓度缓慢上升现象。在反应器稳定运行阶段,各格室的pH值分别为(4.5～6.0)、(5.5～6.8)、(6.8～7.2)、(7.1～7.3),碱度基本处在1 000～1 400 mg/L,反应器出水的发酵产物含量<100 mg/L(乙酸占90%以上),对COD的去除率保持在90%以上。     

Oxidation of pharmaceuticals during water treatment with chlorine dioxide

The potential of chlorine dioxide (ClO2) for the oxidation of pharmaceuticals during water treatment was assessed by determining second-order rate constants for the reaction with selected environmentally relevant pharmaceuticals. Out of 9 pharmaceuticals only the 4 following compounds showed an appreciable reactivity with ClO2 (in brackets apparent second-order rate constants at pH 7 and T = 20 degrees C): the sulfonamide antibiotic sulfamethoxazole (6.7 x 10(3) M(-1) s(-1)), the macrolide antibiotic roxithromycin (2.2 x 10(2) M(-1) s(-1)), the estrogen 17alpha-ethinylestradiol (approximately 2 x 10(5) M(-1) s(-1)), and the antiphlogistic diclofenac (1.05 x 10(4) M(-1) s(-1)). Experiments performed using natural water showed that ClO2 also reacted fast with other sulfonamides and macrolides, the natural hormones estrone and 17beta-estradiol as well as 3 pyrazolone derivatives (phenazone, propylphenazone, and dimethylaminophenazone). However, many compounds in the study were ClO2 refractive. Experiments with lake water and groundwater that were partly performed at microgram/L to nanogram/L levels proved that the rate constants determined in pure water could be applied to predict the oxidation of pharmaceuticals in natural waters. Compared to ozone, ClO2 reacted more slowly and with fewer compounds. However, it reacted faster with the investigated compounds than chlorine. Overall, the results indicate that ClO2 will only be effective to oxidize certain compound classes such as the investigated classes of sulfonamide and macrolide antibiotics, and estrogens.     

二氧化氯/混凝剂工艺处理含铁水的试验研究

通过向含铁水中投加二氧化氯和混凝剂,考察了二氧化氯对水中铁的去除效果及其影响因素。结果表明,二氧化氯投加量、原水pH、预氧化时间和混凝剂投加量对铁的去除效果均有较大的影响。当原水Fe2+浓度为5 mg/L时,二氧化氯最佳投加量为5 mg/L,最佳氧化时间为10 min,混凝剂的最佳投加量为1 mg/L,最佳pH值为7～9,对铁离子的去除率可达到94.0%。     

Hydrolysis and acidification of waste activated sludge at different pHs

The effect of pH from 4.0 to 11.0 on the hydrolysis and acidification of waste activated sludge (WAS) was investigated. Experimental results showed that at room temperature the sludge hydrolysis was in the following order: alkaline>acidic>(neutral and blank test), and between pH 6.0 and 11.0 the sludge hydrolysis increased with pH. The three main components, soluble protein, carbohydrate and volatile fatty acids (VFAs) in the hydrolytic product were analyzed. It was observed that both the soluble protein and carbohydrate increased with pH in the pH range 7.0-11.0, but also increased to a smaller extent with pH from 7.0 to 4.0. The VFAs concentration was also affected by pH. Under alkaline conditions, the VFAs production was significantly higher than under other conditions. The concentration of VFAs on the 8th day of fermentation at pH 4.0, 7.0 and 10.0 was, respectively, 354.49, 842.00 and 2708.02 mg/L, while VFAs in the blank test was only 633.59 mg/L. The VFAs consisted of acetic, propionic, iso-butyric, n-butyric, iso-valeric and n-valeric acids, but acetic, propionic and iso-valeric were the three main products. Also, the release of soluble phosphorus and ammonia and the production of methane was studied during WAS fermentation at different pHs.     

Water remediation by micelle-clay system: case study for tetracycline and sulfonamide antibiotics

Removal of tetracycline and sulfonamide antibiotics from water by micelles pre-adsorbed on montmorillonite was studied. Micelles of benzyldimethylhexadecylammonium (BDMHDA) were used. Batch experiments demonstrated that the micelle-clay complexes (1% w/w) removed 96-99.9% of antibiotics from their water solutions containing from 5 to 50 mg/L of pharmaceuticals. Column filters (25 cm) made of a mixture of quartz sand and BDMHDA micelle-clay complex at 100:1 w/w ratio removed 94-99.9% of above pharmaceuticals from initial solutions containing 10mg/L and 89% of sulfamethizole from an initial solution containing 10 microg/L of this antibiotic. These filters were also very efficient in the removal of antibiotics in the presence of dissolved soil organic matter removing 89-99% of tetracycline and sulfamethizol from initial solutions containing 10 mg/L of antibiotic in the presence of 8 mg/L of humic acid, or 9 mg/L of fulvic acid. These data indicate that micelle-clay complexes are very efficient for water purification from tetracycline and sulfonamide antibiotics.     

Particle size and pH effects on remediation of chromite ore processing residue using calcium polysulfide (CaS5)

A long-term bench scale treatability study was performed to assess the ability to remediate chromite ore processing residue (COPR) using calcium polysulfide (CaS(5)). COPR materials were characterized with respect to particle size, pH, curing period and mineralogy. A stoichiometric ratio of sulfide species to hexavalent chromium (Cr(6+)) of 2 was used for the long-term treatment of COPR. The effectiveness of CaS(5) treatment was assessed using the toxicity characteristic leaching procedure (TCLP), alkaline digestion, and X-ray absorption near edge structure (XANES) analyses. The formation of ettringite, known as a heaving agent, was investigated following the treatment of CaS(5), using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) along with an energy dispersive X-ray spectroscopy (EDX). Overall, after a curing period of 18 months, the TCLP total chromium (Cr) and alkaline digestion (Cr(6+)) results obtained from the treatability study showed that the concentrations were lower than 5 mg L(-1) and 9 mg kg(-1), respectively. However, XANES results obtained from samples cured for 18 months showed that all of the treated samples had higher Cr(6+) concentrations than shown using alkaline digestion. The lowest XANES Cr(6+) concentration of 610.2 mg kg(-1) was obtained from the sample with a particle size less than 0.075 mm and a pH value of 9. Particle size reduction prior to the addition of the reductant, along with pH reduction was found to be strongly associated with the treatment performance. Ettringite formation, due to pH increase over time in the samples, where the initial pH was adjusted to 9, was verified by XRPD and SEM-EDX analyses, indicating that a pH less than 9 should be maintained to avoid ettringite formation.     

The photocatalytic degradation of reactive black 5 using TiO2/UV in an annular photoreactor

The textile effluent is a major industrial polluter because it is highly colored, containing about 15% unfixed dyes as well as high levels of salts that can potentially be discharged into the environment. Photocatalytic oxidation using an thin gap annular UV reactor with TiO2 was used to break down the colour of a synthetic effluent ranging up to 400 ppm in dye concentration of Reactive Black 5 and up to 80 g/L in NaCl. Results show that the reaction kinetics was dominated by the TiO2 loading, the initial dye concentration, and the dissolved oxygen concentration; with the other parameters showing less significant effects. High rates of decolorization were found, with a linear fit to the Langmuir-Hinshelwood equation yielding a reaction rate constant (k) of 2.45 ppm/min, and an adsorption equilibrium constant (K) of 0.048 ppm(-1) based on color removal. The presence of the combination of high dissolved oxygen (15 ppm) and sodium chloride (up to 80 g/L) was found to enhance the decolorization and mineralization rates of the reactive dye. However, pH was found to not significantly affect the degradation rate. Since textile effluent is strongly alkaline, this result is significant, as no solution neutralisation is required and direct treatment of the effluent is possible.