Chemical treatment of cork‐processing wastewaters for potential reuse

The chemical treatment of cork‐processing wastewater by ozonation, alone and in combination with hydrogen peroxide and UV radiation was investigated. A reduction of the chemical oxygen demand (COD) ranging from 42% to 76% was obtained during ozonation after 3 h of reaction, depending on the experimental conditions. The additional presence of hydrogen peroxide and UV radiation enhanced the efficiency of the ozonation treatment due to the contribution of the OH radicals formed in the decomposition of ozone. Thus, final reductions of the COD higher than 90% and a complete elimination of phenolic compounds and absorbance at 254 nm were achieved in both Advanced Oxidation Processes (AOPs), O₃/H₂O₂ and O₃/UV. Therefore the effluent resulting from the ozonation treatments can be reused in the cork‐processing industry. In a second step, the chemical treatment was conducted by means of UV radiation alone and by the action of hydroxyl radicals, which were generated by the following AOPs: UV/H₂O₂, Fenton's reagent, and photo‐Fenton system. The single photochemical process resulted in 9% of the organic matter present being removed, while the AOPs significantly enhanced this reduction with values in the range 20–75%. Kinetic studies for both groups of treatments were performed, and apparent kinetic rate constants were evaluated. In the ozone‐based experiments, the rate constants ranged from 1846 to 10922 dm³ mol^?1 O₃ h^?1, depending on the operating conditions. In the oxidation experiments using oxidants other than ozone, the rate constants varied between 0.06 and 1.19 h^?1. Copyright © 2004 Society of Chemical Industry     

Integration of continuous biological and chemical (ozone) treatment of domestic wastewater: 1. Biodegradation and post‐ozonation

The continuous treatment of domestic wastewater by an activated sludge process and by an integrated biological–chemical (ozone) oxidation process were studied in this work. Chemical oxygen demand (COD), biochemical oxygen demand (BOD), absorbance at 254 nm (UV₂₅₄) and nitrogenous compound content were the parameters followed in order to evaluate the performance of the two processes. Experimental data showed that both UV₂₅₄ and COD reductions are improved in the combined biological–chemical oxidation procedure. Thus, reductions of 59.1% and 37.2% corresponding to COD and UV₂₅₄, respectively were observed after the biological process (hydraulic retention time = 5 h; mixed liquor volatile suspended solids concentration = 3142 g m⁻³) compared with 71.0% and 78.4% obtained when a post‐ozonation step ( D _O3 = 41.7 g m⁻³) was included. During conventional activated sludge treatment, appropriate nitrification levels are only achieved with high hydraulic retention time and/or biomass concentration. Ozonation after the secondary treatment, however, allows improved nitrogen content reduction with total nitrite elimination. Post‐ozonation also leads to a higher biodegradability of the treated wastewater. Thus, the ultimate BOD/COD ratio goes from 0.16 after biological oxidation to 0.34 after post‐ozonation with 41.7 g O₃ m⁻³. © 1999 Society of Chemical Industry     

A three‐phase fluidized bed reactor in the combined anaerobic/aerobic treatment of wastewater

Aerobic degradation or polishing is an essential step in the combined anaerobic/aerobic treatment of wastewater. In this study, a type of porous glass beads was used for immobilization of microbial cells in a three‐phase aerobic fluidized bed reactor (AFBR) with an external liquid circulation. The effects of superficial gas and liquid velocities on bed expansion, solid and gas hold‐ups and specific oxygen mass transfer rate, k_La, were investigated. A tracer study showed that the mixing and flow pattern in the 8 dm³ reactor could be simulated by a non‐ideal model of two continuous stirred tank reactors (CSTRs) in series. By treating an effluent from an upflow anaerobic sludge blanket (UASB) digester, the distribution of suspended and immobilized biomass in the reactor as well as the kinetics of COD removal were determined. The specific oxygen mass transfer rate, k_La, at a superficial gas velocity of 0.7 cm s⁻¹ dropped by about 30% from 32 h⁻¹ in tap water to 22 h⁻¹ after a carrier load of 15% (v/v) was added. The measured k_La further dropped by about 20% to 18 h⁻¹ in the wastewater, a typical value of the bubbling fermenters with no stirring. Compared with the aerobic heterotrophs under optimum growth conditions, the microbes in this reactor which was fed with anaerobic effluent plus biomass behaved like oligotrophs and showed slow specific COD removal rates. This might be attributed to the presence of a significant amount of obligate anaerobes and facultative organisms in the aerobic reactor. This was confirmed by a relatively low intrinsic oxygen uptake rate of the microbial population in the reactor, 94 mg O₂ dm⁻³ h⁻¹ or 19 mg O₂g VS⁻¹ h⁻¹. © 1999 Society of Chemical Industry     

Treatment of green table olive waste waters by an activated‐sludge process

No purification procedure exists for treating the waste waters from the Spanish‐style green olive industry. This study shows that an activated sludge process can be used successfully, yielding a 75–85% COD reduction, due mainly to the removal of organic acids and ethanol present in the waste. In contrast, only a small proportion of polyphenols was consumed. These residual polyphenols can account for most of the remaining COD and the residual brown colour. Grau's model for substrate removal rate was applied to take account of the effect of influent‐substrate concentration on the effluent COD concentration. The constant value with this model (k) was 9.8 day⁻¹. Likewise, increasing the hydraulic retention time and temperature improved the sludge removal. Thus, a COD of 200–300 mg dm⁻³ in the effluent was routinely achieved. Concentrations of NaCl up to 3% did not affect the aerobic system although the sludge volume index was higher than 200 cm³ g⁻¹. © 2000 Society of Chemical Industry     

Abatement of 4-Chlorophenol in Aqueous Phase by Ozonation Coupled with a Sequencing Batch Biofilm Reactor (SBBR)

The aim of this work was to assess the mineralization of 100 and 200 mg L^?1 4-chlorophenol (4-CP) solutions by ozonation-biological treatment. The results show that starting from a 4-CP initial concentration from 100 to 500 mg L^?1 and using an ozone flow rate of 5.44 and 7.57 g h^?1, 4-CP was completely removed. A kinetic constant around 9·10^?2 min^?1 was calculated for the ozone direct attack. The biodegradability (BOD₅/COD) of the pre-ozonated solutions increased from 0 until a range between 0.2–0.37. The combination of the ozonation and aerobic biological treatment in an aerobic sequencing batch biofilm reactor (SBBR) gave an abatement of more than 90% of the initial TOC.     

Joint Treatment of Wastewater from Table Olive Processing and Urban Wastewater. Integrated Ozonation – Aerobic Oxidation

Integrated ozonation‐aerobic biodegradation of table olive wastewater (diluted 1:25 with synthetic urban wastewater) is presented as a suitable technology to purify this kind of effluent. Use of ozone is recommended as a pre‐treatment step since it shows a high reactivity toward phenolic compounds (found in this type of wastewater) reducing, at the same time, the alkalinity of the media for further biological processing. An ozone dose of 45 mg L^–1 (flow rate 20 L h^–1) for a period of 35 min has been found to achieve the following goals: decrease pH, decrease phenolic content, and increase of biodegradability. The aerobic oxidation process followed first order kinetics as measured by COD depletion profiles versus time. The Arrhenius expression k = 183exp(–2214/T) was obtained for experiments of ozonated wastewater biodegradation completed at different temperatures and neutral pH.     

Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV‐C and their sequential application

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H₂O₂ /UV − C oxidation and (3) sequential application of ozonation followed by H₂O₂ /UV − C oxidation was investigated at the natural pH values (8 and 11) of the textile effluents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV–VIS absorption kinetics and the biodegradability factor, f_B. The successive treatment combination, where a preliminary ozonation step was carried out prior to H₂O₂ /UV − C oxidation without changing the total treatment time, enhanced the COD and TOC removal efficiency of the H₂O₂ /UV − C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile effluent, a preliminary ozonation step increased COD removal of the H₂O₂ /UV − C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (f_B) was more pronounced for the biologically pretreated wastewater with an almost two‐fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H₂O₂ /UV − C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (k_app), and the second order OH· formation rates (r_i) have been calculated. © 2001 Society of Chemical Industry     

Organosolv delignification of white‐ and brown‐rotted Eucalyptus grandis hardwood

Sound (undecayed control) and fungally‐pretreated wood samples were submitted to organosolv delignification. The cooking liquor used was methanol/water (78:22 v/v) containing CaCl₂ and MgSO₄ each at a concentration of 25 mmol dm⁻³. The cooking process was performed at 180 °C for reaction times varying from 5 to 100 min. Despite some differences in the lignin removal pattern, pseudo‐first order kinetic models permitted a prediction of delignification rate constants for all experiments. All biodegraded samples provided higher delignification rate constants than the undecayed control (2.0 × 10⁻²min⁻¹ for the undecayed control and, for example, 14.2 × 10⁻²min⁻¹ for the sample decayed by Trametes versicolor for 2.5 months). Biodegraded samples also presented significantly increased xylan removal rates. The type of biodegradation affected the behavior of wood samples under organosolv pulping. The highest delignification and xylan removal rate constants were observed in the sample decayed by T versicolor for 2.5 months (17% weight loss). However, high delignification and xylan removal rate constants were also observed in the sample decayed by Punctularia artropurpurascens for only 0.5 months (1.2% weight loss). Data obtained from a single fungal species pretreatment or data from all fungal pretreatments indicated that there is no clear correlation between the delignification constants and the wood weight or component losses. This lack of correlation suggested that the structure of residual polymers in decayed wood affects the delignification process in the organosolv pulping more than the removal extent of each individual component. © 2000 Society of Chemical Industry     

Disinfection of recycled red‐meat‐processing wastewater by ozone

Ozonation of a real red‐meat‐processing wastewater was conducted in a semi‐batch reactor to explore the possibility of the water reuse. The experimental results revealed that ozone was very effective in disinfection of the red‐meat‐processing wastewater. After 8 min of ozonation with an applied ozone dose of 23.09 mg min^?1 liter^?1 of wastewater, 99% of aerobic bacteria, total coliforms and Escherichia coli were inactivated. Empirical models were developed to predict the microbial inactivation efficacy of ozone from the CT values for the real red‐meat‐processing wastewater. A correlation was also derived to estimate the CT values from the applied ozone dose and the ozone contact time. The results also revealed that under the ozonation condition for 99% inactivation of aerobic bacteria, total coliforms and E coli, the decrease in the chemical oxygen demand and the 5‐day biological oxygen demand of the wastewater were 10.7% and 23.6%, respectively. However, ozonation under this condition neither improved the light transmission nor reduced the total suspended solids (TSS) despite of the decolorization of the wastewater after ozonation. Copyright © 2005 Society of Chemical Industry     

Treatment of olive mill wastewaters by ozonation,aerobic degradation and the combination of both treatments

The degradation of the pollutant organic matter present in olive oil mill wastewaters (OMW) is carried out by a single ozonation, a single aerobic degradation, and the combination of two successives steps: an ozonation followed by an aerobic degradation, and an aerobic degradation followed by an ozonation. In both single processes, the removal of this contaminant load is followed by means of global parameters which are directly related to the concentration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent kinetic constants for the aromatic reduction, k_A. In the aerobic degradation, the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic parameters of this model, K₂ and n. In the combined processes, a higher COD global reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both processes due to the pretreatment conducted is also observed. This enhancement is shown by an increase of the kinetic parameters (K₂ and n in the aerobic degradation of the pre‐ozonated wastewaters; the apparent constant k_A in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried out at the same operating conditions. © 1999 Society of Chemical Industry     

Decolourization and COD removal from reactive dye‐containing wastewater using sonophotocatalytic technology

Decolourization and COD removal from synthetic wastewater containing Reactive Brilliant Orange K‐R (RBOKR) dye using sonophotocatalytic technology was investigated. Experimental results showed that this hybrid technology could efficiently remove the colour and reduce COD from the synthetic dye‐containing wastewater, and that both processes followed pseudo first‐order kinetics. At the condition of 0.1 m³ h^?1 airflow, 0.75 g dm^?3 titanium dioxide and 0.5 mmol dm^?3 RBOKR solution, the rate constants of decolourization and COD removal were 0.0750 and 0.0143 min^?1 respectively for the sonophotocatalytic process; 0.0197 and 0.0046 min^?1 respectively for the photocatalytic process and 0.0005 and 0.0001 min^?1 respectively for the sonochemical process. The rate constants of sonophotocatalysis were greater than that of both the photocatalytic and sonochemical processes either in isolation or as a sum of the individual process, indicating an apparent synergetic effect between the photo‐ and sono‐processes. Copyright © 2003 Society of Chemical Industry     

Evolutionary Catalyst Screening: Iridium‐Catalyzed Imine Hydrogenation

A high throughput catalyst screening is presented employing an evolutionary approach. The method comprises the optimization of initial leads by subjecting the catalysts to iterative rounds of optimization, including structural elaboration of the ligands by creating new focused libraries. Highly modular supramolecular ligands, robotized synthesis combined by high throughput experimentation creates a platform for fast catalyst development. An illustrative example for the asymmetric hydrogenation of cyclic 2,3,3‐trimethyl‐3H‐indole using iridium catalysts is presented. The kinetic investigation of the best catalyst yields an unusual second order in iridium, first order in hydrogen and zeroth order in substrate. Under optimized reaction conditions a TOF of 100 mol mol⁻¹ h⁻¹ with 96% ee could be obtained with the best catalyst. A full catalyst screening and kinetic study was conducted within a three‐week time‐frame.     

Highly Active and Enantioselective Rhodium‐Catalyzed Asymmetric 1,4‐Addition of Arylboronic Acid to α,β‐ Unsaturated Ketone by using Electron‐Poor MeO‐F12‐BIPHEP

The asymmetric 1,4‐addition of phenylboronic acid to cyclohexenone were performed by using a low amount of rhodium/(R)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis[bis(3,4,5‐trifluorophenyl)phosphine] (MeO‐F₁₂‐BIPHEP) catalyst. Because the catalyst shows thermal resistance at 100 °C, up to 0.00025 mol% Rh catalyst showed good catalytic activity. The highest turnover frequency (TOF) and turnover number (TON) observed were 53,000 h⁻¹ and 320,000, respectively. The enantioselectivities of the products were maintained at a high level of 98% ee in these reactions. The Eyring plots gave the following kinetic parameters (ΔΔH^≠=−4.0±0.1 kcal mol⁻¹ and ΔΔS^≠=−1.3±0.3 cal mol⁻¹ K⁻¹), indicating that the entropy contribution is relatively small. Both the result and consideration of the transition state in the insertion step at the B3LYP/6‐31G(d) [LANL2DZ for rhodium] levels indicated that the less σ‐donating electron‐poor (R)‐MeO‐F₁₂‐BIPHEP could be creating a rigid chiral environment around the rhodium catalyst even at high temperature.     

Catalytic removal of phenol from aqueous solutions in a trickle‐bed reactor

The degradation of high concentrations of phenol (1g/dm^?3) in aqueous media at high temperatures (100–190 °C) and pressures (2.0 MPa) has been studied by catalytic wet air oxidation in a trickle‐bed reactor. The effect of reaction temperature, weight hourly space velocity (WHSV) and hydrogen peroxide concentration on phenol concentration, total organic carbon (TOC) and chemical oxygen demand (COD) conversion by using a commercial copper catalyst has been investigated. At 150 °C, TOC removal increased by 28% with the WHSV of 62.5 h^?1. The addition of hydrogen peroxide as a free radical promoter significantly enhanced the depletion rate of phenol. A kinetic study has been carried out leading to the determination of the kinetic constants for the removal of TOC. Copyright © 2005 Society of Chemical Industry     

Oxime‐Derived Palladium Complexes as Very Efficient Catalysts for the Heck–Mizoroki Reaction

Oxime‐derived, chloro‐bridged palladacycles 16 are efficient complexes for the Heck vinylation of aryl halides. The isolated catalysts are thermally stable, not sensitive to air or moisture and easily accessible from inexpensive starting materials. The reaction can be performed under aerobic conditions, with aryl iodides, bromides and chlorides with acrylic esters and olefins displaying turnover numbers (TON) of up to 10¹⁰ for phenyl iodide and turnover frequencies (TOF) of 1.4×10⁸ h⁻¹. Deactivated aryl bromides undergo the Heck reaction with styrene with TON and TOF values up to 97,000 and 6063 h⁻¹, respectively. Even aryl chlorides undergo the coupling reaction with olefins with TON up to 920. Complexes 16 catalyze the synthesis of 2,3‐disubstituted indenones and indoles in good yields via annulation reaction of internal alkynes with o‐bromo‐ or o‐chlorobenzaldehyde and o‐iodoaniline, respectively.     

Multi‐phase electro‐chemical catalytic oxidation of wastewater

The removal of organic pollutants from synthetic wash wastewater by a combined multi‐phase electro‐catalytic oxidation method was evaluated using porous graphite as anode and cathode, and CuO–Co₂O₃–PO₄^3? modified kaolin as catalyst. The synergic effect on COD removal was studied when integrating the electro‐chemical reactor with the effective modified kaolin in a single undivided cell; the results showed that higher COD removal efficiency was obtained than those obtained using the individual processes. Under optimal conditions of pH 3, 30 mA cm^?2 current density, very effective reduction of organic pollutants was achieved with this combined electro‐chemical method. High removal efficiency (90%) of the chemical oxygen demand (COD) was obtained in 60 min in the treatment of simulated wash wastewater (anionic surfactant, sodium dodecyl benzene sulfonate [DBS]). This method was also applied to treat wastewater form paper‐making and resulted in a COD reduction of 84%. Based on the investigation, a possible mechanism of this combined electro‐chemical process was proposed. The pollutants in wastewater could be decreased by the high reactive OH? that were produced via the decomposition of electro‐generated H₂O₂ activated by the synergic effect of electro‐field and catalyst. The results indicate that the multi‐phase catalytic electro‐chemical oxidation process is a promising technique for wastewater treatment. Copyright © 2006 Society of Chemical Industry     

An investigation on the optimal location of ozonation within biological treatment for a tannery wastewater

The objective of this study was to evaluate the optimal location of ozonation within biological treatment for a typical tannery wastewater by giving special attention to biodegradability‐based chemical oxygen demand (COD) characterization. As treating the raw tannery effluent solely by biological treatment is not adequate to meet the discharge standards owing to the high level of biorecalcitrant COD at the outlet, the application of chemical oxidation, i.e. ozone together with biotreatment (pre‐ozonation or in mid‐ozonation or post‐ozonation) was investigated. The tannery effluent under investigation had initially inert soluble COD (S_I1) and particulate COD (X_I1) fractions corresponding to 9% and 13% of the total COD (C_T1), respectively, whereas each component of the biodegradable part—readily biodegradable COD (S_S1), rapidly hydrolysable COD (S_H1), and slowly hydrolysable COD (X_S1)—accounted for around 26% of the total COD (C_T1). Pre‐ozonation, undesirably competing with biotreatment for the removal of degradable organics, was shown to be insufficient both in terms of total COD (C_T1) and inert COD (C_I1) removal efficiencies. The scheme of biological treatment + ozonation + biological treatment could be applied successfully when 42.8 mg O₃ min^?1 was introduced for 5 min with a utilized ozone percentage of 76% at a point in biological treatment where the readily biodegradable COD (S_S1) was depleted through biochemical reactions. Such an alternative yielded satisfactory outcomes when both total COD (C_T) and inert COD (C_I) removal efficiencies per utilized ozone ratios were considered. With post‐ozonation, on the other hand, the highest inert COD (C_I) removal efficiencies together with an effluent quality meeting the discharge standards could be obtained. Copyright © 2006 Society of Chemical Industry     

Ozone-Induced Biodegradability Enhancement and Color Reduction of a Complex Pharmaceutical Effluent

The treatment of a complex pharmaceutical effluent using a combination of ozonation and biological treatment is reported with the use of ozonation as a pre- and posttreatment. Pretreatment facilitated biodegradability index (BI = BOD/COD) enhancement of up to 0.44 along with COD and color reduction of up to 42% and 33%, respectively. Subsequent anaerobic biodegradation of effluent indicated negligible biogas generation; however, aerobic biodegradation of pretreated effluent resulted in COD reduction (73%) and color reduction (62%), which was also indicated by the biokinetic parameters. Further, ozonation as a posttreatment led to higher overall COD (87%) and color (93%) removal.     

Steady-state behaviour of an aerobic mixed culture growing on phenol in a continuous stirred reactor

The kinetic behaviour of an aerobic mixed culture was studied in a well-stirred reactor at various dilution rates with phenol as the sole carbon source and limiting factor. In the range of dilution rates investigated (up to 0.51 h⁻¹), biomass washout from the reactor was not observed. Analysis of steady-state data using the inhibitory kinetic parameters obtained in a previous batch growth study gave a very poor prediction of the reactor's performance. Since microbial growth occurred on the reactor walls, the experimental data were analysed using two steady-state equations (one with Monod, the other with Haldane growth kinetics) together with the Topiwala-Hamer model to describe the wall attachment. The mathematical model using Monod kinetics gave a good fit to the experimental data and the values of the kinetic parameters obtained using this model were as follows: maximum specific growth rate, 0.340 h⁻¹; saturation constant, 1.61 mg l⁻¹; wall growth constant, 2.84 mg l⁻¹. Furthermore, the yield and maintenance coefficients were calculated to be 0.47 mg mg⁻¹ and 0.007 mg mg⁻¹ h⁻¹ respectively.     

Phenoxaphosphino‐Modified Xantphos‐Type Ligands in the Rhodium‐Catalysed Hydroformylation of Internal and Terminal Alkenes

The solubility of the modifying ligand is an important parameter for the efficiency of a rhodium‐catalysed hydroformylation system. A facile synthetic procedure for the preparation of well‐defined xanthene‐type ligands was developed in order to study the influence of alkyl substituents at the 2‐, and 7‐positions of the 9,9‐dimethylxanthene backbone and at the 2‐, and 8‐positions of the phenoxaphosphino moiety of ligands 1 – 16 on solubility in toluene and the influence of these substituents on the performance of the ligands in the rhodium‐catalysed hydroformylation. An increase in solubility from 2.3 mmol⋅L⁻¹ to >495 mmol⋅L⁻¹ was observed from the least soluble to the most soluble ligand. A solubility of at least 58 mmol⋅L⁻¹ was estimated to be sufficient for a large‐scale application of these ligands in hydroformylation. Highly active and selective catalysts for the rhodium‐catalysed hydroformylation of 1‐octene and trans‐2‐octene to nonanal, and for the hydroformylation of 2‐pentene to hexanal were obtained by employing these ligands. Average rates of >1600 (mol aldehyde) × (mol Rh)⁻¹×h⁻¹ {conditions: p(CO/H₂) = 20 bar, T = 353 K, [Rh] = 1 mM, [alkene] = 637 mM} and excellent regio‐selectivities of up to 99% toward the linear product were obtained when 1‐octene was used as substrate. For internal olefins average rates of >145 (mol aldehyde)×(mol Rh)⁻¹×h⁻¹ {p(CO/H₂) = 3.6–10 bar, T = 393 K, [Rh] = 1 mM, [alkene] = 640–928 mM} and high regio‐selectivities up to 91% toward the linear product were obtained.