Effect of Ultrasonic Irradiation on the Treatment of Poly-Aromatic Substances (PAHs) from a Petrochemical Industry Wastewater

The effects of sonication time, nitrogen, N₂(g), increasing temperature, dissolved oxygen (DO) and titanium dioxide (TiO₂) concentrations on the sonodegradation of polyaromatic hydrocarbons (PAHs) in petrochemical wastewaters were investigated. Sonication alone without N₂(g), DO and TiO₂ provided 80% maximum PAH yields at 2 5°C after 150 min. This PAH yield increased to 89–95% at 60 °C after 150 min sonication. The contribution of DO, N₂(g) and TiO₂ on the PAH removal was not significant compared to the control. In the presence of HCO₃ ^?, the degradation of hydrophobic PAH dibenz[a,h]anthracene (DahA)was suppressed in the acceleration step of the sonication. Maximum acute toxicity removal was reached by 30 min N₂(g) sparging, 4 mg/L DO and by 0.1 mg/L TiO₂ after 150 min sonication.     

Aerobic biodegradation and inhibition kinetics of poly‐aromatic hydrocarbons (PAHs) in a petrochemical industry wastewater in the presence of biosurfactants

BACKROUND: In Izmir, Turkey, wastewaters from the petrochemical industry are treated using conventional activated sludge systems. A significant proportion of poly‐aromatic hydrocarbons (PAHs) with high‐molecular weights remains in this treatment system and inhibits the biological activity. Biosurfactants increase PAHs degradation by enhancing the solubility of the petroleum components. The aerobic inhibition kinetics of PAHs has not previously been investigated in the presence of biosurfactants for a real petrochemical industry wastewater. RESULTS: Among the kinetic models used (Monod‐type, zero, first‐order and second‐order) it was found that the Monod kinetic was effective for describing the biodegradation of PAHs in petrochemcal industry wastewater in the presence of three biosurfactants, namely Rhamnolipid (RD), Surfactine (SR) and Emulsan (EM) in an aerobic activated sludge reactor (AASR). The maximum PAH removal rate (R_max) and specific growth rate of PAH degrading bacteria (µ_max) increased, while the half saturation concentration of PAH (K_s) decreased at 15 mg L^?1 RD concentration compared with the control without biosurfactant at a sludge retention time (SRT) of 25 days. CONCLUSION: PAH oxidation is typified by competitive inhibition at RD concentrations > 15 mg L^?1 resulting in increases in K_s values with PAH accumulation. Low inhibition constant (K_ID) values reflect difficulties in the metabolizability of PAHs. Metabolite production decreased at RD = 25 mg L^?1 in the PAHs indeno (1,2,3‐cd) pyrene (IcdP), flourene (FLN), phenanthrene (PHE) and benzo(a)pyrene (BaP). Copyright © 2011 Society of Chemical Industry     

Treatment of wastewaters from the olive mill industry by sonication

BACKGROUND: In this study, the effects of additives (manganese (III) oxide (Mn₃O₄), Cu⁺², Fe⁰ and potassium iodate (KIO₃)) and radical scavengers (sodium carbonate (Na₂CO₃), perfluorohexane (C₆F₁₄) and t‐buthyl alcohol (C₄H₁₀O)) on the dephenolization, decolorization, dearomatization and detoxification of olive mill wastewater (OMW) by sonication were investigated because wastewaters from this industry are not removed effectively. RESULTS: The maximum COD, color, total phenol and total aromatic amines (TAAs) removal efficiencies were 63, 82, 78 and 71%, respectively, at 60 °C with sonication only. The TAAs and phenol yields were increased to 96 and 97% with 6 mg L^?1 KIO₃ and 3 mg L^?1 Fe⁰ while color removal reached 97% with 6 mg L^?1 C₆F_14. The total annual cost with sonication only was 665 € m^?3 year^?1 while the cost slightly increased (666€ m³ year^?1) with C₆F₁₄. The maximum acute toxicity removals were 97‐98% in Daphnia magna and Vibrio fischeri The Microtox acute toxicity test was more sensitive than the Daphnia magna to the OMW samples. CONCLUSION: COD, color, total phenol, TAAs and toxicity in an OMW were removed efficiently and cost‐effectively by sonication. © 2012 Society of Chemical Industry     

Comparative study of nitrification performances of immobilized cell fluidized bed reactor and contact oxidation biofilm reactor in treating high strength ammonia wastewater

BACKGROUND: The immobilized cell fluidized bed reactor and contact oxidation biofilm reactor are two common choices for high strength ammonia wastewater treatment, however, comparative study of the nitrification performance of the two reactors has not been thoroughly studied. The nitrification performance of the two bioreactors when treating strong synthetic ammonia wastewater was investigated and compared. RESULTS: Results demonstrated that the immobilized cell fluidized bed reactor had a shorter acclimation period, and possessed several advantages over the contact oxidation biofilm reactor, in the form of complete oxidation of 150–360 mg L^?1 ammonia wastewater in a shorter time, higher ammonia removal rates (from 9.6 to 4.32 × 10² mgN L^?1 d^?1) over the temperature range 8 to 32 °C, irrespective of organic load. In contrast, a large reduction in ammonia removal was found in the contact oxidation biofilm reactor with chemical oxygen demand (COD) load. The immobilized cell fluidized bed reactor exhibited stable and high rates of nitrification in the long term. CONCLUSION: These facts demonstrated that the immobilized cell fluidized bed reactor is a suitable selection for high strength ammonia wastewater treatment. Copyright © 2007 Society of Chemical Industry     

Removal of 4‐chlorophenol from contaminated water using coconut shell waste pretreated with chemical agents

BACKGROUND: At concentrations higher than 1 mg L^?1, 4‐chlorophenol (4‐CP) is very toxic to living organisms, and if ingested beyond the permitted concentration it causes health disorders such as cancer and mutation. This laboratory study investigates treatment of contaminated water laden with 4‐CP using coconut shell charcoal (CSC) waste. Batch studies were conducted to study the effects of dose, pH, and equilibrium time on 4‐CP removal. To improve 4‐CP removal, surface modification of the adsorbent with TiO₂, HNO₃, and/or NaOH was undertaken. RESULTS: At an initial 4‐CP concentration of 25 mg L^?1 under optimized conditions (dose 13.5 g L^?1, pH 2.0; agitation speed 150 rpm and 50 min equilibrium time), the NaOH‐treated CSC demonstrated a greater removal of 4‐CP (71%) than those oxidized with HNO₃ (40%) and/or coated with TiO₂ (52%). The adsorption capacity of the NaOH‐treated CSC (54.65 mg g^?1) was higher than those treated with HNO₃ (23.13 mg g^?1) or coated with TiO₂ (48.42 mg g^?1). CONCLUSION: Although treatment results using the NaOH‐treated CSC alone were promising, the treated effluents were still unable to meet the required limit of less than 1 mg L^?1. Therefore, subsequent treatments are still required to complement the removal of 4‐CP from the wastewater. Copyright © 2010 Society of Chemical Industry     

Optimization of chromium removal by the chromium resistant mutant of the cyanobacterium Anacystis nidulans in a continuous flow bioreactor

BACKGROUND: Chromium removal potential of the cyanobacterium Anacystis nidulans and its chromium resistant strain Cr^rI8 has been optimized. Optimized parameters include biomass load, pH, temperature and dilution rate of the bioreactor. RESULTS: Results show that chromium resistant strain has high EC₅₀ dose for chromium compared to wild strain. Chromium removal potential of both strains is strongly influenced by various factors. Optimized conditions in batch system included pH 6.5, temperature 28 °C, biomass load 150 µg protein mL^?1 for 30 µmol L^?1 Cr⁶⁺ solution. In continuous flow bioreactor at optimum pH (6.5) and temperature (28 °C) at a fixed biomass of 10 mg protein and 30 µmol L^?1 Cr⁶⁺, metal removal efficiency varied with dilution rate. For A. nidulans continuous flow bioreactor, optimum dilution rate was 0.076 h^?1 (64.6 per cent metal removal) while for Cr^rI8 it was 0.152 h^?1 (85.8 per cent metal removal). Operative time of the Cr^rI8 bioreactor was also more (85 h) compared to A. nidulans bioreactor (45 h). CONCLUSION: Under optimized conditions resistant strain Cr^rI8 removed more Cr⁶⁺ compared to A. nidulans and thus has the potential to be exploited for Cr⁶⁺ removal from industrial effluents at large scale. Copyright © 2007 Society of Chemical Industry     

Degradation of 1‐amino‐4‐bromoanthraquinone‐2‐sulfonic acid using combined airlift bioreactor and TiO2‐photocatalytic ozonation

BACKGROUND: Traditional treatment systems failed to achieve efficient degradation of anthraquinone dye intermediates at high loading. Thus, an airlift internal loop reactor (AILR) in combination with the TiO₂‐photocatalytic ozonation (TiO₂/UV/O₃) process was investigated for the degradaton of 1‐amino‐ 4‐bromoanthraquinone‐2‐ sulfonic acid (ABAS). RESULTS: The AILR using Sphingomonas xenophaga as inoculum and granular activated carbon (GAC) as biocarrier, could run steadily for 4 months at 1000 mg L^?1 of the influent ABAS. The efficiencies of ABAS decolorization and chemical oxygen demand (COD) removal in AILR reached about 90% and 50% in 12 h, respectively. However, when the influent ABAS concentration was further increased, a yellow intermediate with maximum absorbance at 447 nm appeared in AILR, resulting in the decrease of the decolorization and COD removal efficiencies. Advanced treatment of AILR effluent indicated that TiO₂/UV/O₃ process more significantly improved the mineralization rate of ABAS bio‐decolorization products with over 90% TOC removal efficiency, compared with O₃, TiO₂/UV and UV/O₃ processes. Furthermore, the release efficiencies of Br^? and SO₄^2? could reach 84.5% and 80.2% during TiO₂/UV/O₃ treatment, respectively, when 91.5% TOC removal was achieved in 2 h. CONCLUSION: The combination of AILR and TiO₂/UV/O₃ was an economic and efficient system for the treatment of ABAS wastewater. © 2012 Society of Chemical Industry     

Autotrophic biological nitrogen removal from saline wastewater under low DO

BACKGROUND: This study was conducted to investigate the feasibility and performance of nitrogen removal through the complete autotrophic nitrogen removal over nitrite (CANON) process for saline wastewater in a continuous reactor, and to characterize microorganisms in the sludge from the reactor using DNA‐based techniques. RESULTS: The nitrogen removal experiment in the reactor was operated over five phases for 286 days treating a synthetic sewage of 1.2% salinity at 21–25 °C. At dissolved oxygen (DO) concentrations of 0.5–1.0 mg L^?1 and in the presence of glucose, NO₂^? was accumulated, indicating the activity of ammonia‐oxidizing bacteria (AOB). At DO concentration of 0.5 mg L^?1 without organic substrate, the anaerobic ammonium oxidation (Anammox) process was the major pathway responsible for nitrogen removal, with a total nitrogen removal of 70% and an ammonium conversion efficiency of 96%. A maximum ammonium removal rate of 0.57 kg‐N m^?3 d^?1 was achieved during the experimental period. The concentrations of AOB and Anammox bacteria were monitored over the operation of reactor using quantitative real‐time polymerase chain reaction (qRT‐PCR). CONCLUSION: In this study, autotrophic nitrogen removal process was achieved under salinity condition in a one‐reactor system. An over 100 fold increase of AOB was found due to the increased supply of ammonium at the beginning, then AOB concentration decreased temporarily in correspondence with the decreased DO, and the AOB resumed their concentration at the last phase. The Anammox bacteria abundance was about 150 fold higher than that at the beginning, indicating the successful enrichment of Anammox bacteria in the reactor. Copyright © 2010 Society of Chemical Industry     

Performance and microbial population variation in a plug‐flow A2O process treating domestic wastewater with low C/N ratio

BACKGROUND: In this study, a plug‐flow A²O (anaerobic/anoxic/oxic) reactor, with a working volume of 52.5 L, was employed to investigate the performance of biological nutrients removal and microbial population variations when treating low C/N ratio domestic wastewater. RESULTS: Results showed that TN removal was significantly affected by the shortage of carbon source while phosphorus removal was only slightly affected. The effluent soluble orthophosphate‐phosphorus (SOP) concentration was lower than 0.50 mg L^?1 but the TN concentration was over 20 mg L^?1 when the C/N ratio was 4.43. There was denitrifying phosphorus removal in the anoxic reactor and this was enhanced by increasing the volume ratio of anoxic reactor and maintaining appropriate mixed liquor recycle rate. More than 60% of the SOP were removed in anoxic reactors by denitrifying phosphorus removal when the volume ratio of anaerobic/anoxic/oxic was 1/1.4/1.6 and the mixed liquor recycle rate was 250%. The TN concentration of effluent decreased to 11.34 mg L^?1 and SOP concentration was still lower than 0.5 mg L^?1 in this condition. The main microorganisms found in the process by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and the functional biodiversity are discussed. CONCLUSION: Traditional design and operating parameters of A²O are not appropriate for treating low C/N wastewater. Enhancing the denitrifying phosphorus removal ratio in an A²O process is an effective way to increase the removal rate of N and P from low C/N wastewater. Copyright © 2010 Society of Chemical Industry     

Removal of Arsenic from Wastewaters by Airlift Electrocoagulation. Part 1: Batch Reactor Experiments

Abstract

Arsenic removal from wastewater is a key problem for copper smelters. This work shows results of electrocoagulation in aqueous solutions containing arsenic in a newly designed and constructed 1 L batch airlift reactor. Iron electrodes were used in the cell. The airlift electrocoagulation reactor allowed simultaneously a) anodic Fe²⁺ production, b) Fe²⁺ to Fe³⁺ oxidation by air or oxygen, and c) precipitate/coagulate formation due to the turbulent conditions in the cell. A series of electrocoagulation experiments were carried out in the batch airlift reactor. The variables were: initial As(V) concentration, use of either a pure oxygen or an air flow, and electric current density. The results showed that the airlift electrocoagulation process could reduce an initial As concentration from 1000 mg L^?1 to 40 mg L^?1–corresponding to a reduction of 96%. At higher initial concentrations (e.g. 5000 mg L^?1 As) the oxidation of Fe²⁺ to Fe³⁺ seems to be rate determining. Oxidation with compressed oxygen was clearly more efficient than air at high initial As concentration. Arsenate removal from a solution with initially 100 mg L^?1 was efficient with both air and oxygen addition–more than 98% of As precipitated. When the electrocoagulation process was working efficiently, the arsenic removal rate in the cell was found to be around 0.08–0.1 mg As/C. The Fe‐to‐As (mol/mol) ratio, when electrocoagulation was working properly, was in the range of 4–6.     

A high‐efficient rotating disk photoelectrocatalytic (PEC) reactor with macro light harvesting pyramid‐surface electrode

A series of pyramid‐surface TiO₂/Ti electrodes were proposed, fabricated, and used in a rotating disk photoelectrocatalytic (PEC) reactor to treat rhodamine B (RB) solution. Compared with conventional planar electrode, pyramid‐surface electrode exhibited much lower light reflectivity, larger photocurrent, and better treatment efficiency. For samples containing 20 to 150 mg L^?1 RB, 100– 98% color removal, and 87–30% COD removal were obtained in 150 min using 1/3 (h/w) pyramid‐surface electrode, much higher than 98–77% and 48–9% obtained by a conventional planer electrode. The excellent treatment performance attributed to two major reasons: (a) enhanced light harvest resulted from multiple reflections of irradiation light on the pyramid‐surface, and (b) enlarged electrode surface area enabling the electrode to carry more TiO₂ catalyst and pollutants for treatment. Experimental results also showed that the pyramid‐surface electrode consumed less power and exhibited superior performance when treating high concentration wastewater. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2448–2455, 2012     

Sewage sludge treatment using microwave‐enhanced advanced oxidation processes with and without ferrous sulfate addition

BACKGROUND: Microwave‐enhanced advanced oxidation processes with and without the addition of ferrous sulfate (MW/H₂O₂/Fe²⁺‐AOP and MW/H₂O₂‐AOP respectively) were studied for reduction of solids and solubilisation of nutrients from secondary sewage sludge. RESULTS: For the MW/H₂O₂/Fe²⁺‐AOP the yields of solubilisation of orthophosphate and ammonia decreased with increasing temperature. The best results (88.1 mg L^?1 for orthophosphate and 22.7 mg L^?1 for ammonia) were obtained at a treatment temperature of 40 °C. In contrast, the MW/H₂O₂‐AOP had an advantage when it was operated at higher temperatures of 60 and 80 °C. The highest yields of solubilisation were obtained at 60 °C for orthophosphate (81.1 mg L^?1) and at 80 °C for both ammonia (35.0 mg L^?1) and soluble chemical oxygen demand (1954 mg L^?1). Over the temperature range used in this study, the MW/H₂O₂‐AOP gave a better performance than the MW/H₂O₂/Fe²⁺‐AOP. CONCLUSION: For sewage sludge treatment the MW/H₂O₂‐AOP is more effective than the MW/H₂O₂/Fe²⁺‐AOP in terms of solid reduction and nutrient solubilisation. It will also be more cost‐effective, as it does not require iron addition in the process. Copyright © 2008 Society of Chemical Industry     

Simultaneous removal of TOC and TSS in swine wastewater using the partial nitritation process

BACKGROUND: Considering biological nitrogen removal, the partial nitritation connected with the anaerobic ammonium oxidation (anammox) process is a promising alternative for nitrogen elimination at high loading rates. The objective of the present study was to evaluate the establishment and operation of a partial nitritation process in an airlift reactor with simultaneous removal of total organic carbon and suspended solids using swine wastewater. RESULTS: The partial nitritation reactor was inoculated with a nitrifying sludge at 2.1 gTSS L^?1 and fed with an UASB reactor effluent. High organic carbon loading rates, above 2 kgTOC m^?3 d^?1 have been shown to be potential inhibitors of the partial nitritation process due to competition between autotrophic and heterotrophic bacteria. In this study, the partial nitritation process was established using undiluted swine wastewater, with HRT of 24 h, 1.84 mgO₂ L^?1 (SD = 0.41) DO, loading rate of 1.14 gTOC L^?1 d^?1 and 0.91 gN‐NH₃ L^?1 d^?1 for more than 100 consecutive days. At the same time, the system proved to be an effective tool in TOC and TSS removal, reaching 84.9% (SD = 9.3) and 83.1% (SD = 0.1), respectively. CONCLUSION: This result enhances partial nitritation application as a technology for high load nitrogen converting, and allows the possibility of connection with anammox reactors. Copyright © 2012 Society of Chemical Industry     

Bio‐oxidation of ferrous ions by Acidithioobacillus ferrooxidans in a monolithic bioreactor

BACKGROUND: The bio‐oxidation of ferrous iron is a potential industrial process in the regeneration of ferric iron and the removal of H₂S in combustible gases. Bio‐oxidation of ferrous iron may be an alternative method of producing ferric sulfate, which is a reagent used for removal of H₂S from biogas, tail gas and in the pulp and paper industry. For practical use of this process, this study evaluated the optimal pH and initial ferric concentration. pH control looks like a key factor as it acts both on growth rate and on solubility of materials in the system. RESULTS: Process variables such as pH and amount of initial ferrous ions on oxidation by A. ferrooxidans and the effects of process variables dilution rate, initial concentrations of ferrous on oxidation of ferrous sulfate in the packed bed bioreactor were investigated. The optimum range of pH for the maximum growth of cells and effective bio‐oxidation of ferrous sulfate varied from 1.4 to 1.8. The maximum bio‐oxidation rate achieved was 0.3 g L^?1 h^?1 in a culture initially containing 19.5 g L^?1 Fe²⁺ in the batch system. A maximum Fe²⁺ oxidation rate of 6.7 g L^?1 h^?1 was achieved at the dilution rate of 2 h^?1, while no obvious precipitate was detected in the bioreactor. All experiments were carried out in shake flasks at 30 °C. CONCLUSION: The monolithic particles investigated in this study were found to be very suitable material for A. ferrooxidans immobilization for ferrous oxidation mainly because of its advantages over other commonly used substrates. In the monolithic bioreactor, the bio‐oxidation rate was 6.7 g L^?1 h^?1 and 7 g L^?1 h^?1 for 3.5 g L^?1 and 6 g L^?1 of initial ferrous concentration, respectively. For higher initial concentrations 16 g L^?1 and 21.3 g L^?1, bio‐oxidation rate were 0.9 g L^?1 h^?1 and 0.55 g L^?1 h^?1, respectively. Copyright © 2008 Society of Chemical Industry     

Synthesis of vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) catalyzed by rare earth solid super acid SO42‐/TiO2/Ln3+

Rare earth solid super acids SO₄^2?/TiO₂/Ln³⁺ have been successfully developed to synthesize vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) end‐capped with 1,1,3,3‐tetramethyl‐1,3‐divinyldisiloxane. The features of ring opening polymerization reactions have been investigated in detail. The preferable conditions for the ring opening polymerization of D4 are as follows: [Nd³⁺] = 0.07 mol L^?1 and [SO₄^2?] = 1.85 mol L^?1 in the immersing solution; the amount of SO₄^2?/TiO₂/Nd³⁺ calcined at 500 °C was 5 wt% of the amount of D4; polymerization at 80 °C for 1 h. The average molecular weights of the products obtained using various rare earth catalysts were in order Nd > La > Sm > Gd, which shows that the light rare earths were more favorable for higher molecular weight products than the heavy ones. According to the polymerization features, a cationic equilibrium reaction mechanism is proposed. © 2013 Society of Chemical Industry     

Batch treatment of saline wastewater by Halanaerobium lacusrosei in an anaerobic packed bed reactor

BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Halanaerobium lacusrosei . RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD₀ = 1880–9570 mg L^?1), salt concentration ([NaCl] = 30–100 g L^?1) and liquid upflow velocity (V_up = 1.0–8.5 m h^?1) on COD removal from salt (NaCl)‐containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD₀ = 1880 mg L^?1, and efficiency decreased to 43% on increasing COD₀ to 9570 mg L^?1 at 20 g L^?1 salt concentration. COD removal was in the range 50–60% for [NaCl] = 30–60 g L^?1 at COD₀ = 5200 ± .100 mg L^?1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L^?1. Increasing liquid upflow velocity from V_up = 1.0 m h^?1 to 8.5 m h^?1 provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L^?1 to 321 mg L^?1 at V_up = 8.5 m h^?1, resulting in over 92% COD removal at 30 g L^?1 salt‐containing synthetic wastewater. CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. Copyright © 2008 Society of Chemical Industry     

Evaluation of heterotrophic nitrite removal by a sulphide and acetate oxidizing mixed culture originated from an oil reservoir

BACKGROUND: Shortcut biological nitrogen removal (SBNR) has attracted much attention in recent years due to lower aeration and chemical oxygen demand (COD) requirements, shorter residence time and smaller biomass production. In this work an oil reservoir denitrifying culture, with the ability to function under autotrophic and heterotrophic conditions was used for heterotrophic denitritation. Using freely suspended cells, effects of nitrite concentration (10–50 mmol L^?1) and temperature (15–35 °C) on the kinetics of denitritation were investigated and a kinetic model was developed. Potential for enhancement of nitrite removal rate, and impacts of nitrite concentration and loading rate were investigated in a continuous biofilm reactor. RESULTS: Nitrite did not impose any inhibitory effect, even at the highest applied concentration of 50 mmol L^?1. Increase of temperature in the range 15–35 °C enhanced the reduction rate significantly. Fitting the experimental data into the model developed, values of biokinetic coefficients (µ_max?NO2, K_S?NO2, Y_X?NO2, Y_X?Ace?NO2 and Eµ‐_NO2) were determined. In the biofilm reactor increases in nitrite loading rate (through flow rate or feed nitrite concentration) led to a linear increase of nitrite removal rate, with the highest removal rate of 140.6 mmol L^?1 h^?1 achieved with a residence time of 0.19 h. CONCLUSION: The enrichment culture used in this study is not only a superior biocatalyst for simultaneous removal of sulphide, nitrate and BOD, it could also be used effectively in the denitritation step of an SBNR process. The kinetic model developed would certainly have beneficial applications in the design, operation and control of the SBNR process. Copyright © 2011 Society of Chemical Industry     

A novel porous‐dense dual‐layer composite membrane reactor with long‐term stability

A porous‐dense dual‐layer composite membrane reactor was proposed. The dual‐layer composite membrane composed of dense 0.5 wt % Nb₂O₅‐doped SrCo_0.8Fe_0.2O_3‐δ (SCFNb) layer and porous Ba_0.3Sr_0.7Fe_0.9Mo_0.1O_3‐δ (BSFM) layer was prepared. The stability of SCFNb membrane reactor was improved significantly by the porous‐dense dual‐layer design philosophy. The porous BSFM surface‐coating layer can effectively reduce the corrosion of the reducing atmosphere to the membrane, whereas the dense SCFNb layer permeated oxygen effectively. Compared with single‐layer dense SCFNb membrane reactor, no degradation of performance was observed in the dual‐layer membrane reactor under partial oxidation of methane during continuously operating for 1500 h at 850°C. At 900°C, oxygen flux of 18.6 mL (STP: Standard Temperature and Pressure) cm^?2 min^?1, hydrogen production of 53.67 mL (STP) cm^?2 min^?1, CH₄ conversion of 99.34% and CO selectivity of about 94% were achieved. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4355–4363, 2013     

Nitric oxide enhanced reduction in a rotating drum biofilter coupled with absorption by FeII(EDTA)

BACKGROUND: The ongoing emission of nitric oxide (NO) is a serious persistent environmental problem, because it contributes to atmospheric ozone destruction and global warming. A novel and effective system was developed for the complete treatment of NO from flue gases. The system features NO absorption by Fe^II(EDTA) and biological denitrification in a rotating drum biofilter (RDB). RESULTS: After 100 mg L^?1 Fe^II(EDTA) was added to the nutrient solution, the results show that the NO removal efficiency was improved from 70.56% to 80.15%, the optimal temperature improved from 32.5 °C to 40.5 °C, and the pH improved from 7.5 to 8.0–8.3. A maximum NO removal efficiency of 96.5% was achieved when 500 mg L^?1 Fe^II(EDTA) was used in the nutrient solution. CONCLUSION: This experiment demonstrates that Fe^II(EDTA) could not only improve the mass transfer efficiency of NO from gas to liquid, but also serve as an electron donor for the biological reduction of NO to N₂. The new integrated treatment system seemed to be a promising alternative for the complete treatment of NO from flue gases. © 2012 Society of Chemical Industry     

Photo-fenton and UV photo degradation of naphthalene with zero- and two-valent iron in the presence of persulfate

An initial set of 12 kinetic experiments was carried out to remove naphthalene from an aqueous effluent by photo-Fenton involving Fe⁰ and Fe²⁺ at two different concentrations of H₂O₂ (150 and 300?mg?L^?1) and three different pHs (3, 5, and 7) (2²×3¹ experiments). The rate constants (k) for the reaction of naphthalene degradation by involving Fe²⁺ as reactant were in general higher than those with Fe⁰, but the use of Fe²⁺ increased the concentration of naphthalene at equilibrium (C_e) when compared with the same response obtained with Fe⁰ at analogous conditions. A second set of twelve kinetic experiments of photo-Fenton degradation was also performed with persulfate as additive at the conditions already reported, but at a constant concentration of H₂O₂ of 150?mg?L^?1 (2¹×3¹ experiments with NaCl +2¹×3¹ experiments without NaCl). In almost all the runs in which only the source of iron was varied, k from the kinetic data involving Fe²⁺ was higher than that involving Fe⁰, but no difference was observed in terms of C_e that was always zero. The addition of persulfate to treat the effluent either containing or not containing salt enhanced the chemical kinetics, and shifted the equilibrium toward the full removal of naphthalene. A final set of nine experiments of UV photo degradation of naphthalene by involving persulfate without iron, with Fe⁰ and Fe²⁺ in the pH range from 3 to 7 (3² experiments) mainly showed that the use of H₂O₂ may be avoided to remove rapidly and completely naphthalene from wastewater.