Personal Research Database

Full Text: 2000\Wat Res34, 2253.pdf

Abstract: The mineralization process for 2,4-dichiorophenoxyacetic acid (2,4-D) at pH ca. 3 has been studied by advanced electrochemical oxidation processes (AEOPs), such as electro-Fenton and photoelectro-Fenton processes, in which a Pt anode and a carbon-polytetrafluoroethylene O-2-fed cathode, for in situ production of H2O2 are used. A solution of 230 ppm 2,4-D with a low salt content can be completely mineralized by the photoelectro-Fenton process at low current, whereas the electro-Fenton process leads to ca. 90% of mineralization. In both methods. 2,4-D is quickly destroyed at the same rate. The high degradation power of these AEOPs is due to the large production of oxidizing hydroxyl radicals by reaction between electrogenerated H2O2 and Fe2+ added to the solution. The higher mineralization rate found for photoelectro-Fenton is accounted for by the fast photolytic decomposition of some intermediates by UV light. Classical anodic oxidation with a graphite cathode and anodic oxidation in the presence of electrogenerated H2O2 are much less efficient methods to degrade 2,4-D and its oxidation products. 2,4-Dichlorophenol. 4,6-dichlororesorcinol, chlorohydroquinone and chlorobenzoquinone have been identified as intermediates by GC-MS and their evolution for each process has been followed by reverse-phase chromatography. Chloride ion is released from these chloroderivatives and accumulates in the medium. Short-chain acids, as glycolic, glyoxylic, maleic, fumaric and oxalic, have been detected by ion-exclusion chromatography. A general reaction pathway involving all these intermediates is proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: 2,4-Dichlorophenoxyacetic Acid, Mineralization, Water Treatment, Anodic Oxidation, Electro-Fenton Process, Photoelectro-Fenton Process, Waste-Water Treatment, Ptfe O-2-Fed Cathode, Hydrogen-Peroxide, Anodic-Oxidation, 2,4-Dichlorophenoxyacetic Acid, Photoelectro-Fenton, Electro-Fenton, Oh Radicals, Degradation, Aniline

? Barber, W.P. and Stuckey, D.C. (2000), Nitrogen removal in a modified anaerobic baffled reactor (ABR): 1, Denitrification. Water Research, 34 (9), 2413-2422.

Full Text: 2000\Wat Res34, 2413.pdf

Abstract: In order to achieve nitrogen removal within a single reactor unit, an eight compartment anaerobic baffled reactor (ABR) was modified to accommodate an in-situ aerobic stage in the penultimate compartment, which allowed ammonia oxidation to nitrite and nitrate via nitrification, rn theory, the nitrite/nitrate may be recycled to the inlet of the ABR and be reduced via denitrification. This paper deals with the anoxic denitrification of a nitrate feed, while a later paper examines nitrification in the aerobic stage. Denitrification occurred almost exclusively in the front two compartments of the anaerobic baffled reactor, with rates of 0.335 (82% reduction) and 0.085 kg NO₃/kg VSS.d (96% reduction) in compartments 1 and 2, respectively. Denitrification had several positive effects on overall reactor performance, and this was due to the following factors: the utilisation of an oxidisable electron donor in the form of the feed GOD; increased system pH at the reactor inlet thus improving environmental conditions; a high hydrogen demand during dissimilatory nitrate reduction to ammonium, therefore improving conditions for syntrophic bacteria; and, the generation of ammonium from dissimilatory reduction which provided slowly growing bacteria at the front of the ABR with a reduced nitrogen source. The overall effect of these influences was improved hydrogenotrophic methanogenesis. Denitrification also increased the residual COD in the first two compartments, and this was attributed to faster growth/decay rates of denitrifying bacteria. Nitrate reduction also influenced the ratio of volatile fatty acids produced and catabolised, with a significant reduction in propionate and butyrate, while acetate levels increased. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Acetate, Anaerobic Baffled Reactor, Bacteria, Biofilm, Demand, Denitrification, Dissimilatory Nitrate Reduction To Ammonium, Environmental, First, Generation, Glucose, Hydrogen, Kinetics, Microbial Products SMP, Nitrate, Nitrate Reduction, Nitrification, Nitrite, Nitrogen Removal, Oxidation, Performance, pH, Reduction, Removal, Residual COD, Rights, Theory, VFAS, Waste-Water Treatment

? Barber, W.P. and Stuckey, D.C. (2000), Nitrogen removal in a modified anaerobic baffled reactor (ABR): 2, Nitrification. Water Research, 34 (9), 2423-2432.

Full Text: 2000\Wat Res34, 2423.pdf

Abstract: The oxidation of ammonia to nitrite/nitrate using chemolithoautotrophic nitrifying bacteria immobilised in polyvinyl alcohol (PVA) cubes and placed within an aerobic stage of a modified anaerobic baffled reactor (ABR) was investigated. Various system parameters known to affect nitrification were tested to determine the viability of the process. Nitrification efficiency was improved by increased mixing, increased oxygen levels and the initial addition of copper. In contrast, nitrification was reduced by; a reduction in bulk ammonia levels, a reduction in pH, continued copper addition and COD levels above 1000 mg/l. Whilst immobilisation appeared to protect against un-ionised ammonia, it simultaneously increased the saturation constant K-s for both oxygen and ammonia by orders of magnitude. Consequentially, the bacteria could survive in abnormally high bulk ammonia concentrations with no signs of inhibition, but were limited for oxygen below a partial pressure of 0.42 atm, and for ammonia below 160 mg NH₃/l. A series of non-typical trends became evident during this work: the continued dependence of nitrite oxidation on the performance of ammonia oxidation; persistently low bulk nitrite concentrations; the ability of the pellets to produce high levels of nitrate even when bulk un-ionised ammonia concentrations were orders of magnitude higher than the inhibition coefficient for Nitrobacter; and, the high sensitivity of the bacteria to low concentrations of ammonia and oxygen. These results were due to significant increases in apparent K-s values for both groups, and were in accordance with reduced diffusion coefficients for the pellets. These findings were then used to propose a layered structure for the pellets, and in conjunction with other work on denitrification in an ABR, lay the basis for an integrated nitrogen removal technique in a single reactor. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Alcohol, Ammonia, Anaerobic Baffled Reactor, Bacteria, Copper, Copper Stimulation, Denitrification, Diffusion, Dissolved-Oxygen, DO, Efficiency, Gas Mixing, Immobilisation, Inhibition, Kinetics, Nitrate, Nitrification, Nitrite, Nitrogen Removal, Oxidation, pH, Pressure, Reduction, Removal, Rights, Saturation, Structure, Trends, Work

Cimino, G., Passerini, A. and Toscano, G. (2000), Removal of toxic cations and Cr(VI) from aqueous solution by hazelnut shell. Water Research, 34 (11), 2955-2962.

Full Text: W\Wat Res34, 2955.pdf

Abstract: Removal of ions such as Cd²⁺, Zn²⁺, three-and hexavalent chromium from aqueous solutions using hazelnut shell as biosorbent substrate has been performed. Batch equilibrium tests showed that the metal sorption was dependent on both pH and surface loading. For Cd²⁺, Cr³⁺ and Zn²⁺ ions the maximum removal was observed only into a specific pH range. The metal ion sorption obeyed both the Langmuir and Freundlich isotherms. Experiments by mixed solutions showed that more Cr³⁺ ions were removed than both Cd²⁺ and Zn²⁺ ions. The binding capacities acid the affinities observed were consistent with the HSAB theory on hard and soft acid base. The Cr(VI) removal was pH dependent and fitted with the Langmuir isotherm model. It was proceeding effectively into a short acid pH interval (2.5-3.5) where both processes of Cr(VI) reduction and (Cr III) sorption are maximized. Mechanisms for removal of anions and cations studied have been proposed. The observed sorption data showed similarity with that of other fresh cellulosic materials found in literature. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Agricultural By-Product, Biosorbent, Hazelnut Shell, Hexavalent Chromium, Hsab Principle, Toxic Metals, Wastewater Treatment, Heavy-Metals, Biosorption, Adsorption, Chromium(VI), Ions

Chiarle, S., Ratto, M. and Rovatti, M. (2000), Mercury removal from water by ion exchange resins adsorption. Water Research, 34 (11), 2971-2978.

Full Text: W\Wat Res34, 2971.pdf

Abstract: In this paper a detailed experimental and theoretical analysis of the adsorption process of mercury by ion exchange resins is presented. Experiments have been performed to study adsorption efficiency, the effect of pH on the uptake of mercury and the adsorption kinetics. The experimental apparatus was a batch mechanically stirred reactor (volume 1.5 dm³), under almost isothermal conditions (±0.1°C). The resin used in this study is Duolite GT-73, a chelating resin, macroreticular with thiol (S-H) functional groups. The studied resin has a very high adsorption efficiency, reaching 30-40% in weight and the efficiency decreases, decreasing pH, due to competition between ions H⁺ and Hg²⁺. Such a high efficiency confirms previous results and justifies the great interest for the application of ion exchange resins in water treatment plants. As in previous works, measurements of process kinetics show that the adsorption rate decreases as the initial mercury concentration is increased. This fact suggests that intraparticle diffusion rate can be the controlling step for the adsorption process. To verify this, a simplified mathematical model has been identified, accounting for a diffusional resistance inside solid particles and where the equilibrium relationship between Hg concentration in the liquid and in the solid is described by the. Freundlich isotherm, neglecting H⁺ competition: this model is very effective in the prediction of the change in the adsorption kinetics with the initial Hg concentration. Hence this preliminary approach can be held as the reference starting point for the adsorption model: further developments will concern the equilibrium thermodynamics (H⁺ competition). (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Mercury Adsorption, Ion Exchange Resins, Adsorption Kinetics, Diffusional Model, Adsorption Model, Waste-Water, Heavy-Metals

Solisio, C., Lodi, A., Converti, A. and Del Borghi, M. (2000), The effect of acid pre-treatment on the biosorption of chromium(III) by Sphaerotilus natans from industrial wastewater. Water Resources, 34 (12), 3171-3178.

Full Text: W\Wat Res34, 3171.pdf

Abstract: Living cells of a strain of Sphaerotilus natans are employed to remove Cr(III) from acid wastewater. Batch experiments carried out at starting acid conditions (pH 3.0-3.5) show that the pH progressively increases but the removing activity Starts only when conditions closed to neutrality are reached. Studies carried out either at initial acid conditions or at standard conditions for this micro-organism (pH 7.0) confirm that the biomass is able to grow also on acid medium, although the lag phase is longer than the one observed at standard conditions. This strain shows its maximum ability to remove Cr(III) at a biomass concentration of about 0.4 g l^-1 Tests carried out at both lower and higher biomass levels show lower yields, while the time necessary to reach the maximum removal considerably increases. Biomass previously adapted to acid conditions ensures a specific uptake of this metal of 120 mg g^-1, which is much higher than that reported in the literature for other micro-organisms. Continuous tests in CSTR confirm the possibility of developing a biological treatment process for the continuous removal of Cr(III) from acid solutions. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Biosorption, Sphaerotilus Natans, Chromium(III), Acid Wastewater, Batch Tests, Continuous Tests, Removal, Metals, Recovery, Cadmium, Biomass, Copper

Kratochvil, D. and Volesky, B. (2000), Multicomponent biosorption in fixed beds. Water Resources, 34 (12), 3186-3196.

Full Text: W\Wat Res34, 3186.pdf

Abstract: The biosorption of Cu, Zn, Cd and Fe from multicomponent mixtures was studied in a flow-through column packed with Sargassum algal biosorbent in the Ca-form. The effects of competitive ion exchange such as the elution order of toxic metals from the column, and the concentration overshoots in column effluent were investigated both experimentally and by means of an ion exchange equilibrium column model (ECM). The ECM predicted, and the experiments confirmed, that from the feed containing Cu²⁺, Zn²⁺ and Cd²⁺, zinc broke through the column first, followed by cadmium and copper. When the binary mixtures containing 30 mg/l of Cu²⁺ and 4 mg/l of either Cd²⁺ or Zn²⁺ were passed through the column, the concentrations of Zn and Cd ions in the column effluent overshot the 4 mg/l feed concentration. The time interval between the overshoot of Zn and the breakthrough point of Cu was Significantly longer than that between the overshoot of Cd and the breakthrough point of Cu. However, Zn did not overshoot when the feed contained 50 mg/l of Cd and 4 mg/l of Zn. The ECM successfully predicted both the occurrence and the magnitude of the overshoots. The service time of a column treating multimetal mixtures was successfully predicted by combining the ECM with a mass transfer column model (MTCM). (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Biosorption, Sargassum, Muticomponent Sorption, Column, Ion-Exchange, Heavy-Metals, Removal, Column, Adsorption

Perret, S., Morlay, C., Cromer, M. and Vittori, O. (2000), Polarographic study of the removal of cadmium(II) and lead(II) from dilute aqueous solution by a synthetic flocculant. Comparison with copper(II) and nickel(II). Water Research, 34 (14), 3614-3620.

Full Text: W\Wat Res34, 3614.pdf

Abstract: The aim of this work was to assess the possible removal of cadmium(II) or lead(II) from dilute aqueous solution by a synthetic flocculant used in the water treatment held. The cadmium(II) or lead(II) complex formation with the 310⁶ g mol^-1 average molecular weight poly(acrylic acid) (PAA 310⁶) was examined at pH 6.0, 5.0 and 4.0 successively using differential pulse polarography as an investigation mean. The complexing capacity Cc of the polyacid towards lead(II) at pH 6.0 was estimated to be 6.3 mmol Pb(II)/g PAA 310⁶ in the operative conditions considered here (NaNO₃ 0.1 mol l^-1; 25°C). The conditional stability constant of the PAA 3 x 10(6)/lead(II) complex species was determined using the method proposed by Ruzic [(1982) Anal. Chim. Acta 140, 99-113] assuming that only the 1: 1 complex species was formed: log K’ = 5.3±0.2 at pH 6.0. Both values decreased with the pH of the aqueous medium. The results were compared to those previously obtained in the same conditions with copper(II) and nickel(II) [(2000) Wat. Res. 34, 455-462]. It appeared that the binding properties of PAA 3106 increased in the following order, depending on the metal ion: Ni(II) < Cd(II) < Cu(II) < Pb(II). This result confirmed the conclusions of the previous potentiometric study [(1999) Talanta 48, 1159-1166]. Finally, the selectivity of PAA 310⁶ towards copper(II) and lead(II) was examined. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Poly(Acrylic Acid), Flocculant, Cadmium(II), Lead(II), Complexation, Polarography, Metal-Polycarboxylate Complexes, Anodic-Stripping Voltammetry, Weight Poly(Acrylic Acids), Natural-Waters, Speciation, Cu(II), Ni(II)

? Rožić, M., Cerjan-Stefanović, Š., Kurajica, S., Vanćina, V. and Hodžić, E. (2000), Ammoniacal nitrogen removal from water by treatment with clays and zeolites. Water Research, 34 (14), 3675-3681.

Full Text: W\Wat Res34, 3675.pdf

Abstract: The objective of the present study was to investigate the removal of nitrogen in the form of ammonium ions (N-NH⁺₄) from aqueous solutions using natural clay and zeolite. The Croatian zeolite clinoptilolite from the area of Donje Jesenje and Croatian bentonite clay from the Kutina area were used as natural filtration materials. Alkaline and acid modification of natural clay was performed. The N-NH₄⁺ removal efficiency by clays in a dry state as well as in a liquid colloidal state have been investigated. The highest removal efficiency value for N-NH⁺₄ (61.1 wt%) was achieved with the natural zeolite at the lowest used initial concentration, i.e. at a concentration of 100 mg N-NH⁺₄/l. With the increase of the initial concentration of ammoniacal nitrogen, the removal efficiency quickly decreases. This is expected as zeolites and clays have limited sorption capacities. The practical aspect is important since an ammoniacal nitrogen elimination of more than 60.0 wt% for water containing less than 100 mg N-NH⁺₄/l can be achieved. The ammoniacal nitrogen removal efficiency is higher for clays in a liquid colloidal state compared to the clays in a dry state. It has been found that the acid modification of the clay decreases the efficiency of ammoniacal nitrogen removal.

Keywords: Natural Zeolite, Natural Clay, Modified Natural Clay, Clay in A Liquid Colloidal State, Ammoniacal Nitrogen Removal

Notes: highly cited

Brown, P.A., Gill, S.A. and Allen, S.J. (2000), Metal removal from wastewater using peat. Water Research, 34 (16), 3907-3916.

Full Text: W\Wat Res34, 3907.pdf

Abstract: Peat has been investigated by several researchers as a sorbent for the capture of dissolved metals from wastestreams. Besides being plentiful and inexpensive, pear possesses several characteristics that make it an effective media for the removal of dissolved metal pollutants. The mechanism of metal ion binding to peat remains a controversial area with ion-exchange, complexation, and surface adsorption being the prevalent theories. Factors affecting adsorption include pH, loading rates, and the presence of competing metals. The optimum pH range for metals capture is generally 3.5-6.5. Although the presence of more than one metal in a solution creates competition For sorption sites and less of a particular ion may be bound, the total sorption capacity has been found to increase. Studies have also shown that metals removal is most efficient when the loading rates are low. In addition, recovery of metals and regeneration of the peat is possible using acid elution with little effect on peat’s sorption capacity. The utilization of peat and other biomass materials for the treatment of wastewater containing heavy metals is gaining more attention as a simple. effective and economical means of pollution remediation. Pelleting processes can now produce a robust media for a variety of applications where traditional methods of pollutant removal would he economically or technologically difficult. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Peat, Metals, Adsorption, Wastewater Treatment, Soil Organic-Matter, Sphagnum Moss Peat, Ion-Exchange, Heavy-Metals, Humic-Acid, Immobilized Biomass, Adsorption, Kinetics, Water, Copper

Liu, R.X. and Tang, H.X. (2000), Oxidative decolorization of direct light red F3B dye at natural manganese mineral surface. Water Research, 34 (16), 4029-4035.

Full Text: W\Wat Res34, 4029.pdf

Abstract: In this paper, the characteristics of natural manganese mineral collected from Guangxi Province. China, including crystalline properties, elemental composition, organic substrates content (0.17%) and BET surface area (29.8 m²/g), were determined. By X-ray powder diffraction and fluorescence spectrograph analysis, it is shown that manganese oxide in the natural mineral exists in the crystal structure of alpha-Mn₂O₃ and the contents of manganese(II) and manganese(IV) oxides are 4.6 and 42.6%, respectively. The solubility experiments show that manganese dissolved in solution can be ignored at a higher pH value, but its significant solubility is observed with the decrease of pH value. Moreover. the decolorization properties of direct light red F3B dye on natural manganese mineral surface were studied by batch technique. The effects of pH value, temperature, inert electrolyte, light, particles concentration and size, the presence of calcium and phosphate as well as oxygen on the decolorization efficiency of the dye were investigated in detail. The results show that the decolorization of the dye is strongly dependent on pH value, with lower decolorization percentage at higher pH values, and the higher concentration of inert electrolyte and temperature favor the decolorization reaction of the dye on the particle surface. By Arrhenius Equation. the apparent activation energy is found to be at 71.7 kJ/mol, indicating the surface chemical reaction as a rate-limiting step in the overall interface process. The illumination enhances the surface chemical reaction of the dye on manganese mineral particles. The decolorization rate of the dye compound is increased with the increase of particle concentration and the decrease of size since the available surface sires grow in number. The presence of phosphate greatly inhibits the decolorization reaction by competitive adsorption on the mineral surface with the dye anion, while the addition of calcium promotes the decolorization rate of direct light red F3B dye. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Natural Manganese Mineral, Characteristic, Decolorization Properties, Direct Light Red F3B Dye, Effect Factors, Photocatalytic Oxidation, Substituted Phenols, Waste-Water, Oxides, Dissolution, Reduction, Organics, TiO₂

Yetis, U., Dolek, A., Dilek, F.B. and Ozcengiz, G. (2000), The removal of Pb(II) by Phanerochaete chrysosporium. Water Research, 34 (16), 4090-4100.

Full Text: W\Wat Res34, 4090.pdf

Abstract: The removal of Pb(II) by live, resting and dead cells of a lignolytic white-rot fungus, Phanerochaete chrysosporium was investigated. Kinetic studies revealed the fact that adsorption is a two-stage process: a very rapid surface adsorption within the first hour and a slow intracellular diffusion during 2 h of metal exposure. The results showed that the resting cells were able to uptake up to 80 mg Pb(II)/g dry cell. The saturation sorption capacities of live and dead cells were 9 and 20 mg Pb(II)/g dry cell, respectively. The biomass originated from different growth phases and exhibited different adsorption capacities for Pb(II). It appeared that the young resting cells held higher Pb(II) adsorption capacities than old ones. Acid and alkali pre-treatments of the old resting cells increased the sorption capacity; although the capacity of virgin young fungi was never attained. Acid treatment of the young cells reduced the adsorption capacity remarkably; however, alkali treatment improved it. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Pb(II) Removal, White-Rot Fungi, Phanerochaete Chrysosporium, Biosorption, Bioaccumulation, Pretreated Cell Mass, Heavy Metals, Dilute Aqueous-Solutions, Heavy-Metal Biosorption, Saccharomyces-Cerevisiae, Mucor-Miehei, Biomass, Cadmium, Copper, pH, Accumulation, Mechanisms

? Panswad, T. and Luangdilok, W. (2000), Decolorization of reactive dyes with different molecular structures under different environmental conditions. Water Research, 34 (17), 4177-4184.

Full Text: 2000\Wat Res34, 4177.pdf

Abstract: Reactive dyes have been identified as problematic compounds in textile wastewaters as they are water soluble and cannot be easily removed by conventional aerobic biological wastewater treatment systems. Anaerobic systems could reduce the color intensity more satisfactorily than the aerobic processes. However, the intermediate products are carcinogenic aromatic amines which need to be further decomposed by an aerobic treatment. An anaerobic/aerobic SBR system was used to treat a synthetic dye wastewater with glucose and acetic acid (1000 mg/l GOD) as carbon sources, together with 20 mg/l of four different reactive dyes; i.e., bisazo vinylsulphonyl, anthraquinone vinylsulphonyl, anthraquinone monochlorotriazinyl and oxazine. The color reduction of the first three dyes was 63, 64 and 66%, respectively. The decolorization efficiency of the last or oxazine dye was not determined because of a strange phenomenon or re-appearance of the color when samples were disturbed. More color removal was achieved in the anaerobic phase than in the aerobic step. The initial decolorization rate was 11.9, 0.37 and 0.48 SU/h for the first three dyes, respectively. Though the system comprised anaerobic and aerobic tanks, the color reduction did not rely on phosphorus accumulating organisms (PAOs). High temperature and photo-oxidation through exposure to sunlight could increase the decolorization rate, and the decolorization was not possible if viable organisms were not present in the system. Nitrate. when present, could interfere with the color reduction while sulfate did not. The bisazo reactive dye was decolorized by the reductive reaction, which resulted in the cleavage of the azo bond. Meanwhile, the decolorization of anthraquinone dyes was through the adsorption of dyes on Roc materials. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Color Removal, Reactive Dyes, Azo Dyes, Dye Wastewaters, Biological Phosphorus Removal, Anaerobic-Aerobic Process, Biodegradation, Degradation, Dyestuffs

Davis, T.A., Volesky, B. and Vieira, R.H.S.F. (2000), Sargassum seaweed as biosorbent for heavy metals. Water Research,