Microalgae removal with Moringa oleifera.

Moringa oleifera seed extract was tested for algae (Chlorella, Microcystis, Oocystis and Scenedesmus) removal by Jar-test technique. This coagulant can be used in drinking water treatment. Jar-test has been carried out in order to evaluate the efficiency of this natural coagulant agent inside real surface water matrix. The influence of variables has been studied in this process, including operating parameters such as coagulant dosage, initial algae concentration, pH, agitation time and water matrix. Removal capacity is verified for water with high contamination of algae while the process is not affected by the pH and water matrix. Coagulation process may be modelling through Langmuir and Freundlich adsorption hypothesis, so acceptable r2 coefficients are obtained.

Treatment of high strength olive mill wastewater by Fenton's reagent and aerobic biological process.

The present work describes the application of a Fenton's reagent pretreatment combined with an aerobic biological process to remove the olive mill wastewater (OMW) pollutant load. Wastewater treatment was monitored by means of global parameters directly related to the concentration of organic compounds in OMW effluents: chemical oxygen demand (COD) and total phenolic content (TP). The biologic treatment itself allowed conversions from 67 to 83% of COD and 55 to 61% of TP. In the Fenton's reagent process a fixed H2O2/COD ratio of 0.20, a pH = 3.5 and a H2O2/Fe(2+) molar ratio of 15 were defined as optimal conditions to treat the OMW. For an initial COD load of 92.5 g/L(-1)) the Fenton reagent-biologic combined process allowed a global removal of 80.7% COD and 93.7% TP. A kinetic study was performed resorting to the Grau model. The application of this model allowed observing an increase in the kinetic constant of the combined process (kFB = 24.7 g/L(-1) day) when compared to the single aerobic process (kB = 19.4 g/L(-1) day).

Optimization of the synthesis of a new coagulant from a tannin extract.

The current article studies the optimization of a new coagulant agent for water purification and wastewater remediation. Design of experiments is used for optimizing the production of this new tannin-based coagulant by using Acacia mearnsii de Wild tannin extract, NH(4)Cl and formaldehyde. The effectiveness of this product was confirmed on dye-polluted wastewater and surfactant wastewater. This cationic coagulant seems to be sensitive to temperature and tannin-NH(4)Cl ratio (g of ammonium chloride per g of tannin extract). NH(4)Cl ratio was found to be more influent than temperature and no interaction is presented between these two parameters. For each system, an optimum combination NH(4)Cl ratio and temperature was found: 24.9°C and 2 g g(-1) for dye removal and 36.4°C and 1.87 g g(-1) for surfactant elimination. The optimal conditions were merged to produce a combined coagulant that was tested on dye, surfactant, surface river water and municipal wastewater. Predicted levels of remediation were experimentally confirmed.

Surface water and wastewater treatment using a new tannin-based coagulant. Pilot plant trials.

A new tannin-based coagulant-flocculant (Tanfloc) was tested for water treatment at a pilot plant level. Four types of water sample were treated: surface water (collected from a river), and municipal, textile industry (simulated by a 100 mg L(-1) aqueous solution of an acid dye), and laundry (simulated by a 50 mg L(-1) aqueous solution of an anionic surfactant) wastewaters. The pilot plant process consisted of coagulation, sedimentation, and filtration. The experiments were carried out with an average coagulant dosage of 92.2 mg L(-1) (except in the case of the surface water for which the dosage was 2 mg L(-1)). The efficacy of the water purification was notable in every case: total turbidity removal in the surface water and municipal wastewater, about 95% dye removal in the case of the textile industry wastewater, and about 80% surfactant removal in the laundry wastewater. Filtration improved the removal of suspended solids, both flocs and turbidity, and slightly improved the process as a whole. The efficiency of Tanfloc in these pilot studies was similar to or even better than that obtained in batch trials.

Comparison of single-step and two-step purified coagulants from Moringa oleifera seed for turbidity and DOC removal.

The coagulant proteins from Moringa oleifera purified with single-step and two-step ion-exchange processes were used for the coagulation of surface water from Meuse river in The Netherlands. The performances of the two purified coagulants and the crude extract were assessed in terms of turbidity and DOC removal. The results indicated that the optimum dosage of the single-step purified coagulant was more than two times higher compared to the two-step purified coagulant in terms of turbidity removal. And the residual DOC in the two-step purified coagulant was lower than in single-step purified coagulant or crude extract.

Novel tannin-based adsorbent in removing cationic dye (Methylene Blue) from aqueous solution. Kinetics and equilibrium studies.

Natural tannin-based adsorbent has been prepared on the basis of the gelification of Quebracho bark extract. The resulting product, Quebracho Tannin Gel (QTG) was tested as cationic dye adsorbent with Methylene Blue (MB). Kinetics of adsorption process were studied out and a period of 15 days was determined for reaching equilibrium. The influences of pH and temperature were evaluated. As pH or temperature raise q capacity of QTG increases. Theoretical modelization of dye-QTG adsorption was carried out by multiparametric adjustment according to Langmuir's hypothesis. Values of the k(l1), k(l2) and activation energies were calculated.

Improvement of water treatment pilot plant with Moringa oleifera extract as flocculant agent.

Moringa oleifera extract is a high-capacity flocculant agent for turbidity removal in surface water treatment. A complete study of a pilot-plant installation has been carried out. Because of flocculent sedimentability of treated water, a residual turbidity occured in the pilot plant (around 30 NTU), which could not be reduced just by a coagulation-flocculation-sedimentation process. Because of this limitation, the pilot plant (excluded filtration) achieved a turbidity removal up to 70%. A slow sand filter was put in as a complement to installation. A clogging process was characterized, according to Carman-Kozeny's hydraulic hypothesis. Kozeny's k parameter was found to be 4.18. Through fouling stages, this k parameter was found to be up to 6.36. The obtained data are relevant for the design of a real filter in a continuous-feeding pilot plant. Slow sand filtration is highly recommended owing to its low cost, easy-handling and low maintenance, so it is a very good complement to Moringa water treatment in developing countries.

Removal of Alizarin Violet 3R (anthraquinonic dye) from aqueous solutions by natural coagulants.

In this paper the ability of two natural products in removing dyes has been tested. After a preliminary screening for dye removal capacity, a tannin-based coagulant called ACQUAPOL C-1 and a vegetal protein extract derived from Moringa oleifera seed have been fully studied. The influence of several parameters such as pH, temperature or initial dye concentration (IDC) have been tested and the behavior of both coagulants has been compared. pH results to be an interesting variable and dye removal decreases as pH increases. This effect is higher in ACQUAPOL C-1 than in M. oleifera seed extract. Temperature seems not to be so affecting parameter, while IDC appears to be a very important variable in q(c) capacity, which is higher as IDC increases. Langmuir isotherm model fits very well in both cases of ACQUAPOL C-1 and M. oleifera seed extract dye removal.

Removing heavy metals from polluted surface water with a tannin-based flocculant agent.

Many environmental and health problems come from the presence of metals in surface water. Effectiveness of a new commercial tannin-based flocculant has been tested in order to remove Zn(2+), Ni(2+) and Cu(2+) by coagulation-flocculation process. pH has been adjusted in order to evaluate the real heavy metal removal due just to flocculant effect and not to hydroxide precipitation. At least a 75% of metal removal has been reported in every case, depending on pH value. Flocculant doses have been reported to be about 100-150 ppm.

Removal of sodium lauryl sulphate by coagulation/flocculation with Moringa oleifera seed extract.

Among other natural flocculant/coagulant agents, Moringa oleifera seed extract ability to remove an anionic surfactant has been evaluated and it has been found to be very interesting. Sodium lauryl sulphate was removed from aqueous solutions up to 80% through coagulation/flocculation process. pH and temperature were found to be not very important factors in removal efficiency. Freundlich (F), Frumkin-Fowler-Guggenheim (FFG) and Gu-Zhu (GZ) models were used to adjust experimental data in a solid-liquid adsorption hypothesis. Last one resulted to be the most accurate one. Several data fit parameters were determined, as Freundlich order, which was found to be 1.66, Flory-Huggins interaction parameter from FFG model, which was found to be 4.87; and limiting Moringa surfactant adsorption capacity from GZ model, which was found to be 2.13 x 10(-3)mol/g.

Degradation of olive mill wastewater by the combination of Fenton's reagent and ozonation processes with an aerobic biological treatment.

Degradation of olive mill wastewater (OMW) by means of two chemical oxidation processes (Fenton's reagent and ozonation) and their consecutive treatments with aerobic microorganisms have been studied. Fenton's reagent treatment moderately reduces COD and to a greater extent the polyphenolic compounds. Ozonation contributed to low conversion of COD and moderate reduction of polyphenols. The aerobic biological treatments degrade to values higher than 70% and 90% for COD and polyphenolic compounds, respectively. A kinetic study has been carried out in each process, determining the representative kinetic parameters of each model.

Kinetics of the reaction between ozone and phenolic acids present in agro-industrial wastewaters.

The kinetics of the ozonation of three phenolic acids is investigated from ozone absorption experiments in a semi-continuous reactor. After the evaluation of stoichiometric ratios for the individual reactions between ozone and each phenolic acid, the oxidation of p-hydroxybenzoic acid by ozone is performed in a first stage. The influence of the operating variables on the degradation process is established, and the application of a mass transfer with chemical reaction model based on the film theory leads to the determination of the reaction orders and kinetic rate constants. The experimental absorption rates obtained agree well with those calculated theoretically. In the second stage, a mixture of ferulic acid (4-hydroxy-3-methoxycinnamic acid), beta-resorcylic acid (2,4-dihydroxybenzoic acid) and p-hydroxybenzoic acid is ozonated under different experimental conditions. The kinetic study is performed by means of a competitive method that takes p-hydroxybenzoic acid as reference compound. The application of this model allows to determine the kinetic rate constants for each compound, which are correlated as a function of pH and temperature. The results obtained support that the kinetic regime of absorption is fast and pseudo-first order with respect to ozone, a condition required by the competitive method used.

Comparison of the degradation of p-hydroxybenzoic acid in aqueous solution by several oxidation processes.

A comparative study is made of 12 methods of chemical oxidation applied to degrading p-hydroxybenzoic acid in aqueous solution. The oxidation processes tested were: UV, O3, UV/TiO2, O3/Fe2+, O3/H2O2, O3/UV, UV/H2O2, H2O2/Fe2+, H2O2/Fe2+/O3, UV/H2O2/O3, H2O2/Fe2+/UV and O3/UV/H2O2/Fe2+. The 12 processes were ranked by reactivity. In a kinetic study, the overall kinetic rate constant was split up into three components: direct oxidation by UV irradiation (photolysis), direct oxidation by ozone (ozonation), and oxidation by free radicals (mainly OH*).

Rate constants for the reactions of ozone with chlorophenols in aqueous solutions.

The oxidation by ozone of several chlorophenols (CPs): 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4, 6-tetrachlorophenol, tetracholorocatechol (3,4,5, 6-tetrachloro-2-hydroxy phenol) and 4-chloroguaiacol (4-chloro-2-methoxy phenol), is studied in order to provide values of the overall rate constant for the reaction between ozone and these chlorophenols. Single ozonation experiments of 4-chlorophenol were conducted in an homogeneous system, and ozonation reactions of CP mixtures were performed in a heterogeneous system, leading to the evaluation of the overall ozonation rate constants in acidic aqueous solutions. These second order rate constants increase several order of magnitude with the pH as does the degree of deprotonation of the dissolved compounds (i.e. from 10(3) to 10(9)l/(mols) for different CPs). The specific rate constants for the ozonation of the non-dissociated and dissociated forms of the studied CPs are also determined and reported. The values obtained allow calculation of the overall rate constants and prediction of the reactivities of the several CPs at different operating conditions in the whole range of pH.

Contribution of free radicals to chlorophenols decomposition by several advanced oxidation processes.

The chemical decomposition of aqueous solutions of various chlorophenols (4-chlorophenol (4-CP), 2,4-dichlorophenol (2-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)), which are environmental priority pollutants, is studied by means of single oxidants (hydrogen peroxide, UV radiation, Fenton's reagent and ozone at pH 2 and 9), and by the Advanced Oxidation Processes (AOPs) constituted by combinations of these oxidants (UV/H2O2 UV/Fenton's reagent and O3/UV). For all these reactions the degradation rates are evaluated by determining their first-order rate constants and the half-life times. Ozone is more reactive with higher substituted CPs while OH* radicals react faster with those chlorophenols having lower number of chlorine atoms. The improvement in the decomposition levels reached by the combined processes, due to the generation of the very reactive hydroxyl radicals. in relation to the single oxidants is clearly demonstrated and evaluated by kinetic modeling.

Kinetics of p-hydroxybenzoic acid photodecomposition and ozonation in a batch reactor.

The decomposition of p-hydroxybenzoic acid, an important pollutant present in the wastewaters of the olive oil industry, has been carried out by a direct photolysis provided by a polychromatic UV radiation source, and by ozone. In both processes, the conversions obtained as a function of the operating variables (temperature, pH and ozone partial pressure in the ozonation process) are reported. In order to evaluate the radiation flow rate absorbed by the solutions in the photochemical process, the Line Source Spherical Emission Model is used. The application of this model to the experimental results provides the determination of the reaction quantum yields which values ranged between 8.62 and 81.43 l/einstein. In the ozonation process, the film theory allows to establish that the absorption process takes place in the fast and pseudo-first-order regime and the reaction is overall second-order, first-order with respect to both reactants, ozone and p-hydroxybenzoic acid. The rate constants are evaluated and vary between 0.18x10(5) and 29.9x10(5) l/mol s depending on the temperature and pH.

Aerobic degradation of olive mill wastewaters.

The degradation of olive mill wastewater by aerobic microorganisms has been investigated in a batch reactor, by conducting experiments where the initial concentration of organic matter, quantified by the chemical oxygen demand, and the initial biomass were varied. The evolution of the chemical oxygen demand, biomass and the total contents of phenolic and aromatic compounds were followed through each experiment. According to the Contois model, a kinetic expression for the substrate utilization rate is derived, and its biokinetic constants are evaluated. This final predicted equation agrees well with all the experimental data.