Influence of Ozonation of Humic and Fulvic Acids on Diuron Adsorption on Activated Carbon

The effect of ozonation on the competitor effect of humic and fulvic acids against diuron in adsorption on activated carbon in drinking water process has been studied. Ozonation treatment allows the removal of herbicides from drinking waters by modification of humic and fulvic acids structures. These latest are responsible for their adsorption variation on activated carbon. An ozone dose similar to that used in industrial pre-ozonation (1.3?mg ozone/l) does not cause significant transformations of humic and fulvic acids which could decrease their competitor effect and increase significantly the adsorption capacity of the activated carbon for a well-adsorbed pesticide like diuron.     

Treatment of Humic Waters By Ozone

Two different generators for ozone were tested, a traditional electrical discharge generator and a generator based upon UV–irradiation of air at 150–180 nm. It was demonstrated that the traditional generator gave slightly higher reductions in levels of color for equivalent ozone dosages. Both gases affected the molecular weight distribution in the way that the bigger molecules were broken down to smaller ones. No significant difference between the molecular weight reduction efficiency of the gases was found.     

Ozonation of Humic Substances: Effects on Molecular Weight Distributions of Organic Carbon and Trihalomethane Formation Potential

Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight-distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O₃/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, UV absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed.     

Study of the Catalytic Ozonation of Humic Substances in Water and Their Ozonation Byproducts

It is shown that using transition metals, especially Mn(II) and Ag(I), during ozonation of humic substances in water allows important reductions in the content of organic matter. Characterization of the organic compounds resulting from ozonation was made by concentrating the sample through liquid-liquid extraction or derivation with PFBOA.HCl, along with the GC/MS and GC/ECD techniques. In total, 110 different organic compounds were identified using GC/MS; mainly carboxylic acids, aromatics, hydrocarbons, aldehydes, ketones, and furan-carboxylic acids. The percentages of elimination or formation levels reached during ozonation are discussed.     

Removal of Atrazine Through Ozonation in the Presence of Humic Substances

The presence of pesticides in water sources and their removal by treatment processes is of particular interest currently to water companies and research scientists. Although operators and scientists are debating whether the related standards and legislation are too stringent, the current European Drinking Water Directive stipulates a maximum contaminant level (MCL) of 0.1 μg/L for an individual pesticide. Atrazine is amongst the most frequently identified pesticides in water supply sources. Since conventional treatment processes (chlorination, coagulation and filtration) are unable to reduce this micropollutant to an acceptable concentration, two advanced technologies are being investigated extensively; namely, adsorption onto activated carbon, and ozonation, particularly ozone combined with hydrogen peroxide. As for ozonation, several authors (Glaze et al., 1987; McGuire and Gaston, 1988; Terashima, 1988; Ferguson et al., 1991) have reported that the removal of refractory organics (e.g., 2-methyl isoborneol – MIB and geosmin) by ozone appears to be more effective in natural waters than in pure water solution; this was attributed to the action of natural organic material in water (such as humic substances) which promotes the radical reactions of ozone. In other more fundamental studies (Staehelin and Hoigné, 1985; Xiong and Legube, 1991), humic substances were speculated to be involved in radical decomposition of ozone in solution.     

Ozonization of Humic Acids. Medium Term Toxicity Towards Daphnia Magna

The ozonation products of humic acids are toxicologically interesting for two reasons: by their actual toxicity, but also because of their complexing capacity vis-à-vis trace metals present in water which are, because of this fact, incompletely eliminated by potabilization techniques. Determination of the ultimate toxicity of ozonized humic acids is achieved with the aid of the medium term Daphnia magnatest. Statistical treatment of the two lethal parameters and of the four sublethal parameters have shown a toxicity for ozonized humic acids in solution, at a concentration of 100 mg^?1.     

Kinetics and Mechanism of Humic Acids Degradation by Ozone in the Presence of CeO2/AC

This work investigated the catalytic ozonation of humic acids extracted from landfill leachate in the presence of CeO₂/AC with focus on the kinetics of humic acids degradation. It was confirmed that the degradation of humic acids mainly took place in the solution bulk. The direct and indirect reaction constants of ozone against humic acids were determined. By analyzing the contributions of direct ozone oxidation and indirect ?OH radicals oxidation to humic acids removal, it was found that ?OH radicals oxidation predominated at all pH, indicating that the catalytic ozonation of humic acids with CeO₂/AC involved ?OH radicals mechanism.     

Sequential Oxidation of Humic Acids by Ozonation and Photocatalysis

In this study, humic acids, the natural polymerized organic compounds which are responsible for the formation of disinfection by-products such as haloacetic acids and trihalomethanes upon chlorination, are oxidized in a sequential system incorporating ozonation and photocatalysis. Titanium dioxide is used as photocatalyst in the photocatalytic oxidation phase. Humic acid degradation kinetics is evaluated both for ozonation and photocatalysis. The Freundlich adsorption model is used for defining the adsorption characteristics of humic acid solutions on the photocatalyst after the ozonation step. The Langmuir-Hinshelwood model is also studied for explaining the adsorptive and photocatalytic removal of humic acids.     

Decomposition of Aqueous Naphthalene-1,5-Disulfonic Acid by Means of Oxidation Processes

Three different Advanced Oxidation Processes (ozonation at pH 7.5, electron beam irradiation and a combination ozonation/electron beam irradiation) have been applied to study decomposition of aqueous naphthalene-1,5-disulfonic acid (1,5-NDSA) with regard to mineralization and formation of biodegradable intermediates. Formation of biodegradable intermediates could not be indicated for any of the processes used; single electron beam irradiation treatment was the most efficient process for mineralization of organic carbon contained in aqueous 1,5-NDSA. Applied to a real wastewater effluent from a mixed municipal/industrial wastewater, electron beam irradiation with a radiation dose of 2 kGy was sufficient to reduce the concentrations of all naphthalene sulfonic acids and some of the alkylphenol ethoxylates also contained in that water by about 2 orders of magnitude.     

Decomposition of Carboxylic Acids in Water by O3, O3/H2O2, and O3/Catalyst

This paper studies the decomposition of formic, oxalic and maleic acids by O₃, O₃/catalyst, and O₃/H₂O₂. The catalytic effect of Co²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Zn²⁺, Cr³⁺, and Fe²⁺ ions is investigated. The results showed that—Co²⁺ and Mn²⁺ have the highest catalytic activity for the decomposition of oxalic acid while the catalytic effect of the studied ions is insignificant on the rate of decomposition of formic acid. Maleic acid decomposes by ozone into formic acid and glyoxylic acid, which subsequently oxidizes to oxalic acid. Though the studied ions have no effect on the decomposition of maleic acid, they have a significant effect on the produced oxalic and glyoxylic acids. In the presence of Cu²⁺ ions glyoxylic acid is mainly transformed into formic acid and traces of oxalic acid. In such case, a complete decomposition of maleic acid and its degradation products is achieved within 45 min. The results also show that combining H₂O₂ with O₃ results in an increase in the rate of decomposition of oxalic acid. However, O₃/H₂O₂ system is less active than O₃/Co²⁺ or O₃/Mn²⁺.     

Identification of Oxidation Intermediates in Humic Acid Oxidation

The effects of using ultraviolet irradiation (UV), ozone (O₃) and the combined O₃-UV advanced oxidation process (AOP) on humic acid (HA), which is regarded as the main disinfection by-products (DBPs) precursor, have been evaluated and compared. In particular, aromatic acids, short-chain aldehydes and carboxylic acids were measured. The purpose of this study was to determine the different classes and yields of oxidation intermediates, compare O₃, UV and O₃-UV for HA removal, as well as investigate the effects of O₃, irradiation time, UV intensity on the mineralization of HA. Based on that, the knowledge gap of DBPs generation was made up. The results showed that by UV irradiation and O₃ oxidation, HA broke down into smaller molecules that were more hydrophilic, namely formaldehyde, acetaldehyde, propaldehyde, butyraldehyde, glyoxal, methyl-glyoxal, formic, acetic, fumaric, benzoic, phthalic, protocatechuic and 3-hydroxybenzoic acids. Meanwhile, unsaturated conjugated double bonds in the structure of HA were destroyed, which lead to UV₂₅₄ a slight decrease. Due to the synergistic effect of O₃-UV, DOC and UV₂₅₄ significantly decreased and remained stable after the reaction of 10 min, indicating that O₃-UV system had stronger potential of mineralization and lower nonselectivity. Besides, the kinds and concentration levels of the intermediates were obviously reduced with light intensity increasing. Hydroxyl radical (^.OH) could mineralize some organics that could not be mineralized by O₃.     

Formation of Ketoacids in Ozonated Drinking Water

Three ketoacids; glyoxylic acid, pyruvic acid and ketomalonic acid, were identified in ozonated drinking waters and fulvic acid solutions using gas chromatography-mass spectrometry. It was found that the concentrations of ketoacids were much higher than those of aldehydes in ozonated waters. The significance of ketoacids in finished drinking waters is discussed.     

Aqueous Ozonation Of Fatty Acids

The reactivity of a series of fatty acids toward ozone was examined in aqueous solution at low substrate concentration (μg.L^?1 range). Saturated fatty acids were unreactive, unsaturated fatty acids were readily consumed. A number of reaction products or their methylated derivatives were identified by gas chromatography and gas chromatography-mass spectrometry. The products identified are consistent with a 1,3-dipolar cyclo-addotion reaction.     

Bromoform Formation in Ozonated Groundwater Containing Bromide and Humic Substances

The effect of bromide ion, organic carbon concentration (natural aquatic humic substances), pH, and solar irradiation on the formation of bromoform in ozonated groundwater has been studied. The studies were conducted on four unique samples of groundwater taken from different regions of the Biscayne Aquifer in southern Florida. All other conditions being equal, increases in bromide ion concentrations resulted in increases in CHBrg formation. In three of the four samples, CHBr₃ formation decreased as the pH level increased from 5 to 9. The fourth sample exhibited an opposite trend whereby the CHBr₃ concentration increased with increasing pH. Bromoform concentration increased with increased O₃ concentration over an ozone dosage range of 3.4 to 6.7 mg/L.     

Catalytic ozonation of humic acids with Fe/MgO

Humic acids were degraded by ozone at room temperature in a stirred tank reactor and a fixed bed reactor with Fe/MgO catalysts. Experimental results show that the ozonation with Fe/MgO induced a significant reduction in UV absorbance of humic acids as compared to ozone alone. Fe/MgO was the most efficient catalyst to degrade humic acids in the presence of ozone. GPC (gel permeation chromatography) showed that the humic acids with high molecular weight could be severely decomposed into organic compounds with low molecular weight on the Fe/MgO catalyst, indicating that humic acids could be catalytically decomposed. The continuous reaction experiments with the palletized catalysts supported that humic acids can be removed by catalysis as well as adsorption.     

Studies in Radiation Chemistry: Application to Ozonation and Other Advanced Oxidation Processes

Advanced oxidation/reduction processes (AORPs) are an alternative water treatment that is becoming more widely utilized. Our radiation-chemistry based studies are being used to develop a fundamental understanding of AOP treatment options, and are divided into three complementary types of contaminants; disinfection by-products (DBPs), emerging pollutants of concern (EPoCs), and natural organic matter (NOM). More than 600 DBPs have been identified, and one class that appears to have severe potential adverse health effects is the halonitromethanes (HNMs). Of the nine HNMs, trichloronitromethane (chloropicrin) is the most common, with levels up to 180 nM in US drinking waters. EPoCs are of interest because of their biological activity at low concentrations in water and while the initial focus was on endocrine disruptor chemicals (EDCs) this class has now been expanded to include many other recalcitrant chemicals such as hormones, antibiotics, industrial contaminants, and health care products. Natural organic matter is one of the most common radical scavengers in natural waters and therefore may adversely affect AOPs. Our approach is to study NOM both directly and using model compounds thought to be representative of structural components of this complex material.     

Ozonation of VOC's in the Presence of Humic Acid and Soils

The oxidation of several VOCs in the presence of humic acid and soil is described in this paper. It was found that while ozone does react appreciably with humic acid, as indicated by significant changes in the spectral characteristics of humic acid, the TOC levels in these solutions changed by only 3‰ or less. The oxidation of four olefinic VOCs occurred in solutions containing up to 120 mg/L humic acid, however, the extent to which each of the compounds reacted is very much compound specific. The effect of pH and ozone dosage on these reactions was considered. The effects of pH were weak for all compounds except trichloroethane. Ozone dosage had a significant effect on the extent to which each of the VOCs was oxidized, although no simple relationship between ozone dosage and the amount of VOC which reacted could be obtained. Complete oxidation of dy–dichloroethylene by ozone (22 mg/L) occurred in solutions containing 1.0 g of Eustis soil suspended in 10.0 mL water. However, only 40‰ oxidation of tetrachloroethylene was achieved using an ozone dosage of 17.3 mg/L when 1.0 g of Eustis soil was present. The results obtained in this study strongly suggest that the influence of free radicals, generated during the decomposition of ozone, on the oxidation of VOCs is significant. The work described here suggests that ozone may be applicable for the treatment of contaminated soils and waters containing high concentrations of matter.     

AM/AMPS/腐植酸接枝共聚物的合成

采用腐植酸与AM和AMPS接枝共聚合成了一种腐植酸接枝共聚物,并对其性能进行了室内初步评价。结果表明,AM/AMPS/腐植酸接枝共聚物用作泥浆降滤失剂,在淡水泥浆、盐水泥浆、饱和盐水泥浆和人工海水泥浆中具有较好的降滤失和耐温抗盐能力。     

Reaction Mechanisms for DBPS Reduction in Humic Acid Ozonation

In this study, XAD-8 resins were used to extract the natural organic matter (NOM) from samples collected at the intake of Feng Yuan Water Treatment Plant (in central Taiwan) into five groups: humic acids, fulvic acids, hydrophobic neutrals, hydrophobic bases, and hydrophilic fractions. Quantitative results show that hydrophobic and hydrophilic fractions contribute 44.2% and 55.5% of NOM, individually. Ozonation processes will significantly reduce both disinfection by-products formation potential (DBPFP) and average molecular weight of the humic acid sample. Additionally, double carbon bonds are broken up so that hydrophobic fractions were converted to hydrophilic fractions by ozonation leading to the reduction of DBPFP.     

Predicting Hydroxyl Radical Activity and Trace Contaminants Removal in Ozonated Water

There is a renewed interest in predicting R_CT following growing evidence that AOP is effective against many emerging contaminants. Five surface waters were investigated to evaluate the OH-radical activity using the R_CT concept, predict R_CT using traditional water quality characteristics and predict contaminants removal by ozonation and peroxone. It was shown that R_CT was dependent on water quality characteristics and could be modeled (R² = 0.92), using water characteristics and treatment conditions. Predictions of MIB oxidation closely matched the published data of Kawamura (2000 Kawamura, S. 2000. Integrated Design and Operation of Water Treatment Facilities, 2nd, New York: John Wiley & Sons, Inc.  [Google Scholar]) and bench-scale assays performed on one of the water under investigation.