Improving on SUVA 254 using fluorescence-PARAFAC analysis and asymmetric flow-field flow fractionation for assessing disinfection byproduct formation and control

Several challenges with disinfection byproduct (DBP) control stem from the complexity and diversity of dissolved organic matter (DOM), which is ubiquitous in natural waters and reacts with disinfectants to form DBPs. Fluorescence parallel factor (PARAFAC) analysis and asymmetric flow-field flow fractionation (AF4) were used in combination with free chlorine DBP formation potential (DBPFP) tests to study the physicochemical DOM properties and DBP formation in raw- and alum-coagulated waters. Enhanced coagulation with alum became more effective at removing DBP-precursors as the pH decreased from 8 to 6. AF4-UV₂₅₄ fractograms indicated enhanced coagulation at pH 6 preferentially removed larger DOM, whereas no preferential size removal occurred at pH 8. Fluorescence-PARAFAC analysis revealed the presence of one protein-like and three humic-like fluorophore groups; stronger linear correlations were found between chloroform and the maximum intensity (F_MAX) of a humic-like fluorophore (r² = 0.84) than with SUVA₂₅₄ (r² = 0.51). This result indicated that the fluorescence-PARAFAC approach used here was an improvement on SUVA₂₅₄, i.e., fluorescence-based measurements were stronger predictors of chloroform formation.     

Electrochemical oxidation of trace organic contaminants in reverse osmosis concentrate using RuO2/IrO2-coated titanium anodes

During membrane treatment of secondary effluent from wastewater treatment plants, a reverse osmosis concentrate (ROC) containing trace organic contaminants is generated. As the latter are of concern, effective and economic treatment methods are required. Here, we investigated electrochemical oxidation of ROC using Ti/Ru_0.7Ir_0.3O₂ electrodes, focussing on the removal of dissolved organic carbon (DOC), specific ultra-violet absorbance at 254 nm (SUVA₂₅₄), and 28 pharmaceuticals and pesticides frequently encountered in secondary treated effluents. The experiments were conducted in a continuously fed reactor at current densities (J) ranging from 1 to 250 A m⁻² anode, and a batch reactor at J = 250 A m⁻². Higher mineralization efficiency was observed during batch oxidation (e.g. 25.1 ± 2.7% DOC removal vs 0% removal in the continuous reactor after applying specific electrical charge, Q = 437.0 A h m⁻³ ROC), indicating that DOC removal is depending on indirect oxidation by electrogenerated oxidants that accumulate in the bulk liquid. An initial increase and subsequent slow decrease in SUVA₂₅₄ during batch mode suggests the introduction of auxochrome substituents (e.g. -Cl, NH₂Cl, -Br, and -OH) into the aromatic compounds. Contrarily, in the continuous reactor ring-cleaving oxidation products were generated, and SUVA₂₅₄ removal correlated with applied charge. Furthermore, 20 of the target pharmaceuticals and pesticides completely disappeared in both the continuous and batch experiments when applying J ≥ 150 A m⁻² (i.e. Q ≥ 461.5 A h m⁻³) and 437.0 A h m⁻³ (J = 250 A m⁻²), respectively. Compounds that were more persistent during continuous oxidation were characterized by the presence of electrophilic groups on the aromatic ring (e.g. triclopyr) or by the absence of stronger nucleophilic substituents (e.g. ibuprofen). These pollutants were oxidized when applying higher specific electrical charge in batch mode (i.e. 1.45 kA h m⁻³ ROC). However, baseline toxicity as determined by Vibrio fischeri bioluminescence inhibition tests (Microtox) was increasing with higher applied charge during batch and continuous oxidation, indicating the formation of toxic oxidation products, possibly chlorinated and brominated organic compounds.     

Sonophotolytic degradation of azo dye reactive black 5 in an ultrasound/UV/ferric system and the roles of different organic ligands

The sonophotolytic advance oxidation system (US/UV/Fe³⁺) could achieve synergistic degradation of reactive black 5 (RB5), as compared to UV/Fe³⁺ and US/Fe³⁺ systems. A synergy factor of 2.5 based on the pseudo-first-order degradation rate constant (k_obs) was found, along with enhancements in organic detoxification and mineralization. The presence of organic ligands could affect the US/UV/Fe³⁺ system differently. Oxalate, citrate, tartrate and succinate could enhance the RB5 degradation, while NTA and EDTA exhibited strong inhibitions. The influence of these ligands on k_obs(RB5) in the US/UV/Fe(III)-ligand systems followed the sequence of oxalate > tartrate > succinate > citrate > without ligand > NTA > EDTA, while they could be degraded simultaneously with the k_obs(ligand) order of oxalate > citrate > tartrate > succinate > NTA > EDTA. Monitoring of iron species and the generated H₂O₂ and •OH revealed that the ligands in the US/UV/Fe(III)-ligand system could play different mechanistic roles: (1) promoting H₂O₂ production, (2) accelerating Fenton reaction, and (3) competing with RB5 for reacting with •OH. Among the ligands, oxalate exhibited the most significant enhancement of RB5 oxidation in the sonophotolytic system, and the process was pH-dependent. An initial reaction lag in RB5 degradation was observed when Fe²⁺ was used in lieu of Fe³⁺ as the catalyst in the sonophotolytic system.     

Photoassisted reduction of metal ions and organic dye by titanium dioxide nanoparticles in aqueous solution under anoxic conditions

The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO₂ nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO₂ and to enhance the photocatalytic activity of TiO₂ towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO₂, respectively. Results showed that the particle size of metal-deposited TiO₂ was larger than that of Degussa P25 TiO₂. Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k_obs) for MB photodegradation by Degussa P25 TiO₂ was 3.94 × 10^− 2 min^− 1 and increased by 1.4-1.7 times in k_obs with metal-deposited TiO₂ for MB photodegradation compared to simple Degussa P25 TiO₂. The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k_obs for MB degradation increased from 3.94 × 10^− 2 min^− 1 in the absence of metal ion to 4.64-7.28 × 10^− 2 min^− 1 for Ag/TiO₂ and to 5.14-7.61 × 10^− 2 min^− 1 for Cu/TiO₂. In addition, the electrons generated from TiO₂ can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO₂.     

A simple method to assess the quenching effectiveness of fire suppressants

A screening concept is suggested for evaluating the effectiveness of fluids to thermally suppress fires. It is based on measuring a fluid's ability to inhibit (or quench) the temperature rise of a material that is rapidly heated. The experimental design is similar to the transient hot wire technique, in which the evolution of the average material temperature is recorded for a given input power, and internal temperature gradients in the material are minimized. A gold wire (100 μm long and 5 μm diameter) is used as the surface which heats the fluid. The wire temperature response due to a power pulse provides a measure of the effectiveness of the fluid to suppress thermally the temperature increase. The results indicate that the “quenching effectiveness”, QE=(_Tmax−_T∞)/(_Tmax,ref−_T∞)$\mathit{QE}=(T_{\max }-T_{\infty })/(T_{\max ,\mathit{ref}}-T_{\infty })$, correlates with the ratio of the fluid thermal conductivity to that of the wire, k_fluid/k_solid, using different Nusselt numbers (representing both conduction and natural convection) for the liquids or gases. The concept developed here could be included in a more comprehensive screening protocol, which would assess the thermal potential of candidate fire suppressants.     

Modeling monochloramine loss in the presence of natural organic matter

A comprehensive model describing monochloramine loss in the presence of natural organic matter (NOM) is presented. The model incorporates simultaneous monochloramine autodecomposition and reaction pathways resulting in NOM oxidation. These competing pathways were resolved numerically using an iterative process evaluating hypothesized reactions describing NOM oxidation by monochloramine under various experimental conditions. The reaction of monochloramine with NOM was described as biphasic using four NOM specific reaction parameters. NOM pathway 1 involves a direct reaction of monochloramine with NOM (k_doc1=1.05×10⁴-3.45×10⁴ M⁻¹ h⁻¹). NOM pathway 2 is slower in terms of monochloramine loss and attributable to free chorine (HOCl) derived from monochloramine hydrolysis (k_doc2=5.72×10⁵-6.98×10⁵ M⁻¹ h⁻¹), which accounted for the majority of monochloramine loss. Also, the free chlorine reactive site fraction in the NOM structure was found to correlate to specific ultraviolet absorbance at 280 nm (SUVA₂₈₀). Modeling monochloramine loss allowed for insight into disinfectant reaction pathways involving NOM oxidation. This knowledge is of value in assessing monochloramine stability in distribution systems and reaction pathways leading to disinfection by-product (DBP) formation.     

Synergistic effect of nickel ions on the coupled dechlorination of trichloroethylene and 2,4-dichlorophenol by Fe/TiO₂ nanocomposites in the presence of UV light under anoxic conditions

The coupled removal of priority pollutants by nanocomposite materials has recently been receiving much attention. In this study, trichloroethylene (TCE) and 2,4-dichlorophenol (DCP) in aqueous solutions were simultaneously removed by Fe/TiO₂ nanocomposites under anoxic conditions in the presence of nickel ions and UV light at 365 nm. Both TCE and DCP were effectively dechlorinated by Fe/TiO₂ nanocomposites, and the pseudo-first-order rate constants (k_obs) for TCE and DCP dechlorination were (1.39 ± 0.05)×10⁻² and (1.08 ± 0.05)×10⁻² h⁻¹, respectively, which were higher than that by nanoscale zerovalent iron alone. In addition, the k_obs for DCP dechlorination was enhanced by a factor of 77 when Fe/TiO₂ was illuminated with UV light for 2 h. Hydrodechlorination was found to be the major reaction pathway for TCE dechlorination, while DCP could undergo reductive dechlorination or react with hydroxyl radicals to produce 1,4-benzoquinone and phenol. TCE was a stronger electron acceptor than DCP, which could inhibit the dechlorination efficiency and rate of DCP during simultaneous removal processes. The addition of nickel ions significantly enhanced the simultaneous photodechlorination efficiency of TCE and DCP under the illumination of UV light. The k_obs values for DCP and TCE photodechlorination by Fe/TiO₂ in the presence of 20-100 μM Ni(II) were 30.4-136 and 13.2-192 times greater, respectively, when compared with those in the dark. Electron spin resonance analysis showed that the photo-generated electron-hole pairs could be effectively separated through Ni ions cycling, leading to the improvement of electron transfer efficiency of TCE and DCP by Fe/TiO₂.     

Photosensitized degradation of amoxicillin in natural organic matter isolate solutions

Amoxicillin is a widely used antibiotic and has been detected in natural waters. Its environmental fate is in part determined by hydrolysis, and, direct and indirect photolysis. The hydrolysis rate in distilled water and water to which five different isolated of dissolved organic matter (DOM) was added, were evaluated. In the five different DOM solutions hydrolysis accounted for 5-18% loss of amoxicillin. Direct and indirect photolysis rates were determined using a solar simulator and it appeared that indirect photolysis was the dominant loss mechanism. Direct photolysis, in a solar simulator, accounted for 6-21% loss of amoxicillin in the simulated natural waters. The steady-state concentrations of singlet oxygen, ¹ΔO₂ (∼10⁻¹³ M) and hydroxyl radical, •OH (∼10⁻¹⁷ M) were obtained in aqueous solutions of five different dissolved organic matter samples using a solar simulator. The bimolecular reaction rate constant of ¹ΔO₂ with amoxicillin was measured in the different solutions, kΔO₂ = 1.44 × 10⁴ M⁻¹ s⁻¹. The sunlight mediated amoxicillin loss rate with ¹ΔO₂ (∼10⁻⁹ s⁻¹), and with •OH (∼10⁻⁷ s⁻¹), were also determined for the different samples of DOM. While ¹ΔO₂ only accounted for 0.03-0.08% of the total loss rate, the hydroxyl radical contributed 10-22%. It appears that the direct reaction of singlet and triplet excited state DOM (³DOM^∗) with amoxicillin accounts for 48-74% of the loss of amoxicillin. Furthermore, the pseudo first-order photodegradation rate showed a positive correlation with the sorption of amoxicillin to DOM, which further supported the assumption that excited state DOM^∗ plays a key role in the photochemical transformation of amoxicillin in natural waters. This is the first study to report the relative contribution of all five processes to the fate of amoxicillin in aqueous solution.     

Bioavailability of organic pollutants in boreal waters with varying levels of dissolved organic material

Dissolved organic matter (DOM) in 20 surface waters in Eastern Finland were characterized to examine relationships between structural and compositional properties of DOM and partition coefficients (K_p) describing sorption of four model contaminants to DOM and the bioavailability of contaminants by Daphnia magna. The hydrophobic acids (HbA), hydrophobic neutrals (HbN) and hydrophilic (HI) fractions of DOM were separated by XAD-8 resin. The K_Ps were measured by equilibrium dialysis. Model contaminants were benzo(a)pyrene (BaP), naphthalene (NAPH), 3.3′,4.4′-tetrachlorobiphenyl (TCB) and dehydroabietic acid (DHAA).DOM concentrations varied from 2.0 to 38.3 mg org. C/l in the water series. The percentage of HbA and the aromaticity of DOM, as indicated by the absorptivity at 270 nm (A₂₇₀) and hydrogen/carbon ratio (H/C ratio), increased with increasing DOM concentration. Significant correlations were observed between K_P of BAP, A₂₇₀ and HbA content of the DOM from different sources. For the other contaminants similar kinds of relationships between K_ps and quality parameters of DOM could not be found.The bioavailability of model compounds was decreased by increasing DOM concentration in the water series. For all four model contaminants, measured bioconcentration factors (BCF) correlated well with the A₂₇₀ of a water and HbA content of the DOM. These results show that the total DOM concentration is an important factor controlling the bioavailability of xenobiotics in natural waters. Besides the quantity also the quality of DOM, like proportion of HbA, can contribute in bioavailability.     

The impact of bromide/iodide concentration and ratio on iodinated trihalomethane formation and speciation

The objective of this study was to evaluate the formation and speciation of iodinated trihalomethanes (I-THMs) from preformed chloramination of waters containing bromide (Br⁻) and iodide (I⁻) at a Br⁻/I⁻ weight ratio of 10:1. The factors investigated were pH, iodide to dissolved organic carbon (I⁻/DOC) ratio, and NOM characteristics, specifically SUVA₂₅₄. A Br⁻/I⁻ ratio of 1:2 was also evaluated to determine the importance of Br⁻ and I⁻ concentrations and ratio on I-THM formation and speciation. Regulated triholamethanes (THMs) were measured alongside I-THMs for a more complete understanding of trihalomethane formation. The results showed that, in general, both I-THM and THM formation increased with decreased pH. Greater formation at lower pH was likely attributed to monochloramine decomposition and the formation of additional oxidants and substituting agents, most notably chlorine. For pH ≥ 7.5, I-THM yield increased with increasing I⁻/DOC ratio and decreasing specific ultraviolet absorbance (SUVA₂₅₄) of the water. The Br⁻/I⁻, Br⁻/DOC and I⁻/DOC ratios were important factors for I-THM and THM speciation. At pH 6, dichloroiodomethane (CHCl₂I) and bromochloroiodomethane (CHBrClI) were the dominant species at the common bromide and iodide levels. For pH ≥ 7.5 and for elevated bromide and iodide levels, iodoform (CHI₃) was always the dominant specie regardless of the Br⁻/I⁻ ratio. The results demonstrated that it is important to examine I-THM formation and speciation at typical Br⁻/I⁻ ratios (∼10) of natural waters, which have often been overlooked in previous investigations, in order to obtain practical and relevant results.     

Influences of humic acid, bicarbonate and calcium on Cr(VI) reductive removal by zero-valent iron

The influences of various geochemical constituents, such as humic acid, HCO₃⁻, and Ca²⁺, on Cr(VI) removal by zero-valent iron (Fe⁰) were investigated in a batch setting. The collective impacts of humic acid, HCO₃⁻, and Ca²⁺ on the Cr(VI) reduction process by Fe⁰ appeared to significantly differ from their individual impacts. Humic acid introduced a marginal influence on Fe⁰ reactivity toward Cr(VI) reduction, whereas HCO₃⁻ greatly enhanced Cr(VI) removal by maintaining the solution pH near neutral. The Cr(VI) reduction rate constants (k_obs) were increased by 37.8% and 78.3%, respectively, with 2 mM and 6 mM HCO₃⁻ in solutions where humic acid and Ca²⁺ were absent. Singly present Ca²⁺ did not show a significant impact to Cr(VI) reduction. However, probably due to the formation of passivating CaCO₃, further addition of Ca²⁺ to HCO₃⁻ containing solutions resulted in a decrease of k_obs compared to solutions containing HCO₃⁻ alone. Ca²⁺ enhanced humic acid adsorption led to a minor decrease of Cr(VI) reduction rates. In Ca²⁺-free solutions, humic acid increased the amount of total dissolved iron to 25 mg/l due to the formation of soluble Fe-humate complexes and stably dispersed fine Fe (oxy)hydroxide colloids, which appeared to suppress iron precipitation. In contrast, the coexistence of humic acid and Ca²⁺ significantly promoted the aggregation of Fe (oxy)hydroxides, with which humic acid co-aggregated and co-precipitated. These aggregates would progressively be deposited on Fe⁰ surfaces and impose long-term impacts on the permeability of PRBs.     

Determination of user profile at city parks: A sample from Turkey

A survey study conducted randomly in the cities of Erzurum, Erzincan and Kars included 360 subjects interviewed face to face. It was aimed to detect the subjective features of the participants such as gender, marital status, age, educational status and income level and the reflections of these features on the city parks. Conclusively, it was determined that those who are male, unmarried, at the age of between 19 and 24, university graduate and with a monthly income of 65–125 USD use the parks in majority. In the statistical analysis, the SPSS software was used and variables were compared. Chi-square (χ²) test was used to determine the independency correlations. According to the analysis, gender and income had no significant effect on the use of city parks, but marital status, age and education status had significant effects at 5% significance levels (*p<0.05$p<0.05$, χ²: 27.805; *p<0.05$p<0.05$, χ²: 44.073; *p<0.05$p<0.05$, χ²: 39.998, respectively).     

Modeling thermal behaviors of window flame ejected from a fire compartment

A series of reduced-scale experiments were carried out in order to investigate thermal behaviors of window flame, which exposes the upper floors as well as the adjacent buildings to potential risks of fire spread. A stainless pan filled with alcohol was used as the fire source and was placed inside a cubic compartment of 900 mm side. Temperatures and velocities at various points inside and outside of the compartment were measured. The compartment was pressurized during the experiment by mechanically supplying air at several mass inflow rates through an inlet duct set at the bottom part of the compartment. This was for simulating fire conditions under the effect of external wind pressure. On the basis of the experimental observation, line (i.e., two-dimensional) heat source assumption was adopted for developing a model of window flame behavior. A dimensionless parameter Q^′*${Q^{\prime }}^{*}$ was derived from the governing differential equations in order to generalize the measurement results. Expressions for temperature rise along the trajectory ΔT_m and characteristic flame width b_T were developed incorporating the parameter Q^′*${Q^{\prime }}^{*}$.     

Degradation of 32 emergent contaminants by UV and neutral photo-fenton in domestic wastewater effluent previously treated by activated sludge

This study focuses on the removal of 32 selected micropollutants (pharmaceuticals, corrosion inhibitors and biocides/pesticides) found in an effluent coming from a municipal wastewater treatment plant (MWTP) based on activated sludge. Dissolved organic matter was present, with an initial total organic carbon of 15.9 mg L⁻¹, and a real global quantity of micropollutants of 29.5 μg L⁻¹. The treatments tested on the micropollutants removal were: UV-light emitting at 254 nm (UV₂₅₄) alone, dark Fenton (Fe^2+,3+/H₂O₂) and photo-Fenton (Fe^2+,3+/H₂O₂/light). Different irradiation sources were used for the photo-Fenton experiences: UV₂₅₄ and simulated sunlight. Iron and H₂O₂ concentrations were also changed in photo-Fenton experiences in order to evaluate its influence on the degradation. All the experiments were developed at natural pH, near neutral. Photo-Fenton treatments employing UV₂₅₄, 50 mg L⁻¹ of H₂O₂, with and without adding iron (5 mg L⁻¹ of Fe²⁺ added or 1.48 mg L⁻¹ of total iron already present) gave the best results. Global percentages of micropollutants removal achieved were 98 and a 97% respectively, after 30 min of treatments. As the H₂O₂ concentration increased (10, 25 and 50 mg L⁻¹), best degradations were observed. UV₂₅₄, Fenton, and photo-Fenton under simulated sunlight gave less promising results with lower percentages of removal.The highlight of this paper is to point out the possibility of the micropollutants degradation in spite the presence of DOM in much higher concentrations.     

The effects of UV disinfection on drinking water quality in distribution systems

UV treatment is a cost-effective disinfection process for drinking water, but concerned to have negative effects on water quality in distribution system by changed DOM structure. In the study, the authors evaluated the effects of UV disinfection on the water quality in the distribution system by investigating structure of DOM, concentration of AOC, chlorine demand and DBP formation before and after UV disinfection process. Although UV treatment did not affect concentration of AOC and characteristics of DOM (e.g., DOC, UV_254, SUVA₂₅₄, the ratio of hydrophilic/hydrophobic fractions, and distribution of molecular weight) significantly, the increase of low molecular fraction was observed after UV treatment, in dry season. Chlorine demand and THMFP are also increased with chlorination of UV treated water. This implies that UV irradiation can cleave DOM, but molecular weights of broken DOM are not low enough to be used directly by microorganisms in distribution system. Nonetheless, modification of DOM structure can affect water quality of distribution system as it can increase chlorine demands and DBPs formation by post-chlorination.     

The formation of halogen-specific TOX from chlorination and chloramination of natural organic matter isolates

The formation of disinfection by-products (DBPs) is a public health concern. An important way to evaluate the presence of DBPs is in terms of the total organic halogen (TOX), which can be further specified into total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI). The formation and distribution of halogen-specific TOX during chlorination and chloramination of natural organic matter (NOM) isolates in the presence of bromide and iodide ions were studied. As expected, chloramination produced significantly less TOX than chlorination. TOCl was the dominant species formed in both chlorination and chloramination. TOI was always produced in chloramination, but not in chlorination when high chlorine dose was used, due to the limited presence of HOI in chlorination as a result of the oxidation of iodide to iodate in the presence of excess chlorine. The formation of TOI during chloramination increased as the initial iodide ion concentration increased, with a maximum of ∼60% of the initial iodide ion becoming incorporated into NOM. Iodine incorporation in NOM was consistently higher than bromine incorporation, demonstrating that the competitive reactions between bromine and iodine species in chloramination favoured the formation of HOI and thus TOI, rather than TOBr. Correlations between the aromatic character of the NOM isolates (SUVA₂₅₄ and % aromatic C) and the concentrations of overall TOX and halogen-specific TOX in chloramination were observed. This indicates that the aromatic moieties in NOM, as indicated by SUVA₂₅₄ and % aromatic C, play an important role in the formation of overall TOX and halogen-specific TOX in chloramination. THMs comprised only a fraction of TOX, up to 7% in chloramination and up to 47% in chlorination. Although chloramine produces less TOX than chlorine, it formed proportionally more non-THM DBPs than chlorine. These non-THM DBPs are mostly unknown, corresponding to unknown health risks. Considering the higher potential for formation of iodinated DBPs and unknown DBPs associated with the use of chloramine, water utilities need to carefully balance the risks and benefits of using chloramine as an alternative disinfectant to chlorine in order to satisfy guideline values for THMs.     

Adsorption of Cu(II) to schwertmannite and goethite in presence of dissolved organic matter

Sorption processes involving secondary iron minerals may significantly contribute to immobilisation of metals in soils and surface waters. In the present work the effect of dissolved organic matter (DOM) from a concentrated bog-water on the adsorption of Cu(II) onto schwertmannite (Fe₈O₈(OH)₆SO₄) and goethite (α-FeOOH) has been studied. The acid/base behaviour of DOM up to pH 6 was explained by assuming a diprotic acid with a density of carboxylate groups of 6.90 μeq (mg C)⁻¹. The resulting acidity constants, recalculated to zero ionic strength were and .The uptake of DOM to schwertmannite and goethite was highest at low pH although adsorption was significant also under mildly alkaline conditions. Adsorption to the two minerals was similar although at high pH more DOM was adsorbed to schwertmannite than to goethite.DOM enhanced the adsorption of Cu(II) at moderately low pH in the goethite system but there was no effect of DOM in the case of schwertmannite. The presence of Cu(II) resulted in a decreased adsorption of DOM to goethite at weakly acidic pH and increased adsorption at high pH. In the case of schwertmannite, Cu(II) did not affect DOM uptake.