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PubMed2001

Changes of activity inducing chromosomal aberrations and transformations of chlorinated humic acid.

The change of the toxicity of chlorinated water after chlorine injection was examined. For the measurement of toxicity, chromosomal aberration test and transforming test were carried out as indexes to initiating activity and to promoting activity in the carcinogenesis process, respectively. Activity inducing chromosomal aberrations of chlorinated humic acid gradually decreased with time after chlorination. In contrast, activity inducing transformations measured by the two-stage assay gradually increased. Thus, the toxicity that decreases or increases is present in chlorinated water. Furthermore, activity inducing transformations measured by the non-two-stage assay gradually decreased. This direction of change was reverse to that of activity inducing transformations by the two-stage assay and consistent with that of activity inducing chromosomal aberrations. It is speculated that the main reason of decreasing activity inducing transformations by the non-two-stage assay is because initiating activity detected as activity inducing chromosomal aberrations in chlorinated water decreases drastically. Directions of changes of total organic halogen and carbonyl group were qualitatively consistent with that of activity inducing chromosomal aberrations. Directions of changes of chloroform and dichloroacetic acid were qualitatively consistent with that of activity inducing transformations by the two-stage assay. Findings of this study suggest that further research is necessary to compare carcinogenicity of tap water near water purification plant and distant tap water.

Animals↗

PubMed2001

Evaluation of the treatment performance of a multistage ozone/hydrogen peroxide process by decomposition by-products.

The performance of a multistage ozone/hydrogen peroxide (O3/H2O2) process was evaluated with respect to total organic carbon (TOC) removal of waste waters. An aqueous humic acid solution (5.2 mgC l(-1) as TOC) and a sand filtered secondary sewerage effluent (5.6mgC l(-1) as TOC) were used as model waste waters. Appropriate range of hydrogen peroxide (H2O2) dose at each stage depended upon the components of the tested solutions that changed as the process proceeded. Higher hydrogen peroxide dose was required at later stages in which low reactivity compounds with hydroxyl radical (HO*), low molecular fatty acids, were predominant. And, oxalic acid concentration related to H2O2 demand at later stages. This was assumed that the slow decomposition of oxalic acid was rate-determining step for TOC removal after its accumulation. Also, it is important to maintain dissolved ozone at low concentration for efficient TOC removal because rapid ozone consumption is required for the rapid formation of hydroxyl radical (HO*).

Carbon↗

PubMed2001

Particle size distribution in effluent of trickling filters and in humus tanks.

Particles and aggregates from trickling filters must be eliminated from wastewater. Usually this happens through sedimentation in humus tanks. Investigations to characterize these solids by way of particle size measurements, image analysis and particle charge measurements (zeta potential) are made within the scope of Research Center for Science and Technology "Fundamentals of Aerobic biological wastewater treatment" (SFB 411). The particle size measuring results given within this report were obtained at the Ingolstadt wastewater treatment plant, Germany, which served as an example. They have been confirmed by similar results from other facilities. Particles flushed out from trickling filters will be partially destroyed on their way to the humus tank. A large amount of small particles is to be found there. On average 90% of the particles are smaller than 30 microm. Particle size plays a decisive role in the sedimentation behaviour of solids. Small particles need sedimentation times that cannot be provided in settling tanks. As a result they cause turbidity in the final effluent. Therefore quality of sewage discharge suffers, and there are hardly advantages of the fixed film reactor treatment compared to the activated sludge process regarding sedimentation behaviour.

Environmental Monitoring↗

PubMed2001

Membrane and solution effects on solute rejection and productivity.

Limited understanding of the physical and chemical processes involved in membrane processes affects their widespread application in drinking water treatment. Insight into these processes was attained through a systematic manipulation of solution chemistry in membrane filtration with three 'loose' nanofiltration membranes. Eighteen known solutions were created varying pH, ionic strength, and major cation valence in the presence of a commercial humic acid. The membrances varied as well, including a non-ionic hydrophobic, a non-ionic hydrophilic, and an anionic hydrophilic membrane surface. Specific membrane productivity and TOC and conductivity rejection were monitored. In all cases, the presence of divalent cations decreased the rejection of both conductivity and organic matter. Divalent cations also greatly increased the rate of productivity decline over equivalent tests in solutions with monovalent cations. The most hydrophobic membrane had the greatest productivity decline rate under all solution conditions. The lowest ionic strength solutions showed the greatest TOC and conductivity rejection and the greatest rate of productivity decline for each of the membranes.

Filtration↗

PubMed2001

Exploratory analysis of the effects of particulate characteristics on the variation in partitioning of nonpolar organic contaminants to marine sediments.

The partitioning of nonpolar organic contaminants to marine sediments is considered to be controlled by the amount of organic carbon present. However, several studies propose that other characteristics of sediments may affect the partitioning of contaminants. For this exploratory analysis, we measured 19 sediment characteristics from five marine sediments and 11 characteristics of humic acids extracted from the sediments. These characteristics included elemental composition, grain size, soot carbon, polarity indices and molar ratios. Each individual characteristic and combinations of these characteristics were then used to normalize partition coefficients (Kp) generated for three organic contaminants: lindane, fluoranthene and a tetrachlorinated biphenyl (PCB). A coefficient of variation (CV) was then calculated for each contaminant to determine which normalization characteristic (individually or in combination) resulted in the lowest variability in partitioning between study sediments. For lindane and the PCB. normalization by the amount of sediment organic carbon resulted in the lowest variability in partition coefficients with CVs of 16.2% and 37.7%. respectively. However, normalization of fluoranthene by silt content resulted in lower CVs than those generated by organic carbon normalization: 31.0% vs. 37.6%. Normalization of contaminants Kp's by combined values of sediment characteristics resulted in lower CVs but only by a few percent. Using humic acid characteristics, humic organic carbon reduced variability between sediments most effectively. But only the normalized fluoranthene values had a CV (i.e., 25.4%) lower than the one based on normalization by sediment characteristics. When combined, humic acid characteristics resulted in lower CVs than normalization by individual or combinations of sediment characteristics for fluoranthene and the PCB with CVs of 19.3% and 28.7%, respectively. This analysis indicates variability associated with the partitioning of some organic contaminants to marine sediments can be further reduced when normalization by sediment characteristics other than organic carbon are utilized.

Absorption↗

PubMed2002

Photoelectrocatalytic degradation of humic acid in aqueous solution using a Ti/TiO2 mesh photoelectrode.

Humic acid (HA) is one of natural organics existing in water supply as a precursor of trihalomethanes formation in chlorination. The photo-degradation of HA in aqueous solution by photoelectrocatalytic (PEC) oxidation using a Ti/TiO2 mesh electrode was investigated in terms of UV absorbance at 254 nm, colour and TOC concentration. The key factors affecting the PEC oxidation efficiency were studied, including the concentration of electrolyte, electrical bias applied. pH value of HA solution, the intensity of incident light and the area of Ti/TiO2 mesh photoelectrodes. The first-order kinetic model was applied to describe the PEC oxidation, in which the kinetic constant k was verified by the experimental data as a function of the concentration of electrolyte, light intensity, the area of Ti/TiO2 mesh electrode and the voltage of electrical bias applied. It was found that there was an optimal bias voltage of 1.63 V and low pH value was favourable for TOC removal in HA solution. Our investigation showed that PEC oxidation was a convenient way to mineralise the organic matters with high efficiency.

Coloring Agents↗

PubMed2002

Excitation-emission fluorescence matrix to study pH influence on organic matter fluorescence in the Amazon basin rivers.

A study of the three-dimensional excitation-emission fluorescence matrix (EEFM) of organic matter from the Amazon basin rivers is reported in this paper. The EEFM, applied to the fractions obtained from sequential tangential ultrafiltration (STUF), give spectroscopic informations on the fluorescent properties of particulate (>0.22 microm), colloidal and dissolved (< 5 kD) organic matter. STUF process does not seem to alter the characteristic peaks position of humic material. Two characteristic excitation-emission peaks were observed in all fractions of the samples investigated, one stimulated by UV excitation (peak A) and one by visible excitation (peak C). Increasing the pH, fluorescence intensities of the fluorophores A and C, respectively, I(A) and I(C), responded in the same manner to pH, increasing with increasing pH. However, the fluorophore A seems more sensitive to this pH variation because its fluorescence intensity enhancement is always higher. Thus the chemical behaviour of the two fluorophores must be somewhat differentiated. The evolution of the I(A)/I(C) ratio with pH is studied for all samples. This investigation showed a linear relation between I(A)/I(C) and pH. Moreover, this behaviour is water type (black or white) and molecular size independent. Indeed, this linear relationship is observed for all samples and all fractions.

Brazil↗

PubMed2002

Molecular size fractions of treated aquatic humus.

The effects of ozone, chlorine, hydrogen peroxide, and permanganate on the aquatic humic matter with different molecular size fractions and the organic acid formation in drinking water treatment were studied. Aquatic humus in lake water (LW), artificially recharged groundwater (AW), and purified artificially recharged groundwater (PW) were fractionated by high-pressure size-exclusion chromatography (HP-SEC) with UV-254nm detection before and after oxidation, a technique which resulted generally in seven peaks. The sum of the molecular size fractions (SMSF) of the LW was reduced by 47% during the bank filtration process, and the SMSF of the AW was reduced by 55% during the process in the water treatment plant. The oxidation of the AW resulted in reductions in the range of 18-35% of the SMSF; the respective range of the PW was 15-69%. However, the content of the total organic carbon (TOC) reduced only slightly, and a high correlation between the TOC and the SMSF (0.911) was observed in the whole material. The greatest decreases appeared in the highest-molecular-weight fractions while the low-molecular-weight fractions remained nearly unchanged. The total content of the six organic small-molecular-weight acids (sum of the organic acids, SOA) (formate, acetate, propionate, pyruvate, oxalate, and citrate) varied between 0.1-5.1% and 0.1-9.7% of the reduced TOC in the AW and the PW, respectively. The formation of the SOA, especially of oxalate, was the greatest after hydrogen peroxide combined with ozonation (as much as 1,100 microg/L), while chlorination resulted in the SOA of < 50 microg/L.

Chlorine↗

PubMed2002

Cadmium adsorption on goethite-coated sand in the presence of humic acid.

Heat was employed to coat crystalline goethite onto a quartz sand surface so that the adsorbent properties of the coating could be utilized. The adsorption characteristics of cadmium and humic acid onto goethite-coated sand were examined. Results show that the goethite-coated sand surface had a higher specific surface area and more mesopores than the uncoated sand. The adsorption of both cadmium and humic acid was highly pH-dependent: cadmium adsorption increased with pH, but humic acid adsorption decreased as pH increased. The presence of humic acid resulted in increasing cadmium adsorption in a specific pH range. The order of reacting humic acid with cadmium was found to have a noticeable effect on the final adsorption capacity. The adsorption capacity of cadmium for humic acid that is adsorbed onto goethite-coated sand before reacting with a cadmium system, exceeds that of humic acid that is mixed with cadmium ions before goethite-coated sand is added.

Adsorption↗

PubMed2002

Metal ion complexation properties of fulvic acids extracted from composted sewage sludge as compared to a soil fulvic acid.

Complexation properties of an anthropogenic fulvic acid (FA) extracted from a composted sewage sludge (csFA) for Cu(II), Pb(II) and Cd(II) were studied at pH=6 and at a concentration of 25 mg L(-1). For the case of Cu(II), a particular analysis of the complexation phenomena was done at pH values of 3, 4, 5 and 6 and at aqueous FA concentrations of 25, 50 and 100 mg L(-1) by synchronous excitation molecular fluorescence spectroscopy (SyF). Potentiometric titrimetry with Cu(II), Pb(II), Cd(II) and H+ ion-selective electrodes and acid-base conductimetric titrations were used to obtain experimental information about the acid properties and complexation phenomena. A comparison of the results obtained for csFA with a natural soil FA (sFA) was made. Differences have been detected in the structural composition of the two samples and in the structure of the binding sites. In the csFA, binding site structures containing nitrogen probably play an important role in the complexation, besides oxygen containing structures. Complexation by sFA is mainly due to carboxylic and phenolic structures. Nevertheless, this work shows that csFA have macroscopic complexation properties (magnitude of the conditional stability constant and binding sites concentration) somewhat similar to the natural sFA samples.

Benzopyrans↗

PubMed2002

Removal of organic matter from water by PAC/UF system.

The laboratory-scale ultrafiltration (UF) experiments were conducted to determine the effect of the presence of powdered activated carbon (PAC) on the UF process performance, in terms of flux decline and the possibilities of membranes cleaning during backwashing. Poly(vinylidene fluoride) membranes formed by the phase inversion technique were used in the UF experiments. A model solution was prepared as a mixture of humic acids (HA) and phenol in concentration of 10 and 1 mg l(-1), respectively. Commercial powdered activated carbons CWZ 11 and CWZ 30 (Gryfskand Sp. z o. o., Hajnówka, Poland) were used as the adsorbents. PAC dosage was in the range of 10-100 mg PAC l(-1). The process was carried out in the cross-flow system. It was found that PAC addition to the distilled water leads to a small drop in the permeate flux, regardless of PAC dose and its type. Although PAC particles are too large to block the membrane pores inside, they deposit on the membrane surface and partially can plug the surface pores. The experimental results demonstrate that the backwashing process applied in combined PAC/UF system was especially effective when PAC dosages were <20mg PAC l(-1). However, a similar permeate flux was maintained for all carbon dosages used and reached the value of about 1 m3 m(-2) d(-1). Moreover, no further drop in the permeate flux for PAC addition to the solution containing foulants (HA) was observed. Effectiveness of the removal of HA and phenol from the model solutions was also investigated. In the PAC/UF system HA were removed in about 90%, whereas the complete removal of phenol was achieved for PAC dosage equal to 100 mg l(-1).

Charcoal↗

PubMed2002

Aluminum speciation in natural waters: measurement using Donnan membrane technique and modeling using NICA-Donnan.

The study of Al speciation is of interest for the assessment of soil and water quality. For the measurement of "free" aluminum (Al3+), a recently developed Donnan membrane technique was tested by measuring Al3+ in aluminum-fluoride solutions and gibbsite suspensions. It shows that the Donnan membrane technique can measure free Al3+ reliably up to 10(-9) M and the equilibration takes 3-4 days. Next, Al binding to humic acid (HA) purified from a forest soil was measured using either the Donnan membrane technique or gibbsite suspension. Results were compared with those predicted with the non-ideal consistent competitive adsorption (NICA)-Donnan model. The predictions using the generic parameters without fitting were in reasonable agreement with the measured data. Finally, the Donnan membrane technique was used to determine Al binding to dissolved organic matter (DOM) in the solutions of 24 soil samples at pH interval of 3-7. Measurements agree well with the predictions using the NICA-Donnan model assuming 30% of DOM is HA and 30% is fulvic acid. With this model, the effects of pH and DOM changes on the concentration of Al in 81 soil solutions were predicted reasonably without adjustment of model parameters. The comparison between the results of analysis and the modeling provides a mutual validation for the two methods.

Adsorption↗

PubMed2002

Characterization, differentiation and classification of aquatic humic matter separated with different sorbents: synchronous scanning fluorescence spectroscopy.

Aquatic humic solutes were separated by the non-ionic macroporous XAD-8 and DAX-8 resins and a weakly basic DEAE cellulose anion exchanger from seven different fresh water sources. Synchronous fluorescence spectroscopy was applied for characterization, differentiation and classification of the different humic-solute aggregates. Fluorescence properties verified that humic-solute fractions isolated parallelly with the non-ionic XAD-8 and DAX-8 resins resembled very closely each other speaking strongly for their structural similarities. DAX-8 resin separated ca. 19% more aquatic humic matter than did the analogous XAD-8 resin. It was possible to tentatively differentiate the untreated water samples according to their fluorescent materials. Several distinct classes of chromophores were detected in both DOM and isolated humic fractions by the synchronous technique: lambda(ex)/lambda(em) 280/298, 330/348, 355/373, 400/418, 427/445, 460/478, 492/510 and 516/534 nm.

Environmental Monitoring↗

PubMed2002

A study of coagulation mechanisms of polyferric sulfate reacting with humic acid using a fluorescence-quenching method.

A fluorescence-quenching method is developed to assess the effect of pH on the coagulation mechanism of humic acids (HA) reacting with metal ions. A polyferric sulfate (PFS) synthesized in our laboratory is adopted as the coagulant to simplify the hydrolysis process and increase the experimental precision. The following results are discovered. When the concentration of PFS increases from 2 to 10 mg/L, the effective pH range of HA removal changes from 4.0-5.0 to 4.0-7.5. At increased coagulation pH, the ferric ions may still react with HA but unable to neutralize the surface charge completely. The residual concentrations of HA measured by fluorescence spectrophotometer are lower than those by TOC, as a consequence of the fluorescence-quenching effect. This demonstrates that the coagulation of HA by PFS at low pH is mainly due to charge-neutralization. The adsorption of the HA on the pre-formed iron hydroxide flocs is accompanied by the dissociation of Fe ions from the floc structure until the equilibrium has been reached, which is evidenced by the presence of the Fe-HA complexes in the solution during adsorption experiment. This is quite different from the characteristics of flocs formed by PFS associated with HA in the coagulation. Within the pH range investigated, the complex-formation and the hydrolysis are the two competitive reactions happened between the hydroxide ions in solution and the functional groups of HA. Therefore, the removal of HA is not caused by adsorbing onto the iron hydroxide resulted from PFS hydrolysis, but through the complex-formation between the PFS and the HA.

Adsorption↗

PubMed2002

Aminopolyphosphonate removal during wastewater treatment.

Phosphonates are used in large quantities in industry and household products as scale inhibitors and chelating agents. They are not biodegraded during wastewater treatment but are removed by adsorption processes. Field measurements from different wastewater treatment plants affirm that they are removed almost completely during wastewater treatment. Adsorption of nitrilotrismethylenephosphonic acid onto activated sludge, amorphous iron oxide and humic acids (HAs) was studied under controlled conditions. The adsorption onto HAs decreases sharply with increasing pH with negligible adsorption at pH above 6.5. Adsorption onto amorphous iron oxide follows a Langmuir behavior. The presence of 1 mM Ca doubles the maximum surface capacity at pH 7. Adsorption onto activated sludge is not very pH sensitive and is explained to a large extent by adsorption onto amorphous iron oxides, but the contribution of organic matter or other mineral phases cannot be ruled out.

Adsorption↗

PubMed2002

Transformation of the fungicide cyprodinil by a laccase of Trametes villosa in the presence of phenolic mediators and humic acid.

Xenobiotic chemicals can be transformed or covalently bound to humic materials by oxidoreductive enzymes present in terrestrial systems. Chemicals that are not substrates for oxidoreductive enzymes may undergo transformation in the presence of certain reactive compounds, which are often referred to as mediators. In this study, cyprodinil, a broad-spectrum fungicide, did not show any transformation when incubated alone with a laccase from Trametes villosa. It was transformed to a significant extent, however, when a mediator was present. All of the 13 tested mediators belonged to the group of naturally occurring phenols. With some exceptions (2,6-dimethoxyphenol, syringic acid, and ferulic acid), phenols substituted with one or two methoxy groups were very effective mediators. In experiments with 14C-labeled cyprodinil, the radioactive label was largely associated with brown transformation products that precipitated out of the aqueous solution. As determined by mass spectrometry, the products were mixed oligomers resulting from cross-coupling between cyprodinil and a mediator. The addition of large amounts of humic acid (HA) (400 mg/L) to the reaction mixtures involving the most effective mediators reduced cyprodinil transformation (42.6-68.6%) by 12-48%, probably due to an inhibitory effect. The inhibition decreased with decreasing concentration of HA. The addition of HA (400 mg/L) to the reaction mixtures involving the least effective mediators or no mediators (control) enhanced cyprodinil transformation (0.3-17.6%) by 2.9-17.1%, probably as a result of binding to HA.

Basidiomycota↗

PubMed2003

Distribution of rare earth elements in anionic, cationic and particulate fractions in boreal humus-rich streams affected by acid sulphate soils.

The abundance, fractionation and physicochemical forms of rare earth elements (REEs) were determined in five boreal humus-rich streams (dissolved organic carbon, DOC = 14-40 mg/l) affected by acid sulphate soils. The sampling was carried out during high-water flow in autumn when the acid sulphate soils are extensively flushed. The analytical procedures included ion-exchange experiments in field and ICP-MS determination. There was a general decrease in pH (range 4.5-6.2) and increase in the REE concentrations (La range 0.82-23 microg/l) as the proportion of the catchment cover of acid sulphate soils increased, explained by high amounts of REEs in the acidic runoff from such soils. In each stream, four different REE fractions were identified: (1) A cationic fraction, which is dominant in the REE-rich runoff from the acid sulphate soils and which is depleted in HREEs due to hydrochemical and/or geochemical processes, (2) an anionic fraction identified as humus-REE complexes, which in general is more abundant the higher the DOC concentrations and which also becomes increasingly abundant across the lanthanide series, (3) a fraction having a well-developed MREE enrichment, presumably consisting of colloidal REEs, and (4) a minor uncharacterised particle-associated fraction. The REE pool in the streams thus consists of several coexisting and contrasting REE species. The identification and quantification of such species is a prerequisite for the precise and accurate characterisation of the REE hydrochemistry of the streams.

Carbon↗

PubMed2003

Estimating sludge loadings to land based on trace metal sorption in soil: effect of dissolved organo-metallic complexes.

This paper describes the results of research examining the effect of dissolved organo-metallic complexes of copper (Cu) and zinc (Zn) from sewage sludge leachate on sorption by a humic-gley soil A-horizon, and the influence of such complexes on resultant sludge loading estimates. Sorption was described with Linear, Freundlich or Langmuir equations, and compared between a sample of sludge leachate (containing 97.4% of Cu and 63.2% of Zn as dissolved organo-metallic complexes) and a reference solution (which mimicked the leachate, except for a lack of dissolved organic material). This comparison revealed that dissolved organo-metallic complexes significantly depressed Cu and Zn sorption in the study soil. The isotherm equations were then used to estimate sludge-derived Cu and Zn loadings to soil in order to result in an "allowable" output concentration from the soil solution to the surrounding environment. These loadings, together with soil bulk density and "availability" of sludge Cu and Zn, were incorporated in a preliminary model to estimate sludge application rates which are acceptable in terms of off-site movement of these metals through leaching losses. In the absence of dissolved organo-metallic complexes (sorption from the reference solution), levels of Cu and Zn sorption in the study soil indicated a sludge application rate of approximately 3500 kg/ha. However, when Cu and Zn sorption from the sludge leachate with dissolved organo-metallic complexes was considered, calculated loading rates were reduced to approximately 690 kg-sludge/ha. This suggests that for sludge loading estimates based on soil sorption characteristics to be relevant to environmental protection, the sorption depressing effect of dissolved organo-metallic complexes should be quantitatively considered.

Adsorption↗