硫酸铝中Fe3+、Al3+含量的快速检测法

为快速、准确地测定净水剂硫酸铝中的Fe^3＋、Al^3＋含量，研究了采用EDTA络合-铜盐返滴定法的可行性，并考察了该方法的影响因素。结果表明，在优化试验条件下该方法的加标回收率为95．2％-103．5％，可实现对净水剂硫酸铝中Fe^3＋、Al^3＋的连续测定，并具有快速、简便、准确的特点。     

硫酸铝中Fe3+、Al3+含量的快速检测法

为快速、准确地测定净水剂硫酸铝中的Fe3+、Al3+含量,研究了采用EDTA络合-铜盐返滴定法的可行性,并考察了该方法的影响因素.结果表明,在优化试验条件下该方法的加标回收率为95.2%～103.5%,可实现对净水剂硫酸铝中Fe3+、Al3+的连续测定,并具有快速、简便、准确的特点.     

Influence of chitosan characteristics on the coagulation and the flocculation of bentonite suspensions

Ten chitosan preparations with different molecular weights (MW) and degrees of deacetylation (DD) were tested for coagulation of 5 g L(-1) bentonite suspensions at pH 5 and 7 in demineralized water (DW) and in tap water (TW). Coagulation was better in TW than in DW for every condition and lower doses of chitosan were required at pH 5 than at pH 7. More than 95% of residual turbidity (after sedimentation in the absence of chitosan) was removed using less than 0.10 mg L(-1) chitosan in either TW or DW at pH 5 or in TW at pH 7. Higher doses were required for removal of turbidity in DW at pH 7, but in all cases the effective concentrations of chitosan were much lower than required for complete neutralization of the negative charge on the bentonite particles. Removal of turbidity was best for the higher MW chitosans in either the B series (89.5% DD) or the C series (95% DD) of chitosans. Overall, the results were consistent with destabilization of bentonite by the combined mechanisms of electrostatic patch and bridging. The improved performance of chitosan in TW could have been due to improved attachment to bentonite due to the presence of sulfate and other counter-ions in TW.     

Effect of various parameters on the ultraflocculation of fine sorbent particles,used in the wastewater purification from organic contaminants

A sorbent (Organosorb) is used in the wastewater purification from organic contaminants, here simulated by tetradecane. A short hydrodynamic treatment in a rather intense hydrodynamic field (G>10(3)) (called ultraflocculation) is applied to the sorbent suspension to which a flocculant is added. The efficiency of removal of the sorbent is studied. The sorbent concentration, the flocculant concentration, the treatment time, the organic pollutant (which has to be sorbed by the sorbent), the detergent (used for the emulsification of the pollutant), the pH and the calcium concentration of the water all influence the flocculation efficiency (E) of the sorbent particles. For each set of these parameters there exists an optimum intensity of the hydrodynamic treatment at which maximum flocculation efficiency is reached. An increase in the optimum intensity of the hydrodynamic field corresponds to an increased floc break-up, and consequently a lower maximum flocculation efficiency.     

Simulating the performance of fixed-bed granular activated carbon adsorbers: removal of synthetic organic chemicals in the presence of background organic matter

Granular activated carbon (GAC) adsorption is an effective treatment technology for the removal of synthetic organic chemicals (SOCs) from drinking water supplies. This treatment process can be expensive if not properly designed. Application of mathematical models is an attractive method to evaluate the impact of process variables on process design and performance. Practical guidelines were developed to select an appropriate model framework and to estimate site-specific model parameters to predict GAC adsorber performance. Pilot plant and field-scale data from 11 different studies were utilized to investigate the effectiveness of this approach in predicting adsorber performance in the presence of background organic batter (BOM). These data represent surface and ground water sources from four different countries. The modeling approach was able to adequately describe fixed-bed adsorber performance for the purpose of determining the carbon usage rate and process design variables. This approach is more accurate at predicting bed life in the presence of BOM than the current methods commonly used by practicing engineers.     

The impact of differing cell and algogenic organic matter (AOM) characteristics on the coagulation and flotation of algae

The aim of this study was to compare the coagulation and flotation of different algae species with varying morphology and algogenic organic matter (AOM) composition in order to link physical and chemical algae characteristics to treatment. Microcystis aeruginosa (cyanobacteria), Chlorella vulgaris (green algae), Asterionella formosa and Melosira sp. (diatoms) were treated by coagulation with aluminium sulphate and flotation. The AOM was extracted and treated separately. Analyses included cell counts, dissolved organic carbon, aluminium residual and zeta potential. Removal efficiencies in the range 94-99% were obtained for each species. Cells, AOM and aluminium were concurrently removed at a coagulant dose that was related on a log-log basis to both cell surface area and total charge density, although the relationship was much stronger for the latter. This was attributed to a significant proportion of the coagulant demand being generated by the AOM. The implications of such findings are that relatively simple charge measurements can be used to understand and control coagulation and flotation of algae.     

Chemical coupling of photocatalysis with flocculation and adsorption in the removal of organic matter

An experimental investigation was made to study the effects of chemical coupling of flocculation and adsorption with photocatalysis in treating persistent organic pollutants in wastewater. The photocatalysis alone showed initial reverse reaction when titanium oxide (TiO(2)) was used in catalysis. The effect of the pretreatment of adsorption with powdered activated carbon (PAC) on photocatalysis was studied. The results showed that PAC adsorption followed by photocatalysis was not effective in alleviating reverse reaction. On the other hand, when PAC and TiO(2) were added simultaneously, the reverse reaction was eliminated. Further, the organic removal was also improved by simultaneous PAC and TiO(2) additions. When flocculation with ferric chloride (FeCl(3)) was used as pretreatment, the organic removal efficiency was superior. The initial reverse reaction was also eliminated/minimized. However, inadequate doses of FeCl(3) (less than 30 mgl(-1)) resulted in initial reverse reaction and inferior DOC removal.     

Simplification of the IAST for activated carbon adsorption of trace organic compounds from natural water

Recent studies have shown that the ideal adsorbed solution theory (IAST) coupled with the concept of equivalent background compound (EBC) can be simplified for describing trace organic compound adsorption from natural water, provided that the adsorbent surface loading is dominated by competing natural organic matter. The resulting simplified IAST has been used to reduce the complexity of kinetic models for various dynamic adsorption processes. In order to be correctly applied, however, the simplified IAST requires some additional clarification and a quantitative evaluation of the deviation caused by the simplifying assumption. In this study, we derive a simple equation that relates the relative deviation of the simplified IAST directly to the molar ratio of EBC and trace organic compound surface loadings and their Freundlich isotherm exponents. We then verify the simplified IAST using the original IAST and experimental isotherm data from the literature for trace organic compounds at various initial concentrations in natural water. By further assuming that the adsorbed amount of the EBC is substantially greater than what remains in solution, a new pseudo single-solute isotherm equation is derived and a simple relation is subsequently established between the carbon dose and the remaining trace compound concentration. The results show that the adsorption capacity and relative removal of a trace organic compound at any carbon dose can be estimated directly with the simple equations developed here and data from a single isotherm experiment for the target compound conducted in the natural water of interest.     

A methodology for ranking and hazard identification of xenobiotic organic compounds in urban stormwater

The paper presents a novel methodology (RICH, Ranking and Identification of Chemical Hazards) for ranking and identification of xenobiotic organic compounds of environmental concern in stormwater discharged to surface water. The RICH method is illustrated as a funnel fitted with different filters that sort out problematic and hazardous compounds based on inherent physico-chemical and biological properties. The outcomes of the RICH procedure are separate lists for both water phase and solid phase associated compounds. These lists comprise: a justified list of compounds which can be disregarded in hazard/risk assessments, a justified list of stormwater priority pollutants which must be included in hazard/risk assessments, and a list of compounds which may be present in discharged stormwater, but cannot be evaluated due to lack of data. The procedure was applied to 233 xenobiotic organic chemicals (XOCs) of relevance for stormwater. Of these 233 compounds, 121 compounds were found to be priority pollutants with regard to solids phases (i.e. suspended solids, soil, or sediments) when stormwater is discharged to surface water and 56 compounds were found to be priority pollutants with regard to the water phase. For 11% of the potential stormwater priority pollutants the screening procedure could not be carried out due to lack of data on basic physico-chemical properties and/or data on bioaccumulation, resistance to biodegradation, and ecotoxicity. The tiered approach applied in the RICH procedure and the focus on the phases relevant for monitoring or risk assessment in the aquatic environment refines the list of "compounds of concern" when compared to the outcome of existing classification schemes. In this paper the RICH procedure is focused on effects in the aquatic environment exemplified with xenobiotic organic compounds (XOCs) found in urban stormwater, but it may be transferred to other environmental compartments and problems. Thus, the RICH procedure can be used as a stand-alone tool for selection of potential priority pollutants or it can be integrated in larger priority setting frameworks.     

The influence of water treatment processes on the presence of organic surrogates and mutagenic compounds in water

The effects of granular activated carbon filtration and of the combination of ozonation and GAC filtration on the quality of Rhine water were studied in a pilot plant. The scope of the study was to compare both systems in relation to the removal of organic contaminants in water, and to the reduction of the side effects of chlorination. The water quality was measured with organic surrogate parameters (organohalogen, -nitrogen, -phosphorus and -sulphur) and in bacterial mutagenicity assays.In this particular setting, the combination of ozonation and GAC filtration was superior in all points to GAC filtration alone. The effects of ozonation are sometimes quite different, depending on the type of water treated. Its positive influence should be confirmed in a local situation.As GAC treatment causes a shift towards formation of more brominated THM after chlorination, special attention was given to this item. A higher inorganic bromide/DOC ratio resulted in higher brominated THM concentrations after chlorination. However, the mutagens formed during chlorination in presence of more inorganic bromide could be inactivated more easily by rat liver homogenate than in the normal setting. The results of this study confirmed earlier findings stating a negative influence of chlorination on water quality.     

Fate and transport of elemental copper (Cu0) nanoparticles through saturated porous media in the presence of organic materials

Column experiments were performed to assess the fate and transport of nanoscale elemental copper (Cu⁰) particles in saturated quartz sands. Both effluent concentrations and retention profiles were measured over a broad range of physicochemical conditions, which included pH, ionic strength, the presence of natural organic matter (humic and fulvic acids) and an organic buffer (Trizma). At neutral pHs, Cu⁰ nanoparticles were positively charged and essentially immobile in porous media. The presence of natural organic matter, trizma buffer, and high pH decreased the attachment efficiency facilitating elemental copper transport through sand columns. Experimental results suggested the presence of both favourable and unfavourable nanoparticle interactions causes significant deviation from classical colloid filtration theory.     

Fate of coagulant species and conformational effects during the aggregation of a model of a humic substance with Al13 polycations

A model of a humic substance (MHS) obtained from auto-oxidation of catechol and glycine, was aggregated at pH 6 and 8 with Al(13) polycations. The fate of Al(13) coagulant species upon association with MHS functional groups was studied using solid state (27)Al Magic-angle spinning (MAS) NMR and CP-MAS (13)C NMR. Electrophoretic measurements and steady-state fluorescence spectroscopy with pyrene as a fluoroprobe, were combined to investigate structural re-organization of humic material with aluminum concentration. MAS (27)Al NMR revealed that the coagulant species are Al(13) polycations or oligomers of Al(13) units at both pHs. CP MAS (13)C spectra indicated that, at low Al concentration, hydrolyzed aluminum species bind selectively to carboxylic groups at pH 6 and to phenolic moieties at pH 8. At higher coagulant concentrations, the remaining functional groups also interact with hydrolyzed Al to yield similar CP MAS (13)C spectra in the optimum concentration range. Negative values of electrophoretic mobility were obtained at optimum coagulant concentrations even though an overall charge balance was achieved between MHS anionic charge and Al(13) cationic charge at pH 6. The polarity-sensitive fluorescence of pyrene revealed that the interaction of Al(13) coagulant species with MHS functional groups induces the formation of intramolecular hydrophobic microenvironments. Such structural changes were reversed upon further addition of Al(13) polycations.     

Mechanistic and kinetic evaluation of organic disinfection by-product and assimilable organic carbon (AOC) formation during the ozonation of drinking water

Ozonation of drinking water results in the formation of low molecular weight (LMW) organic by-products. These compounds are easily utilisable by microorganisms and can result in biological instability of the water. In this study, we have combined a novel bioassay for assessment of assimilable organic carbon (AOC) with the detection of selected organic acids, aldehydes and ketones to study organic by-product formation during ozonation. We have investigated the kinetic evolution of LMW compounds as a function of ozone exposure. A substantial fraction of the organic compounds formed immediately upon exposure to ozone and organic acids comprised 60-80% of the newly formed AOC. Based on experiments performed with and without hydroxyl radical scavengers, we concluded that direct ozone reactions were mainly responsible for the formation of small organic compounds. It was also demonstrated that the laboratory-scale experiments are adequate models to describe the formation of LMW organic compounds during ozonation in full-scale treatment of surface water. Thus, the kinetic and mechanistic information gained during the laboratory-scale experiments can be utilised for upscaling to full-scale water treatment plants.     

Factors affecting the rejection of organic solutes during NF/RO treatment--a literature review

The incomplete rejection of certain pesticides, disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds has been reported during full- and pilot-scale high-pressure membrane applications. Since the removal of these compounds in water and wastewater treatment applications is of great importance where a high product water quality is desired, an understanding of the factors affecting the permeation of solutes in high-pressure membrane systems is needed. In this paper, findings of a comprehensive literature review are reported, targeting membrane rejection mechanisms and factors affecting rejection. The following key solute parameters were identified to primarily affect solute rejection: molecular weight (MW), molecular size (length and width), acid disassociation constant (pKa), hydrophobicity/hydrophilicity (log Kow), and diffusion coefficient (Dp). Key membrane properties affecting rejection that were identified include molecular weight cut-off, pore size, surface charge (measured as zeta potential), hydrophobicity/hydrophilicity (measured as contact angle), and surface morphology (measured as roughness). In addition, feed water composition, such as pH, ionic strength, hardness, and the presence of organic matter, was also identified as having an influence on solute rejection. From the knowledge gained during the literature review, a rejection diagram was proposed, which qualitatively allows prediction of solute rejection if certain solute and membrane properties are known.     

Behaviour of biological reactors in the presence of toxic compounds

A model of the influence of toxic compounds on the biological processes in waste water treatment reactors has been developed. The model predicts the behaviour of reactors influenced by toxic compounds acting as non-competitive inhibitors. The effects of a toxic compound on a process is quantified in terms of the inhibition coefficient K_i for the compound and the reactor resistance to inhibition values. The proposed model was utilized for the analysis of data obtained in a packed bed reactor for denitrification in the presence of chromium Cr⁶⁺. The inhibition coefficient for chromium was found to be 1.2 mg 1⁻¹ Cr⁶⁺ and the reactor resistance to inhibition was 2.9 mg 1⁻¹ Cr⁶⁺.     

Role of biodegradation in the removal of pharmaceutically active compounds with different bulk organic matter characteristics through managed aquifer recharge: batch and column studies

Natural water treatment systems such as bank filtration have been recognized as providing effective barriers in the multi-barrier approach for attenuation of organic micropollutants for safe drinking water supply. In this study, the role of biodegradation in the removal of selected pharmaceutically active compounds (PhACs) during soil passage was investigated. Batch studies were conducted to investigate the removal of 13 selected PhACs from different water sources with respect to different sources of biodegradable organic matter. Neutral PhACs (phenacetine, paracetamol, and caffeine) and acidic PhACs (ibuprofen, fenoprofen, bezafibrate, and naproxen) were removed with efficiencies greater than 88% from different organic matter water matrices during batch studies (hydraulic retention time (HRT): 60 days). Column experiments were then performed to differentiate between biodegradation and sorption with regard to the removal of selected PhACs. In column studies, removal efficiencies of acidic PhACs (e.g., analgesics) decreased under conditions of limited biodegradable carbon. The removal efficiencies of acidic PhACs were found to be less than 21% under abiotic conditions. These observations were attributed to sorption under abiotic conditions established by a biocide (20 mM sodium azide), which suppresses microbial activity/biodegradation. However, under biotic conditions, the removal efficiencies of these acidic PhACs were found to be greater than 59%. This is mainly attributed to biodegradation. Moreover, the average removal efficiencies of hydrophilic (polar) neutral PhACs (paracetamol, pentoxifylline, and caffeine) with low octanol/water partition coefficients (log K_ow less than 1) were low (11%) under abiotic conditions. However, under biotic conditions, removal efficiencies of the neutral PhACs were greater than 98%. In contrast, carbamazepine persisted and was not easily removed under either biotic or abiotic conditions. This study indicates that biodegradation represents an important mechanism for the removal of PhACs during soil passage.     

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.     

Comparison of selected volatile organic compounds during the summer and winter at urban sites in New Jersey

This paper presents a comparison of summer and winter levels of twenty-five selected volatile organic compounds (VOC) measured as part of the New Jersey project on Airborne Toxic Elements and Organic Substances (ATEOS). Most of the selected VOC were found in the range of 0.01–1.00 ppbv, with the exception of toluene (1–5 ppbv) and benzene (1–3 ppbv). However, peak levels of many compounds increased more than 100 fold during specific pollutant episodes. Generally, VOC levels were higher in the winter than the summer. Day to day variations of measured aromatic VOC showed significant correlations at each site suggesting an area source (motor vehicles), while there was little relationship between chlorinated species. During summer oxidant episodes, selected VOC increased from 2–10 times at Newark and Elizabeth, but not at Camden. In the winter, nocturnal temperature inversions caused levels of selected VOC to increase from 2–3 times seasonal average at all sites.     

Organic compounds in typical surface waters of the northern part of Western Siberia

The article presents the results of hydrochemical research conducted at the end of August 2014 and in spring 2013 in the northern part of Western Siberia. The research concerns unfiltered waters of small streams, medium-sized rivers, the Ob’ River and two large thermokarst lakes. A special mobile laboratory enabled the research team to conduct many on-site analyses several hours after the collection of samples. The results have been assessed in terms of their significance for the general quality evaluation of the examined waters and the nature of organic substances contained in the waters. Additionally, the paper discusses results of chemical and physical tests to evaluate the amount of organic substances. General features concerning the evaluation of organic compounds among different type of surface waters have been suggested on the basis of the studies.     

Sorbic acid as a quantitative probe for the formation, scavenging and steady-state concentrations of the triplet-excited state of organic compounds

Sorbic acid (trans,trans-hexadienoic acid) was developed as a probe for the quantification of the formation rate, overall solution scavenging rate and steady-state concentrations of triplet-excited states of organic compounds. The method was validated against literature data for the quenching rate constant of triplet benzophenone by tyrosine obtained by laser flash photolysis and by Stern-Volmer plots of phosphorescence quenching. In contrast to these methods, the probe method does not require knowledge of the optical properties of triplets to monitor their quenching. Moreover, the probe method permits simultaneous quantification of triplet formation, quenching and steady-state concentrations during illumination of complex chromophore mixtures, such as natural organic matter (NOM), with polychromatic light >315 nm. Application of the method to de-aerated Suwannee River NOM illuminated with polychromatic light (315-430 nm) resulted in a triplet quantum yield of 0.062.