Characteristic transformation of humic acid during photoelectrocatalysis process and its subsequent disinfection byproduct formation potential

In this study, degradation of humic acid (HA) via photoelectrocatalysis (PEC) process and corresponding disinfection byproduct formation potential (DBPFP) were investigated. Particularly, structure variation and subsequent DBPFP of HA during PEC treatment were correlated. The PEC process was found to be effective in reducing dissolved organic carbon concentration by 75.0% and UV absorbance at 254 nm by 92.0%. Furthermore, 90.3% of haloacetic acids formation potential and 89.8% of trihalomethanes formation potential were reduced within 180 min. Based on molecular weight and resin fraction results, it was demonstrated that HA with large aromatic, hydrophobic and long aliphatic chain organics were transformed into small and hydrophilic organics during PEC process. Combined with the fourier transform infrared spectra and ¹³C nuclear magnetic resonance spectra analysis of HA fractions, it was concluded that phenolic hydroxyl and conjugated double bonds tended to be attacked by hydroxyl radicals during PEC process; these groups were reactive with chlorine to produce disinfection byproducts (DBP), especially trihalomethane and trichloroacetic acid. By contrast, amino, carboxyl and alcoholic hydroxyl groups were relatively difficult to be oxidized during PEC process; these groups had the potential to form dichloroacetic acid during chlorination. Results of these studies confirmed that PEC process was a safe and effective technique to decrease DBP formation significantly in water treatment plant.     

Evaluation of different treatment processes with respect to mutagenic activity in drinking water

Treatment processes which are applied in The Netherlands during the preparation of drinking water have been evaluated with regard to introduction and removal of organic mutagens as well as halogenated organics. It appeared that the most efficient processes in reducing mutagenic activity were activated carbon filtration and artificial dune recharge. In general these processes were also the most efficient in removing halogenated organics. Using low doses of chlorine dioxide (< 1 mg C10₂/1) for safety disinfection of drinking water, no change or substantial less mutagenic activity than by chlorination (1 mg Cl/1) was found. This counts too for the formation of halogenated organics. Transport chlorination of stored river Meuse water was able to introduce or activate mutagenic nitro organics which have not been found previously. Ozone treatment under field conditions showed mostly a tendency to decrease the activity of organic mutagens. It was also shown that dependent on the water quality and treatment conditions a slight increase of mutagenic activity occurred, but this activity would be reduced by increasing the ozone dose. It seems possible to optimalize the ozone treatment conditions regarding the level of ozone dose and the contact time to avoid an increase of mutagenic activity. Futhermore it was shown that when a mutagenic raw water source was used a proper combination of treatment processes is able to produce drinking water in which no mutagenic activity could be detected under the test conditions. Finally it is stated that before far-reaching decissions with respect to use mutagenicity data for a selection of water sources or treatment processes will be made, more information on the relation mutagenic activity from drinking water and effects on human health should become available.     

Electrochemical determination and characterization of surface active substances in freshwaters

Surface active material has been analyzed in samples of different freshwater systems: river water, groundwater and tap water, by electrochemical methods based on the measurement of the adsorption effects at the mercury electrode. Two electrochemical methods were used: the measurement of the suppression of the polarographic maxima and a.c. polarography. A rough characterization of predominant surface active compounds was performed through a comparison of the shape and the intensity of the electrochemical responses with those obtained with different model surfactants. It was found that humic substances represent predominant surface active substances in freshwater systems. The total surfactant activity corresponds to approx. 0.5–20 mg dm^?3 of humic substances.Anionic detergents were analyzed by the spectrophotometric methylene blue method. The highest values (100–300 μg dm^?3) were found in river water samples which were taken downstream from the city location. The total surfactant activity values of river water samples as measured by the electrochemical methods were only exceptionally influenced by the presence of detergents.     

Ultrafiltration membrane fouling by extracellular organic matters (EOM) of Microcystis aeruginosa in stationary phase: influences of interfacial characteristics of foulants and fouling mechanisms

This paper focused on the membrane fouling caused by extracellular organic matters (EOM) which was extracted from lab-cultured Microcystis aeruginosa in stationary phase. The characteristics of EOM such as molecular weight distribution, hydrophobicity and fluorescence were measured. It was found that high molecular weight (MW) and hydrophilic organics accounted for the major parts of algal EOM which was comprised of protein-like, polysaccharide-like and humic-like substances. Ultrafiltration (UF) experiments were carried out in a stirring cell and hydrophobic polyethersulfone (PES) membranes which carried negative charge were used. Prefiltration, calcium addition and XAD fractionation were employed to change the interfacial characteristics of EOM. Then the effects of these interfacial characteristics on flux decline, reversibility and mass balance of organics were compared. Algal EOM proved to cause serious membrane fouling during UF. The fraction of algal EOM between 0.45 μm and 100 kDa contributed a significant portion of the fouling. Hydrophobic organics in EOM tended to adhere to membrane surface causing irreversible fouling, while the cake layer formed by hydrophilic organics caused greater resistance to water flow due to hydrophilic interaction such as hydrogen bond and led to faster flux decline during UF. The results also indicated that the algal EOM was negatively charged and the electrostatic repulsion could prevent organics from adhering to membrane surface. In term of fouling mechanisms, cake layer formation, hydrophobic adhesion and pore plugging were the main mechanisms for membrane fouling caused by algal EOM.     

Magnetic ion-exchange resin treatment: impact of water type and resin use

Three raw waters of fundamentally different natural organic matter (NOM) character were treated by magnetic resin using a bench-scale method designed to mimic how the resin is used in continuous operation. Increasing water hydrophobicity resulted in reduced dissolved organic carbon (DOC) removal with removal of 56%, 33% and 25% for waters containing 21%, 50% and 75% hydrophobic NOM, respectively. Study of consecutive resin uses showed that the NOM in the hydrophobic water had high affinity for the resin shown by DOC removal of 65% after the first use of the resin. This dropped to 25% DOC removal after 15 consecutive resin uses. For the more hydrophilic waters, NOM removal remained consistent after each resin use. The hydrophobic sample contained higher MW NOM that was capable of blocking resin sites that prevented continual adsorption of organics on to the resin. The hydrophilic NOM containing a large proportion of hydrophilic acids was consistently removed to around 60%. The water containing algogenic-derived NOM was poorly removed by magnetic resin. Subsequent coagulation showed higher removal with increasing hydrophobicity.     

Suppression of phosphate liberation from sediment by using iron slag

In order to suppress the phosphate liberation from sediment to sea water, several suppressing materials such as four kinds of iron slag, river and sea sands, and glass bead were tested. The sediment and sea water were sampled from Hiroshima Bay which seemed to be a eutrophicated area. The suppressing materials were covered on the surface of sediment, and sea water was introduced in the aquarium. The concentrations of phosphate, sulfide and dissolved oxygen were measured during the incubation period under the condition of anaerobic state. The suppressing effects of slags, sea and river sands were compared with that of glass bead used as control materials, and the suppression efficiencies were measured. The suppression efficiency of glass bead was 54.1%, and those of slag-2, -3 and -4 were 97.3, 96.1 and 98.8%, respectively. The suppression efficiency depended on the amounts of slag used, and about 85% of liberated phosphate were suppressed by slag-3 of 7.5 kg m⁻². The sulphide ion generated under anaerobic state reacted with some metals on the surface of slags and sands, and the dissolution of precipitated phosphate (Fe-P, Al-P and Ca-P) was suppressed by formation of metal sulfide on the surface of slags and sands. The suppression mechanisms on phosphate liberation, such as covering, chemical and adsorption effects were proposed and discussed. The suppression by slag was mainly carried out by the adsorption effect, in addition to the covering effect.     

涂铁砂的直接过滤效果及其再生方法研究

以某低温、低浊江水为研究对象，用表面涂渍氧化铁的石英砂（简称涂铁砂）进行直接过滤试验，考察了涂铁砂对浊度和有机物的去除效果，并与天然石英砂的直接过滤效果进行了对比。试验结果表明，涂铁砂在去除浊度和有机物方面明显优于天然石英砂，但经反冲洗后的涂铁砂对有机物去除经很低。另外，对被穿透的滤柱进行了再生处理，发现用硫酸铝溶液可使涂铁帮的除污能力得到恢复，对浊度和有机物均有显著的去除效果。     

Studies on the effect of humic acids and phenol on adsorption-ultrafiltration process performance

Application of pressure-driven membrane processes, such as ultrafiltration (UF) and microfiltration (MF) for surface water treatment have become very popular during last decades. Membrane fouling by humic substances (HS) is one of the major limiting factors in these processes. In order to alleviate the unfavorable effects of the presence of HS in the feed on the process performance UF and MF are often combined with adsorption on powdered activated carbon (PAC). The main goal of the present study was to evaluate the effect of humic acid (HA) on membrane fouling during UF. Moreover, the effect of PAC addition to the feed on UF process, especially on flux decline was determined. The applicability of the adsorption-ultrafiltration (PAC/UF) system to purification of water containing low (phenol) and high molecular (HA) was also investigated. Three different polymer UF membranes, prepared from polysulfone (PSF), cellulose acetate (CA) or polyacrylonitrile (PAN) were applied. It was found that the membranes prepared from PSF and CA are very susceptible to fouling caused by HA. The permeate flux decreased for ca. 50% during UF of HA solution through the PSF membrane and for ca. 45%-through the CA membrane. In the case of the PAN membrane, a negligible effect of HA on the flux was observed. On the basis of the FTIR spectra it was found that the drop in the permeate flux through these membranes may result from interactions between the negatively charged functional groups present on the membrane surface, such as carboxyl groups (CA) and sulfone groups (PSF) with HA, which results in coating of the membrane surface with HA. When PAC was added to the feed containing HA, the permeate flux through the CA and PAN membranes was maintained on a practically unchanged level. However, in case of the PSF membrane, a 50% drop in the permeate flux in comparison with the flux value, when process was conducted without PAC addition was observed. That was supposed to be due to attractive forces among hydrophobic PAC particles, HA molecules and PSF membrane surface. The performed studies showed that the application of PAC/UF system was very effective in the removal of organic substances having both, low and high molecular weights. The role of PAC suspended in a feed in the PAC/UF system is the adsorption of low molecular organic compounds, which cannot be removed by UF alone.     

重力驱动微滤膜给水处理工艺特性与除污效能

采用浸没式重力驱动微滤膜系统处理松花江地表水,考察了不同重力下微滤膜通量的变化规律及对有机物、微生物和金属离子的去除效能。结果表明,提高重力驱动力可提升膜的初期通量,但长时间运行结果显示,较低重力驱动力反而对保持较高的稳定通量更为有利;浸没式重力驱动膜系统对地表水中的常规污染指标如浊度、UV₂₅₄和细菌总数具有很好的去除效果,去除率分别可达99. 8%、93. 4%和98. 6%以上;同时对典型金属离子的去除率也可达到90%以上,说明浸没式重力驱动微滤膜系统具有很好的抗污染性能和去除污染物能力,可用于以地表水为源水的饮用水净化中。     

聚硅酸铁混凝剂对腐殖酸的氧化性能研究

以水玻璃、硫酸亚铁及氯酸钠为原料，采用独特共聚工艺制备了聚硅酸铁（PSF）混凝剂，考察了PSF对腐殖酸（HA）的氧化性能及高岭土对被氧化HA的吸附效果，同时进行了复合铝铁（PFA）的对比试验。结果表明，PSF是一种具有氧化性能的混凝剂，因其改变了HA的分子结构，从而使HA的表面性质以及HA／水溶液的界面性质发生变化，使亲水性HA转化为憎水性HA,导致高岭土对其吸附性能增强；不同pH值下PSF均有良好的氧化性能，而PFA仅在酸性时具有氧化性；pH值对HA、PSF、高岭土之间的络合模式具有较大影响，中性下时DOMs的去除效果较好。     

两种膜的前端处理技术减缓膜污染的试验研究

通过超滤膜过滤粉末活性炭预处理长江水和混凝沉淀预处理太湖水的上清液试验,比较各工艺中有机物极性含量的变化,结合膜的扫描电镜照片,探讨粉末活性炭和混凝沉淀预处理技术对膜污染的减缓作用。结果表明,疏水性有机物是造成膜污染的主要因素,亲水性有机物对膜污染的影响较小。超滤膜分别过滤经20 mg/L投量的粉末活性炭预处理的长江水样和25 mg/L投量的聚合氯化铝预处理的太湖水样时,相比直接过滤2种原水,超滤膜反洗后膜通量可有效恢复。粉末活性炭和混凝沉淀预处理后,膜表面形成的滤饼层较松散,易被周期性反洗排出膜组件,滤饼层可阻止疏水性有机物直接沉积在膜表面,减缓超滤膜污染,同时也可提高超滤膜出水的化学安全性。     

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.     

炭龄对活性炭工艺去除南水北调水中有机物的影响

基于北方某水厂中试基地,采用新炭、2.5~3.5年炭、4.5~5.5年炭等不同炭龄的活性炭滤柱,进行为期1年的连续运行,对比研究炭龄对南水北调水源水中有机物去除效果的影响。结果表明,长期运行稳定的活性炭滤柱,主要通过生物作用去除水中的有机物;2.5~3.5年和4.5~5.5年炭龄滤柱对有机物的去除效果差异较小,但二者对三氯甲烷的去除效果优于生物膜不稳定的新炭滤柱;通过高通量测序解析发现,鞘氨醇单胞菌、DSSF69等是优势功能菌,炭龄长的生物多样性更丰富,生物膜系统更稳定。此外,活性炭滤柱对有机物的去除效果与进水有机物的污染程度相关,当进水溶解性有机物浓度较低时,活性炭滤柱会出现吸附物质逆扩散的现象,所以当水质较好时,活性炭滤池的有机物去除效果会减弱。     

颗粒活性炭吸附去除黄浦江原水中有机物的研究

采用超滤膜法分析了黄浦江原水和水厂常规工艺处理出水中有机物的分子质量（MW）分布以及颗粒活性炭（GAC）在不同吸附阶段吸附去除不同分子质量有机物的性能.试验结果表明,黄浦江原水及常规工艺出水中的溶解性有机物（DOC）以小分子为主,并主要集中在MW为10～30 ku和MW＜1 ku的区间;活性炭吸附出水中的溶解性有机物仍然主要集中在小分子区间;吸附初期的活性炭对有机物的去除能力较强,其中对CODMn的去除率＞83%,对UV254的去除率＞90%;随着通水倍数的增大则活性炭的吸附能力逐渐下降,当通水倍数达到6 590.9时,对CODMn和UV254的去除率都只有25%左右;活性炭吸附的各个阶段对小分子有机物的去除率均较高,而对大分子有机物的去除率则较低,从吸附初期到吸附后期,对小分子有机物的去除率高出对大分子有机物的去除率,其百分比从10%增大到30%.     

生物陶粒过滤工艺处理微污染原水研究

采用陶粒滤料处理微污染原水,研究了具有不同结构特性的陶粒滤料对有机物、藻类及浊度的去除效果。结果表明：对高锰酸盐指数的去除率〉25％,最高可达38％;对氨氮的去除率〉60％,最高为70％;对亚硝酸盐氮的去除率〉98％;对藻类的去除率可达95％以上;出水浊度〈1NTU。此外,具有较大的比表面积、发达的孔隙及较多的连通等特性的陶粒处理效果好,适合作为水厂工艺改进的首选滤料。     

Interaction of trace elements in acid mine drainage solution with humic acid

The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied by leaching tests. Considerable amounts of Mn, Fe, Al, Ni and Co are dissolved in both simulated rain water (pH 4) and 10 mg L(-1) humic acid (HA) solution (Aldrich humic acid, pH 7). Due to the presence of oxidizing pyrite and sulfide minerals, the pH in both leachates decreases down to approximately 3 combined with high sulfate concentrations typical to acid mine drainage (AMD) water composition. Interaction of the acidic leachates upon mixing with ground- and surface water containing natural organic matter is simulated by subsequent dilution (1:100; 1:200; 1:300; 1:500) with a 10 mg L(-1) HA solution (ionic strength: 10(-3) mol L(-1)). Combining asymmetric flow field-flow fractionation (AsFlFFF) with UV/Vis and ICP-MS detection allows for the investigation of metal ion interaction with HA colloid and colloid size evolution. Formation of colloid aggregates is observed by filtration and AsFlFFF depending on the degree of the dilution. While the average HA size is initially found to be 2 nm, metal-HA complexes are always found to be larger. Such observation is attributed to a metal induced HA agglomeration, which is found even at low coverage of HA functional groups with metal ions. Increasing the metal ion to HA ratio, the HA bound metal ions and the HA entities are growing in size from <3 to >450 nm. At high metal ion to HA ratios, precipitation of FeOOH phases and HA agglomeration due to colloid charge neutralization by complete saturation of HA complexing sites are responsible for the fact that most of Fe and Al precipitate and are found in a size fraction >450 nm. In the more diluted solutions, HA is more relevant as a carrier for metal ion mobilization.     

垂流式人工湿地处理官厅水库入库水研究

在官厅水库永定河入库口处进行了垂流式人工湿地对入库河水的净化试验 ,结果表明 ,在渗滤时间 <1h时垂流式人工湿地对河水就有较好的净化效果 (对有机污染物和NH+ 4 -N的去除率都能达到 80 %左右 ,对TN和TP的去除率为 40 %左右 )。     

Evidence from surface tension and fluorescence data of a pyrene-assisted micelle-like assemblage of humic substances

Surface activity and fluorescence of humic substances (HS) and HS/pyrene solutions were monitored under various pH conditions. For HS alone the surface tension of the solutions decreased with increasing acidity, with a minimum at around pH 4. This effect, which is a consequence of an increase in the amphiphilic character of structures, is much more pronounced in humic (HA) than in fulvic acids (FA). The addition of pyrene (0.1 micromolL(-1)) results, for HA, in a marked reduction in the migration of amphiphilic species to the solution surface. FA profiles are not modified in presence of pyrene at that concentration. A decrease in the pyrene I1/I3 ratio in HS solutions shows that below pH 9 pyrene molecules react progressively to the change to a more hydrophobic environment, the greatest effect being observed at around pH 6 to 7. These signals are followed by a significant increase in the pyrene excimer fluorescence (lambda(exc)/lambda(em)=334 nm/450 nm), which is a consequence of the proximity of pyrene molecules. For FA, the I1/I3 decrease is less significant and no excimers develop. This set of effects is explained in view of conformational adjustments of HS, mainly HA, which become arranged in micelle-like domains in aqueous solution, the aromatic moieties being assembled around the pyrene molecules.     

重庆五座水厂水的有机物致突变活性比较

采用固相萃取技术（GDX-120大孔树脂）于春、夏、冬季对以嘉陵江为水源的A厂和B厂，以长江为源的C厂和D厂以及以两江汇水为水源的E厂提取进厂水和出厂水中的有机物，以Ames试验评估其致突变活性。结果表明：①现行水处理工艺在低温季节及源水污染较为严重的情况下可降低出厂水的致突变活性，而在高温季节及源水污染不太严重的情况下可导致出厂水的致突变活性升高；②以嘉陵江为水源的水厂出水致突变危害均高于以长江为水源的水厂出水；③水中有机物的致突变活性以移码型为主，TA98是测试的敏感菌株。     

Mutagenic activity in drinking water prepared from groundwater: a survey of ten cities in The Netherlands

A survey of the mutagenic activity (Ames Salmonella/microsome assay) in drinking water prepared from groundwater in 10 cities of The Netherlands is presented. Mutagenic activity with strain TA98 with S-9 mix was found in the drinking water of six cities. There are strong indications that this mutagenic activity is caused by organics of natural origin. In the drinking water of three cities, trichloroethane, trichloroethene and tetrachloroethene were detected, which indicates that in these water-catchment areas organic pollutants have reached groundwater.