利用强化混凝去除水源水中天然有机物的研究进展

总结了近年来利用强化混凝去除水源水中天然有机物的研究，重点讨论了其作用机理和主要影响因素。水源水中天然有机物的含量和成分会因水源地和时间的不同而存在差异，对水源水中天然有机物的了解是保证强化混凝效果的基本前提。不同混凝条件下，强化混凝的主导作用机理不同。铁盐混凝剂、较低pH值、较高混凝剂投量和阳离子有利于提高强化混凝的效果。     

强化混凝去除水中的腐殖质

通过一系列试验对混凝去除水中的腐殖质的影响因素进行了评价。结果表明 ,pH值是影响水中腐殖质去除效果的一个关键因素 ,当水中腐殖质浓度为 10 .0mg L ,铝盐作混凝剂时 ,去除腐殖质的最佳pH值在 6.2— 6.6范围内 ;腐殖质浓度升高时 ,最佳pH值向酸性方向偏移。强化混凝调节pH值虽然增加了酸碱费用 ,但是它可以减少混凝剂投量 ,减轻污泥处理负担 ,其总体进行费用并没有增加 ,可认为是一种可行的运行方式     

强化混凝去除水中的腐殖质

通过一系列试验对混凝去除水中的腐殖质的影响因素进行了评价。结果表明，pH值是影响水中腐殖质去除效果的一个关键因素，当水中腐殖质浓度为10．0mg/L，铝盐作混凝剂时，去除腐殖质的最佳pH值在6．2-6．6范围内；腐殖质浓度升高时，最佳pH值向酸性方向偏移。强化混凝调节pH值虽然增加了酸碱费用，但是它可以减少混凝剂投量，减轻污泥处理负担，其总体进行费用并没有增加，可认为是一种可行的运行方式。     

改性膨润土联合混凝剂处理微污染水中有机物

采用十二烷基多糖苷季铵盐作为改性剂制备改性膨润土,研究了改性膨润土联合混凝剂去除有机物的效果,考察了有机改性剂用量、微波辐射功率、辐射时间、膨润土投加量、pH值对有机物去除效果的影响,探讨了改性膨润土的改性和去除机理。结果表明,经微波改性后,实现了十二烷基多糖苷季铵盐阳离子对膨润土的插层,增大了层间距,提高了膨润土的吸附性能。联合混凝剂投加改性膨润土能够改善絮凝性能,显著提高有机物的去除效果。在最佳条件下,改性膨润土与PAC联合后的强化混凝,对初始浓度15.3 mg/L的微污染水中有机物的去除率达到95%以上,吸附符合Freundlich吸附等温方程。     

滦河水体溶解性有机物的综合分级表征及其混凝去除过程

天然水体溶解性有机物(DOM)是微污染物的潜在载体,是消毒副产物的主要前驱物,自身又可能成为微污染物,因此研究其内在特性和去除机理有着重要的基础性科学意义.本研究综合利用化学、物理分级方法(即树脂和超滤分级法),对中国北方典型饮用水源--滦河水体的DOM进行全面分级表征.此水体DOM基本化学分级特征是憎水酸(HoA)、亲水性物质(HiM)含量较高,且具有季节稳定性;其物理分级特征是分子量＜1 kDa及3 kDa～10 kDa的组分含量较高,也表现出一定的时间稳定性.选用工业聚合铝(PAC)研究此DOM的基本混凝特征和内在混凝机理,结果表明,强憎水部分HoA及3 kDa～10 kDa间的有机物较易被去除,而较大分子量范围10 kDa～30 kDa间的有机物去除率较低,说明混凝过程中此DOM的物理性质不起主要作用,而化学性质更为重要.特别对DOM各组分作进一步(结合)分级研究,发现HoA主要在＞10 kDa范围.＜1 kDa的有机物中主要为HiM,但其中还含有HoA和弱憎水酸(WHoA),这使特定条件下部分＜1 kDa有机物被混凝去除成为可能.另外,HoA中按分子量大小仍可分为易去除和难去除部分,但分布不连续,易去除部分在3 kDa～10 kDa和＞30 kDa区间,而其10 kDa～30 kDa部分较难去除,说明可能存在其他结构性影响因素,值得深入研究.     

荷负电超滤膜同时去除水中天然有机物和铅离子

通过特定的化学反应对截留分子量为30 kD的再生纤维素(RC)超滤膜进行改性,得到荷负电超滤膜,并研究了其表面荷电性能。选用腐殖酸作为天然有机物的代表物质,研究荷负电改性膜同时去除溶液中腐殖酸和铅离子,主要考察了pH值和腐殖酸铅离子络合作用对两者截留率的影响,并对比了荷负电膜和未改性膜去除天然有机物和铅离子的研究结果。得到如下结论:(1)在酸性及中性溶液环境下,随着pH值的升高,荷负电超滤膜对腐殖酸和铅离子的截留率都提高。(2)铅离子与腐殖酸共存时,腐殖酸铅离子络合体的荷负电性相比于原腐殖酸分子降低,荷负电超滤膜对混合溶液中腐殖酸的截留率有一定程度降低,络合在腐殖酸表面的铅离子随着腐殖酸的截留而被截留,铅离子截留率得到一定程度提升。(3)由于腐殖酸与铅离子络合体带负电,其与荷负电膜之间存在静电作用,所以荷负电改性膜对腐殖酸和铅离子的截留率比未改性中性膜高。     

介质加载混凝过程中磷和溶解性有机物的去除特征及混凝机理

为考察介质加载混凝过程中污染物去除特征与探讨混凝机理,考察了不同形态的磷和溶解性有机物(DOM)的变化,并结合混凝絮体粒径与形貌,分析了介质加载的混凝机理。结果表明：溶解性污染物主要去除机制为聚合氯化铝(PAC)水解产物的吸附和螯合作用,高芳香性、腐殖化和分子质量为4 000~50 000 Da的DOM去除率较高;石英砂可强化去除悬浮态磷及腐殖酸类DOM;磁种可强化有机磷、${\rm{PO}}_4^{3 - }$-P和DOM的去除效果;回收磁种的微絮体结构使其对磷与大分子DOM具有更好的去除效果。介质加载混凝过程的关键作用在于形成密实性絮体,从而增强了絮体的强度和沉降性能,实现了污泥减量。研究结果可为介质加载混凝在水处理中的推广应用提供参考。     

强化混凝去除尖针杆藻

嘉陵江水系藻类暴发,水源水中的藻类在水厂前处理工艺中难以去除,造成该流域附近10余个水厂发生滤池堵塞现象,其中个别水厂滤池反冲洗周期由正常情况的24 h缩短至2~3 h,严重影响净水厂的正常运行,使得制水能力大幅降低。针对藻类（优势藻为硅藻中的针杆藻）暴发问题,通过对比PAFS、PAC和PFC3种混凝剂的除藻除浊效果,选取PAFS为最佳混凝剂;通过添加预氧化剂和助凝剂强化混凝除藻效果,其结果表明,使用助凝剂PDMDAAC的对PAFS的助凝效果最好,其余药剂结合PAFS的除藻效果为PPC〉ClO2〉PAM〉H2O2〉HCA-1,并将其应用到现有水厂,结果表明,0.6mg/L PDMDAAC＋25 mg/L PAFS在水厂混凝沉淀,尖针杆藻含量降至49×104~55×104cells/L,其除藻率可达70%~75%,大大减轻了滤池的运行负荷,使得水厂运行恢复到正常水平。     

强化混凝去除尖针杆藻

嘉陵江水系藻类暴发,水源水中的藻类在水厂前处理工艺中难以去除,造成该流域附近10余个水厂发生滤池堵塞现象,其中个别水厂滤池反冲洗周期由正常情况的24 h缩短至2~3 h,严重影响净水厂的正常运行,使得制水能力大幅降低。针对藻类(优势藻为硅藻中的针杆藻)暴发问题,通过对比PAFS、PAC和PFC3种混凝剂的除藻除浊效果,选取PAFS为最佳混凝剂;通过添加预氧化剂和助凝剂强化混凝除藻效果,其结果表明,使用助凝剂PDMDAAC的对PAFS的助凝效果最好,其余药剂结合PAFS的除藻效果为PPC>ClO2>PAM>H2O2>HCA-1,并将其应用到现有水厂,结果表明,0.6mg/L PDMDAAC+25 mg/L PAFS在水厂混凝沉淀,尖针杆藻含量降至49×104~55×104cells/L,其除藻率可达70%~75%,大大减轻了滤池的运行负荷,使得水厂运行恢复到正常水平。     

混凝工艺去除合流污水中有机物及营养元素

通过系列杯罐试验混凝处理合流污水,采用硫酸铝（Al₂(SO₄)₃）、硫酸铁（Fe₂(SO₄)₃）、聚合氯化铝（PAC）和聚合氯化铝铁（PAFC）4种混凝剂均能有效去除污水中的 TP、PO^3-₄-P、SS和COD。聚合金属盐（PAC和PAFC）混凝处理效果优于金属盐（Al₂(SO₄)₃和Fe₂(SO₄)₃）,达到相同的处理效果的投加量明显低于后者。助凝剂采用聚丙烯酰胺（PAM）、聚乙烯醇（PVA）、自制的高分子聚合物（AN）和活化硅酸（AS）,在保持较低混凝剂投加量的条件下可明显提高污水处理效果;添加助凝剂对强化PO^3-₄-P的去除作用不明显,PO^3-₄-P的去除仅与混凝剂的投加量相关。混凝剂和助凝剂对污水中NH₃-N的去除作用相对不显著。SS去除率随混凝剂投加量的变化趋势说明混凝的机理较为复杂,可能存在多种混凝机理共同作用。     

Nitrate and natural organic matter in aqueous solutions irradiated by simulated sunlight

By means of simulated sunlight, the influence of natural organic matter (NOM) on the photochemical degradation of halogenated pesticides in the absence and presence of nitrate as a precursor of the highly reactive OH radicals in aqueous solutions and freshwater was investigated. Solutions of dichlorprop or terbutylazine (a) in phosphate-buffered demineralized water containing nitrate and/or NOM and (b) in natural freshwaters were irradiated by a 1000-W Xe short-arc lamp. The collimated beam was filtered using a combination of optical filters (WG 320 and WG 295) to simulate the solar spectrum under summer midday conditions. In the absence of nitrate and NOM, the pesticides were degraded photolytically by simulated sunlight. The degradation rates depended on the absorption spectrum in the UVB range and the quantum yield of the degradation. The photochemical degradation of the pesticides was faster in the presence of nitrate due to the sunlight-induced formation of OH radicals. In the absence of nitrate, low concentrations of NOM of a brownwater lake accelerated the degradation due to the formation of reactive species by NOM. At higher concentrations of NOM, the inner filter effect of NOM lowered the degradation rates. In the presence of 50 mg l−1 nitrate, NOM decreased the degradation rate significantly. In case the natural water samples were used as a matrix for the experiments (nitrate concentrations between 2 mg l−1 and 15 mg l−1, DOC concentrations below 2.3 mg l−1), NOM acted mainly as a radiation filter and as a scavenger of OH radicals. As a consequence, in most freshwater systems, the accelerating effect of NOM by the formation of reactive species is of minor importance compared to the inner filter effect and to radical scavenging.     

硅藻土强化混凝去除微污染原水中的有机物

研究了联用硅藻土与聚合氯化铝（PAC）强化混凝对有机微污染原水中不同性质溶解性有机物的去除效果。采用超滤膜和XAD系列树脂对微污染原水中溶解性有机物进行分级表征,物理分级表明分子量〈4 kD的溶解性有机物占50%以上,化学分级表明原水中以憎水酸（HoA）和亲水物质（HiM）为主。硅藻土助凝去除溶解性有机物,实验结果表明,当PAC投加量30 mg/L,硅藻土投加量0.5 g/L时,溶解性有机碳去除率由22.5%提高到26.3%。     

An overview of the methods used in the characterisation of natural organic matter (NOM) in relation to drinking water treatment

Natural organic matter (NOM) is found in all surface, ground and soil waters. During recent decades, reports worldwide show a continuing increase in the color and NOM of the surface water, which has an adverse affect on drinking water purification. For several practical and hygienic reasons, the presence of NOM is undesirable in drinking water. Various technologies have been proposed for NOM removal with varying degrees of success. The properties and amount of NOM, however, can significantly affect the process efficiency. In order to improve and optimise these processes, the characterisation and quantification of NOM at different purification and treatment processes stages is important. It is also important to be able to understand and predict the reactivity of NOM or its fractions in different steps of the treatment. Methods used in the characterisation of NOM include resin adsorption, size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, and fluorescence spectroscopy. The amount of NOM in water has been predicted with parameters including UV-Vis, total organic carbon (TOC), and specific UV-absorbance (SUVA). Recently, methods by which NOM structures can be more precisely determined have been developed; pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), multidimensional NMR techniques, and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The present review focuses on the methods used for characterisation and quantification of NOM in relation to drinking water treatment.     

一体化水力强化混凝设备及其微污染原水处理工况最优化研究

根据混凝反应的基本原理,针对低浊度微污染原水的特性,设计了一种新型一体化水力强化混凝净水器.研究了使用该设备及相应混凝药剂处理低浊度、微污染珠江原水的最佳工艺条件.实验结果表明,该净水器在较高的进水流速范围内对低浊度原水有很好的处理效果.在适宜条件下,净水器的出水经过沙滤后浊度＜0.12 NTU;在使用CGA和PAC的强化混凝条件下,净水器对原水中所含的有机物也有较好的去除作用.     

Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection by-product control: application in a Western Australian water treatment plant

The removal of organic precursors of disinfection by-products (DBPs), i.e. natural organic matter (NOM), prior to disinfection and distribution is considered as the most effective approach to minimise the formation of DBPs. This study investigated the impact of the addition of powdered activated carbon (PAC) to an enhanced coagulation treatment process at an existing water treatment plant on the efficiency of NOM removal, the disinfection behaviour of the treated water, and the water quality in the distribution system. This is the first comprehensive assessment of the efficacy of plant-scale application of PAC combined with enhanced coagulation on an Australian source water. As a result of the PAC addition, the removal of NOM improved by 70%, which led to a significant reduction (80-95%) in the formation of DBPs. The water quality in the distribution system also improved, indicated by lower concentrations of DBPs in the distribution system and better maintenance of disinfectant residual at the extremities of the distribution system. The efficacy of the PAC treatment for NOM removal was shown to be a function of the characteristics of the NOM and the quality of the source water, as well as the PAC dose. PAC treatment did not have the capacity to remove bromide ion, resulting in the formation of more brominated DBPs. Since brominated DBPs have been found to be more toxic than their chlorinated analogues, their preferential formation upon PAC addition must be considered, especially in source waters containing high concentrations of bromide.     

Coagulation of colloidal material in surface waters: the role of natural organic matter

Organic matter has a great influence over the fate of inorganic colloids in surface waters. The chemical nature and structure of natural organic matter (NOM) will be an important factor in determining whether colloids will be stabilised or destabilised by NOM. Under environmentally relevant conditions, the ubiquitous fulvic acids are likely to be responsible for coating and imparting a negative charge to colloids. If the adsorbed polyelectrolyte coating produces an increase in absolute surface potential, it will act to stabilise colloids in the water column. On the other hand, colloidal organic carbon, especially chain-like structures, has been shown to be involved in the aggregation of inorganic colloids through the formation of bridges. It is highly probable that both adsorption and bridging flocculation are occurring simultaneously in the natural aquatic environment. The importance of each process depends directly on the nature and concentration of organic matter in the system and indirectly on the productivity of the lake, its hydrological pathways, temporal variations, temperature, etc. The present paper reports such results and emphasises the need to discriminate the different kinds of NOM.     

Effect of pre-ozonation on optimized coagulation of a typical North-China source water

Although ozone is widely used as a pre-oxidant before coagulation in water treatment, the effect of pre-ozonation on optimized coagulation for removal of particle and natural organic matter (NOM) is still not fully understood. In this paper, pilot-scale investigation was conducted to examine the impact of pre-ozonation on coagulation for particle and NOM removal. Changes in the particle and NOM distributions were characterized by various methods, including laser light granularity system, particle counter, ultrafiltration, and resin absorbent fractionation. A novel composite flocculant–HPAC was compared with the traditional ferric chloride coagulant in terms of coagulation efficiency under the influence of pre-ozonation. Typical micro-polluted North China surface water was used for pilot coagulation tests. The results show that the effect of pre-ozonation on coagulation is associated with the dosage of ozone, coagulant type, and water contamination characteristics. For FeCl₃, pre-ozonation acts as a coagulation aid at low dosage (1.0 mg L⁻¹ O₃) for turbidity and UV₂₅₄ removal; while at higher dosage (2.0 mg L⁻¹ O₃), pre-ozonation is detrimental to UV₂₅₄ removal although it is still beneficial for turbidity removal. In the case of composite flocculant–HPAC, pre-ozonation demonstrates negligible influence on both turbidity and UV₂₅₄ removal. Ozone can simultaneously aggregate fine particles and break down large ones, making them more mineralized and easier to remove. NOM with intermediate molecular weight and hydrophobic neutral property increases at lower ozone dosage, favoring removal by coagulation. At higher ozone dosages, NOM becomes more hydrophilic and its molecular weight becomes smaller, decreasing NOM removal.     

预氯化输水对表面停留性有机物及混凝除藻的影响

针对预氯化这一常用的预氧化方法,考察了表面停留性有机物(S-AOM)在这一过程中对铜绿微囊藻起到的关键作用。同时,探讨了表面停留性有机物及藻的氧化应激对混凝除藻效果的影响。结果表明,预氯化过程可实现适度预氯化的最佳氯投加量,适度预氯化可以在实现脱附S-AOM的同时不损伤藻细胞,强化后续混凝除藻的效果。此外,经过适度预氯化后的藻细胞在远程输水过程中可能会发生程序性死亡,胞内有机物不断泄漏,这仍会对水厂混凝除藻效果产生不利影响。因此,预氧化后藻细胞发生程序性死亡是预氯化强化混凝工艺需要考虑的关键因素。     

Bottom-up approach for the reaction of xenobiotics and their metabolites with model substances for natural organic matter by electrochemistry-mass spectrometry (EC-MS)

Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model “redox” reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC-MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ-l-Glutamyl-l-cysteinyl-glycine (GSH) and l-histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites.Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC-MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions.EC-MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances.     

臭氧光催化降解地下水中天然有机物的研究

在现场开展了中试规模的臭氧光催化降解天然有机物的研究。研究表明，对大分子天然有机物占很大比例且重碳酸盐含量较高的地下水，臭氧投加量10mg／L和反应时间10min条件下，TOC的去除率不到20％，但uV254和三卤甲烷生成潜力（THMFP）去除率分别达到近60％和33．5％。臭氧光催化与活性炭吸附相连，能显著提高UV254的THMFP的去除率，但TOC去除率并不明显高于单独活性炭吸附。臭氧光催化使大分子有机物转化为小分子有机物，后者在活性炭上的吸附性提高且生化性改善，可望在生物活性炭上更有效地去除。