酪氨酸氯化过程中光谱变化特征及消毒副产物的生成规律

考察酪氨酸在不同投氯量条件下氯化后的余氯,紫外吸光度值和荧光光谱,以及消毒副产物对羟基苯乙腈(4-HBC)的生成特性。结果表明,随着投氯量的增加,余氯呈现先增加再减小再增加的趋势。在投氯量为0～0.5 mmolCl2/L时,增加投氯量可提高氯化后溶液的UV254、UV274和UV280值以及4-HBC的生成量,表明低投氯量时氯化可提高溶液中不饱和键的含量;而投氯量为0.5～1 mmol Cl2/L时,增加投氯量降低UV254、UV274和UV280值以及4-HBC的生成量,表明过量的氯亦可破坏溶液中的不饱和键。荧光光谱测试实验亦发现:在投氯量为0.05 mmol Cl2/L时,酪氨酸溶液氯化后的荧光峰强度明显增加,表明氯化可生成荧光强度较高的产物。过量的氯(0.5～1 mmol Cl2/L)则可破坏溶液中的荧光结构,降低荧光峰强度直至未检出。     

Chlorination of bisphenol A in aqueous media: formation of chlorinated bisphenol A congeners and degradation to chlorinated phenolic compounds

The chlorination of bisphenol A (BPA) in aqueous media was investigated in order to describe the degradation profile of this compound and the formation of chlorinated products. Aqueous solutions of BPA (approx. 1 mg/l) were chlorinated by sodium hypochlorite solution at room temperature and under weakly alkaline conditions. Chlorinated compounds were extracted with dichloromethane and determined by gas chromatography/mass spectrometry (GC/MS). BPA was consumed completely within 5 min of chlorination, when the initial chlorine concentration was 10.24 mg/l (molar ratio to BPA, 58.7). On the other hand, when the initial chlorine concentration was 1.03 mg/l (molar ratio, 6.56), 9.3% of BPA still remained after 60 min chlorination. Five chlorinated BPA congeners, 2-chlorobisphenol A (MCBPA), 2,6-dichlorobisphenol A (2,6-D2CBPA), 2,2'-dichlorobisphenol A (2,2'-D2CBPA), 2,2',6-trichlorobisphenol A (T3CBPA) and 2,2', 6,6'-tetrachlorobisphenol A (T4CBPA) were formed in the earlier stages of chlorination. Several chlorinated phenolic compounds, 2,4,6-trichlorophenol (T3CP), 2,6-dichloro-1,4-benzoquinone (D2CBQ), 2,6-dichloro-1,4-hydroquinone (D2CHQ), C9H10Cl2O2, C9H8Cl2O and C10H12Cl2O2, were also formed by further chlorination.     

Formation and chlorination of polychlorinated naphthalenes (PCNs) in the post-combustion zone during MSW combustion

Non- to octa-chlorinated naphthalenes (PCNs) were analyzed in flue gas samples collected simultaneously at three different temperatures (450 degrees C, 300 degrees C and 200 degrees C, respectively) in the post-combustion zone during waste combustion experiments using a laboratory-scale fluidized-bed reactor. PCN homologue profiles in all samples were dominated by the lower chlorinated homologues (mono- to triCN), with successive reductions in abundance with each additional degree of chlorination. The isomer distribution patterns reflected ortho-directionality behavior of the first chlorine substituent, and the beta-positions, i.e. the 2,3,6,7-substitution sites, seemed to be favored for chlorination. Injection of naphthalene into the post-combustion zone resulted in increased PCN levels at 200 degrees C, demonstrating the occurrence of chlorination reactions in the post-combustion zone. However, the increases were restricted to the least-chlorinated homologue (monoCN), probably because there was insufficient residence time for further chlorination. In addition, an episode of poor combustion (manifested by high CO levels) was accompanied by extensive formation of 1,8-diCN, 1,2,3- and 1,2,8-triCN; congeners with substitution patterns that are not thermodynamically favorable. These are believed to be products of PAH breakdown reactions and/or chlorophenol condensation. Overall, PCN formation is likely to occur via more than one pathway, including chlorination of naphthalene that is already present, de novo synthesis from PAHs and, possibly, chlorophenol condensation.     

The presence of bacterial virus in groundwater and treated drinking water

Ten raw urban well water samples and twelve water samples collected from distribution lines after the well waters were treated were examined for bacteriological and coliphage/bacteriophage populations. The raw well waters were found to contain <1/100 ml total coliforms and fecal streptococci, but they all contained varying concentrations of coliphage and bacteriophage. The treated waters were all found to have <1 total coliforms and fecal streptococci per 100 ml with the exception of one treated water sample from Community C. However, even though the treated water samples contained free and total chlorine levels varying from 0.05 to 1.5 ppm, they were all found to contain usually greater amounts of coliphage and bacteriophage than the raw well waters.     

Influence of chlorination pH and chlorine dose on the formation of mutagenic activity and the strong bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-5(2H)-furanone (MX) in water

Samples from two Dutch raw water sources were chlorinated in the laboratory at different pH:s and chlorine doses, and were analysed for mutagenic activity and the mutagenic compound 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX). Chlorination produced mutagenic activity as well as MX in both waters. The formation of MX was favoured by acidic reaction conditions and high chlorine doses, but in waters treated with excess chlorine at pH 9, no MX was detected. The mutagenicity was approximately on the same level after chlorination of both water types but the MX concentration was significantly higher in the water containing mainly humic material.

MX was found to be quantitatively extracted from acidified waters by the XAD resin adsorption technique.     

Feed-forward dose control of wastewater chlorination using on-line pH and ORP titration

In this study, a simple automatic pH-ORP titration device was developed for identifying the various ammonia concentrations and chlorine dose requirements for wastewater chlorination by identifying the peaks in the ORP-slope profiles and knees/valleys in the pH profiles. In addition, breakpoint chlorination experiments have shown that the ORP values at the monochloramine humps and breakpoints are linearly correlated with the ammonia concentrations. Therefore, a feed-forward control strategy, based on the chlorine/ammonia weight ratio (Cl/N), is proposed in this paper, to control the chlorine doses for a continuous wastewater chlorination experiment in a laboratory-scale reactor. The result of this continuous wastewater chlorination experiment has shown that the pH-ORP titration was able to precisely determine the variations of ammonia concentrations in the chlorination influent. Under this control strategy, effective and stable disinfection efficiencies in terms of total coliform count were obtained.     

臭氧-氯联合灭活饮用水中枯草芽孢杆菌芽孢的研究

以枯草芽孢杆菌芽孢为模型微生物,研究了实际水体中单独氯消毒、单独臭氧消毒和臭氧-自由氯联合作用的灭菌效果.结果表明,枯草芽孢杆菌芽孢对单独氯消毒的抗性很大,6 mg/L氯作用240 min后灭活率仅为0.84个对数级;臭氧对枯草芽孢杆菌芽孢有较好的灭活效果,臭氧作用5 min,对其有4.68个对数级的灭活率.与单独氯消...     

Factors on the formation of disinfection by-products MX, DCA and TCA by chlorination of fulvic acid from lake sediments

[3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] (MX) and chlorinated acetic acids such as dichlorinated acetic acid (DCA) and trichlorinated acetic acid (TCA) have always been the focus of disinfection by-products (DBPs) studies. In order to find out the influences of reaction time, TOC, chlorine dose, pH and temperature on the formation of MX, DCA and TCA, we extracted fulvic acid (FA) from the sediment of Tai Lake, and conducted simulated chlorination of samples rich in FA. Results showed positive relationship between TOC and the yields of MX, DCA and TCA. But the influences of pH, chlorine dose, reaction time, and temperature are quite complex. The optimal chlorination condition for the formation of MX is pH = 2, T = 45 degrees C, C/Cl2 = 1/4, t = 12 h. Lower pH, longer time, greater chlorine dose can result in greater yield of both DCA and TCA, and there is a strong linear relationship between the formation of DCA and TCA.     

回用生活污水的电化学消毒试验研究

对北京某中水站回用于杂用水的生活污水进行电化学消毒试验。试验结果表明 ,生活污水经生物接触氧化、活性炭吸附后 ,流经电化学消毒器停留 2 0s、耗电 0 .30kWh/m3 、消毒器出水放置 1h后 ,总大肠菌群数 <3个 /L ,满足生活杂用水的卫生学指标。当余氯浓度及接触时间相等的条件下 ,电化学消毒法的杀菌效果好于加氯消毒。E .coli细胞经电化学消毒和加氯消毒处理后 ,扫描电镜观察的结果表明 :2种方法作用后的细胞在形态上的变化是不相同的 ,说明电化学消毒的消毒机制不仅仅取决于电解产氯的作用 ,还有其他的杀菌作用     

Formation of PCDDs and PCDFs by the chlorination of water

Two samples of tab water and double distilled water were chlorinated using chlorine gas. A series of PCDFs could be identified from these experiments, however no PCDDs could be found. The two water samples gave very similar isomeric patterns ( . . tetra-CDFs), however the congener profile (Cl₄ --- Cl₈) was different. These experiments indicate that all products formed by chlorination reactions are potentially contaminated by PCDFs by a specific “chlorine pattern”.     

Recycled vertical flow constructed wetland (RVFCW)--a novel method of recycling greywater for irrigation in small communities and households

The use of greywater for irrigation is becoming increasingly common. However, raw greywater is often contaminated and can cause environmental harm and pose health risks. Nevertheless, it is often used without any significant pretreatment, a practice mistakenly considered safe. The aim of this study was to develop an economically sound, low-tech and easily maintainable treatment system that would allow safe and sustainable use of greywater for landscape irrigation in small communities and households. The system is based on a combination of vertical flow constructed wetland with water recycling and trickling filter, and is termed recycled vertical flow constructed wetland (RVFCW). The RVFCW's properties, removal efficiency, hydraulic parameters and feasibility were studied, as well as the environmental effects of the treated greywater, as reflected by soil and plant parameters over time. The RVFCW was efficient at removing virtually all of the suspended solids and biological oxygen demand, and about 80% of the chemical oxygen demand after 8h. Fecal coliforms dropped by three to four orders of magnitude from their initial concentration after 8h, but this was not always enough to meet current regulations for unlimited irrigation. The treated greywater had no significant negative impact on plants or soil during the study period. The feasibility analysis indicated a return over investment after approximately three years. We concluded that the RVFCW is a sustainable and promising treatment system for greywater use that can be run and maintained by unskilled operators.     

Chloroperoxidase-mediated chlorination of aromatic groups in fulvic acid

The aim of the present study is to investigate whether exo-enzymatically mediated chlorination of fulvic acid (FA) results in the formation of chlorinated groups within the macromolecules which correspond to those which were previously detected in soil and surface water samples. The chlorination was carried out by exposing FA to a commercial chloroperoxidase (CPO) in the presence of chloride and hydrogen peroxide. The exposed FA was then chemically degraded using an oxidative technique and finally analysed for four different aromatic groups and their chlorinated analogues. The particular aromatic groups included were the methyl esters of 4-ethoxybenzoic acid, 3-methoxy-4-ethoxybenzoic acid, 3,4-diethoxybenzoic acid, and 3,5-dimethoxy-4-ethoxybenzoic acid, along with their mono- and dichlorinated analogues. Prior to the chemical degradation procedure, the FA was analysed for AOX (adsorbable organic halogens) and chlorinated acetic acids. The original FA contained 1.4 mg Cl(org) g(-1) and detectable amounts of two chlorinated aromatic groups. After exposure to the enzyme, the concentration of AOX increased to 44.3 mg Cl(org) g(-1) and detectable amounts of four chlorinated aromatic groups as well as di- and trichloroacetic acid were found.     

Insights to false positive total cyanide measurements in wastewater plant effluents.

Many publicly owned treatment works in North America are exceeding permitted limits for total cyanide in their wastewater treatment effluents. A recently introduced rapid, segmented, flow-injection analysis procedure using UV digestion and amperometric detection of the membrane-separated cyanide was used to investigate the various scenarios by which elevated cyanide levels might be present in wastewater treatment plant effluent. A number of significant interferences can produce false positive bias during sample analysis with the traditional acid distillation technique, but are minimized or absent with the new analytical method. However, increased levels of cyanide were found in some chlorinated wastewaters compared to the levels before chlorination, suggesting a fast reaction mechanism associated with the disinfectant and some precursor in the wastewater. In particular, the contact of chlorine with nitrite in the presence of a carbon precursor appears to contribute to cyanide formation during wastewater treatment and sample handling. This paper explores the scenarios under which cyanide can form during wastewater treatment as well as those in which a false bias for total cyanide can be obtained during sample processing and provides guidance for appropriate sample handling, screening, and processing to ensure valid analytical results.     

Survival of total coliforms in lawn irrigated with secondary wastewater and chlorinated effluent in the Mediterranean region.

Pregrown, two-month-old lawn was layered in 12 large square pots with an area of 0.25 m2 each, filled with a mixture of topsoil, peat, and sand. In late July, in the heart of the Mediterranean summer, the pots were divided into two groups, with six pots per group. On four different occasions, the pots in each group were sprinkled (surface irrigation) with 2 L of either secondary-treated wastewater (STW, group A) or chlorinated effluent (CHE, group B). Wastewater application always took place at 0700 hours. Samples of the surface soil and grass from each pot were collected at the following times: before irrigation, immediately after irrigation, two hours later (0900 hours), and four hours later (1100 hours). In the samples collected, the number of total coliforms per gram was measured using standard microbiological analyses. Temperature and sunlight intensity were also monitored. There was an increase in the coliforms population in soil and grass samples of both groups immediately after the wastewater application. In group A, the mean number of coliforms recorded in the soil samples reached mean values higher than 5000 cfu/g compared to 312 cfu/g recorded before application. The increase in group B was smaller but still significant. Two hours later, the number of coliforms was reduced substantially in all samples (e.g., group A, soil samples 477 cfu/g). Coliform inactivation is thought to result from the effect of temperature and mainly sunlight. However, four hours after application (1100 hours), there was a noticeable increase in the coliform number again, in all sample categories of both groups. Coliform reactivation could be a result of shadowing effect resulting from the thick foliage of the grass, where the microorganisms were protected by the sunlight radiation and regrowth in a friendly environment (especially of the soil) where moisture and nutrients were present. This, in addition to the fact that coliforms seemed to retain a sizable population between applications, results in three conclusions: (1) coliforms can survive in grass and soil for a substantial period of time, recovering from the destructive effect of chlorination, (2) use of STW, even during the Mediterranean summer, could result in a substantial "contamination" of lawns, without any proof that sun and temperature can reduce the coliform number, and (3) intense sunlight (up to 68 000 lux) was far more effective in coliform suppression than elevated temperature (up to 38 degrees C).     

Chlorination of dibenzofuran and dibenzo-p-dioxin vapor by copper (II) chloride

Dibenzofuran (DF) is formed from phenol and benzene in combustion gas exhaust streams prior to particle collection equipment. Subsequent chlorination at lower temperatures on particle surfaces is a potential source of chlorinated dibenzofuran (CDF). Gas streams containing 8% O₂ and approximately 0.1% DF vapor were passed through particle beds containing copper (II) chloride (0.5% Cu, mass) at temperatures ranging from 200 to 400 °C to investigate the potential for CDF formation during particle collection. Experiment duration was sufficient to provide an excess amount of DF (DF/Cu=3). The efficiency of DF chlorination by CuCl₂ and the distribution of CDF products were measured, with effects of temperature, gas velocity, and experiment duration assessed. Results of a more limited investigation of dibenzo-p-dioxin (DD) chlorination by CuCl₂ to form chlorinated DD (CDD) products are also presented.

The efficiency of DF/DD chlorination by CuCl₂ was high, both in terms of CuCl₂ utilization and DF/DD conversion. Total yields of Cl on CDF/CDD products of up to 0.5 mole Cl per mole CuCl₂ were observed between 200 and 300 °C; this suggests that nearly 100% CuCl₂ was utilized, assuming a conversion of two moles of CuCl₂ to CuCl per mole Cl added to DD/DF. In a short duration experiment (DF/Cu=0.3), nearly 100% DF adsorption and conversion to CDF was achieved. The degree of CDF chlorination was strongly dependent on gas velocity. At high gas velocity, corresponding to a gas–particle contact time of 0.3 s, mono-CDF (MCDF) yield was largest, with yields decreasing with increasing CDF chlorination. At low gas velocity, corresponding to a gas–particle contact time of 5 s, octa-CDF yield was largest. DF/DD chlorination was strongly favored at lateral sites, with the predominant CDF/CDD isomers within each homologue group those containing Cl substituents at only the 2,3,7,8 positions. At the higher temperatures and lower gas velocities studied, however, broader isomer distributions, particularly of the less CDD/CDF products, were observed, likely due to preferential destruction of the 2,3,7,8 congeners.     

The formation of chlorodibenzo-p-dioxins by air oxidation and chlorination of bituminous coal

A well characterized bituminous coal was subjected to high temperature air oxidation and chlorination. After an extensive cleanup procedure, the reaction products were analyzed for chlorinated dibenzo-p-dioxins by gas chromatography-mass spectrometry. Substantial quantities of chlorodibenzo-p-dioxins, some of which are known to be highly toxic, were observed with chlorination by hydrogen chloride and chlorine gas.     

Hazardous air pollutants formation from reactions of raw meal organics in cement kilns

Thermally induced chlorination, condensation, and formation reactions of raw meal organic surrogates were investigated on different types of surfaces. The System for Thermal Diagnostic Studies provided a powerful tool to study these reactions under defined reaction conditions, which were related to typical conditions in the preheater zone of cement kiln. Experiments were conducted with benzene and benzene/myristic acid (C6H6/C13H27COOH) mixtures in a quartz reactor containing different chlorinating catalysts/reagents over a temperature range of 300-500 degrees C. Reaction products were trapped in-line and analyzed by GC-MS. A mixture of chlorides of calcium, potassium, aluminium and iron was highly effective for chlorination/condensation reactions of benzene and benzene/myristic acid mix at temperatures above 300 degrees C. The same behavior was observed only when calcium chloride and potassium chloride were used as chlorinating catalyst/reagent. This result showed that transition metal chlorides like FeCl3 are not necessary for chlorination/condensation of organics under post-combustion conditions. Methylene chloride was the major chlorinated product followed by chloroform and various other C1, C2 and C6 chlorinated products. Yields of chlorinated aliphatics were highest at 400 degrees C for both benzene and benzene/myristic acid mix. C6 products were mainly mono- to hexa-chlorinated benzenes with trace amounts of chlorinated phenols. The major chlorinated products observed in this study (i.e., methylene chloride, chloroform, chloroethanes and monochlorobenzene) were also present as major chlorinated hydrocarbons in the cement kiln field emission data.     

松花江饮用水氯消毒中氯仿形成的优化控制

通过对松花江水进行大量实验 ,找出TOC的含量、投氯量、温度和 pH值等对氯仿形成的定量关系 ,确定了饮用水氯化的优化条件 ,使饮用水氯化过程中形成的氯仿含量不超过国家饮用水的标准     

Chlorination of dibenzofuran and dibenzo-p-dioxin vapor by copper (II) chloride

Dibenzofuran (DF) is formed from phenol and benzene in combustion gas exhaust streams prior to particle collection equipment. Subsequent chlorination at lower temperatures on particle surfaces is a potential source of chlorinated dibenzofuran (CDF). Gas streams containing 8% O₂ and approximately 0.1% DF vapor were passed through particle beds containing copper (II) chloride (0.5% Cu, mass) at temperatures ranging from 200 to 400 °C to investigate the potential for CDF formation during particle collection. Experiment duration was sufficient to provide an excess amount of DF (DF/Cu=3). The efficiency of DF chlorination by CuCl₂ and the distribution of CDF products were measured, with effects of temperature, gas velocity, and experiment duration assessed. Results of a more limited investigation of dibenzo-p-dioxin (DD) chlorination by CuCl₂ to form chlorinated DD (CDD) products are also presented.The efficiency of DF/DD chlorination by CuCl₂ was high, both in terms of CuCl₂ utilization and DF/DD conversion. Total yields of Cl on CDF/CDD products of up to 0.5 mole Cl per mole CuCl₂ were observed between 200 and 300 °C; this suggests that nearly 100% CuCl₂ was utilized, assuming a conversion of two moles of CuCl₂ to CuCl per mole Cl added to DD/DF. In a short duration experiment (DF/Cu=0.3), nearly 100% DF adsorption and conversion to CDF was achieved. The degree of CDF chlorination was strongly dependent on gas velocity. At high gas velocity, corresponding to a gas–particle contact time of 0.3 s, mono-CDF (MCDF) yield was largest, with yields decreasing with increasing CDF chlorination. At low gas velocity, corresponding to a gas–particle contact time of 5 s, octa-CDF yield was largest. DF/DD chlorination was strongly favored at lateral sites, with the predominant CDF/CDD isomers within each homologue group those containing Cl substituents at only the 2,3,7,8 positions. At the higher temperatures and lower gas velocities studied, however, broader isomer distributions, particularly of the less CDD/CDF products, were observed, likely due to preferential destruction of the 2,3,7,8 congeners.     

Formation of aromatic chlorinated compounds catalyzed by copper and iron

This study shows the catalyzing effects of iron and copper on the formation of chlorinated compounds such as chlorobenzenes (ClBzs), chlorophenols (CIPhs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Both total concentrations and congener distributions have been studied. The parameters and conditions varied during the combustion tests were the complete and incomplete combustion and the metal and chlorine addition. The incomplete combustion promoted the formation of organic chlorinated compounds in flue gas particles. Highly chlorinated congeners of PCDD/F were dominant in the flue gas particles, whereas the importance of lower chlorinated congener were increased in the gas phase. In the complete combustion conditions the concentrations of PCDD/Fs increased when the degree of chlorination were high, nevertheless the concentrations of tetra and penta PCDD/Fs were higher in the gas phase than the concentrations in the fly ash particles. Organic chlorine promoted the formation of chlorinated compounds more effectively than inorganic chlorine, which instead promoted the formation of PCDD/Fs in the gas phase, especially with copper catalyst. Different concentration levels of chlorinated compounds were observed in the gas phase and in particles when the chlorine source and combustion conditions were varied from incomplete to optimum conditions. Both copper and iron seem to have a catalytic effect on PCDD/F formation.