Ozonation of polycyclic aromatic hydrocarbons in oil/water-emulsions: mass transfer and reaction kinetics

The ozonation of highly condensed polycyclic aromatic hydrocarbons (PAH) was studied in oil/water-emulsions, which are comparable to poorly water-soluble PAH in industrial wastewaters and at contaminated sites. As there was a lack of knowledge about the ozonation in oil/water-emulsions, first the ozone mass transfer was studied and optimized from the gas to the water phase and from the water to the oil phase. The ratio of mass transfer and oxidation reaction was determined by the Hatta-number and revealed a slow, quasi homogeneous reaction of ozone with PAH inside the oil droplets. Because the ozone gas concentration had no influence under the optimized conditions, the selective PAH-ozonation could be described microkinetically by a direct ozone reaction of pseudo-first order regarding PAH-concentrations. The determined PAH mean reaction rate constants of 1.02 min(-1) in oil/water-emulsions are in the upper range as found for PAH dissolved in water. These results give a new insight into the ozonation in the three-phase systems and into the treatment of highly condensed, hardly biodegradable PAH.     

Superparamagnetic nanoparticles in tap water

Magnetization measurements are a useful tool in the characterization of corrosion products formed in municipal water pipes made of iron or steel. Fine particles formed in corrosion processes exhibit superparamagnetic behavior. The size of such particles, which determines their capacity to adsorb hazardous species, can therefore be found from magnetic measurements. Application of this methodology to samples extracted from flowing and stagnant tap water, respectively, has shown that the flowing water samples contained multidomain (>100nm) ferromagnetic particles as well as aggregates of very fine superparamagnetic subdomain particles. The sizes of the fine particles are of the order of 3.2-5.6nm. In addition to small subdomain superparamagnetic particles stagnant water samples also contained larger subdomain particles with average dimensions of 59-67nm. Both large and small subdomain particles were trapped by the fine charcoal in household filters.     

深度处理水厂臭氧尾气检测

深度处理水厂臭氧接触池尾气浓度是一项重要技术参数,对于验证工艺设计参数与臭氧设备选型、安装调试状况及运行参数等具有重要作用,是对招标书中臭氧传质效率验收的重要指标。     

Effects of ozone and ozone/peroxide on trace organic contaminants and NDMA in drinking water and water reuse applications

An ozone and ozone/peroxide oxidation process was evaluated at pilot scale for trace organic contaminant (TOrC) mitigation and NDMA formation in both drinking water and water reuse applications. A reverse osmosis (RO) pilot was also evaluated as part of the water reuse treatment train. Ozone/peroxide showed lower electrical energy per order of removal (EEO) values for TOrCs in surface water treatment, but the addition of hydrogen peroxide increased EEO values during wastewater treatment. TOrC oxidation was correlated to changes in UV₂₅₄ absorbance and fluorescence offering a surrogate model for predicting contaminant removal. A decrease in N-nitrosodimethylamine (NDMA) formation potential (after chloramination) was observed after treatment with ozone and ozone/peroxide. However, during spiking experiments with surface water, ozone/peroxide achieved limited destruction of NDMA, while in wastewaters net direct formation of NDMA of 6-33 ng/L was observed after either ozone or ozone/peroxide treatment. Once formed during ozonation, NDMA passed through the subsequent RO membranes, which highlights the significance of the potential for direct NDMA formation during oxidation in reuse applications.     

Quantitative risk assessment of Cryptosporidium in tap water in Ireland

Cryptosporidium species are protozoan parasites associated with gastro-intestinal illness. Following a number of high profile outbreaks worldwide, it has emerged as a parasite of major public health concern. A quantitative Monte Carlo simulation model was developed to evaluate the annual risk of infection from Cryptosporidium in tap water in Ireland. The assessment considers the potential initial contamination levels in raw water, oocyst removal and decontamination events following various process stages, including coagulation/flocculation, sedimentation, filtration and disinfection. A number of scenarios were analysed to represent potential risks from public water supplies, group water schemes and private wells. Where surface water is used additional physical and chemical water treatment is important in terms of reducing the risk to consumers. The simulated annual risk of illness for immunocompetent individuals was below 1 × 10^− 4 per year (as set by the US EPA) except under extreme contamination events. The risk for immunocompromised individuals was 2-3 orders of magnitude greater for the scenarios analysed. The model indicates a reduced risk of infection from tap water that has undergone microfiltration, as this treatment is more robust in the event of high contamination loads. The sensitivity analysis highlighted the importance of watershed protection and the importance of adequate coagulation/flocculation in conventional treatment. The frequency of failure of the treatment process is the most important parameter influencing human risk in conventional treatment. The model developed in this study may be useful for local authorities, government agencies and other stakeholders to evaluate the likely risk of infection given some basic input data on source water and treatment processes used.     

Source and occurrence of particulate lead in tap water

Lead samples were collected at the tap from homes with lead service lines (LSLs) in a full-scale utility using both random daytime (RDT) and particulate stimulation sampling (PSS) protocols. Analysis of the results revealed two sources and occurrences of particulate lead. A first source is due to corrosion of lead-bearing elements in the premise plumbing (PP) and occurs mostly at low to moderate concentrations <3 μg/L, with some sporadic higher concentrations (4-12 μg/L). These spikes were consistently observed and considerably increased using PSS, showing that current sampling protocols may miss a significant portion of particulate lead. The second source results from the adsorption of dissolved lead onto iron deposits in LSL/PP, and is continuously present at low to moderate concentrations. Statistical analyses were validated by physical analyses of: (i) lead scales from LSLs; and (ii) lead particles from tap aerators.     

再生水厂臭氧系统的工艺设计

简要介绍了再生水厂为改善水的感官效果,通过对各种处理方式的比较,确定采用臭氧降低水中的色度和嗅味,以及臭氧工艺设计中臭氧投加量、臭氧扩散装置和接触时间等重点环节.     

南水北调工程中碱—骨料反应的问题及防治

结合南水北调工程,介绍了混凝土碱—骨料反应机理和特点,详细阐述了抑制碱—骨料反应的具体措施和方法,并指出抑制碱—骨料反应需注意的几点问题,以及施工过程中应注意的事项,以期杜绝碱—骨料反应给工程带来的危害。     

Occurrence of herbicide oxadiazon in surface waters and tap water

Occurrence of oxadiazon, 2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ²-1,3,4-oxadiazolin-5-one, in surface waters and tap water was investigated. At the Tonda Reservoir site, oxadiazon residue was usually detected. The maximum concentration was observed in August. After that, the concentrations gradually reduced. At the Higashitani, Nishitani and Murasaki River sites, high concentrations of oxadiazon residue were immediately detected after beginning of rice seedling transplantation, and rapidly reduced. The residue levels were between 0.001 and 1.953 ppb. However, oxadiazon residue at the Onga River site was detected over a long period in comparison with other river sites, and also observed in May. The concentration of oxadiazon residue in tap water was ranged about 3–23% of that in raw water.     

Monitoring of micromycetes in tap water of the city of Kiev

Monitoring of tap water samples in different administrative districts of Kiev was carried out. The impact of lifetime of the water-distribution network on the amount and specific composition of micromycetes in selected samples of the water was investigated. The paper has established the presence in the water of the genera Candida, Penicillium, Cladosporium, Fusarium, and Aspergillus. The mean amount of micromycetes varies in the range from 8 to 18 CFU/100 cm³, which is an indication of the necessity to develop regulatory documents on mycological control of water and technologies for the removal from it of micromycetes.     

Oxidation of microcystins by permanganate: reaction kinetics and implications for water treatment

A few genera of cyanobacteria produce toxins which contaminate drinking water resources. Microcystins (MC), widely reported cyanotoxins, cause acute and chronic toxicity effects in living beings including humans and warrant removal from drinking water. In the present study, unknown second-order rate constants for the reactions of microcystin-LR (MC-LR), -RR and -YR with potassium permanganate were determined at pH 6.2-8.2 and temperature 10-25 degrees C. The reaction of permanganate with MCs is second-order overall and first-order with respect to both permanganate and toxin. The second-order rate constant for the reaction of MC-LR with permanganate at pH 7 and 20 degrees C was 357.2+/-17.5M(-1)s(-1). The influence of pH on the oxidation process was not appreciable and the activation energy was 28.8 kJ mol(-1). Slightly higher reactivity with permanganate was found for MC-RR (418.0M(-1)s(-1)) and MC-YR (405.9M(-1)s(-1)). According to the results obtained, permanganate likely attacks the Adda moiety of the MC molecule. The oxidation of MCs in a natural surface water was also investigated. A permanganate dose of 1-1.25mgL(-1) was enough to reduce MCs concentration below the guideline value of 1microgL(-1). Permanganate oxidation is therefore a feasible option for microcystin removal during preoxidation processes. However, the oxidant dose must be carefully optimized in order to remove extracellular MCs without causing cell lysis (due to chemical stress) and further release of MCs.     

A survey of tap water quality in Kuala Lumpur

A safe drinking water programme known as The National Drinking Water Quality Surveillance Programme (NDWQSP) was launched by the Ministry of Health, Government of Malaysia in 1983 to ensure safe practices in water treatment and distribution. The aim of this work was to assess the effectiveness of this programme in the improvement of tap water quality in and around Kuala Lumpur. The results indicate that there was no microbial contamination in 100 random samples collected from 20 selected areas. Other quality parameters such as colour, pH, turbidity, hardness, magnesium, sulphate and chloride were within acceptable limits. Heavy metals such as Cu²⁺, Pb²⁺, Cr (total), Ni²⁺, Cd²⁺, Fe (total) and Mn (total) were also under control. The only exception was Ba²⁺, which did not comply with the standard and was up to ten times higher than the guideline value. Moreover, there was significant variation in water quality as indicated by the test results.     

Composition and particle size of superparamagnetic corrosion products in tap water

Chemical analyses, magnetization, Mössbauer spectrum, and x-ray diffraction measurements were made on solids removed from tap water by means of membrane filters. The taps from which this water was obtained had previously been unused for prolonged periods of time. When these taps were reactivated and water was first drawn, it was observed that the quantity of coarse solids in the water gradually decreased with flow, while at the same time the quantity of fine solids gradually increased. The magnetization, Mössbauer spectra, and x-ray diffraction patterns of the solids showed the presence of a significant number of superparamagnetic particles of magnetite. In the temperature range of our measurements (77 K < T < 300 K), paramagnetic iron-based species, particularly lepidocrocite, were also present in the solids. Contaminants such as Pb, Cu, and As were observed to be present in significant amounts, and it is shown that these are adsorbed to the magnetic nanoparticles. It was observed that almost all of the solid particles could be removed by means of 5-μm filters. This removal process can be explained by means of a model which assumes that initial deposition of coarse aggregates of corrosion products on the filters forms a coating, rich in extremely fine iron oxides. The coating has a high capacity for sorption of very small individual particles.     

Nitrosamines in tap water after concentration by a carbonaceous adsorbent

Ambersorb XE-340 carbonaceous adsorbent removed trace levels of volatile nitrosamines (NAs) that were added to the influent water. Recovery of seven added NAs was between 58–99% as determined by a gas-liquid chromatograph interfaced with a Thermal Energy Analyzer (GLC-TEA). When municipal (tap) water (10–42 l.) was passed through the Ambersorb XE-340 column. N-nitrosodimethylamine (NDMA; 0.003–0.006 μg 1⁻¹) and -morpholine (NMOR; 0.006–0.018 μg 1⁻¹) were the principal NAs found. All of the NDMA and 18 of 20 NMOR samples were confirmed by high resolution mass spectrometry. Secondary amines added to tap water at levels of 1 mg 1⁻¹ and 10 μg 1⁻¹ formed apparent NAs, suggesting a possible component(s) in the water that caused NA formation. Low levels of volatile NAs were detected by GLC-TEA in commercial, pure, adsorbents (activated carbon). NAs were confirmed by high resolution mass spectrometry except where concentrations were too low. In the latter case, the apparent NAs were found to be photolabile when subjected to u.v. light (365 nm) and were reanalyzed by GLC-TEA thus providing additional evidence that the TEA responsive compounds were NAs.     

我国城市居民饮用水结构与发展趋势

目前,我国城市居民饮用水从供给方式分可分为煮沸开水、灌装水和终端处理水;从水质特点可分为煮沸开水、纯净水、矿泉水、直饮水.城市供水水质的恶化为饮用水结构的改变创造了契机,技术与经济的发展为饮用水结构的变化提供了保障,满足健康需求是饮用水发展的方向.     

Determination of ozone in water by the indigo method

The concentration of aqueous ozone can best be determined by the decolorization of indigo trisulfonate (600 nm, pH below 4) whenever the ozone cannot be measured directly by its u.v. absorption. The method is stoichiometric and extremely fast. The change of absorbance vs ozone added is −2.0 ± 0.1 × 10⁴ M⁻¹ cm⁻¹ and is independent of the concentration of aqueous ozone in the range 0.005–30 mg 1⁻¹. The precision of the analysis is 2% or 3 μg 1⁻¹ for low concentrations if a spectrophotometer or a good filter instrument is used. Visual methods can be used to measure 0.01 mgl⁻¹ ozone. Secondary oxidants produced by ozone in natural water, including hydrogen peroxide or chlorite, do not interfere; chlorine can be masked. The reagent solution is stable for 3 months. The method is recommended for kinetic measurements, for studies of ozonation processes and for visual field methods.     

Z县自来水厂设计的几点体会

Z县自来水厂设计的几点体会:1.城镇中小型水厂采用网格絮凝池,结构简单,方便施工安装.2.为避免絮凝池形成的矾花被打碎,穿孔花墙设计采用低流速;3.平流沉淀池池长度方向采用转折布置,取得了较好的效果;4.为提高出水水质,减少平流沉淀池积泥的影响,平流沉淀池设计中应特别注意并采取相应措施,消除池底积泥状况;5.集水槽设计...     

Kinetic regularities of ozone decomposition in water

The paper studied the impact of the pH and temperature on kinetics of ozone decomposition in water. It has been shown that in the pH range 4 to 8 it is well described by the equation of the second order reaction. At an increase of the pH and temperature the rate of ozone decomposition increases. The relationship between the logarithm of the constant and the pH at 19°C corresponds to the equation log k_(pH) = −0.7 + (0.49 ± 0.03)(pH 4). The energy of ozone decomposition activation constitutes 76.0 ± 8.3 kJ/mol. The presence in the solution of phosphate ions and tert-butyl alcohol substantially increases the rate of the decomposition chain process.