FTIR evaluation of functional groups involved in the formation of haloacetic acids during the chlorination of raw water

This work investigated the formation potential of haloacetic acid (HAA) compounds in the raw water for the Bangkhen water treatment plant (Bangkok, Thailand). The resin adsorption technique (with three different types of resins, i.e. DAX-8, AG-MP-50 and WA-10) was employed to characterize the organic content in the raw water into six fractions, i.e. hydrophobic neutral (HPON), hydrophobic acid (HPOA), hydrophobic base (HPOB), hydrophilic neutral (HPIN), hydrophilic acid (HPIA) and hydrophilic base (HPIB). Hydrophilic species appeared to be the predominant organic species in this water source (approximately 60%) with the neutral fraction being the most abundant (approximately 40%). Hydrophobic species, on the other hand, played the most important role in the formation of haloacetic acids as they contributed to as much as approximately 56% of total HAA formation potential. Among the three hydrophobic species, the hydrophobic base exhibited the highest specific HAA formation with 208mugHAAs/mg of dissolved organic carbon (DOC). Each organic fraction was examined for its associated functional groups by Fourier transform infrared (FTIR). The investigation of the formation of HAAs was achieved by tracking the changes in the FTIR results of the same water sample before and after the chlorination reaction. Based on the results obtained from this study, carboxylic acids, ketone, amide, amino acids and aromatic characteristic organics seemed to be the main precursors to HAA formation.     

Reduction of disinfection by-products precursors by nanofiltration process

This research is dedicated to determine the rejection ratios of disinfection by-products (DBPs) precursors including resorcinol, phloroglucinol, 3-hydroxybenzoic acid, and tannic acid solution in the presence of calcium by nanofiltration with NF70 membrane. The rejections of these model compounds also were studied at various compositions of a feed solution by changing pH and concentrations of model compounds. It was found that the model compound rejection and membrane permeability increase with pH due to the conformational transformation of ionizable molecules and electric interaction between the model compounds and NF70 membrane. The interactions of model compounds with calcium have no significant effect on model compounds retentions. Because of the complexation of calcium with model compounds, calcium rejection rises with the presence of model compounds and with an increase of pH.     

Trihalomethanes formation potential of shrimp farm effluents

Shrimp farm effluents along the Bangpakong River in the Chachoengsao Province of Thailand were evaluated for their trihalomethane formation potential (THMFP) and related parameters. The dissolved organic carbon (DOC), salinity and bromide ion concentrations of shrimp farm effluents were in the ranges of 12-14 mg/L, 0.1-14.5 ppt, and 0-14 mg/L, respectively. The dissolved organic matter was fractionated into hydrophobic and hydrophilic fractions having a range concentration of 3-5 and 8-10mg/L, respectively. The THMFP for all shrimp farm effluents analyzed was in the range of 810-3100 microg/L. The hydrophilic organic fraction was found to be a more active precursor of trihalomethanes (THMs) with 700-966 microg/L THMFP obtained from this fraction, while only 111-363 microg/L THMFP was derived from the hydrophobic fraction. The experimental results showed that salinity and bromide played crucial roles in the formation of THMs. At low salinity and bromide levels, chloroform was the dominant THM species, whereas at high salinity and bromide levels, bromoform became the dominant species. A Fourier Transform Infrared (FTIR) spectrum analysis of the samples before and after chlorination illustrated that the functional groups involved in the THM formation reaction were phenolic compounds, amines, aromatic hydrocarbons, aliphatic bromo-compounds, and aliphatic chloro-compounds.     

The formation and distribution of haloacetic acids in copper pipe during chlorination

The formation and distribution of HAAs in copper pipe during chlorination was investigated. To determine the material influence of copper pipe, parallel experiments were performed in glass pipe. Results showed that there was no obvious difference between the sum of haloacetic acids (HAAs) and trihalomethanes (THMs) produced in copper pipe compared to that produced in glass pipe over a 12h period. However, significant differences were observed about the distribution of five haloacetic acids in copper pipe and in glass pipe. Relatively less trichloroacetic acid (TCAA) and more monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), dibromoacetic acid (DBAA) and trihalomethanes (THMs) were produced in copper pipe than those in glass pipe. Corrosion scale on the wall of copper pipe was analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results showed the scales on the pipe surface mainly consisted of Cu2O, CuO and Cu (OH)2 or CuCO3. During 24h stagnation, copper released gradually from copper pipe. The influences of copper (II) and copper oxides on the distribution of HAAs were investigated in designed experiments. Results showed that less amount of TCAA, more amounts of DCAA and MCAA were formed with increasing concentration of copper (II). It was because the accelerative effect of copper (II) on the depletion of chlorination restricted the formation of TCAA precursor and the further formation of TCAA. Owing to the transformation of DCAA precursor to TCAA precursor was limited, more DCAA precursor could yield DCAA. The influences of Cu2O and CuO on the distribution of TCAA and DCAA were the result of copper released at higher content.     

Removal of trihalomethanes from drinking water by nanofiltration membranes

Chlorine reacts with the natural organic matter (NOM) in waters and forms disinfection by-products (DBP). Major of these by-products are trihalomethanes (THM) and haloacetic acids (HAA). They have been known to cause cancer and other toxic effects to human beings. This study determined the removal efficiencies of THM by nanofiltration (NF) techniques with NF200 and DS5 membrane. The rejection of this chlorination by-products was studied at various feed concentration by changing transmembrane pressure. Experimental results indicated that in general increasing operating pressure produces a higher flux but does not have a significant effect on THM rejection. On the other hand, increasing the feed concentration produces a little change in the overall flux and rejection capacity. NF200 membrane removed more THM than DS5 membrane. The higher removal efficiency of dibromochloromethane (DBCM) was attributed to brominating characteristics (higher molecular weight (MW) and molecular size). As a consequence, the results of this study suggest that the NF membrane process is one of the best available technologies for removing THM compounds.     

Seasonal variations of chemical and physical characteristics of dissolved organic matter and trihalomethane precursors in a reservoir: a case study

Dissolved organic matter (DOM) and its potential to form disinfection by-products (DBPs) during water treatment are of great public health concern. Understanding the seasonal changes in DOM composition and their reactivity in DBP formation could lead to a better treatment of drinking water and a more consistent water quality. DOM from the East-Lake, a reservoir in the south-China, was fractionated and characterized by XAD resin adsorption (RA) and ultrafiltration (UF) techniques during different seasons within a year. The properties of chemical fractions (isolated by RA) appeared more stable than those of physical fractions (separated by UF) throughout the sampling period. The relative contribution of each chemical fraction to the total dissolved organic carbon (DOC), UV(254) absorbance and trihalomethane formation potential (THMFP) remained relatively constant across the sampling period. However, the physical (molecular weight) fractions of the DOM exhibited large seasonal changes in UV(254) and THMFP. Compared to the parameter of DOC, the THMFP and specific THMFP (STHMFP) of either chemical or physical fractions were more variable. In terms of DOC concentration, the hydrophobic acids (HoA) and hydrophilic matter (HiM) dominated in the DOM in most of the seasons; while the components with molecular weight of 10-30 kDa and less than 1 kDa were the predominant physical fractions.     

Removal of indigo carmine dye from water to Mg-Al-CO(3)-calcined layered double hydroxides

Layered double hydroxides (LDHs) calcined, denoted as CLDHs, have been shown to recover their original layered structure in the presence of appropriate anions. In the light of this so-called "memory effect", the removal of indigo carmine (IC), an anionic dye, from aqueous solution by calcined Mg-Al-CO(3) LDHs was investigated in batch mode. We looked at the influence of pH values, dye-adsorbent contact time, initial dye concentration and various temperatures of heating of LDHs on the decolorization rate of IC. The adsorption isotherms, described by Freundlich model are L-type. The characterization of the solids CLDHs, both fresh and after removal of IC, by X-ray diffraction and infrared spectroscopy shows that the IC adsorption on CLDHs is enhanced by reconstruction of a matrix hydrotalcite intercaled by the dye, and the intercalation of the organic ion was clearly evidenced by the net increase in the basal spacing from 0.76 nm for [Mg-Al-CO(3)] to 2.13 nm for the organic derivative.     

浅析大连港区海水源热泵的应用

介绍在我国北方沿海港口回填区内,通过打井取水发展海水源热泵,实现节能环保的目标。由于海水温度低,经试验确立海水+地温耦合式海水源热泵系统。针对工程实例在初投资和运行费用方面与集中供暖电制冷空调方案进行对比,说明海水源热泵系统具有明显节能环保的优点及在沿海地区广阔的应用前景。     

Degradation of natural organic matter in surface water using vacuum-UV irradiation

The use of vacuum-UV (VUV) radiation to degrade natural organic matter (NOM) and the main variables affecting the efficiency of this process were investigated using an annular photoreactor. After 180 min of irradiation with VUV, the total organic carbon (TOC) decreased from 4.95 ppm to 0.3 ppm. Also, decadic absorption coefficients of the water at 185 nm and 254 nm decreased from 3.2 cm(-1) to 2.85 cm(-1), and 0.225 cm(-1) to 0 cm(-1), respectively. The reactor operation was kinetically controlled for Reynolds numbers greater than 600, changes of pH between 5 and 9 had little effect, and increases in alkalinity decreased the process efficacy. Additionally, H(2)O(2)/VUV and VUV processes were compared to H(2)O(2)/UV and UV processes, where the formers showed greater effectiveness with complete mineralization of NOM as opposed to partial oxidation with H(2)O(2)/UV, and no mineralization with UV alone. Modeling and analysis of the photon flux and absorption in the reactor showed that 99% of the 185 nm radiation was absorbed by the water in the reactor. In comparison, only 48% of the 254 nm radiation was absorbed by the water. The overall quantum efficiency of the mineralization for VUV was 0.10 for 50% TOC reduction.     

Distribution of polycyclic aromatic hydrocarbons in water, sediment and soil in drinking water resource of Zhejiang Province, China

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in Qiantang River, the most important drinking water resource in Zhejiang Province, China. A total of 270 water samples, 64 sediment samples and 21 soil samples near riverbank were collected during January 2005-July 2006. The total concentrations of PAHs in water, sediments and soils ranged from 70.3 to 1844.4 ng/L, from 91.3 to 1835.2 ng/g and from 85.2 to 676.2 ng/g, respectively. The concentrations of PAHs in rural areas were lower than those in city zones. The concentrations of PAHs in July were the lowest while those in January were the highest during four seasons. The concentrations of PAHs in 2006 were compared with those in 2003 and 2005. The result showed PAHs pollution in this drinking water resource was increasing with time. The relationship between log K(oc) and log K(ow) of PAHs for field data on sediments and predicted values indicated that Qiantang River was mainly contaminated by petrogenic PAHs. The same result was obtained by the ratios of AN/(AN + Phen) and Flur/(Flur + Pye). Ratios of K(oc) for PAHs on sediments to that on corresponding soils indicated that PAHs in Qiantang River were mainly obtained from soil runoff.     

Contact resistance variation in top-contact organic thin-film transistors with the deposition rate of Au source/drain electrodes

We investigated the effect of the deposition rate of Au source/drain electrodes on the contact resistance of the top-contact organic thin-film transistors (OTFTs). For the formation of source/drain contacts, Au was thermally deposited at the different rates of 0.5, 1.0, 5.0, and 13.0 Å/s. With increasing the Au deposition rate, the contact resistance extracted at the gate voltage of − 30 V could be reduced from 14 × 10⁶ to 2.4 × 10⁶ Ω, resulting in the characteristic improvements of the top-contact OTFT. It is also found that the contact resistance significantly affects the off-state currents of the device having the short channel length of 10 μm. The control of the deposition rate of source/drain electrodes is suggested to optimize the contact properties of the top-contact OTFTs as well as the device performance.     

浅析水源热泵空调系统的调试

水源热泵空调系统的性能主要受水系统和制冷剂充注量的影响,通过调节循环水温度和流量以及制冷剂的压力可以使机组在最佳状态下运行,减少故障率,为设备生产企业节约售后服务费用。     

Characterization of etch pit formation via the Everson-etching method on CdZnTe crystal surfaces from the bulk to the nanoscale

A combination of atomic force microscopy, optical microscopy, and mass spectrometry was employed to study CdZnTe crystal surface and used etchant solution following exposure of the CdZnTe crystal to the Everson etch solution. We discuss the results of these studies in relationship to the initial surface preparation methods, the performance of the crystals as radiation spectrometers, the observed etch pit densities, and the chemical mechanism of surface etching. Our results show that the surface features that are exposed to etchants result from interactions with the chemical components of the etchants as well as pre-existing mechanical polishing.     

Microbiological quality assurance of purified water by ozonization of storage and distribution system

Purified water storage and distribution systems at ambient temperature are highly susceptible to microbial contamination and formation of biofilm. The impact of two disinfection regimens with ozone as a function of time, the heterotrophic plate counts (HPC), and the concentration of total organic compounds (TOC) in purified water were investigated over a period of 4 years. We have established that concentrations of ozone of 70 ± 20 ppb in the production regimen and 250 ± 50 ppb in the disinfection regimen are sufficient to maintain a low bioburden and low TOC in a recirculating distribution system. The purified water that entered into the distribution system has low HPC (0.01 CFU/mL), indicating a reduction by ozone in the storage tank by up to approximately 120-fold. Over 4 years, 94-98% of the microbial counts were in the category 0-5 CFU/mL, and none in category ≥50 CFU/mL. In spite of increased TOC in the inlet water, up to 40 ppb, the microbial counts in purified water in the distribution loop were unaffected. The study emphasizes that the critical points regarding microbial contamination of the purified water system are user point valves and the tubes used for transferring water to equipment. The specified ozone level prevents microbial growth and formation of biofilm in the distribution system that might otherwise endanger the water quality by sporadic release of microbes.     

水源水及生活饮用水中铝的新法测定

叙述了采用硝酸镁作为基本改进剂,成功地用石墨炉原子吸收分光光度法直接测定饮用水及水源水中铝,为饮用水及水源水中痕量铝的测定提供了一种灵敏、准确、快捷的方法。     

Characterization of aquatic humic substances to DBPs formation in advanced treatment processes for conventionally treated water

An advanced water treatment demonstration plant consisted of ozone/granular activated carbon processes was operated to study feasibility of the processes. Natural organic matter (NOM) from raw and process waters at the demonstration plant was isolated into humic and non-humic fractions by physicochemical fractionation method to investigate characteristics of humic fraction (i.e., humic substances, HS) as a predominant haloform reactant. Ozone did not significantly oxidize the carboxylic fraction (from 39.1 to 35.9%), while GAC removed some of the carboxylic fraction (from 35.9 to 29.1%). Formation potential of trihalomethanes (THMs) as compared to haloacetic acids formation potential (HAAFP) was highly influenced by HS. Higher yields of THMs resulted from chlorination of HS with a higher phenolic content and phenolic fraction in the HS gradually decreased from 60.5% to 15.8% through the water treatment. The structural and functional changes of HS were identified by elemental, Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H NMR) analyses, and these results were mutually consistent. The functional distribution data obtained by using A-21 resin could be used to support the interpretation of data obtained from the spectroscopic analyses. Decreases in ratio of UV absorbance at 253 nm and 203 nm (A(253)/A(203)) and DBPFPs/DOC showed consistent trends, therefore, A(253)/A(203) ratio may be a good indicator for the disinfection by-product formation potentials (DBPFPs).     

浅析水源热泵测量误差

分析采用载冷剂法测试水源热泵性能时引起不确定度的各种因素,得到主侧与校核侧测试结果间的不确定度传递关系,探讨测试工况等因素对不确定度的影响和处理方法。     

Non-firing ceramics: Effect of adsorbed water on surface activation of silica powder via ball milling treatment

“Non-firing” ceramics have recently attracted much attention because many functional ceramics can be achieved by this method without the sintering process. The underlying idea of this method is to activate the surface of the particles by ball milling. In this study, the effect of adsorbed water on the surface of raw silica powder was investigated. Amorphous silica powder was mechanically treated by a rotating ball mill system and the surface activity of the raw and treated silica powders was measured based on the water adsorbed volume on the powder surface. The results showed that the surface activity of the silica powder increased with the increasing adsorbed water volume on the surface of the silica powder. In addition, better mechanical properties evaluated by the Vickers hardness test were achieved for the silica with more water adsorbed on its surface. The effect of milling energy and ball to powder ratio on activation of the silica was also investigated.     

水源热泵机组的优化设计

本文主要从总体设计、换热器设计、供液控制方式等方面对水源热泵机组的优化设计进行讨论。     

Characterization of titanium dioxide atomic layer growth from titanium ethoxide and water

Atomic layer growth of titanium dioxide from titanium ethoxide and water was studied. Real-time quartz crystal microbalance measurements revealed that adsorption of titanium ethoxide is a self-limited process at substrate temperatures 100–250°C. A relatively small amount of precursor ligands was released during titanium ethoxide adsorption while most of them was exchanged during the following water pulse. At temperatures 100–150°C, incomplete reaction between surface intermediates and water hindered the film growth. Nevertheless, the deposition rate reached 0.06 nm per cycle at optimized precursor doses. At substrate temperatures above 250°C, the thermal decomposition of titanium ethoxide markedly influenced the growth process. The growth rate increased with the reactor temperature and titanium ethoxide pulse time but it insignificantly depended on the titanium ethoxide pressure. Therefore reproducible deposition of thin films with uniform thickness was still possible at substrate temperatures up to 350°C. The films grown at 100–150°C were amorphous while those grown at 180°C and higher substrate temperature, contained polycrystalline anatase. The refractive index of polycrystalline films reached 2.5 at the wavelength 580 nm.