海水淡化工艺设计与经济分析

以珠海市十字门水道的海水淡化处理为例,介绍了该区域的原水水质情况及出水水质要求,从海水取水、预处理、系统控制等方面,阐述了反渗透海水淡化工程的工艺设计流程,并对其运行成本及经济效益进行了分析,指出采用反渗透膜处理淡化法可满足该区域中水给水的使用要求。     

气浮工艺用于海水淡化预处理试验研究

以三氯化铁和聚合氯化铝作为混凝剂,氯水作为氧化剂,考察了气浮工艺用于海水淡化预处理的运行效果.结果表明:预氧化可以强化混凝+气浮预处理工艺对浊度、CODMn、UV254和TOC的去除效果,三氯化铁的最佳投加量为15～20 mg/L,聚合氯化铝最佳授加量为6～10mg/L,最佳气浮回流比为15％;在最佳运行条件下,预处理...     

Time-dependent drift degradation due to the progressive failure of rock bridges along discontinuities

An important element of time-dependent drift degradation is the progressive failure of intact segments along discontinuities, referred to as rock bridges. A fracture mechanics model is developed to simulate the time-dependent failure of rock bridges along discontinuities. The time dependence of the rock bridge failure process is modeled utilizing subcritical crack growth. The rock bridges give an effective cohesion to the discontinuities, and this cohesion is time-dependent due to the time-dependent failure of the rock bridges. The resulting first-order differential equation for joint cohesion is implemented into the UDEC distinct element numerical code to model time-dependent drift degradation. The model and its implementation into UDEC are validated using several simple examples, including a direct shear test and a rigid block on a slope. Two time-dependent drift degradation examples are then shown, one with and one without thermal loading. These examples used similar geometry, material parameters and in situ stresses as for the proposed underground drifts for the storage of nuclear waste at Yucca Mountain. Both with and without thermal loading, a large zone develops around the excavation where the joint cohesion and tensile strength drop to zero due to the failure of rock bridges. This in turn results in an excavation that is significantly less stable than if time dependence was not included. The results demonstrate the importance of time-dependence on the stability of underground excavations in hard rock.     

Variance of the fatigue damage due to a Gaussian narrowband process

The fatigue life of a structure is inherently random when the loading is irregular. There is a vast body of literature on the analysis of the mean fatigue damage, but very few studies have been devoted to the variance. This paper presents an improved method for analyzing the variance of the damage for any narrowband Gaussian process. The field of application is not confined to the linear oscillator, unlike approaches in previous studies. The method is simple to apply; it involves a single summation for arbitrary processes, and closed form solutions are available for special cases (linear oscillator and bandpass process). The effectiveness of the method is demonstrated through case studies encompassing a variety of systems, including a realistic spectrum commonly seen in offshore engineering. Using rainflow counting of simulated time domain stresses as a benchmark, the proposed method is shown to yield a highly precise prediction of the variance. Moreover, it is significantly more accurate than an existing method for the linear oscillator system.     

Mechanical performance of BStIV grade steel bars with regard to the long-term material degradation due to corrosion damage

The mechanical performance of BStIV grade reinforcing steel bars from four different manufacturers was experimentally investigated and evaluated by exploiting the performance indices concept. The experiments included tensile tests, carried out on uncorroded and pre-corroded steel specimens. To corrode the specimens, accelerated laboratory corrosion tests were involved. The later tests were made to assess the expected degradation of the materials mechanical performance with accumulating corrosion damage during the life of a reinforced structure. For the evaluation of the mechanical performance, index Q_D has been introduced. The index Q_D considers the combination of tensile strength and tensile ductility in a single quantity by accounting also for scatter in material’s mechanical properties. Index Q_D can be applied to assess the materials mechanical performance both in the undamaged and in the corroded conditions. In both cases, the materials were ranked based on the outcome of the evaluation of their mechanical performance. Subjective choice is needed in order to consider the effect of corrosion damage on the material’s mechanical performance.     

SBR反应器内基质降解的动力学分析

分析了序批式活性污泥法(SBR法)反应器内基质降解的动力学过程,推导出动力学模式,提出了反应动力学参数的求定方法,利用试验结果对动力学关系式进行了回归分析,求得污水的动力学参数,为应用序批式活性污泥法提供了设计依据。     

Formation of hazardous inorganic by-products during electrolysis of seawater as a disinfection process for desalination

From our previous study, an electrochemical process was determined to be a promising tool for disinfection in a seawater desalination system, but an investigation on the production of several hazardous by-products is still required. In this study, a more intensive exploration of the formation patterns of perchlorate and bromate during the electrolysis of seawater was conducted. In addition, the rejection efficiencies of the targeted by-products by membrane processes (microfiltration and seawater reverse osmosis) were investigated to uncover the concentrations remaining in the final product from a membrane-based seawater desalination system for the production of drinking water. On the electrolysis of seawater, perchlorate did not provoke any problem due to the low concentrations formed, but bromate was produced at a much higher level, resulting in critical limitation in the application of the electrochemical process to the desalination of seawater. Even though the formed bromate was rejected via microfiltration and reverse osmosis during the 1st and 2nd passes, the residual concentration was a few orders of magnitude higher than the USEPA regulation. Consequently, it was concluded that the application of the electrochemical process to seawater desalination cannot be recommended without the control of bromate.     

Characterization of the degradation performance of the sulfamethazine antibiotic by photo-Fenton process

The present study provides results describing the degradation performance of the Sulfamethazine (SMT) antibiotic via photo-Fenton treatment. Experiments were carried out using 1 L solution samples of SMT (50 mg L⁻¹) under different conditions. HPLC results reveal that both Fenton and photo-Fenton reactions were able to completely remove SMT antibiotic from the studied samples in less than 2 min treatment. Half-life times and kinetic parameters (assuming a pseudo-first-order kinetics at reaction initial stage, far from the equilibrium) for SMT degradation were determined and discussed. Hence, appropriate Fenton reagent loads are given to attain different targets proposed. TOC and HPLC data also revealed the presence of reaction intermediates; thus toxicity assays were performed regarding bacterial growth rate. The toxicity of an SMT solution was shown to increase during its degradation by means of photo-Fenton reactions.     

电化学脱盐技术及其效果初探

我国在电化学脱盐防锈技术方面的研究与应用起步较晚,一些技术诀窍,如电解质溶液种类、浓度及电流密度、脱盐时间等对脱盐效果的影响等尚未完全掌握。本文对电化学脱盐技术进行了介绍,初步探讨了电解质溶液的种类、浓度及电流密度等对脱盐效果的影响。试验结果表明,采用0．001mol／L Li2B4O7＋饱和Ca（OH）2溶液和2A／m^2的电流密度可以取得较好的脱盐效果。     

The current state of the problem of removing boron from the sea and brackish waters in the process of reverse osmosis desalination

The technical and economic analysis of existing methods for reducing the boron concentration in permeate of the reverse-osmosis plants to the maximum allowable levels for the drinking and irrigation waters has been performed. Relevant tasks were defined that have to be solved for creating practical reverse-osmosis plants of desalting the sea and subterranean waters.     

Investigation of mechanical properties of soft rock due to laboratory reproduction of physical weathering process

The focus of the present study is on soft rocks (moderately weathered granite and artificial rock) that have suffered physical weathering due to changes in temperature and confining pressure. Unconfined compression tests were conducted on moderately weathered granite, and triaxial compression tests were conducted on artificial rocks. Two test plans were conducted to study the effect of weathering. In the first plan, the specimens suffered weathering process cycles under unconfined conditions, followed by triaxial tests with different confining pressures (0 kPa, 30 kPa, 60 kPa, and 90 kPa). In the second plan, the specimens suffered weathering process cycles under a certain confining pressure (0 kPa, 30 kPa, 60 kPa, and 90 kPa), and the shear strength and initial Young's modulus in each weathering cycle was then studied. Finally, based on the formula of the shear wave velocity and initial Young's modulus, the relationships between normalized shear strength and normalized shear wave velocity were found. These relationships can be used in a further study to understand rock strength on site by detecting the shear wave velocity.The results of this study show that artificial rocks (cement treated sand, CTS) can be used as a homogeneous material to simulate soft rock. In the stress-strain curves, the initial Young's modulus showed no significant change when increasing the confining pressure. The initial Young's modulus showed a nonlinear decrease when the weathering process cycle increased. When soft rocks suffer the weathering process at a certain confining pressure, the relationship between normalized shear strength and normalized shear wave velocity was linear. When soft rocks suffer the weathering process at different confining pressures, the normalized shear strength under a lower confining pressure dropped faster than when the confining pressure was higher.     

水力空化与生物法联用降解苯酚的试验研究

本试验将水力空化作为生物法处理含苯酚废水溶液的预处理工艺,研究了苯酚废水中COD的去除率,并与单独用生物法处理苯酚废水溶液后的COD去除率作对比,确定水力空化作为难降解废水预处理工艺的可行性。     

Effect of pesticide concentration on the degradation process by combined solar photo-Fenton and biological treatment

The influence of pesticide concentration, expressed as dissolved organic carbon (DOC), on combined solar photo-Fenton and biological oxidation treatment was studied using wastewater containing a mixture of five commercial pesticides, Vydate, Metomur, Couraze, Ditumur and Scala. Two initial DOC concentrations, 200 mg L⁻¹ and 500 mg L⁻¹ were assayed. Variation in biodegradability with photocatalytic treatment intensity was tested using Pseudomonas putida. Thus the mineralisation required for combining with biodegradation of intermediates by activated sludge was 33% and 55% at 200 mg L⁻¹ and 500 mg L⁻¹, respectively. Biotreatment was carried out in a stirred tank in sequencing batch reactor (SBR) mode. As revealed by the biodegradation kinetics, intermediates generated at the higher pesticide concentration caused lower carbon removal rates in spite of the longer photo-Fenton treatment time applied. One strategy for treating water with high concentrations of pesticides and overcoming the low biodegradability of photo-Fenton intermediates is to mix it with a biodegradable carbon source before biological oxidation. This combination of photo-Fenton and acclimatized activated sludge in several SBR cycles led to complete biodegradation of a concentrated pesticide solution of 500 mg L⁻¹ DOC in 5 h with a carbon removal efficiency of 90%.     

Factors effecting the freeze thaw process in soils and reduction in damage due to frosting with reinforcement: a review

Bulletin of Engineering Geology and the Environment - Seasonal frozen soil is widely distributed in China. The seasonal freeze-thaw (F-T) process of soil will adversely affect the safety and...     

Characterization of degradation process of cyanobacterial hepatotoxins by a gram-negative aerobic bacterium

A bacterium termed 7CY, capable of decomposing cyanobacterial toxins, was isolated from surface water sample of Lake Suwa and degradation of microcystin-RR and nodularin-Har was investigated. The isolated 7CY was a gram-negative, aerobic bacillus, and a member of a genus Sphingomonas. The strain degraded microcystin-LY, -LW, and -LF completely as well as microcystin-LR within 4 days after their addition (6 microg/ml) whereas degradation of nodularin-Har did not occur at all during experiment. On the contrary, the strain was capable of degrading nodularin-Har in the presence of microcystin-RR and both toxins were completely decomposed within 6 days. The strain scarcely degraded nodularin-Har in the presence of microcystin-RR when glucose and ammonium chloride were added to the medium. The degradation of nodularin-Har did not occur in the medium from which bacterial cells had been removed after degradation of microcystin-RR. Furthermore, when microcystin-RR and nodularin-Har were added to the cytoplasm fraction of 7CY cells, microcystin-RR was rapidly degraded within 18 h, but nodularin-Har was not. The strain 7CY may require an enzyme(s) induced during the degradation of microcystin-RR in order to utilize nodularin-Har as nutrition.     

GFRP筋嵌入式加固混凝土构件黏结破坏性能试验研究

嵌入式(NSM)加同法是FRP材料加固混凝土结构的一种新的应用形式.通过GFRP筋嵌入混凝土黏结试验,研究黏结长度和开槽尺寸对破坏形式和极限承载力的影响.极限承载力随黏结长度增加而增加,平均黏结强度随黏结长度增加而减少.当黏结长度较小时发生GFRP筋与树脂界面破坏和树脂周围混凝土劈裂破坏.当黏结长度较大时,沿GFRP筋...     

脱盐技术在中东及亚洲的影响

地球71％的表面为水所覆盖,然而仅有一小部分是饮用水,这是一种很残忍的讽刺。然而,正如乔纳森·安德鲁斯（Jonathan Andrews）指出的,随着脱盐技术的发展,曾经价格高昂仅富产石油的国家才用得起的工艺,已经成为许多国家都支付得起的选择了。     

Oxidative degradation of N-nitrosodimethylamine by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide

This study investigates the oxidative degradation of N-nitrosodimethylamine (NDMA), a probable human carcinogen, by conventional ozonation and the advanced oxidation process ozone/hydrogen peroxide (AOP O(3)/H(2)O(2)). The rate constants of reactions of NDMA with ozone and hydroxyl radical ((*)OH) were determined to be 0.052+/-0.0016M(-1)s(-1) and (4.5+/-0.21)x10(8)M(-1)s(-1), respectively. The experiments performed with buffered deionized water varying solution pH and employing H(2)O(2) and HCO(3)(-) clearly showed that the reaction with (*)OH dominates the NDMA oxidation during ozonation. Conventional ozonation with up to 160 microM (=7.7 mgL(-1)) ozone led to less than 25% NDMA oxidation in natural waters. The AOP O(3)/H(2)O(2) required 160-320 microM ozone ([O(3)](0)/[H(2)O(2)](0)=2:1) to achieve 50-75% NDMA oxidation. However, multiple injections of ozone of the same overall dose somewhat improved the oxidant utilization efficiency by minimizing (*)OH scavenging contribution of oxidants. Methylamine (MA) was found to be a major amino product from NDMA oxidation initiated by (*)OH. The mechanism of NDMA oxidation to MA is discussed based on the results obtained in this study and the previous literature. Bromate formation may be the limiting factor for NDMA oxidation during ozonation and ozone-based AOPs in bromide-containing waters.     

Separate estimation of adsorption and degradation of pharmaceutical substances and estrogens in the activated sludge process

The removal of three estrogens such as 17beta-estradiol, two endocrine disruptors like bisphenol A, and 10 pharmaceutical substances like ibuprofen (IBP) by activated sludge was experimentally examined. The contribution of adsorption and degradation to the overall removal was estimated separately and successfully. At the neutral pH condition, the target pharmaceutical substances showed little tendency of adsorption to the sludge and their water-sludge partition coefficients were lower than those of the target estrogens. On the other hand, the increasing tendency of adsorption was observed in the lower pH condition. A linear relationship between the log of the partitioning coefficient and logK(ow) was observed when pH was lowered to keep the pharmaceuticals neutral solutes. The acidic operational condition was preferable for the removal of acidic pharmaceutical substances because the limiting stage for the removal was not biodegradation but the transfer of substances from the water phase to the sludge phase.     

Sonolytic degradation of methyl tert-butyl ether: the role of coupled Fenton process and persulphate ion

The sonolytic degradation of methyl tert-butyl ether (MTBE) has been investigated at ultrasonic frequency of 20 kHz. The observed pseudo-first-order rate constant decreased from 1.25 x 10(-4) to 5.32 x 10(-5) s(-1) as the concentration of MTBE increased from 2.84 x 10(-2) to 2.84 x 10(-1) mM. The rate of degradation of MTBE increased with the increase of the power density of ultrasonicator and also with the rise in reactor system temperature. In the presence of oxidising agent, potassium persulphate, the sonolytic rate of degradation of MTBE was accelerated substantially. Tert-butyl formate (TBF) and acetone were found to be the major intermediates of the degradation of MTBE. It is found that the ultrasound/Fe2+/H2O2 method is promising process for the degradation of MTBE. More than 95% degradation of MTBE (2.84 x 10(-2) mM) along with its intermediate products has been achieved during the coupled ultrasound/Fe2+/ H2O2 method. Hence, the coupled ultrasound/Fe2+/H2O2 may be a viable method for the degradation MTBE within a short period of time than the ultrasound irradiation process only. A kinetic model, based on the initial rates of degradation of MTBE and TBF, provides a good agreement with the experimental results.