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。     

基于粒度分布的MRU脱盐闪蒸罐工艺参数优选

乙二醇再生脱盐装置是深水天然气开发中的核心装置之一,常采用蒸发结晶和重力沉降原理来实现高溶解度盐(如NaCl)的脱除。对脱盐闪蒸罐的主要工艺参数,过去主要从能耗的角度进行优选,只能反映工艺参数对蒸发的影响,难以直接反映对结晶与颗粒沉降分离的影响。从晶体粒度分布的角度出发,利用激光粒度仪研究了温度、压力和停留时间等因素对NaCl在乙二醇溶液中晶体粒度分布的影响规律,并据此优选工艺参数。结果表明,在同等条件下,温度越高,晶体的粒度分布越分散,平均粒度越小;真空度越高,晶体的粒度分布越分散,平均粒度越小;停留时间过长或过短都将导致晶体的平均粒度变小。对所讨论的介质,优选后的工艺参数为:闪蒸温度140℃,压力-80kPa,停留时间5min。经研制的连续实验装置验证,优选后的参数能实现稳定的沉降分离和脱盐。     

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.     

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.     

海砂淡化关键工艺参数及氯离子含量缓释的研究

主要研究水洗次数、扰动方式及水洗时间对海砂氯离子含量的影响,以得到最佳淡化海砂的关键工艺参数,并研究了关键工艺参数下的海砂氯离子缓释规律.在试验条件下,关键工艺参数是水洗次数不低于3次;扰动方式中转速是关键;清洗时间延长有利于海砂氯离子的释放.结果表明,淡化工艺可以降低海砂氯离子含量,但是随着放置时间延长,海砂氯离子会...     

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。     

堰塞坝漫顶溃决过程数值模拟及应用

堰塞坝作为自然形成的天然坝体,其结构不稳定性强,绝大多数的堰塞坝最终都将发生漫顶溃决,一旦溃决,将会对下游带来巨大的生命和财产损失。因此,有必要合理预测堰塞坝的溃决流量过程,为溃坝应急预案的编制提供理论与技术支撑。本文充分考虑堰塞坝的形态特征及坝料的物理力学特性,建立了一个可合理模拟堰塞坝漫顶溃坝过程的数学模型。该模型可较好地反映水动力条件下的溃口发展过程和下泄流量过程。选择西藏易贡堰塞坝溃坝案例对模型进行验证,通过计算结果与实测资料的对比发现:计算得到的溃口峰值流量、最终溃口宽度、峰值流量到达时间等参数的最大相对误差均在±15%以内;溃口流量过程与实测资料也吻合较好,有效地验证了模型的合理性;参数敏感性分析结果显示,残留坝高、冲蚀模式(单侧与两侧冲蚀)、冲蚀系数等参数对溃坝过程均有重要影响。     

A review of novel electrode materials and techniques for electro-Fenton process applied to the degradation of phenolic compounds

A major problem coming across humanity in the early 21st century is related to environmental crises, including shortage and pollution of water sources. For this reason, extensive studies have been conducted to find effective techniques for purifying water from industrial pollutants. Advanced oxidation process (AOP) has lately caught the attention of researchers, which is an efficient, clean and contemporary method to remedy wastewater effluents. However, primitive versions of AOP methods lacked several aspects like strict pH requirements and involvement of sediments, which is why further modifications to the technique have been developed, including an electrochemical catalytic degradation approach, namely, electro-Fenton and similar processes. This study will look through a set of novel papers investigating the application of various electrodes for the electrochemical treatment of solutions contaminated with phenol and phenolic compounds, which tried to address several shortcomings of more outdated practices and optimize the method for a set of different scenarios.     

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.     

CFRP 混凝土界面黏结滑移关系试验

为测得FRP 混凝土界面黏结滑移本构关系的下降段,改进了前期提出的双拉试件,设计了水平加载方案.利用MTS加载系统对9个改进试件进行加载测试,实测出18个测区的CFRP 混凝土界面黏结滑移（δ τ）关系曲线的下降段和最大滑移量,从而得到18条完整的实测δ τ关系曲线,并依此给出1个回归公式.所测得的CFRP 混凝土界面间黏结滑移曲线3大关键控制参数为峰值剪应力τf 227～519MPa,峰值剪应力对应的滑移量δf 0031～0077mm,最大相对滑移量δu 0087～0223mm.     

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。     

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...     

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%.     

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.