植物根系固土护坡机理的研究进展及展望

在综合国内外相关研究成果的基础上,详细介绍了近几年来植物根系固土护坡机理的研究进展。文章分别从水文效应和力学效应2个方面对根系固土护坡机理进行了介绍,并着重从根增强的理论模型、根-土相互作用等方面论述了植物根系固土护坡的力学效应。首先介绍了根增强理论的先驱模型Wu和Waldron模型,文章从多方面论证了Wu和Waldron模型假定穿过剪切面的所有根在受力时同时破坏高估了根的增强作用,详细介绍了国外学者对Wu和Waldron模型改进后,最新提出的2种考虑根系逐渐破坏的力学模型——纤维束增强模型FBM和根束增强模型RBM。FBM模型用动态纤维束来模拟根系的渐进破坏,假设荷载被分配给束中的每个根,当载荷增加到其值超过了某单根的抗拉强度时,该根被拉断,而被该根分担的载荷被重新分配到剩下的完好的根中,直到所有的根都拉断。该模型使用应力控制的加载过程,不能得到完整的力-位移关系曲线;且该模型中没有考虑根的直径分布、几何性质、力学性质等的影响。为了克服上述缺陷Schwarz在FBM模型的基础上,又提出了RBM模型。RBM模型是一个以位移控制加载过程的纤维束模型,该模型考虑整个根束的拔出力是位移的函数,并被表示成单根的拔出力之和。文章最后详细论述了根系的拔出机理,探讨了植物根系固土护坡研究的发展方向。     

Migration of manganese and iron during the adsorption-regeneration cycles for arsenic removal

Fe-Mn binary oxide incorporated into porous diatomite (FMBO-diatomite) was prepared in situ and regenerated in a fixed-bed column for arsenite [As(III)] and arsenate [As(V)] removal. Four consecutive adsorption cycles were operated under the following conditions: Initial arsenic concentration of 0.1 mg·L^-1, empty bed contact time of 5 min, and pH 7.0. About 3000, 3300, 3800, and 4500 bed volumes of eligible effluent (arsenic concentration≤0.01 mg·L^-1) were obtained in four As(III) adsorption cycles; while about 2000, 2300, 2500, and 3100 bed volumes of eligible effluent were obtained in four As(V) adsorption cycles. The dissection results of FMBO-diatomite fixed-bed exhibited that small amounts of manganese and iron were transferred from the top of the fixed-bed to the bottom of the fixed-bed during As(III) removal process. Compared to the extremely low concentration of iron (<0.01 mg·L^-1), the fluctuation concentration of Mn²⁺ in effluent of the As(III) removal column was in a range of 0.01–0.08 mg·L^-1. The release of manganese suggested that manganese oxides played an important role in As(III) oxidation. Determined with the US EPA toxicity characteristic leaching procedure (TCLP), the leaching risk of As(III) on exhausted FMBO-diatomite was lower than that of As(V).     

传统过滤器改造连续动态过滤器的研究

结合国外先进的连续过滤技术,针对原有的传统过滤器进行设备改造,过滤过程改为"上向流过滤",滤料清洗技术采用"气提洗砂"技术.与改造前相比,该滤塔结构简单,维护和检修方便,工艺处理效率增加50%,效果稳定,运行成本降低50%.在相关的滤料过滤器系统中,连续动态过滤器改造技术符合我国水处理过滤行业现状,并充分利用原有设备和设施,通过最小投资获得新技术革新,使过滤工艺简单化,更适用于小型再生水回用系统.      

不同物理清洗方式对一体式膜生物反应器过滤特性的影响

通过考察一体式膜生物反应器运行过程中的膜污染情况和不同物理清洗方式减缓膜污染的效果,研究造成膜污染的原因和控制膜污染的方法.结果表明:膜外表面沉积污泥是造成膜污染的主要因素.空曝气减轻膜污染的作用有限,只能将归一化膜比通量从0.26提高到0.39;在活性污泥混合液中搓洗膜丝可以清除膜外表面沉积污泥层,可将归一化膜比通量从0.29提高到0.64,是一种方便而有效的清洗方式,且可在实际生产中实现.间歇式运行方式的停抽期间,最低剩余抽吸压力可以用来表征运行过程中膜过滤性能的变化.      

高锰酸盐复合药剂(PPC)安全强化低温低浊水处理

通过中试试验考察了高锰酸盐复合药剂(PPC)安全强化低温低浊水的处理效能,对其强化混凝,强化过滤效果与预氯化处理进行了对比．试验表明,PPC预处理技术在助凝、助滤、去除水体中有机污染物等方面都具有比预氯化更好的处理效果,该项技术对于低温低浊期的水处理具有很好的应用前景．     

活性炭深床浮滤池以直接过滤方式运行处理低温低浊水研究

活性炭深床滤料浮滤池是一种新型的给水处理组合工艺,它的特点是:气浮过滤一体化;活性炭深床过滤;常规处理和深度处理一体化;运行方式灵活。以直接过滤方式运行处理密云低温低浊水,效果理想,对浊度、色度和嗅味的去除效果显著,对有机物具有一定的去除作用。     

城市污水深度处理中有机物的去除

以城市污水地下水回灌为回用目的 ,研究不同的污水深度处理工艺及对二级生物处理出水中有机物的去除 .研究结果表明 ,原水若未经深度处理 ,直接由土壤含水层处理的出水不能满足推荐的回灌水水质要求 .对原水分别采用混凝沉淀、过滤、臭氧氧化、粉末活性炭和粒状活性炭吸附等处理单元及组合工艺进行深度处理效果的对比 ,最终选用由混凝沉淀 ,砂滤 ,粒状活性炭过滤与土壤含水层处理相结合的工艺流程 .城市污水处理厂的二级出水经该工艺处理后 ,出水中的 DOC可降至 3mg/L以下 ,且活性炭柱的产水床体积可达 350 0 BV.     

高速公路通道集水净化渗透系统及其水质分析

结合河北省大广高速公路衡大段实体工程,针对路表径流污染物的种类及处理机理,提出了通道集水净化渗透系统的好氧兼氧消化-沉淀-人工材料吸附-土壤渗滤一元化的复合工艺,该工艺主要采用蛭石作为过滤材料,将路表径流的污染物控制在饮用水水质标准范围内,不仅有效地解决了通道积水问题,还使得地下水得到补充。     

金属膜生物反应器处理生活污水膜污染的影响因素

采用浸没式平板金属膜生物反应器处理模拟生活污水,考察好氧与缺氧/好氧(anoxic/oxic, A/O) 2种运行模式下ρ(MLSS)和污泥粒径分布对膜过滤性能的影响及膜过滤阻力的组成. 结果表明,对于好氧膜生物反应器,存在一个能获得良好膜过滤性能的ρ(MLSS)范围; 好氧模式下膜过滤阻力主要为滤饼层阻力,且滤饼层能通过在线药洗或机械清洗较好地去除,系统在膜通量为0.80～1.00 　m3/(m2·d)下未进行离线药洗连续运行115 d. A/O模式下膜过滤阻力主要为内部阻力; A/O循环导致污泥破碎解体,产生大量微小粒子,在膜孔内形成吸附和堵塞,使膜过滤性能急剧下降,为维持系统运行,A/O阶段将膜通量从1.00 　m3/(m2·d)降至0.50 　m3/(m2·d),并进行了15次膜清洗.      

Improving safety and availability of complex systems using a risk-based failure assessment approach

This paper presents a structured risk-based failure assessment (RBFA) approach, which provides a complete solution to avoid repeated and potential failures to improve overall plant safety and availability. Technological advancements and high product demand have encouraged designers to design mega-capacity systems to enhance system utilization and improve revenues. However, these benefits make the systems more complex and thus prone to unnoticed failure. It is an overwhelming task to address all the failures due to the limited resources and time constraints. This leads to substandard and poor quality failure assessments, which cause repeated failures. To address this common industry concern, a four phase RBFA framework is proposed which is not limited to the identification of root cause(s) but also includes other actions such as failure monitoring. The four phases include the plan phase, the assessment phase, the analysis phase and the implementation-tracking phase. These phases cover identification of failure, failure analysis, root cause(s) analysis, and failure monitoring. In this paper, the applicability and advantages of the proposed approach are examined through two real case studies pertaining to bearing failure and drive coupling failure. By implementing the proposed approach, significant improvements have been experienced in the system availability in both the cases.