Effect of rainfall characteristics on removal efficiency evaluation in vegetative filter strips

The efficiency of a facility to remove non-point source pollution is likely to fluctuate according to conditions such as facility type and rainfall events; therefore, it is required to use a proper method to estimate removal efficiency. This study was conducted to estimate the efficiency of a facility with vegetative filter strips to remove pollutants by using methods previously used for the estimation of removal efficiency and compensate for weaknesses of the known methods. Other ways were presented to estimate an efficiency by which rainfall events were classified according to meteorological condition and amount of rainfall. Rainfall of frequency and summation of load as rainfall of frequency, where the frequencies per rainfall class were considered in efficiency ratio and summation of loads, respectively, seemed to have higher removal efficiencies than those estimated with the previous methods. Although it rained at the basin site, often in small quantity (below 10 mm), the rainfall events of below 10 mm were less frequent, during the monitored rainfall events, which accordingly resulted in low removal efficiencies. However, if the frequencies per rainfall class were considered, overall removal efficiencies of VFS might be increased because the removal efficiencies of the rainfall class under 10?mm was higher than other rainfall classes. Therefore, it is desirable to take into account such factors as effects of rainfall when it comes to measuring the removal efficiency of a non-point source pollutant of a factor, because those facilities are likely to be influenced by meteorological conditions including rainfall characteristics.     

用改进的DDA方法模拟公路隧道的稳定性

用改进的非连续变形分析(DDA)方法对某公路隧道进行了稳定性分析。采用有限元网格生成方法--行波法,在计算区域内自动生成三角形的DDA块体。块体的边界分为真实节理和虚拟节理,虚拟节理的强度取岩体的真实强度。另外,计算中还考虑了预应力锚杆对隧道围岩的加固作用。将计算得到的隧道拱顶、边墙的位移与现场监测结果进行了对比,两者基本吻合,说明改进的DDA方法在地下隧道的稳定性分析方面具有应有前景。     

Triethylamine removal using biotrickling filter (BTF): effect of height and recirculation liquid rate on BTFs performance

This study investigated the removal of triethylamine using a biotrickling filter. The influence of affecting parameters, such as height and recirculation liquid rate (V _L) on contaminant removal efficiency, was examined in detail. The results demonstrated that in the constant empty bed residence time (EBRT), when V _L was increased, the removal efficiency (RE) increased. Also, for a specific V _L, increasing EBRT could also increase RE values. However, it seems that an increasing V _L is a more cost-effective way to enhance RE as compared to an increasing EBRT. The obtained outcomes represented that for a constant EBRT, an increase in inlet loading (IL) could decrease RE. For lower ILs, the removal of the contaminant could be carried out faster in height. The first part of the bed contributed the most to contaminant removal, and for the lower ILs, the contribution was even further. For the first section of bed in a constant IL, increasing EBRT could increase RE. In a constant IL and EBRT, increasing V _L could increase RE, as well as the removed mass loading by at least 20–25 g/m³/h. Also, the effect of the V _L increase on removal amount in the second and third sections of the bed was negligible.     

绿沸石基复合材料对河道水中氨氮去除效果研究

以绿沸石、硅藻土、膨润土、牡蛎壳为主要原材料,包衣机制粒后马弗炉焙烧制成绿沸石-硅藻土(GZD)、绿沸石-膨润土(GZB)、绿沸石-牡蛎壳(GZO)等3款球状氨氮吸附材料。探究造孔剂-粘结剂配比、物料配比、焙烧温度、焙烧时间对污水中氨氮的吸附量和材料散失率的影响,通过吸附动力学、吸附等温线、氨氮去除率、材料散失率试验探讨其吸附机理。并设计了简易装置,用实际河道水样对比分析了3款复合材料与块状绿沸石原矿对氨氮的吸附效果和重复利用次数,对处理效果最佳的GZD中的主要材料绿沸石和硅藻土进行了SEM和XRF表征。结果表明:GZD的氨氮吸附效果最佳,制备条件为造孔剂、粘结剂、绿沸石、硅藻土的质量比为1.2﹕5﹕9﹕1;在500℃下焙烧3 h;GZD对氨氮的吸附符合准二级动力学,用Freundlich等温线比Langmuir等温线更适合描述其吸附过程;GZD对实际河道水样进行5次吸附再生后仍具有明显效果。     

The effect of nitrogen loading on a brackish estuarine faunal community: A stable isotope approach

Coastal ecosystems worldwide face increased nutrient enrichment from shoreline and watershed development and atmospheric pollution. We investigated the response of the faunal community of a small microtidal estuary dominated byRuppia maritima (widgeon grass) in Maine, United States, to increased nitrogen loading using an in situ mesocosm enrichment experiment. Community response was characterized by assessing quantitative shifts in macroinvertebrate community composition and identifying changes in food web structure using stable carbon and nitrogen isotope ratios of producers and consumers. The community was dominated by brackish water invertebrates including midge larvae, oligochaetes, damselfly larvae, amphipods, and ostracods. Experimental nutrient additions resulted in significantly lower densities of herbivorous chironomids and predatory damselflies and greater densities of deposit feeding oligochaetes. Grazing midge larvae (Chironomidae:Dicrotendipes, Cricotopus) consumed epiphytic algae under both natural and enriched conditions. Deposit feedingChironomus was dependent on allochthonous sources of detritus under natural conditions and exhibited a shift to autochthonous sources of detritus under enriched conditions. PredatoryEnallagma primarily consumed grazing chironomids under all but the highest loading conditions. Experimental nutrient loading resulted in an increase in generalist deposit feeders dependent on autochthonous sources of detritus.     

电解脱氮除磷技术在海产养殖废水治理中的研究

海产养殖迅速发展造成水域富营养化、赤潮频发,海产养殖废水污染的治理迫在眉睫。为解决此问题将电解脱氮除磷技术应用在海产养殖废水处理中,并探讨电压、pH、极板间距和电解时间对脱氮除磷去除率的影响。结果表明:脱氮除磷的去除率与电压成正相关,与极板间距成负相关。在电压为30V,极板间距10cm,pH为7时,NH_4~+-N、NO_3~--N和TP的去除率达到最大分别为72%、90%、85%。     

三种人工湿地脱氮除磷效果比较研究

对沸石潜流湿地、砾石潜流湿地和自由表面流人工湿地脱氮除磷性能进行了中试对比试验研究,结果表明在相同进水水质和水力停留时间为1 d的运行条件下,沸石潜流湿地脱氮效果最佳,总氮去除率接近60%;砾石潜流湿地除磷效果最佳,总磷去除率可达70%;自由表面流人工湿地脱氮除磷效果介于沸石和砾石潜流湿地之间.探讨了三种人工湿地脱氮除磷机理方面的差别,并对其进行了经济性、运行方式等方面的比较.     

深基坑开挖中桩墙体系支护的结构优化设计

针对桩墙加内支撑这种支护型式在常规支护结构设计中所存在的不足,提出了一种优化设计方法,通过决策变量、约束条件、目标函数、优化算法的确立以及计算机程序的编制,成功实现了桩墙体系支护结构的参数优化设计。     

基于WBS-RBS的地铁基坑故障树风险识别与分析

针对地铁基坑工程环境复杂、影响因素多的特点,提出以故障树分析为基础结合工作分解结构（WBS）-风险分解结构（WBS）进行风险识别的方法。此方法引入WBS-RBS将地铁基坑工程工作分解结构和风险源分解结构耦合判断并说明相应风险因素或风险事件,并按照故障树建树原则根据彼此间的逻辑关系,用逻辑门连接上下层事件,形成地铁基坑工程主要故障树。在此基础上,对风险因素进行敏感性分析并提出相应的预防措施。     

高压氮气置换甲烷对煤基质孔隙的影响

为探究高压气体吸附-解吸试验对煤基质中孔隙发育规模和结构的影响,选取安鹤矿区鹤壁六矿二1煤层煤样进行了高压氮气置换甲烷吸附-解吸试验,采用低温液氮吸附方法分别测定了高压氮气置换甲烷前后煤的低温液氮吸附解吸曲线,利用BET、BJH和QSDFT 3种分析模型,对煤基质中1.14~300 nm的孔隙规模、分布与结构特征进行了对比分析。分析结果显示煤样的孔容、比表面积和孔隙结构在高压气体置换过程中均发生了变化,孔隙BET比表面积从12.746 0 m²/g降低到7.227 0 m²/g,总孔容从0.009 0 cm³/g降低到0.006 6 cm³/g;孔隙发育规模与孔径分布均发生明显变化,但孔隙形态基本保持不变,孔径分布的变化主要表现为微孔孔容与比表面积的降低为主,而中孔和大孔基本保持不变。     

菌液注射方式对微生物固化砂土动力特性影响试验研究

微生物固化技术是近年来岩土工程领域兴起的一种新型环保地基处理技术,该技术通过向待固化土体内注入细菌,利用细菌水解尿素,并在引入钙源的条件下,诱导产生碳酸钙晶体以胶结松散土颗粒。在微生物固化过程中,碳酸钙晶体分布的均匀性是目前该技术研究的热点之一。文中尝试通过在纯菌液中引入0.05 mol/L氯化钙溶液(称为混合菌液)对细菌分布进行人为干预,并基于动三轴试验及扫描电镜测试,对比分析了纯/混菌液、混合菌液及传统纯菌液等注射方式对微生物固化砂土动力特性的影响。试验结果表明:纯/混菌液注射方式能有效提高微生物固化砂土中碳酸钙晶体分布的均匀性,从而获得碳酸钙含量较高、动弹性模量较大及耗能能力较强的微生物固化砂土。     

离子类型对石油污染含水层中微生物去除苯的影响

近来利用微生物原位修复受石油污染的含水层已被广泛关注,然而地下水中含有许多离子成分,这些无机离子对微生物降解有机污染物的影响机制还不清楚。本文采用批量实验研究了淄博齐鲁石化污染地下水中常见的7种无机离子(NO3-、PO4 3-、SO4 2-、Cl-、Ca2+、Mg2+、Fe3+)对微生物生长及生物降解苯的影响规律,利用高通量测序技术进一步探究了苯降解菌的种群特征。结果表明：7种离子都存在一个最适宜微生物生长的离子浓度,低于或超过该浓度苯的去除率明显降低,其中NO3-、SO42-、Fe3+最适宜浓度为0. 4mmol/L,PO4 3-、Cl-、Ca2+、Mg2+最适宜浓度分别为0. 2mmol/L、0. 1mol/L、2. 5mmol/L、2mmol/L;从微生物含量及其变化幅度来看,地下水环境中的NO3-离子对微生物的生长及苯的去除影响最显著,其他离子的影响则较小,但微生物对Cl-的耐受浓度较高。高通量测序结果显示驯化出的苯降解菌主要属于脱硫弧菌属(Desulfovibrio sp)、脱硫芽胞弯曲菌属(Desulfosporosinus sp)、不动杆菌属(Acinetobacter sp)和假单胞菌属(Pseudomonas sp)中的菌株。研究结果可为石油污染地下水的原位生物修复提供一定的科学依据。     

Optimization and design of a continuous biosorption process using brown algae and chitosan/PVA nano-fiber membrane for removal of nickel by a new biosorbent

In this study, nickel ions adsorption from zinc ingot factory wastewater by brown algae (Sargassum glaucescens) and chitosan/polyvinyl alcohol nano-fiber membrane at continuous system was studied. The continuous process included a biosorption reactor and fixed-bed reactor that were optimized by predicting two batch steps with response surface modeling, based on the Box–Behnken in the novel approach. Nano-biosorbent characterized by scanning electron microscopy, Brunauer–Emmett–Teller and Fourier transform infrared spectrometer analysis. Maximum biosorption in this continuous system was at pH 6, biosorbent doses 8 g L^?1 S. glaucescens and 0.48 g L^?1 nano-fiber. The study of the reaction rate showed kinetic data best fitted by pseudo-first-order model with R ² > 0.95 than pseudo-second-order and intraparticle diffusion models. Biosorption equilibrium data were performed using Langmuir isotherm and Freundlich isotherm, Langmuir isotherm fit better with equilibrium data.     

Assessment of sediment and erosion rates by using the caesium-137 technique in a Chinese polygonal karst depression

Karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants; yet the sedimentology of many depressions is not well understood in the world. In this paper, the ¹³⁷Cs technique was employed to estimate recent sedimentation rates in a Chinese polygonal karst depression. The results indicate that the sediment deposition rates ranged from 0.91 to 1.97 mm year⁻¹ from 1963 to 2007, and the average sediment deposition rate and specific deposit yield were estimated to be 1.47 mm year⁻¹ and 20 t km⁻² year⁻¹, respectively. These results are consistent with the local monitoring data of runoff fields, which confirms the validity of the overall approach. This shows that the soil loss rate is very low in some karst areas of Southwest China. Above all, the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst depressions, rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes. In addition, the space distribution of surface soil and ¹³⁷Cs inventories are affected remarkably by the inhomogeneous dissolution of limestone under the soil. It may be an important phenomenon, which exists widely in karst areas, and it is significantly different from other places.     

Assessing the natural recovery of a lake contaminated with Hg using estimated recovery rates determined by sediment chronologies

Deer Lake is an impoundment located near Ishpeming, Michigan, USA. Iron mining assay laboratories located in Ishpeming disposed of Hg salts to the city sewer whose outfall was located along an inlet to Deer Lake. An effort to remediate the system in the mid 1980s which consisted of drawing down water in the impoundment in order to volatize Hg from the sediments did not result in recovery of the system. Since the mid 1990s, the remediation strategy has been to allow the continual burial of the contaminated sediments, i.e., natural recovery. The goal of this study was to assess the effectiveness of this strategy. This was accomplished by investigating the state of the system in terms of its recovery and estimating the time frame for recovery. Sediment cores were collected in 2000 to determine historical trends in accumulation rates and concentrations of Hg and other metals. Sedimentation rates and sediment ages were estimated using ²¹⁰Pb. Event-based dating (e.g., peak of ¹³⁷Cs in 1963) was used to supplement ²¹⁰Pb data due to non-monotonic features in the ²¹⁰Pb profile and activities that were not at supported levels at the base of the core. Selected results are that: (1) drawdown significantly influenced sedimentation patterns causing slopes for ²¹⁰Pb profiles that reflected the influx of older sediment, (2) periods of Fe production correlate to Hg loading indicating the point source for contamination, a relationship not previously identified, (3) Hg:Al ratios indicate a recent change to a watershed pathway for Hg loading and (4) Hg concentrations had decreased from their peak, remain elevated, and were increasing after 1997. The cause of the recent Hg concentrations may be related to influx of contaminated watershed soils or sediments. Estimating the time frame for recovery is challenging in this system because the process of natural recovery seems to have been arrested and deeper, uncontaminated sediments, were not recovered as a basis for reference. However, a recovery to background conditions is likely not achievable since rates of Hg loading to nearby lakes and the current rate of atmospheric deposition are greater than an estimate of background conditions for Deer Lake. Assuming recovery continued after 2000, estimates of the time required for recovery varied based on the system state used to define it (e.g., recent rates of wet Hg deposition or Hg surface concentrations/fluxes from similar systems), but were less than 12 a. However, the recent increasing values of recovery indicators (e.g., Hg concentrations) suggests that these estimates are conservative and will be longer if recovery remains arrested, which may in part be due to the legacy of Hg contamination on the landscape. This study shows that estimates of recovery of highly disturbed lake systems can be made in the absence of within lake reference conditions by using comparisons to reference systems and challenges of estimating ages from atypical ²¹⁰Pb activity profiles can be overcome in part using event-based dating techniques.     

共存重金属离子对针铁矿活化过硫酸盐去除水中磺胺吡啶的影响

基于硫酸根自由基的高级氧化技术能有效降解水中磺胺类药物残留。由于在自然环境中共存重金属会对环境修复效果产生一定影响,文中重点研究了不同pH环境条件下不同重金属离子对针铁矿活化过硫酸盐(PS)去除水中磺胺吡啶(SPY)的影响。不同类型重金属离子(Cu^2+、Pb^2+、Cd^2+,0.2mmol/L)在反应体系(初始条件:针铁矿,1.0g/L;PS,4mmol/L;SPY,10mg/L;pH=8.2)中对SPY的降解对比研究发现:在无重金属共存的条件下,针铁矿/PS体系降解SPY的去除率为25.2%;Pb^2+和Cd^2+对针铁矿/PS体系的影响较弱,去除率分别为30.8%和34.8%;Cu^2+的促进作用很大,可以使SPY被完全降解(100%)。机理分析认为,在针铁矿/PS体系中Pb^2+和Cd^2+主要通过影响吸附作用导致磺胺吡啶被去除,而Cu^2+主要通过自身活化PS的作用。不同pH条件(3.0,8.0,12.0)实验证实弱碱性条件下,Cu^2+/针铁矿/PS能够发挥较高的活性从而降解SPY。本文结果为采用针铁矿活化过硫酸盐技术修复类似复合污染地下水环境提供了实验依据。     

Physical evidence of the effect of vertical cyclic loading on soil improvement by rigid piles: a small-scale laboratory experiment using Digital Image Correlation

This paper presents an experimental study focusing on the mechanisms taking place in a granular platform supported by piles in soft soil under vertical cyclic loading. An original three-dimensional laboratory model was developed, with a scale factor of 1/10 on the length. The model contains 20 rigid piles, and the compressible soil is explicitly simulated by a soft material. The case of a thin granular load transfer platform overlaid by a rigid slab is studied. Tests were performed under monotonic or cyclic loading applied on the surface using a pressurized membrane. The analysis is based on a force and displacement sensor instrumentation and application of a Digital Image Correlation technique. The evaluation of the load transfer onto the piles and the settlements in the platform are some of the main points under the scope of this study. The effect of the cyclic loading and the sequence of loading on the structure’s response are examined by a comparative study between the series of cyclic and monotonic tests. Settlement accumulation and increase in the load transmitted to the piles were observed during the cycles. The image analysis gives access to the displacement field within the granular platform, and its evolution during the cycles could be analysed.     

Effect of cyclic loading on the residual strength of over-consolidated silty clay in a ring shear test

In this paper, the effect of cyclic loading on drained residual strength of over-consolidated silty clay is examined based on the results from ring shear tests which were conducted with a sophisticated ring shear apparatus. Initially sheared to form shear zones under different pre-consolidation pressures and at different shear rates (SRs), soil samples were then tested under cyclic loading. After the cyclic loading application, the samples were re-sheared while the corresponding shear strengths were measured. The results show that the effect of cyclic loading on residual strength is noticeable. The effect is related to pre-consolidation history and SR of the soil samples. Under conditions of relatively low over-consolidation ratio (OCR), the soil samples show an increase in residual strength with decreasing SR after cyclic loading. Most of the peak strength values after cyclic loading are higher than the residual strength values obtained before cyclic loading. Two effects of cyclic loading on the residual strength are identified: (a) If OCR is less than or equal to 3.0, the residual strengths measured after cyclic loading are larger than those before cyclic loading; (b) If OCR is greater than or equal to 3.5, the residual strengths after cyclic loading tend to become lower than those in the shear tests before cyclic loading.     

Development of drain hole design optimisation: a conceptual model for open pit mine slope drainage system with fractured media using a multi-stage genetic algorithm

High rainfall in equatorial regions leads to high groundwater levels or pore pressures and a high risk of landslides on the slopes of open pit mines, hindering mining operations. To lower the groundwater level surrounding a slope, a drainage system is needed. A drain hole is a part of a drainage system which utilises gravity to drain groundwater. Drain hole installation in fractured media requires the determination of the number, location, length and other parameters of the drain holes. Drain holes are frequently installed in uniform configurations or in layouts with uniform spacing, which are often ineffective and uneconomical, as some holes are not in the right positions or directions within the fractured media. This paper attempts to develop a conceptual model of an optimised configuration of drain holes by setting the drain hole parameters, or decision variables, such as number, location and length, in such a way that it produces the most effective and efficient outcome by maximising groundwater lowering and minimising cost. The optimisation is supported by the multi-stage genetic algorithm method in combination with a groundwater simulator, hereafter called the multi-stage GWSim-GA SO method. The procedure of the conceptual model will be further developed and used as a framework in the groundwater management of fractured media of an open pit mine slope.