采用浊度监测实现悬移质泥沙监测自动化的探讨

介绍了南宁水文站通过对水体浊度参数测试,得到浊度与含沙量关系,研究新悬移质泥沙监测模式,实现悬移质泥沙监测自动化,推进水文信息化进程适应经济发展,为防灾减灾决策,及时、准确提供科学依据。     

台湾集集堰沉沙池泥沙浓度与浊度率定关系研究

水体浊度观测为水环境及水资源领域中之例常观测项目,泥沙浓度则为水资源及水利工程中重要之水文观测数据。浊度数据对于水生态环境、水资源利用评估及公共用水营运,为极重要判别指标 泥沙浓度数据则为集水区保育及河道稳定评估规划所需之重要基本数据。现行浊度观测方式及仪器,相对于传统泥沙浓度之观测,其仪器自动化程度高、价格较低,且设站较为简易方便且普遍。虽河川中悬移泥沙浓度与浊度之物理定义不同,但在工程实务应用上仍有许多泥沙浓度数据以浊度数据来替代表示。本文研究特定水沙条件下之浊度与浓度率定关系,并以集集拦河堰为案例,探讨试样水体浊度、浓度观测数值在不同含沙量条件下之对应及量化关系规律,并依ISO标准规范,进行不确定度分析及误差分析。研究成果显示,浊度观测方式之重现性及精度良好,且浊度与浓度测值间对应率定关系明确,但此率定关系与泥沙类别、泥沙粒径及分布组成条件密切相关。参照本研究所提出之泥沙浊度与浓度观测之率定关系规律,可以利用现已普遍设站之水质观测站之浊度观测数据,建立推估特定流域河道之水、沙特性关系。     

Relationship between turbidity and total suspended solids concentration within a combined sewer system

This article confirms the existence of a strong linear relationship between turbidity and total suspended solids (TSS) concentration. However, the slope of this relation varies between dry and wet weather conditions, as well as between sites. The effect of this variability on estimating the instantaneous wet weather TSS concentration is assessed on the basis of the size of the calibration dataset used to establish the turbidity - TSS relationship. Results obtained indicate limited variability both between sites and during dry weather, along with a significant inter-event variability. Moreover, turbidity allows an evaluation of TSS concentrations with an acceptable level of accuracy for a reasonable rainfall event sampling campaign effort.     

挟沙水流中悬浮颗粒的漂移—扩散方程

本文基于固液两相流动双流体模型的基本方程推导得到了挟沙水流中悬浮颗粒的漂移-扩散方程，该方程表明，除重力外，作用在颗粒上的升力、虚拟质量力、Basset力等，以及颗粒间相互作用都会影响颗粒浓度分布，对明渠中悬浮颗粒浓度垂线分布分析结果表明，在床面附近有较大值的升力是使得悬浮颗粒浓度在趋近床面时增大趋势趋缓，甚至趋向于零的重要因素，本文公式与明渠实测悬浮颗粒浓度垂线分布的对比也证实了这一点。     

长江口浑浊带枯季悬沙粒度分布特征

根据2011年长江口浑浊带枯季悬沙粒度的实测数据分析,发现浑浊带悬沙粒度分布存在明显的时空差异,同时探讨了近20年的粒度变化过程。浑浊带粒度受动力驱动,大潮垂向分布差异显著且粒径较大,中值粒径表层在7μm左右,中层在10~20μm之间,底层在10~25μm之间;小潮期间垂线分布比较均匀且粒径较小,表中底三层中值粒径分布均在3~6μm之间,中值粒径沿水深的垂向分布梯度很小。浑浊带粒度的空间分布特征表现在:浑浊带核心区域,大潮悬沙粒度中约含有30%黏土,70%粉砂,砂含量较少,砂比例垂向上呈增加趋势;核心区悬沙粒度三组分沿水深的分布在大小潮两个时段变化幅度较大,而浑浊带外缘粒度随潮动力的变化幅度不明显。近20~30年间,浑浊带区域的悬沙粒度中值粒径经历了"小-大-小"的变化过程,三组分也同样经历了一个先粗化再细化的过程。     

Deciphering the science behind electrocoagulation to remove suspended clay particles from water.

Electrocoagulation removes pollutant material from water by a combination of coagulant delivered from a sacrificial aluminium anode and hydrogen bubbles evolved at an inert cathode. Rates of clay particle flotation and settling were experimentally determined in a 7 L batch reactor over a range of currents (0.25-2.0 A) and pollutant loadings (0.1-1.7 g/L). Sedimentation and flotation are the dominant removal mechanism at low and high currents, respectively. This shift in separation mode can be explained by analysing the reactor in terms of a published dissolved air flotation model.     

浑水紊动强度的探讨

本文根据动量交换理论建立了浑水紊动的数学模型。此模型考虑了含沙量，流速梯度和利查逊数对浑水紊动强度的影响，而且与前人结果相比更接近于试验资料。     

长江口最大浑浊带表层水体悬沙粒径对离水光谱反射率的影响

利用长江口最大浊度带2008年3月和2009年5月的现场测量光谱和悬浮泥沙参数,讨论了引入悬浮泥沙粒径因子的反演模式,并尝试将絮凝体粒径参数引入模式,分析悬浮泥沙室内粒径与现场粒径对长江口表层水体离水光谱反射率的影响。结果表明,从理论分析来看,粒径对光谱产生影响的机理很明确,但采用平均粒径和中值粒径作为参数,引入经验模型,模型的精度反而降低。絮凝体粒径受到水动力和盐度影响,短周期性更强,与光谱反射率的相关关系更低。这可能与粒径分布的影响相对悬沙浓度对光谱反射率的贡献要小很多,粒径分布对光谱的影响信息极容易被掩盖掉有关。建议采用更有效的粒径描述方式,比如絮凝体投影表面积参数等以获得更好的结果。     

PAC为混凝剂时高岭土悬浊液的混凝条件及絮凝体形态学特征

通过显微摄像仪对絮凝体的形成过程及其形态学特性进行了系统的研究.试验结果表明,高岭土悬浊液的最佳混凝pH为7～8,在低投药量时,压缩双电层和吸附电中和是主要的混凝机理,在高投药量条件下,则是卷扫絮凝起主导作用.絮凝体平均粒径和分形维数都随搅拌时间的延长而增大,并最终趋于稳定.在pH=7和以PAC作为混凝剂的条件下,形成的絮凝体最大粒径为0.45 mm,对应的分形维数约为1.68.随着投药量的增大,絮凝体分形维数的变化较小,但絮凝体平均粒径显著增加.当投药量过高时,网扫絮凝作用下的絮体结构松散,抗剪切能力差,絮凝体分形维数略有下降(1.60),但絮凝体平均粒径减小明显,降至0.25 mm左右.     

Reproducibility and uncertainty of wastewater turbidity measurements.

Turbidity monitoring is a valuable tool for operating sewer systems, but it is often considered as a somewhat tricky parameter for assessing water quality, because measured values depend on the model of sensor, and even on the operator. This paper details the main components of the uncertainty in turbidity measurements with a special focus on reproducibility, and provides guidelines for improving the reproducibility of measurements in wastewater relying on proper calibration procedures. Calibration appears to be the main source of uncertainties, and proper procedures must account for uncertainties in standard solutions as well as non linearity of the calibration curve. With such procedures, uncertainty and reproducibility of field measurement can be kept lower than 5% or 25 FAU. On the other hand, reproducibility has no meaning if different measuring principles (attenuation vs. nephelometry) or very different wavelengths are used.     

确定固液两相流扩散系数的投影寻踪模型

本文首先指出传统方法在研究悬移质扩散系数时存在的问题及困难，根据两相流理论确定出影响悬移质扩散系数的3个主要因子，并沿着“审视数据－模拟－预测”的途径，建立了固液两相流中悬移质扩散系数的投影寻踪回归（PPR）的数学模型，模拟结果表明本文所建立的模型稳健性和抗干扰性好，预测精度较高。     

Attenuation of an ultrasonic beam by suspended particles and range of acoustic flow meters in sewer networks

Ultrasonic flow meters are commonly used in wastewater management. Under certain circumstances, a reduction in the flow meter range may occur and cause significant error in the flow rate measurement. Attenuation due to suspended particles is one of the phenomena capable of reducing the flow meter range. The present paper examines attenuation resulting from re-suspended pond sediment over a wide range of concentration values. It appears that a formula established for sand suspensions provides a good estimate of ultrasound attenuation for these types of particles as well. Experiments conducted for wastewater under particle concentrations commonly encountered in sewer networks demonstrate that the attenuation by particles only contributes to a negligible extent towards intensity decay, in accordance with theoretical predictions. We also theoretically determine herein the operating conditions under which the range of an ultrasonic flow meter would be significantly reduced due to particle attenuation.     

Nitrogen management in reservoir catchments through constructed wetland systems.

In this study, nitrogen removal was investigated in pilot-scale subsurface flow (SSF) and in free water surface flow (FWS) constructed wetlands installed in the campus of TUBITAK-Marmara Research Center, Gebze, near Istanbul, Turkey. The main purposes of this study are to apply constructed wetlands for the protection of water reservoirs and to reuse wastewater. Experiments were carried out at continuous flow reactors. The effects of the type of plants on the removal were investigated by using emergent (Canna, Cyperus, Typhia spp., Phragmites spp., Juncus, Poaceae, Paspalum and Iris.), submerged (Elodea, Egeria) and floating (Pistia, Salvina and Lemna) marsh plants at different conditions. During the study period HLRs were 30, 50, 70, 80 and 120 L m(2)d(-1) respectively. The average annual NH4-N, NO(3)-N, organic N and TN treatment efficiencies in SSF and FWS wetlands are 81% and 68%, 37% and 49%, 75% and 68%, 47% and 53%, respectively. Nitrification, denitrification and ammonification rate constant (k20) values in SSF and FNS systems have been found as 0.898 d(-1) and 0.541 d(-1), 0.488 d(-1) and 0.502 d(-1), 0.986 d(-1) and 0.908 respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances.     

Investigating public health impacts of deer in a protected drinking water supply watershed

The World Health Organisation's (WHO) Water Safety Plans highlight the need for preventative risk management when managing water contamination risks. As part of this approach, a management framework incorporating multiple barriers is necessary and there is a need to validate those barriers through scientific evidence. This paper reports on a study undertaken to validate the effectiveness, in terms of pathogen numbers, of having protected watersheds. The study aimed to determine if the deer population in a protected watershed carried Cryptosporidium and whether or not it was human infectious. Deer faecal samples were collected from the protected watersheds over a 12 month period and analysed using a new method, developed as part of this project, for genotyping Cryptosporidium. Early results showed the presence of Cryptosporidium, but following a refinement in the method no human infectious Cryptosporidium was detected. The results give some confidence that having protected watersheds is an effective barrier against pathogen contamination. They do not, however, imply that continued monitoring and management of the deer should cease. To maintain compliance with the Water Safety Plans, continual validation of barrier effectiveness is required.     

Characterizations of individual suspended mineral particles in western Lake Erie: Implications for light scattering and water clarity

Light-scattering attributes of minerogenic particles from the water column of the western basin of Lake Erie (13 sites, plus one from the central basin and one from Sandusky Bay), collected after a wind event, were characterized by scanning electron microscopy interfaced with automated image and X-ray analyses (SAX). SAX results specified scattering attributes for individual particles, including size and chemical composition, and were used in forward Mie theory calculations of minerogenic scattering and backscattering coefficients (b_m and b_b,m). Clay mineral particles, in the size range of 1–20 μm, were the dominant form of minerogenic scattering, representing > 75% of b_m and b_b,m. Levels of b_m and b_b,m were high in the western basin, apparently in part due to wind-driven sediment resuspension, and wide spatial variability was observed. The credibility of the SAX-Mie estimates of b_m and b_b,m was supported by the extent of optical closure obtained with paired bulk measurements of particulate scattering and backscattering coefficients (b_p and b_bp), and independent estimates of organic particle contributions based on empirical bio-optical models. Minerogenic particles dominated b_p and particularly b_bp, and regulated spatial differences in the related common metrics of optical water quality, including turbidity and clarity. The b_bp:b_p ratio was found to be a good predictor of the spatial differences in the relative contributions of minerogenic particles versus phytoplankton to scattering.     

Bottom distribution of settled suspended particles on entering a gravitational basin over the entire depth of flow

Results of investigation are cited for laws governing the distribution of settled uniform and nonuniform particles, which proceed past the starting point over the entire depth of flow. __________ Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 2, February, 2007, pp. 33–39.     

Estimation of particulate nutrient load using turbidity meter.

The "Nutrient Load Hysteresis Coefficient" was proposed to evaluate the hysteresis of the nutrient loads to flow rate quantitatively. This could classify the runoff patterns of nutrient load into 15 patterns. Linear relationships between the turbidity and the concentrations of particulate nutrients were observed. It was clarified that the linearity was caused by the influence of the particle size on turbidity output and accumulation of nutrients on smaller particles (diameter < 23 microm). The L-Q-Turb method, which is a new method for the estimation of runoff loads of nutrients using a regression curve between the turbidity and the concentrations of particulate nutrients, was developed. This method could raise the precision of the estimation of nutrient loads even if they had strong hysteresis to flow rate. For example, as for the runoff load of total phosphorus load on flood events in a total of eight cases, the averaged error of estimation of total phosphorus load by the L-Q-Turb method was 11%, whereas the averaged estimation error by the regression curve between flow rate and nutrient load was 28%.     

Estimation and comparison of nitrogen loads and attenuation in agricultural catchments of Japan and Korea.

To help in clarifying the relationship between the time lag and attenuation of nitrogen (N) loads generated in agricultural catchments, long-term trends in activities that generate N loads and in environmental N loads were estimated in catchments in Japan and Korea dominated by non-point-source emissions. Our approach used statistical data and geographical information system software to analyze pollutant loads. The method was successful in both countries because of the availability of well-developed statistics, geographical information, and weather and water quality monitoring systems, and the accumulation of research data concerning the generation of N loads and the fate of N in soils. Comparison of environmental loads with the loads observed in river water at the outlet of each catchment revealed that: (1) the effect of changes in the environmental load in a catchment appeared almost immediately in the river water quality in Korea, but did not appear clearly even 10 years later in Japan; and (2) the strength of the attenuation appeared to be much lower in Korea than in Japan. These findings suggest that regional characteristics play important roles in the sensitivity of water quality to load-generating activities.     

Regionalisation of physically-based water balance models in Belgium. Application to ungauged catchments

More than 60 catchments from Northern Belgium ranging in size from 16 to 3160 km² have been studied by means of a physically-based stochastic water balance model. The parameter values derived from calibration of the model were regionally mapped for the study region. Associations between model parameters and basin lithological characteristics were established and tested. The results show that the simple conceptual monthly water balance model with three parameters for actual evapotranspiration, slow and fast runoff is capable either to generate monthly streamflow at ungauged sites or to extend river flow at gauged sites. This allows a fairly accurate estimation of monthly discharges at any location within the region.