Cryptosporidium monitoring system at a water treatment plant, based on waterborne risk assessment.

The water volume required for daily monitoring of Cryptosporidium (which can statistically ensure an annual risk of infection below 10(-4)), was assessed by evaluating the applicability of the Poisson lognormal (PLN) distribution in microbial risk assessment. PLN showed as good a fit to the observed data as to the negative binomial distribution. From the estimated PLN distributions for the source and finished water, the efficacy of the oocyst removal by the conventional water treatment process was estimated to follow log-normal distribution (median = 3.16 log10, 95% CI = 4.27-2.05 log10). The 365 consecutive negative results of daily monitoring for 180 L of finished water were found to be statistically equivalent to the annual risk of infection below 10(-4). This research also suggested the possibility of applying a qualitative detection method, such as CC-PCR, as a routine monitoring method for the quantitative risk management.     

城市污水中污染物监测与分布规律探讨

为了明确城市污水中各种污染物质的分布规律,对典型城市二级处理出水中有机污染物、大肠杆菌、金属离子、浊度、色度等污染物进行了检测分析,在大量检测数据的基础上,通过概率纸检验和非参数假设检验等方法对污染物的分布规律进行了统计分析,发现二级处理污水中污染物在显著性水平α=0.10的条件下都服从或近似服从对数正态分布,从而可用对数正态分布函数对城市污水中污染物的出现频率进行量化描述,为水质模型的建立和运行提供基础资料.     

Common effluent treatment plant (CETP): Reliability analysis and performance evaluation

Common effluent treatment plants (CETPs) have been installed and are in operation at numerous industrial clusters throughout India. They serve to reduce effluent treatment cost, provide better collective treatment, and reduce land cost for small-scale industrial facilities that cannot afford individual treatment plants. Optimum working conditions for treatment of effluent to be at par with discharge standards is a major mandate for any CETP. In this study, the reliability and removal efficiencies (REs) of a CETP in the industrial area of Maharashtra State in India were examined. An established methodology was adopted to determine the effectiveness of the CETP in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and oil and grease (O&G) concentrations. The CETP's compliance with respect to design standards and its operation were studied in detail. This paper highlights the results of RE and the coefficient of determination (R²) values obtained from the CETP data, estimates the pollutants removed at the highest and lowest rates over a period of time, and highlights the reasons for problem areas along with remedial measures. It was observed that, except O&G, all the parameters (BOD, COD, and TSS) showed fluctuations in removal efficiencies and their reliabilities. This situation can be improved by releasing effluent containing hydraulic and organic loading to the CETP as per standards and optimizing treatment processes, especially primary clari-flocculators and aeration tanks, both of which are important units of any CETP.     

松辽流域国际河流中方侧支流初始水权分配的特殊原则

松辽流域国际河流中方侧支流由于受到国际因素和地域因素的影响而具有特殊性,其初始水权分配不同于一般国内河流,应采取特殊的原则,包括服务国内、充分分配、地域优先、生态需水保障、地表水与地下水统筹分配等特殊原则.基于此,在开发利用发面,要有针对性地采取合理开发、加强合作、适当优先开发、加强水环境保护和水污染治理等开发利用对策.     

Multi-component kinetics of activated sludge treatment of bleached kraft mill effluent.

This study investigated the discrepancies between the BOD removal rates measured during short term assays and those measured during continuous activated sludge treatment of bleached kraft mill effluent (BKME). A combination of batch tests and fed batch tests with oxygen uptake rate (OUR), chemical oxygen demand (COD), biochemical oxygen demand (BOD), and mixed liquor volatile suspended solids (MLVSS) measurements were used to characterize the degradation rates for the activated sludge treatment of BKME and to divide the soluble readily biodegradable substrate into two to five separate fractions based on biodegradation rates. The removal rates varied by over an order of magnitude between the most readily degradable substrates (1 x 10(-3) mg COD/mg MLVSS minute), and the more slowly degradable substrates (2 x 10(-5) mg COD/mg MLVSS minute). If the readily biodegradable fraction of BKME was modeled as one substrate, initial rate kinetic measurements from batch tests were heavily influenced by the fractions with the greatest degradation rates, while any remaining BOD in the treated effluent was predominantly from the slowly degradable fraction, giving inconsistent results. Taking the multi-component nature of the wastewater into account, batch test results can be used to predict fed-batch and continuous activated sludge reactor performance.     

A Versatile Flood Frequency Methodology

ABSTRACT

Many observed annual flood series exhibit reverse curvatures when plotted on lognormal probability paper. The occurrence of these curvatures may be attributed to seasonal variation in flood-producing storm types, relative dominance of within-the-channel or floodplain flow, and variability in antecedent soil moisture and cover conditions. A mixed distribution model is needed to analyze such flood series because of the mixed population of floods. A versatile flood frequency methodology has been developed which considers the probability distribution of an observed flood series as a mixture of the probabilities of two lognormal distributions. Objective detection and modification of any outliers and inliers in an observed flood series in as integral part of the versatile flood frequency methodology. Analyses of about 600 flood series in the USA and other countries in the world show the versatility and superiority of the proposed methodology for satisfactory estimation of design floods for various recurrence intervals.     

A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate

This study examined a novel reuse of alum sludge, an inescapable by-product of drinking water treatment process when aluminium salt is added as a coagulant, as the main medium in a laboratory-scale multi-stage constructed wetland (CW) system for reject water treatment. Such reject water is a main concern in municipal wastewater treatment plant (MWWTP) for increasing the organic and nutrient loading. A 'tidal flow' strategy was employed to enhance the wetland aeration to stimulate organic matters (OM) and ammoniacal-nitrogen (N) oxidation while the 'step feed' operation was adopted to supply the necessary amount of carbon source for denitrification. The results reveal that alum sludge acting as P adsorbent can secure the P removal. Meanwhile, high removals of N and OM can also be obtained due to the active bacteria growth on the alum sludge surface. The results show that average removal efficiencies of 65.4 +/- 12.3% for chemical oxygen demand (COD), 67.8 +/- 9.2% for five-day biochemical oxygen demand (BOD5), 33.6 +/- 17.0% for N and 99.5 +/- 0.49% for P can be achieved over a period of 190 days. This indicates that novel reuse of alum sludge as medium in CW system can provide a promising approach for reject water treatment. Therefore, it will significantly reduce the amount of pollutant feedback through reject water recycling in a MWWTP.     

Regional Frequency Distribution Type of Low Flow in North of Iran by L-moments

A regional low flow frequency analysis in the north of Iran using L-moments was carried out. Low flow events have been represented by the 7-day annual minimum series and the L-moments approach was used to assign these data into homogenous regions. According to the homogeneity measure and climatic properties, two subdivisions were found – one in the west of the study area having a homogenous assemblage of sites, and one in the east in which the sites were found to be heterogeneous. The regional low flow frequency distribution was derived for the western division using L-moments and goodness of fit tests were used to evaluate which of a number of possible distributions best represented this. The evaluation suggested that the Generalized Logistic distribution gives the best overall result. For heterogeneous subdivision, the performance of the 2-parameter distribution such as 2-parameter Log Normal, Normal and Gamma distributions gave the best result for the majority of sites. Regional and at-site frequency curves were also compared for the western division, which showed that the quantile estimates could be very different in the upper and lower tails of the distribution. The influence on flow regime and watershed properties on the type of the best fit distribution was investigated which showed that the 2 and 3 parameter distributions do not have a clear relationship with climatic and physiographic characteristics of the watersheds except the watershed area. This may result in simple scaling laws of low flows.     

Effect of Extraordinary Large Floods on at-site Flood Frequency

The peak flow of extraordinary large floods that occur during a period of systematic record is a controversial problem for flood frequency analysis (FFA) using traditional methods. The present study suggests that such floods be treated as historic flood data even though their historical period is unknown. In this paper, the extraordinary large flood peak was first identified using statistical outlier tests and normal probability plots. FFA was then applied with and without the extraordinary large floods. In this step, two goodness-of-fit tests including mean absolute relative deviation and mean squared relative deviation were used to identify the best-fit probability distributions. Next, the generalized extreme value (GEV), three-parameter lognormal (LN3), log-Pearson type III (LP3), and Wakeby (WAK) probability distributions were used to incorporate and adjust the extraordinary large floods with other systematic data. Finally, procedures with and without historical adjustment were compared for the extraordinary large floods in terms of goodness-of-fit and flood return-period quantiles. The results of this comparison indicate that historical adjustment from an operational perspective was more viable than without adjustment procedure. Furthermore, the results without adjustment were unreasonable (subject to over- and under-estimation) and produced physically unrealistic estimates that were not compatible with the study area. The proposed approach substantially improved the probability estimation of rare floods for efficient design of hydraulic structures, risk analysis, and floodplain management.     

Analyzing the Impacts of Climatic and Physiographic Factors on Low Flow Distributions

Low flow distributions are derived using the derived distribution function approach while considering the variabilities in the dry spell and recession response time to explore the impacts of climatic and physiographic factors on low flow distributions. The low flow distributions are separately derived from the distributions of the dry spell and the recession ratio, i.e., the ratio of the dry spell to the recession response time, on the basis of the linear recession equation, and the dry spell and recession ratio are both assumed to follow normal, gamma, and lognormal distributions. The parameters of these low flow distributions are estimated from the moments of the dry spell and recession ratio series. Applications of these low flow distributions are exemplified in three basins with different hydrological and climatic conditions in China. The gamma distribution outperforms the other two distributions while describing the distributions of the dry spell and the recession ratio. The derived low flow distributions with parameters estimated from the moments of the recession ratio show good consistency with the low flow empirical distributions, and the derived distributions can be applied to estimate the flow quantiles when continuous records of the streamflow are not available. The relationships between the quantiles of the low flow distributions and the moments of climatic factors and watershed characteristic variables show that the recession ratio has the largest influence on the low flow quantiles regardless of the hydrological regime and that the second-largest influencing factor is the dry spell distribution. Meanwhile, the recession response time has a prominent influence on the low flow distributions in erratic hydrological regimes.     

Uncertainty of the Agricultural Grey Water Footprint Based on High Resolution Primary Data

The water footprint has been established as an indicator to assess water use by a product. However, the grey component of the water footprint (GWF) has received the least focus compared to the green and blue components. In developing countries, the GWF estimation is restricted by the availability of data concerning crop practices. The various biophysical and socioeconomic settings configure a system difficult to standardize even for small areas. The objective of this study was to assess the GWF uncertainty due to primary data for the main greenhouse tomato production from Colombia. The GWF for N and P fertilizers and pesticides were estimated based on detailed crop information collected from 2010 to 2013. The uncertainty was evaluated by fitting univariate theoretical distributions to the empirical distributions of the pollutants’ GWFs. Growers applied on average 419.2 and 201.9 kg ha^?1 of N and P fertilizers per cycle, respectively. The average rates of application for fungicides and insecticides were 11.8 and 3.5 kg ha^?1, respectively. The average GWF for N and P fertilizers and pesticides were 79, 6182.1 and 223.2 m³ t^?1, respectively. The empirical distributions of the GWF for N fertilizer and pesticides were fitted to a lognormal distribution while for P fertilizer the Weibull distribution showed the best fit. The pesticides GWF showed the highest coefficient of variation (615.3%), however the results for N and P fertilizers were also high with values of 79.8 and 74.1%, respectively. Additional to the methodological choices involved in the GWF estimation, the primary data is a relevant uncertainty source, which should be considered for systems operating under unstandardized practices. The decision making process to regulate the pollutants losses from the agroecosystem, based on environmental assessments such as the GWF, should consider all sources of uncertainty and address its implications in a quantitatively form.     

Phenol wastewater remediation: advanced oxidation processes coupled to a biological treatment.

Nowadays, there are increasingly stringent regulations requiring more and more treatment of industrial effluents to generate product waters which could be easily reused or disposed of to the environment without any harmful effects. Therefore, different advanced oxidation processes were investigated as suitable precursors for the biological treatment of industrial effluents containing phenol. Wet air oxidation and Fenton process were tested batch wise, while catalytic wet air oxidation and H2O2-promoted catalytic wet air oxidation processes were studied in a trickle bed reactor, the last two using over activated carbon as catalyst. Effluent characterisation was made by means of substrate conversion (using high liquid performance chromatography), chemical oxygen demand and total organic carbon. Biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) were obtained from respirometric tests using activated sludge from an urban biological wastewater treatment plant (WWTP). The main goal was to find the proper conditions in terms of biodegradability enhancement, so that these phenolic effluents could be successfully treated in an urban biological WWTP. Results show promising research ways for the development of efficient coupled processes for the treatment of wastewater containing toxic or biologically non-degradable compounds.     

土体强度的空间分布形式对单桩承载力的影响

土体参数可能服从不同类型的分布,而在考虑土性空间变异性的桩基础承载特性的研究中一般将随机变量假定为服从对数正态分布。以土体的不排水强度为随机变量,考虑不同的变异系数和相关距离,采用随机有限元法分别模拟了竖向和水平向荷载作用下单桩基础的承载性状,对比分析了土体不排水强度分别服从对数正态分布、Beta分布和Gamma分布条件下单桩的承载力均值和标准差。结果表明,土体强度的分布形式对单桩竖向承载力的均值没有影响,而服从对数正态分布的随机场中单桩水平承载力均值最大,服从Beta分布的随机场中单桩水平承载力均值最小;竖向荷载和水平荷载作用下Beta分布得到的承载力标准差均为最大。当地基土强度空间分布形式未知时,建议采用Beta分布确定单桩承载力。     

Predicting joint frequency distributions of depth and velocity for instream habitat assessment

Stream ecosystem structure and function are strongly influenced by patterns of velocity and depth. Simple methods for predicting the spatial distributions of these two variables, as functions of one‐dimensional reach and discharge characteristics, have been recently reported in the literature. These studies have provided valuable insight into the fundamental factors influencing stream behaviour and represent a practical alternative to multi‐dimensional hydrodynamic models. However, these previous studies have handled velocity and depth separately, while there is evidence that meso‐habitats and stream biota are associated with distinct combinations of the two variables. Therefore, we used survey data from 92 stream reaches in New Zealand to develop a model for the joint distribution of depth and velocity. We found that, for each reach, the bivariate distribution of relative velocity and relative depth could be described by a mixture of two end‐member distributions, one bivariate normal and the other bivariate lognormal, each with fixed parameters. The relative contribution of each shape for a particular reach at a particular discharge could then be related to the reach mean Froude number, the reach mean relative roughness, and the ratio of the survey discharge to the mean discharge. As these inputs can be readily estimated for changed channel morphology, our model should provide a useful approach for linking river rehabilitation strategies to hydraulics and ecology. Copyright © 2007 John Wiley & Sons, Ltd.     

An analysis of characteristic discharges for the Adaim River (Iraq) in multiyear period

A major River Tigris tributary in Iraq, the Adaim River, has a Mediterranean river flow regime with a total basin area of 12,482 km². The river catchment responds almost immediately to rainfall with apparently minimum storage (i.e. flashy stream). The river daily hydrograph showed a daily peak flow of 1,476 m³/s with substantial seasonal and random variability; the flow duration curve followed the two‐parameter lognormal probability distribution. Gamma and the two‐parameter Weibull probability distributions fitted the monthly mean river discharge for the period 1937–2012 well. Normal and gamma probability distributions were found to appropriately describe the distribution of the annual mean river discharge for the same period. Gumbel extreme value, Log Pearson type III, and the two‐parameter lognormal distributions gave a reasonable fit to the annual maximum discharge record for the river. A regression formula was used to fit the annual minimum discharge record, which has a significant number of zero values. There was a positive and significant correlation (r = 0.77) between the annual mean discharge at the measuring site and seasonal rainfall measured at Karkuk meteorological station located in the north central part of the basin. The rainfall record at Karkuk showed a significant decline in seasonal rainfall after 1993.     

淮河堤防土体抗剪强度指标概率模型与参数优化估计

进行堤防风险评价和可靠性分析,首先需要确定堤身与堤基土体抗剪强度指标概率的类型与统计参数。针对小区域测试段样本数量少、离散性大的情况,引入历史大范围的勘察钻探资料,利用统计数学上的A-D检验方法对土体抗剪强度指标进行了分布假设检验,发现堤身、堤基土抗剪强度指标可接受正态分布或对数正态分布。将上述结果作为先验信息,与小样本测试结果相结合,使用Bayes理论,实现了具体堤防段抗剪强度指标分布参数的优化估计,降低了参数的变异强度,为堤防风险分析提供了可靠数据。     

淮河堤防土体抗剪强度指标概率模型与参数优化估计

进行堤防风险评价和可靠性分析,首先需要确定堤身与堤基土体抗剪强度指标概率的类型与统计参数。针对小区域测试段样本数量少、离散性大的情况,引入历史大范围的勘察钻探资料,利用统计数学上的A-D检验方法对土体抗剪强度指标进行了分布假设检验,发现堤身、堤基土抗剪强度指标可接受正态分布或对数正态分布。将上述结果作为先验信息,与小样本测试结果相结合,使用Bayes理论,实现了具体堤防段抗剪强度指标概率分布参数的优化估计,降低了参数的变异强度,为堤防风险分析提供了可靠数据。     

基于Copula函数的三峡库区万州段蓄水前后降雨量-径流量关系分析

三峡水库蓄水对其库区降雨量-径流量关系变化的影响程度对于库区水资源规划有着重要意义。选用万县水文站1977-2017共计41 a的降雨量和径流量实测值,确定了各蓄水阶段降雨量和径流量的分布情况,引入Copula函数模型计算各阶段的联合分布函数,定量分析水库调蓄对两者关系的影响,预测了2017年后水文情势。结果表明：采用Copula函数联合分布数学模型能较好计算三峡库区万州段不同阶段的降雨量-径流量关系。万州段从天然河道变为库区河道后,降雨量-径流量关系发生了较大变化。在天然河道阶段,降雨量和径流量均采用皮尔逊III型分布最为合理;三峡水库工程施工期和初步蓄水阶段,降雨量变为Gumbel分布,径流量变为对数正态分布;试验性蓄水阶段,降雨量变为对数正态分布,径流量恢复至皮尔逊III型分布。年降雨量和年径流量在施工期及初步蓄水阶段较天然河道阶段均有所减少,年降雨量变幅区间减小38.4%,年径流量变幅区间减小20.6%;试验性蓄水阶段的年降雨量增多,变幅区间增大24.5%,而年径流量减少,变幅区间减小57%。通过该数学模型预测三峡库区万州段今后年径流量不小于3 490×10⁸ m³（±5%）,最大不超过4 055×10⁸ m³（±5%）;年降雨量不小于1 048 mm（±5%）,最大值不超过1 842 mm（±5%）。该研究可为三峡库区万州段流域水资源开发利用与水文序列的重构工作等提供科学依据,也可为其他库区内河道的水文特性变化关系的研究提供参考。     

Hydrological Drought Assessment in Northwestern Iran Based on Streamflow Drought Index (SDI)

Drought is a natural and worldwide phenomenon that occurs when water availability is significantly below normal levels during a significant period of time and cannot meet demand. This work focused on the hydrologic drought defined by the streamflow drought index (SDI) for overlapping periods of 3, 6, 9 and 12 months at 14 hydrometric stations in the northwest of Iran over the period 1975–2009. It was found that some of the streamflow volume series did not follow the normal distribution. The ability of the log-normal, exponential and uniform probability distributions was examined in order to choose the most suitable distribution, and the log-normal distribution was used to fit the long-term streamflow data. The results of the hydrological drought analysis based on the SDI showed that almost all the stations suffered from extreme droughts during the study period. Additionally, extreme droughts occurred most frequently in the last 12 years from 1997–1998 to 2008–2009.     

山区河流卵石推移质的输移特性

通过对床面颗粒的受力分析，在岷江都江堰河段和青衣江姜射坝河段的实测资料基础上，导出了卵石推移质运动状态数与爱因斯坦的推移质运动强度函数的关系，能较好地反映四川山区河流卵石推移质时均输沙率与水沙因素的关系，用对数正态分布描述卵石推移质输沙率的随机特性，证明在95％的置信水平下是成立。