地下水源热泵流量经济性分析及地下水有效利用

地下水源热泵具有显著的经济性,但对地下水资源保护产生不利影响。本文建立地下水源热泵流量分析模型和典型的基准状态,从节能和地下水节约利用两方面综合分析设计工况下板式换热器循环流量和地下水流量最佳范围,以及地下水取用单价的合理范围。结果表明：在基准状态下,板换循环设计温差应在5～6℃左右,比10℃温差工况系统能耗减少2.6%;水电单价比为0.2：1时,水费仅占总费用的9%,经济工况区范围为循环水温差在5～7℃之间,井水温差在10～13℃之间;水电单价比在0.5：1到0.75：1之间对提高地下水利用率较为适合;水电单价比为1.5：1时,地下水源热泵与空气源热泵的运行费用相当。     

Statistical approaches to groundwater monitoring

Current and proposed regulations require that some form of Student's t-test be used for evaluation of groundwater pollution detection parameters. Several problems arising from that requirement lead to an inflated false alarm rate. Among these are the use of variability among replicates as the estimate of random sampling error, and the failure to take proper account of spatial and temporal sources of variation. In addition, conditions essential for the valid application of the t-test are usually lacking. The requirement that a separate t-test be conducted for each detection parameter, each reporting period, causes an additional severe increase in the likelihood of a false alarm. A dummy variable analysis of covariance is suggested as a desirable alternative. After statistically removing temporal variation from the data the averages of the upgradient and downgradient wells are compared. Examples of the use of this form of analysis are given.     

Four approaches for groundwater development planning

Groundwater system development problems usually involve the placement and the operation of a set of wells. Finding the optimal solution for such problems, when all the corresponding costs are considered is a very difficult task since non-linear models that include discrete variables have to be solved. This is why such problems are often simplified either by ignoring fixed costs or by linearizing the cost functions. In this paper four different approaches are compared: a non-linear programming with polynomial penalty coefficient method; a non-linear programming with exponential penalty coefficient method; a mixed-integer-non-linear programming commercial solver, and a simulated annealing algorithm, in an attempt to solve this kind of problem while keeping a realistic model formulation not requiring simplifications.     

Contaminated groundwater: Above-ground treatment alternatives

Treatment of contaminated groundwater has become increasingly important as contamination incidents are discovered with greater frequency and as increased public and regulatory pressure for corrective action is exerted. This paper examines the differences between treatment of contaminated groundwater and conventional wastewaters. The need for treatability studies and pilot testing, use of adaptable equipment configurations, and importance of operating considerations are discussed. Contaminated groundwater treatment technologies currently employed most frequently for removal of organic contaminants — activated carbon adsorption, air stripping and biological treatment — are then reviewed. Applications and economic considerations, when data are available, are discussed for each process. Finally, several unique or experimental treatment technologies are presented.     

Markov process modeling of groundwater contamination problems

The problem of groundwater contamination is investigated by invoking the analogy to the diffusive Markov process in the probability theory. Special emphases are placed on the following issues: (1) the amount of pollutants entering the protected zone; (2) probability distribution and statistical properties of the random time for a tracer particle to reach the protected zone; and (3) the time rate of contamination arriving at the protected zone. It is shown that these are governed by differential equations analogous to the so-called Kolmogorov backward equation, or derivable from such an equation. Application of the new theory is illustrated by simple examples.     

Storage of surface flows through groundwater recharge

The Ganga basin in India has a serious problem of water availability. The basin, which is only one twelfth of the United States in area, has a population greater than the totalus population, and is increasing at a rate of 2·5% per annum. About 77% of the population is engaged in agriculture which is totally dependent on irrigation, as almost 85% of the rainfall comes down in 2–3 monsoon months. Surface storage possibility is extremely limited, but groundwater recharge appears feasible, since sedimentary alluvial formations extend to depths of thousands of metres. Three alternative schemes of groundwater recharge have been proposed. One involves pumping heavily along perennial rivers prior to the monsoon so as to lower the water-table and promote induced groundwater recharge. The second proposes a similar approach along nonperennial rivers. The third involves irrigation during the monsoon with groundwater lowered adequately in the non-monsoon period so that enough induced groundwater recharge takes place to provide adequate supplies for non-monsoon months. A simulation-optimization model has been developed to study the surface flow-groundwater interaction and has been applied to study comparative cost effectiveness of the three alternate approaches. Sensitivity analysis has also been carried out. It is shown that the third scheme is the most attractive.     

Sinusoidal pumping of groundwater near cylindrical inhomogeneities

A new analytic-element solution is presented for a well with a sinusoidal discharge pumping near cylindrical inhomogeneities. Both the transmissivity and the storage coefficient may be different inside each cylinder. The solution consists of separate series solutions inside and outside each cylinder; asymptotic expansions are presented for cases where the sinusoidal period is small and the radius and transmissivity of the cylinder are large. The complex coefficients in the series solutions are determined by requiring continuity of head and normal flow across the boundary of each cylinder resulting in a linear system of complex equations that may be solved with standard methods. The solution represents one of the few analytic solutions for two-dimensional transient groundwater flow in an aquifer with inhomogeneities. Computer implementation requires truncation of the series; machine accuracy may be reached when enough terms are used in the series solutions. The effect of cylindrical inhomogeneities on the amplitude and phase of the head are investigated. The complex behavior suggests it may be difficult to determine location and properties of cylindrical inhomogeneities from pump tests, which confirms reported difficulties of interpreting pump test results from heterogeneous aquifers.     

Analysis of groundwater quality using fuzzy synthetic evaluation

This paper reports the application of fuzzy set theory for decision-making in the assessment of physico-chemical quality of groundwater for drinking purposes. Methodology based on fuzzy set theory used to express the quality of water in the imprecise environment of monitored data and prescribed limits given in a non-probabilistic sense. Fuzzy synthetic evaluation model gives the certainty levels for the acceptability of the water based on the prescribed limit of various regulatory bodies quality class and perception of the experts from the field of drinking water quality. Application of fuzzy rule based optimization model is illustrated with 42 groundwater samples collected from the 15 villages of Ateli block of southern Haryana, India. These samples were analysed for 16 different physico-chemical water quality parameters. Ten parameters were used for the quality assessment using this approach. The analysis showed that four samples were in "desirable" category with certainty level of 35-58%, 23 samples were in "acceptable" category whose certainty level ranged from 37 to 75% and remaining 15 samples were in "not acceptable" category for drinking purposes with certainty levels from 44 to 100%. This concludes that about 64% water sources were either in "desirable" or "acceptable" category for drinking purposes.     

Remediation of TCE-contaminated groundwater using nanocatalyst and bacteria

The objective of this study was to develop and evaluate the remediation of trichloroethene (TCE)-contaminated groundwater using both a nanocatalyst (bio-Zn-magnetite) and bacterium (similar to Clostridium quinii) in anoxic environments. Of the 7 nanocatalysts tested, bio-Zn-magnetite showed the highest TCE dechlorination efficiency, with an average of ca. 90% within 8 days in a batch experiment. The column tests confirmed that the application of bio-Zn-magnetite in combination with the bacterium achieved high degradation efficiency (ca. 90%) of TCE within 5 days compared to the nanocatalyst only, which degraded only 30% of the TCE. These results suggest that the application of a nanocatalyst and the bacterium have potential for the remediation of TCE-contaminated groundwater in subsurface environments.     

A new approach in modelling groundwater pollution under uncertainty

This article presents a new methodology to model the time and space evolution of a contaminant in a system of aquifers when certain components of the model, such as the geohydrologic information, the boundary conditions, the magnitude and variability of the sources or physical parameters are uncertain and defined in stochastic terms. The method is based on applications of modern mathematics to the solution of the resulting stochastic transport equations. This procedure exhibits considerable advantages over the existing stochastic modelling techniques. In particular, the semigroup solutions are not restricted to small variances in the stochastic elements (perturbation techniques), unsteady dynamic conditions are specifically considered, time and space randomness may be considered in the sources, the boundary conditions or the parameters, and the methodology reflects a well-posed functional-analytic theory. Several basic example problems are presented in order to illustrate the application of the methodology to the modelling of complex spatially and temporally distributed sources of interest in engineering hydrology today. Further potential applications of the method are very promising.     

Microbial community structure during oxygen-stimulated bioremediation in phenol-contaminated groundwater

This research explored the changes in genetic diversity and spatial distribution of microbial communities in association with the changes in phenol concentration during a bioremediation process. Results using the traditional plate count method indicated an increase of average bacteria densities in groundwater from 10(4) to 10(7)CFUml(-1) initially to 10(7) to 10(9)CFUml(-1) after remediation. The diversity and stability of phenol-degrading bacterial communities were investigated by using single-strand-conformation polymorphism (SSCP) genetic profile analysis of 16S rDNA fragments amplified from groundwater samples. The molecular data showed a high degree of genetic similarity between communities from certain monitoring wells during the early phases of remediation, probably due to similar initial physical conditions among wells. Molecular signatures of several cultivated phenol-degrading bacterial strains could be seen in most groundwater profiles throughout the study period, suggesting that these strains were indigenous to the study site. It was also observed that the species diversity of these microbial communities increased as the phenol levels in the groundwater decreased during the 9-month study period, and recovered to the pre-treatment levels after the remediation program was completed.     

Simplified estimation technique for organic contaminant transport in groundwater

The analytical solution for one-dimensional dispersive—advective transport of a single solute in a saturated soil accompanied by adsorption onto soil surfaces and first-order reaction rate kinetics for degradation can be used to evaluate the suitability of potential sites for burial of organic chemicals. The technique can be used to the greatest advantage with organic chemicals that are present in groundwaters in small amounts. The steady-state solution provides a rapid method for chemical landfill site evaluation because it contains the important variables that describe interactions between hydrodynamics and chemical transformation. With this solution, solute concentration, at a specified distance from the landfill site, is a function of the initial concentration and two dimensionless groups. In the first group, the relative weights of advective and dispersive variables are compared, and in the second group the relative weights of hydrodynamic and degradation variables are compared. The ratio of hydr odynamic to degradation variables can be rearranged and written as (a_L·λ)/(q/ε), where a_L is the dispersivity of the soil, λ is the reaction rate constant, q is groundwater flow velocity, and ε is the soil porosity. When this term has a value less than 0.01, the degradation process is occurring at such a slow rate relative to the hydrodynamics that it can be neglected. Under these conditions the site is unsuitable because the chemicals are unreactive, and concentrations in groundwaters will change very slowly with distance away from the landfill site.     

地下水中Fe的ICP-MS检测和修正方法

提出了使用电感耦合等离子体质谱法检测地下水中Fe的过程中,标准系列溶液与样品溶液由于基体不同,随雾化气流量变化时所受到的影响程度不一致,对样品中Fe的分析结果的准确性和可靠性产生不利影响。同时提出在线内标溶液含有一定浓度的Fe,并把相应的检测值带入分析结果,对低含量样品中Fe的分析结果的准确性和可靠性产生不利影响。通过实验研究,说明了使用监控样技术对这两个问题进行修正能够获得良好效果,并且相应说明了监控样的制备方法、保存条件和使用期限及对在线内标溶液的处理方法。在这个基础上,建立了新的电感耦合等离子体质谱法检测地下水中Fe的方法,重新确定了方法参数。方法的检出限(DL)达到18.9ng/mL。方法精密度(RSD)为6.11%～8.56%(n=12)。加标回收率为97.55%。     

A model of groundwater contaminant transport using the CVBEM

The Complex Variable Boundary Element Method or CVBEM has been used to develop a simple but powerful numerical analog of contaminant transport in a saturated, confined groundwater aquifer. The presented numerical technique is based upon a mean-square fit of the boundary conditions which includes the effects of sources and sinks defined within the problem domain. The numerical analogue produces locations of streamlines and the time-evolution of the contaminant front location.     

Application of groundwater cooling scheme for London Underground network

The demand for acceptable thermal comfort conditions within the London Underground network has grown over the years. The operation of the network generates a large heat load, with high temperatures recorded in summer in train and on platforms. Different cooling methods and new sources of cooling have been proposed for cooling the network. Of the new sources of cooling proposed, groundwater cooling is the first to be tried. London Underground Limited unique characteristics of being close to the aquifer of the central London basin, rivers and also because they pump over 30 million litres of water from the network every day make it an ideal site for this technology. This paper investigates thermal issues within London Underground network and presents an overview of groundwater cooling schemes for the network.