MODELING STUDIES FOR PLANNING: THE GREEN BAY PROJECT1

ABSTRACT: A major contaminant monitoring and modeling study is underway for Green Bay, Lake Michigan. Monitoring programs in support of contaminant modeling of large waterbodies, such as for Green Bay, are expensive and their extent is often limited by budget limitations, laboratory capacity, and logistic constraints. Therefore, it is imperative that available resources be used in the most efficient manner possible. This use, or allocation of resources, may be aided through the application of readily available models in the planning stages of projects. To aid in the planning effort for the Green Bay project, a workshop was held and studies designed to aid in the allocation of resources for a year-long intensive field study. Physical/chemical and food chain models were applied using historical data to aid in project planning by identifying processes having the greatest impact on the predictive capability of mass balance models. Studies were also conducted to estimate errors in computed tributary loadings and in-Bay concentrations and contaminant mass associated with different sampling strategies. The studies contributed to the overall project design, which was a collaborative effort with many participants involved in budgeting, field data collection, analysis, processing of data, quality assurance, data management and modeling activities.     

Exploring the effects of multiple management objectives and exotic species on great lakes food webs and contaminant dynamics

A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter (Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will decrease by nearly 20% ifBythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies of dominant organisms) that should be corrected in order to make reliable management decisions.     

A RATING-CURVE METHOD FOR HYDRODYNAMIC SIMULATIONS IN CONTAMINANT TRANSPORT MODELING1

ABSTRACT: Accurate prediction of hydrodynamics is of great importance to modeling contaminant transport and water quality in a river. Flow conditions are needed in estimating potential exposure contamination levels and the recovery time for a no-action alternative in contaminated sediments remediation. Considering highly meandering characteristics of the Buffalo River, New York, a three-dimensional hydrodynamic model was selected to route upstream flows through the 8-km river section with limited existing information based on the model's fully predictive capability and process-oriented feature. The model was employed to simulate changes in water depth and flow velocity with space and time in response to variation in flow rate and/or water surface elevation at boundaries for given bottom morphometry and initial conditions. Flow conditions of the river reach where historical flow data are not available were computed. A rating-curve approach was developed to meet continuous and event contaminant modeling needs. Rating curves (depth-discharge and velocity-discharge relationships) were constructed at selected stations from the 3-D hydrodynamic simulations of individual flow events. The curves were obtained as steady solutions to an unsteady problem. The rating-curve approach serves to link flow information provided by the hydrodynamic model to a contaminant transport model. With the approach, the linking problem resulting from incompatible model dimensions and grid sizes can be solved. The curves will be used to simulate sediment movement and to predict contaminant fate and transport in the river.     

用窄点原理进行节水分析

简要地对窄点原理进行了介绍。用窄点原理对工程设计进行了具体分析，在排污量相同的情况下，分别采用洁净水接纳污染物、采用满足进水浓度要求但无回用的废水接纳污染物和采用窄点技术且可回用废水但无水处理过程的废水接纳污染物三种供水方式。比较不同的供水方式所需的不同耗水量。从而得出窄点分析原理对节水，节能和降污保护环境具有的重大意义。     

LINE SOURCE DISPERSION WITH APPLICATION TO MIXING IN RIVER CHANNELS1

ABSTRACT: Two-dimensional solutions for transient dispersion of nonconservative dispersants in uniform flow resulting from a transverse line source of variable concentration are obtained using multiple integral transformations. In general, the solutions are in integral forms, which can be efficiently evaluated using Filon's quadratures. Examples are presented for cases of practical interest. Applicability of the solution for modeling dispersion in natural river channel where the distribution of flows across the channel are nonuniform is discussed.     

MODELING CONCENTRATION VARIATIONS IN HIGH-CAPACITY WELLS: IMPLICATIONS FOR GROUNDWATER SAMPLING1

ABSTRACT: High-capacity wells are used as a convenient and economical means of sampling groundwater quality. Although the inherent limitations of using these wells are generally recognized, little has been done to investigate how these wells actually sample groundwater. A semi-analytical particle tracking model is used to illustrate the influence of variable vertical contaminant distributions and aquifer heterogeneity on the composition of water samples from these wells during short pumping periods. The hypothetical pumping well used in the simulations is located in an unconfined, alluvial aquifer with a shallow water table and concentration gradients of nitrate-nitrogen contamination. This is a typical setting for many irrigated areas in the United States. The main conclusions are: (1) high-capacity wells underestimate the average amount of contamination within an aquifer; (2) shapes of concentration-time curves for high-capacity wells appear to be governed by the distribution of the contaminant and travel times to the well; (3) variables such as well construction, pumping rate, and hydrogeologic properties contribute to the magnitude of the concentration-time curves at individual high-capacity wells; and (4) a sampling strategy using concentration-time curves based on the behavioral characteristics of the well rather than individual samples will provide a much better framework for interpreting spatial contaminant distributions.     

Tool for assessment of process importance at the groundwater/surface water interface

The groundwater/surface water interface (GWSWI) represents an important transition zone between groundwater and surface water environments that potentially changes the nature and flux of contaminants exchanged between the two systems. Identifying dominant and rate-limiting contaminant transformation processes is critically important for estimating contaminant fluxes and compositional changes across the GWSWI. A new, user-friendly, spreadsheet- and Visual Basic-based analytical screening tool that assists in evaluating the dominance of controlling kinetic processes across the GWSWI is presented. Based on contaminant properties, first-order processes that may play a significant role in solute transport/transformation are evaluated in terms of a ratio of process importance (P_i) that relates the process rate to the rate of fluid transfer. Besides possessing several useful compilations of contaminant and process data, the screening tool also includes 1-D analytical models that assist users in evaluating contaminant transport across the GWSWI. The tool currently applies to 29 organics and 10 inorganics of interest within the context of the GWSWI. Application of the new screening tool is demonstrated through an evaluation of natural attenuation at a site with trichloroethylene and 1,1,2,2-tetrachloroethane contaminated groundwater discharging into wetlands.     

An innovative modeling approach using Qual2K and HEC-RAS integration to assess the impact of tidal effect on River Water quality simulation

Water quality modeling has been shown to be a useful tool in strategic water quality management. The present study combines the Qual2K model with the HEC-RAS model to assess the water quality of a tidal river in northern Taiwan. The contaminant loadings of biochemical oxygen demand (BOD), ammonia nitrogen (NH₃-N), total phosphorus (TP), and sediment oxygen demand (SOD) are utilized in the Qual2K simulation. The HEC-RAS model is used to: (i) estimate the hydraulic constants for atmospheric re-aeration constant calculation; and (ii) calculate the water level profile variation to account for concentration changes as a result of tidal effect. The results show that HEC-RAS-assisted Qual2K simulations taking tidal effect into consideration produce water quality indices that, in general, agree with the monitoring data of the river. Comparisons of simulations with different combinations of contaminant loadings demonstrate that BOD is the most import contaminant. Streeter-Phelps simulation (in combination with HEC-RAS) is also performed for comparison, and the results show excellent agreement with the observed data. This paper is the first report of the innovative use of a combination of the HEC-RAS model and the Qual2K model (or Streeter-Phelps equation) to simulate water quality in a tidal river. The combination is shown to provide an alternative for water quality simulation of a tidal river when available dynamic-monitoring data are insufficient to assess the tidal effect of the river.     

OPTIMAL ESTIMATION OF CONTAMINANT TRANSPORT IN GROUND WATER1

ABSTRACT: Finite element and finite difference representations of the convective-dispersive equation have been widely used in determining contaminant transport in ground water. Due to inherent uncertainties of the transport process, those representations are inexact and contain errors. Errors in field measurements are unavoidable. By combining a numerical model, a measurement equation, and the Kalman filter, optimal estimates of the state variable (contaminant concentration) can be obtained. This paper describes the algorithm and gives a numerical example of contaminant transport in a two-dimensional ground water flow. The results show significant improvement in the estimated concentration distribution by using the filtering technique.     

Design of a representative and cost-effective sampling programs for industrial wastewater with examples from bleached kraft pulp and paper mills

The diagram constructed for selection of sampling methods indicates that, for a systematic error, E ≤ 13%, grab sampling (GS) may be used to characterize effluents with variation coefficient of flow ≤ 120% and of contaminant concentrations ≤ 10%. For the whole studied range of variation coefficient of contaminant concentrations (2–82%), time-proportional compositing (TC) method may be applied with E ≤ 10% for effluents characterized by variation coefficients in flow < 90%. The more complicated flow-proportional compositing (FC) method is required only for effluents with larger variation coefficients or to produce more precise results. The diagram constructed for selection of sampling frequencies indicates that sequential sampling at intervals of approximately 60 min may be applied with E ≤ 10% for effluents characterized by variation coefficients ≤ 30%. Practical application of the diagrams, constructed using normal series, was checked against monitoring data from two pulp and paper mills in Vietnam. The two diagrams provided results on sampling methods and frequencies in good agreement with those obtained from actual monitoring data with percentages of agreement cases of 80 and 75%, respectively. The approach was applied in design of a monitoring program at the Bai Bang integrated pulp and paper mill in Vietnam.     

Tolerance and phytoremediation potential of Calopogonium mucunoides to boron

Soil contamination by trace elements (TEs) is a problem of great concern since the industrial revolution. However, not all TEs are essentially toxic, and several micronutrients such as boron (B) play essential roles during plant development and, in this case, B acts in plants as a structural element. Soil B levels above 3.0 mg dm^–3 may be toxic to many plants and the greatest input of B to the environment occurs through the anthropic way. An environmentally promising alternative is phytoremediation, in which contaminant‐tolerant plants are used to remove or stabilize TEs in soils. Therefore, this work has been carried out to aim C. mucunoides’ tolerance to increasing B concentrations and its potential as a phytoremediator. We found out that C. mucunoides tolerates B doses up to 480 mg dm^?3, the B uptaken is transported at a 1:1 ratio between root and shoot, suggesting that C. mucunoides can be used as a phytostabilizer and phytoextractor due to its potential to be used in phytoremediation techniques because it can tolerate toxic concentrations of B.     

GROUND WATER SOLUTE TRANSPORT,OPTIMAL REMEDIATION PLANNING,AND DECISION MAKING UNDER UNCERTAINTY1

ABSTRACT: A groundwater quality modeling advisory system has been developed for the U.S. Air Force for use in investigating remediation alternatives for the cleanup of subsurface contamination. The system is capable of accounting for uncertainty, not only in the prediction of solute transport but also in the optimization of the remediation scheme through chance constraints. The system guides users in the selection of appropriate transport models through an algorithm independently tested with machine learning codes. An application to Hill Air Force Base, Utah, is presented for which different pump-and-treat strategies are considered: the results are evaluated in terms of the cumulative distribution of the contaminant concentration for each case and the tradeoff relationship between the cost of remediation and the probability that the remediation strategy exceeds an established maximum allowable contaminant concentration.     

EVALUATING THE EFFECTIVENESS OF A FIXED WELLHEAD DELINEATION: REGIONAL CASE STUDY 1

The 1996 Safe Drinking Water Act amendments mandated that every state must determine the hydrogeologic origin of each public drinking water system and assess the degree to which each system may be adversely affected by potential sources of contamination. Wisconsin delineated and assessed one specific class of systems, transient noncommunity drinking water wells, with the least stringent standards of all governed system types. This study evaluates the effectiveness of Wisconsin's arbitrarily fixed radius approach used in determining susceptibility to potential contamination from 1,872 transient noncommunity ground water wells. Nearly 28 percent of the wells with contaminated water did not have any recorded potential sources of contamination within the delineation radii. Additionally, regression models derived from potential contaminant inventories within the delineation radii could not accurately predict actual incidences of water contamination. Differences between observed and expected frequencies of contamination further suggest that some transient noncommunity systems should probably be delineated with larger and more sophisticated methods that would account for varying geology and contaminant susceptibility. The majority of contamination cases without recorded potential sources of contamination within the delineation radii were in a karst area. Subsequently, the arbitrarily fixed radius delineation method should not be used in areas with karst aquifers.     

Linear Superposition in Total Maximum Daily Loads Applications: The Steady‐State Response Matrix Revisited1

Abstract: The steady‐state response matrix has historically proved a valuable tool in computing the water quality response to loadings and in providing insight into the relative impact of individual loading sources. The insight obtained may be is particularly useful in modern applications of increasingly complex water quality models to problems involving multiple point and nonpoint sources, such as in the assessment of total maximum daily loads (TMDLs). Where appropriate and the underlying equations linear, the steady‐state response matrix can be used to synthesize the results of more complicated models and present them in a way easily understood by policy makers. A straightforward method is presented for generating the response matrix using complex models, and example applications discussed. Example applications include a simple demonstration; incorporation of the method into the Mississippi Department of Environmental Quality’s STREAM model used in TMDL development; a TMDL modeling study of the Grand Calumet River and Indiana Harbor Canal, Indiana, using CE‐QUAL‐ICM; and a TMDL modeling study of the Big Sunflower River, Mississippi, using the Water Analysis Simulation Program model.     

Is Denser Greener? An Evaluation of Higher Density Development as an Urban Stormwater‐Quality Best Management Practice1

Abstract: A simple spreadsheet model was used to evaluate potential water quality benefits of high‐density development. The question was whether the reduced land consumed by higher density development (vs. standard suburban developments) would offset the worse water quality generated by a greater amount of impervious surface in the smaller area. Total runoff volume and per acre loadings of total phosphorous, total nitrogen, and total suspended solids increased with density as expected, but per capita loadings and runoff decreased markedly with density. For a constant or given population, then, higher density can result in dramatically lower total loadings than more diffuse suburban densities. The model showed that a simple doubling of standard suburban densities [to 8 dwelling units per acre (DUA) from about 3 to 5 DUA] in most cases could do more to reduce contaminant loadings associated with urban growth than many traditional stormwater best management practices (BMPs), and that higher densities such as those associated with transit‐oriented development could outperform almost all traditional BMPs, in terms of reduced loadings per a constant population. Because higher density is associated with vibrant urban life, building a better city may be the best BMP to mitigate the water quality damage that will accompany the massive urban growth expected for the next several decades.     

Method to Partition Between Attached and Unattached E. coli in Runoff From Agricultural Lands1

Abstract: Remediation of waters impaired by bacterial indicators is usually dictated by total maximum daily load plans, which are heavily dependent on fate and transport modeling of bacterial indicators. Nonpoint source pollution models are most frequently used to assess bacterial transport to surface waters and most models typically simulate bacterial transport as a dissolved pollutant. Previous studies have found that cells preferentially attach to sediments; however, a variety of techniques have been used to assess attachment including filtration, fractional filtration, and centrifugation. In addition, a variety of chemical and physical dispersion techniques are used to release attached and bioflocculated cells from particulates. Here we developed and validated an easy‐to‐replicate laboratory procedure for separation of unattached from attached E. coli which will also identify particle sizes to which E. coli preferentially attach. Physical and chemical dispersion techniques were evaluated and a combined hand shaker treatment for 10 min followed by dilutions in 1,000 mg/l of Tween 85 significantly increased total E. coli concentrations by 31% when compared with a control. In order to separate unattached from attached fractions, two commonly used techniques, fractional filtration, and centrifugation were combined. The filtration and centrifugation treatments did not reduce E. coli concentrations when compared with a control (p > 0.05), indicating that damage was not inflicted upon the E. coli cells during the separation procedure.     

Sustainable three‐well pumping strategy for efficient detection monitoring near waste impoundments

Efficient monitoring systems addressing the difficulty of detecting narrow contaminant plumes originating from unknown point sources are needed for modern landfills. A low‐discharge extraction and accompanying injection wells could potentially address this problem. This hypothetical computer‐modeling study involved a three‐well detection system consisting of one extraction and two injection wells at a rectangular landfill in a shallow, unconfined aquifer. The extraction and injection wells were located near the landfill's downgradient and cross‐gradient corners, respectively. Each injection well pumped at half the rate of the extraction well. A minimum pumping rate of 1.1 cubic meters per day was determined for the three‐well system; at this rate, all contaminant plumes originating within the landfill's footprint entered the extraction well prior to reaching a downgradient property boundary. In comparison, five passive (not pumped) wells detected all contaminant releases from the landfill. Results of this study suggest that a low‐discharge extraction well with accompanying injection wells may be an effective contaminant detection strategy at some waste impoundments.     

ESTIMATING THE PROBABILITY OF EXCEEDING GROUNDWATER QUALITY STANDARDS1

ABSTRACT: A model for estimating the probability of exceeding groundwater quality standards at environmental receptors based on a simple contaminant transport model is described. The model is intended for locations where knowledge about site-specific hydrogeologic conditions is limited. An efficient implementation methodology using numerical Monte Carlo simulation is presented. The uncertainty in the contaminant transport system due to uncertainty in the hydraulic conductivity is directly calculated in the Monte Carlo simulations. Numerous variations of the deterministic parameters of the model provide an indication of the change in exceedance probability with change in parameter value. The results of these variations for a generic example are presented in a concise graphical form which provides insight into the topology of the exceedance probability surface. This surface can be used to assess the impact of the various parameters on exceedance probability.