Water Quality Modeling: A Comparison of Transport Oriented and Biochemistry Oriented Approaches

The author was a rapporteur for the session on "Flow Related Transport Phenomena: Water Quality" at the International Conference on Numerical Modelling of River, Channel and Overland Flow for Water Resources and Environmental Applications, organized by IAHR, WMO, IIASA, and the Czechoslovakian Committee of IAHR, and held in Bratislava, Czechoslovakia, May 4-8, 1981. The request to the rapporteur was to give an overview of the related subject. This formed the first part of the original report and is published here since it considers some typical features and an apparent gap in water quality modeling, and is therefore of more general interest. The papers reviewed are listed in the Appendix

Water Quality Management in Urban Areas: The Challenge for Central and Eastern Europe

The paper discusses past development and present state of urban water resources systems in Central and Eastern Europe which are far from the level of Western countries. High utility loops contribute significantly to often serious contamination of receiving waters. Capital costs of extending the existing capacities of urban water infrastructures are enormous. The management of urban pollutions requires careful planning on the basis of setting national priorities and international ones for shared water resources. The role of systematically prepared laws and environmental legislation is stressed. Main elements of short-term and long-term strategies are outlined. They incorporate among others the introduction of flexible standards and economic instruments for the entire water consumption cycle, a precise scheduling of actions needed furthermore the application of alternative and innovative technologies. The latter are discussed with special emphasis on short-term effectiveness and gradual extension possibilities considering urban and rural areas, and approaches to efficiently close material cycles

Quo Vadis Water Quality Management in Central and Eastern Europe?

Central and Eastern European (CEE) countries are going through unique political, economic, institutional, and social changes associated with the heritage of serious pollution problems from the past. The purpose of this paper is to analyze the water quality management strategies CEE countries may take including the rationale of introducing Western policies in the short run. The policy to be selected must be doable under the existing pressing financial conditions and should feasibly be expanded towards a long-term sustainable scenario as economy improves. As a basis the present economic, social, and institutional setting is outlined, and the state of water quality and the role of emissions of various origins is summarized. A special focus is devoted to municipalities with low and unbalanced levels of infrastructure; the development of these infrastructures could be a burden even for stable economies. An overview and evaluation are given for the water supply, sewerage, and wastewater treatment for urban areas with populations greater than 25.000 in five countries of the CEE region together with a discussion of legislation issues. Major elements of cost-effective development strategies are discussed and illustrated by examples. They incorporate improved demand management and the closing of material cycles, the upgrading of wastewater treatment facilities to match the level of sewerage, the application of regionally variable effluent (and/or ambient) water quality standards and their gradual tightening based on a river basin approach, the innovative selection of combined chemical-biological technologies (for both upgrading and new design) depending on local conditions and the multi-stage development of wastewater treatment plants. The policy suggested for the next couple of decades is characterized by a number of non-uniformities which raises considerable implementation challenges

Potential Impacts of Climatic Change on Lake and Reservoir Water Quality

Climatic change may have very diverse impacts on lakes and their water quality. This paper groups them to hydrologic, thermal, hydraulic, chemical, biochemical, and ecological ones. Their interrelations and potential changes, and their contributions to lake water quality problems, are reviewed and discussed, and checklist tables for planning, management, and impact assessment purposes are provided. Water quality problems are clustered to eutrophication, oxygen depletion, hygienic problems, salinization, acidification, toxic and cumulative substances, turbidity and suspended matter, and thermal pollution. Many of these problems may worsen due to the climatic change, yet an extreme uncertainty exists at any case specific level. Therefore, the possibility of water quality and quantity shifts due to climatic change are suggested to be integrated into contemporary planning and management in an adaptive manner, and the research and development of the impact assessment methodology are suggested to be focused on approaches that can handle extreme uncertainties. The very high uncertainty level in water quality management has obtained an additional highly uncertain component

Water Quality Modeling of the Nitra River (Slovakia): A Comparison of Two Models

IIASA's Water Resources Project deals with the development of least-cost water quality control strategies for degraded river basins in Central and Eastern Europe, which is an important issue due to the lack of financial resources available for environmental management. The Nitra River basin in Slovakia serves as a case study with collaborative research by IIASA, the Water Research Institute (VUVH, Bratislava), and the Vah River Basin Authority from Slovakia. The Nitra River receives large loads of partially or untreated wastewater mostly of municipal origin. The present paper compares the results of two relatively complex water quality models implemented on the Nitra River (which are important elements of developing ambient criteria based control strategies): QUAL2E and RMA2/4q. The well-known QUAL2E is a result of systematic developments by the US EPA over the past twenty years and solves the steady-state advection-diffusion equation for temperature, biochemical oxygen demand (BOD), dissolved oxygen (DO), nitrogen and phosphorus forms, and algae. RMA2/4q was initially developed in the mid-1970s for the US Army Corps of Engineers and has been consistently maintained and extended by Resource Management Associates and researchers at the University of California--Davis. State variables and reaction terms of RMA4q is practically identical to QUAL2E, but it offers more details in computing the flow and physical transport. For the current case, this model was used to solve the unsteady one-dimensional hydrodynamic and advection-diffusion equations for temperature, BOD, and DO. Model comparisons and calibration results showed similar BOD decay rates. DO was overestimated in both models in comparison with DO observations when the O'Connor-Dobbins reaeration method was used. Fixed reaeration coefficients gave better results, with QUAL2E having a larger value than for RMA4q. Sediment oxygen demand was included in the QUAL2E simulations and resulted in better agreement with observed data. Additional data requirements for improved understanding of water quality processes in the Nitra River system are discussed

Uncertainty Analysis and Parameter Estimation for a Class of River Dissolved Oxygen Models

Water quality models are essential to the development of least-cost water quality control strategies based on ambient criteria. Such policies are particularly important if financial resources are limited which is currently the case in Central and Eastern European countries. In turn, the derivation of realistic model parameters is a pre-requisite of successful model application. Often, longitudinal water quality profile measurements are performed for the above purpose, but the traditional evaluation of this data encounters significant difficulties due to measurement and other uncertainties. Thus, probabilistic methods are preferred. This paper discusses two of them: the Hornberger-Spear-Young procedure using Monte Carlo simulation and a Bayesian approach. Both methods are rather generic, but they are applied here solely for the traditional Streeter-Phelps model and its extensions, describing oxygen household of rivers. For the purpose of illustration, water quality measurements from the highly polluted Nitra River in Slovakia are employed as a part of a policy oriented study. The BOD decay rate obtained was rather high due to partial biological wastewater treatment and small water depth, but overall, derived parameter values were in harmony with literature findings. Alternative dissolved oxygen models (2-3 state variables and 2-5 parameters) could be evenly calibrated to the data set. Ranges of probability density functions (PDFs) for model parameters were rather broad calling for a well-suited formulation of a water quality management model

Application of a One-Dimensional Model to Lake Balaton

A one-dimensional, transient hydrodynamic model for Lake Balaton is presented. This is the simplest acceptable approach considering the elongated shape of the lake, which accounts for the fast dynamics of the system. The research reported here is a piece of harmonized efforts, the final objective of which is to describe the spatial mass exchange properly for the eutrophication study. In other words, the relative importance of water motion and the related transport should be weighed against that of the biochemical processes

Cost-Effective Water Quality Management Strategies in Central and Eastern Europe

Many countries in Central and Eastern Europe will be formulating new environmental regulations within the next few years. Among the many topics which these are likely to address is the development of control policies for waste-water dischargers, including municipal sewage treatment plants. In Western Europe and North America, standards have relied heavily upon so-called "best available technology" control policies, which require dischargers to use treatment processes that reduce emissions of BOD, phosphorus, and nitrogen as much as is technically feasible. However, these technologies are often very expensive. Given the state of Central and Eastern European economies, less expensive methods to improve water quality should be seriously considered. In this paper, we investigate control policies, alternative sewage treatment possibilities, water quality models, and optimization methods required to identify least-cost strategies to improve the region's ambient water quality. We survey the costs and technical capacities of a variety of treatment techniques, ranging from simple primary or mechanical treatment to advanced technology to remove nutrients. We also survey existing water quality models and show how they can be adapted to the policy analysis problem. Finally, we characterize a number of potential policies in terms that are amenable to analysis of their costs and ambient quality impacts. Focussing on municipal waste-water treatment plants and water quality in rivers and streams, we show how these techniques can be integrated and applied. We conclude with an empirical example based on the Nitra, a small, heavily contaminated river in Slovakia

Nutrient Loading Estimate for Lake Balaton

One of the principal projects of the Task on Environmental Quality Control and Management in IIASA's Resources and Environment Area is a case study of eutrophication management for Lake Balaton, Hungary. The case study is a collaborative project involving a number of scientists from several Hungarian institutions and IIASA (for details see WP-80-187). As part of the case study, different lake ecological models and water quality management models are under development. The nutrient loads play a distinct role in both kinds of modeling. This is especially so if a comparison of the various approaches is also considered; certainly, the same loading figure must be employed. The objective of the present paper is to determine a nutrient load estimate for Lake Balaton which will then serve as a basis for all the modeling work

River Basin Water Quality Management Models: A State-of-the-Art Review

With the increasing human activities within river basins, the problem of water quality management is becoming increasingly important. Quality management can be achieved through control/prevention measures that have various economic and water quality implications. To facilitate the analysis of available management options, decision models are needed which represent the many facets of the problem. Such models must be capable of adequately depicting the hydrological, chemical and biological processes occurring in the river; while incorporating social, economic and political considerations within the decision framework. Management analyses can be performed using simulation, optimization, or both, depending on the management goal and the size and type of the problem. The critical issues in a management model are the nonlinearities, uncertainties, multiple pollutant nature of waste discharges, multiple objectives, and the spatial and temporal distribution of management actions. Literature on various management models were reviewed under the headings of linear, nonlinear and dynamic programming approaches; their stochastic counterparts, and combined or miscellaneous approaches. Dynamic programming was found to be an attractive methodology which can exploit the sequential decision problem pertaining to river basin water quality problems (downstream control actions do not influence water quality upstream). DP handles discrete decision variables which represent discrete management alternatives, and it is generic in the sense that both linear and non-linear water quality models expressing the relation between emissions and ambient quality levels can be incorporated. An example problem is presented which demonstrates the application of a DP-based management model to formulate least-cost strategies for the Nitra River basin in Slovakia. However, it is hardly possible for a single model to represent all the aspects of a complex decision problem. Different types of management models (e.g. deterministic vs stochastic models) have different capabilities and limitations. The only way to compensate for the deficiencies is to perform the analysis in a sensitivity style. The necessity for sensitivity analyses is further implied due to the fact that water quality problems are rather loosely formulated with respect to the quality and economic goals