Endre Domokos

Dissolved oxygen control of the activated sludge wastewater treatment process using model predictive control

Abstract Activated sludge wastewater treatment processes are difficult to be controlled because of their complex and nonlinear behavior, however, the control of the dissolved oxygen level in the reactors plays an important role in the operation of the facility. For this reason a new approach is studied in this paper using simulated case-study approach: model predictive control (MPC) has been applied to control the dissolved oxygen concentration in an aerobic reactor of a wastewater treatment plant. The control strategy is investigated and evaluated on two examples using systematic evaluation criteria: in a simulation benchmark – developed for the evaluation of different control strategies – the oxygen concentration has to be maintained at a given level in an aerobic basin; and a changing oxygen concentration in an alternating activated sludge process is controlled using MPC technique. The effect of some MPC tuning parameters (prediction horizon, input weight, sampling time) are also investigated. The results show that MPC can be effectively used for dissolved oxygen control in wastewater treatment plants.

Environmental information system for visualizing environmental impact assessment information.

The Institute of Environmental Engineering at the University of Pannonia has undertaken the challenge to develop an online environmental information system. This system is able to receive and process the collected environmental data via Internet. The authors have attached importance to the presentation of the data and have included other comprehensible information for laymen as well in order to work out visualisation techniques that are expressive and attract attention for environmental questions through the developed information system. The ways of visualizing physical and chemical parameters of surface water and the effects of motorway construction were examined.

Simulation of the influence of industrial wastewater on a municipal sewage treatment plant—a case study

PurposeIndustrial wastewater flow caused operational difficulties in the wastewater treatment plant in Debrecen, Hungary. Bioaugmentation was successfully applied to maintain effluent quality in the periods when wastewater of high starch content was accepted, but, at the end of 2008, the nitrification capacity of the plant decreased considerably due to improperly pre-treated pharmaceutical wastewater.Methods and materialDynamic simulations were carried out in a prototype programme developed by the Environmental Expert System Research Group at the University of Pannonia, Hungary. Several parameters for heterotrophic biomass were adjusted in function of time, and the specific growth rate of autotrophic biomass was altered in function of time and temperature in order to describe the effects of inoculation and toxic influence. Simulations were carried out with both constant and adjusted parameters.ResultsThough results on effluent COD of the different modelling versions were similar, the ammonia concentration fitted the measured data only when modified parameters were used. The study revealed that the autotrophic biomass had slowly adapted to the toxic compound. Different control strategies of aeration and decreased excess sludge removal rate were tested to enhance the nitrification in the critical time intervals. The amount of ammonia and inorganic nitrogen decreased in all cases while the oxygen demand increased to a maximum of 10.1%.ConclusionsReducing excess sludge removal rate gave satisfactory results even without changing aeration. Further improvement could be achieved by introducing aeration into the post-denitrification reactor. The combination of the two modifications can compensate for the effect caused by toxicity.

Methodology development on aquatic environmental assessment

The Water Framework Directive aims at reaching the good ecological status of the surface and ground water bodies (László et al. Microchem J 85(1):65–71, 2007). The paper deals with quality evaluation of waters with special focus on the water chemistry parameters as defined in the Water Framework Directive and pertaining legal regulations. The purpose of this paper is to devise a quantitative type of water quality assessment method which could provide rapid, accurate, and reliable information on the quality of the surface waters by using water chemistry parameters. Quality classes have been defined for every water chemistry parameter in light of the legal limit values of the water parameters. In addition to this, weight indices were calculated on the basis of the outcome of the paired comparison of water chemistry parameters and normalized matrix. This was followed by the parametric level analysis of the water chemistry parameters, and finally, the aquatic environment index (AEI) was calculated, which provided general information on the quality of water regarding the water chemistry parameters. The method was illustrated on Lake Balaton, Hungary in which case water samples taken from Balatonfüred City lake area were analyzed and evaluated with the method devised.

Aquatic environmental assessment of Lake Balaton in the light of physical-chemical water parameters

One of the issues of the Hungarian Water Management Strategy is the improvement and upgrading of the water of Lake Balaton. The Water Framework Directive (WFD) specifies and sets forth the achievement of the good ecological status. However, the assessment of the water quality of the lake as a complex system requires a comprehensive monitoring and evaluation procedure. Measurements were carried out around the Lake Balaton at ten different locations/sites and 13 physical-chemical parameters were monitored at each measurement site.For the interpretation of the water chemistry parameters the Aquatic Environmental Assessment (AEA) method devised by authors was used for the water body of the Lake Balaton. The AEA method can be used for all types of the water bodies since it is flexible and using individual weighting procedure for the water chemistry parameters comprehensive information can be obtain. The AEA method was compared with existing EIA methods according to a predefined criterion system and proved to be the most suitable tool for evaluating the environmental impacts in our study.On the basis of the results it can be concluded that the status of the quality of studied area on the Lake Balaton can be categorized as proper quality (from the outcome of the ten measurement sites this conclusion was reached at seven sites).

Using a Decision Support Software in the Course of the Planning of a Waste Management System in Hungary

Modernizing and rearrange the waste management system to the norms of the European Union is one of the most important tasks of the environmental protection in Hungary. Connected to this the Middle-Danube Region Waste Management System is one of the biggest infrastructure investments at present. This investment having an effect on six counties could solve the waste treatment problems of the residents for at least 20 years in the settlements affected. Systems approach mind is needed to complex waste management systems like this, in which beside landfills, plants for separated collection as sorting devices, compost piles, transfer points, waste yards are included and the recultivation of the inconvenient landfills is needed, too. Meeting the systems approach mind is possible only with computational decision support tools. Parmenides EIDOS is a module-based decision support software, specially developed for the economy and the corporate management. The goal of the research was to adapt these software toolkits to environmental field and to examine how the software could be used in the course of the planning of the Middle-Danube Region Waste Management System. According to the authors experience some modules of the software are able to apply well to simplify the complex decision situation and to lay stress on the most important problems. Subjectivity is unavoidable of course, but the subjective elements aid rather than hinder the process due to the group decision-making technique. (Wilkins, 2003) Further advantage is that the data, results are presented visually by this means the time of understanding decreases and keeping in mind become easier than reading naked data or tables. That is why the figures made with EIDOS could be part of a marketing material prepared for the population to increase their support for the investment.

Determining optimal volume fractions of a municipal wastewater treatment plant by dynamic simulation

The aim of this paper is to present the results of an optimisation process of a municipal wastewater treatment plant. The plant was designed to be capable of biological excess phosphorous removal though effluent phosphorous concentrations were above the limit value for several occasions. In the summer period the total nitrogen concentration was also higher than required. It was examined how the adjustment of volume fractions contribute to effluent quality and the optimal ratios were determined by use of dynamic simulation techniques. The aerobic volume fraction was not altered only the two un-aerated phases were modified. The results showed that the anaerobic volume fraction could be lowered up to 11.5 % concluding the anoxic ratio to be 34.5 %.