Analysis of the Methods of Water Systems State Estimation


  • Marius Šileika
  • Asta Marytė Lapinskienė


water system (ecosystem), metabolism, catabolism, energetic potential, chemical oxygen demand COD, biochemical oxygen demand BOD, activity of dehydrogenase, activity of catalase, bioluminescence and total organic carbon TOC


The state of water ecosystem is constantly affected by natural processes. Moving substances and energy in this system form a new dynamic balance which changes the parameters of the system itself. In the system, substances rotate from one link to another, while energy moves to one or the other direction, therefore thermodynamic parameters: mass, energy, entropy, enthalpy and their transfers of a metabolism process are to be estimated.
Oxygen concentration in the system influences the processes of organic substances production and destruction i.e. their intensity, thermodynamic stability, spontaneous purification and ecosystem state. By oxidizing nutrients a cell gathers energy for biosynthesis reactions, movement, and substances transfer. The energy released during oxidation-reduction reactions is consumed to maintain the building of a cell. On the basis of the variation of oxygen concentration, organic chemical impurities in water ecosystem are qualitatively and quantitatively analyzed. Concentration of nutrients in the system is indirectly evaluated by BOD and COD parameters which are susceptible to time and may be unreliable.
For this reason, to monitor the parameters, to prevent the discharge of badly treated wastewater, to control the technological process of wastewater treatment equipment, the efficient, fast and low-cost methods are to be developed.
The existing methods of determining the qualitative parameters of water ecosystems have been studied, compared among each other with the experimental results obtained by the comparative analysis method. When comparative parameters are determined by technological, legal, consumer and scientific approach and their evaluation scale is set up, the methods are evaluated as to the rate of the system state estimation. After the analysis of the methods of water system condition evaluation, all methods based on estimation of chemical, physical and biological parameters have been found to be unsuitable for fast determination of the water system state. To estimate the water system state reliably, authors of this paper recommend adapting the method based on the parameters of thermodynamic nature.

Author Biographies

Marius Šileika

PhD student at the Institute of Environmental Engineering, Kaunas University of Technology

Asta Marytė Lapinskienė

senior lecturer at the Department of Technological Processes, at University of Klaipeda