Abstrakt

Currently, computer modelling together with the simulation tools tailored for that purpose constitute a very important element in planning technological changes within wastewater treatment plant. From the point of view of the WWTP operator every modification should be introduced in order to improve the quality of treated sewage with the lowest financial outlays. These requirements can be met by using computer programmes to effectuate the changes. In the research was performed the construction of computer model of the SBR reactor operating in laboratory scale. Technological data of the bioreactor as well as the data concerning wastewater quality indicators were entered into the GPS-X software package which was used as a simulation tool. The paper presents the simulation results of the 12-hour operation cycle which consisted of six phases: filling, mixing, aeration, settling, decanting and idle (excess sludge wasting). Simulation experiments were conducted in two variants differing in the aeration mode. In the first case the PID controller was used to maintain the dissolved oxygen concentration at constant level of 2 mgO2/L. In the latter case the oscillation of dissolved oxygen concentration during the aeration stage was applied. The oscillation effect was obtained by means of the appropriately elaborated set point of oxygen concentration taking into account specific intervals in oxygen supply. Consequently, the changes in dissolved oxygen concentration ranged between 0.5 and 2.5 mgO2/L. Among the two analysed variants the latter one with the oscillation of dissolved oxygen concentration proved to be more efficacious considering the quality of treated sewage and the electrical energy expenses. Results obtained after introduction of oscillation mode during aeration phase considerably improved the quality of effluent, especially in terms of dephosphatation process. Efficiency values for total phosphorous as well as orthophosphates removal increased significantly.

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