Mathematical simulation of wastewater treatment processes in aeration tanks

Summary

A new version of the mathematical model of wastewater treatment processes in aeration tanks with biological nitrogen removal and biological-chemical phosphorus removal has been developed based on the mutual complementation of the VODGEO/SamGTU and ASM2d methods. The «inverse problem» of technological calculation of aeration tanks has been solved mathematically, i. e. by determining the pollution concentrations in effluent with available data on the qualitative and quantitative composition of the raw wastewater for the specified values of process and design parameters of the facilities. An algorithm for providing quantitative process recommendations has been developed. Following the conducted research, the Potential software was developed designed for the primary acquisition, technological calculations and providing recommendations to the personnel of the treatment facilities. The implementation of the software will reduce the operating costs by optimizing the process flow pattern of the biological wastewater treatment facilities in the shortest possible time.

The study was carried out within the framework of Agreement No. 4951GS1/85526 with the Federal State Budgetary Institution «Foundation for Assistance to Small Innovative Enterprises in Science and Technology».

Key words

wastewater , biological treatment , kinetic constants , mathematic modelling , NII VODGEO/SamGTU methodology , calculation of aeration tanks , ASM2d model , formulas of enzymatic kinetics

Results of the mathematical simulation of wastewater treatment processes in aeration tanks at the Samara Municipal Wastewater Treatment Facilities during the upgrade and commissioning

Summary

The results of mathematical simulation of the operation of the existing biological wastewater treatment facilities using POTENTIAL software that was used for 10 months to optimize the operation of aeration tanks during the upgrade and commissioning are presented. The data on the quantitative and qualitative composition of wastewater supplied to the aeration tanks adopted in the project are compared with the actual data for the period 2023–2024. Calculation of the actual values of the growth and aerobic age of the activated sludge using the formulas included into the POTENTIAL software showed that the sustained required quality of the effluent in relation to ammonium and nitrites was observed with an aerobic age of activated sludge of 24.1–27 days and a wastewater temperature of 19.1–24.8°C, provided the concentration of N–NH₄ was less than 1 mg/l, and N–NO2 was less than 0.1 mg/l. As a result of calibration and verification of the mathematical model embedded in POTENTIAL software, the values of kinetic constants and coefficients were selected for a separate process line «aeration tank No. 7 – secondary settling tank No. 5» resulting in predicting the operation of the aeration tanks with a high degree of accuracy (deviations between the calculated and actual data were less than 8%).

Key words

wastewater , kinetic constants , mathematic modelling , NII VODGEO/SamGTU methodology , calculation of aeration tanks , ASM2d model , formulas of enzymatic kinetics , biological removal of nitrogen and phosphorus from wastewater

Comparison of the results of calculating aeration tanks according to the method of Danilovich–Epov and ASM2d model
(рart 2)

Summary

The analysis of the method for calculating aeration tanks proposed by D. A. Danilovich and A. N. Epov, based on the German ATV method, is continued. Due to certain limitations of the empirical ATV methodology developed on the basis of the data on the wastewater the authors were able to study, the ATV methodology cannot be applied anywhere except the treatment facilities where those studies were carried out. The Methodology has been compared with ASM2d model (a matrix of enzyme kinetics equations describing the growth rates of microorganisms and the rates of the corresponding biochemical processes), as well as with the NII VODGEO/SamGTU method that is a completely theoretical model, and the calculation formulas being enzyme kinetics equations. Calculations of aeration tanks according to the formulas of enzyme kinetics were laid down in SNiP «Sewerage. External Networks and Structures» in 1974; whereas in SNiP 1984, the calculation was given in the form of a proven methodology for biological treatment facilities for the oxidation of organic compounds. The empirical approach proposed in the Methodology opens not only a technological question about the scope of its application, but also the question of its expediency in general. The use of empirical approaches, to which the Methodology belongs, formally connects the inherent parameters in the form of invariable coefficients and empirical dependencies obtained experimentally in a narrow range of parameters and conditions of a particular object bringing the risks of significant errors. It is shown that the Methodology for municipal wastewater provides for underestimated volumes of aeration tanks by tens of percent compared with the results of calculations using the theoretical methods ASM2d and VODGEO/SamGTU developed by V. N. Shvetsov, S. V. Stepanov, K. M. Morozova that describe wastewater treatment processes using enzyme kinetics formulas. Herewith, it is shown that ASM2d and the VODGEO/SamGTU methodology give a high convergence of the results within differences of less than 10% which allows to speak about the robustness of the ASM2d model and the VODGEO/SamGTU methodology, and the limitations of the Method that can be used only for rough estimates.

Key words

wastewater , biological treatment , nitrification , denitrification , activated sludge , kinetic constants , theoretical and empirical mathematical models , ASM2d , NII VODGEO/SamGTU methodology , enzyme kinetics equations , comparative calculation