Comparison of aeration tank calculations using ASM2d and ATV models

Summary

A comparison is made of the results of calculating aeration tanks by ATV model (Standard ATV-DVWK-A131 E «Dimension of Single-Stage Activated Sludge Plants 2000»), that is a stochastic «table» model, and by ASM2d model, that is referred to as theoretical and describes, unlike ATV, biological wastewater treatment processes using enzymatic kinetics formulas. Calculations are performed for the same input data. The calculation results show essentially limited use of ATV model; this model, as originally given in the description of this model by the designers, provides for calculating aeration tanks only for a single value of the effluent quality in terms of ammonia nitrogen as 1 mg/l and does not provide for calculating aeration tanks in terms of nitrites. Moreover, the comparison of ATV and ASM2d show that achieving the specified quality of effluent in terms of ammonia nitrogen as 1 mg/l is possible only at specific values of the kinetic constants determined by the authors in this article; whereas, any change in at least one kinetic parameter of the wastewater results in an increase in the required aerobic age of activated sludge and, as a consequence, in the calculated volume of the aerobic zone by tens of percent, which proves the risk of not achieving the required effluent quality while using ATV model even for ammonium nitrogen concentration of 1 mg/l. Taking into account the fact that ATV Method does not provide for calculating aeration tanks for the effluent quality in terms of nitrites, the results of our calculation show that the aerobic age of activated sludge of 4.05 days for a temperature of 17 ºС proposed in ATV will make it possible to achieve the effluent quality in terms of nitrite nitrogen, 0.35–0.52 mg/l N–NO2, proving the unavailability of ATV, if the requirements to the effluent quality in terms of nitrites are specified. The authors, on the basis of the calculations, make conclusions about the risk of failure to achieve the effluent quality in terms of ammonia nitrogen as well as 1 mg/l while using ATV, because ATV is a stochastic model, that is, all dependencies presented in this method have been determined for the specific operating conditions. Moreover, as specified in the ATV description, this method, even in limited conditions, is applicable strictly for urban wastewater. The calculations show that if there are requirements for the effluent quality in terms of nitrites, regardless of the required concentration value of nitrites, the ATV method is absolutely not suitable, while ASM2d, taking into account the fact that it is based on the formulas of enzymatic kinetics, provides for calculating aeration tanks for any required effluent quality in terms of both ammonium nitrogen and nitrite nitrogen and is applicable for any type of wastewater.

Key words

biological treatment , nitrification , activated sludge , kinetic constants , industrial and municipal wastewater , comparative calculation of the biological treatment facilities , ATV and ASM2d process calculation methods , aerobic age of activated sludge , theoretical and stochastic models

DOI 10.35776/VST.2022.05.03
UDC 628.35

Kharkina O. V.

Comparison of the results of calculating aeration tanks according to the method of Danilovich–Epov and ASM2d model (part 1)

Summary

The analysis of the method proposed by D. A. Danilovich and A. N. Epov for calculating aeration tanks that implement nitrogen and phosphorus removal technologies is carried out. A comparison of the results of calculations by this method and ASM2d method is given. It is shown that, in contrast to the ASM2d method that refers to theoretical models and describes the processes of biological wastewater treatment using the formulas of enzyme kinetics, the method under consideration is, in essence, an empirical calculation that contains constants that are invariable and, for the most part, not having the physical meaning. Since empirical models make a connection between the parameters obtained on the basis of the experimental data of a particular object under strictly limited conditions, these models can only be applied if all the parameters of another object exactly match the data of the object the proposed model was compiled for. Accordingly, using any empiric models, including the method under consideration, at the facilities that were not the objects for the compilation of these empiric models, leads to the risk of obtaining incorrect calculation results. Based on the performed calculations, the risks and constraints of using the method proposed by Danilovich and Epov for the calculation of biological treatment facilities are shown. In the first part of the paper, a design analysis was carried out to determine the values of the aerobic age of activated sludge that were the basic values for calculating the volume of aerobic zones of aeration tanks.

Key words

wastewater , biological treatment , nitrification , denitrification , activated sludge , kinetic constants , theoretical and empirical mathematical models , comparative calculation of the biological treatment facilities , ASM2d

DOI 10.35776/VST.2021.05.02
UDC 628.35

SHVETSOV V. N., Kharkina O. V., Stepanov S. V.

Comparison of the calculation results for aeration tanks using the NII VODGEO/SamGTU and ASM2d models

Summary

Проведено сравнение результатов расчета аэротенков, реализующих процессы аэробного окисления органических соединений, нитрификации, денитрификации и удаления фосфора (химического и биологического) по двум различным математическим моделям (методикам): ВОДГЕО/СамГТУ (Самарского государственного технического уни-
The paper presents a comparison of the results of calculating aeration tanks where the processes of aerobic oxidation of organic compounds, nitrification, denitrification and phosphorus removal (chemical and biological) according to two different mathematical models (methods): VODGEO/SamGTU (Samara State Technical University) and ASM2d have been implemented. These models are theoretical and describe the processes of biological wastewater treatment using enzymatic kinetics formulas. Calculations for the same input and output data showed a high reproducibility in terms of the volumes of the process zones of aeration tanks. For the quality of effluent meeting the MPCs for fishery water bodies (option 1), the discrepancy is –0.3 and 3.3%, respectively, for the anoxid and aerobic zones. With indicators for effluent discharge into a water body of category B (option 2) for large-scale to extremely large-scale facilities, the difference in the results of calculating the volumes was 13.8 and 15.4%, respectively. While making calculations with account of the effluent quality reaching the process indicators for discharge into a water body of category G (option 3) for large-scale to extremely large-scale facilities, the discrepancy in the values of the volumes of aerobic zones was 48% owing to the expediency of ensuring stable nitrification at high loads. Therefore, option 3 according to the VODGEO/SamGTU method was actually performed for a lower sludge load and more enhanced nitrification than according to the ASM2d method (1 instead of 2 mgN–NH₄/l). It is shown that the mathematical models underlying both methods, based on the fundamental equations of the enzymatic reaction, a very high reproducibility and consistency of the calculation results give grounds to assert that both of these models are, to the greatest extent known, acceptable for calculating biological treatment facilities with the removal of nitrogen and phosphorus.

Key words

biological treatment , nitrification , denitrification , activated sludge , kinetic constants , industrial and municipal wastewater , VODGEO/SamGTU and ASM2d process calculation methods , theoretical and empirical mathematical models , comparative calculation of the biological treatment facilities

DOI 10.35776/VST.2022.09.04
UDC 628.35

Kevbrina M. V., Dorofeev A. G., Agarev Anton

Comparison of the results of calculating aeration tanks according to different methods (for discussion)

Summary

The calculation results are compared according to the method described in the book by D. A. Danilovich and A. N. Epov «Calculation and technological design of processes and facilities for the removal of nitrogen and phosphorus from municipal wastewater», and the method given in the book «Wastewater technology. Processing and recovery of resources» (fifth edition, Metcalf & Addy), in a model unit, for which earlier in the article by V. N. Shvetsov, S. V. Stepanov and O. V. Khar’kina «Comparison of the calculation results for aeration tanks using the NII VODGEO/SamGTU and ASM2d models» calculations had been made according to the method of NII VODGEO/SamGTU and following the model developed by ASM2d. It is shown that calculations based on the equations of enzymatic kinetics and microbial growth (NII VODGEO/SamGTU, ASM2d and Metcalf & Addy) give similar results in terms of the volume of aeration tanks with the «tabular» method based on the German standard ATV-DVWK-A131E and revised taking into account the growth kinetics of nitrifying microorganisms. The difference in approaches gives different results as for the age of activated sludge; however, the final results of the volumes of aeration tanks and zones in them have discrepancies that do not exceed 15–20%. Simulation of the operation of aeration tanks in BioWin-3 program, designed on ASDM model that is essentially close to the ASM group of activated sludge models, with zone volumes calculated using different methods, showed a similar calculated quality of effluent. This confirms the possibility of any of the considered methods to adequately calculate the volumes of aeration tanks. The choice of the calculation method for each specific case depends on the availability and ease of use of the methodology, as well as on the personal preferences of the designer.

Key words

nitrification , denitrification , aeration tank , wastewater biological treatment , anaerobic zone , theoretical and empirical mathematical models , comparative calculation of the biological treatment facilities , technological calculation methods , anoxic zone