Abstract
This work shows an integrated analysis method for hydrodynamic investigation of biological reactors for wastewater treatment in order to detect the amount and position of possible defects, such as bypass and dead volume, influencing process efficiency. To reach such a goal, the proposed methodology integrates Residence Time Distribution (RTD) analysis, providing global hydrodynamic information, with Computational Fluid Dynamics (CFD) analysis, showing local flow conditions. RTD analysis was performed through a time-discretized analytical model of in-series mixed-flow reactors with dead volumes and bypass. CFD analysis was carried out with a 3D finite volume model allowing the numerical solution of turbulent incompressible isothermal flow. The method was tested on a scale activated sludge pilot plant with pre-denitrification scheme made of two in-series tanks. Hydrodynamic tests were performed carrying out the stimulus-response experiment using clear water inside the reactor and lithium chloride as a tracer. Two operating conditions of practical interest were investigated: (i) no mixing and (ii) upstream mixing. The RTD analysis of the outflow curve of lithium concentration from the experiment allowed detecting: a) no bypass for both operating conditions, and b) 5% dead volume for condition (i). These results were confirmed by the CFD analysis that allowed localizing the position of the dead volume. The integrated analysis proved to be effective for detection of both types and position of hydrodynamic defects. Therefore the proposed method can be adopted for performance assessment of activated sludge reactors and subsequent improvement of their efficiency.
Similar content being viewed by others
Abbreviations
- E :
-
Residence time distribution function [s−1]
- C :
-
Tracer’s concentration [mg L−1]
- i :
-
Index of the mixed-flow reactor [−]
- i b :
-
Bypass index [−]
- i d :
-
Dead volume index [−]
- M :
-
Tracer’s mass for pulse injection [kg]
- N :
-
Number of in-series mixed-flow reactors [−]
- p :
-
Pressure [Pa]
- Q :
-
Flow rate to the reactor [m3 s−1]
- Q b :
-
Bypass flow rate [m3 s−1]
- t :
-
Physical time [s]
- \( \overline{t} \) :
-
Average hydraulic retention time [s]
- T res :
-
Mean residence time [s]
- V :
-
Volume of the reactor [m3]
- V d :
-
Dead (or interchange) volume [m3]
- v i :
-
Cartesian components of average velocity [m s−1]
- x i :
-
Cartesian coordinates [m]
- ν :
-
Kinematic viscosity [m2 s−1]
- ν T :
-
Eddy viscosity [m2 s−1]
- Θ:
-
Passive scalar concentration [mg L−1]
- ρ :
-
Density [kg m−3]
- g :
-
Gravitational acceleration vector [m s−2]
- v :
-
Ensemble average velocity vector [m s−1]
- x :
-
Position vector [m]
- CAS:
-
Conventional activated sludge
- CFD:
-
Computational fluid dynamics
- DEN:
-
Upstream tank for nitrate removal
- OX-NIT:
-
Downstream tank for oxidation/nitrification
- RANS:
-
Reynolds averaged Navier-Stokes
- RTD:
-
Residence time distribution
- SED:
-
Settling tank
- TAMR:
-
Thermophilic aerobic membrane reactor
- TKE:
-
Turbulent kinetic energy
- TSS:
-
Total suspended solids
- WWTP:
-
Wastewater treatment plant
References
Abbà A, Collivignarelli MC, Manenti S, Pedrazzani R, Todeschini S, Bertanza G (2017) Rheology and microbiology of sludge from a thermophilic aerobic membrane reactor. J Chem Article ID 8764510. https://doi.org/10.1155/2017/8764510
APHA, AWWA, WEF (2012) Standard methods for the examination of water and wastewater, 22nd edn. American Public Health Association, Washington DC
Baléo JN, Le Cloirec P (2000) Validating a prediction method of mean residence time spatial distributions. AICHE J 46:675–683. https://doi.org/10.1002/aic.690460403
Bertanza G, Collivignarelli C (2006) The functional tests for the optimization of urban wastewater treament plants (Le verifiche di funzionalità per l’ottimizzazione della depurazione delle acque di scarico urbane). Collana Ambiente – volume 28. CIPA edn, Milano. ISSN: 1121-8215 (in italian)
Bertanza G, Papa M, Canato M, Collivignarelli MC, Pedrazzani R (2014) How can sludge dewatering devices be assessed? Development of a new DSS and its application to real case studies. J Environ Manag 137:86–92. https://doi.org/10.1016/j.jenvman.2014.02.002
Brouckaert CJ, Buckley CA (1999) The use of computational fluid dynamics for improving the design and operation of water and wastewater treatment plants. Water Sci Technol 40:81–89. https://doi.org/10.1016/S0273-1223(99)00488-6
Collivignarelli C, Bina S (1993) The hydrodynamic behaviour of an anaerobic digester for domestic sludge: comparative tests. Eur Water Pollut Control 3:9–12
Collivignarelli C, Bertanza G, Bina S (1995) Hydrodynamic tests in the water treatment - theoretical basis, application procedures, examples (La verifica idrodinamica nel trattamento delle Acque - Basi teoriche, procedure di applicazione, esempi). Collana Ambiente – volume 8. CIPA edn, Milano. ISSN: 1121-8215 (in italian)
Collivignarelli C, Pergetti M, Riganti V (2000) The management of wastewater treatment plants. Proposals of guidelines for the maintenance, control, verification, upgrading and co-treatment with aqueous special waste (La gestione degli impianti di depurazione delle acque di scarico. Proposte di linee guida per la manutenzione, il controllo, le verifiche, l’upgrading e i trattamenti congiunti di reflui speciali). Il sole 24Ore edn., Milano. ISBN: 88-324-4047-4 (in italian)
Collivignarelli MC, Abbà A, Bertanza G (2015a) Why use a thermophilic aerobic membrane reactor for the treatment of industrial wastewater/liquid waste? Environ Technol 36:2115–2124. https://doi.org/10.1080/09593330.2015.1021860
Collivignarelli MC, Bertanza G, Sordi M, Pedrazzani R (2015b) High-strength wastewater treatment in a pure oxygen thermophilic process: 11-year operation and monitoring of different plant configurations. Water Sci Technol 71:588–596. https://doi.org/10.2166/wst.2015.008
Collivignarelli MC, Abbà A, Alloisio G, Gozio E, Benigna I (2017a) Disinfection in wastewater treatment plants: evaluation of effectiveness and acute toxicity effects. Sustainability 9:1704. https://doi.org/10.3390/su9101704
Collivignarelli MC, Abbà A, Castagnola F, Bertanza G (2017b) Minimization of municipal sewage sludge by means of a thermophilic membrane bioreactor with intermittent aeration. J Clean Prod 143:369–376. https://doi.org/10.1016/j.jclepro.2016.12.101
De Gussem K, Fenu A, Wambecq T, Weemaes M (2014) Energy saving on wastewater treatment plants through improved online control: case study wastewater treatment plant Antwerp-south. Water Sci Technol 69:1074–1079. https://doi.org/10.2166/wst.2014.015
Do-Quang Z, Cockx A, Line A, Roustan M (1998) Computational fluid dynamics applied to water and wastewater treatment facility modeling. Environ Eng Policy 1:137–147. https://doi.org/10.1007/s100220050015
Essemiani K, Vermande S, Marsal S, Phan L, Meinhold J (2004) Optimization of WWTP units using CFD – a tool grown for real scale application. In: Van Loosdrecht M, Clement J (eds.), 2nd IWA leading-edge conference on water and wastewater treatment technologies. IWA Publishing, London, pp. 183–192
Gallati M, Bertanza G, Sibilla S, Collivignarelli MC, Gazzola E (2007) Integrated test to assess the hydrodynamic behavior of a biological reactor using RTD and numerical models (Verifica integrata del comportamento idrodinamico di un reattore biologico mediante metodo RTD e modelli numerici). IA Ingegneria Ambientale XXXVI:392–403 in italian
Guimet V, Savoye P, Audic JM, Do-Quang Z (2004) Advanced CFD tool for wastewater: today complex modelling and tomorrow easy-to-use interface. In: van Loosdrecht M, Clement J (eds) 2nd IWA leading-edge conference on water and wastewater treatment technologies. IWA Publishing, London, pp 165–172
Hirt CW, Nichols BD (1981) Volume of fluid (VOF) method for the dynamics of free boundaries. J Comput Phys 39:201–225. https://doi.org/10.1016/0021-9991(81)90145-5
Hreiz R, Latifi MA, Roche N (2015) Optimal design and operation of activated sludge processes: state-of-the-art. Chem Eng J 281:900–920. https://doi.org/10.1016/j.cej.2015.06.125
Karama AB, Onyejekwe OO, Brouckaert CJ, Buckley CA (1999) The use of computational fluid dynamics (CFD) technique for evaluating the efficiency of an activated sludge reactor. Water Sci Technol 39:329–332. https://doi.org/10.1016/S0273-1223(99)00294-2
Karpinska AM, Bridgeman J (2016) CFD-aided modelling of activated sludge systems. A critical review. Water Res 88:861–879. https://doi.org/10.1016/j.watres.2015.11.008
Kjellstrand R, Mattsson A, Niklasson C, Taherzadeh MJ (2005) Short circuiting in a denitrifying activated sludge tank. Water Sci Technol 52:79–87
Kochevsky AN (2004) Possibilities of simulation of fluid flows using the modern CFD software tools. Cornell University Library, https://arxiv.org/abs/physics/0409104v1
Launder BE, Spalding DB (1974) The numerical computation of turbulent flows. Comput Methods Appl Mech Eng 3:269–289. https://doi.org/10.1016/0045-7825(74)90029-2
Laurent J, Samstag RW, Ducoste J, Griborio A, Nopens I, Batstone DJ, Wicks J, Saunders S, Potier O (2014) A protocol for the use of computational fluid dynamics as a supportive tool for wastewater treatment plant modelling. Water Sci Technol 70:1575–1584. https://doi.org/10.2166/wst.2014.425
Le Moullec Y, Potier O, Gentric C, Leclerc JP (2008) Flow field and residence time distribution simulation of a cross-flow gas–liquid wastewater treatment reactor using CFD. Chem Eng Sci 63:2436–2449. https://doi.org/10.1016/j.ces.2008.01.029
Le Moullec Y, Gentric C, Potier O, Leclerc JP (2010a) Comparison of systemic, compartmental and CFD modeling approaches: application to the simulation of a biological reactor of wastewater treatment. Chem Eng Sci 65:343–350. https://doi.org/10.1016/j.ces.2009.06.035
Le Moullec Y, Gentric C, Potier O, Leclerc JP (2010b) CFD simulation of the hydrodynamics and reactions in an activated sludge channel reactor of wastewater treatment. Chem Eng Sci 65:492–498. https://doi.org/10.1016/j.ces.2009.03.021
Levenspiel O (1999) Chemical Reaction Engineering, Third edn. Wiley, New York
Manenti S, Pierobon E, Gallati M,·Sibilla S, D’Alpaos L, Macchi E, Todeschini S (2016) Vajont disaster: smoothed particle hydrodynamics modeling of the postevent 2D experiments. J Hydraul Eng 142(4): 05015007. doi:https://doi.org/10.1061/(ASCE)HY.1943-7900.0001111
Manenti S, Todeschini S, Collivignarelli MC, Abbà A (2017) CFD-aided modelling for hydrodynamic analysis of biological reactor. Proc. 10th World Congress of EWRA, 5-9 July 2017 Athens (Greece). Eur Water 58:47–51
Meister M, Winkler D, Rezavand M, Rauch W (2017) Integrating hydrodynamics and biokinetics in wastewater treatment modelling by using smoothed particle hydrodynamics. Comput Chem Eng 99:1–12. https://doi.org/10.1016/j.compchemeng.2016.12.020
Morchain J, Maranges C, Fonade C (2000) CFD modelling of a two-phase aerator under influence of a crossflow. Water Res 34:3460–3472. https://doi.org/10.1016/S0043-1354(00)00080-4
Morchain J, Gabelle JC, Cockx A (2014) A coupled population balance model and CFD approach for the simulation of mixing issues in lab-scale and industrial bioreactors. AICHE J 60:27–40. https://doi.org/10.1002/aic.14238
Nauman EB (2007) Residence time distributions. In: Chemical Reactor Design, Optimization, and Scaleup, Second edn. Wiley, Hoboken, pp 535–574
Newell B, Bailey J, Islam A, Hopkins L, Lant P (1998) Characterising bioreactor mixing with residence time distribution (RTD) tests. Water Sci Technol 37:43–47. https://doi.org/10.1016/S0273-1223(98)00000-6
Papa M, Bertanza G, Abbà A (2016) Reuse of wastewater: a feasible option, or not? A decision support system can solve the doubt. Desalin Water Treat 57:8670–8682. https://doi.org/10.1080/19443994.2015.1029532
Patankar SV, Spalding DB (1972) A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows. Int J Heat Mass Transf 15:1787–1806. https://doi.org/10.1016/0017-9310(72)90054-3
Patel VC, Rodi W, Sheuerer G (1985) Turbulence models for near wall and low Reynolds number flows: a review. AIAA J 23:1308–1319. https://doi.org/10.2514/3.9086
Pereira JP, Karpinska AM, Gomes PJ, Martins AA, Dias MM, Lopes JCB, Santos RJ (2012) Activated sludge models coupled to CFD simulations. In: Single and Two-Phase Flows on Chemical and Biomedical Engineering. Eds: Dias MM, Lima R, Martins AA, Mata TM. Bentham Science Publishers Ltd, pp 153–173. https://doi.org/10.2174/97816080529501120101
Raboni M, Gavasci R, Viotti P (2015) Influence of denitrification reactor retention time distribution (RTD) on dissolved oxygen control and nitrogen removal efficiency. Water Sci Technol 72:45–51. https://doi.org/10.2166/wst.2015.188
Rodi W (1980) Turbulence Models and their Application in Hydraulics - a State of the Art Review, Third edn. A.A. Balkema, Rotterdam
Sandberg M (1981) What is ventilation efficiency? Build Environ 16:123–135. https://doi.org/10.1016/0360-1323(81)90028-7
Sorlini S, Collivignarelli MC, Castagnola F, Crotti BM, Raboni M (2015a) Methodological approach for the optimization of drinking water treatment plants' operation: a case study. Water Sci Technol 71:597–604. https://doi.org/10.2166/wst.2014.503
Sorlini S, Collivignarelli MC, Canato M (2015b) Effectiveness in chlorite removal by two activated carbons under different working conditions: a laboratory study. J Water Supply: Res Technol – AQUA 64:450–461. https://doi.org/10.2166/aqua.2015.132
Sorlini S, Biasibetti M, Collivignarelli MC, Crotti BM (2015c) Reducing the chlorine dioxide demand in final disinfection of drinking water treatment plants using activated carbon. Environ Technol 36:1499–1509. https://doi.org/10.1080/09593330.2014.994043
Todeschini S (2012) Trends in long daily rainfall series of Lombardia (Northern Italy) affecting urban stormwater control. Int J Climatol 32(6):900–919. https://doi.org/10.1002/joc.2313
Todeschini S (2016) Hydrologic and environmental impacts of imperviousness in an industrial catchment of northern Italy. J Hydrol Eng 21(7):05016013. https://doi.org/10.1061/(ASCE)HE.1943-5584.0001348
Todeschini S, Ciaponi C, Papiri S (2010) Laboratory experiments and numerical modelling of the scouring effects of flushing waves on sediment beds. Eng Appl Comput Fluid Mech 4(3):365–373
Todeschini S, Papiri S, Sconfietti R (2011) Impact assessment of urban wet-weather sewer discharges on the Vernavola river (Northern Italy). Civ Eng Environ Syst 28(3):209–229. https://doi.org/10.1080/10286608.2011.584341
Todeschini S, Papiri S, Ciaponi C (2012) Performance of stormwater detention tanks for urban drainage systems in northern Italy. J Environ Manag 101:33–45. https://doi.org/10.1016/j.jenvman.2012.02.003
Warhaft Z (2000) Passive scalars in turbulent flows. Annu Rev Fluid Mech 32:203–240. https://doi.org/10.1146/annurev.fluid.32.1.203
Acknowledgements
An initial shorter version of the paper has been presented at the 10th World Congress of the European Water Resources Association (EWRA2017) “Panta Rhei”, Athens, Greece, 5-9 July, 2017 (http://ewra2017.ewra.net/).
The authors wish to thank “ASMia S.r.l.” (Mortara, Pavia) water company for its collaboration during the experimental work.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Manenti, S., Todeschini, S., Collivignarelli, M.C. et al. Integrated RTD − CFD Hydrodynamic Analysis for Performance Assessment of Activated Sludge Reactors. Environ. Process. 5 (Suppl 1), 23–42 (2018). https://doi.org/10.1007/s40710-018-0288-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s40710-018-0288-5