modelling to support re-design and operation of full-scale

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1 Plant-wide modelling to support re-design and operation of full-scale WWTPs F. Ribas, J. Comas and I. Rodríguez-Roda Laboratory of Chemical and Environmental Engineering (LEQUIA), Universitat de Girona and A. Freixò Consorci per a la Defensa de la Conca del Riu Besòs

2 List of contents 1. Motivation 2. Objective 3. Methodology and WWTPs studied 4. Results 5. Conclusions

3 Motivation Influent Process Effluent variability in quality variability in quantity Continuous and uncontrollable Complex and dynamical process (physico-chemical and biological interactions) Limited knowledge of mechanisms Quality demand High quantity of online data and delay in analytical data Great incidence of qualitative and uncertain information Environmental awareness an improvement of WWTP operational reliability is required + Social pressure a real time control is required + Legislation SmallWat07 -in Sevilla, an adequate November cost/benefit 2007 approach!!!

4 Motivation Management strategies Large quantity of data Knowledge Experience Manuals Consultants

5 Motivation EDSS: ATL-EDAR KNOWLEDGE MANAGEMENT MODULE (AI techniques) SIMULATION MODULE PLANT-WIDE MODEL CONTROL MODULE (Fuzzy control, etc.) RULE-BASED EXPERT SYSTEM CASE-BASED REASONING Aeration, recycles, SRT, by-pass, etc. Enables to REASON with any kind of data in a human-like way Saves and retrieves data from previous experiences that are useful for future siutations (EXPERIENCE)

6 Motivation KNOWLEDGE MANAGEMENT MODULE (AI techniques) EDSS: ATL-EDAR SIMULATION MODULE PLANT-WIDE MODEL CONTROL MODULE (Fuzzy control, etc.) Current successfully operating in full-scale WWTPs: Caldes de Montbui ( I.E.), La Garriga ( I.E.), Granollers ( I.E.), Montornès del Vallès ( I.E.) and, La Llagosta ( I.E.)

7 List of contents 1. Motivation 2. Objective 3. Methodology and WWTPs studied 4. Results 5. Conclusions

8 Objective - Identify key aspects in the development (calibration and validation processes) of plant-wide models to be used in fullscale WWTPs, providing a support tool to simulate the effects of a specific action and/or disturbance, or involving a change in the control action: description of the plant layout or flow diagram, required data more important phases for the model calibration and validation processes

9 List of contents 1. Motivation 2. Objective 3. Methodology and WWTPs studied 4. Results 5. Conclusions

10 Methodology and WWTPs studied Plant-wide model = AS model (e.g. ASM2d) + hydraulic model + oxygen transfer model + AD model (e.g. ADM1) + settling model (e.g. Tákacs model) Dynamic calibration for 3 WWTPs of the Besòs River Basin: WWTP Nitrogen removal 1-step process 2-step process Anaerobic digestion La Llagosta X X Montornès del Vallès X X X Caldes de Montbui X X Commercial software: DESASS (DEsing and Simulation of Activated Sludge Systems)

11 Methodology and WWTPs studied Methodology for building and validation of plant-wide models for fullscale WWTPs (based on a simplification of the Biomath protocol) PHASE I DEFINITION OF THE MODELLING OBJECTIVE PHASE II DATA ACQUISITION AND ANALYSIS AND PROCESS CHARACTERISATION Plant layout Plant data characteristics Historical data availability Settling characterisation Influent and biological characterisation Data analysis Data verification PHASE III STEADY STATE CALIBRATION Analysis of the effluent quality PHASE IV DYNAMIC CALIBRATION AND EVALUATION. Analysis of the effluent quality Data verification

12 List of contents 1. Motivation 2. Objective 3. Methodology and WWTPs studied 4. Results 5. Conclusions

13 Results: Plant layout construction Input Primary effluent Effluent Primary waste sludge Biological reactor WAS Example of layout developed in DESASS for the Montornès del Vallès WWTP

14 Results: Data acquisition, data analysis and process characterization Collection and description of good physical and operational data about the WWTPs Both historical (steady state) averaged data and dynamic data for influent and effluent profiles are required COD and N fractionation Historical data (from a time period long enough and without significant changes in the plant operation) Data analysis and verification step, including mass balances Use of respirometries to obtain initial values of kinetic parameters for the calibration

15 Results: Data acquisition, data analysis and process characterization Characterisation of the influent (COD and N fractionation to state variables: S F, S A, etc.) La Llagosta Montornès del Caldes de Vallès Montbui COD Biodegradable Easily biodegradable - Complex (S F ) VFA (S A ) Slowly biodegradable - X S Not Biodegradable Inert soluble (S I ) Inert particulates (X I ) Example of the COD fractionation required for steady state calibration for the three WWTPs modelled

16 Results: Steady state and dynamic calibration Iterative procedure First a steady state calibration phase: SRT (or MLSS concentration), sludge production and the averaged effluent COD and N concentrations Parameter values obtained during the steady state calibration will be used as the starting point for the dynamic calibration Steady state simulation (2 month averaged data) Start of the activated sludge model calibration No X I, Y H, b H, f ns MLSS OK? Steady state simulation (2 month averaged data) Yes Dynamic simulation (1 week data) Nitrification NH4 OK? No µ A µ H, K O2, f ns Yes Denitrification Nitrate OK? No SmallWat07 - Sevilla, November Yes 2007 Complete calibration

17 Results: Steady state and dynamic calibration Then a dynamic calibration is carried out, where dynamic daily profiles are necessary to fine tune those parameters affecting short term behaviour (ammonia, nitrate and phosphorous profile). 70 NH4 calibrat real inicial 7 NO3 calibrat real inicial mg NH4/l mg NO3/l dies dies Parameter Symbol Unit Literature values Calibrated values Heterotrophic yield Y H g DQO/ g DQO Maximum specific heterotrophic growth rate µ maxh d Maximum specific µ autotrophic growth rate maxa d

18 List of contents 1. Motivation 2. Objective 3. Methodology and WWTPs studied 4. Results 5. Conclusions

19 Conclusions Simplified protocol for plant-wide modelling (ASM2d + Tákacs + ADM1) Validated models allow improvements in the operational conditions, possible plant re-designs or different alternatives for WWTP upgrading to be studied Key aspects in plant-wide modelling and calibration of full-scale WWTPs have been identified: collection of good quality physical and operational data characterisation of the influent and, calibration process based on an iterative procedure that involves both steady state and dynamic simulations Difficulties in comparison to pilot plants or only activated sludge calibrations: temperature and influent water quality more controlled in pilot plants data collection and process monitoring are much easier in pilot plants a plant-wide model must consider influent, side streams and sludge line recycles while an AS model considers only one entry, which is usually the effluent of primary clarification difficulties when sampling for the water quality characterisation in full-scale plants (always depends on the weather conditions and other factors of the plant operation)

20 Plant-wide modelling to support re-design and operation of full-scale WWTPs THANKS FOR YOUR ATTENTION