The multiple scales of uncertainty: an engineer's perspective E. Belia, Ph.D., P.Eng. Primodal Inc.

Transcription

1 Quantifying Uncertainty in Integrated Catchment Studies (QUICS) Final Dissemination Event, Amsterdam International Water Week Thursday 2 nd November 2017 The multiple scales of uncertainty: an engineer's perspective E. Belia, Ph.D., P.Eng. Primodal Inc.

2 Overview Current practice Drivers moving us to a new analysis framework Example The big picture a complex system Things to think about

3 Engineering approaches Sensitivity analysis Design guidelines Critical states engineering Based on worst-case analysis Static environment and resource allocation Guaranteed availability of infrastructure Redundancy Scenarios Statistical analysis of past data Models Best effort engineering Average case analysis Dynamic resource management No guaranteed performance

4 The new WRRF: a node within a complex system The usual: Role of environmental protection Subject to catchment dynamics The new: Obligation to provide a product Interdependency with other industries

5 Adaptive engineering Deliver service in interaction with uncertain environments Integrating both critical and best effort engineering Sufficient resources to cover critical events Optimal use of available resources No regret measures

6 Example: achieving reclaimed water quality J. Weiss, LACD Senior Engineer, Rtd. E. Belia, Primodal Inc.

7 East and West WRRF Flow 236,600 (m 3 /d) 62.5 (MGD) COD 295 (mg/l) (lb/d) Ammonia 20 (mg/l) 9750 (lb/d)

8 Regulatory constraints NPDES permit for one of the plant discharge locations Parameter Final Effluent Ammonia (mg/l) Average monthly Average weekly Maximum daily BOD TSS Ammonia-N 4-6 NO 2 -N NOx-N Water Reclamation Permit CT of no less than (90x5) 450 milligram-minutes per liter at all times with a modal contact time of at least 90 minutes, based on peak dry weather design flow; or inactivate and/or remove percent (5-log) of the plaque forming units of F-specific bacteriophage MS2, or polio virus in the wastewater 0 Monthly average Date

9 Steps to meet reclamation permit Implementation of sequential chlorination secondary effluent must not exceed 1 mg N/L EQ tank construction for flow equalization will not be operational until 2020 Optimization of the aeration system 45 3 Primary effluent ammonia (mg/l) Primary 2.5 Effluent Effluent ammonia (mg/l) Reduce flow Hours

10 What is the risk of a disinfection failure caused by excessive secondary effluent ammonia bleed through? Adaptive approach Environmental - Social - Economic

11 Sources of variability and uncertainty Influent variability Flow distribution μ max, AOB MLSS distribution DO control Blower limitations Settling parameter

12 Process model Parametric uncertainty qmax Jeffrey Weiss, LACD Senior Engineer, Rtd. Histogram Burr

13 Calculating the probability of noncompliance (PONC) Synthetic generation of influent time series Random generation of model parameter vectors NO Uncertainty propagation using the model under dynamic conditions Convergence of the statistical characteristics of effluent? 1. Output analysis 2. Calculation of statistical parameters for each effluent constituent YES 1. Estimating the CDFs for wastewater constituents 2. Calculation of PONC Talebizadeh, Probabilistic design of wastewater treatment plants. PhD Thesis

14 A complex problem

15 Catchment events

16 Equipment failures & human errors Air compressor filter failure filter on compressor suction side failed got sucked into compressor destroying inlet guide vanes causing an imbalance in the unit Human error destroys a pump failure to cut off reclaimed water users during hydraulic shutdown water level in the chlorine contact tank got drawn down Nalgene sample bottle sucked into pump

17 A tragedy

18 The next treatment target

19 District objectives Sanitation District Manager Public health & environmental protection Social responsibility Fiscal responsibility Meet NPDES permit Meet reclaimed water permit Maximize water reuse Increase revenue Reduce operational costs Take into account future needs Treat as much flow as possible Reduce plant flow Maximise reclaimed water Maximise reclamed water Operate close to permit Best use of available land Treatment division Reclaimed water division Treatment division Reclaimed water division Treatment division Future shifts in treatment needs New technologies requiring expensive modifications Planning division

20 Level of uncertainty Determinism Indeterminacy Statistical uncertainty Scenario uncertainty Recognised ignorance Total ignorance Quantified outcomes Range of plausible outcomes We are aware that there is something we do not know We do not know what we do not know 5 years 10 years 30 years

21 DOUT uncertainty analysis framework Modeling phase Systems analysis Stakeholder Contract type Project stage DOUT Design and operations uncertainty task group

22 Tackling Uncertainty Analysis (UA) Identify problem: Metrics Sources Prioritize: Identify drivers Sensitivity analysis Reduce: Sampling Experimental design Model: Influent quality CFD Integrated modeling Model predictive real time control Uncertainty propagation: Influent variability Parametric uncertainty PONC and PSE estimates Scenario analysis Fore sighting methods Life cycle assessment Multi-attribute-utility theory Benefit-cost-risk approach Benchmarking and auditing Synthesize and communicate results Jakeman, A.J., Letcher, R.A. and Norton J.P. (2006) Ten iterative steps in development and evaluation of environmental models. Environmental Modelling & Software. 21, pp

23 Steps to accelerated adoption Method development PDF selection Incorporate expert knowledge Correlation Incorporating human error & equipment failures Accounting for temporal and spatial variability (3-D space vs. simulation space) Meaningful composition of heterogeneous components (different sources, large variety of interaction mechanisms, different levels of abstraction) Generating additional key process indicators such as process stability Concept communication Variability vs. uncertainty Moving from single parameter values to distributions Communicating key concepts - PONC Scenario development Visualization Psychology and preferential engineering Method adoption Incorporating existing design concepts e.g. max month Linking SF in guidelines to sources of uncertainty Developing MOP for methods Case studies Post project audits Collaboration: engineer-modelerstatistician Software tools

24 Things to think about Contract delivery mechanism Engaging with regulators Software Human psychology

25 Presenter contact information Evangelina Belia Primodal Inc. USA&Canada cell: (269)