Simulation Overview

Comprehensive guide to ErgoPlanner's simulation capabilities

Not the same as the engineered-template unit simulation. This section covers server-side biokinetic process simulation of a flowsheet — ASM1, ASM2d, ASM3, ADM1 and the Takács clarifier. A placed engineered template has a different simulation: a client-side, PLC-style scan simulation of that one unit, running in your browser, which exercises its control logic and plant physics rather than its biokinetics. The two share no solver, model library or page. See Which "simulation" this section is about.

Introduction

ErgoPlanner provides industry-standard simulation capabilities comparable to SUMO and other professional wastewater modeling software. The simulation engine supports both steady-state and dynamic calculations with multiple biokinetic model options.

Simulation Capabilities

Simulation Types

Type	Description	Applications
Steady-State	Equilibrium calculations	Design, sizing, mass balance
Dynamic	Time-varying response	Upsets, optimization, control

Calculation Modes

Each process unit supports two calculation modes:

Mode	Features	Use Case
Basic	Fixed efficiencies, fast	Preliminary design
Advanced	Full biokinetics, detailed	Detailed design, optimization

See Calculation Modes for details.

Biokinetic Models

ErgoPlanner implements industry-standard biokinetic models:

Model	Application	State Variables
ASM1	Activated sludge, N removal	8
ASM2d	N and P removal	19
ASM3	Storage-based metabolism	12
ADM1	Anaerobic digestion	24

Model Selection Guide

Process	Recommended Model
Conventional AS	ASM1
BNR with Bio-P	ASM2d
High-rate systems	ASM3
Anaerobic digestion	ADM1

Mass Balance

Comprehensive material tracking through the plant:

Component	Tracking
COD	Fractionation, oxidation, sludge
Nitrogen	NH4, NO3, org-N, N2O
Phosphorus	PO4, poly-P, organic
Solids	TSS, VSS, FSS
Alkalinity	pH buffering

See COD Fractionation for details.

Starting from a P&ID

You do not have to build the flowsheet twice. If the works is already drawn, the simulation model can be compiled from it.

From a drawing you have saved

1. Open Drawings.
2. Right-click the model and choose Simulate this drawing.
3. The editor opens on a new simulation model containing one block per process area, with the streams that cross those area boundaries.

A toast tells you what was compiled — how many units and streams — and names anything that could not be placed. Two things stop the compile, both stated rather than silent:

• The drawing is not in a project. A simulation model belongs to a customer project; put the drawing in one first.
• Nothing in the drawing is typed. Blocks come from equipment carrying a process unit type. Set it in the properties panel in Draw (or set a Simulation unit type on the area itself, which overrides it), then try again. Nothing is guessed from how a symbol looks.

From a P&ID template

Templates in the gallery marked Compiled from P&ID are drawings rather than simulation models. They open the same way as any other template — their shapes are translated into process units when you load them.

What to expect on such a template:

• Valves, instruments, controllers and dosing points do not become blocks. They are absorbed into the stream they sit on, and the stream is re-joined through them, so the treatment train stays connected. This is the intended level of detail: one simulation block stands for a whole area of a P&ID, not one symbol.
• A shape with no simulation equivalent is listed, not invented. The card names these before you open the template, so you know what will be missing.
• Some blocks are the nearest match rather than an exact one — a flocculator placed as a mixer, for example. These are flagged so you can change or parameterise them; check them before you trust a mass balance.

After it opens, treat it as any other model: set the influent, check the unit parameters, run.

Simulation Workflow

Basic Workflow

graph LR
    A[Build Diagram] --> B[Configure Units]
    B --> C[Set Influent]
    C --> D[Run Simulation]
    D --> E[Analyze Results]
    E --> F{Acceptable?}
    F -->|No| B
    F -->|Yes| G[Document]

Detailed Steps

1. Build Process Diagram

   • Add process units from stencil
   • Connect units with streams
   • Verify all connections

2. Configure Units

   • Set dimensions and capacities
   • Choose calculation mode
   • Configure operating parameters

3. Define Influent

   • Flow rate
   • Wastewater composition
   • Diurnal patterns (dynamic)

4. Run Simulation

   • Steady-state for design
   • Dynamic for optimization

5. Analyze Results

   • Check effluent quality
   • Verify mass balance
   • Review unit performance

Solver Technology

Steady-State Solver

• Method: Newton-Raphson iteration
• Convergence: Residual < 0.01 (default)
• Max iterations: 100 (configurable)
• Under-relaxation: Automatic adjustment

Dynamic Solver

• Method: Runge-Kutta 4th order
• Time step: 1-15 minutes (adaptive)
• Integration: Variable step with error control
• Events: Step changes, ramps, profiles

Performance

Typical Solve Times

Plant Size	Units	Steady-State	Dynamic (1 day)
Small	10-20	<1 second	5-10 seconds
Medium	20-50	1-3 seconds	15-30 seconds
Large	50-100	3-10 seconds	1-2 minutes

Optimization Tips

1. Start with Basic mode
2. Use coarser time steps initially
3. Enable only needed outputs
4. Run shorter durations first

Units and Conventions

Standard Units

Quantity	Unit
Flow	m3/d
Concentration	mg/L or g/m3
Mass	kg/d
Volume	m3
Area	m2
Time	days (d)
Temperature	degC

Sign Conventions

• Positive flow: Forward direction
• Production: Positive mass rate
• Consumption: Negative mass rate

Key Features

Recycle Loops

• Automatic handling of recycle streams
• Convergence for RAS, sludge returns
• No manual tear streams needed

Split/Mix Nodes

• Flow splitters with ratio control
• Mixers with automatic blending
• Mass balance verification

Controllers

• PID control integration
• 9 controller types available
• Real-time control response

Results Analysis

• Stream compositions
• Unit performance metrics
• Mass balance tables
• Trend charts (dynamic)

Limitations

Current Limitations

Limitation	Workaround
Max 200 units	Split into sub-models
Single-phase only	Use separate gas handling
Ideal mixing assumed	Use multiple CSTRs

Planned Enhancements

• Multi-phase modeling
• Particle size distribution
• CFD coupling interface

Related Topics

• Steady-State Simulation
• Dynamic Simulation
• The Simulation Agent — the read-only agent that checks a saved drawing as a flowsheet
• Calculation Modes
• Biokinetic Models
• Controllers
• Process Units

References

1. Henze, M. et al. "Activated Sludge Models ASM1, ASM2, ASM2d and ASM3" (IWA Publishing, 2000)
2. Batstone, D.J. et al. "Anaerobic Digestion Model No. 1" (IWA Publishing, 2002)
3. Tchobanoglous, G. et al. "Wastewater Engineering" (5th Edition, 2014)