Water Treatment Plant Programming in Structured Text (ST) (IEC 61131-3)

Water Treatment Plant Programming in Structured Text (ST) (IEC 61131-3)

Modern water treatment plants are complex technological facilities with multi-stage filtration, coagulation, flocculation, ozonation, UV treatment, and dozens of pumps, valves, and analysers. Automating such a facility requires a systematic approach, clear architecture, and deep understanding of technological processes.

This practical training manual covers the complete development cycle of a water treatment plant control system using Structured Text (ST) according to IEC 61131-3. It systematically covers all aspects of creating a professional automation system — from data structures to SCADA integration and step-by-step commissioning.

The book covers in detail:

Technological scheme of a water treatment plant — mechanical filtration, coagulation, flocculation, sedimentation, sand filters, ozonation, UV treatment, clean water tank.

Data structures — TAnalogSignal (analog signal with diagnostics), TTank (tank/reservoir), TPump (pump), TFilter (filter with backwash), TPidDose (PID dosing controller), TScadaData (SCADA data) with detailed explanations and configuration examples.

Function blocks — analog signal scaling (FB_ScaleAnalog), PID reagent dosing control (FB_PidDose), pump control by tank levels with alternation and dry-run protection (FB_TankLevelPump), filter control with full backwash cycle (FB_FilterUnit), water quality control and emergency dump (FB_WaterQuality), water and reagent flow statistics (FB_Statistics).

Filter backwash logic — complete state machine: filtration, drain, air wash, backwash, rinse, return to service.

SCADA integration — tag table for data exchange (Modbus TCP, OPC UA), recommended screens (main, water quality, pumps, filters, statistics, alarm log).

Step-by-step commissioning guide — 9 steps: hardware verification, debugging all function blocks, integration testing, on-site commissioning.

All algorithms are accompanied by ready-to-use ST code with detailed comments. The book includes a complete Main program example that integrates all function blocks into a unified control system.

The manual is intended for automation engineers, PLC programmers, water treatment system designers, students and teachers. It will help you master water treatment control system design — from concept to a complete industrial solution with SCADA integration.

Additional information:

Project introduction — manual objectives, plant technological scheme, PLC program architecture (modular structure).

Basic data types and structures — TAnalogSignal (analog signal with diagnostics), TTank (tank), TPump (pump), TPidDose (PID dosing controller), TFilter (filter with backwash), TScadaData (SCADA data) — detailed explanations and configuration examples.

Function blocks — FB_ScaleAnalog (scaling and diagnostics), FB_PidDose (PID with anti-windup), FB_TankLevelPump (pump control by levels with alternation), FB_FilterUnit (filter with backwash state machine), FB_WaterQuality (quality control and emergency dump), FB_Statistics (water and reagent flow statistics).

Main program example — complete skeleton program integrating all blocks, initialisation, calls, integration.

SCADA integration — tag table, recommended screens (main, water quality, pumps, filters, statistics, alarm log).

Step-by-step commissioning and testing — 9 steps: hardware verification, debugging all blocks, integration testing, on-site commissioning.

Conclusion — summary, recommendations for adaptation to specific PLC and facility.