Intelligent turbidity control case

Address the control challenge of sudden raw water quality changes and the large lag in alum dosing processes.

Shifang Water Plant is responsible for drinking water supply to Shifang urban area and surrounding regions, with a daily water supply capacity of 80,000 tons. The plant draws water from the Renmin Canal main channel and the Glacier Lake, and uses a "pre-treatment + conventional treatment" process. Alum dosing (coagulant dosing) is a key step in water purification — its effectiveness directly determines subsequent sedimentation and filtration efficiency, and further affects finished water turbidity safety. However, traditional alum dosing control mostly relies on manual experience or flow-proportional dosing, which has inherent flaws: from chemical dosing and coagulation reaction to sedimentation and filtration, the entire process has a lag of several hours. When raw water encounters sudden quality changes due to rainstorms, upstream discharge, or seasonal algae blooms, manual adjustment cannot respond in time, creating a risk of effluent turbidity exceedance. For a water plant with a capacity of 80,000 tons/day, every raw water fluctuation could escalate into a water supply safety incident.

Smart Alum Dosing Control System Achieves Real-time Feedforward-Feedback Optimization Control

The project adopted a smart alum dosing control system, replacing traditional manual extensive operation. The system is based on a feedforward-feedback composite control strategy: the feedforward stage predicts the required alum dosage in real time based on multiple parameters such as raw water turbidity, pH, and temperature; the feedback stage dynamically corrects the dosage using settled water or filtered water turbidity as the indicator, forming a closed-loop control. This architecture effectively solves the large lag problem in the alum dosing process: even if raw water quality changes dramatically within hours, the system can adjust in advance based on feedforward prediction, rather than passively correcting after effluent turbidity deteriorates. For the Shifang plant, this means coagulation performance shifts from "after-the-fact remediation" to "ahead-of-time prediction," ensuring stable operation of sedimentation and filtration processes from the source.

Stable and Controllable Effluent Turbidity Under Raw Water Fluctuation Conditions

After the system was commissioned, the Shifang plant significantly improved its response speed and alum dosing precision when dealing with sudden raw water quality changes. Alum dosage shifted from "experience-based" to "model-based," making chemical dosing more precise — avoiding chemical waste from excessive dosing and reducing the risk of effluent turbidity fluctuations caused by insufficient dosing. For the Shifang urban water supply system serving over 200,000 residents, smart alum dosing control provides key technical assurance for stable finished water turbidity compliance, and also provides intelligent support for the process stages of the water supply quality and efficiency improvement project being advanced by Shifang Guorun Water Supply Company.