Advanced disinfection control with OaSys iCTâ„¢

The Challenge

Wastewater disinfection is critical for protecting public health and the environment. However, traditional disinfection control strategies—like flow-pacing—struggle to account for dynamic variability in wastewater conditions.

Factors that can influence how much disinfectant is actually needed at any given time include:

• Real-time hydraulics
• Operational fluctuations
• Background disinfectant chemical demand
• Disinfectant decay

Traditional flow-pacing applies a fixed dose of chemical disinfectant proportional to flow but ignores these other parameters. This often leads to overdosing of disinfectant, overspending on chemicals, and inadequate disinfection performance, especially when conditions change rapidly or frequently. Because of these limitations, treatment plants have an opportunity to improve their disinfection processes while reducing chemical costs through more adaptive, data-driven dosing technologies.

Advanced Dosing Control with OaSys iCTâ„¢

Through a research project at a small wastewater facility in Ontario, Canada, USP Technologies was able to demonstrate the impact of adaptive model-based disinfection control with OaSys iCTâ„¢. OaSys iCTâ„¢ is an advanced disinfection control technology designed to address the challenges that often limit traditional disinfection methods. OaSys iCTâ„¢ normalizes disinfection performance by accounting for system variability, including:

• Hydraulics
• Background chemical demand
• Disinfection kinetics

Instead of relying on a simple flow relationship, OaSys iCTâ„¢ calculates the optimal disinfectant dose required to meet a target CT value, to prevent both over- and under-dosing. In this study, USP Technologies and its partners performed computational fluid dynamics (CFD) modeling to characterize the site’s chemical contact basin. Chlorine demand, decay, and disinfection kinetics were measured from secondary effluent samples, and OaSys iCTâ„¢ was tested at full scale against traditional flow-pacing methods.

This approach provided real-time adaptive dose control that better matched the plant’s actual disinfection needs to improve efficiency and performance.

Key Results

Performance Improvements

• Under flow-paced control, the CT dose varied widely throughout the day, with higher levels in the morning and lower levels in the afternoon due to flow variability, resulting in as much as 2-log variation in fecal coliform.
• OaSys iCTâ„¢ maintains the delivered CT dose within a stable performance band and reduced fecal coliform to less than 0.5-log variability. In contrast to flow pacing, coliform level remained consistently well below the 100 CFU target.

Chemical Use Reductions

During the initial14-day research study, the team tested two traditional flow-pacing approaches versus OaSys iCTâ„¢ advanced dosing control. These results showed that OaSys iCTâ„¢ provided a:

• A 54% reduction in disinfectant usage vs. a 2.5 mg/L flow-pacing approach
• A 36% reduction in disinfection usage vs. a 1.75 mg/L flow-pacing approach

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