Point-of-Use Ozonation Control for Legionella Prevention
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Solution Overview
Problem
Existing water heating systems using large thermal storage tanks are prone to Legionella proliferation due to stagnant water conditions, making it difficult to ensure water safety without frequent testing, and central ozone injection is ineffective at points of use.
Innovation Solution
A method for controlling ozonation in a water supply system that includes an ozonator, controller, flow meter, and valve, which determines periods of non-use and non-ozonation to execute counteractions such as turning on the water supply and ozonator, ensuring sanitization at the point of use, reducing the risk of Legionella transmission without the need for continuous testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large thermal storage tanks are used for water heating, then heating demand can be met, but Legionella proliferation occurs due to stagnant water conditions
Solution Approach 1:
The system performs ozonation treatment in advance during periods of non-use to sanitize the water before potential Legionella growth can occur. The controller monitors water usage patterns and activates the ozonator proactively during detected non-use periods to maintain water safety.
Solution Approach 2:
Instead of continuous ozonation, the system implements periodic treatment cycles based on detected water usage patterns. The ozonator is activated during specific non-use periods when Legionella proliferation risk is highest, rather than operating continuously, thus balancing sanitation effectiveness with energy efficiency.
2Object-affected harmful factors
If central ozone injection is used, then water sanitization is achieved, but it is ineffective at points of use due to re-contamination
Solution Approach 1:
The system transitions from centralized ozonation to localized point-of-use ozonation. Each water outlet is equipped with its own ozonator and controller that independently monitors and treats water locally, ensuring sanitation effectiveness at the exact location where water is consumed, preventing re-contamination in distribution lines.
Solution Approach 2:
The centralized water treatment system is divided into multiple independent point-of-use treatment units. Each unit operates autonomously to sanitize water locally, eliminating the single point of failure and ensuring that each outlet maintains independent sanitation control.
3Reliability
If frequent water testing is performed to detect Legionella, then water safety can be monitored, but testing costs and system disruption increase
Solution Approach 1:
The system implements continuous self-monitoring through flow sensors and temperature sensors that automatically detect conditions conducive to Legionella growth. The ozonator responds automatically to sensor inputs without requiring manual intervention or external testing, providing ongoing safety monitoring that eliminates the need for periodic disruptive water sampling and laboratory analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides sanitized hot water at the point of use, reduces the risk of Legionella transmission, and recovers heat energy from drainage, ensuring efficient and safe water supply without the need for frequent testing or halting water consumption.
Implementation Method 1
ozone injection at a central location of a distributed water supply network is ineffective in combating Legionella that exist in the points of use
Implementation Method 2
The heat pump system has a refrigerant path, at least a portion of which is in thermal communication with the water tank volume such that heat transfers from a refrigerant to the water tank volume
Data Source
AI summary
A method for controlling ozonation in a water supply system including an ozonator, a controller functionally connected to the ozonator, a flow meter configured for detecting a flowrate through the water supply system, a valve configured for turning on or off of the water supply system, the method including using the controller for determining a time period in which the water supply system has continuously not been requested and a time period in which the ozonation has continuously not been performed, and if the time period in which the water supply system has continuously not been requested exceeds a lack of water use threshold and the time period in which ozonation has continuously not been performed exceeds a lack of ozonation threshold, executing a counteraction pair including a first action at a start time and a second action at an end time.