Water Filtration & ORP(ORP) for Water Disinfection Monitoring and Control

What is ORP?

ORP is a term used frequently in the water treatment and food processing industry. ORP is the acronym for Oxidation Reduction Potential. ORP is a differential measurement of the mV potentials built up when electrodes are exposed to solutions containing oxidants and reductants.ORP describes the net magnitude and direction of the flow of electrons between pairs of chemical species.

The best definition I can give is that “ORP is a measure of the cleanliness of the water and its ability to break down contaminants”.

How is ORP measured?

ORP sensors are basically two electrochemical half-cells: A measurement electrode in contact with the solution being measured and a reference electrode in contact with a reservoir of highly concentrated salt solution. When the solution being measured has a high concentration of oxidizers, it will accept more electrons than it loses so that the measurement electrode develops a higher electrical potential than the reference electrode.

A voltmeter placed in line with the two electrodes will display this difference in potential between the two electrodes. Once the entire system reaches equilibrium, the resulting net potential difference represents the ORP. A positive reading indicates an oxidizing solution, and a negative reading indicates a reducing solution. The more positive or negative the value, the more powerful the oxidants or reductants, the greater their concentrations or both.

ORP Level (mV)
0 – 150
No practical use
150 – 250
250 – 350
Cooling Towers
400 – 475
Swimming Pools
450 – 600
Hot Tubs
Water Disinfection *
Water Sterilisation **

The chart above identifies ORP levels for various applications.

What does ORP measure?

ORP can be used to determine the efficacy of chemical disinfectants that work via the oxidation or reduction of the structures of microbial contaminants. For example, chlorine, an oxidant, will strip electrons from the negatively charged cell walls of some bacteria. Because ORP measures the total electrons from the negatively charged cell walls of some bacteria. Because ORP measures the total disinfectants in solution.

ORP indicates the effectiveness of only those disinfectants that work through oxidation and reduction. ORP cannot be used to detect the presence of any one particular chemical or chemical species. Nor can it alone be used to determine the concentration of a known species of chemical in solution. This means that although ORP is the best way to know whether or not your sanitizer is working, it can’t tell you how much or what kind of sanitizer is working.

Why ORP?

ORP is a faster, simpler empirical measurement than titration with DPD or other methods, and in many cases it gives the most accurate picture of the effect of all oxidizing and reducing chemicals in solution.

Using ORP disinfectant control can be automated because the measurement produces an electrical signal that can trigger switches when outside established control parameters. And ORP sensors are relatively low-maintenance. If you’re not using ORP to monitor and control chemical additions that work through, you should. You’ll save yourself time, hassle and money.

The equipment is of modular design and can be extended to measure any other parameter in the system that is required. It can also be upgraded with memory and wireless communication to report the data in trnded format to you anywhere anytime.

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