Chlorine Sensor TipThe consumption of raw vegetables is on the rise. As people become more health conscious, the popularity for salads and other prepared raw vegetables has soared in recent years. Whilst there are appreciable health benefits of eating raw produce, there are also risks due to contamination by dangerous pathogens. Only last year, 50 people died after eating raw bean sprouts contaminated with E.coli from an organic farm in Germany. The need for effective, safe and efficient disinfection of our food has never been greater.

There are three primary methods for disinfection: the use of ozone, chlorine dioxide, or the use of of chlorine-based disinfectants (also found in drinking water). All methods rely on the oxidising ability of the respective disinfectants. Oxidation is the process of removing electrons from a substance, thereby altering its chemical properties thereby killing pathogens. In all these methods, regulation and process control are essential for both safety and consumer satisfaction. Pi’s OzoSense (for ozone), DioSense (for chlorine dioxide) and HaloSense (for chlorine),  provide cost effective and reliable solutions to control and regulate these potentially hazardous chemicals.

Chlorine disinfection is the traditional method of rendering drinking water and raw food safe to consume. Usually hypochlorite, (OCI- ) is added to the water in low amounts. Hypochlorite reacts in the water to give hypochlorous acid (HOCl). This is a potent disinfectant and is the major species involved in the destruction of the microorganisms. OCI-  and HOCl exist in the water in varying concentrations, depending on pH (acidity). This can make the regulation of the concentration of the free chlorine (OCI- + HOCI) in the water difficult, and often leads to overdosing, causing browning of leafy foods and ruining taste. The Public also shows increasing reticence towards chlorination. Fortunately, Pi have developed methods that allow accurate and precise measurement and control of free chlorine levels, almost independent of pH.

Levels of free chlorine can be monitored in 2 different ways: using ORP or concentration (PPM) almost independent of pH. ORP measures the oxidation potential of the water- this is cheap but can prove unreliable if pH is abnormal or other oxidants are present. PPM detects free chlorine directly, so provides a much more reliable result for a slightly higher price. Pi provides systems that utilise either or both technologies. ORP is ideal in situations where calibration is difficult (as it requires no calibration). For PPM, Pi utilises a sensor that can measure up to 200ppm, impossible with ORP.