Apparatus and method for measuring hydrogen peroxide in water

An apparatus for measuring hydrogen peroxide in a water treatment system on a periodic basis using a colorimetric assay comprising:

• a. a measurement cell for receiving a water sample from the water treatment system;
• b. a light transmitter configured to emit light at a selected wavelength at the measurement cell;
• c. a photodiode receiver configured to receive light passing through the measurement cell;
• d. a reagent vial comprising:
• a reagent compound configured to react with hydrogen peroxide to form a reaction product, the reaction product adapted to absorb light at the selected wavelength proportional to the amount of hydrogen peroxide in the water sample, and
• a solvent;
• e. a buffer jar for receiving a water sample from the water treatment system and connected to the measurement cell through a supply valve, the buffer jar comprising an overflow tube for returning overflow water to the water treatment system, for maintaining a constant water volume and constant head pressure in the buffer jar, and for maintaining a turn-over of water in the buffer jar;
• f. a first network of pipes for drawing water from the water treatment system, the first network of pipes connecting the water treatment system to the buffer jar, the buffer jar to the supply valve, the supply valve to the measurement cell, and a second network of pipes connecting the reagent vial to a reagent valve, the reagent valve to the measurement cell, and the measurement cell to a drain valve;
• and
• g. a control unit;
• wherein the control unit is programmed to
• control the supply valve in a time-dependent manner,
• cause a first colorimetric measurement of a first water sample free of reagent and a second colorimetric measurement of a second water sample mixed with reagent,
• determine the difference between the first and second measurements, and
• compare the difference against a pre-determined standard curve of diluted hydrogen peroxide to determine and report the concentration of hydrogen peroxide in the water sample, accurate to 0.1 mg/L.