The treatment processes for drinking water have changed during the last several years as increased concerns about disinfection byproducts (DBPs) and waterborne pathogens have become more prevalent. Many treatment processes now incorporate multiple oxidants or disinfectants to address these increased concerns. Other treatment objectives for these multiple oxidants include reducing taste and odor problems and facilitating the removal of dissolved metals.
Learn more about ozone, chlorine dioxide and UV disinfection below.
Ozone (O3), a powerful oxidant, is being increasingly used for water disinfection, primarily preoxidation. It was first used in the Netherlands in the late 1800s to disinfect drinking water and is now used worldwide in drinking water and wastewater facilities, swimming pools, spas and in the bottled water and beverage industries. The major reaction products are oxygen, water and carbon dioxide. For environmental safety, unreacted or residual ozone, while unstable, should be monitored.
Ozone quickly provides microbial sterilization and disinfection, organic compound destruction, and conversion of iron or manganese salts to insoluble oxides which can be precipitated or filtered from the water. However, one of the problems with ozone is that if overfed, it converts those oxides into soluble form. This is why accurate monitoring is critical.
Chlorine dioxide is a deep yellow gas that is generated directly for onsite use as a bleaching agent in industrial processes, such as the manufacture of pulp and paper. It is used increasingly for special treatment objectives in municipal water treatment. Chlorine dioxide forms chlorite, a regulated byproduct and chlorate.
Unlike chlorine, chlorine dioxide does not form trihalomethanes (THMs) in reaction with certain organic compounds. Chlorine dioxide forms significantly fewer halogenated DBPs than free chlorine generates and doesn’t react with ammonia to form less active chloramines.
UV rays can be an effective disinfectant in the water treatment process. It has been used in the commercial space for many years in the cosmetic, beverage, pharmaceutical and electronics industries, particularly throughout Europe.
Due to safety issues around chlorination and advancements in UV technology, UV is becoming increasingly accepted and utilized for water treatment in the U.S. UV light can disinfect water contaminated by bacteria and viruses and can fight protozoans such as Giardia lamblia cysts or Cryptosporidium oocysts.
With any disinfectant, accurate and responsive monitoring and control are critical to avoid negatively affecting the treatment process and finished water quality.
With analytical testing, you can:
Disinfection is a multifaceted process that involves a variety of factors and every facility and operation is different. Whatever your needs, Hach® is ready to help with information, technology and support.
Explore the various parameters and methods associated with ozone, chlorine dioxide and UV disinfectants below.
Disinfectant Preoxidation1 Post-disinfection1 Positive Negative Positive Negative Chlorine gas2 Strong,
inexpensiveHigh DBP, safety/
security issuesStrong,
inexpensiveTaste and odor (T&O),
DBP, safety issuesMonochloramine Less DBP Cost, process
controlLonger living,
less DBPNitrification,
T&OChlorine
DioxideKills giardia,
oocyst, less DBPCost, safety Long living,
activeChlorite/
chlorate, costOzone Strong, less DBP Bromate, little
residual, costNA No residual Hydrogen
Peroxide/PAA3Strong, easy to
handleBromate, no
residual, costNA No residual Permanganate Strong, easy to
handleMnOx
(staining)NA MnOx
(staining)UV Strong, no DBP Cost, no
residualNA No residual
1 Disinfectant activity comparison is based on CT values
2 Hypochlorite is frequently used as an alternative in order to reduce risk of gaseous chlorine leaks and simplify the application
3 Hydrogen peroxide is often used in mixture with peroxyacetic acid (PAA) to increase stability of the oxidizer
Explore the different types of parameters used in ozone, chlorine dioxide and UV disinfection monitoring.
Test for ozone levels being delivered by the ozone generator. Maintain ozone levels to optimize the treatment process to reduce taste and odor problems, reduce disinfection byproduct formation, provide pathogen inactivation and to facilitate removal of iron and manganese. Determine ozone concentrations to calculate CT credits.
