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Effective drinking water disinfection
An assessment of methods using chlorine gas, chlorine dioxide and electrolytic chlorine generation.
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The need for drinking water disinfection is as old as public water supply itself. Microbiological parameters for drinking water treatment include coliform bacteria and specific pathogenic species of bacteria, vira, and protozoan parasites. Although the objective is the same – to provide safe clean water – the methods used to do so are numerous. The most common methods for water disinfection are chemical ones. This article gives a brief overview of chlorine-based disinfection methods and the factors that can influence the choice of method.
“No single method can meet all needs,” explains chemist Dr Carsten Persner at Grundfos Alldos, who designs systems for chlorine gas dosing, and for electrolytic hypochlorite and chlorine dioxide generation. “Local regulations are probably the one factor that makes it most difficult to draw general conclusions and make recommendations. The next is availability of raw materials and the costs associated with each method – energy costs, chemical costs and so on,” |
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| General disinfection effect | Residual effect | pH dependency | Possible by-products | Advantages | Disadvantages | |
| Chlorine gas | High | Hours | Strong | Chloramines, chlorphenoles, THM, AOX |
Low-priced agent
Approved technology |
Demanding chlorine gas storage
Chlorine resistance |
| Chlorine (electrolytic) | High | Hours | Strong | Chloramines, chlorphenoles, THM, AOX |
Cheap reagent (salt NaCl)
Reliable process
No hazard risks |
Salt storage for higher capacities
Chlorine resistance |
| Chlorine dioxide | Very high | Days | Medium | Chlorite, chlorate |
No chlorine resistance
Destroys biofilm |
Min. two chemicals to handle |
A long-proven track record and sustained-release make chlorine a reliable and favoured disinfectant for public water supply.
