The principal health risk from water is waterborne disease by microbial contamination. regulations have emphasized improved microbial controls through multiple-barrier techniques, including filtration for reduction of micro-organisms, disinfection for inactivation of the remaining pathogens, and maintenance of a residual disinfectant in the distribution system.
A comprehensive disinfection strategy provides a “multiple barriers” approach to reduce microbial risk while minimizing the formation of undesirable disinfection by-products (DBP).
Chemical oxidation and UV radiation are the most common commercial and industrial water disinfection methods. However both disinfection mechanisms are fundamentally different with respect to the inactivation process and the response of microorganisms:
| Chemical Disinfection | UV-light radiation | |
|---|---|---|
| Disinfection Mechanism | Micro-organisms are killed by exposure to chemical (destruction of cell wall). | DNA is damaged by UV light and reporduccion is prevented. Cell structure is left untouched. |
| DBP formation | High potential | NO |
| Minimum contact time | Typically 30 min for Chlorine | Very short (1 sec) |
| Residual effect | Yes (except ozone) | No |
| Other factors | PH, temperature, type of disinfectant, contact time |
The germicidal action of chemical disinfectants is based on oxidation-reduction mechanisms.
The most common form of water Chlorination is the use of Sodium Hypochlorite in solution as Chlorine gas presents a number of risk factors not easy to manage in small-to-medium scale applications and Calcium Hypochlorite is a solid and, as such, dosing is more complex.
In general, maintaining 0.5 mg/L residual chlorine with a 30-minute contact time is enough to deactivate most bacteria a virus in water.
The risk of generating taste and THMs must be reduced by:
Watercore Chlorine disinfection systems are equipped with the best dosing technology and proven storage tanks.
Ozone is the strongest of all the available chemical disinfectants however presents a number of drawbacks:
Maintaining 0.4 mg/L of residual Ozone during a 4-minute period is considered enough to deactivate bacteria and virus however, as highlighted before, controlling the appropriate dose requires the use of suitable injectors.
At Watercore, we are always committed to ensuring that our customers are informed of all the available options when choosing the best disinfection method for their application.
UV radiation applied as disinfection treatment is recognised for not producing by-products.
Unlike chemical disinfectants, UV overdosing doesn’t represent any concern to human health and can even be considered a safety factor.
As UV light is generated by the UV lamp inside a highly reflective chamber, it interacts with the materials it encounters through absorption (micro-organisms) and reflection (chamber walls).
In regards to UV dose requirements it is generally accepted that a dose of 40 mJ/cm2 will be sufficient to deactivate 99.999% of bacteria and 99% of all virus. However water flow and UV intensity are the minimum conditions that must be validated whenever UV disinfection is in use.
Silver is occasionally used for disinfection, however there are a number of drawbacks must be considered before deciding its use:
Ultrafiltration (Membrane filtration) provides an excellent barrier against bacteria and most virus. Given sufficient dose and contact time, all common disinfectants (chlorine, UV and ozone) are effective deactivating those micro-organisms that are not retained by filtration.
When deciding the right water disinfection treatment for your commercial and industrial application, Watercore is your best partner.
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