The regulation in many countries requires the disinfection of the treated water in order to protect farmers and consumers. The goal of disinfection is the removal, killing or inactivation of pathogens so that there is no danger for health any more. This means at least a reduction of 4-5 logs in municipal wastewater.

The conventional wastewater treatment with physical and biological technologies is not able to disinfect the wastewater efficiently. Since organic load and suspended solids have an negative impact on the disinfection rate, it is recommended to treat the wastewater biologically before disinfection.

Disinfection methods can generally be grouped in two types: physical and chemical methods. An overview is given in table 3.

+++ very good, ++ good, -bad, --very bad

Table 3: Disinfection efficiency of several technologies (Jacangelo & Trussell, 2001)

If all methods with chlorine are considered as one there are three common methods of disinfection in general: Chlorination, ozonation, and ultraviolet (UV) disinfection. Disinfection is considered to be the primary mechanism for the inactivation/destruction of pathogenic organisms to prevent the spread of waterborne diseases to downstream users and the Environment. It is important that wastewater be adequately treated prior to disinfection in order for any disinfectant to be effective. All three disinfection methods can effectively meet the discharge permit requirements for treated wastewater. However, the advantages and disadvantages of each must be weighed when selecting a method of disinfection.