Wastewater Disinfection
Wastewater treatment processes remove the following from wastewater (sewage):
- Primary treatment – suspended solids;
- Secondary treatment – colloidal and dissolved organic (carbonaceous) matter;
- Tertiary treatment – nitrogen and or phosphorus and or residual suspended solids.
Treated wastewater from sewage from the above processes contains significant numbers of microorganisms (e.g.: treated wastewater from activated sludge processes typically contains bacteria, viruses, protozoan parasites and helminths). For example, treated activated sludge effluent contains between 8 000 and 700 000 MPN/100 mL of both Escherichia. coli and thermotolerant coliforms (median 35 000 MPN/100 mL)). Total coliforms would be 3 times these numbers.
Many wastewater treatment plants include some form of disinfection step in their treatment process, to reduce the load of microorganisms discharged to the environment. Typical treatment processes include disinfection by:
- Lagoon detention;
- Chlorination (with or without dechlorination);
- Ultraviolet irradiation;
- Ozonation;
- Chlorine dioxide; or
- other uncommon oxidant/disinfectant (e.g. peracetic acid).
Wastewater can be disinfected for meeting environmental microbiological requirements, or for meeting microbiological requirements for effluent reuse.
Related Articles
Wastewater Ultraviolet Disinfection 1
Wastewater Ultraviolet Disinfection 2
Wastewater Ultraviolet Disinfection References
Wastewater Lagoon Disinfection
Wastewater Chlorine Disinfection
Wastewater Ozonation
Wastewater Chlorine Dioxide Disinfection
