Secondary & Tertiary Effluent UV Disinfection

The vast majority of wastewater treatment plants around the world provide secondary treatment through conventional activated sludge processes. Some plants have tertiary treatment processes that use an additional filtration process to further improve water quality. The resulting effluent typically requires a disinfection step before discharge back to the environment.

Wastewater - Secondary and tertiary

Municipal wastewater generally requires disinfection to meet specific bacterial limits before discharge to surface waters. The main objective of disinfection is to reduce the number of waterborne pathogens to safe levels, and thereby lowering the risk of exposing the public to infectious diseases. The persistence of some pathogens in receiving waters and soils indicate that disinfection of wastewater effluents provide the first line of defense for drinking water from surface water or groundwater.

Typical disinfection standards for secondary and tertiary wastewater, such as 200 Fecal Coliforms per 100 mL on a 30 day geometric mean, are easily achieved with a suitably sized UV system. These conventional wastewater treatment plants typically discharge effluent to water bodies such as lakes, rivers and streams. The addition of filtration upstream of UV in a tertiary treatment process, while not necessary in most cases, does improve water quality by removing more particles and allows the wastewater treatment plants to meet even more stringent permit requirements – in some cases for water reclamation.

UV is an ideal disinfectant for wastewater since it does not alter the water quality – except for inactivating microorganisms. UV is a chemical-free process that can completely replace an existing chlorination system and also inactivate chlorine-resistant microorganisms like Cryptosporidium and Giardia. Unlike other chemical disinfectants, UV does not produce any carcinogenic disinfection by-products that could adversely affect the water quality. There is also an added benefit of reducing the carbon footprint of the disinfection system when a plant switches to UV since the carbon dioxide emissions from chemical transportation is eliminated.

Other TrojanUV Wastewater Applications

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