UV Disinfection System

A UV disinfection system uses ultraviolet light at the 254nm wavelength (UV-C) to inactivate bacteria, viruses, and protozoa by damaging their DNA and RNA, preventing the organisms from replicating. Unlike chlorination, UV disinfection is a purely physical mechanism with no chemical addition and no chemical residual in the treated water, which means it avoids the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs) that are a known concern with chlorine-based disinfection.

UV dose, measured in mJ/cm², is the key performance parameter — it represents the product of UV intensity and exposure time as water passes through the reactor chamber. Treated sewage reuse applications, such as water destined for flushing, gardening, or cooling tower makeup, typically target a dose of 30–40 mJ/cm² to achieve the log-reduction of pathogens required for safe reuse. The UV transmittance (UVT) of the water matters significantly: turbid or coloured water requires a higher dose or upstream filtration, since suspended particulates physically shield organisms from UV exposure and reduce disinfection efficacy.

A UV disinfection system consists of UV lamps (low-pressure high-output or medium-pressure types) housed inside quartz sleeves that protect the lamps from direct water contact while allowing UV transmission, UV intensity sensors that continuously monitor delivered dose, automatic wiper or mechanical cleaning mechanisms that prevent quartz sleeve fouling from scaling and biofilm, and a control panel that paces the delivered dose against real-time flow rate and measured UVT. Low-pressure lamps typically operate reliably for 9,000–12,000 hours before replacement is needed to maintain rated UV output.

Because UV has zero effect on dissolved solids, TDS, or dissolved chemical contaminants — it acts exclusively on living organisms — it must always follow upstream filtration (sand filtration, ultrafiltration, or equivalent) to remove particulates. UV also provides no residual disinfection protection once water leaves the reactor, so distribution networks requiring ongoing residual protection often pair a UV system with a small terminal chlorine dose. Common applications include the tertiary disinfection stage after MBR or tertiary filtration before treated sewage reuse, pharmaceutical and food industry process water requiring pathogen-free water without chemical residue, and drinking water treatment.