UV Disinfection of groundwater without filtration
Annual Conference
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UV disinfection has been used without filtration to treat Blenheim’s water supply. The water source could not be shown to be secure and required 3 log Cryptosporidium removal or inactivation to meet the Drinking Water Standards for New Zealand 2005 (revised 2008) (DWSNZ) protozoal compliance. UV disinfection was able to achieve this.
Filtration was not required because the groundwater is of good quality with UV transmissivity (UVT) greater than 96%/cm and turbidity less than 0.2 NTU except at pump start-up when the turbidity is elevated. Each bore includes a flush to waste system so that only water of sufficient quality for effective treatment is directed to the UV reactors. This ensures proper disinfection and compliance with the DWSNZ.
The UV reactors will also provide bacterial compliance with the DWSNZ once issues over validation are resolved to the satisfaction of the Ministry of Health.
UV disinfection was lower cost than other treatment technologies available for protozoal compliance. The success of UV disinfection relied upon good quality groundwater and a method for diverting and disposing of poor quality water at bore pump start-up.