UV Disinfection

ELEMENT:

Trojan Ultraviolet Max C UV Disinfection system

AIM:

The aim of the UV disinfection system is to treat the rainwater collected at the Healthy Home to a microbiological standrard that is suitable for human consumption.

STRATEGY:

The Healthy Home uses a 22 000L concrete rainwater tank to store the rainwater that is captured on the roof. Stainless steel screens and First Flush Devices are used to improve the water's quality prior to it's entry into the rainwater tank, however further treatment is required before it is fit for consumption.

To bring the water to a standard fit for human consumption the water is pumped from the rainwater tank through a 20 micron wool filter, followed by a UV disinfection system. The filter is designed to remove particle slarge than 20 microns prior to the water entering the UV disinfection unit. The large particles dis-colour the water and absorb light, preventing the UV system from killing-off the target bacteria.

The UV disinfection unit consists of a UV lamp, located inside a water tight quartz glass sleeve, mounted inside a stainaless steel barrel. The lamp emits light at a wavelength of 257.3nm, which denatures the DNA of the target organisms preventing them from reproducing. Acceptable levels of disinfection (a product of UV light intensity, Watts/square metre, and exposure time) can be achieved at flow rates between 10 and 50L/minute. The basic specifications of the UV disinfection system installed at the Healthy Home are:

Trojan UV Mac Model C Product Specifications
Flow Rates 11-53 litres per minute
Electrical 90-265V
50-60Hz
43W
Dimensions
Chamber Assembly 49.5 x 9cm
Lamp Sleeve Length 40.5cm
Control Module 15 x 10 x 6cm
Max. Operating Pressure 125psi (861kPa)
Audible Visual Lamp Failure Alarm included.

The lamp is illuminated 24 hours per day. The manufacurers recomend replacing the lamp every twelve months. A montiring system records the length of time since the lamp was installed, alerting the residents to a failure of the lamp, or a build up of scale on the quartz sleeve, reducing the transmittance of the UV light. Information on the quality of the rainwater after it has been treated by the UV disinfection system can be found on the Rainwater Tank Technical Detail pages.

Reference:

Trojan UV MAx Product Brochure, 2000, Trojan Technologies, Canada.