So do you (still) pump out your bacteria laden septic tank water 'straight into the land/stream? With all the screams about 'dairy cow poo and wee' in our 'clean green rivers', are you a polluter?

Yes you might have a modern waste water treatment system which works well. Meaning the solids have been munched up by the bacteria, so that you are pumping out 'just water'. So far so good. BUT this water contains some of the highest concentrations of bacteria possible. And because the Council 'lets you' this bacteria laden water migrates through the soil and into your neighbours river water. Well?

Most consider UV treatment for waste and septic water as the best way to destroy pathogenic organisms to prevent the spread of waterborne diseases to down stream users and the environment.

An ultraviolet (UV) disinfection system transfers energy from a mercury arc lamp to an organism’s genetic material (DNA)
When this energy penetrates the cells it destroys its ability to reproduce.

The effectiveness of the UV systems depends on many things.

1.    The power of the lamp
2.    Speed of the water flow – (Time micro-organisms are exposed)
3.    Length of the Stainless Steel chamber
4.    Turbidly of the water

Important information

1.    Power of the lamp is very important and our UV Water Systems Ltd systems run up to 160 watts.

2.    We need to know what flow speeds are involved to adequately design system and the lamp power for each application.

3.    Short chambers are designed for aquariums and spa pools where the water is continuously recirculated. If the water has only one pass, a longer chamber is needed, or a slower flow, so that the water is sufficiently exposed to the UV discharge (to allow time to destroy the bacteria).

Design = Length of the chamber x flow speed x power of the lamp x turbidity.

4.    Turbidity or cloudiness’ of the water also has a huge bearing on design for the power of the lamp and water flow.

Infectious agents potentially in untreated domestic waste water.

Organisum            Disease caused

Escherichia Coli                Gastroenteritis
Leptospira                         leptospirosis
Salmonella Typhi              Typhoid
Shigella                            Shigellosis
Vibrio Cholerae                Cholera

Balantidium Coli               Balantidiasis
Cryptosporidium              Cryptosporidiosis
Entamoeba Histolytica     Amebiasis
Giardia Lamblia               Giardiasis

Ascaris Lumbricoides        Ascariasis
T Solium                            Taeniasis
Trichuris                            Trichuriasis

72 types of Viruses            Gastroenteritis
Coxsakie, Polio etc            Heart anomalies
Meningitis
Hepatitis                            Infectious Hepatitis

Effectiveness of these systems

Very effective if they are serviced and maintained regularly

•    Quartz sleeve cleaning
•    Lamp replacement
•    Filter replacement

Cleaning frequency is very site specific, some need to be cleaned more often than others.

Cost of UV systems

Costs for a system and installation depend on each site and will need to be quoted.

Prices start at around $1700 + GST for a fully assembled, tested water proof system that can be installed externally on two posts. 3 years of testing (in the Rotorua Test Facility) has proven these system manage all that is thrown at them.


You must have a UV system that is matched to your situation:

1    For continuous flow waste water treatment systems
2    For periodic flow waste water treatment systems

Continuous flow systems do not need a timer, whereas Periodic Flow Systems should, to save power, or to allow high wattage.

High wattage UV systems (say greater than 80w) need water passing through the chamber when the lamp(s) are on, otherwise they get too hot and ...trouble.

The timer module: the UV starts up and rises to operational temperature then allows the pump to evacuate the septic tank. When the low level float switch is triggered, the electricity supply to the pump/UV cuts OFF.

UV lamps do not like to be switched of and on, however if the system being used will operate 1 or 2 times a day, this is well within the design parameters of the UV lamp. With the UV lamp only running for maybe an hour a day, it will last 12 time longer (say 12 years!). However this does not mean you have escaped the need to check the SS chamber. The Quartz sleeve will become dirty much quicker than for drinking water systems. After all the filter before the system plus the 50 micron cartridge in the system, allows much greater particle size into the UV chamber. It is for this reason (shadowing) that we derate the system by 70% (a 100 Lpm system is derated to 30 Lpm) Normally the sleeve is replaced every 5 years.

Ballast life is also longer: normally the capacitors last 3 to 5 years for 24/7 systems, so you could expect much longer life ... maybe 12 x 3yrs...

So parts costs for Septic UV Treatment is lower, but labour higher (more frequent sleeve inspection and cleaning).