This stage is required for sensitive discharge points eg. trout streams and bathing waters.
Tertiary treatment involves a further aerobic stage, followed by an oxygen depleted stage, which reduces nitrogen and phosphorous. It can also include a further disinfection process to remove bacteria and viruses.
Tertiary treatment methods include:
- UV disinfection
- Chemical disinfection
Chemical disinfection usually involves the addition of Chlorine to the wastewater. Chlorine kills viruses and bacteria, but it is also harmful to the environment. It also makes the water smell, if not fully removed and alters the pH. For this reason, dechlorination is needed before the sewage water can be discharged to rivers and streams.
UV disinfection does not involve the use of chemicals. It simply uses UV light to disinfect the effluent and is far more environmentally friendy. However, the equipment needed is costly and there is also the electrical consumption to consider.
UV light disinfection is primarily used to remove unwanted bacteria. It does not affect the water in any way and does not change the smell, pH or look of the final effluent.
WTE can design and supply a UV light disinfection system for any sewage treatment plant if required.