Nature eventually cleans water in the water cycle. However, this takes time. A wastewater treatment plant accelerates this natural process by giving Mother Nature a helping hand.
We treat wastewater for a variety of reasons. Wastewater has an extremely large number of water borne bacteria and pathogens. Many of these are responsible for life threatening diseases while others are completely harmless.
Wastewater is also nutrient-rich. It contains high levels of nitrogen and phosphorus, with nitrogen being mainly in the form of ammonia.
In the 1980's Lake Rotorua water quality continued to decline and wastewater was one of the major contribution of nutrients.
The nutrient load to Lake Rotorua from wastewater has been substantially reduced following a major upgrade of the Treatment Plant to include biological nutrient removal followed by forest irrigation.