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.  It is these nutrients that have been a major contributing factor to the deterioration of Lake Rotorua in the past, so we must lower these nutrient levels in our final effluent in order to prevent any further deterioration of Lake Rotorua's water quality.