The majority being domestic household wastewater with a very small percentage being industrial waste. Stormwater or rain water is not part of our sewerage treatment system. We treat wastewater for a variety of reasons. Wastewater has extremely large numbers of water borne bacteria and pathogens. May of these are responsible for life threatening diseases while others are completely harmless.
Wastewater is also nutrient rich.
It contains high levels of phosphorous and nitrogen. The nitrogen mainly in the form of ammonia. We must also lower the levels of these nutrients in our final effluent. These nutrients have been major contributing factors to the evident deterioration of the water quality in Lake Rotorua. With the removal of these nutrients, the quality of the lake water should eventually start to improve.