General (municipal) wastewater is most efficiently treated by biological processes. It is an established technology that has been used for many years. The core of this technology lies in the micro-organisms, which are present in the bioreactor, that can break down the waste products. This is a process that requires little to no energy because the micro-organisms are doing all the work. This is one of the reasons why it is the most preferred treatment for wastewater treatment. Another reason is the absence of chemicals and consumables that are required in other comparable treatment methods. This makes biological treatment one of the most cost-efficient methods of treating wastewater.
Due to the process being biological it is very adaptive meaning that the micro-organism culture will improve to be more efficient at breaking down the waste products. This results in a very stable system that is able to adapt to waste water quality fluctuations.