Examples for more high-tech, intensive or mechanized, often relatively expensive sewage treatment systems are listed below. Some of them are energy intensive as well. Many of them provide a very high level of treatment. For example, broadly speaking, the activated sludge process achieves a high effluent quality but is relatively expensive and energy intensive. 
* Activated sludge systems
* Aerobic treatment system
* Enhanced biological phosphorus removal
* Expanded granular sludge bed digestion
* Filtration
* Membrane bioreactor
* Moving bed biofilm reactor
* Rotating biological contactor
* Trickling filter
* Ultraviolet disinfection