text: 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