Vacuum toilets are flush toilets that use suction for the removal of faeces and urine resulting in a minimal requirement of water (0.5 to 1.5 litres). Vacuum toilets provide the same level of comfort as traditional flush toilets and they help saving costs due to the minimised amount of flush water. Due to the fact that the effluent has a high organic matter content, vacuum toilets are specifically adapted for the use in combination with separate greywater and blackwater treatment; or aerobic digestion treatment for biogas production. Vacuum toilet systems are applicable both in large and small buildings, trains, ships and airplanes.