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.
Basically, there are two different designs for a vacuum toilet system: The constant vacuum system (CVS) and the vacuum on demand (VOD) system. Which one will be applied depends on specific framework conditions.
Costs Considerations
As it is a high-tech system, it is expensive. But in comparison with a common flush-toilet system, it can be slightly cheaper, because piping costs are lower (the dimensions are smaller, 50 to 75 mm) and a on-site treatment system can be more easily installed. Also the installation can be cheaper because piping is independent from the building structure. Vacuum lines may be installed vertically into the suspended ceiling as waste can be lifted.
Operation and Maintenance
The in-house installations require little maintenance and are easy to clean. The suction effect increases hygiene and reduces odour (HEEB et al. 2007). If a composting tank is used, it has to be emptied and cleaned periodically to avoid an overflow. If there are any problems with the technical components, such as valves or pipes, the manufacturer has to be contacted.
Health Aspects
A vacuum toilet system guarantees a high level of comfort and hygiene. As long as the toilet is kept clean, there are absolutely no hazards. When composting such products, special care should be taken as the associated health risk is higher than for common kitchen waste.
Applicability
Vacuum technology for sanitary installations is an advanced technique in both economic and ecologic aspects. Its application is flexible and independent from a (natural) slope. New buildings as well as the sanitation of old buildings or the reconstruction of existing buildings are all appropriate fields of application. Vacuum sanitation systems are preferably used in buildings where the wastewater flow is high or varies greatly (hotels, restaurants, motorway services areas, airports, railway stations etc.), in bigger building complexes and in commercial and industrial halls, where the sanitary installations are often located at remote distances (adapted from ROEVAC 2011). Vacuum toilets are also a convenient solution for decentralised wastewater treatment. Effluents, such as urine and faeces can be treated by a biogas settler or a biotank with a following small scale composting attachment.
