TOILET: AKW A+V Protec's train toilet bioreactor units use bacteria to break down waste (RG 5.10 p68). Heaters sterilise waste water which can then be harmlessly discharged to the track, leaving small volumes of solid waste in the tank for disposal approximately every two months.

The bioreactors can be custom-built for particular trains, making them suitable for retrofitting to existing stock.

The company points out the savings to be made by reducing both the need for retention tank emptying facilities and the requirement to diagram unit movements around the limited capacity of conventional tanks.

The payback time for intalling a bioreactor is estimated at around five years.