Vacuum tanks were the original wastewater collection technology on-board marine vessels. Simple and reliable ejector technology soon replaced vacuum tanks as a more cost-effective alternative at a time when energy consumption was not a significant concern. Vacuum tanks have become relevant again as a result of improvements in production methods and the emergence of robust vacuum pump technology. Excellent energy efficiency, the best feature of vacuum tanks, is today more important than ever.
The Evac EcoVac units are ideal for black and gray water collection on board large vessels, making them a viable option for cruise ships.Vacuum tank systems consist of a tank with a typical capacity of 1–3 m3, vacuum pumps, and sewage discharge pumps.
Unlike online vacuum pump systems such as the Evac OnlineMax R, sewage is collected in the tank and discharged in batches. As with OnlineMax R, the vacuum is created by special vacuum pumps, but the vacuum tank also acts as a large stabilizing vacuum buffer for the system.
In a system with an Evac EcoVac unit, the whole tank is under vacuum. Vacuum generation is controlled by a vacuum sensor and the PLC. Discharge is controlled by high and low-level switches or, optionally, by a timer.