Definitely not a fermentor. It could be a small batch bright tank or even a serving tank. Brew pubs don't keg or bottle their brews that are on tap, the fermentors are connected to these serving tanks that store and hold the beer and the taps are connected to the other end. The valve that is in the middle on one end could be where the beer is pumped into the tank from the fermentor and the valve that is located at the other end that is at the bottom could be where the line for the taps go to.
That is if this was actually used for beer, then again it could be a fuel tank like phijohnwilliams stated.