Woke up this morning at 5AM to visit this place. Just as awesome as I'd thought it was gonna be, w00t :-D
The egg-like structures you see (and a couple of acorns in the front) are "sludge digesters" that process the sewer sludge to extract methane. The methane, in turn, is used to power a huge chunk of the energy consumption required by the water treatment facility. They recently installed two wind turbines (on the other side of the structures you see here), that generate more energy, and I believe they have now become totally self-sufficient in terms of energy needs.
So, yes, this is a very "eco" water treatment facility :-)