A mobile flocculation and water treatment system includes at least one tank, preferably a series of adjoining tanks separated by weirs, and an adjacent pump house mounted on a mobile platform. At least one pump is mounted in the pump house. Fluid conduits run from the pumps to the tank. An overflow is mounted between the downstream tank and the pump house whereby fluid overflow from the tanks is directed into the pump house. The pump house provides a substantially water-tight reservoir zone to provide secondary containment. Water to be treated enters the upstream end of the tanks and is discharged from the downstream end.