Abstract: A wastewater treatment system has been created in which water to be treated is moved into a treatment vessel without pumping action of a pump. Such movement is facilitated by creating and, in some aspects, maintaining a vacuum in the treatment vessel to effect siphoning action to move water to and through the vessel. In one embodiment the treatment vessel is contained within a wastewater collection container, e.g. a below-grade concrete pit of an existing wastewater collection system. In another aspect the system is sealed so undesirable vapors are not vented to the atmosphere.