Patent ID: 7632408

Claim:
A passive drain field assembly comprising: a first chamber placeable in fluid communication with an effluent source of wastewater at an inlet and comprising: a subterranean bundle of pipes comprising a distribution pipe in fluid communication with the inlet, the distribution pipe having a plurality of apertures therethrough and a plurality of void pipes positioned lower than the distribution pipe, the void pipes each having a plurality of apertures therein, the pipe bundle slightly sloping toward an outlet; and a vent extending from an interior of the first chamber to an atmosphere above the pipe bundle; a second chamber having an inlet in fluid communication with the pipe bundle outlet positioned at least partially beneath the first chamber and having a perforated bottom, the second chamber comprising: a reactive carbon-source medium positioned within an inner space of the second chamber; an elevated berm positioned in spaced relation from the second chamber inlet and a downstream end, and having a top in spaced relation from a top of the second chamber; a liquid-impermeable barrier sheet positioned along the second chamber bottom and extending from the inlet to at least the berm top; wherein, in use: effluent is channeled into the first chamber inlet, into the distribution pipe, and into the void pipes, wherein the effluent resides, ammonia in the effluent at least partially converted to a nitrate in the presence of oxygen supplied via the vent; effluent rising above the distribution pipe apertures exits via the first chamber outlet to the second chamber inlet; effluent remains in a retention portion of the second chamber upstream of the berm until the effluent reaches a level higher than the berm top, wherein the nitrate is converted to nitrogen gas and is placed in contact with the reactive medium; and effluent flowing over the berm top to a portion of the second chamber downstream of the berm continues to contact the reactive medium and can seep into soil beneath the second chamber through the perforated bottom.