US Patent 7794596 Method and apparatus for waste water treatment

A method for treating wastewater wherein the wastewater is introduced in prescribed doses of wastewater to a first treatment zone, establishing a negative pressure gradient using mechanical ventilation within said zone causing exhaust air flow to remove gases and promote evaporation in the zone. Excess wastewater passing through the zone is collected and reintroduced. The zone contains particulate material with a large wetted surface area covered in a microbiological slime layer.