Abstract: A method and system are provided for treating water, such as wastewater, landfill leachate, or contaminated groundwater. A single tank is used. A structure with a unique design within the tank promotes growth of immobilized biomass. A recycle stream transports some of the fluid output from near the top of the tank back to the bottom of the tank, the rest of the fluid output leaving the water treatment system as effluent. Oxygenation means within the tank cause fluid to flow upwards, and this together with the recycle stream causes fluid to circulate through the immobilized biomass. The oxygenation means result in the formation of an aerobic zone, and the location and/or aeration flow rate of the oxygenation means result in an oxygen-depleted zone. Different processes occur in the aerobic and oxygen-depleted zones, removing a variety of contaminants.

Abstract: A wastewater treatment system has two separate but interlinked tanks containing four different zones, namely aerobic, microaerophilic, anoxic and anaerobic, for the biological treatment of the wastewater, as well as two clarification zones and a filtration unit for separation of solids from liquid. The first tank contains the aerobic, microaerophilic and anoxic zone as well as a clarification zone, while the second dank includes the anaerobic zone, a solid-liquid separation zone and a filtration unit. The aerobic zone is an airlift reactor that contains air diffusers at the bottom of the zone to introduce air into the zone. The air bubbles mix the liquid and its content of microorganisms, and provide oxygen for the aerobic biological processes that take place in this zone. Aeration also produces circulation of liquid between the aerobic zone and its adjacent microaerophilic and anoxic zones that are located at the sides and under the aerobic zone, respectively.

Abstract: A wastewater treatment system has two separate but interlinked tanks containing four different zones, namely aerobic, microaerophilic, anoxic and anaerobic, for the biological treatment of the wastewater, as well as two clarification zones and a filtration unit for separation of solids from liquid. The first tank contains the aerobic, microaerophilic and anoxic zone as well as a clarification zone, while the second dank includes the anaerobic zone, a solid-liquid separation zone and a filtration unit. The aerobic zone is an airlift reactor that contains air diffusers at the bottom of the zone to introduce air into the zone. The air bubbles mix the liquid and its content of microorganisms, and provide oxygen for the aerobic biological processes that take place in this zone. Aeration also produces circulation of liquid between the aerobic zone and its adjacent microaerophilic and anoxic zones that are located at the sides and under the aerobic zone, respectively.