Bioreactor Technologies

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Waste Management's Aerobic-Anaerobic Bioreactor* is designed to accelerate waste degradation by combining attributes of the aerobic and anaerobic bioreactors. The objective of the sequential aerobic-anaerobic treatment is to cause the rapid biodegradation of food and other easily degradable waste in the aerobic stage in order to reduce the production of organic acids in the anaerobic stage resulting in the earlier onset of methanogenesis. In this system the uppermost lift or layer of waste is aerated, while the lift immediately below it receives liquids. Landfill gas is extracted from each lift below the lift receiving liquids. Horizontal wells that are installed in each lift during landfill construction are used convey the air, liquids, and landfill gas. The principle advantage of the hybrid approach is that it combines the operational simplicity of the anaerobic process with the treatment efficiency of the aerobic process. Added benefits include an expanded potential for destruction of volatile organic compounds in the waste mass. (*US Patent 6,283,676 B1)

WM's Aerobic-Anaerobic Bioractor

Waste Management's Facultative Landfill Bioreactor** combines conventional anaerobic degradation with a mechanism for controlling high ammonia concentrations. Leachate recirculation may cause an increase in the concentration of ammonia to the point to where it is toxic to bacteria. By incorporating nitrogen cycle control, the ammonia can be partially treated to create "nitrated" leachate. Nitrated leachate is leachate that has been treated to convert ammonia to nitrate. The nitrated leachate serves much the same purpose as oxygen or air would in an aerobic landfill, serving as an electron donor. (**US Patent 6,398,958 )

WM's Facultative Landfill Bioreactor