Abstract: A biological reactor which is intermittently aerated to create an environment that alternates from aerobic to anoxic. A programmable logic controller controls the amount and timing of air flow to the biological reactor linking aeration to incoming load.

Abstract: In a wastewater treatment system comprised of an anoxic tank outputting to a biological reactor and outputting from the reactor to a clear well, a process for controlling the rate and timing of flow through the reactor by means of a floating pump within the anoxic tank. Further enhancement of denitrification is achieved by sending internal recycles into the sludge zone of the anoxic tank via a baffle positioned within the sludge layer.

Abstract: A single submerged attached growth bioreactor interconnected to an equalization tank and a clear well. The equalization tank receives raw wastewater and provides primary settling of solids from the waste water. The output from the equalization tank is sent into the bioreactor. The wastewater flow path through the bioreactor biofilter is serpentine. Wastewater enters the first cell of the biofilter and flows downward to an opening at the biofilter bottom that hydraulically connects the first cell to a biofilter second cell. In the second cell the wastewater flows up from the bottom to an opening above the media within the cell, which connects the second cell with a third biofilter cell. Wastewater then flows downward through the third cell to the bottom and exits the biofilter through a pipe connected to a pump in the clear well. The hydrostatic pressure created by the differential liquid levels drives forward flow through the cells and into an effluent pipe at the bottom of the third cell.