Abstract: A filtration system has at least one underdrain lateral, a flume, and at least one metering plate. The metering plate includes a plate member with at least one opening configured to receive liquid or gas therethrough at a first flow rate during a backwash function and is configured to receive liquid or gas therethrough at a second, lower flow rate during filtration. A method of metering gas into a filtration system with a metering plate is also disclosed. The metering plate allows gas to flow into each underdrain lateral at two very different flow rates.

Abstract: A filtration system has at least one underdrain lateral, a flume, and at least one metering plate. The metering plate includes a plate member with at least one opening configured to receive liquid or gas therethrough at a first flow rate during a backwash function and is configured to receive liquid or gas therethrough at a second, lower flow rate during filtration. A method of metering gas into a filtration system with a metering plate is also disclosed. The metering plate allows gas to flow into each underdrain lateral at two very different flow rates.

Abstract: A process for optimizing the carbon feed in a denitrification filter. The process utilizes in-line or off-line measurements of process variables in combination with feed forward and feedback control and increases or decreases the amount of carbon added based on a calculated reset rate determined on a periodic basis. The calculated reset rate may be a percentage of a theoretical value of the necessary carbon feed rate needed to remove the desired amount of nitrate-nitrogen. When the effluent nitrate-nitrogen is at a desired level and no rate change is necessary, the carbon feed rate is set to an average of one or more of the last filter runs. The process may also include a step wherein the carbon addition is increased immediately after backwashing to reestablish the biomass needed to produce the desired effluent in a step to regain process efficiency once that boost reestablishes the biomass.