(a) Required Calculations.      
        (1) The engineering report must include calculations to determine static and dynamic pressure head necessary for operation of each air lift pump. Static and dynamic pressure head requirements for the suction line must be considered in the calculations.       
        (2) Air lift pump systems must be designed to meet the range of required flow rates.       
        (3) The engineering report must include the number of air lift pumps required and the minimum and maximum:                  (A) design airflow rate for each air lift pump;                   (B) design flow rate for each air lift pump; and                   (C) design flow rate for the system.         
      (b) Design.      
        (1) Air lift pumps may not be used to pump sludge from a primary clarifier.       
        (2) Air lift pumps must be at least three inches in diameter.       
        (3) The design air flow rates must be based on the actual submergence of an air lift pump.       
        (4) Blowers for an air lift pump system must be sized to provide the maximum design airflow rate required by the system.       
        (5) The discharge end of an air lift pump must prevent splashing.       
        (6) Air lift pumps located inside of a basin must allow for cleaning without removal from the basin.       
        (7) An air lift pump must provide a way to release trapped air.       
        (8) Air lift pump systems for return activated sludge, waste activated sludge, internal recycle, and other systems that affect overall process performance must have a minimum dynamic submergence of 60%.       
        (9) Air lift pump systems for scum removal, grit removal, or for transfers that do not affect overall process performance must have a minimum dynamic submergence of 50%.       
        (10) Air lift pump systems for return activated sludge, waste activated sludge, internal recycle, and other systems that affect overall process performance must provide a method for flow measurement using:                  (A) an external box with a weir; or                   (B) a rotameter, or other flow measurement device approved in writing by the executive director on the air line to each pump. When flow is measured on the air line, the engineering report must include a graph correlating the air flow rate in the air line to the liquid flow rate of the air lift pump.         
      (c) Redundancy.      
        (1) A backup pump or other means of transfer must be provided for each air lift pump system.       
        (2) Air lift systems for return activated sludge, waste activated sludge, and internal recycle must be able to operate at full capacity with the largest pumping unit out of service.       
     Source Note:        The provisions of this §217.162 adopted to be effective December 4, 2015, 40 TexReg 8254