(a) Application Rates.      
        (1) With one unit out of service, the peak application rate to any multi-compartmented, low head, automatically backwashed (multi-compartmented) filter unit must not exceed twice the design application rate.       
        (2) The engineering report must include manufacturer's recommended filtration and application rates with test data.       
        (3) Single Media. A single media multi-compartmented filter must have a maximum design filtration rate of 3.0 gallons per minute per square foot of media surface.       
        (4) Dual Media. A dual media multi-compartmented filter must have a maximum design filtration rate of 4.0 gallons per minute per square foot of media surface.       
      (b) Media Design. Media sizes and depths must correspond to the values in Table G.5. in Figure: 30 TAC §217.192(b), unless an engineer uses calculations to justify different media sizes, depths, or both in the engineering report.      
        Attached Graphic       
      (c) Backwash System.      
        (1) A backwash system must provide a minimum backwash rate of 20 gallons per minute per square foot of media.       
        (2) The backwash duration must last at least 20 seconds for each compartment and must allow a fluidized media expansion of at least 20% by volume, unless the engineering report includes the manufacturer's recommended backwash rates with test data that supports a shorter backwash duration or less expansion of the fluidized media.       
        (3) The surge control and pumping system requirements must be the same as those detailed in §217.191(c)(2) and (3) of this title (relating to Additional Requirements for Deep Bed, Intermittently Backwashed, Granular Media Filters).       
      (d) Traveling Bridge. A traveling bridge mechanism must:      
        (1) provide support and access to the backwash pumps and equipment;       
        (2) be constructed of corrosion-resistant materials;       
        (3) have provisions for consistent tracking of the bridge and safe support of the power cords; and       
        (4) initiate a backwash cycle automatically when a preset head loss through the filter media occurs.       
      (e) Floating Material Control. A multi-compartmented filter system must provide for automatic removal of any floating material from the surface of the multi-compartmented filter and return the floating material to the headworks of the wastewater treatment facility for further processing.     
     Source Note:        The provisions of this §217.192 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254