1. (a) Application Rates.

   1. (1) With one unit out of service, the peak application rate to any unit must not exceed twice the design application rate.
   2. (2) The report must include manufacturer's recommended filtration rates with test data.
   3. (3) Single Media. A single media filter must have a maximum design filtration rate of 3.0 gallons per minute per square foot of media surface.
   4. (4) Dual Media. A dual media filter must have a maximum design filtration rate of 4.0 gallons per minute per square foot of media surface.
2. (b) Media Design. Media sizes and depths must correspond to the values in the following figure, unless the report justifies different media sizes and/or depths:
   Attached Graphic
   

3. (c) Backwash System.

   1. (1) A backwash system must provide a minimum of 20 gallons per minute per square foot of media being backwashed at a given time.
   2. (2) The backwash duration must last at least 20 seconds for each compartment and must expand the media a minimum of 20% unless the report includes the manufacturer's recommended backwash rates with test data.
   3. (3) The surge control and pumping system requirements must be the same as those detailed in §217.191(d)(2) and (3) of this chapter (relating to Additional Design Requirements for Deep Bed, Intermittently Backwashed, Granular Media Filters).

4. (d) Traveling Bridge. A traveling bridge mechanism must:

   1. (1) provide support and access to the backwash pumps and equipment;
   2. (2) be constructed of corrosion resistant materials;
   3. (3) have provisions for consistent tracking of the bridge and safe support of the power cords; and
   4. (4) initiate a backwash cycle automatically when a preset head loss through the filter media occurs.
5. (e) Floating Material Control. A filter system must provide for automatic and regular removal of any floating material from the surface of a filter and return the floating material to the head of the facility for further processing.

Source Note:The provisions of this §217.192 adopted to be effective August 28, 2008, 33 TexReg 6843.