1. (a) This section applies to the traditional approach for sizing an aeration basin and clarifier based on values that have been used historically as standard engineering practice.

2. (b) Aeration Basin Sizing.

   1. (1) A aeration reactor must be sized using the organic load calculated in §217.32 of this title (relating to Organic Loading and Flows).
   2. (2) Based on this organic load, the aeration basin volume must ensure that the organic loading on the aeration basin does not exceed the rates in the following table:
      Attached Graphic
      
   3. (3) When identifying the reactor temperature for the process design in Table F.1 in paragraph (2) of this subsection, the average of the lowest consecutive seven-day mean reactor temperature from a similar wastewater treatment facility located within 50 miles of the proposed site must be used.

3. (c) Clarifier Sizing.

   1. (1) The following table establishes the maximum surface loading rates and the minimum detention times used to determine the size of an activated sludge clarifier:
      Attached Graphic
      

   2. (2) A clarifier must meet both the detention time and overflow rate criteria.

      1. (A) When calculating overflow rates for a proposed clarifier, sludge recycle flow must not be used in the calculation of the maximum overflow rate, in compliance with Table F.2 in paragraph (1) of this subsection.
      2. (B) When calculating the overflow rate for a proposed clarifier, the surface area of the stilling well may be included as part of the clarifier surface area.

Source Note:The provisions of this §217.154 adopted to be effective August 28, 2008, 33 TexReg 6843.