(a) For the systems and processes used to provide treatment of domestic wastewater prior to the wastewater entering the subsurface area drip dispersal system the applicant shall use the design criteria in Chapter 217 of this title (relating to Design Criteria for Domestic Wastewater Systems) or Chapter 317 of this title (relating to Design Criteria Prior to 2008) as applicable.     
      (b) If using septic tanks as the treatment system, the applicant shall design, construct, and install the tanks in accordance with Chapter 285, Subchapter D of this title (relating to Planning, Construction, and Installation Standards for OSSFs).     
      (c) If using anaerobic biological reactors (ABRs) as the treatment system, the permittee must comply with the following criteria.      
        (1) The ABR must have a container that is a structural unit such as a concrete tank, or an earthen berm with a membrane liner may be used for larger installations.                  (A) The container must be designed for the internal and external stresses that may be placed on the container during fabrication and use.                   (B) Materials used to construct an ABR structural container must meet the requirements for septic tanks in §285.32 of this title (relating to Criteria for Sewage Treatment Systems).                   (C) Containers using compacted earthen berms must use a membrane of vinyl or other plastic with a minimum thickness of 40 mils as the waterproofing component.                   (D) A cover is required unless a covering layer of gravel or other media is placed above the liquid level to present a dry surface.         
        (2) The ABR must have media that is inert, stable, of uniform size, and free of fines.                  (A) Clean washed gravel, crushed rock, or plastic filter media made for trickling filter use is acceptable.                   (B) Minimum media effective size must be one inch and the uniformity coefficient must be less than 3.0.         
        (3) The ABR must have a distribution system over the bottom of the ABR and a collection system near the top of the ABR.                  (A) The piping for the distribution system must be constructed of pipe that:                      (i) is class 200 or schedule 40 polyvinyl chloride (PVC);                       (ii) meets ASTM International (ASTM) Standards D-2241 or D-1785; and                       (iii) has a one-inch nominal diameter.                     (B) The ABR must incorporate a sight well that allows monitoring the liquid level in the unit.                   (C) The ABR must have a means to flush and remove excessive biomat buildup from the media.         
      (d) If using sand filters as the treatment system, the permittee shall use sand filters that have the following components and meet the following requirements.      
        (1) Sand filters must be contained in a structural unit designed for all internal and external stresses that may be placed on the containment device during fabrication and use such as:                  (A) a septic tank unit that meets the requirements in Chapter 285, Subchapter D of this title;                   (B) a poured in place concrete structure; or                   (C) an earthen berm with an impermeable membrane liner that has a minimum thickness of 40 mils and an under-drain leak detection system.         
        (2) The permittee shall use a detention time of at least 24 hours for dosing to a sand filter at rates up to ten gallons per day per square foot.       
        (3) All sand filter containment devices shall provide sufficient freeboard above the filter surface to hold four dosing volumes.       
        (4) A sand filter must have a collection pipe system to collect the filtered effluent that meets the following requirements.                  (A) The piping shall be arranged so that the maximum horizontal travel distance of water through the under-drain media is less than four feet.                   (B) The collection piping and the drain pipe from the filter shall be sized to remove a filter dose volume from the filter within a ten-minute period.                   (C) The ends of the collection lines shall be extended above the surface of the filter to allow aeration of the drained filter.                   (D) The collection piping system shall be constructed of pipe that:                      (i) is class 200 or schedule 40 PVC;                       (ii) meets ASTM Standards D-2241 or D-1785; and                       (iii) has a two-inch nominal diameter.                     (E) The sand filter media must:                      (i) be an inert, clean washed material that is free of fines, dirt, and organic material;                       (ii) have an effective size and uniformity coefficient suitable for the design loading rate;                       (iii) have a depth based on the effective grain size and the design effluent quality with coarse media requiring a greater media depth; and                       (iv) be placed on top of a bottom drain media.                     (F) The sand filter bottom media must:                      (i) cover the effluent collection piping;                       (ii) have an effective grain size from two to four times the effective grain size of the filter media; and                       (iii) support the filter media, prevent washout, and hydraulic removal of the filter media.           
        (5) The surface distribution mechanism must distribute the liquid to be filtered over the surface of the filter in a uniform manner.                  (A) If a filter receives the liquid by gravity, distribution shall be accomplished by troughs or channels using splash pads to reduce surface erosion.                   (B) Pressure-dosed sand filters must have a distribution system that:                      (i) provides even distribution of the liquid;                       (ii) consists of a pipe network with discharge holes or spray nozzles; and                       (iii) provides a uniform pressure at the discharge outlets.           
        (6) Loading rates and filter sizing must be designed to treat the specific characteristics of the incoming wastewater and the effluent quality.       
        (7) The loading rate shall be designed based on the influent qualities, the selected media, and the acceptable run time between filter media cleaning or replacement.       
      (e) The permittee must submit a design that specifies the minimum frequency for solids removal from the treatment system and the justification of the frequency based on the type of system and good engineering practice.     
      (f) The permittee shall design the treatment system with the capacity to process the peak flow from the wastewater producer. The following criteria shall be the basis to determine peak flow:      
        (1) wastewater design values will be determined in accordance with §217.32 of this title (relating to Organic Loadings and Flows for New Wastewater Treatment Facilities); or §317.4(a)(1) or (2) of this title (relating to Wastewater Treatment Facilities); or       
        (2) the peak flows of the particular wastewater generator when the wastewater generator has unusually high peak flows.       
     Source Note:        The provisions of this §222.115 adopted to be effective July 5, 2006, 31 TexReg 5308; amended to be effective January 9, 2020, 45 TexReg 363