Section 217.251 - Sludge Storage(a) This section applies to the storage of sludge after processing but before final disposal or removal from the wastewater treatment facility site.(b) Sludge in liquid, dewatered, or dry form may be stored at the wastewater treatment facility if the solids have been stabilized in a treatment process.(c) General Storage Requirements. (1) A sludge storage facility must prevent nuisance odor conditions and minimize vector attraction.(2) A sludge storage facility must provide storage of waste sludge separate from a biological treatment process.(3) The design of a sludge storage facility must be based on process design, sludge age, waste stream concentration, operational hours, operational volume in tanks, decant or dewatering volumes and characteristics, time frames needed for decanting or dewatering, and volume needed for storage and sampling.(4) The engineering report must include a solids management plan that describes a method for managing the waste solids that will maintain the design sludge age for a biological process.(d) Storage of Solids - Not Dewatered.(1) Aerobically Digested Solids. (A) A storage facility may store aerobically digested solids.(B) A sludge storage basin must have diffused air or mechanical mixing.(C) A diffused air-mixing unit must provide a minimum air capacity of 30 standard cubic feet per minute per 1,000 cubic feet of volume.(D) A mechanical surface aerator must have a minimum of 1.0 horsepower per 1,000 cubic feet of volume.(E) An earthen sludge storage basin must be lined in accordance with § 217.203(d) and (e) of this title (relating to Design Criteria for Natural Treatment Units).(2) Anaerobically Digested Solids. Anaerobically digested solids must be stored in a covered basin with gas release valves and gas control measures.(e) Storage of Dewatered Solids. (1) Dewatered solids must be stored in a steel or concrete container, or in an open stockpile.(2) Dewatered solids with a solids content of less than 35% must not be stored for more than seven days. Dewatered solids with a solids content of at least 35% but not more than 50% must not be stored for more than 90 days.(f) Open Stockpiles. (1) An open stockpile must have an impervious pad underneath the solids to prevent groundwater contamination.(2) An open stockpile must have a system for collecting stormwater runoff and returning it to the headworks of the wastewater treatment facility.(g) Dried Solids Storage. (1) A storage facility may store dewatered solids with a solids content of greater than or equal to 50% in a covered bin or covered facility for a period of time that does not exceed two years.(2) An enclosed storage structure must be mechanically ventilated with at least 20 complete air exchanges per hour and must have an odor control system for the exhaust.30 Tex. Admin. Code § 217.251
The provisions of this §217.251 adopted to be effective August 28, 2008, 33 TexReg 6843; Amended by Texas Register, Volume 40, Number 47, November 20, 2015, TexReg 8336, eff. 12/4/2015