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Design • 0
<br /> Appendix A. Sizing for Primary and Pre-Anoxic Tankage
<br /> All secondary treatment systems are limited in their ability to break down and treat organic material.The purpose of primary tankage in
<br /> AdvanTex Treatment Systems is to reduce and maintain organic material at a level that can be efficiently and economically treated by the
<br /> AdvanTex treatment unit(s). Primary tankage can anaerobically digest organic material, remove solids, modulate flow,and provide emer-
<br /> gency storage volume.To operate effectively, primary tankage must be properly designed and sized,structurally sound,watertight, and
<br /> well-maintained.
<br /> For the application types defined in this Design Criteria,Table A provides recommended minimum tank volumes.To calculate recommended
<br /> minimum tank volumes, multiply the Design Maximum Day Flow specified for the system by the necessary hydraulic retention time (HRT)
<br /> in days. For example, if local regulations require a 10,000 gpd system design (based on Design Maximum Day Flow)for an office facility,
<br /> Orenco recommends a minimum total tank volume of 30,000 gallons. (See Table A,Application Type 2.)To determine preferred tank vol-
<br /> umes,add approximately 50%to the minimum values.
<br /> The minimums in Table A exceed those set by the United States Environmental Protection Agency(USEPA) and the regulatory requirements
<br /> for nearly every state in the United States.With regard to tank sizing, larger hydraulic retention times result in improved primary treatment.*
<br /> Research strongly indicates that the smaller volumes calculated by using the USEPA formula(based on 1940's information),as well as the
<br /> listed volumes for most state and local health agencies, consistently produce poor quality effluent.They are also associated with increased
<br /> pumpout frequencies and costs, increased need for secondary treatment capacity,and an increased need for maintenance activities,with
<br /> their associated costs.
<br /> Orenco recommends the use of pre-anoxic tankage prior to the recirculation-blend tank for all systems. Recommended total primary tank-
<br /> age is provided in Table A,followed in parentheses by the recommended configuration of the primary tankage for specific treatment needs,
<br /> if any,such as a pre-anoxic stage, aeration unit,clarification chamber, or flow equalization.
<br /> Table A is intended as a general guideline for decentralized wastewater treatment designs.The system designer is responsible for ensuring
<br /> adequate primary treatment prior to the secondary treatment system. Check local regulations to ensure that the recommended minimum
<br /> volumes meet applicable regulatory requirements. For questions about special cases where larger tankage or other measures may be nec-
<br /> essary,or for general questions about flow equalization, please call Orenco at(800) 348-9843 or+1-541-459-4449.
<br /> *Metcalf&Eddy,"Wastewater Engineering Collection,Treatment,Disposal,"1972(New York,McGraw Hill).
<br /> Winneberger,John H.Timothy,"Septic Tank Systems,A Consultant's Toolkit,Volume II The Septic Tank,"1984(Butterworth Publishers,Ann Arbor Science).
<br /> Laak,Rein,"Wastewater Engineering Design for Un-Sewered Areas,"1980(Butterworth Publishers,Ann Arbor Science).
<br /> Philip,H,et.al.,"Septic Tank Sludges:Accumulation Rate and Biochemical Characteristics,"1993 Water Science&Technology.
<br /> Orenco Systems°•800-348-9843•+1 541-459-4449•www.orenco.com NDA-ATX-1
<br /> Rev.8,©10/20
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