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Secondary Treatment Configurations

Secondary Treatment Configurations. SOP Pretreatment Workshop August 2011.

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Secondary Treatment Configurations

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  1. Secondary Treatment Configurations SOP Pretreatment Workshop August 2011

  2. NDWRCDP DisclaimerThis work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881-01-0) with Washington University in St. Louis. These materials have not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or recommendation for use.

  3. CIDWT/University Disclaimer These materials are the collective effort of individuals from academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have been peer-reviewed and represent the current state of knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.

  4. Pretreatment components • Section objectives • Describe various engineered systems that maintain high-rate aerobic digestion of organic compounds found in domestic wastewater • Provide an understanding of the typical issues associated with these components • Describe basic operation and maintenance procedures required to keep these systems functional

  5. Basic aerobic treatment environments • Saturated • Suspended growth • Fixed/attached growth • Integrated fixed/activated sludge (IFAS) • Unsaturated • Media filters • Trickling filters

  6. Saturated treatment • Suspended growth • Fixed/attached growth • Integrated fixed/activated sludge (IFAS)

  7. Saturated aerobic units:Primary distinctions • Packaging • Flow of effluent • Aeration method • Biomass management

  8. Suspended growth reactors • Activated sludge process • Biomass is thoroughly mixed with nutrients and biodegradable compounds • Organisms flocculate and form active mass of microbes - biological floc • Extended aeration to limit biomass wasting • Endogenous respiration

  9. Suspended Growth

  10. Suspended growth

  11. Suspended growth

  12. Suspended growth USEPA Manual, 1980

  13. Sequencing Batch Reactor • Suspended growth treatment process • Utilize a single chamber for achieving aeration, clarification and anoxic conditions • Flow equalization chamber for dosing effluent into the treatment chamber

  14. Sequencing batch reactors

  15. Sequencing batch reactors

  16. Fixed/attached growth reactors • Fixed-film process • Inert medium is submerged in the aeration chamber • Effluent circulated through media and attached microbes • Colloidal and dissolved organics compounds absorbed by biological film • Extended aeration to limit biomass wasting • Food brought to bugs

  17. Fixed-film reactors

  18. Rotating Biological Contactor (RBC)

  19. Membrane bioreactors Wikipedia

  20. Flow schemes • Continuous inflow • Batch processes

  21. Aeration • Air supply and delivery component • Distribution device • Venting device

  22. Air supply delivery • Methods • Aspirator/Aerator • Compressor • Blower • Free Air

  23. Aerator/Aspirator

  24. Aerator/Aspirator • Spinning shaft or impeller creates a vacuum (venturi) • Vacuum pulls air into the water

  25. Compressor • Two distinct types of compressors • Rotary • Linear • Both types fitted with filters • Relative to blowers: • Greater pressure • Lower air flow Rotary Linear

  26. Blowers • Fitted with inlet screens/filters • Relative to compressors: • Lower pressure • Greater air flow

  27. Air distribution device • Introduces air into the water • Includes any supply line(s) • Various methods

  28. Aspirator/aerator • Shaft piping delivers the air supply • Distribution relative to pressure

  29. Diffused air distribution • Compressor or blower delivers air • Mode of distribution is manufacturer specific • Solid pipe • Perforated pipe • Holes • Slots • Porous material

  30. Diffused air distribution Perforated Pipe

  31. Diffused air distribution Porous ceramic diffuser

  32. Diffused air distribution • Spargers • small interconnected passageways inside a ceramic matrix

  33. Oxygen transfer into solution • Small diameter bubbles • More surface area per unit volume • Oxygen transfer takes place across interface between air and water

  34. Point of injection • Usually near bottom of tank • more time for oxygen to go into solution • more hydrostatic pressure on bubble • more mixing of contents

  35. “Free” air • Alternately rotates media through air space in top of unit and down into effluent in basin • Water accepts oxygen from air

  36. Aeration and Mixing • Aeration system also encourages mixing • displacement of water as air is introduced causes turbulence

  37. Air supply operation • Continuous • Timed

  38. Venting • Air entering system • Air must exit somewhere • Unit • House vent • Biofilter

  39. Biomass management • Returning sludge to a previous point in treatment system • Keeps the biological processes working • At some point, accumulated solids will have to be removed

  40. Passive sludge return system Settled material automatically returns to the aeration chamber No moving parts Limited flexibility for including anoxic treatment process

  41. Active sludge return system Pump on bottom of settling chamber Control panel with timer Timing of return Volume returned Location for returned material

  42. Proprietary configurations • Modular units with complete configuration • Subcomponents installed in prefab tanks • Specific to proprietary products

  43. Basic aerobic treatment environments • Saturated • Suspended growth • Fixed/attached growth • Integrated fixed/activated sludge (IFAS) • Unsaturated • Media filters • Trickling filters

  44. Unsaturated treatment • Media filters • Trickling filters

  45. Media filters • A container or lined excavation containing a specific media through which wastewater flows • Treatment occurs in unsaturated conditions • Designed to follow primary treatment

  46. Flow regimes for media filters • Single pass • Recirculating

  47. Single-pass media filter NSFC

  48. Recirculating media filter schematic

  49. Typical configuration • 24 – 36 inches of media • Methods of distribution • Pressure distribution - most common • Spray nozzles • Driplines • Gravity

  50. Typical configuration • Increasingly, timer-controlled dosing is being used • Usually lined to collect filtrate for external dispersal • May be configured to drain into rock pad beneath unit in certain soil/site conditions

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