1. Secondary Treatment Configurations SOP Pretreatment Workshop August 2011

2. NDWRCDP Disclaimer This 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 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 Provide an understanding of the typical issues associated with these components Describe basic operation and maintenance procedures required to keep these systems functional Describe basic operation and maintenance procedures required to keep these systems functional

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

9. Suspended Growth

10. Suspended growth

12. USEPA Manual, 1980 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

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 Aspirator/Aerator Compressor Compressor Blower Blower Free Air 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 Rotary Linear Linear  Both types fitted with filters  Relative to blowers: Greater pressure Greater pressure Lower air flow Lower air flow Rotary Linear

26. Blowers  Fitted with inlet screens/filters  Relative to compressors: Lower pressure Lower pressure Greater air flow 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 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 Diffused air distribution Perforated Pipe

31. Diffused air distribution Diffused air distribution Porous ceramic diffuser

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

33. Oxygen transfer into solution  Small diameter bubbles More surface area per unit volume More surface area per unit volume Oxygen transfer takes place across interface between air and water 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 time for oxygen to go into solution more hydrostatic pressure on bubble more hydrostatic pressure on bubble more mixing of contents 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 also encourages mixing mixing displacement of water as air is introduced causes turbulence 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 Unit House vent House vent Biofilter 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 Timing of return Volume returned Volume returned Location for returned material 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 Suspended growth Fixed/attached growth Fixed/attached growth Integrated fixed/activated sludge (IFAS) Integrated fixed/activated sludge (IFAS)  Unsaturated Media filters Media filters Trickling 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 Pressure distribution - most common Spray nozzlesSpray nozzles DriplinesDriplines Gravity Gravity

50.  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 Typical configuration

51.  Single-pass: 1 – 2 gal / ft 2 /day  Multiple-pass filters: up to 5 gal / ft 2 /day  Increased loadings may be allowed for certain proprietary designs Typical hydraulic loading

52.  Single-pass filters: Historically - 4 times/day Historically - 4 times/day Current recommendations - as high as 12-24 times/day Current recommendations - as high as 12-24 times/day  Multiple-pass: 12-72+ times/day Dosing frequency

53. Treatment process  Wastewater applied in small doses  Percolates over media in thin film  Organisms on media contact wastewater  Air is maintained in media pores  Oxygen is transferred into the thin film and to organisms  Aeration typically passive

55. Treatment occurs by:  Filtration and trapping  Adsorption  Biological decomposition  Biochemical transformation Nitrification Nitrification Denitrification (especially if recirculated) Denitrification (especially if recirculated)

56. Types of media  Washed, graded sand  Gravel  Foam chips and cubes  Expanded polystyrene  Peat  Synthetic textile materials  Bottom ash from coal-fired plants  Crushed glass  Other

57. Sand and gravel filters  Single pass or recirculating mode  Sand/Gravel media specifications Must (generally) be processed to provide the right gradation Must (generally) be processed to provide the right gradation Screened for proper gradation Screened for proper gradation Washed Washed  Must be handled carefully after processing to maintain the specification and remain free of fines

58. Cutaway demo

59. Single pass sand filter with pump basin

60. Questions?