Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
SlideShare a Scribd company logo

Waste Water Treatment Secondary treatment (activated sludge, filtration).ppt

•Download as PPT, PDF•
•
H
HussamElddinKhasawne

Waste Water Treatment Objectives Outline of treatment process (flow diagram) Preliminary treatment Primary treatment (sedimentation) Secondary treatment (activated sludge, filtration) Sludge treatment Disinfection Tertiary treatment

1 of 40
Waste Water Treatment (Sewage Treatment)
Outline • Objectives • Outline of treatment process (flow diagram) • Preliminary treatment • Primary treatment (sedimentation) • Secondary treatment (activated sludge, filtration) • Sludge treatment • Disinfection • Tertiary treatment
Objective of Sewage Treatment  To prevent pollution of the receiving water  To prevent offensive odour in the water  To prevent the destruction aquatic life  If the sewage has to be disposed of on land, the soil will become sewage sick after some time and cannot take any more sewage
Outline of Sewage Treatment  Preliminary treatment  Primary treatment  Secondary treatment  Disinfecting  Tertiary Treatment
Preliminary Treatment • Waster water contains floating suspended solids such as rags, wood, metal, plastic, etc. • these suspended impurities have to be removed as they interfere with the treatment processes or mechanical equipment.
Primary Treatment • consists of mainly the sedimentation process to remove suspended organic solids • Chemicals are sometimes added in primary clarifier to assist in the removal of finely divided and colloidal solids or to precipitate phosphorous
Secondary or Biological Treatment • Activated sludge process • Filtration
Activated sludge process • the sewage is biologically treated.
Filtration • is done in contact beds or intermittent sand filters or tricking filters. • It removes finely divided suspended matter.
Sludge & Effluent • The semi-solid that settles down at the bottom after treatment,is called sludge • liquid to be discharged is called effluent.
Disinfecting • Disinfecting is carried out if necessary by chlorination to kill the bacteria which remain in the effluent of sewage
Tertiary Treatment • If the receiving water provides only little dilution or there is a need to preserve a particularly high quality of effluent, tertiary treatment can be used.
PRELIMINARY TREATMENT
Objectives Remove coarse suspended and floating matter such as rags, plastic, pieces of wood, etc., by means of screening Remove grit, sand, broken glass, etc., in grit chambers Remove grease, and oil substances by floatation in skimming tanks
Processes Screening Silt and grit removal Oil and grease removal
PRIMARY TREATMENT
PRIMARY TREATMENT Primary sedimentation tank (Secondary sedimentation tank) - sedimentation after activated sludge process
Advantages • The advantages of coagulation over plain sedimentation are: Sedimentation by coagulation is more effective BOD, colour and turbidity are reduced Less capacity of sedimentation tanks The process is simple
Disadvantages • The disadvantages are: Chemicals destroy the bacteria that digest the sludge Chemicals increase the cost of sedimentation Skilled supervision is required Large quantity of sludge is produced
SECONDARY TREATMENT
SECONDARY TREATMENT • The secondary treatment converts the remaining organic matter into stable form by putting aerobic and anaerobic bacteria into action
Processes Filtration Activated sludge process
Filtration • Aerobic bacteria need a contact surface to live and carry out their activities
Filtration Contact beds Intermittent sand filters Trickling filters
Contact Beds • A contact bed consists of filtering medium. • When the sewage is passed over the medium, a thin film is produced around the particles. • The bacteria present in the film oxidise the organic matter.
Intermittent Sand Filter • the filtering medium consists of sand. • The action of the filter is due to: Mechanical straining and – Bacterial action
Trickling Filters • A trickling filter is an artificial bed of stone or broken brick material • waste water is distributed an applied in drops, films or spray • A zoogleal film is formed on the surface media.
ACTIVATED SLUDGE PROCESS • is a biological sewage treatment process • a mixture of sewage and activated sludge is agitated and aerated. • The activated sludge is subsequently separated from the treated sewage by sedimentation
What is ACTIVATED SLUDGE • is that sludge which settles down after the sewage has been freely aerated and agitated for a certain time.
How Activated Sludge works • Activated sludge contains numerous bacteria and other microorganisms. When it is mixed with raw sewage saturated with oxygen, the bacteria perform: – Oxidise the organic solids Promote coagulation and flocculation and convert the colloidal and suspended solids into settable solids
Steps in Activated Sludge process • Treat raw sewage in the primary settling tank • mix sewage with the activated sludge and aerated for 4-10 hours • final (secondary) settling tank • dispose of effluent • return some sludge to the aeration tanks • dispose of the rest of the sludge
Advantages • Gives clear sparkling treated effluent • Effluent free from offensive odour • Degree of purity can be varied as desired • Cost of installation lesser than for a trickling filter • Small loss of head in the process
Disadvantages Skilled supervision and constant check on the return sludge is necessary When there is change in the quality or quantity of sewage, the process is upset The process does not work for some industrial wastes Large volume of sludge increases difficulty in disposal
Methods of Aeration • The success of the activated sludge process depends on the aeration provided. Diffused air aeration Mechanical aeration Combination of the above two methods
TERTIARY TREATMENT
TERTIARY TREATMENT • MICROSTRAINERS • RAPID GRAVITY SAND FILTERS • UPWARD-FLOW “MEDUIM” SAND FILTERS • SLOW SAND FILTERS • PEBBLE-BED CLARIFIERS • SETTLEMENT • GRASS PLOTS • LAGOONS
SLUDGE TREATMENT AND DISPOSAL
Sludge • Sludge is a semi-liquid • Sludge produced by plain sedimentation • Sludge produced by chemical precipitation • Trickling filter • Activated sludge
Methods of Disposal • Disposal on land • Drying on drying beds • Dumping into the sea • Heat-drying • Incineration • Lagooning or ponding • Sludge Digestion
Sludge Digestion • It transforms a portion of solids into liquids and gases, thereby reducing the sludge volume to be dealt with • It breaks the organic matter of sludge into simpler compounds by the action of anaerobic bacteria.

More Related Content

Waste Water Treatment Secondary treatment (activated sludge, filtration).ppt

  • 2. Outline • Objectives • Outline of treatment process (flow diagram) • Preliminary treatment • Primary treatment (sedimentation) • Secondary treatment (activated sludge, filtration) • Sludge treatment • Disinfection • Tertiary treatment
  • 3. Objective of Sewage Treatment  To prevent pollution of the receiving water  To prevent offensive odour in the water  To prevent the destruction aquatic life  If the sewage has to be disposed of on land, the soil will become sewage sick after some time and cannot take any more sewage
  • 4. Outline of Sewage Treatment  Preliminary treatment  Primary treatment  Secondary treatment  Disinfecting  Tertiary Treatment
  • 5. Preliminary Treatment • Waster water contains floating suspended solids such as rags, wood, metal, plastic, etc. • these suspended impurities have to be removed as they interfere with the treatment processes or mechanical equipment.
  • 6. Primary Treatment • consists of mainly the sedimentation process to remove suspended organic solids • Chemicals are sometimes added in primary clarifier to assist in the removal of finely divided and colloidal solids or to precipitate phosphorous
  • 7. Secondary or Biological Treatment • Activated sludge process • Filtration
  • 8. Activated sludge process • the sewage is biologically treated.
  • 9. Filtration • is done in contact beds or intermittent sand filters or tricking filters. • It removes finely divided suspended matter.
  • 10. Sludge & Effluent • The semi-solid that settles down at the bottom after treatment,is called sludge • liquid to be discharged is called effluent.
  • 11. Disinfecting • Disinfecting is carried out if necessary by chlorination to kill the bacteria which remain in the effluent of sewage
  • 12. Tertiary Treatment • If the receiving water provides only little dilution or there is a need to preserve a particularly high quality of effluent, tertiary treatment can be used.
  • 14. Objectives Remove coarse suspended and floating matter such as rags, plastic, pieces of wood, etc., by means of screening Remove grit, sand, broken glass, etc., in grit chambers Remove grease, and oil substances by floatation in skimming tanks
  • 15. Processes Screening Silt and grit removal Oil and grease removal
  • 17. PRIMARY TREATMENT Primary sedimentation tank (Secondary sedimentation tank) - sedimentation after activated sludge process
  • 18. Advantages • The advantages of coagulation over plain sedimentation are: Sedimentation by coagulation is more effective BOD, colour and turbidity are reduced Less capacity of sedimentation tanks The process is simple
  • 19. Disadvantages • The disadvantages are: Chemicals destroy the bacteria that digest the sludge Chemicals increase the cost of sedimentation Skilled supervision is required Large quantity of sludge is produced
  • 21. SECONDARY TREATMENT • The secondary treatment converts the remaining organic matter into stable form by putting aerobic and anaerobic bacteria into action
  • 23. Filtration • Aerobic bacteria need a contact surface to live and carry out their activities
  • 24. Filtration Contact beds Intermittent sand filters Trickling filters
  • 25. Contact Beds • A contact bed consists of filtering medium. • When the sewage is passed over the medium, a thin film is produced around the particles. • The bacteria present in the film oxidise the organic matter.
  • 26. Intermittent Sand Filter • the filtering medium consists of sand. • The action of the filter is due to: Mechanical straining and – Bacterial action
  • 27. Trickling Filters • A trickling filter is an artificial bed of stone or broken brick material • waste water is distributed an applied in drops, films or spray • A zoogleal film is formed on the surface media.
  • 28. ACTIVATED SLUDGE PROCESS • is a biological sewage treatment process • a mixture of sewage and activated sludge is agitated and aerated. • The activated sludge is subsequently separated from the treated sewage by sedimentation
  • 29. What is ACTIVATED SLUDGE • is that sludge which settles down after the sewage has been freely aerated and agitated for a certain time.
  • 30. How Activated Sludge works • Activated sludge contains numerous bacteria and other microorganisms. When it is mixed with raw sewage saturated with oxygen, the bacteria perform: – Oxidise the organic solids Promote coagulation and flocculation and convert the colloidal and suspended solids into settable solids
  • 31. Steps in Activated Sludge process • Treat raw sewage in the primary settling tank • mix sewage with the activated sludge and aerated for 4-10 hours • final (secondary) settling tank • dispose of effluent • return some sludge to the aeration tanks • dispose of the rest of the sludge
  • 32. Advantages • Gives clear sparkling treated effluent • Effluent free from offensive odour • Degree of purity can be varied as desired • Cost of installation lesser than for a trickling filter • Small loss of head in the process
  • 33. Disadvantages Skilled supervision and constant check on the return sludge is necessary When there is change in the quality or quantity of sewage, the process is upset The process does not work for some industrial wastes Large volume of sludge increases difficulty in disposal
  • 34. Methods of Aeration • The success of the activated sludge process depends on the aeration provided. Diffused air aeration Mechanical aeration Combination of the above two methods
  • 36. TERTIARY TREATMENT • MICROSTRAINERS • RAPID GRAVITY SAND FILTERS • UPWARD-FLOW “MEDUIM” SAND FILTERS • SLOW SAND FILTERS • PEBBLE-BED CLARIFIERS • SETTLEMENT • GRASS PLOTS • LAGOONS
  • 38. Sludge • Sludge is a semi-liquid • Sludge produced by plain sedimentation • Sludge produced by chemical precipitation • Trickling filter • Activated sludge
  • 39. Methods of Disposal • Disposal on land • Drying on drying beds • Dumping into the sea • Heat-drying • Incineration • Lagooning or ponding • Sludge Digestion
  • 40. Sludge Digestion • It transforms a portion of solids into liquids and gases, thereby reducing the sludge volume to be dealt with • It breaks the organic matter of sludge into simpler compounds by the action of anaerobic bacteria.