1. SANITARY ENGINEERING
PRESENTATION

2. THE GROUP MEMBERS ARE,
TESSY S ALEX (UR12CE115)
ANJALI KUMARI (UR12CE013)
SURENDAR N (UR12CE111)
SUJITH ALEN S (UR12CE110)
JAESON ANTONY A (UR12CE046)

3. TOPIC :
SLUDGE
TREATMENT

4. UNIT – IV Sewage Disposal and Sludge Management
Methods of sewage disposal, sewage farming
Sewage sickness and its preventive measures
Final products in Sludge Digester : stages
Factors affecting sludge digestion and control
Design of sludge digestion tank
Sludge thickening
Sludge conditioning and dewatering
Final disposal of digested sludge
Bioremediation: constructed wetlands, stabilization pond
Self purification and oxygen sag curve

5. INTRODUCTION

6. Secondary
Organic
Inorganic
Wastewater Pre
Treatment
Rock
Grit
Plastic
Etc.
Primary
Sedimentation
Tank
Settleable
Suspended
Dissolved
Suspended
Dissolved
Secondary
Sedimentation
Tank
Effluent
Digester
Gas
Digested Sludge
Recycled Water
(Supernatant)
(Stabilized)

7. Pre treatment
• Screening-for removal of objects
Eg: wood logs ,cloths, chappals
etc….
• Grit Chamber
For removing high density inorganic
particles by discrete settling
principle
Eg: Removal of sand, silt etc….
• Primary settling tank
For removal of low density organic
solids

8. Post treatment
• Secondary settling tank-for biomass
settling.
• Sludge from primary and secondary
settling tanks is sent to sludge
treatment unit.

9. WHAT IS SLUDGE ?

10. SLUDGE IS THICK
MUD , SEWAGE
OR INDUSTRIAL
WASTE .

11. SLUDGE
The SETTLEABLE solids
separated from liquids
During processing.

12. FROM WHERE THE
SLUDGE IS
COLLECTED?

13. FROM PRIMARY
AND SECONDARY
SEDIMENTATIO
N TANK .

14. WHY DO WE TREAT
SLUDGE WHICH IS IN
SEDIMENTATION
TANK?

15. SLUDGE DISPOSED BARELY
DECOMPOSITION OF ORGANIC
MATTER
FOUL SMELL
ENVIRONMENTAL POLLUTION

16. HOW TO STABILIZE
SLUDGE?

17. [ ODOURLESS , DISPOSABLE IN NATURE WITHOUT POLLUTING OR
HARMING ]
SLUDGE IS STABILISED BY
DECOMPOSING THE ORGANIC
MATTER UNDER CONTROLLED
ANAEROBIC CONDITION.
[The decomposition of organic and inorganic matter in the
absence of molecular oxygen.]

18. WHAT IS KNOWN
AS SLUDGE
DIGESTION?

19. THE PROCESS OF
STABILISATION
OF SLUDGE IS
CALLED THE
SLUDGE
DIGESTION.

20. THE MAIN TOPICS TO BE DISCUSSED IN THIS
PRESENTATION ARE,
(A) FINAL PRODUCTS IN SLUDGE
DIGESTER.
(B) STAGES IN SLUDGE DIGESTION
PROCESS.
&
(C) FACTORS AFFECTING SLUDGE
DIGESTION AND THEIR CONTROL.

21. (A) FINAL
PRODUCTS IN
SLUDGE DIGESTOR
!

23. AS DAYS PASS SLUDGE BREAKS INTO
3 COMPONENTS.
STABILISED SLUDGE/
DIGESTED SLUDGE/
RIPENED SLUDGE
SLUDGE BREAKS 2.SUPERNATANT LIQUOR
3. DECOMPOSITION OF GASES
1.

24. BRIEF EXPLANATION OF
FINAL PRODUCTS IN
SLUDGE DIGESTER

25. 1. DIGESTED SLUDGE
• HUMUS LIKE SOLID MATTER.
• TARY BLACK IN COLOR.
• REDUCED MOISTURE CONTENT.
• QUALITY IS MUCH BETTER THAN UNDIGESTED
SLUDGE.
• FREE OF PATHOGENIC BACTERIA.

26. 2 . SUPERNATANT LIQUOR
• LIQUIFIED AND FINELY DIVIDED SOLID
MATTER.
• HIGH BOD (3000 ppm).

27. 3. DECOMPOSITION OF
GASES
• METHANE (65 – 75%)
• CARBON DIOXIDE (30%)
• NITROGEN
• HYDROGEN SULPHIDE.

28. HOW THESE
COMPONENTS CAN BE
SEPARATE FROM
SLUDGE DIGESTER?

30. WHAT ARE THE USES OF
THESE COMPONENTS ?
1.DIGESTED SLUDGE
DEWATERED
DRIED UP
FERTILIZER

31. 2.SUPERNATANT LIQUOR
1500 – 3000 ppm OF SUSPENDED
SOLIDS
RETREAT ALONG WITH RAW
SEWAGE

32. 3.DECOMPOSITION OF GAS
METHANE
FUEL

33. (B) STAGES IN THE
SLUDGE DIGESTION
PROCESS

34. STAGES
1. ACID FERMENTATION/ACID PRODUCTION STAGE
2.ACID REGRESSION
3. ALKALINE FERMENTATION
STABILISED SLUDGE /DIGESTED SLUDGERIPENED SLUDGE
+ SUPERNATANT LIQUOR + METHANE GAS

35. 1 . ACID FERMENTATION /
ACID PRODUCTION STAGE
FRESH SEWAGE SLUDGE
ANAEROBIC
+
FACULTATIVE BACTERIA
𝐻2
𝑂
HYDROLYSIS
SOLUBLE PRODUCTS
FERMENT
VOLATILE ACIDS ORGANIC ALCOHOLS OF LOW MOLECULAR
WEIGHT LIKE PROPIONIC
ACID AND ACETIC ACID
ACID FORMERS /
ACIDOGENS
GASES LIKE 𝑪𝑯 𝟒 , 𝑪𝑶 𝟐 & 𝑯 𝟐 𝑺 𝑰𝑺 𝑬𝑽𝑶𝑳𝑽𝑬𝑫

36. • HIGHLY ACIDIC.
• PH < 6
• HIGHLY PUTREFACTIVE ODOURS ARE EVOLVED
FOR 15 DAYS.
• BOD IS INCREASED.

37. 2 . ACID REGRESSION
• INTERMEDIATE STAGE.
• VOLATILE ORGANIC ACIDS
+
NITROGENEOUS COMPOUNDS
(ATTACKED BY BACTERIA)
ACID CARBONATES + AMMONIA COMPOUNDS
+HYDROGEN SULPHIDE + CARBO DIOXIDE
FIRST STAGE

38. • HIGHLY OFFENSIVE ODOUR ARE EVOLVED FOR
3MONTHS.
• PH INCREASES TO ABOUT 6.8. HOW?
• DECOMPOSED SLUDGE ENTRAPS THE GASES
OF DECOMPOSITION. IT BECOMES FOAMY
AND RISES TO THE SURFACE TO FORM SCUM.
• BOD REMAIN HIGH.

39. 3. ALKALINE
FERMENTATION
• FINAL STAGE OF SLUDGE DIGESTION.
• PROTIENS
+
ORGANIC ACIDS
(ATTACKED BY
ANAEROBIC BACTERIA CALLED
METHANE FORMERS / STRICT ANAEROBER)
AMMONIA + ORGANIC ACIDS + GASES
HIGH RESISTANT MATERIALS

40. • THE LIQUID SEPARATES OUT FROM SOLIDS TO
FORM DIGESTED SLUDGE.
• THE SLUDGE IS GRANULAR AND STABLE .
• DOES NOT GIVE OFFENSIVE SMELL.
• IT HAS MUSTY EARTHY ODOUR.
• DIGESTED SLUDGE IS COLLECTED AT THE BOTTOM
OF THE DIGESTION TANK AND IS CALLED RIPENED
SLUDGE.

41. • IT IS ALKALINE IN NATURE.
• PH ≥ 7
• METHANE (60 % – 75%), 𝐶𝑂2 (30%), 𝑁2
• THIS STAGE EXTENTS TO A PERIOD OF 1 MONTH.
• BOD IS REDUCED.

42. CONCLUSION OF STAGES IN THE SLUDGE DIGESTION PROCESS
(NATURALLY)
• 4
1
2
MONTHS ARE REQUIRED FOR THE COMPLETE
PROCESS OF SLUDGE DIGESTION TO TAKE PLACE
UNDER NATURAL , UNCONTROLLED CONDITION AT
ABOUT 210
𝐶.
• DIGESTION DEPENDS ON MANY FACTORS LIKE
TEMPERATURE .
• IF THE FACTORS AFFECTING SLUDGE DIGESTION ARE
CONTROLLED , QUICKER AND EFFECTIVE DIGESTION
CAN BE DONE.

43. (C) FACTORS
AFFECTING
SLUDGE DIGESTION
AND THEIR
CONTROL

44. THE IMPORTANT FACTORS
AFFECTING SLUDGE
DIGESTION ARE ,
1 . TEMPERATURE
2 . PH VALUE
3 . SEEDING WITH DIGESTED SLUDGE AND
4 . MIXING AND STIRRING OF THE RAW SLUDGE
WITH DIGESTED SLUDGE.

45. THE MINOR FACTORS
ARE,
• QUALITY OF WATER SUPPLIED.
• PRESENCE OF –
COPPER,
FLUORIDES,
RADIO ACTIVE SUBSTANCES.

46. BRIEF EXPLANATION OF
MAJOR FACTORS

47. 1. TEMPERATURE
• HIGHER THE TEMPERATURE , HIGHER IS THE
RATE OF DIGESTION .
• THE 2 DISTINCT TEMPERATURE ZONES ARE,
- (a) ZONE OF THERMOPHILIC DIGESTION.
- (b) ZONE OF MESOPHILIC DIGESTION.

48. (a) ZONE OF THERMOPHILIC
DIGESTION
• THERMOPHILIC ORGANISMS MEAN HEAT LOVING
ORGANISMS.
• 400
𝐶 - 600
𝐶
• OPTIMUM THERMOPHILIC TEMPERATURE = 540
𝐶
• DIGESTION PERIOD – 10 TO 15 DAYS
• IT IS NOT PREFFERED BECAUSE OF ODOUR AND
OPERATIONAL DIFFICULTIES.

49. (b) ZONE OF MESOPHILIC
DIGESTION
• 250
𝐶 − 400
𝐶
• OPTIMUM MESOPHILIC TEMPERATURE = 290
𝐶
• DIGESTION PERIOD – 30 DAYS
• EXTERNAL HEATING DEVICES IS FIXED IN DIGESTION
TANK TO CONTROL TEMPERATURE.

50. CONTROLLED SLUDGE DIGESTOR

51. 2. PH VALUE
• VOLATILE ACIDS METHANE FORMERS METHANE GAS
• IF METHANE FORMERS WERE NOT PRESENT IN THE SLUDGE
DIGESTER ,PH VALUE WILL GO BELOW 5 . IT WILL INCREASE THE
ACIDITY, AND THUS SUPPRESS FURTHER BACTERIAL ACTION.
• IN INITIAL STAGE (ACID FERMENTATION/ACID PRODUCTION
STAGE) PH VALUE OF 6.5 HAVE TO BE MAINTAINED.
• SO THAT IN FINAL STAGE (ALKALINE FERMENTATION
STAGE) PH VALUE OF 7.2 – 7.4 WILL BE MAINTAINED.

52. • ACIDITY INCREASES DUE TO
- OVERDOSING OF RAW SLUDGE .
- OVERWITHDRAWAL OF DIGESTED SLUDGE.
• REMEDY
- ADD HYDRATED LIME (2.3- 4.5 𝐾𝐺
1000 𝑃𝐸𝑅𝑆𝑂𝑁) IN RAW SLUDGE.
• FOR THE MAINTENANCE OF OPTIMUM VALUE OF PH
- WEIGHT OF RAW SLUDGE TO BE ADDED SHOULD BE 2 - 3%
WEIGHT OF DIGESTED SLUDGE WHICH IS REMOVING FROM
THE SLUDGE DIGESTER.

53. SEEDING WITH THE
SLUDGE DIGESTER
WHAT IS SEEDING ?
*A SLUDGE DIGESTION TANK .
*WHEN FIRST PUT IN OPERATION –
*DIGESTED SLUDGE FROM OLD SLUDGE DIGESTER
IS KEPT IN IT FOR SOME DAYS .

54. DIGESTED
SLUDGE

55. • WITHOUT SEEDING , IT MAY TAKE A FEW
MONTHS TO GET A TANK TO OPERATE
PROPERLY.
• PROPER SEEDING CAN GIVE GOOD RESULTS
QUICKLY.

56. MIXING AND STIRRING OF
THE RAW SLUDGE WITH
THE DIGESTED SLUDGE
• RAW SLUDGE + DIGESTED SLUDGE
(MIX WELL)
HOMOGENEOUS MIXTURE
*HELPS IN DECOMPOSITION OF ORGANIC MATTER
QUICKLY.
*MIXING IS DONE IN SLUDGE DIGESTOR USING
AGITATOR / OTHER DEVICES.

57. *THIS REDUCES SCUM AND INCREASES THE
PRODUCTION OF GAS.
*EXCESSIVE STIRRING WILL KILL USEFUL
BACTERIAS.

58. CONCLUSIO
N

59. THANK YOU…