Lecture Notes of Environmental Engg-II as per solapur university syllabus of TE Civil, Prepared by Prof S S Jahagirdar, Associate Professor, N K Orchid college of Engg and Technology, Solapur

1. Unit‐ III
ENV ENGG – IIENV. ENGG. II
Prof S S JAHAGIRDAR
BE (CIVIL), ME(ENV.)PhD(persuing)g
NK Orchid college of Engg. and Tech. , Solapur

2. A] SLUDGE TREATMENT
Thickening
DigestionDigestion
Conditioning
Dewatering
DryingDrying
Disposal (Incineration)

3. 1. Thickning
Reduces moisture content of sludge
Th t f thi k iThree types of thickening
1. Gravity thickening1. Gravity thickening
2. Air floatation
3. Centrifugation

4. Gravity
ThickeningThickening

5. 2. Digestion
Aerobic or anaerobic decomposition
of sludgeof sludge
Can be sent to mechanical filters or
sand beds

6. 3. Conditioning
Conditioning improves the drainability of
digested sludge.
Methods adopted –
1. Elutriation (involves passage of air to ( p g
separate particles)
2. Chemical conditioning (addition of g (
coagulants)
3. Freezing etc.3 g

7. 4. Dewatering
Purpose is to reduce volume of sludge and
increase concentrations of biosolids.increase concentrations of biosolids.
Dewatering can be achieved on sand drying
b dbeds.

8. Sludge drying beds

9. 5. Heat drying
Reduces water content
T C Temp @ 350oC
Process carried out in kilnProcess carried out in kiln.
Dried sludge used as soil g
conditioner

10. Heat drying
unit

11. 6. Incineration
Combustion of sludge
Temp @ 650oC to 750oC
Residual ash is send to landfills

12. IncineratorIncinerator

13. B] Anaerobic Digestion
Consists of decomposition of
sludge from settling tankssludge from settling tanks.
Two types of digestersTwo types of digesters
i] Standard rate or conventional
Ii] High rate digester

14. The process of digestion
The process has now been described by the
following four steps: g p
Hydrolysis: large polymers are broken
d b down by enzymes.
Fermentation: Acidogenic
fermentations are most important,
acetate is the main end product. Volatile acetate is the main end product. Volatile
fatty acids are also produced along with
carbon dio ide and h drogen carbon dioxide and hydrogen.

15. Acetogenesis: Breakdown of Acetogenesis: Breakdown of
volatile acids to acetate and
hydrogen.
Methanogenesis: Acetate Methanogenesis: Acetate,
formaldehyde, hydrogen and
carbon dioxide are converted to
th d t methane and water.

18. Cross section of digester

19. Anaerobic Anaerobic
digesters

20. A bi Anaerobic
digester

21. Stratification in conventional digesterStratification in conventional digester

22. T t f di tTwo types of digesters

23. Two stage ‐ high rate digesterTwo stage ‐ high rate digester

24. Sludge drying Sludge drying
beds

25. Sludge drying
beds

26. C] DISPOSAL OF DIGESTED SLUDGE
Spreading on farm land
Dumping ( in abandoned quarries)Dumping ( in abandoned quarries)
Land filling ( Sanitary)
Sl d l iSludge lagooning
Compostingp g
Disposing in Inland water bodies or
Sea Sea.

27. Disposal on
l dland‐1

28. Disposal on
l dland‐2

29. Disposal in
ffarms

30. Disposal into the sea

31. Sludge
L iLagooning

32. Sludge lagoons

33. What is sludge digestion? Explain anaerobic digestion. (Nov 2010, 8
marks)
Write short note onWrite short note on
1. Anaerobic digestion process. (Nov 2009, 6 marks)
2. Sludge drying beds (May 2008, 6 marks)
Explain different methods of sludge disposal. (May 2009, 8
marks)
E l i l bi di i h k h (M 2008 6Explain low rate anaerobic digester with a neat sketch. (May 2008, 6
marks)
Enumerate the methods of sludge dewatering. Explain any one in detail.
(May 2008, 6
marks)
Describe anaerobic sludge digester with neat sketch. Also explain various stages ofDescribe anaerobic sludge digester with neat sketch. Also explain various stages of
anaerobic digestion of sludge. (May 2008, 8
marks)
St t bj ti f l d t t t E t th th d f l d di lState objectives of sludge treatment. Enumerate the methods of sludge disposal.
(May 2007,5 marks
)