The document discusses sludge treatment and disposal methods in wastewater treatment. It describes how sludge is produced from primary and secondary treatment and its characteristics. Key steps in sludge treatment include thickening to increase solid concentration, digestion to reduce volume and pathogens, and final disposal through incineration, landfilling, or use as fertilizer. Anaerobic digestion is most common and converts sludge into gases and residual biomass through acid-forming and methane-forming bacteria. Aerobic digestion is an alternative but is more energy intensive.

1. SLUDGE TREATMENT AND DISPOSAL
 Presented to :-
Dr. Baljinder kaur
 Presented by :- sudha chib
Roll no :- 130181107

2. CONTENTS
 SLUDGE CHARACTERISTICS
 SLUDGE THICKENING
 SLUDGE DIGESTION
 SLUDGE DISPOSAL

3. SLUDGE
 Sludge is the concentrated impurities of waste water
into solid form

4. Secondary
Wastewater
Organic
Inorganic
Pre
Treatment
Rock
Grit
Plastic
Etc.
Settleable
Suspended
Dissolved
Primary
Clarifier
Suspended
Dissolved
Effluent
Secondary
Clarifier

5. SLUDGE CHARACTERISTICS
 Primary settling remove the settleable fraction of raw
wastewater solids , the quantity of this solid on the
dry mass basis can be determined as:-
Mp = ᶓ *SS * Q
Where Mp= mass of primary solids;kg/d
ᶓ = efficiency of primary clarifier
SS=total suspended solids in effluent
Q = flow rate ; m3/d

6.  Secondary sludge is composed primarily of biological
solids , the quantity of which can be estimated by:-
Ms= Y × BOD 5× Q
Where Ms = mass of secondary solids , kg/d
Y = biomass conversion factor
BOD5 =BOD5 removed by secondary treatment
kg/m3
Q = flow rate , m3/d

7. CHARACTERISTICS
 Specific gravity :- sludge have specific gravity of 1.0
 Solid concentration:- it defines the relative fracction
of solids and liquids in a slurry and expressed as
mg/l

8. SLUDGE THICKENING
 Thickening is a procedure used to increase the solid
content of sludge by removing a portion of the liquid
fraction
 Thickening is generally acomplished by physical
means including gravity settling , flotation ,
centrifugation etc
 Location of the thickener in a wastewater treatment
plant is important.

9.  A thickener operates like a settling tank
 The feed enters from the middle , are distributed
radially
 The settled sludge is collected from the underflow
 The effluent exits over the weirs
 The thickening process takes place in settling tank
with long enough solids retention time

10. GRAVITY THICKENER

11.  Gravity thickeners contain pickets on the scraper
cause a horizontal agitation .
 It helps to release water trapped in the flocculent
structure of the sludge
 These are commonly used when suspended culture
system sludges are to be thickened
 These thickeners have ability to double the solid
content of the sludge

13. SLUDGE DIGESTION
 Sludge digestion serves both to reduce the volume of
the thickened sludge still further and to render the
remaining solids and relatively reduce pathogen
 These goals can be achieved by :-
Anaerobic digestion
Aerobic digestion

14. ANAEROBIC DIGESTION
 Anaerobic digestion is the most common method for
dealing with the waste water containing primary
sludge
 The principle function is to convert as much of the
sludge as possible to end products such as liquid and
gases
 Very less residual biomass as possible is produced

15.  The anaerobic sludge digestion often divides the
organisms into broad groups :-
 Acid formers
 Methane formers

16. ACID FORMERS
 The acid formers consist of facultative and anaerobic
bacteria and include organisms that solubilize the
organic solids through hydrolysis
 The soluble products are then fermented to acids and
alcohols of low molecular weight

17. METHANE FORMERS
 Methane formers consist of strict anaerobic bacteria
 Acids and alcohols along with hydrogen and carbon
dioxide are converted to methane

18. Pathway and products of anaerobic digestion

19.  Sludge is fed into the digestor on an intermittent
basis and supernatant is withdrawn and returned to
secondary treatment unit

20.  A typical standard rate anaerobic digester consisting
of a single – stage operation
 The conical bottom facilitates sludge withdrawal
 Floating cover accommodate volume change due to
sludge addition or withdrawl
 Sludge separates in the reactor
 Although some mixing occur in the zone of active
digestion and in the supernatant

21. HIGH RATE DIGESTERS
 These are more efficient
 Require less volume
 The contents are mechanicaly mixed to ensure better
contact between the organics and the
microorganisms
 Unit is heated to increase the metabolic rate of the
microorganisms
 Optimum tempurature is around 35̊ C

22.  Little gas is generated in the second stage
 But the second stage is covered and is equipped for
gas recovery
 The second stage reactor is not heated

24. ADVANTAGES
 Waste stabilisation
 Odour reduction
 Scalable technology
 Low capital cost
 Fuel based renewable/pack generation

25. DISADVANTAGES
 No useful byproduct
 Required expertise
 Affected by changes in loading and conditions

26. AEROBIC DIGESTION
 This process is essentially a continuation of the
aeration process , with the volume being reduced by
thickening in the secondary clarifier and sludge
thickener
 It is an endogenous respiration process

27. ADVANTAGES
 The process is easy to control
 It usually has lower ammonia concentration
 Explosive gases are not produced

28. DISADVANTAGES
 Aerobic digestion is energy consumptive
 Temperature dependent
 Aerobic digestion does not produce energy

29. SLUDGE DISPOSAL
 Several options are available for the ultimate
disposal of wastewater sludges, these include:-
 Incineration
 Placement in sanitary landfill
 Incorporation into as a fertilizer

30. INCINERATION
 Combustion process

31. PLACEMENT IN SANITARY LANDFILL
 Disposal in landfills

32. INCORPORATION INTO AS A FERTILIZER
 Injection of sludge into soil

33. REFERENCES
 Environmental engineering by Howard S .Peavy
 mimoza.marmara.edu.tr/~orhan.gokyay/enve425/ch2.p
df
 www.eea.europa.eu/publications/GH-10-97-106-
EN-C/download
 http://www.lenntech.com/library/sludge/drying/sludge
drying.htm
 www.maths.tcd.ie/~jlennon/miniprojects/biomass.doc
 http://www.wrights-trainingsite.com/aerodigestion.html