Sludge Treatment

1. Unit-v
SLUDGE
TREATMENT
AND
DISPOSAL

2. SLUDGE
• Sludge is an odious, semisolid residual that resembles
thick soft mud produced from the solid–liquid
separation processes in wastewater treatment.
• It is usually very inconsistent in its composition and
most often unmanageable.
• The final destination of treated sewage sludge usually
is the land.
• Dewatered sludge can be buried underground in a
sanitary landfill.
• It also may be spread on agricultural land in order to
make use of its value as a soil conditioner and fertilizer.

3. OBJECTIVES OF THE SLUDGE
TREATMENT
• To decrease moisture content in the sludge
(Volume reduction)
• To remove organic matters
• To destroy microorganisms
• To eliminate toxic materials..

4. SLUDGE DISPOSAL METHOD
Pre-treatment

5. Primary sludge
• Primary sludge is produced following primary
treatment.
• This step consists of physical or chemical
treatments to remove matter in suspension
(e.g. solids, grease and scum).
• The most common physical treatment is
sedimentation.
• Sedimentation is the removal of suspended
solids from liquids by gravitational settling.
SLUDGE DISPOSAL METHOD

6. Primary sludge
• Chemical treatments are coagulation and
flocculation.
• Coagulation is the addition and rapid mixing
of a coagulant to neutralize charges and
collapse the colloidal particles so they can
agglomerate and settle.
• The flocculation is the agglomeration of the
colloidal particles that have been subjected to
coagulation treatment.
SLUDGE DISPOSAL METHOD

7. Secondary sludge
• Secondary sludge is generated from the use of
specially provided decomposers to break down
remaining organic materials in wastewater after
primary treatment.
• The active agents in these systems are micro-
organisms, mostly bacteria, which need the
available organic matter to grow.
• There are various techniques such as lagooning,
bacterial beds, activated sludge as well as
filtration or biofiltration processes.
SLUDGE DISPOSAL METHOD

8. Tertiary sludge
• Tertiary sludge is generated when carrying out
tertiary treatment.
• It is an additional process to secondary
treatment and is designed to remove
remaining unwanted nutrients (mainly
nitrogen and phosphorus) through high
performance bacterial or chemical processes.
SLUDGE DISPOSAL METHOD

9. Screening
• Screening grinders are beneficial for medium-
size plants.
• Reduced-size solids are returned to raw
sewage or mixed with sewage sludge
depending on grinder location related to the
treatment units
• It contains both organic and inorganic matter.
SLUDGE CHARACTERISTICS

10. Grit
• Final grit disposal is by burial.
• It may be in either a sanitary landfill or other
accepted landfill operation.
• The grit must be having a minimum of 6
inches (15 cm) of soil covering.
• This is to prevent vector attraction and odors.
• It involves organic and inorganic matter,
especially fats and grease..
SLUDGE CHARACTERISTICS

11. Scum/Grease
• It consists of the floatable materials, oil and grease,
animal fats, food wastes, vegetable and fruit skins,
paper and cotton, cigarette tips, and plastic materials.
Sludge from chemical
• Industrial wastewater treatment plants produce solids
that are also referred to as sludge.
• This can be generated from biological or physical-
chemical processes.
• In the activated sludge process for wastewater
treatment, the terms "waste activated sludge“ and
"return activated sludge" are used.
• It contains much iron
SLUDGE CHARACTERISTICS

12. Scum/Grease
• It consists of the floatable materials, oil and grease,
animal fats, food wastes, vegetable and fruit skins,
paper and cotton, cigarette tips, and plastic materials.
Sludge from chemical
• Industrial wastewater treatment plants produce solids
that are also referred to as sludge.
• This can be generated from biological or physical-
chemical processes.
• In the activated sludge process for wastewater
treatment, the terms "waste activated sludge“ and
"return activated sludge" are used.
• It contains much iron
SLUDGE CHARACTERISTICS

13. Scum/Grease
• It consists of the floatable materials, oil and grease,
animal fats, food wastes, vegetable and fruit skins,
paper and cotton, cigarette tips, and plastic materials.
Sludge from chemical
• Industrial wastewater treatment plants produce solids
that are also referred to as sludge.
• This can be generated from biological or physical-
chemical processes.
• In the activated sludge process for wastewater
treatment, the terms "waste activated sludge“ and
"return activated sludge" are used.
• It contains much iron
SLUDGE CHARACTERISTICS

14. • Aerobic Digestion Works
• Aerobic digestion is the degradation of the organic sludge
solids in the presence of oxygen.
• The oxygen is introduced as fine bubbles of air into the
reactor.
• The microorganisms in the sludge convert the organic material
to carbon dioxide and water, and the ammonia and amino
species to nitrate.
METHODS OF SLUDGE TREATMENT

15. METHODS OF SLUDGE TREATMENT

16. THICKENING
Gravity thickening
• Gravity thickening is a widespread technique,
performed in tanks usually fitted with a rotating
ploughing system.
• The gravitational forces bring the thickened
sludge at the base of the tank from where it is
extracted.
• Gravity thickening is the process by which bio-
solids are condensed to produce a concentrated
solids product and a relatively solids-free
supernatant.

17. Gravity thickening

18. Gravity thickening
Advantages
• Gravity thickening equipment is simple to operate and
maintain.
• Gravity thickening has lower operating costs than other
thickening methods such as DAF, gravity belt or
centrifuge thickening.
• Truck traffic at the plant and the farm site can be
reduced;
• Trucking costs can be reduced;
• Existing storage facilities can hold more days of
biosolids production;

19. Gravity thickening
Disadvantages
• Scum build-up can cause odors. This buildup, which can
occur because of long retention times, can also
increase the torque required in the thickener. Finally,
scum build-up is unsightly.
• Grease may build up in the lines and cause a blockage.
This can be prevented by quick disposal or a back flush.
• Septic conditions will generate sulfur-based odors. This
can be mitigated by minimizing detention times in the
collection system and at the plant, or by using oxidizing
agents.

20. Gravity thickening
Disadvantages
• Scum build-up can cause odors. This buildup, which can
occur because of long retention times, can also
increase the torque required in the thickener. Finally,
scum build-up is unsightly.
• Grease may build up in the lines and cause a blockage.
This can be prevented by quick disposal or a back flush.
• Septic conditions will generate sulfur-based odors. This
can be mitigated by minimizing detention times in the
collection system and at the plant, or by using oxidizing
agents.

21. Rotary drum filtering
• Rotary drum thickening increases the sludge solids
concentration (i.e. Thickens the sludge) by agitating the
solids in a slowly-rotating vessel with porous walls though
which the water (or filtrate) drains the sample of rotary
drum filtering for sludge disposal.
• A rotary drum thickener (RDT) is based on the same
principle as a gravity belt thickener (GBT), in that water
drains from the sludge through a retaining porous medium.
• For an RDT the porous medium is the cylindrical wall of a
0.5−1.5 m diameter drum which rotates at speeds between
5 and 20 RPM while the sludge continually passes through
it.

22. Rotary drum filtering

23. Rotary drum filtering
Applications
• The rotary filter is most suitable for continuous operation on large
quantities of slurry.
• If the slurry contains considerable amount of solids, that is, in the range of
15-30%.
Advantages
• The rotary vacuum drum filter is a continuous and automatic operation, so
the operating cost is low.
• The variation of the drum speed rotating can be used to control the cake
thickness.
Disadvantages
• Due to the structure, the pressure difference is theoretically limited to
atmospheric pressure (1 bar), and in practice somewhat lower.
• Besides the drum, other accessories, for example, agitators and vacuum
pump,vacuum receivers, slurry pumps are required.

24. Gravity Belt Thickening
• Gravity belt thickening (GBT) increases the sludge solids
concentration (i.e. thickens the sludge) by allowing the water
(or filtrate) to drain from the sludge under gravity through a
permeable medium (a moving belt) on which the sludge sits.
• Gravity thickening is the process by which biosolids are
condensed to produce a concentrated solids product and a
relatively solids-free supernatant.
• The bio solids technology fact sheet for gravity thickening
provides: A description of gravity thickening.
• Applicability to wastewater treatment plants.
• There are two types of belt-based processes for increasing
sludge solids concentration. GBT is a low-pressure process
which operates by allowing the water to drain from the sludge
under gravity.

25. Gravity Belt Thickening

26. Centrifugation

27. VACUUM FILTER

28. BELT PRESSURE FILTER

29. PRESSURE FILTERS

30. PRESSURE FILTERS

31. SLUDGE SAND DRYING BED FILTER

32. FACTOR AFFECTING DEWATERING
PERFORMANCE
Under land disposal the following methods may be included
• Burial
• Fill
• Application as fertilizer or soil conditioner

33. INCINERATION
• Incineration − or combustion of sewage sludge is the most widely-accepted
alternative end disposal method after land spreading.
• It is an oxidative method, converting the organic carbon, nitrogen, sulphur, nitrogen
and phosphorus into gaseous and predominantly mineral (i.e. inorganic) solid
products.

34. INCINERATION

35. Incineration of Sewage Sludge in
Coal-Fired Power Plants