The document provides an in-depth overview of wastewater treatment processes, particularly focusing on biological treatment systems like trickling filters and their components. It categorizes microorganisms based on their nutritional, energy, temperature, and oxygen requirements, and discusses the mechanics and design considerations of trickling filters along with their advantages and disadvantages. Key parameters for optimal filter operation, including loading rates and material properties, are also detailed.

1. Environmental EngineeringEnvironmental EngineeringEnvironmental EngineeringEnvironmental Engineering----IIIIIIII

2. General overview of plant components
Clarifier
Raw Wastewater Influent
PRIMARY
SECONDARY
Preliminary Residuals
(i.e., grit, rags, etc.)
AAAA
PRELIMINARY
Clarifier
Secondary Sludge
Primary Sludge
DISINFECTION
Biological
Treatment
System
SECONDARY
Clean Wastewater Effluent
Discharge to Receiving Waters
BBBB
CCCC
Wastewater
Treatment
Residuals
Biosolids
Processing
and Disposal
(e.g., attached-grwoth
Suspended-Growth,
Constructed Wetland, etc.)
Clarifier
Usually to Landfill

3. Used To remove the suspended solids
& the dissolved organic load from the
WW by using microbial populations.
The microorganisms are responsible
forfor
◦ degradation of the organic matter

4. Nutritional RequirementsNutritional RequirementsNutritional RequirementsNutritional Requirements: On the
basis of chemical form of carbon
required, microorganisms are
classified as
◦ Autotrophic:Autotrophic:Autotrophic:Autotrophic: organisms that use CO or◦ Autotrophic:Autotrophic:Autotrophic:Autotrophic: organisms that use CO2 or
HCO3
- as their sole source of carbon.
◦ Heterotrophic:Heterotrophic:Heterotrophic:Heterotrophic: organisms that use carbon
from organic compounds.

5. Energy RequirementsEnergy RequirementsEnergy RequirementsEnergy Requirements::::
On the basis of energy source
required, microorganisms are
classified as
◦ PhototrophsPhototrophsPhototrophsPhototrophs:::: organisms that use light as
their energy source.
ChemotrophsChemotrophsChemotrophsChemotrophs:::: organisms that employ
their energy source.
◦ ChemotrophsChemotrophsChemotrophsChemotrophs:::: organisms that employ
oxidation-reduction reactions to provide
energy.

6. Temperature Range:
On the basis of temperature range
within which they can proliferate,
microorganisms are classified as
◦ PsychrophilicPsychrophilicPsychrophilicPsychrophilic:::: organisms whose growth is
optimum within 15 to 30°C.
◦ MesophilicMesophilicMesophilicMesophilic:::: organisms whose growth is
optimum within 15 to 30°C.
◦ MesophilicMesophilicMesophilicMesophilic:::: organisms whose growth is
optimum within 30 to 45°C.
◦ ThermophilicThermophilicThermophilicThermophilic:::: organisms whose growth is
optimum within 45 to 70°C.

7. Oxygen RequirementsOxygen RequirementsOxygen RequirementsOxygen Requirements::::
On the basis of oxygen requirement
microorganisms are classified as
◦ Aerobes:Aerobes:Aerobes:Aerobes: organisms that use molecular
oxygen (usually DO) for their metabolism.
◦ Anaerobes:Anaerobes:Anaerobes:Anaerobes: organisms that use some
molecule other than molecular oxygen formolecule other than molecular oxygen for
their metabolism
◦ Facultative organismsFacultative organismsFacultative organismsFacultative organisms :::: organisms that
can use either molecular oxygen or some
other chemical compound for their
metabolism.

8. If the micro-organisms are suspended in
the WW during biological operation then
process is known as suspended growth
processes
Examples :- Activated Sludge process,Examples :- Activated Sludge process,
Aerated lagoons
Recycling of settled biomass i.e.
sludge is required.

9. Process in which the micro-organisms
that are attached to a surface over which
they grow is known as attached growth
processes
Examples:Examples:Examples:Examples:---- trickling filterExamples:Examples:Examples:Examples:---- trickling filter
Rotating biological contactors (RBC)
The biomass attached to media (ex.
rock, plastic, wood)
Recycling of settled biomass i.e. sludge
is not required, but recycling of sewage
may be done.

10. These consists of both attached growth as
well as suspended growth processes.
Examples:Examples:Examples:Examples: ----TF and ASPTF and ASPTF and ASPTF and ASP
ASP and TFASP and TFASP and TFASP and TF
Faccultative lagoonsFaccultative lagoonsFaccultative lagoonsFaccultative lagoonsFaccultative lagoonsFaccultative lagoonsFaccultative lagoonsFaccultative lagoons

12. Trickling
filter
process

14. Trickling
filter
process

15. As wastewater trickles through the
media layer a film is formed around
the media, called slime layer or Biofilm
Depth of aerobic zone within slime
layer, formed on media is 0.1 to 0.2
mm.
The remaining part of film isThe remaining part of film is
anaerobic.
As wastewater flows over the film, the
organic matter is rapidly metabolised
while colloidal organics are adsorbed
onto the surface.

16. Since food concentration at the outer
edge is more, therefore
microorganisms at outer level are in
rapid growth phase.
As microorganisms grow thickness of
biofilm increases.
Diffused oxygen is consumed before
biofilm increases.
Diffused oxygen is consumed before
it penetrates the slime layer.
Therefore anaerobic zone is
established at the media surface.

17. When microorganisms enter into
death phase they loose their ability
to hold the surface, and gets
detached from the surface
The phenomena of scouring of slime
layer is known as roughing orroughing orroughing orroughing or
unloading of filterunloading of filterunloading of filterunloading of filter
layer is known as roughing orroughing orroughing orroughing or
unloading of filterunloading of filterunloading of filterunloading of filter

18. Types of Filters
Trickling filters are classified based
on the organic and hydraulic
loading applied to the unit.
Low rate trickling filter or standardLow rate trickling filter or standardLow rate trickling filter or standardLow rate trickling filter or standard1.1.1.1. Low rate trickling filter or standardLow rate trickling filter or standardLow rate trickling filter or standardLow rate trickling filter or standard
raterateraterate
2.2.2.2. High rate trickling filterHigh rate trickling filterHigh rate trickling filterHigh rate trickling filter

19. S.NoS.NoS.NoS.No....
DesignDesignDesignDesign
FeatureFeatureFeatureFeature
Low RateLow RateLow RateLow Rate
FilterFilterFilterFilter
High Rate FilterHigh Rate FilterHigh Rate FilterHigh Rate Filter
1.1.1.1.
HydraulicHydraulicHydraulicHydraulic
loading,loading,loading,loading,
mmmm3333/m/m/m/m2222.d.d.d.d
1111 ---- 4444 10101010 ---- 30303030
2.2.2.2.
OrganicOrganicOrganicOrganic
loading,kgloading,kgloading,kgloading,kg
0.080.080.080.08 ----
0.320.320.320.32
0.50.50.50.5 ---- 1.01.01.01.02.2.2.2. loading,kgloading,kgloading,kgloading,kg
BOD / mBOD / mBOD / mBOD / m3333.d.d.d.d
0.320.320.320.32
0.50.50.50.5 ---- 1.01.01.01.0
3.3.3.3. Depth, m.Depth, m.Depth, m.Depth, m. 1.81.81.81.8 ---- 3.03.03.03.0 1.31.31.31.3 –––– 1.81.81.81.8
4.4.4.4.
RecirculationRecirculationRecirculationRecirculation
ratioratioratioratio
0000
0.50.50.50.5 ---- 3.0 (domestic3.0 (domestic3.0 (domestic3.0 (domestic
wastewater)wastewater)wastewater)wastewater) up toup toup toup to
8 for strong8 for strong8 for strong8 for strong
industrialindustrialindustrialindustrial
wastewater.wastewater.wastewater.wastewater.

20. rotating distributor arms
Packing
media
Wastewater
media
Underdrain

24. ◦TF consists of mainly following
parts/components:
A rotating armA rotating armA rotating armA rotating arm that sprays
wastewater over a filter medium.
Filter mediumFilter mediumFilter mediumFilter medium: rocks, plastic, or
other material.
◦ Under drainage system:Under drainage system:Under drainage system:Under drainage system: The water is
other material.
◦ Under drainage system:Under drainage system:Under drainage system:Under drainage system: The water is
collected at the bottom of the filter
for further treatment.

26. Filter media should have
- High specific surface area
- High percent void space
- Resistance to abrasion or disintegration
during placementduring placement
- Insolubility in sewage or wastewater and
- Resistance to spalling or flaking
Should be round or cubical in shape
Size 25 to 75 mm

27. PropertyPropertyPropertyProperty Desired valueDesired valueDesired valueDesired value
1. Crushing
strength
Not less than 100
N/mm2strength N/mm2
2. Hardness Not less than 12
3. Percent wear Not more than 4
4. Specific gravity Not less than 2.6

28. Crushed rock
◦ Durable & insoluble
◦ Locally available
◦ But, reduce the void spaces for passage
of air
◦ Less surface area per volume for
biological growthbiological growth
Plastic media
◦ Random packing media
◦ Modular packing media

29. Cross-flow
Tubular
Pall rings

30. Concentration of organics in sewage
decreases as the waste passes the
media depth.
Thus effectiveness of the filter
decreases as the depth increases.decreases as the depth increases.
Hence depth of filter should be
restricted
For slow rate depth in the range of 1.8
to 3.0 m is provided.
Depth of media is 1.8 to 2.4m

33. Perforated blocks are used. Can be
made of precast concrete or vitrified
clay.
Drains shall be designed for partial
flow condition (Less than 50% of flow).
Velocity of flow should not be less
than 0.75 m/s at peak instantaneous
Velocity of flow should not be less
than 0.75 m/s at peak instantaneous
flows.
At design flows velocity should be 0.6
to 0.9 m/s.

34. Function is twofold to circulate the air
and
It collects sewage from all under
drains and conveys it to next unit.
Velocity shall not be less than 0.6
drains and conveys it to next unit.
Velocity shall not be less than 0.6
m/s.
Slope is provided so that sewage can
be carried under gravity

35. Floor should be strong enough to
support media.
RCC slab of 10 to 15 cm thick is
usually provided to carry load ofusually provided to carry load of
entire media.
Usually 1 % slope is provided.

36. Fully plastered stone or brick masonry
walls
Walls are made honeycombed to
circulate the air.circulate the air.
Some times ventilation duct is
provided

37. Natural ventilation takes place
because of difference in temperature
of air and sewage.
Air circulation takes place when
temperature difference is 60C.temperature difference is 60C.
When temperature difference falls
below 1.90C then there will be no air
circulation.
Some times forced ventilation is also
provided

38. The function of rotary distributor is to
spread the sewage uniformly over the
media top surface.
Rate of rotation may be 2 rpm for small
distributors and 1/3 to ½ for largedistributors and 1/3 to ½ for large
distributor.
Clearance between pipe and media should
be 15 t o25 cm.

42. DesignDesignDesignDesignDesignDesignDesignDesign

43. 1.1.1.1. Hydraulic LoadingHydraulic LoadingHydraulic LoadingHydraulic Loading
It is ratio of discharge or flow rate to the
surface area
UnitsUnitsUnitsUnits –––– million lit/ha/day
2. Organic Loading2. Organic Loading2. Organic Loading2. Organic Loading
It is ratio of BOD load to volume of filter
2. Organic Loading2. Organic Loading2. Organic Loading2. Organic Loading
It is ratio of BOD load to volume of filter
media.
Organic loading = (Q x BOD5)/V
Therefore , V = BODV = BODV = BODV = BOD5555 x Q/ Organic loadingx Q/ Organic loadingx Q/ Organic loadingx Q/ Organic loading
UnitsUnitsUnitsUnits---- Kg or gm. of BOD/ m3 of volume/d

45. BOD removal efficiency of HRTF is 90%

47. 1. Effluent obtained from SRTF is highly
nitrified and stabilised.
2. It produces desired quality of effluent
under varying weather conditions.
3. They can remove 80% of solids and80% of solids and80% of solids and80% of solids and3. They can remove 80% of solids and80% of solids and80% of solids and80% of solids and
75 to 80% of BOD75 to 80% of BOD75 to 80% of BOD75 to 80% of BOD
4. Working is simple and cheap and
does not require any supervision.

48. 5.They are self cleansing.
6. As it contains less mechanical
equipments , wear and tear is
small.
7. Electrical power requirement is
less.less.
8. Moisture content of sludge
coming out of TF is very high

49. 1. High head loss.
2. The cost of construction is high
3. Large area is required3. Large area is required
4. PST is must before SRTF (It can
remove 30 to 40% of BOD load).
5. Odour and fly nuisance.

50. 1. Trickling filter is _________________
type of process
2. Detaching of the biofilm from media
is known as ________________.
Dissolved organic load can be
is known as ________________.
3. Dissolved organic load can be
removed by using
___________________ treatment.
4. Unloading of trickling filter starts
when microorganism enter in
_____________ phase.

51. 5. Hydraulic loading rate for low rate TF is
_______ m3/m2/d. (0.5 to 2/1 to 4/ 2 to 5/
5 to 8)
6. Organic loading rate for high rate TF is
_______ gm of BOD /m3/d. (100-400/400-
600/ 500 – 1000/ 1000- 2000)

52. Q1. Give classification of
microorganisms.
Q2. Draw neat sketch of Trickling filter.
Q3. Draw sketch of trickling filter and
explain it w. r. t.explain it w. r. t.
i. Filter media
ii. Under drainage system and
iii. Distributor
Q4. Explain ‘biological process in
trickling filter’ with neat diagram.

53. Q5. Explain working of trickling filter with
neat sketch.(8 marks, May2011, May
2009).
Q6. Write short notes
i. Types of trickling filter (6 marks,
may2009)