2. what is waste water?
• Used water ……includes….
• Food scraps, oil and soaps.
• Human wastes.
• Industrial wastes.
3. • Sewage treatment is the process of
removing contaminants from municipal wastewater, containing
mainly household sewageplus some industrial wastewater.
• Physical, chemical, and biological processes are used to
remove contaminants and produce treated wastewater (or
treated effluent) that is safe enough for release into the
environment. A by-product of sewage treatment is a semi-solid
waste or slurry, called sewage sludge. The sludge has to
undergo further treatment before being suitable for disposal or
application to land.
4. Why treat wastewater?
• To remove pollutants from waste water for its
recycling.
• To promote health concern and public hygiene.
• To preserve aquatic life and wildlife habitat.
• To promote recreation and quality of life.
5. Steps involved in the process
1. Preliminary treatment -Removal of larger objects such
as leaf,timber etc..
2. Primary treatment - removal of fine suspended organic
solids
3. Secondary treatment- removes dissolved and
suspended biological matter.s
4. Tertiary treatment -disinfection of treated water
physically or chemically prior to discharge into stream.
6. Sr.Type of Treatment Type of Name of the Function Type
No. Treatment Unit Units of Impurity
Removed.
1Physical Treatment Physical Screens Large
Suspended and
Floating Matter
Physical Grit Chamber Grit
Physical Clarifiers Silt, Sand &
Other heavier
Matter
2Chemical Treatment Chemical Chemical Reactors Dissolved
Chemicals
3Biological Treatment Biological Trickling filter Dissolved
Activated Sludge Organic
Rotating Chemicals
Biological
Contractors
Digesters
7. physical treatment
•Screen, Clarifiers, grit chamber are all physical
treatment unit.
•it uses gravitation,mechanical straining
• Mechanical Straining takes place in screens
• gravity Settling takes place in Clarifiers.
• Clarifiers are also known as Sedimentation Basin
or Settling tanks.
8.
9. chemical treatment
It is normally preferred when the wastewater discharge is
very small like that produced by industries, which contain
Chemicals.
• It takes place in units which are called reactors,
methods
• coagulation
• precipitation
• oxidation
• Neutralization
• Ion Exchange
10. Primary treatment
• It is aimed at the removal of fine suspended organic solids that
cannot be removed in the preliminary treatment.
• It basically involves the process of sedimintation or settelings.
• Sedimintation is usually carried out twise before the secondary
treatment.
• Sometimes chemical precipitation methods are used.the
chemicals used in chemical aided sedimintation are 2 types
coagulants and coagulant aids.
• Coagulants are the chemicals which form in soluble and
gelatinous precipitates with colloidal particles.eg.alum.
• Example for coagulant aids activated silica.
11. SECONDARY TREATMENT
• Aerobic biological treatment is performed in the presence
of oxygen by aerobic microorganisms (principally
bacteria) that metabolize the organic matter in the
wastewater, thereby producing more microorganisms and
inorganic end-products (principally CO2, NH3, and H2O)
12. Secondary treatment
•Utilizes biological treatment processes
•removes dissolved colloidal and organic matter from waste
water.
•microorganisms convert nonsettleable solids into
settleable solids.
• Ex….Bacteria and protozoa
• :two main approaches are there to accomplish this
13. 1. Aerobic process
a. Activated sludge process
b. Trickiling filters
c. Rotating biological contactors
d. Aerated lagoons
2.Anaerobic process
a. Anaerobic digestion
b. Anaerobic contact process(meat packing wastes)
14. • Micro-organisms on substrates such as rocks, sand or
plastic are cultured.
• Waste water is spread over the substrate .
• Nutrients and organic matter are absorbed by micro-
organisms as they grow in size.
• Eg. trickling filters,rotating biological contactors,and sand
filters.
15. Activated sludge
• In the activated sludge process, the dispersed-growth reactor is
an aeration tank or basin containing a suspension of the
wastewater and microorganisms, the mixed liquor.
• The contents of the aeration tank are mixed vigorously by
aeration devices which also supply oxygen to the biological
suspension.
• Aeration devices commonly used include submerged diffusers
that release compressed air and mechanical surface aerators that
introduce air by agitating the liquid surface
16. • Following the aeration step, the microorganisms are
separated from the liquid by sedimentation and the
clarified liquid is secondary effluent.
• A portion of the biological avtive sludge is recycled to the
aeration basin to maintain a high mixed-liquor suspended
solids (MLSS) level.
• growth of protozoa-indicates healthy condition.
• The remainder is removed from the process and sent to
sludge processing to maintain a relatively constant
concentration of microorganisms in the system.
17.
18. Advantages
• low cost&efficient
• the excess &waste sludge has a higher fertilizer value
Disadvantages:
• large volume of sludge production -difficult to handle
• High power consumption
• supervission by a skilled person is necessory.
19. Trickling filter
• A trickling filter or biofilter consists of a basin or tower filled with
support porousmedia such as stones, plastic shapes, or woode slats.
• Wastewater is applied intermittently, or sometimes continuously, over
the media.
• within 2 weeks microorganisms become attached to the media and
form a biological layer or fixed film.which has a thicness of 0.1 -
2.0mm &rich in micro-organism.
• Organic matter in the wastewater diffuses into the film, where it is
metabolized to Carbon doxide&nitrogen.
20. • Oxygen is normally supplied to the film by the natural flow of air either up or
down through the media, depending on the relative temperatures of the
wastewater and ambient air.
• film is rich in bacteria ,fungi,yeast.eg;Pseudomonas,algae-Chlorella etc.
• The thickness of the biofilm increases as new organisms grow periodically,
portions of the film slough off the media.
• The sloughed material is separated from the liquid in a secondary clarifier and
discharged to sludge processing.
• Clarified liquid from the secondary clarifier is the secondary effluent and a
portion is often recycled to the biofilter to improve hydraulic distribution of the
wastewater over the filter.
21. TRICKLING FILTERS -summary
•Organic material present in the wastewater is metabolised by the
biomass.
•Biological slime grows in thickness as the organic matter
abstracted from the flowing wastewater is synthesized into new
cellular material.
•The liquid then washes the slime off the medium and a new slime
layer starts to grow- sloughing.
•The collected liquid is passed to a settling tank used for solid-
23. Advantages Disadvantages
•Simple, reliable, biological
process
•Low power requirement
•Moderate level of skill and
technical expertise needed
to manage and operate the
system.
•Additional treatment
• may be needed to meet
more stringent discharge
standards.
•Vector and odour problems.
•Requires regular operator
attention.
24. Rotating Biological Contactors
• Rotating biological contactors (RBCs) are fixed-film reactors where organisms are
attached to support media.
• Consists of a series of closely spaced plastic circular disks.
• In the case of the RBC, the support media are slowly rotating discs that are partially
submerged in flowing wastewater in the reactor.Discs are made up of inert material such
as pvc.
• Oxygen is supplied to the attached biofilm from the air when the film is out of the water
and from the liquid when submerged, since oxygen is transferred to the wastewater by
surface turbulence created by the discs' rotation.
25. • Operation, biological growths become attached to the
surfaces of the disks and form a slime layer over the
entire wetted surface.
• The rotation of the disks contacts the biomass in the
wastewater ,then with the atmosphere for adsorption of
oxygen.
• Biomass uses the oxygen & organic matter for food thus
reducing the BOD in the wastewater.
27. Advantages:
• compact&requires moderate energy input
• it has high BOD removal efficiency(90%).
Disadvantages:
• disposal of sludge
• odour formation
• requires skilled person
28. Aerated lagoon
•An aerated lagoon or aerated basin is a holding and/or treatment
pond provided with artificial aeration to promote the biological
oxidation of waste waters.
•There are many other biological processes for treatment of
wastewaters, for
example activated sludge, trickling filters, rotating biological
contactors and biofilters.
•They all have in common the use
• of oxygen (or air) and microbial action to biotreat the pollutants
in wastewaters.
29. Anaerobic process
• It involves decomposition of organic &inorganic matter in
the absence of oxygen.
• used in treatment of sludges&high strength organic
sewage.
• eg:anaerobic digestion
30. Anaerobic digestion
• Used for stabilization of concentrated sludges that are
from industries.
• It is carried out in the air tight reactor
• Sludge is introduced continuously/intermittently.
• Biological degradtion of organic matter of sludge occurs
in 3 stages.
1. Hydrolysis -high mw compounds to low m.w
compounds..eg:A.a
2. Acidogenesis-low moleclular weight comp-acidic
products(lactate).
3. Methanogenesis-production of methane&carbon dioxide.
31. Micro-organisms
1. Acid forming bacteria
• called as acidogens
eg:Clostridium sp , Lactobacillus sp, E.coli etc
1. Methanogenic bacteria
• conversion of acetic acid& hydrogen to methane and
carbon dioxide.
• eg:Methano bacterium,Methano bacillus,Methano coccus
etc
32. Tertiary treatment
• PURPOSE: Destruction of harmful
(pathogenic)microorganisms,i.e.disease causing germs.
• Done through:
• 1.Chlorination
• 2.Ozone:more powerful but unstable to store.
• 3.Ultraviolet light
• 4.Hydrogen peroxide:similar to ozone but activators such
as formic acid is required to improve its working.
33. When the treatment is done…
• Effluent back to stream after
• a final carbon filtration and
• chlorination/dechlorination
• Sludge – very nutrient rich
• applied directly to land as fertilizer
• incinerated (good fuel after drying)
• composted .
34. Reference
• Barwal, et all (2014). "To study the performance of biocarriers in moving bed biofilm
reactor (MBBR) technology and kinetics of biofilm for retrofitting the existing aerobic
treatment systems: a review". Reviews in Environmental Science and
Bio/Technology. Springer.
• Harshman, et all (2000-12-28). "Wastewater Odor Control: An Evaluation of
Technologies". Water Engineering & Management.
• Khopkar, S. M. et all (2004). Environmental Pollution Monitoring And Control
• Sharma et all (2012). Advances in Water Treatment and Pollution Prevention.
Springer Science & Business Media.
• Tchobanoglous et all Wastewater Engineering: Treatment and Resource Recovery.
,y (Fifth ed.)
