environmental science- aerobic and anaerobic wastewater treatment

1. AEROBIC AND ANAEROBIC
WASTEWATER TREATMENT
Ezhilmathi. S
2015006015

2. WASTEWATER TREATMENT
 It is a process used to convert wastewater into an effluent that
can be returned to the water cycle with minimal environmental
issues
 Instead of disposing of treated wastewater it is reused for
various purposes, which is knows as water reclamation
 During the treatment process, pollutants are removed or
broken down
 The infrastructure used for wastewater treatment is called a
wastewater treatment plant or a sewage treatment plant in the
case of municipal wastewater

3. AEROBIC WASTEWATER TREATMENT
 Aerobic processes use bacteria that require oxygen, so
air is circulated throughout the treatment tank
 These aerobic bacteria then break down the waste
within the wastewater
 Some systems utilize a pretreatment stage prior to the
main treatment to reduce the chance of clogging the
system
 Electricity is required for system operation

4. ADVANTAGES
 Minimum odor
 Large BOD removal providing a good quality
effluent
 High rate treatment with less land requirement
 Final discharge may contain DO which reduces the
immediate OD on receiving water

5. DISADVANTAGES
 Energy cost of aeration at an adequate rate to maintain
the DO levels needed
 Some organics cant be efficiently decomposed
aerobically
 These biologically non-reactive components mainly
composed of insoluble materials can account for up to
70% COD
 Reduction in storage capacity of lagoons and/ or ponds

6. ACTIVATED SLUDGE PROCESS
 Process for treating sewage or industrial
wastewaters using aeration and a biological floc
composed of bacteria and protozoa
 is a biological process that can be used for
oxidizing carbonaceous biological matter, oxidizing
nitrogenous matter (NH3 and N2),
removing nutrients (N and P).
 Aeration methods - diffused aeration, surface
aerators (cones) and pure oxygen aeration

7. ACTIVATED SLUDGE PROCESS
 The sludge blanket is measured from the bottom of the clarifier
 The Sludge Volume Index is the volume of settled sludge in mm occupied by 1
gram of dry sludge solids after 30 mins of settling in a 1000 ml graduated
cylinder.
 The Mean Cell Residence Time is the total mass(kg) of mixed liquor suspended
solids in the aerator and clarifier divided by the mass flow rate (kg/day) of MLSS
effluent
 The F/M is amount of BOD fed to the aerator (kg/day) divided by the amount
of MLVSS (kg) under aeration
 Some use Mixed Liquor Suspended Solids for expedience, but Mixed Liquor
Volatile Suspended Solids is considered more accurate for the measure of
microorganisms

8. ACTIVATED SLUDGE PROCESS

9. PROCESS
 Pre-treatment stage to remove large solids and
other undesirable substances
 Aeration stage, where aerobic bacteria digest
biological wastes
 Settling stage allows undigested solids to settle,
forms a sludge that must be periodically removed
from the system
 Disinfecting stage, where chlorine or similar
disinfectant is mixed with water, to produce an
antiseptic output

10. TRICKLING FILTER
 First used by Dibden and Clowes
 It consists of rocks, lava, coke, gravel, slag,
polyurethane foam, sphagnum peat moss, ceramic,
or plastic media over which sewage flows
downward and causes a layer of microbial slime
(biofilm) to grow, covering the bed of media
 Aerobic conditions are maintained by splashing,
diffusion, and either by forced-air flowing through
the bed or natural convection of air if the filter
medium is porous

13. PROCESS
 Sewage flow enters at a high level and flows through the primary
settlement tank
 The supernatant from the tank flows into a dosing device, often a tipping
bucket which delivers flow to the arms of the filter
 The flush of water flows through the arms and exits through a series of
holes pointing at an angle downwards
 This propels the arms around distributing the liquid evenly over the
surface of the filter media
 Both absorption and adsorption of organic compounds and some
inorganic species by the layer of microbial bio film

14. PROCESS
 The filter media is typically chosen to provide a very high surface area to
volume
 Passage of the waste water over the media provides DO which the bio-
film layer requires for the biochemical oxidation of the organic
compounds and releases CO 2 gas, water and other oxidized end
products
 As the bio film layer thickens, it eventually sloughs off into the liquid flow
and subsequently forms part of the secondary sludge
 Other filters utilizing higher-density media do not produce a sludge that
must be removed, but require forced air blowers and backwashing

15. ROTATING BIOLOGICAL CONTACTOR
 RBC is a type of secondary treatment process
 The primary treatment process means removal of grit and sand through
a screening process, followed by settling
 This process involves allowing the wastewater to come in contact with a
biological medium in order to remove pollutants
 It consists of a series of closely spaced, parallel discs mounted on a
rotating shaft which is supported just above the surface of the waste
water.
 Microorganisms grow on the surface of the discs where biological
degradation of the wastewater pollutants takes place

17. BIOFILTER
 Biofiltration is a fixed–film process
 It is a bed of media on which microorganisms attach and
grow to form a biological layer called biofilm
 Biofiltration is used to treat wastewater from a wide
range of sources, with varying organic compositions and
concentrations
 This process is versatile as it can be adapted to small
flows (< 1 m3/d) as well as to flows generated by a
municipality (> 240 000 m3/d)

18. AEROBIC STABILIZATION PONDS
 It reduce the organic content (measured as BOD) and
kill pathogens in the wastewater
 Ponds are depressions holding water confined by earthen
structures
 After treatment, the effluent may be returned to surface water
or reused as irrigation water if the effluent quality is high
enough
 Waste stabilization ponds use no aerators
 High-performance lagoon technology with aerators has much
more in common with that of activated sludge

20. AERATED LAGOON
 This system consisting of a pond with
artificial aeration to promote the biological oxidation
of wastewaters

21. MATURATION POND
 A self-purifying reservoir used to stabilize effluent from mechanized secondary treatment
 Maturation ponds receiving wastes with low BOD concentrations may be clear enough to
accomplish pathogen reduction through exposure to UV solar radiation
 Maturation ponds may be used in combination with a rainwater reservoir to form an
ecological, swimming pond
 It should be saturated with DO throughout the entire pond and shallow enough for light to
penetrate the entire depth of the pond
 It must be shallow with a great surface area so that more oxygen can dissolve into the
water giving the bacteria enough oxygen to properly function
 By adding the fish the ponds bug issues are controlled in a natural and eco- friendly

23. FACULTATIVE LAGOONS
 Organic waste from food or fiber processing may be
catabolized in a system of constructed ponds where
adequate space is available to provide an average
waste retention time exceeding a month
 A series of ponds prevents mixing of untreated
waste with treated wastewater and allows better
control of waste residence time for uniform
treatment efficiency

24. ANAEROBIC LAGOON
 An anaerobic lagoon filled with animal waste that undergoes anaerobic respiration
 The manure settles into two layers: solid, or sludge layer and the liquid layer
 The volatile organic compounds are converted into CO 2 and CH 4
 This allows for preliminary sedimentation of suspended solids as a pretreatment
process
 These substances are emitted through two main pathways: gas emissions and
lagoon overflow
 Gas emissions are continuous
 The most prevalent gasses emitted by the lagoon are: NH 3, H 2 S, CO2 and CH 4

26. ANAEROBIC WASTEWATER TREATMENT
 Anaerobic bacteria transform organic matter in the
wastewater into biogas that contains large amounts of
methane gas and carbon dioxide
 Energy-efficient process
 Often used to treat industrial wastewater that contains
high levels of organic matter in warm temperatures
 It can be used as a pretreatment prior to aerobic
municipal wastewater treatment

28. TYPES OF ANAEROBIC DIGESTER
 The following is a partial list of digesters can be
categorized according to two main criteria: by
whether the biomass is fixed to a surface or can
mix freely with the reactor liquid and by the organic
loading

29. UPFLOW ANAEROBIC SLUDGE BLANKET
 It is a suspended-growth high-rate digester, with its
biomass clumped into granules that
will settle relatively easily and with typical loading
rates in the range 5-10 kg COD/m3/d
 It is a methanogenic (methane-producing) digester
that evolved from the anaerobic clarigester

31. PROCESS
 Forming a blanket of granular sludge which suspends in the tank
 Wastewater flows upwards through the blanket and is processed
(degraded) by the anaerobic microorganisms
 The upward flow combined with the settling action of gravity suspends the
blanket with the aid of flocculants
 The blanket begins to reach maturity at around three months
 Eventually the aggregates form into dense compact biofilms referred to as
"granules"
 Biogas with a high concentration of methane is produced as a by-product,
and this may be captured and used as an energy source, to
generate electricity
 The heat produced as a by-product of electricity generation can be reused
to heat the digestion tanks
 UASB reactors are typically suited to dilute waste water streams (3% TSS
with particle size >0.75mm)

32. EXPANDED GRANULAR SLUDGE BED
 It is a variant of the UASB concept
 Faster rate of upward-flow velocity is either
accomplished by utilizing tall reactors, or by
incorporating an effluent recycle for the wastewater
passing through the sludge bed
 The increased flux permits partial expansion
(fluidisation) of the granular sludge bed, improving
wastewater-sludge contact as well as enhancing
segregation of small inactive suspended particle from
the sludge bed
 It is appropriate for low strength soluble wastewaters (<
1 - 2 g soluble COD/l) or for wastewaters that contain
inert or poorly biodegradable suspended particles

34. ANAEROBIC FILTER
 The digestion tank contains a filter medium
where anaerobic microbial populations can
establish themselves
 They produce a less solid residue than other types
of filter

36. UP-FLOW ANAEROBIC HYBRID REACTORS
 It involves the introduction of a new phase of attached-
biomass into a regular suspended-growth system
 It contains both suspended and attached-growth biomass
which is developed by introducing porous materials into a
regular activated sludge unit
 It combines a UASB reactor with an anaerobic filter
 This combination is an advanced form enabling improved
solid retention time in the treatment of waste water
 This waste water can be built up in the secondary chamber
and must be removed daily

38. FLUIDIZED BED REACTOR
 A type of reactor device that can be used to carry
out a variety of multiphase chemical reactions
 Fluid (gas or liquid) is passed through a
solid granular material at high enough velocities to
suspend the solid
 This process, known as fluidization, imparts many
important advantages

40. MERITS
 High degree of waste stabilization
 Low production of excess biological sludge that can
be directly dried on sludge drying bed without
further treatment
 Low nutrition requirements
 No oxygen requirement
 Production of valuable by product, methane gas
 Organic loading is not limited
 Less land requirement
 Non feed conditions for few month do not affect
adversely to the system (can work seasonally)

41. DISADVANTAGES
 Incomplete break-down of organic compounds
 No thorough nutrient removal
 Again later aerobic purification with nutrient removal is
often needed
 Most efficient purification in the mesophilic range (30-
37°C) whereby the influent must be heated in most
cases
 Less robust system with regards to toxicity and inhibition
 Risk of odor problems

42. REFERENCES
 en.wikipedia.org
 www.sswm.info
 https://greentumble.com
 http://nptel.ac.in
 www.extension.umn.edu
 emis.vito.be