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
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
11.
12.
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
16.
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
19.
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
22.
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
25.
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
27.
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
30.
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
33.
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
35.
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
37.
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
39.
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
