waste energy
TRANSCRIPT
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Week 6, Week 7 & Week 8
IRMA NOORAZURAH MOHAMADMARCH 2012 JULY 2012
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Learning outcome;
1. Be able to describe the sources of wastewater
2. Be able to explain on the conventionalwastewater treatment process.
3. Be able to differentiate centralized and
decentralized system in wastewater treatmentplant.
4. Be able to discuss on the sludge disposal
methods.
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Where itcomes?
Where itgoes?
Compositions?
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What is wastewater?
Any water that has been used by some
human domestic, agricultural or industrial
activity. It also include storm water runoff. All these water go into larger pipes called
sewers.
The sewers take all the wastewater to the
treatment works.
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What is wastewater?
Any water that has been used by some
human domestic, agricultural or industrial
activity. It also include storm water runoff. All these water go into larger pipes called
sewers.
The sewers take all the wastewater to the
treatment works.
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WHERE IT GOES??????
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Sewerage
collection, treatment and disposal ofliquid waste.
Sewerage/sewage works all physical structures
required for collection, treatment and disposal.
Sewageliquid waste; may include domestic and
industrial discharges as well as storm sewage,
infiltration, inflow.
Sewerpipe or conduits, generally closed, normally
not flowing full and carries sewage.
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Storm sewer carries storm sewage & other wastes
discharged into streets or onto surface of the ground.
Sanitary sewer carries sanitary sewage and exclude
storm sewage, infiltration and inflow.
Combined sewer carries both domestic and storm
sewage.
Sewage treatment any process used to favorablymodify the characteristics of the wastewater.
Sewage disposal discharge of liquid wastes to the
environment.
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Combined Sewer System
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Separate Sewer System
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FROM WHERE THE
SOURCES??????
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1. Domestic sewage
2. Non-Domestic sewage
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1. Domestic Sewage
Although the word sewageusually bringstoilets to mind, it actually is used to
describe all types of wastewatergenerated from every room in a house
sinks, bathing, and laundry.
There are two types ofdomestic sewage:
blackwaterwastewater from toilets; and
graywater which is wastewater from all
sources except toilets.
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2. Non Domestic Sewage
This is discharged by manufacturing
processes, hospitals, farms, restaurants
and any other commercial enterprisessuch as laundry.
It also include stormwater is a non-
residential source and carries trash andother pollutants from streets, as well aspesticides and fertilizers from yards andfields.
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Wastewater from some non-residentialsources may require additional treatmentsteps.
For example, stormwater should becollected separately to prevent theflooding of treatment plants during wetweather.
In addition, many industries producewastewater high in chemical andbiological pollutants that can overburdenonsite and community systems.
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Pre-treatmentremoves materials that can
cause operational problems, equalization
optional
Primary treatment
*remove ~60% of solids and ~35% of BOD
Secondary treatment
*remove ~85% of BOD and solidsAdvanced treatment
*varies: 95+ % of BOD and solids, N, P
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Industrial wastewaters must be pre-treated prior to being discharged tomunicipal sewer system e.g. screening,grit chamber, oil and grease removal
Approach is to remove materials that willnot be treated by municipal system
Local authority must monitor and regulateindustrial discharges e.g DOE, IWK.
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CONTAINS IN
WASTEWATER??????
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What is in the wastewater?
1. Organisms
Organism is a living thing (such as animal,plant, fungus, or micro-organism).
An organism may either be unicellular (single-celled) or be composed of as in humans, manybillions of cells grouped into specialized tissuesand organs.
A variety of bacteria, protozoa and worms thatwork to breakdown certain carbon-based(organic) pollution in wastewater byconsuming them.
Organisms turn wastes into carbon dioxide,water, or new cell growth.
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What is in the wastewater?
2. Pathogen
Is a biological e.g parasites, viruses agent
that causes disease or illness to its host.
The termpathogen is derived from the
greek "that which produces suffering.
The body contains many natural defensesagainst some of the common pathogens in
the form of the human immune system
and by some "helpful" bacteria.
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What is in the wastewater?
3. Organic Matter
Organic matter is matter that has come from a once-
living organism; is capable of decay, or the product of
decay; or is composed of organic compounds.
An organic compound is any member of a large class
of chemical compounds whose molecules contain
carbon e.g METHANE.
Originate from plants, animals, or synthetic organiccompounds, and enter wastewater in human wastes,
paper products, detergents, cosmetics, foods, and
from agricultural, commercial, and industrial
sources.
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Maximum Permitted ValueParameter, mg/L
Standard A Standard B
Temperature (C)
pH (units)BOD5 AT 20C
COD
Suspended Soilds
Ammoniacal-Nitrogen
Nitrate-Nitrogen
Phosphorus
Oil & Grease
40
6.0
9.020
50
50
5
10
5
5
40
5.5
9.050
100
100
5
10
10
10
New Proposed Standards for Category 1 Effluent Plants Connected To
Stagnant Water Bodies
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9/8/2010
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In locations where sewers and a
centralized wastewater treatment system
are not available, on site disposal must be
usedSeptic systems (small system)most
common for individual residences
Larger systems required for housing
clusters, rest areas, commercial and
industrial facilities
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http://upload.wikimedia.org/wikipedia/commons/a/aa/Septic_tank_EN.svg -
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Septic Tank settling, flotation and anaerobic degradation
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The oldest, simplest and lowest cost
forms of treatment for domestic waste.
Also used for treating industrial waste.
Wastewater is treated through acombination ofphysical, biological and
chemical processes.
some systems use aeration devices to add
oxygen to the wastewater.
The lagoon that using the aerators can be
called aerated lagoons.
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Pre-treatmentremoves materials that can
cause operational problems, equalization
optional
Primary treatment
*remove ~60% of solids and ~35% of BOD
Secondary treatment
*remove ~85% of BOD and solidsAdvanced treatment
*varies: 95+ % of BOD and solids, N, P
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Conventional wastewater treatment
consists of a combination of physical,
chemical, and biological processes
It operations to remove solids, organicmatter and nutrients from wastewater
In some countries, disinfection to remove
pathogens sometimes follows the lasttreatment step after advance additional
treatment
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OBJECTIVES of STP?
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Objectives of wastewater treatment;
1. One of the principle objectives of
wastewater treatment is to prevent as
much of this "oxygen-demanding" organicmaterial as possible.
2. Other objectives of wastewater treatment
include, removal of objectionable items,
nutrients and heavy metals.
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1. Primary Treatment
Screening Grit & grease Removal
Primary Sedimentation
2. Secondary Treatment Activated Sludge, Aerated Lagoon, Trickling
Filter, Rotating Biological Contactors (RBC)
etc.
3. Sludge Treatment and Disposal
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Sewage
inflow PreliminaryTreatment PrimaryTreatment Secondary Treatment TertiaryTreatment effluentdischarge
screening sedimentation activated sludge filtration
grit removal floatation biofiltration disinfection
grease tank sedimentation tertiary ponds
pre-aeration
flow measurement
flow balancing
/equalisation basin
removal of rags,
rubbish, grit, oil,
greaseremoval of settleable
and floatable materials
biological treatment to
remove organic and
suspended solidsbiological and chemical
treatment to remove nutrients
and pathogensPurposes/Objectives
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Extended Aeration (EA)
Sequence Batch Reactor (SBR)
Oxidation Ditch (OD)
Biofilter (BF)Hi-Kleen (HK)
Conventional Activated Sludge (CAS)
Imhoff Tank (IT)
Aerated Lagoon (AL)
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PROCESS FLOW DIAGRAM
OF EXISTINGIMHOFF TANK PLANT
(ITPS)
Raw Sewage
Pumping Station
Imhoff Tank
Stone Media
Filter Bed
Treated Effluent
Sand Drying Bed
FiltrateRecycle
1
2
3
4
***clarification of sewage by simple settling and sedimentation, along with
anaerobic digestion of the extracted sludge
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PROCESS FLOW DIAGRAM OF EXISTINGOXIDATION DITCH PLANT ODPS
Mechanical RotorFlow
DistributionFinal Clarifier
FlowMeasurement
Screens, Grit Removal
Oxidation Ditch
Return SludgePump Station
ChemicalDosing
Mechanical SludgeThickener
Mechanical SludgeDewatering
Sludge Storage Area
Sludge Holding Tank
Sludge Drying Bed
RawSewage
Inlet
SewagePump Station
EffluentTo River
OPTIONAL
Ultimate Disposal
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***long channel of an elliptical or circular shape equipped with anaeration equipment
***simple structure and can be easily operated as well as being able to
remove nitrogen easily
Preliminary Treatment Secondary Treatment
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PROCESS FLOW DIAGRAM OF SEQUENCING BATCHREACTOR (SBR) PLANT
Preliminary Treatment Secondary Treatment
Dry well & Wet wellPump Sump
Mechanical ScreenMechanical
ScreenGrit Removal
GreaseRemoval
Sequencing Batch Reactor
Washing
Dewatering
Grit
Screenings
Screenings
Liquor
SludgeHoldingTank
ThickenedSludge
Mixing Tank
Water
ChemicalSolutionTank
Haul toSludgeDisposal
Filter Press
SludgeCake
Chlorination Tank
***installation consists of at least two identically equipped tanks with a common inlet,which can be switched between them
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Raw Influent
Flow Measurement
Grit Removal
Pumping
Station
Screen
Coarse
Distribution
Chamber
Polishing
PondAerobic
LagoonFacultative
Lagoon
Surface Aerator
Treated
Effluent
PROCESS FLOW DIAGRAM OF AERATED LAGOONSYSTEM (AL)
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RawSewage
Inlet
SewagePump Station
Screens, Grit Removal
Anoxic Zone Aeration Tank FlowDistribution
Final Clarifier
EffluentTo River
ChemicalDosing
Mechanical SludgeThickener
Liquor
Mechanical SludgeDewatering
Sludge Storage Area
Return Sl udgePump Station
Sludge Holding Tank
Sludge Drying Bed
Ultimate Disposal
OPTIONAL
PROCESS FLOW DIAGRAM OF EXTENDEDAERATED PLANT (EA)
12/8/2010
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12/8/2010
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Sewage
inflow PreliminaryTreatment PrimaryTreatment Secondary Treatment TertiaryTreatment effluentdischarge
screening sedimentation activated sludge filtration
grit removal floatation biofiltration disinfection
grease tank sedimentation tertiary ponds
pre-aeration
flow measurement
flow balancing
/equalisation basin
removal of rags,
rubbish, grit, oil,
greaseremoval of settleable
and floatable materials
biological treatment to
remove organic and
suspended solidsbiological and chemical
treatment to remove nutrients
and pathogensPurposes/Objectives
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Primary treatment involves:
1. Screening to remove large objects
2. Grit chamber slows down the flow to
allow grit to fall out3. Primary sedimentation tank settleable
solids settle out, while oils float to the top
and are skimmed off.
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Screening is the first technique employed
in the wastewater treatment process.
This step removes all sorts of refuse that
has arrived with the wastewater such asplastic, branches, rags, and metals.
The screening process is used primarily to
present the clogging and interference of
the following wastewater treatmentprocesses.
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Types of Screens
1. Coarse Screens: Coarse screens also called racks, areusually bar screens, composed of vertical or inclined bars
spaced at equal intervals across a channel through which
sewage flows.
2. Medium Screens: Medium screens have clear openings of20 to 50 mm.Bar are usually 10 mm thick on the
upstream side and taper slightly to the downstream side.
3. Fine Screens: Fine screens are mechanically cleaned
devices using perforated plates, woven wire cloth or veryclosely spaced bars with clear openings of less than 20
mm. Fine screens are not normally suitable for sewage
because of clogging possibilities.
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This type of screen, called a bar screen,removes debris from wastewater.
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Grit Removal
The purpose of grit removal is to remove the
heavy inorganic solids, which could cause
excessive mechanical wear.
Grit includes sand, gravel, clay, egg shells,
coffee grounds, metal filings, seeds and
other similiar materials.
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These items settle to the bottom of the grit
channels by gravity
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There are several devices or processes used
for grit removal.
All of the processes are based on the fact
that grit is heavier than the organic solids
that should be kept in suspension for
subsequent treatment.
Grit removal facilities basically consist of an
enlarged channel area where reduce flowvelocities allow grit to settle out.
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Many oils can be recovered from open water
surfaces by skimming devices - which is
designed to separate the oil and suspended
solids from their wastewater effluents.
However, hydraulic oils and the majority of
oils that have degraded to any extent will
also have a soluble or emulsified component
that will require further treatment to
eliminate.
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Primary sedimentation simply entails the
physical settling of matter, due to its density,
buoyancy, and the force of gravity.
Most of the suspended solids in wastewater
are sticky in nature and flocculate naturally
type-2 settling without the addition of
coagulants.
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Through sedimentation, the larger solids are
removed in order to facilitate the efficiency
of the following procedures.
The tank is large enough that fecal solids can
settle.
Scum removal is accomplished by having
sludge scrappers.
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After primary treatment process, nearly 50-
70% of the solids settle down under
influence of gravity and 25% 55 % of the
incoming BOD are removed.
But colloidal and dissolved constitutes are
not affected.
Continue with the secondary treatment.
**removal of rags, rubbish, grit, oil, grease, removal
of settleable and floatable materials
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1. Domestic sewage
2. Non-Domestic sewage
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1. Organisms A variety of bacteria, protozoa and worms
that work to breakdown certain carbon-based (organic) pollution in wastewater byconsuming them.
2. Pathogen Is a biological e.g parasites, viruses agent
that causes disease or illness to its host.
3. Organic Matter
Organic matter is matter that has come froma once-living organism; is capable of decay,or the product of decay; or is composed oforganic compounds.
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Typically, sewage treatment involves three (3) stages, calledprimary, secondaryand tertiarytreatment.
THE STAGES
First, the solids are separated from the wastewater stream. Then
dissolved biological matter is progressively converted into a solid
mass by using indigenous, water-borne microorganisms.
Finally, the biological solids are neutralized then disposed of or
re-used, and the treated water may be disinfected chemically or
physically (for example by lagoons and micro-filtration).
The final effluent can be discharged into a stream, river, bay,
lagoon or wetland, or it can be used for the irrigation of a golf
course, green way or park. If it is sufficiently clean, it can also be
used for groundwater recharge.
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To remove large suspended solidsTwo types: Coarse, medium and fine screens
Opening = less 20 mm or more
Reduce problems on machines (ex: blockage)Need to work at high and low flow
Screen cover to block wind and improveaesthetics and reduce odor.
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The main objective of grit removal is to separateby sedimentation all materials that may be
detrimental to the treatment process.
Ex: sand, metal fragments, eggshells
Not benefited because can cause blockage,
promote excessive wear on mechanical
equipment
Each wastewater treatment plant usually has at
least two grit chambers.
Normally, the grit is buried in a sanitary landfill
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Designed to separate the oil and suspendedsolids from their wastewater effluents.
Other hydraulic oils and the majority of oils
that have degraded to any extent will also
have a soluble or emulsified component that
will require further treatment to eliminate.
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The tanks are large enough that fecal solids cansettle and floating material such as grease andoils can rise to the surface and be skimmed off.
The main purpose of the primary stage is to
produce a generally homogeneous liquid capableof being treated biologically and a sludge thatcan be separately treated or processed.
Primary settlement tanks are usually equippedwith mechanically driven scrapers thatcontinually drive the collected sludge towards ahopper in the base of the tank from where it canbe pumped to further sludge treatment stages
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50-70% of the solids settle down
under influence of gravity
25% 55 % of the incoming BOD areremoved.
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Typically utilize biological treatmentprocesses, in which microorganisms
convert non-settleable solids to settleable
solids.
Provide BOD removal beyond what is
achieved in primary treatment:
removal of soluble BOD
additional removal of suspended solids
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How is thisaccomplished?
Create a very rich
environment for growth
of a diverse microbial
community
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High density of microorganisms (keeporganisms in system)
Good contact between organisms and
wastes (provide mixing) Provide high levels of oxygen (aeration)
Favorable temperature, pH, nutrients
(design and operation) No toxic chemicals present (control
industrial inputs)
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Basic approach is to use aerobic biologicaldegradation:organic carbon + O2 + microorganisms CO2 + H2O +
inorganic matter
Two methods of treatment :1. Dispersed Growth suspended organismsActivated sludge ( include aerated lagoons )Oxidation ditches/ponds
2. Fixed Growth attached organismsTrickling filtersRotating Biological Contactors (RBCs)
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Activated sludge refers to biologicaltreatment processes that use a suspended
growth of organisms to remove BOD and
suspended solids. The process requires an
aeration tank and a settling tank.
Part of the settled material, the sludge, is
returned to the head of the aerationsystem to re-seed the new wastewater
entering the tank.
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What happen in aeration tank?
The wastewater flows into large aeration
basins, where it is mixed with air to aid
the growth of microorganisms thatnaturally live in wastewater.
Diffused air enters the tanks from the
bottom, creating bubbles, or surfaceaerator can also be use paddle mixing
stir the water continuously.
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How the treatment process happen? The microorganisms called activated sludge
clean the wastewater by digesting organic
materials and other contaminants.
Activated sludge consists of a mixed community
of microorganisms that metabolize and
transform organic and inorganic substances into
environmentally acceptable forms.
The typical microbiology of activated sludgeconsists of approximately 95% good bacteria
and 5% higher organisms (protozoa, rotifers, and
higher forms of invertebrates).
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Secondary Sedimentation Tank
The wastewater enters basins called
secondary clarifiers, where the activated
sludge settles out of the water; some if it is reused in the treatment
process and the rest is collected,
thickened, and dewatered using large belt
presses that squeeze out the excesswater.
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Excess sludge which eventually
accumulates beyond what is returned is
then removed from the treatment
process to keep the ratio of biomass tofood supplied (wastewater) in balance.
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Three (3) types;
1. Aerobic ponds
2. Facultative ponds
3. Anaerobic ponds Different between ponds and lagoons is,
bulk of the oxygen in ponds provided by
photosynthesis.
Oxygen in lagoons is provided by artificialaeration.
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Using a DIAGRAM briefly discuss the
definition, concept, advantages
and disadvantages ofAerobic,
Facultative and Anaerobic ponds.
Two (2) groups will be selected topresent their findings.
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19/8/2010
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A trickling filter consists of a bed of highlypermeable media on whose surface a mixedpopulation of microorganisms is developed asa slime layer.
The word "filter" in this case is not correctlyused for there is no straining or filteringaction involved.
Passage of wastewater through the mediacauses the development of a gelatinouscoating of bacteria, protozoa and otherorganisms on the media.
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With time, the thickness of the slime layerincreases preventing oxygen from
penetrating the full depth of the slime layer.
In the absence of oxygen, anaerobic
decomposition becomes active near the
surface of the media.
The continual increase in the thickness of the
slime layer, the production of anaerobic end
products next to the media surface
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The maintenance of a hydraulic load tothe filter, eventually causes sloughing ofthe slime layer to start to form.
This cycle is continuously repeatedthroughout the operation of a tricklingfilter. For economy and to preventclogging of the distribution nozzles,
trickling filters should be preceded byprimary sedimentation tanks equippedwith scum collecting devices.
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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.
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The rotating packs of disks (known as themedia) are contained in a tank or trough
and rotate at between 2 and 5 revolutions
per minute.
Commonly used plastics for the media are
polythene, PVC and expanded polystyrene
About 40% of the disc area is immersed in
the wastewater.
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ROTATING BIOLOGICAL CONTACTORS
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Biofilms, which are biological growths orgood organism that become attached to
the discs, assimilate the organic materials
in the wastewater.
Aeration is provided by the rotating
action, which exposes the media to the
air after contacting them with thewastewater, facilitating the degradation
of the pollutants being removed.
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Sewage
inflow PreliminaryTreatment PrimaryTreatment Secondary Treatment TertiaryTreatment effluentdischarge
screening sedimentation activated sludge filtration
grit removal floatation biofiltration disinfection
grease tank sedimentation tertiary ponds
pre-aeration
flow measurement
flow balancing
/equalisation basin
removal of rags,
rubbish, grit, oil,
greaseremoval of settleable
and floatable materials
biological treatment to
remove organic and
suspended solidsbiological and chemical
treatment to remove nutrients
and pathogensPurposes/Objectives
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Advanced level of treatment to removeremove nitrogen, phosphorus, additional
suspended solids, refractory organics, heavy
metals and dissolved solids.
This level of treatment is utilized when theeffluent is discharged to a sensitive receiving
environment or in water reuse applications.
The process can be accomplished using a
variety of physical, chemical, or biological
treatment processes to remove targeted
pollutants.
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Industrial wastes is part of the waste streamsand are not removed in primary and
secondary treatment;
Some are not biodegradable
Some are toxic or hazardous
Tertiary/advanced treatment use
techniques geared to specific problem
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1. Coagulation settling filtration2. Carbon Adsorption
3. Membrane process
4. Nutrients removal
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1. Coagulation
settling
filtration Process is similar to that used in water
treatment
Removes
residual suspended solids
microorganisms
Commonly use dual- or multimedia filters
sand filters (single media) clog too easily
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2.Carbon Adsorption Carbon is heated to about 1500 oC to
activate surfaces
High surface area of particles with vastpore spaces
capable of absorbing high quantity of organics
Wastewater effluent is passed through
filter (under pressure) Removed material that cause odor and
smell as well as toxic organics
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The Reverse Osmosis process uses a semi-permeable membrane to separate and
remove dissolved solids, organics,
pyrogens, submicron colloidal matter,
viruses, and bacteria from water.
The process is called "reverse" osmosis
since it requires pressure to force purewater across a membrane, leaving the
impurities behind.
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Reverse Osmosis is capable of removing 95%-99% of the total dissolved solids (TDS) and
99% of all bacteria, thus providing safe, pure
water
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Electrodialysis Another membraneprocess, uses electrical potential to drive
the positive and negative ions of the
dissolved salts through separate semi-
permeable membranous filters, leaving
fresh water between the filters.
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Eutrophication is an increase in chemicalnutrients compounds containing
nitrogen or phosphorus resultant inexcessive plant growth and further
effects including lack of oxygen and
severe reductions in water quality, fish,
and other animal populations.
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Centralized
andDecentralized
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Centralized processing concepts arecomprised of the collection and treatment of
wastewater in one main location.
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A collection and treatment systemcontaining collection sewers and a
centralized treatment facility.
Centralized systems are used to collect
and treat large volumes of wastewater.
The collection system typically requireslarge-diameter deep pipes, major
excavation, and frequent manhole access.
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At the treatment facility, the wastewateris treated to standards required for
discharge to a surface water body.
The large amounts of biosolids (sludge)
generated in treatment are treated and
either land applied, placed on a surface
disposal site, or incinerated.
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This concept has some decisive drawbacks: In addition to the cost of a central treatment
plant, main sewage lines must be installed,resulting in higher initial investment and
increased operating cost for maintenance ofthe network and associated pumpingstations.
Possible interruptions in the central planthave a major impact on all communitieswithin the network.
Specialized treatment requirements cannoteasily be met.
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Example 1 : Activated Sludge Process
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Example 2 : Trickling filter
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Example 3 : Sequencing Batch Reactor (SBR)
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The major differences between SBR andconventional continuous-flow, activated
sludge system is that the SBR tank carries out
the functions of equalization, aeration and
sedimentation in a time sequence ratherthan in the conventional space sequence of
continuous-flow systems
http://d/nurul.imran%20DOCUMENT/LECTURE%20NOTES/ECW%20502/Dec%202009%20-%20May%202010/Wastewater%20Treatment/SBR%20system/SBR_slides.ppt -
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Sequencing Batch Reactor (SBR) is aspecial form of activated sludgetreatment
All of the treatment process takes placein the reactor tank and clarifiers are notrequired.
This process treats the wastewater inbatch mode and each batch is sequencedthrough a series of treatment stages.
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In a decentralized treatment system,individual sewage lines are combined and
treated locally
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An onsite or cluster wastewater systemthat is used to treat and dispose ofrelatively small volumes of wastewater,generally from dwellings and businesses
that are located relatively close together.
A conventional system is composed of aseptic tank for pre-treatment and a drainfield used for disposal of the wastewater.
Each system, however, must be designedaccording to specific site conditions toensure proper treatment.
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Advantages over a centralized system: The cost of a main sewage line network
equal the investment expenses for an
entire group of decentralized compact
treatment systems, saving the capital
investment of a central treatment plant.
Greater flexibility in accommodatingneeds of individual communities.
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Continue Local industry can be outfitted with their
own separate treatment facility, lowering the
investment cost for the municipal treatment
plant and sewage lines.
Possible interruptions only impact the local
treatment facility.
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Example 1 : Septic Tank The main purpose of the septic tank is to
temporarily retain and store wastewater to
allow solids, and fats, oils, and greases (FOG)
to separate before the wastewater flows tothe drain field.
The tank is generally designed to provide a 2-
day retention time for wastewater settling to
occur. Heavy solids sink to the bottomforming a layer ofsludge, while light solids
and FOG form a floating scumlayer.
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Example 2: Lagoons Lagoon systems: also known as "pond
systems" for onsite wastewater treatment
are less often found in use for single
family residential wastewater treatment.
A residential lagoon system may use a
conventional septic tank, but effluentfrom the tank flows to a storage pond or
lagoon for further treatment.
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Lagoon systems require comparativelylarge land areas and are more likely to befound therefore in rural areas or where acommon wastewater treatment system
has been designed to serve multipledwellings.
For example lagoons are used for effluent
disposal on small farms and for animalwaste treatment/disposal on small andlarge farms or livestock operations.
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Advantages Lagoon septic systems can be very cost
effective, particularly in rural areas wherethe cost of land is low.
They can handle intermittent and very large,sudden loads better than most other types ofsystem, making them ideal for seasonalplaces such as campgrounds & resorts.
They are normally fairly simple to operateand maintain
They are very effective at treatingwastewater
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Disadvantages Lagoon septic systems require more land
than other systems
They don't work as well in cold climates
Odors can be a problem, particularly at
certain times of the year or if not properly
maintained
Some wastewater requires additionaltreatment to meet local regulations
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Disinfection
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Advanced Wastewater Treatment to understand the most common types of
advanced wastewater treatment used
to understand the contaminants removed by each
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Numerous pollutants are present (or can be
present) in untreated wastewater
Some are not removed by conventional
secondary wastewater treatment
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High treatmentefficiency
BOD to ~ 20 - 50 mg/L
SS to ~ 20 mg/L
Low treatmentefficiency
Nitrogen
Phosphorus
Heavy Metals
Poorly-
biodegradable
organic chemicals
Small particles
Resistant organisms
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Presence of small particles that are too smallto be removed by settling.
Attached to these particles can be organicchemicals and metals.
Particles may eventually settle in river orstream (longer detention time).
Particles can also be bacteria, protozoans,etc.
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The disinfection of potable water and wastewater provides adegree of protection from contact with pathogenic organismsincluding those causing cholera, polio, typhoid, hepatitis anda number of other bacterial, viral and parasitic diseases.
Disinfection is a process where a significant percentage of
pathogenic organisms are killed or controlled.
The most common indicator organism used in the evaluationof drinking water is Total Coliform (TC), unless there is areason to focus on a specific pathogen.
The most common indicator organism for wastewaterevaluation is fecal coliform but there has been discussionregarding the use ofEscherichia coli (E. coli) or TotalColiform.
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There are a number of chemicals and processes that willdisinfect wastewater, but none are universally applicable.
Most septic tanks discharge into various types of subsurfacewastewater infiltration systems (SWIS), such as tile fields or
leach fields.
Chlorination/dechlorination has been the most widely useddisinfection technology
ozonation and UV light are emerging technologies &expensive.
2 Each of these three methods have different considerationsfor the disinfection of wastewater.
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Onsite wastewater treatment systems distributing
wastewater on the ground surface are required to
include a disinfection component as part of the
advanced pre-treatment process.
Additionally, some sub-surface drip systems applying
wastewater into shallow soils require disinfection prior
to dispersal.
Disinfection is the destruction or inactivation ofdisease-causing organisms.
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The disinfection component reduces theconcentration of the pathogenic constituents to an
acceptable level. This usually relates to a health
standard or a maximum required number of
organisms for infection.
For onsite wastewater treatment systems, the most
common form of disinfection is chlorination.
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FiltrationCarbon absorption
Membrane process
Phosphorous & Nitrogen removal
UV light
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Process is similar to that used in watertreatment
Removes
residual suspended solids
microorganisms
Commonly use dual- or multimedia filters
sand filters (single media) clog too easily
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Achieves 80% reduction in suspended solids for activated
sludge (~ 10 - 25 mg/L SS)
70% reduction in suspended solids for trickling filter
sludgeNo removal of soluble BOD or COD
soluble phosphate, nitrate, heavy metals, etc.
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Secondary-treated Wastewater Estrogenic hormones, such as the human
hormone 17b-estradiol and the synthetichormone ethinyl estradiol, could be present inwastewater at concentrations high enough to
explain the abnormalities observed in fish
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Refractory (non-biodegradable) organic chemicalsare present as soluble COD
Secondary effluent COD values of ~ 30 to 60 mg/L
The same process as pollutant retardation is soils
(from groundwater hydrology)
More efficient than process on soils
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Carbon is heated to about 1500 oC toactivate surfaces
High surface area of particles with vast
pore spaces
capable of absorbing high quantity of
organics
Surface area > 1,000 m2/g
Wastewater effluent is passed
through filter (under pressure)
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Carbon becomes exhausted indications
removal of material ceases
effluent pollutant level too high
replace carbon in system
regenerate carbon
on-site or off-site
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A phase that acts as abarrier to the flow of
molecular or ionic
species between otherphases
Driven by pressures
Produce product water
and reject stream
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Should achieve 100% removal based onmolecular weight cutoff
Actual removal observed less - may be short-
circuiting
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increase in nutrients andorganic substances,sediments
overstimulation in growth ofalgae and aquatic plants
create conditions thatinterfere with recreationaluses of lakes, and the healthand diversity of indigenouslife
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Usually accomplished with chemical
precipitation (salts)
Ferric chloride: FeCl3
Alum: Al2(SO4)3
14H2O Lime: CaO or Ca(OH)2
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FeCl3 + HPO42- = FePO4 (s) + HClAl2(SO4)314H2O + 2 HPO4
2- = 2AlPO4 (s) + 2H+ + 3SO4
2-
Effective range for alum or ferric chloride is pH 5.5
to 7.0
If insufficient alkalinity - must add lime to
neutralize H+
F Cl
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SecondaryEffluent
RapidMix
ReactionBasin
SettlingBasin
PrimaryEffluent
Activated Sludge
FeCl3Secondary
Clarifier
FeCl3
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Excess nutrients: nitrogeneous BOD exerts
oxygen demand
Anaerobic conditions in stream
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Forms: NH3, NH4+, NO2-, NO3-
Nitrification/ De-nitrification Occurs
in activated sludge process - by increasing the detention
time in activated sludge basin in separate reactor
Nitrification:
NH4+ + 2O2 = NO3
- + H2O + 2H+ (2 steps)
De-nitrification:2NO3- + organic matter = N2+ CO2 + H2O
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Ammonia stripping Raise pH to convert ammonium ions to ammonia
NH4+ + OH- = NH3
+ H2O
Ammonia purged from water in process similar to
aeration
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Tray-type Air Stripper
Packed Column AirStripper
Ultraviolet light is another disinfection method for destroyingdi i i i t t ffl t i it
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disease-causing organisms in wastewater effluent in onsitewastewater treatment systems.
The UV light destroys the genetic material of microorganisms whichprevents them from reproducing.
Wastewater flows parallel to the UV light in a thin film to increasecontact time.
For the UV light to be effective, the UV radiation must come indirect contact with the microorganisms in the wastewater stream.
Constituents allow a hiding place for the pathogenic organisms andshield them from the UV light. If the UV light does not come in
direct contact with the constituents of concern, then it is useless.
Turbidity, suspended solids, and flow rate of the wastewater mustbe kept at low levels to ensure proper treatment. Proper cleaningof the lamp sleeve and selecting the proper advanced pretreatmentcomponents will help ensure proper disinfection of wastewater.
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Sludge Management
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Sludge Treatment and Disposal to understand the origins of sludge
to understand the issues dealing with the disposal
of sludge
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Sludge disposal facilities represent 40 60% of the construction cost for WWTP,
account for 50% of operating cost.
Primary sludge
Contains inorganic solids and coarser fraction of
the organic colloids
3 to 8% solids, 70% organic material
Secondary sludge
Consists of wasted microorganisms and inert
materials; about 90% organic material
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Sludge Thicken Condition Dewater SanitaryLandfill
Stabilize Condition Dewater SoilIncorporation
Reduction Ash
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Increasing the solids content can result indrastic reductions in the sludge volume.
The cost for sludge disposal facilities is
based on the volume of sludge to be
handled.
Thus considerable saving can be attainedby sludge volume reduction sludge
thickening process.
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1. Gravity thickening
Best with primary sludge
Concept is similar to secondary clarifiers tank. Able to double the solids content thereby
eliminating half the volume of the sludge.
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2. Flotation Especially effective on activated sludge
Thickening by dissolved air floatation.
Small quantity of water is aerated under apressure about 400kpa near the bottom of the
sludge tank. The bubble will entrapped in the sludge solids,
floating the solids to the surface.
Then the thickened sludge is skimmed off at the
top of the tank.
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Aerobic Digestion
Extension of activated
sludge
Accomplished by aerationof sludge then followed
by sedimentation
Treated sludge is 3%
solids
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Anaerobic Digestion 2 stages: acid
fermentation followed
by methane production
Advantages:produce methane
do not add oxygen
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1. Chemical Conditioning Add lime, ferric chloride, or alum or polymers
Chemicals are added just prior to de-wateringstage
2. Heat Treatment
High temperatures (175-230 oC), high pressures(10 to 20 atmospheres)
Advantages bound water is released and sludge is easily dewatered
Disadvantages complex process, highly concentrated liquid stream
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1. Sludge Drying Beds Most popular method
Simple, low maintenance
Effected by climate
2. Filtration Apply vacuum to pull out water
Force out water by essentially squeezing water
between two moving filter belts
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Drying bedsVacuum
filtration
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1. Incineration Complete evaporation of water from sludge
Requires fuel
Solid material is inert
Exhaust air must be treated prior to discharge
2. Wet Oxidation
Treated sludge is wet
Requires energy
Solid material is inert
Exhaust air must be treated prior to discharge
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Incinerator
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Land Spreading lawns, gardens
agricultural land
forest land
golf courses and other public
recreational areas
Municipal Solid Waste Landfill
Utilization in other materials
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1. Wastewater treatment process flow
Physical Chemical Biological
2. Advanced Treatment
3. Disinfection
4. Sludge Management
THANK YOU
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THANK YOU