Waste energy

7/31/2019 Waste energy

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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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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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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
http://upload.wikimedia.org/wikipedia/commons/a/aa/Septic_tank_EN.svg


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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





pre-aeration

flow measurement

flow balancing

/equalisation basin

removal of rags,

rubbish, grit, oil,




remove organic and





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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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http://en.wikipedia.org/wiki/Image:Trickle_Filter.png


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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





pre-aeration

flow measurement

flow balancing

/equalisation basin

removal of rags,

rubbish, grit, oil,




remove organic and





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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

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