1 Wastewater Treatment 1 (Wastewater Characteristics)

8/19/2019 1 Wastewater Treatment 1 (Wastewater Characteristics)

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Chapter 4A

Wastewater Treatment: Characteristics and Systems

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http://bjwsa%20wastewater%20treatment.mp4/http://bjwsa%20wastewater%20treatment.mp4/


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Learning Outcomes

At the end of this learning session

students should be able to1! "nderstand what causes water pollution

#! $ecogni%e the sources of wastewater

&! State the characteristics of wastewater

4! Appreciate the importance of w'w treatment

(! Apply systems used to treat the wastewater

#


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What is water pollution)

* Water pollution is any chemical+ physical orbiological change in the ,uality of water that

has a harmful effect on any li-ing thing thatdrin.s or uses or li-es /in0 it!

* When humans drin. polluted water it often

has serious effects on their health! Waterpollution can also ma.e water unsuited forthe desired use!

&


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The Sources of ollution

Water pollution occurs when a

body of water is ad-ersely

affected due to the addition oflarge amounts of materials to the

water! When it is unfit for its

intended use+ water is considered

polluted!

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2omestic and 3ndustrial Sewage+ which

contains decomposable organic matter and

pathogenic agents! 3ndustrial and trade wastes+ which contain

toic agents ranging from metal salts to

comple synthetic organic chemicals!

Agricultural pollutants+ which comprisefertili%ers and pesticides!

hysical pollutants+ such as thermal pollution

and radioacti-e substances!

Sources of Water ollution

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A heavily polluted stream in Guiyu, China. Along side domestic

rubbish the water is badly polluted with toxic waste from the e-

waste recycling yards in the town. 5


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Example of water pollution

Citarum River (West Java) –

Most polluted in the world

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olluted $i-er in 3ndia

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yoto $i-er

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1#

Clean river and

drainage channels in

Kyoto (ug !""#)


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1&

A River in Seoul,Korea


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;ur.y lang $i-er in L

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A River in KL,

Malaysia


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What is Wastewater)

* Wastewater is any water thathas been ad-ersely affected in,uality by anthropogenic influence!

* 3t comprises li,uid wastedischarged by domesticresidences+ commercialproperties+ industry+ and'oragriculture and can encompassa wide range of potentialcontaminants andconcentrations!

* 3n the most common usage+ it refers to the municipalwastewater that contains a broad spectrum of contaminantsresulting from the miing of wastewaters from differentsources!

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Wastewater Contaminants

* Suspended solids < can causesludge deposits and anaerobicconditions in the en-ironment

* Biodegradable organics < cancause anaerobic conditions in

the en-ironment* Pathogens < transmit disease

* Nutrients < can causeeutrophication

* Heavy metals < toicity to biotaand humans

* Refractory organics < toicity tobiota and humans

* Dissolved solids < interferewith reuse

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Characteristics of Wastewater

* Physical < The physical characteristics of waste water

include its solid content==suspended organic

matter+ floating matter and dissol-ed matter+its temperature+ color+ odor'smell+ density+conducti-ity+ specific gra-ity+ transmittanceand specific weight!

< Septic sewage is blac. /due to precipitation ofiron sulfide0

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* Chemical < ;unicipal wastewater also contains a -ariety of inorganic

substances from domestic and industrial sources+ including a

number of potentially toic elements such as arsenic+ cadmium+

chromium+ copper+ lead+ mercury+ %inc+ etc!

< Among the organic substances present in sewage arecarbohydrates+ lignin+ fats+ soaps+ synthetic detergents+ proteins

and their decomposition products+ as well as -arious natural and

synthetic organic chemicals from the process industries!

< >umber of chemicals found in w'w is limitless

< ;easure of w'w strength often use CO2 and ?O2

* CO2 < Chemical Oygen 2emand

* ?O2 < ?iological Oygen 2emand



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* Biological < athogenic bacteria will be present in wastewater

at much lower le-els than the coliform group of

bacteria+ which are much easier to identify and

enumerate /as total coliforms'199ml0!

< Escherichia coli are the most widely adopted

indicator of faecal pollution and they can also be

isolated and identified fairly simply+ with theirnumbers usually being gi-en in the form of faecal

coliforms /@C0'199 ml of wastewater!

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Characteristics of 2omestic

Wastewater

#9


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;unicipal Wastewater

Treatment Systems

* retreatment < remo-es materials

that can cause operational

problems+ e,uali%ation optional

* rimary treatment < remo-e 59B

of solids and &(B of ?O2

* Secondary treatment < remo-e

7(B of ?O2 and solids* Ad-anced treatment < -aries: 8(

B of ?O2 and solids+ >+

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retreatment of 3ndustrial

Wastewaters

* 3ndustrial wastewaters must be pretreated

prior to being discharged to municipal

sewer system* Approach is to remo-e materials that will

not be treated by municipal system

* Local authority must monitor and regulateindustrial discharges

* retreatment re,uirements set by the law

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#&

Primary reatment

Secondary

reatment

!"#$%$&'$(NPrimary reatment


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#(

Sewage

Tunnels

in 2e-elopedCountries


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Treatment lant

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The Stic.ney WWT+ located on (69 acres in Cicero+ 3llinois+

southwest of Chicago+ ser-es #!4 million people li-ing in Chicago

and 4& suburban communities! Capacity: 1!44 billion gallons per

day! #6


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Screens

* Coarse screens < @unction to remo-e

large obDects such as

pieces of wood+ plastic

bottles+ rags+ tetileetc

< Si%e of opening up to

6(=199 mm

< Cleaned eithermanually or

mechanically

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Screens* @ine Screens

< @unction is to remo-efine contaminants+

debris+ plastics that

are not hang on

coarse rac. screen! < Opening si%e small up

to only 1& mm

< ;ost fine screens are

mechanically cleaned

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Erit Chambers

* urpose: remo-e inertdense material+ such as

sand+ bro.en glass+ silt

and pebbles! These

materials is called FgritG

* Erit will cause abrasion

of pumps and other

mechanical de-ices if

not remo-ed

* Erit chambers can be of

rectangular or circular

shape /-orte0

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>ote : All design and calculation are the

same as water supply grit chamber


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Horte Erit Chamber * The screened influent enters

tangentially and flows around the

upper chamber

* AdDustable+ rotating paddles or Det of

air augment the spiraling flow to

create an induced -orte which

settles the grit+ transports it to the

center opening of the fied floor plate

for collection in the lower chamber

* The grit solids are remo-ed from the

lower chamber by an air lift or

recessed impeller pump for further

washing and dewatering!

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1 Wastewater Treatment 1 (Wastewater Characteristics)