CHE 6405 Term Paper

8/16/2019 CHE 6405 Term Paper

1/29

An Overview on Zero Liquid Discharge Technology

and Promoting ZLD in Bangladesh

CHE 6405

Water Pollution and Control

Submitted toDR. MD !A!"#OOR "LAM

Assistant Professor

Department of Chemical Engineering !"E#

Submitted b$

TA#$"R A!M%D

Student %o& '0'50((0()

ABR"#A &!A#

Student %o& '0'50((0(*

Department of Chemical Engineering !"E#


2/29

ABTRA'T

+ero li,uid discharge -+.D/ refers to a treatment process in hich the plant discharges no

li,uid effluent into surface aters in effect completel$ eliminating the en1ironmental

pollution associated ith treatment& Apart from this benefit a +.D process also ma2es

effecti1e use of asteater treatment rec$cling and reuse thereb$ contributing to ater

conser1ation through reduced inta2e of fresh ater& #his paper includes effluent treatment

methods the prospect of +.D in !angladesh the benefits 3 challenges and e,uipment

o1er1ies& +ero discharge solutions can be accomplished b$ concentrating the effluent using

1arious techni,ues including membranebased and multiple effect e1aporationbased

s$stems and reco1er$ and rec$cling of ater&

'


3/29

TABL% O( 'O#T%#T

A!S#AC#&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&i

#A!.E 7 C%#E%#S&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&ii

.8S# 7 789"ES A%D #A!.ES&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&i1

' 8%#D"C#8%&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'

'&' +ero .i,uid Discharge&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'

( Effluent #reatment :ethods&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&;

(&' Ph$sical "nit perations


4/29

4 1er1ie on +ero .i,uid discharge&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'(

4&' Process Selection&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&';

4&( Some +.D Process E?amples&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'6

4&(&' 8onicsB EnChem& A +.Dsolution for the semiconductor industr$&&&&&&&&&&&&&&&&&&&&&&'6

4&(&( #energ$sB plating aste ater reco1er$ s$stem&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&')

5 Achie1ing +.D E,uipment 1er1ie&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'@

5&' e1erse smosis -/&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'@

5&( Electrodial$sis re1ersal -ED/&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'*

5&; E1aporator&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'*

5&4 Cr$stalli>er&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&('

5&5 Spra$ Dr$er&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&('

6 C%C."S8%&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&((

E7EE%CES&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&(;

;


5/29

L"T O( (")*R% A#D TABL%

(")*R%+

7igure (' #$pical 7lo Diagram of a !iological #reatment Plant&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&6

7igure 4' 9eneral +.D #echnolog$ Process&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'(

7igure 4( +ero li,uid discharge s$stem flo diagram&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'4

7igure 4; E?ample of ho a present +.Ds$stem is integrated in a poer plant&&&&&&&&&&&&&&&&'5

7igure 44 8onicsB +.Ds$stem for the semiconductor industr$&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'6

7igure 45 #energ$sB +.Ds$stem for the plating industr$&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&')

7igure 5' 8ndustrial e1erse smosis Process&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'@

7igure 5( 8ndustrial Electrodial$sis re1ersal s$stem&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'*

7igure 5; A falling film e1aporator also called a brine concentrator


6/29

'!APT%R ,

, "#TROD*'T"O#

8n the past se1eral decades industrial production has increased in !angladesh& Water consumption for industrial use has conse,uentl$ risen and ill continue to rise& Ecological

issues are an integral and important part of the en1ironmental issues challenging !angladesh&

Poor air ,ualit$ ater pollution and garbage all affect the ,ualit$ of food and the

en1ironment necessar$ for ecos$stems to thri1e& %oada$s En1ironmental concerns are

steadil$ increasing and regulator$ authorities are constantl$ tightening the en1ironmental

standards insisting that industries adopt ad1anced asteater treatment technologies

including +.D solutions&

#oda$ fe industries are concerned ith de1eloping +.D solutions that address some of the

folloing challenges

'& 8nno1ati1e and customi>ed solution offerings

(& Highl$ corrosi1e effluent and the selection of metallurg$

;& eco1er$ of pure process condensate for reuse and rec$cling

4& perating temperature and pressures and scaling and fouling tendenc$

5& Continuous operation of the s$stem ith minimi>ation of cleaninginplace -C8P/ effluents

6& Selection of appropriate t$pe of e1aporator effects in multi effect e1aporation s$stem

)& ptimi>ation of CAPE and PE for +.D solutions&

,., Zero Liquid Discharge

Any process or combination of processes, by virtue of which there is no liquid effluent, or

discharge from a process plant

8t implies that asteater is treated and effecti1el$ rec$cled and reused such that there is no

effluent discharge& +.D is usuall$ accomplished b$ concentrating the effluent using 1arious

techni,ues including membranebased and multi effect e1aporation based s$stems& +.D

in1ol1es

#he elimination of the li,uid aste effluent stream from the plant

'


7/29

#he rec$cling of reco1ered ater and solids

#he establishment of no li,uid pollutant norms&

8f implemented correctl$ +.D has the potential not ust to alle1iate concerns of effluent

discharge but also to lead to ater conser1ation hich is critical for regions e?periencing

ater scarcit$&

#$picall$ +.D s$stems are used here there are en1ironmental limitations such as ater

insufficienc$ and here strong en1ironmental regulations are obligator$F either because ater

resources are scarce or an industr$Bs acti1it$ is highl$ polluting& 8n principle the end goal of

+.D is to eliminate -to the e?tent feasible/ the discharge or disposal of li,uid aste from a

facilit$ herein no asteater gets discharged to surface ater bodies& #his is ultimatel$

accomplished b$ rec$cling reusing or reducing the 1olume of aste stream primaril$

including aterbased streams& #he nonater components of a asteater come from either

the manufacturing process itself or from a cleaning process and can include an$ number of

materials chemicals oils or solids& #$pical aste streams that produce large 1olumes of

asteater include cooling toer blodon gas scrubber blodon ione?change

regeneration effluent and rinses plant ash don and rain ater runoff and process astes&

#hese come from a ide 1ariet$ of industries including but certainl$ not limited to

• :etal Wor2ing

• :etal 7inishing

• :anufacturingGProduction

• #ransportation

• Water #reatment

• :aterial ec$cling

• Pharmaceutical

• 7ood and !e1erage

'!APT%R -

(


8/29

- %((L*%#T TR%ATM%#T M%T!OD

Effluent can be treated in a number of different a$s depending on the le1el of treatment

re,uired& #hese le1els are 2non as preliminar$ primar$ secondar$ and tertiar$ -or

ad1anced/ e is used to remo1e large solids such as plastics cloth

pol$thene etc& hich ma$ damage process e,uipment reduce the effecti1eness of the E#P or contaminate atera$s&

-.,.- (low %quali2ation

#here are se1eral different steps in the industrial processes and therefore asteater ,ualit$

and ,uantit$ 1aries o1er time& E#Ps are usuall$ designed to treat asteater that has a more

or less constant flo and a ,ualit$ that onl$ fluctuates ithin a narro range& #he

e,uali>ation tan2 o1ercomes this b$ collecting and storing the aste alloing it to mi? and

become a regular ,ualit$ before it is pumped to the treatment units at a constant rate& #o

;


9/29

determine the re,uired 1olume of an e,uali>ation tan2 the hourl$ 1ariation of flo needs to

be determined&

-.,.3 edimentation and (iltration

#he flocs formed in flocculation are large enough to be remo1ed b$ gra1itational settling

also 2non as sedimentation& #his is achie1ed in a tan2 referred to as the sedimentation tan2

settling tan2 or clarifier& Sedimentation is also used to remo1e grit and suspended solids to

produce clarified effluent and to thic2en the sludge produced in biological treatment&

7locculation and sedimentation should remo1e most of the suspended solids and a portion of

the !D


10/29

en1ironmental 1ie point but can corrode stainless steel therefore plastic or appropriatel$

coated pumps and pipes must be used&

-.-.- 'hemical 'oagulation and (locculation

Coagulation is a comple? process but generall$ refers to collecting into a larger mass the

minute solid particles dispersed in a li,uid& Chemical coagulants such as aluminium sulphate

-alum/ or ferric sulphate ma$ be added to asteater to impro1e the attraction of fine

particles so that the$ come together and form larger particles called flocs& A chemical

flocculent usuall$ a pol$electrol$te enhances the flocculation process b$ bringing together

particles to form larger flocs hich settle out more ,uic2l$ 7locculation is aided b$

gentle mi?ing hich causes the particles to collide&

-.3 Biological *nit Processes /01

!iological treatment is an important and integral part of an$ asteater treatment plant that

treats asteater from either municipalit$ or industr$ ha1ing soluble organic impurities or a

mi? of the to t$pes of asteater sources& #he ob1ious economic ad1antage both in terms

of capital in1estment and operating costs of biological treatment o1er other treatment

processes li2e chemical o?idationF thermal o?idation etc& has cemented its place in an$

integrated asteater treatment plant&

!iological treatment using aerobic acti1ated sludge process has been in practice for ell o1er

a centur$& 8ncreasing pressure to meet more stringent discharge standards or not being

alloed to discharge treated effluent has led to implementation of a 1ariet$ of ad1anced

biological treatment processes in recent $ears&

#he obecti1e of biological treatment of industrial asteater is to remo1e or reduce the

concentration of organic and inorganic compounds& !iological treatment process can ta2e

man$ forms -#able (/ but all are based around microorganisms mainl$ bacteria&

Table 2- 2: Biological Treatment Processes

Treatment Processes De4inition

Suspendedgroth processes e&g& acti1ated

sludge

#he microorganisms are maintained in

suspension in the li,uid

Attachedgroth processes or fi?edfilm

processes

#he microorganisms are attached to some inert

medium such as roc2 or inert plastics

Combined processes A combination of suspendedgroth

and fi?edfilm

5


11/29

#hese microorganisms use components of the effluent as their IfoodJ and in doing so brea2

them don to feer comple?es and less ha>ardous compounds& 8n the process the

microorganisms increase in number&

Figure 2-1: T!ical Flow "iagram o# a Biological Treatment Plant

* A sludge recycle line is essential for activated sludge systems but is not needed for fixed film systems. ** The aeration unit can be either activated sludge or a fixed film reactor.

#here are to main t$pes of processes these in1ol1e suspended microbial groth -e&g&

acti1ated sludge/ and attached microbial groth -e&g& fi?ed film/& With both approaches large

populations of microorganisms are brought into contact ith effluent in the presence of an

e?cess of o?$gen& 8n both s$stems the microbial population has to be retained in a tan2

referred to as the reactor& With suspended groth s$stems microbes gro in small aggregates

or IflocsJ -this is 2non as acti1ated sludge/&

-.3., Activated ludge

Acti1ated sludge -AS/ lea1es the reactor ith the treated effluent but is settled out in a

clarifier and returned to the aeration unit to rec$cle the bacteria& 8f the amount of AS is

e?cessi1e some ma$ be disposed of rather than being rec$cled&

-.3.- (i5ed (ilm

8n fi?ed film s$stems the microbial population gros as a thin la$er -a IbiofilmJ/ on the

surface of an inert support medium& #he classical fi?ed film s$stem is 2non as a percolating

6


12/29

or biological filter and uses small stones as a medium to support microbial groth& 8n the

more modern s$stem microbes gro on plastic supports& 8n the traditional percolating filters

effluent is spra$ed o1er the medium and tric2les through a pac2ed bed ith o?$gen entering

from the air& 8n more recent reactor designs the medium -usuall$ plastic/ is submerged in

effluent and air is blon into the base of the reactor& Submerged fi?ed film reactors using

plastic media re,uire much less land& 7i?ed film s$stems re,uire a final clarifier to remo1e

particles of biofilm that become detached from the medium&

!iological treatment plants must be carefull$ managed as the$ use li1e microorganisms to

digest the pollutants& 7or e?ample some of the compounds in the asteater ma$ be to?ic to

the bacteria used and pretreatment ith ph$sical operations or chemical processes ma$ be

necessar$& 8t is also important to monitor and control pH as ad1erse pH ma$ result in death of the microorganisms& #he E#P must be properl$ aerated and must be operated (4 hours a da$

;65 da$s a $ear to ensure that the bacteria are pro1ided ith sufficient IfoodJ -i&e&

asteater/ and o?$gen to 2eep them ali1e& .i2e humans microorganisms need a Ibalanced

dietJ ith sources of carbon nitrogen phosphorus and sulphur&

-.0 Physio6chemical Treatment

#he basic units needed for a standalone ph$siochemical treatment plant are screening an

e,uali>ation unit a pH control unit chemical storage tan2s a mi?ing unit a flocculation unit

a settling unit and a sludge deatering unit&

-.7 Physio6chemical and Biological Treatment

8n this t$pe of treatment a combination of ph$sical operations and ph$siochemical and

biological processes are used& #he basic units needed for a ph$siochemical and biological

treatment plant are screening an e,uali>ation unit a pH control unit chemical storage tan2s

mi?ing units flocculation units a primar$ settling unit an aeration unit and a secondar$

settling unit& #he ph$siochemical unit ala$s comes before the biological unit&

)


13/29

'!APT%R 3

3 "#TROD*'T"O# O( ZLD "# BA#)LAD%!

#he te?tile sector is the bac2bone of !angladeshBs econom$& Hoe1er the industr$ is faced

ith man$ challenges due to high resource -energ$ ater and chemical/ footprint and its

conse,uent en1ironmental impact& Water usage b$ the te?tile industr$ in !angladesh is

estimated to be '500 million cubic meters hich is principall$ made of groundater&

Around )0K of this ater consumption ta2es place in the et processing of te?tiles hich

in1ol1es ashing d$eing and finishing of te?tiles& !esides high ater footprint the te?tile

industr$ also faces the challenge of dealing ith the problem of effluent discharge and the use

of coagulants and chemicals for its treatment&

eali>ing the scale of these issues and the urgent need for addressing them !angladesh

9o1ernment has issued the +ero .i,uid Discharge -+.D/ egulation for the te?tile sector&

#his poses a huge challenge for the industr$ particularl$ for the small and medium si>ed

units& #he 2e$ to its successful implementation ould be a cautious and practical approach

and 1ie this as an opportunit$ to deal ith the pressing en1ironmental challenges in a

sustainable manner


14/29

#he capitalBs groundater le1els are falling rapidl$ due to e?cessi1e e?tractions to meet the

needs of its groing population said Dha2a Water Suppl$ and Seerage Authorit$& #he

capitalBs underground ater le1el has dropped to 60 meters belo ground le1el according to

DWASA& 8n (0'' the capitalBs ground ater le1el as 5' meters belo the ground le1el

according to a stud$ of !angladesh Agricultural De1elopment Corporation& #he groundater

le1els in the capital are falling b$ to to three meters each $ear according DWASA


15/29

#he aste discharge ,ualit$ standards differ according to the point of disposal& So the

standards are different for inland surface ater -ponds tan2s ater bodies ater holes

canals ri1er springs or estuaries/F public seers -an$ seer connected ith full$ combined

processing plant including primar$ and secondar$ treatment/F and irrigated land defined as an

appropriatel$ irrigated plantation area of specified crops based on ,uantit$ and ,ualit$ of

asteater


16/29

1i& Sustainable groth of the industr$ also implies groth in econom$ and sustainable

li1elihood for man$ people ho are dependent on the te?tile d$eing cluster either

directl$ or indirectl$&

3.-.- 'hallenges o4 ZLD

i& +.D results in generation of ha>ardous solid astes -particularl$ aste mi?ed salt/

causing disposal challenges hich is being stored in storage $ards ithin the CE#Ps&

ii& 7or the chemical sludge the best a$ to dispose it off is its gainful utili>ation for

cement coprocessing but it needs tie up ith a illingGrecipient cement compan$&

iii& #he high cost of operation of a +.D is also a maor challenge& #he reco1er$ of ater

and salt -Sodium sulphate and brine/ offsets this costs significantl$ but it ould appl$

onl$ to ater scarce areas here the cost of ater is high&

i1& High Carbon foot print of a +.D facilit$ is another maor concern& #he t$pical poer consumption ranges from @ to '0 2WGm;& #he thermal e1aporators alone consume

about (040 2WGm; in addition to se1eral tons of fireood for the boilers&

1& %on uniform application of +.D standards across the countr$ for similar industries

has serious impact on the competiti1eness of the local industr$&

1i& 8mplementation of +.D re,uires a host of ad1anced asteater treatment

technologies& 8mplementation of +.D in #amilnadu has highlighted se1eral

#echnolog$ shortcomings such as in #hermal e1aporation 3 brine concentration Salt

separation and Cr$stalli>ation Colour remo1al etc&

'!APT%R 0

''


17/29

0 O$%R$"%8 O# Z%RO L"=*"D D"'!AR)%

+ero .i,uid Discharge -+.D/ represents the ultimate cuttingedge treatment s$stem for the

total elimination of asteater effluent into neighboring atera$s& #he +.D S$stem

remo1es dissol1ed solids from the asteater and returns distilled ater to the process

-source/& e1erse osmosis -membrane filtration/ ma$ be used to concentrate a portion of the

aste stream and return the clean permeate to the process& 8n this case a much smaller

1olume -the reect/ ill re,uire e1aporation thus enhancing performance and reducing poer

consumption& 8n man$ cases falling film e1aporation is used to further concentrate the brine

prior to cr$stalli>ation


18/29

re1ersal -ED/& !$ combining these technologies ith e1aporation and cr$stalli>ation +.D

s$stems ha1e become less e?pensi1e& #he$ are hoe1er combined differentl$ depending on

the circumstances see chapter general guidelines& #ogether ith these components a 1ariet$

of other ell2non ater treatment technologies are used in +.Ds$stems for pretreatment

and polishing treatment er -CNS#/

• Spra$ dr$er -SD/ -used onl$ for lo1olume flos/

•

E1aporation pond -EP/• .andfill -.7/

Product ater is produced b$ the !C and CNS# process steps& Processing steps for the

asteater treatment beginning ith concentrate -conc&/ are as follos


19/29

• Scheme ; conc& O .S O O EP

Solids produced from the lime softening and cr$stalli>ation steps go to a landfill&

8f the ater flo rate is small not man$ components are necessar$& #he folloing general

guidelines are accepted toda$ ers andGor spra$ d$ers can be combined&

• '0 50 gpm of feed use a cr$stalli>er alone&

• 50 '00 gpm of unsaturated feed use an GEDGcr$stalli>er combination&

• 50 '00 gpm of saturated feed use an e1aporatorGcr$stalli>er combination&

• '00 500 gpm of feed either an Gcr$stalli>er or an e1aporatorGcr$stalli>er

combination ma$ be the most economical&

• 500 '000 gpm of feed all three should be used

Figure +-3: ero li.uid disc$arge sstem #low diagram

'4


20/29

Figure +-+: /)am!le o# $ow a !resent L"-sstem is integrated in a !ower !lant

'5


21/29

0.- ome ZLD Process %5amles+

0.-., "onics> %n'hem. A ZLD6solution 4or the semiconductor industry

8onic claims that their ater treatment s$stem the EnChem remo1es more than **K of the

contaminating materials& #he EnChem technolog$ is also capable of reducing ater usageduring the semiconductor manufacturing process b$ up to @5K through reclaim& 8onicsB

EnChem technolog$ is a lo pressure ater treatment solution& 8t is specificall$ designed to

reduce ater consumption and operating costs


22/29

0.-.- Tenergys> lating waste water recovery system

#his +.Ds$stem is used for the %i and Cr plating industr$& 7iltration is combined ith

separated bed and an e1aporator& #he s$stem can handle flo rates of 50 gpm&

Figure +-: Tenergs L"-sstem #or t$e !lating industr

8n the pretreatment step ultrafiltration -"7/ is combined ith carbon filter& "7 is used for

remo1al of 1olatile organics 1irus and bacteria and suspended solids& #he carbon filter

contain granular acti1ated carbon media that adsorb impurities ithin moleculesi>ed pores&

?idants such as chlorine are also remo1ed during their interaction ith the carbon surface&

After pretreatment the ater passes through the polishing step hich consists of separate

bed deminerali>ers here the salts in the ater are separated into positi1el$ charged cations

and negati1el$ charged anions& #he process begins hen the ater is passed through cation

e?change resin& #he cation resin is in the h$drogen form -HQ/ and e?changes all the positi1el$

charged ions for h$drogen thus con1erting all the impurities in the ater into acids& #he

ater from the cation e?change is then passed through anion e?change resin& Separate bed

means that there are to tan2s one containing cation resin and the other containing anion

resin& #he anion resin is in the h$dro?$l form -H / and e?changes all the negati1el$ charged

ions into the h$dro?$l form completing the con1ersion of all impurities into ater -HQ

Q H

O H(/ thus pro1iding pure deminerali>ed ater&

#he concentrates finall$ feed an e1aporator pro1iding clean ater for plating thus

completing the closed +.Ds$stem&

')


23/29

'!APT%R 7

7 A'!"%$"#) ZLD+ %=*"PM%#T O$%R$"%8

7., Reverse Osmosis :RO<e1erse osmosis is a process here ater is pressuri>ed so that it passes through a semi

permeable membrane lea1ing dissol1ed inorganic salts and silica behind& As a rough guide to

performance can produce a concentrate containing ;0000 ppm total dissol1ed solids

-#DS/& #o problems ith are that organics ill seriousl$ foul s$stems and that

re,uires a feed stream that is free of suspended solids& !ecause of this it is ad1isable to

remo1e organics from asteater before it enters the so e?tensi1e frontend filtration

e,uipment is re,uired& Some membranes are pH and temperature sensiti1e so pH control and

feed e,uali>ation ma$ be necessar$& is also ,uite energ$intensi1e& #he ad1antage of

o1er e1aporation is that the life c$cle costs of are about half those of e1aporators&

Figure 0-: (ndustrial 4everse 5smosis Process

'@


24/29

7.- %lectro6dialysis reversal :%DR<

Electrodial$sis re1ersal -ED/ is a membrane process in hich electrol$tes migrate across

chargeselecti1e membranes in response to an electrical field& 8n ED the polarit$ of the

electrodes is re1ersed se1eral times an hour and the fresh ater and the concentratedasteater are e?changed ithin the membrane stac2 to remo1e fouling and scaling& ED

differs from in that the ions are remo1ed and the ater is left behind hereas in the

ater is remo1ed and the ions are left behind& !ecause of this silica and dissol1ed organics

are not remo1ed ith an ED process hich is an important aspect to remember hen the

clean stream is reused& .i2e ED re,uires solids and organics remo1al from the feed for

reliable operation&

Figure 0-6: (ndustrial /lectro-dialsis reversal sstem

7.3 %vaorator

E1aporators come in all si>es and shapes for e?ampleF falling film rising film forced

circulation and scraped surfaceGthin film and combination e1aporator& E1aporators produce a

distillate stream that is 1er$ clean t$picall$ containing less than '0 ppm of #DS one of the

main reasons h$ e1aporators are used in a +.Ds$stem& #he most pre1alent t$pe is the

'*


25/29

falling film e1aporator also called brine concentrator see figure 4& #his e1aporator can treat

or ED concentrates to a total solids -#S/ concentration of ;00 000 ppm& At this 1alue

the boiling point rise of the brine results in either an e?cessi1el$ large heattransfer area

-large capital cost/ or an e?cessi1el$ large temperature difference -large operating cost/&

alues higher than this ma2es the combination of a cr$stalli>er and an e1aporator more

economical than an e1aporator alone&

Figure 0-7: 8 #alling #ilm eva!orator9 also called a brine concentrator [1]

(0


26/29

7.0 'rystalli2er

Figure 0-1: T$e $eat #lows in a crstalli;er

#he cr$stalli>er reduces highl$ saturated asteater to dr$ solids for disposal& High purit$

ater is reco1ered from the cr$stalli>er for rec$cling& A cr$stalli>er ma$ also reco1er specific

salts from a mi?ed salt aste stream& #he cr$stalli>er is a forced circulation e1aporator hich

uses a mechanical 1apor compressor or plant steam as the energ$ source&

7.7 ray Dryer

When a cr$stalli>er is not appropriate the spra$ dr$er is another method for deatering the

concentrated slurr$ left o1er from the brine concentrator& #he spra$ dr$er transforms the

slurr$ into a fine poder of mi?ed salts for disposal& #he spra$ dr$er atomi>es the asteater

slurr$ inside a hot chamber instantl$ 1apori>ing the ater droplets and lea1ing onl$ dr$ salts

behind&

('


27/29


28/29

R%(%R%#'%

'& :unter & Industrial Wastewater Treatment !athways "f Industrial #ffluents

Treatment & (0'(& p& '*5('0&

(& Pescod :&!& Wastewater Treatment And $se In Agriculture& '**( 7ood AndAgriculture rgani>ation f #he "nited %ations ome& p& ;)56&

;& Edd$ :&a& Wastewater #ngineering Treatment and %euse& ol& (nd Ed& (00;

:c9ra Hill %e Nor2&

4& Singh R& #ffluent Treatment !lant &esign, "peration And Analysis "f Waste Water

(0'( p& '4(;&

5& Roe !ostancic &.& 'etting to (ero &ischarge )ow %ecycle That ast +it of %eally

+ad Wastewater & (0'; 9EBs Water 3 Process #echnologies&

6& Series P&P& !romoting (ero iquid &ischarge andate for the +angladesh Textile

Industry& (0'5 9o1ernment of "Bs Department for 8nternational De1elopment& p& '

@&

)& :ohammad A& Ho,ue :&:&H& a>i :atin Ahmed &eclining groundwater level

and aquifer dewatering in &ha-a metropolitan area, +angladesh causes and

quantification. H$drogeolog$ Rournal (00)& ,7-@/ p& '5(;'5;4&

@& anagement Information %eport for the month of ovember /001. onthly +ulletin&

(00; WASA -Water Suppl$ and Seerage Authorit$/ DWASA Dha2a !angladesh&

*& :asood :& 'roundwater levels in &ha-a falling rapidly in The ew Age& (0'5

Dha2a !angladesh&

'0& :& A2htaru>>aman A&C& Rerr$ napp :ahbubul A& :ahmood Sami$a Ahmed

2hoosing an #ffluent Treatment !lant & (0'( !angladesh Centre for Ad1anced

Studies Dha2a !angladesh&

''& The #nvironment 2onservation %ules 3445, 6unofficial translation7 D& :inistr$ of

En1ironment and 7orests Editor& (000 9o1ernment of the PeopleBs epublic of

!angladesh Dha2a !angladesh&

'(& (#%" I8$I& &I92)A%'# 6(&7 9:9T# & (0'6F A1ailable from

httpGG&degremonttechnologies&comGTdegremonG+E.8L"8DD8SCHA9E

+.DSNS#E:&

';& #illberg 7& (&;systems An "verview& (004 Department of Energ$ #echnolog$

o$al 8nstitute of #echnolog$ #H Stoc2holm& p& ''5&

'4& :ic2le$ :& 9urvey of )igh;%ecovery and (ero iquid &ischarge Technologies for

Water $tilities& (00@ Wateeuse 7oundation Ale?andria A

'5& #valuation and 9election of Available !rocesses for a (ero;iquid &ischarge 9ystem for the !erris, 2alifornia, 'round Water +asin in &esalination and Water

(;

http://www.degremont-technologies.com/~degremon/ZERO-LIQUID-DISCHARGE-ZLD-SYSTEMhttp://www.degremont-technologies.com/~degremon/ZERO-LIQUID-DISCHARGE-ZLD-SYSTEMhttp://www.degremont-technologies.com/~degremon/ZERO-LIQUID-DISCHARGE-ZLD-SYSTEMhttp://www.degremont-technologies.com/~degremon/ZERO-LIQUID-DISCHARGE-ZLD-SYSTEM


29/29

!urification %esearch and &evelopment !rogram %eport o. 3

Documents

CHE 6405 Term Paper