tehnologii ale statiilor de epurare

8/20/2019 tehnologii ale statiilor de epurare

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Figure 1: Areas Stressed due to Water Demand (World Resources Institute, 2!"

The recycling or reuse of wastewater is one way of supplementing available water supplies Therecent developments in membrane technology have made the recycling of wastewater a realisticpossibility 3ffluent from membrane treatment is able to meet or exceed current drin0ing water

regulations Despite the high !uality" the reuse of water faces several hurdles The perception ofrecycled water by the public is less than favorable /n the 1S the public is generally accepting of the reuse of water for irrigation" but strong opposition of its use for drin0ing water has beenencountered /n areas with greater water scarcity" such as Singapore" the acceptance of recycledwater is much greater %7owell" 4,,8& The additional treatment re!uired for reuse comes at anincreased cost" which may not be #ustified in areas with sufficient water supplies Although onceconsidered uneconomical" membrane technology costs have decreased by 9,: over the past );years" ma0ing the use of membranes and MBR a viable option for the first time %<ayson" 4,,8&

Membrane bioreactors are able to provide the benefits of biological treatment with a physicalbarrier separation 'ompared to conventional treatment processes" membranes are able toprovide better !uality effluent with a smaller" automated treatment process

#embrane $%aracteristics

Membrane treatment is an advanced treatment process that has become increasing popular over the past ten years Membrane processes have been understood but underutili(ed since the)*+,-s due to high capital costs Recent developments in membrane manufacturing haveenabled the production of better !uality membranes at a reduced price 'ompared withincreasing conventional water treatment costs" membrane treatment is now consideredeconomically feasible



Filtration Processes

There are six commercially used membrane separation processes= Microfiltration %M.&"1ltrafiltration %1.&" >anofiltration %>.&" Reverse $smosis %R$&" Dialysis" and 3lectrodialysis %3D&Membrane processes can be classified based on membrane separation si(e and mechanism"membrane material and configuration" or separation driving forces used Membrane processesutili(e set terminology to discuss membrane performance The rate of fluid transfer across themembrane is referred to as the flux" and has units of 0g6m4hThe pressure experienced acrossthe membrane is referred to as the trans?membrane pressure %TM2& The fluid that passesthrough the membrane is the permeate" while the flow retained by the membrane is the retentate%Tchobanoglous" et al" 4,,5&

Separations based on membrane pore si(e include M. %,)? ,4 @m&"1. %,,,4 ,) @m&" and>. %,,,,) ,,,) @m& The ranges are not strictly defined and some overlap exists Thesethree types of filtration rely on a sieving action to remove particulate matter /n comparison R$membranes have a pore si(e of ,,,,) ,,,) @m" but rely on the re#ection of small particles byan adsorbed water layer rather than physical straining %Tchobanoglous" et al" 4,,5& All fourvarieties of membranes rely on hydrostatic pressure differences to drive the separation processMicrofiltration or 1ltrafiltration is the most commonly used membrane si(e in wastewater andMBR treatment Microfiltration is able to remove proto(oa" bacteria and turbidity" while 1. has the

added benefit of virus removal %7owell" 4,,8&

Membrane Materials

Membranes are made from either organic polymers or ceramic materials 2olymers offer theadvantage of low cost production but may contain natural variations in pore si(e" and are prone tofouling and degradation 'eramic membranes offer excellent !uality and durability but areeconomically unfeasible for large scale operations" although they may be well suited for industrialapplications %Scott and Smith" )**+& All of the commercial MBR manufacturers use polymericM. membranes Table ) lists the most common types of polymer materials used to constructmembranes 2olymeric membranes are manufactured in several forms" the most common typesfor MBR are hollow fiber and plate and frame 7ollow fiber membranes are extruded into long

fibers and #oined into bundles" called modules The modules are submerged in the wastewaterand permeate is drawn into the center of the fiber by an applied vacuum 2late and framemodules are made from large membrane sheets loaded into cassettes 2ermeate is drawnthrough the membrane due to an applied pressure differential Thin layer polymeric membranesmay be laminated to a thic0er porous surface to provide additional strength and support %.ane")**+&

&able 1: 'olymer #embrane #aterials and $%aracteristics (ayson, 2)"



Membrane Configuration

.low within a membrane system can be either cross?flow or dead?end /n cross?flow the flow ofwastewater is parallel to the membrane surface and helps to reduce fouling from particulatematter Water not withdrawn as permeate is recycled and mixed with the feed stream /n dead?end flow the water is fed perpendicular to the membrane All of the water applied to themembrane must pass through the membrane" or be re#ected as waste MBR systems use cross?flow due to the high particulate level of the waste and reduced fouling potential %Alexander et al"4,,5&

Membrane systems can be designed with either individual pressuri(ed or submerged modulesSubmerged systems are becoming the industry norm due to the associated advantagesSubmerged systems have reduced capital cost since the need for module housing and pressuremanifold is eliminated The space re!uirement for a submerged system is half that for apressuri(ed system" allowing high rate systems in small spaces Submerged systems are limitedto a maximum TM2 of 9, 02a" since the high pressure side is open to atmosphere 2ressuresystems are able to operate with a TM2 up to );, 02a" but this additional range rarely #ustifiesthe additional capital expense %<ayson" 4,,8& Most MBR systems are operated as submergedsystems" with outside to inside flow hollow fibers and air6water bac0washes Due to the highsolids loading MBR membranes are designed with a lower pac0ing density" pore si(e and flux

rate than water treatment membranes %Alexander et al" 4,,5&

Membrane Integrity

Monitoring membrane integrity is necessary for all processes Membrane brea0age ordegradation can lead to the loss of physical separation and possible contamination of theeffluent Membrane integrity can be monitored by particle counters or pressure decay testing%2DT& 2DT is the preferred method due to its reliability and increased accuracy /n 2DT themembrane module is pressuri(ed to a high pressure and monitored for lea0s" the 2DT issensitive enough to detect the brea0age of a single fiber %<ayson" 4,,5&

Membrane Fouling

Membrane fouling is the largest concern in the design of membrane and MBR systemsMembrane fouling can be due to particulate build?up" chemical contamination or precipitation2articulate fouling occurs as matter in the wastewater collects on the surface of the membrane

As the layer builds up the membrane pores can be bloc0ed reducing the flux through themembrane and increasing the TM2 2articulate matter can foul membranes by either plugging or narrowing the pores or through the formation of a ca0e layer on the surface Membrane foulingcan be controlled through the use of periodic maintenance bac0?flushing and chemical cleans inplace %'/2& Bac0?flushing is completed by reversing the flow of air or water through themembrane to unclog the pores /f the membrane is heavily fouled a chemical clean may benecessary Sodium hydroxide and surfactant solution is the most common chemical used forcleaning" but other chemicals such as citric acid" chlorine" hydrogen peroxide" or aluminum

bifluoride may be used depending on manufacturer-s guidelines <ong term fouling due to theprecipitation of manganese of silica has been observed in some instances" but can generally bereversed with cleaning %<ayson" 4,,5&

/n membrane bioreactors several additional steps are ta0en to reduce fouling due to the highsuspended solids in the retentate 'oarse bubble aeration is introduced at the bottom of hollowfiber membranes and travels vertically along their length This has a two?fold purpose of aeratingthe wastewater and vibrating the membrane fibers to remove particulate matter" increasing thetime between cleanings The membranes are operated near critical flux to minimi(e fouling and ina periodic fashion" with a bac0?flush every ; to ); minutes %7owell" 4,,8&



#embrane *ioreactor

Water reuse with membrane started with the microfiltration of clarified secondary effluent Thisprocess produced high !uality recycled water" but acted as a tertiary treatment step Thedevelopment of MBR technology eliminated the need for large clarification basins /n an MBRsystem a membrane train replaces a traditional settling basin in a conventional system .igure 4illustrates the difference between conventional and membrane treatment options for waterrecycling The main advantage of using membranes is the complete physical retention ofsuspended solids from the permeate /n a conventional activated sludge treatment system the!uality of the effluent is dependant on the settling characteristics of the biomass This re!uiresthe development of well settling bacteria" which can be difficult to maintain and may not be theideal bacteria for treating the waste water The MBR system prevents the loss of biomass"eliminating the need for a settling biomass" allowing a waste specific biomass to develop %Scottand Smith" )**+&

'onventional systems are limited to solids concentrations of ; g6< or less due to hindrancesencountered during solids settling MBR systems are able to handle solids concentrationsbetween ; and 4; g6<" allowing much longer solids retention times within a reduced foot print%ing et al" 4,,,& /n addition" the MBR system allows the complete separation of hydraulic andsolids retention times" enabling greater process control and ad#ustment

Figure 2: $om+arison o $on-entional and #embrane &reatment &rains ($ote, et al., 1//0"



Figure !: *asic #*R Designs (&c%obanoglous, et al., 2!"

There are two main designs for MBR plants as shown in .igure 5 The membranes can besubmerged directly in the bioreactor" or submerged in multiple side tan0s with a constantrecirculation of wastewater The advantage of the first set?up is a smaller foot print and capital

cost The second design is used most because it allows the shutdown of part of the system formembrane or tan0 maintenance without stopping treatment completely" and flow from multipleaeration basins can be directed to a single membrane basin The design and selection of an MBRprocess is dependant on a number of design considerations and is based on the individualpro#ect

Pretreatment

.eed water to the system undergoes pretreatment which generally involves primary clarificationor screening with ,; 5 mm screens to remove large particles and debris The level ofscreening and waste water constituents may affect the process chosen .ibrous materials suchas hair and textiles may be able to pass through standard screens" while grease or oils may plug

fine screens The addition of a coagulant may be needed to condition the filter ca0e and improveflux %<ayson" 4,,5&

Flux Rate

The ideal flux rate of an MBR system is dependant on the wastewater characteristics 2ilot testingis essential for determining design flux rates" due to the wide variation in fouling ratesexperienced between sites The choice of an appropriate flux rate can have a dramatic impact on

membrane life and cleaning fre!uency Standard flux rates between ;, and 4,, <6m4h have been

reported %ing et al" 4,,)& The MBR system should be designed to handle pea0 flows of thesystem to prevent flooding of the system Alternatively an e!uali(ation basin may be needed if themembrane flux rate is inade!uate

Substrate and Solids Removal

$ne of the main advantages of MBR systems is ),,: removal of suspended solids from theeffluent MBR systems are also well suited for treating high strength wastewater with '$D andB$D loads up to )5",,, mg6< and +";,, mg6<" respectively %Scott and Smith" )**+& '$Dremovals ranging from 9* to *C: have been reported %2an0hania et al" )***= Scott and Smith")**+= Rosenburger et al" 4,,4= ing et al" 4,,,= ing et al" 4,,)& .urther investigationrevealed that the ma#ority of '$D removal occurred in the bioreactor with the membraneseparation contributing 9 to )4: of the total removal %ing et al" 4,,,= ing et al"4,,)&



&able 2: &y+ical #*R luent uality (&c%obanoglous, et al., 2!"

'arameter 3nits &y+ical $oncentrations

3ffluent B$D mg6< ;

3ffluent '$D mg6< 5,

3ffluent >75 mg6< )

3ffluent Total > mg6< ),3ffluent Turbidity >T1 )

3ffluent 2E mg6< ,;

E with chemical 2 removal

Nutrient Removal

MBR systems operate aerobically due to the air bubbles used to clean the membrane fibers" andrely on heterotrophic bacteria for B$D and '$D reduction The aeration rate of an MBR systemis controlled by the air flow needed to clean the membranes Due to the high aeration rate in themembrane tan0s the dissolved oxygen concentration of the return flow can reach + mg6<

%'rawford and <ewis" 4,,;& Ammonia present in the feed water is converted to nitrate in theaerobic tan0 Ammonia?nitrogen removals ranging from *+ to *9: have been reported %ing etal" 4,,,= ing et al" 4,,)= Scott and Smith" )**+& Typical MBR effluent !uality is shown in Table4

The high dissolved oxygen concentration can be detrimental to denitrification which re!uiresanoxic conditions to proceed Denitrification can be achieved by creating anoxic (ones within thebioreactor basin" but care must be ta0en to prevent the introduction of air within the recyclestreams Biological phosphorous is difficult but possible in an MBR system" the recycle streamsmust be carefully designed so that nitrate and oxygen does not contaminate the anaerobic (one%'rawford and <ewis" 4,,;& A general process diagram for biological phosphorous removal isshown in .igure 8 2hosphorous removal is more commonly completed chemically by iron co?precipitation adsorption through the addition of ferric chloride coagulant

Figure ): #*R *iological '%os+%orous Remo-al Design (www.usilter.com"



Solids Management

MBR systems are designed with SRTs ranging from ; to 5, days Due to the long sludge agesand the low .6M ratio" biomass production is approximately half that of a conventional system$ver time the biomass concentration within the tan0 will reach steady state without sludgewasting Because of the accumulation of grit and inorganic solids in the tan0s periodic wasting ofsolids is re!uired This wastage will be significantly less than a conventional system due to theincreased biodegradation Rosenburger et al" %4,,4& found that settled sludge in the bottom ofthe aeration tan0s contained +,: inorganic particulate MBR systems are also prone to foamformation on the tops of the bioreactors and provisions must be made for removal

#*R A++lications

MBR treatment is applicable to many sectors" including municipal" industrial" and waterreclamation The use of an MBR process for water reclamation can reduce the demand forpotable !uality water on local supplies" and reduce pollution from waste discharges into localwater bodies

Municipal Treatment

The filtration of municipal activated sludge is an ideal application for MBR treatment" Researchcompleted by Rosenberger et al" %4,,4& found that an MBR system could be used to treatmunicipal waste water A Fenon pilot MBR was operated for ;5; days to study the treatmentcharacteristics of the system The pilot unit was e!uipped with three compartments for aeration"filtration" and denitrification" as shown in .igure ; 7ollow fiber Feeweed membranes with a ,4@m pore si(e were used" with a 5; second bac0?flush every ten minutes A maximum TM2 of ,;bar was allowed The raw wastewater had a mean concentration of C9+ mg6< '$D" 8* mg6< >78?>" )4 mg6< 2$8?2" and M<GSS of 54: The 7RT varied from ),8 to );+ hours" with acorresponding volumetric loading rate of )) to )C 0g '$D6m

5d The MBR system was found to

achieve ),,: suspended solids removal" *;: '$D reduction" ),,: nitrification" and 94:denitrification These results correlate with pilot studies completed by 'ote et al" %)**C& in /ndio"

'alifornia and Maisons?<affitte" .rance /n addition + log removal of total coliforms and 8 logremoval of bacteriophages were found

Figure 4: 'ilot #unici+al &reatment #*R 'rocess Sc%ematic (Rosenberger et al, 22"



Figure 5: &ra-erse $ity #*R Design ayout ($raword and ewis, 24"

The largest operating municipal treatment MBR system in >orth America is located in Traverse'ity" Michigan and capable of treating 9; MHD 3xpansion of the conventional wastewatertreatment plant began in 4,,4 The site was severely limited in the amount of space forexpansion Hiven the community desire for high !uality effluent" MBR was the ideal choice Theuse of MBR technology allowed a 8,: increase in capacity within the same footprint %.igure +&The biological nutrient removal process used was a modified 1niversity of 'ape Town flowconfiguration The process was designed with three recirculation (ones due to the high D$concentration in the membrane tan0 %.igure C& The MBR unit began operation in summer 4,,8and is able to achieve effluent phosphorous concentration of ,4 mg6< %'rawford and <ewis"4,,;&

Figure 0: &ra-erse $ity *iological 'rocess ($raword and ewis, 24"



Industrial Treatment

MBR technology is also well suited for the treatment of industrial wastes Most industrial wastesare high strength and nutrient limited" which generally leads to poor settling biomass" ma0ing theuse of membranes ideal /ndustrial applications for reuse are !uite common and rely onmembrane systems to provide high !uality recycled process water /ndustrial plants commonlyconsume more than a million gallons of potable water per day as process water Reduction ofindustrial consumption through reuse can have a ma#or impact on local environments and wateravailabilities

Scott and Smith %)**+& studied the application of an MBR system for the treatment of ice?creamproduction waste Despite a higher initial cost" a ,4 @m ceramic membrane was used dueincreased longevity and previous experience in industrial applications The ceramic membranewas used for both filtration and aeration The waste stream contained '$D levels between 9,,,

),,,, mg6< and B$D levels between 4,,, 8,,, mg6< at a temperature of 44 ? 54I' Thewaste stream had a B$D;J>J2 ratio of ),,,J)J; %compared to an ideal conventional treatmentratio of ),,J)J;& '$D removals ranged between 95 and *C:" and B$D removals rangedbetween *, and *9: depending on the system configuration Another advantage of the MBRsystem was the ability of the system to maintain a stable p7 of + 9" even at feed concentrationsover ), This was attributed to the presence of lactic acid bacteria

Murray et al %4,,;& presented the application of MBR treatment to beverage manufacturingwaste The MBR process was chosen due to its ability to treat a highly variable" high temperaturehigh strength waste" without the need for settling The limited space available and the high !ualitywater for reuse made MBR the ideal choice The bottling wastewater had an abnormal nutrientprofile high in 7" $" and S %.igure 9& The regulation of nutrients within the MBR had a largeeffect on process performance 1pon start?up the system had a flux rate of 4+ gal6ft

4d and

re!uired cleaning every 4 C days Ad#ustment of the nutrient deficiency improved the flux rate to;5 gal6ft

4d and reduced cleaning re!uirements to once every 5, days A 'J>J2 ratio of ),,J),J4

was found to provide the best results

Figure 6: $om+arison o &y+ical and *ottling Sludge 7utrient 'roiles (#urray et al., 24"

Water Reclamation

The use of MBR technology for reclamation is a rapidly expanding application MBR technology iswell suited for reuse treatment due to its small footprint and relatively easy operation Small MBRsystems can be designed to pull wastewater directly from the sewer at the remote points of reuse"eliminating the need for large central treatment plants and redistribution MBR effluent is ideal forfurther treatment by reverse osmosis The high !uality of the MBR permeate allows increased R$



flux with reduced fouling .ollowing R$ treatment the water generally meets or exceeds alldrin0ing water standards and may be even higher in !uality than KvirginL water Despite the highwater !uality public acceptance within the 1S is difficult Studies have suggested that a hierarchyof acceptable use exists %7owell" 4,,8&

Treatment Reuse 7ierarchyJ

) .orest /rrigation4 .orage 'rop /rrigation5 .ood 'rop /rrigation8 2ar0 and Harden /rrigation; <ivestoc0 Watering+ 'oolingC /ndustrial 'leaning9 /ndustrial 2rocess* .ishery 1se), Recreational Water Supplies)) 2ublic Hrey Water )4 2ublic Drin0ing Water

/n many cases the publics fears are unfounded or irrational as Kde?factoL reuse of drin0ing watersupplies occurs already" often with less treatment than direct reuse designed systems /n areaswith ample water supplies the reuse of economic cost of wastewater reuse cannot usually be

#ustified /n areas with water scarcity such as Singapore" which relies on Malaysia to supply it-swater the reuse of water is highly accepted Reused water is sold under the name >eWater andall wastewater treatment plants are being retrofitted with M." R$ and 1G systems for production%<ayson" 4,,8&

#*R #anuacturers and Full Scale 'lants

Within the 1S three main manufacturers mar0et an MBR system These include Fenon" 1S.ilter"and ubota which is distributed by 3nviro!uip 3ach system is uni!ue in its design and provides

ma0ing it almost impossible to interchange systems within the design process

enon

Fenon 3nvironmental /nc is head!uartered in 'anada and mar0ets the FeeWeed MBR systemFenon is a membrane only manufacturer that has become the industry leader in MBR TheFeeWeed system uses reinforced hollow fiber membranes immersed directly in the aerationbasin Fenon membranes are arranged in rectangular modules which form a cassette %.igure *&'oarse aeration at the bottom of the membranes helps 0eep them clean 2ermeate is drawn fromthe system by a vacuum pump Fenon has full scale plants operating in Traverse 'ity" M/"

American 'anyon" 'A and .ulton 'ounty" HA An MBR plant schematic is shown in .igure ),

Figure /: 8enon aminated 9ollow Fiber #embranes (www.enon.com"



Figure 1: 8enon #*R 'lant (www.enon.com"

!SFilter

1S.ilter is the largest environmental treatment company in the 1nited States MBR systems aremanufactured and sold by the Memcor division located in Ames" /owa Although 1S.ilter hasrecently entered the MBR mar0et they are trying to ma0e up for lost time The Memcor Mem#etMBR system uses hollow fiber membranes arranged in round modules on rac0s submerged in aseparate membrane basin %.igure ))& Aeration and mixed li!uor is introduced together through atwo?phase air?water #et located at the bottom of the module This Mem#et system creates an evendistribution of M<SS across the module and helps scour deposited solids from the membranesurface 1S.ilter also offers an MBR pac0age plant called the .ast2ac MBR that is fully selfcontained for small scale systems %.igure )4& 1S.ilter has full scale MBR plants operating in'rescent 'ity" 'A" >ewhall Ranch" 'A" and 3verglades >ational 2ar0" .<

Figure 11: 3SFilter 9ollow Fiber #embrane #odule Rac; and #em<et System(www.usilter.com"



Figure 12: 3SFilter Fast'ac #*R (www.usilter.com"

"ubota

ubota membranes are distributed within the 1S by 3nviro!uip /nc The system utili(es flat platemembranes loaded within multiple cassettes in a plug flow basin The membrane cassettes areinstalled directly in the aeration basin %.igure )5& ubota has pac0age scale MBR plantsoperating in Running Springs" 'A" Tulalip" WA" and Mcinney Roughs" T

Figure 1!: Kubota 'late and Frame #*R $oniguration (www.en-iro=ui+.com"

$onclusion

The application of MBR technology is rapidly expanding" with new installation occurring everyyear MBR technology is highly suited for the reclamation of waste water due to the ability toproduce drin0ing water !uality effluent The effluent produced can be reused within industrialprocesses or discharged to surface waters without degrading streams and rivers The small footprint and ease of operation of the MBR systems ma0es it ideal for application in remote areaswhere wastewater can be reused for irrigation or ground water recharge /n addition MBR can beadapted to almost any industrial or municipal wastewater" reducing demand on local watersupplies" and pollution in local water bodies



Reerences

) Alexander" = Huendert" D M= 2an0rat(" T M %4,,5& 'omparing M.6R$ 2erformanceon Secondary and Tertiary 3ffluents in Reclamation and Reuse International#esalination $ssociation Conference Proceedings

4 Bontrager" S= Wallis?<age" '= 7em0en" B %4,,;& MBR Steps 1p to Meet Reclamation'hallenge Conference Proceedings %&&' $WW$ Membrane Tec(nical Conference

5 'rawford" H= <ewis" R %4,,;& Traverse 'ityJ >orth America-s <argest $perating MBR.acility Conference Proceedings %&&' $WW$ Membrane Tec(nical Conference

8 Delgado" S= Dia(" .= Gillarroel" R= Gera" <= Dia(" R= 3lmaleh" S %4,,4& /nfluence ofBiologically Treated Wastewater Nuality on .iltration through a 7ollow .iber Membrane#esalination)" 1)5" 8;*

; 'ote" 2= Buisson" 7= 2ound" '= Ara0a0i" H %)**C& /mmersed Membrane ActivatedSludge for the reuse of Municipal Water #esalination)" 11!" )9*

+ .ane" A H %)**+& Membranes for Water 2roduction and Wastewater Reuse #esalination)" 15" )

C 7owell" O A %4,,8& .uture of Membranes and Membrane Reactors in HreenTechnologies and for Water Reuse #esalination)" 152" )

9 <ayson" A %4,,5& Microfiltration 'urrent now?how and .uture Directions MemcorTec(nology Centre* wwwusfiltercom

* <ayson" A %4,,8& /mpact of Water Technology Developments on 3conomics of WaterRecycling and Reclamation in the 2ower /ndustry Memcor Tec(nology Centre*wwwusfiltercom

), Murray" 'W= Abreu" <7= 7usband" OA %4,,;& Three <iters of Soda in a Two <iterBottleJ The use of Membrane Bioreactors at a Bottler-s WWT2 Conference Proceedings%&&' $WW$ Membrane Tec(nical Conference)

)) 2an0hania" M= Brindle" = Stephenson" T %)***& Membrane Aeration Biorectors for Wastewater TreatmentJ 'ompletely mixed and 2lug?flow $peration C(emical+ngineering ,ournal)" 0!" )5)

)4 ubota" wwwenviro!uipcom

)5 Rosenburger" S= ruger" 1= Wit(ig" W= Man(" W= S(ew(y0" 1= raume" M %4,,4&2erformance of a Bioreactor with Submerged membranes for Anaerobic Treatment of Municipal Waste Water Water Researc()" !5" 8)5

)8 Scott" OA= Smith < %)**+& A Bioreactor 'oupled to a Membrane to 2rovide Aerationand .iltration in /ce?'ream .actory Waste Water Water Resources)" !1" )" +*

); Tchobanoglous" H= Burton" .<= Stensel" 7D %4,,5& Waste-ater +ngineeringTreatment and Reuse. Metcalf and +ddy /

t(+d)" McHraw 7ill" >ew Por0" >P" 1SA

)+ 1S.ilter" wwwusfiltercom

)C World Resources /nstitute" 4,,5" wwwwriorg

http://www.usfilter.com/


http://www.enviroquip.com/


http://www.wri.org/


http://www.enviroquip.com/


http://www.wri.org/




)9eon" wwwxenoncom

)*ing" ' 7= Wen" 7= Nian" P= Tardieu" 3 %4,,)& Microfiltration?Membrane?'oupledBioreactor for 1rban Wastewater Reclamation #esalination)" 1)1" +5

4,ing" ' 7= Tardieu" 3= Nian" P= Wen" 7 %4,,,& 1ltraflitration Membrane Bioreactorfor 1rban Wastewater Reclamation ,ournal of Membrane Science)" 100" C5

http://www.xenon.com/

http://www.xenon.com/

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