Bentonite used as Adsorbent Agent of the Coupling Adsorption Ultrafiltration of the Secondary Effluents for their Reuse

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1 Amrican Journal of Environmntal Scincs 4 (6): , 28 ISSN X 28 Scinc Publications Bntonit usd as Adsorbnt Agnt of th Coupling Adsorption Ultrafiltration of th Scondary Efflunts for thir Rus D. Abdssmd and G. Nzzal Laboratory of Procsss Enginring- Environmnt, Univrsity of Scincs and Tchnologis Houari Boumdi n, B.P. 32 El Alia 16111, Bab Ezzouar, Algirs, Algria Abstract: This prsnt study has for principal objctiv to trat scondary fflunts of th Staouli purification plant (Algria) with th avrag charactristics in th Chmical Oxygn Dmand (COD) is 76 mg L 1 and 16 NTU of turbidity by adsorption ultrafiltration coupling for its rus in irrigation or in industry to rduc th watr dmand. A minral ultrafiltration tubular mmbran of CARBOSEP M2 (15 Kg mo L 1 ) in dynamic mod with a transmmbran prssur P = 1 bar and a cross flow vlocity U = 3 msc 1 was usd for this purpos. Th adsorbnt choic was mad on an Algrian blaching ground: th bntonit availabl on th markt with low cost. It has sorptivs proprtis and ions xchang with spcific ara 25 m 2 g 1. In th first stp, w considrd th organic mattr adsorption on bntonit in static mod (jar tst). Th optimal conditions wr dtrmind corrsponding to th bst limination of th Chmical Oxygn Dmand with a final valu qual to 3.6 mg L 1 and turbidity, in jar tst with 1.5 NTU valu for an optimal bntonit concntration qual to g L 1. In th scond stp, th adsorption ultrafiltration coupling, showd a final valu in COD qual to 9.2 mg L 1 and final turbidity qual to 1.2 NTU. An improvmnt of th prmat flux was showd qual to 48.8% for th optimal concntration bntonit g L 1. Th adsorption significantly improvs th ultrafiltration prformancs. Ky words : Bntonit, ultrafiltration, scondary fflunts, adsorption, rus INTRODUCTION Algria is classifid among th poorst countris as rgards hydrous potntialitis, in lowr part of th thortical thrshold of scarcity fixd by th World Bank at m 3 hab yar. It is in this contxt that th rcours to th wastwatr rus is ssntial and bcoms an obvious rality, prmits on th on hand to protct th nvironmnt, in ordr to avoid th surfac contamination and undrground frsh watrs and on th othr hand, to bring additional watr quantitis not rquiring a drinkabl quality to rus thm in agricultur and industry, two sctors larg-scal consumr watr. Adsorption prmits rmoval of organic colloids which play an important rol in fouling phnomna. Kim t al. [1] showd that th coupling of minral clay ultrafiltration allowd a mmbran fouling rduction. Th advantag of such a hybrid mthod is th fast and ffctiv adsorption of th organic mattr by th adsorbnts. Brasqut t al. [2] procdd to th coupling adsorption ultrafiltration whil using lik adsorbing agnt of th fibrous activatd carbon and a Tch Sp mmbran with cut off 3 Kg mo L 1. Th coupling allowd th limination of composd high molcular wight and low-wight molcular. Adsorption isothrms wr ralisd on synthtic solutions containing phnol concntration qual to 125 mg L 1. Th maximum capacitis adsorption ar rspctivly C* = 117 mg g 1 for th granular activatd carbon and 143 mg g 1 for th fibrous activatd carbon. Lin t al. [3] showd that th us of th powdr activatd carbon lik th pr-tratmnt with ultrafiltration or combination, allowd th fouling mmbran rduction. Th powdr activatd carbon is inffctiv for soluts of molcular wights lss than 3 Kg mo L 1 and mor than 17 Kg mol 1. In our prvious study [4] th addition of frric chlorid as coagulant and powdr activatd carbon as adsorbnt in th fd ( scondary fflunt) of an UF quipmnt improvs th prmat flux and th quality of th prmat. So t al. [5] Corrsponding Author: D. Abdssmd, Laboratory of Procsss Enginring- Environmnt, Univrsity of Scincs and Tchnologis, Houari Boumdin, Bab Ezzouar, Algirs, Algria Tl: Fax:

2 Tabl 1: Charactristics of scondary watr of Staouli Paramtr Man valu Tmpratur ( C) 23.5 ph 7.8 Turbidity (NTU) 16. Conductivity (µs CM 1 ) BOD 5 (mg O 2 L 1 ) COD (mg O 2 L 1 ) 76. SS (mg L 1 ) procdd to th coupling of th Biological Powdrd Activatd Carbon (BPAC) with microfiltration with th aim of producing tratd watr abl to b rusd. Th avrag rmoval fficincy of th organic mattr was 83 %, for an initial COT concntration of th fflunt of 9.8 mg L 1. In rfrnc to ths rsarch, th prsnt study is rlatd to limination of th chmical oxygn dmand still prsnt at th lvl of th scondary fflunts. For that, w dirctd our study towards th dtrmination of th optimum conditions for th adsorption coupld with ultrafiltration. Exprimntal conditions: Th xprimntal study was carrid a scondary fflunt sttling at th wastwatr tratmnt plant of Staouli (Algria) functioning by a systm with activatd sludg. Charactristics of th scondary fflunt: Th scondary fflunt of th wastwatr tratmnt plant of Staouli (Algria) has th following avrag charactristics (priod January-Sptmbr 25) ar shown in th Tabl 1. Procdurs: Initially, w considrd th adsorption of th organic mattr on bntonit in static mod (jar-tst) at ambint tmpratur. In th scond tim, variabl bntonit amounts (-2 g L 1 ) ar addd dirctly in th fd tank to th scondary fflunt for its ultrafiltration. Tabl 2: Charactristics physics of Maghnia bntonit Charactristics Dscription Humidity % max Dnsity.5 g cm 3 ph 3-4 Blaching capacity 95-98% Tabl 3: Avrag chmical composition of Maghnia bntonit Elmnts Composition (%) SiO Al 2O F 2O 3 3-Jan Ca O.5-1 Mg O Na 2O 2-Jan K 2O -.74 Fig. 1: Exprimntal st-up And th Tabl 3 hraftr illustrats th chmical composition of bntonit. RESULTS AND DISCUSSION Dtrmination of th adsorption optimal conditions: Th givn optimal conditions corrspond to th bst limination of th Chmical oxygn Dmand with a final valu qual to 3.6 mg L 1 as shown in th Fig. 2a and a turbidity in jar tst with a valu of 1.5 NTU for on optimal bntonit concntration qual to g L 1 (Fig. 2b). Exprimntal st up: This consists of fd tank (1) whr th adsorbnts is addd, a hat xchangr (2), a cntrifugal pump (3), a flow mtr (4), control valvs (5), manomtrs(6), a minral mmbran ultrafiltration tubular (7) CARBOSEP M2 (15 Kg mol 1 ) in dynamic mod with a transmmbran prssur?p = 1 bar and a cross flow vlocity U = 3 m sc 1 (Fig. 1). Ragnts: Th bntonit (blaching ground) is an inxpnsiv local minral. Th bntonit contains mor than montmorillonit 75% and constituts th principal part most activ. Th avrag xchang capacity of montmorillonit varis from 8-15 mq/ g clay. Th physical charactristics of bntonit usd ar givn in Tabl Adsorption kintic: W followd th concntration in COD volution according to tim aftr addition of an optimal bntonit concntration (Fig. 3) on a sampl of scondary fflunt. Th kintic study mad it possibl to not that th tim ncssary to obtain th adsorption quilibrium is 6 h with th rmoval fficincy COD is 63%, a rsidual valu of 28 mg L 1. Adsorption isothrm: Th adsorption isothrms wr stablishd by obsrving aftr a contact tim of 6 h. Th rsults obtaind rval a linar variation btwn th quantity of th organic mattr adsorbd and its quilibrium concntration, in solution C (mg L 1 ) according to Fig. 4.

3 Ths isothrms wr modlld by th Frundlich and Langmuir quations, which giv th quilibrium adsorption capacity X/M (mg g 1 ) according to th quilibrium concntration in solution C (mg L 1 ) according to rspctivly: X/M = kc 1/n (1) and (a) * bcc = (2) + X M 1 bc X/M = Quantity adsorbd pr unit of addd bntonit mass C = Chmical oxygn dmand at th quilibrium, k, 1/n = Frundlich constants b = Langmuir s quilibrium paramtr C* = Maximum adsorption capacity Frundlich modl: Th rprsntation graphic (Ln X/M) according to (Ln C ) givs accss to us th constants k and n, with n = 3.855, k = 2.49,.26 X/M = 2.49 C (b) Fig. 2: Variation of th COD (a) and th turbidity (b) according to th bntonit concntration Langmuir modl: With th graph M/X = f (1/C ), w obtain an avrag straight lins as th Fig. 5b shows it. Th maximum adsorption capacity, is givn by th paramtr C* = 7.6 mg g 1 with th Langmuir s quilibrium paramtr b =.31 L g 1 X/M and th function xprssion is writtn as follows: X.7.7.6C = M 1+.7C (3) Fig. 3: Adsorption kintic for C = g L 1 Fig. 4: Adsorption isothrm at t = 6 h Th isothrm obtaind to 293 K rlats in conformity with that of typ I, of Langmuir to an adsorption according to a monomolcular layr. Evolution of th prmat flux according to tim: Th prmat flux dcrass with th tim, that is du to th progrssiv accumulation of th spcis stoppd on th surfac and th pors of th mmbran thus inducing phnomna of concntration polarization and fouling partial of th pors. Th addition of th various bntonit amounts is an advantagous contribution, bcaus th limit prmat flux valu passs from a 3.5 L h 1 m 2 (without addition) to a maximum valu of 45.3 L h 1 m 2 for a bntonit concntration of g L 1, an incras of 48.8%. This rsults in a comptition btwn th two tchniqus (ultrafiltration and 718

4 Ln (X M -1 ) M/X (g mg 1 ) y =.2594x R 2 = Ln C (a) y = x R 2 = /C (mg L) 1 (b) Fig. 5: Rprsntations graphic according to th Frundlich modl (5a) according to th Langmuir modl (5b) COD (mg L 1 ) C = g L 1 C= 5 g 1 C= g 1 C=15 g 1 C=2 g Tim (mn) Fig. 7: Variation of th COD according to th tim for th various concntrations Turbidity (NTU) C = g L 1 C = 5 g L 1 C = g L 1 C = 15 g L 1 C = 2 g L Tim (mn) Fig. 6: Variation of prmat flux according to th tim for th bntonit for various concntrations adsorption) for th molcular spcis limination. This shows that th bntonit allowd a good adsorption of th molculs which ar at th origin of th ultrafiltration mmbrans fouling (Fig. 6). COD rduction: Figur 7 shows a significant rduction of th COD is 88% compard to th initial valu for th mmbran M2. Thr is thus a vry good complmntarity s btwn bntonit abl to rtain crtain molculs and th ultrafiltration mmbran abl to rtain th larg molculs and colloids. Th bntonit addition contributs to th COD limination with th optimal bntonit C concntration = g L 1. Th rsidual COD valu is 9 mg L 1. Fig. 8: Variation of th turbidity according to th tim for various adsorbnt concntrations COD (mg L 1 ) Raw fflunt Raw fflunt+uf Raw fflunt +Ads+UF Tst Fig. 9: Variation of th COD according to th various tsts Turbidity rduction: According to Fig. 8, turbidity dcrass according to tim for th various bntonit concntrations, howvr, th lowst valu is obtaind for th tst without adsorbnt, a rat of limination of 94.8%. Variation of th Chmical oxygn dmand for diffrnt procss: Figur 9 compars th quality watr obtaind for th various procsss tstd. Th bst 719

5 rsult is obtaind coupling adsorption ultrafiltration with final of COD qual to 9 mg L 1. Th rsidual limiting valus showd that th coupling of th two tchniqus (adsorption-uf) incrass th limination fficincy of th two paramtrs. CONCLUSION W could show th fasibility of th coupling adsorption-ultrafiltration. Th rsults obtaind show a significant rduction in th chmical oxygn dmand for th ultrafiltration mmbran M2 (cut off 15 Kg mo L 1 ). An improvmnt of th prmat flux 48.8% is obtaind. Adsorption improvs in a significant way th ultrafiltration prformancs. Th us of bntonit mad it possibl to rtain crtain molculs of low molcular mass, that ultrafiltration alon dos not mak it possibl to stop (micropollutants). Th COD dcrass from mg L 1 in th cas of only on ultrafiltration and up to 9 mg L 1 in th bntonit prsnc for an optimal concntration of g L 1 for th sam mmbran M2: th prmat obtaind can on th on hand b rusd and on th othr hand, th m mbran pors intrnal fouling is rducd. REFERENCES 1. Kim, C., M. Hosomi, A. Murakami and M. Okada, Effct of clay on th fouling by organic substancs in portabl tratmnt by ultrafiltration. Watr Sci. Tchnol., 3: Brasqut, C., E. Subrnat and P. Lcloirc, Slctiv adsorption on fibrous activatd carbon of organics from aquous solution: Corrlation btwn adsorption and molcular structur. Watr Sci. Tchnol., 35: Lin, C.F., Y. Huang and O.J. Hao, Ultrafiltration procsss from rmoving humic substancs: Effct of molcular wight fractions and PAC tratmnt. Watr Rs., 33: cat.inist.fr/?amodl=affichn&cpsidt= Abdssmd, D., G. Nzzal and R. Bn Aim, 23. Coagulation adsorption ultrafiltration for wastwatr tratmnt and rus. Watr Supply, 3: So, G.T., Y. Suzuki and S. Ohgaki, Biological Powdrd Activatd Carbon (BPAC) microfiltration for wastwatr rclamation and rus. Dsalination, 6: cat.inist.fr/?amodl=affichn&cpsidt=