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<br />~ <br />0) <br />00 <br />CD <br /> <br />In :igure 4.4 *e have shewn a single wa~er trea~~ent :low diagr~~, ~hic~ <br /> <br />illustrates a water trea~~ent scheme for each of e~e t~o systems disc~ss~d <br /> <br />above. lie have shown both pretreatment and postreat..i\ent cperations as muY be <br /> <br />needed. Im~licit in the treatment schemes of Figure 4.4 is that the fluoride <br /> <br />is reduced down to a level that meets discharge standards, but that boron <br /> <br />passes ~hrough unchanged_ We ~ould emphasize that fluoride r2moval may ~ot <br /> <br />be achievable economically by the once-t~rouqh systems ill~strated. In that <br /> <br />case the likely sc~eme would be to treat only part of ~~e mine water by one <br /> <br />of the ~embrane processes and blend ~~e clea~ product water wit~ the untreated <br /> <br />but filtered mine water. T~e blended ?roduc~ wccld then be passed ~~roug~ a <br /> <br />specific ac.sor"?tion system for fluoride rem.oval (e. g.~, activated. alumi!1.a or <br /> <br />bor.e char). for either electrodialysis or reverse osmosis, boron re~oval is <br /> <br />assumed ~o be acccmplished by passing t~e treate= wat~r through a speci:ic <br /> <br />ion exchanger ~e.g. r Rerum & Eaas' Amte~lite I~~-743). As i!1.cicaeec i~ ~he <br /> <br />~ig~re, it migh: also be necessarI to add a ca:=on acsor?tion or resi~ a~sc=p- <br /> <br />tior. ?clishing ~i~ ~f organics removal were also required. This ~$ ~ore <br /> <br />likely to ~e raq~i=ec wi~~ elec~rcdialysi3 tha~ reverse os~osis. <br /> <br />We ha~e costec out both ~e~~ane processes ~i~~out disposa~ of tr.e con~e~- <br /> <br />tratec solution and ~it~ou~ borcn ~e~oval anc =ind the costa for the ~NO <br /> <br />syst~s to =e qu:te c:ose. Cur esti~~es are based on a 1:% annual arnor~i=ation of <br /> <br />capital. <br /> <br />I~ ~able 4-7 are shown ~~e estimated ele~~rodialys~3 c~s~s in <br /> <br />$/1000 gal as d func~ion of the ~ine water =~:oughput a~d total dissol~ed <br /> <br />soli~s in ~~e ~ater. Elect~icity ~os~s are ta~en to be 3Cjkwh. ~te O~1 cos~s <br />ccnstit~~e abo~t two-t~irds 0: ~~e total cost. <br /> <br />TABU: 4-7. COST OF MINE ;lATER TREATm:NT BY ::U:CTRO!JI!\LYSIS <br />(in SIIOOO gall <br /> <br />Flow Rate Ini tial TDS ("'gill <br />(gpm) 900 1350 <br />2,150 0.75 0.28 <br />9,400 0.66 0.74 <br /> <br />34 <br />