. I
i-lazardous Wastes Minimization by Reuse and Recycling --_-I_-
a t a Naval A v i a t f o n Depot
Anthony F. KI amian ~ Pt’ograri bknnger Naval A i r Propul s i ? n Center
P.0. Box 7176 T*-eoton , YJ 98598
Jaries A. H e i s t , V ice P r e s i d e n t H e i s t C n g i n e e r i n g C o r p o r a t i o n
P . O . Box 4513 5929 Flat-ket S t r e e t Wiimington, NC 28405
Hazardous Wastes ill’niiuization by Reuse and Recycling a t a Naval Aviation Depot
Anthony F. Klarman Jaines A . HeIst Vice President Pro gram Man a g e r
Naval Air Propulsion Center i ie is t Engineering C o r p o r a t i o n P . O . Box 7176 11.0. Box 4518 5929 Narket S t
Trenton, NJ O N S O Wi:mington, NC 28405 Ab s t rd c t
A freeze c rys t a l l i za t ion process i s being deinon- s t r a t e d fo r t r ea t ing a wide var ie ty o f wastes generated in the plat ing arid other indus t r ia l s h o p s a t the Norfolk, VA Naval Aviation Depot ( N A D ) . As envisioned the f reeze process w i l l t r e a t various r inses , p l a t i n g ba ths ~ a n d clean- ing so lu t ions for recycle in the NAD, g rea t ly reducing and even el iminat ing discliarges t,o t h e indus t r ia l waste treatiiient plant . The inanner in which the freeze process will be incorporated t o d o t h i s includes:
- reiiiove water Kith s u f f i c i e n t pur7 ty f o r recycle cis r inse water and i n b a t h makeup;
- concentrate the chern:cals i n r inse waters fo r recycle t o pldt ing baths;
- concentrate pickling was tes t o recycle the concentrazed a c i d while prec ip i ta t ing the dissolved rwta l s for reinoval as jnnocuous sludge;
- concentrate paint s t r ippe r s and solvents in r inses and other contaminated waters, separat ing useFiil organics froin resl’dusl aqueous concentrates.
Prel iminai-y ecot!omic f eas ib i l i t y analyses show t h a t recycling o f r inse waters froin chrome, nickel a n d cadiniiini 1 ines 5s economicaUy j u s t i - f ied by the recovery o f metal values, savings i n conventional treatnient cos t s , and reduced haz- ardous niaterial production. l ienefits i n meeting ’ environmental di sciiargc 1 iirii t s , reducer! waste water treatiiient p1 a n t operating 1 a b o r a n d m i I?- tenance cos t s , and t r e a t i rig contain‘inated bathes have n o t been accrued to the ju s . t i f i ca t ion for t h i s techno1 ogy .
2 . introduction
Freeze c rys t a l l izatiori i s a generic separation process t h a t can be used to separate const i - tuents i n solut ions (Ref 1 ) . When applied t o hazardous (and non-.hazardous) waste, i t i s best used t o minimize the waste being generated, a n d where f eas ib l e t o recover pure components fo r recycle t o the process. Because i t i s r e l a t i v e l y insens i t ive t o the type o f contaminant l’n waste waters, arid can provide a very high degree of purif icat- ion in one s t ep , i t has been ident i f ied in a number o f programs as a po ten t ia l ly favor- ab1 e process fo r iiiitil’niizing waste generation and t r ea t ing m s t e s and contam-inated 1 iquids a % b . 0 , I L.i,icdiation s i t e s :
- t h e Navy C.ivil Engineering Laboratory ( N C E L ) has identl’fied freeze crystdl 1 i z a - t i o n as one o f only a few processes t h a t can t r e a t a Hide var ie ty o f the na. ter ia ls t h a t t h e Navy wil 1 have t o dedi with in
- the Cal Vfornia Department o f k a l t h Ser- vices has selected the freeze process f a r support in i t s Innovative Technologies Demoi?stra-tion i)rogram (Ref 3 ) .
- “vi roiiiiien tal Systems Company (ENSCC.) .is iiivesting in the technology with ci dcmon- s t r a t ion corvmercial urii t. t~ support i t s hazardous waste busi t iess a c t i v i t i e s (Ref 4) *
j 4. - b b s i t e remediation prograin (Ref 2).
Section 3 of t h i s paper presents background i tnl’orniation on t he N A D pro jec t , a technical descr ipt ion o f the -freeze process, a n d m s t e t.ia.r;t?rs w j I:.iiin the !)AD t h t i t are be ing crjr!siljered f o r th-is t rea t iwnt . Sectiiin 4. gives d e t a i l s o f the prog ra in conduc’tcd For -the Fldvy. S x t i on 5 presents a synopsjs o f the ecor:om?;cs o f reuse
di) i i teij~ie ~i i i i e L , i ~ t j ~ i > ~ ; i : ~ ~ ' i c j i.;til;~i:~ d ~ i i i q ~ ! i i
Freeze c rys ta l 1 izatiori process. conclusions from t h e prograin a re sumr'idrized in Section 6.
Suiiviiary and
3. Background
3.1 Project History
I n 1909 the Navy NAD Planning Group o f Plant Engineering h a d been 'looking fo r be t t e r ways t o meet t h e i r i ndustrial e f f l u e n t standards arid were approached by Heist Engineering t o consider f reeze c rys ta l1 I'zation For recycle a n d reiisc. The freezing process had been investirja.tc.d fo r such appl icat ions (Ref I.) in p r i o r laboratory work. The respons ib i l i ty for research a n d dev- elopment on new technology fo r use in the I l A U i s the char te r O F the Naval Air Propulsion Cornnand headquartered in Trenton, N J . This g r o u p coor-
-- dinated the prograin, provided Navy funding, a n d has technical oversight responsibi l i t ,y.
A p i l o t p l a n t Tor the Navy progra,n was ,procured i n 1383, with modiFications a n d fn s t a l l a t ion a t the Norfol I< NAD occurri fig iri 1984. The program was suspended unt i l l a t e 3985 while furidiiig was arranged, the progi"am W ~ S adver t i sed , Iiids eval- uated, and a cont rac t negot ia ted. The p i i o t un i t was refurbished in t h e f i r s t h d l f of 19P7, inodi- f i ed t o r e f l e c t perforniance t e s t feedback over a four m o n t h period, a n d t e s t i n g on wastes frorn the MAD commenced i i i September, 1987.
3 .2 Process Ecscription
A simp1 i f i e d process f reeze c rys t a l l i z3 t fon floi.! diagram i s shown in Figure 1. The process i s conipri sed of 'core equipment' a n d then auxi l - 1 i a r i e s t h a t s r e required fo r var iz t ions o f t,i.ie process. f o r opera.tiriy on a var ie ty of f l u i d s . p le , many waste solutiorrs a r e complex mixtures t h a t , as solvent i s removed, have more than one material c rys ta l 1 , !z ing and/or foriii ad&i t io i ia l l i qu id phases. To e f fec t ive ly p u r i Yy "ie sol- veil t , these addi ti ona l phases must be re:i:oved from the solvent c rys t a l s t h a t d r e Forming, arid o.ften the phases tha t forn: must be sepdrated one f ro!n another.
The var ia t ions provide t h e f l e x i b i l i t y F o r exm-
Generally i n deal i n 9 w i t h hazardous w a s t e s and resource recovery appl i ca t ions thc sol v ie i i t f s water, b u t the process i s appl icab?e t o other ' solvents d S well. The value of tile i?r;)CeSS in pur? fyi n g aqueous i.:astwatc?r: 4 s . t l ? d t ;ienrly a ? 1 mater ia l s a re excl tided from tile c rys ta l matrix when ice i s formed, and thus the prsduct wdter t h a t r e s u l t s i s very pure.
I
The -freeze c r j J s t i l lization process i s a coritiil- uous operation. Heat i s renovcci i n t h e c rys t a l - 1 i z e r by d i r e c t con'cact with a v o l a t i l e rePr'ig- e r an t . A s tiie r e f r ige ran t bo i l s o f f , i - t Y'P!~GVCS heat froin the 1 i qui d ~ 1 o w r i n g 'd ie 'temperature unt i l coniponents b e g i n t o c r y s t a l l i z e diie t o lower solubi ' l i ty o r reaching the Freezing point of the components in the so lu t ion .
Typically the c rys t a l s a re grown t o a inaxirnum si'ze of 350 microns and the s lur ry i s maintained a t no niorc t h a n 2 5 w t - % crys ta l Fraction t o fac- i l i t a t e p u m p i n g and minimize inclusions. The s lu r ry i s pumped to a c rys ta l separator where .the mother 1 iqiior i s reiiioved and the sur.Faces of the c rys ta l s are washed o.F adhcri n g impure sol u- t i on . Mother l iquor i s returned t o the c rys t a l - l i z e r so t h a t more c f the desired component i s recovered.,
To minimize energy use, the prodtict c r y s t a l s are remel ted by condensing compressed r e f r ige ran t . This provides a heat pimping arrdngernent in the r e f r ige ra t ion cycle . Since there i s net energy p u t in to the process by the mechanical equiprr;e:it a n d ambient heat leaks, there wiY he sonic t i e a t t o he re jec ted from the sys%:;m. T h i s r e s u l t s in excess reFrigerant which i s coiiipressed i n a second s tage a n d condensed wi t h cool ing water.
Generally process 1 iquids are cross exchanged as shown by the feed exchanger t h a t cools f e e d with col d product a n d concentrate s treatns.
The freeze c rys t a l l i za t ion proccss i s inherent ly in sens i t i ve t o the cornposi t i o n or-' the waste streams i t i s processing. The process adapts auto!natically 'to changes i n i n f 7 ucnt coinposf- t i on . I t can hand!#? a wide var ie ty o-F w a s t e strearn coinponc?nts without pret t *eat i i ;er i t :
- Acids and bases a re concentrated. Me1 ted i ce has d cor:-esfiotidir!y change iii pl.1 o f 3 t o 4 un i t s toward neu t r a l , regardless o f the v o l a t i l i t y o f the so)'Iutc.
- Vola t i le organics remain i n t he mQther i iquor (conceritrateci strfain) .
- Sal ts when at satirrat-ion, c rys ta l 1 i z e and a re rernoved f r o in the process as a sludge.
- A1 1 dissolved coinponetits -in the wnst.e a r e excluded equally frorri t h e . ice crysta: with the same degree o f yeduct-ion -in contai:iii;a- Lion l eve l s in t h e recovered c r y s t a l s ; t i l e reduction r a t i o , or r a t i o o f conce:itration i n the 1 !quid to t h a t in tile recovered c r y s t a l , i s typ ica l ly IO00 t o 10,000. I
The a b i l i t y o f f reeze c r y s t a l l i z a t i o n compnred t o other treati?iet>t processes, .FGr was tes witil varying composition and c h a r a c t e r i s t i c s i s sum- marized in Figure 2 . The i l e x i i j i l i ty o f L i t e f reeze process i!i t r ea t ing hazat-cioius v;ar;tes i s indicated by tbie range - i n contair~innnir; and waste concen t r a t ions t h a t i:t can iiaiidl e .
3.3 HAD Applications
The Norfolk N A D i s a modern industr idl fdc i l i - ty f o r reworking Naval a i r c r a f t and miss i les . Thc e lec t ropla t ing shop was cons.tructed a n d p u t in operation in 1985-Rf5, and i s s ta - te o f ,the a r t w i t h , among other .things, counter current r i n se t a n k s . Paint s t r ipp ing i s in a t r ans i t i on inode t o mechanical retnoval where possible , w i t h corn- merisurate reductions in Tiquid e f f lucn t s . I t i s an t ic ipa ted t h a t about 10% o f the s t r ipp ing will s t i l l have t o be done by ciieinical iiieails, resu l t ing i n coritamiriatcd wastewaters.
The NAD has an extensive inachine shop t h a t generates other wastes t h a t generally d o n ' t y c ~ i n to the stiwer. The inachincs gsnerate cu t t ing f l u i d s t h a t (ire recycled and (Visposed of under cont rac t . S p e n t solvents a re b e i n g reclaimed
.. in-house w l ' t h a major program underway t o add recovery s t a t ions in the v i c i n V t y o f t he . i r USE.
The shops operate di-ound t h e c lock, on a f i ve a n d sometimes s ix d a y week. The f 1 c w o f w a s t e s t o the industr idl waste water t i - e a t " f ac i l i t y (IWTF) averages a b o u t 100,000 ga l per day. The treatment f ac i l i t y incorporates cyanide oxidat ion, cliron:e reduction, me.ta'l hydroxi de p rec ip i t a t ion , organic adsorption on ac t iva ted carbon, a n d s'i udge dewatering. Typica? da i ly loadings o f various contaminants include:
Chrome 25 - 
Cadmium wastes are generated excl usivciy from c y a n m t K 6 F a t t h i s NAD. Ri iises from cadmium r inse tanks are coinbined with other cyanide- containing r inses and trea.ted in batches i n the IWTP, where cyanide i s oxidized with ch lor ine . The waste without cyanide i s then mixed with the acid b a t h wastes where heavy me-tal s a re prccipi- t a t ed . Again, o n l y the r in ses a re t rea ted ; con- centrated bathes are drummed and d.isposed o-F by cont rac t .
Phenolic wdstewaters a re generated from paint ~ s ? ' F T p j p X g ~ r Z - i T f T , using a so l v ? n t composed primarily of iiiethylene chlor ide a n d phenol. The solvent arid loosened paint i s Femoved from the a i r c r a f t surface w i t h high pressure water sp, ~ y . Much of the niethylene chlor ide evaporates, b u t
... the phenol i s qu i te soluble i n water. The r inse water c a r r i e s with i t the softened paint a n d tile dissolved a n d im:!iiscible so lvents . i t i s now t r ea t ed with act ivated carbon, which looses n:uch o f i t s capacity and eFficiencj when h i g h l eve l s o f inethylerie chlor ide o r o ther s o l w n t s a re i n the waste flow. A freeze process plant would remove water fo r reuse with a remaining concen- t r a t e t h a t could be reapplied t o t h e plane; the pa in t so l id s would be f i l t e r e d out before p roc c s s .i n g . I n addition t o wastes tha t c o n t a i n ,the above contaminants t h a t a r e su i t ab le f o r reuse and recycle , thei-e are w a s t e s from a rea waslhdowns a n d sp i l i s ti.1a.t c a n ' t be d i r e c t l y recycled, b u t could be econorn-ical l y 'de-metal 1 i zed ' i f the wastes i n them were preconceritrated ( rcducing the volume to be t rea ted a n d increasing t ! i e e l e c t r i c a l cor;duct.ivity). A concentrate strean; froin the freeze p l a n t , comprising 1 , to 10% o f the to t a l sp.il1 ~slu!iie would be t rea ted j i i an electrowinning operation t3 remove the heavy metal s a n d then mixed with other plant e f f luen t .
4 . [kinonstration PrcSra!:i
4.1 Objectives
'The primary o b j e c t i v e of t h i s ;?roc:ram .fer the Navy was t o deirioris trate .;hat a secondary f r e e z e c rys t a l 1 i z a t i o n process could he econornical'ly operated to recover 2, l a rge Fraction o f inetal f inishi i ig wastes for reuse a ~ i d recycle . idi tii.ii1
accor i ip i i shed t o i ~ e t t h e OY?r3; i gonl , i ncl u d i n g :
t h f s re2lM ~ 1 , .a E\ . w & w I i _ l nf " L C a & s -u tb;t k ~ c j t3
- !nodify and ins ta l 1 a secc!id3t".y re Fri geriin t f reeze crysts'l i i z a tfon pi a n t a t t i l e !\lavy's Naval Aviatiori Dcpot T r i NorFoii;, I//\"
I.
- t e s t the p i l o t plant o n various waste s treaiiis generated .in the M U , i denti fy i ng any operating problems caused by the physical propert ies o f the wastes, and modifying the plant as necessary tr3 overcome these pr.obl enis.
- estimate the costs t o bui ld a n d operate ( a ) freeze c rys t a l l i za t ion p l a n t ( s ) on the various waste streams in the NAD.
- ident i fy and quan t i -F j / a s possible the elements t h a t deterriiine the re1 i a b i l i t y , avai labi l i t iy a n d mainta.indbili ty o f the f reeze p l a n t on these wastes.
- provide sa!nples t o -the Navy o f feed, de- contani nated product a n d concentrra tcs f o r t h e i r evaluaticjn o f s a i t a b i l i t ? .for reuse a n d recycle.
4 .2 Equipment
The .p i lo t p1an.t used for these t e s t s i s shown in
format, t h i s p.ilot p l a n t mirrors very c lose ly t h e s implif ied P & l D o f Figure 1. The p l a n t was designed with maximum f l ex ib i l i ty t o a1 1 ow atldi- t ional process components, recycle between coin-. ponents, a n d vzr , iab i l i ty in t e s t i n g pzrameters. For example, addl ' ti 'onal components included a s l u r r y s t r ippe r between t h e c rys ta? 1 i zer and wash column, a me!-t s-tr lpper f c r me1 ted i ce , a perineabil i t y C G ' I U ~ T R t o determilie i ce c rys ta l s i z e , a n d a decanter to separate r e f r ige ran t from melted i ce before t h e s t r i p p e r . Flexibi l - i t y was b u i l t in by piping t h a t allows indiv-id- ual components could be by-passed.
The c rys ta? 1 i zer here i s a 35" diametGr ver t ica l vessel with a bottooln entry a g i t a t o r run wYth a var i ab1 e spccci drive. Re-Frigerant i s added in u p t o four (4) ports on the bottoin, and vapor i s drawn o u t of ii 2" connection a t the t o p . Level i s control led G Y C ~ a range o f i t o 4 Feet depth. Baff les in the 7iqu'i:d zone 'to prevent vortexing. Slurry i s drdwn o u t o f a 1" connection near the bottom of the vesse l ,
. the photograph O F F'igure 3. In i t s simplest
The wash cal i imn i s a 14:' vesse l , wi.tb 6 f e e t o f sidewall height t o the t 3 p o f the ice-pack. The leve l o f the top o f t h e ice-pack i s i:mir;?aified by a ro.tating kni-fe-edge scrappi- the ' p l o w s ' t h e washed ice in to a perfphtlral repiul p i n g t.atik. Washwater i s applied i-.!ir.ouyh a d i s t r ibu t ion header mounted above and behi inti the szr'aper blades. Feed t o -tile col uriiri i s .through a 1" connection sl igh t ly off.-cent:?r. ii.; tile bot tom head O F tbe column. Brine 'is d r a i n e d ~ ; + G I ? the I ~ e u e u moa a s tannp ipe i;q %ne center o t the c 01 umri . The i c e s lu r ry s t r ippe r was des ignc t l t c reiiiovC entrained r e f r ige ran t from .tne S I tirry before i t ge t s t o the wash colunin, wher? i . t s presence };CIS been surrni sed t o cause GjiPrati rig i n s t a b i l i ty -in
}"CL > d u b ~ i l U f i r d \ \ L . r 3 , , . l i i d 1 f UliLi l
vesse l , I? ' ' i n diameter by 8 f e e t t a l l , wi I h provisions for various types of splash p la tes , spray nozzles, and d i s t r ibu t ion devices . I t operates under a vacuum induced by a separate compressor i n the re f r igera t ion system.
The s lu r ry s t r ipper i s an e l e c t r i c a l l y heated reboi le r i n the bo t tom o f a packed column f i l l e d with 1 /2 " r ings . Tile feed hea.t exchanger i s a she l l a n d t u b e device, as i s the melter d n d heat re jec t ion condcnser. Punips a re generally e i t h e r progressing cavi ty or cen t r i fuga1 , with a gear- type r e f r ige ran t pump. Refrigerant compressors a r e a lobe blower- fo r the prSmary un i t , a n d reciprocat ing dry cy1 inder urii t s .for heat r e j ec t ion .
The permeability colunin i s a d6vice s'imi'lar 'to t h o s e used i n developmcntal p lan ts fo r seawater desa l t ing (Ref e ) . Generally, instrumeti.ta-tion
.- was r e l a t ive?y heavy in t h i s p lan t . Flowmeters a r e on a l l major process 1 ines , tempei-a'iure i s rrieasured a t 24. discree t po in ts , and pressures a r e measured iii each vessel a n d on pump disch- a rges . An on-1 ine conductivity ineter nioriitors t he quali.ty of the inel ted i ce being produced.
4 .3 Methodo? ogy
The general procedures used in demonstrating the ab i ' l i t y o f the freeze process t o separate waste coinponents fo r recycle and reuse corisi stect of t he following sequence:
- Operations are assessed w i t h a s a l t water t e s t ( s i iwla tcd seawater) ; iaod4,fications a n d operations a t varying condi t ions a re used t o es tab l i sh .tile e f f e c t s on process operat ions.
- The systaii i s drained 0.f the simulated sea water and ,t!wroughly riiised in preparation f o r fur ther tes t ing .
.- I\ r inse water i s se lec ted , a l500 t o 2000 ga l . sample obtained, sild ,the p i l o t plznt charged with t h a t sample f o r .test.ing. A sample of the charged waste i s taken for chemical an;llys;is.
- T e s t s are perfornied on the waste, a n d t h e effect iveness o f the process assessed. the waste causes operating problems t h a t haven ' t occured with other feed niateridl s the problems are assessed, physjcal prop- e r t y and cheiriica'! coinposit.ion infoi-ma;:ion i s compiled, and a l l of .this i s used t o postulate causes and support a stratecjy for equipment o r operating changes t h a t 1
w i 11 resol ve the d i f.f.1 cul tv.
sui . table operations t h e p l a r t i s op-.rated a t varying conditions w i t h 'the w a s t e , a n d the resul ts [ire eval iaated to detern?ine optiiiiui:i operating cond't ions. S a ! n p l ~ f , o r
I f
. ..
- Af.ter changes a re made 'that res i i l t in
me'l ted produc c di id tile coricei-t trd te s l;redi;is a r e taken fo r chemical ana lys i s .
t es ted following the draining and cleaning operations out1 incd above .
Testing was supported with regu?ar chemical analyses of the various streams. Pr ior t e s t ing and t h o r o u g h analyt ical work h a s showi t h a t the f reeze process will reduce the contaniination of the i ce by the saine proportion for a l l compon- e n t s in the solut ion (Ref 1 ) . 0 1 - l i n e t e s t ing was conducted by conductivity , wi th t h e meter ca l ib ra t ed to the speci f i c waste being tes ted .
4 .4 iXesu1 'ts
- Additional inaterials are se1cc.ted a n d
The r e s u l t s of tes t ing to ddte-demonstrate or subs t an t i a t e four majoi- accoriipl ishmctlts in t h e p rograin :
The a b i l i t y t o s t r i p r e f r ige ran t from i c e s lur ry su f f i c i en t ly fo r s t ab le wash column operations iias been deirloristrdted. Tests have been conducted with nickle sulfainate and chrornc anodizing r in ses , demonstrating the a b i l i t y o f the freeze process to concentrate the p1at:'ng chemicals and decontd,nina ti? the r inse f o r reuse. Equipment modi ficztior:s have been incor- portated in to the p lan t L h d t overcome operating problems discovered because of the low freezing point depressions of the r inses d n d surfdce ac t ive dgents associJ ted w i t h t ' i e plat ing b c t b s . Economic j b s t i f i c a t i o n for recc,very and reuse of plat ing r inses by tnc f r e e z e crys ta l 1 iza t ion ~ r o c e s s have bc?n estab'l istied.
Process ins tzabi ' i i t i e s caused by ~ X C ~ S S re fr-i Lger- a n t i n the ice s lur ry going t o the viash colunin a r e shown by such things a s : per iodic f l o o d . i n g i n the wash column, and s i l bsequen t decl i i i i n g product q u a l 5 t y ; pump cavi ta t ion duc to f l ash i r ig r e f r ige ran t in s lur ry 1 ines; incl t s t r ? ' p p t ? r over- loading; and l o s s 3 f refr?;ger*aiit ava i lab le t o the f reezer . Any o f t hesc occuranccs i s able t o shut the process dcern Pr-ior secondary rcfrl 'g- e r a n t p i l o t plants have seen these probleins i n s i x t o for ty-eight h o u r s From star-t-up. I n t h i s t e s t program we have operated f o r r m r l y 100 hours without any s.igris O F such i n s t a b i l i t i e s . Tes t durations have been 1 irnited by weekend shut downs. Proper operation of a s7urr.y s t r i p p e r , renii1rPs a t tmt im 6g fa aes?gn ~f c ~ j w ! i liternal s ( i .e . splash pl a t e s ) and witht lrav:al of s l u r r y froin the Dottorri of ,the co7 unin.
., I .
Operations o f the p i l o t plant on wtY! t in isk ing r i n s e waters are complicated by the rsl;t.!vc ' i G w 1 eve1 s o f j inpuri ' t i e s .in t h e s e w a s t e s . Freczi ng po in t depressions a r e hardly measurab1 e in these
W d S k S ; 1 t 1 5 d pi iys ' icd i C i r t i t ' d C i t 2 r ' ' i S L i C 3 1 - 'Ice t h a t i t fornis much harder c r y s t a l s a n d a'llows l e s s subcooling in r e l a t ive ly pure so lu t ions . The r e s u l t in these t e s t s was t h a t i c e formed on t he ba f f l e s in and walls o f vesse i , chol:.ing o-Ff the puiiip suct.ion or breaking f r e e a n d clogging the suct ion. Sur-face wetting agents i n nickel sul fainate a1 so resul ted in excess aggl oiiieration o f the ice p a r t i c l e s , giving l a rge c l u s t e r s in the f reezer t h a t a l so frequen'tly blocked the punip suct ion. There i s sotile ,iiid5cation t h d t the agglomeration may r e s u l t i n some carryover o f excess contamination in to the wash co7 u m ; t h i s wil l require more tes t ing . Modifications t o the p l an t t o p l a s t i c construction (1 ess teridancy for i c e growth), l e s s baf f i ing arid more .ice inacera- t i on has resul ted , i n successful operat ions with- o u t the problems discussed in t h i s paragraph.
Modifications t o the p i l o t p l a n t a r e planned as a precursor t o long term deriionstration o f waste t r e a t a b i l i t y by freezing. The Freezer k i i11 be a1 tered t o have l e s s baFfl ing, more f l ex ib l e ag i t a t ion and the s t a i n l e s s s t ee l vessel w i l l be l i ned . Self contained u t i l i t i e s wi l l a l s o be added so tha t the un i t i s n o t dependent on t h e h o s t s i - te fo r operations.
5 . Econoniics
Ec on om i c j u s t l; f i c a ,t i o n f o r new p r oc e s s e s re q u i r e data on w h a t the new technology cos t s as well as w h a t i t saves. In assessing .the j u s t i i i c a t i o n f o r f reeze crystal1 iza t ion recovery o f e lec t ro- p la t ing wastcs some assumptiot7s were tnade t h a t a f f e c t the r e s u l t s and therefore should be 1 i s t ed :
- Some wastewaters will s t i l l be produced t h a t requi r s conventional treatment, so n o c r ed i t i s a l i o w d .for ' f i x e d ' cos t s o f t h a t operation ( i . e . , equipinerit anortizci- t i o n , maintenance a n d cap i ta l budgets I
personnel reduction, e t c . ) . - Variable cos ts t ha t a re reduced by lower
contaminant loadl'ng t o t ! ie conventional indus t r ia l waste treatinerit f a c i l i t y a re estimated on the fol lowing bases:
Caustic $19 5/ t o t i Ch'l o r i ne $1 (9 5 / t o I1
$2 30/ t o n
Cheiriical Costs :
Sludge Disposal $150/cu yd. - 1'1 d t ing chei:iical val ue -in the re-tilrried
concentrate i s estimated a i tiie Fo.11 owl'ng
Nickel Sul Famate $13.67/h fii Chromic Acid $1 .IO/+ Ct-203 Cadnii u x Cyani de $3.00/$ C d
- SI udge iroin xhe neutrdi izat ion-prccipi ta- tiori operation i z assiwcd der/iteri3d t o 30% s o l i d s with a d3nsiLy o f 1800 pourlds per cubic yard.,
I An d r t rcler1, J - s h y e C O L ~ ~ ~ ~ " ) ' C L ~ ~ T L - ~ I ~ r inw t a n k arrangeinent on each bath i s dssuwd, with adequate drainage Froin thc par t s betwen baths.
Based on these assutiiptions the concentrations of various plat ing bath chemicals in r in se waters were estiinated a n d a per gallon C O S T fo r the var iab le cos t and credi t components was calcu- l a t e d f o r each of the major baths a t the N A D . The r e s u l t s a r e tabulated in F i g c r e 4 , These a r e the per gal 1 ort var i d b l e-component-only treatment cos ts for the specif ied p la t ing baths.
For f reeze c rys ta l1 iza t ion o r any other recovery techno1 ogy t o be cos t cotnpe t i t i ve wi t n conven- t ional treatment, the f u l l vdlile o f t h a t process must be l e s s t h a n the cos t and-credi t s ( t h a t a re 1 o s t w i t h conventional t rea tment ) . Treatment and recovery cos t s by freezing w e r e estimated in the following manner fo r the NAD waste streaiil appli- ca t ions :
- Based on IWTP waste flows we selected a 25,000 gallon per day treatment modul e s i z e fo r each of Four individual waste s treaim.
- A preliminary design exercise for these p lan ts resul ted in estimated capi ta l and O&M cos t s . Assumptions included locd l labor r a t e s a n d u t i l i t y cos t s a t the PIAD i n Elorfol i<.
- Capital for ilie Freeze treatmetit un i t s was amortiren over a f i ve year period a t s t r a i g h t 1 i ne de p rec i a t i on . - Labor was estimated a t one operdtor per un i t in fu l l tiiiie attenddnce, with one foreman on each s h i f t . This i s very conservative d s n l ? un i t s c ln probably he located in the s a m area and attended by one operator , w i ti-) supervision only on one s h i f t .
Based on these lmetiiods and assuiiip t ions , the c a s t t o t r e a t the various wastes i*ie!-E estimated The to td l cos t ended up t o vary insigt i i f icar i t~iy between the individual wastes, w i t n a f a i r l y uniform treatment cos t as. suimdri zed here:
E q u i pnen t $ .05 / gal Labor $ .02 / g a l * E l ec t r i c i ty k .005/ ga l . Supplies $ .006/ g a l Maintenance .E .035/ c j d l .
TOTAL
I f equipment i s aiiiortired over the f u l l 1 i f e expectancy, and labor i s reduced t o 25% cir so o f t h a t assumed here , the process becoiws c l ea r ly economically supcricr t o convcntiona? tT?zZ:icnt. There a re other benefi ts to bc g a j i i r r i as W P I l :
- ?he me1 tcd product f r o v t h e rret-ic u n i t i s recyci ed t o -rep1 ace denii ricral i zed or
~ ~~~~~ ~ ~~ ~
iotteried w & r , k i L I I d k a i h e o t up LU $.01 per gdllon.
- Sludge i s minimized, so t h e long terni r i sk from residues i n l a n d f i l l s i s non- exi stan t For those wastes t rea ted w i th the freeze process.
with t h i s process t o reiiiove the of fending con tami n a n t , and thereby rccycl ed.
- Crl ' t ical mater ia ls are preserved. .- Baths a re no\$ dumped might be t rea ted
6 . Summary a n d Concl usions
Freeze c rys ta l1 iza t ion o f fe r s a technical ly and po ten t i a l ly economically superior a1 te rn3t ive ,to conventional treatiiierit o f metal f in i sh ing waste waters. The a b i l i t y o f the f reeze process t o operate O i l the various segregated waste streams froiii the NAD has been demoiistrated; long term r e l i a b i l i t y , maintainabil i ty and ef f ic iency i i iust s t i 1 1 be addressed,
The iinpact of recycled chemicals on thc p la t ing operat ion a n d rinsewa te rs on r i tisi ng have n o t been demonstrated and wi l l be addressed in fu r the r stages of t h i s prograin. would be fur ther u t i ' l i z c d i f a l l of the p la t ing wastes from one metal could be t r ea t ed together ( i . e . sulfamate, chlor ide and Natts n icke l ) a n d t h i s i s being addressed with the 1.11\1!.
The process
References
1 , H e i s t , J . A . , "Freeze Crys t a l l i za t ion , " Chem.Eng. ('401 E5, No IO), McGraw-Hi1 1 (New E r m Z y 7 , 1979.
2 . Navy C E L I 9 R c i t a t i o n t o be prov ide( ! i a t e r .
3 . Grant Award, Cal i forn ' ia Heal th a n d We? fare Agency, Departirient o f Health Service:;, Grail t Number 85-00165, June 1986.
mental Systeins Company Inc, L i - t t l e Rock ~ AK. 4 . Press Release, 01 December 1987, Er:vicon-
5 . Frazer , Jaiiies 1-1. and Harold E . D a v i s , "Laboratory Invest igat ions O F Concentrating Industr ia l 'il'astes by Freeze CrystVal i ization," A I C h E 7 9 t h National Fleeting, l iouston, TX, 16-20 March 1.975, Paper 7 3 e .
6 . Detiton, W.H., M.J.S. S m i t h , J.T. Kiaschka, R. , F o r g a n , H.R. D'ifFey, C.14 Rmary, a n d K . W , Dawson, "Experiinental Studies o n i i d s i i j ng arid
Refrigerant Freezing Process," Proceedings: 4 t h Inti. S:/m. Fresh !:'a-tcr f ro117
n I c 4. 1 c j ;; t;<,r -fmiffir(:+&#- ~~~~~~~~~~ ~~ ~~~
~~~~~~ ~ ~~~~~ ~~~~~ ~ ~~ -~ i?lel%i+wj Ice C:;siar., .,i
Pa 3e7"4TlT7 r_II__ __ ., L
7 . Robinson, R.S., Owelopmental ’resting o f a Secondary Refrigerant F reezi ng E a T n i - i T n Pi I o t P I anfXT”€he Nri ghtsvi I I e Beach Test7 Tiici I i t y , F i n a l Keport, U.S. Ut ’ r i ce o t Wa€er Research and Technology, Report No PI3 296011, Natl Tech Infor Service, Washington, D C , 1979.
8 . Permeability Column Reference
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