WASTE REDUCTION OPTIONS

GARDNER MIRROR

This r e p o r t i s based on information c o l l e c t e d dur ing an October 13, 1985,

s i te v i s i t by a P o l l u t i o n Prevent ion Program s t a f f member.

reduct ion and management opt ions f o r t h e major wastestream genera ted a t t h e

f a c i l i t y . Addi t iona l information on ways t o improve t h e ope ra t ing performance

of t h e wastewater t rea tment system i s a l s o included.

It con ta ins w a s t e

~

All r e fe rences and vendor materials (when a v a i l a b l e ) mentioned i n t h e r e p o r t

are included.

endorsement by t h e S ta te of North Carol ina. It i s only included f o r i n f o r -

mat ional purposes.

Mention of a vendor o r manufacturer does no t r ep resen t an -

1.0 Product ion Process Waste Reduction Options

1.1 Solvent Waste Recycling from Coating Operat ion

Waste so lven t generated during t h e c l ean ing of t h e c u r t a i n c o a t e r

i s c u r r e n t l y s e n t t o an o f f - s i t e so lvent recovery f a c i l i t y . An

a l t e r n a t i v e t o t h i s procedure i s t o recover t h e so lven t on - s i t e

us ing a s m a l l ba tch d i s t i l l a t i o n u n i t . These u n i t s range i n

capac i ty from 5 t o 55 g a l l o n s and ope ra t e on an 8 hour cyc le .

These systems are a b l e t o recover about 95% of t h e waste so lven t .

The a c t u a l c o s t of a u n i t w i l l depend on t h e manufacture, capac i ty ,

and a v a i l a b l e op t ions . For example, t h e s t i l ls from one f i r m

range from $3,000 f o r a 5 ga l lon capac i ty u n i t t o $14,000 f o r a

55 ga l lon capac i ty u n i t . Typical ope ra t ing c o s t ( inc luding

u t i l i t i e s , l a b o r and s t i l l b o t t o m s d i s p o s a l ) i s about $0.50 pe r

ga l lon of recovered so lven t .

The c o s t sav ings i n v i r g i n so lven t a lone can, i n many cases, pay

f o r t h e system.

capac i ty d i s t i l l a t i o n u n i t t o recover t h e waste xylene used t o

c l ean t h e i r c u r t a i n coa te r . Curren t sav ings are about $20 pe r

day, which pa id f o r t h e system i n about 13 months.

on t h i s a p p l i c a t i o n can be found on page 63 of t h e enclosed manual,

Managing and Recycling Solvents .

For example, Lenoi r Mirror u ses a 1 5 ga l lon

More d e t a i l s

The a c t u a l payback per iod w i l l depend on a number of f a c t o r s

inc luding so lven t used, v i r g i n so lven t c o s t s , c u r r e n t w a s t e

management c o s t s , l a b o r c o s t s and u t i l i t y c o s t s . One f a c t o r that

must be considered i s t h a t t h e d i s t i l l a t i o n bottoms are a hazardous

waste and must be s e n t t o a permi t ted treatment/storage/disposal

f a c i l i t y .

t i o n of t h e a p p l i c a b i l i t y of t h i s recovery technique t o your a c t u a l

w a s t e . Two l o c a l equipment vendors are: Act iva t ion , Inc . , Cha r lo t t e ,

N C , Phone 1-800-558-3127; F in i sh Engineering Company, Raleigh, NC,

Phone 919-846-0062.

The equipment vendors w i l l be a b l e t o make a determina-

1 . 2 Grinding Coolant Recovery

A coo lan t recovery and r ecyc l ing program i s one of t h e b e s t methods

a v a i l a b l e t o reduce your product ion c o s t s . A s your c a l c u l a t i o n s

show, such a program would save about $8,000 p e r year i n coolan t

and l a b o r c o s t s . This sav ings would cover t h e i n i t i a l cos t of t h e

system i n a very reasonable per iod of t ime- -2 t o 3 y e a r s . Addition-

a l l y , recovery and reuse of t h e coo lan t would avoid t h e c u r r e n t

p r a c t i c e of dumping t h e spent coo lan t i n t o t h e main wastewater

t reatment system. This pe r iod ic dumping may be one of t h e causes

of t h e i n c r e a s e i n t h e e f f l u e n t copper concent ra t ion . Cut t ing f l u i d s

con ta in a h igh l e v e l of s u r f a c t a n t s and o t h e r sur face-ac t ive compounds.

These materials can keep metals i n "so lu t ion" , thus s i g n i f i c a n t l y

reducing t h e e f f e c t i v e n e s s of t h e t rea tment system. Addi t iona l ly ,

t h e c u t t i n g f l u i d may reduce t h e o v e r a l l e f f i c i e n c y of t he sedimen-

t a t i o n process and i n c r e a s e t h e s o l i d s loading t o t h e mixed media

f i l t e r s . This could i n t u r n reduce t h e q u a l i t y of t h e e f f l u e n t .

There are a number of d i f f e r e n t techniques which can be used t o

reclaim spent coo lan t .

combination of t h e fol lowing techniques: s e t t l i n g , f l o a t a t i o n ,

hydrocyclone, c e n t r i f u g a t i o n and f i l t r a t i o n . Many of t h e coolan t

recovery systems c u r r e n t l y on t h e market are designed f o r metal-

working f l u i d s and are a b l e t o remove both t r amp o i l and suspended

Most of t h e a v a i l a b l e systems use one o r a

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s o l i d s . S ince f i n e p a r t i c u l a t e removal i s t h e primary concern i n

t r e a t i n g t h e spen t coo lan t , a system employing a hydrocyclone o r

c e n t r i f u g e would be t h e most app l i cab le .

remove p a r t i c l e s i n t h e 5 micron and l a r g e r range.

p a r t i c l e removal, t h e u s e of a hydrocyclone o r c e n t r i f u g e t o f i r s t

remove l a r g e p a r t i c l e s followed by a f i l t e r f o r f i n e p a r t i c l e

removal can b e used.

These techniques can

For f i n e r

These systems c o s t about $15,000 t o $20,000, wi th t h e a c t u a l p r i c e

depending on t h e capac i ty , op t ions and type of system. Thus, a

coo lan t recovery system would pay f o r i t s e l f i n about 2 t o 2% years .

A l i s t of vendors of c e n t r i f u g e and/or hydrocyclone-based coo lan t

recovery systems are shown i n Table 1.

a v a i l a b l e vendors; c o n t a c t s w i t h your coo lan t s u p p l i e r would

i d e n t i f y o t h e r s .

These are j u s t some of t h e

One measure t h a t w i l l prolong t h e l i f e of your coo lan t i s t o u s e

only de ionized w a t e r as make-up.

sa l ts i n t h e c o o l a n t , p revent gummy d e p o s i t s and p o s s i b l e emulsion

' s p l i t t i n g ' .

p l a n t , u s ing i t as make-up would p r e s e n t very l i t t l e problem.

This w i l l reduce t h e bui ldup of

Since deionized water is r e a d i l y a v a i l a b l e i n your

For more informat ion on how t o set up a coo lan t management program,

p l e a s e see t h e fo l lowing enclosed a r t i c l e s : -

-

- Recovering Coolants Sys temat ica l ly"

"Disposal of Metal Working Flu ids"

"Squeeze More from Cut t ing F l u i d s by Managing Them" I 1

1 . 3 Waste Reduction from Copper Coating Operation

The w a s t e w a t e r from t h e copper coa t ing ope ra t ion i s t h e major source

of i r o n and copper from t h e product ion process . There are a number

of ways t h e volume and/or concen t r a t ion of t h i s waste stream can be

reduced. These inc lude removing t h e s o l i d s from t h e wastewater

be fo re i t e n t e r s the wastewater t rea tment system o r s u b s t i t u t i n g

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TABLE 1 Coolant Recovery Systems

Firm Type of Avai lab le System

1. Donaldson Liquid System Cen t r i fuge and hydrocyclone Local Rep: B i l l Poole Stone & Company, Raleigh, NC 919-78 2-7774

2. Master Chemical Corpora t ion Cen t r i fuge Local Rep: Henry Walke Co. Char lo t t e , NC 704-334-5391

3. F i l t e r t e c h Manlius, NY 315-682-8815

4. Alf a-Lava1 F t . L e e , N J 201-59 2-7800

5. Sanborn Assoc ia t e s Wrentham, MA 617-384-3181

Hydrocyclone, s e t t l i n g , f i l t r a t i o n

Cen t r i fuge

Hydrocyclone/centrifuge/pasteurizer

6. B a r r e t t C e n t r i f u g a l s Cen t r i fuge Local Rep: Dixie I n d u s t r i a l Supply, Inc . 919-758-4447

7. Polyclon, Inc. Woburn, MA 617-935-5800

Hydrocyclone and c e n t r i f u g e

8. Hoffman Cen t r i fuge and f i l t r a t i o n Local Rep: Thompson F i l t r a t i o n Products, Inc . , Washington, NC 919-946-8505

9. Lakos Sepa ra to r s Local Rep: as above

10. JWI Holland, PI1 616-399-9130

Hydrocyclone

Cen t r i fuge

11. Air /F lu id P u r i f i c a t i o n Technology F i l t e r /hydrocyc lone Rochester, NY 716-624-3820

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a r euseab le coa t ing s o l u t i o n i n place of t h e c u r r e n t i ron /copper

s u l f a t e system. Each of t hese op t ions are d iscussed i n more

d e t a i l below.

1.3.1 S o l i d s Removal

Removal of t h e i r o n and copper contained i n t h e wastewater

from t h e copper coa t ing tank could reduce t h e q u a n t i t y of

t rea tment chemicals used as w e l l as i n c r e a s e t h e e f f i c i e n c y

of t h e t rea tment system. Add i t iona l ly i t could a l s o reduce

w a s t e w a t e r t reatment s ludge gene ra t ion .

The c u r r e n t copper coa t ing process uses powdered i r o n as a

r eagen t . A s i g n i f i c a n t p o r t i o n of t h e i r o n i s unreac ted and

ends up i n t h e wastewater stream. This p a r t i c u l a t e i r o n i s

probably one of t h e major causes of t h e hydrogen pe r iox ide

demand i n t h e wastewater t rea tment system. A simple overview

of t h e r e a c t i o n s tak ing p l a c e i n t h e wastewater treatment

system is shown i n Table 2. A s can be seen from t h e s e

equat ions , a reduct ion i n t h e amount of suspended i r o n and

copper p a r t i c l e s w i l l reduce t h e hydrogen peroxide demand as

w e l l as t h e q u a n t i t y of sodium hydroxide needed t o p r e c i p i t a t e

t h e metals. Addi t iona l ly , t h i s w i l l h e l p " s t a b i l i z e " t h e

w a s t e w a t e r as t h e i r o n r e a c t i o n s wi th peroxide would tend t o

lower t h e s o l u t i o n ' s pH. It should be noted t h a t t h e oxygen

suppl ied t o t h e w a s t e w a t e r i n t h e a e r a t e d e q u a l i z a t i o n bas in

w i l l s a t i s f y some of t h e wastewater oxygen requirements.

However, t h e r e a c t i o n of oxygen ( 0 2 ) with i r o n and i r o n s a l t s

i s ve ry slow a t pH 3.5 and thus t h e r e w i l l s t i l l be some l e v e l

of hydrogen peroxide requirement.

Removing t h e i r o n from t h e wastewater w i l l a l s o reduce t h e

q u a n t i t y of f e r r i c hydroxide (Fe (OH) ) produced. This

compound forms a bulky g e l a t i n o u s f l o c which h e l p s t h e

m e t a l hydroxide p r e c i p i t a t e se t t le i n t h e c l a r i f i e r .

of t h i s a b i l i t y , i r o n s a l t s are commonly used i n wasewater

t rea tment systems t o improve removal capac i ty . Thus, removal

of t h i s compound could reduce t h e system's e f f i c i e n c y .

111 3

Because

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TABLE 2: Copper Coating Operation Wastestream: Treatment Chemistry*

Hydrogen Peroxide Treatment S tep

1. Peroxide Oxidation of Suspended I r o n and Copper P a r t i c l e s

0 I1

Q I1

Cu + H202 + Cu

F e + H202 --+ Fe (OH)2

r educ t ion i n amount of suspended i r o n and copper w i l l reduce peroxide demand.

2. Peroxide ox ida t ion of I r o n ( I 1 ) S a l t s

I1 I11 2 Fe (OH)2 + H202 -+ 2 Fe

I1 I11 I11 6 Fe SO4 + 3 H202 + 2 Fe + 2 Fe2 ( S O 4 l 3

Peroxide ox ida t ion w i l l reduce t h e q u a n t i t y of d i s so lved i r o n sa l t s i n t h e Y T T t e w a t e r . A l s o Fe i s easier t o p r e c i p i t a t e than Fe due t o i t s lower s o l u b i l i t y .

Thus reducing t h e load ~f t h e p r e c i p i t a t i o n u n i t .

P r e c i p i t a t i o n S tep

1. Role of Fe (OH)3 i n P r e c i p i t a t i o n 1 x 1

I1 Felll(oH) + Fe I1 so4 adsorption Fe(0H)g'nFe S 0 4 J 3 I1 1 x 1 I1

Fe111(OH)3 + nCu SO4 adsorption+ Fe (OH)3'nCu SO4$

2. Hydroxide P r e c i p i t a t i o n

I1 Cu S O 4 + ~N~OH+CU(OH)~ + Na2S04

I1 I1 Fe SO4 + 2NaOH + Fe (OH)2 + Na2S04

Fe2111 ( S 0 4 ) 3 + 6NaOH -+ 2Fe111 (OH) + 3Na2S04

*Note: Information from D r . L i m , Department of Chemical Engineering a t North Caro l ina S t a t e Un ive r s i ty . Telephone: 919-737-2328

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Before t h i s management opt ion can b e pursued, a series of

t e c h n i c a l and economic eva lua t ions must be made. The areas

t h a t must be addressed include:

O Quanti ty and removabi l i ty of suspended s o l i d s i n

t h e wastewater

O Avai lab le removal equipment

O E f f e c t of s o l i d s removed on t h e w a s t e w a t e r treat-

ment system

O Economics of s o l i d s removal

A rough estimate of t h e a b i l i t y of t h e suspended s o l i d s t o

be removed can be accomplished by performing a quick s e t t l i n g

test . More d e t a i l e d eva lua t ions can be obta ined by having

equipment vendors perform test runs on t h e a c t u a l w a s t e w a t e r .

There are several types of s o l i d removal equipment a p p l i c a b l e

t o t h i s w a s t e stream.

O Centr i fuge . A c e n t r i f u g e system s imilar t o t h e one

c u r r e n t l y opera t ing on t h e w a s t e w a t e r from t h e s i l v e r

coa t ing ope ra t ion would be a p p l i c a b l e he re . The only

d i f f e r e n c e is t h a t t h e low pH must be taken i n t o

account when spec i fy ing t h e equipment. The thickened

s o l i d s can be disposed of wi th t h e wastewater treat-

ment s ludge. There are a number of systems a v a i l a b l e

on t h e market. The c o s t w i l l vary depending on t h e

vendor, capac i ty , and opt ions , b u t p r i c e s s tar t a t

about $4,000.

Hydrocyclone. A hydrocyclone could a l s o be used. The

l i m i t on t h i s type of s o l i d s recovery i s t h a t i t can

no t remove very f i n e p a r t i c l e s and the smallest

system can handle a minimum flow of 4 gpm. The

advantage t o t h i s type of system i s t h e c o s t , less

than $1,000 f o r a s t a i n l e s s s t e e l hydrocyclone, p lus

t h e c o s t of valves, p ip ing and a pump which would

add another $1000 o r s o t o t h e t o t a l cos t . This

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would be much less than t h e c o s t of a c e n t r i f u g e .

The s o l i d s from t h e system, a t about 5%, can be s e n t

t o t h e wastewater t rea tment s ludge bas in f o r f u r t h e r

dewatering.

equipment i s included i n Table 3 .

Information on vendors of hydrocyclone

S e t t l i n g . I f t h e p a r t i c l e s have good s e t t l i n g charac-

t e r i s t i c s then a s imple sloped-bottom s e t t l i n g tank

could be used. The c l a r i f i e d wastewater can be

' discharged t o t h e t rea tment system whi le t h e s ludge

( s o l i d s ) can be removed and s e n t t o t h e sludge-

hold ing bas ins . The s i z e of t h e tank w i l l depend on

t h e p a r t i c l e s e t t l i n g c h a r a c t e r i s t i c s . A 500-gallon

tank w i l l c o s t about $2000; a d d i t i o n a l p ip ing , f i t t i n g ,

and pumps may add cons iderably t o t h i s f i g u r e .

F i l t r a t i o n . Depending on t h e pa r t i c l e s i z e of t h e

suspended s o l i d s , a f i l t e r could be used. There are

a wide v a r i e t y of systems a v a i l a b l e a t a wide range

of pr ices . The a p p l i c a b l e type would depend on t h e

so l ids - loading rate and t h e p a r t i c l e s i z e . For

example, a f a b r i c f i l t r a t i o n system would c o s t about

$5000, while a s imple bag f i l t e r might c o s t $500.

Some sources of f i l t r a t i o n systems are l i s t e d i n

Table 3 .

Magnetic Separa t ion .

remove i r o n p a r t i c l e s from wastewater us ing magnets.

The advantage t o t h i s system i s t h a t i t i s easy t o

o p e r a t e and would only remove i r o n , which could be

recyc led back i n t o t h e product ion process . Informa-

t i o n on some sources of magnetic s epa ra t ion equipment

i s l i s t e d i n Table 3.

Equipment is a v a i l a b l e which can

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TABLE 3 Sol id Removal Systems*

Firm

1. Lakos Separa tors Local Rep: Thompson F i l t r a t i o n Products , Inc . , Washington, NC 919-946-8505

2. Polyclon, Inc . Woburn, MA 617-935-5800

3. F i l t e r t e c h Manlius, NY 315-682-8815

4 . Hoffman Local Rep: Thompson F i l t r a t i o n Products , Inc . , Washington, NC 919-946-8505

5. S e r f i l c o , Ltd. Glenview, I L 312-998-9300

Type of System

Hydrocyclone

Hydrocyclone and magnetic s e p a r a t o r s

Hydrocyclone and f i l t r a t i o n

F i l t r a t i o n and magnetic s e p a r a t o r s

F i l t r a t i o n

*Note: These are j u s t a few of t h e a v a i l a b l e vendors. Complete l i s t i n g s can be found in :

1. P o l l u t i o n Equipment News: 1986 Catalog and Buyers' Guide. Nov. 1985.

2 . Chemical Engineering Equipment Buyers' Guide. 1986 Edi t ion .

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1.3.2

The e f f e c t of removing i r o n on t h e w a s t e w a t e r t rea tment

system can be determined from a series of bench and p i l o t

scale s t u d i e s . Such s t u d i e s would determine t h e e f f e c t on

t h e s ludge s e t t l i n g and any a d d i t i o n (o r reduct ion) i n

t reatment chemical dosage. I n i t i a l s t u d i e s can be c a r r i e d

ou t i n your l abora to ry t o see i f removing t h e s o l i d s w i l l

reduce hydrogen peroxide usage o r i nc rease l r educe sodium

hydroxide and polymer dosages.

F i n a l l y , , t h e o v e r a l l economics can be c a l c u l a t e d based on

t h e c o l l e c t e d information. The c o s t of i n s t a l l i n g and

ope ra t ing t h e equipment p l u s any a d d i t i o n a l t rea tment chemical

( p o l y e l e c t r o l y t e s ) c o s t s must be covered by any sav ings

through reduced hydrogen peroxide and t rea tment chemical

(sodium hydroxide) usage. Add i t iona l ly , any reduct ion i n

s o l i d s loading t o t h e t rea tment system would i n c r e a s e i t s

t rea tment capac i ty ( i . e . a l low f o r increased product ion whi le

producing a b e t t e r q u a l i t y e f f l u e n t . )

Modify Copper Coating Technique

A coa t ing system u t i l i z i n g a r eusab le copper process s o l u t i o n

i s a v a i l a b l e which could b e s u b s t i t u t e d f o r your c u r r e n t

i ron lcopper s u l f a t e system (as d iscussed during t h e s i te

v i s i t ) . U s e of t h e new process s o l u t i o n would e l imina te

t h e d i scha rge of t h e concent ra ted copper and i r o n s o l u t i o n .

This would e l i m i n a t e t h e major source of copper from t h e

w a s t e w a t e r , which would s i g n i f i c a n t l y reduce t rea tment c o s t s

and s ludge product ion. Add i t iona l ly , s i n c e t h e copper solu-

t i o n i s recyc led , t h e coa t ing e f f i c i e n c y would be much

h ighe r than t h e 25% es t imated f o r your c u r r e n t system. This

r educ t ion i n process chemical usage may o f f s e t any c o s t

i n c r e a s e f o r t h e new coa t ing s o l u t i o n .

The drawback t o t h e new process i s t h a t i t con ta ins complexing

agen t s . Thus, drag-out from t h e coa t ing process ba th would

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i n t roduce s m a l l q u a n t i t i e s of complexed copper i n t o t h e

wastewater. Complexed m e t a l s , as you w e l l know, can cause

problems i n a t rea tment system i f t h e i r p resence is no t

known. However, t h e t rea tment of complexed m e t a l waste is

w e l l known and r e l a t i v e l y s t r a igh t fo rward . Any added treat-

ment s t e p s can be added t o your t rea tment system. The exac t

method used w i l l depend on t h e type of complexation compound

used i n t h e process s o l u t i o n and can be obta ined from t h e

s o l u t i o n vendor. For example, one method used f o r t h e treat-

ment of wastewater conta in ing EDTA, a common complexing

agen t , i s l i m e t rea tment a t h igh pH. Since t h e t rea tment

system w i l l be handl ing less flow and much lower copper

concen t r a t ion (poss ib ly c l o s e t o t h e d i scha rge l i m i t ) , t h e

o v e r a l l e f f i c i e n c y of t h e system should improve.

A minor process modi f ica t ion can be used t o reduce t h e

q u a n t i t y of process s o l u t i o n removed from t h e coa t ing process

on t h e coated mi r ro r s . This w i l l , i n t u r n , reduce t h e copper

concen t r a t ion i n t h e w a s t e w a t e r . An ' a i r k n i f e ' o r a wiper

can be used t o remove excess s o l u t i o n from t h e su r faces of

t h e mi r ro r and d i r e c t i t back i n t o t h e coa t ing s o l u t i o n tank.

Th i s technique is commonly used i n e l e c t r o p l a t i n g and f i l m

process ing t o remove excess s o l u t i o n from f l a t su r faces .

The key i s t o keep as much of t h e coa t ing s o l u t i o n i n t h e

p rocess tank as p o s s i b l e . An ' a i r k n i f e ' i s j u s t a row of

a i r nozz les d i r e c t e d onto t h e s u r f a c e of t h e mi r ro r i n

o r d e r t o blow t h e excess s o l u t i o n o f f . This s o l u t i o n i s

caught i n a d r i p trough and r e tu rned t o t h e process tank.

F i g u r e 1 g ives a s imple view of such a system. A wiper o r

squeegee can a l s o be used i n p l a c e of an a i r k n i f e i f i t

w i l l no t harm t h e metal coa t ing .

1.4 Waste Reduction from Grinding Operat ions

The w a s t e w a t e r generated from t h e gr inding ope ra t ions w i l l conta in

h igh l e v e l s of g l a s s par t ic les along wi th lower q u a n t i t i e s of

cool ing f l u i d , s i lver , copper and p a i n t . To reduce t h e quan t i ty of

c Top V i e w

S ide V i e w

\ \ Drip Trough

A i r Nozzle

0 A i r Nozzle

1

0 0 0 0 0 0 Drip Trough

A i r Nozzle

0

Process S o h t ion Tank

FIGURE 1: A I R K N I F E SYSTEM

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copper which e n t e r s t he t reatment system from t h i s source , s e v e r a l

housekeeping measures can be taken. These inc lude :

Co l l ec t ing and removing as much of t h e suspended s o l i d s

from t h e washwater as p o s s i b l e be fo re i t i s discharged

t o t h e t reatment system.

Regular ly c l ean out any s o l i d s c o l l e c t i o n t r a p s f o r t h e

washwater o r cool ing f l u i d .

O Clean out a l l t renches and l i n e s which might con ta in

accumulated s o l i d s . This might be one source of copper

t o t h e t rea tment system.

O Reduce, as much as poss ib l e , cool ing f l u i d d ischarge t o

any t rench l ead ing t o t h e main t rea tment system. Surfac-

t a n t s i n t h e cool ing f l u i d could reduce t rea tment

e f f i c i e n c y . O Do not a l low any a c i d i c material t o e n t e r t h e w a s t e w a t e r

as t h i s could s o l u b i l i z e copper. Try t o keep t h e p H of

a l l process water and cool ing f l u i d as a l k a l i n e as

p o s s i b l e (pH 8.5 optimum) t o minimize copper s o l u b i l i t y .

2.0 Wastewater Treatment System

The major problem wi th t h e main t rea tment system i s t h a t t h e c l a r i f i e r i s

no t ope ra t ing a t maximum e f f i c i e n c y . This can be seen by t h e s ludge

b l anke t being j u s t a few inches from t h e top of t h e overf low w e i r , and

s o l i d s can be seen going over t h e w e i r .

impact on t h e e f f l u e n t q u a l i t y as t h e t r e a t e d w a t e r i s f i l t e r e d t o

remove suspended s o l i d s be fo re i t i s discharged. This cond i t ion , though,

w i l l r e q u i r e more f requent backflushing of t h e f i l t e r s and thus more

s o l i d s loading on t h e t rea tment system. Two methods can be used t o he lp

reduce t h i s problem. They are: reducing t h e suspended s o l i d s conten t

of t h e wastewater en te r ing t h e p l a n t ; and improving t h e a b i l i t y of t h e

s o l i d s t o se t t le i n t h e c l a r i f i e r . Each of t hese methods are discussed

below.

2.1 Reduced S o l i d s Loading

Th i s does no t have a major

Before t h e wastewater i s pumped i n t o t h e main wastewater t reatment

system, i t is he ld i n an a e r a t e d in-ground conc re t e bas in . Based

-11- i

on d i scuss ions wi th p l a n t personnel , t h e purpose of t h i s bas in is t o

equa l i ze f low and t o keep t h e s o l i d s i n suspension. However, s o l i d s

do accumulate i n t h e bas in and have t o be p e r i o d i c a l l y removed.

This b a s i n could be used as a "pre-treatment" u n i t t o remove h e a v i e r

p a r t i c l e s from t h e wastewater.

a e r a t i o n and modifying t h e bas in s o t h a t t h e r e i s some qu ie scen t

zone t o promote p a r t i c l e s e t t l i n g . The necessary bas in modi f ica t ions

w i l l depend on a number of f a c t o r s inc luding p a r t i c l e s e t t l i n g rate,

bas in s i z e , ho ld ing t i m e , w a s t e w a t e r f low rate , and i n f l u e n t / e f f l u e n t

p ipe s t r u c t u r e . These modi f ica t ions can range from simply s topping

a e r a t i o n t o i n s t a l l i n g a series of w e i r s i n o rde r t o create a

quiescent s e t t l i n g zone.

This can be done by e l imina t ing

The f i r s t s t e p i n eva lua t ing i f t h i s technique w i l l work i s t o run a

s imple s e t t l i n g test . This w i l l t e l l you t h e rate and q u a n t i t y of

p a r t i c l e s which can be removed. From t h i s da t a you can estimate i f

t h e w a s t e w a t e r can be h e l d i n t h e b a s i n long enough t o achieve some

l e v e l of p a r t i c l e removal.

One of t h e drawbacks t o us ing t h i s u n i t as a s e t t l i n g bas in i s t h a t

t h e r e c u r r e n t l y i s no s ludge removal c a p a b i l i t y . I f t h i s bas in i s

modified as d iscussed above, then s o l i d s w i l l have t o be removed on

a r e g u l a r b a s i s . Techniques can range from simply dewatering and

manual removal t o us ing a vacuum system. The exac t method w i l l

depend on t h e quan t i ty and phys ica l p r o p e r t i e s of t h e s ludge.

2.2 Improved C l a r i f i e r Operation

The ope ra t ion of t h e c l a r i f i e r may be a b l e t o be improved by using

a d i f f e r e n t coagulant a i d (polymer). To eva lua te your c u r r e n t

s i t u a t i o n , an expe r t i n wastewater t rea tment p l a n t opera t ion should

be consul ted . There are s e v e r a l sources of information a v a i l a b l e .

The Wastewater Treatment P l a n t Tra in ing S p e c i a l i s t i n t h e Department

of Environmental Management's Winston-Salem Regional Off ice ,

te lephone number 919-761-2351, can provide some t e c h n i c a l a s s i s t ance .

-12-

Also, a Direc tory of Consulting Engineering Se rv ices i n North

Caro l ina is a v a i l a b l e from:

Pub l i ca t ions I n d u s t r i a l Extension Service North Carol ina S ta te Univers i ty Box 7902 Raleigh, NC 27695

The c o s t of t h i s pub l i ca t ion i s $15 p lus 4.5% sales t ax . This

D i rec to ry inc ludes most of t h e consu l t ing engineer ing f i rms i n

North Caro l ina and l i s t s t h e i r f i e l d s of s p e c i a l i z a t i o n . F i n a l l y ,

i f needed, I can provide con tac t s a t some North Caro l ina f i rms which

gene ra t e and t rea t w a s t e w a t e r s i m i l a r t o yours . They w i l l be a b l e

t o t e l l you what chemicals they u s e and recommend s u p p l i e r s and/or

engineers .

For your information, I have enclosed a chapter from an EPA Manual on

Suspended S o l i d s Removal which d e t a i l s how t o conduct eva lua t ions of

coagulant a i d s . The procedure i s j u s t a series of j a r tests and can

be e a s i l y performed i n your l abora to ry .

information on how t o conduct l abora to ry eva lua t ions , p l e a s e l e t m e

know.

I f you would l i k e more

3.0 Recycling Wastewater E f f l u e n t

One method which could be used t o reduce wastewater genera t ion is t o reuse

p a r t of t h e t r e a t e d e f f l u e n t as r a w water f ed t o t h e p l a n t .

of t h e w a t e r t o b e reused w i l l depend on t h e l e v e l of suspended s o l i d s

and sal ts i t conta ins . Based on t h e r equ i r ed l e v e l of t rea tment , t h i s

w a t e r may be c l o s e t o t h e c i t y water c u r r e n t l y used.

reus ing t h e w a t e r w i l l depend on t h e a b i l i t y of t h e de ion iza t ion system

t o treat t h e w a t e r . The economics of r eus ing t h e w a t e r w i l l depend on

the c u r r e n t r a w w a t e r c o s t s , t h e c a p i t a l and i n s t a l l a t i o n c o s t s of the

needed equipment, t he l e v e l of contaminants i n t h e w a s t e w a t e r , and the

e x t r a c o s t s of de ioniz ing t h e t r e a t e d wastewater.

t r e a t a b i l i t y of t h e wastewater can be determined by your de ion ize r

s u p p l i e r .

The a b i l i t y

The f e a s i b i l i t y of

The determinat ion of