ASSESSMENT OF DISSOLVED A I R FLOTATION SLUDGE MANAGEMENT OPTIONS

I N INDUSTRIAL LAUNDRY WASTEWATER TREATMENT

ASSESSMENT OF DISSOLVED AIR FLOTATION SLUDGE MANAGEMENT OPTIONS

IN INDUSTRIAL LAUNDRY WASTEWATER TREATMENT

DRAFT FINAL REPORT

by R.B. Parker, J r .

Walden Division of Abcor, Inc. 850 Main Street

Wi lmi ngton, Massachusetts 01 887

Contract No. S-804367-01

Pro jec t Officer Ronald Turner

Indus t r ia l Pol lu t ion Control Division Indus t r ia l Environmental Research Laboratory

Cincinnat i , Ohio 45268

T h i s study was conducted i n cooperation w i t h the I n s t i t u t e o f Indus t r ia l Launderers

Washington, D.C. 20036

INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

October 25, 1978 C-798-003

Mr. Mervyn Slu izer , Jr. Institute of Industr ia l Launderers 613 Chel tenham Avenue Philadel phi a, Pennsylvania 191 26

Dear Mr. Sluizer:

S-804367-01, "Assessment o f Dissolved Air Flotation Management Options i n Industr ia l Laundry Wastewater Treatment". I am sending a copy o f this report t o Mr. Manfred Tidor (IIL) and Dr. M. Ramanthan (Roy F. Weston, Inc.).

c

Enclosed is a d r a f t copy of the f ina l r e p o r t f o r EPA Grant No.

A t your request

A copy of t h i s report is a lso being sent d i r ec t ly t o Mr. Ron Turner of the United States Environmental Protection Agency.

Yours t ru ly ,

Rienzi 8. Parker, Jr . Program Manager Techno1 ogy Development Department

RBP/smc

Enclosure t

WALDEN DivisioN OF Abcor INC. 850 Main Street Wilmington MA 01887 617/657/4250 Telex 710 3476537

DISCLAIMER

This report has been reviewed by the Industrial Environmental Research

Laboratory, U .S. Environmental Protection Agency, and approved for pub1 i cation.

Approval does not signify that the contents necessarily ref lect the views

and policies o f the U.S. Environmental Protection Agency, nor does mention o f

trade names or commercial products constitute endorsement or recomnendation

for use.

i i

FOREWORD

When energy and mater ia l resources are e x t r a c t e d , processed, con

and used, the r e l a t e d pol lu t iona l impacts on our environment and even

ou r hea l th of ten r equ i r e t h a t new and increas ingly more efficient pol

erted,

on

u t ion

control methods be used. The Indus t r i a l Environmental Research Laboratory - Cincinnati (IERL-Ci) a s s i s t s i n developing and demonstrating new and improved

methodologies t h a t will meet these needs both e f f i c i e n t l y and economically.

An a n a l y s i s o f disposal and d i s p o s i t i o n a l t e r n a t i v e s f o r sludges

produced a s a result o f treatment of i n d u s t r i a l laundry wastewaters by

dissolved a i r f l o t a t i o n i s presented herein.

this eva lua t ion will a i d both i n d u s t r i a l laundry owners o r managers and

persons working i n the regula tory f i e ld i n developing an understanding o f

I t i s hoped t h a t a review o f

the problems unique t o this indus t ry and will s t imu la t e further development

work i n these a reas .

The Organic Chemicals and Products Branch of the Indus t r i a l Pol lu t ion

Control Division Indus t r i a l Environmental Research Laboratory - Cincinnati

45268 should be contacted f o r further information on this subject.

David G . Stephen Direc tor Indus t r i a l Environmental Research Laboratory Cincinnati

i i i

ABSTRACT

This report presents an assessment of the various alternatives for de-

watering and disposition of dissolved-air-flotation sludges produced as a

result of industrial-laundry wastewater treatment. The assessment i s based

on the structure and capabi 1 i t i e s of the laundry industry; characterization

of sludge based on wastewater analytical data; estimates of sludge quanti t i e s

t h a t may be generated; discussions w i t h dewatering equipment suppliers and

an evaluation of regulatory trends.

Vacuum f i l t r a t ion (presently used i n a few laundries) appears t o be

the dewatering method most readily adaptable t o laundry operations.

f i l t e r presses may be used i f disposal costs r ise sharply. Extensive, i n -

laundry t r i a l s are needed i f performance of specific dewatering equipment

i s t o be proven.

Belt

Industry experience w i t h incineration of oily sludges which may conta in

heavy metals indicates that on-site incineration will no t be feasible for

laundries. Sludge, subsequent t o dewatering, will be disposed of o f fs i te

due t o the nature of most laundry locations.

years, will primarily be in landfi l ls . Disposal costs will vary widely

depending on how the solid waste i s characterized and on laundry location.

In view of regulatory trends, costs i n s tates presently having stringent

solid-waste regulations provide the best guide for anticipating future

costs.

1

Disposition, over the next few

i v

CONTENTS

Foreword ............................................................. i i i Abstract ............................................................. iv Figures .............................................................. vi Tables ............................................................... v i i English-Metric Conversion Table ...................................... v i i i Acknowledgments ...................................................... ix

1 . Introduction ............................................. 1

3. Disposition o f DAF Sludge Without Dewatering ............. 25 4. Dewatering Methods ....................................... 29 5. Sludge Disposition ....................................... 37

. 2. Technical Background ..................................... 8

References ........................................................... 47

V

FIGURES

Paqe . Number

1 Industrial Laundry Wastewater Treatment Steps ................. 9 2 Schematic Diagram of Dissolved Air Flotation Process .......... 10

3 Schematic Diagram of Belt Fil ter Press Operation .............. 35

v i

Number

1 2 3

4

5

6

7

8

9

10

11

1 2

TABLES

Paqe

Suspended S o l i d s Removal by Dissolved Air F l o t a t i o n ........... 13

Physical C h a r a c t e r i s t i c s o f DAF Sludge ........................ Removal o f I n d u s t r i a l Laundry Wastewater Constituents by

Dissolved Air F l o t a t i o n a i Determined by a Five Day Composite Sample Taken a t One Laundry S i t e .................. 16

Ra t ios o f Chemical Oxygen Demand t o Bio logica l Oxygen Demand f o r Wastewaters from E igh t I n d u s t r i a l Laundries ...... 17

Re la t ionsh ip between Suspended Sol i d s , Freon E x t r a c t i b l e s and Tota l S o l i d s i n Laundry Wastewater ...................... 1 8

Removal o f Heavy Metals from Laundry Wastewater by Dissolved Air F l o t a t i o n a t One Laundry S i t e ........................... 20

Rat ios o f Heavy Metals t o Suspended S o l i d s i n I n d u s t r i a l

Suspended S o l i d s i n I n d u s t r i a l Laundry Wastewater from

Bas is f o r Es t imat ing and Es t imates o f Daily Sludge

Approximation o f Trucking Charges f o r Removal o f DAF Sludge

Ta rge t C r i t e r i a f o r Sludge Dewatering Method f o r Purposes

Heavy Metals Content f o r Ref inery Sludges and Assumed

14

Laundry Wastewater .......................................... 22

Various Sources ............................................. 23

Q u a n t i t i e s .................................................. 24

Without Dewatering .......................................... 26

o f Comparison w i t h Calcu la ted Trucking Costs ................ 28

Values f o r DAF Sludges from Se lec t ed Laundries .............. 40

v i i

ENGLISH-METRIC CONVERSION TABLE*

To Convert From To Multiply by

Inch Feet Square i n c h Square f ee t Cubic fee t Gal 1 on Pound Pound per sq. inch Horsepower Gallon per day Gallon per minute Gallon per sq. ft-day Gallon per minute per sq. f t .

Meter Meter Square meter Square meter Cubic meter Cubic meter K i 1 ogram Atmosphere Watt Cubic meter per day Cubic meter per day Cubic meter per sq. meter-day Cubic meter per sq. meter-day

* The units nost faniiliar t o the projected readership of this report have been maintained.

v i i i

ACKNOWLEDGMENTS

The guidance o f Mr. Mervyn S l u i z e r , J r . , and Mr. Manfred Tidor o f the

I n s t i t u t e o f Indus t r i a l Launderers, and Mr. Ron Turner o f EPA throughout

the entire program i s g r a t e f u l l y acknowledged.

Roy F. Weston, Inc., a s consul tan ts t o the I n s t i t u t e of Indus t r i a l

Launderers, served i n a review capac i ty f o r this program.

The au thor thanks the r ep resen ta t ives o f manufacturers o f f l o t a t i o n

and dewatering equipment and of the various industr ia l l aundr ies consulted

a l l o f whom gave generously o f their time i n the course o f the program.

ix

SECTION 1 INTRODUCTION

NATURE OF THE PROBLEM

I n d u s t r i a l l a u n d r i e s c l e a n a number o f types o f items inc lud ing uniforms,

machine wipers, f i l l i n g s t a t i o n wipers, d u s t mops and f l o o r mats. As a result

o f th is mix a wide v a r i e t y o f subs tances can occur i n i n d u s t r i a l l aundry

wastewater w i t h the ind iv idua l laundry o f t e n having l i t t l e con t ro l o v e r con-

I

taminants e n t e r i n g the wastewater s t ream.

The development o f wastewater t r ea tmen t techniques w h i c h a r e ope ra t iona l

w i t h i n the c a p a b i l i t y o f a laundry and a t the same time provide f o r s a t i s -

f a c t o r y wastewater q u a l i t y has been the subject o f cons ide rab le e f f o r t f o r a

number o f y e a r s . As f a r back a s 1963, a program was c a r r i e d o u t by the

Massachusetts Health Research Institute, Inc. a t the r e q u e s t o f the I n s t i t u t e

of I n d u s t r i a l Launderers ( 1 ) . Many o f the conclus ions drawn from this s tudy

remain s i g n i f i c a n t a t this time, and may be sumnarized a s fo l lows:

-- Random, d a i l y samples o f l aundry wastewater i n d i c a t e d g r e a t

v a r i a t i o n s i n contaminant l oad ing w i t h i n a given day. T h u s ,

the need f o r adequate e q u a l i z a t i o n p r i o r t o t r ea tmen t through

the use o f a holding tank was shown.

s o l i d s were found t o vary a s much a s a f a c t o r o f twenty among

the d a i l y samples i n a given laundry .

For example, suspended

1

-- Based on analysis o f composite samples from different laundries i t

was demonstrated t h a t l aundry wastewater i s diff icul t characterize

in a generalized way. Large variations were found from laundry t o

1 aundry .

-- The classical parameters o f BOD, suspended solids and pH are often

such as t o lead t o municipal-sewer surcharges for industrial laundries.

-- The process of chemical treatment o f wastewater and physical

separation by dissolved-air flotation ( D A F ) showed promise in

reduci ng suspended sol i d s in wastewater t o more acceptabl e 1 eve1 s .

A subsequent and more extensive study ( 2 ) essentially confirmed the

above conclusions this work having taken place i n 1972-3 under sponsorship

of IIL and the United States Environmental Protection Agency. Laundry

wastewater was treated by DAF w i t h the resulting sludge ( f loa t ) being then

dewatered by vacuum f i l t ra t ion .

treated by diatomaceous-earth f i l t ra t ion . A1 though the potential for con-

taminant removal by these methods was demonstrated, serious diff icul t ies

were encountered i n achieving consistent operation of the process on an hour-

Effluent from the DAF u n i t was subsequently

to-hour basis. Operating diff icul t ies were shown t o be related t o the mix

o f texti les laundered d u r i n g a given period. The potential fo r removal o f

heavy metals from laundry wastewater using DAF was indicated b u t aga in ,

results were errat ic .

2

Since the s igning o f 1976 Consent Decree, the EPA has sought data on

the occurence and t r e a t a b i l i t y o f 65 po l lu t an t s and c l a s s e s o f po l lu t an t s

i n a va r i e ty o f wastewaters.

and the EPA ( 3 ) wastewater analyses were c a r r i e d o u t a t e i g h t laundr ies

where p r i o r i t y pol 1 u t an t s were expected through p r i o r know1 edge of the

customer base.

In a recent study again supported by IIL

Data taken a t one laundry s i t e again ind ica ted reduction o f BOD, TOC,

suspended s o l i d s and heavy metals through the use o f DAF w i t h an ind ica t ion

t h a t organic p r i o r i t y po l lu t an t s may be removable t o some degree, by the

DAF process.

A t this time a very few laundries are known t o have ins ta l led DAF

On the o t h e r hand i t i s poss ib l e t h a t f u t u r e regula tory capab i l i t y .

requirements and/or pressure brought by municipal-sewer a u t h o r i t i e s r e l a t i v e

t o types and concentrations o f po l lu t an t s will lead t o increased emphasis

on laundry wastewater treatment by DAF w i t h the a t t endan t problems o f DAF

sludge dewatering and d isposa l . The purpose o f this r epor t i s t o provide

an overview o f the problem o f DAF sludge management from the s tandpoin t o f

charac te r and composition o f sl udge, equipment sui t a b i l i t y and sl udge

disposal options w i t h i n the context o f the i n d u s t r i a l -laundry indus t ry and

poss ib le regul a t o r y t rends .

APPROACH

Direct opera t ing experience on DAF sludge generation , sludge dewatering

and sludge d i spos i t i on i n i n d u s t r i a l l aundr ies i s limited i n spi te o f the

long-term recognition o f the problem. Further, DAF sludge from laundr ies

3

can be variable and d i f f icu l t t o characterize. I t was known a t the outset

t h a t bench-scale dewatering tes t s can be misleading ( 1 ) .

scale equipment installed in laundries were no t w i t h i n the scope o f the

assignment.

sources. These ncl ude :

Trials w i t h fu l l -

Use has been made therefore of information from available

-- A thorough review o f p r i o r work on laundry wastewater treatment.

-- Development of an understanding of the nature of laundry operation

t h r o u g h v i s i t s t o laundries, discussions with operating personnel

and w i t h representatives o f IIL.

-- Discussion w i t h suppliers of f lotation and dewatering equipment.

-- Use o f available analytical da t a on laundry wastewater i n an

attempt to characterize sludge, define the quant i t i e s generated

and assess disposal options.

-- A review of current trends i n the management of industrial sludges

which share features in common w i t h DAF sl udge generated i n

laundries.

THE INDUSTRIAL LAUNDRY INDUSTRY

In assessing methods of flotation-sl udge dewatering and disposal which

m i g h t be applicable in industrial laundries i t was believed t h a t some under-

standing of the industry was needed. Although an assessment o f economically

4

a c h i eva b l t re tment technology was n r t o f the ignment, the co 1 -

s i d e r a t i o n o f specif ic sludge management opt ions i s not poss ib le without

know1 edge o f such f a c t o r s a s avai 1 abi 1 i t y o f ski 11 ed personnel , avai 1 abi 1 i t y

o f land f o r on - s i t e d i sposa l , water usage and an approximation o f the

f inanc ia l s c a l e o f laundry washing opera t ions . Information was developed

through v i s i t s t o laundr ies and d iscuss ions w i t h IIL representa t ives and

experience o f equipment suppl iers.

Industry Def in i t ion

An i ndus t r i a l laundry i s defined a s one which washes shop towels, printers

wipers and d u s t mops w i t h discharged wastewater being s i g n i f i c a n t l y s t ronge r

t h a n t h a t o f o t h e r laundries types p a r t i c u l a r l y w i t h regard t o o i l y ma te r i a l .

Location and Surroundings

Approximately f i v e hundred laundr ies which might be c l a s s i f i e d a s

i ndus t r i a l a r e believed t o be opera t ing i n the United S t a t e s .

of these appear t o be loca ted i n urban a reas w i t h contiguous indus t ry o r

housing and very 1 i m i t e d 1 and avai 1 ab1 e f o r sol i d-waste processi ng.

A high f r a c t i o n

Indus t r i a l Laundry S ize and Scope

Laundries range from smal 1 p r i v a t e l y owned enti ties t o corpora te ly owned

f a c i l i t i e s where ten o r more laundr ies may be operated by the parent company.

Those i n the l a t t e r category can have the advantage of cent ra l technical

5

support provided by the corporation.

other ac t iv i t ies such a s garment rental make i t d i f f icu l t to assess the

economic capability of supporting treatment f ac i l i t i e s .

useful technology would have t o be supportable by a l l laundries. For these

reasons, a typical laundry is defined as having gross sales of 500,000 to

2-million dollars and a daily water consumption o f 100,000 gallons.

Integration of washing operations w i t h

On the other hand

Staffing

Industrial laundries clearly depend heavily on a pool o f unskilled labor

w i t h ongoing improvements automated processing equipment leading to a trend

toward assigning an increasing.fraction of expenditures to distribution

and customer service w i t h a consequent reduction i n dollars spent on actual

laundering. Technically trained personnel may be limited t o the manager and

possibly an assistant manager who may also be owners in the business.

Current Status of Wastewater Treatment

Essentially a l l industrial laundries are believed t o discharge to

publically owned treatment works.

Coarse, suspended materials are removed by screening w i t h additional

Free sett leable solid being periodically removed from equalization pi ts .

o i l on the surface may be skimmed. Less than 2% of industrial laundries

appear to further t rea t wastewater. In these few cases, dissolved-air

6

f lo ta t ion i s used.

vacuum f i l t r a t i o n and disposition by contract haulers.

methods are t h u s largely extensions o f o r improvements i n the methods

developed as described i n Reference ( 2 ) .

Dewatering o f DAF sludge or scum i s carried out by

C u r r e n t treatment

7

SECTION 2

TECHNICAL BACKGROUND

Figure 1 depicts steps involved in laundry wastewater treatment with

DAF as the sludge thickening method along with the several options possible

for sludge dewatering and disposition. Both straight sedimentation and DAF

following chemical treatment have been considered as thickening for laundry

wastewater.

ion of a single layer for removal irrespective of suspended material density.

The use of DAF is presumed in this report and background information on this

Early work(1) demonstrated the advantages of DAF in the format- I I I

i I

i ,

I

method of thickening or applied to laundry wastewater is outlined below:

DISSOLVED AIR FLOTATION AS USED ON LAUNDRY WASTEWATER.

The objective of any flotation process is that of concentrating suspen-

ded substances in a floating layer which can be skimmed.

difficult-to-settle particles are first flocculated and then carried to the

In the case of DAF,

surface by large numbers in very small air bubbles.

effected by air saturation of a portion of the waste stream using compressed

air followed by bubble nucleation when the stream is released to atmospheric

pressure.

extensively described ( 4 ) and a flow diagram for a representative DAF process

is shown in Figure 2 .

Chemical Treatment

Bubble formation is

The mechanism of bubble interaction with suspended matter has been

A number o f chemical treatment systems have been tried with laundry

wastewater,generally polyelectrolytes in combination with polyvalent cations

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and pH adjustment. One approach cu r ren t ly used involves an upward pH ad jus t -

ment w i t h NaOH followed by a sequential addi t ion of calcium chlor ide and then

polymer(5).

consumption of 1.5-8.0 lb/day f o r a water usage of 100,000 gal/day.

Air Introduction and Power Requirement

Polymer dosage i s reported i n the range 2-10 mg/l or a da i ly

Dissolved a i r can be introduced through pressur iza t ion of an e f f l u e n t

recycle stream a s shown in Figure 2 .

t i on pressures of 40-60 psi a r e cu r ren t ly used. Plant a i r i s general y used

w i t h a compressor requirement of five basepower estimated.

A recycle r a t e of about 50% and sa tura-

F1 o t a t i on Area/ Equi pment S i ze

Volumetric flow of wastewater handled as re ated t o f l o t a t i o n area i s

re fer red t o as overflow r a t e or hydraulic loading r a t e .

min/ft a r e c h a r a c t e r i s t i c i n c l a r i f i c a t i o n of many indus t r i a l wastewaters

u s i n g DAF.

m i n / f t .

Values of 2-4 gal / 2

For laundry appl ica t ion r a t e s a r e somewhat lower o r 1-2 ga l / 2

One manufacturer cu r ren t ly supplying DAF units t o indus t r i a l laundries

spec i f i e s a rectangular u n i t of w i d t h 6 f t , l e n g t h 26 f t and d e p t h 8 f t f o r

a 100,000 gal/day flow - an overflow r a t e of 1 . 3 gal /min/f t2 . ( 5 ) .

Circular DAF units u t i l i z i n g a counterflow p r inc ip l e a r e supplied w i t h

the p o s s i b i l i t y of g rea t e r overflow r a t e s , reduced f l o o r area b u t g rea t e r

required c e i l i n g h e i g h t (6).

Performance

The DAF process i s reported a s general ly appl icable where suspended so l id s

loadings a r e l e s s than 10,000 mg/l and loadings a r e well below this value f o r

laundry wastewaters as indicated by five-day composite samples taken a t e i g h t

laundries ( 3 ) as well a s by data from other sources. Single discharges, how-

ever from washers can contain higher loadings r e su l t i ng in a need f o r adequ-

11

E

ate equalization time felt to be at least two hours by those currently apply-

ing the DAF process. Data on suspended solids removal by DAF are given are

available from a number of sources and summarized in Table 1. As indicated,

the fraction removal can be high but information on constancy of performance

with time and on effluent quality were not readily available. At this time,

it seems certain that the effectiveness of DAF in industrial laundries will

zation, MATCHING o f

operator ski 11 . udge dewatering and

for the sludge of 5%

depend on many factors including prescreening , equal

chemical treatment to the mix of items laundered and

For purposes of assessing sludge composition, s

disposal, a solids capture of 90% and solids content

are assumed here.

DAF SLUDGE CHARACTERISTICS

The great variability that can occur in DAF sludge results in diffi-

culties in characterization.

separation and spontaneous dewatering upon standing as well as slow chemical

reactions can take place, generally requiring on-site evaluation of a given

property.

case of sludge from wastewater where composition has been averaged through

equalization.

and references from available analytical data on wastewater follow.

Physical Characteristics

In addition, property changes due to phase

Laboratory tests on aged samples can prove misleading even in the

Characteristics of DAF sludge based on available information

Table 2 summarizes information on the physical characteristics of DAF

sludge based on previous studies and direct observation in laundries using

DAF.

Composition

Although DAF sludges were not analyzed as to composition, useful in-

formation could be inferred using recently available data obtained in a

Walden Study on wastewater composition at eight laundry sites under the

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TABLE 2 . PHYSICAL CHARACTERISTICS OF DAF SLUDGE

General : Dark brown o i l y mud containing d iscern ib le g r i t - could be abrasive i n high-speed equipment. slowly under grav i ty . t o a water based pa in t . Foaming not observed t o be a problem. mater ia ls having a wide range of s p e c i f i c g r a v i t i e s

Flows Flow proper t ies s imi l a r

Faint hydrocarbon odor. Contains

Water content: Generally about 95%.

Dewaterability: Varies w i t h mix of t e x t i l e s b e i n g laundered. Can contain co l lo ida l slimes which may blind f i l t e r medi um.

14

I present EPA Grant (3).

A1 1 ana ly t ica l data were f o r five-day composite samples.

Table 3 presents data on in f luen t t o and e f f l u e n t from an operating

DAF u n i t a t one laundry together w i t h percent removal for various parameters.

The reduction i n Freon e x t r a c t i b l e s (comparable t o t h a t f o r suspended

s o l i d s ) suggests t h a t a s i g n i f i c a n t f r a c t i o n o f o i l s , greases and inso luble

drganics must appear i n the sludge and t h a t the material i s best c l a s s i f i e d

as an o i l y sludge which can contain a g rea t var ie ty of organic compounds . BOD5, COD and TOC a r e a l l removed t o a l e s s e r degree, presumably due t o

soluble inorganics not removed by DAF. Nonionic detergents o r p a r t i a l l y

soluble solvents could account f o r these r e s u l t s . An increase i n t o t a l

s o l i d s i n the wastewater i s shown. Barring the p o s s i b i l i t y of ana ly t ica l

e r r o r t h i s i s explainable as inorganic coagulating chemicals added d u r i n g

treatment including a r a i s ing o f the pH w i t h NaOH followed by a pH lowering

w i t h s u l f u r i c acid pr ior t o discharge.

ch lor ide has been reported t o be used(2).

i n the s l u d g e . t o some exten t depending on the degree of dewatering.

As much as 2000 mg/l o f calcium

Soluble compounds will be present

From Table 3 the r a t i o of COD removed from the wastewater t o BOD5

removed can be ca lcu la ted as about 3 . 5 . T h i s r e s u l t i s cons i s t en t w i t h the

concept o f an o i l y sludge somewhat r e s i s t a n t t o the sewage bac ter ia used i n

the BOD5 determination.

samples from a l l e igh t laundry s i t e s suggesting t h a t this feaure i s common

t o laundry wastewaters and may be t o DAF sludge generated i n l aundr ies .

Table 4 gives the r a t i o of COD t o BOD5 i n wastewater

Ratios of suspended t o t o t a l s o l i d s and Freon e x t r a c t i b l e s t o suspended

so l id s i n wastewater a r e given i n Table 5 using data from the e igh t laundry

s i t e s . Generally, material ex t rac ted by Freon exceeds suspended s o l i d s due

15

TABLE 3 . REMOVAL OF INDUSTRIAL LAUNDRY WASTEWATER CONSTITUENTS BY DISSOLVED AIR FLOTATION AS DETERMINED BY A FIVE DAY COMPOSITE SAMPLE TAKEN AT ONE LAUNDRY SITE

Measured Influent t o Effluent Removal parameter DAF from DAF ( X )

Suspended so l ids 940 100 89

Freon ex t rac t i bl es . 1600 2 30 86

Total organic carbon 1750 495 72

Total sb l ids 3500 6020 increased

BOD5

COD

TOC

2400

7060

1750

1000

1980

495

58

72

72

Note: Concentrations i n mg/l BO3 = five-day biological oxygen demand, COD = chemical oxygen demana, TOC = t o t a l organic carbon.

( a ) Data from Reference ( 3 ) - laundry s i t e No. 7

16

TABLE 4. RATIOS OF CHEMICAL OXYGEN DEMAND TO BIOLOGICAL OXYGEN DEMAND FOR WASTEWATERS FROM EIGHT INDUSTRIAL LAUNDRIES

2 4.9

3 9.3

4 3.2

5 6.4

6 7.3

7 2.9

8 2.7

Note: BOD = Five day biological oxygen demand, COD = chemical oxygen demhd. Calculated from data in Reference (3).

17

TABLE 5. RELATIONSHIP BETWEEN SUSPENDED SOLIDS, FREON EXTRACTIBLES AND TOTAL SOLIDS I N LAUNDRY WASTEWATER

R a t i o of Rat io o f Suspended suspended Freon e x t r a c t i b l es

Laundry so l i d s s o l i d s t o t o suspended s i t e (mq/ l ) t o t a l s o l i d s so l i d s

1 965 0.32 1.1

2 3080 0.546 1.07

3

4

2530

344

0.28

0.17

2.57

0.15

5 702 0.234 1.02

6 920 0.27 1.41

7 940 0.27 1.7

8 777 0.20 1.22

Note: Rat ios c a l c u l a t e d from data i n Reference(3).

18

e i t h e r t o soluble organics p a r t i a l l y ex t rac ted by Freon o r , more probably, due

t o f i n e l y emulsified o i l s which pass the f i l t e r used in the suspended s o l i d s

determination. Again i t i s presumed t h a t much of the suspended material

i s o i l y b u t the danger i n general iz ing i s emphasized by the values f o r S i t e 4

wastewater.

material could be inorganic i n nature i n this case.

TOC was a l s o very low in this sample and much of the suspended

The presence of heavy metals in DAF sludge was considered as a prerequ-

i s i t e t o considering sludge d ispos i t ion opt ions.

the e igh t laundry si tes w i t h c e r t a i n heavy metals found i n a l l these waste-

waters.

select.ed w i t h a knowledge of their customer base, proximity o f chemical

producers, and the expectation t h a t metals and o ther p r i o r i t y pol lu tan ts

would be found.

decided t o make a worst case assumption f o r this repor t w i t h regard t o the

presence of heavy metals i n DAF sludge.

Data were ava i l ab le from

However the eight laundries a t which samples were taken had been

Fol 1 owing consul t a t i on w i t h 11L representa t i ves i t was

Previous work(2) had shown t h a t a s i g n i f i c a n t f r ac t ion o f most of the

heavy metals can, under c e r t a i n operating condi t ions , be removed from the

wastewater and concentrated i n DAF sludge.

s i t e samples on DAF i n f luen t and e f f l u e n t a t one laundry a r e summarized i n

Table 6 and serve t o confirm the poten t ia l f o r metals removal.

Recent data from five-day compo-

In evaluat ing the ana ly t ica l data from the e igh t laundry s i t e s i t was

found t h a t heavy metal concentrat ions, when r e l a t ed t o suspended s o l i d s ,

r e s u l t i n l e s s s c a t t e r i n the data than for the concentrations themselves.

Since DAF removes suspended s o l i d s , use o f this f a c t was made i n charac te r iz -

i n g sludge composition from the s tandpoint of heavy metal content . Ratios of

the metals t o suspend s o l i d s i n wastewater from the e igh t laundry s i t e s a re

19

TABLE 6. REMOVAL OF HEAVY METALS FROM LAUN R WASTEWATER BY DISSOLVED AIR FLOTATION AT ONE LAUNDRY SITE s r a

Effluent Metal Influent t o from Percent

analyzed DAF DA F removed

Cadmi um 0.07 0.006 91 +1

Chromi um

Copper

0.99

1.70

0.70

0.38

2951

7825

Lead. 5.40 0.11 9850

Nickel 0.08 0.01 87k13

Zinc 2.77 0.008 9722

Arsenic - - - A n t i mony 0.13 0.31 - Note: Concentrations i n mg/l. Confidence l imits on percent removed based

on estimates o f analytical sens i t iv i ty . Arsenic below l imi ts of detection. Antimony increase unexplainable.

Source: Reference (3)

20

given i n Table 7 along w i t h mean dalues of the r a t i o s .

Analytical da ta f o r a r sen ic ind ica ted presence a t only one s i t e and the

values f o r antimony were c l o s e t o the l imits of ana ly t i ca l s e n s i t i v i t y .

Further, any hexavalent chromium present a s a so luble anion would not be

expected t o be removed by DAF. For the remaining metals, the r a t i o s provide

a means o f cha rac t e r i z ing sludge f o r purposes of eva lua t ing disposal options

i n terms o f pounds o f metal per thousand pounds o f dry s o l i d s . I t should be

emphasized t h a t this cha rac t e r i za t ion assumes t h a t removal e f f i c i ency f o r

each metal by DAF i s comparable t o t h a t f o r suspended s o l i d s present.

Further, the da ta f o r the e i g h t laundr ies sampled may not be representative

of wastewater from laundr ies i n general .

QUANTITIES OF SLUDGE GENERATED

I f the e f f i c i ency of suspended s o l i d s removal by DAF i s assumed t o

be h i g h under s a t i s f a c t o r y opera t ing condi t ions , d a i l y s ludge volumes can

be estimated from da ta on suspended s o l i d s i n the wastewater.

w i t h this approach i s i l l u s t r a t e d by da ta i n Table 8 where wide va r i a t ions

i n suspended s o l i d s concentrations will be seen.

f o r purposes o f es t imat ing q u a n t i t i e s i t was f e l t t ha t the da ta from

five-day composite samples a t e i g h t d i f f e r e n t laundr ies were the most

useful. On the o t h e r hand the magnitude o f the po ten t i a l d i spos i t i on

problem f o r a s i n g l e laundry should not be understated. As a result a

suspended s o l i d s value of 2200 mg/l was se l ec t ed and used a s the bas i s

i n a r r i v i n g a t an approximation of d a i l y s ludge q u a n t i t i e s a s summarized

i n Table 9.

The d i f f i c u l t y

In a r r i v i n g a t a value

21

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23

TABLE 9 . BASIS FOR ESTIMATING AND ESTIMATES OF DAILY SLUDGE QUANTITIES

Basis:

Suspended solids = 2200 mg/l Volume of wastewater in one day = 100,000 gal Solids captured by DAF in sludge = 90% Solids collected in one day = 1660/lb Solids content o f DAF sludge = 5% Solids content o f dewatered sludge = 25%

Daily quantity generated: Gallons Pounds Cubic Yards

DAF sludge 3950 33,200 20.0 Dewatered sludge 790 6,640. 4.0

24

SECTION 3

DISPOSITION OF DAF SLUDGE WITHOUT DEWATERING

P r i o r t o examining approaches t o dewatering DAF sludge the possi b i l i t y

Cal cul a t i o n on re- o f d i spos i t i on o f "as generated" s l udge was considered.

moval charges f o r the est imated d a i l y q u a n t i t i e s of non-dewatered sludge

a r e sumnarized i n Table 10. Actual removal charges wi l l undoubtedly vary

widely depending on numerous f a c t o r s and the purpose o f the ca l cu la t ions

is t o p u t dewatering economics i n perspec t ive .

used because o f ready a v a i l a b i l i t y and i t was assumed t h a t the vehicle must

be ava i l ab le through the day even though not necessa r i ly used a l l day.

Labor was est imated on the bas i s of the length of a round trip. No charges

f o r admission t o a disposal s i t e a r e included. In the future real cos t s

could be s u b s t a n t i a l l y higher depending on the thrust o f s o l i d waste requ-

l a t i o n s .

Rental -truck r a t e s were

$3.00/cubic yard has been indica ted from one source a s c u r r e n t

disposal c o s t s w i t h an expectation of future c o s t s perhaps reaching $10.00/

cubic yard (8) .

Using the figures g iven i n Table 10 a s t rong economic incent ive exists

f o r dewatering providing c e r t a i n condi t ions can be met:

-- Equipment should be e s s e n t i a l l y s e l f opera t ing .

-- Capital costs must be reasonable i n the l i g h t of hoped f o r savings

i n d i spos i t i on cos t s .

25

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26

Tenta t ive s p e c i f i c a t i o n s f o r dewatering equipment are g iven i n Table 11

i n terms o f dewatering c a p a b i l i t y and costs .

approach these c r i t e r i a i t seems c e r t a i n t h a t d i r e c t d i s p o s i t i o n of non-

I f dewatering methods can

dewatered m a t e r i a l w i l l n o t be a v iab le , long-term a1 t e r n a t i v e f o r sludge

27

TABLE 11. TARGET CRITERIA FOR SLUDGE DEWATERING METHOD FOR PURPOSES OF COMPARISON WITH CALCULATED

TRUCKING COSTS

Installed cost $50,000 depreciated l0-year, straight line

Maintenance labor - 0.1 man-year @ $12,00O/yr plus 100% overhead

Energy - 5 hp @ $0.05/KWH, 2000 hours/yr .

Rep1 acement parts

Annual cost ($1

$ 5,000

2,400

500

1,000 $ 8,900

Dewatering capability: mass o f removed material o f 75%.

to 25% sollds 'leading to a,reduction in volume/

28

SECTION 4

DEWATERING METHODS

The apparent unrel i abi 1 i t y o f bench sca l e t e s t s and vari ab1 e proper t ies

of DAF sludge a r e such t h a t in-laundry t r i a l s a r e believed the most e f f e c t i v e

means of eval uating the performance of dewateri ng equipment.

exception of vacuum f i l t r a t i o n , few i f any dewatering methods have received

in-laundry evaluat ion even though s p e c i f i c pieces of equipment a re general ly

ava i l ab le on a t r i a l or ren ta l basis from a number of manufacturers. Exact

reasons f o r lack of a c t i v i t y a r e unknown b u t a few p o s s i b i l i t i e s can be

ci ted :

Wi t h the

-- The laundry must have i n s t a l l e d DAF capab i l i t y . A t present i n s t a l l e d

DAF units appear t o number about ten and in most cases these were

i n s t a l l e d along w i t h a ro t a ry vacuum f i l t e r a s a t o t a l system.

-- Trial and e r r o r experimentation w i t h unfamiliar equipment can be a

cos t ly inconvenience a t a laundry.

-- Equipment manufacturers may question the sui t a b i l i t y of methods o ther

than vacuum f i l t r a t i o n .

29

-- Equipment suppl ie rs may have decided not t o address the poten t ia l

market aggressively believing t h a t laundries wil l p refer t o pay

surcharges t o the POTW r a the r than t r e a t wastewater.

-- Suppliers may have placed emphasis on markets f o r l a r g e r equipment

such as i n municipal-sludge dewatering.

-- The shipment of DAF sludge t o a manufacturers p i l o t plant requires

la rge q u a n t i t i e s t o ge t a t r i a l r u n of reasonable length , i . e . , two

hours, even on small , p i l o t - s c a l e un i t s .

could change w i t h time even i f the material were readi ly ava i lab le .

Further , sludge proper t ies

As a r e s u l t the following comments on dewatering methods a r e l a rge ly

specula t ive and based on a rough charac te r iza t ion of DAF sludge as previously

given along w i t h a review of the problem w i t h manufacturers representa t ives ,

and observations of actual laundry operat ion.

EVAPORATION

Evaporation a s a means o f dewatering DAF s ludge is believed an un-

s a t i s f a c t o r y approach f o r a number of reasons.

-- A1 though se l f -c l eaning evaporators a r e avai 1 ab1 e f o r s

the nature of laundry sludge suggests a problem of fou

t r a n s f e r sur faces .

udge drying,

i n g o f heat

-- The l a rge amount o f water t o be removed will lead t o excessive

charges for energy which could approach the cos t s of trucking the

mater ia l .

30

I 0

-- The presence o f organic so lven t vapors i n the ven t i l a t ed o f f vapor

from an evaporator could result i n a i r -po l lu t ion v io l a t ions o r a t

best a nuisance s i t u a t i o n i n the surrounding neighborhood.

-- The i n e v i t a b l e presence o f de te rgents can result i n problems w i t h

foaming and "carryover" o f the sludge residue s i m i l a r t o the

problems now encountered i n evaporating rad ioac t ive 1 aundry wastes

a t nuc lear power p l an t s .

CENTRIFUGES

Centrifuges can be used t o both t o c l a r i f y a l i q u i d by sedimentation

and t o f i l t e r and d ra in suspended s o l i d s by ex t r ac t ion o f the l i q u i d phase

under cen t r i fuga l force . A wide v a r i e t y o f machine types are a v a i l a b l e

based on one o r the o t h e r of these p r inc ip l e s .

A number of problems can be invisioned i n u t i l i z i n g any o f these machines

i n dewatering DAF sludge. Although scroll and disc cent r i fuges have been

used f o r petroleum and petrochemical s ludges, these a r e genera l ly prec is ion

machines opera t ing a t h i g h speed. Inorganic suspended s o l i d s w h i c h can occur

i n laundry wastewater could lead t o se r ious problems i n erosion o f moving p a r t s .

The DAF sludges examined a l l showed pronounced presence o f g r i t . The occurrence

of small metal chips is not beyond the realm of p o s s i b i l i t y .

such units f o r r e tu rn of parts f o r r e f in i sh ing could be a formidable t a sk f o r

laundry personnel. I t i s not a l l c l e a r how suspended DAF s o l i d s wi l l behave

Disassembly of

31

i n a centrifugal f ie ld where sedimentation i s dependent on a density o f

difference. Both direction of migra t ion and sedimentation rate could depend

on the mix o f items being washed.

may be intimately mixed in floc-like aggregates having a wide range o f

densities.

Inorganic particulates and oil droplets

Any type of centrifugal f i l t r a t ion would involve considerations of

screen selection , bl inding , pl ugging and erosion.

such as food pulps o r crystalline solids permit the design of specific equip-

ment t o achieve dewatering. I t seems certain that the nature o f industrial

laundry operations will result in sludges of continually varying properties

and that the adaption of centrifugal principles t o DAF sludge will require

considerable e f fo r t i n the form of equipment selection and in-laundry t r i a l s .

We1 1 defined products

ROTARY DRUM VACUUM FILTERS

In the laundries visited where DAF sludge was being generated, rotary

vacuum f i l t e r s were being used for sludge dewatering.

machines capable of many hours of continuous operation w i t h minimum main-

tenance providing that techniques f o r avoiding blinding o f the f i l t e r cloth

and satisfactory discharge of the cake are worked o u t . A cake solid of 25%

and higher has been achievable i n laundry usage.

costs and operability given i n Table 11 can probably best be met by units o f

these types. Adaptation of rotary f i l t ra t ion t o the particular problems o f

DAF sludge are believed the most promising area for future development work

i n DAF sludge dewatering. The various types of units w i t h regard t o method

o f cake discharge o r use of precoats are described elsehwere(10) and can be

comnented on the context of laundry operations.

These are slow-speed

The target c r i te r ia for

32

Scraper Discharge

I n this approach t o cake discharge, cake i s loosened from the f i l t ra t ion

cloth i n an a i r blow-back zone and picked up by a deflector knife from which

i t f a l l s t o a receiving container. A u n i t of this type was observed i n

operation on DAF sl udge with satisfactory discharge of the crumbly cake

occuring. Scraper discharge has the advantage of mechanical simp1 ic i ty .

Provid ing the cloth can be kept clean by occasional external washing and

the action of a i r blow-back, this may be the best and most straightforwai

configuration fo r vacuum f i l tration of DAF sludge.

S t r i n g D i scharge

I n str ing discharge, mu1 t iple , parallel and continuous strings travel

w i t h the cloth on i t s surface. When the strings travel t o a separate rol ler

they diverge from the cloth (affixed t o the drum) and the cake i s l i f t ed and

discharged. Although this method has advantages i t i s best used where blinding

i s generally not a problem because the cloth cannot be backwashed and there i s

no a i r blow-back.

Continuous Belt Discharge

In this type of unit the f i l t e r cloth travels as a continuous bel t covering

about two thirds of the circumference of the segmented, vacuum drum.

then travels away from the drum t o a rol ler o f small diameter where a sharp t u r n

The cloth

33

i s taken resulting i n discharge of the cake. The advantage of this design

i s t h a t i t permits backwashing of the c l o t h without f lood ing the dewatered

cake. The advantages of backwashing would have t o be clearly shown as these

units are more expensive t h a n the scraper-discharge type. Further, the

endless cloth f i l t e r belt will wear and require replacement.

believed to have practiced backwashing and since abandoned the practice.

One laundry i s

Precoats

In the precoat approach, a cake of " f i l t e r a i d " i s l a i d down on the c l o t h

in a separate cycle.

Cake discharge i s carried o u t by controlled shaving w i t h a knife - a small

amount of precoat being removed with the cake.

t o indicate t h a t the precoat method will not be applied t o laundry sludge

dewatering .

Diatomaceous earth ( D E ) i s often used as the precoat.

A number of factors combine

-- A main advantage of precoat use i s in achieving h i g h f i l t r a t e c lar i ty

b u t in current laundry practice, f i l t r a t e i s recycled t o DAF influent

where suspended materials can be recaptured.

-- An additional materials-handling system i s required fo r storing the

f i l t e r aid, preparing the precoat slurry and feeding slurry to the

vacuum f i 1 t e r t rough.

-- Operation o f the ro ta ry f i l t e r becomes intermittent and will

require scheduling as t o application o f the precoat.

34

S 0

-7

c, m

L

.Q

)

0

n

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Q)

Q)

LL

I 1

I

+-

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35

-- Any precoat shaved w i t h the cake wil l cont r ibu te t o the problem o f

so l id waste d isposa l .

-- Ins t a l l ed cos t s f o r the e n t i r e system wil l exceed those f o r a

scraper-discharge u n i t .

BELT FILTER PRESSES

I n the event t h a t disposal cos ts f o r laundry sludge r i s e sharply, the

use of b e l t f i l t e r press units may, i n the f u t u r e , receive increased

considerat ion.

oper'ation f o r a two-stage press .

screens, the pressure be ing applied gradually i n order t o avoid forcing

sludge through the screen openings.

ava i lab le w i t h some un i t s .

Figure 3 i s a schematic diagram showing the method of

Sludge i s pressed between two continuous

A t h i r d , high-pressure s tage i s

The s i g n i f i c a n t f ea tu re o f this approach i s the potent ia l f o r producing

On the o ther hand i n s t a l l e d cos t can a d r i e r cake of perhaps 40-50% s o l i d s .

be a s much a s twice t h a t o f a vacuum f i l t e r which must be recoverable i n

reduced disposal costs. Problems o f screen plugging and determination of

achievable cake s o l i d s on laundry sludge may require fu tu re development

work a s well as studies on the use of addi t ional chemical coagulants

immediately p r i o r t o dewatering.

Belt f i l t e r presses may have a g rea t e r maintenance requirement than

vacuum f i l t e r s due t o t h e i r r e l a t i v e mechanical complexity and wil l require

a somewhat g rea t e r f l o o r area f o r equivalent capaci ty . Emphasis a t present

i s on development work w i t h r e l a t i v e l y la rge un i t s for municipal sludge

dewatering o r o f high-volume indus t r i a l waste streams.

36

I

SECTION 5

SLUDGE DISPOSITION

Currently, only a few i n d u s t r i a l l aundr ies t r e a t wastewater by dissolved

a i r f l o t a t i o n b u t the number is expected t o grow over the next few yea r s .

Final r u l e s per ta in ing t o development of pretreatment standards f o e d is -

charges i n t o c e r t a i n POTW's have been issued by the EPA (11) and selected

laun'dry wastewaters can contain some of the 65 t o x i c p o l l u t a n t s ( 3 ) .

t o maximize f l e x i b i l i t y i n s e l ec t ion o f d i spos i t i on procedures f o r municipal

sludge seem c e r t a i n t o draw a t t e n t i o n t o i n d u s t r i a l wastewater streams a s

po ten t i a l sources o f municipal sludge contamination.

E f fo r t s

Treatment o f laundry wastewaters by any method o f physical removal of

suspended ma te r i a l s will i nev i t ab ly result i n the c rea t ion of a solid-waste

stream.

under the Resource Conservation and Recovery Act of 1976 w h i c h was intended by

Congress t o address the question of unregulated disposal of s o l i d wastes (12) .

Future requirements f o r s to rage , handling, t r a n s p o r t and disposal of a number

of types o f s o l i d wastes remain t o be defined.

A t present i t i s not known how laundry sludges will be charac te r ized

In summary the problem o f s o l i d waste disposal for laundries i s only

just beginning t o emerge a t a time when important Federal regula t ions a r e

a l s o being developed. Increasing awarenese of nat ional trends a t the s t a t e and

local level can further complicate the regula tory climate i n w h i c h a p a r t i c u l a r

laundry must approach the question o f sludge d i spos i t i on .

37

As a result i t was decided t o examine waste management practices o f

other industries which have had a relatively long history of wastewater

treatment and of the disposition of wastes similar in nature t o sludge

t h a t a laundry might be expected t o generate.

for municipal sludge were f e l t t o be of l i t t l e value due t o dissimilarities

between municipal and 1 aundry sludge.

Management practices developed

The characteristics of dewatered, DAF generated sludge, as previously

outlined, share certain features i n common w i t h sQlid waste streams generated

by petroleum refineries on the basis of available da ta . I n spite of major

differences between the two industries in terms of quantities of waste

generated, c a p i t a l investment and geographic distribution, waste management

practices f o r refinery-generated sludges were selected as a basis for

comparison.

Refinery solid-waste management practices have been extensively described

i n an EPA sponsored study completed in 1973 (13). Data compiled and

conclusions arrived a t in t h a t study will be heavily drawn on i n the

foll owing sections.

CHARACTERISTICS OF REFINERY SLUDGES

Refineries generate a number of waste streams which are disposed of as

solid waste hav ing widely varying compositions. Analytical da t a for seventeen

different refinery waste streams are reported (13).

median values are 12.5% by weight ( o r total material) f o r oil and 82% by

weight f o r water as an example. Heavy metals concentrations vary widely

among the refinery sludges and for a given sludge type depending on the

refinery sampled.

For refinery "OAF f loat"

38

Table 12 presents a comparison between se lec ted data on r e f i n e r y sludges

and the p rev ious l y assumed values f o r laundry sludge w i t h respec t t o heavy

metals. The f igures fo r laundry waste are sub jec t t o t h e q u a l i f i c a t i o n s

p rev ious l y discussed - t h a t the l aundr ies sampled were se lec ted w i t h t h e

except ion t h a t p r i o r i t y p o l l u t a n t s would be present. The data g iven f o r

r e f i n e r y sludges and taken from Reference (13) are:

-- The h ighes t i n d i v i d u a l values f o r any o f s i x teen types of

s o l i d waste stream

.-- The h ighes t median value repor ted f o r any one o f t h e s ix teen

types.

One r e f i n e r y waste stream (leaded tank bottoms) was e l im ina ted as i t

i s sub jec t t o specia l d isposal precaut ions.

The summary prov ided i n Table 12 i s n o t intended t o suggest t h a t laundry

and r e f i n e r y sludges present i d e n t i c a l d isposal problems. The o i l f r a c t i o n

i n a r e f i n e r y sludge i s composed l a r g e l y o f hydrocarbons.

might con ta in c h l o r i n a t e d hydrocarbons and o t h e r so lvents (3 ) .

data a re much more w ide ly a v a i l a b l e f o r r e f i n e r y sludges.

p o t e n t i a l occurrence o f both metal s and organics i n laundry sludges suggests

t h a t t he experience o f r e f i n e r y managers may be re levan t .

Laundry DAF sludge

A n a l y t i c a l

Nevertheless the

ON-SITE VERSUS OFF-SITE DISPOSAL

Re f ine r ies vary g r e a t l y i n s i z e and i n volume of waste generated w i t h

over f o r t y such i n s t a l l a t i o n s process ing 100,000 b a r r e l s per day o r more

39

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40

and generating s o l i d waste streams many times g r e a t e r than can be expected

from a laundry.

o n s i t e (13) - a s t r a t e g y t h a t i s believed u n r e a l i s t i c f o r most l aundr i e s

f o r the fol 1 owing reasons :

Approximately 40% of a l l wastes generated a r e managed

-- The urban loca t ion of many l aundr i e s precludes the p o s s i b i l i t y

of o n s i t e app l i ca t ion of wastes t o the land due t o unavaila-

b i l i t y of land.

-- Even i f sufficient space i s a v a i l a b l e , the land may be t o t a l l y

unsui tab le from the s tandpoin t o f proximity t o watersources o r

po ten t i a l contamination of groundwater i f t ox ic p o l l u t a n t s a r e

shown t o be present .

-- As disposal techniques become more structured due t o g r e a t e r

regula t ion , laundry managements wi l l prefer de lega te the ac tua l

d i sposa l r e s p o n s i b i l i t y t o ope ra to r s of specific disposal s i tes .

-- Del ibera te loca t ion o f a laundry on a s i t e where land i s both

s u i t a b l e and inexpensive may p u t i t a t a disadvantage i n l abo r

a v a i l a b i l i t y and/or a t an excessive d i s t ance from i t s customers.

INCINERATION

O f the sludge d i spos i t i on opt ions considered, only inc inera t ion

appeared f e a s i b l e as an o n s i t e method where l imi ted land i s ava i l ab le .

41

The use of o n s i t e inc inera t ion was considered through a computer modeling

procedure i n a previous study ( 2 ) .

of excessive space requirement, h i g h cap i t a l cos t s and the necess i ty o f i n -

volving laundry personnel i n operation of a i r -pol lu t ion-cont ro l systems.

The approach was re jec ted on the grounds

Attitudes of r e f ine ry managers toward inc inera t ion a re well documented

i n Reference (13) and serve t o re inforce the above conclusions. Only about

2% of t o t a l re f inery waste generated is inc inera ted . The process i s regarded

as having " h i g h cap i t a l cos t s and reocurring annual operation and maintenance

cos ts . "

of c r ea t ing an explosive air/hydrocarbon mixture - a problem t h a t could

occur w i t h the laundry sludges seen.

of the bed i s s t i l l a major problem w i t h these u n i t s ( 1 3 ) . "

Fluidized-bed inc ine ra to r s a r e needed t o e l iminate the p o s s i b i l i t y

"Loss of f l u i d i z a t i o n and p lugg ing

Fai lure o r i n t e rmi t t en t operation of a i r po l lu t ion control devices in

an urban environment could c rea t e a se r ious l i a b i l i t y f o r a laundry i f

p a r t i c u l a t e metal oxides were t o be emitted. Recently, the EPA Administrator

wasquaaed a s ind ica t ing t h a t lead may be added t o the a i r po l lu tan t c r i t i c a l

l i s t ( 1 4 ) . Implementation of s t r i c t e r a i r pol lut ion cont ro ls is c i t e d a s a

concern of several re f inery managers along w i t h the p o s s i b i l i t y t h a t metals

i n indeterminate q u a n t i t i e s may escape t o the atmosphere even when pol lut ion

control devices a r e present (13) . Removal o f inorganic p a r t i c u l a t e s w i t h wet

scrubbers c rea t e s an add i t iona l , contaminated waste stream t h a t must be

deal t w i t h .

42

In summary, the poss ib le presence of heavy metals and of v o l a t i l e

organic compounds i n laundry sludge can result i n i nc ine ra t ion being a

d i f f i c u l t and c o s t l y technology - the l ik l ihood being t h a t laundry manage-

ments will seek o t h e r so lu t ions f o r s o l i d waste d i sposa l .

LAGOONS AND PONDS

Lagoons, ponds and pits have been used f o r many yea r s a s an expedient

method o f o n s i t e disposal o f o i l y wastes. For reasons previously given,

o n s i t e disposal i s no t believed t o be a v i ab le option f o r laundr ies .

Disposal over a ten y e a r period could r equ i r e a volume equiva len t t o one

half an a c r e o f land f i l l e d t o a depth of ten feet. Several s t a t e s have

taken ac t ion a g a i n s t th is method of disposal o f i n d u s t r i a l s o l i d o r semi-

s o l i d wastes w i t h the l i k l ihood t h a t o t h e r s will follow.

OCEAN DISPOSAL

The Marine Pro tec t ion , Research and Sanctuar ies Act of 1972 w i t h

a t t endan t EPA r e s p o n s i b i l i t y prohi b i t s ocean disposal except by spec ia l

permits r e l a t i n g t o the amount and type of mater ia l t o be dumped. Such

permits will be increas ingly d i f f i c u l t t o get and i t i s s t a t e d t h a t ocean

dumping will be phased ou t by 1981, even f o r municipal sewage sludges (15) .

LAND SPREADING

In the case of municipal sludge the term land spreading refers t o

appl ica t ion on park, f o r e s t o r croplands providing c r i t e r i a f o r heavy-

metal loadings can be met (15) and where s o i l conditioning p rope r t i e s of

43

municipal sludge can be of benefit. The properties of laundry-generated

solid waste as previously outlined are quite dis t inct from those of municipal

sl udge.

Land spreading i s also an active area of research for disposition of

refinery-generated sludges where the motivation i s solely t h a t o f environ-

mentally adequate disposition on land set aside for the purpose.

approach i s variously referred t o as land spreading, land farming and land

cultivation. Use of the land for growing crops i s not anticipated. In

genetal, the method consists of periodic, heavy application of oily sludges

w i t h f e r t i 1 iza t ion and repeated cultivation as out1 ined in Reference (16) .

Oils are biodegraded under aerobic conditions.

development work, however, i s t o provide self sufficiency f o r refineries in

onsite disposal in anticipation of rising costs for offs i te landfilling (13).

The

Much of the impetus f o r

Usefullness o f land spreading t o laundries will depend on access t o a

managed f ac i l i t y on a contract basis since i t seems certain t h a t s i t e

selection, monitoring o r treatment of runoff and monitoring of groundwater

will become integral parts of f ac i l i t y management. A t th i s time i t i s no t

clear whether heavy metal application rates will have t o be monitored o r

whether treatments t o stabi 1 ize metal s will be required. Development of 1 and-

spreading f ac i l i t i e s will undoubtedly depend on total quantities of o i l y

sludges generated in a particular locali ty and in areas total ly lacking

refineries, the quantities may be relatively small w i t h l i t t l e incentive f o r

industry o r local government t o acquire and manage the lands.

44

LANDFILLING

Landfilling i s currently the most widely used method of disposing of

refinery sludges, accounting for approximately one half of the total

generated in 1974 with of fs i te landfilling account for a b o u t one t h i r d ( 1 3 ) -

As pretreatment standards are developed f o r various other industries under

the Clean Water Act, solid waste streams will necessarily be generated and

much of the material directed t o landfi l ls . The result will be t o direct

attention of s ta te and local governments t o proper landfill management.

Federal regulations may require monitoring from source to final disposal

depending on how the waste i s classified ( 1 2 ) .

The environmental adequacy of landfilling will depend hydrogeological

conditions a t the s i t e and on management practices as well as character of

waste t o be disposed of.

a t h i g h pH can be negated t h r o u g h careless disposal of waste acid. A t

present, landfill management practices vary widely b u t the trend will be

For example, stabilization of metallic sludges

of more rigorous management. For example, Connecticut's

the s ta te commissioner

ate i t s disposal by

Solid Waste Management Act gives

ne a waste as hazardous and regu

in the direction

recently enacted

a u t h o r i t y t o def

permit (17 ) .

California solid waste regulations may serve, in the future, a s an

example for other states t o follow.

substances capable of impairing the quality of useable waters, such waste

i s classified, in California as a Group I waste and must be disposed of in

a Class I landfil l where there i s no possibility of discharge t o useable

waters (13) .

If i t i s judged that a waste contains

45

A t present laundry sludge i s disposed of a t o f f s i t e l a n d f i l l s and

barring an unexpected development, this method w i l l , i n a l l l i k l ihood ,

predominate i n the fu tu re . The recovery of useable ma te r i a l s , a t cen t ra l ized

resource-recovery cen te r s , i s an a l t e r n a t e p o s s i b i l i t y b u t will require

extensive fu tu re development work a s t o recoverable mater ia l s and c o s t s a s

well as a c c e p t a b i l i t y of the sludge i n a given process.

The fu tu re economic impact of sludge t r anspor t and disposal on i n -

d u s t r i a l l aundr ies i s d i f f i c u l t to a s ses s a t this time. I f the waste i s

d i r ec t ed , i n a given l o c a l i t y , t o a c l a s s i f i e d l a n d f i l l , this l a n d f i l l could

be a t a much g r e a t e r d i s tance than a conventional s i t e which accepts

ordinary r u b b i s h . Greater hauling d is tances and en t ry cos t s a s well a s t he

cos t s of permits and record keeping could cont r ibu te s i g n i f i c a n t l y t o t o t a l

treatment and disposal c o s t s .

In summary i t appears t h a t most laundry-generated sludge wil l be dis-

posed of o f f s i t e i n l a n d f i l l s . Costs will vary g rea t ly depending on laundry

loca t ion , regulatory changes and how the s ludge i s charac te r ized . Current

laundry experience is highly regulated s t a t e s i s probably the best bas i s

on which t o es t imate fu tu re cos t s . The use of cont rac t haulers versus

company-owned t rucks ; holding pits t o minimize the frequency of tr ips; in-

vestment i n more e f f e c t i v e dewatering methods and o ther s t r a t e g i e s wil l

u l t imate ly have t o be worked ou t by each laundry depending on the prevai l ing

circumstances.

46

1 .

2.

3.

4:

5. 6.

7.

8.

9.

10. 1 1 . 12.

13.

REFERENCES

Rosenthal , B.L . , " Indus t r i a l Laundry Wastewater Treatment Study". P ro jec t No. 48. Department o f Public Health, Commonwealth o f

Massachusetts , Apri 1 1964. Douglas, Gary, "Modular Wastewater Treatment System Demonstration f o r the Textile Maintenance Industry" . EPA-660/2-73-037, January 1974. Cogley, D . R . , and lkxhltery B.A. , "Occurrence and T r e a t a b i l i t y o f P r i o r i t y Pol 1 u t an t s i n Indus t r i a l Laundry Wastewater". Draf t Final Report, Walden Division of Abcor, Inc. EPA Grant No. S-804367- 01 , January 1978. Vrablik, E . R . , "Fundamental Principles o f Dissolved Air Flo ta t ion o f Indus t r i a l Waste," i n Proceedings o f 14th Indus t r i a l Waste Con- ference, Purdue University Bulletin No. 104, May 1960. Technical Bulletin, Winchester Chemical Co., Franklin Park I l l i n o i s . "Countercurrent F lo ta t ion Separator ' ' , Technical Manual , In t e r so l 1 Rond Company, Nashua, New Hampshire. Kleper, M . H . , Goldsmith, R . L . and Gollan, A . Z . , "Demonstration of U1 t r a f i 1 t r a t i o n and Carbon Adsorption For Treatment of Indus t r i a l Laundering Wastewater". Final Report, Walden Division o f Abcor. Inc. , EPA Grant No. S-804367-01, December 1977. Communication t o Mr. Mervyn S l u i z e r , J r . r e l a t i v e t o disposal on the West Coast. Experimental da ta communicated t o Abcor, Inc. from an i n d u s t r i a l 1 aundry . Catalogue FC-574, Ametek, Inc. , East Moline, I l l i n o i s , 1975. Federal Register, Vol. 43, No. 123 - Monday June 26, 1978, page 27736. "Sol id Wastes Programs and The Resource Conservation and Recovery Act o f 1976." Environmental Reporter Monograph No. 6 , October 7 , 1977 "Assessment of Hazardous Waste P rac t i ce in the Petroleum Refining Industry." Jacobs Engineering Co. prepared f o r the U.S. Environmental Pro tec t ion Agency under coh t r ac t No. 68-01-2288, 1976.

47

14. Environment Reporter, December 16, 1977, p 1235. 15. Federal Regis te r , Vol. 42, No. 211, November 2 , 1977, page 57427. 16. "Oil Refinery Sludge: Industry Looks t o Land Cul t iva t ion ,"

Sludge Magazine, May-June 1978. 17. Environment Reporter, Supplement 41 1 , A u g u s t 11 , 1978.

48