- IR2 -3+

6 A- 1 I U N T

Waste Water Treatment and Reuse in a Metal Finishing Job Shop

July 1974

U.S. DEPARTMENT OF COMMERCE National Technical Information Service

.. .

01 .- ~ ~ ~ ~ . .~ ~ .

PB 234 476'

WASTE WATER TREATMENT AND REUSE I N A METAL F I N I S H I N G J O B SHOP

4600 N. 124th Street Wauwatosa, Wisconsin 53225 12010 DSA

13.TYPE OF REPORT A N D PERIOD COVERED >2. SPONSORING AGENCY N A M E A N D ADDRESS

3. SPONSORING AGENCY CODE National Environmental Research Center Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268 -

IS. SUPPLEMENTARY NOTES

'16. ABSTRACT

A cmplete waste water treamt system has beEn installed as part of a new S. X. YIZ iL lk conpmy job p l a a facility, to rake the effluent suitable for dis- chazqe. fibst of the wtal finishing ~epcesses cc" to the Lrdustry are inclded in the plant. Despite the wide range of toxic materials wed in these prmeses, the new treatmat system is providjnq an eff1umt essentially meethg d ~ j m i t a t i o ~ on toxic ions given in the US. pEIs drinking water standards.

Five integrated waste treatment systems, each designed for a specific QW of waste m, are used to p t e tte rinse waters frm Contamination by process solution drag-out. A batch-- t"at system handles miscellan- and intermi tent discharges. The system design aims for a m i n h volurre of sldge pr&u~+Am arsl a &que and eC0ncanica.l sledge dewatein4 tedmique is included. lhpr& rinsing efficiency is achieve3 thrqh the use of the integrated chenicdl rinses, thus

water supply. permitting the plant to operate on a "m

txeatmnt system, to inswe reduced &cal consmptim and i" e~nw of -ation. D a t a is presented on the mating and capitd costs for the "tize system and operating expriences are described.

L-

. . Chemical reaction efficiency was consiclered in the design of each phase of the

- K E Y WORDS AND DOCUMENT ANALYSIS 17.

DESCRIPTORS (b.iOENTIFlERS/OPEN ENOED TERMS IC. COSATI Ficld/GrQup a. . *Metal finishinq, Industrial wastesl*Heavv metals, Waste I 13B - Cyanides, Chromium, Nickel, zinc, water treatment, Copper, Cadmiwn, Waste treatment, Reuse . I - .- I Water treatment, Metals S ~ ~ I I C I I -"

NAT i6kAL TECHNICAL INFORMATION SERVICE

US. MPIRTMW Of COMWiRa IPRIIGFIiLO. W. 22l61

1 121 Nff . OF PAGES 19. SECURITY CLASS (ThM Reporr)

7.0. SECURITY CLASS / T h I J P g C )

la. DISTRIBUTIQN STATEMENT UNCLASSIFIED

RELEASE TO PUBLIC UNCLASSIFIED ---- . #e.-,,, U. I. GOWMNl PWNRUC OfW: 1971-757-58415313 Region No. 5

TEIS DOCUX.ENT E X S a z m R " ; P ~ O D G C E D

? R O N T E E BEST C O 9 V F U R X I S E E D U S B Y

T I 3 2 S P O N S O R I N G A G E N C Y . A L T H O U G Z IT

I S R Z C O G X I Z E D TEXT C E R T A I X T O R T I O N S

A R E I L L E G I B L E , I T IS B E I N G R E L E - t S Z D

I N T E E I N T E R E S T O F XAKING B V A I L X B L E

A 5 X U C Z 12T?OR3lIATIO?S A s 6 o S S I B L % . _. .-

EPA-670/2-74-042 J u l y 1974

WASTE WATER TREATMENT AND REUSE

I N

A METAL FINISHING JOB SHOP

S . K . Williams Company Wauwatosa, Wiscons in 5 3 2 2 5

P r o j e c t No. 1 2 0 1 0 D S A Program Element No. 1 B B 0 3 6

..

P r o j e c t O f f i c e r

C l i f f o r d R i s l e y , Jr. U.S. Envi ronmen ta l P r o t e c t i o n Agency

Region V Ch icago , I l l i n o i s 6 0 6 0 6

F o r

I n d u s t r i a l Waste T r e a t m e n t Resea rch L a b o r a t o r y E d i a o n , New Jersey 0 8 8 1 7

NATIONAL ENVIRONMENTAL RESEARCH CENTER OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY .. . _. .~

CINCINNATI, OHIO 4 5 2 6 8

I

REVIEW NOTICE

The Na t iona l Environmental Research Center -- C i n c i n n a t i has reviewed t h i s r e p o r t and approved

i t s p u b l i c a t i o n . Approval does n o t s i g n i f y t h a t

t he c o n t e n t s n e c e s s a r i l y ref lect t h e views and

p o l i c i e s o f t h e U.S. Environmental P r o t e c t i o n Agency,

n o r does mention o f t r a d e names o r commercial pro-

d u c t s c o n s t i t u t e endorsement or recommendation for

use .

ii

FOREWORD

Man and h i s environment must be p r o t e c t e d from t h e adverse effects of p e s t i c i d e s , r a d i a t i o n , n o i s e and o t h e r forms of p o l l u t i o n , and t h e unwise management of s o l i d waste. Effor ts t o p r o t e c t t h e environment r e q u i r e a focus t h a t r ecogn izes t h e i n t e r p l a y between t h e compo- nents of out. p h y s i c a l environment--air , water, and land . The Nat iona l Environmental Research Centers provide t h i s m u l t i d i s c i p l i n a r y focus through programs engaged i n

s tud ie s on t h e effects o f environmental

0 a s e a r c h f o r ways t o prevent contamina- t i o n and t o r e c y c l e va luab le r e s o u r c e s .

contaminants on man and t h e b iosphere , and

The s tud ies f o r t h i s r e p o r t were undertaken t o demon- strate an e f f i c i e n t waste wa te r t r e a t m e n t system f o r a l a r g e metal f i n i s h i n g job shop. Five i n t e g r a t e d waste treatment systems, each designed f o r a s p e c i f i c t y p e of waste compound,are tJsed t o p r o t e c t t h e r i n s e waters from contaminat ion by process s o l u t i o n drag-out. The e n t i r e des ign pe rmi t s a minimum volume of s ludge -p roduc t ion , minimum watsr usage, reduced chemical consumption and maximum economy of ope ra t ion . This new technology could have a major effect on t h e i n d u s t r y ’ s e f f o r t s t o p r o t e c t our Nation‘s water r e sources .

A. W . Breidenbach, Ph.D. Direct o r Nat iona l Environmental Research Center , C i n c i n n a t i

. . ..... ... . .

. ...... .. . . ..

.. ..

iii

.. ~ .... .. . ~~ . ... -. ...... ~. . .. . ~ ~ ~.. .". .

ABSTRACT

A complete waste water treatment system has heen installed as part of the new S. K. Williams Company job plating facility, to make the effluent suitable for discharge. Most of the metal finishing processes c o m n to the industry are included in the plant. Despite the wide range of toxic mate- rials used in these processes, the new treatment system is providing an effluent essentially meeting the limitations on toxic ions given in the U. S. P. H. S. drinking water standards.

Five integrated waste treatment grstems, each designed for a specific type of waste compound, are used to protect the rinse waters from contamination by process solution drag-out. A batch-type treatment system handles miscellaneous and inter- mittent discharges. The system design aims for a minimum volume of sludge production and a unique and economical sludge dewatering technique is included. Improved rinsing efficiency is achieved through the use of the integrated chemical rinses, thus permitting the plant to operate on a minimum water supply.

Chemical reaction efficiency was considered in the design of each phase of the treatment system, to insure reduced chemi- cal consumption and maxi" economy of operation. presented on the operating and capital costs fo r the entire system and operating experiences are described.

This report was submitted in fulfillment of Project No. 12010 DSA by S. K. Williams Company under the partial spon- sorship of the Environmental Protection Agency. completed as of February, 1971.

Data is

Work was

c

n

iv

CONTENTS

Abstract

List of Figures

List of Tables

Acknowledgments

Sections

I

I1

I11

IV

V

VI

VI1

VI11

IX

X

XI

Conclusions

Recommendations

Introduction

Waste Producing Operations

Waste Treatment System Design Considerations

Operation of Integrated Treatnent System

Operation of Batch Waste Treatment System

Operation of Rinse Water System

Sludge Handling Operations

General Economic Considerations

References

5

i v

v i

v i I

v i i i

1

3

4

8

15

26

32

3a

48

5 2

5 1

V

. ... . . ~ . ~ .

F I G U R E S

No.

1 -

2 ..

3

4

5

6

7

8

9

10

11

Plant Layout

Automatic Nickel-Chromium Plating Machine (Department 100)

Manual Hoist Line (Department 200)

Automatic Programmed Hoist fo r Zinc and Cadmium Rack Plating (Department 600)

Typical Integrated Treatment System

Sludge Filter Bed

Waste Treatment Room Equipment Layout

Batch Acid and Alkali Treatment Tanks

Caustic-Soda Storage Tank

Rinse Water Settling Tank

Thickened Sludge in Filter Bed

10

12

-

13

14

16

23

24

25

25

3a

51

vi

.-

TABLES

NO. Page

1 Summary of Integrated Treatment Systems 19

2 Chemical Consumption of Integrated Treatment 29

-

Systems - November, 1970 \

3 Plant Production for November, 1970 3 1

4 Sludge Filter Bed Effluent Analyses 3 5

5 Chemical Consumption of Batch Treatment System - November, 1970 3 1

6 Results of Rinse Water Effluent Analyses 42

7 Results of Combined Effluent Discharge 44

8 Relative Consumption of Fresh and Reused Water 45

9 Distribution of Water Consumption by 4 6

_.- Production Departments

10 Chemical Consumption of Rinse Water System 47

11 Comparison of Sludge Filter Bed Performance 5 0

12 Sununary-of Capital Costs 5 2

13 Summary of Monthly Waste Treatment System 5 3

14 Distribution of Treatment Chemical Costs by 5 5

Operating Costs - November, 1970

Production Time

15 Waste Treatment Chanical Coats per Unit of 5 6 Production

16 Waste Treatment Chemical Costs 5 7

vii

ACKNOWLEDGEMENTS

Supervision of the waste treatment operation and assistance in gathering data for this report were provided by S. K. Williams personnel, M r . Alan Williams, Mr. Robert Steuernagel, Jr., an8 Mr. Wtlliam P. McDonough.

The design of the waste treatment system and preparation of this report were supervised by Leslie E. Lancy, Ph.D., President of Lancy Laboratories, Division of Dart Industries, Chemical Group, Zelienople, Pennsylvania. The report was prepared by Mr. F. A. Steward, Project Engineer with Lancy Laboratories.

The advice and cooperation of M r . William Lacy, Chief of Industrial Polltuion Control Branch; Mr. Edward Dkilaney, Program Manager for Metal and Metal Products; and M r . Clifford Risley, Jr., Project Officer; all of the Research and Monitoring Office of the Environmental Protection Agency, is acknowledged with sincere thanks.

This report was submitted in fulfillment of Project No. 12010 DSA-tmder the partial sponsorship of the Environmental Protection Agency, United States of America.

viii

SECTION I

CONCLUSIONS

A waste t r e a t m e n t f a c i l i t y based upon use o f t h e i n t e - g r a t e d t r ea tmen t systems a l lows a j o b p l a t i n g shop t o p rov ide complete waste t r e a t m e n t , whi le main ta in ing t h e f l e x i b i l i t y of p rocess ing c y c l e s which i s e s s e n t i a l t o t h a t bus iness .

Accomplishing waste t r ea tmen t w i th r e c i r c u l a t e d chemi- c a l r i n s e s is an e f f e c t i v e and economical approach wi th minimum s ludge g e n e r a t i o n and chemical consumption. A n a l y t i c a l r e s u l t s spanning a one y e a r pe r iod show aver- age e f f l u e n t c o n c e n t r a t i o n s of:

7 . 8 1 cu 0.09 mg/l CN 0 . 0 3 mg/l N i 0 . 2 1 mg/l Ph

C r + 6 0 . 0 2 mg/l Zn 1 . 1 2 mg/l C r + 3 0 . 0 1 mg/l Cd 0 . 2 5 mg/l

The t o t a l waste treatment c o s t s , i n c l u d i n g d e p r e c i a t i o n , chemicals , u t i l i t i e s , and Labor add only 3.3C t o each d o l l a r of t h e company's sales.

By improving t h e c o n d i t i o n s under which p r e c i p i t a t i o n , f l o c c u l a t i o n , and s e t t l i n g occur , t h e i n t e g r a t e d treat- ment sys tems produce metal hydroxide s ludges which con- t a i n f a r l e s s water and are more amenable t o f u r t h e r dewater ing than those produced by t r e a t m e n t o f d i l u t e r i n s e water wastes.

To accomplish e f f e c t i v e and economical waste t r e a t m e n t , p l a t i n g shop o p e r a t o r s and managers must i n c o r p o r a t e i n t o t h e i r t h i n k i n g some new approaches and a t t i t u d e s , such as c o n s i d e r i n g t h e f l o o r as a c o l l e c t i o n system f o r a c c i d e n t a l d i scha rges r a t h e r t h a n an ex tens ion of t h e i r sewer i n l e t .

Lack o f a t t e n t i o n t o d e t a i l s , such as unnecessary water runn ing on t h e f l o o r or a c i d s and c l e a n e r s being mixed px-ior t o t r e a t m e n t , can i n f l a t e waste t r ea tmen t expenses as i n d i c a t e d by t h e ba t ch t rea tment c o s t s i n t h i s system.

S u p p l i e r s of process chemicals f o r t h e meta l f i n i s h i n g i n d u s t r y a r e making i n c r e a s i n g use o f o rgan ic c h e l a t i n g and complexing a g e n t s , and t h e s e are c r e a t i n g e n t i r e l y new waste t r e a t m e n t problems which may prove t o be more seve re and c o s t l y t h a n t h e p r e s e n t ones.

1.

2 .

3 .

4.

5 .

6.

7.

.

- 7

... . ~ ... - , .. . . . . ~ ~ ~ . . . .

8. Waste t r ea tmen t c o s t s do add t o t h e o v e r a l l o p e r a t i n g expenses o f a p l a t i n g shop, b u t t h e y can be a t least p a r t i a l l y o f f s e t by jud ic ious conserva t ion of water and process chemicals , both o f which a r e commonly wasted.

9. Proper des ign o f a waste t rea tment system can permit a r educ t ion i n water and sewer charges t o o f f s e t a major p o r t i o n o f i t s ope ra t ing c o s t s ; ( 4 7 % i n t h i s r e p o r t ) .

1 0 . Since chemical wash s o l u t i o n s are more e f f e c t i v e than water for r i n s i n g , t h e i n t e g r a t e d t reatment systems a c t u a l l y improve t h e p l a t i n g processes as shown by t h r e e examples ( see page 26). An a d d i t i o n a l advantage of t h e i n t e g r a t e d systems i s t h a t c o n d i t i o n s i n i m i c a l t o t rea tment q u a l i t y w i l l f r e q u e n t l y cause an undes i r ab le e f f e c t on t h e work p i e c e s ( s e e page 2 7 ) . This g i v e s t h e o p e r a t o r s a d d i t i o n a l i n c e n t i v e t o main ta in good c o n t r o l of t h e t r e a t m e n t systems.

11. Concrete block s ludge f i l t e r beds, as used i n t h i s sys- t e m for dewater ing t h e waste s ludges , can be adve r se ly a f f e c t e d by o i l and by t h e i n t r o d u c t i o n of wastes t r e a t e d in t h e presence of p e p t i z i n g agen t s and/or l a r g e volumes o f d r I u t i o n water .

,

2

SECTION I1

RECOMMENDATIONS

1. If the practice of stripping work pieces in the acid pickles cannot be discontinued, an integrated treat- ment system should be installed to eliminate the carry- over of zinc and cadmium into the rinse waters.

2 . Alkaline cleaners should be neutralized and discharged to the sanitary sewer system rather than treated with metal-containing solutions. The cleaning solutions contain organic peptizing agents and detergents which do not need chemical treatment and which interfere with the chemical treatment of the other solutions. Biological treatment is necessary for these organic materials and the neutralized cleaning solutions are suited for discharge into such a sewage treatment system.

3 . Suppliers of process chemicals for the metal finishing industry must begin to appreciate waste treatment problems when they formulate new materials. If the use of a particular chelating compound in a process offers numerous advantages, but also increases waste treatment costs disproportionately, then it would not be an improvement in t3e technology. Under certain conditions, such as plating on plastics, the use Qf such organics is necessary, but their use should be avoided when possible.

4 . All oil must be kept out of the treatment system, acids should be discharged in such a manner that they are as concentrated as possible when treated, and all unneces- sary waste must be kept off the floor.

5 . The north sludge filter bed, which now dewaters sludge only very slowly, should be equipped with a Sludge Filter Decant Panel which would restore its effective- ness and assist in removing the excess water which is being hauled away with the sludges.

3

SECTION 111

INTRODUCTION

The S. K. Williams Company has been engaged in the job elec- troplating business in the Milwaukee area for many years. 1967, they began plans to erect a new building for consoli- dation and enlargement of their electroplating and metal finishing activities. The building project was initiated due to anticipated future expansion of their activities, and the building design was such that the plant area could be expanded to accommodate additional equipment facilities and to provide storage capacity for work in process for their customers. The first portion of the new plant was completed and placed into operation in 1969. Ultimately, about four times as much area is to be included under roof, but the present building houses the majority of the types of plating processes to be used, and will account for the major portion of the production and waste generation.

Both existing finishing equipment, moved from the former plant locations, ana-additional new equipment to automate and stream- line the operations are housed in the new structure. finishing activities are performed on various basis materials such as steel, stainless steel, copper, brass, aluminum, zinc die castings, magnesium, plastics, etc. The metal finishing operations, including cleaning and descaling of the basis metals and electroplating with the finish metals, are processes requiring water. Without proper treatment, the waste water from this building would be contaminated with many different types of toxic chemical compounds, and would be unsatisfactory for discharge to either a sanitary sewer system or a storm sewer or surface water course. treatment provisions in such a job plating shop is a partic- ularly demanding one because of the wide variety of waste mate- rials involved, the severe toxicity of many of the contami- nants, and the extremely large quantities of water normally used.

In this particular case, an additional factor to be considered in designing the plating plant and waste treatment system was the limited availability of fresh water. The continuation of past practices would have required a total of 800 gallons per minute of water after all anticipated expansions had been com- pleted. The normal water consumption for the portion of the plant now in operation would have been about 600 gallons per

In

Metal

The requirement for waste

4

minute. However, the State of Wisconsin restricted the per- missible pumping rate at the company's well to 300 gallons per minute so as to avoid a reduction in the water table in the area. Such a reduction would seriously interfere with

necessary to design the plant so that it would operate on a maximum of 5 0 % of the normal water consumption.

The design, installation, and initial operation of a unique waste treatment system to neutralize all toxic waste con- stituents, while at the same time drastically reducing water consumption in the plant, was undertaken as a demonstration project partially financed by an EPA Research and Develop- ment Grant. This report describes the new metal finishing plant and waste treatment system as well as the findings and conclusions resulting from the initial year of operation.

Lancy Laboratories of Zelineople, Pennsylvania, was chosen as consultant for the design of the waste treatment system. Their design centered around the use of Integrated Waste Treatment Systems for each specific type of contaminant to be encountered.

The Integrated approach2 consists of a recirculated chemical treatment wash solution, integrated into the metal finishing process line. Parts being removed from a toxic process solu- tion are rinsed in this treatment wash solution before being rinsed in water. Because the use of this approach greatly reduces the input Qf dissolved salts to the rinse water, as compared to conventional rinsing, far less water is required to aacomplish satisfactory rinsing. For this reason, a water reuse system was an integral part of the design, and it was anticipated that as much as 80% of the rinse water, which would normally be wasted from the plant, could be pumped back for reuse in the processing lines.

Additional advantages to be expected from the use of the Inte- grated systems were reduced treatment chemical consumption and reduced sludge handling expenses, compared with conven- tional treatment approaches. Finally, a novel method for de- watering the sludges produced by the waste treatment re- actions was included in the system. In metal finishing waste treatment, the final disposition of the sludges pro- duced is one of the largest factors in the operating expenses3 and the dewatering system used here is a major improvement in the economical handling of such sludges.

. the needs of other water users in the vicinity. Thus it was

- _-

5

_-

The following were considered as objectives for the demonstra- tion project: .

(a) To demonstrate the feasibility of operating a high-production, job electroplating installa- tion, utilizing nearly all common electroplating processes, while maintaining a waste water efflu- ent of the highest quality in a simple and eco- nomical manner.

(b) To show that, in view of the uncontiminated rinse water effluent, it is possible to reuse 80-90% of the waste effluent in the process rinses without any chemical purification or mechanical filtration.

(tj 'TFdemonstrate that the various chemical rins- ing steps employed--the Integrated Treatment Solutions--have no deleterious effect upon the work pieces and can, in some cases, be advan- tageous, yielding improved quality, freedom from staining, better adhesion, and a lower rate of rejects due to mis-plating.

for the complete precipitation and settling of the metal ions which are in the thin film of process solution carried by work pieces when they are removed from the solution. The method relies upon the fact that the chemical reactions occur in the presence of a high excess of treatment chemicals and a relatively high concentration of precipitated solids as compared to the usual method of settling these same metallic precipi- tates from dilute rinse waters.

(d) To demonstrate a simple and economical method

(e) To demonstrate a new technique for dewatering the collected sludges, avoiding high-cost filtration and the usual problems encountered when pressure or vacuum filtration of metal hydroxides is attempted.

6

The uniqueness of this demonstration project is based upon the fact that the waste treatment system serves a job plating plant utilizing an extensive variety of metal finishing pro- cesses containing various toxic compounds and yet the level of effluent contamination can be less than the established criteria for public drinking water supply. Also unique is the fact that approximately 80% of the rinse water effluent may be reused in the processing plant because of the very low level of dissolved salts. (See page 20). Of primary interest is the fact that these unique benefits are accomplished with less operating expense than would be encountered in treating the wastes from the same plant using available alternative approaches.

The only alternative approaches which are practical and re- liable for treating a waste water effluent containing the variety of contaminants involved here are based on the treat- ment of the flowing rinse waters for removal of the con- taminants. Since the concentrations of the contaminants in a rinse water stream would be very low, and the flow rate o f the stream would be relatively high, chemical treatment and solids separation would both be inefficient-and expen- sive. Furthermore, when the drag-out of process solu- tions and the additions of treatment chemicals both con- tribute to the dissolved solids in the rinse water stream, reuse of the water is far less practical and economical than with the system here employed. -

7

SECTION IV

WASTE -P RODUCING OPERAT I ON S

In a job-plating plant such as this, aqueous wastes re- quiring treatment normally result from:

(1) Water rinses following the various pro-

( 2 )

cess solutions containing toxic chemicals.

The periodic discarding of expended pro- cess solutions, such as cleaners, acid dips, anodizing solutions with high aluminum content, etc.

( 3 ) Accidental overflows of solutions contain- ing toxic chemical compounds, and drippage from work in process between the various process solution and rinse tanks.

in the event that a heating coil imersed in a toxic chemical process solution would develop a leak.

- ( 4 ) Discharges of contaminated steam condensate

- -

The first of these sources represents the most demanding waste treatment requirement as the rinse waters consist of trace quantities of the various contaminants in large volumes of water. Attempting chemical reactions under such dilute conditions is cumbersome and inefficient and re- quires large reaction vessels because of the hydraulic load. Furthermore, the sludges which result when toxic metals are precipitated from dilute solutions are very voluminous and difficult to separate as they have nearly the same density as the water itself. Typical sludges resulting from treatment of dilute rinse waters contain 9 9 . 5 % water and only 0.5% sludge. Thus, the sludge hand- ling and disposal provisions must be designed for slurries which are nearly all water. Where the solid wastes must be hauled away from the plant site, a significant portion of the total waste treatment operating costs may be attributed to hauling away water.

tamination by the same materials as the rinse waters, but their safe and effective elimination is primarily a problem of proper waste treatment system design. The discarded pro- - cess solutions are relatively concentrated and can thus be treated with reasonable chemical efficiency while the floor

Wastes from Sources 2 , 3 , and 4 are subject to con-

s p i l l s and contaminated condensate are normally very low volume wastes.

The general types of processes that are installed in the plant's various metal finishing lines consist of:

Cleaning, for oil and grease removal;

Acid descaling and pickling of steel, copper, brass, aluminum, zinc-base die castings, etc.

Metal plating from the cyanide complexes of zinc, cadmium, copper, silver, and gold;

Metal plating based on the acid complexes of nickel, copper, and chromium;

Metal plating based on the alkaline complex of tin;

Sulfuric and chromic acid anodizing of aluminum;

Chromium-compound-based conversion coatings on aluminum, cadmium, and zinc;

Dyeing of anodized aluminum surfaces. -.-

Figure No. 1 shows the present layout of the metal finishing equipment in the plant.

9

, .

. ~. __

. ...~

. .. .

.

10

The waste treatment facilities for the plant were designed to also fill the requirements of additional metal finishing equipment which may be installed in the future. However, the present finishing equipment includes nearly all of the metal finishing processes which will be encountered. There- fore, it is anticipated that most of the future facilities will only be duplications of existing processes, but with different mechanical equipment to handle various types of work pieces with maximum efficiency. All of the high- production finishing operations are included at the present time. The new equipment will be needed for additional flexibility in handling unusual or small-lot items, so that most of the rinse water and chemical consumption will be attributed to this existing equipment, even after all planned expansions have been completed.

Figures 2, 3 , and 4 are photographs of three of the major high-production plating areas.

11

. .. . . . . ~ . .

~ ~. . . ..~ . . . . . .. ~ . . . . ... ... -__ .. .. ... ~ .. .. ..

Figure 2

Automatic Nickel - Chromium Plating Machine (D@partment 100)

Figure 3

Manual Hoist Line (Department 200)

~ __ ~ .. .... . ~ .. .~ .. . .

Figure 4

Automatic Programmed Hoist for Zinc and Cadmium Rack Plating (Department 600)

14

SECTION V

WASTE TREATPENT SYSTEM DESIGN CONSIDERATIONS

As mentioned earlier, dilute rinse water wastes are the most expensive and difficult to treat properly. These wastes re- sult when work pieces, carrying a thin film o€ process solu- tion (drag-out), are rinsed in water prior to further processing.

The Integrated waste treatment systems employed in this facility prevent the formation of dilute wastes by removing the,process solution film from the parts before they are rinsed with water. Each chemical wash solution, used to rinse the parts, is recirculated in a closed-loop system which includes the treatment wash tanks in the plating lines and a reservoir tank connected by piping to the wash tanks. Figure 5 shows a typical integrated treatment system.

Since the treatment wash solutions contain excess treatment chemicals at all times, the reactions between the contami- nants and the treatmerit chemicals occur at the surface of the work pieces where the process solution film is still in a concentrate& state. Since the reactions occur under con- centrated conditions, and in the presence of sxces6-treat- ment chemicals, they are very rapid and the consumption of chemicals is kept to a minimum. The sludges, which are pro- duced when the metal ions precipitate, accumulate in a dense, dewatered condition because they are precipitated under con- centrated conditions. Furthermore, they are kept within the closed-loop system so that newly-formed sludge particles become mixed with older, conditioned sludge, giving excel- lent flocculation and compacting.

Some of the sludge which accumulates in the treatment reser- voirs is removed by a periodic "sludge-blowdown" wherein sludge solution is pumped from the reservoirs to a sludge filter bed. The volume removed by this operation is re- placed with fresh water, thus reducing the dissolved salt concentration of the treatment solution. The timing of the blowdowns controls both the salt level in the solution and the amount of accumulated sludge.

15

16

Since the treatment wash solution must be chemically formu- lated to suit the particular contaminant for which it is in- tended, a separate closed-loop syscem must be provided for each type of contaminant. In this plant, the following types of toxic contaminants are distinguished: -

Cyanide compounds such as sodium and potassium cyanide and also their metal complexes with zinc, cadmium, copper, silver, and gold.

Chromic acid waste containing high concentra- tions of free chromic acid.

Chromate compounds containing l o w concentrations of chromate chemicals.

Nickel from sulfate and chloride-based solu- tions.

Copper from acid solutions such as sulfuric- nitric type bright dips, acid copper plating solutions, and chelated copper complex solu- tions as used in the process of plating on plastics.

Thus, five Integrated Systems are provided to-protect the rinse waters from contamination due to drag-out of process solution. These are known as the Integrated Cyanide, Chromium I, Chromium 11, Nickel and Copper Treatment Systems. The chemistry of these systems is as follow^:^ Cyanide

2NaCN + 8NaOH + 5C1, + 10 NaCl + 2C024 + N2.t. + 4H20 Chromium I

2H2Cr0+ + 3S0, + Cr, (SOL,) 3 + 2 H 2 0

Chromium I1

Cr2 (SO,+) + 3Na2C03 + 2 8 2 0 + Cr2 (OH) 4C03c + 3Na,SO, +

2C024

and

17

.. .~ . . ...... . . . . ~~ .. . . . .

2Na2Cr0, + 3Na2S20, + Na2C03 + 2 H 2 0 +. Cr2(OH)4C03i

+ 6Na2S0,

Nickel

2NiS0, + 2NaOH + Na2C03 +. Ni2(0H)2C03 + 2Na,S04 Copper

2CuSOI, + H2S0, + Na2S204 + 8NaOH +. Cu20S

+ 2Na2S03 + 3Na2SOk +

It should be explained that the Chromium I1 treatment solu- tion contains both reducing and neutralizing chemicals, and thus provides for both the reduction of hexavalent chromium to the trivalent form, and the precipitation of trivalent chromium. It is used as a single-step chromium treatment wash after low-concentration chromate dips. On the other hand, the Chromium I treatment solution is operated at a low pH range and can thus use a much less expensive re- ducing agent than can the Chromium I1 system. Following highly concentrated chromium process solutions, the Chromium I treatment wash is used first to accomplish re- duction of the hexavalent chromium economically. The Chromium I1 wash, which follows, then neutralizes the acidic Chromium I film and precipitates the trivalent chromium as the basic carbonate.

Table 1 lists, for each of the five Integrated Systems, the type of process accommodated, the primary treatment chemi- cals added, and the metals precipitated to form the sludge.

18

Table 1. SUMMARY OF INTEGRATED TREATMENT SYSTEMS

Metals Treatment Chemicals & System Process Treated Concentrations Precipitated

Cyanide

Chromium I

Chromium I1

Nickel

Copper

Zinc, Cadmium, Copper Silver and Gold Plating

Chromium Plating; ' Etching of Plastics

Chromium Plating; Chro- mate Dipping of Zinc, Cadmium and Aluminum; Etching of Plastics; Chromic Acid Anodizing

Nickel Plating

Acid Copper Plating, Copper and Brass Bright Dipping

I I

Chlorine Gas (C12) - Caustic Soda (NaOHI

Sulfur Dioxide Gas (SO21 - 1,000-2,500 mg/l

Sodium Hydrosulfite (Na2S201,) - 200-500 mg/l Soda Ash (Na2C03) -

800-2500 mg/l

pH 11-12.8

pH 7.5-8.5

Zinc, Cadmium Copper, Gold

--- Chromium, Zinc, Cadmium, and Aluminum

Soda Ash (NaZCO3) - Caustic Soda (NaOH) pH 8.5-9.5

Sodium Hydrosulfite

Caustic Soda (NaOH) - (Na,S,O,) - 500-700 mg/l pH 8.5-9.5

!

Nickel

Copper Zinc

I

< .

.. .. .~ . .. . .~ .. .. . . .. . ~ ~ ~. . . . . .... 'I.. . .

The total dissolved salt Concentration in the Integrated treatment solutions (typically 75-120 g/l) is much lower than in the preceding process baths (typically 250-400 g/l), and the volume of solution film carried on a given work piece is the same when it emerges from either solution. Thus, the water which is used to rinse the piece receives far less salt input when it follows an Integrated Solution than when it follows a process bath. Furthermore, when following conventional practice, and removing the toxic materials with rinse water, all of the treatment chemicals must also be added to the water. They must be added in excess of requirements to insure complete reaction. The result is that the rinse waters in conventional practice carry approximately four times the concentration of dis- solved salts found in rinses following Integrated treatment washes.

All rinse waters in this plant are collected - in a common sewer system which leads to a pH Adjustment Sump. The rinses fol- lowing toxic process solutions are protected by Integrated Treatment Washes and the remaining rinses are those follow- ing alkaline cleaners, acid dips, and other non-toxic pro- cess solutions. Since the sludges resulting from the major treatment reactions accumulate in the Integrated systems, the only sludges to he found in this combined rinse water stream are traces of precipitated iron, alumi- num, and water hardness. To remove these traces, a settling tank is provided following the pH Adjustment Sump. After passing through the settling tank, the clarified rinse waters overflow into a chamber from where the Reuse Water Supply Pump returns a portion (as high as 80%) of the flow to the plating lines. To control the accumulation o f dissolved salts in the rinse water system, a certain amount of fresh well water is added at selected rinse tanks in the plating lines. This amount of fresh water input creates an overflow from the teuse water pump chamber, and this overflow is the rinse water effluent discharged from the plant to the storm sewer.

Discharge to a sanitary sewer system was avoided because the quality of the water, and thus the total discharge of waste materials to the environ, could not be improved by passage through a biological treatment plant. Furthermore, dilution of the input to the sewage plant with essentially pure water can only reduce the efficiency of the biological processes. For this reason, discharge of a properly-treated industrial waste effluent to a sanitary sewer is ecologically harmful.

a

20

The additional waste chemical load from future expansions will be countered by increased chemical feed rates in the five Integrated systems, which are not limited in the amount of chemical input which can be handled. Even at full antic- ipated expansion, the plant will have a maximum fresh rinse water consumption of 300 GPM, and the dissolved salt con- centration in the water will be less than that which would be found in 800 GPM with conventional treatment methods.

A batch collection and treatment system is provided for the discarded process solutions and the accumulated floor spills. It is essential that the discarded process solutions be treated in the concentrated form so that chemical reactions are efficient and sludges are as concentrated as possible. Thus, an overhead acid collection line is provided with quick disconnect fittings located throughout the plant. A portable pump is to be connected to the nearest fitting on this line and used to transfer the solution directly to the Batch Acid Treatment Tank. On the other hand, dis- carded alkaline solutions are drained through the underfloor sewer to the Alkali Sump from where they are pumped auto- matically to the Batch Alkali Treatment Tank.

A plating shop will inevitably have an appreciable amount of floor spill resulting from: drippage as parts are trans- ferred from tank to tank; overflows of tanks due to over- filling; spills and drips of the concentrated Chemicals which must he regularly added to the process solutions; and leaks in tanks, piping, filters, etc. These floor spills can be contaminated with any of the chemicals used in the plant, and they can vary widely in concentration. Therefore, a system to collect the floor spillage and hold it for man- ual hatch treatment is essential. The best approach for treating this type of waste can only be decided upon after the operator has examined and analyzed it. The floor in this plant is designed so that all floor spills are con- tained and prevented from entering the rinse water sewer system. Areas of heavy acid usage, such as the hard chromium plating, and aluminum anodizing areas, have the floor drained through vitrified clay sewers to an Acid Sump which is equipped with a pump and level control to automat- ically pump to the Batch Acid Treatment Tank. All other processing areas have the floor drains connected with cast iron sewers to the Alkali Sump mentioned previously.

In the Batch Treatment System, appropriate chemicals are added to treat the collected wastes, depending upon what the operator's examination reveals about their composition. When cyanide is indicated by analysis, caustic soda and

21

chlorine gas or calcium hypochlorite are added. When hexa- valent chromium is found, it is reduced with sodium meta- bisulfite (in acid solutions) or sodium hydrosulfite (in neutral or alkaline solutions). Following treatment for cyanide and hexavalent chromium, each batch is neutralized with fresh sulfuric acid or caustic soda to pH 8.0-9.5. Following the addition of treatment chemicals, the treated batch is allowed to mix for at least fifteen minutes to insure that reactions are completed, and then it is analyzed for toxic materials prior tQ discharge to the Sludge Filter Bed.

All sludges from the treatment reactions accumulate as follows:

(1) Those from treatment of process solution drag-out accumulate in the five integrated treatment system reservoirs.

(2 ) The traces of precipitate in the treated rinse water effluent accumulate as a sludge blanket in the bottom of the Rinse Water

_ . Settling Tank; and

( 3 ) The treatment of various wastes in the Batch Treatment System generates sludges which are pumped out with each treated batch.

All of these sludges are discharged to a Sludge Filter Bed of concrete block construction. This device5 serves to de- water and thicken the sludges through a unique and effective combination of gravity filtration, capillary dewatering, and greatly increased evaporation. Thickened sludges from the filter beds are periodically removed by pumping them into a septic waste hauling truck which dumps them on a sanitary landfill.

Figure 6 is a photograph of the two filter beds with the sludge hauling truck and its suction hose visible.

2.2

Figure 6 - Sludge Filter Bed . . . ..-

-- ____

Tha equipment layout in the waste treatment room is shown in Figure 7, and photographs of some of the waste treatment equipment are shown in Figures 8 and 9.

23

. . . . . .... . . . . . ........ . . . . . . . . . . . . . . . . . . ...-.. ~. . , I

0 .-

R i,. )I w \ / I

1 CHRDUE I SUUP TANK 2 CYANIDE SUYP TANK 3 CHRDUE II 9WP TAW 4 NICKEL WU? TANK 5 COPPER SUW TANK 8 ALKALI SUUC TANK 7 ACID W Y P 8 FLASH UlXlNO TANK 8 Ph CONTROL UNIT

IO NOW SUPPLY TANK I 1 \,SQ SUPPLY TANK 12 ACID CDDLIND WITER

HOLDlNO TANU I3 CYANIDE CODLIN0 WATLR

14 WATER SEAL UNIT HOLDINO TANU

0. No,&&- NqCO, UIXINS T A N I *. CLCCTRICAL CONTROL PANEL IT. llrcR YIXINE TANU IO. N&&- N O W YlXlNO TANU IS. mbn’ h R A O C TANK 150% L l O U l D I to CYANIDE TReATYCNT RESERVOIR TANK 21. M O U E II lWCA1YEUT R L S S I Y m I T I Y l .. . . . .- a t NUKEL TRLATUENT R E s c R v o m TANU 2s. CDPPER TRCATYENT RESERVOIR TANU MN.,S,O, uixma TANK m . C w y E I T M A T U I L N T RLSLRVOIR TANK m. ALKALI COLLLCTION TANK

Figure 7 - Waste Treatment Room Equipment Layout

24

3

c. m E3 ar 0

m U 0 4J m

5

a 0

co I

QI

25

SECTION VI

OPERATION OF INTEGRATED TREATMENT SYSTEM

Treatment chemicals are added to the Integrated Systems from stock solution mixing tanks, with the exception of chlorine, which is added to the Cyanide Treatment System as a gas, and sulfur dioxide which is also fed as a gas to the chromium Treatment System. The stock feed solutions are prepared once per shift and added to the system by manually- set proportioning pumps. Since relatively large excesses of treatment chemicals are maintained in the treatment solutions, and the large volumes of solution resist rapid changes in concentration, chemical control of the systems is simplified. The reserve of treatment chemical in a system is adequate for several hours of operation even in the event of a complete failure of chemical feed. Thus, periodic checks on the concentration of excess chemical in a solution serve as adequate controls of the system. These tests on the Integrated solutions are run by the waste treatment operator and recorded on a log sheet, which is kept as a permanent record of the performance of the systems. As a confirmatory check, the rinse water effluent is tested once per-day f6r the major contaminants, and it is given a complete, quantitative analysis once per month. All of the routine control analyses are performed using simplified test procedures6, developed so that plating shops without elaborate laboratory facilities can operate and control their waste treatment systems.

Theoretically, chemical rinsing is far more effective in removing a film of process solution than is normal water rinsing.7 While such improvements in rinsing efficiency are very difficult to demonstrate quantitatively in an operating plant, three instances of the effect were noticed in this installation. The first was a nearly complete elimination of chromium staining on parts which had been bright chromium plated for decorative purposes. Chromium staining results when chromic acid, which has been trapped in cracks, or in blind holes, or between the rack tip and the part, bleeds out onto the plated surface during hot water rinsing and drying. The Integrated treatment solution eliminates this problem by chemically attacking the chromic acid solution, rather than attempting to displace or dilute it, as does water. The second observed improvement was an increase in the adhesion of plated nickel coatings to copper substrates which had been previously deposited from an acid copper

c

2 6

plating bath. in the Integrated Treatment Solution, subseguent nickel adhesion was significantly better than when the same part was water rinsed. Finally, an improvement in the rinsing of chromic acid etch solution from plastic parts was noted. The etch solution has a high viscosity and is thus diffi- cult to remove completely from the porous plastic surface. However, as in the case of chromium staining, the chemical attack of the treatment wash solution effectively removes all traces of the etch. The amount of time and labor required for rinsing the parts where bath reduced, but perhaps most important is the fact that the life of the subsequent process solution was increased. This subsequent bath is a proprie- tary "sensitizer" which prepares the etched plastic surface to receive the deposit of electroless copper plating. This sensitizer is a relatively expensive solution which is adversely affected by trace contamination of hexavalent chromium.

When the acid-copper-plated part was rinsed

In one case, the chemical treatment wash solution did have a detrimental effect upon the work pieces in process. After six months of trouble-free operation, the freshly zinc- plated parts started to turn a dark gray color when dipped into the cyanide treatment wash, and the zinc surface then resisted bright dipping and ohromating. were that ions of a metal more noble than zinc were present in the treatment solution. Mdny. previous installations using the same treatment solution for the samamixture of metals had established that when precipitation of cadmium and copper from the solution was sufficiently complete, no problem should exist when rinsing the zinc-plated parts. However, investigation revealed that a new, "low-cyanide"

. z i n c plating bath had been put into use d few weeks previous to the appearance.of the problem. As it turned out, the addition agents used in the new plating solution contained some complexing 01 chelating agents which accumulated in the treatment solution and held excessive copper and/or cadmium in solution.

A simple modification in the chemical additions to, the system eliminated the problem by replacing the copper and cadmium in the chelates with harmless caicium and magnesium ions.8 A mixture of calcium and magnesium chlorides was added to the system with a proportioning pump, thus preferentially occupying the chelated positions and allowing the heavy metals to precipitate. After a few months of use, the new "low-cyanide" brightener system was abandoned because the complexing-type addition agents for the plating bath proved more troublesome and expensive than the treatment of the cyanide which they were to eliminate.

All indications

However,

27

. . . .. . . .~ .

~ . ... . .-

additions of the calcium and magnesium to the treatment system have continued because elimination of the complexers from the plating bath is a very slow process since they are lost only by dxag-out. Complete elimination of the troublesome compounds from the plating bath could take years. . Another modification in the operation of the treatment systems was made after nearly a year of operation. It involved the use of hydrazine hydrate as the reducing agent in the Integrated Copper and Chromium I1 Treatment Systems. Originally, sodium hydrosulfite (Na,S,O,) was used as the reducing agent, but this compound is rather unstable and is readily oxidized by the air in contact with the solution surface. A large portion of the hydrosulfite added to the systems each day was lost due to this breakdown, rather than being consumed in reducing the metal ions. Hydrazine hydrate was found to be an effective reducing agent for the application, and it was not lost through wasteful breakdown. Therefore, the systems were converted to hydrazine use in early 1970, after nearly a year of opera- tion, and the costs for reducing chemicals were drastically reduced. In the copper treatment system, a monthly chemi- cal cost of $69.97 (April 21 to May 19, 1970) with hydra- zine, jumped t o $248.24 (May 20 to June 17, 1970) when the hydrazine supply ran out and hydrosulfite was substituted for a month.

For purposes of tabulating operating costs, the month of November, 1970, was chosen as representative of current conditions. Prior to this, some of the processes intended for inclusion in the plant were not in full production. Table 20n the following page lists the chemicals consumed in each of the Integrated Systems during the subject month,

Three other factors which enter into the total operating costs for these systems are the operator's wages, the sludge disposal costs, and the power costs for the pumping equipment. These factors are included in the overall economic summaries given in Section VIII, but no attempt is made to allocate appropriate portions of the three factors to the operation of the Inte- grated Systems.

.and indicates the respective cost figures.

28

TABLE 2 - Chedcal Consumution of Integrated Treatment Systems

November. 1970

Quantity Unit Monthly

Cyanide Caustic Soda (50% 704 gal. $0.318/gal. $223.87

Treatment System Chemical Comuound Consumed Price cost

liquid)

Chlorine 4096 1b. 9.05/cwt. 370.69

Inhibitor LD 12.5 gal. 9.60/gal. 120.00

Calcium Chloride 57 lb. 5.20/cwt. 2.96

Magnesium Chloride 57 lb. 7.50/cwt. 4.28

$721.80

(proprietary)

44 gal. 50.318/gal, $ 13.99 Sulfur Dioxide 390 lb. 8.15/cwt. 31.79

Chrome I Caustic Soda -..

$ rr5.78

Chrome I1 Soda Ash 193 lb. $3.50/cwt. $ 6.76

Hydrazine Hydrate 17.75 gal. 8.12/gal. 144.13 (85%)

$150.89

560 lb. $3.50/cWt. $ 19.60

76 lb. $3.5O/cWt. $ 2.66 Nickel - Soda Ash

copper Soda Ash Hydrazine Hydrate 14.75 gal. 8.12/gal. $119.77

$122.43

T o t a l Chemical Cost f o r Integrated Treatment Systems $1060.50

29

So that these cost figures may be related to the productive output of the plant, Table 3 lists the amount of work plated and the dollar sales volume for the same period of time. The aluminum anodizing facilities were not yet in operation.

30

Department

TABLE 3

Plant Production f o r November, 1970

Quant i ty of Work Processed

No. 100 Nickel Plated 45,600 ft2

Nickel-Chrome Nickel-Chrame Automatic Plated

No. 200 Copper-Nickel Chrome Plated 22,275 i t z

Hoist Line Nickel Plated 12,375

Other

No. 250 Hard Chrome Plat ing

No. 300 P la s t i c Plat ing

No. 400 Miscellaneous

No. 450 Zinc Barrel Aut omat i c

14,850 9,500 f f 2

Sales Volume

$ 7,919.67

22,374.76

6,144 ft' Copper-Nickel Chrome-Plated

6,231.24

4,326.76 . - -.

Cadmium Plated 496 barre l s

Nickel Plated 99

Zinc Plated 13

12 Other T T G r r e l s 7,006.79

1060 bar re l s

No. 500 Passivating & Blackening

3,684.70

6,102.22

No. 600 Zinc & Cadmium Rack 68,310 f t 2 Automatic Zinc Plated

12,611.21 Cadmium Plated

T o t a l $ 70,257.35

31

- 7

,. .~ . .. .. . .... . . . . . . ... . .. ~ .~ . . . .~ ~ ~. . . . ~

SECTION VI1

OPERATION OF BATCH WASTE TREATMENT SYSTEM

In the original design, the Batch System was intended pri- marily for handling discarded process solutions such as acid pickles, bright dips, chromate dips, cleaners, etc. A secondary function was to provide treatment for any floor spillage and contaminated steam condensate which might accu- mulate. With proper operation, floor spillage and contaminated condensate would both be very low-volume wastes, with appre- ciable quantities resulting only accidentally as when a tank or pipe line would leak or when a liose would be left running unintentionally. Nevertheless, an overhead acid collection line was provided so that discarded acidic process solutions could be delivered to the batch acid treatment tanks €ully concentrated. As mentioned earlier, the minimum chemical consumption and mini” resultant sludge volume can only be realized when wastes are treated in the concentrated €orm. Since most of the metals which produce sludge upon pre- cipitation, are found in acidic solutions, the isolated acid collection line was considered essential. Alkaline cleaners, which generate essentially no sludge upon neutralization were to be transferred to the alkali treatment tank via the floor spill system.

As plant production increased through the first year of opera- tion, it developed that far more waste was being batch treated than had been anticipated. siderable quantities of water and steam condensate were being allowed to enter the floor spill system. The water was backing up out of the rinse water sewer line inlets because the sewers were hydraulically overloaded, and the condensate was being discharged to the floor rather than returned to the boiler as originally planned. overloaded because large volumes of cooling water were being discharged into them. Since the pH adjustment sump and settling tank for the rinse waters could accept only a limited flow of water before being hydraulically overloaded, the sewer system feeding them was designed for the anticipated rinse water flow. Rather than use a conventional recirculated water system to cool the plating solutions, the Company elected to use well water on a “once-through“ basis and dis- charge it to the rinse water sewers. Since the flow of cooling water at times equaled the design rinse water flow, the sewer - system was overloaded and water backed up out of the inlets and onto the floor.

Investigation revealed that con-

The rinse water sewers were

32

In addition to these problems, the portable pump which was recommended for discharging acidic process solutions into the overhead line developed several problems and failed to oper- ate properly. Because of the pump difficulties, plant per- sonnel started discharging acid solutions by draining them to the floor spill system. This practice exposes the con- crete floor and other equipment to corrosions and also pre- sents an opportunity for the acids to be diluted with water or mixed with alkaline cleaners, both of which are deleterious to treatment results. Specifications and recommendations for the purchase of a more suitable portable pump where supplied to the company in May of 1969.

As i~ result of these problems, the waste treatment operator was required to batch treat and test an average of 8,000- 10,000 gallons per day of mixed dilute wastes as opposed to 2,500-3,500 gallons per day of known process solution, discarded under controlled conditions. If the intended pro- cedures were followed, the operator could empty the treat- ment tank prior to a scheduled dump, and then proceed to add the amount of treatment chemical which his experience indicated would be needed for the given process solution. Because of the water problem, operation of the batch system was nearly a full-time job during the daylight shift, and frequent problems arose on the night shifts because of excessive waste accumulation and flooding of the system.

Slow, steady progress has been made toward eliminating this problem by attempts at sealing the rinse water inlets and returning the steam condensate, but the cooling water is still wasted into the rinse water system, and the seals on the sewer inlets are not completely effective. In November, 1970, 159,647 gallons were batch treated while only 54,310 gallons of process solution, waste treatment solution, and filter backwashings actually required treatment. The dif- ference of 105,337 gallons consisted of water which should not have required operator attention and chemical consumption.

In an attempt to improve the situation, two holding tanks were recommended to receive the cooling waters from acidic and alkaline process solutions. These tanks will allow automatic instruments to monitor the waters for possible contamination by process solution, and they will permit the water to be pumped back into the plating shop for use as rinse water in the tanks which now receive fresh well water. The recommended location of the two tanks is shown in Figure 4.

33

To ease the scheduling of batch treatments and allow the safe accumulation of floor spillage during the night shifts, the Company has considered installation of two large holding tanks to supplement the existing collection-treatment tanks, but the load on the batch system is slowly decreasing, due to reduced spillage.

In January of 1970, the analyses on the sludge filter beds began to show excessive levels of copper and nickel and further investigation showed that ammonium ion was accumu- lating and probably complexing them. The operation of the system was then modified to include additions of calcium (lime) and sulfide (sodium polysulfide) compounds to each treated batch so as to assist in completely precipitating the metals.

Following treatment, the wastes from the batch system are pumped directly into the Sludge Filter Beds. These beds also receive sludges from-the rinse water settling tank and from the Integrated systems, but 75% of the input is from the batch treatment system. Therefore, the quality of the water in the beds is most directly related to the effectiveness of the batch treatment. Table 4 lists the analyses done-n the supernatant liquid from the beds during the first year of operation and also for the month of November, 1970.

34

Table 4 . SLUDGE FILTER BED EFFLUENT ANALYSES

All figures e x c e p t pH are in mg/l

Sample d a t e pH CM C r f cu Mi Zn Cd

May, 1969 9.63

June, 1969 9.50

Oct., 1969 9.11

Nov., 1969 9.20

Dec., 1969 9.20

Jan., 1970 9.60

Feb., 1970 9.40

Nov., 1970 7.60

0.01 0.03

0.04 none

0.02 none

none

0.02 none

0.02 1.21

none none

0.43 0.13

0.63 0.43

2.21 6.2

0.15 1.85

2.34 2.63 0.72 4.67

3.05 15.23 0.65 1.74

7.50 8.20 1.14 2.34

0.31 0.25 0.14 0.17

. .

-. . . . . ~ . . . . . ..~ . ..... . . . ~ .. .. ~ -

The cost of operating the batch treatment system has been excessive because of the problem with unnecessary water accumulation described earlier. This situation requires the operator to be in nearly constant attendance and makes the chemical consumption unnecessarily high. When treating cyanide and chromium, the cost of the chemicals required to adjust the pH of the collected batch before and after the chlorination (cyanide) or reduction (chromium) can be more of a factor than the cost of the chlogine or reductant.9 For example, one pound of cyanide (CN ) in one gallon of waste solution can be treated for approximately $0.92, while the same amount of cyanide in 800 gallons of solution costs about $1.68 to treat. The difference is due to the requirements for acid and alkali for pH correction and to the inefficiency of the chlorination reaction in dilute solution. these costs are even more excessive. Thus, the regenera- tion and control of the material entering the batch treat- ment system are extremely important. The more dilute the wastes to be treated, the more exhorbitant are the chemi- cal costs. Table -5 lists the chemical consumption and cost figures for the Batch Treatlwnt operation during November , 1970,

If cyanide and chromium are mixed in a waste,

36

Table 5 . CHEMICAL CONSUMPTION OF BATCE TREATIIENT SYSTEM - NOVEMBER, 1970

Chemical Consumed Quantity Unit Price Monthly Cost

Sulfuric Acid 337 gal. $0.534/gal. $ 179.96

Caustic Soda (50% liquid) 7 5 2 gal. 0.318/gal. 239.14

Sodium Metabisulfite 1072 lbs. 10.30/cwt. 110.42

Sodium Hydrosulfite 368 lbs. 29.75/cwt. 109.48

Calcium Hypochlorite - 240 lbs. 30.00/cwt. 72.00

Sodium Polysulfide 399 lbs. 52.00/cwt. 207.48

Hydrated Lime 645 lbs. 10.25/cwt. 66.11

Total Chemical Cost for Eatch Treatment System - $ 984.59

37

SECTION VI11

OPERATION OF RINSE WATER SYSTEM

An automatic pH controller-recorder maintains the rinse water effluent within the desired range by adding either 10% sul- furic acid solution or 20% caustic soda solution to the pH adjustment sump. Following this pH correction, the stream enters a rectangular, open-basin settling tank for separation of the precipitated solids. (See Figure 10) The sludge which accumulates in the settling tank must be removed three times per year. A portable pump is used to draw the sludge from the bottom of the tank and transfer it to one of the adjacent sludge filter beds.

Figure 10 - Rinse Water Settling Tank

3 8

At the overflow end of the settling tank, a wet well is

portion (see page 4 5 ) of the rinse water stream to the plating shop. That portion not returned overflows the pump well and is combined with the filtrate from the sludge filter beds before it is discharged to the storm sewer. It was intended to control the dissolved salt concentration in the rinse water system by using fresh well water in selected rinse tanks in the plating lines. The amount of fresh water added at these tanks would then determine the rate of over- flow from the reuse water pump well. This overflow to sewer would constitute a "blow-down" of the system which could be regulated to achieve the optimum amount of water reuse. If too little fresh water were added, inadequate rinsing would laver the quality of the finishes. It is still impossible to determine the maxi" percentage of the rinse water stream which can be reused because the cooling waters are discharged into the system causing an excessive blow- down.

However, the total amount of fresh water available to the plant is limited to 300 GPM by the pumping rate o f the well, and the evidence indicates that there will be no problem in doubling the plant's production facilities with only this amount of fresh water input.

Once per day the rinse water is checked for the major con- taminants using semi-quantitative spot test procedures, and the results are recorded on the analysis record sheet. Until recently, the effluent was also given a complete analysis by an outside laboratory once per month. the plant's laboratory which is equipped for full colori- metric analyses. The electrodes of the pH controller are removed from the control sump bi-weekly for cleaning, inspec- tion, and standardization against buffer solutions.

provided for the Reuse Water Supply Pump which returns a _-

~

This work is now done in

One of the advantages shared by the Integrated Treatment Systems and the water reuse system is that they serve as their own enforcement of good operating practice. If proper control is not maintained, and the recirculated solution or water becomes contaminated, the quality of the metal finishing suffers since the parts are being rinsed in the contaminated solution. Ordinarily, when a waste treatment system goes out of control and the effluent discharge becomes contaminated, the plant personnel have only their conscience with which to contend. Here they must also contend with sub-standard production. An example of this occurred when a night-shift operator on the aluminum anodizing line mistakenly rinsed his work pieces in

39

- 1

. . . , ....... ~ ~ . ... . . . .. . . . . . . . ~.~ ~I..-..__........ . . . ~

the De-ionized water rinse after removing them from the bright dip solution which is very high in phosphoric acid concentra- tion. The deionized water is intended to be an ultra-pure rinse, used only after a normal fresh water rinse. In the morning, when the mistake was discovered, the deionized water rinse was immediately discarded. Since this tank has its drain connected to the rinse water sewers, the entire re- use water system soon contained phosphate ion in the range of 8-10 ppm. A mysterious resistance of zinc-plated work to bright dipping and chromating the next day was traced to the fact that the fresh zinc surface becam passive while sitting for more than ten minutes in reuse water on the programmed hoist machine. The combination of unusually long residence in the rinse station and a few parts per million of phos- phate thus interfered with production on that machine, Re- duction of the phosphate level restored normal operation.

After the plant had been in operation for several months, but before the aluminum anodizing equipment was installed, Lancy Laboratories recommended that the installation of an additional Integrated system be considered. The new pro- cess, which had just been developed, was intended to slimi- nata the carry-over of large amounts of aluminum to the rinse water system. The aluminum which precipitates from dilute rinses is a very voluminous sludge which settles easily, but does not compact or dewater well. As a result, the fre- quency of settling tank and sludge filter bed clean-out would be greatly increased when the anodizing line was placed in operation, as would the costs for sludge hauling. The newly developed Integrated Aluminum Treatment System creates a sludge having less than one-tenth the volume of that pro- duced by normal neutralization and settling of the rinse waters, and its cost can be amortized by savings in sludge handling expenses. However, the system was not installed, and to eliminate sludge handling, the Company elected to discharge the rinse waters from the anodizing line to the municipal sanitary sewer system.

Table 6, which follows, gives the results of a number of analyses of the Rinse Water Effluent from the plant. is the stream which is discharged as a "blow-down" from the rinse water settling tank, and it is the same water as is being returned to the plant by the Reuse Water Pump. "grab samples" taken at midday when th@ contaminant concen- trations would be at a maximum. Since this is a reuse water system with more than 50% of the flow being recycled, the need

to average and accumulate contaminants over many hours of

This

All are

for composite sampling is obviated. The system itself serves -

4 0

operation, and since the samples are taken after several hours of peak production, the results indicate the worst possible condition of the system.

The analysis results shown in Tables 6 and 7 were obtained by use of the following procedure:

Cyanide - "ASTM Standards - Part 2 3 - Industrial Water;

Dissolved and Suspended Solids - EPA - "Methods for Atmospheric Analysis" (Oct. 1968)

Chemical Analysis of Water and Wastes" - Nov. 1969.

All Others - "Standard Methods for the Examination of Water and Wastewater" - Twelfth Edition - 1965.

where "none" is reported, the results were below the limits of detection for the procedure employed. For all parameters listed, the limit of detection can be considered to be 0.01 mg/l.

, . . .~ .. . __ . .

41

TABLE 6 t

Results or Rinse Water Brrluent Analyses All values except pfl a m in .dl.

Sample Date e!! April. 1969 7.88

May. 1969 8.26

June, 1969 8.59

July. 1969 7.55

August.1969 7.99 September.1969 7.61

October, 1969 7.41

November, 1969 7.86

December, 1969 7.91

January, 1970 7 .60

February. 1970 7.70

April, 1970 7-30

November, 1970 8.06

February, 1971 8.23

CN - cr+g - 0.06 0.10

0.08 0 .06

none none

none none

0.03 none

none none

none none

none none

0.06 none

0.12 none

none none

0.02 none

0.01 none

none 0.13

- none

- none

none

none

none

none

none

none

none

none

none

0.10

none 0.58

none 0.10

0.01 0.20

0.02 0.24

0.06 0.12

0.19 0.13

0.04 0.60

0.02 0.46

0.06 none

0.10 0.20

0.02 0.06

0.17 0.05

0.14 none

0.40 0.25

Hardness Suspended Dissolved - _ Zn Cd As CaCO3 solids Solids

none 0.15

0.13 0.25

0.12 0.07

0.55 0.111

0.79 0.22

1.57 0.32

1.31 0.23

2.02 0.28

1.10 0.21

1.36- 0.42

1.06 0.29

2.20 0.45

0.56 0.25

2.94 0.25

- - - 212

218

218

212

212

- 225

255

218

198

219

10.2 738

15.1 704

14.0 1003

10.6 564

16.0 611

18.1 701

8.6 1041

13.6 724

11.6 719

21.3 881

17.1 641

14.9 655

12.0 530

16.0 540

I

The levels of zinc and cadmium in the effluent are somewhat higher than desirable (i.e. - 1.0 mg/l Zn and 0.01 mg/l Cd) and this is due to drag-out of these metals from the acid pickle solutions in the zinc and cadmium plating lines. The pickle solutions are intended to clean and descale the surface of the work pieces prior to electroplating. How- ever, when a rack of parts with bad plating comes off the machine, it is recycled and the cadmium o r zinc on the pieces is stripped in the pickle solution. As the concen- trations of these metals increase in the pickle, the levels in the effluent follow. Additional treatment facilities may be required if this input of heavy metals to the pickles cannot be eliminated.

The actual effluent discharged by the plant to the stonn sewer is a combination of the Rinse Water Effluent and the filtrate which drains away from the Sludge Filter Beds. This Combined Effluent Discharge is sampled just before it enters the storm sewer and the results of a number of analyses are summarized ia Table 7.

~

43

Sample -P!! Date

Hay.1969 9.06

July.1969 7.92

Aug..1969 8.34

8- Sept.1969 7.37

Oct. 1969 7.49 Nov. 1969 7.65

Dec. 1969 7.40

Jan. 1970 9-10

Peb. 1970 7.80

Apr. 1970 7.30

No.?. 1970 8.82

8-

TABLE 7.

Result8 of Combined kffluent DischerRe

Analyse/

All values except pH ere In mg/l

- - cn G ~ + c ' =+3 E g 0.01 0.05 none none 0.08 0.04 0.16

none 0.18 0.08 0.02 0.18 0.15 0.15

none 0.32 - - 0.01 0.18 0.28 0.14

0.15 none none 0.08 23.5 2.0 0.92

none none none 2.21 6.2 1.02 0.23

none none none 0.03 0.50 2.25 0.28

none none none 0.03 0.05 1.55 0.21

0.02 0.07 none 0.11 0.45 0.20 0.30

none none none none 0.45 0.88 0.35

none none none 0.15 0.60 2.28 0.45

none none 0.05 0.09 none 0.03 0.07

- - - - 0.24 170 142 none

0.18 272 355 1.1

0.25 200 425 none

0.45 513 1063 3.3

0.60 880 . 283 0.15 0.75 400 177 0.82

none 163 76 none

Herd- Sua- Dissolved ness e8 pended

oil CaC03 Solids -- - - - 20.0 -

- none

none

none

none

none

none

none

- - 66.8

- - 15.2

- - 63.1

212 9.0

211 13.1

246 14.0

225 38.9

255 17.1

218 16.8

212 12.0

- 847

5940

595

1727

1028

3214

770

773

550

i

!

I

While the maximum percentage of the total water flow which can be reused has not yet been determined, the following table gives the relative amounts of fresh and reused water passed through the system over a week of recent production.

Table 8 . RELATIVE CONSUMPTION OF FRESH AND REUSED WATER

Fresh Water Reused Water Reused Water Date consumption Consumption Percentage

2 /22 /71 2 5 0 , 1 0 0 gallons 3 2 3 , 1 0 0 gallons 5 6 . 3 7 %

2 /23 /71 3 2 7 , 8 0 0

2 /24/71 3 1 8 , 6 0 0

2 /25/71 2 9 2 , 2 0 0

2 /26 /71 2 7 0 , 6 0 0

3 3 2 , 7 0 0 5 0 . 3 7

3 6 7 , 5 0 0 5 3 . 5 3

3 3 2 , 7 0 0 5 3 . 2 4

3 3 2 , 7 0 0 5 5 . 1 5

2 / 2 7 / 7 1 1 1 8 , 3 0 0 1 0 2 , 0 0 0 4 6 . 3 0

1 , 5 7 7 , 6 0 0 gal. 1 , 7 9 0 , 7 0 0 gal. 5 3 . 1 6 % ave.

If the company were required to purchase their water from the local municipal water supply system, they would be charged at the rate of $ 0 . 2 2 per 100 cu. ft. At this rate, the re- used water system would be saving them $ 5 2 6 . 6 8 per week based on the above consumption figures. Since well water is being used presently, and the pumping costs are negligible, these savings are merely theoretical. However, they are included as an example of the economics which would apply to a plating shop not able to draw so readily on a natural resource. The distribution of water through the plant is summarized in the following table. The Department numbers correspond to those used in Table 3 and Figure 1.

45

~ .. . ~ . .~ . . . . .. ... ..... ~ . .

Table 9. DISTRIBUTION OF WATER CONSUMPTION BY PRODUCTION DEPARTMENTS

All values are in gallons per minute.

Reuse Water Fresh Water Dept. No. Dept. Name Consumption Consumption

100 Nickel Chromium Automatic

200

250

300

400

450

500

600

800*

850

880*

900

Hoist Line

Bard Chromium Plating

Plastic Plating

Miscellaneous Barrel Line

Zinc Barrel - Automatic

Passivating & Blackening

Zinc & Cadmium Rack Automatic

Z h c Black & Tin Plating on Aluminum

Anodizing

Iriditing

Stripping

48.6

24.3

15.0

-- 60.0

27.9

6.0

70.0

25.0

24.0

48.0

12.0

360.8 GPM

22.1

49.8

9.1

60.8

49.1

5.1

10.9

8.0

---

34.1

6.8

--- 255.8 GPM

* Areas put into production recently and not shown in Figure 1.

46

Chemical costs f o r the ri.?se water treatment i n c l u d s o n l y t h e sulfuric ac id and. caus t i c sobs.usec! fo r pl! cont ro l . For the same month of Erovember, a s considered f o r the other sk'stems, the c!ie;nical c o s t s a r e :

Table LO. CI<E>IIC.XL CO:I'SUi?2TION OF RINSE WATEK SY,CT%':

November, 1 9 7 0

Chemical Consumed Quantity U n i t P r i ce Monthly Cost

S u l f u r i c Acid 27 gal. $ 0.534/gal. $ 14.42

Caust ic Soda ! 5 0 % l i q u i d ) 216 g a l . 0.318/gal. - 68.69

Tota l Chemical C o s t for Rinse Water Systea $ 83.11

Offse t t i ng some of t h e opera t ing c o s t s f o r the waste t r e a t - ment systems are t h e savings due t o water reuse. equiva len t purc!;ase c o s t of t h e reuse water i s consid.ercc! for t h e same month of November, it represents a savings of $2,106.72.

I f the

47

SECTION I X

SLUDGE HANDLING OPERATIOPIS

All psec ip r t a t e s formed by t h e var ious t r e a t n e n t r-acticjns are accumulated i n concrete block sludge f i l t e r ha& w h x h opera te on a unique p r inc ip l e t o dewater a n d thici.an the co l - lected sludges. Two beds are provided and they a r e used a l t e r n a t e l y wi th one being allowed t o dewater for seve ra l weeks while sludges are directed i n t o the o ther . Before the bed i n use i s f i l l e d , t h e f i r s t one is emptied by a s e p t i c waste haul ing t ruck which carries the thickened s l u r r y t o a s a n i t a r y l a n d r i l l area. be emptied approximately every 2-1/2 weeks. i n t o t h e f i l t e r s from each of t h e f i v e In tegra ted Systems, from t h e batch t reatment system, and from the r i n s e water s e t t l i n g tank.

The moun t of v a t e r held by a f loccu len t metallic p r e c i p i t a t e is d i r e c t l y deyeazent udon t h e condi t ions pze ra i l i ny when t h e p r e c i p i t a t e d Caq-OUnd is formed. While the sludges can be "conditioned" a f t e r they are formed, t h e e f f ec t iveness >f this condi t ioning depends upon t h e i n i t i a l na tu re c f t h e s l u r r y and thus, on t h e i a f luences present during formation. As discussed e a r l i e r , t h e sludges i n t h e Integrarcd Systems are formed under concentrated condi t io3s and are thus r e l a t ave ly dense and dewatered when pumped t o t h e f i l t e r hed. Idea l ly , ba tch t reatment of d i scs rded process so:utisns would l ikewise genera te good sludgcc, bu t d i f f i c u l t i e s 'with this opera t ion have prevented t h i s desirable r e s u l t . Sl idges formed i.1 the r i n s e water system are very l i g h t and ty:,ically contain gnly 0.258-0.50% dry solids, b c t they are a very neg l ig i3 l e por t ion of tke sludge produced a t t h i s p lan t .

Roughly speaking, t h e discarded prucess so lu t ions conta in 80-908 of t h e chemical waste load i n a p l a t i n g operat ion and t hus the hatch t reatment system c o n t r i b u t r s most of tfle sludge t o the f i l ter beds. The aforementioned d i f f i c u l t i e s with t h e hatch t raatment opera t ion therefore have a direct and s igniz- i c u n t effect upm bcth the perfurmance of t h e f i l t e r beds and the c o s t s f o r s l u l g s hauling.

The p r i n c i p l e of o p e r i t i o n of t h e f i l t e - bed is complex and involves a number of phenomena which CP b i n e t o inf luence t h e overall perforvancs of t h e u n i t . Howevf'r, it i s e s s e n t i a l t h a t the input sludges be menab la t o f loccu ia t ion , coagulat ion, rVre s e t t l i n g . I f compounds which i n t e r f e r e with these th ree func t ions a r e presant i n t h e s l u r r y pumped i n t o the f i l t e r , i t s opera t ion w i l l be severe ly r e s t r i c t e d .

A t t h e present t i m e t h e f i l t e r s must Sludges are pumped

Some a l k a l i n e

48

cleaning compounds contain high levels of peptizing agents which are effective in holding extremely small particles in suspension. When precipitates are formed in the presence of high concentration of these materials, the tiny particles of precipitated compound which are formed initially, cannot coagulate so as to form flocs large enough to settle. When such a waste is put into the sludge filter, the water es- caping through the concrete block wall naturally carries along the dispersion of fine particles which can deposit in the pores of the concrete and eventually stop further seepage. Wastes which are dilute prior to treatment are more susceptible to the effects of a given concentration of such a peptizing agent since the initially-formed particles are more widely separated at formation. Thus, dilution and the presence of peptizing agents are two factors which ad- versely affect the filter performance and which are syner- gistic in their effects. Oil is another material which interferes with filter performance by collecting in the pores of the concrete and displacing water thus preventing capillary attraction which is one of the primary mechanisms in the func- tioning of the unit.

Of the two filter beds in this installation, one is still functioning reasonably well, while the other is almost com- pletely ineffective. same time and of identical materials, and both performed properly when new. As described earlier, the operation of the plant and waste treatment system have been such that: (1) acids are diluted prior to treatment, (2) alkaline cleaners may be mixed with acids or metal-containing wastes prior to treatment, and ( 3 ) oil was allowed to drain to the floor inadvertently in Department 500. Thus it may be assumed that the inoperative filter bed is in its present condition as a result of one or more instances where a com- bination of factors caused the concrete block to be adversely affected. While the south filter bed performs much better than the north one, neither of them even approaches the rates which were experienced when they were new. While in use, both beds require that some clear, supernatant water be manually decanted to avoid overfilling. This may be attributed to a combination of the fact that five to ten times as much waste is put into the beds as was antici- pated during design and the fact that both beds may have been adversely affected by the methods of operation men- tioned above. Table 9 compares the performance of the two beds by indicating the amount of water discharged through the block wall in a similar period of time.

~

The units were constructed at the

'

4 9

_. . . ~ ~ . . .~

Table 11. COMPARISON OF SLUDGE FILTER BED PERFORMANCES

North Filter South Filter Bed Bed

Time Period 3/6 - 3/25/71 2/22 - 3/5/71 93,217 gal.

at Cleanout 11,480 gal. 7,000 gal.

Slurry Input to Filter 92,940 gal.

Sludge Removed from Filter

Water Decanted from Filter 53,480 gal. 5,460 gal.

Water Removed by Filter 27,980 gal. 80,757 gal.

Recommendations have been made to eliminate the conditions antagonistic to filter performance by: (1) using the overhead acid collection line to keep dilution effects to a minimum: (2) avoiding discharges of oil to the floor; and (3) discharging the neutralized alkaline cleaning solu- tions directly to the sanitary sewer system so as to avoid their being mixed with sludge-producing raw wastes. in addition to the long-standing recommendation to eliminate unnecessary discharges of water to the floor spill system.

To indicate the effectiveness of the filter beds as sludge thickening devices, the solids content of the slurries put into, and removed from, the south bed were checked for the same period as covered by the above study. A composite sample of all material pumped into the bed during the two- week period was collected and the dry solids content found to be 0.51%. At the end of this period (3/5/71), sludge discharges were switched to the north bed and the south bed was allowed to dewater for five days before being emptied by the sludge hauling truck. The slurry pumped into the truck had a dry solids content of 5.12%, indicating a ten to one reduction in the volume of material to be hauled away. Figure 11 is a photograph showing the condition of the sludge as it is pumped to the truck. The log is to pre- vent damage to the concrete block walls by freezing.

These are

50

. . 7, 5

Figure 11 - Thickened Sludge in Filter Bed

A special sludge filter panel, which works on essentially the same principles as the concrete block walls has been recom- mended to improve the performance of the north bed, but it has not yet been installed.

For the month of November, 1970, about 5,700 gallons of sludge were hauled away from the Filter Eeds at a cost of $103.00. The slurry, at the time of clean-out of the bed, contained about 5% dry solids by weight.

51

SECTION X

GENERAL ECONOMIC CONSIDERATIONS

The capital costs associated with the waste treatment system are summarized in the following table:

Table 12. SUMMARY OF CAPITAL COSTS

A. Equipment Costs

1. Waste Treatment Room $ 44,292.01 2. Treatment Wash Tanks in

Process Lines 20,637 .OO 3. Miscellaneous 6,465.68 $ 71,394.60

B. Installation Costs

1. Piping $ 60,830.56 2. Electrical 7,248.11 3. Mechanical Construction

and Erection 40,500 .OO 4. Underground Sewers 30,441.00 $ 139,019.67

C . Engineering Costs

1. Process Design $ 12,500.00 2. Detail and Mechanical !

Engineering 4,536.10 $ 17,036.10

Total Capital Cost $ 227,450.46

c

Konthly operating costs were tabulated for November, 1970, and are summarized in the following table. The savings attributed to water reuse are indicated as partially off- setting the operating costs.

52