United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA 600 7 78 090
June 1978
Assessment of
Technology for
Control of Toxic
Effluents from the
Electric Utility Industry
Interagency
Energy/Environment
R&D Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports m this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of. and development of. control technologies for energy
systems; and integrated assessments of a wide'range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161.
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EPA-600/7-78-090
June 1978
Assessment of Technology
for Control of Toxic Effluents
from the Electric Utility Industry
by
J.D. Colley, C.A. Muela, M.L. Owen,
N P. Meserole, J.B. Riggs, and J.C. Terry
Radian Corporation
8500 Shoal Creek Boulevard
Austin, Texas 78766
Contract No. 68-02-2608
Task No. 9
Program Element No. EHE624A
EPA Project Officer: Julian W. Jones
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
CONTENTS
Page
FIGURES vii
TABLES ix
SECTION 1 - INTRODUCTION 1
SECTION 2 - RESULTS AND CONCLUSIONS 5
CONCLUSIONS 8
RECOMMENDATIONS 9
SECTION 3 - IDENTIFICATION OF POLLUTANT SOURCES IN
EFFLUENT STREAMS FROM UTILITY POWER PLANTS 11
UTILITY EFFLUENT STREAMS 12
PRIORITY POLLUTANTS IN EFFLUENT STREAMS .... 14
SECTION 4 - PRELIMINARY SURVEY OF PRIORITY POLLUTANT
CONTROL TECHNOLOGIES 19
STRATEGY 20
SUMMARY OF PRELIMINARY SURVEY 21
EVALUATION OF RESULTS 26
SECTION 5 - ASSESSMENT OF SELECTED CONTROL TECHNOLOGIES 27
METHODOLOGY FOR THE TECHNICAL AND ECONOMIC
ASSESSMENT OF THE SELECTED PROCESSES 27
Technical Assessment 28
Economic Assessment 29
ACTIVATED CARBON ADSORPTION 29
iii
-------
CONTENTS (Continued)
Page
Process Description 30
Control Effectiveness 31
Costs 34
Energy Requirements 34
Secondary Process Emissions 37
LIME PRECIPITATION 37
Process Description 37
Control Effectiveness 38
Costs 41
Energy Requirements 44
Secondary Process Emieeions 44
REVERSE OSMOSIS 44
Process Description 45
Membrane Development 45
Membrane Configurations 47
Membrane Fouling 47
Membrane Life 48
Control Effectiveness 49
Costs 49
Energy Requirements 51
Secondary Process Emissions 51
DEEP BED FILTERS 51
Process Description 51
-------
CONTENTS (Continued)
Page
Control Effectiveness 54
Costs 54
Energy Requirements 54
Secondary Process Requirements 54
VAPOR COMPRESSION DISTILLATION 54
Process Description 54
Control Effectiveness 58
Costs 59
Energy Requirements 59
Secondary Process Emissions 60
EVAPORATION PONDS 60
Process Description 60
Control Effectiveness 61
Costs 61
Energy Requirements 64
Secondary Process Emissions 64
SOLID WASTE DISPOSAL 66
Process Description 66
Control Effectiveness 66
Costs 66
Energy Requirements 67
Secondary Emissions 67
v
-------
CONTENTS (Continued)
Page
BIBLIOGRAPHY 68
APPENDIX A - DISCUSSION OF THE CHARACTERISTICS OF
UTILITY POWER PLANTS EFFLUENT STREAMS 74
APPENDIX B - PRELIMINARY SURVEY OF TECHNOLOGIES FOR THE
CONTROL OF PRIORITY POLLUTANTS IN UTILITY
EFFLUENTS 101
ABSTRACT 153
-------
FIGURES
Number page
3-1 Sources of wastewater in a fossil-fueled
steam-electric plant 13
5-1 Downflow in parallel carbon adsorption/
regeneration system 32
5-2 Carbon adsorption installed capital costs .... 35
5-3 Carbon adsorption operating maintenance costs 36
5-4 Lime precipitation flow diagram 39
5-5 Theoretical solubilities of metal ions as a
function of pH 40
5-6 Lime precipitation installed capital costs ... 42
5-7 Lime precipitation operating and maintenance
costs 43
5-8 Typical reverse osmosis plant arrangement .... 46
5-9 Capital costs for reverse osmosis 52
5-10 Operating costs for reverse osmosis 53
5-11 Capital costs for conventional sand or graded
media filters 55
5-12 Operating costs for conventional sand or
graded media filters 56
5-13 VCD simplified system schematic 57
5-14 Capital costs for evaporation ponds 62
5-15 Evaporation pond operating costs 63
5-16 Dike cross-sections 65
A-l Sources of wastewater in a fossil-fueled
steam-electric plant 75
B-l Carbon adsorption capital cost relationship .. 105
vii
-------
FIGURES (Continued)
Number Page
B-2 Cost of phenol removal by activated carbon ... 107
B-3 Carbon adsorption reactivation costs 107
B-4 Flowsheet for electrodialysis 121
B-5 Primary sedimentation capital cost
relationship 127
B-6 Filtration capital cost relationship 128
B-7 Carbon adsorption capital cost relationship .. 129
B-8 Minimum pH values for complete precipitation
of metal ions as hydroxides 136
B-9 Heavy metal precipitation vs. pH for tailing-
pond effluent pH adjustments by lime addition 137
B-10 Flowsheet for reverse osmosis 144
-------
TABLES
Number page
1-1 DISCHARGE LIMITS FOR THE UTILITY INDUSTRY .... 2
1-2 LIST OF PRIORITY POLLUTANTS 3
2-1 PRIORITY POLLUTANTS POTENTIALLY CONTROLLED
BY SELECTED TECHNOLOGIES 6
2-2 COMPARISON OF CONTROL TECHNOLOGIES 7
3-1 PRIORITY POLLUTANTS POTENTIALLY PRESENT IN
UTILITY EFFLUENTS 15
3-2 SUMMARY OF CHEMICAL CHARACTERISTICS OF
UTILITY EFFLUENT STREAMS 16
4-1 PRELIMINARY SURVEY SUMMARY OF EFFLUENT
CONTROL FOR THE ELECTRIC UTILITY INDUSTRY 22
5-1 CARBON ADSORPTION TOXIC POLLUTANT REMOVAL
EFFECTIVENESS 33
5-2 LIME PRECIPITATION POLLUTANT REMOVAL
EFFECTIVENESS 41
5-3 COST OF WATER TREATMENT BY REVERSE OSMOSIS ... 50
5-4 CAPITAL AND 0/M COSTS FOR VAPOR COMPRESSION
DISTILLATION 59
A-l CHEMICAL TREATMENT SUMMARY FOR RECIRCULATING
COOLING SYSTEMS 79
A-2 RECOMMENDED LIMITS OF TOTAL SOLIDS AND
SUSPENDED SOLIDS IN BOILER WATER FOR DRUM
BOILERS 81
A-3 CHEMICAL ADDITIVES COMMONLY ASSOCIATED
WITH INTERNAL BOILER TREATMENT 82
A-4 OPERATIONAL CLEANING OF A HIGH PRESSURE,
ONCE-THROUGH BOILER 86
A-5 OPERATIONAL CLEANING OF A LOW PRESSURE, DRUM
BOILER 87
ix
-------
TABLES (Continued)
Number Page
A-6 OPERATIONAL CLEANING, MAIN CONDENSER
WATER-SIDE 88
A-7 ION EXCHANGE MATERIAL TYPES AND REGENERANT
REQUIREMENT 91
A-8 ASH POND EFFLUENT ANALYSES FROM A LARGE
COAL-FIRED PLANT 94
A-9 INORGANIC CONSTITUENTS OF OIL-ASH 95
A-10 PLANT DATA RELATING TO WATER QUALITY
PARAMETERS FOR COAL PILE RUNOFF 98
B-l CONTROL TECHNOLOGIES ELIMINATED FROM
FURTHER EVALUATION 102
B-2 CARBON ADSORPTION REMOVAL EFFICIENCIES 104
B-3 CARBON ADSORPTION CAPITAL COSTS 106
B-4 CARBON ADSORPTION PROCESS; ESTIMATE-10 MILLION
GAL-DAY PLANT 108
B-5 REMOVAL EFFICIENCIES FOR ALUM PRECIPITATION
AND ACTIVATED CARBON ADSORPTION 114
B-6 REMOVAL EFFICIENCIES FOR CHLORIDE
PRECIPITATION AND ACTIVATED CARBON 126
B-7 CONCENTRATIONS OF HEAVY METALS AFTER
HYDROXIDE PRECIPITATION 136
B-8 HEAVY METAL CONCENTRATIONS AFTER LIME
PRECIPITATION 137
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SECTION 1
INTRODUCTION
Effluent guidelines, including new source performance stan-
dards (NSPS) for the steam-electric power generating industry
were first published in 1974. Discharge limits to be met by
July of 1983 (as required in the 1972 Federal Water Pollution
Control Act) were established as those attainable by the best
available technology economically achieavble (BATEA). The NSPS
were based upon best available demonstrated technology. The
BATEA and NSPS limits, which are summarized in Table 1-1, are
currently undergoing comprehensive review by the EPA (RI-160) .
The EPA review will focus primarily on regulation of pri-
ority pollutants. More specifically, this will include the 129
"unambiguous" chemicals listed in Table 1-2 (RI-160). Based on
preliminary EPA findings, the pollutants in this list which are
most likely to be present in utility effluents are indicated by
ao. asterisk.
The EPA has initiated a three-pronged effort to develop
background information to support the establishment of effluent
standards for priority pollutants. The objectives of this effort
are (1) identification and quantification of priority pollutants
in utility discharges, (2) identification and assessment of exis-
ting control technologies applicable to the control of those
pollutants, and (3) detailed economic analyses of the costs of
applying the identified control technologies to utility industry
wastewater streams. This report presents the results of a study
which concentrated on the second of the aforementioned tasks.
More specifically, this study was intended to assist EPA's
Effluent Guidelines Division in identifying and assessing po-
tential priority pollutant control technologies. The specific
objectives of the study included:
Identification of available technologies
used by utilities or related industries
to control priority pollutants,
-------
TABLE 1-1. DISCHARGE LIMITS FOR THE UTILITY INDUSTRY
1 i 2
- - -
Slreum Hoi lutaiit
All Ntruuma
|>H (cxcc-pi once- through
cooling
PCHx
Luw-voluMi waste strounui
TSS
Oil and greaae
Bottom-uuti transport uutur
TSS
Oil and greusu
fly aeli transport water
TSS
Metal-cleaning wustus
TSS
Oil and greuae
Copper (total)
Iron (total)
Bollur hlowdown
TSS
' Oil and greaae
1 Copper (total)
Iron (total)
Once-through cooling water
Free available chlorine7
Cooling tower blowdown
free available chlorine'
Zinc'
Chromium*
Phosphorus*
Max1
N o
100
20
100
20
100
20
100
20
1
1
100
20
1
1
0.5
0.5
BPCTCA 11 ml I.
H/l ,
' Av«?
6.0-9.0
Discharge
1C
15
10
IS
10
15
10
15
1
1
10
15
1
1
0.2
0.2
Hoxi
N o
100
20
I004
20*
100
20
100
20
1
1
100
21)
1
1
0.5
0.5
1
0.2
5
BATEA limit.
H/l
Avg*
6.0-9.0
1) 1 a c li a r x e
11)
IS
10*
IS*
10
15
10
15
1
I
10
IS
1
1
0.2
0.2
1
0.2
5
Limit fur new
Silurian. ny/1
Max ' AVH
6.0-9.1)
No 1. 1 a c h
1UU
20
I00k
20'
N u I) 1 a L 1
100
20
1
1
100
20
1
1
0.5
0.5
I*
a r g c-
10
15
)0k
15'
o r g v
10
15
1
1
10
15
1
1
0.2
0.2
Other corrosion Inhibitors
Material-storage runoff*
TSS
pll
Llaiits determined
SO
6.0-9.0
-case
i a 1 a
SO
6.0-9.0
SO
6.0-9.0
Kacept vhero specified otherwise, allowable dlachargu equal* flow multiplied by concentration limitation. Uheru wustu atreama from varluua aourcea
are combined for treatment or discharge, uuantltiea of each pollutant attributable to each waate aonrce ahull not exceed the apeclfled limitation for
that eource.
1 All sources muet meet State Water Quality Standards by 1977 (Section '101 (b)(l)(c)).
1 Maximum for any om> day.
* Averag* of dally values for 10 consecutive daye.
5 Allowable discharge equal* flow multiplied by concent rutlou divided by 12.5.
' Allowable discharge .-uuuls flow multiplied by concentration divided by 20.0.
Limits given are maximum and average concentrations. Neither frue available chlorine nor total realdual chlorine may bu discharged from any unit for
more than 2 hr in one day; not more than one unit of any plant muy discharge frue available or total realdual Chlorine ;it the samu time, unless the
utility can demonstrate that the units in u particular location cannot operate at or below this level of chlmtnntlun.
Only runoff flow from material-storage pllua aaaoclutcd with the reference 10-yr, 24-hr rainfall Is exempt fiom thuxu limitations.
' Not applicable f»i BFLTCA, no detectable diachurge frn» new aourcoa.
Source: KI-160
-------
TABLE 1-2. LIST OF PRIORITY POLLUTANTS
u>
Acenaphthene
* Acrolela
Aciylonltrlle
* Benzene
Benzldlne
* Carbon eetrachlorlde (cecrachloro-
oathano)
* Chlorobenzene
* 1,2,4-Trlcblorobenzene
* Hexachlorobenzene
* 1,2-Dlcnloroethane
* 1,1,1-Trichloroethane
* Hexachloroethone
" 1,1-Dlchloroethane
* 1.1.2-Trlchloroechane
1,1,2-Tecrachloroethane
Chloroethane
* Bls(chloroaethyl) acher
* Bi3(2-chloroechyl) echer
* 2-Chloroethyl vinyl acher (mixed)
2-Chlorohaphthaleoe
* 2.4,6-Trlchloropheaol
4-rhloro-o-cresol
* Chloroform (crlchlorooechane)
* 2-Chlorophaaol
* 1,2-Dlchlorobenzene
* 1,3-Dlchlorobenzene
* 1,4-Oichlorobenzena
3, 3-Dlchlorobenzldine
1,1-Dlchloroethylene
1,1-Trana-dichloroechylene
* 2,4-Dichlorophenol
1,2-Dlcbloropropana
1,3-Dichloropropylane (1,3-Dlchlor-
opropene
2,4-DlBethylphenol
2,4-Dlnltrotoluene
2,6-Dlnltrotoluene
1,2-Dlphenylhydrazlne
Echylbenzene
Pluoranthene
i-Chlorophenylphenyl echer
-Bronophenylphenyl echer
31s-(2-chlorolsopropyl) echer
31si2-:hloroetnoxyj methane
''eth1;lene chloride idichlorA-
acchane)
Mechyl chloride (chloronethnnej
Mechyl bronlde (bronoBCChane)
Bromoform (trlbromoMChane)
Dich lo rob rononethane
Trlchlorofluorooechane
Dlchlorodlfluoronechane
Chlorodlbroooaechaae
Hezachlorobucadlene
UaxachlorocyclopenCadlene
laophorana
* Haphchalena
Hltrobmzcna
2-Nltropheaol
4-Nlcrophenol
2,4-Dlolc rophenol
4,6-Dlnlcro-o-creaol
* N-olcroaodlnachylaalne
* N-nltroaodlphenylaalne
* N-nltroaodl-n-propylaolne
Pancacblorophenol
* Phenol
Blg(2-«thylhexyl) phchalace
Bucylbenzyl phchalace
Dl-n-bucyl phchalate
Dlechyl phchalaca
Dimethyl phchalace
1,2-Benzanthracene
3,4-Benzopyrene
3,4-BenzofluoranChene
11,12-Benzofluoranchene
Chryaaoe
Acenaphchylene
* Anthracene
1,12-Benzoperylene
Fluorene
* Phenanthrene
1,2,5,6-Dlbenznachracene
lndeno(l,2,3-c,d) pyrene
Pyrene
2,3,7,6-TecrachlorodIbenio-p-
dloxln (TCDD)
Tecrachloroechylene
* Toluene
Trichloroechylene
Vinyl chloride (chloroethylene
Aldrln
Dleldrln
Chlordane (technical mixture
and mecalbollces)
-.,4'-DDE (?,p"-DDX)
4,*'-ODD (p,p'- TOE)
a-Endosulfan
S-Endoaulfan
Eodoaulfao sulfaee
Endrln
Eadrln aldehyde
Endrln kecoae
Hepcachlor
Hepcachlor epoxlde
3-Hexachlorocyclohexane
B-Hesachlorocyclohexane
'-Hexachlorocyclohexane
{-Hexachlorocyclohexane
* Polychlorlnaced alphenyl
1016)
* Polychlorlnaced blphenyl
1221)
* Polychlorlnaced blphenyl
1232)
* Polychlorlnaced blphenyl
1242)
* Polychlorlnaced blphenyl
1248)
* Pol/chlorinated blphenyl
1254)
* Polychlorlnated blphenvl
1260)
Toxaphene
* Antloony (total)
* Arsenic (total)
* Aabeatoa (flbro)
* Beryllium (cocal)
* Cadmium (total)
* Chromium (total)
* Copper (cocal)
* Cyanide (total)
* Lead (total)
Mercury (total)
* Nickel (total)
* Selenium
* Silver (cocal)
* Thallium (cocal)
* Zinc (cocal)
(lindane)
(Arochlor
(Arochlor
(Arochlor
(Arochlor
(Arochljr
(Arochlor
(Arochlor
* Subscancei aoac likely Co be present In utilltv effluence baaed on preliminary data and literature survey.
SOUHCE: Rl-UO, prelimlnarv EPA daca.
-------
Preliminary assessment of the identified
technologies to select those which appear
to be the most applicable to the utility
industry, and
Detailed assessment of the potential
effectiveness and economics of each
selected process in a utility application.
Throughout the performance of the task, primary emphasis was
placed on the identification and assessment of control technolo-
gies which are currently used or available commercially. Tech-
nologies in the research and development stage received secondary
emphasis, particularly in cases where detailed or reliable infor-
mation on performance and cost was not available.
The results of the effort to identify and quantify the pri-
ority pollutants (Objective 1 - as described above) were not
available for this assessment of control technology effective-
ness. As a result since discharge limits for priority pollutants
have not been identified, it was not possible to address the
feasibility of meeting specific effluent limits by applying the
treatment technologies considered to specific levels of pollu-
tants. With these limitations in mind, the question of what
pollutants to address was based on the preliminary EPA list
shown in Table 1-2. Applicable control processes and potential
control levels for these pollutants were quantified to the max-
imum extent possible.
-4-
-------
SECTION 2
RESULTS AND CONCLUSIONS
A brief summary of the results of the study is presented
in this section. Section 5, Assessment of Selected Control
Technologies contains a more indepth discussion of the results.
Wastewater control technologies potentially applicable to
the utility industry were surveyed and the most promising con-
trol processes were selected for more intensive review. These
processes are listed in Table 2-1 along with a qualitative
assessment of priority pollutant removal potential of each.
This table addresses only the question of removal potential
because the specific performance achieved in a given application
will depend upon the concentrations of the effected species
as well as the physical characteristics of the treatment sys-
tem and the stream(s) treated.
Detailed evaluations of the treatment processes listed "in
Table 2-1 were made as part of this study. These evaluations
involved comparing the processes with respect to their:
estimated priority pollutant control
capabilities
energy requirements
secondary pollutant emission problems
capital and operating costs
The results of this comparative analysis are summarized
in Table 2-2.
The priority pollutant removal estimates which are shown
in Table 2-2 were based for the most part on performance data
derived from industries other than the utility industry. The
cost data reported are based upon designs for 200,000 gal/day
treatment systems.
-5-
-------
TABLE 2-1. PRIORITY POLLUTANTS POTENTIALLY CONTROLLED BY SELECTED TECHNOLOGIES
HROCESS
ACTIVATED CARBON
.IME PRECIPITATION
(EVERSE OSMOSIS
IAPOR COMPRESSION
>ISTILLATION
VAPORATION PONDS
Highly slte-apacific
CLASSES OF PRIORITY POLLUTAHTS CONTROLLED
Acrolein
J
J
J
V
(0
ft
8
4
>>
«j
5
/
/
/
/
I
§
Arsenic & C
*
/
/
J
J
Benzene
/
*
J
/
u
Q
C
0
Beryllium &
*
/
/
/
pounds
g
Cadmium & C
/
*
J
J
u
hlorid
0
<
ti
«
H
§
I
/
/
/
/
u
enzene
CO
orinated
6
/
/
/
/
thanes
M
Lorinaced
&
J
/
J
/
Chers
Id
oroalkyl
6
/
/
/
/
«
t-i
0
A.
Lorinated
6
/
/
/
/
orofonn
6
/
/
j
/
IA
|
3
Chromium &
*
t*
J
J
/
w
1
4
S
O.
1
/
/
/
/
Cyanides
*
/
/
/
f-4
O
i
0.
0
2.A-Dichlor
/
^
/
/
a
"S
«
"8
3
/
/
/
/
w
1
Mercury & C
/
/
/
/
Napchalene
J
/
/
/
M
1
|
s
-0
tH
3
T<
/
/
/
/
a
Nicrosamine
/
/
/
(-4
O
s
^
a
Fencachloro
/
/
/
/
<0
X
s
J2
5-
(O
0
Cl
u
«
Polychlorin
/
/
/
/
u
-r4
«J
I
h u
^g
Folynuclear
Hydrocarb
/
/
/
«
1
fr
o
u
Selenium &
*
/
/
*"
1
o
B-
3
«
M
S!
f-H
H
VI
/
/
/
/
IA
T»
§
5
Thallium &
/
/
/
/
Toluene
/
^
/
m
0
1
*o
u
B
H
M
*
f
/
/
-------
TABLE 2-2. COMPARISON OF CONTROL TECHNOLOGIES
Control Technology
Activated Carbon
Lime Prui Ipltat Ion
Reverse Osmosia
Vapor Compression
Ulbi 11 lailon
1 Evaporation Ponds
J
1
Graded Media
Filter
Solid Uaste
Dlspoaol by
Landfill
.Projected
Effectiveness
Good removal (BO-99Z) of
arunidtlcs; poor reroval
efficiency for heavy metals
Good fur removal of heavy metals
Residual concentrations for
moat metals are lens than
.1 ppm
90-987. rejection uf dissolved
solids; 95Z removal uf
organic*; /5Z wdiei
recovery
99. 9Z salt rejection;
90Z water recovery
Seepage It* the only liquid
discharge from evaporation
ponds and Is dependent upon
thu type of pond and liner.
Removes suspended solids In
the particle alze range of
.1 to 50 u.
Seepage In the only liquid
discharge 1 ron sludge ponda
and la dependent upon the
Estimated
Knerxv Beaulremeata Sour
(kW-hr/1000 gal) Air
. 35 From regenera-
tion step
8
8-10
BO- 100 Vent from
aerator
. J- . 5 Evaporation of
organlca In the
feed water
.3
<2* Evaporation of
organlca In
sludge
tea of Secondary
Water
Quench water
Liquid occluded
with solid
sludge
Concentrated
brine and mem-
brane backwash
Concentrated
brine slurry
Suuptige
Miter buckwauh
SuupUKc
Emlaslonu
Solid
Spent carbon if
no regeneration
la used
Sludge produced
from precipitation
Solids in concen-
trated slurry
PreclpltJl ton
products produced
in pond
Sol Ida In I liter
backwash
Estimated CoutsQ
Capital Operating
($10') S/1000 gal
. 25 . 10
.9 1.0
.3 .75
^.0 1.9
1.6A l.6A
.07 .12
-V ---V
type uf liner used and whether
the sludge Is fixed or not
Site specific
abased upon 216,000 gal/day system capacity
Abased upon JO inchea/yeur effective net evaporation rale, and $100u/ncre land co
VCobtB are not applicable on a flow rale baula
-------
Two technologies, reverse osmosis and filtration, are in-
cluded in Table 2-2 even though they appear to be applicable
primarily as pretreatment steps. Any of the other technologies
may use one or both of these processes for pretreatment prior
to the main treatment process. Filtration may be required to
remove solids and prevent plugging problems in such processes
as activated carbon. Reverse osmosis may be used to reduce
the quantity of effluent streams and thus reduce treatment
costs for expensive processes such as vapor compression distil-
lation.
The energy requirements for the selected control technolo-
gies presented in Table 2-2 vary greatly between the controls.
For example, brine concentration is very energy intensive, and,
therefore, is most cost-effective when treating streams that
have been concentrated and/or pretreated.
The data gathered for many of the control technologies were
not of sufficient quality to accurately assess cost versus
wastewater flow rate or to determine the effectiveness of the
control method for the various priority pollutants. For these
controls, available data were presented and used for rough
comparisons. However, additional information should be obtained
on those processes that continue to appear applicable to utility
effluents in subsequent studies to better define their perfor-
mance characteristics.
The results of the study indicate that there are several
control alternatives that can potentially control the priority
pollutants present in utility effluents. However, a more com-
plete definition of the pollutants in utility streams will be
required to determine the most appropriate controls. Also,
since the operational characteristics and water management
strategies are different from plant to plant, different priority
pollutant control strategies will be required depending on
the situation.
CONCLUSIONS
This preliminary assessment of technology for the control
of priority pollutants in electric utility industry wastewaters
resulted in the following conclusions:
1) Wastewater control technologies have been
identified that have a high potential for
controlling the priority pollutants present
in electric utility industry wastewaters.
-8-
-------
2) Some of the control technologies reviewed
in this report have been used for wastewater
treatment in the. electric utility industry.
These include vapor compression distillation
and evaporation ponds. Such technologies
should be useful in removing certain priority
pollutants from wastewaters. However, their
effectiveness has not been confirmed in re-
moving certain materials at present and sec-
ondary emissions associated with ultimate
disposal could reduce their overall effec-
tivene s s.
3) The applicability of carbon adsorption has
not been demonstrated in the utility industry.
Chemical precipitation and reverse osmosis
have been used in some applications but not
for the control of a large number of the
priority pollutants. These technologies have
a high potential for effectiveness in removing
priority pollutants.
4) A major problem in projecting control tech-
nology effectiveness data for the utility
industry is the low priority pollutant
concentrations expected. Once these tech-
nologies are evaluated in applications involv-
ing these low concentrations, it will be
possible to make more definitive judgements
about them.
RECOMMENDATIONS
This assessment of technology for the control of effluents
from the electric utility industry resulted in the following
recommendations:
1) The control technologies evaluated as having
the highest potential for removal of priority
pollutants should be further defined in the
following areas:
control effectiveness and cost data for the
processes should be gathered in an operating
utility plant test program
secondary emissions and techniques for their
control should be further defined.
-9-
-------
2) Additional analytical work should be performed
to identify specific compounds and complexes
in utility streams to further assess both
their toxicity and potential strategies for
their control. This is especially applicable
to heavy metals.
3) From subsequent studies, typical utility control
situations should be determined and more reliable
assessments of control alternative cost and effec-
tiveness should be performed.
4) Since water treatment costs are a function of
flow rate, it is anticipated that recycle/reuse
strategies will be employed in utilities to
reduce effluent rates. The impact of recycle/
reuse alternatives on utility treatment options
should be assessed.
-10-
-------
1ECTION 3
O '0? POLLITAKT SOURCES IN
'n1 STREAM? -/R0_" UTILITY POUER PLANTS
As 'discussed in'the in troche tier. , : Iv preliirir.a, -:atji
were available on the concentrations of prievicy Dolluttants ^n
utility effluent streams. ' To property assess the feasibility
of applying -rastewater treatment tec;vno^oeies to those streams,
more specific information was needed to identify not only the
existence of priority pollutants in the effluents but al?b :he
mechanisms by which these materials snter the variou? utility
water systems .
The sources of priority pollutants present in utility
wastewater were identified as a result of the following three
step procedure:
identification of wastewater streams
in utility power plants ,
identification of chemical additives
or other sources of chemicals that
impact priority pollutants concentra-
tions in the wastewater streams iden-
tified in the first step, and
identification of significant
priority pollutants which are added
to the system.
Information was collected by the above procedure to charac-
terize the utility plant streams as follows:
identify general stream characteristics,
such as pH and physical relationship
to plant, and
identify sources of chemicals and concen-
trations in the streams, especially for
priority pollutants.
-11-
-------
This type of information is necessary to provide a preliminary
basis for the evaluation of the suitability of the control tech-
nologies for utility streams. The performance of the various
control technologies may be very dependent upon the characteris-
tics of the stream to which it is applied, such as pH, flow rate,
priority pollutants concentration, etc.
Water system arrangement alternatives or water management
within a power plant is also dependent upon the characteristics
of utility streams. Water management involves the use of water
recycle/reuse strategies and can result in the reduction of plant
effluent rates. While this report examines end-of-pipe treatment,
water management schemes based on utility water stream character-
istics can have a very significant impact on the quantity and
quality of plant effluents, perhaps strongly affecting applica-
bility and economics of the treatment process.
UTILITY EFFLUENT STREAMS
The steam-electric power industry uses large quantities
of water, primarily for cooling purposes. There are, however,
several other water utilizing processes which produce wastewater
streams. The quality of wastewater from these processes varies
considerably depending on intake water quality and/or the chemi-
cal character of the fuel used. Generalized descriptions of the
water utilizing processes and the wastewater streams associated
with them are contained in this section.
Figure 3-1 graphically summarizes the sources of wastewater
in a fossil fuel generating station and depicts the interrelation
of the various processes producing these waters. The sources of
wastewater are:
cooling water systems,
boiler operations,
ash handling,
coal storage and handling,
water treatment,
general plant drainage,
process spills and leaks, and
miscellaneous operations.
-12-
-------
a
EOEMO-
-LIQUID FLOW
HAS * STEAM FLOW
r CHEMICALS
-OPTIONAL FLOW
> WASTE WATER SOURCES
CHEMICALS
CHEMICALS
EMICA
WATER fOR
PERIODIC CLEANIHO
,,1,-msPlltllt
1
1
BOILER TUBE
CLEANING. FIRESIDE
I AIR PREIIEATER
WASHWO.S
Hl.HUiJ JINli L'^VIi;!;
TjM WA&1E 10
hSl! li*HJllllG
svsrew
RAW WATER
Figure 3-1. Sources of wastewater in a fobsil-fueled st«.am-electric
-------
The various water systems and wastewater sources were sur-
veyed to characterize the water streams and identify their rela-
tionship with plant operations. The findings are summarized and
presented in Appendix A.
PRIORITY POLLUTANTS IN EFFLUENT STREAMS
Priority pollutants potentially present in utility waste-
water streams were identified in a previous EPA study (see Table
1-2). The 51 priority pollutants listed in that table were re-
duced to 31 by creating several general categories (i.e., chlor-
inated benzenes, chlorinated alkalenes, chlorinated phenols, etc.).
The potential sources of these compounds or classes of compounds
are identified in Table 3-1.
Radian's survey of the effluent streams and chemical compo-
sitions of these streams was used to generate the data in Table
3-2. Detailed information on the streams identified is presented
in Appendix A.
Table 3-2 summarizes the chemicals added to streams or the
compounds entering the various streams from such sources as ash
dissolution or boiler tube cleaning, This links the priority
pollutants potentially present in the various utility effluent
streams to the treatment chemicals added to those streams. The
chemicals listed as additives in the table are those common to
water treatment for the indicated use.
-14-
-------
TABLE 3-1.
PRIORITY POLLUTANTS POTENTIALLY
PRESENT IN UTILITY EFFLUENTS
Sources 3 , = ]
-^ ! i ; \> , j
2, 3 1 = ' t
r3 «j M ^ . ;>
" ' 2 , a = ^ : = ' i
-3 ^ . a i -r -j
3 > -H 31 _ I j c
- p - 01 -i
33 : a; £ j
-* « ^ T . C I C . 3
Toxic Species Potentially s ' 3 - J "= i - -
Present in Utility Effluents i - r 7 "s ' ~ ' - ' i
" J " 1 ~ ! < | -
Acrolein ! j \ x '
Antimony and compounds ', ', . x
Arsenic and compounds i x x
Asbestos i ,
Benzene x ', ,
Beryllium and compounds ! . , !x !x
t i it
Cadmium and compounds ! ^ I x ' x
Carbon tetrachloride i x ' 1
. . .1
Chlorinated benzenes , x !
! ' ' ' j
Chlorinated ethanes ' ! * 1 '
i i It
Chloroalkyl ethers ! i x > !
I . ,
Chlorinated phenols . x ' i i
Chlorofora ' ' '
' i ' '
Chromium and compounds x , x i x
Copper and compounds . x | jx !x
1 ' ' i
Cyanides x ! i x ! ! i x
1 ' !
-,4-Dichlorophenol x | jx i 1
Lead and compounds , i ! ! x 1
Mercury and compounds ! y x j
Naphthalene ! '.
' i
Nickel and compounds ' I x i x
it ' i
Nitrosamines ! 1 , x 1 >
i ' i i ' i
Pentachlorophenol , ! x 1 x '
!
\
1 ! ! ! 1 '
Polychlorinrted biphenyls i , :
Polynuclear aromatic hydrocarbons i . , !
i i . i
Selenium and compounds ' i j x |
Silver and compounds i ! 1 x I
i i j I
Thallium and compounds ! I 1 x .
.,, , , , i
Toluene , j | x
Zinc and compounds i ! x ! ' x ! x
Source: Prelininarv EPA data
i i
~ i
'u ,~ 1 .
- i '
^- ^ '
s i r ^ 1 1-
'r = ^
3 ' i - - *
^ H = ^ j t =
a "3 ^ r ^" '-
^t '. -
re-
' 5 ^ -I " i
1 - '
i
1
i
1 t '
X -X ' I i
1
; t ; ;x
i , i
! ' '
I ,
i 1
I ' x
' ! '
tiii'
.
i 'i
i > i
!x , ;
, X
! ' '
j
i i ! '
1(1;
t ' 1
1 i i
1 j ,
i X
t ;
i i x -
i i i i
1 r | -
1 1 i \
\ j : |
: ; i
1 ! 1
' X i
i
' \
, . 1
'' , |
i 1 II
: i ; : '
1 i
! '
i
i ^
t '
-15-
-------
TABLE 3-2. SUMMARY OF CHEMICAL CHARACTERISTICS OF UTILITY EFFLUENT STREAMS
Kffluunt Strain*
Cooling Towur Slowdown
Process or
Operation
m Corrosion Inhibi-
tion
Stule Control
Biological
Fouling (Algae,
SI lacs, Fungi)
Control
Suspended Solids
Dispersion
Leaching of wood
preservatives
froa wood cool-
Ing towers
Chealuol
AddHtvn(s)
Chr ornate
Zinc
Phos|ihutu
Sll Icutes
Proprietary
Urgnnlca
Acid (HiSOt)
Inorganic
Polyphosphates
Chela ting Agents
Polyelectrolyte
Antlpreclpitantt
Orgunlc/Polyaer
Dlspersanta
Chlorine
llypochlurltu
Chliirophendtes
Tlilocyanatua
Organic Sulfur
CoupnunJtt
Tannins
Llgnlus
Proprietary
Organlca/Polyaera
PolyalectrolytOM/
Nonlonlc Polyaers
Acid Copper
Chroaate
Ch routed Copper
Arsonate
Creosote
Pentauliloro-
phenol
Typical CLIIC. of
Additive or
Pol Illluilt
1U-5U ag/t as Crl)H
8- IS Bg/t UM Z.I
15-60 Bg/l an PO,
-
J-10 Bg/l as
organic
2-5 ag/t
1-2 Bg/l
20-50 ag/t
<0.5 ag/t realdual
Cl,
v.30 ag/t residual
concentration!
20-50 Bg/t
1-2 ag/t
Unknown
Unknown
Unknown
Unknown
Kesultlng Priority bxuuciud (.one. nl
Pulliitunl Kxpucted Pnlluiuntu In
In Kf fluent Ktrluc-ul
Clirunlua 10-50 ag/l
Zinc 8-J5 ag/l
Potuntlal priority
organ Irs
Potential priority
organlcs
Chlorinated Phenols
Cyanide
>
Potential priority
urganlcs
Cliroalua
Araenlc
Pentachlorophenol
CoBBfntH
Urganlcs can rcui t with
rculilujil t'lilttrlnc in
faun chli>r Indt uil fitm-
poundu
Orgunlca can react with
rufildual fhlnrlnt.* to
fura chlorinated com-
pounds
Supplies freu clilurlnu
for ruurtiun with
oruiinlfs to lorn
clilur inated organlcs
Urganlcs can react with
residual chlorine to
Corn chlorinated com-
pounds
(Continued)
-------
TABLE 3-2. (Continued)
Process or Chemical
Kf fluent Stream Operation Addltlves(s)
Boiler Hater Systems Scale Control Ul & Trl Sodium
Phosphates
Echylene
dlanilnetetracutlt:
acid (EDTA)
Nltrolutrlacetlc
acid (NTA)
Algl nates
Polyacrylates
Po 1 yme thac ry la tcs
Corrosion Sodium SulClce
Control Uydrazlne
Morphuline
pH Control Sodium Hydroxide
Sodium Carbonate
Ammonia
Morpholine
llydrazlne
Typical Cunc. of Resulting Priority Kxpectutl Cone, of
Additive or Pollutant Expected Pol Imams in
Pollutant in Effluent Effluent Comments
3-60 mg/t of PO.,
20-100 mg/l
10-60 mg/£
50-100 mg/l
50-100 mg/t
50-100 rag/8.
<200 mg/l
5-45 ug/t
5-45 mg/4
\
variable added
to adjust pH
to 8-11.0
Solids
Deposition
Ion Exchange
Hater Treatment
Starch
Alglnates
Polyacrylamldes
Polyacrylatea
Tannins
Llgnln Derivatives
Polyuuthocrylates
Kegancrant Solutions
addud to reactivate
bud
20-50 ng/K
20-50 mg/£
20-50 ng/t
20-50 ffig/H
<200 ng/l
<200 mg/i
20-50 mg/t
Priority pollutants
present In source
valur
Significantly higher
conceit I rut Ions than
source* water
Chemical Cleaning
boiler waterside
cleaning and
condenser water-
side divining
bull or fireside
Acid Solvents and
Toxic Solvents
Water or allgluly
alkaline wash
NajCOi
NuOll
Phosphates
Nickel
Zinc
Aluminum
Copper
iron
ntrkcl
chromium
vunudliun
zinc
Heavy metals arc
dissolved Into Liu-
clean 111); solut Um
tiuiu equipment sur-
faces
Much ul tile pi lor il y
pullul.mts COIIIL* I i inn
J lUSullll Lull 111 0<-'|K>H-
L t a on bo 11 u r L nbc
bur t .11 c-ij. Tin.1 dupuH-
lib »i Itjlnalu In tliu
coal ui oil bullied.
(Cent iuucd)
-------
TABLE 3-2. (Continued)
I'rucesil or
Opuratlon
AddUlvttiidi)
Typlcul Com1, ut
Additive or
Pollutant
Huaultlitg Priority
Pollutant Expected
In Effluent
KxpuctuJ Coin.. of
Pol lul mil i, )
Attli Hand I I nj;
Auli Sluli-liiK
Co.i 1 Aah
(fly J>h an
buttoK
None
Pollutnnl In In addition to
sluice water Source Water:
before sluicing Cudnlua
Cuppur
Lead
MugenaluB
Nickel
Trace Becals In the
coul ur ull ate
leachod Inio ilu-
sluicing liquor
Miscellaneous
Operations
Oil A»h Sluicing
Vanadliui
Nickel
Chroalua
Runoff
oo
i
Rainfall/runoff
Iron
CsdBlun
Bury11 tun
Nickel
CliroBlun
Vanudliw
Zinc
Copper
Dissolution of tm
etuis Into wutur
Cunurnl Plant
Drainage
Rulnfall/runoff
Any uf the above
pollutants depending
on suilntunance pro-
cedures at plant
Process Spills and
Leaks
Accidents Involving
general plant oper-
ations
Any of the above
pollutants depending
on where the waste-
water originates
-------
SECTION 4
PRELIMINARY SURVEY OF PRIORITY
POLLUTANT CONTROL TECHNOLOGIES
A preliminary survey was conducted to identify technologies
currently in use which have exhibited some control of priority
pollutants in effluents from the electric utility industry.
In addition to the utility industry, other industries were
examined for control technologies potentially applicable. The
non-utility industries surveyed were:
Petroleum Refining,
Chemical Producing,
Metal Plating,
Metal Finishing,
Mining and Ore Dressing, and
Metal Smelting.
As discussed in Section 3, effluent producing processes at
power plants for which control technologies were examined include:
Cooling Water Systems,
Boiler Operations,
Ash Handling,
Coal Pile Runoff,
General Plant Drainage,
Process Spills and Leaks, and
Miscellaneous Sources.
-19-
-------
End-of-pipe treatment technologies were identified which
have exhibited some control effectiveness for the priority
pollutants identified in utility streams. Information on the
performance of the controls was obtained for the most part from
applications to waste streams from non-utility industries.
Therefore, the performance is not always related to the priority
pollutant concentration or other stream characteristics that
would normally be encountered in utility streams.
A preliminary assessment was then made for each control
technology identified to evaluate its potential for use by
utilities. Those judged most generally applicable were then
subjected to a more detailed assessment.
STRATEGY
This survey was conducted using a number of readily
available information sources. The major ones included:
EPA Effluent Guideline Documents,
EPA Water Pollution Control Research Series,
Technical Journals and Publications, and
Radian In-House Files.
In addition, vendors of control processes and equipment, and
in some cases, industrial users were contacted to obtain current
information on performance, applications, and costs. A process
description summary sheet containing the following information
was then prepared for each technology.
Process Name,
State of Development,
Applications to Date,
Process Description,
Expected Performance,
Costs,
Secondary Process Emissions, and
References.
-20-
-------
The individual summary sheets for the technologies identified
in the preliminary survey are presented in Appendix B.
The findings of the preliminary survey were screened to
select technologies for the control of priority effluents which
justified further in-depth evaluation. This screening process
was based on the following criteria:
Priority Pollutants Controlled,
Effectiveness of Control,
Applicability to Utility Streams,
Process Reliability, and
Commercial Availability.
A control technology was eliminated from further considera-
tion when it clearly failed to meet one or more of the above
criteria. The criteria that the eliminated control technologies
failed to meet are presented in Appendix B.
The various control alternatives identified in the prelimi-
nary survey are summarized in Table 4-1. This summary table
provides a basis for comparing the various control technologies
so that the more applicable controls can be selected for further
study.
SUMMARY OF PRELIMINARY SURVEY
The control technologies identified in the preliminary
survey of the utility and non-utility industries are listed
below.
Activated Carbon Adsorption
Activated Sludge
Aerated Lagoons
Air Oxidation
Alum Precipitation and Activated
Carbon Adsorption
Barium Salt Precipitation
Chemical Oxidation
Chemical Reduction
Complex Formation and Activated
Carbon Adsorption
Coprecipitation
Deep Well Disposal
Electrodialysis
Foam Fractionation
High Density Sludge
Neutralization
Ion Exchange
Lime Neutralization and
Precipitation
Liquid Waste Incineration
Photochemical Oxidation
Reverse Osmosis
Skimming and Flotation
Solvent Extraction
Sulfide Precipitation
Ultrafiltration
-21-
-------
TABLE 4-1
PRELIMINARY SURVEY SUMMARY OF EFFLUENT CONTROL
FOR THE ELECTRIC UTILITY INDUSTRY
iU>ii 1 1 o I Compounds
i'tn-liiiulogy Controlled
A, ilvaled Carbon Organic*, sus-
Admiipi Ion pended nolldy,
dmtunld
K( fuctlvouuuH
91-981 fur BUD
60- 90Z for suspended
solids
90-99Z for phenols
31-87X for Hid
70-95X for oil
Industry and
Streams Applied to
Petroleum Refining
Streams Applicable
In Electric Utility
Coal Pile Kunufl
Yard Drainage
Cuullng Tower Bloudown
Lab Drains
Ash Pond Effluent
Sludge
Ai!rated t.agoons
rO
N>
I
Air Oxidation
Algsclde Substitu-
tion
Organlca, sus-
pended solids,
ossnnla, sulfldus
Orgaiiius, sus-
pended solids,
suitIdes
Phenol
80-991 for BOD
60-851 for suspended
solids
9S-99Z for phenols
33-99Z for Nil,
97-100$ for aulfldes
75-95* for BOD
40-651 for suspended
solids
90-991 for phenols
95-1001 fur sulfldes
70-90Z for oils
60-851 for COD
80-85Z rosioval
possible
Acrolein, arsenic. Total ollnlnatlon
benrene, carbon of toxic algacldea
tetrachlorlde,
chlorinated
benzene, chlor-
inated phenols,
cyanide, Mercury,
nickel, penta-
chlorophenol.
phenol, zinc
Aluai Precipita-
tion and Acti-
vated Carbon
Adsorption
Heavy ectals Natal
and sone organlcs Zn
Cr
Cu
Sb
Bii
Cd
Pb
Se
Ag
Til
Hg
Nl
Z Reaoval
28
97
98
71
99
56
97
56
99
19
98
37
Petroleua) Refining
Municipal wastewoter
Petrochemical
Petroleum Refining
API Separator Effluent
Various industrial
application*
Utility cooling water
Municipal raw waatewater
piked with ealia of
heavy Be tale.
Coal Pile Hunoff
Yard Drainage
Sanitary Wastes
Coal Pile Runulf
Yard Drainage
Sanitary Wasted
Yard Drainage
Coal Pile Runoff
Cooling tower Bloudown
Cooling Tower Bloudown
Ash Pond Effluent and
Overflow
Yard Drainage
KconoBica
50.67-$!.57 per gpd
capital cost.
90.24-S0.55 per gpd
annual cost.
Alao see preliminary
survey process des-
cription.
50.65-$!.00 per gpd
for capital coat.
50.28-$0.40 per gpd
for annual cost.
$0.20 par gpd fur
capital costs,
very low annual
coat due to minimus
equipment.
Reference*
KN-407
HI-265
HE-188
BU-215
VA-127
Ul-121
ES-020
DA-OS2
EH-407
BU-215
TE-111
BK-156
EN-407
BU-215
KI-072
BE-156
$Q.01/lb of phenol KI-026
^$5.000 capital In- EH-127
vestment. BR-394
No change in operating
coyts.
See Preliminary
Survey Process
Description
CO-576
DA-052
-------
TABLE 4-1. (Continued)
i
ho
u>
Control
Technology
Barium Salt Pre-
cipitation
Chemical Oxidation
Chemical Keiluctlun
Complex Formation
and Activated
Carbon Adsorption
Copiei Ipitution
Deep Well Disposal
ICleclrodlalysIs
Elei troly tic
Oxidation
Electrolytic
Kediictlon
Compounds
Controlled
Hcxavalent
chromium
Cyanide and
phenols
Cr ' reduced
followed by
neutralization
to precipitate
Cr ' and other
heavy metals.
Cymilde and
heavy metals
Ka, Mo
I'hosphute, Fe,
Cu, Al, An
Desalination
Ionic dissolved
solids
Phenol
Chromium
Effectiveness
1 ppm Cr ' residual
<0.001 ppm residual
level for phenols
and cyanides
Typical results are
0.02 ppm Cr ' and
0.01 ppm Cr ]
residual.
' 1 ppm CN and Fe
residual attainable
1 picogram/t Ka
residual
0.02-0.1 ppm Mo
residual
loot
60-98Z removal c>(
dissolved solids
95Z
0.05 ppo residual
Industry and
Streams Applied to
Electroplating wastcwater
Wastewater from mining,
milling, and electropla-
ting
Metal finishing and elec-
troplating waste water.
Electroplating waste
water
Control of radium in
uranium industry, control
of molybdenum in fcroulluy
industry.
Oil tlcld brine and
chemical wastes.
Desalination
Experl mental
Rellulng, Petrochemical,
Cooling Tower Blowdown
Streams Applicable
1» Electric Utility
Cooling Tower Blowdown
Ash Pond Effluent and
Over f 1 ow
Boiler Blowdown
Cleaning Wastes
Water Pretreotment Wastes
Cooling Tower Blowdown
Ash Pond Effluent and
Overflow
Boiler Blowdown
Cleaning Wastes
Water Pretreutment Wastes
Cooling Tower Blowdown
Ash Pond Effluent und
Overflow
Boiler Blowdown
Cleaning Wastes
Water Treatment Wastes
Cooling Tower Slowdown
Ash Pond Effluent and
Overflow
Boiler Blowdown
Cleaning Wastes
Water I'retreattuent Wastes
Cooling Tower Blowdown
Ash Pond Effluent and
Overflow
boiler Ulowduwn
All
Cooling Tower Blowdown
Yard Drainage
Boiler Ulowdown
Coal Pile Kunoft
Yard Drainage
Coal Pile Runoff
Cooling Towel Blowdown
Economics
No data available
Direct chemical costs
for alkaline chlorina-
tlon are $1.93/lb. CN~
oxidized.
$0.50 per Ib of Cr
treated using 11. Sc
per Ib bisulfite and
6.5c per Ib raustlc
S0.16-S0.87 per Ib
CN operating cost
No data aval lul.li:
Extremely site-
specific.
$0.40- $0.50 pur 1000
gal operating cost
$1.53-$3.06/lb of
phenol
$500,000 capital
$136,000 operating
Referent.'
SH-159
RE- 165
Ml- 260
EN-394
110-293
WI-2dO
SM-159
EN- 12 7
EN-394
RE- 165
EN-J94
EN- 39 2
EN- 127
EN- 394
Rl-160
Vendor
Contacts
El 026
Dl-150
DU 1 34
Evaporation
All
100Z
Mining and milling opera-
tions and some utilities
In western and southwes-
tern states.
All
costs for 500 gpu
Site-specific
KN--19-!
-------
TABLE 4-1. (Continued)
Control Compounds
technology Controlled
KeirK Chloride Pre- Heavy aetJla
ci|iltstlon and Ac-
tivated Carbon
Adsorption
Me
Zn
Cr
Cu
Sb
Be
Cd
Pb
Se
AH
Th
An
Effectiveness
tul X KeMoval
94
99
96
72
99
99
98
80
99
45
97
Industry and
Serenas Applied to
Municipal raw wasceuater
piked with aalta of
heavy Metala.
StreaBs Applicable
In Electric Utility EconoiilcB Heti-rences
Cooling Tower Bluwduwn See PreHnlnury CO-S/6
Ash Pond Effluent and Survey Proc«afc DA-052
Overflow Description
Yard Drainage
to
J>
I
Foam Fractionalion
High Deiwlty Sludge
Acid Neutralise-
tlon
Ion Exchange
Line Neutrallza-
11 nn
Phenol
B5X
Llae Precipita-
tion and Acti-
vated Carbon
Adsorption
Acid and heavy
sietals
Trace nutal,
cyanide, phenols
As, Cd, Cu,
Cr ', Fa, Hg,
Hn, Nl, Pb. An
and heavy aotals
generally.
Heavy Metal and
gone organics
Heavy aetals ceaova.
l>ll dependent
Trace akitalu
0.001-0.4 pp«
residual
-O.I CN
Example of residual
levels that are
attainable.
As 0.05 ppB
Cd 0.05
Cu. 0.03
Cr ' 0.05
Fe 1.0
llg 0.0001
Hn 1.0
Nl 0.05
Pb 0. 10
Zn 0.15
(fatal X Removal
llg 91
Nl 99
Zn 76
Aa 84
Cu 90
Sb 52
Be 99
Cd 99
Pb 99
Se 95
Ag 98
Th 72
Developmental Stage
Acid or Bine wastewatur
Widespread couerclal
use, denlnerallze boiler
feud water, etc.
Widespread c
use
rclal
Municipal raw wastevater
aplked with Baits of
heavy act a Is.
Yard Drainage
Coal Pile Runutl
Cooling Tnwer Slowdown
Ash Pond Effluent and
Overflow
Yard Drainage
All except uanltary
and prutroatnent
waste
Cooling Tower Blowdown
Ash Pond Effluent and
Overflow
Boiler Blowdown
Cleaning Wastes
Water Treatment Wastes
Yard Drainage
Cooling Tower Blowdown
Aali Pond Effluent and
Overflow
$0.09 pur cb phenol tl-O2h
No data available EN-194
$275,000 capital cost HA-69i
for 500,000 gpd sys- 1)1-150
tea, $1.79 04M per
1000 gal treated
$150,000 capital and EN-J91
$53.000/year operating EN-192
cost In 1971 dollars EN-JVJ
for 100 gpm waatewater EN-J9n
See PreUnlnory
Survey Process
Deacrlptlon.
COS/6
IA-261
DA-052
-------
TABLE 4-1. (Continued)
Control
Technology
Uquid Waste
Incineration
Photochemical
Oxidation
Reverse Usmoslu
Skimming and
Flotation
Solvent Extraction
Sulflde Precipi-
tation
1
S3
-------
Electrolytic Oxidation Ultrasonic Oxidation
Electrolytic Reduction Vapor Compression
Evaporation Distillation
Ferric Chloride Precipitation Zero Discharge Strategies
and Activated Carbon Adsorption
Description sheets for these processes can be found in Appendix
B. Information summarizing the pertinent features of the pro-
cesses is given in Table 4-1.
EVALUATION OF RESULTS
The wastewater control techniques just listed were evalu-
ated using the criteria outlined at the first of this section.
The objective was to identify those processes with the most
potential for removing priority pollutants in utility plant
effluent streams. Those processes were then examined in more
detail. As a result of this evaluation, the processes listed
below were selected for further analysis:
Activated Carbon,
Precipitation,
Evaporation Ponds, and
Vapor Compression Distillation.
In addition, reverse osmosis and filtration were evaluated as
pretreatment processes. Solid waste disposal techniques were
also evaluated as a means of controlling secondary solid wastes
resulting from wastewater controls.
-26-
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SECTION 5
ASSESSMENT OF SELECTED CONTROL TECHNOLOGIES
This section presents the methodology and results of the
preliminary evaluation of the effluent control technologies
deemed most applicable to utilities. A description of the
assessment techniques used to evaluate the selected processes,
and a discussion of each technology evaluated is presented.
The process evaluation subsections include a brief process de-
scription and flow sheet, the effectiveness of control for the
appropriate species, and capital and operating costs. The pro-
cess summaries also address the state of development and appli-
cations to date, energy requirements, and secondary process
emissions. The applicability of each technology to steam/elec-
tric utility streams is discussed.
METHODOLOGY FOR THE TECHNICAL AND ECONOMIC ASSESSMENT OF THE
SELECTED PROCESSES
The methodology used for completing the preliminary assess-
ment of the selected technologies to control effluents - from the
utility industry is discussed below. The results of the assess-
ment are presented in the remainder of Section 5.
The assessment of the selected control processes consists
of two parts:
technical
economic
Both types of assessments of the selected controls were conduc-
ted by extending the broad literature survey of processes begun
in Section 4 to focus on the specific processes. The additional
information from the process specific literature survey was com-
bined with that from the preliminary survey to provide the data
base for the assessment of the selected processes. When appro-
priate, vendors of wastewater treatment systems were contacted
to gather technical and economic information on the selected
processes to augment the information obtained from the litera-
ture survey
-27-
-------
Technical Assessment
The major thrust of the technical assessment was to evalu-
ate the applicability of the selected control technologies to
the utility industry. For the controls not presently used in
the utility industry, this involved an engineering assessment
of the ability of the control technologies to remove the mater-
ials for which they were identified to be effective. This
evaluation required that the mechanism for pollutant removal
by each process be compared on a chemical and engineering basis
to the chemical and physical characteristics of the utility
streams as presented in Section 3.
In general, at the time of this study, the priority pollu-
tants which are present in utility streams and their concentra-
tions are poorly defined. Also, the available information on
the effectiveness of control technologies for reducing priority
pollutants is related primarily to industries other than the
utility industry. As a result, the estimates of the performance
and costs for the control of the priority pollutants are not
based upon specific utility data. However, efforts were made to
interpret the available information and apply it to the utility
situation.
As part of the technical evaluation, the following specific
items were examined:
state of development - the degree to which the
technologies have been developed and applied
from bench-scale to commercial scale application,
applications to date - the industry and, where
possible, specific application of the control
technology,
process description - the general description of
the process and the mechanism for priority
pollutant reduction,
expected performance - the comparison of the
performance of the control technology in the
industry it is used to the expected performance
in the utility situation,
energy requirements - the energy directly
associated with the control technology in the
utility situation, and
-28-
-------
secondary process emissions the air, water,
and solid emissions of priority pollutants
resulting from the application to wastewater
streams of the control technology, e.g., vents,
blowdown streams, sludges, backwash water, and
process wastes.
Economic Assessment
The data base for the economic assessment of the selected
technologies was established in the same manner as that for the
technical assessment. After the process specific literature
survey was completed and appropriate vendors were contacted,
the economic information was examined for consistency between
sources and applications. The control technology costs which
were determined to be most applicable to the utility situation
were selected for further assessment.
The capital and operating costs for each process were deter-
mined as a function of stream flow rate and characteristics.
When appropriate for the various controls, the site specific im-
pacts of the controls upon costs were identified. However, the
cost of site specific aspects were not assessed. All costs were
adjusted to 1977 dollars using standard engineering cost escala-
tion indices.
The capital costs are total installed capital costs and in-
clude equipment, engineering, and overhead. Costs for retrofit-
ting are not included due to the highly site-specific nature of
applying the controls to the utility industry and the lack of a
firm data base relating to the utility situation. Operating costs
include raw materials, labor, energy requirements, and maintenance
The energy requirements are confined to those directly associated
with the control technology.
ACTIVATED CARBON ADSORPTION
Activated carbon adsorption has been widely applied in the
field of water and wastewater treatment. With the development of
high surface area carbon that could be reactivated, carbon adsorp-
tion has emerged as an economically practical and efficient waste-
water treatment system for organic pollutant removal in many in-
dustries .
The overall flexibility of the carbon adsorption process
has resulted in its application in a wide variety of situations.
Carbon adsorption is currently being used in the following indus-
tries :
-29-
-------
Detergent manufacturing where xylene, alcohols,
and TOC are removed from effluent wastewater,
Oil refining where COD is removed from effluent
wastewater,
Chemicals manufacturing where phenols and resin
intermediates are removed from wastewater,
Resin manufacturing where xylene and phenols
are removed from effluent wastewater,
Herbicide manufacturing where toxic phenols
are removed from wastewater,
Coking plants where phenols are removed from
ammonical liquor, and
Municipal wastewater plants.
Process Description
Carbon adsorption systems designed for utility wastewater
treatment would consist of carbon bed contact equipment, pre-
treatment facilities, if necessary, and carbon regeneration fac-
ilities, if economically practical. Pretreatment equipment is
needed if excessive quantities of suspended solids, oils, or
grease are present. If not removed, these constituents would
otherwise filter out on the carbon beds and increase the pressure
drop. Pretreatments commonly used are chemical clarification,
oil flotation, and filtration. Following pretreatment, the waste-
water is contacted with the activated carbon beds. The beds may
be arranged in several different configurations. Some common
ones include:
fixed beds in series,
moving beds,
fixed beds in parallel, and
upflow expanded beds.
An important consideration in the design and proper operation
of a carbon adsorption system is the contact time or residence
time of the water in the carbon bed. The optimum contact time
for a given carbon system is dependent upon several conditions,
including the type and concentration of organics being removed,
stream pH, stream temperature, and effluent quality. Since
the organic concentrations and especially the priority organic
-30-
-------
concentration of utility plant effluents are generally low,
special consideration should be given to these conditions as
to how they affect the carbon selectivity and, ultimately,
bed contact time. The relationship between contact time and
residual concentration of organics would need to be determined
for each adsorption system installed.
.Several general rules can be applied to predict preferential
adsorption of organics by carbon. High-molecular-weight organic
molecules of a given class adsorb preferentially to those in the
same class having lower molecular weights. Also, nonpolar or-
ganic molecules are preferentially adsorbed over polar organics.
Very little information, however, is available on the effective-
ness of carbon treatment on industrial wastewaters with very low
concentrations of organics as found in most utility applications.
Other major factors affecting adsorption specificity is
stream pH and temperature. The pH affects the solubilities of
various organics and, therefore, their capacity for adsorption.
The temperature of the stream being treated can affect activated
carbon's performance as well. Higher temperatures can increase
the solubility of certain organic compounds, therefore hindering
their adsorption on activated carbon.
Once the carbon bed becomes saturated, or breakthrough
occurs, the bed must be taken offstream. Treatment of the
saturated carbon is based on economic considerations. Options
available include disposal of the used carbon or either on-site
or off-site regeneration. Basically, for systems which need to
regenerate less than about two hundred pounds per day of carbon,
it is more economical to dispose of the carbon or use off-site
regeneration. For large carbon regeneration requirements, on-
site equipment is economically attractive. Regeneration is ac-
complished by thermally partially oxidizing used carbon in either
multiple-hearth furnaces or rotary kilns to reactive exhausted
carbon for reuse. Heating exhausted carbon to 1500-1800°F
drives off moisture and volatilizes the organic contaminants.
The off gas from the regeneration step is routed to an incin-
erator to reduce secondary emissions. Due to attrition, about
5-10 percent of the carbon sent to regeneration is lost. Fig-
ure 5-1 illustrates a carbon adsorption/regeneration system.
Control Effectiveness
Carbon adsorption is capable of removing certain organic
species found in utility wastewater streams. Table 5-1 pre-
sents some reported control efficiencies for carbon adsorption.
The data reported in the table for acrolein, benzene, and toluene
-31-
-------
REGENERATED CARBON
10
I
CARBON ABSORPTION BEOS
i
1
i
1
i
1
\ '
1
T
i
i
i
REGENERATION FURNACE
« i
BED BEINQ
REGENERATED
SPENT CARBON
^-
Jf
QUENCH TANK
^_. TO n'THARGE
OR FURTHER TREATMENT
Figure 5-1. Downflow in parallel carbon adsorption/regeneration system.
-------
TABLE 5-1. CARBON ADSORPTION TOXIC POLLUTANT REMOVAL EFFECTIVENESS
Toxic Pollutant % Removal Efficiency Residual Concentration (mg/Jl)
Acrolein
Cyanides
Phenol
Benzene
Toluene
31
1
99
95
79
ND
ND
0.005
ND
ND
ND - no data
References: GI-121, VA-127, PA-120.
are based upon bench-scale studies. As such, the numbers could
differ significantly from what may be observed in a utility
application. The cyanide and phenol data are based upon coke
plant and refinery wastewater treatment data, respectively.
Therefore, these numbers may be more representative, especially
the phenol data, since the carbon system operated on low-organic
concentration water such as might be found at utility plants.
Certain trace metals in municipal wastewaters have been
removed to varying extents by carbon adsorption. Since acti-
vated carbon does not effectively remove dissolved metals
through adsorption, it is suspected that the metal removal
occurs through some other mechanism. One possible mechanism
is the adsorption by the carbon of an organic molecule which
has formed a complex with a metal. Whether or not metals
removal through organic complexing would occur in utility waste-
waters treated by carbon adsorption is unknown. For this reason
no removal efficiencies for metals are reported for carbon
adsorption.
Because carbon adsorption is effective for phenol, benzene,
and toluene removal and to a limited extent acrolein, it is ex-
pected that this treatment process could be applied to the fol-
lowing streams:
Coal Pile Runoff
Yard Drainage
Cooling Tower Slowdown
Lab Drains
Ash Pond Effluent
-33-
-------
Costs
The costs associated with wastewater treatment by carbon
adsorption are discussed below. Figures 5-2 and 5-3 present
cost curves for carbon adsorption capital costs and operating
and maintenance costs. The cost curves include on-site regener-
ation equipment above a flow of 800,000 gallons per day. This
flow approximately represents the break-even-point above which
on-site regeneration of the carbon becomes economical.
Capital costs for carbon adsorption are not only a function
of the wastewater flow rate, but also of the carbon regeneration
rate. The effect of different regeneration rates are shown in
Figure 5-2. Curve I represents the capital cost for a system
where the regeneration rate is 400 pounds of carbon per million
gallons treated, Curve II is for a regeneration rate of 300 pounds
per million gallons treated, and Curve III is for a regeneration
rate of 200 pounds per million gallons treated.
Operating and maintenance costs are also a function of flow
rate as well as the carbon regeneration rate. Regeneration rate
is dependent upon the saturation of the bed and breakthrough of
the least selectively adsorbed organic. The selectivity of ad-
sorption on carbon of a given organic is a function of certain
stream conditions as well as the nature of the organic compound,
as discussed earlier. Figure 5-3 presents curves which show the
effect of different regeneration rates. Curve I is for a regen-
eration rate of 400 pounds of carbon per million gallons treated
and Curve III is for a regeneration rate of 200 pounds per mil-
lion gallons treated.
Energy Requirements
Energy requirements for the adsorption step include pumping
to overcome the pressure loss through the carbon beds. The esti-
mated power requirements for pumping is 0.32 kW-hr/1000 gallons.
This number is only approximate since the actual amount will vary
with each system design and total dynamic head requirements (EN-
088). For the systems using on-site regeneration, the energy
requirements include the fuel needed for heating the spent
carbon, generating steam for reactivation and for electricity
to transport the carbon between adsorption and regeneration steps.
The fuel required is estimated to be about 425,000 Btu per 100
pounds of carbon regenerated. The electrical power required is
estimated to be 5.8 kW-hr per 100 pounds of carbon regenerated
(EN-088). Off-site regeneration costs would include the 425,000
Btu per 100 pounds of carbon regenerated plus that for trans-
portation.
-34-
-------
100
100
SYSTEM CAPACITY (MILLION GALS/DAY)
CARBON REGENERATION RATE (/MILLION GALS TREATED)' ,! 40° LBS
II 200 LBS
Figure 5-2. Carbon adsorption installed capital costs
-35-
-------
10-
m
§
at
8 ,-
H-
35
cc
01
o
co
O
o
Ul
0.1-
I
0.0
0.01
SYSTEM CAPACITY (MILLION GALS/DAY)
I 400 LBS
CARBON REGENERATION RATE (/MILLION GALS TREATED)' II 300 LBS
III 200 LBS
Figure 5-3. Carbon adsorption operating and maintenance costs
-36-
-------
Secondary Process Emissions
Secondary process emissions from carbon adsorption systems
are associated entirely with the regeneration step. The hot re-
generated carbon is cooled in a water quench step before being
transported back to the beds. The quench water contains suspen-
ded solids which may need removing. Also, the stack gas from
the carbon furnace may contain unoxidized organics and carbon
fines. Incineration and scrubbing of the gas may be required
if these pollutants are present in large quantities. Incinera-
tion and scrubbing were included in the costs for regeneration.
If the quantity of carbon is too small to justify regenera-
tion, it can be disposed of in landfills. For coal-fired utili-
ties, the carbon could be blended with the coal and combusted in
the boiler. Organics adsorbed on the carbon are assumed to be
completely oxidized in the boiler.
LIME PRECIPITATION
Lime precipitation is an effective and economical treatment
process for removing dissolved metals from wastewaters. Lime
precipitation has found extensive application in treating waste-
waters from different industries. The following is a list of the
industries which use lime precipitation:
*-,
Electric utility industry
Ore mining and dressing industry
Metals plating industry
Wood preserving industry
Municipal water and wastewater
treatment
Process Description
Lime* precipitation removes contaminants by reducing
their solubility and precipitating them from solution or by
their coprecipitation with other insoluble compounds. Therefore,
to be successful, lime precipitation depends primarily upon two
factors:
sufficient lime to drive the precipitation
reaction to completion, and
removal of the resulting solids from the
treated stream.
-37-
-------
A typical lime precipitation system is illustrated in Figure
5-4. Generally, the wastewater containing the contaminants to
be removed is mixed in a tank with a slurry of lime and water
to adjust the wastewater pH. The amount of lime added depends
upon several parameters including stream alkalinity, pH, and
metals concentration. The treated water is then discharged to
a flocculation/clarification unit. This unit may be circular
or rectangular. Rectangular units are usually more economical
for larger flow rate applications.
In the flocculation/clarfication unit, coagulant aids and
more lime may be added depending upon design consideration and
wastewater characteristics. Formation of the insoluble compounds
called floe is prompted by agitation and circulation of the water.
Sedimentation of the floe is accomplished in a quiescent zone of
the unit. Accumulated sludge is removed and may be processed
in a thickener and vacuum filter or filter press for dewatering
prior to disposal.
The treatment conditions, lime and coagulant dosages, and
final pH must be optimized for any given waste stream, but,
in general, a pH of at least 9 and as high as 12 may be necessary
to insure removal of heavy metals. Figure 5-5 shows the relation-
ship between pH and solubility for selected metals. However,
the levels of concentration attainable in an actual operating
system may vary from the limits predicted on the basis of the
solubility curves in Figure 5.5 due to interfering species in
the wastewater. Many factors, such as the effect of widely dif-
fering solubility products, mixed metal hydroxide complexing, and
metal chelation may make theoretical limits presented in Figure
5-5 difficult or impossible to reach.
Control Effectiveness
Lime precipitation is capable of removing certain metals
found in utility wastewaters. Among the metals removed by lime
precipitation are: arsenic, cadmium, copper, trivalent chromium,
manganese, nickel, lead, and zinc. Table 5-2 presents residual
concentrations to which lime precipitation theoretically would
be able to remove the above listed metals. This information is
based upon published sources, industry data, and analysis of
samples for the ferroalloy-ore mining and milling industry
(EN-394). As mentioned, the data in Table 5-2 is not based upon
utility plant applications. For this reason, it may not repre-
sent the results that might be expected from the application of
lime precipitation to utility wastewaters. Factors which might
alter the results for utilities are the much lower metals con-
centrations, organic-metal complexing, and differences in
stream characteristics. In addition, other phenomena such as
coprecipitation and floe entrapment can increase metals removal
beyond solubility limitations.
-38-
-------
UTILITY
WASTEWATER
U>
VO
I
TO Disr.iiAnr.E on
FURTHER TnCATMfMl
DEWATERED
SLUDOE TO
(JISI'OSAl
Figure 5-4. Lime precipitation flow diagram.
-------
100
0.001
0.0001
SOURCE: ADAPTED FROM REFERENCE EN-127
Figure 5-5. Theoretical solubilities of metal ions
as a function of pH.
02-1488-1
-40-
-------
TABLE 5-2. LIME PRECIPITATION POLLUTANT
REMOVAL EFFECTIVENESS
Toxic Pollutant Residual Concentration (mg/fc)
Arsenic 0.05
Cadmium 0.05
Copper 0.03
Trivalent chromium 0.05
Manganese 1.0
Nickel 0.05
Lead 0.10
Zinc 0.15
Source: EN-394, PA-120
More work is needed in determining the effectiveness of
lime precipitation for removing metals from utility effluents.
Several aspects should be given special consideration. Co-
precipitation is a mechanism which is not discussed in the
literature that may enable metals in utility effluents to be
removed below their theoretical solubilities. It is also
suspected that the flocculation step in precipitation systems
could remove by physical enmeshment some organics from utility
wastewater streams. More information is needed on the potential
removal mechanism.
Based on typical utility wastewater characteristics and
the ability of lime precipitation to control the listed metals,
this control process may potentially be applied to the following
utility waste streams:
Ash pond effluent and overflow,
Cooling tower blowdown,
" Cleaning wastes,
Roof and yard drainage,
Boiler blowdown.
Costs
i
The costs associated with wastewater treatment by lime pre
cipitation are discussed below. Figures 5-6 and 5-7 present
curves for lime precipitation capital costs and operation and
-41-
-------
100-
co
cc. 10
o
Q
CO
z
o
o>
O
O
&
<
O
0.1
0 1
10
100
SYSTEM CAPACITY (MILLION GALS/DAY)
Figure 5-6. Lime precipitation installed capital costs
-42-
-------
0.01
0.1
:oo
SYSTEM CAPACITY (MILLION GALS/DAY)
I I IQOmg
' LIME DOSAGE (/LITER)- II 1000 mg
| III 5000 mg
Figure 5-7. Lime precipitation operating and maintenance costs.
-43-
-------
maintenance costs. The equipment on which the cost curves are
based include a lime feeder, flash mix tank, clarifier/floccula-
tor with sludge recycle, sludge thickener, vacuum belt filter
for sludge dewatering, and a filter for final effluent polishing.
This equipment selection represents the most capital intensive
treatment system. If effluent standards could be met and if
land were available, settling ponds and lagoons could be utilized.
Capital costs and operating and maintenance costs might be sub-
stantially decreased with such an arrangement since it involves
less equipment. However, for the application of precipitation
for metals removal, the low concentrations may require the more
expensive arrangement to obtain adequate overall removals. The
costs in Figures 5-6 and 5-7 do not include the costs of dispo-
sing of the dewatered sludge. The discussion on solid waste
disposal presents these costs later in this section.
The effect of different lime requirements on the operating
and maintenance costs due to varying inlet stream alkalinity,
pH, and metals concentration is shown in Figure 5-6. Curve I
represents a lime dosage of 100 mg/2.. Curve II is for a dosage
of 1000 mg/Jl and Curve III for a dosage of 5000 mg/Jl.
Energy Requirements
The energy requirements for lime precipitation include those
for operating the lime feeders, wastewater pumps, clarifier agi-
tator drive, sludge rake drive, and the vacuum filter. For a
500,000 gpd system with a 100 mg/fc lime dosage, the energy re-
requirement is estimated to be about 8 kW-hrs per 1000 gallons
treated. For a 1500 mg/2, lime dosage, the energy requirement is
about 14 kW-hrs per 1000 gallons.
Secondary Process Emissions
The precipitated solids formed in the clarifier represent
a secondary waste when separated from the wastewater. The sludge
is usually processed by dewatering in a thickener and vacuum fil-
ter to reduce its volume prior to disposal. However, if land
is available, it may be sent directly to ponds for disposal.
Care must be exercised to prevent the priority pollutants from
being leached or discharged from disposal sites or ponds.
REVERSE OSMOSIS
Turnkey reverse osmosis processes are commercially marketed
by a number of companies. Reverse osmosis units have been used
to treat cooling tower blowdown water to recover water for reuse.
Reverse osmosis has also been used to produce drinking water
from both sea water and inland brackish water.
-44-
-------
Reverse osmosis and electrodialysis produce similar results
for water treatment applications and have been used industrially
for similar situations. The costs and applications of the two
systems are similar. Reverse osmosis will be more effective in
reducing non-polar priority pollutants. As a result, only reverse
osmosis will be discussed in this section.
Process Description
Reverse osmosis processes utilize semipermeable membranes
to purify water. Using pressure as a driving force, water is
forced through a membrane resulting in a deionized water and a
brine concentrate. The net driving force for flow through the
membrane in a reverse osmosis system is the total applied pressure
less the osmotic pressure of the system. In general the osmotic
pressure of a solution is approximately 0.068 atm (1 psi) for
each 100 mg/Jl of dissolved salt concentration (LY-006).
A schematic flow diagram of a typical reverse osmosis plant
is presented in Figure 5-8. The heart of the plant is a semi
permeable membrane system and a high pressure pump. Auxiliary
systems for handling and processing the feedwater makeup to the
process, the purified product water, and the concentrated waste
are also important to the plant's operation.
Membrane Development--
Semipermeable membranes used in reverse osmosis processes
are all very similar. Although there are many inorganic and
synthetic organic materials that possess the property of semi-
permeability, cellulose acetate is the most common membrane
material employed (GI-009). Nylon aromatic polyamide membranes
are also used in selected membrane systems (LY-006). The cell-
ulose acetate membranes are approximately 100 microns thick.
Two performance parameters by which reverse osmosis mem-
branes are commonly judged are (1) the rate of water flux
through the membrane and (2) salt rejection. These parameters
indicate'the membrane's permeability to water and to dissolved
impurities, respectively. Conventional cellulose acetate mem-
branes achieve maximum water flux rates of 0.0035 to 0.0088 m /
day/m2 (10 to 25 gal/day/ft ) when desalting water of inter-
mediate salinity (approximately 5000 mg/fc TDS). Approximately
90-98% rejection of the salts in the feed stream can be achieved
(LY-006). Flux rate and salt rejection are related to membrane
parameters and are not independent of each other. 'Tight mem-
branes are characteristic of high salt rejection but they produce
the lowest rate of water flux through the membrane. Conversely,
"loose" membranes achieve low salt rejection but have high rates
-45-
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REJECT BRINE PUMP
DI30HARQE
PH
ADJUSTMENT
INTAKE
[FILTRATION
CHEMICAL
ADDITION
1
t i
FEEDWATER
PUMP
HIQH
PRESSURE
PROCESS
PUMP
PRODUCT PUMP
f
f
RO MODULES
PRODUCT STREAM
PRODUCT WATER
STORAGE TANK
Figure 5-8. Typical reverse osmosis plant arrangement.
Source: HI-041
-------
of water flux (CL-037). Membranes with a broad range of salt
rejection parameters and corresponding flux rates can be pre-
pared and are commercially available. The maximum feedwater
salt concentration that can be tolerated is reported to range
from 5.0 to 50.0 x 103 mg/£ (LY-006, PA-120) .
Membrane Configurations--
Although basically the same type of membrane is used for
all reverse osmosis plants, significant variations exist for
the membrane configuration that is employed. Configuration in
relation to reverse osmosis systems refers to the membrane sup-
porting mechanism. The basic configurations available are:
plate and frame
tubular
spiral wound
hollow fine fiber
Membrane Fouling--
Reverse osmosis membranes are subject to fouling from any
number of many different fouling agents. The most significant
of these agents are:
biological growths
suspended solids or particulate matter
scale
manganese and iron
organics
To control membrane fouling, a feedwater pretreatment step is
often dictated and certain limitations are imposed on the process
Process feed pretreatment can take several forms depending upon
each particular feedwater, i.e., softening and filtration.
In addition to pretreatment, scale control also imposes
restrictions or limitations on the reverse osmosis process.
Scale formation is driven by supersaturation of a solution with
respect to a chemical salt. Calcium carbonate (CaCOs), calcium
sulfate (CaSOO, and magnesium hydroxide lMg(OH)2J are the pri-
mary scaling salts due to their low solubilities. Therefore,
-47-
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these salts must be kept below their saturation concentrations
in order to avoid precipitation and scale formation. The con-
version of saline water to desalted water by reverse osmosis
is obviously limited by the feedwater concentration that can
be achieved. The degree of concentration varies with the qual-
ity of feedwater to the process.
A scaling problem that sometimes occurs in the reverse
osmosis process is attributed to concentration polarization.
This phenomenon results from inadequate mixing of the saline
water layer adjacent to the membrane's surface with the bulk
of the saline water concentrate. Localized supersaturations
can occur in this water layer even though the bulk waste
stream remains subsaturated. Concentration polarization is
minimized by proper hydrodynamic control of the concentrate
stream.
Membrane Life--
The service life of a reverse osmosis membrane is deter-
mined by its ability to maintain water flux rates and salt re-
jection characteristics. Significant reduction in either per-
formance parameter below prescribed levels is grounds for
removing a membrane from service. The maximum life expectancy
of cellulose acetate membranes ranges from 1 to 2 years. Nylon
fiber membranes have a maximum service range of approximately
3 years.
The water flux rate and salt rejection properties of cell-
ulose acetate membranes are significantly affected by membrane
compaction and membrane hydrolysis, respectively. Compaction
refers to the physical crushing of a membrane's porous struc-
ture. Subjection to extended periods of high hydraulic pres-
sure causes compaction. As the degree of compaction becomes
more severe, the rate of water flux through a membrane contin-
ually decreases. A maximum operating pressure of approximately
40-50 atm (600-800 psi) is generally adopted for cellulose
acetate membranes (LY-006). Higher pressures accelerate the
rate of membrane compaction without producing significantly
higher rates of water flux (GI-019). The membranes are period-
ically backflushed to remove any plugging or fouling that might
have occurred. The backflush stream is usually routed to the
reject brine stream.
Hydrolysis refers to the chemical reaction that occurs
between membrane material and water. Hydrolysis results in a
deterioration of salt rejection properties for the membrane.
Feedwater temperature and pH influence the rate of membrane
hydrolysis. They are important operating parameters to control
in extending membrane life. Cellulose acetate membranes have
-48-
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a maximum temperature limitation of 40°C (100°F). The hydroly-
sis rate for these membranes significantly increases at higher
operating temperatures. The pH range suggested for cellulose
acetate membranes is 3 to 8 (GO-063). Nylon membranes used in
hollow fine fiber modules can withstand more severe pH extremes;
pH values of 1.5 to 12.0 can be tolerated (GO-063). 'Thus, the
nylon fibers give more operating flexibility with respect to
pH. For certain membranes, chlorine concentrations greater than
0.1 ppm significantly reduce membrane life (PR-166).
Control Effectiveness
Reverse osmosis units have typically demonstrated 90-98%
salt rejection for feedwater with dissolved solids as high as
12,000 ppm. This results in product water TDS levels of about
200 ppm with 75% water recovery with one stage. Multiple stage
reverse osmosis systems can be used to achieve product TDS levels
as low as 50 ppm. The metallic priority pollutants generally
are reduced as the TDS is lowered. Also, reverse osmosis will
remove more than 9570 of organics and all colloidal particles
down to 0.05 microns (DI-149). Reverse osmosis could be applied
to all waste streams from the electric utilities except cleaning
water because of pH considerations and lab drains because of high
organic concentrations. Reverse osmosis would probably not be
used alone to treat streams to remove priority pollutants because
of the large volume of the waste stream. For example, reverse
osmosis could be used as a pretreatment with its reject brine
sent to a vapor compression distillation unit.
Costs
The major factors influencing the cost of a reverse osmosis
unit are the feedwater rate, membrane replacement costs, and
the number of stages employed. The concentration of the priority
pollutants should not significantly effect reverse osmosis costs.
Listed in Table 5-3 are cost data for reverse osmosis water
treatment at different system capacities. These data are based
upon TDS of 3000 ppm and purified water TDS of 50 ppm with 80%
recovery of water (GE-122).
Another vendor (DI-151) reports installed capital costs be-
tween $0.80 and $1.00 per gallon per day of water processed for
capacities greater than 80,000 gallons per day. These reverse
osmosis processes are one stage and provide 98% salt rejection
for feedwater up to 12,000 ppm TDS. Operating costs are about
$0.75 per 1000 gallons of water processed which included membrane
replacement costs.
-49-
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TABLE 5-3. COST OF WATER TREATMENT BY REVERSE OSMOSIS
1
Ul
0
1
System Capacity1
Capital Cost (Installed)
Membrane Cost
Operating Costs ($/1000 gal)
Membrane Replacement2
Power ((§ $.02c/kW-hr)
Labor ((§ $10/hr)
Maintenance and Repairs
Chemicals and Filters
Wastewater3 Disposal
TOTAL OPERATING COST ($/1000 gal)
10,000 GPD
$20,000
2,200
0.25
0.34
1.28
0.15
0.12
0.04
$2.18
25,000 GPD
$39,900
5,500
0.25
0.27
0.51
0.12
0.10
0.04
$1.29
100,000 GPD
$91,000
22,000
0.25
0.18
0.14
0.10
0.08
0.04
$0.79
500,000 GPD
$365,000
110,000
0.25
0.17
0.07
0.08
0.05
0.04
$0.66
Assumed Operating Schedule: 85% Service - 350 Days/Year
2Assumed 125% Membrane Replacement every three years
3At 80% Fractional Recovery and Water Cost of $53/Acre-Foot
Source: MA-693
-------
Figures 5-9 and 5-10 show capital and operating costs,
respectively, for a reverse osmosis process as a function of
the flow rate. These costs are for sinele stage reverse osmo-
sis which achieves 75% water recover;/ ?nd 90-98% salt rejection.
With 12,000 ppm TDS feedwater, the Dr.. duct water '.-ill have about
500 ppia TDS.
Energy Requirements
The major power consumer in a reverse osmosis unit is the
pumps. For 100,000 gpd units and larger, the energy require-
ments are between 8 and 10 kW-hr/1000 gallon of water processed
for one stage. If multiple stage reverse osmosis processes are
used, the energy requirements will increase almost directly
with the number of stages.
Secondary Process Emissions
The major waste stream from a reverse osmosis unit is the
reject brine stream. This stream carries the majority of the
dissolved solids brought into the process by the feedstream.
This reject brine stream will be a large volume waste stream
(-25% of the original stream); therefore, reverse osmosis can
be used to concentrate toxic species to make other controls
less expensive and more effective.
DEEP BED FILTERS
Turnkey deep bed filters are commercially available. Deep
bed filters have been used by many industries, including the
electric utility industry, which uses these filters to remove
suspended solids from effluent streams. Deep bed filters would
be used only as a pretreatment step to remove suspended solids
prior to priority pollutant control technologies.
Process Description
Deep bed filters utilize a bed of granular filter medium
to separate suspended matter from an aqueous solution. The
beds are usually arranged with the smaller particle size filter
media at the inlet side of the filter bed ami the larger parti-
cle size media at the end of the filter bed. Accumulation of
suspended matter within the filter media increases the bed's
resistance to liquid flow. When the pressure drop across the
bed becomes excessive, the filter bed must be regenerated. Re-
generation is usually accomplished by backwashing the filter.
Feedwater flows to conventional sand filters range from 0.07
to 0.14 ma/min/m? of filter cross-sectional area (2 to 4 gpm/ft2)
-51-
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55
-------
10O-
55
3
a
\
-------
Control Effectiveness
Deep bed filters remove suspended solids in the uarticle
size range of 0.1 to 50y. These filters can be applied to
treat dilute suspensions containing up to 1000 mg/£ of suspen-
ded matter.
Costs
Figures 5-11 and 5-12 shows capital and operating costs
for conventional sand or graded media filters (SM-176).
Energy Requirements
The only energy requirements would be for pumping the
solution through the filter. The energy requirements should
be in the range of 0.3 to 0.5 kW-hr/1000 gallon.
Secondary Process Emissions
The filter backwash which is produced during filter regen-
eration is a waste stream from a deep bed filter. This stream
can be sent to a settling pond.
VAPOR COMPRESSION DISTILLATION
Vapor compression distillation (VCD) can be used to treat
and recover water from the continuous waste streams of an elec-
tric-power generating station. The process produces a high
quality water stream while concentrating the dissolved solids
in a slurry of about 1070 the original stream volume (RE-259) .
Thus, VCD processes can be used to concentrate non-volatile
effluents from steam-electric utilities into a stream which
can be more easily treated. The concentrated reject brine
stream is usually ponded in arid regions. For non-arid regions,
the brine stream is either sent to an ash pond or treated with
a vaporization crystallizer.
Turnkey VCD processes have been commercially available for
over ten years. VCD processes have been installed in electric
power generating stations in the western and southwestern states
to recover deionized water from cooling tower blowdown (LE-299).
Process Description
Figure 5-13 shows the flow diagram for a VCD unit. The
water stream is first treated in a feed tank to adjust the pH
to between 5.5 and 6.5 for decarbonation. The waste stream is
then pumped through a heat exchanger to raise its temperature to
the boiling point. Softening may be required to prevent scaling
-54-
-------
10-
m
(E
< 1-
_l
o
Q
u.
O
CO
O
_i
i
CO
O
u
_j
t 0.1-
o.
o
0.01
O.T
10
ICO
SYSTEM CAPACITY (MILLION GALS/DAY)
Figure 5-11.
Capital costs for conventional
sand or graded media filters.
-55-
-------
CO
3.00"
0.1
1 I
1
10
100
SYSTEM CAPACITY (MILLION GALS/DAY)
Figure 5-12. Operating costs for conventional
sand or graded media filters.
-56-
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VENT
Ui
^>i
i
FEED
FEED
TANK
FEED
PUMP
PRODUCT
EVAPORATOR
-wv-
N/W
HEAT
XCIIANQE
R
D
<
:AER^
1
J ' 's
PRODUCT
TANK
STEAM
COMPRESSOR
TO WASTE
DISPOSAL
WASTE
PUMP
PRODUCT
PUMP
RECIRCULATION
PUMP
Figure 5-13. VCD simplified system schematic,
Source: RE-259
-------
in the heat exchanger. After passing through a deaerator to
remove dissolved gases, the hot waste stream is combined with
the slurry concentrate in the evaporator sump. The brine slurry
is constantly circulated from the sump to the top of the evap-
orator tubes. The slurry flows as a film on the inside of the
tubes down to the sump. As the slurry falls down through the
tubes, part of the slurry water is vaporized by the steam con-
densing on the outside of the tubes. This vapor is compressed
and introduced to the shell side of the tube bundle. As this
stream condenses, it returns its heat of vaporization to the
brine slurry. This condensate (<10 ppm TDS) is pumped through
the feed preheater to return as much heat as possible to the
process before it is recycled to the plant for reuse. The brine
slurry is continuously removed from the sump to maintain constant
slurry concentration. The waste brine can be sent to a pond or
mechanical drying system for final disposal.
The VCD process is able to avoid scale formation on heat
transfer surfaces by preferential precipitation of calcium
sulfate and silica on seed crystals in the slurry. Also, a
small temperature difference across the heat transfer tubes is
maintained to minimize scale formation on the evaporating sur-
faces .
The VCD unit is constructed of corrosion-resistant mater-
ials: titanium, stainless steel, and special steel alloys.
Inspection of corrosion levels in existing facilities indicated
that the designed 30-year life of the equipment should be
achieved. A 957., service factor has been observed (LE-299) .
Control Effectiveness
VCD units have taken inlet waters with 10,000 ppm TDS and
produced a condensate stream with less than 10 ppm TDS while
recovering approximately 90% of the water (RE-259). Therefore,
non-volatile and organic metal species should also be reduced
by about the same proportions as TDS. VCD processes can be
applied to all utility wastewater streams except streams con-
taining a significant level of organic compounds.
VCD has been applied to cooling tower blowdown in the
electric utility industry with the product water returned to
the plant for reuse as cooling tower makeup water and boiler
feed water.
If significant amounts of priority pollutants are vented
from the deaerator, some control process (such as carbon adsorp-
tion) may be required on the vent.
-58-
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Costs
The basis of the cost data (LE-299) for a turnkey vapor
compression distillation unit assumes 907, water recovery for
a waste stream containing 10,000 ppm TDS producing a purified
condensate (<10 ppm TDS) Two sizes are available on the market
from one vendor and cost data for these sizes are presented in
Table 5-4. The cost data does not include the cost for the dis-
posal of the waste brine.
TABLE 5-4. CAPITAL AMD 0/M COSTS FOR VAPOR
COMPRESSION DISTILLATION
216,000 gDd 432,000 gpd
Vendor A (LE-299)
Capital Cost (installed) $2,000,000 $3,700,000
0/M $1.8-2.0/1000 pal $1.8-2.0/1000 gal
Vendor B (BO-290)
Capital Cost (installed) $1,500,000 $2,800,000
0/M $1.8-2.0/1000 gal $1.8-2.0/1000 gal
Another vendor (BO-290) offers a VCD unit which has the same
specifications as a brine concentrator for about three-fourths
the capital costs with comparable 0/M costs as shown in Table 5-4
Because of the large capital costs for relatively low treat-
ment water rates and the high operating costs, it is probably
more cost effective to have a VCD unit: preceded by a pretreat-
ment process, i.e., reverse osmosis. A reverse osmosis unit
would reduce the volume of water to be treated by about 75"' at
a much lower cost than if VCD were used to treat it.
Energy Requirements
VCD units are verv energy intensive processes requiring
approximately 90 kW-hr/1000 gallon of water processed (RE-259).
Almost all this energy goes into driving the electric vapor
compressor. It is possible that stean-driven vapor compressors
would have certain economic advantages if low cost waste steam
were available. The concentration of priority pollutants do
not affect the energy requirements.
-59-
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Secondary Process Emissions
The major waste stream from a VCD process is the waste
brine concentrate slurry. This stream carries the majority of
the dissolved solids brought into the process by the feedwater.
This reject brine stream is usually ponded. Costs should be
charged for the disposal of this waste stream. In nonarid
regions, significantly more disposal costs may result. A vapor-
ization crystallizer, which is a very energy intensive process,
may be required in certain nonarid regions to dispose of the
waste brine slurry.
The dearator also produces a gaseous stream which is ven-
ted. This stream will contain mostly C02, N2, and 02. If there
are volatile pollutants in the feed, they may be flashed and
vented by the aerator.
EVAPORATION PONDS
Evaporation ponds use solar energy to evaporate water from
plant waste streams and thus, collect, concentrate, and precipi-
tate dissolved solids in the waste streams. These precipitated
dissolved solids are usually allowed to accumulate on the bottom
of the pond or, in some instances, are periodically dredged from
the pond.
Evaporation ponds have been used throughout the chemical
industry and the electric utility industry. Evaporation ponds
may be required to be lined to prevent seepage of dissolved
chemicals into underground water supplies. Evaporation ponds
can be constructed by excavating the pond, enclosing an area
with dikes, building a dam, or a combination of these methods.
The applicability of evaporation ponds depends upon the
net evaporation rate, i.e., the gross evaporation rate minus
rainfall. Geographical areas with less than 50 cm (20 in.) net
annual evaporation rate should not be considered for evaporation
pond use. Land must be available where the evaporation pond
can be built. Low cost land is desirable. The difficulty in
excavation of the land is also a factor. Finally, local regula-
tions must permit the use of such ponds.
Process Description
Solar evaporation may be performed in a single pond or in
a series of ponds. A graduated increase in brine salinity is
obtained by evaporation ponds in series. Chemical salts with
lower solubilities precipitate in the first ponds while more
soluble salts precipitate in latter ponds. As the salinity
increases, the pond evaporation rates decrease due to effects
on the partial vapor pressure of water.
-60-
-------
The area required for a single evaporation pond which evap-
orates G galIons/minute is given by
Area (Acres) = 19y5G (5-1)
where V is the effective net evaporation rate (inches/year).
The effective net evaporation rate is less than the net evapor-
ation rate due to the reduction of the water vapor pressure that
is caused by the dissolved salts in the water in evaporation
ponds. Some experimental evidence (FO-130) indicates that the
effective net evaporation rate is in the range of 507; to 70?0 of
the net evaporation rate.
Control Effectiveness
All streams could be potentially controlled by evaporation
ponds, but land availability and evaporation rate limit high
flow rate streams from being discharged to a pond. The major
limitations to the control effectiveness of evaporation ponds
in arid regions is the problem of seepage of pollutants into
underground water supplies. Even with the most carefully de-
signed lined evaporation pond, the possibility exists that the
lining may rupture. There is also the question as to the ef^ec-
tiveness of pond liners. Additional experimental work is needed
to adequately determine their permeabilities.
Costs
In Figures 5-14 and 5-15, capital and operating costs of
evaporation ponds are shown as a function of water rate to the
pond with the effective net evaporation rate as a parameter
The effective net evaporation rate is less than the net evapor-
ation rate due to the reduction of the water vapor pressure that
results from the dissolved salts in the wr.ter in evaporation
ponds. The capital cost figure is based upon assuming $2/cubic
yard of land moved to form a 4 foot high dike with a 27 foot
base. It is also assumed that the pond liner costs $0.25/ft2
and land costs $1000/acre. The cost of excavation ranges from
$2 to $6/'cubic yard depending upon the type of land to be ex-
cavated. Liner costs range from $0.20 to $0.40/ft2 depending
upon the type and thickeness of liner used. Land costs can
range anywhere from $200/acre to $10,000/acre or more. The
operating costs are for pumping and dike area maintenance.
-61-
-------
100-
co
o
0
o
3
i
u
0.1-
0.1
rl
1
10
100
SYSTEM CAPACITY (MILLION GALS/DAY)
I 60 INCHES
EFFECTIVE NET EVAPORATION RATE (/YEAR). II 30 INCHES
III 20 INCHES
Figure 5-14. Capital costs for evaporation ponds
-62-
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0.01
SYSTEM CAPACITY (MILLION GALS/DAY)
I 60 INCHES
EFFECTIVE NET EVAPORATION RATE (/YEAR) II 30 INCHES '
III 20 INCHES j
Figure 5-15. Evaporation pond operating costs
-63-
-------
As an example of the cost breakdown, consider a 150 gpm ash
pond overflow rate for a utility located in a region where the
effective net evaporation rate is 30 inches/year. From Equation
5-1, the pond area required to evaporate 150 gpm is 97.5 acres.
The installed capital costs of this evaporation pond with a dike
having a cross section shown in Figure 5-16 (A) is:
Land cost ($1000/acre) $ 100,000
Excavation and building dikes $ 45,000
3-inch thick asphalt liner $1,060,000
Pumps and lines (installed) $ 10.000
TOTAL INSTALLED COSTS $1,215,000
The 3-inch thick asphalt liner costs approximately 25c/ft2
(FO-130). The excavation and dike building costs were calcu-
lated assuming $2/cubic yard of land moved to form the dike.
If the land is not easily excavated, the cost will significantly
increase. The operating costs are estimated to be 12c/1000
gallons treated assuming that the solids can be allowed to ac-
cumulate on the bottom of the pond.
A western utility (FO-130) reported building three 20-acre
evaporation ponds to evaporate 300 gpm (an effective net evapor-
ation rate of 97 inches/year) at a cost of $1,550,000 excluding
land costs. The ponds were lined with 3-inch thick asphalt,
AS 4000, using a prime coat of MC250 (FO-130). This liner was
chosen because of its superior resistance to seepage. Each pond
has a 14-foot high dike with the cross section as shown in Fig-
ure 5-16 (B).
Energy Requirements
The major energy requirements for evaporation ponds are
for pumping the stream to the pond. The energy requirements
for pumping a distance of 1000 feet at a rate of 150 gpm is
about 0.5 kW-hr/1000 gallons based upon a 5 feet/second flow
velocity.
Secondary Process Emissions
If the pond is designed for solids settling and is designed
to eiminate seepage, there should be no process emissions from
an evaporation pond except for the potential evaporation of vol-
atile compounds to the atmosphere. If the pond is periodically
dredged, a disposal of solid waste is required.
-64-
-------
7'
4'
-27'-
(A)
SCALE
h It HIM HH. IH
0 4 8 12 16 FEET
91'
(B)
Figure 5-16. Dike cross-sections.
-65-
-------
SOLID WASTE DISPOSAL
Solid waste disposal is discussed here as a means of con-
trolling secondary solid wastes resulting from control technol-
ogies. Solid wastes can result from treatment of wastewater by
precipitation, carbon adsorption, or vapor compression distil-
lation. It is not presented as a primary effluent control
technology.
Process Description
The sludge resulting from lime precipitation can be ponded
or possibly chemically fixed and used as a landfill. When ponds
are used, they are usually required to be lined to prevent seep-
age into underground water supplies. Lining the pond is usually
not necessary when the pond bottom is composed of clay and is
at least a couple of feet in thickness. Chemical fixing involves
adding chemicals (e.g., fly ash and lime) to solid wastes which
results in cement reactions which render the mixture a strong,
relatively impermeable solid. This solid is well suited for
landfill.
When the activated carbon from a carbon adsorption process
is not regenerated, the spent carbon must be disposed of. The
carbon can be mixed with the coal and burned in the boiler or
used in a landfill.
Vapor compression distillation produces a brine slurry that
must be disposed of. This slurry can be sent to an evaporation
pond or the water can be removed from the slurry and the remaining
solid used as landfill or placed in a lined pond. Deep well dis-
posal may also be a possibility for disposal of this brine slurry.
Control Effectiveness
Data is generally unavailable on the effectiveness of solid
waste disposal on priority pollutants. Loss of effectiveness of
solid waste disposal can occur due to seepage of water entrained
with the solids. Rain run-off can also be a problem.
Costs
Very little information is available for the disposal costs
of these three different solid wastes. An example of solid
waste disposal costs is presented with cost data for the dispo-
sal of flue gas desulfurization sludge and fly ash. These costs
are reported in terms of dollars per dry ton of solid.
-66-
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Disposal Method $/dry ton of solid wastes (LE-278)
Lined Pond 6.4 to 8.8
Chemical Treatment 8.2 to 12.8
The basis for these costs are:
1000 MW power plant producing sludge
at a rate of 125 tons/day on a dry basis
transporting the solid waste 5 miles
from the power plant
The annualized costs include the cost of labor, maintenance,
and capital costs of 18 percent.
Energy Requirements
The only energy requirements are for pumping or hauling
the solid wastes to the disposal site. The energy requirements
are highly site-specific and depend upon the type of solid waste
and the method chosen to dispose of it.
Secondary Emissions
Seepage of the waste liquors into underwater water supplies
is a possible emission from solid waste disposal. If organics
are present, they may evaporate into the atmosphere.
-67-
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BIBLIOGRAPHY
AS-054 Aschoff, A. F., "Water use and reuse in the power
industry", Paper No. 72-PID-4. Presented at the
ASME Meeting, New Orleans, March 1972.
AV-018 Avery, Noyes L. and William Fries, "Selective removal
of cyanide from industrial waste effluents with ion-
exchange resins", I & EC Chem., Prod. Res. Dev. 14(2),
102 (1975).
AY-007 Aynsley. Eric and Meryl R. Jackson, Industrial waste
studies: steam generating plants, Draft Final Report.
EPA Contract No. WQO 68-01-0032. Rosemont, IL. ,
Freeman Labs, Inc., 1971.
AZ-009 Azad, Hardam Singh, ed., Industrial wastewater manage-
ment handbook. New York, McGraw-Hill, 1976.
BA-185 Babcock & Wilcox, Steam: its generation and use,
38th ed., New York, 1972.
BE-012 Berkhout, H. W. and G. H. Jongen, Chemist Analyst 45.
6 (1956).
BE-156 Beychok, Milton R., "Wastewater treatment", Hydrocarbon
Proc. 50(12), 109 (1971).
BE-162 Bell, William E. and E. Dennis Escher, "Disposal of
chemical cleaning waste solvents", Mat. Protect. Per-
form. 9. 15 (1970).
BO-290 Bober, John, Private communication, Ecodyne, Union,
New Jersey, 31 May 1977.
BR-394 Brungs, William A., Effects of wastewater and cooling
water chlorination on aquatic life.EPA Contract No7
600/3-76-098. Duluth, MN, EPA, Environmental Research
Lab., August 1976.
BU-215 Bush, Kenneth E., "Refinery wastewater treatment and
reuse", Chem. Eng. 83(8). 113 (1976).
CL-037 Clifton, M. J. and R. T. Fowler, "Water purification
by reverse osmosis. The state of the art", J. Inst.
Eng. Australia Sept. 1972, 8.
CO-576 Cohen, Jesse M. , "Trace metal removal by wastewater
treatment", Tech. Transfer 1977 (January).
-68-
-------
DA-052 Davis, John C., "S02 removal still prototype", Chem.
Eng. 79(13). 52 (1972).
DE-079 D'Elia, Robert A., Donald L. Howard, and Donald K.
Cameron, "Want better feedwater?", Water Wastes Eng. 9
(9), E-20 (1972).
DI-149 Dillingham, Ted, Private communication, Hydronautics,
Goletia, CA, May 5, 1977.
DI-150 Dillard, Frank, "Alternatives for chrome reduction in
cooling tower blowdown", Presented at the ASCE 1977
Spring Convention, Dallas, Texas, April 1977.
DI-151 Dillingham, Ted, Private communication, Hydronautics,
Goletia, CA, May 31, 1977.
DO-048 Donohue, John M., "Making cooling water safe for steel
and fish, too", Chem. Eng. 78(22), 98 (1971).
DO-051 Donohue, John M. , "Chemical Treatment", Ind. Water
Eng. 7(5), 35 (1970).
DU-134 Duffey, Joseph G., Stephen B. Gale, and Stanley
Bruckenstein, "Operating experience with the electro-
chemical chromate removal unit", Presented at the
Cooling Tower Institute Annual Meeting, Houston, TX,
February 1975.
EI-026 Eisenhauer, Hugh R., "Dephenolization of water and
wastewater", Water Poll. Control 106(9), 34, 38-41
(1968).
EM-019 Emergy, Frederic H., "Production of hydrogen for
gasified coal and laser fusion atomic energy", ACS,
Div. Fuel Chem., Prepr. 19(5), 43-48 (1974).
EN-088 Environmental Protection Agency, Office of Technology
Transfer, Process design manual for carbon adsorption.
.Research Triangle ParkT N.C., 1973.
EN-127 Environmental Protection Agency, Office of Air and
Water Programs, Effluent Guidelines Division,
Development document for proposed effluent limitations
guidelines and new source performance standards for
the steam-electric power generating point source cate-
gory. 1974.
-69-
-------
EN-391 Environmental Protection Agency, Effluent Guidelines
Division, Development document for interim final
effluent limitations guidelines and proposed new
source performance standards^ for the lead segment
of the nonferrous metals manufacturing point source
category"EPA 440/1-75-032a, Group I, Phase II.
Washington, D.C., February 1975.
EN-392 Environmental Protection Agency, Effluent Guidelines
Division, Development document for interim final
effluent limitations guidelines and proposed new
source performance standards for the primary -copper
imelting subcategory^and the primary copper refining
subcategory of the copper segment of the nonferrous
metals manufacturing point source category.
EPA 440/1-75/032-b, Group I, Phase II. Research
Triangle Park, N.C., February 1975.
EN-393 Environmental Protection Agency, Effluent Guidelines
Division, Development document for interim final
effluent limitations guidelines and proposed new
source performance standards for the zinc segment
of the nonferrous metals manufacturing point_source
category"EPA 440/1-75-032, Group I, Phase II.
Washington, D.C., February 1975.
EN-394 Environmental Protection Agency, Effluent Guidelines
Division, Development document for interim final and
proposed effluent limitations guidelines and new
source performance standards for the ore mining~and
dressing industry, point source category, 2 vols.
EPA 440/1-75/061, Group II.Washington, D.C., October
1975.
EN-407 Environmental Protection Agency, Effluent Guidelines
Division, Development document for effluent limita-
tions guidelines and new source performance standards
for the petroleum refining point source category.
final report.by Martin Halper.EPA 440/1-74-014-a,
PB 238 612. Washington, D.C., April 1974.
EN-487 Environmental Protection Agency, Office of Water and
Hazardous Materials, Effluent Guidelines Division,
Supplement for pretreatment^ to the development docu-
ment for the steam-electric power generating point
source category"! Washington, D.C.7 Nov. 1976.
ES-020 Esmond, Steven E. and Albert C. Petrasek, Jr.,
"Trace metal removal", Ind. Water Eng. 11(3). 14-17
(1974).
-70-
-------
FO-130 Ford, Walt, Private communication, Southern California
Edison, Laughlin, NV. 26 May 1977.
GE-122 Gentry. R., Private communication, Triton Water System,
Irvine, CA, 5 May 1977.
GI-009 Gilbert, Paul T., "Flame-photometric determination of
chlorine by indium chloride band emission", Anal.
Chem. 38, 1920-2 (1966).
GI-019 Gilliam, W. S. and H. E. Podall, "Recent developments
on the reverse osmosis process for desalination",
Desalination 9(2) , 201-11 (1971).
GI-121 Giusti, D. M., R. A. Conway, and C. T. Lawson,
"Activated carbon adsorption of petrochemicals",
J. WPCF 46(5), 947-65 (1974).
GL-028 Glover, G. E., "Cooling tower blowdown treatment
costs", in Industrial Process Design for Water
Pollution Control, Vol. 2, Proceedings of the Work-
shop.N.Y., AIChE, pp. 74ff:
GO-063 Golomb, A. and F. Besik, "Reverse osmosis for waste-
water treatment", Ind. Water Eng. 7(10), 16 (1970).
HA-603 Harrison, J. W., Technology and economics of flue gas
NOX oxidation by ozone, final report. EPA 600/7-76-033,
EPA Contract No. 68-02-1325, Task 38. Research Triangle
Park, N.C., Research Triangle Institute, December 1976.
HE-188 Henshaw, Tom B., "Adsorption/filtration plant cuts
phenols from effluent", Chem. Eng. 78(12) , 47 (1971).
HI-041 Hittman Associates, Inc., Reverse osmosis desalting
state-of-the-art (1969). Columbia, MD, 1970.
HO-293 Hoffman, D. C., "Oxidation of cyanides adsorbed on
.granular activated carbon", Plating 60(2), 157-62
(1973).
KI-048 Kirk-Othmer, Encyclopedia of Chemical Technology,
2nd ed., vols. 1-22. New York, Wiley. 1963-1970.
KI-072 Kilpert, Richard, "Petroleum refinery effluent
quality control", Paper II/9. in Water Resources,
Environment & National Development, Vol. 2. Selected
Papers. Proceedings of Regional Workshop by Science
Council of Singapore and Nat^l. Academy of Sciences,
Singapore, March 1972. Science Council of Singapore,
1972, pp. 224-30.
-71-
-------
LA-261 Lanquette, Kenneth H. and Edgar G. Paulson,
"Treatment of heavy metals in wastewater", Poll.
Eng. 8(10), 55-57 (1976).
LE-278 Leo, P. P. and J. Rossoff, Control of waste and water
pollution from power plant flue gas cleaning systems:
First annual R and D report.EPA 600/7-76-018, EPA
Contract No. 68-02-1010.El Segundo, CA, Aerospace
Corp., October 1976.
LE-299 Lepper, F. R. , Private communication, Resources
Conservation, Renton, WA, April 29. 1977.
LU-013 Lund, Herbert F., Industrial pollution control
handbook. New York, McGraw-Hill, 1971.
LY-006 Lynch, Maurice A., Jr., and Milton S. Mintz, "Membrane
and ion exchange processes - a review", J. AWWA 64(11),
711-25 (1972).
MA-230 Marshall, Wm. L., "Cooling water treatment in power
plants", Ind. Water Eng. 9(2), 38 (1972).
MA-246 Mayhue, Luther F., Solvent extraction status report.
PB 211 458, EPA-R2-72-073.EPA, Rob't. S. Kerr Water
Research Center, 1972.
MA-693 Mason, James W., Economics of boiler feed water treat-
ment, reverse osmosis vs. ion-exchange. Technical
Report No. 1. Triton Water Systems, Inc., undated.
MI-265 Minor, Paul S., "Organic chemical industry's waste
waters", Env. Sci. Tech. 8, 620 (1974).
OT-029 Ottinger, R. S., et al., Recommended methods of reduc-
tion, neutralization, recovery, or disposal of hazard-
ous waste, 16 voTsTEPA 670/2-73-053 a-q, PB 224-
580-594, EPA Contract No. 68-02-0089. Redondo Beach,
CA, TRW Systems Group, August 1973.
PA-120 Patterson, James W. and Roger A. Minear, Wastewater
treatment technology. 2nd ed. Rept. No. IIEQ 73-1.
State of Illinois Inst. for Environmental Quality,
1973.
PR-166 Prato, Sal, Private communication, Ionics, Watertown,
MA, 17 May 1977.
-72-
-------
RE-165 Reed, A. K. et al., An investigation of techniques
for removal of cyanide from electroplating wastes.
12010 EIE 05/71. Upper Montclair, New Jersey, Metal
Finishers' Foundation, May 1971.
RE-259 Resources Conservation Co., "Brine concentrator",
Company brochure. Renton, WA, undated.
RI-160 Rice, James K. and Sheldon D. Strauss, "Water-pollution
control in steam plants", Power 120(4), SI-20 (1977).
SC-267 Schwieger, Robert G., "Identifying hardware for curbing
water pollution", Power 1971 (June), 518-24.
SM-159 Smithson, G. R., Jr., An investigation of techniques
for removal of chromium from electroplating wastes,
final report.12010 EIE, 3/71.Columbus, Ohio,
Battelle-Memorial Institute, March 1971.
SM-176 Smith, Robert, "Cost of conventional and advanced
treatment of wastewater", J. WPCF 40(9), 1546 (1968).
ST-135 Strauss, Sheldon D., "Water treatment", Power 117(6),
S51-S24 (1973).
TE-111 "Technology. Water pollution control", Chem. Eng. 78
(14), 65 (1971).
VA-127 Van Stone, G. R. , "Treatment of coke plant waste
effluent", Iron Steel Engr. 49(4). 63 (1972).
WI-260 (S. K.) Williams Company, Wastewater treatment and
reuse in a metal finishing job shop.EPA 670/2-74-042,
Wauwatosam, WS7 July 19747
-73-
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APPENDIX A
DISCUSSION OF THE CHARACTERISTICS OF UTILITY
POWER PLANTS EFFLUENT STREAMS
The steam-electric power industry uses large quantities
of water primarily for cooling purposes. There are, however,
several other water utilizing processes most of which produce
a wastewater stream. The qualities of the wastewaters from
these processes vary over wide ranges depending primarily on
intake water quality and/or the characteristics of the power
generating facility involved. Generalized descriptions of the
water utilizing processes and the wastewater streams associated
with them are contained in this section. '
Figure A-l graphically summarizes the sources of waste-
water in a fossil-fueled generating station and depicts the
interrelation of the various processes producing these waters.
The sources of wastewater are:
cooling water systems,
boiler water systems,
ash handling systems,
coal pile,
general plant drainage systems,
process spills and leaks, and
miscellaneous operations.
Wastewater discharges associated with flue gas scrubbing will
not be evaluated in this document.
-74-
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LEOENDi
LIQUID FLOW
* * CHEMICALS
. . . OPTIONAL FLOW
v^ WASTE WATER SOURCES
A WASTE!
vy WATER p
CIIEM GALS
1
tn
' RAW WATER ^ «*TEB «?§"&",.
TREATMENT
,
WASTE /l
WATER ^J
CHEMICALS I
* * * V M DEM
WAT
CIIEM CALS PEHIO
DOILER TUBE
CLEANING; . FIRESIDE
1 AIR PREIIEATER
WASHINGS
FJJ|i_»
AIR ^
OOTT
A
TO
ATMOSPHERE
ER FOR i
HIP CLEAHIHO 1
1
r -_.
\
ST£AM . (_ _..__,
t 1
1 1 _ -
FLUE P 1UnBINE
STliAM lAofj L^GIENEHATOR
OEHERATINQ f ~~
BOILER x-^-^a
BH V^^yt
urnjuirrnL . " OONDENSATE WATER 4
1 r
_L-
WASTE A
WATER \^
FLV ' ASH |
COLLECTION j ., ^ AL
U, *- . ,. .
union so:.
UDDING UEVICL '
_.
"AT-." W»« : TC
_ . _ J
Clll ( ..II i
I' -» ':;,,n ';!!' /*K' ,
I liEClJ .1 , MN.1' L. i Jl HU v-,/ l '
1 ' 1
>--r; I
IDISCHAHOE ml \ cu^i ina ' -'
WATER BODY | \ Tll.1/,n ./ ,..,!
ASH «£-**-₯-
MIHLINQ
YaiEM ,_«*iia..
MAKt III' *»11 H / ' i
,.' ./ ; . '
i . i ^
T
I WASTE] A
I WATER [ ^.
Ml I A''Ji -v
FIEHEIItNCC: DU 007
Figure A-l. Sources of wastewater in a fossil-fueled steam- eL.rti \i
-------
In the following discussion, each of the wastewater sources
just listed will be described in terms of the potential priority
pollutants which it contains. To the greatest extent possible,
the composition and flow rate of the streams will be characterized.
This review provides a basis for the discussions of treatment
technologies presented in the Sections 4 and 5 of this report.
COOLING WATER SYSTEMS
The primary water user in utility power plants is the
cooling water system. Plants employ either once-through or
recirculating systems in which the cooling water is recycled
and a blowdown stream is drawn off to control water quality.
These systems are described below.
Once-Through Cooling Water
Once-through cooling systems are unique since the total
cooling water flow is discharged as a wastewater effluent. This
cooling water flow rate is approximately 0.1 liters/Kcal of heat
removal for every 10 °C of cooling water temperature rise (12 gal/
1000 Btu of heat removal for every 10°F of cooling water temper-
ature rise). After passing through the condenser, the cooling
water is discharged to a receiving body (i.e., river, lake, pond).
Due to the nature of a once-through system, the chemical
composition of the effluent water is essentially equivalent to
that of the influent water. Water quality parameters such as
total dissolved and suspended solids, pH, etc., should be largely
governed by the characteristics of the cooling water source,
and not by the operation of the cooling system. Slight changes
in the chemical compositions between influent and effluent for
these systems may occur, however, due to (1) formation of cor-
rosion products and/or (2) addition of treatment chemicals.
Water-side corrosion of the main condenser will result in
corrosion products (i.e., metal oxides) appearing in the cooling
water effluent. Condenser metallurgy would normally be selected,
so as to minimize water-side corrosion problems. For this reason,
negligible quantities of corrosion products should appear in the
effluent cooling water (EN-127).
Extensive cooling water treatment is normally precluded in
once-through system due to the large quantities of raw water used.
However, chemical treatment with biocides is often necessary to
control the growths of algae and slime that can accumulate on
condenser surfaces, retard heat transfer, and obstruct cooling
water flow. Chlorine is the most common biocide used. Sodium
hypochlorite is also used extensively in the utility industry.
-76-
-------
.""cclir)'? '.vfactr systems -.ir-r _:crr? jilv .-.'- .--.-. ;;.-.-' '- -
o~ "s.l^g" .l:-c-at-.ia_ T<_ chocs ..">.- /oraci^n :" :u.e t-.-;-.;-. --..-.:
range _jir~~ five'''"'-1- -.C^s *$-, >v/c '.*.-- :-'--:t ""oif. ~ Vi-r -<-?- ~."
^- -5 ' * . - - - s. - - .
iuira'te i Trie r^'jiir'^cv ?f fhlorl"^ i r-; -a -"^er-1 jj.ri rai;~ rr"r. one
to .ten. tlr.es cer "da".' (^"pioa.l'J. r once -er -'P1 ft " ' . v^.1 . .-
per'dav; ;MA-230)f " ,'Lirin? chiorr., acf.cn . t -ee rp-.^v. ^.^' _;) .cr...'ie
is usually r-epc :evrveen j. .. and f'' ^.--.f:-.; < or') :.; -.lie U',n.:2n\-.
seawster, chlorine concentration as ai-^n .-:? 12 iTi.~, ' (".":-Tn5 :^
more "may be used:-to ^in.ibir crustacec.n growth ii-IA-^3G/.
Cooling Tower Blowaown
Recirculating cooling systems employ cooling devices such
as cooling towers, spray ponds/canals, etc., which allow the
reuse of cooling water. These devices promote cooling primarily
by evaporating a portion of the recirculating water flow. For
this reason, dissolved, non-volatile impurities and contaminants
that come into the system with makeup water are concentrated.
A blowdown stream must be withdrawn from these systems to con-
trol the concentrations of impurities and contaminants. This
stream represents the recirculating cooling system wastewater.
Blowdown quantity is set by the maximum concentration of a limi-
ting impurity (i.e., hardness, dissolved solids, suspended solids)
that can be tolerated in the system or by the solubility limit
of scaling salts such as calcium sulfate, calcium carbonate, etc.
The blowdown rate typically ranges between 0.5 and 3.070 of the
recirculating water flow (DQ-051). The recirculating flow re-
quired is about 0.1 £/Kcal of heat removal for every 10°C of
cooling water temperature rise (12 gal/1000 Btu for 10°F).
The blowdown from a recirculating cooling system will have
the same chemical composition as the recirculating water. The
major factors that influence cooling water composition include:
makeup water characteristics,
chemical treatment of the recirculating
cooling water,
intimate contacting of air-water in the
cooling device, and
cycles of concentration.
-77-
-------
Makeup water to recirculating cooling systems replenishes
water lost due to evaporation, entrainment (or drift) and blow-
down. Makeup water brings soluble chemical species such as
sodium (Na+) , potassium (K+;, calcium (Ca++), magnesium (Mg++) ,
chloride (Cl~) , nitrate (NOl") , sulfate (S0i») , and carbon dioxide
(HCOl and CO 3) into the system. The degree of concentration of
these species is governed by the operating characteristics of
the cooling system, such as blowdown, drift, and evaporation
rates. Soluble constituents in makeup water are concentrated
to levels typically ranging from 1,500 to 10,000 mg/£ before
being removed in the blowdown stream (MA-230). The chemical
species contributing to the salinity of the blowdown is primarily
determined by makeup water composition.
Chemical treatment is commonly practiced in recirculating
cooling systems to control corrosion, scaling, and biological
fouling. Table A-l summarizes some of the treatment methods
employed and also presents their impact on the quality of the
blowdown stream.
The intimate contact which occurs between air and water in
the cooling device enables particulate matter and soluble gases
to be scrubbed from the air contacted. In addition, cooling
towers can introduce contaminants into the air. Airborne solids
captured by the cooling water can contribute significantly to
the solids that accumulate in the cooling system. It is esti-
mated that, in dusty regions, up to 80% of the suspended solids
in recirculating systems originally come into the system as air-
borne particulates (GL-028). Upon dissolution, water soluble
particulates will increase the concentrations of dissolved species
in the circulating water as well. Soluble gases give rise to
anionic species in the cooling water. For example, carbon dioxide
(C0.2, nitrogen oxides (NOy) , sulfur oxides (S0x)_yield carbonates
(CO 3 and HC01), nitrates (NOD, and sulfates (SOlT) in the cooling
water, respectively, when these gases are scrubbed from the air.
Leaching of preservatives from treated wood cooling towers
constitutes an additional source of potentially hazardous com-
ponents in cooling water blowdown. Preservatives commonly used
include acid copper chromate (ACC), chromated copper arsenate
(CCA), creosote and pentachlorophenol. The extent of this leach-
ing is not currently known.
Additional potential contaminants which may be present in
some cases include insecticides and herbicides from agricultural
runoff, or phenolic compounds from vegetation decay, most of
which are considered toxic. Chlorine addition to control bio-
logical fouling can result in chlorination of these or other
hydrocarbons entering with the makeup and result in highly un-
desirable reaction products.
-78-
-------
TABLE A-l. CHEMICAL TREATMENT SUMMARY FOR RECIRCULATING COOLING SYSTEMS
Treatunt Objective
ChemKal Additive
Corrosion Inhibition
Chrouca
Zinc
Fhoaphate
Silicates
Fropriacary Organic!
Typical Additive
Concsntratlons In Slowdown
10-50 mg/l as CrO,
8-35 OIR/I as Zn
15-60 alt> (I , . CaCO,. CaSO. ,
etc ) below thi: ^idling Halt (the
('Olnt at which thiy will pruct pi tdtc
frc».n bulntiun) Pu 1 yclccl rul y tc anti-
pl'L-cipl t jnta alluw aupiM saturation uf
the cooling udier with mspcct to
c/lllnr> saltk without precipitation
of these baits oicuiilng Divpersanta
Jo not ii.Mliii »t.ili- pieulpltAti<>n,
but prevent prucipitared salts from
settling dud adhering tu heat transfer
sui taccr.
AY-007
MA-2 JO
Biological Fouling
(algae, slines,
fungi) Control
Hypochlorltc
(hloruphtfnatea
TKlocyanaLvs
OrK«nlc Sulfui
ConipounJs
U 5 Kf.lt resldu.il 1.1.
> JO mg/t ceol.lunl
funtlatIons
Bloildi;b u^cd tu COlllrul biological
f4iulin^: arc eithur the oxidizing t>r
ntm tiKiill^lng ty^ea UxldlzinK blo-
ciilt-a (t.Kli>iine mid hypoch lor 1 (c) havu
Lae.it dlscu^srj tor unce through cooling
Hystems In the "Um-e -Thioup.h Cooling
Water" »ertlun llH'bo blocldes are
used In ret i rcul.ii ing cooling syatums
In a fi.hlon similar to that described
for oni-e -1 liiouRh systems Non-oxidizing
biui idrs (clili>rophenatfs. thlucyanares,
organic bulftir lompounds, etc ) are
enployutl when ulti«T chtiinii-al aduillvcs
such nk organic cnrroalon inhibitors.
sculo L-mttrnl u>;i. or solld» control
agiintb are tlebtroycd by the conventional
oxidizing bluciileb
KN \fl
AY UO?
MA- .! 10
Suspended Solids
Ulspcision
l.lgn Inn
Proprietary Urgmilc
I'ulymars
I'ol yc-lei I rolyl ea/Ni
Illllt I I'L>1 VIIK rk
^U-50 ing/I
I -' »K/I
Lhenlcul dlspi.r-.ai,l.. maintain bila|itnili->l AY till/
uollil-. from stttllriK and adhering to IKJ o<,b
huat tiahbfer hurTact's
-------
BOILER OPERATIONS
The operation of the boiler involves several water streams,
for steam makeup as well as for cleaning heat transfer surfaces.
These systems are described below.
Boiler Slowdown
Power plant boilers are either of a once-through or drum-type
design. Once-through designs are generally employed in high pres-
sure, super-critical boilers and have no wastewater streams dir-
ectly associated with their operation. However, some once-through
boilers operate in the sub-critical pressure range. Drum-type
boilers operate at sub-critical conditions where the steam gener-
ated is in equilibrium with liquid boiler water. Boiler water
impurities are, therefore, concentrated in the liquid phase as
steam is generated in these units. These impurities must ulti-
mately be removed in a liquid blowdown stream, the wastewater
from this system.
The blowdown from drum-type boilers generally contains
soluble inorganic species that occur in natural waters (i.e.,
Na , K+, Cl~, SO , etc.); precipitated solids containing the
calcium/magnesium cation; soluble and insoluble corrosion pro-
ducts or iron, copper, and other metals; plus a variety of
chemical compounds added to the system. Dissolved solids are
present in excess of all other boiler water impurities. The
concentrations of impurities in drum-type boiler blowdown is
largely governed by boiler operating conditions. Table A-2
presents recommended limits of total and suspended solids in
drum-type boilers as a function of drum pressure.
A number of chemical additives may be present in the boiler
blowdown as a result of internal boiler water treatment. Inter-
nal treatment is usually designed to control scale formation and
corrosion. A summary of these internal treatment control prac-
tices is presented in Table A-3.
Scale formation is commonly inhibited by inorganic phosphate
and chelating agent (EDTA and NTA) additives. Phosphates chemi-
cally combine with calcium and magnesium to form a soft sludge
that is easily maintained in the fluid state. Chelating agents
form soluble complexes with calcium as well as other metallic
cations such as iron.
Corrosion, caused by chemical/electrochemical attack of
boiler metal, can be controlled by oxygen scavenging chemical
additives. Sodium sulfite and hydrazine are the oxygen scaven-
gers most commonly employed. Their oxygen scavenging reactions
are described in the following equations.
-80-
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TABLE A-2. RECOMMENDED LIMITS OF TOTAL SOLIDS AND
SUSPENDED SOLIDS IN BOILER WATER FOR
DRUM BOILERS
Limits Recommended for Boiler Feedwater
Below40 to68 to Over
Drum Pressure 40 atm 68 atm 136 atm 136 atm
Total solids, mg/ -L * * 0.15 0.05
Total hardness as
mg/£ CaC03 0 00 0
Iron, mg/fc 0.1 0.05 0.01 0.01
Copper, mg/i 0.05 0.03 0.005 0.002
Oxygen, mg/£ 0.007 0.007 0.007 0.007
pH 8.0-9.5 8.0-9.5 8.5-9.5 8.5-9.5
Organic 0 00 0
*No value reported
Limits Recommended for Total
(Dissolved and Suspended) Solids
Drum Pressure
(atm)
0 -
20.41 -
30.51 -
40.81 -
51.01 -
61.11 -
68.01 -
102.01 -
>136
(psi) Total Solids (mg/O
20.4
30.4
40.8
51.0
61.1
68.0
102.0
136
0
301
451
601
751
901
1001
1501
- 300
- 450
- 600
- 750
- 900
- 1000
- 1500
- 2000
>2000
3500
3000
2500
2000
1500
1250
1000
750
15
SOURCE: BA-185
-81-
-------
TABLE A-3.
CHEMICAL ADDITIVES COMMONLY ASSOCIATED
WITH INTERNAL BOILER TREATMENT
Control
Objective
Candidate Chemical Additives
Residual Concentration
in Boiler Water
Reference
Scale
di- and tri-sodiuin phosphates
Ethylene diaminetetracetic
acid (EDTA)
Nitrilotriacetic acid (NTA)
Alginates
Polyacrylaces
PolymethacryLatea
3-60 mg/l as PO*
20-100 mg/1
10-60 rug/1
up to 50-100 mg/t
up to 50-100 mg/l
up to 50-100 mg/l
BA-185
EN-127, AY-007. BL-036
EN-127, AY-007, BL-036
AY-007, BL-036
AY-007. BL-036
AY-007, BL-036
00
S3
I
Corrosion Sodium sulfite and catalyzed
sodium sulfite
Hydrazine
Morpholine
less than 200 mg/1
5-45 mg/l
5-45 mg/t
MA-230. BL-036
AY-007
AY-007
Sodium hydroxide
Sodium carbonate
Ammonia
Morpholine
Hydrazine
Added to adjust
boiler water pH
to the desired
level, typically
8.0 - 11.0.
EN-127, AY-007. BA-185,
BL-036
Solids
Deposition
Starch
Alginates
Polyacrylamides
Polyacrylates
Polymethacryla tea
Tannins
Lignin derivatives
20-50 mg/l
20-50 mg/l
20-50 mg/l
20-50 mg/l
20-50 mg/l
<200 mg/l
<200 mg/l
AY-007
AY-007
AY-007
AY-007
AY-007
AY-007
AY-007
-------
Na2S03 + %02 -» Na2S04
N2HU + 02 - 2H20 + N2
Since sodium sulfite contributes to the dissolved solids of
boiler water, it is used only in boilers operating below 122 atm
(1800 psi) (BA-185). Hydrazine has volatile reaction products
and does not contribute to the dissolved solids content of boiler
water. It is used exclusively in high pressure boilers.
Boiler water pH control is also a form of corrosion protec-
tion. Alkaline compounds are added to boiler water to maintain
a pH of 8.0 to 11.0. At this pH level acidic species formed in
boiler water will be neutralized before acid corrosion can occur.
Carbon dioxide (C02), the primary cause of acid corrosion, is
formed upon decomposition of carbonates which are present in
boiler water. pH adjustment is made with neutralizing amines
such as cyclohexylamine or other alkaline additives such as
caustic soda, sodium carbonate, or ammonia.
Dispersing agents are designed to inhibit solids ouch as
precipitated scale, sludge, corrosion products, etc., from
settling and adhering to boiler heat transfer surfaces. Tannin
and lignin derivatives are usually used, although a number of
proprietary, synthetic organic dispersants are also available.
The quantity of blowdown water from a modern, high-pressure
boiler ranges from effectively zero to an upper limit of 2.070
of the stream generation rate. The blowdown rate is typically
0.1% (AY-007). Much higher blowdown rates, typically 10%, are
associated with lower-pressure steam generating systems in cases
where the makeup is not demineralized. Boiler blowdown may be
performed in either an intermittent or continuous fashion.
Chemical Cleaning
Operational cleaning of heat transfer surfaces is designed
to remove scale and corrosion products that accumulate on the
boiler*.s water-side and the water-side of the steam condenser.
The frequency at which chemical cleaning is needed varies from
plant to plant. For example, the mean time between boiler
chemical cleaning is approximately 36 n.onths. However, plant
data indicate extreme variations in frequency ranging from once
in 7 months to onco in 100 months (EN-127)
Chemical cleaning is accomplished by Cither soak or circula-
tion methods. The soak method for boiler water-side cleaning in-
volves completely filling the boiler water-side to capacity with
cleaning solution. The solution remains in stagnant contact
with the boiler internals until the desired degree of cleaning
-------
is achieved. The solution circulation method is similar to the
soak method in every respect, except the cleaning solution is
pumped or circulated through the boiler internals. For both
methods, spent cleaning solutions are discharged as a waste
effluent.
The active reagents in cleaning solutions are acidic or
alkaline in nature depending primarily upon the deposits they
are to attack. Ninety percent of all cleaning operations employ
acidic formulations that attack all forms of alkaline scale
(i.e., CaC03, Mg(OH)2, etc.), silica scale, and corrosion depos-
its containing iron. In many cases, these corrosion deposits con-
tain copper and some acid type solvents also incorporate a copper
removing solvent. The majority of these formulations contain
hydrochloric acid in solution strengths ranging from 5.0 to 7.5%
(AY-007). Other acid solutions contain the following constitu-
ents which are present alone or in various combinations (EN-127,
AY-007, BA-185, BE-162) are the following:
Inorganic Acids Organic Acids
Hydrochloric (HC1) Citric fHOC(CH2C02H)2C02H]
Sulfuric (H2SOO Formic (HC02H)
Sulfamic (NH2S03H) Hydroxyacetic (HOCH2C02H)
Phosphoric (HsPOO
Hydrofluoric (HF)
Inorganic acids are used primarily in drum-type boilers
while organic acids are used on drumless, once-through boilers.
Complementary additives employed with acid solutions include
(1) inhibitors to decrease acid attack of bare metal surfaces,
(2) wetting agents to accelerate attack on insoluble organics,
and (3) complexing agents to increase removal of specific depos-
its such as metallic copper.
Alkaline solutions are employed (1) to provide additional
attack of deposits passive to acid attack and (2) to neutralize
acid residuals resulting from acid cleanings. Alkaline solutions
of ammonium sulfate and carbonate are used with oxidizing agents
to remove metallic copper deposits. The oxidizing agents convert
metallic copper to copper oxide (CuO) . The ammonium cation (NH"t)
dissolves CuO to allow removal with the cleaning solution. Com-
mon oxidizing agents used for attacking copper deposits include
bromates, chlorates, persulfates, nitrates, nitrites, or possibly
caustic soda (EN-127). Chelating agents such as EDTA added to
alkaline solutions facilitate removal of iron and calcium depos-
its. Caustic soda combined with special additives also dissolve
rust as well as disperse and emulsify organic deposits (BE-162).
-84-
-------
Alkaline rinses are also commonly used to neutralize or
passivate acid residuals remaining after acid Cleaning. This
rinse solution generally contains caustic sodas C'aOK) or soda
ash (Na2C03) at approximately 1.0% solution strengths (AY-007)
High pressure, once-through boilers are rinsed with ammonia or
hydrazine passivating solutions. Solution strengths are 50 and
500 mg/fi,, respectively (BA-185)
Data for three separate cleaning operations are presented
in Tables A-4 through A-6. The data are for cleaning the steam-
side of a high pressure, once-through boiler and a low pressure,
drum boiler plus the water-side of a main condenser, respectively.
Alkaline and acidic solutions are shown for both cleanings while
only an acidic solution is shown for condenser cleaning.
Spent chemical cleaning solutions can have extreme pH,
high dissolved solids concentrations, and significant oxygen
demands (BOD and/or COD). The pH of spent solutions ranges from
1.0 to 11.0 depending on whether acidic or alkaline cleaning
reagents are employed. The dissolved solids include sodium,
hardness, heavy metals, chloride, bromide, and fluoride. Tables
A-4. through A-6 report only iron and copper concentrations for
heavy metals. However, additional metal constituents may include
nickel, zinc, and aluminum. Heavy metals for combined boiler
cleaning wastes follow the general concentration trend of (EN-127)
iron > copper > nickel > zinc > aluminum
The quantity of cleaning wastes varies directly with liquid
holding volume of equipment to be cleaned (BA-185). For example,
Tables A-4 and A-5 show spent alkaline and acid cleaning solution
quantities as equal to the water-side boiler volume. Rinse solu-
tion quantities are generally one or two times this volume.
-85-
-------
TABLE A-4. OPERATIONAL CLEANING OF A HIGH PRESSURE, ONCE-THROUGH BOILER
00
pH
Acidity, ppm total hot,
as CaC03
Alkalinity, ppm as CaC03
NH3, (%)
Fe , ppm
Cu
BOD
Suspended Solids, ppm
Volume, gal
Temperature,
as drained, °F
Stage 1
11.0
90,000
1
720+
-
500
30.000
100
Stage 1
Rinse
9.0
_
9,000
0.1
75
-
5
60,000
100
Stage 2
2.5-3.0
27,000
(a)
60,000
-
high
100
30,000
200
Stage 2
Rinse
6.0-7.0
low
(2)
600
-
high
5
60,000
200
(l)
(2)
The use of ammonium salts of organic acids raises this number.
Capacity-20,000 gallons; solvent system Stagel, ammonium persulfate solvent;
Stage 2, inhibited 3% organic acid; deposit inventory, 200 Ibs copper as Cu
and 1500 Ibs iron as Fe203.
Source: BE-162
-------
TABLE A-5. OPERATIONAL CLEANING OF A LOW PRESSURE, DRUM BOILER
d)
I
oo
pH
Acidity, ppm total hot
as CaC03
Alkalinity, ppm as CaCOi
NH , (%)
Chloride, ppm
Fe , ppm
Cu, ppm
Bromide, ppm
Suspended Solids, ppm
Volume, gal
Stage 1
11.0
_
90,000
1
-
-
720+
1,500
500
30,000
Stage 1
Rinses
9.0
_
9,000
0.1
-
-
75
150
5
60,000
Stag~ 2
<1.0
70,000
-
0.01
68,000
6,000
75
15
500
30,000
Stage 2
Rinses
7.0-9.0
_
1,000
-
-6,800
600
-
-
100
60,000
Temperature, as
drained,°F
150
150
150
125
''
Capacity, 30,000 gallons; solvent svstem Stage 1, bromate solvent; solvent
system Stage 2, inhibited 570 hydrochloric acid and copper complexing
agent; deposit inventory, 200 Ibs copper as Cu and 1,500 Ibs iron as
Source: BE- 162
-------
TABLE A-6. OPERATIONAL CLEANING,
MAIN CONDENSER WATER-S IDE
pH
Acidity, hot, ppm CaC03
Alkalinity, ppm CaCOa
Ca, Mg, ppm
Fe, ppm total
Cu, dissolved, ppm
Suspended solids , ppm
Temperature, as
drained, °F
Solvent
2.0
30,000
-
5,000
11,000
1,000
2,000+
140
Rinses
7.0-9.0
-
1,000
50
100
50
200
120
^'Capacity - 1000 gallons; solvent system, 10%
sulfamic acid, inhibited, 1% NaCl; Rinse -
Na2C03 + sodium phosphates; depository inven-
tory, 100 Ibs Ca and Mg salts, 100 Ibs Fe203,
10 Ibs copper.
Source: BE-162
-88-
-------
BOILER WATER TREATMENT
Ion Exchange
i *- ~
-------
Spent regenerant solutions contain ions that are eluted
from the ion exchange material plus the excess regenerant that
is not consumed during regeneration. The eluted ions represent
the chemical species that were removed from water during the
service cycle of the process. For example, regeneration of a
hydrogen cycle cation exchange resin will elute such species
as sodium, potassium, calcium, magnesium, etc. Similarly, ions
eluted from anion exchange units will include chloride, nitrate,
bicarbonate, sulfate, carbonate, etc. The distribution of these
species in spent regenerant solutions vary with the quality of
influent water and the efficiency of the ion exchange process.
The excess regenerant required for ion elution varies with
the ion exchange resins employed. Table A-7 presents a summary
of ion exchange material types and the regenerant requirements
of each. With the exception of sodium cycle ion exchange, excess
regenerant creates an effluent of extreme pH. Spent regenerant
from cation exchange units is acidic (low pH). Alkaline (high
pH) regenerants are characteristic of anion exchange units.
The final step in the regeneration process is rinsing spent
regenerant solution from the ion exchange bed. The rinse water
quantity varies with each resin type, but it is typically 8.0 m3
of water per m3 of resin for cationic resins and 10 m3 of water
per m of resin for anionic resins (EN-127). Rinse water quality
characteristics range from those of the spent regenerant solution
to those of treated water.
Evaporation
Evaporation is a demineralization process sometimes used
to treat boiler feedwater whereby raw feedwater is distilled to
produce a pure condensate. Feedwater impurities concentrated
in the evaporator are removed as a waste blowdown stream.
Evaporator blowdown has a high dissolved solids content.
The concentration of the dissolved solids varies with the level
of dissolved salts in the influent water and with the degree of
concentration in the evaporator. The degree of concentration
which can be achieved in the evaporator is limited by the solubil-
ity limits of calcium, magnesium, and other scaling salts. There-
fore, as the scaling potential of influent water increases, the
allowable degree of concentration in the evaporator decreases.
For fresh water applications the blowdown quantity necessary
to maintain acceptable scaling potentials ranges from 10-407,, of
the water charged to the process (AY-007). This corresponds to
maximum TDS of approximately 3000 mg/S,. However, concentrations
on the order of 1000-2000 mg/J, are more commonly observed (EN-127,
AY-007). The distribution of soluble species in the blowdown is
-90-
-------
TABLE A-7. ION EXCHANGE MATERIAL TYPES AND REGENERANT REQUIREMENT
Ion Exchange Material
Description of Operation
Regenerant Solution
Theoretical Amount
Cation Exchange
Sodlua Cycle
Sodluei cycle Ion exchange la uaad as a water
aoftenlng process. Calcium, magneylum, and
otlier divalent cstlonu are exchanged for
more aoluble eodlum catlona, I.e.,
2R -Ma -I- Ca
2R -Na » Mg+
(R )i-Ca + 2 Na
(Hc)i-Mg
2 NaT
10X brine (NaCI.) volution or some
other solution vltli a relatively
high aodlum content aucli as sea
water
Hydrogen Cycle
Weak Acid
Strong Acid
Weak ucld Ion exchange removes cations fton
uaCur In quuntltlea equivalent to the total
alkalinity present In the water. I.e.,
2R -H + Ca(IICO,)2
(R )j-Ca -»- 211,CO,
Strong acid ion exchange removes cations
of all soluble salts In water, I.e.,
HjSO, or IIC1 solutions with acid
strengthu aa low ua 0.5*
U2SO, or IIC1 solutions with acid
BtrengChs renglng from 2.0 - 6.OX
110 -120X
200 - 400X
An Ion Exchange
Weak Base
Weak base Ion exchange removes anlona of
all strong mineral acids (II2SOS, HC1,
UNO), etc.). I.e.,
2R -Oil + HiSOs
A
2HOH
NaOII, Nil»Oil, NajCO, solutions of
variable utrength
120 - 140X
Strong Base
Strong base Ion exchange runuvua anlona
of all aoluble aalta In water, I.e.,
NiiUH Holullona at appioxJmate 4.OX
strength.
150 - 300X
R -HCOi + HOII
A
Sources: ST-13S. DE-079
-------
ASH HANDLING
Ash, a solid byproduct of fuel oil and coal combustion,
appears in a power plant boiler in two distinct forms: bottom
ash and fly ash. Bottom ash must be removed from the boiler in
order to maintain system operability. Fly ash is normally col-
lected in flue gas cleaning equipment. The conveyance of both
bottom ash and fly ash to their ultimate points of disposal con-
stitutes ash handling.
Ash handling systems employ either pneumatic or hydraulic
mechanisms for ash transportation. This section addresses only
the hydraulic (or wet sluicing) systems. The wastewater charac-
teristics for coal ash and oil ash sluicing systems are discussed
in the subsections below.
Coal Ash Sluicing
Coal-fired generating stations require formal ash handling
facilities due to the quantity of ash produced during coal com-
bustion. The ash content of U.S. coals ranges from 6 to 20 wt.%-
The average value is approximately 11 wt. % (EN-127). The dis-
tribution between bottom ash and fly ash is greatly influenced
by boiler furnace design and operating mode. The ash distribu-
tion can affect the water balance for a hydraulic ash handling
system. The chemical differences between fly ash and bottom ash
can also affect sluicing water quality.
Bottom ash generally forms as a fused, clinker-type material
and is removed by wet sluicing. Hydraulic design considerations
dictate the minimum sluice water requirements as 10-18 tons per
ton of bottom ash transported. In actual practice, as high as
165 tons of water per ton of bottom ash are used depending on
such factors as plant design, location, and operating circum-
stances (AY-007). Bottom ash has excellent settling character-
istics; therefore, sluice water will be relatively free of sus-
pended solids if adequate residence time is supplied for sedimen-
tation. The chemical composition of sluice will change from
sluice influent to sluice effluent due to the dissolution of
soluble bottom ash species into water (SC-267, AS-054).
Fly ash is collected ir the dry form by cyclones, fabric
filters, dry electrostatic precipitators, etc., and in a water
slurry by wet scrubbers, wet electrostatic precipitators, etc.
Fly ash collected in either the wet or dry form is commonly
sluiced to ash ponds for sedimentation of the suspended fly ash
solids. Sluice water in the pond may be (1) discharged as a
waste effluent, (2) recycled for additional ash sluicing, or
(3) evaporated where meteorological conditions are favorable.
-92-
-------
The minimum sluice water quantities are set by hydraulic design
considerations. For fly ash, the minimum sluice water require-
ment ranges from 5 to 12.5 tons per ton of fly ash transported.
However, as with bottom ash sluicing, the sluice water require-
ment may be as high as 165 tons per ton of ash (AY-007). Flows
range from 1200 to 40,000 gpd/Mw, while a typical rate for coal
is 10,000 gpd/Mw.
Although fly ash has somewhat poorer settling characteris-
tics than does bottom ash, low turbidities are observed in sluice
effluents if adequate retention time in the ash pond is provided.
Fly ash contains a broad spectrum of soluble inorganic salts
which give rise to sodium, potassium, calcium, magnesium, chlor-
ides, sulfates, etc., in solution. The level of these dissolved
solids in solution may range from a few hundred to many thousand
mg/fc. In addition, varying concentrations of approximately 30
different elements have been detected in both bottom ash and
fly ash sluice water (AS-054). Table A-8 presents ash-pond
effluent analyses for a large coal-fired plant where separate
bottom ash and fly ash ponds are employed.
Sluice water pH is also affected by soluble chemical species
in fly ash. Fly ash from pulverized coal burning units contain
alkaline species such as oxides of sodium, potassium, calcium,
and magnesium (Na20, K20, CaO, and MgO) . Dissolution of these
salts can increase sluice water pH to levels on the order of 10.0
On the other hand, fly ash from cyclone furnaces can yield sluice
water pH as low as 5.5 due to adsorption of acidic species such
as S02, S03, HC1, etc., on fly ash surfaces (AS-054). The type
of coal also influences sluice pH. Western coals generally pro-
duce ashes with high lime content, while eastern coal ashes con-
tain lower levels of alkaline species and, in some cases, higher
chloride levels, resulting in acidic ash pond effluents.
Oil Ash Sluicing
The ash content of fuel oil is significantly lower than that
of coal. For example, the heaviest residual fuel oil is expected
to have an ash content that rarely exceeds 0.2 wt. % (BA-185).
Typically oil ash is on the order of 0.1 to 0.15 wt. % for resi-
dual fuels (EN-127). The quantity of ash produced in an oil-
fired plant is very small, but the settling characteristics of
oil ash are not as favorable as those of coal ash. A typical
flow ash for sluicing oil ash is 2000 gpd/Mw.
Oil ash contains water soluble constituents that dissolve
in sluicing water. These oil ash constituents are presented in
Table A-9. Sodium and vanadium compounds are commonly present.
Also present are oxides and salts of nickel, chromium and iron
plus organometallic compounds and carbon (soot). The soot may
-93-
-------
TABLE A-8. ASH POND EFFLUENT ANALYSES FROM A
LARGE COAL-FIRED PLANT
Parameter
Plow (gp«)
Total alkalinity
(aa CaCO,)
Phen. alkalinity
(u CaCO,)
Conductivity
(mhos/cm)
Total hardness
(aa CaCO,)
pB
Dissolved solids
Suspended solids
AluainuB
aavcmla (as H)
Arsenic
Barium
Sarylliua
Cadaiia
Calclu*
Chloride
CbroBluB
Copper
Cyanide
Iron
Laad
Hacnealusi
Manganese
Mercury
Hlckel
Totel Phosphate (as P)
Selenium
SUlca
Sliver
Sulzatc
Zinc
Mln
3100
-
0
615
195
3.6
141
2
3.6
0.02
<0.005
0.2
<0.01
0.023
94
5
0.012
0.16
<0.01
0.33
<0.01
9.4
0.29
<0.0002
0.06
<0.01
O.001
10
<0.01
240
1.1
Flyash Pond
Ave
6212.5
-
0
810
260.5
4.4
508
62.5
7.19
0.43
0.010
0.25
0.011
0.037
136
7.12
0.067
0.31
<0.01
1.44
0.058
13.99
0.48
0.0003
1.1
0.021
0.0019
12.57
<0.01
357.5
1.51
Bo c too Ash Pond
Max
3300
-
0
1125
520
6.3
820
256
8.8
1.4
0.023
0.4
0.02
0.052
180
14
0.17
0.45
<0.01
6.6
0.2
20
0.63
0.0006
0.13
0.06
0.004
IS
<0. 01
440
2.7
Mln
4500
30
0
210
76
4.1
69
5
0.5
0.04
0.002
<0.10
<0.01
<0.001
23
5
<0.005
<0.01
<0.01
1.7
<0.01
0.3
0.07
O.0002
0.05
O.01
<0.001
6.1
<0.01
41
0.02
Ave
16152
85
0
322
141.5
7.2
167
60
3.49
0.12
0.006
0.15
<0.01
0.0011
40.12
8.38
0.009
0.065
<0.01
5.29
0.016
5.85
0.16
0.0007
O.059
0.081
0.002
7.4
-------
TABLE A-9. INORGANIC CONSTITUENTS OF OIL-ASH
Aluminum Oxide, A1203
Aluminum Sulfate, A12(SOO3
Calcium Oxide, CaO
Calcium Sulfate, CaSOi,
Ferric Oxide, Fe203
Ferric Sulfate, Fe2(SO.»)3
Nickel Oxide, NiO
Nickel Sulfate, NiSO,*
Silicon Dioxide, Si02
Sodium Sulfate, Na2SO.»
Sodium Bisulfate, NaHSO*
Sodium Pyrosulfate, Na2S20?
Sodium Ferric Sulfate, Na3Fe(SOO3
Vanadium Trioxide, V203
Vanadium Tetraoxide, V20i»
Vanadium Pentoxide, V20s
Sodium Metavanadate, Na20»V205(NaV03)
Sodium Pyrovanadate, 2Na20*V2Os
Sodium Orthovanadate, 3Na;0*V205
Sodium Vanadylvanadates, Na20-V20^'V205
5Na20-V20,,-llV205
Source: BA-185
-95-
-------
constitute a source of polynuclear hydrocarbons. The sodium
compounds are highly water soluble. Their dissolution will
significantly contribute to the TDS of oil ash sluice water,
Vanadium is a trace element that is commonly present in heavy
petroleum products although some oil sources are very low in
vanadium. Vanadium and other heavy elements may also appear
in sluice water as the sulfate at low pH. However, the concen-
trations in sluice water are presently undetermined. Suspended
matter will consist of siliceous and carbonaceous particles.
Fly ash recycle in oil-fired boilers has effectively allowed
collection of oil ash in the furnace as bottom ash. Dry bottom
ash can actually be a saleable byproduct depending upon the vana-
dium content of the oil burned. Collection and dry handling of
oil ash can thus eliminate wastewater discharges from oil ash
sluicing operations.
COAL PILE RUNOFF
Coal-fired power stations maintain reserve fuel on the plant
premises in active and/or inactive coal storage piles. Active
coal storage is open and is exposed to all ambient conditions.
Inactive coal piles are commonly sealed with a tar spray or some
other impervious covering which provides protection from the
weather. Runoff from active coal storage piles is of primary
concern in this section.
Precipitation runoff from active coal storage piles commonly
exhibits extreme pH and contains soluble chemical species and
suspended solids. The primary cause of runoff contamination
is a reaction mechanism similar to the one that produces acid
mine drainage. Inorganic sulfur in the coal reacts with mois-
ture and oxygen in air to produce sulfuric acid. Also, organics
may be present in the runoff.
When rainwater seeps into the coal pile, sulfuric acid is
leached from the coal. The pH of the runoff effluent can be as
low as 2-3 units. The acidic nature of this water drives the
dissolution of inorganic salts that are present in the coal.
In addition to a high sulfate anion concentration, the runoff
contains high concentrations of cations such as iron, aluminum,
and manganese. Cadmium, beryllium, nickel, chromium, vanadium,
zinc, and copper have also been reported in trace amounts. Coal
fines and other insoluble material appear in the runoff as sus-
pended solids.
-96-
-------
Table A-10 presents plant data for coal pile runoffs. Coal
type has a great influence on runoff characteristics. For exam-
ple, some coals such as are burned at Plant 5305 have sufficient
alkalinity to neutralize all of the sulfuric acid formed. The
resulting effluent pH in such cases ranges from 6.5 to 7.5. The
higher pH range decreases the solubility of many inorganic salts,
thus affecting runoff effluent quality. The runoff at Plants
1729, 3626, 0107, on the other hand, is very acidic because of
the high-sulfur fuel burned. Other factors causing variations
in the effluent quality besides coal type are coal pile history
and runoff flow rate.
The quantity of runoff effluent is a strong function of coal
pile area and local meteorological conditions. Coal pile area is
primarily determined by generating station size. Power plants
store from 600 to 1,800 cubic meters (0.5 to 1.5 acre-feet) of
coal for each Mw of generating capacity. The storage piles are
typically 8 to 12 meters (25 to 40 feet) in height (AY-007).
This corresponds to a coal storage area of 50 to 225 square meters
(0.013 to 0.060 acres) for each Mw of capacity, depending on pile
height. An annual precipitation rate of one meter (40 inches),
for example, will result in an annual runoff of between 50 and
225 cubic meters (13,000 to 60,000 gallons) per Mw of generating
capacity. The typical runoff rate is 20 to 25 x 10s gallons per
year at most coal-fired generating stations (EN-127, AY-007).
GENERAL PLANT DRAINAGE
General plant drainage refers to liquid that accumulates
in floor and yard drains in the process area of a power plant as
a result of precipitation runoff.
Plant drainage generally contains a high level of suspended
solids consisting of such materials as soil, dust, coal fines,
fly ash, etc., that are entrained in the runoff flow. Any signi-
ficant degree of dissolution of these solids will also add to the
dissolved salts present in the water. The specific characteris-
tics of runoff vary radically from plant to plant and from time
to time for a given plant. The general trend is that highest
impurity levels are observed as initial runoff occurs. Subsequent
runoff is observed to have lower impurity concentrations.
PROCESS SPILLS AND LEAKS
Liquid spills and leaks are commonly associated with over-
filling of storage vessels; tank or pipe ruptures; failure of
valves, pump seals, etc. Waste effluent characteristics resul-
ting from spills and leaks depend upon the type of fluid that
escapes containment. Potential fluids include:
-97-
-------
TABLE A-10. PLANT DATA RELATING TO WATER QUALITY
PARAMETERS FOR COAL PILE RUNOFF
Plant Code
Alkalinity (aj/i)
BOD (ng/i)
COO (mgK)
TS
TDS
TSS
AoDonia
Nitrate
Phosphorous
Turbidity
Acidity
Total Hardness
Sulfate
Chloride
Alvmlnia
Chrooiua
Copper (at/ I)
Iron (m&/i)
XagaesluB (zg/l)
Zinc (mg/l)
Sodium (ng/l)
pB
3-02
6
0
1080
1330
720
610
0
0.3
505
-
130
525
3.6
-
0
1.6
0.168
-
1.6
1260
2.8
3401
0
0
1080
1330
720
610
0
0.3
-
505
-
130
52S
3.6
-
0
1.6
0.168
1.6
1260
2.8
3936
0
10
806
9999
7743
22
1.77
1.9
1.2
-
-
1109
5731 .
431
-
0.37
-
-
«0
2.43
160
3
1825
-
-
85
6000
5800
200
1.35
1.8
-
-
-
1850
861
-
-
0.05
-
0.06
174
0.0006
-
4.4
1726
82
3
1099
3549
247
3302
0.35
2.25
0.23
-
-
133
23
-
-
-
-
-
0.08
-
7.8
1729 3626
-
-
-
-
- 28970
100
-
-
-
-
21700
-
6837 19000
-
1200
15.7
l.S
0.368 4700
-
12.5
-
l.l 2.1
.0107 . 5305
0 21.36
-
-
45000
44050
950
-
-
-
8.37
27810 8.68
-
21920
-
325
0.3
3.4
93000 1.0
-
23
-
2.8 6.7
5305 5305
14.32 36.41
-
-
-
-
-
-
-
-
2.77 6.13
10.25 3.8»
-
-
-
-
-
-
1.05 0.9
-
-
-
6.6 6.6
Source: EN-127
-98-
-------
acid, alkalis, and brine solutions
for ion exchange regenerants as well
as other water treating chemicals
fuel oil, transformer oil, and circuit
breaker oil
water used in plant operation such as
cooling water.
MISCELLANEOUS OPERATIONS
Several miscellaneous sources of wastewater at power plants
are listed below:
laboratory and sampling operations
auxiliary cooling system(s)
water intake screen washings
other
Although the impact of wastewater from these miscellaneous oper-
ations is less significant than those discussed in previous sec-
tions, these sources nevertheless contribute to the total waste-
water problem.
Quantitative data which characterize wastewater from these
miscellaneous sources is limited. The only data available are
for auxiliary cooling systems, which remove heat from mechanical
equipment items such as those listed below:
bearing and/or gland cooling for
pumps, fans, and other rotary
equipment
air compressor water jackets
. generator cooling
Auxiliary cooling systems can be either the once-through or
closed-cycle types.
Once-through auxiliary cooling systems do r.ot usually in-
volve chemical treatment, with the exception of chlorination.
Thus, water quality of the waste is determined by the influent
water to the system. During chlorination of these systems.
residual chlorine levels in the effluent are approximately the
same as presented for condenser cooling systems as presented
-99-
-------
earlier in the sections entitled Once-Through Cooling Water and
Cooling Tower Blowdown. However, the frequency of chlorination
is considerably reduced.
The flow through the once-through auxiliary cooling circuit
ranges from 0.0019 to 0.133 m3/min (0.5 to 35 gpm) per Mw of
rated generating capacity The typical flow is approximately
0.040 mVmin (10 to 11 gpm) (AY-007) . This total flow represents
the wastewater stream for once-through auxiliary cooling.
Wastewater from a closed-cycle auxiliary cooling system is
a blowdown stream. Water in the closed cooling circuit is treated
to control corrosion with inhibitors such as chromates (at levels
up to 250 mg/£) and borates or nitrates (at levels ranging from
500 to 2000 mg/2,). Water pH is maintained between 9.5 and 10 by
addition of caustic soda or soda ash (AY-007). Alternatively,
some plants use stream condensate ammonia and hydrazone in this
cooling circuit (EN-127). The water recirculation rate is typic-
ally 0.091 to 0.095 m3/min (23-25 gpm) per Mw of rated generating
capacity. Blowdown rates vary from zero to 0.0019 m3/day (0-5
gpd) (EN-127, AY-007).
-100-
-------
APPENDIX B
PRELIMINARY SURVEY OF TECHNOLOGIES FOR THE
CONTROL OF PRIORITY POLLUTANTS IN UTILI'lY EFFLUENTS
This appendix presents the results of the preliminary survey
to select technologies for the control of priority pollutants in
the utility industry. The controls were screened to select the
technoloigies that are applicable to the utility industry
Each technology examined is presented in this appendix. The
technologies that were eliminated from farther consideration are
presented in Table B-l along with the reasons for elimination.
The selected control technologies are presented in detail in Sec-
tion 5.
-101-
-------
TABLE B-l. CONTROL TECHNOLOGIES ELIMINATED FROM FURTHER EVALUATION
o
tsi
Technology
Activated Sludge
Aeratpd SliiHRp
Alt Ilildnilnn
AliM I'irr Ipli al Inn and
l^lihim Ma«'t|»l Ion
Mrlm Sill rrr, Iplntlon
(cnpln Fnr«'«rlnn rtn«t
< rln.n Ailnnrpt Inn
(lit*l..il 0. Mm Inn
I MIT ri 1 |i 1 1 iitl mi
IVl p Uel 1 |I|API>MH1
Rlrriradlftlynli
Flritrnlyl |c Onlditloa
Clectroljrl Ir MpJiirttan
Frrrtr rhlnrlile Precipitation
and turhon MHorptlun
fitam Frnrt ItmAt Inn
High rvmlly Slnd|( and
NrulrnlliM Ion
Inn CiichanM
LIT. .Id Wam« InclMrallnn
Cli.-lcal ».!... i Ion
PhntorhcHlral Oiildalion
Shlonlnit and Fli.lallon
Solvvnl Catracilon
SuKldr rn-cl|>ltatlon
llllra(ll(i«lli| «|i|»llr.iMu to ill .(union*.
iHnlynln with rvRiird m ro«t .ippllcatlon.
by tlir utility InJuairjr; thtrtfort*, only
rvvrrnv nnr«nM in u.i*4 (mi A 1 tlerrd .
SlulUr to 11 prtclpltat Ion.
SiNlUr to \\»* prrrlpltatlon.
Alrrtvly in uia m IOM location*.
Already in uaa at *OM location*.
Slnilnr to MM precipitation .
t*rhnolofty .
The evaluation ol the effectIvmi « of tlip rnnl-nl terhnnloRlp. l> tinned upon the low cunrentrallona .ntlrl|inleil In the utility Imlu.try.
-------
ACTIVATED CARBON ADSORPTION
State of Development - Adsorption is currently being used in
varied industrial applications. Several companies market carbon
adsorption processes commercially.
Applications to Date -
General - Used to remove dissolved organics from
waste streams regardless of their origin.
Specific - Applied to upgrading various waste streams
in the following industries:
Detergent manufacturing in New Jersey (removal of
xylene, alcohols, TOC from effluent wastewater)
Oil refining in California and Pennsylvania (removal
of COD from effluent wastewater)
Chemicals manufacturing in Alabama (removal of
phenols, resin intermediates from wastewater)
Resin manufacturing in New York (removal of xylene,
phenols from effluent wastewater)
Herbicide manufacturing in Oregon (removal of
toxic phenols from wastewater)
Coking plants in Pennsylvania (removal of phenols
from ammonical liquor)
Process- Description - Activated carbon adsorption can be used to
remove a variety of organic and some inorganic toxic contaminants
from industrial wastewaters. When the carbon becomes saturated,
it is regenerated and returned to service. Carbon losses during
regeneration are usually 5-10% of the original volume.
Expected Performance - Carbon adsorption has exhibited the fol-
lowing removal efficiencies in various applications (Table B-2).
-103-
-------
TABLE B-2. CARBON ADSORPTION REMOVAL EFFICIENCIES
Contaminant \ Removal Efficiencv Reference
Acrolein 30.6 GI-121
Arsenic (and compounds) 13.0 ES-020
Chlorinated Benzenes Some removal expected MI-265
Chlorinated Phenols Some removal expected MI-265
Cyanides 1.0 VA-127
Mercury 30.0 ES-020
Nickel 32.0 ES-020
Pentachlorophenol Some removal expected MI-265
Phenol 99 VA-127
Zinc 6.0 ES-020
Benzene 95.0 GI-121
Toluene 79.2 GI-121
2,4 Dichlorophenol Some removal expected GI-121
Chromium Some removal expected GI-121
Copper 15 GI-121
Cadium 0 ES-020
Selenium 50 ES-020
Lead Some removal expected ES-020
-104-
-------
Costs - Capital costs
Capital cost (Replacement cost not installed cost) vs
design capacity (1968 dollars).
»
5*
E
<
V
:-^~
LO
X
iL
X..:
U I t*
K3WH c*r«crrv - uto
iM
I i
h
-r
KM JO
Figure B-l. Carbon adsorption capital cost relationship
Source: DA-052
Herbicide manufacturing installed capital cost
. (1971 dollars) (Table B-3) .
-105-
-------
TABLE B-3. CARBON ADSORPTION CAPITAL COSTS
Activated carbon system
2 Adsorber vessels (wooden) $ 13.300
2 Carbon storage vessels 10,400
Recycle water vessel 3,500
Quench tank 500
Pumps and eductors 5,900
Reactivation furnace* 35,400
Afterburner and stack 6,300
Stack gas scrubber 10,000
Dewatering screw 6,900
Piping and misc. material 26,500
Electrical 11,000
Instruments 5,800
Structures and foundations 22,800
Carbon inventory 18,500
Construction labor 31,400
Engineering 21,800
Subtotal $230,000
Neutralization system 40,000
Water collection system 30,000
Total $300,000
*Excluding installation
Source: HE-188
Operating Costs
Coke plant waste effluent (1972 dollars)
(Figures B-2 and B-3 are on next page)
-106-
-------
o
3
O
O
r -
2000 4000 eooo
IBS PHENOL REMOVED PER DAY
8030
Figure B-2. Cost of phenol removal by activated carbon.
t/LB
OPERATING COST BREAKDOWN
FOR GRANULAR CARBON PROCESS
FUEL SOOO BTU/LB CARSON REACTIVATED
*0.7S/10S BTU
STEAM 1 LB ST6AM/LS CARBON
S100/1000LB STEAU
ELECTRICITY 1.1$/KW HR
LABOR
MAKE-UP
CARBON
12 MAN-HOURS/DAY
JBOO/MAN-HOJR
!% LOSS PER CYCLE
30C/LB
NOTE: MAINTENANCE COSTS ARE BETWEEN 3 AND
S PERCENT OF CAPITAL INVESTMENT.
USUALLY THIS COST IS BETV/ESN 0.1 AND
0.24/LB REACTIVATED.
10.000 20.000 30.000 40.000 SO.i.O
LBS/OAY REACTIVATED
Figure B-3.
Source: VA-127
Carbon adsorption reactivation costs
-107-
-------
Water treating plant (1971 dollars)
TABLE B-4. CARBON ADSORPTION PROCESS;
ESTIMATE-10 MILLION GAL/DAY PLANT
Amortization of Capital
$1,860,000; 20 years @ 5%
Operation and Maintenance
Power $ 8.50
Labor 18.00
Maintenance Materials 5.00
Carbon Regeneration
Power, Gas and Water 2.50
Makeup Carbon (10% Loss) 11.00
$/106 Gallons
$41.00
TOTAL = $86.00
Source: EM-019
Other Process Emissions - Activated carbon adsorption does not
generate any polluted effluents. However, the regeneration
process generates a stream containing suspended solids and
potentially contaminated flue gas.
References - ES-020, GI-121, MI-265, VA-127, DA-052, HE-188,
EM-019.
-108-
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ACTIVATED SLUDGE
State of Development - In commercial use.
Applications to Date - Numerous petroleum refineries in the U.S.
use this process currently. It is used as an end-of-pipe treat-
ment system for removing colloidal solids and carbonaceous
wastes. Thus, it primarily controls organic compounds and
suspended solids.
Process Description - Activated sludge procedures are used
extensively for coagulating and removing nonsettleable colloidal
solids, as well as to stabilize organic matter. EPA reports (8)
removal efficiencies of 80-99% for BOD, 50-95% for COD, 60-85%
for suspended solids, 80-99% for oil, 95-99+% for phenol, 33-99%
for ammonia, and 97-100% for sulfides. Thus, a high quality ef-
fluent is obtainable from a properly designed and operated acti-
vated sludge system.
This particular process is an aerobic biological procedure
containing, within a reaction tank, a high concentration of
microorganisms, which is maintained by recycling activated
sludge. Oxygen is supplied to the wastewater in the reaction
tank either by mechanical aerators or a diffused-air system.
Inasmuch as the microorganisms remove the organic materials by
biochemical synthesis and oxidation reactions, the converted
organic matter must be removed by sedimentation, prior to final
discharge.
The main components of the process are the aeration, or
reaction vessel and the sedimentation tank. Sludge removed from
the sedimentation tank is recycled to the aeration vessel to
maintain.the required concentration of microorganisms. Since a
portion of the sludge must be discarded, it is first dewatered
and then used as landfill.
Expected Performance - EPA reports removal efficiencies of
80-99% for BOD, 50-95% for COD, 60-85% for suspended solids,
95-99% for phenol, 33-99% for ammonia, and 97-100% for sulfrdes.
Within the electric utility industry it has potential for remov-
ing organics and trace metals. Therefore, it could be used for
controlling toxic pollutants in every utility effluent stream.
-109-
-------
Costs - The following costs were obtained from EN-487, p. 129-131
Initial investment; $.097/gpd'; $0.75/gpd2; $0.65/gpd3.
Annual Osts - Case 1 2 3
Capital (10%) $0.097 0.075 0.065
Dep. (20%) 0.194 0.150 0.130
Operating 0.078 0.065 0.057
Energy (40% Oper. 0.031 0.026 0.023
Cost) $0.400/gpd $0.316/gpd $0.275/gpd
1 3.12 x 106 gals/day wastewater flow
2 7.6 x 106 gals/day wastewater flow
315.6 x 106 gals/day wastewater flow
Other Process Emissions - Activated sludge systems result in a
solid waste discharge.The sludge which is discharged is first
dewatered and then used as landfill. Incineration offers an
improved method of disposal of the sludge, but its application is
is not widespread.
References - EN-407, BU-215, TE-111, BE-156.
-110-
-------
LAGOONS
State of Development - In commercial use.
Applications to Date - Numerous petroleum refineries in the U.S.
use this process currently.
Process Description - Aerated lagoons operate generally by the
same basic principles as do oxidation ponds. Mechanical-aeration
equipment, associated with aerated lagoons, results in a higher
concentration of bacteria than is present in oxidation ponds.
Consequently, land requirements are less for aerated lagoons than
for oxidation ponds having equal loadings. Retention time is
usually 3-10 d. Removal efficiencies are 75-95% for BOD, 60-85%
for COD, 40-65% for suspended solids, 70-90% for oil, 90-99% for
phenol, and 95-100% for sulfides.
Aeration of the lagoon keeps most of the solids in suspen-
sion. One method of decreasing the suspended solids in the ef-
fluent is to have a sedimentation section in the lagoon, where
the water is calm enough and the residence time is adequate to
allow sedimentation of the solids. Otherwise, it may be neces-
sary to include a settling tank.
Since, like the oxidation pond, an aerated lagoon is sensi-
tive to temperature, in colder climates the performance is ham-
pered during the winter months. Some sources recommend that
solids be returned to the lagoon during the winter to improve
performance, so as to operate the lagoon essentially the same
as the activated sludge process. In a development program, it
is very convenient for the aerated lagoon to be the first step,
so that simply by adding clarifiers, sludge-return pumps, and
additional aeration equipment, the lagoon becomes an activated
sludge system.
Expected Performance - Reported removal efficiencies for aerated
lagoons is 75-79% for BOD, 60-85% for COD. 40-65% for suspended
solids 70-90% for oil, 90-99% for phenol, and 95-100% for sul-
fides.
Costs - Capital cost - $0.20/1000 gpd of wastewater flow.
-Ill-
-------
Other Process Emissions - Aerated lagoons result in a solid
waste discharge of sludge. The sludge is usually dewatered
and then landfilled or incinerated for disposal.
References - EN-407, BU-215, KI-072, BE-156, BE-012, BA-185.
-112-
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AIR ".;-.: IDAHO::
State of Development - Commercially available
Applications to Date - This technique is applied in various
industries.
Process Description - Air is the least expensive and, therefore,
potentially the most desirable oxidizing agent. Phenols are
slowly oxidized by bubbling air through their aqueous solutions.
Indeed, 70-80% of the phenols in normal sewage may be removed
by vigorous aeration with compressed air for 1-2 hours. The
phenols are thus oxidized to slightly soluble polymers which can
be removed by filtration. The oxidation of phenols by this
method is favored in the presence of suspended matter, particu-
larly lime. Industrial phenolic wastes may be aerated in the
presence of powdered coal or iron- or magnesium-containing slag
or ash. These materials appear to exert a catalytic effect on
the air oxidation reaction and, after several hours, the phenol
concentration will be reduced by 80-8570. The initial oxidation
products are believed to react with the monophenols to produce
insoluble materials which are adsorbed by the slag. Soil or
wood charcoal may be used in a similar manner.
In a process described recently, phenolic wastes, at pH
7-11 and 60-70 , are sprayed into the top of a cooling tower
and recycled for a total residence time of 16 hours. Monobasic
phenols are completely oxidized to aliphatic acids and carbon
dioxide. It is not clear whether this system operates by the
direct oxidation of the phenols by air or is, in fact, an example
of biological oxidation using the "oxidation tower" process.
Expected Performance - Air oxidation has exhibited the ability
to remove 80-857o of the phenols in the wastewater.
Cost - The treating costs associated with attaining 80-85% phenol
removal are $.01/lb phenol (not including pretreatment costs).
Other Process Emissions - This process does not generate any
contaminated streams.
References - EI-026
-113-
-------
ALUM PRECIPITATION AND ACTIVATED CARBON ADSORPTION
State of Development - All the unit processes in this control
scheme are commercially available.
Process Description - This control scheme consists of: 1) chem-
ical addition, 2)Settling, 3) filtration, and 4) carbon adsorp-
tion. The primary function of this scheme is to remove heavy
metals from a waste effluent.
Application to Date - This control scheme was investigated by
the Wastewater Research Division of EPA at Cincinnati, Ohio,
and is being proposed for application to several types of
wastewaters.
Expected Performance Highly concentration dependent
TABLE B-5.
REMOVAL EFFICIENCIES FOR ALUM PRECIPITATION
AND ACTIVATED CARBON ADSORPTION
Contaminant
% Removal Efficiency
Concentration
In (mg/Jl) Out (yg/fc)
Chlorinated benzenes
Chlorinated phenols
Cyanides
Mercury
Nickel
Zn
Cr
Cu
Sb
Be
Cd
Pb
Se
Ag
Th
Pentachlorophenol
Phenol
Benzene
Toluene
2 , 4-Dichlorophenol
Some removal expected
Some removal expected
Some removal expected
98.3 0.06 1.0
37.0 0.9 567.0
28
97
98
71
99
56
97
56
99
39
Some removal expected
Some removal expected
Some removal expected
Some removal expected
Some removal expected
-114-
-------
BARIUM SALT PRECIPITATION
State of Development - In commercial use
Applications to Date - Specialized applications such as electro-
plating wastes.
Process Description - Hexavalent chromium can be removed from
waste waters by precipitation as a barium salt. Barium chloride
is added in strictly controlled amounts to effect the formation
of insoluble barium chromate according to the reaction:
BaCl: + NajCrO- -* BaCrO. + 2NaCl
The major disadvantages of these processes are that a toxic
sludge is produced and that the Bad,, must be carefully controlled
as it is a highly toxic chemical.
Expected Performance - The solubility of barium chromate is given
as 4.4x10 -* grams per 100,cc at 28 C. Thus, a residual concen-
tration of about 1 ppm Cr b would be expected due to the solu-
bility of BaCrO..
Costs - No data available
Other Process Emissions - A toxic barium chromate sludge
References - SM-519
-115-
-------
CHEMICAL OXIDATION
State of Development - In commercial use
Applications to Date - A number of the waste components resulting
from mining, milling, and electroplating may be removed or
rendered less harmful by oxidation. Among these are cyanide,
sulfide, ammonia, and a variety of materials presenting high COD
levels.
Process Description - Alkaline chlorination of rinse waters
completely decomposes cyanide at room temperature. The cyanide
radical is converted to carbonate and nitrogen gas according to
the following reaction:
2NaCN + 5C12 + L2NaOH -» N2 + Na2C03 + LONaCl + 6H20
The use of caustic to produce high or alkaline pH also results
in the precipitation of heavy metal hydroxides. Cyanide can
also be destroyed using hypochlorites.
Cyanide is converted to cyanite, CNO, as an intermediate
step in complete oxidation. Among the other oxidants used to
convert cyanide to cyanate is hydrogen peroxide which has been
used in Europe for treating cyanide waste streams from metal
finishing plants. Ammonia may also be removed through oxidation
by ozonation.
Expected Performance - Chemical oxidation can remove cyanides and
phenols to very low residual levels. Chlorine, ozone, and
chlorine dioxide are all capable of removing cyanides and phenols
to below 0.003 mg/H residual concentration. Chemical oxidation
could potentially be applied to the control of cyanides or phenols
in the following utility plant streams: cooling tower blowdown,
metal cleaning wastes, ash pond overflow, coal pile runoff, and
yard drainage.
Costs - Direct chemical costs for alkaline chlorination of cyanide
are given as $1.93/lb of CN based on chlorine to cyanide ratio
of 10:1 and caustic to cyanide ratio of 6:1. Liquid chlorine
is valued at 11.5c/lb and liquid 50% caustic at 13c/lb.
-116-
-------
Energy Requirements - Ozonation is the only chemical oxidation
technique which requires significant energy input.. This require-
ment is approximately 23.15 kW-hrs per kilogram of ozone produced.
This is equivalent to about 20 kW-hrs/day for treating a 100 rpm
stream containing a cyanide/phenol total concentration of 1 mg/ .
Other Process Emissions - The use of alkaline chlorination nearly
always results in sludge formation. The sludge is composed of
the precipitated metal hydroxides and, if lime is used to provide
alkalinity, it also contains calcium carbonate and possibly
calcium sulfate.
References - EN-394. HO-293, RE-165, WI-260, HA-603
-117-
-------
COMPLEX FORMATION AND CARBON ADSORPTION
State of Development - In commercial use.
Applications to Date - Removal of cyanide from electroplating
rinse waters.
Process Description - The addition of ferrous sulfate to cyanide
solutions produces less toxic complexes which precipitate as
sludge. The process produces highly colored solutions and dark
blue sludge. The process is inexpensive where cheap ferrous
sulfate is available. Residual uncomplexed cyanide may be as
high as 5-10 ppm and ferrocyanides in receiving streams may be
decomposed by sunlight to again form cyanides. Polysulfides
can also be used to form rxontoxic sulfocyanates .
Copper sulfate can also be used to complex cyanide at
a pH of 10. In combination with an activated carbon adsorption
column, removal of 99+% of cyanide and all of the copper can be
achieved.
Expected Performance - The formation of ferrocyanides results in
residual cyanide levels of 5-10 ppm and possible regeneration
of cyanide by sunlight decomposition. With carbon adsorption
cyanide and iron levels less than 1 ppm are obtainable.
Costs - For ferrocyanide formation costs are relatively low
if cheap ferrous sulfate is available. With carbon sorption,
operating costs range from $0.16-0.87 per Ib. of cyanide treated
Other Process Emissions - Copper and ferrous cyanide sludges.
References - RE-165
-118-
-------
COPRECIPITATTON
State of Development - In commercial use
Applications to Date Coprecipitation has been used in the
uranium and ferroalloy industries for control of radium and
molybdenum.
Process Description - In this process materials are precipita-
ted indirectly by combining them into particles of another pre-
cipitate. Radium in solution is controlled by the addition of
barium chloride in the presence of excess sulfate. for example,
down to a level of about 1 picogram per liter
Molybdenum may also be removed from mine and mill effluents
by coprecipitation with ferric hydroxide. The formation of
ferric hydroxide is optimum at pH 4.5 and thus the typically
alkaline mill waste streams must be acidified before coprecipi-
tation is effected. A base is then added to neutralize the ef-
fluent prior to discharge.
Expected Performance - Method requires more study before perfor-
mance level in other system could be specified.
Costs - No data available.
Other Process Emissions - Sludge
References - EN-394
-119-
-------
DEEP WELL DISPOSAL
State of Development - In commercial use.
Application to Date - Oil field brines and chemical wastes.
Process Description - Disposal of wastes, especially oil field
brines and chemical wastes, in deep wells is becoming increas-
ingly popular as restrictions on discharging wastes to navigable
waters become tighter. Such wells can be costly, especially when
several are needed and depths are one or two thousand meters. as
sometimes is required. Geologic conditions must be suitable, and
in many parts of the country, deep wells are not practical.
Sand strata at depth, especially those already naturally saline,
are among the most suitable candidates for deep well disposal.
Expected Performance - Technique not commonly used but could
have application in the disposal of effluents from blowdown,
chemical cleaning, floor and yard drainage, plant laboratory,
water treatment, coal ash handling, and coal pile drainage.
Costs - Extremely variable dependent primarily on geologic
conditions.
Other Process Emissions - Potential secondary pollution of
underground water.
References - EN-392, EN-127,
-120-
-------
ELECTRODIALYSIS
State of Development - Commercially available.
Application to Date - Desalination of water.
Process Description - Under the influence of an electric field
the ionic species are transferred through ionic membranes leaving
a desalinared water Some water pretreatment may be required.
:Na
4
- i
' i
+
iCl
Concentrated^ ' ': !
Brine Water ^ '
h re.-^^ Ptodu-, '
- Aa'_-
Figure B--^. F]ow>heet £or --le- r r^.'iialysis .
Expected'Performance - 60-95% TDS removal
Costs - Operating costs 40c-5070/1000 gal of water processed
Energy Requirements - 7-15 kW-hr/1000 gal of water processed
Other Process Emissions - Concentrated brine
References - EN-394, RI-160, Vendor contract (Ionics, Inc.,
Watertown, Massachusetts).
-121-
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ELECTROLYTIC OXIDATION
State of Development - Exists on a laboratory scale, however,
no industrial applications cited.
Applications to Date - No industrial applications cited.
Process Description - An electrolyte, such as sodium chloride,
is added to the wastewater, and, using an anode of platinum,
lead oxide or carbon and an iron or stainless steel cathode, a
potential of 3-4 volts is applied at a current density of 0.5-
0.8 amps/sq. in. Phenol concentrations as high as several g/i
may be effectively reduced with a power consumption of 0.3-0.5
kW-h/g of phenol. During electrolysis, the oxygen formed at the
anode oxidatively degrades the phenol at a rate proportional to
the current density and inversely proportional to the phenol
concentration. During the oxidation reaction, phenols are con-
verted to polyhydroxy benzenes, quinones, and by ring cleavage,
to oxalic and formic acids. Only 6-17% of the phenol is comp-
letely oxidized to carbon dioxide.
Expected Performance - For an initial phenol concentration of
2000 ppm,electrolytic oxidation has achieved a 95% removal
efficiency of phenols.
Costs For an initial phenol concentration of 2000 ppm and a
95% phenol removal efficiency, the treating costs of electroly-
tic oxidation are $1.53-$3.06/lb. phenol.
Other Process Emissions - None
References - EI-026
-122-
-------
ELECTROLYTIC REDUCTION
State of Development - In commercial use.
Applications to Date Electrolytic reduction is currently being
used for the treatment of cooling tower blowdown for chromate
and zinc removal in the chemical processing industry It is
also being applied for silver recovery from photographic indus-
try wastewaters.
Process Description - The electrolytic reduction process uses
iron anodes and cathodes to remove chrome from cooling tower
blowdown. Basically, chromate is removed from the blowdown
stream according to the following reaction:
Cr207~2 + 6Fe(OH)2 + 7H20 -" 2Cr(OH)3 + 6Fe(OH3) + 20H~
The ferrous hydroxide is formed at the cathode. The completed
reaction is followed by the subsequent precipitation of ferric
hydroxide and chromic hydroxide as a complex.
Operationally, the cooling tower blowdown enters an electro-
chemical cell near the top of its outer jacket. The wastewater
flows down through the jacket to the cell bottom and then up
through the center compartment. Here it contacts the electrodes
where the chromate is reduced and then overflows from the cell
top. The pH range of the water must remain between 6 and 9 for
proper operation.
Following reduction, the chromium hydroxide precipitate must
be removed. This may be accomplished by a number of methods in-
cluding lagooning, clarification, or filtration.
Operation of this electrochemical process is continuous ex-
cept for the short-term shutdowns required for replacement of
electrodes and daily acid washes. Electrodes must be replaced
every two to three weeks.
Expected Performance - Electrolytic reduction is potentially
capable of removing chromium and zinc in cooling tower blowdown
from power plants. Chromium can be consistently removed to
below 0.05 ppm and zinc can be removed to 0.10 ppm (DI-150).
-123-
-------
Costs - The installed capital cost for an electrolytic reduction
system for chromate removal to 0.05 mg/£ residual for a 500 gpm
flow rate is about $500,000. The operation and maintenance costs
run about $0.55 per 1000 gallons treated.
Energy Requirements - The power requirements for electrolytic
reduction generally run below 5 kW-hrs per pound of hexavalent
chrome removed. This is equivalent to about 0.36 kW-hrs of en-
ergy per 1000 gallons of water treated (DI-150). This energy
is primarily that used for the electric current to the electrodes
Other Process Emissions - The chromium hydroxide and iron
hydroxide precipitates constitute a secondary process emis-
sions from electrolytic reduction. The precipitate must be
treated for removal by a clarification step prior to discharge.
References - DI-150, PA-120.
-124-
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EVAPORATION POND
State of Development -'In commercial use.
Applications to Date - In present practice, many of the mining
and milling operations in the western and southwestern United
States employ solar evaporation as a principal means of water
treatment. Similarly, some utilities as well as other industries
rely on solar ponds in water management.
Process Description - The solar evaporation of water from a
solution to leave a solid residue is a low cost treatment
technique. Except for solar energy as a means for evaporation,
this method has limited applications. Energy requirements are
very high for non-solar methods and the residues are water sol
uble materials which may present a disposal problem.
Expected Performance - Evaporative losses of water at some
installations may exceed 7,572 cubic meters (2,000,000 gallons)
per year for each 0.4 hectare (1 acre) of evaporative surface;
with adequate surface acreage, this loss may allow for zero-
effluent- discharge operation.
Costs - Costs are low, and energy demands are virtually nil.
Land availability and cost of excavation are major factors in
the applicability of evaporation ponds.
Other Process Emissions - Volatile toxics in effluent streams
may result in secondary air emissions.
References - EN-392, EN-394.
-125-
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FERRIC CHLORIDE PRECIPITATION AND ACTIVATED CARBON
State of Development - All the unit processes in this control
scheme are commercially available.
Application to Date - This control scheme was investigated by
the Wastewater Research Division of EPA at Cincinnati, Ohio, and
is being proposed for application to several types of wastewaters
Process Description - This control scheme consists of: 1) chem-
ical addition, 2) settling, 3) filtration, and 4) carbon adsorp-
tion. The primary function of this scheme is to remove heavy
metals from a waste effluent.
Expected Performance - Highly concentration dependent.
TABLE B-6.
REMOVAL EFFICIENCIES FOR CHLORIDE PRECIPITATION
AND ACTIVATED CARBON
Contaminant
% Removal Efficiency
Concentration
In (mg/Jl) Out
Chlorinated benzenes
Chlorinated phenols
Cyanides
Mercury
Nickel
Pentachlorophenol
Phenol
Benzene
Toluene
2 , 4-Dichlorophenol
Zinc
Chromium
Copper
Antimony
Beryllium
Cadmium
Lead
Selenium
Silver
Thallium
Arsenic
Some removal expected
Some removal expected
98.
99.
37.0
Some removal expected
Some removal expected
Some removal expected
Some removal expected
Some removal expected
94.
99.3
96.0
72.0
98.9
98.6
98.1
80.0
75.0
99.1
45.0
97.1
.05
.05
5.0
5.0
5.0
5.0
.5
.1
5.0
5.0
.1
.05
.5
.6
5.0
1.0
3150.
330.
35.
36.
140.
1.
70.
45.
20.
13.
5.
330.
140.
-126-
-------
Costs -
Chemical Costs (1976 dollars)
Ferric chloride - $5 per 100 pounds (Ref. March
21, 1977, Chem. Mark. Report.)
Settler Costs v!968 dollars) - not installed
1000-
*--1 >-".'' I !,_l:ix:±.
Figure B-5. Primary sedimentation capital cost relationship
Source: DA-052
-127-
-------
Filtration Costs (1968 dollars) - not installed
KXO-
LO
-f-fl
f'.-TT-
m
-tr
" " 7" ' '~ ":"
LO W.O
FLOW - HOC
100.0
Figure B-6. Filtration capital cost relationship
Source: DA-052
-128-
-------
Capital Adsorption Costs (1968 dollars) not
installed
r-'-t-r- -r-^-
o
V
jK
^.^ u__
-:-_L-J+-
-.i-U
i i
Tf
T
y -\
S\- i
tj«a±t
tH-
-.1-.
rn:
;}:->
I U I
I I
1.0
to A
DEilON CAPACITY - U«0
OOJi
Figure B-7. Carbon adsorption capital cost relationship.
Source: DA-052
Other Process Emissions - Sludges and streams contaminated with
suspended solids are generated by this system.
References' - DA-052, CO-576.
-129-
-------
FOAM FRACTIONATION
State of Development - Relatively new development, no industrial
uses sited.
Applications to Date - No specific uses of this process were
cited in the literature.
Process Description - Foam fractionation can be used to remove
phenols from wastewater. This process involves the addition of
a surfactant to the wastewater and then passing air through the
mixture. The air causes the surfactant to bubble and rise to
the surface. Any phenols present in the wastewater are attracted
by phsycial forces to the bubbles and are carried to the surface
where they are skimmed off.
Expected Performance - For an initial phenol concentration of
50 ppm foam fractionation as achieved an 8570 removal efficiency.
Costs - For an initial phenol concentration of 50 ppm and an 8570
removal efficiency, the cost of using foam fraction is $.09/lb.
phenol. (This cost does not include cost of surfactant.)
Other Process Emissions - Aqueous stream that contains suspended
solids and surfactant.
Reference - EI-026.
-130-
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HIGH DENSITY SLUDGE ACID NEUTRALIZATION
State of Development - In commercial use
Application to Date - Neutralization of acid or mine waters.
Process Description - The lime neutralization of acidic and mine
wastewaters results in the formation of sludges which are dif-
ficult to filter and dewater. Ground limestone avoids this
problem but does not result in sufficiently high pH for effec-
tive removal of zinc and cadmium. A process which utilizes
extensive recycle of sludge precipitates allows the attainment
of sludges of much higher density. This allows rapid settling
and eases solid-disposal problems.
Expected Performance - Results should approach those obtained
with lime.Refer to summary sheet for Lime Neutralization and
Precipitat ion.
Costs - No data available.
Other Process Emissions - Sludge
Reference - EN-394
-131-
-------
ION EXCHANGE
State of Development - In commercial use.
Applications to Date - Ion exchange is used in many different
applications today. Among its major uses is for water softening
by Ca*+ and Mg2+ removals. Ion exchange is also being used for
demineralizing water for high-pressure boiler systems and for
chromium recovery from metals plating wastes and cooling tower
blowdown.
Process Description - The ion exchange process is based on the
reversible interchange of ions between a solid and a liquid phase
in which there is no permanent change in the structure of the
solid. Ion exchange materials are the heart of the ion exchange
process. Ion exchange materials have the ability to: 1) sorb
soluble ions from solutions, 2) temporarily hold these sorbed
ions in chemical combination, and 3) release these ions when
treated with a regenerant. The most widely used ion exchange
material are resins of styrene-divinylbenzene copolymers. These
resins contain functional groups which impart the actual ion ex-
change qualities. Sulfonic and carboxylic functional groups are
employed for cation exchange resin. Conventional anion exchange
resins employ amine or ammonium functional groups (ST-135).
The basic ion exchange process is the well-known two-bed
demineralizer. Each bed is contained in a separate pressure
vessel. The first bed consists of a cation exchange resin in
the hydrogen or acid form (R-H), while the second bed consists
of an anion exchange resin in the hydroxyl or base from (R-OH).
The service cycle of operation achieves ion sorption by these
resins. Feedwater is charged to the first resin bed containing
cation exchange material. Feedwater cations are exchanged for
hydrogen, i.e.
R-H + NaCl £ R-Na + HC1
Effluent from the cation exchanger is charged to the second bed
for anion sorption. Feedwater anions are exchanged for hydrox-
ide , i.e.
R-H + HC1 ± R-C1 + HOH
-132-
-------
The hydrogen and hydroxide ions introduced from cation and anion
exchange, respectively, combine to form neutral demineralized
water.
A degasifier is often employed to remove the soluble car-
bon dioxide (C02) in the feedwater. This C02 contributes to
the anion content of the water which must otherwise be removed
by anion exchange. Degasification is performed after cation
exchange and prior to anion exchange, and it proceeds as shown.
H2C03 gasification^ ^ + CQ^^
The quantity of C02 removed by degasification decreases the load
on the anion exchanger by an equivalent amount.
A regeneration cycle is employed to release feedwater ions
sorbed by the exchange resins and to restore these resins to
their original hydrogen and hydroxide forms. Cation exchange
resins are regenerated with an acid - usually sulfuric acid.
Sorbed cations are eluted to the acid regenerant solution in
exchange for hydrogen, i.e.
2(R-Na) + H2SCU t 2(R-H) + Na2S04
Similarly, sorbed anions are eluted by an alkaline regeneration
solution - usually caustic soda - in exchange for hydroxide,
i.e.
R-C1 + NaOH t R-OH + NaCl
Rinse water is used to remove excess regenerant and eluted ions
from each resin bed.
Expected Performance - Ion exchange is capable of removing a
number of toxic pollutants from wastewater. Cadmium has been
reported to be removed to a residual level of 0.001 mg/£, chro-
mium to 0.05 mg/£, copper to 0.03 mg/fc, cyanide to less than
0.1 mg/fc, lead to 0.0015 mg/£, mercury to 0.005 mg/£, nickel to
0 mg/£, selenium to 0.001 mg/A, silver to 0.001 nig/i, and zinc
to 0.40 mg-/£. Phenols reportedly are also capable of being re-
moved effectively by ion exchange treatment.
Costs - The installed capital cost for an ion exchange system
capable of removing hexavalent chromium from a cooling tower
blowdown stream of 500 gpm flow is about $1.7 million. The
operating and maintenance cost for this system is approximately
$0.10 per 1000 gallons treated.
-133-
-------
Those utility plant effluent streams potentially containing
the pollutants removable by ion exchange include cooling tower
blowdovm, ash pond effluent and overflow, chemical cleaning wastes
wastes, coal pile runoff, water pretreatment wastes, yard drain-
age, and boiler blowdown. Therefore, ion exchange could poten-
tially be used to treat those wastes for toxic pollutant control.
Energy Requirements - The energy requirement for ion exchange
treatment is for pumping. The average energy requirements is
approximately 1.1 kW-hrs per 1000 gallons of water treated.
Secondary Process Emissions - The treatment of utility effluent
streams by ion exchange result in resin regeneration wastes.
These wastes contain the pollutants removed from the effluent
stream that is treated. The pollutants are concentrated in the
acidic or basic regeneration solution. The two solutions are
usually combined for neutralization. Further treatment of these
wastes is required prior to their discharge.
References - DI-150, MA-693, PA-120, KI-048, AV-018, ST-135.
-134-
-------
£. "I'JTRA1 IZ.i" "IV I'.?'
Stane oi Devt . winer.t
Application _a:- ??~--: en -- . ~e.f ,-r \~: ." ^ _n .or.
with other c<. ~ . ::_T processor _r
wastewater treating points,
metal plating industry to upgrade waste
effluent streams, and
ore mining and dressing industry.
Process Description - Lime precipitation of heavy metals enjoys
widespread use due to its ease of handling, economy, and effec-
tiveness. The use of other alkaline substance is possible but
lime for neutralization is the best known and studied method.
In typical lime neutralization and precipitation systems
water is discharged to settling ponds to reduce the level of
suspended solids. Lime is delivered as a slurry into the waste-
water stream in the primary or in secondary settling ponds. A
pH level of about 9 is usually needed to remove most heavy metals
A pH of 10-12 may be necessary in some cases. The attached table
illustrates pH levels required.
Expected Performance - Among the metals effectively removed at
basic pH are: As, Cd, Cu, Cr+3, Fe, Mn, Ni, Pb, and Zn. Based
on published sources, industry data, and analysis of samples,
it appears that the concentrations given below may be routinely
and reliably attained by hydroxide precipitation in the ferro-
alloy-ore mining arid milling Indus* rv cEN-394)
-135-
-------
TABLE B-7.
CONCENTRATIONS OF HEAVY METALS
AFTER HYDROXIDE PRECIPITATION
Metal
As
Cd
Cu
Cr+3
Fe
Concentration
(mg/A)
0.05
0.05
0.03
0.05
1.0
Metal
Mn
Ni
Pb
Zn
Concentration
(mg/A)
1.0
0.05
0.10
0.15
70
5.0
4J>
3.0
10
1.0
0.0
J
'
(
(
U
M
4
U
U
U
M
F.2
M
U
u
1
l£
1.7
1
LI
1
UME
NEUTRAUZATION
UMC PflEQPITATlON
Figure B-8. Minimum pH values for complete precipitation
of metal ions as hydroxides.
-136-
-------
?L sme-i t-r _
precipitation ',-oor
n. and
". J001
'i. JL;
0. "0
50. n
1.2
Figure B-9 reflects the experience gained from a zinc plant/lead
smelter. 50
60
*
I
f
* 70
H
is so
90
100 _
I HO
9 11
13
Figure B-9.
Heavy metal precipitation vs. pH for tailing-pond
effluent pH adjustments by lime addition.
-137-
-------
Costs - The costs for treating 545 cu. m/day (100 gpm) of process
wastewaters prior to release to navigable waters by lime and set-
tling are estimated (EN-391) as follows:
Capital Costs (1971 dollars)
Lime and settle treatment plant ($150,000)
Operating Costs ($/year)
Operating and maintenance ($53,200)
Other^Process Emissions - A metal hydroxide sludge is produced
which must be periodically removed from settling ponds.
References - EN-391, EN-392, EN-393, EN-394.
-138-
-------
LIQUID WASTE INCINERATION
State of Development: - In commercial use.
Applications to Date - Liquid waste incineration is used for
chemical plant and refinery cleaning operations when the cleaning
residues are not recovered for economic reasons. Numerous other
applications are found where disposal of liquid organic compounds
is necessary.
Process Description - In order that a liquid waste may be con-
sidered combustible, there are several rules of thumb which
should be used. The waste should be pumpable at ambient temper-
atures or capable of being pumped after heating to some reason-
able temperature level. The liquid must be capable of being
atomized under these conditions. If it cannot be pumped or
atomized, it cannot be burned as a liquid but must be handled
as a sludge or solid. Liquid waste incineration generally in-
volves liquids having viscosities up to approximately 1,000 SSU,
although lower viscosities are desirable.
In order to be considered a combustible liquid waste, the
material must sustain or support combustion in air without the
assistance of an auxiliary fuel. This means that the waste will
generally have a calorific value of 8,000 to 10,000 Btu/lb or
higher. Below this calorific value, the material would not
exhibit properties which would enable it to maintain a stable
flame in a commercial combustor or burner. Materials which fall
into this category (>8,000 Btu/lb) are light solvents (such as
toluene, benzene, acetone, ethyl alcohol) and heavy organic tars
and still bottoms similar to residual fuel oil. The wastes may
be combinations of both, which would give a mixture having an
intermediate viscosity and heating value. These wastes come from
cleaning operations in chemical plants and refineries or are the
residues from distillation processes and are usually not recovered
for economic reasons.
The equipment which is used to incinerate combustible liquid
waste can also vary from manufacturer, but its basic form will be
that of a combustor or burner designed to handle a liquid waste
through a steam, air, or mechanical atomizing nozzle High heat
release combustors require minimal secondary incineration chambers ,
but usually incineration is carried out in combustion chambers
-139-
-------
having volumes which provide for a heat release of 25,000 Btu/hr-
cu. ft. of combustion volume. Residence times within an inciner-
ator burning liquid waste will vary from 0.5 to 1 sec. The com-
bustion chamber is usually cylindrical in shape and may be used
in a vertical or horizontal arrangement. The vertical chamber
has the advantage that the incinerator acts as its own stack,
but obviously it is not well adapted to a tall stack arrangement.
Horizontal incinerators can be more easily connected to tall
chimneys or stacks. Some specially designed rotary kilns have
been applied to the disposal of liquid chemical warfare agents.
Expected Performance - Incineration of the liquid cleaning wastes
from utility equipment would result in effectively 100% removal
by disposal of the organics before they are discharged to the
plant sewer system.
Costs - H.F. Lund reports the equipment cost for incinerators
handling combustible liquid wastes to be about $200-350 per
gallon/hr capacity.
Other Process Emissions - If the waste stream contains inorganic
salts,halogen compounds, or sulfur compounds an air pollution
problem will result. Incinerator ash constitutes a small solid
waste stream.
References - AZ-009, LU-013, OT-029.
-140-
-------
CHEMICAL REDUCTION
State of Development - In commercial use
Applications^ to Date - Chemical reduction is commonly used to
remove chromium by reduction of hexavalent chromium to the
trivalent ion. Trivalent chromium is then removed by chemical
precipitation. Variations of processes to reduce hexavalent
chromium find use in metal finishing, electroplating and utility
industries .
Process Description - The chemical reduction of hexavalent
chromium is carried out by adjusting the pH to about 3 followed
by the addition of a reducing agent such as sulfur dioxide. The
trivalent chromium produced is then precipitated by lime addition
at a pH of about 9 .
Typical chemical reactions are :
2H2CrO,( + 3S02 -» Cr2 (SOO 3 + 2H20
Cr2 (SCU) 3 + 3Na2C03 + 2H20 -» Cr2 (OH) uCOa^ + 3Na2SC\ + 2C02 '
+ 3Na2S20,, + Na2C03 + 2H20 -> Cr2 (OH) MC03+ + 6Na2S03
The reduction of Cr+6 with S02 can be carried out on highly con-
centrated streams and is operated at low pH. The reactions with
sodium carbonate and sodium hydrosulfite result in both neutral-
ization and reduction. The treatment levels for use of S02 with
chromium plating and etching wastes is 1,000-2.500 mg S02/H and
for sodium carbonate - sodium hydrosulfite is 200-500 mg
Na2S20,,/2. and sufficient Na2C03 to provide a pH of about 8.
zero"
Expected Performance - Reported effluent levels vary from+"
to 1 mg/£. Typical results for chromium are 0.02 mg/£ Cr s and
0.01 mg/£ Cr+3. The neutralization of streams after hexavalent
chromium reduction will result in the precipitation of Sn, Fe,
Al, Pb, Cu, Zn, Ni, Cd, Mn, etc. The effectiveness of neutral-
ization on removal of metals as hydroxides is pH dependent.
Costs - The use of bisulfite as the reducing agent and caustic
soda to adjust pH costs about $0.50 per pound of chromium assum-
ing 6.5c/lb of caustic and 11.5
-------
Other Process Emissions - If the chemical reduction step is
followed by neutralization or alkaline pH adjustment, a metal
hydroxide sludge will result.
References - WI-260, SM-159, EN-127, EN-394.
-142-
-------
PHOTOCHEMICAL OXIDATION
State of Development - Presently only a laboratory experiment.
Application to Date - No industrial applications for this process
are known.
Process Description - Phenol solutions which are exposed to light
will also degrade by an oxidative mechanism. Exposure to sunlight
or aritficial light leads to the consumption of oxygen and the
conversion of the phenol to low molecular weight acids, carbon
dioxide and water. Similarly, flash photolysis of phenol solu-
tions will lead to their oxidative degradation by a free radical
mechanism.
Expected Performance - For an initial phenol concentration of
5400 ppm,photochemical oxidation has attained a phenol removal
efficiency of 70%.
Costs - For an initial phenol concentration of 5400 ppm and a
7070 removal efficiency, the treating costs of photochemical
oxidation are $0.22-0.26/lb phenol (not including pretreatment
costs).
Other Process Emissions - None are expected.
Reference - El-026
-143-
-------
REVERSE OSMOSIS
State of Development - Commercially available.
Application to Date - Limited use in the electric utility
industry.
Process Description - Desalination of water is accomplished by
pumping through a membrane at high pressure (~400 psi). Pre-
treatment of the inlet water is required.
Pretreatment
( \
y
RO
I
Purified
H20
PPT
Concentrated
Dissolved
Solids
Figure B-10. Flowsheet for reverse osmosis.
Expected Performance - >90% removal for dissolved solids
>95% organics
Costs - Capital costs $l/gal/day. 0/M costs (including membrane
replacement) = $0.75/1000 gal.
Energy Requirements - Pumping costs
Other Process Emissions - PPT from pretreatment, concentrated
dissolved solids stream from RO section
References - Vendor contract - Hydranautics
-144-
-------
SKIMMING AND FLOTATION
State of Development - In commercial use
Application to Date - Removal of oil from wastewater
Process Description - Oil is generally removed from wastewater
by passing the water through a lagoon or through a series of
inverted weirs; the oil floats to the top and is skimmed off
Granular absorbents may be used to assist in the collection and
removal of the oil. Air flotation can also be used to aid in
the agglomeration and separation of the oil phase.
Expected Performance Removal of oil to form an oil concentrate
Specific residual level not known.
Costs - No data available.
Other Process Emissions - Oil concentrate
References - EN-392
-145-
-------
SOLVENT EXTRACTION
State of Development - Developmental
Applications to Date - Solvent extraction has not been applied
to wastewater treatment on a commercial scale. It is used pri-
marily for separating mixtures of liquids. In the petroleum
refining-petrochemical industries solvent extractions is used in
numerous processing steps and in the minerals processing industry
it is used for the separation of uranium from vanadium in ore-
leach liquors. Currently, few extraction processes involve sep-
aration from water, and almost none involve water as the major
phase.
Process Description - Fundamentally, solvent (liquid) extraction
involves the separation of components of a solution. The separ-
ation requires that the components have different relative solu-
bilities in two immiscible, or only partially miscible liquid
solvents.
The extraction is accomplished by passing two phases counter-
current to each other. This is done on a multistage contactor
which may be considered to be divided into two parts, the extrac-
tion section and the scrubbing section. The aqueous or original
solution is usually fed into the contactor near its middle. The
solvent is introduced at one end of the extraction section through
which it flows countercurrent to the aqueous feed. The extraction
section is so-called since it is here the desired component of
the aqueous feed (the solute) is extracted. The purpose of the
scrubbing section is to provide a means to wash the solvent leav-
ing the extraction section to remove any undesirable solutes.
After the solvent has exited the contactor the final process
step involves separating the solute from the solvent. The regen-
eration depends upon whether the original extraction involved
interaction between the solvent and solutes or whether the extrac-
tion depended only on physical effects. In the latter case, dis-
tillation is by far the most common means of regeneration. In
the other case, regeneration involves reversal of the solvent/
solute interaction which is usually done by chemical conditioning.
Expected Performance - No data were found discussing the removal
effectiveness of solvent extraction for toxic pollutant control.
-146-
-------
Costs - No economic information was found on solvent extraction
applied to wastewater treatment.
Energy Requirements - No information.
Other Process Emissions - Intimate contact between the solvent
and wastewater stream being treated could result in carryover
of some of the solvent in the wastewater discharge. Further
treatment would then be necessary for solvent removal.
References - MA-246
-147-
-------
SULFIDE PRECIPITATION FOR REMOVAL OF HEAVY METALS
State of Development - This process is commercially available
and used.
Application to Date - This process has been used to control
mining and milling wastewaters.
Process Description - This process accomplishes more complete
removal of heavy metals than the use of hydroxide for precipita-
tion. The treatment of wastewater with either sodium sulfide or
H2S can effectively remove Cd, Cu, Co, Fe, Hg, Mn, Ni, Pb, Zn,
and other metals. On the whole, this process removes both heavy
metals and some sulfur from waste streams but requires some
energy expenditure (it involves an energy loss in the partial
oxidation of carbon).
In practice, this technique can only be applied when the
pH is sufficiently high (>8) to assure generation of sulfide ion
rather than bisulfide or H2S. Because of the toxicity of the
sulfide ion and H2S, the case of this process may require both
pre- and post-treatment and close control of reagent additions.
Pretreatment involves raising the pH of the waste stream to mini-
mize the evolution of H2S.
Expected Performance - The following control effectiveness was
exhibited in a chlor-alkali plant:
Removal Range Avg. Removal
Hg 87-99% 97%
Comment: Hg present in cone. 10-100 ppm.
For use in the utility industry, this control process should
be suitable for application to:
and pond effluent,
cooling tower blowdown, and
yard drainage.
-148-
-------
Costs - For chlor-alkali plant:
Cap. cost = $143,000
Oper. cost = SOc/1000 gal.
Other Process Emissions - A metal-sulfide sludge is produced by
this process.
References - EN-391, EN-394.
-149-
-------
ULTRAFILTRATION
State of Development - In commercial use in the petrochemical,
refining and mining industries.
Applications to Date - Ultrafiltration has been applied on a sig
significant commercial scale to the removal of oil from oil
emulsion, yielding a highly purified water effluent and an oil
residue sufficiently concentrated to allow reuse, reclamation,
or combustion.
Process Description - This process is similar to reverse osmosis
in that pressure is used to force water through semi-permeable
membranes. Ultrafiltration retains materials of 500 or greater
molecular weight. Pressures of 259 to 517 cm of Hg are generally
used.
Equipment is readily available, and present-day membranes
are tolerant of a broad pH range. Use of Ultrafiltration in
mining and milling may provide a means for removing high levels
of oils used in flotation.
Expected Performance - Retain materials of molecular weight of
500 or greater.
Costs - No data available.
Other Process Emissions - Oil or concentrated residue.
References - EN-394.
-150-
-------
ULTRASONIC OXIDATION
State of Development - Presently experimental -
Applications to Date - Since this process is experimental, the
practical aspects o? this process have not yet been exploited.
Process Description - When phenol solutions are subjected to an
ultrasonic field in the range 800-1000 kc/sec for up to two
hours, the phenol is oxidized in turn to hydroxylated interme-
diates, quinones, aliphatic acids and carbon dioxide. The rate
of oxidation increases with the intensity of the ultrasonic field
and is practically independent of pH in the range 3-9.
Expected Performance - For an initial phenol concentration of
50 ppm, ultrasonic has exhibited a 10070 removal efficiency.
Costs - No treating cost information is available.
Other Process Emissions - None are expected.
Reference - EI-026.
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ZERO DISCHARGE
State of Development - Components are all commercially available.
Applications to Date - Several power plants have implemented
this technology.
Process Description - No water discharges from the power plant.
Water reuse/recycle management combined and/or water purification
step can be used to eliminate water discharges.
Flow Sheet - There are various site-specific flow schemes for
implementing zero discharge. Detailed flow diagrams for the
major methods of obtaining zero discharge are listed in the
detailed analysis of zero discharge.
Expected Performance - Complete recycle of liquid.
Costs - For a zero discharge system using a brine concentrator:
Capital investment - $10/gpd
0/M - $2.00/1000 gal
Energy Requirements - Dependent upon which type system used.
References - EN-127, RI-160.
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TECHNICAL REPORT DATA
iPlcase read Inuncnuns an ;/K m^nc S./VY a
- .
EPA-600/7-78-090
i. TITLE AND SL3TITLE
Assessment of Technology for Control of Toxic
Effluents from the Electric Utility Industry
5 PE>=CRT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
7 AUTHORlS)
J.D.Colley. C.A.Muela, M.L.Owen, N. P.Meserole
J. B. Riggs, and J. C. Terry
8. PERFORMING ORGANIZATION REPORT \o
9 PERFORMING ORGANIZATION NAME AMD ADDRESS
Radian Corporation
8500 Shoal Creek Boulevard
Austin, Texas 78766
10. PRC GRAM cLEMENT NO.
E HE 62 4 A
11. CONTRACT GRANT NO.
68-02-2608, Task 9
12. SPCNSOS;\G AGENCY NAME AND ADDRESS
EPA. Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PEHICO COVERED
Task Final: 4-12/77
14. SPONSORING AGE\CY COCE
EPA/600/13
is.SUFPLEVENTARYNOTESffiRL-RTP project officer is Julian W. Jones, Mail Drop 61. 919/
541-2489.
is. ABSTRACT The report assesses the applicability of control technologies for reducing
priority pollutants in effluents from the steam-electric power generating industry.
It surveys control technologies, identifying those that have demonstrated some con-
trol effectiveness for priority pollutants. From the preliminary survey. the control
technologies most applicable to the utility industry were identified. The selected
control technologies were evaluated to determine their effectiveness in reducing
priority pollutants in utility streams and their associated costs.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/'OPEN ENDED TERMS
c. COSATI I lulu Group
Pollution
Effluents
Toxic ity
Assessments
Electric Utilities
Pollution Control
Stationary Sources
13B
06T
14B
19. SECURITY CLASS iTlia Report:
Unclassified
21. .NO. Or P.
163
Unlimited
20. SECURITY CLASS (Tills pajet
Unclassified
22 PRICE
EPA Form 2220-1 ,9-73)
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