-------
Membrane flux is normally dependent on operating pressure,
temperature, fluid velocity, solids concentration (both total
dissolved solids and total suspended solids), membrane permea-
bility, membrane thickness, and fluid viscosity. Membrane
flux is also affected by th§ surface tension of the solution
being processed. With a fixed geometry, membrane flux will
increase as the fluid velocity is increased in the system.
This increase in fluid velocity will require greater capacity
and more horsepower. Less membrane area is, therefore,
required per unit of effluent to be treated with higher fluid
velocities; membrane replacement and initial capital costs
decrease. Opposing these cost decreases is the increase in
power and its resultant cost, and the fact that these operating
conditions may decrease membrane life, resulting in higher
maintenance costs. ;
Application
Ultrafiltration is employed in metal finishing plants for the
separation of oils, toxic organics, and residual solids. The
major applications of ultrafiltration in the metal finishing
industries have been to electropainting wastes and oily waste-
waters. Successful commercial use has been proven for the
removal of emulsified oils from wastewater1 and for recovery of
rinse water and detergent solutions in phosphate washers.
Recovery operations are common because of the increasing value
of oils, but ultrafiltration is used for end-of-pipe treatment
in industrial plants.
Ultrafiltration is a proven technique for the removal of oily
or paint contaminated wastes from the procpss.waste streams.
This permits reuse of both the permeate and concentrate. With
segregated oily wastes, the concentrate is, essentially the
recovered oils and application of ultVafiltration for this
purpose is increasing. Ultrafiltration of; the waste from
electropainting (electrocoating) provides an excellent example
of this process. Car manufacturers and mapiy other U.S.
companies use electropainting for priming purposes. In this
application, the ultrafiltration unit splits the electro-
painting rinse water circulating through the unit into a
permeate stream and paint concentrate stream. The permeate is
reused for rinsing, and the concentrate is returned to the
electropainting bath.
Bleeding a small amount of the ultrafiltrate, which contains
low suspended solids and generally two or three percent of
organic solids, to the waste system enables ionic contaminants
to be removed from the paint itself. Situations where tanks
of 150,000 to 190,000 liters (40,000 to 50>00'0gallons')" of
paint were periodically dumped because of contamination have
now been eliminated by using ultrafiltration, thus reducing
effluent problems arising from this dumping process.
VII-194
iliS";!!,,;; it, i!1""' i"'-:1'
-------
The permeate or effluent from the ultrafiltration unit is
normally of a quality that can be reused in industrial applica-
tions or discharged directly.
Ultrafiltration is sometimes an attractive alternative to
chemical treatment because of lower capital equipment,
installation, and operating costs with a very high oil removal
efficiency. Little, if any, pretreatment is required and
because of its compact equipment, it utilizes only a small
amount of floor space.
A limitation of ultrafiltration for treatment of process
effluents is its narrow temperature range (18°C to 70°C) for
satisfactory operation. Membrane life is decreased with
higher temperatures, but flux increases at elevated temperatures.
Therefore, surface area requirements are a function of temperature
and become a tradeoff between initial costs and replacement
costs for the membrane. In addition, ultrafiltration is limited •
in its ability to handle strong oxidizing agents, some solvents,
and other organic compounds which can cause dissolution of the
membrane.
The reliability of an ultrafiltration system is dependent on
the application of proper filtration to incoming waste streams
to prevent membrane damage. The tubular membrane configuration
does not require prefiltration. A limited amount of regular
maintenance is required for the pumping system. In addition,
membranes must be periodically changed.
Ultrafiltration is used primarily for recovery of solids and
liquids. It therefore eliminates solid waste problems when
the solids (e.g., paint solids) can be recycled to the process.
Otherwise, the stream containing solids must be treated by
additional erid-rof-pipe equipment.
Demonstration Status
The ultrafiltration process is well developed and is commercially
available for the treatment of wastewater or the recovery of
certain liquid and solid constituents. Ultrafiltration is
used at 20 plants in the present Metal Finishing Category data
base and these are identified in Table 7-70.
TABLE 7-70
METAL FINISHING PLANTS EMPLOYING ULTRAFILTRATION
06062
06071
06102
12065
12074
13041
13324
15193
19462
23076
2.5010
f30100
30516
31022
31032
33092
33617
36074
38217
44048
VII-195
-------
Segregated Oil;
to Option 1
Waste Treatment System Performance - Alternative
The raw waste and effluent concentrations of oils and toxic
organics for streams entering into and discharged from ultra-
filtration systems in the data base are displayed in Tables
7-71 and 7-72. The performance (removal efficiency) of these
ultrafiltration systems is tabulated for oil removal and for
the removal of toxic organics. Removal performance was
calculated by computing the percentage of oil removal at each
plant using ultrafiltration and then finding the mean of the
individual performances. For both oils and toxic organics,
the removal performance was calculated by the following
formula: !
Removal Efficiency =
(raw waste - effluent)100
raw waste
TABLE 7-71
ULTRAPILTRATION PERFORMANCE DATA FOR OIL & GREASE REMOVAL
Plant Oil & Grease Concentration (mg/1)
ID
13041
13041
13041
13324
15193
19462
19462
30516
38217
38217
In
95.0
1,540.
38,180.
31,000.
1,380.
3,702
1,102
7,500
360
70.0
Mean
Out ;
22.0
52.0
267. i
21.4 !
39.0 i
167. !
195.
640. ;
18.0 i
10.0
Removal Efficiency
TABLE 7-72
ULTRAFILTRATION PERFORMANCE DATA FOR TOTAL
Plant
ID
13041
13324
15193
19462
19462
30516
TTO Concentration (mg/1)
In
1037
12.0
802.
1425.
853.
57.4
Out \
l-
14.8 ;
1.48
§0.0
233.
202. :
4.54 '.
j
Mean Removal Efficiency
\-
i
VII-196
Removal
Efficiency ( % )
76.8
96.6
99.3
99.9
97.2
95.2
* 82.3
91.5
95.0
85.7
92.0%
TOXIC ORGANICS
Removal
Efficiency (%)
98.6
87.7
89.9
83.7
76.3
92.1
88.0%
•
-------
SEGREGATED OILY WASTE TREATMENT SYSTEM - POLISHING TECHNIQUES
The Option 1 treatment system for segregated oily wastes which
includes polishing techniques is illustrated in Figure 7-65.
As shown, the system is comprised of the components that make up
the Option 1 oily waste treatment system (or its alternative)
with the addition of a final polishing component. Two possi-
bilities for this polishing process are reverse osmosis and
carbon adsorption. A reverse osmosis unit or a carbon adsorp-
tion unit will remove additional oils and toxic organics
not removed by the Option 1 system. In both the case of '
reverse osmosis and carbon adsorption, heavy loadings of
oil will render the unit ineffective. Oil can plug the
membrane of a reverse osmosis system or foul a carbon adsorption
system. As with the Option 1 system, the effluent from the
polishing waste treatment components is directed to the solids
removal components of the metal waste treatment system, to reuse
or discharge as applicable.
The following paragraphs describe reverse osmosis and carbon
adsorption techniques that are applicable for the treatment of
segregated oily wastes for polishing.
Reverse Osmosis ,
Reverse osmosis, which is explained in detail in Section
XIII, "Innovative Treatment Technologies", is the process of
applying a pressure to a concentrated solution and forcing a
permeate through a semipermeable membrane into a dilute solution.
This principle has found use in treating oily wastes. In terms of
oily wastewater, reverse osmosis is used primarily as a polishing
mechanism to remove oils and metals that are still remaining
after treatment such as emulsion breaking or ultrafiltration*
Examples of reverse osmosis performance are shown in Table 7-73.
TABLE 7-73
REVERSE OSMOSIS PERFORMANCE (mg/1)
30166
3B040
Day 1
38040
Day 2
Parameter
Oil&Grease
TOC
BOD
TSS
Iron
TTO
Influent Effluent Influent Effluent Influent Effluent
117.
371.
183.
9.,6
1.46
8.5
78.
60.
1.2
0.55
10.6
139.
60.
37.
1.91
4.30
4.1
94.
58.
14.
.182
1.04
129.
116.
27.
13.
1.94
41.
108.
53.
1.0
.22
VII-197
-------
Oily Wastes-
Oily Wastes-
Segregated
Oily Wastes
I
Option 1
Emulsion Breaking
And
Skimming
(or Ultrafiltration
Alternative)
Reverse Osmosis
or i
Carbon Adsorption
I
To Metals/Solids Removal,
or Discharge as Applicable
I,;,ii i.i. i, r,:,!,!1!!'".' ii .ill,! h'ii, :i ••. i1 iii. i;;., mi, 'MSI' ,i ,:,!' .'.vs •» a *:t.'iwi:" 'tis an I
FIGURE 7-65
I , , ,,
TREATMENT OF SEGREGATED OILY WASTES
POLISHING TECHNIQUES
VII-198
-------
Carbon Adsorption*
Carbon adsorption in industrial wastewater treatment involves
passing the wastewater through a chamber containing activated
carbon. The use of activated carbon has been proven to be
applicable for removal of dissolved organics from water and
wastewater. In fact, it is one of the most efficient organic
removal processes available. This process is reversible, thus
allowing activated carbon to be regenerated and reused by the
application of heat and steam.
The term activated carbon applies to any amorphous form of
carbon that has been specially treated to give high adsorption
capacities. Typical raw materials include coal, wood, coconut
shells, petroleum base residues and char from sewage sludge
pyrolysis. A carefully controlled process of dehydration,
carbonization, and oxidation yields a product which is called
activated carbon. This material has a high capacity for
adsorption, 500-1500 square meters/gram, resulting from a
large number of internal pores. Pore sizes generally range
from 10-100 angstroms in radius.
Activated carbon removes organic contaminants from water by
the process of adsorption, or the attraction and accumulation
of,one substance on the surface of another. Activated carbon
has a preference for organic compounds and, because of this
selectivity, is particularly effective in removing organic
compounds from aqueous solutions.
Some important but general rules based on considerations
relating to carbon adsorption capacity are:
Higher surface area will give a greater adsorption capacity,
Larger.pore sizes will give a greater adsorption capacity
for large molecules.
Adsorptivity increases as the solubility of the solute
decreases. For hydrocarbons, adsorption increases with
molecular weight.
Adsorption capacity will decrease with increasing
temperature.
For solutes with ionizable groups, maximum adsorption
will be achieved at a pH corresponding to the minimum
ionization.
The rate of.adsorption is also an important consideration.
For example, while capacity is increased with the adsorption
of higher molecular weight hydrocarbons, the rate of adsorp-
tion is decreased. Similarly, while temperature increases will
decrease the capacity, they may increase the rate of removal
of solute from solution.
VII-199
-------
1
Carbon adsorption requires pretreatment to remove* excess
suspended solids, oils, and greases. Suspended solids in the
influent should be less than 50 ppm to minimize backwash
requirements; a downflow carbon bed can handle much higher
levels (up to 2000 ppm), but frequent backwashing is required.
Backwashing more than two or three times a day is not desirable;
at 50 ppm suspended solids, one backwash will suffice. Oil
and grease should be less than about 10 ppm. A high level of
dissolved inorganic material in the effluent may cause problems
with thermal carbon reactivation (i.e., scaling and loss of
activity) unless appropriate preventive steps are taken; such
steps might include pH control, softening, or the use of an
acid waste on the carbon prior to reactivation.
Activated carbon is available in both powdered and granular
form. The equipment necessary for a granular activated carbon
adsorption treatment system consists of the following: a
preliminary clarification or filtration unit to remove the
bulk of suspended solids; two or three adsorption columns
packed with activated carbon similar to the one shown in
Figure 7-66; a holding tank located between the adsorbers; and
liquid transfer pumps. Unless a reactivation service is
utilized, a furnace and associated quench tanks, spent carbon
tank, and reactivated carbon tank are necessary for reactiva-
tion.
Powdered carbon is less expensive per unit weight than granular
carbon and may have slightly higher adsorption capacity but it
does have some drawbacks. For example, it is more difficult
to regenerate; it is more difficult to handle (settling characteris-
tics may be poor); and larger amounts may be required than for
granular systems in order to obtain good contact. One innova-
tive powdered carbon system uses wet oxidation for regeneration
instead of fluidized bed incineration. This technique has
been applied mainly to municipal treatment but can be used in
industrial systems. ;
The necessary equipment for a two stage powdered carbon unit
is as follows: four flash mixers, two sedimentation units,
two surge tanks, one polyelectrolyte feed tank, one dual media
filter, one filter for dewatering spent carbon, one carbon
wetting tank, and a furnace for regeneration of spent carbon.
Thermal regeneration, which destroys adsorbates, is economical
if carbon usage is above roughly 454 kg/day (1000 Ibs/day).
Reactivation is carried out in a multiple hearth furnace or a
rotary kiln at temperatures from 870°C to 988°C. Required resi-
dence times are of the order of 30 minutes. With proper
control, the carbon may be returned to its original activity;
carbon losses will be in the range of 4-9% and must be made up
with fresh carbon. Chemical regneration may be used if only
one solute is present which can dissolve off the carbon. This
allows material recovery. Disposal of the carbon may be required
if use is less than approximately 454 kg/day (1000 Ibs/day)
and/or a hazardous component makes regeneration dangerous.
VII-200
-------
WASTE WATER
INFLUENT
DISTRIBUTOR
WASH WATER
BACKWASH
BACKWASH
REPLACEMENT CARBON
SURFACE WASH
MANIFOLD
CARBON REMOVAL PORT
TREATED WATER
-S-UPPORT PLATE
FIGURE 7-66
ACTIVATED CARBON ADSORPTION COLUMN
VEI-201
-------
A new type of carbonaceous adsorbent is made by pyrolizing ion
exchange resins. These spherical adsorbents appear to have
the best characteristics of adsorbent resins and activated
carbon. They have a greater physical strength, attrition
resistance, and regeneration flexibility than either activated
carbon or polymeric resins. One type is particularly suited
for halogenated organics and has greater capacity than selected
carbons for compounds such as 2-chloroethyl ether, bromodichloro-
methane, chloroform, and di*eldrin. Another type (based on a
different polymeric resin) is best suited fpr removing aromatics
and unsaturated hydrocarbons. A third type has a particularly
mg/1) for phenol and other relatively polar organic molecules.
These adsorbents are commercially available but have not yet
been proven in large scale operation. !
Application
The principle liquid-phase applications of activated carbon
adsorption include sugar decolorization; municipal water
purification; purifications of fats, oils, foods, beverages
and Pharmaceuticals; and industrial/municipal wastewater
treatment. Potentially, it is almost universally applicable
because trace organics are found in the wastewatei: of almost
every industrial plant. \
The major benefits of carbon treatment include applicability
to a wide variety of organics, with high rertioval efficiency.
Inorganics such as cyanide, chromium, and mercury are also
removed effectively. Variations in concentration and flow rate
are well tolerated. The system is compact, and recovery of
adsorbed materials is sometimes practical. However, destruc-
tion of adsorbed compounds often occurs during thermal regenera-
tion. If carbon cannot be thermally desorbed, it must be
disposed of along with any adsorbed pollutants. When thermal
regeneration is utilized, capital and operating costs are
relatively high. Cost surveys show that thermal regeneration
is generally economical when carbon usage exceeds about 454
kg/day (1,000/lbday). Carbon cannot remove low molecular
weight or highly soluble organics. It also^has a low tolerance
for suspended solids, which must be removed to at least 50 ppm
in the influent water.
This system should be very reliable assuming upstream protec-
tion and proper operation and maintenance procedures. It
requires periodic regeneration or replacement of spent carbon
and is dependent upon raw waste load and process efficiency.
Solid waste from this process is contaminated activated
carbon that requires disposal. If the carbon undergoes regenera-
tion, the solid waste problem is reduced because of much less
frequent replacement. ',
VEI-202
-------
Performance
Carbon adsorption, when applied to well-treated secondary
effluent, is capable of reducing COD to less than 10 mg/1 and
BOD to under 2 mg/1. Removal efficiencies may be in the range
of 30% to 90% and vary with flow variations and different bed
loadings. Carbon loadings in tertiary treatment plants fall
within the range of 0.25 to 0.87 kg of COD removed per kg of
carbon, and if the columns are operated downflow, over 90%
suspended solids reduction may be achieved.
Quite frequently, segregated industrial waste streams are
treated with activated carbon. The contaminants removed
include BOD, TOC, phenol, color, cresol, polyesters, polynitro-
phenol, toluene, p-nitrophenol, p-chlorobenzene, chlorophenols,
insecticides, cyanides and other chemicals, mostly organic.
The flows being treated are generally small in comparison with
tertiary systems (less than 75,700 liters/day (20,000 gpd)).
Thermal reactivation of the carbon does not become common
until flows are above 227,100 liters/day (60,000 gpd). Some
installations reactivate their carbon chemically and the
adsorbate is recovered. Recoverable adsorbates are known to
include phenol, acetic acid, p-nitrophenol, p-chlorobenzene,
p-cresol, and ethylene diamine. Carbon loadings approach one
kg COD removal per kg carbon in installations where the adsorbates
are easily adsorbed and present in relatively high concentra-
tions. In other cases, where influent concentrations are
lower and where the adsorbates are not readily adsorbed, much
lower loadings will result. For example, it was determined
that brine wastewaters containing 150-750 ppm phenol and .
1500-1800 ppm acetic acid could be reduced to about 1 ppm
phenol and 100-200 ppm acetic acid with phenol loadings in the
range of 0.09-0.16 kg per kg and acetic acid loadings in the
range of 0.04-0.06 kg per kg.
From metal finishing, loadings for cyanide removal have been
found to be on the order of 0.01 kg for influent concentrations
around 100 ppm. Loadings for removal of hexavalent chromium
have been shown to be as high as 0.07 kg/kg carbon at 100 ppm
and 0.14 kg/kg carbon at 1000 ppm.
EPA isotherm tests have indicated that activated carbon is
very effective in adsorbing 65 percent of the organic priority
pollutants and reasonably effective for another 22 percent.
Specifically, for the organics of particular interest, activated
carbon was very effective in removing 2,4-dimethylphenol,
fluoranthene, isophorone, naphthalene, all phthalates, and
phenanthrene. It was reasonably effective on 1,1,1-trichloroe-
thane, 1,1-dichloroethane, phenol, and toluene. Table 7-74
summarizes the treatability effectiveness for most of the
organic priority pollutants by activated carbon as compiled by
EPA. Table 7-75 summarizes classes of organic compound together
with examples of organics that are readily adsorbed on carbon.
VII-203
-------
TABLE 7-74
RATING OF PRIORITY POLLUTANTS UTILIZING 'CARBON ADSORPTION
Priority Pollutant
1.
2.
3.
4.
5.
6.
7.
8.
9.
10,
11,
12,
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
acenaphthene
acroleln
acrylonitrile
benzene
benzidine
carbon tetrachloride
(tetrachlocomethane)
chlorobenzene
1,2,4-trichlorobenzene
hexachlorobenzene
1,2-dichloroethane
1,1,1-trichloroethane
hexachloroethane
1,1-dichloroethane
1,1,2-trichloroethane
1,1,2,2-tetrachloroethane
chloroe thane
bis(chloromethyl)ether
bis(2-chloroethyl)ether
2-chloroethyl vinyl ether
(mixed)
2-chloronaphthalene
2,4,6-trichlorophenol
parachlorcmeta cresol
chloroform (tridiloromethane)
2-chlorophenol
1,2-dichlorobenzene
1,3-dlchlorobenzene
1,4-dichlorobenzene
3,3'-dichlorobenzidine
I,l-dichlorc3ethylene
I/2-trans-dichloroethylene
2,4-dichlorophenol
1,2-dichloropropane
1,2-didilorcpEopylene
(1,3,-dichloropropene)
2,4-diroethylphenol
2,4-dinitrotoluene
2,6-dinitrotoluene
1,2-diphenylhydrazine
ethylbenzene
fluoranthene
4-chlorophenyl phenyl ether
4-brotnpphenyl phenyl ether
bis(2-chloroisopropyl)ether
bis(2-chloroethoxy )methane
roethylene chloride
(dichlorona thane)
methyl chloride (chloromethane)
methyl-bromide (bromomethane)
brcrooform (tribromomethane)
dichlocobronomethane
*Renoval Rating
H
L
L
M
H
M
H
H
H
M
M
H
M
M
H
• L
M
L
H
H
H
L
H
H
H
H
H
L
L
H
M
M
H
H
H
H
M
H
H
H
M
M
L
L
L
H
M
Priority Pollutant
*Removal Rating
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
106.
107.
108.
109.
110.
111.
112.
* NOTE; Explanation of Removal Ratings
Category H (high removal)
adsorbs at levels >_ 100 mg/g carbon at C, = 10 mg/1
adsorbs at levels >_ 100 mg/g carbon at C^ < 1.0 mg/1
Category H (moderate removal)
adsorbs at levels .> 100 mg/g carbon at C- = 10 mg/1
adsorbs at levels < 100 mg/g carbon at C^ < 1.0 mg/1
Category L(lew removal)
adsorbs at levels < 100 mg/g carbon at C, = 10 mg/1
adsorbs at levels < 10 mg/g carbon at Cfr< 1.0 mg/1
Cf = final concentrations of priority pollutant at equilibrium
trichlorofluoromethane M
dichlorodifluoromethane L
chlprodibromomethane M
hexachlorobutadiene H
hexachlorocyclopentadiene H
isophorone H
naphthalene H
nitrobenzene H
2-nitrophenol H
4-nitrophenol H
2,4-dinitrophenol H
4,6-dinitro-o-cresol H
N-nitrosodimethylamine M
N-nitrosodiphenylamine H
N-nitrosodi-n-propylamine M
pentachlorophenol H
phenol M
bis(2-ethylhexyl)phthalate H
butyl benzyl phthalate H
di-n-butyl phthalate H
di-n-octyl phthalate H
diethyl phthalate H
dimethyl phthalate H
l,2Tbenzanthracene (benzo H
(a)anthracene)
benzo(a)pyrene (3,4-benzo- H
pyrene)
3,4-benzofluoranthene H
(benzo(b)fluoranthene)
11,12-benzofluoranthene H
(benzo(k)fluoranthene)
chrysene H
acenaphthylene H
anthracene H
l,12r-benzoperylene (benzo H
(ghi;)-perylene)
fluorene H
phenanthrene H
1,2,5,6-dibenzathraosne H
(dibenzo (a,h) anthracene)
indeno (1,2,3-cd) pyrene H
(2,3-o-phenylene pyrene)
pyrene
tetrachloroethylene M
toluene M
trichloroethylene L
vinyl chloride L
(chloroethylene)
PCB-1242 (Arochlor 1242) H
PCB-1254 (Arochlor 1254) H
PCB-1221 (Arochlor 1221) H
PCB-1332 (Arochlor 1232) H
PCB-1248 (Arochlor 1248) H
PCB-1260 (Arochlor 1260) H
PCB-1016 (Arochlor 1016) H
VTI-204
-------
TABLE 7-75
CLASSES OF ORGANIC COMPOUNDS ADSORBED ON CARBON
Organic Chemical Class
Aromatic Hydrocarbons
Polynuclear Aromatics
Chlorinated Aromatics
Phenolics
Chlorinated Ehenolics
*High Molecular Weight Aliphatic and
Branch Chain Hydrocarbons
Chlorinated Aliphatic Hydrocarbons
*High Molecular Weight.Aliphatic Acids
and Aromatic Acids
*High Molecular Weight Aliphatic Amines
and Aromatic Amines
*High Molecular Weight Ketones, Esters,
Ethers & Alcohols
Surfactants
Soluble Organic Dyes
of Chemical Class
benzene, toluene, xylene
naphthalene, anthracene
biphenyls
chlorobenzene, polychlorinated
biphenyls, aldrin, endrin,
toxaphene, DDT
phenol, cresol, resorcenol
and polyphenyls '
trichlorophenol, pentachloro-
phenol
gasoline, kerosine
1,1,1-Trichloroethane, tri-
chloroethylene, carbon tetra-
chloride, perchloroethylene
tar acids, benzole acid
aniline, toluene diamine
hydroquinone, polyethylene
glycol
alkyl benzene sulfonates
methylene blue, Indigo carmine
* High Molecular Weight includes compounds in the range of
4 to 20 carbon atoms ,
VII-205
-------
Samples were taken of influent and effluent streams around the
carbon adsorption unit at Plant ID 38040
sampling are presented below.
Plant JED 38040 (mg/1)
Day 1
The results of this
Day 2
Parameter
oil and Grease
BOD
TOG
TSS
TTO
Influent Effluent Influent Effluent
4.1
58.0
93.9
14.0
1.04
3.3
*
87.7
11.0
0.29
41.0
53.0
108.0
1.0
1.34
2.0
8.0
77.5
9.0
0.43
* Lab analysis experienced interference
Demonstration Status ,
Carbon adsorption systems have been demonstrated to be practical
and economical for the reduction of COD, BOD and related
parameters in secondary municipal and industrial wastewaters;
for the removal of toxic or refractory organics from isolated
industrial wastewaters; for the removal and recovery of certain
organics from wastewaters; and for the removal, at times with
recovery, of selected inorganic chemicals from aqueous wastes.
Carbon adsorption must be considered a viable and economic
process for organic waste streams containing up to 1-5% of
refractory or toxic organics; its applicability for removal of
inorganics such as metals, although demonstrated in a few
cases, is probably much more limited. I
!
Carbon adsorption is being used in 10 plants in the present
Metal Finishing Category data base. These plants are identified in
Table 7-76.
t
TABLE 7-76 j
METAL FINISHING PLANTS EMPLOYING CARBON ADSORPTION
04236
04690
12065
14062
17061
18538
19120
25033
31044
38040
SUMMARY OF OILY WASTE TREATMENT OPTION LIMITATIONS
The effluent limitation concentrations for the oily waste
treatment option and alternatives are summarized in Tables 7-77
and 7-78 (concentrations are in mg/1). Plants which certify that
VII-206
-------
no discharge of spent solvents occurs will not be required to
monitor for TTO.
TABLE 7-77
COMBINED WASTEWATER - COMMON METALS WASTEWATER
Parameter
Option 1
Daily Max. 30 -day Avg. Daily Max
30 -day Avg
Oil & Grease
Total Toxic Organics
35.9
0.58
15.8
0.083
21.4 9.4
(single option)
TABLE 7-78
SEGREGATED OILY WASTEWATER
Option 1
Parameter Daily Max. 30-Day Avg.
Oil & Grease 106.0 34.0
ADDITIONAL OILY WASTE TREATMENT TECHNOLOGIES
In addition to the treatment methods j
Coalescing
The basic principle of coalescing involves the preferential
we?ting ofPa coalascing medium by oil droplets which accumulate
on the medium, and then rise to the surface of the solution.
The mos? important requirements for coalescing media are
wettability for oil and large surface area.
with gvi eparation. In this unit, the oily waste enters
the senator where the large droplets immediately move to the
Inl surface of the separator because of the specific gravity
d°i?feren?ial?f Thl smSller droplets enter thV?hTo^droP?e?s
area where laminar flow produces coalescing of the oil droplets
The oil droplets deposit on the surface of the plates and
st?e2m upward through weep holes in the plates to the surface,
wherSadjustable skimmers remove the oil. Heavy solids are
deposited in the entrance chamber before the oily wastewater
enters the plate area.
VII-207
-------
W
O
M
CD
CO
O
CO
w
VII-208
-------
Application
Coalescing is used in the Metal Finishing Category for treatment
of oily wastes. It allows removal of oil droplets too finely
dispersed for conventional gravity separation/skimming technology
It can also significantly reduce the residence times (and
therefore separator volumes) required to achieve separation of
oil from some wastes. Because of their simplicity, coalescing
oil separators provide generally high' reliability and low
capital and operating costs. Coalescing is not generally
effective in removing soluble or chemically stabilized emulsi-
fied oils. To avoid plugging, coalescers must be protected by
pretreatment from very high concentrations of free oil anj
qrease and suspended solids. Frequent replacement of prefliters
may be necessary when raw waste oil concentrations are high.
Coalescing is inherently highly reliable because there are no
movinq parts., and the coalescing substrate is inert in the
process and therefore not subject to frequent regeneration or
replacement'requirements. Large loads or inadequate prior
treatment, however, may result in plugging or bypassing of
coalescing stages Maintenance requirements are generally
limited to replacement of the coalescing medium on an infre-
quent basis.
No appreciable solid waste is generated by this process, but
when coalescing occurs in a gravity separator, the normal
solids accumulation is experienced.
Performance
The analysis results of samples taken before and after a _ .
coalescing gravity separator at Plant ID 38217 are shown below
(Concentrations are in mg/1).
Plant ID 38217 (mg/1)
Day 1
Day 2
Parameter
Oil &
TOC
BOD
TSS
TTO
Grease
Raw
8320.
923.
2830.
637.
1.65
Effluent
490.
1050.
2950.
575.
1.18
Raw
4240.
1980.
1610.
4.11
Effluent
619.
535.
1530.
620.
0.66
Demonstration Status
Coalescing has been fully demonstrated in the Metal Finishing
Category and in other industries that generate oily wastewater,
Coalescers are used at 3 facilities in the present data base:.
Plant ID'S 14001, 20173, and 38217.
VII-209
-------
Flotation
Flotation, as was explained in the "Treatment of Common Metals
Wastes" section, is the process of causing particles such as
oil or metal hydroxides to float to the surface of a tank
where they can be concentrated and removed. This is brought
about by releasing gas bubbles which attach themselves to the
particles, increasing their buoyancy, causing them to rise to
the surface and float. Flotation units are commonly used in
industrial operations to remove free and emulsified oils and
grease. For these applications in the Metal Finishing Category,
the flotation technique commonly referred to as disso]ved air
flotation (DAP) is employed. Dissolved air flotation utilizes
the emulsion breaking techniques that were ; previously discussed
and in addition uses the bubbles of dissolved air to assist in
the agglomeration of the oily droplets and to provide increased
buoyancy for raising the oily droplets to the surface. A
typical dissolved air flotation system is shown in Figure
7~68 . ;
Application
The use of dissolved air for oily waste flotation subsequent
to -emulsion breaking can provide better performance in shorter
retention times (and therefore smaller flotation tanks) than
with emulsion breaking without flptation. ;A small reduction
in the quantity of chemical for emulsion breaking is also
possible. Dissolved air flotation units have been used success-
fully, in Conjunction with further subsequent processes, to
reclaim oils for direct reuse and/or use as power plant fuels
in the Metal Finishing Category. :
Performance
Performance of a flotation system depends upon having
sufficient air bubbles present to float essentially all of the
suspended solids. An insufficient quantity, of air will result
in only partial flotation of the solids, and excessive air
will yield no improvement. The performance; of a flotation
unit in terms of effluent quality and solids concentration in
the float can be related to an air/ solids ratio. The shape
of the curve obtained will vary with the nature of the solids
in the feed. i
VII-210
-------
•a
"o1
0
UH
C A
?T
H
e
o
4J.14
(C C
4-) (0
O EH
&4
I
04
(0
Cn
3
U-l
O
6^
GO
10
I
M
EH
en
t*
CO
g
H
I
H
o
co
co
M
Q
J
O
H
PU
H
VII-211
-------
The results of sampling done at Plant ID 33692 are presented
below (Concentrations are in mg/1).
Parameter
Plant ID 33692 (mg/1)
Day 1
Influent Effluent
Oil & Grease 412.
TOC 3000.
BOD 130.
TSS 416.
Demonstration Status
108.
132.
78.
210.
Day 2
Influent
65.8
98.
31.
166.
Effluent
28.9
86.
24.
103.
Flotation is used in 25 facilities in the present data base
and these are identified in Table 7-40. ! .
Centrifugation | •
Centrifugation is the process of applying a centrifugal force
to cause the separation of materials. This'force is many
times the force of gravity so it allows for:solids separation
in a much shorter time than that required by settling. When a
suspension is centrifuged, the components of the solution with
the greatest specific gravity accumulate at the farthest
distance from the axis of the centrifuge and those with the
least specific gravity are located nearest the axis. So when
oily wastes containing suspended solids are!centrifuged, the
solids portion collects at the outside of the centrifuge, the
oil forms the innermost layer, and the water portion is sand-
wiched in between. The different layers that are formed can
VH-212
-------
then be collected separately. Centrifuges are currently avail-
able that have been specifically designed to separate either
oil/water mixtures or oil/solids/water mixtures. Centrifugation
equipment is in use as a pretreatment technique to separate
oil/water mixtures prior to further wastewater treatment.
The performance of the centrifuge at plant ID 19462, which
employs centrifugation to lower the oil concentration of the
wastewater prior to further oil removal by ultrafiltration,
was established by sampling the influent and effluent streams.
The results are presented below (Concentrations are in mg/1).
Parameter
Oil and Grease
TSS
Plant ID 19462 (mg/1)
Day 1
In Out In
Day 2
373,280
6866
3402
1266
14,639
8938
Out
1102
1154
A detailed discussion on the various types of centrifuges is
presented under the heading "Treatment of Sludges".
Centrifugation is used on oily wastes by 5 plants in the
present data base: Plant ID's 06019, 11184, 14062, 19462, and
30166. 1
':? ' „......''
Integrated Adsorption
Application
The integrated adsorption process is designed for disposal of
materials in dilute aqueous emulsion, such as oils and paints.
The active agent is any of several aluminum silicate-based
formulations in powder form. This material is added to the
wastewater, and the mixture is agitated for six minutes.
During this period, the powder adsorbs the emulsified materials.
Next, the solid material is allowed to settle for two minutes,
and the water phase is then decanted through a disposable belt
filter, leaving any unsettled solids on the filter. Finally,
the sludge phase is ejected on the disposable belt filter,
where it is partially dewatered. Both the belt and the material
retained on it feed into a disposal container. The filtered
water is collected for reuse or discharge.
The integrated adsorption process is available as a commercial
system. Equipment consists of a reagent feed hopper, an
associated automatic feed device, a wastewater feed pump, a
reaction vessel, a high-speed turbine mixer, a disposable
belt, a band filter, a clean water pump, a clean water tank,
and associated controls.
VII-213
-------
The integrated adsorption system does not add anything to the
processed water, the pH and salinity of which are unaffected.
The system is designed for automatic operation, and the sludge
is leach-resistant because of the strong bonding of the adsorbed
materials. The system obviates the need for other chemical
treatment or physical separation, but it does entail both
capital and operating expense.
Performance
< i
The integrated adsorption system consistently removes greater
than 99 percent of the paints, detergents, and emulsified oils
in the feed stream. The sludge is 20 to 40 percent solids,
and is strongly resistant to leaching.
I
Demonstration Status .
I
The system is employed for treating paint booth water and
emulsified oils by a leading European auto .maker, among others.
There are more than 100 units presently in service.
Resin Adsorption :
!
Adsorption of trace organics on synthetic resins is similar to
adsorption on activated carbon. The basic materials are
different and the means of regeneration are different. A
potential advantage is that rfesins are more easily tailored
for removal of specific pollutants.
i
The resins are generally microporous styrene-divinylbenzenes,
acrylic esters, or phenol-formaldehydes. Each type may be
produced in a range of densities, void volumes, bulk densities,
surface areas, and pore sizes. The formaldehyde resins are
granular, and the others are in the form of beads.
I
Adsorptive resins are in limited commercial use for removal of
priority and other organics. There are existing operations
for removal of phenols in two plants (one in Indiana and the
other at a coal liquefaction plant in West Virginia), for
removal of fats at a food processing plant, and for removal of
organic dyes at several plants. Pilot plant operations have
been designed for removal of trinitrotoluene, 2,4-dinitrotoluene,
cyclomethylenetrinitramine, cyclotetramethylenetetranitramine,
Endrin, other pesticides, laboratory carcinogens (unspecified),
2,4-dichlorophenol, ethylene dichloride and vinyl chloride.
In a non-industrial application, organic carbon removal effi-
ciency decreased from 58 percent to 40 percent during a through-
put of 5,000 bed volumes, with an input concentration of about
6 mg/1. ;
|
Regeneration of the resins is done chemically, while regenera-
tion Deactivated carbon is thermal. The chemical may be an
inorganic acid, base, or salt, or an organic solvent such as
acetone.
Vll-214
-------
Ozonation
ozone is effective in the treatment of phenols. It is about
tlicl as powerful as hydrogen peroxide and is not as selective;
Sus i"ol?S?Zes a wider range of material. For low concentra-
tion phenolic wastes, the usual practice is to oxidize the
phenolic compound to intermediate organic compounds that are
toxic but readily biodegrdable. For this application, ozone
requirement! are^n thewnge of 1.5 to 2.5 parts of ozone per
pa?t of phenol. As the concentration decreases, the relative
amount of ozone needed increases. If other material with COD
is present, the ozone requirement will be still greater. When
pi ?alue£ of 11.5 to 11.8 are maintained, this range appears
to result in selective or preferential oxidation of phenol
over other substances.
For concentrated or intermediate level phenolic wastes chemical
oxidation by ozone may not be economical as a primary treatment
System; however, it is useful as a polishing process following
a biological system. In treating phenolic refinery wastes,
ozone is used as tertiary treatment to produce final effluents
as low as 3 ug/1 phenol.
Several manufacturers have begun using ozone for the treatment
of phenolic industrial wastewaters. They are listed and
briefly described below:
A. An oil refinery in Canada treats waste effluent of
1,514,000 liters/day (400,OOQ gallons/day) with the
phenol concentration averaging 50 mg/1.
Pretreatment consists of pre-aeration and a biologi-
cal trickling filter. Ozonation is the final treat-
ment step and utilization is 86 kg/day (190 pounds/
day). This treatment results in an effluent of less
than 0.012 mg/1 residual phenol.
B. A manufacturer of a thermoplastic resin in New York
treats a phenolic effluent by biological oxidation.
Further treatment was necessary to meet state stan-
dards. The effluent had a high COD of about 1500
mq/1 which competed with the phenol for ozone;
therefore a large ozone dosage level, 300 ppm, was
required to reach the desired phenol effluent con-
centration. At a flow rate of 946,250 liters/day
(0.25 MGD), a total of 283.5 kg (625 pounds) of
ozone was required daily. The air feed generating
equipment represents a capital investment of $220,000
and requires daily operating expenditures of $98.43
including electrical costs of 1.5^/kwh. Concurrent
with phenol removal, 30 percent of the color, ^y
percent of the turbidity and 17 percent of the COD
were removed.
VII-215
-------
™«Y various coke plant wastes shows that various
ozone requirements are necessary to oxidize the phenol
The results are displayed in Table 7-79. The great
variation in the ozone-to-phenol ratios of samples
from different sources illustrates the differences
in the composition of the wastes.
TABLE 7-79
OZONE REQUIREMENTS FOR PHENOL OXIDATION
Initial
Phenols
mg/1
1240
800
330
140
127
102
51
38
290
605
Ozone
Demand
mg/1
2500
1200
1700
950
550
900
1000
700
400
11,000
Source
Coke Plant A
B
C
n n D
it „ E
M it F
it n G
H
Chemical " A*
Refinery A
*This plant effluent contained 2,4-dichlorbphenol and the
results are expressed as such.
Ozone/
Phenol
ratio
2.0
1.5
5.2
6.8
4.3
8.8
20
18
1.4
18.0
enol and the
Residual
Phenols
mg/1
*~^ '
1.2
0.6
1.0
1.0
0.2
0.0
0.4
0.1
0.3
2.5
Ki t0 5° c?mmercial installations utilizing ozone
for bleach regeneration and photoprocessing wastewatir treatment
Ozone is also effective in treating wastewaters containing
other organics and organo-metal complexes. In organo-metal
complexes the metals can be released and then precipitated
One kilogram of COD should consume three kilograms of ozone
and yield two kilograms of molecular oxygen.
Chemical Oxidation
Chemical oxidation can be effective in destroying some of the
priority organic compounds. Oxidation can'be accomplished
by ozone, by ozone with ultraviolet radiation, by hydroqen
peroxide, and possibly by electrolytic oxidation. Oxidation
by chlorine is more likely to generate priority organics than
to destroy them.
VEI-216
-------
These oxidation techniques are used industrially primarily for
cyanide destruction. They are therefore discussed in detail
under the general heading of "Treatment of Cyanide Wastes ,
earlier in this section. Where information is available,
these discussions include consideration of ability to destroy
priority organics.
Aerobic Decomposition •
Aerobic decomposition is the biochemically actuated decomposi-
tion or digestion of organic materials in the presence of
oxygen. The chemical agents effecting the decomposition are
microorganism secretions termed enzymes. The principal products
in a properly controlled aerobic decomposition are carbon
dioxide and water. Aerobic decomposition is used mainly in the
treatment of organic chemicals and lubricants used in the film
industry and such other industries that use organic lubricants.
As a waste treatment aid, aerobic decomposition plays an
important role in the following organic waste treatment
processes:
1. Activated Sludge Process
2. . Trickling Filter Process
3. Aerated Lagoon
The activated sludge process consists of the aeration of a
biodegradable waste for a sufficient time to allow the formation
of a iSge mass of settleable solids. These settleable solids
are masses of living microorganisms and are termed activated
sludge.
A schematic diagram of the basic process is shown as Figure
7-69. The wastes enter the aeration tank after being mixed
with return sludge. The microorganisms from the returned
sludge aerobically stabilize the organic mixture which then
flows to a sedimentation tank. Sedimentation allows the
activated sludge to flocculate and to settle out, producing a
clear effluent of low organic content. A portion of the waste
sludge is returned to the aeration tank, thereby repeating the
process. Excess sludge is discharged from the process for
further treatment or disposal.
The trickling filter is basically a bed of stones or other .
suitable material covered with slime over which organic*wastes
slowly flow. A schematic cross section of a trickling filter
is shown as Figure 7-70. As wastewater passes through the
filter, it diffuses into the slimes where aerobic and anaerobic
decomposition occurs. After primary sedimentation, the waste-
water is introduced onto the filter by a rotary distributor so
designed that the wastes are discharged at a uniform_volume
per unit of filter surface. The waste flows by gravity over
the filter bed into an underdrain system. The liquid is collected
into a main effluent channel which flows to a final sedimenta-
tion tank. A schematic diagram of a single stage trickling
VII-217
-------
SETTLED
WASTES
SECONDARY
SEDIMEN-
TATION
WASTE EXCESS
SLUDGE
FIGURE 7-69
SCHEMATIC DIAGRAM OP A CONVENTIONAL ACTIVATED SLUDGE SYSTEM
VII-218
-------
7 Rotary distributor
Stone media
6-10' depth
»**
Vitrified clay underdrains
Reinforced concrete floor
FIGURE 7-70
SCHEMATIC CROSS SECTION OF A TRICKLING FILTER
VII-219
-------
filter is shown as Figure 7-71.
An aerated lagoon is a large shallow pond to which raw waste
is added at one end or in the center and the treated effluent
discharged at the other end. Aeration is accomplished by
mechanical aerators or diffusers in the wastewater. Aerobic
decomposition is pne of the factors involved in degradation of
the organic matter and is carried out by bacteria in a manner
similar to activated sludge. It is necessary to periodically
dredge the oxidation pond in order to maintain the proper
ecological balance. ;
Application ,
Aerobic decomposition can be applied to the treatment of oily
wastes from the Metal Finishing Category. !
Advantages of aerobic decomposition include; 1) low BOD concentra-
tions in supernatant liquor, 2) production iof an odorless,
humuslike, biologically stable end product |with excellent
dewatering characteristics that can be easily disposed, 3)
recovery of more of the basic fertilizer values in the sludge,
and 4) few operational problems and low initial cost. The
major disadvantages of the aerobic decomposition process are
1) high operational cost associated with supplying the required
oxygen, and 2)_sensitivity of the bacterial; population to
small changes in the characteristics of their environment.
Reliability can be high, assuming adequate temperature, pH,
detention time, and oxygen content control. Prior treatment
to eliminate substances toxic to the microorganisms affecting
decomposition may be necessary. (In some cases, adaptation
will increase the tolerance level of the miproorganisms for
toxic substances).
Maintenance of the three main waste treatment techniques
employing aerobic decomposition is detailed; in the following
table:
Process
Activated Sludge
Trickling Filter
Aerated Lagoon
Maintenance
Periodic removal of excess sludge and skimming
of scum layer.
i
Periodic application of: insecticides to reduce
the insect population and periodic chlorination
to reduce excess bacterial population.
Periodic dredging to remove excess sludge, and
periodic aeration to maintain the pond's aero-
bic character.
VII-220
-------
RAW
SEWAGE
SECONDARY
SEDIMENTA
TION
PRIMARY
SEDIMENTA
TION
FIGURE 7-71
SCHEMATIC DIAGRAM OF A SINGLE-STAGE TRICKLING FILTER
VII-221
-------
Performance
Aerobic decomposition is very effective for organic constituents
that are readily biodegradable. The toxic organics, however,
represent a range of biodegradability. Performance of a pilot
scale_activated sludge system is reported in "Removal of
Organic Constituents in a Coal Gasification Process Wastewater
by Activated Sludge Treatment", Argonne National Laboratory, 1979.
In this system, phenol was reduced from 250 mg/1 to an undetectable
level, naphthalene was reduced from 0.405 to 0.009 mg/1, and
ethylbenzene at 0.015 mg/1 concentration was not reduced.
Another source of information on organics (Handbook of Environmental
Data on Organic Chemicals, Verschueren, 1977) indicates treatability
for a number of priority organics. These data are summarized in
Table 7-80. ;
j
An additional source of information on priority organics (Estimated
Theoretical Treatability of Organic Priority Pollutants, USEPA,
May, 1979) lists the effluent levels shown in Table 7-81 for those
compounds effectively treated by biological means (compounds only
moderately well removed are not shown and corresponding influent
concentrations are not provided).
The activated sludge process also reduces concentrations of toxic
metals, by agglomeration of precipitates and by adsorption of
dissolved metals. However, effectiveness is highly variable
and unpredictable.
TABLE 7-80 '.
ACTIVATED SLUDGE REMOVAL OF SOME PRIORITY ORGANIC COMPOUNDS
Compound
Benzene
1,2-Dichloroethane
11
it
2,4~Dimethylphenol
Ethylbenzene
n
Phenol
Influent Concentration
(mg/1)
500
200
400
1000
500
50-100
500
Reported Removal
Efficiency, Percent
33
45
30
9
94.5
27
8
33
VII-222
-------
TABLE 7-81
ESTIMATED BIODEGRADATION PERFORMANCE
Compound
acrolein
acrylonitrile
benzene
benzidine
1,2,4-trichlorobenzene
parachlorometa cresol
2-chlorophenol
1,4-dichlorobenzene
2,4-dichlorophenol
2 r4-dinitrotoluene
naphthalene
4-nitrophenol
2,4-dinitrophenol
4, 6-dinitro-o-cresol
N-nitrosodiphenylamine
pentachlorophenol
phenol
Average Effluent
Concentration/ ug/1
100-1000
100-1000
50
25
10
50
50
25
50
50
50
50
25
25
1-10
10
50
VII-223
-------
Demonstration Status
Aerobic digestion is a widely used unit process to reduce
?Jg;?1£hCOTn^ °f wastewaters. It is currently employed at
in ?able 7P-82 " ^ baSe' ThSSe plants are identified
TABLE 7-82 i
METAL FINISHING PLANTS EMPLOYING AEROBIC DECOMPOSITION
\i *%'?&.*! .$'1 f'M'" » 'II 1 1 ......... Ill1 If f '
23041
30927
31050
33050
33263
44050
05050 11560
06067 11179
08172 13031
11050 14062
Thermal Emulsion Breaking i
Thermal emulsion breaking is usually a continuous process. In
most cases, however, these systems are operated intermittentlv
ThJ S, ?h%baSCh dUmp nat?re of most emulsified oujwastls Y'
The emulsified raw waste is collected in a holding tank until
sufficient volume has accumulated to warrant operating the
thermal emulsion breaking system. One such system is an
evaporation-distillation-decantation apparatus^ which separates
•
which is partially submerged in the emulsion. Some water
evaporates from the surface of the drum and; is carried upward
is^f^ flJteVnd a condensing unit. Th^ condensed watJr
is discharged and can be reused as process makeup, while the
air is reheated and returned to the evaporation stage. \s the
concentration of water in the main conveyorized chamber decreases
oil concentration increases and some gravity separation occu?S
The oils and other emulsified wastes which LparatJoSw over
,,in ?-A Decanting chamber. A rotating drum skimmer
f nn;^hfr°m thS sur?ace of this chamber and discharges
for possible reprocessing or contractor removal. Mean-
°ilY Watur 1S being drawn from the bottom of the decant-
;mb|^ reh|at?d ' . an<3 sent back into the main conveyorized
chamber. This aids in increasing the concentration of oil in
the main chamber and the amount of oil which floats to the
top. Solids which settle out in the main chamber are remove
by a conveyor belt. This conveyor, called a ?ligh? scrJper?
£?^S4.K WlY S2 as.not to d^turb the settling action. As
with the use of acids for chemical emulsion breaking? thermal
emulsion breaking is more commonly used for oil recovery than
for oily waste removal. i y
i
VII-224
-------
MAKE UP TO
OPERATING
EMULSION SYSTEM
REHEATING
COIL V CONDENSING
UNIT
AIR
RECIRCULATION
FAN
AIR ft
MOISTURE
WARM
DRY
AIR
SLUDGE
CONVEYOR
DISTILLED
WATER
TRANSFER
.-"•"PUMP
SLUDGE
DISCHARGE
DECANTING
CHAMBER
MAIN CONVEYORIZED
CHAMBER
FROM SPENT
EMULSION TANK
OIL
DISCHARGE
TRANSFER
PUMP
FIGURE 7-72
THERMAL EMULSION BREAKER
VII-225
-------
Application
to
Performance
Demonstration Status
VII-226
-------
TREATMENT OF SOLVENT WASTES - ALL OPTIONS
INTRODUCTION
The treatment of solvents that inadvertently enter wastewater
streams from rinses or cleaning operations is covered under
the subsection that deals with "Treatment of Oily Wastes".
Spent solvents that contain priority pollutants should be
segregated and either contract hauled or reclaimed on site.
Under no circumstances should priority organics be discharged ,<
directly to waste streams or combined with any wastes that
will enter the waste treatment system.
WASTE SOLVENT CONTROL OPTIONS .
The following paragraphs discuss the segregation of waste
solvents, contract hauling of waste solvents, and cleaning
alternatives that can be substituted for solvent degreasing to
reduce or eliminate the quantity of waste solvent generated.
Waste Solvent Segregation
Spent degreasing solvents should be segregated from other
process fluids to maximize the value of the solvents, to
preclude the contamination of other segregated wastes (such as
oily wastes), and to prevent the discharge of priority pollu-
tants to any wastewaters. This segregation can be accomplished
by providing and identifying the necessary storage container(s),
establishing clear disposal procedures, training personnel, in
the use of these techniques, and checking periodically to
ensure that proper segregation is occuring. Segregated waste
solvents are appropriate for on-site solvent recovery or can
be contract hauled for disposal or reclamation.
Contract Hauling
The DCP data identified several waste solvent haulers most of
whom haul solvent in addition to their primary business of
hauling waste oils. The value of waste solvents seems to be
sufficient to make waste solvent hauling a viable business.
Telephone interviews indicate that the number of solvent
haulers is increasing and that their operations are becoming
more sophisticated because of the increased value of waste
solvent. In addition, a number of chemical suppliers include
waste hauling costs in their new solvent price. Some of the
larger solvent refiners make credit arrangements with their
clientele; for example it was reported that one supplier
returns 50 gallons of refined solvent for every 100 gallons
hauled.
Cleaning Alternatives tp_ Solvent Degreasing
The substitution for solvent degreasing of cleaning techniques
that use no solvents or use lesser amounts of solvents would
VII-227
-------
1 •• '• •'
I •.
eliminate or reduce the quantity of priority organics that are
found in wastewaters. Alternative cleaning methods for the
removal of oils and grease include wiping> immersion, and
spray (both liquid and vapor phase) techniques using water,
alkaline or acid mixtures, and solvent emulsions. Various
methods of agitation, including ultrasonic and electrolytic
are helpful wherever they are applicable.; Table 7-83 presents
a generalized matrix of these cleaning approaches, each of
which has the capability for cleaning oily metal parts.
Fundamentally, the factors required to remove oil and clean
the metal surfaces of a part are: :
2.
3.
4.
A fluid to transport the cleaning agent to and the
soil particles away from the surface to be cleaned,
A chemical in which oily residues are soluble.
Heat (temperatures above 150°F) to lower the
viscosity of the oil and enhance the activity
of the chemical agent. ]
A scrubbing or wiping mechanism !to physically
remove the cleaner and soil. '
In the metal finishing industry, the factors that dictate the
cleaning needs include:
1.
2.
3.
4.
5.
6.
Production volume
Product size
Product material (eg-ferrous, non-ferrous)
Product shape and complexity (eg-blind holes, internal
corners)
Degree of cleanliness required (eg-surface purity)
Surface preparation required (eg'-dry, oil film,
oxide/scale removal, oxidation resistance)
Obviously, a single cleaning approach is npt practicable for
all of these diverse product and manufacturing requirements.
The task of identifying feasible cleaning alternatives to
solvent degreasing then becomes one of identifying areas which
have similar cleaning requirements so that substitution for •
solvent degreasing is practicable. Typical areas that are
amenable to cleaning techniques other than solvent degreasing
are: :
VII-228
-------
TABLE 7-83
CLEANING APPROACHES
CLEANING METHOD
WIPING
A. Dry
B. Wet
IMMERSION
A. Cold
CLEANING AGENT
SORBENT WATER ALKALINE ACID EMULSION SOLVENT
X
X
1. without agitation
2. with agitation
B. Hot
1. without agitiation
2. with agitation
SPRAY
A. Liquid
1. Cold
2. Hot
B. Vapor
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
VII-229
-------
1.
2.
3.
4.
5.
6.
Low to medium volume production levels where cleaning
cycle time does not impact the cost of production
Non-ferrous products
Simple product shapes
Small parts (adaptable to automated processes)
Oily film residue not objectionable
No exacting surface finishing required.
All of the previously described cleaning methods are applicable
to some of these cleaning needs. For comparative purposes,
these cleaning processes have been ranked on the relative
«£!!i!10f«OS!:' qmu^ity ?f 9leaniness' and significant environ-
mental effects. This relative ranking is presented in Table
7-84 for the five general cleaning methods. The bases for the
criteria used for relative ranking are defined as follows:
1. Cost - include equipment, facilities, chemicals,
heat, power, maintenance, operation (rinsing and
drying where applicble) and wastewater treatment.
2. Cleanliness Quality - surface purity.i
3. Pollution - environmental effects of the process.
4. Energy - thermal and electrical energy requirement.
TABLE 7-84
CLEANING PROCESS RELATIVE RANKING
(LOWEST NUMBER IS BEST)
CLEANING METHOD
Solvent Degreasing
Emulsion Cleaning
Alkaline Cleaning
Acid Cleaning
Hot Water/Steam
Cleaning
CLEANINESS
COST QUALI1:
1
3
2
4
5
3
4
2
1
5
t
5
4
2
3
1
*ONM
sTERG
1
2
3
4
5
[ENTAL
1Y COMBINED
3
3
2.5
3.5
3
MEAN
OVERALL
RANKING
2.5
3.25
2.25
3
4
YII-230
-------
Alkaline cleaning is the most feasible substitute for solvent
degreasing. This selection is based in part on the fact that
the combined alkaline cleaning environmental ranking and the
mean overall ranking are lowest. Further, data derived from
existing cleaning processes, shows that alkaline cleaning is
only 14% less cost effective than vapor degreasing. It is
believed that further development of alkaline cleaners and the
associated equipment should make its cost effectiveness equiva-
lent to or better than that for solvent degreasing. The major
advantage of alkaline cleaning over solvent degreasing is the
elimination or reduction in the amount of priority pollutants
being discharged. A major disadvantage connected with alkaline
cleaning is the energy consumption. Another disadvantage is
the fact that the process itself tends to dilute the oils
removed and discharges these diluted oils as well as the
cleaning additive, whereas in solvent degreasing, the oils are
contractor hauled along with the spent solvent and not dis-
charged. However, at least one firm produces a close-loop
alkaline cleaning system oil separator that is illustrated in
Figure 7-73.
This system provides in-process removal of oils and metals
wastes which extends the useful alkaline cleaner life and
significantly reduces treatment requirements because the spent
cleaning solution is normally contract hauled. Only the
alkaline solution dragout to a subsequent rinsing operation
produces a waste that requires treatment. Best described as a
continous-batch oil separator, the system has 'dual compartments
holding caustic wash solution, each equipped with an oil
skimmer and separated by a waste tank. Piping leads from each
compartment to a series of washers and back to a pump. Auto-
mated valves control flow from the pump to one of the compart-
ments. One compartment continuously supplies caustic solution
to a group of washers as the other stands for 24 hours, allowing
heavy materials to settle to the bottom as sludge and permitting
the oils to float to the surface. There, surface oils are
skimmed off, drained into the waste tank, and periodically
drawn off for reclamation or reuse. While one wash solution
in the first compartment is undergoing treatment, the clean
solution in the other compartment is circulated to the washers.
Four plants have these systems in operation and one installation
has been in use since June 1975. At this facility they report
zero discharge (via contract hauling the spent c'leaning solu-
tion) and the reclamation of 25,000 gallons of oil annually
from a cleaning operation prior to heat treatment. The, specific
advantages of.-applying this type of in-process o'il/metaT
treatment are as follows:
1. The concentrated discharges of spent alkaline cleaning
baths are eliminated by contract hauling the reduced
volume of spent cleaner.
VII-231
-------
)
H
I
w
i-r
S3
en
VII-232
-------
2. Energy requirements are lowered because of water
conservation.
3. Water and air pollution resulting from alkaline
cleaning are less than for the solvent degreasing
operation.
4. Oil reclamation is accomplished.
5. Lower cleaning costs are available through the con-
servation of cleaning agent and heat; less frequent
waste hauling; the use of cold cleaners; and lowered
treatment requirements.
VII-233
-------
TREATMENT OP SLUDGES
INTRODUCTION ;
i
Sludges are created by waste treatment alternatives which
remove solids from wastewater. Removal of;sludges from the
treatment system as soon as possible in the treatment process
minimizes returning pollutants to the waste stream through
re-solubilization. One plant visited during this program (ID#
23061) utilized a settling tank in their treatment system that
required periodic cleaning. Such cleaning had not been done
for some time, and analysis of both their raw and treated
wastes showed little difference. The accumulation of sludge
apparently decreased the effective residence time to a point
where the sedimentation process was unsuccessful. Subsequent
pumping out of this settling tank resulted j in an improved
effluent (Reference Table 7-85). i
Once removed from the primary effluent stream, waste sludges
must be disposed of properly. If landfills are used for
sludge disposal, the landfill must be designed to prevent
material from leaching back into the water supply. Mixing of
waste sludges which might form soluble compounds should be
prevented. If sludge is disposed of by incineration, the
burning must be carefully controlled to prevent air pollution.
A licensed scavenger may be substituted for plant personnel to
oversee disposal of the removed sludge. ,
TABLE 7-85
COMPARISON OF WASTEWATER AT PLANT ID 23061
BEFORE AND AFTER PUMPING OF SETTLING TANK
Parameter
Concentration (mg/1)
Before Sludge Removal
Concentration (mg/1)
After Sludge Removal
Total Raw Treated
Waste Effluent
Cyanide, Amen, to
Chlorination 0.007 0.001
Cyanide, Total 0.025 0.035 '
Phosphorus 2.413 2.675
Silver 0.001 0.001
Gold 0.007 0.010
Cadmium 0.001 0.006
Chromium, Hexavalent 0.005 0.105
Chromium, Total 0.023 0.394
Copper 0.028 0.500
Iron 0.885 3.667
Fluoride ' 0.16 0.62
Nickel 0.971 1.445
Lead 0.023 0.034
Tin 0.025 0.040
Zinc 0.057 0.185
Total Suspended Solids 17.0 36.00
Total Raw
Waste
0.005
0.005
14.35
0.002
0.005
0.005
0.005
0.010
0.127
2.883
0.94
0.378
0.007
0.121
0.040
67.00
Treated
Effluent
0.005
0.005
13.89
0.003
0.005
0.002
0.005
0.006
0.034
1.718
0.520
0.312
0.014
0.134
0.034
4.00
VII-234
-------
TREATMENT TECHNIQUES
Sludges can typically vary between one and five percent solids.
The sludge should be dewatered to lessen space requirements if
sludges are landfilled on the plant site and to decrease shipping
costs if sludges are hauled away by a contractor. Applicable sludge
dewatering techniques include gravity sludge thickening,
pressure filtration, vacuum filtration, centrifugation and
sludge bed drying. These techniques are discussed in the
following subsections, -
Gravity Sludge Thickening
In the gravity thickening process, dilute sludge is fed from a
primary settling tank or clarifier to a thickening tank.
Rakes stir the sludge gently to densify the sludge and to push
it to a central collection well. The supernatant is returned
to the primary settling tank. The thickened sludge that ' .
collects on the bottom of the tank is pumped to dewatering
equipment or hauled away. Figure 7-74 shows the construction
of a gravity thickener.
Application
Thickeners are generally used in facilities where the sludge
is to be further dewatered by a compact mechanical device such
as a vacuum filter or centrifuge. Doubling the solids content
in the thickener substantially reduces capital and operating
cost of the subsequent dewatering device and also reduces cost
for hauling. The process is potentially applicable to almost
any industrial plant.
The principal advantage of a gravity sludge thickening process
is that it facilitates further sludge dewatering. Other
advantages are high reliability and minimum maintenance require-
ments. Limitations of the sludge thickening process are its
sensitivity to the flow rate through the thickener and the
sludge removal rate. These rates must be low enough not to
disturb the thickened sludge. ,
Reliability is high assuming proper design and operation. A
gravity thickener is designed on the basis of square feet per
pound of solids per day, entering and leaving the unit.
Thickener area requirements are also expressed in terms of
mass loading, grams of solids per square meter per day (pounds
per square foot per day).
Twice a year, a thickener must be shut down for lubrication of
the drive mechanisms. Occasionally, water must be pumped back
through the system in order to clear sludge pipes. Thickened
sludge from a gravity thickening process will usually require
further dewatering prior to disposal, incineration, or drying.
The clear effluent may be recirculated in part, or it may be
subjected to further treatment prior to discharge.
VII-235
-------
^THICKENING;
-TANK:
SLUDGE PUMP
to
*
OVERFLOW
RECYCLED
THROUGH
PLANT
FIGURE 7-74
MECHANICAL GRAVITY THICKENING
VII-236
-------
Performance
Organic sludges from sedimentation units of one to two percent
solids concentration can usually be gravity thickened to six
to ten percent; chemical sludges can be thickened to four to
six percent.
Demonstration Status ,
Gravity sludge thickeners are used throughout industry to
reduce water content to a level where the sludge may be effi-
ciently handled. Further dewatering is usually practiced to
minimize costs of hauling the sludge to approved landfill
areas.
Sludge thickening is used in 78 plants in the present data
base. These are identified in Table 7-86.
TABLE 7-86
METAL FINISHING PLANTS EMPLOYING GRAVITY/SLUDGE THICKENING
03043
04069
04071
04263
04719
04981
05021
05035
06052
08004
11156
11177
11182
11704
12033
12074
12075
12078
12091
12100
Pressure Filtration
12102
12709
13031
13040
14061
15042
15044
17061
18050
18091
19063
20005
20010
20064
20073
20075
20078
20082
20085
20116
20120
20157
20165
20248
20291
21078
23062
23337
25001
27044
28082
28115
30079
30087
30090
30151
30153
30927
30967
33065
33070
33113
33120
36085
36090
36091
36092
36112
36130
36180
36623
40061
40063
41151
43003
43052
44044
62032
Pressure filtration is achieved by pumping the liquid through
a filter material which is impenetrable to the solid phase.
The positive pressure exerted by the feed pumps or other
mechanical means provides the pressure differential which is
the principal driving force. Figure 7-75 represents the
operation of one type of pressure filter.
A typical pressure filtration unit consists of a number of
plates or trays which are held rigidly in a frame to ensure
alignment and are pressed together between a fixed end and a
VII-237
-------
*;1;1!111!!1:,11!:,!;?!*"!! M!*Ari
PERFORATED
BACKING PUATE
FABRIC
FILTER MEDIUM
FABRIC
FILTER MEDIUM
SOLID
RECTANGULAR
END PLATE
ENTRAPPED SOLIDS
PLATES AND FRAMES ARE PRESSED
TOGETHER DURING FILTRATION
CYCLE
RECTANGULAR
METAL PLATE
FILTERED LIQUID OUTLET
RECTANGULAR FRAME
FIGURE 7-75
PRESSURE FILTRATION
VII-238
-------
traveling end. On the surface of each plate is mounted a
filter made of cloth or a synthetic fiber. The sludge is
pumped into the unit and passes through feed holes in the
trays along the length of the press until the cavities or
chambers between the trays are completely filled. The solids
in the sludge are then entrapped, and a cake begins to form on
the surface of the filter material. The water passes through
the fibers, and the solids are retained.
At the bottom of the trays are drainage ports. The filtrate
is collected and discharged to a common drain. As the filter
medium becomes coated with sludge, the flow of filtrate through
the filter drops sharply, indicating that the capacity of the
filter has been exhausted. The unit must then be cleaned of
the sludge. After the cleaning or replacement of the filter
media, the unit is again ready for operation.
Application
Because dewatering is such a common operation in treatment
systems, pressure filtration is a technique which can be found
in many industry applications concerned with removing solids
from their waste stream.
The pressures which may be applied to a sludge for removal of
water by filter presses that are currently available range
from 5 to 13 atmospheres. Pressure filtration may also reduce
the amount of chemical pretreatment required. The sludge,
retained in the form of the filter cake, has a higher percent-
age of solids than either a centrifuge or vacuum filter yield.
Thus, the sludge can be easily accommodated by materials
handling systems.
Two disadvantages associated with pressure filtration in the
past have been the short life of the filter cloths and lack of
automation. New synthetic fibers have largely offset the
first of these problems. Also, units with automatic feeding
and pressing cycles are now available.
Assuming proper pretreatment, design, and control, pressure
filtration is a highly dependable system. Maintenance consists
of periodic cleaning or replacement of the filter media,
drainage grids, drainage piping, filter pans, and other parts
of the system. If the removal of the sludge cake is not
automated, additional time is required for this operation.
Because it is generally drier than other types of sludges, the
filter sludge cake can- be handled with relative ease. Disposal
of the accumulated sludge may be accomplished by any of the
accepted procedures.
Performance
In a typical pressure filter, chemically preconditioned sludge
detained in the unit for one to three hours under pressures
VII-239
-------
varying from 5 to 13 atmospheres exhibited final moisture
content between 50 and 75 percent. ;
Demonstration Status
Pressure filtration is a commonly used technology that is
currently utilized in a great many commercial applications.
Pressure filtration is used in 66 plants"in the present data
base and these are identified in Table 7787.
TABLE 7-87 !
METAL FINISHING PLANTS EMPLOYING PRESSURE FILTRATION
01002
01003
10007
03043
04069
04146
04276
04284
05050
06050
06077
06107
06153
06960
08060
09046
11096
11103
11115
12005
12065
12071
12074
13031
14060
19066
19083
20022
20070
20083
20115
20255
20483
23039
23076
27042
27044
27045
28043
28121
30087
30927
30967
31021
31033
31035
31068
31070
33110
33113
33148
33172
33195
33293
34050
35041
36102
36176
38223
40047
41051
41068
42030
44044
47025
47074
Vacuum Filtration
In wastewater treatment plants, sludge dewatering by vacuum
filtration is an operation that is generally accomplished on
cylindrical drum filters. These drums have a filter medium
which may be cloth made of natural or synthetic fibers, coil
springs, or a wire-mesh fabric. The drum' is suspended above
and dips into a vat of sludge. As the drum rotates slowly,
part of its circumference is subject to ah internal vacuum
that draws sludge to the filter medium. Water is drawn through
the porous filter cake to a discharge port, and the dewatered
sludge, loosened by compressed air, is scraped from the filter
mesh. Because the dewatering of sludge on vacuum filters is
relativley expensive per kilogram of water removed, the liquid
sludge is frequently thickened prior to processing. A vacuum
filter is shown in Figure 7-76.
VII-240
-------
FABRIC OR WIRE
FILTER MEDIA
STRETCHED OVER
REVOLVING DRUM
DIRECTION OF ROTATION
MEDIA
MEANS
VACUUM
ROLLER
SOLIDS SCRAPED
OFF FILTER MEDIA
64
V*
SOLIDS COLLECTION
HOPPER
TROUGH
\
FILTERED LIQUID
INLET LIQUID
TO BE
FILTERED
FIGURE 7-76
VACUUM FILTRATION
VII-241
-------
Application
Vacuum filters are frequently used both in municipal treatment
plants and in a wide variety of industries for dewatering
sludge. They are most commonly used in larger facilities,
which have a thickener to double the solids content of clari-
fier sludge before vacuum filtering.
Although the initial cost and area requirement of the vacuum
filtration system are higher than those of a centrifuge, the
operating cost is lower, and no special provisions for sound
and vibration protection need be made. The dewatered sludge
from this process is in the form of a moist cake and can be
conveniently handled.
!
Vacuum filter systems have been proven reliable at many indus-
trial and municipal facilities. At present, the largest
municipal installation is at the West Southwest wastewater
treatment plant of Chicago, Illinois, where 96 large filters
were \nstalled in 1925, functioned approximately 25 years, and
then were replaced with larger units. Original vacuum filters
at Minneapolis-St. Paul, Minnesota now have over 28 years of
continuous service, and Chicago has-some units with similar or
greater service life. !
Maintenance consists of the cleaning or replacement of the
filter media, drainage grids, drainage piping, filter pans,
and other parts of the equipment. Experience in a number of
vacuum filter plants indicates that maintenance consumes
approximately 5 to 15 percent of the total time. If carbonate
buildup or other problems are unusually severe, maintenance
time may be as high as 20 percent. If intermittent operation
is to be employed, the filter equipment should be drained and
washed each time it is taken out of service and an allowance
for wash time should be made in the selection of sludge filter-
ing schedules. |
Vacuum filters generate a solid cake. All of the metals
extracted from the plant wastewater are concentrated in the
filter cake as hydroxides, oxides, sulfides, or other salts.
These metals are subject to leaching into ground water, espe-
cially under acid conditions.
Performance
The function of vacuum filtration is to reduce the water
content of sludge, so that the proportion of solids increases
from about 5 percent to about 30 percent.'
Demonstration Status
.
Vacuum filtration has been widely used for many years. It is
a fully proven, conventional technology for sludge dewatering.
VEI-242
-------
Vacuum filtration is used in 67 plants in the present data
base and these are identified in Table 7-88.
, TABLE 7-88
METAL FINISHING PLANTS EMPLOYING VACUUM FILTRATION
02062
03041
03042
06037
06074
06087
06088
06152
09052
09060
11182
11704
12002
12014
12042
12075
12078
12091
12709
15058
15070
16544
17030
18050
19084
19090
20005
20010
20073
20077
20080
20100
20161
20175
20248
20249
20291
21078
28115
30079
30090
30153
30927
31044
31047
33092
33110
33120
33124
33195
33263
34036
36040
36092
36113
36130
36623
38217
40037
40063
40067
40079
41097
41151
42030
43003
44036
Centrifugation
Centrifugation is the application of centrifugal force to
separate solids and liquids in a liquid/solid mixture or to
effect concentration of the solids. The application of cen-
trifugal force is effective because of the density differen-
tial normally found between the insoluble solids and the
liquid in which they are contained. As a waste treatment
procedure, centrifugation is applied to dewatering of sludges.
One type of centrifuge is shown in Figure 7-77.
There are three common types of centrifuges: the disc, basket,
and conveyor type. All three operate by removing solids under
the influence of centrifugal force. The fundamental difference
between the three types is the method by which solids are
collected and discharged.
In the disc centrifuge, the sludge feed is distributed between
narrow channels that are present as spaces between stacked
conical discs. Suspended particles are collected and dis-
charged continuously through small orifices in the bowl'wall.
The clarified effluent is discharged through an overflow weir.
VII-243
-------
i™ : "•"•' ':
CONVEYOR DRIVE
•BOWL DRIVE
REGULATING
RING IMPELLER
CYCLOGEAR
FIGURE 7-77
CENTRIFUGATION
VTI-244
-------
A second type of centrifuge which is useful in dewatering
sludges is the basket centrifuge. In this type of centrifuge,
sludge feed is introduced at the bottom of the basket, and
solids collect at the bowl wall while clarified effluent
overflows the lip ring at the top. Since the basket cen-
trifuge does not have provision for continuous discharge of
collected cake, operation requires interruption of the feed
for cake discharge for a minute or two in a 10 to 30 minute
overall cycle.
The third type of centrifuge commonly used in sludge dewater-
ing is the conveyor type. Sludge is fed through a stationary
feed pipe into a rotating bowl in which the solids are settled
out against the bowl wall by centrifugal force. From the bowl
wall, they are moved by a screw to the end of the machine, at
which point they are discharged. The liquid effluent is
discharged through ports after passing the length of the bowl.
Application
Virtually all of those industrial waste treatment systems
producing sludge can utilize centrifugation to dewater it.
Centrifugation is currently being used by a wide range of
industrial concerns.
Sludge dewatering centrifuges have minimal space requirements
and show a high degree of effluent clarification. The opera-
tion is simple, clean, and relatively inexpensive. The area
required for a centrifuge system installation is less than
that required for a filter system or sludge drying bed of
equal capacity, and the initial cost is lower.
Centrifuges have a high power cost that partially offsets the
low initial cost. Special consideration must also be given to
providing sturdy foundations and soundproofing because of the
vibration and noise that result from centrifuge operation.
Adequate electrical power must also be provided since large
motors are required. The major difficulty encountered in the
operation of centrifuges has been the disposal of the concen-
trate which is relatively high in suspended, non-settling
solids.
Reliability is high, assuming proper control of factors such
as sludge feed, consistency, and temperature. Pretreatment
such as grit removal and coagulant addition may be necessary.
Pretreatment requirements will vary depending on the composi-
tion of the sludge and on the type of centrifuge employed.
Maintenance consists of periodic lubrication, cleaning, and
inspection. The frequency and degree of inspection required
varies depending on the type of sludge solids being dewatered
and the maintenance service conditions. If the sludge is
abrasive, it is recommended that the first inspection of the
rotating assembly be made after approximately 1,000 hours of
VII-245
-------
operation. If the sludge is not abrasive or corrosive, then
the initial inspection might be delayed. Centrifuges not
equipped with a continuous sludge discharge system require
periodic shutdowns for manual sludge cake removal.
i
Performance ;
i
The performance of sludge dewatering by cehtrifugation depends
on the feed rate, the rotational velocity of the drum, and the
sludge composition and concentration. Assuming proper design
and operation, the solids content of the sludge can be increased
to 20-35 percent. !
Demonstration Status ,
Centrifugation is currently used in a greatmany commercial
applications to dewater sludge. Work is underway to improve
the efficiency, increase the capacity, and lower the costs
associated with centrifugation.
Centrifugation is used in 55 plants in the;present data base
and these are identified in Table 7-89.
i
TABLE 7-89 '.
METAL FINISHING PLANTS EMPLOYING CENTRIFUGATION
02032
04151
04153
06006
06071
06075
06086
06148
11050
11125
11127
12005
12033
12061
12075
12077
14062
15044
17050
19067
19068
19104
19107
19462
20070
20079
20106
20140
20149
20241
20708
21062
21065
21074
23048
27044
30097
30111
30155
30927
31022
33024
33071
34051
36091
36937
38052
41086
41116
41629
41869
44040
44150
45041
47041
Sludge Bed Drying
As a waste treatment procedure, sludge bed drying is employed
to reduce the water content of a variety of sludges to the
point where they are amenable to mechanical collection and
removal. These beds usually consist of 15.24 to 45.72 cm (6
to 18 inches) of sand over a 30.48 cm (12 inch) deep gravel
drain system made up of 3.175 to 6.35 mm (1/8 to 1/4 inch)
graded gravel overlying drain tiles.
VII-246
-------
Drying beds are usually divided into sectional areas approxi-
mately 7.62 meters (25 feet) wide x 30.48 to 60.96 meters (100
to 200 feet) long. The partitions may be earth embankments,
but more often are made of planks and supporting grooved
posts.
To apply liquid sludge to the sand bed, a closed conduit or a
pressure pipeline with valved outlets at each sand bed section
is often employed. Another method of application is by means
of an open channel with appropriately placed side openings
which are controlled by slide gates. With either type of
delivery system, a concrete splash slab should be provided to
receive the falling sludge and prevent erosion of the sand
surface.
Where it is necessary to dewater sludge continuously throughout
the year regardless of the weather, sludge beds may be covered
with a fiberglass reinforced plastic roof. Covered drying
beds permit a greater volume of sludge drying per year in most
climates because of the protection afforded from rain or snow
and because of more efficient control of temperature. Depend-
ing on the climate, a combination of open and enclosed beds
will provide maximum utilization of the sludge bed drying
facilities.
Application
Sludge drying beds are a common means of dewatering sludge
from clarifiers and thickeners. They are widely used both in
municipal and industrial treatment facilities.
The main advantage of sand drying beds over other types of
sludge dewatering is the relatively low cost of construction,
operation, and maintenance. Its disadvantages are the large
area of land required and long drying times that depend, to a
great extent, on climate and weather.
Maintenance consists of periodic removal of the dried sludge.
Sand removed from the drying bed with the sludge must be
replaced and the sand layer resurfaced. The resurfacing of
sludge beds is the major expense item in sludge bed mainte-
nance, but there are other areas which may require attention.
Underdrains occasionally become clogged and have to be cleaned.
Valves or sludge gates that control the flow of sludge to the
beds must be kept watertight. Provision for drainage of lines
in winter should be made to prevent damage from freezing. The
partitions between beds should be tight so that sludge will
not flow from one compartment to another. The outer walls or
banks around the beds should also be watertight.
The full sludge drying bed must either be abandoned or the
collected solids must be removed. These solids contain what-
ever metals or other materials were settled in the clarifier.
Metals will be present as hydroxides, oxides, sulfides, or
VII-247
-------
other salts. They have the potential for leaching and contami-
nating ground water, whatever the location of the semidried
solids. Thus an abandoned bed should include provision for
runoff control and leachate monitoring *
Performance
Dewatering of sludge on sand beds occurs by two mechanisms:
filtration of water through the bed and evaporation of water
as a result of radiation and convection. Filtration is gener-
ally complete in one to two days and may tresult in solids
concentrations as high as 15 to 20 percent. The rate of
filtration depends on the drainability of the sludge.
The rate of air drying of sludge is related to temperature,
relative humidity, and air velocity. Evaporation will proceed
at a constant rate to a critical moisture content, then at a
falling rate to an equilibrium moisture content. The average
evaporation rate for a sludge is about 75 percent of that from
a free water surface.
Demonstration Status
Sludge beds have been in common use in both municipal and
industrial facilities for many years. However, protection of
ground water from contamination is not always adequate.
Sludge bed drying is used in 77 plants in the present data
base and these are identified in Table 7-9,0.
i
Sludge Disposal
There are several methods of disposal of sludges from indus-
trial wastewater treatment. The two most common techniques
are landfilling by the company on its own property and removal
by licensed contractor to an outside landfill or reclamation
point. Other disposal techniques proposed for industrial
waste_sludges include chemical containment, encapsulation,
fixation, and thermal conversion. All of these techniques
require landfilling, but they reduce the probability of
groundwater contamination. [
The chemical containment approach has been demonstrated commer-
cially. The heavy metal sludge is placed in pits lined with
powdered limestone. This keeps the pit-soil interface at an
alkaline pH, reducing the solubility of metals at the interface
to a very low value. This minimizes heavy metal leaching,
even by acid rainfall. y
Encapsulation consists of two approaches. 'One is to seal the
sludge in a heavy concrete container. The 'other is to coat
the material with a nondegradable, waterproof polymer.
VII-248
-------
TABLE 7-90
METAL FINISHING PLANTS EMPLOYING SLUDGE DRYING BEDS
01067
01068
04076
04262
05050
06002
06035
06051
06067
06073
06076
06081
06083
.06084
06091
06094
06101
06113
06117
06119
06124
06128
06138
06360
08061
08072
09025
09047
11008
11113
11152
11173
12075
13041
14061
14062
15048
17061
18050
19050
20003
20064
20082
20085
20247
21003
22735
23039
23070
23072
25001
30009
30031
30064
30519
31032
31050
31067
33024
33047
33050
33179
33184
33200
33287
36001
36082
36083
36592
38039
40062
40075
40079
40836
41068
45035
47412
VII-249
-------
IN-PROCESS CONTROL TECHNOLOGY
i ; ; - ; ••
INTRODUCTION ! " L!j!I "I"1; :!:'::"! ; : "".'"'.
This section presents flow guidance and process controls in
the form of available methods and practices which can help
reduce the water usage and pollution discharge at metal finish-
ing facilities.
CONTROL TECHNIQUES
The in-process control techniques described below include
techniques for: j
!
. Flow reduction through efficient rinsing
Process bath conservation
Waste oil segregation
. Process bath segregation
Process modification .
Cutting fluid cleaning :
Integrated waste treatment ;
Good housekeeping '
These techniques deal with reducing water usage and with
efficient handling of process wastes. All of the areasof
in-process control are presented in the following sections,
Flow Reduction Through Efficient Rinsing
Reductions in the amount of water used in metal finishing can
be realized through installation and use o|f efficient rinse
techniques. Cost savings associated with water use reduction
result from lower cost for rinse water and reduced chemical
costs for wastewater treatment. An added benefit is that the
waste treatment efficiency is also improved. It is estimated
that rinse steps may consume over 90 percent of the water used
by a typical metal finishing facility. Consequently, the
greatest water use reductions can be anticipated to come from
modifications of rinse techniques.
Rinsing is essentially a dilution step which reduces the
concentration of contaminants on the work piece. The design
of rinse systems for minimum water use depends on the maximum
level of contamination allowed to remain on the work piece
(without reducing acceptable product quality or causing poison-
ing of a subsequent bath) as well as on the efficiency or
effectiveness of each rinse stage. . .
A rinse system should be considered efficient if the dissolved
solids concentration is reduced just to the point where no
noticeable effects occur either as a quality problem or as
excessive drag-in to the next process stepi. Operation of a
rinse tank or tanks which achieve a 10,000 to 1 reduction in
concentration where only a 1,000 to 1 reduction is required
VII-250
-------
represents inefficient use of water. Operating rinse tanks at
or near their maximum acceptable level of contamination provides
the most efficient and economical form of rinsing. Insufficient
operation manifests itself in higher operating costs not only
from the purchase cost of water, but also from the treatment
of it.
Dragout Control
Since the purpose of rinsing is to remove process solution
dragout from the surface of the workpiece, the best way to
reduce the amount of rinsing required is to reduce the dragout.
A reduction in dragout results in a reduction of waste that
has to be treated. Dragout is a function of several factors
including workpiece geometry, viscosity and surface tension of
the process solution, withdrawal and drainage time and racking.
These factors affecting dragout are described below.
Geometry of_ the Part r- This partly determines the amount of
dragout contributed by a part and is one of the principal
determinants for the type of rinsing arrangement selected. A
flat sheet with holes is well suited for an impact spray rinse
rather than an immersion rinse, but for parts with cups or
recesses such as a jet fuel control, a spray rinse is totally
ineffective.
Kinematic Viscosity of_ the Process Solution - The kinematic
viscosity is an important factor in determining process bath
dragout. The effect of increasing kinematic viscosity is that
it increases the dragout volume in the withdrawal phase and
decreases the rate of draining during the drainage phase. It
is advantageous to decrease the dragout and increase the
drainage rate. Consequently, the process solution kinematic
viscosity should be as low. as possible. Increasing the tempera-
ture of the solution decreases its viscosity, thereby reducing
the volume of process solution going to the rinse tank. Care
must be exercised in increasing bath temperature, particularly
with electroless plating baths, because the rate of bath
decomposition may increase significantly with temperature
increases.
Surface Tension of the Process Solution - Surface tension is a
major factor that~controls the removal of dragout during the
drainage phase. To remove a liquid film from a solid surface/
the gravitation force must overcome the adhesive force between
the liquid and the surface. The amount of work required to
remove the film is a function of the surface tension of the
liquid and the contact angle. Lowering the surface tension
reduces the amount of work required to remove the liquid and
reduces the edge effect (the bead of liquid adhering to the
edges of the part). Surface tension is reduced by increasing
the temperature of the process solution or more effectively,
by use of a wetting agent. , '
VII-251
-------
Time °f Withdrawal and Drainage - The withdrawal velocity of a
part from a solution has an effect similar to that of kinematic
viscosity. Increasing the velocity or decreasing the time of
withdrawal increases the volume of solution that is retained
by the_part. Since time is directly related to production
rate, it is more advantageous to reduce the dragout volume
initially adhering to the part rather than attempt to drain a
large volume from the part.
Racking - Proper racking of parts is the most effective way to
reduce dragout. Parts should be arranged!so that no cup-like
recesses are formed, the longest dimension should be horizon-
tal, the major surface vertical, and each part should drain
freely without dripping onto another part!. The racks them-
selves should be periodically inspected to insure the integ-
rity of the rack coating. Loose coatings can contribute
significantly to dragout. Physical or geometrical design of
racks is of primary concern for the control of dragout both
from the racks and the parts themselves. :Dragout from the
rack itself can be minimized by designing it to drain freely
such that no pockets of process solution can be retained.
Rinsing Techniques
The different types of rinsing commonly used within the metal
finishing industry are described below. :
Single Running Rinse - This arrangement requires a large
volume of^water to effect a large degree of contaminant removal.
Although in widespread use, single running rinse tanks should
be modified or replaced by a more effective rinsing arrangement
to reduce water use.
Countercurrent Rinse - The countercurrent rinse provides for
the most efficient water usage and thus, where possible, the
countercurrent rinse should be used. There is only one fresh
water feed for the entire set of tanks, and it is introduced
in the last tank of the arrangement. The overflow from each
tank becomes the feed for the tank preceding it. Thus, the
concentration of dissolved salts decrease^ rapidly from the
first to the last tank. }
In a situation requiring a 1,000 to 1 concentration reduction,
the addition of a second rinse tank (with ,a countercurrent
flow arrangement) will reduce the theoretical water demand by
97 percent.
Series Rinse - The major advantage of the .series rir.se over
the countercurrent system is that the tanks of the series can
be individually heated or level controlled since each has a
separate feed. Each tank reaches its own iequilibrium condi-
tion? the first rinse having the highest concentration, and
the last rinse having the lowest concentration. This system
uses water more efficiently than the single running rinse, and
VII-252
-------
the concentration of dissolved salts decreases in each succes-
s ive tank.
Spray Rinse - Spray rinsing is considered the most efficient
of the various rinse techniques in continuous dilution rinsing.
The main concern encountered in use of this mode is the effi-
ciency of the spray (i.e., the volume of water contacting the
part and removing contamination compared to the volume of
water discharged). Spray rinsing is well suited for flat
sheets. The impact of the spray also provides an effective
mechanism for removing dragout from recesses with a large
width to depth ratio.
Dead, Still, or Reclaim Rinses - This form of rinsing is
particularly applicable for initial rinsing after metal plating
because the dead rinse allows for easier recovery of the metal
and lower water usage. The rinse water can often be periodi-
cally transferred to the plating tank that precedes it. The
dead rinse is followed by spray or other running rinses.
Effect on Water Use - The use of different rinse types will
result Tn wide variations in water use. Table 7-91 shows the
theoretical flow arrangements for several different rinse
types to maintain a 1,000 to 1 reduction in concentration.
Table 7-92 shows the mean flows (1/m ) found at sampled
plants for three rinse water-intensive operations.
TABLE 7-91
THEORETICAL RINSE WATER FLOWS REQUIRED TO MAINTAIN A
1,000 TO 1 CONCENTRATION REDUCTION
Type of Rinse
Single
Series
Countercurrent
Number of Rinses
Required Flow (gpm)
1
10
2
Oo61
3
0.27
2
0.31
3
0.1
TABLE 7-92
COMPARISON OF RINSE TYPE FLOW RATES FOR SAMPLED PLANTS
Operation
Alkaline Cleaning
Nickel Electroplate
Zinc Electroplate
Rinse Type and Mean Flow (1/m )
Single 2 Stage 2 Stage 3 Stage
Stage Series Countercurrent Countercurrent
1504.
322.9
236.8
235.6
88.96
33.78
67.36
26.54
21.79
28.76
7.44
7.84
Vll-253
-------
Rinsing Systems
By combining different rinse techniques, a plant can greatly
reduce water consumption and in some cases form a closed loop
rinsing arrangement. Some examples of primary rinse types and
specialized rinsing arrangements applicable to metal finishing
are discussed below. '.
Closing The Loop With A Countercurrent Rinse - This particular
arrangement is well suited for use with heated process baths.
The overflow from the countercurrent rinse becomes the evapora-
tive makeup for the process bath. By installing the proper
number of countercurrent tanks, the fresh feed rate for a
given dilution ratio is sized to equal the bath's evaporative
rate. This arrangement is easily controlled by using liquid
level controllers in both the process bath and rinse tank, a
pump to transfer rinse solution to the process bath, and a
solenoid valve on the fresh feed line for the rinse tanks.
Plant ID'S 06037, 06072, and 20064 use this arrangement.
i
Closing The Loop With Spray Followed By Countercurrent Rinse -
The spray followed by countercurrent rTriseis well suited for
flat sheets and parts without complex geometry. The spray is
mounted over the process bath, and the work is fogged before
moving to the countercurrent rinse. A majjor advantage of this
arrangement is that the spray reduces concentration of the
dragout on the part, returning the removed portion to the
process tank. This provides for evaporative makeup of the
process bath and a lower water usage and/or a smaller number
of tanks necessary for the countercurrent rinse. Plant ID
40062 utilizes this rinse technique.
Closing The Loop With Countercurrent Rinsing Followed By Spray
Rinsing - The countercurrent followed by spray rinsing approach
can be used when a very clean workpiece (and, therefore, final
rinse) is required. The spray is mounted above the,last
countercurrent rinse. Depending on the evaporation rate of
the process solution, the evaporative makeup can come from the
first countercurrent tank. !
Closing The Loop With Dead Rinse Followed By Countercurrent -
The dead rinse followed by countercurrent rinse arrangement is
particularly useful with parts of a complex geometry. Evapora-
tive losses from the original solution tank can be made up
from the dead rinse tank and the required flow for the counter-
current system can be greatly reduced. The following plants
VII-254
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make use of this rinsing arrangement: 04045, 06036, 06072,
06081, 06088, 20064, 20073, 20080, 21003, 21651, 30022, 31022,
33065, 33070, 33073, 36041, 41069, 61001.
Closing The Loop With Recirculatory Spray - When the geometry
of the work permits, the recirculating spray offers an improved
alternative to the dead rinse. Operating with a captive
supply of rinse solution, the solution is sprayed onto the
work. The advantage of this system is that the impact of the
spray is used to remove dragout, particularly for work with
holes in it. The basic equations for concentration buildup
hold but are modified by the removal efficiency of the spray.
The required flow rate of the spray is dependent on the
geometry of the parts, the production rate and the solution
evaporation rate. Plant ID'S 15608 and 27046 have this
rinsing system.
Rinse Water Control
Another method of conserving water through efficient rinsing
is by controlling the flow of the feed water entering the
rinse tanks. Some flow control methods are listed below.
Conductivity Controllers - Conductivity controllers provide
for efficient use and good control of the rinse process. This
controller utilizes a conductivity cell to measure the conduc-
tance of the solution which, for an electrolyte, is dependent
upon the ionic concentration. The conductivity cell is tied
to a controller which will open or close a solenoid on the
makeup line. As the rinse becomes more contaminated, its
conductance increases until the set point of the controller is
reached, causing the solenoid to open and allowing makeup to
enter. Makeup will continue until the conductance drops below
the set point. The advantage of this method of control is
that water is flowing only when required. A major manufacturer
of conductivity controllers supplied to plants in the Metal
Finishing Category claims that water usage can be reduced by
as much as 50-85% when the controllers are used.
Liquid Level Controllers - These controllers find their great-
est use on closed loop rinsing systems. A typical arrangement
uses a liquid level sensor in both the process solution tank
and in the first rinse tank, and a solenoid on the rinse tank
makeup water line. When the process solution evaporates
to below the level of the level controller, the pump is acti-
vated, and solution is transferred from the first tank to the
process tank. The pump will remain active until the process
tank level controller is satisfied. As the liquid level of
the rinse tank drops due to the pumpout, the rinse tank con-
troller will open the solenoid allowing fresh feed to enter.
Manually Operated Valves - Manually operated valves are suscep-
tible to misuse and should, therefore, be installed in conjunc-
tion only with other devices. Orifices should be installed in
VII-255
-------
addition to the valve to limit the flow rate of rinse water.
For rinse stations that require manual movement of work and
require control of the .rinse (possibly due to low utilization),
dead man valves should be installed in addition to the orifice
to limit the flow rate of rinse water. They should be located
so as to discourage jamming them open.
Orifices or Flow Restrictors - These devices are usually
installed~Ebr rinse tanks that have a constant production
rate. The newer restrictors can maintain ^ constant flow even
if the water supply pressure fluctuates. Orifices are not as
efficient as conductivity or liquid level controllers, but are
far superior to manual valves. '
Process Bath Conservation
There are a number of techniques that are utilized to recover
or reuse process solutions in the Metal Finishing Category.
The costs and reduced availability of certain process solutions
have encouraged finishers to recognize process solutions as a
valuable resource rather than a disposal problem. Some examples
of chemical recovery and reuse are: reprocessing of oil,
reclamation of oil, recycling of oil, reuse of spent etchants,
recovery of metal from spent process baths^ regeneration of
etchants and dragout recovery. These techniques are described
below. !
Oil Recovery '!
Reprocessing of Oil - Reprocessing consists of contaminant
removal by physical separation, filtering, centrifuging, or
magnetic separation, as previously discussed. Reprocessing
also includes the preparation of waste oils for burning as a
fuel supplement.
Reclamation of Oil - Oil reclamation combines the elements of
reprocessing along with mechanical or chemical steps. Reclama-
tion is used to remove solids and water, fuel or solvents, and
degradation products such as acid. Two common processes are
flash distillation and chemical adsorption.: The addition of
heat with a partial vacuum and filtration are employed to
remove degradation products in used oil. [
Reclamation is used with synthethic fluids ;or highly refined
mineral oils. Reclamation systems are available for either
fixed or portable operation, and outside reclamation services
are available.
Recycling of Oil - Recycling is the most comprehensive treatment.
The waste oil is prefiltered to remove most of the solids,
solvents/ fuel, and water, leaving essentially base oil and
additives. Removing the additives leaves a high quality
basestock. The basestock is then formulated with conventional
additives and can be used in the same application as the
VEI-256
-------
virgin basestook. Re-refining provides the best economics
when large volumes of waste oil are available. Re-refiners
may accept industrial oil wastes when a large source or many
smaller sources of waste oils are available for collection in
a region.
Other Recovery Operations
Reuse of Spent Etchant - If a facility maintains both an
additive and a conventional subtractive line for the manufac-
turing of printed boards, a two-fold incentive exists for
reuse of spent copper etchant. The copper etchant used in a
conventional subtractive process is normally dumped when the
copper concentration reaches approximately 45,000 mg/1.
However, by removing the iron and chromium from the etchant,
it can become an inexpensive source of copper for the additive
plating baths. This technique can be extended to recover the
copper bearing waters from copper etchant rinse tanks as well
as from the etch tank and is practiced at Plant ID 11065.
Some concentrating devices, such as vacuum distillation, may
be required to reduce the volume of the rinse.
Recovery of Metal from Spent Plating Baths - Spent plating
baths contain a significant percentage of metal in solution.
Recovery can be effected by electrolizing the solution at low
voltage or by decomposing a hot bath with seed nuclei. The
resultant material, while pure, can be refined or sold to
recover some of its original value. The advantage of this
type of treatment is that a large percentage of the metal is
recovered and does not require treatment. This type of metal
recovery is performed by Plant ID's 17061 and 11065.
Regeneration of Etchants - Regeneration of etchants from a
copper etchant solution can be achieved by partially dumping
the bath and then adding fresh make-up acid and water. If
this is done, the etchant life can be extended indefinitely.
Another method practiced for the regeneration of etchants used
in the electroless plating of plastics is to oxidize the
trivalent chromium back to the active hexavalent chromium.
The oxidization is done by an electrolytic cell. Plant 20064
regenerates its preplate etchants in this manner. Use of this
method reduces the amount of material requiring waste treatment,
Reclamation of Paint Powders - A plant which uses powder
coating does not need water wash spray booths to catch over-
spray. The oversprayed particles can be collected with a
vacuum arrangement in a dry booth, filtered, and reused on the
production line.
Dragout Recovery - If the overflow water from a rinse tank can
be reused, it does not have to be treated, and additional
water does not have to be purchased. One approach currently
in use is to replace the evaporative losses from the process
bath with overflow from the rinse station. This way a large
VII-257
-------
percentage of process solution normally lost by draqout can be
returned and reused.
The usefulness of this method depends on the rate of evapora-
tion from the process tank. The evaporation from a bath is a
function of its temperature, surface area, and ventillation
rate, while the overflow rate is dependent on the dilution
ratio, the geometry of the part, and the dragout rates. If
the rinse is noncritical, i.e., where the part is going to
another finishing operation, closing the loop (returning .rinse
overflow to the process tank) can be accomplished with far
fewer rinse tanks than a critical rinse (following the last
process operation). For example, if a particular line is
always used to plate base metals only, and afterwards the work
always goes to another process, then this permits a lower flow
rate with consequently higher buildup of pollutants in the
rinse. Under these conditions, an external concentrator, such
as an evaporator, is not required, and the rinse overflow can
be used directly for process bath makeup. The reverse is
often true with the rinse following the final finishing step.
The flow rate in this instance may be high enough that it
exceeds the bath evaporation rate and some form of concen-
trator is required.
When using any rinse arrangement for makeup of evaporative
losses from a process solution, the quality of the rinse water
must be known and carefully monitored. Naturally occurring
dissolved solids such as calcium and magnesium salts can
slowly build up and cause the process to go out of control.
Even using softened water can cause process control problems.
For this reason, deionized water is often used as a feed for
rinsing arrangements which will be used for evaporative makeup
of process solutions.
Oily Waste Segregation ,
Many different types (or compounds) of oils and related fluids
are common in oily wastes and include cutting oils, fluids,
lubricants, greases, solvents, and hydraulic fluids. Segrega-
tion of these oily wastes from other wastewaters reduces the
expense of both the wastewater treatment and the oil recovery
process by minimizing the quantity and number of constituents
involved. In addition, segregated oily wastes are appropriate
for hauling to disposal/reclamation by a contractor in lieu of
on-site treatment. Additional segregation of oily wastes by
type or compound can further reduce treatment or hauling
costs. Some oils have high reclaimer values and are more
desirable if they are not contaminated by other oils.
Properly segregated spent oils containing common base oils and
additives will retain much more of their original value and
can be efficiently processed. Spent oils, properly segregated,
can be reprocessed in-house or sold to an outside contractor.
Some plants purchase reprocessed oils which results in substan-
tial savings.
VII-258
-------
The true value of oils and cutting fluids should be realized
during its entire use cycle, from purchase to disposal and
reuse. This is particularly true during used oil collection
and storage.
Process Bath Segregation
Process baths which are to be sent to waste treatment rather
than being shipped out should be segregated from one another.
The purpose of .this is the same as for segregating raw waste
streams. Mixing together of process solutions may form com-
pounds which are very difficult to treat or create unneces-
sarily larger volumes of water requiring specialized treatment
such as chromium reduction or cyanide oxidation.
Process Modification
Process modifications can reduce the amount of water required
for rinsing or reduce the load of certain pollutants on a
waste treatment facility. For example, a rinse step can be
eliminated in electroless plating by using a combined sensiti-
zation and activation solution followed by a rinse in place of
a process sequence of sensitization-rinse-activation-rinse.
Another potential process modification would be to change from
a high concentration plating bath to one with a lower concen-
tration. Parts plated in the lower concentration bath require
less rinsing (a dilution operation) and, thus, decrease the
water usage relative to high concentration baths.
There are also constantly increasing numbers of substitute
bath solutions and plating processes becoming commercially
available. A number of these are listed below:
Non-chromic acid pickling solutions
Non-cyanide zinc and copper plating
Non-aqueous plating processes
Trivalent chromium plating
Etch recovery and recirculating systems
Non-chromium decorative plating
Substitutions for cadmium where applicable
Phosphate-free and biodegradable cleaners
These options have been formulated in an effort to reduce the
level of critical pollutants generated.
For plants which are currently using spraying as their painting
application method, there are several.alternative methods of
application which could reduce the amount of wastewater gene-
rated by the painting operation. Among these methods are
electrostatic spraying, powder coating, flow coating and dip
coating. Electrostatic spraying has a smaller percent of
overspray so less paint enters into the wastewater stream.
Powder coating, flow coating and dip coating generate no
wastewater and the powders or paints used can be recycled.
VII-259
-------
The selection of an application method is highly dependent
upon the geometry of the part being painted so not all of the
methods mentioned above will work for a specific work piece.
A plant which has a painting operation and employs water wash
spray booths to capture overspray may reduce its pollutant
generation by modifications to the spray booths. One possi-
bility is switching over to dry filter booths or oil wash
booths. Neither of these produces any wastewater. Another
alternative is improving the existing booths by adding auto-
matic screening or electrostatic treatment. Both of these
features continuously remove paint solids from the water and
allow for less frequent dumps of the booth wa"ter, thereby
reducing wastewater generation. j
Another process modification applicable to metal finishing
plants is the replacement of solvent degreasing, where possi-
ble, with an alternative cleaning method such as alkaline
cleaning. Typical areas that are amenable to cleaning tech-
niques other than solvent degreasing are: '
1. Low to medium volume production levels when cleaning
cycle time does not impact the cost of production.
3.
4.
5.
6.
Non-ferrous products.
i .
I
Simple product shapes >
Small parts (adaptable to automated processes)
i
Situations where an oily film residue is not
objectionable,,
Situations where no exacting surface finishing
is required.
Cutting Fluid Cleaning
i
Essential to efficient machining operations is a clean and effi-
cient cutting fluid cleaning system. An efficient cleaning
system allows for recycling and reuse of oils. In maintaining
clean fluid, the operation, the metal, and the fluid must be
considered. Settling and skimming is only efficient when large
volumes of fluid and long retention times are available. When
fine particles or micro-debris are involved, the cleaning or
maintenance of a cutting fluid also depends on whether it is a
straight oil or an aqueous emulsion. Many operations and
metals will produce coarse debris while brittle metals produce
fine debris requiring a more sophisticated type of treatment.
Filtration, centrifuging, or magnetic separation may be necessary,
VII-260
-------
Straining
Oil or water solutions require straining to ensure pump protec-
tion. Double strainers should be inserted and kept free of
rags, lint, or other clogging elements. Stainless mesh
strainers are recommended for aqueous systems to minimize
corrosion.
Settling
Large sumps or central systems permit settling. Particle size
and retention time are important considerations to ensure
debris or sediment removal. Settling is essential to other
methods of fluid cleaning by helping reduce sediment loads on
filters and centrifuges.
Baffles above and below the surface of the fluid level will
improve settling and deposition. Tramp oils, scums, and soaps
may be skimmed either continuously or intermittently. Dense
debris and sediment can be removed by drag chains, periodic
sump cleanout, scum gutters, or surface paddles and sweeps.
Centrifuging
As an accelerated settling process, the centrifuge is largely
limited to low solids content removal. It may be used to
enhance the efficiency of low volume systems and will remove
fine particles.
Magnetic Separators
Magnetic separators are an effective means of removing ferrous
or magnetic metals and are most efficiently used with low
viscosity fluids or aqueous systems.
Filtration
The pore size or opening of a filter medium will determine the
particle size which may be removed. The most common filtering
systems consist of self-advancing rolled fabric. Filtration
may be enhanced by vacuum or negative pressure. Supplemental
coatings on filter media, such as diatomaceous earth, add
depth to barrier filtration.
Flotation
The cleaning of cutting fluids can utilize the aeration process,
which causes fine particles to attach themselves to air bubbles,
producing an efficient flotation system. Floating matter,
foam, and scum are then removed by continuous skimmers or froth
paddles. Flotation by aeration has the advantage of high
solids removal in relation to liquid losses and effectively
conserves coolant. In general, the flotation-type system
works best with emulsifiable coolants, but foam must be con-
VH-261
-------
trolled. This system cannot be used with water miscible
fluids of high wettability.
Integrated Waste Treatment ;
Waste treatment can be accomplished in the production area
with constant recycling of the effluent. This process is
generally known as integrated waste treatment. Integrated
waste treatment can be applied to oily wash waters and elec-
troplating rinse waters.
i
The washing of oily metal parts, rinses following oil quenches/
machine system leaks, and some testing washes or rinses produce
the largest majority of oily wastewater. Steps should be
taken in-plant to segregate cutting fluids, hydraulic oils,
crankcase oil, quench oils, and solvents from these waste
streams.
Closed loop systems are available for removing oils, metal
fines, and other residues from wash water 'through a combina-
tion of settling and skimming. A typical \closed loop system
consists of two compartments holding caustic wash solution,
each equipped with an oil roll skimmer. $hile one compartment
supplies wash solution to a series of washers, the other
remains dormant, allowing heavy material to settle and oils
float to the surface. The solids are collected as sludge and
the oils are skimmed off. An alternative .system would be an
ultrafiltration system which can recycle water back to rinse
and wash make-up stations.
Integrated treatment for plating processes uses a treatment
rinse tank in the process line immediately following a process
tank (plating, chromating, etc). Treatment solution (usually
caustic soda in excess) circulating through the rinse tank
reacts with the dragout to form a precipitate and removes it
to a clarifier. This clarifier is a small reservoir usually
designed to fit near the treatment rinse tank and is an
integral part of water use in the production process. Further
treatment may take place in the clarifier (cyanide oxidation,
chromium reduction) or settling alone may be used to separate
the solids. Sludge is removed near the spillover plate on the
effluent side of the clarifier, and the effluent is returned
to the treatment rinse tank. Consequently, no pollutants are
directly discharged by the waste treatment process. Although
further rinsing of the parts is required to remove treatment
chemicals, this rinse will not contain pollutants from the
original process tank, and no further treatment is needed.
Good Housekeeping
Good housekeeping, proper selection and handling of process
solutions, and proper maintenance of metal finishing equipment
are required to reduce wastewater loads to the treatment
system. Good housekeeping techniques prevent premature or
VII-262
-------
unnecessary dumps of process solutions and cooling oils.
Examples of good housekeeping are discussed below.
Frequent inspection of plating racks for loose
insulation prevents excessive dragout of process
solutions. Also, periodic inspection of the condi-
tion of tank liners and the tanks themselves reduces
the chance of a catastrophic failure which would
overload the treatment system.
Steps should be taken to prevent the formation of
hard-to-treat wastes. Separation of cyanide wastes
from nickel or iron wastes is advisable to avoid
formation of cyanide complexes. Proper tank linings
in steel tanks prevent the formation of ferrocyanides.
Periodic inspection should be performed on all
auxiliary metal finishing equipment. This includes
inspection of sumps, filters, process piping, and
immersion steam heating coils for leaks. Filter
replacement should be done in curbed areas or in a
manner such that solution retained by the filter is
dumped to the appropriate waste stream.
Chemical storage areas should be isolated from high
hazard fire areas and arranged such that if a fire
or explosion occurs in the storage area, loss of the
.stored chemicals due to deluge quantities of water
would not overwhelm the treatment facilities.
To, prevent bacterial buildup on machines, sump walls
and circulatory systems should be sterilized at regular
intervals. Centralized cooling systems are self-cleaning
to some extent, but physical and biological cleaning
..are required. The physical cleaning entails the
removal of metallic fines, oxidized oil and other
sludge forming matter. Biological cleaning involves
the use of antiseptic agents, detergents and germi-
cides.
Chip removal from machining operations should include
oil recovery and salvage provisions.
A lubrication program schedule keeps track of leakage
.and contamination. By analyzing records of consump-
tion, it is possible to identify high consumption
equipment. Premature drain intervals may indicate
> .abnormal system contamination which should be corrected.
A general accounting of oils and fluids throughout
their life cycle (purchasing, storage, application,
cleaning and disposal) will lead to oil and fluid
conservation.
VII-263
-------
It is important that proper lubricants should be
employed in a particular piece of machinery. Marking
each piece of equipment with the product type required
is practiced throughout the industry. This helps
prevent the use of an improper oil and the subsequent
premature dumping of that oil.
Training and educating the operators of production
equipment and waste treatment equipment can prevent
unnecessary waste. !
: 41:1 iii, (JJlii;
-------
STATISTICAL ANALYSIS
INTRODUCTION
To establish effluent guideline limitations for the Metal
Finishing Category, the available data were examined statisti-
cally to determine the performance levels that were attained
by properly operated treatment systems in that industry. Two
distinct sets of sampling data were available for this assess-
ment. The first set consists of raw and effluent concentra-
tion data that were collected during sampling visits to repre-
sentative plants in the industry. Typically, these data
cover a period of 3 days of sampling. The other data con-
sisted of sets of long term self-monitoring data (usually
effluent concentration only) that were submitted by plants in
the Metal Finishing Category. These historical data cover-
periods of continuous effluent monitoring up to a year, with
much of the data collected on a daily basis.
Statistical analysis of the data for visited plants yielded
mean and median effluent concentration values for each pollut-
ant parameter. More information (than mean or median concen-
trations) is available from the historical data because even
properly operating treatment systems experience fluctuations
in the pollutant concentrations discharged. These fluctua-
tions result from variations in process flow, raw waste
loading of the pollutants, treatment chemical feed, mixing
effectiveness during treatment, and combinations of these or
other factors. Statistical analysis of these historical data
allows a quantitative assessment of the variability of the-
effluent pollutant concentrations. Allowance for the day-to-
day variation in the effluent concentration of a pollutant was
accounted for in the determination of the limitations by the
use of a variability factor, which is always greater than l.O.
Application of a variability factor for each pollutant allows
the establishment of an upper limit for the effluent concen-
tration of each pollutant.
The following paragraphs describe the statistical methodology
used to calculate the variability factors and to establish the
pollutant limitations.
CALCULATION OF VARIABILITY FACTORS
Variability factors are used to account for effluent concen-
tration flucta-tions in the establishment of reasonable ef-
fluent limitations. Calculation of these factors is discussed
here, while their application is discussed under the next
heading. A daily maximum variability factor and a 30-day
average variability factor were calculated for each pollutant
parameter at each treatment option level.
These calculations were based on the following three assump-
tions: (1) the daily pollutant concentration data for each
VII-265
-------
plant are lognormally distributed; (2) monitoring at each
plant was conducted using standardized testing procedures such
that the resulting measurements can be considered statistically
independent and amenable to standard statistical procedures; (3)
treatment facilities and monitoring techniques at each plant
were substantially constant throughout the monitoring period.
The lognormality assumption was supported by plotting the data
on lognormal probability graph paper. A straight line approx-
imation confirms lognormal distribution of the data. Examples
of these graphs are shown in Figures 7-78 through 7-84. The
other two assumptions, which concern self-consistency of the
data, were supported by direct examination of the data and by
consideration of supplemental information accompanying the
data. Suspect parameters or entire plant data sets were
removed from the analysis.
Once lognormality was verified, the variability factors were
calculated from appropriate equations. The derivations of
these equations are presented in Appendix ;XII-A1 of the
Development Document for Electroplating Pretreatment
Standards, EPA 440/1-79/003, August, 1979. The calculations
were designed so that application of the resulting variability
factors would result in effluent limitations that a plant
could be expected to meet 99 times out of 100.
I
The daily maximum variability factor was calculated in either
of two ways, depending on the number of data points for a
particular plant. For instances of 100 or more data points,
the daily variability factor for each plant was calculated by
dividing the 99th percentile data point by the mean value of
all the data points. Thus, for 100 data points the second
highest value would be divided by the mean value of the 100
points. When fewer than 100 data points were available, the
daily variability factor for each plant (VF) was calculated
from the equation
In VF = 2.326 (sigma) - 0.5 (sigma)2
In this equation, 2.326 is the Z value corresponding to the
99th percentile point for the normal distribution curve and
sigma is the standard deviation of the natural logarithms of
the concentrations.
The 30-day average variability factor (VF*) for each plant was
•calculated from the equation
VF* » 1.0 + 2.326 (S/M)
i
In this equations, 2.326 is the Z value corresponding to the
99th percentile point for the normal distribution curve; S is
the estimated standard deviation of the monthly average,
obtained by dividing the estimated standard deviation of the
daily pollutant concentrations by the square root of 30; and M
is the mean value of the daily pollutant concentrations.
VII-266
-------
1.0
i
c
o
•H
-U
(8
U4
4J
£
(V
O
c
o
e-
•H
g
•o
(0
4J
c
0)
3
0.1
0.01
0.001
2
o o
10 15 20 30 40 bO 60 70
Percentile Distribution
80 85 90
95
98
FIGURE 7-78
CUMULATIVE DISTRIBUTION OF 51 DAILY CADMIUM
EFFLUENT CONCENTRATIONS FROM PLANT ID 47025
VII-267
-------
10.0
1.0
o
4J
a
o
o
u
c
X)
c
3
i-l
u-i
0.1
0.01
O
10 15 20 30 40 50 60 ;70 80 85 90
Percentile Distribution
95
98
FIGURE 7-79
CUMULATIVE DISTRIBUTIONS OF 13 DAILY ZINC
EFFLUENT CONCENTRATIONS FROM PLANT ID 06051
VII-268
-------
10000.0
rH
1
1000. 0
c
o
•H
4J
(rt
Effluent Oil and Grease .Concentr.
H
s ?
0
X
2
\.s
.X
X
x*1
_x^
'
jy
—
X
5 0 5 20 30 40 50 60
X
^
^
X
^
.
0 80 85 90 95 9i
Percentile Distribution
FIGURE 7-80
CUMULATIVE DISTRIBUTIONS OF 10 DAILY OIL & GREASE
EFFLUENT CONCENTRATIONS FROM PLANT ID 20254
VII-269
-------
1.0
o
•rt
4J
C
a)
u
I
S
.c
o
c
4)
•a
0.1
0.01
0.001
^
10 15 20 30 40 50 60 70
Percentile Distribution
80 85 90
95
98
FIGURE 7-81
CUMULATIVE DISTRIBUTIONS OF 49 DAILY CHROMIUM
EFFLUENT CONCENTRATIONS FROM PLANT ID 30090
VII-270
-------
1000.0
100.0
o
4J
c
o
o
tJ
0)
•a
c
OK
3 10. 0
cn
c
-------
i1
o
4J
(D
0)
O
c
o
CJ
•o
(0
3
4J
01
3
U-l
H
1.0
0.1
0.01
^
>- o a
H-O-^
tfo'
^
MV;
^}
op,
™*
^
i
i
j
'
x^
•cT*
<«
^
j>
2 S 10 15 20 30 40 50 60 70 80 8 9 9 9
Percentile Distribution
FIGURE 7-83
CUMULATIVE DISTRIBUTIONS OF 49 DAILY LEAD
EFFLUENT CONCENTRATIONS FROM PLANT ID 44045
VII-272
-------
100.0
10.0
o
(0
iJ
JJ
c
0)
o
o
9?
Cu
o
o
JJ
•*
0
50 0 0 0 0 70
Percentile Distribution
80 85 90
95
8
FIGURE 7-84
CUMULATIVE DISTRIBUTIONS OF 28 DAILY COPPER
EFFLUENT CONCENTRATIONS FROM PLANT ID 11118
VII-273
-------
Using these techniques, a set of daily maximum variability
factors (one for each plant) and a set of 30-day average
variability factors were calculated for each pollutant para-
meter. For each pollutant parameter, the median variability
factor (both daily and 30-day factor) of the set was selected
as the variability factor to be used to establish the concen-
tration limitations. !
CALCULATION OF EFFLUENT LIMITATIONS |
The effluent limitations are based on the premise that a
plant's treatment system can be operated to maintain average
(mean) effluent concentrations equal to those determined from
the sampled data from visited plants. As explained in the
introduction, the day-to-day concentrations will fluctuate
below and above these average concentrations. Thus the ef-
fluent limitations must be set far enough above the average
concentrations that plants with properly operated treatment
systems will not exceed them (99 percent of the time). The
effluent limitations were obtained for each parameter by
multiplying the average concentration (based on visit data) by
the appropriate daily and 30-day variability factors (based on
historical data) to obtain the effluent limitations. Ex-
pressed as equations, |
L =
L*
VF x A
= VF* x A
In these equations, L is the daily maximum limitation, L* is
the 30-day average limitation, VF is the daily maximum varia-
bility factor, VF* is the 30-day average variability factor,
and A is the average concentration based on plant visit data.
VII-274
-------
SECTION VIII
COST OF WASTE WATER CONTROL AND TREATMENT
INTRODUCTION . ,
This section presents estimates of the cost of implementation of
wastewater treatment and control options for each of the sub-
categories included in the Metal Finishing Category. These
costs estimates, together with the pollutant reduction perform-
ance for each treatment and control option presented in Section
VII provide a basis for evaluation of the options presented.
The cost estimates also provide the basis for the determination .
of the probable economic impact of regulation at different
pollutant discharge levels on the Metal Finishing Category. In
addition, this section addresses non-water quality environmental
impacts of wastewater treatment and control alternatives includ-
ing air pollution, noise pollution, solid wastes, and energy
requirements.
To arrive at the cost estimates presented in this section,
specific wastewater treatment technologies and in-process con-
trol techniques from among those, discussed in Section VII were
selected and combined in wastewater treatment and control sys-
tems appropriate for each waste type. The different waste
treatment systems were combined for cost estimation in six
different plant treatment systems corresponding to the most
common types of facilities operating within -the Metal Finishing
Category. As described in more detail below, investment arid
annual costs for each system were estimated based on wastewater
flows and raw wastewater characteristics for each waste type as
presented in Section V. Cost estimates are also presented for
individual treatment technologies included in the waste treat-
ment systems.
COST ESTIMATION METHODOLOGY
Cost estimation is accomplished using a computer program which
accepts inputs specifying the treatment system to be estimated,
chemical characteristics of the raw wastewater streams treated,
flow rates and operating schedules. The program accesses models
for specific treatment components which relate component invest-
ment and operating costs, materials and energy requirements, and
effluent stream characteristics to influent flow rates and
stream characteristics. Component models are excercised sequen-
tially as the components are encountered in the system to deter-
mine chemical characteristics and flow rates at each point.
Component investment and annual costs are also determined and
used in the computation of total system costs. Mass balance
calculations are used to determine the characteristics of com-
bined streams resulting from mixing two or more streams and to
determine the volume of sludges or liquid wastes resulting from
treatment operations such as chemical precipitation and set-
tling, filtration, and oil separation.
VIII-1
-------
Cost estimates are broken down into several distinct elements in
addition to total investment and annual costs: operation and
maintenance costs, energy costs, depreciation, and annual costs
of capital. The cost estimation program incorporates provisions
for adjustment of all costs to a common dollar base on the basis
of economic indices appropriate to capital equipment and operat-
ing supplies. Labor and electrical power costs are input vari-
ables appropriate to the dollar base year for cost estimates.
These cost breakdown and adjustment factors as well as other
aspects of the cost estimation process are ;discussed in greater
detail in the following paragraphs.
Cost Estimation Input Data
The wastewater treatment system descriptions input to the com-
puter cost estimation program include both a specification of
the wastewater treatment components included and a definition of
their interconnections. For some component's, retention times or
other operating parameters are specified in the input, while for
others, such as reagent mix tanks and clarifiers, these para-
meters are specified within the program based on prevailing
design practice in industrial wastewater treatment. The waste-
water treatment system descriptions may include multiple raw
wastewater stream inputs and multiple treatment trains. For
example, cyanide bearing waste streams are segregated and
treated for cyanide oxidation and chromium bearing wastes are
segregated for chromium rlduction prior to subsequent chemical
precipitation treatment with the remaining process wastewater.
i
The specific treatment systems selected for cost estimation for
each subcategory were based on an examination of raw waste
characteristics, consideration of manufacturing processes, and
an evaluation of available treatment technologies discussed in
Section VII. The rationale for selection of these systems and
their pollutant removal effectiveness are also addressed in
Section VII.
The input data set also includes chemical characteristics for
each raw wastewater stream specified as input to the treatment
systems for which costs are to be estimated. These character-
istics are derived from the raw wastewater sampling data pre-^
sented in Section V. The pollutant parameters which are pre-
sently accepted as input by the cost estimation program are
shown in Table 8-1. The values of these parameters are used in
determining materials consumption, sludge volumes, treatment
component sizes, and effluent characteristics. The list of
input parameters is expanded periodically as additonal pollut-
ants are found to be significant in wastewater streams from
industries under study and as additional treatment technology
cost and performance data become available. Within the Metal
Finishing Category, individual waste types commonly encompass a
number of different wastewater streams which are present to
varying degrees at different facilities. The raw wastewater
characteristics shown -as input to wastewater treatment represent
vrii-2
-------
a mix of these streams including all significant pollutants
found and will not in general correspond precisely to process ...
wastewater at any existing facility. The process by which these
raw wastewaters were defined is explained in Section V.
TABLE 8-1
COST PROGRAM POLLUTANT PARAMETERS
Parameter, Units
Flow, MGD
pHf pH units
Turbidity, Jackson Units
Temperature, degrees C
Dissolved oxygen, mg/1
Residual Chlorine, mg/1
Acidity, mg/1 CaCOS
Alkalinity, mg/1 CaCOS
Ammonia, mg/1
Biochemical Oxygen Demand mg/1
Color, Chloroplatinate units
Sulfide, mg/1
Cyanides, mg/1
Kjeldahl Nitrogen, mg/1
Phenols, mg/1
Conductance, micromhos/cm
Total Solids, mg/1
Total Suspended Solids, mg/1
Settleable Solids, mg/1
Aluminum, mg/1
Barium, mg/1
Cadmium, mg/1
Calcium, mg/1
Chromium, Total, mg/1
Copper, mg/1
Fluoride, mg/1
Iron, Total, mg/1
Lead, mg/1
Magnesium, mg/1
Molybdenum, mg/1
Total Volatile Solids, mg/1
Parameter, Units
Oil, Grease, mg/1
Hardness, mg/1 CaCOS
Chemical Oxygen Demand, mg/1
Algicides, mg/1
Total Phosphates, mg/1
Polychlorobiphenyls, rag/1
Potassium, mg/1
Silica, mg/1
Sodium, mg/1
Sulfate, mg/1
Sulfite, mg/1
Titanium, mg/1
Zinc, mg/1
Arsenic, mg/1
Boron, mg/1
Iron, Dissolved, mg/1
Mercury, mg/1
Nickel, mg/1
Nitrate, mg/1
Selenium, mg/1
Silver, mg/1
Strontium, mg/1
Surfactants, mg/1
Beryllium, mg/1
Plasticizers, mg/1
Antimony, mg/1
Bromide, mg/1
Cobalt, mg/1
Thallium, mg/1
Tin, mg/1
Chromium, Hexavalent, mg/1
VTII-3
-------
I,
The final input data set comprises raw wastewater flow rates for
each subcategory input stream addressed. Six treatment scenar-
ios corresponding to different types of manufacturing facilities
within the Metal Finishing Category are addressed in the cost
estimates. Each scenario entails a different combination of
individual subcategory wastewater streams., For each, costs are
estimated for five total plant wastewater ;£low rates spanning
the range of flows generally encountered within the Metal
Finishing Category (1,000 - 10,000,000 I/day). From these data,
graphs have been prepared showing total treatment system invest-
ment costs and total annual costs as a function of flow rate for
each scenario.
I
System Cost Computation
]
A simplified flow chart for the estimatatipn of wastewater
treatment and control costs from the input data described above
is presented in Figure 8-1. In the computation, raw wastewater
characteristics and flow rates are used as input to the model
for the first treatment technology specified in the system
definition. This model is used to determine the size and cost
of the component, materials and energy consumed in its opera-
tion, and the volume and characteristics of the stream(s) dis-
charged from it. These stream characteristics^ are then used as
input to the next component(s) encountered in the system defini-
tion. This procedure is continued until the complete system
costs and the volume and characteristics of the final effluent
stream(s) and sludge wastes have been determined. In addition
to treatment components, the system may include mixers in which
two streams are combined, and splitters in which part of a
stream is directed to another destination.; These elements are
handled by mass balance calculations and allow cost estimation
for specific treatment of segregated process wastewaters prior
to combination with other process wastewaters for further treat-
ment, and representation of partial recycle of wastewater.
!
As an example of this computation process, the sequence of cal-
culations involved in the development of cost estimates for the
simple treatment system shown in Figure 8-2 may be described.
Initially, input specifications for the treatment system are
read to set up the sequence of computations. The subroutine
addressing chemical precipitation and clarification is then
accessed. The sizes of the mixing tank and clarification basin
are calculated based on the raw wastewater;flow rateto provide
45 minute retention in the mix tank and 4 hour retention with a
33.3 gal/hr/sq ft surface loading in the clarifier. Based on
these sizes, investment and annual costs fpr labor, supplies for
the mixing tank and clarifier including mixers, clarifier rakes
and other directly related equipment are determined. Fixed
investment costs are then added to account !for sludge pumps,
controls, piping, and reagent feed systems.
Based on the input raw wastewater concentrations and flow rates,
the reagent additions (lime, alum and polyelectrolyte) are
VIII-4
-------
SIMPLIFIED LOGIC DIAGRAM
SYSTEM COST ESTIMATION PROGRAM
NON-RECYCLE
SYSTEMS
INPUT
A) RAW WASTE DESCRIPTION
B) SYSTEM DESCRIPTION
C) "DECISION" PARAMETERS
D) COST FACTORS
PROCESS CALCULATIONS
A) PERFORMANCE - POLLUTANT
PARAMETER EFFECTS
B) EQUIPMENT SIZE
C) PROCESS COST
(RECYCLE SYSTEMS)
CONVERGENCE
A) POLLUTANT PARAMETER
TOLERANCE CHECK
(NOT WITHIN
TOLERANCE LIMITS)
(WITHIN TOLERANCE LIMITS)
COST CALCULATIONS
A) SUM INDIVIDUAL PROCESS
COSTS
B) ADD SUBSIDIARY COSTS
C) ADJUST TO DESIRED DOLLAR BASE
OUTPUT
A) STREAM DESCRIPTIONS-
COMPLETE SYSTEM
B) INDIVIDUAL PROCESS SIZE AND
COSTS
C) OVERALL SYSTEM INVESTMENT
AND ANNUAL COSTS
FIGURE 8-1
COST ESTIMATION PROGRAM
-------
CHEMICAL
ADDITION
RAW WASTE
(FLOW, TSS. LEAD.
ZINC. ACIDITY)
EFFLUENT
SLUDGE
(CONTRACTOR
REMOVED)
FIGURE 8-2
SIMPLE WASTE TREATMENT SYSTEM
VIII-6
-------
calculated to provide fixed concentrations of alum and poly-
electroly,te and 10% excess lime over that required for stoichio-
metric reaction with the acidity and metals present in the
wastewater stream. Costs are calculated for these materials,
and the suspended solids and flow leaving the mixing tank and
entering the clarifier are increased to reflect the lime solids
added and precipitates formed. These modified stream character-
istics are then used with performance algorithms for the clari-
fier (as discussed in Section VII) to determine concentrations
of each pollutant in the clarifier effluent stream. By mass
balance, the amount of each pollutant in the clarifier sludge
may be determined. The volume of the sludge stream is deter-
mined by the concentration of TSS which is fixed at 4-5% based
on general operating experience, and concentrations of other
pollutants in the sludge stream are determined from their masses
and the volume of the stream.
The subroutine describing vacuum filtration is then called, and
the mass of suspended solids in the clarifier sludge stream is
used to determine the size and investment cost of the vacuum
filtration unit. To determine manhours required for operation,
operating hours for the filter are calculated from the flow rate
and TSS concentration. Maintenance labor requirements are added
as a fixed additional cost.
The sludge flow rate and TSS content are then used to determine
costs of materials and supplies for vacuum filter operation
including iron and alum added as filter aids, and the electrical
power costs for operation. Finally, the vacuum filter perform-
ance algorithms are used to determine the volume and character-
istics of the vacuum filter sludge and filtrate, and the costs
of contract disposal of the sludge are calculated. The recycle
of vacuum filter filtrate to the chemical precipitation and
settling system is hot reflected in the calculations due to the
difficulty of iterative solution of such loops and the general
observation that the contributions of such streams to the total
flow and pollutant levels are, in practice, negligibly small.
Allowance for such minor contributions is made in the 20% excess
capacity provided in most components.
The costs determined for all components of the system are summed
and subsidiary costs are added to provide output specifying
total investment and annual costs for the system and annual
costs for capital, depreciation, operation and maintenance, and
energy. Costs for specific system components and the character-
istics of all streams in the system may also be specified as
output from the program.
Treatment Component Models
The cost estimation program presently incorporates subroutines
providing cost and performance calculations for the treatment
technologies identified in Table 8-2. These subroutines have
been developed over a period of years from the best available
VIII-7
-------
information including on-site observations of treatment system
performance, costs, and construction practices at a large number
of_industrial facilities, published data, and information ob-
tained from suppliers of wastewater treatment equipment. The
subroutines are modified and new subroutines added as additional
data allow improvements in models for treatment technologies
presently available,.and, as additional treatment technologies
are required for the industrial wastewater streams under study.
Specific discussions of each of the treatment component models
used in costing wastewater treatment and control systems for the
Metal Finishing Category is presented later in this section
where cost estimation is addressed, and in Section VII where
performance aspects were developed. '
TABLE 8-2 :
TREATMENT TECHNOLOGY SUBROUTINES
Treatment Process Subroutines
Spray/Fog Rinse
Countercurrent Rinse
Vacuum Filtration
Gravity Thickening
Sludge Drying Beds
Holding Tanks
Centrifugation
Equalization
Contractor Removal
Reverse Osmosis
Landfill
Chemical Reduction of Chromium
Chemical Oxidation of Cyanide
Neutralization
Clarification (Settling
Tank/Tube Settler)
API Oil Skimming
Emulsion Breaking (Chem/Thermal)
Membrane Filtration
Filtration (Diatomaceous Earth)
Ion Exchange - w/Plant Regeneration
Ion Exchange - Service Regeneration
Flash Evaporation
Climbing Film Evaporation
Atmospheric Evaporation
Cyclic Ion Exchange
Post Aeration
Sludge Pumping
Copper Cementation
Sanitary Sewer Discharge Fee
Ultrafiltration
Submerged Tube Evaporation
Flotation/Separation
Wiped Film Evaporation
Trickling Filter
Activated Carbon Adsorption
Nickel Filter
Sulfide Precipitation
Sand Filter
Chromium Regeneration
Pressure Filter
Multimedia Granular Filter
Sump
Cool ing Tower
Ozonation
Activated Sludge
Coalescing Oil Separator
Non Contact Cooling Basin
Raw Wastewater Pumping
Preliminary Treatment
Preliminary Sedimentation
Aerator - Final Settler
Chlorination
Flotation Thickening
Multiple Hearth Incineration
Aerobic Digestion
''.•Mill1 „!,,: ,.; • '•' ii'',!iii!,."i ', ,
VIII-8
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In general terms, cost estimation is provided by mathematical
relationships in each subroutine approximating observed cor-
relations between component.costs and the most significant
operational parameters such as water flow rates, retention
times, and pollutant concentrations. In general, flow rate is
the primary determinant of investment costs and of most annual
costs with the exception of material costs. In some cases,
however, as discussed for the vacuum filter, pollutant concen-
trations may also significantly influence costs.
Cost Factors and Adjustments
As previously indicated, costs are adjusted to a common dollar
base and are generally influenced by a number of factors in-
cluding: Cost of Labor, Cost of Energy, Capital Recovery Costs
and Debt-Equity Ratio. These cost adjustments and factors are
discussed below.
Dollar Base - A dollar base of August 1979 was used for all
costs.
Investment Cost Adjustment - Investment costs were adjusted to
the aforementioned dollar base by use of Sewage Treatment Plant
Construction Cost Index. This cost is published monthly by the
EPA Division of Facilities Construction and Operation. The
national average of the Construction Cost Index for August 1979
was 337.8.
Supply Cost Adjustment - Costs of supplies such as chemicals
were related to the dollar base by use of the Producer Price
Index (formerly known as the Wholesale Price Index). This
figure was obtained from the U.S. Department of Labor, Bureau of
Labor Statistics, "Monthly Labor Review". For August 1979 the
"Industrial Commodities" Producer Price Index was 240.3. Pro-
cess supply arid replacement costs were included in the estimate
of the total process operating and maintenance cost.
Cost of Labor - To relate the operating and maintenance labor
costs~the hourly wage rate for non-supervisory workers in sani-
tary services was- used from the U.S. Department of Labor, Bureau
of Labor Statistics October, 1979, publication, "Employment and
Earnings". For August 1979, this wage rate was $6.71 per hour.
This wage rate was- then applied to estimates of operation and
maintenance man-hours within each process to obtain process
direct labor charges. To account for indirect labor charges, 15
percent of the direct labor costs was added to the direct labor
charge to yield estimated total labor costs. Such items as
Social Security, employer contributions to pension or retirement
funds, and employer-paid premiums to various forms of insurance
programs were considered indirect labor costs.
VIII-9
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Cost of Energy - Energy requirements were calculated directly
within each process. Estimated costs were than determined by
applying an electrical rate of 4.5 cents per kilowatt hour.
This electrical charge was determined by assuming that any
electrical needs of a waste treatment facility or in-process
technology would be satisfied by an existing electrical distri-
bution system, i.e., no new meter would be required. This
eliminated the formation of any new demand load base for the
electrical charge.
Capital Recovery Costs - Capital recovery costs were divided
into straight line five-year depreciation and cost of capital at
a thirteen percent annual interest rate foraperiod of five
years. The five year depreciation period was consistent with
the faster write-off (financial life) allowed for these facili-
ties even though the equipment life is in the range of 20 to 25
years.
The annual cost of capital was calculated by using the capital
recovery factor approach.
The capital recovery factor is normally
allocate the initial investment and the
operating cost of the facility. It is
used in industry to help
interest to the total
equal to:
where i is the annual interest rate and N is the number of years
over which the capital is to be recovered. The annual capital
recovery was obtained by multiplying the initial investment by
the capital recovery factor. The annual depreciation of the
capital investment was calculated by dividing the initial invest-
ment by the depreciation period N, which was assumed to be five
years. The annual cost of capital was then equal to the annual
capital recovery minus the depreciation. ;
Debt-Equity Ratio - Limitations on new borrowings assume that
debt may not exceed a set percentage of the shareholders'
equity. This defines the breakdown of the capital investment
between debt and equity charges. However, due to the lack of
information about the financial status of various plants, it was
not feasible to estimate typical shareholders equity to obtain
debt financing limitations. For these reasons, capital cost was
not broken into debt and equity charges. Rather, the annual
cost of capital was calculated via the procedure outlined in the
Capital Recovery Costs section above. ;
Subsidiary Costs i
j
The waste treatment and control system costs presented in
Figures 8-34 through 8-65 for end-of-pipe and in-process waste-
water control and treatment systems include subsidiary costs
VIII-10
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associated with system construction and operation. These sub-
sidiary costs include:
administration and laboratory facilities
- garage and shop facilities
- line segregation
- yardwork
piping
instrumentation
- land
- engineering
- legal, fiscal, and administrative
- interest during construction
Administrative and laboratory facility treatment investment is
the cost of constructing space for administration and laboratory
functions for the wastewater treatment system. For these cost
computations, it was assumed that there was already an existing
building and space for administration and laboratory functions.
Therefore, there was no investment cost for this item.
For laboratory operations, an analytical fee of $105 (August
1979 dollars) was charged for each wastewater sample, regardless
of whether the laboratory work was done on or off site. This
analytical fee is typical of the charges experienced by the EPA
contractor during the past several years of sampling programs.
The frequency of wastewater sampling is a function of waste-
water discharge flow and is presented in Table 8-3. This fre-
quency was suggested by the Water Compliance Division of the
USEPA.
For industrial waste treatment facilities being costed, no
garage and shop investment cost was included. This cost item
was assumed to be part of the normal plant costs and was not
allocated to the wastewater treatment system.
Line segregation investment costs account for plant modifica-
tions to segregate wastewater streams. The investment costs for
line segregation included placing a trench in the existing plant
floor and installing the lines in this trench. The same trench
was used for all pipes. The pipes were assumed to run from the
center of the floor to a corner. A rate of 2.04 liters per hour
of wastewater discharge per square meter of area (0.05 gallons
per hour per square foot) was used to determine floor and trench
dimensions from wastewater flow rates for use in this cost
VIII-11
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estimation process. It was assumed that 3 transfer pump would
be required for each segregated process line in order to trans-
fer the wastes to the treatment system.
TABLE 8-3
WASTEWATER SAMPLING FREQUENCY
Waste Water Discharge
(liters per day)
0 - 37,850
37,850 - 189,250
189,250 - 378,500
378,500 - 946,250
946,250+
Sampling Freqency
once per month
twice per month
j
once per week
twice per week
i
thrice per week
The yardwork investment cost item includes the cost of general
site clearing, lighting, manholes, tunnels, conduits, and gen-
eral site items outside the structural confines of particular
individual plant components. This cost is typically 9 to 18
percent of the installed components investment costs. For these
cost estimates, an average of 14 percent was utilized. Annual
yardwork operation and maintenance costs are considered a part
of normal plant maintenance and were not included in these cost
estimates. ;
The piping investment cost item include the cost of inter-
component piping, valves, and piping required to transfer the
wastes to the waste treatment system. This cost is estimated to
be equal to 20 percent of installed component investment costs.
i
The instrumentation investment cost item includes the cost of
metering equipment, electrical wiring and cable, treatment
component operational controls, and motorjcontrol centers as
required for each of the waste treatment systems described in
Section VII of the document. The instrumentation investment
cost is estimated based upon the requirements of each waste
treatment system. For continuous operation, a fixed investment
cost of $29,300 is included to cover the cost of instrumentation
not included in any treatment components.
No new land purchases were required. It was assumed that the
land required for the end-of-pipe treatment system was already
available at the plant. ;
Engineering costs include both basic and special services.
Basic services include preliminary design reports, detailed
design, and certain office and field engineering services during
VIII-12
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construction of projects. Special services include improvement
studies, resident engineering, soils investigations, land sur-
veys, operation and maintenance manuals, and other miscellaneous
services. Engineering cost is a function of process installed
and yardwork investment costs and ranges between 5.7 and 14%
depending on the total of these costs.
Legal, fiscal and administrative costs relate to planning and
construction of waste water treatment facilities and include
such items as preparation of legal documents, preparation of
construction contracts, acquisition of land, etc. These costs
are a function of process installed, yardwork, engineering, and
land investment costs, ranging between 1 and 3% of the total of
these costs.
Interest cost during construction is the interest cost accrued
on funds from the time payment is made to the contractor to the
end of the construction period. The total of all other project
investment costs (process installed; yardwork; land; engineer-
ing; and legal, fiscal, and administrative) and the applied
interest affect this cost. An interest rate of 13 percent was
used to determine the interest cost for these estimates. In
general, interest cost during construction varies between 3 and
10% of total system costs depending on the total costs.
COST ESTIMATES FOR INDIVIDUAL TREATMENT TECHNOLOGIES
Table 8-4 lists those technologies which are incorporated in the
wastewater treatment and control options offered for the metal
finishing category and for which cost estimates have been devel-
oped. These treatment technologies have been selected from
among the larger set of available alternatives discussed in
Section VII on the basis of an evaluation of raw waste character-
istics, typical plant characteristics (e.g. location, production
schedules, product mix, and land availability), and present
treatment practices within the subcategory addressed. Specific
rationale for selection is addressed in Section IV, X XI and
XII. Cost estimates for each technology addressed in this
section include investment costs and annual costs for deprecia-
tion, capital, operation and maintenance, and energy.
Investment - Investment is the capital expenditure required to
bring the technology into operation. If the installation is a
package contract, the investment is the purchase price of the
installed equipment. Otherwise, it includes the equipment cost,
cost of freight, insurance and taxes, and installation costs.
Total Annual Cost - Total annual cost is the sum of annual costs
for depreciation7 capital, operation and maintenance (less
energy), and energy (as a separate function).
Depreciation - Depreciation is an allowance, based on tax
regulations, for the recovery of fixed capital from an
investment to be considered as a non-cash annual expense.
VIII-13
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It may be regarded as the decline in value of a capital
asset due to wearout and obsolescence. ;
Capital - The annual cost of capital is the cost, to the
plant, of obtaining capital expressed as an interest rate.
It is equal to the capital recovery cost (as previously
discussed on cost factors) less depreciation.
Operation and Maintenance - Operation and maintenance cost
is the annual cost of running the wastewater treatment
equipment. It includes labor and materials such as waste
treatment chemicals. As presented in the tables, operation
and maintenance cost does not include energy (power or
fuel) costs because these costs are shown separately.
] ""
Energy - The annual cost of energy is shown separately,
although it is commonly included as pjart of operation and
maintenance cost. Energy cost has been shown separately
because of its importance to the nation's economy and
natural resources.
TABLE 8-4
INDEX TO TECHNOLOGY COSTS
Technology
Figure or Table
CN Oxidation
Chromium Reduction
Clarification
Emulsion Breaking
Holding Tanks
Multimedia Filtration
Ultrafiltration
Carbon Adsorption
Sludge Drying Beds
Vacuum Filtration
Contract Removal
Countercurrent Rinse
Evaporation
Cyanide Oxidation
Figures
Figures
Figures
Figures
Figures
Figures
Figures
Figures
Figures
Figures
8-3 : to 8-5
8-6 , & 8-7
8-8 to 8-10
8-111 to 8-13
8-14 to 8-16
8-17 & 8-18
8-19 to 8-21
8-22 to 8-24
8-25 & 8-26
8-27 to 8-29
Tables 8-6 & 8-7
Figures 8-30 to 8-32
In this technology, cyanide is destroyed by reaction with sodium
hypochlorite under alkaline conditions. A complete system for
accomplishing this operation includes reactors, sensors, con-
trols, mixers, and chemical feed equipment1. Control of both pH
and chlorine concentration (through oxidation-reduction poten-
tial) is important for effective treatments
Investment Costs - Investment costs for cyanide oxidation as
shown in Figure 8-3 include reaction tanks, reagent storage,
mixers, sensors and controls necessary for operation. Costs are
estimated for both batch and continuous systems with the oper-
ating mode selected on a least cost basis.1 Specific costing
assumptions are as follows:
VIII-14
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Por^batch teatment, oxidation is accomplished by the addition of
sodium hypochlorite. Sodium hydroxide and sulfuric acid are
added to maintain the proper pH level. A manually controlled
feed pump is included for each treatment chemical. Chemical
storage for the limited quantities generally involved in batch
treatment is assumed to be in shipping containers, and no invest-
ment costs for storage facilities are calculated. Reaction tank
costs are based on two fiberglass tanks, each of which is sized
to provide four hours retention based on process flow rates.
Mixers, based on one horsepower per 1000 gallons of reaction
tank volume (0.5 HP minimum) are also provided. Investment
costs also include a transfer pump and a manual instrumentation
set including:
j
2 pH probes j
1 pH probe maintenance kit
1 pH meter
3 ORP probes }
1 ORP meter \
Installation is included as 60% of the sum of the component
costs.
For continuous treatment, oxidation is accomplished using chlo-
rine obtained as a gas. Sodium hydroxide and sulfuric acid are
used for pH control. Investment costs include a chlorination
system and automatically controlled pH control systems for two
treatment tanks (for the two-stage cyanide: destruction process).
These systems include:
pH Control and Instrumentation
2 Pump stands
2 Feed pumps
2 Liquid Level detectors j
15 days storage for acid and sodiumj hydroxide
2 pH probes ,
2 pH meters • ,
1 pH probe maintenance kit ' i .. ,
2 pH controllers
3 ORP probes
2 ORP meters
2 ORP controllers
2 Recorders
Chlorination System
Chlorinator
Pressure Reducing valves
Venturi ejector
Diffuser
Piping and fittings
Evaporator
VIII-16
-------
Weighing scale
Gas detector
Emergency vent system
Hoisting equipment
Installation and start-up service
Costs are estimated for fiberglass reaction tanks providing O.5
hours retention for the first stage of treatment and 1 hour
retention for the second stage. Mixers based on 1 horsepower
per 1000 gallons with a minimum of 1 horsepower are costed for
each tank. Cost estimates also include 2 emergency vent fans, 3
circulation pumps, and 2 transfer pumps.
Operation and Maintenance Costs - Costs for operating and main-
taining cyanide oxidation systems include labor and chemical
expenses. Annual operation and maintenance expenses for batch
and continuous cyanide oxidation systems are shown in Figure 8-4
as a function of waste stream flow rate.
Labor expenses for the batch treatment system are estimated
based on 1.5 hours of labor per batch of waste treated plus 2
hours of maintenance labor per week plus additional labor for
chemical handling based on the amounts of treatment chemicals
consumed. For continuous treatment, maintenance labor is esti-
mated at 4 hours per week, and operating labor at 1 hour per
shift plus an additional 0.5 hours per cylinder (1 ton) of
chlorine consumed.
Chlorine or sodium hypochlorite addition is calculated based on
a 10% excess over stoichiometric requirements calculated from
measured cyanide concentrations plus concentrations of some
metals, (copper, iron, and nickel) which form cyanide complexes.
Sodium hydroxide requirements to maintain pH are calculated
based on the flow and the amount of cyanide being treated, and
sulfuric acid consumption is based on flow and sodium hydroxide
consumption. ' '.
Chemical costs have been based on the following unit prices:
$ 600 Per ton of chlorine (August, 1,979 price)
$1462 Per ton of sodium hypochlorite (August, 1979 price)
$ 699 Per ton of sodium hydroxide (August, 1979 price)
$ 113 Per ton of sulfuric acid (August, 1979 price)
The assumption has been made that the plants operate 24 hours
per day, 260 days/year.
Energy Costs - Motor horsepower requirements for chemical mixing
have been described above. Mixing equipment is assumed to
operate continuously over the operation time of the treatment
system for both the continuous and batch modes. Pump motor
VIII-17
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-------
horsepower requirements are calculated based on several var-
iables. These include system flow, pump head and system oper-
ating time.
Annual energy expenses for batch and continuous cyanide oxida-
tion systems are shown in Figure 8-5 as a function of waste
stream flow rate. Energy expenses have been estimated based
upon a rate of $0.045/kilowatt hour of required electricity.
Plant operation was assumed to be for 24 hours/day, 260 days/
year. For continuous treatment, the treatment system operates
during plant operation. Batch treatment operation schedules
vary with flow rate as discussed above.
Chromium Reduction
This technology provides chemical reduction of hexavalent chro-
mium under acidic conditions to allow subsequent removal of the
trivalent form by precipitation as the hydroxide. Treatment may
be provided in either continuous or batch mode; cost estimates
are developed for each. Operating mode for system cost esti-
mates is selected on a least cost basis.
Investment Cost - Cost estimates include all required equipment
for performing this treatment technology including reagent
dosage, reaction tanks, mixers and controls. Different reagents
are provided for batch and continuous treatment resulting in
different system design considerations as discussed below.
For both continuous and batch treatment, sulfuric acid is added
for pH control. The acid is purchased at 93% concentration and
stored in the cylindrical drums in which it is purchased.
For continuous chromium reduction a single chromium reduction
tank is used. Costs are estimated for an above-ground cylin-
drical rubber lined tank with a 4 hour retention time, and an
excess capacity factor of 1.2. Sulfur dioxide is added to
convert the influent hexavalent chromium to the trivalent form.
The control system for continuous chromium reduction consists
of:
1 immersion pH probe and transmitter
2 immersion ORP probes and transmitter
1 pH and ORP monitor
2 slow process controllers
1 sulfonator and associated controls, diffuser,
evaporator, and pressure regulator
1 sulfuric acid pump
2 dilute acid pumps and pump stands
1 transfer pump for sulfur dioxide ejector with
pump stand
2 maintenance kits for electrodes, and miscellaneous
electrical equipment and piping
VIII-19
-------
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For batch chromium reduction, the dual chromium reduction tanks
are sized as above-ground cylindrical rubber-lined tanks, with a
variable retention time, depending on flow rates. Up to a flow
of 400 I/day to chromium reduction, one batch is treated per 5
days of operation, and treatment tanks are sized to contain 5
days' flow. Above this flow rate, one batch is treated each
day. Sodium bisulfite is added to reduce the hexavalent chro-
mium.
A completely manual system is provided for batch operation.
Subsidiary equipment includes:
2 immersion pH probes
1 pH probe maintenance kit
1 pH meter
3 immersion ORP probes (one stand by)
1 ORP motor
1 sulfuric acid transfer pump and stand
1 sulfuric and dilution tank
1 sulfuric acid feed pump and stand
1 reduction tank drain transfer pump
Investment costs for batch and continuous treatment systems are
presented in Figure 8-6.
Operation and Maintenance - Costs for operating-and"maintaining
chromium, reduction systems include labor and chemical expenses.
Annual operation and maintenance expenses for batch an<3 continu-
ous chromium reduction systems are shown in Figure 8-7 as a
function of waste stream flow rate.
Labor requirements for batch treatment include 2 hours/week
maintenance, 45 minutes/batch treated and additional labor for
chemicalihandling depending on the amount of sulfuric 'acid
consumed. For •continuous treatment, labor requirement's are 4
hours/week maintenance, 1 hour/day operation and' additional
labor for,, chemical handling depending on the amount of sulfuric
acid consumed.
For the continuous system, sulfur dioxide is added according to
the following:
(Ibs S02/day) = (15.43) (flow to unit-MGD) (Cr+6 mg'/l)
In the batch mode f sodium bisulfite is added in place o'f' sulfur
dioxide according to the following:
(Ibs .NaHS03/day = 22.85) (flow to unit-MGD) (Cr+^'mg/lf'"
Costs for these labor and chemical requirements are estimated
based on the following:
VIII-21
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$6.71 per manhour +15% indirect labor charge
$760. per ton of sulfur dioxide
$600. per ton of sodium bisulfite
Energy Costs - The horsepower required for chemical mixing is
estimated based on tank volumes at 1 hp per 1,000 gallons. The
mixers are assumed to operate continuously over the operation
time of the treatment system. Pump motor ^horsepower require-
ments are calculated based on system flow* pump head, and oper-
ating time. Energy expenses are estimated based on a rate of
$0.045/kilowatt hour of required electricity.
i
Chemical Precipitation and Settling
This technology removes dissolved pollutants by the formation of
precipitates by reaction with added lime and subsequent removal
of the precipitated solids by gravity settling in a clarifier.
Several distinct operating modes and construction techniques are
costed to provide least cost treatment over a broad range of
flow rates. Because of their interrelationships and integration
in common equipment in some installations, both the chemical
addition and solids removal equipment are ;addressed in a single
subroutine. The chemical precipitation/sedimentation subroutine
also incorporates an oil skimming device on the clarifier for
removal of floating oils. i
Investment Costs - Investment costs are determined for this
technology for both batch and continuous treatment systems using
steel tank or concrete tank construction. ' The system selected
is based upon least cost on an annual basis as discussed previ-
ously in this section of the development document. Continuous
treatment systems include a mix tank for reagent feed addition
(flocculation basin) and a clarification basin with associated
sludge rakes and pumps. Batch treatment systems include only
reaction settling tanks and sludge pumps.
The flocculator included in the continuous chemical precipita-
tion and sedimentation system can be either a steel tank or
concrete tank unit. The concrete unit is based on a 45 minute
retention time, a length to width ratio of 5, a depth of 8 feet,
a wall thickness of 1 foot, and a 20 percent excess capacity
factor. The steel unit size is based on a 45 minute retention
time, and a 20 percent excess capacity factor. Capital costs
for the concrete units include excavation ;(as required). A
mixer is included in flocculators of both constructions.
The concrete settling tank included in the continuous chemical
precipitation and clarification system is an in-ground unit
sized for a hydraulic loading of 33.3 gph/square foot, a wall
thickness of 1 foot, and an excess capacity factor of 20 per-
cent. The steel settling tank included in the continuous chem-
ical precipitation and sedimentation system is a circular above-
VIII-24
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ground unit sized for a hydraulic loading of 33.3.gph/square
foot, and an excess capacity factor of 20 percent. The depth of
the circular steel tank is assumed to increase linearly between
six and fifteen feet for tanks with diameters between eight and
twenty-four feet respectively. For tanks greater than twenty-
four feet in diameter, the depth is assumed to be a constant
fifteen feet. An allowance for field fabrication for the larger
volume steel settling tanks is included in the capital cost
estimation.
For batch treatment systems, dual above ground cylindrical steel
tanks sized for an eight hour retention period and a 20 percent
excess capacity factor are employed. The batch treatment system
does not include a flocculation unit.
A fixed cost of $3,756 is included in the clarifier investment cost
estimates for sludge pumps regardless of whether above-ground
steel tanks (in the batch or continuous operation modes) or the
in-ground concrete settling tank are used. This cost covers the
expense of two centrifugal sludge pumps. Fixed costs of $2,346
and $12,902 are included to cover the expense of polymer feed
systems for the batch and continuous operation modes respec-
tively. The $12,902 figure is included regardless of whether
concrete or steel tank construction is employed for the contin-
uous operation mode.
Lime addition for chemical precipitation in the batch mode is
assumed to be performed manually. A variable cost allowance for
lime addition equipment is included in the continuous operation
mode. This cost allowance covers the expense associated with a
lime storage hopper, feeding equipment, slurry formation and
mixing and slurry feed pumps. The cost allowance increases as
clarifier tank size increases.
Figure 8-8 shows a comparison of investment cost curves for
batch and continuous chemical precipitation and sedimentation
systems. The continuous treatment system investment cost
is based on a steel flocculation unit followed by a steel clari-
fication basin. This combination of treatment components was
found to be less expensive than the concrete flocculation
basin, concrete clarification basin combination, or any
combination of steel and concrete flocculation and clarification
units. The batch treatment investment curve is based upon two
above-ground cylindrical steel tank clarifier units. Both the
continuous and batch system investment curves include allowances
for the sludge pump, polymer feed systems, and lime addition .~,
equipment (continuous system only). . . : •:-
All costs presented above include motors, controls, pump stands,
and piping specifically associated with each treatment compo-
nent.
Operation and Maintenance Costs - The operation and maintenance
costs for the clarifier routine include the cost of chemicals
VIII-25
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added (lime, flocculants), and of labor for operation and mainte-
nance. Each of these contributing factors is discussed below.
Figure 8-9 presents the annual manhour requirements for the
continuously operating chemical precipitation and settling
system. For the batch system, maintenance labor is calculated
from the following equation:
Annual manhours for maintenance = 0.75 x (Days of operation per
year)
Operational labor for the batch system is calculated from the
following equation:
Annual manhours for operation = 780 + (1.3) (Ibs of lime added
per day)
Labor expenses have been estimated using a labor rate of $6.00
per manhour plus an additional 15% to cover indirect labor ex-
penses .
Lime is added to the waste solution in order to precipitate
dissolved metals so that the metal may be removed from the waste
stream as settleable particulates. The amount of lime required
for addition is based on equivalent amounts of various pollutant
parameters present in the waste stream entering the unit. The
coefficients used for calculating lime requirements are shown in
Table 8-5.
The cost of lime required has been determined using a rate of:
$44.61 per ton of lime (August, 1979 price)
Figure 8-10 presents annual operation and maintenance cost
curves for the continuous and batch operation modes of the
chemical precipitation and settling system as a function of
waste stream flow rate. The cost curves have been based on the
assumption that the was-te treatment system will operate 24 hours
per day, 5 days per week, 260 days per year.
Energy Costs - The energy costs are calculated from the clar-
ifier and sludge pump horsepower requirements.
Continous Mode - The clarifier horsepower requirement is assumed
constant over the hours of operation of the treatment system at
a level of 0.0000265 horsepower per 3.8 I/hour (1 gph) of flow
influent to the clarifier. The sludge pumps are assumed opera-
tional for 5 minutes of each operational hour at a level of
0.00212 horsepower per 3.8 I/hour (1 gph) of sludge stream flow.
Batch Mode - The clarifier horsepower requirement is assumed to
occur for 7.5 minutes per operational hour at the following
level:
VIII-27
-------
800
SO
100
ISO
200
(IOOOL/HR)
300
350
too-
FIGURE 8-9
CHEMICAL PRECIPITATION AND SETTLING
ANNUAL OPERATION AND MAINTENANCE LABOR REQUIREMENTS
VIII-28
-------
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VI11-29
-------
influent flow < 3944 I/hour; 0.0048 hp/gph
influent flow > 3944 I/hour; 0.0096 hp/gph
The power required for the sludge pumps in the batch system is
the same as that required for the sludge pumps in the continuous
system. Energy costs for these requirements are estimated based
on a unit cost of $0.045/kilowatt hour of required electricity.
i
TABLE 8-5 '
LIME ADDITIONS FOR LIME PRECIPITATION
Stream Parameter
Aluminum
Antimony
Arsenic
Cadmium
Chromium
Cobalt
Copper
Iron (Dissolved)
Lead
Magnesium
Manganese
Mercury
Nickel
Selenium
Silver
Zinc
Chemical Emulsion Breaking
Lime Addition
kg/kg jlbs/lb)
0.81
4.53
1;75
2;
,84
2^73
2,35
,38
,28
1,
1,
2.19
0.205
3.50
1,48
0.42
1,45
3^23
1,25
Chemical emulsion breaking removes emulsified oil droplets from
suspension through chemical destabilizatiqn. Destabilization
allows the oil droplets to agglomerate, rise to the surface of
the separation tank, and be removed from the wastewater by
surface skimming mechanisms. This technology assumes that the
waste oil emulsion is capable of being broken through chemical
addition only, and that addition of heat will not be required.
In this waste treatment system, emulsified oil wastes are mixed
with alum and chemical polymers, then allowed to separate via
gravity separation in a settling tank. Once separation has
occurred, the waste oils can be skimmed from the tank surface
and disposed. The remaining wastewater is either passed on to
further treatment or discharged depending on the waste treatment
system. ;
Chemical emulsion breaking can be performed in either a continu-
ous or a batch mode. Each operating mode,: the equipment asso-
ciated with each mode, and the design and operating assumptions
incorporated are discussed in the following paragraphs.
VIII-30
-------
Investment Costs - The investment costs associated with the
continuous and batch operating modes for chemical emulsion
breaking are shown in Figure 8-11 as a function of waste stream
flow rate. For the continuous operating mode, the cost curve is
based upon the purchase and installation of the following equip-
ment:
2 946 liter (250 gallon) alum dilution tanks
2 Alum dilution tank mixers
2 Variable speed alum feed pumps (with pump
stands and associated automatic control equipment)
2 946 liter (250 gallon) polymer dilution tanks
2 Polymer dilution tank mixers
2 Variable speed polymer feed pumps (with pump
stands and associated automatic control equipment)
1 Steel mixing tank with liner for chemical addition
(sized for 15 minute retention time)
1 Mixing tank mixer (motor horsepower variable with
mixing tank volume)
1 Steel gravity separation tank with liner, weirs,
and baffles (sized for 1 hour retention time)
1 Separation tank,surface oil skimming mechanism
1 Skimmed oil transfer pump
1 Waste oil storage tank (steel tank with liner, sized
for 20 day retention)
1 Separation tank effluent transfer pump
For the chemical emulsion breaking unit operated in the batch
mode, the cost curve is based upon the purchase and installation
of the following equipment:
1 946 liter (250 gallon) alum dilution tank
1 Alum dilution tank mixer
1 Alum feed pump with pump stand ,
1 946 liter (250 gallon) polymer dilution tank
1 Polymer dilution tank mixer
1 Polymer feed pump with pump stand
2 Steel gravity, separation tanks with liners
(sized for variable retention depending on least cost
mode)
2 Tank mixers (motor hp variable with separation
tank volume)
1 Separation tank effluent transfer pump
The chemical emulsion breaking system (both batch and continuous
operating modes) have been sized for a 20% excess capacity
factor. Selection of the operating mode is based on a least
cost basis as discussed previously in the Section VIII text.
Operation and Maintenance Costs - The operation and maintenance
costs associated with the chemical emulsion breaking unit con-
sist of labor and material expenses.
VIII-31
-------
VIII-32
-------
Annual labor expenses for both the continuous and batch op-
erating modes for the chemical emulsion breaking unit are shown
in Figure 8-12 as a function of waste stream flow rate. For the
continuous operating mode, labor requirements are based on
estimated manhours required for diluting and mixing the polymer
and alum solutions and operating the unit. General operation
labor has been estimated at 0.75 manhours per 8 hour shift.
General maintenance of the entire system has been estimated at 2
manhours per week.
For the batch operating mode, labor requirements are based on
estimated manhours required for diluting and mixing the polymer
and alum solutions and operating the unit. General operation
labor has been estimated at 0.75 manhours required per batch.
General maintenance of the entire system has been estimated at 1
manhour per week.
Labor expenses have been calculated using a labor rate of $6.71
per manhour plus an additional 15% to cover indirect labor
costs.
Material costs are associated with the alum and polymer chemical
addition requirements. Polymer'is added to the wastewater until
a concentration of 150 mg/1 is attained. Alum is added to the
wastewater until a concentration of 25 mg/1 is attained. Chem-
ical costs have been based upon the following unit prices:
$0.38 per kg of alum
$1.55 per kg of polymer
The assumption has been made that the unit operates 24 hours per
day, 5 days per week, 52 weeks per year. , .
Energy Costs - Annual energy expenses for the chemical emulsion
breaking system (both batch and continuous operating modes) are
shown in Figure 8-13 as a function of waste stream flow rate.
These costs are based on operation of the dilution tank mixers,
chemical feed pumps, mixing and separation tank mixers (as
applicable), oil skimmer (as applicable), and solution transfer
pumps (oil and separation tank transfer pumps, as applicable).
Energy expenses have been estimated based upon a rate of $0.045/
kilowatt-hour of required electricity. It has been assumed that
the unit operates 24 hours per day, 5 days per week, 52 weeks
per year.
Holding Tanks
Tanks serving a variety of purposes in wastewater treatment and
control systems are fundamentally similar in design and construc-
tion and in cost. They may include equalization tanks, solution
holding tanks, slurry or sludge holding tanks, mixing tanks, and
settling tanks from which sludge is intermittently removed
manually or by sludge pumps. Tanks for all of these purposes
are addressed in a single cost estimation subroutine with addi-
tional cos£s for auxilliary equipment such as sludge pumps added
as appropriate.
VTII-33
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VI11-35
-------
Investment Costs - Costs are estimated for; steel tanks. Tank
construction may be specified as input data, or determined on a
least cost basis. Retention time is specified as input data
and, together with stream flow rate, determines tank size.
Investment costs for steel tanks sized for 0.5 days retention
and 20% excess capacity are shown as functions of stream flow
rate in Figure 8-14. These costs include mixers, pumps and
installation. '
i
I
Operation and Maintenance Costs - For all holding tanks except
sludge holding tanks, operation and maintenance costs are min-
imal in comparison to other system O&M costs. Therefore only
energy costs for pump and mixer operation ;are determined. These
energy costs are presented in Figure 8-15.
For sludge holding tanks, additional operation and maintenance
labor requirements are reflected in increased O&M costs. The
required manhours used in cost estimation are prsented in Figure
8-16. Labor costs are determined using a labor rate of $6.71
per manhour plus 15% indirect labor charge.
Where tanks are used for settling as in lime precipitation and
clarification batch treatment, additional operation and mainte-
nance costs are calculated as discussed specifically for each
technology.
Multimedia Filtration i
• i
i
•!
This technology provides removal of suspended solids by filtra-
tion through a bed of particles of several distinct size ranges.
As a polishing treatment after chemical precipitation and clar-
ification processes, multimedia filtration provides improved
removal of precipitates and thereby improved removal of the
original dissolved pollutants.
Investment Costs - The size of the granular bed multimedia
filtration unit is based on 20%pexcess flow capacity and a
hydraulic loading of 81.5 Ipm/m . Investment cost is presented
in Figure 8-17 as a function of flow installation.
j
Operation and Maintenance - The costs shown in Figure 8-18 for
operation and maintenance include contributions of materials,
electricity and labor. These curves result from correlations
made with data obtained by a major manufacturer. Energy costs
are estimated to be 3% of total O&M.
Ultrafiltration :
Ultrafiltration is a separation process involving the use of a
semipermeable polymeric membrane. The porous membrane acts as a
barrier, separating molecular sized particulates from the waste
stream. Membrane permeation by particulates is dependent upon
particulate size, shape and chemical structure. Solvents and
lower molecular weight solutes are typically passed through the
VIII-36
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membrane, while dissolved or dispersed materials with molecular
weights in the range of 1,000 to 100,000 are removed from solu-
tion.
The ultrafiltration process occurs when a:waste solution is
pumped under a fixed head (10 to 100 psig) through a tubular
membrane unit. Water and low molecular weight materials pass
through the membrane and are recycled, passed on to further
treatment or are discharged. Emulsified oils and larger sized
suspended particulates are blocked by the membrane and are thus
concentrated in a continuously discharged'waste stream. The
concentrated waste solution can then be passed on to further
treatment or disposal.
Investment Costs — The investment cost curve for the ultra-
filtration unit has been calculated usinginformation supplied
by leading manufacturers in the industry. Figure 8-19 presents
investment cost information for ultrafiltration systems as a
function of waste stream flow rate. This^cost curve has been
generated based upon purchase and installation of a complete.
package ultrafiltration system. This system includes the fol-
lowing equipment: :
1
1
1
1
1
wastewater flow equalization tank
wastewater process tank :
set of ultrafiltration membrane modules (quantity
variable with wastewater flow rate)
set of transfer and circulationjpumps
acid feed system (includes storage and pumps as
required for membrane cleaning)
set of process controls and instrumentation
Operation and Maintenance Costs - Annual operation and main-
tenance costs for the ultrafiltration system are shown in Figure
8-20 as a function of waste stream flow rate.This cost curve
includes labor and materials required for'system operation. The
operation and maintenance cost curve has been estimated based
upon information supplied by a leading ultrafiltration system
manufacturer. The curve is based on the assumption that the
system operates 24 hours per day, 5 days per week, 52 weeks per
year.
Energy Costs - Annual energy costs for the ultrafiltration
system are shown in Figure 8-21 as a function of waste stream
flow rate. This cost curve has been generated based upon infor-
mation supplied by a leading ultrafiltration system manufac-
turer. The curve is based on the assumption that the system
operates 24 hours per day, 5 days per week, 52 week per year.
Carbon Adsorption
This technology removes organic pollutants and suspended solids
by pore adsorption, surface reactions, and physical filtering by
the carbon grains. It typically follows other types of treat-
VIII-42
-------
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FUOW (U/DAY)
FIGURE 8-19
ULTRAFILTRATION INVESTMENT COSTS
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VIII-43
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ANNUAL ENERGY COSTS (DOLLARS - AUG, '79)
x.
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FIGURE 8-21
ANNUAL ENERGY COSTS VS. FLOW RATE FOR ULTRAFILTRATION
'onv - savmoa) SJ.SOD
VIII-45
-------
merit as a means of polishing the effluent. A variety of carbon
adsorption systems exist: upflow, downflow, packed bed, ex-
panding bed, regenerative, and thrOwaway. Regeneration of
carbon requires an expensive furnace and fuel for regeneration
that are not required for a throwaway system. Large systems may
find that the high cost of replacement carbon makes a regenera-
tive system economically attractive.
Investment Costs - The investment costs presented in Figure 8-22
are for a packed-bed throwaway system as based on the EPA
Technology Transfer Process Design Manual for Carbon Adsorption.
They include a contactor system, a pump station, and initial
carbon. The design assumes a contact time_of 30 minutes, a
hydraulic loading of 1.41 liters/minute/ft ; (4 gpm/ft ,) and 20%
excess capacity. j
i
Operation and Maintenance Costs - The chief operation and mainte-
nance costs are labor and replacement carbon. The labor hours
required are computed using Figure 8-23 which is taken from an
EPA Technology Transfer. The labor unit cost used is $6.71/hr
plus 15% indirect charges. The replacement carbon cost was
calculated by assuming: '
i
1) One pound of replacement carbon is required
per pound of organics removed. ;
2) The influent organic concentration (materials
effectively adsorbed) is 0.42 mg/;l.
3) Activated carbon costs $2.62/kg. ;($1.19 Ib).
Energy Costs - Energy is required for carbon adsorption operated
in the throwaway mode for the operation of pumps. Costs for
this electrical energy requirement based on a unit cost of
$0.045/kilowatt hour of required electricity are shown as a
function of wastewater flow rate in Figure |8-24.
Sludge Drying Beds
i
This technology provides for the dewatering of sludge by means
of gravity drainage and natural evaporation. Beds of highly
permeable gravel and sand underlain by drain pipes allow the
water to drain easily from the sludge. This is a non energy-
intensive alternative to sludge dewatering.
Investment Costs - The curve shown in Figure 8-25 illustrates
the correlation used to estimate the cost of sludge drying beds,
The investment cost is a function of both the flow rate to the
beds and the settleable solids concentration in the stream
influent to the sludge beds; however, the effect of solids
concentration is very small in comparison to the dependence on
flow rate. The cost estimates presented include excavation,
fill, drain and feed pipes, and concrete splash boxes.
VIII-46
-------
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FIGURE 8-24
ANNUAL ENERGY COSTS VS. FLOW RATE FOR CARBON ADSORPTION
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VIII-49
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VIII-50
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Operation and Maintenance - Operation and maintenance costs for
sludge drying beds include labor and materials. Labor require-
ments include routine operation and maintenance and periodic
removal of sludge from the beds. Material costs include the
replacement of sand and gravel removed with the sludge.
The cost of labor and material required to maintain and operate
the sludge beds is shown as a function of flow rate to the beds
in Figure 8-26.
Vacuum Filtration
Vacuum filtration is widely used to reduce the water content of
high solids streams. In the metal finishing category, this ,-'
technology is applied to dewatering sludge from clarifiers,
where the ^volume of sludge is too large for economical dewater-
ing in sludge drying beds.
Investment Costs - The vacuum filter is sized based on a typical
loading of 14,6 kilograms of influent solids per hour per square
meter of filter area (3 Ibs/ftVhr) . The investment costs are
shown as a function of sludge flow rate to the filter in Figure
8-27. The investment costs shown on this curve include installa-
tion costs and correspond to a solids content of 4.5% in the
influent to the filter, typical of the sludge stream from a
clarifier.
Operation and Maintenance Costs - Annual costs for operation and
maintenance for vacuum filtration include both operation and
maintenance labor and the cost of materials and supplies. These
costs are presented as a function of sludge flow rate to the
filter in Figure 8-28.
The vacuum filtration subroutine calculates operating hours per
year based'on flow rate and the total suspended solids concentra-
tion in the influent stream. Maintenance labor for vacuum
filtration is fixed at 24 manhours per year.
The cost of materials and supplies needed for operation and
maintenance includes belts, oil, grease, seals, and chemicals
required to raise the total suspended solids to the vacuum
filter. The amount of chemicals required (iron and alum) is
based on raising the TSS concentration to the filter by 1 mg/1.
Energy Costs- - Electrical costs needed to supply power for pumps
and controls are presented in Figure 8-29. The required horse-
power of the pumps is dependent on the influent TSS level. The
costs shown are based on a unit cost of $0.045/kilowatt hour of
required electricity.
Countercurrent Rinsing
This technology is applied in rinsing operations to substan-
tially improve the efficiency of rinse water use and decrease
VI11-51
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the volume of wastewater generated. In coIantercurrent rinsing
the product is rinsed in several tanks in series. Water flows
counter to the movement of product so that clean water enters
the last rinse tank from which clean product is removed, and
wastewater is discharged from the first rinse tank which re-
ceives the contaminated product to be rinsed. Two different
countercurrent rinsing modes are addressed in costing depending
on whether wastewater is discharged from the rinse or is used as
make-up for evaporative losses from a process bath. The costs
of countercurrent rinsing without using the first stage for
evaporative loss recovery are presented in1Table 8-6 as a func-
tion of the number of rinse tanks utilized. Costing assumptions
are: ,
Investment Costs - Unit cost is based on open top stainless
steel tanks with a depth of 1.22 meters (4 feet), length of 1.22
meters (4 feet), and width of 0.91 meters (3 feet). Investment
cost includes all water and air piping, a blower on each rinse
tank for agitation, and programmed hoist line conversions.
Operation and Maintenance Costs - Operation and maintenance
costs include a cost for electricity for the blowers based on a
capacity of 1,219 liters/min./sq. meter of;tank surface area (4
cfm/sq. ft.) at a discharge pressure of 1,538 kg/meter /meter of
tank depth (1 psi/18 in.). Fan efficiency is assumed to be 60
percent. A water charge based on a rinse ratio of 8,180 is also
included. Rinse maintenance charges are assumed to be negli-
gible when compared to normal plating line |maintenance and are.
ignored. '<
TABLE 8-6 i
COUNTERCURRENT RINSE (FOR OTHER THAN RECOVERY
OF EVAPORATIVE PLATING LOSS)
Number of Rinse Tanks: 345
Investment: 10,794 13,^85 16,978
I
Annual Costs: •
i
Capital Cost 909 1,170 1,430
Depreciation 2,158 2,777 3,396
!
Operation & Maintenance !
Costs (Excluding Energy ;
& Power Costs) 27 12 8
Energy & Power Costs 511 682 851
Total Annual Costs $3,605 $4,641 $5,685
VIII-56
-------
The costs of countercurrent rinsing with a rinse flow rate
sufficient to replace plating tank evaporative losses are pre-
sented in Table 8-7. The results are tabulated for various
evaporative rates which are equal to the rinse water flow rates,
Costing assumptions are:
TABLE 8-7
COUNTERCURRENT RINSE USED FOR RECOVERY OF
EVAPORATIVE PLATING LOSS
Evaporative Rate
(Liters/Hr):
Investment:
Annual Costs:
Capital Costs
Depreciation
Operation & Maintenance
Costs (Excluding Energy
& Power Costs)
Energy & Power Costs
Total Annual Cost
15.3 24.0 50.8
$15,430 $12,736 $10,042
1,301
3,086
1,074
2,547
847
2,008
5 7 16
714 572 428
$ 5,105 $ 4,200 $ 3,300
Note: Savings due to recovery of plating solution are .not
presented in this table.
Investment Costs - Unit cost is based on a sufficient number of
rinse stages to replace the evaporative loss from a plating bath
at approximately 43 degrees C while also maintaining a rinse
ratio of 8,180.
Investment costs include open top stainless steel tanks with a
depth of 0.91 meters (3 feet), length of 1.22 meters (4 feet),
and width of 1.22 meters (4 feet). All water and air piping, a
blower on each rinse tank for agitation, a liquid level con-
troller, solenoid, and pump are also included in the investment
cost. Operation is assumed to be programmed. Hoist and line
conversion costs are included. . .
Operation and Maintenance Costs - Operation and maintenance
costs include a cost for electricity for the blowers based, on a
capacity of 1.219 liters/min/sq. meter of tank surface area (4
cfm/sq. ft.) at a discharge pressure of 1,538 kg/sq. meter/meter
of tank depth (1 psi/18 in.). A fan efficiency of 6Q percent is
assumed. A water charge is also included. Rinse maintenance
charges are assumed to be neglible when compared to normal
plating line maintenance and are ignored.
VIII-57
-------
Submerged Tube Evaporation
In this technology, contaminants present in process wastewater
are concentrated by removing the water as vapor. Evaporation is
accomplished by applying heat, and the evaporated water is
condensed using non-contact cooling water, and reclaimed for
process use. Costs generated in this subroutine are based on
double effect evaporation in which heat contained in vapor from
the first stage (effect) is used to evaporate water from the
second.
Investment Costs - Investment costs for thjis technology are
estimated based on data supplied by a manufacturer of submerged
tube evaporation equipment. As shown by the plot of costs
versus wastewater flow rate in Figure 8-30, costs were supplied
for units of specified capacities which are available from the
manufacturer. Cost estimates are based on the smallest avail-
able unit which is adequate for the specified wastewater flow
rate. The investment costs shown include the evaporation unit
and purification devices required for the return of the evapora-
tion concentrate to a process bath. Costs for installation of a
non-contact cooling loop are not included. The availability of
this service on-site is assumed.
Operation and Maintenance Costs - Estimates for operation and
maintenance costs are based on manufacturer supplied data.
These costs are shown as a function of wastewater flow rate in
Figure 8-31. ;
Energy Costs - Energy is required in this technology primarily
to supply the heat of vaporization for the evaporated water.
The use of a double effect evaporator significantly reduces the
total amount of heat consumed per unit of water evaporated.
Energy requirements are based on an evaporative heat of 583
cal/gram of water which is reduced to an effective value of 292
cal/gram in the double effect unit. Fuel consumption is based
on a lower heat value of 10,140 cal/gram wjith an 85% heat re-
covery efficiency. Energy costs based on these factors are
shown in Figure 8-32 as a function of wastewater flow rate to
the evaporator. ,
Contract Removal
____MM^_^^^^^^_____—__ ,
Sludge, waste oils, and in some cases concentrated waste solu-
tions frequently result from wastewaster treatment processes.
These may be disposed of on-site by incineration, landfill or
reclamation, but are most often removed on; a contract basis for
off-site disposal. System cost estimates presented in this
report are based on contract removal of sludges. In addition,
where only small volumes of concentrated wastewater are pro-
duced, contract-removal or off-site treatment may represent the
most cost effective approach to water pollution abatement.
Estimates of solution contract haul costs are also provided by
VIII-58
-------
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VIII-61
-------
this subroutine and may be selected in place of on-site treat-
ment on a least-cost basis.
Investment Costs - Investment for contract removal is zero.
i
Operating Costs - Annual costs are estimated for contract re-
moval of total waste streams of sludge and oil streams as spec-
ified in input data. Sludge and oil removal costs are further
divided into wet and dry haulage depending 'upon whether or not
upstream sludge dewatering is provided. The use of wet haulage
or of sludge dewatering and dry haulage is based on least cost
as determined by annualized system costs over a ten year period.
Wet haulage costs are always used when the volume of the sludge
stream is less than 100 gallons per day.
Both wet sludge haulage and total waste haulage differ in cost
depending on the chemical composition of the waste removed.
Wastes are classified as cyanide bearing, hexavalent chromium
bearing, or oily and assigned different haulage costs as shown
below.
Waste Composition
>0.05 mg/1 CN-
M).l mg/1 Cr+6
Oil & grease-TSS
All others
Haulage :Cost
i
$0.16/liter ($0.60/gallon)
$0.18/liter ($0.56/gallon)
$0.08/liter (0.30/gallon)
$0.06/liter (0.24/gallon)
Dry sludge haul costs are estimated at $0.07/liter ($0.27/
gallon). |
TREATMENT SYSTEM COST ESTIMATES
|
This section presents estimates of the total cost of wastewater
treatment and control systems for metal finishing process waste-
water incorporating the treatment and control components dis-
cussed above. Flows in the Metal Finishing Category vary from
approximately 378 to 3,785,000 liters/day (100 gpd to 1,000,000
gpd). This wide variation in flow rate necessitates the presen-
tation of treatment system total annual cost curves for each
option. Total annual costs have been plotted against flow in
units enabling the determination of cost for any flow rate. All
available flow data from industry data collection portfolios
were used in defining the raw waste flows. , Raw waste character-
istics were determined based on sampling data as discussed in
Section V. :
Cost curves for each option are presented f;or six different cases
for Option 1 and five different cases for Options 2 and 3. Each
case corresponds to different types of plants encountered in the
Metal Finishing Category. Cases one and two represent facilities
primarily engaged in electroplating. In case two electroless pla-
ting is performed resulting in the presence of complexed metal
wastes. Cases three and five represent integrated facilities com-
bining electroplating with other metal finishing operations. In
VIII-62
-------
case five electroless plating is practiced. Case four represents
plants performing a variety of metal finishing operations including
heat treating, but without on-site electroplating, while case six
represents plants generating only oily wastewater. The flow splits
for those cases as shown in Table 8-8 are based on the ratios of
the average wastewater flow rates from all subcategories included
in each case. These flow splits are presented to show examples of
a broad range of cases which occur within the Metal Finishing
Category.
TABLE 8-8
FLOW SPLIT CASES FOR OPTIONS 1, 2, AND 3
Case
Waste Type Flows (% of total plant flow)
Oily
Cyanide Chromium Metals
Complexed
Metals
1
2
3
4
5
31.5
30
30
100
7
6
4.5
13
12.5
9
80
75.5
55
70
52.5
4.5
Five examples of varying total daily waste volumes (gallons per day)
have been presented for each of the six cases in order to provide a
range of estimated system costs. The system costs presented include
component costs as discussed above and subsidiary costs including
engineering, line segregation, administration, and interest expenses
during construction. In developing cost estimates for these option
systems, it is assumed that none of the specified treatment and con-
trol measures is in place so that the presented costs represent total
costs for the systems.
Several of these system cost curves show discontinuities. Some
of these result from transitions occurring in specific component
cost subroutines, and others result from changes in system cost
factors. Sludge dewaterina costs are of particular signif-
icance. For flows below 10° I/day sludge dewatering is accom-
plished using sludge drying beds, and cost estimates reflect
VIII-63
-------
this technology. Above this flow sludge dewatering is accom-
plished using a vacuum filter. Since the degree of dewatering
achieved (typically 40% solids from a sludge drying bed and 20%
solids from a vacuum filter) is influenced by this change,
system costs are influenced not only by the dewatering costs
themselves, but also through an effect on the volume of sludge
requiring contract removal. At very high flow rates, the cost
of removing sludge at 20% solids may become substantial, and the
most economical system design would incorporate further dewater-
ing of the vacuum filter product. This refinement, however, has
not been included in these cost estimates.
System Cost Estimates (Option 1) - ' -,
This section presents the system cost estimates for the Option 1
end-of-pipe treatment systems. The representative flow rates
used in these system cost estimates were determined based upon
actually sampled flows and flow information received in the data
collection portfolios. The complete system block diagram appli-
cable to Ceases 1-5 is shown in Figure 8-33. Option 1 treatment
for the isolated oily waste stream addressed in case 6 is shown
in Figure 8-34. i
The costing assumptions for each component of the Option 1
system were discussed above under Technology Costs and Assump-
tions. In addition to these components, contract sludge removal
was included in all cost estimates.
Table 8-9 presents costs for each of the six cases discussed
above for various treatment system influent flow rates. The
basic cost elements used in preparing these tables are the same
as those presented for the individual technologies: investment,
annual capital costs, annual depreciation, annual operations and
maintenance cost (less energy cost), energy cost, and total
annual cost. These elements were discussed in detail earlier in
this section.
For the cost computations, a least cost treatment system selec-
tion was performed. This procedure calculated the costs for a
batch treatment system and a continuous treatment system over a
5 year comparison period. Figures 8-35 through 8-46 show the
investment and total annual costs for each case shown in Table
8-9. j
The investment costs shown assume that the treatment system must
be specially constructed and include all subsidiary costs dis-
cussed under the Cost Breakdown Factors segment of this section.
It is also assumed all plants operate 24 hours a day, 5 days per
week, for 52 weeks per year (260 total days).
VIII-64
-------
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VIII-66
-------
OILY RAW WASTE
.EMULSION
BREAKING
SKIMMED OIL
TREATED
EFFLUENT
FIGURE 8-34 «
OPTION 1 TREATMENT SYSTEM
FOR SEGREGATED OILY WASTE STREAMS
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VIII-79
-------
System Cost Estimates (Option 2) i
System cost estimates of the effects of adding a multimedia
filter to the previously discussed end-of-pipe systems were
developed to provide Option 2 Treatment Cost Estimates. A
schematic of the system for cases 1-5 is shown in Figure 8-47.
The cases used are the same as those for Option 1 and are shown
in Table 8-8. The costing assumptions for the multimedia filter
were discussed above under the technology costs and assumptions
subsection.
i
Several flow rates were used for each case to effectively model
a wide spectrum of plant sites. Figures 8-48 through 8-57
present the investment and total annual costs for each case in
Option 2.
Table 8-10 presents Option 2 treatment costs for construction of
the entire end-of-pipe system. These costs would be representa-
tive of expenditures to be expected to attain Option 2 for a
plant with no treatment in place.
System Cost Estimates (Option 3)
i
The Option 3 system takes the Option 1 system and makes one signi-
ficant change. The one change requires thei closed loop operation
(zero discharge) of any processes using cadmium. For cost-
ing purposes, an evaporative system has been used with the
condensate reused for rinsing and the concentrate hauled for
disposal. This may also be accomplished by other means selected
by the individual plants. Closed loop precipitation with reuse
of the treated water and licensed hauling of the sludge, or ion
exchange with reuse of the water and treatment and hauling of
the regenerant solution are two possible options. The schematic
for the complete Option 3 system for cases 1-5 is shown in
Figure 8-58. The investment and total annual cost curves for each
case are shown in Figures 8-59 through 8-68. Table 8-11 presents a
summary of the Option 3 costs.
Use of Cost Estimation Results '
1
Cost estimates presented in the tables and figures in this
section are representative of costs typically incurred in imple-
menting treatment and control equivalent toj the specified op-
tions. They will not, in general, correspond precisely to cost
experience at any individual plant. Specific plant conditions
such as age, location, plant layout, or present production and
treatment practices may yield costs which are either higher or
lower than the presented costs. Because the costs shown are
VIII-80
-------
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total system costs and do not assume any treatment in place, it
is probable that most plants will require smaller expenditures
to reach the specified levels of control from their present
status.
The actual costs of installing arid operating a system at a
particular plant may be substantially lower than the tabulated
values. Reductions in investment and operating costs are pos-
sible in several areas. Design and installation costs may be
reduced by using plant workers. Equipment costs may be reduced
by using or modifying existing equipment instead of purchasing
all new equipment. Application of an excess capacity factor,
which increases the size of most equipment foundation costs
could be reduced if an existing concrete pad or floor can be
.utilized. Equipment size requirements may be reduced as a
result of treatment conditions (for example, shorter retention
time) for particular waste streams. Substantial reduction in
both investment and operating cost may be achieved if a plant
reduces its water use rate below that assumed in costing.
IN-PROCESS FLOW REDUCTIONS
The use of in-process techniques to achieve reductions in waste
flows can result in significantly reduced operating and mainte-
nance costs. Although an additional initial investment will be
required for a countercurrent rinse or other flow reducing
equipment, downstream treatment components may be sized for
smaller flows. This reduces the initial investment for down-
stream treatment components.
ECONOMIC IMPACT ANALYSIS OF SYSTEM COST ESTIMATES
The individual waste treatment component and system cost estimates
presented in this section of the development document can be ap-
plied to each manufacturing facility in the Metal Finishing Cate-
gory. The cost estimates can be used to estimate the value of
existing in-place waste treatment components and to estimate the
economic impact of a proposed level of waste treatment upon an
individual manufacturing facility.
In order to establish the economic impact of the various proposed
waste treatment systems upon actual Metal Finishing firms, treat-
ment system cost estimates were developed for one hundred (100)
captive indirect dischargers, one hundred three (103) captive
direct dischargers, and forty (40) job shop direct dischargers.
These firms were determined to be representative of the Metal
Finishing Category and these cost estimates were used to assess
the economic impact of the proposed regulations upon the entire
VIII-105
-------
Metal Finishing Industry. Cost estimates;were not developed for
job shop indirect dischargers because these firms are regulated
under the Pretreatment Regulations for the Electroplating Point
Source Category (Ref. EPA 440/1-79/003, August 1979)„
System cost estimates for the previously described groups of
plants were provided to the Office of Analysis and Evaluation
of the EPA for use in Economic Impact Analysis (EIA) of the
Metal Finishing Category.
ENERGY AND NON-WATER QUALITY ASPECTS
Energy and non-water quality aspects of the wastewater treatment
technologies described in Section VII are summarized in Tables
8-12 and 8-13. Energy requirements are listed, the impact on
environmental air and noise pollution is noted, and solid waste
generation characteristics are summarized, The treatment proc-
esses are divided into two groups, wastewater treatment proc-
esses on Table 8-12 and sludge and solids handling processes on
Table 8-13. ;
Energy Aspects
' ™ ' "" j
j
Energy aspects of the wastewater treatment processes are impor-
tant because of the impact of energy use on our natural re-
sources and on the economy. Electrical power and fuel require-
ments (coal, oil, or gas) are listed in units of kilowatt hours
per ton of dry solids for sludge and solids handling. Specific
energy uses are noted in the "Remarks" column.
Evaporation as applied in Option 3 is an energy intensive tech-
nology for waste treatment. However, its ;energy consumption is
significantly reduced by the use of double effect evaporation
and by the use of countercurrent rinsing to limit the volume of
wastewater flowing to the evaporator. With the effective imple-
mentation of these techniques the total energy requirements for
evaporation in this category will be small and will probably not
exceed the energy consumed in treating and pumping the volume of
water which would be used in rinsing without these techniques.
i
Non-Water Quality Aspects
It is important to consider the impact of each treatment process
on air, noise, and radiation pollution of the enviroment to
preclude the development of a more adverse environmental impact.
VIII-106
-------
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-------
In general, none of the liquid handling processes causes air
pollution. Alkaline chlorination for cyanide destruction and
chromium reduction using sulfur dioxide also have potential
atmospheric emissions. With proper design and operation, how-
ever, air pollution impacts are eliminated. Incineration of
sludge or solids can cause significant air pollution which must
be controlled by suitable bag houses, scrubbers, or stack gas
precipitators as well as proper incinerator operation and main-
tenance. Care must be taken to insure that solids collected in
air pollution control do not become a water pollution threat.
None of the wastewater treatment processes causes objectionable
noise and none of the treatment processes has any potential for
radioactive radiation hazards.
The solids waste impact of each sludge dewatering process is
indicated in two columns on Table 8-13. The first column shows
whether effluent solids are to be expected and, if so, the
solids content in qualitative terms. The second column lists
typical values of percent solids of sludge or residue. The
third column indicates the usual method of solids disposal
associated with the process.
The processes for treating the wastewaters from this category
produce considerable volumes of sludges. In order to ensure
long-term protection of the environment from harmful sludge
constituents, special consideration of disposal sites should be
made by RDRA and municipal authorities where applicable. All
landfill sites should be selected to prevent horizontal and
vertical migration of these contaminants to ground or surface
waters. In cases where geological conditions may not be ex-
pected to prevent this, adequate mechanical precautions (e.g.,
impervious liners) should be used for long-term protection of
the environment. A program of routine periodic sampling and
analysis of leachates is advisable. Where appropriate, the
location of solid hazardous materials disposal sites should be
permanently recorded in the appropriate office of legal juris-
diction.
VI11-109
-------
-------
SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
INTRODUCTION
This section describes the best practicable control technology
currently available (BPT) for the treatment of process waste-
waters generated within the Metal Finishing Category. BPT re-
flects existing treatment and control practices at metal finish-
ing plants of various sizes, ages, and manufacturing processes.
The factors considered in defining BPT include the total cost of
application of technology in relation to the effluent reduction
benefits from such application, the age of equipment and facili-
ties involved, the processes employed, non-water quality environ-
mental impact (including energy requirements), and other factors
considered appropriate by the Administrator. In general, the BPT
technology level represents the best existing practices at plants
of various ages, sizes, processes, or other common characteristics.
Where existing practice is uniformly inadequate, BPT may be trans-
ferred from a different subcategory or category. Limitations based
on transfer of technology must be supported by a conclusion that
the technology is, indeed, transferrable and a reasonable predic-
tion that it will be capable of achieving the prescribed effluent
limits (see Tanner's Council of America v. Train Supra). BPT fo-
cuses on end-of-pipe treatment rather than process changes or in-
ternal controls, except where such are common industry practice.
IDENTIFICATION OF BPT
Plants in the Metal Finishing Category generate process wastewater
streams of several distinct types. As described in Sections V and
VI, waste streams produced in this category may contain common
metals (e.g., copper, nickel, zinc, etc.), precious metals
(e.g., gold, palladium, silver), cyanide, hexavalent chromium,
oil and grease, and a variety of toxic organic compounds (de-
signated total toxic organics, TTO) associated with oils, greases,
and solvents used within the category. Individual process waste-
water streams characteristically contain only some of these pollu-
tants, and metal finishing facilities generally produce several
distinct streams differing in their chemical composition and treat-
ment requirements. These considerations are reflected in pre-
vailing wastewater treatment practices within the category, and
in the identified BPT.
The BPT wastewater treatment system (Option 1 System in Section
VII) for the Metal Finishing Category is illustrated in Figure
9-1. This treatment system provides for the removal of metals
IX-1
-------
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IX-2
-------
from all process wastewater streams by chemical precipitation and
clarification, and specific treatment of some waste streams for
the removal of other process wastewater pollutants. Extensive
description of these treatment components is provided in Section
VII. individual plants in the Metal Finishing Category that do
not produce all of the distinct wastewater types shown need to
install only the system components necessary for the treatment of
those wastewater types existing at the plant to achieve compliance
with BPT.
Where some process waste streams contain complexed metals, BPT
includes the segregation of these wastes and separate treatment
for the precipitation of metals and removal of suspended solids.
Precipitation of metals from these wastes is characteristically
accomplished at a high pH (11.6 - 12«5) to induce dissociation of
the metal complexes. Lime or other calcium compounds are used
to adjust the pH to the high levels required to induce precipita-
tion of the free metals as hydroxides. Sedimentation is then
used in order to allow the resulting suspended solids to settle
out of solution.
Waste streams containing cyanide or hexavalent chromium are also
segregated for treatment in the BPT system. Cyanide bearing
wastes are treated chemically to oxidize the cyanide, and streams
containing hexavalent chromium are subjected to chemical chromium
reduction. After these separate treatment operations are com-
pleted, these waste streams are combined with other process waste-
water for the chemical precipitaion of metals and clarification.
Concentrated oily waste streams are segregated and treated for the
removal of oil and greases prior to treatment for metals removal.
Oils and greases are removed by gravity separation and skimming
of free oils followed by chemical emulsion breaking and subsequent
skimming for the removal of emulsified oils. Some oily waste
streams produced in this category may contain very low concen-
trations of emulsified oils making chemical emulsion breaking
unnecessary, while others may contain low free oil concentrations
obviating the need for skimming prior to emulsion breaking.
Some oily waste streams containing very low concentrations of
dissolved metals may be of a quality suitable for discharge af-
ter oil removal treatment. In these cases, further treatment
for metals removal with other process waste streams would not
be necessary to achieve compliance with BPT.
Following separate stream treatment the effluents are combined and
the metals are removed by precipitation and subsequent clarifica-
tion. Precipitation is accomplished by the addition of lime,
caustic, sodium carbonate, or acid to achieve a favorable pH.
Most metals precipitate as hydroxides although some, such as lead
and silver, preferentially form other compounds (e.g. carbonates
or chlorides). The optimum pH for precipitation is generally in
the range of 8.8-9.3, although it will vary somewhat depending on
the specific waste composition. The use of coagulents or flocculants
to enhance the effectiveness of clarification is also specifically
included in BPT.
IX-3
-------
Alternative technologies are available whi,ch are equivalent to
BPT^for the removal of the pollutants encountered in the Metal
Finishing Category. Some of these technologies as well as those
discussed above as BPT have been described in detail in Section
VII of this document. The specific technologies implemented at
each individual plant to achieve compliance with BPT limitations
will depend on economic and operational considerations specific
to the facility.
RATIONALE FOR THE SELECTION OF BPT
The BPT system identified above has been selected on the basis
of: proven effectiveness in treating pollutants present in
metal finishing process wastewaters; present practice within
the category; and non-water quality considerations. All of the
elements of the selected BPT are presently practiced at many plants
within the Metal Finishing Category and have been proven to be
reliable and effective in treating industrial wastewater.
Energy requirements for these technologies are moderate. However,
sludges and waste oils which prove to be hazardous must be handled
and disposed of in accordance with the Resource Conservation and
Recovery Act regulations.
I
!
Chemical precipitation is a proven technology which is widely
applied at Metal Finishing Category plants. As is shown in
Section VII, over 100 facilities employing hydroxide precipita-
tion and sedimentation for the removal of metals from process
wastewaters are identified. With appropriate control of pH and
settling conditions, this technology can be effectively applied
to process wastewaters containing any of the metals commonly
encountered in this category. Because this technology has been
applied at many facilities over extended periods of time, its
performance capabilities were established On the basis of a
large body of data from industrial effluents within the Metal Fi-
nishing Category.
Chemical chromium reduction is also a proven and widely applied
technology. Over 300 plants in the Metal Finishing Category
which employ this technology were identified. It may be imple-
mented using a variety of equipment, reagents, and operating pro-
cedures, and is readily adaptable to the wide range of flow
rates and hexavalent chromium concentrations encountered in the
Metal Finishing Category. .Similar to chemical precipitation,
its pollutant reduction performance capabilities were established
from effluent data from a number of plants within the category.
Chemical oxidation of cyanide using chlorine is also a common
wastewater treatment practice within the Metal Finishing Category.
Over 200 plants employing this technology were identified within
the surveyed data base. As a result, considerable data establishing
the reliability and performance of this technology were available
from industrial sites within the Metal Finishing Category.
IX-4
-------
Treatment of process wastewater for the removal of oils and
greases is common practice in the Metal Finishing Category. A
variety of oil removal techniques are employed as discussed in
Section VII. These correspond to the wide range of waste stream
compositions encountered. The identified BPT provides for the
removal of both free and emulsified oils commonly encountered in
metal finishing wastewaters. Twenty-nine plants in the data base
were identified which employ emulsion breaking technology. The
number of plants employing skimming for the removal of oils and
greases is much larger. Performance capabilities for these
technologies were firmly established on the basis of extensive
long-term practice in treating industrial process wastewater.
The specific technologies identified as BPT are relatively simple
and reliable; however, comparable effluent performance can be
achieved by numerous technical alternatives.
The technical merits, present practice, and demonstrated per-
formance of the BPT technologies are discussed in detail in
Section VII. The costs and non-water quality environmental
aspects of these technologies are presented in Section VIII.
BPT LIMITATIONS
The effluent limitations attainable by
presented in Table 9-1.
TABLE 9-1
application of BPT are
Parameter
BPT EFFLUENT LIMITATIONS
Concentration (mg/1)
Daily Maximum
TSS 61
Cadmium 1.29
Chromium, Total 2.87
Copper 3.72
Lead 0.67
Nickel 3.51
Zinc 2.64
Silver 0.44
Oil & Grease 42
Total Toxic Organics 0.58
Cyanide, Total 1.30
30-Day Average
23
0.27
0.80
1 .09
0.23
1
0
0
17
26
80
13
0.28
IX-5
-------
These limitations are based on demonstrated performance at metal
finishing plants employing the identified BPT technologies. As
described in Section VII, both on-site sampling and observations,
and long-term effluent monitoring data are reflected in the limi-
tations. They therefore incorporate both plant to plant varia-
tions in raw wastes and treatment practices and the day-to-day
variability of treatment system performance. The effluent con-
centrations shown in Table 9-1 represent levels attainable by a
well run BPT system 99% of the time.
The concentrations shown are all applicable to the treated ef-
fluent prior to any dilution with sanitary wastewater, noncon-
tact cooling water, or other non-process water. The total cyanide
concentration limitation applies to the discharge from cyanide
oxidation prior to mixture with any other process wastes.
The derivation of these performance limitations from effluent
data for Metal Finishing Category plants is described in detail
in Section VII. After technical analysis!of the effluent data
and supporting information to identify plants with properly
operating treatment systems, the data were screened to. ensure
that only effluent data corresponding to raw waste streams which
contained significant levels of each pollutant were used to
establish limitations for that parameter. These data were then
analyzed statistically as described under Statistical Analysis
(reference Section VII) to derive 99% confidence limits on both
single day and 30-day average effluent concentrations.
PRESENT COMPLIANCE WITH BPT
Table 9-2 shows the compliance of two distinct data bases of
plants with the BPT effluent limitations. The two groups of
plants for which compliance is tabulated are: plants that were
visited and sampled by the EPA, and plants which submitted long
term self-monitoring data (historical). For each pollutant, the
visited plant data base was further subdiyided into two separate
data sets: the visited (after deletions) set and the entire set.
The deleted visited data set contains those plants with properly
operating BPT systems that had significant raw waste concentra-
tions of the pollutant. Certain plants were deleted from the
visited plant data base due to improper treatment system opera-
tion evidenced by one or more of the following; the pH of the raw
waste was variable or too low to effect proper metals removal;
the effluent flow was greater than the influent flow (indicating
possible dilution); effluent concentrations greater than influent
concentrations; clarifier retention times were inadequate;
IX-6
-------
TABLE 9-2
BPT DAILY MAXIMUM LIMITATIC3N COMPLIANCE SUMMARY
Percent < Daily Maximum Conccaitration (%)
Data Base
Parameter
TSS
Cadmium
Chromium, Total
Copper
Lead
Nickel
Silver
Zinc
Oil & Grease
Cyanide, Tbtal
Visitea
(After Deletions)
100.0
100.0
100.0
98.0
100.0
95.6
100.0
93.8
100.0
100.0
Visted
(Entire)
84.0
95.2
93.4
90.0
94.6
89.8
100.0
90.7
96.2
97.1
Historical
99.8
97,
99,
99,
97,
99.
70.6
99,
99,
98.3
IX-7
-------
shortages of treatment chemicals during the sampling visit; or
the effluent TSS concentration exceeded 50,,mg/l (indicating
inadequate removal of metals). The entire visited data set in-
cludes all plants that employ the BPT system regardless of the
raw waste levels or whether proper operation occurred. Tables 9-
3 and 9-4 present a detailed summary of the historical data
relative to compliance with the limitations for the parameters.
Table 9-3 shows the number of data points in compliance with the
BPT limitations and the total number of da^a points for each
parameter at each BPT plant. Table 9-4 presents the corres-
ponding compliance percentage values. Tables 9-5 and 9-6 present
the same information for total cyanide, segregated oil and grease,
and silver. These parameters are presented in separate tables
because they are addressed in a single treatment and control
option applicable to both BPT and BAT.
BENEFITS OF BPT IMPLEMENTATION
The estimated environmental benefits of th4 application of BPT
to all plants in the Metal Finishing Category are summarized in
Table 9-7. This table presents estimates of the total mass of
several major pollutants in raw wastewaters from all metal
finishing plants and of the remaining mass of these pollutants
discharged after application of BPT at all 'facilities with direct
discharges. The differences between these lvalues are presented
as quantitative estimates of the environmental benefits of imple-
menting BPT. These benefits may be compared to the costs of BPT
(Option 1) as presented in Section VIII.
The estimates of raw waste pollutant masses a're derived from the
raw waste characteristics and flows presented in Section V. The
estimates of effluent pollutant masses are based on the same
wastewater flow rates and the BPT (Option 1) effluent concentra-
tions shown in Section VII. !
IX-8
-------
TABLE 9-3
BPT HISTORICAL DATA COMPLIANCE SUMMARY
EftTA POINTS £ BPT LIMITATIONS/TOXAL DATA POINTS
Plant
01067
03049
04140
05020
06002
06035
06051
06053
06087
06103
06107
06111
11008
11118
11477
12002
17030
19063
20080
20082
20116
22735
23076
30050
30079
30090
30165
30698
33050
33092
33692
34037
36040
44045
44150
45741
47025
OVERALL
TSS
148/149
49/49
4/4
-
6/6
12/12
13/13
12/12
12/12
12/12
10/10
3/3
140/140
-
69/69
_
-
10/10
269/269
-
243/243
28/28
_
278/278
47/47
-
-
<••
-
50/50
-
-
335/337
1750/1753
Cadmium
230/230
-
—
-
6/6
9/9
13/13
-
-
—
-
—
184/185
15/28
—
-
_
~
-
-
-
—
—
—
_
-
-
—
-
—
-
-
50/51
507/522
Chromium
230/230
-
—
226/226
6/6
12/12
13/13
12/12
12/12
—
10/10
3/3
185/185
28/28
—
-
350/358
237/237
269/269
249/252
243/243
35/35
228/233
275/275
49/49
-
-
*"•
235/235
—
42/42
357/358
255/255
3561/3570
COEper
230/230
-
3/4
231/231
6/6
-
13/13
-
12/12
—
8/10
— •
185/185
28/28
—
47/47
-
248/248
-
239/252
243/243
— •
228/233
227/278
257/257
63/63
104/104
44/45
-
49/49
124/127
-
— •
.2639/261
lead
21/21
237/237
52/63
Nickel
230/230
2/4
230/230
6/6
9/9
13/13
12/12
185/185
27/28
10/10
252/252
243/243
231/233
75/75
32/32
9/10
184/184
28/28
24/24
269/269
248/249
55/63
100/100
48/49
40/40
234/234
49/49
41/42 42/42
Oil & Grease
49/49
13/13
2/2*
66/66
52/52
268/269
45/45
74/75
13/11
45/45
2/2
9/9
48/48
1881/1887 1211/1222 684/686
IX-9
-------
TABLE SMI
BPT HISTORICAL DATA COMPLIANCE SUMMARY
PERCENT OF Eftm POINTS < BPT
Plant
01067
03049
04140
05020
06002
06035
06051
06053
06087
06103
06107
06111
11008
11118
11477
12002
17030
19063
20080
20082
20116
22735
23076
30050
30079
30090
30165
33050
33092
34037
36040
44045
44150
45741
47035
OVERALL
TSS
99.3
100
100
_
100
100
100
100
100
100
100
100
100
—
100
—
_
100
100
—
100
100
100
—
100
-
-
—
—
-
100
-
—
99.4
99.8
Cadmium
100
_
_
_
100
100
100
—
—
_
—
—
99.5
53.6
—
—
-
—
—
—
-
_
_
_
—
-
_
-
-
—
—
-
-
—
98.0
97.1
Chromium
100
-.
..
100
100
100
100
100
100
..
100
100
100
100
-.
—
100
100
100
98.8
100
100
97.9
100
-.
100
..
..
-
..
100
..
100
99.7
100
99.7
Dogger
100
-
75
100
100
-
100
-
100
—
80
—
100
100
—
100
-
100
—
94.8
100
_
97.4
100
—
100
100
100
—
97.8
100
97.6
_
-
99.0
Lead
—
- ;
—
—
•p
—
— |
-
—
_ ,
- '.
— !
_
100
—
-
-
100
- ',
— ',
—
_
_
—
-
- '
82.5
—
_
.... i
••
98.0
100
—
-
99.0
Nickel
100
-
50
100
100
100
100
-
100
_
-
—
100
96.4
—
-
-
100
-
100
100
_
99.1
100
-
-
„
—
100
100
100
97.6
-
99.7
Zinc
100
-
75
-
100
_
100
-
~
—
90
-
100
100
-
100
-
-
100
99.6
_
_
—
-
_
-
87.3
100
_
_
«•
100
-
99.1
Oil & Grease
—
100
-
-
•-
-
100
-
_
100
-
—
-
-
100
100
-
-
99.6
-
_
100
—
98.7
100
100
100
100
_
100
99.7
IX-10
-------
TABLE 9-5
SINGLE OPTION - HISTORICAL DATA COMPLIANCE SUMMARY
DATA POINTS < LIMITATION/TOTAL DATA POINTS
Plant ID
01067
03043
06002
06051
06087
06107
11008
11118
11125
15193
20080
20082
31021
36082
38223
44045
47025
Cyanide, Total
230/230
89/89
6/6
13/13
7/10
178/179
28/28
17/29
12/12
217/217
244/245
111/119
121/121
50/50
138/138
Silver
12/12
0/5
OVERALL 1461/1486
- No data or material not applied
12/17
IX-11
-------
TABLE 9-6
SINGLE OPTION - HISTORICAL DATA COMPLIANCE SUMMARY
PERCENT OP DATA POINTS < BPT LIMITATIONS
Plant ID
01067
03043
06002
06051
06087
06107
11008
11118
11125
15193
20080
31021
36082
38223
44045
47025
Cyanide, Total
100.0
100.0
100.0
100.0
70.0
99.4
100.0
58.6
100.0
100.0
93.3
100.0
100.0
100.0
Silver
OVERALL 98.3
- No data or material not applied
100.0
70.6
IX-12
-------
Pollutant Parameter
Cadmium
Chromium, Total
Copper
Lead
Nickel
Silver
Zinc
TOXIC METALS TOTALS:
Cyanide, Total
Total Toxic Organics
OVERALL TOTALS:
TABLE 9-7
BPT TREATMENT BENEFIT SUMMARY
Discharge (Metric tons/year)
Raw Loading
102
9886
4547
119
557
8
4489
19708
3582
1101
24391
BPT
Effluent
3
136
206
14
237
6
110
712
60
19
796
BPT
Benefit
99
9750
4341
105
320
2
4397
18996
3517
1082
23595
IX-T3
-------
-------
SECTION X
BEST AVAILABLE TECHNOLOGY
ECONOMICALLY ACHIEVABLE
INTRODUCTION
This section describes the best available technology economically
achievable (BAT) for the treatment and control of process waste-
water generated within the Metal Finishing Category. BAT represents
the best existing economically achievable performance of plants
of various ages, sizes, processes or other shared characteristics.
The Federal Water Pollution Control Act of 1972 required that BAT
represent reasonable further progress (beyond BPT) toward elimina-
ting the discharge of all pollutants. In fact, elimination of
discharge of all pollutants is required if technologically and
economically achievable. The Clean Water Act of 1977 specifically
defined both the conventional and toxic pollutants that must be
regulated (See Section V of this document for identification of
these pollutants) and also established a class of nonconventional
pollutants for regulation.
BAT has been further defined as the very best control and treatment
technology within a subcategory or as superior technology transferred
from other industrial subcategories or categories. This definition
encompasses in-plant process improvements as well as more effective
end-of-pipe treatment.
IDENTIFICATION OF BAT
BAT is the technology defined under Option 1 in Section VII of
this document and is shown in Figure 10-1. For toxic metals
and toxic orgaincs, oil and grease, cyanide and TSS, BAT effluent
control is achieved by the BPT system described in Section IX.
For waste streams containing complexed metals, BAT will be identi-
cal to BPT. This will require the segregation of the complexed
metals waste stream with separate treatment for the precipitation
of metals and removal of suspended solids. Precipitation of
metals from this waste stream can be accomplished by adjusting
the pH of the wastewater to 11.6-12.5 in order to promote dis-
sociation of the metal complexes and subsequent precipitation
of the free metals. Sedimentation is then employed in order
to allow the resulting suspended solids to settle out of solution.
The BAT treatment systems (Option 1 system in Section VII) is
adequate to achieve the BAT effluent limitations presented later
in this section. However, a plant may elect to supplement this
system with other equipment or use an entirely different treat-
ment technique in order to attain the BAT limitations. Alterna-
tive technologies (both end-of-pipe and in-process) are described
in Section VII of this document. In-plant techniques such as
evaporative recovery or reverse osmosis may substantially reduce
the end-of-pipe treatment requirements.
X-l
-------
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X-2
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RATIONALE FOR SELECTION OF BAT
The BAT treatment system identified previously was selected
because it has been proven in metal finishing plants to represent
reasonable performance. This is demonstrated by the Option 1
system performance in Section VII.
Although demonstration of BAT at a single plant is adequate for
its selection, the common metals Option 1 system is identified in
Section VII as presently employed at over 100 known metal
finishing plants. Precipitation and filtration, without an in-
termediate sedimentation step, has been demonstrated to be effec-
tive at several plants.
Compared to BPT, BAT has identical impact on energy requirements
and nonwater quality aspects.
BAT LIMITATIONS
The BAT effluent limitations are presented in Table 10-1.
TABLE 10-1
BAT EFFLUENT LIMITATIONS
Parameter
Cadmium
Chromium, Total
Copper
Lead
Nickel
Zinc
Silver
Total Toxic Organics
Cyanide, Total
Concentration (mg/1)
Daily Maximum 30-Day Average
29
87
72
0.67
3.51
2.64
0.44
0.58
1 .30
0.27
0.80
1 .09
0.23
1
0,
0.
26
80
13
0.28
As discussed in Section VII of this document, these limitations
represent the effluent concentrations attainable by a properly
operating BAT system 99 percent of the time. The concentrations
presented
X-3
-------
in Table 10-1 reflect treated effluent undiluted by sanitary
wastewater, noncontact cooling water, or other nonprocess water.
The total cyanide concentration limitation applies to the discharge
from cyanide oxidation prior to mixture with any other process
wastes.
The development of these effluent limitations from performance
measurements of existing BAT systems is described in Section VII.
The statistical rationale used in developing these limitations is
presented at the end of Section VII under the heading of Statis-
tical Analysis.
PRESENT COMPLIANCE WITH BAT
Table 10-2 shows the percent compliance of two distinct data
bases with the BAT effluent limitations. The two groups of
plants for which compliance is tabulated are: plants visited and
sampled by the EPA, and plants which submitted long term self-
monitoring data (historical). The visited plant data base was
further subdivided into two separate data sets: the visited
(after deletions) and the entire data set. The deleted visited
data set contains only those plants with properly operating BAT
systems that had significant raw waste concentrations of the
pollutant. The entire visited data set includes all plants that
employ the BAT systems regardless of the raw waste levels or
whether proper operation occurred. Tables 10-3 and 10-4 present
a detailed summary of the historical data relative to compliance
with the limitations. Table 10-3 shows the'number of points in
compliance with the BAT limitation and the total number of data
points for each BAT plant. Table 10-4 presents the corresponding
percentage compliance for each plant. The BAT compliance for
total cyanide, segregated oil and grease, and silver is the same
as that presented in Section IX for BPT compliance because the
BAT limitations for these pollutants are identical to the BPT
limitations.
BENEFITS OF BAT IMPLEMENTATION
i
Since the BAT treatment system is identical to the BPT system, no
increased environmental benefit above that 4erived from BPT
treatment is attained.
X-4
-------
TABLE 10-2
BAT DAILY MAXIMUM LIMITATION COMPLIANCE SUMMARY
Percent
-------
TABLE 10-3
BAT HISTORICAL DATA COMPLIANCE SUMMARY
DATA POINTS £ BAT LIMITATIONS/TOTAL DATA POINTS
Plant
01067
03049
04140
05020
06002
06035
06051
06053
06087
06103
06107
06111
11008
11118
11477
12002
17030
19063
20080
20082
20116
22735
23076
30050
30079
30090
30165
30698
33050
33092
33692
34037
36040
44045
44150
45741
47025
OVERALL
TSS
148/149
49/49
4/4
—
6/6
12/12
13/13
12/12
12/12
12/12
10/10
3/3
140/140
—
69/69
—
-
10/10
269/269
—
243/243
28/28
-
278/278
47/47
-
-
_
_
50/50
—
—
335/337
1750/1753
Cadmium
230/230
—
-
—
6/6
9/9
13/13
—
-
—
-
—
184/185
15/28
—
—
-
-
-
-
—
_
-
—
—
-
_
_
—
-
—
—
50/51
507/522
Chromium
230/230
—
-
226/226
6/6
12/12
13/13
12/12
12/12
—
10/10
3/3
185/185
28/28
—
—
350/350
237/237
269/269
249/252
243/243
35/35
228/233
275/275
49/49
-
mm
_
235/235
_
42/42
357/358
255/255
3561/3570
Copper
230/230
_
3/4
231/231
6/6
—
13/13
_
12/12
_
8/10
_
185/185
28/28
-
47/47
_
248/248
-
239/252
243/243
_
227/233
278/278
257/257
63/63
104/104
44/45
—
49/49
124/127
—
-
2639/2665
Lead
_
_
_
_
«•
_
_
_
_
_
_
_
21/21
_
_
_
237/237
_
_
_
_
_
_
52/63
-
:
_
48/49
40/40
_
-
398/410
Nickel
Zinc
230/230
2/4
230/230
6/6
9/9
13/13
230/230
3/4
6/6
-
13/13
12/12
185/185
27/28
10/10
252/252
243/243
231/233
75/75
32/32
9/10
184/184
28/28
24/24
269/269
248/249
52/63
100/100
Oil & Grease
49/49
13/13
2/2
66/66
52/52
268/269
45/45
74/75
11/11
45/45
2/2
9/9
234/234
49/49
41/42 42/42
48/48
1881/1887 1211/1222 684/686
X-6
-------
TABLE 10-4
BAT HISTORICAL DATA COMPLIANCE SUMMARY
PERCENT OF IftTA POINTS < BAT LIMITATIONS
Plant
01067
03049
04140
05020
06002
06035
06051
06053
06087
06103
06107
06111
11008
11118
11477
12002
17030
19063
20080
20082
20116
22735
23076
30050
30079
30090
30165
33050
33092
34037
36040
44045
44150
45741
47035
OVERALL
TSS
99.3
100
100
_
100
100
100
100
100
100
100
100
100
100
—
_
100
100
_
100
100
«.
100
_
100
-
-
-
_
—
100
—
—
99.4
99.8
Cadmium
100
—
_
—
100
100
100
-
-
—
-
_
99.5
53.6
—
-
—
—
—
_
-
—
—
—
—
_
-
-
-
-
-
-
—
_
98.0
97.1
Chromium
100
—
-
100
100
100
100
100
100
—
100
100
100
100
—
-
100
100
100
98.8
100
100
97.9
100
—
100
-
-
—
-
100
-
100
99.7
100
99.7
Copper
100
—
75
100
100
• -
100
—
100
—
90
—
100
100
—
100
—
100
-
94.8
100
—
97.4
100
—
100
100 ,
100
_
97.8
_
100
97.6
_
-
99.0
Lead
_
—
-
—
-
-
-
—
-
—
-
-
-
100
—
-
-
100
--
-
-
—
—
-
—
—
82 .-5
_
_
_
_ .
98.0
100
_^
-
97.1
Nickel
100
—
50
100
100
100
100
-
100
—
—
-
100
96.4
—
—
-
100
-
100
100
—
99.1
100
—
—
-
_
100
_
100
100
97.6
-
99.7
Zinc
100
—
75
—
100
- ,
100
-
—
—
90
-
100
100
—
100
—
-
100
99.6
~
—
-
-
—
—
87.3
100
_
_
_
_
100
-•
99.1
Oil & Grease
100
100
100
100
100
99.6
100
98.7
100
100
100
100
100
99.7
X-7
-------
-------
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
INTRODUCTION
This section describes the new source performance standards
(NSPS) for the treatment and control of process wastewaters
generated within the Metal Finishing Category. NSPS reflects
existing treatment and control practices or demonstrations that
are not necessarily in common practice.
The Federal Water Pollution Control Act of 1972 required that
NSPS represent the best available demonstrated control tech-
nology, processes, and operating methods. Where practicable, no
pollutant discharge at all is to be allowed. Where pollutant
discharge is unavoidable, these standards are to represent the
greatest degree of effluent reduction achievable. They apply
to new sources, which are defined as any building, structure,
facility, or installation that discharges pollutants and for
which construction is started after proposal of the standards.
IDENTIFCATION OF NSPS
NSPS is the technology defined under Treatment of Common Metals
Wastes - Option 3 in Section VIII of this Development Document.
The NSPS waste treatment system is shown in Figure 11-1. For
common metals, precious metals, oil and grease and cyanide wastes,
NSPS is achieved by the previously described BPT and BAT treat-
ment systems, plus the use of in-process treatment modifications
for controlling the discharge of cadmium. The BPT or BAT waste
treatment systems have been previously described in Sections IX
and X of the document.
The in-process modifications for controlling cadmium consist of
using evaporative recovery or ion exchange on segregated cadmium
bearing waste streams prior to mixing with other common metals
bearing wastewaters for end-of-pipe treatment. These in-process
modifications will reduce cadmium discharges to the background
levels detailed in Section VII of the document.
For complexed metals bearing waste streams, NSPS will be identi-
cal to the BPT and BAT waste systems. This requires segregation
of the complexed metals waste stream with separate treatment for
the precipitation of metals and removal of suspended solids.
Precipitation of metals from this waste stream is accomplished by
pH adjustment of the wastewater to 11.6-12.5 in order to promote
dissociation of the metal complexes and subsequent precipitaiton
of the free metals. This is followed by sedimentation in order-
to allow the resulting suspended solids to settle out of solution.
XI-1
-------
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XI-2
-------
The NSPS treatment system will, with proper operation, achieve
the NSPS effluent limitations presented later in this section.
However, a plant may elect to supplement this system with other
equipment or use an entirely different treatment technique in
order to attain the NSPS limitations. Alternative technologies
(both end-of-pipe and in-process) are described in Section VII of
this document. In-plant treatment modifications such as the use
of evaporated recovery may substantially reduce end-of-pipe
treatment requirements.
RATIONALE FOR SELECTION OF NSPS TECHNOLOGY
The. NSPS treatment components identified previously for control
of cadmium were selected because they have been proven in metal
finishing plants to represent reasonable performance improvement
beyond the BPT and BAT levels of treatment. This improvement is
demonstrated by the comparison of Option 1 and Option 3 system
performance for cadmium in Section VII.
Option 3 effluent limitations for cadmium represent background
levels detected in effluents from plants which do not apply this
metal in their production operations (a detailed explanation of
this approach is provided in Section VII).
When compared to BPT and BAT, NSPS has only minor incremental
impact upon energy requirements and other nonwater quality
aspects.
NSPS LIMITATIONS
The NSPS effluent limitations are presented in Table 11-1.
XI-3
-------
TABLE 11-1
NSPS EFFLUENT LIMITATIONS
Parameter
TSS
Cadmium
Chromium, Total
Copper
Lead
Nickel
Zinc
Silver
Oil & Grease
Total Toxic Organics
Cyanide, Total
Concentration
Daily Maximum
61
0.064
2.87
3.72
0.67
3.51
2.64
0.44
42
0.58
1 .30
(mg/1)
30-Day Average
23
0.018
0.80
1 .09
0.23
1 .26
0.80
0.13
17
0.28
As discussed in Section VII of this document, these limitations
represent the effluent concentrations attainable by a well oper-
ating NSPS system 99 percent of the time'. The concentrations
presented in Table 11-1 reflect treated effluent undiluted by
sanitary wastewater, non-contact cooling water, or other non-
process water. The total cyanide concentration limitation
applies to the discharge from cyanide oxidation prior to the
mixture with any other process wastes. The cadmium limitation
applies to the discharge from in-process modifications (for this
pollutant) prior to mixture with any other process wastes.
The development of the NSPS effluent limitations is described in
Section VII under Common Metals Waste Treatment System
Performance - Option 3, and the statistical rationale is
presented at the end of Section VII under the heading of
Statistical Analysis.
PRESENT COMPLIANCE WITH NSPS j
The NSPS compliance for all parameters other than cadmium is the
same as that presented in Sections IX and X (for BPT and BAT
compliance respectively) because the NSPS limitations for all
parameters other than cadmium are identical to the BPT and BAT
limitations. Present compliance with the Option 3 cadmium
limitation cannot be determined because data are not available
from metal finishing plants using the specified technology.
XI-4
-------
BENEFITS OF NSPS IMPLEMENTATION
Table 11-2 shows the estimated benefit of reduced cadmium dis-
charge in terms of concentration reduction that results
from the implementation of the NSPS limitations. An incremental
reduction benefit of 0.252 mg/1 of cadmium would be achieved.
The estimated environmental benefits for all pollutant para-
meters other than cadmium were presented in Section IX (for
BPT) and Section X (for BAT). Quantitative benefits cannot
be determined for NSPS because installation of future facilities
cannot be predicted, and the wastewater flow rates and concen-
trations of pollutants in the raw wastewater resulting from
new sources cannot be projected.
TABLE 11-2
NSPS TREATMENT BENEFIT SUMMARY
Concentration Reduction (mg/1)
Pollutant Parameter
Cadmium
BPT/BAT
Effluent
0.27
NSPS
Effluent
0.018
NSPS
Reduction
0.252
XI-5
-------
-------
SECTION XII
PRETREATMENT STANDARDS
INTRODUCTION
This section describes the pretreatment standards for existing
sources (PSES) and the pretreatment standards for new sources
(PSNS) for the treatment of wastewaters generated within the
Metal Finishing Category that are discharged to a publicly owned
treatment works (POTWK These standards are intended to provide
an equivalent degree of toxic metals and toxic organic pollutant
removal as provided by direct discharge limitations.
The Federal Water Pollution Control Act of 1972 stated that the
pretreatment standards shall prevent the discharge to a POTW of
any pollutant that may interfere with, pass through, or otherwise
be incompatible with the POTW. The Clean Water Act of 1977
further stipulated that industrial discharges must not interfere
with use and disposal of municipal sludges. In accordance with
the Clean Water Act, individual POTWs may specify more stringent
standards or (after meeting specified criteria) may relax the
standards presented here.
IDENTIFICATION OF PRETREATMENT TECHNOLOGY
Pretreatment technology for PSES is the same as that defined in
Section IX for BPT, with the exception that treatment for control
of oil and grease and TSS is not required.
Pretreatment technology for PSNS is the same as that defined in
Section XI for NSPS, with the exception that treatment for
control of oil and grease and TSS is not required.
RATIONALE FOR SELECTION OF PRETREATMENT TECHNOLOGY
Toxic metals, and toxic organics may pass through a POTW, or they
may contaminate its sludge, or they may interfere with the
treatment process. These pollutants must therefore be controlled
by pretreatment. Treatment for oil and grease is generally
unnecessary because oil and grease are compatible with the POTW
treatment process. If an individual POTW chooses to limit oil
and grease effluents, some plants may have to install suitable
removal equipment. Toxic organics could be contained in the oils
and pass through a POTW, therefore oil and grease removal may
also be necessary to meet the pretreatment standard for toxic
organics.
XII-1
-------
PRETREATMENT STANDARDS
Pretreatment standards are the same as BAT preference Section X)
for existing sources and NSPS (reference Section XI) for new
sources, with the exception of control of oil and grease and TSS.
Table 10-1 quantifies the PSES requirements and Table 11-1 pre-
sents the requirements for PSNS. Although specific control of
TSS is not required, it will be effectively controlled by the
need to control metals.
PRESENT COMPLIANCE WITH PRETREATMENT STANDARDS
Compliance with PSES is discussed in Section X for BAT,
compliance with PSNS is discussed in Section XI for NSPS.
BENEFITS OF IMPLEMENTATION
and
Table 12-1 shows for existing sources the estimated benefit of
reduced metals, cyanide, and total toxic organics discharge in
terms of metric tons of pollutant per day that results from the
implementation of the pretreatment limitations. A reduction of
toxic metals (52549 metric tons/year), total cyanide (7699 metric
tons/year), and total toxic organics (3953 metric tons/year) may
be achieved by pretreatment prior to discharge to the municipal
sewer. Benefits derived from implementing new source performance
standards cannot be predicted. However, the impact on cadmium
effluent concentration reduction is presented in Section 11,
Table 11-2.
XII-2
-------
TABLE 12-1
PRETREATMENT BENEFIT SUMMARY
Discharge (kkg/yr)
Pollutant Parameter
Raw Loading
Pretreatment
Effluent
Pretreatment
Benefit
Cadmium 223
Chromium, Total 21638
Copper 9952
Lead 261
Nickel 12190
Silver 18
Zinc 9826
6
296
451
30
522
14
240
217
21342
9501
231
11668
4
9586
TOXIC METALS TOTALS: 54108
1559
52549
Cyanide, Total
Total Toxic Organics
7841
3995
142
42
7699
3953
OVERALL TOXIC TOTALS:
65944
1743
64201
XII-3
-------
-------
SECTION XIII
INNOVATIVE TECHNOLOGY
INTRODUCTION
The Clean Water Act of 1977, Public Law 95-217, provides that di-
rect discharging facilities which make use of innovative tech-
nology that results in an effluent reduction greater than that
required by the limitations may have a date of July 1, 1987 for
compliance with the limitations.
Specifically, this compliance date extension is authorized by
Section 47 of the Act and is reproduced herein for reference:
Compliance
date
extension.
Supra.
INNOVATIVE TECHNOLOGY
Sec. 47. Section 301 of the Federal Water Pollution
Control Act is amended by adding at the end thereof
a new subsection as follows:
"(k) In the case of any facility subject to a
permit under section 402 which proposes to comply
with the requirements of subsection (b) (2) (A) of
this section by replacing existing production capa-
city with an innovative production process which
will result in an effluent reduction significantly
greater than that required by the limitation other-
wise applicable to such facility and moves toward
the national goal of eliminating the discharge of
all pollutants, or with the installation of an in-
novative control technique that has a substantial
likelihood for enabling the facility to comply with
the applicable effluent limitation by achieving a
significantly greater effluent reduction than that
required by the applicable effluent limitation and
moves toward the national goal of eliminating the
discharge of all pollutants, or by achieving the
required reduction with an innovative system that
has the potential for significantly lower costs than
the system which have been determined by the Admin-
istrator to be economically achievable, the Admini-
strator (or the State with an approved program un-
der section 402, in consultation with the Admini-
strator) may establish a date for compliance under
subsection (b) (2) (A) of this section no later than
July 1, 1987, if it is also determined that such
innovative system has the potential for industry
wide application".
This section describes pollution control techniques that have the
capability of achieving the significant effluent reduction neces-
sary to qualify as an innovative technology.
XIII-1
-------
INNOVATIVE TECHNOLOGY CANDIDATES
The following paragraphs describe control techniques that can
qualify, if applied properly, as innovative technology. Included
among these candidate systems are evaporative systems, ion exchange,
electrolytic recovery systems, electrodialysis, revserse osmosis,
and electrochemical chromium regeneration.
Evaporation
Evaporation is a concentration process. Water is evaporated
from a solution, increasing the concentration of solute in the
remaining solution. If the resulting water vapor is condensed
back to a liquid, the evaporation-condensation process is
called distillation. However, to be consistent with industry
terminology, evaporation is used in this report to describe
both processes. Both atmospheric and vacuum evaporation are
commonly used in industry today. Specific ^evaporation tech-
niques are shown in Figure 13-1 and discussed below.
I
Atmospheric evaporation could be accomplished simply by boiling
the liquid. However, to aid evaporation, heated liquid is
sprayed on an evaporation surface, and air ;is blown over the
surface and subsequently released to the atmosphere. Thus,
evaporation occurs by humidification of the air stream, similar
to a drying process. Equipment for carrying out atmospheric
evaporation is quite similar for most applications. The major
element is generally a packed column with an accumulator
bottom. Accumulated wastewater is pumped from the base of the
column, through a heat exchanger, and back into the top of the
column, where it is sprayed into the packing. At the same
time, air drawn upward through the packing by a fan is heated
as it contacts the hot liquid. The liquid ;partially vaporizes
and humidifies the air stream. The fan then blows the hot,
humid air to the outside atmosphere. A scrubber is often
unnecessary because the packed column itself acts as a scrubber.
Another form of atmospheric evaporation combines evaporative
recovery of plating chemicals with plating tank fume control.
A third form of atmospheric evaporation also works on the air
humidification principle, but the evaporated rinse water is
recovered for reuse by condensation. These air humidification
techniques operate well below the boiling point of water and
can utilize waste process heat to supply the energy required.
i
In vacuum evaporation, the evaporation pressure is lowered to
cause the liquid to boil at reduced temperature. All of the
water vapor is condensed and, to maintain the vacuum condition,
noncondensible gases (air in particular) are removed by a
i.'siiiii:it:11" ii'i'i ii:ii!!iii:i,i /"
XIII-2
-------
Ed
«
D
a
M
fej
II
f
a
I
XIII-3
-------
vacuum pump. Vacuum evaporatio'n may be either single or
double effect. In double effect evaporation, two evaporators
are used, and the water vapor from the first evaporator (which
may be heated by steam) is used to supply beat to the second
evaporator. As it supplies heat, the water vapor from the
first evaporator condenses. Approximately equal quantities of
wastewater are evaporated in each unit; thus, the double
effect system evaportes twice the amount of water that a
single effect system does, at nearly the same cost in energy
but with added capital cost and complexity. The double effect
technique is thermodynamically possible because the second
evaporator is maintained at lower pressure (higher vacuum)
and, therefore, lower evaporation temperature. Another means
of increasing energy efficiency is vapor recompression (thermal
or mechanical), which enables heat to be transferred from the
condensing water vapor to the evaporating wastewater. Vacuum
evaporation equipment may be classified as submerged tube or
climbing film evaporation units.
In the most commonly used submerged tube evaporator, the
heating and condensing coil are contained in a single vessel
to reduce capital cost. The vacuum in the^ vessel is maintained
by an eductor-type pump, which creates the required vacuum by
the flow of the condenser cooling water through a venturi.
Wastewater accumulates in the bottom of the vessel, and it is
evaporated by means of submerged steam coils. The resulting
water vapor condenses as it contacts the condensing coils in
the top of the vessel. The condensate then drips off the
condensing coils into a collection trough that carries it out
of the vessel. Concentrate is removed froijn the bottom of the
vessel. The major elements of the climbing film evaporator
are the evaporator, separator, condenser, and vacuum pump.
Wastewater is "drawn" into the system by the vacuum so that a
constant liquid level is maintained in the separator. Liquid
enters the steam-jacketed evaporator tubesi, and part of it
evaporates so that a mixture of vapor and liquid enters the
separator. The design of the separator is\ such that the
liquid is continuously circulated from the!separator to the
evaporator. The vapor entering the separator flows out through
a mesh entrainment separator to the condenser, where it is
condensed as it flows down through the condenser tubes. The
condensate, along with any entrained air, is pumped out of the
bottom of the condenser by a liquid ring vacuum pump. The
liquid seal provided by the condensate kee£>s the vacuum in the
system from being broken.
Application
!
Evaporation is used in the Metal Finishing;Category for recov-
ery of a variety of metals, bath concentrates, and rinse
waters. Both atmospheric and vacuum evaporation are used in
metal finishing plants, mainly for the concentration and
recovery of plating solutions. Many of these evaporators also
recover water for rinsing. Evaporation has also been applied
XIII-4
-------
to recovery of phosphate metal cleaning solutions. There is
no fundamental limitation on the applicability of evaporation.
Recent changes in construction materials used for climbing
film evaporators enable them to process a wide variety of
wastewaters (including cyanide-bearing solutions), as do the
other types of evaporators described in this report.
Advantages of the evaporation process are that it permits
recovery of a wide variety of process chemicals, and it is
often applicable to removal and/or concentration of compounds
which cannot be accomplished by any other means. The major
disadvantage is that the evaporation process consumes relatively
large amounts of energy for the evaporation of water. However,
the recovery of waste heat from many industrial processes
(e.g., diesel generators, incinerators, boilers and furnaces)
should be considered as a source of this heat for a totally
integrated evaporation system. For some applications, pretreat-
ment may be required to remove solids and/or bacteria which
tend to cause fouling in the condenser or evaporator. The
buildup of scale on the evaporator surfaces reduces the heat
transfer efficiency and may present a maintenance problem or
increased operating cost. However, it has been demonstrated
that fouling of the heat transfer surfaces can be avoided or
minimized for certain dissolved solids by maintaining a seed
slurry which provides preferential sites for precipitate
deposition. In addition, low temperature differences in the
evaporator will eliminate nucleate boiling and supersaturation •
effects. Steam distillable impurities in the process stream
ar-e carried over with the product water and must be handled by
pre or post treatment.
Performance
In theory, evaporation should yield a -concentrate and a deion-
ized condensate. Actually, carry-over has resulted in condensate
metal concentrations as high as 10 mg/1, although the usual
level is less than 3 mg/1, pure enough for most final rinses.
The condensate may also contain organic brighteners and anti-
foaming agents. These can be removed with an activated carbon
bed, if necessary. Samples from one metal finishing plant
showed ,1,900 mg/1 zinc in the feed, 4,570 mg/1 in the concen-
trate, and 0.4 mg/1 in the condensate. Another plant had 416
mg/1 copper in the feed and 21,800 mg/1 in the concentrate.
Chromium analysis for that plant indicated 5,060 mg/1 in the
feed and 27,500 mg/1 in the.concentrate. Evaporators are
available in a range of capacities, typically from 15 to 75
gph, and may be used in parallel arrangements for processing
of higher flow rates.
Demonstration Status
Evaporation is a fully developed, commercially available
wastewater treatment system. It is used extensively to recover
plating chemicals, and a pilot scale unit has been used in
connection with phosphate washing of aluminum coil.
XIII-5
-------
Evaporation has been used in 20 percent ofithe visited plants
in the present data base and these are identified as follows:
METAL FINISHING PLANTS EMPLOYING EVAPORATION
04266
04276
04284
06009
06037
06050
06072
06075
06087
06088
06090
06679
08060
12065
12075
13031
19069
20064
20069
20073
20147
20160
20162
23071
28075
30096
33033
33p65
33^12
34p50
36062
36Q84
36162
38Q50
38052
40062
40836
43Q03
61001
Ion Exchange
Ion exchange is a process in which ions, held by electrostatic
forces to charged functional groups on the;surface of the ion
exchange resin, are exchanged for ions of similar charge from
the solution in which the resin is immersed. This is classified
as a sorption process because the exchange occurs on the
surface of the resin, and the exchanging ion must undergo a
phase transfer from solution phase to solid phase. Thus,
ionic contaminants in a waste stream can be exchanged for the
harmless ions of the resin. \
I
Although the precise technique may vary slightly according to
the application involved, a generalized process description
follows. The wastewater stream being treated passes through a
filter to remove any solids, then flows through a cation
exchanger which contains the ion exchange resin. Here, metallic
impurities such as copper, iron, and trivalent chromium are
retained. The stream then passes through the anion exchanger
and its associated resin. Hexavalent chromium, for example,
is retained in this stage. If one pass does not reduce the
contaminant levels sufficiently, the stream may then enter
another series of exchangers. Many ion exchange systems are
equipped with more than one set of exchangers for this reason.
The other major portion of the ion exchange process concerns
the regeneration of the resin, which now holds those impurities
retained from the waste stream. An ion exqhiange unit with
in-place regeneration is shown in Figure 13-2. Metal ions such
as nickel are removed by an acidic cation exchange resin,
which is regenerated with hydrochloric or sulfuric acid,
replacing the metal ion with one or more hydrogen ions.
Anions such as dichromate are removed by a basic anion exchange
XIII-6
-------
WASTE WATER CONTAINING
DISSOLVED METALS
OR OTHER IONS
DIVERTER VALVE
REGENERANT
SOLUTION
SUPPORT
REGENERANT TO REUSE.
TREATMENT. OR DISPOSAL
DIVERTER VALVE
METAL—FREE WATER
FOR REUSE OR DISCHARGE
FIGURE 13-2
ION EXCHANGE WITH REGENERATION
XIII-7
-------
resin, which is regenerated with sodium hydroxide, replacing
the anion with one or more hydroxyl ions. The three principal
methods employed by industry for regenerating the spent resin
are: ;
A) Replacement Service - A replacement service replaces the
spent resin with regenerated resin, and regenerates the
spent resin at its own facility. The service then has the
problem of treating and disposing of the spent regenerant.
B) In-Place Regeneration - Some establishments may find it
less expensive to do their own regeneration. The spent
resin column is shut down for perhaps an hour, and the spent
resin is regenerated. This results in one or more waste
streams which must be treated in an appropriate manner.
Regeneration is performed only as the resins require it.
C) Cyclic Regeneration - In this process), the regeneration
of the spent resins takes place in alternating cycles with
the ion removal process. A regeneration frequency of
twice an hour is typical. This very short cycle time
permits operation with a very small quantity of resin and
with fairly concentrated solutions, resulting in a very
compact system. Again, this process varies according to
application, but the regeneration cycle generally begins
with caustic being pumped through the anion exchanger,
carrying out hexavalent chromium, for example, as sodium
dichromate. The sodium dichromate stiream then passes through
a cation exchanger, converting the sodium dichromate to
chromic acid. After concentration by evaporation or other
means, the chromic acid can be returned to the process line.
Meanwhile, the cation exchanger is regenerated with sulfuric
acid, resulting in a waste acid stream containing the metallic
impurities removed earlier. Flushing the exchangers with
water completes the cycle. Thus, the wastewater is purified
and, in this example, chromic acid is recovered. The ion
exchangers, with newly regenerated resin, then enter the ion
removal cycle again.
Application • ;
Many metal finishing facilities utilize ion exchange to concen-
trate and purify their plating baths.
The list of pollutants for which the ion exchange system has
proven effective includes aluminum, arsenic, cadmium, chromium
(hexavalent and trivalent), copper, cyanide, gold, iron, lead,
manganese, nickel, selenium, silver, tin, zinc, and more.
Thus, it can be applied to a wide variety of industrial concerns.
Because of the heavy concentrations of metals in their wastewater,
the metal finishing industries utilize ion exchange in several
ways. As an end-of-pipe treatment, ion exchange is certainly
feasible, but its greatest value is in recovery applications.
It is commonly used, however, as an integrated treatment to
XIII-8
-------
recover rinse water and process chemicals. In addition to
metal finishing, ion exchange is finding applications in the
photography industry for bath purification, in battery manufac-
turing for heavy metal removal, in the chemical industry, the
food industry, the nuclear industry, the pharmaceutical industry,
the textile industry, and others. It could also be used in
the copper and copper alloys industry for recovery of copper
from pickle rinses. Also, many industrial and non-industrial
concerns utilize ion exchange for reducing the salt concentra-
tions in their incoming water.
Ion exchange is a versatile technology applicable to a great
many situations. This flexibility, along with its compact
nature and performance, make ion exchange a very effective
method of waste water treatment. However, the resins in these
systems can prove to be a limiting factor. The thermal limits
of the anion resins, generally placed in the vicinity of 60° C,
could prevent its use in certain situations. Similarly,
nitric acid, chromic acid, and hydrogen peroxide can all
damage the resins as will iron, manganese, and copper when
present with sufficient concentrations of dissolved oxygen.
Removal of a particular trace contaminant1 may be uneconomical
because of the presence of other ionic species that are prefer-
entially removed. The regeneration of the resins presents its
own problems. The cost of the regenerative chemicals can be
high. In addition, the waste streams originating from the
regeneration process are extremely high in pollutant concentra-
tions, although low in volume. These must be further processed
for proper disposal.
Performance
Ion exchange is highly efficient at recovering metal finishing
chemicals. Recovery of chromium, nickel, phosphate solution,
and sulfuric acid from anodizing is in commercial use. A
chromic acid recovery efficiency of 99.5% has been demonstrated.
Typical data for purification of rinse water in electroplating
and printed circuit board plants are shown in Table 13-1.
Plant ID 11065, which was visited and sampled, employs an ion
exchange unit to remove metals from rinsewater. The results
of the sampling are displayed in Table 13-2.
Demonstration Status
All of the applications mentioned in this document are available
for commercial use. The research and development in ion
exchange is focusing on improving the quality and efficiency
of the resins, rather than new applications. Work is also
being done on a continuous regeneration process whereby the
resins are contained on a fluid-transfusible belt. The belt
passes through a compartmented tank with ion exchange, washing,
and regeneration sections. The resins are therefore continually
used and regenerated. No such system, however, has been
reported to be beyond the pilot stage.
XIII-9
-------
Ion exchange is used in 63 plants in the present data base and
these are identified in Table 13-3.
TABLE 13-1
TYPICAL ION EXCHANGE PERFORMANCE DATA
Parameter
All Values mg/1
Zinc (Zn)
Cadmium (Cd) _
Chromium (Cr*g
Chromium (Cr
Copper (Cu)
Iron ( Fe )
Nickel (Ni)
Silver (Ag)
Tin (Sn)
Cyanide (CN)
Manganese (Mn)
Aluminum (Al)
Sulfate (SO4)
Lead (Pb)
Gold (Au)
)
Electroplating Plant
Prior ToAfter
Purifi- Purifi-
cation cation
14.8
5.7
3.1
7.1
4.5
7.4
6.2
1.5
1.7
9.8
4.4
5.6
0.40
0.00
0.01
0.01
0.09
0.01
0.00
0.00
0.00
0.04
0.00
0.20
Printed Circuit Board Plant
Prior TO
Purifi-
cation
43.0
1.60
9.10
1.10
3.40
210.00
1.70
2.30
After
Purifi-
cation
0.10
0.01
0.01
0.10
0.09
2.00
0.01
0.10
TABLE 13-2
SAMPLING RESULTS FROM PLANT ID 11065'
Parameter
TSS
Cu
Ni
Cr, Total
Cd
Sn
Pb
Day 1
Input To
Ion Exchange
6.0
52.080
.095
.043
.005
.06
.010
Effluent From
Ion Exchange
4.0
.118
.003
.051
.005
.06
.011
', Day 2
Input To
Ion Exchange
' 1.0
189.3
: .017
! .026
( .005
i .06
1 .010
Output From
Ion Exchange
1.0
.20
.003
,006
.005
.06
.010
XIII-10
-------
TABLE 13-3
METAL FINISHING PLANTS EMPLOYING ION EXCHANGE
02033
02034
02037
04145
04221
04223
04236
04263
04541
04676
04690
05050
06103
06679
08073
09025
11065
12065
12075
12080
13040
17030
17050
17061
18538
19081
19120
20017
20075
20120
20162
20483
21059
21065
21066
21075
23065
25033
27046
28111
28121
30153
30967
31032
31050
31070
33130
33172
33186
33187
36087
36623
37060
38036
38039
40048
40061
41086
41089
44062
46035
61001
62032
XIII-11
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Electrolytic Recovery :
Electrolytic recovery is a process in which there is
electrochemical reduction of metal ions at the cathode where
these ions are reduced to elemental metal. At the same time,
there is evolution of oxygen at the anode. Electrolytic
recovery is used primarily to remove metal ions from
solutions. |
i
Conventional Electrolytic Recovery
Conventional electrolytic recovery equipment consists of a
drag-out recovery tank located in the production line and an
electrolytic recovery tank and recirculation pump, remote from
the line. A typical electrolytic recovery tank uses stainless
steel cathodes of approximately 15 cm. width upon which the
recovered metal is deposited. After the coating is
sufficiently thick (0.06 cm.), the metal ideposited can be
peeled off and returned to the refiner or; the metal plated
stainless steel can be used for anodes in, a plating bath.
j
To get high recovery efficiencies, it is Desirable that the
solution be reasonably well agitated in the electrolytic cell
where the cathode sheets are in use. The electrolytic
recovery tank is designed to produce high flow rates in a
narrow channel. .
To avoid buildup of harmful impurities in the recirculated
solution, approximately 20 percent of the solution should be
dumped to waste treatment each week. •
Application of Conventional Electrolytic Recovery -
Electrolytic recovery is used to recover copper, tin, silver,
and other metals from plating and etching bath dragout.
Because the electrolytic process maintains a low concentration
of metal in the drag-out recovery process relative to that in
the process bath, metal dragover into the succeeding rinse
tank is minimized. This, in turn, minimizes the load on the
waste treatment system and the eventual pollutant discharge
rate.
XIII-12
-------
Performance of Conventional Electrolytic Recovery- Performance
is best illustrated by the actual examples tabulated below:
Parameter
Plating Bath Concentration, g/1
Drag-out Tank Concentration, g/1
Drag-out Rate, gph
Recovery Efficiency, %
Cathode Area, sq. ft.
Current Density, amp/sq. ft.
Current Efficiency, %
Current, amp
Tin Plating Silver Plating
81
1.2
1.2
97-99
45
5-10
70
240
82
0.2
0.8
99.8
35
3-5
25-50
175
Advanced Electrolytic Recovery
The extended surface electrolysis recovery system (ESE) dis-
cussed here recovers metal better at low concentrations than
at high concentrations, whereas the conventional electrolytic
recovery system is good for recovery of metal only at high
concentrations. An extended surface electrolytic recovery
unit removes contaminant metals by electroplating them onto a
specially constructed flow-through electrode.
The electrolytic processing technique involves reduction of
the metal ions at the cathode to form the elemental metal,
with evolution of oxygen at the anode. Other cathodic reactions,
such as the reduction of ions to produce hydrogen gas, may
also occur depending on the chemical composition of the streams
being treated.
The ESE spiral cell is of sandwich construction containing a
fixed "fluffy" cathode, a porous insulating separator, an
anode of screenlike material and another insulating separator.
The anode and cathode material may vary with the particular
effluent stream to be treated. Typically, cathode material is
a fibrous woven stainless steel mesh with a filament size of
2-5 mils. This sandwich structure cathode, separator material,
and anode are rolled into a spiral and inserted into a pipe.
This type of cell construction results in a very open structure
with a void volume of 93 percent to 95 percent, which provides
a low resistance to fluid flow.
A number of cells can be stacked as modules so that a large
fraction of contaminant metals can be recovered from an effluent.
The solution to be treated is pumped in at the top of the
module and flows down through the cells where the metals are
plated out on the cathode. Figure 13-3 shows that as a copper-
containing solution flows through the cell stack, copper ions
XIII-13
-------
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XIII
-------
are attached to the cathode and deposited as copper metal,
hydroxyl ions are attracted to the anode, and hydrogen and
oxygen gas are given off. The following reactions take place
at the cathode:
Cu
+2
2e- = Cu
and at the anode:
2(OH-) =
1/2
These reactions take place continuously as the fluid is pumped
through the various cells in the cell stack.
Application of_ Advanced Electrolytic Recovery - Extended
surface electrolysis cells may be used commercially to plate
out copper, lead, mercury, silver and gold. This system
should provide a very efficient means of removal because of
its low mass transfer requirements, larger electrode surface
area and, because of the construction of the electrodes,
increased electrical efficiency. This unit can be used in
conjunction with conventional electrodialysis or other forms
of treatment.
Performance of Advanced Electrolytic Recovery - Pollutants re-
covered by tHe ESE modules are independent of concentration
levels. Under mass-transfer-limiting conditions, this device
will operate as efficiently at 100 mg/1 as at 1000 mg/1. The
effluent concentration decreases exponentially with the length
of the module and its available cathode area. Complexing of
metals in solution is a problem in some applications.
The following table shows the level of achievable copper
concentrations for three influent levels. The final concentra-
tions for all three cases are less than 1 mg/1.
Solution Concentration, mg/1
At Various Points in a Cell Stack
Untreated After _! Cell After 2 Cells After 3^ Cells After £
Cells
20.0 8.2 3.4
45.5 15.5 5.4
15.5 5.6 2.8
1.3
2.1
1.7
0.6
0.9
0.7
With the addition of one more cell in all three cases, the
cell effluent level would be below 0.05 mg/1.
Flow to the ESE unit must be interrupted once a day for approxi-
mately one hour so that the accumulated metals in the cell can
be stripped out by circulating an acidic cleaner through the
cell. A schematic diagram, Figure 13-4, shows how the cell is
placed in a plating line. The graph in Figure 13-5 compares
the effect of electrical efficiency in metals reduction for
ESE and planar electrodes.
XIII-15
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XIII-17
-------
As indicated by the preceding table, a cell stack is at least 90
percent efficient in removal of metals from solution. A 200
1/min waste stream containing 50 mg/1 copper requiring a 100:1
concentration reduction could be treated in| a20 cm diameter ESE
unit having 48 inches of active electrode length. The electrical
energy needed to treat this stream in an ESJE cell would approxi-
mate the energy expended to drive the rake on a clarifier to
treat the same wastewater. i
I * '
Demonstration Status j
j
Electrolytic recovery is currently being used at 11 plants in the
present data base and these are identified p.n Table 13-4.
TABLE 13-4
METAL FINISHING PLANTS EMPLOYING ELECTROLYTIC RECOVERY
01068
02033
04069
04071
04690
19063
19069
20162
28122
31070
36623
Electrodialysis
Electrodialysis is a process in which dissolved species are
exchanged between two liquids through selective semipermeable
membranes. An electromotive force causes concentration of the
species from a waste stream, thereby providing purified water.
Water to be treated by electrodialysis is pumped through a stan-
dard cartridge filter and into the membrane:stack. The stack
consists of about fifty cell pairs operated!in parallel flow.
Each cell pair consists of an anion-selective membrane, a cation-
selective membrane, and membrane spacers. These membranes and a
membrane from the adjacent cell pair define a diluting compart-
ment and a concentrating compartment. \
Water to be treated flows through the diluting compartments. As
it does so, the contained ions (e.g. nickel and sulfate) are
drawn toward the electrodes at either end of the stack. Negative
and positive ions are drawn in opposite directions through the
selective membranes on either side of the diluting compartment
into the adjacent concentrating compartments. Water of hydration
goes with them. The ions continue in each direction across the
concentrating compartments but are trapped there because they are
blocked by membranes having a selectivity opposite to the one
they passed through. The net effect is that the water passing
through the diluting compartments is deioni^ed, while a concen-
trate (the ions and
XIII-18
-------
their water of hydration) is formed in the concentrating
compartments (the concentrating compartments have no inlet,
only an outlet).
The end (electrode) compartments are different. They are
continously flushed with a common-ion liquid (e.g. sodium
sulfate for nickel sulfate plating solution) to remove oxygen,
hydrogen, and chlorine formed by electrolysis at the
electrodes. These gases are vented from the electrode wash
solution reservoir.
The overall effect is that the total mineral content of the
treated water is reduced to about 1,000 mg/1. Further reductic
in concentration is not efficient and is not practical because
of excessive electrolysis. Thus, electrodialysis functions more
like ion exchange than like reverse osmosis and evaporation.
That is, ions are removed from wastewater rather than concen-
trated. Non-ionic constituents such as organic brighteners
remain in the treated water rather than in the concentrate.
Figure 13-6 shows the application of a simple electrodialysis
cell to separate potassium sulfate solution (K2S
-------
(CATHODE) _
H2
t
CATION- ANION-
PERMEABLE PERMEABLE
MEMBRANE MEMBRANE
I
I
K2S04
K +
(ANODE)
FIGURE 13-6
i
i
SIMPLE ELECTRODIALYSIS CELL
XIII-20
-------
CATHODE
PURIFIED
WATER
CONCENTRATE
CATHODE
PLATE
ANODE
PLATE
WASTWATER
ANODE
FIGURE 13-7
MECHANISM OF THE ELECTRODIALYTIC PROCESS
XIII-21
-------
through the ED unit and back. This maintains a low concentra-
tion (about 1,000 mg/1 of total mineral content) in the dead
rinse, minimizing the flow needed in the following running rinses.
If desired, these running rinses could be cpunterflowed through
an RO unit, with the concentrate directed to the ED unit.
i
Present applications include nickel, gold (cyanide and citrate),
silver, and cadmium plating. Any type of plating solution is
potentially recoverable for direct return to the plating tank.
Electrodialysis has been shown to be an effective method for
concentrating rinse waters to a high percentage of bath strength.
Nickel, copper, cyanide, chromic acid, iron and zinc can be
removed from process wastes by electrodialyjsis. The natural
evaporation taking place in a plating bath iwill often be suffi-
cient to allow electrodialysis to be used to close the loop
without the addition of an evaporator. j
At the time of the sampling visit, conventional electrodialysis
was being used by plant ID 20064 as a meansofconcentrating and
recovering chromic acid etch solution. Ele'ctrodialysis can be
combined with an existing treatment system 'for recovery of metals,
or it can be used with other treatment to effect recirculation of
rinse water. Many possibilities exist for electrodialysis and
with recent developments in membrane materials and cathode design
and increased knowledge of their applications, it may become a
major form of treatment for metals.
Performance
I
Little information is available on performance for treatment of
chromic acid; however, information is avail'able on copper cyanide
performance. Copper cyanide rinse water is treated in an electro-
dialysis unit for return of the concentrated chemicals to the
process bath. The copper cyanide chemicals in the rinse water
can be concentrated to slightly more than 70 percent of the bath
strength. For most copper cyanide plating, this concentration
may be sufficient to permit the direct return of all chemicals to
the processing operation, One manufacturer guarantees 94 percent
recovery of dragged-out plating metals. Figure 13-8 shows an
electrodialysis recovery system.
XIII-22
-------
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XIII-23
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I
Demonstration Status
I
Commercial electrodialysis units are manufactured by at least
two major suppliers to the metal finishing industry. At least
20 units have been installed. ',
i ,
i
Three metal finishing plants in our data base indicate the use
of electrodialysis. These plant ID'S are: 20064, 20069, and
41003. !
j
Advanced Electrodialysis ;
i
This particular electrodialysis system is used to oxidize chro-
mium (in spent chromic acid) from a trivalbnt form to a hexa-
valent form. Its design uses a circular, permeable anode,
separated from the cathode by perfluorosulfonic membrane. The
anode material is a specially designed lead alloy. The cathode
is made from Hastelloy C tubing, which is a nickel alloy. The
cathode is located in the center of the circular, permeable anode
and has a catholyte (10 percent sulfuric acid) which is circulat-
ing through it and surrounds the cathode. This solution is used
as a transfer solution. Figure 13-9 shows the physical construc-
tion of this circular electrodialysis cell.
The etchant is pumped in at the bottom of the unit through the
anode so that it remains in the chamber between the anode and the
perfluorosulfonic membrane. Chromium in the trivalent form is
contained in the etchant and, when a current is passed through
this etchant solution, electrons are stripped from the trivalent
chromium causing oxidation of the trivalen^ chromium to hexavalent
chromium. The newly stripped electrons migrate through the
perfluorosulfonic membrane into the catholyte solution. Converted
hexavalent chromium is pumped back into the chromium etch tank
for reuse, while at the same time the cathplytic solution is
being recirculated. The reaction which occurs at the anode is as
follows :
Cr
*3
12
3e- = Cr0
~2
6e-
This reaction is continually taking place as both the etchant and
the catholyte are circulated through the cell.
Application ;
Electrodialysis of chromium, oxidizing trivalent chromium to
hexavalent chromium, is not a widely practiced method of waste
XIII-24
-------
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XIII-25
-------
treatment as yet. It is, however, a very .efficient method for
waste treatment of chromium, and it is used at one company visited
(ID 20064). This electrodialysis cell closes the loop on chromium
so that there is no need to reduce hexavalent chromium. The only
application, current or predicted, for this electrodialysis cell
system is the oxidation of chromium wastes.
I
Performance I
The electrical efficiency of the unit varies with the concentration
of both hexavalent chromium and trivalent chromium. The electro-
chemical efficiency of the unit is generally between 50 to 90
percent, depending on the concentrations. This corresponds to an
energy consumption of 8 to 16 kwh/kg of chromic acid from reduced
chromium. The metal removed efficiency of the electrodialysis
unit is 90 percent for 8 mg/1 of trivalent chromium and 95 percent
for 12 mg/1. ,
Reverse Osmosis
The process of osmosis involves the passage of a liquid
through a semipermeable membrane from a dilute to a more
concentrated solution. Reverse osmosis (RO) is an operation in
which pressure is applied to the more concentrated solution,
forcing the permeate to diffuse through the membrane and into
the more dilute solution. This filtering action produces a
concentrate and a permeate on opposite sides of the membrane.
The concentrate can then be further treatejd.. or returned to the
original operation for continued use, while the permeate water
can be recycled to the rinse tanks. Figure 13-10 represents a
reverse osmosis system. ;
As illustrated in Figure 13-11, there are three basic
configurations used in commercially available RO modules:
tubular, spiral-wound, and hollow fiber. 'All of these operate
on the principle described above, the only difference being
their mechanical and structural design characteristics.
The tubular membrane module utilizes a porous tube with a
cellulose acetate membrane-lining. A common tubular module
consists of a length of 2.54 cm (1 inch) diameter tube wound
on a supporting spool and encased in a plastic shroud. Feed
water is driven into the tube under pressures ranging from
40.8 - 54.4 atm (600-800 psi). The permeate passes through
the walls of the tube and is collected in a manifold while the
concentrate is drained off at the end of tfie tube. A less
widely used tubular RO module uses a straight tube contained
in a housing, under the same operating conditions.
XIII-26
-------
MACROMOLECULES
AND
SOLIDS
MEMBRANE
Ap=450 PS I
WATER
MEMBRANE CROSS SECTION,
IN TUBULAR. HOLLOW FIBER,
OR SPIRAL-WOUND CONFIGURATION
PERMEATE (WATER)
FEED
CONCENTRATE
(SALTS)
O SALTS OR SOLIDS
„ WATER MOLECULES
FIGURE 13-10
SIMPLIFIED REVERSE OSMOSIS SCHEMATIC
XIII-27
-------
7tf5-R5*
O-HING" MEMBRANE
OACKIWQ MATERIAL
MESA SPACE*
Porouj Support Tub*
with MtmbraiM
BfacWsh
r
*jl8 FMdFlowA
(1
Product Watir Pirmeiu Flow
"a.'S'°
o • •.•«-.•
0°
V » "^T"^
Product Wattr
SPIRAL MEMBRANE MODULE
1 Brint
Concintrata
Flow
TUBULAR REVERSE OSMOSIS MODULE
CONCENTRATE
SNAP RING OUTLET
OPEN ENDS
OF FIBERS
EPOXY
TUBE SHEET
XT RING SEAL
END PLATE
POROUS
BACK-UP DISC
SNAP mm
FIBER
SHELL
•0' RING SEAL
POROUS FEED END PLATE
DISTRIBUTOR TUBE
HOLLOW FIBER MODULE
FIGURE 13-11
REVERSE OSMOSIS MEMBRANE CONFIGURATIONS
XIII-28
-------
Spiral-wound membranes consist of a porous backing sandwiched
between two cellulose acetate membrane sheets and bonded along
three edges. The fourth edge of the composite sheet is attached
to a large permeate collector tube. A spacer screen is then
placed on top of the membrane sandwich and the entire stack is
rolled around the centrally located tubular permeate collector.
The rolled up package is inserted into a pipe able to withstand
the high operating pressures employed in this process, up to 54.4
atm (800 psi) with the spiral-wound module. When the system is
operating, the pressurized product water permeates the membrane
and flows through the backing material to the central collector
tube. The concentrate is drained off at the end of the container
pipe and can be reprocessed or sent to further treatment facili-
ties.
Application
The largest industrial wastewater application of reverse osmosis
has been in plating to recover nickel and rinse water from nickel
deposition rinses. Reverse osmosis is used to close the loop
between plating and rinsing operations in the metal finishing
industry. The overflow from the first rinse in a countercurrent
setup is directed to a reverse osmosis unit, where it is separa-
ted into two streams. The concentrated stream contains dragged
out process chemicals and is returned to the process bath to
replace the loss.of solution due to evaporation and dragout. The
dilute stream (the permeate) is routed to the last rinse tank to
provide water for the rinsing operation. The rinse flows from
the last tank to the first tank and the cycle is complete.
The closed-loop system described above may be supplemented by the
addition of a vacuum evaporator after the RO unit in order to
further reduce the volume of reverse osmosis concentrate. The
evaporated vapor can be condensed and returned to the last rinse
tank or sent on for further treatment. Another variation is to
increase the rate of evaporation in the process bath to make room
for reverse osmosis concentrate.
It has been shown that RO can generally be applied to most acid
metal baths with a high degree of performance, providing that the
membrane unit is not overtaxed. The limitations most critical
here are the allowable pH.range and maximum operating pressure
for each particular configuration. Adequate prefiltration is
also essential, in metal finishing, reverse osmosis has been
found attractive for recovery in Watts-type nickel, nickel sulfa-
mate, copper pyrophosphate, nickel fluoborate, zinc chloride,
copper cyanide, zinc cyanide, and cadmium cyanide systems.
Application to chromic acid and very high pH systems has not been
successful.
XIII-29
-------
One manufacturer claims that several RO units are being used to
dewater sludges generated by photographic processes. Reverse
osmosis has also been effective in removing zinc from diazo
solutions in laboratory experiments. Another company has demon-
strated the usefulness of RO in removing cutting oils and machining
coolants from wastewater streams in a pilot plant operation.
Several new membrane materials are under development. A Japanese
firm has conducted experiments with a new RO membrane consisting
of a polybenzimidazolone (PBIL) polymer. The manufacturer claims
that it can handle a pH range from 1 to 12t temperatures as high
as 60°C and is resistant to oxidation by chromic acid. Test
results for acid copper plating have been encouraging. In con-
trast, performance of a polybenzimidazole (FBI) membrane has been
disappointing. Another membrane is being considered for treatment
of cyanide plating baths and has shown pH tolerance in the 1 to
13 range. I
It is made up of a crosslinked polyethyleneimine structure and is
claimed to exhibit excellent stability and!RO performance. A
polyamide composite membrane also shows promise for both acid and
alkaline cyanide service, and a polyfurfuryl alcohol hollow fiber
composite membrane is effective for acid copper solutions. The
only membranes readily available commercially are the three
described earlier, and their overwhelming use has been for the
recovery of various acid metals plating baths.
The major advantage of reverse osmosis for handling process
effluents is its ability to concentrate dilute solutions for
recovery of salts and chemicals with low power requirements. No
latent heat of vaporization or fusion is required for effecting
separations; the main energy requirement is for a high pressure
pump. It requires relatively little floorjspace for compact,
high capacity units, and it exhibits good recovery and rejection
rates for a number of typical process solutions. Capital and
operating costs are relatively low. A limitation of the reverse
osmosis process for treatment of process effluents is its limited
temperature range for satisfactory operation. For cellulose
acetate systems, the preferred limits are 18.3 to 29.4 degrees C
(65 to 85 degrees F); higher temperatures will increase the rate
of membrane hydrolysis and reduce system life, while lower temper-
atures will result in decreased fluxes with no damage to the
membrane. Another limitation is inability: to handle certain
solutions. Strong oxidizing agents, strongly acidic or basic
solutions, solvents, and other organic compounds can .cause
dissolution of the membrane. Poor rejection of some compounds
such as borates and low molecular weight organics is another
XIII-30
-------
problem. Fouling of membranes by slightly soluble components in
solution or colloids has caused failures, and fouling of membranes
by feed waters with high levels of suspended solids can be a
problem. A final limitation is inability to treat or achieve
high concentration with some solutions. Some concentrated solu-
tions may have initial osmotic pressures which are so high that
they either exceed available operating pressures or are uneco-
nomical to treat.
Performance
Plant 33065 has a reverse osmosis unit on its nickel plating
line. The sampling results (mg/1) of the raw input, permeate,
and concentrate are shown as follows:
PLANT 33065
Parameter Input
TSS 1.0
Copper .617
Nickel 276.
Chromium, Total .050
Zinc .846
Cadmium <.005
Tin .417
Lead <.01
Demonstration Status
Permeate
2.0
.092
81.
.033
.159
<.005
.375
Concentrate
.067
20,700
.051
17.6
.006
.500
.021
There are presently at least one hundred reverse osmosis wastewater
applications in a variety of industries. In addition to these,
there are thirty to forty units being used to provide pure process
water for several industries.
Despite the many types and configurations of membranes, only the
spiral-wound cellulose acetate membrane has had widespread success
in commerical metal finishing applications. RO is used in 8
plants in the present data base and these are identified in Table
13-5.
TABLE 13-5
METAL FINISHING PLANTS EMPLOYING REVERSE OSMOSIS
04236
18534
30166
31032
33065
38040
38050
43003
XIII-31
-------
Electrochemical Chromium Regeneration '
]
Chromic acid baths must be continually discarded and replenished
to prevent buildup of trivalent chromium. An electrochemical
system employing a lead anode and nickel cathode has been de-
veloped to recover chromium by converting the trivalent form to
the hexavalent form. In this process, trivalent chromium is
electro-oxidized to hexavalent chromium at ;the lead anode while
hydrogen is released at the nickel cathodes This process is
similar to the electrodialytic chromium oxidation process, but no
membrane is used to separate concentrate from dilute solution.
The reaction is carried out at 68C, a cell -voltage of 4.5 volts,
and an anode-to-cathode area ratio of 30:1.| The same process can
also be used to recover chromium from chroirjic oxide sludges
precipitated by conventional chemical chromium waste treatment.
The sludges are dissolved in 200 g/1 chromic acid and electro-
oxidized under slightly different operating conditions than
those previously described.
Application !
t
Electrochemical chromium regeneration can be used in metal fini-
shing to prolong the life of chromium plating and chromating
baths. Chromic acid baths are used for electroplating, anodizing,
etching, chromating and sealing. The electro-oxidation process
has been commercially applied to regeneration of a plastic etchant.
In this particular installation, chromic acid dragged out of the
etching bath into the first stage of a countercurrent rinse is
concentrated by evaporation and returned to| the etching bath.
This closed loop system tends to cause a rapid buildup of. trivalent
chromium. However, when the etchant is reciirculated through an
electrochemical regeneration unit, the trivalent chromium is
oxidized to the hexavalent form. The process has also been
applied to regeneration of a chromic acid scaling bath in the
coil coating industry.
i
Some advantages of the electrochemical chrofnium regeneration
process are its relatively low energy consumption, its operation
at normal bath temperature, eliminating need for heating or
cooling, its ability for recovering and reusing valuable process
chemicals, and elimination of sludges generated by conventional
chromium treatment processes. Some limitations of chromium
electro-oxidation are low current efficiencies for baths with
less than 5.0 g/1 trivalent chromium, need for control of impuri-
ties which can interfere with the process, and dependence on
electrical energy for oxidation to take place.
XIII-32
-------
Performance
The current efficiency for this process is 80 percent at concen-
trations above 5 g/1. If a trivalent chromium concentration of
less than 5 g/1 were treated, research has shown that the current
efficiency would drop.
Demonstration Status
One automobile plant (Plant ID 12078) is using the system experi-
mentally to regenerate a chromic acid etching solution. In
addition, one coil coater (Plant ID 01054) is using it on a full
scale basis to regenerate a chromic acid sealing bath. Standard
equipment is not commercially available.
Water Reducing Controls for Electroplaters
To minimize pollution problems, electroplaters have discovered
that relatively simple strategies can effectively be made
operational. First, water can be used more efficiently. Second,
water can be kept clean to begin with and, therefore, will not be
a problem that requires wastewater treatment.
Efficient water use means getting the most rinsing from each
gallon of water. A single rinse tank is the least efficient
means to obtain adequate rinsing because a much larger volume of
water must be used in comparison to counterflow rinsing.
(Counterflow rinsing is an effective flow reduction technique but
it can also be expensive.) Electroplaters have found that using
rinse water two or three times before it is purified or discarded
not only reduces water consumption, but it can actually improve
rinsing and save process chemicals. Moreover, rinse water reuse
techniques are not expensive to implement and are not subject to
space constraints to the same extent as counterflow rinsing.
Low cost pollution control strategies further benefit
electroplating frims by reducing costs for raw water and
wastewater treatment. In addition, the strategies can often be
operated by in-shop fabrication instead of expensive high
technology controls or end-of-pipe treatment. Two effective and
inexpensive means to minimize pollution problems are described in
this section, multiple dragout and reactive rinsing.
Multiple Drag-Out Control: Techniques and Effectiveness
By controlling the amount of plating solution that is dragged
from work pieces upon their removal from the process tank, the
amount of contamination in subsequent rinse tanks can be reduced.
A dragout tank, consisting of nothing more than a still rinse,
installed immediately following the plating process will capture
some of the contamination.
XIII-33
-------
The multiple dragout method uses the same .number of rinse tanks
as counterflow rinsing. The difference is that instead of a
single dragout tank and several running rinse tanks, several
dragout tanks and a single running rinse tank are used.
Most of the solution dragged from the plating tank is captured in
the first dragout tank. The multiple drag-out tank protect the
running rinse from intense contamination and often allows the
rinsewater to be discharged with little or no treatment because
it already meets the Federal standards. As a result, the
multiple drag-out method greatly reduces the cost the wastewater
treatment. Likewise, because wastewater treatment is minimized
so is sludge generation and sludge management costs.
I
Periodically, some of the solution from the first tank must be
drained and replaced by the less contaminated solution from the
second drag-out tank. Fresh water is than used to fill the
second tank. The solution drained from the first drag-out tank
can be (1) recycled to the plating process; (2) processed to
recover the metals; or (3) sent to a waste treatment plant.
Multiple drag-out tanks are a simple and efficient means to
reduce drag-out contamination. Two or more drag-out tanks
operated in series assure almost complete control of drag-out
losses. ;
I
Reactive Rinsing: Techniques and Effectiveness
Reactive rinsing means reusing or recycling the rinse water. By
flowing rinse water back through the electroplating process and
taking advantage of the chemical reactivity of contaminated
water, water use can be minimized.
As an example, consider a nickel plating process composed of an
alkaline cleaning tank, an acid dip tank, and a plating tank,
with a rinse tank after each process. In a conventional plating
process, water would be individually fed to each rinse tank.
Using reactive rinsing, water fed to the rinse tank following the
planting tank would supply the rinse tank following the acid dip;
the water from this rinse would supply the '. tank following the
alkaline cleaner.
Reactive rinsing allows a pH neutralization reaction to occur as
the rinse water from the acid dip is fed back to the rinse water
from the alkaline cleaner. The reaction does not harm the
plating process, and actually improves the rinsing effectiveness
following the cleaner. Cleaner solution is greasy and hard to
rinse; however, with acid rinsewater the alkaline solution is
neutralized and rinses easily. Drag-out contamination may also
be reduced because rinse water from the tank following the
plating tank (i.e., water containing drag-out) is fed back to the
rinse tank preceding the plating tank. Accordingly, the drag-in
to the nickel tank will contain some nickel solution.
XIII-34
-------
This example describes an in-process, counterflow reactive
rinsing technique, other reactive rinsing opportunities are
possible. Depending upon the particular plating process, it may
be possible to feed rinse water forwards. In some instances, it
is be possible to feed rinse water across processes to obtain the
desired reaction. The possibilities for interprocess reuse at
plating shops are great but have been largely unexplored.
XIII-35
-------
-------
SECTION XIV
ACKNOWLEDGEMENTS
Mr. Richard Kinch, of the EPA's Effluent Guidelines Division
served as the Project Officer during the preparation of this
document and limitations. Mr. Jeffery Denit, Director, Effluent
Guidelines Division, and Mr. G. Edward Stigall, Chief, Inorganics
Chemicals and Services Branch, offered guidance and suggestions
during this project. Appreciation is extended to Mr. Devereaux
Barnes and Mr. J. Bill Hanson for their previous work in the
Electroplating Pretreatment Regulations which were useful in
developing the Metal Finishing Category Regulations.
The Environmental Protection Agency was aided in the preparation
of this Development Document by Hamilton Standard, Division of
United Technologies Corporation. Mr. Kenneth J. Dresser, Mr.
Jeffrey M. Wehner, and Mr. Jack Nash directed the engineering
activities and field operations were under the direction of Mr.
Richard Kearns. Hamilton Standard's effort was managed by Mr.
Daniel J. Lizdas, Mr. Walter M. Drake, and Mr. Robert W. Blaser.
Significant contributions were made by Mr. Dwight Hlustick, Mr.
Frank Hund, Mr. David Pepson, Mr. John Newbrough, Mr. James
Berlow and Mr. Walter Hunt of EPA's Effluent Guidelines Division;
by Mr. James Spatarella of EPA's Monitoring and Data Support
Division; by Mr. Bruce Clemens of EPA's Office of Analysis and
Evaluation; by Mr. Michael Dworkin of EPA's Office of General
Eric Auerbach, Steven Bauks, David Bowker,
Lewis Hinman, Steven Klobukowski, Raymond
Lewis, Lawrence McNamara, Jeff Newbrough, Joel
Parker, James Pietrzak, Donald Smith, and Peter Williams of
Hamilton Standard. Data and information acquisition, analysis,
and processing were performed by Clark Anderson, Michael
Derewianka, Remy Halm, Robert Patulak, and John Vounatso of
Hamilton Standard. Mr. Richard Kotz of EPA's Office of Analysis
and Evaluation provided analytical guidance and suggestions.
Acknowledgement and appreciation is also given to Glenda Nesby,
Pearl Smith and Carol Swann of EPA's word processing staff, Mrs.
Lynne McDonnell, Ms. Lori Kucharzyk, and Ms. Kathy Maceyka of
Hamilton Standard.
Finally, appreciation is also extended to those metal finishing
industry associations and plants that participated in and con-
tributed data for the formulation of this document; the companies
that have already installed pollution control equipment; the
developers of pollution control and recovery equipment; and the
states and regional offices that have addressed pollution control
in the Metal Finishing Industry.
Counsel; and by
Charles Hammond,
Levesque, Robert
XIV-1
-------
-------
SECTION XV
REFERENCES
XV-1
-------
"i T • f'"!''i ",'p,,, r "y •
OIL, SOLVENT, AND CHEMICAL RECOVERY
"Alcoa Employs Ultrafiltration to Recycle 90,000 GPD", news item,
Ind. Water Bug., Jan/Peb., 1981.
Allen, Paul, "Reclaiming Four Plating Solutions", Products Finishing,
Aug., 1979.
MA Low-Cost Answer to Oil Recycling?"
Factory Management, January 1977, pp. 32-33.
i
Easily, William, •" Industrial Waste Water Treatment Facility,
Charleston Plant", General Electric, April 5, 1978.
Bech, E.G., Giannini, A.P., and Ramirez, E.R.,
"Electrocoagulation Clarifies Food Wastewater", Reprinted
from Food Technology, Vol. 28, No. 2, 1974, pp. 18-22.
i
Belinke, Robert J., "Central Filtration for Coolants",
American Machinists, December 1976, pp. 86-88.
Bolster, Maurice, "How to Maintain Emulsion Coolant Systems",
Modern Machine Shop, March 1977, pp. 112-115.
i
Bowes, H. David, "In-House Solvent Reclamation Eliminates
Quality Problems at Low Cost", Plastics Design & Processing,
May 1978, pp. 20-32. ;
i
Chonisby, J. and Kuhn, D., "Practical Oil Reclamation,
Purification", Hydraulics & Pneumatics, April 1976, pp. 71-73.
i
Chua, John P., "Coolant Filtration Systems",
Plant Engineering, December 23, 1976, pp. 46-51.
"Coolant Failure and How to Prevent It", Sun Coolant
Control Inc., Southfield, Mich.
"Coolant Tripples Tool Life", Modern Macnine Shop,
June 1979, pp. 140-141.
Cutting and Grinding Fluids; Selection and Application,
American Society of Tool and Manufacturing lEngineers,
Dearborn, Mich., 1967. |
Dinius, B., "How to Choose an In-Plant Oil Reclamation System",
Hydraulics and Pneumatics, July 1978, pp. ^2-64.
"Economic Impact of the Proposed Illinois Special Waste Hauling
Regulations (R76-10)11, Illinois Institute of Environmental
Quality, Project No. 80.089, IIEQ Document ;No. 77/26,
October 1977. ;
XV-2
-------
Electrostatic Separation of Solids from Liquids", Filtration &
Separation, March/April 1977, pp. 140-144.
"EPA/AES Conference . . .The Third Time Around: Recovery",
Plating and Surface Finishing, June, 1980.
Ford, Davis L., and Elton, Richard L., "Removal of Oil and Grease
from Industrial Wastewaters", Chemical Engineering/Deskbook Issue,
October 17, 1977, pp. 49-56. '~
Gransky, Michael, "The Case for Electrodialysis", Products
Finishing, April 1980.
Hura, LCdr Myron, USN and Mittleman, John,
"High Capacity Oil-Water Separator", Naval Engineers Journal,
December 1977, pp. 55-62.
"Ion Transfer Recovers Chrome", Industrial Finishing, April, 1980.
"IX for Nickel Recovery at Oldsmobile", Products Finishing, May, 1979,
Johnson, Ross E. Jr., Wastewater Treatment and Oil Reclamation
at General Motors, St. Catherines, pp. 345-357.
Kellogg, Jack, "Cutting Oil and Coolant Reclamation Pays Its
Way at Twin Disc".
Kelley, Ralph, "The Use of Cutting Fluids and Their Effect on
Cutting Tools and Grinding Wheels in Solving Production Problems",
Cincinnati Milacron/Products Division.
Kostura, John D., "Recovery and Treatment of Plating and Anodizing
Wastes", Plating and Surface Finishing, Aug., 1980.
Koury, Anthony J., and Gabel, M.K., and Wijenayake, Anton P.,
"Effect of Solid Film Lubricants on Tool Life", Journal of the
American Society of Lubrication Engineers, June 1979, Volume 35,6.,
pp. 315-316, 329-338.
Kremer, Lawrence N., "Prepaint Final Rinses: Chrome or Chrome-
Free?", Products Finishing, Nov., 1980.
Lewis, Tom A., "How to Electrolytically Recovery Metals from
Finishing Operations", Industrial Finishing, April, 1980.
Luthy, Richard G., and Sellech, Robert E., and Galloway, Terry R.,
"Removal of Emulsified Oil with Organic Coagulants and Dissolved
Air Flotation", Journal WPCF, February 1978, pp. 331-346.
XV-3
-------
Lutz-Nagey, Robert C., "Detroit Experimentors Reveal New Ways
to Save Cutting Oil", Production Engineering, June 1977, pp. 54-55.
"Making Recycling Work for You Through Proper Process Selection",
ibid, p. 10.
McNutt, J.E. and Swalheim. D.A., "Recovery and Re-use of Chemicals
in Plating Effluents", AES Illustrated Lecture Series,
American Electroplaters Society, Inc., Winter Park, FL, 1975.
McNutt, James. E., "Electroplating Waste control", Plating and
Surface Finishing, July, 1980.
Miranda, Julio G., "Designing Parallel-Plates Separators",
Chemical Engineering, January 31, 1977.
"Model Plant for Plastics Painting-Decorating", Industrial
Finishing, Feb., 1980.
"Oil Audit and Reuse Manual for the Industrial Plant", Illinois
Institute of Natural Resources, Project NoJ 80.085, Document
No. 78/35, November 1978.
"Oil/Water Splitter Snags Emulsified Oil", 'Chemical Engineering.
July 18, 1977, p. 77.
Parker, Konrad, "Renewal of Spent Electroless Nickel Plating
Baths", Plating and Surface Finishing, Mardh, 1980.
i
"Plastics Plated at Norris Meet Rigid Specifications", Industrial
Finishing, March, 1981.
"Plating on Plastics Etchants Regenerated", Products Finishing,
May, 1979.
I
Quanstrom, Richard L., "Central Coolant Systems-Closing the Loop
on Metalworking Fluids", Lubrication Engineering, January 1977,
Volume 33,1, pp. 14-19.
Rasquin, Edgar A. and Lynn, Scott and Hanson, Donald N.,
"Vacuum Steam Stripping of Volatile, Sparingly Soluble Organic
Compounds from Water Streams", Ind. Eng. Chemical Fundam.,
Vol. 17, No. 3, 1978, pp. 170-174.
. j. .
"Recovery Pays at Sommer Metalcraft", Industrial Finishing, June,
1980. j
"Recycling Etchant for Printed Circuits", Metal Finishing,
Metals and Plastics Publications Inc., Hackensack, NJ,
March 1972, pp. 42-43.
XV-4
-------
Reininga, O.G. and Wagner, R.H. and Bonewitz,
"Thermopure for Processing Water-Oil Emulsions",
Wire Journal, October 1976, pp. 48-53.
Roberts, David A., "Romicon Ultrafiltration for Waste Oil Re-
clamation", Paper presented to the Water Pollution Control Asso-
ciation of Pennsylvania, June 15, 1977.
"Selection of Lubricants for Drawing and Cleaning", Daniel Brewer,
Ceramic industry Magazine, June 1978, pp. 34-35.
Seng, W.C. and Kreutzer, G.M., "Resume of Total Operation of
Waste Treatment Facility for Animal and Vegetable Oil Refinery",
Reprinted from the Journal of the American Oil Chemists' Society,
Volume 52, No. 1, 1975, pp. 9A-13A.
Shah, B. and Langdon, W., and Wasan,, D., "Regeneration of Fibrous
Bed Coalescers for Oil-Water Separation", Environmental Science
and Technology, Volume 11, No. 2, February 1977, pp. 167-170.
"Simple Dragout Recovery Methods", Products Finishing, Oct., 1979.
Sutcliffe, T. and Barber, S.J., "How to Select a Water-Base
Coolant", American Machinist, April 1977.
"System Strips Solvents, Separates Solids Simultaneously",
Chemical Engineering, November 22, 1976, pp. 93-94.
Taylor, J.W., "Evaluation of Filter/Separators and Centrifuges
for Effects on Properties of Steam Turbine Lubricating Oils",
Journal of Testing and Evaluation, Volume 5, No. 5, September 1977,
pp. 401-405.
Teale, James M., "Fast Payout from In-Plant Recovery of Spent
Solvents", Chemical Engineering, January 31, 1977, pp. 98-100.
"The First Step-Reducing Waste Oil Generation", ibid, p. 16.
"Used Oil Recycling in Illinois", Data Book, Illinois Institute
of Natural Resources, Project No. 80.085, Document No. 78/34,
October, 1978.
Vucich, M.G., "Emulsion Control and Oil Recovery on the Lubricating
System of Double-Reduction Mills", Iron and Steel Engineer,
December 1976, pp. 29-38.
Wahl, James R., and others, "Ultrafiltration for Today's Oily
Wastewaters: A Survey of Current Ultrafiltration Systems", Pro-
ceedings of the 34th Industrial Waste Conference, Purdue University,
May, 1979, Ann Arbor Science.
XV-5
-------
"Waste Oil Reclamation", The Works Managers Guide to Working
Fluid Economy, Alfa-Laval' NO .Ijb4u494 is2.\
"Waste Oil Recycling - Coming Up a Winner", Fluid and Lubricant
Ideas, Volume 2, Issue 3, Summer 1979, p. 8.
Young, James C., "Removal of Grease and Oil by Biological Treatment
Processes", Jl.WPCF, Vol. 51, no. 8, Aug., 1979.
I
PLATING AND COATING ;
Adams, P., "Getting the Most Out of Vacuum Metalizing",
Products Finishing, Gardner Publications, Inc., Cincinnati,
Ohio, November, 1977, pp. 43-51.
I
"Alkaline Zinc Bath Solves Low-CD Problems", Products Finishing,
Aug., 1980. !
i
Allied Chemical Company and Aluminum Companyiof America,
"Chromic Acid Anodizing of Aluminum", AES Illustrated
Lecture Series, American Electroplaters Society, Inc.,
Winter Park, FL, 1973. \
I
Atimion, Leo, "A program of Conservation, Pollution Abatement",
Plating and Surface Finishing, March, 1980.
Baker, R. G. et al, "Gold Electroplating Part 2", AES
Illustrated Lecture Series, American Electroplaters Society,
Inc., Winter Park, FL, 1978.
Bellis, H.E. and Pearlstein, F., "Electroless Plating of Metals",
AES Illustrated Lecture Series, American Electroplaters Society
Inc., Winter Park, FL, 1972. '
Blount, Ezra A., "How Guide Recovers Nickel and Chromium",
Products Finishing, Dec., 1980.
Breslou, Barry R., and others, "Hollow Fiber Ultrafiltration
Technology", Ind. Water Eng., Jan./Feb., 1980.
"Cheminator", Chemical Engineering, McGraw Hill, New York, NY,
September, 1975, p. 26.
"Current Events and Cadmium Plating", Platingand Surface Finishing,
July, 1980.
i
"Developments to Watch", Product Engineering, Morgan-Grampian,
New York, NY, October 197"5, p. 5.
XV-6
-------
DiBari, G.A., "Practical Nickel Plating", AES Illustrated
Lecture Series, American Electro-platers Society, Inc., Winter
Park, FL, 1977.
Duva, R., "Gold Electroplating Part I", AES Illustrated
Lecture Series, American Electroplaters Society, Inc., Winter
Park, FL, 1977.
Electroplating Engineering Handbook, Third Edition, edited
by A.Kenneth Graham, Van Nostrand Reinhold Company, New York,
NY, 1971.
Electroplating - Fundamentals of Surface Finishing, Frederick
A. Lowenheim, McGraw-Hill,Inc., New York, NY, 1978.
General Motors Research Laboratories, "Factors Influencing
Plate Distribution", AES Illustrated Lecture Series, American
Electroplaters Society, Inc., Winter Park, FL, 1975.
Halva, C.J. and Rothschild, B.F., "Plating and Finishing of
Printed Wiring/Circuit Boards", AES Illustrated Lecture Series,
American Electroplaters Society, Inc«, Winter Park, FL, 1976.
Harrison, Albert, Coil Coater Cuts Effluent Treatment Costs",
Products Finishing, November, 1980.
Hubbell, F.N., "Chemically Deposited Composites - A new Gener-
ation of Electroless Coatings", Plating and Surface Finishing,
American Electroplaters Society, E. Orange, NJ, Vol. 65, Dec.
1978, p. 48.
11 Ion Transfer Method Developed for Metal Plating", Industrial
Finishing, Hitchcock Publishing Co., Wheaton, Ohio, April 1979,
p. 95.
Logozzo, Arthur W., "Hard Chromium Plating", AES Illustrated
Lecture Series, American Electroplaters Society, Inc., Winter
Park, FL, 1973.
MacDermid, Inc., "Chromate Conversion Coatings" AES Illus-
trated Lecture Series, American Electroplaters Society, Inc.,
Winter Park, FL, 1970.
Mazzeo, D.A., "Energy Conservation In Plating and Surface
Finishing", Plating and Surface Finishing, American Electroplaters
Society, Inc.,, Winter Park, FL, July, 1979, pp. 10-12.
M&T Chemical Inc., "Decorative Chromium Plating", AES Illus-
trated Lecture Series, American Electroplaters Society, Inc.,
Winter Park, FL, 1972.
XV-7
-------
Mohler, J.B., "The Art and Science of Rinsing", AES Illustrated
Lecture Series, American Electroplaters Society, Inc., Winter
Park, FL, 1973.
Montgomery, D.C., "The Coloration of Anodic Coatings for
Architectural Applications by Using Organic Dyes", Plating
and Surface'Finishing, American Electroplaters Society, E.
Orange, NJ, Vol. 65, Dec. 78, p. 48.
Ostraw, R. and Kessler, R.B., "A Technical and Economic Com-
parison of Cyanide and Cyanide-Free Zinc Plating", Plating,
American Electroplaters Society, Hackensack, NJ, April 1970.
Pearlstein, F., "Selection and Application of Inorganic Fini-
shes - Part 1", Plating and Surface Finishing, American Elec-
troplaters Society, E. Orange, NJ, Vol. 65, Dec. 1978., p. 32.
Pearlstein, F. et al, "Testing and Evaluation of Deposits",
AES Illutrated Lecture Series, American Electroplaters Society
Inc., Winter Park, FL, 1974. '
j
"Plater Turns Fire Woes into Golden Opportunity", Industrial
Finishing, Nov., 1980.
1
"Plating Aluminum Busbar", Industrial Finishing, Feb., 1979.
Rajagopal, I., and Rajam, K.S., "A New Addition Agent for
Lead Plating", Metal Finishing, Metals and Plastics Publi-
cation Inc., Hackensack, NJ,December, 1978.
i
Riley, Thomas C., "Benefits are Bountiful ;with Elco's Bright
Zinc Process", Industrial Finishing, Jan. 1981.
Roberts, Vicki, "A Low-Cyanide Zinc for Champion Spark Plugs",
Products Finishing, Sept., 1979.
I
Rose, Betty A., "Bulk Plater Saves with Evaporative Recovery",
Industrial Finishing, Jan. 1979.
Rose, Betty A., "Design for Recovery", Industrial Finishing,
May, 1979. ;
"Slide into Compliance", Industrial Finishing, Dec., 1979.
"Tri-Chrome Takes on New Importance to Platers", Industrial
Finishing, Nov., 1980.
XV-8
-------
SURFACE PREPARATION
Axelspn, Willianir "Specialized Cleaning Equipment Supports
Efficient Maintenance", Pit & Quauy, October 1976, pp. 95-98.
Bauks, S.V., and Dresser, K.J., Cleaning Alternatives to Solvent
Degreasing, EPA, December 7, 1971TT
Jackson, Lloyd, C., "How to Select a Substrate Cleaning Solvent",
Adhesives Age, April 1977, pp. 23-31.
Jackson, Lloyd C., "Rempval of Silicone Grease and Oil
Contaminants", Adhesives Age, April 1977, pp. 29-32.
Jackson, Lloyd C., "Solvent Cleaning Process Efficiency",
Adhesives Age, July 1976, pp. 31-34.
Maloney, J.E., "Low Temperature Cleaning", Metal Finishing,
June 1976, pp. 33-35.
Metal Cleaning Fundamentals, Materials and Methods, Oakite
Products, Inc., F 10646R13-379.
Metals Handbook, American Society for Metals, 8th Edition, Volume
T", "Heat Treating, Cleaning, and Finishing", 1964, pp. 307-314.
Mohler, J.B., "Guidelines for Cleaning Metal Parts", Plant
Engineering, October 2, 1975, pp. 93-95.
Obrzut, John J., "Metal Cleaning Bends with Social Pressures",
Iron Age, February 17, 1974, pp. 41-44.
Taller, R.A. and Koleske, J.V., "Energy Conservation in Metal
Pretreatment and Coating Operations", Metal Finishing,
August 1977, pp. 18-19.
Tonis, Paul G. , "Try Steam Cleaning/Phosphatizing", Products
Finishing, January 1979, pp. 56-57.
SURFACE PREPARATION - ACID CLEANING
Frey, S.S. and Swalheim, D.A., "Cleaning and Pickling for
Electroplating", AES Illustrated Decture Series, American
Electroplaters Society, Inc., Winter Park, FL, 1970.
Metals Handbook, American Society for Metals, 8th edition.
Volume 2, "Heat Treating, Cleaning and Finishing", 1964.
Rodzewich, Edward A., "Theory and Practice of Phosphating",
AES Illustrated Lecture Series, American Electroplaters
Society, Inc., Winter Park, FL, 1974.
Roebuck, A.H., "Safe Chemical Cleaning - The Organic Way",
Chemical Engineering, July 31, 1978, pp. 107-110.
XV-9
-------
SURFACE PREPARATION - ALKALINE CLEANING
Erichson, Paul R. and Throop, William M., "Alkaline Treatment
System Reduces Pollution Problems", Industrial Wastes, March/
April 1977. ; '
Erichson, Paul R. and Throop, William M., "Improved Washing of
Machined Parts", Production Engineering, March 1977.
Graham, A. Kenneth, Electroplating Engineering Handbook, 1971,
pp. 152-176. ;—
Metals Handbook, American Society for Metals, 8th Edition,
Volume 2, "Heat Treating, Cleaning and Finishing", 1964,
pp. 317-325.
SURFACE PREPARATION - EMULSION CLEANING
Connolly, James T., "Metal Cleaning with Emulsions - An Update",
Lubrication Engineering, December 1976, pp. 651-654.
Safer Cleaners?",
Glover, Harry C., "Are Emulsified Solvents o
Production Engineering, July 1978, pp. 41-43.
Metal Handbook, American Society for Metals, 8th Edition,
volume 2, "Heat Treating, Cleaning and Finishing", 1964,
pp. 326-330.
SURFACE PREPARATION - VAPOR DECREASING
Bauks, S.V. and Dresser, K.J., Solvent Degreasing Unit Operation
Report, EPA, September 17, 1979"~~~
Metals Handbook, American Society for Metals, 8th Edition,
Volume 2, "Heat Treating, Cleaning and Finishing", 1964,
pp. 334-340.
"Organic Solvent Cleaning-Background Information for Proposed
Standards", US EPA, EPA-450/2-78-045, May 1979.
Suprenant, K., "Vapor Degreasing or Alkaline Cleaning?11,
Products Finishing, March 1979, pp. 67-71.
XV-10
-------
TREATMENT
Barrett, F. , "The Electroflotation of Organic Wastes",
Chemistry and industry, October 16, 1976, pp. 880-882.
Bell, John P., "How to Remove Metals from Plating Rinse Waters",
Products Finishing, Aug., 1979.
Chin, D.T., and Echert, B., "Destruction of Cyanide Wastes
with a Packed-Bed Electrode", Plating and Surface Finishing,
October 1976, pp. 38-41.
DeLatour, Christopher, "Magnetic Separation in Water Pollution
Control", IEEE Transactions on Magnetics, Volume Mag-9, No. 3,
September 1973, p.
"Development Document for Proposed Exisiting Source Pretreat-
ment Standards for the Electroplating Point Source Category",
EPA 440/1-78/085, United States Environmental Protection
Agency, Washington, DC, 1978.
"Economic Analysis of Proposed Pretreatment Standards for
Existing Sources of the Electroplating Point Source Category" ,
EPA 230/1/78-001, United States Environmental Protection
Agency, Washington, DC, 1977.
"Electrotechnology Volume 1, Wastewater Treatment and Separation
Methods", Cheremisinoff , Paul N. , King, John A., Oullette, Robert P. ,
Ann Arbor Science Publishers, Inc., Ann Arbor, MI, 1978.
"Emerging Technologies for Treatment of Electroplating
Wastewaters" , f or presentation by Stinson, M.K., at AICHE
71st Annual Metting, Session 69, Miami Beach, Florida,
November 15, 1978.
Flynn, B.L. Jr., "Wet Air Oxidation of Waste Streams", CEP,
April 1979, pp. 66-69.
Grutsch, James F. , "Wastewater Treatment: The Electrical
Connection", Environmental Science and Technology, Volume 12,
No. 9, Sept. 1978, pp. 1022-1027.
Grutsch, James F. , and Mallatt, R«,C., "Optimizing Granular
Media Filtration", GEP, April 1977, pp. 57-66.
"Handbook of Environmental Data on Organic Chemicals", Karel
Verschueren, Van Nostrand Reinhold Company, New York, NY 1977.
Henry, Joseph D. Jr., Lowler, Lee F. , and Kuo, C.H. Alex,
"A Solid/Liquid Separation Process Based on Cross Flow and
Electrof iltration" , AIChE Journal, Volume 23, No. 6, November
1977, pp. 851-859.
XV-11
-------
Hochenberry, H.R.^and Lieseir, J.E., Practical Application
of Membrane Techniques of Waste Oil Treatment, presenter!
at tne Jist Annual Meeting in Philadelphia, Pennsylvania
Q 7 ^ Am^V* T /•"• r?» »•» f>^. ^.4^*.J ^»4T T.-1-.. ' -i_» v^ - •
or JbUDirication Enginoers 9
Humenich, Michael j. and Davis, Barry j. , "high Rate
Filtration of Refinery Oily Wastewater Emulsions",
Journal WPCF, Agusut 1978, pp. 1953-1964.
4.T, ~ Upgrading Metal Finishing
to Reduce Pollution", EPA Technology Transfer Semi-
mar Publication, Environmental Protection Agency, July 1973.
Kaiser, Klaus L.E. arid Lawrence, John, Polyelectrolytes:
Potential Chloroform Precursors, Environment Canada, Canada
Centre for Inland Waters, Burlington, Ontario, January 25, 1977
./ ?' and Nishik*wa, Y. and Frankenfeld, J.W. and LiW
"Wastewater Treatment by Liquid Membrane Process",
Environmental Science and Technology, Volume 11, No 6
June 1977, pp. 602-605. ; '
*«cility lAcheives Zero Discharge",
m ?T' "The Large-Scale Manipulation of Small Particles",
IEEE Transactions on Magnetics, Vol. Mag-11 , No. 5, Sept
pp. 1567-1569. ' ' f
Lancy, L. E. , "Metal Finishing Waste Treatment Aims Accomplished
pr°9ress
Lancy, L.E. and Steward, F.A., "Disposal of Metal Finishing
Sludges - The Segregated Landfill Concept", gating and Surface
Finishing, American Electroplaters Society, E. Oranqe, NJ, -
Vol. 65, Dec. 1978. p. 14. \
Lawes, B.C. and Stevens, W.F., "Treatment of: Cyanide and
Chromate Rinses", AES Illustrated Lecture Series, American
Electroplaters Society, Inc., Winter Park, PL, 1972.
Lee, Carl, "Huge New Plating Facility Built for the Future",
Products Finishing, Nov., 1979.
Lorenzo, George A., and Hendrickson, Thomas N. , "Ozone in the
Photoprocessing Industry", Ozone; Science and Engineering. P
~~ --
Press, 1979.
Pergamon
Lowder, L.R. , "Modifications Improve Treatment of Plating Room
Wastes", Water and Sewage Works, Plenum Publishing <2>co , New
York, NY, December, 1968. p. 581. > "
XV-12
-------
Nakayama, S., and others, "Improved Ozonation in Aqueous Systems",
Ozone: Science and Engineering, Pergamon Press, 1979.
"No More Woes for Custom Plater", Industrial Finishing, Jan., 1979.
Novak, Fred, "Destruction of Cyanide Wastewater by Ozonation",
Paper presented at the International Ozone Assn. Conf., Nov., 1979.
Oberteuffer, John A., "High Gradient Magnetic Separation",
IEEE Transaction on Magnetics, Volume Mag-9, No. 3,
September 1973, pp. 303-306.
Okamato, S., "Iron Hydroxide as Magnetic Scavengers",
Institute of Physical and Chemical Research, Waho-shi,
Saitama-hen, 351 Japan.
Oulman, Charles S. and Baumann, Robert E., "Polyelectrolyte
Coatings for Filter Media", Industrial Water Engineering,
May 1971, pp. 22-25.
Pietrzak, J., Unit Operation Discharge Summary for the Mechanical
Products Category, EPA, September 7, 1979.
Pinto, Steven, D., Ultrafiltration for Dewatering of^Waste
Emulsified Oils, Lubrication Challenges in Metalworking and
Processing Proceedings, First International Conference, IIT
Research Institute, Chicago, Illinois 60616, USA, June 7-9, 1978.
"Physiochemical Processes for Water Quality Control", Wiley-
Interscience Series, Walter, J. Weber, Jr., John Wiley and Sons
Inc., New York, NY 1972.
"Pollution Control 1978", Products Finishing, Gardner Publica-
tions, Inc., Cincinnati, Ohio, August, 1978, pp. 39-41.
Read, H.J., "Principles of Corrosion", AES Illustrated Lecture
Series, American Electroplaters Society, Inc., Winter Park,
FL, 1971.
Rice, Rip G., "Ozone for Industrial Water & Wastewater Treatment",
Paper presented at WWEMA Industrial Pollution Control Conf.,
June, 1980.
Robison, Thomas G., "Chromecraft's New High-Production Plating Line",
Products Finishing, Feb., 1981.
Robinson, G.T., "Powder Coating Replaces Zinc Plating for
Pulleys", Products Finishing, Gardner Publications Inc.,
Cincinnati7~OH, Feb., 1974, pp. 79-81.
Rose, Betty A., "Managing Water at Helicopter Plant", Industrial
Finishing.
XV-13
-------
Sachs, T.R., "Diversified Finisher Handles Complex Waste
Treatment Problem", Plating and Surface Finishing, American
Electroplaters Society, E. Orange, NJ, Vol. 65, Dec. 1978, p. 36.
"Semiconductor Technique Now to Plate Auto Parts", Machine
Design, Penton Publishing, Cleveland, OH, p. 18.
i
Shambaugh, Robert T. and Melhyh, Peter B., "Removal of Heavy
Metals via Ozonation", Journal WPCF, Jan. 1978, pp. 113-121.
"Simple Treatment for Spent Electroless Nickel", Products
Finishing, Feb., 1981. .
i
Spooner, R.C., "Sulfuric Acid Anodizing of Aluminum and Its
Alloys", AES Illustrated Lecture Series, American Electro-
platers Society, Inc., Winter Park, FL, 1969.
i
Staebler, C.J. and Simpers, B.F., "Corrosion Resistant Coatings
with Low Water Pollution Potential", presented at the EPA/AES
First Annual Conference on Advanced Pollution Control for the
Metal Finishing Industry, Lake Buena Vista, FL, January 17-19, 1978
Sundaram, T.R. and Santo, J.E., "Removal of Suspended and
Colloidal Solids from Waste Streams by the Use of Cross-Flow
Microfiltration", American Society of Mechanical Engineers,
77-ENAs-Sl.
Swalheim, D.A. et al, "Cyanide Copper Plating", AES Illustrated
Lecture Series, American Electroplaters Society, Inc., Winter
Park, FL, 1969. i
i
Swalheim, D.A. et al, "Zinc and Cadmium Plating", AES Illustrated
Lecture Series, American Electroplaters Society, Inc., Winter
Park, FL. ',
Tang, T.L. Don, "Application of Membrane Technology to Power
Generation Waters", Industrial Water Engineering, Jan./Feb., 1981.
i
"The Electrochemical Removal of Trace Metals for Metal Wastes
with Simultaneous Cyanide Destruction", for presentation by
H.S.A. Reactors Limited at the First annual' EPA/AES Conference
on Advanced Pollution Control for the Metal Finishing Industry,
Dutch Inn, Lake Buena Vista, FL, Jan. 18, 1978.
"Treating Electroless Plating Effluent", Products Finishing,
Aug., 1980. i
Tremmel, Robert A., "Decorative Nickel-Iron Coatings", Plating
and Surface Finishing, Jan., 1981.
Udylite Corporation, "Bright Acid Sulfate Copper Plating",
AES Illustrated Lecture Society, American Electroplaters Society,
Inc., Winter Park, FL, 1970. .
XV-14
-------
Ukawa, Hiroshi, Koboyashi, Kaseimaza, and Iwata, Minoru "Analysis
of Batch Electrokinetic Filtration", Journal of Chemical Engineering
of Japan, Volume 9, No. 5, 1976, pp. 396-401.
Wahl, James R., Hayes, Thomas C., Kleper, Myles.H., and Pinto,
Steven D., Ultrafiltratibn for Today's Oily Wastewaters;
A Survey ofTurirent Ultrafiltration Systems, presented at the
34th Annual Purdue Industrial Waste Conference, May 8-10, 1979.
Wing, R.E., and others, "Treatment of Complexed Copper Rinsewaters
with Insoluble Starch Xanthate", Plating and Surface Finishing,
Dec., 1978.
"Wooing Detroit with Cheaper Plated Plastic", Business Week,
McGraw-Hill Inc., New York City, NY, May 9, 1977, pp. 44c-44d.
Yost, Kenneth J., and Scarfi, Anthony, "Factors Affecting Copper
Solubility in Electroplating Waste", Journal WPCF, Vol. 51, No. 7,
July, 1979.
Zabban, Walter, and Heluick, Robert, "Cyanide Waste Treatment
Technology - The Old, the New, and the Practical", Plating and
Surface Finishing, Aug., 1980.
XV-15
-------
-------
SECTION XVI
GLOSSARY
Abrasive Belt Grinding - Roughing and/or finishing a workpiece by
means of a power-driven belt coated with an abrasive, usually
in particle form, which removes material by scratching the
surface.
Abrasive Belt Polishing - Finishing a workpiece with a power-driven
abrasive-coated belt in order to develop a very good finish.
Abrasive Blasting - (Surface treatment and cleaning.) Using dry or
wet abrasive particles under air pressure for short durations
of time to clean a metal surface.
Abrasive Cutoff - Severing a workpiece by means of a thin abrasive
wheel.
Abrasive Jet Machining - Removal of material from a workpiece by a
high-speed stream of abrasive particles carried by gas from a
nozzle.
Abrasive Machining - Used to accomplish heavy stock removal at high
rates by use of a free-cutting grinding wheel.
Acceleration - See Activation.
Acceptance Testing - A test, or series of tests, and inspections
that confirms product functioning in accordance with specified
requirements.
Acetic Acid - (Ethanoic acid, vinegar acid, methanecarboxylic acid)
CH3_COOH. Glacial acetic acid is the pure compound (99.8% min.),
as distinguished from the usual water solutions known as acetic
acid. Vinegar is a dilute acetic acid.
Acid Cleaning - Using any acid for the purpose of cleaning any mater-
ial. Some methods of acid cleaning are pickling and oxidizing.
Acid Dip - An acidic solution for activating the workpiece surface
prior to electroplating in an acidic solution, especially after
the workpiece has been processed in an alkaline solution.
Acidity - The quantitative capacity of aqueous solutions to react
with hydroxyl ions. It is measured by titration with a standard
solution of a base to a specified end point. Usually expressed
as milligrams per liter of calcium carbonate.
XVI-1
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Act - Federal Water Pollution Control Act Amendments of 1972.
s
Activitated Sludge Process - Removes organic matter from sewage by
saturating it with air and biological active sludge.
Activation - The process of treating a substance by heat, radiation
or the presence of another substance so that the first mentioned
substance will undergo chemical or physical change more rapidly
or completely. ',
I
Additive Circuitry - 1. Pull - Circuitry produced by the buildup of
an electroless copper pattern upon an unclad board. 2. Semi -
Circuitry produced by the selective "quick" etch of an electro-
less layer; this copper layer was previously deposited on an
unclad board.
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Administrator - Means the Administrator of the United States Environ-
mental Protection Agency.
Adsorption - The adhesion of an extremely thin layer of molecules
(as of gas, solids or liquids) to the surface of solid or
liquids with which they are in contact.
Aerobic - Living, active, or occurring only in the presence of oxygen.
Aerobic Biological Oxidation - Any waste treatment process utilizing
organisms in the presence of air or oxygen to reduce the pol-
lution load or oxygen demand of organic substance in water.
Aerobic Digestion - (Sludge Processing) The biochemical decomposition
of organic matter, by organisms living or active only in the
presence of oxygen, which results in the formation of mineral and
simpler organic compounds. ,
Aging - The change in properties (eg. increase in tensile strength and
hardness) that occurs in certain metals \at atmospheric temperature
after heat treatment.
Agitation of Parts - The irregular movement given to parts when they
have been submerged in a plating or rinse solution.
Air Agitation - The agitation of a liquid medium through the use of
air pressure injected into the liquid.
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Air Flotation - See Flotation i
Air Pollution - The presence in the outdoor (ambient) atmosphere of one
air pollutants or any combination thereof in such quantities and
of such characteristics and duration as to be, or be likely to be,
injurious to public welfare, to the health of human, plant or
animal life, or to property, or as unreasonably to interfere with
the enjoyment of life and property.
XVI-2
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Air-Liquid Interface - The boundary layer between the air and the
liquid in which mass transfer is diffusion controlled.
Aldehydes Group - A group of various highly reactive compounds
typified by actaldehyde and characterized by the group CHO.
Algicides - Chemicals for preventing the growth of algae.
Alkaline Cleaning - A process for cleaning basis material where
mineral and animal fats and oils must be removed from the
surface. Solutions at high temperatures containing casutic
soda, soda ash, alkaline silicates and alkaline phosphates
are commonly used.
Alkalinity - The capacity of water to neutralize acids, a property
imparted by the water's content of carbonates, bicarbonates,
hydroxides, and occasionally borates, silicates, and phosphates.
Alloy Steels - Steels with carbon content between 0.1% to 1.1% and
containing elements such as nickel, chromium, molybdenum and
vanadium. (The total of all such alloying elements in these type
steels is usually less than 5%.)
Aluminizing - Forming an aluminum or aluminum alloy coating on a metal
by hot dipping, hot spraying or diffusion.
Amines - A class of organic compounds of nitrogen that may be considered
as derived from ammonia (NHJ3) by replacing one or more of the
hydrogen atoms by organic radicals, such as CH_3 or C6HJ5, as in
methylamine and aniline. The former is a gas at ordinary tempera-
ture and pressure, but other amines are liquids or solids. All
amines are basic in nature and usually combine readily with hydro-
chloric or other strong acids to form salts.
Anaerobic Biological Treatment - Any waste treatment process utilizing
anaerobic or facultative organisms in the absence of air to
reduce the organic matter in water.
Anaerobic Digestion - The process of allowing sludges to decompose
naturally in heated tanks without a supply of oxygen.
Anaerobic Waste Treatment - (Sludge Processing) Waste stabilization
brought about through the action of microorganisms in the absence
of air or elemental oxygen.
Anhydrous - Containing no water.
Anions - The negatively charged ions in solution, e.g., hydroxyl.
Annealing - A process for preventing brittleness in a metal part.
The process consists of raising the temperature of the metal
to a pre-established level and slowly cooling the steel at a
prescribed rate.
XVI-3
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Annual Capital Recovery Cost - Allocates the initial investment and
the interest to the total operating cost. The capital recovery
cost is equal to the initial investment multiplied by the capital
recovery factor. |
Anode - The positively charged electrode in an electrochemical process.
j ' •
Anodizing - The production of a protective oxide film on aluminum or
other light metal by passing a high voltage electric current
through a bath in which the metal is suspended.
Aquifer - Water bearing stratum. ',
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Ash - The solid residue left after complete combustion.
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Assembly - The fitting together of manufactured parts into a complete
machine, structure, or unit of a machine;.
Atmospheric Evaporation - Evaporation at ambient pressure utilizing
a tower filled with packing material. Air is drawn in from
the bottom of the tower and evaporates feed material entering
from the top. There is no recovery of the vapors.
Atomic Absorption - Quantitative chemical instrumentation used for the
analysis of elemental constituents.
Automatic Plating - 1. Full - Plating in whichtheworkplaces"are
automatically conveyed through successive cleaning and plating
tanks. 2. Semi - Plating in which the (wprkpieces are conveyed
automatically through only one plating tjank.
Aus temper ing - Heat treating process to obtaijn greater toughness and
ducticity in certain high-carbon steels. The process is charac-
terized by interrupted quenching and results in the formation of
bainite grain structure.
Austenitizing - Heating a steel to a temperature at which the structure
transforms to a solution of one or more elements in face-centered
cubic iron. Usually performed as the essential preliminary of
heat treatment, in order to get the various alloying elements
into solid solution. \
Barrel Finishing - The process of polishing a workpiece using a rotat-
ing or vibrating container and abrasive grains or other polishing
materials to achieve the desired surface appearance.
Barrel Plating - Electroplating of workpieces in barrels (bulk).
Basis Metal or Material - That substance of which the workpieces are
made and that receives the electroplate and the treatments in
preparation for plating.
XVI-4
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Batch Treatment - A waste treatment method where wastewater is collect-
ed over a "period of time and then treated prior to discharge.
Bending - Turning or forcing by a brake press or other device from a
straight or even to a curved or angular condition.
Best Available Technology Economically Achievable (BAT) - Level of
technology applicable to effluent limitations to be achieved
by J984 for industrial discharges to surface waters as defined
by Section 301(b) (2) (A) of the Act.
Best Practicable Control Technology Currently Available - Level of
technology applicable to effluent limitations to be achieved
for industrial discharges to surface waters as defined by
Section 301 (b) (1) (A) of the Act.
Biochemical Oxygen Demand (BOD) - The amount of oxygen in milligrams
per liter used by microorganisms to consume biodegradable organics
in wastewater under aerobic conditions.
Biodegradability - The susceptibility of a substance to decomposition
by microorganisms; specifically, the rate at which compounds may
be chemically broken down by bacteria and/or natural environmental
factors.
Blanking - Cutting desired shapes out of sheet metal by means of dies.
Slowdown - The minimum discharge of recirculating water for the purpose
of discharging materials contained in the water, the further build-
up of which would cause concentration in amounts exceeding limits
established by best engineering practice.
BODS - The five-day Biochemical Oxygen Demand (BODS) is the quantity
of oxygen used by bacteria in consuming organic matter in a sample
of wastewater over a five-day period. BOD from the standard five-
day test equals about two-thirds of the total BOD. See Biochem-
ical Oxygen Demand.
Bonding - The process of uniting using an adhesive or fusible
ingredient.
Boring - Enlarging a hole by removing metal with a single or occasion-
ally a multiple point cutting tool moving parallel to the axis of
rotation of the work or tool. 1, Single-Point Boring - Cutting
with a single-point tool. 2. Precision Boring - Cutting to
tolerances held within narrow limits. 3. Gun Boring - Cutting
of deep holes. 4. Jig Boring - Cutting of high-precision and
accurate location holes. 5. Groove Boring - Cutting accurate
recesses in hole walls.
XVI-5
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Brazing - Joining metals by flowing a thin layer, capillary thickness,
of non-ferrous filler metal into the space between them. Bonding
results from the intimate contact producejd by the dissolution of
a small amount of base metal in the molten filler metal, without
fusion of the base metal. The term brazing is used where the
temperature exceeds 425°C(800°F). !
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Bright Dipping - The immersion of all or part of a workpiece in a
media designed to clean or brighten the surface and leave a
protective surface coating on the workpiece.
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Brine - An aqueous salt solution.
Broaching - Cutting with a tool which consists of a bar having a
single edge or a series of cutting edges (i.e., teeth) on its
surface. The cutting edges of multiple-tooth, or successive
single-tooth, broaches increase in size and/or change in shape.
The broach cuts in a straight line or axial direction when
relative motion is produced in relation to the workpiece, which
may also be rotating. The entire cut is made in single or
multiple passes over the workpiece to shape the required surface
contour. 1. Pull Broaching - Tool pulled through or over work-
piece. 2. Push Broaching - Tool pushed over or through work-
piece. 3. Chain Broaching - A continuous high production
surface broach. 4. Tunnel Broaching - Work travels through an
enclosed area containing broach inserts.
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Bromine Water - A nonmetallic halogen liquid, normally deep red,
corrosive and toxic, which is used as an oxidizing agent.
Buffing - An operation to provide a high luster to a surface. The
operation, which is not intended to remove much material,
usually follows polishing.
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Buffing Compounds - Abrasive contained by a liquid or solid binder
composed of fatty acids, grease, or tallow. The binder serves
as lubricant, coolant, and an adhesive of the abrasive to the
buffing wheel. .
Burnishing - Finish sizing and smooth finishing of a workpiece
(previously machined or ground) by displacement, rather than
removal, of minute surface irregularities with smooth point or
line-contact, fixed or rotating tools.
Calendering - Process of fo'rming a continuous sheet by squeezing the
material between two or more parallel rolls to impart the desired
finish or to insure uniform thickness. •
Calibration - The application of thermal, electrical, or mechanical
energy to set or establish reference points for a part, assem-
bly or complete unit. I
XVI-6
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Calibration Equipment - Equipment used for calibration of instruments.
Capital Recovery Costs - Allocates the initial investemnt and the inter-
est to the total operating cost. The capital recovery cost is
equal to the initial investment multiplied by the capital recovery
•C ci C uO 1C • . ...
Capital Recovery Factor - Capital Recover Factor is defined as:
i + i/(a - 1) where i = interest rate, a = (1 + i) to the power n,
n = interest period in years.
Captive Operation - A manufacturing operation carried out in a facility
to support subsequent manufacturing, fabrication, or assembly
operations. •*
Carbides - Usually refers to the general class of pressed and sintered
tungsten carbide cutting tools which contain tungsten carbide plus
smaller amounts of titanium and tantalum carbides along with
cobalt which acts as a binder. (It is also used to describe hard
compounds in steels and cast irons.)
Carbon Adsorption - Activated carbon contained in a vessel and
installed in either a gas or liquid stream to remove organic
contaminates. Carbon is regenerable when subject to steam which
forces contaminant to desorb from media.
Carbon Bed Catalytic Destruction - A non-electrolytic process for the
catalytic oxidation of cyanide wastes using filters filled with
low-temperature coke.
Carbon Steels - Steel which owes its properties chiefly to various
percentage of carbon without substantial amounts of other alloyinq
elements. * y
Carbonate - A compound containing the acid radical of carbonic acid
(CO3^ group).
Carbonitriding - Process for case or core hardening of metals. The
heated metals absorb carbon in a gaseous atmosphere.
Carburizing - (Physical Property Modification) Increasing the carbon
content of a metal by heating with a carburizing medium (which
may be solid, liquid or gas) usually for the purpose of producing
a hardened surface by subsequent quenching.
Carcinogen - Substance which causes cancerous growth.
Case Hardening - A heat treating method by which the surface layer of
alloys is made substantially harder than the interior. (Carburiz-
ing and nitriding are common ways of case hardening steels.)
Cast - A state of the substance after solidification of the molten
substance.
XVI-7
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Casthouse - The facility which melts metal, holds it in furnaces for
degassing (fluxing) and alloying and then casts the metal into
pigs, ingots, billets, rod, etc.
Casting - The operation of pouring molten metal into a mold.
Catalytic Bath - A bath containing a substance used to accelerate the
rate of chemical reaction.
Category - Also point source category. A segment of industry for
which a set of effluent limitations has| been established.
Cathode - The negatively charged electrode in an electrochemical
process.
Cation - The positively charged ions in a solution.
Caustic - Capable of destroying or eating away by chemical action.
Applies to strong bases and characterized by the presence of
hydroxyl ions in solution.
Caustic Soda - Sodium hydroxide, NaOH, whose solution in water is
strongly alkaline.
Cementation - The electrochemical reduction of metal ions by contact
with a metal of higher oxidation potential. It is usually used
for the simultaneous recovery of copper^ and reduction of
hexavalent chromium with the aid of scrap iron.
Centerless Grinding - Grinding the outside or inside of a workpiece
mounted on rollers rather than on centers. The workpiece may be
in the form of a cylinder or the frustrum of a cone.
Central Treatment Facility - Treatment plant! which co-treats process
wastewaters from more" than one manufacturing operation or co-
treats process wastewaters with non-contact cooling water, or
with non-process wastewaters (e.g., utility blowdown, miscellan-
eous runoff, etc.).
Centrifugation - An oil recovery step employing a centrifuge to remove
water from waste oil.
Centrifuge - A device having a rotating container in which centrifugal
force separates substances of differing densities.
Chelated Compound - A compound in which the metal is contained as an
integral part of a ring structure and is not readily ionized.
XVI-8
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Chelating Agent - A coordinate compound in which a central atom
(usually a metal) is joined by covalent bonds to two or more
other molecules or ions (called ligands) so that heterocyclic
rings are formed with the central (metal) atom as part of each
ring. Thus, the compound is suspending the metal in solution.
Chemical Brightening - Process utilizing an addition agent that leads
to the formation of a bright plate or that improves the brightness
of the deposit.
Chemical Deposition - Process used to deposit a metal oxide on a
substrate. Ther film is formed by hydrolysis of a mixture of
chlorides at the hot surface of the substrate. Careful control
of the water mixture insures that the oxide is formed on the
substrate surface,
Chemical Etching - To dissolve a part of the surface of a metal or
all of the metal laminated to a base.
Chemical Machining - Production of derived shapes and dimensions
through selective or overall removal of metal by controlled
chemical attack or etching.
Chemical Metal Coloring - The production of desired colors on metal
surfaces by appropriate chemical or electrochemical action.
Chemical Milling •- Removing large amounts of stock by etching
selected areas of complex workpieces. This process entails
cleaning, masking, etching, and demasking.
Ch.emica1 Ox id at i on - (Including Cyanide) The addition of chemical
agents to wastewater for the purpose of oxidizing pollutant
material.
Chemical Oxygen Demand (COD) - The amount of oxygen in milligrams per
liter to oxidize both organic and oxidizable inorganic compounds.
Chemical Precipitation - A chemical process in which a chemical in
solution reeicts wit'h another chemical introduced to that solution
to form a third substance which is partially or mainly insoluble
and, therefore, appears as a solid.
Chemical Recovery Systems - Chemical treatment to remove metal or
other materials from wastewater for later reuse.
Chemical Reduction - A chemical reaction in which one or more electrons
are transferred to the chemical being reduced from the chemical
initiating the transfer (reducing agent).
XVI-9
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Chemical Treatment - Treating contaminated water by chemical means.
Chip Dragout - Cutting fluid or oil adheringito metal chips from a
machining operation. '
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Chlorinated Hydrocarbons - Organic compounds containing chlorine
such as many insecticides.
Chlorination - The application of chlorine to water generally for
purposes of disinfection, but frequently for accomplishing
other biological or chemical results.
Chromate Conversion Coating - Protective coating formed by immersing
metal in an aqueous acidified solution consisting substantially
of chromic acid or water soluble salts of chromic acid together
with various catalysts or activators.
Chromatizing - To treat or impregnate with a chromate (salt of ester •
of chromic acid) or dichromate, especially with potassium
dichromate. '
Chrome-Pickle Process - Forming a corrosion-resistant oxide film on
the surface ofmagnesium base metals by immersion in a bath of
an alkaline bichromate. •
Clarification - The composite wastewater treatment process consisting
of flash mixing of coagulants, pH adjusting chemicals, and/or
polyelectrolytes, flocculation, and sedimentation.
Clarifier - A unit which provides for settling and removal of solids
from wastewater. '
Cleaning - The removal of soil and dirt (including grit and grease)
from a workpiece using water with or without a detergent or
other dispersing agent. ;
See Vapor Degreasing '-
Solvent Cleaning |
Contaminant Factor j
Acid Cleaning !
Emulsion Cleaning
Alkaline Cleaning
Salt Bath Descaling
Pickling
Passivate . ;,,ii!,,,li! ,, ;| ,; r ,, : ,, , „, lik , ,, .,,,,„
Abrasive Blast Cleaning |
Sonic and Ultrasonic Cleaning
!
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Closed-Loop Evaporation System - A system used for the recovery of
chemicals and water from a chemical finishing process. An
evaporator concentrates flow from the tinse water holding tank.
The concentrated rinse solution is returned to the bath, and
distilled water is returned to the final rinse tank. The
system is designed for recovering 100 percent of chemicals nor-
mally lost in dragout for reuse in the process.
XVI-10
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Closed Loop Rinsing - The recirculation of rinse water without the
introduction of additional makeup water.
Coagulation - A chemical reaction in which polyvalent ions neutralize
the repulsive charges surrounding colloidal particles.
Coating See Aluminum Coating
Hot Dip Coating
Ceramic Coating
Phosphate Coating
Chromate Conversion Coating
Rust-Preventive Compounds
Porcelain Enameling
COD - See Chemical Oxygen Demand
Cold Drawing - A process of forcing material through dies or other
mandrels to produce wire, rod, tubular and some bars.
Cold Heading - A method of forcing metal to flow cold into enlarged
sections by endwise squeezing. Typical coldheaded parts are
standard screws, bolts under 1 in. diameter and a large variety
^of machine parts such as small gears with stems.
Cold Rolling - A process of forcing material through rollers to produce
bars and sheet stock.
Colorimetric - A procedure for establishing the concentration of impur-
itites in water by comparing its color to a set of known color
impurity standards.
Common Metals - Copper, nickel, chromium, zinc, tin, lead, cadmium,
iron, aluminum, or any combination thereof.
Compatible Pollutants - Those pollutants which can be adequately
treated in publicly-owned treatment works without upsetting
the treatment process.
Complexing Agent - A compound that will join with a metal to form
an ion which has a molecular structure consisting of a central
atom (the metal) bonded to other atoms by coordinate covalent
bonds.
Composite Wastewater Sample - A combination of individual samples of
water or wastewater taken at selected intervals, generally hourly
for some specified period, to minimize the effect of the varia-
bility of the individual sample. Individual samples may have
equal volume or may be proportioned to the flow at time of
sampling.
Conductance '- See Electrical Conductivity.
XVI-11
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Conductivity Surface - A surface that can transfer heat or electricity.
Conductivity Meter - An instrument which displays a quantitative
indication of conductance.
Contact Water - See Process Wastewater.
Contamination - Intrusion of undesirable elements.
Continuous Treatment - Treatment of waste streams operating without
interruption as opposed to batch treatment; sometimes referred
to as flow=through treatment.
Contractor Removal - Disposal of oils, spent solutions, or sludge
by a scavenger service.
I
Conversion Coating - A coating produced by chemical or electrochemical
treatment of a metallic surface that gives a superficial layer
containing a compound of the metal. For;example, chromate coating
on zinc and cadmium, oxide coatings on steel.
Coolant - See Cutting Fluids.
Cooling Water - Water which is used to absorb and transport heat
generated in a process or machinery.
Copper Flash - Quick preliminary deposition of copper for making
surface acceptable for subsequent plating.
Coprecipitation of Metals - Precipitation of a metal with another
metal.
Corrosion Resistant Steels - A term often used to describe the stain-
less steels with high nickel and chromium alloy content.
Cost of Capital - Capital recovery costs minus the depreciation.
Counterboring - Removal of material to enlarge a hole for part of
its depth with a rotary, pilot guided, end cutting tool having
two or more cutting lips and usually having straight or helical
flutes for the passage of chips and the admission of a cutting
fluid.
Countercurrent Rinsing - Rinsing of parts in such a manner that the
rinse water is removed from tank to tank,counter to the flow of
parts being rinsed.
Countersinking - Beveling or tapering the work material around the
periphery of a hole creating a concentric surface at an angle
less than 90 degrees with the centerline of the hole for the
purpose of chamfering holes or recessingjscrew and rivet heads.
XVI-12
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Crystalline Solid - A substance with an ordered structure, such as
a crystal.
Crystallization - 1. Process used to manufacture semiconductors
in the electronics industry. 2. A means of concentrating
pollutants in wastewaters by crystallizing out pure water.
Curcumine or Carmine Method - A standard method of measuring the
concentration of boron (B) within a solution.
Cutting Fluids - Lubricants employed to ease metal and machining
operations, produce surface smoothness and extend tool life
by providing lubricity and cooling. Fluids can be emulsified
oils in water, straight mineral oils when better smoothness
and accuracy are required, or blends of both.
Cyaniding - A process of case hardening an iron-base alloy by the
simultaneous absorption of carbon and nitrogen by heating in a
cyanide salt. Cyaniding is usually followed by quenching to
. produce a hard case.
Cyclone Separator - A device which removes entrained solids from gas
streams.
Dead Rinse - A rinse step in which water is not replenished or dis-
charged .
Deburring - Removal of burrs or sharp edges from parts by filing,
grinding or rolling the work in a barrel with abrasives sus-
pended in a suitable medium.
Deep Bed Filtration - The common removal of suspended solids from
wastewater streams by filtering through a relatively deep
(0.3-0.9 m) granular bed. The porous bed formed by the granular
media can be designed to remove practically all suspended
particles by physical-chemical effects.
Degassing - (Fluxing) The removal of hydrogen and other impurities
from molten primary aluminum in a casthouse holding furnace by
injecting chlorine gas (often with nitrogen and carbon).
Degradable - That which can be reduced, broken down or chemically
separated.
Demineralization - The removal from water of mineral contaminants
usually present in ionized form. The methods used include ion-
exchange techniques, flash distillation or electrolysis.
XVI-13
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Denitrification (Biological) - The reduction of nitrates to nitrogen
gas by bacteria.
Deoxidizing - The removal of an oxide film from an alloy such as
aluminum oxide. j
Depreciation - Decline in value of a capital asset caused either by use
or by obsolescence. ]
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Descaling - The removal of scale and metallic oxides from the surface
of a metal by mechanical or chemical means. The former includes
the use of steam, scale-breakers and chipping tools, the latter
method includes pickling in acid solutions.
Desmutting - The removal of smut (matter that soils or blackens)
generally by chemical action.
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Dewatering - (Sludge Processing) Removing water from sludge.
Diaminobenzidene - A chemical used in the standard method of measuring
the concentrations of selenium in a solution.
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Dioasic Acid - An acid capable of donating two protons (hydrogen
ions). •
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Dichromate Reflux - A standard method of measuring the chemical
oxygen demand of a solution. i
Die Casting - (hot chamber, vacuum, pressure) Casting are produced
by forcing molten metal under pressure into metal mold called
dies. In hot chamber machines, the pressure cylinder is sub-
merged in the molten metal resulting in•a minimum of time and
metal cooling during casting. Vacuum feed machines use a
vacuum to draw a measured amount of melt from the molten bath
into the feed chamber. Pressure feed systems use a hydraulic
or pneumatic cylinder to feed molten metal to the die.
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Digestion - A standard method of measuring organic nitrogen.
Dipping - Material coating by briefly immersing parts in a molten
bath, solution or suspension. '
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Direct Labor Costs - Salaries, wages and other direct compensations
earned "by the employee. :
Discharge of Pollutant(s) - 1. The addition of any pollutant to
navigable waters from any point source. 2. Any addition of any
pollutant to the waters of the continguous zone or the ocean
from any point source, other than from a vessel or other floating
craft. The term "discharge" includes either the discharge of a
single pollutant or the discharge of multiple pollutants.
XVI-14
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Dispersed-air Flotation - Separation of low density contaminants from
water using minute air bubbles attached to individual particles
to provide or increase the buoyancy of the particle. The bubbles
are generated by introducing air through a revolving impeller or
porous media.
Dissolved-air Floatation - Separation of low density contaminants from
water using minute air bubbles attached to individual particles
to provide or increase the buoyancy of the particle. The air is
put into solution under elevated pressure and later released under
atmospheric pressure or put into solution by aeration at atmos-
pheric pressure and then released under a vacuum.
Dissolved Oxygen (DO) - The oxygen dissolved in sewage, waterr or other
liquid, usually expressed in milligrams per liter or percent of
saturation. It is the test used in BOD determination.
Distillation - Vaporization of a liquid followed by condensation of
the vapor.
Distillation Refining - A metal with an impurity having a higher vapor
pressure than the base metal can be refined by heating the metal
to the point where the impurity vaporizes.
Distillation-Silver Nitrate Titration ~ A standard method of measuring
the concentration of cyanides in a solution.
Distillation-SPADNS - A standard method of measuring the concentration
of fluoride in a solution.
Dollar Base - A period in time in which all costs are related. Invest-
ment costs are related by the Sewage Treatment Plant Construction
Cost Index. Supply costs are related by the "Industrial Commod-
ities" Wholesale Price Index.
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Drag-in - Water or solution carried into another solution by the work
and the associated handling equipment.
Dragout - The solution that adheres to the objects removed from a bath,
more precisely defined as that solution which is carried past the
edge of the tank.
Dragout Reduction - Minimization of the amount of material (bath or
solution) removed from a process tank by adherring to the part
or its transfer device.
Drainage Phase - Period in which the excess plating solution adhering
to the part or workpiece is allowed to drain off.
XVI-15
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Drawing - Reduction of cross section area ana increasing the length
by pulling metal through conical taper dies.
Drawing Compounds - See Wire Forming Lubricants.
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Drilling - Hole making with a rotary, end-cutting tool having one or
more cutting lips and one or more helical or straight flutes or
tubes for the ejection of chips and the passage of a cutting
fluid. 1. Center Drilling - Drilling a conical hole in the
end of a workpiece. 2. Core Drilling - Enlarging a hole with
a chamer-edged, multiple-flute drill. 3. Spade Drilling -
Drilling with a flat blade drill tip. 4. Step Drilling - Using
a multiple diameter drill. 5. Gun Drilling - Using special
straight flute drills with a single lip and cutting fluid at high
pressures for deep hole drilling. 6. Oil Hole or Pressurized
Coolant Drilling - Using a drill with one or more continuous
holes through its body and shank to permit the passage of a
high pressure cutting fluid which emerges at the drill point
and ejects chips.
I
Drip Station - Empty tank over which parts are allowed to drain
freely to decrease end dragout. j
Drip Time - The period during which a part is suspended over baths
in order to allow the excessive dragout to drain off.
Drying Beds - Areas for dewatering of sludge by evaporation and
seepage. !
i
BDTA Titration - EDTA - ethylenediamine tetraacetic acid ( or its
salts). A standard method of measuring the hardness of a
solution. I
i
Effluent - The water and the quantities, rates, and concentrations
of chemical, physical, biological, and other constituents
which are discharged from point sources.
Effluent Limitation - Any restriction (including schedules of compli-
ance) established by a state or the federal EPA on quantites,
rates, and concentrations of chemical, physical, biological,
and other constituents which are discharged from point sources
into naviigable waters, the waters of the contiguous zone, or
the ocean. ;
Electrical Conductivity - The property which allows an electric current
to flow when a potential difference is applied. It is the re-
ciprocal of the resistance in ohms measured between opposite
faces of a centimeter cube of an aqueous solution at a specified
temperature. It is expressed as micromhos per centimeter at
temperature degrees Celsius.
XVi-16
-------
Electrical Discharge Machining - Metal removal by a rapid spark dis-
charge between different polarity electrodes, one the workpiece
and the other the tool separated by a gap distance of 0.0005 in.
to 0.035 in. The gap is filled with dielectric fluid and metal
particles which are melted, in part vaporized and expelled from
the gap.
Electrobrightening - A process of reversed electro-deposition which
results in anodic metal taking a high polish.
Electrochemical Machining (ECM) - A machining process whereby the part
to be machined is made the anode and a shaped cathode is maintain-
ed in close proximity to the work. Electrolyte is pumped between
the electrodes and a potential applied with the result that metal
is rapidly dissolved from the workpiece in a selective manner and
the shape produced on the workpiece complements that of the
cathode.
Electrocleaning - The process of anodic removal of surface oxides and
scale from a workpiece.
Electrode - Conducting material for passing electric current into or
out of a solution by adding electrons to or taking electrons
from ions in the solution.
Electrodialysis - A treatment process that uses electrical current and .
and arrangement of permeable membranes to separate soluble minerals
from water. Often used to desalinate salt or brackish water.
Electroless Plating - Deposition of a metallic coating by a control-
led chemical reduction that is catalyzed by the metal or alloy
being deposited.
Electrolysis - The chemical decomposition by an electric current of
a substance in a dissolved or molten state.
Electrolyte - A liquid, most often a solution, that will conduct an
electric current.
Electrolytic Cell - A unit apparatus in which electrochemical react-
ions are produced by applying electrical energy or which supplies
electrical energy as a result of chemical reactions and which
includes two or more electrodes and one or more electrolytes con-
tained in a suitable vessel.
Electrolytic Decomposition - An electrochemical treatment used for the
oxidation of cyanides. The method is practical and economical
when applied to concentrated solutions such as contaminated baths,
cyanide dips, stripping solutions, and concentrated rinses.
Electrolysis is carried out at a current density of 35 amp/sq.
ft. at the anode and 70 amp/sq. ft. at the cathode. Metal is
deposited at the cathode and can be reclaimed.
XVI-17
-------
i
Electrolytic Oxidation - A reaction by an electrolyte in which there
is an increase in valence resulting from a loss of electrons.
Electrolytic Reduction - A reaction in which there is a decrease in
valence resulting from a gain in electrons.
Electrolytic Refining - The method of producing pure metals by making
the impure metal the anode in an electrolytic cell and depositing
a pure cathode. The impurities either .remain undissolved at the
anode or pass into solutions in the electrolyte.
Electrometallurgical Process - The application of electric current to
a metallurgical process either for electrolytic deposition or as
a source of heat. ;
Electrometric Titration - A standard method of measuring the alkalin-
ity of a solution.
Electron Beam Machining - The process of removing material from a
workpiece by a high velocity focused stream of electrons which
melt and vaporize the workpiece at the point of impingerent.
Electroplating - The production of a thin coating of one metal on a
surface by electrodeposition. i
Electropolishing - Electrolytic,corrosion process that increases the
percentage of specular reflectance from a metallic surface.
Embossing - Raising a design in relief against a surface.
Emulsified Oil and Grease - An oil or grease dispersed in an immis-
cible liquid usually in droplets of larger than colloidal size.
In general suspension of oil or grease within another liquid
(usually water). !
Emulsifying Agent - A material that increases Jthe stability of a
dispersion of one liquid in another.
Emulsion Breaking - Decreasing the stability of dispersion of one
liquid in another. :
Emulsion Cleaning - A cleaning process using organic solvents dis-
persed in an aqueous medium with the aid of an emulsifying agent.
End-of-Pipe Treatment - The reduction and/or removal of pollutants by
treatment just prior to actual discharge.
Environmental Protection Agency - the United States Environmental
Protection Agency. !
XVI-18
-------
EPA - See Environmental Protection Agency.
Equalization - (Continuous Flow) - The balancing of flow or pollutant
load using a holding tank for a system that has widely varying
inflow rates.
Equilibrium Concentration - A state at which the concentration of
chemicals in a solution remain in a constant proportion to one
another.
Ester - An organic compound corresponding in structure to a salt in
inorganic chemistry. Esters are considered as derived from the
acids by the exchange of the replaceable hydrogen of the latter
for an organic alkyl radical. Esters are not ionic compounds,
but salts usually are.
Etchant - The material used in the chemical process of removing glass
fibers and epoxy between neighboring conductor layers of a PC
board for a given distance.
Etching - A process where material is removed by chemical action.
Evaporation Ponds - Liquid waste disposal areas that allow the liquid
to vaporize to cool discharge water temperatures or to thicken
sludge.
Excess Capacity Factor - A multiplier on process size to account for
shutdown for cleaning and maintenance.
Extrusion - A material that is forced through a die to form lengths
of rod, tube or special sections.
4-AAP Colorimetric - A standard method of measurement for phenols
in aqueous solutions.
Fermentation - A chemical change to break down biodegradable waste.
The change is induced by a living organism or enzyme, specific-
ally bacteria or microorganisms occurring in unicellular plants
such as yeast, molds, or fungi.
Ferrite - A solid solution in which alpha iron is present.
Ferrous - Relating to or containing iron.
Filtrate - Liquid after passing through a filter.
Filtration - Removal of solid particles from liquid or particles
from air or gas stream by means of a permeable membrane.
Types: Gravity, Pressure, Microstraining, Ultrafiltration,
Reverse Osmosis (Hyperfiltration).
XVI-19
-------
Flameless Atomic Absorption - A method of measuring low concen-
tration values of certain metals in a solution.
Flame Hardened - Surface hardened by controlled torch heating
followed by quenching with water or air.
I
Flame Spraying - The process of applying a metallic coating to a
workpiece whereby finely powdered fragments or wire,, together
with suitable fluxes, are projected through a cone of flame
onto the workpiece.
Flash Evaporation - Evaporation using steam heated tubes with feed
material under high vacuum. Feed material "flashes off" when
it enters the evaporation chamber.
Flocculation - The process of separating suspended solids from waste-
water by chemical creation of clumps or floes.
Flotation - The process of removing finely divided particles from
a liquid suspension by attaching gas bubbles to the particles,
increasing their buoyancy, and thus concentrating them at the
surface of the liquid medium. i
I
Fluxing - (Degassing) The removal of oxides and other impurities
from molten primary aluminum in a casthouse holding furnace by
injecting chlorine gas (often with nitrogen and carbon monoxide).
1
Fog - A type of rinse consisting of a fine spray.
Forming Compounds (Sheet) - Tightly adhering lubricants composed of
fatty oils, fatty acids, soaps, and waxes and designed to resist
the high surface temperatures and pressures the metal would
otherwise experience in forming.
Forming Compounds (Wire) - Tightly adhering lubricants composed of
solids (white lead, talc, graphite, or molybdenum disulfide)
and solible oils for cooling and corrosion protection. Lubri-
cants typically contain sulfur, chlorine, or phsophate additives.
Free Cyanide - 1. True - the actual concentration of cyanide radical
or equivalent alkali cyanide not combined in complex ions with
metals in solutions. 2. Calculated - the concentration of
cyanide or alkali cyanide present in solution in excess of that
calculated as necessary to form a specified complex ion with a
metal or metals present in solution. 3. Analytical - the free
cyanide content of a solution as determined by a specified
analytical method.
Freezing/Crystallization - The solidification of a liquid into
aggregations of regular geometric forms (crystals) accomplished
by subtraction of heat from the liquid. This process can be used
for removal of solids, oils, greases, and heavy metals from
industrial wastewater.
XVI-20
-------
Galvanizing - The deposition of zinc on the surface of steel for
corrosion protection.
Gas Carburizing - The introduction of carbon into the surface layers
of mill steel by heating in a current of gas high in carbon.
Gas Chromotagrophy - Chemical analytical instrumentation generally
used for quantitative organic analysis.
Gas Nitriding - Case hardening metal by heating and diffusing nitro-
gen gas into the surface.
Gas Phase Separation - The process of separating volatile constitu-
ents from water by the application of selective gas permeable
membranes.
Gear Forming - Process for making small gears by rolling the gear
material as it is pressed between hardened gear shaped dies.
Glass Fiber Filtration - A standard method of measuring total sus-
pended solids.
Good Housekeeping - (In-Plant Technology) Good and proper mainten-
ance minimizing spills and upsets.
GPP - Gallons per day.
Grab Sample - A single sample of wastewater taken without regard
to time or flow.
Gravimetric 103-105C - A standard method of measuring total
solids in aqueous solutions.
Gravimetric 550C - A standard method of measuring total volatile
solids in aqueous solutions.
Gravity Filtration - Settling of heavier and rising of lighter
constituents within a solution.
Gravity Flotation - The separation of water and low density contam-
inants such as oil or grease by reduction of the wastewater
flow velocity and turbulence for a sufficient time to permit
separation due to difference in specific gravity. The floated
material is removed by some skimming technique.
Gray Cast Irons - Alloys primarily of iron, carbon and silicon along
with other alloying elements in which the graphite is in flake
form. (These irons are characterized by low ductility but have
many other properties such as good castability and good damping
capacity.)
XVI-21
-------
Grease - In wastewater, a group of substances including fats, waxes,
free fatty acids, calcium and magnesium soaps, mineral oils,
and certain other nonfatty materials.' The type of solvent
and method used for extraction should be stated for quantifi-
cation.
j
Grease Skimmer - A device for removing floating grease or scum from
the surface of wastewater in a tank. !
Grinding - The removal of stock from a workpiece by use of abrasive
grains held by a rigid or semi rigid binder. 1. Surface
Grinding - Producing a flat surface wpLth a rotating grinding
wheel as the workpiece passes under the wheel. 2. Cylindrical
Grinding - Grinding the outside diameters of cylindrical work-
pieces held between centers. 3. Internal Grinding - Grinding
the inside of a rotating workpiece by use of a wheel spindle
which rotates and reciprocates through the length of depth of
the hole being ground.
Grinding Fluids - Water based, straight oil, or synthetic based
lubricants containing mineral oils, soaps, or fatty materials
lubricants serve to cool the part and maintain the abrasiveness
of the grinding wheel face.
i
Hammer Forging - Heating and pounding metal to shape it into the
desired form.
Hardened - Designates condition produced by various heat treatments
such as quench hardening, age hardening and precipitation
hardening.
Hardness - A characteristic of water, imparted by salts of calcium,
magnesium and iron such as bicarbonatfes, carbonates, sulfates,
chlorides and nitrates, that cause curdling of soap, deposition
of scale, damage in some industrial processesandsometimes
objectionable taste. It may be dtermined by a standard labora-
tory procedure or computed from the amounts of calcium and
magnesium as well as iron, aluminum, manganese, barium,
strontium, and zinc and is expressed as equivalent calcium
carbonate. '•
I
Heading - (Material forming) Upsetting wire, rod or bar stock in
dies to form parts having some of the cross-sectional area
larger than the original. Examples ate bolts, rivets and
screws.
Heat Resistant Steels - Steel with high resistance to oxidation and
moderate, strength at high temperatures above 500 Degrees C.
XVI-22
-------
Heat Treatment - The modification of the physical properties of a
workpiece through the application of controlled heating and
cooling cycles. Such operations are heat treating, tempering,
carburizing, cyaniding, nitriding, annealing, normalizing,
austenizing, quenching, austempering, siliconizing, martemper-
ing, and malleabilizing are included in this definition.
Heavy Metals - Metals which can be precipitated by hydrogen sulfide
in acid solution, e.g., lead, silver, gold, mercury, bismuth,
copper, nickel, iron, chromium, zinc, cadmium, and tin.
High Energy Forming - Processes where parts are formed at a rapid
rate by using extremely high pressures. Examples: Explosive
forming, Electrohydraulic forming.
High Energy Rate Forging (HERF) - A closed die process where hot or
cold deforming is accomplished by a high velocity ram.
Bobbing - Gear cutting by use of a tool resembling a worm gear in
appearance, having helically-spaced cutting teeth. In a single-
thread hob, the rows of teeth advance exactly one pitch as the
hob makes one revolution. With only one hob, it is possible to
cut interchangeable gears of a given pitch of any number of
teeth within the range of the bobbing machine.
Honing - A finishing operation using fine grit abrasive stones to
produce accurate dimensions and excellent finish.
Hot Compression Molding - (Plastic Processing) A technique of
thermoset molding in which preheated molding compound is closed
and heat and pressure (in the form of a downward moving ram)
are applied until the material has cured.
Hot Dip Coating - The process of coating a metallic workpiece with
another metal by immersion in a molten bath to provide a pro-
tective film.
Hot Rolled - A term used to describe alloys which are rolled at tem-
. peratures above the recrystallization temperature. (Many alloys
are hot rolled, and machinability of such alloys may vary because
of differences in cooling conditions from lot to lot.
Hot Stamping - Engraving operation for marking plastics in which roll
leaf is stamped with heated metal dies onto the face of the
plastics. Ink compounds can also be used.
Hot Upset Forging - The diameter is locally increased i.e. to upset
the head of a bolt, the end of the barstock is heated and then
deformed by an axial blow often into a suitably shaped die.
Hydrofluoric Acid - Hydrogen fluoride in aqueous solution.
XVI-23
-------
Hydrogen Embrittlement - Embrittlement of a metal or alloy caused by
absorption of hydrogen during a pickling, cleaning, or plating
process. •
Hvdrometallurgical Process - The treatment of ores by wet processes
such as leaching. [
Hvdrophilic - A surface having a strong affinity for water or being
readily wettable.
Hydrophobia - A surface which is non-wettable or not readily wettable.
Hydrostatic Pressure - The force per unit area measured in terms of
the height of a column of water under the influence of gravity.
Immersed Area - Total area wetted by the solution or plated area plus
masked area.
Immersion Plate - A metallic deposit produced by a displacement re-
action in which one metal displaces another from solution, for
example: Fe + Cu(+2) = Cu + Fe(+2) ,
Impact Deformation - The process of applying impact force to a work-
——piece such that the workpiece is permanently deformed or shaped.
Impact deformation operations such as shot peening, peening,
forging, high energy forming, heading, or stamping.
Incineration - (Sludge Disposal) The combustion (by burning) of
organic matter in wastewater sludge after dewatering by
evaporation.
Incompatible Pollutants - Those pollutants which would cause harm to,
adversely affect the performance of, or; be inadequately treated
in publicly-owned treatment works.
Independent Operation - Job shop or contract' shop in which electro-
plating is done on workpieces owned by the customer.
Indirect Labor Costs - Labor-related costs paid by the employer
other than salaries, wages and other direct compensation such as
social security and insurance.
I
Induction Hardened - Surface or through hardened using induction
heating followed by quenching with water or air.
Industrial User - Any industry that introduces pollutants into public
sewer systems and whose wastes are treated by a publicly-owned
treatment facility. j
Industrial Wastes - The liquid wastes from industrial processes, as
distinct from domestic or sanitary wastes.
XVI-24
-------
Inhibition - The slowing down or stoppage of chemical or biological
reactions by certain compounds or ions.
In-Process Control Technology - The regulation and the conservation
of chemicals and the reduction of water usage throughout the
operations as opposed to end-of-pipe treatment.
Inspection - A checking or testing of something against standards or
specification.
Intake Water - Gross water minus reuse water.
Integrated Chemical Treatment - A waste treatment method in which a
chemical rinse tank is inserted in the plating line between the
process tank and the water rinse tank. The chemical rinse
solution is continuously circulated through the tank and removes
the dragout while reacting chemicals with it.
Integrated Circuit (1C) - 1. A combination of interconnected circuit
elements inseparably associated on or within a continuous sub-
strate. 2. Any electronic device in which both active and
passive elements are contained in a single package. Methods of
making an integrated circuit are by masking process, screening
and chemical deposition.
Intraforming - A method of forming by means of squeezing.
Investment Costs - The capital expenditures required to bring the
treatment or control technology into operation.
Ion Exchange - A reversible chemical reaction between a solid (ion
exchanger) and a fluid (usually a water solution) by means of
which ions may be interchanged from one substance to another.
The superficial physical structure of the solid is not
affected.
Ion Exchange Resins - Synthetic resins containing active groups
(usually sulfonic, carboxylic, phenol, or substituted amino
groups) that give the resin the property of combining with
or exchanging ions between the resin and a solution.
Ion-Flotation Technique - Treatment for electroplating rinse waters
(containing chromium and cyanide) in which ions are separated
from solutions by flotation.
Iridite Dip Process - Dipping process for zinc or zinc-coated objects
that deposits protective film that is a chromium gel, chromium
oxide, or hydrated chromium oxide.
Isolation - Segregation of a waste for separate treatment and/or
disposal.
XVI-25
-------
Kiln - (Rotary) A large cylindrical mechanized type of furnace.
i
Kinematic Viscosity - The viscosity of a fluid divided by its density.
The C.G.S. unit is the stoke (cm2/sec).
i
Knurling - Impressing a design into a metallic surface, usually by
means of small, hard rollers that carry the corresponding design
on their surfaces. :
Lagoon - A man-made pond or lake for holding wastewater for the removal
of suspended solids. Lagoons are also qsed as retention ponds,
after chemical clarification to polish the effluent and to safe-
guard against upsets in the clarifier; for stabilization of
organic matter by biological oxidation; for storage of sludge;
and for cooling of water.
Laminate - 1. A composite metal, wood or plastic usually in the form
of sheet or bar, composed of two or more layers so bonded that
the composite forms a structural member.! 2. To form a product
of two or more bonded layers.
Landfill - Disposal of inert, insoluble waste solids by dumping at an
approved site and covering with earth.
Lapping - An abrading process to improve surface quality by reducing
roughness, waviness and defects to produce accurate as well as
smooth surfaces.
Laser Beam Machining - Use of a highly focused mono-frequency colli-
mated beam of light to melt or sublime material at the point of
impingement on a workpiece. \
Leach Field - A area of ground to which wastewater is discharged.
Not considered an acceptable treatment method for industrial
wastes.
i
Leaching - Dissolving out by the action of a percolating liquid,
such as water, seeping through a landfill.
Ligands - The molecules attached to the central atom by coordinate
covalent bonds. I
Liquid/Liquid Extraction - A process of extracting or removing contam-
inant(s) from a liquid by mixing contaminated liquid with another
liquid which is immiscible and which has a higher affinity for
the contaminating substance(s).
Liquid Nitriding - Process of case hardening a metal in a molten
cyanide bath.
XVI-26
-------
Liquid Phase Refining - A metal with an impurity possessing a lower
melting point is refined by heating the metal to the point of
melting of the low temperature metal. It is separated by sweat-
ing out.
Machining - The process of removing stock from a workpiece by forcing
a cutting tool through the workpiece removing a chip of basis
material. Machining operations such as turning, milling, drill-
ing, boring, tapping, planing, broaching, sawing and filing, and
chamfering are included in this definition.
Maintenance - The upkeep of property or equipment.
Malleablizing - Process of annealing brittle white cast iron in such
a way that the combined carbon is wholly or partly transformed
to graphitic or temper carbon nodules in a ferritic or pearlitic
microstructure, thus providing a ductile and machinable material.
Manual Plating - Plating in which the workpieces are conveyed manually
through successive cleaning and plating tanks.
Maraged - Describes a series of heat treatments used to treat high
strength steels of complex composition (maraging steels) by
aging of martensite.
Martensite - An acicular or needlelike microstructure that is formed
in quenched steels. (It is very hard and brittle in the quenched
form and, therefore, is usually tempered before being placed into
service. The harder forms of tempered martensite have poorer
machinability.)
Martempering - Quenching an austentized ferrous alloy in a medium at a
temperature in the upper part of the martensite range, or slight-
ly above that range, and holding it in the medium until the
temperature throughout the alloy is substantially uniform.
The alloy is then allowed to cool in air through the martensite
range.
Masking - The application of a substance to a surface for the pre-
vention of plating to said area.
Material Modification - (In-Plant Technology) Altering the substance
from which a part is made.
Mechanical Agitation - The agitation of a liquid medium through the
use of mechanical equipment such as impellers or paddles.
Mechanical Finish - Final operations on a product performed by a
machine or tool. See: Polishing, Buffing, Barrel Finishing,
Shot Peening, Power Brush Finishing.
XVI-27
-------
Mechanical Plating - Providing a coating wherein fine metal powders
are peened onto the part by tumbling or other means.
j
Membrane — A thin sheet of synthetic polymer through the apertures
of which small molecules can pass, while larger ones are re-
tained.
i
Membrane Filtration - Filtration at pressures ranging from 50 to 100
psig with the use of membranes or thin films. The membranes
have accurately controlled pore sites anda typically low flux
rates. !
Metal Ion - An atom or radical that has lost or gained one or more
electrons and has thus acquired an electric charge. Positively
charged ions are cations, and those having a negative charge
are anions. An ion often has entirely differnt properties from
the element (atom) from which it was formed.
Metal Oxidation Refining - A refining technique that removes impuri-
ties from the base metal because the impurity ""oxidizes more
readily than the base. The metal is heated and oxygen supplied.
The impurity upon oxidizing separates by gravity or volatilizes.
i
Metal Paste Production - Manufacture of metal;pastes for use as pig-
ments by mixing metal powders with mineral spirits, fatty acids
and solvents. Grinding and filtration are steps in the process.
Metal Powder Production - Production of metal particles for such uses
as pigments either by milling and grinding of scrap or by atomi-
zation of molten metal.
i
Metal Spraying - Coating metal objects by spraying molten metal upon
the surface with gas pressure.
Microstraining - A process for removing solids from water/ which con-
sists of passing the water stream through a microscreen with
the solids being retained on the screen.
Hilling - Using a rotary tool with one or more teeth which engage the
workpiece and remove material as the workpiece moves past the
rotating cutter. 1. Face Milling - Milling a surface perpendi-
cular cutting edges remove the bulk of the material while the
face cutting edges provide the finish of the surface being
generated. 2. End Milling - Milling accomplished with a tool
having cutting edges on its cylindrical sufaces as well as on
its end. In end milling - peripheral, the peripheral cutting
edges on the cylindrical surface are used; while in end milling-
slotting, both end and peripheral cutting edges remove metal.
3. Slide and Slot Milling - Milling of the side or slot of a
workpiece using a peripheral cutter. 4. Slab Milling - Milling
of a surface parallel to the axis of a helical, multiple-toothed
cutter mounted on an arbor. 5. Straddle Milling - Peripheral
milling a workpiece on both sides at once using two cutters
spaced as required. ',
XVl-28
-------
Molecule - Chemical units composed of one or more atoms.
Monitoring - The measurement, sometimes continuous, of water quality.
Multi-Effect Evaporator - A series of evaporations and condensations
with the individual units set up in series and the latent heat of
vaporization from one unit used to supply energy for the next,
Multiple Operation Machinery - Two or more tools are used to perform
simultaneous or consecutive operations.
Multiple Subcategory Plant - A plant discharging process wastewater
from more than one manufacturing process subcategory.
National Pollutant Discharge Elimination System (NPDES) - The federal
mechanism for regulating point source discharge by means of
permits.
Navigable Waters - All navigable waters of the United States; tribu-
taries of navigable waters of the United States; interstate
waters,intrastate lakes, rivers and streams which are utilized
for recreational or other purposes.
Neutralization - Chemical addition of either acid or base to a solu-
tion such as the pH is adjusted to 7.
New Source - Any building, structure, facility, or installation from
which there is or may be the discharge of pollutants,, the con-
struction of which is commenced after the publication of proposed
regulations prescribing a standard of performance under Section
306 of the Act which will be applicable to such source if such
standard is thereafter promulgated in accordance with Section
306 of the Act.
Nitriding - A heat treating method in which nitrogen is diffused into
the surface of iron-base alloys. (This is done by heating the
metal at a temperature of about 950 degrees F in contact with
ammonia gas or other suitable nitrogenous materials. The surface,
because of formation of nitrides becomes much harder than the
interior. Depth of the nitrided surface is a function of the
length of time of exposure and can vary from .0005" to .032"
thick. Hardness is generally in the 65 to 70 Re range, and,
therefore, these structures are almost always ground.)
Nitriding Steels - Steels which are selected because they form good
case hardened structures in the nitriding process. ( In these
steels, elements such as aluminum and chromium are important
for producing a good case.)
Nitrification (Biological) - The oxidation of nitrogenous matter into
nitrates by bacteria.
XVl-29
-------
Noble Metals - Metals below hydrogen in the electromotive force series;
includes antimony, copper, rhodium, silver, gold, bismuth.
Noncontact Cooling Water - Water used for cooling which does not come
into direct contact with any raw material, intermediate product,
waste product, or finished product.
i
Nonferrous - No iron content.
Non-Water Quality Environmental Impact - The ecological impact as a
result of solid, air, or thermal pollution due to the appli-
cation of various wastewater technologies; to achieve the effluent
guidelines limitations. Associated with the non-water quality
aspect is the energy impact of wastewater treatment.
i
Normalizing - Heat treatment of iron-base alloys above the critical
temperature, followed by cooling in still air. (This is often
done to refine or homogenize the grain structure of castings,
forgings and wrought steel products.)
Notching - Cutting out various shapes from the edge or side of a
sheet, strip, blank or part, '
[
NPDES - See National Pollutant Discharge Elimination System.
Oil Cooker - Open-topped vessel contining a hejat source and typically
maintained at 68°C (180°F) for the purpose of driving off excess
water from waste oil.
i
Operation and Maintenance Costs - The cost of running the wastewater
treatment equipment. This includes labor costs, material and
supply costs, and energy and power costs.
Organic Compound - Any substance that contains the element carbon,
with the exception of carbon dioxide and various carbonates.
ORP Recorders - Oxidation-reduction potential recorders.
"™"™~™~-~™™™~~™™~"™™~™~~"~"~^ . j
Oxidants - Those substances which aid in the formation of oxides.
Oxidizable Cyanide - Cyanide amenable to oxidation.
Oxidizing - Combining the material concerned with oxygen.
Paint Stripping - The term "paint stripping" Shall mean the process
of removing an organic coating from a workpiece or painting
fixture. The removal of such coatings using processes such
as caustic, acid, solvent and molten salt stripping are included.
XVI-30
-------
Parameter - A characteristic element of constant factor.
Passivation - The changing of the chemically active surface of a
metal to a much less reactive state by means of an acid dip.
Patina - A blue green oxidation of copper.
Pearlite - A microstituent found in iron-base alloys consisting of
a lamellar (Patelike) composite of ferrite and iron carbide.
(This structure results from the decomposition of austenite
and is very common in cast irons and annealed steels.)
Peenincf - Mechanical working of metal by hammer blows or shot im-
pingement.
pH - A unit for measuring hydrogen ion concentrations. A pH of 7
indicates a "neutral" water or solution. A pH lower than 7,
a solution is acidic. At pH higher than 7, a solution is
alkaline.
pH Buffer - A substance used to stabilize the acidity or alkalinity
in a solution.
Phenols - A group of aromatic compounds having the hydroxyl group
directly attached to the benzene ring. Phenols can be a con-
taminant in a waste stream from a manufacturing process.
Phosphate Coating - Process of forming a conversion coating on iron
or steel by immersing in a hot solution of manganese, iron or
zinc phosphate. Often used on a metal part prior to painting
or porcelainizing.
Phosphate - Salts or esters of phosphoric acid.
Phosphatizing - Process of forming rust-resistant coating on iron
or steel by immersing in a hot solution of acid manganese,
iron or zinc phosphates.
Photoresists - Thin coatings produced from organic solutions
which when exposed to light of the proper wave length are
chemically changed in their solubility to certain solvents
(developers). This substance is placed over a surface which
is to be protected during processing such as in the etching
of printer circuit boards.
Photosensitive Coating - A chemical layer that is receptive to
the action of radiant energy.
XVI-31
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Pickling - The immersion of all or part of a workpiece in a
corrosive media such as acid to removed scale and related
surface coatings.
|
Planing - Producing flat surfaces by linear reciprocal motion of
the work and the table to which it is attached relative to
a stationary single-point cutting tool.
Plant Effluent or Discharge After Treatment - The wastewater
discharged from the industrial plant. In this definition,
any waste treatment device (pond, trickling filter, etc.)
is considered part of the industrial plant.
Plasma Arc Machining - The term "plasma arc machining" shall mean
the process of material removal or shaping of a workpiece
by a high velocity jet of high temperature ionized gas.
i
Plated Area - Surface upon which an adherent layer of metal is
deposited.
Plating - Forming an adherent layer of metal upon an object.
Point Source - Any discernible, confined, and discrete conveyance
including, but not limited to, any pipe, ditch, channel,
tunnel, conduit, well, discrete fissure, container, rolling
stock, concentrated animal feeding operation, or vessel or
other floating craft from which pollutants are or may be
discharged.
i
Point Source Category - See Category.
Polishing - The process of removing stock irrom a workpiece by the
action of loose or loosely held abrasive grains carried to
the workpiece by a flexible support. Usually, the amount of
stock removed in a polishing operation is only incidental to
achieving a desired surface finish or appearance.
Polishing Compounds - Fluid or grease stick lubricants composed
of animal tallows, fatty acids, and waxes. Selection depends
on surface finish desired.
Pollutant - Dredged spoil, solid waste, incinerator residue, sewage,
garbage, sewage sludge, munitions, chemical wastes, biological
materials, radioactive materials, heat, wrecked or discarded
equipment, rock, sand, cellar dirt and industrial, municipal
and agricultural waste discharged into water. It does not
mean (1) sewage from vessels or (2) water, gas, or other mat-
erial which is injected into a well to facilitate production
of oil or gas, or water derived in association with oil or
gas production and disposed of in a well, if the well, used
either to facilitate production or for disposal purposes, is
XVI-32
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approved by authority of the State in which the well is
located, and if such State determines that such injection
or disposal will not result in degradation of ground or
surface water resources.
Pollutant Parameters - Those constituents of wastewater deter-
minded to be detrimental and, therefore, requiring control.
Pollution - The man-made or man-induced alternation of the
chemical, physical, biological, and radiological integrity
of water.
Polychlorinated Biphenyl (PCS) - A family of chlorinated biphenyls
with unique thermal properties and chemical inertness which
have a wide variety of uses as plasticizers, flame retardants
and insulating fluids. They represent a persistent contam-
inant in waste streams and receiving waters.
Polyelectrolyte - A high polymer substance, either natural or
synthetic, containing ionic constituents; they may be either
cationic or anionic.
Post Curring - Treatment after changing the physical properties
of a material by chemical reaction.
Pouring - (Casting and Molding) Transferring molten metal from
a furnace or a ladle to a mold.
Power Brush Finishing - This is accomplished (wet or dry) using a
wire or nonmetallic-fiber-filled brush used for deburring,
edge blending and surface finishing of metals.
Precious Metals - Gold, silver, iridium, palladium, platinum,
rhodium, ruthenium, indium, osmium, or combination thereof.
Precipitate - The discrete particles of material rejected from a
liquid solution.
Precipitation Hardening Metals - Certain metal compositions which
respond to precipitation hardening or aging treatment.
Pressure Deformation - The process of applying force, (other than
impact force), to permanently deform or shape a workpiece.
Pressure deformation operations may include operations such
as rolling, drawing, bending, embossing, coining, swaging,
sizing, extruding, squeezing, spinning, seaming, piercing,
necking, reducing, forming, crimping, coiling, twisting,
winding, flaring or weaving.
Pressure Filtration - The process of solid/liquid phase separation
effected by passing the more permeable liquid phase through a
mesh which is impenetrable to the solid phase.
XVI-33
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Pretraatment - Treatment of wastewaters from sources before intro-
duction into municipal treatment works.
I ' . ;•
Primary Settling - The first treatment for the removal of settle-
able solids from wastewater which is ipassed through a treat-
ment works. ! •
Primary Treatment - The first stage in wastewater treatment in
which floating or settleable solids are mechanically removed
by screening and sedimentation.
Printed Circuit Boards - A circuit in which the interconnecting
wires have been replaced by conductive strips printed, etched,
etc., onto an insulating board. Methods of fabrication in-
clude etched circuit, electroplating, and stamping.
Printing - A process whereby a design or pattern in ink or types
of pigments are impressed onto the surface of a part.
I
Process Modification - (In-Plant Technology) Reduction of water
pollution by basic changes in a manufacturing process.
i
Process Wastewater - Any water which, during manufacturing or
processing,comes into direct contact with or results from
the production or use of any raw material, intermediate
product, finished product, byproduct,; or waste product.
Process Water - Water prior to its direct contact use in a process
or operation. (This water may be any combination of raw water,
service water, or either process wastewater or treatment facil-
ity effluent to be recycled or reused).
Punching - A method of cold extruding, cold heading, hot forging or
stamping in a machine whereby the mating die sections control
the shape or contour of the part.
Pyrolysis - (Sludge Removal) Decomposition of materials by the
application of heat in any oxygen-deficient atmosphere.
Pyrazolone-Colorimetric - A standard method of measuring cyanides
in aqueous solutions.
Quantity GPP - Gallons per day.
'
Quenching - Rapid cooling of alloys by immersion in water, oil, or
gases after heating.
I
Racking - The placement of parts on an apparatus for the purpose
of plating.
I
i
Rack Plating - Electroplating of workpieces on racks.
XVI-34
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Radiography - A nondestructive method of internal examination
in which metal or other objects are exposed to a beam of
x-ray or gamma radiation. Differences in thickness, density
or absorption, caused by internal discontinuities, are
apparent in the shadow image either on a fluorescent screen
or on photographic film placed behind the object.
Raw Water - Plant intake water prior to any treatment or use.
Reaming - An operation in which a previously formed hole is sized
and contoured accurately by using a rotary cutting tool (reamer)
with one or more cutting elements (teeth). The principal sup-
port for the reamer during the cutting action is obtained from
the workpiece. 1. Form Reaming - Reaming to a contour shape.
2. Taper Reaming - Using a special reamer for taper pins. 3.
Hand Reaming - Using a long lead reamer which permits reaming
by hand. 4. Pressure Coolant Reaming (or Gun Reaming) -
Using a multiple-lip, end cutting tool through which coolant is
forced at high pressure to flush chips ahead of the tool or
back through the flutes for finishing of deep holes.
Receiving Waters - Rivers, lakes, oceans, or other water courses
that receive treated or untreated wastewaters.
Recirculating Spray - A spray rinse in which the drainage is pumped
up to the spray and is continually recirculated.
Recycled Water - Process wastewater or treatment facility effluent
which is recirculated to the same process.
Recycle Lagoon - A pond that collects treated wastewater, most of
which is recycled as process water.
Reduction - A reaction in which there is a decrease in valence
resulting from a gain in electrons.
Redox - A term used to abbreviate a reduction-oxidation reaction.
Residual Chlorine - The amount of chlorine left in the treated
water that is available to oxidize contaminants.
Reverse Osmosis - The application of pressure to the surface of
solution through a semipermeable membrane that is too dense
to permit passage of the solute, leaving behind the dissolved
solids (concentrate).
Reused Water - Process wastewater or treatment facility effluent
which is further used in a different manufacturing process.
Ring Rolling - A metals process in which a doughnut shaped piece of
stock is flattened to the desired ring shape by rolling between
variably spaced rollers. This process produces a seamless ring.
XVI-35
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Rinse - Water for removal of dragout by dipping, spraying,
fogging, etc.
Riveting - Joining of two or more members of a structure by means
of metal rivets, the undeaded end being upset after the rivet
is in place.
Routing - Cutting out and contouring edges!of various shapes in a
relatively thin material using a small diameter rotating
cutter which is operated at fairly high speeds.
i
Running Rinse - A rinse tank in which water continually flows in
and out.
Rust Prevention Compounds - Coatings used to protect iron and steel
surfaces, against corrosive environment during fabrication,
storage, or use.
i
Salt - 1. The compound formed when the hydrogen of an acid is
replaced by a metal or its equivalent (e.g., an NH4 radical).
Example: HC1 + NaOH = NaCl + H20
This is typical of the general rule that the reaction of an
acid and a base yields a salt and water. Most salts ionize
in water solution. 2. Common salt, sodium chloride, occurs,
widely in nature, both as deposits left by ancient seas and
in the ocean, where its average concentration is about 3%.
Salt Bath Descaling - Removing the layer o£ oxides formed on some
metals at elevated temperatures in a salt solution. See:
Reducing, Oxidizing, Electrolytic.
Sand Bed Drying - The process of reducing the water content in a wet
substance by transferring that substance to the surface of a
sand bed and allowing the processes of drainage through the
sand and evaporation to effect the required water separation.
Sand Blasting - The process of removing stock including surface
films, from a workpiece by the use of:abrasive grains
pneumatically impinged against the workpiece.
Sand Filtration - A process of filtering wastewater through sand.
The wastewater is trickled over the bed of sand where air and
bacteria decompose the wastes. The clean water flows out
through drains in the bottom of the bed. The sludge accumulat-
ing at the surface must be removed from the bed periodically.
i
I
Sanitary Water - The supply of water used for sewage transport and
the continuation of such effluents to ;disposal.
Sanitary Sewer - Pipes and conveyances for sewage transport.
1
Save Rinse - See Dead Rinse.
XVl-36
-------
Sawing - Using a toothed blade or disc to sever parts or cut
contours. 1. Circular Sawing - Using a circular saw fed
into the work by motion of either the workpiece or the
blade. 2. Power Band Sawing - Using a long, multiple-
tooth continuous band resulting in a uniform cutting
action as the workpiece is fed into the saw. Power Hack
Sawing - Sawing in which a reciprocating saw blade is fed
into the workpiece.
Scale - Oxide and metallic residues.
Screening - Selectively applying a resist material to a surface
to be plated.
Secondary Settling - Effluent from some prior treatment process
flows for the purpose of removing settleable solids.
Secondary Treatment - The second step in most sanitary waste
treatment plants in which bacteria consume the organic
portions of the waste. This removal is accomplished by trick-
ling filters, an activated sludge unit, or other processes.
Sedimentation - The process of subsidence and deposition of suspended
matter carried by water, wastewater, or other liquids by
gravity. It is usually accomplished by reducing the velocity
of the liquid below the point at which it can transport the
suspended material. Also called settling.
Sensitization - The process in which a substance other than the
catalyst is present to facilitate the start of a catalytic
reaction.,
Sequestering Agent - An agent (usually a chemical compound) that
"sequesters" or holds a substance in suspension.
Series Rinse - A series of tanks which can be individually heated
or level controlled.
Service Water - Raw water which has been treated preparatory to
its use in a process or operation; i.e., makeup water.
Settleable Solids - That matter in wastewater which will not stay
in suspension during a preselected settling period, such as one
hour, but either settles to the bottom or floats to the top.
Ponds - A large shallow body of water into which indus-
Suspended solids settle
Settling t
trial wastewaters are discharged
from the wastewaters due to the large retention time of water
in the pond.
XVI-37
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Shaping - Using single point tools fixed to a ram reciprocated in
a linear motion past the work. 1. Form Shaping - Shaping
with a tool ground to provide a specified shape. 2. Contour
Shaping - Shaping of an irregular surface, usually with the
aid of a tracing mechanism. 3. Internal Shaping - Shaping
of internal forms such as keyways and guides.
Shaving - 1. As a finishing operation, the accurate removal of a
tnin layer by drawing a cutter in straight line motion across
the work surfaces. 2. Trimming parts like stampings, forgings
and tubes to remove uneven sheared edges or to improve accuracy.
Shearing - The process of severing or cutting of a workpiece by
forcing a sharp edge or opposed sharp edges into the workpiece
by forcing a sharp edge or opposed sharp edges into the work-
piece stressing the material to the point of sheer failure and
separation.
Shipping - Transporting. '
Shot Peening - Dry abrasive cleaning of metal surfaces by impacting
the surfaces with high velocity steel shot.
i
Shredding - (Cutting or Stock Removal) Material cut, torn or broken
up into small parts. |
SIC - Standard Industrial Classification - Defines industries in
accordance with the composition and structure of the economy
and covers the entire field of economic activity.
Silica - (Si02j Dioxide of silicon which occurs in crystalline form
as quartz, cristohalite, tridymite. Used in its pure form for
high-grade refractories and high temperature insulators and in
impure form (i.e. sand) in silica bricks.
Siliconizing - Diffusing silicon into solid metal, usually steel,
at an elevated temperature for the purposes of case hardening
thereby providing a corrosion and wear-resistant surface.
Sintering - The process of forming a mechanical part from a
powdered metal by bonding under pressure and heat but below
the melting point of the basis metal. ;
Sizing 1. Secondary forming or squeezing operations, required
to square up, set down, flatten or otherwise correct surfaces,
to produce specified dimensions and tolerances. See restriking.
2. Some burnishing, -broaching, drawing and shaving operations
are also called sizing. 3. A finishing operation for correct-
ing ovality in tubing. 4. Powder metal. Final pressing of
a sintered compact. !
XVI-38
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Skimming - The process of removing floating solid or liquid wastes
from a wastewater stream by means of a special tank and skim-
ming mechanism prior to treatment of the water.
Slaking - The process of reacting lime with water to yield a
hydrated product.
Sludge - Residue produced in a waste treatment process.
Sludge Dewatering - The removal of water from sludge by introducing
the water sludge slurry into a centrifuge. The sludge is
driven outward with the water remaining near the center. fhe
water is withdrawn and the dewatered sludge is usually land-
filled.
Slurry - A watery suspension of solid materials.
Snagging - Heavy stock removal of superfluous material from a work
piece by using a portable or swing grinder mounted with a
coarse grain abrasive wheel.
Soldering - The process of joining metals by flowing a thin
(capillary thickness) layer of nonferrous filler metal into
the space between them. Bonding results from the intimate
contact produced by the dissolution of a small amount of base
metal in the molten filler metal, without fusion of the base
metal. The term soldering is used where the temperature range
falls below 425°C (800°F).
Solids - (Plant Waste)
dewatered.
Residue material that has been completely
Solute - A dissolved substance.
Solution - Homogeneous mixture of two or more components such as a
liquid or a solid in a liquid.
Solution Treated - (Metallurgical) A process by which it is
possible to dissolve micro-constituents by taking certain
alloys to an elevated temperature and then keeping them in
solution after quenching. (Often a solution treatment is
followed by a precipitation or aging treatment to improve
the mechanical properties. Most high temperature alloys which
are solution treated and aged machine better in the solution
treated state just before they are aged.)
Solvent - A liquid used to dissolve materials. In dilute solutions
the component present in large excess is called the solvent
and the dissolved substance is called the solute.
Solvent Cleaning - Removal of oxides, soils, oils, fats, waxes,
greases, etc. by solvents.
XVI-39
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Solvent Degreasing - The removal of oils and grease from a
workpiece using organic solvents or solvent vapors.
Specific Conductance - The property of a solution which allows
an electric current to flow when a potential difference is
applied.
Spectrophotometry - A method of analyzing a wastewater sample by
means of the spectra emitted by its constituents under
exposure to light.
Spray Rinse - A process which utilizes the expulsion of water
through a nozzle as a means of rinsing.
i ,—
Spinning - Shaping of seamless hollow cylindrical sheet metal parts
by the combined forces of rotation and pressure.
Spotfacing - Using a rotary, hole piloted end facing tool to produce
a flat surface normal to the axis of rotation of the tool on or
slightly below the workpiece surface.
Sputtering - The process of covering a metallic or non-metallic
workpiece with thin films of metal. The surface to be coated
is bombarded with positive ions in a gas discharge tube,
which is evacuated to a low pressure.
I
Squeezing - The process of reducing the size of a piece of heated
material so that it is smaller but more compressed than it
was before. |
i
Stainless Steels - Steels which have good or excellent corrosion
resistance. (One of the common grades contains 18% chromium
and 8% nickel. There are three broad;classes of stainless
steels - ferritic, austenitic, and martensitic. These various
classes are produced through the use of various alloying
elements in differing quantities.
Staking - Fastening two parts together permanently by recessing
one part within the other and then causing plastic flow at
the joint. ;
i
Stamping - A general term covering almost all press operations.
It includes blanking, shearing, hot or cold forming, drawing,
bending and coining.
Stamping Compounds - See Forming Compounds;(Sheet).
Standard of Performance - Any restrictions\established by the Admin-
istrator pursuant to Section 306 of ttye Act on quantities,
rates and concentrations of chemical, physical, biological,
and other constituents which are or may be discharged from
new sources into navigable waters, the waters of the contiguous
zone or the ocean.
XVI-40
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Stannous Salt - Tin based compound used in the acceleration process
Usually stannous chloride.
Utill Rinse - See Dead Rinse.
Storm Water Lake - Reservoir for storage of storm water runoff
collected from plant site; also, auxiliary source of process
water.
Stress Relieved - The heat treatment used to relieve the internal
stresses induced by forming or heat treating operations.
(It consists of heating a part uniformly, followed by cooling
slow enough so as not to reintroduce stresses. To obtain low
stress levels in steels and cast irons, temperatures as high
as 1250 degrees P may be required.)
Strike - A thin coating of metal (usually less than 0.0001 inch in
thickness) to be followed by other coatings.
Stripping - The removal of coatings from metal.
Subcategorv or Subpart - A segment of a point source for which
specific effluent limitations have been established.
Submerged Tube Evaporation - Evaporation of feed material using
horizontal steam-heat tubes submerged in solution. Vapors
are driven off and condensed while concentrated solution is
bled off.
Subtractive Circuitry - Circuitry produced by the selective etching
of a previously deposited copper layer.
Substrates - Thin coatings ( as of hardened gelatin) which act as a
support to facilitate the adhesion of a sensitive emulsion.
Surface Tension - A measure of the force opposing the spread of
a thin film of liquid.
Surface Waters - Any visible stream or body of water.
Surfactants - Surface active chemicals which tend to lower the
surface tension between liquids, such as between acid and
water.
Surge ~ A sudden rise to an excessive value, such as flow, pressure
temperature.
Swaging - Forming a taper or a reduction on metal products such as
rod and tubing by forging, squeezing or hammering.
Tank ~ A receptacle for holding transporting or storing liquids.
XVI-41
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Tapping - Producing internal threads with a cylindrical cutting
tool having two or more peripheral cutting elements shaped
to cut threads of the desired size and form. By a combination
of rotary and axial motion, the leading end of the tap cuts
the thread while the tap is supported mainly by the thread it
produces.
Tempering - Reheating a quench-hardened or normalized ferrous alloy
to a temperature below the transformation range then cooling
at any rate desired.
Testing - The application of thermal, electrical, or mechanical
energy to determine the suitability or functionality of a
part, assembly or complete unit.
Thermal Cutting - The term "thermal cutting" shall mean the process
of cutting, slotting or piercing a workpiece using an
oxy-acetylene oxygen lance or electric arc cutting tool.
Thermal Infusion - The process of applying a fused zinc, cadmium or
other metal coating to a ferrous workpiece by imbueing the
surface of the workpiece with metal powder or dust in the
presence of heat. i
Thickener - A device or system wherein the solid contents of slurries
or suspensions are increased by gravity settling and mechanical
separation of the phases, or by flotation and mechanical separ-
ation of the phases.
Thickening - (Sludge Dewatering) Thickening or concentration is the
process of removing water from sludge after the initial separ-
ation of the sludge from wastewater. The; basic objective of
thickening is to reduce the volume of liquid sludge to be
handled in subsequent sludge disposal processes.
Threading - Producing external threads on a cylindrical surface.
1. Die Threading - A process for cutting external threads
on cylindrical or tapered surfaces by the use of solid or
self-operning dies. 2. Single-Point Threading - Turing
threads oa a lathe. 3. Thread Grinding - See definition
under grinding. 4. Thread Milling - A method of cutting
screw threads with a milling cutter.
Threshold Toxicity - Limit upon which a substance becomes toxic or
poisonous to a particular organism.
Through Hole Plating - The plating of the inner surfaces of holes in
a PC board. '
Titration - 1. A method of measuring acidity of alkalinity. 2. The
determination of a constituent in a known volume of solution by
the measured addition of a solution of known strength for complet-
ion of the reaction as signaled by observation of an end point.
XVI-42
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Total Chromium - The sum of chromium in all valences.
Total Cyanide -r The total content of cyanide expressed as the
radical CN- or alkali cyanide whether present as simple or
complex ions. The sum of both the combined and free cyanide
content of a plating solution. In analytical terminology,
total cyanide is the sum of cyanide amenable to oxidation
by chlorine and that which is not according to standard
analytical methods.
Total Dissolved! Solids (TDS) - The total amount of dissolved solid
materials present in an aqueous solution.
Total Metal - Sum of the metal content in both soluble and insoluble
form.
Total Organic Carbon (TOG) - TOC is a measure of the amount of
carbon in a sample originating from organic matter only. The
test is run by burning the sample and measuring the CO£
produced.
Total Solids - The sum of dissolved and undissolved constituents
in water or wastewater, usually stated in milligrams per liter.
Total Suspended Solids (TSS) - Solids found in wastewater or in the
stream, which in most cases can be removed by filtration. The
origin of suspended matter may be man-made or of natural
sources, such as silt from erosion.
Total Volatile Solids - Volatile residue present in wastewater.
Tool Steels - Steels used to make cutting tools and dies. (Many of
these steels have considerable quantities of alloying elements
such as chromium, carbon, tungsten, molybdenum and other
elements. These form hard carbides which provide good wearing
qualities but at the same time decrease machinability. Tool
steels in the trade are classified for the most part, by their
applications, such as hot work die, cold work die, high speed,
shock resisting, mold and special purpose steels.)
Toxic Pollutants - A pollutant or combination of pollutants including
disease causing agents, which after discharge and upon exposure,
ingestion, inhalation or assimilation into any organism either
directly or indirectly cause death, disease, cancer, genetic
mutations, physiological malfunctions (including malfunctions
in such organisms and their offspring.
Treatment Facility Effluent - Treated process wastewater.
Trepanning - Cutting with a boring tool so designed as to leave
an unmachined core when the operation is completed.
XVI-43
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Trickling Filters - A filter consisting of an artificial bed of
coarse material, such as broken stone, clinkers, slate, salts, or
brush over which an effluent is distributed and applied in drops,
films, or spray from troughs, drippers, moving distributors, or
fixed nozzles and through which it trickles to the underdrains
giving opportunity for the formation of zoological slimes which
clarify and oxidize the effluent.
]
Tumbling - See Barrel Finishing.
Tubidimeter - An instrument for measurement of turbidity in which
a standard suspension is usually used for reference.
Turbidity - 1. A condition in water or wastewater caused by the
presence of suspended matter resulting in the scattering and
absorption of light rays. 2. A measure of fine suspended
matter in liquids. 3. An analytical quantity usually report-
ed in arbitrary turbidity units determined by measurements of
light diffraction.
Turning - Generating cylindrical forms by removing metal with a
single-point cutting tool moving parallel to the axis of
rotation of the work. 1. Single-Point Turning - Using a
tool with one cutting edge. 2. Face Turning - Turning a
surface perpendicular to the axis of the workpiece. 3.
Form Turning - Using a tool with a special shape. 4.
Turning Cutoff - Severing the workpiece with a special
lathe tool. 5. Box Tool Turning - Turning the end of
workpiece with one or more cutters mounted in a boxlike
frame, primarily for finish cuts.
Ultrafiltration - A process using semipermeable polymeric membranes
to separate molecular or colloidal materials dissolved or
suspended in a liquid phase when the liquid is under pressure.
I
Ultrasonic Agitation - The agitation of a liquid medium through
the use of ultrasonic waves.
Ultrasonic Cleaning - Immersion cleaning aided by ultrasonic waves
which cause microagitation.
Ultrasonic Machining - Material removal by means of an ultrasonic-
vibrating tool usually working in an abrasive slurry in close
contact with a workpiece or having diamond or carbide cutting
particles on its end.
Unit Operation - A single, discrete process as part of an overall
sequence, e.g., precipitation, settling and filtration.
Vacuum Deposition - Condensation of thin metal coatings on the cool
surface of work in a vacuum. \
XVI-44
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Vacuum Evaporization - A method of coating articles by melting
and vaporizing the coating material on an electrically
heated conductor in a chamber from which air has been
exhausted. The process is only used to produce a decor-
ative effect. Gold, silver, copper and aluminum have been
used.
Vacuum Filtration - A sludge dewatering process in which sludge
passes over a drum with a filter medium, and a vacuum is
applied to the inside of the drum compartments. As the
drum rotates, sludge accumulates on the filter surface,
and the vacuum removes water.
Vacuum Metalizing - The process of coating a workpiece with
metal by flash heating metal vapor in a high-vacuum
chamber containing the workpiece. The vapor condenses on
all exposed surfaces.
Vapor Blasting - A method of roughing plastic surfaces in prepar-
ation for plating.
Vapor Degreasing - Removal of soil and grease by a boiling liquid
solvent, the vapor being considerably heavier than air. At
least one constituent of the soil must be soluble in the
solvent.
Vapor Plating - Deposition of a metal or compound upon a heated
surface by reduction or decomposition of a volatile compound
at a temperature below the melting points of either the
deposit or the basis material.
Viscosity - The resistance offered by a real fluid to a shear
.stress.
Volatile Substances - Material that is readily vaporizable at a
relatively low temperature.
Volumetric Method - A standard method of measuring settleable
solids in an aqueous solution.
Waste Discharged - The amount (usually expressed as weight) of
some residual substance which is suspended or dissolved
in the plant effluent.
Wastewater Constituents - Those materials which are carried by
or dissolved in a water stream for disposal.
*T1.S. GOVERHKENI. HUNTING OFFICE : 1982 0-361-085/4468
XVI-45
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