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DRAFT
Waste Constituents
The results of the waste constituent analysis of raw waste streams
sampled from photographic film sensitizing operations are shown in
Table 5-11 in terms of both concentration (mg/1) and production ori-
ented levels (mg/hr-m2_) for each parameter. As can be seen from this
table, the principle pollutant constituents are cyanide, phenols, sus-
pended solids, oil and grease, COD, PCB's, zinc, and silver.
Analysis of the individual raw waste streams does not totally identify
the exact source of each raw waste load, and photographic manufacturers
as a group are unwilling to discuss their proprietary processes. It
can be stated generally, however, that the cyanide probably originates
in the silver recovery process. The suspended solids, oil and grease,
and COD are probably from the gelatine production and application,
and the metals from metal salts used in manufacturing of various types
of films.
SUBCATEGORY ILL - DOCKSIDE SHIPBUILDING ACTIVITIES
Process Description
Dockside shipbuilding and repair refers to those activities within a
shipyard that are performed in graving docks, floating drydocks, marine
railways, and shipways. Waste characteristics for each of these areas
is discussed in the following sections.
Graving Docks - A graving dock is a basin into which a ship may be
floated for repairs or in which a ship may be constructed. Once the
ship enters, it is positioned on keel blocks, and the basin is isolated
from the adjacent waterway and dewatered with pumps. Wastes generated
during ship repair or construction fall, to the floor of the graving
dock and may be discharged to waterways when the dock is flooded or
when sump pumps operate to remove rain and leakage water.
The most significant pollutants from graving docks are heavy metals that
are present in spent abrasive and old paint which can accumulate on the
floor of a graving dock during blasting operations. Because blasting is
followed by painting, paint can also be discharged to receiving waters
when flooding graving docks. Paint lost to the graving dock can result
from spills, drips and oversprays. Miscellaneous trash also accumu-
lates on the floor of graving docks during construction and repair
activities and, if not removed prior to flooding, it can enter waterways,
5-34
-------
DRAFT
TABLE 5-il
HASTE CHARACTERISTICS OF RAH HASTE
SUBCATEGORY 10
STREAMS
PARAMETER
PH. ACIDIC
PH. ALKALINE
TURBIDITY
TEMPERATURE
DISSOLVED OXYGEN
RESIDUAL CHLORINE
-CTOITY
ALKALINITY
AMMONIA
B. 0. 0. 5
COLOR
SULFIOE
CYANIDE, TOTAL
KJELDAHL NITROGEN
PHENOLS
CONDUCTANCE
TOTAL SOLIDS
TOT. SUSPENDED SOS.
SETTLEABLE SOLIDS
ALUMINUM
&ASIUM
CADMIUM
CALCIUM
CHLORIDE
CHROMIUM, TOTAL
CHROMIUM.HEXAVALENT
COPPER
FLUORIDE
I1* ON, TOTAL
HCM* -DISSOLVED
L EAD
MAGNESIUM
MANGANESE
MTLYBDENUM
TIL, fiREASE
HARDNESS
'. 0. D.
T?TiL PHOSPHATES
P.C.3. ' S
=TTAS?! J"
s : v i c A
>ODIUM
S'JLFAie
4S56NIC
BORON
MERCURY
NICKEL
N! TBATE
\ ; T a [Tf
TIN
ALOEHIDES
HYDROQUINCNE
I?SUlFATE/SULF ITE
MINIMUM
MG/L
2.400
7.400
10.000
24.000
5.400
0.100
1.000
71.000
0.040
0.500
5.000
0.100
0.010
0.350
0.008
0.210
608.000
2.000
0.300
0.030
0.030
0.002
20.970
6.100
0.005
0.005
0.013
0.200
0. 154
0.549
0.008
5.210
0.023
0.010
0.668
70.000
86.200
1.200
0.300
3. 760
4.800
48.000
2.300
0.500
0.025
0.020
0.002
0.050
0.002
0.005
2.500
0.090
0.002
0.050
0.024
0.019
0.010
1.000
1 .030
CONCENTRATION
MAXIMUM
MG/L
6.800
9.400
440.000
29.000
10.200
0.100
68.000
6383.000
110.000
1260.000
1200.000
0.700
4.900
233.000
120.000
5200.000
3245.000
724.000
14.000
20.480
2.000
16.230
1893.000
169.800
0.464
0.027
0.8R4
2.100
12.760
4.167
2.647
17.020
0.737
0.052
2237.000
1256.000
5120.000
9.600
123.900
345.100
28.600
533.300
1036.000
18.000
0.400
4.180
0.002
1.160
0.019
0.074
85.700
8.000
0.250
1.220
0.100
1.539
1.030
5.100
9. 100
PRODUCTION ORIENTED
MEAN
MG/L
5.875
8.310
95.000
27.200
7.743
0.100
20.892
650.400
16.620
389.061
145.417
0.217
1.2*5
52.771
19.610
936.734
1557.333
182.678
6.478
1.822
0.800
1.468
251.332
75.356
0.111
0.008
0.323
0.561
2.908
1.996
0.557
9.882
0.197
0.013
386.485
298.667
1228.633
3.413
28.136
60.568
16.318
186.668
260.970
2.95R
0.060
1.428
0.002
0.406
0.008
0.025
21.808
1.347
0.050
0.472
0.055
0.496
0.168
1.810
3.642
MINIMUM
MG/HR-H2
2.40000
7.40000
10.00000
24.00000
3.23897
0.05998
0.59981
42.58652
0.11866
0.29991
5.00000
0.05998
0. 006 00
0.29563
0.00798
0.21000
364.68457
11.25932
0.17994
0.07198
0.01799
0.00169
17.71249
26.52228
0.00300
0.00300
0.00780
0.11996
0.33204
0.32930
0.00720
4.40067
0.01500
0.00600
0.66607
57.58179
395.69458
0.83973
0.17994
2.25529
2.87909
28.79088
12.94821
0.29991
0.01799
0.10136
0.00199
0.02999
0.00120
0.00420
1.49953
0.05398
0.00180
0.02999
0.03390
0.01140
0.00600
0.59980
0.87000
MAXIMUM
MG/HB-MZ
6.800
9.400
4*0.000
29.000
7.011
0.060
40.787
3828.590
65.979
3040.016
1200.000
0.420
2.939
139.756
71.977
5200.000
1946.385
934.523
8.397
20.421
1.200
9.735
1135.441
101.848
0.681
0.028
2.466
2.094
7.654
2.499
1.588
10.209
0.442
0.031
1341.776
753.362
4324.652
6.756
74.316
206.995
17.155
450.456
5832.324
10.797
0.240
5.247
0.002
0.696
0.107
0.045
51.404
4.793
0. 150
0.732
0.563
4.960
5.798
5.630
34.903
LEVELS
MEAN
MG/Hft-M?
5.0790
8.3100
95.0000
27.2000
4.9346
Oi060Q
12.7290
393.4370
10»O*«
442.5334
145.4167
0.1320
0.7470
31.6596
ll.7«23
936.7336
980.0940
1 92. 24*4
3.8990
1.6932
0.4905
0.8837
151.1791
58.2545
0.1490
0.0118
0.381J
0.4051
2.1773
1.21*3
0.3555
6.0334
0.1574
0.0083
260.2734
140.5715
1105.2866
2.6599
16.8898
36.7694
9.7878
122.8469
483.7158
1.8152
0.0367
1.1777
0.0020
0.2631
0.0175
0.0219
14.16*4
0.8081
0.0314
0.7859
0.1938
0.7670
0.7489
2.5106
5.7336
-------
DRAFT
Floating Drydocks - A floating drydock consists of a platform and asso-
ciated ballast tanks and is used to raise ships above water level dur-
ing construction and repair activities. By flooding the ballast tanks,
the dock sinks, and a ship can be moved over it and secured. Dewater-
ing of the ballast tanks floats the drydock and, thus, raises the ship
out of water. The waste characteristics discussed for graving docks
are applicable to drydock operations and could enter waterways from
the drydock platform when it is sunk.
Marine Railways - A marine railway consists of an inclined groundway
extending into the water with a support structure that moves. Ships
are drawn up the railway and out of the water and positioned for re-
pairs. Pollutants generated in the operation of marine railways or-
iginate from blasting, scrubbing, washing, or painting vessels. These
pollutants are carried to receiving waters by tidal action, precipita-
tion, and miscellaneous work area water flows.
Shipways - Shipways are areas used for the construction of new ships.
Normally inclined, the shipway may be either entirely above water level
or partially below. Those that are entirely above the water level are
analagous to marine railways, while those partially above the water
level are similar to graving docks.
Water Usage
Process water is not normally used for dockside shipbuilding and re-
pair activities. However, water can enter dockside facilities from
precipitation, leakage (graving docks), tidal action (marine railways
and shipways), and from general cleanup procedures. The amount of
such water entering a dockside facility cannot be quantified because
of the intermittent nature of the sources. However, if water enters
a dockside area that contains significant quantities of spent abra-
sives, paint, scale and trash, it could carry these pollutants to a
receiving waterway during dewatering or flooding of a graving dock,
sinking of a drydock, or from tidal action or rain around marine rail-
ways and shipways.
Waste Characteristics
Much of the pollutional material from dockside shipbuilding and repair
activities is in the form of solids. Blasting abrasives, dry paint and
primer, and marine fouling organisms encompasses the bulk of these
solids xvhich can be either suspended or settleable.
Materials containing heavy metals are used extensively on ships and in
shipyards to inhibit marine organisms and corrosion. Red lead and zinc
chromate are widely used primers, while copper, tin, mercury, and arse-
nic constitute a significant portion of ar.tifouling paints. All of
these pollutants may enter waterways fror. shipyards in quantities dam-
aging to the marine environment. Therefore, good housekeeping practices
are a must in order to reduce pollution of aajacent waterways.
5-36
-------
DRAFT
SUBCATEGORY 12_ - LEAD ACID BATTERY MANUFACTURE
Process Schematic
£ typical process flow diagram depicting water use and overall opera-
tions for lead acid storage battery manufacture is shown in Figure 5-11.
Initially, lead pigs are melted and cast to the grid configuration and,
in roost plants, the molten lead is also used for manufacturing lead
oxide. The grids are cast in grid casting machines which use either
contact or noncontact cooling water. These cast grids are then coat-
ed with a paste consisting primarily of lead oxide, sulfuric acid and
it-er to form the battery plates. Water is used in the pasting area
;or washing down the area and for noncontact cooling. After pasting,
:-ne plates are allowed to dry and cure and are then stacked with a
spacer material between the positive and negative plates and electric-
ally connected to form the battery cells.
The wet charge battery cells are assembled into the battery case, elec-
trically connected, sealed, pressure tested, filled with acid and rinsed,
The rinsing removes any acid spills from the case and also removes heat
raused by the addition of acid. An electrical charge is then applied
ro the wet charge battery to "form" the plates where the negative plate
becomes sponge lead and the positive plate converts to lead peroxide.
After forming, the wet charge batteries are washed, decorated, and
readied for shipment.
The dry charge batteries are stored and shipped without acid to improve
the shelf life of the product. Its assembly differs from that of the
wet charge battery primarily in the forming operation which requires
t.nat the plate be in contact with acid. For dry charge batteries, the
: c.rTTtir.g operation is accomplished with the connected cells either in
trie battery case or in acid tanks called forming tanks. After removal
rrom the forming tanks, the connected cells are rinsed and dried and
t.nen assembled in the battery case which is sealed, pressure tested,
decorated, and readied for shipment. For dry charge batteries where
forming operations are completed in the battery case, the acid is dumped
and recovered, and the battery is rinsed, decorated, and readied for
shipment.
vcater Us_agjs
'''\ater is used by the lead acid storage battery industry for cooling
.contact and noncontact), air pollution control in the lead oxide mill
-nci for washing and rinsing of battery cases and battery plates. The
ruajor portion of this contact water for dry charge batteries is for
/•ashing and rinsing assembled battery cases. Battery plates are
vashed and rinsed after the forming operation. Dry charge battery
5-37
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DRAFT
manufacture can use about the same amount of water as wet charge
battery manufacture. This conclusion is based on the fact that two
manufacturers of dry charge batteries had less contact water use per
dry charge battery than per wet charge battery. This was accomp-
lished by using proprietary methods to limit water use for dry charge
batteries.
Waste Constituents
The results of an analysis of the constituents of raw waste streams
from lead acid battery plants sampled are presented in Table 5-12 in
rerms of both concentration (mg/1) and production oriented levels
(r-g/hr-m2_) for each parameter. As can be seen from the table, high
concentrations of acidity, iron, chlorides and sulfates were found in
these raw waste streams. Since the major materials used in this sub-
category do not include iron, it can be concluded that the acidity of
the waste stream has caused a chemical reaction with the iron com-
ponents within the wastewater collection systems (i.e., pumps, valves,
piping). The high sulfate content is a result of the chemical break-
down of the sulfuric acid used in acid batteries and subsequent rins-
ing operations after the battery is sealed.
It is interesting to note that a relatively low lead concentration was
found in battery manufacture waste streams even though it is a major
ingredient in lead acid battery manufacturing. This is because most
use noncontact water for grid casting or use a proprietary method for
forming dry charge battery plates.
5-39
-------
DRAFT
TABLE 5-12
HASTE CHARACTER ISTICS OF RAH HASTE
SUBCATEG09Y 12
STREAMS
CONCENTRATION
PARAMETER
PH, ACIDIC
PH, ALKALINE
TURBIDITY
TEMPERATURE
DISSOLVED OXYGEN
RESIDUAL CHLORINE
ACIDITY
AMMONIA
8, 0. D. 5
COLOR
SULFIDE
CYANIDE, TOTAL
CYANIDE AMN.TO CHLOR
KJELOAHL NITROGEN
PHENOLS
CONDUCTANCE
TOTAL SOLIDS
TOT. SUSPENDED SDS.
ALUM I MUM
BARIUM
CADMIUM
CALCIUM
CHLORIDE
CHROMIUM.TQTAL
CHROMIUM, HEXAVALENT
COPPER
FLUORIDE
RON, TOTAL
I^ON, DISSOLVED
LEAO
MAGNESIUM
MANGANESE
•KH.Y8OENUM
OIL, GSEASE
HABDNESS
C. 0. 0.
TOTAL PHOSPHATES
P.C,B.'S
ear ASS! UK
SILICA
SQOIUH
SULFATE
SULFITE
TITflNIUM
ZINC
BORON
MERCURY
juauu.
NITRATE
NITRITE
ieiiJxiuH
SILVER
STRONTIUM
TOT. VOLATILE SOLIDS
ANT I HQfiY
COBALT
THALLIUM
TJJJ
MINIMUM
MG/L
0.500
7.600
10.000
13.000
1.000
4.000
1800.000
0.025
0.300
5.000
0.020
0.007
0.006
0.233
0.005
212.000
1819.000
8.000
0.050
0.030
0.008
6.350
6.500
o.on
0.005
0.025
0.190
1.719
3.410
0.229
5.670
0.015
0.005
1,000
166.000
I. 000
0.200
7.500
3.3TO
3.200
40.000
100.000
0.500
0.020
0.080
0.260
0.004
0.003
4.000
0.004
0.010
0.002
0.083
0.150
0.110
0.007
0.010
0.046
MAXIMUM
MG/L
4.900
7.600
45.000
74.000
3.000
4.000
6440.000
3.820
27.000
20.000
0.200
0.100
0.007
10.000
0.800
79300.000
3863.000
40.100
28.500
0.060
0.038
60,000
1729.000
1.026
0.050
2.52s
13.000
96.950
J2.400
9^500
175.700
1.160
0,020
56.000
500. 000
374.000
4,500
30,000
12.500
10. COO
284.500
9028.000
1.000
0.120
1.027
0.750
0.006
0.354
9.700
0.029
0.010
0.008
0.540
0.150
0.778
0.007
0.038
0.098
MEAN
MG/L
1.993
7.600
25.000
23.150
2.000
4.000
3467.250
1.449
13.850
11.750
0.105
0.033
0.006
3.308
0.105
26771.000
3295,750
22.800
5.090
0.047
0.020
45.415
346.530
0,220
0 , 0 I i
0,530
1 ,83£
32.299
1^.322
2.150
59.135
0.257
0.01*
15.450
257.550
92.53Q
1.275
18,750
6.225
5.900
111.342
4130. OOC
0.833
0.057
0.573
0.472
0.005
0,088
6.175
0.016
0.010
0.003
0.373
0.150
0.328
0.007
0.016
0.061
PRODUCTION ORIENTEO
MINIMUM
MG/HR-M2
0.50000
7.60000
10.00000
13.00000
3.84485
6.06445
2306.90869
0.03518
0.42213
5.00000
0.02563
0.00173
0.00173
0.32786
0.00116
212.00000
2757.80957
1.97247
0.14068
0.07036
0.00345
8.9351?
9.14415
C. 01970
O.OOU3
C.G35! 7
0,12328
2,41827
4,79856
C. 17111
8.54838
0.02 HO
0.00641
3.04976
Zi2.T,SZ5
I. 51611
0.28136
9.61212
4. 74198
4,85156
51.26462
140.67917
1.40711
0.02814
0.10253
0.36585
0.00099
0.004-22
5.25463
0.00606
0.01407
0.00074
0.11679
0.21107
Q.0271Z
0.00985
0.00247
0.01159
MAXIMUM
MG7HR-M2
4.900
7.600
45.000
74.000
11.190
6.064
33122.273
28.982
167.849
20.000
1. 1 19
0.141
0.018
23.835
1.025
79300.000
41313.324
143.231
L6.0T1
0.336
0.123
695.l<2t
5273,031
0.492
Q.l%5
3.83f
13.288
204.231
201,195
404.305
419.623
1.753
0.112
71.770
2126.092
1140,610
6.714
42.213
JS.717
111.900
681.133
2793-7.754
5.555
0.336
2.462
4.476
0.018
0,*50
77.211
0.037
0,014
0.022
4.476
0.211
2*373
0.010
0.116
0.299
LEVELS
MEAN
MG/HR-M2
1.9929
7.6000
25.0000
23.1500
7.5174
6.0645
12237.1328
4.3775
35.3063
11.7500
0.3971
0.0474
0.0100
9,5744
0.2087
26771 .0000
13595.4258
49.8295
3.4T33
0.13
-------
DRAFT
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
INTRODUCTION
The wastewater constituents found during the sampling of 240 raw waste-
water streams in the Machinery and Mechanical Products Manufacturing
point source category which are of a significant pollution nature and
present in significant quantities to warrant their control and treatment
are listed in Table 6-1 for each applicable subcategory. Effluent limi-
tations are established for each of these pollutants in Sections IX,
X, and XI of this development document. These wastewater constituents
selected as significant pollutants were chosen from a broad list
of analyzed parameters shown in Table 6-2. Also shown in Table 6-2
are the number of plant samples which were analyzed for each con-
stituent as well as the number of plants where the particular waste-
water constituent was found in a quantity greater than the minimum
detectable level.
The following rationale was used to determine whether or not to include
a given wastewater constituent for consideration as a significant
pollutant.
*1. The pollutant nature of the constituent is severe enough to
warrant control in effluent discharges.
2. The pollutant was found in a significant quantity in many
of the streams sampled (reference Table 6-2 and Section V).
3. The wastewater pollutant can be controlled by Best Practical
Control Technology Currently Available (BPT). (Reference
Section VII).
4. The wastewater constituent is not removed simultaneously with
another pollutant by such processes as coprecipitation and
clarification, i.e. a treatment for only one of the pollu-
tants would control the other to an acceptable level.
The application of the first three of these considerations to all of
the wastewater parameters considered and analyzed for the Machinery and
Mechanical Products Manufacturing point source category is shown in
Table 6-3. A check against each of these three considerations was nec-
essary to select a wastewater constituent as a significant pollutant
parameter. The following sections present a detailed rationale for the
selection or rejection of each of the considered constituents.
6-1
-------
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CN
rH
/
X X
AJO
X X
/ao
X X
X X
X X
X X
X X
X X
X X
If)
t
c
in
a
0)
T
C
Q
u
a u
XXX
6at}i?oqr
x
Bs^Boqr
X X
H X x x
X X
X
XX X
X X
E
1
0 -P
M C
£ 01
6 U -1
3 ra 1-1
H •-! > Q)
S n) « Q
3 *> X Q
a o ai o
U E-i X U
X X
S ST4J
X X
S siqj
X
X X
X X
X X
X
X X
X
V
41 a
O H
C 0 C
n) 3 C
X
s ^C
X
„ Jc
< X
« X
< X
<
<
l<
)^
i
3 I
» <
X
3
X
>* '
< X
X
x X
x x
X X
X X
X X
(Nickel
Oil - Grease
x
91
X
n
X
X
X
X
X
X
X
1 Chemical Oxyqen Demand
x
q«
X
q^
X
X
X
X
to
0)
-P
(I
c
to
o
ff
o
X
3-
X
X
X
X
X
u
a
u;
X
X
X
X
X
X
X
X
o
c
tsi
ddv 3ON
ddy }ON
6-2
-------
Of* AM
TABLE 6-2
RAW WASTE ANALYSIS SUMMARY
Test
Parameter
Color
Turbidity
0
-------
TABLE 6-3
Test
Parameter
Color
Turbidity
. Odor
pH*
Acidity
Alkalinity
Ammonia
Dissolved Oxygen
Conductance
Residual Chlorine
Sulfide
Hardness
Tptal Solids
SuspUnd'ed Solids*
Settleable Solids
Algicides
Aluminum
Arsenic
Barium
Boron
Cadmium*
Calcium
Chloride
Chromium*
Copper8
Cyanide*
Fluoride*
Iron Tptal*
Iron Dissolved
Lead11
Magnesium
Manganese
Mercury"
Molybdenum
Nickel*
N Itra'te
Mitrite
(__KjeTaaM£i_tro2en____
Oil and Grease -
BiocheEicaT Oxygen Demand
Chemical Ox^en Demand-
Phenols
Phosphorous -Phosphates*
PCB ' s
Potassivun
Selenium
Silica
Silver*
Sc3ium
Strontium
Sulfate
Sulfite
Titanium
Zinc*
Chlorinated Hv~3rbcar¥bns
Total Volalite Solids
Surfactants
Plaaticizers
Bromide
Antimony
Beryllium
- COtfJf
Thallium
Tin
Aldehydes +
^ydrbquinone ^
Thiocyanate +
Thiosulfate/Sulfite
POLLUTANT
SELECTION
Significant
Pollutant
X
x
X
X
X
X
X
X
X
X
X
X
X
X
X
r x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
- ... - X_.
X
X
X
PARAMETER
RATIONALE
Signi f icant
Quantity
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1" x
X
X
X
•A
X
X
x
X
X
X
X
X
X
X
X
X
X
x
X
X
X
X
X
Treatment
Achievable
(BPT)
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
X
X
X
X
X
X
X
X
X
X
x - -
X
X
X
x ~i
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
x
X
X
X
X
X
X
X
NOTES
Measured by ether parare-_ers
Measured by total iroi
—
COD cc vers broader ranae
N/A - Not Applicable
* - Selected for Pollutant Parameter
*< - Fur Film Sensitising Industry Only
6-4
-------
DRAFT
RATIONALE FOR THE SELECTION OF POLLUTANT PARAMETERS
gH
Although not a specific pollutant, pH is related to the acidity or al-
kalinity of a wastewater stream. It is not, however, a measure of
either. The term pH is used to describe the hydrogen ion concentration
or activity present in a given solution. Values for pH range from 0 to
14, and these numbers are the negative logarithim of the hydrogen ion
concentration. A pH of 7 indicates neutrality. Solutions with a pH
above 7 indicate that the solution is alkaline, while those solutions
with a pH below 7 indicate that the solution is acid. The relationship
of pH and acidity and alkalinity is not, however, necessarily linear or
direct.
Knowledge of the water pH is useful in determining necessary measures
for corrosion control, sanitation, and disinfection. Its value is also
necessary in the treatment of industrial wastewaters to determine
amounts of chemicals required to remove pollutants and to measure their
effectiveness since removal is affected by the pH of the wastewater,
particularly the precipitation of dissolved solids.
Waters with a pH below 6.0 are corrosive to water works structures,
distribution lines, and household plumbing fixtures and can thus
add such constituents to drinking water as iron, copper, zinc, cadmium,
and lead. The hydrogen ion concentration can affect the "taste"
of the water and at a low pH, water tastes "sour". The bactericidal
effect of chlorine is weakened as the pH increases, and it is
advantageous to keep the pH close to 7. This is very significant
for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress conditions or
kill aquatic life outright. Even moderate changes from "acceptable"
criteria limits of pH are deleterious to some species. The relative
toxicity to aquatic life of many materials is increased by changes in
the water pH. For example, metalocyanide complexes can increase a
thousand-fold in toxicity with a drop of 1.5 pH units.
-------
DRAFT
Because of the universal nature of pH and its affect on water quality
and treatment, it is selected as a pollutant parameter for all sub-
categories in the Machinery and Mechanical Products Manufacturing
point source category. A neutral pH range (6-9) is generally desired
because either extreme beyond this range has a deleterious effect on
receiving waters or the pollutant nature of other wastewater con-
stituents.
Total Suspended Solids
All undissolved solids in water, unless they have settled to the
bottom in one hour are suspended solids. The fraction, of undissolved
solids that are settleable is dependent on quiescense, temperature,
density, stability, size, flocculation, and many other factors.
Suspended solids include both organic and inorganic materials. The
inorganic compounds include sand, silt, and clay. The organic frac-
tion includes such materials as grease, oil, tar, and animal and
vegetable fats.
Suspended solids in water interfere with many industrial processes,
cause foaming in boilers and incrustations on equipment exposed to
such water, especially as the temperature rises. They are unde-
sirable in process water used in the manufacture of steel, in the
textile industry, in laundries, in dyeing and in cooling systems.
Solids in suspension are aesthetically displeasing. When they settle
to form sludge deposits on the stream or lake bed, they are often
much more damaging to the life in water, and they retain the capacity
to displease the senses. Solids, when transformed to sludge deposits,
may do a variety of damaging things, including blanketing the stream
or lake bed and thereby destroying the living spaces for those benthic
organisms that would otherwise occupy the habitat. When of an
organic nature, solids use a portion or all of the dissolved oxygen
available in the area. Organic materials also serve as a seemingly
inexhaustible food source for sludgeworms and associated organisms.
Disregarding any toxic effect attributable to substances leached out
by water, suspended solids may kill fish and shellfish by causing
abrasive injuries and by clogging the gills and respiratory passages
of various aquatic fauna. Indirectly, suspended solids are inimical
6-6
-------
DRAFT
to aquatic life because they screen out light, and they promote and
maintain the development of noxious conditions through oxygen depletion
This results in the killing of fish and fish food organisms. Suspended
solids also reduce the recreational value of the water.
In consideration of the extensive occurrence of suspended solids
in the Machinery and Mechanical Products Manufacturing point source
category and the pollutant nature of suspended solids, not with-
standing toxic effects of substances leached out by the water, they
are considered a pollutant parameter requiring an effluent guideline
limitation for all subcategories of the point source category.
Cadmium (Cd)
Cadmium is a relatively rare element that is seldom found in sufficient
quantities in a pure state to warrant mining or extraction from the
earth's surface. It is found in trace amounts of about 1 ppm through-
out the earth's crust. Cadmium is, however, a valuable by-product
of zinc production.
Cadmium is used primarily as a metal plating material and can be
found as an impurity in the secondary refining of zinc, lead, and
copper. Cadmium is also used in the manufacture of primary cells of
batteries and as a neutron adsorber in nuclear reactors. Other
uses of cadmium are in the production of pigments, phosphors,
semi-conductors, electrical contactors, and special purpose low tem-
perature alloys. With the exception of its use in nuclear reactors,
all of the above uses and occurrences and uses of cadmium are applicabL
to the Machinery and Mechanical Products Manufacturing point source
category.
Toxic effects of cadmium on man have been reported from through-
out the world. Cadmium is normally ingested by humans through food
and water and also by breathing air contaminated by cadmium. Its
effects range from none to being highly toxic and causing death
with the specific effect being dependent on the amount ingested
and the time period involved. Cadmium is primarily a respiratory
poison and has a higher lethal potential than most other metals. It
can cause emphyzema after prolonged exposure. Cases of cadmium poison-
ing have resulted from the consumption of foods or liquids prepared
and left in cadmium plated containers. Cadmium tends to remain
in the body tissues for many years after exposure or consumption.
Excretion in the urine is extremely low. Cadmium usually concentrates
in the liver, kidneys, and spleen after prolonged exposure.
6-7
-------
Few studies have been made on the toxicity of cadmium in the aquatic
environment. Most quantitative data on the toxicity of cadmium are
based on the specific salts of the metal. Expressed as cadmium,
these data indicate that the acute lethal level to fish varies from
about 0.01 to about 10mg/l depending on the test animal, the type of
water, the temperature, and the time of exposure. Cadmium also acts
synergistically with other substances, particularly copper and zinc,
to increase its toxicity and can be biologically concentrated in living
tissues.
The toxic effects of cadmium on man have caused a limitation of the
amount of this metal allowed in water supplies. The cadmium concentra-
tion in drinking water is set as low as 0.01 mg/1 in the U. S. and as
high as 0.10 mg/1 in Russia.
Based on the toxicity of cadmium and its salts and the potential for
its existence in the wastewater effluents of the Machinery and Mechanical
Products Manufacturing industries, it is selected as a pollutant para-
meter requiring the establishment of an effluent limitation.
Chromium (Cr)
Chromium is an elemental metal usually found as a chromite (FeO Cr2_03_) .
The metal is normally processed by reducing the oxide with aluminum.
Chromium and its compounds are used extensively throughout industry.
It is used to harden steel and as an ingredient in other useful alloys.
Chromium is also used in the electroplating industry as an ornamental
and corrosion resistant plating on steel and can be used in paint pig-
ments (lead chromate) and as a pickling acid (chromic acid).
The two most prevalent chromium compounds found in industry wastewaters
are hexavalent and trivalent chromium. Chromic acid used in industry
is a hexavalent chromium compound which is partially oxidized to the
trivalent form during use and thus can exist as either trivalent or
hexavalent chrome in raw waste streams. Hexavalent chromium treat-
ment involves reduction to the trivalent form prior to removal of
chromium from the waste stream as a hydroxide precipitate.
6-8
-------
DRAFT
From tests made previously there have been no deleterious affects shown
from drinking water containing up to 5.0 mg/1 of chromium except for
mild nausea. Chromium salts impart color to water at levels above 1.5
mg/1, and the taste threshold for the most sensitive person is 1.5 mg/1.
The toxicity of chromium salts for fish and other aquatic life varies
widely with the species, temperature, pH, valence of the chromium and
synergistic or antagonistic effects, especially that of hard water.
Studies have shown that trivalent chromium is more toxic to fish of
some types than hexavalent chromium. Other studies have shown opposite
effects. These same results have been realized for other aquatic organ-
isms. Therefore, both hexavalent and trivalent chromium must be con-
sidered toxic to particular fish or organisms.
Based on the toxicity of chromium in either the hexavalent or trivalent
forms, chromium is selected as a pollutant parameter requiring an efflu-
ent limitation within the Machinery and Mechanical Products Manufacturing
point source category.
Copper (Cu)
Copper is an elemental metal that is sometimes found free in nature and
is found in many minerals such as cuprite, malachite, azurite, chalcopy-
rite, and bornite. Copper is obtained from these ores by smelting,
leaching, and electrolysis.
Copper is used throughout the Machinery and Mechanical Products Manu-
facturing points source category primarily for applications requiring
a metal with a high conductivity or corrosion resistance. It is castf
machined and formed, and used as a plating metal and a pigment in some
paints. Significant industrial uses are in the plating, electrical r
plumbing, and heating equipment industries. Copper is also commonly
used with other minerals as an insecticide and fungicide.
Traces of copper are found in all forms of plant and animal life, and it
is believed to be an essential trace element for nutrition. It is not
considered to be a cumulative systemic pc'',aon like lead or mercury and
is readily excreted by the body* Thare r<4.~ beer: iic evidence of poison-
ing a3 a result or the consumption of copper in v?ater. The limiting
factor in domestic water supplies is- tastt. Ccrin^ntrs.^Ions of 1-0 to
2.0 rag/1 are considered * '.~i^.v-io; d amounts v:hile b. \;o 7.5 mg/1 he>ve made
water .- ompleraly
Coppo,. salts cause undfcsJrable color reacuicnc in the food industry and
cause pitting whej; deposited on some other metals such as aluminum and
galvanized steel. The textile industry is affected when copper salts ar<
present in water used for processing of fabrics. Irrigation waters con-
taining more than minute quantities of copper can be detrimental to cer-
tain crops. There has been very little information on copper in water
available for livestock, and most toxicity results are from feed related
-------
UKAh
sources rather than water related sources. The toxicity of copper to
aquatic organisms varies not only with the species but with the physi-
cal and chemical characteristics of the water. Toxicities vary from
highly toxic at low concentrations to almost no toxicity at high
concentrations.
Although copper concentrations high enough to be detrimental to humans
cause water to be disagreeable to taste, these same concentrations can
be toxic to a wide variety of aquatic forms. Because of this and the
wide use of copper in the Machinery and Mechanical Products Manufactur-
ing point source category, copper is considered as a pollutant para-
meter requiring an effluent limitation.
Cyanide (CN)
Cyanide is a compound that is widely used in industry primarily as
sodium cyanide (NaCN) or hydrocyanic acid (HCN). In the Machinery and
Mechanical Products Manufacturing point source category, the cyanide
acid is used in metal surface treatments and electroplating. It can
also be found as an impurity in ore processing as the CN negative ion
radical. The major use of cyanides is in the electroplating industry
where cyanide baths are used to hold ions such as zinc and cadmium in
solution. Cyanides in various compounds are also used in steel plants,
chemical plants, photographic processing, textile dying, and ore pro-
cessing.
Of all the cyanides, hydrogen cyanide (HCN) is probably the most toxic
compound. HCN dissociates in water to hydrogen ions and cyanide ions in
a pH dependent reaction. The cyanide ion is less toxic than HCN. The
relationship of pH to HCN shows that as the pH is lowered to below 7
there is less than 1% of the cyanide molecules in the form of the CN
ion. When the pH is increased to 8, 9, and 10, the percentage of cya-
nide dissociated is 6.7, 42, and 87%, respectively.
In the body, the CN ion, except for a small portion exhaled, is rapidly
changed into a relatively non-toxic complex (thiocyanate) in the
liver and eliminated in the urine. There is no evidence that the CN
ion is stored in the body. The safe ingested limit of cyanide has been
estimated at something less than 18 ing/day, part of which comes from
normal environment and industrial exposure. The average fatal dose of
HCN by ingestion by man is 50 to 60 mg. No information for the average
daily intake of HCN is available.
The toxicity of the cyanides on aquatic life is affected by the pH,
temperature, dissolved oxygen content, and the concentration of miner-
als in the water. The biochemical degradation of cyanide is not
affected by temperature in the range of 10 degrees C to 35 degrees C
while the toxicity of HCN is increased at elevated temperatures.
6-10
-------
DRAFT
On lower forms of life and organisms, cyanide does not seem to be as
toxic as it is toward fish. The organisms that exert BOD were found to
be inhibited at 1.0 mg/1 and at 60 mg/1 although the effect is more one
of delay in exertion of BOD than total reduction.
Certain metals such as nickel may complex with cyanide to reduce leth-
ality, especially at higher pH values. On the other hand, zinc and
cadmium cyanide complexes are exceedingly toxic.
Because of its toxicity, cyanide with its various compounds is selected
as a pollutant parameter in the Machinery and Mechanical Products Manu-
facturing point source category and requires the establishment of an
effluent limitation.
Fluoride
Fluorine is the most reactive of the nonmetals and is never found free
in nature. It is a constituent of fluorite or fluorspar, calcium
fluoride, cryolite, and sodium aluminum fluoride. Fluorides in high
concentrations are not a common constituent of natural surface waters
due to their origins.
In the Machinery and Mechanical Products Manufacturing industries,
fluoride is not normally found in the wastewater streams except in
trace amounts in plating rinses. It can also be found in glass etch-
ing rinse waters. It could, however, be found in high concentrations
due to spills of either plating baths or glass etching solutions.
Fluorides are also used as a flux in the manufacture of steel and for
preserving wood and mucilages.
Fluorides in sufficient quantities are toxic to humans with doses of
250 to 450 mg giving severe symptoms and 4.0 grams causing death. A
concentration of 0.5 g/Kg of body weight has been reported as a fatal
dosage.
Fluorides may be harmful in certain industries, particularly those in-
volved in the production of food, beverages, pharmaceutical, and
medicines. Fluorides used in irrigation waters in high concentrations
(up to 360 mg/1) have caused damage to certain plants exposed to these
waters. Fish and other aquatic life have had direct toxic effects from
fluoride ions.
Fluorides have had much publicity in the reduction of cavities in human
teeth. Present USPHS drinking water standards have set mandatory limits
on fluorides in drinking water.
Because of the toxicity of fluoride, it is selected as a pollutant par-
ameter requiring a limitation for the Machinery and Mechanical
Products Manufacturing point source category.
-------
Iron (Fe)
Iron is an elemental metal and the fourth most abundant metal found in
the earth's crust. The most common iron ore is hematite from which iron
is obtained by reduction with carbon. Other forms of commercial ores
are magnetite and taconite. Pure iron is not often found in commercial
use, but it is usally alloyed with other metals and minerals, the most
common being carbon.
Iron is used extensively throughout all industry segments in the Machin-
ery and Mechanical Products Manufacturing point source category. It is
the basic element in the production of steel and steel alloys. Iron
with carbon is used for casting of major parts of machines and it can be
machined, cast, formed, and welded. Machined parts can then be plated
and painted. Ferrous iron is used in paints, while powdered iron can
be sintered and used in powder metallurgy. Steel can be hardened and
heat treated to change its molecular structure for various properties.
Iron compounds are also used to precipitate other metals and undesirable
minerals from industrial wastewater streams.
Iron is very reactive chemically and corrodes rapidly in the presence
of moist air and at elevated temperatures. In water and in the presence
of oxygen, iron corrodes and the resulting products of corrosion, in
which the iron is in the ionic or molecular state, may be pollutants in
water. Natural pollution occurs from the leaching of soluble iron salts
from soil and rocks and is increased by industrial wastewater from pic-
kling baths and other solutions containing iron salts.
Corrosion products of iron in water cause staining of porcelain fixtures,
and ferric iron combines with the tannin in tea to produce a dark violet
color. The presence of excessive iron in water prevents cows from
drinking and, thus, reduces milk production. High concentrations of
ferric and ferrous ions with chloride and hydrogen in water kill most
fish introduced to the solution within a few hours. The killing action
is attributed to coatings of iron oxides and hydroxide precipitates on
the gills. Iron bacteria are dependent on iron in water for growth.
These bacteria form slimes that can affect the esthetic values of bodies
of water and cause stoppage of flows in pipes.
Iron is an essential nutrient and micronutrient for all forms of growth.
Drinking water standards in the U. S. have set a recommended limit of
0.3 mg/1 of iron in domestic water supplies based not on the physiolog-
ical considerations, but rather on aesthetic and taste considerations
of iron in water.
Based on the fact that most natural water has iron in the ferric or
ferrous state in solution and that further additions of iron from the
Machinery and Mechanical Products Manufacturing industries could cause
6-12
-------
DRAFT
receiving bodies of water to have an excessive amount of iron in solu-
tion, iron is selected as a pollutant parameter requiring the establish
ment of an effluent limitation.
Lead (Pb)
Lead is used in various solid forms both as a pure metal and in several
compounds. Lead appears in some natural waters, especially in those
areas where mountain limestone and galena are found. Lead can also be
introduced into water from lead pipes by the action of the water on the
lead.
Some of the major uses for lead in the Machinery and Mechanical Product
Manufacturing point source category are in the manufacture of storage
batteries, bearings, solder, waste pipelines, radiation shielding, soun
insulation, ammunition, printer's type, weights and ballasts, and as a
surface protective coating.
Lead is a toxic material that is foreign to humans and animals. The
most common form of lead poisoning is called plumbism. Lead can be
introduced into the body from the atmosphere containing lead or from
food and water. Lead cannot be easily excreted and is cumulative in
the body over long periods of time, eventually causing lead poisoning
with the ingestion of an excess of 0.6 mg per day over a period of
years.
Chronic lead poisoning has occurred among animals at levels of 0.18
mg/1 of lead in soft water and by concentrations under 2.4 mg/1 in hard
water. Farm animals are poisoned by lead more frequently than any
other poison. Sources of this occurrence include paint and water with
the lead in solution as well as in suspension. Each year thousands of
wild water fowl are poisoned from lead shot that is discharged over
feeding areas and ingested by the water fowl. The bacterial decompo-
sition of organic matter is inhibited by lead at levels of 0.1 to 0.5
mg/1.
Fish and other marine life have had adverse toxic effects with lead anc
salts in their environment. Experiments have shown that small concen-
trations of heavy metals, especially of lead, have caused a film of co-
agulated mucus to form first over the gills and then over the entire
body probably causing suffocation of the fish due to this obstructive
layer. Toxicity of lead is increased with a reduction of dissolved
oxygen concentration in the water.
Because of its toxicity, lead is selected as a pollutant parameter
in the point source category.
C—1 1
-------
Mercury (HgJ \
Mercury is an elemental metal that is rarely found as a free metal. The
most distinguishing feature is that it is a liquid at ambient conditions.
Mercury is relatively inert chemically and is insoluble in water. Its
salts occur in nature chiefly as the sulfide (HgS) known as cinebar.
In the Machinery and Mechanical Products Manufacturing point source
category, mercury is used extensively in measuring instruments and in
mercury batteries. It is also used in electroplating and in some
pigments for paints. The electrical equipment industry uses mercury
in the manufacture of lamp switches and other devices.
Mercury can be introduced into the body through the skin and the res-
piratory system. Mercuric salts are highly toxic to humans and can be
readily absorbed through the gastrointestinal tracts, and fatal doses
can vary from 3 to 30 grams.
Mercuric salts are extremely toxic to fish and other aquatic life.
Mercuric chloride is more lethal than copper, hexavalent chromium,
zinc, nickel, and lead towards fish and aquatic life. In the food
cycle, algae containing mercury up to 100 times the concentration of
the surrounding sea water are eaten by fish which further concentrates
the mercury and predators that eat the fish in turn concentrate the
mercury even further.
Because of the toxic nature of mercury and the probability of finding
it in the Machinery and Mechanical Products Manufacturing industries,
this pollutant parameter is selected for the establishment of an ef-
fluent limitation.
Nickel (N.i)
Elemental nickel is seldom found in nature in the pure state. Nickel
is obtained commercially from pentlendite and pyrrhotite. It is a rel-
atively plentiful element and is widely distributed throughout the
earth's crust. It occurs in marine organisms and is found in the oceans.
Depending on the dose, the organism involved, and the type of compound
involved, nickel may be beneficial or toxic. Pure nickel is not soluble
in water but many of its salts are.
The uses of nickel are many and varied throughout the Machinery and Me-
chanical Products Manufacturing point source category. It is machined
and formed for various products as both nickel and as an alloy with
other metals. Nickel is also used extensively as a plating metal pri-
marily for a protective coating for steel.
_1 A
-------
DRAFT
The toxicity of nickel to man is believed to be very low and system-
atic poisoning of human beings by nickel or nickel salts is almost
unknown. However, nickel has been found extremely toxic to some plant
life but has been found less toxic to some fish than copper, zinc,
brass, and iron. Nickel salts have caused the inhibition of the bio-
chemical oxidation of sewage. They also caused a 50 percent reduc-
tion in the oxygen utilization from synthetic sewage in concentrations
of 3.6 mg/1 to 27 mg/1 of various nickel salts.
Based on the potential toxicity of nickel and its salts and the known
existence of nickel in many of the waste streams of the point source
category, it is selected as a pollutant parameter requiring the es-
tablishment of an effluent limitation.
Oil and Grease
Oil and grease are used extensively throughout the Machinery and Mechan
ical Products Manufacturing point source category primarily to lubricat
and cool workpieces and as a lubricant and hydraulic fluid for process-
ing machinery. Because of the widespread use, oil and grease occur
often in wastewater streams. These oily wastes may be classified as
follows:
1. Light Hydrocarbons - These include light fuels such as gaso-
line, kerosene, and jet fuel, and miscellaneous solvents used
for industrial processing, degreasing, or cleaning purposes.
The presence of these light hydrocarbons may make the removal
of other heavier oily wastes more difficult.
2. Heavy Hydrocarbons, Fuels, and Tars - These include the crude
oils, diesel oils, #6 fuel oil, residual oils, slop oils, and
even in some cases, asphalt and road tar.
3. Lubricants and Cutting Fluids - These generally fall into two
classes: non-emulsifiable oils such as lubricating oils and
greases and emulsifiable oils such as water soluble oils, rol
ling oils, cutting oils, and drawing compounds. Emulsifiable
oils may contain fat soap or various other additives.
4. Fats and Fatty Oils - These materials originate primarily
from processing of foods and natural products. Fats result
from processing of animal flesh. Fatty oils for the most
part come from the plant kingdom.
Oils and grease even in small quantities cause troublesome taste and
odor problems. Scum lines from these agents are produced on water
treatment basin walls and other containers. Fish and water fowl are
6-15
-------
adversely affected by oils in their habitat. Oil emulsions may adhere
to the gills of fish causing suffocation, and the flesh of fish is
tainted when they eat microorganisms that were exposed to oil spills.
Deposition of oil in the bottom sediments of water can serve to inhibit
normal benthic growth.
Levels of oil and grease which are toxic to aquatic organisms vary
greatly, depending on the type and the species susceptibility. How-
ever, it has been reported that crude oil in concentrations as low
as 0.3 mg/1 is extremely toxic to fresh-water fish.
Oil and grease in quantities of 100 1/sq km show up as a sheen on
the surface of a body of water. The presence of oil slicks prevent the
full aesthetic enjoyment of water. The presence of oil in water can also
increase the toxicity of other substances being discharged into the
receiving bodies of water.
Based on its harmful effects on the environment and in consideration of
aesthetic values of receiving streams and bodies of water, oil and grease
is selected as a pollutant parameter requiring the establishment of an
effluent limitation.
Chemical Oj£v_g_en Demand
The chemical oxygen demand is a measure of the quanitity of many organic
and inorganic oxidizabie materials present in water and varie? with
water composition, temperature, and other functions. Dissolved, oxygen
(DO) in water is a quality that, in appropriate concentrations, is
essential not only to keep organisms living but also to sustain species
reproduction, vigor, and the development of populations. Organisms
undergo stress at reduced DO concentrations that make their: less, cor--
petit!ve and able to sustain their stocks with.ii; the aquatic environ-
meac* For example, reduced DO coucentia ,io:iki have; Vx-cn Eho^r, to in-
terfere with iJ-sh population through delayed ho.tchir.g cf egns , reduced
si^e and vigor of embryos, production of deformities in young,-
interference with food digestion, acceleration of blood clotting, de-
creased tolerance to certain toxicaaLs. reduced food efficiency and
grovrch rale, cmcl maxirauiu sustciinod s^i.idling DPCOCU rish food orgardsr.s
are likewise affected adversely xn conditions v;itft suppressed DO.
Since all aerobic aquatic cr--9r a niseis need a. certain amount of oxygen,
the consequences of total lack of dissolved oxygen due to a high COD
can kill all the inhabitants of the aff«ctecl area.
:-5 f"
It lias been shown that fish may, under naturs.3 coudj t i onsf becor.se
matizfcd to low oxygen concentrations. Within certain limits, fish car1.
adjust their rate of respiration to compensate for changes in the con-
centration of dissolved oxygen. It is generally agreed, moreover, that
those species which are sluggish in movement (e.g.,carp, pike, eel)
6-16
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DRAFT
can withstand lower oxygen concentrations than fish (such as trout or
salmon) which are more lively in habit.
The lethal affect of low concentrations of dissolved oxygen in water
appears to be increased by the presence of toxic substances, such as
excessive dissolved carbon dioxide, ammonia, cyanides, zinc, lead,
copper, or cresols. With so many factors influencing the affect of
oxygen deficiency, it is difficult to estimate the minimum safe con-
centrations at which fish will be unharmed under natural conditions.
Another pertinent test for measuring oxygen demand is the Biochemical
Oxygen Demand (BOD) test. The COD parameter, however, is selected over
BOD because it is faster and easier to test and more reliable in
analysis. Further, the COD parameter is more applicable to the Machin-
ery and Mechanical Products Manufacturing industries since was-ewater
constituents are both organic and inorganic and COD is a measure of
both oxygen demands whereas BOD is a measure of the organic oxygen
demand.
Within the Machinery and Mechanical Products Manufacturing poir.r source
category, COD is a pollutant parameter for all segments where zhere is
a potential for wastes that lead to oxygen consumption. Such wastes
include nitrites, sulfides, and sulfites.
Phosphates
Phosphorous occurs in natural waters and in wastewaters almost soley in
the form of various types of phosphate. These forms are commor.ly class-
ified into orthophosphates, condensed phosphates (pyro-, meta-, and
polyphosphates), and organically bound phosphates. These may occur in
the soluble form in particles of detritus, or in the bodies of aquatic
organisms.
The various forms of phosphates find their way into wastewaters from a
variety of sources within the Machinery and Mechanical Products Manu-
facturing point source category. Small amounts of certain condensed
phosphates are added to some water supplies in the course of treatment,
while large quantities of the same compounds may be added when the
water is used for laundering or other cleaning since these materials
are major constituents of many commercial cleaning preparations. In
addition, phosphate coating of metals is a major source of phosphates
in effluents in the point source category.
6-17
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UNA1- I
The increasing problem of the growth of algae in>5t£eaiEs^and; lak<|s .%.
appears to be associated with the increasing pres^ce^ofe^ejtt.ain dis»-
solved nutrients, chief among which is phosphoropSI ^hjospnorous is an*
element which is essential to the growth of organisms 'arid., it can often
be the nutrient that limits the growth that a body, jqf^water can supper-
In instances where phosphorous is a growth limiting nutrient, £he disj-
charge of sewage, agricultural drainage or certain -fndujit;ri-ai w _
a receiving water may stimulate the growth, in nuilsarice quantities, "ofTir
photosynthetic aquatic microorganisms and macroorganisms.; ^ "••«*>'
The increase in organic matter production by algae and plants
undergoing eutfophication has ramifications throughouf;:..tne aquatic
system. Greater demand is placed on the dissolved oxygen i«*the water
as the organic matter decomposes at the termination of the life^cycles,,
Because of this process, the deeper waters of the Ifake ~may becqr
tirely depleted of oxygen, thereby, destroying fish habitats
to the elimination of desirable species. The settling of partispulate
matter from the productive upper layers changes the character
bottom mud, also leading to the replacement of certain species by less
desirable organisms. Of great importance is the fact,,,that nutrients
inadvertently introduced to a lake are, for the most^part, trapped there
and recycled in accelerated biological processes, ^prisequentlypl
age done to a lake in a relatively short time "requires a many fold in-*
crease in time for recovery of the lake. , *" "** v_
^
Due to its potentially hazardous nature on receiving wat%rs, phosphates
are selected as a pollutant parameter requiring the establishmejat of
limitation.
Silver (Ag)
Silver is a soft lustrous white metal that is insoluble in watery-
and alkali. It is readily ionized by electrolysis andJias a parti-
cular affinity for sulfur and halogen elements. Irf'riature, silver
is found in the elemental state and combined in ores Such as
argentite (Ag2S), horn silver (AgCl), proustite (Ag3A5S3) , and
rgyrite (AgjlsEsB) .
From these ores, silver ions may be leached into ground waters and
surface waters, but since many silver salts such as the chlori
sulfide, phosphate, and arsenate are insoluble, silver ions ca
be expected to occur in significant concentration in natural waters
6-18
-------
uriAr i
Within the Machinery and Mechanical Products Manufacturing industries,
silver is used extensively. It is employed primarily in electroplating,
photographic equipment manufacture, soldering and brazing and battery
manufacture. Of these, the two major sources of soluble silver wastes
are the photographic and electroplating industries with about 30% of
U. S. industrial consumption of silver going into the photographic
industry. Silver is also used in its basic metal state for such items
as jewelry and electrical contacts. (Pure silver has the highest elec-
trical and thermal conductivity of all metals and processes the lowest
contact resistance.) In addition, silver is used in paints for making
printed circuits.
While silver itself is not considered to be toxic, most of its salts
are poisonous due to anions present. Silver compounds can be absorbed
in the circulatory system and reduced silver deposited in the various
tissues of the body. A condition known as argyria, a permanent greyish
pigmentation of the skin and mucous membranes, can result. Concentra-
tions in the range of 0.4-1 mg/liter have caused pathologic changes in
the kidneys, liver and spleen of rats.
Because of its toxic potential and its extensive use, silver is selected
as a pollutant parameter requiring the establishment of an effluent
limitation.
Zinc (Zri)
Occurring abundantly in rocks and ores, zinc is readily refined into a
stable pure metal and is used extensively in the Machinery and Mechani-
cal Products Manufacturing point source category as a metal, an alloy,
and a plating material. In addition, zinc salts are also used in paint
pigments, dyes, and insecticides. Many of these salts (for example,
zinc chloride and zinc sulfate) are highly soluble in water; hence, it
is expected that zinc might occur in many industrial wastes. On the
other hand, some zUnc salts (zinc carbonate, zinc oxide, zinc sulfide)
are insoluble in water and, consequently, it is expected that some zinc
will precipitate and be removed readily in most natural waters.
In soft water, concentrations of zinc ranging from 0.1 to 1.0 mg/1 have
been reported to be lethal to fish. Zinc is thought to exert its toxic
action by forming insoluble compounds with the mucous that covers the
gills, by damage to the gill epithelium, or possibly by acting as an
internal poison. The sensitivity of fish to zinc varies with species,
age, and condition, as well as with the physical and chemical character-
istics of the water. Some acclimatization to the presence of the zinc
-------
UKAfl
is possible. It has also been observed that the effects of zinc poi-
soning may not become apparent immediately so that fish removed from
zinc-contaminated to zinc-free water (after four to six hours of expo-
sure to zinc) may die 48 hours later. The presence of copper in water
may increase the toxicity of zinc to aquatic organisms, but the presence
of calcium or hardness may decrease the relative toxicity.
A complex relationship exists between zinc concentrations, dissolved
oxygen, pH, temperature, and calcium and magnesium concentrations.
Prediction of toxicities has been less than reliable and controlled
studies have not been extensively documented.
Concentrations of zinc in excess of 5 mg/1 in raw water used for drink-
ing water supplies cause an undesirable taste which persists through
conventional treatment. Zinc can have an adverse effect on man and
animals at high concentrations.
Observed values for the distribution of zinc in ocean waters varies
widely. The major concern with zinc compounds in marine waters is not
one of actute toxicity, but rather one of the long term sublethal ef-
fects of the metallic compounds and complexes. From an acute toxicity
point of view, invertebrate marine animals seem to be the most sensitive
organisms tested.
A variety of freshwater plants tested manifested toxic symptoms at con-
centrations of 10 mg/1. Zinc sulfate has also been found to be lethal
to many plants and it could impair agricultural uses.
Due to its toxicity, zinc is selected as a pollutant parameter re-
quiring the establishment of an effluent limitation.
RATIONALE FOR NOT SELECTING CERTAIN POLLUTANTS
AS PARAMETERS foil EFFLUENT LIMITATIONS
Color
Color is not used normally for the measurement of pollutants in waste-
water streams, but is a parameter for determinirig the presence of cer-
tain dissolved solids. Color may be the effect of natural mineral or
vegetable origins, or it could be caused by metallic substances, tannins,
algae, weeds, and protozoa. Color cannot determine the toxicity of sub-
stances. It is effectively controlled by limitations on other pollu-
tants that could color the effluent. Therefore, color is not considered
a significant pollutant parameter in itself in the Machinery and Mechan-
ical Products Manufacturing point source category.
-------
DKAh I
Turbidity
Turbidity of water is related to the amount of suspended and colloidal
matter contained in the water stream. It affects the clearness and
penetration of light. The degree of turbidity is only an expression
of one effect of colloidal solids upon the character of the water.
Turbidity is thus indirectly measured and controlled independently by
a limitation on suspended solids.
Odor
Disagreeable odors and tastes in water are usually associated with a
large variety of objectionable substances. In particular, living
micorscopic organisms, decaying vegetation, decaying organic matter,
sewage and industrial waste products could cause odor problems. Odor-
ous substances in water must be vaporizable in order to be detected.
This method of detection is not objective and due to the lack of pre-
cision, odor is not considered as a pollutant parameter for the
Machinery and Mechancial Products point source category. In addition,
specific causes of an odor problem can be detected by monitoring other
pollutant parameters.
Acidity
Acidity is a measure of the effects of a combination of substances
and conditions in water. It is defined as the ability of a water
to neutralize hydroxyl ions and is expressed in terms of the calcium
carbonate equivalent of the hydroxyl ions neutralized. Acidity should
not be confused with pH value. Depending on the buffering capacity
of the water, water may have a higher total acidity at pH values of
7.0 than other waters with a pH value of 6.0.
Excessive acidity in water is detrimental to equipment in treatment
plants and can cause zinc to go into solution when in contact with
galvanized pipes. Nickel in soils may be put into solution when
irrigation water is highly acidic and cause severe injury to plants.
6-21
-------
In general, however, moderate acidity is beneficial to plants in
alkali soils.
Mineral acid pollution of natural water is detrimental to fish even
when introduced into waters which are originally acid in pH ranges
as low as 4.1.
Acidity is not a pollutant in itself. With the control of pH of
effluent waste streams in the point source category, the addition
of acidity as a pollutant parameter subject to an effluent limitation
is not required because the control of pH will maintain a balance
between the acidic and alkaline content of wastewaters.
Alkalinity
Alkalinity is not considered a pollutant in itself but is a combined
effect of several substances and conditions. Alkalinity is caused
by the presence of carbonates, bicarbonates, hydroxides and to a lesser
extent by borates, silicates, phosphates and organic substances. Alka-
linity is related to pH, but high alkalinity in water should not be
confused with high pH values.
Alkalinity in itself is not detrimental to humans, but it is asso-
ciated with high pH values, hardness and excessive dissolved solids.
All of these may be deleterious. Alkalinity is detrimental in some
industries such as food processing, but is beneficial in some metal
working industries primarily because it neutralizes acids.
In fish and other aquatic life, concentrations of strong alkalis,
insufficient to raise the pH value of natural water above 9.0,
have not proved to be harmful to full grown fish. Harmful effects
to normal development of fish may occur, however, at lower values of
pH. This is dependent upon other substances that are introduced into
the water.
In the Machinery and Mechanical Products Manufacturing point source
category, alkalinity is not selected as a pollutant parameter sub-
ject to effluent limitations. An effluent limitation for pH is
sufficient to control the balance between alkalinity and acidity of
waste streams.
6-22
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DRAFT
Ammonia (NH3J
Ammonia occurs in surface and ground waters as a result of the decom-
position of nitrogenous organic matter. It is one of the constituents
of the complex nitrogen cycle. It may also result from the discharge
of industrial wastes from chemical or gas plants, from ice plants, or
from scouring and cleaning operations where "ammonia water" is used.
Ammonia exists in its non-ionized form only at higher pH levels and is
the most toxic in this state. The lower the pH, the more ionized am-
•onia is formed, and its toxicity decreases. Ammonia, in the presence
of dissolved oxygen, is converted to nitrate (NO3J by nitrifying bac-
teria. Nitrite (N02J, which is an intermediate product between ammonia
and nitrate, sometimes occurs in quantity when depressed oxygen condi-
tions permit. Ammonia can exist in several other chemical combinations,
including ammonium chloride and other salts.
Although ammonia is toxic, it is not selected as a pollutant parameter
requiring an effluent limitation because there is no BPT treatment
available. The application of air stripping for ammonia removal is
not considered practical without segregation of high ammonia bearing
waste streams which requires process modification. Although ammonia
is n«t selected for the application of an effluent limitation, care
should be taken by plants using it to limit its discharge because of
its toxicity.
Dissolved Oxygen
Inadequate dissolved oxygen in surface waters may contribute to an
unfavorable environment for fish and other aquatic life, and the
absence of dissolved oxygen may give rise to odoriferous products of
anaerobic decomposition. The specific impact of dissolved oxygen on
the aquatic environment was covered under the heading of chemical
oxygen demand(COD). * Because dissolved oxygen is incorporated into
the COD parameter (selected as a pollutant parameter), it is not
selected as a parameter requiring the establishment of a specific
limitation.
Conductance
Conductance is a measure of the ion-concentration activity in water.
In studies of water for use in irrrigation and fish production, salin-
ity is often expressed as specific electrical conductance. The effect
of salinity or salt concentration in water is to increase the osmotic
pressure. With an increase of osmotic pressure, water may be drawn
from the gills and other delicate organs of the fish causing exten-
sive damage.
1
-------
The effluent limitation for specific metals controls some of the
ion concentration of waste streams. Therefore/ there is no nec-
essity to also make conductance a pollutant parameter.
Chlorine (Cl)
Chlorine is not a normal constituent of waters and should not be con-
fused with chlorides which are. Chlorine is the elemental form of a
greenish-yellow gas that dissolves readily in water. Free available
chlorine (HOC1 and the OC1 negative ion) and combined available
chlorine (the chloramines) may appear briefly in surface or ground
waters as a result of discharges from municipal sewage treatment
works or industrial processes. In the chlorination of sewage and
treatment plant effluents before discharge to a water course, it is
customary to add chlorine in an amount equivalent to or exceeding the
chlorine demand.
Industrial processes most likely to contain free or combined chlorine
are those employing bleaching operations, e.g., textile mills and
paper pulping operations, or those using chlorine for the control of
organisms in cooling waters.
It is generally agreed that the small amounts of chlorine present in
chlorinated water are dissipated by reaction with saliva and gastric
juices as soon as the water is swallowed. It has been reported that
50 to 90 mg/1 of chlorine in drinking water have been used by humans
without adverse effect.
Because of its relatively non-toxic character and because it is an
integral part of industrial waste treatment, chlorine is not selected
as a pollutant parameter requiring the establishment of an effluent
limitation.
Sulfides
Sulfides are constituents of many industrial wastes such as those from
tanneries, paper mills, chemical plants, and gas works. They are also
generated in sewage and some natural waters by the anaerobic decom-
position of organic matter. When added to water, soluble salts such
as Na^S dissociate into sulfide ions which in turn react with the
hydrogen ions in the water to form the HS negative ion or H2S, the
proportion of each depending upon the resulting pH value.
6-24
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DRAFT
Owing to the unpleasant taste and odor which results when sulfidas
occur in water, it is unlikely that any person or animal will consume
a harmful dose. The toxicity of solutions of sulfides on fish in-
creases as the pH value is lowered. Thus, the H2S or HS ion (present
at low pH) , rather than the sulf ide ion (present at high pH) , appears
to be the toxicity cause.
Due to the relatively low concentrations of sulfides found within the
Machinery and Mechanical Products Manufacturing point source category,
and because they are sometimes employed in waste treatment as metal
precipitators , sulfides are not selected as a pollutant parameter re-
quiring the establishment of an effluent limitation.
Hardness
Hardness is the term applied to the soap precipitizing power of water.
Any substance that forms an insoluble curd with soap causes hardness
in water. This is principally attributable to calcium and magnesium
ions.
Hardness, like acidity and alkalinity, is expressed in terms of
but the hardness of water is not necessarily equal to either acidity
or alkalinity. Hardness above 120 mg/1 is considered unsuitable for
general domestic purposes, but levels of hardness over 2 mg/1 is a
limiting value for boiler feedwater operating over 400 psi.
Hardness in itself is not considered to be toxic but it can reduce
the toxicity of many metals that appear in industrial wastes. Because
of the beneficial effects of hardness in reducing toxic effects of
other pollutants in the Machinery and Mechanical Products Manufactur-
ing point source category and the non-toxic nature of the parameter,
no limitations are established for hardness.
Total Solids
Total solids consist of dissolved solids, suspended solids and settle-
able solids. Suspended solids can be segmented further into fixed
and volatile solids. Settleable solids are that volume of solids that
settle out in one hour under certain conditions.
Total solids is not selected as a pollutant parameter because indivi-
dual tests for each of the constituents is required and it is thus
more definitive to handle total solids by its constituents. Of the
tests for the various solids constituents, the test for suspended
solids shows the best results in determining the wastewater solids
characteristics and is thus the one selected for an effluent limitation.
-------
Settleable Solids
Settleable solids are those solids that are held in suspension in
water streams and tend to settle to the bottom after a period of time.
These solids can be made up of sewage and industrial sludges.
Settleable solids cover stream bottoms smothering bottom organisms,
destroying spawning beds, blanketing bacteria, fungi and decomposing
organic wastes. Deposits of solids interfere with recreation, navi-
gation, fish and shellfish production and destroy aesthetic values of
water.
Criteria for controlling suspended solids (selected as a pollutant para-
meter) effectively control Settleable solids since any solid that is of
sufficient size to be Settleable will be removed from waste streams by
methods controlling suspended solids. Because of this, settleable
solids in the Machinery and Mechanical Products Manufacturing indust-
ries do not require an effluent limitation.
Algicides
Algicides are chemicals which are added to solutions for the purpose
of killing algae or preventing the growth of algae. In industry, they
are sometimes used in cooling towers, added to closed loop cooling
water systems, and added to water soluble cutting oils to extend their
life. Such uses, however, are not widespread.
Because of their rare occurrence within the Machinery and Mechanical
Products Manufacturing point source category, algicides are not select-
ed as a pollutant parameter requiring the establishment of an effluent
limitation.
Aluminum (Al)
Aluminum is the most abundant metal to be found in the earth's crust
(8.1%), but is never found free in nature. Pure aluminum, a silvery-
white metal, possesses many desirable characteristics. It is light,
non-toxic, has a pleasing appearance, can easily be formed, machined,
or cast, has a high thermal conductivity, and has excellent corrosion
resistance. It is non-magnetic and non-sparking and stands second
among metals in the scale of malleability and sixth in ductility.
Although the metal itself is insoluble, some of its salts are readily
soluble. Other aluminum salts are quite insoluble, however, and con-
sequently aluminum is not likely to occur for long in surface waters
because it precipitates and settles or is absorbed as such compounds
as aluminum hydroxide and aluminum carbonate. Aluminum is also non-
toxic and its salts are used as coagulants in water treatment. Further-
more, aluminum is commonly used as a base metal in cooking utensils
and there is no known physiological effect on man from low concen-
trations of this metal in drinking waters.
6-26
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DRAFT
Due to its non-toxic nature and affinity for settling out of surface
waters, aluminum is not selected as a pollutant parameter.
Antimony (Sb)
Antimony is an elemental metal that is not abundant in nature in a pure
state but is found in over 100 mineral species. Antimony forms salts
with +3 and +5 valences. The trichloride, sulfate, potassium tartrate,
and pentachloride are soluble in water, but the anitmony tends to be
precipitated as Sb203_ or Sb205^. The sulfides are insoluble in water.
Consequently, any cfissolved antimony that might be discharged to natural
waters soon precipitates and is removed by sedimentation or adsorp-
tion.
In the Machinery and Mechanical Products Manufacturing industries, anti-
mony is found as an alloy in lead, zinc, and copper and, thus, machined
and processed as an alloy. It is also found in paints and in the manu-
facture of batteries, type metals, and cable sheathing.
There is no evidence that anitmony is an essential element in human
nutrition, but it has been found to be toxic. The compounds of antimony
are poisonous and classed as acutley moderate or chronically severe.
According to this categorization, moderate toxicity includes injury to
internal organs and severe toxicity means debilitating effects or
death. A dose of 97.2 mg of antimony has reportedly been lethal to
an adult. Antimony has been used for treatment of certain tropical para-
sitic diseases but is no longer recommended because of the frequency
and severity of toxic reactions.
Antimony can be concentrated by certain forms of aquatic life to over
300 times its concentration in the surrounding waters. The salts of
antimony in tests on various fish and aquatic life give mixed results
on toxicity dependent on the salt, temperature, hardness of the water,
and dissolved oxygen present.
Although toxic, antimony is not selected as a pollutant parameter
requiring an effluent limitation since it was only found in relatively
low concentrations in the raw waste streams of the point source category,
Arsenic (As)
Arsenic is found to a small extent in nature in the elemental form.
It occurs mostly in the form of arsenites of metals or as pyrites.
In the Machinery and Mechanical Products Manufacturing industry, arse-
nic is sometimes used for hardening and improving the sphericity of
shot, as a constituent in some plating baths, and is finding an in-
creasing use as a doping agent for solid state devices, especially
transistors. It is also found as an ingredient in dyes and in the
smelting and refining of some metals, particularly lead and zinc.
-------
The major use of arsenic is as an insecticide and poison for pest con-
trol in the home and in industry. Recently, arsenicals have found some
usefulness in livestock production, mainly as a coccidiostat in poultry
feeding or in "dip" solutions for animals. Up to 5 mg/1 of sodium arsenat
in drinking water functions in some way to reduce selenium poisoning
in farm animals.
Severe human poisoning can result from injection of as little as 100 mg
of arsenic and less than 130 mg has proved fatal. Arsenic can accumu-
late in the body faster than it is excreted and can build to toxic
levels from small amounts taken periodically through the respiratory and
intestinal walls from air, water and food. Surface water criteria
for public water supplies have set a permissible level of arsenic in
those waters at .05 mg/1.
Arsenic in forms such as lead arsenate, calcium arsenate and paris
green (copper acetoarsenite) have been used as insecticides with the
most toxic of these substances being paris green. Since the advent
of DDT and other substances these compounds have been replaced.
Because of the relatively small quantities of arsenic and its com-
pounds found within the Machinery and Mechanical Products Manufac-
turing point source category, it is not selected as a pollutant
parameter. However, because of its toxicity, care should be taken by
industries that use it to prevent it from being discharged in waste-
waters .
Barium (Ba)
Barium is an alkaline earth metal rapidly decomposed by water to form
barium ions. Many of its salts are soluble, but the carbonate and
sulfate are highly insoluble. Consequently, it is to be expected
that any barium ions discharged to natural waters are quickly precipi-
tated and removed by adsorption or sedimentation. Barium and its salts
have many uses in the metallurgical industry (for special alloys), in
the paint industry, in the ceramic and glass industries, and in the
medical technology industry (for x-ray diagnosis).
Barium has no proven accumulative effects on humans and is eliminated
more rapidly than calcium. However, a mandatory limit of 1 mg/liter
has been issued for the amount of barium in domestic water supplies due
to possible toxic effects of barium on the heart, blood vessels and
nerves. A fatal dose is somewhere in the order of 550 to 600 mg.
The ease with which barium is precipitated causes it to be removed
from wastewater streams of the Machinery and Mechanical Products Man-
ufacturing point source category with a limitation on suspended solids.
Because of this, barium is not considered as a pollutant parameter.
6-28
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DRAFT
Beryllium (Be)
Beryllium is found in some 30 mineral species, the most important com-
mercial source being beryl. A relatively rare element, it is not likel
to occur in natural waters. Although the chloride and nitrate forms ar
very soluble in water and the sulfate moderately so, the carbonate and
hydroxide are almost insoluble in cold water.
Beryllium is employed as an alloying agent in producing beryllium cop-
per which is used extensively for springs, electrical contacts, spot
welding electrodes, and non-sparking tools. It is also used to produce
special alloys in the manufacture of x-ray diffraction tubes and elec-
trodes for neon signs. It is finding application as a structural mater
ial for high speed aircraft, missiles, and spacecraft and is now used
in nuclear reactors as a reflector or moderator. It also finds use in
gyroscopes, computer parts, and inertial guidance systems.
Beryllium and its compounds, when present in the environment, are of
concern because of their effect on the health of humans and animals
since beryllium is among the most toxic and hazardous of the nonradio-
active substances being used in industry. Almost all the presently
known beryllium compounds are acknowledged to be toxic in both the sol-
uble and insoluble forms. The toxicity of beryllium is much less in
water than in the atmosphere since absorption of beryllium from the
alimentary tract is slight (about 0.006 percent of that ingested), and
excretion is fairly rapid. Beryllium is considerably more toxic in
soft water than in hard water. In nutrient solutions at acid pH values
beryllium is highly toxic to plants.
Concentrations of beryllium sulfate complexed with sodium tartrate up
to 28.5 mg/1 are not toxic to goldfish, minnows, or snails. The
96-hour minimum toxic level of beryllium sulfate for fathead minnows
has been found to be 0.2 mg/1 in soft water and 11 mg/1 in hard water.
The corresponding level for beryllium chloride is 0.15 mg/1 in soft
water and 15 mg/1 in hard water.
Although toxic, beryllium is not selected as a pollutant parameter
requiring an effluent limitation since it was only found in relatively
low concentrations in the raw waste streams of the Machinery and
Mechanical Products Manufacturing point source category.
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Boron (B)
Never found in nature in its elemental form, boron occurs as sodium
borate (borax) or as calcium borate (colemanite) in mineral deposits
and natural waters of Southern California and Italy. Elemental boron
is used in nuclear installations as a shielding material (neutron
absorber). It is also used in metallurgy to harden other metals.
Boric acid and boron salts are used extensively in industry for such
purposes as weatherproofing wood, fireproofing fabrics, manufacturing
glass and porcelain and producing leather, carpets, cosmetics and
artificial gems. Boric acid is used as a bactericide and fungicide
and boron, in the form of boron hydrides or borates, is used in high
energy fuels.
Boron is present in the ordinary human diet at about 10 to 20 mg/day,
with fruits and vegetables being the largest contributors. In food
or in water, it is rapidly and completely absorbed by the human system,
but it is also promptly excreted in urine. Boron in drinking water
is not generally regarded as a hazard to human beings as it has been
reported that boron concentrations up to 30 mg/1 are not harmful.
Due to its non-toxic nature and the small amount found within the
Machinery and Mechanical Products Manufacturing point source category,
boron is not selected as a pollutant parameter requiring the establish-
ment of a limitation.
Calcium (Ca)
Calcium as an elemental metal does not occur naturally because it
is oxidized readily in air and reacts in water to form hydrogen
gas. Calcium is the fifth most abundant metal in the earth's crust
and its most common form is limestone and appite.
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DRAFT
Calcium is used as a reducing agent in preparing other metals and as
a dexodizer, desulfurizer or decarburizer for various ferrous and
nonferrous alloys. It is also used as an alloying agent with alumi-
num, beryllium, copper, lead and magnesium.
Calcium is essential to human body development and minimum daily re-
quirements have been set for proper nutrition. However, calcium is
a hardness element in water and limits in domestic water are set not
because of hazards to health, but because of hardness disadvantages
to other household uses.
Calcium reduces the toxicity of many chemical compounds and is used
extensively in water treatment in the form of lime. Due to the benefi-
cial qualities and the use of calcium in the treatment of effluents
in the Machinery and Mechanical Products industries, calcium is not
considered as a pollutant parameter requiring an effluent limitation.
Chlorides
Chlorides are found in practically all natural waters. They may be: (a)
of natural mineral origin or derived from a sea-water contamination
of underground supplies, (b) salts spread on fields for agricultural
purposes, (c) human or animal sewage, or (d) industrial effluents,
such as those from paper works, galvanizing plants, water softening
plants, oil wells and petroleum refineries.
The human tolerance for chlorides varies with climate and exertion.
Chlorides lost through perspiration are replaced by chlorides in
either the diet or drinking water. From hot dry areas, there are
reports that chloride concentrations up to almost 900 mg/1 have not
been harmful. Chloride concentrations of 1500 mg/1 are reported to
be safe for cattle, sheep, swine and chickens. Also, 2000 mg/1 of
chloride has been reported as not harmful to some fish.
Because of its non-toxic nature, chlorides are not selected as a
pollutant parameter requiring the establishment of a limitation.
Chlorinated Hydrocarbons
The chlorinated hydrocarbons include a large number of chemicals with
high insecticidal and biocidal activity. Included in this group are
DDT, dieldrin, chlordane, toxaphene, aldrin, heptachlor, DDE, benzene
hexachloride, and chlorinated benzenes. The chlorine-carbon bond is
relatively stable. Few bacteria and fungi are equipped to break it.
Thus, they are especially resistant to degradation to nontoxic end
products, and many persits for months or years following application.
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In industry, a major use of chlorinated hydrocarbons is for degreasing
with such agents as trichloroethylene and perchloroethylene. They are
also intermediates in the manufacture of phenol, ahiline, DDT, and
dyes and are employed as solvents in film and fiber manufacturing and
are key components in the production of certain plastics.
Chlorinated hydrocarbons are not very soluble in water but are very
soluble in nonpolar media such as lipids. They are, therefore, read-
ily concentrated by organisms from the environment and accumulated
in fatty tissues. Species higher in the food chain subsequently ac-
cumulate the chlorinated hydrocarbons in their food. Since the
chlorinated hydrocarbon biocides are toxic to a wide spectrum of
animal life, they have the capacity to cause harm to many nontarget
organisms.
Although chlorinated hydrocarbons are toxic and persistent, they are
not selected as a pollutant parameter requiring the establishment of
an effluent limitation because there is not BPT treatment for them.
Care should be taken to preclude them from effluent waste streams
and they may be controlled as a toxic pollutant under Section 307A
of the Act.
Dissolved Iron
Dissolved iron results primarily from the leaching of iron salts
from rocks and soils in natural waters. This quantity of dissolved
iron is further increased from industrial wastes, primarily from
pickling operations. Although many of the ferric and ferrous salts
are highly soluble in water, the ferrous ions are readily oxidized
in natural surface waters to the ferric condition to form insoluble
hydroxides. These precipitates tend to agglomerate, flocculate and
settle or be absorbed on surfaces; hence, the concentration of iron
in well-aerated waters is seldom high.
With limitations recommended for total iron and suspended solids and
the natural propensity of the ferric and ferrous ions to precipitate
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DRAFT
out of solution, the establishment of a limitation for dissolved iron
is not required.
Magnesium jMg)
Magnesium is an elemental metal that is the eighth most abundant ele-
ment in the earth's crust. It is not found uncombined but is found
in large deposits in the form of magnestite, dolomite and other
minerals. Magnesium is an essential element in the manufacture of
lightweight alloys and in the manufacture of electrical and optical
apparatus. It is also used in photography, flares, pyrotechnics and
in incendiary bombs. Some of its salts are used extensively in medi-
cine as an antacid and laxative.
Magnesium is an essential mineral element for humans, animals and
normal plant growth. Most of its salts are freely soluble in water.
At high pH values the magnesium ion is precipitated. High concentra-
tions of some magnesium salts have been reported as toxic to some
fish and retard growth of rats.
Magnesium is effectively controlled by establishing effluent limita-
tions for other heavy metals, such as iron. Because of this and
the fact that it is essential to human, animal and plant nutrition,
magnesium is not considered a pollutant parameter requiring an effluent
limitation.
Manganese (Mn)
Manganese is an elemental metal whose minerals are widely distributed
primarily as oxides, silicates and carbonates. The metal and its
salts are used extensively in steel alloys, in dry cell batteries,
in glass and ceramics, in inks and dyes, in the manufacture of paints
and varnishes, in matches and fireworks, and in agriculture.
Manganese is an essential nutrient in plant and animal life. Defi-
ciencies of manganese in animals produce lack of growth, bone abnor-
malities and symptoms of central nervous system disturbance. However,
manganese is toxic to humans but only in extremely high concentrations
and appears somewhat antagonistic to the toxic action of nickel on fish.
The toxicity of manganese to animals is considered small, although some
cases of manganese poisoning have been reported due to unusually high
concentrations.
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The overall nontoxic nature of manganese, except at very high concen-
trations, and its requirement as an essential nutrient for plant
and animal life precludes it from consideration as a pollutant requiring
an effluent limitation. Further, effluent limitations and required
treatments for iron and other metals effectively reduce the quantity of
manganese in wastewater streams of the Machinery and Mechanical Products
point source category.
Molybdenum (Mo)
Molybdenum is used principally in the metallurigal industry as an al-
loying element for the production of high strength alloys. It is also
used in the electrical and electronic industries as wire for filament,
grid and screen material in electronic tubes.
Molybdenum appears to be an essential requirement as a trace element
in low concentrations for some animals and in soils for some plants.
The metal and its salts are not considered to be a water pollutant at
this time in some studies.
Due to its apparent nontoxic nature (at least at relatively low con-
centrations) and the fact that high concentrations are controlled by
treatment for other heavy metals, molybdenum is not considered as a
pollutant parameter for the Machinery and Mechanical Products Manufac-
turing industries. Limitations for other heavy metals effectively
control concentrations of molybdenum.
Nitrates
Nitrates are the end product of the aerobic stabilization of organic
nitrogen, and as such, they occur in polluted waters that have under-
gone self-purification or aerobic treatment processes. Nitrates also
occur in percolating ground waters as a result of an excessive appli-
cation of fertilizer or leaching from cesspools. In a few instances,
nitrates may be added to a stream or ground water by natural degrada-
tion or added directly by inorganic industry wastes, but such sources
are insignificant. Wastes from chemical fertilizer producing plants
are an important source of nitrate pollution.
In spite of their many sources, nitrates are seldom abundant in natural
surface waters for they serve as an essential fertilizer for all types
of plants, from phytoplankton to trees. Photosynthetic action con-
stantly utilizes nitrates and converts them to organic nitrogen.
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DRAFT
High nitrate concentrations in water stimulate the growth of plankton
and aquatic weeds. By increasing plankton growth and the development
of fish food organisms, nitrates indirectly foster increased fish
production.
However/ in high concentrations nitrates may produce in man a condi-
tion known as methemoglobinemia ("blue baby syndrome") if converted to
nitrite. This generally affects infants under six months old.
Due to their relatively low toxicity at the concentrations found with-
in the Machinery and Mechanical Products Manufacturing industries,
nitrates are not selected as a pollutant parameter requiring the es-
tablishment of a limitation.
Nitrites
In water, nitrites are generally formed by the action of bacteria upon
ammonia and organic nitrogen. Because they are quickly oxidized to
nitrates, they are seldom present in surface waters in significant
concentrations. In conjunction with ammonia and nitrate, nitrites in
water are often indicative of pollution. In addition, nitrates in high
concentrations may cause methemoglobinemia in infants.
Because of their propensity to oxidize to nitrates and because of
the relatively low concentrations found within the Machinery and Mech-
anical Products Manufacturing point source category, nitrites are not
selected as a pollutant parameter requiring the establishment of a
limitation.
Kjeldahl Nitrogen
Total kjeldahl nitrogen approximates the total ammonia and a portion
of organic nitrogen in water. The organic nitrogen content in water
is contributed to in various degrees by amino acids, polypeptides and
proteins - all products of biological processes.
For irrigation purposes, nitrogen in any form is seldom deleterious.
In fact, it is usually beneficial since nitrogen compounds form the
basis of most organic and chemical fertilizers.
For algae, Crustacea, and other fish-food organisms, the total con-
centration of nitrogen is not as important as the form in which it
exists. Organic nitrogen, amino acids and ammonia may inhibit
biological growth, nitrates stimulate phytoplankton. On the other
hand, fish production is highest in ponds and streams containing the
most organic nitrogen.
Since ammonia is non-toxic and organic nitrogen is usually beneficial,
the sum of the two, Kjeldahl nitrogen, is not selected as a pollutant
requiring the establishment of a limitation.
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Biochemical Oxygen Demand (BOD)
Biochemical Oxygen Demand is the quantity of oxygen required by bac-
teria in water to utilize some of the organic matter (misses some
slowly oxidized matter) introduced into the water. The rate of this
reaction is assumed to be proportional to the concentration of the
remaining degradable organic matter, measured in terms of dissolved
oxygen.
As a parameter indicating the detrimental effects of organic matter
upon a surface water, BOD value alone means very little. In itself,
BOD is not a pollutant. Only by depressing the dissolved-oxygen content
to levels that are inimical to fish life and other beneficial uses does
BOD exert an indirect effect. Where reaeration, dilution, and/or phot-
synthetic action offset or minimize this depletion, BOD does not inter-
fere with the uses of water.
Because the COD test is considered faster and oxidizes more organic
and inorganic material than the BOD test, biochemical oxygen demand
is not selected as a parameter requiring the establishment of a lim-
itation.
PCB's
Polychlorinated biphenyl (PCB's) is a generic term covering a family
of partially or wholly chlorinated isomers of biphenyl. The commercial
mixtures generally contain 40-60% chlorine with as many as 50 different
detectable isomers present. The PCB mixture is a colorless, viscous
fluid relatively insoluble in water that can withstand very high
temperatures without degradation. PCB's do not conduct electricity,
and the more highly chlorinated isomers are not readily degraded in
the environment.
Within the Machinery and Mechanical Products Manufacturing industries,
PCB's could be used in paints, inks, and plastics. They are also
found in hydraulic systems and in the manufacture of transformers
and capacitors.
The major uses of PCB's are a result of its nonconductivity and persis-
tence. These uses can be grouped in three major categories: open
uses, partially closed system uses, and closed system uses. Open
uses include paints, inks, plastics, and paper coatings. The PCB's
in all of these products contact with the environment and can be leached
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DRAFT
out by water. The so-called carbonless carbon paper contains PCB's
in the encapsulated ink and is claimed to be responsible for the PCB's
found extensively in recycled paper. PCB's have been used as plas-
ticizers in polyvinyl chloride (PVC) and chlorinated rubbers.
Uses of PCB's in partially closed systems include the working fluid
in heat exchangers and hydraulic systems. These systems have a po-
tential for leakage of the PCB fluid either during use or after being
discarded.
The electrical industry is the single major consumer of PCB's, mainly
in a closed loop system in transformers and capacitors. The fluid
is generally sealed into the unit so that the loss, if any, is small.
Transformers and capacitors account for about 63% of all PCB use.
It is not known exactly how PCB's are released into the environ-
ment or in what quantities. Analyses of water samples from 30 major
tributaries to the Great Lakes indicate widespread contamination,
with 71% of all samples having detectable concentrations (greater
than 10 parts per trillion). PCB's have been found in all organisms
analyzed from the north and south Atlantic, even in animals living
under 11,000 feet of water. The U. S. EPA has reported that one-third
of the human tissue sampled in the United States contains more
than one part per million (ppm) of PCB's.
Once in the environment, PCB's appear to persist for a very long
time. Evidence for this can be seen in the fact that in most areas
of the continent and throughout the Atlantic Ocean more PCB than
DDT is found in the animals, even though three times more DDT is pro-
duced each year, and all of it is put directly into the environment.
Based on present available data, it seems safe to assume that PCB's
are present in varying concentrations in every species of wildlife
on earth.
Liver damage is a common effect of PCB's while the occurrence of
edema, skin lesions, and reproductive failure depends on the species.
Hatchability of eggs is noticeably decreased by exposure to PCB's.
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Although PCB's are highly toxic and extremely persistent, they
are not selected as a pollutant parameter requiring the establish-
ment of an effluent limitation because there is no BPT treatment for
PCB's. Care should be taken to keep them from effluent waste streams
and they may be controlled as a toxic pollutant by Section 307A of
the Act.
Phenols
Phenols, defined as hydroxy derivatives of benzene and its condensed
nuclei, may occur in domestic and industrial wastewater and in drink-
ing water supplies. Chlorination of such waters can produce odoriferous
and objectionable tasting chlorophenols which may include o-chlorophenol,
p-chlorophenol, 2, a-dichlorophenol, and 2, 4-dichlorophenol.
Although described in the technical literature simply as phenols, the
phenol waste category can include a wide range of similar chemical
compounds. In terms of pollution control, reported concentrations of
phenols are thus, the result of a standard methodology which measures
a general group of similar compounds rather than being based upon
specific identification of the single compound, phenol (hydroxybenzene).
Within the Machinery and Mechanical Products Manufacturing industries,
phenols are used in some cutting oils and in the molding of plastics.
Cutting fluids can contain phenolic compounds since these materials
are normal constituents of hydrocarbon mixtures. In addition, phenolic
compounds are added to oils as preservatives or for odor control.
Phenolic compounds may affect fish in two different ways: first, by a
direct toxic action, and second, by imparting a taste to the fish
flesh. The toxicity of phenol towards fish increases as the dissolved
oxygen level is diminished, as the temperature is raised, and as the
hardness is lessened. Phenol appears to act as a nerve poison causing
too much blood to get to the gills and to the heart cavity and is
reported to have a toxic threshold of 0.1-15 mg/1.
Mixed phenolic substances appear to be especially troublesome in im-
parting taste to fish flesh. Chlorophenol produces a bad taste in
fish far below lethal or toxic doses. Threshold concentrations
for taste or odor in chlorinated water supplies have been reported as
low as 0.00001-0.001 mg/1. Phenols in concentrations of only one part
per billion have been known to affect water supplies.
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DRAFT
The ingestion of concentrated solutions of phenol by humans results
in severe pain, renal irritation, shock, and possibly death. A
total dose of 1.5 grams may be fatal.
Although they are toxic, phenols are not selected as a pollutant
parameter requiring the establishment of an effluent limitation
because there is no BPT treatment for phenols. Care should be taken
to preclude them from effluent waste streams and they may be controlled
as a toxic pollutant under Section 307A of the Act.
Potassium (K)
One of the more common elements, potassium constitutes 2.4 percent
of the crust of the earth and occurs in many minerals. It is one
of the most active metals and reacts vigorously with oxygen and water.
For this reason, it is not found free in nature but only in the
ionized or molecular form. Potassium resembles sodium in many of its
properties, and potassium salts can be substituted for sodium salts
in many industrial applications. The sodium salts, however, are gen-
erally less expensive and hence more frequently used. For fertilizers,
some varieties of glass, and a few other purposes, however, potassium
salts are indispensable. Because the common salts of potassium
(even the carbonate and hydroxide) are extremely soluble, they are
not readily separated from water by natural processes other than
evaporation.
In low to moderate concentrations potassium is essential as a nutri-
tional element for man, animals and plants. At higher levels, how-
ever, it acts as a cathartic towards humans and can be toxic to
fish in soft or distilled waters. The toxicity towards fish, how-
ever, can be reduced by calcium and to a lesser extent by sodium.
Because of the low concentrations found within the Machinery and
Mechanical Products Manufacturing industries, potassium is not
selected as a pollutant parameter requiring the establishment of a
limitation.
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UfJMT I
Selenium (Se)
Many organic compounds of selenium are known and wastewaters may
contain selenium in any of its four valence states. Analogous to
sulfur in many of its chemical combinations, selenium is used in
its elemental form and as several salts in a variety of industrial
applications, such as a pigment in paints, dyes, and glass production;
as a component of rectifiers, semiconductors, photo-electric cells,
and other electrical apparatus; as a supplement to sulfur in the
rubber industry; as a component of alloys; and for insecticide
sprays.
Selenium poisoning of humans and animals from ingestion of foods con-
taining toxic amounts of selenium has been and still is a problem of
great concern in the U. S. Arsenic and selenium are apparently anta-
gonistic in their toxicity, tending to counteract each other. Sele-
nium has a toxic effect upon man and animals comparable with that of
arsenic, giving rise to similar symptoms. Selenium salts are rapidly
and efficiently absorbed from the gastro-intestinal tract and excreted
largely through the urine. Selenium has also been suspected of caus-
ing dental cavities in man, and has been cited as a potential carcino-
genic agent.
Minute concentrations of selenium appear not to be harmful to fish
during an exposure period of several days. However, constant
exposure to traces of selenium has caused disturbances of appetite
and equilibrium, pathological changes, and even deaths of fish after
several weeks. Concentrations considered safe for human beings over
a period of weeks have been toxic to fish.
Because of the relatively small quantities of selenium found in the
Machinery and Mechanical Products Manufacturing Industries, it is
not selected as a pollutant parameter requiring the establishment of
a limitation. However, because of its toxicity, care should be taken
by industries that use it to prevent it from being discharged in
wastewaters.
Silica/Silicates/Silicon
The element silicon is not found free in nature but occurs as silica
in sand or quartz and as silicates in feldspar, kaolinite and other
minerals. Silica is used throughout the Machinery and Mechanical
Products Manufacturing industries, primarily as a mold for castings.
In addition, sodium silicates have been used as coagulants for the
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removal of turbidity and iron from wastewater streams.
Silica and silicates appear to have caused no adverse effects physio-
logically. Silica in water along with other necessary nutrients
favors the growth of diatoms. Silica is undesirable in boiler feed
water because it deposits on the tubes of heaters and on turbine
blades. Silica and silicates, except for hydrofluoric acid, are
insoluble in water or acid.
Silica/Silicate is not considered as a pollutant parameter since sili-
cates are used as a coagulant for other metals and silica/silicate is
non-toxic and possibly necessary for essential nutrition. Industries
requiring limits for silica below drinking water standards have norm-
ally set up treatment facilities to reduce the amount of silica in
their influent streams for their particular process.
SodiuM (Na)
Sodium does not occur free in nature but sodium compounds constitute
2.83% of the earth's crust. The most common compound is sodium chlo-
ride (NaCl). Most sodium salts are extremely soluble in water and
any sodium that is leached from soils or discharged into streams from
industrial wastes remains in solution. Sodium is the cation in many
salts used in industry and is the most common ion found in industrial
wastes.
Since sodium is so active as a metal and is normally the cation of
other metals, the treatment of effluents for various metals effectively
reduces the amount of sodium in wastewater. Therefore, sodium is not
considered a pollutant parameter subject to an effluent limitation for
the Machinery and Mechanical Products Manufacturing industries.
Strontium jSr)
This elemental metal is not found free in nature, but is found largely
with calcium or barium minerals. The finely divided metal ignites
spontaneously in air. Strontium salts are used in pyrotechnics,
signal lights, flares and matches. Its salts are also used extensive-
ly in medicine, in the refining of beet sugar (it is being replaced by
lime), in the manufacture of glass and paint, and in ceramics.
Strontium is thought to be essential for the growth of animals, espe-
cially in the calcification of bones and teeth. Non-radioactive
strontium salts taken orally by humans and animals have not produced
any deleterious effects. Fish and aquatic life have been found to
tolerate fairly large amounts of strontium salts.
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in the point source category„ &ec&ase oi: this and because of its
apparent non-toxic effects and its necessity as a trace element in
human and animal growth, it is not considered as a pollutant parameter
in the Machinery and Mechanical Product* Manufacturing industries.
Caution, however, must be taken to be certain that any strontium in
wastewater streams is not radioactive. The discharge of radioactive
material is regulated by the Atomic Energy Commission.
Sulfates
Sulfates occur naturally in waters, particulary in the western
United States, as a result of leachings from gypsum and'other common
materials. They also occur as the final oxidized state of sulfides,
sulfites and thiosulfates. Sulfates may also be present as the
oxidized state of organic matter in the sulfur cycle, but they in
turn, may serve as sources of energy for sulfate splitting bacteria.
Sulfates may also be discharged in numerous industrial wastes, such
as those from tanneries, sulfate-pulp mills, textile mills, and other
plants that use sulfates or sulfuric acid.
In moderate concentrations, sulfates are not harmful and it has been
reported that concentrations up to 1000 mg/1 are harmless. Irriga-
tion concentrations less than 336 mg/1 are considered to be good to
excellent.
Because of their relatively harmless nature and based on the low
levels found in the Machinery and Mechanical Products Manufacturing
industries, sulfates are not selected as a pollutant parameter requir-
ing the establishment of a limitation.
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urtAr i
Sulfites
Sulfur dioxide, a colorless, non-flammable gas with a suffocating odor,
is soluble in water at over 100,000 mg/1 at 20 Degrees C. The dissol-
ved gas combines with water to form sulfurous acid which in turn dis-
sociates to form the sulfite ion (98% of time at pH levels above 7).
In the presence of oxidizing agents such as dissolved oxygen and
chlorine, the sulfite ion is gradually oxidized to sulfate with the
sulfur changing oxidation number.
In domestic water, sulfur dioxide and sulfites are deleterious prim-
arily in that they lower the water pH value and increase its cor-
rosivity. Being oxidized and consuming dissolved oxygen, sulfates
may retard corrosion.
Because of the propensity of sulfites to oxidize to sulfates,
which are negatively harmless, sulfites are not selected as a pol-
lutant parameter requiring the establishment of a limitation.
Titanium (Ti)
Abundantly distributed in the earth's crust, titanium ores and salts
constitute 0.5 to as much as 10 percent of soil. Titanium is an inert
element that is similar to silicon in chemical and biological behavior.
It is present in plants, chiefly in the leaves, and trace amounts are
found in most animal tissues and organs.
Titanium metal is used as a constituent in several alloys. Titanium
salts, primarily the oxide, are used as pigments in the paint indus-
try, as a filler in paper making, as mordants in the dyeing industry,
in the manufacture of electronic apparatus, and in the glass and
ceramics industry. Although several of the salts (e.g. the ammonium
oxalate, nitrate, sulfate, and trichloride) are highly soluble. Tit-
anium dioxide is insoluble and tends to precipitate as a granular
material.
There is no evidence that tianium is essential for plant or animal
nutrition. It is not absorbed to any measurable degree by the human
intestine, but appears to be almost completely inert and innocuous
in the human alimentary system.
Because of the low concentrations of titanium in the point source
category and because of its inert and non-toxic nature, titanium is
not selected as a pollutant parameter requiring the establishment of
a limitation.
HI-
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Volatile Solids
Volatile solids are normally organic matter held in suspension in waste-
water streams. Standard methods determine the total amount of volatile
matter contained in a sample of water by evaporation and volatilizing
the residue. The appearance of volatile matter in wastewater streams
of the Machinery and Mechanical Products Manufacturing industry probably
comes where organic compounds are used such as in paints and oils.
Volatile solids are not selected as a pollutant parameter in the Machinery
and Mechanical Products Manufacturing industries because of the low
incidence of organic materials used in this industry (except in oils
which are recommended for control). Further, when volatile solids
do appear other than from oil, they are somewhat controlled with the
effluent limit set for suspended solids, ie, that portion of the volatile
solids that are suspended.
Surfactants
Certain solutes, even when present in low concentrations, have the pro-
perty of lowering the surface tension or other interfacial properties.
Such solutes are known as surface-active agents (surfactants), and their
unique effect is called surface activity. The surface-active agents
include soaps/ detergents, emulsiers, wetting agents, and penetrants.
Of these substances, the synthetic detergents are economically most im-
portant and are used in the greatest amounts.
Because some surfactants are biodegradable, their presence in effluent
streams will cause an oxygen demand and thus the limitation on
COD in the point source category will control the surfactants in
wastewater discharges.
Plasticizers
Plasticizers are chemicals which are added to natural and synthetic
rubbers and resins for flexibility. A limitation for plasticizers is
not set because of their rare appearance in the Machinery and Mechanical
Products Manufacturing point source category.
Bromide (Br)
Bromide is a compound derived from hydrobromic acid (HBr). Bromide
properties are similar to those of chlorides and iodides. Bromides are
usually produced from bromine, which in turn is obtained from salt brines
or sea water.
Bromides are used in medicine as sedatives in the treatment of nervous
disorders. Silver bromide is used in photographic films and paper.
Bromide is not considered as a pollutant parameter in the Machinery
and Mechanical Products Manufacturing industries since they have
not been found in any significant quantities in raw wastewater streams.
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DRAFT
Cobalt (Co)
Cobalt and its salts are used for making alloys, in nuclear technology,
as a pigment in the china and glass industry, and as binders in the tung-
sten-carbide tool industry. The chloride is used in ink, barometers,
hydrometers, and for galvanoplating. The nitrate is used as a pigment.
Cobalt salts may be divalent or trivalent. Solutions containing cobal-
tous ions are relatively stable, but cobaltic ions are powerful oxidizing
agents and consequently they are unstable in natural waters.
It has been reported that cobalt has a relatively low toxicity to man
and that traces of cobalt are essential to nutrition. Because of this
low toxicity and the small concentrations found in the Machinery and
Mechanical Products Manufacturing industries, cobalt is not selected
to be a pollutant parameter requiring the establishment of a limitation.
Thallium (Tl)
Thallium is an elemental metal. In its natural state, it is a mixture
of two isotopes. When freshly exposed to air it displays a metallic
luster, but soon develops a blueish-gray tinge. The metal is very soft
and malleable and can be cut with a knife. Thallium is found in crook-
site, lorandite and hutchinsonite. It is also present in pyrites
and is recovered from this ore in connection with the production of sul-
furic acid. It is also obtained as a by-product in the smelting of
lead and zinc ores.
Thallium does not have any important uses in industry, but can be
found with many of the low melting metals. It has been used with
lead as a strengthening agent. Thallium is used primarily as a rodenti-
cide and ant killer, but it is also used in the manufacture of photo
cells and infrared detectors. In addition, it has been used in the
production of low'temperature glasses and glass with a high index of
refraction. Its salts are used in dyes and in pigments for fireworks.
Thallium is a cumulative poison, four times as toxic as arsenious
oxide, and it affects the sympathetic nervous system. It causes muscula
pains, endocrine disturbances, burning of the skin, loss of coordination
and loss of hair. It does not occur normally in animal tissues, but
when taken into animal bodies, it is cumulative. Thallium salts, for
the most part, are highly soluble in water and, consequently, any indus-
trial discharges of this element are not likely to form precipitates
as carbonates, hydroxides, or other common compounds.
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DKAI-T
The turnover of thallium in the human body is extremely slow. Under
normal conditions, the tissues contain trace amounts of the metal. The
biological mechanism by which thallium produces its effects on the human
body is not well understood, but as with other metals, it appears to
block some enzyme systems.
Because of the relatively small quantities of thallium found in the
Machinery and Mechanical Products Manufacturing industries, it is not
selected as a pollutant parameter requiring the establishment of an eff-
luent limitation. However, because of its toxicity, care should be taken
by industries that have it as a by-product or use it in their processes
to prevent it from being discharged with effluent streams.
Tin (Sn)
Tin is not present in natural water, but it may occur in industrial wastes
Stannic and stahnous chloride are used as mordants for reviving colors,
dyeing fabrics, weighting silk, and tinning vessels. Stannic chromate
is used in decorating porcelain, and stannic oxide is used in glass
works, dye houses, and for fingernail polishes. Stannic sulfide is
used in some lacquers and varnishes. Tin compounds are also used
in fungicides, insecticides, and anti-helminthics. Tin salts may reach
surface waters or ground water from many of these processes, but because
many of the salts are insoluble in water, it is unlikely that much of the
tin will remain in solution or suspension.
No reports have been uncovered to indicate that tin can be detrimental
in domestic water supplies. Traces of tin occur in the human diet from
canned foods, and it has been estimated that the average diet contains
17.14 mg of tin per day. Man can apparently tolerate 850 to 1000 mg per
day of free tin in his diet.
On the basis of feeding experiments, it is unlikely that any concentratior
of tin that could occur in water would be detrimental to livestock. In
regards to fish, they can withstand fairly large concentrations of tin,
and in fact, trace concentrations of tin are beneficial to fish.
Because of its non-toxic nature, tin is not selected as a pollutant
parameter requiring the establishment of a limitation.
Aldehydes
Aldehydes are a family of organic compounds containing carbon, hydrogen
and oxygen atoms in varying combinations. Saturated aldehydes result
in a high BOD, and are easily biodegraded, while unstaturated aldehydes
are inhibitory to biological treatment systems.
Aldehydes were found in low concentrations in raw waste streams in the
film sensitizing industry. These most probably came from residue on the
acetate film base, but the definite source is unknown. Since traces of
6-46
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DRAFT
aldehydes are more likely to appear during developing (washed off film
base), and this is not part of the point source category, aldehydes
are not selected for limitations in the Machinery and Mechanical
Products point source category.
Hydroquinone/Sodiuro Thiosulfate/Thiocyanates
These chemicals are used primarily in film processing and thus were
tested for only in plants engaged in Subcategory 10, Film Sensitizing.
These parameters were found in low concentrations in wastewaters
from the film sensitizing industry as they are primarily used in
film processing and as such are only used for processing small quan-
tities of film to insure quality. On this basis, no limitation for
these parameters is included within the Machinery and Mechanical Pro-
ducts point source category, but all manufacturers are referred to the
limitations on the film processing industry for hydroquinone, sodium
thiosulfate and theircyanates.
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DRAFT
SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
INTRODUCTION
This section describes the treatment techniques currently used or avail-
able to remove pollutants from wastewaters normally generated in the
Machinery and Mechanical Products Manufacturing point source category.
Following a discussion of individual technologies, there is a discussion
of the treatment systems describing the best practical control technol-
ogy currently available (BPT) and the best available technology econom-
ically achievable (BAT) for each subcategory. Each system is capable
of meeting a high level of reduction for the subcategory and technology
level indicated. A total of 20 systems have been defined and checked
by a computer analysis to verify that they accomplish the desired re-
duction. In addition to each recommended system, substitute technol-
ogies are suggested which will also achieve high levels of reduction.
To minimize the total mass of pollutants discharged, a reduction in
either concentration or flow or both is required. Several techniques
are being employed to effect a significant reduction in total pollution.
These techniques can be readily adapted to other existing manufactur-
ing facilities. These are:
1. Avoidance of unnecessary dilution. Diluting waste streams
with unpolluted water makes treatment more expensive (since
most equipment costs are directly related to volume of waste-
water flow) and more difficult (since concentrations may be
too low to treat effectively). Precipitated material may
also be cedissolved by unpolluted water.
2. Reduction of flow to contaminating processes. Use of counter
current flow rinses, sprays, and fogs greatly reduce the vol-
ume of water requiring treatment. After proper treatment,
the amount of a pollutant (based on maximum removal efficien-
cies and the solubility of the pollutant) that remains in the
solution is a function of the volume of water. Hence, less
water, less pollutant discharged.
3. Treatment under proper conditions. The use of the proper pH
can greatly enhance pollutant precipitation. Since metallic
ions precipitate best at various pH levels, waste segregation
and proper treatment at the correct pH will produce improved
results. The prior removal of compounds which increase the
solubility of waste materials will allow significantly more
efficient treatment of the remaining material. An example
is the removal of ammonia from wastewater containing toxic
metals. This will improve water discharge quality since
ammonia forms a highly soluble complex with most toxic metals.
7-1
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DRAFT
4. Timely and proper disposal of wastes. Removal of sludges
from the treatment system as early as possible will further
minimize returning pollutants to the waste stream through
re-solution. 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 incinera-
tion, 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.
To further reduce or eliminate the discharge of pollutants, treated
process water can be recycled for reuse in the manufacturing processes.
There are three basic approaches to water treatment and recycle. These
are: 1) once-through use followed by treatment and water recycle; 2)
multi-use operation and treatment; and 3) treatment at each manufac-
turing operation. Each of these approaches has advantages as well as
drawbacks.
Once-through use of water followed by treatment and reuse is shown
schematically in Figure 7-la. This approach can be economical if an
existing facility can be used or improved to provide usable quality
water. Operator training is minimized, and new construction may be
minimized or eliminated. Products from a central facility may often
be sold to a reclaiming company and thus reduce ultimate disposal
costs. Disadvantages of this approach involve the economics of treat-
ment of fairly high flow rates compared to the other approaches. Chem-
ical usage may be high, and operation of the entire treatment facility
may be required full time to supply water to a single manufacturing
process which cannot be shut down.
The quantity of once-through water requiring treatment can be reduced
in many instances where the same stream can be used for more than one
manufacturing process with minimal or no treatment. This multi-use
operation is shown in Figure 7-lb. Benefits may be realized for both
treatment of the individual manufacturing processes and the once-through
approach.
Treatment at the individual manufacturing operation, shown in Figure
7-lc, can save on overall space requirements since this type of treat-
ment is normally quite compact. Costs of operator training and multiple
treatment stations can often be offset by reclamation of valuable solu-
tions or salts which might otherwise be destroyed or diluted beyond
economical reclamation in a central facility.
As can be seen, no single approach can be universally recommended as
a cure-all for industrial wastewater treatment and reuse. Each plant
situation is unique making the proper approach for one, uneconomical
or not feasible for another. A complete analysis of each situation
tion should be conducted.
7-2
-------
DRAFT
MAKE UP WATER
RECYCLE AND REUSE
MFC
OPERATION 1
MFC
OPERATION 2
CENTRAL
WASTE
TREATMENT
FACILITY
EFFLUENT
DISCHARGE
ONCE THROUGH
FIGURE 7-1A ONCE THROUGH USE OF WATER, TREATMENT.AND REUSE
MAKE-UP WATER
RECYCLE WATER
MFC
OPERATION 1
RINSE
1
MFC
OPERATION 2
RINSE
2
CENTRAL
WASTE
TREATMENT
FACILITY
DISCHARGE
FIGURE 7-1B MULTI-USE OPERATION ANDTREATMENT
MFG
OPERATION 1
TREAT-
MENT
RECYCLE
MFG
OPERATION Z
TREAT-
MENT
RECYCLE
FIGURE 7-1C SINGLE OPERATION AND TREATMENT
-------
DRAFT
IN-PLANT TECHNOLOGY
Several approaches are being utilized in the Machinery and Mechanical
Products Manufacturing industries to reduce pollution. These approaches
include:
1. Process Modification - Changes in the approach to manufacture
which eliminate or reduce use of the polluting material.
2. Material Modification - Changes in materials which obviate
the need for the polluting material.
3. Waste Segregation and Pretretment - Treatment of low volume,
concentrated solutions rather than treating the entire plant
effluent for all pollutants.
4. Reuse of Process Liquids - Purification or concentration of
process liquids so that they may be returned to the process
stream.
5. Good Housekeeping - Many pollutants are the result of spills
and poor in-plant control. They may be greatly reduced or
eliminated entirely by good housekeeping practices.
The use of one or combinations of the above techniques can produce mul-
tiple benefits including savings in operating costs for waste treatment
and capital costs for new existing or expanded installations.
Process modifications which may prove environmentally beneficial and
economical include the use of:
1. Non-cyanide plating processes for zinc, tin, and cadmium such
as found in plants with ID numbers 924, 5 and 111.
2. Biodegradable coolants in place of normal hydrocarbons such
as found in plant 53.
3. Phosphate free, biodegradable cleaners such as found in
plants 924 and 407.
4. Use of metals and processes which do not require lubrication
and cooling during machining, e.g. friction sawing.
Material modifications which may eliminate discharge of pollutants
involve the whole gamut of manufacturing materials. A few general
examples are:
1. Use of plastic or electrostatically painted metals to replace
plated trim and other parts such as found in plants 79 and
195.
7-4
-------
DRAFT
2. Use of powdered metallurgy forming to replace some parts cur-
rently requiring machining such as was done in plants 132 and
359.
Segregation of_ waste streams provides the maximum benefit of all the
in-plant efforts toward pollution control. Treatment of oily wastes
can often be reduced to contractor hauling by total segregation of
these fluids and using filtering to permit maximum reuse. This elim-
inates separators/ emulsion breaking, skimming, large holding tanks,
and some operator expenses while providing a product which may have
value to a "scavenger" service. Plating wastes can often be treated
at the point of origin and made reusable providing concurrent recovery
of valuable materials. Some paint solids can be recovered and reused
not only reducing pollutants but providing a cost saving at the same
time. Good examples of waste stream segregation were found in plants
345, 515 and 717.
Reuse of process liquids is a natural outfall of the segregation and
pretreatment of water. As shown above, many valuable materials are
wasted by dumping process effluent directly into a composite plant-wide
waste stream. Once the effort has been expended to segregate these
wastes, treatment to recover and reuse the products is more frequently
the economical approach. Ion exchange, ultrafiltration, and reverse
osmosis are frequently used to return process wastes to a reusable
form. The description of these unit processes later in this section
points out specific applications of each process. Reuse of typical
materials in the Machinery and Mechanical Products industries was seen
in plants 932 and 214.
Good housekeeping can prevent a major source of pollution. Spill con-
trol, normal cleanup, and reduction of pollution leaking from stored
material are ways of preventing many pollutants from entering the plant
waste stream. One plant visited had a serious oil pollution problem
from chips collected from machining and stored in an open area. Oil
was rinsed from the chips by rain and washed into the plant waste system
after each storm. Another plant had lead and acid going into the waste
stream from used storage batteries stored in an open, uncovered section
outside of the plant. Proper storage and containment could signifi-
cantly reduce the pollutants in the waste stream and reduce overall
treatment costs. Several plants visited have detailed spill cleanup
plans to prevent specific pollutants from entering the waste stream.
In other plants, normal cleanup as well as spills are fed directly to
the industrial waste stream. This latter procedure often causes surges
at the treatment facility which overload the facility causing signifi-
cant increases in pollutants discharged. This can be prevented by using
suitable holding tanks so that the flow can be metered at a constant
rate to the waste treatment plant.
INDIVIDUAL TREATMENT TECHNOLOGIES
The. following major headings provide descriptions of individual treat-
ment technologies that are used to varying degrees in the Machinery and
-------
DRAFT
Mechanical Products Manufacturing industries. For each technology, a
description of the process, its advantages and limitations, its relia-
bility and maintenance requirements, and its demonstration status are
discussed.
NEUTRALIZATION
Definition of_ the Process
Neutralization is a chemical reaction in which a substance capable of
furnishing hydrogen ions in aqueous solution (acid) reacts with a sub-
stance capable of furnishing hydroxyl ions in aqueous solution (base)
to form water. In a theoretically complete neutralization reaction,
the concentration of hydrogen ions becomes equal to the concentration
of hydroxyl ions and attains the value of 1 x 10 (-7) moles/liter
(pH 7.0) .
Common alkaline neutralizing agents are sodium hydroxide, sodium car-
bonate, and a variety of limestone compositions. Sulfuric acid is the
most common acidic neutralizing agent employed.
Description of_ the Process
In actual waste treatment practice, the term neutralization is applied
to the adjustment of the effluent pH to within a given range usually
6 to 9. Neutralization is accomplished by addition of alkali to acids
or by addition of acid to alkalies as required to effect the required
pH adjustment.
A typical dilute acid neutralization technique for rinse waters from
pickling, plating, and other metal finishing processes exists at many
plants in the U.S., and these have been studied in detail (see Figure
7-2). Typical effluent water contains sulfuric, phosphoric, hydrochlo-
ric, and chromic acids as well as ions of iron, nickel, and chromium.
Alkaline cleaning solutions containing soaps, abrasives, and lubricants
are also discharged to neutralization. The combined wastewater stream
may have a pH ranging from 1.5 to 3.0, and an average flow rate up to
3,785 1/min or more.
Any effluent stream containing hexavalent chromium must be kept segre-
gated from other effluent streams and subjected to a reduction process
before joining the main stream for neutralization.
In one plant visited, neutralization occurs in three 27,820 liter
(7,350 gallon) capacity lead-lined steel tanks connected in series.
Each tank is equipped with a turbine-type agitator designed to re-
circulate the tank contents 2.7 times per minute.
Neutralization is effected by the automatic addition of lime slurry to
the first and third neutralization tanks. The first tank is maintained
at a pH level of 4.5, and the third tank is maintained at a pH level
between 6 and 7 which results in a pH of 8.0 to 8.5 in the effluent
7-6
• si
-------
DRAFT
,PH CONTROLLER
SEDIMENTATION
~_^
SLUDGE
FIGURE 7-2
FLOW DIAGRAM OF 3-STAGE WASTE ACID NEUTRALIZATION UNIT.
7-7
-------
DRAFT
from final sedimentation. The neutralized mixture flows from the th.ird
reaction tank to two settling tanks. The settled effluent is discharged,
and the sludge is pumped to a lagoon.
The following is reported as a typical analysis of the effluent of t^e
plant visited.
pH 8.1
Iron 0.5 ppm
Chromium 0.05 ppm
Suspended Solids 10 ppm
Advantages and Limitations
Some advantages of neutralization in handling process effluents are ^.s
follows:
1. Operation at ambient environments, e.g., 15.5 to 32.2
Degrees C (60 to 90 Degrees F).
2. Processes are well suited to automatic control.
3. Proven effectiveness.
Some limitations of neutralization for treatment of process effluents
are as follows:
1. Careful control is required to minimize scaling of tanks arad
conduits.
2. Mixed waste neutralization may require a large amount of
neutralizing agent.
3. A potentially hazardous situation will exist when concentrated
acids and alkalis are stored and handled as in a batch treat-
ment system.
Specific Performance
The removal of excessive hydrogen or hydroxyl ions from industrial
wastewater (pH adjustment) is chemically achievable in all cases
assuming sufficient neutralizing agent and adequate mixing.
Operational Factors
Reliability - High, assuming sufficient neutralizing agent and proper-
mixing .
Ma in t a i nab i 1 i ty - Maintenance consists of periodic removal of sludge,,
with life as a function of input concentrations and detrimental
constituents.
7-8
-------
DRAFT
Collected Wastes - Dewatering of sludge generated in the neutralization
process or^in an "in line" process may be desirable prior to contractor
removal or disposal to landfill.
Demonstration Status
The neutralization of industrial waste by acid/alkali addition is a
classic process and is found in use by numerous plants employing acid
pretreatments (bonderizing, etching) and alkali cleaning operations.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-1 were contacted during this study and were found to currently
employ neutralization as part or all of their wastewater treatment
system.
CHEMICAL REDUCTION
Definition of_ the Process
Reduction is a chemical reaction in which one or more electrons are
transferred to the chemical being reduced from the chemical initiating
the transfer (reducing agent) .
Sulfur dioxide, sodium bisulfite, sodium metabisulfite, and ferrous sul-
fate form strong reducing agents in aqueous solution and are/ therefore,
useful in industrial waste treatment facilities for the reduction of
hexavalent chromium to trivalent chromium.
Description of the Process
The main application of chemical reduction to the treatment of waste-
water is in the reduction of hexavalent chromium to trivalent chromium.
The reduction enables the trivalent chromium to be separated from solu-
tion in conjunction with other metallic salts by alkaline precipitation.
Gaseous sulfur dioxide is a reducing agent widely employed for the pro-
cess. The reactions involved may be illustrated as follows:
3SO2_ + 3H20 - 3H2,SO3_
3H2S03 + 2H2Cro - Cr2S0)3 + 5H20
The above reaction is favored by low pH. A pH of from 2 to 3 is normal
for situations requiring complete reduction. At pH levels above 5, the
reduction rate is slow. Oxidizing agents such as dissolved oxygen and
ferric iron interfere with the reduction process by consuming the re-
ducing agent.
The theoretical requirement for this reduction reaction on a weight
basis is 1.85 parts SO2_ per part hexavalent chromium. However, an
overdose of reducing agent amounting to 10 to 200 percent is common
practice. The overdose is necessary to react with dissolved oxygen or
-------
DRAFT
TABLE 7-1
PLANTS VISITED USING NEUTRALIZATION
Neutralization is used by 224 plants contacted
5
50
88
135
194
229
287
345
372
390
413
477
530
558
598
626
679
727
755
868
937
955
980
6
53
100
140
195
234
296
347
376
392
416
509
531
561
600
647
687
730
756
923
940
960
1218
7
58
107
143
210
246
301
359
378
393
428
511
535
562
609
652
689
731
774
924
942
961
1481
12
59
108
144
214
247
304
360
380
397
429
514
537
563
611
654
702
736
780
926
945
962
1498
15
61
111
149
217
249
310
361
381
398
431
515
539
564
617
656
707
737
786
927
946
967
26
64
116
153
219
256
321
363
382
399
447
519
542
567
618
658
709
739
800
929
947
969
29
70
118
171
221
278
336
365
383
404
457
520
543
569
621
665
711
740
114
931
948
970
30
78
120
177
222
282
339
366
384
407
464
521
548
572
623
672
712
741
826
932
949
974
39
79
121
182
223
284
342
369
387
409
475
525
549
579
624
677
717
749
835
934
591
975
49
83
131
183
224
286
343
370
388
410
476
529
550
590
625
678
721
752
836
936
954
976
7-10
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DRAFT
other oxidizing agents present in the wastewater. The greater over-
dose will be required for wastes low in chromate and high in dissolved
oxygen.
Other reducing agents frequently employed for reduction of hexavalent
chromium are ferrous sulfate, sodium bisulfite, and sodium metabisulfite.
The reactions of the sulfites are similar to those given for sulfur
dioxide. Reduction of chromium by ferrous sulfate is also most effec-
tive at pH levels of less than 3.0.
A typical wastewater treatment facility used to treat metal finishing
wastewaters containing chromates is presented in Figure 7-3. The treat-
ment consists of two hours detention in an equalization tank followed
by 45 minutes detention in each of two reaction tanks connected in
series. Each reaction tank has an electronic recorder-controller to
control process conditions with respect to pH and oxidation reduction
potential (ORP). Gaseous sulfur dioxide is metered to the reaction
tanks to maintain the ORP within the range of 250 to 300 millivolts.
Sulfuric acid is added to maintain a pH level of from 1.8 to 2.0. Each
of the reaction tanks is equipped with a propeller agitator designed to
provide about one turnover per minute. Following reduction of the hex-
avalent chromium, the waste is combined with other waste streams for
final neutralization to a pH of 8 to remove chromium and other metals
by precipitation.
Advantages and Limitations
Some advantages of chemical reduction in handling process effluents are
as follows:
1. Operation at ambient environments, i.e., 15.6 to 32.2
degrees C (60 to 90 degrees F).
2. Processes, especially those using sulfur dioxide, are well
suited to automatic control.
3. Proven effectiveness in its principal application.
Some limitations of chemical reduction for treatment of process
effluent are as follows:
1. Careful pH control is required for effective hexavalent
chromium reduction.
2. Chemical interference is possible in the treatment of mixed
wastes.
3. A potentially hazardous situation will exist when sulfur
dioxide gas is stored and handled.
-------
DRAFT
OVERFLOW TO
PRESSURE
FILTER
AOCMUJCALI IMNK* AND
WENT MLVTIONf I
WMTtS
66* B« 9ULFURIC
ACID
STORA6E TANK
SULFURIC ACID
FEED PUMPS
<»H CONTKOLLCD)
ACID tntTC ftU
FROM ACID
TANK
SULFUR DIOXIDE
FEEDERS
I MP CONTROLLED )
CHROMATE RUNMNt
RINSE LIME
1
1 t
CHROMATE
SURGE TANK
~e^
rS^-
CHEMICAL
TRANSFER
PUMP
SULFUR CNCMOE
EVAPORATOR
FIGURE 7-3
FLOW DIAGRAM FOR TREATMENT OF HEXAVALENT
CHROMIUM WASTE BY REDUCTION WITH SULFUR DIOXIDE
7-12
-------
DRAFT
Specific Performance
The following efficiency determination was generated by the study of an
operational waste treatment facility chemically reducing hexavalent
chromium to trivalent chromium (Cr):
Parameter %^ Reduction
Hexavalent Cr 99.7
Operational Factors
Reliability - High, assuming proper monitor and control and proper
pretreatment to control interfering substances.
Maintainability - Maintenance consists of periodic removal of sludge
with life as a function of input concentrations and detrimental
constituents.
Collected Wastes - Pretreatment to eliminate substances which will
interfere with the process may be necessary. In general, there are
no wastes produced by the reduction process except for the trivalent
chromium stream which goes to precipitation/coagulation/flocculation
process. There may, however, be small amounts of sludge collected
due to minor shifts in solubility of the contaminants. This is pro-
cessed in the main sludge treatment equipment.
Demonstration Status
The reduction of chromium waste by sulfur dioxide is a classic process
and is found in use by numerous plants employing chromium compounds in
operations such as bonderizing and electroplating.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-2 were contacted during this study and were found to currently
employ chemical reduction as part or all of their wastewater treatment
system.
SKIMMING
Definition of the Process
Skimming is the process of removing floating solid or liquid wastes from
a wastewater stream by means of a special tank and skimming mechanism
prior to treatment of the water. This process is effective if the waste-
water contains oil or grease, soap, or other floating debris.
The process is similar to flotation in regard to scum removal but dif-
fers in that the contaminants float naturally, rather than requiring
gas bubbles to assist flotation. Also, the contaminant particles are
generally of a larger size.
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DRAFT
TABLE 7-2
PLANTS VISITED USING CHEMICAL REDUCTION
Chemical reduction is used by 136 plants contacted
5 6 7 12 15 29 49 58 59 64
78 83 88 108 118 120 121 132 135 140
143 144 149 153 171 182 193 194 210 221
222 223 224 246 247 249 256 278 282 284
286 287 301 304 310 321 339 342 343 345
359 360 363 365 369 370 372 376 ' 380 381
382 383 384 387 388 390 392 393 399 404
407 410 413 431 447 464 476 477 509 510
511 515 519 521 525 531 537 543 549 550
558 561 564 567 569 590 611 618 623 624
625 646 647 654 665 672 677 678 679 687
689 707 711 731 732 737 740 741 749 755
756 826 835 924 926 935 936 937 940 941
954 960 961 974 975 1498
7-14
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DRAFT
labile skimming is usually included as an integral part oi sf.w.ral oth«;:
wastewater operations, such as air flotation mxJ ciarif icaticu, it, is
treated as a separate operation in this disov.ssjcn.
Description of_ the_ Process
Skimming normally takes place in a tank so arranged that floating matte
can rise and remain on the surface of the wastewater, while the liquid
flows out through a baffled outlet well below the scum .layer on the tiM.
surface. Skimming may be performed as a separate process or combined
with other processes such as flotation, sedimentation, or clarification
The skimming tank, may be circular or rectangular in shape, with the
cutlet submerged at the opposite end or side from the jnlefc. Typical
retention times of 1 to 15 minutes are used fct this proce,ss,
A skimming mechanism is provided to collect the resultant scum at the
end of the tank opposite from the inlet. Wooden flights may b^ used '„,.
move the scum to the collection area where mechanical scrapers push
the scum up an incline into a hopper. Depending on the scum character-
•j sties i a rotatable slotted pipe may be used to draw off the scum.
This works well for oily scums, but a large volume of water is mixed
with the collected scum when this technique is used,
containing oils may be reclaimed. Other scum will generally be
disposed of with other sludges collected in the treatment piocess.
Advantages and Limitations
The advantage in using a skimming pretreatment is that the rer-oval of
naturally floating waste material is effected at a relatively high ef-
ficiency, thus reducing the necessary treatment downstream in the
treatment process.
Since a retention time is associated with tho proper.?,-, ta'< degree '>r'
removal is related to the time spent by the water in the skimming tank,
The process is, of course, only applicable where a significant amount
of naturally flotable waste material is present in the wastewater.
Specific Performance
The removal efficiency for floating waste is a function of the retention
time of the water in the skimming tank. Larger, more bouyant particles
require a shorter retention time than small particles. Typical reten-
tion times are 1-15 minutes. Typical removal efficiencies obtained are
in the 70-90 percent range, depending on the characteristics of the scum.
Operational Factors
Reliability - The skimming mechanism, with motor and chain drive, wooden
flights, and an associated collector mechanism, constitute the major
-------
DRAFT
areas of potential breakdown. Broken chains, chains off sprockets,
broken flights, etc. all contribute to downtime. Attention to mair
ance and timely replacement minimize downtime due to failure and re
in a highly reliable system.
Maintainability - The only maintenance parts in the system are in t
skimming mechanism itself. Periodic lubrication, replacement of we
parts, and proper adjustment will minimize unscheduled downtime.
Collected Wastes - Collected wastes may be disposed of by trucking
a landfill or,Tn some cases, by incineration.
Demonstration Status
Skimming is a common operation in waste treatment plants which is w
developed and is used when a significant amount of floating materia
present in the wastewater.
The Machinery and Mechanical Products Manufacturing plants listed i
Table 7-3 were contacted during this study and were found to curren
employ skimming as part or all of their wastewater treatment systeir
CLARIFICATION
Definition of_ the Process
Clarification is the composite wastewater treatment process consist
of flash mixing (of coagulants, pH adjusting chemicals, and/or poly
electrolytes), flocculation, and sedimentation. A flocculant is ad
to the wastewater, which is then allowed to remain at low velocitie
a sedimentation tank where the suspended matter can settle out. Cl
ification is preferred to simple sedimentation for suspended matter
with slow settling rates, for reducing the oil content of the water
and for removing heavy metal soluble salts (by changing them to hy-
droxides and then precipitating them).
Generally, the clarification system requires less space than a simj
sedimentation system because of the increase in settling rates ach;'
by the use of chemical coagulants added to the wastewater.
Description of the Process
The clarifier tank may be circular or rectangular in design and gen
ally employs mechanical sludge collection. Rectangular clarifiers
usually collect the sludge at the effluent end of the tank, while c
cular clarifiers have a sloping funnel shaped bottom for sludge col
tion and draw off. Bottom slopes of at least 8.33 cm per meter are
required for bottom sludge withdrawal. The sludge collection mecha
helps the sludge to overcome inertia and prevents adherence to the
bottom.
7-16
-------
DRAFT
TABLE 7-3
PLANTS VISITED USING SKIMMING
Skimming is used by 88 plants contacted
15
282
256
399
543
627
707
746
971
26
189
284
404
549
628
711
826
972
41
193
296
407
561
629
712
836
974
79
217
300
409
563
654
713
864
976
108
219
342
413
567
664
737
926
1110
121
224
343
416
572
665
739
942
1196
131
229
359
425
590
687
740
946
1481
143
235
380
433
606
698
741
947
1497
158
247
390
477
623
700
744
969
177
249
393
510
625
702
745
970
-------
DRAFT
The sludge is formed by first adding chemical coagulants to the water
and pH adjusting the water if necessary to form a stable, rapid settling
floe which is then allowed to settle. Aluminum or iron salts, such as
aluminum sulfate, sodium aluminate, ferrous or ferric sulfate, and fer-
ric chloride are frequently used as coagulants. Polyelectrolytes are
also used as coagulants in clarification since they form large, high
molecular weight particles which are effective in trapping suspended
particles in the water. The resulting dense floe settles rapidly.
Polyelectrolytes may be used alone or with other chemicals to achieve
the best results.
Once the sludge is collected, it may be pumped out or hydraulically re-
moved from the clarifier. Depending on the impurities present, the
retention time and the chemical treatment used, solids concentrations
of one to three percent are achievable.
In cases of metal hydroxide sludges, recycling of the sludge back to
the clarifier inlet results in a densification of the sludge. At one
plant (ID 380), sludge densification resulted in sludge concentrations
as high as 25 percent dry solids.
Advantages and Limitations
Clarification is effective in removing slow settling suspended matter
in a shorter time and in less space than a simple sedimentation system.
The chemical treatments used are also effective in removing oil and
soluble metal salts which is not done in a sedimentation system.
The clarifier has a higher operating expense since chemical coagulants
and pH adjusting chemicals must be added to the clarifier.
An improvement may often be obtained by an adjustment of the pH to 9 or
higher. This increases the rate of flocculation and, in many cases,
improves effluent quality noticeably. One drawback to this technique
is that downstream equipment such as filters, pumps, etc. may be rapidly
fouled and require flushing or other maintenance.
Specific Performance
A properly operating clarification system is capable of efficient re-
moval of suspended solids, precipitated metal hydroxides, and other in-
purities from wastewater. A typical efficiency of 90 percent or higher
for removal of metals, reduction of TSS to 15 mg/1, is achievable using
45 minute retention time flocculation followed by a two hour settling
period. Higher removal efficiencies are achieved with slightly longer
retention times.
Effectiveness of the process depends on a variety of factors, including
ratio of organics to inorganics, effective charge on suspended particles,
and types of chemicals used in the treatment. Frequently, two or more
chemicals are used for treatment, and the proper quantities are usually
best determined by laboratory analysis.
7-18
-------
DRAFT
Operational Factors
Reliability - The reliability of a typical clarification process is re-
duced by the increased number of associated systems involved in the
clarification process, e.g., coagulant dispensing equipment, stirring
mechanisms, etc. In addition to normal wearout, corrosion due to
caustic chemicals used for pH adjustment may cause premature failures.
Care must be taken to minimize leakages of chemicals. Proper mainten-
ance should also be carried out to minimize failures.
Maintainability - The associated systems used for chemical addition,
stirring, and sludge dragout must be maintained on a regular basis.
Systems external to the clarifier tank present minimal problems from
a system operation viewpoint, while systems within the clarifier may
require emptying for maintenance to be accomplished. Routine mainten-
ance will generally consist of lubrication, checking for excessive wear,
and part replacement as required.
Collected Wastes - The sludge collected from the clarifier is usually
dewatered and then either buried in a landfill, incinerated, or hauled
away by a contractor.
Demonstration Status
Clarification is a common step in many industrial wastewater treatment
systems due to its size advantage and effectiveness. Work is being dons
to further improve the process using polyelectrolytes to produce larger,
faster growing floes with less chemical addition.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-4 were contacted during this study and were found to currently
employ clarification as part or all of their wastewater treatment
system.
FLOTATION
Definition of the Process
Flotation is the process of removing finely divided particles from a
liquid suspension by attaching gas bubbles to the particles, increasing
their buoyancy, and thus concentrating the bubble/particle combinations
at the surface of the liquid medium. Flotation is generally carried
out in a liquid medium, using air to form the gas bubbles.
Flotation may be performed in several ways; froth, dispersed air, dis-
solved air, gravity, and vacuum flotation are the most commonly used
techniques. Chemical additives may also be used to enhance the perfor-
mance of the flotation process.
Flotation is used primarily in the treatment of wastewater cent?•'"ing
large quantities of industrial wastes that carry heavy loads of finely
-------
DRAFT
divided suspended solids and grease. Solids having a specific gravity
only slightly greater than 1.0, which would require abnormally long
sedimentation times, may be removed in much less time by flotation.
Description ojf the Process
The principle difference between types of flotation is the method of
generation of the minute gas bubbles, usually air, in a suspension of
water and small particles. The use of chemicals to improve the effic-
iency may be employed with any of the basic methods. The following
paragraphs describe the different flotation techniques and the method
of bubble generation for each process.
Froth Flotation - Froth flotation is based on the utilization of dif-
ferences in the physiochemical properties in various particles.
Wettability and surface properties affect the particles' ability to
attach themselves to gas bubbles in an aqueous medium. When the valu-
able materials are separated into the froth product, the process is
called direct flotation, and it is called reverse flotation when the
worthless material is drawn into the froth product. In froth flotation,
air is blown through the solution containing flotation reagents. The
particles in the solution, with water repellent surfaces, stick to air
bubbles as they rise and are brought to the surface. A mineralized
froth layer, with mineral particles attached to air bubbles, is formed.
Particles of other minerals which are readily wetted by water do net
stick to air bubbles and remain in suspension.
Dispersed Air Flotation - In dispersed air flotation, gas bubbles are
generated by introducing the air by mechanical agitation with impellers
or by spraying air through porous media. Bubble size is of the order
of 2.54 x 10 to the minus third cm diameter. Dispersed air flotation
is used in the metallurgical industry.
Dissolved Air Flotation - In dissolved air flotation, bubbles are pro-
duced as a result of the release of air from a supersaturated solution.
The average bubble size is about 2 x 10 to the minus fourth cm. There
are two types of contact between the gas bubbles and particles. The
first type is predominant in the flotation of flocculated materials and
involves the entrapment of rising gas bubbles in the flocculated par-
ticles as they increase in size. The bond between the bubble and par-
ticle is one of physical capture only. The second type of contact is
one of adhesion. Adhesion results from the intermolecular attraction
exerted at the interface between the solid and gaseous phases.
Vacuum Flotation - This process consists of saturating the wastewater
with air either 1) directly in an aeration tank, or 2) by permitting
air to enter on the suction of a wastewater pump. A partial vacuum is
applied, which causes the dissolved air to come out of solution as mi-
nute bubbles. The bubbles attach to solid particles and rise to the
surface to form a scum blanket, which is normally removed by a skimming
mechanism. Grit and other heavy solids that settle to the bottom are
7-20
-------
DRAFT
TABLE 7-4
PLANTS VISITED USING CLARIFICATION
Clarification is used by 120 plants contacted
/
107
229
310
390
477
563
647
721
802
947
1 -)
.1. i-
120
235
339
397
511
564
658
"30
c •• t
w _ 1
962
15
121
247
342
404
519
567
665
732
826
969
29
135
249
343
409
520
569
672
737
835
970
49
143
256
365
413
521
590
677
740
836
972
59
158
284
369
425
525
621
687
741
864
974
70
194
286
372
431
537
623
699
748
924
981
78
195
287
380
447
539
625
704
749
927
1110
79
219
296
381
464
542
626
711
752
934
1218
83
221
301
382
475
543
628
713
756
937
1498
100
224
304
384
476
550
646
717
788
946
-------
DRAFT
generally raked to a central sludge pump for removal. A typical vacuum
flotation unit consists of a covered cylindrical tank in which a partial
vacuum is maintained. The tank is equipped with scum and sludge removal
mechanisms. The floating material is continuously swept to the tank per-
iphery, automatically discnarged Into a &com trough, and removed from
the unit by a pump also under partial vacuum. Auxiliary equipment in-
cludes an aeration tank for saturating the wastewater with air, a short
period detention tank for removal of large air bubbles, vacuum pumps,
and sludge and scum pumps.
Advantages and Limitations
Because flotation is very dependent on the type of surface of the par-
ticulate matter, laboratory and pilot plant tests must usually be per-
formed to yield the necessary design criteria. Factors that must be
considered in the design of flotation units include the concentration
of particulate matter, quantity of air used, the particle rinse veloc-
ity, and the solids loading rate.
Specific Performance
The performance of a flotation system depends upon having sufficient
air bubbles present to float substantially 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 per-
formance of a flotation unit in terms of effluent quality and solids
concentration in the float can be related to an air/solids ratio which
is usually defined as pounds of air released per pound of solids in the
effluent waste. The relationship between the air/solids ratio and ef-
fluent quality and float solids is shown in Figure 7-4. It should be
noted that the shape of the curve obtained will vary with the nature of
the solids in the feed.
The primary variables for flotation design are pressure, feed solids
concentration, and retention period. The effluent suspended solids de-
crease, and the concentration of solids in the float increase with in-
creasing retention period. When the flotation process is used primarily
for clarification, a detention period of 20 to 30 minutes is adequate
for separation and concentration.
Operational Factors
Reliability - The reliability of a flotation system is normally high
and is governed by the sludge collector mechanism and by the motors and
pumps used for aeration.
Maintainability - Routine maintenance is required on the pumps and motors;
The sludge collector mechanism is subject to possible corrosion or break-
age and may require periodic replacement.
7-22
-------
0.06
0.05
(fi
Q 0.04
8
cc
5 0.03
0.02
0.01
DRAFT
_L
I
2 3
PERCENT SOLIDS
(A)
50 100 150
PPM EFFLUENT SUSPENDED SOLIDS
(B)
20
(A) THE RELATIONSHIP BETWEEN AIR/SOLIDS RATIO AND
FLOAT-SOUDS.CONCENTRATIONj
(B) THE RELATIONSHIP BETWEEN AIR/SOLIDS RATIO AND
EFFLUENT SUSPENDED SOLIDS.
FIGURE 7-4
AIR/SOLIDS RATIO
7-23
-------
DRAFT
Collected Wastes - Chemicals are commonly used to aid the flotation pro-
cess .Th~ese chemicals, for the most part, function to create a surface
or a structure that can easily adsorb or entrap air bubbles. Inorganic
chemicals, such as the aluminum and ferric salts and activated silica,
can be used to bind the particulate matter together and, in so doing,
create a structure that can easily entrap air bubbles. Various organic
chemicals can be used to change the nature of either the air-liquid in-
terface or the solid-liquid interface, or both. These compounds usually
collect on the interface to bring about the desired changes.
Demonstration Status
Flotation units are commonly used in industrial operations to remove
emulsified oils and grease as well as dissolved solids with a specific
gravity close to water.
In addition, a Swedish company has developed a "micro flotation system"
which uses hydrostatic pressure to control the aeration step by means
of which suspended solids are swept to the surface. Several plants are
operational, with metal plating and pickling liquors, chemicals, dye-
stuff, paper, glue, and sewage being treated with this system. Solids
removal is reported to be 90-99%. The most significant factor in the
operation of this system is that small bubbles, typically 5-50 microns,
are released very gradually, causing twice as many bubbles with a higher
affinity for solids, and the gradual release is less disruptive to sludge
formation.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-5 were contacted during this study and were found to currently
employ flotation as part or all of their wastewater treatment system.
OXIDATION BY_ CHLORINE
Definition of the Process
Oxidation is a chemical reaction in which one or more electrons are
transferred from the chemical being oxidized to the chemical initiating
the transfer (oxidizing agent).
Wastewater treatment by chemical agents for the purpose of oxidizing
contaminants is limited to special situations because biochemical reac-
tions employing natural processes usually perform such degradation op-
erations at minimum cost. The oxidation of contaminants resistant or
toxic to biochemical action is an example of a situation where chemical •
oxidation is appropriate. Chemical oxidation is also appropriate in
situations where a desired change can be effected by the addition of a
relatively small dosage of chemical to react with specific components
of a waste. Examples of such a situation are the removal of color or
odor in a polishing operation.
Chlorine, in elemental or hypochlorite salt form, has a strong oxidizing
potential in aqueous solution and is, therefore, used in industrial
waste treatment facilities primarily to oxidize cyanide.
7-24
-------
DRAFT
TABLE 7-5
PLANTS VISITED USING FLOTATION
Flotation is used by 39 plants contacted
26 41 108 111 116 121 131 177 189 193
219 242 246 247 249 298 342 390 407 416
433 475 510 563 627 647 665 692 702 ~04
781 836 926 943 946 947 970 971 1481
7-25
-------
DRAFT
Description of_ the Process
Cyanide Waste - Chlorine as an oxidizing agent is primarily used in in-
dustrial waste treatment to oxidize cyanide. This classic procedure can
be illustrated by the following two step chemical reaction:
1. C12_ + NaCN + 2NaOH = NaCNO + 2NaCl + H20
2. 3C12_ + 2NaCNO + 6NaOH = Na2C03_ + C02_ + N2_ + 6NaCl + 3H20
The reaction indicated by equation (1) represents the oxidation of cy-
anides to cyanates. The oxidation of cyanides to cyanates is accom-
panied by a marked reduction in volatility and a thousand fold reduc-
tion in toxicity.
The reaction presented as equation (2) for the oxidation of cyanate is
the final step in the oxidation of cyanide to carbon dioxide and nitrogen.
A typical wastewater treatment facility is shown in Figure 7-5 and il-
lustrates modern practice for treating metal finishing wastewaters con-
taining cyanides. Continuous flow treatment facilities are provided
for cyanide-bearing wastes which are discharged from plating and heat
treating operations. In the plating operation, copper and cadmium are
plated from cyanide baths, and nickel and chromium are plated from acid
baths. The plating lines consist of a flow of operations consisting of
alkaline degreasing, acid descaling, plating, and drying. Except for
drying, all steps are followed by rinsing operations.
The cyanide waste flow is treated by the alkaline chlorination process
for oxidation of cyanides to carbon dioxide and nitrogen. The treatment
consists of four hours detention in an equalization tank followed by 100
minutes detention in each of three reaction tanks connected in series.
Each reaction tank has an electronic recorder-controller to maintain
required conditions with respect to pH and oxidation reduction potential
(ORP). In the first reaction tank, conditions are adjusted to oxidize
cyanides to cyanates. To effect the reaction, chlorine is metered to
the reaction tank as required to maintain the ORP in the range of 350 to
400 millivolts, and 50% aqueous caustic soda is added to maintain a pH
range of 9.5 to 10. In the second reaction tank, conditions are main-
tained to oxidize cyanate to carbon dioxide and nitrogen. The desirable
ORP and pH for this reaction are 600 millivolts and 8.0 respectively.
The third reaction tank is also controlled to an ORP of 600 millivolts
and a pH of 8.0. Each of the reaction tanks is equipped with a propeller ,
agitator designed to provide approximately one turnover per minute.
Phenolic Wastes and Colored Wastes - Chemical oxidation is effective
for removal of phenolic and some colored wastes. Chlorine and chlorine
dioxide have been used as oxidants with chlorine having the.widest
application.
A flow sheet of the treatment process developed by pilot plant studies
for the destruction of phenols and chromophores is shown in Figure 7-6 .
7-26
-------
DRAFT
OVERFLOW TO
PRESSURE
FILTER
ACID-ALKALI RINSES
> CHROMATE WASTES
CAUSTIC PUMPS ARE pH CONTROLLED
f I
CONTINUOUS
NEUTRALIZATION
TANK
CYANIDE RUNNIN8
RINSE LINE
CYANIDE
PUMP LINE
CHEMICAL
PROPORTIONING PUMPS
H
^
*""
CHLORINE FEEDERS
(OftP CONTROLLED)
TRANSFER
PUMP
0*»£OU» CHLORINI
LIQUID CHLORINE
CHLORINE
EVAPORATOR
FIGURE 7-5
FLOW DIAGRAM FOR TREATMENT OF CYANIDE
WASTE BY ALKALINE CHLORINATION PROCESS
-------
DRAFT
§1
a _ • •*
I
Ull
O
96 *
S**
flC
s 5
y i
N
1
i
X
Z
£ J
p o
u. z
U) W
w ?
LU CL
I3
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a 3 <
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C fefe
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LU LU
111
7-28
-------
DRAFT
Advantages and Limitations
Some advantages of chlorine oxidation for handling process effluents
are as follows:
1. Operation at ambient environments, i.e., 15.5 to 32.2
Degrees C (60 to 90 Degrees F).
2. Process is well suited to automatic control.
3. Lowest cost and convenience of application.
Some limitations or disadvantages of chlorine oxidation for treatment
of process effluents are listed below.
1. Toxic volatile intermediate reaction products must be
controlled by careful pH adjustment.
2. Chemical interference is possible in the treatment of mixed
wastes.
3. A potentially hazardous situation will exist when chlorine
gas is stored and handled.
Specific Performance
The following efficiency figures were generated by a study of an
operational waste treatment facility using chlorine as an oxidant.
Parameter %_ Reduction (1)
Cyanide (as CN-) 99.6
Phenol 100
Color 99 (2)
Turbidity 99.4(2)
Odor 85 (2)
(1) Optimum conditions assumed.
(2) Variable depending on exact
nature of contaminant.
Operational Factors
Reliability - High, assuming proper monitoring and control and proper
pretreatment to control interfering substances.
Maintainability - Maintenance consists of periodic removal of sludge,
with life as a function of input concentrations and detrimental
constituents.
Collected Wastes - Pretreatment to eliminate substances which will
interfere with the process may be necessary. Dewatering of sludge gen-
•7_oa
-------
DRAFT
erated in the chlorine oxidation process or in an "in line" process may
be desirable prior to contractor removal or disposal to a landfill.
Demonstration Status
The oxidation of cyanide wastes by chlorine is a classic process and
will be found in use by numerous plants using cyanides in operations
such as heat treating and electroplating.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-6 were contacted during this study and were found to currently
employ oxidation by chlorine as part or all of their wastewater treat-
ment system.
OXIDATION BY_ OXYGEN
Description of_ the Process
Oxygen, as a component of air (21% by weight) in a pure form or in its
allotropic form (ozone), is an oxidizing agent. Air or oxygen are not
considered effective as chemical agents in the treatment of industrial
waste, i.e. cyanide wastes are not oxidized to dischargeable concentra-
tions. Ozone, therefore, is the only oxygen form used extensively in
industrial chemical waste treatment. Ozone as an oxidizing agent is
primarily used to oxidize cyanide, to cyanate, and to oxidize phenols
and chromophores to a variety of colorless nontoxic products. The
cyanide oxidation can be illustrated by the following ionic equation:
CN(-l) + 03_ = CNO(-l) + 02_
The reaction indicated by the above equation represents the oxidation
of cyanides to cyanates.
Since ozone will not readily effect further oxidation, breakdown of the
cyanate waste is dependent on processes such as hydrolysis and bio-oxi-
dation.
Ozone is also effective in the treatment of phenolic waste. Oxidation
with ozone, when preceded by proper pretreatment, provides a solution
to the problem of phenols in a variety of industrial wastes. Most
wastes require at the most only an adjustment in the initial pH as a
pretreatment to the oxidation process. Refinery or other high sulfide
wastewater may require sulfide removal. By destruction of phenols, a
significant reduction in toxicity of such wastes can be realized.
In the treatment of chromcphores, ozone has been shown to be effective
in removing the yellow-brown color due to humic substances in dissolved
or colloidal form. The amount of ozone necessary (to reduce colors of
50-60% Hazen to below 5% Hazen) would normally be between 1.5 and 4
mg/liter.
A typical ozone plant for wastewater treatment is shown in Figure 7-7.
7-30
-------
DRAFT
TABLE 7-6
PLANTS VISITED USING CHEMICAL OXIDATION
Chemical oxidation is used by 88 plants contacted
5 7 12 15 29 58 88 116 118 135 140
143 144 153 171 193 222 223 242 246 249 256
28 282 284 286 287 301 304 339 343 359 \H
3« 369 370 380 381 382 383 384 387 388 39?
397 3" 404 509 511 514 515 519 531 542 5^8
549 558 561 590 609 623 625 647 656 672 678
687 689 709 711 717 737 739 740 741 749 752
756 78° 835 923 931 935 942 946 954 958 962
7-31
-------
Controls
Ozone
Dry Air
?i
Ozone
Mixing
Tank
-cxh
X
Settling
Tank
CN
Acidic
Metals
"IGURE 7-7
TYPICAL 02CM ^LANT FOR WASTE TREATMENT
7-32
-------
DRAFT
Advantages and Limitations
Some advantages of ozone oxidation for handling process effluents are
as follows:
1. Operation at ambient environments, i.e., 15.5 to 32.2
Degrees C (60 to 90 Degrees F).
2. Process is well suited to automatic control.
3. On site generation eliminates procurement and storage
problems.
4. Reaction product (oxygen) is beneficial to receiving waters.
Some limitations or disadvantages of ozone oxidation for treatment of
process effluents are listed below.
1. High initial cost.
2. Chemical interference is possible in the treatment of mixed
wastes.
3. Cyanide will not be effectively oxidized beyond the cyar.ate
level.
Specific Performance
Tests carried out in France on the effluent from a large metal finishin<
factory showed that an ozone dose of 80 to 90 mg/liter could remove 25
mg/liter of cyanide. The results of initial pilot tests are as follows
Cyanaide content of effluent before ozonation = 25 mg/liter
Cyanide content of effluent after ozonation = 0
Concentration of ozone in 7 14 20
air (gr/cu m)
Total ozone applied 7.3 5.7 4
(Kg/Kg cyanide)
Ozone lost to atmosphere 3.8 2.5 0
(Kg/Kg cyanide)
Ozone used in destruction 3.5 3.2 3.2
of cyanide (Kg/Kg cyanide)
The use of ozone oxidation of phenols is in widespread use throughout
many industries. The levels of phenols normally found in the wasres
from the Machinery and Mechanical Products industries are such that
7-33
-------
DRAFT
this process has not found much use in this area. To provide examples
of treatment by this process, Table 7-7 is included.
Table 7-7
Oxidation of Phenolic Wastes
Initial
Phenols
P.P.M.
Ozone
Demand
P.P.M.
Ozone/
Phenol
Ratio
1
11
,240
800
330
140
127
102
51
38
290
605
,600
2,
1,
1,
1,
11,
500
200
700
950
550
900
000
700
400
705
000
2.0
1.5
5.2
6.8
4.3
8.8
20
18
1.4
1.3
1.0
Residual
Phenols
P.P.M.
1.2
0.6
1.0
0,
0
0.0
0.4
0,
0,
0,
2.5
Reduction
99.9
99.9
99.7
99.9
99.8
100
99
99
99.9
99.9
100
2
7
Results are
Source
Plant A
Plant B
Plant C
Plant D
Plant E
Plant F
Plant G
Plant H
Plant I*
Plant J
Plant K
*This waste contained 2,4-dichlorophenol.
expressed as 2,4-dichlorophenol.
Operational Factors
Reliability - High, assuming proper monitor and control and proper
pretreatment to control interferring substances.
Maintainability - Maintenance consists of periodic removal of sludge,
and periodic renewal or replacement of filter (s) and desiccator (s)
required for the input of clean dry air with life as a function of
input concentrations and detrimental constituents.
Collected Wastes - Pretreatment to eliminate substances which will
interfere with the process may be necessary. Dewatering of sludge
generated in the ozone oxidation process or in an "in line" process
may be desirable prior to contractor removal or disposal to a landfill.
Demonstration Status
The first commercial size plant using ozone in the treatment of cyanide
waste was installed by a manufacturer of aircraft. This plant is cap-
able of generating 54.4 Kg (120 pounds) of ozone per day. The amount
of ozone used in the treatment is approximately 20 milligrams per liter.
In this process, the cyanide is first oxidized to cyanate, and the cya-
nate is then hydrolized to C02_ and NH3_. The final effluent from this
treatment passes into a lagoon. Because of an increase in the waste
flow, the installation has been expanded to produce 163.3 Kg (360 pounds)
of 02one per day.
7-34
-------
DRAFT
As a typical example of treatment efficiency for the removal of phenol
to meet a prescribed maximum of 15 parts per billion, the refinery of
the British-American Oil Company at Bronte, Ontario, Canada used 86.2
Kg (190 pounds) of ozone per day to treat a waste flow of 1,135.5 liters
(300 gallons) per minute. The phenol concentration in the final efflu-
ent is less than 3 ppb, well under the maximum limit set by the regula-
tory authorities.
CHEMICAL PRECIPITATION
Definition of_ the Process
Chemical precipitation is a chemical process in which a chemical in
solution reacts with another chemical introduced to that solution to
form a third substance which is partially or mainly insoluble and,
therefore, appears as a solid.
The principal application of chemical precipitation is for the remo-
val of metals insoluble in neutral or alkaline solutions such as iron,
copper, zinc, and trivalent chromium. Since the metallic salts are
usually present in acid solutions, the process involves pH adjustment
as well as precipitation. The process is theoretically applicable to
any substance that can be transformed into an insoluble form such as
soaps, sulfides, fluorides, and a variety of other substances.
Description p_f the Process
Chemical precipitation as a waste treatment technique is a process in
which purification is effected by the addition of reagents to react
with specific contaminants to form insoluble products. The process
is different from chemical coagulation in that the contaminant itself
enters into reaction with the reagents instead of being adsorbed by
the coagulant floe. The precipitated material is removed from the
wastewater by sedimentation, centrifugation, filtration, or flotation.
Figure 7-8 shows a typical flow diagram for chemical precipitation.
The reagents needed to effect precipitation may be as various as the
pollutional constituents being treated. For economic reasons, how-
ever, the following chemicals are commonly employed in industrial
waste treatment facilities.
1. Calcium hydroxide is used to precipitate trivalent chromium
and other heavy metal ions as insoluble hydroxides. It will
also precipitate phosphates as insoluble calcium phospate.
Metallic hydroxides tend to be collodial in nature, and coag-
ulating agents such as ferrous sulfate may be added to facil-
itate sedimentation. The desired ferrous sulfate will be
present if it is added in excess to reduce hexavalent chromiun
in a prior treatment.
2. Hydrogen sulfide or soluble sulfide salts such as sodium sul-
fide will precipitate heavy metal ions as insoluble metal
-------
WASTE ACID
DRAFT
pH CONTROLLER
EFFLUEK
SLUDGE
FIGURE 7-8
FLOW DIAGRAM OF CHEMICAL PRECIPITATION UNIT
EMPLOYING PH ADJUSTMENT AND SEDIMENTATION.
7-36
-------
DRAFT
sulfides. Metal sulfides tend to be less soluble and less
collodial than metal hydroxides, but this advantage is
countered by toxicity problems.
3. Organic precipitants, known in analytical chemistry as being
effective in the removal of metallic ions, have been consid-
ered uneconomical for waste treatment application. A recent
development, the "starch xanthate process", for metal precip-
itation is presently in the experimental stage and may prove
to be economically feasible for waste treatment application.
The treatment of metal-finishing wastes at a plant that manufactures
parts for slide fasteners from ferrous and copper-bearing metals has
been studied in depth. The metal finishing processes employed are
annealing, pickling, deburring, enameling, lacquer application, and
plating,
Effluent from the plant manufacturing operations is divided into two
flows - an alkaline cyanide bearing waste and an acidic waste. Cyanide
bearing waste is generated from heat treating, plating, and cleaning
operations. The acid waste also contains metals, cutting oils, and
detergent solutions. Acids present include sulfuric, nitric, hydro-
chloric, acetic, and phosphoric.
Separate batch treatment facilities are provided for the cyanide and
the acid effluent. Six 182.4 cu meter (50,000 gallon) capacity
wooden tanks are provided for holding and treating the acid waste.
The treatment process for the acid wastewater consists of reduction
of hexavalent chromium with ferrous sulfate and chemical precipitation
of metals with lime. The sludge is separated from the liquid efflu-
ent by sedimentation and is thickened prior to disposal.
The acid waste treatment tanks are automatically filled to working
level, and the contents of the tank are agitated for 30 minutes. The
required dosage of ferrous sulfate is added, and the tank is agitated
for 45 minutes. Lime is then added to effect precipitation and ad-
justment to a pH of 9.5, and the solids are allowed to settle for
approximately 72 hours.
Advantages and Limitations
Some advantages of chemical precipitation in handling process
effluents are as follows:
1. Operation at ambient environments, i.e., 15.5 to 32.2
Degrees C (60 to 90 Degrees F).
2. Processes are well suited to automatic control.
3. Proven effectiveness in its principal application.
4. Often aided by necessary "in line" treatments.
-------
DRAFT
Some limitations of chemical reduction for treatment of process
effluents are as follows:
1. Careful pH control is required (see Fiqure 7-9) .
2. Chemical interference is possible in the treatment of -ixed
wastes.
3. A potentially hazardous situation will exist if hydroger.
sulfide is elected as a precipitating agent due to its
toxicity.
Specific Performance
The following efficiency determination was generated by the study zf an
operational waste treatment facility employing chemical precipitation
as a treatment technique:
% Reduction
Parameter (Optimum Conditions)
Copper (as Cu(+l) or Cu(+2)) 96.6
Nickel (as Ni( + 2)) 91.7
Chromium (total) 98.8
Zinc (as Zn(+2)) 99.7
Phosphate (as P03_(-3) ) 93.6
Operational Factors
Reliability - Fairly high assuming proper monitor and control and
proper pretreatment to control interferring substances.
Maintainability - Maintenance consists of periodic removal of sludre,
with life as a function of input concentrations and detrimental
constituents.
Collected Wastes - Pretreatment to eliminate substances which will
interfere with the process may be necessary. Dewatering of sludge
generated in the reduction process or in an "in line" process may
be desirable prior to contractor removal or disposal to landfill.
Demonstration Status
The chemical precipitation of contaminants is a classic process ar.d
will be found in use by numerous plants employing electroplating ar.d
other metal treatments such as etching and bonderizing. Oxidaticr. of
cyanide and/or reduction of hexavalent chrome will in most cases be
"in line" treatments.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-8 were contacted during this study and were found to currently
employ chemical precipitation as part or all of their wastewater
treatment system.
7-38
-------
DRAFT
2
a
a
4.0
2
3 3.0
2
o
-------
DRAFT
TABLE 7-8
PLANTS VISITED USING CHEMICAL PRECIPITATION
Chemical precipitation is used by 137 plants contacted
7 15 29 49 50 58 64 79 83 84
100 107 108 116 121 132 135 140 143 144
177 182 189 193 194 195 214 217 219 221
223 224 229 235 246 247 249 256 282 284
286 287 296 301 304 310 339 342 343 345
361 365 366 369 370 372 376 380 381 382
384 388 390 392 393 397 398 399 404 409
413 416 425 428 431 447 464 476 477 509
511 519 520 521 525 530 542 543 549 561
562 564 567 569 590 611 612 617 621 623
632 646 658 665 672 677 678 687 692 698
699 700 702 704 711 712 727 731 741 749
780 814 826 835 836 924 926 937 949 958
960 974 981 1110 1218 1481 1498
7-40
-------
DRAFT
COAGULATION/FLOCCULATION
Definition o_f the Process
Coagulation is a chemical reaction in which polyvalent ions neutralize
the repulsive charges surrounding colloidal particles. Flocculation is
defined as the random collision and subsequent clustering of these neu-
tralized particles. The random collisions result from brownian motion
significantly aided by mixing, and the clustering results from the oper-
ation of Van de Waals attractive force.
The coagulation process is principally applied for the purpose of form-
ing non-settleable dispersed materials into aggregates more amenable to
sedimentation or filtration. These materials may be color, soaps, pro-
teins, fibers, mineral fines, oil emulsions, or colloidal precipitants.
Description p_f the Process
As a waste treatment process, coagulation is the addition of chemicals
(coagulants) to affect charge neutralization and the resultant aggrega-
tion of dispersed materials, followed by separation of the aggregated
material from the suspending liquid. The first operation in the coagu-
lation process is a rapid mix often lasting a minute or less in which
•coagulants and chemicals for pH adjustment are evenly blended throughout
the waste. The mixing operation and chemical addition may consist of
several steps. The next operation is f locculaticr., which consists of a
slow mix lasting 10 to 40 minutes employed to promote collisions between
neutralized particles, resulting in the formation of settleable aggregat
The last operation in the process entails the separation of the neutral-
ized aggregates from the suspending liquid, by sedimentation as in Figur
7-10 or by flotation. Filtration may be substituted or used in conjunc-
tion with sedimentation to effect separation of aggregated materials.
Since most colloids encountered in industrial waste are dispersed by
negative charges, cations (positively charged ions) are employed as co-
agulating agents. Cations such as Al(+3), Fe(+2), Fe(+3), and Ca(+2)
are generated in aqueous solution by the following commonly used
coagulants:
Alum A12_(S04_)3_ . 14 H2p
Copperas FeS04_ . 7 H2_0
Chlorinated Copperas Fe2_(SO£)_3 . FeC13_
Ferric Chloride FeCl_3
Ferric Sulfate Fe2(S04_)3_ . 2 H20
Lime CaTOH)2_
Advantages and Limitations
Some advantages of coagulation/flocculation in handling process efflu-
ents are as follows:
7-41
-------
DRAFT
COAGULANT CHEMICALS
EFFLUENT
MIXING A CHEMICAL
ADDITION
SLUDGE
FIGURE 7-10
FLOW DIAGRAM OF CHEMICAL COAGULATION UNIT EMPLOYING
MIXING, FLOCCULATION, AND SEDIMENTATION.
7-42
-------
DRAFT
1. Operation at ambient environments, i.e., 15.5 to 32.2
Degrees C (60 to 90 Degrees F) .
2. Processes are well suited to automatic control.
3. Proven effectiveness.
Some limitations of coagulation/flocculation for treatment of process
effluents are as follows:
1. Careful pH control is required in many coagulation processes.
2. Chemical interference is possible in the treatment of hydro-
philic suspensions.
3. Coagulating agents especially ferric chloride and lime are
subject to air/moisture degradation.
Specific Performance
The following reduction efficiency was determined from data collected
from operational waste treatment facilities coagulating and flocculatinc
oily wastes:
Oil Concentration, Raw Waste, mg/1 807
Oil Concentration, Effluent, mg/1 25
Mean Oil Reduction, Percent 97
Effluent, pH 7.2
Removal efficiencies for other wastes range from 40% for BOD to 98% for
some color constituents. Typical suspended solids removal ranges from
80 to 95%.
Operational Factors
Reliability - Fairly high assuming proper monitoring and control.
Maintainability - Maintenance consists of periodic removal of sludge
and normal maintenance of pumps, motors, and gear drives involved with
mixing and adding chemicals.
Collected Wastes - The use of coagulant aids such as fullers earth or
pulverized limestone may be desirable in special situations. Dewaterin<
of sludge generated in the coagulation process or in an "in-line" pro-
cess may be desirable prior to contractor removal or disposal to land-
fill.
Demonstration Status
The coagulation of colloidal suspensions is a classic process and will
be found in use by numerous plants generating suspended contaminants in
their manufacturing operation or in their waste treatment operation.
7-43
-------
DRAFT
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-9 were contacted during this study and were found to currently
employ coagulation/flocculation as part or all of their wastewater
treatment system.
SEDIMENTATION
Definition of the Process
Sedimentation is the separation of suspended particles that are heavier
than water from water by gravitational settling. It is one of the most
widely used unit operations in wastewater treatment. This operation is
used for grit removal, particulate matter removal in the primary set-
tling basin, biological floe removal in the activated sludge settling
basin, chemical floe removal when the chemical coagulation process is
used, and for solids concentration in sludge thickeners. In most cases,
the primary purpose is to produce a clarified effluent, but it is also
necessary to produce sludge with a solids concentration that can be
easily handled and treated. In other processes, such as sludge thick-
ening, the primary purpose is to produce a concentrated sludge that can
be treated more economically.
Description o_f_ the Process
Particles in suspension may be classified as granular or flocculant.
Granular particles (sand, silt) settle at constant velocity, independent
of one another and without change in size, shape, or weight. Flocculant
particles (organic matter, floes formed by coagulants or biological
growths) tend to cluster during settling with changes in size, shape,
and relative density. The clusters ordinarily settle more rapidly than
individual particles. Settleable solids comprise that portion of the
granular and flocculant material which settles under quiescent condi-
tions in a reasonable time. This period is commonly, though arbitrar-
ily, taken as one hour. Non settleable solids are so finely divided
that they will not settle, even under these conditions.
Wastewater Characteristics - Sedimentation is affected by the strength
and freshness of the wastewater and the density, shape, and size of the
particles. Strong wastewater usually settles more readily than weak
wastewater. On the other hand, stale wastewater settles less readily
than fresh wastewater because the particle sizes are reduced by bio-
logical degradation, and also the particles tend to be buoyed by gas.
A dense particle settles more rapidly than a light one; a particle with
a large surface area, in relation to its weight, settles slowly; and
one v/ith irregular shape has greater frictional draft and settles more
slowly than a particle with a regular shape.
Detention, Period - This is the time required for the wastewater to flow
throu"gh~~the tank at a given rate of flow. The detention period should
be sufficient to allow practically complete removal of settleable sol-
ids. Excessively long detention periods do not materially improve re-
moval and may actually be harmful by allowing the wastewater to become
7-44
-------
DRAFT
stale. In plain sedimentation, surface loadings of 36,667 to 48,890
Iiters/m2/day (900 to 1,200 gpd/sq. ft.) and depths of from 2.44 to 3.]
meters (8 to 10 ft.) are common.
Tank Dimensions - Rate of removal of granular particles settling at
uniform velocities depend almost entirely on tank surface area. Rate
of removal of flocculent particles settling at variable velocities
depends on both tank surface area and depth.
Inlets and Outlets - Inlets are designed to reduce entrance velocity
and distribute flow uniformly throughout the cross section of the basir
by means of suitable openings, baffles, or other means.
Outlets for removal of clarified wastewater may be ports or weirs.
They should be of sufficient area or length so that velocities at the
outlet end of the tank are low enough to prevent carry-over of bottom
deposits. Baffles should be provided ahead of outlet weirs in primary
tanks to prevent loss of floating solids and grease. In the design of
sedimentation basins, due consideration should be given to production
of both a clarified effluent and a concentrated sludge.
Chemical Treatment - Chemical treatment is used when it is desired to
remove more finely dividied suspended and colloidal material than is
possible with plain sedimentation. The chemicals used react with con-
stituents of the wastewater or with other chemicals added for this pur-
pose to form a heavy, flocculent precipitate. As the precipitate set-
tles, the suspended and colloidal particles are entrapped and adsorbed
on the large and sticky surface. Organic polymers offer high levels of
efficiency of solid-liquid separation.
Sedimentation tanks may be built in either of two types, a) rectrngulai
and b) circular (or square). In the rectangular type, wastewater flows
from one end of the tank to the other, and the settled sludge is moved
by counter flow scrapers toward the inlet end. In the circular or sqiic
type, the wastewater usually enters at the center and flows radially tc
the periphery, with the settled sludge pushed or otherwise transported
back to the center. There are some designs, howeverf in which waste-
water enters circular tanks tangentially st the outer edge ano flows
inward.
Small rectangular or circular tanks may have a sludge collection hopper
covering the entire bottom of the tank in liou of a sludge collection
mechanism. Since hopper slopes must be steep, this type of tank is
confined to small sizes to avoid excessive tank depth and attendant
construction costs.
Rectangular tanks may be in single units or in a series of units. The
length of the tank is usually several times the width. Settled sludge
is moved to a hopper at one end, either by wood flights mounted on par-
allel strands of conveyor chain or by single bottom scraper mounted on
a carriage moving on rails fastened to the tank walls.
Chains and flights are carried on submerged sprockets, shafts and bear-
ings, and are driven by a motor through a speed reducer. The flights
-------
DRAFT
PLANTS VISITED USING COAGULATION/FLOCCULATION
Coagulation/FlocculatJon is used by 137 plants contacted
7
100
177
223
286
361
384
413
511
512
632
699
780
15
107
182
224
287
365
388
416
£19
564
646
700
814
29
108
189
229
296
366
390
425
520
56V
653
702
826
49
116
193
235
301
369
392
428
521
569
665
704
e:E-
50
1*1
11-4
246
304
370
3^3
4 J> 1
525
590
672
711
B?6
53
132
195
247
310
372
397
447
530
611
677
712
924
64
135
214
249
339
376
398
464
542
612
678
727
926
79
140
217
256
342
380
399
476
543
617
687
731
937
83
143
219
282
343
381
404
477
549
621
692
741
949
84
144
221
284
345
382
409
509
561
623
698
749
958
960 974 981 1U«,' 12 j 8 1481 1498
7-46
-------
DRAFT
INFLUENT PIPE
DRIVE MOTOR
OUTER WALL
FIGURE 7-11
MECHANICAL GRAVITY THICKENER
7-48
-------
DRAFT
INFLUENT PIPE
DRIVE MOTOR
OUTER WALL
FIGURE 7-11
MECHANICAL GRAVITY THICKENER
7-48
-------
DRAFT
Operational Factors
Reliability - The possible failures that can occur in a sedimentation
system will most likely involve the sludge dragout equipment (broken
flights, or chain, chain off sprocket, etc.). Less frequently, pro-
blems may occur with the sedimentation tank itself, such as structural
defects, loose fittings, etc. An additional problem with open sedi-
mentation ponds open to the elements involves flooding and overflow of
the side due to heavy rains.
Maintainability - Routine maintenance includes the following:
1. Remove accumulations regularly from the inlet baffles and
effluent weirs. Generally, this can be done with a hose and
broom. The necessary frequency can be determined only by
experience.
2. Clean scum removal equipment regularly. This equipment is a
major source of obnoxious odors and unsightly appearance when
neglected.
3. Preparing a lubrication chart for all mechanical equipment.
The requirements for each piece of equipment can be obtained
from the manufacturer.
The underwater portion of the sedimentation tank should be inspected
periodically (once a year is usually sufficient). The best time for
doing this depends on the weather, treatment requirements, and avail-
able personnel. Essentially, the following work is required for this
operation:
1. Dewater the tank, discharging its contents to another tank
whenever possible.
2. Inspect all mechanical equipment for wear and corrosion.
3. On rectangular tanks with mechanical sludge collectors, check
wood flights, wearing shoes, main chains, drive chains, sproc-
kets, guide rails, and grease skimmers.
4. Replace or repair all defective, broken, or badly worn parts.
5. Adjust chains and be sure flights have proper clearance at
tank walls (at least 2.54 cm (1.0 in.)).
Collected Wastes - Depending on the composition of the collected sludge,
it may be incinerated, buried in a landfill, or reclaimed. Sludge con-
taining precious metals (gold or silver) is usually worth reclamation,
while sludge containing pickling scale or similar materials, is usually
buried in a landfill.
7-49
-------
DRAFT
Demonstration Status
Sedimentation, or a close variation, is a common step in the treatment
of industrial waste since it is a simple process, yet effective in
removing suspended solids from a wastewater stream.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-10 were contacted during this study and were found to currently
employ sedimentation as part or all of their wastewater treatment system.
MICROSTRAINING
Definition of the Process
Microstraining is a process for removing solids from water. It operates
by passing the stream through a microscreen (23, 35, or 60 ir.icron holes)
with the solids being retained on the screen.
Description of the Process
A typical microscreen forms the cylindrical surface of a rotating drum.
One end of the drum is closed off, and the other is open for— ir.g the
inlet. As illustrated in Figure 7-12, the water is fed through the
open end to the inside of the drum and flows through the screen to the
outlet. The solids, retained on the rotating screen, are rer.cved by a
backwash into a collection trough. The solids are normally rer.cved
manually and disposed of with other sludge.
The principle of microstraining is primarily mechancial interference of
the screen with the solids. However, this is not the only necl-.anism
which takes place in the process. In many cases, particles r.uch smaller
than the openings in the screen are effectively removed. Mcs^ of the
literature suggests that the larger particles collect on the screen in a
thin layer and effectively reduce the mesh openings.
Advantages and Limitations
The principle advantages of microstraining are:
1. No chemical additions.
2. Low cost of operation and maintenance.
3. High efficiency for relatively large particles.
Specific Performance
Microstraining has been used in Europe since the 1950"s for tertiary
treatment and the removal of algae prior to sand filtration. in some
cases, it can be used in place of sand filtration. Solids rer.cval
efficiencies range from 70 to 80 percent for 23 micron screens and 50
to 60 percent for 35 micron screens.
7-50
-------
DRAFT
TABLE 7-10
PLANTS VISITED USING SEDIMENTATION
Sedimentation is used by 132 plants contacted
6
110
177
246
345
390
477
550
611
658
711
786
936
1481
7
111
182
247
359
392
509
552
612
665
717
799
941
1497
39
116
194
256
361
393
515
561
617
678
721
802
942
49
120
195
278
363
398
519
562
624
690
727
814
943
50
121
217
284
365
399
520
563
625
692
736
826
954
53
131
221
287
376
404
521
564
626
698
737
836
955
58
132
223
298
378
428
530
567
628
TOO
"39
923
970
64
135
229
300
382
429
537
590
646
702
740
926
972
108
143
235
339
384
433
548
606
654
704
755
929
976
109
153
242
342
388
457
549
609
657
709
779
935
1110
7-51
-------
DRAFT
Solids Collection
and Removal
Thru Axle
Micros creer.
Drum
Feed
Water
Effluent
Filtered
Water
Inlet
FIGURE 7-12
MICRO SCREENING SCHEMATIC
7--52
-------
DRAFT
Operational Factors
Reliability - Reliability is high due to the small number of moving
parts and the low complexity of a system employing this technique.
Maintainability - Normal maintenance consists of routine cleaning and
lubrication.
Collected Wastes - Solids collected are of such a size that, further
sludge dewatering is relatively simple. Drying beds or similar device-
will be adequate for this purpose.
Demonstration Status
Several microstraining installations are operating in the Unit ^.d States
but they are primarily in municipal water supply plants. The applica-
bility for industrial wastewaters can be easily determined with a tesi
kit to determine the "filterahility index" of a particular stream.
Using this index, th« size and efficiency of a microstraining installa-
tion can be predicted.
No Machinery and Mechanical Products Manufacturing plants were conta.>:t-^.;
during this study which currently employ microstraining at= part or ail
of their wastewater treatment system.
DEEP BED FILTRATION
Definition of_ the Process
Suspended solids are commonly removed from wastewater streams by fil-
tering through a relatively deep 0.3-0.9 m (1-2 ft) granular bed. The
porous bed formed by the granular media can be designed tc remove prac-
ticably all suspended particles by physical-chemical effects. Even
colloidal suspensions (roughly 1 to 100 microns) are adsorbed on the
surface of the media grains as they pass in close proximity in the
narrow bed passages.
Description of the Process
Filtration is basic to water treatment technology, and experience with
the process dates back to the 1800'", Filtration occurs ir, ne.ture as
the auL.. urface ground waters are pu: i f j.ed L;. rand. Silica sand, anthra-
cite cc.-il. ;;fid garnet ar-; co'/uinon filter meclie used in water treatment
plants, These are usually supported by gravel. The media may be use-a
singularly or in combinations. The n.ulti-media filters may be arranged
to maintain relatively distinct layers (multi-layered) by -'irture of
balancing the forces of gravity, flow, and bouyancy on the individual
particles. This is accomplished by selecting appropriate filter flow
rates liters/min/sq meter (gpm/sq ft), media grain size, and density.
In recent years, vast improvements have been realized in filtration
efficiency by the use of mixed media beds, wherein the process water
passes from coarse to fine bed characteristics. In mixed media beds,
7-53
-------
DRAFT
the various media and operating parameters are selected to achieve a
natural mixing of the media which yields the relatively continuous
variation of bed characteristics desired.
Deep bed filtration process equipment can be further defined in terms
of other major operating characteristics. The most common filtration
approach is the conventional gravity filter which normally consists of
a deep bed granular media in an open top tank of concrete or steel.
Direction of flow through the filter is downward, and the flow rate is
dependent solely on the gravity induced hydrostatic pressure of the
process water above the bed.
One variation of the gravity filter is commonly referred to as a pres-
sure filter (see Figure 7-13). In this case, the basic approach is the
same as the gravity filter, but it is enclosed in a steel tank and
pressurized. Other variations are commonly referred to as upflow,
biflow, radial flow, and horizontal flow.
Additional characteristics used to classify the various deep bed filters
are the type(s) of filter media used, multi-layered, mixed media, and the
flow rates slow, rapid and fast. But these are all deep bed filters
which take advantage of certain economic or operating characteristics
over others for specific conditions in specific applications.
As wastewater is processed through a filter bed, the solids are stored
in the spaces between the media grains. Periodically, the media must
be cleaned. This is accomplished by backwashing (reversing the flow
through the filter bed). The flow rate for backwashing is selected
such that the bed is expanded by lifting the media particles a given
amount. This expansion and the subsequent minor motion provides a
scouring action which effectively dislodges the entrapped solids from
the media grain surfaces. The backwash water fills the tank up to the
level of a trough below the top lip of the tank wall. The backwash is
collected in the trough and fed to a storage tank and recycled into
the waste treatment stream. The backwash flow is continued until the
filter is clean.
Auxiliary filter cleaning is sometimes employed in the upper few inches
of filter beds. This is conventionally referred to as surface wash and
is in the form of water jets just below the surface of the expanded bed
during the backwash cycle. These jets enhance the scouring action in
the bed by increasing the agitation.
An important feature for successful filtration and backwashing is the
underdrain. This is the support structure for the media bed. The
underdrain provides an area for collection of the filtered water with-
out clogging from either the filtered solids or the media grains. In
addition, the underdrain prevents loss of the media with the water, and
during the backwash cycle it provides even distribution of the flow
over the bed. Failure to dissipate the velocity head during the filter
or backwash cycle will result in bed upset and major repair.
7-54
-------
DRAFT
FINAL
POLISHING
ZONE
OUTLET
FINE
GRADATION
MEDIUM
GRADATION
COARSE
GRADATION
FIGURE 7-"-
TYPICAL PRESSURE FILTER
7-55
-------
DRAFT
Several standard approaches are employed for filter underdrains. The
simplest one consists of parallel porous pipe imbedded under a layer of
coarse gravel and manifolded to a header pipe for effluent removal.
Other approaches to the underdrain system are known as the Leopold and
Wheeler filter bottoms. Both of these incorporate false concrete bot-
toms with specific porosity configurations to provide for drainage and
velocity head dissipation.
Filter system operation may be manual or automatic. The filter backwash
cycle may be on a timed basis, a pressure drop basis with a terminal
value which triggers backwash, or a solids carry-over basis from turbi-
dity monitoring of the outlet stream. All of these schemes have been
successfully used.
The state-of-the-art in filter technology has progressed during the last
twenty-five years to produce improved performance and increased under-
standing of the basic principles. However, it has not progressed to
the point where adequate sizing and performance predictions can be made
with confidence prior to testing. The use of pilot plant filters for a
specific application is a necessity as part of the engineering design
procedure.
Filters in wastewater treatment plants are often employed for polishing
following clarification, sedimentation, or other similar operations.
Chemical additives which enhance the upstream treatment equipment may
or may not be compatible with or enhance the filtration process. It
should be borne in mind that in the overall treatment system
effectiveness and efficiency are the objectives, not the performance of
any single unit. The flow rates for various types of filters are as
follows:
Slow Sand
Rapid Sand, Multi-layered
Hicrh Rate Mixed Media
2.04-5.30 Liters/Square Meter
40.74-51.48 Liters/Square Meter
81.48-122.22 Liters/Square Meter
Advantages and Limitations
The principle advantages of filtration are:
1. Low initial and operating costs.
?. Reduced land requirements over other methods to achieve the
same level of solids removal,
3, No chemical additions which add to the discharge stream.
4. Increase of flow rates can be handled by paralleling added
filter(s).
Some disadvantages encounted with filters are:
7-56
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DRAFT
1. Require pretreatment if solids level is high (from 100 to
150 mg/1).
2. Operator training is fairly high due to controls and periodic
backwashing.
3. Capability limited to suspended solids and oils and greases.
4. Backwash must be stored and dewatered to be economically
disposed.
Specific Performance
Properly operating filters following some pretreatment should produce
water with less than 0.2 JTU (Jackson Turbidity Units), and mixed media
filters can process water having average turbidities as high as 50 JTU
without pretreatment. Peaks as high as 200 JTU can be tolerated. Above
these conditions, pretreatment such as settling basins may be required.
Operational Factors
Reliability - The recent improvements in filter technology have signifi-
cantly improved filtration reliability characteristics. Control systems,
improved designs, and good operating procedures have made filtration a
highly reliable method of water treatment.
Maintainability - Yearly checks of the filter media condition plus
normal maintenance of pumps are the extent of the scheduled maintenance
required for most filter systems.
Collected Wastes - Table 7-11 presents a comparison of many of the fil-
tration techniques and their applicability. Those processes having a
rating under "Cake Dryness" are applicable to sludge filtering only,
Demonstration Status
Because of the increased understanding, performance, and reliability,
filtration is becoming a standard for water treatment plants in the
United States. More than 250 nixed media plants are in operation pro-
ducing over one billion gallons per day of municipal watfir. Industries
returning process water to municipal supplies should consider filtration
as part of their wastewater treatment.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-12 were contacted during this study and were found to currently
employ deep bed filtration as part or all of their wastewater treatment-
system.
SCREENING
Definition of the Process
The first unit operation usually encountered in wastewater treatment
plants is the filtering operation of screening. A screen is a device
7-57
-------
DRAFT
TABLE 7-11
Relative Performance and Application
Characteristics of Solid/Liquid Separation Eauipnent
Equipment
Centrifuges
Basket
Conical set i-cn
(no scroll )
Disk, manual
Disk, nozzle
Disk, self-cleaning
Osciilati ng
Scraper
Pusher
Screen-bcwn decanter
Scroll decanter
Scroll screen
Gravity filters
Drum
Flat bed
Rotating screen
Sand
Table/pan
Travelling screen
Vibrating screen
Compression filter
Automatic filter press
Press pan
Screw
Pressure filters
Cartridge
Drum
Edge
Filter press
Leaf, horizontal
Leaf, vertical
Sand
Strainers
Tubular element
Vacuum filters
Band/pan
Disk
D r urn
Leaf
Precoat-drum
Suction strainers
Table/pan
Tubular -element
* Approximate values.
A - average; B - below
Solids content*
for which effective
(weight %)
1 0 to '> 0
10 to 40
0.005 to 0.08
0.1 to 2
0.08 to 1
40 to 70
10 to 50
20 to 80
9 to 40
7 to 60
30 to 60
0.08 to 0.8
0.05 to 5
0.009 to 0.1
0. 002 to 0.01
5 to 70
0. 009 to 0.1
0.1 to 1
0.2 to 40
10 to 60
10 to 70
0.002 to 0.2
0.7 to 8
0.002 tc 0.1
O.OC2 to 30
0.002 to 0.06
0.008 to 0.04
C.002 to 0.02
0.002 to 0.02
0. 002 to 0.1
8 to 5 0
4 to 40
5 to 70
0.07 to 2
0.01 to 0.1
0.02 to 0.09
8 to 50
O.C8 to 2
average; G •= good; V
Particle-size
range* (microns)
2 to 30,000
60 to 30,000
0.1 to 100
0.1 to 100
0.1 to 100
60 to 30,000
2 to 30,000
40 to 70,000
30 to 30,000
1 zc 30,000
100 tc 20,300
50 to 6,000
1 tc 90,000
100 to 10,000
0.1 to 50
50 to 80,000
100 to 10,000
30 to 100,000
1 to 200
1 to 200
1 to 200
0 . 6 to 3C
5 tc 200
1 to 20C
1 to IOC
1 to 100
] to 11C
C . 2 tc 60
4 to 60C
0 . 5 to 100
20 to SC , CCO
1 to 700
1 to 6C C
1 to 500
0 . 6 t o 100
50 tc 20C
20 tc SC,000
1 to 150
= very good.
Cake
dryness
*-
G
_
A
A
G-V
V
y
Q
1
G
-
-
-
A-C
-
A
^
G
G
.--G
A
G
A-G
-
-
A
i, —(3
B-A
A
A
-
-
A-G
^ ~ A
Pelative
Cake
cashing
G
-
-
_
-
A
G
\
A
A
A
_
G
-
-
V
-
A
G
G
-
G
G
G
G
V
A
-
_
G
J
E
G
'•'
-
-
V
~
Performance
Filtrate
clarity
A
G
G
G
A
A
A
A
A
A
G
V
G
V
G
G
G
G-V
G-V
-
G-V
G-V
G-V
G-V
V
G-V
G-V
G
G-V
G
G
G-V
G
V
Q
G
G
7-58
-------
DRAFT
TABLE 7-12
PLANTS VISITED USING FILTRATION
Filtration is used by 102 plants contacted
5 7 12 49 58 61 83 100 108 111
121 131 143 153 177 182 189 193 210 219
234 246 247 300 376 378 381 383 384 387
388 393 399 413 429 431 447 457 464 476
509 510 530 533 535 537 549 564 590 606
617 618 621 623 625 627 628 632 646 647
654 657 658 664 672 678 692 700 702 704
711 712 717 720 730 737 752 755 779 787
803 833 924 926 934 937 941 942 946 948
949 954 958 961 962 972 974 976 1218 1481
1482 1497
7-59
-------
DRAFT
with openings, generally of uniform size, used to retain coarse solids.
The screening element may consist of parallel bars, rods or wires,
grating, wire mesh, or perforated plate, and the openings may be of any
shape, generally circular or rectangular slots. A screen composed of
parallel bars or rods is called a rack.
There are two principle methods of designating racks and screens, first
according to the method of cleaning, i.e., as hand cleaned or mechanic-
ally cleaned, and second according to the size of openings with coarse
designated for those screens of 0.635 cm (1/4 inch) or more, and fine
screens for those with less than 0.635 cm (1/4 inch) opening.
Coarse screening devices in treatment facilities consist mainly of bar
racks which are used to protect pumps, valves, pipelines, and other
equipment from damage or clogging by rags and large objects. Suspended
particles greater than 0.635 cm (1/4 inch) can be removed more economi-
cally by screening than by other unit operations.
Fine screens are generally of the disk or drum type. The microstrainer
is a fine screening device of the drum type.
Description of the Process
There are three types of screening facilities. These are a) coarse
screens or racks, b) bar screens, and c) comminuting devices.
Coarse Screens - Coarse screens are constructed with evenly spaced rec-
tangular or round bars set in a channel. The clear opening is usually
5.1 to 10.2 cm (2 to 4 inches), and the bars are sloped at an angle
45^3 to 60k from the vertical and terminate in a horizontal platform.
A rake is used to remove objects from the rack.
Bar Screens - Bar screens are installed in nearly all plants as either
the only screening unit or as a standby for a comminuting device. Hand
cleaned screens consist of a series of bars evenly spaced to form a
rack. The slope of the rack is often 60 deg from the horizontal, termin-
ating at a platform onto which the screenings may be raked for dewatering,
Openings between the bars are commonly between 1.9 to 5.1 cm (0.75 to
2 inches).
When bar screens are used at plants as the primary screening device,
they usually are cleaned mechanically. The bars may be set vertically
or at a small angle from the vertical. Screenings are moved by travel-
ing rakes and deposited either on a platform or in buckets, cans, or
trucks. They also are deposited in hammer mill type shredders for size
reduction and returned to the wastewater stream. The cleaning mechanisms
may be operated continuously or intermittently.
Comminuting Devices - A comminuting device is a mechanically cleaned
screen whxch incorporates a cutting mechanism that cuts the retained
material without removing it from the wastewater flow. One type of
7-60
-------
DRAFT
comminuting device has a submerged revolving drum with 0.6 cm (0.25
inch) slots in the smaller units, and 1.0 cm (0.375 inch) in the larger
machines. The coarse material is cut by the cutting teeth and shear bs
on the revolving drums which pass through a stationary comb. The com-
minuted solids pass with the wastewater into the downstream channel.
Another type of device has revolving cutters that travel up and down th
bar screen, cutting the coarse material to a size that will pass tlirouc
the screen.
An arrangement used in some plants is to have an alternate waste streair
channel with a manually cleaned bar screen installed sr. that screenab.le
objects may be intercepted when the mechanical cleaning device is out
of service for maintenance or repair.
Advantages and Limitations
The principal advantage to screening is the protection of treatment equ
ment which might be damaged by material entering the treatment plant.
This factor is significant in the case cf industrial waste treatment
plants with drainage from parking lots and other storm runoff and of
minor effect in industrial waste systems from Machinery and Mechanical
Products Manufacturing plants which completely segregate their wastes.
In this case, a small screen may be used ahead of the pump for pump
protection.
This process, however, has a minor effect on the industrial wastes
treatment. It is a protection device and filters out large objects.
It does nothing to reduce the pollutants in normal industrial wastes.
Specific Performance
Screening is effective in removing impurities which are at least 50
percent larger than the screen opening, and the probability of passing
objects 25 percent larger than the screen hole size is small.
Operational Factors
Reliability - The reliability of a manual screen system is inherently
high since there are no moving parts to jam. The only possible failure
mode would be structural damage caused by a large obstruction. This
failure mode is improbable if a properly sizrd screen is used.
An automatic raking system is more prone to failure since, if it should
jam, it can shear a pin in the drive system or trip a circuit breaker,
either of which require operator attention. In addition, there axe
rake tines, a chain drive, and a motor drive, all with breakable parts.
Maintainability - Maintenance on a manual screening system consists of
regularly scraping collected debris from the screen to prevent blockage,
7-61
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DRAFT
Maintenance on an automatic cleaning rake system involves periodic lub-
rication, replacement of shear pins, chain links, and other parts as
failures occur. The system must also be cleared if a jam occurs in the
automatic rake Astern.
Collected Wastes - Collected waste from the screen is normally sold or
hauled to a landfill or may be reduced in size and incinerated.
Demonstration Status
Automatic cleaning screens are commonly found in medium and large in-
dustrial treatment plants, while the manual variety are common in small
plants.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-13 were contacted during this study and were found to currently
employ screening as part or all of their wastewater treatment system.
ION EXCHANGE
Definition o_f the Process
Ion exchange is a process in which ions held by electrostatic forces to
charged functional groups on the surface of a solid matrix are exchanged
for ions of similar charge in a solution in which the solid matrix is
immersed. Ion exchange is classified as a sorption process because the
exchange occurs on the surface of the solid, and the exchanging ion must
undergo a phase transfer from solution phase to surface phase.
Ion exchange is used extensively for water and wastewater treatment of
a variety of industrial wastes to allow for recovery of valuable waste
materials or by-products, particularly ionic forms of precious metals
such as silver, gold, and uranium.
Description of the Process
In general, a synthetic ion-exchange resin consists of a network of
hydrocarbon radicals to which are attached soluble ionic functional
groups. The hydrocarbon molecules are linked in a three-dimensional
matrix to provide strength to the resin. The amount of cross-linking
determines the internal pore structure of the resin and must allow
free movement of exchanging ions.
The behavior of the resin is determined by the ionic groups attached to
the resin. The total number of ionic groups per unit of resin deter-
mines the exchange capacity, and the group type affects both the equil-
ibrium and the selectivity. Cation exchangers, those resins carrying
exchangeable cations, contain acid groups. The term "strongly acidic"
is used in reference to a cation exchange resin containing ions from a
strong acid such as H2_S04^ and "weakly acidic" designates cation ex-
change resins made from a" weak acid such as H2_CO_3^ Anion resins con-
tainina c^~*-->-*- ^™~>^^\um compounds are refer^r! to as "ctrcr^y K^ir'',
and those with weak base amines are referred to as "weakly basic".
7-62
-------
DRAFT
TABLE 7-13
PLANTS VISITED USING SCREENING
Screening is used by 25 plants contacted
7 121 219 235 247 249 390 407 413 563
567 572 690 692 702 711 732 740 786 814
835 926 927 1110 1481
7-63
-------
DRAFT
A schematic representation of a cation exchange resin is given in
Figure 7-14.
The majority of cation exchangers used in water and wastp treatment op-
erations are stongly acidic, and they are able to exchange all cations
from the solution. Both types of anion exchangers are employed.
Strongly basic anion resins are capable of exchanging all anions, in-
cluding weakly ionized materials such as silicates and dissolved carbon
dioxide, and weakly basic resins exchange only strongly ionized anions
such as chlorides and sulfates.
Characteristic selectivities of commercial resins are well-known and
useful for determining which resin is most suitable for a specific ap-
plication. Further, it is possible to construct a resin with high
selectivity for the polluting ions involved in a particular operation.
The rate at which an exchange reaction reaches equilibrium normally is
controlled by the rate of transport of the exchange ions in the solution.
In a well stirred batch system or in a normal flow through system, the
exchange is generally determined by either the diffusion of ions to the
exterior of each particle of exchange resin or the diffusion of ions
through the pores of the resin itself.
The two principal methods of operation for application of ion exchange
in water and wastewater treatment are batch and column operations.
Column operation is preferred for most applications. One method of
batch treatment involves mixing the resin with the waste in a large
tank. The water and resin are in intimate contact, and the transport
rate is reduced due to mixing. In a column operation, the bed is con-
structed similar to a filter bed, and water is passed through on a
continuous basis. The column operation is essentially a series of
batch operations in which, even though the selectivity of exchange may
be relatively low, an efficient use is made of a resin because of fav-
orable driving force (concentration difference) conditions. One common
mode of column operation in ion exchange application is a packed fixed
bed.
Advantages and Limitations
Treatment of wastes by ion exchange is complicated by the presence of
materials or conditions which may clog, attack, or foul resins. Most
current synthetic resins resist serious chemical or thermal attack.
High concentrations of oxidizing agents such as nitric acid can attack
these resins at vulnerable cross-links. Regarding temperature stabil-
ity, most resins are stable to 100 Degrees C or higher.
The selectivity characteristics of exchangers can often be exploited by
employing specially prepared resins. Even the separation of similar ions
has been achieved, notably the separation of the rare earth metals, by
taking advantage of their dissimilar complexing characteristics in solu-
tion. The major disadvantages of a high degree of selectivity in an
7-64
-------
L/r\MT I
FIGURE 7-14
CATION EXCHANGE RESIN
-------
DRAFT
exchange reaction are the tight bonds formed and poor regeneration
characteristics.
In a column packed fixed bed, a high degree of settleable or suspended
solids will cause a rapid and excessive pressure loss significantly
reducing operating efficiency.
Specific Performance
The following Table 7-14 gives typical efficiencies attained for heavy
metals by ion exchange as reported by a chemical company using the
process.
TABLE 7-14
ION EXCHANGE REMOVAL EFFICIENCIES FOR HEAVY METALS
Contaminant
Cyanide
Chromium
Copper
Iron (Total)
Cadmium
Nickel
Zinc
Phosphate
Sulfate
Aluminum
Removal Efficiency
(Percent)
94
98
95
100
92
100
75
90
97
98
Operational Factors
Reliability - A properly operated system with appropriate pretreatment
to prevent clogging or damage to the resin should provide excellent
continuous service with high reliability. Caution must be exercised to
keep regenerants out of any direct discharge lines since these are
usually highly concentrated solutions.
Maintainability - Regeneration plus normal maintenance of waste transport
equipment(plumbing, pumps, etc.) should be all the normal maintenance
required. Resin replacement should not be required for several years,
unless it is damaged by application of harmful substances.
Collected Wastes - Regeneration typically creates a more concentrated
waste stream containing the same ions which were removed in the initial
process. In some instances, this concentrated stream can be reused in
the initial process, such as removal of chromic acid solutions from
wastewater. The basic ion exchange process produces high quality water
for reuse as a rinse, and regeneration produces chromic acid which can
7-66
-------
DRAFT
be returned to the process tank. Nickel and copper plating solutions
treated with ion exchangers provide high quality rinse water and a con-
centrated stream from which the metals may be recovered. Each situation
where ion exchange is considered requires a complete analysis to deter-
mine the economics of the system.
Demonstration Status
Ion exchange is an ancient method for the removal of inorganic ions
from water. The first uses were to purify drinking water. This was
done with naturally occurring materials. Modern technology has devel-
oped synthetic resin materials with the appropriate exchange ions held
to the matrix electrostatically.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-15 were contacted during this study and were found to currently
employ ion exchange as part or all of their wastewater treatment system.
ADSORPTION
Definition of the Process
Adsorption is the adhesion in an extremely thin layer of molecules (as
of gases, solutes, or liquids) to the surface of solid bodies or liquids
with which they are in contact. Activated carbon or synthetic adsorbents
remove organic contaminants from water by the process of adsorption which
results from the attraction and accumulation of one substance on the sur-
face of another. In general, the chemical nature of the surface is of
relatively minor significance in the adsorption of organics from water
and secondary to the magnitude of the surface area available. For this
reason, high surface area is the prime consideration in adsorption.
Description of the Process
Granular activated carbon can be manufactured using a number of source
materials including bituminous coal, coconut shells, and pulp mill
blackash. Synthetic adsorbents are manufactured to provide equal or
larger surface areas than the activated carbon. The product is essen-
tially inert. The hardness and density vary based on the raw material
employed. During the manufacturing process, the carbon granules are
permeated with a network of submicrospic channels or pores, and it is
this network which provides the vast surface area upon which adsorption
can occur. Typical synthetic adsorbent granules are composed of sintered
grains.
When a wastewater containing organic chemicals passes through a bed of
carbon or synthetic adsorbent, the chemical molecules come in contact
with the surface and are held there by weak physical forces called
Van der Waals forces. The water continues through the bed; and organic
contaminants are left behind.
When there is a mixture of organic molecules present, adsorption selec-
tivity determines the efficiency of the process. The adsorbent will
-------
DRAFT
TABLE 7-15
PLANTS VISITED USING ION EXCHANGE
Ion exchange is used by 14 plants contacted
58 69 83 132 246 247 519 521 569 624
756 780 836 924
- -M -y j-r: •- - [• ^> 39-i ;• r:
7-68
-------
DRAFT
preferentially adsorb some organic molecules over others. This selec-
tivity is determined by three properties of the molecules: molecular
structure, molecular weight, and polarity of the molecule. For example
if a wastewater contains a combination of an organic dye and a solvent,
the dye -- being a larger compound with a higher molecular weight than
the solvent -- would be more readily adsorbed.
An adsorption isotherm is usually run on representative samples of
wastewater to determine the feasibility of using adsorption to remove
the crganics. The test consists of contacting a fixed quantity of
wastewater with varying amounts of adsorbent for a fixed length of time
The amount of organic removal at varying dosages then gives an indica-
tion of the amount required to treat this particular wastewater.
Advantages and Limitations
The following are some advantages of the adscrption process for treatmei
of wastewater.
1. Ability to remove difficult compounds such as organo-metallic
dyes, phenols, chlorophenols, insecticides, alcohols, and
detergents. (See Table on next page.)
2. Low power requirements.
3. Operation at ambient temperature.
4, Compact design.
5. Low cost approach to removal of various chemicals not readily
treated by other means.
The following are some limitations of adsorption.
1. Beds can be contaminated by wastewater containing high
suspended and/or oil.
2. Beds must be regenerated or replaced when porous surfaces
are used up.
3. Losses occur in the regeneration process which affect the
ability of the adsorbent to adsorb certain molecules.
Specific Performance
The following table provides a general list of the pollutants most
effectively treated by adsorption. This list is not intended to be an
exhaustive list of all pollutants since continuing investigations are
establishing new areas constantly.
7-69
-------
DRAFT
Acetaldehyde
Acetic Acid
Acetone
Activated Sludge Effluent Impurities
Air Purification Scrubbing Solutions
Alcohol
Amines
Ammonia
Amyl Acetate and Alcohol
Antifreeze
Benzine
Biochemical Agents
Bleach Solutions
Butyl Acetate and Alcohol
Calcium Hypochlorite
Can and Drum Washing Contaminants
Chemical Tank Wash Water Contaminants
Chloral
Chloramine
Chlorobenzene
Chlorine
Chlorophenol
Chlorophyl
Chromi urn
Copper
Cresol
Dairy Process Wash Water Contaminants
Decayed Organic Matter
Defoliants
Detergents
Dissolved Oil
Dyes
Operational Factors
Ethyl Acetate and Alcohol
Gasoline
Glycol
Herbacides
Hydrogen Sulfide
Hypochlorous Acid
Insecticides
Iodine
Isopropyl Acetate and Alcohol
Ketones
Lactic Acid
Mercaptans
Methyl Acetate and Alcohol
Methyl-Ethyl-Ketone
Naptha
Nitrobenzenes
Nitrotoluene
Odors
Organic Compounds
Phenol
Potassium Permanganate
Sodium Hypochlorite
Solvents
Sulfonated Oils
Tastes (Organic)
Toluene
Trichlorethylene
Trickling Filter Effluent
Turpentine
Vinegar
Well Water Impurities
Xylene
Reliability - Adsorption systems have been used extensively enough to
provide a good experience base and to have most of the "bugs" worked
out or understood so they may be circumvented. A key consideration in
all adsorbers is the type of underdrain system employed. The Leopold
Block, Wagner, Wheeler, and even a pipe lateral system are common under-
drain systems which may be employed to obtain uniform distribution.
Experience indicates most underdrain systems will work effectively as
long as there is about 0.07 ATM (1 psi) pressure drop through it.
Ma i nta inability - It may be necessary to treat wastewater prior to ad-
sorption. Excessive suspended solids content can collect in the bed
and create excessive head loss. Fibrous substances can also cause pre-
mature pressure drop and problems by clogging pumps and valves. General
practices employed for suspended solids and/or fiber removal are screen-
ing devices, sand filters, diatomaceous earth filters, or conventional
clarifiers. Adjustments in pH may also be necessary to destabilize
colloidal materials and/or optimize the adsorption process.
7-70
-------
DRAFT
Demonstration Status
Carbon adsorption has received wide use in various sewage and industrial
applications. The existence within the machinery and mechanical products
area of the organics most readily removed by adsorption should be suffic-
ient cause to thoroughly investigate this treatment process. Table 7-16
provides a list of some of the applications of carbon adsorption.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-17 were contacted during this study and were found to currently
employ adsorption as part or all of their wastewater treatment system.
TABLE 7-17
PLANTS VISITED USING ADSORPTION
Adsorption is used by 2 plants contacted
627
1497
DISTILLATION
Definition of the Process
Distillation is vaporization of the liquid in a wastewater stream fol-
lowed by condensation of the vapor. The water evaporated from the
stream and subsequently condensed is collected as a purified effluent
stream. The remaining concentrated impurities are collected for reuse,
further treatment, or disposal.
Distillation processes were originally developed for desalination, but
are also being utilized for wastewater treatment where a high degree of
purity is required or where less expensive methods are not available.
Description of the Process
The mechanics of the evaporation distillation cycle are widely varied
in practice, but four methods are in general use: multistage flash
distillation, multiple-effect long-tube vertical evaporation, submerged
tube evaporation, and vapor compression. To a limited extent, solar
distillation has been employed to demineralize saline waters and could
have application in waste treatment.
Submerged tube distillation is used in many plants for reclamation of
water and chemicals from rinses following dips in chemical solutions
such as pickling baths. It is basically a simple, compact distillation
concept with many possible variations. Heat for evaporation is supplied
from tubes submerged in the water to be processed. The heat source may
be steam, hot water (or other liquid), or electrical resistance heating.
The unit may be run at atmospheric pressure or, to reduce operating
temperature, under partial vacuum. The unit may be single effect or it
7-71
-------
DRAFT
TABLE 7-16 GRANULAR ACTIVATED CARBON APPLICATIONS
Industry
Location
1. Carpet Mill
British Columbia
2. Textile Mill
Virginia
3 . Oil Re finery
California
4. Oil Refinery
Pennsylvania
5 . Detergent
New Jersey
6. Chemicals
Alabama
1. Resins
New York
8. Herbicide
Oregon
9. Chemicals
New York
10. Chemicals
Texas
11. Chemicals
New Jersey
12. Explosives
Switzerland
13 . Pharmaceuticals
Switzerland
14. Insecticide
England
15. Hood Chemicals
Mississippi
16. Dyes tuff s
Pennsylvania
Installation
Date
6/73
7/70
i /^ i
j/ / 1
3/73
6/72
11/72
3/73
11/69
3/69
11/71
3/72
10/72
1962
8/73
8/73
D*SLqn
Flow
Rate
(000 gals/day)
5C
60
4200
2200
15
SCO
22
150
15
1500
100
5
25
3000
1500
Organic
Contaminants
Dyes
Dyes
SOD
Xylene
Alc»hols
TOC
Phenolics
Resin
Intermediates
Xylene
Phenolics
Hesorcinol
Chlorophenols
Cresol
phenol
COD
Nitrated
Arovatics
Polyols
Kitrated
Phenols
Phenol
Chlorophenol
TOC
Color
TOC
Pretreatment
Screens
Filtration
Oil Flotation
Equalization
Oil Flotation
Filtration
None
Chemical
Clarification
Chemical
Clarification
None
Equalization
Activated
Sludge
Filtration
Equalization
Clarification
Equalization
Equalization
pH Adjusted
Settling
Equalization
Clarification
pH Adjustment
Flotation
Filtration
Equalization
Clarification
Filtration
Adsorption
Contact
time
minutes)
57
60
540
173
30
105
200
40
150
90
50
50
Adsorber
Type
Moving
Bed
Moving
Bed
Beds In
Parallel
Moving
Bed
Furnace
Down flow
Beds In
Series
Moving
Beds
Downf low
Beds Ir.
Series
Upflow
Beds In
Series
Downf low
Beds In
Series
Moving
Beds
Moving
Bed
Downf low
Beds Ir.
Series
Downf low
Beds In
Series
Downf low
Beds In
Series
Moving
Beds
Moving
Beds
vstem
Carbon
Reactivation
None
None
Hearth
Furnace
Multiple
Hearth
Multiple
Hearth
Furnace
Multiple
Hearth
Furnace
Rotary
Kiln
Multiple
Hearth
Furnace
None
Rotary
Kiln
Multiple
Hearth
Furnace
None
None
Rotary
Kiln
Multiple
Hearth
Furnace
Multiple
Hearth
Furnace
7-72
-------
may be double effect to increase effectiveness while conserving energy
In the double effect unit, the wdter to be processed flows through two
stages in series. Each stage is operated at a different pressure so
that the hot vapor from the first stage may be used as the heat sou.*: en
for the second stage.
In iT.ultistac/e flash disti Hat:' cnf the water is heated to about S 2 < 2
degrees C (200 degrees F) and flashed into an >2v iiporater at a pressure
J over than e tmospheric . The steam produced is condensed to producL
water > The residual concentrated waste is flawed through additional
evaporators, each at a lower pressure than the previous one, and each
cru-i produces product water and &. i.iore concentranid \v
The' TIM;} uiple-effeet long-tube vertical distillation process involves a
sind Jar principle of successive evaporation. ~«;ch tvapc: ct:or c.v .if.::..1
co;:-';c-ins long vcjtiesl tubes 'L-hjiow:,'.- -/,'hicli pirehc-.ste.' influent ir.HE,
.t falls. Vapor and hot v^ter ccliert at the batten of i;hr
Th'i hot. water is pv.iaped to the tu.::,-,£ ir. the sacon-:, ^ff:;"-.:
w.her^ the. process is repeated, ? number of effects can be provided
v:-*.::. 1 efficie.jicy reaches an c}:tr:-]\-Ti\ > Steam is ' ced ?s vhs ir,i^i.-\l l.c-a1
uourci, p: eking up the ver:?r; ::ioving :"roro one effect t.c uhc oths::.
dcr. iic.tf-. -'.s collectec*. from e^ch evc.pQi stor.
j,r, vapor compression distillation; the influent, is evaporated under ct
itiosph.er:' c pressure. The r^suJ.v.ing vapor is compressed and is returns-'
' o neat v.he evaporator c The. teirrper?. ture difference between tha cora-
p;:e£'.':td r-t,e'?,ia ar.d influent ir- the evaporator mahes this possible. ''"he
pvroess li£.s an adventaoe over other r,ieti;od£ in that no cool duo ws^ei.1 i
;:c:CG!?Bc.:cy 1:0 effect ocndensation.r however,- there is mi increase in n:hi
r-ty/sr (for the compressor} required,
In addition £ wiped- film eveporators are used as a second stege to con-
vert; first stags ccncentxate to a nearly dry residue. Ir. v.his device,
ru&chanical scrapers spread the residue- ever the inside surface of a
heat- jacketed pipe.
J-dvantsce£ aiui Limitations
Some advantages of the distillation process are:
1. The water recovered from the distillation process is of high
purity. This process can be used to convert waste effluent
to pure or process water where other water supplies are
inadequate or nonexistent.
2. The distillation process may be applicable, to removal and/or
concentration of waste effluent which cannot be accomplished
by any other means.
Some limitations or disadvantages of the distillation process are:
1, In general, the distillation process consumes relatively larc
amounts of energy for the evaporation of water. However, th<
7-7:
-------
recovery of waste heat from many industrial processes (e.g.,
diesel generators, incinerators, etc.) should be considered as
a source of this heat for a totally integrated distillation
system.
2. For some applications, pretreatment may be required to remove
solids and/or bacteria which tend to cause fouling in the
condenser or evaporator.
3, The buildup of scale on the evaporator plates reduces the heat
transfer efficiency and may present a maintenance problem or
increase operating cost. However, it has been demonstrated
that fouling on 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, ]ow temperature differences in the
evaporator will eliminate nucleate boiling and supersaturation
effects.
4. Steam distillable impurities in the process stream are carried
over with the product water and must be handled by pre or post
treatment if they cannot be tolerated.
Specifi c Performance
Removal ol contaminants is very high for those items with a boiling
point trigrif icantly greater then water at the system operating pressure.
Contaminants whose boiling point is less than or only slightly greater
than water will be carried over in the water and require pre or post
treatment for removal.
Reliability - Reliability of the submerged tube distillation concept is
relatively high. Little data exists to evaluate larger units.
Maintainability - Little maintenance is required with the submerged
tube concept other than normal cleaning. Other concepts are not suf-
ficiently demonstrated on which to base maintainability information.
Demonstration Status
Primarily because of their compactness and relatively low price, the
predominant type of distillation system utilized in the Machinery and
Mechanical Products industries is the submerged tube type.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-18 were contacted during this study and were found to currently
employ distillation as part or all of their wastewater treatment system.
7-74
-------
DRAFT
TABLE 7-L8
PLANTS VISITED USING DISTILLATION
Distillation is used by 12 plants contacted
7 69 83 214 371 520 529 561 679 687
717 932
REVERSE OSMOSIS
Definition of the Process
The more familiar process of osmosis is the passage, through a semi-
permeable membrane, of a liquid from a dilute to a more concentrated
solution. The transfer from one side of the membrane to the other con-
tinues until the head (pressure) is large enough to prevent any further
transfer of water to the more concentrated solution.
In reverse osmosis, applying pressure on the more concentrated solution
side of the semipermeable membrane will cause the permeate (pure water)
to diffuse through the membrane in the direction opposite osmotic
pressure. Left behind are the dissolved solids (concentrate) which can
be further treated or returned for reprocessing.
Process
In commercially available RO systems, three basic modules are used: the
tubular configuration, the spiral-wound, and the hollow fiber. Each,
however, works on the same RO principle, the only difference is how the
various membrane structures are mechanically designed and supported to
take the operating pressures.
Hollow-fiber modules consist of polyamide fibers, each having approxi-
mately 0.0076 cm (3 mils) OD with about 0.0043 cm (1.7 mil) ID. A
typical RO module will contain several hundred thousand of these fibers
in a long tube. The fibers are wrapped around a flow screen which is
then rollled into a spiral. Each end of the roll is potted in epoxy.
The module consists of lengths of the fiber membrane bent into a U shape
with their ends supported by the epoxy. Feed water, under 28.2 atm
(400 psig) , is brought into the center of the module through a porous
distributor tube where it flows through the membrane to the inside of
the fibers and from there to the end where it is collected. The concen-
trate is returned to the process or to further treatment.
Tubular membrane systems use a cellulose acetate membrane-lined porous
tube. In a typical tube system, a length of 2.54 cm (1 in) diameter
tube is wound on a support spool and enclosed within a plastic shroud.
Feed water is driven into the tube at approximately 55.4 atm (800 psig).
Permeate which passes through the walls of the coiled tube is collected
and drained off for use. Another type system module employs this prin-
ciple in a straight tube within a housing.
-------
DRAFT
Spiral-wound flat sheet membranes consist of a porous backing material
sandwiched between two membranes and glued along three edges. The
fourth edge of the "bag" is bonded to a product collection tube. A
spacer screen is placed on top of the bag, and the whole is rolled
around the central product collection tube. The spiraled unit is then
placed inside a pipe capable of supporting the feed water pressure.
In operation, the product water under pressure will permeat the mem-
brane and travel through the backing material to the central product
collection tube. The concentrate, containing dissolved solids, is then
led to drain, returned to the process, or fed to further treatment
facilities.
Advantages claimed for the hollow fiber and spiral-wound membranes over
the tubular-wound system include an ability to load .a large surface
area of membrane into a relatively small volume. On the other hand,
with regard to fouling tendencies, the tubular system is less suscepti-
ble to fouling than the others owing to its larger flow channel.
Although all three systems theoretically can be chemically regenerated,
it can be very difficult to remove deposits from the hollow fiber and
spiral-wound membrane types. One manufacturer claims that their helical
tubular module can be physically wiped clean by passing a soft porous
polyurethane plug under low pressure through the module.
In selecting reverse osmosis devices for use in treatment of wastewater,
the effect of temperature on any reverse osmosis device is significant.
As water temperature increases, viscosity of water decreases, and the
semipermeable membrane passes more water, approximately 3% per degree
centigrade. Therefore, the capacity is a straight line function of
temperature. However, pollutant permeability is also increased so that
water quality remains essentially constant. Membrane systems are often
rated at 20 degrees C (68 degrees F), and wastewater temperature should
be considered in sizing a RO unit.
Advantages and Limitations
Some advantages of reverse osmosis for handling process effluents are:
1. Ability to concentrate dilute solutions for recovery of salts
and chemicals.
2. Ability to purify water sufficiently for reuse.
3. Ability to operate under 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).
4. Operation at ambient temperature, i.e., about 15.5 to 32.2
degrees C (60 to 90 degrees F).
5. Relatively small floor space requirement for compact high
capacity units.
7-76
-------
DRAFT
Some limitations or disadvantages of the reverse osmosis process for
treatment of process effluents are:
1. 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 temperature will
increase the rate of membrane hydrolysis and reduce system
life, while lower temperature will result in decreased fluxes
with no damage to the membrane.)
2. Inability to handle certain solutions (strong oxidizing
agents, solvents and other organic compounds can cause
dissolution of the membrane).
3. Poor rejection of some compounds (some compounds such as
berates and organics of low molecular weight exhibit poor
rejection).
4. Fouling of membranes by slightly soluble components in
solution.
5. Fouling of membranes by feed waters with high levels of sus-
pended solids (such feed must be amenable to solids separation
before treatment by reverse osmosis).
6. Inability to treat highly concentrated solutions (some con-
centrated solutions may have initial osmotic pressures which
are so high that they either exceed available operation pres-
sures or are uneconomical to treat).
7. Normally requires pretreatment to achieve adequate life.
Specific Performance
Table 7-19 shows the removal efficiencies attainable with a properly
designed RO system.
Table 7-19
Pollutants Vs. Removal Efficiency
Pollutant Removal %^ Demonstrated
Ni 99 +
S04 99+
Cl" 98+
Org. Brighteners 95+
TDS 93
Cd 99+
CaCCn 98+
Na 86 +
Mg 96+
Fe 99+
-------
DRAFT
K 83 +
Silica 66+
Bicarbonate as EC03_ 90
Cu 99+
Zn 99+
NaCl 96
Cr 97+
Pb 99+
Cu 99 +
Ca 97 +
Ba 97+
Pesticides 98+ for most common
Phenols 95
Oils 95+
NOTE; This list contains many of the common constituents of industrial
wastewaters. It is not an exhaustive list of items tested or demonstra-
ted with RO. No composite tests exist showing all pollutants. Test
conditions (pH and other factors) may have been varied to produce the
indicated rejection rate for a specific item.
Operational Factors
Reliability - Reliability is fairly high if proper pretreatment is
employed to prevent fouling or membrane deterioration due to chemical
erosion.
Maintainability - Maintenance consists of replacement of membrane
modules, with life as a function of input concentrations and detri-
mental constituents.
Collected Wastes - Increasing stream concentrations 20 to 40 times often
enables reuse of the concentrate (plating rinses) or destruction of
wastes in a more economical manner. Pretreatment to reduce suspended
solids and slightly soluble compounds in solution is required. Pre-
treatment may also be necessary for solvents and organics which may
affect membrane life. Post-treatment for oils with activated carbon
may be desirable to produce rejection rates to 99+%. Low molecular
weight organics, if present, will require post-treatment since current
membrane technology has a low rejection capability.
Demonstration Status
The reverse osmosis units installed at Plant Number 230 as part of an
end-of-process water recovery system remains to be demonstrated as a
part of a total successful system. A project sponsored by the American
Electroplating Society has demonstrated that cellulose acetate membrane
can operate successfully on nickel and copper sulfate rinse waters and
that spiral wound and hollow fiber polyamide membranes can be used to
treat copper, zinc, and cadmium cyanide baths. A second phase of this
study is a demonstration in a plating shop of a full scale reverse
osmosis system on copper cyanide rinse water.
7-78
-------
DRAFT
A major brass products manufacturing company in the northeast has in-
stalled a system to produce 95-99%' recovery of 3,103.7 cu m/day (820K
gpd) wastewater. An electronics manufacturer produced 378.5 cu m/day
(100K gpd) ultra pure process water for the manufacture of semiconduc-
tors .
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-20 were contacted during this study and were found to currently
employ reverse osmosis as part or all of their wastewater treatment
system.
Table 7-20
Typical Industrial RO Installations
Company Market Application
136 Electronics ' Process
269 Metals Waste
214 Metals Process
230 Metals Process
526 Electronics Process
984 Electronics Process
983 Electronics Process
30 Electronics Process
Plant A Electronics Process
(Ottawa, Canada)
Plant B Electronics Process
(Ottawa, Canada)
Plant C Electronics Process
(Carrollton, Tex.)
ULTRAFILTRATION
Definition o_f the Process
Ultrafiltration (UF) is a process using semipermeable polymeric membrane
to separate molecular or colloidal materials dissolved or suspended in
a liquid phase when the liquid is under pressure. The membrane of an
ultrafilter forms a molecular screen which separates molecular particles
based on their differences in size, shape, and chemical structure. The
-------
DRAFT
membrane permits passage of solvents and lower molecular weight solutes
while barring dissolved or dispersed molecules above a predetermined
size. At present, an ultrafilter is capable of separating materials
with molecule weights in the range of 5,000 to 100,000.
An ultrafiltration-based process provides a very attractive solution to
the problem of disposal of soluble oil wastes.
Description of_ the Process
In an ultrafiltration process, the feed solution is punped through 3.
membrane unit (Figure 7-15) . Water and some low molecular weight mater-
ials pass through the membrane under the applied pressure. Emulsified
oil droplets and suspended particles are retained, concentrated, and
removed continuously. In contrast to ordinary filtration, retained
materials are washed off the membrane filter rather than by being held
by the filter.
The pore structure of the membrane acts as a filter, passing small par-
ticles, such as salts, while blocking larger emulsified and suspended
matter. The pores of ultrafiltration membranes are much smaller than
the blocked particles. Therefore, these particles cannot clog the
membrane structure.
Once a membrane is chosen that provides maximum attainable removal of
the desired particles, t.he next, most important design criterion is the
membrane capacity,, Here the term flux is used. Flux is the volume of
water passed through the membrane ares per unit time. The standard
units are cu m/day/sq m (gpd/sq ft). Both membrane equipment and op-
erating costs increase with the membrane area required. It is, there-
fore, desirable to maximize flux.
Membrane flux is normally dependent on operating pressure, temperature,
fluid velocity, solids concentration (both total dissolved solids and
total suspended solids), membrane permeability, membrane thickness, and
fluid viscosity. Membrane flux is also affected by the hydrophilic
nature 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 pumping capacity
and more horsepower. Less membrane area is, therefore, required per
unit of effluent to be treated with higher fluid velocities so the mem-
brane replacement and initial capital costs decrease. Opposing these
cost decreases is the increase in power and its attendant cost.
Advantages and Limitations
Ultrafiltration should be considered as an alternative to chemical
flocculation and coagulant systems which are followed by dissolved
air flotation because of the following major advantages:
1. Lower capital equipment, installation, and operating costs;
2. Insensitivity to the chemical nature of influent wastes;
7-80
-------
ULTRAFI LTUAT I.OH
DRAFT
MACROMOLECULES
ft?
.P-10-50 P.SJ c .
MEMERAHI*; /
WATER SALTS
c-
U c
O °
(' O
r '-"-~i
,^
• °* ° « s O '• ^OKCENTRM.'E
c . O "" «s=it^'-
"e O
«. O Q,
,0*0 c Ci o f>
,- f
c
CjL' f
t> OIL PARTICLES - DISSOLVED JiAIiTS AND LOW-
MOLECULAR-WEIGHT ORGAN1CS
FIGURE 7-15
SIMI'LIFIKD tlLTRAPir.'JL-RftTTON FLOW SCHEMATIC,
7-81
-------
DRAFT
3. Very high oil removal efficiency, independent of influent oil
content;
4. No chemical additions required;
5. No oily sludge generated;
6. Little, if any, pretreatment required;
7. Concentrated waste can be incinerated and may be self
sustaining;
8. Very compact; utilizes small amount of flow space;
9. Provides a positive barrier between oil and effluent. This
eliminates the possibility c^ oil discharge which might occur
due to operator error .
Some limitations or disadvantages of the ultraf iltration process for
treatment of process effluents are:
1. Limited temper atra:e roinje Ivi to 30 Degrees C tor most
satisfactory operation. Membrane life is decreased vritn
higher temperatures , but i:luy increases at elevated temp-
eratures. Therefore, surface araa requirements are a
function of temperature and become a trade off between
initial costs ^nd «rf-,plaoGiaeivi.; coctfj for the rvujmb-^.if1 ,
2. Inability to haadle certain Boli.xioiis, strong oxidizing
agents ; solvents, and other organic compounds can cause
dissolution of the memb?:ane ,
3. Poor rejection of some compounds.
4, Fouling of membrane £.- by slightly sioluble components in
solution.
Specific Per f ormarce
The most common applications of 'ult.raf i Itration involve the fo3.il owing:
Application Percent Removal Demons t r a t ed
Removal of Paint Solids .'.00?
Removal of Cutting Oils and
-------
Inks and Dyes 100%
Total Solids 95+%
pH and other conditions may vary in attaining the removal percents
shown. No known test exists which demonstrates these levels of
removal simultaneously from a waste stream or sample.
Operational Factors
Reliability - Reliability is high if proper control of input is main-
tiilned to prevent chemical damage to the membrane. Membrane life of
about two years can be assumed for proper systems.
Maintainability - Low scheduled maintenance of the membrane package and
normal maintenance of the pump package and lines are all that are
required.
Collected Wastes - A generalized membrane schematic is also shown in
Figure 15. Waste cutting oil emulsions, typically containing one to
five percent oi 3,, are concentrated by ultraf iltration to oil levels of
30 to 70 perrent.
The penmate or c^f fluent fiom the ultraf iltration unit is normally of a
guaijty that can be reined in inrkr^txlrj applications or discharged
roroctly, The concentrate from the ultraf iltration unit, can be disposed
of ieadiJy by incineration or by contract hauling. If incineration is
employed, additional fuel is not required because the concentrated emul-
sion will support combustion. If contract hauling is used, the cost is
lowered because the waste volume is small, and a usable product is
available to the contractor.
Ultrafiltration of the effluent obtained from electrophoretic painting,
which has developed over the past three years, provides an excellent
example of this process. Most of the automotive manufacturers and many
other U.S. companies use e3ectrophoretJc painting foi priming purposes.
^11 this application, ultraliItration is applied to the paint rather than
the- fc.f tlwont, because the ultraf13 irate from the paint has the same pH
and solvent level, as the paintc Tim use of the ultrafiltr^-te i;« tlto
Fiprc-y station, and returning the concentrate to the tank, maintains the
paint s'Glj.ds ;'n a ytable posiAion« Using ultraf iltration d:rectly on
the eiflnent for the purposes of concentration was not feasible owing
to the effluent's unstable nature. Application to the paint has allowec
many plants to increase paint solids to 15 percent from the previous
8-10 percent levels,
Flecding a small amount of the ultrafiltrate which contains no suspended
solids and generally two to 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 50,000
gallons) of paint were periodically dumped because of contamination hav«
now been eliminated by using ultrafiltration, thus reducing effluent
problems arising from this dumping process.
-------
DRAFT
The economics of the recovery of high price paint have allowed many
industrial ultrafiltration plants to be paid off in as little as six to
nine months, and this has fostered rapid acceptance of ultrafiltration
within the industry.
Demonstration Status
A manufacturer of aircraft engines, turbine generator sets, and gear
drives for both land and marine use generates soluble wastes consisting
of three general types:
1. Emulsified Machine Coolants;
2. Synthetic and Semisynthetic Coolants;
3. Oil-Contaminated Water.
In addition, ultrafiltration is used:
1. To remove these oily wastes from the effluent.
2. To remove dyes and printing inks for dye or ink-free water
discharge.
3. Followed by reverse osmosis of a portion of the UF permeate,
is used in conjunction with electrocoated paint to achieve
closed-loop rinsing. This results in zero effluent discharge,
substantial paint saving, and greater paint bath control.
4. With aqueous enamel over spray rinse water for paint free
water discharge and substantial paint recovery.
5. To produce an oil-free permeate and an oil concentrate for
disposal from an oily, emulsified waste.
There is an increasing acceptance of ultrafiltration as a proven tech-
nique for the removal of oily or paint contaminated wastes from the
effluent stream which permits rexise of both the permeate and concentrate
The concentrate is in a form which simplifies disposal through a.
scavenger or on site destruction.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-21 were contacted during this study and were found to currently
employ ultrafiltration as part or all of their wastewater treatment
system.
TABLE 7-21
PLANTS VISITED USING ULTRAFILTRATION
Ultrafiltration was used by 2 plants contacted
924
983
7-84
-------
•i
DRAFT
ELECTRODIALYSIS
Definition of_ the Process
Dialysis is a process in which solute or collodial species are exchanged
between two liquids through a selective semipermeable membrane in re-
sponse to differences in chemical potential between the liquids. The
membrane acts as a sieve allowing the passage of certain species and
rejecting the passage of others by a complex process of membrane
solution interaction.
Electrodialysis is the application to the above system of an electro-
motive force which effects separation of species according to their
charge. It is used primarily to remove and concentrate dilute solutions
of salts and other chemicals from a waste stream, thereby, providing
purified water.
Description of the Process
A simple electrodialysis system consists of an anode and a cathode sep-
arated by an anion permeable membrane near the anode and a cation per-
meable membrane near the cathode. An anode chamber, cathode chamber,
and center chamber are thereby formed. Upon application of an electric
charge, anions pass from the center chamber to the anode chamber, and
cations pass from the center chamber to the cathode chamber. The con-
centration of sale in the center chamber is, thereby, decreased.
Figure 7-16 shows the application of a simple electrodialysis cell tc
effect separation of a potassium sulfate solution (K2_SO^4) into its
components. ~
Practical electrodxaLysis installations contain from ten to hundreds of
compartments between one pair of electrodes. The application of an
electric: charge draws the anions to the cathode and cations to the anode
Industrial wastewater containing metallic salts enters the center cell,
and the charge takes the positive ions to the cathode and negative ions
to the anode. The result is a significant reduction in brine (salt and
water) in the center cell with an increase in solution concentrations in
the adjacent cells. Thus, the water from the center of each of three
adjacent cells is purified and metal ions concentrated in the cathode
cell with sulfates, chlorides, etc. concentrated in the anode cell. At
the outlet end of the stack, streams are drawn off from the individual
cells either as the purified water or as brine for recovery for
further treatment.
Figure 7-17 illustrates the operation of a seven chamber electrodialysis
cell.
In large electrodialysis installations, two or more stacks are linked in
series. The dilute effluent from the first stage is passed through an
-------
DRAFT
^CATHODE) —
H
CATION- ANION-
PERMEABLE PERMEABLE
MEMBRANE MEMBRANE
I I
OH
K2S04
(ANODE)
02
FIGURE 7-16
SIMPLE ELECTROD1AYSIS CELL.
7-86
-------
DRAFT
PURIFIED
WATER
CONCENTRATE
WASTE WATER
FIGURE 7-17
MECHANISM OF THE ELECTRODIALYTIC PROCESS.
7-87
-------
DRAFT
identical second stage, and so forth, the effluent from the final stage
reaching the desired concentration.
Advantages and Limitations
Some advantages of electrodialysis for handling process effluents are
as follows:
1. Ability to concentrate dilute solutions for recovery and
reuse of salts and other chemicals.
2. Ability to recover purified water for reuse.
3. Relatively small floor space requirement for compact high
capacity units.
4. Ability to handle simple or complex anions and cations.
Some limitations or disadvantages of the electrodialysis process for
the treatment of process effluents are:
1. Fouling of membranes by feeds high in particulate matter.
2. Corrosion of electrodes snd luembrsnes.
3. Purification will become increasingly more difficult as the
contamination level decreases due to the increase in the
electrical resistance cf the v;c,ter.
Specific Performance
Table 7-22 jllustrates the contaminants removal efficiency of electro-
dialysis in the treatment of a. variety of highly mineralized waters.
This table emphasizes thet laroe flow rates can be and are currently
processed with electrodialysis.
Operational Factors
Reliability - Reliability is fairly high with proper treatment to pre-
vent fouling or membrane deterioration due to chemical erosion. For
high effluent purity, a polishing operation is recommended.
Maintainability - Maintenance consists of replacement of membranes
and elecfcrod'es as a function cf input concentrations and detrimental
constituents.
Collected Wastes - High stream concentrations will often enable reuse
of the concentrate or will enable its destruction in s. more economical
manner. Pretreatment to reduce suspended solids and slight soluble
compounds in solution is required. Pretreatment may also be necessary
for solvents and organics which may affect membrane life.
7-88
-------
DRAFT
TABLE 7-22
SUMMARY LIST OF TEN ELECTRODIALYSIS
INSTALLATIONS_OP 250,000 GPD OR GREATER CAPACITY
Location
Buckeye, Arizona
Port Mansfield, Texas
Siesta Key, Florida
FIAT Factor, Bari,
Italy
Brindisi, Italy
Gilette, Wyoming
Sanibel, Florida
Petromin, Riyadh,
Raw Water
Total Solids
(ppm)
2,200
2,400
1,300
2,000
2,000
3,400
2,200
4,500
Treated Water
Total Solids
(ppm)
500
500
500
400
500
500-1,000
500
200
% Reduction
of Total Solids*
77
79
62
80
75
71-85
77
96
Saudi Arabia
Sonatrach, Arzew, 1,500 80 95
Algeria
Foss, Oklahoma 2,000 300 85
*Optimum conditions assumed.
7-89
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DRAFT
Demonstration Status
Several demonstrations have shown that electrodialysis is a promising
method. Further development and use of the method may be expected.
Copper cyanide rinse water may be concentrated sufficiently to be re-
turned to the bath by using two units on a double counter flow rinse
system. Copper may be recovered, and chromic acid regenerated in a
spent etching solution for printed circuits.
Electrodialysis as a workable waste treatment technique is also being
demonstrated in the removal and reuse of hydrofluoric acid contamin-
ation from rinse tanks. Prior to the application of electrodialysis,
these tanks rapidly became contaminated and had to be dumped biweekly.
With an electrodialysis cell added to the system, these tanks are not
detrimentally contaminated after six months of operation.
No Machinery and Mechanical Products Manufacturing plants were contacted
during this study which currently employ electrodialysis as part or all
of their wastewater treatment system.
LIQUID/LIQUID EXTRACTION
Definition of_ the Process
Liquid/liquid extraction is a process of extracting or removing contam-
inant (s) from a liquid by mixing the contaminated liquid with another
liquid which is immiscible and which has a higher affinity for the con-
taminating substance (s}« The contaminant (s) will be removed from the.
original liquid as the two immiscible liquids separate. A major appli-
cation 4K liquid/liquid separation is found in the removal of phenols
from wastewater.
Description of the Process
Liquid/liquid solvent extraction as a wastewater treatment technique
entails the contact of the effluent with an immiscible solvent. The
solute will distribute itself between the two solvents relative to the
solubilities involved. Depending on the nature of the contaminant, the
solvent system may consist of a pure solvent, or it may consist of a
solvent/dimer (a polymer chain of two monomer units length) solution.
In the latter case, the transfer of contaminants from the water to the
organic solvent is effected by an additional reaction of the contam-
inant (s) with the dimer rather than by a true solution process.
In a typical installation designed to remove phenolics (see Figure 7-18) ,
the waste flow is washed concurrently with a light oil solvent in five
stages, using Holley-Mott washers with a removal efficiency of about 80
percent in each stage. In the separator, the lighter density oil
(liquid A) moves to the upper half, and the denser phenolic waste
(liquid B) moves to the lower half. The mixed liquid flows through
channel Y and causes the solvent to flow through valve X into the mix-
ture. Similarly, the phenolic waste will flow through valve Z. Fresh
7-90
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DRAFT
Stirrer
Separator
Mixing
tank
FIGURE 7-18
HOLLEY^MOTT WASHER APPLIED IN THE REMOVAL OF PHENOLS
FROM WASTEWATER
7-91
-------
DRAFT
liquids are added to the mixing tank, and treated liquids are withdrawn
from the separator. By adjusting valves X and Y, it is possible to
maintain control over contact time, thereby, effecting the optimum
separation.
Another application of liquid/liquid separation in wastewater treatment
technology is in the removal of heavy metal ions from metal treating
effluent. Solvent extraction studies of a waste solution containing
nickel, zinc, and phosphate yield the following data.
Zinc was 99 percent extracted by di-2-ethylhexyl phosphoric acid in
kerosine, and nickel was 99 percent extracted by dinonyl naphthalene
sulfonic acid in butyl ether. Essentially all the phosphate remained
in the aqueous residue. Stripping each organic phase with dilute
sulfuric acid recovered the metal and regenerated the organic phase
for recycling. Figure 7-19 illustrates this extraction process.
Advantages and Limitations
Some advantages of liquid/liquid separation for handling process
effluents are as follows:
1. Ability to concentrate dilute solutions for recovery or for
more efficient destruction.
2. Ability to recover purified water for reuse.
3. Ability to operate under low power requirements.
4. Ability to recover organic solvent for reuse.
Some limitations or disadvantages of the liquid/liquid separation process
for treatment of process effluent are listed below.
1. Chemical interference is possible in the treatment of mixed
waste.
2. Solvent system may deteriorate with repeated use.
3. Process not highly developed with respect to many actual
industrial waste treatment situations.
4. Effluent pollution by the solvent employed in the separation
process is an undesirable possibility.
Specific Performance
Table 7-23 shows efficiency figures which were generated by the study
of a variety of industrial facilities.
7-92
-------
DRAFT
FEED
(AQUEOUS)
-ORGANIC
1
ZINC
EXTRACTION
I
ORGANIC
PHASE
SEPARATION
r
ORGANIC-
ORGANIC
•AQUEOUS
ZINC STRIP
1
H2S04
Tl
NICKEL
EXTRACTION
PHASE
SEPARATION
I
I
•ORGANIC
PHASE
SEPARATION
ZINC
PRODUCT
-AQUEOUS
1 1
H2S04
ORGANIC
PHOSPHATE
PROCESSING
1
NICKEL
STRIP
PHOSPHATE
PRODUCT
I
PHASE
SEPARATION
NICKEL
PRODUCT
FIGURE 7-19
FLOW DIAGRAM OF NICKEL/ZINC EXTRACTION
FROM PHOSPHATE SOLUTION
7-93
-------
DRAFT
Table 7-23
Liquid/Liquid Extraction Efficiencies
Percent Reduction
Parameter (Ideal Conditions) Demonstration Status
Phenols 99 Full Scale Facility
Chromium 99 Laboratory Facility
Nickel 99 Laboratory Facility
Zinc 99 Laboratory Facility
Nitric Acid & 95 Pilot Plant Facility
Nitrates
Hydrofluoric Acid 68 Pilot Plant Facility
& Fluorides
Iron 99 Pilot Plant Facility
Molybdenum 90 Pilot Plant Facility
Operational Factors
Reliability - Reliability should be high assuming the absence of sub-
stances which could adversely alter the character of the solvent or
affect the distribution ratio of the solute. This process does not have
widespread industrial use and, therefore, complete reliability data is
not available.
Maintainability - Maintenance consists of periodic solvent and stripping
solution renewal.
Collected Wastes - High stream concentrations will often enable reuse
of the concentrate or will enable its destruction in a more economical
manner. Pretreatment to reduce substances detrimental to the process
is required.
Demonstration Status
Liquid/liquid extraction systems are not known to be operating on a
practical level for the treatment of metal contaminants. There are,
however, a number of operational extraction systems applied in the
removal of phenols. One company is presently employing extractors in
several of its facilities to this end. Centrifugal extractors are in
use by another company in many of their plants. Both of these systems
are capable of removing 99 percent of the phenols from the effluent
stream.
7-94
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DRAFT
No Machinery and Mechanical Products iManufacturing plants were contact
during this study which currently employ liquid/liquid extraction as
part or all of their wastevater treatment system.
GAS PHASE SEPARATION
Definition of the^ Process
Gas phase separation is the process of separating volatile constituent
from water by the application of selective gas permeable membranes to
the wastewater '"flow.
Pollutants amenable to separation by this technique are carbonates
(low pH required to effect a gaseous state), ammonia (high pH required
to effect a gaseous state), and low molecular weight nonpolar organic
compounds.
Description o_f the Process
As an industrial waste treatment technique, gas phase separation is
effective in treating a dilute waste stream containing dissolved gases
which is passed through tubes lined with, or made from, selective gas
phase membranes. In this respect, it is similar to ultrafiltration in
that the product to be removed is passed through a selective membrane,
leaving behind the uncontarr.inated water. The removed gases remain
attached to the outer surface of the membrane until they are "washed"
off by a tangential flow of air or nitrogen. The concentrated contam-
inant gas can then be economically removed or disposed of.
At the present time, more development work is required before this prc
cess can be applied as a practical waste treatment, technique. Figure
7-20 shows a laboratory scale gas phase separator being applied in the
removal of carbon dioxide from water.
Advantages and Limitations
Some advantages of gas phase separation for handling process effluents
are as follows:
1. Ability to concentrate dilute solutions for recovery or for
more efficient destruction.
2. Ability to recover purified water for reuse.
3. Ability to operate under Jow power requirements.
4. Operation at ambient temperatures, i.e., 15.5 to 32.2
degrees C (60 to 90 degrees F).
Some limitations or disadvantages of the gas phase separation process
for treatment of process effluents are listed below:
-------
DRAFT
K, G
7-96
-------
DRAFT
FREEZ iNG/CRYSTaLI ZATIQH
Definition of the Process
Freezing/crystal ization is the solidification of a liquid into aggre-
gations of regular geometric forms (crystals) accomplished by subtrac-
tion of heat from the liquid. This process can be used for removal of
solids, oils, greases, and heavy metals from industrial wastewater.
Description of_ rhe_ Pi-oce_s_s_
As a waste treatment procedure, the freezing/crystal ization process is
based on the concept that when impure water is frozen the ice crystals
formed are of high purity. In this process, ice crystals ai e formed
in the water producing an ice slurry of 30 to 50% water ty weight.
Following the freezing operation, the ice crystals are separated from
the liquid and the ice washed with pure water to remove surface con-
taminants. The washed ice is melted to form purified water,
The drained liquid and wash water can be recycled for additional
treatment.
Actual freeze separation processes, can be classified into two basic
types - indirect refrigeration and direct refrigeration. In the djrect
refrigeration process, the refrigerant is in direct contact with the
water to be purii'ied. The indirect, refrigeration process requires a
heat exchanger for cooling the wastewatei. .
w
Iii the indirect refrigeration method, the incoming wastewater is pre-
coded and flowed to a freezing chamber. This freezing chamber is
cooled by iriear.s cf the cooliny coils of a refrigeration Eyt.ten.
The wastewater is cooled to the temperature where ice crystals axe
formed , The ice slurry is then flowed to a separation unit- for
separation and washing.
A method of direct refrigeration is in the introduction of refrigerant
directly into a water freezing chamber. The refrigerant used must have
a boiling point near the freezing point of water and be insoluble in
water. A refrigerant meeting these requirements is d nsobutane .
In this method, a compressor system for recovery of the refrigerant and
a separator to remove water vapor from the refrigerant are required.
In the f roezing/crystalization process, ice separation is usually ef-
fected by counter flow washing with purified water in a vertical, movin
bed of ice (Figure 7-21).
The ice slurry is fed in at the bottom, and most of the impure water is
strained from the purified ice. The ice crystals are then pushed up
vertically and simultaneously washed by a counter flow of purified wate
-------
DRAFT
Chute
Harvested ice
t& melt tank
Slush in
High impurity
weter out
FIGURE 7-21
COUNTER FLOW ICE WASHING
7-98
-------
FT
lc Only highly volatile pollutants wil,} be removed by this
technique .
2. Fouling of membranes by feeds high in suspended solids.
3. Unproven in practical waste treatment applications.
Specific Performance
The following Table 7-24 presents efficiency figures generated by the
study of. a laboratory scale gas phase separator treating prepared water
Table 724
S epa r a t i on
Percent
Parameter Reduction (?)
Carbonate (as Carbon Dioxide) 99%
Oxygen (1) 96%
Ammonia 1JO%
Organic Volatiles Data Not Available
11} Not a pollutant but included for completeness,
(2) Optirr.uiTi conditions assumed.
Cp n ? •
-------
DRAFT
t applied to the top of the ice bed. The ice is continuously scraped off
at the top and transferred to the melting unit.
Advantages and Limitations
Some advantages of freezing/crystalization for handling process effluents
are as follows:
1. No membrane to be fouled by the concentrate or other
contaminants.
2. Suspended solids do not affect the process.
3. Ability to recover purified water for reuse.
4. Low operational temperature inhibits corrosion.
Some limitations or disadvantages of the freezing/crystalization process
are as follows:
1. High energy requirement to operate compressors and pumps.
2. Process not highly developed with respect to actual industrial
waste treatment situations.
3. In the direct contact process, the refrigerant becomes
contaminated by water vapor and must be purified before reuse.
4. Improper temperature control wil) allow the entrapment in the
crystal conglomerate of an excessive amount of contaminant.
Specific Performance
The feasibility of using freezing for treatment of industrial wastewater
was demonstrated on a laboratory scale using a solution containing about
100 mg/1 each of nickel, cadmium, chromium, and zinc, along with 30,000
mg/1 of sodium chloride. Greater than 99.5 percent removal of the metal-
lic ions was achieved in the experiments, with the purified water effluent
containing less than 0.5 mg/1 each of the individual heavy metals.
Operational Factors
, Reliability - High, assuming proper monitor and control temperature.
, iMaintainability - Maintenance consists of cleaning or replacement of
* screens/filters with life as a function of input concentrations and
detrimental constituents.
Collected Wastes - High stream concentrations often enable reuse of
the concentrate or enable its destruction in a more economical manner.
Demonstration Status
No commercial utilization of freezing/crystalization for the treatment
7-100
-------
DRAFT
of induotris? vr.rlowpic.y it, hi.o-/,;f ^ow.vu. , a pilot plant operation
vitla a rapacity ci < ,bCe liU
-------
DRAFT
| that can be used in 3arge facilities. Hypochlorite forms have been
used primarily in smell systems or in large systems where safety con-
cerns outweigh economic concerns.
A typical assembly for the application of gaseous chlorine to wastewater
is shown as Figure 7-22,
ta t ion &
Some advantages of disintection for handling process effluent are as
follows :
1. Operation at ambient temperatures, i.e., 15.5 to 32.2
Degrees C (60 to 90 Degrees F) .
2. Proven effectiveness.
3. Process well s\\? ted to automatic control.
Seise Imitations of disinfection for treatment of process effluent are
as follows:
1. Chenc' 'cal interfei once is possible in the treatment of mixed
i-ja^ter .
2. Process it; extremely sensitive to "short circuiting"
necessitating highly efficient dispersal of disinfectant.
3* .\ p?>« eiiliel \y ha.tardows situation will exist when chlorine
gas is stored and handled.
Specific
; In the disinfection of wastewater, it is not necessary or desirable to
j achieve a total bacterial kill. With the proper disinfectant dosage
j and necessary pretreatmeut, effective control of a bacterial population
1 can be maintained«
Table 7=25 gives typical disinfectant dosages (chlorine) for a variety
of waste treatment operations„
T_cjble_ 7-25
Typical Chlorine Dosages For Disinfection
Dosage Range
Effluent From mg/liter
Untreated Wastewater G-?5
(Prechlorineticn)
Primary Sedimentation 5-20
Chemical-Precipitation Plant 2-C
7-102
-------
DRAFT
DitctMrge.
Water prusjur*
g«ug»
Regulator MMmbly
Chlorine-preisure
gauge
- — -^
1
'
~\
|
N
LI
icf~
u
Vent to
outdoor* c,rwnic
fiftw
Solution
ditcharg*
Rotmwtw
•djuttnwn
W*Mr
Chkxin*
lolutian
FIGURE 7-22
TYPICAL VACUUM-FEED CHLORINATOR.
-------
DRAFT
Trickling-Filter Plant 3-15
Activated-Sludge Plant 2-8
Multimedia Filter Following 1-5
Activated~Sludge Plant
Operational Factors
Reliability - High, assuming sufficient disinfectant and proper mixing.
Mainta inabi1ity - If an automatic feed system is used/ maintenance con-
sists of periodic loadings of hoppers or replacement of gas cylinders,
with life as a function of input concentrations and detrimental
constituents.
Collected Wastes - Pretreatment to eliminate substance which will in-
terfere with the process may be desirable. The generation of sludge
which must be removed from the waste stream is not inherent in the
disinfection process.
Demonstration Status
The disinfection of wastewater is a classic process and will be found
in numerous industrial waste treatment facilities.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-26 were contacted during this study and were found to currently
employ chemical disinfection as part or all of their wastewater treat-
ment system.
ANAEROBIC DIGESTION
Definition of_ the Process
Anaerobic digestion is the biochemically actuated decomposition or di-
gestion of organic materials in the absence of oxygen. The chemical
agents effecting this deomposition are microorganism secretions termed
enzymes. The principal products in a properly controlled anaerobic di-
gestion process are methane and carbon dioxide. Figure 7-23 illustrates
the anaerobic digestion process.
Anaerobic digestion has a limited usefulness in the Machinery and Me-
chanical Products industries because of the low number of manufacturing
operations generating high concentrations of organic waste.
Description ojE the Process
The principal application of anaerobic bioactivity as a waste treatment
procedure is in anaerobic sludge digestion tanks in municipal treatment
plants.
7-104
-------
DRAFT
>-.?C
VISITED USIKG CJKLORIHtTlON
Chitarination is used by 36 plants contacted
5-8 88 118 1*4 149 158 27'8 282 2'84 267
304 357 413 433 477 535 567 $09 62'5 628
64C 699 707 713 732 752 756 779 923 924
927 931 936 937 942 972
7-105
-------
DRAFT
Conventional sludge digestion ie carried out as either a one step or a
two step process. The sludge in the digestion tank is heated by means
of internal or external heating coils., In the one step process, diges-
tion, thickening, and supernatant formation are carried out simultan-
eously. Raw sludge is added in the ?one where the sludge is actively
digesting, As the gas generated in the digestion process rises to the
surf ace , it lifts some of the lighter wastewater components such as
oils, greases, and fats to the surface forming a scum layer.
As a result of digestion, i.he sludge becomes more mineralised and set-
tles and thickens due to gravity. This leads to the formation of a
supernatant layer above the digesting sludge. Due to this stratifica-
tion and the lack of intimate mixing, the volume of a one step digester
tank is not more than 50 percent utilized. Recognizing these limita-
tions, most conventional digestion operations are carried our; as a two
step process.
In the two step proce.sc- .. the first tank is used for digestion and is
equipped with heating and mixing facilities. The second tank Is used
for storage and concentration of digested sludge and. for formation of
the r^lstivf j.y e] yar supernat^ti*, liquid, I-' oqv-;'t)yf the I auks; are
iaude identical, in wh.' ch case either one may be the primary. In ot;htir
C3S3S.7 t.L;'-! second tgnk may be an open tank,, an unheated tank,, or a
s 1 udge 1 agoon .
Since the gas evolved in the anaerobic digestion process forms an explo-
sive mixture with air,, the flight ion tanks- re covered , The entrapped
yas is drr.w.a ol"',' periodically x.-r u^e> a?; a fuel or tor naf^ disposal. The
tenks £i..r'5 nominally circular and, are seldom ]ess than 8.1 meters (20 feet)
or mere thr-i- 35 softer & (3,1£ f^e-i,} in oiyyacater, ax'id they should have a water
depth 01 xroru 7»62 to 13.72 muters (/,:: i '• 4b fe« t) or xaoxe at the center.
Tho bottom shuulti alope to 1/a^ s? udge drawoif in the center with a
m;n?nmu> I'lc^pe of one unit vprti-j?] f.o J^oux' unitb horizontal.
An uuva\.ced iuethod of ai.i@,ei"obic digestion is the anaerobic contact pro
cess- In tl:-ia ->rocesu,- r.aw wa^l ei» are mixed w;' th recycled sludge and
then, digested in a nixed digestion cnarnbc'r. The recycled sludqe pro-
vides a soui'r« of anaorobj r bacteria, thereby accelerating t.he ^jocess.
After digastionF the .u.at1 th--"1 supei'Jia'-,,-int; is dischaigr^d as effluei',t(. Self-tied
sludge is theu recy«,;]f.(7 to secsd the j,,icoming was-fa. 'fJhis proceaa has
been used successfully f.or i he stabilisation of meat packing arid other
high strength soluble wastes. Figure */-23 shows the operation of the
anaerobic cmtact process.
and
, This type of treatment process is less expensive than the conventional
j activated sludge process. It can accept shook loads and is capable of
| being shut down for extended periods without loss of efficiency.
Due to the low cellular growth rate ana the conversion of organic matter
to methane gas and carbon dioxide f the resulting solid matter is well
7-1CC
-------
DRAFT
GAS
RAW SNLCT
"'v,.
GAS
•V
I MIXING
V
VACUUM
; SCTTUNG
CKFLU
4*
SOLIDS RECYCLED
/
FIGURE 7-23
ANAEROBIC CONTACT
-------
DRAFT
stabilized and frequently suitable for disposal after drying or dewater-
ing in dumps or on land as a soil conditioner.
Because of the low microorganism growth rate in anaerobic waste treat-
ment, there is a low requirement for biological nutrients, such as
nitrogen and phosphorus as compared to aerobic processes such as the
activated sludge process, The slow growth rate of the methane bacteria
also limits the ai-aerobic treatment of an organic waste, in that these
microorganisms ..react sluggishly to changing conditions in their environ-
ment. Thus, relatively long periods of time are required to establish
a balanced sysiezn.
Specific Peyformance^
Anaerobic digestion is not normally found in the Machinery und Mechanical
Products industries due to the low organic content of the waste streams.
The c jilo'wing 'Table 7-27 provides examples of the use of this process in
other indvistri es.
Table 7-27
Maize
Whiskey Distillery
Cotton KierJng
CJ trins
Brewery
Starch-Gluten
Wine
Yeast
Molasses
Meat-Packing
Meat-Packing
Meat-Packing
Meat-Packing
Meat-Packin«
Detention
3.3
6.2
1.3
1.3
2 .3
3^8
2-0
2.0
3.8
1.3
0.5
0.5
0.5
Raw Waste
BOD mg/Iiter
6,280
25,000
1,600
4,600
3,900
14,000 (2)
23,400 (2)
11,900 (2)
32,800
2,000
1,380
1,430
1,310
1,110
(2)
Percent
Removed (!)
95
67
87
36
80
85
65
69
95
91
95
94
91
(1) Optimum conditions as stored.
(2) Volatile suspended solids, Esther than BOD.
Operational Factory
Reliability - High, assuming adequate temperature, pH/ and detention
time control. Pretreatinent to eliminate substances toxic to the micro-
organisms effecting the digestion may be necessary. In some cases,
adaptation will increase the tolerance level of the microorganisms for
toxic substances.
Maintainability - Maintenance consists of periodic removal of digested
sludge, drawing off of entrapped gas, and skimming of the scum layer
7-108
-------
DRAFT
generated in the process with life being a function of input concentra-
tions and detrimental constituents.
Collected Wastes - Pretreatment to eliminate substances toxic to the
process may be necessary. Dewatering of digested sludge generated in
the process may be desirable prior to a contractor removal, incinera-
tion, or disposal to landfill. The collected gas from the digestion
may be used as a fuel.
Demonstration Status
Anaerobic digestion has been used to treat sewage since the 1800's. At
the present, the process is widely used for large municipal systems.
Little difference exists in the methods and practices used 40 years ago
and those used todaye but great progress has been made in the fundamen-
tal understanding and control of the process, the sizing of tanks, and
the design and application of equipment.
No Machinery and Mechanical Products Manufacturing plants were contacted
during this study which currently employ anaerobic digestion as part or
all of their wastewater treatment system.
AEROBIC DIGESTION
Definition of the Process
Aerobic digestion is the biochemically actuated decomposition or diges-
tion 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 control! led aerobic di-
gestion are carbon dioxide and water. Aerobic digestion is used mainly
in the treatment of organic chemicals and lubricants used in the film
industry and such other industries that use organic lubricants«
Description of_ the Proce£S
As a waste treatment aid, aerobic digestion plays an important role in
the following organic waste treatment processes:
1. Activated Sludge Process
2. Trickling Filter Process
3. Oxidation Pond Process
The activated sludge process consists of the aeration of a biodegrad-
able waste for a sufficient time to allow the formation of a large
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 7-24. The
westes 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
•7_i no
-------
DRAFT
SET* LED
WASTES
AERATION
U
•TD • ---JUT -*,-i-*.
RETURN SLUDGE
SECONDARY\ EFFLUENT
SEDJMEN-
- TAT ION
V,,
, WASTE CXCFSS
SLUDGE
FIGURE 7-24
SCHEMATIC DIAGRAM OF A CONVCNT!OE^AL ACTIVATED SLUDGE SYSTEM.
7-110
-------
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 trjLcj£rinc[ filter is basically s bed of stones or other suitable
material covered with slime over which organic wastes slowly flow. A
schematic cross section of a trickling filter iu shown as Figure 7-25.
As wastewater passes through the filter, it diffuses into the slimes
where aerobic and anaerobic digestion occurs. After primary sedimenta-
tion, the wastewater is introduced onto the filter by a rotary distri-
butor 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 sedimentation tank. A schematic
diagram of a single stage trickling filter is shown as Figure 7-26.
^ oxidation pond 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. Aerobic digestion is one of the factors responsible to
periodically aerate and dredge the; oxidation pond in order to maintain
the proper ecological balance.
Advantages and Limitations
Advantages of aerobic digestion as compared to anaerobic digestion in-
clude 1) lower BOD concentrations in supernatant liquor, 2) production
of an odorless,, humus-like, biologically stable end product with excel-
lent dewaterimj characteristics that can foe easily disposed, 3) recov-
ery of more of the basic fertiliser values in the sludge,, and 4} fewer
operational problems and lower initial, cost,, ','be major disadvantages
of t.hti aerobic digestion process are 1} higher operational cost asso-
ciated with supplying the required, oxygen, and 2 } methane (a. useful,
by-product) is not generated in the process . Comparing ;,he advantages
and disadvantages, it appears thr^' aerobic digestion is an alternative
that should be consi de-red more often, especially for use in the smaller
treatment. >:aci.lltv. Aerobic digestion has a limited usefulness in in-
dustry because ot tee "Sow number •„•<.' manufacturing operations generating
high concentrations of organic waste.
The following efficiency figures were generated by the atudy of a vari-
ety of waste treatment facilities using the activated sludge process
for treating organic wastes. This type treatment is not in common use
in the Machinery and Mechanical Product, s industries. The examples given
in Table 7~2S are provided to shov? typical, removal efficiencies mid to
provide a basis for the tranfej; oi technology from other industries to
the Machinery and Mechanical, Products industries.
7-111
-------
DE3> /°> C" "P^"
RAFT
-
Stone media
(2"'-4")
\««. /
-
era rains
Reinforced concrete floor
FIGURE 7-25
SCHEMATIC CROSS SECTION OF A TRICKLING FILTER
7-112
-------
DRAFT
11 Waste
[{sludge
Secondary
sedimenta-
tion
Raw sewage /Primary
sedimenta-
tion
FIGURE 7-26
SCHEMATIC DIAGRAM OF A SINGLE-STAGE TRICKLING FILTER.
-------
DRAFT
TABLE 7-28
TYPICAL BOD REMOVAL EFFICIENCIES
Type of Waste
Combined Pulp, Paper,
and Domestic
Kraft and Neutral
Sulfite Mill
Dairy
Germantown, Ohio
Dayton, Ohio
Cannery
Tomatoes
Peaches and Tomatoes
Apples and Tomatoes
Apples
Paper Mill
Dairy
Chemung, 111.
Huntley, ill.>
Kraft Mill
Pulp and Paper
Pulp and Paper
Kraft Mill
Ammonia Still
Refinery
White Water
Pulp and Paper
No. 1
No. 2
No. 3
N/A - Not Available
Flow
mcjd
10.9
14
0.0072
0.0044
0.62
0.75
0.49
13 ' '
0.053
0.015
16
21.0
N/A
N/A
N/A
N/A
Initial
BOD, ppm
198
183
673
567"
412
740
492
630
208
1,150
.950 .
140
188
446
144
100
1,100
2,000
249
191
218
Detention
Time , Hr
6.5
3.0
41.2
39.4
0.8
0.65
1.0
4.75
3.5
14.7
21.0
3.0
2.3
10.2
8.0
5.0
4.0
8.0
0.5
1.0
2.0
BOD
Removed
83.5%
78%
• 95.4%
96.7%
85%
58%
89.7%
81.6%
70%
80%
91%
85%
84%
91%
85%
93%
87%
86%
72%
87%
93%
7-114
-------
DRAFT
Operational Factors
Reliability - High reliability assuming adequate temperature, pH, de-
tention time, and oxygen content control. Pretreatment to eliminate
substances toxic to the microorganisms effecting digestion may be
necessary. (In some cases, adaptation will increase the tolerance
level of the microorganisms for toxic substances.)
Maintainability - Maintenance of the three main waste treatment techniques
employing aerobic digestion is detailed in the following table:
Process Maintenance
Activated Sludge Periodic removal of excess sludge and
skimming of scum layer.
Trickling Filter Periodic application of insecticides to
reduce the insect population and periodic
chlorination to reduce excess bacterial
population.
Oxidation Pond Periodic dredging to remove excess
sludge, and periodic aeration to maintain
the pond's aerobic character.
Collected Wastes - Pretreatment to eliminate substances toxic to the
process may be necessary. Dewatering of digested sludge generated in
the activated sludge process may be desirable prior to contractor
removal, incineration, or disposal to landfill.
Demonstration Status
Aerobic digestion is a widely used unit process to reduce organic con-
tent of wastewaters. Although this process is completely proven, a
test (pilot) plant should be run prior to full scale incorporation in
an industrial treatment facility.
No Machinery and Mechanical Products Manufacturing plants were contacted
during this study which currently employ aerobic digestion as part or
all of their wastewater treatment.
THICKENING
Definition of_ the Process
Thickening is the concentrating of solids in a solid-liquid system by
the application of a force which will effect a physical separation of
the phases. As a waste treatment technique, thickening is employed to
concentrate sludge prior to dewatering. Two techniques commonly applied
to thicken sludge are gravity thickening and oil flotation thickening.
Description of_ the Process
in the gravity thickening process, dilute primary or activated sludge
is fed from a primary settling tank to a thickening tank. Rakes stir
7-115
-------
DRAFT
the sludge gently to release water, air, and gas and to push the con-
centrated sludge to a central collection well. The supernatant flow
that results is returned to the primary settling tank. The thickened
sludge that collects on the bottom of the tank is pumped to digesters
or dewatering equipment as required. Figure 7-27 shows the design and
construction of a gravity thickener.
In the air flotation thickening process, the waste flow or a portion of
clarified effluent is pressurized to approximately 3.40 atm (50 psi) in
the presence of sufficient air to approach saturation. This pressurized
liquid is released to atmospheric pressure in the flotation tank where
it gives up dissolved air in the form of minute bubbles. These bubbles
become trapped by the sludge floe and float the sludge to the surface
,;here, in its thickened condition, it is amenable to skimming and
further processing.
The clear effluent is removed from the bottom of the flotation unit for
discharge, further treatment, or recirculation. Figure 7-28 shows the
operation of two types of flotation thickening systems.
Advantages and Limitations
The principal advantage obtained by the application of a sludge thick-
ening process is that it facilitates further sludge processing. Other
advantages are high reliability and minimum maintenance requirements.
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.
Specific Performance
Primary sludges from sedimentation units of one to two percent solids
concentration can usually be gravity thickened to six to ten percent;
biological and chemical sludges can be thickened to four to six percent.
Flotation thickeners are used primarily with activated sludge and nor-
mally will produce a sludge with approximately four percent solids.
Concentrations averaging six percent and ranging as high as eight per-
cent have been obtained with mixtures of activated and primary sludges.
Flotation thickeners are more efficient than gravity thickeners and
may be operated at the solid loadings given in Table 7-29.
Table 7-29 - Loading of_ Dissolved-Air Flotation Units
Loading
Type of Sludge Kg/Sq M/Day
Activated (Mixed Liquor) 2.27-6.80
Activated (Settled) 4.53-9.08
50% Primary + 50% Activated (Settled) 9.08-18.15
Primary Only to 24.94
7-116
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DRAFT
^THICKENING:
•TANK;
SLUDGE PUMP
OVERFLOW
RECYCLED
THROUGH
PLANT
FIGURE 7-27 MECHANICAL "KA.VITY THICKENING
-------
DRAFT
Air
Retention
tank
»ste I
uent V-v
—~LH
Waste
influent
Flotation tank
1 H
Thickened
sludge
Pressurizmg Pressure
pump reducing
valve
1
Effluent
(A)
Influent waste
Pressure
reducing valve
•*—•
L
JL Air release
Recycle
Retention
tank
I Air
injection
(B)
FIGURE 7-28
SCHEMATIC REPRESENTATION OF FLOTATION SYSTEMS.
(A) FLOTATION SYSTEM WITHOUT RECIRCULATION
(B) FLOTATION SYSTEM WITH RECIRCULATION.
7-118
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DRAFT
Operational Factors
Reliability - Reliability is high assuming proper design and operation.
A gravity thickener is designed on the basis of a unit area, square
feet per pound of solids per day, in which the required surface area is
related to the solids entering and leaving the unit. Thickener area
requirements are also expressed in terms of mass loading, grams solid
per square meter per day (pounds solids per square foot per day).
Maintainability - Twice a year a thickener must be shut down for lub-
rication of the drive mechanisms. Occasionally, water must be pumped
back through the system in order to clear sludge pipes.
Collected Wastes - Thickened sludge from a gravity or flotation thicken-
ing process will usually require dewatering prior to disposal, incinera-
tion, or drying. If the sludge consists of raw organic waste, aerobic
or anaerobic digestion will be a process requirement.
The clear effluent may be recirculated in part, or it may be subjected
to further treatment prior to discharge.
Demonstration Status
Sludge thickeners are widely used throughout industry to reduce water
content to a level where the sludge may be efficiently handled. Further
dewatering is usually practiced to minimize hauling costs to approved
landfill areas.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-30 were contacted during this study and were found to currently
employ thickening as part or all of their wastewater treatment system.
PRESSURE FILTRATION
Definition of the Process
Pressure filtration is 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. The positive pressure ex-
erted by feed pump(s) or other mechanical means provide the pressure
differential and is the principal driving force.
As a waste treatment procedure, pressure filtration is used to dewater
sludge. A typical pressure filter 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 and moving end.
Description of_ the Process
On the face of each individual plate is mounted a filter cloth. The
sludge is fed by a suitable pumping method into the press and passes
-------
DRAFT
TABLE 7-30
PLANTS VISITED USING THICKENING
Thickening is used by 71 plants contacted:
7 12 15 17 49 64 78 79 107 108
140 182 194 219 221 246 247 249 256 282
284 287 301 304 310 342 363 365 381 382
383 392 397 416 428 509 511 525 530 542
543 549 558 564 567 590 609 623 625 646
665 675 677 678 692 704 711 712 713 717
739 740 749 752 756 826 835 924 932 960
1498
7-120
-------
DRAFT
through feed holes in the trays along the length of the press until the
cavities or chambers between the trays are completely filled. The
sludge is then entrapped, and a cake begins to form on the surface of
the cloth. The water passes through the fibers of the cloth, and the
solids are retained.
At the bottom of the trays, drainage ports are provided. The filtrate
is collected and discharged to a common drain. As the filter media be-
comes coated with sludge cake, the flow of filtrate through the pressure
filter drops to near zero indicating that the capacity of the filter has
been exhausted. The filter is then vented and opened to discharge the
dewatered sludge to a hopper or conveyor. After closure, the filter is
ready for a new cycle. Figures 7-29 and 7-30 show the design and op-
eration of a typical pressure filter.
Advantages and Limitations
The pressures which may be applied to a sludge for removal of water by
pressure filters now available range from 341 atm to 1,362 atm. In
comparison, a centrifuge may provide forces at 239 atm and a vacuum
filter, 69 atm. As a result of these greater pressures, filter presses
offer the following advantages:
1. Filtration efficiency is improved, especially on materials
which are difficult to filter.
2. Requirements for chemical pretreatment are frequently reduced.
3. Solids concentration in the final cake is increased.
4. Filter cakes are more easily accommodated by material handling
system.
5. Filtrate quality as measured by suspended solids content is
improved.
6. Maintenance is minimal because very few moving parts are
involved.
Two disadvantages associated with past operations have been the short
life of filter cloths and lack of automation. New, synthetic fibers
have largely offset the first of these and have increased cloth life up
to 12-18 months. Units with automated feeding and pressing cycles are
also now available, and it is only at the end of the cycle that the
process becomes semiautomatic as no foolproof method of discharging the
filter cake automatically is yet available.
Specific Performance
In a typical pressure filtration, chemically preconditioned sludge de-
tained in a pressure filter for one to three hours under pressures vary-
ing from 5.1 to 13.2 atm (60 to 180 psig) exhibited final moisture con-
-------
DRAFT
w
u
H
I
B
Q
2
W
w
eu
o
w
c^
u
§
I I I I
T T
-------
DRAFT
FIXED END
FILTER CLOTHS
FILTRATE DRAIN HOLES
FIGURE 7-30
FEED FLOW AND FILTRATE DRAINAGE.
7-123
-------
DRAFT
tents between 50 and 75 percent.
Operational Factors
Reliability - High, assuming proper design and control. Sludge charac-
teristics vhich will dictate design and control parameters are listed
below:
1. Size, shape, and electrical charge of the solid particles
2. Solids concentration and volatiles content
3. Chemical composition
4. Compressibility
5. Viscosity
Pretreatment such as screening or coagulant addition may be a process
requirement.
Maintainability - Maintenance consists of periodic cleaning or replace-
ment of the filter media, drainage grids, drainage piping, filter pans,
and other parts of the equipment. Since the removal of the dewatered
sludge cake from the filter media is not a fully automatic process, a
manual scraping operation is also a maintenance requirement.
Collected Wastes - Sludge dewatered in the pressure filtration may be
heat dried and processed as a fertilizer, or it may be disposed of by
incineration or by direct application as landfill. The clarified ef-
fluent may require further treatment prior to discharge if it is high
in dissolved or suspended solids.
Demonstration Status
Pressure filtration of sludge, although used more extensively in Europe
than in the United States, has been effectively employed at the munici-
pal treatment plant in Atlanta, Georgia and at the Sobrante filter
plant of the East Bay municipal system in the San Francisco Bay Area,
California.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-31 were contacted during this study and were found to currently
employ pressure filtration as part or all of the wastewater treatment
system.
TABLE 7-31
PLANTS VISITED USING PRESSURE FILTRATION
Pressure filtration is used by 16 plants contacted
53 149 193 221 399 431 457 511 590 632
657 731 787 962 974 1498
7-124
-------
DRAFT
HEAT TREATMENT
Definition of the Process
Heat treatment is the addition of heat to a substance to effect a tem-
perature increase in that substance which results in its permanent
physical or chemical alteration. In waste treatment, heat treating is
used to reduce the water content of sludge and is mainly applicable to
municipal waste treatment plants.
Description of_ th_£ Process
As a waste treatment procedure, heat treatment is a sludge conditioning
process that involves heating the sludge under pressure resulting in
coagulation of solids, breakdown of gel structure, and reduction of the
solids affinity for water. The treated sludge is sterilized, deodorized,
and is amenable to dewatering.
Two processes applied in the heat treatment of sludge are the Porteus
process and the Zimpro process.
In the Porteus process, sludge is preheated and channeled to a reactor
vessel. Steam is injected into this vessel to bring the temperature to
within the range of 143 to 199 degrees C (290 to 390 degrees F) under
pressures of l.j.2 to 14.6 atm (150 to 200 psig) . After a 30 minute
detention in the reactor, the sludge is discharged through a. heet
exchanger into a decant tank.
In the Zimpro process, the sludge is treated as in the Porteus process
except that air is injected into the reactcr vessel with the sludge.
The reactor vessel is heated by steam to temperature-,s in the range of
149 to 204 Decrees C (300 to 400 Degrees F) under pressures varying
from 11.2 to 41.8 atm (150 to 300 psig). Heat released as the result
of air induced oxidation increases the operating temperature tc a range
cf 177 to 316 Degrees C (350 to 600 Degrees F), The partially oxidized
sludge may be dewatered by filtration, centrifugaticn, or drainage or.
beds.
The supernatant or filtrate liquid obtained from both of these processes
contains high concentrations of short-chain water-soluble organic com-
pounds that are amenable to biological treatment.
Advantages and Limitations
Heat treatment processes are relatively expensive to install and oper-
ate. The heat treatment process will, however, affect cost savings in
the subsequent process of landfilling or contractor hauling by render-
ing it more amenable to these techniques. A limitation of heat treat-
ment is that the BOD of the sludge is solubilized and, appearing in the
liquid effluent, necessitates more extensive aeration or detention cf
that liquid effluent before discharge.
7-125
-------
DRAFT
Specific Performance
Sludge thickened in the Porteus process can be filtered to a solids con-
tent of 40 to 50 percent. Filter yields up to 97.7 Kg/m2/hr (20 Ib/sq
ft/hr) have been obtained.
In the Zimpro process, the solids content of the dewatered sludge can
range from 30 to 50 percent depending on the degree of oxidation desired.
Essentially, complete oxidation of volatile solids (approximately 90
percent reduction) can be accomplished with higher pressures and temper-
atures .
Operational Factors
Reliability - High, assuming proper temperature/pressure control and
adequate detention time. Pretreatment of the sludge to remove grit and
stones may be required.
Maintainability - Maintenance includes periodic lubrication of pumps
and repair and cleaning of high temperature steam pipes. One process
modification involves use of hot water rather than steam as a heat
transfer fluid, thereby minimizing pipe corrosion.
Collected Wastes - Sludge from the heat treatment process will usually
require dewatering prior to disposal, incineration or drying. The clear
effluent, usually high in BOD, can be recirculated to the main flow, or
it may be treated separately by aeration and/or digestion.
Demonstration Status
Although heat treatment is not presently in wide use, the following
communities are known to be using or constructing a heat treatment
system for their municipal wastes:
1. Springfield, Massachusetts Zimpro System
2. Akron, Ohio Zimpro System
3. Mentor, Ohio Porteus System
4. Colorado Springs, Colorado Porteus System
The use of heat treatment in the processing of industrial wastes is not
known.
No Machinery and Mechanical Products Manufacturing plants were contacted
during this study which currently employ heat treatment as part or all
of their wastewater treatment system.
HEAT DRYING
Definition of_ the Process
Heat drying is the process of reducing the water and voltailes content
of a substance by the application of auxiliary heat. The auxiliary heat
7-126
-------
DRAFT
increases the vapor holding capacity of the air and accelerates the
evaporation of volatiles from the substance being dried.
Description of_ the Process
As a waste treatment procedure, heat drying is employed to reduce the
moisture content of wet sludge so that it can be efficiently incinerated
or otherwise disposed.
The principal systems employed in the drying of sludge are:
1. Flash Drying
2. Spray Drying
3. Rotary Kiln Drying
4. Multiple Hearth Drying
The flash drying operation involves pulverizing the sludge ir. the pre-
sence cf hot gases. The equipment is designed so that the sludge par-
ticles remain in contact with the hot gases long enough to accomplish
the required moisture transfer.
One particular operation involves a cage mill that receives a mixture
of wet sludge or sludge cake and recycled dried sludge. The hot gases
and the pulverized sludge are forced up a duct in which most of the
drying takes place. They are then channeled to a. cyclone which sepa-
rates the vapor from the solids. The dried sludge may be used for
landfill, or it may be further incinerated.
The spray drying process utilizes a high speed centrifugal bowl into
which liquid sludge is fed. The centrifugal force disperses the sludge
into fine particles and sprays them into the top of the drying chamber
where the transfer of moisture to hot furnace gases takes place. The
gas and dried sludge are separated, and the sludge is fed by spiral
conveyor to storage.
The rotary kiln drying process involves a rotating drum into which the
wet sludge is introduced for drying or incineration. The drum contains
plows or louvres for lifting and agitating the material as the drum
revolves.
The drum interior is directly or indirectly heated with hot furnace gas.
Many variations of this system exist depending on the particular process
requirements.
The multiple hearth drying process is a countercurrent operation in
which heated gases pass by finely pulverized sludge that is continually
raked to expose new surfaces. The raking allows the sludge to fall
through openings to lower hearths. Drying occurs on the upper two
hearths which prepare the sludge for efficient incineration on the
lower hearths. Airborne ash is water scrubbed, and the ash/water
slurry is pumped to disposal.
7-127
-------
DRAFT
Advantages and Limitations
Heat drying provides a method of sludge thickening which requires a
minimum of space. This, in turn, reduces the cost of hauling to a
landfill and lessens the likelihood of leaching contaminants into the
ground water supply.
Heat drying is not as economical as sludge drying beds and imposes an
energy requirement not necessary with natural evaporative processes.
Specific Performance
It is not necessary to completely dry sludge in order for it to be
suitable for further processing. One of several heat drying techniques
nay be elected to obtain the desired degree of drying sludge.
Eased on a practical operating facility, the flash drying system has
demonstrated its ability to reduce the moisture content of sludge from
50 percent to an acceptable 8 percent.
Operational Factors
Reliability - Reliability is high assuming proper periodic cleaning and
lubrication of pumps.
Maintainability - Maintenance consists of periodic cleaning of con-
stricted areas of the drying/incineration system as a guard against
buildup and clogging with life being a function of the concentration
of corrosive waste constituents.
Collected Wastes - Dewatering of the sludge prior to heat drying may
be desirable. Depending on its composition, the dried sludge may be
sold, disposed of to landfill, or incinerated.
Demon s t r a t i o n Status
Rotary kiln dryers have been used in several plants for the drying of
sludge and for the drying and burning of municipal refuse and industrial
wastes. Coal, oil, gas, municipal refuse, or the dried sludge may be
used as fuel.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-32 were contacted during this study and were found to currently
employ heat drying as part or all of their wastewater treatment system.
TABLE 7-32
PLANTS VISITED USING HEAT DRYING
Heat drying is used by 7 plants contacted
247 376 563 800 927 1481 1498
7-128
-------
DRAFT
SAND BED DRYING
Definition of the Process
Sand bed drying is 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 the drainage through the sand and evap-
oration to the atmosphere to effect the required water separation.
This process is used for the drying of sludge prior to removal to a
landfill.
Description of the Process
As a waste treatment procedure, sand 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 to landfill. 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
tlx8 to 1/4 inch) graded gravel overlying drain tiles.
Drying beds are usually divided into sectional areas approximately 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. A typical sand drying bed is shown
ir. Figure 7-31.
7c 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 appro-
priately placed side openings which are controlled by slide gates. With
either type of delivery system, a concrete splash slab should be pro-
vided to receive the falling sludge and prevent erosion of the sand
surface.
"•."here 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. Depending on the climate, a combination of open and
enclosed beds will provide maximum utilization of the sludge bed drying
facilities.
Advantages and Limitations
The main advantage of sand drying beds over other types of sludge drying
is the relatively low cost of construction, operation, and maintenance.
Its disadvantages are the large area of land required and lona drying
tines that depend to a great extent on climate and weather.
7-129
-------
DRAFT
^
k
3
]
-0-*
6-in
w
]
Splash box
^.
1
*„.
vitrified pipe
L j
|j
i
i
laid-/
h plastic joints
[
[
_ r~
)
]
i
1
t,.
#"•
I
r
•? — c£===b— T
-o
1 |i
*O C
0) a>
"E o
55
c S
CD
]
V|
!
]
|[
II
(
*
B'' shear gate "fTl
S If- 1
:::::::.:::=•; I. in::::]-::::-^:::::::::-!-.!;:::::::::::-!'-:::::::::^:!--^::;:::::::-
-i — rji fa- E
I
1
— V£
1
J
r
-::::. ::::OK
[
C
^
[
[
3
i . .
A
t
1 1 ^- 2-m plank
PLAN
6 in fine sand
3-in coarse sand
3-m fine gravel
3-m medium gravel
3 10 6 m coarse gravel
walk
Pipe column fof
glass-over
'• J 3-m medium gravel'
2 m coarse sand
SECTION A-A
taif~^~
5-in underdram laid
with open joints
FIGURE 7-31
PLAN AND SECTION OF A TYPCIAL SLUDGE DRYING BED.
7-130
-------
DRAFT
Specific Performance
Dewatering of sludge on sand beds occurs by two mechanisms: filtration
of water through the bed and evaporation cf water as a result of radia-
tion and convection. Filtration is generally complete in one to two
days and may result in solids concentrations as high as 15 to 20 percent
The rate of filtration depends on the drair.ability of the sludge.
The rate of air drying of sludge is related tc 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 e%*aporation rate for a
sludge is determined to be about 75 percent of that from a free water
surface.
Operational Factors
Reliability - High, assuming favorable clinatic conditions, proper bed
design, and care to avoid excessive or unequal sludge application. If
climatic conditions in a given area are nor favorable for adequate
drying, a cover may be necessary.
Maintainability - Maintenance consists basically 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 item of expense in sludge
bed maintenance, but there are other areas which may require attention.
Underdrains occasionally become clogged ar.d have to be cleaned. Valves
or sluice gates that control the flow of sludge to the beds must be kept
watertight. Provision for drainage of lir.es ir. winter should be pro-
vided to prevent damage from freezing. The partitions between beds
should be tight so that sludge will not flew from one compartment to
another. The outer walls or banks around the beds should also be
watertight.
Collected Wastes - Dried sludge from sand drying beds is conventionally
disposed of to landfill. Economic considerations may justify its further
processing for application as a fertiliser.
Demonstration Status
Sand bed drying of sludge is a classic process and is found in use by
numerous plants generating a high solids waste flow.
The .Machinery and Mechanical Products Manufacturing plants listed in
Table 7-33 were contacted during this study ar.d were found to currently
employ sand bed drying as part or all of their wastewater treatment
systeir..
•7-1
-------
DRAFT
TABLE 7-33
PLANTS VISITED USING SAND BED DRYING
Sand bed drying is used by 10 plants contacted
1 83 116 356 530 549 566 579 656 752
VACUUM FILTRATION
Definition of! the Process
Vacuum filtration is a process of solid/liquid phase separation effected
by passing the more permeable liquid phase through a mesh which is im-
penetrable to the solid phase. A pressure differential is obtained by
drawing a vacuum and is the principal driving force. As a waste treat-
ment procedure, vacuum filtration is used to dewater sludge. In waste-
water 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 a cloth 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 an 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. A typical vacuum
filter system is shown as Figure 7-32. Vacuum filtration is a widely
used technique applied in sludge dewatering especially in smaller in-
stallations since it requires less space than a sludge drying bed.
Description of_ the Process
Because the dewatering of sludge on vacuum filters is relatively expen-
sive per pound of water removed, the liquid sludge is frequently thick-
ened prior to processing. If coagulating agents are to be employed in
the thickening process, elution (washing) of the sludge to remove sol-
uble materials will reduce its chemical demand, thereby, effecting a
coagulant cost savings.
Advantages and Limitations
Although the initial cost and area requirement of the vacuum filtration
system are higher than that of a centrifugal system, the operating cost
is lower, and no special provisions for sound and vibration protection
need be made.
The sludge effluent from this process is in the form of a moist cake
and can be conveniently handled. A disadvantage of this process is
that its liquid effluent, although of higher purity than the liquid
effluent from the centrifugal process, may require treatment prior to
discharge.
7-132
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DRAFT
Air inlet for
cake discharge
FIGURE 7-32
VACUUM FILTRATION SYSTEM.
7-133
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DRAFT
Pretreatment such as thickening and elution may also be a process
requirement.
Specific Performance
The function of vacuum filtration is to reduce the water content of
sludge, whether raw, digested, or elutriated, so that the proportion
of solids increases from the 5 to 10 percent range to about 30 percent.
At this higher percentage, the sludge is a moist cake and is easily
handled.
Operational Factors
Reliability - High, assuming proper design and control. Sludge charac-
teristics which will dictate design and control parameters are listed
below.
1. Size, shape, and electrical charge of the solid particles
2. Solids concentration and volatile content
3. Chemical composition
4. Compressibility
5. Viscosity
Maintainability - 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. For this reason,
it is desirable in the selection of vacuum filters to provide one or
more spare units.
If intermittent operation is to be employed, the filter equipment should
be drained and washed each time it is taken out of service and allowance
for wash time should be made in the selection of sludge filtering
schedules.
Collected Wastes - Sludge dewatered in the vacuum filtration process
may be heat dried and processed as a fertilizer, or it may be disposed
of by incineration or by direct application as landfill. The clarified
effluent, if high in dissolved or suspended solids, may require further
treatment prior to discharge and is usually returned to the treatment
facility influent.
Demonstration Status
Vacuum filter systems have been used successfully at many treatment
facilities. At present, the largest installation of vacuum filters is
at the West Southwest wastewater treatment plant of Chicago, Illinois
where 96 large units have been in service for many years. At the
Milwaukee, Wisconsin treatment plant, the initial filters installed in
1925 functioned approximately 25 years and then were replaced with
larger units. Original vacuum filters at Minneapolis-St. Paul,
7-134
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Minnesota now have over 28 years of continuous service, and Chicago
has some units with similar or greater life periods. It is a widely
used process with industrial wastes and has been found in 12% of the
plants contacted during this study.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-34 were contacted during this study and were found to currently
employ vacuum filtration as part or all of their wastewater treatment
system.
CENTRIFUGATION
Definition of the Process
Centrifugation is the application of centrifugal force to rapidly effect
the concentration of solids contained in a solid/liquid system. The
application of centrifugal force is effective because of the density
differential normally found between the insoluble solids and the liquid
in which they are contained.
As a waste treatment procedure, centrifugation is applied to the
dewatering of sewage and waste sludges.
Description of^ the Process
There are three common types of centrifuges applicable to waste streams.
These are disc, basket, and conveyor type centrifuges. All three oper-
ate by removing solids under the influence of a centrifugal field. The
fundamental difference between the three types is the method by which
solids are collected in and discharged from the bowl.
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 discharged continuously through
small orifices in the bowl wall. The clarified effluent is discharged
through an overflow weir.
A second type of centrifuge which is useful in dewatering waste sludges
is the basket centrifuge. In this type of centrifuge, the 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.
As the basket centrifuge does not have facilities for continuous dis-
charge 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 dewatering is the
conveyor type. In this 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 discharges out of effluent ports after passing the
-7_1
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DRAFT
TABLE 7-34
PLANTS VISITED USING VACUUM FILTRATION
Vacuum filtration is used by 33 plants contacted
15 26 49 70 79 108 135 193 219 229
249 376 384 387 388 390 413 464 476 521
561 567 623 647 704 711 717 924 926 927
954 958 1110
7-136
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DRAFT
COVER
DIFFERENTIAL SPEED
GEAR Box
ROTATING
BCWLy
^-ROTATING
CONVEYOR
\
CENTRATE
DISCHARGE
SLUDGE CAKE
DISCHARGE
•.
MAJN
DRIVE
SHEAVE
—FEED PIPES
(SLUDGE a
CHEMICAL)
BEARING
BASE NOT SHOWN
FIGURE 7-33
CONVEYOR TYPE SLUDGE DEW ATE RING CENTRIFUGE
7-137
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DRAFT
length of the bowl under centrifugal force. Figure 7-33 shows the de-
sign and operation of a typical conveyor type centrifuge.
Advantages and Limitations
Some of the advantages of sludge dewatering centrifuges are that they
have minimal space requirements, dewater to well concentrated cakes, and
show a high degree of effluent clarification. The operation is simple,
clean, and relatively inexpensive. The area required for a centrifuge
installation is less than that required for a vacuum filter of equal
capacity, and the initial cost is lower.
Some limitations are that higher power costs will partially offset the
lower initial cost. Special consideration must also be given to pro-
viding 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 centrate which is relatively high in suspended, non-
settling solids.
Specific Performance
The efficiency of the dewatering of sludge by centrifugation is depen-
dent on such factors as feed rate, rotational velocity of drum, and
sludge composition and concentration. As a general rule, assuming cor-
rect design and operation, moisture may be reduced to a point where the
total moisture content of the dewatered sludge is in the range of 65 to
70 percent.
Operational Factors
Reliability - High, assuming proper control of operational factors such
as sludge feed rate, consistency, and temperature. Pretreatment such
as grit removal and coagulant addition may be necessary. Pretreatment
requirements will vary depending on the composition of the sludge and
on the type of centrifuge employed.
Maintainability - Maintenance consists of periodic lubrication, cleaning,
and inspection. The frequency and degree of inspection required will
vary depending on the type of sludge solids being dewatered and mainten-
ance service conditions. If the sludge is abrasive, it is recommended
that the first inspection of the rotating assembly be made after approx-
imately 1,000 hours of operation. If the sludge is not abrasive or cor-
rosive, then the initial inspection might be delayed. Centrifuges not
equipped with a continuous sludge discharge system will require periodic
shutdowns for manual sludge cake removal.
Collected Wastes - Sludge dewatered in the centrifugation process may
be "heat "dried "and processed as a fertilizer, or it may be disposed of
by incineration or by direct application as landfill. The clarified
effluent (centrate), if. high in dissolved or suspended solids, may
require further treatment prior to discharge,
7-138
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Demonstration Status
The solid bowl conveyor centrifuge is the machine most commonly used
and is currently being developed by several equipment companies for ap-
plication to the problem of wastewater sludge dewatering. A major
treatment plant utilizes this type of centrifuge for dewatering 5,70U
cu m/day (1/5 mgd) of sludge. This tupe of machine has found wide
industrial application from which useful operating experience may be
desired and applied to wastewater sludge dewatering.
The Machinery and Mechanical Products Manufacturing plants listed in
Table 7-35 were contacted during this study and were found to currently
employ centrifugation as part or all of their wastewater treatment
system.
TABLE 7-35
PLANTS VISITED USING CENTRIFUGATION
Centrifugation is used by 19 plants contacted
6 29 110 121 143 195 219 223 286 380
431 621 687 689 741 787 814 937 946
SLUDGE DISPOSAL
General
There are several methods of disposal of sludges from industrial waste-
water treatment. The two most common techniques are landfilling by the
company on its own property and removal by licensed contractor to an
outside landfill, incinerator or reclamation point. Other disposal tech-
niques used for industrial waste include incineration, lagooning, and
evaporation ponds, and pyrolysis. These latter techniques produce a
dewatered ash or sludge which requires ultimate disposal by either con-
tractor hauling or on-site landfilling. Finally, wet oxidation, land
spreading, and ocean disposal are used by municipal facilities to dis-
pose of treated sewage. Under some circumstances, these processes
could be used by in industrial facility, but careful investigation of
overall impact would be required first. In the Machinery and Mechanical
Products industries, waste oils are normally either burned for the heat
value reclaimed or hauled away by a contractor, and sludges are norm-
ally taken to a landfill. The remaining techniques are included for
completeness.
Landfill
A landfill can be used for disposal of sludge, grease and grit whether
it is stabilized or not, if a suitable site is convenient. The econo-
mies of hauling sludge will usually indicate that dewatering for volume
reduction will result in justifiable savings. In a good landfill, the
wastes are deposited in a designated area, compacted in place with a
tractor or roller and covered with a 0.3048 meter (12 inch) layer of
7-139
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DRAFT
clean soil. With daily coverage of the newly deposited wastes, nui-
sance conditions such as odors and flies are minimized. In addition,
landfills should be so located that large amounts of water cannot col-
lect in the landfill and designed to prevent leaching into the surround-
ing water table.
In selecting a proper site for a landfill, consideration must be given
to the nuisance and health hazards that they may cause. Trucks carrying
wet sludge and grit should be able to reach the site without passing
through heavily populated areas or business districts. The site should
have good drainage so that runoff would not create boggy conditions that
would interfere with vehicular movement. Drainage from the site that
would cause pollution of ground water supplies or surface streams must
also be prevented. Another major consideration is that wastes put in a
landfill must be sufficiently segregated to prevent chemical combinations
which may be hazardous.
Demonstration Status - The Machinery and Mechanical Products Manufac-
turing plants listed in Table 7-36 were contacted during this study
and were found to currently employ landfill as part or all of their
wastewater treatment system.
Incineration
Incineration is the process of converting the sludge into an inert ash
which can be disposed of easily. Dewatering of combustible sludges to
approximately 30 percent solids can make the process self-sustaining
without the need for additional fuel, except for warm-up and heat
control. The following types of incinerators are available.
Multiple Hearth - Multiple hearth incinerators are the most common type
used for combustion of sludge. In 1968, there were approximately 160
multiple hearth incinerators in use or under construction in the United
States. There are examples of the use of this process for sludge dis-
posal in the industrial sector. Sludges containing large amounts of
oil can be incinerated, and the oil will add fuel value to the process.
The cylindrical furnace contains a number of horizontal hearths with
openings alternately located at the center and periphery. Stoking is
by arms attached to a slowly rotating center shaft. The arms are equip-
ped to mix sludge and move it across the hearths to the openings through
which it falls to the next lower hearth. There are three basic zones
in a multiple hearth furnace. First, the upper hearth dries the sludge.
The sludge is burned in the middle hearth at temperatures of 760 to 927
degrees C (1,400 to 1,700 degrees F), and sludge is cooled on the bottom
hearths. The transition point between the drying, burning, and cooling
is dependent on the operation of the furnace and on the characteristics
of sludge being fed.
Cooling air is passed through the center shaft and to further heat the
combustion air. The air then enters the combustion hearths. Exhaust
7-140
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DRAFT
TABLE 7-36
PLANTS VISITED USING LANDFILL
Landfill is used by 82 plants contacted
15 49 64 70 78 83 100 107 108 109
110 135 153 193 195 214 221 224 242 246
282 304 321 342 343 369 370 372 388 398
399 410 413 416 428 429 457 477 509 510
511 515 533 548 563 567 569 572 579 590
621 623 627 632 646 656 678 702 707 709
713 721 727 731 740 749 779 780 788 799
826 835 836 924 926 938 941 947 954 969
974 1218
7-141
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DRAFT
gases from the combustion zone dry the sludge in the upper hearths.
Air pollution control equipment must be used to remove pollutants from
the exhaust gases.
Atomized Spray Combustion - This process involves atomizing ground sludge
solids at the top of a reaction vessel. Small droplets approximately
25 microns diameter form at the nozzle. They dry rapidly and then burn
to give heat which sustains the process. The exhaust gases go upward in
the outer annulus at a velocity high enough to transport the ash and to
assure efficient heat transfer through the inner shell to the drying
zone.
Fluidized Bed - Fluidized bed incineration makes use of a bed composed
of sand suspended in the combustion air. Dewatered sludge is introduced
into the bed, oxidized, and the ash is carried away with exhaust gases
and removed with a scrubber.
One system utilizes a fluidized bed of sand as a heat reservoir to pro-
mote uniform combustion of sludge solids. The sludge is dewatered with
a centrifuge or vacuum filter before it enters the fluidized bed reactor.
The resultant combustion gases, ash, and water vapor exit through a wet
scrubber where the ash is removed. The gases and vapor are then ex-
hausted through a stack. The ash is separated from the scrubber water
in a cyclone separator. The scrubber water is recycled to the treat-
ment plant. The combustion process is controlled by varying the sludge
feed rate and the air flow to the reactor to oxidize completely all of
the material. If the process is operated continuously or with shutdowns
of short duration, there is no need for auxiliary fuel after startup *
Incineration cannot technically be called a disposal method. The pro-
cess produces an ash or sludge that requires ultimate disposal. The
ultimate disposal must finally be accomplished by some form of land-
filling, however, the products have been reduced to a relatively harm-
less state.
Demonstra.ticm Status - The Machinery and Mechanical Products Manufac-
turfhg pTants listed" in Table 7-37 were contacted during this study
and were found to currently employ incineration as part or all of
their wastewater treatment system,
Lagoons
The most common method now used for handling of waste treatment plant
sludges is lagooning. The operating costs of this technique are low,
but the land requirements are high. Because of the space requirement,
lagooning may be more attractive for small, isolated plants.
Lagoons are generally built by enclosure of a land area by dikes or ex-
cavation with no attempt to maximize drainage with underdrains or by a
sand layer. Sludge is added until the lagoon is filled with solids at
7-142
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DRAFT
TABLE 7-37
PLANTS VISITED USING INCINERATION
Incineration is used by 25 plants contacted:
121 144 171 193 219 247 409 457 475 476
511 515 563 647 664 679 698 699 702 713
740 836 942, 946 1481
7-143
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DRAFT
which time it is removed from service until the solids have dried to
the point that they can be removed for landfill disposal if, in fact,
the sludge can dewater to this point. Lagooning is not so much a dis-
posal technique as it is one for thickening, dewatering, and temporary
storage. Sludge may also be stored indefinitely in a lagoon.
Alum sludges have proven difficult to dewater in lagoons to the point
that they can be handled for landfill. A detailed study of a lagoon
receiving alum sludges indicated that the solids concentrated increased
from about 1.7 percent at the sludge interface to a maximum of 14 per-
cent at the lagoon bottom. The average solids concentration of the
sludge was 4.3 percent with a majority of the sludge having less than
10 percent solids concentration. It was concluded that the lagoon did
/ot produce a sludge suitable for landfill disposal without further
dewatering.
Lime sludges are more easily dewatered in lagoons than alum sludges.
Several reports indicate that a solids content of 50 percent may be
achieved with lime sludges, which is adequate for handling and disposal
in a landfill. Based upon a 50 percent solids content, the lagoon ca-
pacity requirements are about 0.163 to 0.180 cubic meters/year/cu
m/day/100 mg/1 (0.5 to 0.7 acre-ft/year/mgd/100 mg/1) hardness removed.
Lagoon depths are usually 0.91 to 3.05 meters (3 to 10 ft).
Demonstration Status - The Machinery and Mechanical Products Manufac-
turing plants listed in Table 7-38 were contacted during this study
and were found to currently employ lagoons as part or all of their
wastewater treatment system.
Land Spreading
Certain sludges with high organic content such as sewage sludge may be
disposed of by spreading over farm lands and plowing under after it has
dried. Land spreading does not have wide application for the Machin-
ery and Mechanical Products industries because the sludges produced are
characteristically low in organics. Land spreading is discussed briefly
here, however, because of the potential benefit for the isolated cases
where the resultant sludge contains significant amounts of organics and
no harmful constituents. Cases where sewage is combined with industrial
waste for treatment are potential users of land spreading.
The humus in the sludge conditions the solid, improving its moisture
retentiveness. Several cities have disposed of dried sludge by bagging
it and selling it as a soil conditioner. The digested sludge may be
heat dried, ground in a mill, and fortified with nitrogen to give it
some fertilizer value. Air-dried sludge may also be sold or given away
for use as a soil conditioner, but the demand is usually seasonal. The
major problem in disposing of sludge in this manner lies in the econom-
ical marketing of the product. Heat-dried activated sludge is sold as
fertilizer by several large cities, notably Chicago, Milwaukee, and
Houston.
7-144
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DRAFT
TABLE 7-38
PLANTS VISITED USING LAGOONS
Lagoons are used by 90 plants contacted
5 7 12 26 49 64 78 84 88 107
109 110 111 116 120 132 135 144 149 194
219 224 242 246 278 282 284 300 304 339
342 360 361 365 366 381 382 387 390 392
404 409 428 429 431 433 437 447 457 476
510 515 530 533 535 539 562 567 572 579
611 617 618 621 625 646 654 656 672 678
699 700 704 707 711 713 721 732 737 740
744 752 774 780 802 836 942 970 1196 1481
7-145
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DRAFT
Wet Air Oxidation
Wet air oxidation is a basically different type of combustion than in-
cineration. It involves burning of organic matter in the absence of
flame and in the presence of liquid water. This is accomplished by
operating at temperature and pressure conditions such that water does
not "boil" even though oxidation of sludge organics takes place. Tem-
peratures and pressures on the order of 222 to 361 degrees C (400 to
650 degrees F) and 81.66 to 122.49 atm (1,200 to 1,800 psi) are used
for "complete" oxidation of organics. The purpose of the high pressure
is to prevent the vaporization of water so that combustion by use of dis-
solved molecular oxygen can occur, A flow diagram for the wet air ox-
idation process showing temperature and pressure conditions at various
stages is shown in Figure 7-34. In addition to recovery of heat energy
from the oxidized product, as shown in the flow diagram, it is possible
to pass gases through an expansion engine for additional energy recla-
mation .
As with other combustion processes, ash from the wet air oxidation pro-
cess requires disposal. However, the problem is somewhat different with
wet air oxidation because the ash is conveyed in a significant volume of
water, Significant concentrations of nutrients and soluble organic ma-
terial are contained in the liquid phase of the product of wet air oxi-
dation and should be recycled to the treatment plant. Air pollution
control must also be considered with the wet air oxidation process .
Ocean
Ocean disposal of sludge is considered by some as an alternate to land-
fill. The benefits of large area and no immediate impact on man's en-
vironment are offset by the unknown long term effects on a major food
source. Even under ideal conditions and with inert pollutants, the long
term effects which are not known make this an extremely poor choice for
sludge disposal, and it is definitely not recommended for use,
Pyrolysis for Sludge Disposal
Developments in other national problems being faced should be considered
for potential concepts for water treatment. An example is the develop-
ment of pyrolysis process as a potential solution for solid waste dis-
posal problems combined with energy conservation. In this process, the
application of high heat to refuse is used to recover the fuel value in
the form of flammable gas or oil. The residue is basically carbon or
in some cases an inert slag.
In at least one pyrolysis concept, moisture, must be added to the refuse
as a means of maintaining the product gases at manageable temperatures,
and the addition of wastewater treatment sludge is a convenient method
of adding the required water,
It is anticipated that: large manufacturing facilities will increasingly
utilize the pyrolysis approach to solid waste disposal, and this should
7-146
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7-147
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DRAFT
be investigated and exploited where feasible for sludge disposal,
Demonstration Status - One plant was visited (ID 563) in the Machinery
and Mechanical Products Manufacturing industries contacted during this
study and found to currently employ pyrolysis as part of its wastewater
treatment system.
Other Methods
Any discussion of the techniques available to treat industrial pollu-
tants should include the recent investigations of biological treatment.
In Europe and to a limited extent in the U. S., bullrushes and water
hyacinths have been found to thrive in the wastes from certain indus-
trial operations. These plants have been shown to remove cadmium, zinc,
nickel, phenols, carbolic acid, phosphates, and nitrogen. Experiments
have also been conducted using plants to dehydrate sludge with results
reducing volume by 98%.
Further study is continuing in the area of mixing waste materials. The
mixed wastes produce a self-floe which precipitates not only metals but
other constituents of the wastewater. At least one company visited
(ID 283) during the study had no treatment other than dumping all wastes
in a very large lagoon. The results were that these mixed wastes and
the long residence time produced a fairly clear effluent which was not
toxic to marine life.
EMULSION BREAKING
Definition of the Process
Emulsion breaking is the process of separating an emulsified oil and
water mixture. Emulsified oil is used as a coolant and lubricant in
many machining operations and must be separated from the water in order
to allow the oils to rise to the surface for skimming or decanting.
Description of the Process
Emulsion breaking is accomplished as a batch process. The mixture of
emulsified oil and water is collected in large tanks equipped with agi-
tators and a skimmer or some method of decanting. Decanting can be ac-
complished with a series of tap-off pipes at various levels allowing the
separated oil to be drawn off the top, or the water can be drawn off the
bottom until oil appears in the wastewater line at which time the oil is
diverted to oil storage tanks for reprocessing or hauling by a licensed
contractor.
The emulsion breaking process involves several steps. First, the pH of
the solution is lowered to an acidic state (usually a pH of 3 to 4 is
preferred). The second step is the addition of an iron or aluminum salt
such as ferrous sulfate, ferric chloride, or aluminum sulfate. These
salts are used to break the emulsifier barrier and free the oil from the
water. With the addition of the metallic salts, the mixture is agitated
7-148
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DRAFT
to insure complete contact of the wastewater/oil mixture with the demul
sifying agent. With the addition of the proper amount of metallic salt
and thorough agitation, emulsions of 5% to 10% oil can be reduced to
approximately 0.01% remaining emulsified oil. The third step in the
emulsion breaking process is to allow sufficient time for the oil water
mixture to separate. Differences in specific gravity will permit the
oil to rise to the surface in approximately 2 to 8 hours. After sepa-
ration, the normal procedure involves skimming or decanting the oil
from the top of the tank. Heat, in the form of steam, can be added tc
decrease the separation time. The fourth and final step is the additio
of a chemical to desalt by precipitating the remaining wastewater solu-
tion. Calcium chloride or lime are normally used as the desalting ager.
and will precipitate out the metallic ions in the wastewater.
Advantages and Limitations
The emulsion breaking process described above is the best technique fcr
removing emulsified oil from wastewater. Removal efficiencies as high
as 99+% are attained by many existing installations. The major disad-
vantage in this process is that proper treatment requires complete seg-
regation of the oil/water mixture and transport to the treatment area.
A separate tank for storage and treatment is required, and chemical
and energy costs can be high, especially if heat is used to speed the
separation process.
Specific Performance
The performance attainable by an emulsion breaking process is dependent
on addition of the proper amount of de-emulsifying agent, good agitatioa
and sufficient time for complete separation. Since there are several
types of emulsified oils, a detailed study should be conducted to deter-
mine the most effective treatment techniques and chemicals for a partic-
ular application. Reduction of concentrations of emulsified oil from
50,000 ppm to approximately 100 ppm are attainable with proper treatmeni
and adequate rise time.
Operational Factors
Reliability - This technique of removing emulsified oils from wastewatej
can be highly reliable assuming adequate analysis in the selection of
chemicals and proper operator training to ensure that the established
procedures are followed.
Maintainability - Routine maintenance is required on pumps, motors, and
valves as well as periodic cleaning of the treatment tank to remove any
sediment which may accumulate in the tank. The use of acid or acidic
conditions will require a lined tank, and the lining should be checked
periodically.
Collected Wastes - The oils removed after de-emulsification and separa-
tion are usually hauled away by a licensed contractor. Several compar.it
7-149
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DRAFT
are using the recovered oil for its fuel value by burning in steam gen-
erating boilers. Separated emulsified oils can also be processed and
reused.
Demonstration Status
Emulsion breaking is a common technique used in the Machinery and Mechan-
ical Products industries. The plants listed in Table 7-39 were contacted
during this study and were found to currently employ emulsion breaking as
part or all of their wastewater treatment system.
TABLE 7-39
PLANTS VISITED USING EMULSION BREAKING
Emulsion breaking is used by 42 plants contacted
6
249
416
702
974
79
296
425
712
1481
108
342
457
741
143
343
475
826
182
384
476
836
217
399
477
864
219
404
561
926
235
407
590
942
246
409
692
962
247
413
698
972
TABLE 7-40
DOES NOT APPEAR
INTENTIONALLY OMITTED
7-150
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DRAFT
SYSTEM TECHNOLOGY - BPT AND BAT
The individual technologies discussed in the first part of this sectio:
describe the components available from which the treatment systems en-
countered in the Machinery and Mechanical Products industries are con-
structed. Many combinations of these technologies are used in the in-
dustries surveyed, therefore, the systems depicted for best practical
technology currently available (BPT) and best available technology
economically achievable (BAT) are representative of common approaches.
Each of the significant pollutants selected in Section VI has been ex-
amined in relation to the representative systems selected for BPT and
BAT. The examination has involved reviewing the current technology fo
treatment of each pollutant and verifying that the BPT and BAT systems
contain an acceptable approach for the reduction of each pollutant.
A computer analysis was made of each representative system to determin
the effluent quality attainable using treatment technology efficiencie
actually witnessed at operating facilities in the field. The raw wast
loads used in this computer analysis were obtained from data obtained
at visited facilities in each subcategory and are considered typical o
the subcategory.
BEST PRACTICAL TECHNOLOGY CURRENTLY AVAILABLE (BPT)
A baseline BPT system has been defined which is in widespread use in
the industries visited and will effectively treat the pollutants most
commonly found in the Machinery and Mechanical Products Manufacturing
industries. Further, based on the waste characterization of Section V
and the pollutant parameters defined in Section VI, modifications have
been made to the baseline system for specific subcategories, where un-
usual wastes exist, to achieve BPT.
This baseline system has been observed in plants visited during the
study. Plant ID'S 924 and 015 use systems basically identical to the
baseline system, and they achieve excellent pollutant removal results.
Plant ID!s 2.32, 925, and 926 use similar systems with only minor mod-
ifications. All the component technologies of the baseline system hav
wide industrial use. Table 7-41 presents a summary of the current tec
nologies used in the industries contacted during the program. This
table gives the percentage of contacted plants using each technology a
well as the ID numbers of the plants where the technique exists.
Contractor removal of all wastes, although technically not a treatment
method, has proven both economical and environmentally beneficial for
many plants. Most states have a licensing and supervision program whi
sets and maintains a level of pollutant discharge for scavengers. Use
of scavengers to haul wastes is a function of volume, distance, and
chemical nature of the wastes. Volume determines the number of trips
per unit time and the size of equipment needed. Distance from the
7-151
-------
DRAFT
TABLE 7-41
WASTE TREATMENT DISTRIBUTION FOR ALL PLANTS SURVEYED
Ultraf iltration
Screening
Emul.-ior. Freaking
Skir.mir.v:
Chemical Oxidation
Chemical Reduction
Neutralization
Flocculation
Flotation
Sedimentation
Clarification
Filtration
Ion Exchange
Reverse Osmosis
Adsorption
Distillation
Chlorination
Lagoon
Electrodialysis
Aeration
Thickenir.g
Centrifugation
Vacuum Filtration
Pressure Filtration
Lagooning
Landfill
Incineration
Pyrolysis
Contractor Removal
Incineration/Combust
No. of Plants
2
25
42
88
88
136
242
137
39
132
120
60
14
8
2
12
36
90
0
0
71
19
33
16
46
82
7
1
174
25
Percent Utilization
0.5
5.4
9.0
19.0
19.0
29.4
48.4
29.5
8.4
28.5
25.9
13.0
3.0
1.7
0.5
2.6
7.8
19.4
0.0
0.0
15.3
4.1
7.1
3.5
9.9
17.7
1.5
0.2
37.6
5.4
7-152
-------
DRAFT
TABLE 7-41 (CONTINUED)
SCREENING
T 121 219
7*0 7»6 «14
EMULSION BftFtKING IS USED BY 42 PLANTS
. ,2.6. 79 198 1*3 J82 _ 2\1_ 219 135 2_4J>
4U *Z5 457 *75 47* 477 56) 590 6»2
914 1*S1
UlfUUNG IS USED ar sa PLANTS
15 26 41 79 108 121 131 143 150
256 2B4 296 300 1*2 343 359 3 80 390
1*3
177 182 ^89 193
393 399 *04 407
826
2ir
707 Til 712 fl3 737
-£HPUUL QXIDAtltm IS USED BY.
93.1 935 94~2 9*6 954 458 462
CAL REDUCTION
144 149 1S3 171 182 193 194 210 221 222 223
287 301 304 310 321 339 3*2 343 3*5 359 JftO
383 384 387 188 390 392 JS1 J99
515 519 521 525 531 557 543 549 550 55* 5ft 1 564 567
108 lit 120 121 132 135 140
246 24? 249 256 2~7B~~ '787 -- 71* "
365 J6» 37-7 37^ J ft 380 )«[
431 4*7 46* * 76 477 509 510
~~
590 fill
as 100 (07 108 in 116 ua 120 121 131
194 195 210 214 217 219 221 222 223 224
287 296 301 304 310 321 336 339 342 343
247 249 256 278 212 7W n»
360 361 363 365 366 969 3TO
411 416 428 429
476 4TT 509 511 514 SI 5 M9 523 571
679 687 689 702 707 709 711 T12 TIT 721 727 7JO 711 736 7)7 7T4 740 7*1
900 121ft 1*81 t493
LUtWLiMO* IS USED
I 15 29 49 5(
177 182 189 193 19* 195 21
137 PLANTS
2B6
672 677 678 fc67
FLOTATION is USED BY 39 PUNTS:
26 41 108 111 116 121 131 17
IS USFO i*Y 132 PLANTS
561 562 564 5&T 569 590 All 413 5IT ~«7T"~"«73
b98 699 700 712 704 711 *12 7?7 Tit T41 T49
958 960 974 981 UU 1218 1*11 1498
UO 111 lift 120 121 131 1 32
7 12 15
IS USED BY 12"0 PLAHTSj
219
672 677 607 699 704 711 713 717
814 826 835 8)6 864 924 927 934
IS USED BY 60 PLANTS:
84 100 IOC 121 131 1*3 177 193
477 Ml 51V
974 9tl "IITB"T7T1—mt~
J42 3TS !Tf
ION EXCHANGE
30 136
ADSORPTION
627 14ST
DISTILLATION
CHLORINAFIW*
IS USFD BY
IS USED BY 2 CLANTS:
IS USEO BY 12 PLANTS.
36 PLANTS:
278 2(J2
609 62? 62T
IS USFO BY
26 49 64
68 107 109 110 111
120 132 135 144 149
617
COXTH HEMOVAL tALL) IS USED BY 1 PLAMSt
433
THICKENING IS USEO BY 71 PLANTS-
15 17 49 64
2 94
74 107 108
140 182 194 219 221 246 247 249 256 282
29 UO 12|
95+ 95* 1119
IS USED BY 46 PIAHTS:
109 111 120 132 14* 1H2 194 246 282 296 I'M 310
381 392 $04 j4Q9 4*7 515 519 543 562 617 (,21 625
IS USEO BY 82 PLANTSi
T? 78 63 100 IQ
342 343 369 170 372
974 1218
IMCINEMTIQN
247 376
PYRQLYSIS
563
.CONTRACTOR REMOVAL
IS USEO BY
•00 .917 1* 61
IS USEO flY
7 FLAMTS:
L*«
i PLANTS:
143 1** 141
2TS 214 2B<
3-17 391 39
612 617 61
689 690 69
70A MO 61
914 955 M
Ut 144 17
T4Q 836 94
19* 177 1B2 189 19
2«T Z96 29* 100 30
397 40 f 409 410 41
42i 625 626 628 62
691 699 702 704 10
•6* 926 927 929 S3
961 962 970 974 97
193 2(9 24? 409 45
946 14*1
195
334
416
6"2
T09
S34
971
*!*
10
43
25
54
11
J5
m t
T*
14
54
29
57
12
1*
10 1
11 5
7
0
1
6
0
7
6 U
15 5
1
1
)
5
0
8
91 14
41 6
t 223
3 3*5
7 464
9 6T2
2 736
40 942
82
47 44 +
2
6
7
?4
*7
23
37
*1
67
H
94
69
1 6
1 24* 2*6
l~3Mfi-
7 679 687
6-~T»r— nr~
46 **•_ 1*1
^9 702 __...?! j_
7-153
-------
DRAFT
scavenger's treatment facility has its obvious effect on time and man-
power. The chemical nature of the wastes determines whether or not
there is reclamation value, fuel value, or other uses. These values
normally ck crease the removal costs. Chemical which are particularly
difficult to treat will increase costs. The removal of one or two
truck loads per day over short distances can often prove less costly
than construction and maintenance of a treatment facility.
BASELINE SYSTEM DESCRIPTION (BPT)
The primars water pollutants generated in most facilities in the
Machinery and Mechanical Products industries can be characterized
generally as:
Free and emulsified oils and greases
Suspended and dissolved solids
Dilute acid and alkaline chemicals
The dilute acid and alkaline chemicals and the suspended and dissolved
solids are normally contained rLn the same waste stream. Free and er.ul-
sified oils and greases are frequently separated to permit the most
efficient treatment of these pollutants.
A baseline system to treat these characteristic wastes is shown sche-
matically in Figure 7-35. In an existing plant employing the best
practical control technology currently available, there are at least
three waste streams entering the treatment facility. These are the
streams numbered 1, 2, and 3 in Figure 7-35.
Stream 1 contains the segregated emulsified oils which immediately
enters the emulsion breaking tank. The emulsion breaking can be ac-
complished several ways. The most common approach is to add sulfuric
acid and heat, usually steam, to the emulsion. This reduces the solu-
bility of the oil in the water. The oil rises to the surface and is
then separated from the water by use of a skimmer. When the soluble
oils have nearly the same specific gravity as water, separation by the
above method may be too slow to be practical. In this case, lime, alum,
ferrous sulfate, soda ash, or ferric chloride may be used as chemical
coagulants followed by dispersed air flotation to bring the floe and
oil to the surface. The selection of a coagulant will determine the
pH level for optimum oil removal. In some cases, air flotation without
chemical coagulation can be used. Oil removal efficiencies ranging
from 60 to 90% can be expected with the above methods. The solubility
of other contaminants may be altered in the oil removal section as the
pH level is adjusted. Some pollutants may precipitate, while others
become more soluble. For most contaminants, the removal will be slight
unless by coincidence the pH of minimum solubility coincides with that
7-154
-------
DRAFT
r
L<-J-
I
I
J
_L/
^.
i
X
1 'H
1 s
1
"•ft
w nj
?. 1 K
T3
< 1
x^
-^
L
I
id
3
tr
w
*
N^S^^^^S^^^^
a.
m
o
in
CO
LU
I
O
o:
Ss LU
kl
Z
J
LU
cn
<
m
C D>
0 C
m C
co O
u
s
o
0
[u
o
O O
-------
DRAFT
for optimum oil removal. Unless the oil skimmer is equipped with sludge
removal rakes, high precipitation rates should be stopped by adjusting
the pH to a point where the participate is soluble. The participate
can be taken out in the clarifier by readjusting pH. In general, some
sludge will be generated in the oil removal equipment which must be re-
moved periodically to prevent interference with the oil removal process.
Stream 2, consisting of the segregated wastes containing free oils,
enters the treatment facility directly into the oil skimmer. Also en-
tering the skimmer is the oil/water mixture discharged from the emulsion
breaking tank. The free oil is allowed to rise to the surface of the
tank where it is swept into a receiving channel and pumped to an oil
holding tank to await ultimate disposal. Final disposal of the oil may
be by contract removal, burning for its heat content, or processing for
euse in the plant. Free oil removal efficiencies as low as 60% to a
high of 99+% have been observed in plants visited. The water in the
skimmer is discharged to the equalization tank.
Stream 3, consisting of the dilute segregated acid and/or alkali waste-
waters, as well as suspended and dissolved solids, enters directly into
the equalization tank from the plant. Also, dumping into the equaliza-
tion tank is the effluent from the oil skimmer with some remaining free
and emulsified oil. The equalization tank provides a mixing place for
the oily waste stream and the dilute acid/alkaline wastes. Here, also,
any spills or batch dumps which may upset the treatment process may be
metered into the waste stream at a low enough rate to be properly
handled. The schematic shown in Figure 7-35 provides a holding tank for
these unusual wastes which can be transported to the treatment plant by
either barrel, truck, or separate plumbing lines.
From the equalization tank, the combined waste stream enters the chemi-
cal treatment section of the facility. The flocculation and clarifica-
tion section is where coagulation and precipitation occur which effec-
tively removes from 60 to 98 percent of dilute oils and greases, sus-
pended solids, most heavy metals, fluorides, and phosphates. In addi-
tion, the clarifier effluent water will, in many cases, be neutralized
to an acceptable pH by the chemical treatment. Chemical oxygen demand
(COD) will also be reduced as the water is clarified of the oxygen
demanding contaminants. COD can also be reduced by the incorporation
of dispersed air systems in the equalization tank or by using air
flotation.
The optimum precipitation of the individual pollutants will occur at
various pH values (see Table 7-42) which may, depending on the com-
bination of pollutants, require multiple steps of precipitation/coag-
ulation/flocculation/clarification. Chemicals commonly used are:
lime, sulfuric acid, ferric chloride, ferric hydroxide, alum, soda ash
(sodium carbonate), hydrogen sulfide, and sodium sulfide. The chemi-
cals selected for use in any given system will depend on the specific
7-156
-------
DRAFT
TABLE 7-42
TECHNIQUES FOR METAL REMOVAL
Chromium
Trivalent
Copper
Iron
Lead
Mercury
Nickel
Silver
Zinc
Precipitant and Form Optimum
of Precipitate pH Range
- Lime then as 10
Hydroxide
- Sodium Sulfide 7.5-8.5
then as a
Sulfide
- Lime then as 8.0-8.5
Hydroxide
- Reduce to Cuprous 8.0-8.5
then add Lime to
Precipitate as
Hydroxide
- Ferrous to Ferric 8 . 0+
by Chlorination,
add Lime then as
Hydroxide
- Pb CO^-Caustic or 8.0-9.0
Soda Ash
- Sodium Sulfide as 7.5-8.5
Sulfide
- Sodium Sulfide as 7.0
Sulfide
- Soda Ash 8.0-8.5
- Electrolytic N/A
Deposition or
Ion Exchange
- Lime, then as 7.0-9.0
Hydroxide
Minimum
Attainable
Concentrations
Without Dilution
0.02
0.02
0.1
0.2
0.3
0.05
0.05
0.005
0.1
Trace
0.2
7-157
-------
DRAFT
combination of pollutants to be treated. In most cases, 80 to 98 per-
cent removal can be expected for heavy metals.
The design of the system from the point of pH adjustment and floe add-
tion to the point of thorough precipitation should be based on gravity
flow, since pumping of the streams with large amounts of precipitates
has, in general, buen found damaging to the pumps and consumes power,
Furthermore, water treatment system design should include extensive
pilot plant testing with consideration of transient influents, antic-
ipated increases in loads, redundancy of equipment, natural disasters
such as floods and earthquakes, hazards in the treatment, no:; wd-K-r
quality aspects, and exposure to fire and exp Jos ions fror... with:u or
without the system.
Final neutralization of the treated water, when required, may be done
with an acid or base as applicable. These additions are commonly
sulfuric acid or lime.
Sludge thickening and sludge drying beds have been selected as a repre
sentative approach to reducing water content of the sludge for economi
cal removal to landfill. These two techniques are discussed in detail
in the first part of this section. Alternates which also accomplish
equivalent water reduction, such as vacuum filtration, are available
and may be more desirable where land availability is a problem- As in
the case of water treatment techniques,, sludge treatment should bo the
result of a thorough engineering study prior to installation of any
equipment,
An optional recycle loop is shown on the schematic which,- if used,
signi f ic'sntly
qu
thr
offset by the reduction in purchased water.
n optional recycle loop is shown on the schematic which,- if used, ran
igni f ic'sntly reduce the amount of ;,/ate~: discharged by the plairt.. Fre-
uently. the quality of th^ wa'r^r ^iuohar-j-d is u noble in many opo.^!: on-j
hroughout the pjant, and. the cost jf any r ecaspo.ry pipiao changes caa be
Polychlori rsateu biphenyls (PCB!<~) tns ;? b° foar.d i". many industries viihir.
the Machinery anr? Mechanical Prodbc?:^ -?r ••-.'. The toxic'1. t.y and. per'j.is-te^e
of these chemicals ir- such that they Tiust. \e complete] y removed Crora
plant discharges. The cnly way to assure thai the?:e i ;-; nc discharge of
PCB's in ~;-he was tews ter is to attain complete segregation, of uhose ciiera-
icalr, . PCS' s ere found in some paints, inks, plastics, and coated paper.
Products used, in a plant which contain PCB's should be completely iso-
lated, and disposal should be by licensed contractor or the plant, itself
Destruction of PCR 's can be accomplished ir a sper-la] furr,,ece at t crape r-
aturcs above 1,480 degrees C (2,700 degree? F) .
LRN/VrE APPROACHS
The baseline treatment system shown in Figure 7-35 is considered as
representative of the better wastewater treatment plants currently
utilized in the Machinery and Mechanical Products Manufacturing cate-
7-158
-------
DRAFT
gory. However, many factors must be considered in the application of
this technology. As an example, many small plants have all dry oper-
ations or have a low water use and, consequently, have a low discharge
rate. In this case, contractor hauling of the entire untreated dis-
charge may be cost effective. The licensed contractor hauls the wastes
to a centralized treatment facility or approved landfill.
In cases where oil is found to be below about 100 mg/1, the emulsion
breaking and oil skimmer at the front end of the baseline system may
be deleted. The main clarifier will remove dilute oil by flotation
or with the floe added, usually to less than 15 mg/1.
The equalization tank can be deleted from the baseline system for many
applications. When the variety of contaminant sources is low and nearl;
constant and within the operating ranges of the system components fol-
lowing, there is little need for the equalization tank. Also under cer-
tain conditions, equalization may be combined with other mixing operati
Precipitation, flocculation, and clarification can be performed separ-
ately as shown in Figure 7-35, or they can be performed within one mul-
tifunction clarifier unit. An alternative to the above clarification
series is an air flotation unit.
The final neutralization shown in the baseline system can be deleted in
many cases where the pH of the water from the clarifier is nearly neutr,
On the other hand, certain clarifiers may not remove sufficient solids.
In such cases, a deep bed filter may be required for final polishing of
the effluent.
Sludge treatment and disposal can be handled in many ways other than
thickening, drying, and landfill. Lagoons, sand drying beds, vacuum
filtration, centrifugation, lime sludge pelletization, and pressure
filtration are all methods of sludge thickening or dewatering which
may be used. Licensed contractor removal and incineration are accept-
able methods of sludge disposal in place of the landfill method selectee
for the baseline.
Table 7-43 provides a summary of some of the alternate methods available
as replacements for selected components of the baseline system. Addi-
tional technologies are available and were discussed earlier in this
section. These added technologies are not included as alternates for
the baseline system, primarily because they lack widespread use in in-
dustrial waste treatment. It is not the intention of this section to
provide a description of a single acceptable system but to show that
the proper use of currently accepted treatment techniques can maintain
an effluent sufficiently clean to materially benefit the environment.
SUBCATEGORY !_, CASTING AND MOLDING - METALS - BPT
The baseline system, shown schematically in Figure 7-35, is representa-
tive of the treatment required to effectively reduce the pollutant dis-
charge of this subcategory. Table 7-44 provides a list of pollutants,
-------
Baseline
Process
Emulsion
Breaking
Oil Skimming
Equalization
Rapid Mix
Flocculation
Clarification
TABLE 7-43
ALTERNATE SYSTEM PROCESSES
Alternate
Process(es)
- Flocculation and
tube settling.
- Flocculation and
tube settling.
- Use of clarifier
- Surge pond or
lagoon.
- Turbulent flow to
clarifier inlet
- Air flotation
- Ultrafiltration
- Reverse Osmosis
- Filtration
- Microscreening
Alternate
Process Effects
- Limited to low oil
concentrations. ,-,,:
- Limited to lox^ oil
concentrations,
- Decrease in mixing
efficiency.
- Increased land
required.
- Decrease iiv effic-
iency requires good
settling waste
characteristic(s).
- Increased costs
- Since some pollutants are
not neutralized, concentrated
waste stream requires addi-
tional treatment.
7-160
-------
DRAFT
Parameter
Flow (1/hr)
pH
Suspended Solids
Cadmium
Copper
Iron
Lead
Nickel
Oil and Grease
COD
Silver
Zinc
Raw
Waste
n>g/l
15,771
TABLE 7-44
SUBCATEGORY 1 - BPT
Treated
Waste
mg/1
15,771
Percent
Reduction
N/A
8.2
1490
0.04
9.7
13.8
0.6
4.6
1050
2420
0.02
8.5
17.9
0.02
0.2
0.5
0.1
0.2
8.1
72.9
0.02
N/A
98.8
50
98
96
83
96
99
97
0
Remarks
Equivalent to 100,000 gal/
day
No reduction due to low ra
waste values found as an
average for this sub-
category.
10.8
0.5
95
-------
DRAFT
a typical raw waste concentration, and the effect of treatment attain-
able with the baseline system.
The use of the baseline system for this subcategory is most cost effec-
tive for larger installations. Small plants having low discharge rates
find hauling by a licensed contractor to a central treatment facility
to be more economical. Segregation of oily wastes and hauling by li-
censed contractor can also reduce the treatment facility capital and
operation and maintenance costs for those companies with small oil waste
loads.
There were 126 verified Subcategory 1 plants contacted during the study.
Of these, 4 were single subcategory, and 122 had multiple subcategories.
There were 28 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory regardless of point of discharge, are shown
in Table 7-45.
SUBCATEGORY 2_, MECHANICAL MATERIAL REMOVAL - BPT
The baseline system, shown schematically in Figure 7-35, is representa-
tive of the treatment required to effectively reduce the pollutants
characteristic of this subcategory. Table 7-46 provides a list of the
pollutants, a typical raw waste concentration, and the effect of
treatment attainable with the baseline system.
The use of the baseline system for this subcategory is most cost effec-
tive for larger installations. Small plants having low discharge rates
find hauling by a licensed contractor to a central treatment facility
to be more economical. Segregation of oily wastes and hauling by li-
censed contractor can also reduce the treatment facility capital and
operation and maintenance costs for those companies with small oil waste
loads.
There were 598 verified Subcategory 2 plants contacted during the study.
Of these, 8 were single subcategory, and 590 had multiple subcategories.
There were 65 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in detail
in this subcategory, regardless of point of discharge, are shown in
Table 7-47.
SUBCATEGORY 3_, MATERIAL FORMING - ALL MATERIALS EXCEPT PLASTICS - BPT
The baseline system, shown schematically in Figure 7-35, is representa-
tive of the treatment required to effectively reduce the pollutants
characteristic of this subcategory. Table 7-48 provides a list of the
pollutants, a typical raw waste concentration, and the effect of
treatment attainable with the baseline system.
7-162
-------
DRAFT
TABLE 7-45
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 1 SURVEYED
No. of Plants Percent Utilization
Screening 7 17.5
Emulsion Breaking 11 27.5
Skimming 19 47.5
Chemical Oxidation 5 12.5
Chemical Reduction 12 30.0
Neutralization 22 55.0
Flocculation 18 - 45.0
Flotation 14 35.0
Sedimentation 18 45.0
Clarification 14 35.0
Filtration 8 20.0
Ion Exchange 4 10.0
Distillation 1 2.5
Chlorination 4 10.0
Lagoon 14 35.0
Thickening 7 17.5
Centrifugation 1 2.5
Vacuum Filtration 6 15.0
Pressure Filtration 2 5.0
Lagooning 7 17.5
Landfill 12 30.0
Incineration 3 7.5
Contractor Removal 16 40.0
Incineration/Combust 7 17.5
-------
DRAFT
TABLE 7-46
SUBCATEGORY 2
Parameter
Flow (1/hr)
PH
Suspended Solids
Cadmium
Chromium Total
Copper
Fluoride
Iron
Lead
Nickel
Oil and Grease
COD
Phosphates
Zinc
Raw
Waste
mg/1
15,771
9.1
1220
2.4
18.9
4.5
8.5
9.0
2.0
3.4
668
3090
10.2
7.1
Treated
Waste
mg/1
15,771
8.5
15.0
0.02
0.4
0.2
2.0
0.5
0.1
0.2
5.8
92.7
2.7
0.5
Percent
Reduction
N/A
99
99
98
96
76
94
95
94
99
97
74
93
Remarks
Equivalent to 100,000 gal/
day
7-164
-------
DRAFT
TABLE 7-47
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 2 SURVEYED
Screening
Emulsion Breaking
Skimming
Chemical Oxidation
Chemical Reduction
Neutralization
Flocculation
Flotation
Sedimentation
Clarification
Filtration
Ion Exchange
Adsorption
Distillation
Chlorination
Lagoon
Thickening
Centrifugation
Vacuum Filtration
Pressure Filtration
Lagooning
Landfill
Incineration
Contractor Removal
Incineration/Combust
No. of
Plants
15
22
39
31
44
67
50
18
45
39
24
2
1
1
10
28
22
7
13
5
8
30
1
68
13
Percent Utilized
13.6
20.0
35.5
28.8
40.0
60.9
45.5
16.3
40.9
35.5
21.8
1.8
0.9
0.9
9.1
20.9
20.0
6.4
11.8
4.5
7.3
27.3
0.9
61.8
11.8
-------
DRAFT
Parameter
Flow (1/hr)
Raw
Waste
mg/1
15,771
pH 8.8
Suspended Solids 1030.0
Copper 8.5
TABLE 7-48
SUBCATEGORY 3
Treated
Waste
mg/1
15,771
8.5
15.0
0.2
Percent
Reduction
N/A
N/A
98
98
Remarks
Equivalent to 100,000 gal/
day
Iron
29.3
0.6
98
Lead
2.8
0.1
90
Nickel
5.8
0.2
96
Oil and Grease
COD
Phosphates
Silver
Zinc
600
2830
6.5
0.01
5.4
84.9
1.7
0.01
99
97
69
0
No reduction due to low raw
waste values found as an
average for this sub-
category.
10.8
0.5
95
7-166
-------
DRAFT
The use of the baseline system for this subcategory is most cost effec-
tive for larger installations. Small plants having low discharge rates
find hauling by a licensed contractor to a central treatment facility
appears to be more economical. Segregation of oily wastes and hauling
by a licensed contractor can reduce the treatment facility capital and
operation and maintenance costs for those companies with small oil waste
loads.
There were 479 verified Subcategory 3 plants contacted during the study.
Of these, 6 were single subcategory, and 473 had multiple subcategories.
There were 37 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in detail
in this subcategory, regardless of point of discharge, are shown in
Table 7-49.
SUBCATEGORY 4_, PHYSICAL PROPERTY MODIFICATION - BPT
In addition to the wastes handled by the baseline system, listed under
Subcategories 1, 2, and 3, Subcategory 4 can contain cyanide wastes
associated with the heat treating process of Subcategory 4. Figure 7-36
illustrates the baseline wastewater treatment system schematic modified
to handle the cyanide wastes. The cyanide bearing wastewaters must be
segregated for cyanide oxidation prior to combining with the main waste
treatment stream in the equalization tank. Table 7-50 provides a list
of the pollutants, the raw waste concentrations, and the effect of
treatment attainable with the system.
There were 320 verified Subcategory 4 plants contacted during the study.
Of these, 2 were single subcategory, and 318 had multiple subcategories.
There were 45 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown in
Table 7-51.
SUBCATEGORY 5_, ASSEMBLY OPERATIONS - BPT
Subcategory 5 manufacturing facilities have characteristic pollutants
which can be handled by a baseline system. Figure 7-35 shows the base-
line treatment system schematic. Table 7-52 provides a list of the
pollutants, a raw waste concentration, and the effect of treatment
attainable with the system.
There were 626 verified Subcategory 5 plants contacted during the study.
Of these, 3 were single subcategory, and 623 had multiple subcategories.
There were 37 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
-------
TABLE 1-49
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 3 SURVEYED
No. Of
Plants Percent Utilized
Screening 11 16.9
Emulsion Breaking 15 23.1
Skimming 24 36.9
Chemical Oxidation 13 20.0
Chemical Reduction 18 27.7
Neutralization 34 52.3
Flocculation 27 41.5
Flotation 16 24.6
Sedimentation 26 40.0
Clarification 23 35.4
Filtration 10 15.4
Ion Exchange 4 6.2
Adsorption 2 3.1
Distillation 1 1.5
Chlorination 8 12.3
Lagoon 17 26.2
Thickening 16 24.6
Centrifugation 3 4.6
Vacuum Filtration 10 15.4
Pressure Filtration 2 3.1
Lagooning 8 12.3
Landfill 14 21.5
Incineration 2 3.1
Contractor Removal 33 50.7
Incineration/Combust 8 12.3
7-168
-------
DRAFT
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DRAFT
Parameter
Flow (1/hr)
pH
Suspended Solids
Cyanide
Iron
Lead
Nickel
Oil and Grease
COD
Raw
Waste
mg/1
15,771
TABLE 7-50
SUBCATEGORY 4
Treated
Waste
mg/1
15,771
Percent
Reduction
N/A
9.0
716
67.2
14.5
2.8
1.3
681.0
2360.0
8.5
15
0.05
0.5
0.1
0.2
5.5
70.8
N/A
98
99+
97
96
85
99
97
Remarks
Equivalent to 100,000 gal/
day.
7-170
-------
DRAFT
TABLE 7-51
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 4 SURVEYED
Screening
Emulsion Breaking
Skimming
Chemical Oxidation
Chemical Reduction
Neutralization
Flocculation
Flotation
Sedimentation
Clarification
Filtration
Ion Exchange
Adsorption
Chlorination
Lagoon
Thickening
Centrifugation
Vacuum Filtration
Pressure Filtration
Lagooning
Landfill
Incineration
No. of
Plants
9
15
29
26
31
46
33
17
33
26
19
4
1
9
19
16
6
13
3
6
12
2
Percent Utilized
13.8
23.1
44.6
40.0
47.7
70.8
50.8
26.2
50.8
40.0
29.2
6.2
1.5
13.8
29.2
24.6
9.2
20.0
4.6
9.2
18.5
3.1
-------
DRAFT
TABLE 7-52
SUBCATEGORY 5
Parameter
Flow (1/hr)
pH
Suspended Solids
Cadmium
Copper
Fluoride
Iron
Lead
Mercury
Nickel
Oil and Grease
COD
Phosphates
Silver
Raw
Waste
mg/1
15,771
8.7
1060
1.3
3.6
14.8
9.6
3.3
0.01
2.3
720
2440
8.0
0.01
Treated
Waste
mg/1
15,771
8.5
15
0.06
0.2
3.0
0.5
0.1
0.01
0.2
6.1
73.2
2.1
0.01
Percent
Reduction
N/A
N/A
98
95
94
80
95
97
0
91
99
97
74
0
Remarks
Equivalent to 100,000
gal/day
No reduction due to low raw
waste value found as average
in this subcategory.
No reduction due to low raw
waste value found as average
in this subcategory.
Zinc
2.9
0.5
83
7-172
-------
DRAFT
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-53.
SUBCATEGORY 6_, CHEMICAL-ELECTROCHEMICAL OPERATIONS - BPT
A waste treatment system for subcategory 6 differs from the baseline in
that chromium must be segregated and treated prior to mixing with the
main treatment stream as shown in Figure 7-37.
Chrome values found in the wastewater in this subcategory originate in
chromic acid pickling operations. The treatment for hexavalent chrom-
ium involves alkaline reduction of the hex-chrome to trivalent chrome
by the addition of SO2^ The wastewater containing trivalent chromium
can now be sent to the main treatment facility.
Table 7-54 provides a list of the pollutants normally found in this
subcategory and the reduced levels attainable with the baseline system
as modified for chrome treatment.
There were 33 verified Subcategory 6 plants contacted during the study.
Of these, 5 were single subcategory, and 28 had multiple subcategories.
There were 19 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-55.
SUBCATEGORY ]_, MATERIAL COATING - BPT
A waste treatment system for Subcategory 7 differs from the baseline in
that chromium wastes must be segregated and treated prior to mixing with
the main treatment stream as shown in Figure 7-38. Table 7-56 provides
a list of the pollutants, a typical raw waste concentration, and the
effect of treatment attainable with the baseline system.
The use of this modified baseline system for this subcategory is most
cost effective for larger installations. Small plants having low dis-
charge rates find hauling by a licensed contractor to a central treat-
ment facility to be more economical. Segregation of oily wastes and
hauling by licensed contractor can also reduce the treatment facility
capital and operation and maintenance costs for those companies with
small oil waste loads.
There were 436 verified Subcategory 7 plants contacted during the study.
Of these, 10 were single subcategory, and 426 had multiple subcategories
There were 58 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-57.
-------
DRAhT
TABLE 7-53
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 5 SURVEYED
No. of
Plants Percent Utilized
Screening 10 14.5
Emulsion Breaking 16 23.1
Skimming 30 43.5
Chemical Oxidation 12 17.4
Chemical Reduction 23 33.3
Neutralization 40 58.0
Flocculation 35 50.7
Flotation 15 21.7
Sedimentation 31 44.9
Clarification 33 47.8
Filtration 14 20.3
Ion Exchange 5 7.2
Adsorption 2 2.9
Chlorination 8 11.6
Lagoon 15 21.7
Thickening 19 27.5
Centrifugation 2 2.9
Vacuum Filtration 9 13.0
Lagooning 10 14.5
Landfill 17 24.6
Incineration 1 1.4
Contractor Removal 44 63.8
Incineration/Combust 7 10.1
7-174
-------
DRAFT
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-------
DRAFT
TABLE 7-54
SUBCATEGORY 6
Parameter
Flow (1/hr)
PH
Suspended Solids
Chromium Total
Chromium Hex
Copper
Fluoride
Iron
Oil and Grease
COD
Raw
Waste
mg/1
15,771
3.7
337.0
11.5
3.8
22.9
1.6
30.4
97.0
419.0
Treated
Waste
mg/1
15,771
8.5
15
0.2
0.05
0.5
1.6
0.6
2.0
12.6
Percent
Reduction
N/A
N/A
98
98
99
98
0
98
98
97
Remarks
Equivalent to 100,000 gal/
day
No reduction due to low raw
waste values found as an
average for this subcategory,
7-176
-------
DRAFT
TABLE 7-55
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 6 SURVEYED
Emulsion Breaking
Skimming
Chemical Oxidation
Chemical Reduction
Neutralization
Flocculation
Flotation
Sedimentation
Clarification
Filtration
Lagoon
Thickening
Centrifugation
Vacuum Filtration
Pressure Filtration
Lagooning
Landfill
Incineration
Contractor Removal
Incineration/Combustion
No. of
Plants
1
5
43
9
13
9
2
16
9
5
7
3
2
2
3
4
4
1
7
1
Percent Utilized
2.23
11.6
7.0
20.9
30.2
20.9
4.7
13.9
20.9
11.6
16.3
7.0
4.7
4.7
7.0
9.3
9.3
2.3
16.3
2.3
-------
DRAFT
TABLE 7-56
SUBCATEGORY 7
Parameter
Flow (1/hr)
PH
Suspended Solids
Cadmium
Chromium
Chromium (Hex)
Copper
Fluoride
Iron
Lead
Mercury
Oil and Grease
COD
Phosphates
Silver
Raw
Waste
mg/1
15,771
8.9
918.0
2.0
20.0
1.5
21.1
6.9
21.6
1.7
0.01
545.0
1,840.0
9.6
0.01
Treated
Waste
mg/1
15,771
8.5
15
0.1
0.4
0.02
0.4
2.0
0.5
0.1
0.01
4.7
55.2
2.5
0.01
Percent
Reduction Remarks
N/A Equivalent to 100,000
gal/day
N/A
97
90
98
98
98
71
97.7
94
0 No reduction attained due to
the low raw waste loads
found in this subcategory.
99
97
74
0 No reduction attained due to
the low raw waste loads
found in this subcategory.
Zinc
4.7
0.5
89
7-178
-------
DRAFT
TABLE 7-57
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 7 SURVEYED
Screening
Emulsion Breaking
Skimming
Chemical Oxidation
Chemical Reduction
Neutralization
Flocculation
Flotation
Sedimentation
Clarification
Filtration
Ion Exchange
Chlorination
Lagoon
Thickening
Centrifugation
Vacuum Filtration
Pressure Filtration
Lagooning
Landfill
Incineration
Contractor Removal
Incineration/Combust
No. of Plants
15
24
41
31
52
76
54
20
43
43
22
5
13
27
26
7
16
5
13
31
2
63
12
Percent Utilization
14.7
23.5
40.2
30.4
51.0
74.5
52.9
19.6
42.2
42.2
21.6
4.9
12.7
26.5
25.5
6.96
15.7
4.9
12.7
30.4
2.0
6.86
1.86
-------
DRAFT
SUBCATEGORY £, SMELTING AND REFINING OF NONFERROUS METALS - BPT
The baseline system, shown schematically in Figure 7-35, is representa-
tive of the treatment required to effectively reduce the pollutants char-
acteristics of this subcategory. Table 7-58 provides a list of the pol-
lutants, a typical waste concentration, and the effect of treatment
attainable with the baseline system.
The use of the baseline system for this subcategory is most cost effec-
tive for larger installations. Small plants having low discharge rates
find hauling by a licensed contractor to a central treatment facility to
be more economical. Segregation of oily wastes and hauling by licensed
contractor can also reduce the treatment facility capital and operation
and maintenance costs for those companies with small oil waste loads.
There were 17 verified Subcategory 8 plants contacted during the study.
Of these, 6 were single subcategory, and 10 were multiple subcategories.
There were 9 plants in this subcategory discharging to rivers or
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-59.
SUBCATEGORY 9_, MOLDING AND FORMING OF_ PLASTICS - BPT
The technology currently exists to eliminate the effluent from this
subcategory. Currently, 92% of the plants contacted in this subcategory
have no point source discharge. The method generally employed by these
zero discharge companies that use contact process water involves recycle
of contact cooling or heating water through a filter and a heat exchanger,
With the heat exchanger connected to a small cooling tower, the desired
temperature can be maintained in the contact process water loop. In
general, the quantity of contact cooling water is low.
There were 109 verified Subcategory 9 plants contacted during this study,
of which 8 discharged to rivers or streams.
SUBCATEGORY 10, FILM SENSITIZING - BPT
In addition to the wastes handled by the baseline system, listed under
Subcategories 1, 2, and 3, Subcategory 10 can contain cyanide wastes.
Figure 7-36 illustrates the baseline wastewater treatment system
schematic modified to handle these cyanide wastes. The cyanide bearing
wastewaters must be segregated for cyanide oxidation prior to combining
with the main waste treatment stream in the equalization tank. Table
7-60 provides a list of the pollutants, a raw waste concentration, and
the effect of treatment attainable with the system.
The use of the recommended system for this subcategory is most cost
effective for larger installations. Small plants having low discharge
rates find hauling by a licensed contractor to a central treatment fa-
7-180
-------
DRAFT
TABLE 7-58
Parameter
Flow (1/hr)
PH
Suspended Solids
Cadmium
Copper
Iron
Lead
Mercury
Nickel
Oil and Grease
COD
Silver
Zinc
SUBCATEGORY 8
Raw
Waste
mg/1
15,771
2.7
2,090.0
.8
7.10
96.4
4.6
0.03
16.5
166.0
1,650.0
.05
Treated
Waste
mg/1
15,771
8.5
25
0.04
0.2
1.9
0.2
0.01
0.5
2.8
49.5
.05
Percent
Reduction
N/A
N/A
99
95
97
98
96
67
97
98
97
0
Remarks
Equivalent to IOC,000 gal/day
No reduction due to low raw
waste values foosad as an
average for this subcategory.
23.5
0.71
97
7-181
-------
DRAFT
TABLE 7-59
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 8 SURVEYED
No. Of
Plants Percent Utilization
Screening . 1 9.1
Skimming 3 27.3
Chemical Oxidation 2 18.2
Neutralization 9 81.8
Flocculation 6 54.5
Sedimentation 8 72.7
Clarification 5 45.5
Filtration 3 27.3
Chlorination 2 18.2
Lagoon 6 54.5
Thickening 4 36.4
Vacuum Filtration 3 27.3
Lagooning 2 18.2
Landfill 7 63.6
Contractor Removal 4 36.4
7-182
-------
DRAFT
TABLE 7-60
SUBCATEGORY 10
Parameter
Plow (1/hr)
PH
Suspended Solids
Raw
Waste
mq/1
15,771
5.9
183
Treated
Waste
mg/1
15,771
8.5
15.0
Percent
Reduction
N/A
N/A
92
Remarks
Equivalent to 100,000 gal/day.
Cadmium
1.5
0.07
95
Cyanide
1.2
0.0
99
Iron
2.9
0.5
83
Mercury
Oil and Grease
COD
Phosphates
Silver
Zinc
0.01
0.01
386
1,230
3.4
0.05
3.8
36.9
1.0
0.05
99
97
70
0
No reduction due to low raw
waste values found as an
average for this subcategory.
No reduction due to low raw
waste values found as an
average for this subcategory.
1.4
0.5
64
7-183
-------
iic% •>.,, JoyZci'j-3-c-^-i-1*1 ox~ oily wast."3s anc iiauiing
by licensed contractor can reduce the treatment facility capital and
operation and maintenance costs for those coiapar.ies with small oil
waste loads.
There were 3 verified Subcategory 10 plants contacted during the study.
Of these, 2 were single subcategory, and 1 had multiple subcategories.
There were 2 plants in this subcategory discharging to rivers and
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-61.
SUBCATEGORY 11, DOCKSIDE SHIPBUILDING ACTIVITIES - BPT
The baseline system is not applicable to the pollutant characteristics
of dockside shipbuilding activities because there are no discrete waste
streams associated with this subcategory. Rather, contaminants are ac-
cumulated around the work area and can be carried to receiving waters
during rainstorms, from tidal action, when flooding or pumping out grav-
ing docks or when sinking drydocks. Thus, recommended treatment pro-
cesses for this subcategory are primarily associated with housekeeping
practices to clean up work areas or positive methods to preclude water
from contacting contaminants in work areas.
Housekeeping practices for BPT include use of front-end loaders or shov-
el for gross contaminant removal followed by sweeping of the area. Clean-
ups can be expedited by installation of a smooth impervious surface in
the work area, by diligent use of waste receptables while work is pro-
gressing and schedule periodic housekeeping activities to prevent large
accumulation of waste material. Vacuum devices instead of sweeping have
been used, however, they are not selected for BPT because exceptionally
large units necessary to pick up wet abrasive have proven unsatis-
factory. New, smaller mobile vacuum cleaners and low profile sweepers
which sweep the material into a hopper are expected to become available
in the future. Since these devices are not yet available, they are not
recommended for BPT.
For BPT, the prevention of water from contacting contaminants can be
accomplished by use of shrouds, covering spaces between working planks
and use of temporary platforms.
There were 4 verified Subcategory 11 plants contacted during this study.
These 4 plants were all multi-subcategory plants. The only discharge
from these plants was water run off to a river.
SUBCATEGORY 12, LEAD ACID BATTERY MANUFACTURE - BPT
The baseline system, shown schematically in Figure 7-35, is representa-
tive of the treatment required to effectively reduce the pollutants
7-184
-------
DRAFT
TABLE 7-61
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 10 SURVEYED
NO. of
Plants Percent Utilized
Screening 2 50.0
Neutralization 2 50.0
Flocculation 2 50.0
Sedimentation 1 25.0
Clarification 2 50.0
Filtration 1 25.0
Chlorination 1 25.0
Lagoon 1 25.0
Centrifugation 1 25.0
Vacuum Filtration 1 25.0
Incineration 1 25.0
Contractor Removal 2 50.0
-------
DRAFT
characteristic of this subcategory. Table 7-62 provides a list of the
pollutants, a typical raw waste concentration and the effect of treat-
ment attainable with the baseline systems.
There were 9 verified Subcategory 12 plants contacted during the study.
Of these, 8 were single subcategory, and 1 was multiple subcategory.
There were 3 plants in this subcategory discharging to rivers and
streams.
The treatment techniques currently used by industries surveyed in de-
tail in this subcategory, regardless of point of discharge, are shown
in Table 7-63.
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE (BAT)
The use of the Best Available Technology will make it possible to elim-
inate the discharge of all pollutants by 1983. This technology consists
of proper product design using low or nonpolluting materials, minimiza-
tion of water use by using reverse flow rinsing, recycle and low water
use processes, good housekeeping to prevent unnecessary pollutants from
entering any waste stream and the use of existing proven technologies.
These existing, proven technologies, needed for wastewater treatment by
1983, are currently available and are being used by some plants. Use
of some processes such as reverse osmosis, distillation, and ultrafil-
tration is fairly widespread, however, most applications have been for
in-plant treatment rather than for end-of-pipe or total flow treatment.
However, the scaleability of these technologies is well proven since
installations exist with flows ranging from 50 cubic meters per day to
3,500 cubic meters per day. The actual use of equipment over a 70 to 1
flow range is a sound basis for both scaleability and proven technology.
Using the technologies shown in Table 7-41 and an analysis of the waste
characteristics common to the Machinery and Mechanical Products indus-
tries, recommendations have been developed for both in-plant segregation
and treatment of wastes, as well as a single point treatment plant for
all wastewater. Total in-plant treatment, total end-of-pipe treatment,
or combinations of each approach can be used to produce a water of suf-
ficient quality to be reused by a plant. A plant having very high con-
centrations of pollutants or desiring particularly low levels in the
water for reuse may require more than one stage of treatment. The re-
moval percentages given for each technology and pollutant under each
subcategory are for a single stage unit. A multi-stage unit would
achieve an additional reduction equal to the original reduction percent-
age times the remaining concentration, i.e. an ion exchange system of
two stages treating nickel would achieve 96% reduction in the first
stage and 96% reduction of the remaining 4% in the second state, leaving
0.16% of the original pollutant in the final treated stream.
7-186
-------
DRAFT
TABLE 7-62
Parameter
Flow (1/hr)
PH
Suspended Solids
Cadmium
Chromium, Total
Chromium (Hex)
Iron
Lead
Nickel
Oil and Grease
COD
Phosphate
Zinc
SUBCATEGORY 12
Raw
Waste
mg/1
15,771
2.0
22.8
.02
0.2
0.01
32.3
2.2
.09
15.4
92.5
1.3
0.6
Treated
Waste
mg/1
15,771
8.5
15.0
.02
0.2
0.01
0.6
0.1
.09
1.0
2.8
1.0
0.5
Percent
Reduction
34
0
0
0
98
95
0
94
97
23
17
Remarks
Equivalent to 100,000 gal/day.
No reduction due to low raw
waste values found as average
in this subcategory.
No reduction due to low raw
waste values found as average
in this subcategory.
No reduction due to low raw
waste values found as average
in this subcategory.
No reduction due to low raw
waste values found as average
in this subcategory.
7-187
-------
DRAFT
TABLE 7-63
WASTE TREATMENT DISTRIBUTION FOR SUBCATEGORY 12 SURVEYED
NO. of
Plants Percent Utilized
Neutralization 3 30.0
Flocculation 1 10.0
Sedimentation 2 20.0
Filtration 1 10.0
Lagoon 2 20.0
Thickening 1 10.0
Landfill 2 20.0
Contractor Removal 1 10.0
7-188
-------
DRAFT
In-Plant Techniques
The five major points brought out in the in-plant discussion at the
beginning of this section to reduce or eliminate potential pollutant
discharge must be reemphasized for BAT. They are: *
1. Process Modification - Changes in the approach to manufacture
which eliminate or reduce use of the polluting material
2. Material Modification - Changes in materials which obviate
the need for the polluting material
3. Waste Segregation and In-Plant Treatment - Treatment of low
volume, concentrated solutions rather than treating the
entire plant effluent for all pollutants
4. Reuse of Process Liquids - Purification or concentration of
process liquids so that they may be returned to the process
stream
5. Good Housekeeping - Reduction or elimination of spills and
leaks by means of good housekeeping practices
Maximum effort must be applied to each of these steps to minimize
pollutants and water use.
Of the above five steps, waste segregation and in-plant treatment pro-
vides the most economical approach to eliminating pollutants by 1983.
In many instances, the costs of segregation and treatment within the
plant are completely offset by the savings in raw materials and water
purchased. Table 7-64 shows the pollutant parameters normally found
in the Machinery and Mechanical Products industries. Opposite each
pollutant is a technique for in-plant treatment.
Treatment plant size and, therefore, equipment costs are a function of
water flow. Minimizing water flows is, therefore, a prime concern of
all manufacturers attempting to treat their wastes. Reverse flow rins-
ing, conversion to electrostatic painting, and segregation of cooling
and process water are three of the many ways of reducing water flow.
This reduction can reduce the investment costs for treatment equipment
significantly.
Concurrent with reduction in water flow should be a concerted effort to
control the level of pollutants. This reduction in level will reduce
treatment costs further by prolonging equipment life and reducing con-
tractor hauling charges for ultimate disposal.
End-Of-Pipe Treatment
Some processes will ultimately produce wastes which must be treated in
a central facility, usually external to the manufacturing facility.
Backwashes and regeneration concentrates from in-plant treatment may be
sent to a central facility. Batch dumps or continuous overflows from
.1 on
-------
DRAFT
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DRAFT
washers and rinse baths as well as plant air pollution scrubbing water
also may be sent to a central treatment. Also in the case of small
process flows or low value materials, the most economical treatment may
be in a centralized facility. The central facility schematic shown in
Figure 7-38, defined as the BAT baseline schematic, is designed to pro-
duce good quality reusable water and a sludge which can be sent to a
landfill or reclamation center depending on the value and quanity of
material contained.
The first major components of the end-of-pipe treatment facility is a
device to reduce the solids in the wastewater to a level tolerable to
the succeeding components. Precipitation in a clarifier has been sel-
ected as one method of accomplishing significant solids reduction.
Multimedia filtration, micro-straining, or ultrafiltration have also
been observed serving the same purpose depending on the wastewater
contents. The clarifier will also remove some metals and oils and
greases which may be in the waste stream. Keeping oils and greases
below 100 mg/1 will add life to the downstream components. The efflu-
ent from this first step may be suitable for reuse in certain manufac-
turing processes.
The use of a clarifier can reduce installation costs for the total
treatment system needed for BAT by allowing use of already existing
equipment. Oil separation in a skimmer already in place can be used
in place of installation of in-plant treatment to further reduce in-
vestment costs. In summary, the addition of a reverse osmosis (RO)
system and a distillation unit to treat the RO concentrate could up-
grade an end-of-pipe treatment facility to permit recycle of high
quality wastewaters.
The second major component in the system is the reverse osmosis (RO)
unit. Properly designed for the pollutants normally found in a plant's
waste stream, the RO unit will produce a permeate of such quality that,
for many uses, it may be piped directly back to the plant. The size of
the RO unit will be a function of water flow. Multiple units in paral-
lel may be used to increase flow handling capability as well as provide
redundancy for reliability and a backup unit for scheduled maintenance.
Effluent permeates from the reverse osmosis unit containing appreciable
amounts of low molecular weight organics may require further treatment
with adsorption prior to reuse in certain manufacturing operations. Th
adsorption by activated carbon has not been shown on the baseline sche-
matic since low molecular weight organics are not common constituents o
the wastewater from the Machinery and Mechanical Products industries.
The third major component in the system provides the final treatment
step which is distillation of the RO unit concentrate to reduce the
concentrate to reusable water and a directly disposable sludge. Alter-
nates to distillation could be large evaporation ponds in certain cli-
mates or direct contract hauling if the RO concentrate quantity is low
enough. Another alternate available under certain conditions is feed-
-------
DRAFT
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7-192
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DRAFT
ing the RO concentrate back into the clarifier. This process has many
similarities with sludge densificatior. as practiced by plant ID #380
where sludge densities in a clarifier have been increased from 3% to
20% by routing some of the clarifier sludge back to the inlet stream
to provide a better floe.
Treatment of the sludge from the clarifier may be handled in several
ways. These processes have been discussed under the individual tech-
nologies part of this section. A sludge thickener and sludge drying
beds were selected for the baseline system as representative of the
techniques currently employed in the industries surveyed. This com-
bination of technologies provides an economical approach to reducing
the water content of the sludge to a point where it can be placed in
a landfill.
SUBCATEGORY !_, CASTING AND MOLDING - METALS - BAT
The significant pollutants generated in this subcategory are listed in
Table 7-65 along with a potential in-plant treatment technique. The
reduction in pollutant level attainable by these in-plant techniques is
also shown on the table.
The BAT baseline system (Figure 7-38) for end-of-pipe treatment will
also handle the wastes from this subcategory if in-plant treatment is
not desired. The reductions in pollutant level attainable with this
system are also shown in Table 7-65.
After a thorough engineering and cost study of the individual plant, a
selection can be made relative to the method of treatment of each indi-
vidual pollutant. All in-plant, all end-of-pipe or some combination of
in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. Higher
removal efficiencies can be attained by adding additional treatment
stages in series.
Note that for many applications in this subcategory; namely, cooling of
castings, sand washing, and water reclaimed by using BPT methods may be
entirely adequate for reuse without further treatment. In this case,
only further dewatering of sludge would be required.
SUBCATEGORY £, MECHANICAL MATERIAL REMOVAL - BAT
The significant pollutants normally generated by a typical plant in
this subcategory are listed in Table 7-66 along with one potential
in-plant treatment technique. The reduction in pollutant level at-
tainable by this technique is also shown on the table.
The baseline system for end-of-pipe treatment will also handle the
wastes from this subcategory if in-plant treatment is not desired. The
reductions in pollutant level attainable in the system prior to recycle
-------
DRAFT
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7-194
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DRAFT
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DRAFT
of the water are shown in the third column of Table 7-66.
After a thorough engineering and cost study of the individual plant, a
selection can be made relative to the method of treatment of each indi-
vidual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. Higher
removal efficiencies may be attained by putting a second stage treatment
in series.
SUBCATEGORY 3_, MATERIAL FORMING - ALL MATERIALS EXCEPT PLASTICS - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-67 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on the table.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of Table 7-67.
After a thorough engineering and cost study of the individual plant, a
selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment "consider a single stage treatment technique. High-
er removal efficiencies may be attainted by putting a second stage
treatment in series.
SUBCATEGORY 4^ PHYSICAL PROPERTY MODIFICATION - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-68 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on the table.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of Table 7-68.
After a thorough engineering and cost study of the individual plant,
a selection can be made relative to the method of treatment of each
individual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat-
7-196
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ment in series.
SUBCATEGORY 5, ASSEMBLY OPERATIONS - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-69 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on Table 7-69.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of the table.
After a thorough engineering and cost study of the individual plant,
a selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable frojn a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat
ment in series.
SUBCATEGORY 6_, CHEMICAL-ELECTROCHEMICAL OPERATIONS - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-70 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on the table.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of Table 7-70.
After a thorough engineering and cost study of the individual plant,
a selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat
ment in series.
SUBCATEGORY 7_, MATERIAL COATING - BAT ,
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-71 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on Table 7-71.
-------
DRAFT
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DRAFT
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of the table.
After a thorough engineering and cost study of the individual plant,
a selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat-
ment in series.
SUBCATEGORY 8, SMELTING AND REFINING OF NONFERROUS METALS_ - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-72 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on Table 7-72.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of the table.
After a thorough engineering and cost study of the individual plant,
a selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat-
ment in series.
SUBCATEGORY 9^, MOLDING AND FORMING OF PLASTICS - BAT
Contact water required is recyclable with BPT Technology.
SUBCATEGORY 10, FILM SENSITIZING - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-73 along with one potential in-plant treat-
ment technique. The reduction in pollutant level attainable by this
technique is also shown on Table 7-73.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant level attainable in the system prior to recycle
of the water are shown in the third column of the table.
-------
DRAFT
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selection can be made relative to the method of treatment of each in-
dividual pollutant.. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in~plant treatment consider a single stage treatment technique. High-
er removal efficiencies nay be attained by putting a second stage treat-
ment in series,
SUBCATEGORY 11., DOCKS IDE SHIPBUILDING ACTIVITIES - BAT
The baseline system is not applicable to the pollutant characteristics
of dockside shipbuilding activities because there are no discrete waste
streams for this subcategory. Contaminants are accumulated around the
work area and can be carried to receiving waters during rainstorms, from
tidal action, when flooding or pumping out graving docks, or when sinking
drydocks. Thus, BAT treatment processes for this subcategory are pri-
marily involved with good housekeeping or preventing water from contact-
ing contaminants in work areas.
In addition to the broom cleaning of work areas recommended for BPT,
vacuum cleaning using low profile sweepers are recommended for BAT to
provide a step increase in contaminant removal over BPT. The vacuum
cleaner should be capable of removing wet shot, loose paint particles
and scale and other foreign material.
SUBCATEGORY ,12, LEAD ACID BATTERY MANUFACTURE - BAT
The pollutants normally generated by a typical plant in this subcate-
gory are listed in Table 7-74 along with one potential in-plant treat-
ment, technique. The reduction in pollutant level attainable by this
technique is also shown on Table 7-74.
The baseline system for end-of-pipe treatment will handle the wastes
from this subcategory if in-plant treatment is not desired. The re-
ductions in pollutant, level attainable in the system prior to recycle
of the water are shown in the third column of the table.
After a thorough engineering and cost study of the individual plant, a
selection can be made relative to the method of treatment of each in-
dividual pollutant. All in-plant, all end-of-pipe, or some combination
of in-plant and end-of-pipe may be most desirable from a recycle water
quality and economics standpoint. Also, the percentages shown for
in-plant treatment consider a single stage treatment technique. High-
er removal efficiencies may be attained by putting a second stage treat-
ment in series.
7-206
-------
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-------
-------
-------
U.S. ENVIRONMENT U PROTECTION AGENCY (4-107)
WASHINGTON. DT , i>460
POSTAGE AND FEES PAID
ENVIRONMENTAL PSQTFCTION AGENCY
EPA-335
-------