Introduction
Several trace metals are known to be harmful to mar-
ine organisms. Examples of such elements include cadmium,
lead, copper, silver, and zinc (Bowen,1966 ). Thus it is
neccessary to determine the rate of introduction of these
metals into local environments. In attempting to explain
incongruencies of trace metal concentrations found in cer¬
tain marine organisms sampled from different locations around
Monterey Bay (Fitz, 1971 ), it was thought that local sew¬
age outfalls were acting as point sources of trace metal
induction into the Bay. Therefore, having picked for study
the primary sewage treatment plants of Seaside and Pacific
Grove and the secondary plants of Nonterey and Salinas, the
aim of this project was to first develope a viable technique
for quantitatively analyzing for the trace metals, cadmium,
lead, copper, silver, zinc, and manganese, in influent, efflu¬
ent, and sludge of a given treatment plant and second to
obtain first estimates of the amounts of these trace metals
entering Monterey Bay from each of these sewage plants.
This study was also intended, simultaneousy, to determine
the mode of transport of trace metals through the sewage
treatuent, the prunary systens of Seaside and Pacifie Grove,
the secondary, activated sludge system of Monterey, or the
secondary, trickling filter system of Salinas (Imhoff and
Fair, 1956 ) was the most effective in removing trace metals.
Methods and Materials
Sanples were obtained from one of the four treatment
plants on one of four consecutive Mondays between 10:00
and 11:00 A.M., the time when the plants were experiencing
their daily "peak flow". The samples collected usually con¬
sisted of two liters of influent, four liters of effluent,
and 100 mls. of sludge collected in polyethylene bottles.
To seperate liquid and solid fractions, a minimum of 1.5
liters of influent and 2.0 liters of effluent were first cen¬
trifuged at 10,000 rpms for five minutes. The centrifugate
was collected for analysis. After centrifugation the liquid
phase still contained a modicum of colloidal material that was
for the most part removed by filtration through a glass
fibre filter followed by filtration through a 47 mm., .45u
Millipore filter. The filtrate was then passed through a
"Chelex 100" chelating resin column (Riley and Taylor, 1968 ).
The metals were eluted from the resin colunn with 40 ml. of
AN HNO,: The eluted solutions were analyzed for trace metals
with atomie absorption spectroscopy (Christian and Feldman,
1970 ).
The solid centrifugate obtained from centrifugation of
the influent, effluent, and sludge samples were dried at
80°c. Aliquots of approximately .5 grams were measured out
into 30 ml. beakers and were either oxidized in a muffle fur-
nace at 4000c for eight hours or digested in 906 HNO, and
oxidized with H,02: After samples had been digested, the
volume of acid was evaporated to 5 ml. and then made up to
a volume of 25 ml. with distilled water. The samples that
were ashed in the muffle furnace were dissolved in 5 ml. of
90% HNO, and then diluted to 25 ml. with distilled water.
The 25 ml. samples were anlyzed for trace metals with an
atomic absorption spectrophotometer.
Due to the very limited amount of solid in the effluent
of the Salinas plant, it was neccessary to use a different
method for trace metal analysis than those previosly de¬
scribed. The method employed was similar to that used by
Spencer and Sachs (1970 ). In this case, 100 ml. of ef¬
fluent was filtered through two pre-weighed.8u Millipore
filters, the bottom filter being used as a blank. The fil¬
ters were dried and weighed to determine the amount of
solid that was to be analyzed. Both filters were oxidized
seperately in a nuffle furnace. 5 ml. of 906 hmo, was
added to the ashed filters, followed by dilution to 25 ml.
Both samples were analyzed for trace metals with the spec-
trophotometer, again with the "bottom" fülter used as a
blank.
To determine the weight of solid in a liter of influent
of effluent, two 25 ml. aliquots of each influent and efflu-
ent sample were fitered through two pre-weighed Millipore
filters. The filters were dreid and weighed, and the bottom
filter was used as a blank. From these weighings, the
amount of sold, dry weight, was calculated per liter.
Sediments were sampled at stations of 30, 200, and
600 feet from the Monterey plant outfall aperture. Par-
ticles suspended in the water were allowed to fall into glass
tubes vertically positioned at each station. Sediments were
dried at 800c, and one gram aliquots were ashed in a muffle
furnace and analyzed for trace metals with atomic absorption.
Results and Discussion
Determinations of the amounts of dry weight solid per
liter of influent and effluent are recorded in Figure 1. It
should be remembered that these values are representative
of "peak flow". It is noted that the two primary plants,
Seaside and Pacific Grove, operate at roughly similar effic¬
iencies in removing solids. The secondary plant of Salinas
removes approximately 91% of the solids that enter, while
the secondary palnt of Monterey, being overloaded during
peak flow, removes only about 20% of the solids. The ef¬
fluent solid of Monterey is comprised mainly of an activated
sludge flocculent.
Results of trace metal analyses of solid and liquid
phases of influents and effluents, as well as sludge, are
listed in Table 1. All trace metal concentrations in the
solids are clearly much higher than those found in the liquid.
This is probably due to adsorbtionof metals onto particulate
matter. Perhaps further support for adsorbtion of metals
onto particulate matter is that the concentrations of metals
in the liquids usually derease from influent to effluent in a
given plant, while the concentrations of metals on the solids
usually increase from influent to effluent. It was particu¬
larly interesting that no silver was found in the liquid phase
of any influent or effluent sample. Possibly the silver con¬
centrations were to small to be detected as opposed to no
silver being in solution at all.
Given the concentration of metals in a liter of influent
the weight of solid in that liter, and the concentrations of
metals in that solid, values can be calculated for total micro¬
grams of metals per liter of influent. The same calculation
can be made for effluent samples. Figure 2 compares metal
concentrations found in influent and effluent samples. In
the case of the Salinas, Seaside, and Pacific Grove plants,
it is observed that the amount of a given metal entering the
plants is greater than the amount of that metal leaving the
plant. This is only reasonable, since the removal of trace
metals is synonomous with the removal of solids. The Mon¬
terey plant, however, does not follow this pattern, for it
is seen that the concentrations of all metals except cadmium
are higher leaving the plant than entering. This trend is
explained by the fact that during peak flow the plant is re¬
leasing a great amount of activated sludge flocculent which
although is less dense than Nontereys influent sold, occu
pies a much greater volume, and thus the surface area for
adsorbtion is much larger. The activated sludge probably
also concentrates trace metals, since it is constantly being
recycled and because it is digesting partieles that contain
metals. In every case, the effluent solid from the Monterey
plant is much more concentrated in all trace metals than the
influent solid. At times other than peak flow, the Monterey
plant is quite efficient in that very few solids leave the
plant. Since sludge is being removed, there is surely an
overall decrease in the amount of metals leaving than enter¬
ing.
By multiplying the micro-gram per liter concentrations
of a given metal in the influent of each plant (Figure 2
times the number of liters of sewage flow experienced by
the respective plant, estimated values can be obtained for
the total number of grams of that metal leaving the plant
a day ( see Figures 3 and 4). The Monterey figures are
the highest because of the large amounts of solid being
emitted from the plant. The Salinas plant also brings into
view an important aspect to be considered in trace metal
570
pollution, for although the Salinas plant is the most efficient
plant in removing solids, it is dealing with a much larger vol¬
ume of sewage. Thus, the Salinas plant has the potential of
polluting much more than an inefficient primary plant with:
much lower flow rate.
Figure 5 also lists grans per day of metals leaving each
plant, and gives an intra-plant comparison of which metals
are the heavily emitted. In the Pacific Grove, Salinas, and
Seaside plants zinc is the most heavly emitted trace metal,
followed by copper, lead, manganese, cadmium, and silver in
that order. Nonterey is similar except that it disseminates
more manganese than lead and more silver than cadmium. The
pattern is surprisingly regular.
Values which may be of concern in Figure 4 are those of
Montereys lead and Salinas' cadmium out put. It is known that
lead and cadmium are extremely toxic, and these values ap¬
pear to be rather high. Monterey also appears to be putting
out a great deal of siver which could potentially be of concern.
The disposal of sludge is an important aspect of consid-
eration for the concentrations of trace metals in sludge mul-
tiplyed by the large volumes of sludge accumulated from sew¬
age treatment, acounts for a sizeable amounts of trace metals
(Hickman, 1970 ). The Monterey plant incinerates its sludge
and removes the resulting ash to a city disposal center.
The Seaside plant dries its sludge in drying beds, and then
gives the sludge away as fill dirt, fertilizer, etc. Hick¬
amn warns that the deposition of sludge onto agricultural
lands could in certain instances be veryharmful due to high
concentrations of trace metals in the sludge. The Pacific
Grove sewage plant, operating with an ineffective digester
periodically dumps all of its sludge into the Bay. Thus,
Pacific Grove is effectively no removing any metals from
its influent at all. The Salinas plant also digests its sludge,
however, a constant level is kept in the digesting tank by
recycling partially digested materials back into the influent
where it can then be processed further. Therefore, since
the system remains "closed" and no wastes are being ac¬
tively removed from the plant, all trace metals entering the
plant will ultimately end up in the effluent.
Figure 6 shows the results of trace metal analyses
made of sediments collected near the Monterey outfall. Ap
parently what seems to be happening is that most of the
heavier particles disseminated from the outfall which con¬
tain trace metals are sedimenting rather evenly within the first
20 feet. Although lichter partieles may be travellig
large distances from the outfall, fewer particles from
the outfall are reaching station 3, 600 feet away. As
a result, sediments bund at station 3 have the smallest
concentration of metals. It was estimated in Figure 5
that the Monterey plant was emitting its greatest amount
trace metal in zinc, followed by copper, lead, manganese,
silver, and cadmium in that order, however, the concen¬
trations found near the outfall, from highest to lowest,
were of manganese, zinc, lead, copper, silver, and cadmium.
Although slightly similar, the incongruence illustrates the
fact that little is known about the behavior of various
trace elements deposited from fresh water effluents into
marine waters, such as the percent of a given metal that
precipitates, which metals remain in solution, and the dis¬
semination and transportation behavior of sewage particu-
late matter (Krauskopf, 1956).
This study is only perliminary. Due to time factors,
only a modicum of samples were able to be analyzed from
each of the treatment plants. Since samples were taken
when each of the plants were experiencing peak flow, the
values obtained probably more closely represent maximums.
Since the Monterey Bay area has only a limited amount
of industry, it is fairly safe to assume that the amount
of trace metals being deposited into the Bay from local
sewage systems is substantially less than the amount of
metals emitted from sewage plants in more industrialized
areas. Nontheless, it appears that the four sewage plants
tested in this work are dumping large volumes of dangerous
trace metals into the Bay. It is my belief that if these
sewage plants are not made more efficient in removing trace
metals from sewage, trace metal pollution will begin to cause
serious detrimental effects in various aspects of the Monterey
Bay ecology.
Abstract
The four sewage plants of Monterey, Seaside, Salinas,
and Pacific Grove were analyzed for trace metals in their
influents, effluents, and sludges. Totalled from the four
plants it was estimated that 196 grams of cadmium, 1,550
grams of lead, 3,500 grams of copper, 1,600 grams of man-
ganese, 14,100 grams of ainc, and 430 grams of silver were
being dumped into the Bay daily.
Acknouledgenents
I would like to express my utmost gratitude
Georgt
Knauer for his untiring assistance and guidance and without
whom this work could not have been possible, Dr. John for
all his help, and Paul Fako fron the Monterey Water Pollu-
tion Control Plant.
This work was made possible
Gran
the
undergraduate research program of the National Science
Foundation.
14
Table Legends
Table 1: The concentrations of Cadmium, Lead, Copper,
Zinc, Manganese, and Silver found in the influents,
effluents, and sludges of the Monterey, Salinas,
Seaside, and Pacific Grove sewage treatment plants.
15
Figure Legends
Figure 1: The amounts of dry weight solid found in both the
influents and effluents of the four treatment plants.
Figure 2: Total micro-grams of each metal in one liter of in-
fluent from each plant compared to the number of
micro-grams of the same metal in the respective
effluent.
Figure 3: The average sewage flow, expressed in liters, exper¬
ienced by the respective sewage treatment plants
one day.
Figure 4: Estimated amounts of each trace metal that are
emit ted from each sewage plant in one day.
Figure 5: An intra-plant comparison of the amounts of trace
emitted from each plant in one day.
Figure 6; Fatrs per million concentrations of trace metals
found in sediments vs. distance from the Monterey
outfall. Sediments were analyzed at stations of
30, 200, and 600 feet from the out fall.
References
Bowen, H. J. M. 196. Trace Elements in Biochemistry
Acedemic Press, 241 p.
Christian, G. D: and F. J. Feldman. 1970. Atomic Absorp¬
tion Spectroscopy: Applications in Agricultre, Biology,
and Medicine. John Wiley and Sons, 490 p.
Fitz, J. D. 1971. Trace metal Conc. in Emerita analoga from
Monterey Bay. Unpublished, on file at H.M.S. library.
Hickman, H. L. 1970. Sanitary Landfill Facts, in U.S. Public
Health Service Publication No. 1792, Wash. D. C., 36 p.
Inhoff, K. and G. M. Fair. 1956. Sewage Treatment. John
Wiley and Sons, 333 p.
Krauskopf, K. B. 1956. Factors controlling the Concentration
of Thirteen Rare Metals in Sea Water. Geochim Cosmo-
chim. Acta. 9; 1-32B.
Kley, J. P. and D. Taylor. 1968. Chelating Resins for the
Concentration of Trace Elements From Sea Water and
Their Analytical Use in Conjunction With Atomic Absorp¬
tion Spectroscopy. Anal. Chim. Acta., 40: 479-485.
Spencer, D. and P. Sachs. 1970. Some Aspects of the Dis
tribution, Chemistry, and Mineralogy of Suspended Matter
in the Gulf of Maine. Marine Geol., 9: 117-136.
58
Table
Influent liquid
Effluent liquid
Influent solid
Effluent solid
Sludge
Influent liquid
Effluent liquid
Influent solid
Effluent solid
Sludge
Influent liquid
Effluent liquid
Influent solid
Effluent solid
Sludge
.0074
.0013
8.8
6.5
11.8
7.1
5.2
0065
.0039
220.5
149.6
239.1
202.6
212.0
0057
.0062
279.9
397.3
610.3
250.1
269.6
Cadmium (ppm)
Sa.
.0004
.0056
12.9
14.3
23.6
20.3
8.5
Lead (ppm)
Sa.
.0028
nd
331.9
354.7
365.0
963.2
366.4
Copper (ppm)
Sa.
.0009
.0136
177.8
317.0
327.9
882.7
370.1
Ss.
.0047
.0007
16.5
16.9
13.7
20.5
21.6
Ss.
.0046
nd
940.2
759.9
158.7
549.0
605.8
.0178
.0049
1036.2
851.1
471.4
747.0
827.9
P.G.
.0004
nd
4.5
2.7
6.9
3.4
2.
P.G.
.0053
.0047
111.7
140.4
318.0
240.6
240.0
P.G.
.0143
.0102
271.2
371.4
435.2
147.1
135.4
Table 1 (cont.
Influent liquid
Effluent liquid
Influent solid
Effluent solid
Sludg
Influent liquic
Effluent liquid
Influent solid
Effluent solid
Sludge
Influent liquid
Effluent liquid
Influent solid
Effluent solid
Sludge
Zinc (ppm)
Sa.
Ss.
1676
.0598
.1161
.1279
.1283
.0655
1475.0
1664.0
1066.0
1057.0
1199.0
2670.0
1934.0
1740.0
1310.0
930.1
2684.0
3293.
1412.0
3096.0
850.4
Manganese (ppm)
Sa.
.0197
.0491
.0266
.0487
0131
.0276
60.6
81.
53.
41.2
51.
77.2
70.0
128.
02.2
29.
112.
28.4
44.
ilver
(ppr
nd
nd
67.1
12.4
35.3
50.8
47.1
11.1
89.3
7.2
95.5
36.3
114.9
13.9
36.8
48.8
14.0
P.G
.0293
.0277
603.7
1031.0
1567.0
686.8
610.0
:0323
.0403
78.4
76.4
163.3
51.1
48.9
nd
nd
3.0
3.4
6.6
6.3
4.3
Figure 1
5.

41
—

—
—
I3

°2
2

c5
INFLUENT
EFFLUENT
M.
Sa.
§S.
P.G.
58
o
Figure 2
10
200
100
50
900
500
100-
Cd
S a.
Cu
Sa.
Tn
Sa.
INFLUENT
§ 5.
SS.
§5.
P. G.
P. G.
P. G
EFFLUENT
200
100
90
5(
101
20
10
M.
Ph
Sa.
Sa.
§S.
§ 5.

P. G.
P.6.
M.
S a.
S5.
58
c2
Figure
20
15.
10.
Flow Rate
M.
Sa.
§5.
PG.
21
589
Figure 4
100
50
M.
2000
1000


ooo0
5000
Sa.
Sa.
Sa.
Cd
SS.
Cu
SS.
2n
SS
PG.
P G.
PG
1o0c
500
1000
100
50
M.
M.
37
Sa.
Sa.
Sa.
Ph
Mn
SS.
S5.
SS
P 6.
P.G.
P.G
590
10004
1,000
00
Figute
In
59.
a 60
1
Mn
Cu
a Cd
100
500
300
Feet
595
Influent liquid (ugns/1)
Effluent liquid (ugms/1)
Influent solid (ppm)
Effluent solid (ppm)
Sludge (ppm)
Influent lquid (ugms/1)
Effluent liquid (ugms/1)
Influent solid (ppm)
Effluent solid (ppm)
Sludge (ppm)
Influent liquid (ugms/1)
rrluent liquid (ugms/1)
Irluent solid (ppm)
riluent sold (ppm)
adge (pp.)
Zinc
167.6 59.8 116.1 29.3
127.9 128.3 65.5 27.7
1475.0 1066.0 1664.0 603.7
1057.0 1199.0 2670.0 1031.0
1740.0 1310.0 1934.0 1567.0
930.1 3203.9 2684.0
686.8
850.4 1412.1 3096.0 610.0
Mänganese
20.6
49.1
19.7
32.3
48.7
13.1
27.6 40.3
60.6
81.4
53.4
78.4
41.2
51.0
77.2 76.4
70.0 128.3 102.2 103.3
29.9 112.9
66.0
51.1
28.4 44.7
67.5
48.9
Silver
nd
nd
ne
nd
nd
nd
nd
67.1
35.3
12.4
3.0
50.8
47.1
11.1
3.4
89.3
95.5
7.2
6.0
35.3
114.9
3.9
6.3
36.8
18.8
14.0
+.3
59