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Influent (Other) - At three of the plants covered in this Interim Report,
additional influent points were sampled. At Plant 14 an additional set of
samples was taken on the industrial side influent. At Plant 15 an addi-
tional set of samples was taken at the City's second treatment plant
(domestic sewage only). Plant 16 plant had two treatment trains that were
both sampled independently. The same criteria were used in choosing the
Influent (Other) points as were applied to the Influent (Total) points.
Primary Effluent - At two of the 20 POTW's, primary settling tank
overflows, prior to secondary treatment, were sampled. In both instances,
automatic samplers were set up in the channel between primary and secondary
treatment. The channels represented the well-mixed combined effluent flow
from all primary tanks.
Secondary Effluent (Unchlorinated) - At 11 of the 20 plants, samples were
collected prior to chlorine disinfection. This sample was collected either
at the secondary clarifier overflow or in the channel leading to the
chlorine contact chamber or discharge pipe. In the majority of plants the
next step in the treatment process was chlorine disinfection, but in some
plants additional treatment prior to disinfection was practiced. At other
plants the unchlorinated effluent was the last accessible sampling point
before final discharge.
Secondary Effluent (Chlorinated) - This sample point represents the
effluent fromthe chlorinecontact chamber, prior to discharge to the
receiving water.
Secondary Effluent (Other) - Two of the 20 POTW's had two chlorinated
effluent discharge conduits; one each for separate activated sludge and
trickling filter processes. One of the points was considered secondary
effluent (chlorinated) and for clarity the other was labeled "Secondary
Effluent (Other)." Automatic samplers were used at both points.
Tertiary Effluent (Chlorinated) - Three of the plants covered in this
Interim Report utilized mixed media filtration as a tertiary treatment
step. At each of these plants an additional sample was taken after the
mixed media filters. In each case the wastewater was chlorinated after the
filters and prior to the accessible sample point.
Primary Sludge (Raw) - At each plant an attempt was made to sample the pri-
mary sludge as it was removed from the primary settling tanks, before any
further treatment. Samples of the sludge were always collected as grab
composites for two reasons: sludge consistency and lack of continuous
availability. The majority of these samples were taken from taps either on
the sludge pumps themselves or on the lines conveying the sludge to storage
or further treatment. Occasionally, the sludge point would be in a rising
well controlled by telescoping valves. The consistency of this sample
varied depending upon the means utilized by the respective plants for
drawing the sludge from the primary tanks. Samples were taken so as to
attempt to represent the average sludge consistency. This involved
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collecting sludge grabs spaced over the sampling day, or grab composites
spanning definite pumping periods.
Primary Sludge (Thickened) - At two of the plants the raw primary sludge
was not accessible, necessitating collection of primary sludge after gra-
vity thickening. Sampling procedures and techniques for this point were
the same as the sampling procedures for the raw primary sludge.
Primary Sludge (Digested) - At one plant the raw primary sludge was pumped
directly to digesters, with no accessible intermediate taps or valves for
sampling. Consequently, a sample of the digested primary sludge was taken.
This sample was collected from a pump tap as a manual grab composite.
Combined Sludge (Raw from Primary) - A number of plants recycle their
secondary sludge directly back into the primary settling tanks. At these
plants a combined sludge sample was taken in the same manner described pre-
viously for primary sludge. These samples were composited directly from
the primary tanks, prior to any sludge conditioning.
Combined Sludge (Untreated) - At one of the 20 POTWs sludge from the pri-
mary tanks was not accessible and a sample of the sludge after it had com-
bined with the waste activated sludge was taken. At another plant a manual
flow composite sample of both primary and waste activated sludges was taken
and analyzed as a combined sample of the total waste sludge being removed
from the system.
Combined Sludge (Secondary Thickened) - This sample is the same as
"Combined Sludge - Untreated" except that the wasted secondary sludge had
already been thickened prior to combination with the primary sludge.
Combined Sludge (Both Thickened) - At the two plants where sludge from the
secondary settling tanks was not immediately accessible, samples were taken
after the sludge had been gravity thickened and combined with the thickened
primary sludge.
Combined Sludge (Digested) - At three of the plants covered in this report
the secondary sludge by itself was not accessible prior to digestion, so
that a combined sludge sample after digestion was taken.
Combined Sludge (Heat Treated) - In an effort to explore the effects of the
heat treatment process on toxic pollutants in sludge treatment, sludge
samples from two heat treatment systems at POTWs covered in this study
were sampled.
Combined Sludge (Other) - At one plant which had two parallel treatment
trains, two separate primary settling tank sludges were sampled. At this
particular plant, the primary tank sludges included the waste secondary
sludges because the waste secondary sludges were recycled to the head of
the primary settling basin.
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Waste Activated Sludge (Untreated) - Waste activated sludge (WAS) sample
points varied from plant to plant, depending on WAS stream accessibility.
At some plants, WAS was accessible in rising wells prior to sludge con-
ditioning. If the rising wells were sufficiently mixed, automatic samplers
were used to gather WAS samples. At plants without rising wells, or when
the well was not mixed, samples were taken from taps on the sludge pumps.
Often, however, there were no accessible sampling points on the WAS line.
In these cases, since WAS and return activated sludge are usually iden-
tical, samples were taken from the return sludge pumps or return sludge
lines.
Waste Activated Sludge (DAF Thickened) - At one plant covered in this
report, an additional sample of the waste activated sludge was taken after
it had been conditioned in a dissolved air flotation system. This was a
single grab sample.
Waste Activated Sludge (Other Thickened) - At another POTW, two manually
collected composite samples were taken of the waste activated sludge after
centrifugation. The samples were taken from a tap on the pump conveying
the thickened sludge to the digesters.
Secondary Sludge (Untreated) - These samples represent the trickling filter
humus collected at two of the plants covered in this report. Manual com-
posite samples were taken at both plants because sludge consistency and
availability prevented using automatic sampling.
Nitrification Sludge - One of the 20 POTW's followed its activated sludge
process with nitrification. At this plant two grab samples of the waste
nitrification sludge were taken. These samples were taken directly from
the waste sludge pumps as single grab samples.
Heat Treatment Decant - At the two plants sampled that conditioned the
sludge by heat treatment, decant or supernatant samples from the heat
treated sludge holding tanks were manually composited to correspond to the
"Combined Sludge (Heat Treated)" samples taken from the same plant. At
Plant 7, these samples were taken from a sample tap on the side of the
decant tank (gravity flow), while at Plant 8 the decant samples were
grabbed from the sludge decant tank overflow weir.
Gravity Thickener Overflow - A single grab sample of the overflow from the
gravity thickener was taken at Plant 3. The sample was taken directly from
the overflow weir.
Vacuum Filter Filtrate - A single grab sample of the filtrate from the
vacuum filter at Plant 1 was grabbed from the pressure line from the
filters. All fractions were filled as one grab sample via an intermediate
vessel.
Floatables - Also at Plant 1, a complete set of samples of the skimmings
from the primary settling tanks was taken. Manual composite samples were
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gathered by dipping into the floating layer at the collection end of the
primary settling tanks.
Combination of Sources - At Plant 10, two manual composite samples of the
aerobic digester feed were taken. The sample was a combination of the
thickened waste activated sludge and the fleatables. Manual samples were
taken at this point from a tap on the sludge feed pump.
Tap Water - Background samples of the domestic water as supplied to the
plants' service areas were taken at 9 of the 20 plants covered in this
report. Samples were taken at a frequently used sink within the plant pre-
mises. The tapwater was allowed to run for a period of time prior to
sample collection.
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V.
DATA
OVERALL POTW DATA
At the first 20 plants of the 40 plant study, 632 individual samples were
collected and analyzed for toxic pollutants. Combining data from all
liquid and sludge samples, in total, 103 toxic pollutants were measured at
least once at levels above their detection limits. The toxic pollutants
never found include acrolein, benzidine, hexachloroethane, hexach-
lorocyclopentadiene, nitrobenzene, several ethers, all nitrosoamines, endo-
sulfans and metabolites, endrin and metabolites, all but two PCB mixtures,
and toxaphene.
Tables 3 and 4 present occurrence data and concentration ranges for POTW
influent and secondary effluent samples. In influent samples across the
20-plant data base, 93 toxic pollutants were measured at least once above
their detection limits. Likewise, in secondary effluents, 84 toxic pollu-
tants were found at levels above their detection limits. Finally, of the
24 toxic pollutants found in more than 50 percent of the influent samples,
all were detected less frequently in effluent samples.
In all, 76 toxic pollutants were found in raw sludges. For the purposes of
this discussion, raw sludges include thickened sludges. Table 5 summarizes
the occurrence of these pollutants in sludges across the 20 POTW data base.
Twelve of the 15 most frequently occurring and most highly concentrated
toxic pollutants in raw sludge are metals.
Figures A-l to A-8 in Appendix A present cumulative distribution curves of
pollutant removal and effluent concentration for selected priority pollu-
tants. These curves are discussed in Section VI.
Tables B-l to B-60 in Appendix B present detailed data summaries for each
of the 20 POTW's. For each plant, a Summary of Analytical Data is included
which presents averages of each pollutant parameter found at each sample
point covered. A Mass Balance is also included for each POTW. In these
tables, the average pounds per day of each pollutant entering the POTW are
tabulated, as well as the daily pounds exiting the POTW. Finally, for each
POTW, a Summary of Percent Occurrence is presented that tabulates the per-
cent of times each pollutant was found at each sampling point at each
plant.
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