-------
STABLE 24. COMPARISON OF VARIOUS FILTERING RATES (ACTIVATED CARBON is)
,1971
Jan-Feb
March-April
May-June
July-August
Temp.
°C
5.1
8.3
17.4
20.6
pH value
raw
water
7.87
7.91
7.95
8.03
F 1/2
7.71
7.77
-
-
1/4
7.b9
7.62
7.40
7.44
3/4
7.65
7.67
7.52
7.53
DO (mg/1)
raw
niater
11.6
11.0
8.7
7.9
F 1/2
9.9
8.9
-
-
1/4
8.7
7.0
1.9
1.3
3/4
9.7
8.5
4.5
3.4
oxygen consumed*
mg/1
raw
water
12.6
13.1
15.8
16.4
F 1/2
10.2
11.2
-
-
1/4
8.6
9.Q
10.4
11.1
3/4
9.5
10.2
11.8
12.0
Colony
nos/ml
Fl/4
17
32
67
50
3/'
16
29
85
11
Filter 1/2 and 1/4 with vf = 5 m/hr 1/2 = 3 m bed depth
Filter 3/4 with vf =10 m/hr 1/4 = 6 m bed depth
3/4 = 6 m bed depth
* measured by the alkaline permanganate method
Source; Eberhardt, Madsen & Sontheimer, 1974
-------
TABLE 25. COMPARISON OF TWO ACTIVATED CARBON FILTERS OF THE SAME BED DEPTHS WITH DIFFERENT
FILTERING RATES
parameter
PH
DO (mg/1)
oxygen consumption (mg/1)*
DOC (mg/1)
COD (mg/1)
UV extinction
no. of colonies
rapid sand filtrate
7.94
9.7
14.4
3.3
12.7
0.139
activated carbon filtrate at
v = 10 m/hr. v = 5 m/hr.
7.59
6.0 ;
10.9 '
2.7
9.5
0.110
26 ,
7.51
3.5
9.7
2.5
8-9
0.109
37
-p*
r
* measured by the alkaline permanganate method
Source: Eberhardt, Madsen & Sontheimer, 1974
-------
rates must have been a result of biological decomposition of adsorbed organics,
since total dissolved organic removal was about the same regardless of the
filtration rates.
Varying GAG Grain Sizes—Two samples of Hydraffin LSS granular activated
carbon having different average grain sizes (1 m and 1.8 mm) were compared
over a period of 6 months. For this study, analyses were made at the start
of the experiments using fresh GAC samples and data are listed in Table 26.
It can be seen that although during the first month the larger grain size
carbon removed more organics (as measured by the differences in KMn04
consumption values), for the subsequent 5 months, the smaller grain size GAC
gave better organics removal. In addition, the differences between the two
granular activated carbons in removing organics were widening in favor of
the smaller grain sized GAC as time progressed.
Recycling Through 3AC to Study Biological Regeneration—After two years
of operation in a once-through mode, all of the effluent from the fourth
column of the GAC adsorber unit containing Hydraffin LS was aerated and
recycled back to the first column. This recycling was continued for the
next two months, during which time the effluent from column #4 and the
influent to column #1 were monitored for KMn04 consumption, CO, CO? formed
and UV absorption. Data gathered over this period are listed in Table 27.
During the initial recycling period, the dissolved organic content of
the effluent from column #4 increased, but then decreased after about 1
month to its original value. After the initial recycling period, the
amount of C0£ produced decreased to about 5 mg/1. During this time, however,
the amount of dissolved organic material removed from solution per pass
through the GAC (as measured by the permanganate consumption method) remained
about the same. Also during this time, the amount of dissolved oxygen
consumed was about equal to the amount of C02 produced (about 5 mg/1). The
rate of COj production (from biochemical oxidation) was always greater than
the amount of organics removed from solution; thus biochemical degradation
of adsorbed organics was occurring during the 2-month recycling period.
These data suggest that it may be possible to regenerate granular
activated carbon columns 1n place, biologically, by employing this recycling
technique. However, an estimated 6 month recycling period would have been
required to attain total biological regeneration at the Bremen pilot plant,
and this may not be practical. Nevertheless, these recycling data indicate
strongly that biological regeneration does occur, and that it 1s at least
technically feasible to consider biological regeneration in place, rather
than by installing thermal reactivation facilities. Even partial biological
regeneration processes could be effective in reducing thermal regeneration
costs during times when the GAC is fully loaded with organic materials and
the organic content of the raw water is low.
Granular Activated Carbons of Different Structures—It had been shown
by Van der kooij (1975) and by Klotz, Werner & Schweisfurth (1975) that
bacteria are too large to fit Into the mlcropores of granular activated
carbon which comprise about 99% of the available surface area. Only the
larger pores near the GAC outer surface are large enough to house the
143
-------
-TABLE 26. COMPARISON OF DIFFERENT GAC GRAIN SIZES (LS ACTIVATED CAR&QN)
Date
September 1971
October
November
December
January 1972
February 1972
Average, Sept. 1971-
Feb. 1972
Temp.
°C
16.65
12.93
7.16
7.23
2.58
4.06
8.44
3/2 with 0.5 - 1.5 mm range
4/2 with 0.5 - 3.0 mm range
pH value
raw
water
7.83
7.89
7.84
7.77
7.87
7.84
7.84
3/2
/.88
7.78
7.68
7.61
7.71
7.59
7.71
4/2
7.91
7.77
7.66
7.59
7.73
7.61
7.72
DO content
mg/1
raw
water
8.5
9.2
10.1
9.3
11.8
10.3
9.8
3/2
7.1
7.3
8.1
7.3
10.2
7.1
7.8
4/2
7.2
7.3
8.1
7.0
10.5
7.6
7.9
oxygen
consumption*
mg/1
raw
water ,
18.0
22.1
22.1
18.9
18.5
23.2
20.4
3/2
3.4
11M
15.9
14.0
13.9
18.5
11.4
4/2
2.8
11.8
16.6
14.4
14.9
19.7
11.5
* measured by the alkaline permanganate method.
Source: Eberhardt, Madsen & -Sontheimer, 1974
-------
TABLE 27. RESULTS OF RECYCLING TFSTS AT BREMEN WATER WORKS
1972
•
July 4
July 4
July 5
July 5
July 7
July 7
July 18
July 18
July 19
July 19
July 21
July 21
July 25
July 25
August 1
August 1
August 15
August 15
August 29
August ?9
Average-July 4-Aug. 29
Average-July 4-Aug. 29
difference
PH
7.70
7.43
7.67
7.1b
7.40
6.93
8.05
6.98
7.30
6.80
7.15
6.73
7.30
6.92
7.42
6.95
7.40
7.00
7.27
6.95
7.47
6.95
0.52
oxygen
consumed*
ma/l
11.1
10.4
12.0
13.6
18.0
17.4
14.2
12.3
14.2
13.3
17.1
15.5
13.6
12.0
10.1
9.8
10.8
10.4
10.7
8.5
13.2
12.3
0.9
DO
ma/ 1
6.9
3.5
5.3
0.9
5.8
1.0
8.2
1.4
6.1
1.4
5.6
1.3
b.8
1.3
6.1
1.0
6.0
3.1
6.8
3.2
6.4
1.8
4.6
CO
£
ma /I
5.7
10.1
7.1
16.3
5.5
11.2
3.1
13.2
6.6
11.4
6.6
12.1
7.0
9.7
7.6
11.0
6.6
9.7
7.0
10.1
6.3
11.5
5.2
UV
extinction
240 nm, 1 cm
0.113
0.110
0.148
0.146
0.177
0.175
0.165
0.160
0.172
0.168
0.206
0.195
0.174
0.168
0.155
0.138
0.154 '
0.147
0.140
0.120
0.160
0.152
0.008
Sampling
' Point
before filter 1
after " 4
before " 1
after " 4
before " 1
after " 4
before " . 1
after " 4
before " 1
after " 4
before " 1
after " 4
i
before " 1
after " 4
before " 1
after " 4
]
before " 1
after " 4
l
before " 1
after " 4
before " 1
after " 4
01
* measured by the alkaline permanganate method
Source: Eberhardt, Madsen & Sontheimer, 1974
-------
bacteria. Therefore, tests were conducted next with Hydraffin B-12, which -
contains a higher number of large inlet pores than do the other Hydraffins
tested. Data obtained are listed in Table 28, and these were taken over an
8-ir.onth period.
During the first 4 months of use, more dissolved organic carbon was
removed from solution (by adsorption) than was inorganic carbon produced.
However, during the fifth month, the amount of inorganic carbon produced
became about the same as the amount of organic iraterials being removed.
After the sixth month, the amount of inorganic carbon produced was greater
than the amount of dissolved organic carbon being removed. Comparing the
results obtained with Hydraffin B-12 with those from other activated carbons,
it is clear that the B-12 GAC removed a higher percentage of dissolved
organic materials.
Further testing using fine grained (1 mm) Hydraffin LSS (which has a
higher adsorption capacity for dissolved organics) was conducted for 11
months. Results from these tests and those shown in Table 24 are plotted in
Figure 48. The ratios of A(DOC removed/cu m of GAC/hr) are plotted on the
ordinate against time, and data obtained for Hydraffins BR, B-12 and LSS
(0.5-1.0 mm grain size) are presented. Both B-12 and LSS gave better removals
of dissolved organic materials than did Hydraffin BR. After the initial
period of biology buildup, 32 to 38% of the influent DOC was biochemically
decomposed at a steady rate in the Hydraffin B-12 adsorber. On the other
hand, 50 to 53% DOC removal occurred in the Hydraffin LSS adsorber, but only
after a somewhat longer initial adjustment period.
At the end of these 11-month long studies, samples of the different
granular activated carbons were extracted with dioxane, then DMF9 to determine
their total organic loadings. An average loading of 115 g/kg of GAC was
found for the fine grained LSS, and 85 g/kg for the B-12 carbon.
Summary of Bremen Pilot Plant Test Results --
1) Dissolved organic substances were first adsorbed by GAC resulting in
high loadings on the GAC during the first 3 to 5 months of GAC use.
Thereafter, biological activity reached a steady state, from which
point a significant fraction of the adsorbed organics was degraded
biochemically to C02 and water.
2) After the biological steady state had been attained, 100 to 140 g of
dissolved organic carbon was bacterially oxidized/cu m of activated
carbon per day. Consumption of dissolved oxygen averaged 360 g/cu m of
granular activated carbon/day and 240 g/cu m/day during winter.
3) For 30 minute empty bed contact times, about 2 mg/1 of DOC could be
removed from solution. This corresponds to about 5 mg/1 of dissolved
organic materials removed.
4) Organic materials must be biodegradable. The amount of biodecomposable
components present could be increased by preoxidation with ozone.
.146 _
-------
TABLE 28. TESTS WITH B-12 ACTIVATED CARBON
Date
Sept. 26 Oct. 17, 1972
Oct. 24-Nov. 14, 1972
Nov. 21-Dec. 12, 1972
Dec. 19-Jan. 9, 1973
Jan. 16-Feb. 6, 1973
Feb. 13-Mar. 13, 1973
Mar. 20-Apnl 10, 1973
April 17-May 15, 1973
May 22- June 12, 1973
Raw Water
oxygen
consumed*
mg/1
16.6
16.5
14.1
15.3
19.3
14.8
14.9
14.0
16.5
UV-
extinction
Corr.
0.126
0.150
0.125
0.126
0.173
0.133
0.120
0.110
0.135
% decrease in
oxygen
consumed*
Ir2 1-4
60.3 67.2
39.1 56.2
27.5 48.4
24.6 45.1
18.6 36.7
17.2 36.9
14.9 38.2
22.7 36.0
24.5 36.9
UV
1-4
69.8
49.2
47.8
36.2
31.3
33.3
28.8
32.3
37.0
A02
mg/1
1-4
3.5
3.6
2.6
4.1
4.6
2.4
3.4
3.3
6.9
&co2
mg/1
1-4
1.92
2.98
2.07
3.40
5.85
3.85
4.14
6.73
4.67
A DOC
mg/1
1-4
2.31
1.94
1.56
|.20
I'42
].16
6.90
0.94
1.31
iiinorg. (
mg/1
1-4
O.b2
0.81
O.b6
0.43
1.47
1.05
1.13
1.84
2.64
* measured by the alkaline permanganate method.
Source: Eberhardt, Madsen & Sontheimer, 1974
-------
specific
capacity,
g aDOC/m3 GAC
5-
4-
3-
2-
BR-GAC,
1-3 mm
B-12 GAC,
formed £'
"'
LS-supra GAC,
*" 0.5-1.0 mm
slow filter for comparison
i ndj
am] j asondj f mamj j asond
1970
1971
jfmamjjasond
1972
j f mam JJ a sondh f
1973
1974
Figure 48. Variation in specific capacity for dissolved organic carbon
(DOC) of a GAC filter with operating time for normal (BR)
and more highly activated carbons.
(Eberhardt .el aL.,1974)
-------
Preozonation also Increased the rate of DOC removal at low temperatures,
during winter.
5) Biochemical regeneration of GAC was be followed by measuring the
amount of C02 generated and relating this to the amount of DOC removed
from solution. When the ratio A(DOC removed)/A(inorganic carbon produ-
ced) was less than 1, the source of the additional CO? must have been
from organic materials previously adsorbed by the GAC? When this ratio
was greater than 1, adsorption of organics was proceeding at a faster
rate than biodegradation. When the ratio was about 1, the two processes
were occurring at approximately the same rate.
6) During the 3+ years of testing at Bremen, the ratio A(DOC removed) to
A(inorganic carbon produced) was about 1 most of the time. During
periods of low water temperature (winter) the ratio was greater than 1;
during summer the ratio was less than 1.
7) The maximum amount of DOC removal occurred during the initial period of
GAC use, when adsorption was the dominating process. About 80% of the
DOC was removed during the initial 6 week period. Thereafter, the COC
of the GAC effluent rose to a level which remained constant and was
related to the influent DOC level. Under the best conditions found at
the Bremen pilot plant (large inlet pore GAC, high Initial adsorption
capacity for the dissolved organic materials present in the Bremen raw
water, fine grain size), about 50£ of the influent DOC could be removed
constantly after the biological steady state had been reached. For
other granular activated carbons, the rate of DOC removal at the biologi-
cal steady state was 20 to 33X.
8) Satisfactory ^8- and 72-hour colony numbers/ml were obtained after
passage through biologically active GAC. However, when the GAC influent
had been preoxidized with ozone or with chlorine, the 72-hour colony
counts rose to very high levels. Installation of a rapidly driven slow
sand filter after the GAC adsorber lowered the 72-hour colony counts to
acceptable values.
9) Coliform counts/100 ml were very low and acceptable in all GAC filtrates.
10) All GAC experiments conducted at the Bremen pilot plant utilized rapid
sand filtrate from the full-scale plant, which had been pretreated with
1 to 3 mg/1 of KMn04- No experiments were conducted to determine
whether this permanganate pretreatment increased the biodegradation
rates. Treatment of the plant rapid sand filtrate with chlorine (unrepo-
rted dosage) did not increase the rate of biodegradation as did preozona-
tion.
11) Ammonia levels in the River Weser raw waters remained low (below 2
mg/1) throughout the 3+ years of testing. Nitrification occurred in
the rapid sand filters of the full-scale plant, in the biologically
active GAC adsorbers and in the slow sand filters. The amount of
dissolved oxygen required to satisfy the requirements for nitrification
_ _ 149
-------
in the GAC and following slow sand filters was sufficiently low that
additional oxygen was not necessary.
MUlheim, Federal Republic of Germany
The Rheinlsch-Westfaiische Wasserwerksgesellschaft mbH has taken
advantage of biological activated carbon to radically change the drinking
water treatment process at the 48,000 cu m/day (12.7 mgd) Dohne plant in
MUlheinij, Germany (Sontheimer et al., 1978; Heilker, 1979). Raw water for
this plant is the River Ruhr,~whTch until mid-April, 1977 was treated by
breakpoint chlorination for ammonia removal, flocculation, sedimentation,
granular activated carbon for dechlorination, then ground filtration. Over
the years, ammonia concentrations have increased, requiring prechlorination
doses as high as 10 to 50 mg/1. In turn, these high chlorine doses produced
large amounts of chlorinated organics (Table 29) which not only were incomple-
tely adsorbed by the carbon columns and passed through the plant into the
distribution system, but also caused frequent regeneration of the activated
carbon columns (every 4 to 8 weeks).
TABLE 29. ORGANO-CHLOROCOMPOUNDS PRESENT AFTER BREAKPOINT CHLORINATION
Sampling Point
raw water (Ruhr river)
after flocculation + sedimen-
tation
after filtration
after GAC filters
after ground passage + safety
chlorination
DOC1*
PPb
17
—
203
151
92
DOC IN**
ppb
5
—
30
17
18
Sum of halo-
forms, ppb
9
15
23
21
23
CHC13
PPb
<1
6
7
7
9
* DOC1 = dissolved organic chlorine
** DOC1N = dissolved organic chlorine, non-polar
Source: Sontheimer et^a^. (1978).
During a two year pilot study on the use of preozonation followed by
activated carbon adsorption for removal of ammonia and of organics, it was
found that breakpoint chlorination could be eliminated completely and the
BAC operation could be relied upon totally for removal of ammonia. At the
same time the DOC was reduced to the desired levels.
This process, involving ozonation ahead of sand filtration and granular
activated carbon adsorption, was installed and began operating in mid-April,
1977._At the time, the GAC columns at this plant were 2 meters deep (EBCT =
_ 150
-------
5.5 minutes) and the GAC, exhausted during use under the old process, was
used from mid-April until July, 1977. During late summer, 1977, the carbon
bed depths were increased to 4 meters (EBCT = 11 minutes). Fresh GAC was
charged to the deeper columns and these began operating in November, 1977.
The process at MUlheim has been operating as predicted by the pilot studies
and the carbon columns have not yet required regeneration. The performance
of the full scale plant process is as effective as was the pilot process at
the same stage of development (Sontheimer, 1978).
The newly installed process at Dohne involves preoxidation with about 1
mg/1 of ozone with addition of poly-aluminum chloride and lime as flocculants.
Preozonation oxidizes manganese and aids in flocculating the organics.
After flocculation and sedimentation, 2 mg/1 of ozone is added to oxidize
dissolved organics. After a retention time of 15 to 30 minutes, the ozonized
water initially was again preflocculated using 0.2 mg/1 aluminum chloride
and 0.1 mg/1 polyelectrolyte, filtered through sand, then passed through
biological activated carbon where the bulk of DOC and ammonia are removed.
During the period April-July, 1977, it was found that the preozonation
step, coupled with high speed agitiation was so successful in removing
suspended solids that the second Aids plus polyelectrolyte addition step
was eliminated when the process was re-started in November, 1977. However,
nitrification is promoted by addition of 20 mg/1 of oxygen (obtained from
liquid oxygen cylinders) before sand filtration (where most of the nitrifica-
tion occurs). The ammonia content of the Ruhr River has risen to nearly 6
mg/1 as of June, 1978. Addition of gaseous oxygen is controlled by a DO
residual level of 7 mg/1 monitored after the BAG columns.
Table 30 summarizes the the process changes which were made at the
Dohne plant during the period 1977-1978. A comparison of the performance of
the new process versus the old process is given in Table 31. The COC of
treated water today is less than half of that treated by the old process.
Even lower DOC values are being obtained since the depths of the GAC columns
have been increased. Finally, no chlorinated organics are being generated
by prechlorination.
After activated carbon adsorption, the treated water is sent to ground
infiltration (12* to 50 hours retention time), after which it is chlorinated
(0.2 to 0.3 mg/1) and sent to the Mdlheim distribution system. Ground
infiltration at Dohne no longer is considered to be necessary, because of
the high quality of water which the plant produces. It will be maintained,
however, as a convenient and functional water reservoir (Heilker, 1978).
Table 32 shows the bacterial content of waters at the various points in
the new treatment process. E. coli counts/100 ml are essentially zero after
"filtration and remain essentially zero after BAC filtration as well. There
should be no concern for E. coli passing through the BAC media into the
product waters because this" strain of bacteria does not survive in the
presence of the other bacterial strains present in the GAC (Van Der Kooij,
1978; Schweisfurth, 1978).
151
-------
TABLE 30. PROCESS PARAMETERS AT THE DOHNE WATERWORKS (MULHEIM) BEFORE AND
AFTER CHANGE OF TREATMENT
Treatment Step
preoxi elation
dosing
power input
flocculation
sedimentation
filtration
with
preflocculation
activated
carbon filter
ground passage
safety
chlorination
Old Treatment
(before 1977)
10-50 mg/1 C12
4-6 mg/1 AT*3
0.1 kW/m3
Ret. time =0.5 min
5-12 mg/1 Ca(OH)2
Ret. time = 1.5 hr
v* - 10.7 m/hr
v* = 22 m/hr
h** = 2 m
Ret. time 12-50 hr
0.4-0.8 mg/1 C12
New Treatment
(April-July 1977)
1 mg/1 03
4-6 mg/1 Al+3
2.5 kW/m3
Ret. time a0.5 min
5-15 mg/1 Ca(OH)2
Ret. time = 1.5 hr
2 ma/1 (]-3
Ret. time = 5 min
v* = 9 m/hr
0.2 mg/1 Al+3
0.1 mg/1 poly-
electrolyte
v* = 18 m/hr
h** = 2 m (4 m)
Ret. time 12-50 hr
0.2-0.3 mg/1 C12
New Treatment
(Nov. 77-June 78)
1 mg/1 03
4-6 mg/1 Al+ 3
2.5 kW/m3
Ret. tine =0.5 Tiin
5-15 mg/1 Ca(OH)2
Ret. time= 1.5 hr
2 mo/1 O1?
Ret. time - 5 min
20 mg/1
liquid oxygen
v* = 28 m/hr
h** = 4 -n
Ret, time 12-50 hr
0.2-0.3 mg/1 Cl,
*v = filter velocity
**h = bed height
Sources: Sontheimer e_t al_., 1978
Jekel, 1978 and 1979
152
-------
TABLE 31. MEAN COC VALUES AFTER THE DIFFERENT TREATMENT STEPS (MULHEIM)
sampling point
raw water (Ruhr river)
after flocculation + sedi-
mentation
after filtration
after GAC filtration
after ground passage
1975
DOC,
mg/1
3.9
3.2
3.2
3.0
1.8
1976
DOC,
mg/1
5.0
4.0
3.8
3.7
2.1
April -July
1977, DOC,
mg/1
3.6
2.9
2.6
2.3*
0.9
Nov. 1977 -
June 1978,
DOC, mg/1
2.4 - 3.7
1.8 - 3.0
1.7 - 3.1
1.0 - 2.6**
—
* filters filled with fully loaded GAC, used in old treatment process
** filters doubled in height and filled with new GAC
Sources: Sontheimer et al., 1978; Jekel, 1978
Pilot plant data are presented in Table 33 which show the effects of
variation of activated carbons on removal of DOC, inorganic carbon, arraronia
and dissolved oxygen. In addition, this table also compares the removal of
these same parameters with carbon column depths of 2.5 m and 5.0 m for two
different activated carbons.
Conversion of ammonia and dissolved oxygen consumption are fairly
independent of carbon type or column depth. On the other hand, removals of
DOC and inorganic carbon produced are affected by the carbon type. Most
significant, the amount of DOC removed with 5.0 m columns is about 50%
higher than with 2.5 m columns, although the amount of inorganic carbon
measured increases only slightly.
During pilot studies at the Dohne plant with the BAG process, activated
carbon columns were found to have operational lives of at least one year,
and in some cases two years, without requiring regeneration. Life of the
full scale carbon colutrns at Dohne now is estimated to be at least two years
(Sontheimer, 1978). No signs of loss in performance of the activated carbon
have been noted during the first year of operation, and the new carbon
columns have not yet had to be regenerated (Jekel, 1978).
Additionally, preozonation has extended the running times of the sand
filters from two to seven days before backwashing is required. Backwashing
of the four GAC filters (each of which contains a different granular activated
carbon being tested on full scale) varies, but was conducted during initial
stages of plant operation every 10 days9 on the average. However, during
the summer of 1978, "a population explosion of nematodes" was observed in
both the rapid sand filters and GAC adsorbers. These growths were caused by
the long intervals between backwashes, during which the nematodes developed.
153
-------
TABLE 32. GEOMETRIC MEAN VALUES OF BACTERIAL COUNTS FOR THE MULHEIM,
GERMANY (DOHNE) PLANT USING OZONE
Sampling place
Raw water (Ruhr)
After flocc'n + sediment1 n
After filtration
After activated carbon
After ground passage
Total Bacterial
Counts/ml
v
14,490
2,340
6,010
3,700
27
**
g
2.0
4.2
4.9
4.0
2.3
E-Col
V
1,620
6.7
«1
«1
«1
i/100 ml
**
g
1.7
3.2
—
—
—
* M = geometric mean
** a = geometric standard deviation
TABLE 33. PERFORMANCE OF BIOLOGICAL ACTIVATED CARBON FILTERS. MEAN VALUES
FOR 6-MONTH OPERATION AFTER A 3-MCNTH STARTING PERIOD (DOHNE
PTI n" PIAN~. yniHFTM. RFRMANYI
Activated carbon
type
LSS
LSS
ROW
ROW
NK12
F40D
BKA
bed depth
(m)
2.5
5.0
2.5
5.0
2.5
2.5
2.5
A DOC
mg/1
0.92
1.69
1.09
1.59
0.99
1.26
1.00
A (inorg C)
mg/1
0.83
0.96
0.97
1.05
1.36
1.11
0.97
A NH4+
mg/1
1.31
1.34
1.31
1.34
1.28
1.32
1.28
A02
mg/1
6.32
6.67
6.49
6.71
6.03
6.95
5.99
Source: Sontheime£_et_aK, 1978_
154
-------
When the backwashing intervals were reduced to 3 days (just below the time -
of the reproduction cycle of this genus of microorganisms), the nematodes
disappeared (Heilker, 1979).
Elimination of breakpoint chlorination at the beginning of the MUlheim
process eliminates formation of chlorinated organics which caused the acti-
vated carbon columns to have to be regenerated every 2 months under the old
process. The 10 to 50 mg/1 dosage of chlorine previously required for this
step now has been replaced with 3 mg/1 total dosage of ozone, applied in 2
stages. Additional cost-savings associated with this change include the
labor which was required with breakpoint chlorination. Formerly, a technician
was required to sample water every two hours and to analyze for chlorine and
for ammonia. This labor requirement has been eliminated (Sontheimer, 1977a,b).
Increased algae levels occur in the Ruhr River near MUlheim in the
spring and fall. These are compensated for at the Donne plant simply by
increasing the preozonation dosage from one to two mg/1 until the algae
bloom has subsided. The plant operating characteristics remain normal with
this procedure (Nolte, 1978).
Because of the success of the BAG process in replacing breakpoint
chlorination at the Dohne plant, the Rheinisch-Westfaiische Wasserwerk-
gesellschaft mbH now is designing BAG into two of its other plants in the
MUlheim area of Germany. Neither of these plants will employ ground infiltra-
tion of treated water.
It is important for the reader to realize that Dohne1s raw water (the
Ruhr River) does not contain significant amounts of of synthetic organic
chemicals. TOG! levels are very low. In fact, the German government prohi-
bits the discharge of industrial wastes into the Ruhr, because 1t is the
source of drinking water for many cities in the area. There is considerable
pollution in the Ruhr because of sewage discharges, but the components of
this generally are biodegradable, or can be made so by oxidative pretreatment.
As a result, there is only a small chance for non-biodegradable organic
materials to be present after ozonation, and most of the organics entering
the BAG media are expected to be biodegradable. Therefore, the life of the
BAG columns at the Dohne plant should be at least two years before regenera-
tion is required, based on pilot studies of that length of time.
At the present time, the criteria to be used to determine when the GAG
is to be regenerated at 3ohne are the breakthrough of DOC and of the organic
materials which absorb at 254 ran in the ultraviolet region. These criteria
probably will be adjusted on the basis of overall plant performance and the
changes which are noted in the water quality parameters currently being
monitored. TOC1 analyses are being conducted routinely at Dohne, and it is
possible that this parameter can become a regeneration criterion, if pollu-
tional levels of such halogenated organic materials increase in the future.
155
-------
Rouen-la-Chapelle, France
At the 50,000 cu m/day (13.2 mgd) plant at la Chapel!e St. Etlenne de
Rouvray in Seine Maritime (west of Paris near the Atlantic Ocean), well
waters drawn from near the Seine contain 2 to 3 mg/1 ammonium ion, 0 to 0.2
mg/1 manganese, various micropollutants (detergents, phenols, Substances
Extractable with Chloroform, etc.) and are practically devoid of dissolved
oxygen. Since 196?, the ammonia content of the raw water has risen from an
average of 0.3 mg/1 to an average of 2.6 mg/1. This increase required that
the treatment process be improved. Breakpoint chlorination was discarded
because it would have required very large contact chambers (close to 7,000
cu m) and would have produced chlorinated organics which then would have to
be removed.
After three years of pilot plant testing, the following process (Figure
49) was developed, was installed and began operating in February 1976 (Gomella
& Versanne, 1977; Rice, Cornelia & Miller, 1978):
t Pre-ozonation (0.7 mg/1) for Mn, organics and adding dissolved oxygen
to the water
t Filtration through quartz sand
• Adsorption in GAC beds
• Ozonation for disinfection (1.4 mg/1)
» Post-chlorination (0.4 to 0.5 ng/1)
This single operation of preozonatlon assures the following:
8 oxygen demands of the materials in water are satisfied,
• water is oxygenated,
t complex, biorefractory molecules are broken down and become biode-
gradable,
• the content of various micropollutants is lowered,
• manganese is oxidized and precipitates, to be retained on the sand
filter so that it does not block adsorption sites on the biological
activated carbon.
About 80% of the nitrification occurs in the sand filter beds (100 cm
deep). Periodic backwashing of these sand filters to remove oxides of
manganese does not upset the action of these bacteria. Similarly, bacterial
activity on the activated carbon beds (75 cm deep) is not displaced during
backwashing. The BAC beds are backwashed (by bumping with air, then using
water) once each month, but have not yet had to be regenerated after 2.5
years of operation. However, one GAC bed was reactivated in early 1979 so
156
-------
OZOnemnm» I
polluted
well water
T
I
I
I
|
preozonatlon
1
sand
filtration
GAC
adsorption
h
i
I
1
post-ozonatlon
(disinfection)
1
recycle
of
off-gas
ozone
f~j
post -ch lor Inationl
(for residual) I
Figure 49. The Rouen-la-Chapelle process,
Rouen, France.
157
-------
as to allow plant personnel to become familiar with the operation (Schulhof,
1979).
This plant began operating in February, 1976 and showed the perfor-
mances listed in Table 34 for the first two years of operation, respectively.
During the first year the empty bed contact time for the carbon beds was 9
minutes. During the second year, this was increased to 18 minutes by
decreasing the flow rate of water through the plant. The percent pollutant
renovals are somewhat better with the longer empty bed contact time.
TABLE 34. ROUEN-LA-CH"PELLE PLANT OPERATIONAL DATA 0976 AND 1977)
parameter
turbidity
(mastic drops)
ammonia (mg/1
NH4+)
Mn (mg/1)
detergents
(mg/1 DBS)
phenols
(microg/1)
SEC***
(microg/1)
substances
extractable
with cyclo-
hexane
(microg/1)
raw
water
4
1.80
C.15
0.12
6.5
590
1,335
preozo-
nized
-
1.80
0.07
0.09
4.0
470
740
filtered
(sand &
GAC)
-
0.40
0.04
0.06
1.5
250
535
post
ozoni-
zed
2
0.26
0.02
0.03
0
150
410
1
eliml
1976*
—
8656
87*
752
100%
75%
69%
»
nation
1977**
~
95%
90%
75%
100%
75%
70%
av. NH, content of raw water: 0.3 mg/1 in 1968; 2.6 mg/1 in 1975
* EBCT = 9 minutes
** EBCT = 18 minutes
*** SEC = Substances Extractable With Chloroform
Sources-
* Gomel! a & Versanne, 1977
** Versanne, 1978
158
-------
During a site visitation to the Rouen plant in June, 1977, it was
learned that neither air nor oxygen are added after sand filtration or
before GAC adsorption, and that the dissolved oxygen content of the water
exiting the BAG beds is zero (Versanne, 1978). This would indicate the
possibility that there may be incomplete nitrification or some denitrification
occurring in the lower part of the 75 cm deep GAC beds.
Cornelia & Versanne (1977) reported that even though 1 gram of ammoniacal
nitrogen requires 4.57 g of oxygen to be converted to nitrate ion (stoichio-
metry not indicated), only 3.2 g are required at the Rouen plant. This is
further indication of the occurrence of denitrification processes. In this
situation, the oxygen source for the nitrifying bacteria would be the nitrate
ion, and as oxygen is removed from the nitrate ions, both nitrite ions and
nitrogen gas can form.
There should be no dangers from this practice at Rouen, however,
because after BAG treatment, the product water is subjected to ozonation for
disinfection. The French standard for this process involves first attaining
a dissolved ozone residual of 0.4 mg/1, then maintaining that 0.4 mg/1
residual ozone concentration for a minimum of 4 minutes. Under these condi-
tions, Rouen's BAC-treated waters are disinfected, viruses are inactivated,
any nitrite ions formed in the GAC beds are oxidized to nitrate ions and
high dissolved oxygen levels are restored.
A case history of the Rouen plant has been published recently by Rice,
Gonrella & Miller (1978). At least 29 specific organic hydrocarbons and 16
oxygenated organics have been identified in Rouen's raw waters. Only chloro-
form, carbon tetrachlor1de9 trichloroethylene and trlchlorobenzene were
identified as chlorinated organic impurities. Rouen does not monitor for
TOC1, but is testing that procedure for possible use as a GAC reactivation
criterion.
Under these circumstances, it is probable that most of the organic
compounds present in the Rouen raw water are biodegradable after ozonation.
The amounts of identified chlorinated organic compounds are very low.
Therefore, it is to be expected that most of the organic pollutants present
are being removed by the biologically active GAC, and the BAC should have a
long useful life at Rouen. Nevertheless, the presence of some chlorinated
organic compounds indicates that TOC1 should be monitored frequently, as a
check on the cumulative loading of these materials on the GAC. When this
practice is instituted at Rouen, perhaps TOC1 will be chosen as the key
regeneration parameter, and the useful life of the BAC at Rouen may turn out
to be shorter than indicated by the parameters listed in Table 34.
159
-------
SECTION 10
EUROPEAN MICROBIOLOGICAL STUDIES IN ACTIVATED CARBON FILTERS & ADSORBERS
INTRODUCTION
Many Investigators have observed the rapid growth of bacteria in
activated carbon media used as filters and/or adsorbers in drinking water
treatment (McCreary & Snoeylnk, 1977, references cited therein; references
cited throughout this sub-section). For purposes of differentiation, the
term "activated carbon filter" will be used to describe the use of activated
carbon in place of sand filters, when the primary function of the activated
carbon is as a filtration medium. On the other hand, the term "activated
carbon adsorber" will be used to describe the same activated carbon unit
after sand or dual media filters.
High levels of bacteria also have been observed in the effluents from
6AC filters and adsorbers used for periods of more than a few months.
Several pertinent observations in this regard were presented at the Conference
on Activated Carbon in Water Treatment held in England during April, 1973
and sponsored by the Water Research Association, Medmenham, England. The
Proceedings of this conference provide valuable information regarding the
status of activated carbon used for treating drinking water supplies at that
time. In this sub-section we will discuss the status of European microbiolo-
gical studies as it existed in 1973, as reported in five presentations made
at that conference. Next, more recent European studies will be discussed.
A portion of these later studies has been presented briefly 1n Section 6.
EUROPEAN STATUS AS OF 1973
Melbourne & Miller (1973) reported details of an extensive study
conducted over the period 1968 to 1971 at the Colwick (England) plant which
treats River Trent water. The plant treatment process consisted of biological
sedimentation (for ammonia conversion), chemical addition, sedimentation,
anthracite/sand filtration, GAC adsorption and post-chlorination. During
this study the behavoir of the plant stream was compared with that of a
second stream which was pretreated by chloHnation or caustic soda softening.
Over the 3-year period of this study- it was found that the GAC adsorbers
removed about 80% of the bacteria present 1n the plant stream entering the
carbon beds under "normal conditions" (without prechlorination or presoften-
inq) However, when prechlorination or presoftening were practiced, signifi-
cantly Increased growths of organisms across the GAC adsorbers were observed.
On the average, waters from the sand filters containing no col1forms/lOO ml,
zero E. coli/lOO ml and no 22'C plate counts/ml showed an average of about
160
-------
10 coliforms/100 ml, zero to 9 E. Coli/100 ml, but 1,000 to 8,500 22°C plate
counts/ml in the GAC effluents over an 8-week period (Table 35).
On the other hand, even when these high levels of organism growths
occurred, final chlorination successfully eliminated them, except in a few
instances.
- Knoppert & Rook (1973) had studied the treatment of River Rhine water
at the Rotterdam (The Netherlands) Waterworks with granular activated
carbon over the period 1970 to 1972. At the time, this plant used the
process consisting of microstraining, breakpoint chlorination, iron (III)
coagulation, powdered activated carbon, flocculation, sedimentation and
rapid sand filtration.
Knoppert & Rook (1973) stated, "The only objection to locating GAC beds
at the end of the purification process is the generally-known bacterial
growth in the beds, which may give rise to high bacterial counts in the
delivered water". Therefore these investigators conducted a program to
study the possibilities of diminishing this bacterial development by backwash-
ing the GAC beds frequently.
Two equivalent GAC columns were operated in parallel and threshold odor
numbers were monitored in the effluents. One column was backwashed daily
and the other twice monthly. The column which was backwashed daily ran 52
weeks before taste breakthrough occurred. During this time, the measured
22°C bacterial count levels rose to 10,CCO/ml after 8 weeks, then diminished
steadily to about 25/ml by the end of this run (52 weeks).
The second GAC column, bctckwashed twice monthly, ran only 40 weeks
before taste breakthrough occurred. Bacterial counts in the effluents also
rose to 10,000/ml after 8 weeks of operation, decreased to 100/ml after 24
weeks and then rose to nearly 1,000/ml at breakthrough (40 weeks).
The 37°C colony counts of both GAC beds remained at levels less than
10/ml throughout the test period. The 22°G colony counts of both GAC bed
effluents were easily controlled by post-chlorination.
Ford (1973) reported studies conducted at the Foxcote Treatment Works
of the Bucks Water Board (England), where GAC was introduced into the plant
process for taste and odor control in 1960, after an 18-month pilot plant
study conducted during 1957 and 1958. The treatment process at this 11,400
cu m/day (3 mgd) plant involved coagulation (ferric sulfate or alum), break-
point chlorination (to 0.5 mg/1 free residual chlorine), rapid sand filtra-
tion, GAC, rechlorination and ammoniation. The GAC adsorber bed was 0.91 m
high x 2.44 m in diameter (volume 34.2 cu m) and had a 97 second actual
contact time (assuming 30* interstitial voids in the carbon), or a superficial
contact time of 325 seconds at a filtration rate of 2.8 mm/sec.
r a
-------
CT(
ro
1ABLE 15 KtMOVAl Of MCHHIA OUHIW. LA SI 1C SOUA SCFlLnlnG ADO l-KlUllOKItlAT ION AT COIWICK. MIAhL
send filtered""
f 1
toll"
foms/
100.1
500
1.700
1.200
1.400
1.000
3.600
2.600
4,400
340
IkO
820
2.300
2.100
2.300
100
400
220
1,940
960
.600
.240
.500
580
.400
.600
.200
.040
500
000
.620
760
t coll
per 100"
•1
20
35
150
50
455
45
J60
10
4
50
156
90
20
a
a
nil
24
20
130
24
24
240
124
120
42
44
4
168
4
10
22'£ plate
cowit/100
•1
far
1 ,500
1.340
3.900
2.460
2.400
5.400
410
2,500
1,300
BO
60
8511
>5.000
2.800
610
fan
190
920
80
6.000
440
HO
3.200
4,000
400
370
3,900
820
6.400
1.46(1
1.200
G 1
coll
foras/
100 Hi
fc sulf
900
580
490
290
290
550
270
480
40
BO
60
284
550
130
40
1C tulf
360
120
1,080
100
1.390
140
ISO
560
10
110
bb
45
25
60
3.000
80
r coll 22"C plate
per 100 Icount/lOO
•1 1 Hi
te coagu
34
24
8
4
6
2
2
3
1
4
56
34
a
2
te coagu
10
nil
20
5
46
nil
4
30
nil
16
2
nil
nil
nil
38
5
atlon
780
520
730
226
70
M
72
320
21 B
43
55
240
580
370
260
acton
10
850
40
<10
31
89
1.000
360
600
68
380
30
140
>5.000
500
HI (2
coTl
fonts/
100.1
nil
nil
nil
nil
nil
230
nil
1
nil
nil
nil
nil
nil
•11
nil
nil
•11
nil
>500
nil
aa
35
•11
a
nil
nil
38
27
nil
F coll
per TOO
Hi
nil
nil
nil
nil
2
nil
nil
nil
nil
•11
nil
nil
nil
nil
nil
nil
•11
21
nil
7
12
nil
•11
nil
nil
•11
7
•11
TPC. p'ate
count/100
•1
1
5
nil
nil
nil
60
nil
nil
7
2
nil
e
3
2
nil
nil
nil
850
nil
98
800
2
I
nil
Ml
30
6
4
foil
foras/
100 ail
5,000
350
100
680
1.200
1,700
1.160
-lion
700
>5.000
3.000
>5.000
8,600
>2.000
6,000
8.500
>1,200
>3.000
2.400
700
3.200
3.600
3.000
disinfected
« J
coll
fonas/
100 »1
bo
nil
nil
14
1
220
• 11
250
220
nil
1
37
100
9
nil
19
4
nil
nil
nil
3
nil
nil
500
4
at)
3
nil
1
nil
bfTTO
nl
nil
nil
nil
nil
nil
nil
15
a
nil
nil
6
11
3
nil
nil
nil
nil
nil
•II
nil
nil
nil
nil
nil
•I)
nil
nil
nil
nil
22'C plate
count/ 100
al
320
12
nil
250
nil
1.200
nil
nil
>5,000
2
126
156
280
210
150
274
29
nil
nil
>2.000
560
1.600
>1.200
>3.000
nil
630
nil
nil
1
week
no
19
20
20
21
21
22
22
23
23
It
24
25
25
26
27
31
32
32
31
33
34
34
35
35
36
37
37
38
38
39
39
Source Melbourne t Miller. 1973
-------
nated and ammoniated) "over the 5-year period 1968 to 1972. In 71% of the
cases, the GAC effluents showed higher plate counts than did the sand fil-
trates, and in 42% of the samples the GAC effluent count exceeded that of
the sand filtrate by a factor of 10 or more. Rechlorination and airmoniation
to a level of 0.45 mg/1 of chloramine, did not restore the bacterial counts
of the GAC effluents to the levels of the sand filtrates.
90-
final water-
non-chlorinated
431 samples
sand filtrate
495 samples
GAC filtrate
446 samples
0- 111- \101-\500+l 0- 111- \101-\500+10-
10 \100\500\ \10 BOOBOO\ \IO
11- \101-\500 +
00 BOO
plafe count colonies/cm3
Figure 50. Histogram of agar plate counts, 3 days at 22'C.
(Ford. 1973)
The Water Research Association (England) examined samples of Foxcote
water and tentatively identified the predominant microorganisms in the GAC
filtrates as chlorine-forming Flavo bacteria, along with some spore-fonr.ing
bacteria. Their work also demonstrated that three days incubation is too
short a period of time for the development of easily visible colonies of
these bacteria8 and that much higher counts were obtained after 7 days
incubation. Using 7 day incubation times, bacterial counts obtained with
sand filtrates remained very low.
The occurrence of biological activity in the GAC adsorbers and their
effluents in spite of approximately 0.5 mg/1 free chlorine residuals in the
influent waters thus was amply demonstrated.
Ford (1973) also noted that "animal infestation problems have occurred
when (activated) carbon units have been taken out of service ?nd,]eft *tan-
ding". Apart from this aninal infestation tendency to occur in idle filters,
163
-------
Nais worms were found on only one occasion In the Foxcote activated carbon
effluents. These were eradicated by addition of NaOCl to the backwash water
to give a chlorine residual of 5 mg/1.
Richard (1973) reported on treatnent studies of Seine River water at
the Vigneux plant upstream of Paris, France. At this 1,500 cu m/hr (36,COO
cu m/day; 9.5 mgd) treatment plant comparative tests were conducted using
powdered- and granular activated carbons. The Vigneux plant process at the
time consisted of microstraining, clarification (with powdered activated
carbon), filtration, breakpoint chlorination (with 6 to 8 mg/1 of gaseous
chlorine), coagulation (alum) and flocculatlon (activated silica). At the
time of the reported study, 10 to 20 mg/1 of powdered activated carbon was
being injected upstream of the clarifiers. Chlorine dioxide (0.15 to 0.25
mg/1) was injected upstream of the reservoirs.
Three test processes were studied by Richard (1973):
1) clarification with powdered activated carbon, sand filtration;
2) clarification without powdered activated carbon, 3AC filtration;
3) clarification without powdered activated carbon, sand filtration,
GAC adsorption.
After 250 days of operation, a monitor was installed which controlled
the breakpoint chlorination step to a free residual chlorine level of 0.25
to 0.40 mg/1 from that point on. Under these conditions the pretreated
plant water gave negative coliforn (24 hours at 37°C) and E_. coli counts.
Treatment without either powdered or granular activated carbon produced
waters having very low plate counts. However, addition of powdered activated
carbon to the clarifier produced filtered water showing less than 10 colonies/-
ml during cold weather and 10 to 100 counts/ml during summer. Passage
through granular activated carbon, acting either as a filter or as an adsor-
ber, gave colony counts of about the same order, although slightly higher.
Final sterilization with chlorine dioxide (0.15 to 0.25 mg/1 dosages) produced
waters having zero plate counts/ml.
Kfllle & Sontheimer (1973) discussed experiences with activated carbon
in West Germany and specifically reviewed the role of biology in water
pretreatment. They proposed that the action of microorganisms in granular
activated carbon media is integrally connected with the enrichment of organic
substances (by adsorption) which can result in improvement of substrate
utilization by the bacteria. As waters containing organic materials pass
through granular activated carbon columns or beds, some organics are adsorbed
physically and/or are incorporated into the biomass and/or are oxidized to
carbon dioxide. In addition, products and intermediates of biological
assimilation had been observed (Koppe & Giebler, 1966) in the effluents from
activated carbon media.
KBlle & Sontheimer suggested several experimental approaches to obtain
more detailed information on the operable physical and biochemical processes
.164
-------
occurring 1n activated carbon filters and adsorbers. These media can be
operated and their efficiencies in eliminating organic materials from solution
can be studied after exhaustion of their theoretical adsorption capacities.
However, in operational water treatment plants, steady state conditions are
difficult to establish, even over long operating periods, because compositions
of raw waters being treated usually vary from day to day. Organic conpounds
which are rapidly adsorbed and tightly bound to the activated carbon surface
will displace previously adsorbed organic compounds which are not as tightly
held by the activated carbon surface.
A second approach is to follow, simultaneously, both the decrease in
dissolved oxygen consumption and increase in carbon dioxide produced during
passage of water through the activated carbon medium, comparing data treasured
in both the influents and effluents. The activated carbon filter or adsorber
also can be used as a "bioassay bottle" by recycling effluent to become
influent and following the changes in CO consumption and C02 production.
Studies of this type were being conducted at the Auf-dem-Werder plant in
Bremen, Federal Republic of Germany. Oxygen consumption upon passage through
activated carbon rose to 7 mg/1 during summer and dropped to 2 mg/1 during
winter, showing that surface water temperature variations affect biological
activities significantly (Eberhardt, Madsen & Sontheimer, 1974).
Another factor complicating such studies is the kind of pretreatirent
applied before activated carbon treatment. Kfille & Sontheimer (1973)
state, "There is practically no waterworks without pretreatment -- irostly
using oxidation by ozone". Some laboratory tests have shown that it is
desireable to add a flocculation step between oxidation (with ozone) and
activated carbon filters or adsorbers, especially with respect to rerroving
UV-absorbing organic substances (Kdlle & Sontheimer, 1973).
Summary of European Studiesin J973
The status of published European knowledge of microbiological activity
in activated carbon filters and adsorbers used in drinking water treatment
as of 1973 can be sunirarized as follows:
1) Bacterial growths in activated carbon were known to occur in plant
scale media to a significant extent, even when influent waters contained
as high as 0.5 mg/1 of free residual chlorine (after breakpoint chlori-
nation).
2) Biological activity develops rapidly with fresh carbon charges. GAC
units used for taste and odor control over a 1-year period developed
maxima of 10,000 colony counts (22°C)/ml in the effluents in about 8
weeks. During this time the 3AC influent waters contained zero colony
counts/ml.
3) Prechlorination or presoftening of influent waters had been observed to
increase the amount of biological growth in the GAC ledia in some
cases.
165
-------
4) Effluents from biologically active GAC media contain a much greater
number of colonies than do effluents from slow sand filtrates.
5) Treatment of effluents from biologically active carbon media with
chlorine or (0.15 to 0.25 mg/1 dosage) chlorine dioxide lowered colony
counts/ml to acceptable local biological standards.
6) Speciation studies of microorganisms in effluents from biologically
active carbon media had shown the presence of chlorine-resistant
flavobacteria (from waters which had been treated by breakpoint chlorina-
tion) along with some spore-forming bacteria.
7) Indications were that two and three day incubation periods were insuffi-
cient, even at 37°C, for development of easily visible colonies, and
that 7 days of incubation gave much higher counts.
8) Animal infestation had been observed in activated carbon units which
had been taken out of service and left standing for two days.
4
9) Bacterial activity was higher in the summer than in winter.
10) Products and intermediates from biological assimilation had been
observed in effluents from activated carbon nedia.
CURRENT EUROPEAN MICROBIOLOGICAL STUDIES
At present, there are only two European groups known to have published
results of continuing research into the microbiological aspects of activated
carbon systems with respect to treatment of drinking water. These studies
are being conducted at the KIWA (The Netherlands) by Dr. D. Van der Kooij
and at the University of Saarlands (Federal Republic of Germany) by Professor
Dr. R. Schweisfurth and his students. A third research program on this
subject has been established recently at the Engler-Bunte Instltut der
UniversitSt Karlsruhe during 1979.
Research Studies At The KIWA
Microbiological studies at the KIWA were published by Van der Kooij in
1975 and 1978. Additional unpublished information was provided by Dr. Van
der Kooij In a personal interview during June 1978. These two published
articles will be reviewed in this subsection and the discussion will be
supplemented by the private communications supplied during June, 1978.
In work presented in 1975, Van der Kooij conducted s1de-by-s1de experi-
ments with Norit ROW 0.8 Supra (the 0.8 refers to the particle size in
millimeters) granular activated carbon (GAC), the same granular carbon but
not activated (GNAC) and sand (0.85 to l.CO mm particle size). Test columns
containing each of these materials were fed with non-chlorinated tap water
(13 to 17°C) at the rate 3.5 m/hr (3 minutes apparent contact times) over a
period of 10 months. Colony counts in the columns were deternined at inter-
vals on diluted nutrient agar (0.36 g/1 beef extract, 0.65 g/1 peptone, 10
g/1 agar) after 10 days of incubation at 25°C. The bacteria were removed
166
-------
from the sand, GNAC and GAC by subjecting the samples to ultrasonic energy.
The numbers of bacteria found on the filtering materials were expressed as
numbers/ml of filter volume and are shown in Figure 51.
This figure shows that the numbers of bacteria found on the activated
carbon were always about 10 times higher than the numbers on the non-activated
carbon and on sand. Using more re*ined Tieasurements, Dr. Van der Kooij
(1978a) showed that the numbers oc bacteria on activated carbon were only 2
to 3 times higher than on the other two media.
n
5s
3 O
O >
e —
o «-
"3
o
108
10'
10
10"
6.
02 4 6 8 10 12 14
months »-
""•"" activated carbon, Norit ROW 0.8 supra
o.-..^ non-activated carbon, Norlt ROW 0.8
•«!•».. sand, 0.85-1.00 mm
Figure 51. Bacterial numbers on GAC, granular
non-activated carbon and sand, each
fed with non chlorinated tap water.
(van der Koolj, 1975)
In a second experiment, samples of used SAC and 3NAC (ROW 0.8 Supra)
were taken from adsorbers fed with prefiltered river water for a period of
one year. Wet carbon sanples (150 ml) were treated with 50 ml of non-
chlorinated tap water and aerated at 25°C. The numbers of conforms,
pseudomonads and actinomycetes proliferating in these carbons were determined
weekly. The total numbers of viable bacteria were estimated by colony
counts on diluted nutrient agar and expressed per cu m of filter volume.
Oxygen consumption was expressed in mg of 02/1 of filter volume/hr. Results
are plotted in Figures 52 and 53. Tab'e 36 shows the times to attain 50%
reductions in the levels of bacteria present in the activated and non-
activated carbons (5C% reduction times).
Van der Kooij (1975) estimated that since the hypothetical cylindrical
surface area of granular activated carbon is about 40 sq cm/cu cm of GAC
present, when the colony count is lO^/cu cm, then a single bacterium occupies,
167
-------
on the average, 40 sq microns of this available surface area. Since the
available surface area of GAC is much higher than 40 sq cm/cu cm, it was
concluded that there is only a low density of bacteria occupying the surface
of the activated carbon, even allowing for the fact that colony count techni-
ques measure only a portion of the bacteria present. Scanning electron
microscope measurements made at the KIWA confirmed this conclusion, as did
similar studies by Weber, Pirbazari & Melson (1978) on GAC samples contacted
with chemically coagulated and settled sewage.
10
10 20 30 40 50 60 70 80
days »•
Figure 52. Numbers of pseudomonads (•«) and
co'iforms UA) or. GAC ROW 0.8 supra (*
and on non-activated carbon ROW 0.8
(OA) during aeration at 25'C.
(van der Koolj, 1975)
TABLE 36. 50% REDUCTION TIME (DAYS) OF DIFFERENT GROUPS OF BACTERIA ON
ROW 0.8 SUPRA SAC AND ROW 0.8 GNAC
Type of Bacteria
Colony Forming Units
(25°C, 10 days)
Col i forms
Pseudomonads
Actinomycetes
ROW 0.8
Supra
9
3
4.5
>50
ROW 0.8
not act.
8.5
3.5
4.0
>50
Source; Van der Kooij, 1975.
168
-------
Based on these ireasurements, Van der Kooij (1975) concluded that
adsorption processes operative in granular activated carbon are not hindered
by the presence of bacterial growths on the activated carbon.
Figure 51 also shows that the number of bacteria on GAC samples decreased
after reaching a maximum value. Van der Kooij (1975) concluded that this
decrease is not caused by exhaustion of the adsorptive capacity of the SAC,
since the same relative decrease also was noted with 3NAC and sand. Van der
Kooij points out that the decline also might be explained by a shift in the
types of bacterial flora originally present to types of bacteria which do
not participate 1n colony counts.
a
o
co
a
o
o
c
o
io8i
10".
» 103
!„••«««*•
100
0.1
0.01
0.001
cs
O
o>
e
c"
o
+•*
a
E
3
-------
10/cu on of filter volume and collforms dropped to 10/cu cm in 23 days from
100 to 1,000.
On the other hand, the numbers of actinomycetes and the oxygen consump-
tion rates did not show clear decreases during 60 days. Therefore, from the
data of Figure 52 and of Table 36, it can be seen that the conforms disappear
faster than do other bacteria. Since there is hardly any difference in the
50% reduction tiires for the selected bacteria on GAC versus GNAC, Van der
Kooij (1975) concluded that neither coliforms nor pseudomonas nor total
colony-forming bacteria gained any advantage from the organic substances
which were present on the activated carbon which had been in contact with
river water for the one-year period.
The oxygen consumption rate during passage through either GAC or GNAC
did not decrease with decreasing colony counts, nor did the number of actino-
mycetes (Figure 53). Van der Kooij (1975) therefore suggested that it is
possible that the oxygen consumption values observed with both carbons were
caused by chemical rather than bacterial processes. He also suggested that
the relatively constant numbers of actinomycetes bacteria observed over the
60 day period might have been due to their ability to fragment into smaller
organisms (to produce spores).
Curing June, 1978, Dr. Van der Kooij supplied the following additional
information regarding his studies of biologically active filtration and
adsorber media:
1) For sampling of filtration of adsorption media, 1 g samples of wet
medium are taken into sterile, non-chlorinated tap water, then subjected
to ultrasonics for 2 to 3 minutes. The supernatant liquid then is
treated by normal dilution and plate counting. When water was added to
the 1 g activated carbon sample treated once by ultrasonics and the
ultrasonic exposure repeated, more bacteria were found in the second
supernatant. The process was repeated 10 times on the same 1 g sample
of activated carbon. About 40% of the total bacteria determined were
found in the first supernatant, 20% in the second, 10% in each of the
third and fourth extracts, etc. Even after the tenth ultrasonic treat-
ment of the original 1 g sample, significant bacterial counts were
being obtained. This indicates that bacteria are very tightly held by
the activated carbon.
2) Samples from operational water treatment plant granular activated
carbon filters or adsorbers were taken in 10 to 20 g quantities and at
various depths.
3) A bioassay test for biologically assimilable organic carbon in raw
waters has been developed by the KIWA at one of"the large Dutch water
treatment plants using river water. Pseudomonads were cultured in raw
river water at 15°C and their rate of growth was determined. Next the
river water was ozonized, then seeded with the sarre pseudomonad culture
and their rate of growth again measured. The growth rate was found to
be higher after ozonation than in the raw river water. Such a test
again shows that ozonation converts some of the dissolved organics
170
-------
present (which are not easily biodegraded) into organlcs which are more
readily biodegradable. In addition, this procedure might be considered
as a screening test at U.S. water treatment plants to determine whether
detailed evaluation of an early stage biological processing step would
be worthwhile. If no increase in biodegradability is observed after
ozonation, then preoxidation of any sort will be ineffective in this regard.
4) Fresh samples of GAC have shown ireasureable levels of oxygen consump-
tion before measureable levels of bacterial activity have built up in
the medium. Therefore, GAC seems to cause some degree of surface
catalyzed oxidation of dissolved organic substrates.
5) £. coli bacteria taken into a biologically active granular activated
carbon filter or adsorber cannot survive in competition with the other
species of microorganisms present. Therefore, in a properly sized and
operated biologically active filter/adsorber medium, no E. coli bacteria
are found in the filtrates. This is confirmed by long term experiences
1n Europe with slow sand filters.
In a paper presented in 1978(b), Van der Kooij reported continued
studies of the microbiological processes occurring in granular carbon
samples. In introducing the subject, Van der Kooij reported that "some
investigators have concluded that an increased contact time between organisms
and adsorbed organic substrates is allowing the microorganisms to adapt to
the less readily biodegradable organic substances", thus allowing these
harder-to-decompose organic compounds to be degraded during "biological
regeneration" of the activated carbon adsorption sites.
In this more recent work, 6 cm diameter columns were filled with Norit
ROW 0.8 Supra activated carbon (GAC), the same carbon but not activated
(GNAC) and 0.8 to 1.0 mm sand. Again in s1de-by-s1de tests, the columns
were treated with non-chlorinated tap water (14 to 18°C) containing an
average of 3 mg/1 of dissolved organic carbon at 3.5 m/hr filtration rates
(3 minute apparent contact time) for a period of one year. Numbers of
colony-forming units/ml were estimated by the surface spread technique on 8-
fold diluted Lab-Lemco broth (Oxford CM 15) agar plates. Samples were
exposed to ultrasonic energy for 3 minutes to detach the microorganisms,
then samples were incubated for 10 days at 25°C. Removal of organic substan-
ces from solution was followed by measuring the ultraviolet absorption at
275 nm in 5 cm cuvettes.
Figure 54 shows the colony counts on the filter materials and in their
filtrates measured over the one year period. Maximum values were attained
in all three media during the first 20 to 30 days. After these naxima were
reached, the adsorber effluents showed counts of l.OCO to 10,OCO/ml. Ultra-
violet absorption measurements showed that immediate breakthrough of organic
materials occurred with the GNAC and sand media. The GAC medium reached 80%
of breakthrough in 30 days and 90% of breakthrough in 9C days, with respect
to dissolved organic Tiaterials.
Figure 55 compares colony counts found on the three filter materials, -.
which usually were higher on the GAC medium and reached a maximum of 7 x 10
171
-------
E
^
3
•^
U
v
.•.in QAC filter
ln GNAC ••
MO In sand "
In GAC effluent
"»ln GNAC
••••• In drinkinc weter
X
10
10
10
0 20 40 6O 80 1OO 12O 140 16O 180 2OO 22O 240 260 280 30O 320340
Figure 54. Colony counts In GAC, GNAC and sand filters and In their
effluents over 340 days.
(van der Kooij, 1978)
-------
cfu/ml. Colony counts on GNAC and sand were similar to each other. Figure
56 shows that the cfu/ml numbers found in all three effluents were about the
same.
Van der Kooij (1978b) concluded that adsorption of organic materials by
activated carbon therefore is not the cause of the high colony counts usually
observed in the GAC filter/adsorbers. This was confirned by noting that the
majority of microorganisms isolated from the GAC were able to grow only on
simple, non-adsorbing compounds like acetate, pyruvate and "actate, whereas
adsorbing substances such as aromatic compounds (which are ireasured by
ultraviolet absorption) were not utilized.
CH3COO" CH3COCOO" CH3CH(OH)CCO~
acetate pyruvate 1actate
Effluents from the slow sand filters (which are known to remove bacteria)
at the water treatment plant at the Hague (0.3 m/hr flow rate) were studied.
Bacterial contents in these slow sand filters were 20,000 to 30,COO cfu/ml,
but were less than 100 cfu/ml in the filtrates. Similar observations had
been made earlier by Schmidt (1963). Comparing these slow sand filtrate
counts with those of the side-by-side experiments (Figures 55 and 56) sugges-
ted that there was a relationship between flow rates and the nurrber of
micro'organisms in the sand and in the filtrates. Therefore, colony counts
in the GAC (Norit PKST) present on the slow sand filters of the Hague (probab-
ly a thin layer on top of the sand) were estimated in samples taken from 8
of the operational plant filters (Figure 57).
Comparison of the data of Figure 55 with those of Figure 57 shows that
colony counts in samples of 3AC taken from the top of the slow sand filters
were 1 to 2 orders of magnitude lower than those observed in the experimental
GAC filters supplied with non-chlorinated tap water. This confirmed the
conclusion that flow rate through a filter bed strongly affects colony count
levels in the filter materials.
Since the colony counts in 3AC media usually were greater than those in
GNAC and in sand, even though colony counts in the filtrates did not differ,
Van der Kooij (1979) concluded that this behavior probably was due to the
relatively large surface area/unit volume of 3AC upon which microorganisms
utilizing substrate from the passing water can attach. Therefore, Van der
Kooij (1979) concluded that granular activated carbon is a favorable material
for biological filtration processes.
Effects of microorganisms on adsorption of organlcs by GAC—
Some laboratory experiments next were conducted by Van der Kooij (1979)
to determine the influence of bacterial cells attached to GAC on the adsorp-
tion of 4-nitrophenol (a readily adsorbed but difficult to biodegrade organic
compound) and 4-hydroxybenzoate anion (a readily adsorbed and readily biode-
gradable organic compound) by Norit ROW 0.8 Supra granular activated carbon.
173
-------
A_» GAC
a— GNAC
• «. sand
10
O 20 40 60 80 100
cum. % of samples
c
3
•fr-
it-
41
"o
E
3
O
O 20 40 60 80 100
—*- cum % of samples
Figure 55. Colony counts In GAC, GNAC
end sand.
(van der Kooij. 1978)
Figure 56. Colony counts In effluents from
GAC, GNAC and sand filters.
(van der Kooij, 1978)
-------
4-n1trophenol
COO"
4-hydroxybenzoate anlon
Adsorption isotherms and rates of adsorption of these compounds were deter-
mined with growths of the bacteria Pseudomonas fluorescens (Strain 17) or
Pseudomonas alcaligenes (Strain 131) being present on the GAC.
o
<
-------
To cultivate bacteria on the GAC, ammonium acetate was added to the
sterilized solution to a final concentration of 10 mg/1 of acetate carbon.
Bottles were inoculated with either Strain 17 or 131 and incubated 3 days at
25°C in a rotary shaker (120 revolutions/minute). The bacteria developed to
a maximum level of 4 x 107 cfu/ml of medium and the GAC contained about 2 x
108 cfu/ml (6 x 108 cfu/g) of GAC.
Under these conditions, either 4-nitrophenol or 4-hydroxybenzoate was
added from sterilized solutions in final concentrations of 100, 50, 25 and
10 mg/1. These compounds also were added to bottles containing sterilized
GAC without bacteria. The bottles were placed in a rotary incubator at 25°C
and the concentrations of 4-hydroxyphenol and 4-hydroxybenzoate were measured
by UV absorption at 254 and 269 nm, respectively in 5 ml of membrane filtered
samples after 24, 48 and 144 hours of incubation. Ultraviolet absorption
was measured every hour during the first 8 hours after addition in bottles
containing an initial adsorbate (phenol or benzoate) concentration of 100
mg/1. All experiments were performed in duplicate.
Adsorption isotherms of 4-nitrophenol and 4-hydroxybenzoate on the
activated carbon in the presence and absence of bacteria were calculated
from measured concentrations and are presented in Figure 58. The disappear-
ance of these compounds from solutions initially containing 100 mg/1 of
adsorbate is shown in Figures 59 and 60. Figures 58, 59 and 60 show that
the phenol was better adsorbed by the GAC than was the hydroxybenzoate.
With both compounds, however, the adsorption equilibrium was reached within
48 to 144 hours.
Results shown in Figure 58 indicate that the adsorption isotherms are
not affected by the presence of bacteria. Moreover, adsorption of the
adsorbates in the 100 ml bottles also was not affected by the presence of
bacteria on the activated carbon. The adsorption rate of 4-hydroxybenzoate
in the presence of bacteria could not be calculated because both bottles
were infected by adsorbate-consuming microorganisms. Infection also occurred
in some other bottles containing 4-hydroxybenzoate because this compound is
so easily biodegraded, compared with 4-nitrophenol.
Van der Kooij (1979) concluded the following:
1) The number of microorganisms present on a filter/adsorber medium
depends upon the flow rate of water through the medium, and is probably
due to limited transport (diffusion) of the soluble substrate to the
microorganisms.
2) Adsorption of organic compounds by GAC is not Inhibited by the presence
of a large number of bacteria on activated carbon.
3) Granular activated carbon adsorbers or filters in operational drinking
water treatment plants sampled by Van der Kooij always contained lower
colony counts than the levels applied in the laboratory experiments
described in this paper. Therefore, in GAC adsorbers used to prepare
drinking water, hindrance of adsorption of organic compounds by micro-
organisms is very unlikely.
176
-------
2 6-
2.4-
2.2-
2.0-
1.8-
1.6-
1.4-
1.2-
« 1.0
o-
2 0.6
0.4-
0.2-
4 nltro phenol „.-««»•—••""""""""""""'
J.. "-1Do>
-------
on
so
ng
10
E
0
«
u
"c
9
100-
90
80-
70-
60
50-
40
30-
20
10-
4-hydroxy benzoate
^ssczry—* <
A GAC without bacteria
A GAC with bacteria
234
time, hrs
Figure 59. Removal of 4-nltrophenol and 4-hydroxy ben-
zoate on passage through ROW 0.8 Supra
GAC.
(van der Koolj.1978)
On the other hand, Van der Kooij (1979) points out that hindrance of
adsorption by microorganisms might occur when the influent water contains
relatively large amounts of easily blodegraded materials. In these situations
"extremely large numbers of microorganisms" develop on the activated carbon.
Also, adsorption may be affected by the contamination of granular activated
carbon by colloidal and suspended matter. These last two effects were not
investigated during the 1979 study of Van der Kooij.
178
-------
• 1 «
olo
i '
H °
olu
9
0
c
a
a
0
a
a
a
a
a
5
o
o
«*
a
0.8
0.7-
0.6
0.5-
0.4-
0.3-
0.2-
0.1 -I
\
a GAC without bacteria
• GAC with bacteria
\ T:
\ 4-nltrophenol
X
'*V,
Xx
A
—^
4-hydroxybenzoate
012345678
time, hrs.
Figure 60. Rate of disappearance of 4-nitrophenol and
4-hydroxybenzoate on passage through ROW
0.8 Supra GAC.
(van der Koolj, 1978)
Research Studies at the University of Saarland
In 1972, a cooperative research program between the City of Wiesbaden
and the University of the Saarlands (Federal Republic of Germany) was begun
with the objective of studying the microbiology which was present in the GAC
adsorbers at Wiesbaden's Schierstein water treatment plant. Two doctoral
candidates at the University (P. Werner and M. Klotz) completed their Ph.D.
thesis studies in 1979 based on these studies which were directed by Prof.
Dr. Reinhart Schweisfurth. These scientists have published three progress
reports of their studies, all of which will be reviewed here. In addition,
179
-------
all three investigators were interviewed in June, 1978 and provided additional
information on their studies in the form of private communications.
In work presented in 1975, Klotz, Werner & Schweisfurth reported
studies at the Schierstein water treatment plant at Wiesbaden, which had
been conducted since 1972 on plant operating granular activated carbon
columns and pilot plant columns. Initially, these investigators found that
the determination of colony numbers as recommended by the DEV (Deutsche
EinheitsVerfahren = German Standard Methods, 1962) (2 days incubation at
27°C) proved to be inadequate, because only a small portion of the microflora
present are revealed by this technique. However, all nutrient media tested
showed considerably increased colony numbers after breeding for 7 days, and
this incubation time was used throughout this program and those which these
investigators have reported subsequently.
The best medium for determination of microorganisms was found to be P-
Agar which contained few nutrients and SPC-Agar which was rich in nutrients
(Standard Methods, 1971). Both were incubated at 27°C for more than 7 days.
The activated carbon samples were crushed in a simple mixer and the homogeni-
zed material then was processed for the determination of colony numbers in
the sane manner as were the water samples. The cell numbers (the total of
all living and dead bacteria) were determined by counting microscopically
after collecting on membrane filters and coloring. Apart from a few modifica-
tions (not delineated) all other tests were carried out as recommended by
the DEV whenever possible.
The Schierstein Treatment Process—
At this plant, Rhine River water, not river sand bank filtered, is
pretreated directly before ground infiltration to augment groundwater supplies.
The treatment process involves aeration, settling, chlorination, flocculation,
rapid sand filtration, activated carbon adsorption, then ground infiltration.
During the course of this study some of the plant 3AC adsorbers were operated
as long as 3 years without being reactivated. At the end of this time, 30%
of the influent dissolved organic carbon still was being removed *rom solution
during passage through the GAC media.
In Figure 61 are shown the mean values of colony numbers determined at
different points in the plant for the period March 1973 to Varch 1974.
There was a decrease in colony numbers between the Rhine and the entrance to
the activated carbon adsorbers, the largest effect being obtained following
breakpoint chlorination. However, fresh populations of microorganisms were
formed in the activated carbon media, such that very high colony numbers
were found at the GAC media exits using the 7-day incubation method. By the
2-day incubation method normally applied for measuring colony counts, as
recommended by the DEV for the control of drinking water, the water quality
at this point in the process generally was satisfactory.
Composition of microorganism populations in GAC effluents—Populations
were examined in freshly filled plant GAC adsorbers and in pilot plant test
columns. The test columns consisted of four successive glass tubes each
with an inside diameter of 4 cm and the total 3AC bed depth was 3.2 m (4 x
180
-------
0.8 m). Passage of water through each individual 0.8 m deep column is
referred to as "a filter step".
09
a
u
W
a
S
|
C
O
"3
u
105J
104J
103J
102J
101J
t^\
%-" •> "" *"
— "5 2
e I ^
K S g
(A
1
G;
2
&C
3
4
II
5
t<
6
"f
T.
9
ollectlng outlet|
treatment steps-
Figure 61. Mean colony numbers at various points in
the Schierstein plant, March '73-March '74.
(Klots et, aj,., 1975)
The behavior of the microorganism populations was found to be the same
in both the pilot plant test adsorbers and in the full scale plant adsorbers.
During the first 20 days the colony numbers rose linearly and reached a
maximum of 10$ to 10^/ml of waterj, after which they declined and remained at
a slightly lower level closer to IG^/ml. In the early stages of the pilot
plant testing there were large differences in colony numbers between the
individual filter steps, but these disappeared after about 30 days when the
level stage (with respect to colony numbers) had been reached. Figure 62
shows the establishment of microorganism populations in the effluents from
181
-------
the pilot plant test adsorbers and Figure 63 shows similar microorganism
establishments in the test adsorbers themselves.
filter 1
filter 2
•mm" filter 3
•••• filter 4
20 30
time, days
40
50
60
Figure 62. Development of colony counts in pilot
plant GAC adsorber effluents at the
Schlersteln plant.
(Klotz et Ji.,1975)
Flow rate studies were conducted in the test columns using 4, 8 and 20
m/hr water velocities. The slope of the microorganism establishment curves
(Figure 62) during the initial phase decreased with increasing velocity and
with increasing column depth. The maxima were more pronounced as the velocity
decreased. When the level stage was reached, there were only slight differen-
ces, however, the lowest colony numbers being observed at the lowest flow
rate.
Microbiological & chemical conditions in a plant operating GAC adsorber—
In Figure 64 are shown the colony numbers (living bacteria), cell numbers
(living + dead bacteria) and free residual chlorine contents plotted against
the adsorber depth (after an increasing number of filter steps). The low
levels of colony numbers measured after the first two filter steps are
182
-------
explained by the low adsorber depth and the lack of sufficient contact time
of the water passed through the SAC to destroy the free chlorine residual.
The largest increase in colony numbers took place between steps 2 and 3
(after the free chlorine residual dropped to less than 0.1 mg/1), and there
was no further increase between step 4 and the outlet.
10
o
QL
in
o
a
^s
in
E
3
C
o
u
104-|
103-|
io2-]
"""• filter 1
""""*• filter 2
"" filter 3
•••* filter 4
10
20
30
40
50
60
time) days
Figure 63. Development of colony counts in GAC of
pilot plant adsorbers at Schiersteln plant.
(Klotz e_t. aL, 1975)
In the uppermost activated carbon layers the residual chlorine content
fell below 0.1 mg/1, where it no longer had any influence on the levels of
living bacteria. Before the free chlorine concentration was lowered by the
first GAC adsorber, the level of living bacteria was low, although the total
cell numbers were high. After the chlorine content was lowered, the number
of living bacteria increased rapidly, although the total cell numbers remained
relatively constant.
Changes in dissolved oxygen and carbon dioxide contents of the water
are indicators of the amount of microbial activity, as shown in Figure 65.
183
-------
I)
*•*
(B
I
in
v
E
a
c
«t
u
C
a
o
u
105,
104-]
103J
101-
ceil number^ ^^.-m.-^
Figure 65 Oxygen and CO2 contents of GAC
effluents vs. adsorber depth.
(Klotz et. aj,. 1975)
-------
During passage through the GAC media there was an oxygen consumption of
approximately 1.5 mg/1, most of which occurred after step 2, and a concurrent
production of approximately 4.5 mg/1 of C02, which also occurred nostly
after step 2.
TOC.mg/l
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c
£* JH *i
v »* J>
« «
Figure 66. Organics content of GAC effluents
vs. adsorber depth.
(Klotz £t .ai.. 1975)
The change in organic content was followed (Figure 66) by three parare-
ters. By UV absorption at 240 nm and TOC analyses, the content of organlcs
decreased 55% after the fourth GAC filter step, and by about 45% as rreasured
by the KMnO^ consumption.
Behavior of mlcrobial populations over a three year period—Figure 67
shows the colony counts/ml at the plant processing inlet (after aeration and
settling), at the 3AC adsorber inlet (after rapid sand filtration) and after
passage through GAC adsorbers during the 3-year period May 1972 through
August 1975. The numbers 1, 2 and 3 in this figure indicate changes 1n raw
water qualities which resulted in distinct changes in colony numbers at the
points indicated.
It appears noteworthy to the current reviewers of this work that there
was an apparent breakthrough of colony counts through the GAC adsorbers
after about three years of use. This indicates that there should be a 3AC
regeneration parameter based on colony counts as well as an organic component
185
-------
CO
en
•••••M raw water inlet
• ---» sand filtrate
•«•«• GAC adsorber outlet
10C
H. 10*
u>
0)
c
o
"o
u
4)
**
U
0}
to
10"
103
102
10
1
*•••—
\£\
^£X^^.
-r^-Mr^
r v /v -i
N.
m j jason
J972
^
HV
M
I f m a m | j a s o n
'73
I f m a m | Jason
'74
I f m a m
'75
I I
Figure 67. Behavior of microbial populations on GAC over 3 years
at Wiesbaden, F.R.Germany.
(Klotz, Werner & Schweisfurth. 1975)
-------
parameter, at least in plants opting to install a biological activated
carbon process involving aeration and chlorination as the pretreatment
steps. No data are available on microbial breakthrough, however, with
processes using ozonation as the preoxidation step. This possibility of
bacterial breakthroughs under BAG processing conditions should be evaluated.
Klotz, Werner & Schweisfurth (1975) also reported that they had determi-
ned large differences in colony numbers, as determined by the 7-day versus
2-day incubation technique, at five other German waterworks, each of which
uses different treatment rrethods and utilizes different raw water qualities.
They also stated that similar observations have been reported by scientists
in Switzerland and the Netherlands, without giving supporting data or citing
specific references.
Klotz, Werner & Schweisfurth (1975) also state that there seerred to be
a tendency for decreased microbial activity in the Schierstein plant GAC
adsorbers during winter, as indicated by lower oxygen consumption and C0?
production data (which are not presented).
Activity of microorganisn populations in the GAC adsorbers—In order to
determine the relative contribution to removal of organic materials frcm
solution by adsorption alone and by adsorption plus microbial activity,
parallel tests were conducted using two pilot plant GAC adsorber test
units. Each test unit consisted of four glass tubes connected in series
(water passed through the tubes one after the other). Each glass tube had
an inside diameter of 6 cm. The GAC bed depth in each glass column was 0.5
m, therefore the total GAC bed depth in each test unit was 2 m (4 x 0.5 m)
and both 4-column pilot plant test units were operated under similar condi-
tions. One of the test units was kept free of microorganisms by sterile
filtration for nore than two nonths, during which time about 15 cubic meters
of water was passed through this sterile unit before it became bacterially
contaminated. All other methods of keeping the test units sterile have the
disadvantages of the presence of an additional bactericidal agent and of a
large number of dead organisms.
In order to increase the amount of biodegradable organic substances,
the inlet water was loaded with about 50 mg/1 of phenol during the second
phase of the test. This level of phenol is not toxic to the bacteria (Werner,
Klotz & Schweisfurth, 1978).
Results of these tests are listed in Tables 37 and 38. When the 3AC
adsorber inlet was unloaded (the sand filtrate), the microorganism contribu-
tion to removal of organics was very small, as far as could be measured by
UV absorption, dissolved organic carbon (DOC) and KMn04 consumption. On the
other hand, the contribution of microorganisms to the decrease in easily
biodegradable organics concentration was very high. This is of special
inportance because it rreans that the regrowth of bacteria, which can occur
in distribution systems (feeding upon the easily biodegradable organics),
now can be made to occur in the waterworks itself.
187
-------
TABLE 37. PERCENTAGE OF BIOLOGICAL REMOVAL OF ORGANIC SUBSTANCES DURING
PASSAGE THROUGH GRANULAR ACTIVATED CARBON
Raw Water Parameter
DOC
KMn04 consumption
UV Absorption, 240 nm
UV Absorption, 254 nm
BOC?
BODs
BOD20
Sand Filtrate
<1.0%
3.7%
<1.0%
1.2%
69%
46%
17%
Sand Filtrate Using
Phenol -loaded Influent
6,0%
3.1%
2.8%
6.2%
Source: Klotz, Werner & Schweisfurth, 1975
TABLE 38. MICROBIOLOGICAL SHARE OF OXYGEN CONSUMPTION AND CO? PRODUCTION
DURING PASSAGE THROUGH GRANULAR ACTIVATED CARBON
Raw Water rarameter
Oxygen cionsunption
Carbon Dioxide Production
Sard Filtrate
58*
61%
Phenol -loaded Sand
Filtrate
68%
64%
Source: Klotz, Werner & Schweisfurth, 1975
When the GAC adsorber inlet contained 50 mg/1 of phenol, the activity
of the microorganisms was slightly higher in the GAC media. It must be
remembered, however, that the adsorption capacity of GAC for phenol is very
high.
Electron-scan microscopic examination of GAC adsorber granules—During
passage of water through SAC adsorbers, the concentration of microorganisms
increases from about 10 colonies/ml to about 100,000/ml. Since the doubling
period (under optimum conditions in the laboratory) for bacteria is about 20
minutes, this led to the conclusion that the increase in numbers of microor-
ganisms actually measured has to emanate from the bacteria already present
on the activated carbon. This is because the water remained in contact with
the GAC for a short time only, which was insufficient to allow for the
increases in colony numbers/ml actually measured.
o
Tests showed that there were colony numbers of up to 10 /g of wet
material on the activated carbon. The actual cell number, obtained by
counting cells, could exceed these numbers by almost 100%.
A variety of electron-scan microscopic tests of activated carbon
samples treated differently showed the sane general distribution of the
microorganisms on 3AC adsorber granules. As a rule, the microorganisms were
found to be sparsely scattered, and were always in the form of a single
bacterial layer. The activated carbon surface area available (up to a pore
diameter of 1 micron) was only fractionally utilized (about 1%). This was
shown to be the case even when the activated carbon had been in contact with
188
-------
a nutrient solution for some time. These findings tend to confim those of
Van der Kooij (1975), who found that only a single bacterium was present, on
the average, for each 40 sq microns of available surface area.
Adsorption of n-icroorganisms onto activated carbon—Tests to determine
the degrees of adsorption of microorganisms on activated carbon were conducted
using starved and washed bacteria (mixed populations) in nitrogen-free
environments. Figure 68 shows an adsorption isotherm of bacteria loaded on
activated carbon as a function of the adsorptive concentration. At high
colony numbers (above lO1^) the system tended tcward saturation. At colony
numbers of 107, 90% of the bacteria were adsorbed.
o
S>
m
o
c
c
o
"o
o
s^
O)
c
•5
(0
o
1012-
1011H
1010H
109H
108H
107H
106 107 108 109 10101011 1012
adsorptive concentration
(colony numbers/200 ml buffer).
100-
t«
^
o>
75-
50-
25-
0
106 107 108 109 101°10111012
adsorptive concentration
(colony numbers/200 ml buffer).
Figure 68. Microbiological loading of GAC--
dependence on adsorptive capacity.
(Klotz,Werner & Schwelsfurth, 1975)
189
-------
Study of the influence of time on bacterial adsorption proved to be
difficult, since it was impossible to avoid bacterial increase followed by
bacterial extinction processes over extended periods of time (Figure 69).
After an incubation period of 20 to 30 hours, adsorption and desorption of
bacteria were nearing a steady state equilibrium condition. With increasing
ion concentration (phosphate buffer at pH 7.2) the bacterial loading of the
activated carbon Increased as shown 1n Figure 70. No dependence of adsorption
on temperature in the range of 5° to 37°C nor of pH over the range 5 to 8
was noted. Dead bacteria were found to be slightly better adsorbed by
activated carbon than were living bacteria.
50-,
40-
- 30
a
c
•o
<9
2. 20-
u
4
O
10
° colony numbers
• cell numbers
\
10
2*0 30
time) hrs.
40
50 <>0
Figure 69. Dependence of microorganism loading
of GAC with time.
(Klotz et.£j.., 1975)
In a later report of continuing work at the Schierstein plant, Klotz,
Werner & Schweisfurth (1976) pointed out that their technique for removing
bacteria adhering to activated carbon samples was to mix them with water
using a simple, domestic blendor (Braun MX 32) set at exactly the same
rotational speed and for the saire lengths of time for each sample. Both low
nutrient P-agar (Wolters & Schwarz, 1956) and high nutrient SPC-agar gave
the optimum numbers of colonies after 7 days of Incubation at 27°C. Lower
colony numbers were found using meat extract agar incubated at 27° and 37°
as well as using gelatin incubated at 22°C (see German Unit Standards for
Water, Wastewater and Mud Testing, 3rd Edition, 1960).
190
-------
25-,
o>
c
TO
a
o
o
<
o
200 ml buffer, pH T.2;
KH2PO4/Na2HPO4 , mmoles
Figure 70. Dependence, of microorganism loading
of GAC with ion concentration.
(Klotz et aj,.,1975)
Colony numbers were measured using these three nutrient media at the
outlet of the Schierstein plant 3AC adsorbers for nearly one year (Figure
71). The colony counts/ml of the GAC adsorber influent were about 100/ml,
but the effluents contained 1,000 to 100,000/nl, depending upon the season
of the year (temperature) and upon changes in raw water quality.
When the full-scale pilot plant GAC adsorbers were used for the first
time with new charges of GAC, colony numbers increased both 1n the adsorbers
and in the new 3AC effluents, even though the adsorber influent waters
contained, as a rule, 0.5 to 1.0 mg/1 of free residual chlorine, and sometimes
contained even 4 mg/1 (see Figure 72). The maximum colony numbers (105 to
106/ml of water in the effluents) were attained within 10 to 20 days after
placing the GAC in service.
Different numbers of colonies were found at various GAC column depths,
depending upon the length of time the particular carbon adsorber had been 1n
service. This behavior was explained on the basis of free residual chlorine
content. In the first of four pilot plant test columns connected 1n series,
low colony numbers and greater than 0.1 mg/1 concentrations of free residual
chlorine were found. However a significant decrease in residual chlorine
191
-------
and an increase in bacterial numbers were measured after stage 2, which then
remained constant after stages 3 and 4. Samples of spent GAC from the plant
adsorbers were found to contain about 108 faacteria/g of wet weight carbon.
V
*•
s
E
^.
in
w
0
1
3
e
e
o
o
o
10SJ
104J
103J
102J
10'
A
V
SPC-agar
*W»"'X
P-agar
;
A A
V'i
gelatine
100
200
300 days
'jan
nov
Figure 71. Fluctuation of colony numbers in GAC
adsorber effluents at Schierstein plant
during 1 year.
(Klotz et aJL, 1976)
Increasing the length of the adsorber columns (by connecting two or
more in series) did not increase the number of colonies measured in adsorber
effluents.
Short time reductions in the number of colonies present in the GAC
adsorber effluents were brought about by backwashing using water from the
adsorber outlets. The backwash water showed an increase in colony numbers
after being used for backwashing (Figure 73), and these increases could
result only from a lowering of the counts in the activated carbon adsorption
media. This ireans that some of the bacteria were washed out of the activated
carbon columns. However, the magnitude of the colony count lowering upon
backwashing was not significant, in terms of decreasing the biochemical
degradation efficiency for removing dissolved orgam'cs. Figure 73 shows
that the numbers of colonies/ml in the activated cardon adsorber effluents
at the steady state (before backwashing) was 5 to 8 x 104. This level rose
192
-------
above TO5 just before backwashing and dropped to TO3 to" 104 just after
backwashing. However, the steady state level of colony counts/ml was reat-
tained after passage of 1,000 to 1,500 cubic meters (0.25 to 0.4 million
gallons) of water. This required about 2 days.
outlet
days »-
Figure 72. Development of microbiological activity
in full scale adsorber with new GAC at
Schierstem plant.
(Klotz e_t a±., 1976)
In all Investigations conducted by Klotz, Werner & Schwelsfurth (1976)
none of the effluents from any of the biologically operating activated
carbon adsorbers showed the presence of any fecal indicators. Filamentous
fungi and yeasts occurred randomly, but rarely in all Investigations. Yeast
numbers were lower than those of filamentous fungi. No substantial differen-
ces were found in comparing waters from the Wiesbaden (Schlerstein) plant
with those of the Frankfurt (Niederrad) Waterworks. Both of these plants
are located near each other 1n the southern part of the Federal Republic of
Germany. Schierstein draws water directly from the River Rhine and Frankfurt
draws water from the River Main, It is important to recognize, however,
that the quality of the River Rhine is much better than that of the River
Main (Werner, 1979).
193
-------
step 2
step
4)
J3
3
>
o
S
10.
backwashing
I f\ outlet
,•••••«•
T
8
9
10
11
water throughput, in 10 cu m
Figure 73. Changes In colony numbers at each GAC
step and outlet in Schlersteln plant.
(Klotz ej.al.,1976)
In all test results reported using the Schierstein plant GAC adsorbers,
Klotz, Werner & Schweisfurth (1976) found correlations between microbio-
logical and chemical/physical data only with respect to chlorine content and
temperature.
In pilot plant tests conducted at the Schlersteln plant, Klotz, Werner
& Schweisfurth (1976) employed four identical glass tubes (4 cm diameter,
1.2 m in length) and connected in series, then filled with 80 cm of the same
granular activated carbon used to charge fresh GAC into the full-scale
Schierstein plant. This amount of GAC corresponded to a wet weight of about
1 kg. The adsorbers then were filled with chlorinated sand filtrate water
from the main plant.
Flow velocities of water through the (fresh) GAC adsorbers (4, 8 and 20
m/hr) were found to influence the development of microbiological activities.
The higher the velocity the more slowly the maximum values of colony counts/nl
194 _
-------
were reached in the filtrates (Figure 74). The maxima were highest for the
slowest flow rate (4 m/hr) and they were attained faster at the slow flow
rate. On the other hand, at the highest flow rate (20 m/hr), higher colony
counts/g of GAC eventually resulted (Figure 75). Therefore, more bacteria
were formed per unit time at such flow rates, which resulted in higher
amounts of microbiological activity.
(0
£
E
^
ia
k
V
1
3
C
C
o
"o
o
Figure 74. Development of colony numbers in effluents
of new GAC pilot plant adsorbers as a
function of flow rate at Schierstein plant.
(Klotz et al.,1976)
On the other hand, at slow flow rates, media conditions were created
which had a favorable effect on the reproduction of filamentous fungi.
Yeasts were found infrequently. Bacfcwasning resulted in lowering the
colony numbers in the adsorber effluents for a short period of time, and
this effect was most pronounced for the adsorber group having the slowest
throughput flow rate.
Similar behaviors with respect to bacterial growth rates in new batches
of granular activated carbon were observed with LWS, ROW, ROW Supra and
195
-------
F-100 carbons (Figure 76). LWS Carbon showed about one-half an order of
magnitude lower colony counts/ml in the adsorber outlets than did the other
three activated carbons tested.
9
a
i
3
c
S=»
C
o
o
u
20 30
days *>
40
50
60
Figure 75. Development of colony numbers In new
GAC charges in Schierstein pilot plant
adsorbers as a function of flow rate.
(Klotz et. a\., 1976)
This work of Klotz, Werner & Schweisfurth (1976) confirmed that data
obtained using the pilot plant test units could be related directly to data
obtained using the full scale plant GAC adsorbers, with respect to colony
numbers and the trends noted in these numbers with time.
Werner, Klotz & Schweisfurth (1979) presented additional data to
substantiate their earlier conclusions regarding the extent of microbio-
logical activity in the Schierstein (Wiesbaden) water treatment works
granular activated carbon adsorbers. Raw water before chlorination generally
contained 2 x 105 colony counts/ml and these decreased to about 1,000/ml
before entering the activated carbon adsorbers. With high level prechlorina-
196
-------
Figure 76. Development of colony numbers in effluents
of pilot plant adsorbers with different
types of GAC at Schiersteln plant.
(Klotz et ai,, 1976)
197
-------
tion, almost all the bacteria originally present were kil'ed and the GAC
adsorber inlet waters contained very few colony counts.
In the activated carbon adsorbers the number of bacteria again increased
to values around 7 x loVml. The activated carbon media were shown to
contain about 1,000 times more bacteria per unit volume than did the carbon
adsorber effluents.
The nunber of living cells was determined by enzymatic methods, rather
than by culture methods, and the total number of cells (living plus dead
bacteria) was determined microscopically by counting them after neirbrane
filtration. Colony count determinations measured up to 2Q% of all living
bacteria and up to 5% of the total (living + dead) cells.
Through a population comparison made by numerical taxonomy methods and
comparison of the morphological and biochemical qualities of the bacterial
strains identified as being present in the activated carbcn -edia (using a
computer program), it was found that:
1) The ability of the bacteria to adapt in the activated carbon adsorbers
was less marked than their ability to adapt in raw water.
2) There was a higher percentage of pseudomonas bacteria present In the
carbon adsorbers than in the raw water,
3) Bacterial populations can be differentiated clearly by the use of
substrate, and especially by their reactions to toxic substances.
Based on these findings, Werner, Klotz & Schweisfurth (1979) concluded
that a special microorganism population forms in the activated carbon
adsorbers (at least those in use at the Schlerstain water treatment plant).
Identification of microorganism populations—To date, 26 species of 11
genera of microorganisms have been isolated from the Schierstein plant GAC
adsorber effluents by the University of Saarland scientists (Werner, Klotz &
Schweisfurth, 1979), and these are listed in Table 38A. Most of the microorga-
nisms present belong to the genera Pseudomonas. The families Bacillus and
Azomonas also are represented to a considerable extent. These bacteria
found to date are non-pathogenic in nature, and are generally found in
water.
Table 39 lists the filamentous fungi and yeasts found in the effluents
from the biologically-loaded granular activated carbon adsorbers of the
Schierstein water treatment plant. These filamentous fungi and yeasts
occurred rarely and irregularly in the effluents, hence their role in water
treatment is considered by Werner, Klotz & Schweisfurth (1979) to be of
secondary importance. The fungi identified to date all are apathogenic.
Performance of the bacteria—Activated carbon adsorbs dissolved organic
substances, which can act as substrate for bacteria, but also adsorbs
bacteria. Figure 77 shows the Freundlich adsorption isotherms for the
adsorption of bacteria onto activated carbon.
198
-------
10 —
o
<
a
w
E
3
C
>>
C
O
o
u
a>
o
5—
100
80 1
c 60 H
•o
(8
O
40
20 -
t'o
I
5
I
10
absorptive concentration
Hog colony number/200 mil
Q=32 xc°'77 c^— a Q=10KC
°'85
Figure 77. Bacterial adsorption on GAC.
(Werner et al.,1978)
__ _ 199
-------
TABLE 33A. BACTERIAL SPECIES FOUND IN EFFLUENTS OF GRANULAR ACTIVATED
CARBON ADSORBERS AT THE SCHIERSTEIN (FRG) PLANT
Pseudomonas alcall genes thromobacterium vlolaceum
Pseudomonas cepacla Neisseria slcca
Pseudomonas facills Acinetobacter calcoaceticum
Pseudomonas fluorescens Mlcrococcus luteus
Pseudomonas lemoignei Staphylococcus saprophyticus
Pseudomonas mendocina Bacillus cereus
Pseudomonas ruhlandii Bacillus circulans
Pseudomonas stutzeri Bacillus licheniformls
Pseudomonas spec. Bacillus megaterium
Gluconobacter oxidans Bacillus pumulis
Azomonas agilis Bacillus thuringensis
Azomonas insignis Corynebacterium spec.
Azomonas macrocytogenes Micromonospora spec.
Source: Werner, Klotz & Schweisfurth, 1978
TABLE 39. TYPES OF FUNGI AND YEASTS FOUND IN EFFLUENTS OF GRANULAR
ACTIVATED CARBON ADSORBERS AT THE SCHIERSTEIN (FRG) PLANT
FTTarrentous fungi PhiaTopnora hoffmannii
Phialophora mutabilis
Taphrina spec.
Yeasts Rhodctorula minuta var. texensis
Cryptococcus uniguttulatus
Candida guillermondii var. guillermondii
Hansenula anorcala var. anomala
Source: Werner, Klotz & Schweisfurth, 1978
Because of the great difference in size between bacteria and organic
molecules, the two are separated from each other after adsorption because of
the porous structure of the activated carbon. The smaller, organic molecules
are adsorbed mostly in the micropores of the activated carbon, which represent
about 992 of the total available surface area. On the other hand, the much
larger bacteria cannot be adsorbed in the micropores, but only on the surface
and in the macropores, which make up about "56 of the total activated carbon
surface area available for adsorption. This has a negative secondary effect
on the metabolism of the bacteria.
In the absence of activated carbon, both bacteria and substrate are
uniformly distributed in the aqueous medium.
As confirmation of these statements, Figure 78 shows plots of the
metabolic activity of bacteria (measured by oxygen consumption) versus time.
The initial colony counts/ml of bacteria with or without activated carbcn
being present were 1.2 x I08/ml and the water solution also contained 0.1
_ 200
-------
c
o
E
3
U)
C
O
u
c
V
O)
>
X
o
J
•= 1
1
2
bacteria
1.2 x 108/ml
substrate
phenol
0.1 g/l
r •"...
GAC
0.5g
1 1. 25 mm
10 20 30 40 50 60 70 80
times hrs.
Figure 78. Effect of GAC on metabolic activity of bacteria.
(Werner et al., 1978)
201
-------
g/1 (TOO mg/1) of phenol to act as a substrate for the bacteria. The upper
curve (data obtained in the absence of activated carbon) shows that the
phenol substrate was utilized rapidly by the bacteria (most within the first
24 hours). On the other hand, when 0.5 g/1 (500 mg/1) of granular activated
carbon (1 to 1.25 mm particle size) was added to a second solution containing
the sane number of colony counts/ml and the same amount of phenol, less than
half of the substrate was utilized after 80 hours of contact than was utilized
within 24 hours when activated carbon was absent.
Activated carbon also provides a positive effect on the metabolism of
bacteria, however. It enriches the concentration of organic substances in
the adsorber media and increases their residence times in the adsorber. In
addition, there is provided a "buffering action" of the system for organic
substances which are toxic to the bacteria present. These effects are shown
by the data plotted in Figure 79, in which 8 experiments were conducted with
solutions initially containing 3.5 x 108 colony counts/ml. To four sets of
two solutions were added 2.5, 1.0, 0.3 and 0.1 g/1 quantities of phenol. In
lower concentrations, phenol can serve as substrate (food) *or the bacteria,
but in the higher concentrations, phenol is toxic to the same bacteria.
To one of each of the four sets of solutions containing 3.5 x 108
bacterial colony counts/ml and added phenol now was added 0.5 g/1 of granular
activated carbon (1 to 1.25 mm particle size) and the rates of oxygen consump-
tion were determined over a period of 200 hours.
At the highest phenol concentration (2.5 g/1 -- 2,500 mg/1) ) the
solution without activated carbon showed no metabolic activity (zero oxygen
consumption over 160 hours) (curve 1), proving that at this concentration
phenol is toxic to the bacteria present. However, when 0.5 g/1 of granular
activated carbon was added to the duplicate solution containing 2.5 g/1 of
phenol, this sample showed the highest rate of oxygen consumption of all
samples tested (curve 2). Therefore, it can be concluded that the activated
carbon adsorbed the toxic quantity of phenol, rendering the aqueous solution
harmless to the bacteria. This allowed the bacteria to remain viable. The
adsorbed phenol then was slowly released into solution, in non-toxic concen-
trations (probably by desorption mechanisms), where it either passed through
the activated carbon adsorber to the effluent and/or was captured and metabo-
lized by the bacteria. Once adsorbed on the activated carbon, high initial
concentrations of toxic materials, such as phenol, can become a slow releasing
source of dissolved organic carbon substrate for the bacteria.
Similarly, the solution containing 1 g/1 of phenol also was toxic to
the bacteria (no oxygen uptake noted after 160 hours) and the duplicate
sample treated with 3.5 mg/1 of activated carbon showed the second highest
oxygen consumption rate over 160 hours.
Data obtained at the lower phenol concentrations, however, seemed to
conflict with the hypothesis developed 'or the higher phenol concentrations.
The sample containing 0.3 g/1 of phenol and.no activated carbon consumed
oxygen at more than twice the rate than did the duplicate sample containing
activated carbon. This apparently reversed behavior can be explained,
however, by considering that the adsorption capacity of the weight of
202
-------
13-
10-
c
o
«w
a
E
3
w
c
o
o
09
X
O
1
2
3
4
5
6
7
8
bacteria
3.5 x 108 ml
ohenol substrate
2Sg/l
_, . ":...: i" •-;-..
- i
1
, >
^ < f
-
-
1
1 fl/l
jw-. , :
0.3 g/l
•• - '
; • ^ ;
01 g/l
- • •. ;
GAG, 0 5 g
1 1.25mm
\
: ^
*
Figure 79. Effect of GAG on metabolic activity of bacteria.
(Werner et^ aj... 1 978)
203
-------
activated carbon added was sufficient to adsorb the total amount of phenol
present. In this case, even low levels of phenol were not released into
solution, and the net effect was total removal of biodegradable substrate
from solution.
This postulate is supported by the fact that the solution containing
0.3 g/1 of phenol was not toxic to the bacteria; the oxygen consumption
measured for this sample was the third highest of the eight samples tested.
Further confirmation of this hypothesis can be developed by considering
the data obtained with the samples containing 0.1 g/1 of phenol. Again, the
sample to which activated carbon was added showed no metabolic activity
(zero oxygen consumption after 160 hours) whereas the sample without added
activated carbon rapidly attained a low level of oxygen consumption.
The rapid attainment of a constant level of oxygen consumption by the
samples containing 0.1 and 0.3 g/1 of phenol without added activated carbon
shows that the oxygen uptake rates are independent upon the concentration of
phenol (over this concentration range). With the sample containing 0.3 g/1
of phenol, the fact that this amount of oxygen consumption was not attained
until after about 40 hours can be explained either by there being an insuffi-
cient concentration of bacteria present initially or that this phenol concen-
tration exerts scrre toxicity to the bacteria, which is overcome later either
by adaptation or by the increase in bacterial populations over that period
of time.
Contribution of Bacteria to Water Treatment—-
The following -merits were found by Werner, Klotz & Schweisfurth (1979)
to hold true for the treatment of Rhine River water with high level chlorina-
tion prior.to filtration and granular activated carbon adsorption. At the
time this phase of the research program at the Schierstein plant was conducted,
the efficiency of the activated carbon adsorbers in removing dissolved
organic materials was about 80%. During this study the bacterial contribu-
tions to the removal of organic iraterials (as measured by consumption of
dissolved oxygen and production of C02 compared with the total dissolved
organic carbon removed) were found to be as follows:
• 5% reduction in levels of dissolved organic carbon,
t about 702 reduction in levels of easily decomposed organic substances
(BOD2),
• about M% reduction in levels of difficult-to-decompose organic substan-
ces (BOD2Q),
• about 60% of theoretical oxygen consumption,
• about 60% of theoretical production of carbon dioxide.
It was noted by Werner, Klotz and Schweisfurth (1979), however, that as
the adsorption efficiency of the activated carbon for dissolved organic
substances decreased, the bacterial contribution to removal of organics
204
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increased considerably". At the Schierstein plant, the already low biodegra-
dability of the organic components originally present in the raw water was
further lowered by the high level chlorination step.
Lowering the amounts of easily biodegraded organic substances in
biologically operating granular activated carbon adsorbers has a significant
effect on the regrowth of bacteria in water supply distribution systems.
Through biologically active activated carbon adsorbers these organic materials
are at least partially removed in the plant, rather than in the distribution
system. Furthermore, the bacterial activity present causes a continuing
partial regeneration of the activated carbon, and thus prolongs its operating
life before reactivation is required (Werner,, Klotz & Schweisfurth, 1979).
During June, 1978, Prof. Dr. Schweisfurth and his students, Drs. Klotz
and Werner were interviewed regarding some of the unpublished details of
their 6 years of microbiological studies at the Schierstein plant. The
following additional information was supplied by these scientists in the
form of unpublished information:
1) Normal plate counting techniques measure only 5 to 10% of the living
bacteria actually present. However, enzymatically, 20% of the total
cell numbers can be counted. Tctal colony counts determined on culture
nedia provide information only regarding those types of bacteria which
grow on the media. Not all types of bacteria grow on specific culture
media.
2) E. coli bacteria present in the influents of biologically active
7iHer/adsorber r.edia are not found in the effluents because other
bacterial strains dominate in the media and E_. coli cannot grow under
tneje conditions. They simply die off.
3) The Schierstain plant in Wiebaden has an operating rule which does not
allow a GAC column to stand idle and off-line for more than two days.
Otherwise plate counts increase significantly and the biology changes.
4) The dissolved organic content of the Rhine at Wiesbaden is 3 to 4 mg/1,
which is comprises mostly of municipal sewage. No industries discharge
in the area. Wiesbaden recently has prolonged the residence time in
reservoirs ahead of the Schierstein plant, to provide 3-day residence
times for Rhine River waters, and which are biologically active.
Before the reservoir residence time was increased, the 4 mg/1 DOC level
of the plant influent water was lowered to 2.5 at the inlet to the GAC
media, and to 1 mg/1 exiting the biologically active GAC adsorbers.
Since the increased reservoir residence times COC levels in the inlet
to the GAC adsorbers are even lower.
5) Although BAC media may seen to operate somewhat like trickling filters,
they are not the same. Trickling filters irust have a skin of.slime
(formed by multiple layers of bacteria) in order to be effective. BAL
media remove about 3 times the amount of dissolved organics from solution
as do trickling filters. In trickling filter operation, dissolved
SgSlS Jri adsorbed only by_the slime coat-Ing, which is of very low
205
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surface area, and then 1s degraded. In BAC operation, organlcs are
adsorbed on the carbon surface, in the macropores and also 1n the
micropores, then are degraded.
6) Only about 1% of the available GAC surface area (the macropores) is
occupied by bacteria, which are all greater than 1 micron in particle
size. Therefore, bacteria occupy only about 1 sq cm/cu m of GAC.
7) No clogging of the BAC media has been observed at the Schierstein plant
during the past 6 years of use. On the other hand, the Rhine River at
Wiesbaden does not contain nutrients which are optimum for good bacterial
.growths. If such optimal nutrients were present, it is possible that
clogging could occur.
8) Waters passed through sterile, virgin GAC with no bacteria present
contained measureable quantities of C0£ and consumed measureable
amounts of dissolved oxygen. This shows that GAC can participate in
chemical oxidation reactions, and these may continue to occur even
after bacterial activity has reached a steady state. In the experiment
reported earlier (Klotr, Werner & Schweisfurth, 1975) in which a GAC
column had been kept sterile for two months, C02 was produced, after
which time the column became biologically active and the experiment was
discontinued, "he amount of C02 produced represented 1.5% of the total
generated.
9) In Warburg apparatus studies (measuring iretabolic bacterial activity by
oxygen consumption and C02 production), the size of the GAC granules
was important. The smaller the particle size the faster was the rate
of oxygen consumption, until the carbon granule approaches 1 mm. At
this point clogging became prevalent and the apparatus then could not
be aerated or backwashed. With large GAC particle sizes the time for
transfer of adsorbed organlcs to the bacteria becomes longer. The
mechanism probably involves desorption of the organic material from the
micropores, followed by diffusion to meet the bacteria. With larger
GAC particles, the process is believed to become diffusion controlled;
with smaller 3AC particles the process is desorption controlled.
10) In considering biological mechanisms occurring during GAC operation, it
is possible that some bacterially secreted enzymes can leave the ,
bacterial cells, then may diffuse into the GAC micropores and act on
the adsorbed organics, desorbing them so that they can diffuse out of
the micropores and into the areas occupied by the bacteria.
11) In another water works (not Schiersteln) the GAC was removing about 30*
of the dissolved organics present in the adsorber influents after 5
years of operation.
12) For sampling of an operating pilot plant GAC adsorber, the containers
are opened (at the top) and a 0.5 cm diameter sterile pipe is inserted
into the carbon medium to the measured depth. The open end of the pipe
is closed with the thumb of the person sampling and the filled tube is
removed and emptied. The 0.5 cm sampling pipe allows 4 g samples to be
206
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taken. The Schierstein plant GAC adsorbers are 4 neters high, 3 meters
in diameter and contain 2 to 3 meters of 3AC depth. When the full-
scale plant GAC was charged, 10 to 20 g samples of used 3AC were taken
at 4 to 5 column depths. Samples also were taken from the center out
to the periphery of each bed. The samples were found to be homogeneous
(with respect to the bacterial parameters measured) at the sane bed
depth of GAC out to the peripheries, and also were homogeneous after
the first 30 cm of depth.
13) GAC samples were homogenized in sterilized tap water using a Waring
Blendor type of nixer. After establishing the optimum dilution to
provide the best number of colonies for counting, the Blendor should be
calibrated. This is done by plotting time of horrogenization versus
colony counts. The peak is taken as the optimum time of homogenization
for that Blendor (which is always operated at the same speed).
14) The amount of dissolved organic carbon removed from solution bacterially
is not precisely equivalent to the arount of C02 produced. This is
because some organic carbon is used by the bacteria for self-synthesis,
and does not becone liberated as C02. However, some bacteria die and
are attacked by living bacteria. When this occurs, some of the carbcn
contained by the dead bacteria is released as COj. These two effects
of carbon consumption and carbon release tend to balance each other,
and it should be possible to follow the biological degradation of
organics reasonably quantitatively by ireasuring the rate of COg formed
as well as the rate of consumption of dissolved oxygen.
CONCLUSIONS REGARDING MICROBIOLOGICAL ASPECTS OF BAC SYSTEMS
From the published works and private communications described in this
sub-section and elsewhere in this report, the following major conclusions
can be drawn concerning the nicrobiology present in operational BAC systeirs
in drinking water treatment plants:
1) Bacterial activity develops rapidly in fresh charges of granular
activated carbon (within 5 to 12 days of initiation or flow) and
reaches a peak of 104 to 106 colony counts per ml of water or 1C6 to
108 per g of GAC present in 10 to 20 days. At biological equilibrium,
counts usually are higher in the GAC media than in the effluents.
2) Standard plate count techniques (incubation at 27°C over 2 days) show
relatively low colony counts in the filter/adsorber media and their
effluents. Incubation over 7 days shows much higher colony counts, and
is the procedure being used by German microbiologists at the University
of Saarlands in their studies.
3) These high bacterial activities occur even in the presence of free
residual chlorine in the 3AC rredia influents. There is an indication
that when chlorinated influents (containing as high as 0.5 mg/1 free
residual chlorine after breakpoint chlorination) are passed through
biologically operating activated carbon media, chlorine-resistant
bacteria can be present in the effluents.
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4, High bacterial levels in the activated carbon effluents can be destroyed
using low dosage levels of chlorination (0.2 to 0.3 mg/1 in Germany; up
to 0.5 mg/1 1n France) or of chlorine dioxide (0.15 to 0.3 mg/1) provided
that extraneous chlorine- or chlorine dioxide-demanding materials are
absent.
5) At least 20 species of bacteria, 3 species of filamentous fungi and 4
species of yeasts have been identified in effluents from operating GAC
units at the Schierstein plant at Wiesbaden. During the studies
reported, this plant used aeration, breakpoint chlorination and rapid
sand filtration as pretreatment before GAC adsorption. All mlcrobial
populations identified to date are non-pathogenic soil and water
organisms.
6) E_. coli bacteria do not appear to survive in competition with other
types of bacteria present in biological activated carbon media used for
treating drinking water. Therefore, E_. cpli baterla are not normally
found in BAG media effluents. However, this conclusion must be based
on the assumption that the BAG adsorber is properly sized (provides
sufficient empty bed contact time) and is operated at a sufficiently
slow throughput velocity.
7) No publications are known which deal with the question of endotoxins
present in effluents from operational BAG systems.
8) Backwashing of operating BAG units lowers bacterial counts in the
activated carbon media (and raises them in the backwash water), but not
sufficiently to lower the degree of water treatment being sought (organic
compound removal or nitrification). Counts return to noriral within 2
days after backwashing.
9) GAC units containing microbiological growths taken off-line are not
allowed to stand idle for more than two days, otherwise the microbiology
changes and colony counts increase significantly.
10) There are no known incidents of biological fouling of operating BAG
systems in Europe. If anything, the use of ozone as the preoxidant
lengthens the tiire between backwashing of both the sand filters and GAC
adsorbers (at the Dohne plant, Mill helm, FRG).
11) After 5 years of uses GAC adsorbers at another German water works (not
Schierstein) were removing 30% of the dissolved organic carbon present
1n the adsorber influents.
12) On the other hand, results obtained by Van der Kooij (1979) showed
that colony counts in the filtrates from sand, granular non-activated
carbon and granular activated carbon filters were about the sane. This
indicates that the high colony counts usually observed in GAC filter/ad-
sorbers are Independent of the amount of organic materials adsorbed by
the GAC.
208
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13) The maximum removal of organic materials present in BAG adsorber
influents (50% at biological equilibrium) was found during pilot plant
studies at the Auf-dem-Werder plant at Bremen, FRG, but without the use
of preozonation. In this case, a special 6AC was employed which had a
high percentage of macropores (to house a higher level of biological
activity). In all other water treatment plants known to be utilizing
BAG processes, the degree of removal of dissolved organic materials at
the biological steady state 1s 25% to 35%, even with preozonation. It
is worthy of noting that 30% removal of dissolved organics is found at
Wiesbaden (the upper Rhine which is not so heavily polluted) using
aeration and prechlorination without river sand bank filtration. On
the other hand, the same 30% removal of organics is obtained in the
lower Rhine area at DUsseldorf, where river sand bank filtration is
followed by ozonation. BAG units can be allowed to remain on line at
water works in southern Germany for longer times (up to several years)
before reactivation 1s required,, because of the absence of significant
levels of halogenated organics 1n the Rhine at this point. On the
other hand, in the Dtlsseldorf area, reactivation tines of BAG rredia are
controlled by the presence of halogenated organics progressing through
the GAG.
14) At the Schierstein plant in Wiesbaden, bacterial breakthroughs were
noted after 3 years of use of GAG columns for taste and odor control.
This suggests that water utilities Installing 3AC systems should
consider a bacterial monitoring test to use as a regeneration control
parameter, in addition to whatever organic parameters are also adopted.
15) In operational BAG systeirs, bacteria occupy only the outer surface and
nacropores of the activated carbon granules. These account for 1 to 2%
of the total GAG surface area in most activated carbons currently
available. On the average, a single bacterium occupies 40 square
microns per cubic meter of GAG surface area in operating BAG systems.
This amount of bacteria present does not appear to Interfere with
dissolved organic adsorption processes 1n operational BAG systems.
16) High levels of phenol in the SAG adsorber influent(which are toxic to
the bacteria present in the absence of GAG) are lowered by GAG adsorption
to levels at which phenol can be utilized as bacterial substrate.
Thus, BAG can be considered as a "sink" for adsorbable toxic (to bac-
teria) organic materials,, which then may be biodegraded in the biologi-
cally active adsorber.
17) Cne postulated mechanism of BAG operation Involves rapid adsorption of
dissolved organics by the GAG mlcropores, followed by slow desorption
and diffusion of the organics to areas where bacteria are present. The
snail er the GAG partUle size the greater 1s the rate of biochemical
degradation of organics, possibly because the diffusion path is shortened
f1-
problems of clogging and reducing attainable flow rates.
209
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18) Bacterial activities are higher in BAG media during summer than during
winter, probably because of higher water temperatures.
19) Samples of GAC known to be bacterlally sterile cause some oxygen
consumption and CC>2 production 1n waters being passed through such
media. At biological steady state conditions, however, this amount of
C02 produced represents only about 1.5% of the total produced.
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SECTION 11
ESTIMATED COSTS FOR BAC SYSTEMS
It must be kept in kept in mind that the capital and operating costs
for biologically enhanced granular activated carbon systems are determined
by a number of factors:
the type and amount of oxidative pretreatment required,
the organic composition of the raw water (conponents which can and
cannot be converted into biodegradable materials),
the necessity to add oxygen,
the necessity to maintain pH between 6 and 8 (to maintain optirral
bacterial activity),
the empty bed contact time of the GAC colurns or beds,
the necessity to pretreat the wastewaters to remove components
which may be toxic to the bacteria.
In addition, the frequency of regeneration of the GAC will have a major
impact on the GAC operating costs. In fact, one of the primary advantages
of operating GAC media in biologically enhanced modes is the saving in
reactivation costs (including attrition losses which occur during nrovement
and handling of SAC during reactivation) which can be obtained in certain
cases by installing a preoxygenstion or preoxidation step. If the saving in
GAC reactivation costs more than offset the installation of pretreatment to
promote biological activity, then BAC will be cost-effective for the specific
wastewater under consideration.
In this section, estimated costs for the nrajor components of BAC
systems wi',1 be discussed. These will include preoxidation with ozone (the
highest cost preoxidation system), GAC adsorption contactors, Initial loading
of GAC to the contactors and GAC thermal regeneration equipment.
COSTS FOR OZONATION SYSTEMS
Oxidation with ozone will be the highest cost oxidation step, compared
with using oxidants such as chlorine, chlorine dioxide, potassium perman-
ganate, hydrogen peroxide, etc., adding pure oxygen or simply the addition
of air. However, the most widely known biologically enhanced GAC systems to
date utilize ozonatlon as the preoxidation step. Therefore, for purposes of
this discussion, the costs for ozonation will be summarized. Those BAC
systems which can utilize lower cost oxidants effectively, or simply oxygen
or air, will be able to lower this portion of their total costs
proportionately.
211
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Capital Costs For Ozonation Systems
Major factors affecting the capital costs of ozonatlon systems Include:
t Capacity of ozone generation system
• Number of stages of ozone use
• Type of ozone contactor off-gas destruction
« Type of ozone control system
• Space requirements
• Standby generation capacity required
o Use of air versus oxygen for ozone generation
Capital costs for ozone generation systems range from $850 to $1,150/16
of ozone generated per day when up to 100 Ibs/day are required. This range
drops to $300 to $500/lb of ozone per day when 1,000 Ibs/day of ozone are
required (Table 40; G.W. Miller, 1979). To these equipment costs must be
added the costs for contacting, building space, control systems, contactor
off-gas destruction, etc. Capital costs for fully installed ozonation
systems are given in Table 41 (Gumerman, Gulp & Hansen, 1978). Costs for
construction of diffuser contactors (concrete columns, 18 feet deep with a
length/width ratio of approximately 2/1) are listed in Table 42 for various
sizes of chambers (Gumerman, Gulp & Hansen, 1978).
TABLE 40. COST RANGE OF OZONATION SYSTEMS (FROM AIR)
Ozone Generation Capacity,
Ibs/day of ozone
100
200
300
400
500
1,000
Approx. Capital Cost,
$/lb production cap. /day
850 -
600 -
500 -
450 -
400 -
300 -
1,150
800
700
650
600
500
Source: G.W. Miller (1979)
Clark and Stevie (1978) assembled available capital cost data for
ozonation systems and converted 1t into capital costs per mg/L of ozone
dosage per 1,000 gallons of drinking water disinfected. These cost data are
presented in Table 43 for plant sizes ranging from 1 mgd to 150 mgd. At the
lower flow rates (10 mgd and below), the capital costs for generation of
ozone from air are lower than those for generating ozone from oxygen.
However, above 10 mgd, the capital costs for generating ozone from oxygen
become less than those for air. For a 10 mgd treatment plant, the capital
cost to provide an ozone (generated from air) dosage of 1 mg/L is estimated
by Clark & Stevie (1978) to be on the order of l.U/1,000 gal.
One year later, Hansen, Gumerman & Gulp (1979) developed more detailed
capital cost estimates for air-fed ozone generators capable of producing 0.5
to 10 Ibs of ozone/day. These are given in Table 44, and include costs for
212
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TABLE 41. CONSTRUCTION COST: OZCNE GENERATION SYSTEMS
Mfgd.
Eqpmt.
Concrete
Steel
Labor
Housing
Subtotal
lisc. &
^ontinq'y
Total
Ozone Generation Capacity, Ibs/day
10
$32,250
--
—
4,840
6,000
43,909
6,460
$49,550
100
143,610
--
--
33,690
8,400
185,700
27.86C
213,560
500
511,960
1,540
1,520
114,110
12,700
642, 70C
96,410
739,110
1,000
685,810
1,540
1,520
143,110
23,400
855,380
128,310
983,690
2,000
1,075,540
2,250
2,210
207,500
35,700
1,318,200
197,730
1,515,930
3,500
1,523,240
2,250
2,210
272,300
41,800
1,841,800
276,270
2,118,070
Source: Gumerman, Culp & Hansen, 1978
TABLE 42. CONSTRUCTION COST: CONCRETE OZONE CONTACT CHAMBERS
Concrete Chamber Volume
c\m.
gallons
Excavation &
Sitework
Concrete
Steel
Labor
Subtotal
Misc. &
Contingency
Total
460
3,441
$ 470
850
1,470
2,150
4,940
740
& 5,680
4,600
34,413
1,630
4,950
8,400
12,200
27,180
4,080
31,260
23,000
1/2,063
2,570
8,280
13,570
19,510
43,930
6,590
50,520
46,000
344 J 26
5,150
15,450
23,330
36,120
82,050
12,310
94,360
92,OCO
688,252
10,290
29,810
48,550
69,330
157,980
23.700
181,680
basis: 18 ft deep; length/width ratio = 2/1
Source: Gumerman, Culp & Hansen, 1978
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TABLE 43. CAPITAL COSTS FOR DRINKING WATER DISINFECTION WITH OZONE
Capital Costs, i/1,000 gal.
(ozone generated from
air or oxygen)
Capital Cost (from air)
Capital Cost (from oxygen)
Desiqn Caoadtv (mad)
~"l
2.90
4.46
5
1.36
1.50
10
1.11
1.08
100
0.76
0.61
150
0.73
0.58
Source: Clark & Stevle, 1978
TABLE 44. CONSTRUCTION COSTS FOR SMALL SCALE OZONE GENERATION SYSTEMS*
Cost Category
Manufactured Equipment
Labor
Housing
Subtotal
Miscellaneous & Contingency
Ozone Generation Capacity (Ibs/day)
0.5
$ 11,540
1,860
6,000
19,400
2,910
TOTAL 22,310
Ozone Generating Equipment Costs
($/lb/day of 03 generated) 23,080
Construction Costs
($/lb/day of 03 generated) 44,620
5.0
$ 19,880
3,300
6,000
29,180
4,380
33,560
3,976
6,712
10.0
$ 28,530
4,840
6,000
39,370
5,910
45,280
2,853
4,528
* Assumes ozone is generated from air. Costs include ozone generator,
dissolution equipment, electrical equipment, control instrumentation, but
lot contact chamber. Figures are not stated to include costs for air prepa-
ration equipment (which would add 20% to 25% to capital costs of manufactured
equipment), nor for equipment to destroy ozone in contactor off-gases.
Source: Hansen, Gumerman & Gulp, 1979
214
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the ozone generator, dissolution equipment and all required electrical
equipment and Instrumentation, labor and housing, but not costs for the
ozone contact chamber itself, since these are a function of water flow to be
treated and contact time. These capital costs are not stated to include air
preparation equipment or ozone destruction apparatus for contactor off-gas
treatment. If not Included, these costs must be considered to be somewhat
low. For example, ozone generator suppliers normally estimate the capital
costs for air preparation equipment to be about 20% to 25% of the total
capital cost of the ozone generation system (Larocque, 1977, Private
Communication).
Separate construction costs vere estimated by Hansen, Sumerman & Cjlp
(1979) for 18 ft high (water depth 16 ft) fiberglass reinforced plastic
ozone contact chambers to be used 1n conjunction with ozone generation
systems capable of producing 0.5 to 10 Ibs/day. Costs for the contacting
equipment itself are included with those of the ozone generation system.
Contactor construction costs are listed in Table 45.
For larger sized ozone generation systems (10 to 3,500 Ibs/day),
Gumerman, Culp & Hansen (1979) estimated capital costs based upon air feed
to the generator for up to ICO Ibs/day of ozone generated and from oxygen
above 100 Ibs/day. They also assumed that all oxygen used for ozone genera-
tion would be generated on-site, and that although the ozonation equipment
would be housed, the oxygen generation equipment would be located outside on
a concrete slab.
These assumptions made by Gumerman et al. (1979) are not representative
ot current ozone generation practice, eitFer for municipal water or wastewater
treatment, for the nrost part. In drinking water treatment plants, Miller e_t
a/L (1978) have shown that of the approximately 1,100 plants which were
using ozone during 19779 only 2 generate their ozone from oxygen. Only one
of these plants (Duisburg, Federal Republic of Gertrany) recycles the oxygen-
rich ozone contactor off-gases to the ozone generator. Even the largest and
newest water treatment plants using ozone generate more than 5,000 Ibs/day
from air feed,,
On the other hand, most of the newer and larger U.S. wastewater treatment
plants using ozone also employ the oxygen activated sludge process. This
means that the oxygen source for ozone generation comes from an on-s1te,
oxygen generation plant which generates tons/day quantities of oxygen at the
lowest cost, mostly for use in plant biological reactors. Therefore, oxygen
is available at a lower cost than 1f oxygen generating equipment were to be
sized simply to produce the volume necessary to feed the ozone generators
alone.
In addition, 1n oxygen activated sludge plants using ozone, the oxygen-
rich ozone contactor off-gases are not usually recycled to the ozone genera-
tor, but rather are passed into the~bTological reactor. This use of ozone
contactor off-gases is referred to as a "once-through (the ozone generator)
oxygen" system. In this manner, the only loss of oxygen in the system Is
that which is dissolved in the ozone-treated wastewater. Bhargava (1979)
described an ozone generation system which uses partial recycle of oxygen
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TABLE 45. CONSTRUCTION COST FOR OZONE CONTACT CHAMBERS (SMALL SCALE*)
Cost Category
Manufactured Equipment
Concrete
Steel
Labor
SUBTOTAL
Miscellaneous & Contingency
TOTAL
Contactor Volume (gallons)
850
$ 690
20
10
170
890
130
1,020
2,350
$ 1,270
50
20
280
1,620
240
1,860
5,290
$ 3,160
100
40
470
3,770
570
4,340
8,480
$ 6,960
140
50
610
7,760
1,160
8,920
13,540
$ 8,640
190
70
760
9,660
1,450
11.110
* for use with 0.5 to 10 Ibs/day ozone generation capacity. Contact chambers are
18 ft high, fiberglass reinforced plastic.
Source; Hansen, Gumerman & Culp, 1979
-------
and which has been installed 1n the 8 mgd sewage treatment plant at Murphrees-
boro, Tennessee. This oxygen activated sludge plant using ozone disinfection
was scheduled to become operational by mid-1980. More details on the design
of oxygen recycle systems for generation of ozone can be found in a paper by
Lestochi et al.. (1979). *
Therefore, as with the estimates for small ozone generators, capital
costs estimated by Gumeman et al_. (1979) are considered to be low (in those
cases in which large quantitTes of ozone are generated from air -- for most
drinking water treatment purposes), but are high by the amount of oxygen
recycle equipment which normally is not employed.
Capital costs for large scale ozone generation (10 to 3,500 Ibs/day)
estimated by Gumerrran et^al. (1979) are given in Table 46 and include
equipment for gas preparation (assumed to be generation of oxygen), ozone
generation (from oxygen at more than ICO Ibs/day), dissolution, off-gas
oxygen recycling (but may not include destruction of ozone in the contactor
off-gases), electrical and instrumentation costs, all required safety and
monitoring equipment, labor and housing costs.
The ozone contact chamber for large scale ozone generation was assumed
by Gumerman et al. (1979) to be a covered, reinforced concrete structure, 18
feet deep ancTwrth a length/width ratio of approximately 2:1. Construction
costs for such contact chambers are given in Table 47 (costs for the ozone
dissolution equipment Itself are included with the ozone generation equipment
in Table 46).
It should be recognized that once an ozonation system has been installed
for any single purpose, additional applications for ozone at the same plant
will involve only the incremental costs for additional ozone generation
capacity plus e second contacting system. All of the one-tire costs associa-
ted with installing the Initial ozone generation system (power, housing,
controls, air treatment, off-gas destruction, etc.) already will be present,
and the incremental cost per pound of ozone generated now will be less than
those required for initial installation.
Operating & Maintenance Costs Of Ozonation Systems
Most of the operating expense to produce ozone is the cost of electrical
power; this has been estimated to amount to about 80% of the total ozone
generation costs. Much information on operating and maintenance costs steirs
from European drinking water treatment plants, some of which have been
employing ozone since 1906. Miller et. a]_. (1978) summarized the costs for
ozone treatment of drinking water supplies in Europe and Canada. With
ozonation doses ranging from 1.5 to 3.0 mg/L and with ozone generation
capacities of 1S000 to 3,000 Ibs/day (from air), ozonation costs ranged from
1.75 to 4.0 cents/1,000 gallons of water treated in 1977. These figures
include the amortized capital costs (usually over 20 years at 8% Interest)
for air preparation equipment, ozone generation, ozone contacting, treatment
of off-gases from ozone contacting, instrumentation and automation for the
ozonation subsystem, and installation and housing for the ozonation system,
operation and maintenance.
217
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TABLE 46. CONSTRUCTION COSTS FOR OZONE GENERATION SYSTEMS (LARGE SCALE)
Cost Category
Manufactured Equipment
Concrete
Steel
Labor
Housing
SUBTOTAL
Miscellaneous & Contingency
TOTAL
Manufactured Equipment Cost,
$/lb/day of 03 generating
capacity
Construction Costs in
$/lb/day of 03 generating
capaci ty
Ozone Generation Capacity (Ibs/dav)
10
$ 34,210
0
0
5,090
6,430
45,730
6,860
$ 52,590
3,421
5,259
TOO
$152,350
0
0
35,410
9,000
196,760
29,510
226,270
1,524
2,263
500
$543,130
1,630
1,680
120,850
13,600
680,890
102,130
783,020
1,086
1,566
1,000
$ 727,560
1,630
1,680
150,420
25,060
906,350
135,950
1,042,300
728
1,042
2,000
$1,135,720
2,380
2,440
218,100
38,230
1,396,870
209,530
1,606,400
568
803
3,500
$1,615,980
2,380
2,440
286,200
44,770
1,951,770
292,770
2,244,540
462
641
Source: Gumerman, Culp & Hansen, 1979
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TABLE 47. CONSTRUCTION COSTS FOR OZONE CONTACT CHAMBERS (LARGE SCALE*)
Contact Chamber Volume
cu ft 460
Cost Category gallons 3,441
Excavation & Sitework
Concrete
Steel
Labor
SUBTOTAL
Miscellaneous & Contingency
TOTAL
$ 490
900
1,620
2,260
5,270
790
6,060
4,600
34,413
$ 1,710
5,250
9,270
12,820
29,050
4,360
33,410
23,000
172,063
$ 2,700
8,780
14,980
20,510
46,970
7,050
54,020
46,000
344,126
$ 5,410
16,380
25,750
37,960
85,500
12,820
98,320
92,000
688,252
$ 10,820
31,600
53,580
72,870
168,870
25,330
194,200
* Concrete chambers, 18 ft deep; length to width ratio = 2/1
Source: Gumerman, Culp & Hansen, 1979
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The rather broad range of European ozonation system costs is affected
mainly by the cost of housing for the ozonation system and variations in the
local costs of electrical energy. If the ozonation system is housed in a
separate bui'ding, as opposed to being retrofitted into an existing building,
then the costs will be about 25% higher (Miller et al_., 1978).
Small Scale Ozone Generation—
Hansen e_t a]_. (1979) developed operation and maintenance costs for
generation of ozone at the rate of 0.5 to 10 Ibs/day, from air.' Electrical
energy is required for building, heating, lighting and ventilating, as well
as for ozone generation. It is not clear from the report by Hansen e£a1_.
(1979) whether costs for air preparation and for destruction of ozone in the
contactor off-gases are included. Process energy for ozonation is based on
Ib kWh/lb of ozone generated for the smallest system to 11 kWh/lb for the 10
Ibs/day system. Maintenance costs were estimated to be U of the capital
equipment costs. Annual operation and maintenance costs for small scale
ozone generators are given in Table 48.
Large Scale Ozone Seneration--
Gumerman, Gulp & Hansen (1979) developed operation and maintenance
costs for systems generating 10 to 3,500 Ibs/day of ozone. Below 100
Ibs/day, ozone is assunred by these authors to be generated from air; oxygen
is the feed gas above 100 Ibs/day and is generated on-s1te in a quantity
necessary to feed the ozone generators. For air feed, power requirements
were based on 11 kWh/lb of ozone generated, but 7.5 kWh/lb from oxygen.
Annual operation and maintenance costs are estimated in Table 49.
LePage (1979) has reported the results of 8 months of operational
experience at the 18 mgd Monroe, Michigan drinking water treatment plant
which began operating with osonation (for taste and odor control) in February,
1979. This plant is capable of generating 450 Ibs/day of ozone from air and
is designed to apply 3 mg/L of ozone to the raw water. After 8 months of
operation, an average ozone dosage of 1.65 mg/1 had been employed at an
average ozonation cost of 0.634tf/l,000 gal of water treated.
Knorr (1979) reported that the new 10 mgd sewage treatment plant being
constructed at El Paso, Texas will incorporate an average ozone dosage of 5
mg/1 prior to GAC adsorption for an estimated operational cost of 4
-------
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IN)
TABLE 48. OPERATION AND MAINTENANCE SUMMARY FOR SMALL SCALE OZONE GENERATION SYSTEMS*
Ozone Generation
Rate (Ibs/day)
0.5
5.0
10.0
Electrical Energy
Building
6,570
6,570
6,570
Process
2,560
21,900
40,150
kHhr/yr)
Totai
9,130
28,470
46,720
Maintenance
Material
($/yr)
$ 120
200
290
Labor
(hrs/yr)
370
550
550
Total
Cost**
($/yr)
$ 4,090
6,550
7,190
* Ozone 1s generated from air
** Calculated using $0.03/kWh and $10.00/hr for labor
Source: Hansen, Gumerman & Gulp, 1979
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TABLE 49. OPERATION AND MAINTENANCE SUMMARY FOR LARGE SCALE OZONE GENERATION SYSTEMS*
Ozone Generation
Rate (Ibs/day)
10
100
500
1,000
2,000
3.500
Electrical Energy (kWh/yr)
Building
5,750
9,850
16,420
30,780
71 ,820
123,120
Process
40,150
401,500
1,368,750
2,737,500
5,475,000
9,581,250
lotal
45,900
411,350
1,385,170
2,768,280
5,546,820
9,704,370
Maintenance
Material
($/yr)
$ 1,430
3,060
10,770
14,270
22,120
31,150
Labor
(Hrs/yr)
550
550
910
1,830
2,190
2,920
Total
Cost**
($/yr)
$ 8,310
20,900
61,430
115,620
210,430
351,480
* Assumes ozone is generated from oxygen, except for first line, which 1s ozone generated
from air.
** Calculated using $0.03/kWh and $10.00/hr labor cost.
Source; Gumerman, Culp & Hanssn, 1979
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On the basis of information published to date, the empty bed contact
times which have produced the most effective removals of ammonia and dissolved
organics from aqueous solutions by combinations of adsorption and biological
activity have been close to 10 minutes. However, longer empty bed contact
times of 20 to 30 minutes have been recommended-in some European drinking
water treatment plants (Sontheimer, 1978b).
Regeneration of GAC normally is done on-site at large water and waste-
water treatment plants, especially when the daily volumes of GAC to be
regenerated or frequencies of reactivation warrant. On the other hand, when
the GAC does not have to be regenerated frequently, then it usually is cost-
effective for the plant to send its spent GAC back to the manufacturer for
reactivation. Many of the larger European drinking water treatment plants
using GAC do not have on-s1te GAC reactivation facilities (Rice et al.,
1979).
Gulp (1980) points out that "good cost data are available from operating
(GAC) installations at: (1) The South Lake Tahoe Public Utility District,
South Lake Tahoe, California (13 years), (2) the Orange County Water District,
Fountain Valley, California (4 years) and (3) the Upper Occoquan Sewage
Authority, Manassas Park, Virginia (capital cost data only ~ plant in
operation only a few months)." In addition to these three plants, there are
an additional 17 or so operating municipal advanced waste treatment plants
which use GAC in the USA, and these plants also provide detailed cost informa-
tion. However, Culp (1980) also cautions that "costs taken from wastewater
cost curves which are plots of flow in mgd versus cost (capital or operation
and maintenance costs) cannot be applied directly to drinking water treatment.
Allowance must be made Tn~tEe~ capital costs for the different reactivation
capacity needed (for the two types of application), and in the operation and
maintenance costs for the actual amount of carbon to be reactivated or
replaced." These factors are site- and water- (or wastewater)-specific.
Capital Costs For GAC Systems
Components of capital costs for GAC systems Include the contactor, site
modifications, piping, pumps and valves, GAC fill, contingencies, fees and
regeneration furnaces (assuming on-site reactivation). The summations of
these capital costs for eirpty bed contact times of 9 and 18 minutes have
been estimated by J.C. Clark (1979) and are presented in Figure 80 for flows
up to 300 mgd. Of greatest significance is the fact that the SAC capital
costs decrease sharply for plant flows up to 50 mgd, then decrease much more
slowly up to 300 mgd.
Small Scale, Package GAC Columns—
Gumerman, Culp & Hansen (1979) developed construction costs for factory-
assembled, package GAC columns, which were sized with 7.5 minutes empty bed
contact time to treat volumes of 2,SCO gal/day to 0.5 mgd. GAC bed depths
were taken to be 5 feet and the surface hydraulic loading rate was taken to
be about 5 gpm/sq ft. Conceptual design parameters for these package GAC
units are listed in Table 50.
223
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TABLE 50. CONCEPTUAL DESIGN PARAMETFRS FOR PACKAGE GAC COLUMNS (7.5 m1n EBCT)*
Plant Flow
gpm gpd
1.7 2,500
17 25,000
70 100,000
175 250,000
350 500,000
Flow Rate
(gpm/sq ft)
5.1
5.4
5.6
5.1
5.5
GAC Coluirns
"TJo.
1
1
1
1
1
Bed Area
(sg ft)
0.34
3.14
12.6
34
64
Diameter
(ft)
0.67
2
4
6.5
9
Housing
Area (sq ft)
60
150
300
375
450
* GAC columns are 5 ft deep; surface loading = 5 gpm/sq ft
Source; Gumerman, Gulp & Hansen, 1979
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a
a>
O
O
O
4001
300
200
100-
100 200 300 400 500
av. daily flow In max. month (mgdl
Figure 80. Capital costs for 9- and 18-min. GAG
'empty bed contact times.
(J.C.Clark, 1979)
Costs for these package GAC columns are based on the use of cylindri-
cal, pressurized, downflow steel contactors designed to operate manually at
50 psi. Housing costs are included. Not included are supply piping to the
GAC column and handling or conveyance systems for spent or regenerated GAC.
Construction costs for this size GAC package unit (to handle plant flows of
2,500 gal/day to 0.5 mgd) are given in Table 51.
Large Scale GAC Contactors--
For plants treating larger flows (1 to 200 mgd), Gumerman, Culp &
Hansen (1979) have developed cost estimates for gravity flow GAC contactors
(concrete and steel construction) and for pressure GAC contactors.
Concrete construction—Gravity flow GAC contactors are assumed to be
essentially Identical to gravity flow filtration structures. Construction
costs were developed for GAC bed depths of 5 ft and 8.3 ft, which provide
empty bed contact times of 7.5 and 12.5 minutes, respectively, at a water
application rate of 5 gal/m1n/sq ft (Tables 52 and 53, respectively). Costs
of these facilities Include the contactor structures cylinder-operated
butterfly valves, liquid and carbon handling piping with headers in a pipe
gallery, flow measurement and other instrumentation, master operations panel
and a housing building. Not included are costs for backwashing pumping, the
initial 3AC charge, spent or regenerated GAC handling outside of the contactor
pipe gallery and SAC regeneration and preparation facilities. It was assumed
that all GAC in a single contactor would be removed and replaced with regene-
rated GAC in a single operation. In turn, this requires that regeneration
facilities be designed to store both spent and regenerated GAC in quantities
equal to the amount in one contactor.
225
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TABLE 51. CONSTRUCTION COSTS FOR PACKAGE 6AC COLUMNS (7.5 m1n EBCT)
Cost Category
Excavation &
Site Work
Manufactured
Equipment
Concrete
Labor
Pumps, Valves &
Piping
Electrical &
Instrumentation
Housing
SUBTOTAL
Miscellaneous &
Contlnqencv
TOTAL COST
Source: Han
Plant Flow
1.7 gpm
2,500 qpd
$ 50
740
100
1,100
•*
500
600
5,100
8,190
1,230
9,420
17 gpm
25,000 qpd
$ 50
2,900
250
3,900
1,200
600
6,910
15,810
2,370
18,180
70 gpm
100tOOO qpd
$ 50
7,070
480
6,240
4,300
850
9,180
28,170
4,230
32,400
175 gpm
250^000 qpd
$ 80
14,600
580
9,500
6,400
1,100
10,300
42,560
6,380
48,940
350 gpm
500,000 qpd
$ 80
27,100
700
13,000
8,800
1,300
11,400
62,380
9.360
71,740
sen, Gumerman & Culp, 1979
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TABLE 52. CONSTRUCTION COSTS FOR CONCRETE GRAVITY CARBON CONTACTORS*
Total Contactor Volume (cu ft) and Area (sq ft)
ICU
Cost Category (so
Excavation &
SUework
Manufactured
Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical &
Instrumentation
Housing
SUBTOTAL
M1sc. & Contingency
TOTAL
Volume/Single Contactor
Cost/Single Contactor
ft) 700
ft) 140
$ 1,660
29.000
12.330
10.630
37.330
33.570
14,730
17,400
156.650
23,500
180.150
3bO ft3
(90.070
3,500
700
$ 3,050
62.660
24,880
18.360
81,410
108.700
42.250
40.480
381,790
57,270
439,060
875 ft3
$109.770
7.000
1.400
$ 4,660
86,130
38,330
27,710
138,800
206,130
42,250
70,590
614,600
92,190
706,790
1.750 ft3
$176.700
35,000
7.000
$ 13,670
335,690
87,850
67,650
327.870
597,380
109,050
291,940
1,831,100
274,670
2,105,770
3,500 ft3
$210.580
/O.OOO
14,000
$ 21,600
582,300
142,410
113,300
468,260
863.970
185.720
514.330
2,891 ,890
433,780
3,325,670
5,000 ft-
$237,550
140,000
28,000
t 36,630
1,080.360
253,520
193.160
920.890
1.463,150
291 .840
968,520
5.208,070
781,210
5,989,280
6,360 ft3
$290.460
* 7.5 mln EBCT; 5 ft GAC bed depth
Source: Gumerman,
Culp & Hansen. 1979
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TABLE 53. CONSTRUCTION COSTS FOR CONCRETE GRAVITY GAC CONTACTORS*
ro
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oo
Total Contactq
(cu ft) 1,160
Cost Category (sq ft) 140
Excavation &
Site Work
Manufactured
Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical &
Instrumentation
Housing
SUBTOTAL
Misc. S Contingency
TOTAL
Volune/Slngle Contactor
Cost/Single Contactor
$ 2,220
29,000
15,010
12,940
45, 4M)
33,570
14.730
17,400
170,320
25,550
195,870
580 ft3
$ 97,940
5,810
700
$ 4.080
62,660
30,300
20,690
99,170
108,700
42.250
40f480
408,330
61,250
469.580
1.450 ft-
$117,400
r Voluire
1 1,620
1.400
$ 6,210
86,130
51.180
38.800
168,990
206,130
42.250
70,b90
670,280
100,540
770,820
2,905 ft3
$192.710
cu ft) and Area (sq ft'
58, 160
7.000
$ 18,240
335.690
111.090
82,360
399.150
597,380
109.050
291,940
1,944,900
291,740
2,236,640
5,810 ft3
$223,660
116,200
14,000
$ 28.800
582.300
1«0,500
137,940
570,050
863,970
185,720
&14.330
3,063,610
459,540
3,523,150
8,300 ft3
$251 ,650
232.400
28,000
$ 48.770
1,080.630
308,640
235.150
1,159.990
1.463.150
291 .840
969,520
5.556,690
833,500
6,390,190
10,560 ft3
$290.460
* 12.5 m1n EBCT, 8.3 ft GAC bed depth
Source. Gumerman, Culp 4 Hansen, 1979
-------
_ Steel construction-These types of contactors are assumed by Gumerman,
Gulp & Hansen (1979) to be utilized when more than 30,000 cu ft of 3AC
contact volume 1s required. Costs were developed for such contactors
(-Iu ^c?ec! as °PP°sed to factory-built) of 20 and 30 ft diameters, each
with a GAC bed depth of 20 ft and an overall vessel height of 35 ft. System
hydraulics were sized for an application rate of 5 gal/m1n/sq ft, which
provides a 30 minute EBCT. Other conceptual design parameters are listed in
Table 54.
Steel vessels are constructed of factory- formed steel plates, erected
at the job-site. Units are provided with a nozzle-style underdrain; GAC 1s
removed as required for regeneration through multiple carbon drawoff pipes
in the underdrain support plates. Regenerated GAC is returned through a
piping system to the top of each contactor. Costs presented are for a
complete GAC contacting facility, Including vessels, face and interconnecting
piping, access walkways, cylinder-operated butterfly valves on all hydraulic
piping and manually operated ball- or knife-type valves on the carbon handling
system, flow control and other Instrumentation, master operations control
panel and a building to house the contactors.
Not included are costs for GAC supply punplng, surface wash and backwash
pumping, the initial GAC charge, spent or regenerated GAC handling 'acilities
(exclusive of the piping within the contactor building) or GAC regeneration
or preparation facilities. Estimated construction costs for gravity f'ow
steel GAC contactors are presented in Tables 55 and £6 for 20 and 30 ft
diameter units, respectively, both providing 30 minute EBCTs.
Pressure GAC Contactors--Gumerman, Culp & Hansen (1979) developed
construction costs for pressure GAC contactors constructed of shop-fabri-
cated steel tankage. Bed depths of 5, 10 and 20 ft were estimated, providing
enrnty ted contact times o* 7.58 15 and 30 minutes0 respectively, at a hydrau-
lic loading rate of 5 gal/min/sq ft. Conceptual design parameters are
listed in Table 57. The practical upper limit plant size for this type of
GAC contactor system is 20 to 25 mgd.
Costs are based upon downflow operation at a design working pressure of
50 psi using cylindrical ASME code pressure vessels, which are either 10 or
12 ft in diameter by 14, 23 or 33 ft in height, furnished with a nozzle-
style underdrain and designed for rapid removal of spent GAC and recharge of
virgin or reactivated carbon.
Estimated construction costs are presented 1n Tables 58, 59 and 60 for
7.5, 15 and 30 minute EBCTs, respectively, and are for complete GAC contacting
facilities. These Include vessels, cylinder-operated butterfly valves,
bui -
.
liquid and GAC handling face piping with headers in the ^c ""J^
?
the GAC columns are totally enclosed
229
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TABLE b4. CONCEPTUAL DESIGN PARAMETERS FOR STEEL GRAVITY FLOW GAC CONTACTORS; 20 FT GAC DEPTH*
Plant
Flow
(mgd)
10
50
100
200
Total Con
Bed Area
20 ft diam
1,570
7,850
15,700
31 ,400
tactor
(so ft)
30 ft diam
—
7,065
14,130
28,260
No. of Contactors
20 ft diam
5
25
50
100
30 ft dlair
--
10
20
40
Fotal GAC Volume, ft3
20 ft diam
31,400
157,000
314,000
628,000
30 ft diam
—
141,300
282,600
565,200
Plant Area
Requirements (sq ft)
26 ft cliam
6,500
33,000
66,000
126,000
30 ft diam
—
26,000
50,000
95,000
* 30 minute EBCT
Source: Gumerman, Culp & Hansen, 1979
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TABLE 55. CONSTRUCTION COSTS FOR STEEL GRAVITY FLOW GAC CONTACTORS*
Cost Category
Excavation & Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical &' Instrumentation
Housing
SUBTOTAL
Miscellaneous & Contingency
TOTAL
Volume/Single Contactor (ft1)
COST/SINGLE CONTACTOR
Total Contactor Volume (cu ft)
"31 ,4ti<5
$ 2,050
340,970
7,650
3,810
66,220
140,730
50,460
169,000
$ 780,890
117,130
$ 898,020
6,280
$ 179,600
157,000
$ 6,560
1,619,750
27,470
14,040
314,270
675,500
207,800
792,000
3,657,390
548,610
4,206,000
6,280
168,240
314,000
$ 11,600
3,170,980
47,290
24,370
584,390
1,437,110
406,820
1^584,000
7,266,560
1,089,980
8,356,540
6,280
167,130
628,000
$ 21,760
6,137,800
91,580
45,690
1,075,550
2,644,620
787,250
3,024,000
13,828,250
2,074,240
15,902,490
6,280
159,020
* 20 ft diameter GAC tanks; 30 minute EBCT
Source: Gumerman, Culp &
Hansen, 1979
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TABLE 56. CONSTRUCTION COSTS FOR STEEL GRAVITY FLOW SAC CONTACTORS*
Cost Category
Excavation & Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical & Instrumenta
Housing
SUBTOTAL
M1sc. & Contingency
TOTAL
Volume/Single Contactor,
cu ft
COST/SINGLE CONTACTOR
Total Contactor Volume (cu ft)
T4T, 30(T
$ 7,150
1,327,160
29,680
15,230
263,820
565,490
tion 170,640
624,000
$3,003,170
450,480
$3,453,650
14,140
$ 345,370
282,600
$ 13,140
2,595,980
56,180
28,690
488,740
1,092,710
332,910
1,200,000
$5,808,350
871S250
6,679,600
14,140
$ 333,980
565,200
$ 25,020
5,139,970
111,290
55,180
942,800
2,111,020
659,530
2,280,300
$11,324,810
1,698,720
13,023,530
14,140
$ 325,590
* 30 ft diameter GAC tanks; 30 minute EBCT
Source; Gumerman, Gulp & Hansen, 1979
Operating & Maintenance Costs Of GAC Systems
Major components of operating and maintenance costs include GAC replace-
ment (for losses incurred during backwashing, handling and reactivation),
GAC contactor operation, regeneration furnace labor and materials, fuel and
miscellaneous expenses. Of these, costs for GAC replacement are the most
significant (7% estimated losses during reactivation at more than 55£/1b),
followed by fuel (5,000 BTU/lb of GAC reactivated), regeneration furnace
labor and materials, then contactor operation.
Package GAC Columns--
Hansen, Gumernan & Culp (1979) estimated operation and maintenance
costs based on the conceptual design parameters given in Table 50, which
assume that GAC adsorber units can be preceded by filtration and that the
GAC would be replaced with virgin or regenerated carbon once per year.
232
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TABLE 57. CONCEPTUAL DESIGN PARAMETERS FOR PRESSURE GAC CONTACTORS
Plant
Flow
(mgd)
1
10
50
No. of
Contactors
2
12
60
Contactor
Diam. (ft)
10
12
12
Total Contactor
Area*** (sq ft)
157
1,357
6,786
Total Contactor Vol.*
(cu ft G> detention times }
7.5 mTii
780
6,790
33,930
15 min
1,570
13,570
67,860
30 m1n
3,140
27,140
135,720
Plant Area**
Requirements (sq ft)
1,750
4,800
21 ,000
* Volumes determined at bed depths of 5, 10 and 20 ft.
** Assumes that GAC contactors are totally enclosed.
*** GAC contactors sized for 5 gpm/sq ft application rates
Source: Gumerman, Culp & Hansen, 1979
IN)
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Backwashing is assumed once per week, but the facilities otherwise operate
essentially unattended, except for routine maintenance and monitoring the
performance of the 6AC column. No allowance for administrative or for
laboratory labor (other than for minimal routine quality assurance testing)
is included. Estimated operation and maintenance costs for the package 3AC
contactors are summarized in Table 61.
TABLE 58. CONSTRUCTION COSTS FOR PRESSURE GAC CONTACTORS*
Total Contactor Vol. 'cu ft) & Area (sq ft)
Tcu ft)
Cost Category (sq ft)
Excavation & Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical & Instrumentation
Housing
SUBTOTAL
Misc. & Contingency
TOTAL
Volume/Single Contactor, ft3
COST/SINGLE CONTACTOR
780
157
$ 530
49,010
2,190
1,130
8,500
15,250
15,630
32,550
$124,790
18,720
$143,510
390
$ 71,760
6,790
1,357
$ 1 ,440
409,290
5,650
2,830
55,200
135,310
82,910
125,160
817,790
122,670
940,460
565
78,370
33,930
6,786
$ 6,180
1,944,170
24,730
12,360
262,400
679,880
429,660
512,400
3, 871 ,780
580,770
4,452,550
565
74,210
* 5 ft GAC bed depth; 7.5 minute EBCT
Source: Gumerman, Culp & Hansen, 1979
Gravity Flow GAC Contactors - Concrete Construction—
Gumerman, Culp & Hansen (1979) estimated costs for this type of SAC
contactor (5 and 8.3 ft depths, which equate to 7.5 and 12.5 minute EBCTs,
respectively), which are given in Table 62. Building energy costs are for
heating, ventilating and lighting. Process energy is required for backwashing
234
-------
(once/day for 10 m1n at 12 gal/m1n/sq ft) and GAC slurry pumping during
carbon removal and replacement (assumes regeneration frequency of every 2
months and a slurry concentration of 3 1b of GAC/gal of water utilized).
Process energy requirements are essentially Identical for the two different
GAC depths.
TABLE 59. CONSTRUCTION COSTS FOR PRESSURE GAC CONTACTORS*
Total Contactor Vol. (cu ft) & Area (so rt'
(cu «7
Cost Category (sq ft)
Excavation & Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical & Instrumentation
Housing
SUBTOTAL
Misc. & Contingency
TOTAL
Volume/Single Contactor, ft
COST/SINGLE CONTACTOR
1,570
157
$ 530
55,460
2,190
1,130
8,990
16,780
15,680
41,850
$142,610
21,390
$164,000
785
$ 82,000
13,570
1,357
$ 1,490
452,720
5,650
2,830
58,570
147,490
82,910
163,000
914,660
137,200
1 ,051 ,860
1,130
87,660
67,860
6,786
$ 6,180
2,161,360
24,730
12,360
280,050
728,540
429,660
700,290
4,343,170
651,480
4,994,650
1,130
83,240
* 10 ft GAC bed depth; 15 minute EBCT
Source: Gumerman, Culp & Hansen, 1979
Maintenance material costs Include costs for general supplies, backwash
pump and GAC transport pump maintenance, instrumentation repair and other
miscellaneous items. The cost for replacement of GAC (lost during contactor
operation and GAC regeneration) is not included. Labor costs Include the
cost of operating the GAC contactorsT"backwashing pumps, GAC slurry pumps,
instrument and equipment repairs and supervision.
235
-------
Gravity Flow GAC Contactors - Steel Construction-
Operating and maintenance parameters are the same as for the GAC
concrete contactors. Backwash frequency was assumed to be once/day for 10
minutes at 12 gal/min/sq ft and the GAC regeneration frequency was assumed
to be every 2 months. Makeup carbon is not included in the annual operation
and maintenance costs, listed in Table 63~Tor both 20 and 30 ft diameter
columns (30 m1n EBCTs).
TABLE 60. CONSTRUCTION COSTS FOR PRESSURE GAC CONTACTORS*
Total Contactor Vol. (cu ft) & Area (sq ft)
leu ft)
Cost Category (sq ft)
Excavation & Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
Electrical & Instrumentation
Housing
SUBTOTAL
Misc. & Contingency
TOTAL
Volume/Single Contactor, ft
COST/SINGLE CONTACTOR
3,140
157
$ 530
77,300
2,630
1,240
10,340
18,500
16,420
79,050
$ 206,010
30,900
$ 236,910
1,570
$ 171,520
27,140
1,357
$ 1,400
749,560
6,780
3,110
67,370
221,730
87,100
303,420
1,440,460
216,070
1,656,530
2,250
154,140
135,720
6,786
$ 6,180
3,560,370
29,680
13,600
322,060
1,120,350
451,200
1,332,250
6,835,690
1,025,350
7,861,040
2,250
143,960
* 20 ft GAC bed depth; 30 minute EBCT
Source; Gumerman, Culp & Hansen, 1979
Pressure GAC Contactors--
Electrical energy requirements were developed assuming that this type
of GAC contactor serves both as a filter and adsorber. Backwashing require-
ments were assumed to be once/day for 10 minutes at a rate of 12 gal/min/sq
236
-------
TABLE 61. OPERATION AND MAINTENANCE SUMMARY FOR PACKAGE GAC COLUMNS
ro
CO
Plant Flow
_2£2L»
1.7
17
70
175
350
JU2L™
2,500
25,000
100,000
250S000
500,000
Enerq
Building
6,140
15,400
30,800
38,500
46,170
v (kWh/yr)
Process
120
1,200
4,840
9,690
24,210
Total
60 260
16C600
35 , 640
48,190
70 , 380
Maintenance
Material ($/yr)
$ 100
275
1,000
2,650
4,880
Labor
(hrs/yr)
100
100
160
210
260
Total
Cost* ($/yr)
$1,290
1,770
3,670
6,200
9,590
* Calculated using $0.03/kWh and $10.00/hr for labor cost
Source: Hansen, Gumerman & Culp, 1979
-------
ro
OJ
00
TABLE 62. OPERATION AND MAINTENANCE SUMMARY FOR GRAVITY GAC CONTACTORS
Total Con-
tactor Vol ,
(cu ft)
Electrical Energy (kWh/yr)
Building 1 Process J Total
Maintenance
Material
($/yr)
Labor
(hrs/yr)
Total Cost*
($/yr)
7.5 minute EBCT; 5 ft GAC bed depth
700
3,500
7,000
35,000
70,000
140,000
1,160
5,810
11,620
58,200
116,200
232,400
44,120
151,850
279,070
1,190,160
2,165,890
4,123,490
12.5
44,120
151,850
279,070
1,190,160
2,165,890
4,123,490
690
3,410
6,820
34,080
68,150
136,540
44,810
155,260
285,890
1,224,240
2,234,040
4,260,030
800
2,510
4,020
13,200
21,600
36,700
minute EBCT; 8.3 ft GAC depth
690
3,410
6,820
' 34,080
68,150
136,540
44,810
155,260
285,890
1,224,240
2,234,040
4,260,030
800
2,510
4,020
13,200
21,600
36,700
900
1,500
2,100
4,600
9,000
18,000
11,140
22,170
33,600
95,930
178,620
344,500
900
1 ,500
2,100
4,600
9,000
18,000
11,140
22,170
33,600
95,930
178,620
344,500
* Calculated using $0.03/kWh and $10.00/hr for labor cost
Source : Gumerman, Gulp & Hansen, 1979
-------
TABLE 63. OPERATION AND MAINTENANCE SUMMARY FOR STEEL GRAVITY GAC CONTACTORS*
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co
ID
Contactor
Diam. (ft)
20
20
20
20
30
30
30
GAC volume
(cu ft)
31 ,400
157,100
314,000
628,000
141,300
282,600
565,200
Electrical Energy (kWh/yr)
"BullcTing
666,900
3,385,800
6,771,600
12,927,600
2,668,000
5,130,000
9,750,000
Process
12,030
60,170
120,340
240,680
54,150
108,300
216,600
Total
678,930
3,445,970
6,891,940
13,168,280
2,722,150
5,238,300
9,966,600
Maintenance
Material
($/yr)
5,350
21,380
37,420
69,490
16,040
26,730
42,760
Labor
(hrs/yr)
3,000
7,000
14,000
27,000
6,800
13,500
26,000
Total Cost**
($/yr)
55,720
194,760
384,180
734,540
165,700
318,880
601,760
* 30 minute EBCT
** Calculated using $0.03/kWh and $10.00/hr for labor cost
Source: Gumerman, Culp & Hansen, 1979
-------
ft. Energy requirements are for backwash pumping, for pumping of spent GAC
to the on-site regeneration facilities and return. GAC was assumed to be
removed and replaced every 2 months. Energy for supply pumping to the GAC
contactors 1s not included, nor are costs for makeup GAC or on-site regenera-
tion. The contactors are assumed to be completely housed. Other parameters
are the same as for the preceeding types of large scale GAC contactors.
Annual operation and maintenance requirements for pressure GAC contactors
are listed in Table 64.
COSTS FOR REPLACEMENT GAC
Costs were developed by Gumerman, Culp & Hansen (1979) for purchase and
placement of virgin GAC for use in any of the above-discussed GAC contactors.
Figure 81 shows a curve for the total costs of purchase, delivery and replace-
ment of virgin GAC. This curve may be used to derive the complete cost of a
GAC contactor and to determine the cost of makeup GAC lost during contactor
operation and GAC regeneration.
COSTS FOR GAC REGENERATION
Gumerman, Culp & Hansen (1979) estimated costs for GAC reactivation
both off-site (when space limitations or volumes of GAC being regenerated do
not warrant installation of on-site equipment) and the several different
types of on-site GAC regeneration equipment.
Off-Site Regional GAC Regeneration - Handling and "ransportation
In addition to the capital equipment costs for ozonation and GAC
adsorption discussed above, when GAC is to be reactivated off-site it will
be necessary for the plant to have available carbon dewaterlng/storage bins.
Two different design configurations were used by Gumerman, Culp & Hansen
(1979) to develop cost estimates for these facilities. Storage bins of
2,000 cu ft and less are elevated, 12 ft diameter, 30 ft height, cylindrical
tanks with conical bottoms, field-fabricated of braced, 0.25 Inch, shop-
formed steel plate protected by a suitable coating system. Bins of 5.COC cu
ft volumes are elevated, 3-hopper, rectangular tanks. For larger storage
requirements, multiple units would be used.
Construction costs for such GAC dewaterlng/storage facilities are
listed in Table 65. Not Included in these costs are paving for the access
area nor for trucks necessary to haul dewatered GAC to the regional regenera-
tion facility.
A summary of operation and maintenance costs for off-site GAC reactiva-
tion is presented in Table 66. The regeneration plant is assumed to be
within ICO miles of the GAC-using facility. Annual fuel requirements for
transportation are based on 3.5 miles/gal diesel fuel consumption, and
maintenance materials for the trucks only were estimated at a unit cost of
$0.30/mi1e. Included in Table 66 are the costs for fuel, labor and mainten-
ance to load spent GAC from dewatered GAC storage tanks to 30 cu yd semi-
dump trailers/haul to the regeneration facility, unload, reload reactivated
240
-------
TABLE 64. OPERATION AND MAINTENANCE SUMMARY FOR PRESSURE GAC CONTACTORS
Total
Surface
Area (ft2)
157
1.357
6,786
Energy (kWh/yr)
"Process
916
7,967
39.746
Building
179,550
492,480
2,154,600
Total
180,470
500,450
2,194,350
Maintenance
Material
($/yr)
1,600
8,020
37,420
Labor
(hrs/yr)
2,000
3,500
7,500
Total Cost*
($/yr)
27,010
58,030
178,250
* Calculated using $0.03/kWh and $10.00/hr for labor cost
Source: Gumertnan, Culp & Hansen, 1979
-------
GAC from bulk storage, return to the treatment plant and discharge either to
on-site storage tanks or directly to the GAC contactors. It was also assumed
that all these operations would be accomplished within an 8-hr day. The
costs in Table 66 do not include the costs of regeneration at the regional
facility. These woulcTEe charged by the owner/operator at a rate probably
based on the reactivation equipment available, which are discussed below.
10'
10"
10=
(A
I
«rf
III
o
u
o
10'
1 I I I I It
104 105 106
GAC quantity - Ibs
10'
Figure 81. Material cost for GAC, including cost
for purchase, delivery and placement.
(Gumerrnan, Gulp & Hansen, 1979)
On-Site GAC Regeneration
Gumerman, Gulp & Hansen (1979) present details of capital and operation
and maintenance costs for multiple hearth, infrared and fluidized bed 3AC
regeneration equipment. Conceptual design parameters, construction costs
and operation and maintenance costs are presented in Tables 67 through 75
for each of the 3 types of equipment. All regeneration furnaces are assumed
242
-------
to be inside buildings, and operation is assumed to be 24 hours/day, 365
days per year.
TABLE 65. CONSTRUCTION CCSTS FOR OFF-SITE REGIONAL GAC REGENERATION --
ON-SITE HANDLING AND TRANSPORTATION FACILITIES
Cost Category
Excavation and Site Work
Manufactured Equipment
Concrete
Steel
Labor
Pipe & Valves
SUBTOTAL
Miscellaneous & Contingency
TOTAL
On-Site Storage Capacity (cu ft)
1,0'tifl
$ 210
3,240
1,170
5,630
12,090
1,380
23,720
3,560
$ 27,280
5,000
$ 370
13,050
1,750
30,900
29,430
3,830
79,330
11.9CO
$ 91,230
20,000
$ 1,470
50,600
6,360
122,500
123,640
14,990
319,560
47,930
$ 367,490
Source: Gunerman» Culp & Hansen, 1979
Kittredge (1980) sumnarized the economics of GAC regeneration and
described the costs estimated for a fluidized bed 3AC regeneration system
which has been installed at the Manchester Water Works, Manchester, New
Hampshire. This system has a designed operating capacity of 12.CCO Ibs/day
(500 Ibs/hr) of regenerated GAC and a projected total operating cost of
6.4<£/lb. The estimated annual operating costs for the Manchester system are
presented in Table 76. Notice that the cost of makeup GAC represents nearly
54% of the total direct costs and 43% of the total annual operating costs.
The need for makeup GAC is caused largely by losses Incurred during regenera-
tion. If the frequency of GAC reactivation could be lowered, a significant
savings in GAC operating costs would be obtained.
Kittridge concluded that GAC can be regenerated by several different
methods and options at costs ranging from 5
-------
ro
-£»
TABLE 66. OPERATION AND MAINTENANCE SUMMARY FOR OFF SITE REGIONAL GAC REGENERATION -
HANDLING AND TRANSPORTATION ONLY
GAC Regene
rated (lbs/yr)
30,000
150.000
500.000
1,000,000
3,000.000
Diesel Fuel* (gal/yr)
10 ml*
haul
5.7
28.6
97
194
582
25 ml
haul
14.2
71.4
243
486
1,430
100 ml
haul
57
286
971
1,943
>,829
Maintenance
Material ($/yr)
10 ml
haul
6
30
110
210
650
25 ml
haul
20
90
280
550
1,640
100 mi
haul
60
320
1,090
2.180
6.540
Labor** (hrs/yr)
10 nl
haul
6.8
34
116
232
780
25 ml
haul
11
55
187
374
1.200
100 nr
haul
14
70
238
476
1,428
Total Cost***($/yr)
10 ml
haul
80
380
1.310
2,620
8.710
25-ml
haul
140
670
2.260
4,510
14.280
100 ml
haul
230
1,150
3.910
7.810
23.440
* Based on 3.5 miles/gal for 30 cu yd semi-dump truck
** Labor for loading and unloading GAC and for hauling
*** Calculated using dlesel fuel at $0.45/gal and labor at $10.00/hr
* All distances are one way
Source: Gumennan, Culp & Kansen, 1979
-------
of GAC treatment (18 m1n EBCT) including GAC regeneration, decreases from
13.3
-------
TABLE 68. CONSTRUCTION COSTS FOR MULTIPLE HEARTH GAC REGENERATION
Cost Category
Manufactured Equipment
Labor
Pipe & Valves
Electrical and
Instrumentation
Housing
SUBTOTAL
M1sc. & Contingency
TOTAL
Furnace Hearth Area (sq
27 37 47
$220.660
117,720
8,330
8,290
109,670
$ 464,670
69.700
$ 534,370
$275,830
147,150
8,330
3,340
109,670
549.320
82.400
631,720
$ 519,830
273,280
8,330
8,340
124,230
934,010
140,100
1,074,110
359
$ 647,140
346,850
14,480
9,190
175.100
1,192,760
178,910
1,371,670
ft)
732
tl, 039, 660
557,060
23,450
14,930
245,790
1,880,890
282,130
2,163,020
1.509
$1,304,880
704,210
48,800
26,980
334.460
2,419,330
362.900
2,782,230
Source: Gumerman, Culp & Hansen, 1979
-------
TABLE 69. OPERATION AND MAINTENANCE SUMMARY FOR MULTIPLE HEARTH GAC REGENERATION
Effective
Hearth
Area, ft2
27
37
147
359
732
1,509
Regenerated
GAC,
Ibs/day
1,224
1,670
6,624
13,680
32,400
66,960
Flectrical Energ
Building
14,630
14,630
17,550
23,400
35,100
46,800
Process
261,400
326,750
424,770
588,150
849,550
1,307,000
y, kWh/yr
Total
276,030
341,380
442,320
611,550
884,650
1,353,800
Natural Gas
(scf/yr x 106
5.80
7.72
26.2
48.26
108.40
207.75
Maintenance
Material
($/yr)**
$ 2,990
3,740
6,410
8,550
11,760
16,040
Labor
(hrs/yr'
900
950
3,400
6,200
lO.bOO
17,000
Total Cost*
($/yr)
$ 27,810
33,520
87,740
151,630
284,220
496,730
* Calculated using $0.03/kWh, $0.0013/scf and $10.00/hr for labor.
** Makeup GAC costs are not included
Source: Gumerman, Gulp & Hansen,, 1979
-------
ro
.£»
00
TABLE /I. CONSTRUCTION COSTS FOR INFRARED GAC REGENERATION FURNACES
Cost Category
Manufactured Equipment
Labor
Pipe & Valves
Electrical & Instrumentation
Housing
SUBTOTAL
Miscellaneous & Contingency
TOTAL COST
2,400
$160,000
48,000
3,500
21,000
21,000
$ 2b3,500
38,030
$ 291,530
Furnace Ca
16,800
$360,000
100,000
5,500
53,000
60,000
578,500
86,780
paclty (lbs/da\
38,400
$ 620,000
174,000
7,500
81,000
82,000
964,500
144,680
665,280 1,109,180
J
60,000
$ 940,000
235,000
10,000
113,000
149,000
1,447,000
217,050
1,664,050
Source: Gumerman, Culp & Hansen, 1979
-------
TABLE 72. OPERATION AND MAINTENANCE COST SUMMARY FOR INFRARED GAC REGENERATION FURNACE
GAC Regene-
ration Rate
(Ibs/day)
2,400
16,800
38,400
60,000
Enerqy (kWh/yr
Budding
7,540
39,300
61,300
94,300
Process
701,680
4,522,000
10,206,000
15,820,000
Oldl
709,220
4,561,300
10,267,300
15,914,300
Maintenance \
Material ($/vr)\
8,900
21,000
28,000
33,600
Labor \Total Cost*
hrs/yr) \ ($/vr)
2,380
4,900
9,380
13,300
53,980
206,840
429,820
644,030
* Calculated using $0.03/kWh and $10.00/hr for labor
Source; Gumerman, Culp & Hansen, 1979
IS}
.£»
IO
-------
TABLE 73. CONCEPTUAL DESIGN PARAMETERS FOR GAC REGENERATION -
FLUIDIZED BED PROCESS
GAC Regeneration
Capacity (Ibs/day)
6,000
12,000
18,000
24,000
Reactor Bed
Area (sq ft)
4
8
12
16
Housing
Requirements (sq ft)
1,400
1,800
2,200
2,600
Source; Gumerman, Gulp & Hansen, 1979
TABLE 76. SUMMARY OF ESTIMATED OPERATING CCSTS - FLUIDIZED BED SAC
REGENERATION SYSTEM, MANCHESTER. N.H. WATER WORKS
Item Costs:
Makeup GAC
Labor
Maintenance
Fuel
Power
Steam
Water
Total Direct Cost
Depreciation
Insurance & Taxes
Administration & Overhead
Total Indirect Costs
Total Annual Operating Cost
$/yr
115,500
9,450
13,000
21,000'
7,560
11,740
36,290
$ 214,540
39,250
7,850
7,850
54,950
$ 269,490
4/1 b
2.75
0.22
0.31
0.50
0.18
0.28
0.86
5.11 tf/lb
0.92
0.19
C.19
1.30
-------
TABLE 74. CONSTRUCTION COSTS FOR 6AC REGENERATION - FLUIDIZED BED PROCESS
Cost Category
Manufactured Equipment
Labor
Electrical & Instrumentation
Housing
SUBTOTAL
Miscellaneous & Contingency
TOTAL COST
GAC Regeneration Capacity (Ibs/day)
6,000
$ 570,000
180,000
10,000
60,000
$ 820,000
123,000
$ 943,000
12,000
$ 650,000
205,000
11,000
75,000
$ 941,000
141, IbO
$1,082,150
18,000
$ 710,000
225,000
11,000
90,000
$1,036,000
155,400
$1,191,400
24.000
$ 755,000
240,000
12,000
106,000
$1,113,000
166,950
$1,279,950
Source: Gumerman, Culp & Hansen, 1979
-------
TABLE 75. OPERATION AND MAINTENANCE COST SUMMARY FOR GAC REGENERATION - FLUIDIZED BED PROCESS
GAC Regene-
ration Rate
(Ibs/day)
6,000
12,000
18,000
24,000
Process
Energy
(kWh/yr)
131,400
262,800
394,200
525,600
Natural
Gas
(scf/yr)
6,830,700
13,660,000
20,440,000
27,322,860
Maintenance
Material
($/yr)
$ 15,540
17,940
19,400
20,860
Labor
(hrs/yr)
2,400
2,650
3,050
3,330
Total Cost*
($/vr)
$ 52,360
70,080
88,300
105,450
* Calculated using $0.03/kWh, $0.0013/scf for natural gas and $10.00/hr for labor
Source
: Gumerman, Culp & Hanson, 1979
ro
r\>
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on
CO
TABLE 77. COSTS OF GAG TREATMENT (18 MIN EBCT), INCLUDING REGENERATION
Type of
GAC unit
Pressure
Pressure
Gravity,
steel
Gravity,
steel
Type of GAC
Regeneration
off -site
on-s1te, IR
furnace
on-s1te, mul-
tiple hearth
on-s1te, mul-
tiple hearth
Size of Treatment
Plantj mgd
2
20
75
110
Total Annual
Cost*
$ 117,920
$ 681,180
$2,097,950
$2,919,760
tf/1,000 gal
treated
23.1 t
13.3 t
10.9 t
10.4 t
* Includes amortized capital costs @ 8% (20 yrs), labor @ $10.00/hr, electricity
@ 3tf/kWh and maintenance materials; also natural gas cost @ 0.175 tf/scf and
dlesel fuel @ 45^/gal, when necessary.
Source; Clark, Gulp & Gumerman, 1980
-------
the total costs decrease much more slowly with reactivation periods from 3
months (lU/1,000 gal) to 8 months (7<£/l,COO gal). Thus, pretreatment
concepts which can extend the GAC reactivation period beyond 2 months will
have a significant cost-savings impact on the GAC treatment process.
TABLE 78. ASSUMPTIONS FOR 18 MINUTE EBCT GAC ADSORPTION
Item
Number of Contactors
Diameter of Contactors (ft)
Depth of Contactors (ft)
Volume of GAC/Contactor
(cu ft)
Design Capacity (rrqd)
"T"
3
8
13
653
5
6
12
13
1,469
10
12
12
13
1,469
100
40
20
14
4,396
150
60
20
14
4,396
Source: Clark, Culp & Gumerman, 1980
TABLE 79. AMORTIZED CAPITAL AND OPERATING & MAINTENANCE COSTS FOR
GAC ADSORPTION (18-MINUTE EBCT). t/1.000 GALLONS
Item
Amortized Capital Cost
Operating & Maintenance
TOTAL COSTS
Desian Capacity (mgd)
~~T~
29.4
22.1
51.5
5
12.7
12.6
25.3
10
9.8
10.8
20.6
100
4.9
7.4
12.3
150
4.6
7.1
11.7
Source; Clark, Culp & Gumerman, 1980
COST SAVINGS WITH BAC SYSTEMS
As stated earlier, one primary benefit of optimizing biological activity
in GAC adsorber systems involves extending the operating time of GAC adsor-
bers, thus effecting savings in costs for regeneration. In some BAC systems
operating in European drinking water treatment plants, operating lives of
GAC adsorbers are extended 2 to 5 times (Sontheimer, 1979) by incorporating
chemical preoxidation with ozone before GAC adsorption. Schalekamp (1979)
noted that in treating Swiss lake waters for potable purposes, the SAC
operating tine is only 6 months if preoxidation with ozone is not used.
When ozonation is placed before GAC filtration/adsorption, the GAC can be
used for about 3 years, an increase in longevity before thermal regeneration
is required of a factor of five.
254
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34-
30-
o>
o
o
o
24- •
in
O
o
o
*«
u
3
•o
O
16 •
10
8-
1 234567
months between reactivation
Figure 82. Production cost for GAC adsorbers vs
period between reactivations.
(Clark, Gulp & Qumerman, 1980)
The question arises, however, as to the cost-effectiveness of Installing
a high capital cost, energy-Intensive ozonation system ahead of SAC adsorption
to attain the cost savings which result from extending the period of GAC
use. In order to quantify these savings 1n GAC regeneration, a basis for
comparison and several operating assumptions was developed by J.C. Clark
(1979).
Ttie primary direct cost benefit of the BAG process relative to conven-
tional use of GAC with frequent reactivation is the reduction 1n the number
of reactivation cycles required per year, ""emple, Barker & Sloane (1977)
have shown that the majority of GAC operating expenses can be attributed to
reactivation. For a typical United States water supply utility, reactivation
costs account for approximately 70 to 75% of the GAC adsorber operating
costs when six reactivation cycles are scheduled annually (2-month GAC
life).
255
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Accepting this cost basis and drawing upon the Information about the
performance of BAG presented above, a useful operating assumption for making
these calculations is that the maximized biological activity in the carbon
bed enhanced by chemical preoxidation with ozone (the highest initial cost
chemical oxidant currently in use) will allow a reduction in the number of
reactivation cycles from six to one annually for the attainment of comparable
water quality (GAC useful life extended from 2 months to 1 year).
For the activated carbon adsorber operation, this decrease in number of
reactivation cycles per year will cut annual operation costs by about 50%.
This calculation is based on two key assumptions: first, that each of the
six reactivation cycles adds about 12% (70 to 75% divided by 6) to the
annual operating cost; second, that a utility required to reactivate its GAC
fill only once per year will be unlikely to install a smaller, therefore
less efficient, reactivation furnace and carbon transfer facility, and
therefore will face higher costs for a single off-site reactivation cycle
per year than a facility having its own on-site reactivation system and
which reactivates six times per year. Instead, it 1s assumed that the
utility requiring only one reactivation per year would choose to send its
GAC out for reactivation.
The use of chemical preoxidation with ozone will increase the plant's
operating costs, thereby offsetting to some extent the savings achieved by
the reduction in reactivation frequency. The anount of this increase depends
upon whether the plant treatment process already included ozone generation
equipment and contact chambers before the introduction of GAC and also on
the level of preozonation dosage required for the particular raw water
quality to be treated prior to GAC adsorption.
A Hypothetical Case Example (J.C. Clark, 1979)
To illustrate the cost savings more accurately and to avoid the generali-
zations in the introductory section above, an exanple water treatment plant
is used in this section to apply the principles directly. Since one objective
of this report is to assess the potentials of transferring this recently
developed European water treatment practice to the United States, a prototype
U.S. water treatment plant is used as an example with the technical assump-
tions based upon successful European experiences with BAG.
The example plant is described fully 1n an EPA report (Temple, Barker &
Sloane, 1977). Briefly, the plant supplies a cotrmunity of 265,000 populaticn
with an average daily production of 50 mgd. The maximum plant capacity is
75 mgd and its treatment process includes conventional prechlorlnation,
coagulation, sedimentation, rapid sand filtration and post-chlorination.
The capital costs for this plant to add GAC in a post-filtration
adsorber/contactor mode to achieve 9 minutes empty bed contact times have
been estimated at $10 million, whereas simply replacing the sand with GAC in
existing filter beds would cost $5 million. These costs include carbon
transfer systems and reactivation furnaces. The associated annual operating
costs, assuming 6 reactivation cycles, are estimated to be $1.1 million for
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GAC post-contactors and $1.3 million for replacement of sand by GAC, Including
debt service.
The capital costs of adding an ozone treatment system capable of
applying ozone at dosages up to 2 mg/1 at 50 mgd are shown 1n this same
report (Temple, Barker & Sloane, 1977) to be $2.4 million. Operating costs
for the full ozonatlon system (air treatment, ozone generation, contacting
and off-gas destruction) are estimated to total $50,000 per year, Including
the savings likely to result from reduced chlorine dosage.
Applying the cost savings attributable to the combination of ozonation
followed by GAC (post-contactor mode) to BAG, a new set of cost calculations
can be made. The basic design assumptions are that the plant would install
an ozonation system capable of applying up to 2 mg/1 of ozone at 50 irgd and
add GAC 1n the existing sand filter beds, providing a 9 minutes empty bed
contact time. Moreover, the operating costs would include one annual reacti-
vation cycle off-site rather than six cycles on-s1te.
The resulting capital cost for the ozonation + GAC system would be
about $5.5 million, slightly more than the $5.0 million cost of the conven-
tional GAC system using existing sand filter beds.
Even though the capital costs are a bit higher, the savings are substan-
tial on the operating cost side. The annual 3AC system operating costs
would decrease by between $500,000 and $600,000, while the ozonation costs
would increase by only some $50,COO. Thus annual operating savings of
between $450,000 and $550,000 would be achieved under the assumed conditions.
When both operating costs and the annual debt service expense on the
capital expenditures are combined, the ozone/GAC system would add $1.1
million per year to the total annual costs of this typical water utility.
This compares to $1.6 million per year for the conventional GAC system
discussed above, showing the combined ozone/GAC system to be about 302 less
expensive.
Energy Considerations (J.C. Clark, 1979)
Both the reactivation of GAC and the generation of ozone are energy
intensive processes. Although the amount of energy needed to reactivate a
pound of GAC varies according to furnace type and operating practice, nost
estimates are in the range of 3,500 and 7,000 BTUs per pound, with 5,000
BTUs per pound being a frequently estimated average. Estimates of electricity
use for the generation of ozone are generally 1n a narrower range, with 10.5
kwhr per pound of ozone generated (from air) being a currently accepted
figure. (This Includes the energy required for air preparation, ozone
generation, controls and instrumentation, but not contacting.) Since 11,000
BTUs are needed to generate one kilowatt-hour 1n a typical mixture of the
various types of electric generating stations (which generate electricity at
a fuel efficiency of about 33%), each pound of ozone generated requires the
use of 115,500 BTUs of fossil fuel energy (although nuclear generation of
electricity is a lower energy cost substitute).
257
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The conventional use of GAC with 6 reactivation cycles per year and 2.6
million pounds of GAC per cycle would use 78 billion BTUs annually, plus the
energy needed to produce the 1.1 million pounds of makeup GAC, which 1s
estimated to require another 11 billion BTUs. Thus the total energy use by
the conventional GAC system would be 89 billion BTUs annually.
By contrast, the example ozone/GAC system fuel use would consist of one
annual reactivation cycle for the activated carbon, rather than six, plus
the energy used by the ozonatlon equipment. The single GAC reactivation
would account for 13 billion BTUs plus 2 billion BTUs for manufacturing the
makeup GAC. The ozone generation would require 1.8 million kilowatt-hours
annually, or 20 billion BTUs of primary fuel energy. The total fuel use for
the example ozone/GAC system thus totals 36 billion BTUs annually.
By the measure of energy use, the ozone/GAC system clearly 1s more
efficient under these assumptions. The use of 36 billion BTUs annually 1s
only 402 of the use by the conventional GAC system of 89 billion BTUs. If
the GAC reactivation can be prolonged to every two years (as is anticipated
at the Dohne plant, MUlhelm, Federal Republic of Germany), the total savings
would be even more substantial. On the other hand, if the amount of ozone
required for preoxidation should be 5 mg/1 Instead of 2 mg/1 to prolong the
GAC reactivation time to one year, then the energy costs for ozone/GAC would
be about equal to those for GAC alone which would require 6 reactivations
per year. In addition, if the types of organic materials present In the
specific raw water to be treated already are biodegradable, such that chemical
preoxidation with ozone is not required and a cheaper oxidant can be used to
provide the same extension of GAC operating life before reactivation is
required (one year), additional cost savings will be effected.
Sensitivity Analysis and Inflation Effects (J.C. Clark, 1979)
The preceding text has noted several assumptions about the operation
and costs of a BAC system operated with chemical preoxidation using ozonation,
as well as the conventional GAC system against which 1t is being compared.
Since many of these assumptions may vary somewhat in future circumstances,
the findings shown above need to be discussed 1n terms of their sensitivity
to key assumptions. In addition, since 1t appears likely that inflation
will continue, Its effects on tradeoffs between capital investment and
operating costs is important to consider 1n maximizing the benefits of
biological activated carbon systems.
The basic conclusions noted above were that the ozone/BAC system was
30% less expensive on an annual basis than the conventional SAC system, and
that the ozone/GAC design used 612 less fuel. More specifically, the annual
costs were lower due to smaller operating and maintenance costs which, nore
often than not, offset the higher capital costs of the ozone/GAC combination.
This offsetting effect then was annual1 zed to show the combined effect of
the capital, operating and maintenance costs in the first year of the project.
Although these cost estimates have been considered above as If they
were exact figures, they are more accurately considered as midpoints of a
range of likely future costs. This range depends largely on specific
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design assumptions which, in turn, depend upon regeneration frequencies,
local differences in sites, existing plants, raw water quality, desired
finished water quality, etc. The range of costs can vary under a typical
set of characteristics to plus or minus 2C% of the point estimates noted
above. This range is enough to alter the conparison substantially, depending
upon these factors.
A more likely influence on costs though, 1s the pace of inflation in
coming years. The basic direction of inflation increases will influence the
comparison between the ozone/GAC treatment combination and conventional GAC
systems and favors the ozone/3AC system. Inflation will Increase future
operating costs, while capital costs will remain as fixed amounts based on
investments made in a particular year.
More specifically, while the ozone/GAC system 1s 3C% less expensive in
the first year (as shown above), it would become 40% less expensive in the
10th year with an average 7% annual inflation rate. If inflation should
rise at a higher average rate, the ozone/GAC combination will be favored
even more substantially.
Effect Of Operating Variables Cn GAC And BAG Treatment Costs
Clark and Dorsey (1980) reviewed the cost data developed by Gumerman,
Culp & Hansen (1978) to examine the influence of changes in the level of
operating variables on the cost of GAC treatment (18 m1n EBCT). Losses cf
GAC per regeneration cycle of 6% were assumed. Most variables were fcund to
have a greater impact on smaller than on larger treatment plant costs. The
only exceptions to this finding were reactivation frequency and capital
cost.
Those variables having the greatest effect on operation and maintenance
costs are the system size, reactivation frequency, activated carbon loss and
GAC cost. Power cost has a greater impact on smaller systems than do some
of the other variables. Figure 83 shows a total GAC system cost versus GAC
reactivation frequency for a 100 mgd post-filter GAC adsorption system at 3
different 3AC costs. Assuming 6C<£/lb for the 3AC being reactivated at a
frequency of 1.1 months, the total system operating cost is about 16<£/1,000
gal (point Pi). If GAC cost Increases to 80i/lb, the reactivation period
would have to increase to 1.7 months (point Pa) for total costs to remain
constant.
Figure 84 shows an analysis made by Clark & Dorsey (1980) in which
ozone treatrent is followed by GAC adsorption. Total production costs in
(t/l,COO gal are plotted against GAC reactivation frequency. These authors
concluded that if the system initially requires regeneration each month
without ozonation, then the addition of ozone would have to decrease the
reactivation frequency to 2.6 months to break even (pay for the cost ot
installing ozonation facilities). However, if the system w thout ozonation
has an initial GAC reactivation frequency of 2 months, Clark & Dorsey cone ude
that no break-even point exists to justify the costs of addition of ozonation.
259
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35-
OJ
o
o
o
in
O
u
c
o
*«
o
3
•o
O
1.00/lb GAC
0.80
0.60
0.5 1.0 1.5 2.0 2.5 3-0 3.5 4.0
reactivation frequency, months
Figure 83.
Total production cost vs. reactivation frequency
for SO.60, 0.80 11.00/lb GAC for 100 mgd
contactor system.
(Ciark & Dorsey, i960)
Practical Examples
Drinking Water Installations —
Dohne Plant, MUlheim, Federal Republic of Germany—Heilker (1979) has
noted that a BAG process (preozonation, flocculation, sedimentation, ozona-
tion, dual media filtration, GAC, ground passage and safety chlorination)
has replaced the older process (breakpoint chlorination, flocculation,
sedimentation, GAC, ground passage and safety chlorination). The older
process used breakpoint chlorination for removal of ammonia; the newer
process removes ammonia biologically.
Heilker's statement regarding cost comparisons between the two processes
1s as follows:
"The treatment plants in the Cohne waterworks have been operating for
more than 1.5 years using the revised process. The drinking water
quality has been significantly improved without increasing treatment
costs. The Dohne plant Is less susceptible to disturbance and as a
result can be operated with 50% of the former staff size. The activated
carbon filter runs are 3 to 5 times longer than before."
260
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ID
CO
o
o
o
o
o
c
o
*«
o
3
•o
o
20- -
15- -
10- -
8 mg/L
6 mg/L
4 mg/L
2 mg/L
GAC without ozone
•4-
24 6 8 10 12
reactivation frequency, months
14
Figure 84. Cost of ozone and GAC in combination.
(Clark & Dorsey, 1980)
Dohne's new process required doubling the height of the GAC adsorbers,
adding ozone generation facilities and pure oxygen evaporators (for addition
of oxygen after filtration and before GAC adsorption), all of which increased
costs. On the other hand, savings were obtained in the amount of chlorine
used (10 to 15 mg/1 dosages for prechlorination were eliminated), GAC regene-
ration costs (every 4 months with the old process, 1 to 2 years with the new
process), and labor costs (half the former plant operating staff).
Windhoek Process. South Africa—Van Leeuwen (1979) has indicated that
the 1 mgd process used at Windhoek, South West Africa to reclaim sewage for
potable purposes, since 1968, involves breakpoint chlorination 'ollowed by
2-stage GAC adsorption. Under these circumstances, the GAC must be regenera-
ted every 90 days. By contrast, when breakpoint chlorination was replaced
by ozonation (8.5 to 10.5 mg/1 applied dosage at 95% ozone transfer efficien-
cy) 1n a 1 mgd pilot plant process, the 3AC was operated for at least one
year without requiring reactivation. This resulted in overall process cost
savings of 13% at 1 mgd, and are projected to reach 24% at 10 mgd. These
cost savings are dependent upon the clarification agent used, lime treatment
being more costly than ferric chloride. Longer periods of GAC use without
reactivation (greater than 1 year) are expected to result 1n even higher
cost savings.
261
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Inclusion of the ozonatlon unit process added 1.8 to 3.3£/cu m (6.81 to
12.49<£/1,000 gal) In costs to the 1 mgd treatment line. This caused a
decrease 1n GAG operating costs of 2.5 to 5
-------
SECTION 12
ENGINEERING DESIGN CONSIDERATIONS FCR BAG SYSTEMS
INTRODUCTION
As a first step, the parameters to be considered in designing biological-
ly enhanced GAC systems are the saire as those which must be taken into
consideration when designing granular activated carbon beds or columns to
act purely as adsorbers. However, there are several additional parameters
related to optimizing the biological aspects of specific organic materials
present in the system being treated which must be considered. These include
control of pH and DO levels, pretreatment to remove substances toxic to
microorganisms, and possibly increased frequency of column backwashing
because of increased biological growths.
Initially, adsorption isotherms should be measured for the organic
components present in the wastewater and which are desired to be rerroved.
This can be accomplished by the procedure described by Rodman, Shunney &
Perrotti (ly78). Several concentrations of the wastewater to be treated are
allowed to cone to equilibrium with weighed samples of pulverized GAC. The
equilibrated mixtures are filtered and the 'iltrates are analyzed for the
constituents of concern. Results are plotted on log-log paper, with the
abscissa being in units of Impurities remaining in solution and with the
ordinate being in units of impurities adsorbed per unit weight of 3AC.
The phrase "allowed to come to equilibrium" should not be viewed as a
simple matter of several minutes, several hours, or even several days. Peel
& Benedek (1980a) found that the adsorption of phenol required up to 3 weeks
to attain equilibrium, and that o-chlorophenol required up to 5 weeks to
attain equilbrium. Sufficient time must be allowed for equilibrium conditions
to be attained, in order to result in an accurate measure of adsorption
isothems. The required time to attain equilibrium conditions can vary,
depending upon the nature of the specific organic materials present.
Adsorption isotherms provide a good estimate of the effectiveness of
activated carbon to adsorb the impurities present in the wastewater to a
given level. They also provide an indication of the maximum amount of
impurities which can be adsorbed by the GAC being tested. Because of this,
adsorption isotherms are helpful in selecting the most suitable type of GAC
to adsorb specific impurities. However, it must be recognized that adsorption
isothems are equilibrium measurements, and will not indicate how the GAC
will perform during continuous operation. Continuous flow studies on pilot
plant scale are the best way to obtain data from which to design full scale
plant adsorbers.
263
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It should also be borne in mind that wastewaters which contain high
levels of readily biodegradable organic materials usually can be treated
biologically at much lower cost than by GAC adsorption. Appropriate biologi-
cal treatment of high strength, highly biodegradable wastewaters also will
lower the amount of GAC subsequently required for adsorption of refractory
contaminants, thereby lowering overall system costs.
After adsorption isotherms have been determined, empty bed contact
times can be developed for the type of GAC best suited to the adsorption of
the particular pollutants to be removed from solution. At this point, those
factors which will affect biological growth and proliferation should be
considered.
PARAMETERS AFFECTING BIOLOGICAL GROWTH IN GAC MEDIA
The major parameters to be considered in optimizing BAG systems for
treatment of industrial wastewaters are:
(1) Presence of materials which are toxic to biological growths (pesti-
cides, heavy metals, etc.) — if present, the wastewater must be
pretreated to remove or destroy them,
(2) Chemical nature of materials to be removed (organic* and/or ammonia) —
necessity for chemical preoxidation of organic constituents versus
preaeration or preoxygenation,
(3) GAC pore size distribution — presence of a high proportion of rracropores
to house bacteria,
(4) Necessity for sand or other "inert" media filtration before GAC adsorp-
tion -- for removal of insoluble nateHals generated by preoxidation
and as support media for possible biological activity,
(5) Need for supplemental oxygenation before GAC adsorption — to increase
rate of formation of C02 and maintain aerobic conditions,
(6) Extension of empty bed contact tiire over that determined by adsorption
isotherms — usually 11 to 18 minutes EBCT will be required for BAC
versus 5 to 15 minutes for GAC acting by adsorption only,
(7) Initial period of operation (several days) required to develop and
establish biological growths. Nitrifying organisms require several
weeks to develop, and may not develop at all if overpowered by other
species which may be present. Necessity for biological seeding and/or
adaptation of biological organisms to organic substrates to be removed
from solution. Possible need to add nutrients (nitrogen and/or phospho-
rus) if feed solutions are deficient,
(8) pH must be maintained between 5 and 9 (preferably between 6 and 8) for
optimum biological activity,
264
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(9) Methods for controlling BAG media — analytical monitoring for dissolved
organic carbon, TOC, COe (produced biochemically), dissolved oxygen,
ammonia, nitrate, nitrite, bacterial levels In 3AC effluents, etc.,
(10) Determination of 3AC regeneration parameters — breakthrough of surro-
gates or specific compounds,
(11) Backwashing of 3AC and prefilters ~ need for air scouring 1n addition
to water backwashing,
(12) Materials of construction,
(13) Safety of GAC systems.
Each of these design parameters will be discussed in more detail
below,
DISCUSSION OF SPECIFIC DESIGN PARAMETERS
Raw Water Con-position
There are three important parameters of the raw water being considered
for treatment by biologically enhanced granular activated carbon systems.
These are:
(a) The toxicity of the organic materials present to the biological
organisms present in the support media,
(b) The bicdegradability of the organic materials present (with or
without a preoxidation treatment step),
(c) The pH of the aqueous solution to be treated.
If materials are present which are toxic to biological growth, they
must be removed from solution in order that biological growths 1n the inert
media filters and GAC adsorbers rray survive and proliferate. Common toxicants
include heavy meta1ss cyanides and certain organics such as persistent
pesticides (polyhalogenated materials).
If the organic materials present are not biodegradable but are adsor-
bable, they will be adsorbed by 3AC. However, as soon as the GAC medium
becomes saturated with these compounds, they will break through and reactiva-
tion will be necessary. On the other hand, 1f chemical oxidation will
render these refractory organics even slowly biodegradable, then they can
become nutrients for the bacteria present. As a result, the useful adsorption
life of the GAC adsorbers will be extended.
Preliminary batch testing using ozonation will indicate whether a
chemical preoxidation step will enhance the biological removal of organic
contaminants. The blodegradabillty of the wastewater to be treated should
be measured (say by oxygen uptake) before ozonation and then again after
ozonation at various dosage levels. If the biodegradabHUy does not. increase
265
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upon oxidation, then biological activated carbon will be no more effective
than treatment with GAC acting as an adsorber alone.
In conducting these preliminary biodegradation batch tests, care
should be taken to use microorganisms which have become acclimated to the
oxidized organic contaminants.
Biological growths occur best at pH 6 to 8 and not at all at high or
low pH values. Therefore, acid or alkaline wastewaters will have to be
adjusted to this pH range before passage through GAC. In addition, if
pretreatment of the wastewater is necessary, this pH factor must be
considered.
Type of GAC
The GAC utilized for treating the specific wastewater should have a
high adsorptive capacity for the particular organic materials present. In
addition to this, the work of Eberhardt, Madsen & Sontheimer (1974) at the
Bremen, Federal Republic of Germany waterworks showed that GAC which contained
a high proportion of macropores removed a higher proportion of DOC from
solution than did GAC containing a smaller percentage of macropores. Normal-
ly, macropores in GAC constitute about U of the total surface area. The
more effective GAC used by Eberhardt, Madsen & Sontheimer (1974) contained
about 2% macropores. At biological equilibrium, the 2% iracropore GAC removed
about 50" of the DOC present, compared with only 25% to 33% DCC removal
using GAC containing 1% nacropores.
These data indicate that research should be conducted on GAC which has
been designed to contain even higher levels of macropores.
Necessity For Filtration Before GAC Adsorption
In European drinking water treatment plants, it has been noted that
ozone oxidation causes "nlcroflocculation" of dissolved organic materials.
This is explained on the basis of oxidative formation of carboxyl, alcohol
and aldehydic groups, which are capable of forming hydrogen bonds with
similar groups present in other organic molecules (Maier, 1979). Such
hydrogen bonding effectively increases the molecular weights of dissolved
organic materials present. If these molecular weights become sufficiently
high, the materials will come out of solution in the form of floes.
Furthermore, polar carboxyl groups are capable of linking with inorganic
cations normally present in waters e.g., calcium, magnesium, iron, aluminum,
etc. Such linkages with polyvalent inorganic cations also cause precipitation
of dissolved organic materials.
Formation of such Insoluble materials can be significant, and, therefore,
can cause fouling of GAC adsorbers, blinding of the adsorption sites, or
simply cause premature headlosses. As a minimum, buildup of such Insoluble
materials can require that the GAC adsorbers be backwashed more frequently
than would be necessary in the absence of these insoluble materials. Thus,
in those cases when chemical preoxidation is required, or when chemical
266
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flocculants are added In pretreatment, a filtration step should be inserted
prior to GAC adsorption.
Need For Supplemental Oxygenation Prior To GAC Adsorption
When one atom of dissolved organic carbon is converted into 1 molecule
of C02, 2 atoms of oxygen (1 molecule) are required. When 4 atoms of hydrogen
(the maximum number which can be associated with the dissolved organic
carbon atom) are converted to water, still another molecule of dissolved
oxygen is required. To convert 1 molecule of ammonium ion to nitrate ion,
hydrogen ion and water stoichiometrically requires at least 4.57 molecules
of dissolved oxygen.
For these reasons, it is important that sufficient dissolved oxygen be
present in solution so that biochemical oxidations can proceed as nearly to
completion as feasible. The solubility of oxygen in water when added by
aeration is between 6 and 10 mg/L, depending upon the water temperature. On
the other hand, when pure oxygen is added to water, dissolved oxygen concen-
trations as high as 45 to 55 mg/L can be achieved, again depending upon the
water tenperature.
Therefore, it is important for the wastewater treatment chemist to know
the biodegradability of his wastewater, so that sufficient oxygen can be
provided to maintain the biological organisms in an aerobic condition. He
should also know how much biodegradation occurs in the inert media filters,
so that sufficient oxygen can be supplied prior to this treatment stage as
well.
Dissolved oxygen requirements can be determined by measuring oxygen
uptake in a Warburg type of apparatus. When conducting such measurements,
however, it is Important to be sure that the bacteria used have had tine to
adapt to the particular organics present. Depending upon the amount of
biodegradable materials present in the wastewater, provision should be made
to provide sufficient DO in the GAC influent so as to maintain a level of DO
in the GAC effluent of at least 3 mg/L (Sontheimer, 1978). At the Cohne
drinking water plant (Mdlheim, Federal Republic of Germany), for example,
the CO in the GAC column effluents is controlled at 7 to 8 mg/L (Heilker,
1979b).
If chemical preoxidation of the wastewater is required, the use of
ozone generated from oxygen will provide a higher DO level than will ozone
generated from air.
Empty Bed Contact Time
Adsorption of dissolved organics by GAC is a rapid process. Therefo-e,
empty bed contact times of GAC columns which act strictly as adsorbers
normally are on the order of 5 to 15 minutes. On the other hand, biological
oxidation processes are slower than adsorptive processes, and longer EBCTs
are required. In the Federal Republic of Germany, for example, GAC columns
2 meters high were first Installed in drinking water treatment plants in
Dtisseldorf and in Mulheim for taste and odor control and for dechlor1 nation,
267
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respectively. When the benefits of biological activity in GAC media were
recognized, however, the depths of the Ddsseldorf and Mulheim GAC columns
were doubled to 4 meters. Not only did this produce longer EBCTs, but also
provided greater adsorptive capacities for trace organics. On the other
hand, capital costs for GAC are approximately doubled, as are costs for the
initial charges of GAC.
On the basis of European drinking water treatment plants using BAG
systems, it appears that EBCTs of 7 to 10 minutes are optimum for maximizing
the benefits of biological activity.
Initial Period Of Biological Adjustment
From European drinking water experiences, virgin GAC columns require
several days to a week of feeding with water to be treated in order for
significant biological activity to develop which converts COC to C02.
Nitrifying organisms require even longer to develop, on the order of 2 to 3
weeks. It is probable that some industrial wastewaters will contain specific
organic components which require even longer for adaptation of microorganisms.
For example, Benedek e_taj_. (1979) have shown that after ozonation, solutions
of p-nitroaniline are not readily biodegradable (as measured by oxygen
uptake rate) until after about 3 weeks of acclimation of the microorganisms.
These microorganisms previously had been acclimated to p-nitroaniline.
Once the bacteria have adapted to the particular industrial wastewater,
however, continuous operation of GAC systems should be easily maintainable.
Analytical Monitoring
Measurements for specific contaminants of the industrial wastewater
being treated, COD, TOC, ammonia, dissolved oxygen, etc., in the influent
and/or effluent of the GAC adsorbers are apparent. In addition to these
determinations, however, it is also helpful to analyze effluents from
biologically operating filtration or GAC adsorption media for carbon dioxide
content (which can be followed in some cases by accurate determination of
pH). By comparing the amount of inorganic carbon produced (the amount of
elemental carbon contained in the C02 measured) with the amount of dissolved
oxygen being consumed during the same period of time, one can determine that
his treatment system is or is not in biological equilibrium. At biological
equilibrium, the ratio of DO consumed to inorganic carbon produced will te
close to 1.
Knowing the ratio of Inorganic carbon produced to the amount of orcanic
carbon removed from solution also is useful. If this ratio is greater than
1, more CO? is being produced than organic carbon is being removed from
solution. This situation indicates that biological regeneration °f some of
the active adsorption sites of the GAC is occurring Converse Y. when the
ratio is less than 1, this indicates that more dissolved organic carbon :s
being removed by adsorption than by biochemical decomposition.
As indicated in preceding sections, it is Important to provide suffi-
cient DO to the solutions being treated to maintain the bacteria in an
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aerobic state. Since industrial wastewaters fed to GAC adsorbers are
expected to contain considerably more DOC than drinking waters, it likely
will be necessary to add pure oxygen before sand or other inert media filtra-
tion. This can be accomplished during ozonation, in the event that chemical
preoxidation with ozone is chosen as a pretreatment step, by generating the
required ozone from pure oxygen.
Monitoring the sand or inert medium filter influents and effluents for
dissolved oxygen also will be necessary, so as to determine the amount of 20
consumed biologically during filtration, as well as to determine the amount
of additional oxygen necessary to be added prior to passage o* the solution
through biologically enhanced GAC.
GAC Regeneration Parameters
GAC regeneration parameters should be developed on the basis of the
specific organic materials which must be removed from the wastewater and for
which_GAC was selected as the treatment process to deal with them. If
chlorinated organics are the contaminants to be removed, for example, then
GAC reactivation frequency should be based upon their breakthrough. Once
the specific polluting contaminants to be removed have been identified, then
specific or surrogate chemical analytical procedures can be developed for
lower cost monitoring. The use of TOC as a surrogate analysis probably will
be a useful procedure in this regard.
It should be recognized that the objective of GAC treatment 1s to
remove those contaninants which can be removed by adsorption; the objective
of promoting aerobic biological activity In the GAC is to remove as much of
the biodegradable fraction as possible. Under Ideal circumstances,, break-
through of the GAC system will be determined only by those chemicals which
are adsorbed but which cannot be made biodegradable. If breakthrough of
biodegradable organics occurs first, this means that the system has not yet
been designed optimally.
Backwashing of Filtration Media and GAC Adsorbers
Air scouring is used initially during backwashing 1n all European
drinking water treatment plants known to be using biologically enhanced SAC
adsorption processes. Air scouring is required to loosen the biological
growths adhering to the filtration or GAC media. In actuality, air scouring
is more akin to "bumping", and as soon as the agglomerated filtration or GAC
medium has been broken up by such bumping, then backwashing is continued
with water.
Biologically operating European sand filters normally are backwashed
first by air scouring, then with a mixture of air plus water, then with
water alone. In backwashing 3AC media, however, air scour then water
backwashing is practiced. Apparently the density of GAC is too low to allow
use of the (air + water) treatment without incurring significant losses of
GAC.
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Air scour or air backwash is a concept which has found considerable
application recently in wastewater treatment, but little or no application
in United States drinking water facilities. In water treatment practice,
the combined effects of heavy prechlorination dosages as well as so-called
surface washing have been sufficient to enable satisfactory filter cleaning
during the backwashing cycle.
A report of the American Water Works Association Subcommittee on
Backwashing of Granular Filters (Cleasby et al., 1977) recommends provisions
for air scour or for surface wash when comTitTbns exist sjch as those which
occur with biological activity promoted in the beds. While surface wash
units are common in modern U.S. water treatment plants, air scour systems
are not. Cleasby et aj_. (1977) categorized backwashing methods as follows:
(1) High rate backwash - full bed fluidization and substantial bed expansion
(20 to 50%) normally is proceeded and followed by a Icwer rate backwash.
This backwash system can be used for single or multi-media filters.
(2) Low rate backwash with little or no bed fluidization or ted expansion -
auxiliary scour is essential to low rate backwash. This backwash
system can be used for single nedium filters only.
(3) Water backwash with surface water wash only.
(4) Water backwash with air auxiliary:
(a) Air scour followed by low rate water backwash - for use with
single medium filters only.
(b) Air scour followed by high rate water backwash - for use with
single and multi-media filters.
(c) Simultaneous air scour and low rate water backwash, followed by
high rate water backwash alone - for use with single medium
filters alone.
(d) Simultaneous air scour and low rate water backwash, followed by
high rate water backwash alone - for use with single and multi-
media filters.
It appears that filter backwash techniques nust be reviewed if chlorina-
tion ahead of filtration 1s discontinued. Based on the AWWA Filtration
Committee's findings and European practice, provisions of either air scour
or surface wash appear to be necessary. Provision of surface wash without
prechlorination would appear to result in shorter filtration runs with
associated Increases 1n operating costs. For example, a midwest water
treatment utility with filters equipped with surface wash estimated a re<;uc:
tion in backwash cycles from 60 hours to 30 hours. Conversion of a filtration
system from water backwash to water backwash with air auxiliary would require
complete reconstruction of existing filter bottoms to accomodate the air
distribution systems.
270
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In those European water treatment plants in which biologically enhanced
GAC has been installed to replace breakpoint chlorination followed by GAC
later in the process for dechlorination (for example, at the 3ohne plant,
Mulheim, Federal Republic of Germany), both the sand filters and the 3AC
adsorbers have been found to be able to operate nearly twice as long without
breakpoint chlorination and with ozone preoxidation before backwashing
becomes necessary. This is clear indication that the anticipated biological
fouling of filters when prechlorination is eliminated may not occur, or, if
it does, that it may be controlled by the low level preozonation required to
promote aerobic bacterial activity in the filter and adsorber rredia.
The frequency with which backwashing of biologically enhanced filters
or GAC adsorption media will be required usually is determined by headlosses.
However, at the Cohne drinking water treatment plant (Mulheim, Federal
Republic of Germany), filter runs as long as 1 week could be achieved before
headlosses built up sufficiently to require backwashing. On the other hand,
during the summer of 1978, a "population explosion" of nematodes was observed
to occur in the rapid sand filters and SAC adsorbers. Since the reproduction
cycle of these organisms is just over 3 days, it was concluded that nematode
development was a result of the more than one week backwashing intervals.
When backwashing intervals were lowered to 3 days, the nematodes disappeared
completely (Heilker, 1979).
Valencia and Cleasby (1979) have recently published an excellent
discussion of ve^dty gradients in granular filter backwashing, which
provides the engineer with a valuable tool for analyzing shear forces in
filter beds and their effects upon the media cleaning process.
Materials of Construction
Granular activated carbon systems will cause corrosion problems 1f they
are not anticipated and provided for in the original design. It 1s not
expected, however, that there will be any significant increase in corrosion
behavior of GAC media as a result of operating with maxinized biological
activities. Perhaps the best source of information as to antl-corrosion
measures to be taken is the carbon supplier himself, as well as operational
plants where GAC has been in use.
At the new Kra'ingen drinking water treatment plant in Rotterdam, The
Netherlands, the granular activated carbon adsorbers are constructed of
carbon steel, but are coated on the inside with a proprietary coating. GAC
is supported on a coated steel plate with plastic nozzles inset in the plate
to provide flow distribution (Rice et_al_., 1979).
Heilker (1979) has described construction and corrosion inhibition
aspects of the GAC adsorbers recently enlarged and rebuilt at the Dohne
drinking water treatment plant in MUlheim, Federal Republic of jermany.
Steel GAC adsorbers were selected initially, because they were better
suited for overall process design and were easier to work with in modifying
existing water treatment plants. However, corrosion problems caused high
repair costs.
271
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After 10 years of testing different adsorbers with additional cathodic
corrosion protection, a method has been adopted at Mill helm which offers
"nearly complete protection against defects". The 12 double-staged adsorbers
are being modified as follows: all interior welded seams are being straigh-
tened and ground. Rust is being removed by sand blasting. Condensate is
prevented by aeration during coating. Solvent-free epoxy resin, resistant
to abrasion and to ozone, 1s used, and a 450 to 500 ym layer is applied.
The pore!ess coating is tested with 1.5 to 2 kV.
Further experimentation has shown that the interior adsorber surfaces
can be "completely protected" if a combined cathodic protection with sacrifi-
cial anodes is used and the electric power supply is transmitted over plati-
num-covered titanium anodes.
Costs for all corrosion protective devices being applied to GAC adsorbers
at Mill helm amount to approximately 10% of the total cost of the treatment
plant modifications required to convert the old (breakpoint cnlorination)
process to the BAG process recently installed (Heilker, 1979).
Mechanical Considerations
Culp (1980) reviewed GAC use in advanced wastewater treatment (AWT)
systems and pointed out that the experience has varied from excellent to
very poor. Culp also states that the failures of 3AC systems in AWT applica-
tions have not stemmed from deficiencies in the basic GAC processes of
adsorption oTbrganics, but, rather, from mechanical probleirs, which have
included:
e failure of GAC column linings due to improper Installation or faulty
material,
• corrosion of GAC storage tanks,
t corrosion of surface wash equipment and other metal parts in GAC
contact tanks,
t numerous failures of GAC column underdrains, where the wrong type of
sand filter type underdrains had been installed, or where the Installa-
tion was defective,
• failure to make provisions for maintaining aerobic conditions at all
times in the GAC column influent water,
• failure to provide means for excluding air or venting air from GAC
column backwash lines prior to initiation of backwashing,
ft lack of adequate means to dewater and feed measured amounts of spent
GAC to the reactivation furnace,
• corrosion of furnace parts.
272
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• installation of sub-standard or defective refractories 1n reactivation
furnaces,
• improper installation of furnace refractories,
• inadequate pretreatment of wastewater prior to application of GAC,
• lack of adequate means for GAC movement and conveyance, apparently due
to the lack of knowledge concerning the physical handling properties of
GAC.
Culp (1980) concludes that any and all of these rather serious problems
could have been avoided quite easily by proper application of the best
current engineering design knowledge and practices for GAC systems.
Taking GAC Filter/Adsorbers Out Of Service
Plant personnel at European drinking water treatment plants which have
been using granular activated carbon for some years advise that GAC columns
or beds that have been in plant operation should not be allowed to stand
idle or off-line for more than one day. If this caution is not heeded, the
biomass in the activated carbon medium changes and when the unit is placed
back in-line, contamination of the product drinking water occurs. When
operating units are taken out of service, the activated carbon is sent for
reactivation. If the units are to be taken off-line only for a few days,
water is passed through the units continuously until they are placed back 1n
line (Engels, 1978, Private Communication).
Safety Considerations oF GAC Adsorbers
Strudgeon e_t_ al_. (1979) have discussed several serious accidents which
have occurred with GAC systems and which have resulted in at least two
fatalities. These accidents occurred in adsorbers which contained wet GAC,
which is an excellent adsorber of atmospheric oxygen. In two instances,
workers apparently entered enclosed GAC adsorbers without positive pressure
masks to provide oxygen and were suffocated because of the lack of sufficient
oxygen.
Other potential hazards associated with GAC systems include the
following:
(1) GAC in dry form contains significant quantities of fines and dust. As
a result, all GAC handling systems pose the possibility for creating a
dust explosion hazards unless precautions are taken.
(2) If biological growths within 3AC adsorbers are allowed to become
anaerobic, and if sulfates are present, quantities of HeS can be
generated. This toxic gas also can pose a hazard to workers entering
the adsorbers, although its presence usually can be readily detected
nasally in small quantities.
273
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(3) When dry and confined, GAC provides a relatively solid footing.
However, after having been fluidized with the proper amounts of water,
it has the characteristics of a mixture with virtually no support, thus
allowing a heavier weight to sink within the mixture. The term "quick-
sand effect" has been applied to this meretricious behavior of GAC and
similar systems.
(4) GAC also will "bridge", as soil does, and personnel entering a GAC
vessel must insure that the bed is well drained and that bridging has
not developed, which possibly could collapse and bury the individual.
Alternative GAC Adsorber Designs
Recently, Carnes and Burstein (1980) have addressed all of the engineer-
ing factors involved with designing GAC adsorption systems. This elegant
treatise should be consulted by those wishing more detailed information on
this subject. In addition, Bernardin (1980) has discussed the subject of
problems and solutions of granular activated carbon operations.
274
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Frick, B., Bartz, R., Sontheimer, H. & DiGiano, F., 1977, "Problems of
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300
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Maran, E. & Sulik, D.J., 1977, "Advanced Waste Treatment Design Protects
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Martin, R.J. & Iwugo, K.O., 19785 "Studies on Residual Organics in Biologi-
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Masschelein, W.J.. 1979, "Belgian Experiences in Practical Applications of
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Matsuoka, H., 1973, "Ozone Treatment of Industrial Wastewater", PPM 4(10):-
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Matthews, J.E., 1978, "Treatment of Petroleum Refinery, Petrochemical and
Combined Industrial-Municipal Wastewaters With Activated Carbon —
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Environmental Research Lab., U.S. EPA, Ada, Oklahoma 74820.
Mattson, J.S., Mark, H.B., Jr. & Weber, W.J., Jr., 1969, "Identification of
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McCarty, P.L., Reinhard, M. & Argo, D.3., 1977, "Organics Removal by Advanced
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McCrodden, B.A., 1974, "Operation of a Refinery Wastewater Treatment Plant
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held in Ottawa, Ontario, Canada, Oct. 247^974. Environmental Protection
Service, Environment Canada, Ottawa.
McCrodden, B.A., 1979, "Treatment of Refinery Wastewater Using A Filtration-
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Kerr Environmental Research Lab., U.S. EPA, Ada, Oklahoma 74820.
McGuire, M.J., 1978, "Feasibility Analysis and Implementation of Synthetic
Organic Chemical Control Strategies", presented at Symp. on Activated
Carbon Adsorption of Organics From the Aqueous Phase, Miami, Fla.,
Sept., 1978. Am. Chem. Soc., Washington, D.C.
McGuire, M.J. & Suffet, I.H., 1979, "Adsorption of Organics From Domestic
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Meijers, A.P., 1979, "The Use of Carbon Filtration in The Netherlands",
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Miller, 3.W., Rice R.G., & Robsonc C.M., 1978, "Large Scale Applications of
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Activated Carbon Adsorption of Organics From the Aqueous Phase, Miami,
Fla., Sept., 1978, Am. Chem. Soc., Washington, D.C.
Miller, R., 1979, "Treatment of Ohio River Water", presented at NATO/CCMS
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Apr. 30-May 2. U.S. EPA, Office of Drinking Water, Washington, CC.
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Miltner, R.J., 1979, "Results for Chio River Valley Water Sanitation Corrmis-
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Moss, W.H., Schade, R.E., Sebesta9 S.J., Scheutzowf K.A., Beck P.V. & Gerson,
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309
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Myers, L.H., 1976, "Pilot Plant Activated Carbon Treatment of Petroleum
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National Research Council, 1979, "An Evaluation of Activated Carbon For
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Osborne, D.J., 1979b, "Experience With Multi-Hearth Furnace at Wilne Treat-
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U.S. EPA, Office of Drinking Water, Washington, DC.
Otte, G. & Rosenthal, H., 1978, "Water Quality During a One Year Operation
of a Closed, Intensive Fish Culture System", presented at Intl. Ozone
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Oulman, C.S., 1980, "The Logistic Curve as a Model ror Carbon Bed Design",
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Pendygraft, G.W., Schlegel, F.E. & Huston, M.J., 1979, "The EPA-Proposed
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Perrotti, A.E. & Rodman, C.A., 19745 "Factors Involved With Biological
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Perry, D.L., Smith, O.K. & Lynch9 S.C., 1980,, "Development of Basic Data and
Knowledge Regarding Organic Reiroval Capabilities of Commercially Avail-
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Peyton, G.R., Burleson, C., Huang, F., Lin, S. & Glaze, W., 1979, "Treatment
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311
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Popper, K., Camirand, W.M., Williams, G.S. & Mecchi, E.P., 1978, "Regenera-
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Rice, R.3., Miller, 3.W., Robson, C.M. & KUhn, W., 1977, "Biological Activa-
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Rice, R.G., Miller, G.W. & Robson, C.M., 1978a, "Potentials of Biological
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312
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Rice, R.G., 1979a, "Biological Activated Carbon"9 presented at EPA Seminar
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Rice, R.3., 1980, "Ozone Gives Boost To Activated Carbon", Water & Sewage
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Rice, R.G., Robson, C.M. & Miller, G.W., 1981, "Biological Activated Carbon
and its Potentials for Treating Industrial Wastewaters", Final Report
of Grant No. R-804385-01 to Public Technology, Inc. U.S. EPA, Office
of Environmental Engrg, & Techno!., Washington, DC.
Richard, Y., 1972, "Experiment on the Industrial Treatment of Drinking Water
by Activated Carbon", Degr€mont S.G.E.A., Rueil Malmaison, France, 5
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Richard, Y. & Fiessinger0 F.9 undated9 but after 1972, "Le Traitement
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S.G.E.A., Rueil Malmaison, France.
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May. Intl. Ozone Assoc., Vienna0 VA.
Richard, Y., Brener, L. & Leblanc, C.9 1979,, "Optimization of Potable
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52-56.
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Water Research Activities, p. 1. U.S. EPA, Water Supply Research Lab,
Cincinnati, Ohio 45268.
Robertaccio, F.L., Mutton, O.G., Grulich, 5. & Goltzer, H.L., 1972, "Treat-
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313
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Roberts, P., Gujer, W. & Eugster, J., 1977, "Re1n1gung von Kommunalem
Abwasser Mittels Aktivkohle Nach Schwach Belasteter Biologischer
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Rodman, C.A. & Shunney, E.L., 1970, "A New Concept For The Biological
Treatment of Textile Finishing Waters", Water — 1970, Chem. Engrg.
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Rodman, C.A., 1971, "Bio-Regenerated Activated Carbon Treatment of Textile
Dye Wastewater", EPA Report No. 12090 DWM. U.S. Environmental Protection
Agency, Indl. Environ. Research Lab., Cincinnati, Ohio 45268.
Rodman, C.A. & Shunney, E.L., 1971, "New Concepts For "Treating Coloured
Organic Contaminated Wastewater", Presented at Symp. on Environ.
Engrg. Aspects of Pollution Control, London, England, June 22-23, Soc.
Environmental Engrs., London.
Rom, D., Wachs, A.M. & Rotel, M., 1980, "Pilot Plant Studies of Water Renova-
tion in a System Combining Ozonation With Activated Carbon Treatment",
presented at 53rd Annual WPCF Conf., Las Vegas, Nev., 1 Get. Water
Poll. Control Fed., Washington, DC.
Rosenthal, H. fit Sander, E., 1975, "An Improved Aeration Method Combined
Waste Foam Renoval in a Seawater Recycling System", Intl. Council for
the Exploration of the Sea, Mariculture Committee, E:14, 1-16 (Fisheries
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Quality in Laboratory Scale Sea Water Recycling Systems", Intl. Council
for the Exploration of the Sea, Mariculture Committee Report, C.M.
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Rosenthal, H. & Otte, G., 1979, "Ozonation in an Intensive Fish Culture
Recycling System", Ozone Sci. & Engrg. 1(4):319-327.
Sander, R., 1977, "Formation and Removal of Chlorinated By-Products in a
Pilot Plant Unit", presented at Seminar on Activated Carbon, Karlsruhe,
Federal Republic of Germany, Oct. 30-31, 1977. Engler-Bunte Inst. der
Univ. Karlsruhe.
Sander, R.: "979, "Effect of Prechlorination on Activated Carbon Adsorp-
tion", presented at NATO/CCMS Conf. on Adsorption Techniques in Drinking
Water Treatment, Reston, VA, Apr. 30-May 2. U.S. EPA, Office of
Drinking Water, Washington, DC.
Savage, P.R., 1979, "Waste Disposal With An Energy Bonus", Chem. Engrg., vay
21, p. 116-117.
Scaramelli, A.B. & DiGiano, F.A., 1970, "Upgrading the Activated Sludge
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314
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Schalekamp, M. & Bakker, S.P., 1978, "Use and Thermal Regeneration of
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Drinking Water From Surface Sources", C. Am. Water Works Assoc. 71(11):-
638-647.
Scherm, M. & Lawson, C.T., 1977, "Pilot Demonstration of Renovation and
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Engrg., Oct./Nov. issue, p. 16-22.
Schulhof, P., 1979, "An Evolutionary Approach to Activated Carbon Treatment",
J. Am. Water Works Assoc. 71(ll):648-659.
Schuliger, W.G., 1974, "Equipment Design Considerations", in Proc. Physical-
Chemical Treatment Activated Carbon Adsorption in Pollution Control,
Seminar held in Ottawa, Ontario, Canada, Oct. 24T 1974.Environmental
Protection Service, Environment Canada, Ottawa.
Schuliger, W.G., 1978, "Purification of Industrial Liquids With Sranular
Activated Carbon: Techniques For Obtaining and Interpreting "ata and
Selecting the Type of Commercial System", in Carbon Adsorption Handbook,
P.N. Chereirisinoff & F. Ellerbusch, editors, op. cit., pp. 55-84.
Semmens, M.J. & Goodrich, R.R., Jr., 1977, "Biological Regeneration of
Ainnoniurn-Saturated Clinoptilolite. I. Initial Observations", Environ.
Scu & Techno!. 11(3):255-265.
Semmens, M.J., 1977V "The Feasibility of Using Nitrifying Bacteria To
Assist The Regeneration of Cl InoptilolUe", in Proc. 32nd Purdue Univ.
Indl. Waste Conf., May 10-12, 1977. Ann Arbor Science Publishers,
Inc., Ann Arbor, Michigan, pp. 733-744.
Semrens, M.J., Wang, J.T. & Booth,, A.C., 1977, "Nitrogen Removal by Ion
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Semmens, M.J. & Porter, P.S., 1979, "Ammonium Removal by Ion Exchange:
Using Biologically Restored Regenerant", J. Water Poll. Control Fed.
51(12):2928-2940.
Shelby, S.E., Koon, J.H., Marks, D.R. & Scott, H.A., Jr., 1980, "Adsorption
of Chlorinated and Non-Chlorinated Organics From a Pesticide Manufactur-
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Nev., 1 Oct. Water Poll. Control Fed., Washington, DC.
Shanra, B. & Ahler, R.C., 1977, "Nitrification and Nitrogen Removal",
Water Research 11:897-925.
Shuckrow, A.J., Bonner, W.F., Presecan, N.L. & Kazmierczak, E.J., 1972, "A
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Shunney, A.L., Perotti, A.E. & Rodman, C.A., 1971, "Decolorization of
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38, 40.
Siemak, R.C., Trussell, R.R., Trussell, A.R. & Umphres, M.D., 1979, "How to
Reduce Trihalomethanes in Drinking Water", Civil Engrg., Feb. 1979, pp.
49-51.
Skovronek, H.S., Dick, M. & des Rosiers, P.E., 1977, "Selected Uses of
Activated Carbon for Industrial Wastewater Pollution Control", Indl.
Water Engrg., 14(3):6-13.
Skovronek, H.S. & Becker, D.L., 1977, "Pollution Control by Adsorption",
presented at 7Cth Annual Meeting of the Am. Inst. Chenu Engrs., New
York, N.Y., Nov. 13-17, 1977. AIChE, New York, N.Y.
Skovronek, H.S., 1978, "Industrial Case Histories", in Carbon Adsorption
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Slade, J.S., 1978, "Enteroviruses in Slow Sand Filtered Water", J. Inst.
Water Engrs. & Scientists 32(6).-530-536.
Smith, O.K., Lynch, S.C., Gebhart, J.E. & Monteith, C.S., 1979, "Development
of Basic Data and Knowledge Regarding Organic Removal Capabilities of
Commercially Available Home Water Units Utilizing Activated Carbon -
Preliminary Report - Phase I", U.S. Environmental Protection Agency,
Office of Water Supply, Washington, DC.
Smith, S.A., Chapman, R.L. & Butterfield, O.R., 1979, "Tahoe-Truckee Water
Reclamation Plant First Year in Review", Proc. Water Reuse Symp.,
Washington, D.C., Mar. 25-30, pp. 1435-1445. Am. Water Works Assoc.
Research Foundation, Denver, Colo.
Smith, S.B., 1974, "Techniques of Activated Carbon Regeneration", in Proc.
Physical-Chemical Treatment Activated Carbon Adsorption in Pollution
Control, Seminar held in Ottawa, Ontario, Canada, Oct. 237 1974.
Environmental Protection Service, Environment Canada, Ottawa.
Smithson, G.R., 1978, "Regeneration of Activated Carbon: Thermal, Chemical,
Solvent, Vacuum and Miscellaneous Regeneration Techniques", in Carbon
Adsorption Handbook, P.N. Cheremisinoff & F. Ellerbusch, editors, op.
cTtT8 pp. 379-904.
Snoeyink, V.L., McCreary, J,J. & Murin, C.J., 1977, "Activated Carbon
Adsorption of Trace Organic Compounds", U.S. EPA Report No. 6CO/2-77-
223, U.S. EPA, Indl. Environ. Research Lab., Cincinnati, Ohio 45268.
Snyder, A.J. & Alspaugh, T.A., 1974, 'Catalyzed Bio-Cxidation and Tertiary
Treatment of Integrated Textile Wastewaters", U.S. EPA Report No.
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Cincinnati, Ohio 45268.
316
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Sontheimer, H., 1975a, "The Importance of Adsorption Processes 1n drinking
Water Treatment", 1n Translation pjf Reports on Special Problens of_
Water Technology, Vol. 9 - Adsorption, H. Sontheimer, editor, op_. ctt.,
pp. 1-T5-;
Sontheimer, H., 1975b, "Basic Principles of Adsorption Process Techniques",
1 n Translation of. Reports on_ Special Proble-ns of_ Water Techology, Vol.
9_, op_. cit., p. 29-66.
Sontheimer, H., 1975d, "Realistic Laboratory Test Methods for the Evaluation
of Activated Carbon", in Translation of Reports on Special Problems of_
Water Techno!ogy, Vol. 9 - AdsorptTon7~H~SontheTm'erSi editor, op. cit.,
ppTT50-268.
Sontheimers H.9 1975e, "Theory and Practice in the Use of Adsorption Proces-
ses", in Translation of Reports pj^ Special Problems of Water Technology,
Vol. £- Adsorption, H7 Sontheiner. editor,~op cit., pp. 414-417.
Sontheimer, H., Wtilfel, P. & Safert, F., 1977, "Verbesserung der Biologis-
chen Abbaubarkeit der Organischen Stoffe in Biologlsch Gereinigten
Abwflssern Durch Fine Ozonbehandlung", presented at 3rd Intl. Symp. or
Ozone Technology, Paris, France, May. Intl. Czone Assoc., Vienna, VA.
Sontheirer, H., 1978a, 'Biological Treatment of Surface Waters in Activated
Carbon Filters", OZONews, July, 1978, Part 2 - Technical Paper Section.
Intl. Ozone Assoc., Cleveland,, Ohio.
Sontheiner, H., 1970a, "Process Engineering Aspects in the Combination of
Chemical and Biological Oxidation", in Oxidation Techniques in Drinking
Water Treatment, W. KOhn a H. Sontheimer, editoFs. U.S. EPATeport Nol
EPA-570/9-79-020. U.S. EPA, Office of Drinking Water, Washington, pp.
702-714.
Sontheimer, H., 1979b, "Biologisch-Adsorptive Trinkwasseraufbereitung in
Aktivkohlefiltern -- Das VUlhelmer Verfahren", Rhe1n1sch-Westf3l1sche
Wasserwerksgesellschaft mbH (MUiheirr a.d. Ruhr) & DVGW-Forschungsstelle
am Engler-Bunte Institut der University Karlsruhe, Feb.
Sontheimer, H., 1979c, "German Experience in Activated Carbon Treatment",
presented at NA70/CCMS Conf. on Adsorption Techniques in Drinking Water
Treatment, Reston, VA, Apr. 3C-May 2. U.S. EPA, Office of Drinking
Water, Washington, DC.
Sontheimer, H., 1979d, "Applying Oxidation and Adsorption Techniques: A
Summary of Progress", J. Am. Water Works Assoc. 71(11):612-617.
Sontheimer, H., 1979e, "Design Criteria and Process Schemes for 3AC Filters",
J. Am. Water Works Assoc. 71 (11).-618-622.
Spahn, H., Brauch, V., Schlunder, E.U. & Sontheimer, H., 1974, "Auslegung
von Aktivkohlefiltern zur Wasserreinigung. Tell I: Untersuchung der
Adsorption am Eizelkorn", Verfahrenstechnik 8(8), 8 pp.
317
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Spahn, H., Brauch, V., SchlUnder, E.U. & Sonthelmer, H., 1975, "Auslegung
von Aktivkohlefiltern zur Wasserreinlgung. Tell II. Theoretische und
Experimented Bestimmung der Beladungsfelder In Aktlvkohlefestbetten",
Verfahrenstechnlk 9(1), 5 pp.
Stephenson, P., 1979, "The Effect of Ozone on the BiodegradabHity of
Refractory Organics In Water", M. Engr. Thesis, McMaster Univ., Hamilton,
Ontario, Canada.
Stevens, A.A., Seeger, D.R., DeMarco, J. & Moore, L., 1979, "Removal of
Higher Molecular Weight Organic Compounds by the Granular Activated
Carbon Adsorption Unit Process", presented at NATO/CCMS Conf. on
Adsorption Techniques 1n Drinking Water Treatment, Reston, VA, Apr. 30-
May 2. U.S. EPA, Office of Drinking Water, Washington, DC.
Stewart, D.R. & Sierka, R.A., 1979, "Effects of Preozonatlon of Domestic
Wastewater on Activated Carbon Adsorption", presented at 52nd Annual
WPCF Conf., Houston, TX. Water Poll. Control Fed., Washington CC.
Strack, B., 1975, "Operation, Problems and Economy of Activated Carbon
Regeneration", in Translation of Reports on Special Problems of Water
Technology, Vol. 9 - Adsorption, 0£_. at., pp. 284-311.
Suffett, I.H., Brenner, L., Coyle, O.T. & Cairo, P.R., 1978, "Evaluation of
the Capability of Granular Activated Carbon and XAD-2 Resin to Remove
Trace Organlcs From Treated Drinking Water", Env. Sci. & Techno!.
12(12):
Suffett, I,H.S McGuire, M.J., Josephson, 0. & Ember, L.R., 1978, "Cleanup:
That Cld Black Magic Works Again!11, Environ. Sc1. & Technol. 12(10):-
1138-1149.
Suffet, I.H., 1980, "An Evaluation of Activated Carbon for Drinking Water
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-------
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319
-------
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320
-------
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321
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Vienna, VA.
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2661-2677.
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Sour 3as Plant Process Wastewaters", J. Can. J. Petrol. Technol.,
April-June, 1976, pp. 39-47.
Zanitsch, R.H. & Stenzel„ M.N., 1978, "Economics of Granular Activated
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Handbook, P.N. Cheremislnoff & F. Ellerbusch, editors, op. cit., pp.
215-240.
322
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Zeff, J.D., Leitis, E. & Crosby, D.G., 1979, "Study of the Chemistry of the
UV-Ozonation of Refractory Organic Compounds in Water", Presented at
4th World Ozone Congress, Houston, Texas, Nov. 26-29. Intl. Ozone
Assoc., Vienna, VA.
Zobell, C.E., 1937, "The Influence of Solid Surfaces Upon the Physiological
Activities of Bacteria in Sea Water", J. Bact. 33:86.
Zogorski, J.S. & Faust, S.D., 1978, "Operational Parameters for Cptimun
Removal of Phenolic Compounds From Polluted Waters by Columns of
Activated Carbon", in Carbon Adsorption Handbook, P.N. Cheremisinoff &
F. Ellerbusch, editors, op_. cit., pp. 753-778.
Zuckerman, M.M. & Molof, A.M., 1970, "High Quality Reuse Water by Chemical -
Physical Wastewater Treatment". C. Water Poll. Control Fed. 4Z(3):437-456.
323
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APPENDIX A
AUBERGENVILLE PLANT (SUBURBS OF PARIS, FRANCE)
BACKGROUND
The Aubergenville water treatment plant of the SociSte" Lyonnaise des
Eaux et de TEclairage (SLEE) produces approximately 100,000 cubic meters of
water per day (26.4 mgd) from 23 wells which are situated along the south
side (left bank) of the Seine River downstream of Paris, between Les Mureaux
and EpOne.
1961 CONSTRUCTION
The plant was designed to treat groundwater drawn from an area between
the Seine River and the Alluets Forest by means of wells driven In the
Senonian limestone strata. The groundwater initially contained only a small
amount of ammonia and iron with iron bacteria. The original treatment plant
which was placed in service in 1961 Included the following process steps:
!al
(b)
cascade aeration
biological nitrification
filtration
post-disinfection with chlorine dioxide.
A few months of operation caused a drawdown of the groundwater level of
the originally high quality water source. This resulted in an intrusion of
groundwater from other sources, particularly from the Seine River. The
quantity of flow from the Seine was accentuated by increases in the river
level due to the construction of reservoirs and locks to allow passage of
larger barges in the Seine. As a result, water from certain wells developed
unpleasant tastes and exhibited increased levels of organic matter, detergents
and bacteria. In particular, there was a large increase in the number of
filamentous iron bacteria.
1969 ADDITIONS
Major additions to the treatment plant were'made operational in 1969.
These modifications Included chemical clarification ahead of nitrification.
Chemical addition ahead of clarification included aluminum sulfate for
coagulation, activated silica for flocculation and powdered activated carbon
for elimination of detergents, organics and bad tastes. Facilities were
provided to enable ozonation of the water after the filtration step. Ozone
addition is for taste and odor elimination, virus inactivation, removal of
micropollutants and detergents.
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Since 1969, the treatment process has been as follows: chemical
clarification, cascade aeration,, biological nitrification, ozonation and
post-disinfection with chlorine. In Figure 85 the treatment process schema-
tics of this plant are compared from 1961 to 1969, then from 1969 until
1978.
DETAILED PLANT DESCRIPTION
(a) Twenty-three, 30-meters deep wells,, each producing 30 to 40 cubic
meters per hour of water.
(b) Chemical Addition:
Aluninum sulfate - 10 mg/1
Activated silica - 2 mg/1
Powdered activated carbon- 10 mg/1
(c) Four, 1.5CO cubic meters/hour Pulsator flocculator-clarlfier units.
Each unit is 22.3 x 21.6 x 5.1 meters water depth.
(d) Cascade aeration.
(e) Twenty-one biological nitrification units (described in detail below).
(f) Gravity sand filtration - 5 cubic meters/sq m/hr.
(g) One ozonation systems, consisting of the following components:
Two, 440 cu m/hr variable speed, positive displacement blowers.
One, water-cooled, heat exchanger type, after-cooler.
One, Freon refrigerant-cooled drier to reduce air temperature to 5°C.
One, 2-cell, activated alumina desiccator drier to reduce air dew point
to minus 60° C.
One, 550 tube, horizontal tube, Welsbach water-cooled ozone generator
operating at 50 Hertz, with a production capacity of 22 kg of ozone per
hour.
One, 2-compartment, countercurrent flow (ozone/water), 5 meters water
depth, porous tube diffuser, ozone contactor. Each compartment provides
6 minute ozone contact tiires, with an overall ozone contact time of 15
minutes. Total ozone dosage - 0.5 mg/1.
One, 200°C contactor off-gas ozone destructor.
(h) Post-disinfection - Chlorine is added at a booster pump station 189
meters from the plant.
325
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1961 to 1969
Cascade
Aeration
Biological
Nitrification
Filtration
Post-Disinfection
(C102)
aluminum sulfate
activated silica
powdered activated carbon
-Phosphorus
1969 to present
Coagulation
Flocculation
Clarification
Cascade
Aeration
Biological
Nitrification
Filtration
Ozonation
J/
Post-Disinfection
(Chlorine)
Figure 85. Aubergenville water treatment plant. Process Diagrams,
326
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Biological Nitrification System
The details of biological nitrification at Aubergenville are as follows:
There are 21 nitrification beds at the AubergenvWe plant, each with
dimensions of 4.9 m (16.1 ft) by 5.9 m (19.3 ft) for a surface area of
28.9 m (311 ft). They have the following characteristics:
Bed depth 1s 2.5 m (8.2 ft).
Filtration rate at design flow 1s 11.65 m/hr (4.76 gpm/sq ft).
Upflow type.
Intermittent aerations, on for 2 minutes and off for 6. This 6
minute aeration time is less than the time required for water to
pass across the filters. This mode of aeration decreases the
bicarbonate equilibrium by decreasing the quantity of CCg eliminated
by stripping and does not hinder nitrification.
The filter material used is pozzolanic (volcanic stone) with a
grain size of 0.5 to 0.15 cm.
Aeration is accomplished by blowing air through the bed.
The quantity of phosphorus added is between 0.1 and 0.2 mg/1,
expressed as P20s. A phosphorus residual is not detected at the
outlet.
Nitrification beds are backwashed with water, once per week.
Once every six months, the media are dosed with hypochlorite to
eliminate filamentous bacteria. This dosing is carried out for
24 hours. Reseeding of the filter then requires one week.
Once every two years the media are removed from the beds, washed
in media scour and put back in place. Reseeding then is immediate.
Efficiency: An influent ammonia concentration of 3 mg/1 is
reduced further to only trace quantities of ammonia after sand
filtration.
327
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APPENDIX B
CHOISY-le-ROI (EDMOND PEPIN PLANT), SUBURBS OF PARIS, FRANCE
BACKGROUND
This plant currently is designed to treat 800,000 cubic meters per day
(211 mgd) of River Seine water and has an average dally flow of 470,000 cu
m/day (124 mgd). In 1961 the first 300,000 cu m/day leg of the plant was
installed, and by 1969 the balance of the 800,000 cu m/day treatment capacity
was operational. Ozonation was installed in 1967 for color removal, taste
and odor control, removal of phenols, detergents, polyaromatics, micropollu-
tants (dissolved organic materials) and for bacterial disinfection and viral
inactivation. The plant is owned by the Syndicat des Communes de la Banlieue
de Paris pour les Eaux, a public agency, but is operated under contract by
the Compagnie G§n€ra1e des Eaux.
ORIGINAL PROCESS (Chfidal. 1976)
Seine River water (which commonly contains 6 to 10 mg/1 of total
organic carbon), is chemically treated with flocculant (hydrolyzed aluminum
chloride), powdered activated carbons, then by breakpoint chlorination (for
ammonia removal), with sodium hydroxide for pH correction and chlorine
dioxide for destruction of organic manganese complexes. Following addition
of these chemicals, the water is treated by sedimentation and rapid sand
filtration, dechlorinated by addition of sodium bisulfite, then ozonized (2
to 5 mg/1 applied dosage, average dosage 4 mg/1) and treated with chlorine
to provide a residual disinfectant for the distribution system.
In 1977, the post-disinfectant was changed to chlorine dioxide to
provide a more stable distribution system residual.
This process has the disadvantage of producing chlorinated organic
materials which are not readily removed during subsequent processing nor by
the dechlorination step.
BIOLOGICAL REMOVAL OF AMMONIA
Gerval (1978) has described experiments which have led to replacement
of the breakpoint chlorination step by a biological process for the conversion
of ammonia to nitrate. This is done by preozonizing the raw Seine River
water as it enters the plant raw water reservoirs. After preozonation, the
water is retained about two days in the raw water reservoirs before being
treated further by addition of the same chemicals as used in the old process,
with the exception of chlorine and sodium bisulfite.
328
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The preozonation step itself involves addition of low levels of ozone
(up to 1.25 ng/1) over a short contact time (2 minutes). In Table 81 are
listed values obtained for detergents, organic carbon, COD and ammonium ion
concentrations contained by the raw water, by the water after 2-day storage
with no preozonation, and by the water after preozonation (1.25 mg/1 ozone
dosage) plus 2-day storage. The contents of detergents and CCD are nearly
halved, the organic carbon content is lowered from 8 to 7 mg/1 and the
ammonium content is lowered from 4 to 3.2 mg/1 by preozonation followed by
2-day retention. Nitrification now also can occur in the sand filters.
Several advantages have been realized from the preozonation treatment
which produce savings in both chemicals and processing costs, as well as
producing a higher quality finished water. First, the post-ozonation dosage,
required for viral inactivation, can be lowered by at least 2Q%. According
to French public health standards,, whenever ozone 1s used for disinfection
purposes, it must be applied under the following conditions: after satisfying
the Initial ozone demand and attaining a 0.4 mg/1 of residual ozone in the
water, this 0.4 mg/1 residual then must be maintained for a mlnimutr of 4
minutes. In plant practice, this residual normally is iraintained 6 to 12
minutes, to be certain of meeting the 4 minute requirement. This treatment
standard for viral inactivation is based on the pioneering work of Coin et
al_. (1964; 1967) and is further described by Miller et.al_., (1978). ~~~
Gerval (1978) states that by the old treatment process, without preozona-
tion, the average ozone dosage necessary to provide viral inactivation (to
attain and maintain 0.4 mg/1 of dissolved ozone) was 4.2 mg/1. During the
period of time the pilot plant studies were conducted employing 1.25 mg/1 of
preozonation, the average amount of ozone required for post-ozonation was
halved, to 2.1 Tig/1. Thus the total amount of ozone dosage required was
1.25 mg/1 preozcnation plus 2.1 mg/1 post-czonation, or 3.35 mg/1, a savings
of about 20%.
Preozonation also was found to lower the amount of process chemicals
normally added, not only by eliminating the need for chlorine (used in the
breakpoint step) and sodium bisulfite, but also because of the flocculation
effect caused by ozone oxidation which lowers the amount of flocculant,
powdered activated carbon and chlorine dioxide required. In addition, the
tirre between backwashings of the sand filters was doubled. Finally, when
the amrronium ion concentration 1n the inlet water was not greater than 1
mg/1, the ammonia level in the sand filter outlet did not exceed 0.1 mg/1.
As a result of these process improvements, it is now possible for the
Choisy-le-Roi plant to employ very low levels of chlorine for post-disinfec-
tion and formation of residual for the distribution system. Using the
modified process which Includes the preozonation technique, organic halogen
compounds (probably trihalomethanes) were less than 10 m1crog/l In the pilot
plant work reported by Gerval (1978).
Preozonation of raw water followed by retention over a period of time
to allow biological activity to lower the contents of ammonia and organic
carbon, as well as to allow reductions in levels of chemicals added and
reduction in the amount of ozone required for viral Inactivation has been
329
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practiced for several years at the Moscow, Russia water treatment plant
(Schulhof, 1979). Based on the successful use of the process 1n Moscow,
preozonation is being installed to replace breakpoint chlorination at the
Choisy-le-Roi plant in the Paris suburbs. The process is scheduled for
full-scale operation in 1980 (Schulhof, 1979). In addition, pilot plant
studies are being conducted at other water treatment plants in the Paris
suburbs and at most of the large scale water treatment plants operated by
Compagnie G£n£rale des Eaux (Le Pauloue1, 1978).
Figure 86 shows the comparative schematic diagrams of the treatment
process used at Choisy-le-Roi in 1978 and the modified process which includes
preozonatlon.
TABLE 81. EFFECT OF PREOZONATION (1.25 mg/1) BEFORE STORA3E
Raw water
2-day storage
(no preozonation)
2-day storage
with
preozonation
Detergents
(irq/1)
0.16
0.13
0.08
Organic C
(mg/1)
8.3
8
7
COD
(mg/1)
19
n
6
[NH4+1
(mg/1 )
6.2
4
3.2
Source: Gerval , 1978
A recent article by Schulhof (1980) gives more details of the benefits
of preozonation at Choisy-le-Roi and two other suburban Paris plants and the
improvements being Incorporated at these three plants to maximize biological
removal of pollutants in (1) preoxidized reservoirs ahead of the treatment
processes (2) in biologically operating sand filters and (3) in biologically
operating GAC adsorbers.
330
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1967 to 1980
starting 1n 1983
Seine River raw
water
^
chlorine (breakpoirt)
Seine River raw
water
1
preozonation
(up to '.25 ng/1)
^
^.. _ ,. nU aHi ictr,£nt /NafHl , Z
Sedlneitatlon
i
rapid sard
filtration
4.
dechloriratlon
(NaHSO,)
1
Czonatlon
(4 ng/1)
I
CIO,
^
/
Sedirentafon
i
rapid sand f'ltra
tion (nitrification
\
r
Post ozonation
(2.1 Tig/')
^
ozone
}-. Off-
' gas
, recycle
1
1
1
A
1
1
1
) 1
1
I
I
1
1
i
— i
t
:io2
T
to distribut-on to distribution
Figure 86. Choisy "e Roi water treatmeit plant Process Diagrans.
331
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APPENDIX C
DUSSELDORF, FEDERAL REPUBLIC OF GERMANY
BACKGROUND
Three water treatment plants are operated by the City of DUsseldorf
currently, and include the Flehe (88,000 cu m/day), Am Staad (119,200 cu
m/day) and Holthausen (192,000 cu m/day) installations. These three plants
use the identical process to treat river sand bank filtered water from the
River Rhine, and which is described below. The Am Staad plant has been
using the process of ozonation followed by GAC since 1961, and is the longest
operating water treatment plant known to use this sequential combination of
water treatment steps.
However, there are at least two other water treatment plants in the
vicinity of 3Usseldorf which also draw water from the same region of the
Rhine and use closely similar treatment processes. These are the Duisburg
Wittlaer III Wasserwerk and the Wuppertal Benrath plants. Plant data
presented in this section of the report for unnamed water treatment plants
utilizing river sand bank filtration was obtained from one or more of the
plants noted above.
A detailed discussion of the CUsseldorf water treatment process was
presented in Section 9 of this report, along with pertinent data showing the
effectiveness of the various process steps. These will not be duplicated
here. Instead, additional plant performance data will be presented and
discussed.
RIVER SAND BANK FILTRATION
The five plants noted above make excellent use of the natural aquifers
adjacent to the River Rhine. Figures 32 and 33 illustrate that the majority
of water treatment is achieved in the so-called bank filtration (German:
(Jferfiltration) step. On the other hand, a disadvantage of using this
method of pretreatnent of organics is the necessity for subsequent ozone
treatment for removal of iron and manganese.
Water is drawn from 10 m (32.8 ft) to 30 m (98.4 ft) deep wells situated
50 m (164 ft) to 250 m (820 ft) from the banks of the River Rhine. The
aquifers in which the wells are located consist of sand and gravel deposits.
Removal of turbidity and associated pollutants in the sand bank treatment
results in a high quality sand bank filtered water. Additional treatment
removes iron, manganese, taste, odor and dissolved organics.
332
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OZONATION
Ozone Is generated by means of horizontal tube, water cooled, ozone
generators manufactured by Gebruder Herrmann of Koln (Cologne), Federal
Republic of Germany. Each of the ozone generators contains 432 glass tubes
and generates ozone from dried air by the application of power at 50 Hertz
and voltages ranging from 9,000 to 16,000 volts. These tube-type generators
were installed 1n the early 1970s and replaced the water-cooled, Otto plate
units originally Installed 1n 1961. Cooling of the ozone generators is by
means of a closed loop cooling water system using chemically treated boiler
feed water. The cooling water is cooled, in turn, by passing it through a
heat exchanger located in the raw water supply line.
Ozonized air 1s drawn from the ozone generator by means of the negative
pressure induced by passing treated water (approximately 1% of the total
plant flow) through a ventuH nozzle situated near the top of a vertical
pipe having 10 meter submergence. The ozonized water mixes with the sand
bank filtrate which passes down the vertical pipe and discharges Into the
contact charrber. The 10 meter submergence and overall contact chamber size
provides a retention time of five minutes. The ozonized water from the
contact chamber proceeds to a holding tank which provides an additional 30
minutes retention time.
Over the life of the Am Staad plant 'since 1961), the ozone dosage
necessary to produce the desired quality of finished water has had to be
increased from an average of 1 mg/1 to an average of 3 mg/1. This ozone
dosage is set manually to maintain approximately 0.1 mg/1 of ozone in
the off-gases from the 30-m1nute detention tanks. This level of ozone 1s
determined both by the potassium Iodide wet chemistry procedure and by plant
personnel "sniff-testing" the off-gases,, Residual ozone 1n the off-gases
from the contact chambers and the holding tanks is destroyed by passage
through wet granular activated carbon. However, catalytic destruction of
the ozone-containing off-gases has been tested at DUsseldorf plants and will
be installed to replace the wet GAC procedure (Welssenhorn, 1977).
FILTRATION AND GAC ADSORPTION
Water is punped at pressures of 6 bars (87 ps1) to 7 bars (101 psi)
from the ozonation holding tanks to the bilevel filtration/adsorption
units. These units are constructed of steel, 8 rreters high and 5 meters in
diameter. Water flows downward through an upper 1.5 meter deep filter layer
and then downward through a 2.5 meter depth of granular activated carbon.
Both the filter layer and the adsorption layer rest on layers of support
gravel, each based on a steel support plate containing plastic nozzles
(approximately 31 per sq m). Each layer can be backwashed separately.
The hydraulic loading rate in the filtration/adsorber units has been 20
cu m/sq m/ hr (m/hr), or 8.8 gpm/sq ft, but recent plant expansions have
reduced the loading rate to 12 m/hr (4.8 gpm/sq ft). The older coated steel
units have been on-Hne since 1961 with satisfactory service from the coating,
with the exception of physical wear in the vicinity of the media removal and
changing fittings.
333
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The filtration medium is a so-called "preactivated" carbon having the
following characteristics:
Granule size - 0.9 to 2.5 mm
Mean granule diameter - 1.7 mm
Bulk weight - 580 kg/cu m
Biological nitrification, as well as high degrees of removal of mangan-
ese, iron and turbidity, is achieved in the filtration stage with provision
of 1.5 meters of filter media.
The adsorption medium consists of a mixture of Lurgi LS Supra and
Chemviron (Calgon) F-300 granular activated carbons having the following
characteristics:
Granule size - 0.5 to 2.5 mm
Mean granule size - 1.4 to 1.6 mm
Filtration layer runs of approximately 24 to 48 hours are observed.
Backwash cycles for the adsorption stage are 4 to 6 weeks, with periods
between regeneration ranging from 5 to 6 months. Initial air scouring,
followed by a 5-minute water backwash, is the procedure used for both the
upper and lower layers.
FINAL TREATMENT STEPS
The final treatment steps include the addition of sodium hydroxide 'or
pH control (to neutralize C02 produced biochemically) and 0.1 to 0.3 mg/1 of
chlorine dioxide to disinfect and to maintain a residual within the distribu-
tion system.
The three City of Dusseldorf water treatment plants are unique in that
there is very little reservoir storage for finished water. As a result, all
three plants are designed to operate on demand.
GRANULAR ACTIVATED CARBON REGENERATION
Over the years since the ozone/GAC process was installed in Tusseldorf,
the increased GAC levels of halogenated organics (TOC1) in the Rhine (which
are not removed during river sand bank filtration) has shortened the GAC
regeneration cycles to such a point (every 5 to 6 months) that it became
economical to install reactivation facilities at the Dusseldorf plants.
Spent GAC now is transported from the Am Staad and Flehe facilities to the
fluidized bed regeneration furnace situated at the Holthausen plant. This
furnace, which was in shakedown during a site visit in May, 1977, was fully
operational in June 1978,
The GAC regeneration furnace was supplied by Lurgi and has a GAC
regeneration capacity of 6 metric tons per day. It is to be the central
regeneration facility for Dusseldorf, and space 1s available for two additio-
nal furnaces to be Installed if and when needed. Spent GAC is flushed from
a storage hopper to a dewatering screw which regulates the carbon to the
334
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upper or drying stage of the fluidized bed furnace which is maintained at a
terrperature of 200° to 300°C by means of natural gas heating. The dried GAC
passes to the lower or reactivation stage where steam is injected into the
chamber which is maintained at a temperature of 600°C to 800°C, again using
natural gas heating. The SAC enters a quench tank from which it is flushed
to a storage hopper. The furnace off-gas is treated by means of a cyclone
after-burner and heat exchanger.
Another fluidized bed granular activated carbon regeneration furnace is
installed at the Wuppertal Benrath water treatment plant. While this plant
was not inspected by the 1978 site visitation team, it is known that the
unit was designed and constructed by WABAG, a design/construction engineering
firm headquartered in Kulmbach, Federal Republic of Germany. The Wuppertal
regeneration facility was installed in January, 1978 but was still in'shake-
down in June, 1978. The maximum capacity of the unit is 240 kg of GAC/hr,
but the recommended rate of application is 100 to 150 kg of GAC/hr.
A third fluidized bed GAC regeneration furnace is in operation at the
ZUrich (Switzerland) Lengg water treatment plant (Grombach, 1975).
It has also been reported (Water Research Center, 1977) that there is a
multiple hearth GAC regeneration furnace at the Alelyckan water treatment
plant at Goteberg, Sweden. This same reference notes that "one granular
activated carbon regeneration plant is currently in use at Church Wilne,
England." This English regeneration unit has been discussed by Osborne
(1979).
PLANT OPERATIONAL DATA
Operational data from the individual plants 1n and around CUsseldorf
are not readily available either from the plants or from the Engler-Bunte
Institute of the University of Karlsruhe, which conducts research for many
German waterworks. The Institute places great emphasis on the confidentiality
of the raw and/or unpublished analytical data developed by and for their
client waterworks. However, information was provided for unnamed plants on
the lower Rhine which utilize the same treatment process as does Dtlsseldorf.
Similar data for other water plants treating river waters in the Federal
Republic of Germany were provided as well, identifying only the river source
and the treatment process.
Table 82 contains actual plant operational data showing the degree of
purification obtained at the various stages of treatment of River Rhine
waters in the Dlisseldorf area. Table 83 lists DOC and halogenated organlcs
data obtained during a single day of operation at one of the five plants in
the region.
Table 84 shows data obtained at a lower Rhine water treatment plant
which uses a process consisting of river sand bank filtration, permanganate
(oxidation)/polymer sedimentation, filtration and GAC treatment. These data
were determined from the three operating trains in the plant, and are averages
of data obtained throughout 1977.
335
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TABLE 82. LOWER RHINE RIVER WATER TREATMENT DATA FOR PLANTS UTILIZING
RIVER BANK FILTRATION/OZONATION/FILTRATION/GAC ADSORPTION.
AVERAGES FOR 1977
Parameter
PLANT #3
DOC (mg/1)
COD (mg/1)
UV
PLANT #4
DOC (mg/1)
COD (mg/1)
UV
PLANT #5
DOC (mg/1)
COD (mg/1)
UV
Raw Rhine
River Water
4.55
12.7
11.62
4.46
13.11
11.07
4.03
11.13
11.20
After River
Bank Filtration
1.8
4.88
3.95
2.16
5.54
5.13
2.17
6.07
5.10
After Ozonation
& Filtration
1.70
2.83
2.03
••**
2.41
1.90
3.30
After
GAC
1.15
3.33
1.23
1.45
3.47
1.47
1.43
3.19
1.87
tote: DCC = dissolved organic carbon
COD s chemical oxygen demand
UV = relative absorbance at 250 nm
Table 85 shows data obtained at a plant utilizing river sand bank
filtration, followed by GAC adsorption directly. Data presented are the
averages obtained during 1977.
Table 86 shows average data for 1977 at a River Danube plant (without
river sand bank filtration) using ozonatlon, filtration and GAC adsorption.
The following conclusions may be drawn from the data of Tables 82
through 86:
1) River sand bank filtration is an effective method of removing waterborne
pollutants, as measured by DOC, COD and UV adsorption. The degree of
pollutant removal is variable, however, as 1s seen by comparing data
from Plants No. 3, 4 and 5 with those from Plants 2 and 6.
2) Data from Plants No. 3, 4 and 5 are in general agreement as to the
levels of treatment attained after river sand bank filtration. Percen-
tage removals of COC, COD and UV absorbing materials by the treatment
process consisting of ozonation/filtration/GAC adsorption is as follows:
336
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TABIE 83. PLANT J4. CHLORO-ORGANIC MATERIAL DATA FROM A SINGLE DAY'S SAMPLING IN 1977
Water Treatment
Process
Rhine River
raw water
river banK
filtration
ozonation
filtration + GAC
adsorption
0.2 mg/1 chlori-
nation
Parameter
DOC CHC13 CHBrCl2 CHBr2Cl CHBr3 CC14
jag/l^g/i
4.7 3o9
2.2 1.4
2.0 0.9
1.6 1.1
1.3 1.3
C2H4C12 JC2HC13 C2C14 C2H2C14
.
—
—
—
—
0.1
—
—
--
—
0.2
; -- 2.4
— 0.03
— 0.02
— 0.04
0.8 0.04
—
—
--
—
__
0.8 1.1
0.9 0.7
0.2 0.3
0.1 0.05
0.2 0.06
—
—
—
—
—
OJ
OJ
—I
-------
% Reduction 1n Levels of
Plant No. 3
Plant No. 4
Plant No. 5
TABLE 84. LOWER RIVER RHINE WATER TREATMENT DATA FOR PLANTS USING RIVER BANK
FILTRATION/KMnOi/POLYMER SEDIMENTATION/FILTRATION/GAC. AVERAGES
FOR 1977
DOC
36
33
34
COD
32
37
47
UV
69
71
63
Parameter
PLANT #6
TRAIN #1
DOC (mg/1)
COD (mg/1)
UV
TRAIN #2
DOC (mg/1)
COD (mg/1)
UV
TRAIN #3
DOC (mg/1)
COD (mg/1)
UV
Raw Rhine
River Water
4.64
14.10
11.07
4.64
14.10
11.07
4.64
14.10
11.07
After River
Bank Filtration
2.46
7.17
6.37
2.46
7.17
6.37
2,46
7.17
6.37
After KMnOd
& Sedimentation
2.07
3.75
2.05
3.78
2.24
3.81
After
3AC
0.96
0.95
1.26
1.63
0.99
2.50
0.81
TABLE 85. LOWER RHINE RIVER WATER TREATMENT DATA FOR PLANT UTILIZING RIVER
BANK FILTRATION/GAC ADSORPTION. AVERAGE FOR 1977
Parameter
PLANT #2
DOC (mg/1)
COD (mg/1)
UV
Raw Rhine
River Water
4.25
11.23
9.13
After River
Bank Filtration
0.88
2.77
1.47
After
GAC
0.74
2.47
1.16
338
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TABLE 86. UPPER DANUBE RIVER WATER TREATMENT DATA FOR PLANT UTILIZING
SEDIMENTATION/OZONATICN/FILTRATION/GAC. AVERAGE FOR 1977
Parameter
PLANT #1
DOC (mg/1)
COD (mg/1)
UV
Kaw Danube
River Water
2.26
5.51
4.98
After
Treatment
1.61
1.49
COSTS
Only limited cost data were made available during the site visit to the
Dusseldorf waterworks. This brief Information 1s presented below.
Total revenues for the waterworks in 1976 were about 73 million Ceutsch
marks (DM), up from 55 million DM in 1974. The average rate charged for
water was 0.9 DM per cubic meter 1n 1978, with the flat residential customer
rate set at 1.2 CM/cu m, approximately equivalent to $2.20/1,000 gallons.
Treatment costs (exclusive of distribution and administration) were
reported (Poggenburg, 1978) to comprise somewhat less than 40% of the total
annual Dusseldorf water utility costs. The figure of 0.28 DM/cu m was
mentioned as the total water cost in a recent year, excluding returns on
capital. Costs at CUcseldorf should not be compared with those of nearby
MUlheim, for example, because the Dusseldorf Wate>" Works pays more for
street usage.
The waterworks provides capital for new projects from its own funds set
aside in previous years and from new bond issues. Bonds were sold recently
(prior to 1978) at an interest cost of about 6.5%. The waterworks is a
private stock corrpany, with the City of Dusseldorf owning 100% of the stock.
Due to its private status, Its revenues are drawn entirely from rates
charged for water and its financing 1s separate from other city capital
projects.
The new fluidlzea bed furnace for reactivating spent GAC from all three
DUsseldorf water treatment plants has been operating for over a year. The
two-stage furnace operates at 200° to 300°C at the first stage for drying
and at 600° to 800°C at the second stage for reactivation. An afterburner
(which attains 600°C outlet temperatures) prevents air pollution and prevents
even a visible steam plume. Absence of a visible steam plume is required by
local air pollution control regulations. A cyclone removes particulates to
a level of 75 parts per billion.
Energy requirements are 55 to 65 cu m/hr of natural gas (AHgas ^8,40)
kcal). At present, the furnace is operating with 4 to 5% GAC losses in the
furnace, with a total loss of 8 to 9% (the difference 1s lost 1n transporting
GAC from the adsorber to the furnace and returning). However, the 4 to 5%
339
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furnace losses depend to some degree on the quality of the GAC and the
temperature and precision of the furnace operations. The regeneration
capacity is 6 tons/day (250 kg/hour).
Although no cost figures were made available on either the capital
invested tn the furnace or its operating costs, the total cost of regene-
ration was said to be a bit less than 30% of the cost of virgin GAC. With
European GAC prices 1n the range of 70 to 80<£/lb, this percentage suggests a
reactivation cost on the order of 20£/1b.
Capital costs for a single GAC column at DUsseldorf were said to be
120,000 DM, without outside piping. The installed total capital cost for
water treatment was 3,000 DM/cu m of water treated per hour. For each 1,000
cu m/hr of installed treatment capacity, the capital cost was 1,OCO x 3,000
= 3,000,000 DM.
The City of DUsseldorf treats 400,000 cu m/day of water and pumps
500,000 cu m/day from the wells. The additional 100,000 cu m/day of well
water is sent to industries and nearby cities for local treatment. The
staff at Dusseldorf totals 375 people, but only 2 people operate the plants
around the clock.
340
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APPENDIX D
MORSANG-SUR-SEINE (SUBURBS OF PARIS)
GENERAL CHARACTERISTICS
The Morsang plant is located on the Seine River, 35 km upstream of
Paris near the new town of Evry and supplies water to Evry as well as to the
Paris suburbs. In concept and when completed about the year 2000, Morsang
is expected to produce about 1,000,000 cu m/day (264.2 mgd) of drinking
water from the Seine River.
Morsang is being constructed in successive, star-shaped plant stages,
with each star being capable of producing 225,COO cu m/day (59.4 mgd). Each
star at Morsang will be constructed around a central station with each
treatment stage occupying one point of an In-aginary three pointed star. At
the center of each star will be the central station, which will house chemi-
cals, activated carbon and ozonation equipment. Laboratories, pumping
station and administration are housed in a separate building. The general
plant layout-is shown in Figure 87.
The first stage of the first 3-pointed star began operating in 1970.
In 1975 the second stage of the first star was completed, and construction
of the third stage of the first star will depend upon results obtained from
a detailed pilot plant testing program, which was to be completed during
1979.
The Morsang plant is owned and operated by the Soci§t£ Lyonnaise des
Eaux et de TEclairage, one of two large, integrated water making companies
in France.
Raw Seine River water at Morsang is fairly clean: TOC is about 3 mg/1,
humic acids about 7 mg/1, ammonia about 0.5 mg/1 and taste threshold about
12.
PLANT OPERATION
Raw Seine River water is coarse screened (1.5 mm mesh), then is subjected
to breakpoint chlorination (for removal of ammonia, usually less than 0.5
mq/1) with 3 to 6 mg/1 of chlorine added as the gas. Prechlorinated water
then is pumped to the center of the first star where it is split into two
streams. One stream of 50,000 cu m/day (13.2 mgd) is sent to the first
stage of the star, and the second stream of 75,000 cu m/day (19.8 mgd) is
sent to the second stage of the star.
341
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Control
Room
Future treat-rent
building
Certral Co-trol SJuilding
for f ret Treat-iert &. d ng
Figure 87. General layout of the Morsang-sur-Seine treatment works.
First Stage of the Star (Maximum flow: 3,300 cu m/hr -- 871,860 gal/hr)
Prechlorinated water is settled and clarified using a 665 sq m s'udge
blanket Pulsator clarifier (Degremont) operated at an hydraulic loading rate
of 3.15 cu m/sq m/hr (m/hr), then filtered through six type T Aquazur V
(DegrSmont) sand filters. Coagulation 1s accomplished with addition of 60
to 80 g/cu m of aluminum sulfate and is monitored by flocculation tests and
zeta potential measurements. Activated silica (1 to 2.5 g/cu m) is made by
adding sulfuric acid to alkaline sodium silicate, and its dosage depends
upon the measured sludge cohesion coefficient. Powdered activated carbon
normally is added ahead of the clarifier at 15 to 25 g/cu m.
Water is passed through the sand *11ters, each having an area of 60
sq m, at an hydraulic rate of 6 cu m/sq m/hr (m/hr). After sand filtration,
the water is ozonized in two baffled contact chambers, each having a volume
of 215 cu m (10.5 m long and 4.5 m high) and designed to achieve a contact
time of 8 minutes at peak flow. About 67% of the total ozone generated is
added to the first contact chamber in which the initial ozone demand is
satisfied and a residual ozone concentration of 0.4 mg/1 is attained. The
remaining 33% of the total ozone dosed is added in the second chamber, where
the Tevel of residual dissolved ozone is maintained at 0.3 to 0.4 mg/1. The
contact time 1n each chamber 1s 4 minutes at maximum flow (8 minutes total
ozonation at peak flow). Water flow 1n each chamber 1s countercurrent to
the direction of the upward flow of ozone-containing air (see Miller et_ al..
1978, p. 120). The residual dissolved ozone is monitored at the outlet of
both contact chambers at 0.3 to 0.4 g/cu m.
342
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This treatment sequence will be referred to subsequently as Process #1.
Second Stage of the Star; (Maximum flow: 3,300 cu m/hr -- 871,860 gal/hr)
Settling and clarification of the prechlorinated water are conducted
with a 208 sq m Superpulsator clarifier (DegrSmont). Filtration is through
four Aquazur sand filters, each having a unit surface area of 63 sq m, at an
average hydraulic loading of 8.75 m/hr and a peak hydraulic loading of 13
m/hr.
Ozone is produced (for the first two stages of the star) by two Degremont
generators, each having a production capacity of 6.6 kg/hr. Contact times
(8 minutes at maximum flow) and other ozonation conditions are identical
with those of the first stage.
Following ozonation is 6AC adsorption through 1 m deep beds of Chemviron
F-400 carbon, using four Aquazur filters each having a surface area of 63
sq m. These are operated at a filtration velocity of 13.1 m/hr at maximum
flow. These Aquazur filters are especially designed for activated carbon
and are called Mediazur filters.
After sand filtration and before ozonation,, the water is divided into
two equal portions. The first fraction is ozonized before GAC adsorption
and the second is passed through the GAC adsorbers then ozonized. These two
sequences of treating water in the second stage of the star (termed Process #2
and Process 13, respectively) have been monitored full-time since October,
1975 and the water qualities compared with those of Process #1 conducted
over the same period of time. Initial results of this comparative study
(obtained over the period October, 1975 through December, 1976) were reported
by Richard & Fitssinger (1977) and are discussed below. The three processes
are shown schematically in Figure 88, along with a fourth pilot plant process
(Process #4) which will be discussed later.
Parameters studied during the 15-month program reported by Richard &
Fiessinger (1977) for Processes #1, #2 and #3 included:
(a) Organic matter — expressed as mg/1 of oxygen consumed as measured by
. KMnO- oxidation in an acid medium,
(b) Taste threshold — measured at 30°C by the dilution method,
(c) Organo-halogen derivatives -- detected by gas chromatography combined
with an electron capture detector. These were extracted with Uvasol
pentane (Merck). Results given by Richard & Fiessinger (1977) were
limited to chloroform and dichloromethane only.
RESULTS OF 15 MONTH STUDY COMPARING PROCESSES #1, #2 & #3
Organic Matter
Figure 89 shows the percent reduction in concentration of organic
matter obtained by each of the three processes.
343
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RAW SEINE RIVER WATER
PRECHLORINATED RAW WATER
CLARIFICATION WITH
POWDERED ACTIVATED
CARBON (PAC)
\
SAND FILTRATION
OZONATION
CLARIFICATION
WITHOUT PA':
SAND FILTRATION
CLARIFICATION
WITHOUT PAC
SAND FILTRATION
1
i
OZONATION
1
\
GAC
ADSORPTION
i
Treatnu
Line t
(full-see
r
»nt
tz
lie)
i
G,
ADSO
OZO
i
Tr
L
(ful
r
\C
OPTION
'
NATION
r
satment
ine #3
1-scale)
i
OZONA
1
G
ADSO
1
Trea
Lin
(pilot
TION
r
AC
RPTION
F
tment
e #4
plant)
Treatment
Line #1
(full-scale)
Note: all treated water leaving the plant is chlorinated for residual
Tigure 88. Morsang-sur-Seine water treatment plant—processes operating in
1977.
344
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100 .
90 -
80 -
* 70 -
4)
o
co 7: 6O -
•£» c
tn ™
o>
o
c 5O.
c
o
1 40-
•o
** 30 .
treatment line 1 10° -
A clarification with PAC
90 -
* send filtration
* ozonatlon
so-
il /"•/ A* y\ 7°
1 \ r^Jr%\
JaWx^ JSr/4" 6° "
*7 1 7 v v ?
*"* 1 / i 50 -
1 /
1*
* 40-
G
1
J
1
1
F
j<
""f
I
1
treatment line 2 10° -
clarification w/o PAC
90 -
* sand filtration
| & ozonatlon
i 80 -
1 • GAC adsorption
J .^-A
JSM^-^-Vi 7° "
1 / V-A ...
it X t,^^ \ ^«"'*
fcj j ^ f »^ ja 1
*•*» f O W-*
-------
Process #1 —
Starting with a raw water level of 3 mg/1, some 30 to 60% of the
organic material is eliminated by clarification with 10 to 20 mg/1 of
powdered activated carbon. During the summer of 1976, this dose was increased
to 25 to 30 mg/1. Sand filtration removed all carbon fines and increased
overall organics removal to 55 to 65%.
The dosage rate of ozonation was found to affect the organics removal
greatly. During the first three months, the ozonation dosage was too low
and the organic content was the same as or higher than that obtained after
sand filtration. Increasing the ozone dosage to 1.2 mg/1 raised the total
percent removal of organic matter to 60 to 70%, an additional 8% over sand
filtration.
Processes #2 and #3—•
Clarification at the rate of 8.75 m/hr without powdered activated
carbon removed 40 to 50% of the organic material and sand filtration removed
an additional 5% (total organic removal by powdered activated carbon and
sand filtration: 45 to 55%.
Process j2--During the first three months of the study the ozone
dosage again was too low, but when this was increased to 1.2 mg/1, the total
removal of organic material increased to 55% to 70%. However, water treated
with powdered activated carbon by Process #1 was of higher quality, with
regard to organic matter content, after ozonation (1.4 mg/1 of ozone) than
that obtained from Process #2 (1.6 mg/1 ozone).
During the first three tr.onths, GAC adsorption (after sand filtration
and ozonation) increased the overall percent removal of organic materials to
80 to 85%. This figure fell to 70% when the water was cold and rose to 75%
when the water was warm. The increased organics removal observed during
warm weather could have been a result of bacterial activity in the GAC
adsorbers. The 80% to 85% levels of organics removal were obtained after
the first three months period and Indicates that the additional 5% to 10%
removal also may have been a result of bacterial activity in the GAC beds.
Process #3--Sand filtered water was passed through granular activated
carbon. This increased the total organics removal to 80 to 85%, but this
level fell to 70% when the water was cold.
A drought occurred during this test program, and the level of organics
removal fell to 67% by Process #3 but was 75% by Process #2. This higher
rate of organics removal by Process #2 was attributed to "the intense oxygena-
tion of the ozonized water and the biological oxidation which it causes in
the water".
When the drought ended, the quality of water which passed through the
GAC adsorbers in Process #3 improved, but was still slightly lower (about
50%) than that obtained by Process #2.
346
-------
Taste Threshold
During the 15 month study the raw water taste threshold rose from 10 up
to a level of 20 to 30 units during the drought.
Process #!--
Clarification with powdered activated carbon followed by sand filtration
lowered taste thresholds to two units in most cases. Upon ozonation, however,
"new, unpleasant tastes" were formed, and the threshold level rose to three
units. During the drought the taste threshold of clarified water rose to 4
to 10 units (even with powdered activated carbon dosages being increased to
20 to 25 mg/1) and the level 1n sand filtered water rose from 3 units to 6
units. During this period, the level in ozonized water remained at 2 to 3
taste units. This level was considered to be "not perfect, but acceptable
to customers".
Process #2—
After ozonation and GAC adsorption, the taste threshold remained
consistently at 1 unit over the 15 month period.
Process #3—
Sand filtration followed by GAC adsorption without ozonation produced
taste threshold values of 1 for the first 10 months, then the carbon "comple-
tely lost its capacity for removal of taste" and the threshold value rose to
2 units.
The difference in activated carbon performances (with ozonation in
Process #2 and without ozonation in Process #3) was attributed to "the dual
role of. ozone1':
a) Ozone oxidized non-polar, or taste-causing, organic molecules Into
polar molecules which have a less powerful taste; and
b) Ozonation aerates the water and stimulates biological activity in
the GAC adsorbers.
Formation and Elimination of Halogenated Organic Derivatives
The chloroform content of the Seine raw water at the Morsang plant 1s
well below 1 microg/1. Chlor1nat1on at the clarlfier (with 3 to 6 mg/1 of
chlorine) produces chlorinated organics, and chloroform levels of 5 to 15
microg/1 are found routinely at this point. Figure 90 shows results of
chloroform analyses obtained during the 15 month study.
Process #1 —
Powdered activated carbon treatment lowered the chloroform content 40
to 50X, leaving 0.1 mg/1 of total chlorine in the clarified water. Additional
chlorine (0.2 mg/1) had to be added to the filter Inlet to protect it from
algae and zooplankton, but this additional chlorine dose produced "no more
than 1 microg/1 of additional chloroform". After clarification and sand
filtration, chloroform levels found were 5 to 7.5 microg/1.
347
-------
15-
10-
CO
o>
4.
n
O
i
o
line 1
15-
10
raw water 5
water
o clarification with PAC
A sand filtration
» ozonatlon
son
month
A '! \
line 2
15-
10-
* raw water
» raw water +
clarification w/o PAC 5
4 sand filtration
o ozonatlon
• GAC adsorption
line 3
•raw water
*raw water + CI2
o clarification w/o PAC
A sand filtration
• GAC adsorption
6 ri d
month
j f
Figure 90. Evolution of CHCI3 in Morsang waters.
(Richard & Fiessinger, 1977)
-------
Ozonation lowered the chloroform level to 3.5 to 6.5 m1crog/l, but by
air stripping, not by chemical oxidation.
Processes #2 and #3—
Prechlorinated water was clarified without addition of powdered activated
carbon. The amount of chloroform produced tended to increase with longer
retention times in the clarifier, and vice-versa. After sand filtration,
the average chloroform concentration was 10 microg/1.
Process #2--After ozonation followed by GAC adsorption, the chlorofom
concentration varied between 7 and 13 microg/1. (It is apparent that the 1
meter deep GAC beds had been saturated with chloroform and that breakthrough
had been attained early in the 15 month study).
Process 13--The same chloroform range (7 to 13 microg/1) was obtained after
sand filtration followed by GAC adsorption (no ozonation). Thus, ozonation
followed by GAC adsorption should have no capability to remove chloroform
after the adsorption capacity of the GAC for chloroform has been exceeded.
Conclusions From the 15-Month Study of Processes #1, #2 and #3
Richard & Fiessinger (1977) drew the following conclusions from this
15-month comparative study:
1) Formation of chloroform can be reduced by optimizing the coagulation
step (before chlorination), which lowers the hunvic content to a minimum.
2} After prechlorinat^on, powdered activated carbon (PAC) removes residual
chlorine from the water, adsorbs chloroform precursors and reduces the
level of chloroform by about bO%.
3) Over the 15-month period, sand filtration followed by GAC adsorption at
10 m/hr (no ozonation) removed 40% of the chloroform.
4) Ozonation before or after GAC adsorption removed some chloroform, but
by air stripping, not by chemical oxidation.
5) Chloroform concentrations at Morsang have never exceeded 16 microg/1.
6) Process #1 (clarification with powdered activated carbon, final treatment
with ozone) produces "less than perfect" organoleptic qualities, which
will be affected directly by any change in the amount of raw water
pollution.
7) Process #3 [clarification (without powdered activated carbon), sand
filtration, GAC adsorption, post-ozonation] produces water with "very
good organoleptic qualities". With sudden surges of raw water pollution,
however, it is better to use powdered activated carbon so as to prolong
the useful life of the GAC.
8) Process #2 [clarification (without powdered activated carbon), sard
filtration, ozonation, GAC adsorption] gave "very appreciably improved
349
-------
results". Ozone aerates the water and oxidizes non-polar compounds
which cause unpleasant tastes. This "Increases the activity of the
carbon and prolongs Its useful life considerably".
(No data are reported by Richard & Fiessinger, 1977, regarding the
criteria measured to determine the useful life of the GAC adsorbers.
However, these are presumed to be organoleptlc parameters, such as
taste threshold, 1n order to maintain low taste thresholds.)
9) Biological phenomena 1n the GAC appear to be stimulated by ozonatlon of
the water before passage through the GAC adsorbers.
The next phase of the research program at ^lorsang-sur-Seine was a pilot
plant study of the treatment of raw Seine water by a process 1n which break-
point chlorlnatlon was eliminated (Process #4). This pilot plant study
began 1n early 1977 and was to have been completed during 1979, after which
a decision was to be made as to the treatment process to be Installed on
full-scale 1n the third stage of the first star. Very recent data (Fiessinger
& Montiel, 1980) presented at the 1980 Annual American Water Works Association
Conference Indicates that the decision will be to install Process #4.
PILOT PLANT STUDIES WITHCUT PRECHLORINATION
In Process #4, the prechlorination step has been eliminated. Raw Seine
River water is clarified with alum and lime (no powdered activated carbon),
decanted, sand filtered, ozonized, passed through GAC adsorbers and post-
chlorinated. Chemviron F-400 granular activated carbon is used in Process
#4 and the bed depth is 1.4 m. Dissolved oxygen levels in the raw Seine
River water at Morsang are 3 to 5 mg/1. Prior to the GAC adsorption step in
Process #4 the DO is 10.4 mg/1 and drops to 8.8 mg/1 after GAC adsorption.
Ammonia levels 1n the Seine River raw water are 0.1 to 0.2, but 0.1 mg/1 in
the product water. Therefore, nitrification 1s Insignificant in Process #4.
For all four processes, data on organic materials content (by the KMnC4
and UV absorbance methods), percent reduction of organic materials content,
TOC, taste threshold, fluorescence, humlc acids content and chloroform
content at various points in the different treatment processes are presented
in Figures 91 through 94 (for Processes #1, #2, #3 and #4, respectively).
Figure 95 1s an overview diagram of the four treatment processes showing the
points where samples for the analyses given In Figures 91 through 94 were
taken. Data presented in Figures 91 through 94 are averages of 5 samples
taken from side-by-side process operation.
For comparison, data for all four processes are summarized in Table 87.
The quality of water produced by Process #4 appears to be the highest of all
processes, but comparison 1s difficult to make since the GAC used in Process
#4 was placed in use about 2 years after that used in Processes #2 and #3.
Therefore, the advantages of not prechlorinating at Morsang remain
debatable. It is still too early to predict the final process that will be
installed in the third stage of the first star (Richard, 1979).
350
-------
4-
3-
2-
1-
0
org. mat*Is. -KMnO4
100
50-J
org. mat'ls. -
% removal
5-| fluorescence
4-
10-f numic acids
8-
org. mat'ls. by UV
0.5-
11
haloform comp'ds.
2
-CHCI3
11
1-raw waters 2-after prechlorinatloni 3-after clarifi
cation; 6~after sand filtrationj 11-after ozonation
Figure 91. Process 1 performance parameters at
Morsang plant.
(Rlchard,1978)
351
-------
5-
org. mat'ls.-KMn04 5— JOG
org. mat'ls. -
% removal
taste number
th=threshold
12
5-
4
3-
2-
1
0
fluorescence
10-
8-
6-
4-
9 12 2-
humic acids
1.0-«
0.5.
org. mat'ls. 50-
haloform
comp'ds.- CHCIg
9-,12
7-after sand filtravion; 9-after ozonation;
12-after GAC adsorption
Figure 92. Process 2 performance parameters at
Morsang plant.
(Richard, 1978)
352
-------
org.mat'ls.- KMnO^ 5*. TOG
org. mat'ls. -
% removal
taste number
= threshold
0.5
halof orm
comp'ds.- CHCI3
1.3 14
13-after GAG adsorption,- 14-after ozonation
Figure 93. Process 3 performance parameters
at Morsang plant.
(Richard, 1978)
353
-------
5-
4-
3-
2-
1-
100-
50-
5-
4-
3-
2-
1-
1.0-
0.5-
0-
org. m
1
or
fl
1
org
nniaHIHB
1
BKH
5
at is.- r\mnu4 -
03 4-
G 3-
10 ^ 24
g. mat'ls..
removal 1O
5
uor<
. m<
5
•BH
rr ^ 10"
iscence 1Q-
8-
6-
4.
8 1C 15 2.
it Is. by UV 5Q_
40-
30-
20-
•BaaMABBBMBM 0-
1
TOC
G
A
10 C
8 \* 1S
taste number
th=threshold
1
5 8 10 15
humic acids
1
5 TV0 15
haloform comp'ds.
CHCI3
1 8 10 IS
5-after clarification! 8-after sand filtration;
10-after ozonation; 15- after GAC adsorption
Figure 94. Process 4 performance parameters
at Morsang plant.
(Richard, 1978)
354
-------
to
PARIS
NOTE.
indicates sampling point
Figure 95.
Analytics" sarpling points for the 4 water treatnent processes
at Horsang-sjr Seire p'ant, Frarce
355
-------
CO
en
CTl
TAB
IF 87 COMPARISON OF PROCESSES 1, 2, 3 AND 4 AT MOR'ANG SUR SEINE DATA AVERAGED OVER 5 MONTHS OF SIDE BY SIDE OPERATION.
Parameter
Organic
Materials
(by KMnOj)
TOC
Raw
Water
3.8
mg/1
3.0
mg/1
Taste Threshold 12
Fluorescenc
Organic
Materials
(by UV)
Humlc
Acids
CHCla
i 3.9
0.9
7
mg/1
1
m1crog/1
Finished Water Parameter by Process
Process 11
1.6 mg/1
1.2 mg/1
1
0.8
0.2
1.8 mg/1
26 mlcrog/1
Process 12
1.4 mg/1
1.2 mg/1
none perceptable
0.4
0.2
1.0 mg/1
30 m1c rog/1
Process #3
1.3 mg/1
1.1 mg/1
2
0.5
0.2
1.2
26 ralcrog/1
Process 14
0.8 mg/1
0.9 mo/1
none perceptable
0.2
0.05
0.5 mg/1
1 mlcrog/1
Note: Post-chlorln-
atlon (0.5 0.6 mg/1
dosage) follows all
treatment processes
for distribution
systems
process II.
chlorlnatlon,
coagulation,
flocculatlon,
clarification (pow
dered activated
carbon),
sand filtration,
ozonatlon
Process »2:
chlorlnatlon,
coagulation,
flocculatlon.
clar1f1cat1on(w1thout
powdered activated
carbon),
sand filtration,
ozonatlon,
GAC filtration
Process 13:
chlorlnatlon,
coagulation.
flocculatlon,
clarification (without
powdered activated
carbon),
sand filtration,
GAC filtration,
ozonatlon
Process 14:
coagulation,
flocculatlon,
clarification (without
powdered activated
carbon,
sand filtration,
ozonatlon,
GAC filtration
-------
FUTURE PLANS AT MORSANG
The pilot plant study of the process without prechlor1nation was to
have been continued through 1979, then a decision was to have been made as
to the process to be installed in the third stage of the first star. A
recent presentation (Fiessinger & Montiel, 1980) implies that the decision
will be to install Process #4.
Granular activated carbon adsorption has been proven to be an efficient
process step and is being retrofitted into the first stage of the star
(Process #1) followlr, ozonation.
When 3AC adsorption in Process #1 becomes operational in 1979, powdered
activated carbon was to be eliminated as a permanent treatment step, but
will be maintained in the ready state for discontinuous addition in the
event of incidents of pollutlonal surges.
After the first stage at Morsang has been retrofitted with GAC adsorp-
tion, there will be sufficient GAC installed in the South Paris region
plants of SocietS Lyonnaise des Eaux et de TEclairage (in the Viry, Vigneux
and Morsang plants) to warrant a central GAC regeneration facility. Plans
for constructing such a facility were being considered during 1978.
The Degr§mont water treatment plant at Crly (in Paris), which currently
uses ozone treatment, also is being retrofitted with GAC adsorption to
follow after ozonation.
BIOLOGICAL REMCVAL CF ORGANIC MATERIALS BY GRANULAR ACTIVATED CARBON -
RESULTS OF A MODELING STUDY AT MORSANG-SUR-SEINE
In 1977, Benedek reported a study conducted at the Morsang-sur-Seine
treatment plant using data obtained from Processes #ls #2 and #3 of the
full-scale plant. The objective of this study was to try to establish the
mechanism(s) of organics removal in the biologically active activated carbon
adsorbers and, thereby, to attempt to develop application and design princi-
ples for the ozonation/granular activated carbon treatment combination.
This study will be reviewed during this discussion because it presents
further insights into the 15-month study previously conducted by Richard &
Fiessinger (1977).
A mathematical model for describing activated carbon particles with
biological activity has been developed by Maqsood and Benedek (1977) and by
Peel and Benedek (1977). The basis of this model Involves mass transfer 1n
a differential SAC column segirent containing percolating water, a bacterial
"film" and activated carbon. The concept of a uniform bacterial "film" was
presented to allow simplification of the mathematical expressions derived.
The major required Inputs for the model were based on batch tests for
(a) adsorbable Isotherms for the carbon surface equilibrium reaction (with
adsorbable solutes) and (b) batch adsorption kinetics of solutes. In addir
tion, an estimate was -nade of the bacterial degradation rates of solutes,
357
-------
and these are expressed as zero order, carbon surface-based reactions in
either batch or continuous column tests. AdsorbablHty and blodegradability
were assumed to be operative on the same organic fractions. Finally, the
presence of refractory organics, possibly produced by the bacteria, was
considered to be negligible.
Respiration measurements were made in a Hach BOD apparatus on pulverized
activated carbon samples, to determine the amounts and rates of blodegradation
of organic materials.
Isotherms were determined on ozonated and non-ozonated water and
pulverized activated carbon 1n terms of TOC, COD (determined by !
-------
o
o
emoved/g
y
o
H-
0)
0.12-
.
0.10-
-
0.08-
.
0.06-
«
0.04-
0.02-1
J
a
Q
m
n a
a °
a n
a n
S Q
o
B 0
1 °
on
t
• a a with 03
o
D without 03
13
&
0.02 0.06 0.10 0.14 0.18 0.22 0.26 0.30
g TOC applied/g GAC
Figure 96. Effect of ozone on GAC adsorption at
IViorsang plant.
(Eenedek. 1M77)
359
-------
Bacterial respiration rates also were similar, although more activity
was observed at the top of the adsorber receiving ozonized water. Respiration
rates corresponded to the degradation rates of the organic materials.
In these modeling studies, Benedek (1977) used the isotherms and
kinetic constants determined at Morsang to predict breakthrough curves, as
well as cumulative adsorption curves. Figure 97 is a plot of C/C0 versus
the throughput parameter, I, which represents the ratio of substrate fed to
the adsorptive capacity of the GAC.
The non-adsorbable component of the feed immediately broke through
(Figure 97). Thereafter, the concentration of solute in the effluent
remained unchanged until a value of Z = 0.7 was reached (27 days for the
ozonized feedwater). Subsequently, complete breakthrough occurred in an
additional 27 days.
On a cumulative plot (Figure 98) using a GAC adsorber containing no
biological activity, the adsorption curves rise rapidly and thereafter level
off as no more adsorption occurs. The lower capacity of the activated
carbon for TOC in the ozonized water may be caused by ozonation rendering
the TOC more polar and less readily adsorbed.
With biological activity present in the GAC adsorber, cumulative plots
showed a non-zero slope after adsorptive exhaustion. Figure 99 shows that
TOC removals are very sensitive to the assumed values of Rf, the biological
reaction rate. Moving from the observed value of Rf = 2.6 x 10-11 g/sq
cm/sec to 5.0 x 1Q-11 would result in virtually complete elimination of
adsorbable and biodegradable organic materials in the feed waters.
The cumulative removals expected on the basis of Benedek1s modeling
studies for the Morsang GAC adsorbers used with preozonized versus non-
ozonized water are shown in Figure 100. Up to an applied TOC loading of 0.23
g/g of GAC, the GAC adsorber which followed non-ozonized water would have
adsorbed more organic materials (both biodegradable and non-biodegradable).
After 0.23 g/g of GAC applied TOC loading, however, the GAC adsorber which
followed ozonized water would be superior in all respects (because of biodeg-
radation occurring 1n the GAC adsorber), although under the conditions of
Process #3 at Morsang, only slightly more so.
Ozonized water data (Figure 96) and prediction (Figure 100) are compared
in Figure 101. The apparent agreement is acceptable, although the data
should match reasonably well since Rf was obtained from the data of Figure
96. This agreement shows that the model is capable of matching operational
data.
360
-------
t.oo-
0.90-
0.80-
0.70-
0.60-
0.50-
0.40-
0.30-
C.2O-
0.10-
0
0 O.2 0.4 0.6 0.8 1.0 1.2 1.4 t.6 1.8 2.0 2.2 2.4
throughput parameter, Z
Figure 97. Breakthrough curve for the ozonated GAG
adsorber without biological activity (DQ=2.8 x10 cm2/sec).
(Benedek,1977)
-------
co
a\
ro
O
0
CO
T3
93
remoi
O
O
O.14-
0.12-
0.10-
0.08
0.06
O.04
0.02
without O3
S^ with 03
'
0-020.04°-060.080-10 0.12 °'14 0.16 °-180.20°-220.24
g TOC applied/g GAG
Figure 98. Cumulative plots* GAG adsorption vs. loading 5 with
and without ozone (DQ= 2.8 x 108cm2/sec,- Rp-0.0)
(Benedek, 1977)
-------
CO
cr>
CO
O
OB
^
TJ
V
»
O
E
4)
^
O
O
!-
Oi
0.20-
0.18-
0.16
0.14-
0.12-
0.10-
0.08-
0.06
0.04
0.02-
0
-11
= 0.0
° °-020.04a06O.Oa010 0.12 °'14 0.16 °-180.20°-220.24
g TOC appiied/g GAC
Figure 99. Effect of bloiogica! activity on the cumulative TOC
removal of a GAC adsorber.
(Benedek. 1977)
-------
u
<
o
a
O
E
o
o
H
co
0.20-
0.18-
0.16-
0.14-
0.12-
0.10
0.08
0.06
0.04
O.O2
without O3
03
0 0.020-040.060-080.100-120.14°.160.180-200.220-24
g TOO applied/g GAC
Figure 100. Comparison of ozonated* and non-ozonated" GAC
adsorbers ('Rf=2.1 x10"11i "Rf = 1.8 x 10'11).
(Benedek,1977)
364
-------
0.12-
O
<
a
•o
V
>
o
E
o
o
H-
O>
computer prediction
0 o.o#-04ao6Q08aioa12o.i4°-16o.i eW
g TOG applied/g GAG
Figure 1O1. Comparison of actual vs. computer-predicted data
for ozonized water/GAC adsorber.
(Benedek,
365
-------
APPENDIX E
THE DOHNE PLANT AT MULHEIM, FEDERAL REPUBLIC OF GERMANY
BACKGROUND
From 1962 until April, 1977, the Donne plant at Mdlheim processed Ruhr
River water directly (without sand bank filtration) by the following sequence:
breakpoint chlorination (for the removal of ammonia), chemical coagulation,
f"occulation, clarificaticn, filtration, dechlorination (by passage through
- GAC columns), ground passage and chlorination for residual before introduction
into the three MUlheim distribution systems. Prior to 1962, the Ruhr at
Mulheim was treated simply by slow sand filtration followed by chlorination.
German law prohibits discharges of industrial wastes into the Ruhr
because the Ruhr is used as a drinking water supply by a number of cities,
but allows the discharge of sewage (which is biodegradable). Local industrial
wastes are transported 60 to 80 km north of MUlheim to the Emscher River for
discharge. Treatment of the Emscher for potable water applications is
prohibited by German law because of the allowed industrial discharges.
Ammonia levels frequently rise to as high as 4 to 6 ng/1 because of the
prevalence of sewage in the Ruhr. This results in prechlorination dosages
as high as 50 mg/1 for conversion of ammonia-nitrogen to elemental nitrogen.
German law allows a maximum level of 0.6 mg/1 of ammonia in finished drinking
water. Higher levels will require addition of more than 0.6 mg/1 of chlorine
to produce a stable chlorine residual. A maximum dosage of 0.3 mg/1 of
chlorine is allowed by German drinking water laws, but this can be raised to
0.6 mg/1 dosage in exceptional circumstances, with prior approval of health
authorities.
THE DOHNE TREATMENT PROCESS, 1970 to 1977
High prechlorination dosages were employed (10 to 50 mg/1) to reirove
ammonia. These chlorination levels produced high levels of chlorinated
organic materials (above 200 m1crog/l) which were not easily removed by SAC
"dechlorination" or by subsequent ground passage. Table 88 shows the old
Dohne water treatment process and the median levels of Dissolved Organic
Chlorine (DOC1), Dissolved Non-polar Organic Chlorine (OOC1N), total haloforms
and amounts of chloroform produced over the last two years that the old
process was employed (1975 and 1976) (Sontheimer e_t al., 1978). Maximum
DOC! values as high as 0.5 mg/1 (500 microg/1) have been observed at Dohne
under extreme conditions.
366
-------
During the period 1969 through 1972, detailed pilot plant studies had
been conducted at the Bremen, Gernany water works on the biological activated
carbon process (Eberhardt, Madsen & Sontheimer, 1974; Eberhardt, 1975). The
BAG studies at Bremen showed that amnonia can be "removed" biologically
(converted to nitrate) rather than by employing breakpoint chlorination with
its attendant production of chlorinated organics. German drinking water
regulations allow a maximum of 50 mg/1 of nitrate in finished water.
TABLE 88. OLD TREATMENT PROCESS AT 'HE COHHE PLANT, MULHEIM, GERMANY, AND MEDIAN VALLEr DF
CHLORINATED ORGANICS PRODICEO "HJRISG 1976 AMD 1977
Process Stage
taw water (10
mg/1 SS,
mostly
organics
Chemical
addition
Hocculatlon S
sedimentation
Sand filtration
iranular
activated
carbon
'.round passage
Safety chlor1rat1on
Treatnent
—
10 50 mg/1 Clz
4 6 Ttg/1 Al+3
0.1 '
-------
The pilot plant testing program was continued until mid-1978, to check
the full scale plant operations. At all times, the performances of the full
scale plant have paralleled those of the pilot plant. Through 1979, the GAC
columns have not had to be regenerated and, based on the length of time that
the pilot plant GAC columns functioned without regeneration, it is predicted
(Sontheimer, 1978) that the full scale plant GAC columns should operate up
to at least two years before regeneration will be required.
The Dohne plant can process 48,COO cu m/day (12.7 mgd) of Ruhr River
water (without sand bank filtration), and is located in the center of a
residential neighborhood; in fact, 4 residential back yards butt against the
plant property. Breakpoint chlorination had been employed as a pretreatment
step since 1962, and because of the residential location, special attention
had been paid to guard against chlorine leaks or spills,.
THE DOHNE PILOT PLANT PROGRAM (Jekel, 1977)
This pilot plant facility began operating at the Dohne plant in Septem-
ber, 1976, under the direction of Prof. Dr. H. Sontheimer. Dr. Martin Jekel
of the Engler-Bunte Institut der UniversitSt Karlsruhe carried out the pilot
plant investigations at the Dohne water treatment plant. The BAC process
currently being used on full-scale by the Dohne plant is based upon the work
performed by Dr. Cekel in this pilot plant.
A schenatic diagram of the Cohne pilot plant is shown in Figure 102.
Ruhr River water (without being treated by river sand bank filtration) was
saturated by air using an injector, then treated with po1y(aluminum chloride),
clarified in a Pulsator, and the Pulsator effluent ozonized in a bubble
column using ozone generated in air.
The major portion of the ozonized water was filtered directly through a
two-stage sand filter then passed through GAC column adsorbers. The pilot
plant filters consisted of two groups of two sand filters each and the
adsorbers consisted of three single GAC contactors, each filled with 2.5 m
of GAC.
A minor portion of the ozonized water was mixed with a small amount of
aluminum sulfate (2.5 mg/1 = 0.2 mg/1 Al+3), filtered through a double layer
sand filter, then passed through two GAC adsorbers.
A parallel pilot plant process was operated in which full-scale plant
water which had been treated by breakpoint chlorination and flocculation
then was treated by ozonation, sand filtration and GAC adsorption.
All GAC adsorber/contactors were operated at flow rates of 10 cu n/sq
rn/hr, which was equivalent to an empty bed contact time of 15 minutes. Five
different commercial grades of GAC were tested in the Dohne pilot plant.
In addition to the two parallel pilot plants described above, two
fluidi/ed bed reactors were set up for studying the biological oxidation of
ammonia to nitrate. One of these reactors was supplied with air-saturated
Ruhr River water, the other with ozonized effluent from the flocculator.
368
-------
air
Inject 01
~>
J r^ J
(.> ^^^^
£
dec
1f*n
ve
k.
o
4-t
u
s
t
f
O> Ruhr
U3 River
(raw water)
tossing and
•ssure
sel
3
"1r — s.
Injector '
Ruhr — ££V-
a
V
flocculating ^
agent '
r
itxlng
tth aj
chamber
1 tat ion
Y
u
lA
Q.
I-
3
3
U
U
o
I*.
i
River v
(raw water)
Figure U2
t-
u
a
t
X
V
ozone
gassing and
reaction
(Col unns/
.
-
•*
i
1
ozone
ozone
jjenrtr
_l
^
\J
dual granular
iredia activated carbon filters—.
filter / / 7 / ^^ --^
1
!
floccu^ting
agent — /
Scrematlc diagram of Donne pilot plant process (MUlhelir)
W/ft
ifm
I
'////.
M
W
^J
P
f-
O
c
r
J
x
^^
.
"^
T
*"*
~\
p
P
J
""
•#
i
I
V
—
_
-
f
Source Jekel, 1977.
-------
The purpose of these studies was to obtain information concerning collapses
or poisonings of the blomass which had been noted during the proceeding
year.
Comparison of Treatment With & Without Breakpoint Chior1nation
Table 89 compares the performance of the two pilot plants with and
without breakpoint chlorlnatlon. These plants were operated side by side
under the same processing conditions. Data shown in Table 89 are the mean
values of DOC (Dissolved Organic Carbon) obtained during October and November,
1976. Prechlorination led to almost no reduction In the initial 5.3 mg/1
DOC content after flocculation, whereas without prechlorlnation, a 1.4 mg/1
reduction in DOC level was obtained after flocculation. In later treatment
steps (ozonation, filtration, GAC adsorption), the pilot plant without
prechlorination produced better DOC removals than did the pilot plant with
prechlorination.
TABLE 89. COMPARISON OF TREATMENT WITH & WITHOUT BREAKPOINT CHLORINATION
Treatment Step
Ruhr River water
After flocculation
After 03 & sand filtration
After GAC adsorption
DOC, mg/1
WithU2 without Cl2
5.3
5.3
4.7
3.4
5.3
3.9
3.7
2.4
Mean values of pilot plant data obtained during Oct. & Nov., 1977
Source: Jekel, 1977
The higher DOC concentration in the prechlorinated water caused an
early breakthrough of the GAC adsorber, as shown in Figure 103. This
figure shows the percent reduction in concentration of organic materials (as
measured by UV absorption at 254 nm) versus the amount of water passed
through the GAC for the two process waters. The upper curve (with biological
treatment in the GAC) was extended at least up to a flow of 40 cu m/1 of
GAC, without any significant decrease in DOC removal efficiency. This
amount of flow corresponded to a GAC column operating time of more than 1
year.
GAC Adsorption Versus Biological Activity
Fable 90 compares the mean DOC concentrations in GAC column effluents
obtained during the first three months of use (during which time COC removal
was primarily by adsorption) with the COC concentrations obtained during the
next 8 months of operation (during which time DOC removal was primarily by
370
-------
biodegradation). Significant differences were observed for the five activated
carbons during the initial adsorptive period. On the other hand, during the
biological period which followed, few differences in :OC removals were
observed. Only the F-400 GAC, which has a smaller grain diameter, performed
better than the other four carbons. This indicates that biological activity
does not depend upon adsorptive capacity, but may depend upon grain size of
the GAC. 10Q.
3 =
c c
•o «-
4, x
t- «>
without breakpoint
chlorination
with breakpoint
chlorination
2 4 6 8 10 12 14 16 18 20
water/liter of GAC,
Figure 103. Influence of prechlorination on the
effectiveness of a process consisting
of flocculation, sedimentation, ozona-
tion, filtration and GAC treatment.
(Sontheimer et,a±., 1978)
Figure 104 shows the removal perfornances of the pilot plant GAC adsor-
bers in g of DOC/cu m of 3AC/day and the total organic loadings of the
various types of GAC tested during the first 18 months of operation (Jekel,
1979). These data were interpreted by Cekel (1979) as indicating that the
breakthrough behavior of biologically active GAC adsorbers is influenced,
among other factors, by the adsorbed biologically resistant organic substances.
Figure 104 also shows that an average of about 75% of the total organic
materials removed is biologically oxidized, while the remainder, primarily
biologically-resistant materials, is removed by adsorption. Due to the
enrichment of these compounds on the GAC surfaces, recognizable by the
increased GAC loading values in the lower section of Figure 104, the total
removal performance of the GAC adsorbers clearly falls off, particularly
during the third half-year period of operation.
Ouring this third half-year period, a clear improvement in the quality
of the raw water occurred in the Ruhr river, the influent COC decreasing
from about 2.5 to 1.8 mg/1. This intensified the observed decrease in 3AC
performance. Nevertheless, Cekel (1979) concluded that the operating time
of biologically active GAC adsorbers for the treatment of Ruhr river water
371
-------
175---T- r-i
« 100--
1 w
5 C
E a
o M 50--
t, -
a
(Adsorption
,Biological
Oxidation
«JL
^ eo-
g 60-
yj 40-
= 20-
s
• •
0 0
C
»
—
^^
—
^™ '
^"™
—
""""
—
^™*
1st half-jr 2nd half-vr 3rd half-y
Figure 104. Performance & loading of
BAG adsorbers.
(Jekel.1979)
372
-------
at the Cohne pilot plant was prolonged by a factor of approximately 4 1n
comparison with GAC columns operating purely by adsorption.
TABLE 90. COMPARISON OF DOC REMOVED DURING FIRST 3 AND SECOND 8 MONTHS OF
USE OF GRANULAR ACTIVATED CARBON FOR 5 ACTIVATED CARBONS
Treatment Step
After sand filtration
After GAC contacting
LSS 2.5 m
LSS 5.0 m
ROW 2.5 m
ROW 5.0 m
NK-12 2.5 m
F-400 2.5 m
BKA 2.5 m
DOC, mq/1
10-12, 1976
(adsorption)
3.5
2.2
1.2
1.9
1.0
2.4
1.6
1.9
1-8, 1977
(biological)
2.6
1.7
1.1
1.8
1.3
1.8
1.5
1.8
Source; Jekel , 1977
Ozonized clarifier effluent treated with 2.5 mg/1 of aluminum sulfate
then passed through LSS GAC during the adsorption period (October to December,
1977) resulted in further reduction in DOC levels, due to precipitation of
insoluble alum saHs of (probably) organic acids, formed by oxidation during
ozone treatment. Pertinent data are compared in Table 91, which also show
that a deeper GAC column removed nore DOC.
Chemical Balancing of Biological Activity
It was concluded that biological activity in an aerobic, filter -
adsorber system leads to:
1) biological degradation of dissolved organic compounds (DOC)
2) the formation of C02 (from which the amount of inorganic carbon
formed was calculated) from the DOC,
3) oxidation of ammonia to nitrate and
4) consumption of dissolved oxygen by both processes.
Measurement of these three parameters yielded information as to the
rate of biological activity occurring during passage through GAC adsorbers.
Each mg/1 of DOC removed biologically consumed 1 mg/1 of dissolved oxygen
and produced 1 mg/1 of inorganic carbon (calculated from the amount of
373
-------
measured). Each mg/1 of ammonia oxidized used 3:6 mg/1 of DO (based upon
the equation Nfy* + ZOg—*-N03' + 2H+ + H£0) and produced 3.4 mg/1 of
nitrate ion.
TABLE 91. REMOVAL OF DOC AFTER TREATING OZONIZED WATER WITH Al+3
Treatment Step
After flocculation + 03 +
alum + sand filtration
After GAC adsorption
LSS 2.5 m
LSS 5.0 m
DOC, mg/1
10-12, 1977
(adsorption)
3.2
1.8
0.9
Mean values of data obtained during the period of study
Source: Jekel, 1977
Table 92 shows the mean values for reduction in levels of DOC, NH4+ and
DO and mean values for increases in inorganic carbon found over the period
vlanuary to March, 1977. During this time the nrean water temperature was
6.8°C. Nearly all DOC removed in the first 2.5 m of GAC columns was found
as inorganic carbon in the effluent. The ratio, -ADOC/+A(inorganic carbon)
was unity or slightly higher for all GACs tested, except for the NK-12, for
which the ratio was 0.83. A ratio of less than 1 indicates that nearly all
of the DOC being reiroved was being degraded biologically. A ratio of about
1 indicates that the BAC system was in biological equilibrium.
However, in the next 2.5 m of activated carbon (see data for 5 m SAC
columns), the ratio -ADOC/+A(inorganic carbon) was significantly greater
than 1. Therefore, more DOC was being removed from solution than was being
degraded biologically. Since the data for 2.5 m GAC column heights show
that biological equilibrium had been attained (rate of COC removal was equal
to the rate of inorganic carbon production), the additional DOC being removed
by the 5 m high columns must have been a result of adsorption in the lower
half of the columns, in which biological equilibrium had not yet been attained.
Data in Table 92 also show that the ammonia levels were reduced to near
zero in the first 2.5 m of GAC depth without showing any significant perfor-
mance differences between 3AC types. Increasing the GAC depth to 5m did
not increase the amount of ammonia converted to ftfa* J1?;!'}"^-*
means that nearly all of the ammonium ion was oxidized in the first 2.5 m
depth of GAC.
374
-------
TABLE 92. BIOLOGICAL ACTIVITY IN PILOT PLANT GAC COLUMNS, JAN.-MAR., 1977
Treatment Step
After GAC adsorpffo
LSS 2.5 m
ROW 2.5 m
NK-12 2.5 m
F-400 2.5 m
BKA 2.5
LSS 5.0 IT
ROW 5.0 m
ADOC
mg/1
i
1.1
1.2
1.0
1.3
1.2
1.6
1.7
A (inorganic
carbon)
mg/1
1.0
1.1
1.2
1.2
0.9
1.2
1.3
iboc/A(in-
org C)
l.T
1.09
0.83
1.08
1.33
1.33
1.31
ANH4*
IP9/1
1.43
1.41
1.45
1.43
1.44
1.46
1.47
A02
mg/1
7.2
7.2
7.1
7.1
7.1
7.7
7.7
Sand filtrate contained 2.6 mg/1 DOC and 1.53 mg/1 NH4+
Mean water temperature: 6.8°C
Mean values of data obtained over the 3 month period
Source: Jekel , 1977
Table 93 shows similar data obtained during the summer period of June
to August, 1977 when the mean water temperature was 19.5°C. The feed to the
GAC adsorbers was ozonized water from the full-scale plant after floccula-
tion and sand filtration. As a result, the ammonia concentration was zero
and the pilot plant GAC columns thus showed no nitrification activity.
Comparison of the amount of DOC removed with the amount of inorganic carbon
produced at 19.8° (Table 93) or at 6.8°C (Table 92) showed no significant
differences because of water temperature.
However, it j_s_ significant that during the June to August, 1977 period,
the ratio of ADOC/A(inorganic carbon) was slightly less than 1 for the
activated carbons NK-12, F-400 and BKA (at 2.5 m bed depths) and for LSS and
ROW activated carbons at 5.0 m depths. This Indicates that more DOC was
being converted to Inorganic carbon than was being removed from the inf'uent
solution, which implies that biological regeneration of the GAC was occurring.
The biological reactivation of GAC is believed to have been demonstrated
unequivocally later in the full-scale plant (see Figure 108, later in this
Appendix).
375
-------
.TABLE 93. BIOLOGICAL ACTIVITY IN PILOT 6AC COLUMNS, JUNE-AUG., 1977
Treatment Step
After GAC Adsorpti
LSS 2.5 m
ROW 2.5 m
NK-12 2.5 m
F-400 2.5 m
BKA 2.5 m
LSS 5.0 m
ROW 5.0 m
ADOC
mg/1
on
0.9
0.9
1.0
1.2
1.0
1.3
1.3
A (inorganic
carbon)
mg/1
0.8
0.8
1.1
1.3
1.2
1.4
1.4
ACOC/A
(inorg C)
1.13
T.13
0.91
0.92
0.83
0.93
0.93
mg/1
0
0
0
0
0
0
0
AO?
mg/1
2.8
2.7
2.4
3.0
2.0
3.5
3.5
Sand filtrate contained 2.8 mg/1 COC and ^ess than 0.05 mg/1 NH^"1"
Mean water temperature: 19.5°C
Mean values of data obtained over the 3 month period
Source:
Jekel, 1977
Table 94 presents data obtained over the 6-month period (January to
June, 1977) after a 3-month starting period, "he ratios of £.DOC/A(inorganic
carbon) were always greater than 1, except for NK-12 activated carbon (at
2.5 m bed depth). These data, gathered over double the "length of time than
those of either Table 92 or Table 93, indicate that slightly more DOC was
being removed than was being converted into inorganic carbon. Therefore,
slightly more adsorption of DOC was occurring than was biological degradation.
Bacterial Counts in the GAC Adsorber Effluents
Table 95 shows total bacteria counts in the effluents of a 2.5 and 5.0
m high GAC column with pilot plant process water involving no prechlorination.
The data indicate that as biodegradable DOC was removed in the 3AC columns,
the number of bacteria in the effluents decreased. This shows that it is
possible to convert DOC into biodegradable organic materials which then can
be biodegraded in the water treatment plant (in the GAC contactors); The
greater the amount of biodegradable DOC that can be removed in the treatment
plant, the less will be the amount of biological aftergrowth which can occur
after safety chlorination and after the chlorinated water is sent to the
distribution system. Such treatment practice also can be expected to lower
the amount of chlorine required to provide a measureable chlorine residual
in the distribution system.
376
-------
TABLE 94. BIOLOGICAL ACTIVITY IN PILOT GAC COLUMNS. MEAN VALUES FOR A
6-MONTH PERIOD (JAN-JUNE. 1977) AFTER A 3-MONTH STARTING PERIOD
<\fter
SAC
LSS
LSS
ROW
ROW
NK-12
F-400
BKA
Bed
Depth
2.5 m
5.0 m
2.5 m
5.0 m
2.5 m
2.5 m
2.5 m
A(in-
ADOC org C)
mg/1 mg/1
0.92 0.83
1.69 0.96
. 1.09 0.97
1.59 1.05
0.99 1.36
1.26 1.11
1.00 0,97
Source: Sonthelmer et al.
-
ADOC/A(in-
org C)
1.11
1.76
1.12
1.51
0.73
1.14
1.03
ANH4*
ng/1
1.31
1.34
1.31
1.34
1.28
1.32
1.28
, 1978
A02
mq/1
6.32
6.67
6.49
6.71
6.03
6.95
5.99
!
|
" . " - -i
TABLE 95. TOTAL BACTERIAL COUNTS IN BIOLOGICALLY ACTIVE GAC ADSORBERS
Treatment Step
<\fter sand filtration
After GAC Adsorption0 2.5 m
After GAC Adsorption, 5.0 m
M = geometric mean value
MG
On
6,040
747
253
4.9
8.1
4.8
= geometric standard deviation
Source; Sontheimer et a1.s 1978
Fluidized Bed Reactors For Ainnonia Oxidation
During the suraner of 1976S pilot plant studies were conducted at the
Donne plant using air-saturated Ruhr River water passed upflow through
fluidized sand beds for biological removal of amrronia rather than breakpoint
chlorination. Aeration provided sufficient dissolved oxygen to allow
nitrification of all aononia originally present at the time. This technique
has been developed at the Water Research Center at Medmenham, England. The
biological activity was very effective during the first months but then two
377
-------
collapses of the biomass occurred. High concentrations of heavy metals were
found 1n the fluidlzed sol Ids, adsorbed or incorporated from the river
water, and these were suspected of having poisoned the nitrifying biomass.
A new fluidized bed pilot plant reactor was set up and was fed with
ozonized effluent from the full-scale plant (no breakpoint chlorinatlon).
Heavy metals were removed effectively during the flocculation step. The
fluidized bed reactor was operated during the June to August, 1977 period at
the rate of 10 m/hr and the mean water temperature was 19.5°C.
Mean data obtained during this period are shown in Table 96, which also
shows data obtained from aerated Ruhr River water without flocculation and
ozonation. The level of ammonia decreased with no collapses or poisoning of
the biomass using the flocculated and ozonized water over a period of 1
year. In addition, about 1 mg/1 of DOC was removed biologically in each
reactor. The amount of dissolved oxygen utilized corresponded to that
expected from the biological oxidation reactions observed.
TABLE 96. BIOLOGICAL OXIDATION IN FLUIDIZED BED REACTORS
Treatment Step
Ruhr River water + aeration
After amnonia reactor
Decreases in levels
After clarification + 03
After ammonia reactor
Decreases in levels
NH4+
mg/1
0.91
0.09
0.82
0.39
0.05
0.34
DOC
mg/1
4.5
3.5
1.0
3.1
2.2
0.9
DO
mg/1
8.5
2.6
5.9
9.1
4.6
4.5
Flow velocity: 10 m/hr
Mean water temperature: 19.5°C
Mean data values obtained over the 3 month period
Source: Jekel, 1977
378
-------
THE BAG PROCESS AS INSTALLED, APRIL 1977
Based on the successful early pilot plant results with the new ozonatlon
process, the breakpoint chlorination step at the full-scale Cohne plant was
eliminated in April, 1977 and ozonation of the clarifier effluent was begun.
Dohne's treatment process as 1t was instituted in mid-April, 1977 is shown
in Figure 105 (Sontheimer et al., 1978). Ruhr River water, which contains
about 10 ng/1 of suspended soTTds (mostly organics) is pumped into a flash
mixing tank {1.8 x 1.8 x 5.2 m) which contains a high speed aspirating
turbine which uses 2.5 kw of power per cu m of tank volume. Water is dosed
with 4 to 6 mg/1 of poly(aluminum chloride) and an average of 1 mg/1 of
ozone. Most of the ozone used in this preozonation step is obtained frorr
the off-gases from the second (major) ozonation step. In fact, all of the
off-gases from the second ozonation step are drawn into the flash mixing
tank by the suction action of the aspirating turbine. Additional quantities
of fresh ozone, as required, are added to these off-gases. Additional ozone
is required whenever the manganese content o* the raw water is high (see
below) or when algae levels rise in the river (Spring and Fall).
Residence time in the flash mixing chamber is about 0.5 minute.
During this time, nearly all of the ozone added in this chamber is utilized
in performing various oxidation functions. Only 3% of the ozone originally
generated is present in the off-gases from the flash mixing chamber. The
combination of ozone plus high speed mixing results in inproved flocculation
of suspended solids in the presence of the hydrolyzed aluminum chloride.
After flash mixing, the water is pumped to a Degremont Pulsator for
clarification where 5 to 15 mg/1 of Ca(OH)2 could be added, if needed. The
Pulsator consists of 2 basins, each 27.7 x 13.2 x 4.2 meters in dinension.
Distribution of water in the Pulsator is achieved by means of perforated
asbestos cement pipes, which allows for good final flocculation within the
floe blanket. Clarification tine is 1.5 hrs. By this treatment, turbidity
of the water is lowered to 0.4 to 0.8 FTU.
The ozonation system is supplied by Trailigaz, and consists of 2 ozone
generators, each containing, 220 water-cooled dielectric tubes and each
capable of generating 4 kg of ozone/hr at a concentration of 20 to 25 g of
ozone/cu m of air (8 kg/hr total ozone generating capacity).
The ozone dosage at this point in the process averages 2 mg/1, the
contact time is 5 minutes, and this step is controlled by nonitoring 0.3
mg/1 of dissolved ozone residual at the exit of the contact chamber. Ozone
contacting efficiency in this single dlffuser chamber is 90%. A further
reduction of turbidity level usually is achieved at this point by the forma-
tion of larger floes, caused by agglomeration of residual solids. In addi-
tion, organics are oxidized to more polar compounds which are capable of
being flocculated by aluminum cations and also become more biodegradable.
Off-gases from this primary ozonation step (containing 10% of the
originally generated ozone) are drawn back into the flash mixing tank by the
high speed aspirating turbine and are injected into the raw water. If the
manganese content of the water after the Pulsator clarification step is
379
-------
poly(a1um1ni.m chloride)
Ca(OH)7
**• distribution
Mgure 105. Process schers for surface water treatnent at trp ;orne water
atnity 1n Millheiir after introduction of coirtrneci chemical and
biological oxidation.
(Sonthener et. al_., 1978)
380
-------
greater than 0.05 mg/1, then additional fresh ozone 1s added to the flash
mix chamber. Manganese content is monitored at this point in the process.
Additional ozone also is required when the algae content of the raw water
rises (in the Spring and Fall). During such periods, simply doubling the
preozonation dosage from 1 mg/1 to 2 mg/1 overcomes any tendencies of the
algae to clog the filters; the treatment process is otherwise unaffected
(Nolte, 1978).
The use of off-gases from the primary ozonation step in the flash
mixing chamber allows 97% of the generated ozone to be utilized in performing
useful work. The flash mixer off-gases contain only 3% of the ozone genera-
ted, and this is destroyed by passage through a Degussa catalytic destruction
unit (palladium on alumina) at 60°C before the gases are'discharged to the
atmosphere.
Ozone is monitored (1) in solution after the primary contact chamber,
(2) in the primary contactor off-gases (by a Hartman & Braun monitor, Metz,
France) and (3) in the ozoneur room atmosphere (by a Wallace & Tiernan KI
monitor). This last monitor will cause an alarm to be signalled at the
control panel If the ozone concentration in the room atmosphere exceeds 0.05
ppm. In addition, the plant provides DrSger tubes for plant personnel to
determine the ozone concentration nanually at various places in the plant,
if desired.
After ozonation, the water is pumped to 4 horizontal pressure sand
filters (1.6 m high — see Figure 106), for filtration at the rate of '.1 cu
m/sq m/hr (11 m/hr). It had been planned to dose 0.2 ng/1 of poly(aluminum
chloride) and 0.1 ng/1 of polyelectrolyte after installation of new dual
iredia filters in December, 1978, if necessary for further turbidity removal.
After sand filtration, the water is passed through 4 GAC adsorbers,
each containing media which is 2 m high and 5 m in diameter, at the rate of
22.5 cu m/sq m/hr. During the period April to July, 1977, these carbon
contactors contained the same GAC as had been used for dechlorination in the
old process. Because of this, the GAC was "fully loaded" with chlorinated
organics. Empty bed contact times of these 2 m high GAC contactors is 5.5
minutes.
Following passage through the GAC columns, the water then passes into
15 injection wells for storage in the ground where it remains 12 to 50
hours. When removed for distribution (from wells within 50 m of the infiltra-
tion points), 0.4 to 0.8 mg/1 of chlorine is added. This low dosage provides
a stable, measureable 0.1 mg/1 chlorine residual in the Maiheim distribution
system. The measureable O.T mg/1 chlorine residual is required by German
drinking water regulations. However, even the 0.4 to 0.8 mg/1 safety chlori-
nation dosage is above that normally authorized under German drinking water
regulations (0.3 mg/1, maximum), and an exception had to be applied for and
granted to allow this high a dosage to be used at the Cohne plant.
381
-------
30 meters long, 3.9 meters diameter
Sand media: 1.6 meters deep, 1.2 to 1.8 mm particle size
Support Gravel: Three layers 2 to 3 mm particle size
3 to 7 mm
7 to 15 mm
3.9 m
plastic nozzle
1.6m quartz sand
support gravel
;oncrete
Filter hydraulic loading rate:
backwashing rate :
18 cu m/sq m/hr
: 20 cu m/sq m/hr
Chemical filter aid: 0.2 mg/1 Al+3
0.1 mg/1 polyelectrolyte
In Decembers 1978, convert media to:
bottom layer 0.6 to 1.2 mm particle size hydroanthracite
top layer 2 to 3 mm particle size low density GAC
Figure 106. Pressure filters at the Dohne (MUlheim) plant.
382
-------
PROCESS PERFORMANCE, APRIL-JULY, 1977
In Table 97 are listed the Dissolved Organic Carbon (COC), ultraviolet
absorbances and ratios of UV/DOC measured at various process points for 1975
(old process), 1976 (old process) and April to July, 1977 (new process using
old GAC). DOC is determined after passing the sample through a 0.45 micron
filter by oxidizing all dissolved carbonaceous materials with ultraviolet
radiation and measuring the amount of CO? formed (Wfllfel & Sontheimer,
1974).
Ultraviolet absorbance of process waters is measured at 254 ran in 1 or
5 cm cells, but then is calculated for cell lengths of 1 meter. This
measurement relates to the amount of carbon-carbon unsaturatlon contained in
the molecular structures of the dissolved organic materials. Unsaturatlon
can consist of individual carbon-carbon double bonds, aromatic nuclei (multi-
ple and conjugated C=C bonds) or carbon-oxygen (C=0, carbonyl) functions.
Ozonation destroys many isolated carbon-carbon bonds and most aromatic
moieties, converting them to COg or to carbonyl groups, thus lowering (but
not totally eliminating) the total UV absorbance value.
The UV/DOC ratio by itself is not as meaningful as is the change of
this ratio 1n coirparison with changes 1n both components. If DOC values
remain constant while the UV absorbance decreases, this indicates that
unsaturated organics are being converted to saturated, dissolved, oxidized
organic products (which may contain more carbonyl functions), but not to C02
and water. If both UV absorption and DOC decrease, this indicates that
unsaturated organics are being destroyed and that DOC 1s being converted to
C02 and water.
Table 98 compares the mean DOC values obtained by the old process
during 1975 with the mean values obtained during May to August, 1977.
During this later period, the GAC adsorbers were operated with the exhausted
carbon used in the old treatment process. It is apparent that ozoration
enhanced the blodegradation of DOC during ground passage. In addition, it
is also clear that chlorinated organics were not being synthesized since the
prechlorination step had been eliminated. Ammonia levels were reduced from
an average of 1.07 mg/1 in the Influent to zero after ground passage. Some
ammonia (0.25 mg/1) was removed biologically during flocculatlon and most of
it (0.60 mg/1) during sand filtration.
PROCESS MODIFICATIONS, NOVEMBER, 1977
After the initial testing period of April to July, 1977, the following
plant modifications were made during August to October, 1977, the plant was
restarted in November, 1977 and has been operating continuously since:
1) The granular activated carbon depths were doubled from 2 meters to 4
meters (see Figure 107). This increased the empty bed contact time in
each filter from 5.5 to 11 minutes. At the same time, each of the four
GAC columns was charged with a different fresh granular activated
carbon (NK-12, F-300, LSS and AG-1). Three of these four activated
carbons had been studied 1n the pilot plant. The intent of the Dohne
383
-------
TABLE 97. MEAN DOC AND UV-EXTINCTION VALUES FOR THE DIFFERENT TREATMENT STEPS AT THE DOHNE PLANT
Sampling Point
Raw water (Ruhr)
After floccula-
tion & sedimen-
tation
After filtration
After GAC
adsorption
After ground
passage
1975
T5UCT
mg/1
3.9
3.2
3.2
3.0
1.8
UV
254 nm
m-1
6.8
4.5
4.4
4.0
3.1
Dv/DOC
ratio
1.8
1.4
1.4
1.3
1.8
1976
"DUC~
rig/1
5.0
4.0
3.8
3.7
2.1
UV
254 nm
m-1
9.1
5.5
5.6
5.3
4.0
OY/TJOTT
ratio
1.8
1.4
1.4
1.4
1.9
Aoril-Julv 1977*
DOC
mg/1
3.6
2.9
2.6
2.3
0.9
UV
254 nm
m-1
6.1
3.2
1.8
1.6
1.4
UV/DOC
ratio
1.7
1.0
1.0
0.7
1.6
Nov. 1977-
June, 1978**
DfiC, mg/1
2.4 - 3.7
1.8 - 3.0
1.7 - 3.1
1.0 - 2.6
—
* GAC adsorbers filled with fully loaded GAC, used during old process
** Source: Jekel, 1978, otherwise Sontheimer et al_. , 1978
co
00
-------
ventilation
4 it
Sranular
Activated
Carbon
3 layer support »
(gravel)
3AC outlet pi
.5 -\
\- raw water
backwash
water
treated water
Inlet for
backwash air
3AC backwash rate: 27 to 30 n/nr; air ther water;
backwash each iQ to "4 days
Figure "07. 3AC adsorbers at ;ohne plant, MUlheim, Feteral Republic of
3enany.
385
-------
plant management 1s to test all four activated carbons in the full
scale plant, side by side, to select the best performing type at some
future date. One-fourth of the sand filtered water is passed through
each GAC contactor. Thus the water is in contact with only one of the
four activated carbons being tested. After GAC contacting, the effluents
from the four GAC contactors are blended in the slow sand filters, in
the injection wells and in the underground reservoir.
TABLE 98. COMPARISON OF OLD & NEW PLANT PROCESSES FOR REMOVAL OF DOC &
Treatnent Step
Ruhr River water
After flocculation
After 03 + sand filtration
After GAC contacting
After ground passage
old process
1975
DOC
mg/1
3.9
3.2
—
3.0
1.8
new process
Mav-Auqust, 1977
DOC
mg/1
4.0
3.1
2.8
--
0.9
NH4*
mg/1
1.07
0.82
0.22
—
0
Source; Jekel , 1977
2) Pure oxygen is added after ozonation, at the pumps which send'ozonized
water to the sand filters. Some 80% of the nitrification has,been
found to occur in the sand filters and the remainder occurs iii the GAC
contactors. During the summer, all of the nitrification occurs in the
sand filters.
Since each mg of ammonia-nitrogen requires 3.6 mg of dissolved oxygen
for conversion to nitrate (assuming the equation: NH4* + 202 NOj-
+ 2H+ + H20), it is apparent that a raw water ammonia level of 5 to 6
mg/1 will require 18 to 22 mg/1 for nitrification alone. In addition,
biological conversion of dissolved organic carbon to C02 and water also
requires dissolved oxygen (2 mg of DO for each mg of DOC converted to
0)2). Such levels of dissolved oxygen cannot be supplied solely rrom
air, which saturates the water during ozonation. Aeration produces
maximum DO levels of only 8 to 11 mg/1, depending upon the water tempera-
ture. Addition of pure oxygen, however, can provide DO levels up to 45
mg/1.
Liquid oxygen (LOX) is stored in a 3 cu m tank in the room which used
to house the chlorine cylinders. This is vaporized (2 LOX evaporators
are installed, one for backup) and the gaseous oxygen is introduced to
the ozonized water at the pumps which send the water to the sand
386
-------
filters. This pump provides considerable mixing action for water and
gas. No special corrosion problems have been encountered during the
first seven months of operation and no changes in the materials of
construction of the pumps have been required.
The DO is monitored at the outlet of the GAC contactors. Addition of
gaseous oxygen is controlled by maintaining a level of 7 mg/1 at the
GAC column outlets. Average oxygen dosage to attain this 7 ng/1 residual
DO level usually is around 10 mg/1. As a rule, excess dissolved
oxygen can cause outgassing, which can cause mechanical problems
during filtration. However, since the oxygenated water at the Dohne
plant is under 1.6 bar pressure, no outgassing problems have been
observed during the first 7 months of operation.
3) The second poly(a1uminum chloride) * polyelectrolyte addition step
(after the primary ozonation step) has not yet been found to be neces-
sary. This is because the flash mixing step utilizing poly(aluminum
chloride), 1 mg/1 of ozone and high speed agitation has been so effective
in lowering turbidity (to 0.1 FTU after sand filtration). Sigrist
turbidity meters have been installed after sand filtration to monitor
turbidities at this point (see later discussion on head loss vs turbidity
breakthrough of the sand filters).
As of June, 1978, the Dohne plant had a total of 41 monitoring points
in the plant.
PERFORMANCE OF MODIFIED BAC PLANT PROCESS
Plant performance data obtained over the period November 1977 through
May, 1978 are listed on the far right hand side of Table 97. It is c'ear
that the DOC of water exiting the GAC contactors was lower than that obtained
at the same point during the April to July, 1977 study. This difference may
be due to one or more of several factors:
1) the Increased EBCT of the 4 m SAC columns (11 minutes vs 5.5)
2) the use of virgin GAC in November 1977 vs "fully loaded" 3AC used
earlier
3) higher levels of dissolved oxygen (pure oxygen was not added
during the April to July, 1977 tests). This effect would be
expected to be minor compared with the first two.
When the four new GAC columns were started up In November 1977, DOC
values in their effluents were very lows on the order of 1.2 to 1.6 mg/1.
However, these effluent levels increased over the next few months, reaching
2.1 to 2.6 mg/1 during the May to June, 1978 period. These increases were
attributed to the Spring algae bloom. Pertinent data in this regard are
listed in Table 99.
387
-------
TABLE 99. DOHNE PLANT PERFORMANCE DATA SINCE NOV. 1977. DOC DATA, mg/1
Sample Point
Raw water
After 03 + floccln
After sand filtrn
After GAC
-Lurgl NK-12
-Calgon F-300
-Lurgi LSS
-Essen Rsch AG-1
11 -12/77
3.0
2.5
2.5
1.3
1.2
1.6
1.4
1-2/78
3.0
2.7
2.6
1.7
1.0
1.9
1.5
3-4/78
2.4
1.8
1.7
1.5
1.2
1.6
1.5
i
5-6/78
3.7*
3.0
3.1
2.5
2.1
2.6
2.6
* higher COC levels during this period are attributed to the Spring algae
bloom
Data of Table 99 are Interpreted by Dr. M. Jekel of the Engler-Bunte
Institute of the University of Karlsruhe as indicating adsorptive removal of
DOC during the initial 6 month period of carbon use. During this time,
biological activity was building up to equilibrium very slowly (because of
the low water temperatures) and the ratio -ADCC/+A(Inorganic carbon) was
greater than 1. The May to June 1978 data indicate that biological activity
had increased. The ratio of -ADOC/+A(inorganic carbon) passed through unity
and became slightly less than 1.
The values for ADOC and A(inorgan1c carbon) are plotted in Figure 108
for the period November, 1977 through July, 1978. During July, the rate of
formation of inorganic carbon increased significantly, and the ratio
-ADOC/+A(inorganic carbon) decreased to 0.55.
This behavior confirms the data obtained during the Bremen pilot plant
studies. During the initial 3 to 4 months, the removal of dissolved organics
by virgin GAC took place primarily by adsorption. The maximum removal of
organics by adsorption took place for about 6 weeks, after which the degree
of removal of organics decreased to 25 to 33% over the next 3 to 4 months.
As the biological activity in the GAC media increased, however, the amount
of dissolved organic carbon removed from solution by adsorption plus biologi-
cal activity increased (at the Donne plant) to just over 50% of the amount
removed by virgin GAC. This 50+% removal remained constant over the last
two months for which data are reported (the 6th and 7th months after virgin
GAC startup).
388
-------
co
00
6
1.0-
0.6-
U O 2
O
.,]
cur IM»II
ADO<:
(Jekel, 1979)
Dec Jan Fek Alar Apr May June July
'77 1978
Figure 108. Initial performance of BAG adsorbers
in the Dohne water works
-------
Based upon the nore than two year long pilot plant program which he
conducted at the Dohne plant, Dr. Jekel anticipates that this 5Q+% dissolved
organics removal will continue for up to 2 years before reactivation of the
GAC may be required. Dohne's plant management has budgeted for regeneration
on this basis (see later section in this Appendix on Costs).
Dr. Jekel also believes that had the new GAC columns at Dohne been
started up during the summer period of higher water temperatures, high
levels of biological activity would have been established in a much shorter
time, say 2 to 3 months.
Substantiation of the increasing biological activity in the GAC columns
is shown in Table 100, which lists the increase in inorganic carbon concentra-
tions obtained during passage through the GAC contactors for the periods
January to April, 1978, and May to June, 1978. During the May to June
period, production of C02 more than doubled in all 4 GAC columns. These
data should be coupled with those of Table 99, which show that the COC in
the GAC column effluents was about 67% higher during the same period than
during March to April, 1978.
TABLE ICO. OOHNE PLANT PERFORMANCE DATA, JAN.-JUNE, 1978. BIOLOGICAL
PRODUCTION OF INORGANIC CARBCN IN SAC CONTACTORS
Inorganic Carbon Produced
(C02 as C), mg/1)
SAC Contactor Contg*
NK-12
F-300
LSS
AG-1
Jan-April, 1978
0.2
0.2
0.3
0.3
May- June, 1978
0.5
0.6
0.6
0.8
k During these studies there was no ammonia in the GAC influent.
Therefore, no nitrification was occurring.
When the water temperature rose in the Spring of 1978, the biological
activity in the activated carbon columns increased significantly, and the
amount of C02 produced more than doubled. The amount of CO? produced
during the May to June, 1978 period with the carbons LSS and AG-1 actually
was greater than the amount of DOC being removed from the GAC influent
(Table 101). This indicates that some biological regeneration of the SAC
must have been occurring. Since the only sources of dissolved organic
carbon to produce C02 were the influent water and what had been adsorbed by
the GAC during the winter period, the excess C02 produced over that present
in the influent water must have arisen from the biodegradation of adsorbed DOC.
390
-------
TABLE 101. DOHNE PLANT PERFORMANCE DATA. COMPARISON OF DOC REMOVED VERSUS
INORGANIC CARBON PRODUCED IN BIOLOGICALLY ACTIVE GAC CONTACTORS
DURING MAY - JUNE, 1978
GAC Type
LSS
AG-1
BUT
NK-12
F-300
Source:
DOC removed, mg/1
0.5
0.5
0.6
1.0
1norg C produced, mg/1
0.6
0.8
0.5
0.6
Jekel, 1978. Private Communication
A significant benefit of the new BAC process to the Rheinisch WestfSlis-
chen Wasserwerksgesellschaft mbH, is that the amount of chlorine dosage
required to produce the 0.1 mg/1 of chlorine residual has been lowered fron
0.4-0.8 mg/1 to 0.2-0.4 mg/1, halving the amount of chlorine formerly used
for this purpose and bringing Dohne's chlorine dosage down to levels used
with less polluted and treated surface waters, such as lakes, reservoirs and
some groundwaters.
During the pilot plant testing program at Dohne, pronounced slowing
down of biological activity was noticed in the GAC adsorbers whenever the
DOC in the influent to the adsorber dropped below 2 mg/1 and approached 1
mg/1. This slowing down of biological activity is believed to have been
caused by a shortage of biodegradable substances over a longer period.
RELATIONSHIP OF EPA'S PROPOSED ORGANICS REGULATIONS REGARDING GAC TO DCHNE
PLANT PERFORMANCE
EPA's proposed regulations for the use of GAC to remove synthetic
organic chenicals (SOCs) from U.S. waters would require that the GAC be
regenerated when the TCC in the GAC effluent becomes 0.5 mg/1 higher than
that obtained with virgin GAC. The proposed regulations also would require
that the TOC removed by virgin GAC be at least 50% of that in the water
influent to the GAC column.
It can be seen from the data of Table 99 that if EPA's proposed regula-
tions were to have been applied to the modified Dohne treatment process (4 m
GAC columns; 11 minute EBCT) that 50% TOC removal was obtained by only one
of the four activated carbons being used. Only the F-300 carbon removed 50%
or more of the influent (to the GAC column) TOC,and continued to provide
this amount of TOC removal through April, 1978 (5 months). However, It Is
probable that longer empty bed contact times with the other three activated
carbons would have produced the desired initial 50% removal of TOC.
391
-------
On the other hand, continued removal of TOC by all four activated
carbons at Dohne would have met the proposed EPA requirement of no more than
a 0.5 mg/1 maximum increase in effluent TOC concentration through April,
1978 (5 months).
On the basis of these considerations alone, one would conclude that
only the F-300 3AC would meet the proposed EPA requirements at Dohne, with
an 11 minute EBCT, and that this carbon would have to be regenerated after 5
months of use.
However, when biological equilibrium had been obtained in April, 1978
(after 5 months of use), the F-300 activated carbon now allowed 0.9 mg/1 of
DOC more in the GAC column effluent than did the virgin activated carbon.
At this time, only about 33% of the DOC in the GAC influent was being renoved.
After an additional 2 months of use, however, the degree of COC removal had
risen to about 50% (see Figure 1C8). This performance was expected to
remain essentially constant (33 to 50% DOC removal) for at least the next 18
months (through 1979). At this 11 minute enpty bed contact time, F-300 3AC
would not, however, meet the proposed EPA regulation which would Unit the
effluent TOC level to only 0.5 mg/1 above that obtained with virgin GAC.
On the other hand, performances of all four of the biologically active
GAC colunns at Dohne during the period Kay to June, 1978 are considered to
be satisfactory by the RWVI, and no plans are being made to reactivate the
GAC until after two years of use. Even though only 33 to 50% of the influent
DOC is being removed, the GAC is not saturated with the very strongly
adsorbed, more refractory, halogenated organic materials which are present
in the Ruhr River only in very low concentrations. GAC column performances
at Dohne are being followed closely, not only by DOC, UV and UV/DOC ratios,
but also by TOC1 and TOC1N analyses. As long as the rate of COC removal
remains constant at 33 to 50% and there is no indication of TOC1, TOC1N or
bacterial breakthroughs, Dohne plant management does not plan to regenerate
the GAC, at least during the first two years of use.
SAND FILTER OPERATIONS
Donne's 4 sand filters (before the GAC contactors) are 3.9 m diameter,
30 m long cylinders, with sand 1.6 m deep and fed with ozonized then oxygena-
ted water at the rate of 11 m/hr (9 to 10 minutes EBCT). Before ozonation
was incorporated into the process, the running time of these filters was 2
days, then backwashing was required because of increased head loss. Since
ozonation has been installed, however, the running times have increased to 7
days. Furthermore, the indicator of backwashing need during 1978 no longer
was head loss, but rather breakthrough of turbidity (0.4 to 0.8 FTU before
sand filtration -- 0.1 FTU after). When the turbidity of the filtered water
rises above 0.2 FTU, the filters are backwashed. Breakthrough of turbidity
rather than head loss is the reason that ~ohne has installed turbidity
monitors after sand filtration (Jekel, I978b).
In December, 1978, however, Dohne plant management planned to change
the sand filters, because it wants to control this sand filtration step by
head loss, not by turbidity breakthrough. The new filters will be composed
392
-------
of dual carbon media. The lower layer will be hydroanthracite and the upper
layer will be a light density granular activated carbon. This light density
GAC is a filtration medium, and has very poor adsorption qualities.
During the summer of 1978, "a population explosion of nematodes" was
observed to have developed both in the rapid sand filters and in the following
GAC adsorbers at the Cohne plant. These growths were shown to have been
caused by the extended intervals between backwashes, during which the nema-
todes developed. When the backwashing cycles were reduced to 3 days (just
below the time of reproduction of these microorganisms), the nematode problem
disappeared (Heilker, 1979).
GAC COLUMN BACKWASHING
Dohne's GAC contactor columns are backwashed first with air to loosen
the biomass which tends to cause GAC particles to stick together at times.
After loosening the mass with air, water alone is pumped through the columns
at the rate of 27 to 30 m/hr. The time between backwashings is controlled
by head loss through the columns. Because of the fact that there are four
different granular activated carbons being tested in the Dohne plant, backwash-
ing frequencies of the four GAC contactors are not the same. Each GAC has a
different grain size, and head loss buildup occurs at a different rate for
each of the four contactors. On the average, however, backwashing was being
performed every 10 to 14 days during early 1978. However, because of the
development of nematodes (see above), the backwashing time subsequently has
been lowered to 3 days (Heilker, 1979).
Turbidity of the water after the GAC contactors ranges from 0.1 to 0.2
FTU, and averages 0.14 FTU.
The four activated carbons being studied in the Dohne plant have
different adsorption capacities, which were determined during the pilot
plant testing program. The full-scale plant 4 meter virgin GAC columns were
started up during the winter of 1977, when water temperatures were below 8°C
for the first 3 to 4 months of operation. As a result, bacterial growth
buildup was very slow in the GAC media. This was confirmed by the data of
Table 100, which show low levels of C02 being produced during this period.
During backwashing, only small amounts of carbon fines are removed.
These had not been sufficient to require the addition of any makeup SAC
during the first 7 months of plant operation.
No buildup of slimes has been observed at the Dohne plant in either the
sand filters or in the GAC contactors during the first 7 months of operation.
Neither were slimes observed during the 2 year pilot plant study. Therefore,
it can be concluded that the pretreatment steps, including ozonation, prevent
the buildup of such detrimental materials.
BACTERIAL TESTING
Table 102 shows bacterial count data obtained at various points in the
Dohne plant process. It 1s clear from these data that the SAC effluents
393
-------
from the old GAC columns contained considerable biological activity. After
5 months of use, effluents from virgin GAC columns showed much lower bacterial
counts. However, it is equally clear that E_._ coli are not present in the
effluents from columns containing old or new GAC. Two groups of European
microbiologists (KIWA — The Netherlands and Univ. of Saarlands — Federal
Republic of Germany) agree that IE. coli cannot survive in the GAC columns in
the presence of the other strains of water and soil bacteria which are
present.
TABLE 102. BACTERIAL COUNT DATA AT DOHNE PLANT WITH BAG TREATMENT PROCESS
sampling Point
tew water
\fter flocln +
sediment.
Hfter sand filt.
Ifter GAC
^fter ground
passage
With Old GAC*
Total Counts'/ml
M
0
14,490
2,340
6,010
3,700
27
°g
2.0
4.2
4.9
4.0
2.3
E. COl
"g
1,620
6.7
« 1
« 1
« 1
7100 ml
ag
1.7
3.2
—
—
—
April, 1978 (new SAC)**
counts/ml
20,000
20,000
90
57
22
E. coli/ICO ml
—
—
0
0
2.2***
M = geometric mean a = geometric standard deviation
k Source; Sontheimer et_ aj_. , 1978
** Source; Heilker, 1978, Private Communication
*** About 20% of the water present after ground passage comes from
infiltration from the Ruhr River. This infiltrated water is the
source of the E. colls found.
The Dohne plant waters are analyzed routinely for total bacterial
counts, £. coli and algae in the raw water, filtered water, after ozonation,
after GAC and after ground passage. Raw water from the Ruhr River is
analyzed once each day and groundwater stations are analyzed once each week.
COSTS
Substantial cost data were obtained during visitation to the Cohne
plant in June, 1978. These will be presented in three sections: (a) Costs
For Enlarging GAC Contactors And For GAC, (b) Costs For Ozonation Equipment
and (c) General Cost Data, which include Costs For Plant Operations and
rates charged to water customers.
394
-------
Costs for Enlarging GAG Contactors and for GAG
The originally installed GAC contactors (which provided a 2 m depth of
GAC) were enlarged in late 1977. Plant managenent had planned for this
eventuality when the original GAC contactors were installed, and had designed
the building and associated appurtenances to be able to accomodate the
enlarged GAC depths. Currently, the four GAC contactors are 5 m in diameter
and 8.5 m high. The current depth of GAC contained in each contactor is 4
meters.
Enlargement of the four GAC contactors was completed at a cost of
300,000 Deutsch marks (DM) ($150,000 at an exchange rate of 2 CM/$), including
necessary modifications to the building. On the other hand, four new GAC
contactors of the current size at the Donne plant would have cost an estimated
600,000 DM ($300,000). A single new GAC contactor would have cost approxi-
mately 250,000 DM ($125,000) on a turnkey basis.
In addition, 450,000 DM ($225,000) were expended for the purchase of
320 cubic meters (about 100 netric tons) of GAC to charge these contactcrs
with virgin GAC in November, 1977. The GAC cost represents an average of
about 75
-------
only on a weekly basis. These extended backwashing cycles are attributed
largely to the new ozonation process. It had been hoped that extended
backwashing times would have provided substantial cost savings both in
pumping costs and 1n wastewater treatment charges. However, the nematode
problem arose, which necessitated lowering the backwashing times to every 3
days, in order to avoid their development.
Ozonation System Costs
The capital cost of the total ozonation system for the Dohne plant was
2,200,000 DM in 1976. This figure includes air compressors and driers,
ozone generators, associated piping and control instrumentation and construc-
tion of the ozone contact chambers. The ozone generation capacity is 8
kg/hr (422 Ibs/day), which provides for ozone dosages of 3.5 to 5 mg/1,
depending upon the rate of water flow through the plant.
The energy demand of the ozone generation system at Dohne is 20 kwhr/kg
of ozone generated, or 9.1 kwhr/lb. It was not clear whether this figure
includes electricity used by the air preparation unit. If not, an additional
21% (1.9 kwhr/lb)* should be added. This would result in a total energy
demand of 11 kwhr/lb for air preparation and ozone generation. An additional
1.8 kwhr/lb* of energy is required by the ozone contact system (diffusers
plus off-gas recycling to the preozonation step). This makes a grand total
of 12.8 kwhrs/lb of ozone generated and applied. [The figures of 1.9 and
1.8 kwhr/lb required for air preparation and ozone contacting, respectively,
were obtained from a questionnaire completed by The RWW during 1977 (see
Miller et al_., 1978)].
Although the addition of ozonation to the Cohne water treatment process
involved a capital cost of 2,200,000 DM ($1,100,000) and an Increase in
purchased electricity, 5,086 kwhrs/day (523 to 755 DM; $262 to $378 at 0.09
to 0.13 DM/kwhr local power cost), these increased costs have been offset by
several operating cost savings:
1) Much less chlorine is used in the new process than in the old process.
A minimum of 96% of the chlorine formerly required (1,059 to 5,295
Ibs/day) has been eliminated.
2) A reduction in labor force by 7 or 8 persons for an estimated total
annual savings of 300,000 DM ($150,COO).
3) The GAC reactivation cycle has been extended from a conservatively
estimated hypothetical 6 months to a projected minimum of two years —
an annual1zed savings of just over 600,000 DM ($300,000)/year in GAC
reactivation costs alone. • *
Although individual Items of cost savings can be deduced by comparing
the old and new treatment processes, other modifications of the process
required increases in costs. Heilker (1979) summarized the cost comparisons
for water treatment at the Dohne plant by the old and by the new processes
and made the following ststement:
396
-------
"The treatment plants 1n the Donne waterworks have been operating for
more than 1.5 years using the revised process. The drinking water
quality has been significantly improved without increasing treatment
costs. The Dohne plant is less susceptible to disturbance and as a
result can be operated with 50% of the former staff size. The activated
carbon filter runs are 3 to 5 times longer than before."
In addition to the Dohne plant, the Rheinisch-Westfaiischen Wasser-
werksgesellschaft mbH also owns and operates several other plants near
MUlheim. Based upon the performance and cost benefits obtained using the
ozone/GAC process at the Dohne plant, two other plants have been redesigned
and are being modified to use the ozone/GAC process for both plants. Comple-
tion and startup of these plants is expected during 1979.
Bids were received in early 1978 for the ozonatlon equipment for both
new plants. The larger of the two plants requires a 36 kg/hr (1,900 ibs/day)
ozone generation system which cost 2.9 million DM ($1.45 MM). This price
included all related hardware, such as the air preparation equipment, ozone
generators, turbines (for first stage ozonatlon), contacting (for second
stage ozonation), associated instrumentation and controls and contactor off-
gas destruction equipment. On the other hand, this price does not include
the second stage ozone contact chambers or buildings.
The ozonation system at the smaller plant will generate 14 kg/hr (739
Ibs/day) and has been purchased for 1.6 million DM ($800,OCO). This price
included and excluded the same items as the larger plant, but was described
as a more complicated installation requiring more piping at several points
in the water treatment system.
In Table 103 cost figures and ozone generation capacities are compared
for the three RWW ozone installations discussed above. It is evident that
economies of scale result in lower costs per unit of ozone generation at the
larger installation. However, site-specific factors (such as the need for
relatively more piping at the smaller plant) also affect the cost/lb of
ozone generation capacity/day.
General Cost Data
Residential customers of the RWW in Mill helm were charged 0.89 CM/cu 11
of water supplied during 1978. This is somewhat lower than the rate charged
by other major German municipalities. At the exchange rate prevailing
during June, 1978 (slightly under 2 DM/$), this rate converts to about
$1.65/1,000 gallons.
Costs of treatment plant operation at Dohne were described by RWW
management as falling into three catagorles — treatment, distribution and
pumping (for both treatment and distribution). These categories account
for, respectively, 21%, 462 and 33% of total operating costs. A breakdown
of the costs within each of these categories is included 1n Table 104.
Several interesting conclusions can be drawn from these data in comparing
German treatment practice at the Dohne plant of MUlheim with typical United
States practices. Treatment costs of 2U are a relatively low percentage of
397
-------
TABLE 103. COSTS FOR OZONATION SYSTEMS* IN MULHEIM, FEDERAL REPUBLIC OF GERMANY
GO
£
Plant
Dohne
"A"
"B"
Ozone Generation
Capacity
kg/hr
8
14
36
kg/day
192
336
854
Ibs/day
423
741
1,905
Capital
Cost
MM of DM
2.2 (1976)***
1.6 (1978)
2.9 (1978)
Cap Cost of
Ozone Generation
DM/kq/dav
11,458
4,762
3,356
$/lb/day*
2,600
1,080
761
* includes cost of air preparation, ozone generation, turbine contacting, contactor
off-gas treatment, controls, but no contact chambers.
** at an exchange rate of 2 DM/$
*** includes building costs
-------
total costs. Labor also represents a snraller part of the total. On the
other hand, costs related to capital (interest and depreciation) are high.
Taken together, these three observations show that a irore capital-intensive
system is used at Dohne, which relies less on labor than is typical in
United States plants.
TABLE 104. BREAKDOWN OF COSTS AT DOHNE PLANT. MULHEIM. FRG
Category of
Cost
Labor
Energy
Materials
Taxes
Depreciation (c)
Interest (d)
Notes;
Treatment
(21% of Total)
10%
15%
17%
2%
17%
39%
TOOT"
Distribution
(46% of Total )
10%
1%
2%
7%(a)
29%
35%
TCOT"
Pumping
(33% of Total)
32%
36%
1%
1%
17%
13%
TOOT"
(a) Property taxes to local communities
(b) Taxes to authorities providing raw water supply
(c) Includes capital set aside for future building
(d) Interest costs estimated to be 5 to 6%
Cost of water to MUlheim's residential customers averaged 89 pfennigs/-
cu m (1.68^/1,300 gallons) in 1978. Power costs are 9 to 13 pf/kwhr (4.5 to
6.5i/kwhr) at Dohne, but are lower at other MUlheim plants where power is
generated on-site. The RWW did not raise the price of water to their custo-
mers when the BAG process went on-stream in 1977.
Labor costs at Dohne are 2,800 DM ($1,400)/month.
employs 10 machine operators (2/shift) + 1 plumber.
FUTURE PLANS AT MULHEIM
Dohne currently
Based upon the successful incorporation of the BAC process into the
Dohne p'ant, the RWW management is incorporating the process into two
additional plants which also draw Ruhr River water. These plants will
process 72.0CO and 25,000 cu m/day of drinking water.
399
-------
Both processes will be nearly "identical to the current Donne process,
except that ground passage of treated water will be eliminated. Ground
passage could be eliminated at Dohne now, from a treated water quality point
of view, but will be retained to act as a storage reservoir. In addition, a
Superpulsator will be used at the smaller plant instead of the Pulsator,
because the newer equipment can be used at much higher upflow rates (12
m/hr).
Additionally, the sand filters at Dohne were scheduled to be replaced
in December, 1978 with dual media filters. These were to be hydroanthracite
(0.6 to 1.2 mm particle size) covered with a layer of light density (2 to 3
mm particle size) GAG (which has very little adsorption capability. The
reason for this change is to allow backwashing of the filters to be controlled
by headless rather than by turbidity, which is the present control mechanism.
400
-------
APPENDIX F
ROTTERDAM, THE NETHERLANDS — KRALINGEN WATER TREATMENT PLANT
Background
The new Kralingen plant became operational in March, 1977. It wai
constructed to replace the older Honingerdtjk plant which dated back to
1874. Raw water for the Kralingen plant is supplied by the River Maas
through two Biesbosch storage reservoirs. An alternate water source is the
Berenplaat storage reservoir and, under emergency conditions, River Rhine
water may be drawn through the Nieuwe Maas emergency Intake. Figure 109
shows the Kralingen plant water sources.
RHINE RIVER
i
ME;SE RIVER
(HAAS)
RhBIE RIVER
OVDE MAAS
DGR3JMCY
HISJWE MAAS
areY INTAKE
BEREMPLAAT
3TCRA3E
BIES BOSCH
STORASH R2S
KRALBGEN RESERVCIR
Figure 139. Kra'lngen (Rotterdai) plant water sources.
The Kralingen plant is of interest to students of European water
treatnent practices for a number of reasons, including the following:
1) Kralingen is a totally new plant which incorporates the latest knowledge
of water treatnent processes,
401
-------
2) Being recently constructed, Kralingen provides contemporary cost
information,
3) Kralingen incorporates a high level of process monitoring for organic
chemicals, especially trihalomethanes, due to the interest in these
problems by Dr. Johannes J. Rook, Chief Chemist. Dr. Rook is a pioneer
in studying and identifying the mechanisms of formation of trihalo-
methanes in drinking water. Dr. Rook's basic objective is to minimize
the amount of chlorine used in treating Rotterdam's surface water
supplies, while producing high quality finished drinking water.
The Biesbosch Reservoirs
These two reservoirs store River Maas water, which flows sequentially
through the first reservoir, then the second. Each reservoir is 20 meters
deep and the two provide a combined retention time of three months. This
storage time equalizes wide variations in River Maas flows, which are especial-
ly affected by the annual Spring thawing of snows.
The second reservoir has been fitted with aeration devices, prinarily
for the control of algae, to prevent stratification, to promote biological
decomposition of dissolved organic materials and to promote conversion of
ammonia to nitrate ion by nitrification. Airmonia levels in the reservoir
influent from the Maas are as high as 4.5 mg/1 during winter months, but
this usually drops to less than 1 mg/1 during the 90-day reservoir storage
in winter and to zero during summer. Coliform levels drop to about 10% of
their influent levels during the first 30 days of storage in these reservoirs.
Promotion of aerobic biological activity in the Biesbosch reservoirs
incorporates biological pretreatment into the Kralingen plant treatment
scheme.
The cost for installing these two reservoirs was equal to the cost for
installing the Kralingen treatment plant itself (see cost section).
Water flows from the Biesbosch reservoirs to the Kralingen plant
through a 20 kilometer long transmission line which requires 15 hours
residence time. The Kralingen plant is designed to operate without prechlori-
nation, however unacceptable head losses occur in the transmission line when
water temperatures exceed 10°C during summer months. This is due to buildup
of biological growths in the main. Therefore, up to 4 mg/1 of chlorine is
added at the reservoir to control biogrowths in the transmission line during
summer periods. Prechlorination dosage is controlled by monitoring head
loss in the transmission main. Nominal prechlorination dosage is set at 1
mg/1, but when head losses increase, more chlorine is added. Prechlorination
at the reservoir for protecting the transmission line is referred to as
"transport chlorination".
Prechlorination is not required during winter months when the water
temperatures are below 10°C. Therefore, trihalomethanes are produced at
Kralingen only during summer periods when transport chlorination must be
practiced.
402
-------
The Kralingen Treatment Plant
The site of the Kralingen plant is adjacent to that of the old Honinger-
dijk plant, as this is the focal point of the Rotterdam water supply system.
Transmission irains and the Nieuwe Maas intake previously used by the Honinger-
dijk plant can be used by Kralingen.
Process selection was based on a lengthy (about 2 years) semi-industrial
scale pilot plant study. Figure 110 shows details of the individual process
steps and Table 105 summarizes the number of operational units and their
capacities for each process step.
Low lift pumps draw water from the raw water storage reservoir at the
end of the 20 km transmission line from the Biesbosch reservoirs. Iron
sulfate coagulant is added in static mixers prior to discharge to floccula-
tion, which is achieved in a 4-compartment unit utilizing horizontal shaft
paddle mixers. The flocculated water is clarified in 55° lamella settlers
(Parkson process).
Clarified water flows to a 5-minute retention time, aspirating turbine,
ozone contacting chamber, and subsequently to an 11-minute retention time
tank. A design dosage of 3 mg/1 of ozone is added to produce a residual
dissolved ozone level of approximately 0.4 mg/1 in the water emerging from
the contactor. However, the ozonation step is controlled by monitoring the
level of ozone in the contactor off-gases at the level of 1 g of ozone/cu
meter. This is done because Kralingen plant personnel have lore confidence
in being able to monitor ozone in the gaseous phase than in solution. Ozone
is analyzed in both phases spectrophotometrically (with a Sigrist unit), but
in solution a *i1m of oxidized (by ozone) micropolljtants gradually builds
up which interferes with light transmission and results in inaccurate readings.
Ozone in the contactor off-gases is destroyed in heated catalytic
units.
Ozonized water flews to multi-media filters (20 cm of anthracite on
sand, supported on gravel) at a rate of 15 to 20 cu m/sq m/hr (m/hr).
Filter backwashing is provided by air, then water backwash, when the headless
reaches a maximum of 1.5 meter.
Filtered water is pumped from the dual media compartment filter clearwell
below the filters by medium lift pumps to the pressurized GAC columns.
Filter and GAC column backwash water also is drawn from the filter clearwell.
A depth of 4 neters of GAC is provided in the twelve, 8-meter high, 6-meter
diameter, cylindical steel GAC contactors. These GAC contactors are construc-
ted of carbon steel with a special proprietary coating on the inside surfaces.
The GAC is supported by a coated steel plate with plastic nozzles inset in
the plate for flow distribution. A 10-minute empty bed contact time is
provided in the 3AC contactors.
Backwashing of 3AC columns is conducted about once/week by using the
filter backwash pumps. The process is controlled by head loss of 5 11 WC.
403
-------
River Haas
1
Biesbosch ReservoTs
Raw Water Storage Reservoir
Low Head Punping Station
F'occulators
Clar-*-ers
Czore Coitacto-s
I
3AC Contactors
Fin-shed Water Reservoirs
aerat-on
Dual Media Filters
>
f
F-lter Clear Well
,
f
Medium -ift Pjrpirg Station
' transport chlorTation
'summer only)
chenlcals
che-rca's
H-gh Lift Purpirg Stafon
i ,
Water Oistr-butioi Systen I
post chlor-nation
(C 5 ng/' dosaqe
Figjre "1C. Process flow d^agran of the Kralingen water treatment
plant, Rotterdam, "he Netherlands.
404
-------
TABLE 135. DESCRIPTION OF TREATMENT PROCESS UNITS AT KRALINGEN PLANT
description of unit
raw water storage basin:
low lift pumping station:
constant speed
variable speed
coagulation: static mixer
flocculation: four compartment,
horizontal shaft, paddle
flocculators
clarifiers: lamella (Parkson
process) separators
ozonation: single stage, 5-minute
retention time, aspirating turbine
holding tank
filtration: dual media (0.8 m sand,
0.8 m anthracite). Unit filter
area -- 36 m^
medium lift pumping station:
medium lift pumps
filter & GAC backwash pumps
GAC contactors: 10 minute EBCT,
4 m GAC depth; unit filter area =
28.1 m2
finished water storage reservoirs
high lift pumping station: pumps
number of
capacity operational
of unit units
87,984 m3
1.5 m3/sec
1.5 m /sec
1.94 m /sec
3
0.4 m /sec
3
0.4 m /sec
3
0.4 m /sec
0.4 m /sec
1 m /sec
1 m /sec
0
0.194 m /sec
30,000 m3
0.83 m3/sec
1
1
1
1
5
5
5
5
10
1
1
10
2
6
number of
backup
units
—
—
2
1
1
1
1
1
2
3
3
2
—
2
405
-------
The GAC 1n the columns is manufactured by Norit (currently Super,
Normal and mixed Super/Normal) and leased from Norit. Spent GAC is returned
to the Norit plant, some 20 miles distant, for reactivation. Any losses of
the leased GAC during backwashing or transportation to Norit are charged to
the Kralingen plant at the rate of 1,300 Dutch gilders/cu m.
During the plant visitation (June, 1978), only 8 of the GAC columns
were being used. Of the eight, seven were scheduled to be on-line at any
one time, with the GAC from the eighth column being regenerated at the Norit
plant. Currently, GAC regeneration is expected to be required every one to
two years, based on chemical laboratory analyses being developed by Dr. Rook
(see later section).
Water flows from the GAC columns to above-ground, enclosed finished
water reservoirs having a capacity of 30,000 cu m. High lift pumps draw
from the reservoirs and discharge to the Rotterdam distribution system.
Prior to storage, the processed water is treated with chlorine to attain a
free residual of 0.1 to 0.2 mg/1, which normally requires chlorine dosages
(total of 0.3 to 0.6 mg/1). During summer, a peak chlorine dosage of 1 mg/1
is required to attain these chlorine residuals. At the extremities of the
distribution system, total chlorine residual is zero to 0.1 mg/1.
Water Quality
Table 106 lists typical water analyses obtained during January, 1978.
Biesbosch raw water analyses after entry into the plant but prior to treatment
are shown as "raw water". Finished water analyses are made after residual
chlorination. It should be noted that influent CCD and TOC levels of 8 and
4 trg/1 were lowered to 4 and 2.8 mg/1, respectively, by the Kralingen treat-
ment process. Dr. Rook believes COD to be a better parameter for monitoring
effectiveness of GAC adsorption efficiency than is TOC.
Trihalomethane Production & Removal by GAC
Several well-known papers by Dr. Rook detail his pioneering studies on
the formation of trihalomethanes in Rotterdam drinking water. These papers
are cited in the bibliography section of this report. In addition, Dr. Rook
provided the unpublished data of Table 107, which show that removal of THM
precursors by the Kralingen water treatment process (ozonation followed by
GAC adsorption) is efficient only with virgin (or freshly regenerated)
activated carbon. From June through November, 1977 prechlorination of
Biesbosch reservoir water was practiced at levels of 4 mg/1. Total THM
levels over this period averaged 108 microg/1 in the plant influent, 72
microg/1 before ozonation and 71 microg/1 after ozonation.
Without GAC adsorption and following 0.5 mg/1 post-chlorination dosage,
TTHM levels in ozonized water were 100 microg/1. With virgin GAC and post-
chlorination, TTHM levels in ozonized water dropped to 17.5 microg/1, but
with 4-month old GAC, TTHM levels in ozonized and post-chlorinated waters
rose to 61 microg/1.
406
-------
TABLE 106. ANALYSIS OF RAM AND FINISHED MATERS AT KRALINGEN. JANUARY 1978
parameter
color, mg Pt/1
temperature, °C
turbidity, JTU,
KMnO. demand, mg/1
nitrite, mg/1
nitrate, mg/1
sulfate, mg/1
NH. saline, mg/1
NH. albuminoid, mg/1
Fe, mg/1
Mn, v-g/1
DO, mg/1
phenol, yg/1
detergents, yg/1
COD, mg/1
TOC, mg/1
Br, yg/1
hexachlorobenzene, i.g/1
- HcH, yg/1
- HcH, yg/1
- HcH, yg/1
cholinesterase inhibitors, in
parathion equivalents, yg/1
raw water*
mih.
9
5.5
0.60
10
0.019
18.5
78
0.20
0.17
0.02
6
11.2
1
45
8
3.5
120
—
<0.01
<0.31
0.01
0.04
avg.
12
6.0
1.6
11
0.050
18.8
83
0.26
0.20
0.03
7
12.2
1
50
8
3.9
125
<0.01
<0.01
<0.01
0.01
0.07
max.
14
7.5
3.9
12
0.070
19.0
90
0.33
0.22
0.05
9
12.6
2
55
9
4.1
135
--
<0.01
<0.31
3.01
0.08
finished water
mm.
<1
5.5
0.05
3
--
19.5
113
0.34
0.09
0.01
2
11.2
<1
10
2
2.2
60
<0.01
--
0.01
3.31
0.02
avq.
<1
6.0
0.10
4
0.000
19.9
116
O.C6
0.11
0.02
3
12.4
<1
11
4
2.8
65
<0.01
—
0.01
0.01
0.03
max.
1
7.5
0.25
5
—
20.0
119
C.ll
0.13
0.04
3
13.0
<1
15
5
3.7
80
<0.31
--
C.01
0.01
3.34
* raw water = water influent to the plant
407
-------
TABLE 107. HALOFORM PRODUCTION IN KRALIN6EN PLANT. JUNE 1977 - MARCH 1978
sampling point
plant Influent
after coagulation,
lamella settling, sand
filtration & evap'n.
after 5 min. ozonation
no GAC +0.5 mg/1 post-
chlorf nation
after virgin GAC +0.5
mg/1 post-chlori nation
after 4 month old GAC +
0.5 mg/1 post-chlori-
nation
data taken
average data,
June-Nov. 1977
average data,
June-Nov. 1977
average data,
June-Nov. 1977
prechlorlnatlon
at reservoir
4 mg/1
4 mg/1
4 mg/1
0
0
0
haloforms produced (mtarog/1!)
CHC13
55
35
34
51
3.3
22
CHCl2Br
34
23
24
34
3.6
15
CHBr2Cl
17
12
11.3
14
4.6
13
CHBr3
2
1.6
1.8
1
6.0
11
total
THMs
108
72
71
100
17.5
61
o
00
-------
Thus Dr. Rook concludes that GAC 1s effective in removing THMs from his
waters only for short periods of time (less than 4 months). He also concludes
that once his waters have been prechlorinated, ozonation is not effective
either in reducing THM concentration levels or in preventing formation of
more THMs upon subsequent post-chlorination.
From July to December 1977, the chloroform levels in Kralingen plant
influent water and in one GAC column effluent followed the behavior pattern
shown in Figure 111. Prior to July, 1977 the plant influent water was not
chlorinated, therefore chloroform levels in the plant influent were zero.
Starting in July, 1977, the amount of chloroform formed immediately increased
to levels of 30 to 60 m1crog/l. Most of this was adsorbed quickly by the
GAC, but the SAC effluent quickly began to show the presence of chloroform.
During September/October, 1977 the chloroform level in the GAC effluent
peaked at about 15 to 20 mg/1 then began to fall. When prechlorination was
ceased in December, 1977, however, chloroform still was measured in the GAC
effluent for several months thereafter, falling to levels near zero by
March/April, 1978. A second GAC column showed the same behavior over the
same period, except that the chloroform concentration in the effluent levelled
off more slowly after prechlorination was ceased.
Dr. Rook concludes from these and other data that GAC adsorbs chloroforn,
but that desorption of chloroform begins almost immediately. After cessation
of prechlorination, all chloroform measured in the 3AC ^iltrates is present
because of desorption.
Biologically Active 3AC
Dr. Rook has noticed biological activity in the Kralingen GAC adsorbers,
but its buildup was slow during the first year of operation. Its current
contribution to the overall efficiency of the treatment process is relatively
small. At water temperatures above 10°C (summer) biological activity is
operative in both the double layer filters and in the GAC adsorbers. Ammonia
levels of 0.3 mg/1 (winter) drop to 0.10 to 0.15 mg/1 by nitrification in
the dual media filters. There Is no ammonia 1n the Kralincen plant influent
during summer because it 1s all nitrified in the Biesbosch reservoirs.
The new Kralingen plant began operation in March, 1977 with virgin 3AC.
Reactivation of GAC did not begin until March, 1978. With virgin GAC,
effluents from the adsorbers contained 0.9 mg/1 of TOC and 1 to 2 irg/1 of
COD (from Influent values of 4 and 8 mg/1, respectively). After the second
month, the GAC effluent contained 2 mg/1 TOC. By January, 1978, the TOC of
the GAC effluent had risen to 2.8 mg/1 (622 of that 1n the plant influent'.
At the same time, the average COD level in the GAC effluent was 50% of that
in the plant Influent. Therefore, 1n terms of EPA's proposed GAC regeneration
criteria (remove 50% of the influent TOC), the effective life of the Kralingen
activated carbon was less than 1 year. However, this GAC performance was
considered to be satisfactory at Rotterdam.
Detergent levels in the Kralingen water averaged 50 microg/1 during
January, 1978 and were lowered to 11 microg/1 during treatment. Dr. Rook
noted that new GAC removed nearly all of the detergents originally present.
409
-------
30-60
nncrog/1
A
in
1C
t—
0}
O
O
O
Influent-
July, 1977
THMs due to transport chlorinatlon
10,000 12,000
bed volumesi
ceased prechlorination
elution of CHCU adsorbed;
^hows desorptlon is operative
Sept Oct
Dec
Figure 111. Desorption of trihalomethanes from GAC at Kralingen plant.
-------
However, after some 6.0CO bed volumes had passed through the GAC, hardly any
detergent removal occurred. However, after continued passage of an additional
6,000 bed volumes of water through the same GAC, renoval of detergents
increased up to a level of about 50% (Figure 112). Dr. Rook believes that
desorption of detergents may have been occurring during the period when no
removal was apparent and that the biological activity had not yet reached a
point at which biodegradation of detergents was significant. Upon continued
use. however, biological degradation (and/or desorption) became responsible
for the removal of about 50% of the influent detergent concentrations.
Biological activity in the Kralingen plant dual media filters and GAC
adsorbers is present, but does not appear to be removing as nuch ~OC and
ammonia as at the MUlheim, Germany Donne plant. This can be explained on
the basis of the biological decomposition reactions which occur 1n the
Biesbosch reservoirs during 90-day storage with constant aeration. During
this storage period, most of the amnonla is nitrified and the readily
degraded carbonaceous organic materials are decomposed 1n the reservoir.
The balance of the TOC and COD which is removed in the Kralingen plant
proper is a result of flocculatlon, clarification, ozonation, filtration,
GAC adsorption and biological degradation 1n the filtration media and GAC
adsorbers.
GAC Regeneration Parameters
Dr. Rook began sending the Kralingen GAC out for regeneration in
March, 1978 (one or two columns at a time). However, he believes that even
though the GAC may be passing relatively high levels of TOC through it in
the form of dissolved organic materials which are not strongly adsorbed by
GAC (or are easily desorbed), the less polar, more strongly adsorbed halogen-
ated organic materials of concern still are being adsorbed. This belief is
based upon work which had been conducted on Rhine River waters by the Engler-
Bunte Institute of the University of Karlsruhe, Germany.
As a result, Dr. Rook has been developing analytical procedures for the
measurement of chlorinated organic materials. TOC1 and DOC1 analyses are
conducted following the Engler-Bunte Institute procedures. In addition, an
"Ether-extractable Organic Chlorine" (EOC1) analysis has been developed by
Dr. Rook. This extraction procedure employs petroleum ether (30°C boiling
point) for extracting GAC effluent. As soon as the level of EOC1 rises
significantly, Dr. Rook plans to regenerate the particular GAC column(s)
involved.
The March, 1978 GAC regeneration was based on TOC rise in the 3AC
effluent. However, as of June, 1978, regeneration now will be based on a
maximum level of TOC1 and/or EOC1. These parameters for GAC regeneration
may be changed in the future by Dr. Rook as more data are gathered regarding
the Kralingen plant performance.
Colony Counts
Table 1C8 lists representative colony counts/ml obtained during March,
1978 and May, 1978. There is little question that counts are low after the
411
-------
100%
-**
ro
o
03
01
S-
O)
12,000 bed volumes
Y
time
Figure M2. Removal of detergents by Kralingen plant GAC.
-------
TABLE 108. REPRESENTATIVE COLONY COUNT DATA AT KRALINGEN PLANT
sampling point
reservoir - before
chlori nation
reservoir - after
chlorinatlon
plant Influent
after lamella settling
after ozonatlon
after GAC
plant Influent
after lamella settling
after ozonatlon
after sand filtration
after GAC
data obtained
during
March 1978
March 1978
March 1978
March 1978
March 1978
March 1978
May 1978
May 1978
May 1978
May 1978
May 1978
* incubated at 22°C; grown on agar
no. of
samples
123
122
colony
counts/ml*
—
19-20
7
3
10
150
2,000-
5,000
70
10,900
5,800
no. of samples having counts of
oTmT
109
64
1-10/ml
12
32
10-100/ml
2
24
100-1,000/ml
2 (av. 500)
-------
ozonation step but high after GAC adsorption. However, the post-chlorination
step (0.5 iig/1 chlorine dosage) lowers plate counts 1n the Kralingen product
water to levels which meet the required public health standards.
Capital Costs And Financing
The Kralingen plant was completed in 1977 at a total capital cost of
170 million Dutch gilders, stated in April, 1978 values. Since the Rotterdam
accounting procedure includes the statement of all assets in estimated
current market values, figures were quoted to the site visitation team and
are discussed below in April, 1978 values. The market exchange rate during
June, 1978 was approximately 2.1 Dutch gilders per U.S. dollar. Hence, the
Kralingen plant cost $81 million.
Table 109 breaks down the capital costs of the components of the
plant; the figures are in millions of Dutch gilders and 1n U.S. dollars.
TABLE 109. CAPITAL COSTS OF KRALINGEN PLANT
Cost Categories
General items (land purchase, engi-
neering, financing, overhead, archj
tects, city planning fee, etc.)
Service building (offices, labora-
tory, mechanical workshop, pilot
plant)
Streets, landscaping
Storage reservoir for raw water,
pumping station
Emergency inlet pump station
Treatment plant (see separate
breakdown of components)
Carbon facilities (excluding GAC)
Finished water storage tanks
High lift pumps
Shelter facilities for war
emergencies
Items unaccounted for
TOTAL
April 1978 values
(•nil! Ions of Dutch gilders)
40
24
12
5
2
46
7
9
6
1
18
170
millions
of $ I'S
19.05
11.43
5.71
2.38
0.95
21.90
3.33
4.29
2.86
0.48
8.57
80.95
414
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Additional information was provided on the costs of each component of
the treatment plant itself. The elements making up the total of 46 MM
gilders are shown in Table 110.
TABLE 110. TREATMENT COMPONENTS AT THE KRALINGEN PLANT
Plant Component
Construction - concrete portions
Piping
Heating, cooling, ventilation
Electrical
Chemicals - initial stock
Electrical installations for
chemical dosing and metering
Coagulation
Sedimentation
Sludge treatment & drying
Ozonation equipment*
Filtration
Medium lift pump station
Control system - automation
TOTAL
April 1978 values
(millions of Dutch gilders)
13.5
1.8
1.9
2.2
3.7
2.1
1.2
3.0
0.1
4.3
3.4
2.2
7.0
46.4
millions of
$ US
6.43
0.86
0.90
1.05
1.76
1.00
0.57
1.43
0.05
2.05
1.62
1.05
3.33
22.10
* 'includes air preparation, ozone generation, turbine contactors and off-
gas destruction equipment
These costs were financed by the authority through funds drawn from
general revenues rather than through Issuance of new debt. Since it is a
stock company owned by the city of Rotterdam, the water authority incorporates
its capital needs with those of the city and acquires funds in this way. In
return, the water company pays for the cost of this capital in the form of
"interest" and depreciation payments to the city in future years. For the
Kralingen plant, that annual payment is 7 MM gilders ($3.33 MM) annua'ly,
for a plant presently worth 170 MM gilders ($81 MM), about 4% per year for
the current worth of the plant and a higher percentage of its original cost.
415
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The total gross assets for the water company were 540 fM gilders ($257
MM) in April, 1978 values. Including the new plant less accumulated deprecia-
tion of 140 MM gilders ($66.67 MM), net assets totalled 4CO MM gilders
($190.5 MM). Hence the new plant was a large portion — about 75% — of the
net assets of the coirpany existing before its construction. Such a large
capital program would strain the capabilities of utilities lacking the
resources and city ownership which Rotterdam enjoys.
Annual Operating Costs
In this section are discussed first the operating costs of the Kralingen
plant and then a breakdown of the overall system operating costs. The plant
costs are based only on general categories of expenses, while the system
costs are based on the generalized steps in water supply from raw water
procurement to treatment and distribution.
The operating costs of the plant total about 7 MM Dutch gilders ($3.33 YM)
annually. Table 111 presents an approximate breakdown of these costs.
TABLE 111. ANNUAL OPERATING COSTS OF KRALINGEN PLANT
Cost Category
Wages - management & technical staff
Wages - operators
Maintenance
Utilities
Chemicals
Miscellaneous
TOTAL
millions of
Dutch gilders
0.9
1.0
2.5
1.2
0.5
0.9
7.0
millions of
$ US
C.43
0.48
1.19
0.57
0.24
0.23
3.34
In addition to the 7 MM gilders for operating the Kralingen plant, the
water company pays 7 MM gilders to the City of Rotterdam to cover the cost
of the capital funds provided for the construction of the plant. Hence, a
total of 14 MM gilders ($6.67 MM) is required annually to cover the full
plant costs. On a unit basis, assuming average annual production from the
plant of about 120,000 cu m/day (32 mgd), these total treatment costs amount
to 1.2C gilders/1,COO gallons, or 57(t(U.$.)/!,000 gallons.
Water treatment, however, is only one part of the total process of
potable water supply. For the entire Rotterdam system, plant treatment
costs about 30 MM gilders ($14.29 MM), or only about 26% of the total costs
of potable water supply. The Kralingen plant costs of 14 MM gilders ($6.67 VM)
represent 47% of this total, while the plant provides about 38% of the
416
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system production. Table 112 presents a breakdown of the Rotterdam system
annual costs, excluding costs associated with a distilled water plant which
offsets its own operating expenses with separate revenues.
TABLE 112. ANNUAL KRALINGEN WATER SYSTEM COSTS
cost category
Raw water - procurement &
reservoirs
Treatment/production
Distribution
Administration & laboratory
City use of water
Other
TOTALS
costs in millions
of Dutch gilders
41
30
32
5
6
4-
118
% of total I millions
5 of $ US
35%
26%
27%
4%
5%
3%
100%
19.52
14.29
15.24
2.38
2.86
1.90
56.19
Company Revenues And Rates
The Rotterdam City Council establishes the rates to be charged for
water. The stated intent of this rate-setting authority is to cover ful'.y
all of the costs of providing water services.
The total revenues in 1977 were 112 MM gilders ($53.33 MM), which is
slightly less than the operating expenses shown above due to the unbilled
provision of water to the city itself. The total amount of water delivered
during the year was 118 MM cu m (31,175.6 million gallons), at a calculated
average rate of C.95 gilder/cu m ($1.20/1,000 gal). Table 113 shows these
totals and a breakdown by class of service.
Since the water system serves 1.1 million people on a direct retail and
a wholesale basis, the usage and revenues per person served can be calculated
from these figures. The usage is 59 cu m/person/year, which converts to 42
gallons/capita/day. At the assumed rate of 1.16 gilders/cu m ($1.46/1,000
gal), this amounts to about 70 gilders ($33.33)/person/year, or about 23
gilders ($10.95)/month for a family of four.
417
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TABLE 113. ROTTERDAM UATER SYSTEM REVENUES, WATER DELIVERIES AND RATES
use category
Residential
Industrial
Wholesale
City use &
unaccounted for
TOTAL
revenues - millions
of Dutch gilders
49.7
45.0
14.6
2.4
111.7
deliveries -
millions of
cu m
42.8
51.0
22.4
1.4
117.6
calculated
rates, gilders
per cu m
1.16
0.88
0.65
0.95
US $ per
l.COO
gal
1.46
1.11
0.82
$1.195
418
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