-------
Table 4. Plant Performance During Semi-Volatile Organics Study
October 1, 1979 through August 8, 1980
oo
Parameter
TSS
COD
TOC
T-P
NH3-N
N02 and N03~N
Alkalinity (as CaCC^)
TSS
COD
TOC
T-P
NH3-N
N02 and N03~N
Alkalinity (as CaC03)
Influent
(mg/1)
490
650
180
8.3
20
.1
—
430
640
180
8.1
20
.1
-
Sewer
Simulator
Effluent
(mg/1)
505
660
194
8.0
19
.1
—
505
640
185
7.9
17.3
.1
-
Grit Primary
Chamber Clarifier
Effluent Effluent
(mg/1) (mg/1)
Control Sequence
408
700
198
8.7
19
.1
290
.
Spiked Sequence •
490
670
190
8.6
17.3
.1
290
265
390
122
5.6
19
.1
300
257
365
114
5.6
18.3
.1
290
Activated
Sludge
Effluent
(mg/1)
26
74
18
2.9
1.5
3.6
188
26
76
19
2.7
.9
5.2
170
Overall
Removal
(%)
95
89
90
65
93
-
-
94
88
90
67
96
-
-
-------
Table 5. Mean Recovery Values for Various Sample Locations
and Classes of Compounds.
PESTICIDES/PCB's
Arochlor 1254
Heptachlor
Lindane
Toxaphene
Mean Recovery
PHENOLS
2 ,4 -dimethyl phenol
Phenol
Pentachlorophenol
Mean Recovery
PHTHALATES
Bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Diethylphthalate
Dime thy Iphthalate
Di-n-butylphthalate
Di-n-octylphthalate
Mean Recovery
Reported^3)
ribn
42
49
64
83
60
72
54
84
70
66
49
65
66
58
88
65
Average
Inf.
54
71
60
60
61
60
72
74
69
86
70
77
73
74
65
74
Recovery
Sample
Act.
Sludge
Eff.
74
98
71
64
77
54
68
120
81
76
58
70
62
70
68
67
for
Sets
Pri.
Sludge
61
28
32
66
47
44
28
49
74
34
25
69
56
57
31
45
Eight
Return
Act.
Sludge
53
68
72
74
67
17
31
79
42
50
62
31
15
68
62
48
POLYNUCLEAR AROMATIC HYDROCARBONS
Acenaphthene
Anthracene
Benz (a )anthracene
Chrysene
Fluor an thene
Fluorene
Naphthalene
Phenanthrene
Pyrene
Mean Recovery
78
79
51
77
63
88
89
79
68
75
79
64
59
48
62
79
66
71
60
65
77
71
55
71
58
81
84
65
61
69
71
45
48
63
64
75
25
67
62
58
58
60
35
56
58
59
41
60
52
53
a Industrial and municipal wastewaters.
Recovery expressed as percent.
815
-------
in the wastewater matrices are comparable to those reported by Kleopfer (21)
as representative of reasonable analytical performance.
The Cincinnati raw wastewater with a high average COD of 650 provides
a stronger background of extractable interferences than typical municipal
wastewaters. This wastewater produced sludges, especially primary sludges,
which were intermittently very difficult to handle, especially during the
extraction process. As expected the recoveries in the sludge matrices were
generally lower than those encountered in the wastewater matrices.
Semi-Volatile Organics Removal
The results of the analyses for the organic priority pollutants in the
control and spiked systems are presented in Tables 6 and 7. The data
reported are the arithmetic means for all eight sample sets and all
concentrations are in micrograms per liter. Additionally, all concen-
trations used for computing the mean concentration were corrected for
recovery factors determined from the quality control spikes for each sample
set.
Most of the selected organics in the unspiked raw wastewater were found
at or near the detection limits (1 to 10 /ig/1) of the analytical methods.
Phenol, several phthalates and napthalene were observed in relatively
substantial concentrations in the unspiked raw wastewater. Spiking, sub-
stantially increasing the concentrations of the organics in the wastewater,
permitted evaluation of the removals across the plant.
In general, the concentrations of the spiked organic priority pollu-
tants found in the effluent of the primary clarifier (Table 7) were slightly
higher than the influent concentrations. Even a cursory examination of the
data for the primary sludge samples indicates that considerable removal of
these materials did occur in the primary clarifier. The inconsistency
between the influent and primary effluent data can be understood when one
realizes that the standard deviations for both the influent and the primary
effluent samples typically ranged from 50 to 100 percent, which is normal
for GC/MS quantitation at low concentrations.
A comparison of the influent and activated sludge effluent data of the
spiked system indicated that the treatment sequences were generally
effective in reducing the concentrations of the organic compounds in the
wastewater streams. The spiked system typically produced a more than 97
percent reduction in the concentrations of the compounds being spiked. Most
of the residual concentrations of the chemicals were below the detection
limits in the activated sludge effluent. Lindane, bis-(2-ethylhexyl)-
phthalate, di-n-octylphthalate pentachlorophenol, and phenol were found in
analytically significant concentrations (< 4.8 to 25.8 ;ig/l) in the
secondary effluent.
Substantial concentration increases occurred in both the primary and
return activated sludges. Typically a two order of magnitude increase in
concentration, based on the influent values, occurred in the primary sludge
samples. Concentration increases observed in the return sludge ranged from
0.5 to 1.5 orders of magnitude depending on the specific compound.
816
-------
Table 6. Mean Concentrations of Semi-Volatile Organics in
the Control Treatment System.
CO
Influent
(yg/D
PESTICIDES/PCS' s
Arochlor 1254
Heptachlor
Lindane
Toxaphene
PHENOLS -
2,4-dimethylphenol
Phenol
Pentachlorophenol
PHTHALATES
Bis (2-ethylhexyl )phthalate
Butylbenzylphthalate
Diethylphthalate
Dimethylphthalate
Di-n-butylphthalate
Di-n-octylphthalate
POLYNUCLEAR AROMATIC HYDROCARBONS
Acenaphthene
Anthracene
Benz(a)anthracene
Chrysene
Fluoranthene
Fluorene
Napththalene
Phenanthrene
Pyrene
< 2.9
< 1.0
< 2.0
< 2.9
< 17.5
111.0
8.9
63.1
< 7.2
< 7.1
< 3.2
16.0
< 6.3
< 1.8
< 5.4
< 0.8
< 5.1
< 2.1
< 2.4
< 95.4
8.8
< 1.8
Activated
Primary Sludge
Effluent Effluent
(yg/l) (yg/l)
< 2.9
< 1.0
< 1.0
< 2.9
< 13.6
46.0
< 5.7
30.5
< 5.6
< 12.3
< 17.5
< 11.8
< 3.6
< 2.9
< 2.7
< 0.8
< 2.1
< 1.3
< 2.1
< 74.7
< 4.5
< 1.3
< 2.6
< 1.0
< 1.0
< 2.6
< 0.9
< 8.2
< 1.8
6.4
< 4.4
< 1.0
< 0.7
< 2.4
< 2.2
< 1.0
< 1.0
< 0.8
< 0.8
< 0.6
< 0.7
< 1.0
< 0.9
< 0.7
Primary
Sludge
( yg/D
< 403.0
< 52.9
< 146.0
< 1,063.0
< 57.9
983.0
853.0
6,384.0
2,841.0
< 75.8
< 13.6
1,255.0
< 770.0
< 121.0
< 560.0
< 292.0
431.0
< 488.0
< 175.0
3,583.0
< 646.0
< 844.0
Activated
Sludge
( yg/D
< 200.0
< 58.7
< 88.2
< 97.9
< 197.0
< 35.5
< 52.4
928.0
< 294.0
< 180.0
< 12.6
< 190.0
< 13.9
< 53.0
< 89.6
< 59.1
< 132.0
< 84.1
< 46.8
< 37.5
< 69.0
< 110.0
-------
Table 7. Mean Concentrations of Semi-Volatile Organics in
the Spiked Treatment System.
oo
i—'
oo
Influent
(yg/D
PESTICIDES/PCB's
Arochlor 1254
Heptachlor
Lindane
Toxaphene
PHENOLS
2,4-dimethylphenol
Phenol
Pentachlorophenol
PHTHALATES
Bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Diethylphthalate
Dimethylphthalate
Di-n-butylphthalate
Di-n-octylphthalate
POLYNUCLEAR AROMATIC HYDROCARBONS
Acenaphthene
Anthracene
Benz ( a ) anthracene
Chrysene
Fluoranthene
Fluorene
Napththalene
Phenanthrene
Pyrene
< 33.5
31.7
45.5
< 47.4
< 82.1
261.3
7.6
51.7
33.5
46.4
< 41.8
43.8
28.2
39.8
34.8
23.8
38.9
30.6
37.9
76.7
40.4
30.4
Primary
Effluent
( yg/D
< 114.0
< 28.5
< 41.8
< 87.5
60.9
> 196.2
13.0
52.4
37.5
57.7
< 37.2
54.4
< 34.4
53.6
33.9
24.9
36.6
39.9
51.6
242.5
44.3
39.1
Activated
Sludge
Effluent
( yg/D
< 2.9
< 2.3
25.8
< 2.9
< 0.9
< 13.5
< 6.3
11.3
< 1.3
< 1.2
< 0.8
< 2.7
< 4.8
<1.2
<0.9
<0.6
< 1. 2
< 1.9
<0.7
<0.7
< 1.1
<2.0
Primary
Sludge
( yg/D
13,500.4
< 2,152.0
< 1,130.3
< 8,213.1
< 20.7
< 2,348.3
< 410.7
< 6,713.0
< 8,160.0
< 710.3
< 37.2
3,482.4
< 5,278.0
3,354.0
4,809.8
< 3,241.5
5,982
5,281.0
< 3,921.0
< 3,463.0
< 4,931.0
< 6,640.0
Return
Activated
Sludge
( yg/D
5,403.0
526.7
< 173.7
<1,655.4
< 20.0
< 92.1
< 20.0
978.0
< 123.3
< 196.7
< 39.5
< 233.8
< 580.7
< 68.3
< 84.6
< 208.9
< 240.9
< 196.0
< 57.9
< 18.3
< 28.4
< 104.2
-------
Mass distributions (Table 8) were computed for each compound based on
the mean concentrations observed in the influent, secondary effluent,
primary sludge, and return activated sludge, and the operating parameters
presented in Table 3. Since most of the compounds studied are biodegradable
to some extent, the probability of accounting for 100 percent of any given
chemical was expected to be low; additionally, good accounting
of the chemicals in the distribution balances was not anticipated due to the
inherent variability in the GC/MS data. The results of the distribution
calculations for the spiked system, in general, are much better than
anticipated; the total percentages of the different compounds which were
accounted for are reasonable.
The pesticides and PCB's partitioned approximately equally between the
primary sludge and the waste activated sludge. A substantial portion of
lindane, 55 percent, was found in the activated sludge effluent. The three
phenols studied were not found to concentrate in either of the sludge
streams. These data indicate that two of the phenols studied are relatively
biodegradable. Pentachlorophenol substantially passed through the treat-
ment plant.
On a mass flow basis the phthalates were unevenly distributed between
the two sludge streams; more of the compounds were found in the primary
sludge. The results indicate that diethyl and dimethylphthalate are more
biodegradable than the other compounds studied in that class. Since these
two compounds have the simplest structure, this finding is not surprising.
The PAH's are the least polar of all the compounds. One would,
therefore, assume their preferential adsorption to the solids, which are
removed in primary treatment. As a class, the PAH's concentrated in the
primary sludge to the greatest degree. In contrast, only low amounts of
the PAH's were found in the WAS samples.
This research did demonstrate that a typical POTW, with the processes
studied, significantly reduced the concentrations of the 22 organic
priority pollutants; however, certain compounds, most notably lindane,
bis(2-ethylhexyl)phthalate, phenol, and di-n-octylphthalate were present
in the activated sludge effluent in relatively significant concentrations.
The impact of these low-level residuals on the aquatic environment would be
a function of many site-specific factors, such as ambient water quality and
dilution flows. However, based on the potential for bioaccumulation (22),
toxicity data reported in the literature (23), suggested water quality
criteria (24), and the presence of the materials in the secondary effluent,
one can only conclude that the POTW is not a totally effective system for
controlling the entry of some compounds into the environment via the
wastewater discharge. Furthermore, although some compounds were bio-
degraded, many of the chemicals studied were present in the sludges in very
high concentrations. The fate of these materials in the solids handling
processes is not known at this time, and additional research must be
conducted to provide answers to this pressing question.
819
-------
Table 8. Distribution of Semi-Volatile Organics in the Spiked
Treatment System.
oo
ro
o
Influent
(gm/day)
PESTICIDES/PCB ' s
Arochlor 1254
Heptachlor
Lindane
Toxaphene
PHENOLS
2 ,4-dimethylphenol
Phenol
Pentachlorophenol
PHTHALATES
Bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Diethylphthalate
Dimethylphthalate
Di-n-butylphthalate
Di-n-octylphthalate
POLYNUCLEAR AROMATIC HYDROCARBONS
Acenaphthene
Anthracene
Benz(a)anthracene
Chrysene
Fluoranthene
Fluorene
Napththalene
Phenanthrene
Pyrene
0.977
0.240
0.345
0.977
0.622
1.979
0.058
0.392
0.254
0.352
0.317
0.332
0.214
0.302
0.264
0.180
0.295
0.232
0.287
0.581
0.306
0.230
Percent in
Primary
Sludge
51
33
12
31
0
4.4
26
63
119
7
0.3
39
91
41
67
67
75
84
51
22
59
107
Percent in
Waste
Activated
Sludge
60
35
8
27
0.5
0.8
c
39
7
9
2
11
43
4
5
18
13
13
3
0.5
1
7
Percent in
Final
Effluent
2
7
55
2
1.1
5
81
21
4
3
2
6
17
3
3
f\
3
6
2
1
3
6
Total Mass
Recovered
(percent)
113
75
75
60
1.6
10.2
112
123
130
19
4.3
56
151
48
75
87
91
103
56
23.5
63
120
-------
Volatile Organic Study
Pilot Plant Operations
The study on the volatile organics is ongoing. The results presented
represents a preliminary assessment of the available data. Quality control
refinement has not been applied to the data. The operations of the two pilot
systems (Figure 2) for the volatile studies are summarized in Table 9. The
two systems exhibited stable and straight-forward operation. The water
quality performance for the treatment sequences (Table 10) indicated the
pilot systems provided good treatment. The operations data and performance
in both control and spiked systems indicate essentially the same operation
for both systems.
The 16 volatile organics in the initial phase of the work were
nominally spiked into the experimental treatment system at 50 jig/1. Higher
spiking concentrations will also be employed. Organic analysis, in
addition to the usual wastewater and sludge process streams, will include
gas phase analyses of the air streams from the aeration basin.
Volatile Organics Removal
The selected volatile organics (Table 11) are usually present in the
Cincinnati raw wastewater in analytically measurable quantities (0.2 ug/l).
The spiking substantially increased the concentrations of the organics to
improve the evaluation of the removability by the treatment plant.
The initial evaluation of the data (Table 12) reveals excellent
removals for most of the purgeable organics with 90 percent or better
removals. Two organics, 1,1,2-Trichloroethane and Dibromochloromethane
exhibited relatively low removals of approximately 70 percent with sub-
stantial residuals in the secondary effluent. Toluene, Ethylbenzene, the
combination of tetrachloroethylene and tetrachloroethane, and 1,2-Di-
chloropropane, while exhibiting nearly 90 percent removals or better,
passed through the treatment system into the secondary effluent with
concentrations greater than 2 Jig/1. The ongoing work will provide further
evaluation of the fate and distribution of these organics.
METALS REMOVAL.AND IMPACT
The metals studies involved two separate operational periods; an
evaluation of the distribution and removal of indigenous metals in the
Cincinnati raw wastewater by the control treatment system (6) during the
semi-volatile organics studies? and subsequent studies in 'which four
specific metals~Cd (7), Pb (8), Hg (9), and Cr (10)—were spiked into the
small pilot systems (Figure 1) in a sequence of increasing concentrations of
the individual metal. The studies on the individually spiked metals
included an unspiked control system in order to compare the impacts of the
increasing metal concentrations with the conventional plant operation and
performance.
821
-------
Table 9. Operations Summary, Volatile Priority
Pollutant Sequence; January-June 1981
Influent Flow, Q (gpm)
Flow, Qr (gpm)
Waste AS, Qw (gpd)
Primary Sludge, Qp (gpd)
OUR3- ML (mg-hr/1)
OUR - RAS (mg-hr/1)
Normalized ML OUR
Normalized RAS OUR
MLSS (mg/1)
RAS (mg/1)
ML Cent. Vol. (%)
RASbCent. Vol. (%)
SRT (days)
SVI (ml/gm)
System
Control
38.4
8.5
1,472
897.0
37.8
96.6
0.015
0.006
2,694
12,954
3.4
17.3
4.6
114.0
Spiked
34.7
8.4
1,471
1,219
47.8
87.2
0.016
0.005
2,940
13,326
3.7
15.8
5.1
111.0
a = Oxygen Uptake Rate (OUR).
b = Return Activated Sludge (RAS).
822
-------
TABLE 10. Performance of Volatile Priority Pollutant
Treatment Sequences; January-June 1981
Parameter
TSS
COD
Total-P
ro TKN
oo
Organic N
NHy-N
N02 & N03-N
Total-N
Turbidity (NTU)
UCOD(a)
Influent
(mg/1)
447.0
557.0
9.3
43.5
20.4
23.1
0.2
43.7
-
683.0
Primary
Effluent
(mg/1)
214.0
317.0
6.0
36.7
14.2
22.5
0.2
36.9
-
421.0
Removal by
Primary
Clarifier
52.0
45.0
35.0
16.0
30.0
3.0
-
16.0
-
38.0
Activated Sludge Eff.
(mg/1)
Control
30.0
91.0
3.1
19.4
5.7
13.2
6.4
25.8
12.0
152.0
Spike
23.0
87.0
2.8
18.4
5.2
13.2
6.3
24.7
10.0
148.0
Overall Removal
(percent)
Control
93.0
84.0
67.0
55.0
72.0
43.0
-
41.0
78.0
Spike
95.0
85.0
70.0
58.0
75.0
43.0
-
43.0
78.0
a UCOD = Ultimate Combined Oxygen Demand = COD +4.6 (NK^-N).
-------
Table 11. Mean Concentrations^a' Observed in Eight Sample Sets:
January 12 through July 28, 1981.
Control System
Inf.
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 ,2-Dichloropropane
Trichloroethylene
oo 1,1,2-Trichloroe thane
ISJ
*" Dibromochloromethane
Benzene
1 ,1 ,1-Trichloroe thane
Bromodichlorome thane
Chlorobenzene
Tetrachloroe thy lene
and
Tetrachloroe thane
Toluene
Ethylbenzene
47
0
11
3
<0
4
1
0
0
83
< 0
57
19
114
19
.1
.3
.3
.6
.2
.3
.5
.7
.5
.0
.2
.0
.3
.0
.5
Pri.
Eff.
33.2
< 0.2
7.4
4.0
< 0.2
1.5
1.0
0.3
0.8
32.7
< 0.2
36.5
10.0
98.6
27.3
Activ.
Sludge
Eff.
5.8
< 0.2
0.5
< 0.2
< 0.2
< 0.2
1.2
< 0.2
< 0.2
1.7
< 0.2
< 0.2
< 0.2
18.1
< 0.2
Return
Activ.
Sludge
2.0
< 1.0
7.2
< 1.0
1.8
< 1.0
16.6
1.9
< 1.0
2.4
< 1.0
1.8
6.8
122.8
26.0
Pri.
Sludge
32.3
< 1.0
3.5
< 1.0
< 1.0
9.2
2.9
< 1.0
14.4
41.9
< 1.0
702.5
161.6
591.3
522.6
Inf.
84.3
43.5
45.8
20.3
55.6
36.5
62.0
42.0
35.0
254.3
19.7
169.3
71.7
162.7
41.8
Pri.
Eff.
76.0
9.6
37.2
6.7
52.7
32.7
50.8
31.2
16.5
63.2
19.8
126.3
74.2
158.6
39.7
Spiked
Activ.
Sludge
Eff.
1.0
< 0.2
1.4
0.3
2.3
1.2
22.5
12.1
0.2
1.5
0.9
0.3
3.8
13.7
4.9
System
Return
Activ.
Sludge
1.2
< 1.0
3.6
< 1.0
< 1.0
< 1.0
17.4
1.3
< 1.0
< 1.0
< 1.0
1.5
5.6
2.9
3.6
Pri.
Sludge
111.4
0.7
9.7
0.6
63.2
263.3
18.9
2.9
224.3
40.3
0.2
736.7
570.9
627.9
570.7
a All concentrations in Ug/1.
-------
Table 12. Distribution of Volatile Priority Pollutants
In the Spiked Treatment Sequence
Methylene Chloride
1 , 1-Dichloroethene
Chloroform
Carbon Tetrachloride
1 ,2-Dichloropropane
Trichloroethylene
1,1, 2-Trichloroethane
Dibromochlorome thane
Benzene
1,1, 1-Trichloroethane
Bromodichlorome thane
Chlorobenzene
Tetrachloroethylene
and Tetrachloroethane
Toluene
Ethylbenzene
a = Removals based on mass
Percent
Found in
Primary
Sludge
3.2
0.04
0.52
0.08
2.76
17.54
0.74
0.16
15.63
0.39
0.02
10.62
19.42
9.42
33.29
balance.
Removal
by Primary
Clarifier
(percent)
9.9
77.9
18.7
66.9
5.2
10.4
8.1
25.7
52.9
-
NR
25.4
NR
2.5
5.1
Percent
Found in
Waste Act.
Sludge
0.04
0.07
0.23
0.16
0.06
0.09
0.83
0.09
0.09
0.01
0.16
0.03
0.23
0.06
0.25
•a
Removal by
Treatment
Sequence
98.9
> 99.5
99.4
98.7
96.1
97.0
65.6
72.7
99.4
99.4
95.7
99.8
95.0
97.1
88.9
NR = Not removed.
825
-------
Distribution and Removal of Metals
The pilot plant operating conditions (Table 3) and overall plant
performance (Table 4, control system) are the same as those in semi-volatile
organics study. The pilot system exhibited very stable operations and very
satisfactory plant performance with the background metals in the influent
wastewater.
The metals concentrations in the Cincinnati raw wastewater (Table 2) is
typical of U.S. cities with substantial industrial contributions. Com-
parison to the mean influent metals in Washington, B.C. (25) and Dallas,
Texas (26) revealed significantly higher metals concentrations. In many
cases (Zn, Pb, Mn, Cu, and Cr), the concentration difference exceeded one
order of magnitude. The Cincinnati metals concentrations, however, are all
less than the maximums reported for twenty municipal treatment plants (2).
The metals concentrations for plant process streams and the primary and
secondary sludges, except for the soluble Cu and Mg and Hg (concentration
below or near the detection limit), were presented as log normal probability
distributions. Summary highlights of the data analyses for this metals
overview work are presented in Tables 13, 14, and 15.
Table 13 summarizes the metals removals, computed from the mean concen-
trations, for the primary clarifiers, activated sludge process, and the
overall system. As one would predict, there was no significant removal of
either Ca or Mg. The ambient Hg concentrations were too low to permit the
quantitation of removal in a proper manner. The total removals for the
remainder of the metals range from 19 percent for As to 80 percent for Cu, and
are representative of typical plant removals.
Metals concentration factors are presented for the primary and return
activated sludges in Table 14. The concentration factor was computed by
dividing the mean sludge concentration (mg/1 basis) by the mean influent
concentration.
Mass balance calculations were performed using the mean contaminant
concentrations and the pilot plant operating data presented in Table 4. The
results of the mass balances are summarized in Table 15. For the 13 cations
reported the average closure on the mass balance was 94.2 percent for the
total system, and 94.0 percent on the primary clarifier. Cd and Fe were the
two metals with the worst closures. Examination of the Cd data indicates
that the concentration in the waste activated sludge is probably low, while
the problem with iron appears to be low concentrations in both sludges.
Metals Impact
Soluble salts of the metals Cd, Pb, Hg, and Cr(+6) were added to the
small pilot systems (Figure 1) and the spiking concentration periodically
increased to ultimately stress the treatment process to failure. A parallel
control system without the spike was operated identically during each metal
study. The operating conditions at each metal concentration level were
maintained relatively constant, but were varied during the course of the
826
-------
Table 13. Metals Removal in Control Treatment Systems.
Metal
A
Ag
As
Ca
Cd
Cr
Cu
Fe
Hg(a, b)
Mg
Mn
Ni
Pb
Zn
Influent
(mg/1)
8.0
20.6
86.0
20.9
0.63
0.80
4.29
2.0
17.6
0.65
0.45
0.88
1.24
Removal
Pri. by
Eff. Pri. Clar.
(mg/1) (percent)
9.0
16.0
81.0
17.0
0.51
0.57
2.44
2.0
18.0
0.55
0.27
0.58
1.28
0.0
22.3
5.8
18.7
19.0
28.8
43.1
-
0.0
15.4
40.0
34.1
0.0
Act
Sludge
Eff.
(mg/1)
5.0
16.7
81.0
7.9
0.34
0.16
1.01
2.0
17.9
0.40
0.18
0.11
0.46
Removal
by
Act. Sludge
(percent)
44.0
0.0
0.0
53.5
33.3
71.9
58.6
-
0.0
27.3
33.3
81.0
64.1
Total
Removal
(percent)
37.5
18.9
5.8
62.2
46.0
80.0
76.5
-
0.0
38.5
60.0
87.5
62.9
a Micrograms/liter.
b The Hg concentration is near the detection limit for the metal
removals cannot properly be calculated.
and
827
-------
fable 14. Metals Concentration Factors into Sludges
in Control Treatment System.
Metal
Ag(a)
As^a'
Ca
Cd
Cr
Cu
Fe
HgU)
Mg
Mn
Ni
Pb
Zn
Inf.
(rag/1)
8.0
20.6
86.0
20.9
0.63
0.80
4.29
< 2.0
17.6
0.65
0.45
0.88
1.24
Return
Act.
Sludge
(mg/1)
117
156.6
106
88
15.8
18.0
42.6
9.0
24.0
10.7
4.5
15.1
19.0
RAS
Cone.
Factor
14.6
7.6
1.2
4.2
25.1
22.5
9.9
> 4.5
1.4
16.5
10.0
17.2
15.3
Primary
Sludge
(mg/1)
179
114
524
139
20.4
31.0
51.5
18.0
64.3
20.5
14.6
32.2
46.4
P.S.
Cone .
Factor
22.4
5.5
6.1
6.7
32.4
38.8
12.0
> 9.0
3.7
31.5
32.4
36.6
37.4
a Micrograms/liter.
828
-------
Table 15. Metals Mass Balances in Control Treatment System.
Parameter
Ag
As
Ca
Cd
Cr
Cu
Fe
oo
S Hg
Mg
Mn
Ni
Pb
Zn
Cl
F
S04
Si02
TDS
Percent
Influent
Primary
Effluent
112.3
97.3
93.7
80.7
80.6
70.9
56.6
< 100.0
101.8
84.2
59.8
65.6
102.7
102.5
116.9
96.8
103.1
93.6
of
in
Primary
Sludge
10.7
0.3
2.9
3.1
15.4
18.4
5.7
< 0.4
1.7
15.0
15.3
17.4
17.7
0.6
0.1
0.1
0.7
0.8
Mass
Balance
Primary
Clarifier
123.0
97.6
96.6
83.9
96.0
89.3
62.3
< 100.4
103.5
99.2
76.1
83.0
120.5
103.1
117.0
96.9
103.8
94.4
Percent
Influent
A.S.
Effluent
61.1
78.4
91.5
36.7
52.5
19.4
22.9
of
in
Waste
A.S.
34.6
17.9
0.0
9.9
59.1
53.0
23.4
< 99.5 < 10.9
98.8
59.8
38.8
12.2
36.0
105.1
113.4
97.5
86.2
87.8
3.2
38.6
23.3
40.5
36.1
2.5
2.0
0.3
11.0
4.4
Mass
- Balance
Total
System
106.4
96.5
94.4
49.8
126.9
90.8
52.0
100.8
103.8
113.4
77.4
70.1
89.9
108.2
115.5
98.0
97.9
92.9
-------
spiking sequence such that the control system was essential to assess the
metal impact performance. While the principal operating control, the sludge
retention time (SRT), was varied from below 2 to over 12 days, most of the
spiking operations were performed with about 5- to 8-day SRT. The data
analyses have been completed for three of the metals. The chromium
evaluation is ongoing.
In addition to the conventional operations and water quality parameters
(Tables 3 and 4), the spiked and control systems were monitored for effluent
turbidity and their mixed liquors microscopically examined using dark field
and 645X. A series of photomicrographs were taken to document changes in
microbiota as the metal concentration was increased.
The experimental results were used to evaluate the principal effects of
the metals addition on the plant operation as a function of increasing metal
concentration. The studies also provided process and system metal removals,
metal partitioning to the plant's sludges, and passthrough of the metal from
the treatment plant; all as functions of the spiked influent metal
concentration.
Limited highlights of the results are presented in Tables 16 and 17 and
Figures 3-8. Table 16 presents the effects of three of the metals on the
activated process. Significant deterioration of the overall plant per-
formance generally requires substantial influent metals concentrations, well
above typical background metals concentrations.
The metals concentration correlations, usually as a function of system
or process influent concentration, exhibited reasonable correlation co-
efficients (Table 17) and can be used to predict process or system
performance for the removal of metals. The graphical presentations of the
metals concentrations in the spiked systems process and sludge streams as a
function of the influent metal concentration (Figures 3-5) reveal a break-
through discontinuity for Cd in the activated sludge effluent but con-
tinuously increasing final effluent breakthroughs for Pb and Hg. Repre-
sentative graphical presentations for the concentration correlations on the
spiked metals are provided in Figures 6-8.
TOXICITY REMOVAL
Even with extensive removability data and occurrence concentrations on
the individual toxics, health or ecosystem effects from the complex mixture
of metals in municipal or industrial wastewaters and treated effluents are
very difficult to evaluate. A biomonitoring approach to assess health and
ecosystem impacts and to supplement the specific occurrence and removal data
is being evaluated in the MERL toxics studies.
The EPA's Newtown Fish Toxicology Station in Cincinnati is assessing
removal of toxicity from the spiked and control raw wastewater during
conventional treatment of the MERL toxics studies. The Fish Toxicology
Station is using fathead minnows, rainbow trout and Daphia magna as testing
targets in 96-hour static (LC50) acute toxicity tests for the fish and in 48-
hour static (EC50) acute toxicity tests for Daphia magna. The acute toxicity
830
-------
Table 16. Summary of Effects of Metals Spiking
on the Activated Sludge Process.
Metal Concentration, mg/1, Entering
Activated Sludge Process
Effect Observed
Breakthrough of metal into
secondary effluent
Increase in effluent COD
Increase in SVI
Inhibition of nitrification
Decrease in respiration rates
Cd
2.0
4.1
8.6
8.6
10-20
Pb Hg
continuous continuous
-
0.76 .16
1.7 12.5
3.3
Decrease in colonial stalked
ciliates
Significant turbidity increase
Floe destabilization and
complete process failure
8.6
30.5
30.5
30.5
71
3.3
831
-------
Table 17. Removal Correlations for Cd, Pb and Hg.
I. Activated Sludge Effluent -y vs Primary Effluent -x:
Cadmium (mg/1):
log y = 0.731 log x -0.964 r = 0.89
Lead (mg/1):
log y = 1.060 log x -1.070 r = 0.93
Mercury
log y = 0.890 log x -0.618 r » 0.95
II. Primary Sludge -y (Mg/Kg) vs Influent Wastewater -x (mg/1):
Lead:
log y = 0.31 log x +2.34 r = 0.86
Mercury:
log y = 1.248 log x -1.756 r = 0.96
III. Waste Activated Sludge -y (mg/kg) vs Primary Effluent -x (mg/1)
Cadmium:
log y = 1.005 log x +3.077 r = 0.96
Lead:
log y = 1.140 log x +2.350 r = 0.97
Mercury:
log y = 0.653 log x +1.254 r = 0.90
832
-------
1000
500
\ I I ITII ! 1—I I I I I II 1 1 1 I I I I II 1 1 1 I I I IL
0.01
0.01
0.05 0.1 0.5 1 5 10
NOMINAL SPIKE CONC. ( MG/L )
50 100
Figure 3. Cadmium Concentrations in Spiked System.
833
-------
10,000 F
1,000
100 :
o
o
.a
Q.
O
UJ
>
o:
UJ
m
o
RETURN
ACTIVATED
SLUDGE
ACTIVATED
SLUDGE
EFFLUENT
0.01
0.01
100
ACTUAL Pb SPIKE CONC (mg/l)
Figure 4. Lead Concentrations in Spiked System.
834
-------
1,000,000
100,000
10,000
o
z
o
o.
o»
I
o
UJ
(T
bJ
V)
CD
o
1,000
100
10
1 1 1 1 1 1 1
1 1 1 1 1 1 1
PRIMARY
SLUDGE
A*/
*7
RETURN
ACTIVATED
SLUDGE „
1 1 1 1 1
PRIMARY
EFFLUENT
1 1 1 1 1 1 1
1 1 1 II 1
7-V
ACTIVATED
EFFLUENT
1 1 1 1 1 1
100
1,000 10,000
INFLUENT Hg CONC (ug/l)
100,000
Figure 5. Mercury Concentrations in Spiked System.
835
-------
CO
CO
01
10,000
.a
Q.
ill
o
Q
ID
o:
<
5
(E
Q.
1,000
100
' I I I I I I
log y -
0.31 logx +2.34
r« 0.86
I 10
Pb SPIKE CONC (mg/l)
100
Figure 6. Primary Sludge Pb Concentrations as a Function
of the Influent Pb Concentration.
-------
100,000 r 1 1 I [ I I I I
10,000
o
o
1,000
100
O.I
1 1 1 | I I I I
log y =
1.14 log x + 2.35
r = 0.97
T 1 1 I I I I U
I 10
PRIMARY EFFLUENT Pb (mg/l)
I I
I . . I
100
Figure 7. RAS Pb Concentration as a Function of the Primary
Effluent Pb Concentration.
837
-------
10
9 I
E
UJ
UJ
o
o
to
UJ
t-
>
0.1
0.01
10
log y =
0.90 log * - 1.07
r = 0.83
100
1000
INFLUENT Pb (mg/l)
Figure 8. Lead Concentration in the Activated Sludge Effluent
as a Function of Influent Pb Concentration.
838
-------
reductions by the treatment systems are based upon the reduction of lethal
units measured in the influent and effluents from the treatment systems or
processes. The lethal units are calculated from:
LU. = 100%
LC50 or EC50 in percent wastewater
Chronic toxicity residuals are also determined in the wastewater or
effluents using the early-life-stage (ELS) chronic test on fathead minnow
embryos. The chronic exposures with various dilutions of wastewater are
initiated with eggs less than 24 hours old and continue through 30 days after
hatching. The effects on embryo survival and larvae survival and growth are
measured to estimate chronic toxicity of the wastewater to the fish embryo-
larvae as a representative ecosystem organism.
Finally, an assessment of mutagenicity reduction by the treatment
systems has been recently initiated using the Ames Test as the indicator. The
work with the Cincinnati Health Effects Research Laboratory involves
extracting the raw wastewater, primary effluent, secondary effluent, and
chlorinated secondary effluent from an unspiked treatment system with
methylene chloride. The extraction separates the bacteria and viral cells in
the wastewater from the toxic organics. The organic extracts are solvent
transferred to dimethyl sulfoxide (DMSO) and the DMSO extracts are used in
the Ames test to assess the reduction in mutagenicity by the treatment
processes. Results are not yet available on this work.
Ecosystem Toxicity Removal
The ecosystem toxicity work was performed during the semi-volatile
organics studies. The operating conditions, water quality levels in the
wastewaters and effluents, and specific toxics concentrations encountered in
the semi-volatile studies describe the wastewaters used by the Fish
Toxicology Station.
The results to date on the acute toxicity reductions are summarized in
Tables 18 and 19. In Table 18, the unspiked raw wastewater exhibited moderate
acute toxicity which increased when the priority pollutants were added. The
conventional treatment system essentially eliminated the acute toxicity from
the wastewater in the control (unspiked) study. Conventional treatment also
reduced but did not eliminate the acute toxic effects of the effluent from
spiked wastewater system. The initial study also revealed that de-
chlorination of chlorinated secondary effluent essentially prevented in-
creased acute toxicity from chlorination (Table 19) of the secondary
effluent.
The embryo-larvae chronic testing for five percent and lower concentra-
tions of unchlorinated final effluent from the spiked system (Table 20)
revealed no statistical difference in the embryo/larvae survivals or in the
growth of the larvae-juveniles compared to the control. The application
of chlorination/dechlorination to the final effluent, however, produced
(Table 21) a statistically significant reduction in larvae-juvenile survival
and in growth rate at the 5 percent concentration level of plant effluent in
diluent water.
-------
Table 18. Acute Toxicity (96-hour) of Municipal Wastewater Before and After
Conventional Wastewater Treatment: Fathead Minnow - Phase I
OD
-&
LC-50, Percent
Sample
Date
12-14-79
12-19-79
1-16-80
1-22-80
4-2-80(b)
4-15-80(b)
4-24-80(b)
5_5_80(c)
5-13-80(c)
6-4-80
3 Spiked samples
b Slight excess
Unspiked
Influent
-
—
30
11.0
(9.3-12.5)
9.3
(7.9-11.2)
30
10.2
(8.5-13.0)
18.5
(16.5-20.7)
10.1
(98.3-11.1)
20.6
(17.8-25.3)
- mixtures of 22
Unspiked
Effluent
100
64.4
(59.2-70.5)
100
100
100
100
100
100
100
100
Percent
Toxicity
Reduction
-
-
100
100
100
100
100
100
100
100
organic priority pollutants
control fish mortality in sample
c Samples were 24-hour composites - others were
NOTE: Toxicity reductior calculations based on
NllTnViOT*c in r»a Y"o-n f"Vic. o o o aT*o QS1^ r* r^n 4~i H £»r»r*
s .
grab samples.
lethal units
o 1 t -m-i f* c
LC-50,
Spiked(a)
Influent
-
4.6
(3.5-16.2)
2.7
(2.2-3.3)
9.5
(8.1-11.1)
4.5
(3.2-5.8)
4.3
(3.3-6.5)
5.8
(4.8-7.6)
6.5
(5.6-7.6)
1.9
(1.0-2.3)
Percent
Spiked (a)
Effluent
36.1
(28.5-43.4)
22.3
(18.7-25.8)
13.1
(10.0-16.0)
16.1
(13.6-19.0)
35.5
(30.3-43.3)
6.6
9.4
(7.9-11.5)
30
30
8.0
Toxicity
Reduction
-
-
65
83
73
32
55
81
78
76
in pilot treatment system.
(LU = 10° )
LC50
-------
Table 19. Acute Toxicity of Municipal Wastewaters^3) With and Without Chlorination.
Sample
Date
6-30-80
7-7-80
7-16-80
7-24-80
7-31-80
8-5-80
Test
Animals
Fathead Minnow
Rainbow Trout
Daphnia magna
Fathead Minnow
Rainbow Trout
Daphnia magna
Fathead Minnow
Rainbow Trput
Daphnia magna
Fathead Minnow
Rainbow Trout
Daphnia magna
Fathead Minnow
Daphnia magna
Fathead Minnow' 8'
Daphnia magna
Influent
(10.4-14.2)^)
_(e)
(14.6-22.3)
15.1
(12.8-19-7)
-
1.6
12.8
(11.3-14.9)
-
1.6
10.5
(8.6-13.3)
-
1.9
(1.0-2.6)
5.4
(4.1-6.8)
1.6
1.6
1.6
Pre-Chlorinated
Effluent
27.9
(24.4-32.0)
9.7
(7.2-12.8)
16.8
(14.3-19.7)
44.7
(40.4-51.2)
17.2
' (14.7-20.8)
23.5
(22.0-34.4)
39.9
(34.6-44.9)
13.4
(10.2-18.7)
6.4
(1.9-11.4)
24.5
(19.3-29.9)
17.2
(14.7-20.8)
21.8
(18.0-25.6)
32.3
(26.5-41.2)
9.1
(6.7-12.2)
5.0
22.6
(17.2-27.8)
Chlorinated/
Dechlorinated
Effluent
32.3
(28.0-38.1)
14.2
(10.8-20.2)
11.2
(9.4-13.5)
60
17.8
(15.4-21.4)
9.8
49.0
(42.6-61.1)
16.1
(13.4-19.7)
10.2
23.2
(18.0-28.3)
17.8
(15.7-21.4)
8.0
42.7
(34.0-52.4)
1.6
5.5
15.2
(10.8-20.1)
Percent
Toxicity
Reduction^)
63
-
+ 51
75
-
16.3
74
-
84
55
-
76
88
0
71
89
a Influent wastewater continuously spiked with 22 organic priority pollutants.
b Toxicity reduction based on lethal units of influent and chlorinated/dechlorinated effluent.
c Fish - 96-hr LC50 percent waste.
d 95% confidence limits.
e Indicates no data.
f Daphnia magna 48-hr EC50 percent waste.
8 Slight excess control fish mortality.
841
-------
TABLE 20. Survival and Growth of Early-Life-Stages of Fathead Minnows
Exposed to Activated-Sludge Effluent in Spiked System.
oo
.£»
ro
Nominal Embryo
concentration survival
5.0 88
82
2.5 92
86
1.2 86
88
0.62 88
88
0.31 88
90
0.16 86
92
Control 90
88
Larval- juvenile
survival (%)
at 30 days
_
93
97
90
100
93
_
90
97
93
100
80
93
100
Juvenile weight (mg)
mean + S . D .
at 30 days
113
117
167
155
167
178
197
207
207
196
183
200
196
188
+ 38
± 36
+ 49
± 36
+ 49
+ 49
+ 53
+ 60
+ 55
+ 64
+ 57
+ 35
+ 53
+ 63
Juvenile length (mm)
mean + S.D.
at 30 days
20.6 +
23.5 +
23.1 +
22.9 +
23.3 +
24.1 +
24.5 +
24.7 +
24.5 +
24.4 +
23.9 +
24.6 +
24.3 +
24.5 +
2.4
1.5
2.4
1.7
2.5
2.2
2.8
2.7
2.3
2.7
2.1
1.5
2.1
2.5
-------
TABLE 21. Survival and Growth of Early-Life-Stages of Fathead Minnows Exposed
to Chlorinated/Dechlorinated Effluent from Spiked System.
Nominal
concentration
5.0
2.5
1.2
00
to
0.62
0.31
0.16
Control
Embryo
survival
86
80
90
92
88
80
94
90
86
82
78
92
86
82
Larval- juvenile
survival (%)
at 30 days
10(a)
7 (a)
100
93
80
93
83(a)
67(a)
83
100
97
97
100
90
Juvenile weight (mg)
mean + S.D.
at 30 days
66 + 8 (a)
72 _+ 12 (a)
130 + 52(a>
129 + 47 (a)
165 + 53
162 + 53
173 + 54
165 + 29
170 + 44
203 + 49
191 + 40
200 + 44
213 + 67
186 + 46
Juvenile length (mm)
mean + S.D.
at 30 days
18.3 + 0.58
19.0 + 1.4
22.3 + 2.5
21.8 + 2.4
23.4 + 2.6
23.0 + 2.4
23.4 + 2.5
23.1 + 1.2
23.9 + 1.9
24.7 + 1.6
24.0 + 1.7
24.6 +_ 1.6
24.8 + 2.3
24.8 + 2.2
a Significantly different (P=0.05) from control,
-------
SUMMARY
The U.S. EPA's Municipal Environmental Research Lab is assessing, at
it's Test and Evaluation Facility in Cincinnati, the removability of toxic
substances from municipal wastewater by conventional wastewater treatment
processes. The raw wastewater used at the Test Facility is a mixed domestic/
industrial wastewater from the highly industrialized Mill Creek area of
Cincinnati. The studies feature pilot-scale primary/secondary treatment of
the raw wastewater spiked with selected priority pollutants (metals and
organics). In the studies, the treatment plant performance on spiked waste-
water is compared to the performance of identical treatment-on the unspiked
raw wastewater. The assessment employs costly analyses (GC/MS and atomic
absorption methods) for the selected toxic substances in the various process
streams and sludges of the conventional treatment plant.
From the studies to date, conventional treatment is generally effective
in removing selected toxic substances, typically achieving better than 90%
removal of organics and from 60-80% removal of the metals. A few of the toxic
substances, however, pass through into the treatment plant final effluent in
sufficient concentrations which, based upon EPA recommended water quality
standards, may present a possible environmental hazard.
Even with extensive removability data on the individual toxic substances,
health effects or ecosystem effects from the complex mixtures of materials in
municipal or industrial wastewaters and effluents are very difficult to
evaluate. A biomonitoring approach to assess health and ecosystem effects is
also being evaluated to supplement the specific toxic substance removal data
being collected in the EPA studies. The EPA's Newtown Fish Toxicology Station
in Cincinnati is assessing the removal of acute toxicity to ecosystems from t..e
spiked and control raw wastewater during various stages of treatment. The fish
toxiciology station is using fathead minnows, rainbow trout, and Daphnia magna
as testing targets in 96hr static (LC5Q) acute toxicity tests for the fish and
in 48 hr static (EC5g) acute toxicity tests for the Daphnia. The acute toxicity
reductions by the treatment systems are based on the reduction of lethal units
(L.U.) measured in the plant's influent and effluent.
Chronic toxicity residuals are also determined in the final effluents
from the spiked system using the early-life-stage (ELS) chronic test on fathead
minnow embryos. The effects on embryo survival and on larvae survival and
growth are measured to estimate chronic toxicity for various dilutions of
plant effluent.
From results to date, the unspiked raw wastewater exhibited moderate
acute toxicity which increased when the priority pollutants were added. The
conventional treatment system essentially eliminated the acute toxicity from
844
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control (unspiked) wastewater. Conventional treatment also reduced, but did
not eliminate, the acute toxic effects from the spiked wastewater.
The initial study has also revealed that dechlorination of chlorinated
secondary effluents essentially prevented increased acute toxicity from the
chlorination. The embryo/larvae chronic testing for 5% and lower concen-
trations of unchlorinated final effluent from the spiked system revealed no
statistical differences in the embryo/larvae survivals or in the growth of the
larvae/ juveniles compared to the control. The application of chlorination/
dechlorination to the final effluent, however, produced a statistically
significant reduction in larvae/juvenile survival and in the growth rate of the
larvae/juneniles at the 5% concentration level of plant effluent in diluent
water.
An important overall observation from the above work on toxic substances
is that the treatment of the strong domestic/industrial wastewater at the
Cincinnati plant has exhibited remarkable stability over a wide range of
operating conditions and produced consistent and excellent treatment of the
wastewater, even when spiked with large doses of metals or toxic organic1'. In
contrast, earlier experience in treating domestic wastewater over similarly
wide ranges of operating conditions has revealed operating areas where the
growth of organisms such as Sphaerotilus natans predominate in the activated
sludge process and contribute to poor settling characteristics of the sludge.
These organisms produce plant effluent deterioration through carryover of
solids. One possible explanation to the improved treatment stability in the
Cincinnati study is that the background of toxic contaminants in the Cincinnati
raw wastewater reduces the biological competitiveness of the exposed filamentous
organisms.
In any event, the EPA work indicates that the central municipal waste-
water treatment plant potentially represents a cost effective alternative to
industrial pretreatment for the control of many toxic substances. Use of the
treatment plant for toxics control, however, requires evaluation of the impact
of the toxics on the sludge handling and final disposal processes. In
addition, the use and practical management of the central municipal treatment
plant for toxicity control would greatly benefit from the availability of
suitable biomonitoring tests for determining the removal of overall toxicity,
both acute and chronic, for health and ecosystem protection.
845
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REFERENCES
1. Natural Resources Defense Council (NRDC) et al. vs. Train 8 ERC 2120
(DDC 1976).
2. Feiler, H., "Fate of Priority Pollutants in Publicly Owned Treatment
Works, Interim Report." Report No. EPA 440/1-80/301 (1980).
3. DeWalle, F.B., et al., "Presence of Priority Pollutants in Sewage and
their Removal in Sewage Treatment Plants," Draft Final Report Grant
R-806102, Municipal Environmental Research Laboratory, U.S. EPA,
Cincinnati, Ohio.
4. Petrasek, A.C., et al., "Behavior of Selected Organic Priority Pollutants
in Wastewater Collection and Treatment Systems," Presented at the 53rd
Annual conference of the WPCF, Las Vegas, Nevada (Sept. 1980).
5. Petrasek, A.C., et al., On-going work at the U.S. EPA Test and Evaluation
Facility, Municipal Environmental Research Laboratory, Cincinnati, Ohio.
6. Petrasek, A.C., "Distribution and Removal of Metals in a Pilot-Scale
POTW," Internal Report, U.S. EPA, Municipal Environmental Research
Laboratory, Cincinnati, Ohio.
7. Petrasek, A.C., "Inhibition of the Activated Sludge Process by Cadmium,"
Internal Report, U.S. EPA, Municipal Environmental Research Laboratory,
Cincinnati, Ohio.
8. Petrasek, A.C., "Inhibition, Removal, and Partitioning Interactions
between Lead and the Activated Sludge Process," Internal Report, U.S.
EPA, Municipal Environmental Research Laboratory, Cincinnati, Ohio.
9. Petrasek, A.C., Mercury Report in preparation, U.S. EPA, Municipal
Environmental Research Laboratory, Cincinnati, Ohio.
10. Petrasek, A.C., Chromium Report in preparation, U.S. EPA, Municipal
Environmental Research Laboratory, Cincinnati, Ohio.
11. Horning, W., Robinson, E., and Petrasek, A.C., "Organic Priority
Pollutant Toxicity Reduction by Conventional Wastewater Treatment,"
Draft Report, U.S. EPA, Environmental Research Laboratory-Duluth,
Newtown Fish Toxicology Station, Cincinnati, Ohio.
12. Pickering, Q.H., Report in Preparation, Newtown Fish Toxicology Station,
Cincinnati, Ohio.
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13. Convery, J.J., Cohen, J.M., Bishop, D.F., "Occurence and Removal of
Toxics in Municipal Wastewater Treatment Facilities," Presented at the
Seventh Joint United States/Japan Conference, Tokyo, Japan, May 1980.
14. Methods for Chemical Analysis of Water and Wastes, EPA-600/4-79-020,
Environmental Monitoring and Support Laboratory, Cincinnati, Ohio
(March 1979).
15. Standard Methods for the Examination of Water and Wastewater, 14th Ed.,
APHA, Washington, B.C. (1976).
16. Federal Register, 44 (233), December 3, 1979, "Guidelines Establishing
Test Procedures for Analysis of Pollutants, Proposed Regulations,"
pp. 69526-69558.
17. "Interim Methods for the Measurement of Organic Priority Pollutants
in Sludge," U.S. EPA, Environmental Monitoring and Support Laboratory,
Cincinnati, Ohio, September 1979.
18. Warner, J.S., et al., "Analytical Procedures for Determining Organic
Priority Pollutants in Municipal Sludge," EPA-600/2-80-030, Municipal
Environmental Research Laboratory, U.S. EPA, Cincinnati, Ohio, March
1980.
19. Bishop, D.F., "GS/MS Methodology for Priority Organics in Municipal
Wastewater Treatment," U.S. EPA, Cincinnati, Ohio, EPA-600/2-80-196,
NTIS #PB81 127813, November 1980, 43 pages.
20. Prairie, R. , et al., Report in Preparation, U.S. EPA, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio.
21. Kleopfer, R.D., et al., "Priority Pollutant Methodology Quality
Assurance Review," U.S. EPA, Region VII Laboratory, Kansas City,
Kansas (1980).
22. Callahan, M.A., "Water-Related Environmental Fate of 129 Priority
Pollutants," EPA-440/4-79-029a, U.S. EPA, Washington, D.C., 1979, 714
pages.
23. McKee, J.E., and Wolf, H.W., Water Quality Criteria, Publication No. 3-
A, State Water Quality Control Board, Sacramento, California (1963).
24. Criteria For Water Quality, U.S. EPA, Washington, D.C., U.S. Govt.
Printing Office, 546-312/146 1-3, 1973.
25. Warner, H.P., "Wastewater Treatment for Reuse and Its Contribution
to Water Supplies," EPA-600/2-78-027, Municipal Environmental Research
Laboratory, Cincinnati, Ohio (March 1978).
26. Esmond, et al., "The Removal of Metals and Viruses in Advanced Wastewater
Treatment Sequences," EPA-600/2-80-149 (August 1980).
847
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AN INDUSTRIAL PERSPECTIVE ON
JOINT MUNICIPAL-INDUSTRIAL WASTEWATER MANAGEMENT
Gerald N. McDermott
Senior Engineer
Environmental Control
The Procter & Gamble Company
Cincinnati, Ohio
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Prepared for Presentation at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Cincinnati, Ohio
849
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AN INDUSTRIAL PERSPECTIVE ON JOINT MUNICIPAL-INDUSTRIAL WASTEWATER
MANAGEMENT
G. N. McDermott, Senior Engineer
Gentlemen from Japan, I welcome this opportunity to discuss with you
one subject in your program this afternoon. My talk concerns largely
policy matters, the organizational arrangement of wastewater treatment,
rather than the technical matters.
I have looked forward to talking to you about this subject. I have
enjoyed the papers you have presented during the past two days and I have
taken occasion to study the papers from your previous conferences. In
high school I experienced the value and enjoyment of working with
Japanese people. I had the experience of sharing two years of high
school with two boys of Japanese ancestry named James Kowabata and Frank
Iwatsuki. I was well acquainted with them because James and Frank plus
Kelly Berkeley and myself were the four llth graders selected to be
allowed to attend honor study hall in that high school. I learned to
appreciate the ability of Frank and James during the work solving prob-
lems in physics and chemistry in that study period. I learned to benefit
from their good minds. I had reason to remember them because they estab-
lished grade averages better than mine. I have lost track of Frank and
James over the years but no doubt they are out there making a technical
contribution someplace. Not only did I experience this scholarship com-
petition but dealt with Fumico Iwatsuki, the fastest typist in the
school, and Shogo Adachi the best wrestler in my weight class.
The subject that I want to talk to you about this afternoon is that
of the treatment of the entire wastewaters from a community in one common
or shared system. Such a system is one that accepts the wastewaters from
the homes, from commercial establishments and from industrial plants and
conveys them to a shared treatment plant. In the United States this is
often referred to as joint treatment.
The reason I want to talk to you about joint treatment is to be sure
you understand its advantages, its problems and its administration.
The topic of my talk to you gentlemen today is an old and frayed
one. Yet, it is timely to talk about this subject with you because of
recent attention to it in this country by way of emphasis on pretreatment
programs. A pretreatment program is a term which the Federal agency
people brought forth about 1980. The term speaks to the controls and
restraints on use by industry of publicly owned wastewater treatment
works. This Federal agency attention is new; that is the only thing new
about the subject. The practice has existed from the very first develop-
ment of wastewater collection systems. The first published reference I
have come across is a declaration by the Royal Commission on Pollution
Control of London. In 1903, these gentlemen proclaimed "the most
economic way to dispose of trade wastes is to discharge them to the city
sewers and treat them along with domestic sewage".
850
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This joint treatment practice has been followed in practically every
community sewer system in this country. Only in a few instances have
municipalities and local industry built separate wastewater treatment
plants. Table 1 illustrates the number of major industries using the
sewer system in each of five representative cities in this country.
Each of the industrial plants included in these numbers are large
enough dischargers that the cities go to the trouble and expense of mea-
suring and sampling their wastewaters. These figures do not include the
small industrial and commercial users—there are at least an equal number
of them.
The practice is widespread among the various categories of indus-
try. Most and in some cases all of many industrial categories discharge
their wastewaters to municipal systems as shown in the Table 2. All
soluble coffee plants, all but one major soap and detergent plant, 95
percent of the edible oil refining plants, 15 percent of paper converting
plants discharge their wastewaters to municipal systems. At the other
extreme only a small percentage of petroleum refining plants discharge
process wastewaters to municipal systems. Likewise few if any steel
rolling, blast furnace and by-product coking plants discharge to muni-
cipal systems. A recent EPA wastewater plant survey indicates on a flow
basis industrial wastes constitute an average of 16 percent of municipal
wastewater treatment plant inflow.
The practice is so common and widespread one might well ask if there
is any need for discussion of the subject by way of relating information
to persuade people to continue or institute the practice. My answer is
yes there is. There is a need for several reasons. One is that there
have been a couple of problems throughout the history of the practice
which have never been completely settled. One of these is the degree of
control most appropriate to discharge of wastewaters containing fat, oil
or grease. A second problem area is the control needed for stormwater
runoff from industrial plants. Still another is control of slug loads—
short-time abnormal flows or masses of treatable pollutants.
Then there is a perennial question about fair sharing of the costs
among industrial, commercial and residential users.
The most current topic of joint treatment is the control of toxics
that may be present in some industrial wastewaters. Toxics can interfere
with treatment or pass through without sufficient removal.
The Federal EPA beginning about June of 1978, launched a significant
part of their huge resources on a mission to control what they chose to
call indirect dischargers. Indirect industrial dischargers are dis-
chargers to publicly owned treatment works. The EPA had concentrated
their early efforts on control of industry that treated their wastewaters
in their own facilities and discharged them directly to public water-
ways. This newly initiated EPA control effort directed at indirect dis-
851
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chargers was a part of an interest in control of toxic pollutants. The
EPA had started the program of establishing limitations on toxics for
direct dischargers at about this time and it was natural to implement at
the same time control of indirect dischargers.
This attention to control of toxics by requiring pretreatment pro-
grams of communities has caused an aura of alarm and a certain confusion
in minds of non-specialists about joint treatment. This confusion and
excitation has caused a questioning, a certain skepticism, a negativism
about joint treatment. For example cities have entertained or pressed
for unreasonable and unrewarding control of ordinary compatible everyday
treatable wastes—wastes that are perfectly compatible with transport and
treatment in publicly owned treatment works. Wastes that are adequately
characterized by conventional pollutant parameters such as BOD and sus-
pended solids. Cities have begun to question and propose that no capac-
ity be provided for industrial growth when treatment facilities are
enlarged. Municipalities have said to their industrial members we do not
have sufficient capacity for the loads of treatable wastes you are dis-
charging; therefore we are going to limit each of you to a specified
maximum daily load.
Some of the language in the Federal regulations on limiting excess-
ive short time loads of compatible wastes seems to encourage municipali-
ties to limit the industrial use for compatible wastes. When considering
a limit on a high load from industry, a consideration of the maximum
capacity of the treatment plant likely is involved. Thus the control of
excessive loads to prevent pass through of above limit concentrations of
BOD may very well limit industrial use. The need for a slug load limit
is recognized for any parameter. We are concerned and have serious
objections to restrictions that will prevent ordinary day-to-day use.
Joint treatment is threatened in the matter of eligibility of the
share of treatment faciities built with Federal grant funds for the
treatment of the wastes from industries of the community. The way that
industrial users of municipal systems are dealt with in the Federal grant
program is complex. Too complex to go into here and there is still hope
for change. Industry believes generally that they should be fully eligi-
ble to use the grant supported public works just like other members of
the community are on the basis that industry has provided a significant
part of the Federal grant funds via corporate profits tax.
My introduction of the subject to you has been long. I wanted to be
sure you had opportunity to understand the problems and to learn the
solutions we advocate. My talk is not going to be nearly so technical in
terms of processes or equipment as have been the excellent discussions
you have previously heard. I hope my dwelling on administration or
policy will be of interest.
I would like to sell you on joint treatment. I would like to point
out the best road to follow in certain problem areas in its practice. I
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would like to provide assurance in the turmoil, quiet your concerns,
point out how to overcome true problems and send you back to your home as
evangelists for this cause.
Let us look now at the advantages of joint treatment.
The dominant one is economic. A larger plant is simply cheaper to
construct and operate than a number of smaller ones. This is brought
home in real terms by this graph which shows the capital costs per
million gallons per day of capacity for biological treatment plants of a
range of sizes, Figure 3. This data is from an EPA report. The line of
best fit to the data exhibits a marked decline in the costs per million
gallon capacity as the size increases. Figure 4 shows the operating,
maintenance and replacement costs per 1000 gallons of normal domestic
sewage from biological waste treatment plants of a range of sizes. There
is a marked decline in the costs as the size increases.
Most emphatically this information proves joint treatment is lower
in costs than separate treatment. A fair wastewater service charge
system furthermore will result in all users benefitting from lower costs,
homeowners as well as industrial users.
I must call attention to the possibility that in some special situa-
tions an industrial plant may be able to treat their own wastewaters more
economically. For example, for wastewaters that are highly seasonal and
where land treatment during the warm season is practical. Another ex-
ample would be an industrial plant at a location so remote that convey-
ance costs were prohibitive. A third situation would be an industry with
adequate and low cost land and effluent quality limitations such that an
aerated lagoon system would suffice. But for the vast majority of situa-
tions I feel sure joint treatment is the most economic for industry and
saves the homeowner money too.
Some lesser but important advantages include a savings in land space
devoted to treatment plants. A single large plant takes up less space
than would a number of smaller ones.
Some industrial wastes are lacking in the nutrients-nitrogen and
phosphorous needed. Domestic sewage has an excess of these. Thus joint
treatment saves the cost of chemical addition.
Finally, the large staff of specialists in wastewater treatment that
would be found in a large joint treatment plant will do a superior job of
providing a good uninterrupted effluent quality. A number of smaller
plants would much more likely suffer upsets and occasional poor quality
because of part-time and non-specialist operators.
Having been convinced of the advantages of joint treatment, I would
like to lead you through some problem areas.
853
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The Fat, Oil and Grease Misunderstanding
The wastewater treatment technologists have suffered a great hand-
icap in control of oil-bearing wastewaters being discharged to municipal
systems. Early information and recommendations were incompletely pre-
sented and easily misunderstood. Only recently has an adequate control
strategy been developed. Substantial information on treatability and
removal of oil in municipal wastewater treatment plants is just currently
appearing in the literature. The equipment and processes used in munic-
ipal wastewater treatment have changed so that many old concerns have
disappeared. Most concerns have been moderated or eliminated. Controls
other than limitations on concentration have been established as best
solutions. Let me tell you the details of this subject and lay out for
you where I believe the practice should be in control of oil in waste-
waters in industrial wastewaters discharged to municipal systems. Pre-
treatment programs have been saddled with precidents and recommendations
that are unnecessarily harsh, and restrictive. They have caused economic
waste.
One cause of the problem is the analysis for oil measures two kinds
of oil and some miscellaneous other compounds. The two kinds of oil are
different in their significance and control needs. Their treatability
and therefore the restrictions that are appropriate for one are inappro-
priate for the other. The two kinds of substances that are generally
involved are oils of animal and vegetable origin and oils of petroleum
origin. The chemical structure of these kinds is very different. The
material of animal and vegetable origin is in its original form a struc-
ture known as a triglyceride. A triglyceride is the three carbon mole-
cule to which is attached three fatty acids. The fatty acids are
detached from the glyceride base in the making of soap and other deriva-
tives. The fatty acids themselves measure as oil as are the soap com-
pounds made from them. Chemists call this whole family of animal and
vegetable oil compounds lipids. Remember that term as I am going to use
it frequently. The petroleum kind of oil can include a hugh number of
structures the predominance of which in the usual situation are a
straight chain of carbon and hydrogen atoms. Petroleum can also contain
the ring form of linked carbon atoms known as aryl and cyclic compounds.
The lipids are natural constituents of food and are virtually every-
where in nature. They constitute a significant portion of the diet of
people in the United States, in Japan and other places. Estimates have
been made that such oils constitute 25 to 40 percent of the calories in
the average diet in this country. They are a major constituent in meat,
poultry, nuts, many baked goods, milk, salad dressings, etc. They are
used as a heat transfer liquid in frying and as an anti-sticking coating
in baking. Compounds of lipid origin are a major functional part of much
of the household soaps and in some laundry products. They are excreted
on the skin and hair. It is little wonder then that they constitute a
large percent of the organic matter in domestic sewage from households.
From at least fifteen to twenty-five percent of the organic matter in
854
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sewage is estimated to be lipids. The human feces itself has been found
to contain five percent or more of oil on a dry—weight basis* So the
lipid type of oil is a natural and universal major constituent of domes-
tic sewage. Therefore, a municipal wastewater treatment plant that can-
not adequately transport and treat wastewaters containing lipids is not
appropriate to use. A satisfactory plant has to be able to handle waste-
waters containing major amounts of lipids. A look at the data available
on the concentration of oil in municipal wastes indicates a range of
about 30 to 50 mg/1.
The lipid type of oil is biologically degradable at rates comparable
to other organics such as carbohydrates and proteins. The latest re-
searcher to make observations of this is Professor Hrudey of the Univer-
sity of Edmonton in Canada. He published a landmark paper on this in
June of 1981. Preceding him there were noteworthy contributions by
Dr. James Young of Iowa State University, Dr. Perry McCarty of Stanford
University, Messrs. Pico and Watson of Kraft Foods, Dr. Loehr of Cornell
University, and the consulting firm of AWARE with which Professor
Eckenfelder of Vanderbilt University is associated.
Portions of the lipid in the wastewater inflow to a municipal system
will be separated as scum in the primaries, will be a significant con-
stituent in the primary sludge, and will be present at a low percentage
in the waste biological sludge. The lipids in these sludges is readily
converted to methane gas in anaerobic sludge digesters. The kinetics of
this conversion is such that the lipids will be converted at higher rates
than carbohydrate and protein fractions in the sludges. Lipids are the
major contributor of methane in such sludges. These facts have been
established in research described in articles by Dr. O'Rourke,
Dr. McCarthy and others.
Please understand that such bacterialogical degradation will take
place rapidly for lipids sufficiently dispersed. The exposed surface of
large particles is too low relative to the quantity of lipid to permit
rapid degradation. Fortunately domestic sewage contains dispersing
agents which cause oil to disperse and sustain it in suspension. Primary
settling will remove lipids in floatable size particles. The oil reach-
ing the biological treatment process will be, therefore, sufficiently
dispersed for rapid biodegradation.
As for anaerobic process, the modern digestors provide enough mixing
that sufficient dispersion of the lipids occurs. The former problems of
solid oily scum forming have been practically eliminated.
We have, therefore, arrived at the point in this discussion to deal
with the heart of the matter, the decision that you may be involved in,
namely, what are the appropriate controls for the lipids in industrial
wastewaters. The evidence I have presented established that dispersed
lipids (animal or vegetable oil or fats) are perfectly compatible for
855
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transport and treatment in municipal systems. Dispersed lipids are BOD
and suspended matter which biological treatment is capable of removal and
degradation. Our position is that no limit is appropriate for dispersed
lipids.
Wastewaters of many industrial categories contain significant con-
centration of dispersed lipids, such as
Edible oil refining
Margarine manufacture
Fish oil processing
Milk processing
Cheese making
Meat processing
Poultry processing
Candy manufacture
Rendering plants
Soap manufacture
Certain food plants
This pretreatment capital costs for thousands of industrial plants
to meet some arbitrary and unrewarding limit could amount to great
amounts of money. The primary process for removal of the dispersed
lipids is dissolved air flotation enhanced by the use of chemical coagu-
lants. In order for the recovered material to have value it must be
treated to remove the coagulating chemicals. The costs are such that
there seldom is a payout in the value of lipid recovered. We all are
conservationists to a degree and do not like to condone waste. However,
in this situation in case after case the dispersed lipid is not econom-
ically recovered. The float of lipid and chemical simply becomes a waste
material. Our recommendation is do not force this pretreatment process
on industrial users. The treatment of these dispersed lipids in the
municipal treatment is perfectly feasible and is the most economic
solution.
Lipids in a floatable form may cause distribution and fouling prob-
lems. By floatable form is meant oil or fat in a droplet or scum form of
sufficient bulk that the droplets will tend to rise to the surface under
quiescent conditions. In other words, oil or fat which will float to the
surface in a gravity settling system. The settling system in mind would
be one which was designed according to primary settling basin criteria.
The floatable oil is removable by simple equipment and can be made
use of for animal feed or other use. Recovery of floatable oil where
significant quantities are involved can have a return. So the removal of
floatable oil by the provision of gravity settling systems is a logical
pretreatment regulation. The simple regulation needed is simply a pro-
vision that floatable oil, fat and grease be removed. Floatable oil must
be defined in the ordinance as oil that is removed by gravity settling in
a facility meeting design guidelines of the district. The only decision
the agency must make is whether or not to require an industrial user to
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install a gravity settling system for floatable oil removal. In most
cases the decision will be obvious and undisputed. In a rare case some
testing may be necessary to learn of the presence or absence of signif-
icant quantities of floatable oil in an effluent. A simple bench scale
test can be designed to establish this. There is no need to become con-
cerned over a small quantity of floatable oil because after all there is
considerable floatable lipids in household wastes.
The wastewaters from restaurant and food preparation establishments
are a frequent target of control agencies in control of incidence of
obstruction of sewers. One major city has pursued a policy for such
control which has worked well. After finding a sewer obstruction in the
sewer serving such establishments the owner is required to install a
suitable size gravity separation system. These are called fat traps in
the restaurant business. In no case has an obstruction incident occurred
after such a facility was installed in this one city's experience.
There is no need to try to relate an oil concentration to likelihood
of obstruction of sewers. Ordinances use general descriptive language
prohibiting materials that cause obstructions. This control suffices.
It is just as easy to police good operation of a fat trap as it is to
police for a concentration violation.
You may have noted my preceding remarks were directed at the
lipids—their treatability and their logical control. I earlier men-
tioned another kind of oil—petroleum oil. Petroleum oil is referred to
also as hydrocarbons.
Hydrocarbons are not nearly as biodegradable in aerobic systems as
are lipids. They are not degradable at all anaerobically. These facts
do not mean that they are not removable in a municipal treatment plant.
Some will be degraded as it becomes associated with suspended biological
matrix and remains under treatment for long periods. Other such oil may
find an outlet through being included in the residues disposed of by
incineration or otherwise.
However, investigations have shown that there is a limit to the con-
centration of hydrocarbons which can be allowed to reach the biological
floe. Data I have seen indicate that when the concentration of hydro-
carbons in the feed is greater than about 25 mg/1 some of the floe
particles will have a specific gravity the same as water and will not
settle in the final clarifiers.
In the anaerobic part of the process, anaerobic sludge digestion,
petroleum oil in the skimmings feed to the digester will rise into the
digester supernatant. When this supernatant is returned to the raw
sewage the oil can become again part of the skimmings. Thus there is
created a recirculating oil-laden stream within the treatment plant.
Therefore, a limit on hydrocarbons in the discharge of users to the
system is a logical element of a pretreatment program. Since about
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25 mg/1 in the total mix of community wastes received at the treatment
plant is no problem, a higher concentration in individual plants effluent
can be allowed. Such a concentration can be selected appropriate to the
particular wastewater system. An analytical method for hydrocarbons has
been available in standard methods since the Fifteenth Edition.
As a final point, I want to mention that in early literature, in
manuals of practice of the Water Pollution Control Federation, in early
textbooks on treatment technology, a limit of 100 mg/1 on oil—total
fats, oil and grease that is—was recommended. This was a mistake, was
used in a way not originally intended, and is no longer a recommendation
of the Water Pollution Control Federation or the United States Environ-
mental Protection Agency. In spite of the fact that city after city has
this limit in their ordinance it is not needed and is inappropriate.
This is witnessed by the fact that very few cities enforce it. So my
advice to you is not to follow that precedent.
Rainfall RunoffFrom Certain Areas of Industrial Plants
There is another rather minor appearing problem that I would like to
call to your attention. The managers of municipal systems will in many
cases do their very best to minimize the flow of rainfall runoff into the
sewers leading to their treatment plant. Regulations will typically pro-
vide that no stormwater is allowed to be discharged to the municipal sys-
tem. Campaigns to find roof drain connections and leaky manhole covers
and the like are commonly conducted. Yet many industries will find them-
selves with a rainfall runoff from limited areas of the industrial plant
which is polluted with leaks, spills, dusty materials, etc. The areas
involved are those along the railroad siding or the truck stations where
bulk materials are unloaded. Typically there will be pumps at these
places. The locations I am speaking of will not be inside of buildings
or under roof. Consequently the rain will fall on these areas, wash off
any leakage or spill that is there and produce some polluted wastewater.
A strict sewer use code will not allow this to be dumped into the sani-
tary sewer. Segregation and storage of this water is very costly and
troublesome. We believe that the runoff from these limited spill prone
areas should be considered a legitimate industrial waste and be allowed
to be discharged with the other wastes to the sewer. The volume is small
and will not stress the usual system. The industries generally provide
spill protection such as curbs or retention tanks for these areas so that
a large spill may be kept from the sewer. Sometimes discharge of rain-
fall can be delayed somewhat.
Control of Peak Loads From Industry
Another hard-to-deal-with subject that I mentioned in the introduc-
tion is control of industrial loads. The management of a municipal sys-
tem must be supplied information on the discharge schedule, average daily
volume, and average daily load of the significant industrial users. The
information is needed for design, for operation, and for revenue program
858
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planning. Likewise the peak load and flows expected must be known. Many
industries have a difficult time maintaining a constant load for exten-
sive periods of time. Equipment fails, raw materials change, people fail
and some accommodation to variation on loading is a necessity. So there
can be a problem with high short-duration volumes or mass discharge of
pollutants—a high day or high week. A short period, high load-for say
an hour or two is usually meaningless because the dispersion of the load
in other flow in the system in the sewers and at the treatment facility
will average out the peak so that the effect is the same as a daily or
half day peak.
Most treatment facilities have a built-in ability to accept and
adequately handle a peak daily load. Domestic sewage has a daily varia-
tion in flow and strength which allows off peak hours for catch up after
unusual industrial loads are received. Activated sludge has a remarkable
ability to handle a great increase without a marked impact on effluent
quality.
A real potential problem with an excessive peak load would be when
the effluent quality is significantly adversely affected. In most
receiving water situations the damages from excursions out of the ideal
water quality standards for short times is not serious. The criteria are
based on long-term exposure. Short term modest excesses could not be
considered serious.
A good way to regulate industrial peak loads via a general easily-
interpreted meaningful ordinance has not been invented.
Limitations on concentrations is one approach. It is okay for
toxics. For compatible pollutants it is too simplistic to warrant atten-
tion. The mass of pollutants is the critical issue. Any such concen-
tration limit is anti-conservation of water. A concentration limit on
compatible (easily treated) pollutants is not a good way to control loads.
Equalization requirements is another approach. Cities have been so
extreme as to suggest 24-hour retention basins for evening out effluents
to their system. Equalization basins require aeration to keep odors from
developing. They need mixers to keep solids from accumulating. Equali-
zation basins remove nothing. Generally they are not cost effective.
The money would better be spent on more treatment plant capacity.
A definition of an unlawful load is a load the discharger knows or
has reason to know will cause interference with the treatment facili-
ties. This is an illusion as a practical solution in my opinion. The
provision is an invitation for debate, for endless talk and controversy,
and ill-will and external frustration.
What then can be recommended in the face of absence of precedence of
practical control systems? My suggestion is to obtain needed control by
addressing this subject in each industrial permit. The peak volumes and
loads could be specified for those industrial dischargers large enough to
859
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be of concern. Each specification could be tailored to specific circum-
stances. Real problems only could be addressed and most economic control
assured.
Fair Charges to Users
Arriving at fair charges for wastewater services for all users
commercial, residential, and industrial is a complicated matter. A
rational and detailed analysis can produce a revenue program that can be
defended as fair. Technical societies such as the American Society of
Civil Engineers, the Water Pollution Control Federation, and the American
Public Works Association have jointly sponsored manuals setting for the
principles for a fair revenue program.
The basic philosophy of a fair charge system is that the users and
beneficiaries of the system be made to pay in proportion to the costs of
providing the use and benefit each received. Key to application of this
philosophy is the proper recognition of the cost causative agents and the
uses and benefits of the system. For instance in distributing capital
costs each element of the system—the pipes, pumps, treatment tanks—is
assigned to the appropriate cost-causing agent or agents. Pipes or
sewers for example are sized to carry certain peak flows therefore the
costs should be distributed according to the peak flow of each user.
Another example would be the cost-causing agent assigned the air blowers
for the activated sludge system. The air blowers are for the ultimate
purpose of removing BOD and are sized to deliver enough air for the BOD
load. Therefore, the capital cost of the blowers is assigned to BOD of
each user.
A necessity to fairness of application of this principle is that all
the uses must be recognized and all the cost-causing agents in the system
recognized. The uses that are neglected in defective cost distribution
systems can be the use for the conveyance and treatment of stormwater,
the use for conveyance of infiltration, and the capacity for future
users. In every system in spite of trying to exclude stormwater by
careful construction there will be experienced significantly higher flows
after storms. Likewise practically every system in this country exper-
iences a great deal of leakage or infiltration. A representative case
will have fifty percent of the annual flow attributable to infiltration.
Logical planning indicates that considerable capacity for growth ought to
be included in any conveyance and treatment system. These three uses and
perhaps others are referred to as community costs or public costs by some
rate engineers. The insinuation is that these uses cannot be identified
with any particular user of the system. For example most of the storm-
water will originate in the streets which are of course publicly owned.
Infiltration comes into the sewers owned by the district in the streets
largely. The revenue program for these public use related costs must be
carefully thought out. The recommendation in the guidance referred to
above is that these costs be considered a general obligation of the city
and therefore should be assigned according to ownership of property in
the city, in other words from property taxes. In many cases in this
860
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country it is not practical to levy new taxes. Property benefit charges
may be possible. An alternative is to distribute costs equally per
customer or equally per customer in each class.
The point I wish to leave with you is that the simple concept of
sharing costs proportionate to use and benefit is complex in its appli-
cation. If public use is not recognized the large deliberate users such
as manufacturing industry are assigned an unfairly large portion of the
public use costs. For example an industry that discharges 25 percent of
the flow would in a simple apportionment receive 25 percent of the costs
for stormwater, infiltration, and future capacity in the system. This is
obviously not fair. So I advise you to get the help of experts in
designing your revenue program. There are engineering firms who have the
expertise and experience.
Toxic Pollutants
The portion of this subject which I have left for last is the part
of the subject of use by industry of a municipal wastewater system that
has caused so much recent concern and is probably the first that comes in
your mind when contemplating the subject. The topic is the discharge of
toxics to the municipal system. In earlier years of control of indus-
trial use of these systems the effort was directed largely at the metals
such as copper, nickel, and zinc. Concerns were 1) interfering with the
biological processes and 2) harmful effects on fish. In recent years the
interests have broadened the meaning of a great range of effects such as
causing birth defects, mutagens, cancer, etc., harm to any organism in
the environment, bio-concentration, etc. The Federal law has focused
attention on over 100 organic compounds with the potential of exerting
some such environmental effect in wastewaters. Research on health and
environmental effects being conducted will likely bring attention to
other compounds in time. Experience to date indicate that a monitoring
program will not be easy, it will not be cheap. A practical problem in
analysis may make it very difficult to learn whether the material is
present or not in the mix of biological residues in a treated effluent.
The control scheme proposed by the Federal EPA could be so complicated
that municipal administrators will find it too much administrative
trouble to use. This could harm the cause of joint treatment severely.
Even though the vast majority of such organic compounds will be subject
to biological degradation and will, with good biological treatment, not
be present in the effluent at harmful concentrations.
I do not mean to make light of the need for attention to control of
toxics. Of course the public recreational waters, the desirable array of
fish and other aquatic organisms, and particularly public water supplies,
must be protected. We only ask for addressing only real problems and
management of the significant risks.
We believe it is possible to control and manage the use of municipal
systems for the treatment of many of these organic compounds through a
variet> of monitoring and control systems that would be developed for
861
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each individual system. Practically speaking, each system is unique, the
treatment may differ slightly, the mix of other wastes will differ, the
dilution with other wastes will differ, the most economic way to limit
the toxic may differ, and the concentration of concerns in the effluent
may well differ from location to location. We feel the system that will
work best and which the municipal managers will find most manageable and
economic will be for them to first determine the concentration of the
candidate toxics present in the wastes as discharged from the municipal
treatment plant. Readily biodegradable toxics will not be found and the
concern for them can be minimal. Any compound found above a concentra-
tion of concern can be controlled by such means as the management of the
facility may choose. The choice may be to limit it severely at the
source or limit the toxic just sufficient to equal the capacity of the
treatment plant to satisfactorily remove or some other means.
Gentlemen, I do not wish to make light of a real problem. We want
to be sure there is a real problem. We must use the most practical con-
trol system taking into account effectiveness, economics, including the
utility of the product involved and manageability. I do not believe we
will have trouble working such out in a cooperative effort.
Close
I hope you have become more aware of the value of joint treatment
and industrial interest in it. Many industrial plant executives recom-
mend their plant managers view the municipal wastewater treatment plant
that serves them as an extension of their own manufacturing facility.
The same regard is recommended to be held for its proper functioning and
its quality of effluent as there would be for the functioning of the
product manufacturing equipment and product quality.
The concern is illustrated by the story of one paper plant manager
who received a call from the local sewage treatment plant manager. This
industry made a great deal of colored paper. The treatment plant person
said, "You have dyed my whole treatment plant blue, the primaries are
solid blue and there is blue all over, even in the final tanks". Of
course the industrial plant manager was concerned. He was anxious to do
the best thing to correct the situation to the satisfaction of the treat-
ment colleague. So he thought of the most accommodating thing he could
do. So he said, "We have a variety of colors out here, what color would
like the plant to be?"
That is a sick, sick joke of course. I tell it to emphasize that we
are aware of the need to cooperate, to value, to nurture our colleagues
in the waste end of the business. Please call on us if you think we
could be of any help.
862
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TABLE 1
NUMBER OF INDUSTRIAL PLANTS USING COMMUNITY SEWER SYSTEMS
CITY
Atlanta
Chicago
Dallas
Salem
South San Francisco
TOTAL USERS
100,000
2,000,000
230,000
50,000
20,000
SIGNIFICANT
INDUSTRIAL USERS
66
350
119
18
24
PERCENTAGE OF TOTAL
FLOW BOD
15
6
10
9
13
19
50
39
47
TABLE 2
USE OF COMMUNITY WASTEWATER SYSTEMS BY INDUSTRIAL CATEGORIES
INDUSTRY CATEGORY
Laundry detergents
Bar soap
Coffee
Edible oil refining
Fruit and vegetable canning
Paper converting
Steel rolling
Blast furnace
By-product cooling
Paper pulping
PERCENT OF INDUSTRIAL PLANTS
PRACTICING JOINT TREATMENT
95
99
100
92
0
0
0
5
TABLE 3
CAPITAL COST OF SEDIMENTATION FOR VARIOUS PLANT CAPACITIES*
CAPITAL COST OF SEDIMENTATION
CAPACITY
OF
PLANT
mgd
1
10
100
*1971 costs
TOTAL
$ 42,000
$160,000
$920,000
PER mgd
CAPACITY
42,000
16,000
9,200
PERCENT
OF 1 mgd
CAPACITY
38
22
863
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TABLE 4
CAPITAL COST OF DIFFUSED AIR SYSTEMS FOR ACTIVATED SLUDGE PLANTS
CAPITAL COST OF AIR SYSTEM
CAPACITY
OF
PLANT
mgd
1
10
100
*1971 costs
TOTAL
65,000
320,000
1,820,000
PER mgd
CAPACITY
I
65,000
32,000
18,200
PERCENT
OF 1 mgd
CAPACITY
49
28
TABLE 5
CAPITAL COST OF TOTAL ACTIVATED SLUDGE PLANT*
CAPITAL COST
CAPACITY
OF
PLANT
mgd
1
10
50
*1967 costs
TOTAL
550,000
3,200,000
11,000,000
PER mgd
CAPACITY
550,000
320,000
220,000
PERCENT
OF 1 mgd
CAPACITY
58
40
TABLE 6
LABOR COSTS FOR DIFFUSED AIR SYSTEM OPERATION
LABOR MAN HOURS/YEAR
CAPACITY
OF
PLANT
mgd
1
10
100
TOTAL
1,480
4,400
16,100
PER mgd
CAPACITY
1,480
440
161
PERCENT
OF 1 mgd
CAPACITY
30
11
864
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COST-EFFECTIVENESS AND WATER QUALITY
JUSTIFICATION FOR ADVANCED WASTEWATER
TREATMENT (AWT) FACILITIES
Robert J. Foxen
Office of Water
U.S. Environmental Protection Agency
Washington, D.C.
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Washington, D.C.
865
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COST-EFFECTIVENESS AND WATER QUALITY JUSTIFICATION FOR ADVANCED
WASTEWATER TREATMENT (AWT) FACILITIES
Robert J. Foxen
Office of Water
U.S. Environmental Protection Agency
Washington, D.C.
I. INTRODUCTION
In 1977, the "Vertex" draft report(l) prepared by an EPA consultant
concluded that many advanced wastewater treatment (AWT) projects funded by
the U.S. Environmental Protection Agency (EPA) were too costly and resulted
in few, if any, water quality benefits. AWT was basically defined as any
treatment beyond secondary, which is the minimum required by law. The Vertex
report recommended that all further funding of AWT projects be stopped until
questions concerning the accuracy of water quality analyses used to justify
these projects and the high project costs could be resolved.
Spurred by this report, and by a growing concern about high cost waste-
water treatment projects, the Appropriations Conference Committee of the U.S.
Congress issued a directive in October 1978 which required that EPA grant fund-
ing for AWT projects with incremental capital costs for treatment beyond second-
ary of greater than $1.0 million may be provided only if the EPA Administrator
"personally" determines that the project "will definitely result in significant
water quality and public health improvement."* The House and Senate Appropri-
ations Committees raised the incremental cost to $3.0 million for projects
reviewed during fiscal year 1980. For projects with lower marginal costs, AWT
approval is given by Regional EPA Administrators.
To implement the requirements of this directive, EPA issued Program Re-
quirements Memorandum (PRM) 79-7, which outlined the criteria for review of AWT
projects. PRM 79-7, which requires that effluent limitations for AWT projects
must be fully justified by technically sound water quality analysses. This
will ensure that expenditures for AWT processes will result in significant water
quality benefits; however, this evaluation does not involve a cost-benefit
analysis in which the "worth" of the benefits is weighed against the cost.
Rather, given a specified water use goal, this analysis seeks to assure that
this goal will be achieved at minimum cost.
*There have been various arguments that this directive is inconsistent with
the Clean Water Act, and Section 510 of the Act in particular which allows
States to set water quality standards more stringent than the Federal minimum
if they choose. The main question is whether the Act requires EPA to fund
projects to meet these standards.
**These criteria include evaluation of water quality modeling, appropriateness
of beneficial use classifications and water quality criteria, and a review of
cost-effectiveness. The State of Illinois (IEPA) sued EPA in December 1979,
claiming that the AWT review violated the Clean Water Act. IEPA and EPA reached
an-out-of court settlement on the case, and EPA agreed to simplify some of the
review requirements. As a result of this settlement, a final revised PRM will be
issued and specify the review criteria to be used in future AWT reviews nationwide,
866
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An EPA Headquarters AWT Task Force has reviewed 68 AWT projects,
with capital costs for AWT of over $500 million. As of this writing, these
reviews have resulted in deferral of EPA funding for over $114 million worth
of unjustified AWT processes. The findings in these reviews have created
intense controversy among affected cities, states, EPA regional offices,
and EPA Headquarters.
This paper explains the rationale for the review criteria and
approach used in the AWT review at EPA Headquarters, provides an assessment
of removal capabilities and marginal costs of various AWT processes, and
describes case studies to indicate the results and implications of the
reviews conducted to date. This paper also analyzes the accuracy of water
quality models used to justify AWT processes.
II. REVIEW CRITERIA AND APPROACH
A. General Approach
In typical water quality management planning studies, water quality
analysts established permit effluent limitations based on results of water
quality modeling studies, but without regard for the costs of unit processes
required by those limitations. Engineers were then required to design
facilities to meet these limitations, regardless of the uncertainities in
the water quality analysis, or the costs of the unit processes that were
required. The efforts of the water quality analyst and the design engineer
stopped at opposite ends of the pipe, with neither venturing into the sphere
of the other.
Now this may be changing. The justification for AWT projects
reviewed in Headquarters has basically involved balancing the uncertain-
ties in the water quality analyses against the marginal costs of the unit
processes being considered. For unit processes with relatively high marginal
costs, more rigorous water quality analyses have been required than for unit
processes with lower marginal costs. This approach allows more flexibility
in establishing permit limitations.*
*This approach in effect results in deferral of EPA funding in cases where
it is not conclusively shown that these processes are needed. It has been
argued that this approach is inconsistent with the Clean Water Act, which
requires that a "margin of safety" must be provided to compensate for
uncertainties in the water quality analysis. This may be a valid argument,
although the definition of a "margin of safety" is subject to interpretation.
Nevertheless, EPA made a policy decision to carry out the Congressional
directive in this manner.
867
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B. Evaluation of AWT Processes
Nitrification and Tertiary Filtration Systems
A summary of the types of advanced unit processes proposed and
approved by the Headquarters AWT Task Force appears on Table 1. As shown
on this table, the most commonly proposed AWT processes were various nitri-
fication and tertiary filtration systems. In nearly all cases where filtra-
tion was proposed, it was an add-on to nitrification rather than following
secondary treatment.
Table 1 shows that nitrification was proposed in 55 cases and
approved in 51 cases. On the other hand, tertiary filtration was proposed
in 48 cases and approved in only 21 cases. Moreover, in many cases where
filtration was approved, approval was based on a consideration of the in-
flationary impacts that would result from delays for redesign following
elimination of filtration, rather than on technically sound water quality
analyses. Thus, the number of cases where there was adequate water quality
analyses to justify filtration was less than the approvals indicated by
Table 1.
The high approval rate for nitrification, and low approval rate for
filtration, resulted from two major reasons. First, nitrification has a
relatively low marginal cost per unit of ultimate oxygen demand (UOD)*
removed, and removes a large percentage of UOD. Filtration, on the other
hand, has a high marginal cost per unit of UOD removal, and removes only
a small percentage of UOD.**
The second reason involves the predictive accuracy of water quality
models. Generally, it is relatively easy to develop water quality models
accurate enough to determine whether the level of UOD removal provided by
nitrification is needed. However, since filtration following nitrification
removes only a small percentage of UOD, inherent uncertainties in water
quality modeling make it more difficult to accurately predict whether
filtration is needed. These issues are discussed in more detail in the
following sections.
*UOD is defined as the total carbonaceous and nitrogenous oxygen demand.
This may be estimated as follows:
UOD, mg/1 = 1.5 x CBOD5, mg/1 + 4.57 x NH3~N, mg/1
where CBOD5 = total carbonaceous BOD5 which includes SS.
**Filtration should obviously not be used to remove UOD after nitrification
since little UOD remains in the wastewater. Filtration could be used for
suspended solids removal, total phosphorus removal, or for disinfection.
868
-------
Cost Effectiveness
A schematic diagram showing the removal capabilities of a typical
AWT facility providing nitrification followed by tertiary filtration
appears on Figure 1. This figure shows that nitrification will reduce
ammonia concentration from about 20 mg/1 (following secondary treatment)
to an average of about 1 mg/1, and reduce CBOD5 concentrations from 30 mg/1
to about 8 mg/1. Nitrification thus increases UOD removal from 67 percent
to 96 percent. In addition, nitrification has the added benefit of reduc-
ing ammonia toxicity in the receiving water.
Graphical presentations showing the marginal present worth cost
per mg/1 UOD removed for secondary, nitrification and tertiary filtration
appear on Figure 2.* The figure shows that the marginal cost per mg/1 UOD
removed by nitrification is significantly less than for tertiary filtration,
and even less than the marginal cost per unit of UOD removed for secondary
treatment. Specifically, Figure 2 shows that the marginal present worth
cost per mg/1 UOD removed by nitrification in a typical 10 MGD two stage
activated sludge system is about $24,000, as compared to a marginal cost
for secondary treatment of about $42,000 per mg/1 UOD removed. The marginal
cost for tertiary filtration following nitrification is over $1.0 million
per mg/1 UOD removed. Thus, the high approval rate for nitrification and
low rate for filtration in part resulted from differences in the marginal
costs and removal capabilities of these processes.
Predictive Accuracy of Water Quality Models
These findings have significant implications for the water quality
analyses used to justify nitrification and tertiary filtration. Since
nitrification has relatively low marginal costs and provides significant
reduction in UOD, simplified water quality analyses were often adequate
to justify this process.** On the other hand, since filtration has a
high marginal cost for UOD removal and removes only a small amount of
UOD, more detailed water quality analyses, often involving a calibrated
and/or verified water quality model, were generally required. More
accurate water quality models were also generally required to justify
filtration because it is more difficult to predict in-stream responses
to the relatively small UOD removals provided by filtration than for the
relatively large UOD removals provided by nitrification.
*These estimates are based on the "typical" values shown on Figure 1,
and would vary from plant to plant. UOD removal efficiencies assume
CBOD5 tests are used.
**New guidance for using simplified DO modeling techniques for justify-
ing filtration was recently issued by EPA. These techniques require
sensitivity analyses to justify filtration, and would require gather-
ing calibration and/or verification data if the results of the sensi-
tivity analysis do not conclusively establish that filtration is needed.
869
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The adequacy of simplified DO models and calibrated/verified DO
models for justifying AWT processes depended on the technical accuracy of
the model, and the marginal cost and removal capabilities of the process
in question. In general, simplified approaches were adequate to justify
nitrification, but calibration and/or verification data were generally
required to justify tertiary filtration. The case studies presented in
Section III provide several examples where simplified and calibrated DO
models were used to justify AWT processes, and explain the rationale for
accepting or rejecting these justifications.
The most significant parameters affecting the predictive accuracy
of water quality DO models are the deoxygenation rates (Kd day-1) (i.e.,
including both day-1 carbonaceous and nitrogenous deoxygenation), and the
reaeration rates (Ka). In simplified models, these rates are determined
based on literature values for similar water quality scenarios, from data
from nearby similar receiving streams, or, for Ka's, from empirical form-
ulas. Since the rate constants used in these simplified approaches is not
based on site specific data, the accuracy of these models is limited.
For calibrated and verified model, rate constants are determined
based on site specific in-stream measurements. For example, carbonaceous
BOD (CBOD) decay rates would be determined by measuring CBOD decay in-stream.
However, the accuracy of these rates to predict future water quality impacts
of treatment levels may be questionable, since Kd values are generally lower
at higher treatment levels, and the exact amount of the reduction cannot be
estimated with certainty. This concern can be reduced if the water quality
analyst performs adequate sensitivity analyses within the range of typically
expected Kd values.
Nitrogeneous oxygen demand (NOD) decay may be determined by measur-
ing ammonia decay. However, this approach may have to be modified in cases
where high algal populations exist, since ammonia depletion may actually
result in large part due to algal uptake, rather than oxidation. In these
cases, the rate of nitrate increase may be a more accurate measure of
ammonia oxidation.
The greatest amount of variability in most DO models involves Ka.
There are several empirical formulas available for estimating Ka (e.g.
O'Connor - Dobbins(2), Tsivoglou, et^a^.O), Owens, et^aju(4)), and suitabil-
ity of each varies depending on the characteristics of the receiving water.
For a typical low flow stream, Ka values may vary anywhere from 1.5 to 7.0
per day, base e. It is not unusual to find Ka values as high as 20 per day
in some models. On the other hand, typical Kd values resulting from dis-
charge of a well treated secondary or nitrified effluent into a low flow
stream generally range from about 0.3 to 0.6 per day, base e. Thus, the
possible range for Ka is much greater than for Kd.
Ka values in most water quality models reviewed in EPA Headquarters
were determined from empirical formulas. These Ka values were usually ad-
justed to fit observed DO data, where available, which is the generally
870
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correct procedure for model calibration. However, the accuracy of this
approach is often uncertain since the initial difference between observed
and predicted DO may be due to factors other than inaccuracies in the
estimate of Ka.
The most accurate means for determining Ka is use of the inert gas
tracer'^) technique. This approach basically involves actual measurement
of gas transfer in the receiving water in question. However, even this
approach has inherent uncertainties, because of differences in conditions
at the time of the gas tracer measurement and the prediction conditions,
and because of uncertainties in measurement techniques. Thus, Ka rates
estimated by gas tracer techniques may also have to be adjusted during
calibration.
There are also several other variables that may introduce addi-
tional uncertainty into water quality models. These include measurement
and prediction of sediment oxygen demand, effects of algal activity, and
background DO concentrations. These factors are not addressed in detail
in this paper, but should be considered in determining the accuracy of DO
models, and the expected improvements from AWT.
Despite these uncertainties, even simplified models are often
adequate to show whether nitrification is needed, since the DO impacts
of the UOD removed by nitrification are generally much greater than the
uncertainties in DO models. However, in the case of tertiary filtration
following nitrification, the confidence limits of DO models (even with
calibrated and verified models) often exceeds the predicted incremental
DO benefits resulting from providing tertiary filtration following nitri-
fication. Therefore, water quality models are often not accurate enough
to show whether tertiary filtration is definitely required following nitri-
fication to meet a given DO criteria.
The effects of the uncertainties in DO models on the ability to
determine the need for filtration following nitrification are illustrated
on Figures 3, 4, and 5. Figure 3 shows the expected DO improvement result-
ing from providing filtration after nitrification, as a function of varying
Ka to Kd ratios, assuming a stream to effluent dilution ratio of 1:1. For
example, for Ka/Kd = 6, filtration following nitrification would improve DO
by about 0.25 mg/1.
Figure 4 shows estimated confidence bands for the DO deficit result-
ing from discharge of a nitrified effluent. These confidence limits were
estimated by assuming that Ka has been determined with certainty (i.e.,
either via calibration or using gas tracers), and that Kd could vary by 25
percent to 75 percent. Uncertainties in estimating loadings sediment oxygen
demand (SOD), algal effects, etc., were not considered. Thus, this Figure
represents a minimum amount of uncertainity associated with a calibrated
DO model. However, even given these conditions, Figure 5 shows that for
a Ka/Kd = 6, the DO deficit resulting from discharge of a nitrified effluent
would be 1.0 mg/1, but that it could range anywhere from 0.7 mg/1 to 1/3 mg/1
due to modeling uncertainties (i.e. uncertainties in Kd).
871
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To illustrate the effects of these uncertainties on determining
the need for tertiary filtration, Figure 5 shows that the DO improvement
resulting from providing tertiary filtration falls within the range of
confidence limits associated with the effects of a nitrified effluent.
An example illustrates the effect of this problem. Assuming a
Ka/Kd = 6 and a background DO of 5.8 mg/1, Figure 5 shows that discharge
of a nitrified effluent would depress DO by about 1.0 mg/1 to 4.8 mg/1.
This is below the DO criteria for warm water fisheries. If filtration
were provided following nitrification (and Ka/Kd again = 6), the DO would
be depressed by about 0.7 mg/1, to about 5.1 mg/1. This is above the DO
criteria. However, if Kd is reduced to 0.3 per day, which is well within
the acceptable range for Kd's, DO resulting from discharge of a nitrified
effluent would only be depressed by about 0.6 mg/1, to about 5.2 mg/1.
This also is above the DO criteria. Thus, it would not be possible to
determine whether tertiary filtration following nitrification would
definitely be needed to achieve DO criteria, or whether nitrification
alone would be adequate to achieve this DO level. If other modeling
uncertainties are introduced, the ability to determine the need for
tertiary filtration would be limited even further. These uncertainties
warrant particular attention in view of the high marginal costs associ-
ated with tertiary filtration for UOD control.
There are two possible options for resolving this issue. One is
to construct only the nitrification facilities, and then to monitor water
quality to determine whether more treatment is needed. This approach has
the advantage of providing precise site-specific data for determining
treatment needs; the disadvantage is that delays while data is monitored
and analyzed would increase costs for additional treatment if needed, and
could prolong discharge of inadequately treated wastewater.
The other option is to use post-audit water quality data from
similar nitrification facilities to refine modeling accuracy and more
precisely determine whether tertiary filtration is needed. However,
while this approach could reduce modeling uncertainties, and preclude
project delays, it would still be limited in its predictive accuracy.
C. Phosphorus Controls
Phosphorus removal was proposed for 24 projects and approved for
16 (see Table 1). In most cases where phosphorus removal was approved,
the projects discharged either into the Great Lakes or the Chesapeake Bay,
where there had been extensive studies of the potential impacts of phos-
phorus on the trophic state of the receiving waters.* For dischargers
into other water bodies, adequate water quality analyses existed in only
a few cases. However, where phosphorus removal was not justified, it was
recommended that the plant be built to account for the possibility that
phosphorus removal may be required in the future, in order to avoid
possible retrofit problems.
*These studies have resulted in an international agreement between the U.S.
and Canada which limits phosphorus discharges into the Great Lakes and their
tributaries to 1.0 mg/1 for all municipal discharges greater than 1 MGD.
872
-------
The primary reason for the lack of adequate water quality justi-
fication for phosphorus removal is the inherent complexity of accurately
modeling phosphorus-chlorophyll relationships. Modeling the effects of
phosphorus requires an assessment of non-point loadings, and bio-assay
studies to identify the limiting nutrient. Other complicating factors,
such as predicting reaction rates, bio-feedback, turbidity, light pene-
tration, etc., also make this analysis relatively complex.
Because of the complexities mentioned above, EPA Headquarters has
re-evaluated the criteria for approval of phosphorus removal. This re-
evaluation considered the following issues:
0 modeling of phosphorus-chlorophyll relationships is
difficult, and could not be done in many cases due to
limitations in man-power, technical expertise, etc.
0 potential adverse impacts from not controlling phosphorus
could be severe and difficult to reverse
0 capital costs for phosphorus control are relatively low, at
least down to about the 1.0 mg/1 level. (Clarification would
generally not be capable of meeting effluent limits below
1.0 mg/1. Thus, more stringent limits would require some
type of filtration system or other costly processes)
Based on these considerations, simplified procedures are being
developed for justifying phosphorus removal.* Criteria for justification
using simplified procedures include:
0 demonstrating that there is an existing or potential (marginal)
phosphorus-related water quality problem
0 if the water quality problem is only marginal, demonstrating
(supporting data) that phosphorus loadings will increase
significantly
0 demonstrating that phosphorus is the limiting nutrient
0 demonstrating that point sources contribute a significant
portion of total phosphorus loading
0 demonstrating that phosphorus controls will not result in
significant cost impacts (both capital and operating costs)
These criteria will be applied to future projects where phosphorus
removal is proposed, and may also be applied to projects where EPA funding
for phosphorus removal has previously been deferred.
*The decision to allow simplified approaches to evaluate phosphorus removal
evolved during the review process. Specific criteria and procedures to be
used in this regard will be included in the revised PRM, to be issued
shortly, and other subsequent water quality guidance.
873
-------
D. Separate Stage Denitrification
Separate stage denitrification was proposed in only two cases, and
was not justified in either case. Like phosphorus, the impact of nitrates
on a receiving waters' trophic state is relatively difficult to model. Even
predicting future nitrate concentrations may be difficult since denitrifi-
cation could occur in-stream. However, unlike phosphorus removal, both
capital and operating costs for separate stage denitrification with methanol
are high.* Therefore, justification for nitrogen control would have to be
more rigorous than for phosphorus controls. This justification may involve
gathering field data to calibrate the results of model predicted in-stream
reactions, as well as nutrient limiting studies, and an assessment of non-
point sources.
III. CASE HISTORIES
Manasquan, New Jersey
The Manasquan project provides a good example of the use 01 simpli-
fied modeling procedures for justifying effluent limitations. The proposed
Manasquan project is a new 8.1 MGD oxidation ditch unit, using the Carrousel
system. The project involved regionalizing several small package plants
located further upstream. The project had originally included tertiary
filtration following the Carrousel unit, but the Regional EPA Office in
New York determined that the filters were not justified.
The facility would discharge to the Manasquan River Estuary, several
miles upstream from the Atlantic Ocean. The river is designated for contact
recreation, fishing and shellfish harvesting. Shellfish harvesting had been
discontinued due to pollution from upstream package plants. The DO standard
for the river is 5.0 mg/1.
The effluent limitations included a 10 mg/1 limitation for CBOD5, and
a 2.0 mg/1 seasonal limitation for ammonia, which applied from May through
October. A simplified desk-top water quality (estuary) model was used by the
EPA Regional Office to verify the need for these effluent limitations. Since
no discharge existed near the proposed outfall, the Kd rate constants used in
the model had to be based on literature values. To account for inherent in-
accuracies in using these literature values, the Region performed sensitivity
analyses to indicate the in-stream DO responses under various possible scenar-
ios. Results of this analysis showed that the allowable UOD loading ranged
between 400 Ibs/day and 2,000 Ibs/day, depending on which rate constants
were used. The Regions' "best" estimate of allowable UOD loading was 1,200
Ibs/day. If secondary treatment were provided, the effluent UOD loading
would be 12,700 Ibs/day, or more than six times the maximum estimated allow-
able concentration. If tertiary filters and nitrification were provided,
effluent UOD loading would be 750 Ibs/day. If the Carrousel system were
used without filtration, the UOD loading would be about 1,600 Ibs/day.
*Where methanol is not used for denitrifIcation, partial denitrification
( ~ 80% removal) in single sludge in extended aeration or Carrousel
systems would not be high.
874
-------
The marginal present worth costs per mg/1 UOD removal for second-
ary, nitrification and tertiary filtration for this project are shown in
Figure 6. Figure 6 shows that the marginal costs per mg/1 UOD removed for
secondary and nitrification are about $76,000 and $13,000, respectively. The
total cost for nitrification was estimated to be only about $1.0 million.
In contrast, the marginal cost per mg/1 UOD removed for filtration would be
over $1.0 million. The capital cost for filtration would be about $3.0
million. Because the simplified analysis showed it is very likely that
treatment beyond secondary is needed, and because the marginal cost for
nitrification is relatively small, the Region concluded that the Carrousel
unit is justified. Although the UOD loading from the Carrousel process
without filtration would be slightly greater than the "best estimate"
allowable UOD loading, the Region concluded that the filters were not
justified because of their relatively high marginal cost, and because of
the inaccuracies inherent in the simplified mode. The Headquarters AWT
Task Force concurred with these conclusions.
Rochester, New Hampshire
The Rochester project provides an example where both nitrification
and filtration were justified.
The proposed project involves construction of a new 4 MGD facility,
using two-stage nitrification, followed by dual media tertiary filtration.
The city currently discharges raw sewage. The nitrification system would
include a roughing trickling filter, followed by separate stage activated
sludge.
The receiving water is the Cocheco River. The designated uses
(recently upgraded) of the river include swimming and cold water fishery.
Large oyster beds exist downstream, but these have been closed due largely
to pollution from Rochester. Thus, one potential benefit from the project
would be to re-open the oyster beds. In addition, the State is implementing
plans, including installing fish ladders, to establish salmon spawning.
The critical design flow (7 day once in 10 year low-flow) in the
river is about 2.2 cubic feet per second (CFS). The river is currently
highly polluted due to the Rochester discharge. The water quality standards
require a DO of 6.0 mg/1 or 75 percent of saturation, whichever is greater.
The design effluent CBOD5 and ammonia limitations were 5.0 mg/1 and
1.0 mg/1, respectively. A calibrated (but not verified) DO model was used
to determine these limitations.
In its original final AWT report, the Headquarters AWT Task Force
concluded that the water quality analyses did not justify the need for the
dual media filters. This conclusion was reached because the proposed ter-
tiary filtration system had a cost of about $1.3 million, and would provide
only slight additional reduction in UOD. Similarly to other projects, the
marginal cost per mg/1 UOD removed for filtration vis-a-vis secondary treat-
875
-------
ment and nitrification was very high. In addition, since the city currently
discharges raw sewage, there were uncertainties in the water quality analyses
because of inherent difficulties in estimating rate coefficients under future
conditions with highly treated effluents.
Following a review of this report, the State submitted new information
supporting the need for tertiary filtration. This information provided lower
cost estimates which showed that there would be negligible savings if the
filters were eliminated. These lower costs resulted from changing the filtra-
tion system from dual media to sand, which reduced the capital cost of the
filters from about $1.3 million to about $550,000.
In addition, the State noted that additional chlorine would be required
without filters because of higher suspended solids concentrations. This would
necessitate dechlorination, further reducing potential savings from eliminating
the filters. Using these assumptions, the present worth cost of retaining the
filters exceeded the cost without filters by only about $95,000.
The Task Force also considered the possibility that further water q"ali-
ty analyses would justify filtration. Despite some questions and shortcomings
concerning the existing water quality modeling efforts, the overall work was
reasonable. The water quality model was properly calibrated, and showed that
filtration is needed. Thus, it was not unlikely that verification of the
existing model might also show that filtration is required.
Finally, more specific evidence was provided showing steps being taken
by the State to establish a salmon fishery, including spawning grounds, below
the discharge point. The State also planned to re-open oyster beds that are
now closed due to pollution from Rochester. Although not demonstrated (and
difficult to prove), the reduced suspended solids loading with the filters
might enhance these uses. In view of these considerations, it was considered
likely that filters would prove to be justified if additional water quality
studies were conducted.
Based on the above considerations, the Task Force concluded that sand
filters were justified for this project.
IV. CONCLUSIONS
A rigorous review of water quality related effluent limitations should
occur prior to facility planning. Such review should provide for flexibility
in establishing effluent limitations by allowing the marginal costs for AWT
processes and uncertainties in water quality analyses to be weighed before
final effluent limits are set. Generally, water quality analyses for AWT
processes with higher marginal costs should be more rigorous than analyses
for processes with lower marginal costs.
876
-------
Nitrification and tertiary filtration were the most commonly pro-
posed AWT processes. Nitrification was justified in most cases because
it has a relatively low marginal cost per unit of UOD removed, and because
water quality models are usually accurate enough to determine whether this
level of treatment is needed. Tertiary filtration was not justified in
most cases because it has a relatively high marginal cost per unit of UOD
removed and because inherent uncertainties in water quality modeling make
it difficult to accurately predict whether the level of treatment provided
by filtration following nitrification is needed to meet water quality
standards.
Water quality analyses for justifying phosphorus or nitrogen removal
are complex. Since phosphorus removal is generally relatively inexpensive,
simplified water quality analyses are often adequate. Since nitrogen
removal is more costly to remove, more sophisticated analyses, possibly
involving a calibrated model, may be required.
REFERENCES
1. Horowitz, J. and Bazel, L., "An Analyses of Planning for Advanced
Wastewater Treatment (AWT)", U.S. EPA, Office of Planning and
Evaluation. Final Report, Contract No. 68-01-4338, Washington,
B.C., July 1977.
2. O'Connor, D. J., and Dobbins, W. E., "American Society of Civil
Engineers Transactions, 123, 641 (1958).
3. Tsivoglou, E. C., e£ aJN, "Tracer Measurements of Stream Reaeration
II, Field Studies ""journal Water Pollution Control Federation,
40, 285 (1968)
4. Owens, M., et al., "Some Reaeration Studies in Streams", Inter-
national JournaT of Air and Water Pollution, 8, 469 (1964).
877
-------
FIGURE 1
Two Stage Nitrification -- Typical Removal Efficiencies
Raw Sewac
CBOD5 (mg/1) 200
(% Removal)
00
00
NH3-N (mg/1) 25
(% Removal )
UOD (mg/1)* 414
(% Removal)
je — - Primary —
130
35%
25
0%
309
25%
— Secondary —
30
85%
20
20%
136
67%
-— Nitrification —
8
96%
1
96%
17
96%
Tertiary
— Filtration
4
98%
1
96%
12
97%
Cost ($ million)**
* UOD - 1.5 (CBOD5) + 4.57 (NII3-N)
** Based on 10 MGD facility
11.7
2.87
3.5
-------
FIGURE 2
MARGINAL COSTS FOR TYPICAL
TWO-STAGE 10 MGD NITRIFICATION FACILITY
1200
1100
1000
100
75
50
25
$1,100,000
TERTIARY
FILTRATION-
$42,000
SECONDARY
$24,000
NITRIFICATION
I
,97
20
40 60 67
% "UOD REMOVED
80
96
879
-------
FIGURE 3
00
00
o
(Ka/Kd)
12
10
8
2
0
DO Improvement from Tertiary Filtration
Nitrification
Filtration'
0.5
1 1.5
DO (mg/1)
2.5
-------
FIGURE 4
Confidence of DO Models
00
00
(Ka/Kd)
12
10
8
6
4
2
0
\ Nitrification
x
0.5
1.5 2
DO (mg/1)
2.5
-------
FIGURE 5
Need for Tertiary Filtration
00
00
ro
(Ka/Kcl)
12
10
8
6
4
2
0
Filtration
0.5
1.5
2.5
DO (mg/1)
-------
FIGURE 6
OXIDATION DITCH - MAMASQUAN, N. J.
8.0 MGD - REMOVAL COSTS
1,175
1,150
1,125
1,100
1,075
1,050
1,025
1,000
100
75
5C
25
0
$75.899
SECONDARY
$1,140,000
FILTRATION
$13,210
NITRIFJC/VTION
20 40 60
% UOD REMOVAL
67
eo
96 100
883
-------
PRXESS
Nitrification
Tertiary Filtration
Phosphorus Removal
Denitrification
TABLE I
ADVANCED TREATMENT PROCESSES
PROPOSED AND APPROVED
NUMBER
PROPOSED
55
48
22
2
NUMBER
APPROVED
51
21
14
0
884
-------
EFFECTS OF MULTIPLE DIGESTION ON SLUDGE
Wilbur N. Torpey, Consultant, New York, New York
John F. Andrews, University of Houston, Texas
James V. Basilico, U.S. EPA, Office of Research & Development,
Washington, D.C.
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Prepared for Presentation at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Washington, D.C.
885
-------
EFFECTS OF MULTIPLE DIGESTION ON SLUDGE
Wilbur N. Torpey, Consultant, New York, New York
John F. Andrews, University of Houston, Texas
James V. Basilico, EPA, Office of Research & Development,
Washington, D.C.
ABSTRACT
This paper presents the development and application of the mesophilic-
thermophilic process that has been pioneered by the City of New York at
their Rockaway wastewater treatment plant. This was accomplished by the
use of a two-stage digestion system, consisting of a mesophilic stage fol-
lowed by a thermophilic stage. A part of the thermophilically digested
sludge was also recycled through the aeration tanks to obtain additional
destruction of organic solids. The advantages of the thermophilic process
are retained without the disadvantages. Results Indicate that the physical
characteristics of meso-thermo digested sludge are changed to the extent
that the economics of dewatering are significantly improved. Moreover,
has met the time-temperature requirements for pathogen destruction.
INTRODUCTION
\
Coastal cities , including the City of New York, being under Federal
mandate to cease ocean dumping of sludge derived from the treatment of
wastewater, have been engaged in studies of land-based disposal alterna-
tives for the past couple of years. Many of these studies were aimed at
determining the optimal methods of dewatering digested sludge as well as
the subsequent steps for ultimate land disposal.
In studying the work performed by Kraus in 1946(1), it was noted that
exposing volatile solids to both anaerobic and aerobic environments
resulted in improved destruction of volatile solids. This led to the idea
that alternate exposure of volatile solids to different environments could
substantially reduce the quantity of sludge for ultimate disposal. The
work of Kraus when considered in conjunction with the work of Buhr and
Andrews(2) on the thermophilic digestion process led to the concept of the
new process proposed herein. The idea was advanced that, as a fundamental
and first priority part of the management program, present plant facilities
should be tested for use in reducing to a minimum the rate of sludge pro-
duction from an activated sludge plant, both as to volume and volatile
matter. The rationale would be based on the exploitation of biochemical
mechanisms; namely, that improved destruction of volatile solids could be
886
-------
obtained by exposing the mesophilically digested solids to the enzyme sys-
tems of thermophilic digestion and activated sludge. Advantage gained in
this investigation would be reflected commensurately in the economics of
all the sludge dewatering and post-dewatering processes that were pre-
viously studied.
Present Practice of Thermophilic Anaerobic Digestion
Thermophilic anaerobic digestion is very similar to mesophilic
anaerobic digestion except the temperature at which it operates is
120-130° F instead of 90-100° F. It thus takes advantage of the fact that
biochemical reaction rates can be increased by increasing temperature. It
is only natural, therefore, that conversion of existing mesophilic
digesters to thermophilic operation should be considered as a low-cost
technique for increasing the sludge processing capability of wastewater
treatment plants. Full-scale studies by the Metropolitan Sanitary District
of Greater Chicago, (3), the Ontario Ministry of the Environment, Canada,
(4) and in Moscow, U.S.S.R. (5) have indicated that the sludge processed
per unit volume of digester capacity could be doubled by converting from
mesophilic to thermophilic operation.
Besides its increased sludge processing capability, thermophilic
operation also offers two other significant advantages over mesophilic
operation: improved sludge dewatering characteristics and increased
destruction of pathogens.
Garber's work on the vacuum filtration of thermophilic sludge at the
Hyperion plant in Los Angeles provides an example of how sludge dewatering
can be improved by the thermophilic digestion.(6) He reported a 270 per-
cent increase in vacuum filter yields with a 48 percent decrease in coagu-
lant dosage for thermophilic, compared to mesophilic sludge. Improved
solids-liquid separation is important in land application of sludge by
decreasing the quantity of wet sludge for disposal and thus lowering
transportation costs.
An example of the increased destruction of pathogens by thermophilic
digestion is given by Popova and Bolotina (5) in their report of the practice
of thermophilic digestion in Moscow, U.S.S.R. They state: "The most
essential advantage of this process is the sanitary quality of the
thermophilic sludge. According to the sanitary officials of the health
department, viable eggs of helminths are absent from such a sludge." This
improvement in sanitary quality is of special significance in light of the
current trend toward land disposal of digested sludge.
Development of the Mesophilic-Thermophilic Process
The Rockaway wastewater treatment plant, having a connected population
of 100,000, was chosen for a full-scale test. The plant employs conven-
tional facilities for the activated sludge process, and the sludge generated
undergoes mixed primary and secondary sludge thickening prior to mesophilic
887
-------
digestion. The digested sludge is transported to sea. As presently oper-
ated, the primary tanks provide a detention of about 2 hours; the aeration
tanks provide 3.3 hours, with step feed provisions; and the final tanks pro-
vide 3 to 5 hours of settling depending on the number in use. Two 45-ft.
diameter thickening tanks are used for mixed sludge thickening and the
mesophilic digestion is accomplished in a 1 cu.ft./capita tank.
For purposes of this test, the following steps were taken: (1) an
additional 1 cu.ft./capita digestion tank was placed in service to receive
the overflow sludge from the mesophilic digester and its contents heated up
to 120-122° F, the lower limit of the thermophilic digestion range;
(2) piping was installed to carry a portion of the overflow from the ther-
mophilic digester directly to a single 45-ft. diameter tank to be employed
as a rethickening and elutriating tank; (3) piping was installed to conduct
the remainder of the flow from the thermophilic digester into the primary
effluent and thereby directly into the aerator of the secondary treatment
system, and (4) city water was conducted to the elutriation tank. The ele-
ments of this new method of sludge processing therefore involved: (1) sub-
jecting the mesophilically digested sludge to subsequent thermophilic
digestion; (2) recirculating part of the sludge leaving the thermophilic
digester directly to and through the secondary treatment system; and
(3) subjecting the other part of the sludge leaving the thermophilic
digester to a rethickening and elutriation step.
The thermophilic digester was placed in operation in September 1979.
On January 15, 1980, the necessary piping additions were completed and on
that date the recirculation and rethickening elements of the new method
were brought into service.
Effect of Recirculation on Process Performance
At the time the full-scale test was started, the activated sludge had
a rather low sludge density index of 0.6 to 0.7. Microscopic examination
revealed a significant population of bacterial filaments along with
colonies of stalk ciliates and some rotifers. After the digested sludge
recirculation was in practice for only a few days, the sludge density index
was found to have risen to 1.0 and the bacterial filaments were found to
have diminished substantially. During the entire course of the following
test, the sludge density index continued to lie in the stable range of 1.0
to 1.4.
Since the flow received at the plant approximates 200 gals/capita/day,
the influent wastewater strength is low, averaging about 100 rag/leach of sus-
pended solids and BOD5. Prior to the test, the suspended solids and BOD5
in the effluent averaged about 12 and 12 mg/1, respectively. The monthly
treatment results for the prior period July to December 1979 are presented
in Table I, as well as the treatment results during the course of this test
run from January 15 through May 29, 1980, for comparative purposes. It can
be seen from these data that no significant effect on treatment efficiency
was experienced as a result of the continuous recirculation of digested
-------
Table I
Rockaway Wastewater Treatment Plant (WTP) Treatment Efficiency - July 1979 to May 1980
oo
oo
Month
July
August
September
October
November
December
Average Pre-Test
January (15-31)
February
March
April
May
Average Test
Flow
(M.G.D.)
22
22
23
25
22
21
21
19
23
27
29
Influent Wastewater
SS BOD5
(mg/1)
88
83
93
116
140
125
107
86
86
106
94
94
95
111
117
90
103
112
124
109
91
85
57
49
43
65
Final Effluent
SS BOD5
(mg/D
12
16
12
18
13
10
14
8
9
13
15
15
12
13
12
10
12
11
11
12
8
8
8
6
6
7
-------
sludge through the aeration system, at least during the first three
months. In the latter two months, suspended solids in the effluent did
increase by about 3 mg/1 with a substantial increase in flow rate from
about 20 M.G.D. to 27-29 M.G.D.
Nutrient Removal
In order to further evaluate whether the recirculation of digested
sludge through the secondary system had an adverse effect on effluent
quality, the data pertaining to the parameters nitrogen and phosphorus
shown in Table II. The effluent values are of special interest since the
raw wastewater samples did not contain the recirculating flow. Inspection
of the data for the two periods, pre-test and test, shows that the
total average inorganic N was 8.2 ppm vs. 9.6 ppm, respectively. Although
the individual months vary based on the period averages, inorganic nitrogen
shows an increase of 1.4 ppm in the effluent during the test period over
the pre-test period. On the other hand, the organic nitrogen showed a
decrease of 4.3 ppm. Phosphorous concentrations in the effluent remained
essentially unaffected when comparing the two periods. It would appear
that the digested sludge recirculation had a rather minor effect on the
effluent quality with respect to the nutrients nitrogen and phosphorus.
Heavy Metals Removal
The results of the monthly metal analyses of composite influent and
effluent samples for the pre-test period July to December 1979, and for the
test period January to May 1980, are presented in Table III. Comparing the
overall averages of these test periods and focusing on the two metals that
have been demonstrated to be able to exert a major effect on human physi-
ology, namely cadmium and mercury, there does not seem to be a significant
difference between the removals. In fact, the activated sludge process
does not appear capable of reducing appreciably the very low concentration
of either of these metals. It should also be pointed out that mass balance
studies of the metal data, except cadmium and mercury, have been generally
good. Because of the low concentrations of the metals cadmium and
mercury, and the sensitivity of the testing procedure, the mass balances
were not good. As to the other heavy metals, comparative inspection of the
data presented indicates some variable effects of treatment during individ-
ual months with the overall averages not significantly changed for the sub-
ject periods.
Effect of Recirculation on Oxygen Requirements
As to the influence of digested sludge recirculation on the dissolved
oxygen requirements, there was no change in air compressor output over the
course of the test. Unfortunately, the air compressor was operating at a
level to produce more than adequate dissolved oxygen and its rate could not
be lowered before or during the test to specifically attempt to evaluate
any demand changes. A calculated estimate, based on the fact that meso-
digestion (without the benefit of subsequent thermo-digestion) destroys 90%
890
-------
Table II '
Rockaway UTP Nutrient Concentrations Influent & Effluent
Month
July 78
August
September
October
November
oo December
i— »
Average
Pre-Test
January 80
February
March
April
May
Aver. Test
Feb. to May
N (mg/1)
NH -N Org.-N N03 N02
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
Infl.
Effl.
13.0
1.6
7.8
1.8
_ *
_ *
7.8
0.6
12.5
9.4
10.4
9.2
10.3
4.5
9.4
0.6
11.6
2.6
9.6
3.0
7.0
1.0
9.4
2.4
9.4
2.3
5.8
2.9
8.4
3.0
10.5
9.6
8.4
3.0
15.1
8.6
16.0
14.8
10.8
7.0
9.8
3.0
10.6
2.2
15.6
4.2
8.6
3.2
9.2
1.2
11.0
2.7
0
7.0
2.3
5.9
_ *
_ *
0
5.2
0.1
0.4
0.3
0.2
0.5
3.7
0.2
6.3
0.3
8.2
0.8
10.0
0.3
5.6
0.3
5.4
0.4
7.3
0
2.0
.5
.9
_ *
_ *
0
0.2
0.2
0.5
0
0
0
0.5
0.1
0
0
0
0
0.2
0
0
0
0
0
0
Total
Inorg. N
13.0
10.6
10.1
9.7
-
7.8
6.0
12.8
10.3
10.7
9.4
10.8
8.2
9.6
6.9
11.9
10.8
10.4
13.2
7.3
9.8
9.7
7.8
9.8
9.6
P
Total
2.3
1.8
2.5
2.1
2.5
2.1
2.0
1.2
2.7
1.6
1.8
1.6
2.4
1.7
2.7
1.8
2.8
1.7
3.9
2.0
2.9
2.4
2.5
2.0
3.0
2.0
(mg/1)
Ortho
1.7
1.8
1.8
1.4
1.1
1.7
1.4
1.2
1.9
1.2
3.5
3.0
1.9
1.7
1.6 Transition
1.5 Month
1.8
1.4
1.9
0.7
1.2
1.1
1.3
1.6
1.6
1.2
* Analytical results deleted
-------
Table III
Rockaway WTP Metal Data in (mg/1)
00
Cu
Cr
Ni
Zn
Pb
Fe
Cd
Ca
Mg
Hg
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
July
.11
.07
.001
.006
.07
.04
.11
.14
.017
.006
.8
.2
.0001
.0001
41.0
36.0
94.0
98.0
.0010
.0006 '
August
.11
.05
.020
.015
.02
.02
.26
.35
.024
.006
.9
1.0
.0001
.0001
40.0
48.0
107.0
112.0
.0007
.0006
1979
September
.13
—
.012
.008
.02
.01
.23
.16
.110
.006
1.5 1
.7 1
.0004
.0002
41.0 29
32.0 41
102.0 94
105.0 101
.0007
.0002
October
.13
.03
.009
.002
.01
.01
.09
.17
.014
.008
.5
.2
.0001
.0001
.0
.0
.0
.0
.0005
.0005
November
.16
.06
.011
—
.02
.02
.12
.15
.027
.020
1.6
2.0
.0010
.0015
19.0
20.0
85.0
88.0
.0026
.0028
December
.11
.05
.034
.007
.01
.02
.08
.08
.023
.007
1.1
.1
.0008
.0006
13.0
15.0
76.0
77.0
.0005
-.0009
Average
.12
.05
.014
.008
.03
.02
.15
.17
.036
.009
1.2
.9
.0004
.0004
30.0
32.0
93.0
97.0
.0010
.0009
-------
Table III (Continued)
Rockaway WTP Metal Data in (mg/1)
Cu
Cr
Ni
Zn
00
S pb
Fe
Cd
Ca
Mg
Hg
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
Inf.
Eff.
January
.095
.22
.0007
.0012
.015
.018
.066
.070
.014
.030
.57
1.00
.0018
.0005
14.0
14.0
70.0
72.0
.0009
.0011
February
.080
.0035
.0012
.001
.009
.021
.093
.086
.049
.0024
.65
.16
.0005
.0004
16.0
17.0
60.0
64.0
.0005
.0003
1980
March
.110
.0400
.0038
.003
.0042'
.0024
.090
.065
.0089
.0016
.55
.21
.0011
.0009
14.0
15.0
58.0
59.0
.0009
.0002
April
_____
.010
.005
.0068
.014
.21
.079
.0088
.0034
.84
.13
.0046
.0029
13.0
14.0
54.0
55.0
.0003
.0005
May
.075
.0380
.0038
.001
.0086
.011
.085
.10
.010
.0064
.83
.46
.0011
.0017
23.0
21.0
59.0
62.0
.0003
.0004
Average
February to May
.088
.027
.0047
.002
.0072
.012
.12
.082
.018
.0035
.72
.24
.0018
.0015
16.0
17.0
58.0
60.0
.0005
.0004
-------
of BOD5, indicates that the BODs of the part of the digested sludge
continuously recirculated would add less than 5% to the oxygen demand of
the primary effluent.
Operating Results
As was pointed out previously, a 1 cu. ft./capita tank was placed in
service as a thermo-digester at about 121° F. Its contents overflowed by
gravity to both the primary effluent and to a 45-ft. diameter rethickening
and elutriating tank where about 3:1 of city water was added to the
influent sludge. The rethickened underflow sludge was pumped by a duplex
plunger pump, actuated by time clock, to spare empty digesters where its
volumetric rate was measured by filling the tanks during the months of
March and April. Very importantly, such procedures did not involve the use
of any manpower except for periodically blowing back clogged lines.
The data obtained are presented in Table IV. Here it can be seen that
the volatile matter leaving the meso-digester averaged 9,000 Ibs./day, thus
effecting a reduction of 16,200-9,000 = 7,200 Ibs./day. The thermo-
digester accounted for a further reduction of 9,000-7,200 = 1,800 Ibs./
day. It should be pointed out that such reductions were being effected on
the combination of raw primary solids, activated sludge solids and the
recirculating solids that had been previously subjected to meso- and thermo-
digestion.
The conventional activated sludge treatment units are represented
in Figure 1. Since the economics of sludge disposal is fundamentally a
function of the amount of volatile material to be disposed of, only the
rates of production of volatile matter (V.M.) are discussed. In an over-
all sense, it can be seen that the reduction of volatile matter by the
meso-digester of 7,200 Ibs./day, added to 1,800 Ibs./day by the thermo-
digester, results in a total of 9,000 Ibs./day. Additionally the aerator
destroyed 2,000 Ibs. V.M./day for a total reduction of 11,000 Ibs. V.M./day.
Since the treatment system was removing a total of 12,900 Ibs. V.M./day, the
net amount requiring disposal was reduced to 1,900 Ibs. V.M./day. Previous
data show that the average amount of volatile matter carried to sea in the
period just prior to this work (thermo-digestion was being started in August
and September 1979) was 5,700 Ibs. Thus, the amount of volatile solids was
reduced by 5,700 - 1,900 = 2/3. Volume reduction was in the same proportion;
5,700
that is, 4,800 cu. ft./day to 1,650 cu. ft./day, or about 2/3.
The daily amount of gas generated during the entire course of the
thermo-digestion is shown in Table V. Based on the averages for the period
February to May, the meso-digester accounted for an 83,900 cu.ft./day rate,
slightly less than the comparable preceding period without digested sludge
recirculation through the aerator. The gas generated by the thermo-
digester increased from an average of 7,000 cu.ft./day to 14,000 cu.ft./day
894
-------
Table IV
Rockaway WTP Amount and Concentration of Solids Passing Through System!
00
VO
en
Month Flow
1980 MGD
Jan. 21
Feb . 19
Mar. 23
April 27
May 29
Average
Feb. to 25
May
#VSS
Capt. @
75% V.M.
10400
9500
14800
13400
14200
12900
Raw
Thick
Pump
Cu.ft./Day
5900
7300
8400
6500
8500
7700
%
Raw
Thick
3.9
3.6
3.3
3.5
3.0
3.4
Cone.
V.M.
Meso
Dig.
1.6
1.8
1.7
1.9
2.0
1.9
Thermo
Dig.
1.1
1.3
1.5
1.5
1.6
1.5
#V.M.
From
Thick.
14500
16500
17500
14500
16200
16200
#V.M./Day Leaving
Meso
Dig.
6000
8200
8900
8000
10800
9000
Thermo
Dig.
4100
5900
7800
6400
8600
7200
Rethickener &
Elutriator
Under Over
Flow Flow
-
-
1800 2
2000 2
1900
-
-
500
400
600
500
Note - (1) Calc. of V.M. inventory in digesters after February show the inventory change does not
significantly influence the data.
(2) Measured volume March 1600 cu. ft/day x 63 x 1.8% = 1800 # V.M./day
April 1700 cu. ft/day x 63 x 1.9% = 2000 // V.M./day
-------
00
VO
CM
Flow 20-29
•BOD5 85-110
SS 20-90
mgd
mg/1 BOD5 6-8 mg/1
mg/1 SS 8-15 mg/1
fj.ant
Plant Influent _ Primary _ Aeration ^ Final Effluent _
)
Figure 1
Rockaway Wast
Before Thermo
1 Sedimentation 1 Tank Clarification *~~
T i
1 w
1 , Return Sludge ^ f
^"'Waste
^^Vated Dilution Water
/ Mixed \ /MesophilicV /Thickenlnk
VThickening/ V 950 F / telutriation/ To Final
\^ y \^ / \ / Disposal
ewater Treatment Plant
philic Digestion Addition
-------
Table V
Rockaway WTP Daily Gas Production
oo
vo
Month
*
September 197?
October
November
December
Average No
Recirculation
January 1980
February
March
April
May
Average With
Recirculation
Feb. to May 1980
Mesophilic
Digester
cu. ft. /day
79200
93800
90300
77200
87600
79200
88000
86800
76400
84300
83900
Thermophilic
Digester
cu. ft. /day
5300
8200
6900
7500
7000
8500
12700
13600
11900
17700
14000
-------
during recirculation. The gas mixers in both digesters were found to be
causing the formation of large solids masses in the digesters with conse-
quent clogging of the overflow; it was found necessary to operate the
mixers only a few minutes per day to alleviate the condition.
Garber (6) in Los Angeles had determined that the thermo-digested
sludge required half the dose of iron coagulant and produced almost four
times the yield on a vacuum filter as meso-digested sludge. Accordingly,
to obtain some estimate of the improvement on coagulability achieved by the
use of the thermo-digestion in this instance, the meso- and thermo-digested
sludges were subjected to polymer treatment. It was found, on a laboratory
scale, that using a high-molecular-weight, low-charge polymer //2535CH (as
manufactured by American Cynamid), the coagulability improved radically.
Specifically, dosages of up to A,000 ppm on meso-digested sludge did not
produce an end point, although some flocculation was observed. In contrast,
the thermo-digested sludge released 73% of the water in 30 minutes in gravity
settling at a dose of 2,500 ppm. Thenao-digested sludge, after a 3:1 elutri-
ation, required a lesser comparative dose of 1,650 ppm of the same polymer
to release 64% of the water within 30 minutes in gravity settling.
Destruction of Pathogens
An effective way for the destruction of pathogenic organisms in sludge
is exposure to high temperature for an adequate period of time. Many
researchers have shown that the effectiveness of disinfection increases
with temperature or time. For example, Rudolfs et al. (1951)(7), using
Ascaris suum, found that:
at 45° C, 2 hours: had no effect
at 50° C, 30 minutes: retarded development
at 50° C, 2 hours: killed all ova
at 55° C, 10 minutes: killed all ova
Work by many others show similar findings with heat death of ascaris
eggs (8). Table VI also shows the effect of temperature and time on
other pathogenic organisms (11).
For the past several years, Garber and co-workers at the Hyperion
Treatment Plant in the City of Los Angeles have been operating a full-size
digester in the thermophilic temperature range of about 49 ° C, in parallel
with other digesters operating in the mesophilic temperature range of about
35° C (9). For approximately two years, in a cooperative program between
the Hyperion plant staff and the Municipal Environmental Research Labora-
tory (MERL), grab samples of raw, mesophilic and thermophilic sludges were
forwarded to MERL for pathogenic organisms analyses. A summary of the
analyses of bacteria is shown in Table VII (10). Thermophilic digester
treatment consistently reduced the Salmonella densities to below the
detectable limits of the analytical procedure, whereas Salmonella were
consistently detected after mesophilic digestion. The density of the
indicator organisms was reduced 2 to 3 logs more than was the case for
898
-------
00
VO
IO
Table VI
Temperature and Time for Pathogen Destruction in Sludges
Exposure Time (Minutes) for Destruction
at Various Temperatures ( C)
Microorganisms
Cysts of Entamoeba histolytica
Eggs of Ascaris lumbricoides
Brucella abortus
Corynebacterium diphtheriae
Salmonella typhi
Escherichia coli
Micrococcus pyogenes var. aureus
Mycobacterium tuberculosis var.
Viruses
50°'C 55° C 60° C 65° C 70° C
, 5
60 7
60 3
45 4
30 4
60 5
20
20
25
-------
Table VII
Reduction in Bacterial Densities in Mesophilic and Thermophilic Anaerobic
Digestion (20-day detention)
Bacterial Densities (number/100 ml)*
o
o
Fecal Streptococcus
Fecal Coliform
Total Coliform
Salmonella
Raw Sludge Mesophilic
Feed Digestion
(36° C)
2.7 x 107 2.0 x 106
3.6 x 108 5.5 x 106
5.2 x 109 7.0 x 107
7530 62
Thermophilic
Digestion
(50° C)
3.7 x 104
2.9 x 104
6.4 x 104
BDL
NOTE: BDL - Below detection limits (< 3/100 ml)
*Average of measurements taken over 2-year period
-------
mesophilic digestion by thermophilic digestion. Mesophilic digestion
reduced the density of Salmonella by 2 logs and indicator organisms
1 to 2 logs, as compared to raw sludge.
Twelve sets of animal enteric virus analyses were conducted over the
2-year period (10). Test results are as follows:
PFU/GRAM OF LIQUID SLUDGE
TYPE OF SLUDGE (2 to 5% SOLIDS)
Raw 25.40
Mesophilic Digested 2.10
Thermophilic Digested 0.03
Thermophilic digestion produced a 2-log improvement over mesophilic
digestion. In fact, viruses were not detected in 6 out of the 12
samples analyzed. Based on the limited data, there was essentially
no effect on Ascaris lumbricoides concentrations in either type of
digester treatment. The findings are in conflict with the reported
reasons for using the thermophilic process in the U.S.S.R. Popova and
Bolotina (5), in their report on the practice of thermo-digestion in
Moscow, state "The most essential advantge of this process is the sanitary
quality of the thermophilic sludge. According to the sanitary officials
of the health department, Viable eggs of helminths are absesnt from such
sludge."
The Moscow and Los Angeles data agree on the degree of viral and
bacterial destruction but differ in the effect on helminths. Note, how-
ever, that the Los Angeles digester was operated at 49°C and Rudolph's
results indicate that temperature is very important in hulminth destruction.
It appears then that operation of the thermophilic stage slightly in excess
of 50°C would produce a sludge that is hygienically safe for disposal.
Potential Process Applications
Since the 1980 EPA Municipal Wastewatear Facilities Construction
Need Survey showed that there will be over 4,200 municipal treatment plants
utilizing anaerobic sludge digestion by 1986, the EPA Office of Research
and Development initiated a separate study (12) that investigated the
feasibility of applying meso-thermophilic digestion to a major treatment
facility. The District of Columbia Blue Plains treatment plant was selected
because it had anaerobic digesters in operation and the sludge management
methodology needed upgrading for operating and economic reasons.
Based on review of the anaerobic sludge digestion options and how
they could be adapted to the existing facilities, the study recommends that
the thermophilic anaerobic digestion process be implemented on a full-scale
basis. This recommendation is based on a thorough review of the present
state of practice in the United States and other countries.
901
-------
Although the meso-thermophillc digestion process could be the optimum
solution for other plants, the thermophilic process is recommended for Blue
Plains because it could be implemented with a miniunum of time and money.
Other significant advantages are: (1) increased sludge processing capa-
bility; (2) improved sludge dewatering as to coagulant demand and yield;
and (3) increased destruction of pathogens, all of which are pertinent to
the needs of the Blue Plains plant.
It is especially important to check the structural competency of the
existing digesters and piping at the thermophilic temperatures, as well as
the temperature control system prior to start-up.
A carefully formulated transition plan should be prepared so that
the transition can be carried out effectively and with minimum interference
with plant operations.
DISCUSSION
It has been noted in the literature that the thermophilic digestion
process, by itself, presents a problem in that an excessively long period
of 6 to 12 months may be required to achieve a satisfactory operating per-
formance. This required long period of adaptation of the biological species
to the hostile high temperature environment interferes with plant operation
and is costly in economic terms. Therefore, to reduce substantially this
time period, it becomes mandatory to effectively seed thermophilic digesters.
In the case of meso followed by thermo, it is less critical that the thermo-
philic digester promptly achieve satisfactory performance. Consequently, it
is elective to seed the thermo digester to expedite the operating performance
at a satisfactory level.
The reader is cautioned that each plant will have a maximum upper
limit of the amount of digested sludge that can be recirculated. It
should be pointed out that the proportion of digested sludge recirculated
continuously through the secondary treatment system should lie in the range
of 30% - 60%. Moreover, operation should generally be conducted in the
lower part of this range at wastewater temperatures near 75° F, and in
the higher part of this range at temperatures near 55° F.
SUMMARY
A full plant-scale test was conducted at the Rockaway Plant in
New York City with a connected population of 100,000 for a period of
5 months to evaluate a new method of reducing the amount and volume of
sludge produced from the activated sludge process. This method involved
the novel use of: (1) high stability thermophilic digestion following
mesophilic digestion and (2) the recirculation of a portion of such
thermo-digested sludge directly to and through the secondary system
902
-------
of the activated sludge process while the remainder was conducted to
a rethickening and elutriation step. Operating results have demon-
strated that the volatile matter normally transported to sea after
meso-digestion was reduced by 2/3. Moreover, the volume of sludge
produced was lowered by 2/3 without chemical or mechanical aids.
It was determined on a laboratory scale that the residual solids
exhibited improved coagulability having undergone thermo-digestion,
which change would improve the economics of all subsequent dewater-
ing processes. The treatment process performed without significant
adverse effect on any accepted parameter due to the continuing re-
circulation of digested sludge through the activated sludge process.
903
-------
REFERENCES
1. Kraus, L.S., "Digested Sludge - An Aid to the Activated Sludge
Process," ibid., Vol. 18, No. 6, p. 1099 (Nov. 1946).
2. Buhr, H.O. and J.F. Andrews, "Review Paper: The Thermophilic
Anaerobic Digestion Process," Water Research, 11, 129-143 (1977).
3. Rimkus, R.R., J.M. Ryan, and E.J. Cook, "Full Scale Thermophilic
Digestion at the West-Southwest Sewage Treatment Works," Paper pre-
sented at the Annual Water Pollution Control Federation Conference,
Las Vegas (October 1980).
4. Smart, J. and B.I. Boyko, Full Scale Studies on the Thermophilic
Anaerobic Digestion Process, Report No. 59, Ontario Ministry of the
Environment, Toronto (1977).
5. Popova, N.M. and O.T. Bolotina, "The Present State of Purification of
Town Sewage and the Trend in Research Work in the City of Moscow,"
Advances in Water Pollution Research, Vol. 2 (W.W. Eckenfelder, ed.).,
MacMillan Co., New York (1964).
6. Garber, W.F., G.T. Ohara, S.K. Raksit, and D.R. Olson, "Studies of
Dewatering Anaerobically Digested Wastewater Solids at the Hyperion
Treatment Plant," Progress in Water Technology, 8_, No. 6, 371-378
(1977).
7. Rudolfs, W., L.L. Falk, and R.A. Rogotzkie, "Contamination of
vegetables grown in polluted soil: V helminthic decontamination,"
Sewage Ind. Waste, 23:853-860 (1951).
8. Graham, H.J., "Parasites and the Land Application of Sewage Sludge,"
Research Report No. 110, p. 10-11, Ontario Ministry of the Environ-
ment, Toronto (1981).
9. Ohara, G.T. and J.E. Colbaugh, "A Summary of Observations in Ther-
mophilic Digester Operations," Proc. of the 1975 National Conference
on Municipal Sludge Management and Disposal, Anaheim, California,
August 18-20, 1975, pp. 218-222. Available from Information Transfer,
Inc., 1160 Rockville Pike, Rockville, Maryland 20852.
10. Farrell, J.B. and G. Stern, "Sludge Disinfection Techniques," Proc. of
the National Conference on Composting of Municipal Residues and
Sludges, (1977), pp. 142-153. Available from Information Transfer,
Inc., 1160 Rockville Pike, Rockville, Maryland 20852. Library of
Congress Catalog No. 77-94492.
904
-------
11. Roediger, H., "The Technique of Sewage-Sludge Pasteurization: Actual
Results Obtained in Existing Plant," International Research Group on
Refuse Disposal (IRGRD), Information Bulletin Nos. 21-31, August 1964
- December 1967, pp. 330-340.
12. Torpey, W.N., J.L. Andrews, and N.A. Mignone, "Evaluation of the
Full-Scale Application of Anaerobic Sludge Digestion at the Blue
Plains Wastewater Treatment Facility - Washington, D.C.," EPA Project
Summary 600/52-81-105, July 1981; Complete Report Available from
National Technical Information Service, Springfield, Virginia 22161
(Order No. PB 81-219-123).
905
-------
-------
RESEARCH SUPPORTED BY THE NATIONAL SCIENCE FOUNDATION RELATING TO TREATMENT
OF WASTEWATER AND MANAGEMENT OF RESIDUAL SLUDGES
Edward H. Bryan
National Science Foundation
Washington, D. C.
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
Prepared for Presentation at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Washington, D.C.
907
-------
RESEARCH SUPPORTED BY THE NATIONAL SCIENCE FOUNDATION RELATING TO TREATMENT
OF WASTEWATER AND MANAGEMENT OF RESIDUAL SLUDGES
Edward H. Bryan
National Science Foundation
Washington, D.C.
ABSTRACT
Scientific research has played an important role in development of our
present understanding of all matters relating to management of water. This
knowledge has been applied by engineers in solving problems of availability,
quality, treatment, and use of water and in treatment of wastewater for reuse
of discharge to minimize adverse environmental impacts. The roles of science
and engineering as they relate to management of water are becoming progres-
sively more important as pressures mount for its more intensive use.
Since its establishment in 1950 as an independent agency of the Executive
Branch of the Federal Government, the National Science Foundation (NSF) has
provided support for research to broaden the base of understanding on topics
directly and indirectly relating to management of wastewater. Between 1973
and 1981, NSF supplied substantial support for research on innovations in
management of sludges and in using wetlands to provide a degree of treatment
equivalent to that obtained through capital and energy-intensive, physical,
and chemical advanced (tertiary) treatment processes.
Wetlands have been shown to be potentially capable of absorbing the
nutrient load from conventional secondary treatment processes without adverse,
short-term effects. Full-scale use of a wetland for placement of a secondary
effluent is currently in its fourth year of operation and evaluation at
Houghton Lake, Michigan.
The combined capacity of two installations for disinfection of sludges
using energized electrons in the United States, will be 300,000 gallons per
day with scheduled completion of the unit at Miami, Florida, in 1981. The
concept of combining disinfection of sludges by use of energized electrons,
pipeline transport, and direct injection into topsoil on land dedicated to
use for stabilization of sludges appears to be a promising new approach to
management of sludges.
Dr. Edward H. Bryan is Program Director, Water Resources and Environ-
mental Engineering in the Engineering Directorate's Division of Civil and
Environmental Engineering. His prior program management responsibilities
since joining the National Science Foundation in 1972 have included Regional
Environmental Systems, Systems Integration and Analysis, Regional Environ-
mental Management, Community Water Management and Appropriate Technology.
908
-------
INTRODUCTION
In 1973, the National Science Foundation (NSF) began supporting research
on problems that had regional significance with regard to their potential
adverse environmental impact. One concerned the pollutional impact of
effluents from secondary wastewater treatment plants on receiving waters from
nutrients remaining in the effluent. Another concerned the currently large
and rapidly growing problem of managing sludges produced during treatment of
wastewater. A common factor linking these two interrelated problems was a
desire to find solutions that were less capital and energy intensive than
conventional physical, chemical, and biological methods.
INNOVATION IN SLUDGE MANAGEMENT
The context within which NSF's support of research on sludge management
started in 1974 was the projected increase in the amounts of sludge resulting
from implementation of new water pollution control legislation and imminent
foreclosure of ocean placement and incineration as options for dealing with
sludges. NSF's program sought a better understanding of the basic elements
that comprise all systems for processing sludges as a step toward a new
concept that would be more efficient and acceptable than simple refinement
of current practices (1).
The approach that NSF's program took was strongly influenced by results
from the initial project (2). Investigators at the University of Texas found
that during conventional treatment of wastewater, most of the viruses were
concentrated in sludges where they remained viable during subsequent process-
ing. When these sludges were incorporated into soil, viruses were adsorbed
on soil particles, remained viable for long periods of time* and were capable
of being released under conditions simulating rainfall. These findings
suggested that disinfection of sludges might become an essential pretreatment
step for infected sludges that would be managed by placement on land, and the
need for a transport and placement method that would minimize the risk and
nuisance associated with processing, transporting, and application of sludge
to land.
Since 1974, NSF's allocation in support of research directly relating
to sludge management totalled about $4 million. The interdisciplinary
nature of this problem and the diversity of issues that were addressed is
evident from the summaries in Tables 1 and 2. Research personnel from
more than 20 public and private institutions and organizations participated
in this effort and over 150 reviewers were consulted in evaluating the
unsolicited proposals that led to actions necessary to sustain this effort.
The cost of sludge management is directly proportional to the amount
produced. An initial logical step to minimize cost of sludge management would
be to select treatment processes for wastewater that minimize production of
sludges, consistent with other treatment objectives. The quality of sludges
also affects the cost of additional processing and management. Regulation of
industrial discharges into the collection system to limit or prohibit entry
of heavy metals and toxic organic compounds is likely to be more
909
-------
TABLE 1- RESEARCH SUPPORTED st THE NATIONAL SCIENCE FOUNDATION APPLIED TO MANAGEMENT of SLUDGES DERIVED FROM TREATMENT OF MUNICIPAL WASTEWATER
Ha-
1.
2-
j.
1.
5.
b-
7.
8.
9.
10.
11.
12.
13-
11.
15.
16.
17.
18.
19.
20.
21-
22.
23.
21.
INVESTIGATOR
BERNARD P. SAG IK
JAMES L- SMITH
JOHN G. TRUMP
EDWARD G- MERRILL
ANTHONY SINSKEV
THEODORE G. METCALF
RICHARD I. DICK
KOY HARTENSTEIN
MARY BETH KIRKHAM
WILLIAM J. MANNING
P.C- CHEO
C- FRED GURNHAM
JACK E- COLLIER
STEPHEN C. HAVLICEK
ROBERT S- INGOLS
GEORGE D- WARD
CHARLES FINANCE
ROGER BLOBAUM
STEPHEN J- MARCUS
LEON W. WEINBERGER
ROBERT W. KAUFMAN
CLARENCE GOLUEKE
ROGER HAAG
GEORGE 0- HARD
GEORGE D- WARD
ROY HARTENSTEIN
JAMES E. ALLEMAN
MARY BETH KIRKHAM
l2fJ£S_, .
DISCIPLINE
MICROBIOLOGY
AGRICULTURAL ENGINEERING
ELECTRICAL ENGINEERING
CHEMICAL ENGINEERING
NUTRITION/FOOD SCIENCE
MICROBIOLOGY
CIVIL ENGINEERING
INVERTEBRATE ZOOLOGY
AGRONOMY
PLANT PATHOLOGY
PLANT PATHOLOGY
CHEMICAL ENGINEERING
INDUSTRIAL ENGINEERING
ORGANIC CHEMISTRY
BIOLOGY
CIVIL ENGINEERING
FILM PRODUCTION
COMMUNICATIONS
ENGINEERING
SANITARY ENGINEERING
POLITICAL SCIENCE
ENVIRONMENTAL ENGINEERING
CIVIL ENGINEERING
CIVIL ENGINEERING
CIVIL ENGINEERING
INVERTEBRATE ZOOLOGY
CIVIL ENGINEERING
AGRONOMY
INSTITUTIONS. INVESTIGATORS AND THEIR DISCIPLINES
INSTITUTION
UNIVERSITY OF TEXAS
SAN ANTONIO, TEXAS
COLORADO STATE UNIVERSITY
FORT COLLINS, COLORADO
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE, MASSACHUSETTS
UNIVERSITY OF NEW HAMPSHIRE
DURHAM, NEW HAMPSHIRE
UNIVERSITY OF DELAWARE INITIALLY, THEN
CORNELL UNIVERSITY, ITHACA, NEW YORK
STATE UNIVERSITY OF NEW YORK
SYRACUSE, NEW YORK
OKLAHOMA STATE UNIVERSITY, STILLWATER
UNIVERSITY OF MASSACHUSETTS, AMHERST
(WALTHAM FIELD STATION)
CALIFORNIA ARBORETUM FOUNDATION, Los
ANGELES ARBORETUM, ARCADIA, CALIFORNIA
GURNHAM AND ASSOCIATES, INC.
CHICAGO, ILLINOIS
COLLIER EARTHWORM COMPOSTING SYSTEMS,
INC., SANTA CLARA, CALIFORNIA
GEORGIA INSTITUTE OF TECHNOLOGY
ATLANTA, GEORGIA
GEORGE D- WARD AND ASSOCIATES
PORTLAND, OREGON
MEDIA FOUR PRODUCTIONS, INC.
HOLLYWOOD, CALIFORNIA
KOGER BLOBAUM AND ASSOCIATES
DES MOINES, IOWA
ENERGY RESOURCES COMPANY, INC.
CAMBRIDGE, MASSACHUSETTS
ENVIRONMENTAL QUALITY SYSTEMS, INC.
KOCKVILLE, MARYLAND
WESTERN MICHIGAN UNIVERSITY
KALAMAZOO, MICHIGAN
CAL RECOVERY SYSTEMS, INC.
RICHMOND, CALIFORNIA
KICKEL MANUFACTURING CORPORATION
SALINA, KANSAS
GEORGE D- WARD AND ASSOCIATES
PORTLAND, OREGON
GEORGE D. WARD AND ASSOCIATES
PORTLAND, OREGON
STATE UNIVERSITY OF NEW YORK
SYRACUSE, NEW YORK
UNIVERSITY OF MARYLAND
COLLEGE PARK, MARYLAND
KANSAS STATE UNIVERSITY
SUBJECT OF RESEARCH - TITLE OF PROJECT
POTENTIAL HEALTH RISKS ASSOCIATED WITH INJECTION OF
DOMESTIC WASTEWATER TREATMENT PLANT SLUDGES INTO
SOIL
MANAGEMENT OF SUBSURFACE INJECTION OF WASTEWATER
TREATMENT PLANT SLUDGES INTO TOPSOIL
DISINFECTION OF MUNICIPAL WASTEWATER TREATMENT
PLANT SLUDGES BY USE OF HIGH ENERGY ELECTRONS
INACTIVATION OF ENTERIC VIRUSES IN MUNICIPAL
WASTEWATER SLUDGES BY USE OF ENERGIZED ELECTRONS
PROCESS INTEGRATION FOR OPTIMAL MANAGEMENT OF
SLUDGES DERIVED FROM TREATMENT OF MUNICIPAL
WASTEWATER
STABILIZATION OF DOMESTIC WASTEWATER TREATMENT
PLANT SLUDGES BY SOIL INVERTEBRATES
AGRICULTURAL VALUE OF MUNICIPAL WASTEWATER
TREATMENT PLANT SLUDGES IRRADIATED WITH
ENERGIZED ELECTRONS
MECHANISMS OF PLANT VIRUS INACTIVATION IN SOILS
INJECTED WITH MUNICIPAL WASTEWATER AND SLUDGES
SOURCES AND CONTROL OF HEAVY METALS IN MUNICIPAL
WASTEWATER TREATMENT PLANT SLUDGES
CONVERSION OF MUNICIPAL WASTEWATER TREATMENT PLANT
SLUDGES INTO EARTHWORM CASTINGS FOR AMENDMENT OF
SOIL
EFFECT OF INFRARED RADIATION ON COMPACTION OF
MUNICIPAL WASTEWATER SLUDGES
CONTROLLED SOIL MICROBIAL DETOXIFICATION OF PHENOXY
HERBICIDE RESIDUES
SYNTHESIS OF A SYSTEM FOR MANAGEMENT OF MUNICIPAL
WASTEWATER TREATMENT PLANT SLUDGES, A 16 MM FILM
BASED ON RESEARCH IN ABOVE-LISTED PROJECTS (1) -
(6), INCLUSIVE
AN ASSESSMENT OF THE POTENTIAL FOR APPLYING URBAN
WASTES TO AGRICULTURAL LAND
PUBLIC HEALTH AND NUISANCE ASPECTS OF COMMUNITY
WASTEWATER SLUDGE MANAGEMENT
PREDICTION AND CONTROL OF HEAW METALS AND Toxic
ORGANIC SUBSTANCES IN MUNICIPAL SLUDGES
WORKSHOP ON THE ROLE OF EARTHWORMS IN STABILIZATION
OF ORGANIC RESIDUALS FROM DOMESTIC AND INDUSTRIAL
SOURCES
BENEFITS AND PROBLEMS OF COMPOSTING MIXTURES OF
MUNICIPAL SLUDGES AND SOLID HASTES
AGRICULTURAL UTILIZATION OF SLUDGES Dt <;VED FROM
TREATMENT OF COMMUNITY WASTEWATER
SUSCEPTIBILITY OF Mr. ST. HELEN'S VOLCANIC ASH TO
STABILIZATION BY USE OF ORGANIC SLUDGES
ELIMINATION OF SEPTIC TANK SLUDGE TRANSPORT BY
MANAGEMENT ON SITE OF ITS PRODUCTION
EARTHWORM-MICROBIAL INTERACTIONS DURING
STABILIZATION OF ORGANIC WASTES FOR RECOVERY OF
THEIR RESOURCE VALUES
BENEFICAL USE OF SLUDGES IN PRODUCTION OF BUILDING
COMPONENTS
PRODUCTIVITY OF LAND AND QUALITY OF WHEAT GROWN
25. RAYMOND C. LOEHR
EDWARD F. NEUHAUSER
MANHATTAN, KANSAS
CIVIL/SANITARY ENGINEERING CORNELL UNIVERSITY
SOIL BIOLOGY ITHACA, NEW YORK
USING SLUDGES AS ORGANIC SOURCES OF PLANT NUTRIENTS
STABILIZATION OF ORGANIC RESIDUES DERIVED FROM
TREATMENT OF SELECTED INDUSTRIAL AND MUNICIPAL
WASTES
910
-------
TABLE I- SUMMARY 2£ AWARDS £X 1UI NATIONAL SCIENCE FOUNDATION in SUPPORT JJE RESEARCH m SjjjpjiE. MANAGEMENT. FISCAL YEARS 12Z2 - 128J.1
FISCAL YEAR OF AWARDS - AMOUNTS ARE IN THOUSANDS OF DOLI
No- INSTITUTION (PRINCIPAL INVESTIGATOR)
!• UNIVERSITY OF TEXAS (BERNARD P. SAGIK)
2- COLORADO STATE UNIVERSITY (JAMES L- SMITH)
3. MASSACHUSETTS INSTITUTE OF TECHNOLOGY
(JOHN G- TRUMP)
4. UNIVERSITY OF NEW HAMPSHIRE
(THEODORE G- METCALF)
5. UNIVERSITY OF DELAWARE AND CORNELL UNIVERSITY
(RICHARD 1. DlCK)
b- STATE UNIVERSITY OF NEW YORK - SYRACUSE
(RoY HARTENSTEIN)
7. OKLAHOMA STATE UNIVERSITY (MARY BETH KIRKHAM)
UNIVERSITY OF MASSACHUSETTS (WILLIAM J. MANNING)
8- Los ANGELES ARBORETUM FOUNDATION. (P-C. CHEO)
9< GURNHAM S ASSOCIATES, INC- (C- FRED GURNHAM)
10. COLLIER EARTHWORM COMPOSTING SYSTEMS, INC.
(JACK E. COLLIER)
11- GEORGIA INSTITUTE OF TECHNOLOGY
(STEPHEN C- HAVLICEK AND ROBERT S. INGOLS)
12. GEORGE D. WARD & ASSOCIATES (GEORGE D- WARD)
13- MEDIA FOUR PRODUCTIONS (CHARLES FINANCE)
14- ROGER BLOBAUM 8 ASSOCIATES (ROGER BLOBAUM)
15. ENERGY RESOURCES COMPANY, INC. (STEVEN MARCUS)
16. ENVIRONMENTAL QUALITY SYSTEMS, INC-
(LEON W. WEINBERGER)
17. WESTERN MICHIGAN UNIVERSITY (ROBERT KAUFMAN)
18- CAL RECOVERY SYSTEMS, INC- (CLARENCE GOLUEKE)
19. RICKEL MANUFACTURING CORPORATION (ROGER HAAG)
20. GEORGE D. WARD & ASSOCIATES (GEORGE D. WARD)
21. GEORGE D- WARD & ASSOCIATES (GEORGE D. WARD)
22- STATE UNIVERSITY OF NEW YORK - SYRACUSE
(ROY HARTENSTEIN)
23. UNIVERSITY OF MARYLAND (JAMES E- ALLEMAN)
24. KANSAS STATE UNIVERSITY (MARY BETH KIRKHAM)
25- CORNELL UNIVERSITY
(RAYMOND C. LOEHR AND EDWARD F. NEUHAUSER)
TOTALS
1972/73 1971 1975 1978
263-0 - 58-9 72-4
51-0 68-9 86-1
113-7 198-0 200.0
70.
43-0
59.1
40.7
65-0
88.5
19/7 1978 1979 198.1L _1J8J_ JJUAL.
89.2 87.5 - - - 571-0
15.4 - 221.4
285-0 27.2 90-0 - - 983.9
35.0
111.7
87.8
39.0
110.9
9-7
21.9
25.0
49.6
92.13
17-0
77-2 77.8
150-7 90-0
37.8
15.6
183.4
2-8
126-4
201-4 123-2
- 43.9"
19.6
25-0
11.75
24./5
73.85
41.15
63- 85
180.
135-/
279.1
440-9
87-8
76.8
110.9
25.?
21-9
208-4
52-4
92-1
126.4
324-6
48-?
19-6
25-0
11-7
24.7
7J.8
.1.1
63.8
180-0
16177
ALL AWARDS LISTED WERE MADE FROM THE WASTE MANAGEMENT STRATEGIES AND RESIDUALS MANAGEMENT ELEMENTS OF PROGRAMS IN REGIONAL
ENVIRONMENTAL SYSTEMS/MANAGEMENT AND COMMUNITY WATER MANAGEMENT EXCEPT AS NOTED IN ITEMS 2, 3, 4 AND 5, BELOW-
2
MNTERAGENCY TRANSFER OF FUNDS FROM THE U-S- ENVIRONMENTAL PROTECTION AGENCY'S MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY,
CINCINNATI, OHIO- ,
RESOURCE SYSTEMS PROGRAM, DIVISION OF. ADVANCED ENERGY AND RESOURCES RESEARCH AND TECHNOLOGY, NATIONAL SCIENCE FOUNDATION-
OFFICE OF PROBLEM ANALYSIS, DIRECTORATE FOR ENGINEERING AND APPLIED SCIENCE IN SUPPORT OF PLANNING FOR A PROGRAM IN APPROPRIATE
TECHNOLOGY-
PROGRAM IN APPROPRIATE TECHNOLOGY, NATIONAL SCIENCE FOUNDATION.
911
-------
efficient in improving the quality of sludges in that respect than subsequent
detoxification. However, the presence of unstabilized organic matter and
pathogenic bacteria, protozoa, viruses and intestinal parasites is an inherent
characteristic of all wastewaters derived from or associated with human con-
tacts. All sludge processing and management systems address common issues of
disinfection, detoxification, stabilization, transport and final placement.
The most efficient total system is the one that minimizes costs of achieving
acceptable resolution of these issues, consistent with the effect on treat-
ment operations with which it must be integrated.
The concept that emerged from the NSF program pointed toward disinfection
by use of energized electrons, pipeline-transport to a suitable land appli-
cation site where the sludge would be injected into topsoil for stabilization
under carefully controlled conditions as having the attribute of minimum •
total cost. The advantages of this concept beyond those directly associated
with elimination of costly dewatering processes and other capital and energy-
intensive manipulations include:
• Retention of the nutrient values that are lost during processing
by digestion, composting and other treatment procedures.
• Elimination of conditioning agents and their residuals as
potential contaminants of the final product.
• Elimination of construction and operating costs associated with
plant capacity no longer needed to accommodate strong and process-
disruptive return-flows from thickeners, digesters, elutriation
devices, ash pits, drying beds, centrifuges, vacuum filters and
similar equipment.
The concept of coupling electron-beam disinfection with direct injection of
sludges into topsoil was portrayed in a brief 16mm film entitled: "New
Concepts in Sludge Management" (3). A more comprehensive film was also
produced for use in briefing potential participants in a planned large-scale
experiment to study those attributes of the integrated concept that were
necessary to understand sufficiently to permit their use in engineering desigi
of full-scale systems (4). In addition, a preliminary step was taken to
design the experiment itself as a basis for estimating its potential cost (5).
Research to determine the role of soil invertebrates in stabilizing
sludge led to new insights into the nature of stability as the concept is
used to characterize sludges (6). Studies initiated to provide background
for determining the effect of high-energy electrons on chlorinated hydro-
carbons in sludges led to the observation of the complete destruction of a
herbicide (monuron) and two polychlorinated biphenyls (3,4,2'-trichlorobi-
phenyl and 4-chlorobiphenyl) in water solutions (7).
Two recent publications summarized progress toward implementation of
large-scale disinfection of sludges by use of energized electrons (8) (9).
The 170,000 gallon per day unit currently under construction at the Miami-
Bade Water and Sewer Authority's Wastewater Treatment Plant on Virginia Key
in Florida is expected to be operational during 1981, providing disinfection
912
-------
capability for one-fourth of the plant's production of sludge. The original
unit used for the NSF-supported research at the Metropolitan District
Commission's Deer Island Wastewater Treatment Plant in Boston was recently
modified by the High Voltage Engineering Corporation, expanding its nominal
capacity from the original 100,000 gallons per day to 170,000. This unit is
currently operational and was used to refine the engineering design for the
Florida installation.
WETLANDS FOR WASTEWATER MANAGEMENT
Complementary to research on management of sludges from primary and
secondary treatment processes for wastewater, the National Science Foundation
has been supporting research to better understand the potential role that
wetlands can play in managing both the water and nutrients contained in
effluents from conventional secondary treatment processes. While placement
of a wastewater that had been freed of its demand for oxygen but which was
rich in nutrients into a wetland appeared to have only desirable consequences
of increasing the wetland1s productivity, questions remained as to potential
negative effects of this practice on the wetland ecosystem (10).
Ecosystem models constructed during the initial two years of a study in-
volving potential application of a secondary effluent to a peat wetland near
Houghton Lake, Michigan (11) (12), led to a two-year pilot-scale evaluation of
the concept (13). Results of that study were sufficiently encouraging to in-
itiate the full-scale placement of effluents from the Houghton Lake commun-
ity's secondary oxidation pond of the 2000-acre wetland. The wetland is so
large in comparison to the load imposed on it that nutrient-removal has been
observed to be virtually complete within 100 meters from the line of entry.
A 20-year monitoring program was established by the Houghton Lake community
to determine any changes in the biota of the wetland attributable to its use
for wastewater management. Initial results (14 (15) (16) (17) have been
utilized to guide formulation of engineering design criteria for further
application of this concept (18). A wetland that emerged upon failure of a
land-application system to fully absorb wastewater placed on it has also been
studied to provide guidance for potential use of the "wetland-concept" by
communities lacking nearby natural wetlands (19).
In Florida, extensive studies have been conducted on cypress dome wet-
lands near Gainesville (20) (21) (22) and on a cypress stand wetland ne,,.r
Jasper (23) to characterize both seepage and flow-through type wetlands for
their potential role in conserving nutrients and renovating wastewater. Over
a six-year period, a test dome received the effluent from a small, activated
sludge treatment plant serving a trailer park. Studies included effects on
local groundwater quality, tree-growth rate, seedling germination, mosquito
population and the survival characteristics and mobility of viruses. Hydro-
logical characteristics, concepts of site management and characterization of
the wetland's metabolism were studied and related to potential general use of
this concept in Florida. Studies at the Jasper site, which has received
wastewater varying in degrees of prior treatment over a period of 60 years,
are expected to provide insights into long-range effects of using wetlands
for treatment of wastewater.
913
-------
TABLE ?• SUMMARY at AWARDS MADE 12 SUPPORT RESEARCH JH£ PROGRAM DESCRIBED m IHE FILM; "WETLANDS, - OUR NATURAL PARTNERS in WASTEWATEB MANAGEMENT*
TITLE OF THE PROJECT NSF PROGRAM AND PROGRAM MANAGER
FISCAL
YEAR
1971/72
1973
19/3
1971
1975
19/5
1976
1976
1976
1976
TO
1976
TQ
1977
1977
1978
1978
1978
1978
1978
1979
1979
1979
1980
I960
1980
INSTITUTION AND PRINCIPAL INVESTIGATOR AMOUNT OF AWARD
(GRANT NUMBER) AND DURATION
UNIVERSITY OF MICHIGAN, JOHN A. KADLEC $133,550 FOR
(61 34812) 12 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T- ODUM
(GI 37821)
$321,700 FOR
24 MONTHS
UNIVERSITY OF MICHIGAN, JOHN A. KADLEC $128,700 FOR
AND ROBERT H- KADLEC (GI 34812) 12 MONTHS
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $131,800 FOR
(61 34812) 12 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T. ODUM
(ENV 73-0/823)
$223,000 FOR
12 MONTHS
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $110,000 FOR
(ENV 75-08855) 12 MONTHS
WILLIAMS 8 WORKS, JEFFREY C- SUTHERLAND
(ENV 76-20812)'
$31,200 FOR
7 MONTHS
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $129,900 FOR
(ENV 75-08855) 16 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T- ODUM $223,600 FOR
(ENV 73-07823) 12 MONTHS
BOYLE ENGINEERING Co-, WALTER R. FRITZ $43,'700 FOR
(ENV 76-23276) 12 MONTHS
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $43,500 FOR
(ENV 75-08855) 4 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T. ODUM $91,500 FOR
(ENV 77-06013) 21 MONTHS
WILLIAMS 8 WORKS, JEFFREY C- SUTHERLAND $6,100 FOR
(ENV 76-20812) 1 MONTHS
BOYLE ENGINEERING Co., WALTER R. FRITZ $163,759 FOR
(PFR 78-19199) 21 MONTHS
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $111,711 FOR
(ENV 77-23868) 12 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T. ODUM $20,800 FOR
(PFR 77-06013) 0 MONTHS
WILLIAMS & WORKS, JEFFREY C. SUTHERLAND $85,103 FOR
(PFR 77-20273) 19 MONTHS
FLORIDA, STATE DEPARTMENT OF HEALTH AND $18,072 FOR
REHABILITATION, FLORA MAE WELL INGS 12 MONTHS
(FfR 77-26819)
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $152,275 FOR
(ENV 77-23868) 12 MONTHS
FORUM, LTD., RONALD 6- CAPALACES $59,381 FOR
(PFR 79-19067) 8 MONTHS
IMAGE ASSOCIATES, CLAYTON EDWARDS $3,OUO FOR
(PFR 79-19066) 1 MONTH
UNIVERSITY OF MICHIGAN, ROBERT H. KADLEC $37,528 FOR
(ISP 80-11690) ' 12 MONTHS
UNIVERSITY OF FLORIDA, HOWARD T- ODUM $27,299 FOR
(ISP 80-14973) 12 MONTHS
FORUM, LT-, RONALD G- CAPALACES $14,500 FOR
(PFR 79-19067) 1 MONTH
"THE .EFFECTS OF SEWAGE EFFLUENT ON WETLAND
ECOSYSTEMS"
"CYPRESS WETLANDS FOR WATER MANAGEMENT,
RECYCLING AND CONSERVATION"
"THE EFFECTS OF SEWAGE EFFLUENT ON WETLAND
ECOSYSTEMS"
"THE EFFECTS OF SEWAGE EFFLUENT ON WETLAND
ECOSYSTEMS
"FEASIBILITY OF UTILIZING CYPRESS WETLANDS
FOR CONSERVATION OF WATER AND NUTRIENTS IN
EFFLUENT FROM MUNICIPAL WASTEWATER TREATMENT
PLANTS
"FEASIBILITY OF UTILIZATION OF WETLAND
ECOSYSTEMS FOR NUTRIENT REMOVAL FROM
SECONDARY MUNICIPAL WASTEWATER TREATMENT
PLANT EFFLUENTS"
"USE OF WETLANDS FOR MANAGEMENT OF POND-
STABILIZED DOMESTIC WASTEWATER"
"FEASIBILITY OF UTILIZATION OF WETLAND
ECOSYSTEMS FOR NUTRIENT REMOVAL FROM
SECONDARY MUNICIPAL WASTEWATER TREATMENT
PLANT EFFLUENTS"
"FEASIBILITY OF UTILIZING CYPRESS WETLANDS
FOR CONSERVATION OF WATER AND NUTRIENTS IN
EFFLUENT FROM MUNICIPAL WASTEWATER TREATMENT
PLANT EFFLUENTS"
"TERTIARY TREATMENT OF MUNICIPAL WASTEWATER
USING CYPRESS WETLANDS"
"FEASIBILITY OF UTILIZATION OF WETLAND ECOSYSTEMS
FOR NUTRIENT REMOVAL FROM SECONDARY MUNICIPAL
WASTEWATER TREATMENT PLANT EFFLUENTS"
"UTILIZATION OF CYPRESS WETLANDS FOR MANAGEMENT
OF MUNICIPAL WASTEWATER TREATMENT PLANT EFFLUENTS"
"USE OF WETLANDS FOR MANAGEMENT OF POND-
STABILIZED DOMESTIC WASTEWATER"
"ADVANCED TREATMENT OF COMMUNITY WASTEWATER BY
FLOW-THROUGH CYPRESS STRAND WETLANDS"
"WETLAND UTILIZATION FOR MANAGEMENT OF COMMUNITY
WASTEWATER"
"UTILIZATION OF CYPRESS WETLANDS FOR MANAGEMENT
OF MUNICIPAL WASTEWATER TREATMENT PLANT EFFLUENTS"
"UTILIZATION OF WETLANDS FOR MANAGEMENT OF POND-
STABILIZED DOMESTIC WASTEWATER"
"MOBILITY AND SURVIVAL OF VIRUSES IN CYPRESS DOME
WETLANDS"
REGIONAL ENVIRONMENTAL SYSTEMS
WASTE MANAGEMENT STRATEGIES
JEROME S- DAEN
REGIONAL ENVIRONMENTAL SYSTEMS
WASTE MANAGEMENT STRATEGIES
RICHARD C. KOLF
REGIONAL ENVIRONMENTAL SYSTEMS
WASTE MANAGEMENT STRATEGIES
EDWARD H. BRYAN
REGIONAL ENVIRONMENTAL SYSTEMS
URBAN/ RURAL ENVIRONMENTS
EDWARD H. BRYAN
REGIONAL ENVIRONMENTAL MANAGEMENT
RESIDUALS MANAGEMENT
EDWARD H. BRYAN
REGIONAL ENVIRONMENTAL MANAGEMENT
COMMUNITY WATER MANAGEMENT
EDWARD H. BRYAN
"WETLAND UTILIZATION FOR MANAGEMENT OF COMMUNITY
WASTEWATER
"UTILIZATION OF WETLANDS FOR WASTEWATER
MANAGEMENT," TREATMENT AND PRODUCTION OF A FILM
"UTILIZATION OF WETLANDS FOR WASTEWATER
MANAGEMENT," TREATMENT CONCEPT ONLY
COMMUNITY WATER MANAGEMENT
EDWARD H- BRYAN
COMMUNITY WATER MANAGEMENT
EDWARD H. BRYAN
GOVERNMENT AND PUBLIC PROGRAMS
SUSAN BARTLETT
"SOLIDS MOVEMENT IN WETLANDS"
"APPROPRIATE ENVIRONMENTAL SYSTEMS FOR
WASTE MANAGEMENT"
"UTILIZATION OF WETLANDS FOR WASTEWATER
MANAGEMENT" (SUPPLEMENTAL AWARD)
APPROPRIATE TECHNOLOGY
EDWARD H- BRYAN
APPROPRIATE TECHNOLOGY
EDWARD H- BRYAN
914
-------
The wetlands projects in Michigan and Florida are the subject of a documentary
film produced in 1980 to summarize progress and to assist in bringing the
availability of the results of this research to the attention of potential
users (23). A summary of awards made to support this research program is
contained in Table 3.
SUMMARY AND CONCLUSIONS
New concepts for management of sludges produced during treatment of
wastewater and to manage effluents from treatment processes for conservation
of their nutrient and water content are needed which meet acceptable standards
of public health and environmental quality and which also conserve capital,
material and energy resources. Wetlands appear to provide that potential for
effluents that have received primary and secondary treatment by conventional
physical and biological processing. This concept is especially compatible
with the first principle of good sludge management, the introduction of a
tertiary step that in contrast to other physical, chemical or biological
processes does not produce sludge. Direct injection of sludges into topsoil
is already in actual use in many locations in the United States. The
concept of applying sludge to land that is dedicated to "receiving sludge
in perpetuity" was recently described as underway at the Reno-Sparks Joint
Water Pollution Control Facility at Reno, Nevada (25).
The combined capacity of the Miami-Dade Virginia Key facility and that
at the Deer Island plant in Boston will total in excess of 300,000 gallons
per day for electron-beam disinfection of sludges by the end of this year.
The concept of combining disinfection, pipe-line transport and direct
injection of sludges into topsoil on land dedicated to function as a stabil-
ization bed remains as a promising concept for assessment of its acceptability
with regard to risk, technical and economic feasibility, and environmental
compatibility.
REFERENCES
1. Bryan, Edward H. "Future Technologies of Sludge Management" in Proc. of
the 1980 Spring Seminar: "Sludge Management in the Washington, D.C.
Area," National Capital Section, American Society of Civil Engineers,
pp. 52-62 (May 1980).
2. Malina, Joseph F., Ranganathan, K. R., Moore, B.E.D. and Sagik, B. P.,
"Poliovirus Inactivation by Activated Sludge," pp. 95-106 in Virus
Survival in Water and Wastewater Systems, Water Resources Symposium
No. 7, Center for Research in Water Resources, The University of Texas
at Austin (1974).
3. "New Concepts in Sludge Management," 16mm Film No. A04088/CJ, National
Audiovisual Center, Washington, D.C. 20409 (National Science Foundation,
5 minutes, Color 1978).
915
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4. "Synthesis of a Municipal Wastewater Sludge Management System," Media
Four Productions, Hollywood, California. Contact Edward H. Bryan,
National Science Foundation for information regarding its availability.
5. Smith, James L., Lutkin, Maurice H., Latham, James S. and de Haai, Alan,
"Land Management of Subsurface-Injected Wastewater Liquid Residuals,"
Interim Report, NTIS Accession No. PB 280162 (November 1977).
6. Hartenstein, Roy, "Sludge Decomposition and Stabilization," Science,
Vol. 212, pp. 743-749 (May 15, 1981).
7. Merrill, Edward W., Mabry, David R., Scholz, Robert B., Coleman, Walter D.
Trump, John G. and Wright, Kenneth A. "Destruction of Trace Toxic
Compounds in Water and Sludge by Ionizing Radiation," Water 1977,
AIChE Symposium Series No. 178, Vol. 74, pp. 245-250 (1977).
8. Trump, John G. "Energized Electrons Tackle Municipal Sludge," American
Scientist, Vol. 69, No. 3, pp. 276-284 (May-June 1981).
9. Thorburn, Brewster A. "Sludge Management Using Electron Disinfection,"
Proc. of the 1981 Conference on Environmental Engineering, American
Society of Civil Engineers, pp. 540-547 (July 1981).
10. Bryan, Edward H. "The Potential Role of Aquaculture in Management of
Wastewater," in Individual Onsite Wastewater Systems, pp. 273-280,
National Sanitation Foundation (1981).
11. Dixon, Kenneth R. and Kadlec, John A. "A Model for Predicting the Effects
of Sewage Effluent on Wetland Ecosystems," Interim Report, NTIS Accession
No. PB 273024 (1975).
12. Parker, P. E., Gupta, P. K., Dixon, K. R., Kadlec, R. H. and Hammer, D. E.
"REBUS, A Computer Routine for Predictive Simulation of Wetland
Ecosystems," Interim Report, NTIS Accession No. PB 291587 (1978).
13. Kadlec, Robert H., Tilton, Donald L., Schwegler, Benedict R., "Wetlands
for Tertiary Treatment, a Three-Year Summary of Pilot Scale Operations
at Houghton Lake," NTIS Accession No. PB 295965 (1979).
14. Kadlec, Robert H., Hammer, David E. and Tilton, Donald L., "Wetland
Utilization for Management of Community Wastewater," NTIS Accession
No. PB 80-108228 (1978).
15. Kadlec, Robert H. "Wetland Utilization for Management of Community
Wastewater, Operation Summary, 1978, Houghton Lake Wetlands Treatment
Project," NTIS Accession No. PB 298308 (1979).
16. Kadlec, Robert H., and Hammer, David E. "Wetland Utilization for Manage-
ment of Community Wastewater, 1979 Operations Summary, Houghton Lake,
Michigan," NTIS Accession No. PB 80-170061 (February 1980).
916
-------
17. Kadlec, Robert H. and Hammer, David E. "Wetlands Utilization for Manage-
ment of a Community Wastewater, 1980 Operations Summary, Houghton Lake
Wetlands Treatment Project," NTIS Accession No. PB 81-235954 (March
1981).
18. "Aquaculture Systems for Wastewater Treatment: An Engineering Assess-
ment," U.S. Environmental Protection Agency 430/9-80-006 and 007, MCD
67 and 68, (June 1980).
19. Sutherland, Jeffrey C. "Investigation of the Feasibility of Tertiary
Treatment of Municipal Wastewater Stabilization Pond Effluent Using
River Wetlands in Michigan," Final Report, NTIS Accession No. PB 275283
(1977).
20. Odum, Howard T. and Ewel; Katherine C. "Cypress Wetlands for Water
Management, Recycling and Conservation," Annual Report, NTIS Accession
No. PB 80-104714 (1975).
21. Odum, Howard T. and Ewel, Katherine C. "Cypress Wetlands for Water
Management, Recycling and Conservation," Annual Report, NTIS Accession
No. PB 273097 (1976).
22. Odum, Howard T. and Ewel, Katherine C. "Cypress Wetlands for Water
Management, Recycling and Conservation,',' Final Report, NTIS Accession
No. PB 282159 (1978).
23. Fritz, Walter R. and Helle, Steven C. "Cypress Wetlands as a Natural
Tertiary Treatment Method for Secondary Effluents," Final Report,
NTIS Accession No. PB 294566 (1978).
24. "Wetlands - Our Natural Partners in Wastewater Management," 16mm Film
No. A03093/CJ, National Audiovisual Center, Washington, B.C. 20409
(National Science Foundation, 39 minutes, Color, 1980).
25. Briscoe Maphis Environmental Update, Volume 1, No. 6 (April 1980).
ADDITIONAL REFERENCES - REPORTS FROM PROJECTS LISTED IN TABLES BUT NOT CITED
1. Appelhof, Mary. "Workshop on the Role of Earthworms in the Stabilization
of Organic Residues," Vol. I - Proceedings and Vol. II - Bibliography,
Beech Leaf Press, Kalamazoo, Michigan (1981).
2. Blobaum, Roger. "Assessment of the Potential for Applying Urban Wastes to
Agricultural Lands," Final Report, NTIS Accession No. PB 296037 (May
1979).
3. Connery, Jan. "Proceedings of a Workshop on the Health and Legal
Implications of Sewage Sludge Composting," Energy Resources Company, Inc.
NTIS Accession No. PB 296566 (February 1979).
917
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4. Dick, Richard I. "Process Integration for Optimum Management of Municipal
Wastewater Treatment Sludges," NTIS Accession Nos. PB 295950 and
PB 296910.
5. Gurnham, G. Fred. "Control of Heavy Metal Content of Municipal Wastewater
Sludge," Final Report, NTIS Accession No. PB 295917 (May 1979).
6. Hartenstein, Roy. "Stabilization of Community Wastewater Sludges by Soil
Invertebrates," Final Report, NTIS Accession No. PB 286018 (September
1978).
7. Kirkham, Mary Beth. "Agriculture Value of Irradiated Municipal Wastewater
Treatment Plant Sludges," Final Report, NTIS Accession No. PB 80-107865
(November 1979).
8. Lutkin, Maurice H. and Smith, James L. "On-Land Disposal of Municipal
Sewage Sludge: A Guide to Project Development," Interim Report, NTIS
Accession No. PB 271144 (July 1977).
9. Metcalf, Theodore G. "Control of Virus Pathogens in Municipal Wastewater
and Residuals by Irradiation With High Energy Electrons," Final Report,
NTIS Accession No. PB 272347 (September 1977) and PG 80-104086
(November 1979).
10. Sagik, Bernard P. and Sorber, Charles A. (Editors). "Risk Assessment
and Health Effects of Land Application of Municipal Wastewater and
Sludges," University of Texas at San Antonio, NTIS Accession No.
PB 289675 (December 1977).
11. Smith, James L. and Bryan, Edward H. (Editors). "Williamsburg Conference
on Management of Wastewater Residuals," Publications No. 18599 (1976)
and 20182, revised (1977), Colorado State University, 162 pp., NTIS
Accession No. PB 262544.
12. Trump, John G. "High Energy Electron Radiation of Wastewater Liquid
Residuals," NTIS Accession No. PB 279489 (December 1977).
13. Trump, John G., Merrill, Edward H. and Sinskey, Anthony J. "High
Energy Electron Radiation of Wastewater Liquid Residuals," NTIS
Accession No. PB 297593 (February 1979).
918
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REMOTE SENSING OF SEPTIC SYSTEM PERFORMANCE
USING COLO,R INFRARED AERIAL PHOTOGRAPHY
David W. Hill and Rebecca B. Slack
Surveillance & Analysis Division
Region IV
U.S. Environmental Protection Agency
Athens, Georgia
Technical information developed and provided by:
E. Terrance Slonecker
Environmental Photographic Interpretation Center
U.S. Environmental Protection Agency
Warrenton, Virginia
This paper has been reviewed in accordance with
the U.S. Environmental Protection Agency's peer
and administrative review policies and approved
for presentation and publication.
Presented at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Washington, D.C.
919
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REMOTE SENSING OF SEPTIC SYSTEM PERFORMANCE
USING COLOR INFRARED AERIAL PHOTOGRAPHY
David W. Hill and Rebecca B. Slack
Surveillance & Analysis Division
Region IV
U.S. Environmental Protection Agency
Athens, Georgia
Technical information developed and provided by:
E. Terrance Slonecker
Environmental Photographic Interpretation Center
U.S. Environmental Protection Agency
Warrenton, Virginia
ABSTRACT
Failed septic leach fields resulting in surfacing of partially
treated wastewater to the ground surface can frequently be detected by
remote sensing. The surfacing nutrients may increase the growth of vege-
tation which shows as a brighter red on color infrared (CIR) aerial
photographs. Effluent continually ponded on the surface will eventually
kill the vegation by suffocating the roots. Thus, depending upon the
severity of the failure, CIR photographs may reveal red stripes that
delineate the tile field, bright red plumes in a downslope direction,
brown spots where vegetation has died, and dark blue spots denoting
standing surfaced effluent.
INTRODUCTION
As a result of the Federal Water Pollution Control Act (P.L.
92-500) and the 1977 Clean Water Act (P.L. 95-217), the Environmental
Protection Agency (EPA) was given the authority to grant funds for the
construction of sewage collection systems. Under the eligibility require-
ments for the construction grants program, Federal rules and regulations
clearly state that the need for wastewater treatment facilities be proven
by documenting the number of septic field failures within the existing
target area, and assessing their effect upon water quality and public
health in general (1).
"New collector sewers should be funded only when the
systems in use (e.g., septic tanks or raw discharges from
homes) for the disposal of wastes from the existing population
are creating a public health problem, contaminating groundwater,
or violating the point source discharge requirements of the Act.
Specific documentation of the nature and extent of health,
groundwater and discharge problems must be provided in the
facility plan. Where site characteristics are considered to
restrict the use of on-site systems, such characteristics
920
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(e.g., groundwater levels, soil permeability, topography,
geology, etc.) must be documented by soil maps, histori-
cal data, and other pertinent information. The facility
plan must also document the nature, number and location
of existing disposal systems (e.g., septic tanks) which
are malfunctioning. A community survey of individual
disposal systems if recommended for this purpose, and
is grant eligible."
Originally, the only way to satisfy this program requirement
was the door-to-door survey. This, however, required large commit-
ments of personnel, time, money, and technical assistance. Also, a
question of validity often arose because of local controversy some-
times surrounding sewer projects. Clearly, an alternative survey
method was needed.
Surface failure of septic leach fields is usually caused by
one or more of the following:
• The soil is too compacted causing very slow perco-
lation rates.
• There is a close, underlying, impervious layer
below the drainage field.
« The water table is close to the surface during
the wet season.
• Breakage or mechanical malfunctions exist.
« The septic tank itself is overdue for a cleaning.
This allows the loss of normally removed materials
to coat and seal the sides and bottom of the perco-
lation trenches.
Only those malfunctions which are noticeable on the surface
can be detected on aerial imagery. Failures related to sewage back-
ing up into the home, or too rapid transport through the soil into
the groundwater, cannot be detected via remote sensing. In instances
where the latter is occurring, the groundwater monitoring studies may
be necessary to determine the existence of a problem.
HISTORY
The first known documentation of septic field problems using
remote sensing was in Greensboro, North Carolina, in 1974. Although
the results of this initial survey were not definitive, it did show
promise that a specialized technique for septic system analysis was
feasible (2). By employing stereo pairs of "false-color" infrared
and conventional color photography, an analytical technique was
developed in 1977 at the EPA-Environmental Photographic Interpreta-
921
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tation Center (EPIC) that has since been shown to be reason-
ably successful depending upon the climatic and soil conditions
at the time of over flight. EPIC produced several photo interpre-
tation "keys" on septic field analysis and initially tested them
on seven communities in EPA, Region V. This technique was touted
to have $36 million over conventional techniques (3). In early
1978, EPIC's technique was tested again in Hawkins, Greene and
Union Counties in Tennessee. These communities were chosen
because of their geologic structure, soil and topographic condi-
tions, and their pressing need for a disposal system. The photo-
graphic interpretation was field checked, and out of 55 suspected
failures, 52 were confirmed - an accuracy of 94.5 percent. This
aerial survey reinforced the suspicions of Tennessee public health
officials that current septic tank systems were not satisfactory
for disposal of wastes within the study area.
The EPIC and other remote sensing techniques for septic
field analysis have been used often as a part of the 201 Construc-
tion Grants Process. The primary document describing the photo-
interpretative keys is still being reviewed within EPA and will
be published by the Agency as a separate document.
METHODOLOGY
The technique currently uses both color (Kodak Ektachrome
2448) and color infrared (Kodak Ektachrome 2443) photography. Color
infrared is the primary tool; standard color photographs are also
used for orientation purposes and sometimes for verification. A 60
percent end lap of each photograph is required for stereo viewing to
obtain topographic information. The photo interpreter scrutinizes
the lot of each house for signatures of septic tank leachate such as
vegetative distress or enhanced growth, and excessive soil moisture.
A signature is an identifiable pattern characteristic of a certain
specific object or situation. The signature key for septic tank
failure developed by EPIC is summarized as follows (2).
Surface Failure
The obvious, blatant manifestations of septic system failure
on CIR photographs are characterized by a deep red color and one or
more dark gray or black spots where the actual septic effluent has
surfaced and killed the surrounding vegetation (see Figure 1).
Often, if the failure is severe, the effluent will break out into
the driveway or street and run into storm sewers or surface waters.
This type of failure may represent a health problem, especially if
the effluent is standing stationary or occurs many times in a given
area.
922
-------
Figure 1. Black and White Copy of a Color Infrared Photograph,
Typical Signatures of Septic Field Failures Are:
(A) Overflow Into Street,
(B) Dead Grass,
(C) Lateral Lines Defined by Lush Grass.
923
-------
Seasonal Failure
This signature is less definitive than the surface failure
but nevertheless is readily identifiable with a high degree of
accuracy. The seasonal failure may not show surfacing effluent
when the photograph was taken but there are signs that either all
or part of the system has failed in the past, or will probably
fail in the future when seasonal conditions, such as excessive
rain or a high water table, will strain the system. This signa-
ture is characterized by unusually lush growth caused by excessive
surface moisture. In many cases, all or part of the disposal system
will be well defined by the lush growth directly above it. Clear
delineation of the lateral lines is usually cause for subsequent
ground verification, even though such systems may not be failing.
Also, evidence of past failure on the surface, such as dead vege-
tation in the form of a plume over all or part of the septic
leachate field, is similarily classified.
Seasonal Stress
This signature is the least definitive of all the septic
signatures but is still very important from a planning viewpoint.
Seasonal stress signatures depict excessive moisture at or near
the ground surface that may be related to septic system problems.
Seasonal stress signatures are characterized by faint or partial
definition of the lateral lines, excessive growth of vegetation
over the probable location of the leach field, or any general sign
that there is moisture near the surface.
Failure signatures are not always obvious and training is
required to produce a proficient photo-interpreter. Similar signa-
natures can be caused by common occurrences such as uneven spreading
of lawn fertilizer, manure piles, compost heaps and animal droppings.
For these reasons, field checking a perentage of the area is always
recommended. In some cases, depending upon the soils of the partic-
ular area, the outline of the drainage line(s) of a properly function-
ing septic system can be distinguished on aerial photography. This
peculiarity points up the need for tailoring "photo interpretation
keys" to specific geographic areas (4).
EXAMPLES
Using the above "signatures" as photo interpretation keys,
potential septic system failures have been identified in several
study ares. The following examples are chosen from the Southeastern
United States (5):
« Louisville (Jefferson County), KY
(Flown in November 1979)
Very extensive failure was noted.
A field check in January 1980 of 70 percent of the
924
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area showed 323 surface failures and 565 seasonal
failures. During rainy weather, drainage from these
failed systems would wash into the combined sewers
which serve as a direct conduit to the Ohio River.
• Maryville (Blount County), TN
(Flown in October 1980)
This study showed the greatest number of failures
or problems yet recorded in a single study:
259 surface failures
1,445 seasonal failures
1,095 seasonal stress
2,799 total problems
• Orlando (Orange County), FL
(Flown November and December 1980)
This was a pilot study that determined the success of
these techniques when applied to the unique climate and
sandy soils of central Florida. Results in the test
area showed:
47 surface failures
232 seasonal failures
167 seasonal stress
446 total problems
• Apalachicola area (Gulf, Franklin, and Wakulla Counties),
FL (Flown January and February 1981)
These detection techniques for this coastal area are
currently being studied as a research project. Normally,
remote sensing is not suitable for use along beaches or
other areas of unconsolidated sand. However, this area
is part of the "Piney Woods Flatlands" which is underlain
by an extensive hardpan. The hardpan may make use of this
technique possible. This project was undertaken to determine
possible sources of cholera organisms which are reaching
production shellfish beds in Apalachicola Bay.
Nationwide, septic field failure surveys using this remote sensing
sensing technology have been conducted in the following locations
including those detailed above) during the fiscal years shown:
1978 USER
Lake Geneva, WI U.S. EPA Region V
Crystal Lake, MI " V
Silver Lake, WI " V
Otter Trail Lake, MN " V
925
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Crooked & Pickerel Lakes, MI " V
Nettle Lake, OH " V
Steuben Lakes, IN " V
Green Lake, MN " V
Spearfish, SD " VIII
Smith Mountain Lake, VA " III and
Virginia State Water Pollution Control Board
Hatboro/Horsham, PA U.S. EPA Region III
Upper Nazareth, Bushkill & Plainfield, PA " III
Surgoinsville, Baileytown & Luttrell, TN " IV
Stanley Co., NC Stanley Co.
Dept. of Health
1979
Topeka, KS U.S. EPA Region VII
Jefferson Co., KY " IV
Chalfont, New Britain & Doylestown, PA " III
1980
Lower Morel and, Abington & Bryn Athyn, PA " III
Blount Co., TN " IV
Seattle, WA " X
1981
Delaware Co., OH V
Clermont Co., OH " V
Orlando, FL " IV
Lewes/Rehoboth, DE "III
CONCLUSIONS
Based upon the results obtained thus far, the manifestations
or photo signatures of failed septic leach fields are best distinguish-
ed on normal color or color infrared photographs at scales of 1:10,000
or larger depending upon the quality of the film and camera system.
Some limitations on the use of remote sensing for septic tank
system failure analysis have been encountered. Two of the most signi-
ficant limitations are related to soil/vegetation "homogeneity" and
tree cover. Failing systems situated in soils which exhibit a wide
range of photo signatures, such as varying soil color/tone and "patchy"
vegetative cover (e.g., some sandy soils around lakes), are sometimes
difficult to distinguish from naturally occurring phenomena. In areas
with a large percentage of tree cover, failing septic systems may be
obscured by foilage and/or shadows. These conditions can be minimized
by flying at specific times of the day or year. This type of technique
optimization is continuing to further reduce the problem of "false nega-
tives," i.e., systems which are actually failing but are not identified
926
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by the photographs. This aspect of the technique is critical to the
ultimate acceptance of procedure, since "false positives," i.e., the
apparent failure of well-operating on-site systems, merely cause an
increase in the ground verification effort, while a significant number
of false negatives can obviate the utility of the whole procedure.
The big advantage of this technique is cost-savings. The cost
may be as little as 10 percent of the cost of a door-to-door survey.
In fact, Region V estimated a savings of $51 million during 1980,
attributed, in significant part, to this technique. For this a team
of seven empolyees was awarded the Excalibur Award for Excellence
in Government Service.
This technique is an excellent example of how color infrared
aerial photography can be put to practical use in saving millions of
taxpayer dollors.
REFERENCES
1. Rhett, J. T., 1978. Construction Grants Program Requirements
Memorandum PRM 78-9, "Funding of Sewage Collection Systems
Projects," U.S. Environmental Protection Agency, Washington, D.C.
2. Slonecker, E. T., 1981. Septic Systems Failure Analysis via
Color/Color Infrared Aerial Photography, Virginia Polytechnic
Institute, Blacksburg, Va.
3. EPA Journal. May 1980. Office of Public Awareness, Vol. 6,
Number 5, p. 30.
4. Crouch, L. W., 1979. Remote Sensing as a Field Method for
Assessment of Soil Moisture, University of Miami, Oxford, OH.
5. Hill, D. W., Slack, R. B., and Slonecker, E. T., 1981. "Remote
Sensing of Failed Septic Leachate Fields," The Proceedings of
the 1981 National Conference on Environmental Engineering, ASCE
Environmental Engineering Division, Atlanta, GA.
927
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-------
TWO-PHASE ANAEROBIC DIGESTION OF ORGANIC WASTES
Sambhunath Ghosh, Ph.D.
Manager, Bioengineering Research
Institute of Gas Technology
Chicago, Illinois
The work described in this paper was not funded by the
U.S. Environmental Protection Agency. The contents do
not necessarily refelct the views of the Agency and no
official endorsement should be inferred.
Prepared for Presentation at:
8th United States/Japan Conference
on
Sewage Treatment Technology
October 1981
Washington, D.C.
929
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TWO-PHASE ANAEROBIC DIGESTION OF ORGANIC WASTES
Sambhunath Ghosh, Ph.D.
Manager, Bioengineering Research
Institute of Gas Technology
Chicago, Illinois
ABSTRACT
Anaerobic digestion is a multi-step biochemical process mediated by
several microbial groups (phases) having significantly different physiology,
nutritional requirements, growth kinetic and metabolic characteristics, en-
vironmental optima, and sensitivity to environmental stresses. Conventional
engineering application of this process provides for concurrent enrichment
of the various microbial phases under an identical environment; this leads to
slow overall process kinetics, higher capital costs, low net energy production
efficiency, and other disadvantages. A multi-stage advanced digestion process
in which the microbial phases are enriched in separate optimized environments,
and the substrate is stabilized by sequential acidogenic and methanogenic fer-
mentations is discussed. The process, known as two-phase digestion, is a
generic system, and could consist of two or more continuous stirred-tank,
plug-flow, packed-bed, or fluidized-bed fermentors. The energetic,
kinetic, and economic advantages of the two-phase process are
discussed with reference to its application to several soluble and solid
organic wastes. The status-of development of the two-phase process,
potential problems, and research needs are discussed.
INTRODUCTION
Anaerobic digestion is a multi-step biochemical process which is mediated
by several symbiotic microbial groups or phases. As indicated in Figure 1.
the overall digestion process consists of the following major coupled reaction
steps;
• Enzymatic hydrolysis of particulate and high-molecular-weight substrates
to simple monomers
• Conversion of the monomers to higher fatty acids, carbon oxides (mainly
C02), hydrogen, and acetate
• Degradation of the higher fatty acids to acetate and CO-
• Cleavage of acetate and/or reduction of C0~ to form methane.
The first two steps outlined above are carried out by a group of acidogenic
bacteria, It is believed that the third reaction step is conducted by the
so-called "acetogenic" organisms which derive energy by oxidizing the higher
fatty acids to acetate, hydrogen, and C02 (1). Little information exists on
the physiology, kinetic properties, and nutritional and metabolic character-
istics of the acetogens. Cleavage of acetic acid, which is believed to be
the major substrate for methane formers in digestion of wastes, is the
930
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slowest and the least energy-yielding of the two methane-forming reactions (2).
In view of the above, anaerobic digestion of organic wastes may be viewed
as a two-phase process in which acid-forming organisms convert the process
feed to acetic acid, which is next transformed to methane and CC^ by the
methane-forming bacteria. The acid-forming phase could be controlled by any
one of the steps of hydrolysis, conversion of the hydrolytic products to
acetate, or formation of acetate from higher fatty acids.
There is ample information in the literature to indicate that the dominant
digesting populations differ significantly from each other with respect to
physiology, nutritional requirements, metabolic characteristics, growth kinetic
capability, environmental optima, and sensitivity to environmental stresses (3,4),
Two approaches could be employed in engineering application of the multi-
phase digestion process to stabilization and gasification of organic wastes:
• Coculturing of the several microbial groups in a single fermentor
(digester) under identical operating and environmental conditions
• Enrichment culturing of the microbial groups under optimized environments
in separate digesters.
ENGINEERING APPLICATION - CONVENTIONAL DIGESTION
In traditional engineering application, anaerobic stabilization of
concentrated organic feeds is provided by one of the following process
configurations (3):
• Standard-rate digestion
• High-rate digestion
• Stage digestion
• Anaerobic contact process.
These processes provide for the coculturing of the acid-forming and methane-
forming populations in slurry-phase digesters under the same physical and
chemical environments. The design and operation of these processes are dic-
tated by the sensitivity and kinetic limitations of the slow-growing methane
formers. Because the generation time of methane organisms has been estimated
to be between 2 and 11 days for waste digestion conditions (4), a minimum
retention time between 3 and 16 days is required to prevent washout of the
rnethanogenic organisms. In actual practice, a digester retention time of 10
to 30 dayo is provided, depending on waste properties, degree of mixing, etc.,
for reliable process performance (5),
There are serious limitations as to the retention time as well as organic
loading that can be applied on conventional mixed-phase digestion to obtain
stable process performance, and acceptable gasification and stabilization
931
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efficiencies. This point is illustrated in Figure 2, which depicts the results
of mesophilic (35°C) conventional high-rate digestion of a high-chemical oxygen
demand (COD)(12,000-26,000 mg/&) soft drink-bottling waste at various loadings
and retention times (6). The data show that as the loading was increased from
a low value of 0.04 Ib VS/ft3-day to a modest level of 0.125 Ib VS/ft3-day, the
feed, because of its high biodegradability, was rapidly metabolized by the acid
formers to volatile fatty acids which accumulated to high levels inhibitory to
methanogenic activity. The underlying reason for the resulting digester upset
was the kinetic imbalance between the rates of production and utilization of
volatile acids, which in this case ensued when a retention time of 10 days and
a feed volatile solids (VS) concentration of only 20 g/£ were applied. The
degree of this imbalance increased when attempts were made to operate the high-
rate digester at still shorter retention times and higher loading rates
(Figure 3). Digester upsets like this which arise due to unbalanced activities
of acid and methane formers are difficult to prevent or correct because it is
not possible to control and manipulate the activity of either group of organisms
without affecting the activity of the other. In view of the above, the primary
disadvantages of conventional mixed-phase anaerobic digestion are:
• Long retention times
• Low loading rates
• Occurrence of unbalanced digestion.
Long retention times and low loading rates in turn lead to the following
additional disadvantages:
• Large digestion tanks and large land area requirement
• High capital investment for the installation of the large digestion
tanks and associated equipment
• Difficulty of mixing in large tanks --- up to 60% of the volume of
conventional digestion tanks is occupied by scum, sludge deposits,
incrustations, or dead space
• Low overall stabilization and gasification rate
• Maintenance of the acid formers in the stationary growth phase, and
consequent retardation of the hydrolysis and acidification reactions.
Also, as indicated above, the conventional digestion process is vulnerable to
varying -loading rates and retention times which could easily lead to unbalanced
digestion, process instability, and unreliable performance.
Last, but not least important is the fact that conventional anaerobic
digestion processes could easily have a negative energy balance: that is, the
total external energy input (excluding the energy content of the waste organics)
could exceed plant methane energy output, when dilute organic slurries are
digested at low loading rates. This is illustrated in Figures 4 and 5 which
932
-------
depict the net energy production ratio (NEPR) [defined as the ratio of the
energy value of the useable energy product (methane), Ep, and the sum of all
other energy inputs, E^, excepting that of the feed] as functions of feed
consistency and loading rate. Net energy production ratios are less than
one — this indicates that the process has a negative energy balance and is a
net energy consumer — when the feed slurries are so dilute that the sludge
heating requirement is excessive, or when the loading rate is so low that
unduly large digesters are required and excessive heat inputs are needed to
compensate for heat losses from these digesters.
ADVANCED DIGESTION - - THE TWO-PHASE CONFIGURATION
Advanced digestion utilizes process configurations that could over-
come the aforementioned limitations of conventional digestion, it also
permits process operation at much higher loading rates and shorter hydraulic
retention times (HRT's) than those of the conventional process. As depicted
in Figures 2 and 3, digester operation at increased loadings and reduced
HRT's leads to the enrichment of an acid-forming culture precluding the
establishment of a stable methane-fermentation phase. Since the natural
response of an anaerobic digester to high-loading short-HRT operation is
separation of the acid-forming phase, it appears reasonable to assist this
process and develop a staged system in which conversion of the feed to fatty
acids is optimized in the first stage. Because conditions promoting optimum
substrate-to-acids conversion are not conducive to stable and efficient acid-
to-methane conversion, acidic effluents from the first-stage acid digester must
be methanated in a separate 'methane-phase digester operated in tandem with the
first-stage acid digester. Thus, a multi-stage two-phase process, as first
suggested by Babbitt and Baumann (7) and later developed by Pohland and Ghosh
(3,8), Ghosh et^ al^. (9), and others, evolves naturally when anaerobic digestion
is conducted at high loading rates and short retention times in the interest of
enhanced substrate conversion rate, reduced plant capital cost, and increased
net energy production efficiency. Thus, two-phase digestion is an advanced
generic multi-stage process in which the acid-forming and the methane-forming
bacterial phases are optimized in separate reactors (stages) to substantially
enhance the overall process kinetics and NEPR, and reduce plant capital cost.
Reactor Designs
The simplest two-phase system consists of two separate digesters operated
in series. If CSTR reactors are used, then the acid digester is usually much
smaller than the methane-phase digester. Anaerobic settlers can be used in
tandem with each digester to permit densification and recycling of settled
effluent solids to increase microbial and substrate solids retention times
(SRT's) (8, 10). Depending on the feed properties and operating modes, other
reactor designs including plug~flow, packed-bed (anaerobic filter), or
fluidized-bed (also referred to as expanded bed and upflow sludge blanket)
could be used. For low suspended-solids (SS) feed, an upflow anaerobic
filter appears more attractive for methane-phase fermentation, since it allows
process operation at a substantially lower HRT. Finally, it should be noted
that a two-phase digestion process could conceivably consist of more than two
digesters with more than one reactor design used to optimize each digestion
phase.
933
-------
Culture Enrichment Techniques
Several techniques have been proposed for selective enrichment and op-
timization of the acid-forming and methane-r-f orming phases. Among them are;
• Selective inhibition of methane formers by chloroform, carbon tetra-
chloride, limited oxygenation, adjustment of redox potential, etc.
in the acid digester (11)
• Dialysis separation of the acid- and methane-forming cultures (12, 13)
• Kinetic control of nonmethanogenic and methanogenic organism growth by
adjustment of HRT5 reactor loading rate, and microbial and substrate
SRT's by effluent recycling around each digester of a two-phase system
(3, 6, 8, 9, 10). Of the above techniques, phase separation by kinetic
control is expected to be superior because:
a) It does not have the operating problems of membrane separation.
b) It is free from the uncertainties of inhibitor action on both
groups of digester organisms.
c) The technique is successfully applied to two-phase digestion of
soluble and solid substrates (3,9).
TWO-PHASE DIGESTION OF SOLUBLE SUBSTRATES
The application of kinetic control to separate the acid-forming and
methane-forming phases of anaerobic digestion of soluble substrates was first
demonstrated by Pohland and Ghosh (3, 8), and later by Pohland and Massey (14),
Ghosh et al. (9). Ghosh and Klass (15, 16), Heertjes and van der Meer (17),
Smith et al. (18), Cohen et al. (19), and Ghosh and Henry (6).
Pohland and Ghosh (3) „ and Ghosh and Klass (15) studied the following
reaction systems to study the kinetic characteristics of acid-forming and
methane-forming organisms derived from a digested sewage sludge inoculum and
enriched in separate CSTR digesters:
A. Nutrients + glucose 10 * volatile acids + C°2
B. Nutrients + glucose continuous-digester „ volatile ac±ds + co
0
acidxf icatxon
, . . , . , f T, continuous-digester ^ ,,„ , rn
C. Nutrients + volatile acids from B - methanatlo£ - -** CH4 + C02
t-i j continuous -digester ^ _ pn
D. Nutrients + acetate methanatiog - ^ CH4 + C02
Kinetic constants derived from these digestion data are presented in Table 1.
The kinetic information is used to project the performance characteristics
of the digestion phases as functions of such control variables as detention
time, feed substrate concentration, and loading rate. The parameter selected
for evaluation of process performance is substrate conversion rate per unit
culture volume, R9 given by Equation 1 below!
934
-------
Table 1. Kinetic Constants for Mesophilic (37°C) .Acidogenic
and Methanogenic Cultures Developed on Soluble Substrates.
Methane Formers
Kinetic
Constants
- , -1
y , day
K, mg/£
Y
Acid Formers £
on Glucose Si
Batch
7.2
400 (glu)
0.15
Continuous
30.0
23 (glu)
0.17
lixed Volatile Acid
ibstrate From Glucose
(Continuous)
3.4
600 (acetate)
_-
Acetate
(Semicontinuous)
0.49
4200 (acetate)
0.28
"Kinetic constants shown here are the maximum specific growth rate, y f the
saturation constant, K, and the growth yield, Y.
[1]
( y 9 - 1)
where
S = feed substrate concentration,
o
e = IIRT.
Figure 6 shows that detention times for maximized acidification of glucose
and methanation of acetate differ greatly from each other, and optimized high-
rate glucose digestion is not expected in a single-stage mixed-phase conven-
tional digester. However, a two-phase system in which CSTR-type acid and
methane digesters are operated at IIRT's of 3.6 hours and 3 days can, in
theory, result in a maximum glucose-to-methane conversion rate. Substantial
reduction in these HRT's could be obtained by utilizing reactor designs that
provide for maintenance of long SRT's (10).
Various reactor designs, differing from the CSTR digesters initially em--
ployed by Pohland and Ghosh (3) and Ghosh and Klass (15), were studied by
other researchers. Cohen et al. (19) experimented with a two-phase system
consisting of a CSTR acid-phase reactor and a plug-flow type upflow methane
digester with a built-in settler to conduct anaerobic digestion of glucose.
The cell yield coefficient for acid-phase digestion of glucose at 30°C was
0.11, compared with a yield coefficient of 0.17 at 37°C reported by Ghosh (20)
and Ghosh and Pohland (21). Ethanol, acetateP propionate, butyrate, formate,
lactate, carbon dioxide,and hydrogen were the main products of acidogenesis.
Butyrate v?as produced in the largest concentrations, followed by acetate.
The acidogenic reaction products were gasified in the upflow methane digester
to produce head gases having 84.3 mol % methane and 15.7 mol % CO .
935
-------
Ghosh (22) , and Ghosh and Henry (6) operated a CSTR acid-<-phase and an
upflow packed-bed methane digester with real soft-drink bottling waste,, and
demonstrated that a two-phase digestion process could be operated at about 7
times the loading rate and one-half the HRT of the conventional process and
still obtain the same methane production as and a slightly higher COD reduction
than the conventional process (Table 2). An important advantage of the
Table 2. High-Rate and Two-Phase Mesophilic (35°C)
Digestion of Soft^Drink Bottling Waste.
Conventional
High Rate
0.04
15
10.3
61.1
0.4
72
84
198
Loading, Ib VS/ft -day
HRT, days
Gas Yield, SCF/lb VS added
Methane Content, %
Gas Production Rate, vol/vol-day
Digestion Efficiencies, %
VS Reduction
COD Reduction
Digester Volume for 20,000 Ib/day
TS Load, 1000 ft3
Net Energy Production
106 Btu/day
Percent of Total Production
Two Phase
Acid
Phase
1.0
2.2
1.02
0.2
1.03
Methane
Phase
*
0.4
5.2X
9.44
70.5
3.68
Overall
0.3
7.4
9.76
63.1
2.90
22
44
64
96
66
46,3
37
80
64
Loading and HRT of the upflow filter were calculated on the basis of the
gross volume of the packed bed.
two-phase process was that gases from the methane phase had a significantly
higher methane content than those of the conventional digester. Two-phase
operation allowed the total digester volume (and associated capital and
operating costs) to be reduced by 67% and the net energy production to be
increased by more than 73% relative to those of the conventional process.
Also, while the conventional high-rate digester failed at an HRT of 10 days
and a feed COD concentration of 26,000 mg/£, the two-7phase crocess exhibited
stable and efficient performance at a system HRT of 7.4 days and a feed COD
concentration up to 45,000
936
-------
Heertjes and van der Meer (17) also conducted two^-phase digestion of
saccharose and sodium acetate in an upflow digester with an internal settler
built at the top (effluent end) of this digester. High conversion efficiencies
were obtained at 3- to 6-hour residence time and a relatively low loading
(0.12 Ib TOC/ft -day). A two-reactor two-phase system exhibited increased
stability at higher loadings up to 0.74 Ib TOC/ft3-day.
Smith et al. (18) operated a packed-bed mesophilic (37°C) upflow methane
digester ("anaerobic filter") with solids-free acidic substrates derived
from animal wastes. Satisfactory acid-phase digestion could not be developed
with this waste. Methane digester gas production rates from 0.24 to a high
value of 2.77 volume/digester volume-day were observed at hydraulic retention
times of 40.5 to 1.1 days.
In a recent study, Pipyn et al, (23) investigated anaerobic digestion of
distillery wastewaters (>vLO,000 mg/£ COD) in a two-phase pilot plant consisting
of a 36-m3 CSTR acid-phase digester and a 5-m3 upflow methane-phase digester.
The acid-phase was operated at 42°±2°C at an KRT of 16 to 72 hours, while the
methane-phase digester was maintained at 39°±2°C and an HRT of 14 hours.
Overall COD and BOfi (biochemical oxygen demand) reductions of 84 percent and
92 percent were obtained. The methane digester gases had a methane content
of 75±3mol percent.
TWO-PEASE DIGESTION OF SOLID SUBSTRATES
Ghosh et al. (9), and Ghosh and Klass (15) first demonstrated the feasi-
bility of separating the acid and methane phases of anaerobic digestion of a
particulate feed (activated sludge) by kinetic control. Satisfactory acid-
phase digestion occurred at detention times of 10 to 24 hours and high
loadings of 2 to 5 Ib VS/ft3-day. Acidogenesis occurred at an oxidation-
reduction potential (EC) of —240 mV and a pH of 5.7, compared to --400 mV and
7.0 for methane formers. Kinetic constants determined for acidogenesis of
activated sludge and biomethanation of acetate, which was the primary substrate
for methanogens, are reported in Table 3.
Table 3, Kinetic Constants for Mesophilic (37°C)
Two-Phase Digestion of Chicago Activated Sludge.
Kinetic Constants Acidogenesis of S_ludge Biomethanation of Acetate
y , day'1 3.84 0.49
K, g/i 4.3 (as VS) 4.2 (as acetate)
Y 0.4 0.28
Figure 7, developed from the above kinetic constants, shows that with a con-
centrated (5 wt percent VS) sludge feed, maximum acidogenesis and methanation
rates occurred at HRT's of 0.75 and 3 days, respectively, indicating that
high-rate conversion of sludge to methane could be achieved in a two-phase
system having an overall HRT of about 4 days. These figures also indicate
937
-------
that the substrate conversion rate decreases and the HRT for maximum conversion
rate increases substantially as the system sludge feed concentration decreases-
this means that the HRT of the overall two-phase system increases significantly
as the system feed becomes more and more dilute. Thus, for dilute feeds, a
two-phase process may not be as superior to the conventional process as it is
for concentrated feeds.
Two-phase mesophilic digestion of 1.7 to 2.5 weight percent VS Chicago
sludge at an overall HRT of 6.9 to 7.7 days exhibited an average methane yield
of 4.3 SCF/lb VS added and a VS reduction of 40 percent (9) compared with
3.5 SCF/lb VS added and 34 percent observed during conventional digestion of
this sludge at an HRT of 14 days. The methane content of the conventional
digester gases was 60 mol percent compared with 70 percent in the head gases
of the methane-phase digester.
Eastman and Ferguson (24) conducted acid-phase digestion of primary sewage
sludge at detention times of 9 to 72 hours, and concluded that hydrolysis of
the solid sludge particles was the rate-dimiting step of the overall acidogenic
phase. Lipids were not biodegraded, and 50 percent of the non-lipid COD of
primary sludge was solubilized. Acidogenic sludge was difficult to settle.
Hydrogen evolution occurred at the minimum detention time of 9 hours. Volatile
acid production and distribution of acid species in the effluent appeared to
be influenced by the reactor pH. Brown (25) indicated that hydrolysis of
particulate substrate was favored at an acidic pH (pH 6), and methane fermenta-
tion of the acid-digestion products was better at an alkaline pH (pH 7.5).
Detailed investigation of the pH effect was not conducted to delineate the
pi! optima, however. The methane digester gases contained 80 mol percent methane.
Norrman and Frostell (26) conducted mesophilic (33°C) two-phase digestion
of a semisolid synthetic feed (blended dog food) in a laboratory system com-
prised of a completely mixed acid-phase digester and a packed-bed upflow
methane digester. The acid digester was followed by a 500-ml gravity settler,
the supernatant from which was fed to the packed-bed methane digester. Acid
digester pH was low (pH 4). Solid-liquid separation was a problem with
the acid-digester effluent, The overall system was operated at detention
times of 2.7 to 12.1 days and low loadings of 0.026 to 0.14 Ib VS/ft3-day. A
long start-up time was required for the anaerobic filter. The methane digester
gases contained 65 to 80 mol percent methane. Like Norrman and Frostell.
Therkelsen and Carlson (27) also investigated the two^-phase digestion chai ac-
teristics of dog food, but at a thermophilic temperature of 50°C. The per-
formances of completely mixed and plug flow acid digesters were compared.
Surprisingly, lactate was the major acidic product. The pH of the acid
digester dropped to 4. Grease and organic nitrogen were not reduced signifi-
cantly. One interesting observation was that acid production in a plug-flow
acid digester was much higher than that in the complete-mix reactor. At the
test loadings (0.37 to 0.62 Ib VS/ft3-day) and detention times (4.3 to 7.5
days), two-phase thermophilic digestion of dog food was slightly better than
thermophilic conventional digestion.
Keenan (28) conducted two-phase digestion of simulated solid waste
(Purina Dog Chow) at 22° and 48°C. The acidr-phase digester had relatively
938
-------
long detention times of 4.5 and 6 days: the methane digester had a detention
time of 10 days. Acid digester gases contained mainly CC^ and a small amount
of hydrogen. Gases from the methane digester had 80 mol percent methane. The
acid digester effluent had 13,000 to 14,000 mg/i of volatile acids. There was
no significant difference in acid conversion efficiencies at 22°C and 48°C.
The two-phase process provided more stability than the conventional mixed-
phase high-rate process.
In contrast to the two-reactor systems studied by most researchers,
Johnson (29) found evidence of separation of the acidogenic and methanogenic
phases during anaerobic fermentation of pig excrement and biomass leachate in
a four-stage system. The two-phase multi-stage process was superior to
conventional high-rate digestion.
BENEFITS OF TWO-PHASE DIGESTION
Analysis of the laboratory and pilot plant research data presented above
shows that a multi-stage two-phase process evolves naturally when anaerobic
digestion is conducted at high loadings and short HRT's in the interest of
enhanced substrate conversion and gasification rates, reduced plant capital
cost, and increased net energy production efficiency. Investigators of the
two--phase digestion process presented ample experimental evidence to indicate
that this advanced digestion process is potentially far superior to the
conventional "high-rate" digestion process.
The feasibility of phase separation by kinetic control has been demon*-
strated for both soluble and solid substrates by several authors. Acid-phase
digestion can be conducted at residence times as low as 3 to 6 hours for
soluble organics, and 9 to 24 hours for particulate organic material. With
proper process design, the overall two-phase system could be operated at
residence times of 2 to 5 days, a substantial improvement over conventional
high-rate digestion conducted at residence times of about 12 to 20 days.
In summary, the two-phase process has the following demonstrated and
potential benefits;
• Capability to optimize the environment and operating conditions for each
digestion phase
• Maximization of the overall substrate conversion rate per unit culture
volume without sacrificing conversion efficiency
• Decreased digester volume, and plant capital and operating costs
• Improved mixing in low-residence time digesters
• Higher methane content (up to 85 mol percent) of the final product gas
• Enhanced net energy production efficiency
• Reduced nitrogen content in the final product gas owing to increased
939
-------
denitrification of the feed in the acid digester
• Increased process reliability owing to separation of the sensitive meth-
ane bacteria and their protection from environmental shocks of sudden
bursts of acid production, pH drops, and direct exposure to inhibitors.
PROBLEMS AND RESEARCH NEEDS
A careful consideration of the work of various investigators indicates
that several potential problems including inefficient acetate formation,
substrate inhibition in methane—phase digestion, retarded digestion of such
substrate components as lipids and certain nitrogenous compounds could arise
during two-phase digestion. Considerable fundamental research should be
undertaken to alleviate these problems and to develop an understanding of the
behavior of each microbial digestion phase in response to manipulation of
important fermentation parameters, operating modes, and reactor design.
REFERENCES
1. 11. P. Bryant, in Microbial- Energy Conversion, H. C. Schlegel and
J. Earned, Eds. (Pergamon Press, Oxford, 1977), pp. 107-117.
2. D. R. Omstead, T. H. Jeffries, R. Naughton, and H. P, Gregor, in
Biotechnology and Bioengineering Symp. No^ 10, C. D. Scott, Ed.
"(John Wiley, New York, 1979), pp. 247-2^8.
3. F. G. Pohland and S. Ghosh, "Developments in Anaerobic Treatment
Processes," Biotechnol. & Bioeng. Symp. No. 2, 85-106; In Biol. Waste
Treatment, R. P. Canale (Ed.), Wiley Interscience Publishers, New York,
57 Y. (1971).
4. Fisher, J. A., et al., "Pilot Demonstration of Basic Designs for
Anaerobic Treatment of Petrochemical Wastes," Chem. Eng. Progr. Symp.
Ser., Am. Inst. of Chem. Engr., 485 (1970).
5. P. L. McCarty, "Anaerobic Waste Treatment Fundamentals- I. Chemistry and
Microbiology," Public Works, 95_, 9, 107 (1964).
6. S. Ghosh and M, P. Henry, "Stabilization and Gasification of Soft-Drink
Manufacturing Waste by Conventional and Two-Phase Anaerobic Digestion."
Paper presented at the 36th Annual Purdue Industrial Waste Conference,
West Lafayette, Indiana, May 12-14 (1981).
7. H. E. Babbitt and E. P. Baumann, Sewerage and Sewage Treatment, 8th
Edition, John Wiley & Sons, New York, 1964.
8. F. G. Pohland and S. Ghosh, "Developments in Anaerobic Stabilization of
Organic Wastes — The Two-Phase C on cep t,a En vi r on, Letters , !_, 4, 225
(1971).
940
-------
9. S. Ghosh et al. ., "Anaerobic Acidogenesis of Sewage Sludge," Jour. Water
Pollut. Control Fed. _47, 1, 30 (1975).
10. S. Ghosh, '"Kinetics of Acid-Phase Fermentation in Anaerobic Digestion."
Paper presented at the Third Symp. on Biotechnol. in Energy Prod, and
Coservation, Gatlinburg, Tenn., May 12-15, 1981.
11. F. D. Schaumburgh and E* J, Kirsch, "Anaerobic Simulated Mixed Culture
Systern." App1. Microblpl.- 14, 761 (1966).
12. J. A, Borchardtf nAnaerobic Phase Separation by Dialysis Technique,"
Anaerobic Biological Treatment Processes, ACS Advances in Chemistry
Series 105 and 108, Washington, D.C., 1971.
13. J. A. Borchardt, "A Discussion/' Proc, Third Intl. Conf, on Water Pollut.
Res._, 1, 309 (1967). ~" — —-
14. F. G. Pohland and M. L. Massey, "An Application of Process Kinetics for
Phase Separation of the Anaerobic Stabilization Process," Progr. Wat.
Techno!. 7, 1, 173-189 (1975). " "
15. S. Ghosh and D. L. Klass, "Two-Phase Anaerobic Digestion," Proc. Biochem.
1J3, 15-24 (1978) April. ""*"""
16. S. Ghosh and D. L. Klas's, "Two-Phase Anaerobic Digestion," U.S. Patent
4,022,665, May 10 (1977).
17. P. M. Heertjes and R. R. van der Meer, "Comparison of Different Methods
for Anaerobic Treatment of Dilute Wastewaters." Paper presented at
Purdue Ind. Waste Conf., West Lafayette, Ind., May 8-10 (1979).
18. R. E. Smith, et al. , "Two-Phase Anaerobic Digestion of Poultry Waste,1'
Paper No. 75-4544,, presented at the ASAE Winter Meeting, Chicago,
December 15-18 (1975).
19. A. Cohen, et al., "Anaerobic Digestion of Glucose With Separated Acid
Production and Methane Formation," Wat;. Res, _13, 571-580 (1979).
20. S. Ghosh, ''Kinetics of Substrate Assimilation and Product Formation in
Anaerobic Mixed Culture Systems." Paper presented at the Symp. on Appli-
cation of Cont. Culture Theory to Biol. Waste Treatment Processes, 162nd
Natl. Meeting of ACS, Washington, D.C., September 1971.
21. S. Ghosh and F. G. Pohland, "Kinetics of Substrate Assimilation and
Product Formation in Anaerobic Digestion," Jour. Wat. Pollut. Control
Fed._, 46, 4, 748-59 (1974).
22. S. Ghosh, "Alleviation of Environmental Problems of Waste Disposal With
Production of Energy and Carbon Dioxide." Paper presented at the 28th
Annual Meeting, Soc. of Soft Drink Technologists, Colorado Springs,
Colorado, August 26-29 (1981).
941
-------
23. P. Pipyn, W. Verstraete, and J. P. Ombregt, "A Pilot Scale Anaerobic
Upflow Reactor Treating Distillery Wastewatersrv Biotechno1. Letters,
1, 495-500 (1979).
24. J. A. Eastman and J. F. Ferguson, "Solubilization of Particulate Organic
Carbon During the Acid Phase of Anaerobic Digestion." Paper presented
at the 51st Annual Conference, Water Pollution Control Federation,
Anaheim, Calif., October 3 (1978).
25. A. H. Brown, "Bioconversion of Solar Energy,"1 Chemtech. , 434-37 (1975)
July.
26. J. Norrman and B. Frostell, "Anaerobic Waste Water Treatment in a Two-
Stage Reactor of a New Design." Paper presented at Purdue University
Industrial Waste Conference, West Lafayette, Ind. , May 10, 1977.
27. H. II. Therkelsen and D. A. Carlson, "Thermophilic Anaerobic Digestion of
a Strong Complex Substrate." Paper presented at the 50th Annual Conf-
erence,Water Pollution Control Federation, Philadelphia, October 2-7,
1977.
28. J. D. Keenan, "Two-Stage Methane Production From Solid Wastes." Paper
No. 74-WA/Ener-ll presented at the ASME Winter Annual Meeting, New York,
November 17-22, 1974.
29. A. L. Johnson, "Final Report on Research in Methane Generation,"
U.S. Office of Sci, and Techno1.„ Work performed under Contract No.
AID/ta-G-1278, Project No. 931-17-998^-001^73, El Segundo, Calif., The
Aerospace Corporation. September 1976,
942
-------
AMMONIA
^SULFIDES
CARBOHYDRATE
PROTEIN
FAT
Figure 1. Reaction Steps in Anaerobic Digestion.
-------
OQ
i-i
ro
tt> CO
en o
it V
H- nr
o H-
3 M
H-
O O
CO CO
O Ui
Hi o
rt n
I ^*™^
o
II
*s
03 rt
cn H-
rt O
fD 3
PC
H-
•5.
RETENTION LOADING(L), C/N VOLATILE ACIDS, TOTAL AND METHANE
TIME(fi), |bVS/ft3-day RATIO mg/i as acetic YIELDS, SCF/lb VS added
ooo
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-
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-
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-
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-
-
-
-
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ll ^
-------
O -O
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O ^
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7 5
50
2 5
I I
>W34>
hJ-L
O
o
Z Jl
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o -*
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60
-!
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20
0
075
050
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0
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n
"*~^fl-|n ""---^, tf = 7 ! ^
-
1 1 1 1 1 1 1 1 1 1 ! 1 1 1 1 1 1 1 1 1 1 1 1 | I I I I | ! I I I
• — -_^ 9 = 45
1 1 1 1 1 1 ! 1 1 1
76 80 85 9O 95 100 105
ACCUMULATIVE TIME, days
110
115 120
B8I0509I „
Figure 3. Response of a Continuous-Flow High-Rate Soft-Drink Waste Digester
to Increased Loadings and Reduced Detention Times:
Development of an Acid-Phase Culture.
945
-------
CH4 YIELD,
SCF/lb VS added
6 8 10 12 14 16 18
SLUDGE SOLIDS, wt %
20 22 24
A8I09I930
Figure 4. Dependence of the Net Energy Production Ratio on the
Feed Sludge Solids Concentration for Mesophilic (35°C)
Digestion of a 60-wt Percent VS-Content Feed at a Loading
Rate of 0.1 Ib VS/ft3-day (The feed slurry is
assumed to have a temperature of 15°C).
946
-------
LJ
\
Q.
LJ
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.01
CH4 YIELD,
SCF/lbVS added
I
I
0.05 O.I
0.5
1.0
LOADING RATE,lbVS/ft3-day
5 10
A8I09I93I
Figure 5. Dependence of the Net Energy Production Ratio on the
Digester Loading Rate for Mesophilic (35°C) Digestion of a
60-wt Percent VS-Content Feed (The feed slurry has a
3-wt percent solids concentration and a temperature of 15°C).
947
-------
300
I 5% GUI FEED
_
41% GLU FEED
14
12
I »
o
0 0.1 0.2 0.3 04 05 06 0.7 0.8 0.9 Ifl I.I 1.2 13 14 15 1.6 1.7 I.B 1.9 2.0
DETENTION TIME, days ASIWBM
-3 DAYS
CONDITIONS
A'0.49 DAY'1
K,=4.2g//
4.5 DAYS
-5%HOAc FEED
0.5% HOAc FEED
,l%HOAcFEED
0 2 4 6 6 10 12 14 16 IB 20
DETENTION TIME, days A81O9I932
Figure 6. Glucose Acidification and Acetic Acid Methanation Rates
Per Unit Acid Digester Volume as Functions of Detention Time
and Substrate Concentration Under Mesophilic (37°C) Conditions.
948
-------
8 10 12 14
DETENTION TIME, days
16
18 20
A8I09I934
0.5% HOAc FEED
i% HOAC FEED
6 8 x tQ .12 14
' DETENTION TIME.'days.
A809I932
Figure 7, Sewage Sludge Acidification and Acetic Acid Methanation Rates
Per Unit Acid Digester Volume as Functions of Detention Time and
Substrate Concentration Under Mesophilic (37°C) Conditions.
949
ft US GOVERNMENT PRINTING OFFICE. 1984 - 759-102/10684
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