United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/2-80-099
Laboratory July 1980
Cincinnati OH 45268
Research and Development
Fine Solids Removal
Following Combined
Chemical-Trickling
Filter Treatment
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4, Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7, Interagency Energy-Environment Research and Development
8. "Special" Reports
9, Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-80-099
July 1980
FINE SOLIDS REMOVAL FOLLOWING COMBINED
CHEMICAL-TRICKLING FILTER TREATMENT
by :
James C. Brown
UNC Wastewater Research Center
Department of Environmental Sciences and Engineering
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina 27514
Contract No. 68-03-0225
Project Officer
Richard C. Brenner
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY ;
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
-------
FOREWORD
The U.S. Environmental Protection Agency was created because of increas-
ing public and government concern about the dangers of pollution to the health
and welfare of the Anerican people. Noxious air, foul water, and spoiled
land are tragic testimonies to the deterioration of our natural environment.
The complexity of that environment and the interplay of its components require
a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem" solution;
it involves defining the problem, measuring its impact, and searching for
solutions. The Municipal Environmental Research Laboratory develops new and
improved technology and systems to prevent, treat, and manage wastewater and
solid and hazardous waste pollutant discharges from municipal and community
sources, to preserve and treat public drinking water supplies, and to minimize
the adverse economic, social, health, and aesthetic effects of pollution.
This publication is one of the products of that research and provides a most
vital communications link between the researcher and the user community.
The studies described here were conducted to evaluate techniques for
removing fine solids carryover from a full-scale trickling filter facility
dosed with aluminum sulfate (alum). Alum has been shown in other work to be
compatible with the trickling filter process for precipitating phosphorus and
coagulating unsettled biological Tloc. This report documents the potential
of several tertiary options for additonal solids removal when final clarifier
loadings become too high to realize maximum benefits of combined chemical-
trickling filter treatment without supplemental upgrading.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
iii
-------
ABSTRACT
The addition of alum ahead of the final clarification stage of the
trickling filter process has been observed to improve effluent quality.
Soluble phosphorus is precipitated,and fine biological floe is entrained in
the alum floe matrix and thereby rendered settleable. One of the important
factors affecting the removal efficiency obtained with alum addition is the
hydraulic loading applied to the final clarifier. When the surface overflow
rate is above 24.4 m3/day/m2 (600 gpd/ft2), significant amounts of fine alum
floe, biological sol ids, and precipitated phosphorus are carried over with the
clarifier effluent.
This research project was designed to evaluate the effectiveness of two
methods of fine solids removal for possible application following normal
clarification when alum is applied ahead of the clarification stage. The
methods investigated were:!) fine solids settling ponds and 2) various types
of granular media filters.
Two pilot settling ponds, one covered and one open, were operated at
experimental detention times ranging from 8 to 30 hr. In addition, two
pilot granular media filters were operated at filtration rates ranging from
88 to 176 m3/day/m2 (1.5 to 3.0 gpm/ft2). The filters were operated in, both
the normal downflow and upflow modes. Various filter media were used in
each operational mode.
The pilot settling ponds did not perform as expected. Anaerobic condi-
tions which developed in the settled sludge disrupted the floe structure with
consequent resuspension of the previously settled solids. Algal growth in
the uncovered pond was a problem.
The use of pilot fine solids settling ponds following combined alum/
trickling filter treatment resulted in a very modest improvement in final
effluent quality. The application of fine splids settling ponds appears to. be
inappropriate where more than a 25 percent improvement in effluent quality is
required.
The two filters, when operating in the downflow mode with two different
configurations of anthracite and sand media, proved about equal in perfor-
mance. Both filters performed fairly well when the main plant effluent was
good. Poor plant effluent (filter influent) resulted in short runs, rapid
buildup of head!ess, and low quality filter effluent.
Upflow filters produced a slightly lower effluent quality than the down-
flow models. The upflow mode of operation, however, did result in lower
iv
-------
rates of headless buildup; substantially longer filter runs proved feasible.
This report was submitted in fulfillment of Contract No. 68-03-0225 by
the University of North Carolina under the sponsorship of the U.S. Environ-
mental Protection Agency. The report covers the experimental period of
September 10, 1973, through March 6, 1975.
-------
-------
CONTENTS
Foreword n 1-1
Abstract .]Y
Fi gures V1 "•n
Tables 1x
Acknowledgements x
1. Introduction 1
Reason for the study , 1
Project scope 1
2. Conclusions 4
3. Recommendations 5
4. Experimental Program 6
Equipment and method of operation - ponds 6
Equipment and method of operation - granular media filters .. 7
5. Operation and Performance •. 11
Sett! i ng ponds 11
Granular media filters 15
References
25
-------
FIGURES
Number Page
1 Suspended solids removal as a function of flow and
final clarifier overflow rate for initial project 2
2 Phosphorus removal as a function of flow and final
clarifier overflow rate for initial project 3
3 Pilot settling pond flow control system 7
4 Pi 1ot settli ng pond arrangement 8
5 Photograph of pilot settling ponds 8
6 General arrangement of pilot granular media filters 9
7 Granular filter media configurations 16
vm
-------
TABLES
Number
1 Pi 1 ot Sett! 1 ng Pond Data ...................... ...
2 Daily Data - Downflow Media A vs. Downflow Media B ---- .
3 Summary Results - Downflow Media A vs. Downflow Media B
4 Daily Data - Downflow Media A vs. Upflow Media C ..... .
5 Summary Results - Downflow Media A vs. Upflow Media C
6 Daily Data - Downflow Media A vs. Upflow Media D
7 Summary Results - Downflow Media A vs. Upflow Media D
Page
12
17
19
21
22
23
24
-------
ACKNOWLEDGEMENTS
This project was conducted at the UNC Wastewater Research Center of the
Department of Environmental Sciences and Engineering, School of Public Health,
University of North Carolina at Chapel Hill.
The pilot plants were constructed by George Burns, Some of the experi-
mental work with granular media filters was conducted by Philip Braswell, a
graduate student in the Department of Environmental Sciences and Engineering.
The manuscript was typed by Mrs. Del ores E. Plummer,
-------
SECTION 1
INTRODUCTION
REASON FOR THE STUDY ' !
Significant carryover of fine alum floe solids was observed in final
effluent during earlier plant-scale studies of alum addition to the final
clarifier of a high-rate trickling filter train of the Chapel Hill, North
Carolina wastewater treatment plant (1). Data generated during these studies
revealed that although phosphorus insolutilization is relatively unaffected,
overall alum treatment effectiveness in terms of suspended solids and pre-
cipitated phosphorus floe capture becomes increasingly limited as the hydrau-
lic loading on the final clarifier increases. The effect of final clarifier
overflow rate on effluent total suspended solids (TSS) and total phosphorus
as recorded in the previous project is illustrated in Figures 1 and 2,
respectively.
Simple laboratory experiments indicated that additional physical separa-
tion of suspended solids, either by means of fine solids settling ponds or
with granular media filters, held potential for producing significantly
improved final effluent quality when applying alum at wastewater treatment
plants equipped with trickling filters. Follow-up pilot plant evaluations
were conducted on sidestreams of Chapel Hill plant effluent to compare these
two methods of upgrading alum-flocculated trickling filter effluent. The
results of those follow-up evaluations are the subject of this report.
PROJECT SCOPE
Solids escaping the final clarifier during plant-scale tests of alum
treatment were mostly fine alum floe and would reform and settle in labora-
tory jars. It was anticipated that these solids would settle in a pond and
would form a relatively stable sludge layer as in a water treatment plant
with non-mechanical settling tanks. These accumulated solids could then be
removed from the ponds at 3-6 mo intervals.
Two outdoor pilot settling ponds were constructed, one covered and one
uncovered. They were designed to operate at various hydraulic detention
times ranging from 8 to 30 hr. Observations were taken on pond influent
(plant effluent) and effluent quality. Monitoring plans included measuring
sludge accumulation on the pond bottoms.
-------
FINAL CLARIFIER SURFACE OVERFLOW RATE (gpd/ft*)
300 400 500 600 700 800 900 -1000 MOO
NOTES'1 mgd=3785 mVdow'irf
1 gpd/ft * 0.0*1 mVdoy/m*
# EXPERIMENTAL PERIODS 1-4 AND 6-12
I I I
80
0.4 0.6 0.8 1.0 1.2 1.4
FLOW (mgd)
1.3
FIGURE 1. Suspended solids removal as a function of flow and final
clarifier overflow rate for initial project (1).*
A pair of granular media filters were fabricated and installed inside
the University of North Carolina's pilot research building on the grounds of
the Chapel Hill plant. The filters were designed to explore the effect of
different filtration media, varying filtration rates, and operating in two
different filtration modes (upflow and conventional downflow).
Two downflow media configurations were evaluated: a dual media anthra-
cite over sand system and a four media system of fine anthracite over coarse
anthracite over sand over garnet. Two upflow media configurations were also
studied. One upflow unit employed three grades of granite chips topped with
sand; the other used just two grades of granite chips with no sand topping.
During this investigation,the Chapel Hill plant was operated with an
average dosage of 198 mg/£ of alum (as Al2(S04)3.14.3 ^0) applied to one-
half the plant, i.e.,at the influent to the final clarifier of one of the
two trickling filter trains. The clarifier overflow rate ranged from 9.7 to
100.7 m3/day/m2 (239 to 2472 gpd/ft2). The alum treated trickling filter
effluent passed through this single clarifier, and the effluent from the
clarifier was used to supply influent to both the pilot settling ponds and
the pilot filters.
Experimental studies were initiated in mid-September 1973. Work was
terminated in July 1974 on the filters and in March 1975 on the ponds.
-------
FINAL CLARIFIER SURFACE OVERFLOW RATE (gpd/ft»)
300 400 500 600 700 800 900 1000 1100
IOO
9O
80
^b
I
I
70
60
51
T
T
T
T
T
T
T
NOTES11 mgd * 3785 mVdqy
/ft» 0.041 nf/
'/day/m'
SOLUBLE PHOSPHORUS-
* EXPERIMENTAL PERIODS 1-4 AND 6-O
\ ' I
J_
-"r
D
a a a a
—I L
-------
SECTION 2
CONCLUSIONS
The settling ponds did not function as expected. The removal of BOD,
suspended solids, and phosphorus in the ponds was lower than expected and
erratic. Pond effectiveness Appeared unrelated to detention time in the
range of 8 to 30 hr. Anaerobic conditions developed in the sludge accumula-
ting on the pond bottoms. The floe structure then broke up, and a large por-
tion of the previously settled solids was resuspended. Also, algal growth
in the uncovered pond was a nuisance and resulted in a fairly heavy scum
layer of dead algal cells at the surface of the pond. On the basis of data
obtained during this investigation, the use of settling ponds following
trickling filter plants in which alum is applied will provide a modest im-
provement in final effluent quality; however, their performance is not reli-
able or predictable.
The two downflow filter configurations tested proved approximately equal
in performance. Both filters performed fairly well when the main plant
effluent, was good. When the influent to the pilot downflow filters was of
lesser quality, i.e., BODr of approximately 20 mg/£ and TSS of approximately
30 mg/A, the removal of both BODg and TSS ranged from 55 to 72 percent. Per-
cent removal was not affected by filtration rate. When filter influent was
of better quality, the percentage BODg removal was lower, probably indica-
ting a large fraction of the BOD,- was in soluble form; .however, the removal
of total suspended solids was not significantly effected. Poor plant effluent
(pilot filter influent) resulted in high rates of headless buildup and short
filter runs. The rate of headless buildup was, of course, greatest at the
highest filtration rates. (The rate of headless buildup increases in direct
proportion to filtration rate when filtering clean water). The rate of head-
loss buildup was also affected by the quantity and quality of suspended sol-
ids in the filter influent.
In comparing a conventional downflow media configuration with two upflow
configurations, both upflow configurations proved slightly less effective
than the downflow configuration with regard to effluent quality. However,
the rate of headless buildup in the upflow filters was less than half that of
downflow models. Prototype upflow filters should be capable of much longer
runs than downflow models. During this investigation, in a period when
personnel were available for round-the-clock operation (5/28/74-6/4/74 - see
Table 6), the upflow filter operated up to three times longer than the down-
flow filter. The second upflow configuration which consisted of generally
coarser media and greater media depth than the first upflow model proved
simpler to operate as it was not prone to media separation during filtration.
-------
SECTION 3
RECOMMENDATIONS
The application of fine solid ponds following combined alum-trickling
filter treatment results in a modest improvement in final effluent quality.
Such units should not be used in cases where more than a 25 percent improve-
ment in effluent quality is required.
Additional work should be undertaken to explore the potential of coarse
media upflow filtration for tertiary solids removal at wastewater treatment
plants utilizating chemical treatment.
-------
SECTION 4
EXPERIMENTAL PROGRAM
EQUIPMENT AND METHOD OF OPERATION - PONDS
The pilot settling ponds consisted of two steel tanks fabricated of
4.8-mm (3/16-in.) plate, 3.7 m (12.0 ft) in diameter with side wall height
sufficient to permit a water depth of 2.1 m (7.0 ft). One tank was covered
with black plastic sheeting supported on an angle iron framework and chicken-
wire. The other pond was not covered. This was done to study the effect of
the presence and absence of natural light on algal growth in the ponds.
Influent flow to the pilot ponds (and granular media filters) was sup-
plied by a self-priming centrifugal pump mounted above the effluent channel
of the main plant final clarifier. Flow to each settling pond was controlled
by means of a double weir box which divided the flow equally to each pond.
The actual flow to each pond at any time was determined by the level in the
head box. This level was adjusted by raising or lowering the head box over-
flow pipe. Diurnal flow variation was simulated using two solenoid operated
valves controlled with a timer. In this way, two different rates of flow
were obtained at different times of the day.
The head box and splitter are illustrated diagramatically in Figure 3.
Figure 3 also illustrates how the flow rates obtained by sequenced operation
of the solenoid valves compare with a typical diurnal fluctuation in main
plant flow.
Figure 4 shows the general configuration of the two pilot settling
ponds. A photograph of the ponds is presented in Figure 5.
The pilot ponds were operated at detention times of 8, 12, 16, 20, 24,
and 30 hr. Overall flow rates were adjusted, as required to obtain the
desired detention time, by raising or lowering the overflow level in.the head
box.
Since the ponds were operated continuously for fairly long periods of
time, the flow-weighted plant effluent samples from that side of the plant
receiving alum treatment were used for pond influent samples. The pond efflu-
ent sampling lines flowed continuously, under gravity, to a flow proportional
sampler. Pre-set timers operated valves to divert small equal portions of
pond effluent to sample containers in a refrigerated box. Intervals between
operation of the diversion valves were inversely proportional to flow; there-
fore, flow-weighted,24-hr composite samples were obtained.
-------
ED VALVE
JO POND NO.]
rv? SOLENOID VMVES OPEN
FIGURE 3. Riot settling pood flow control syst<>m.
"*
EQUIPMENT AND METHOD OF OPERATION - GRANULAR MEDIA FILTERS
iiu ii rr, ,nnJ °L • + S f re constructed with clear lucite
uu.u rt; long with mternal diameters of 29.2 cm (11% in )
(3/16-in )'diameter "^ °f St^ Plate dr111ed wi^ ^ equal
Qaskets Filt'/apoH +• ' 11 • •> « «*!..>»
general drawing of the arrangement of
shown in Figure 6.
-------
BLACK PIASTIC COVEB
NOTE: 1tt»0305m
FIGURE A. Pilot settling pond orrong«n«r*.
R6URE 5. Photograph of pilot settling ponds.
-------
FILTER NO. 1
HEAD TANK
FILTER NO.2
JfiL.
MEASURING TANK
•*- TO DRAIN
\ BACKWASH (SuHiecnt
^ — • (
.
,
••••MBMi
1 I ,
PIEZOMETERS f
RGURE 6. General arrangement of pilot granular media filters.
-------
Influent for the filters (plant effluent) was pumped to a head tank
which was maintained in a completely mixed state with air mixing. The same
mixed effluent flowed to each filter. The two filter units treated the amount
of water discharged by the individual filter control pumps. These pumps acted
as effluent pumps when the filters were operated in the downflow mode and as
feed pumps when operating in the upflow mode.
The filter pumps, which also functioned as rate controllers, consisted
of Jabsco, flexible rotor, positive displacement pumps with direct current
motors controlled with silicon rectifers (SCR units), which permitted com-
plete variable speeds from the stall speed of the motor (about 50 rpm) to the
maximum speed of the motor (1,750 rpm). The pump discharge rate was measured
for various control settings and a calibration curve was developed. The
desired filtration rate was set at the beginning of a run and checked by timed
volumetric measurements. The rate was checked several times during each fil-
ter run. This system was found to be very reliable. When operating in the
downflow mode, influent from the head tank flowed through the filter to the
control pump and thence to discharge. In the upflow mode, water flowed from
the head tank to the control pump and thence upward through the filter.
A backwash rate of 8.8 to 10.2 A/sec/m2 (13 to 15 gpm/ft2) proved to be
sufficient to expand downflow media A and B and upflow media C at least 20
percent. Approximately 10 min of backwash proved sufficient to clean the
filters. In backwashing, water alone did not prove as effective as air scour
followed by water. As shown in Figure 6, an air scour system was provided.
In backwashing upflow media D, it was not possible to suspend the coarse media
in the bottom layers of the filter with the amount of service water available.
It was, however, possible to effectively clean the filter with a combination
of hydraulic backwash and air scour. Approximately 2 min of combined air
scour and low rate hydraulic backwash followed by 8 to 10 min of hydraulic
backwash (without air) was sufficient to clean the filter.
Filter influent samples were obtained automatically from the head box at
regular time intervals. Filter effluent samples were also obtained at regu-
lar time intervals from the filter discharge. Samples were composited over
the length of the filter run and stored in a refrigerated box.
Headless buildup during filter runs was observed by means of piezometer
tubes installed in each filter.
In general, the pilot filters functioned well. They were easy to operate
and backwash. Regardless of the success or failure of any particular experi-
mental program, these filters would have been excellent teaching units.
10
-------
SECTION 5
OPERATION AND PERFORMANCE
SETTLING PONDS
The data obtained during the settling pond experiments as summarized in
Table 1 followed no consistent pattern. The best removal efficiencies were
obtained at a 12-hr detention period, but relatively poor removal efficiencies
were obtained at all other detention periods. During some experimental
periods, the covered pond performed better than the uncovered; in other
periods, the opposite was observed. The best .performance for both the covered
and uncovered ponds, i.e., during the 12-hr detention period, was during the
warmest weather. Table 2 compares average influent and effluent parameter
concentrations for the various detention periods investigated.
Little sludge was found to accumulate on the bottom of either the covered
or uncovered ponds. The TSS in the pond underdrain varied from a high of 108
mg/£ to a low of 35 mg/£. Dissolved oxygen (D.O.) analyses conducted at
various liquid depths in the ponds showed a range of concentrations of be-
tween 6 and 8 mg/£ at the surface to less than a detectibM concentration in
the bottom 0.6 m (2 ft); the D.O. concentration decreased more rapidly with
depth in the covered tank. It is believed that anoxic conditions in the
lower level of the tanks resulted in anaerobic decomposition of solids and
that this process destroyed the physical structure of the alum floe, disper-
sing fine solids throughout the tank. It is further believed that the over-
all removal of BOD, TSS, and other parameters in the ponds was a result of
biological conversion rather than physical separation by settling.
During all warm weather periods, the uncovered pond was blanketed with
an algal scum and the effluent from this pond had a pale green color. These
conditions did not develop in the covered pond. Significantly higher D.O.
concentrations were observed in the uncovered pond, and measurable concentra-
tions persisted to greater depths within the pond. Neither the algae nor the
coincident higher D.O. levels in the uncovered tank resulted in any signifi-
cant difference in performance as compared with the-covered tank.
11
-------
TABLE 1. PILOT SETTLING POND DATA
Pond Effluent
Parameter
mg/£
BOD
TOC
TSS
TVSS
N02-N + N03-N
NH4-N
Total P04-P
Filtered P04-P
Turbidity (JTU)
BOD
TOC
TSS
TVSS
N02-N + N03-N
NH4-N
Total P04-P
Filtered P04-P.
Turbidity (JTU)
No. of
Samples
8-hr
21
19
22
20
21
21
22
22
21
12-hr
11
15
15
15
13
13
14
14
15
Pond
Influent
Detention
41
44
70
51
0.5
21.7
6.2
2.7
34
Detention
28
39
68
40
2.7
20.4
6.2
1.1
33
No. 1
cov'd
1/30/75 -
__
—
—
—
—
—
—
—
—
7/10/74 -
14
21
32
23
1.0
20.4
2.3
0.6
13
No. 2
3/6/75
39
39
60
44
0.5
22.5
6.4
3.1
28
10/8/74
15
24
35
22
1.1
20.6
2.5
0.5
15
% Removal
No. 1
cov'd
__ ,
--
--
--
—
—
--
--
50
46
53
43
63
0
63
45
61
No. 2
5
11
14
14
0
(4)
(3)
(15)
18
46
38
49
45
59
(1)
60
55
55
TSS in Settled
Sludge from Pond
Drains (mg/&)
84
108
(continued on next page)
12
-------
TABLE 1. (continued)
Pond Effluent % Removal
Parameter
mg/£
No, of
Samples
Pond No
. 1
Influent cov'd No.
16-hr Detention 4/3/74 -
BOD
TOC
TSS
TVSS
N02-N + N03-N
NH4-N
Total P04-P
Filtered P04-P
Turbidity (JTU)
TSS in Settled
Sludge from Pond
Drains (mg/Jl)
BOD
TOC
TSS
TVSS
N02-N + N03-N
NH4-N
Total P04-P
Filtered P04-P
Turbidity (JTU)
19
24
24
23
24
24
24
18
20
8
14
14
15
15
15
15
15
15
14
17
18
34
22
1.2
20.7
.2.2
0.9
17
..
20-hr Detention
35
34
54
27
2.2
23.7
4.4
0.9
23
12
15
35
21
0.5
19.3
1.6
0.5
13
44
2/13/74
20
30
43
26
0.5
26.3
3.3
0.5
18
12
18
31
19
0
18
1
0
14
63
_
22
33
46
26
•0
25
4
0
20
No. 1
2 cov'd
6/10/74
• ; 29 ;
17-
.__•
5
.7 58
.9. 7
.7 27
.5 44
' '- 24
3/10/74
43
12
20
4
.7 77
•7 (11)
.0 25
.5 44
22
No. 2
29
0
9
14
42
9
23
44
18
37
3
15
4
68
(8)
9
44
13
TSS in Settled
•Sludge from
Drains (mg/£)
35
80
(continued on next page)
13
-------
TABLE l.(continued)
Pond Effluent
Parameter
mg/£
BOD
TOG
TSS
TVSS
NO£-N + N03-N
NH4-N
Total P04-P
Filtered PO^-P
Turbidity (JTU)
BOD
TOC
TSS
TVSS
N02-N + N03-N
NH4-N
Total P04-P
Filtered P04-P
Turbidity (JTU)
No. of
Samples
24-hr
12
13
13
9 *
9
13
13
13
13
30-hr
7
8
8
5
8
8
8
8
7
Pond
Influent
Detention
11
25
38
20
2.3
21.8
2.6
, 0.6
17
Detention
19
35
55
35
1.9
26.3
5.5
--
24
No. 1
cov'd
10/31/73
10
22
30
15
1.0
23.3
1.8
0.4
13
9/13/73
15
30
35
25
0.8
28.6
4.3
1.0
20
No. 2
- 12/24/73
9
. 21
31
16
0.7
23.4
1.8
0.3
12
- 10/4/73
20
35
56
32
0.9
28.4
5.2
0.9
36
% Removal
No. 1
cov'd
9
12
21
25
57
(7)
31
33
24
21
14
36
29
58
(9)
22
—
17
No. 2
18
16
18
20
70
(7)
31
50
29
(5)
.0
(2)
9
53
(8)
5
--
(50)
14
-------
GRANULAR MEDIA FILTERS
Downflow Media A vs. Downfl'ow Media B
The first phase of experiments with the pilot filters v/as designed to
compare the two filters in a downflow mode of operation with a different
filter media configuration in each unit. Specific information concerning the
media configurations and other important parameters are shown in Figure 7
under the label, 1st Series of Tests. Media configurations for subsequent
test series are also given in this figure. Filter No. 1 was a typical dual
media unit as commonly used in water treatment with 56 cm (22 in.) of anthra-
cite over 25 cm (10 in.) of Sand (Media A). Filter No. 2 was a four media
unit composed of 15 cm (6 in.) of fine anthracite over 36 cm ("14 in.) of
coarse anthracite over 15 cm (6 in.) of sand over 15 cm (6 in.) of fine garnet
(Media B). The general idea.in both filters was to obtain, to the extent
possible, a decreasing particle interstitial space with increasing depth
in the filter. In theory, this should allow all levels of the filter to
function in the removal of solids. It had been suggested that the four media
unit would be more effective as it more closely approached the desired geome-
try. The total depth of filter media in each unit was 81 cm (32 in.).
The 5 cm (2 in.) of coarse garnet in the bottom of each unit served only for
support of the media.
The downflow filters were operated at filtration rates varying from 1.0
to 2.7 £/sec/n/ (1.5 to 4.0 gpm/ft^) during the period from September 9, 1973,
through April 4, 1974. The daily data collected are displayed in Table 2.
Summary results are presented in Table 3 for each of the four filtration rates
employed.
TSS removals generally ranged from 65 to 80 percent except for the
lowest filtration rate, 1.0 a/sec/nr (1.5 gpm/ft^), evaluated. At this rate,
TSS removals of only 55 to 60 percent were achieved. Absolute effluent
quality in terms of suspended solids and total phosphorus, but not BOD, was
also poorer. This anomalous performance at the filtration rate where the
best effluent quality would normally be expected cannot be explained by the
author.
The rate of headless buildup at filtration rates of 1.0, "1.4, and 2.0
a/sec/m* (1.5, 2.0, and 3.0 gpm/ft^) seemed not to be affected by filtration
rate. It should not, however, be concluded that headless buildup and filtra-
tion rate are unrelated; in this investigation, the normally expected direct
relationship of the two rates is obscured by the effect of variable quality
filter influent on the rate of headless buildup.
There was very little difference in the performance of the two downflow
filters. For this reason, the simpler, more economical type, i.e., the dual
15
-------
16
-------
z <
o
z
o
o
i i
„ £
z
0
s
o
II EFHUENT
1
u
>-
c
o X
z *
CC J
"J a
o 2
0
. z
• z
o £
S <
o £
H
o
z
I I
z
I
i
l •
o •>
cnio
sum
=
si
o J1
SSA
(|/6m)
SSI
!!/'")
SOJ
'C1
CBH ''HI )
SSO10V3H
jo aiva
(S3HDNI)
SSO1OV3H
(saw)
Nna ^o
H1ON31
mm
earn ,
£o-
si
e f
SSA
[ 1 /6u.)
SSI
{ ,/Su,)
301
t /B^J
CSH '-HI j
sSoiorjH
jo Jjvjj
SS010V3H
f SHH)
NOB JO
HJ.ON31
inir)
fiuru
1
§'
sl
oj
N-CHN
SSA
( l/6«")
301
FOOS
|| /Bui;
3OVSOQ
ON10VO1
V13 INVId
D
, , ,s,«|.a.rms«mnNNn
1 1 l-HOIOOr-)OIOOOOOIOO
I 1 lOrHlcHiHCMoaiOf-JOOOlOO
I I 1 1 CO 1 1 1 1 t !<-l 1
i i iwr-tmcoHvcicstnr^ojTv^m
i i tHoIodt-Ioioodooddo
j i !r-tnifNiDtAoir^nM I
rtmOOOOOOOOHOOO 1
N in .-i M m .H ri in [ l co^rnM l
|H rH l-l 1
--2asqS3HS3SSdra!
HHt-IHrilNf1incO->J'!- j I-1M (
*-l
r, g «, co « 5 r-
"S^SSS^SSSSSH10
'-1 1
t-4 r-{ *
SgS3S?KSSSP5p!Ra
CN H r-i i-l C--J CN
3S^a,3S;g3?!dSSCO(, ,
o,»«a)inin.).«c«.cMVrtrtrt l
OOOOOOC3OOOOOOO 1
335388 S888K338!
SS3SSS:SP!?SSKSIQi
•saaaaaaaRRaaa i
t-ioj ifHr^r- i ^« r- N *t i MCM i
I 1 r-1 r~{ r-i H I 1
^•^•Ot— ICOCOrHfH 1 CT^<3imfr)t*-fn
l5sssssSsls£Ssl
r^r-r-r-r-i ilititii?
l l l l lOui\i)r-r«jcDc\OrHI
^SS^^^'n'**^1''5'''"''1'^''1
17
-------
13
i
j *
o
o
r*
0
S
: §
o
o
0
r
miYW IVNU INVU
>-
<
—
=
1 =
O 2
c
a
-
-
*"
< s
i i
*
o
z
a
i
i
1 i
=: 5 -i
(HID
KOI
i §!
i 2 1
SSA
(IX6UI)
SSI
DO1
C»H ''Ml )
SSO10T3H
JO 31VS
IS3H5NI)
SS01CK3H
CS8H)
Nna jo
H10N31
inir)
•am
1 si
i 2.1
^rrHCO 1 r*l
rH CNi-CrHM i-trHCN rH IrH
r^r_{l_(l-{OirN'<0arMcnn>nvou>u>ou>o^rtnm l r-
OOOOO«-tMrHOOOOO«HOlMOOO 1 C*
tH 01 CN rH 1 t
-"-se°3ss«d-H<""u>PiS!3"S'-:^
H
'
K S
OiHrHnmcNoioiocoiDcNiorNCNrHcovo^rinin
rH rH rH rH rH rH «-l
•
inoom\o«iinincninin\DinvDP-cO'C'initf)rr in
t-cor.t-vovD^r-mo^^mvl^omcou.r-^vo
Q
cMnnntM^QoNtMtMUjrfMrHinncMM I r-
OOOOOOSSOOOOOOOOOOOO 1 O
^^TOUJCMncNOOOr-linrtmoirtuiTTj en
McMNrf^t^.in^rt^.-lcM.-lrir-jn.-trt.N i n
SSSSSSSSSSSSSSSKSSS ! S
cM^^CMr,^c~m-q-CMCMNfo^mlnrf^r, | n
CM4nE_rtcM[M I n
iovo>oDQ^coQno
s a a B 3
«HrHrHCN rH rH rH i-H CN CN CN CN rH rH CN CN CN | |
— t rH
i i i i\ri"rrrrrrrrtTr'>?r-r>-r-i i i i i
i i t i t i i i i i i i i i i > i i i t i
: DOWNFLOW i MEDIA - B
1.5 GPM/ FT2
o
S
1
0
o
X
I
dS!m--S
r* in in "a1 ^?= r- n
o o o o o o o
CO CN CO (N rH rH O*
I I 1 1 1 rH rH
rH rH rH rH rH rH rH
f> Ol CT* O O O O
CN CN M CN OJ CN 04
I | 1 m CN M rH
1 1 1 «H
«. r> m m «* ro <.
m rH CN co m m n
r~- tn r*- co cri CQ co
CN co I en r*> 01
p- in in -a- in TT m
o o o o o o o
M CN co tn en in CN
CO CN Ol Ol rH rH Ol
1 1 1 1 1 rH CD
1 1 1 I 1 *H
CN rH CN rH rH rH
m rH CO rH rH O O
CN CN CN CN 01 0) CN
1 I l o rp CN m
1 1 1 rH
• o o vo
vo ^T i in p- 10 in
rH | rH rH rH rH
r- CM oi o o \o oj
m ^r in vo tn tD 10
CN
r— r- -T TT T •o- ^r
i l r** f*» r^ r* r*
m vo i i i i i
CN O) rH OJ n ^ m
t i l i i i i
u
Si
.s !
lii
18
-------
TABLE 3. SUMMARY RESULTS - DOWNFLOW MEDIA A VS. DOWNFLOW MEDIA B
2
1.5 gpm/ft
BOD
TSS
Total P04-P
Rate of Headless
2,0 gpm/ft2
BOD
TSS
Total P04-P
Rate of Head! oss
3.0 gpm/ft2
BOD
TSS
Total P04-P"
Rate of Headless
4.0 gpm/ft2
BOD
TSS
Total P04-P
Rate of Headless
Effluent
Influent
mg/&
18
38
3.8
Buildup (in./hr)
16
48
3.9
Buildup (in./hr)
7
31
1.7
Buildup (in./hr)
22
34
2.4
Buildup (in./hr)
Downflow
mg/£- 5
5
16
2.3
2.4
4
15
1.3
7.6
4
8
0.8
5.0
7
12
1.1
8.9
Media A
I removal
72
58
39
75
. 69
67
43
74
53
68
65
54
Down flow
mg/A
5
17
2. 4
3.9
5
1C)
1.2
8.4
5
6
0.2
5.0
8
11
* 1.0
11.2
Media B
% removal
72
55
37
69
79
69
29
81
88
64
68
58
Notes: 1 in = 2.54 cm
1 gpm/ft2 = 0.679 Jl/sec/m2
19
-------
media filter (Media A), was chosen for further evaluation in comparison with
upflow models.
Downflow Media A vs. Upflow Media C
The first upflow media configuration was constructed in Filter No. 2 as
shown previously in Figure 7 (2nd Series of Tests, Filter No. 2,Media C).
This filter and dual media Filter No. 1 (Media A) were operated in parallel
at a filtration rate of 1.4 Vsec/m2 (2.0 .gpm/ft2) during the period from
April 23, 1974,through May 16, 1974. Daily data collected during this phase
are presented in Table 4.
The first upflow filter did not function well. As headloss built up in
the upper layers of the sand media, a point was reached at which the im-
mersed weight of an overlying layer of sand was equal or less than the head-
loss through that layer. The overlying layer then lifted as a unit, separa-
ting from the lower layers. Somewhat later, the upper, separated layer would
collapse. This would result in a major breakthrough of previously removed
particulate matter. This situation was controlled by the installation of a
removable grid in the'upper layers of the upflow media. The grid seemed to
retard, but did not entirely prevent, media separation. Because of this
problem, work with Media C was stopped and a modified upflow filter (Media D)
was constructed.
The air scour was found to be essential for properly backwashing the
upflow filters. Because of the direction of flow, the lower layers of the
filter accumulated a much heavier solids deposit than did the upper layers.
Also, the coarse granite media in the bottom of the upflow filters could be
moved, but not actually suspended, with the quantity of backwash water avail-
able. As a result, some of the deposited materials tended to cling to the
media unless air scour was applied prior to the water wash. Air scour was
applied for approximately 2 min along with a small flow of backwash water.
Following this, the air was turned off and a normal amount of backwash water
was applied for 8 to 10 min. This procedure effectively cleaned all upflow
filter media used. In downflow filtration, it was found that the occasional
use of air scour prevented the formation of mud (sludge) balls .
Downflow Media A performed slightly better than upflow Media C with
regard to effluent quality. However, the rate of headloss buildup in the
upflow filter was only 42 percent of that in the downflow model. This
indicates that much longer filter runs might have been possible before
backwash was necessary. Because of the problem of bed separation experienced
with upflow Media C, it was not possible to operate this upflow filter con-
figuration for extended periods to demonstrate' its full economic potential.
Pertinent summary results observed during experiments with downflow
Media A and upflow Media C are presented in Table 5. TSS removal averaged
approximately 75 percent for both units.
20
-------
0
z
2
**"
<
o
•?
H
3
r*
O
0
<
<
a
X
5
r«i
r
B
2
u
g
z
•<
7,
<
t
C
5
£
OPERATIN
<
O
Z
£
=
g S
s ^
0 5
-
o
£
2
z
DC
S
S
5 •
iniri
vzni
-
i g 1
=•.
1 si
M/Bui)
SSA
( l/Cui)
ssi
C|/fiui|
DO!
l|/6ai)
caos
CBH '••NI j
•jo Siva
(53HOKI)
IS«H)
nna JO
r ION 51
•in in
s»m
*o ~
?. 21
£ o J
(1/fioJJ
SSA
(I/60J)
SSi
( , /6ui)
D01
nyBiu;
CGOS
f'BH '*Nt )
SSO10V3H
JO 31VS
{S3HDNI}
S5O1OV3H
[S8H)
NHB JO
H10N31
tnin
earu
«rt *
5 of
o -.-
5^ ^
i gj
(I/BUI)
N-CHM
t |/6w)
S5A
{|/6ui,
SSi
(!/*»)
DO!
( I/6*";
foOB
(J/6"')
3OVSOQ
( jiJ/OdO)
IY1D 1NVU
<
O
t— lO'nmotM^rinieoi !
vo iMtntf)'cr'^'*>'w' ir>ic>JCN
C IOOOOOOO 1 O O O
CO t-^r^r-CDTTT l.tNINCM
^1 1 OOO>- itOr-i^-t-iinmcD I von-a-
CN 1 CN .-1 i-4 >H 1
titinmii icotovoro
lit 1 I I f-l I
III III 1
n«>^TNt*- OMMO«HVDCD»-I
(NWMNHtNr-inMrow^M
^MOxcoM^om^incneot^-
\otneooot^i*"CO\Dr-CDO\oco
nit-troMcyim^tMi I I f»
WlrtOiHi-IOMTHI 1 IO
tn ir>oin^rmcjfnMcs I »-t
Q.IOOOOOOOOO I O
c* imr^ooirjLntnfon i m
rH IOOO--cor-r*co^Dr-cDcr>CTico
coiHooiOOr^cornrni i
.-{It-i'-f f-Jr-(.-lrHrHr-(l I
r-itnm mnmiD^ni i
OIOO1OOOOOO1 1
" 1 • • • • *
TT IOrH*HM»-I»-iNM^IOf-l
c> ino«T'^iCDO'yi»-i^-om
CJ lN(NO)M«-lCNeMt-l»HfHr-l
M iin^crio^npncgojncoo
n i n^-m-rn^Tf-ifNdioioj
-4*-H 1 1 IMrOrH t-l
111 III
ioioMOfsitr>(NI'~t'~( ' ococn
ocnmocnp-cor-o i eocncn
^^r-irHr-i'HrTlrHCM 1 rHt-lr-I
^
-------
TABLE 5. SUMMARY RESULTS - DOWNFLOW MEDIA A VS. UPFLOW MEDIA C
Effluent
2.0
BOD
TSS
gpm/flT
Total P04-P
Influent
mg/H
16
49
1.8
Down flow
mg/Jl /
4
12
0.7
Media A
I removal
75
76
61
Up flow
mg/a
7
13
0.7
Media C
% removal
56
73
61
Rate of Headloss Buildup (in./hr) 5.2
Notes: 1 in. = 2.54 cm
1 gpm/ft2 = 0.679 &/sec/m2
2.2
Downflow Media A vs. Upflow Media D
The third series of filtration experiments was conducted with the same
dual media downflow filter (Media A) previously described and a modified
upflow filter (Media D). No sand was used in this upflow model. The filter
consisted of 56 cm (22 in.) of fine granite chips, 30 cm (12 in.) of coarse
granite chips, and 20 cm (8 in.) of ballast stone about 2% cm (1 in.) in
nominal size. This media configuration was previously illustrated in Figure
7 under the heading, 3rd Series of Tests, Filter No. 2, Media D. The dual
media downflow and modified upflow filters were operated at filtration rates
of 1.4 and 2.0 &/sec/m2 (2.0 and 3.0 gpm/ft2) during the period from May 28,
1974 through July 9, 1974. The daily data collected are displayed in Table
6.
Modified upflow Media-D eliminated the layer separation problem, and no
hold-down grid was required.
I
The upflow Media D filter composed entirely of granite chips performed
well. The rate of headless buildup was 63 percent less than that of the
downflow Media A filter. Although the average upflow filter effluent qual-
ity as summarized in Table 7 was slightly poorer, much longer filter runs
were possible. Hhen personnel were available for round-the-clock operation,
the upflow filter runs ranged from 21 to 27 hr. Downflow filter runs on
these dates ranged from 7 to 10 hr. TSS removals during this series of runs
ranged from 70 to 90 percent, the highest percentage levels achieved
throughout the filtration experiments.
The upflow Media D filter should be more economical to operate at plant
scale as it would require much less frequent ba.ckwashing. In addition, the
filter media itself is readily available at farm supply wholesalers. The
media was purchased as "chicken grit" in 22.7-kg (50-1 b) bags from a local
farm supply store. The material is closely graded and when purchased in
22
-------
<* 0
6 ^
H *
o
3
5
5 *
X °
'I
o
o
0
Z
1
1
o !
-c
O CL,
1
r
! 2
" 1
-
-
<
3
3
K 3
i 1
- 5
Z £>
^ 5!
i
£ I -i
tmr
1 §1
i sl
SSI
( |/6ut)
DOJ
5CO8
SS010V3M
=.'O 3IVH
(S3HDNI)
SSO1CV3H
(SUM)
H1ON3T
(run
L 81
i s!
SSA
1 1 /6"0
SSI
3O1
=S
run '-MI j
sscnavsH
jo 3iva
SSO1CV3H
(SBH) 1
H1ON31
tnm
i £—
r si
( |/6wJ :
( I/Bojj
(,/Buij j
ssi ;
( | /Bui)
3Oi
ffoo«
3OV5OO
mv JNy-M
jid/OdOJ
ON1QYO1 ;
Q
T 'l ^m^-«=- 1 CMMeMmrarHCM-q-o
rs i fMrsrsrs i .i.wwmwwfsn^
O 1 OOOO 1 1 COCr — TCOO
«n l ocacnm I romrrinmrMCMn^r
O 1 OOOO 1 OOOOOOOOO
inirHc^rMi l 1 l l l |OJ*rr^m
••Hi rH 1 t 1 1 1 1 1
*H 1 rH rH 1 rH **
sisssd'ssa-assssss
1 1 1
32^-22°-!;"^°n2"^
" S S S R m 5 S 2 ?! 3 m S 2 S m
rn i OTcnr- i coojrMcMocNr-i o
r*a l rHtNCMCN l j rHCMrimoJM i m
OIOOOOI IOOOOOOIO
• 1 .... I ....... 1 .
O I OOOO I OOOOOOO 1 O
OimrirHt I l l i i irsniro
CN 1 rH 1 1 t 1 1 1 1 1
"
r*l I {N*HinO 1 ^*"*f*lOfNOrH 1 O
•a-|eorH(neNjompg irHrHCNioi
i lit
rHvDw;rHn i •=7c>ir>-r-r-Tfn^' i in
SSSSS ! SSaSSSKS ! S
cocoor-co i eocococncnr-r-cD i r-
rH 1
S ! 2S3S ! SrHrHSSSSS:!
fMlr-CJrgCMI ICNCMCN CN ^ in m -3-
O I OOOO 1 1 OOOOOOOO
in i r— m^-co i^rHr^'^r^moOrH
•H | CN OJ t-t (N I rNrMCMOJtNrHr^rHfNI
chir*rHni i i i i i ino^rrH
ft 1 rH ^ l l l i i i i r> "w tn ni
^r I CMin \D I cNinmovDmt^-mc^
S ! KSSS 1SSSSSKSSS
1 rH
icggsssgggsssg : ss
slssgpgsaSpii!
^,.^ ^.^^.^.^.^.^_^.^
oc^.ot i io*Hr^n«rr-ocnOrH
l i l i t i i i i i i i t l i l
o
?
ft-
0
0
DOWNFIOW : MEDI
M
O
fO
ncs ^r-^r co^1 om
; : . i i : :
ItSt 111
l t l l iii
1 l i 1 ill
III! Ill
M-^- mvo nmp^r^,
rH CM rH
rH rH rH r- rH fN rH
rH H CM
^r CM ^3- n r*i m rH N
(NCOUIrHr-iCOr^CO
^T rH n ro CS rH rH
1
cnr-cocor-Ovflr-
;
r i i i i i i
i i i i t i i
i i i i t i i .
! 1 1 1 I1 I 1
1 1 I 1 1 1 t
1 1 1 I 1 1 1
rH
r-f «H
rH rH «-l rH rH
Ol *H
r-:-^;;^
SSSSPiSSS
mmomr.. o>or-
SSSSK5S5
I 1 1 1 li 1 1 1
1 I 1 t f I 1 1
1 1 1 1 1 1 1 1
tn n tn i r i t i
• • -i 11 it
CD rH O^ 1 1 1 1 1
rH M rH 1 1 I 1 1
OJ-rj-rHrH^' mfOm
SSSSESSS
BSSaSSSK
i-H CN rH ri CN W f*>
r~-mcr*«*io>crv l o
en o en rH c* o l oj
^-i
•«• ^r rr rr
i I i T T" r— r- r*
T, in i-. CD i i i i
fN fM PJ CM -* CM r- C".
1 1 I 1 1 1 1 1
O \o o vr> r- r^ p- r-
23
-------
large quantities should cost much less than more conventional filter media.
TABLE 7. SUMMARY RESULTS - DOWNFLOW MEDIA A VS. UPFLOW MEDIA D
2,0 gpm/ft2
BOD
TSS
Total P04-P
Rate of Headless
3.0 gpm/ft2
BOD
TSS
Total P04-P
Rate of Head! oss
Effluent
Influent
rag/A
25
57
2.9
Buildup (in./hr)
22
46
1.4
Buildup (in./hr)
Down flow
tug/A %
3
9
0,3
5.3
9
5
-
7.6
Media A
removal
88
84
90
, 59
89
--
Upflow Media D
mg/fc %
5
9
0.4
1,8
9
13
-
3.2
removal
80
84 '
86
59
72
--
Notes: 1 in. = 2.54 cm
1 gpm/ft2 = 0.679 5,/sec/m2
24
-------
REFERENCES
1. Brown, J. C. and Little, L. W., "Methods for Improvement of Trickling
Filter Plant Performance, Part II - Chemical Addition," U.S. Environ-
mental Protection Technology Series Report No. EPA-600/2-77-012,
Cincinnati, Ohio, January 1977.
25
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-80-099
3. RECIPIENT'S ACCESSIOWNO.
4. TITLE AND SUBTITLE
FINE SOLIDS REMOVAL FOLLOWING COMBINED CHEMICAL-
TRICKLING FILTER TREATMENT
5. REPORT DATE
July 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James C. Brown
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of North Carolina at Chapel Hill
Department of Environmental Sciences & Engineering
School of Public Health 201H
Chapel Hill, North Carolina 27514
10. PROGRAM ELEMENT NO.
35B1C, D.U. B-124, Task D-l/16
11. CONTRACT/GRANT NO.
Contract #68-03-0225
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final, Sept. 1973-March 1975
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Richard C. Brenner, (513) 684-7657
16. ABSTRACT
This research project was designed to evaluate the effectiveness of settlin
ponds and several types of granular media filters for removing residual fine solids
from the effluent of a conventional, high-rate, rock media trickling filter plant
when alum is applied ahead of secondary clarification. Two pilot settling ponds,
one covered and one open, were operated at detention times ranging from 8 to 30 hr.
Two pilot granular media filters were operated at filtration rates ranging from 1.0
to 2.0 1/sec/m2 (1.5 to 3.0 gpm/ft2). The filters were operated in both downflow
and upflow modes, with various media used in each operational mode.
The pilot settling ponds did not perform as expected. Anaerobic conditions,
which developed in the settled sludge, disrupted the floe structure and resuspended
previously settled solids. Very modest improvement in final effluent quality,
generally less than 25 percent, was observed.
The two filters, when operating in a downflow mode with two different configura-
tions of anthracite and sand media, proved about equal in performance, achieving
65-85 percent incremental removals of suspended solids. Upflow, filter operation
produced a slightly lower effluent quality but resulted in lower rates of headless
buildup and substantially longer filter runs.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
*Sewage treatment, *Trickling filters,
*Filtration, *Chemical removal (sewage
treatment), Coagulation, Upgrading,
*Aluminum sulfate
*Fine solids removal,
Settling ponds,
Granular media filters
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
36
2O. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
26
U.S. GOVERNMENT PRINTING OFFICE: 1980--657-165/0126
-------
-------
2* °
o
o
O
CD CD ^
CO o O O
co-< ^. n
cn 03
15 CD
CD
CD
cn
-OC
Q)
------- |