FIGURE 4. Secondary Separation: Hydrocyclones

assembled by DEMCO Incorporated. The unit consisted of four model 16-17-51
filters, each of which contained 51 permanent sand cartridges with filter
openings rated at 25 microns. An on-line automatic backflush cycle was in-
stalled so that one filter unit could be backflushing while the other three re-
mained on-line. Figure 5 shows this cartridge filter unit. Selection of this
type of polishing filter was based on the following:
(1) Its compatibility with the hydrocyclone unit over its entire range
of working pressures. Therefore, no booster pumps were required.
(2) Relative ease of maintenance and ability to change filter cartridges.
(3) Range of flow rates available for cartridge elements with various
rated openings.
(4) Small size in that only 87.5 square feet were required for a fully

automated unit which could handle the expected 500 gpm of flow.

12


When this happened, the entire solids loading from the dredge flowed
through the bins directly to the hydrocyclones. Figure 9 shows the sedi-
ment accumulated in the first bin after approximately two hours of contin-

uous dredging.

To empty the bins of sediment, the dredging operation was shut down and
the water was decanted from the bins. This operation was usually scheduled
for either directly before the midday break or before final shut down at the
end of the day. The sediment was then allowed to dry during the break,
and emptying of the bins through the bottom doors began immediately after
lunch or the first thing the next morning. At this time, the sediment was
never fluid enough to drop unaided into the dump trucks underneath the
bins. Therefore, standard hand-held concrete vibrators were utilized to
help fluidize and drain the sediment into the trucks. Normally, cleaning of
both bins by this process, once the water was decanted, took two men about
one hour. This assumes that an adequate number of trucks were available

for continuous loading.

ETO eg, a

FIGURE 9. Sediment Accumulated in First Bin After
Two Hours of Dredging

33


SECTION VI

DISCUSSION OF FIELD DEMONSTRATION

REMOVAL SYSTEM

During the field demonstration period, approximately 10,000 cubic yards of
material was removed from the pond. Of this total, 3000 cubic yards was
pumped into the bins for processing, and the remaining 7000 cubic yards
was disposed of in a conventional settling basin. Table 8 shows the destin-
ations of the various quantities of material from the total sediment removed

from the pond.

Table 8. DESTINATION OF DREDGED SEDIMENT

Destination Quantity (cu.yd.)
Settled in Bins 750
Processed Through Remainder of System 250
Total Removed by System 1,000
Bins Overflow to Holding Basin 2,000

Total Pumped to Head End of System 3,000
Pumped to Conventional Settling Basin 7,000

Total Removed from Pond 10,000

The MUD CAT dredge proved very efficient in removing the deposited sedi-
ments from the pond bottom and in preventing the resuspension of the sedi-
ments during the dredging operations. Minor perturbations to the smooth

dredging operation were the result of:

(1) Clogging of the pump or fouling of the auger by large debris and

objects such as tree stumps, logs, large rocks, or lengths of barbed wire.

29


too costly and time consuming.

The small diameter hoses appear to have caused bridging of the sediment.
Figure C-1 in Appendix C shows the amount of hoses which were found to
be completely bridged by sediment when the hoses were changed after
three weeks of operation. Out of the 720 total hoses, 484 or 67.2 percent
were completely blocked with sediment. No significant pattern of bridging

was found to exist.

The average flow through the system over the entire field demonstration of the
system was approximately 220 gallons per minute. This is only about one-half
of what was originally expected. The two limiting factors for the flow rate
were the blockage of the Uni-Flow filter hoses and the build up of backpressure
in the cartridge filter unit. Only when completely new hoses were installed

on the Uni-Flow filter and the cartridge filter unit was thoroughly flushed

with clean water did the flow rate of the system during the processing of

dredged slurry approach 500 gallons per minute.

The high efficiency of suspended solids removal of the Uni-Flow filter yet

the accompanying quick blockage of its hoses when fed a concentrated slurry
was illustrated in Table 7. This table presented the summarized results of
the processing of the dredged slurry utilizing only the elevated bins and the
Uni-Flow filter. When this test was stopped, essentially all of the hoses were
blocked with sediment and would have had to be changed if further utilization

of the Uni-Flow was desired.

The promise which the Uni-Flow filter demonstrated during the field trials
prompted further investigations into its use as a filter for suspended solids.
Additional experiments were performed on a small prototype test stand after
the field demonstration was completed. These tests concentrated on larger
diameter hoses in order to prevent the blockage problem with the small, one-

inch diameter hoses which was experienced during the demonstration of the

38


SECTION Iv
REMOVAL AND PROCESSING SYSTEMS

REMOVAL SYSTEM

The system utilized for removing sediment from the demonstration pond bot-
tom consisted of a 30-foot 2-inch long MUD CAT dredge manufactured by
National Car Rental System, Inc., MUD CAT Division. The dredge moves in
straight-line directions by winching itself along a taut, fixed cable. Figure 1

is an overall view of the MUD CAT dredge.

Bottom sediment removal equipment on the dredge consists of an eight-foot
long, horizontally-opposed, adjustable depth, power-driven auger and a pump

which is rated at approximately 1500 gallons per minute with a 10-30 percent

FIGURE 1. MUD CAT Dredge


Table B-1._ RESUSPENSION OF POND SEDIMENTS DURING DREDGING ~ 7/5/73

Operating Distance from Depth below Suspended
Condition Front of Dredge Surface (ft.) Solids Concen.
(ft.) (mg/1)
Before
Dredging 5 1 39
5 3 50
5 5 64
5 7 (bottom) 523
Dredging 5 1 88
(forward cut)
5 5 179
5 7 (bottom) 1260
10 1 54
10 5 86
20 1 39

66


samples, using the procedure in part 224C, Total Suspended Matter, in
Standard Methods For the Examination of Water and Wastewater .?

TEST RESULTS
First Phase

A summary of the results of the first phase of the five-inch diameter hose test-
ing in which the four different fabrics were tested is given in Table 11. At

the conclusion of the first phase tests it was evident that the multifilament
polypropylene fabric performed the best, both in terms of the effluent quality
and the average flow rate through the hose. All of the first phase tests sum-
marized in Table 11 were performed utilizing the filter wash from the top of

the hose during the backflush cycle. The average pressure, and consequently,
the average flow rate at which the polypropylene hose was tested was higher
than the other three fabrics could be tested at. This was because the poly-

propylene did not bow out as much under pressure. This bowing of the hose

Table 11. SUMMARY OF FIRST PHASE FIVE-INCH
UNI-FLOW HOSE TESTS

Fabric Filter Effluent Quality Influent Quality Aver. Aver. Aver.

Type (mg/I susp. solids) (mg/I susp. solids) Pressure Flow Filtration
Max. Min. Avg. Max. Min. Avg. (psi) (gpm) Tam /n2)
Polypropylene 740 0 95 19,950 1940 5065 11.2 3.2 0.23
Nylon 1260 205 525 3,555 540 1445 6.7 0.8 0.06
Homopolymer
Acrylic 3870 0 400 =26,065 1095 5230 10.8 2.6 0.19
Nylon Sateen 3340 17 +1500 8,080 4030 5985 9.7 2.8 0.20

48


During this phase of the testing, three different backflushing, that is, sludge

drainage and filter washing methods were also experimented with:

(1) A simple one-time draining of the hose.

(2) A-simple one-time draining of the hose followed by an internal
washing of the hose by allowing approximately five to six gallons of influent
water to wash down the inside of the hose.

(3) Multiple draining and refilling of the hose during the backflush

cycle.

In the second phase, the best-performing fabric was subjected to a series of
tests in which the operating and physical parameters of the hose were varied
to provide more detailed information on the performance of the filter. The

parameters that were varied were:

(1) Type of backflushing operations

(2) Presence of wire mesh cylinder inside filter column

(3) Presence of wire mesh cylinder outside filter column

(4) Presence of wire mesh cylinder outside and inside filter column
(5) Length of the fabric filter column

(6) Time duration of the test

(7) | Suspended solids concentration of the influent

The wire mesh cylinders were added so that their effects on the performance
of the filter as indicated by effluent quality. backflushing time, and filtration
rate as well as pressure handling ability could be investigated. The basic
function of the wire mesh cylinder was, in the case of the external cage, to
impart increased rigidity to the filter column to enable it to withstand higher
Pressures and thus, hopefully, produce a greater effluent flow with the same
quality; and to prevent the fabric filter from collapsing during backflushing,
thus helping the sediment deposited on the hose to be washed off, when the

wire cage was placed inside the filter hose.

46


ts

5.0

4.0

3.0

2.0

Flow (gpm),

8' polypropylene,cages inside and
outside

average pressure = 20/psi

A= beginning of backflush

A A a a A A MA or rr
r T T — v T T ¥ T 7
20 40 60 80 100 120 140 160 180 200
Time (Min.)
FIGURE 11. Flow vs. Time (Eight-Foot Hose)


The ten foot long polypropylene filters which were. rinsed from the top during
backflushing had the highest average filtration rates. The filters which were
not rinsed during backflushing exhibited filtration rates of about one-third to
one-half the filtration rates of the filters which were rinsed during backflush-
ing. Filters tested in the first and second phases are ranked in order of

decreasing filtration rates in Table 15.

Operating Pressure

The 10-foot long polypropylene fabric filter columns were tested at a maxi-
mum pressure of 15 psi. The 10~foot polypropylene fabric filters which in-
corporated wire mesh columns on the inside and outside were tested at an
average pressure of 18.5 psi. The eight-foot long fabric filter columns in-
corporating wire mesh columns both inside and outside the filter column
were tested at an average pressure of 20 psi and withstood a maximum oper-

ating pressure of 24 psi.

With increased pressure, the fabric filter columns bow outwards such that
deflection from the centerline of the filter columns increased with increased
pressures. Deflections of up to 12 inches were measured in the polypro-
pylene fabric hoses at high pressure, and similar deflections were measured
at much lower pressures for the other fabric hoses. Cages on the outside of

the hoses prevented this bowing.

Effluent Quality

The effluent quality of the various configurations of polypropylene hoses
tested followed comparable cycles during the tests. The quality was usually
lowest immediately following a backflush and improved as the hose became

coated with sediment. A decrease in the average effluent quality was evident

56


air bag houses for stack gas filtering. The underlying consideration during
the large diameter hose test program was to investigate the adaptability of
standard air bag technology to the water filtration field, and in particular, to
the processing of slurries with high suspended solids concentrations. If
larger diameter hoses proved feasible for water filtration, available, off-the-

shelf equipment might then be adapted to solve a current problem.

Four different fabrics were initially identified as being potentially applicable

to water filtration and were subsequently tested. These were:

(1) Multifilament polypropylene
(2) Nylon
(3) Nylon with a sateen weave

(4) Homopolymer acrylic

The apparatus for testing of the nominal five-inch diameter fabric filter

hoses is shown in Figure 10. Basically it consisted of:

(1) Fabric filter hose column test stand.
(2) Elevated bin for influent slurry .

(3) Influent pump.

(4) Effluent bin.

(5) Hose internal pressure gauge.

(6) Effluent flow meter.

(7) Influent sampling valve

Testing was performed in two phases. In the first phase, the four fabric
filter materials were subjected to tests of about 1 hour in length, and the
results of the tests were compared to determine the fabric material which
exhibited the best performance characteristics in terms of the seven hand-

ling characteristics described above.

44


MUD CAT discharge

Ks
ce
Sy

Initial Separation
Two 36-yard

approx. 1500 pgm

9L

Temporary Holding/
Settling Basin

Secondary Separation

Final Filtration Final Filtration

Elevated Bins

trucking

Bin Solids
Disposal Area

approx. Hydrocyclones | Cartridge Filter] | Uni-Flow Filter
500 gpm Unit
backflush backflush backflush

Return Water
to pond

Sludge Disposal

Area

Figure 7. Schematic of Processing and Sludge Disposal System


Two other methods for cleaning of the sediment from the bins were experi-
mented with during the course of the field demonstration. One involved
draining of the sediment into trucks without first decanting the water.
Utilization of this method took less time to empty the bins than it took when
the water was decanted first, since the sediment was more fluid. However,
more sediment spills were created by this method since the excess sediment-
laden water either drained away from under the bins during loading of trucks

or was spilled from the trucks during hauling.

Another bins cleaning method tried involved the draining of the accumulated
sediment from the bottom of the bins while the processing system was in full
operation. This method often created an even greater amount of spilled,
sediment-laden water. The accumulated sediment was solid enough to drain
directly onto trucks during full system operation. However, precise control
needed to be exercised on the dump gates since once the solids were drained,
the dredged slurry in the bins began to rapidly drain out the open gate,

creating a muddy environment below the bins if much was allowed to drain out.

These two alternate methods of bin cleaning, although faster than the one
in which the bins were decanted of water, were judged to be more messy.
Consequently. the "cleaner" but slower method of bin cleaning by first de-

canting the water was the one primarily utilized during the remainder of

the field demonstration.

Hydrocyclones

The feed to the hydrocyclones averaged 131,200 mg/I of suspended solids
during the field demonstration. Approximately 74 percent of these solids
had a particle size less than 75 microns in diameter (Table C-5), that is,

the large majority of the solids loading to the hydrocyclones was in the

34


APPENDIX B

Contained herein are the data collected during the investigation of the
resuspension of bottom sediments by the MUD CAT dredge during normal

dredging operations.

65


CONTENTS

Abstract... 0... cece cece cece ete tee teen ene e nese enee
Table of Contents......... 0... cece cece eee ee eee ene
List of Figures... 0... cece cece eee eee eee e eens
List of Tables... 0... e eens
Acknowledgments..........0.:e ee eeee cece cere teeter teens
SECTIONS
1 Conclusions..........: cece eee eee en neces
W Recommendations............ 20s cece eee ee
it Introduction......... eee ence eee e eee
Iv Removal and Processing Systems..........
Vv Field Demonstration................0.eee ee
vi Discussion of Field Demonstration.........
Vil Additional Tests-Large Diameter Fabric
Filter HoseS........ 0. ee cee cece eee eee
vill References........ 6... cece cece eee cena
APPENDICES.......... 0.0 cece cece e eee ene cere eeeees

W7

29

43

60

61


Table B-3. RESUSPENSION OF POND SEDIMENTS DURING DREDGING - 7/11/73

Operating Distance from Depth below Suspended
Condition Dredge (ft.) Surface (ft.) Solids Concen.
(mg/1)

Before Dredging 5 ft. from front 1 18

4 75

7 (bottom) 1000
Dredging
(forward cut) 5 ft. from front 1 72

7 (bottom) 1257
Dredging
{forward cut) 5 ft. from side 1 89
Dredging
{forward cut) 1 ft. behind 1 1262

68


Table B-2, RESUSPENSION OF POND SEDIMENTS DURING DREDGING 7/6/73

Operating Distance from Depth below Suspended
Condition Front of Dredge Surface (ft.) Solids Concen.
(ft.) (mg/1)
Before Dredging 5 Depth Integrated 89
Composite -
0 ft. to bottom
Dredging
(forward cut) 4 1 900
Dredging
(forward cut) 10 1 649
10 5 175
Dredging
(forward cut) 20 1 226

67


APPENDIX C

This Appendix contains additional detailed data collected during the water
quality sampling and analysis program conducted on the portable sediment

processing system, and other operational data on the field demonstration.

70


Le

Table 7. RESULTS OF BINS TO UNI-FLOW FILTER RUN

Time (min.) Suspended Solids Concentration (mg/I) System Flow Uni-Flow
MUD CAT Bins Uni-Flow {gpm) Pressure (psi)
Discharge Effluent Effluent

15 250 8
158,200} 135, 900} 20s}

30 120 10

45 70 12
96, 200} 70, 100} 7}

60 60 12

75 50 10
145,900 24, 500} za}

90 30 11


FIGURE 5. Final Filtration: Cartridge Filter Unit

Previous experiments with the Uni-Flow filter indicated that such filters
showed promise for use as a final polishing filter for suspended sediment
slurries, in that high quality effluent water could be expected. Basically,

the Uni-Flow filter is a system of hollow fabric "soaker" hoses that present
amore or less solid, impermeable barrier to suspended material. The dredged
slurry is pumped into the center of the hoses, the suspending liquid permeates
through the hoses and is collected in a filtrate collector and is piped away.
The loose sludge within each hose is periodically discharged into a sludge

collector and is removed from the filter unit.

Further experiments were conducted under this program in order to arrive
at design criteria for a prototype unit which would be capable of processing
the expected 500 gpm of flow. Relying on the previous basic data, one-inch
diameter, 10 to 20-foot long hoses of both cotton and polypropylene fabrics

was tested on a small, three-hose test stand.

13


Table 3. PHYSICAL CHARACTERISTICS OF COMPOSITE
SEDIMENT IN POND BEFORE DREDGING

Grain Diameter (microns) Percent Finer
250 99
150 95
100 91
40 12
8 7
3 6
1 2

Average Specific Gravity = 2.3

In-Place Moisture Content = 28.8 to 50.3 percent

19


OVERALL SYSTEM DESCRIPTION

Figure 7 is a schematic diagram of the overall processing and sludge disposal
system. Bypass lines were constructed within the system so that selected com
ponents of the system could be bypassed in order to test the operating aspects
of the system with the different units on-line. During the field demonstration,

a number of different system configurations were tested. These were:

(1) Entire system

(2) Bins, hydrocyclones, and cartridge filter unit
(3) Bins, hydrocyclones, and Uni~Flow filter

(4) Bins to Uni-Flow filter

Samples of the dredged slurry were taken periodically before and after each
Piece of equipment, and of the backflushes or sludges from each piece of
equipment. With this sampling program, many other system configurations
could be tested besides the four listed above. For example, samples from
the process stream immediately after the elevated bins would define how
efficiently a processing system consisting of only the bins would be in re-
moving suspended sediment. Similar analySes could be made at each point

in the processing stream.

The portability of the system was evidenced by its ability to be transported
entirely on two standard, flat-bed, semitrailer trucks. Auxiliary equipment
such as valves, air compressor, miscellaneous piping, etc. all fit on a stan-

dard pick-up truck.

15


Other Water Quality Parameters

Seven additional water quality constituent parameters were intermittently
measured during the testing program. The parameters measured were:
orthophosphate (PO, ) , nitrate and nitrite nitrogen (NO, + NO, )

iron (Fe’’), sulfate (Soz). hydrogen ion concentration (pH) and turbidity
measured in Jackson Turbidity Units (JTU). The phosphate, nitrate, nitrite,
iron, and sulfate chemical analyses were performed with a Hach Chemical
Company portable water quality laboratory kit. Turbidity and pH measure-
ments were performed with a Hach turbidimeter and a Fisher Accument pH
meter respectively. Summary data results for five days of test operations

are presented in Appendix C, Table C-2.

Because the parameters measured were, with the exception of turbidity,
essentially completely dissolved upon entering the settling bins (sample
point #5), it was generally expected that the physical sediment separation
unit processes being evaluated would have little or no effect on their con-
centration. Speculation was made that interactions between the various ions
and suspended sediment particles might result in some ion removal, partic-

ularly with the Uni-Flow filter unit.
Inspection of the test data results indicates that no substantial ion removals

occurred. The accuracy of the test results are such that the data are in-

conclusive as to whether minor amounts of ion removal were effected.

28


FIGURE 3. Initial Solids Removal Phase: Elevated Bins

0.023 ft/sec is produced. Based on the theoretical settling velocities for vz
ious size particles presented in Table 1, all particles down to approximatel

100 microns in size could be expected to be settled-out in the initial solids

removal step.

Table 1. THEORETICAL SETTLING VELOCITY OF
PARTICLES IN WATER AT 50° F

Settling Velocity

Diameter of Particles

(microns) (ft/sec)
1000 0.328
500 0.174
200 0.069
150 0.049
100 0.026
50 0.010

10


Table B-4. RESUSPENSION OF POND SEDIMENTS DURING DREDGING ~ 7/18/73

Operating Distance From Depth below Suspended
Condition Front of Dredge Surface Solids Concen.
(ft.) (mg/))
Before Dredging 5 1 34
Dredging
(forward cut) 5 1 83
10 1 19

69


OBSERVATIONS AND ANALYSES

Blockage by Sediment

The nominal five-inch diameter fabric filters tested all developed a build-up
of sediment of less than one-quarter of an inch at the point where the effluent
flow had decreased to just less than 0.9 gpm. Consequently, there was no

blockage of the fabric filter columns with sediment.

Shedding of Sediment During Backflushing

All fabric filters tested shed most of the built-up sediment during simple—
draining backflushing (no rinsing from the top). However, backflushing
with rinsing from the top produced a cleaner filter and consequently a greater
average flow rate than when rinsing from the top was not used. The instal-
lation of a wire cage on the inside of the hose helped the hose to shed sedi-
ment during the simple-draining backflush used during the second phase.
The cage prevented the collapse of the hose during draining. Collapse of

the hose prevented the sediment from sliding off the side of the hose.
Filtration Rate

The filtration rates for the fabric filters tested ranged from 0.07 gpm/ft2
for the second phase tests to a maximum of 0.44 gpm/ft 2 for the first phase
tests. Filtration rates for the large diameter fabric filters are compared to
the filtration rates of previously tested one-inch diameter fabric filters in
Table 14.

54


slurry unless the suspended solids concentration of the slurry could

first be reduced to near the design level of the units.

Overall, the removal system utilized proved to be a labor-intensive

operation.

This program demonstrated that sediment basins can be cleaned without
the availability of adjacent sediment deposition sites and that a high
quality return water can be produced through use of a portable sediment

processing system.

Five-inch diameter polypropylene hoses tested on a prototype test stand
performed better than the one-inch hoses utilized on the Uni-Flow filter

during the field demonstration.


by each component of the system when it is in a fully automatic mode of oper-

ation. Figure 8 presents this system solids balance.

The Uni-Flow filter was observed to have a very high efficiency in re-
moving suspended solids from the dredged slurry. even when the cartridge
filter unit as an initial final filtration step was bypassed. Consequently,
an experiment was conducted during the field trials in which both the
hydrocyctones and the cartridge filter units were bypassed, that is, the
dredged slurry was pumped directly from the effluent of elevated clarifier

bins to the Uni-Flow filter. Table 7 summarizes the results of this run.

The run began with clean bins and clean but used hoses on the Uni-Flow
filter. Five of the six banks of hoses were in operation. The system
was run at the maximum Uni-Flow pressure (and consequently the maxi-
mum flow rate) which it could be operated at without causing excessive
bowing of the hoses and their consequent bursting. As can be seen from
Table 7, the Uni-Flow filter still had a high efficiency of removal of sus-
pended solids in this configuration. However, due to the high solids
concentrations in the influent, the hoses soon became blocked with sedi-
ment, and the flow rate through the system decreased rapidly. The
automatic backflush cycle of 5 1/2 minutes between flushes with a one-
half minute duration flush was not sufficient to prevent the hoses from
becoming blocked with accumulated sediment. Consequently, the run had
to be terminated after 90 minutes when the hoses became completely

blocked with sediment and the system throughflow decreased to near zero.

25


APPENDIX A

This Appendix contains the detailed background data on the quality of the
pond water before dredging began and basic data on the water quality par-

ameters of the dredged slurry. These data were collected as part of the base

line survey.

61


Table A-2. ANALYSIS OF COMPOSITE POND WATER SAMPLE

Constituent Concentration (ppm unless stated otherwise)
Zinc, as Zn 0.0
Chlorinated Hydrocarbons 0.000
Oil and Grease 24
Total Organic Carbon 12
Mercury. as Hg 0.0
Lead, as Pb 0.0
Oxidation-Reduction Potential -4 mv
Total Dissolved Solids, @ 105° C. 148
Phenolphthalein Alkalinity, as caco, 0
Total Alkalinity. as CaCO 36
Carbonate Alkalinity, as éaco3 0
Bicarbonate Alkalinity, as Caco, 36
Carbonates, as CO3 0
Bicarbonates, as HCO3 43.9
Hydroxides, as OH 0
Carbon Dioxide, as co, 6
Chloride,as Cl 42
Sulfate, as SO, 52
Fluoride, as F 0.0
Phosphate, as POy 0.3
pH (Laboratory) 7.1
pHs 8.8
Stability Index 10.5
Saturation Index -1.7
Total Hardness, as CaCO3 39
Calcium Hardness, as CaCO3 18
Magnesium Hardness, as CaCO3 21
Calcium, as Ca 7.2
Magnesium, as Mg 5.1
Sodium, as Na 9.6
Iron, as Fe 5.6
Manganese, as Mn 0
Copper, as Cu 0.02
Silica, as SiO, 6
Color, Standard Platinum Cobalt Scale 65
Odor Threshold 0
Turbidity, Jackson Units 20

63


Table A-3. ANALYSIS OF COMPOSITE DREDGED SLURRY SAMPLE

Constituent Concentration (ppm unless stated otherwise)
Zinc, as Zn 0.0
Chlorinated Hydrocarbons 0.000
Oil and Grease 7.5
Total Organic Carbon 68
Mercury, as Hg 0.0
Lead, as Pb 0.0
Oxidation - Reduction Potential +14 mv
Total Dissolved Solids, @ 105° Cc. 77
Phenolphthalein Alkalinity. as CaCO3 0
Total Alkalinity, as CaCO3 15
Carbonate Alkalinity, as CaCO3 0
Bicarbonate Alkalinity. as CaCO3 15
Carbonates, as co; 0
Bicarbonates, as HCO, 18.3
Hydroxides, as OH 0
Carbon Dioxide, as CO2 200
Chloride, as Cl 30
Sulfate, as SOy 39
Fluoride, as F 0.0
Phosphate, as PO, 0.55
pH (Laboratory) 5.1
pHs 9.3
Stability Index 13.5
Saturation Index -4.2
Total Hardness, as CaCO, 15
Calcium Hardness, as CaCO3 12
Magnesium Hardness, as CaCO, 3
Calcium, as Ca 4.8
Magnesium, as Mg 0.7
Sodium, as Na 8.1
Iron, as Fe 9
Manganese, as Mn 3.7
Copper, as Cu 0.0
Silica, as SiO 1
Color, Standard Platinum Cobalt Scale 80
Odor Threshold 6
Turbidity, Jackson Units 100+

64


urations, including bypassing of the cartridge filter units, and processing

directly from the elevated bins to the Uni-Flow filter.

Appendix C contains the detailed data on the water quality monitoring
program for the processing system. Table 4 is a summary of the sus-
pended solids concentrations in the effluents of the components of the
processing system when the full system was in operation. Similarly,
Table 5 is a summary of the concentrations of suspended solids in the
sludges or backflushes of the system components. This table gives an
indication of the solids concentration in the sludge which can be expected
or achieved from the system during fully automatic operation. Basically,
the sludge from the hydrocyclones ranged from 2 to 29 percent solids,
with an average of 10 percent; the backflush from the cartridge filters
ranged from 2 to 28 percent solids with an average of 8 percent; and the
sludge from the Uni-Flow filter ranged from 5 to 19 percent solids, with

an average of 11 percent.

Table 6 gives an indication of the average efficiency of the system as a
whole, and of the individual components, in removing suspended solids
from the dredged slurry. This table indicates that the largest amount of
solids are removed by two components, the clarifier bins and the Uni-

Flow fabric filter. This data confirms the field observations.

A solids balance for the entire processing system was computed utilizing
the average suspended solids concentrations shown in Table 6, a MUD CAT
pumping rate of 2000 gallons per minute, which was the average during the
field demonstration, the reported average specific gravity of the pond sedi-
ments of 2.3, and the average total system flow rate during the field demon-
stration of 220 gallons per minute. This solids balance was computed in

order to give an indication of the amount of solids generated and processed

22


Table C-5. GRAIN SIZE DISTRIBUTION OF SOLIDS IN EFFLUENT

FROM BINS
Particle Size (microns) Percent Finer (7/13/73)
420 100
250 99.9
105 92.9
75 73.6

74


10

11

12

13

14

15

TABLES

Theoretical Settling Velocity of Particles in
Water at 10° Co... eee eee ees

Demonstration Pond Characteristics............

Physical Characteristics of Composite Sediment
in Pond Before Dredging ......---+.++.+0055

Summary of System Component Effluent Concen-
trations (Mg/I) ©... . 6. eee eee eee eee eee

Summary of Sludge (Backflush) Concentrations
(mg/l). 0.6... eee Vee eee eee eee e eee

Removal Efficiencies of System Units (All
Units On Line) .... 6-6. eee ee eee eee eens

Results of Bins to Uni-Flow Filter Run ....--.--
Destination of Dredged Sediment.............--

Capital Costs of the Portable Sediment Pro-
cessing System ....... see cece e eee eee eee ee

Six-Week Operating and Maintenance Costs of
the Portable Sediment Processing System
(Excluding Trucking) «----+-++eeeee cece eee

Summary of First Phase Five-Inch Uni-Flow
Hose Tests -- +++. esse eee eee ee eee eee ee eee

Summary of Results of Second Phase Poly-
propylene Testing --+--+-++eeeee eee e eee eee

Summary of Results of Second Phase Poly-
propylene Testing for Influent Concentrations
near 10,000 mMg/I +--+ eee eee ete e cece eee eee

Performance History of Uni-Flow Fabric Filters, -

Filtration Rate Ranking of Polypropylene Fabric
Filters 0+. . ee ec cece ccc cece eee eee eens

PAGE

10

17

19

23

23

24
27

29

40

rm)

48

51

51

55

57


10
11
12

FIGURES

MUD CAT Dredge ............- cee eee cece ees
Close-up of MUD CAT Auger.................006

Initial Solids Removal Phase: Elevated Bins .....
Secondary Separation: Hydrocyclones ..........
Final Filtration: Cartridge Filter Unit ...........
Final Filtration: Uni-Flow Filter ................

Schematic of Processing and Sludge Disposal

Sediment Accumulated in First Bin After Two

Hours of Dredging ........ 6. eee cece eee eee ee

Large Diameter Fabric Filter Hose Test Apparatus .

Flow vs. Time (Eight-Foot Hose) ................

Effluent Concentration vs. Time (Eight-Foot

PAGE

10
12
13
14

16
26

33
45

52

53


Secondary Separation

A bank of hydrocyclone cones comprised the secondary separation step of
this portable sediment handling system. Hydrocyclones are excellent devices
for use in portable sediment processing installations. Their advantages over
conventional water treatment alternatives in these situations include:

(1) Compact units make them easily portable.

(2) Automatic operation.

(3) No backwash or filter cleaning cycle is required.

(4) Generally maintenance-free since there are no moving

parts.
(5) Removal of particles in the desired size range can be simply

accomplished through the selection of the proper cone size.

The hydrocyclones utilized for this demonstration project were manufactured
by DEMCO Incorporated and consisted of six four-inch, style H cones with

abrasion-resistant urethane liners, and equipped with three-gallon silt pots,
a closed underflow header, and automatic solids unloading. Figure 4 shows

the hydrocyclone unit as installed in the sediment processing system.

Final Filtration

Final filtration of the dredged slurry was required so that a high quality
effluent could be returned to the pond. Two separate filtering schemes were
utilized for this step:

(1) A commercially available polishing filter

(2) A prototype of the Uni-Flow wet bag-house type filter

The commercially-available filter selected for the field trials was of the

cartridge filter type and was manufactured by Crall Products, Inc. and

abi


SECTION |
CONCLUSIONS

The MUD CAT dredge proved very efficient in removing the deposited
sediments from the pond bottom and in preventing the resuspension of
the sediments during the dredging operations. Overall, it lived up to
its design criteria of being an efficient means of removing sediment from

ponds and lakes up to 10.5 feet in depth.

Overall, the portable sediment processing system, consisting of two
elevated clarifier bins, hydrocyclones, a cartridge filter unit, and a
Uni-Flow bag-type fabric filter, proved efficient in removing suspended

sediment from a dredged slurry.

The most efficient components of the system for sediment removal were
the elevated bins (initial solids removal phase) and the Uni-Flow filter.
They were both very effective in removing suspended solids from the

dredged slurry during the field demonstration.

The hydrocyclones were not as efficient in removing suspended solids
from the dredged slurry as originally anticipated. Use of a closed
underflow header with silt collection pots and automatic solids unload-
ing on the hydrocyclones is probably not justified in a portable sedi-
ment processing system. In addition, the use of hydrocyclones for
dredged spoil processing should be limited to removing sand-size,

i.e., 74 microns, or larger particles.

The usefulness of the cartridge filter unit in the processing system was
marginal. Operating and maintenance restrictions would probably pre-

clude the widespread utilization of such units for processing dredged


APPENDIX D

This Appendix contains the particle size distributions of the solids in the
influent for the large diameter fabric filter hose tests. Periodic samples of
the influent were taken and analyzed in order to ensure that the particle
distribution of the soil approximated a dredged slurry that would be obtained
from actual dredging operations.

76


SECTION V
FIELD DEMONSTRATION

TEST SITE

The site selected for the field demonstration of the removal and processing
system was located in Prince George's County, Maryland, at what is known
as the Bowie Airpark Site. This site contains a pond which was designed
and built as a sediment retention basin to control sediment produced by
airpark construction. Table 2 presents the pertinent characteristics of

this pond.

Table 2.__DEMONSTRATION POND CHARACTERISTICS

Surface Area 1.7 acres

Maximum depth 9.0 feet

Present Condition 99 percent filled with sediment
Age 2 years

Estimated Capacity 14,000 cubic yards

Since the maximum water depth of the pond before dredging began was
less than the minimum depth required to float the MUD CAT dredge, that
is, approximately 21 inches, it was necessary to raise both the normal
and emergency spillway elevations in order to acquire enough freeboard to
float the MUD CAT. A small spring fed the pond and helped to provide
adequate water for dredging.

The processing system was set-up on a 50-foot high knoll, approximately

600 feet from the edge of the pond. From this site, the overflow (split

17


Environmental Protection Technology Series



Table 9. CAPITAL COSTS OF THE PORTABLE SEDIMENT
PROCESSING SYSTEM

Item Cost ($)
oe
Elevated Bins: ganged together with common central
columns and air operated gates 7,300

Hydrocyclones: assembly including six 4~inch cones
with replaceable urethane liners, 3 gal. silt pots, a
closed underflow header, and automatic, air-actuated
solids unloading 4,987

Cartridge Filter Unit: assembly including four units
with 51 cartridges each and automatic, air-actuated

backflushing in sequence 7,875
Uni-Flow Filter:
basic assembly $10,450
header valves 55
sludge dump valve and actuator 319
cycle timer and box 33
720 10' polypropylene hoses @30¢/yd 720
1440 hose clamps & tape gaskets 203
pressure gages and protectors 63
Subtotal $11, 843 11,843
Pumps:
1-500 gpm @ 200 ft. of head 858
1-500 gpm @ 25 ft. of head 579
1-gasoline for bin decanting 101
Subtotal $ 1,538 1,538

Air compressor: including hoses, regulator, couplings,
and filter 637

Miscellaneous Equipment: including connecting and bypass
piping, flanges, valves, overflow pipe, railroad ties,

sludge culvert, etc. 2,045

TOTAL $ 36,225

40


SECTION Il
INTRODUCTION

In recent years, more and more developments are being built around natural
and man-made lakes. These lakes serve as recreational and aesthetic focal
points for the surrounding communities. Unfortunately, these lakes often be-
come choked with sediment rather early in their lifetime due to soil erosion
resulting from construction activity in the watershed. In order to restore these
lakes to their original condition, some type of cleaning operation is necessary.
In many cases, however, little premium land is available near the lake to con-
duct the necessary conventional dredging operations or for the standard sett-

ling ponds or diked disposal areas.

In numerous other cases, the disposal of dredged spoil and the return of the
effluent to the water body has had severe restrictions placed upon it. The
disposal of dredged material from small boat harbors onto the surrounding
wetlands is no longer allowed in most cases; the disposal of dredge spoil on
floodplains is being severely limited; and the effluents from dredging opera-
tions are receiving increased attention as water pollutants. Another problem
associated with most conventional dredging operations is the turbidity im-

parted to the water body by the dredging operations themselves.

Consequently, Hittman Associates, Inc., under contract to the Environmental
Protection Agency, conducted a demonstration of the separation and disposal
of concentrated sediments from the dredging operations on a small lake. The
purpose of the demonstration project was twofold. One, was to demonstrate

a technique for relatively small maintenance dredging operations which would
have minimal adverse effects on the surrounding water body. The second

purpose of the program was to demonstrate a portable sediment processing


SECTION II
RECOMMENDATIONS

It is recommended that the MUD CAT dredge or its equivalent be utilized for
dredging of unconsolidated sediments from water bodies within its operational
capabilities, since it produces a minimum of resuspension of the sediments

into the water column.

Systems similar to the portable sediment processing system demonstrated
should be considered for areas where dredging is required and adequate
space is not available for conventional settling basins. The sizing and selec-
tion of the individual components should be done on a site by site basis. The
clarifier bins, hydrocyclones, and Uni-Flow filter are all applicable to the
processing of dredged sediments but must be sized with the physical charac-
teristics of the dredged sediment and the solids loading rate expected in mind.
Utilization of a cartridge-type water filter for processing of dredged slurry is
not recommended due to the operational difficulties encountered while using

it on influents with high suspended solids contents.

It is recommended that five-inch diameter hoses be utilized in any future
Uni-Flow filter applications. It is also recommended that the Uni-Flow filter,
in the form of an adapted air bag house, be utilized for processing wastes
where the removal of suspended solids is a primary consideration. Further,
it is recommended that further tests be performed on the five-inch diamater
Uni-Flow hoses for their applicability to the filtering of other types of wastes

and pollutants.


€s

20004

18004

1600]

14004

1200.

1000 |

800

600)

Effluent Concentration (mg/I)

8' polypropylene cages
inside and outside
Average pressure = 20 psi
A= beginning of backflush

40

a 60 A 80 ry 100, 120 WM AA
Time (Min.)

FIGURE 12. Effluent Concentration vs. Time (Eight-Foot Hose)

T +

160 A a A 1894

A A 200


Cartridge Filter Unit

Cartridge filters are generally designed and utilized as polishing filters. In
such applications, they are usually used to produce effluent water of drinking
water quality from influents which contain at most a few thousand mg/I of
suspended solids. Thus, the operating conditions to which the cartridge
filter unit was subjected during the field demonstration, when it was sub-
jected to an average influent of 88,300 mg/l, far exceeded its design capacity.
As a result, frequent backflushing of the filters was necessary. This was
done at six-minute intervals for the majority of the demonstration program.
Even at this frequent rate, the cartridge filters frequently blocked-up with
sediment prematurely, causing excessive backpressure to build up in the

system and the total system flow rate to consequently decrease.

Midway through the field trials, the internals of each filter unit were thor-
oughly inspected. This inspection revealed a buildup of sediment in the
"dead water" areas of each filter unit as well as a number of broken filter
cartridges. Of the 204 total cartridges which were in the four subunits, 20,
or approximately 10 percent were found to be broken. It was speculated
that excessive backpressure during backflushing caused the cartridges to
rupture. The broken cartridges were replaced and the cartridge filter unit

was placed back in operation.

Broken cartridges were speculated to be the cause of the relatively dirty
effluent from the unit. Frequent spot inspections revealed continuing break-
ing of cartridges while trying to maintain adequate system flows. Therefore,
the usefulness of the cartridge filter unit in such a processing system was
marginal. Operating and maintenance restrictions would probably preclude
the widespread utilization of such units unless the suspended solids concen-

tration in the dredged slurry could be reduced to near the design level of

36


“LL

TABLE D-1. INFLUENT GRAIN SIZE DISTRIBUTIONS -
LARGE DIAMETER HOSE TESTS

Test 10'-Wire Inside 8'-Wire Inside 8'-Wire Inside 8'-Wire Inside
Parameters: 10'-No Wire 10'-Wire Outside 10'-Wire Inside and Outside and Outside and Outside and Outside

Particle Size

(microns) Percent Finer

420 100 100 67 100 97 99 98

250 99 89 53 96 92 95 88

105 84 66 33 74 63 79 74
75 58 46 18 56 32 67 67
54 31 12 4g 23 55 4
39 28 9 48 18 51

28 25 8 46 16 45

13 18 5 29 23
10 4 3 22 5 22 16
7 10 2 16 4 15 WwW
5 7 1 10 2 9 8
4 3 2 1 3


nz

Table 6. REMOVAL EFFICIENCIES OF SYSTEM UNITS
(AIL Units On Line)

Component Aver. Suspended Solids Percent of Inflow Percent Removed Percent Removed
Concentration (mg/l) Solids Remaining Through System per Component

MUD CAT Discharge 170,300 100 7 ~

Bins Effluent 131,200 77.0 33.0 33.0

Hydrocyclones Effluent 88,300 51.8 48.2 15.2

Cartridge Filters Effluent 57,200 33.6 66.4 18.2

Uni-Flow Effluent 445 0.3 97.7 31.3

(Return Water to Pond)


Table 10. SIX-WEEK OPERATING & MAINTENANCE COSTS
OF THE PORTABLE SEDIMENT PROCESSING SYSTEM
(Excluding Trucking)

Item Cost($)
Elevated Bins: rental! of concrete vibrators 180
Hy drocyclones: 0

Cartridge Filter Unit: 20 replacement cartridges

@ $3.50 ea. 70
Uni-Flow Filter: 730, 10' replacement hoses @ 30¢/yd 730
1460 tape gaskets 8

Labor: 600 man-hours @ $5.35/hr. av. 3,210

Miscellaneous: electricity, gasoline for air compressor,
etc. 30

TOTAL 4,228

Cost per cubic yard removed by system = 4228/1000 = $4.23 per cubic yard

Cost per cubic yard removed, excluding labor = 1018/1000 = $1.02 per cubic yard

41


Table 4. SUMMARY OF SYSTEM COMPONENT EFFLUENT CONCENTRATIONS

(mg/1)
Component Max. Run Min. Run Run Aver.
MUD CAT Discharge 261,000 107,000 170,300
Elevated Bins Effluent 254,000 55,800 131,200
Hydrocyclones Effluent 179,600 31,400 88,300
Cartridge Filters Effluent 105,400 22,700 57,200
Uni-Flow Filter Effluent 1,770 100 445

(Return Water to Pond)

Table 5. SUMMARY OF SLUDGE (Backflush) CONCENTRATIONS

(mg/I)
Component Max. Run Min. Run Run Aver.
Hydrocyclones 293,000 22,000 103,500
Cartridge Filters 284,600 22,000 82,800
Uni-Flow Filter 191,600 51,000 114,300

23


SECTION VIII

REFERENCES

Camp, T. R. Sedimentation and the Design of Settling Tanks.
Transactions of the American Society of Civil Engineers.
111: 895-958, 1946.

Tiederman, W. G., and M. M. Reischman, Feasibility Study of
Hydrocyclone Systems for Dredge Operations. Oklahoma State
University. Vicksburg, Mississippi, Contract Report D-73-1.
U. S. Army Engineer Waterways Experiment Station. July 1973.
176 pp.

Taras, M. J., A. E. Greenberg, R. D. Hoak, and M. C. Rand,
eds. Standard Methods for the Examination of Water and Waste-
water, 13th edition. Washington, D. C., APHA, AWWA, and WPCF
August 1971. p. 537-538.

60


ACKNOWLEDGMENTS

The support and technical guidance received from Mr. John J. Mulhern,
serving as Project Officer for the Environmental Protection Agency, is greatly
appreciated. His guidance, timely suggestions, and technical expertise in

the area of filter bag technology were especially helpful.

The field demonstration of the dredging and processing of the dredge spoil
was done in cooperation with the Prince George's County, Maryland, Depart-
ment of Public Works. They allowed unrestricted use of their sediment pond
for dredging operations, and the surrounding land for the processing. They
also provided access roads and grading at the processing site, constructed
the necessary disposal basins, and provided dump trucks for hauling of the

separated solids.

vi


The final design criteria arrived at through these tests produced a unit which
contained 720 one-inch diameter, 10-foot long, woven polypropylene hoses.
The hoses were arranged in six banks of 120 hoses each. This enabled the
shutting-down of one bank for hose maintenance or replacement while the
other five banks could be kept on-line. The slurry was pumped into a top
header which distributed the influent to each bank of hoses. The filtrate
from the hoses was collected in a bottom tray and allowed to flow by gravity
back to the pond. Every 5 1/2 minutes, the sludge within the hoses was
drained for 30 seconds into a collection trough and allowed to flow by gravity

into a sludge disposal basin. Figure 6 shows this prototype Uni-Flow filter.

FIGURE 6. Final Filtration: Uni-Flow Filter

14


SELECTED WATER
RESOURCES ABSTRACTS

INPUT TRANSACTION FORM

3. Accession No.

4 Title Demonstration of The Separation and
Concentrated Sediments

7. Author(s) iE
Nawrocki, Michael A. 10. Project No.

4% Organization PE 1B2042
Hittman Associates, Inc. 1, Contract/Grant No.
Columbia, Maryland 21045

15. Supplementary Notes

Environmental Protection Agency report No. EPA-660/2-74-072, June 1974

Io. Abstract

A demonstration was conducted of a system for removing and processing sedimen
from impoundment bodies. A MUD CAT dredge was used to remove the sediment from a
pond. The dredged slurry was then pumped through a processing system consisting of a
pair of elevated clarifier bins in series, a bank of hydrocyclones, a cartridge filter unit,
and a Uni-Flow bag-type fabric filter consisting of 720 one-inch diameter hoses.

The MUD CAT proved efficient in removing sediment from the pond bottom
without imparting a substantial amount of turbidity to the pond water. The processing
system was effective in removing suspended sediment from the dredged slurry. Its
effluent averaged 445 mg/I with an average influent suspended solids of 170,300 mg/I.

Experiments were also conducted on the use of five-inch diameter hoses on the
Uni-Flow filter. These produced better results than the one-inch hoses in that they were
not prone to blockage by sediment.

17a, Descriptors :
*Dredging, *Sediment Deposition, *Filtering Systems, *Separation techniques,
Impoundments, Water Quality Control, Desilting

17b, Identifiers
*Suspended solids separation, Pond dredging ©

Isc. COWRR Field & Group Q5G

18. Availability Send To:

WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S, DEPARTMENT OF THE INTERIOR
WASHINGTON, D. c, 20240

Abstractor ____ Michael A. Nawrocki Institution Hittman Associates, Inc.

WRSIC 102 (REV. JUNE 1971) =



10'
Filter Column

10°
Filter Column

8!
Filter Column

8t
Filter Column

Table 12.

SUMMARY OF RESULTS OF SECOND PHASE
POLYPROPYLENE TESTING

Test Parameters Average Average Average Average
Influent Effluent Flow Rate Test
Concen. Concen. Pressure
(mg/1) (mg/1) (gpm) (psi)
No Cages 7,765 1020 1.4 16.0
Cage Outside 7,840 605 1.3 18.5
Cage Inside 25,480 980 1.5 18.5
Cages Outside € Inside 11,685 1580 1.2 17.5
Cages Outside € Inside 18,200 1220 1.1 19
Test 1
Cages Outside & Inside 8,990 520 1.2 19
Test 2
Cages Outside & Inside 11,640 330 1.2 20
Test 3
Table 13. SUMMARY OF RESULTS OF SECOND PHASE
POLYPROPYLENE TESTING FOR INFLUENT CON-
CENTRATIONS NEAR 10,000 mg/I
Test Type Average Average Average Average
Influent Effluent Flow Rate Test
Concen. Concen. Pressure
(mg/1) (mg/!) (gpm) (psi)
No Cages 9995 665 1.5 16.0
Cage Outside 8310 275 1.2 18.5
Cage Inside 9330 240 1.8 18.5
Cages Outside & Inside 9090 1030 1.3 17.5
Cages Outside & Inside
Test 1 7830 1420 1.2 20.0
Cages Outside & Inside 9575 750 1.3 19.0
Test 2
Cages Outside & Inside 9885 160 1.3 20.0

Test 3

51


SL

TOP VIEW (not to scale)
60* 70* 74* 95* 101* Bux
(50.0%) (58. 3%) (61.7%) (79.23) (84.2%) (70.0%)

O Influent

Overall percentage of hoses completely blocked = 67.2%

* number of completely blocked hoses out of 120 total hoses in header

(

FIGURE C-1.

) = percentage of completely blocked hoses in header

Pattern of Blockage of Uni-Flow Hoses



when cages were added to the outside of the fabric filter column.

Filtration Cycle Time (Time Between Backflushes)

Filtration time between backflushes was greatest for the tests of ten-foot long
polypropylene fabric filters which were rinsed from the top. It should be
noted that the times between backflushes reported for these tests are from

the time when the influent slurry reached the top of the filter to the time when
the effluent flow was two and one-half gallons per minute as opposed to the one
gallon per minute criteria for backflushing in the other tests. Therefore, the
time between backflushes for the ten foot long polypropylene filters which
were rinsed from the top would have actually been much greater than the
values reported if backflushing had been initiated when the effluent flow fell

to below one gallon per minute.

The filtration times between backflushes for the ten-foot long filters in the
second phase of testing were very much lower than the filtration time between
backflushes for the ten- foot long polypropylene filters of the first phase.
During this second phase, as seen from Table 15, the tests of ten-foot long
filters with both no cages and a cage only on the inside produced a higher
average filtration time between backflushes than the two configurations of
filters with wire mesh outside the column. As discussed previously, wire
mesh inside the filter column increases the filtration time between required

backflushes.

A comparison can be made between the tests of ten and eight-foot long filters
with wire mesh both inside and outside the filter column. The shorter filter
exhibited average backflush times of one and one-half times those for the
longer filter when considering the results of the entire tests. However,

the second test on eight foot long fabric filters was performed on a thoroughly

58


(2) Since the MUD CAT was not built for dredging through undis-
turbed ground, there is probably little danger of inadvertently puncturing
the natural pond or lake bottom and causing leakage.

(3) The MUD CAT can usually be unloaded directly into the lake or

pond from a standard-size, tilt-bed trailer.

PROCESSING SYSTEM

Overall, the processing system proved effective in removing the large
majority of suspended sediment from the dredged slurry. The average
return water quality to the pond contained 445 mg/I of suspended solids.
Each component's individua! contribution to the efficiency of the total sys-
tem varied, however. The operational aspects of each component are dis-

cussed in the succeeding paragraphs.

Elevated Bins

The elevated clarifier bins performed very efficiently as an initial solids
removal phase in the sediment processing system. Their actual efficiency,

in fact, was discovered to be better than their expected efficiency as predicted
by ideal settling theory. Tables C-3 through C-5 in Appendix C show the
grain size distributions of composite samples taken of the sediments in both

elevated bins and in the effluent from the bins (influent to the hydrocyclones) .

According to ideal settling theory, the elevated bins could be expected to
settle out all particles down to approximately 100 microns in size. The data
in Tables C-3 and C-4 indicate that a substantial portion of the material below
75 microns in size was also settled out in the bins. In the first bin, approx-
imately 26 percent of the trapped sediment was less than 75 microns in

diameter. In the second bin, about 36 percent, on the average, of the trap-

31


Table C-1. SUSPENDED SOLIDS CONCENTRATIONS IN PROCESSING SYSTEM

Suspended Solids at Sampling Point (mg/I) _ Average Remarks
Date #5 #1 #2 #3 #4 System Flow
(gpm)
6/25/73 158,000 29,500 * 190 300 3 hr. composite samples;
2 Uni-Flow hoses with holes
* 1440 300 sample after 1 Uni-Flow
hose burst
6/26/73 150 250 2 hr. composite sample
136 250 " " ”
340 250 " " "
1/2/73 261,000 231,700 149,500 105, 400 240 300 4 hr. composite samples
TNT3 * 47 250 2 hr. composite sample
* 491 250 " " "
* 1127 250 " " ”
7/92/73 195,200 151,200 108,000 97,200 100 200 3. hr. composite sample
1/13/73 76,400 52,400 * 184 200 2 hr. composite sample; cartridge
filters bypassed
254,000 254,000 ©=—'179,600 © 50, 400 227 200 2 hr. composite sample; bins
completely full of sediment
7/14/73 392 250 2 hr. composite sample; bins
completely full of sediment
7/23/73 129,200 61,300 40,400 26,200 230 100 composite sample of run
7/26/73___107,600___87,600 31,400 22,700 570 100 Composite sample of run.
7/27/73___107,000__67, 400 44,700 26,200 660 300 Composite sample of run
7/30/73____138,000__55,800 49,500- 34,700 520 250 Composite sample of run
8/1/73 140,500 ___ 103,000 94,400 1770 200 Composite sample of _run
8/6/73 + * 250 15 min. av. flow; Uni-Flow
pressure = 8 psi
158,200 135,900 + * 208 120 15 min. av. flow; Uni-Flow
pressure 10 psi; 1/2 hr.
composite samples
+ * 70 15 min. av. flow; Uni-Flow
pressure 12 psi
96,200 70, 100 + * 27 60 15 min. av. flow; Uni-Flow
pressure 12 psi; 1/2 hr.
composite samples
+ * 50 15 min. av. flow; Uni-Flow
pressure = 10 psi
145,900 84, 500 + * 424 30 15 min. av. flow; Uni-Flow

pressure = 11 psi; 1/2 hr.
composite samples

+ hydrocyclones bypassed
* cartridge filters bypassed

Sampling Point Key

= MUD CAT discharge into elevated bins

Bin effluent Influent to hydrocyclones
Hydrocyclone effluent - Influent to cartridge filters
Cartridge filter effluent - Influent to Uni-Flow filter
Uni-Flow effluent (return water to pond)

sete eee
BuNauw
wu

71


ped particles were below 75 microns in diameter. Table C-5 in Appendix C
shows the grain size distribution of the solids in the effluent from the bins
(influent to the hydrocyclones). It shows that almost all of the particles
over 105 microns in diameter remained in the bins. Thus, as evidenced
by these data, the elevated bins performed better than expected in that
almost all of the particles down to the expected size (100 microns) were
removed as well as an additional fraction of the particles below 100 microns

in size.

The factors which produced this deviation from ideal settling theory during

the field demonstration included:

(1) The effects of turbulence on the settling of particles produces
perturbations from ideal settling theory. Some small fraction of material
larger than the size expected to be settled (in this case, 100 microns) can be
expected to be lost over the overflow due to turbulence. However, a lar-
ger fraction of particles below the critical size are deposited due to turbu-
lence effects. | The distribution of particle sizes settled in the bins cor-
respond roughly to those predicted by the theory of turbulence effects on
settling.

(2) Some collision and/or agglomeration of small size particles with
larger-sized particles may have occurred in the turbulent regions of the
elevated clarifier bins. This action would either slow down particles or
produce larger particles, both of which conditions would cause settling of
the smaller than critical size particles to occur more readily than would

normally be expected.
During the field demonstration, cleaning of the elevated bins was necessary

after approximately two to three hours of continuous dredging. After this

time, the bins were essentially full and no additional settling occurred.

32


The length of the fabric filter column was shortened from a nominal ten feet
to eight feet towards the end of the testing program. Wire mesh cylinders
were placed both inside and outside the shortened fabric filter column and
remained in place for all tests of the eight foot long filter. The eight-foot
filter was always tested with wire mesh on both the inside and outside of the
tube.

Three tests of the eight-foot long filters were conducted. The first was a
short duration test of approximately one hour, and the second and third

together were a long duration test of about five hours.

TEST PROCEDURE

The procedure for testing the nominal five-inch diameter fabric filter hoses

is described in the following steps:

(1) An influent slurry was mixed in the sediment reservoir to the
approximate desired concentration of suspended solids.

(2) The influent pump was started.

(3) When the influent water reached the top of the fabric filter column,
the time was recorded, samples of the influent and effluent were taken simul-
taneously, and readings of the pressure gauge and flow meter were taken
simultaneously and recorded.

(4) The pressure was recorded at two minute intervals for short
duration tests and ten minute intervals for the long duration test. Flow
readings were taken continuously.

(5) Backflushing was performed when the flow rate fell to below one
gallon per minute.

(6) After backflushing, the procedure began at step three (3) again.

After all samples were taken, laboratory analyses were performed to deter-

mine the concentrations of suspended solids in the influent and effluent

47


(1) The automatic dump cycle on the hydrocyclones was shortened
to provide the capability to unload accumulated solids at intervals less

than 15 minutes apart.

(2) Automatic backflushing of the cartridge filters was similarly

specified at less than 10 minute intervals between cycles.

During the initial dredging operations, a number of samples were taken
of both the undisturbed pond water and of the MUD CAT discharge.

These samples were composited and subjected to a more rigorous water
quality analysis. A comparison between the water quality of the pond
water and that of the dredged slurry could thus be obtained. This
comparison gives an indication of constituents which might be present in
the pond sediments but which are not present in significant quantities in
the pond water itself. Tables A-2 and A-3 in Appendix A present the

complete results of these baseline water quality tests.

RESUSPENSION OF BOTTOM SEDIMENT DURING DREDGING

A sampling and analysis program was initiated to determine the amount of
sediment which was resuspended into the pond water as a result of the
dredging operations. Samples were taken around the periphery of the
dredge at various distances from the dredge and at various depths. These

samples were analyzed for their suspended solids concentrations.

Generally, the MUD CAT dredges more efficiently during a backward cut
than during a forward cut. This is true from both a solids removal and
a resuspension of sediment aspect. During a backward cut, the mud

shield is lowered over the auger (see Figure 2), and the bottom sediment

is dragged into the auger. This allows a deeper cut along with less

20


hose would require less supporting superstructure in a full-scale filter. The
wire cages used were built of galvanized, 16-gage welded wire fencing with
openings of 2" x 2 5/8".

Table 12 presents a summary of the results for the entire second phase of
testing. In order to compare the performance of the hoses under approximately
the same test conditions, the tests in which the concentration of suspended
solids in the influent was approximately 10,000 mg/I were analyzed. A
summary of these tests is presented in Table 13. As can be seen from this
table, the addition of wire cages to the polypropylene hose did not produce a
substantial increase in flow at the 10,000 mg/I influent level. However,
reducing the length of the hose to eight feet did not substantially reduce the
flow rate at this influent concentration. The average effluent quality for

all tests summzaized in Table 13 (influent concentrations of approximately
10,000 mg/l) were comparable.

Figures 11 and 12 are plots of the flow and effluent concentrations respec-
tively, on the last long duration.test on the eight-foot long hose with cages on
both the inside and outside. These figures show the typical flow and effluent
quality patterns evident during the test program. As seen on Figure 11,
immediately after backflushing the flow increases to some higher point, and
then decreases as sediment builds up on the inside of the hose. As the
sediment builds up on the inside of the hose the flow rate drops. Back-
flushing washes the accumulated sediment from the hose and the flow rate
again increases. During the test shown in Figure 11, the hose was back-
flushed when the flow rate fell below approximately 0.9 gpm.

The effluent quality is usually low after a backflush and becomes better

as the sediment forms a coating on the inside of the hose. However, as seen
from Figure 12, the effluent quality did not follow as regular a pattern as the
flow rate curve. This may be due to a number of factors, such as variance
in the cleansing action of the backflushes, amount of soil particles trapped
within the fabric, soil particle agglomeration, etc.

50


cleaned filter. The average backflush time for the rinsed filter increased
by about five times over the backflush time for the previous test of the

unrinsed filter, considering results for the entire tests.

A third test on the eight-foot filter was started after the rinsed filter of the
second test had operated for two hours. At thirty minutes into the third

test, the backflush time had decreased to the range of backflush times found
for the first test. Therefore, in two and one-half hours, the performance of
the rinsed filter deteriorated to the performance level of one used extensively

without rinsing.

The backflushing method was varied at certain times during the long term
test of the eight-foot filter so that immediately after the concentrated sediment
slurry had been discharged from the filter, influent water was pumped into
the filter from the bottom and the quick-open backflush valve was opened
when the water level reached the top of the filter column. This procedure is
evidenced by the relatively short times between backflushes shown toward

the end of Figures 11 and 12.

59


ABSTRACT

A demonstration was conducted of a system for removing and processing sedi-
ments from pond bottoms. The removal system consisted of a MUD CAT dredge,
which is specifically designed to dredge without imparting substantial turbid-
ity to the water column. The 500 gpm processing system consisted of, in order
of flow, a pair of elevated clarifier bins arranged in series, a bank of hydro-
cyclones, a cartridge filter unit, and a Uni-Flow bag-type fabric filter consist-

ing of 720 one-inch diameter polypropylene hoses.

The MUD CAT dredge proved efficient in removing the pond sediments and
did not produce a substantial amount of resuspension of the sediments. An
average final effluent quality of 445 mg/I of suspended solids was achieved
by the processing system, with a reported range of from 47 to 1770 mg/l. The
most effective components of the system in removing suspended sediment were

the clarifier bins and the Uni-Flow filter.

After the field demonstration, further experiments were conducted on larger,
five-inch diameter Uni-Flow hoses. Different materials, methods of screen-
ing, and lengths were tested in order to optimize the operating parameters of
the hoses. It was determined that eight-foot long, polypropylene hoses with
wire caging on both the inside and outside of the hose were more suited for
further development than the other configurations tested. This hose yielded
comparable effluent qualities and throughflow rates and required less hard-

ware than the other hoses.

This report was submitted in fulfillment of Contract Number 68-01-0743 by
Hittman Associates, Inc. under the sponsorship of the Environmental Protec-

tion Agency. Work was completed as of November 30, 1973.


portable sediment processing system in the field. The results of these larger

diameter hose tests are presented in Section VII.

COSTS

Table 9 shows the capital costs of the major components of portable sediment
processing system and the various pieces of required auxiliary equipment
which were used in the field demonstration. Similarly, Table 10 is a com-
pilation of the operating and maintenance costs incurred during the six-week
field demonstration of the system, excluding the costs of trucking the sedi-

ment from the elevated bins.

As is seen from Table 10, the operating and maintenance costs of the overall
system were $4.23 per cubic yard of sediment removed. This relatively high
cost was due to a number of factors, all of which were directly related to the
amount of labor required. The factors which required a labor-intensive

effort were:

(1) Changing of the Uni-Flow filter hoses
(2) Removal of sediment from the bins

(3) Cleaning and replacing filter cartridges
Since the system demonstrated in the field was a prototype system, it is
probable that the operating and maintenance costs could be reduced by
approximately 30 percent through the judicious streamlining of the system.

Suggestions for streamlining of the system include:

q) Elimination of the cartridge filter unit

39


the units. Such a situation might arise if the dredged material consisted of
mainly sand-sized and larger particles and these particles were effectively
removed before being fed to the cartridge filters by clarifier tanks and/or
hydrocyclones. In such a situation, the cartridge filters would be perform-

ing the polishing function for which they were designed.
Uni-Flow Filter

The Uni-Flow filter, a fabric hose type filter, proved to be very effective in
removing suspended solids from a dredged slurry during the field demon-
stration. The Uni-Flow delivered a very good effluent: as low as 47 mg/I
of suspended solids, with a normal average of a few hundred mg/! unless a
hose burst or a puncture developed in a hose and the effluent water quality

deteriorated corresponding.

It was observed during the field demonstration that the average effluent
quality could have been even better if an inexpensive, easily installed,
completely watertight method of fastening the ends of the hoses to the pipe
nipples could be found. Minor but numerous leaks were observed to occur
around the hose clamp and gasket seals which fastened the hoses to the

nipples in the six Uni-Flow filter headers.

After three weeks of operation, the hoses became so blocked with sediment
that the installation of a completely new set of hoses became necessary.
Previous to this, simple shaking of the hoses by hand after the sediment had
dried was tried as a simple maintenance cleaning procedure. Although this
method produced acceptable results in that the sediment was loosened from
the sides of the hoses and fell into the sludge collection hopper, it proved to
be very time consuming. Blockage of a large number of the hoses occurred

daily, but daily maintenance cleaning of the hoses in this manner proved

37


Table A-1.

POND WATER QUALITY BEFORE DREDGING OPERATIONS

Constituent

Concentration (mg/I unless stated otherwise)

Sulphate

Phosphate

Iron

Copper

Zinc

NH 3

coD

Total Nitrogen
Coliform (Presumptive)
pH

Suspended Solids
Volatile Solids

Total Dissolved Solids
Total Solids

Turbidity (TU)

Oxidation-Reduction Potential (mv)

* Location Description:

Pond inflow from watershed

Location*

1 2 3 4

10 - 23 50
0.9 - 0.7 1.4
0.45 - 0.3 0.7
0.35 - 0.3 0.5
0.00 - 0.01 3.25
0.8 - 0.7 1.6
- - 3.4 7.6
12.0 - 9.0 13.0
- Positive 5/5 - -
6.0 - 6.75 6.1
- - 381 745
531 - 67 68
- - 57 21
2980 - 505 834
- - 130 135
50 - 60 75

2,3 - Near the inflow end of the pond
4 ~ Near the discharge end of the pond
5 - Pond discharge

62

0.4

1.6

14.0

6.1

37

42

48

13

20


solids concentration of the slurry. A retractable mud shield over the auger
minimizes mixing of the disturbed bottom deposits with the lake water. Figure
2 is a close-up view of the auger on the MUD CAT dredge. The dredge also
comes equipped with a rock box into which objects greater than eight inches
in diameter (the diameter of the discharge line) are automatically discarded

before the dredge spoil is pumped into the discharge line.

PROCESSING SYSTEM UNITS

The development of a portable sediment separation system centered around
the use of a hydrocyclone initial stage followed by the Uni-Flow filter. Other
alternative or additional devices were also evaluated for possible inclusion
in the processing system based on the equipment's degree of portability, cost,

expected performance, and the physical characteristics of the dredge spoil.

FIGURE 2. Close-up of MUD CAT Auger


was especially evident in the nylon hose, which had to be run at a very low
pressure (flow) in order to prevent its breaking away from its seals at the

ends of the test column.

Second Phase

After the polypropylene fabric was determined to be the most suitable for
the filtration of suspended solids of the fabrics tested, experiments were
conducted in order to better define the operating parameters and to try to
optimize the performance of five-inch polypropylene hoses. The goal of
this second phase of five-inch hose testing was to maximize the flow rate
through the hose yet maintain a high overall effluent water quality. An
additional consideration was to reduce the operational hardware require-

ments of any full scale prototype as much as possible.

In order to reduce the hardware requirements, washing of the filter from
the top was eliminated during the second phase tests, and a simple draining
of the hose during backflushing was substituted instead. This simple drain-
ing of the tube did not produce as clean a hose as with a wash from the top,
and consequently the average flow rates of the nonrinsed hose were corres-
pondingly lower. Filling and draining the hose a number of times during
the backflush cycle was also tried and produced a somewhat cleaner hose, but
the amount of backflush water required was more than the hose throughput.
The sequence of testing during the second phase involved first the testing

of the wire cages on the inside, outside, and both inside and outside of the
hose, and the reducing the length of the hose to eight feet. In all tests
during the second phase, the hoses were run until their flow dropped below
0.9 gpm, at which time they were backflushed and the tests continued. The
reduction in length was designed to see if a somewhat shorter hose would

produce the approximate same flow rate as a 10-foot long hose. A shorter

49


SS

Table 14. PERFORMANCE HISTORY OF UNI-FLOW FABRIC FILTERS

Test Fabric Type- Operating Filtration Average Average
Influent Pressure Rate Operating Filtration
Range Range 2 Pressure Rate
psi gpm/ft psi gpm/ft
Aqua-lon Corp. Cotton -Acid 12-20 0.13 12-20 0.13
1" dia. testing Mine Drainage Waste
model (EPA Contract No. 68-01-0043)
Hittman Assoc. Cotton -Sediment 5-33 0.05-0. 13 11 0.06
1" dia. testing Slurry
model
Hittman Assoc. Polypropylene- 5-12 0.06-0.19 10 0.13
1" dia. full Sediment Slurry
scale proto-
type field tests
*
Hittman Assoc. Polypropylene- 10-23 0.07-0.44 12 0.24...
5 1/4" dia. Sediment Slurry OM ay
testing model 0.13

* 10' long, rinsed from top
** 10'long, not rinsed from top (simple draining)
*** 8' long, not rinsed from top


Initial Solids Removal

The alternatives considered for the initial solids removal phase were narrowed
down to either provide a type of portable settling tank or utilize one of the
various coarse screening techniques available. The first alternative, that is,
the settling tank, in the form of elevated bins of the type used for concrete
batch plants, was found to be the most attractive alternative. Advantages of

the elevated bins over the various screening techniques include:

(1) Settled solids can be loaded directly onto trucks by gravity flow.

(2) The bins are self-cleaning with steep-sloped sides.

(3) The elevated bins provide head for the pump which feeds the
secondary separation phase (hydrocyclones) .

(4) Ease of incorporation of a flow splitter device which would
enable gravity flow to the holding basin.

(5) Elevated bins are not subject to clogging as some screens are.

(6) Elevated bins are less costly and remove a greater portion of
the suspended solids at the given flow rate of approximately

1500 gpm.

Two elevated bins, each with an initial capacity of 36 cubic yards were in-
stalled in series as the initial solids removal phase. The discharge from the
dredge was pumped directly to the first bin where settling of suspended
solids occured. The slurry was then allowed to overflow into the second
bin, where additional settling occured. From the second bin, the flow was
split to either the temporary holding basin or to the feed pump for the hydro-

cyclones. Figure 3 shows the elevated bins used for the field demonstration.

Each of the elevated bins selected for testing in the portable sediment separ-
ation system provided about 144 square feet of surface area for settling. At

the expected 1500 gpm flow rate, a theoretical upflow velocity of approximately


EPA-660/2-74-072
June 1974

DEMONSTRATION OF THE SEPARATION
AND DISPOSAL OF CONCENTRATED
SEDIMENTS

By
Michael A. Nawrocki

Contract No. 68-01-0743
Program Element 1B2042
Roap/Task PEMP 03

Project Officer

John J. Mulhern
Office of Research and Development
Washington, D. C. 20460

Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.45


No damage is done to the dredge due to this blockage or fouling, and dredg-
ing can be continued as soon as the pump and auger are shut down and the
debris is removed.

(2) Bars of sediment which protrude above the water level. Dredging
operations are slowed by cuts which must be made above water level. In
this case, the auger and intake must be raised and the sediment must be
dragged back into the pond by the mud shield. This operation must be
repeated until adequate draft (approximately 18 inches) is available for
passage of the MUD CAT. Naturally, this operation takes longer than a
normal dredging operation, but is well within the capabilities of the MUD
CAT.

(3) The need for quite a number of positioning moves of the dredge
in order to dress-up the banks of the pond. Since movement of the MUD
CAT is limited to a straight line along a taut, fixed cable, this cable must
be moved a greater number of times per cubic yard of sediment dredged

when short cuts are being made in order to dress-up the pond banks.

Overall, the MUD CAT dredge lived up to its design criteria of being an
efficient means of removing sediment from ponds and lakes up to 10.5 feet
in depth. It or an equivalent dredge's application to such lake cleaning
operations is thus recommended. Some additional advantages of the MUD

CAT in this connection include:

(1) The dredged slurry can be pumped to a remote site for disposal,
thus eliminating the near shore mess that is usually associated with conven-
tional dragline operations. The engine and pump on the MUD CAT permit
the slurry to be moved up to 3000 feet from the lake without the use of a

booster pump.

30


(aa

Table C-2. OTHER WATER QUALITY CONSTITUENTS IN PROCESSING SYSTEM

Date Sampling _ Constituent Concentration (mg/1)

Point PO. NO, + NO,” Fet* so. Total pH Turbidity (JTU)

4 3 2 4 : :
Dis. Solids

6/25/73, #1 5.9

#2 6.0

#3 6.0

#4 16 5.8 153

#6 6.0

#7 6.0

#8 6.0
6/26/73, #1 1.8 9.0 0.35

#2 1.6 12.0 0.15

#3 1.8 14.0 0.35

#4 1.8 11.0 0.27 120 140
7/2/73 #1 1.5 13.0 0.15

#2 2.8 12.0 0.10

#3 1.5 11.0 0.05

#6 1.8 14.0 0.10

#8 7 15.0 0.10
7/6/73 #5 5.2 13.0 0.75

#1 8.0 11.0 1.50
7/12/73, #5 2.3 13.0 17.0

#2 0.6 8.0 25.0

#3 0.7 13.0 22.0

Sampling Point Key:

# 5 = MUD CAT discharge into bins

# 1 = Bin effluent - Influent to hydrocyclones

# 2 = Hydrocyclone effluent - Influent to cartridge filters
# 3 = Cartridge filter effluent - Influent to Uni-Flow filter
# 4 = Uni-Flow effluent (return water to pond)

# 6 = Hydrocyclones sludge

#7 = Cartridge filters sludge

# 8 = Uni-Flow sludge


flow) from the bins and the backwash sludges from the hydrocyclones,
cartridge filter unit, and Uni-Flow filter could flow by gravity to, respec-
tively, the temporary holding/settling basin and the sludge disposal basin.
Both these basins were formed by earthern dikes. The clean water efflu-

ent from the processing system could also return to the pond by gravity

flow. After decanting the excess water, the solids from the elevated bins were
emptied directly into dump trucks and were trucked to a disposal area in

another part of the Bowie Airpark Site.
BASELINE SURVEYS

Approximately two months before dredging and processing operations be-
gan, a number of water quality and sediment samples were taken in the
demonstration pond in order to establish the natural pond conditions and
to aid in the final design of the equipment for the sediment processing
system. The pond water was sampled at a number of points throughout
the pond. These samples were analyzed for a number of the standard
water quality indicators. The results of these analyses are given in

Table A-1 in Appendix A.

Six core samples, up to two feet in depth, of the undisturbed pond bottom
were acquired. These sediment samples were analyzed for their grain
size distribution and specific gravity. These analyses were useful in
providing final specifications and design criteria for the hydrocyclone
and cartridge filter units in the processing system, even though full-
depth core samples of the pond sediments could not be obtained. Table
3 shows the composite grain size distribution of the undistrubed pond
sediments. As can be seen from the table, the large majority of the
sediment is finer than 100 microns. This affected the design of the

equipment for the sediment processing system in the following ways:

18


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development,
Environmental Protection Agency, have been grouped into five
series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface

in related fields. The five series are:

1, Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research

4. Environmental Monitoring

5. Socioeconomic Environmental Studies

This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed

to develop and demonstrate instrumentation, equipment and
methodology to repair or prevent environmental 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 report has been reviewed by the Office of Research and
Development. Approval does not signify that the contents
necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.


(2)

(3)

Utilization of a Uni-Flow filter with larger diameter hoses to
eliminate the hose blocking problem

Investigation of applicable available equipment or alteration of
equipment to permit automatic solids unloading at an acceptable
moisture content from the initial solids removal stage clarifier

tanks.

42


97

MUD CAT
discharge

3152 Ib/min.

2109 tb/min.

Initial Separation
Two 36-yard

Temporary
Holding/Settling
Basin

Secondary Separation

Final Filtration Final Filtration

Elevated Bins 261 Ib/min.
trucking
782 |b/min.
Bin Solids
Disposal Area
FIGURE 8.

Hydrocyclones

Cartridge Filter

171 Unit 109 Uni-Flow Filt :r
ib/min. m tb/min.

backflush backflush backflush

90 Ib/min. 62 Ib/min. 108 Ib/min.

Return Water
to pond
S{b/min.

Sludge Disposal

Area

260 Ib/min. total

Solids Balance for Processing System


silt and clay range. The solids concentration in the underflow averaged

about 10 percent over the course of the entire field demonstration.

Some observations on the efficiency of the hydrocyclones in processing

the sediment at the field demonstration site are:

(1) The hydrocyclones were not as efficient in removing suspended
solids as anticipated. This was thought to be due to two factors present
during the demonstration: the high influent solids loadings and the small
particle sizes in the influent. Both of these factors are thought to have
reduced the efficiency of removal of the hydrocyclones.

(2) The use of a closed underflow header with silt collection pots
and automatic solids unloading is probably not justified in a portable sedi-
ment processing system. The higher underflow solids loadings anticipated
through use of this configuration did not materialize, probably due to the

factors mentioned in (1) above.

A recently completed study on the use of hydrocyclones for the processing of
dredged slurry also arrived at conclusions similar to the observations in (1)
above. The study concluded that the hydrocyclone is not applicable to dredged
spoils with high solids contents and high viscosity at low shear rates. Sand
spoils with low organic content were applicable for separation by a hydrocy-
clone. It was also recommended that the influent have a suspended solids

concentration of less than 10,000 mg/I. 2

The use of hydrocyclones in dredged spoil processing systems should thus
be limited to the separation of particles down through the sand size range,
that is, 74 microns or greater in size. Within these constraints, hydrocy-
clones should prove even more efficient in removing suspended solids than

was demonstrated during the field trials under this program.

35


sediment being imparted to the water. During a forward cut, the dredge
proceeds with the mud shield raised. The auger alone then acts to convey
the solids into the pump intake line. This not only imparts a greater
amount of turbidity to the surrounding water, but also is a less efficient

method of picking-up the bottom sediment.

Consequently, the sampling and analysis program concentrated on deter-
mining the resuspension during the worst case, that is, during the forward
cut mode of operation. Appendix B contains the detailed data from this

sampling and analysis program.

In general, the suspended sediment plume imparted to the surrounding
water during dredging is confined to within 20 feet of the dredge. The
maximum suspended solids concentration reported within the plume was
1260 mg/l. Also, the major part of this plume is confined to the area
directly in front of the dredge. In addition, some turbidity is occasion-
ally imparted to the water behind the dredge. This is not a direct result
of the dredging operations, but due to the fact that the fresh water system
intake is located at the rear of the dredge. The system is used to flush
the main pump bearings and the auger bearings. The fresh water intake
will sometimes stir up the bottom sediments if the pond is relatively shallow,
thus imparting a small plume of suspended sediment to the water behind

the dredge.

PROCESSING SYSTEM EFFICIENCY

Suspended Solids Removal

Slurry from the dredging operations was pumped through the portable
Processing system described in Section IV for a total of seven weeks.

During this time, the system was tested in a number of different config-

21


system which could be set up to process the dredge effluent in a relatively
small area, remove the majority of the solids, return clean water to the pond,

and then be dismantled and moved after the dredging operation is complete.

The dredge used was a MUD CAT dredge manufactured by National Car Ren-
tal Systems, Inc. It is specially designed for use on small lakes, and to im-
part minimum turbidity to the water while dredging. It can discharge approx-
imately 1500 gallons per minute (gpm) of slurry with a solids concentration

of 10 to 30 percent.

The portable sediment processing system consisted of a pair of elevated

settling bins, a bank of hydrocyclones, a standard cartridge-type water

filter unit, and a bag-type filter known as a Uni-Flow. Basically, the Uni-
Flow filter consists of a number of hanging hoses. The dirty water is pumped
into the inside of the hoses and is allowed to filter through them. Periodically,
the collected sludge is flushed from the inside of the hoses. The design of

the Uni-Flow filter was based on experiments performed on a full-scale test
stand. The total processing system was tested in a number of different arrange

ments during the course of dredging operations.

Additional experiments were also performed on the Uni-Flow bag-type filter.
These tests were done on full-scale test stand after experiments with the
total processing system in the field were complete. The purpose of these
additional experiments was to refine the technology of the Uni-Flow filter to
a point where additional prototype units could be built for other water and

waste filtering applications.

This report constitutes the final report on the entire project. It includes the
system design, the results of the field trials of the dredged slurry processing
system, and the results of the additional testing of the Uni-Flow filter hoses

on the test stand.


LS

Table 15. FILTRATION RATE RANKING OF POLYPROPYLENE FABRIC FILTERS

Polypropylene Filter

Filtration Rate

Average Effluent

Average Time Between

Parameters (gpm/ft") Quality (mg/ 1) Backflushes (min.)
10' long, no cages, rinsed from top 0.24 95-140 10-16

10' long, cage inside 0.13 240 5

8' long, cages inside and outside 0.13 750 8

10' long, no cages 0.11 665 10

10' long, cages inside and outside 0.10 1030 2

10' long, cage outside 0.09 275 4


Table C-3."-GRAIN SIZE DISTRIBUTION OF SEDIMENT IN FIRST BIN

Particle Size (microns) Percent Finer (7/2/73)
4760 99.8
2000 99.7
420 99.1
250 98.0
105 41.9
75 24.4

Moisture Content = 263

Table C-4. GRAIN SIZE DISTRIBUTION OF SEDIMENT IN SECOND BIN

Percent Finer

Particle Size (microns) Date: 7/2/73 7/10/73 7/13/73
4760 100
2000 99.3 100
420 98.4 100 99.9
250 97.4 99.9 99.8
105 59.9 82.8 85.0
75 27.3 36.5 45.0

Moisture Content = 26%

73


SECTION VII

ADDITIONAL TESTS - LARGE DIAMETER FABRIC
FILTER HOSES

BACKGROUND

Fabric filter hoses of greater than one inch in diameter were tested and eval-
uated on a separate system after the field demonstration of the portable sedi-
ment processing system was completed. The project was undertaken for the
purpose of determining whether larger diameter fabric filters exhibit perfor-
mance characteristics superior to those of one-inch diameter fabric filters.
The investigation centered on the use of the fabric filters for the clarification
of suspended sediment slurries and the concentration of the sediment sludge.
In particular, larger diameter filters were investigated for their ability to
resist bridging with sediment, the cheif problem with the smaller diameter
fabric filters. In addition, the larger diameter filters were tested for:

(1) Filtration rate, expressed as the ratio of gallons per minute
of effluent to square feet of filter surface area.

(2) Pressure handling ability (psi)

(3) Tendency of the filter tubes to bow with increased pressures
(deflection in inches)

(4) Quality of the effluent (milligrams per liter of suspended solids)

(5) Total effluent flow (gallons per minute)

(6) Filtration cycle time (time between backflushes)

(7) Ease of cleaning during a normal backflush (sludge draining)

cycle.

The sediment used in the influent slurry was made from a mixture of sand and
the finer silts and clays. These materials were taken from dredged spoil
disposal areas and mixed to simulate typical dredged slurries. Appendix D
contains the measured particle size distributions of the influent solids for

various large diameter hose tests.

Five-inch nominal diameter hoses were selected for testing. This size was
selected because it is one of the standard diameter bags which are used in

43


Flow
Meter

Effluent

Back flush

FIGURE 10.

Control Valve For

ae Filter Rinse

Sediment
Slurry
Reservoir

/ p—___
—
50
—| =
Fabric Filter
Hose
~—5- 1/4"
9-1/2!
1"
Effluent Reservoir
Pressure
Gage
= su
3" i
"
Sample
Port

ao

XL Quick-Open

Backflush Valve

1-1/2"

Influent Pump

Large Diameter Fabric Filter Hose Test Apparatus

45


Under normal conditions, the discharge from the MUD CAT dredge can be
expected to contain between 10 and 30 percent solids by weight. This rela-
tively high concentration of solids is an advantage in that less dredge spoil
needs to be processed to remove a given amount of sediment. However, at
the expected flow rates, such solids loadings exceed the design capacity of
standard hydrocyclone units. In addition, some larger diameter gravel and
rock can be expected to be pumped by the MUD CAT. The larger particles
would be too large to be processed by the hydrocyclones. Consequently, an
initial solids removal phase was deemed to be required in order to remove the
larger particles and to generally reduce the overall suspended solids loading

of the dredged slurry before processing by the hydrocyclones.

In order to achieve as clean a return water to the pond as possible, a final
filtration step was added to the portable sediment processing system. Two
different filters were installed and tested as part of this final filtration step.
One was the Uni-Flow bag-type filter concept. The other was a commercially

available cartridge-type water filter.

Basically. therefore, the portable sediment separation system consisted of

three general steps:

1. Initial solids removal
2. Secondary separation (hydrocyclones)
3. Final filtration (cartridge filter unit and/or Uni-Flow filter)

In order to economically demonstrate a fully portable system, the total flow
from the dredge was split after the initial solids removal phase. Thus, the
fully portable system was designed to process a nominal 500 gpm. The re-
maining flow of approximately 1000 gpm was sent to a temporary earthen

holding/settling basin.