Environmental Protection Technology Series Demonstration of The Separation and Disposal of Concentrated Sediments £o I 55 \ 5SS \ UJ Office of Research and Development U.S. Environmental Protection Agency Washington, D.C. 20460 ------- 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. ------- 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 1 B2042 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 ol Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.45 ------- 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-FIow 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/l 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-FIow filter. After the field demonstration, further experiments were conducted on larger, five-inch diameter Uni-FIow 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. ii ------- CONTENTS PACE Abstract i i Table of Contents i i i List of Figures iv List of Tables v Acknowledgments vi SECTIONS I Conclusions 1 II Recommendations 3 III Introduction 4 IV Removal and Processing Systems 6 V Field Demonstration 17 VI Discussion of Field Demonstration 29 VII Additional Tests-Large Diameter Fabric Fi Iter Hoses 43 VI11 References 60 APPENDICES 61 in ------- FIGURES NO. PAGE 1 MUD CAT Dredge 6 2 Close-up of MUD CAT Auger 7 3 Initial Solids Removal Phase: Elevated Bins 10 4 Secondary Separation: Hydrocyclones 12 5 Final Filtration: Cartridge Filter Unit 13 6 Final Filtration: Uni-Flow Filter 14 7 Schematic of Processing and Sludge Disposal System 16 8 Solids Balance for Processing System 26 9 Sediment Accumulated in First Bin After Two Hours of Dredging 33 10 Large Diameter Fabric Filter Hose Test Apparatus . 45 11 Flow vs. Time (Eight-Foot Hose) 52 12 Effluent Concentration vs. Time (Eight-Foot Hose) 53 IV ------- TABLES NO. PAGE 1 Theoretical Settling Velocity of Particles in Water at 10° C 10 2 Demonstration Pond Characteristics 17 3 Physical Characteristics of Composite Sediment in Pond Before Dredging 19 4 Summary of System Component Effluent Concen- trations (mg/l) 23 5 Summary of Sludge (Backflush) Concentrations (mg/l) 23 6 Removal Efficiencies of System Units (All Units On Line) 24 7 Results of Bins to Uni-Flow Filter Run 27 8 Destination of Dredged Sediment 29 9 Capital Costs of the Portable Sediment Pro- cessing System 40 10 Six-Week Operating and Maintenance Costs of the Portable Sediment Processing System (Excluding Trucking) 41 11 Summary of First Phase Five-Inch Uni-Flow Hose Tests 48 12 Summary of Results of Second Phase Poly- propylene Testing 51 13 Summary of Results of Second Phase Poly- propylene Testing for Influent Concentrations near 10,000 mg/l 51 14 Performance History of Uni-Flow Fabric Filters / 55 15 Filtration Rate Ranking of Polypropylene Fabric Fi Iters 57 ------- 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 ------- SECTION I 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 ------- 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. ------- 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. ------- SECTION III 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 ------- 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. ------- 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 ------- 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 ------- 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. ------- 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 ------- FIGURE 3. Initial Solids Removal Phase: Elevated Bins 0.023 ft/sec is produced. Based on the theoretical settling velocities for vj 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 Diameter of Particles (microns) Settling Velocity (ft/sec) 1000 500 200 150 100 50 0.328 0.174 0.069 0.049 0.026 0.010 10 ------- 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 11 ------- 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 ------- 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 a more 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 ------- 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 ------- 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 ------- Temporary Holding/ Settling Basin MUD CAT discharge approx. 1500 pgm Initial Separation Two 36-yard Elevated Bins approx. 500 gpm Secondary Separation Hydrocyclones Final Filtration Cartridge Filter Unit Final Filtration Uni-Flow Filter foackflush backflush trucking backflush Return Water to pond Bin Solids Disposal Area Sludge Disposal Area Figure 7. Schematic of Processing and Sludge Disposal System ------- 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 ------- 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 tv 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 ------- 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 ------- (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 ------- 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 ------- 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 4. SUMMARY OF SYSTEM COMPONENT EFFLUENT CONCENTRATIONS (mg/l) Component MUD CAT Discharge Elevated Bins Effluent Hydrocyclones Effluent Cartridge Filters Effluent Uni-Flow Filter Effluent (Return Water to Pond) Max 261, 254, 179, 105, 1, . Run 000 000 600 400 770 Min. Run 107,000 55,800 31,400 22,700 100 Run Aver. 170,300 131,200 88,300 57,200 445 Table 5. SUMMARY OF SLUDGE (Backflush) CONCENTRATIONS Component Hydrocyclones Cartridge Filters Uni-Flow Filter Max 293, 284, 191, (mg/l) . Run 000 600 600 Min. Run 22,000 22,000 51,000 Run Aver. 103,500 82,800 114,300 23 ------- Table 6. REMOVAL EFFICIENCIES OF SYSTEM UNITS (All Units On Line) Component Aver. Suspended Solids Percent of Inflow Percent Removed Percent Removed Concentration (mq/l) Solids Remaininq Through System per Component MUD CAT Discharge Bins Effluent Hydrocyclones Effluent Cartridge Filters Effluent Uni-Flow Effluent 170,300 131,200 88,300 57,200 445 100 77.0 33.0 51.8 48.2 33.6 66.4 0.3 97.7 - 33.0 15.2 18.2 31.3 (Return Water to Pond) ------- 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 hydrocyclones 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 ------- MUD CAT discharge 3152 Ib/min. K) 2109 Ib/min. Initial Separation Two 36-yard Elevated Bins trucking 782 b/min. Bin Solids Disposal Area 261 Ib/min. Temporary Holding/Settling Basin Secondary Separation Hydrocyclones back flush 90 Ib/min. 171 Ib/min. Final Filtration Cartridge Filter Unit 109 Ib/min. backflush 62 Ib/min. Final Filtration Uni-Flow Filt :r backflush 108 Ib/min. Sludge Disposal Area Roturn Water to pond I Ib/mln. 260 Ib/min. total FIGURE 8. Solids Balance for Processing System ------- Table 7. RESULTS OF BINS TO UNI-FLOW FILTER RUN Time (min.) Suspended Solids Concentration (mg/l) 15 30 45 60 75 90 MUD CAT Discharge 158, 200> / 96, 20o} * 145,90ol / Bins Effluent 135,900> / 70,10ol / 84, 50o} / Uni-Flow Effluent 208\ J \ 127} 424} System Flow (gpm) 250 120 70 60 50 30 Uni-Flow Pressure (psi) 8 10 12 12 10 11 ------- 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 (SO=), 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 ------- 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 thetotal 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 ------- 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 ------- (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/l of suspended solids. Each component's individual 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 ------- 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 ------- 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. FIGURE 9. Sediment Accumulated in First Bin After Two Hours of Dredging 33 ------- 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/l 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 ------- 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 2 concentration of less than 10,000 mg/l. 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 ------- 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/l 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 ------- 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/l of suspended solids, with a normal average of a few hundred mg/l 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 ------- 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 ------- 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 $4.23 per cubic yard of sediment removed. This relatively high cost was due to a number of factors, all of which were directly related to the amount of labor required. The factors which required a labor-intensive effort were: (1) Changing of the Uni-Flow filter hoses (2) Removal of sediment from the bins (3) Cleaning and replacing filter cartridges Since the system demonstrated in the field was a prototype system, it is probable that the operating and maintenance costs could be reduced by approximately 30 percent through the judicious streamlining of the system. Suggestions for streamlining of the system include: (1) Elimination of the cartridge filter unit 39 ------- Table 9. CAPITAL COSTS OF THE PORTABLE SEDIMENT PROCESSING SYSTEM Item Cost C$) \ -, 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 @30C/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 ------- Table 10. SIX-WEEK OPERATING & MAINTENANCE COSTS OF THE PORTABLE SEDIMENT PROCESSING SYSTEM (Excluding Trucking) Item Cost($) Elevated Bins: rental of concrete vibrators 180 Hydrocyclones: 0 Cartridge Filter Unit: 20 replacement cartridges @$3.50ea. 70 Uni-Flow Filter: 730, 10' replacement hoses @ 30C/yd 730 1460 tape gaskets 8 Labor: 600 man-hours @ $5. 35/hr. av. 3,210 Miscellaneous: electricity, gasoline for air compressor, etc. 3jO 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 ------- (2) Utilization of a Uni-Flow filter with larger diameter hoses to eliminate the hose blocking problem (3) 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. ------- 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 ------- 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 ------- Flow Meter Effluent Backflush 9-1/2' ^- ği ğ - > '/ 5" 5" 8" Fabric Filter -~^ Hose 5-1/4" 1" *- Effluent Reservoir ? Pressure Cage ' , T U i D Sample r _J Port J Control Valve Fc *^ Filter Rinse m^c^i Sediment Slurry Reservoir 1-1/2"^ /^ Quick-Open Backflush Valve Influent Pump FIGURE 10. Large Diameter Fabric Filter Hose Test Apparatus ------- 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 ------- 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 ------- 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/l susp. solids) (mg/l susp. solids) Pressure Flow Filtration Rate 2 Max. Min. Avg. Max. Min. Avg. (psi) (gpm) (gpm/ft ) 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 ------- 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 ------- 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/l 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/l 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 hot 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 ------- Table 12. SUMMARY OF RESULTS OF SECOND PHASE POLYPROPYLENE TESTING c E 3 23 1 il c 3 o eo U j_ 0) il Test Parameters No Cages Cage Outside Cage Inside Cages Outside & Cages Outside & ITest 1 Cages Outside £ Test 2 Cages Outside £ Test 3 Table Average Influent Concen. (mg/l) 7,765 7,840 25,480 Inside 11,685 Inside 18,200 Inside 8,990 Inside 11,640 Average Effluent Concen. (mg/l) 1020 605 980 1580 1220 520 330 Average Flow Rate (gpm) 1.4 1.3 1.5 1.2 1.1 1.2 1.2 Average Test Pressure (psi) 16.0 18.5 18.5 17.5 19 19 20 13. SUMMARY OF RESULTS OF SECOND PHASE POLYPROPYLENE TESTING FOR INFLUENT CON- CENTRATIONS NEAR 10,000 mg/l c 3 23 i_ 0) M c 3 0 w U Test Type No Cages Cage Outside Cage Inside Cages Outside Cages Outside (Test 1 Cages Outside Average Influent Concen. (mg/l) 9995 8310 9330 & Inside 9090 & Inside 7830 £ Inside 9575 Average Effluent Concen. (mg/l) 665 275 240 1030 1420 750 Average Flow Rate (gpm) 1.5 1.2 1.8 1.3 1.2 1.3 Average Test Pressure (psi) 16.0 18.5 18.5 17.5 20.0 19.0 il Test 2 Cages Outside & Inside 9885 Test 3 160 1.3 20.0 51 ------- 5.0 -1 4.0 3.0 tn NJ 2.0 1.0 ? Q. O U. 81 polypropylene,cages inside and outside average pressure = 20/psi /\ = beginning of backflush A A A A AAAA A r~ 60 20 40 80 100 120 Time (Min.) 140 160 I 180 200 FIGURE 11. Flow vs. Time (Eight-Foot Hose) ------- Ln U> 400. 200 8' polypropylene ,cages inside and outside Average pressure = 20 psi A = beginning of backflush ~r 20 40 A 60 80 T 100A 120 Time (Min.) ~T 140/j 160 A rt /\ 180^, A A 200 FIGURE 12. Effluent Concentration vs. Time (Eight-Foot Hose) ------- 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 2 The filtration rates for the fabric filters tested ranged from 0.07 gpm/ft for the second phase tests to a maximum of 0.44 gpm/ft 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 ------- Table 14. PERFORMANCE HISTORY OF UNI-FLOW FABRIC FILTERS en en Test Aqua- Ion Corp. 1" dia. testing Fabric Type- Influent Cotton -Ac id Mine Drainage Waste Operating Pressure Range psi 12-20 Filtration Rate Range gpm/ft 0.13 Average Operating Pressure psi 12-20 Average Filtration Rate gpm/ft 0.13 model (EPA Contract No. 68-01-0043) Hittman Assoc. 1" dia. testing model Hittman Assoc. 1" dia. full scale proto- type field tests Hittman Assoc. 5 1/4" dia. testing model Cotton-Sediment 5-33 Slurry Polypropylene- 5-12 Sediment Slurry Polypropylene- 10-23 Sediment Slurry 0.05-0.13 0.06-0.19 0.07-0.44 11 10 12 0.06 0.13 0.24 0.11 0.13 ** *** 10' long, rinsed from top 10'long, not rinsed from top (simple draining) *** 8' long, not rinsed from top ** ------- 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 ------- Table 15. FILTRATION RATE RANKING OF POLYPROPYLENE FABRIC FILTERS Polypropylene Parameters 10 10 8' 10 10 10 1 long 1 long long. 1 long 1 long 1 long Filter , no cages, rinsed from top , cage cages inside inside and outside , no cages , cages inside and outside , cage outside Filtration Rate Average Effluent Average Time Between (gpm/ft ) Quality (mg/ 1) Backflushes (min.) 0 0 0 0 0 0 .24 .13 .13 .11 .10 .09 95-140 240 750 665 1030 275 10-16 5 8 10 2 4 ------- 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 often 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 ------- 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 ------- SECTION VIII REFERENCES 1. Camp, T. R. Sedimentation and the Design of Settling Tanks. Transactions of the American Society of Civil Engineers. 111: 895-958, 1946. 2. Tiederman, W. C., 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. 3. Taras, M. J . , A. E. Creenberg, R. D. Hoak, andM. 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 ------- 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-1. POND WATER QUALITY BEFORE DREDGING OPERATIONS Constituent Sulphate Phosphate Iron Copper Zinc NH3 COD Total Nitrogen Coliform (Presumptive) pH Suspended Solids Volatile Solids Total Dissolved Solids Total Solids Turbidity (JTU) Concentration (mg/l unless stated Location* 1 2 3 10 - 23 0.9 - 0.7 0.45 - 0.3 0.35 - 0.3 0.00 - 0.01 0.8 - 0.7 3.4 12.0 - 9.0 Positive 5/5 6.0 - 6.75 381 531 - 67 57 2980 - 505 130 otherwise) 4 50 1.4 0.7 0.5 3.25 1.6 7.6 13.0 - 6.1 745 68 21 834 135 5 28 0.2 0.25 0.15 0.00 0.4 1.6 14.0 - 6.1 37 42 48 137 13 Oxidation-Reduction Potential (mv) 50 60 75 20 * Location Description: 1 - Pond inflow from watershed 2,3 - Near the inflow and of the pond 4 - Near the discharge end of the pond 5 - Pond discharge 62 ------- 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 CaCOs 0 Bicarbonate Alkalinity, as CaCO 36 Carbonates, as CO3 0 Bicarbonates, as HCO3 43.9 Hydroxides, as OH 0 Carbon Dioxide, as CO2 6 Chloride,as Cl 42 Sulfate, as SO4 52 Fluoride, as F 0.0 Phosphate, as PO4 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 SiO2 6 Color, Standard Platinum Cobalt Scale 65 Odor Threshold ° 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° C. 77 Phenolphthalein Alkalinity, as CaCO3 0 Total Alkalinity, as CaCO3 15 Carbonate Alkalinity, as CaCO3 0 Bicarbonate Alkalinity. as CaCO3 15 Carbonates, as CO3 0 Bicarbonates, as HCO3 18.3 Hydroxides, as OH 0 Carbon Dioxide, as CO2 200 Chloride, as Cl 30 Sulfate, as SO4 39 Fluoride, as F 0.0 Phosphate, as PO4 0.55 pH (Laboratory) 5.1 pHs 9.3 Stability Index 13.5 Saturation Index -4.2 Total Hardness, as CaCO, 15 j Calcium Hardness, as CaCO3 12 Magnesium Hardness, as CaCO3 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 SiO2 11 Color, Standard Platinum Cobalt Scale 80 Odor Threshold 6 Turbidity, Jackson Units 100+ 64 ------- 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 ------- Table B-1. RESUSPENSION OF POND SEDIMENTS DURING DREDGING" 7/5/73 Operating Condition Before Dredging Dredging (forward cut) Distance from Front of Dredge (ft.) 5 5 5 5 5 5 5 10 10 20 Depth below Surface (ft.) 1 3 5 7 (bottom) 1 5 7 (bottom) 1 5 1 Suspended Solids Concen (mg/l) 39 50 64 523 88 179 1260 54 86 39 66 ------- Table B-2. RESUSPENSIQN OF POND SEDIMENTS DURING DREDGING- 7/6/73 Operating Condition Distance from Front of Dredge (ft.) Depth below Surface (ft.) Suspended Solids Concen. (mg/l) Before Dredging Depth Integrated 89 Composite - 0 ft. to bottom Dredging (forward cut) 900 Dredging (forward cut) 10 10 649 175 Dredging (forward cut) 20 226 67 ------- Table B-3. RESUSPENSION OF POND SEDIMENTS DURING DREDGING - 7/11/73 Operating Condition Distance from Dredge (ft.) Depth below Surface (ft.) Suspended Solids Concen. (mg/l) Before Dredging 5 ft. from front 1 4 7 (bottom) 18 75 1000 Dredging (forward cut) 5 ft. from front 7 (bottom) 72 1257 Dredging (forward cut) 5 ft. from side 89 Dredging (forward cut) 1 ft. behind 1262 68 ------- Table B-4. RESUSPENSION OF POND SEDIMENTS DURING DREDGING - 7/18/73 Operating Condition Distance From Front of Dredge (ft.) Depth below Surface Suspended Solids Concen. (mg/l) Before Dredging 34 Dredging (forward cut) 5 10 83 19 69 ------- 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 ------- Table C-1. SUSPENDED SOLIDS CONCENTRATIONS IN PROCESSING SYSTEM Date 6/25/73 6/26/73 7/2/73 7/11/73 7/12/73 7/13/73 7/14/73 7/23/73 7/26/73 7/27/73 7/30/73 8/1/73 8/6/73 Suspended Solids at Sampling Point (mg/l) Average #5 #1 #2 #3 #4 System Flow (gpm) 158,000 29,500 * 190 * 1440 150 136 340 261,000 231,700 149,500 105,400 240 * 47 * 491 * 1127 195,200 151,200 108,000 97,200 100 76,400 52,400 * 184 254,000 254,000 179,600 50,400 227 392 129,200 61,300 40,400 26,200 230 107,600 87,600 31,400 22,700 570 107,000 67,400 44,700 26,200 660 138,000 55,800 49,500- 34,700 520 140,500 103,000 94,400 1770 + * 158,200 135,900 + * 208 + * 96,200 70,100 t- * 127 + * 145,900 84,500 + * 424 300 300 250 250 250 300 250 250 250 200 200 200 250 100 100 300 250 200 250 120 70 60 50 30 Remarks 3 hr. composite samples; 2 Uni-Flow hoses with holes sample after 1 Uni-Flow hose burst 2 hr. composite sample n n n n M n 4 hr. composite samples 2 hr. composite sample M n n n n ii 3 hr. composite sample 2 hr. composite sample; cartridge filters bypassed 2 hr. composite sample; bins completely full of sediment 2 hr. composite sample; bins completely full of sediment composite sample of run Composite sample of run Composite sample of run Composite sample of run Composite sample of run 15 min. av. flow; Uni-Flow pressure = 8 psi 15 min. av. flow; Uni-Flow pressure 10 psi; 1/2 hr. composite samples 15 min. av. flow; Uni-Flow pressure 12 psi 15 min. av. flow; Uni-Flow pressure 12 psi; 1/2 hr. composite samples 15 min. av. flow; Uni-Flow pressure = 10 psi 15 min. av. flow; Uni-Flow pressure = !1 psi; 1/2 hr. composite samples f hydrocyclones bypassed * cartridge filters bypassed Sampling Point Key # 5 = MUD CAT discharge into elevated 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) 71 ------- Table C-2. OTHER WATER QUALITY CONSTITUENTS IN PROCESSING SYSTEM -j KJ Date Sampling Point 6/25/73 # 1 # 2 # 3 # 4 # 6 # 7 # 8 6/26/73 # 1 # 2 # 3 # 4 7/2/73 # 1 # 2 # 3 # 6 # 8 7/6/73 # 5 # 1 7/12/73 # 5 # 2 # 3 Sampling Point Key: P°4 1.8 1.6 1.8 1.8 1.5 2.8 1.5 1.8 1.7 5.2 8.0 2.3 0.6 0.7 Constituent N03- + NO. 9.0 12.0 14.0 11.0 13.0 12.0 11.0 14.0 15.0 13.0 11.0 13.0 8.0 13.0 # 5 = MUD CAT discharge into bins # 1 = Bin effluent - Influent to hydrocyclones # 2 = Hydrocyclone effluent - Influent to cartrii Concentration (mg/l) ~ Fe++ SO = Total pH Turbidity (JTU) Dis. Solids 5.9 6.0 6.0 16 5.8 153 6.0 6.0 6.0 0.35 0.15 0.35 0.27 120 140 0.15 0.10 0.05 0.10 0.10 0.75 1.50 17.0 25.0 22.0 dge 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 ------- Table C-3. GRAIN SIZE DISTRIBUTION OF SEDIMENT IN FIRST BIN Particle Size (microns) 4760 2000 420 250 105 75 Moisture Content = 26% Percent Finer (7/2/73) 99.8 99.7 99.1 98.0 41.9 24.4 Table C-4. GRAIN SIZE DISTRIBUTION OF SEDIMENT IN SECOND BIN Percent Finer Particle Size (microns) Date: 4760 2000 420 250 105 75 7/2/73 100 99.3 98.4 97.4 59.9 27.3 7/10/73 7/13/73 100 100 99.9 99.9 99.8 82.8 85.0 36.5 45.0 Moisture Content = 26% 73 ------- 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 ------- TOP VIEW (not to scale) 60* (50.0%) 70* (58.3%) 74* (61.7%) r^> 95* (79.2%) Influe \J nt 101* (84.2%) 84* (70.0%) Overall percentage of hoses completely blocked = 67.2% * number of completely blocked hoses out of 120 total hoses in header ( ) = percentage of completely blocked hoses in header FIGURE C-1. Pattern of Blockage of Uni-Flow Hoses ------- 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 ------- TABLE D-1. INFLUENT GRAIN SIZE DISTRIBUTIONS - LARGE DIAMETER HOSE TESTS Test Parameters: Particle Size (microns) 420 250 105 75 54 39 28 13 10 7 5 4 IG'-NoWire lO'-Wire Outside 100 100 99 89 84 66 58 46 31 28 25 18 14 10 7 3 10'-Wire 67 53 33 18 12 9 8 5 3 2 1 lO'-Wire Inside Inside and Outside Percent Finer 100 96 74 56 49 48 46 22 16 10 2 8'-Wire Inside and Outside 97 92 63 32 23 18 16 5 4 2 1 8'-Wire Inside and Outside 99 95 79 67 55 51 45 29 22 15 9 3 8'-Wire Inside and Outside 98 88 74 67 41 23 16 11 8 ------- SELECTED WATER RESOURCES ABSTRACTS INPUT TRANSACTION FORM w Demonstration of The Separation and Disposal of Concentrated Sediments : 5. 7. Author(s) Nawrocki, Michael A. .9. Organization Hittman Associates, Inc. Columbia, Maryland 21045 10. PtojcctNo. PE 1B2042 11. Contract/Great Mo. 68-01-0743 Environmental Protection Agency report No. EPA-660/2-Tl)0?2, June In. 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/l with an average influent suspended solids of 170,300 mg/l. 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. 17st. Descriptors *Dredging, *Sediment Deposition, *Filtering Systems, *Separation techniques. Impoundments, Water Quality Control, Desilting 17b. Identifiers *Suspended solids separation. Pond dredging l~c. COWRR Field. & Group Q^Q IS. Availability Send To: WATER RESOURCES SCIENTIFIC INFORMATION CENTER U.S. DEPARTMENT OF THE INTERIOR WASHINGTON, D. C. 2O24O Abstractor Michael A. Nawrocki \institution Hittman Associates, Inc. fj R SIC 10 Z ! P E V J U N E 1 fl 7 1) ------- |