CA1115436A - Method of removing mud from mud-water suspensions - Google Patents
Method of removing mud from mud-water suspensionsInfo
- Publication number
- CA1115436A CA1115436A CA317,712A CA317712A CA1115436A CA 1115436 A CA1115436 A CA 1115436A CA 317712 A CA317712 A CA 317712A CA 1115436 A CA1115436 A CA 1115436A
- Authority
- CA
- Canada
- Prior art keywords
- mud
- flocculating agent
- water
- vessel
- suspension
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F7/00—Equipment for conveying or separating excavated material
- E02F7/04—Loading devices mounted on a dredger or an excavator hopper dredgers, also equipment for unloading the hopper
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
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- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Treatment Of Sludge (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
Abstract
Ref. 3112 METHOD OF REMOVING MUD FROM MUD-WATER SUSPENSIONS
Abstract of the Disclosure Disclosed is a method for removing mud from mud-water suspensions in rivers,lakes, harbor basins and so forth. The method removes mud from the suspension by filling a floating vessel with the suspension mixed with a flocculating agent, permitting the mud to settle, removing the resulting clear supernatant water and repeating the sequence of steps until the vessel contains the desired amount of mud.
Abstract of the Disclosure Disclosed is a method for removing mud from mud-water suspensions in rivers,lakes, harbor basins and so forth. The method removes mud from the suspension by filling a floating vessel with the suspension mixed with a flocculating agent, permitting the mud to settle, removing the resulting clear supernatant water and repeating the sequence of steps until the vessel contains the desired amount of mud.
Description
rhe inventiorl relates to a method of removing ~inely and very finely divided muds of all kinds from waters, for example ~rom rivers, lakes, harbour basins, and the like.
The problem of keeping such waters clean after their state of pollution has passed acceptable limits is widely known.
As the pollution of water progresses, the ~ine and very i'ine particles of solid matter, which at first are suspended in the water, also increase and in a matter of weeks or months give rise to a continuous rise o~ the level of mud in the waters. The fauna and flora o~ many lakes, including some situated in recreation areas near centres oi population, already have their existence mos* serious threatened through choking with mud. In rlver mouths situated in brackish water districts, where the silting of the water ls ~urther intensi-fied by the ~act that microorganisms, which live only in iresh water, perish and sink on encountering seawater because of the excessive salt content, navigation is even hindered by the increasing mud or silt at certain points. It is attempted to master this silting in various ways. In par-ticularly ai'i'ected port installations, $or example i'erry embarkation and disembarkation points, underwater ploughs-also known as underwater rakes or harrows - are pulled through the masses oi mud during the ebb-tlde with the aid of tugs, in the hope that the mud swirled up under the water will be carried out towards the sea with the ebbing water.
This operation has very little ef~ect because the high tide brings the mud back again. Dredging wlth the aid of grab dredgers or chain and bucket-conveyor excavators is far more effective. Grab dredgers can be used only ~or removlng smaller amounts of mud. Suction dredgers and chain and bucket-conveyor éxcavators can be used only when anchored iast and while in use -fi they constitute an obstacle to trai'i'ic in port installations and water-ways. The floating suction dredger usually conveys the excavated material through a floating pipeline and a land line connected to the latter to an artii'icially constructed polder. Since the length ofiloating pipelines is li~ited in places where weather gives rise to heavy seas or where strong tidal currents occur, the method cannot be applled everywhere.
The combination of suction dredgers and barges so-called dumb barges, into which the excavated material is loaded and which are transported to the unloading site by means oi' t~lgs, would be an uneconomical solution to the problem, since in~the case of suction dredging of mud the large amounts o~ water, which are always carried off at the same time because o~ the nature o~
the process, remain in the mud, which does not readily settle, and thus considerably lncrease the frequency of the barge journeys. A dumb barge cleaner (pump ship) is also necessary at the unloading station. It is more expedient to combine the use o~ barges, tugs, and barge cleaning ships with a chain and bucket-conveyor excavator, which continuously raises the mud, in practically its original concentration, i'rom the seabed with the aid o~ its buckets suspended on an endless chain, and empties it into barges lying alongside the excavator ship.
When a chain and bucket-conveyor excavator is used it is oi' course inevitable that the suri'ace water will be polluted. Depending on the nature of the subsoil a chain and bucket-conveyor excava-tor, unlike a normal suctlon dredger, will generally be able to cut to plan a desired water pro1'ile modification, that is to say to lower the bed or widen the expanse o~ water. Since in most cases it is only desired to remove mud from the water and not to effect any particular modification of the profile, the use of a chain and bucket-conveyor excavator solely i'or mud removal is too complicated and too expensive.
The term "hopper" or "hopper suction dredger" is applied to a ship which combines all the functions necessary Yor dredging operations (the functions of a suction dredger, barge, tug, and barge cleaner~ and which i5 much used for the removal of sand from waters. A hopper requires no anchoring for the purpose of dredging and can, therefore, be removed at any time from the dredging site under its own power, so that it does not constitute an obstacle to shipping.
A loading tank (hopper tank) occupying almost the entire ship servesto receive the sand brought up. The sand ~ixed with water is sucked up continuously through a vertically movable nose-like suction pipe mounted on the outside of the hopper dredger, and is passed into a connecting pipe system which ends in two hopper tank inlet pipes extending on the port and star-board sides above the hopper tank and provided with numerous closable ~laps. The mixture of water and sand flows out of the inlet pipes over the entire length into the hopper tank, in which the sand, having a higher specific gravity, settles immediately, while the separated water flows off continuously into the sea by way of overflow hatches which are provided, directly under the top edge of the deck, in the ships's side and are vertically adjustable. In this way a mixture of water and sand is continuously sucked up from the bed and passed into the hopper tank untll the latter is ~illed with sand.
After the hopper tank has been ~illed and the suction pipe nose has been raised and stowed away, the hopper dredger sails under its own power to an unloading site, which may be at a distance of several kilometres, and is there unloaded either by means of a discharge flap provided in the bottom of the hopper or by a ilushing operation with the aid o~ its :, : : ~: -own pump and of bottom valves (slide valves). Because of the nature of its operation the hopper dredger works economically.
For sand dredging a hopper tank having a capacity of e.g. 500 to 5000 cubic metres can be effortlessly filled with sand by the overflow process within 1 to 3 hours. Attempts to use hopper dredgers for removing mud from waters have failed because even dredging for days on end does not enable the hopper tank to be filled with a worthwhile amount of solid material. The suspen-sions of mud and water pumped into the hopper tank show no tendency to settle because of the slight difference between the density of the solid material and the water, but are washed out of the overflow hatch with the same concentration of solid material, when the overflow process characteristic of a hopper dredger is applied, as when they flow into the hopper tank. The concentration of solid material in the suspension of mud and water pumped up is far too low to permit economic operation.
The object of the present invention therefore is to provide a simple, economical method of removing mud from waters.
According to the present invention, there is provided a method of removing mud from a water-mud suspension comprising the steps: a) passing a water-mud suspension mixed with a flocculat-ing agent into a vessel; b) permitting the mud to settle to the bottom of said vessel; c) drawing off and removing a resulting supernatant water layer without significant disturbance of the settled mud; d) repeating steps a) through c) until a desired amolmt of mud has been collected in the vessel; and then e) removing said mud which has collected in the vessel.
Preferably the method of the present invention for the removal of mud from waters is characterised in that the mud is sucked up and the suspension of mud and water sucked up is filled together with a flocculating agent into a floating vessel, the B
4~
filling is interrupted as soon as the vessel is full, and after the mud has settled the supernatant layer of water is removed, and the filling with the addition of flocculating agent, allowing to settle, and removal of supernatant water are repeated until the vessel is filled with mud.
In order to ensure that the mud from the suspension of mud and water will settle to form a supernatant layer of clear water, it is necessary to add a flocculating agent. Flocculat-- 4a -,.
ing agent. Flocculating agents are known. They are usually high polymeric products, such as for exàmple rubber phosphonium c;alts, starch products, proteins, polyacrylates, bone glue, poly-ethylene oxides, polyacrylamides, polyethyleneimines, and so on.
Flocculating agents are divided into non-ionic, anionic, and cationic agents. In order to be able to select the most suitable flocculating agent for any particular mud, sedimentation tests are carried out in the laboratory with a sample of suspension of mud and water which has been pumped up, and the optimum amount of flocculating agent for~total flocculation is determined. Good results are obtained in practice with flocculating agents based on e.g. polyacrylamide, partia~y saponified polyacrylamide, non-ionic polyethylene oxide, cationic polyethyleneimine, cationic polyethyleneamine, cationic poly-dimethylaminoethyl methacrylate, and/or poly-dimethylaminoethyl acrylate, cationic copolymerisates of dimethylaminoethyl methacrylate and acrylate, and/or acrylamide.
The flocculating agent is normally added in the form of an aqueous solution direct to the suspension of mud and water pumped up, expediently immediately downstream of the pump, in the optimum amount determined by previous tests.
The aqueous solution of flocculating agent may have a con-centration of 0.0001~ by weight or higher, particularly from 0.01 to 0.5% by weight. If aqueous solutions having a concen-tration higher than 0.5% by weight can still be metered, more concentrated solutions can also be used. It may be expedient to measure the concentration of the mud in the suspension of mud and water continuously during the pumping operation, for example by radiometry and to meter the flocculating agent in accordance with the mud concentration measured. From 10 to 100 ppm of flocculating agent (referred to 100% flocculating agent) are normally added per cub~c metre of mud and water suspension pumped up. Mud or silt deposited on a bed usually contains from to 50% by weight of solids. During the pumping operation it is normally diluted with water in the ratio 1 : 1 (1 to Z0).
In some favourable cases a certain separation already occurs between the mud and the water during the filling of the floating vessel with the suspension of mud and water mixed with flocculating agent, so that a layer of clear water first reaches the level boundary in the floating vessel. In such cases it is expedient for the layer of clear water to be removed during the actual filling operation, which can most simply be done by allowing to clear water to overflow over the edge of the vessel or through overflow hatches provided in the wall of the vessel. However, even in favourable cases a layer of clear water can be removed in this way only for the space of a i'ew minutes, whereupon the suspension of mud and water reaches the level boundary of the vessel. The filling operation ls then interrupted. After the mud has settled, the supernatant layer of clear water is removed, and the filling allowing to settle, and the removal of the layer of clear water are repeated until an economic amount of mud has collected in the vessel, whereupon the latter i5 transported to the unloading site and the mud is there emptied out.
Known suction devices are used for pumping up the mud deposited on the bed, in the form of a suspension of mud and water, and for filling it into the floating vessel. The layer of clear water above the mud deposited in the floating vessel can be removed in various ways. For example, a vertically adjustable slide valve can be provided in the wall of the vessel, this slide valve closing an outlet opening, for example a discharge hatch, when in its highest position. After .
the suspension has separated into a layer of mud and a layer of clear water the outlet opening, for example the outlet hatch, is gradually opened, so that the layer of clear water can flow off into the sea. A separate receiving chamber, into which the supernatant layer of clear water can flow off through a closable opening, may also be provided in the floating vessel, to clear water being removed from this chamber for example with the aid of a pump.
~ urthermore, the layer of clear water can be removed through an outlet pipe or outlet hose, through which the water flows freely into the sea or is pumped of~.
Various possible ways of removing the layer of clear water may also be combined. In all cases the removal of the layer of clear water should be effected in suc~ a manner that as little swirling as possible is produced in the layer of mud.
This can for example be achieved by arranging for the overflow, admission, or sucking-off of the water always to take place just below the surface of the clear water. The overflow edges, inlet and outlet openings must for this purpose be adapted to the falling surface of clear water, that is to say must be continuously lowered as the level of clear water falls. It is useful for the inlet openings of outlet pipes, suction hoses, or the like to be so disposed that the clear water can flow from above downwards into the outlet pipes, suction hoses, or the like. The clear water flowing into the inlet openings thus comes mainly from the surface of the water. By this means it i5 ensured that none of the collected mud will be entrained, during the drawing-off of the clear water, through the action of suction, such as may occur with unfavourably constructed or disposed inlet openings.
In addition, it is expedient for the inlet opening of an outlet or SUCtiOII pipe to be made funnel-shaped, because the overflow rate of clear water flowing from the surface will thereby be reduced. It is also advantageous for overflow edges and inlet openings for the clear water to be serrated.
It is useful i'or the suspension of mud and water pumped up to be introduced into the vessel, together with the flocculating agent, in such a manner that during the filling operation also the least possible turbulence is caused. In the case of elongated vessels, such as are generally provided, for example, in boats and ships, it is expedient for the suspension of mud and water together with the flocculating agent to be introduced only at one longitudinal end. It is thereby ensured that the heaviest turbulence occurs during the i'illing operation only at one longitudinal end, while the deposition of the mud is already started during the filling operation. The apparatus for removing the layer of clear water is advantageously disposed at the other longitudinal end of the vessel. It is also advantageous for the suspension of mud and water to be filled into the vessel below the level of liquid present during the filling operation. The suspension is thereby prevented from impinging on the surface of the liquld in the vessel, with the consequent destruction o~ the i'lakes of mud already formed, and in addition with the disturbing formation of foam.
~ urthermore, it is expedient to effect the filling of the vessel with suspension of mud and water at one end of the elongated vessel, and for this part to be separated, in the region of higher liquid levels, from the remainder oi' the vessel. With higher liquid levels a pacification zone is thereby formed and the rate o~ sedimentation is increased.
~t~ fi Before the next removal of the layer of clear water, however, the division between the filling region and the remainer of the vessel must be removed. Normally after a few cycles, for example 2 - 4 cycles, of the process of the invention - which can be carried out within a few hours, for example 1 to 3 hours -a container of e.g. 500 to 5000 cubic metres capacity is already filled with so large an amount of highly concentrated mud that it is economic for it to be transported away. At the unloading station the mud is removed from the vessel, ~or example by way of flaps in the bottom of the vessel. The mud in the vessel can also be diluted with water at the removal point ~o a pumpable state and then pumped off.
The floating vessels used for applying the process of the invention may for example be suitable boats and ships, for example dumb barges, but are preferably hoppers or hopper dred-gers. When a hopper dredger is used the ~inely and very finely divided mud suspension entering the hopper tank during the dredging operation, which may be a suspension of any kind, is mixed with a flocculating agent and the hopper tank is ~illed to a point just below the overflow. Dredging is then suspended for a short time. The layer of clear water forming above the layer of mud is drawn off with the aid o~ a suitable apparatus, -and dredging is then resumed with the addition of a i'locculat-ing agent to the incoming mud suspension, until the hopper tank is once again filled to a point just below the overflow. The new layer of clear water ~ormed is drawn of~, and filling with the addition of flocculating agent, allowing to settle, and removal of the layer of clear water lying above the solid material are repeated until the hopper tank is ~illed with an economic amount of flocculated mud. Unlike the practice of continuous filling of the hopper which was customary up to the present time, the process o~ the invention is carried out fi discontinuously.
In order to apply the method of the invention an ordin-ary hopper dredger must practically be simply provided with an apparatus for removing the clear water, for which only slight conversion is usually required.
In view of numerous unsuccessful attempts to use hoppers for removing mud from water in an economic manner, the method of the invention must be regarded as surprising. It was also not to be expected that by working in accordance with the invention it would be possible for a vessel to be sub-stantially filled with concentrated mud within a relatively short time, particularly as it had to be feared that because the hopper tank is unfavourably shaped for rapid separation of mud, and also because of the movements of the ship caused by heavy seas, it would not be possible to achieve reasonable settling speeds or high concentrations of the mud.
The invention will be further explained with the aid of the accompanying drawings. The drawings illustrate diagram-matically and by way of example a hopper dredger suitable for carrying out the method of the invention.
Figure 1 shows diagrammatically a cross-sectional side view of a hopper dredger, the ship's wall being partly broken away.
Figure 2 is a top plan view of the hopper dredger shown in Figure 1.
The drawings show only those devices which are of ~ importance for the carrying-out of the method of the invention.
Apparatus for the propulsion of the ship, for navigation, and for accommodation of the crew, and so on, is not shown in the drawings.
The hopper dredger is designated 1 and floats in the water 2. The actual hopper tank is désignated 3. The ` 10 vertically movable suction pipe 4 is f~stened to the ship by means of the ioint 5. The pump for sucking up the suspension of mud and water is designated 7. The two pipes 6 and 37, in which valves 8 and 9 are disposed lead into the suction side of the pump 7. From the delivery side of the pump 7 the two pipes 10 and 11 in which the valves 12 and 13 are provided lead off. Through the suction pipe 4 and the pipe 6 con-nected to it the pump 7 pumps up a suspension of mud and water when the valve 8 is open and the valves 9 and 13 are closed this suspension being pumped through the open valve 12 into the pipe 10 and then into the two outlet pipes 14.
The two outlet pipes 14 are mounted one on each side of the hopper tank 3. The outlet pipes 14 have outlet openings 15 and 16, through which the suspension of mud and water is pumped into the hopper tank 3. The outlet pipes 14 are arranged with their outlet openings 15 and16 in such a position that the suspension of mud and water flows into the hopper tanls only at the stern end. A solution of flocculating agent is supplied in metered amounts from the reservoir 17 containing an aqueous solution of flocculating agent by way of the pipe 18 by the metering pump 19 to the pu~ped-up suspension of mud and water downstream of the pump 7.
Perfect mixing of the suspension of mud and water with the flocculating agent is thereby effected by the time the mixture passes out of the openings 15 and 1~, and substantial flocculation of the mud is thereby achieved. In the frontpart, that is to say the bow end of the hopper tank 3 an outlet pipe 20 adapted to be raised and lowered is disposed. The outlet pipe 20 is fastened by means of a flexible, incompressible rubber sleeve 21 and of suitable flange elements on the box 22, which covers the outlet opening 23 provided in the bottom fi of the hopper tank 3. The apparatus for raising and lowering th~ outlet pipe 20 is not shown in the drawings. A suitable mounted pulley block arrangement can for example be used for r~ising and lowering the outlet pipe 20. In the hopper tank additional outlet openings 24 to 29 are provided, which can be separately opened and closed by the valves 30 to 36 and which lead into the common pipe 37. In the rear, stern part of the hopper tank 3 a plate 38 is disposed which extends over the entire width of the hopper tank and which is mounted for rotation about the horizontal axis 39. The plate 38 in its vertical arrangement extends downwards about 70 - 150 cm from the highest possible filling level of the hopper tank, and thus forms a pacification zone in the rear, stern part of the hopper tank.
For the purpose of filling the hopper the outlet pipe 20 is raised above the highest filling level of the hopper tank and the valves 9, 13, and 30 to 36 are closed, the plate 38 is brought into the position in which it points vertically down-wards. By means of the suction pipe 4 and of the pipe 6, with the valve 8 open, a suspension of mud and water is sucked up by the pump 7, and at the same time ilocculating agent solution is metered through the pipe 18 downstream of the pump 7. The suspension of mud and water accompanied by flocculating agent is delivered through the pipe 10 into the two outlet pipes 14 and pumped by way of the outlet openings 15 and 16 into the rear part of the hopper tank. The filling operation is inter-rupted when the maximum possible level of liquid has been reached in the hopper tank. As soon as the ~locculated mud has settled, which i5 usually the case after 10 to 25 minutes, the plate 38 is swung up into its horizontal position, which is shown in phantom outline, and the suction pipe 20 is lowered below the level of the clear water layer. At the same time L~
the valve 30 is opened and the water flowing off through the pipe 20, the box 22, and the opening 23 into the pipe 37 is pumped back into the sea by the pump 7, with the valves 9 and 13 open and the valves 8 and 12 closed, by way of the pipe 12 and the connection 40 provided in the ship's wall. The outlet pipe 20 is lowered in accordance with the falling level of clear water, until the opening of the suction pipe 20 reaches the surface of the deposited mud layer. The suction pipe 20 is th~n again raised above ~he maximum filling height of the hopper tank 3, the valves 23, 9, and 13 are closed, and the valves 8 and 12 are opened, while the plate 38 is brought back into the vertical position. The filling operation is then repeated, After the layer o~ mud has again been allowed to settle, the supernatant layer of clear water ls removed in the manner already described. After repeating the process steps described only three times the hopper tank is normally filled to the extent of more than 70% with mud whose con-centration is normally practically identical with that of the mud or silt deposited on the bed of the sea or other expanse of water. The suction pipe 4 of the hopper dredger is then raised the hopper moves under its own power to the discharge point, where the mud is emptied out.
Example Silt was removed from a brackish water region o~ the Weser with a hopper dredger converted in accordance with Figure 1. The capacity of the hopper tank amounted to 1200 cubic metres. The overflow hatches provided in the stern part of the hopper tan~ were closed watertightly. The optimum quality and quantity of the flocculation agent to be used were previous-ly determined in the laboratory by means of known tests for determining the rate of sedimentation. For the silt which was to be removed a commercially available partly saponified polyacrylamide flocculation agent (Hydropur ~ of Cassella, Frankfurt am Main-Fechenheim, Germany was found to be suitable, this agent being used in a 0.5a by weight solution and in an amount o~ 19 ppm (referred to 100~ flocculating agent) and added to the suspension of silt and water pumped up. As diagram-matically indicated in Figure 1, the filling zone was separated by a rotatably mounted pacification wall, having a height of about 120 cm and extending vertically, from the forward part of the hopper tank. The outlet pipe 20 in the front part of the hopper tank had a diameter of 40 cm. The first filling operation, comprising about 1200 cubic metres, lasted twenty minutes. At that time solid flocculated particles threatened to be entrained through the front overflow hatches together with the clear water flowing overboards. 15 minutes after termination of the filling operation, removal of the layer of clear water which had formed in the meantime was commenced.
Removal of the clear water with the aid of the outlet pipe in the manner described took 15 minutes. The hopper tank then contained about 460 cubic metres of concentrated silt with a concentration of more than 40% by weight. For the next filling operation therefore a loading space of 1200 - 460 = approximate-ly 740 cubic metres was available. The outlet pipe 20 was raised and the hopper tank refilled in the manner previously described. The second filling operation was suspended after 12 minutesj after 15 minutes more the removal of the new layer of clear water formed by the method already described was started. The removal of the second layer of clear water took 10 minutes. About 745 cubic metres of concentrated mud were now contained in the hopper tank. The hopper tank was then filled for the third time, the filling taking 7 1/2 minutes.
After 15 minutes more the removal of the clear water was begun.
:
This lasted about 6 minutes. About 920 cubic metres of concentrat-ed mud were now contained in the hopper tank. The entire opera-t;ion lasted in all scarcely two hours.
Divers~tests ascertained that the concentration of the silt deposits on the riverbed was identical with the concentra-tion of the silt in the hopper tank, containing about 40~ by weight of solid matter. The hopper dredger then moved to the polder unloading site and unloaded the silt with the aid of the usual flushing process.
. , ~ . . : .
The problem of keeping such waters clean after their state of pollution has passed acceptable limits is widely known.
As the pollution of water progresses, the ~ine and very i'ine particles of solid matter, which at first are suspended in the water, also increase and in a matter of weeks or months give rise to a continuous rise o~ the level of mud in the waters. The fauna and flora o~ many lakes, including some situated in recreation areas near centres oi population, already have their existence mos* serious threatened through choking with mud. In rlver mouths situated in brackish water districts, where the silting of the water ls ~urther intensi-fied by the ~act that microorganisms, which live only in iresh water, perish and sink on encountering seawater because of the excessive salt content, navigation is even hindered by the increasing mud or silt at certain points. It is attempted to master this silting in various ways. In par-ticularly ai'i'ected port installations, $or example i'erry embarkation and disembarkation points, underwater ploughs-also known as underwater rakes or harrows - are pulled through the masses oi mud during the ebb-tlde with the aid of tugs, in the hope that the mud swirled up under the water will be carried out towards the sea with the ebbing water.
This operation has very little ef~ect because the high tide brings the mud back again. Dredging wlth the aid of grab dredgers or chain and bucket-conveyor excavators is far more effective. Grab dredgers can be used only ~or removlng smaller amounts of mud. Suction dredgers and chain and bucket-conveyor éxcavators can be used only when anchored iast and while in use -fi they constitute an obstacle to trai'i'ic in port installations and water-ways. The floating suction dredger usually conveys the excavated material through a floating pipeline and a land line connected to the latter to an artii'icially constructed polder. Since the length ofiloating pipelines is li~ited in places where weather gives rise to heavy seas or where strong tidal currents occur, the method cannot be applled everywhere.
The combination of suction dredgers and barges so-called dumb barges, into which the excavated material is loaded and which are transported to the unloading site by means oi' t~lgs, would be an uneconomical solution to the problem, since in~the case of suction dredging of mud the large amounts o~ water, which are always carried off at the same time because o~ the nature o~
the process, remain in the mud, which does not readily settle, and thus considerably lncrease the frequency of the barge journeys. A dumb barge cleaner (pump ship) is also necessary at the unloading station. It is more expedient to combine the use o~ barges, tugs, and barge cleaning ships with a chain and bucket-conveyor excavator, which continuously raises the mud, in practically its original concentration, i'rom the seabed with the aid o~ its buckets suspended on an endless chain, and empties it into barges lying alongside the excavator ship.
When a chain and bucket-conveyor excavator is used it is oi' course inevitable that the suri'ace water will be polluted. Depending on the nature of the subsoil a chain and bucket-conveyor excava-tor, unlike a normal suctlon dredger, will generally be able to cut to plan a desired water pro1'ile modification, that is to say to lower the bed or widen the expanse o~ water. Since in most cases it is only desired to remove mud from the water and not to effect any particular modification of the profile, the use of a chain and bucket-conveyor excavator solely i'or mud removal is too complicated and too expensive.
The term "hopper" or "hopper suction dredger" is applied to a ship which combines all the functions necessary Yor dredging operations (the functions of a suction dredger, barge, tug, and barge cleaner~ and which i5 much used for the removal of sand from waters. A hopper requires no anchoring for the purpose of dredging and can, therefore, be removed at any time from the dredging site under its own power, so that it does not constitute an obstacle to shipping.
A loading tank (hopper tank) occupying almost the entire ship servesto receive the sand brought up. The sand ~ixed with water is sucked up continuously through a vertically movable nose-like suction pipe mounted on the outside of the hopper dredger, and is passed into a connecting pipe system which ends in two hopper tank inlet pipes extending on the port and star-board sides above the hopper tank and provided with numerous closable ~laps. The mixture of water and sand flows out of the inlet pipes over the entire length into the hopper tank, in which the sand, having a higher specific gravity, settles immediately, while the separated water flows off continuously into the sea by way of overflow hatches which are provided, directly under the top edge of the deck, in the ships's side and are vertically adjustable. In this way a mixture of water and sand is continuously sucked up from the bed and passed into the hopper tank untll the latter is ~illed with sand.
After the hopper tank has been ~illed and the suction pipe nose has been raised and stowed away, the hopper dredger sails under its own power to an unloading site, which may be at a distance of several kilometres, and is there unloaded either by means of a discharge flap provided in the bottom of the hopper or by a ilushing operation with the aid o~ its :, : : ~: -own pump and of bottom valves (slide valves). Because of the nature of its operation the hopper dredger works economically.
For sand dredging a hopper tank having a capacity of e.g. 500 to 5000 cubic metres can be effortlessly filled with sand by the overflow process within 1 to 3 hours. Attempts to use hopper dredgers for removing mud from waters have failed because even dredging for days on end does not enable the hopper tank to be filled with a worthwhile amount of solid material. The suspen-sions of mud and water pumped into the hopper tank show no tendency to settle because of the slight difference between the density of the solid material and the water, but are washed out of the overflow hatch with the same concentration of solid material, when the overflow process characteristic of a hopper dredger is applied, as when they flow into the hopper tank. The concentration of solid material in the suspension of mud and water pumped up is far too low to permit economic operation.
The object of the present invention therefore is to provide a simple, economical method of removing mud from waters.
According to the present invention, there is provided a method of removing mud from a water-mud suspension comprising the steps: a) passing a water-mud suspension mixed with a flocculat-ing agent into a vessel; b) permitting the mud to settle to the bottom of said vessel; c) drawing off and removing a resulting supernatant water layer without significant disturbance of the settled mud; d) repeating steps a) through c) until a desired amolmt of mud has been collected in the vessel; and then e) removing said mud which has collected in the vessel.
Preferably the method of the present invention for the removal of mud from waters is characterised in that the mud is sucked up and the suspension of mud and water sucked up is filled together with a flocculating agent into a floating vessel, the B
4~
filling is interrupted as soon as the vessel is full, and after the mud has settled the supernatant layer of water is removed, and the filling with the addition of flocculating agent, allowing to settle, and removal of supernatant water are repeated until the vessel is filled with mud.
In order to ensure that the mud from the suspension of mud and water will settle to form a supernatant layer of clear water, it is necessary to add a flocculating agent. Flocculat-- 4a -,.
ing agent. Flocculating agents are known. They are usually high polymeric products, such as for exàmple rubber phosphonium c;alts, starch products, proteins, polyacrylates, bone glue, poly-ethylene oxides, polyacrylamides, polyethyleneimines, and so on.
Flocculating agents are divided into non-ionic, anionic, and cationic agents. In order to be able to select the most suitable flocculating agent for any particular mud, sedimentation tests are carried out in the laboratory with a sample of suspension of mud and water which has been pumped up, and the optimum amount of flocculating agent for~total flocculation is determined. Good results are obtained in practice with flocculating agents based on e.g. polyacrylamide, partia~y saponified polyacrylamide, non-ionic polyethylene oxide, cationic polyethyleneimine, cationic polyethyleneamine, cationic poly-dimethylaminoethyl methacrylate, and/or poly-dimethylaminoethyl acrylate, cationic copolymerisates of dimethylaminoethyl methacrylate and acrylate, and/or acrylamide.
The flocculating agent is normally added in the form of an aqueous solution direct to the suspension of mud and water pumped up, expediently immediately downstream of the pump, in the optimum amount determined by previous tests.
The aqueous solution of flocculating agent may have a con-centration of 0.0001~ by weight or higher, particularly from 0.01 to 0.5% by weight. If aqueous solutions having a concen-tration higher than 0.5% by weight can still be metered, more concentrated solutions can also be used. It may be expedient to measure the concentration of the mud in the suspension of mud and water continuously during the pumping operation, for example by radiometry and to meter the flocculating agent in accordance with the mud concentration measured. From 10 to 100 ppm of flocculating agent (referred to 100% flocculating agent) are normally added per cub~c metre of mud and water suspension pumped up. Mud or silt deposited on a bed usually contains from to 50% by weight of solids. During the pumping operation it is normally diluted with water in the ratio 1 : 1 (1 to Z0).
In some favourable cases a certain separation already occurs between the mud and the water during the filling of the floating vessel with the suspension of mud and water mixed with flocculating agent, so that a layer of clear water first reaches the level boundary in the floating vessel. In such cases it is expedient for the layer of clear water to be removed during the actual filling operation, which can most simply be done by allowing to clear water to overflow over the edge of the vessel or through overflow hatches provided in the wall of the vessel. However, even in favourable cases a layer of clear water can be removed in this way only for the space of a i'ew minutes, whereupon the suspension of mud and water reaches the level boundary of the vessel. The filling operation ls then interrupted. After the mud has settled, the supernatant layer of clear water is removed, and the filling allowing to settle, and the removal of the layer of clear water are repeated until an economic amount of mud has collected in the vessel, whereupon the latter i5 transported to the unloading site and the mud is there emptied out.
Known suction devices are used for pumping up the mud deposited on the bed, in the form of a suspension of mud and water, and for filling it into the floating vessel. The layer of clear water above the mud deposited in the floating vessel can be removed in various ways. For example, a vertically adjustable slide valve can be provided in the wall of the vessel, this slide valve closing an outlet opening, for example a discharge hatch, when in its highest position. After .
the suspension has separated into a layer of mud and a layer of clear water the outlet opening, for example the outlet hatch, is gradually opened, so that the layer of clear water can flow off into the sea. A separate receiving chamber, into which the supernatant layer of clear water can flow off through a closable opening, may also be provided in the floating vessel, to clear water being removed from this chamber for example with the aid of a pump.
~ urthermore, the layer of clear water can be removed through an outlet pipe or outlet hose, through which the water flows freely into the sea or is pumped of~.
Various possible ways of removing the layer of clear water may also be combined. In all cases the removal of the layer of clear water should be effected in suc~ a manner that as little swirling as possible is produced in the layer of mud.
This can for example be achieved by arranging for the overflow, admission, or sucking-off of the water always to take place just below the surface of the clear water. The overflow edges, inlet and outlet openings must for this purpose be adapted to the falling surface of clear water, that is to say must be continuously lowered as the level of clear water falls. It is useful for the inlet openings of outlet pipes, suction hoses, or the like to be so disposed that the clear water can flow from above downwards into the outlet pipes, suction hoses, or the like. The clear water flowing into the inlet openings thus comes mainly from the surface of the water. By this means it i5 ensured that none of the collected mud will be entrained, during the drawing-off of the clear water, through the action of suction, such as may occur with unfavourably constructed or disposed inlet openings.
In addition, it is expedient for the inlet opening of an outlet or SUCtiOII pipe to be made funnel-shaped, because the overflow rate of clear water flowing from the surface will thereby be reduced. It is also advantageous for overflow edges and inlet openings for the clear water to be serrated.
It is useful i'or the suspension of mud and water pumped up to be introduced into the vessel, together with the flocculating agent, in such a manner that during the filling operation also the least possible turbulence is caused. In the case of elongated vessels, such as are generally provided, for example, in boats and ships, it is expedient for the suspension of mud and water together with the flocculating agent to be introduced only at one longitudinal end. It is thereby ensured that the heaviest turbulence occurs during the i'illing operation only at one longitudinal end, while the deposition of the mud is already started during the filling operation. The apparatus for removing the layer of clear water is advantageously disposed at the other longitudinal end of the vessel. It is also advantageous for the suspension of mud and water to be filled into the vessel below the level of liquid present during the filling operation. The suspension is thereby prevented from impinging on the surface of the liquld in the vessel, with the consequent destruction o~ the i'lakes of mud already formed, and in addition with the disturbing formation of foam.
~ urthermore, it is expedient to effect the filling of the vessel with suspension of mud and water at one end of the elongated vessel, and for this part to be separated, in the region of higher liquid levels, from the remainder oi' the vessel. With higher liquid levels a pacification zone is thereby formed and the rate o~ sedimentation is increased.
~t~ fi Before the next removal of the layer of clear water, however, the division between the filling region and the remainer of the vessel must be removed. Normally after a few cycles, for example 2 - 4 cycles, of the process of the invention - which can be carried out within a few hours, for example 1 to 3 hours -a container of e.g. 500 to 5000 cubic metres capacity is already filled with so large an amount of highly concentrated mud that it is economic for it to be transported away. At the unloading station the mud is removed from the vessel, ~or example by way of flaps in the bottom of the vessel. The mud in the vessel can also be diluted with water at the removal point ~o a pumpable state and then pumped off.
The floating vessels used for applying the process of the invention may for example be suitable boats and ships, for example dumb barges, but are preferably hoppers or hopper dred-gers. When a hopper dredger is used the ~inely and very finely divided mud suspension entering the hopper tank during the dredging operation, which may be a suspension of any kind, is mixed with a flocculating agent and the hopper tank is ~illed to a point just below the overflow. Dredging is then suspended for a short time. The layer of clear water forming above the layer of mud is drawn off with the aid o~ a suitable apparatus, -and dredging is then resumed with the addition of a i'locculat-ing agent to the incoming mud suspension, until the hopper tank is once again filled to a point just below the overflow. The new layer of clear water ~ormed is drawn of~, and filling with the addition of flocculating agent, allowing to settle, and removal of the layer of clear water lying above the solid material are repeated until the hopper tank is ~illed with an economic amount of flocculated mud. Unlike the practice of continuous filling of the hopper which was customary up to the present time, the process o~ the invention is carried out fi discontinuously.
In order to apply the method of the invention an ordin-ary hopper dredger must practically be simply provided with an apparatus for removing the clear water, for which only slight conversion is usually required.
In view of numerous unsuccessful attempts to use hoppers for removing mud from water in an economic manner, the method of the invention must be regarded as surprising. It was also not to be expected that by working in accordance with the invention it would be possible for a vessel to be sub-stantially filled with concentrated mud within a relatively short time, particularly as it had to be feared that because the hopper tank is unfavourably shaped for rapid separation of mud, and also because of the movements of the ship caused by heavy seas, it would not be possible to achieve reasonable settling speeds or high concentrations of the mud.
The invention will be further explained with the aid of the accompanying drawings. The drawings illustrate diagram-matically and by way of example a hopper dredger suitable for carrying out the method of the invention.
Figure 1 shows diagrammatically a cross-sectional side view of a hopper dredger, the ship's wall being partly broken away.
Figure 2 is a top plan view of the hopper dredger shown in Figure 1.
The drawings show only those devices which are of ~ importance for the carrying-out of the method of the invention.
Apparatus for the propulsion of the ship, for navigation, and for accommodation of the crew, and so on, is not shown in the drawings.
The hopper dredger is designated 1 and floats in the water 2. The actual hopper tank is désignated 3. The ` 10 vertically movable suction pipe 4 is f~stened to the ship by means of the ioint 5. The pump for sucking up the suspension of mud and water is designated 7. The two pipes 6 and 37, in which valves 8 and 9 are disposed lead into the suction side of the pump 7. From the delivery side of the pump 7 the two pipes 10 and 11 in which the valves 12 and 13 are provided lead off. Through the suction pipe 4 and the pipe 6 con-nected to it the pump 7 pumps up a suspension of mud and water when the valve 8 is open and the valves 9 and 13 are closed this suspension being pumped through the open valve 12 into the pipe 10 and then into the two outlet pipes 14.
The two outlet pipes 14 are mounted one on each side of the hopper tank 3. The outlet pipes 14 have outlet openings 15 and 16, through which the suspension of mud and water is pumped into the hopper tank 3. The outlet pipes 14 are arranged with their outlet openings 15 and16 in such a position that the suspension of mud and water flows into the hopper tanls only at the stern end. A solution of flocculating agent is supplied in metered amounts from the reservoir 17 containing an aqueous solution of flocculating agent by way of the pipe 18 by the metering pump 19 to the pu~ped-up suspension of mud and water downstream of the pump 7.
Perfect mixing of the suspension of mud and water with the flocculating agent is thereby effected by the time the mixture passes out of the openings 15 and 1~, and substantial flocculation of the mud is thereby achieved. In the frontpart, that is to say the bow end of the hopper tank 3 an outlet pipe 20 adapted to be raised and lowered is disposed. The outlet pipe 20 is fastened by means of a flexible, incompressible rubber sleeve 21 and of suitable flange elements on the box 22, which covers the outlet opening 23 provided in the bottom fi of the hopper tank 3. The apparatus for raising and lowering th~ outlet pipe 20 is not shown in the drawings. A suitable mounted pulley block arrangement can for example be used for r~ising and lowering the outlet pipe 20. In the hopper tank additional outlet openings 24 to 29 are provided, which can be separately opened and closed by the valves 30 to 36 and which lead into the common pipe 37. In the rear, stern part of the hopper tank 3 a plate 38 is disposed which extends over the entire width of the hopper tank and which is mounted for rotation about the horizontal axis 39. The plate 38 in its vertical arrangement extends downwards about 70 - 150 cm from the highest possible filling level of the hopper tank, and thus forms a pacification zone in the rear, stern part of the hopper tank.
For the purpose of filling the hopper the outlet pipe 20 is raised above the highest filling level of the hopper tank and the valves 9, 13, and 30 to 36 are closed, the plate 38 is brought into the position in which it points vertically down-wards. By means of the suction pipe 4 and of the pipe 6, with the valve 8 open, a suspension of mud and water is sucked up by the pump 7, and at the same time ilocculating agent solution is metered through the pipe 18 downstream of the pump 7. The suspension of mud and water accompanied by flocculating agent is delivered through the pipe 10 into the two outlet pipes 14 and pumped by way of the outlet openings 15 and 16 into the rear part of the hopper tank. The filling operation is inter-rupted when the maximum possible level of liquid has been reached in the hopper tank. As soon as the ~locculated mud has settled, which i5 usually the case after 10 to 25 minutes, the plate 38 is swung up into its horizontal position, which is shown in phantom outline, and the suction pipe 20 is lowered below the level of the clear water layer. At the same time L~
the valve 30 is opened and the water flowing off through the pipe 20, the box 22, and the opening 23 into the pipe 37 is pumped back into the sea by the pump 7, with the valves 9 and 13 open and the valves 8 and 12 closed, by way of the pipe 12 and the connection 40 provided in the ship's wall. The outlet pipe 20 is lowered in accordance with the falling level of clear water, until the opening of the suction pipe 20 reaches the surface of the deposited mud layer. The suction pipe 20 is th~n again raised above ~he maximum filling height of the hopper tank 3, the valves 23, 9, and 13 are closed, and the valves 8 and 12 are opened, while the plate 38 is brought back into the vertical position. The filling operation is then repeated, After the layer o~ mud has again been allowed to settle, the supernatant layer of clear water ls removed in the manner already described. After repeating the process steps described only three times the hopper tank is normally filled to the extent of more than 70% with mud whose con-centration is normally practically identical with that of the mud or silt deposited on the bed of the sea or other expanse of water. The suction pipe 4 of the hopper dredger is then raised the hopper moves under its own power to the discharge point, where the mud is emptied out.
Example Silt was removed from a brackish water region o~ the Weser with a hopper dredger converted in accordance with Figure 1. The capacity of the hopper tank amounted to 1200 cubic metres. The overflow hatches provided in the stern part of the hopper tan~ were closed watertightly. The optimum quality and quantity of the flocculation agent to be used were previous-ly determined in the laboratory by means of known tests for determining the rate of sedimentation. For the silt which was to be removed a commercially available partly saponified polyacrylamide flocculation agent (Hydropur ~ of Cassella, Frankfurt am Main-Fechenheim, Germany was found to be suitable, this agent being used in a 0.5a by weight solution and in an amount o~ 19 ppm (referred to 100~ flocculating agent) and added to the suspension of silt and water pumped up. As diagram-matically indicated in Figure 1, the filling zone was separated by a rotatably mounted pacification wall, having a height of about 120 cm and extending vertically, from the forward part of the hopper tank. The outlet pipe 20 in the front part of the hopper tank had a diameter of 40 cm. The first filling operation, comprising about 1200 cubic metres, lasted twenty minutes. At that time solid flocculated particles threatened to be entrained through the front overflow hatches together with the clear water flowing overboards. 15 minutes after termination of the filling operation, removal of the layer of clear water which had formed in the meantime was commenced.
Removal of the clear water with the aid of the outlet pipe in the manner described took 15 minutes. The hopper tank then contained about 460 cubic metres of concentrated silt with a concentration of more than 40% by weight. For the next filling operation therefore a loading space of 1200 - 460 = approximate-ly 740 cubic metres was available. The outlet pipe 20 was raised and the hopper tank refilled in the manner previously described. The second filling operation was suspended after 12 minutesj after 15 minutes more the removal of the new layer of clear water formed by the method already described was started. The removal of the second layer of clear water took 10 minutes. About 745 cubic metres of concentrated mud were now contained in the hopper tank. The hopper tank was then filled for the third time, the filling taking 7 1/2 minutes.
After 15 minutes more the removal of the clear water was begun.
:
This lasted about 6 minutes. About 920 cubic metres of concentrat-ed mud were now contained in the hopper tank. The entire opera-t;ion lasted in all scarcely two hours.
Divers~tests ascertained that the concentration of the silt deposits on the riverbed was identical with the concentra-tion of the silt in the hopper tank, containing about 40~ by weight of solid matter. The hopper dredger then moved to the polder unloading site and unloaded the silt with the aid of the usual flushing process.
. , ~ . . : .
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of removing mud from a water-mud suspension comprising the steps:
a) passing a water-mud suspension mixed with a flocculat-ing agent into a vessel;
b) permitting the mud to settle to the bottom of said vessel;
c) drawing off and removing a resulting supernatant water layer without significant disturbance of the settled mud;
d) repeating steps a) through c) until a desired amount of mud has been collected in the vessel; and then e) removing said mud which has collected in the vessel.
a) passing a water-mud suspension mixed with a flocculat-ing agent into a vessel;
b) permitting the mud to settle to the bottom of said vessel;
c) drawing off and removing a resulting supernatant water layer without significant disturbance of the settled mud;
d) repeating steps a) through c) until a desired amount of mud has been collected in the vessel; and then e) removing said mud which has collected in the vessel.
2. A method according to claim 1 wherein the vessel is a floating hopper dredger.
3. A method according to claim 1 wherein the passage of water-mud suspension and flocculating agent into the vessel in step a) is continued as long as clear water overflows an edge of the vessel and the passage is discontinued when there is a risk that mud flakes will overflow the edge of the vessel.
4. A method according to claim 1 wherein said suspension is pumped into the vessel and the flocculating agent is added down-stream of the pump viewed in the direction of suspension flow.
5. A method according to claim 4 wherein the flocculating agent is directly added downstream of the pump.
6. A method according to claim 1 wherein the flocculating agent is metered into the suspension of mud and water in amounts dependent on the concentration of mud.
7. A method according to claim 1 wherein the flocculating agent is an anionic flocculating agent.
8. A method according to claim 1 wherein the flocculating agent is a non-ionic flocculating agent.
9. A method according to claim 1 wherein the flocculating agent is a cationic flocculating agent.
10. A method according to claim 1 wherein said flocculating agent is polyacrylamide or partially saponified polyacrylamide.
11. A method according to claim 8 wherein said non-ionic flocculating agent is polyethylene oxide.
12. A method according to claim 9 wherein said cationic flocculating agent is polyamine.
13. A method according to claim 9 wherein said cationic flocculating agent is selected from the group consisting of polyethyleneamine, polyethyleneimine, poly-dimethylaminoethyl methacrylate, poly-dimethylamino ethyl acrylate, copolymers of dimethylaminoethyl methacrylate with acrylamide and copolymers of dimethylaminoethyl acrylate with acrylamide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19772755125 DE2755125A1 (en) | 1977-12-10 | 1977-12-10 | METHODS FOR REMOVING SLUDGE FROM AQUATIC AQUATIC ENVIRONMENT |
| DEP2755125.3 | 1977-12-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115436A true CA1115436A (en) | 1981-12-29 |
Family
ID=6025814
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA317,712A Expired CA1115436A (en) | 1977-12-10 | 1978-12-11 | Method of removing mud from mud-water suspensions |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0002704B1 (en) |
| JP (1) | JPS5489368A (en) |
| CA (1) | CA1115436A (en) |
| DE (2) | DE2755125A1 (en) |
| EG (1) | EG13607A (en) |
| ES (1) | ES475833A1 (en) |
| IE (1) | IE47896B1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE1005478A3 (en) * | 1991-10-30 | 1993-08-03 | Dredging Int | Procedure and equipment for selective removal of contaminated anduncontaminated dredged material |
| DE4315764C2 (en) * | 1993-05-07 | 1997-12-18 | Gemeinnuetzige Ges Fuer Bescha | Device for desludging shallow water |
| FR2860532B1 (en) * | 2003-10-03 | 2007-04-27 | Michel Poteur | DEVICE FOR DEVASEMENT WITHOUT POLLUTION OR NOTABLE WATER CONSUMPTION |
| BE1018577A4 (en) * | 2009-04-22 | 2011-04-05 | Dredging Int | Dredging vehicle and method for loading the dredging vehicle with dredging spoil. |
| DE102017103437B4 (en) | 2017-02-20 | 2021-10-07 | Werner Möbius Engineering GmbH | Process for the treatment and disposal of dredged material from a port region |
| CN109663410B (en) * | 2019-01-04 | 2024-05-17 | 河海大学 | Movable clogging intelligent cleaning mud decrement system and method |
| AT522689B1 (en) * | 2020-06-15 | 2021-01-15 | Andritz Delkor Pty Ltd | DEVICE AND METHOD FOR SEPARATING A SUSPENSION |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE884778C (en) * | 1949-05-04 | 1953-07-30 | Aannemersbedrijf Voorheen T De | Watercraft with a hold for mud or similar water-bearing substances |
| US3544456A (en) * | 1968-09-18 | 1970-12-01 | Calgon C0Rp | Dredging process |
| NL6815921A (en) * | 1968-11-08 | 1970-05-12 | ||
| DE1918332A1 (en) * | 1969-04-10 | 1970-10-15 | Konink Mij Tot Het Uitvoeren V | Thickening sludge using polyelectrolytes or cellulose |
-
1977
- 1977-12-10 DE DE19772755125 patent/DE2755125A1/en not_active Withdrawn
-
1978
- 1978-12-06 EG EG690/78A patent/EG13607A/en active
- 1978-12-07 ES ES475833A patent/ES475833A1/en not_active Expired
- 1978-12-08 EP EP78101609A patent/EP0002704B1/en not_active Expired
- 1978-12-08 JP JP15121178A patent/JPS5489368A/en active Pending
- 1978-12-08 DE DE7878101609T patent/DE2861798D1/en not_active Expired
- 1978-12-08 IE IE2433/78A patent/IE47896B1/en unknown
- 1978-12-11 CA CA317,712A patent/CA1115436A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EG13607A (en) | 1981-12-31 |
| ES475833A1 (en) | 1979-04-16 |
| EP0002704B1 (en) | 1982-05-05 |
| DE2755125A1 (en) | 1979-06-13 |
| IE782433L (en) | 1979-06-10 |
| JPS5489368A (en) | 1979-07-16 |
| DE2861798D1 (en) | 1982-06-24 |
| EP0002704A1 (en) | 1979-07-11 |
| IE47896B1 (en) | 1984-07-11 |
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