SLUDGE PROCESSING ASSEMBLY AND METHOD FOR DRYING AQUEOUS WASTE STREAMS

The invention relates to a sludge processing assembly that is configured to form drying structures for drying aqueous waste streams. The invention also relates to a method for drying aqueous waste streams, such as sludge, especially wastewater treatment plant sludge or (in)organic slurries.

It is known that a wide range of industrial activities produce aqueous waste streams that need to be processed. This includes both responsible disposal as well as reuse and/or treating such waste streams to extract products for other uses. Examples of such waste streams are for example sludge from municipal and industrial wastewater treatment plants, drinking water production plants, organic slurries such a manure, but also mining operation waste streams such as red mud.

A common denominator in such streams is that they have a high moisture, often water, content. This can be higher than 90%, and in some cases as high as 95% - 98% moisture content. As a result, handling, processing, transportation and/or disposal of such streams is often expensive.

An example of such an aqueous waste stream is Waste Activated Sludge (WAS), which is a by-product of municipal wastewater treatment. Managing such WAS typically comprises about 20-50% of the total operational costs of wastewater treatment plants (WWTPs). With a growing population and improved sanitation that connect ever growing amounts of people to sewerage systems, sludge production is growing worldwide. Although WAS is rich in carbon and nutrients such as nitrogen (N) and phosphorous (P), not all WAS can be beneficially reused in agriculture depending on the quality and stabilization process used. For example, the presence of heavy metals is a key factor limiting the use in agriculture in various regions in the world, including the United States and Europe. Consequently, in these regions incineration and landfilling are more common practices for disposal of WAS.

Also, ever more strict regulations with respect to WAS are expected to be developed to protect human and environmental health, for example due to growing concerns about the presence of emerging contaminants such as Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) and microplastics.

In most cases, the processing of the abovementioned aqueous waste streams requires dewatering to a low moisture content, such as lower than 50%, or even to lower than 20%. Since commonly used dewatering methods, such as centrifugation and belt presses, only achieve moisture contents of 70% - 90%, drying techniques are needed to reach low moisture contents, such as lower than 50%, or even to lower than 20%. Such techniques for example include dryers, such as thin film dryers, fluidized bed dryers or belt dryers, or natural drying in greenhouses or sludge drying beds.

A disadvantage of dryers is that a significant amount of energy is required to operate them. This is expensive as well as environmentally unfriendly. A disadvantage of natural drying, for example in greenhouses, is that a large area is required to allow the aqueous waste stream to dry to a sufficiently low moisture content. Moreover, drying beds also have the disadvantage of not being covered, which introduces the risk of rainfall adding water during the drying process.

Therefore, there is a need for a more efficient aqueous waste stream processing assembly that enables more efficient and cost-effective drying of such waste streams.

Thereto, the present invention provides a sludge processing assembly, the assembly comprising: a waste stream inlet for supplying aqueous waste; a forming unit that is configured to form from the aqueous waste stream at least one drying structure having a length and a width; and a transport assembly that is configured to transport the at least one drying structure from the forming unit to a drying location, wherein the length and the width have a ratio of length width in the range of at least 3:1 .

It is noted that the word ‘sludge’ in the application should not be interpreted in a limited manner. For the purpose of this application, the word ‘sludge’ also is considered to encompass similar terms and phrases, including but not limited to aqueous waste streams, such as slurry, waste stream mixtures of liquid with solid fractions, waste streams that are suspensions, liquid waste streams containing a solid fraction of organic material and/or liquid waste streams containing a solid fraction of inorganic material, such as red mud. It also includes liquid waste streams containing a solid fraction of both organic and inorganic material. These terms are used interchangeably throughout the application.

It is further noted that the term ‘forming’ or ‘to form’ in the application is used interchangeably with the term ‘manufacturing’ or ‘to manufacture’.

It is noted that the term ‘length’ as used in the application is measured along the elongated direction of the structure.

It is further noted that the drying location may be a static location or may be a dynamic location in that the drying structure is, during drying, (semi-)continually moved.

The assembly according to the invention is aimed at providing elongated drying structures that have a high length to width ratio, because this increases the surface area of the elongated drying structure that is exposed to the surrounding environment or medium (i.e. surrounding air). This is achievable with a variety of different shapes and/or structures. A drying structure may in a non-limiting example, be a cylindrical or ‘sausage-like’ shape, that extends over a predetermined length. In this example, the width would be defined as the diameter of the cylinder, with the length being at least 3 times the width. The length would preferably extend in (and be measured in) an upward or vertical direction.

It is noted that the length, width and distance (or depth) can be measured in for example a first, second and third direction. In particular, the length is measured in a first, vertical direction. The width is preferably measured in a second direction that is perpendicular to the first direction, wherein the width is (substantially) smaller than the length. The third direction is perpendicular to both the first and the second direction and preferably is a distance or depth direction.

A drying structure may in another non-limiting example be formed by a (solid or semisolid) column-like shape having a rectangular base surface. In this example, the width of the drying structure is measured along the shortest side of the rectangular base surface. The length would preferably extend in (and be measured in) an upward or vertical direction.

In a further non-limiting example, the drying structure may be formed as a hollow column having a square base surface. The length is defined as the length of the column. In this example, the width is the sum of both wall thicknesses when viewed along a first direction that is not the length direction. In other words, when viewed along a first direction, the width W is the distance Wi between a first outside wall surface and the accompanying first inside wall surface summed with the distance W ₂ between a second inside wall surface, that is positioned across from the first inside wall surface, and the accompanying second outside wall surface. Simply formulated W = Wi + W ₂ . This particular formula is valid for defining width W for most hollow structures, because the hollow nature increases the available exposed wall surface.

In a further example, the drying structure may be a wall, such as a straight wall or a wall that, when viewed in a top view, for example has a sinusoidal shape. In the case of a wall or other 3D structure, the width is defined as the distance between the first face and the second face of the wall that is formed by the length (preferably measured in an upward direction) and a distance D over which the wall extends.

The common denominator in each of these cases is that the width of the structure is kept as small as possible compared to the length of the structure in order to increase the surface area without (unduly) increasing the footprint of the drying structure. This maximizes the exposed surface area, which increases the drying rate.

Conversely, an increase of the width W of the drying structure decreases the exposed surface area and increases the amount of aqueous waste or sludge that is not exposed to the surrounding environment (i.e. the surrounding air). This is for example present in greenhouse drying, which provides a small length and a large width (i.e. the distance along the ground or horizontal surface).

An advantage of increasing, or even maximizing, the exposed drying surface and minimizing the surface footprint of the drying structure, a high drying efficiency is achieved.

The assembly according to the invention is configured to manufacture or form drying structures that have a length to width ratio in the range of at least 3:1 . This allows the structures to be placed in an upright or vertical direction, which increases the amount of sludge or waste material per unit of floor surface and reduces the amount of space needed to dry the waste or sludge from the waste stream.

Another advantage of the assembly according to the invention is that the ratio maximizes the surface area, while still providing sufficient structural integrity.

Another advantage of the assembly according to the invention is that existing greenhouse drying locations may be retrofitted with a sludge processing assembly according to the invention.

Another advantage of the assembly according to the invention that it allows (semi-) continuous operation and thus is suitable for installations having a (semi-)continuous supply of a waste stream, such as wastewater treatment plants (WWTPs). It is noted that batch-wise operation nevertheless also belongs to the possibilities.

A further advantage is that the vertical structures require only limited support or even no (external) support at all. This not only reduces the investment in support structures to uphold the dryings structures, it also increases the amount of drying structures that can be positioned on a predetermined surface.

It is noted that the assembly according to the invention may for example be configured to manufacture and/or form column-like structures, wall-like structures or even tube-like and/or cylindrical structures from the waste material.

In an embodiment of the sludge processing assembly according to the invention, the length to width ratio, or L:W, may be in the range of 4:1 , 6:1 , 10:1 or more.

The higher the L:W ratio, the higher the amount of sludge or waste material per unit of floor surface. Simultaneously, such a high ratio increases, or even maximizes, the surface area that is exposed to the surrounding environment (i.e. a surrounding medium such as air). This increase in exposed surface area significantly increases the drying rate, while only occupying a small surface area.

In addition, the drying structures, which are elongated 3D structures, still provide sufficient structural integrity to maintain in an upright position.

In an embodiment of the sludge processing assembly according to the invention, the drying structure may have a length or height in the range of 0.5 meter to 30 meter, preferably in the range of 1 meter to 20 meter and more preferably in the range of 1 .5 - 5 meter. The length of the structure in use extends in a vertical or height direction, and therefore the length and height are equivalent. An advantage of providing a height in the abovementioned ranges is that a large drying surface is obtained that has a small footprint. The footprint is preferably measured in a horizontal plane.

In an embodiment of the sludge processing assembly according to the invention, the drying structure may have a width in the range of 0.05 centimeter to 5 centimeter, preferably in the range of 1 centimeter to 2.5 centimeter and more preferably in the range of 1 - 2 centimeter.

The width of the structure is measured in a direction perpendicular to the height direction and extends in a substantially horizontal direction. An advantage of a width in the abovementioned ranges is that it reduces the amount of aqueous waste that is not exposed to a surrounding environment.

In an embodiment of the sludge processing assembly according to the invention, the drying structure may have a depth or distance in the range of 0.5 meter to 30 meter, preferably in the range of 1 meter to 20 meter and more preferably in the range of 1 .5 - 5 meter.

An advantage of the abovementioned range is that, especially in combination with the height/length of the structure, a large surface is formed that is exposed to the surrounding environment. This allows more contact with the air and thus increases the drying rate of the structure. In particular, a combination with the abovementioned ranges of the width provides a large and thin structure, which may include a support structure, that is positioned upright (i.e. the surface extending upwards) and that provides a large drying surface.

It is noted that in the above embodiments, the length, width and distance (or depth) can be measured in for example a first, second and third direction. In particular, the length is measured in a first, vertical direction and is therefore a height direction. The width is preferably measured in a second direction that is perpendicular to the first direction, wherein the width is (substantially) smaller than the length. The third direction is perpendicular to both the first and the second direction and preferably is a distance or depth direction.

In an embodiment of the sludge processing assembly according to the invention, the drying structure may be a porous drying structure or may be a (semi-)solid drying structure having perforations and/or openings in a side wall thereof.

An advantage of providing a porous drying structure or perforations/openings in a side wall thereof, is that the surface area that is effectively used to dry the drying structure is increased even further.

In an embodiment of the sludge processing assembly according to the invention, the assembly may comprise a skeleton builder supply unit that is positioned upstream of the forming unit. The skeleton builder supply unit is configured to add a predetermined amount of skeleton building material to the aqueous waste stream. Skeleton building material is a material that is added to the aqueous waste stream, which increases the solid fraction in the waste stream. This increase in solids in the waste stream results in a thickening of the waste stream to a paste-like substance.

An advantage of the skeleton builder supply unit is that it allows the composition (in terms of solid content) to be changed to create a more paste-like structures. This allows (semi)solid (shapes of) drying structures to be constructed with waste from the aqueous waste stream.

Another advantage is that the consistency of the waste stream is increased, which provides a more reliable composition of the waste or sludge material.

The skeleton builder supply unit may be configured to provide a specific amount of material, which may be provided in dependence of the drying structure to be build.

It is preferred that the skeleton building supply unit is positioned between the waste stream supply inlet and the forming unit. The addition of the skeleton builder material increases the volume and/or weight of the waste stream. Therefore, it is advantageous to supply the material just before it enters the forming unit.

Another advantage is that the skeleton building material increases the porosity of the drying structure(s) formed by the assembly, which increases the drying surface of the semisolid drying shapes and/or drying structures.

In an embodiment of the sludge processing assembly according to the invention, the skeleton building material is selected from the group of lime, gypsum, quicklime, coal dust, saw dust, shredded cardboard/paper, woodchips, rice husk, hay, straw, fiber material, shredded coconut shells, dry organic material, hair, bagasse and/or shredded fabric.

It was found that the abovementioned substances are highly effective in increasing the porous structure and thickening the waste stream. As a result, the waste stream can very effectively and efficiently be used in forming drying structures, especially 3D structures, such as walls, and/or elongated drying structures, including cylindrical drying columns.

A specific advantage of (quick)lime is that it stabilizes the sludge by destroying pathogens as well as reduces/assimilates odours from the drying structure. Another specific advantage of (quick)lime is that the reaction thereof with sludge is exothermic, which reduces the moisture content even further.

A specific advantage of saw dust and especially of coal dust is that these substances have a high energy content, which increase the overall energy content of the drying structure. As a result, a relatively high amount of energy can be generated when the drying structure is used in energy generation (after drying). In an embodiment of the sludge processing assembly according to the invention, the forming unit comprises a storage tank having at least one outlet and a press that is associated with the storage tank and that is configured to dispense aqueous waste from the at least one outlet.

An advantage of a storage tank is that a steady supply of aqueous waste is available for forming into a drying structure, which allows a continuous processing into drying structures. This increases the operational efficiency of the assembly by levelling out increases and/or decreases in the supply.

Another advantage is that the storage tank can be used with various types of additional processing units and can even be integrated with such units.

An advantage of having a press that is associated with the storage tank is that it provides a simple and reliable installation to accurately dispense the aqueous waste from the storage tank. The press may comprise a plunger that is capable of providing a pressure in the storage tank to dispense the aqueous waste.

It is preferred that the press is switchable between a loading state, in which aqueous waste can be loaded into the storage tank, and a dispensing state in which pressure is applied to the aqueous waste in the storage tank to dispense aqueous waste from the at least one outlet opening. It is further preferred that the press, preferably the plunger thereof, is positioned in the storage tank. In the loading state, the press, preferably the plunger thereof, may be drawn to a position outside the storage tank, or to a position in which an inlet of the storage tank is open for supply of aqueous waste to the storage tank.

In an embodiment of the sludge processing assembly according to the invention, the press is a hydraulic or a pneumatic press.

It has been found that an advantage of a hydraulic or a pneumatic press in the invention is that such presses are capable of providing a high amount of pressure onto the aqueous waste in the storage tank, while simultaneously requiring a relatively low amount of energy to generate the pressure. Therewith, such presses are efficient and cost-effective.

Furthermore, a hydraulic or pneumatic press requires less space than another press, such as a mechanical press, capable of providing a similar pressure.

Another advantage, especially when compared to for example a pumping assembly, is that a press, in particular a hydraulic or pneumatic press, is robust and low-maintenance. This reduces operational costs and increases uptime and operational life-time of the sludge processing assembly.

In an embodiment of the sludge processing assembly according to the invention, the forming unit comprises a storage tank having at least one outlet and a pump assembly that is configured to dispense aqueous waste from the at least one outlet. An advantage of a pumping assembly is that the storage tank and a specific forming part, such as a dispensing outlet, do not need to be positioned adjacent or close to each other. The dispensing outlet may be positioned at some distance and be connected, for example via a feed line or conduit, to the at least one outlet of the storage tank.

In an embodiment of the sludge processing assembly according to the invention, the pump assembly is a hydraulic pump assembly or a pneumatic pump assembly.

An advantage of a hydraulic pump or pneumatic pump assembly is that it can provide large pumping forces, while simultaneously being energy efficient, in particular when compared to traditional pump assemblies. A similar advantage is present with a pneumatic press.

In an embodiment of the sludge processing assembly according to the invention, the forming unit comprises a storage tank having at least one outlet, a press that is associated with the storage tank and a pumping assembly, wherein the press and the pumping assembly are configured to dispense aqueous waste from the at least one outlet.

In an embodiment of the sludge processing assembly according to the invention, the storage tank is a container, such as a (modified) shipping container, a bulk liquid tank, a tank structure, a building, a solid structure basin, such as a concrete basin, or even a lorry or truck containing a tank for holding aqueous waste.

It is noted that the storage tank may also be used separately, without specific use of a (hydraulic or pneumatic) pumping assembly and/or a (hydraulic or pneumatic) press. In addition, a pumping assembly or press may be provided at a different location then in combination with the storage tank.

In an embodiment of the sludge processing assembly according to the invention, the at least one outlet may be connected to a transport means for transporting the aqueous waste from the storage tank to a further processing unit. The transport means may for example comprise a conveyor belt, a supply conduit, a cart or a carriage. It may however also be a movable or unmovable support structure or another form of transport assembly.

An advantage of providing transport means is that a further processing means may be independent from the storage tank. This is especially relevant in a situation in which the processing means, which may form the at least one drying structure into its (final) shape, are movable in one or more directions. The transport means then obviate the need to provide the storage tank as a movable storage tank, which reduces costs.

In an embodiment of the sludge processing assembly according to the invention, the forming unit may comprise an extruder that is configured to form at least one elongated drying structure.

An advantage of this embodiment is that a plurality of drying structures, such as column-like structures, can be manufactured in a single manufacturing or forming step. The extruder preferably comprises a plate or plate-like structure that is provided with a plurality of forming openings that are used to extrude the aqueous waste into the drying structures.

An advantage of the extruder is that it can be integrated with the storage tank. The extruder may for example be formed by providing a plurality of openings in a bottom plate of the storage tank. The press, which preferably is then a hydraulic or pneumatic press, and more preferably a hydraulic or pneumatic press having a plunger, can be used to press the waste or sludge material through the extruder to form elongated drying structures. These structures may for example be formed in a substantially upright position, that is that the length of the structure extends parallel to a vertical axis of the storage tank. The structure may also be formed by moving the extruder along a horizontal surface and subsequently upending the one or more structures to a vertical or upright position. It is noted that the plurality of openings may also be provided in another wall, such as a side wall.

An advantage of the extruder is that it can be integrated with the press, which allows the drying structures to be formed in the storage tank. The press, especially the plunger thereof, may for example comprise a plate-like structure having a plurality of openings, which are used to form elongated drying structures during the movement of the extruder in the storage tank. In particular, the elongated structures are than formed by pressing the plunger with the integrated extruder, downwards in the storage tank, which forces the material through the plurality of outlet openings.

An advantage is that the extruder can also be provided separate from or connected to the storage tank. The extruder may for example be positioned at a distance from the storage tank and be connected thereto. This allows the extruder to be independently moveable with respect to the storage tank and thus allows more flexibility to form specific shapes of the drying structure.

In an embodiment of the sludge processing assembly according to the invention, the assembly further may comprise a positioning assembly that is configured to upend the at least one elongated aqueous waste structure to a substantially vertical position.

An advantage of providing a positioning assembly is that the drying structure may be formed in a substantially horizontal plane, and afterwards may be upended to a drying position in which the surface footprint is relatively small.

Another advantage of the positioning assembly is that it allows a highly precise upending and positioning of the drying structures relatively to each other. This increases the efficiency of the assembly even further.

In an embodiment of the sludge processing assembly according to the invention, the extruder may be moveable in at least one direction over a surface on which the drying structure is to be placed, and preferably is moveable in two or three different directions over the surface. In an embodiment of the sludge processing assembly according to the invention, the extruder may be moveable in two directions, wherein the two directions extend in a horizontal plane and are substantially perpendicular to each other.

An advantage of providing a moveable extruder, especially in two or three dimensions, it that the drying structures can be formed with a high degree of precision and flexibility. This is especially relevant if the drying structures are to be positioned close to each other or in a predetermined pattern that increases the air flow in between the structures in order to enhance the drying even further.

In some embodiments, the air flow may be an air flow to provide a laminar flow to the surface of the drying structures. In other embodiments, the air flow may be directly at the surface to create a turbulent air flow between the drying structures.

In an embodiment according to the sludge processing assembly according to the invention, the at least one support structure is a movable support structure.

An advantage of providing a moveable support structure is that a (semi-)continuous process can be achieved by forming the drying structures and subsequently moving them to a drying location using the moveable support.

Another advantage is that the moveable support can efficiently be used to positioning the drying structures in a drying chamber and/or under a drying structure such as a drying roof, thereby protecting it from precipitation, while simultaneously allowing ventilation.

In an embodiment of the sludge processing assembly according to the invention, the moveable support may be a carriage, a railway carriage, a flatbed, a trolley, an open support structure or a container.

In an embodiment of the sludge processing assembly according to the invention, the moveable support may be moveable in two directions in a substantially horizontal plane, wherein the two directions are substantially perpendicular to each other.

In an embodiment of the sludge processing assembly according to the invention, the moveable support may be moveable in two directions, the directions being a substantially vertical direction and a substantially horizontal direction, wherein the two directions are substantially perpendicular to each other.

In an embodiment of the sludge processing assembly according to the invention, the moveable support may be moveable in three directions that are substantially perpendicular to each other.

An advantage of providing a support that is capable of a two- or three-dimensional movement allows the drying structures to be positioned on the support without having to move the forming unit. In other words, the support can be moved underneath and/or along the forming unit to form the drying structures on the support. Subsequently, the support can be moved away from the forming unit to a position in which the drying structures can be dried, preferably to a predetermined and/or desired moisture content.

In an embodiment of the sludge processing assembly according to the invention, the forming unit may comprise a 3D printer that is configured to form at least one drying structure, such as a wall or another vertical sheet-like structure, of aqueous waste and/or sludge.

An advantage of a 3D printer is that it is capable to form a wide variety of 3D drying structures, which includes for example walls, cylindrical structures, (semi-)hollow columns or other shapes. It can also be used to manufacture slanted and/or sloped structures, which preferably are formed to improve the drying process of the drying structures.

In an embodiment of the sludge processing assembly according to the invention, the 3D printer may be connected to a support frame, and the assembly may further comprise a support that, during forming, is moveably positioned under the 3D printer to allow manufacturing of at least one 3D drying structure.

In an embodiment of the sludge processing assembly according to the invention, the 3D printer may be moveable in at least one direction over a surface on which the drying structure is to be placed, and preferably may be moveable in two different directions and more preferably may be moveable in three different directions over the surface.

An advantage of this embodiment is that the 3D printer, due to the freedom of movement, can be used to form virtually any shape of drying structure. Additionally or alternatively, the 3D printer can be moveable over a larger area, which allows the forming of multiple, preferably larger, 3D drying structures in open air.

Another advantage is that the 3D printer is useable to manufacture or form 3D drying structures in (partially) closed spaces, or in support structures, such as open walled containers. In addition, the 3D printer can be used in an indoor environment, even when the storage tank is positioned outside the indoor structure. This is for example relevant in case a (closed) drying chamber or similar is used in which the 3D drying structures are built up.

It is preferred that, when the 3D printer is moveable in two directions, the two directions extend in a horizontal plane and are substantially perpendicular to each other. In case of three different directions, it is preferred that, in addition to the abovementioned two directions, the third direction is, when viewed with reference to the horizontal plane, is a vertical direction.

It is noted that, instead of moving the 3D printer over a surface, it is also possible to move the surface underneath a stationary 3D printer. Therefore, the abovementioned embodiments relate to relative movement between the 3D printer and the support surface on which the (at least one) drying structure is formed.

In an embodiment of the sludge processing assembly according to the invention, the assembly may comprise at least one movable support, wherein the forming unit is configured to position the at least one drying structure of aqueous waste on the movable support. An advantage of a moveable support is that the forming unit can completely or partially be stationary, which simplifies operation of the sludge processing assembly according to the invention.

A further advantage of the moveable support is that it allows a (semi-)continuous process due to the fact that a plurality of subsequent moveable supports can be moved along and/or underneath the forming unit. In this respect, the term ‘along’ means either passing in front of the forming unit along a horizontal direction (i.e. from left to right or vice versa) or along a vertical direction (i.e. from bottom to top or vice versa).

In an embodiment of the sludge processing assembly according to the invention, the at least one movable support may be chosen from the group of nets, mesh, mesh sheets, timber frames, netting, such as woven or non-woven netting, textile or other suitable supports.

An advantage of these materials is that they provide a good support to the aqueous waste material. In addition, these materials provide a cost-effective support. It is noted that combinations of different materials are also possible.

A specific advantage of textile is that it can be used to hold aqueous waste having a relatively high moisture content. As a result, preprocessing to reduce the amount of moisture in the aqueous waste, such as dewatering by belt press or centrifugation, can be obviated. It has been found that aqueous waste streams having a solid content of as low as 2-8% can be used to form the drying structures when textile is used as support. It is noted that the term textile is considered to be similar to the term cloth and both terms are used interchangeably within the application.

A specific advantage of mesh is that the aqueous waste can easily be removed from the support structure after is has dried. This reduces the time that is required to prepare the support structure for a new amount of aqueous waste to be dried and therewith increases efficiency of the assembly according to the invention.

In an embodiment of the sludge processing assembly according to the invention, the at least one movable support comprises a frame enclosing a mesh or textile sheet.

This embodiment provides a support that can easily be handled and transported. In particular, it allows the support to be rotated, lifted and/or tilted during transport substantially without deformation. The frame and mesh or textile may be formed as a panel, which provides the advantage that it is easily transportable, for example by a transport assembly.

It is preferred that the frame is also provided with coupling means that are couplable to the transport assembly.

In an embodiment of the sludge processing assembly according to the invention, the at least one movable support comprises a support bar or support rod and a mesh or textile sheet connected thereto. This embodiment provides a support that can easily be handled and transported. In particular, it allows the support to be easily rotated, lifted and/or tilted during transport. In use, the mesh or textile is suspended on the support bar or support rod and extends in a downward direction therefrom. It is preferred that the support bar or support rod is provided with coupling means that are couplable to the transport assembly.

In an embodiment of the sludge processing assembly according to the invention, the at least one movable support comprises a three dimensional structure having an inner space configured for receiving aqueous waste, wherein the three dimensional structure preferably is at least partially manufactured from mesh.

An advantage of providing a three dimensional mesh structure is that a relatively high amount of aqueous waste can be provided into the structure while simultaneously maintaining a large effective drying surface. This structure can also be used to provide a hollow drying structure that is formed as a column or wall having an open inner space. This requires that the aqueous waste is applied to both (opposite) sides of the mesh structure.

In an embodiment of the sludge processing assembly according to the invention, the 3D structure comprises a front and a back surface that extend substantially parallel to each other, and comprises a width that is defined by the distance between the front and back surface.

The width between the front and back or rear surface is preferably relatively small compared to the front and/or rear surfaces. In other words, the surfaces have a length and/or a depth that is larger, preferably significantly larger, than the width in order minimize the thickness and optimize the drying surface.

It is noted that the distance (i.e. the width) is measured substantially perpendicular to the front and/or back surface and may, in case of the front and/or back surface are non-flat or curved surfaces, also be a mean value of the different widths measured between the front and back surface.

In an embodiment of the sludge processing assembly according to the invention, the movable support is provided with attachment or coupling means that are configured to couple the moveable support to a transport assembly

An advantage of attachment or coupling means is that the support is couplable to a transport system, for example a rail system or a chain drive.

In an embodiment of the sludge processing assembly according to the invention, the forming unit and the at least one movable support are moveable with respect to each other.

An advantage of this embodiment is that depending on the specific situation, either one (or both) of the forming unit and the support can be moved to provide the drying structure.

It is noted that the moveable support structure as mentioned in several of the abovementioned embodiments may also be replaced by static support structure without further changing the scope of the embodiments. Preferably, the forming unit is in such cases moveable relative to the one or more static support structures.

In an embodiment of the sludge processing assembly according to the invention, the aqueous waste may be supplied to the support structure to form a drying structure that includes the combination of the support structure and the aqueous waste.

In an embodiment of the sludge processing assembly according to the invention, the assembly comprises a discharge station that is configured to separate dried solids obtained from the aqueous waste from the support structure to or in which the aqueous waste is applied.

An advantage of a discharge station is that the aqueous waste, or at least the dried solids obtained therefrom after drying, can be separated from the support structures in an effective manner. The discharged or dislodged dried solids can be removed, for example for further processing such as combustion for power generation, whereas the support structures can be reused in the sludge processing assembly.

In an embodiment of the sludge processing assembly according to the invention, the mixing unit may be configured to mix the aqueous waste and/or mix the aqueous waste with the skeleton building material.

An advantage of this embodiment is that the skeleton building material is mixed to a uniform composition with the sludge. In case no skeleton building material is used, it still is advantageous to mix the aqueous waste to a uniform composition to be used for forming. Furthermore, a mixing unit is advantageous when multiple different types and/or streams of aqueous waste are combined into a single stream to be processed.

In an embodiment of the sludge processing assembly according to the invention, the mixing unit may be positioned downstream of the inlet and upstream of the forming unit.

An advantage of providing the mixing unit between the inlet and the forming unit is that the aqueous waste is mixed to a consistent composition before entering the forming unit. This in turn results in a consistent drying structure. In case of a mixture of aqueous wastes and a skeleton building material, the mixing unit additionally serves to mix these materials to a uniform composition.

In an embodiment of the sludge processing assembly according to the invention, the mixing unit may be positioned between the skeleton builder supply unit and the forming unit.

An advantage of providing the mixing unit between the skeleton builder supply unit and the forming unit is that the waste and/or sludge is mixed with the skeleton builder material to a consistent composition before entering the forming unit. This in turn results in a consistent drying unit, in which a good mixture of skeleton builder material and waste and/or sludge is achieved.

In an embodiment of the sludge processing assembly according to the invention, the mixing unit may be integrated in the storage tank. An advantage of providing the mixing unit in the storage tank is that the waste stream is consistent throughout the forming process.

Another advantage is that it reduces the footprint of the sludge processing assembly according to the invention.

In an embodiment of the sludge processing assembly according to the invention, the assembly may further comprise a drying chamber that, in use, contains at least one drying structure, wherein the drying chamber preferably contains at least one air displacement unit.

Although it has been found that the drying structures can be dried in open air, it is advantageous, especially in geographic areas with much rain, to provide a drying chamber in which the drying structures can be positioned during drying. Such a drying chamber may be a closed chamber, yet may also be a chamber with one or more open sides. The chamber may be formed of any suitable material or materials, which may include concrete, wood, metal or other materials. The chamber may also be provided with doors or openings which can be used to enter and/or remove drying structures from the chamber. The chamber may also be positioned over a conveyor or a track on which moveable support structures for drying structured can be transported in and/or out of the chamber.

In an embodiment of the sludge processing assembly according to the invention, the drying chamber may be configured to hold a plurality of drying structures, such as columns or walls, that are positioned adjacent to each other.

An advantage of the drying structures is that, due to their vertical orientation, a large amount of drying structures is positionable on a small surface area. As a result, the drying chamber can be provided with a high amount of aqueous waste in the form of drying structures, thus increasing drying efficiency. This is particularly true if the waste streams are provided in the form of column-like and/or wall-like structures.

In an embodiment of the sludge processing assembly according to the invention, the assembly may further comprise a roof structure under which the drying structure, during drying, are positionable, wherein the drying chamber preferably is associated with at least one air displacement unit.

As an alternative to a drying chamber, the assembly may also be provided with a roof structure only. This reduces the investment cost, while simultaneously providing the advantage of sheltering the drying structures against (heavy) rain and/or snow. Another advantage is that providing a roof structure also enhances the drying process due to natural ventilation.

It is noted that the abovementioned air displacement unit may be a continuous air displacement unit or may be regulated based on sensor input, for example relatively humidity and/or wind speed and/or other sensor input. In such case, the assembly is provided with one or more sensor for providing the sensor input, and preferably also with a control unit for processing the sensor data and controlling the air displacement unit.

The air displacement unit is preferably positioned such that it forces the flow of air in a certain direction in order to enhance the drying process, for example by creating more turbulence.

In an embodiment of the sludge processing assembly according to the invention, the assembly comprises flow guides, preferably turbulence enhancers, which enhance the intensity and/or direction of the air flow to increase the amount of moisture that is extracted from the drying structures. Therewith the drying process is enhanced.

In an embodiment of the sludge processing assembly according to the invention, the air displacement unit in the drying chamber or associated with the roof structure may comprise a fan.

An advantage of a fan is that it provides a cost-efficient and energy-efficient air displacement unit.

In an embodiment of the sludge processing assembly according to the invention, the aqueous waste has a predetermined moisture content that may be lower than 95%, preferably lower than 90%, and more preferably in the range of 70% - 90%, or the predetermined moisture content may be higher than 90% and the assembly may further comprise a dewatering unit configured to reduce the moisture content to a moisture content in the range of 70% - 90%.

It is preferred that the moisture content of the wastewater stream or sludge that is provided to the forming unit is lower than 90%, preferably between 70% and 90%. In some cases, for example with sludge from WWTPs, the moisture content at the inlet may exceed 90%, such as up to 97%. In such cases, it is advantageous if the assembly is provided with a dewatering unit that is capable of a first dewatering step in which the moisture content of the stream from the inlet is reduced to about 90%, or lower.

In other words, an advantage of the dewatering unit according to this embodiment is that even (very) wet waste streams, for example having a moisture content of higher than 90%, can be processed in the assembly to form the drying structures.

In an embodiment of the sludge processing assembly according to the invention, the skeleton builder supply unit is positioned upstream of the dewatering unit.

An advantage of providing the skeleton builder supply unit upstream of the dewatering unit, that is between the inlet and the dewatering unit, is that the skeleton builder material can be used to enhance the dewaterability.

Another advantage is that the skeleton builder is already mixed with the dewatered sludge upon entering the forming unit, especially when the mixing unit is provided upstream or directly downstream of the dewatering unit. In an embodiment of the sludge processing assembly according to the invention, the aqueous waste may be selected from the group of:

- wastewater treatment plant sludge, including industrial or municipal wastewater treatment plant sludge;

- organic slurry, such as manure, preferably animal manure, or a suspension containing microbial biomass, such as algae or other biosolids; and

- aqueous waste streams containing inorganic substances, such as drinking water treatment sludge, red mud from mining operations and/or fracking fluids.

An advantage of the abovementioned wastewater streams is that processing, due to the high moisture content therein, is difficult. The assembly according to the invention provides the advantage that the abovementioned (aqueous) waste streams can be processed, especially dried, in an efficient, cost-effective manner.

In an embodiment of the sludge processing assembly according to the invention, the skeleton builder material waste may be selected from the group of: lime, gypsum, quicklime, coal dust, saw dust, shredded cardboard, shredded paper, woodchips, rice husk, hay, straw, fibre material, shredded coconut shells, dry organic material, hair, bagasse, shredded fabric.

An advantage of the abovementioned materials is that these materials have a relatively large fluid uptake (i.e. they are dry materials) that increase the solid content in the waste stream and reduce the (relative) moisture content.

Another advantage is that the materials do not shrink during the drying process, thereby increasing the porosity of the drying structure further enhancing the drying process. This is mainly due to the fact that the aqueous waste material does, to a certain extent, decrease in volume during drying.

A specific advantage of coal dust, saw dust and woodchips is the high energy content thereof, which makes the drying structure, once dried, useable as energy source. The dried drying structures may for example be co-fired in a coal or biomass plant.

A specific advantage of (quick)lime is that it stabilizes the sludge by destroying pathogens as well as that it reduces/assimilates odours from the drying structure. Another specific advantage of (quick)lime is that the reaction thereof with sludge is exothermic, which reduces the moisture content even further.

In an embodiment of the sludge processing assembly according to the invention, the drying structure may be configured to be positioned substantially upright in the drying location, such that the length of the structure, when viewed from a base or ground surface, extends in a substantially vertical direction.

An advantage of positioning the drying structure in a substantially vertical direction on the drying location increases the amount of sludge or waste material per unit of floor surface that can be dried, and reduces the amount of space needed for drying. It is preferred that the vertical structures have the mentioned ratio of length to width.

In an embodiment of the sludge processing assembly according to the invention, the step of drying may comprise positioning the drying structure such that the length of the structure, when viewed from a base or ground surface, extends in under an angle with said base or ground surface in a vertically upward direction, wherein the angle of the drying structure with the base or ground surface preferably is 45° to 90° and more preferably about 60°.

An advantage of positioning a drying structure under an angle is that predetermined structures can be build using the drying structure.

This particular embodiment can be freely combined with drying structures that extends in a substantially upright or vertical position as described in the previous embodiments.

It is however noted that the vertical positioning may also be used without the mentioned ratio, i.e. for smaller ratios of length and width. Therefore, this particular embodiment may also be used separately from the mentioned ratio as an independent aspect of the invention.

In an embodiment of the sludge processing assembly according to the invention, the assembly may comprise a (aqueous waste) transport assembly comprising a press that is configured to be positioned in a storage tank and a pumping assembly that is configured to be positioned at an outlet of the storage tank, wherein the press and the pumping assembly are configured to cooperate to transport aqueous waste from the storage tank to other parts of the assembly, such as the forming unit or the skeleton building material supply unit.

It has been found that the aqueous waste stream can advantageously be transported throughout the assembly by using a combination of a press and a pumping assembly. This combination allows the, often paste-like, aqueous waste to be transported in an energy efficient and effective manner. To that end, the press of the transport assembly is positioned in a storage tank, and the pumping assembly is operatively connected to an outlet of the storage tank. Preferably, the pumping assembly is positioned at or near the outlet.

In use, the (aqueous waste) transport assembly has a transport state, in which the press provides a pressure on the aqueous waste in the storage tank and the pump pumps aqueous waste from the storage tank, and a loading state, in which the storage tank is loaded with aquaeous waste and preferably in which substantially no pressing and/or pumping takes place. The transport assembly is switchable between the transport state and the loading state.

In the loading state, the storage tank is filled with aqueous waste to be processed. In the loading state, the press does not exert pressure on the aqueous waste and the pumping assembly preferably is switched off. In the transport state, the press exerts a pressure, for example a mechanical, hydraulic or pneumatic pressure, on the aqueous waste, while the pumping assembly is simultaneously used to transport the aqueous waste from the storage tank by pumping.

In an embodiment according to the sludge processing assembly, the transport assembly comprises a conveyor system, preferably an overhead conveyor system.

An advantage of a conveyor system is that the drying structures, which may be positioned partially in or on a support structure, can easily be transported from the forming unit to a separate location. The conveyor system can be embodied in various ways, including for example a belt drive on which the drying structures are formed. It may also be provided as a (rail) cart system or another suitable form.

An advantage of an overhead conveyor system in particular is that it has a small footprint, especially on a ground surface, which allows a more compact assembly. This allows other equipment and/or installations to be positioned at the ground surface. Additionally or alternatively, it also may provide movement space for staff.

Another specific advantage of an overhead conveyor system is that it allows the drying structures may, by virtue of the moveable supports as part thereof, also be transported in a substantially vertical direction.

In an embodiment according to the sludge processing assembly, the overhead conveyor system may comprise a drive unit, for example an electric drive unit and/or a chain drive, to drive the conveyor.

An advantage is that only a single drive unit is required to drive the entire system.

In an embodiment according to the sludge processing assembly, the overhead conveyor system comprises a closed-loop conveyor system.

An advantage of a closed loop system is that it can be operated continuously and, in some embodiments, also substantially (semi-)automatically, which increases efficiency of the assembly. Another advantage is that only a single drive unit is required to operate the entire transport assembly.

In an embodiment according to the sludge processing assembly, the overhead conveyor system comprises coupling means for coupling a drying structure and/or a support structure to the conveyor.

An advantage of providing a coupling system is that the support structure and/or the drying structures can be attached and/or detached from the transport assembly, for example in order to perform maintenance and/or increase or decrease capacity of the sludge processing assembly. This provides a high amount of flexibility and allows a high processing efficiency.

In an embodiment according to the sludge processing assembly, the transport assembly may comprise a processing frame that is configured to cooperate with the forming unit to position and/or support one or more support structures relative to the forming unit during forming of the drying structure.

An advantage of the processing frame is that it is specifically mentioned to position the support structure relative to the forming unit to allow the support structure to be provided with the drying structure. This may include displacing a support structure towards, and preferably in front of, the forming unit and/or holding the support structure in position and/or displacing the said support structure away from the forming unit.

In an embodiment according to the sludge processing assembly, the processing frame is configured to displace the support structure in a lateral direction and/or in a height direction.

An advantage of allowing the support structure in a lateral and/or height direction is that an improved flexibility of the sludge processing assembly can be achieved.

It is noted that the processing frame may be (integral) part of the conveyor system or may be a separate frame that is operatively coupled to the conveyor system.

In an embodiment according to the sludge processing assembly, the conveyor system may comprises one or multiple transport lanes, wherein, when provided with multiple lanes, the transport lanes are positioned side-by-side or adjacent to each other and/or are positioned above each other in a stacked configuration.

The conveyor system according to the invention may be constructed in various different configurations including a single lane of multiple lanes. An advantage of providing multiple lanes is that the processing capacity is increased compared to traditional sludge processing assemblies.

The lanes may be positioned side-by-side, or at least at the same vertical level, to provide flexibility to the system. In a three-lane system, the lanes may for example be attributed to specific functions, such as applying aqueous waste, discharging aqueous waste and/or buffer capacity. These functions may also be exchangeable, for example in that an ‘buffer lane’ can also be used as a ‘discharge lane’ or ‘application lane’.

In another configuration, the lanes are positioned in a vertical direction, which means they extend above each other and preferably also substantially parallel to each other. This configuration decreases the footprint of the sludge processing assembly while maintaining a high processing capacity.

Naturally, a combination of a side-by-side and stacked configuration is also possible to even further increase capacity and efficiency of the sludge processing assembly.

Moreover, in any one configuration, the conveyor system may be adapted and/or expanded by adding lanes to an existing system. Preferably, the conveyor system is configured to allow integration of new lanes into the existing system.

It is noted that the transport assembly may also be used as a stand-alone unit. It may also be used in other applications, that which are not related to the formation of drying structures, such as transportation of aqueous waste in (existing) wastewater treatment plants WWTPs or transportation of aqueous materials for other applications.

In an embodiment according to the sludge processing assembly, the assembly may further comprise a discharge station that is configured to discharge the drying structure and/or that is configured to discharge the solids from the dried aqueous waste from the support structure.

An advantage of having a discharge system is that is may expedite the removal of (sufficiently) dried solids from the assembly. When the drying structure is manufactured completely from aqueous waste, the removal may for example be performed by removing the entire drying structure from the assembly. In case the drying structure is formed by a support structure and aqueous waste connected thereto or at least partially embedded therein, the removal may entail cleaning the support structure from the solids.

In an embodiment according to the sludge processing assembly, the discharge station may comprise one or more of: one or more brushes, a vacuum suction assembly, a hammering assembly or a shaking assembly configured to dislodge solids by tremors.

In an embodiment according to the sludge processing assembly, the assembly may further comprise a heating assembly, for example a heating assembly including a heat pump, the heating assembly being configured to provide heat to the drying structures.

An advantage of a heating assembly is that the drying process may be expedited even further. Instead of a heat pump, other sources of heat for the heat assembly, including for example waste heat, may be used.

The invention also relates to a method for drying aqueous waste streams, such as sludge, the method comprising: providing an aqueous waste stream, such as a sludge;

- forming, from the aqueous waste stream, at least one drying structure that has a length and a width, wherein the ratio of length to width is in the range of at least 3:1 ;

- drying the drying structure by evaporating moisture from the drying structure to a water content below 50%.

The method according to the invention has similar effects and advantages as the sludge processing assembly according to the invention. It is noted that the embodiments described for the sludge processing assembly can also be applied, alone or in combination, with the method according to the invention.

It is noted that the first direction in this application is to be understood as a substantially vertical and/or substantially upward direction. The vertical and/upward direction is to be viewed from a ground surface or from a base surface. The term vertical and/or upright may also be indicated in the application with synonyms as upright, which are to be understood as falling within the scope of the application. An advantage of the method according to the invention is that it provides efficient drying of sludge or other aqueous waste streams by building vertically extending structures. This is due to the fact that the vertical structures on the one hand allow a high amount of sludge or waste to be dried on a relatively small surface area, while on the other hand still provide a high amount of surface area that is in contact with the surrounding air/air stream. As a result, the moisture exchange is increased, leading to reduced drying times.

Another advantage of the method according to the invention is that the drying structures require only minimal support structures, or even no support structures at all. This reduces investment costs, such as for expensive frameworks or drying tables.

In addition, the amount of aqueous waste (in the form of the drying structures) per unit of surface area can be increased due to the fact that no space is used for support structures.

In an embodiment of the sludge processing method according to the invention, the step of providing the aqueous waste stream may comprise the step of providing an aqueous waste stream having a water content in the range of 95% or lower, preferably in the range of 70% - 90%, or may comprise the steps of: providing an aqueous waste stream having a water content of more than 90%; and

- dewatering or thickening the sludge to a moisture content of less than 95%, preferably in the 70% - 90%; and the dewatering may preferably comprise one or more of:

- dewatering by belt press;

- centrifuging the sludge; and the thickening may preferably comprise one or more of: gravity thickening; or

- centrifugal thickening.

An advantage of this particular embodiment is that the moisture content of the waste stream and/or sludge that is used to form or manufacture the drying structures is substantially constant over time. This allows the drying structures to be formed in a consistent manner.

It is noted that this embodiment is especially relevant if the moisture or water content of the aqueous waste stream to be processed differs over time. This may for example be dependent on the type of waste stream and/or the use of dewatering steps that are performed prior to using the method according to the invention.

It is preferred that the moisture content of the waste stream after application of this particular embodiment, especially the dewatering or thickening, less than 90% and preferably is in the range of 70% - 90%.

In an embodiment of the sludge processing method according to the invention, the method may further comprise adding a skeleton building material to the aqueous waste stream. An advantage of providing a skeleton building material is that the composition of the waste stream is changed. The increase in solid content (or the relative reduction in moisture content) leads to a more paste-like structure, which may simplify forming vertical drying structures. The amount of skeleton building material to be added may be used to regulate the moisture content of the aqueous waste to a desired moisture content.

Another advantage of the skeleton builder material is that it increases the consistency of the waste stream, therewith allowing (semi-)solid drying shapes and/or drying structures to be constructed with waste from the aqueous waste stream.

It is preferred that the skeleton building material is added shortly before it is subjected to the step of forming. This is particularly relevant, because the addition of the skeleton builder material increases the volume and/or weight of the waste stream. Therefore, it is advantageous to supply the material just before it enters the forming unit.

Another advantage is that the skeleton building material increases the porous structure of the waste stream, which increases the drying surface of the semi-solid drying shapes and/or drying structures.

In an embodiment of the sludge processing method according to the invention, the step of adding skeleton building material is performed prior to the step of dewatering.

An advantage of adding the skeleton building material prior to the dewatering is that the skeleton building material enhances the dewaterability.

Another advantage is that the skeleton builder is already mixed with the dewatered sludge upon entering the sludge processing assembly.

In an embodiment of the sludge processing method according to the invention, the skeleton building material is selected from the group of lime, gypsum, quicklime, coal dust, saw dust, shredded cardboard/paper, woodchips, rice husk, hay, straw, fiber material, shredded coconut shells, dry organic material, hair, bagasse and/or shredded fabric.

It was found that the abovementioned substances are highly effective in increasing the porous structure and thickening the waste stream. As a result, the waste stream can very effectively and efficiently be used in forming drying structures, especially 3D structures, such as walls, and/or elongated drying structures, including cylindrical drying columns.

A specific advantage of (quick)lime is that it stabilizes the sludge by destroying pathogens as well as that it reduces/assimilates odours from the drying structure. Another specific advantage of (quick)lime is that the reaction thereof with sludge is exothermic, which reduces the moisture content even further.

A specific advantage of saw dust and especially of coal dust is that these substances have a high energy content, which increase the overall energy content of the drying structure. As a result, a relatively high amount of energy can be generated when the drying structure is used in energy generation (after drying). In an embodiment of the sludge processing method according to the invention, the step of drying may comprise positioning the drying structure substantially upright in a drying location, such that the length of the structure, when viewed from a base or ground surface, extends in a substantially vertical direction.

An advantage of positioning the drying structure in a substantially vertical direction on the drying location, is that the surface area that is exposed to a surrounding environment, i.e. a surrounding medium such as air, is increased relative to differently, especially horizontally, positioned drying. This significantly increases the efficiency of the drying process.

Another advantage of positioning the drying structure in a substantially vertical direction on the drying location increases the amount of sludge or waste material per unit of floor surface that can be dried, and reduces the amount of space needed for drying. It is preferred that the vertical structures have the mentioned ratio of length to width.

It is however noted that the vertical positioning may also be used without the mentioned ratio, i.e. for smaller ratios of length and width. Therefore, this particular embodiment may also be used separately from the mentioned ratio as an independent aspect of the invention.

In an embodiment of the sludge processing method according to the invention, the step of drying may comprise positioning the drying structure such that the length of the structure, when viewed from a base or ground surface, extends in under an angle with said base or ground surface in a vertically upward direction, wherein the angle of the drying structure with the base or ground surface preferably is 45° to 90° and more preferably about 60°.

An advantage of positioning a drying structure under an angle is that predetermined structures can be build using the drying structure.

This particular embodiment can be freely combined with drying structures that extends in a substantially upright or vertical position as described in the previous embodiments.

In an embodiment of the sludge processing method according to the invention, the method may further comprise the step of mixing the aqueous waste.

An advantage of mixing the aqueous waste or sludge is that a uniform composition is achieved, which in turn results in a constant quality of the drying structures. This provides a common, substantially equal drying period of each drying structure. It also provides certainty that the consistency of the sludge or waste is sufficient to allow the forming the drying structures.

In an embodiment of the sludge processing method according to the invention, the mixing may alternatively comprise mixing the aqueous waste(s) with the skeleton building material.

An advantage of mixing the skeleton building material with the aqueous waste or sludge is that a uniform composition is achieved. This increases the stability of the drying structures. In addition, it also increases the overall porosity and thus surface area of the drying structures.

In an embodiment of the sludge processing method according to the invention, the step of forming the drying structure may comprise the step of extruding elongated structures of aqueous waste material, wherein the step of extruding comprises performing the extrusion in a vertical direction to form vertically extending elongated structures.

An advantage of extruding is that it is cost-efficient and can be performed in a semicontinuous manner. Another advantage of extruding is that it can be used to manufacture different shapes, such as cylindrical shapes, column-like shapes or other suitable shapes. This may for example comprise the aforementioned shapes having a circular, triangular, starshaped, polygonal, square or rectangular cross-section.

In an embodiment of the sludge processing method according to the invention, the step of forming the drying structure may comprise the step of: extruding elongated structures of aqueous waste material; positioning the elongated structures on or at least partially in a support structure to form the drying structure; and upending the support structure, such that it extends in a substantially vertical direction.

An advantage of extruding is that it is cost-efficient and can be performed in a semicontinuous manner. Another advantage of extruding is that it can be used to manufacture different shapes, such as cylindrical shapes, column-like shapes or other suitable shapes. This may for example comprise the aforementioned shapes having a circular, triangular, starshaped, polygonal, square or rectangular cross-section.

Another advantage is that, when extruding elongated structures and positioning them on a support structure, the extrusion may be performed in a horizontal plane, after which the support structures carrying the drying structures are upended to a vertical position. This allows a more efficient extrusion process to be performed. The support structure may be chosen from the group of nets, mesh, mesh sheets, timber frames, netting, such as woven or non-woven netting, textile or cloth or other suitable supports. The support structures are preferably lightweight and/or flexible structures. It may however also be (partially) rigid structures.

It is noted however that it is also possible to extrude the elongated structures of aqueous waste material and position them on a support structure to form the drying structure when the support structure is positioned in a vertical position.

In an embodiment of the sludge processing method according to the invention, the step of forming may comprise 3D printing a drying structure, such as a wall, from the aqueous waste material.

An advantage 3D printing is that it provides a high degree of freedom with respect to the shape of drying structure to be formed. Additionally or alternatively, 3D printing can be, especially when the 3D printer is mounted on a support frame, provided over a larger area, which allows the forming of multiple, preferably larger, 3D drying structures in open air.

Another advantage is that 3D printing can also be applied in (partially) closed spaces, or in support structures, such as open walled containers.

In an embodiment of the sludge processing method according to the invention, the 3D printing is performed using a 3D printer that is moveable in two directions which extend in a horizontal plane and are substantially perpendicular to each other.

In an embodiment of the sludge processing method according to the invention, the 3D printing is performed using a 3D printer that is moveable in three different directions, with the third direction, when viewed with reference to the horizontal plane, is a vertical direction.

An advantage 3D printing is that it provides a high degree of freedom with respect to the shape of drying structure to be formed. In addition, by allowing movement in three directions, positioning of the drying structure can also be more precisely controlled. This for example allows a drying structure to be formed using a moveable support and aqueous waste that is at least partially embedded therein.

In an embodiment of the sludge processing method according to the invention, the drying structure may comprise forming the drying structure on a moveable support structure, and the step of moving the moveable support structure to a drying location.

An advantage of providing a moveable support structure is that a (semi-)continuous process can be achieved by forming the drying structures and subsequently moving them to a drying location using the moveable support.

It is noted that the drying structures may also be formed by the combination of the moveable support and the aqueous waste provided thereto. This is mostly the case when the waste is at least partially embedded or provided in the moveable support.

In an elaboration of the abovementioned embodiment of the sludge processing method according to the invention, the method comprises the step of positioning the drying structures in a drying position, which may include a drying chamber and/or a drying structure such as a drying roof.

In an embodiment of the sludge processing method according to the invention, the method may further comprise the step of storing the aqueous waste in a storage tank.

An advantage thereof is that a continuous supply and/or regulated supply of aqueous waste is achieved.

In an embodiment of the sludge processing method according to the invention, the method may further comprise providing an assembly comprising a storage tank, a forming unit and a press, and wherein the method further may comprise the step of dispensing the aqueous waste from the storage tank to the forming unit, or a part thereof, that is configured to perform the forming step using the press. An advantage of dispensing the aqueous waste between the storage tank and the forming unit (or the forming outlet thereof) is that the storage tank and the forming unit do not need to be positioned adjacent or close to each other. This allows the aqueous waste to be transported (i.e. dispensed) over (larger) distance and/or allows dispensing in a more controlled manner.

The press may be a hydraulic or pneumatic press and the dispensing may be hydraulically or pneumatically dispensing.

A specific advantage of hydraulic or pneumatic dispensing is that it can provide large dispensing forces, while simultaneously being energy efficient. It is preferred that the hydraulic or pneumatic press is moveable between a loading state and a dispensing state and that the method comprises the one or more of the steps of moving the hydraulic or pneumatic press, preferably a plunger thereof, to a loading state, loading the storage tank, and subsequently moving the hydraulic or pneumatic press, preferably the plunger, to a dispensing state in which a pressure is applied to the aqueous waste in the storage tank, such that aqueous waste is dispensed to the forming unit.

In an embodiment of the sludge processing method according to the invention, the aqueous waste may be selected from the group of:

- wastewater treatment plant sludge, including industrial or municipal wastewater treatment plant sludge;

- organic slurry, such as manure, preferably animal manure, or a suspension containing microbial biomass, such as algae or other biosolids; and

- aqueous waste streams containing inorganic substances, such as drinking water treatment sludge, red mud from mining operations and/or fracking fluids.

The method according to the invention is particularly suited for processing the abovementioned aqueous waste, since these waste types have a high moisture content.

In an embodiment of the sludge processing method according to the invention, the method may comprise the step of discarding and/or discharging the at least one drying structure after drying to a predetermined moisture content of 50% or less.

The invention further relates to a sludge processing system, the sludge processing system comprising:

- a sludge processing assembly according to the invention;

- an aqueous waste supply that is operatively connected to the sludge processing assembly; and

- a discharge system that is configured for discharging dried solids from the aqueous waste after drying thereof.

The sludge processing system according to the invention has similar effects and advantages as the sludge processing assembly and the sludge processing method according to the invention. It is noted that the embodiments described for the sludge processing assembly and/or the sludge processing method can also be applied, alone or in combination, with the sludge processing system according to the invention.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

Figures 1 a and 1 b show a schematic overview of an example of an assembly according to the invention;

Figure 2 shows a schematic overview of an example of a forming unit according to the invention;

Figure 3 shows a schematic overview of a second example of a forming unit according to the invention;

Figure 4a shows a schematic top view of an example of an extruder die according the invention;

Figure 4b shows a schematic top view of examples of drying structure shapes according the invention;

Figure 5 shows a schematic overview of a third example of a forming unit according to the invention;

Figure 6 shows a schematic overview of a fourth example of a forming unit according to the invention;

Figures 7a - 7d show schematic overviews of a hydraulic press according to the invention;

Figure 8 shows a schematic overview of examples of drying structures according to the invention;

Figure 9 shows a schematic overview of an example of the method according to the invention;

Figure 10 shows a schematic overview of a second example of the method according to the invention;

Figure 1 1 shows a schematic overview of a fifth example of a forming unit according to the invention;

Figure 12 shows a schematic overview of a sixth example of a forming unit according to the invention;

Figure 13 shows a perspective view of a part of an example of a transport assembly according to the invention;

Figure 14 shows a detailed view of a part of the transport assembly according to figure 13; Figure 15a shows a detailed view of a part of a second example of a transport assembly according to the invention;

Figure 15b shows a detailed view of a part of a second example of a transport assembly according to the invention;

Figure 16 shows a side view of example of figure 15a;

Figure 17 shows a top view of a second example of the sludge processing assembly according to the invention;

Figure 18 shows a side view of the example of figure 17; and

Figures 19 to 21 shows examples of support structures according to the invention.

In an example according to the invention, assembly 2 comprises waste stream inlet 4 that is connected to mixing unit 6 by means of transport assembly 8. Transport assembly 8 is configured to transport aqueous waste A to mixing unit 6. Between waste stream inlet 4 and mixing unit 6 skeleton builder supply unit 10 is positioned, which is configured to dispense or discharge skeleton builder material S to transport assembly 8. The skeleton builder material S and aqueous waste A are transported together to mixing unit 6. Downstream of mixing unit 6, storage tank 12 is positioned, which is in turn connected to forming unit 14. In this example, the transport of mixture M between mixing unit 6 and storage tank 12 is performed using (second) transport assembly 7.

In this example, forming unit 14 is a 3D printer 16 that is moveably positioned on a moveable frame 18. Moveable frame 18 is configured for movement in transport direction T, whereas 3D printer 16 is configured for movement in direction P, which is perpendicular to transport direction T. Directions P and T in this example both extend in horizontal direction. 3D printer 16 is further configured to be moveable in direction V, which is a vertical direction. As such, forming unit 14 is capable of forming or manufacturing 3D drying structures 20, which in this example are depicted as cylindrical columns 20. In this example, storage tank 12 and 3D printer 16 are connected by means of flexible conduit 22.

Storage tank 12 is provided with hydraulic pump assembly 24, which in this example comprises hydraulically moveable closure 26, which allows the mixture M of aqueous waste A and skeleton builder material S to be discharged to 3D printer 16.

In use of assembly 2, aqueous waste A is supplied to transport assembly 8 via waste stream inlet 4. Aqueous waste A is, during transport along transport assembly 8, supplied with skeleton builder material S from skeleton builder supply unit 10 that is positioned adjacent or above transport assembly 8. The skeleton builder material S and aqueous waste A are subsequently provided to mixing unit 6 and mixed to mixture M of skeleton builder material S and aqueous waste A. After mixing, mixture M is transported, in this example via transport assembly 28, to storage tank 12. When storage tank 12 is sufficiently filled, hydraulic pumping assembly 24, in this example closure 26, is moved downwards using hydraulic pressure, which discharges mixture M via flexible conduit 22 to 3D printer 16. 3D printer 16 is positioned above a drying location 30 and starts to discharge mixture M. During discharge, 3D printer 16 moves in direction V, in this case upward, therewith forming drying structure 20 in the form of a cylindrical column. After forming a single drying structure 20, 3D printer 16 is moved to a subsequent spot to form another drying structure 20. In practice, the second drying structure 20 will be positioned adjacent first drying structure 20 with gap G in between. Gap G will allow a flow of air in between the drying structures 20. Depending on the particular set-up of forming unit 14, the second drying structure 20 may be positioned adjacent in direction P or in direction T. The forming unit 14 disclosed in figure 1 is one of several options to provide forming unit 14.

In a second example, forming unit 114 (see figure 2) comprises storage tank 112 that is support on ground or support surface U and that is provided with aqueous waste A or mixture M by means of transport assembly 107. Forming unit 114 further comprises moveable closure 126, which preferably is a hydraulically driven closure 126. Closure 126 is provided with integrated extruder die 132 that is configured to form one or more drying structures 230 from mixture M or aqueous waste A that is present in storage tank 112.

In use, storage tank 112 is at least partially filled with aqueous waste A or mixture M by transport assembly 107. Subsequently, closure 126 is, preferably under hydraulic pressure, moved downwards. As a result, drying structures 130, in this example in the form of columns, are extruded by extruder die 132. The drying structures are transported to a drying location (not shown) by means of a transport means (not shown). It is noted that the forming unit 114 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

In a third example, forming unit 214 (see figure 3) comprises storage tank 212 that is supported above support or ground surface U. Bottom surface 212a of storage tank 212 in this example comprises openings 212b that together form extruder die 232 for extruding drying structures 230. Drying structures 230 are extruded through extruder die 232 by means of pressure applied by, preferably hydraulic, pressure closure 226. After forming, drying structures 230 are positioned on support 234. Although support 234 is not part of forming unit 214, it is shown here for clarity purposes. It is noted that drying structures 220 may optionally be pressed onto, or even partially into, support 234. To that end, support 234 may for example be made of mesh material. Moveable support 234 is moved to the drying location 230. Before, during or after transport to the drying location 230, support 234 is upended by positioning assembly 236. Positioning assembly 236 may thus be positioned at any location between storage tank 212 and drying location 230. In this example, positioning assembly 236 is formed by crane 236, although any other positioning assembly suitable for upending support 234 can be used as well. Crane 236 in this example is provided with a single pivot point 236a and arm 236b provided with connecting means 238 in the form of chains 238.

It is noted that the forming unit 214 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

An example of extruder die 132, 232 is shown in figure 4a. This example shown extruder die 132, 232 in the form of, preferably metal, plate 132, 232 having a plurality of openings 132a, 232a which are used to form drying structures 130, 230. It is noted that the shapes of the drying structures, viewed in cross section, may also be different from circular. Several different shapes are shown in figure 4b, which include square, rectangular, triangular, polygonal or star-shaped shapes.

In a third example of forming unit 314 (see figure 5), forming unit 314 comprises storage tank 312 that is supplied by means of transport assembly 307 with mixture M or aqueous waste A. Forming unit 314 further comprises pressure closure 326, which preferably is hydraulically driven. Storage tank 312 further comprises outlet 340 that is connected to, in this example, a first end of flexible conduit 342. A second end of flexible conduit 342 is connected to dispensing unit 344, which is provided with a number of dispense openings 346 or dispense nozzles 346. In this example, the number of dispense openings is five, although any other number including 1 , is possible. For clarity purposes, support 334 is shown here as well. Support 334, which is a movable support 334, in this example comprises mesh 334a and frame 334b positioned around it.

It is noted that the forming unit 314 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

In use of forming unit 314, storage tank 312 is filled with aqueous waste A or mixture M after which closure 326 is pressed into storage tank 312. As a result, aqueous waste A or mixture M is pressed through outlet opening 340 into flexible conduit 342 towards dispensing unit 344. In dispensing unit 344, aqueous waste A or mixture M is divided over the number of openings 346 and dispensed onto support 334. Dispensing unit 344 can be positioned such that the dispensed aqueous waste A or mixture M is partially pressed onto or into mesh 334a. To form drying structures 320, dispensing unit 344 is moved over mesh 334b during dispensing. Preferably, the movement takes place in a straight line to form straight drying structures 320.

Subsequently, structures 334 is upended by means of (not shown) positioning assembly to a vertical position. It is positioned in a drying location in the upended or vertical position. In a fourth example of forming unit 414 (see figure 6), forming unit 414 comprises storage tank 412 that is supplied by means of transport assembly 407 with mixture M or aqueous waste A. In many respects, forming unit 414 resembles forming unit 314 of the previous example. Forming unit 414 comprises pressure closure 326, which preferably is hydraulically driven. Storage tank 412 also comprises outlet 440 that is connected to, in this example, a first end of flexible conduit 442. Although outlet 440 is positioned in a side wall of storage tank 412, it is noted that it also may be positioned in a bottom wall of storage tank 412. A second end of flexible conduit 442 is connected to dispensing unit 444, which is provided with a number of dispense openings 446 or dispense nozzles 446. In this example, the number of dispense openings is five, although any other number including 1 , is possible. For clarity purposes, support 434 is shown here as well. Support 434, which is a movable support 434, in this example comprises mesh 434a and frame 434b positioned around it. Support 434 is positioned in a vertical or upward direction z, which means that it extends over a length LS that is larger than a width WS, in vertical direction z. In this example, width WS extends in (horizontal) direction x.

It is noted that the forming unit 414 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

In use of forming unit 414, storage tank 412 is filled with aqueous waste A or mixture M after which closure 426 is pressed into storage tank 412. As a result, aqueous waste A or mixture M is pressed through outlet opening 440 into flexible conduit 442 towards dispensing unit 444. In dispensing unit 444, aqueous waste A or mixture M is divided over the number of openings 446 and dispensed onto support 434. Dispensing unit 444 can be positioned such that the dispensed aqueous waste A or mixture M is partially pressed onto or into mesh 434a. To form drying structures 420, dispensing unit 444 is moved over and/or along mesh 434b during dispensing. Preferably, the movement takes place in a straight line in direction z to form straight drying structures 420. Subsequently, support 434 is moved to a drying location for drying.

In a fifth example of forming unit 514 (see figures 7a - 7d), forming unit 514 is hydraulic press 514 that is provided with press assembly 526 and extruder die 532. In this example, storage tank 512 is a moveable storage tank 512 that is moved underneath frame 525 of hydraulic press assembly 514. Extruder die 532 is provided with extruder die openings 532a which in use form drying structures (not shown).

It is noted that the forming unit 514 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10. In use, storage tank 512 is moved in transport direction T until it is positioned underneath frame 525 and lines up with extruder die 532. Subsequently, hydraulic press assembly 526 is used to form drying structures by moving extruder die into storage tank 512. Drying structures so formed after removed by means of transport means to a drying location (not shown). After substantially all aqueous waste A or mixture M in storage tank 512 is formed into drying structures, extruder die 532 is extracted from storage tank 512, after which storage tank 512 is moved further along in transport direction T and can subsequently be used to collect a new amount of aqueous waste A or mixture M to be processed.

In a fifth example, forming unit 612 is provided with aqueous waste A or mixture M to be processed by transport assembly 607 (which is not part of forming unit 614). Forming unit 614 comprises storage tank 612, which in this example is pressure tank 612, and pressure unit 650. Storage tank 612 comprises outlet 640 and closure 652, which is configured to pressure seal storage tank 612.

In use, storage tank 612 is at least partially filled with aqueous waste A or mixture M and subsequently closed by closure 652. The aqueous waste A or mixture M is than pressed from storage tank 612 by increasing the pressure in storage tank 612 using pressure unit 650. If storage tank 612 is substantially empty, the pressure is released and closure 652 can be opened to refill storage tank 612 and renew the hydraulic pumping cycle.

It is noted that the forming unit 614 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

In a sixth example, forming unit 712 is provided with aqueous waste A or mixture M to be processed by transport assembly 707 (which is not part of forming unit 714). Forming unit 714 comprises throughput tank 712, which may also act at least partially as storage tank 712. Throughput tank 712 comprises inlet 754, outlet 740 and is provided with screw transporter 756, which is positioned in inner space 758 of throughput/storage tank 712. Screw transporter 756 is driven by means of motor 760.

In use, a continuous supply of aqueous waste A or mixture M is provided by transport assembly 707 to inlet 754 of throughput tank 712. The aqueous waste A or mixture M is transported by screw transporter 756 from inlet 754 to outlet 740 to dispense it to a dispensing unit.

It is noted that the forming unit 714 can be combined with one or more aspects of assembly 2 according to the previous example, such as (but not exclusively) mixing unit 6 and/or skeleton builder supply unit 10.

It is noted that assembly 2 according to the invention, for example by using one of the forming units, 4, 114, 214, 314, 414, 614, 714 can be used to manufacture a great variety of different drying structures 20, 120, 220, 320, 420. A number of non-limiting examples of drying structures is provided in figure 8. Figure 8 shows, in a first example, drying structure 820-1 that formed as elongated cylindrical (hollow) tube 820-1 . In a second example, drying structure 820-2 is an elongated hollow column 820-2 with a square circumference. In a third example, drying structures 920-1 and 920-2 are formed as elongated walls that extends over a predetermined distance D. For each of the examples 820-1 , 820-2, 920-1 , 920-2 as well as for all other examples of drying structures 20, 120, 220, 320, 420 according to the invention, length L is measured in (and thus extends in) a vertical direction. In this example, the vertical direction is direction z.

For the shown examples, width W is defined as the (total) wall width (or thickness) W of drying structure 820-1 , 820-2, 920-1 , 920-2. For drying structure 820-1 according to the first example, total width W is formed by width Wi plus width W2. Similarly, for drying structure 820- 2 according to the second example, total width W is formed by width W1 plus width W2. For the third example, width W of drying structure 920-1 is measured between first face 920-1 a and second face 920-1 b. For the fourth example, width W of drying structure 920-2 is measured between first face 920-2a and second face 920-2b.

In each example of drying structure 820-1 , 820-2, 920-1 , 920-2, the ratio between length L and width W, or L:W is more than 3:1 . In fact, L:W is more than 6:1 .

In other words, for drying structures 820-1 , 820-2, the width W, when viewed along direction x, is the distance W1 between a first outside wall surface and the accompanying first inside wall surface summed with the distance W2 between a second inside wall surface, that is positioned across from the first inside wall surface, and the accompanying second outside wall surface. Simply formulated W = W1 + W2. This particular formula is valid for defining width W for most hollow structures, because the hollow nature increases the available exposed wall surface.

The assembly according to the invention is aimed at providing elongated drying structures that have a high length to width ratio, because this increases the surface area of the elongated drying structure that is exposed to the surrounding environment (i.e. surrounding air). By maximizing the exposed drying surface and minimizing the surface footprint of the drying structure, a high drying efficiency is achieved.

Especially wall-like structures, such as drying structures 920-1 , 920-2, and column or ‘sausage’-shaped drying structures 20, 120, 220, 320, 420, provide a high amount of exposed surface area and a low footprint.

In a first example of method 1000 according to the invention, the method comprises the step of providing 1002 an aqueous waste stream, such as a sludge. The waste stream may comprise, for example, a water content of 90% or lower, and preferably a water content in the range of 70% - 90%. This step may optionally comprise the step of providing 1008 an aqueous waste stream having a water content of more than 90% and the step of dewatering 1010 the aqueous waste stream, such as sludge, to a moisture content of less than 90%, and preferably in the range of 70% - 90%. Method 1000 according to this example further comprises the step of forming 1004, from the aqueous waste stream, at least one drying structure that, when viewed from a support surface, extends substantially in a first direction and the step of drying 1006 the drying structure by evaporating moisture from the drying structure to a water content below 50%. Optionally, method 1000 comprises the step 1012 of discarding and/or discharging the at least one drying structure after drying to a predetermined moisture content of 50% or less.

Further optionally, method 1000 may also include the step of adding 1014 a skeleton building material to the aqueous waste stream and/or the step of mixing 1016 the aqueous waste. When step 1014 and step 1016 are both included in method 1000, the step of mixing 1016 comprises mixing 1016 the aqueous waste with the skeleton building material.

In a second example of method 2000, method 2000 includes the steps of method 1000, which steps are denominated with similar reference numbers. Method 2000 comprises the step of providing 2002 an aqueous waste stream, such as a sludge, comprising a water content less than 90%, and preferably in the range of 70% - 90%. This step may optionally comprise the steps of providing 2008 an aqueous waste stream having a water content of more than 90% and dewatering 2010 the aqueous waste stream, such as sludge, to a moisture content of less than 90%, and preferably in the range of 70% - 90%.

Method 2000 in this example further comprises the step of adding 2014 a skeleton building material to the aqueous waste stream to, inter alia, increase the solid content thereof. Method 2000 further includes the step of mixing 2016 the aqueous waste with the skeleton building material and the step of storing 2018 the aqueous waste in a storage tank. After the step of adding 2014, the sequence of storing 2018 and mixing 2016 can be performed in two different ways. In a first option, the aqueous waste stream including the skeleton building material is subjected to the step of mixing 2016 and subsequently to the step of storing 2018 the material in a storage tank. In a second option, the aqueous waste stream including the skeleton building material is stored 2018 in the storage tank and subjected to the step of mixing 2016 when present in the storage tank.

In this example, method 2000 further comprises pumping 2020, preferably hydraulically pumping 2020, the aqueous waste from the storage tank to a forming unit to perform the step of forming 2004, from the aqueous waste stream, at least one drying structure that, when viewed from a support surface, extends substantially in a first direction, which is a vertical direction.

The step of forming 2004 in this example may comprise the steps of extruding 2022 elongated structures of aqueous waste material and positioning 2024 these elongated structures on a support structure to form the drying structure. Optionally, it may also include the step of upending 2026 the support structure from a horizontal position to a vertical position, such that it extends in a substantially vertical direction. This last step is only necessary if the step of positioning 2024 has taken place on a horizontally extending support structure. The steps of extruding 2022 and positioning 2024 may also be performed on a vertically extending support structure, which obviates the need for the step of upending 2026.

The step of forming 2004 may, alternatively to the steps of extruding 2024, positioning 2024 and, optionally, upending 2026, comprise the step of 3D printing 2028 a drying structure, such as a wall from the aqueous waste material.

In this example, method 2000 the step of forming 2004 includes forming 2004 the drying structure on a moveable support structure and the step of moving 2030 the moveable support structure to a drying location. This may include positioning 2032 the drying structures in a drying position, which may include a drying chamber and/or a drying structure such as a drying roof.

In another example (see figure 13), sludge processing assembly 3002 comprises processing frame 3062, which is part of transport assembly 3064. Processing frame 3062 is configured to support, and preferably also position, support structures 3034 relative to forming unit 3014, such that aqueous waste may be applied to support structure 3034. Processing frame 3062 in this example comprises two lanes 3066a, 3066b which are positioned side-by- side with each other. Both lanes 3066a, 3066b are part of conveyor system 3066, which in this example is overhead conveyor system 3066. Each lane 3066a, 3066b comprises rail system 3068 having two rails 3068a, 3068b (see figure 14). Each support structure 3034 in this example comprises support rod (or bar) 3070 and mesh sheet 3034a that is connected thereto. Support rod 3070 is provided with coupling means 3072, which in this example are wheels 3072a, 3072b that are positionable in associated rails 3068a, 3068b of conveyor system 3066. It is noted that support rod 3070 and coupling means 3072 are omitted in figure 13 for clarity purposes.

In a second example (see figure 17, figure 18), sludge processing assembly 3002 comprises processing frame 3062 (see figures 13, 14) and forming unit 3014, the latter of which is positioned at front side 3062a of processing frame 3062. Forming unit 3014 is moveably provided in forming unit support frame 3086 and in this example can be moved in a vertical direction. Transport assembly 3064, which comprises processing frame 3062, further comprises conveyor system 3066. Conveyor system 3006 is overhead conveyor system 3066 that forms closed outer loop 3066c and further is provided with two central lanes 3066a, 3066b. Central lanes 3066a, 3066b each comprise two rails 3068a, 3068b in which the support structures 3034 are transported towards forming unit 3014 where they, in use, are provided with aqueous waste to form drying structure 3020. It is noted that support structures 3034 are moved with a support structure surface 3074 towards forming unit 3014. Outer loop 3066c comprises single rail 3076 which is operatively connected to rails 3068a, 3068b of each of central lanes 3066a, 3066b. Overhead conveyor system 3066 is in this example powered by drive unit 3078 and operated by drive chain 3080 that extends around rail 3076 of outer loop 3066c. Other drive units and/or drive systems amy however also be used.

In use of sludge processing assembly 3002, a support structure 3034 is moved towards forming unit 3014 through processing frame 3062. When support structure 3034 is positioned facing forming unit 3014, aqueous waste is supplied onto, and in some cases partially into, support structure 3034 to form drying structure 3020. Subsequently, the formed drying structure 3020 is transferred to rail 3078 of outer loop 3066c and transported along rail 3078. During transport along rail 3078, the aqueous waste is dried to form a substantially dry mass on support structure 3034. This dried mass, which comprises dried solids of the aqueous waste, is removed in discharge station 3082 (see figure 17). Cleaned support structure 3034 is subsequently fed into one of lanes 3066a, 3066b to anew receive aqueous waste to form drying structure 3020. If necessary, drying structures 3020 may be transported along rail 3078 of outer loop 3066c multiple times.

It is preferred that, especially in case drying structures are circled multiple times, discharge station 3082 is provided with sensing means 3084 that are for example capable of measuring a moisture content of the drying structure. This allows discharge station 3082 to be operated selectively based on a predetermined moisture content. In other words, discharge station 3082 is only operated if sensing means 3084 detect a moisture level that is lower than a predetermined moisture threshold thus indicating that the aqueous waste has sufficiently dried. It is noted that this second example of figure 17 may also be provided with processing frame 4064 according to figures 15a, 15b, 16 instead of processing frame 3062 of figures 13, 14.

A more detailed view of an example of discharge station 4082 is provided in figure 15b. Discharge station 4082 in this example is a vacuum-based discharge station 4082. Discharge station 4082 comprises supports 4081 that support vacuum unit 4083 that is moveable in a vertical direction along support structure 4034 to discharge the dried solids by suction. The dried solids that are sucked off are transferred via discharge channel 4085, in this example discharge tube 4085, to discharge container 4087. Discharge container 4087 may be replaced when full, or may be continuously or intermittently be emptied. It is noted that discharge station 4082 may also be used in combination with other examples and is thus not limited to use with the depicted stacked configuration as shown.

In another example (see figure 15a, 15b), lanes 4066a, 4066b are positioned above each other in a ‘stacked’ configuration. Each lane 4066a, 4066b comprises rail system 4068 having two rails 4068a, 4068b (see figure 15a, 15b). Each support structure 4034 in this example comprises support rod (or bar) 4070 and mesh sheet 4034a that is connected thereto. Support rod 4070 is provided with coupling means 4072, which in this example are wheels 4072a, 4072b that are positionable in associated rails 4068a, 4068b of conveyor system 4066.

In case of a stacked configuration (see figure 15a, 15b), processing frame 4064 (see figure 16) is preferably provided with lifting device 4088 to displace support structures 4034 between the upper lane 4066a and lower lane 4066b.

Figures 19 to 21 show various examples of support structures according to the invention. Support structure 5034 (see figure 19) comprises mesh sheet 5034a having support structure surface 5074 and coupling means 5074 that in this example are embodied as connectors 5074. In a further example (see figure 20), support structure 6034 comprises mesh structure 6034a having a coarser structure than the mesh 5034a of the example of figure 19. Mesh structure 6034a can advantageously be hooked or lifted using coupling means provided on a (not shown) conveyor system. In an even further example (see figure 21), support structure 7034 comprises a 3D mesh structure 7034a. Support structure 7034 has front facing support structure surface 7074, rear facing support structure surface 7090 and inner space 7092. In use of support structure 7034, aqueous waste can be supplied into inner space 7092 and/or can be provided on both front and rear facing support structure surfaces 7074, 7090. This structure therewith has an increased aqueous waste holding capacity compared to examples of other support structures, including support structures 3034, 4034, 5034 and 6034.

The present invention is by no means limited to the above described preferred embodiments and/or experiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.