WASTE WATER RECOVERY Field of the invention The invention relates to the field of waste water recovery. Background to the invention In the built environment, rain water run-off and waste water is typically directed into sub-surface water drainage systems, and then to water treatment plants or into rivers or the sea. Commonly, debris and particulate matter is removed from the water entering such drainage systems in sedimentation tanks known as "gully pots". It is required for gully pots (or alternative sedimentation facilities) to be periodically cleaned of debris, in order to prevent blockage of water drainage systems. Commonly, this is achieved by flushing the appropriate chamber with water in order to mobilise the contents and pumping the resulting wet waste from the chamber, usually using an appropriately equipped tanker vehicle. Typically, therefore, a tanker vehicle having a tank of clean water dispenses said water from the tank into a gully pot and pumps water contaminated with debris from the gully pot back into the tank. In addition, surface drainage channels (for example roadside gutters) are periodically cleaned of debris, in order to reduce the amount of material washed into gully pots and to prevent surface drainage channels from becoming blocked and creating a risk of localised flooding. Typically, surface drainage channels are cleaned by introducing water into the drainage channel, mixing the debris with the water using rotating brushes, thereby generating wet waste, and applying suction to remove the wet waste from the drainage channel. The wet waste comprises solids, typically comprising particles having a range of sizes. For example, the wet waste might comprise gravel and stones in addition to smaller particulates such as sand, and/or fine particulates such as silts. Wet waste from the built environment may comprise other solids such as small metal objects (screws, bolts and the like), litter, particles scrubbed from vehicle tyres, worn brake pad material, worn road material, etc. Wet waste additionally comprises a high water content. The wet waste material collected from surface drainage channels and from gully pots is unsuitable for disposal into landfill, due to its high water content. Typically also, the waste and any water which may be extracted from it, is contaminated (with, for example, organic chemicals such as automotive fuels and lubricants or heavy metals). Therefore, the waste must be treated prior to disposal. Not only is this treatment costly, but the water used for cleaning gullies is typically discharged into the environment following treatment and, as such, gully cleaning is both wasteful of water and expensive. Solid waste recovered from wet waste typically comprises particulates with a wide range of sizes and may comprise other types of materials such as plastics materials or metal. Solid waste recovered from wet waste is typically suitable for disposal in landfill sites. However, much of the material within solid waste is reusable and disposal in landfill is both wasteful and environmentally damaging. Facilities for sorting particulate material by particle size are known, for example in quarrying, and such apparatus has been applied to the sorting of waste material. However conventional processes consume considerable volumes of water in addition to the undesirable costs and environmental impact of transporting the solids for sorting. Therefore, there remains a need for apparatus and methods for the treatment of gully and similar wet waste that is both cost effective and water efficient. Summary of the invention According to a first aspect of the present invention there is provided a wet waste treatment facility for recovering water and sorted solid waste from wet waste comprising:

water extraction apparatus comprising an inlet for receiving wet waste, a coarse filter for filtering received wet waste and thereby retaining a retentate comprising solid waste while allowing coarse-filtered fluid to pass through, and water cleaning means for cleaning fluid waste, some or all of which is coarse-filtered fluid which has been discharged by the coarse filter, to thereby produce cleaned water;

waste washing and sorting apparatus having a waste inlet for receiving solid waste, a water inlet for receiving water, and washing apparatus for washing at least some of the said received solid waste using said received water, to thereby produce sorted solid waste; and

water transport apparatus for conducting cleaned water to the water inlet of the waste washing and sorting apparatus. Solids obtained from retantate are typically contaminated, for example with organic contaminants or dissolved organic or inorganic contaminants, and must be washed before disposal in landfill, or re-use. Use of cleaned water obtained from the wet waste to wash solid waste in the waste washing and sorting apparatus enables sorted solid waste to be recovered from the wet waste with the consumption of a minimum amount of additional water. In conventional facilities, substantial amounts of water from external sources is required to wash solid waste obtained from wet waste. Preferably, the facility further comprises solid waste transport means to transport the said retentate comprising solid waste to the waste inlet of the waste washing and sorting apparatus. The solid waste transport means may comprise a vessel for conveying solid waste, which may be mounted on a vehicle, such as a motor vehicle. The solid waste transport means may comprise a conveyor belt and/or mechanical solid waste lifting apparatus such as an Archimedes screw. The water extraction apparatus may comprise a hopper having an inlet for receiving wet waste and a coarse filter, and the solid waste transport means may comprise lifting apparatus adapted to lift and/or tip the hopper and deposit retentate through the inlet of the waste washing and sorting apparatus. Preferably, the water cleaning means further comprises an outlet from which cleaned water may be recovered. In some embodiments, the water cleaning means comprises an inlet to receive coarse-filtered fluid. Preferably, the water cleaning means is adapted to receive dirty water from the waste washing and sorting apparatus, and thereby produce cleaned water, such that, in use, sorted solid waste may be recovered from the waste washing and sorting apparatus and cleaned water may be recovered from the outlet of the water cleaning means. Accordingly, the facility is operable to enable sorted solid waste and cleaned water to be recovered from wet waste. Dirty water produced by washing the solid waste is, in use of conventional facilities, required to be recovered and further processed elsewhere. Typically, in use of conventional facilities, coarse-filtered fluid waste is also required to be recovered and further processed elsewhere. Thus, the facility according to the present invention advantageously eliminates the need to transport waste water for further processing. In some embodiments, the water cleaning means comprises an inlet to receive dirty water through a conduit extending from the waste washing and sorting apparatus to the water cleaning means. In some embodiments, the water cleaning means comprises one or more inlets to receive water, which is typically waste water, from one or more further sources. For example the water cleaning means may be adapted to receive rain water run-off. Typically, the water extraction apparatus comprises a fluid pathway extending from the inlet for receiving wet waste to the water cleaning means, wherein the coarse filter is positioned in the fluid pathway. In some embodiments, the fluid pathway extends from the inlet for receiving wet waste to the water inlet of the waste washing and sorting apparatus, and the water cleaning means is positioned in the fluid pathway, wherein the portion of the fluid pathway between the water cleaning means and the waste washing and sorting apparatus functions as the water transport apparatus. In some embodiments, the fluid pathway extends from a water outlet of the waste washing and sorting apparatus to an inlet for dirty water of the water cleaning means. The water transport apparatus may, in some embodiments, comprise a fluid retaining vessel for receiving cleaned water from the water cleaning means and adapted to conduct cleaned water to the water inlet of waste washing and sorting apparatus. For example, the water transport apparatus may comprise a conduit releasably securable to the inlet of the waste washing and sorting apparatus. The water transport apparatus may comprise a pump for pumping cleaned water through the inlet of the waste washing and sorting apparatus. In some embodiments the water transport apparatus is mounted on a vehicle, such as a motorized vehicle. The water transport apparatus may comprise a collection tank (which may be the fluid retaining vessel), for storing water received from the water cleaning means. For example, a collection tank of water transport apparatus may be positioned between the water cleaning means and waste washing and sorting apparatus. The collection tank may be positioned in the fluid pathway. In some embodiments the water transport apparatus, the collection tank, or the fluid retaining vessel, as the case may be, may comprise an outlet from which cleaned water may be recovered. Preferably, the waste washing and sorting apparatus comprises at least one size exclusion filter and, in use, solid waste is washed and sorted into a first grade of solids and at least one second grade of solids. In some embodiments, the waste washing and sorting apparatus comprises material sorting means for extracting materials of a certain type. For example, the material sorting means may comprise a magnet for extracting ferrous materials, or a sedimentation chamber for extracting buoyant materials, such as plastics materials, or a vibrating platform, which may be a moving platform such as a conveyor, for extracting large solid particles. A first grade of solids may be re-used in different applications to a second grade of solids. For example, a first grade of solids, obtained from washed and sorted solid waste may comprise material suitable for use as sand, for example in preparation of mortar, cement or concrete, whereas a second grade of solids may comprise material for use as rubble, for example in road building. In contrast, unsorted solid waste comprising both a first and second grade of solids may only be suitable for some of these uses, or none of the uses, of washed and sorted solid waste. Thus, sorting of washed and sorted solid waste into solids of a first and second grade enables a greater proportion of the solids in the wet waste to be recovered and re-used, such that a smaller proportion of solids in the wet waste are disposed of in landfill. Washed and sorted solid waste comprising certain types of material cannot be re- used for certain applications, and must be disposed of in landfill. For example, washed and sorted solid waste comprising ferrous materials are unsuitable for use in concrete, since corrosion of such materials would limit the working lifetime of the concrete. Thus, material sorting means for removing certain materials of a certain type from the solid waste enables a greater proportion of the solids from wet waste to be recovered and re-used, such that a smaller proportion of solids in the wet waste are disposed of in landfill. In some embodiments, the waste washing and sorting apparatus comprises chemical treatment means. For example, the waste washing and sorting apparatus may comprise an inlet for mixing a chemical treatment agent, such as a flocculent, with cleaned water, such that the received solid waste is washed with a mixture of cleaned water and a chemical treatment. Preferably, the coarse filter comprises a permeable membrane filter and/or a liquid permeable solid support. Alternatively, or in addition, the coarse filter may comprise a grill or a grid, or one or more weirs. Preferably, the coarse filter functions as the flow- through filter. Preferably, the inlet for receiving wet waste comprises a ramp which slopes downwards towards the coarse filter. Preferably the ramp is configured to receive vehicles carrying wet waste. Preferably, the water cleaning means comprises at least one sedimentation chamber and may, in some embodiments, comprise two, or more than two, sedimentation chambers. In some embodiments, the water cleaning means comprises one or more upflow filters. Preferably, the one or more upflow filters are positioned to receive fluid from the at least one sedimentation chamber. Typically, the one or more upflow filters are positioned in the fluid pathway downstream of the one or more sedimentation chambers (where present) and downstream of the coarse filter. Preferably, the water cleaning means, or any component thereof (such as the or each sedimentation chamber and/or the or each upflow filter), is adapted to be readily accessed for maintenance. In some embodiments, the water cleaning means comprises chemical treatment means. The water cleaning means may comprise an inlet for mixing a chemical treatment, such as a flocculent, with coarse-filtered fluid, so as to facilitate cleaning of the coarse-filtered fluid using the chemical treatment. In some embodiments, the water extraction apparatus is gravity fed, such that water contained within wet waste flows under the influence of gravity through the coarse filter and the water cleaning means, to thereby produce cleaned water. In some embodiments, the water transport apparatus is gravity fed, such that cleaned water flows under the influence of gravity from the water cleaning means to the water inlet of the waste washing and sorting apparatus. In embodiments of the facility comprising a fluid pathway, the fluid pathway may be gravity fed. In some embodiments, a region or regions of the fluid pathway are gravity fed. A facility arranged such that, in use, fluid (such as coarse-filtered fluid and/or dirty water and/or cleaned water) moved around a portion, or portions, or all, of the facility under the influence of gravity is more energy efficient than a facility requiring the use of pumps, or other apparatus, to move fluid around the facility. Optionally, the facility comprises one or more pumps operable to pump fluid through one or more regions of the fluid pathway. Preferably, some or all of the fluid pathway is a conduit, such as a pipe. In some embodiments some or all of the fluid pathway is a gully or a gutter and may be open. In some embodiments, the facility is adapted to receive fluid waste, or water, from one or more further sources, such as rain water run-off from an area surrounding the facility, rain water run-off from the roofs of adjacent buildings, collected rain water, or run-off from vehicle cleaning operations. In some embodiments the facility is adapted to receive water from a mains water supply. For example, water from a mains water supply, and/or collected rain water, and/or cleaned water obtained from passing waste water from one or more further sources through water cleaning means, may be required to wash solid waste in the waste washing and sorting apparatus, in addition to cleaned water obtained by passing coarse-filtered fluid through the water cleaning means. Preferably, the fluid waste from one or more further sources is received by the water extraction apparatus, or the water cleaning means of the water extraction apparatus. According to a second aspect of the present invention there is provided a wet waste treatment facility for recovering water and solids from wet waste, comprising:

an inlet for receiving wet waste;

a coarse filter for filtering received wet waste and thereby retaining a retentate comprising solid waste while allowing coarse-filtered fluid to pass through; and water cleaning means comprising at least one sedimentation chamber, for cleaning coarse-filtered fluid, adapted to receive fluid waste, some or all of which is the coarse-filtered fluid which has been discharged by the coarse filter to thereby produce cleaned water and an outlet from which cleaned water may be recovered. Preferably, the facility comprises a fluid pathway extending from the inlet to the outlet. Accordingly, the invention extends to a wet waste treatment facility for recovering water and solids from wet waste, having a fluid pathway having an inlet and an outlet comprising:

a coarse filter for filtering received wet waste and thereby retaining a retentate comprising solid waste in the fluid pathway upstream of the coarse filter, while allowing coarse-filtered fluid to pass through; and

water cleaning means comprising at least one sedimentation chamber positioned in the fluid pathway downstream of the coarse filter and adapted to receive fluid waste, some or all of which is the coarse-filtered fluid which has been discharged by the coarse filter, to thereby produce cleaned water. Thus, in use, cleaned water may be recovered from the outlet of the fluid pathway, downstream of the water cleaning means. The coarse filter separates a large proportion of the solids from the wet waste, for recovery, and the water cleaning means comprising at least one sedimentation chamber removes a large proportion of remaining solids from the fluid waste, enabling separation and recovery of the cleaned water and the solids in a manner which utilises the coarse filter and sedimentation chamber or chambers of the water cleaning means most efficiently. Positioning of the water cleaning means comprising at least one sedimentation chamber in the fluid pathway downstream of the coarse filter ensures that the at least one sedimentation chamber receives, from the wet waste, only coarse-filtered fluid. Since the at least one sedimentation chamber is not required to receive wet waste directly, the rate of solids build-up in the or each sedimentation chamber is reduced and thus the required frequency with which the water cleaning means has to be emptied is also reduced. Preferably, the inlet of the wet waste treatment facility, the coarse filter and the water cleaning means together function as water extraction apparatus. Preferably, the facility further comprises waste washing and sorting apparatus having a waste inlet for receiving solid waste, and washing apparatus for washing at least some of the said received solid waste using said received water, to thereby produce sorted solid waste: and

water transport apparatus for conducting cleaned water to the water inlet of the waste washing and sorting apparatus. Preferably, the facility further comprises solid waste transport means to transport the said retentate comprising solid waste to the waste inlet of the waste washing and sorting apparatus. The coarse filter preferably retains more than 60% of the solids from the wet waste, or more than 70% or more than 80%. Coarse-filtered fluid comprises water, which may be contaminated with organic contaminants and/or inorganic contaminants, and small particulates and/or silt carried by the water. Preferably the coarse filter comprises a filter and a liquid permeable solid support. The solid support provides additional mechanical support to the filter and is typically positioned in the fluid pathway downstream of the filter. Preferably the solid support comprises shredded recycled tyres. The coarse filter may alternatively, or in addition comprise a grill or a grid, or one or more weirs. In some embodiments, the filter comprises a permeable membrane, such as a geotextile membrane. Preferably the coarse filter functions as a flow-through filter. The retentate, which may, in embodiments comprising a fluid pathway, be in the fluid pathway on the upstream surface or surfaces of the coarse filter, may be compostable. Retentate that is compostable is of sufficiently low water content as to be suitable for landfill or use as a filler, for example in the construction industry. Preferably the portion of the fluid pathway in which solids are retained by the coarse filter is adapted to enable recovery of retentate. In some embodiments the portion of the fluid pathway in which solids are retained by the coarse filter is the inlet of the fluid pathway. The inlet of the fluid pathway may be a ramp, for example a ramp providing access to the fluid pathway for vehicles to deposit wet waste and/or for vehicles to recover retentate. Thus, the portion of the fluid pathway in which solids are retained by the coarse filter is readily accessible for retentate to be removed. Ready access to this region of the fluid pathway is advantageous as a high percentage, for example more than 60%, or more than 70% or more than 80%, of the solids within the wet waste are retained by the coarse filter, which are therefore required to be recovered on a regular basis. In some embodiments, one or more regions, or all, of the fluid pathway are gravity fed, such that fluid flows through the fluid pathway to the outlet under the influence of gravity. Preferably, the fluid pathway is gravity fed, such that water contained within the wet waste introduced through the inlet flows through the fluid pathway to the outlet under the influence of gravity. Preferably the water cleaning means comprising the at least one sedimentation chamber is positioned lower than the coarse filter, such that coarse-filtered fluid drains from the coarse filter into the at least one sedimentation chamber. Optionally, the facility comprises one or more pumps operable to pump fluid through one or more regions, or all, of the fluid pathway. In some embodiments, the water cleaning means comprises two, or more than two, sedimentation chambers. Preferably, the water cleaning means comprises one or more upflow filters. Preferably, the one or more upflow filter is positioned to receive fluid from the at least one sedimentation chamber. Typically, the one or more further upflow filters are positioned in the fluid pathway (where present) downstream of the sedimentation chamber or chambers. In embodiments having a plurality of sedimentation chambers, the or each upflow filter may be positioned in the fluid pathway downstream of the plurality of sedimentation chambers, or one or more upflow filters may be positioned in the fluid pathway between sedimentation chambers. Preferably, the or each sedimentation chamber and/or the or each upflow filter is adapted to be readily accessed for maintenance. For example, the or each sedimentation chamber may be an open tank, with access provided from above to remove sediment from the tank. Alternatively, the or each sedimentation chamber may be provided with an access port. The or each upflow filter may similarly be provided with an access port or, alternatively, may be positioned in an open region of the fluid pathway, in order to provide access to replace or clean the or each filter. Preferably the or each upflow filter is adapted to remove very fine particulate matter and/or organic contaminants such as hydrocarbon contaminants and/or inorganic contaminants such as heavy metals or chloride contaminants. For example, the or each upflow filter may comprise MyCelx® filter material (MyCelx is a Trademark of MyCelx Technologies Corporation, Gainesville, USA). In some embodiments having a plurality of upflow filters, each said upflow filter comprises the same filter material. Alternatively, two or more filters may comprise different types of filter material. For example, a first upflow filter may comprise filter material adapted to remove organic contaminants, and a second upflow filter may comprise filter material adapted to remove inorganic contaminants. The effectiveness of any given filter degrades if the filter becomes clogged with particulate matter. Particulate matter having a density greater than water may become trapped by the filter material of an upflow filter, during the treatment of a load of wet waste. A particular advantage of upflow filters is that, when such trapped particular matter again comes into contact with water, for example when a subsequent load of wet waste is introduced into the fluid pathway, any particulate matter which is re-mobilised tends to fall under the influence of gravity away from the filter. This "self-cleaning" of upflow filters renders them less prone to blockage by particulate matter (as might typically be present in the coarse-filtered fluid) than other filter arrangements. The provision of one or more sedimentation chambers upstream of each said upflow filter also ensures that waste impinging the upflow filter carries reduced levels of particulates, as compared to the levels present in unfiltered wet waste or coarse- filtered fluid. Advantageously, the cleaned water recovered from the outlet may be re-used without the requirement for further treatment, whereas water from wet waste processed by known wet waste treatment facilities is required to be further processed prior to disposal into the environment or re-use, and this is typically conducted in another facility or by another process. In some embodiments, the wet waste treatment facility further comprises a collection tank adapted to receive cleaned water from the outlet. Alternatively, or in addition, the wet waste treatment facility further comprises one or more pumps, adapted to receive cleaned water from the outlet. For example, in embodiments wherein the inlet of the fluid pathway comprises a ramp for enabling vehicles to deposit wet waste into the fluid pathway, water may be pumped from the outlet of the fluid pathway into a vehicle located at the ramp. Advantageously, the wet waste treatment facility is thereby operable to recover solids and to recycle water. For example, in use, a vehicle carrying wet waste may deposit wet waste at the inlet of the fluid pathway and receive cleaned water pumped from the outlet of the fluid pathway. An arrangement of this type obviates the requirement for the vehicle to discharge wet waste at one location and receive water at a second location. In some embodiments, fluid waste enters the fluid pathway from one or more further sources. For example, rain water run-off from an area surrounding the waste treatment facility, rain water run-off from the roofs of adjacent buildings, or run-off from vehicle cleaning operations. The fluid waste from one or more further sources may enter the fluid pathway at the inlet of the fluid pathway, upstream of the coarse filter or or upstream of the water cleaning means, or by the water cleaning means upstream of at least one sedimentation chamber, or upstream of the at least one upflow filter (where present), or at any other part of the fluid pathway. In embodiments where fluid waste enters the fluid pathway from one or more further sources, the fluid pathway may further comprise overflow filters or fluid bypass means, such as those disclosed in WO 2006/114621. The flow of fluid in the fluid pathway resulting from these additional sources may be subject to sudden changes. The provision of overflow filters and/or fluid bypass means enable the fluid pathway to receive sudden high volumes of fluid waste. Optionally, the fluid pathway may comprise one or more sensors for detecting flow of fluid through the bypass means and/or overflow filters (where present) or alternatively, or in addition, to detect levels of contaminants in the water. Preferably some or all of the fluid pathway is a fluid conduit such as a pipe. Some or all of the fluid pathway may be a gully or a gutter and may be open. In some embodiments open portions of the fluid pathway are protected by mesh or a grill, to prevent ingress of particulate material, for example from rain water run-off. Preferred and optional features of the first aspect correspond to preferred and optional features of the second aspect. Preferred and optional features of the second aspect correspond to preferred and optional features of the first aspect. According to a third aspect of the present invention, there is provided a mobile wet waste treatment facility for recovering water and solids from wet waste, comprising: an inlet for receiving wet waste;

a coarse filter for filtering received wet waste and thereby retaining a retentate comprising solid waste while allowing coarse-filtered fluid to pass through; and water cleaning means comprising at least one sedimentation chamber, for cleaning coarse-filtered fluid, adapted to receive fluid waste, some or all of which is the coarse-filtered fluid which has been discharged by the coarse filter to thereby produce cleaned water and an outlet from which cleaned water may be recovered. According to a fourth aspect of the present invention, there is provided a mobile wet waste treatment facility for recovering water and solids from wet waste, having a fluid pathway comprising a coarse filter and at least one sedimentation chamber, wherein the coarse filter is adapted to receive wet waste and retain solids therefrom and to discharge coarse-filtered fluid, and wherein the at least one sedimentation chamber is positioned in the fluid pathway downstream of the coarse filter and adapted to receive fluid waste, some or all of which is the coarse-filtered fluid which has been discharged by the coarse filter. Preferably, the mobile wet waste treatment facility comprises a fluid pathway extending from the inlet to the outlet. Accordingly, the invention extends to a mobile wet waste treatment facility for recovering water and solids from wet waste, having a fluid pathway with an inlet and an outlet comprising:

a coarse filter for filtering received wet waste and thereby retaining a retentate comprising solid waste in the fluid pathway upstream of the coarse filter, while allowing coarse-filtered fluid to pass through; and

water cleaning means comprising at least one sedimentation chamber positioned in the fluid pathway downstream of the coarse filter and adapted to receive fluid waste, some or all of which is the coarse-filtered fluid which has been discharged by the coarse filter, to thereby produce cleaned water. Preferably, the mobile wet waste treatment facility is adapted to be installed on a trailer. For example, the mobile wet waste treatment facility may be adapted to be installed on a flat bed trailer and transported by road. Accordingly, the invention also extends to a vehicle, or a vehicle trailer, having a said mobile wet waste treatment facility according to the third or fourth aspects thereon. The coarse filter preferably retains more than 60% of the solids from the wet waste, or more than 70% or more than 80%. In some embodiments having a plurality of upflow filters, each said upflow filter comprises the same filter material. Alternatively, two or more filters may comprise different types of filter material. Preferably the coarse filter comprises a filter. The coarse filter may alternatively, or in addition comprise a grill or a grid, or one or more weirs. In some embodiments, the filter is a water permeable membrane, such as a geotextile membrane. Preferably the coarse filter comprises a filter and a liquid permeable solid support. The solid support provides additional mechanical support to the coarse filter and is typically positioned in the fluid pathway downstream of the filter. Preferably the solid support comprises shredded recycled tyres. The retentate, which may be retained on the upstream surface or surfaces of the coarse filter, may be compostable. Preferably the portion of the fluid pathway in which solids are retained by the coarse filter is adapted to enable recovery of retentate. In some embodiments the portion of the fluid pathway in which solids are retained by the coarse filter is the inlet. The inlet may be a container, for example a skip operable to receive wet waste. Preferably the container is removably secured to the mobile wet waste treatment facility. For example, the container may be removed from the mobile wet waste treatment facility (which may be a trailer) in order to receive wet waste and/or to recover solids retained therein. Preferably the container comprises the coarse filter. In some embodiments, one or more regions, or all, of the fluid pathway are gravity fed. Optionally, the facility comprises one or more pumps operable to pump fluid through one or more regions, or all, of the fluid pathway. Preferably, the fluid pathway is gravity fed, such that water contained within wet waste introduced into the inlet of the fluid pathway flows through the fluid pathway to the outlet under the influence of gravity. Preferably the water cleaning means comprising the at least one sedimentation chamber is positioned lower than the coarse filter, such that coarse-filtered fluid drains from the coarse filter into the at least one sedimentation chamber. In some embodiments, one or more regions, or all, of the fluid pathway are gravity fed, such that fluid flows through the fluid pathway to the outlet under the influence of gravity. Preferably, the fluid pathway is gravity fed, such that water contained within the wet waste introduced through the inlet flows through the fluid pathway to the outlet under the influence of gravity. Preferably the water cleaning means comprising the at least one sedimentation chamber is positioned lower than the coarse filter, such that coarse-filtered fluid drains from the coarse filter into the at least one sedimentation chamber. Optionally, the facility comprises one or more pumps operable to pump fluid through one or more regions, or all, of the fluid pathway. In some embodiments, the water cleaning means comprises two, or more than two, sedimentation chambers. Preferably, the water cleaning means further comprises one or more upflow filters, positioned in the fluid pathway downstream of the sedimentation chamber or chambers. In embodiments having a plurality of sedimentation chambers, the or each upflow filter may be positioned in the fluid pathway downstream of the plurality of sedimentation chambers, or one or more upflow filters may be positioned in the fluid pathway between sedimentation chambers. Preferably, the or each sedimentation chamber and/or the or each upflow filter is adapted to be readily accessed for maintenance. For example, the or each sedimentation chamber may be an open tank, with access provided from above to remove sediment from the tank. Alternatively, the or each sedimentation chamber may be provided with an access port. The or each upflow filter may similarly be provided with an access port or, alternatively, may be positioned in an open region of the fluid pathway, in order to provide access to replace or clean the or each filter. Preferably the or each upflow filter is adapted to remove very fine particulate matter and/or organic contaminants and/or inorganic contaminants such as heavy metals or chloride contaminants. For example, the or each upflow filter may comprise MyCelx® filter material. Preferably, water is recovered from the outlet. Advantageously, water having passed through the coarse filter and the at least one sedimentation chamber and the at least one upflow filter (where present) is re-useable. Preferably, the mobile wet waste treatment facility further comprises one or more pumps, adapted to receive cleaned water from the outlet. One or more pumps may be adapted to pump cleaned water from the outlet to a tank, which may be a tank installed on a vehicle. Alternatively, or in addition, one or more pumps may be adapted to pump wet waste from a vehicle carrying wet waste and to introduce said wet waste to the inlet. The mobile wet waste treatment facility may be adapted to receive wet waste from a vehicle carrying wet waste, and pump cleaned water to a vehicle having a water tank (which may be the same vehicle) and thereby recover solids and recycle water from the wet waste. Preferably some or all of the fluid pathway is a fluid conduit such as a pipe. Some or all of the fluid pathway may be a gully or a gutter and may be open. Further preferred and optional features of the mobile wet waste treatment facility of the third and fourth aspect correspond to preferred and optional features of the wet waste treatment facility of the second aspect. According to a fifth aspect of the present invention there is provided a method for recovering solids and water from wet waste, comprising the steps of:

passing the wet waste through a coarse filter, thereby retaining a retentate comprising solid waste;

recovering at least some of the said retained solid waste;

receiving coarse-filtered fluid which has been extracted from the wet waste by the coarse filter; and

passing coarse-filtered fluid through water cleaning means, to thereby produce cleaned water. Preferably, the coarse filter and the water cleaning means together function as water extraction apparatus having an inlet for receiving wet waste, and the method comprises the step of introducing wet waste to the inlet of the water extraction apparatus. In some embodiments, the method comprises the step of introducing wet waste to the inlet from a vehicle carrying wet waste. Preferably, the method comprises the further steps of:

transporting solid waste retained by the coarse filtering means to waste washing and sorting apparatus; and

washing the recovered solids in the waste washing and sorting apparatus with cleaned water, to thereby produce sorted solid waste. In some embodiments, the method comprises the step of transporting the said solid waste to waste washing and sorting apparatus in a vessel for conveying solid waste, which may be mounted on a vehicle, such as a motor vehicle. In some embodiments, the method comprises the step of transporting the said solid waste to waste washing and sorting apparatus using solid waste transport means, such as a conveyor belt and/or weight lifting apparatus such as an Archimedes screw. In some embodiments, the water extraction apparatus comprises a hopper and lifting apparatus adapted to lift and/or tip the hopper, and the method comprises the steps of introducing wet waste to water extraction apparatus comprising a hopper, lifting and/or tipping the hopper so as to deposit retentate into an inlet of waste washing and sorting apparatus. Preferably, the method comprises the step of receiving dirty water obtained by washing recovered solids in the waste washing and sorting apparatus with cleaned water, from the waste washing and sorting apparatus, and passing dirty water through the water cleaning means, to thereby produce cleaned water. The method may comprise the step of recovering cleaned water from an outlet of the water cleaning means. The method may alternatively, or in addition, comprise the step of recovering sorted solid waste from the waste washing and sorting apparatus. In some embodiments, the method comprises the steps of receiving cleaned water from the water cleaning means to a fluid retaining vessel, and introducing cleaned water from the fluid retaining vessel to waste washing and sorting apparatus. Preferably, the method comprises the step of washing solid waste with cleaned water in the waste washing and sorting apparatus comprising at least one size exclusion filter, to thereby wash and sort the solid waste into a first grade of solids and at least one second grade of solids. In some embodiments, the method comprises the step of extracting material of a certain type from solid waste in the waste washing and sorting apparatus. For example, ferrous material may be extracted using a magnet, and/or plastics material may be extracted using waste washing and sorting apparatus comprising a sedimentation chamber, and/or large solid particles may be extracted using waste washing and sorting apparatus comprising a vibrating platform, which may be a moving platform such as a conveyor. Preferably, the method comprises the step of passing coarse-filtered fluid through water cleaning means comprising at least one sedimentation chamber. In some embodiments, the method comprises the step of passing the waste through water cleaning means comprising two, or more than two, sedimentation chambers. Preferably the coarse filter comprises a filter and alternatively, or in addition, a grill or a grid, or one or more weirs. In some embodiments, the coarse filter comprises a permeable membrane, such as a geotextile membrane. In some embodiments, the coarse filter comprises a liquid permeable solid support. Preferably the solid support comprises shredded recycled tyres. Preferably, the method comprises the step of passing the waste through water cleaning means comprising one or more upflow filters. In some embodiments comprising the steps of passing the waste through water cleaning means comprising a plurality of upflow filters, each said upflow filter comprises the same filter material, or two or more filters may comprise different types of filter material. In some embodiments, the method comprises the step of receiving cleaned water from an outlet of water extraction apparatus (which may be an outlet of water cleaning means). The cleaned water may be received into a collection tank or, in some embodiments, the cleaned water is received into water transport apparatus for conducting cleaned water to the water inlet of waste washing and sorting apparatus. Alternatively, or in addition, the method comprises the step of pumping the cleaned water from the outlet, or a collection tank (as the case may be). In some embodiments the method comprises the step of receiving wet waste from a vehicle carrying wet waste, for example a vehicle comprising a tank for holding wet waste or fluid. In some embodiments, the method comprises the step of pumping water to a vehicle adjacent to the inlet of the water extraction apparatus, which may be a vehicle from which wet waste was introduced to the inlet, such that the method is a method of recovering solids and recycling water from wet waste. In some embodiments, the method comprises the step of introducing fluid waste from one or more further sources to one or more of:

the inlet, the coarse filter, the water cleaning means and the waste washing and sorting apparatus. In some embodiments, the method comprises the step of introducing fluid waste from one or more further sources (for example, rain water from the surrounding area, rain water run-off from the roofs of adjacent buildings, or run-off from vehicle cleaning facilities) to the fluid pathway. Further preferred and optional features of the fifth aspect of the invention correspond to those disclosed in relation to the first to fourth aspects of the invention. By wet waste we mean waste comprising solids (typically having a distribution of sizes and typically comprising fine particulates) and having a water content above the threshold allowable for disposal of waste in landfill. Typically, the water component of wet waste is contaminated, for example with organic contaminants and/or other contaminants such as dissolved contaminants (for example metal salts). By cleaned water, we mean water having been cleaned by water cleaning means so as to remove all, or a substantial proportion, of particulates. Fluid introduced to water cleaning means may additionally, or alternatively, be contaminated with organic contaminants and/or other contaminants such as dissolved contaminants (for example metal salts), and cleaned water may be water having been cleaned by water cleaning means so as to remove all, or a substantial portion, of the organic or other contaminants. Description of the Drawings An example embodiment of the present invention will now be illustrated with reference to the following Figures in which: Figure 1 is a schematic diagram of a wet waste treatment facility according to the present invention. Figure 2 is a perspective view of a mobile wet waste treatment facility according to the present invention. Figure 3 is a schematic diagram of a further embodiment of a wet waste treatment facility according to the present invention. Detailed Description of an Example Embodiment Figure 1 schematically depicts a wet waste treatment facility 1. The facility comprises an entrance ramp 3, a loading area 5 and a downward sloping loading ramp 7. The loading area and loading ramp are confined within a water-retaining wall 9. A coarse filter assembly 11 is positioned at the base of the loading ramp and within the water retaining wall. The coarse filter assembly comprises a solid support of shredded, recycled tyres, surrounded by a geotextile membrane on the faces 12 adjacent to the loading ramp. Drainage pipes 13 connect the coarse filter assembly to conduit 15, which leads to a sedimentation chamber 17. The sedimentation chamber comprises a filter basket 19 positioned to receive fluid exiting the conduit, and a pierced pipe 21 positioned above the base of the sedimentation chamber. Conduit 23 connects the pierced pipe and upflow filter chamber 25, which comprises upflow filter 27. The upflow filter entirely covers the internal cross section of the upflow filter chamber and comprises MyCelx® hydrocarbon-contamination removing filter material. Outlet pipe 29 leads from the upflow filter chamber, above the upflow filter, to outlet valve 31 , via pump 33. Thus a continuous fluid pathway is provided between the loading ramp and the outlet. Overflow pipe 37 is connected to conduit 23, between the pierced pipe and the upflow filter chamber, and is connected to overflow filter 39, within the sedimentation chamber. Sedimentation chamber 17 is provided with access port 41 , positioned above the filter basket, and access port 43, positioned above the overflow filter. Upflow filter chamber 25 is similarly provided with access port 45. Fluid waste conduit 47 is positioned to direct rain water run-off collected by a drainage system (not shown) into the filter basket. Optionally, the sedimentation chamber may be adapted to receive fluid waste (via additional fluid waste conduits), from other sources, such as from vehicle cleaning operations in the vicinity of the wet waste treatment facility (not shown). In use, wet-waste carrying vehicles (which may be gully cleaners) are driven onto the loading area 5 and wet waste is deposited onto loading ramp 7. The wet waste flows down loading ramp 7 and impinges upon the coarse filter assembly 11. Solids within the wet waste are retained upstream of faces 12, by the geotextile membrane. Coarse-filtered fluid (typically comprising small particulates, or silt, carried within contaminated water) passes through the solid support and is retained within water- retaining walls 9 until it drains through drainage pipes 13 and along conduit 15, under the influence of gravity. The coarse-filtered fluid is directed by conduit 15 into the sedimentation chamber 17, at filter basket 19. Filter basket 19 serves to diffuse the flow of fluid into the sedimentation chamber and reduce turbulence, thereby facilitating sedimentation of small particulates 49 from the water. The water, which may be contaminated (for example with hydrocarbons, or heavy metals, or chlorides) exits the sedimentation chamber, under the influence of gravity, through pierced pipe 21 (which may additionally be covered with a geotextile membrane), along conduit 23 and into upflow filter chamber 25. The water then flows through upflow filter 27, comprising MyCelx® filter material, wherein hydrocarbon contamination is removed, and cleaned water exits the upflow filter chamber through outlet pipe 29. Thus, the sedimentation chamber, upload filter chamber and associated apparatus together function as water cleaning means 4 and the water cleaning means, together with the loading ramp, water-retaining wall, coarse filter assembly and the drainage pipes together function as water extraction apparatus 2. The cleaned water is recycled into the gully cleaner vehicle connected to the fluid pathway at outlet valve 31 , under the influence of pump 33. In alternative embodiments, outlet pipe 29 directs the cleaned water to a storage tank. The solids retained at the coarse filter assembly are compostable (that is to say that their water content is sufficiently low for their use as building material, or their disposal as landfill) and are recovered from the loading ramp, such that the loading ramp is cleared in order to receive further wet waste. Most of the solids from the wet waste are retained by the coarse filter assembly, at the surface where they can be easily removed. This arrangement is more convenient and energy efficient than, for example, removal of such solids from a chamber (such as sedimentation chamber), which may be below ground level. Removal of solids from a chamber typically requires special apparatus, such as pumping or lifting apparatus, and may consequently be both time consuming and use additional energy, in comparison to the removal of solids from an open part of the fluid pathway, such as the loading ramp. Over time, the sedimentation chamber fills with small particulates 49 and restricts the flow of water into the pierced pipe. Access port 41 provides access to the sedimentation chamber to facilitate the removal of small particulates and, optionally, replacement or cleaning of the filter basket. Similarly, over time, the upflow filter will become saturated and access port 45 provides access to replace the upflow filter. The removal of the majority of solids from the wet waste by the coarse filter assembly upstream of the sedimentation chamber ensures that the frequency with which the sedimentation chamber fills with small particulates, and that the upflow filter requires maintenance, is reduced in comparison to arrangements lacking a coarse filter assembly. The flow of fluid waste from rain water run-off into the sedimentation chamber through fluid waste conduit 47 is variable and, for example in storm conditions, the flow of fluid through the sedimentation chamber and into the upflow filter chamber may exceed the maximum flow rate of the pierced pipe 21. In this case, water, which may be contaminated or carry higher than normal levels of silt (the increased flow permitting less time for sedimentation to occur), passes through overflow filter 39 through overflow pipe 37 and into conduit 23. In this condition, overflow filter 39 performs the same function as the pierced pipe. When the flow rate falls below the maximum flow rate of the pierced pipe, circulation of water through the overflow pipe stops and the wet waste treatment facility returns to normal operation. Access port 43 provides periodic access, for maintenance, to the overflow filter. Figure 2 shows a mobile wet waste treatment facility 100, comprising a vehicle trailer 101 , on which is removably mounted a skip 103, a sedimentation chamber 117 and an upflow filter chamber 125. The sedimentation chamber 1 17 and upflow filter chamber 125 are analogous to the sedimentation chamber 17 and upflow filter chamber 25 described in relation to Figure 1 , but lacking an additional waste water conduit, overflow pipe and overflow filter. The mobile wet waste treatment facility additionally comprises a second sedimentation chamber 118 and a second upflow filter chamber 126, analogous to chambers 117 and 125. A drainage pipe 113 and conduit 115 extend under trailer 101. Additionally, a pump 133 is positioned in line with conduit 115 and is operable to pump fluid into sedimentation chamber 117, and around the fluid pathway to outlet valve 131. The skip comprises a mesh 111 which functions as a coarse filter. In alternative embodiments, the skip comprises a coarse filter assembly analogous to coarse filter assembly 11 , discussed above. A drain port 112 is positioned in the base of the skip and is releasably connectable to the drainage pipe 113. Connection of the drain port 112 to the drainage pipe provides a fluid pathway between the conduit 115 and the skip. In alternative embodiments, a drain pipe extends into the skip from above and provides a fluid pathway between the skip and the sedimentation chamber 117 via a pump. In use, wet waste is placed in the loading region 107 of the skip 103. Typically, wet waste is pumped into the skip from a gully cleaner. Optionally, the skip may be demounted from the trailer, using hydraulic lifting apparatus 102, such that the skip may be positioned to facilitate this process, and the skip subsequently remounted on the trailer. Wet waste drains through the mesh 111 and solids 132 are retained in loading region 107. Coarse-filtered fluid 134 drains through drain port 112, drainage pipe 113 and into conduit 115 and is pumped by pump 133 into sedimentation chamber 117. Fluid passes through sedimentation chamber 117 and upflow filter chamber 125, in the manner described in relation to sedimentation chamber 17 and upflow filter chamber 25, above. Additional waste treatment is provided by second sedimentation chamber 118 and second upflow filter chamber 126, and the cleaned water may optionally be stored in the second sedimentation chamber until required. In an alternative embodiment, a collection chamber appears in place of the second sedimentation chamber. Cleaned water is directed from the second upflow filter chamber 126 through outlet pipe 129 and is pumped, by outlet pump 130, to a gully cleaner (or a tank) via outlet valve 131. Figure 3 shows a further embodiment of the wet waste treatment facility 200 of the present invention, comprising water extraction apparatus 202 having water cleaning means 204. The water extraction apparatus is substantially as described in relation to the embodiment of Figure 1 , and comprises a loading area 205, a loading ramp 207 and a coarse filter assembly 211 made of shredded recycled tires covered in a geotextile membrane, all bounded by water retaining walls 209. The water cleaning means comprises a sedimentation chamber 217, containing filter basket 219 and a pierced pipe 221. The pierced pipe is connected to an upflow filter chamber 225 by a conduit 223. The upflow filter chamber contains an upflow filter 229. The water extraction apparatus is connected to the water cleaning means by conduit 215. Conduit 232 connects the outlet 230 of the water cleaning means to the inlet 234 of the waste washing and sorting apparatus 236. Pump 233 is positioned in line with conduit 232 and is operable to pump fluid along conduit 232. Valve 238 (also positioned in line with conduit 232) is operable to divert some or all of the flow of fluid along conduit 232 through conduit 240 outlet 241. The waste washing and sorting apparatus comprises a water retaining chamber 242 with a sloping base 244, configured such that the fluid entering the chamber 242 through inlet 234 flows to the outlet 246, through size exclusion filters (247,248,249) positioned across the chamber 242. The size exclusion filters (247,248,249) are adapted to retain solids with particle sizes above a predetermined threshold whilst permitting solids below that threshold to pass through. Conduit 250 connects the outlet 246 of chamber 242 to conduit 215 upstream of the inlet to the water cleaning means. In the embodiment shown, pump 252 is positioned in line with conduit 250 and is operable to pump fluid therein, however in other embodiments the portion of the fluid pathway extending from inlet 234 to the inlet of the water cleaning means, and/or to the outlet 230 of the water cleaning means is gravity fed. In some embodiments, conduit 240 and outlet 241 are positioned upstream of pump 233. In use, wet waste is deposited onto the loading ramp and solids within the wet waste 260 are retained by the coarse filter assembly. Coarse-filtered fluid from the wet waste, typically comprising small particulates, such as fine silt, and contaminated water drains through conduit 215 and into the filter basket in the sedimentation chamber of the water cleaning means. The fluid permeates out of the filter basket and into the sedimentation chamber, where the majority of the small particulates 218 collect. Contaminated water then flows to the upflow filter chamber through the perforated pipe and the conduit 223 under the influence of gravity. The contaminated water then flows up through the upflow filter and cleaned water is pumped out of the water cleaning means through outlet 230 by pump 233 along conduit 232 and into the waste washing and sorting apparatus via inlet 234. Solid waste 260 is transported to the waste washing and sorting apparatus and deposited in chamber 242 upstream of size exclusion filter 247, as indicated by A. A flow of cleaned water washes the solids against size exclusion filter 247. Solids 261 having particle sizes above a first threshold are retained upstream of size exclusion filter 247, and the remaining solids pass through the filter and are carried by the flow of water to size exclusion filter 248. Solids 262 having particle sizes above a second threshold (which is smaller than the first threshold) are retained upstream of size exclusion filter 248 and the remaining solids pass through the filter and are carried by the flow of water to size exclusion filter 249. Similarly, solids 263 having the particle size above a third threshold (which is smaller than the second threshold) are retained upstream of size exclusion filter 249 and solids 264 are retained within the chamber 242, downstream of size exclusion filter 249. Washed and sorted solids (261 ,262,263,264), which have been sorted by size, may be recovered from chamber 242 and reused. In other embodiments (not shown) the waste washing and sorting apparatus comprises a conveyor belt to convey solids along at least a part of A, and an electromagnet to extract ferrous material from the solids on the conveyor before the remaining solids are introduced into the chamber 242. Alternative embodiments may also comprise a sedimentation chamber, or other material extraction apparatus, to extract buoyant material such as plastics from the solids before the remaining solids are introduced into the chamber 242. The water used to wash and sort the solids in the waste washing and sorting apparatus is typically dirty water, contaminated with, for example, hydrocarbon materials. The dirty water is pumped along conduit 250 by pump 252 to conduit 215, upstream of the water cleaning means. Accordingly, a maximum amount of the water in the wet waste is cleaned. Cleaned water may be drawn from the facility from outlet 241 by operating valve 238. As discussed in relation to Figure 1 , the water cleaning means is adapted to receive water from one or more further sources, for example rainwater run-off may be received through conduit 270. Optionally, where additional water is required to wash and sort the solids 260, clean water from a mains supply may be introduced into the chamber 242 through conduit 272. Thus, the facility 200 is operable to recover cleaned water from outlet 241 which maybe reused, and washed and sorted solids (261 ,262,263,264), which may also be reused, from wet waste. In alternative embodiments, the facility may further comprise a water collection tank positioned in line with, or arranged to receive and discharge cleaned water from, conduit 232. Optionally, further pumps may be provided to pump water into and out of the water collection tank to the outlet 241 or the inlet 234 of the waste washing and sorting apparatus. Further variations and modifications of the embodiments disclosed herein may also be made while remaining within the scope of the following claims.