The invention relates to a method of selecting a continuous filter belt for a wastewater screening apparatus and a device for testing a sample of filter material.

Wastewater screening apparatus are known which separate solid material from wastewater and also compact the solid material for disposal. Such apparatus may be used, for example, to remove solids from a flow of sewage so that the water from the sewage can proceed to further treatment prior to discharge or reuse. The separated solids may be disposed of in landfill or be an input to additional treatment, resource or energy recovery processes.

An example of such a screening apparatus is described in US 8,302,780. US 8,302,780 describes a screening apparatus which uses a continuous filter belt to filter solid material from an aqueous mixture. The filtered solid material is removed from the filter belt and may be passed to a dewatering device in the form of a screw press which mechanically extracts liquid from the solid material through compaction.

It is desirable that the wastewater screening apparatus be configured to remove a minimum proportion of solid material from the aqueous solution. Further, the wastewater screening apparatus may have a minimum operational speed (feed rate of the filter belt) and so the filter belt should be able to achieve the required removal rate at that speed. However, determining whether a filter belt will satisfy these criteria in a specified wastewater screening apparatus or determining the correct size and configuration of a wastewater screening apparats for a specified filter belt is a difficult, expensive and time- consuming process requiring extensive testing of the wastewater screening apparatus.

It is therefore desirable to provide a method and device that addresses this issue.

According to a first aspect, there is provided a method of selecting a continuous filter belt for a wastewater screening apparatus, the method comprising: testing a sample of a filter material to determine a first average flow rate of a flow through the sample over a first period of time, wherein the first period of time is set such that the first average flow rate corresponds to a flow rate through a filter belt comprising the filter material when the belt is moving at a known first speed; providing a wastewater screening apparatus with a filter belt comprising the filter material based on the testing of the sample of the filter material.

The first speed may be a maximum speed of the filter belt, a minimum speed of the filter belt, a fixed speed of the filter belt, a mean speed of the filter belt, a median speed of the filter belt or a modal speed of the filter belt.

Testing the sample may further determine a second average flow rate through the sample over a second period of time, wherein the second period of time is set such that the second average flow rate corresponds to a flow rate through a filter belt comprising the filter material when the belt is moving at a known second speed which is different from the first speed.

The first speed may be a maximum speed of the filter belt and wherein the second speed is the minimum speed of the filter belt.

The flow through the sample of the filter material over the first period of time and the flow through the sample of the filter material between the end of the first period of time and the end of the second period of time may be collected separately and analysed so as to determine the level of filtration that has occurred during the first period of time and the second period of time.

T esting the sample may comprise locating the sample in a testing column with an influent liquid sample held above the sample of the filter material, and releasing the influent liquid sample such that it flows through the sample of the filter material.

The average flow rate through the sample may be calculated by determining the change in height of the influent liquid sample over time.

The height of the influent liquid sample may be determined using a sensor.

The height of the influent liquid sample may be determined using a pressure sensor. The first and/or second average flow rates through the sample of filter material may be determined by measuring a change in pressure at the sample of the filter material over the first and/or second period of time.

The first and/or second average flow rates through the sample of filter material may be determined by measuring a change in volume of the influent liquid sample above the material sample over the first and/or second period of time.

The method may further comprise testing the sample with a plurality of different influent liquid samples.

The influent liquid sample may have different pollutant concentrations.

The method may further comprise testing a plurality of samples of different filter materials and selecting one of the filter materials for the filter belt.

The method may further comprise determining a required size of filter belt based on the testing of the sample of the filter material.

The sample of filter material may be held stationary during testing.

According to a second aspect, there is provided device for testing a sample of filter material, the device comprising: a sample receiving portion for receiving a sample of filter material; a vessel extending upwards of the sample receiving portion for holding an influent liquid sample above the sample of filter material; a first valve configured to be selectively opened to allow the influent liquid sample to exit the vessel through the filter material; and a sensor for determining a height of the influent liquid sample above the sample of filter material.

The device may further comprise a container for receiving at least a portion of the influent liquid sample after passing through the sample of filter material.

The device may further comprise a second valve located between the container and the first valve and fluidically connected to the first valve by a conduit, wherein the first and second valves are configured to be controlled to collect another portion of the influent liquid sample in the conduit between the first and second valves. The sensor may be a pressure sensor operatively connected to a region of the vessel adjacent the sample receiving portion. For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a front perspective view of a prior art wastewater screening apparatus;

Figure 2A is a side sectional view of the apparatus of Figure 1 ;

Figure 2B is a partial sectional view of a lower portion of a filter belt thereof; Figure 3 is a front sectional view of the apparatus of Figure 1 ;

Figure 4 is a rear sectional view of the apparatus of Figure 1 ;

Figure 5 is a perspective view of a testing apparatus;

Figure 6 is a side view of the testing apparatus of Figure 5;

Figure 7 is an end view of the testing apparatus of Figure 5; Figure 8 is a flowchart of a method of preparing the testing apparatus for testing;

Figure 9 is a flowchart of a method of testing a material sample using the testing apparatus; Figure 10 is a graph produced from data gathered during the method of testing the material sample; and

Figure 11 is a further graph produced from data gathered during the method of testing the material sample.

The presently described apparatus processes wastewater to extract most of the water content leaving a semi-dry organic cake which has value in post processes. The process receives the wastewater, referred to as“dirty water” and first filters it to remove most of the liquid content and then compresses the remaining cake to extract most of the remaining water. The filtration step uses a fine mesh continuous filter belt filter cloth to capture solids and then an auger drive to press most of the remaining water out of the cake. A wash spray is directed on the back of the filter which not only washes away debris that is attached on the outside of the filter cloth, but also clears debris normally clogged within pores of the filter cloth. In the auguring step, the cake and debris is compressed, which squeezes out the remaining dirty water and the wash water. A free water drain is located at one end of an auger channel while the cake/debris are compressed and moved by the auger screw within the auger channel in the opposite direction.

The debris captured by the filter cloth is driven downwardly into an open collection chamber which delivers the debris into the auger screw which conveys the debris to a compression chamber. Wash water that is not absorbed in the debris is free to flow above and around the auger's flights and by gravity flows toward and into the free water drain. The free water drain is located in an enclosed obstructed location so that only overflow liquid is able to freely flow into the drain. By allowing this drainage, a liquid level in the collection chamber is controlled and the dewatering drain located under the dewatering section is able to drain the remainder of water absorbed in the solid debris so that the solids debris that exits the device can meet a specified moisture content.

Figure 1 illustrates a prior art industrial separator and dewatering plant 10 used for processing wastewater 15A (also referred to as a wastewater screening apparatus). Components of plant 10 are supported within and attached externally to a structural enclosure 20. Locations of a plant inlet 30 for receiving the wastewater 15A, wastewater overflow outlets 40, a wash water pump 50, an outlet 60 for filtered water 15B, and a dewatering device 70 are shown. Techniques for joining in-feed and out-feed conduits to elements 30, 40 and 60 are well known in the art.

Figure 2A shows locations of a filter belt 80 supported by bottom 205 and top 210 rollers, belt 80 being a fine mesh filter which has an upper belt portion 82 moving above a lower belt portion 84, a conveyor cavity 85 within which filter belt 80 operates, spray wash nozzle(s) 90, a belt scraper 100, a cake collection basin 110, an auger 120, collection manifold 130, a diverter panel 140, and a catch shelf 150. Wastewater inlet 30 is shown at the left in Figure 2A.

Figure 2B shows filter belt 80 as it moves around lower pulley 205 and carries wastewater 15A on upper belt portion 82 upwardly to the left with filtered water 15B shown dripping through upper belt portion 82 onto diverter pan 170 and flowing through window 172. A lower dam plate 174 prevents filtered water 15B from reaching lower pulley 205 and lower belt portion 84. An upper dam plate 176 is positioned to prevent incoming wastewater 15A, illustrated by a large arrow, from flowing past filter belt 80. Cake 15C remains on and within upper belt portion 82 and is carried upwardly.

Figure 3 shows locations of the diverter pan 170 which, for clarity, is not shown in Figure 2A, framework ribs 180 which support upper belt portion 82, and rubber gasket seals 190 and 192 which constrains filtered water 15B so it can be captured without being contaminated by cake 15A after dribbling onto pan 170. Portions of the enclosure 20, the filter belt 80, the conveyor cavity 85, and also the wash water pump 50 and the filtered water outlet 60 are also shown in Figure 3.

Figure 4 shows locations of a cylindrical wire cage 200, the top roller 210 which is shown in cross-section, a belt drive 220 of the filter belt 80, an auger drive 230, an auger overflow drain 240 for releasing wash water 15D, a dewatering drain 250 for receiving wash water 15D and extracted water 15E, and a compression door 260. Figure 4 also shows: the wastewater overflow outlet 40, filtered water collection basin 130, filtered water outlets 60, and belt scraper 100.

Plant 10 separates and dewaters wastewater 15A entering plant 10 at inlet 30. Wastewater 15A may have a total suspended solids (TSS) in the range of from about 100 to 5000 mg/L. This wastewater 15A may be collected from an industrial (i.e. non municipal) system which might have about 500 mg/L TSS. Trash, garbage and other materials usually found in wastewater drainage may be separated using a pre-filter. Downstream of pre-filter wastewater 15A enters plant 10 at inlet 30 where it encounters diverter panel 140 dropping onto catch shelf 150 whereupon it spills onto filter belt 80 as shown in Figure 2B. The diverter panel 140 and catch shelf 150 shown in Figure 2 direct the incoming wastewater 15A to filter belt 80 while absorbing most of its incoming kinetic energy. When the inflow of wastewater 15A is in excess of what belt 80 is able to accommodate, it flows out of wastewater overflow outlets 40 shown in Figure 1 and into an overflow storage tank 85 shown in Figure 7 and may be returned to plant 10 later through inlet 30. The filter belt 80 is made of a filter mesh material of a fineness selected for capturing a desired degree of the TSS carried by wastewater 15A. Once on filter belt 80 wastewater 15A drains by gravity through the top portion 82 of belt 80 and, as shown in Figure 2, falls onto diverter pan 170 and from there into alleys 172 and collection manifold 130 to then leave plant 10 via outlets 60 as filtered water 15B. Gravity drainage continues during the entire time wastewater 15A rides on belt 80, that is, as belt 80 moves upward.

A cake 15C left behind on and in filter belt 80 comprises between 40-90% of the TSS of the wastewater 15A depending on the type and fineness of the filter material of which belt 80 is made. Filter belt 80 moves continuously as an inclined rotating linear conveyor. Both upper 82 and lower 84 portions of belt 80 may be planar and may move in parallel with each other in opposite directions and over spaced apart top roller 210 and bottom roller 205 (FIGS. 2A and 2B).

As belt 80 moves over top roller 210 some portion of cake 15C may fall into cake collection basin 1 10 and therefore into auger screw 120 as best illustrated in Figure 2. As belt 80 starts to move downward wash water 15D, a high pressure low volume spray is delivered from one or more nozzles 90 against the inside of the lower belt portion 84 of belt 80 where further cake 15C is washed into cake collection basin 110. Subsequently residue of cake 15C is dislodged by scraper 100 and falls into cake collection basin 110 as well. Cake 15C and the wash water 15D is collected in auger screw 120 and conveyed thereby to the wire cage 200 as best shown in Figure 4, and as described below. Scraper 100 is in position to deflect overspray of wash water 15D into collection basin 110 which may prevent the overspray from entering conveyor cavity 85.

Cake 15C and wash water 15D are carried by auger screw 120 to the left in Figure 4 into wire cage 200 as described above, where wash water 15D drains into dewatering drain 250. Cake 15C is compacted by auger screw 120 where most of its water content 15E is extracted. Brushes 123 attached to, and extending outwardly from the flights of auger screw 120 keep the approximately 1 mm (or approximately 250 pm to 1000 pm) gaps between adjacent wires of the wire cage 200 clear so that extracted water 15E may flow freely out of wire cage 200 and into dewatering drain 250.

Overflow drain 240, located at the right end of auger screw 120 in Figure 4 removes excess wash water 15D within auger screw 120 when the level of such water rises high enough to flow around auger flights of auger screw 120 which keeps the screw 120 from flooding.

With the water extraction step described above, cake 15C is converted to a semi-solid consistency which passes out of plant 10 though door 72 when pressure within the wire cage 200 is sufficient to push open door 260 against tension springs. The semi-solid cake 15C may have a water content of between only 50% and 60%.

The auger screw 120 is mechanically rotated within auger trough 122 by an electric auger drive motor 230, as shown in Figure 4. A further drive 220 of belt 80 is also shown in Figure 4. As shown, auger trough 122 is open above auger screw 120 so that cake 15C and wash water 15D may freely fall into it from belt 80. Wash water 15D and extracted water 15E may be jointly collected into a common manifold outside of plant 10 and may have between 1500 and 5000 mg/L TSS. There are commercial uses for this water because of its high concentration of biological matter.

The filter belt 80 of the industrial separator and dewatering plant 10 is driven at variable speed so as to maintain a constant driving head (i.e. pressure head) on the filter belt 80. The wastewater 15A can therefore be in contact with the filter belt 80 for varying time periods, depending on the speed at which the filter belt 80 is driven. When the filter belt 80 is driven at its maximum speed, the wastewater 15A is in contact with the filter belt 80 for the minimum time. When the filter belt 80 is driven at its minimum speed, the wastewater 15A is in contact with the filter belt 80 for the maximum time. The longer the wastewater 15A is in contact with the filter belt 80, the more solids accumulate in or over the pores of the filter belt 80 and the slower the wastewater 15A passes through filter belt 80 (i.e. the lower the filtration rate).

The rate at which the wastewater 15A passes through the filter belt 80 is also dependent on the material used in the filter belt 80. For example, the rate at which wastewater 15A passes through a filter belt 80 made of a material having large pores will be greater than the rate at which wastewater 15A passes through a filter belt 80 made of a material having small pores. Accordingly, the quality of the filtered water 15B (i.e. the effluent) varies inversely to the treatment flow rate for a given unit size. Figure 5 shows a testing apparatus 300 for testing a sample of filter material such as that forming the continuous filter belt 80 of the wastewater screening apparatus described with reference to Figures 1 to 4. The testing apparatus 300 generally comprises a test column 302, a support structure 304 and a data logger 305. The test column 302 is supported by the support structure 304. The data logger 305 is shown schematically in Figures 5 to 7.

Figure 6 is a side view of the testing apparatus 300. The test column 302 comprises an upper tube 306 (i.e. vessel or standpipe), a coupler 308, a middle tube 310, an upper valve 312 (i.e. a first valve), a lower tube 314 and a lower valve 316 (i.e. a second valve) which are all connected in series. In this example, the upper, lower and middle tubes 306, 310, 314 are transparent and have a circular cross-sectional profile.

An upper end of the upper tube 306 forms an inlet 320 into the test column 302. A lower end of the upper tube 306 is provided with an upper filter seal 307. An upper end of the middle tube 310 is provided with a lower filter seal 309. The upper filter seal 307 and the lower filter seal 309 form a sample receiving portion. The upper tube 306 extends upwards of the upper filter seal 307 and the lower filter seal 309. The coupler 308 may be used to temporarily secure the upper filter seal 307 to the lower filter seal 309, and thus temporarily secure the upper tube 306 to the middle tube 310. A drain tube (not shown) is connected to a first through hole 311 that extends through a side wall of the upper filter seal 37. The drain tube is provided with a valve for selectively opening and closing the drain tube. A pressure sensor tube (not shown) is connected at a first end to a second through hole that extends through the side wall of the upper filter seal 37 via a fitting 315. A second end of the pressure sensor tube is attached to a pressure sensor 324. The pressure sensor 324 is in turn connected to the data logger 305 using a cable (not shown; a wireless connection between the pressure sensor 324 and the data logger 305 may also be used). The second through hole acts as a pressure tapping point. The pressure sensor 324 is configured to measure and output a signal indicative of the pressure of fluid within the test column 302 to the data logger 305. The pressure sensor 324 is provided with a bleed valve 326 for releasing air from the pressure sensor tube.

The upper valve 312 is attached to a lower end of the middle tube 310 and an upper end of the lower tube 314. The upper valve 312 is movable between an open position (as shown in Figure 6) and a closed position. When the upper valve 312 is in its open position, fluid is able to pass from the middle tube 310 to the lower tube 314. When the upper valve 312 is in its closed position, fluid is prevented from being able to pass from the middle tube 310 to the lower tube 314. A lower portion of the upper valve 312 is provided with an air relief valve 313 for venting air from the lower tube 314.

The lower valve 316 is attached to a lower end of the lower tube 314. The lower valve 316 is also movable between an open position (as shown in Figure 6) and a closed position. When the lower valve 316 is in its open position, fluid is able to pass from the lower tube 314 out of the lower end of the test column 302. Accordingly, a lower end of the lower valve 316 forms an outlet 322 out of the test column 302. When the lower valve 316 is in its closed position, fluid is prevented from being able to pass from the lower tube 314 out of the lower end of the test column 302.

Figure 7 is an end view of the testing apparatus 300 shown in Figure 6. The features of the testing apparatus 300 are denoted using corresponding reference numerals.

Figure 8 is a flowchart of a method of preparing the testing apparatus 300 for testing.

In a first step P1 of the method, the upper tube 306 is removed from the middle tube 310 by releasing the coupler 308. The upper valve 312 is closed and the lower valve 316 opened.

In a second step P2 of the method, clean water is poured directly into the middle tube 310 so as to fill the middle tube 310 with clean water.

In a third step P3 of the method, a material sample (i.e. a sample of the filter) is placed on top of the lower filter seal 309 such that the material sample extends across the entire width of the middle tube 310. The upper tube 306 is then placed onto the middle tube 310 such that the material sample is positioned between the lower filter seal 309 and the upper filter seal 307. The coupler 308 is then used to secure the lower filter seal 309 to the upper filter seal 307, and, thus, the upper tube 306 to the middle tube 310. The material sample is held stationary during testing.

In a fourth step P4 of the method, more clean water is poured into the upper tube 306 via the inlet 320 such that the level of clean water in the test column 302 is greater than the height of the material sample. In a fifth step P5 of the method, the material sample is agitated so as to remove air from under the material sample. Similarly, the valve of the drain tube and the bleed valve 326 are temporarily released so as to fill the drain tube and pressure sensor tube with water, respectively.

In a sixth step P6 of the method, the upper valve 312 is opened so as to release water from the middle tube 310 out of the test column 302. This in turn causes the water level in the upper tube 306 to decrease. The upper valve 312 is closed once the level of clean water is level with the material sample.

In a seventh step P7 of the method, the pressure sensor 324 and data logger 305 are switched on and a bucket (or other container) for collecting a first volume of effluent is placed under the outlet 322.

Figure 9 is a flowchart of a method of testing the material sample using the testing apparatus 300.

In a first step S1 of the method, a liquid sample is poured into the upper tube 306 via the inlet 320. The liquid sample has a known volume (e.g. 3 litres) and a known concentration of solids suspended therein. The liquid sample can be analysed prior to it being poured into the upper tube 306. The length of the upper tube 306 and the starting volume of liquid sample therein are sized to represent the driving head on the continuous filter belt 80 of a full-scale industrial separator and dewatering plant, such as plant 10 described previously.

In a second step S2 of the method, the upper valve 312 is opened, thereby allowing a first portion of the liquid sample to pass through the material sample, along the test column 302, out of the outlet 322 and into the bucket.

In a third step S3 of the method, after a period of 4 seconds from opening the upper valve 312 has elapsed, the lower valve 316 is closed. A second portion of the liquid sample continues to pass through the material sample and collects in the lower tube 314.

In a fourth step S4 of the method, after a period of 14 seconds from opening the upper valve 312 has elapsed, the upper valve 312 is closed so as to prevent any more of the liquid sample entering the lower tube 314. In a fifth step S5 of the method, the bucket containing the first portion of the liquid sample is removed from beneath the outlet 322 and an additional bucket is placed below the outlet 322. The lower valve 316 is opened such that the second portion of the liquid sample passes out of the outlet 322 and into the additional bucket.

In a sixth step S6 of the method, data collected by the data logger 305 during the 14 second period (i.e. the 4 second period and the 14 second period) and the first and second portions of the liquid sample are analysed.

Figure 10 is a graph produced from data collected by the data logger 305 testing a material sample having a pore size of 158 micrometres when exposed to a liquid sample having a TSS of 500 mg/L. The pressure sensor 324 measures the pressure at the upper surface of the material sample. The pressure at the upper surface of the material sample is proportional to the depth of the liquid sample above the upper surface of the material sample. Accordingly, the pressure measured by the pressure sensor 324 and recorded by the data logger 305 can be used to determine how the level (i.e. the height) of the liquid sample above the material sample varies over time. In Figure 10, the level of the liquid sample above the material sample is plotted on the y- axis against time on the x-axis. As shown, the rate at which the level of the liquid sample above the material sample decreases reduces over time, indicating that the flow rate of the liquid sample through the material sample decreases over time. This is as a result of solids accumulating in or over the pores of the sample, thereby reducing the effective porosity of the material sample (i.e. the proportion of the material sample through which the liquid sample can pass), as per the full-scale continuous filter belt 80 of the industrial separator and dewatering plant 10.

The average volumetric flow rate Qi through the material sample over the first period of time A (i.e. from 0 to 4 seconds) is calculated using the following equation, where A is the cross-sectional area of the interior of the test column 302 and Aim is the change in height of the liquid sample above the material sample during the first period of time Ati : In the example data shown in Figure 10, the change in height Ahi is 320 mm (i.e. from approximately 370 mm to approximately 50 mm) and the cross-sectional area A is 7,760 mm ² . Accordingly, the average volumetric flow rate Qi is 0.65 L/s. The average volumetric flow rate Q ₂ through the material sample over the second period of time DΪ2 (i.e. from 0 to 14 seconds) is calculated using the following equation, where A is the cross-sectional area of the interior of the test column 302 and DII ₂ is the change in height of the liquid sample above the material sample during the second period of time

Dΐ _2!

In the example data shown in Figure 10, the change in height DII ₂ is 330 mm (i.e. from approximately 370 mm to approximately 40 mm) and the cross-sectional area A is 7,760 mm ² . Accordingly, the average volumetric flow rate Q ₂ is 0.19 L/s.

The average volumetric flow rate Qi through the material sample over the first period of time Ati when exposed to the liquid sample is approximately equal to the average volumetric flow rate through an equally sized section of the full-scale continuous filter belt 80 made of the same material exposed to an influent having an equivalent concentration to the liquid sample and operating at maximum speed. Further, the average volumetric flow rate Q ₂ through the material sample over the second period of time Dΐ ₂ when exposed to the liquid sample is approximately equal to the average volumetric flow rate through an equally sized section of the full-scale continuous filter belt 80 made of the same material exposed to an influent having an equivalent concentration to the liquid sample and operating at minimum speed. Accordingly, the average volumetric flow rates Qi, Q ₂ determined for the sample material when exposed to the liquid sample can be used to predict how an equally sized section of a full-scale continuous filter belt 80 made of the same material will perform when exposed to an influent of equivalent concentration when the continuous filter belt 80 is operated at maximum and minimum speeds, respectively.

The above is true irrespective of the concentration of the liquid sample or the type of sample material being used. Accordingly, average volumetric flow rates Qi, Q ₂ determined using the testing apparatus 300 can be determined for sample materials having a variety of different characteristics exposed to liquid samples having a variety of different concentrations (e.g. pollutant concentrations) so as to determine the required size and/or configuration of a full-size industrial separator and dewatering plant 10 and associated continuous filter belt 80 formed of equivalent material and exposed to influents having equivalent solids concentrations. Likewise, it can be determined whether a variety of different filter materials will be suitable or unsuitable (i.e. whether they should be selected) for a continuous filter belt of fixed size and configuration. For example, a plurality of samples of different filter materials can be tested and one of the plurality of filter materials can be selected for the continuous filter belt. Accordingly, the need for full-scale testing of the apparatus is eliminated, which can be costly, time consuming and potentially hazardous.

The abovementioned equivalency between the average volumetric flow rates Qi , Q ₂ and the average volumetric flow rate through an equally sized section of the full-scale continuous filter belt 80 for different influent concentrations is demonstrated by Figure 11. In Figure 11 , the average volumetric flow rates Qi , Q ₂ determined using the testing apparatus and the average volumetric flow rates through an equally sized section of the full-scale continuous filter belt 80 have been converted into average linear filtration rates and plotted against the solids concentration of influent. As shown, the filtration rate of the sample material over the first period of time Ah correspond to the filtration rate of the continuous filter belt 80 moving at the maximum speed at all tested concentrations.

When testing a material at multiple different liquid sample concentrations, a new sample material can be used for each test. Between each test, the valve of the drain tube 311 can be temporarily opened so as to drain excess liquid sample from the upper tube 306.

Further analysis of the filtration process carried out by the sample material can take place. Firstly, the sample material itself can be analysed after the filtration process has finished. Secondly, the first volume of effluent and the second volume of effluent can be analysed. For example, the first volume of effluent and the second volume of effluent can be analysed to determine the removal rate of the sample material during the first and second periods of time Ati , At ₂ . The removal rate represents the proportion of solids contained within a volume of the liquid sample passing through the material sample that are removed by the material sample. The removal rate of the sample material during the first and second periods of time Ati , At ₂ corresponds to the removal rate of the continuous filter belt 80 when the continuous filter belt 80 is driven at its maximum and minimum speeds, respectively. Accordingly, the removal rate of a material for a continuous filter belt 80 running at various speeds can be predicted solely using the testing apparatus 300, again eliminating the need for full-scale testing of the apparatus. The removal rate Ri over the first period of time Ati is calculated based on the following equation, where p, is the concentration of solids in the liquid sample (i.e. the influent) and p _ei is the concentration of solids in the effluent passing through the sample material over the first period of time Ati : R 1 —

Pi

The concentration p _ei of solids in the effluent passing through the sample material over the first period of time Ah is calculated using the following equation, where p _ci is the concentration of solids in the first volume of effluent (which includes the volume of clean water previously contained in the middle tube 310), V _ci is the volume of the first volume of effluent (which again includes the volume of clean water previously contained in the middle tube 310) and V _m is the volume of clean water contained in the middle tube 310 prior to opening the upper valve 312 in step S2:

Pci ^x Vg

Pel—

Vci ^~ V _m

Accordingly, the removal rate Ri over the first period of time Ati can be calculated using the following equation:

Pci ^x Vci

pi(y _cl - V _m )

The removal rate R ₂ over the second period of time At ₂ is calculated based on the following equation, where p, is the concentration of solids in the liquid sample (i.e. the influent) and p _e2 is the concentration of solids in the effluent passing through the sample material over the second period of time At ₂ : The concentration p _e 2 of solids in the effluent passing through the sample material over the second period of time At ₂ is calculated using the following equation, where p _c2 is the concentration of solids in the second volume of effluent and V _c2 is the volume of the second volume of effluent:

Accordingly, the removal rate R2 over the second period of time At ₂ can be calculated using the following equation:

Although it has been described that the wastewater 15A that enters the plant 10 at inlet 30 may have a total suspended solids (TSS) in the range of from about 100 to 5000 mg/L, this is only exemplary. The wastewater 15A may have a TSS outside of this range. Further, although it has been described that the wastewater 15A may be collected from an industrial system which might have about 500 mg/L TSS, the wastewater may instead be collected from a typical municipal sewage system. Such wastewater may have a far smaller TSS than the wastewater 15A collected from an industrial system. For example, the wastewater collected from the municipal sewage system may have a TSS in the range of from about 100 to 2000 mg/L. In particular, the wastewater collected from the municipal sewage system may have a TSS of about 300 mg/L.

Although it has been described that the upper valve 312 and the lower valve 316 are operated to create a first portion of the liquid sample and a second portion of the liquid sample, if analysis of distinct portions of the liquid sample is not required, only one of the upper valve 312 and the lower valve 316 needs to be operated. In such circumstances, a test column 302 having only a single valve (i.e. a single valve corresponding to either the upper valve 312 or the lower valve 316) can be used.

In alternative arrangements, the test column 302 can be provided with one or more additional valves in addition to the upper valve 312 and the lower valve 316, such that three or more portions of the liquid sample can be created during the testing process. Although it has been described that the height (i.e. depth) of the fluid within the test column 302 (i.e. the influent liquid sample) is determined by measuring the pressure at the sample of material using a pressure sensor, this need not be the case. The height of the fluid within the test column 302 may instead be determined using different types of sensors such as ultrasonic sensors or radar. Alternatively, the height of the fluid within the test column 302 may be determined without the use of a sensor (i.e. manually) by visually inspecting how the height of the fluid within the test column 302 changes over time.

Although it has been described that a period of time of 4 seconds can be used to characterize the performance of the material sample at a maximum filter belt speed and a period of time of 14 seconds can be used to characterize the performance of the material sample at a minimum filter belt speed, different periods of time can be used to characterize the performance of the material sample at different filter belt speeds. Suitable periods of time that correspond to suitable filter belt speeds can be determined empirically or theoretically.

Although two periods of time have been used to characterize the material sample at two different filter belt speeds, in alternative arrangements it may only be necessary to characterize the performance of the material sample at a single filter belt speed, such that analysis over a single period of time can instead be carried out. This may be done when the filter belt operates at a fixed (i.e. single) speed, in which case the first speed referred to previously is the fixed speed of the belt. Alternatively, this may be done when the filter belt operates at a variable speed. In such circumstances, the first speed referred to previously may be an average speed of the belt. The average speed of the belt may be the mean speed of the belt, the median speed of the belt or the modal speed of the belt. Alternatively, more than two periods of time can be used to characterize the performance of the material sample at more than two filter belt speeds.

Although it has been described that multiple liquid sample concentrations are used to characterise the performance of the material sample at multiple different solids concentrations, in alternative arrangements it may only be necessary to characterize the performance of the material sample at a single solids concentration, such that analysis of only a single liquid sample concentration needs to be carried out. Although it has been described that the method and apparatus are used to test a sample of filter material for use in an industrial separator and dewatering plant having a continuous filter belt, the method and apparatus can alternatively be used to test a sample of filter material for use in other systems employing continuous filter belts, such as rotary filters.

Although it has been descried that the upper, lower and middle tubes 306, 310, 314 have a circular cross-sectional profile, they may have any suitable shape. For example, they may have a square cross-sectional profile. Although it has been described that the upper, lower and middle tubes 306, 310, 314 are transparent they may be non transparent. The components of the testing apparatus 300 may be formed of any suitable material.

Although it has been described that the material sample extends across the entire width of the middle tube 310, in alternative arrangements the material sample need only extend across part of the width of the middle tube 310.

The connections between the upper tube 306, the coupler 308, the middle tube 310, the upper valve 312, the lower tube 314 and the lower valve 316 are only exemplary, and other connection methods may be used. In alterative arrangements, the test column 302 may be a one-piece column with additional components for valves provided where necessary, for example.