AN APPARATUS FOR HOUSING A SUSPENDED MEDIUM

Abstract: The present invention provides an apparatus (10) for housing a suspended medium in a fluid, for particular use in treating aquaculture waters, the apparatus (10) comprising a chamber (12) in which the suspended medium is housed, the suspended medium preferably comprising a bio-film supported on a plurality of carrier elements and/or an activated sludge culture, the chamber forming a looped flow path, in which the fluid and the suspended medium circulate.

Description: An Apparatus for Housing a Suspended Medium The present invention concerns an apparatus for housing a suspended medium. The apparatus was developed to treat aqua-culture waters but can be adapted for use with many effluent and culture systems requiring aerobic, anoxic or anaerobic conditions. Such applications include integrated processing of domestic, commercial and industrial waste effluent treatment. The apparatus is described below in detail with reference to aqua-culture water processing but is by no means limited thereto. Aquaculture, like agriculture, is now progressing towards intensively controlled environmental production units (i.e. intensive recirculation systems). Operating an aquaculture system properly requires knowledge of many facets of marine biology and an understanding of diseases and health risks to fish and other aquatic organisms in the aquatic environment. From the indoor aquarium through to water gardening, fish farming and breeding, the aquaculturist requires a knowledge of engineering to build recirculating systems and an understanding of the different processes involved and how they influence each other. System design must not only address the various processes involved, but also the monitoring and control elements, which should not be viewed as independent or mutually exclusive of each other. Therefore, the design criteria employed for this technology must comply with the fundamental constraints of the processes involved and be tailored to suit each specific application. There is a tendency in intensive recirculating systems to rely on an overabundance of technology to defend against problems and losses. This can lead to a false sense of security, the result usually being that the aquaculturist is caught unprepared if he/she suffers a system failure or large losses of fish. The key to maintaining a successful aquaculture ecosystem does not so much involve looking after the animals as it does in looking after the water. Good water quality is the most important factor in ensuring the health and vitality of the system. Aquaculture systems are recirculating closed systems and are subject to the accumulation of metabolic wastes released from the living organisms present. The development and operation of an efficient and successful aquaculture effluent processing system involves individual and integrated process control which is sufficient for the loading rate on the system. It is equally important to provide flexibility in system design, operation and expansion at initial set-up to avoid large expenses being incurred through scale-up and advances in technology. Accordingly, the present invention provides an apparatus for housing a suspended medium in a fluid, the apparatus comprising a chamber, in which the suspended medium is housed, the chamber having an inlet and an outlet and defining a looped flow path, in which the fluid and the suspended medium circulate. Advantageously, the inlet is a vortex inlet cell and the outlet is a vortex outlet cell or other solids removal/recycling device. Preferably, the apparatus includes a sparging tube or diffuser, having its outlet within the chamber, such that aeration is introduced into the looped flow path. Preferably, the apparatus includes an exhaust for venting excess gas from the apparatus. Preferably, the configuration of the apparatus and/or the flow path may be reversed, thereby providing a mechanism requiring no additional fluid to back flush the apparatus. Preferably, the suspended medium is a biofilm supported on a plurality of carrier elements. Preferably, the density of the or each carrier element and respective biofilm is marginally less than that of the circulating fluid. Preferably, the carrier elements include fin projections to promote a scrubbing action between adjacent carrier elements within the chamber. Preferably, the suspended medium is in the form of an activated sludge culture. Preferably, the fluid is sterilised using ultra-violet light or other device prior to entering the apparatus. Preferably, the suspended medium comprises both carrier elements supporting a biofilm and an activated sludge culture which may be regulated by removal through at least one vortex cell, sludge concentrator/recycling cell or other device. Preferably, the chamber outlet is screened to remove particles of a specified size. Preferably, sludge removed from the apparatus can be returned and recycled through the chamber. Preferably, the apparatus includes a venturi in fluid communication with the chamber for injecting a gas into the chamber. Preferably, the apparatus includes an eductor in fluid communication with the chamber for injecting suspended solids into the chamber. The present invention will now be described with reference to the accompanying drawings in which; Figure 1 illustrates a front elevation of a first embodiment of an apparatus according to the present invention; Figure 2 illustrates a front elevation of the apparatus of Figure 1 schematically indicating the directions of flow of the fluid and suspended medium within the apparatus; Figures 2a to 2g illustrate a front elevation of a second, third, fourth, fifth, sixth and seventh embodiment of the apparatus of the present invention schematically indicating the directions of flow of the fluid and suspended medium within the respective apparatus; Figure 3 illustrates a perspective view of a dual flow coupling included in the apparatus of Figure 1; Figure 4 illustrates a side elevation of the dual flow coupling of Figure 3; Figure 5 illustrates a perspective elevation of a recirculating column forming part of the apparatus of Figure 1; Figure 6 illustrates a perspective view of an inlet screen/outlet screen/packing retainer forming part of the apparatus of Figure 1 ; Figure 7 illustrates a perspective view of an inlet vortex cell/outlet vortex cell forming part of the apparatus of Figure 1; Figure 8 illustrates a process flow diagram incorporating the apparatus of Figure 1; Figure 9 illustrates an enlarged system utilising the apparatus of Figure 1; Figure 10 illustrates a front elevation of an eighth embodiment of an apparatus according to the present invention. In the drawings, similar numerals have been given to like parts. Referring now to Figures 1 and 2 there is illustrated an apparatus for housing a suspended medium, the apparatus being generally indicated as 10, for the treatment of aquaculture effluent. The apparatus 10 may be comprised of a number of interconnected chambers or cells through which compound processing can be independently controlled, as illustrated in the process flow diagram of Figure 8. Additional apparatus 10 may be connected in series or in parallel to expand the system. For larger systems, a parallel configuration should be adopted to avoid total system failure occurring. The apparatus 10 consists of three main cells, namely, a vortex inlet cell 16, a recirculating suspended bio-film cell or chamber 12, and a vortex outlet cell 18. The vortex inlet cell 16 removes any suspended solids entering the apparatus 10 before the effluent is directed through an inlet screen 24 (see Figure 6) into a dual flow coupling 25 (see Figures 3 and 4). The second cell, the recirculating suspended bio-film cell 12. contains carrier elements (not shown) supporting, for example, a bio-film of growth thereon. The recirculating suspended bio-film cell 12 is designed to create a recirculating suspended bio-film which promotes efficient oxygen transfer and bio-mass production. Accelerated cell division and activity is also induced by an increased cell dilution rate caused by a scrubbing effect between carrier elements (not shown). This mechanism also serves to break up any suspended solids still in the effluent and thus prevent sludge build-up. The third and final cell included in the apparatus 10 is the vortex outlet cell 18 utilised for post-clarification of the effluent. Process control can be regulated through the vortex outlet cell 18, and additional apparatus 10 can be attached in series or in parallel to expand the effluent treatment system. The vortex outlet cell 18 may be replaced by any other solids removal/recycling device. The apparatus 10 utilises primary and secondary treatments in order to effectively process the aquaculture effluent. Primary treatment is the term used to describe the physical processes that are used to remove any solids that are found in the effluent and includes for example, the processes of screening and clarification. Screening involves passing the untreated effluent through coarse and fine screens to remove large debris which could damage equipment and block piping. Clarification removes suspended solids from the effluent. Suspended solids are generally small particles of food, bacteria, algae, clay and silt which remain in the system's water for an extended period of time. Large organic particles create a serious loading problem by consuming excessive amounts of oxygen, whereas finely suspended solids tend to reduce the clarity of the water. Secondary treatment is the term used to describe the processes used to modify the effluent on a molecular level and includes chemical, biological and biophysical processes. Those aquaculture systems which are recirculating closed systems, are subject to the accumulation of metabolic wastes released from the living organisms present. Biological filtration involves utilising micro-organisms to convert organic materials and ammonia into carbon dioxide, water and nitrogen compounds. In effluent, four types of nitrogen are generally found, namely organic nitrogen, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen. The predominant forms of nitrogen in effluent are organic nitrogen and ammonia. Ammonia is excreted directly by fish and also derived from organic materials by terminal mineralisation and oxidative deamination. It is the rate of production and concentration of these metabolic waste products that determines the biological load on the system. To remove nitrogen from the effluent, the ammonia must be oxidised to nitrate. This process is commonly referred to as nitrification. An oxygenated environment must be maintained for a sufficient period of time in order to promote nitrification. In the presence of dissolved oxygen, the micro-organisms convert stored BOD (biochemical oxygen demand) to carbon dioxide, water and increased cell mass. Biological nitrification occurs, producing nitrite in an intermediate step and ultimately producing nitrate. Following nitrification, the nitrogen may be removed from the waste water by reducing the nitrate to nitrogen gas. which is then released to the atmosphere. Referring now to Figures 1 and 7, the vortex inlet cell 16 represents the first stage of treatment of the aquaculture effluent. The vortex inlet cell 16 removes any suspended solids from the effluent before it enters the secondary treatment stage. Effluent enters the vortex inlet cell 16 via an angled inlet port 52 and is directed around the periphery of the vortex inlet cell 16 in a clockwise direction. This centrifugal action causes the suspended solids to fall out of solution by dynamic separation by driving the suspended solids out towards the boundary layer, this being the slow-moving region, caused by drag, nearest the wall of the vortex inlet cell 16. The heavier solids settle out due to the force of gravity and collect in an inlet sump 48 at the bottom of the vortex inlet cell 16. A second property of the vortex can be employed to remove finer suspended solids from the effluent. Regulating the flow rate to create a whirlpool at the centre of the vortex attracts the finer solids which then rotate about their own axis and settle out in the inlet sump 48. The inlet sump 48 can be drained at regular intervals via an inlet drain 20. The rotational force produced as the effluent passes through the inlet screen 24 (Figure 6) into the secondary treatment stage, in the form of the recirculating suspended bio-film cell 12, provides the energy necessary to generate an effective suspended bio-film. After passing through the inlet screen 24. the effluent enters a recirculation inlet 26 forming part of the dual flow coupling generally indicated as 25. Referring to Figures 3 and 4, the dual flow coupling 25 comprises a recirculating elbow 28 mounted within the recirculation inlet 26. The recirculating elbow 28 is mounted such that its upper face is located concentrically within the dual flow coupling 25, thereby defining a penannular channel 27 through which the effluent can enter the recirculating suspended biofilm cell 12. The recirculating elbow 28 turns through 90° as it projects downwardly into the recirculation inlet 26, thereby exiting substantially horizontally through a side wall thereof. Mounted to an inner rim 29 of the upper face of the recirculating elbow 28. in fluid tight manner, is a recirculation column 14. Referring to Figures 1 and 5, it can be seen that the recirculation column 14 is capped with a flange-like rim 32 having a plurality of substantially circular vents 30. Mounted about an outer rim 31 of the upper face of the recirculation inlet 26, also in fluid tight manner, is an inlet tube 1 1, shaped and dimensioned such that the recirculating column 14 is mounted concentrically therein. The effluent flows upwardly through an annular channel 17 defined by the outer wall of the recirculating column 14 and the inner wall of the inlet tube 1 1. The drag caused by the laminar flow created therein causes finer suspended solids to fall out of suspension into the inlet sump 48. When the water passes through the vents 30 it enters into a recirculating looped flowpath defined by the upper portion 15 of the inlet tube 1 1, the recirculating column 14, the recirculation elbow 28, a lower cross tube 36, an outlet tube 13, and an upper cross tube 34. The flow diagram of Figure 2 illustrates the direction of flow of the effluent through the apparatus 10. The entire recirculation loop is filled with carrier elements (not shown), each supporting a growth of bio-film. Each individual carrier element and its respective bio-film have a density marginally less than that of the effluent, such that the carrier elements are suspended within the effluent and flow with it around the recirculation loop. As the effluent flows around the suspended bio-film, nitrification occurs. The level of suspended solids in the effluent will be partially due to the extent of oxidative treatment, but also the quality of settlement and the sludge loading on the system. Identifying that the solids in the final effluent are derived from insufficient treatment or from poor settlement, offers an important aid in pinpointing the optimum processing perameters. With the recirculating suspended biofilm process the combination of its mixing properties and carrier elements (not shown), having fin projections which constantly scrub the effluent, prevent sludge build-up and provide excessive biomass separation. This homogenous process therefore provides maximum efficiency and throughput. As previously stated, an oxygenated environment must be maintained for a sufficient period of time to promote nitrification. An oxygenated environment is achieved by pumping air through a sparging tube 42 (or diffuser) located within the outlet tube 13. The sparging tube 42 runs down the inner wall of the outlet tube 13 and forms a penannular loop about and above a lower packing retainer 38 located proximal the base of the outlet tube 13. The flow of air from the sparging tube 42 introduces counter current aeration into the recirculating loop, thereby maximising oxygen transfer. It will also be appreciated that the flow of air from the sparging tube 42 aids the flow of effluent around the recirculating loop. The diameter of the bubbles exiting the sparging tube 42 are approximately 4-5mm in diameter for coarse bubble aeration. This maximises the oxygen transfer rate with minimum energy input. In order to retain the carrier elements (not shown) within the recirculating loop, an upper packing retainer 38 " (see Figures 1 and 6) is mounted in the upper portion of the outlet tube 13 while, oppositely disposed, is the lower packing retainer 38 located proximal the lower end of the outlet tube 13. The packing retainers 38, 38 ' each comprise a disc having a plurality of spaced-apart slits 23. The slits 23 and vents 30 are shaped and dimensioned to prevent any of the carrier elements (not shown) from migrating down the outside of the recirculating column 14. The carrier elements (not shown) offer a large surface area for colonisation, having a diameter of approximately 9mm and an increased surface area due to the plurality of fins projecting from each carrier element (not shown). The uniform oxygen saturated effluent produced by recirculating the carrier elements (not shown) through an oxygenated recirculating looped flowpath. aerated by coarse bubble aeration for energy minimisation, promotes more active growth resulting in increased colony forming unit density. The carrier elements (not shown) also incorporate fin projections which result in a scrubbing effect between adjacent carrier elements (not shown). The scrubbing effect promotes increased cell growth due to cell lysis which causes a cell dilution effect. In addition, the scrubbing effect also mechanically breaks up suspended solids and prevents sludge build up (self cleaning). This ensures that the apparatus 10 does not clog and result in anaerobic areas occurring. This also prevents the need to systematically clean the apparatus 10 and reduces the need for back washing. However, in the case of a blockage, effluent can be returned to the system through an overflow port 40. The overflow port 40 also prevents the loss of effluent by returning excess water to an outfall in the event of a system failure. The effluent is recirculated through the apparatus 10 for a predetermined period, known as the retention time, until sufficient biological filtration has taken place. At this stage a right-angled outlet port 54, located within a vortex outlet cell 18, is opened. The treated effluent flows through a lower packing retainer 38 (see Figures 1 and 6). and around an angularly disposed flap 46 (see Figures 1 and 6). The flap 46 is at an angle of about 30° relative to the wall of the outlet tube 13 and directs the treated effluent into the vortex outlet cell 18 on the side oppositely disposed to the outlet port 54. In this way. a vortex is set up in the vortex outlet cell 18, thereby removing any remaining suspended solids from the effluent before it enters a second apparatus 10 or is returned to an outfall. The vortex outlet cell 18 enables process control. The flow rates through the vortex inlet cell 16 and the inlet and outlet tubes 11, 13 are directly controlled by the outlet port 54. Secondary control over the apparatus 10 and additional cells which may be coupled for integrated processing also occurs through the vortex outlet cell 18. This also minimises the number of independent controls and provides a central location for monitoring the system. The apparatus 10 can be operated as a recirculating or continuous type system by using different loading rates. It can also be used as a gravity feed system or be adapted to a pressure feed system, further increasing the process diversity. It is often the case with aerobic fermentations, particularly during exponential phase or with continuous/fed batch systems, that oxygen enrichment under pressure is necessary. Referring now to Figures 2a to 2g there is illustrated a front elevation of various embodiments of the apparatus 10 of the present invention, schematically indicating the directions of flow of the fluid and suspended medium within the respective apparatus. Figure 2a illustrates an apparatus 110 having a directional vane 160 to aid the flow of the effluent and carrier elements around the recirculating suspended biofilm cell. The overflow port 140 of the apparatus 110 is located above and behind the directional vane 160, thereby shielding it from the flowpath of the effluent and carrier elements. Referring to Figure 2b. the apparatus 210 also includes a directional vane 260 at the outlet side of the upper cross tube 234. The directional vane 260, along with the radiused upper portion of the outlet tube 213 provide a smoother flowpath for the effluent and carrier elements within the recirculating suspended biofilm cell. The overflow port 240 is also located above and behind the directional vane 260, thereby removed from the flow path of the effluent and carrier elements. Referring now to Figure 2c. the apparatus 310 is similar in configuration to the apparatus 10 of the first embodiment of the present invention. The recirculating column 314 extends radially into engagement with the upper cross tube 334 and consequently a transfer tube 362 is provided to allow the incoming effluent to enter into the recirculating loop. The apparatus 310 is further provided with a pair of overflow ports 340, one located on either side of the recirculating suspended biofilm cell. The apparatus 410 of Figure 2d includes the extended recirculating column 414 similar to that of the apparatus 310 of Figure 2c. However, the outlet tube 413 is reduced in height and the overflow port 440 transferred to the upper portion of the inlet tube 411. Figure 2e illustrates a further embodiment of the present invention, similar in configuration to apparatus 2d, but lacking a recirculating elbow 28. Referring now to Figure 2f, the apparatus 610 includes a recirculating suspended biofilm cell 612, a UV clarifier cell 664 connected to the inlet of the recirculating suspended biofilm cell 612 to provide pre-processing of the effluent, and a sludge concentrator cell 666 connected to the outlet of the recirculating suspended biofilm cell 612. thereby providing post-processing of the water. Processed water exits the apparatus 610 via the outlet ports 672, 674. The recirculating suspended biofilm cell 612 also includes a ring sparger 642. The apparatus 710 of Figure 2g includes all of the components of the apparatus 610, similarly numbered, with the configuration of the recirculating suspended biofilm cell 712 reversed in relation to that of the apparatus 610. Figure 10, illustrates a front elevation of an eighth embodiment of an apparatus according to the invention. The apparatus 810 of Figure 10 illustrates a further embodiment of the present invention, schematically indicating the directions of flow of the fluid and suspended medium within the apparatus and similar in configuration to the apparatus 610 of Figure 2F. The apparatus consists of 4 main cells, namely, a venturi/eductor inlet cell (876), a recirculating suspended bio-film cell (812), a sludge concentrator cell (866), and a counter current clarifier cell (878) . The venturi/eductor inlet cell (878) injects air into the inlet water and recycles suspended solids from the water in the counter current clarifier cell (878). The water is directed into the recirculating suspended bio-film cell (812) where it undergoes processing as previously described. The sludge concentrator cell (866) enables suspended solids to be drawn off at a controlled rate, regulated by a sludge concentrator cell regulator valve (868), from water leaving the recirculating suspended bio-film cell (812) where they are compacted into a sludge blanket (880) and spill over into the collection cup (882) for recycling or disposal. Clean water is finally screened by passing through a sludge concentrator cell outlet screen (884) and combining with the main flow (886) having passed tlirough the sludge concentrator cell regulator valve (868). The total volume of water passing through the apparatus 810 enters the counter current clarifier cell (878) where the remaining suspended solids are recycled tlirough the eductor of venturi/eductor inlet cell (876). Clarified water passes up through the counter current clarifier cell (878) and finally through a counter current clarifier cell outlet screen (888) returning to the outlet port (854). Referring now to Figure 9 it will be appreciated that various other cells may be coupled to the apparatus 10 in order to process specific effluents and/or achieve desired results with particular contaminants. Cells 1, 2 and 3 correspond to the vortex inlet cell 16, the recirculating suspended bio-film cell 12 and the vortex outlet cell 18 respectively, forming the apparatus 10, as hereinbefore described. In order to achieve a total nitrogen standard, cell 4, an anaerobic cell, is coupled to the apparatus 10. Effluent is directed through a redistribution tray into a sealed trickling column. In addition to denitrification. the coral gravel used as a support medium maintains the pH of the effluent and water hardness. Cell 5, the calcium reactor cell, operates on the principle of injecting carbon dioxide into the cell which contains a form of aragonite. This releases trace metals and calcium, promoting efficient nitrification and de-nitrification. It also serves to buffer the systems water and increase carbonate hardness. Cell 6 is a counter current foam fractionator. This cell not only reduces the concentration of soluble proteins, amino acids, organic dyes, carbohydrates, fats, fatty acids, enzymes, detergents and many other organic compounds, but in addition, but also removes tiny buoyant particles, preventing sludge build up. This configuration is used for total nitrogen removal and calcium regulation. However, it will also be appreciated that there are many other configurations that may be used to suit the particular svstem.

Claims: Claims 1. An apparatus for housing a suspended medium in a fluid, the apparatus comprising a chamber in which the suspended medium is housed, the chamber having an inlet and an outlet and defining a looped flow path, in which the fluid and the suspended medium circulate. 2. An apparatus according to Claim 1 wherein the inlet is a vortex inlet cell and the outlet is a vortex outlet cell. 3. An apparatus according to any preceding claim wherein the apparatus includes a sparging tube, having its outlet within the chamber such that aeration is introduced into the looped flow path. 4. An apparatus according to any preceding claim wherein the apparatus includes an exhaust for venting excess gas from the apparatus. 5. An apparatus according to any preceding claim wherein the configuration of the apparatus and/or the flowpath may be reversed, thereby providing a mechanism requiring no additional fluid to back flush the apparatus. 6. An apparatus according to any preceding claim wherein the suspended medium is a bio-film supported on a plurality of carrier elements. 7. An apparatus according to Claim 6 wherein the density of the or each carrier element and respective bio-film is marginally less than that of the circulating fluid. 8. An apparatus according to Claim 6 or 7 wherein the carrier elements include fin projections to promote a scrubbing action between adjacent carrier elements within the chamber. 9. An apparatus according to any preceding claim wherein the suspended medium is in the form of an activated sludge culture. 10. An apparatus according to any preceding claim wherein the fluid is sterilised using ultra-violet light prior to entering the apparatus. 1 1. An apparatus according to any preceding claim wherein the suspended medium comprises both carrier elements supporting a bio-film and an activated sludge culture which may be regulated by removal through at least one vortex cell. 12. An apparatus according to any preceding claim wherein the chamber outlet is screened to selectively remove particles of a specific size. 13. An apparatus according to any preceding claim wherein the sludge removed from the apparatus can be returned and recycled through the chamber. 14. An apparatus according to any preceding claim wherein the apparatus includes a venturi in fluid communication with the chamber for injecting a gas into the chamber. 5. An apparatus according to any preceding claim wherein the apparatus includes an eductor in fluid communication with the chamber for injecting suspended solids into the chamber.

Inventors: ALEXANDER NICHOLAS, ALEXANDER, NICHOLAS
Applicants: ALEXANDER NICHOLAS, ALEXANDER, NICHOLAS
Application year: 2000
Main classification: A01K63
IPC codes: A01K63, C02F3