WO2019022660A1

WO2019022660A1 - Aquaculture system and method of rearing aquatic creatures

Info

Publication number: WO2019022660A1
Application number: PCT/SG2017/050380
Authority: WO
Inventors: Kok Choon Jo LENG
Original assignee: Fin Fish Aquaculture Pte. Ltd.
Priority date: 2017-07-26
Filing date: 2017-07-26
Publication date: 2019-01-31

Abstract

The present invention provides an aquaculture system for rearing aquatic creatures. The aquaculture system includes a rearing tank adapted to contain water for rearing the aquatic creatures, wherein the aquatic creatures produces waste which produces ammonia, a first denitrification apparatus adapted to convert the ammonia to nitrate, such that the first denitrification apparatus includes a least one culture media adapted to culture denitrifying bacteria and is adapted to channel a first water flow from the rearing tank through the first denitrification apparatus and back to the rearing tank, and a second denitrification apparatus adapted to convert the nitrate to nitrogen gas, such that the second denitrification apparatus includes at least one culture media adapted to culture denitrifying bacteria and is adapted to channel a second water flow from the rearing tank through the second denitrification apparatus and back to the rearing tank, such that the first water flow is faster than the second water flow. The present invention further provides a method of rearing aquatic creatures using the aquaculture system.

Description

Aquaculture System and Method of Rearing Aquatic Creatures Field of Invention

[0001] The present invention relates to an aquaculture system. For example, the present invention relates to a recirculating aquaculture system. Further, the present invention relates to a method of rearing aquatic creatures.

Background

[0002] Aquaculture, or aquafarming, is the farming of aquatic creatures, e.g. fish, shellfish etc. Aquaculture has increased tremendously over the recent years due to the increase demand of fish and shellfish as a food source. There are many types of aquaculture methods, e.g. mariculture, recirculating aquaculture system (RAS).

[0003] RAS are highly encouraged as the system have positive environmental and economical effects as compared to other methods which may cause adverse environmental effects and negative impact on wild marine life. In order to achieve good results in RAS, it is important to be able to control the parameters in the system, e.g. acceptable amount of ammonia and nitrate in the system, the feed and nutrients required, stocking rate, etc.

[0004] Ammonia is constantly produced by aquatic creatures and released into the water as part of their natural biological processes. Also, ammonia is produced by the decay of excess uneaten food and other organic matter, such as dead leaves from plants, in the tank. Ammonia, nitrites and nitrates are all byproducts of organic waste breaking down in the tank, and high concentration of these byproducts, especially ammonia, in the aquaculture system will lead to detrimental effects on the health of aquatic creatures.

[0005] In order to maintain the health of the aquatic creatures, the removal of the byproducts is necessary. Denitrification may be performed to convert the byproducts into nitrogen gas which may then be safely released into the atmosphere. There are denitrification systems available in the market to convert nitrates to nitrogen. However, such systems require high level of expertise and are expensive to purchase and maintain. Alternatively, some aquaculture systems require a portion of the water in the breeding tank to be changed periodically in order to reduce the concentration of the byproducts in the system. Such a process may be costly and time consuming. In addition, the removal of the water not only removes the byproducts, it may also destabilise the aquatic environment and induce stress to the aquatic creatures. One of the ways to denitrify the byproducts is to use denitrifiying bacteria to convert ammonia into nitrite, nitrite to nitrates and nitrates to nitrogen. Other available methods include ozone or ultra-violet treatment to the water. However, such methods require all the water to be treated, e.g. by passing all the water through the apparatus, in order for it to be effective. Besides, such methods may kill the denitrifying bacteria as well.

[0006] Therefore, it is an object of the present invention to provide a relatively economical recirculating aquaculture system that is easier and therefore more cost effective to implement and maintain.

Summary

[0007] According to various embodiments, the present invention provides an aquaculture system for rearing aquatic creatures. The aquaculture system includes a rearing tank adapted to contain water for rearing the aquatic creatures, wherein the aquatic creatures produces waste which produces ammonia, a first denitrification apparatus adapted to convert the ammonia to nitrate, such that the first denitrification apparatus includes a least one culture media adapted to culture denitrifying bacteria and is adapted to channel a first water flow from the rearing tank through the first denitrification apparatus and back to the rearing tank; and a second denitrification apparatus adapted to convert the nitrate to nitrogen gas, such that the second denitrification apparatus includes at least one culture media adapted to culture denitrifying bacteria and is adapted to channel a second water flow from the rearing tank through the second denitrification apparatus and back to the rearing tank, such that the first water flow is faster than the second water flow.

[0008] According to various embodiments, the present invention may further include a waste removal apparatus adapted to remove waste from the aquatic creatures from the rearing tank, such that the waste removal apparatus may include a waste tank in fluid communication with the rearing tank, an inlet in fluid communication with the rearing tank, the inlet adapted to inject the water from the rearing tank into the waste tank, a coagulating device adapted to coagulate the waste, at least one opening adapted to allow the waste to be discharged from the waste tank, and an outlet in fluid communication with the rearing tank, the outlet adapted to channel the water back to the rearing tank.

[0009] According to various embodiments, the coagulating device may include a charge inducer adapted to induce a charge on the waste, such that the charged waste is coagulated by being attracted to each other.

[0010] According to various embodiments, the charge inducer may include a plurality of charge inducing fins spaced apart from each other.

[0011] According to various embodiments, the present invention may further include a hollow column extending along a longitudinal axis within the waste tank, such that the plurality of fins extend radially from the hollow column and each of the plurality of fins extends lengthwise along the hollow column in a direction parallel to the longitudinal axis.

[0012] According to various embodiments, the at least one opening is disposed on the hollow column, such that each of the at least one opening is adjacent each of the plurality of fins.

[0013] According to various embodiments, the at least one opening may include a plurality of slots, such that each of the plurality of slots extends in a direction parallel to the longitudinal axis.

[0014] According to various embodiments, the present invention may further include a swirler adapted swirl the water within the waste tank around the hollow column.

[0015] According to various embodiments, the swirler may include the inlet adapted to introduce an inlet jet of water into the waste tank to swirl the water around the hollow column. [0016] According to various embodiments, the present invention may further include a toxin extractor adapted to extract toxin from the water in the rearing tank, such that the toxin extractor may include a holding tank adapted to hold water from the rearing tank, a water inlet in fluid communication with the rearing tank, the water inlet adapted to introduce water from the rearing tank into the holding tank, a frothing device adapted to froth the water, an exhaust opening adapted to exhaust the toxin removed from the water, and an outlet in fluid communication with the rearing tank and adapted to channel the water back to the rearing tank.

[0017] According to various embodiments, the frothing device may include the water inlet connected to an air inlet such that the water from the water inlet is mixed with air from the air inlet to froth the water before introducing it into the holding tank.

[0018] According to various embodiments, the toxin extractor may include an inspection tank in fluid communication with the exhaust opening such that the inspection tank is adapted to allow the toxin from the exhaust opening to flow into the inspection tank and to be inspected before being exhausted from the toxin extractor.

[0019] According to various embodiments, the present invention further provides a method of rearing aquatic creatures. The method includes containing water in a rearing tank for rearing the aquatic creatures, such that the aquatic creatures produces waste which produces ammonia, converting the ammonia to nitrate using a first denitrification apparatus comprising at least one culture media adapted to culture denitrifying bacteria, such that a first water flow from the rearing tank is being channelled through the first denitrification apparatus before being channelled back to the rearing tank, and converting the nitrate to nitrogen gas using a second denitrification apparatus comprising at least one culture media adapted to culture denitrifying bacteria, such that a second water flow from the rearing tank is being channelled through the second denitrification apparatus before being channelled back to the rearing tank, such that the first water flow is faster than the second water flow.

[0020] According to various embodiments, the present invention may further include removing the waste from the aquatic creatures from the rearing tank, such that removing the waste may include coagulating the waste in a waste tank, discharging the waste from the waste tank, and channelling the water back to the rearing tank.

[0021] According to various embodiments, coagulating the waste may include inducing a charge on the waste, such that the charged waste is coagulated by being attracted to each other.

[0022] According to various embodiments, inducing the charge may include swirling the water around a hollow column extending along a longitudinal axis within the waste tank, the hollow column may include a plurality of charge inducing fins extending radially from the hollow column and each of the plurality of fins extending lengthwise along the hollow column in a direction parallel to the longitudinal axis, such that the charge on the waste is induced by the plurality of fins.

[0023] According to various embodiments, the present invention may further include extracting toxin from the water in the rearing tank, such that extracting the toxin may include introducing the water from the rearing tank into the holding tank, frothing the water, exhausting the toxin removed from the water and channelling the water back to the rearing tank.

[0024] According to various embodiments, frothing the water may include mixing air into the water to froth the water before being introduced into the holding tank.

[0025] The present aquaculture system enables farming of aquatic creatures indoor. In addition, the system enables the control and removal of toxin in the water for farming as well as the control of any outbreak of virus that may harm the creatures. In this way, the present aquaculture system enables a healthier stock of aquatic creatures and possibly a higher density farming than conventional method and therefore the present aquaculture system may produce a higher yield.

Brief Description of Drawings [0026] Fig. 1 shows a schematic diagram of an example of an aquaculture system for rearing aquatic creatures.

[0027] Fig. 2 shows a schematic view of an example of the first denitrification apparatus.

[0028] Fig. 3 shows a flow diagram of an example of a method of rearing aquatic creatures.

[0029] Fig. 4 shows a schematic diagram of an example of a waste removal apparatus in fluid communication with the rearing tank.

[0030] Fig. 5 shows a schematic view of an example of the waste removal apparatus. [0031] Fig. 6 shows a top view of the waste removal apparatus.

[0032] Fig. 7 shows an example of a toxin extractor in fluid communication with the rearing tank.

[0033] Fig. 8 shows a schematic diagram of an example of the toxin extractor. Detailed Description

[0034] Fig. 1 shows a schematic diagram of an example of an aquaculture system 100 for rearing aquatic creatures. Aquaculture system 100 may be known as a recirculating aquaculture system. While water is mentioned in the description, the aquaculture system 100 may be suitable for seawater. Aquaculture system 100 includes a rearing tank 110 adapted to contain water for rearing the aquatic creatures that produces waste which produces ammonia. Aquaculture system 100 includes a first denitrification apparatus 120 adapted to convert the ammonia to nitrate, such that the first denitrification apparatus 120 includes a least one culture media 122 adapted to culture denitrifying bacteria and is adapted to channel a first water flow from the rearing tank 110 through the first denitrification apparatus 120 and back to the rearing tank 110; and a second denitrification apparatus 130 adapted to convert the nitrate to nitrogen gas, such that the second denitrification apparatus 130 includes a least one culture media 132 adapted to culture denitrifying bacteria and is adapted to channel a second water flow from the rearing tank 110 through the second denitrification apparatus 130 and back to the rearing tank 110, such that the first water flow is faster than the second water flow. Aquaculture system 100 is relatively easy to operate. In addition, the aquaculture system 100 may be easier and cheaper to maintain as compared to other denitrification systems that are costly and complex to operate.

[0035] Fig. 2 shows a schematic view of an example of the first denitrification apparatus 120. First denitrification apparatus 120 may include a housing 124, an inlet 126 for input of water from the rearing tank 110 into the housing 124, an outlet 128 for output of the water in the housing 124 back to the rearing tank 110. First denitrification apparatus 120 may include more than one inlet 126. Housing 124 may include an upper portion 124U and a lower portion 124L below the upper portion 124U. Inlet 126 may be disposed at the lower portion 124L of the housing 124 and the outlet 128 may be disposed at the upper portion 124U of the housing 124. Outlet 128 may be disposed at the top of the housing 124. Housing 124 may include an inverted funnel connected to the outlet 128 to funnel the water to the outlet 128. Water from the rearing tank 110 may flow from the lower portion 124L to the upper portion 124U. Water may be pumped into the housing 124 at a first flow rate. Culture media 122 may be a filter adapted to filter the water through the first denitrification apparatus 120. First denitrification apparatus 120 may be adapted to filter toxic organic matter that is about 1000- 5000 microns. As the water is being filtered, the denitrifying bacteria may be trapped within the culture media 122. The speed of the water may affect the type of denitrifying bacteria that may be housed within the housing 124. As the denitrifying bacteria increases, the ability of the first denitrification apparatus 120 to convert ammonia to nitrate improves. It is possible to connect more than one first denitrification apparatus 120 together in a series. For example, the outlet 128 of one of the first denitrification apparatus 120 may be connected to the inlet 126 of another first denitrification apparatus 120. Consequently, the outlet 128 of the another first denitrification apparatus 120 may be connected to the rearing tank 110. As it would be clear to a skilled person that it is possible to connect as many first denitrification system 120 as required to convert the ammonia to nitrate. Culture media 122 may be supported in the housing 124 by supports (not shown in Fig. 2) mounted to the inner wall of the housing 124. Housing 124 may include a drainage outlet (not shown in Fig. 2) adapted to drain fluid, e.g. to drain fluid for cleaning the housing 124 when the housing 124 is being cleaned. First denitrification apparatus 120 may include a vortex generator (not shown in Fig. 2) adapted to create a water vortex in the housing 124. Vortex generator may be disposed at the lower portion 124L of the housing 124. It would be clear that the water that is being channelled back to the rearing tank 110 may be cleaned of ammonia or has a lower level of ammonia.

[0036] Second denitrification system 130 may have the same features and structure as the first denitrification system 120 (as shown in Fig. 2). First denitrification apparatus 120 and the second denitrification apparatus 130 may be identical. Water from the rearing tank 110 may be pumped into the second denitrification system 130 at a second flow rate. Typically, the second flow rate of the water through the second denitrification system 130 may be determined. As mentioned earlier, the speed of the water through the culture media may affect the type of denitrifying bacteria that may be housed within the housing 124. Therefore, the speed of the second flow rate may be slower than the speed of the first flow rate so as to filter denitrifying bacteria suitable for converting nitrate to nitrogen gas. As the denitrifying bacteria accumulates and are being contained in the housing of the second denitrifying system 130, the second denitrifying system 130 would be able to convert nitrate to nitrogen gas. As shown, the systems for denitrifying ammonia to nitrogen gas are simple to implement and operate. In addition, the systems are easy to maintain. Consequently, the costs for installing, operating and maintaining the systems are much lower than conventional complex systems. It would be clear that the water that is being channelled back to the rearing tank 110 may be cleaned of nitrate or has a lower level of nitrate.

[0037] Fig. 3 shows a flow diagram of an example of a method 1000 of rearing aquatic creatures. Method 1000 may include containing water in the rearing tank 110 for rearing the aquatic creatures in step 1100, converting the ammonia to nitrate using a first denitrification apparatus 120 in step 1200, such that a first water flow from the rearing tank 110 is being channelled through the first denitrification apparatus 120 before being channelled back to the rearing tank 110, and converting the nitrate to nitrogen gas using a second denitrification apparatus 130 in step 1300, such that a second water flow from the rearing tank 110 is being channelled through the second denitrification apparatus 130 before being channelled back to the rearing tank 110, such that the first water flow is faster than the second water flow. [0038] Fig. 4 shows a schematic diagram of an example of a waste removal apparatus 140 in fluid communication with the rearing tank 110. Aquaculture system 100 may include the waste removal apparatus 140. Waste removal apparatus 140 may be adapted to remove waste from the aquatic creatures from the rearing tank 110. Waste removal apparatus 140 may be adapted to remove toxic organic matter that is about 0.15-1000 microns. Waste removal apparatus 140 may include a waste tank 142 in fluid communication with the rearing tank 110 and an inlet 142X in fluid communication with the rearing tank 110. Inlet 142X is adapted to inject the water from the rearing tank 110 into the waste tank 142. Waste removal apparatus 140 may include a coagulating device 150 adapted to coagulate the waste, at least one opening 144 adapted to allow the waste to be discharged from the waste tank 142, and an outlet 142Y in fluid communication with the rearing tank 110. Outlet 142Y may be adapted to channel the water back to the rearing tank 110. Coagulated waste is heavier than loose waste and therefore would sink to the bottom of the waste tank 142. In this way, the waste collection and removal process is improved. As such, removing the waste may include coagulating the waste, discharging the waste from the waste tank 142, and channelling the water back to the rearing tank 110. It would be clear that the water that is being channelled back to the rearing tank 110 may be cleaned of waste or has a lower level of waste.

[0039] Fig. 5 shows a schematic view of an example of the waste removal apparatus 140. Waste removal apparatus 140 may include the waste tank 142 having an upper portion 142U and a lower portion 142L below or adjacent the upper portion 142U. Inlet 142X may be disposed in the upper portion 142U of the waste tank 142 and adapted to allow water from the rearing tank 110 to enter the waste tank 142. Outlet 142Y may be disposed in the upper portion 142U of the waste tank 142. Outlet 142Y may be disposed above the inlet 142X. As the waste enters the waste tank 142 at the inlet 142X, the waste may sink to the bottom of the waste tank 142 and the water cleared of waste or with reduced waste at the upper portion 142U of the tank 142 may exit the waste tank 142 at the outlet 142Y. As the outlet 142Y is above the inlet 142X, waste may be prevented from exiting the waste tank 142 as the waste may not reach the inlet 142X. Coagulating device 150 may extend from the base 142B of the waste tank 142 along the length of the waste tank 142. Coagulating device 150 may be disposed at the centre of the waste tank 142. Alternatively, the inlet 142X may be disposed at the upper portion 142U or the lower portion 142L and the outlet 142Y may be disposed at the lower portion 142L or upper portion 142U so that water may enter from one side of the waste tank 142, flow along the length of the waste tank 142 from one portion to the other and exit from an opposite side of the waste tank 142.

[0040] Coagulating device 150 may include a charge inducer 152 adapted to induce a charge on the waste so that the charged waste can be coagulated by being attracted to each other. Charge inducer 152 may include the plurality of charge inducing fins 152F spaced apart from each other. Plurality of fins 152F may cause friction to the waste when the waste is brushed again them thereby inducing a charge on the waste particles. As the water containing the waste enters the waste tank 142, the waste in the water may brush against the plurality of charge inducing fins 152F. Fins 152F may be disposed along the length of the charge inducer 152 so that the waste may be brushed against the fins 152F as the water flows from the inlet 142X to the outlet 142Y. Plurality of fins 152F may be disposed radially and from the centre of the waste tank 142 and may be evenly spaced from each other. Each of the plurality of fins 152F may extend lengthwise traverse to the flow of the water in the waste tank 142. Coagulating device 150 may include a hollow column 154 extending along a longitudinal axis 142A within the waste tank 142. Opening 144 (not shown in Fig. 5) may be disposed on the hollow column 154 between the plurality of fin 152F. As the waste is being directed to between the plurality of fins 152F, the waste may exit the waste tank 142 via the opening 144 between the plurality of fins 152F. Waste tank 142 may include a funnel 156 at the bottom of the coagulating device 150. Funnel 156 which may be at the base 142B of the waste tank 142. Coagulating device 150 may extend from within the funnel 156. Funnel 156 may be adapted to funnel the waste from the side of the waste tank 142 towards the hollow column 154. In this way, the waste may be channelled towards the openings 144 on the hollow column 154 and exit the waste tank 142. As shown in Fig. 5, the waste removal apparatus 140 may include a channel 146 connected to the hollow column 154, such that the channel 146 may be adapted to channel the waste from within the hollow column 154 out of the waste tank 142.

[0041] Fig. 6 shows a top view of the waste removal apparatus 140 in Fig. 5. Waste removal apparatus 140 may include a swirler 148 adapted swirl the water within the waste tank 142 around the hollow column 154. For example, the swirler 148 as shown in Fig. 6 may be adapted to swirl the water in a counter-clockwise direction. Swirler 148 may be adapted to swirl the water within the waste tank 142 to create a vortex around the hollow column 154. Swirler 148 may include the inlet 142X adapted to introduce an inlet jet of water into the waste tank 142 to swirl the water around the hollow column 154. Inlet 142X may be directed at an angle from the centre of the waste tank 142. Preferably, the inlet 142X may be directed in a direction parallel to a tangent to the tank wall 142W of the waste tank 142. Swirler 148 may be a rotatable device disposed within the waste tank 142 and adapted to swirl the water therein. Plurality of fins 152F may extend radially from the hollow column 154 and each of the plurality of fins 152F may extend lengthwise along the hollow column 154 in a direction parallel to the longitudinal axis 142A. Referring to Fig. 6, the at least one opening 144 may be disposed on the hollow column 154 such that each of the at least one opening 144 may be adjacent each of the plurality of fins 152F. Each opening 144 may be disposed at about the base of fin 152F. Each opening 144 may be disposed at the side of the fin 152F where the fin 152F faces the oncoming water. The at least one opening 144 may include a plurality of slots such that each of the plurality of slots extends in a direction parallel to the longitudinal axis 142A. Plurality of fins 152F may be a protrusion or an extension from the hollow column 154. Plurality of fins 152F may be curved instead of linear as shown in Fig. 6 so as to improve the diversion of the waste and water into the plurality of openings 144. For example, the plurality of fins 152F may be concaved facing the oncoming water.

[0042] Referring to Fig. 6, as the water is being injected into the waste tank 142 from the inlet 142X, the jet of water causes the water in the waste tank 142 to move in the same direction around the hollow column 154 thereby causing the water to swirl around hollow column 154 hence causing a vortex centred at the hollow column 154. As the water swirls, the waste in the water is being brushed against the plurality of charge inducing fins 152F and a charge is being induced on the waste particles. As more waste is being charged, the waste is attracted to each other and coagulates into larger masses. As the waste gets larger, it becomes heavier and sinks to the bottom of waste tank 142. In addition, the waste may be directed by the plurality of fins 152F towards the plurality of openings 144 and enters the hollow column 154. As the waste within the hollow column 154 sinks to the bottom of the hollow column 154, the waste may be channelled out of the waste tank 142 via the channel 146. As shown in Fig. 146, the waste tank 142 may be cylindrical, i.e. circular cross section. As such, it is shown that inducing the charge may include swirling the water around the hollow column 154 such that the charge on the waste may be induced by the plurality of fins 152F. [0043] Fig. 7 shows an example of a toxin extractor 160 in fluid communication with the rearing tank 110. Aquaculture system 100 may include the toxin extractor 160. Toxin extractor 160 may be adapted to extract toxin from the water in the rearing tank 110. Toxin extractor 160 may be adapted to extract toxic organic matter of about 0.1-25 microns. Toxin extractor 160 may include a holding tank 162 adapted to hold water from the rearing tank 110, a water inlet 162X in fluid communication with the rearing tank 110, the water inlet 162X adapted to introduce water from the rearing tank 110 into the holding tank 162. Toxin extractor 160 may include a frothing device 164 adapted to froth the water, an exhaust opening 166 adapted to exhaust the toxin removed from the water, and a water outlet 162Y in fluid communication with the rearing tank 110 and adapted to channel the water back to the rearing tank 110.

[0044] Holding tank 162 may have an upper portion 162U and a lower portion 162L. Frothing device 164 may be disposed at the upper portion 162U of the holding tank 162. Frothing device 164 may be adapted to froth the water to create foam in the holding tank 162. Frothing device 164 may be adapted to introduce air into the water to create the foam. As the foam is formed, it dissolves the toxin and maintains the toxin on top of the water surface within the holding tank 162. At the same time, dead bacteria may be trapped in the foam. Exhaust opening 166 may be disposed at the top or at the upper portion 162U of the holding tank 162. As the foam builds up, it rises towards the exhausting opening 166 and eventually may overflow out of the holding tank 162. In this way, the foam, together with the toxin, may be exhausted out of the holding tank 162 through the exhaust opening 166. Exhaust opening 166 may be connected to a collection tank (not shown in Fig. 7) to be collected for further processing or to a drainage to be drained to an appropriate location. Water that has been cleaned may remain at the bottom of the holding tank 162 and may exit the holding tank 162 via the water outlet 162Y and be channelled back to the rearing tank 110. Water outlet 162Y may be disposed at the lower portion 162L of the holding tank 162. Water outlet 162Y may be an inverted L-shaped channel where one end of the channel faces the base of the holding tank 162 and the other end protrude out of the holding tank 162. The other end of the reshaped channel may be at the upper portion 162U while the one end of the L-shaped channel may be at the lower portion 162L of the holding tank 162. As such, extracting toxin from the water in the rearing tank 110 may include introducing the water from the rearing tank 110 into the holding tank 162, frothing the water, exhausting the toxin removed from the water and channelling the water back to the rearing tank 110.

[0045] Fig. 8 shows a schematic diagram of an example of the toxin extractor 160. Water inlet 162X may incorporate the frothing device 164 such that the frothing device 164 may include the water inlet 162X connected to an air inlet 164 A such that the water from the water inlet 162X is mixed with air from the air inlet 164 A to froth the water before introducing it into the holding tank 162. Due to the flow of the water, air is being sucked into the water inlet 162X. As the mixed air and water enters the holding tank 162, foam is formed in the holding tank 162 and toxin may be dissolved in the foam. As mentioned earlier, as the foam containing the toxin, being lighter, floats on the water and as the foam rises, it exits the exhaust opening 166. It would be clear that the water that is being channelled back to the rearing tank 110 may be cleaned of toxin or has a lower level of toxin. As the toxin extractor 160 is adapted to introduce air into the water, the toxin extractor 160 may be an oxygenator adapted to oxygenate the water in the toxin extractor 160. Thereafter, the oxygenated water may be pumped back from the toxin extractor 160 to the rearing tank 142. Preferably, the ratio of air to water may be about 36 cubic feet of air to 36 ton of water.

[0046] Toxin extractor 160 may include an inspection tank 168 in fluid communication with the exhaust opening 166 such that the inspection tank 168 may be adapted to allow the toxin from the exhaust opening 166 to flow into the inspection tank 168 and the foamed be inspected before being exhausted from the toxin extractor 160. Foam may be exhausted from the toxin extractor 160 via the inspection tank 168. As shown in Fig. 8, the holding tank 162 protrudes into the inspection tank 168 and the connection between the holding tank 162 and the inspection tank 168 is water-tight. The foam may overflow from the exhaust opening 166 into the inspection tank 168. Inspection tank 168 may include a viewing window (not shown in Fig. 8) for someone to inspect the foam. Inspection tank 168 may be made from a transparent material so as to allow the foam to be visible from outside the inspection tank 168. The colour of the foam may indicate the level of toxin within the aquaculture system 100. Therefore, the inspection tank 168 provides a simple, quick and preliminary way of determining the toxin level in the toxin extractor 160 and hence the toxin level of the aquaculture system 100. [0047] Aquaculture system 100 may include a water treatment system adapted to treat the water in the rearing tank 110. Water may be treated before entering the rearing tank 110.

[0048] As shown above, the aquaculture system 100 includes the first denitrification apparatus 120 and the second denitrification apparatus 130. Aquaculture system 100 may further include the waste removal apparatus 140, the toxin extractor 160 and/or the water treatment system. It can be appreciated by the skilled person that it is not necessary that the aquaculture system 100 includes all the systems and apparatus and may include one or more of them. For example, the aquaculture system 100 may include the first denitrification apparatus 120, the second denitrification apparatus 130 and the waste removal apparatus 140 but not the toxin extractor 160. In another example, the aquaculture system 100 may include the first denitrification apparatus 120, the second denitrification apparatus 130 and the toxin extractor 160 but not the waste removal apparatus 140. Further, each of the systems or apparatus may be in direct fluid communication with the rearing tank 110, i.e. water from the rearing tank 110 is returned directly to the rearing tank 110 without going through other system or apparatus. In another example, the system or apparatus may be in fluid communication with each other such that water from the rearing tank 110 may enter one of the system of apparatus and then to another before being returned to the rearing tank 110. For example, the water from the rearing tank 110 may first be pumped into the first denitrification apparatus 120 to convert the ammonia to nitrate. Thereafter, the water from the first denitrification apparatus 120 may be pumped into the second denitrification apparatus 130 to convert the nitrate to nitrogen gas. Thereafter, the water from the second denitrification apparatus 130 may be pumped into the waste removal apparatus 140 for the waste to be removed before being pumped back to the rearing tank 110. Aquaculture system 100 may include a sump tank between the rearing tank 110 and the respective systems and apparatus to provide a buffer between them. As pump pressure to and from the systems and apparatus may be high, the sump tank would be able to provide a barrier to the high water pressure and prevent distress to the aquatic creature in the rearing tank 110. Sump tank may also be used to segregate the water treatment from the rearing tank 110. [0049] In this way, it is shown that the contaminated water from the rearing tank 110 may be cleaned and re-circulated back to the rearing tank 110. There may be a necessity to add a small percentage, e.g. 3%, of water into the rearing tank due to loss of water due to normal operation of the system. While the aquaculture system 100 treats and cleans the water, regular dosing of mineral, vitamins, nutrient, water conditional and/or denitrifying bacteria may be necessary to maintain the aquatic creatures. As shown, the aquaculture system 100 is eco- friendly as it does not discharge toxic organic waste into the environment. The toxic organic waste is being removed and properly processed while the ammonia is being converted to nitrogen gas. In addition, the aquaculture system 100 enables the isolation and tackling the bad bacteria without harming the good bacteria, e.g. denitrifying bacteria.

[0050] A skilled person would appreciate that the features described in one example may not be restricted to that example and may be combined with any one of the other examples.

Claims

Claim

1. An aquaculture system for rearing aquatic creatures, the aquaculture system comprising:

a rearing tank adapted to contain water for rearing the aquatic creatures, wherein the aquatic creatures produces waste which produces ammonia;

a first denitrification apparatus adapted to convert the ammonia to nitrate, wherein the first denitrification apparatus comprises a least one culture media adapted to culture denitrifying bacteria and is adapted to channel a first water flow from the rearing tank through the first denitrification apparatus and back to the rearing tank; and

a second denitrification apparatus adapted to convert the nitrate to nitrogen gas, wherein the second denitrification apparatus comprises at least one culture media adapted to culture denitrifying bacteria and is adapted to channel a second water flow from the rearing tank through the second denitrification apparatus and back to the rearing tank,

wherein the first water flow is faster than the second water flow.

2. The aquaculture system of claim 1, further comprising a waste removal apparatus adapted to remove waste from the aquatic creatures from the rearing tank, wherein the waste removal apparatus comprises a waste tank in fluid communication with the rearing tank, an inlet in fluid communication with the rearing tank, the inlet adapted to inject the water from the rearing tank into the waste tank, a coagulating device adapted to coagulate the waste, at least one opening adapted to allow the waste to be discharged from the waste tank, and an outlet in fluid communication with the rearing tank, the outlet adapted to channel the water back to the rearing tank.

3. The aquaculture system of claim 2, wherein the coagulating device comprises a charge inducer adapted to induce a charge on the waste, wherein the charged waste is coagulated by being attracted to each other.

4. The aquaculture system of claim 3, wherein the charge inducer comprises a plurality of charge inducing fins spaced apart from each other.

5. The aquaculture system of claim 4, further comprising a hollow column extending along a longitudinal axis within the waste tank, wherein the plurality of fins extend radially from the hollow column and each of the plurality of fins extends lengthwise along the hollow column in a direction parallel to the longitudinal axis.

6. The aquaculture system of claim 5, wherein the at least one opening is disposed on the hollow column, wherein each of the at least one opening is adjacent each of the plurality of fins.

7. The aquaculture system of claim 5 or 6, wherein the at least one opening comprises a plurality of slots, wherein each of the plurality of slots extends in a direction parallel to the longitudinal axis.

8. The aquaculture system of claim 5 to 7, further comprising a swirler adapted swirl the water within the waste tank around the hollow column.

9. The aquaculture system of claim 8, wherein the swirler comprises the inlet adapted to introduce an inlet jet of water into the waste tank to swirl the water around the hollow column.

10. The aquaculture system of any one of the claims 1 to 9, further comprising a toxin extractor adapted to extract toxin from the water in the rearing tank, wherein the toxin extractor comprises a holding tank adapted to hold water from the rearing tank, a water inlet in fluid communication with the rearing tank, the water inlet adapted to introduce water from the rearing tank into the holding tank, a frothing device adapted to froth the water, an exhaust opening adapted to exhaust the toxin removed from the water, and an outlet in fluid communication with the rearing tank and adapted to channel the water back to the rearing tank.

11. The aquaculture system of claim 10, wherein the frothing device comprises the water inlet connected to an air inlet wherein the water from the water inlet is mixed with air from the air inlet to froth the water before introducing it into the holding tank.

12. The aquaculture system of claim 10 or 11, wherein the toxin extractor comprises an inspection tank in fluid communication with the exhaust opening wherein the inspection tank is adapted to allow the toxin from the exhaust opening to flow into the inspection tank and to be inspected before being exhausted from the toxin extractor.

13. A method of rearing aquatic creatures comprising:

containing water in a rearing tank for rearing the aquatic creatures, wherein the aquatic creatures produces waste which produces ammonia;

converting the ammonia to nitrate using a first denitrification apparatus comprising at least one culture media adapted to culture denitrifying bacteria, wherein a first water flow from the rearing tank is being channelled through the first denitrification apparatus before being channelled back to the rearing tank; and

converting the nitrate to nitrogen gas using a second denitrification apparatus comprising at least one culture media adapted to culture denitrifying bacteria, wherein a second water flow from the rearing tank is being channelled through the second denitrification apparatus before being channelled back to the rearing tank,

wherein the first water flow is faster than the second water flow.

14. The method of claim 13, further comprising removing the waste from the aquatic creatures from the rearing tank, wherein removing the waste comprises coagulating the waste in a waste tank, discharging the waste from the waste tank, and channelling the water back to the rearing tank.

15. The method of claim 14, wherein coagulating the waste comprises inducing a charge on the waste, wherein the charged waste is coagulated by being attracted to each other.

16. The method of claim 15, wherein inducing the charge comprises swirling the water around a hollow column extending along a longitudinal axis within the waste tank, the hollow column comprising a plurality of charge inducing fins extending radially from the hollow column and each of the plurality of fins extending lengthwise along the hollow column in a direction parallel to the longitudinal axis, wherein the charge on the waste is induced by the plurality of fins.

17. The method of any one of claims 14 to 16, further comprising extracting toxin from the water in the rearing tank, wherein extracting the toxin comprises introducing the water from the rearing tank into the holding tank, frothing the water, exhausting the toxin removed from the water and channelling the water back to the rearing tank.

18. The method of claim 17, wherein frothing the water comprises mixing air into the water to froth the water before being introduced into the holding tank.