Multi-stage biofilter for removing microplastic particles and biochemical waste from aquaculture water

Abstract

A water filtration system and corresponding method for removing particulate and biochemical waste from water is provided. The system includes a first compartment containing algae in suspension. The algae can be used to agglomerate the particulate and biochemical waste in the water to form algal particles. The water and algal particles are provided to a second compartment through a fluid transfer conduit. The second compartment includes a first set of hanging assemblies, each containing a bivalve mollusk that can be used to siphon the algal particles from the water.

Description

[Technical Field]

[0001] The present disclosure relates generally to water treatment, and more particularly to biofilters for microplastic particles and biochemical waste from water, such as aquaculture water. [Background technology]

[0002] Protecting the oceans and other water sources is important for the continued global development of these resources and for harnessing the potential of sustainable practices such as aquaculture. Marine microplastics are now found in oceans around the world, raising serious concerns for the overall health of the oceans (Van Cauwenberghe & Janssen 2014). Summary of the Invention [Problem to be solved by the invention]

[0003] Ingestion of these microplastic particles has been shown to occur in several marine organisms, including bivalve mollusks such as the blue mussel (Mytilus edulis). In bivalve mollusks, ingested microplastics are present in their soft tissues. Laboratory tests have shown that the average concentration of microplastic particles in bivalve mollusks is 0.36 particles per gram of soft tissue (wet weight). This ingestion of microplastics by various marine species poses a potential threat to consumers of seafood raised in open-pen aquaculture environments, as even market-sized fish are at risk of microplastic ingestion in these environments (Van Cauwenberghe & Janssen, 2014).

[0004] The generation of nitrogen and phosphorus waste poses challenges for the aquaculture industry because high concentrations of components such as ammonia, nitrates, and phosphorus can have harmful effects on both the environment and human health. When discharged into surface or groundwater, ammonia and phosphorus can promote algal blooms, resulting in increased algal toxins and reduced oxygen content for other aquatic organisms. Nitrates pose a potential risk to human health because high concentrations of nitrate in drinking water can directly contribute to methemoglobinemia (blue baby syndrome), which is of particular concern to infants.

[0005] Therefore, there is a need for a solution to address or ameliorate at least some of the problems identified above. [Means for solving the problem]

[0006] This specification generally describes a water filtration system for removing microplastic particles and biochemical waste from water, such as aquaculture water in an aquaculture facility. As described below, the filtration system includes a biofilter that contains a combination of bivalve mollusks and algae arranged within different filtration stages of the filtration system.

[0007] According to a first broad aspect of the present invention, there is provided a water filtration system for removing particulate waste and biochemical waste from water, the system comprising: a first compartment containing algae in suspension, the algae usable to agglomerate the particulate waste and biochemical waste in the water to form algal particles; a second compartment receiving the water and the algal particles from the first compartment through a fluid transfer conduit; and a first set of suspension assemblies disposed within the second compartment, each suspension assemblies containing a bivalve mollusk usable to siphon the algal particles from the water.

[0008] According to another aspect of the present invention, there is provided a water filtration system as described above, comprising a third compartment containing a mesh filter for removing a portion of the particulate waste from the water to produce pretreated water, the pretreated water being provided to the first compartment through a second fluid transfer conduit.

[0009] According to another aspect of the invention, there is provided a fourth compartment for receiving water and algae particles from the second compartment through a third fluid transfer conduit, the fourth compartment including a second set of suspension assemblies, each of which includes a bivalve mollusk that can be used to siphon the algae particles from the water.

[0010] According to another aspect of the present invention, there is provided a water filtration system as described above, comprising a fluid recirculation conduit that recirculates a portion of the water and algae particles from the fourth compartment to the third compartment.

[0011] According to another aspect of the present invention, there is provided a water filtration system as described above, comprising a fluid recirculation conduit that recirculates a portion of the water and algae particles from the fourth compartment to the first compartment.

[0012] According to another aspect of the present invention, there is provided any of the above water filtration systems, wherein the first compartment has at least one baffle structure for containing the algae within the first compartment.

[0013] According to another aspect of the present invention, there is provided a water filtration system as described above, wherein the algae and bivalve mollusks correspond to algae species and bivalve mollusks, respectively, present in the geographic location of the system.

[0014] According to another aspect of the present invention, there is provided a filtration system as described above, wherein the algae is nutritious for the bivalve mollusks used in the filtration system. According to another aspect of the present invention, there is provided a water filtration system as described above, wherein the species of algae and bivalve mollusks are selected based on at least one of: (i) the uptake rate of the bivalve mollusks; (ii) the uptake range of the bivalve mollusks; (iii) the survival rate of the bivalve mollusks relative to the pump; (iv) the lifespan of the bivalve mollusks; (v) the coagulation of nitrogen by the algae; (vi) the coagulation of ammonia by the algae; and (vii) the coagulation of the particulate waste by the algae.

[0015] According to another aspect of the present invention, there is provided a water filtration system as described above, wherein the bivalve mollusks are either American oysters (Crassostrea virginica) or mussels (Mytilus edulis), and the algae are phytoplankton.

[0016] According to another aspect of the present invention, there is provided any of the above-described water filtration systems, wherein the bivalve is a mussel (Mytilus edulis) and the algae is a haptophyte (Isochrysis sp.).

[0017] According to another aspect of the present invention, there is provided any of the above-described water filtration systems, comprising 200 bivalve mussels (Mytilus edulis) and 2 L of haptophyte (Isochrysis sp.).

[0018] According to a second broad aspect of the present invention, there is provided a method of filtering water to remove particulate waste and biochemical waste, comprising: providing a first filter containing algae in suspension; directing water containing the particulate waste and the biochemical waste to the first filter, wherein the algae in the first filter aggregate the particulate waste and the biochemical waste to form algal particles; and directing the water and the algal particles to a second filter containing bivalve mollusks that can be used to siphon the algal particles from the water.

[0019] According to another aspect of the present invention, there is provided a method according to any of the above, further comprising pretreating the water by directing the water containing the particulate waste and biochemical waste through a third filter including a mesh filter before directing the water containing the particulate waste and biochemical waste through the first filter.

[0020] According to another aspect of the present invention, there is provided a method as described above, which includes directing the water and the algae particles from the second filter towards a fourth filter containing bivalve mollusks that can be used to siphon the algae particles from the water.

[0021] According to another aspect of the present invention, there is provided a method according to any of the above, comprising recirculating a portion of the water and algae particles from the fourth filter to the third filter. According to another aspect of the present invention, there is provided a method according to any of the above, comprising recirculating a portion of the water and algae particles from the fourth filter to the first filter.

[0022] According to another aspect of the present invention, there is provided a method as described in any of the above, comprising providing the first filter with at least one baffle structure to contain the algae within a first compartment of the first filter.

[0023] According to another aspect of the present invention, there is provided a method as described above, wherein the algae and bivalve mollusks correspond to a combination of algae species and bivalve mollusks present in the geographic locations of the first filter and the second filter, respectively.

[0024] According to another aspect of the present invention, there is provided a method according to any of the above, wherein the algae species is nutritious for the bivalve mollusks. According to another aspect of the present invention, there is provided a method as described in any of the above, wherein the species of algae and bivalve mollusks are selected based on at least one of: (i) the uptake rate of the bivalve mollusks; (ii) the uptake range of the bivalve mollusks; (iii) the survival rate of the bivalve mollusks relative to the pump; (iv) the lifespan of the bivalve mollusks; (v) the concentration of nitrogen by the algae; (vi) the concentration of ammonia by the algae; and (vii) the concentration of the particulate waste by the algae.

[0025] According to another aspect of the present invention, there is provided any of the above-mentioned methods, wherein the bivalve is any of the American oyster (Crassostrea virginica) and the mussel (Mytilus edulis), and the algae is phytoplankton.

[0026] According to another aspect of the present invention, there is provided any of the above methods, wherein the bivalve is a mussel (Mytilus edulis) and the algae is a haptophyte (Isochrysis sp.). According to another aspect of the present invention, there is provided any one of the above methods, further comprising 200 bivalve mussels (Mytilus edulis) and 2L of haptophyte (Isochrysis sp.).

[0027] Further aspects of the present invention will become apparent from consideration of the following description. Features and advantages of embodiments of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of a water filtration system according to at least one embodiment. [Figure 2] FIG. 1 is a schematic diagram of a water filtration system according to another embodiment. [Figure 3A] FIG. 1 is a perspective view of a vertically stacked filtration system according to another embodiment. [Figure 3B] FIG. 1 is a perspective view of a vertically stacked filtration system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following description and the embodiments described therein are provided as illustrations of examples of particular embodiments of the principles of the present invention. These examples are provided for purposes of illustration, not for purposes of limitation of those principles and the present invention.

[0030] Embodiments herein disclose an autonomous filtration system and corresponding method for removing particulates, such as microplastics, and biochemical wastes, e.g., nitrogen and phosphorus wastes (collectively referred to as "pollutants"), from aquaculture water in aquaculture facilities, such as open-pen aquaculture facilities. It is intended that the disclosed filtration system be configurable or adaptable for operation in other similar operations within the aquaculture industry, including, but not limited to, land-based flow-through facilities, recirculating aquaculture systems (RAS), bivalve hatcheries, and finfish holding facilities. During use, contaminant-laden water passes through a biofilter installed in the filtration system. As described below, the biofilter may include multiple filtration stages, such as an inorganic mesh filter, an algae-based biochemical filter, and a bivalve-based particulate filter. The water to be treated may be cycled through upstream filtration stages in a specific order to maximize contaminant removal.

[0031] Similar to land-based aquaculture facilities, marine aquaculture facilities can maintain clean water conditions for optimal fish and shellfish growth and health by implementing filtering systems using extractive species (e.g., algal biochemical filtration and bivalve particulate filtration) to remove harmful chemicals and particles. These systems can improve influent water quality by filtering out volatile organic compounds (VOCs) such as dioxins and furans, or harmful chemicals such as mercury, as well as larger particles that contribute to environmental concerns, such as microplastics or sea lice (Webb et al., 2013). Filtration can also improve the wastewater discharge from the farm, potentially addressing significant environmental concerns raised by society and many nongovernmental organizations (NGOs) regarding marine aquaculture. Systems installed in offshore or coastal net cages or onshore free-flow facilities can remove influent toxic substances while simultaneously removing harmful by-products from the facility's wastewater. Systems installed in land-based RAS facilities can also remove biological contaminants from the facility's products, ensuring high water quality and ultimately enabling the delivery of higher-quality products.

[0032] Aquaculture provides an opportunity for bivalve mollusks to utilize their filtering capabilities in the removal of nitrogenous waste products. While many land-based facilities are able to remove solids such as feces, significant amounts of dissolved nitrogen compounds, such as nitrates, nitrites, and ammonia, remain, potentially posing a risk to the health of cultured finfish. By combining these dissolved nitrogen compounds with microalgae that actively utilize and grow them, bivalve mollusks such as the blue mussel (Mytilus edulis) can consume the algae, ultimately improving water quality. This is a proven method for water purification (Gifford et al., 2004).

[0033] As the population grows and marine environments deteriorate, the creation of self-sustaining filtration systems is an effective way to produce affordable, high-quality seafood. Without such systems, aquaculture continues to face a choice between risking environmental impacts on fish raised in marine aquaculture facilities and vice versa, or maintaining controlled land-based facilities with much higher installation and maintenance costs. Capital costs are an important consideration when encouraging the expansion of this industry, as transitions to recirculating land-based systems are becoming more common and can require more than US$50 million. Extractive species-based filtration could offer a new, cost-effective technology for the industry to continue growing sustainably.

[0034] The use of the disclosed biofilter system in marine aquaculture farms for growing fish and other seafood is intended to improve the viability of expanding marine facilities. Such use is intended to have less adverse environmental impact, less potential for disease or parasites (i.e., sea lice), less energy use, and maintain significantly lower operating costs (up to 1.50 EUR / kg lower in Norwegian salmon farms) compared to their land-based counterparts (Intrafish, 2018).

[0035] Expanding the definition of biochemical waste, Canadian law, under the Fisheries Act, defines a deleterious substance as "any substance that, when added to any water, deteriorates or alters the quality of that water, or forms part of a process of deterioration or alteration, thereby becoming or may become deleterious to fish, fish habitats, or human uses of that water." Therefore, considering the deterioration and alteration it can cause to fish and human health, hazardous substances could include microplastic particles. Furthermore, hazardous substances could also include nitrogenous, phosphate, and other dissolved solids contained in aquaculture wastewater. For example, nitrogenous wastes such as ammonia and nitrites can be harmful to the health of fish in aquaculture systems if they are in excess, and can be equally harmful if discharged without due consideration. Therefore, it is a best practice in aquaculture to dilute circulating water to 0.5 mg / L or less of nitrogenous compounds, otherwise fish in the system will die. Therefore, land-based aquaculture facilities currently address this issue with dissolved solids biofilters, which utilize bacteria as the primary source of nitrification and denitrification. The following is, of course, a more efficient alternative.

[0036] 1 is a schematic diagram of a water filtration system 100 in accordance with at least one embodiment of the present invention. Filtration system 100 can operate as an autonomous system that cycles input water, such as seawater, through multiple filtration stages to reduce and / or remove potentially harmful constituents, providing improved water quality for marine fish farming, such as finfish, in coastal areas. This system 100 is suitable for removing harmful chemicals, microplastics, and parasites, such as sea lice. In this embodiment, there are three primary filtration stages, arranged across multiple chambers or cells, as described more fully below.

[0037] The multiple cells of filtration system 100 may be fabricated using any suitable method or technique. For example, filtration system 100 may be a unitary body (e.g., a molded metal or plastic body) with separate chambers separated by walls. In other implementations, filtration system 100 may be comprised of multiple separate vessels connected with appropriate tubing connecting each vessel.

[0038] The filtration system 100 includes a water inlet 102 for receiving contaminant-laden input water (e.g., water containing microplastics and biochemical compounds desired to be removed) into a first cell corresponding to the first filtration stage 110 of the water filtration system 100. Wastewater may be actively pumped into the first cell corresponding to the first filtration stage 110 of the water filtration system 100. An arrow labeled 104 indicates the direction of water flow. The first filtration stage 110 includes a sieve with appropriately sized holes. In this embodiment, a primary fine mesh 112 and a secondary fine mesh 114 are included to capture or filter out larger particulates present in the water and debris too large to be consumed by the organisms present in the biofilter in subsequent filtration stages. The size of the screens may vary based on the prevalence of large particulate matter in the location where they are deployed. For example, in this embodiment, holes sized between 0.5 mm and 0.25 mm may be used. In some embodiments, pretreatment of the input water may be omitted if the input water does not contain significant amounts of large debris or if filtration is performed in a separate pretreatment step. Water exiting the first filtration stage 110 enters a first transfer conduit 116, which transfers the water from the first filtration stage 110 to a second cell corresponding to the second filtration stage 120 of the system 100. In this embodiment, similar to conventional flocculation processes used to treat drinking water, microalgae in suspension are provided to the second filtration stage 120 to interact with contaminants in the wastewater. More specifically, as the algae in suspension flow in the direction indicated by the arrow labeled 124, they may attach or flocculate particulates and other biochemical contaminants in the water, forming large algal particles suitable for ingestion by bivalve mollusks located in the third filtration stage 130. In some embodiments, macroalgae may be used instead of microalgae. Alternatively, a combination of macroalgae and microalgae may be used. The algae may be sourced from any suitable location, taking into account the potential risk of introducing invasive species. In some embodiments, highly productive monoculture strains of algal cells may be utilized to improve growth and nutrient removal efficiency for a given influent condition.Alternatively, more potent mixed strains can be advantageously utilized in situations where multiple growth and removal parameters may be present. The algal growth rate at typical algal densities during normal operation of the filtration system is sufficient to compensate for losses due to dilution and runoff, thus maintaining the algal density. The inventors used macroalgae and microalgae sourced from Sober Island, Nova Scotia, Canada, for use in benchmark and initial prototype testing.

[0039] Also shown in second filtration stage 120 is a baffle structure 122 that may be used in some embodiments to provide attachment sites for algae within the cells corresponding to second filtration stage 120 and promote interaction between the algae species and contaminants in the water. Thus, the algae species can act similar to a flocculant and be used to attract contaminant particles into the algae cells, so that when the algae cells are consumed by bivalve mollusks in subsequent filtration stages of filtration system 100, the same bivalve mollusks also consume the contaminants, allowing them to be removed from the water.

[0040] Water to be filtered can be circulated from the second filtration stage 120 to a third cell 130-1 corresponding to the third filtration stage 130 via a second transfer conduit 126 connecting the two stages. In the third filtration stage 130, the wastewater passes through a flow path of bivalve mollusks suspended from one or more hanging assemblies 132. The direction of fluid flow is indicated by arrows labeled 134. The compartments of bivalve mollusks can siphon (i.e., ingest or consume) algae and associated particulates from the water in a process similar to clarification or sedimentation in conventional drinking water treatment plants. More specifically, in the third filtration stage 130, the bivalve mollusks consume the algae cells transferred from the second filtration stage 120, thereby consuming contaminants already absorbed by the algae cells. Thus, the bivalve mollusks can be used to remove contaminants from the water. Additionally, bivalve mollusks can promote the deposition of nitrogenous wastes onto the substrate within the bioreactor, sequestering the nitrogenous wastes from the water body and allowing microorganisms to more easily initiate denitrification. Examples of bivalve mollusks include, but are not limited to, the American oyster (Crassostrea virginica) and the blue mussel (Mytilus edulis).

[0041] In this embodiment, the suspension assembly 132 comprises removable bivalve hangers attached to the mussel beds using a coarse-grained substrate. Such suspension assemblies promote water flow over the bivalves, allowing for more effective diversion of water flow closer to the bivalves. The coarse-grained material may be a nylon netting, allowing the bivalves to attach and hang from the beds. The bivalves may be vertically distributed along the assembly 132 to allow for suction at different depths. However, other methods of fabricating the suspension assembly 130 may be suitable. In this embodiment, the bivalves used in the third filtration stage 130 may be native to the farm location. For example, the inventors used bivalve mollusks native to Atlantic Canada, where the exemplary filtration system 100 is installed. To avoid the introduction of invasive bivalve species, appropriate native bivalve mollusk species may be used based on the location of the filtration system 100. This type of flexible selection principle can also be applied when selecting the algae species to use, ensuring that the least invasive, most efficient species is selected based on the site location where the filtration system will be installed. Thus, the filtration system 100 can be adapted, configured, or modified to best suit the site of the aquaculture facility.

[0042] Also, as shown in this embodiment, the third filtration stage 130 spans two cells of the filtration system 100: a third cell designated by reference numeral 130-1 and a fourth cell designated by reference numeral 130-2. A third transfer conduit can be provided to facilitate water flow between the third cell 130-1 and the fourth cell 130-2. The fourth cell 130-2 also contains bivalve shellfish for further removal of algal cells and, therefore, contaminants. The direction of fluid flow is indicated by the arrows designated by reference numeral 134-2. Together, the third cell 130-1 and the fourth cell 130-2 effectively provide a clarification process similar to that found in drinking water treatment by removing contaminants present in the algal cells. The filtered water can then exit the filtration system 100 at outlet 150 and is intended to provide land-based quality water for farmed seafood with the benefits of marine aquaculture facilities (i.e., reduced cost, energy use, and carbon footprint). Additional cells containing bivalve mollusks may be included as desired. However, it is contemplated that a single cell containing bivalve mollusks may be sufficient to achieve the desired level of filtration. During operation of the filtration system 100, the water being filtered may be recirculated back to an earlier or "upstream" location. For example, in the embodiment depicted in FIG. 1 , a recirculation process is employed in which a portion of the water in the fourth cell 130-2 of the third filtration stage 130 is recirculated back to the third cell 130-1 of the same stage. Recirculation may be accomplished by pumping the water in the fourth cell 130-2 back to the third cell 130-1 through a recirculation conduit 136. In an exemplary embodiment, the flow rate may vary between approximately 240 gallons per hour (GPH) and approximately 1000 GPH. This recirculation process may be implemented to ensure removal of algal cells by the bivalve mollusks. The water being treated may be actively pumped between these two cells to ensure that the wastewater moves through each cell as intended.

[0043] In some embodiments, as shown in Figure 1, a second recirculation path is also provided via a second recirculation conduit 140. This recirculation path returns water being treated in the fourth cell 130-2 of the third filtration stage 130 to the second cell of the second filtration stage 120.

[0044] In other embodiments, the same filtration system 100 can be used or configured to filter waste / effluent generated at a fish farm. Wastewater may enter a first filtration stage 110 to screen out large particles. Nitrogen compounds and phosphates can then be utilized by algae in a second filtration stage 120. These algae can then be ingested by bivalve mollusks in a third filtration stage 130 to remove excess nitrogen and phosphorus from the body of water before the water is released into the surrounding water through an outlet 150. Alternatively, in some embodiments, the water exiting outlet 150 can be directed to a second filtration system of the same or a different configuration for further filtration.

[0045] Generally, any bivalve / algae combination can be used in the filtration system 100 of the present disclosure. In an exemplary embodiment for the North Atlantic marine market, 2 L of haptophyte (Isochrysis sp.) and 200 mussels (Mytilus edulis) may be used as algae species. These species and amounts were determined through multiple laboratory experiments during the pilot phase to ensure the appropriate algae:bivalve ratio was appropriate for the goal of 95% nitrogenous waste removal. In the exemplary embodiment, haptophyte and mussels may be present, but the species may be varied based on the location of the biofilter to ensure optimal conditions (i.e., temperature, salinity) for the algae / bivalve filtering effect. This ensures that there is no risk of introducing invasive or exotic species if these species are released outside the system.

[0046] As can be appreciated from the present disclosure, the combination of algae and bivalve mollusks can be used to remove microplastics and nitrogenous waste from their surrounding aquatic environment. Therefore, as long as the bivalve mollusks can obtain the nutrients they need by consuming algae, the filtration system 100 can function. Therefore, the system described above can function with a minimum of two cells to house the algae and bivalve mollusks for water treatment. Additional cells can be introduced as needed for redundancy or to achieve desired treatment results. For example, additional cells containing filter mesh can be added.

[0047] The inventors have found that macroalgae (Ulva) can be used as a nutrient source for bivalve mollusks. Additionally, phytoplankton can also be used. For example, in Atlantic Canada, phytoplankton can be sourced from the Dalhousie Aquatron, the NRC Marine Research Station at Ketch Flarbour, Acadian Seaplants, and other local sources. By sourcing bivalve mollusks and phytoplankton cultures from local sources, a template known as the Biofilter Method Template (BMT) can be established. The inventors developed this template to simplify the procurement and selection of bivalve mollusks and algae species for use in the filtration system 100. BMT is a process that mimics the water clarification relationship found in nature between bivalve mollusks and algae species and utilizes this relationship for application within a mechanical filtration system or process. BMT establishes a combination of symbiotic algae and bivalve mollusks within a given location's ecosystem, similar to the amounts / ratios of the previously described exemplary embodiment for the North Atlantic marine market, that meet certain characteristics and suggest suitability for use in the filtration system 100. Examples of such criteria include bivalve mollusks' uptake rate and range, bivalve mollusks' survival rate relative to the pump, bivalve mollusks' lifespan, algae's flocculation of nitrogen and ammonia, and algae's flocculation of particulates. Using BMT to appropriately localize bivalve mollusks and algae can mimic the natural filtering relationship between bivalve mollusks and algae within the filtration system 100, facilitating location-based species sourcing / selection. In one example combination, the inventors found that locally sourced phytoplankton is highly nutritious and suitable for use with American oysters utilized in deployments in Atlantic Canada. Furthermore, this phytoplankton is capable of flocculating nitrogen and ammonia.

[0048] BMT can be applied to any area of ​​the world where it is desired to deploy a filtration system 100. It is preferable to find species in those local aquatic environments that are capable of filtering large amounts of particulate matter.

[0049] Phytoplankton, which is most capable of aggregating particulates such as microplastics, furans, dioxins, nitrogen, phosphorus, and other particularly harmful substances (PFIS), may also be considered. BMT provides the dynamism necessary to determine the location of the filtration system 100. Therefore, the application of BMT allows bivalve mollusks to be obtained from local aquaculture facilities around the world, allowing any operator of the filtration system 100 to operate globally without concern for introducing potentially invasive foreign species into the local ecosystem. Tests can be conducted on local algae and bivalve mollusks species combinations to determine their filtration rates, or the rate at which the bivalve mollusks and algae "process" or ingest undesirable particulates in the water to achieve a predetermined level of water purity. This evaluation can be used to determine the ability of those species to filter particulates, i.e., the viability of the species used in the filtration system 100, as well as the operating conditions (e.g., water flow rate, temperature, aeration, etc.) required by the algae and bivalve mollusks combination for optimal filtration performance. Optical spectral measurements can be used in the test procedure to evaluate the reduction in wastewater turbidity (i.e., the increase in water clarity as a result of particulate reduction) as a function of time. A control sample containing a phytoplankton / algae culture can be taken. Another sample can be taken after a period of time to determine the change in turbidity. This evaluation allows the operator to determine the filtration rate of a given bivalve and algae combination. In other embodiments, the filtration system 100 can be configured to consist of three compartments or cells connected by appropriate tubing (not shown). Water flow can be induced at least in part by gravity or at least in part by a pump.

[0050] The first compartment may be configured to receive wastewater containing microplastics, which may be passed through an inorganic mesh filter positioned above the bottom of the compartment to use gravity to filter out larger microplastics.

[0051] This sieved water may be collected in a second cell or compartment for comparison with the original input water and then pumped to a third cell or compartment. This third compartment may be filled with bivalve mollusks, and the water may be allowed to settle for a residence time, allowing the bivalve mollusks to siphon off any remaining microplastic particles not captured by the inorganic mesh. In one embodiment, hard clams (formerly known as Mercenaria mercenaria) are used to perform clarification under the pressure of the pumped water. Varying flow rates, water temperatures, and water volumes can be tested to determine the optimal parameters for clarification by this species of organism.

[0052] Another embodiment of the filtration system may include four compartments consisting of four large vessels arranged in a linear fashion, rather than the gravity-driven water-pump combination used in the previous embodiment. FIG. 2 illustrates a linearly configured filtration system 200. Elements corresponding to those in the filtration system 100 of FIG. 1 are similarly numbered. Water enters the filtration system via inlet 202 into a first compartment corresponding to the first filtration stage 210. A corresponding sieve filter (not shown) may be provided within the first filtration stage 210 to filter out large particulate matter. The water then travels via first transfer conduit 216 to a second compartment corresponding to the second filtration stage 220 for contaminant agglomeration or coagulation, before passing via transfer conduits 226 and 236 to third and fourth compartments 230-1 and 230-2 corresponding to the third filtration stage 230, respectively. A recirculation conduit 240 may also be provided to recirculate water from the third filtration stage 230 to the second filtration stage 220. The filtered water exits through an outlet 250 located in the fourth compartment 230-2.

[0053] The configuration of this embodiment of FIG. 2 may be operable to treat wastewater on a larger scale (i.e., a larger volume over a given period of time). Additional connections can be added to recirculate water between compartments to maximize filtration. Similar to the filtration systems described above, an inorganic mesh filter can be used in the initial filtration stage to physically filter out larger particles. The final two compartments of the system, with a fourth compartment, can be used to contain local bivalve mollusks to siphon smaller particles from the water. An additional compartment 220 can be added between the mesh filtration compartments 210 and before the first compartment 230-1 containing the bivalve mollusks to house additional algae for further parallel biological (bio)filtration. FIG. 3A shows another embodiment of a filtration system 300 in a vertically stacked configuration, in which each of the containers corresponding to the compartments or cells are stacked in a vertical arrangement. Corresponding elements found in the filtration systems 100 and 200 of FIGS. 1 and 2 are similarly numbered. Wastewater entering the filtration system via an inlet (not shown) enters the first compartment, which corresponds to the first filtration stage 310. A corresponding sieve filter (not shown) may be provided within the first filtration stage 310 to filter out larger particulate matter. Additionally or alternatively, a particulate filter (not shown) may be included within the first stage 310 to remove fine particles. The wastewater then travels through a first transfer conduit 316 to a second compartment corresponding to the second filtration stage 320 for agglomeration or coagulation of particles and contaminants, before being passed through transfer conduits 326 and 336 to third and fourth compartments corresponding to the third filtration stage 330, respectively. The vertical arrangement of the compartments in this embodiment allows the wastewater to flow between the compartments without additional pumps. A recirculation conduit 340 may also be provided for recirculating the wastewater from the third filtration stage 330 to the second filtration stage 320 by a pump. The filtered water exits through an outlet 350 located in the fourth compartment 330-2. In some embodiments, compartment 320 may be equipped with LED grow lights and mechanical aerators, which provide the appropriate light intensity and aeration, respectively, to promote algae growth.The aerator also serves to mix and agitate the wastewater and inhibit biofouling. In some embodiments, the wastewater from outlet 350 may be passed through additional filtration stages using different filtration technologies so that the described filtration system can be used to complement other commonly available filtration systems.

[0054] FIG. 3B shows an alternative configuration in which each filtration compartment is provided on a shelf 360 . The following examples are provided to further illustrate embodiments of the present invention, but are intended to be illustrative only and not to limit the scope of the invention in any way.

[0055] Example 1 A series of experiments were conducted to determine whether nutrients could be removed from aquaculture wastewater by a bioremediation process. The schematic diagram below (Scheme 1) shows the process flow diagram of the experiments conducted in this study. The experiments were conducted at bench scale to determine (1) the feasibility of the bioremediation process, (2) the optimal flow rate and residence time in the bioreactor, and (3) the optimal bioreactor conditions and species for enhanced nitrogen and phosphorus removal.

[0056] [Table 1] Initial experiments to assess the viability of this process were conducted using a benchtop biofilter unit with aquaculture wastewater from a local Nova Scotia hatchery. Samples were taken at the inlet, outlet, algae chamber, and bivalve chamber to determine where and to what extent nitrogen and phosphorus removal was occurring within the biofilter system. Experiments were conducted with marine and freshwater algae and bivalve species and the corresponding influent aquaculture wastewater. The results for algae and bivalve species in freshwater are shown in Graph 1 below.

[0057] [Table 2] To further evaluate the biofilter's multiple processes, a series of experiments were conducted to determine the optimal combination of flow rate and retention time in the algal chamber. Three flow rates were calculated based on bench-scale algal chamber volumes and retention times of 6 hours, 1 day, and 2 days. The objectives of these experiments were two-fold: (1) to determine which retention time resulted in the highest nitrogen and phosphorus removal rates, and (2) to use the data from these experiments to calculate the size of a full-scale biofilter for aquaculture facilities based on flow rate data collected from a Nova Scotia hatchery.

[0058] Samples were collected as follows: For the first six hours, samples were collected every two hours at four locations for all three residence times: the influent wastewater, the algae chamber, the bivalve chamber, and the system effluent. For residence times greater than six hours, sampling increments increased to every six hours on the first day and every 12 hours on the final day. Duplicate samples were collected and stored in accordance with U.S. Environmental Protection Agency guidelines for sample storage.

[0059] A wild-type mixed strain obtained from Lake McGowan was used, with flow rate and retention time optimized. To evaluate the effectiveness of this wild-type mixed strain, a single strain of Chlorella sp. was tested. Chlorella was chosen as a comparison because it is known for its robustness and fast growth among freshwater algae and has been extensively studied. To evaluate the efficiency of the use of Chlorella and the wild-type mixed strain, two benchtop experiments (Figure 1) were conducted. The first used Chlorella sp. in an algal bioreactor, and the second used a high-concentration wild-type mixed strain from Lake McGowan. Each experiment was conducted with a retention time of 2 days and a flow rate of 0.026 L / min. The system's phosphorus and nitrogen waste removal capacity, as well as the effect on other water quality indicators (pH, BOD, COD, and TSS), were observed. All tests were conducted using wastewater collected from the Cape Breton Provincial Hatchery, and untreated wastewater was collected as a negative control for each sample.

[0060] As with the previous two-day test, samples were collected every two hours for the first eight hours of the detection period, every six hours for the next 18 hours, and every 12 hours for the final 24 hours. Duplicate samples were also collected at each treatment stage within the benchtop system (wastewater influent, algae bioreactor, bivalve bioreactor, and treated wastewater). These samples were stored in accordance with U.S. Environmental Protection Agency guidelines for sample storage. Chemical analysis was contracted to the Centre for Water and Resource Studies at Dalhousie University.

[0061] During each experiment, duplicate water samples were collected at least in duplicate, and triplicate if possible. Water samples were analyzed at the Innovative Waste Management Laboratory at Dalhousie University for nitrate-nitrogen (NO3-N) and ammonia-nitrogen (NH4-N) concentrations using a Bran and Luebbe AutoAnalyzer III (Seal Analytical Inc., Mequon, WI, USA) and a colorimeter.

[0062] The examples and corresponding figures used herein are for illustrative purposes only. Different configurations and terminology may be used without departing from the principles expressed herein. While the present invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the scope of the invention. The scope of the claims should not be limited by the exemplary embodiments set forth in the examples, but should be accorded the broadest interpretation consistent with the description as a whole.

[0063] List of References ·Cauwenberghe LV, Janssen CR. 2014. Microplastics in bivalves cultured for human consumption. Environmental Pollution 193:65-70. ·Gifford S, Dunstan R, Oconnor W, Roberts T, Toia R. 2004. Pearl aquaculture - profitable environmental remediation? Science of The Total Environment 319:27-37. ·IntraFish. 2018. Land-based salmon farming Aquaculture’s new reality. ·Webb JL, Vandenbor J, Pirie B, Robinson SM, Cross SF, Jones SR, Pearce CM. 2013. Effects of temperature, diet, and bivalve size on the ingestion of sea lice (Lepeophtheirus salmonis) larvae by various filter-feeding shellfish. Aquaculture 406-407:9-17.

Claims

1. 1. A water filtration system for removing particulate and biochemical waste from water, comprising: a first compartment containing algae in suspension, the algae usable to agglomerate the particulate waste and the biochemical waste in the water to form algal microparticles; a second compartment that receives the water and the algae particles from the first compartment through a fluid transfer conduit; a first set of suspension assemblies disposed within the second compartment, each suspension assembly including a bivalve shell usable to siphon the algae particles from the water; A water filtration system comprising:

2. a third compartment containing a mesh filter for removing a portion of the particulate waste from the water to produce pretreated water, the pretreated water being provided to the first compartment through a second fluid transfer conduit; The water filtration system of claim 1 .

3. a fourth compartment for receiving water and algae particles from the second compartment through a third fluid transfer conduit, the fourth compartment including a second set of suspension assemblies, each of the second set of suspension assemblies including a bivalve shell usable to siphon the algae particles from the water; The water filtration system of claim 1 .

4. a fluid recirculation conduit for recirculating a portion of the water and the algae particles from the fourth compartment to the third compartment. The water filtration system of claim 3 .

5. a fluid recirculation conduit for recirculating a portion of the water and the algae particles from the fourth compartment to the first compartment. The water filtration system of claim 3 .

6. the first compartment having at least one baffle structure for containing the algae within the first compartment; The water filtration system of claim 1 .

7. the algae and the bivalve mollusks correspond to algae species and bivalve mollusks, respectively, present in the geographic location of the system; The water filtration system of claim 1 .

8. The algae is nutritious for the bivalve mollusks used in the filtration system. The water filtration system of claim 1 .

9. The species of algae and bivalve mollusks are selected based on at least one of: (i) the uptake rate of the bivalve mollusks; (ii) the uptake range of the bivalve mollusks; (iii) the survival rate of the bivalve mollusks relative to the pump; (iv) the lifespan of the bivalve mollusks; (v) the flocculation of nitrogen by the algae; (vi) the flocculation of ammonia by the algae; and (vii) the flocculation of the particulate waste by the algae.

9. The water filtration system of claim 8.

10. The bivalve is either an American oyster (Crassostrea virginica) or a mussel (Mytilus edulis), and the algae is phytoplankton. The water filtration system of claim 1 .

11. The bivalve is a mussel (Mytilus edulis) and the algae is a haptophyte (Isochrysis sp.), The water filtration system of claim 1 .

12. It contains 200 bivalve mussels (Mytilus edulis) and 2L of haptophyte (Isochrysis sp.), 12. The water filtration system of claim 11.

13. 1. A method for filtering water to remove particulate and biochemical waste products, comprising: providing a first filter containing algae in a suspension; directing the water containing the particulate waste and the biochemical waste into the first filter, wherein the algae in the first filter aggregate the particulate waste and the biochemical waste to form algal microparticles; directing the water and the algae particles to a second filter containing bivalve mollusks operable to siphon the algae particles from the water; A method for filtering water, comprising:

14. and pretreating the water by directing the water containing the particulate waste and biochemical waste through a third filter including a mesh filter before directing the water containing the particulate waste and biochemical waste through the first filter. The method of claim 13.

15. directing the water and the algae particles from the second filter toward a fourth filter containing bivalve mollusks that can be used to siphon the algae particles from the water; The method of claim 13.

16. recirculating a portion of the water and algae particles from the fourth filter to the third filter.

16. The method of claim 15.

17. recirculating a portion of the water and algae particles from the fourth filter to the first filter.

16. The method of claim 15.

18. providing the first filter with at least one baffle structure to contain the algae within a first compartment of the first filter; The method of claim 13.

19. the algae and the bivalve mollusks correspond to a combination of algae species and bivalve mollusks present at the geographic locations of the first filter and the second filter, respectively; The method of claim 13.

20. the algae species is nutritious to the bivalve mollusks; 20. The method of claim 19.

21. The species of algae and bivalve mollusks are selected based on at least one of: (i) the uptake rate of the bivalve mollusks; (ii) the uptake range of the bivalve mollusks; (iii) the survival rate of the bivalve mollusks relative to the pump; (iv) the lifespan of the bivalve mollusks; (v) the flocculation of nitrogen by the algae; (vi) the flocculation of ammonia by the algae; and (vii) the flocculation of the particulate waste by the algae.

21. The method of claim 20.

22. The bivalve is either an American oyster (Crassostrea virginica) or a mussel (Mytilus edulis), and the algae is phytoplankton. The method of claim 13.

23. The bivalve is a mussel (Mytilus edulis) and the algae is a haptophyte (Isochrysis sp.), The method of claim 13.

24. It contains 200 bivalve mussels (Mytilus edulis) and 2L of haptophyte (Isochrysis sp.), 24. The method of claim 23.

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