Patent Application
20240415102
The present disclosure relates to an additive based on vitamins, minerals, among others, and its use to improve the efficiency of biofilters used in recirculating aquaculture systems (RAS) which will allow improving the ammonia treatment, and in general, the quality of the water in said systems.
Nowadays, aquaculture is a protein key provider around the world by providing several species such as salmon, tilapia, catfish, or others. Due to this, thousands of tons of fish are farmed every day in freshwater hatcheries and sea cages to be consumed throughout the world.
An example of on-land hatcheries is the one that farms salmon wherein this species is farmed from the egg stage until it can be delivered to the sea in the case of fish going to the sea and which are called smolt the size of which is approximately 100-120 grams.
In general, salmon aquaculture or of any other species can be carried out by means of three different approaches:
However, in order to achieve these benefits, the hatchery of a RAS system must include, in addition to the fish tank, the following components:
It is worth highlighting that component (h), i.e., the biofilter, is one of the key elements in the hatchery using a RAS system and is often a limiting factor. In the biofilter there are elements with a large surface area generically called bio blocks to which bacteria are attached which transform the ammonia produced by the fish first into nitrite (NO2) and afterwards, from NO2, produce nitrite (NO3).
In view of the above, the object of the present application is to address the technical problem related to the production of ammonia which leads to an increase in the concentration of nitrite and nitrate in the biofilter of the hatchery, wherein this component is the main point where the proposed additive works, as explained in further detail below.
Currently, there is a trend to increase the size of the hatchery farmed fish to a post-smolt size of 500 to 600 grams or, in some cases, up to a final commercial size of 5 kilograms. The basic principles of the technologies remain the same, however in order to accomplish the aforementioned, it is necessary to increase the size of the hatchery plant and, thus, the investment.
As mentioned above, the biofilter is a key component of the RAS system, where the feed being delivered to the fish has approximately 50% protein content comprising nitrogen as one of its key components such as an amide radical (NH2). The proteins in the feed are consumed by the fish and a part is excreted as NH3 through the gills and another part as undigested protein in the feces.
There is also a part of the food which is not consumed by the fish and that is dissolved in the water. Nitrogen from protein in food and feces eventually breaks down into NH4+ in the water and is bound to the amount excreted through the gills of the fish. The NH4+ or ammonium ion in water is in equilibrium with NH3, which is dissolved ammonia, an equilibrium that depends on the pH range in which a pH 7 or less begins to predominate the NH4+ (
In addition, given the fact that this is a recirculating system, the amount of NH4+ increases, depending on the make-up water to 50 times the amount produced by the fish. As is known, both the NH4+ and the NH3 are toxic to fish depending on the species being farmed and can be found at levels as low as 0.012 ppm.
The current way to avoid toxic levels of NH4+—NH3 is to transform these compounds into other less toxic forms of nitrogen, which can be done biologically using the following bacteria:
NH4++2O2→NO2−+2H20 Nitrosomonas
2NO2−+O2→2NO3− Nitrobacter
Where nitrite or NO2− is also toxic to fish at a low level, however nitrate or NO3− can be supported at higher levels.
The biofilter, which can be a fixed or fluid component, contains a structure of a material that, for example, is made of plastic with a large surface area. The water passes through this biofilter and since it is rich in nutrients, it allows bacteria to slowly begin to attach themselves to its surface. Among the bacteria being attached to the biofilter, there are the Nitrosomonas bacteria that first convert NH4+ in NO2−.
Subsequently, the presence of NO2− allows for the appearance of Nitrobacter bacteria to convert NO2− into NO3−. This phenomenon is called filter priming and can take between 14 and 21 days (
If fish are removed from the farming tank, the bacteria quickly starve due to the lack of food and in this case the biofilter will have to be primed again. This is a major disadvantage of biofilters, unlike mechanical parts such as pumps, biofilters cannot increase or decrease their production, they cannot be replaced in case of failure and depend on the amount of living bacteria which, in turn, depends on the amount of food available for the bacteria to grow, and also depends on the appropriate conditions of oxygen and space.
To further complicate the operation of a RAS system, the 2-step digestion of the NH4+ species means that the levels of NO2− and NO3− present in water depend on the rate of digestion of both bacteria and also on the amount of NH4+ being incorporated throughout the day into the water. This amount is not constant throughout the day, as it is highly influenced by the times the fish are fed. Although the biofilter focuses on these 2 bacteria, there are also other bacteria that digest the carbon-based byproducts in the water and compete with these bacteria for space and oxygen in the biofilter. Even under certain anoxic conditions, bacteria can proliferate that generate highly toxic compounds to the fish such as H2S or CH4.
That is, the decomposition of solid and dissolved organic waste can be achieved in a recirculation facility by means of this wide variety of naturally occurring bacteria. Different groups of bacteria have unique and different growth requirements, i.e., macro, and micronutrient needs. Since they compete for the same growth substrates and organic raw materials, at times, the availability of specific micronutrients (vitamins and minerals) is the limiting factor for bacterial growth. Due to this reason, the input of selected micronutrients can cause significant and beneficial changes in the nature and efficiency of the dominant bacterial populations.
As previously mentioned, bacteria typically thrive in the biofilter substrate, which is a space where water has a certain residence time and has a large surface area where biofilms of bacteria form. The biofilter material can be made of plastic, metal or other material having different geometrical shapes and can be fixed bed, fluidized bed, with or without injection of air or oxygen.
Recirculating system hatcheries (RAS) are normally designed for a certain number of kilograms of feed per day that can be added and digested by the existing bacteria in the biofilter.
However, there are currently a number of problems that occur in RAS systems such as:
In the state of the art there is a wide variety of documents related to the technical field of the present application, such as:
US 2008/210630 (A1) relates to apparatus, methods, and applications for treating wastewater, and more particularly to biological processes for removing pollutants from wastewater. This invention further relates to apparatus and methods for growing microbes on-site at a wastewater treatment facility, and for economically inoculating sufficient microbes to solve various treatment problems rapidly.
US2010/209988 (A1) Microbially colonized charred biological material, such as charcoal, wherein the colonizing microbes are capable of metabolizing at least one selected environmental substance, such as a pollutant, and wherein a selective amount of the substance that is present in the charred material provides protected colonies of environmentally active microbes useful in bioremediation.
However, the state of the art of the technical field of the present application does not disclose or suggest an additive composed of organic micronutrients of plant origin and minerals in specific proportions that allow stimulating all types of bacteria in a recirculation system (RAS) used in aquaculture thus improving the efficiency of biofilters.
The proposed additive is designed to optimize the activity of bacteria located in a biofilter related to the fish farming keeping in mind and considering that the water has to maintain an equilibrium under optimal conditions for the rearing of farmed fish. In addition, there is no additive comprising specific types of nutrients that can be used for stimulating multiple bacteria.
In accordance with the aforementioned, the present application proposes as a technical solution to the previously mentioned problems, an additive that is a product composed of organic micronutrients of plant original and minerals which have been shown to stimulate all types of bacteria that will be useful in all types of biofilters used in aquaculture. Once these micronutrients and minerals are made available to the biological community in wastewater, the metabolic rates of specific bacterial populations increase drastically wherein the beneficial impact of micronutrients is more significant for facultative anaerobic populations.
An aspect of the present invention provides an additive that is a product composed of organic micronutrients of plant origin and minerals which have been shown to be useful for stimulating all types of bacteria. Once these micronutrients are made available to a biological community in wastewater, the metabolic rates of bacterial populations can be increased drastically wherein the beneficial impact of micronutrients is more significant for facultative anaerobic populations, which allows to improve the efficiency of biofilters used in RAS systems.
This product comprised of micronutrients consists of a mixture of vitamins, amino acids, and minerals:
Vitamins and other organic compounds:
Minerals:
This additive by stimulating the different types of bacteria will achieve better digestion of feces and undigested food, which will allow less protein to be converted into ammonia, thereby reducing the general levels of ammonia per kilo of biomass.
This additive will also allow facultative bacteria to digest the carbon side of the organic matter faster thus allowing more space and oxygen to be available in the biofilter for the ammonium and nitrite converting bacteria.
Furthermore, the proposed additive will be able to inhibit anoxic bacteria that produce compounds such as H2S or CH4.
In summary, the proposed additive composed of micronutrients and minerals, added to a recirculating RAS system in aquaculture will significantly improve the efficiency of the biofilter by reducing the levels of toxic chemical compounds such as ammonium and nitrite, reducing oxygen consumption and providing better general conditions of water quality that cause lower mortality, feed conversion ratio hereinafter also known as FCR (Feed Conversion Ratio) and daily growth rate also known as SGR (Standard Growth Rate).
In order to provide a clear and detailed description of the present invention, a specific example, using salmon aquaculture will be provided, a major export species compared to other aquaculture species. However, it should be kept in mind that the technical problem and the state of the art for the technical field addressed in this application must be considered of a similar nature for any species cultivated by aquaculture.
Solid and dissolved organic waste in recirculating hatcheries are degraded by bacteria that are generally classified by their ability to survive and multiply in the presence or absence of oxygen.
Aerobic bacteria function in the presence of oxygen, anaerobic bacteria function in the absence of oxygen, and facultative bacteria can function in the presence or absence of oxygen.
All biological wastewater treatment plants include one or more of these three main bacterial groups. Typically, the rate-limiting step in the removal of organic solids from wastewater is hydrolysis. An important factor contributing to this problem is that hydrolyzing bacteria do not function at full capacity due to limitations related to the availability of nutrients necessary for their operation and activity.
Once the micronutrients and minerals are made available to the biological community in wastewater, the metabolic rates of specific bacterial populations increase drastically. Comparatively, the beneficial impact of micronutrients is more significant for facultative anaerobic populations. Micronutrients allow facultative anaerobes to actively degrade organic compounds in unaerated portions which are not normally designed to work in reactors such as surge tanks or settling tanks, making the entire plant more efficient.
As a result, facultative anaerobes convert a much higher proportion of acetic acid into atmospheric gases, rather than additional biosolids. This also results in a significantly lower oxygen demand in aerobic bioreactors because a significant part of the acetic acid load is diverted from pure aerobes to facultative anaerobes. The net effect is a less volume of sludge/biosolids requiring processing and disposal and less energy demand for aeration.
In systems related to aquaculture, when there is improved digestion of feces and undigested food this has an impact on the fact that less proteins are converted into ammonia, thus reducing general levels of ammonia per kilo of biomass.
On the other hand, facilitating faster digestion of the carbon side of the organic matter by facultative bacteria allows for increased space and oxygen availability in the biofilter for ammonium and nitrite converting bacteria.
Nitrobacter and Nitrosomonas bacteria are the main bacteria that convert ammonia into nitrite and then produce nitrate.
The proposed additive enables an elevated metabolism rate in these bacteria, leading to a stable state of the biofilter for approximately 14 days. This results in a reduced peak of NH4+ l and NO2, along with an enhanced overall capacity for processing feed in the biofilter. Consequently, it contributes to better water quality.
Additionally, the proposed additive, which is a product comprised of organic micronutrients of plant origin, has been proven to stimulate all types of bacteria present in biofilters.
This product, composed of micronutrients, consists of a mixture of vitamins, amino acids, and minerals.
Vitamins and other organic compounds:
Amino acids including alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, leucine, phenylalanine, proline, serine, threonine, total lysine, tyrosine, valine 0.5-1.0% w/w
Minerals:
The proposed additive has 3 aspects that are not evident in the current state of art. Although this additive comprises compounds that belong to generic categories of vitamins, amino acids, and minerals it features specific proportions and ingredients designed for a distinct purpose that is related to the improved yield of a biofilter used in aquaculture within a RAS system.
The above implies the following:
The combination of point B and C achieves a significant increase in the capacity of bacteria in the water to digest ammonium and nitrite, thus allowing the biofilter to process a greater amount of kilograms of food per day per cubic meter of biofilter.
These advantages will be obvious from the examples below.
The following examples aim to illustrate the invention and its preferred embodiments, however they should not be considered, under any circumstances, as limiting the scope of protection of the invention which is determined by the content of the claims attached to the present application.
In order to verify the efficiency of the proposed additive, two tests were carried out at the ATC and R&D facilities in Puerto Montt, Chile. The ATC laboratories are a world class R&D facility owned by Biomar and Empresas Aquachile, which are used to test vaccines, feed, disease control and other aquaculture-related experiments.
In order to carry out these tests, the proposed additive was added by means of a peristaltic pump or the like with flow control to the aquaculture recirculation system wherein there is a water tank and no direct contact between the additive and the fish being farmed, just as it is in the biofilter, rotary drum filter or sump pump reservoir.
The proposed additive is added in an amount between 12 to 20 ml of additive per kilo of food that is provided to the fish, determined based on the monitored concentration of ammonia and that can reach a constant value.
In order to maintain an oxygen level of not less than 35% in the water leaving the biofilter, a means that supplies oxygen to the water pumped to the biofilter must be employed, either through a venturi or an oxygen cone. This should be monitored online through an oxygen sensor that operates a control valve incorporating oxygen via one of the previously mentioned injection methods.
In a recirculation system (RAS), over a period of 30 days, the activation time or priming of a biofilter was evaluated by means of the proposed additive, for which 1500 fish of the Atlantic salmon species (Salmo salar) were selected with an average weight of 75.8 grams. These were distributed in the same biomass in rooms 4A and 4B of the ATC Patagonia research center using 5 tanks of 0.5 m3 each (150 fish/tank) where fish were fed with a commercial diet to satiety and kept in a freshwater recirculation system with a photoperiod of 24 hours of light at a temperature of 14±0.2° C. and, at a pH 7.5±0.3.
The control group without additive was kept in room 4A and in room 4B was kept the test group where the proposed additive was added by means of a pulse dosing pump.
On the other hand, both the control group and the test group were kept under the same operational conditions of biomass, feed, and abiotic parameters of the farming system.
To monitor the biofilter nitrification process, that is, the biological oxidation process by means of bacteria that convert ammonium (NH4+) into nitrite (NO2) and then into nitrate (NO3), three water quality samples were taken daily at 9, 16 and 20 hours. Where the total ammoniacal nitrogen (TAN) (NH4+—N+NH3—N), 3 samples of nitrite nitrogen (NO2−—N) and 1 sample of nitrate nitrogen (NO3−—N) were measured.
Daily measurements of oxygen, temperature as well as daily feeding portions and mortality were also recorded. Furthermore, weekly measurements of other water indicators, such as chemical profile levels of water, biological oxygen demand (BOD), biochemical oxygen demand (COD) were carried out.
Before beginning the bioassay, the selected fish had an acclimatization period in a 5m3 tank in room 5A in fresh water at a temperature of 14±0.2° C. and at 5 ppt of salinity, fed with a commercial diet of the Brand Skretting, Nutra Parr 60, caliber 2.9 mm. Before being transferred to rooms 4A and 4B, a weight sampling was carried out to homogeneously distribute 150 fish per pond or tank.
Feeding began the day after the pond formation with a Specific Feeding Rate (SFR) of 0.7% commercial diet with approximately 43% protein. Feeding hours were from 9:00 a.m. to 4:00 p.m. Once the period ended, the unconsumed food was quantified, thereby adjusting the feeding rate for the following day considering an additional supply of 15% daily.
During the first week, the system was maintained with 100% recirculation and only the water lost in the daily feed recovery process was replaced. Based on the performance of the biofilter and the well-being of the fish, a replacement rate of 20% of the total volume of the system was considered.
All fish included in the test (dead or alive at the end of the test) were removed by the ATC Patagonia's silage system, thus complying with the current regulations. The silage was removed by an approved company by the corresponding authority which issues a final disposal certificate.
Table 3 shows the results obtained for the concentrations of total ammoniacal nitrogen (TAN) (NH4+—N+NH3—N), nitrite nitrogen (NO2'1—N) and nitrate nitrogen (NO3−—N).
On the other hand, the results of
For a second test, 750 fish of the same size (100 gr) were added to the test group room 4B and control group room 4A and farmed for another 30 days. After 21 days, NH4+ levels in the control group increased beyond the biofilters ability to process said compound, causing significant suffering to fish, increased mortality, decreased feeding rate, and dangerous levels of NH4+.
At the end of 35 days, the test group was being fed between 30% and 50% more than that considered for the biofilter design. The test groups on average grew a 4% faster and had an improved feeding conversion rate of 8.5%.
This second test shows that significant improvements were obtained regarding NH4+ and NO2− levels, thus reducing the global level of these toxic elements for the fish by 70% and 30%, respectively.
The results obtained in this second test are shown in Tables 4 to 7 and
From the results shown in Table 4, it can be seen that the fish in the room of test group 4B experienced a greater weight gain, which implies that there is a more positive impact on the growth and well-being of the fish in the presence of the proposed additive.
From the results shown in Table 5, it can be seen that the fish in test room 4B have a higher value of biomass gained, which directly affects the feed conversion ratio.
From the results shown in Tables 6 and 7 it can be clearly seen an improved growth rate and a higher food conversion ratio in the test groups 4B compared to control groups 4A due to presence of the proposed additive.
Furthermore,
In these
In
The same trends are evident in the results presented in Tables 8 and 9.
Finally,
It is worth highlighting that the use of the proposed additive in a recirculating system (RAS) presents the following advantages:
| Number | Date | Country | Kind |
|---|---|---|---|
| 1761-2021 | Jul 2021 | CL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CL2022/050054 | 5/24/2022 | WO |
