CA2549299A1

CA2549299A1 - System and process to purify water in a freshwater fish farm plant with and without water recirculation by means of metallic foam filter

Info

Publication number: CA2549299A1
Application number: CA 2549299
Authority: CA
Inventors: Joaquin Ruiz Tirado
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-06-02
Filing date: 2006-06-02
Publication date: 2007-12-02

Abstract

A process for purification of water from freshwater fish farm systems which includes the stages, of feeding the water originating from the fish farm pools to a disc filter (2) which operates as mechanical filtration process, directing the water originated in the filter disc (2) to a pumping pool (3), from which it passes to a submerged biological filter (4), a portion of the originating water of the mentioned biological filter passes on to a de-nitrifying filter (5) and from said point it is directed to a percolator filter (6); after passing through the mentioned percolator filter (6), the water passes through a second pumping stage; a portion of the water is passed through a metallic foam filter (9) and then it returns to the fish farm pools;
the rest of the water passes through the oxygenation cones (10) and from there it returns to the pisciculture pools. It also mentions, the use of a porous metallic foam, as a catalyst in the purification of recirculation water in a freshwater fish farm plant with the purpose of eliminating bacteria, pathogens, virus and fungi present in said waters.

Description

SYSTEM AND PROCESS TO PURIFY WATER IN A FRESHWATER
FISH FARM PLANT WITH AND WITHOUT WATER RECIRCULATION BY MEANS
OF A METALLIC FOAM FILTER

The present invention relates in general, to fish farm industry and, particularly, to water purification systems with and without recirculation of said water for fry and salmon and trout, smolt, pisciculture plants, in addition warm water fish such as eels and sea bass, among others.

Through the water recirculation at the fish farm facilities a better control is ob-tained and regulation of the pisciculture environment, a reduction of the entrance of pathogenic organisms originating from external means to the pisciculture systems, a total control of the pro-ductive cycles and a reduction of the environmental impact of the pisciculture activity due to the reduction of the effluent water volume.
A water recirculation system is defined as a productive system that uses water in more than one opportunity at the same pisciculture unit, after being treated and renewed up to a certain percentage. The most usual form to define the degree of water recirculation, relates to daily percentage of renewed water volume in relation to the total flow or volume used in the sys-tem. Thereby, a pisciculture system that incorporates the water recirculation technology is con-formed by two clearly defined important units, namely, destined to the pisciculture of the organ-isms or frys and others to the pisciculture water treatment. A fundamental aspect in the piscicul-ture systems with and without water recirculation is the purification of the flowing water with the purpose of eliminating the fish detrimental microorganisms.

BACKGROUND OF THE INVENTION
The productive yield of fish depends, among other factors, on the nutrition, the productive handling and daily operation, the genetic line quality in use and specially, the health T88001\TOR_LAW\ 6318905\1 2 conditions of the cultivated fish. Considering this last point, it is possible to mention that the in-dustry has been giving more and more importance to the sanitary conditions of the fish in pis-ciculture like a determining factor of the success in the productivity and business yield. In fresh water, one of the main productive restrictions is the high prevalence of bacterial diseases as the Flavobacteriosis in the case the salmon and trout fry. Under the Flavobacteriosis expression a set of diseases produced by bacteria pertaining to the Flavobacteria sort is included, between which they emphasize Flavobacteria columnare, Flavobacteria branquiophilum and principally Flavo-bacteria psicrophylum. Flavobacteria psicrophylum is the agent cause of the rainbow syndrome of trout fry (RTFS), the one that affects different size of fry. The mentioned disease is described in countries of Europe, Japan, Korea, Australia and Chile. Fry mortalities vary from 10 to a 70%
of the affected fish. Another important aspect that appears in fry corresponds to the cold water bacterial disease, which has been responsible for mortalities of 85% in fish farm. The vertical transmission of the disease is discussed, but there is sufficient evidence of the importance of the bacteria transfer through the parent fluids. The diseases associated to Flavobacteria are related to the unfavorable environmental conditions, such as the excess of organic matter, a low oxygen content, fish overcrowding, etc. The capacity of these bacteria to produce acute and chronic dis-eases, together with its presence like in normal water and fish flora, cause that the described ad-verse conditions favour the appearance of an epizootic disease.
The Flavobacteria presence in small fish is associated with injuries in gills, in the skin, as well as fin discoloration. The severity of injuries is variable, giving rise to erosions of the mouth, fins and caudal stalk. In the case of septicemic pattern, a brittle consistency of the spleen is observed and renal inflammation.
Actually a variety of alternatives exist to mitigate the appearance of these and other diseases produced by bacteria, virus either fungi in the cultures of freshwater fishes, some of effective and more or the less verified. However, the control of the fresh water pathologies go through implemented prophylactic programs that significantly avoid or diminish the probability of appearance of the factors involved in the appearance of a disease.

T88001\TOR_LAW\ 6318905\1 3 In this scope, where the present invention is located, it discusses about a filtration process or of purification of the water with and without recirculation in the pisciculture plant of fry and other freshwater fishes based on metallic foam type filter, well known like METAL
FOAM (TM), with the objective to eliminate bacteria, virus and possibly fungi.
Specially the me-tallic foam type filter is adapted to eliminate the Flavobacteria bacteria (in particular Flavobacte-ria psicrophylum) in water with and without recirculation in freshwater fish farm plants.
Among documents of the previous art nearer the matter of the present invention it is a patent application US 6,585,111, granted on July 1, 2003 to The BOC Group plc, titled "Metal Foam Container"; US 5,503,941, granted on Apri12, 1996 to the company Stork Screens B.V; the US 6,706,239, granted on March 16, 2004 to Porvair PLC titled "Method of Co-forming metal foam articles and the articles formed by the method thereof"; US
6,464,933, granted on October 15, 2002 to Ford Global Technologies, Inc., US 5,865,237, granted on February 2, 2002 to Leichtmetallguss-Kokillenbau-Werk Illichmann GMBH, titled "Method of producing molded bodies of a metal foam"; US 5,584,983 granted on December 17, 1996 to Stork Screens B.V, with the title "Method for the production of a metal foam"; US 4,099,961, granted on July 11, 1978 to the Department of Energy of the USA, titled "Closed cell metal foam metal", which are herein incorporated in their totality like reference.
Particularly, the patent US 6,464,933 to Ford Global Inc. Technologies, describes a procedure of manufacture of a foam metal structure from a dust metallic particle provision, which includes: (a) to introduce the particle raw material altogether with an sponging agent in a gas propellant in such way to form a current of gas/particles mixture; (b) to project the mixture current at a critical velocity of speed of sound on a metallic substratum to at least create a metal-lic a particle deposit pressure welded including the sponging agent mixture;
and (c) submit at least the covering of the formed substratum an effective thermal excursion to activate the expan-sion of the sponging agent with which the metallic particles are re softened to produce a plastic deformation of the same ones under the influence of expansion gases.

BRIEF DESCRIPTION OF THE FIGURES
T88001\TOR_LAW\ 6318905\1 4 Figure 1 shows a flow chart of the water recirculation system in a pisciculture, in-corporating the metallic foam filter of the present invention;
Figure 2 is a perspective view of the used metallic foam of the present invention;
and Figure 3 shows a schematically design of the pisciculture pools in the alternatives (a) with filter and (b) without treatment filter.
DETAILED DESCRIPTION OF THE INVENTION
Through numerous studies has been documented that the metals are effective dis-infectants, acting against an extensive variety of microorganisms. For example, it is a widely known fact that the metals interfere with important enzymatic activities of microbes and they pay attention to cellular proteins, like also with the bacterial DNA. The metals are known as toxic and poisonous agents for the mentioned microorganisms. The metallic foam used in the water purification system of the present invention consists of copper/silver metal material, based on the principle already established, that the copper and the silver are excellent antimicrobial agents, being very effective in killing bacteria and other microorganisms. The mentioned metal foam is constituted of approximately between an 85% and a 95% in weight of copper and a 15% and a 5% in silver weight, more preferably a 90% in copper weight and a 10% in silver weight and has a pores size range included between 60 and 10 pores by inch (23.6 up to 3.9 pores by cm). The metallic foam make preferably with cylindrical form, not excluding other forms that can be suit-able, depending on the particular application. The dimensions of metallic foam discs used in the present invention vary between 5 to 100 cm of diameter and 2.0 cm of height.
In addition, for increase the contact surface several discs in series can be placed.
Unlike the facilities and the use of ionisers the copper/silver use of the previous art, the present invention applies the same metallic foam filter in the line with or without recircu-lation of the water in the pisciculture, without the application of an electrical current, that is to say, in this case, the filter does not act like a sacrifice electrode of an electrochemical system. In the present invention, the action of the metallic foam is exclusively in the quality of an average T88001 \TOR_LAV1l\ 6318905\1 5 catalyst of the enzymatic reactions between the metal and the cellular metabolism of the micro-organism. Consequently, an electrochemical degradation of the material of the metallic foam does not take place. Additionally to the described phenomena of ionisation either, also the idea sets out to use metals or alloys of two or more metals that so allow the electricity use that not necessarily it means an ion emission towards the water. For it, is even considered the use of foam the metal made on the hard metal base such as titanium or stainless steel.
The idea is that when a potential difference is applied to two plates of metal foam which are separated by a small distance from each other and placed in a water flow, a propor-tional electrical current will be generated as an inverse of the resistance of the aqueous means resulting in the elimination of the pathogenic microorganisms which exist in the water. This ap-plication will have a special place in the treatment of piscicultures in salt water. The effective-ness of average the metallic foam for the purification of the water in a system of fresh water re-circulation in a pisciculture experimentally evaluated in a research laboratory and development in Chile, obtained the following results.
The experiments realized had as purpose to quantitatively evaluating the effec-tiveness of a system for water purification based on a metallic filter (METAL
FOAM TM) as op-posed to the presence of the Flavobacteria bacteria psicrophylum in recirculation controlled conditions.

EXPERIMENTAL DESIGN
A Flavobacteria psicrophylum suspension will prepared which has been isolated from fry with clinical symptomatology originating from a pisciculture in the south of Chile. The bacteria was identified by means of API-ZYM enzymatic battery. A bacteria 2 suspension was prepared, according to the Mc Farland scale, the one that corresponds to l x 109 bacteria by ml;
the suspension was diluted in 100 ml of sterile water. The suspension was divided in two aliquot of 50 ml each one, which were spilled in the water contained in the aquariums.
The aquariums were disinfected properly and in parallel to it, 120 litres of water were boiled, said water origi-nating from a pisciculture from the tenth Region in he south of Chile, with the purpose of elimi-T88001 \TOR_LAW\ 6318905\1 6 nating the bacteria psicrophylas that these could contain. The water was spilled in the aquariums and it was expected until it reached the room temperature (15 C). The volume of water spilled in the aquariums was 50 liters. For the test two aquariums were used, where the first (a) was con-sidered for the treatment and the second (b) was considered like control. In the experiment a sys-tem was devised that emulates the pisciculture usage conditions, consisting basically in a series of PVC pipes with an adaptable diameter to the filter Foam Metal (50 mm). For the water pro-pulsion a pump with a capacity of 50 liters per minute is adapted. The metal foam filters were placed in the centre of the pipe. A similar system was considered for the pool control, with ex-ception of the inclusion of the purifying metallic foam filter according to the present invention.
The purifying metallic foam type filters where installed in a vertical position in the aquariums, so that the elevation of the water column took place and allowed the passage by the metallic foam filters; the water after passing through the filters was given back to the water body of the aquar-ium simulating a real recirculation system in a pisciculture.
For the experiment, two recirculation systems were designed: one with the metal-lic foam type filter, the other without said filter or conventional (see Figure 3). Once installed, both systems, the bacteria suspensions was added to pools (50 ml per pool) and it was allow to rest during one hour. Once the stabilization period passed, the first sample was taken with the intention of establishing the bacterial load of the pools. After the first measurement the recircula-tion system was connected. A second sample was taken after one hour from the start of the test and then a third sample was taken 5 hours after the test. The samples were derived to the labora-tory of the Instituto de Investigacion (Investigation Institute) in charge of the tests, where they were processed by means of membrane filtration method by, making 4 dilutions with the purpose of obtaining the 100 ml bacteria concentration of the sample; the used dilutions were the follow-ing ones: direct, -3, -4 and -5.
For the results interpretation the statistical test x2 was used, between the treat-ments. The obtained results have been resume in the following tables:
a) Treatment 1: Pool subject to the action of the metallic foam filter.
T88001\TOR_LA1M 6318905\1 7 Dilution Initial recount Time 1 hour Time 5 hours Total recount Greater than 30.000 110.000 ufc/100ml 68.000 ufc/100ml ufc/I OOmI

a) Treatment 2: Pool control (without filter) Dilution Initial recount Time 1 hour Time 5 hours Total recount Greater than 30.000 1.120.000 ufc/100m1 840.000 ufc/100m1 ufc/ l 00m1 According to the results obtained in the tests, under the same conditions of ex-perimentation, it can be observed that the pool subject to the purification, has significant differ-ences in comparison to the control pool. In general the effectiveness of the filter, can be observed in that the difference is close to a factor which is 10 times smaller than the bacterial load of the control pool, demonstrating the effectiveness of the metallic foam type copper/silver filters in the purification system according to the present invention. In an industrial pisciculture plant it is necessary to integrate the metallic foam filter to the unit of treatment of the recirculation water, which is shown schematically in the flow chart of Figure 1. According to this flow chart, the water originating from the pisciculture pools (1) is directed towards the water treatment unit by gravity. The disc filter (2) removes pool solids in suspension in the pisciculture by means of a process known like "mechanical filtration". The resulting mud is directed to a stabilization pool and later to an accumulation pond. After leaving the disc filter (2), the water enters a pumping pool (3) from where it is directed to the submerged biological filter (4) where the metabolic resi-dues excreted by the fish in the pisciculture water are removed, by means of an aerobic process, which generates carbon dioxide and water and the urea is turned into ammonia.
Part of the origi-nal water of the biological filter is lead to a de-nitrifying filter (5).

T88001\TOR_LAVN\ 6318905\1 8 The de-nitrification is an anaerobic process, by means of which the nitrate is re-moved to form nitrogen, a non-toxic gas that escapes to the atmosphere, that is to say nitrate be-comes gaseous nitrogen (N2).
Most part of the water flow is directed from the submerged biological filter (5) towards a percolator filter (6), where the ammonia is removed to form a nitrate. As well, in the percolator filter the removal of carbon dioxide takes place and the water ventilation. The water after passing through the percolator filter (6) is directed to the pumping pool (7). Through line (8) a fraction of the water flow is pumped towards the metallic foam filter (9) where it is disin-fected and later directed to the pisciculture pools. The remaining fraction of the water is pumped towards the oxygenation cones (10) by means of, preferably, two pumps of pressure. The oxy-genation cones (10) saturate the water with oxygen, process that is carried out under pressure with the purpose of assuring an efficient gasification. The water coming from the oxygenation cones (10) returns to the pisciculture pools.
The metallic copper-silver foam type purifying filter (9) consists of a porous disc made by process of special sintering. In this process the copper/silver raw material is based on a porous sacrifice base, adopting the metal alloy the form of the foam. A porous metal foam is obtained with an increased surface area of around 5,000% compared with the metal that has the same weight. Thanks to the considerable metal alloy exposed surface, the catalytic effect of the foam is obtained through the development of enzymatic reactions of the metabolism of the pathogenic micro organisms present in the recirculation water. It is estimated that the mechanism involved in this water purification process consists in that the filter metal acts like an oxidation catalyst for the oxygen that circulates through the filter, eliminating the necessary enzymes for the survival of the bacteria, virus and probably fungi present in the water.
Also it is possible that the microorganisms are captured on the surface of the metallic foam catalyst.
Approximately once a month the purifying filter must be cleaned by retro washing process, in order to eliminate the solid material accumulated inside. As a difference from the original application of the foam filter in pool water purification, the metal degradation by means T88001\TOR_LAW\ 6318905\1 9 of an electrochemical effect, in this application the water purification of pisciculture recircula-tion, such chemical degradation of the filter does not exist, inasmuch as it acts like a catalyzer which presents the same composition at the end of the process, like the initial. In open fish farm systems, which do not use water recirculation, the water is collected from the river and it is passed once through pisciculture pools, which had been previously filtered through a metallic foam filter, being soon returned downstream of the same river from which it had been extracted.
Consequently, this system has the advantage of accumulating a smaller amount of polluting ma-terial, which originates from the fish metabolic process.

T88001\TOR_LAV11\ 6318905\1 10

Claims

1. ~A process for water purification in freshwater fish farm systems, CHARAC-TERIZED in that it includes the stages of feeding the water originating in fish farm pools to a disc filter (2) in which starts a process of mechanical filtration, by passing the water originating in the disc filter (2) to a pumping pool (3), from which it passes to a submerged biological filter (4), where a part of the water originating from the mentioned biological filter, passes through a de-nitrifying filter (5) and from said point it is directed to a percolator filter (6); after having passed through the mentioned percolator filter (6), the water passes through a second pumping stage; a fraction of the water is passed through a metallic foam filter (9) and then it is returned to the fish farm pools; the rest of the water is passed through the oxigenation cones (10) and from there it returns here to the pisciculture pools.

2. ~The process according to claim 1, CHARACTERIZED in that the mentioned process includes the recirculation of the pisciculture water.

3. ~The process according to claim 1, CHARACTERIZED in that the mentioned process does not include the recirculation of the pisciculture water, this is, it considers a single pass through the pisciculture system.

4. ~The process according to any of the preceding claims, CHARACTERIZED in that the mentioned metallic foam filter (9) consist of a metal copper-silver alloy foam, with a proportion approximately of 85% and a 95% in copper per weight and a 15% and a 10% of sil-ver, with a porosity between approximately 60 pores by square inch up to 10 pores by square inch (23.6 up to 3.9 pores by cm2).

5. ~A system to purify the water of fish farm freshwater CHARACTERIZED in that it includes a disc filter (2) in which makes a process of mechanical filtration, a first pumping pool (3) from which the water passes to a submerged biological filter (4), a de-nitrifying filter (5) that receives a part of the originating water of the mentioned biological filter, a percolator filter (6), a second pumping pool, a set of oxygenation cones (10) which receives one first fraction of the water originating from the pisciculture of the pumping pool, and which includes, addition-ally, a metallic foam type purifying filter (9) that receives a second fraction of the filtered and decontaminated water.

6. The system according to claim 5, CHARACTERIZED in that said system is a pisciculture water recirculation system.

7. The system according to claim 5, CHARACTERIZED in that it is a non recir-culation pisciculture water system.

8. The system according to claim 5, CHARACTERIZED in that the metallic type foam filter, (9) consists of a metal copper-silver alloy foam, with a proportion of approximately a 85% and a 95% in weight of copper and a 15% and a 10% of silver, with a porosity between ap-proximately 60 pores by square inch up to 10 pores by square inch (23.6 up to 3.9 pores by cm2).

9. Use of a porous metallic foam, CHARACTERIZED in that it is useful as cata-lytic in the purification of recirculation waters in a plant of freshwater fish farm with the inten-tion of eliminating bacteria, virus and pathogenic fungi present in said waters.

10. Use according to claim 9, CHARACTERIZED in that it is useful for the treatment of the fish diseases of well-known pisciculture like flavobacteriosis, preferredly in the control of the Flavobacteria bacteria psicrophylum.

11. Use according to claim 9, CHARACTERIZED in that the mentioned metallic foam filter (9) consists of a metal copper-silver alloy foam, with a proportion of approximately 85% and a 95% in copper weight and a 15% and a 10% of silver, with a porosity between ap-proximately 60 pores by square inch up to 10 pores by square inch (23.6 up to 3.9 pores by cm2).

12. Use according to claim 9, CHARACTERIZED in that it useful for the control of different sizes fry syndrome in the pisciculture of salmons and trout.

13. Use according to claim 9, CHARACTERIZED in that the mentioned purifying filter (9) is incorporated to the treatment unit with and without water recirculation of the fresh-water fish farm plant.