System for the treatment and recirculation of freshwater or saltwater to restore water quality to optimum levels in fish farming cages

Abstract

A water treatment and recirculation system includes means to transport water flows at required pressures, a mechanical filter of approximately 100 microns to capture coarse particles, oxygen production means, autonomous electricity generation means, and variable control means using a PLC that administers parameters such as pressure, oxygen and CO.sub.2 levels, flows, pH, etc. The system also includes means to ultrafilter and remove particles of up to 0.02 microns, the purpose being removing organic material macromolecules, disinfecting bacteria and viruses with mechanical removal, and eliminate harmful contaminants such as ammonia, degasifying means to eliminate CO.sub.2 with a multitubular exchanger with membranes made of hydrophobic materials and micro perforations to take CO.sub.2 away to an extraction gas in atmospheric or vacuum conditions; and means to oxygenate water with a multitubular exchanger having membranes constituted by hydrophobic materials and microperforations that inject O.sub.2 into water of a gas under atmospheric conditions.

Claims

1. A water treatment and recirculation system to restore water quality to optimum levels, in a fish farming system mainly aimed at the freshwater and saltwater fish farming industry and/or stocking centers, comprising: means for transporting water flows at required pressures, a coarse mechanical filter of approximately 100 microns, whose focus is to capture coarse particles, oxygen production means, autonomous electricity generation means; and variable control means using a PLC that administers parameters comprising pressure, oxygen and CO2 levels, flows, and pH, and further comprising: a) means to ultrafilter and remove particles of up to 0.02 microns, with a purpose of removing organic material macromolecules, disinfecting bacteria and viruses with mechanical removal, and eliminating harmful contaminants including ammonia; b) degasifying means to eliminate CO2 with a multitubular exchanger with membranes made of hydrophobic materials and micro perforations taking the CO2 to an extraction gas in atmospheric or vacuum conditions; and c) means to oxygenate water with a multitubular exchanger made up of membranes constituted by hydrophobic materials and micro perforations that inject O2 of a gas under atmospheric conditions into water.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 (Prior Art) shows a general schematic of a prior art water recirculation and treatment system.

(2) FIG. 2 shows a general schematic of the water recirculation and treatment system in this invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) As shown in FIG. 2, water treatment and renewal means are essential because we are in the presence of a closed system so that this renewal water must be in special conditions in order to maximize the survival of fish in freshwater or saltwater cages.

(4) First, it is necessary to raise water pressure with a pump in order to generate pressure and in this way drive water flows at the required pressures.

(5) Second, water goes into a prefiltering system to remove coarse particles, which comprises a coarse mechanical filtration with a wire mesh of approximately 100 microns.

(6) Next, and as an element of this invention, there is an ultra filtration process by means of a PES (Polyethersulfone) membranes system that disinfects water with the physical removal of bacteria and viruses, eliminates organic material and ammonia, and improves water quality.

(7) The ultrafiltration system, having very small 20 nanometers pores, performs several functions disinfecting water because pathogens have larger sizes. In fact, the size of bacteria is around 1 micron, the size of spores is 1 micron, and the size of viruses is around 100 nanometers. The ultrafiltration system also removes all solids suspended in water, considerably improving its quality and also removes nitrogen and carbon organic molecules that normally degrade to NH.sub.4 and CO.sub.2; this brings down the quantity of generated ammonia and, consequently, the need for bio filtration. Finally, heavy metals are removed from the water.

(8) This system allows the removal of all the above through mechanical filtration and consequently avoids the dependence on living organisms, such as a bio filter in an online system, that does not lose line pressure and having a modular design that allows growth and easy maintenance.

(9) In addition, it is also necessary to degasify and eliminate the CO.sub.2 by means of a multitubular exchanger with membranes made of hydrophobic material and micro perforations that take away the CO.sub.2 to an extraction gas in atmospheric or vacuum conditions.

(10) This gas exchange system has great advantages in respect of traditional degassing equipment and oxygen cones because its hydrophobic fibers with nanometric pores provide conditions for a very high transfer of gas between the liquid outside the fiber and the gas, thereby easily reaching the point of equilibrium with equipment having a very high transfer ratio versus size. For example, the capacity of equipment with a diameter of 40 [cm] and a length of 1.2 [m] is 80 m.sup.3/h.

(11) The flow of gas will be from the liquid to the gas or from the gas to the liquid depending of the Henry Law equation. For example, if there is liquid water with an O.sub.2 saturation of 6 [ppm] and a flow rich in O.sub.2 as exchange gas, injecting oxygen to the water at 1 [atm] it is possible to reach a saturation of 50 [ppm] and, if pressure is increased to 2 [atm], a saturation of 100 [ppm] can be reached. On the other hand, using O.sub.2 downgraded gas as a 100% N.sub.2 flow, water will turn over its O.sub.2 to the gas flow and may reach concentrations as low as 20 parts per billion [ppb].

(12) This is how this system firstly uses air in vacuum conditions as degassing equipment to remove CO.sub.2 from water and subsequently uses O.sub.2 to inject oxygen into water, using cones or systems made of hydrophilic membranes or a multitubular system with micro perforations and pressures above atmospheric pressure.

(13) The injected oxygen may be produced in situ with a VPSA technology oxygenation system. The VPSA technology generates in situ oxygen with fuel consumption significantly lower than alternative technologies. It is also possible to use purchased oxygen stored in Liquid Oxygen Cylinders (LOX).

(14) Finally, all this water treatment and recirculation process may be controlled with a PLC in order to administer variables such as pressure, oxygen and CO.sub.2 levels, and flows, among others.