JP4825434B2 - How to kill aquatic life - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a killing method of aquatic organisms of high safety capable of simply and certainly killing various organisms living in seawater, river water, lake and marsh water and especially ship ballast water using them, that is, aquatic organisms such as zooplankton, phytoplankton, cyst being plankton in a dormant period, microorganisms such as bacterial or the like, fine shellfishes and the like and capable of discharging water to be treated after treatment to the natural field without anxiety without leaving a chemical component in the water to be treated after treatment. <P>SOLUTION: Hydrogen peroxide or a hydrogen peroxide producing compound is added to water to be treated, in which aquatic organisms live, to kill the aquatic organisms in the water to be treated and, before the water to be treated is discharged or when the aquatic organisms in the water to be treated are killed, the water to be treated is irradiated with ultraviolet rays of a wavelength region of 240-300 nm in an irradiation quantity of 5 mW&times;sec/cm<SP>2</SP>or above or 3 mW&times;sec/cm<SP>2</SP>or above. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method for killing aquatic organisms that can easily and reliably kill aquatic organisms that inhabit seawater, river water, and lake water. The present invention can be suitably used for the killing treatment of harmful aquatic organisms that live in stagnant water such as ship ballast water.

  In the seawater, river water, and lake water, harmful aquatic organisms such as plankton, their cysts, and pathogenic bacteria such as cholera, Escherichia coli, and enterococci may inflict environmental problems. Particularly recently, harmful aquatic organisms inhabit the ship's ballast water.

  When a ship is not loaded with a load or its load is small, the draft surface is lowered and it is difficult to maintain a balance. Therefore, the ship carries seawater or fresh water as ballast water in order to navigate the ocean safely. Such ballast water is drawn into the ship before leaving the unloading port and discharged outside the ship before entering the loading port or when loading the load.

  Seawater or fresh water as ballast water is absorbed by a pump or the like and stored in a sealed compartment configured inside the ship. At this time, aquatic organisms such as various microorganisms such as plankton and bacteria and minute shells that inhabit the water absorption area are taken in. Discharge of such ballast water at the coastal area or harbor near the loading port has caused a problem that the ecosystem in the surrounding sea area is disturbed. At the same time, there is a concern that fish and shellfish may die due to the large outbreak of shellfish poisons and red tides, causing various diseases.

  As mentioned above, since ballast water is kept in a dark reduced state for a long time, plankton and aerobic bacteria that require light and dissolved oxygen are less likely to live in the ballast water, and plankton is in a dormant cyst. And anaerobic bacteria tend to breed. This cyst is extremely durable because its outer wall is completely different from the plankton cell wall membrane and has a very strong structure.

  In view of the above problems, Applicants have identified a harmful plankton cyst comprising maintaining an effective amount of hydrogen peroxide or a hydrogen peroxide generating compound in a ship's ballast water to kill the harmful plankton cyst. Has been proposed (Japanese Patent No. 2695071: Patent Document 1).

On the other hand, a water purification method and an apparatus used therefor have been proposed in which ultraviolet rays are irradiated on water to be treated such as ship ballast water simultaneously with or before steam injection (Japanese Patent Laid-Open No. 2004-160437: Patent Document). 2).
However, there is a need for a method that can more easily and reliably kill aquatic organisms in the water to be treated.

Japanese Patent No. 2695071 JP 2004-160437 A

  The present invention relates to various organisms inhabiting seawater, river water, lake water, especially ship ballast water using them, such as zooplankton, phytoplankton, cysts in which plankton is dormant, microorganisms such as bacteria, and microshells To provide a highly safe killing method for aquatic organisms that can easily and reliably kill aquatic organisms and can be safely discharged into the natural world without any chemical components remaining in the treated water after treatment. This is the issue.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have added hydrogen peroxide or a compound that generates hydrogen peroxide to the water to be treated inhabited by aquatic organisms. Before killing organisms and discharging treated water, or when killing aquatic organisms in treated water, treat them by irradiating ultraviolet rays in a specific wavelength region at a specific dose. It was found that various aquatic organisms that inhabit water can be killed reliably, hydrogen peroxide remaining in the water to be treated is decomposed, and the water to be treated can be discharged into the natural world with peace of mind. .

Thus, according to the present invention, hydrogen peroxide or a compound that generates hydrogen peroxide is added to the treated water inhabited by aquatic organisms to kill the aquatic organisms in the treated water and discharge the treated water. Further, there is provided an aquatic organism killing method (Invention 1) characterized by irradiating ultraviolet rays having a wavelength region of 240 to 300 nm with an irradiation amount of 5 mW · sec / cm ² or more.

In addition, according to the present invention, when hydrogen peroxide or a hydrogen peroxide generating compound is added to water to be treated inhabited by aquatic organisms to kill the aquatic organisms in the water to be treated, There is provided a method for killing aquatic organisms (Invention 2) characterized by irradiating ultraviolet rays in a region of 240 to 300 nm at an irradiation dose of 3 mW · sec / cm ² or more.

  In the present invention, the term “aquatic organism” refers to aquatic microorganisms such as zooplankton, phytoplankton, cysts in which plankton is dormant, microorganisms including pathogenic bacteria such as cholera bacteria, Escherichia coli, and enterococci, and marine microorganisms. It means living organisms such as live microorganisms and small shellfish.

According to the present invention, various organisms that inhabit seawater, river water, and lake water, that is, zooplankton, phytoplankton, cysts in which plankton is dormant, microorganisms such as bacteria, and aquatic organisms such as microshells are easily and reliably obtained. Can be killed.
In addition, according to the present invention, particularly the invention 1, hydrogen peroxide remaining in the water to be treated is rapidly decomposed by irradiation with ultraviolet rays, so that the water to be treated after treatment is discharged to the sea, rivers, lakes, etc. with peace of mind. It is extremely useful in industry.

Furthermore, according to the present invention, particularly the invention 2, hydrogen peroxide added by irradiation with ultraviolet rays is dissociated to generate active OH radicals having strong oxidizing power. A fast-acting killing effect is obtained against living organisms.
In addition, according to the present invention, the turbidity component in the water to be treated is agglomerated and precipitated by the reaction of iron or the like in the water to be treated with hydrogen peroxide. Can stably maintain the killing effect, and can surely kill plankton and cysts that have damaged cell wall membranes by hydrogen peroxide.

In the method for killing aquatic organisms of the invention 1, hydrogen peroxide or a hydrogen peroxide generating compound is added to treated water inhabited by aquatic organisms to kill the aquatic organisms in the treated water. Before discharging, ultraviolet rays having a wavelength region of 240 to 300 nm are irradiated at an irradiation dose of 5 mW · sec / cm ² or more.

The aquatic organism killing method according to the second aspect of the invention includes adding hydrogen peroxide or a hydrogen peroxide-generating compound to the water to be treated inhabiting the aquatic organism to kill the aquatic organism in the water to be treated. Water is irradiated with ultraviolet rays having a wavelength region of 240 to 300 nm at an irradiation amount of 3 mW · sec / cm ² or more.

  In both Invention 1 and Invention 2, first, hydrogen peroxide or a hydrogen peroxide generating compound is added to the water to be treated. Thereby, aquatic organisms in the water to be treated are killed by OH radicals generated by dissociation of hydrogen peroxide. Therefore, it is preferable to keep the water to be treated for a certain period of time after the addition of hydrogen peroxide or a hydrogen peroxide generating compound.

Hydrogen peroxide used in the present invention is a highly safe component that easily decomposes into water and oxygen in water.
As the hydrogen peroxide used in the present invention, an aqueous hydrogen peroxide solution having a concentration of 3 to 60% which is commercially available for industrial use is usually mentioned.
The hydrogen peroxide generating compound (also referred to as “hydrogen peroxide supply compound”) means a compound capable of generating hydrogen peroxide in water, and includes inorganic peracids such as percarbonate, perboric acid, peroxysulfuric acid, Organic peracids such as peracetic acid and their salts. Examples of such salts include sodium percarbonate and sodium perborate.
When adding these to the water to be treated, hydrogen peroxide or a compound that generates hydrogen peroxide (hereinafter also referred to as “hydrogen peroxides”) is appropriately diluted or dissolved in seawater or fresh water so as to have a desired concentration. It may be used.

  Further, hydrogen peroxide generated in water containing seawater or fresh water can also be used. Methods for generating hydrogen peroxide in water include electrochemical decomposition of water or alkaline solutions, irradiation of water with high-energy rays such as ultraviolet rays and radiation, or aquatic organisms [for example, Poecillia vellifere Method)] and the like.

  What is necessary is just to select suitably the hydrogen peroxide density | concentration of to-be-processed water, and the retention time after addition according to the kind and quantity of the aquatic organism to be killed which exists in to-be-processed water, water temperature, etc. Generally, it may be maintained for a long time when the hydrogen peroxide concentration is low, and for a short time when the hydrogen peroxide concentration is high. Further, when the temperature of the water to be treated is as low as 15 ° C. or lower, for example, the hydrogen peroxide concentration may be increased and held for a long time.

  In the method of the present invention, the hydrogen peroxide or the hydrogen peroxide generating compound is added in such an amount that the hydrogen peroxide concentration of the water to be treated is 5 to 500 mg / L, preferably 10 to 300 mg / L. It is preferable to hold in the treated water for 3 hours or more, preferably 3 to 48 hours, more preferably 24 to 48 hours.

  When the hydrogen peroxide concentration is less than 5 mg / L, it is not preferable because aquatic organisms living in the water to be treated cannot be sufficiently killed. In addition, when the hydrogen peroxide concentration exceeds 500 mg / L, a killing effect corresponding to the amount added cannot be expected, and hydrogen peroxide may remain after the treatment, which is not preferable.

  In addition, when the retention time is less than 3 hours, it is not preferable because aquatic organisms that inhabit the treated water cannot be sufficiently killed. In addition, when the holding time exceeds 48 hours, a killing effect corresponding to the time cannot be expected, which is not preferable.

  That is, the hydrogen peroxide concentration and the retention time after the addition are based on the fact that the most difficult to kill cysts can be killed among the aquatic organisms to be killed in the treated water. What is necessary is just to set from said range in consideration of the temperature of treated water.

  For example, when the water to be treated is ship ballast water, it is generally 1 to 2 weeks or more when navigating the ocean, and several hours to several tens of hours when navigating the sea near Japan. What is necessary is just to set suitably the hydrogen peroxide concentration and the retention time after addition according to time, temperature conditions, etc.

In any of the inventions 1 and 2, the aquatic organism killing treatment is preferably performed in a closed system in which natural light to the water to be treated is blocked.
The blocking system is not particularly limited as long as natural light to the water to be treated is blocked and the water to be treated can be held for a certain period of time. For example, tanks such as ballast tanks for ships, and retention tanks and water areas provided on the coast, such as the sea, rivers, and lakes.

In the first aspect of the present invention, hydrogen peroxide or a compound that generates hydrogen peroxide is added to kill the aquatic organisms in the water to be treated, and the wavelength region is added to the water to be treated before discharging the water to be processed, that is, immediately before discharging. Ultraviolet rays with a wavelength of 240 to 300 nm, preferably 250 to 270 nm are irradiated at an irradiation dose of 5 mW · sec / cm ² or more, preferably 15 mW · sec / cm ² or more. Thereby, hydrogen peroxide remaining in the water to be treated is decomposed and aquatic organisms in the water to be treated are killed by ultraviolet rays.
If ultraviolet rays are in the above-mentioned wavelength region, the killing effect of aquatic organisms can be effectively exhibited by a combination with the addition of hydrogen peroxide or a hydrogen peroxide generating compound in the previous stage.

Further, the upper limit of the irradiation amount of the ultraviolet rays is not particularly limited as long as the ultraviolet rays do not adversely affect the others, but is usually about 20 mW · sec / cm ² .
When the irradiation amount of ultraviolet rays is less than 10 mW · sec / cm ² , it is not preferable because aquatic organisms living in the water to be treated cannot be sufficiently killed.
In addition, since the ultraviolet rays irradiated in nature are limited to a region of 300 nm or more, they are much lower than the ultraviolet energy in the present invention.

Irradiation with ultraviolet rays is carried out using a low pressure mercury vapor discharge lamp that emits a baseline spectrum of wavelengths 185 nm and 254 nm and / or an ultraviolet light source of an intermediate pressure / high pressure mercury vapor discharge lamp that emits a continuous spectrum in the wavelength region 180 to 400 nm. Are preferred. Moreover, such an ultraviolet ray generation light source is not particularly limited as long as it can irradiate ultraviolet rays in the above-mentioned wavelength region, and examples thereof include an ozone ultraviolet type high-speed water treatment device.

In Invention 2, when hydrogen peroxide or a hydrogen peroxide generating compound is added to kill aquatic organisms in the water to be treated, that is, immediately after the addition of hydrogen peroxide or hydrogen peroxide generating compound, until pre-flush, the wavelength region 240~300nm to the water to be treated, preferably with ultraviolet rays at 250~270nm dose 3mW · sec / cm ² or more, preferably irradiated with 10mW · sec / cm ² or more. Thereby, hydrogen peroxide is dissociated to generate active OH radicals, and aquatic organisms in the water to be treated are killed by OH radicals, active OH radicals and ultraviolet rays. It is considered that the irradiation with ultraviolet rays greatly contributes to the killing of bacteria, particularly durable enterococci.

If ultraviolet rays are in the above-mentioned wavelength region, the killing effect of aquatic organisms can be effectively exhibited by a combination with the addition of hydrogen peroxide or a hydrogen peroxide generating compound in the previous stage.
Further, the upper limit of the irradiation amount of the ultraviolet rays is not particularly limited as long as the ultraviolet rays do not adversely affect the others, but is usually about 20 mW · sec / cm ² .
When the irradiation amount of ultraviolet rays is less than 3 mW · sec / cm ² , the production amount of active OH radicals due to dissociation of hydrogen peroxide is insufficient, so that aquatic organisms living in the treated water can be sufficiently killed. It is not preferable because it cannot be done.

The binding energy of H—OH of water molecules is 499 kJ / mol, and ultraviolet rays of 240 nm or less can directly dissociate this bond to generate active OH radicals. Therefore, hydrogen peroxide can be dissociated in water by using a low-pressure mercury vapor discharge lamp that emits baseline spectra at wavelengths of 185 nm and 254 nm and / or a medium- and high-pressure mercury vapor discharge lamp that emits a continuous spectrum in the wavelength range of 180 to 400 nm. Both the OH radicals generated in this way and the active OH radicals generated by ultraviolet irradiation act, so that the killing effect of aquatic organisms is further enhanced.
Therefore, the irradiation with ultraviolet rays is preferably performed immediately after the addition of hydrogen peroxide or a hydrogen peroxide generating compound.

The method of the present invention can be suitably carried out with the processing apparatus shown in FIGS. 1 and 2, but these are examples of Invention 1 and Invention 2, respectively, and are not intended to limit the present invention.
FIG. 1 is a schematic diagram of a processing apparatus installed in a ship's ballast tank, where T is a ballast tank, F is a filter for removing garbage, P1 is a water intake pump, H is a hydrogen peroxide tank, and P is A hydrogen peroxide addition pump, B is a valve, P2 is a drainage pump, UV1 is an ultraviolet irradiation device, and SL is the sea surface.

In the processing apparatus of FIG. 1, first, seawater (not shown) is pumped by a pump P1 through a filter F and introduced into a ballast tank T which is a culvert section in a ship. Simultaneously with or after the introduction of seawater, the valve B is opened, and a predetermined amount of hydrogen peroxide is injected (added) from the hydrogen peroxide tank H by the pump P. It is preferable to inject hydrogen peroxide simultaneously with the introduction of seawater because the effect of stirring the added drug can be obtained. Next, the seawater is held in the ballast tank T for a predetermined time. Thereafter, the seawater in the ballast tank T is pumped up by the pump P2, passed through the ultraviolet irradiation device UV1, and discharged by irradiating the seawater with ultraviolet rays (Invention 1).
Irradiation of ultraviolet rays is not necessarily performed during drainage, and an ultraviolet ray generating light source installed in the ballast tank T may be turned on to irradiate the seawater with ultraviolet rays (Invention 2). In FIG. 1, the seawater that has passed through the ultraviolet irradiation device UV1 may be returned to the ballast tank T again to perform a circulation process.

FIG. 2 is a schematic diagram of another processing apparatus installed in a ballast tank of a ship. In this processing apparatus, an ultraviolet irradiation device UV2 is further installed on the water intake side of the processing apparatus of FIG.
That is, in the processing apparatus of FIG. 2, seawater is irradiated to the seawater by the ultraviolet irradiation apparatus UV2 as a pretreatment for carrying out the method of the present invention.
By such pretreatment, since pathogen bacteria in seawater are killed in advance, more efficient treatment can be performed.

  The method of the present invention may be carried out in combination with an existing method for purifying water such as ship ballast water, for example, cavitation addition, so-called slit method, shear stress addition, heating and steam injection, as appropriate. it can.

EXAMPLES The present invention will be specifically described by the following test examples, but these do not limit the scope of the present invention.

Test example 1 (phytoplankton and bacteria killing effect confirmation test)
The treatment apparatus shown in FIG. 1 was installed on the quay near the harbor and tested.
Seawater having a capacity of 20 tons was pumped through the filter F by the pump P1 and introduced into the ballast tank T which is a culvert section in the ship. Simultaneously with the introduction of seawater, valve B was opened, and hydrogen peroxide was added from the hydrogen peroxide tank H to the concentration shown in Table 1 by pump P. Next, seawater was held in the ballast tank T for a predetermined time shown in Table 1.
After that, the seawater in the ballast tank T is pumped by the pump P2, and 8 tons per hour is applied to an ultraviolet irradiation device UV1 equipped with a low pressure mercury vapor discharge lamp that emits a baseline spectrum of 185 nm and 254 nm of 28 W in a 2.6 liter container. The water was allowed to pass through at a flow rate, and the seawater was discharged by irradiating it with ultraviolet rays. Since the transmittance of ultraviolet light having a wavelength of 254 nm in seawater was improved to 95% or more with respect to 92% of the raw water by the addition of hydrogen peroxide, the irradiation amount was 14.96 mW · sec / cm ² .

The seawater before and after treatment, that is, the pumped seawater and the discharged seawater were collected, and the killing rate of phytoplankton, general bacteria and E. coli was evaluated.
1000 mL of seawater before and after the treatment was collected, and the number of normal cells of all phytoplankton contained therein was observed with a biological microscope and weighed to determine the phytoplankton kill rate (%).
In the same manner as in the case of phytoplankton, 1000 mL of seawater before and after treatment was collected, 1 mL of the seawater was appropriately diluted, inoculated on a plate agar medium, and cultured at 37 ° C. for 48 hours. The number of viable bacteria after culture was measured to determine the kill rate (%) of general bacteria and E. coli.
The obtained results are shown in Table 1 together with the concentration of hydrogen peroxide and the retention time after the addition.

Test example 2 (cyst killing effect confirmation test)
We identified and collected polykrikos schwatzii cysts belonging to the dinoflagellate network Gymnodinium from submarine sediments near the harbor and conducted germination tests.
First, a petri dish containing only seawater into which hydrogen peroxide has not been injected and three kinds of three petri dishes containing seawater added with hydrogen peroxide to have the hydrogen peroxide concentration shown in Table 1 total 10 We prepared 10 pieces of Polykrikos schwatzii cysts for each. Next, each petri dish was allowed to stand in a dark room, and the nine petri dishes into which hydrogen peroxide had been injected had low pressures that emitted baseline spectra of wavelengths 185 nm and 254 nm from the top surface after 3 hours, 24 hours, and 48 hours, respectively. The mercury vapor discharge lamp was irradiated for 9 seconds. At this time, the ultraviolet illuminance on the irradiated surface was 1.8 mW / cm ² , and the irradiation amount was 16.2 mW · sec / cm ² . Thereafter, each petri dish was allowed to stand in a thermostatic chamber at 23 to 25 ° C., and the presence or absence of germination was observed 1 day, 2 days, 3 days, and 4 days after UV irradiation, and the number of germinated cysts (pieces) was determined. The petri dish made only of seawater was not irradiated with ultraviolet rays.
The results obtained are shown in Table 2 together with the concentration of hydrogen peroxide and the retention time after addition.

It is a schematic diagram of the processing apparatus installed in the ballast tank of a ship for implementing the killing method of the aquatic organism of this invention. It is a schematic diagram of another processing apparatus installed in the ballast tank of a ship for implementing the killing method of the aquatic organism of this invention.

Explanation of symbols

B Valve F Filter H Hydrogen peroxide tank P Hydrogen peroxide addition pump P1 Water intake pump P2 Drainage pump SL Sea surface T Ballast tank UV1, UV2 UV irradiation equipment

Claims (3)

The treated water inhabited by aquatic organisms selected from zooplankton, phytoplankton, cysts in which the plankton is dormant, and bacteria including pathogenic bacteria, the hydrogen peroxide concentration of the treated water is 5 to 500 mg. When hydrogen peroxide or a hydrogen peroxide generating compound is added so as to be / L and held in the water to be treated for 3 to 48 hours to kill the aquatic organisms in the water to be treated, A method for killing aquatic organisms, comprising irradiating water with ultraviolet rays having a wavelength region of 240 to 300 nm at an irradiation dose of 3 mW · sec / cm ² or more.   The method for killing aquatic organisms according to claim 1, wherein the killing treatment of the aquatic organisms is performed in a closed system in which natural light to the treated water is blocked.   The UV irradiation is performed using a UV light source that generates a low-pressure mercury vapor discharge lamp that emits a baseline spectrum with wavelengths of 185 nm and 254 nm and / or a medium-pressure / high-pressure mercury vapor discharge lamp that emits a continuous spectrum with a wavelength range of 180 to 400 nm. The method for killing aquatic organisms according to claim 1 or 2, which is carried out.

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