JP2014100673A - Method for controlling ballast water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling ballast water, in which the amount of a chlorine-based active substance to be added to the ballast water can be determined optimally when the ballast water is treated therewith.SOLUTION: The method for controlling ballast water comprises the steps of: sampling untreated ballast water to which a chlorine-based active substance is not added; adding the chlorine-based active substance to the sampled ballast water; measuring a temporal change of the total concentration of residual oxidizing substances in the chlorine-based active substance-added ballast water; calculating a and b values satisfying a logarithmic expression: C=a×ln(t)+b by using the total concentrations of residual oxidizing substances (including the initial total concentration of residual oxidizing substances) measured at three or more measurement times; and determining the amount of the chlorine-based active substance to be added to the ballast water so that the total concentration of residual oxidizing substances becomes 0.1 mg/L or higher at a scheduled time to discharge the ballast water.

Description

  The present invention relates to a method for controlling ballast water by optimally determining the addition amount of a chlorinated active substance in ballast water treatment.

  In general, since ships, especially cargo ships, are designed to include the weight of cargo, etc., ships that are unloaded or lightly loaded must be able to ensure proper submersion depth and safe navigation during unloaded conditions. From the necessity, seawater is taken in the port before leaving the port to balance the ship. The water used as this ballast is called ship ballast water. When the ship ballast water leaves the port without loading, the seawater of the port is loaded into the ballast tank at the port of departure, while the ship ballast water is drained when loading in the port.

  By the way, when the ship ballast water is poured and discharged by a ship that goes back and forth between the loading port and the unloading port in different environments, the difference in microorganisms contained in the ship ballast water at the loading port and the unloading port. There are concerns that it will adversely affect coastal ecosystems. Therefore, an international convention for the regulation and management of ship ballast water and sediment of ships was adopted in February 2004 at the international conference on ship ballast water management of ships, and the treatment of ship ballast water became obligatory. .

The standard set by the International Maritime Organization (IMO) as a standard for the treatment of ship ballast water is that the number of organisms (mainly zooplankton) of 50 μm or more contained in the ship ballast water discharged from the ship is less than 10 in 1 m ³ , The number of organisms (mainly phytoplankton) of 10 μm or more and less than 50 μm is less than 10 in 1 ml, the number of Vibrio cholerae is less than 1 cfu in 100 ml, the number of E. coli is less than 250 cfu in 100 ml, and the number of enterococci in 100 ml Less than 100 cfu.

  In order to meet such ballast water treatment standards, microbes such as sodium hypochlorite and calcium hypochlorite such as sodium hypochlorite are added to the ship's ballast water to ensure residence time. The ship ballast water processing method which kills etc. is proposed. The addition amount of the chlorinated active substance in this ballast water treatment is determined using the maximum allowable addition amount (MAD) set at the time of basic approval of IMO as an index.

However, when chlorinated active substances are added to ballast water, chlorine is consumed over time, so the consumption rate of chlorinated active substances is calculated, and the required amount until the end of the voyage, that is, the discharge of ballast water It is desirable to add. In general, as a method for calculating the consumption rate of chlorine, a chlorine decay prediction method using the following calculation formula described in Patent Document 1 is known.
C = z · C ₀ · e ^−kt
(Where C ₀ is the chlorine concentration at the chlorine injection tube outlet, C is the chlorine concentration at time (t), k is the reaction constant, t is the elapsed time, and z is the chlorine after chlorine injection. Residual coefficient.)

Japanese Patent Laid-Open No. 08-41670

  However, the chlorine attenuation prediction method described in Patent Document 1 often adds a chlorine-based active substance at a high concentration to ballast water for prediction. In such a case, the initial attenuation rate of the chlorine-based active substance is high. Since the correlation between the initial chlorine consumption rate and the subsequent chlorine consumption rate is small, it is possible to predict the chlorine concentration after several days from the chlorine consumption in a relatively short time such as 120 minutes or less after the addition of the active substance. There was a problem that it was difficult.

  Furthermore, the quality of actual ballast water changes depending on many factors, such as the contamination status of the sampling site, the depth of sampling, the timing of sampling, and the duration of the voyage. This change in water quality depends not only on SS but also on the types and amounts of DOC, POC, ammonia, nitrous acid, inorganic salts, and organic substances. However, the conventional method has a problem that it cannot follow that the consumption rate of the chlorine-based active substance varies with the change in water quality.

  To cope with this, it may be possible to add an excessive amount of chlorinated active substance that can be expected to have a sufficient residual chlorine concentration even after several days, but add more chlorinated active substance than the maximum allowable addition amount (MAD). I can't do it. In addition, when the amount of chlorinated active substance added to clear water is determined, most of the active substance remains at the time of discharge, which increases the toxicity of the discharged water and decomposes the remaining active substance. For this reason, there is a problem in that the amount of the neutralizing agent added becomes enormous. Thus, conventionally, the amount of chlorine-based active substance added while maintaining the total residual oxidizing substance concentration (residual chlorine concentration) that can maintain the bactericidal properties until the discharge of ballast water and suppressing the addition amount is reduced. There was no way to control the ballast water that could be optimally determined.

  An object of the present invention is to provide a method for controlling ballast water, which can solve the above-described problems and can optimally determine the addition amount of a chlorinated active substance in ballast water treatment.

In order to solve the above problems, the present invention provides ballast water to which a chlorinated active substance for sterilizing aquatic microorganisms in the ballast water is added when supplying ballast water taken from a water intake to a ballast tank. It is a control method in which untreated ballast water to which no chlorinated active substance is added is collected in advance, and the chlorinated active substance is added to the untreated ballast water and the total residual oxidizability by the chlorinated active substance Based on the total residual oxidant concentration (including the initial total residual oxidant concentration) for three or more measurement times, the following logarithm formula C = a · ln (t) + b
(Wherein, a and b are reaction constants, t is the elapsed time, and C is the total residual oxidizing substance concentration). A control method for ballast water is provided that determines the amount of chlorinated active substance added so that the total residual oxidizing substance concentration in the scheduled discharge time of ballast water is 0.1 mg / L or more (Invention 1) .

  As in the above invention (Invention 1), untreated ballast water is collected before actually adding the chlorine-based active substance, and the chlorine-based active substance is added to the ballast water, so that the total residue due to the chlorine-based active substance is obtained. When the change with time of the oxidizing substance concentration is measured, this change with time is simulated by a logarithmic expression. The inventors have found that this logarithmic expression can be calculated with high accuracy based on the result of a short-term change over a short period of time, for example, 120 minutes or less. Therefore, a logarithmic formula is calculated based on a short-time change in the total residual oxidizing substance concentration, and the total residual oxidizing substance concentration in the estimated ballast water drainage time is 0.1 mg / L or more from this logarithmic formula. By determining the addition amount of the chlorine-based active substance, it is possible to prevent excessive addition or insufficient addition of the active substance. Moreover, the effect that the toxicity of discharged water can be reduced and the amount of neutralizing agent added can be reduced.

  In the said invention (invention 1), it is preferable that the said chlorinated active substance is 1 type, or 2 or more types chosen from the dichloro isocyanurate, the trichloro isocyanurate, and the hypochlorite (invention 2). .

  According to this invention (Invention 2), these chlorinated active substances are excellent in bactericidal properties of microorganisms contained in ship ballast water and the like, and are calculated and measured by logarithmic formulas based on the total residual oxidizing substance concentration. Is suitable for determining the amount of addition of the chlorinated active substance.

  According to the ballast water control method of the present invention, untreated ballast water to which no chlorinated active substance is added is collected in advance, and the chlorinated active substance is added to the untreated ballast water by adding the chlorinated active substance. Measure the time-dependent changes in the total residual oxidant concentration due to the substance, and based on the total residual oxidant concentration (including the initial total residual oxidant concentration) for three or more measurement times, Since the addition amount of the chlorinated active substance at which the residual oxidizing substance concentration is 0.1 mg / L or more is determined, the addition amount of the chlorinated active substance can be optimally determined. Excessive or insufficient addition can be prevented. Moreover, the toxicity of discharged water can be lowered and the amount of neutralizing agent added can be reduced.

It is a graph which shows the attenuation | damping behavior of a sodium hypochlorite (oxidizing substance) density | concentration in four types of seawater in the control method of the ballast water which concerns on one Embodiment of this invention. It is a graph which shows the logarithm curve computed based on the total residual oxidizing substance density | concentration after the initial stage in FIG. 1, 5 minutes, and 30 minutes. It is a graph which shows the calculated value of the total residual oxidizing substance density | concentration after 5 days based on the logarithmic curve of FIG. 2 of 4 types of seawater, and the measured value of the total residual oxidizing substance density | concentration after 5 days of 4 types of seawater. Based on the calculation method of the comparative example (Patent Document 1) of four types of seawater, the calculated value of the total residual oxidant concentration after 5 days and the actual measurement value of the total residual oxidant concentration after 5 days of the four types of seawater It is a graph to show.

  Hereinafter, the control method of ballast water of the present invention is explained in detail based on one embodiment.

  The ballast water control method of the present embodiment is for determining the amount of addition of a chlorinated active substance that sterilizes aquatic microorganisms in the ballast water when supplying the ballast water taken from the water intake to the ballast tank. The untreated ballast water to which no chlorinated active substance is added is collected in advance, the chlorinated active substance is added to the untreated ballast water, and the total residual oxidizing substance concentration of the chlorinated active substance is reduced. Measure changes over time.

Next, based on the total residual oxidizable substance concentration (including the initial total residual oxidizable substance concentration) for three or more measurement times, the following logarithmic expression C = a · ln (t) + b (1)
(Wherein, a and b are reaction constants, t is the elapsed time, and C is the total residual oxidizing substance concentration), and the values of a and b are calculated. Then, from the calculated logarithmic expression, the addition amount of the chlorinated active substance at which the total residual oxidizing substance concentration in the estimated drainage time (discharge elapsed time) of the ballast water is 0.1 mg / L or more is determined.

  As a result of the inventors' research, almost all harbor waters are treated with chlorinated water from ports all over the world. Chlorine-based active substances (total residual oxidizing substances) are approximated to the above logarithm. It was discovered that it can be assumed that it will be consumed according to the curve. The total residual oxidizing substance concentration is TRO (Total Residual Oxidants). The oxidizing chlorine concentration due to the addition of the chlorine-based active substance and other oxidizing components generated by the reaction with this oxidizing chlorine include included. This total residual oxidizing substance concentration can be measured at room temperature using a commercially available high precision TRO meter using the DPD absorbance method.

  Specifically, the following operation may be performed. First, ballast water such as untreated seawater to which no chlorinated active substance is added is collected, and a chlorinated active substance is added experimentally. Here, as the chlorinated active substance, dichloroisocyanuric acid salt, trichloroisocyanuric acid is excellent because it is excellent in bactericidal properties and approximates to some extent the calculation by the logarithmic formula by the total residual oxidizing substance concentration described later and the actual measurement value. One or more selected from salts and hypochlorites can be used, and hypochlorites such as sodium hypochlorite are particularly preferred.

  Moreover, it is preferable that the addition amount of the experimental chlorine-based active substance is a maximum allowable addition amount (MAD) or an approximation not exceeding this. Here, the maximum allowable addition amount is a concentration at which the maximum amount of ballast water set at the time of IMO basic approval can be added, and the person to be approved must add a chlorinated active substance to the ballast water beyond this concentration. I can't. In this way, by setting the experimental addition amount of the chlorinated active substance as the maximum allowable addition amount, in the calculation of the logarithmic formula by the total residual oxidizing substance concentration as described later, the chronological change of the chlorinated active substance consumption is A well-simulated logarithmic approximation curve can be obtained.

  When chlorinated active substances are added to the ballast water sampled in advance in this way, first measure the total residual oxidizing substance concentration (initial total residual oxidizing substance concentration) immediately after the addition, and leave it as it is. Check several changes in the concentration of oxidizing substances.

  Here, the time for confirming the transition of the total residual oxidizing substance concentration is preferably shorter in view of the efficiency of the ballast water treatment, but conventionally, in the short measurement time, the chlorine system to the actual ballast water There was a problem that the accuracy of the addition amount (concentration) of the active substance was low. However, in the present embodiment, the concentration of the chlorine-based active substance added to the actual ballast water can be accurately determined only by measuring the transition of the total residual oxidizing substance concentration of about 1 to 120 minutes, particularly about 1 to 40 minutes. Can be determined. In addition, the number of measurements between 1 and 120 minutes is preferably as high as possible, but in this embodiment, it may be 2 points (3 points including the initial total residual oxidizing substance concentration).

  Based on the total residual oxidizing substance concentration (C) at the elapsed time (t) of three or more points, the values of a and b satisfying the logarithmic formula (1) are calculated to complete the logarithmic formula, and logarithmic approximation Create a curve. Since the chlorine-based active substance begins to decay immediately after the addition, it is difficult to accurately measure the active substance concentration immediately after the addition. Therefore, when creating a logarithmic approximation curve, the concentration immediately after the addition of the chlorine-based active substance is set as the maximum allowable addition amount, and the time (t) at this time is assumed to be an extremely short time of about 0.1 seconds. It is possible to obtain a logarithmic approximation curve that well simulates the change with time of the consumption of the system active substance.

  Then, using the created approximate curve, the number of days of voyage is simulated as the discharge time (t) of ballast water, and this ballast water discharge time (t) is applied to the logarithmic approximate curve to calculate the total residual oxidation during ballast water discharge. The initial total residual oxidizing substance concentration at which the concentration of the active substance becomes 0.1 mg / L or more is set, and based on this, the addition amount of the chlorine-based active substance to the actual ballast water may be determined. If the total residual oxidizing substance concentration is less than 0.1 mg / L, it becomes difficult to maintain the bactericidal properties of the micro-animals in the ballast water until the end of the voyage. In particular, if the voyage time is longer than planned and there is no residual chlorine for a long time, bacterial regrowth, durable egg hatching, etc. may occur. Therefore, the amount of chlorinated active substance added depends on the ballast water discharge time (t It is preferable to add so that the total residual oxidizing substance concentration of 1) to 10 mg / L, particularly 2 to 5 mg / L. Thereby, the effect that the dispersion | variation in water quality, the dispersion | variation in chlorine consumption, and the dispersion | variation in an approximated curve can be corrected is also show | played.

  When discharging the ballast water, a reducing agent is supplied to the discharged ballast water to reduce the remaining chlorine, and the residual chlorine concentration is reduced to the target residual chlorine concentration, and then discharged to the external environment. As the reducing agent supplied from this reducing agent supply mechanism, sodium sulfite, sodium bisulfite (sodium hydrogen sulfite), sodium thiosulfate, or the like can be used.

  As mentioned above, although this invention has been demonstrated based on one Embodiment, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible. For example, the total residual oxidizing substance concentration is not limited to the measurement using a TRO meter using the DPD absorbance method, and various measuring means can be applied as long as similar measurement values can be obtained. Is possible.

The following specific examples further illustrate the present invention.
[Example 1 and Comparative Example 1]
Seawater (Tokyo Bay A (seawater (i)), Tokyo Bay B (seawater (ii)), Shizuoka fishing port A (seawater (iii)) and Shizuoka fishing port B (seawater (iv)) The salinity, pH, turbidity, SS concentration, POC (suspended organic carbon) concentration and DOC (dissolved organic carbon) concentration of these seawaters are as shown in Table 1, and the water quality depends on the location. It was very different.

  Sodium hypochlorite was added to these seawaters so that the total residual oxidizing substance concentration was 30 mg / L as measured by a TRO meter using the DPD absorbance method. Table 1 shows the results of measuring the transition of the total residual oxidizing substance concentration using the DPD method up to 14 days after the addition of sodium hypochlorite. . Also, the transition of the total residual oxidizing substance concentration up to 5 days after this measurement value is shown in FIG.

  Next, in the above measured value, assuming that the total residual oxidant concentration immediately after the addition of sodium hypochlorite is 30 mg / L, and subsequently calculating the formula (1) from the total residual oxidant concentration after 5 minutes and 30 minutes. The logarithmic approximate curves of seawater (i) to (iv) were respectively created based on the a and b in the logarithmic formula. The results are shown in FIG.

  Furthermore, the total residual oxidizing substance density | concentration after five-day progress of seawater (i)-(iv) calculated | required from these logarithmic curves was calculated, and the result compared with the measured value is shown in FIG. For comparison, FIG. 4 shows the result of comparing the calculated value of the total residual oxidizable substance concentration after 5 days with the actual measurement value based on the calculation method of Patent Document 1.

  As apparent from FIGS. 3 and 4, the actual measurement values are simulated with high accuracy in Example 1, whereas in Comparative Example 1 based on the calculation method of Patent Document 1 which is a conventional method, the total remaining after 5 days Almost no oxidant concentration was simulated. From these facts, the ballast water control method of the present invention can accurately simulate the total residual oxidant concentration after a long period of time from the measured value of the total residual oxidant concentration in a short time. It was found that the amount of the chlorinated active substance added so that the total residual oxidizing substance concentration in the planned water drainage time is 0.1 mg / L or more can be set without excessive addition or insufficient addition.

  According to the ballast water control method of the present invention, it is possible to accurately simulate the total residual oxidant concentration after a long period of time from the measured value of the total residual oxidant concentration in a short time. It is possible to determine the amount of substance added, thereby enabling optimization of the loading amount, space, and equipment of the drug on the ship, and consequently providing a cost-competitive processing apparatus. It becomes possible.

Claims (2)

When supplying ballast water taken from a water intake to a ballast tank, a ballast water control method for adding a chlorinated active substance for sterilizing aquatic microorganisms in the ballast water,
Pre-collecting untreated ballast water to which no chlorinated active material has been added, adding a chlorinated active material to the untreated ballast water, and changing the concentration of all residual oxidizing substances over time due to the chlorinated active material And the following logarithm formula C = a · ln (t) + b
(Wherein, a and b are reaction constants, t is the elapsed time, and C is the total residual oxidizing substance concentration.)
Calculate the values of a and b that satisfy
A control method for ballast water, characterized in that, from the calculated logarithmic formula, an addition amount of a chlorine-based active substance at which a total residual oxidizing substance concentration in a scheduled discharge time of ballast water is 0.1 mg / L or more is determined.   The method for controlling ballast water according to claim 1, wherein the chlorinated active substance is one or more selected from dichloroisocyanurate, trichloroisocyanurate and hypochlorite. .

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