Plant operation assistance system

Abstract

Provided is a plant operation assistance system that makes it possible to supply an appropriate amount of nutrient salts to a specific point in a managed water area. A plant operation assistance system (S) comprises: a nutrient salt control target value setting unit (3) that sets a control target value for nutrient salts discharged from one or more water treatment plants (1) that discharge the nutrient salts and cause the nutrient salts to flow to a managed water area (8); a management item constraint condition setting unit (4) that sets constraint conditions for management items in the managed water area (8); a management item measurement unit (5) that measures the management items in the managed water area (8); a managed water area environmental zone setting unit (6) that sets a point where the constraint conditions for the management items in the managed water area (8) are corrected; and a nutrient salt control target value correction unit (7) that calculates a corrected result of the control target value on the basis of the measurement values measured by the management item measurement unit (5) and the constraint conditions set by the management item constraint condition setting unit (4). The nutrient salt control target value setting unit (3) corrects the control target value on the basis of the corrected result.

Description

Plant operation support system

[0001] This invention relates to a plant operation support system.

[0002] Excessive nutrients cause an abnormal increase in phytoplankton in the sea area where the wastewater is discharged, leading to environmental pollution such as red tides and the destruction of ecosystems. During the period of rapid economic growth, as water pollution in enclosed water bodies became apparent as environmental pollution, advanced treatment methods that remove not only organic matter but also nutrients such as nitrogen and phosphorus from wastewater became widespread in water treatment plants, including sewage treatment plants, with the aim of improving the water environment of public water bodies. As a result, water quality improved in enclosed water bodies such as Tokyo Bay, Osaka Bay, Ise Bay, the Seto Inland Sea, and Lake Biwa, and ecosystems recovered.

[0003] However, excessive removal of nutrients such as nitrogen and phosphorus has diluted the nutrient concentration in the sea areas into which the treated wastewater flows. As a result, this has led to poor growth of seaweed, seagrass, and algae that grow or are cultivated in the sea due to nutrient deficiencies, and a decline in zooplankton and fish populations due to poor growth of phytoplankton, which is the primary product. For this reason, in recent years there has been a growing demand to maintain good water quality while appropriately supplying nutrients from water treatment plants to ensure greater biodiversity and productivity.

[0004] The ocean is considered important not only for the harvesting of seaweed, seagrass, and fish, but also from the perspective of decarbonization. In October 2009, the United Nations Environment Programme (UNEP) reported that carbon incorporated into marine ecosystems such as seaweed beds and shallow areas was named "blue carbon," and CO2 ２ This was presented as a new option for addressing the absorption of carbon monoxide.

[0005] Recent research has shown that the amount of carbon absorbed and sequestered by marine ecosystems (blue carbon) is comparable to the amount of carbon absorbed and sequestered on land (green carbon). Therefore, there are high expectations for the utilization of blue carbon as an initiative to enrich marine ecosystems while achieving carbon neutrality. Furthermore, in recent years, research has focused on the CO2 sequestering effect of marine ecosystems that sequestrate and store blue carbon (blue carbon ecosystems). ２To play a role as a carbon sink and to accelerate efforts toward climate change mitigation and adaptation in other coastal areas and oceans, trials and applications for "J Blue Credits" as carbon credits have begun. J Blue Credits are quantifiable blue carbon credits that can be traded. Through trading these credits, it is expected that economic value can be enjoyed through sales profits, and social and environmental value can be contributed to the creation of rich marine ecosystems along coastlines and the role of natural breakwaters through creation and purchase.

[0006] The amount of blue carbon is expressed as the distribution area of ​​the target ecosystem × absorption coefficient (wet weight per unit area × blue carbon retention rate). Examples of target ecosystems include seagrass beds such as eelgrass beds, eelgrass, dwarf eelgrass, slender eelgrass, and Ryukyu slender eelgrass; seaweed beds such as Sargassum beds, Sargassum fuscoguttatum, Sargassum erythrosora, Sargassum fuscoguttatum, Sargassum sarmentosum, and Sargassum sarmentosum; kelp beds such as kelp beds, Laminaria japonica, Laminaria tetrandra, Laminaria japonica, and Sargassum fuscoguttatum; Wakame seaweed beds, Wakame seaweed, and Sargassum fuscoguttatum; Tengusa seaweed beds, Laminaria japonica, and Sargassum fuscoguttatum; mangroves, tidal flats, phytoplankton, and zooplankton.

[0007] Structures such as artificial reefs, seawalls, aquaculture facilities, and offshore wind power plants serve as footholds for seaweed beds, contributing to the stable growth of seagrass and seaweed. For this reason, J-Blue Credit applications are often made for seagrass and seaweed beds located at sites related to these structures.

[0008] CO ２ Blue carbon ecosystems, which act as carbon sinks, increase in rich oceans where nutrients are properly managed. Managing nutrients, which are equivalent to fertilizers, is crucial for increasing the distribution area and wet weight per unit area, thereby enhancing the value of blue carbon credits. Therefore, monitoring nutrients in marine areas and managing water treatment plants such as sewage treatment plants, which are sources of these nutrients, are essential.

[0009] Under these circumstances, for example, Patent Document 1 proposes an invention aimed at providing an operation support device for a wastewater treatment facility that incorporates a method / process for contributing to an increase in the amount of blue carbon. Specifically, Patent Document 1 describes an operation support device that assists in the operation of a wastewater treatment facility that discharges treated wastewater. This device has a managed water area information acquisition mechanism that acquires observation results of predetermined management items in a managed water area to which the treated wastewater discharged by the wastewater treatment facility flows. This device has a management item constraint condition setting mechanism that sets constraint conditions for the predetermined management items in the managed water area. This device has a nutrient control target setting mechanism that sets control targets for nutrients contained in the treated wastewater. This device has a nutrient control target modification mechanism that compares the observation results of the predetermined management items from the managed water area information acquisition mechanism with the constraint conditions and sets modified control targets. This device has a nutrient control mechanism that controls the concentration of nutrients contained in the treated wastewater based on the modified control targets.

[0010] Japanese Patent Publication No. 2024-33452

[0011] However, the invention described in Patent Document 1 did not adequately consider supplying appropriate amounts of nutrients to specific locations in blue carbon ecosystems, such as seagrass beds and seaweed beds, within the managed water area, and there was room for improvement in this respect.

[0012] The present invention has been made in view of the above circumstances. The object of the present invention is to provide a plant operation support system that can supply an appropriate amount of nutrients to a specific point within a controlled water area.

[0013] The plant operation support system according to the present invention, which solves the above problems, comprises: a nutrient control target value setting unit that sets a control target value for nutrients discharged from one or more water treatment plants that discharge nutrients and allow them to flow into a controlled water area; a control item constraint condition setting unit that sets constraint conditions for control items in the controlled water area; a control item measurement unit that measures control items in the controlled water area; a controlled water area environment classification setting unit that sets points for correcting constraint conditions for control items in the controlled water area; and a nutrient control target value correction unit that calculates a correction result for the control target value based on the measured value measured by the control item measurement unit and the constraint conditions set by the control item constraint condition setting unit, wherein the nutrient control target value setting unit corrects the control target value based on the correction result.

[0014] According to the present invention, a plant operation support system can be provided that can supply an appropriate amount of nutrients to specific points within a controlled water area. Other problems, configurations, and effects not mentioned above will be revealed by the following description of embodiments. Further features related to the present invention will be evident from the description herein and the accompanying drawings.

[0015] This is a diagram illustrating the configuration of a plant operation support system S according to the first embodiment of the present invention. This is an explanatory diagram illustrating the controlled water area 8.

[0016] Hereinafter, a plant operation support system S according to one embodiment of the present invention will be described with reference to the drawings as appropriate. Note that common components in the following description and drawings may be denoted by the same reference numerals, and redundant descriptions may be omitted. Furthermore, the present invention is not limited to the following embodiments. Moreover, the description herein is merely a typical example and does not limit the scope of the claims or applications in any sense.

[0017] [First Embodiment] Figure 1 is a configuration diagram of a plant operation support system S according to the first embodiment of the present invention. This plant operation support system S supports the operation of a water treatment plant 1. As shown in Figure 1, the plant operation support system S includes a nutrient control target value setting unit 3, a management item constraint condition setting unit 4, a management item measurement unit 5, a management water area environmental classification setting unit 6, and a nutrient control target value correction unit 7. The plant operation support system S also includes a monitoring control unit 2.

[0018] Water treatment plant 1 discharges nutrients and allows them to flow into the controlled water area 8. Monitoring and control unit 2 monitors and controls water treatment plant 1. Nutrient control target value setting unit 3 sets control target values ​​for nutrients discharged from one or more water treatment plants 1 that discharge nutrients and allow them to flow into the controlled water area 8. Control item constraint condition setting unit 4 sets constraint conditions for control items in the controlled water area 8. Here, constraint conditions are lower and upper limits that are set as appropriate, as will be described later. Control item measurement unit 5 measures control items in the controlled water area 8. Control water area environmental classification setting unit 6 sets points for correcting the constraint conditions for control items in the controlled water area 8. Nutrient control target value correction unit 7 calculates the correction result (correction policy) of the control target value based on the measured values ​​measured by the control item measurement unit 5 and the constraint conditions set by the control item constraint condition setting unit 4. In this embodiment, the nutrient control target value setting unit 3 corrects the control target value based on the correction result described above. A specific embodiment will be described below.

[0019] Water treatment plant 1 has a monitoring and control unit 2 that acquires sensor values ​​and operates equipment. Water treatment plant 1 treats public sewage, industrial wastewater, agricultural wastewater, domestic wastewater, etc., according to the nutrient control target value setting unit 3 which sets control target values ​​for nutrients, and discharges the treated water into rivers, lakes, and sea areas. The discharged treated water merges with the surrounding environmental water and treated water from other water treatment plants, etc., and reaches a managed water area 8 such as a lake, bay, inner bay, inland sea, open sea, sea area, or body of water. A management item measurement unit 5 is located in the managed water area 8. Nutrient control target value correction unit 7 calculates the correction result for the nutrient control target value based on the measured values ​​of the management items measured by the management item measurement unit 5 and the constraint conditions set by the management item constraint condition setting unit 4 which sets constraint conditions related to the management items. Nutrient control target value setting unit 3 corrects the nutrient control target value based on the above correction result. Furthermore, the management area points in the management area 8 (i.e., the points where the constraints of the management items in the management area 8 are corrected) are classified and set by the management area environment classification setting unit 6. Note that the prior art (for example, the invention described in Patent Document 1 mentioned above) does not have a management area environment classification setting unit 6, and therefore differs from the present invention in that it may not be possible to appropriately classify and set the points where the constraints of the management items in the management area 8 are corrected. The management item constraint setting unit 4 corrects the constraints based on the setting information classified and set by the management area environment classification setting unit 6.

[0020] In the first embodiment, the control item targeted by the nutrient control target value setting unit 3 is the total nitrogen discharge rate, the management area 8 is an inner bay, and the management item in the management area 8 is the total nitrogen concentration. Total nitrogen concentration is an indicator that correlates with phytoplankton concentration. Phytoplankton concentration fluctuates due to factors such as number density, cell density, and whether it is the same species or different species. If the total nitrogen concentration or phytoplankton concentration is too high, it can cause environmental damage such as red tides. On the other hand, if the total nitrogen concentration or phytoplankton concentration is too low, it can impair the growth of marine ecosystems or result in economic losses due to energy consumption from excessive processing.

[0021] Figure 2 is an explanatory diagram illustrating the managed water area 8. In the example shown in Figure 2, effluent discharged from the water treatment plant 1 is discharged into the managed water area 8 (sea area) via a river. The managed water area within the sea area is divided into a 4x6 zone, within which there are points PA and PB. The settings for this zone and points PA and PB are made by the managed water area environmental zone setting unit 6 as described above. Points PA and PB are also measurement points for total nitrogen concentration. That is, management item measurement units 5 are installed at points PA and PB. However, there are no special scaffolding or other structures installed at point PA to reinforce seaweed beds, and there are no seaweed beds there. On the other hand, structures that serve as scaffolding for seaweed beds are installed at point PB. The other points (zones shown as blanks) are neither measurement points (i.e., no management item measurement units 5 are installed), and there are no seaweed beds or scaffolding.

[0022] Table 1 below shows an example of the first constraint value, second constraint value, and correction value at point PB for total nitrogen concentration in managed water area 8 (points PA and PB). For example, the water quality target value in managed water areas in the Hyogo Prefecture Nutrient Management Plan (draft) (URL: https: / / www.kankyo.pref.hyogo.lg.jp / jp / info_list / 22742) is set as the range from the lower limit of the prefectural ordinance to the environmental standard value as the desirable nutrient concentration. In Table 1, the lower limit of the prefectural ordinance for total nitrogen in cumulative water area II is set as the first constraint value, and 90% of the environmental standard value is set as the second constraint value (i.e., upper limit). The reason why 90% of the environmental standard value is set as the second constraint value is that the second constraint value in this embodiment is an indicator that determines how to respond assuming that it may be exceeded, while the environmental standard value is assumed not to be exceeded, so a margin of 10% is taken and set to 90%. Since site PB is a location where structures that serve as a foothold for seaweed beds are installed, it is desirable that sufficient nutrients be supplied to the seaweed beds. Therefore, for site PB, the first constraint value is increased by adding a correction value (0.03 mg-N / L) to the first constraint value (0.20 mg-N / L) to obtain a new first constraint value of 0.23 mg-N / L, thereby increasing the impact of total nitrogen concentration on the seaweed beds. The second constraint value is set based on values ​​that must be complied with, such as environmental standards, so no correction value is set to relax it. As mentioned above, the first constraint value, which is the lower limit, i.e., the correction of the constraint conditions is performed in the management item constraint condition setting unit 4.

[0023]

[0024] The description of the embodiments so far concerns planning, modification, and control. The following describes the control aspects. Since the growth of seaweed beds may not be promoted if the total nitrogen concentration falls below the first constraint value (i.e., the lower limit), the first constraint value corresponds to a target value related to economic value. On the other hand, since adverse environmental effects such as red tides may occur if the total nitrogen concentration rises above the second constraint value (i.e., the upper limit), the second constraint value corresponds to a target value related to environmental value. In other words, the total nitrogen concentration, which is a management item in the managed water area 8 of this embodiment, is a management item that has both a first constraint value and a second constraint value that is greater than the first.

[0025] If the measured value of a control item is smaller than the first constraint value related to economic value, the control item for nutrients will be set to "increase," and if it is larger, the control item for nutrients will be set to "maintain." In other words, if the measured value falls below the first constraint value after correction using the correction value, the instruction for the control target value corresponding to that location will be set to "increase." Also, if the measured value exceeds the first constraint value after correction using the correction value, the instruction for the control target value corresponding to that location will be set to "maintain." If the measured value of a control item is smaller than the second constraint value related to environmental value, the control item for nutrients will be set to "maintain," and if it is larger, the control item for nutrients will be set to "decrease." In other words, if the measured value exceeds the second constraint value, the instruction for the control target value corresponding to that location will be set to "decrease."

[0026] Therefore, in the case of a control item having both a first constraint value and a second constraint value that is greater than the first, as in this embodiment, if the measured value of the control item is less than the first constraint value, the control item for nutrients will be "increased". If the measured value of the control item is between the first and second constraint values, the control item for nutrients will be "maintained". If the measured value of the control item is greater than the second constraint value, the control item for nutrients will be "decreased".

[0027] Based on these measured values ​​and constraints (constraints), the correction policies (i.e., correction results) of "increase," "maintain," and "decrease" are calculated by the nutrient control target value correction unit 7. Here, Table 2 shows the measured values ​​of the management items X at point PA. Ａ This shows the correction policy for the control target value A of nutrients. Table 3 shows the measured values ​​X of the control items at site PB. Ｂ This document outlines the correction policy for the target value B of nutrient control.

[0028]

[0029] Location PA is in a normal sea area. Therefore, as shown in Table 2, the measured value X of the total nitrogen concentration, which is a control item, is... Ａ If it is smaller than the first constraint value, the control target value A for nutrients at point PA, which is the total nitrogen discharge rate, will be "increased". Measured value X of the total nitrogen concentration, which is the control item. ＡIf it is equal to or greater than the first constraint value, it will be "maintained".

[0030]

[0031] On the other hand, the location PB is a location where a structure serving as a foothold for the kelp forest is installed, and more nutrient supply is required compared to the location PA which is a normal sea area. Therefore, in the present embodiment, the value obtained by adding the correction value to the first constraint value of the location PA is treated as the first constraint value of the location PB. In this case, the measured value X of the total nitrogen concentration of the management item Ｂ If it is less than the first constraint value of the location PB, the control target value B of the total nitrogen discharge amount of the nutrient salts, which is a nutrient salt in the control item, at the location PB will be "increased". The measured value X of the total nitrogen concentration of the management item Ｂ If it is equal to or greater than the first constraint value of the location PB, it will be "maintained".

[0032] In the case of the control target value A of the nutrient salts and the control target value B of the nutrient salts, which are divided into two types: "increase" and "maintain", the number of cases (permutations) is 4 cases. Table 4 shows the correction policy of the control target value of the nutrient salts (that is, the control policy of the water treatment plant 1) set for each case of the control target value A of the nutrient salts and the control target value B of the nutrient salts.

[0033]

[0034] As described above, since the first constraint value is a constraint value related to economic value, there is a desire to set it as high as possible. Therefore, as shown in Table 4, only when both the control target value A of the nutrient salts and the control target value B of the nutrient salts are "maintained" (Case 4), the nutrient salt control target value correction unit 7 sets the correction policy of the control target value of the nutrient salts to "maintain". When either one or both are "increased" (Cases 1 to 3), the nutrient salt control target value correction unit 7 sets the correction policy of the control target value of the nutrient salts to "increase".

[0035] Table 5 shows an example of a correction value calculation method when the correction policy for the control target value of nutrients is "increase". Here, the management item is the total nitrogen concentration, and the control item is the total nitrogen discharge amount. In the example shown in Table 5, based on the difference Z between the first constraint value and the measured value X, the correction amount (correction value) of the control target value of nutrients is determined. Also, in this example, when the difference is greater than 0, that is, when the economic value is impaired, the total nitrogen discharge amount, which is a nutrient, is increased to promote the growth of the seaweed bed. Note that the correction of the correction amount (correction value) of the control target value of nutrients is performed by the nutrient control target value setting unit 3 based on the above-described correction policy (correction result). By correcting the control target value of nutrients so as to increase the nutrients in this way, the growth of the seaweed bed can be promoted.

[0036]

[0037] In this embodiment, the total nitrogen concentration is taken as the management item of nutrients, but it may also be the ammonia nitrogen concentration, nitrate nitrogen concentration, nitrite nitrogen concentration, organic nitrogen concentration, total phosphorus concentration, phosphate phosphorus concentration, organic phosphorus concentration, etc., or a combination of a plurality of these. With any of these, the control of nutrients for the point PB in the management water area 8 can be suitably performed. These management items preferably have first and second constraint values arbitrarily determined in consideration of economic value and environmental value.

[0038] In this embodiment, the management item with the first constraint value relates to economic value. In this embodiment, total nitrogen concentration was chosen as the management item with the first constraint value, but the target ecosystem could be a seagrass bed, specifically a seagrass bed, and its distribution area could also be used. In other words, it could be the distribution area of ​​the target ecosystem. Furthermore, the management items in the managed water area 8 could be other than the distribution area of ​​the target ecosystem, such as the absorption coefficient of the target ecosystem, wet weight per unit area, blue carbon retention rate, blue carbon amount, or a combination of several of these. In this case, it is preferable that these management items have a first constraint value arbitrarily determined considering economic value. This ensures economic value. In addition, the target ecosystems may also include, besides seagrass beds (eelgrass beds), eelgrass, dwarf eelgrass, Japanese dwarf eelgrass, Ryukyu dwarf eelgrass, seaweed beds (garamo beds), red seaweed, sawtooth seaweed, sargassum, Sargassum, Sargassum, Sargassum, kelp beds, kelp beds, kelp beds, narrow-leaved kelp, kelp beds, Ecklonia cuneata, Ecklonia serrata, Ecklonia kelp, Ecklonia sericea

[0039] In this embodiment, point PB is defined as a location where a structure that serves as a foothold for seaweed beds is installed, but any location that influences the growth of seaweed beds is acceptable. For example, point PB could be a location near a seaweed bed that corresponds to the upstream area where currents flow into the seaweed bed, a location where fish that increase as a result of seaweed bed growth gather (a location where a large amount of plankton, which serves as food for fish, is needed, and therefore a large amount of nutrients are needed), or a location empirically selected as necessary to enrich the ecosystem. Therefore, the location set in the managed water area environmental classification setting unit 6 should be a location where a structure that serves as a foothold for seaweed bed growth exists and / or within the area of ​​influence thereof. In this way, the ecosystem in that location and area of ​​influence can be enriched.

[0040] Regarding the frequency of correction based on the measured values of the management items in this embodiment (that is, the frequency of correction of the control target value by the nutrient control target value correction unit 7), since it is targeted at the growth of the ecosystem, short-term frequencies such as per hour or per day may be used, but it is preferable to monitor the average trend at medium- to long-term frequencies such as per week, per month, per season, or per year and reflect it in the correction. By doing so, long-term growth promotion effects or growth inhibition effects can be obtained. From such a perspective, it can be said that the frequency of correction of the control target value by the nutrient control target value correction unit 7 is more preferably, for example, once a month at most.

[0041] In this embodiment, it is preferable to simultaneously display the measured value by the management item measurement unit 5 and the control target value of the nutrient on the display screen. In this case, for the nutrient items for which the control target value of the nutrient is corrected, the items that increase or decrease may be distinguished so that they can be visually confirmed.

[0042] In this embodiment, a table in which predetermined numerical values are input is used as the correction method, but a function format may also be used, or the result of a simulation that calculates the relationship between the measured value and the correction value of the control target value of the nutrient may also be used.

[0043] In this embodiment, the total nitrogen discharge amount is used as the control item targeted by the nutrient control target value setting unit 3, but it may also be the ammonia nitrogen discharge amount, nitrate nitrogen discharge amount, nitrite nitrogen discharge amount, organic nitrogen discharge amount, total phosphorus discharge amount, phosphate phosphorus discharge amount, organic phosphorus discharge amount, etc., or a combination of a plurality of these. Also, in this embodiment, the discharge amount, which is the product of the flow rate and the concentration, is used, but the concentration or the flow rate may also be used.

[0044] Nutrients can be broadly classified into nitrogen-based (total nitrogen, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, organic nitrogen) and phosphorus-based (total phosphorus, phosphate phosphorus, organic phosphorus). The discharge rate from water treatment plant 1 and the concentration measured after reaching the controlled water area 8 show a positive correlation for both nitrogen-based and phosphorus-based nutrients, suggesting that nitrogen-based and phosphorus-based nutrients are independent of each other. In this embodiment, the control item was total nitrogen discharge rate and the management items were total nitrogen concentration and nitrogen-based nutrients. However, if the control item were total phosphorus discharge rate, the management items would be phosphorus-based nutrients such as total phosphorus concentration and phosphate concentration.

[0045] Furthermore, in this embodiment, pre-specified values ​​were used for the first constraint value and the correction value, but these values ​​may also be predicted values ​​based on past performance data, measurement history, or simulation results related to seaweed bed cultivation. In that case, the difference between the first constraint value and the predicted value of the measurement item will arise due to changes in environmental conditions or differences in assumed coefficients, and based on this, the nutrient control target value setting unit 3 will correct the control target value of the nutrient item.

[0046] In this embodiment, an inner bay is used as an example for the managed water area 8 (sea area), but any water area to which the effluent from the water treatment plant 1 reaches, such as lakes, bays, inner bays, inland seas, or open seas, is acceptable. In this embodiment, a method for correcting the nutrient discharge rate of one water treatment plant 1 has been described, but the nutrients of the entire watershed, including multiple water treatment plants 1, may also be targeted. In that case, the nutrient correction can be applied to the multiple water treatment plants 1 by allocating them according to predetermined distribution ratios, distribution ratios according to treatment efficiency, or predetermined load acceptance order. Furthermore, the allocation to multiple series within each water treatment plant 1 can also be applied according to predetermined distribution ratios, distribution ratios according to treatment efficiency, or predetermined load acceptance order. The management items may be indicators related to organic matter, such as biochemical oxygen demand (BOD) and chemical oxygen demand (COD), or indicators related to potassium.

[0047] [Second Embodiment] Next, a second embodiment will be described. The plant operation support system S according to the second embodiment has the same configuration as the first embodiment (see Figure 1). In addition, the plant operation support system S according to the second embodiment manages and controls nutrients in the controlled water area 8 in the same way as the first embodiment (see Figure 2).

[0048] In the second embodiment, the control item targeted by the nutrient control target value setting unit 3 is the total nitrogen discharge rate, the management area 8 is an inner bay, and the management items in the management area 8 are the total nitrogen concentration and chlorophyll a concentration. Total nitrogen concentration and chlorophyll a concentration are indicators that correlate with phytoplankton concentration. Phytoplankton concentration fluctuates due to factors such as number density, cell density, and whether they are of the same species or different species. If the total nitrogen concentration, chlorophyll a concentration, and phytoplankton concentration are too high, it can cause environmental damage such as red tides. On the other hand, if the total nitrogen concentration, chlorophyll a concentration, and phytoplankton concentration are too low, it can impair the growth of marine ecosystems or result in economic losses due to energy consumption from overtreatment. As described in the first embodiment, the indicator corresponding to the target value related to the latter economic value is the first constraint value. The indicator corresponding to the upper limit related to the former environmental damage is the second constraint value. In this embodiment, total nitrogen concentration and chlorophyll a concentration are management items that have both a first constraint value and a second constraint value that is greater than the first constraint value.

[0049] As explained in the first embodiment, if the measured value of a control item is smaller than the first constraint value related to economic value, the control item for nutrients is set to "increase," and if it is larger, the control item for nutrients is set to "maintain." In other words, if the measured value falls below the first constraint value after correction by the correction value, the instruction for the control target value corresponding to that location is set to "increase." Also, if the measured value exceeds the first constraint value after correction by the correction value, the instruction for the control target value corresponding to that location is set to "maintain." If the measured value of a control item is smaller than the second constraint value related to environmental value, the control item for nutrients is set to "maintain," and if it is larger, the control item for nutrients is set to "decrease." In other words, if the measured value exceeds the second constraint value, the instruction for the control target value corresponding to that location is set to "decrease."

[0050] Therefore, in the case of a control item having both a first constraint value and a second constraint value that is greater than the first, as in this embodiment, if the measured value of the control item is less than the first constraint value, the control item for nutrients will be "increased". If the measured value of the control item is between the first and second constraint values, the control item for nutrients will be "maintained". If the measured value of the control item is greater than the second constraint value, the control item for nutrients will be "decreased".

[0051] Based on these measured values ​​and constraints (constraints), the correction policies (i.e., correction results) of "increase," "maintain," and "reduce" are calculated by the nutrient control target value correction unit 7. Table 6 shows an example of the first constraint value, second constraint value, and correction value of the first constraint value at point PB for the total nitrogen concentration and chlorophyll a concentration of the managed water area 8 in the second embodiment. As mentioned above, the water quality target values ​​in the managed water area in the Hyogo Prefecture Nutrient Management Plan (draft) are set as the lower limit of the prefectural ordinance to the environmental standard value as desirable nutrient concentrations. In Table 6, the lower limit of the prefectural ordinance for total nitrogen in cumulative water area II is set as the first constraint value, and 90% of the environmental standard value is set as the second constraint value (i.e., upper limit). The reason why 90% of the environmental standard value is set as the second constraint value is that the second constraint value in this embodiment is an indicator that determines the response assuming that it may be exceeded, while the environmental standard value is assumed not to be exceeded, so a margin of 10% is taken and set to 90%. Furthermore, the chlorophyll a concentration used as an indicator of red tide varies by municipality, but in some cases, 50 μg / L is used as a guideline for red tide detection. In Table 6, 50% of 50 μg / L, i.e., 25 μg / L, was set as the second constraint value. The first constraint value for chlorophyll a concentration was arbitrarily set. The correction value was set to 10% of each upper limit. Since the second constraint value was set based on values ​​that should be complied with, such as environmental standards, no correction value to relax it was set.

[0052]

[0053] The description of the embodiments so far concerns planning, modification, and control. The following describes the control aspects. Table 7 shows an example of a correction policy for the control target value of nutrients based on measured values ​​of control items. In the example shown in Table 7, there are a total of nine cases, divided into three categories based on the total nitrogen concentration of control item 1 and three categories based on the chlorophyll a concentration of control item 2. Each cell in Table 7 shows both the correction policy for control item 1 (left side) and the correction policy for control item 2 (right side). For example, if the measured value X (mg-N / L: nitrogen equivalent concentration) of the total nitrogen concentration is smaller than the first constraint value, and the measured value Y of the chlorophyll a concentration is larger than the second constraint value, the control target value for the total nitrogen discharge, which is a nutrient, contradicts the policy of "increase" or "decrease". In this case, prioritizing environmental protection, the safer direction, i.e., "reduction" rather than "increase", is prioritized. Similarly, if the policies for "increasing," "maintaining," and "reducing" the target values ​​of nutrients are contradictory, the nutrient control target value correction unit 7 prioritizes "reduction" first, then "maintaining," and finally "increase." In other words, if the measured value exceeds the second constraint value, the nutrient control target value correction unit 7 sets the instruction for the target value corresponding to that location to "reduction." If "reduction" is included in the instruction for the target value at all locations, the nutrient control target value correction unit 7 sets the instruction for the target value to "reduction."

[0054]

[0055] Table 8 shows an example of a correction calculation method when the total nitrogen concentration and chlorophyll a concentration exceed the second constraint value, and the correction policy for the nutrient control target value is "reduction." The control item is the total nitrogen discharge. In the example shown in Table 8, the correction amount (correction value) for the nutrient control target value is determined based on the difference Z between the second constraint value and the measured value X for both the total nitrogen concentration and the chlorophyll a concentration. In this example, if the difference Z for the total nitrogen concentration is greater than 0.03 mg-N / L, or if the difference Z for the chlorophyll a concentration exceeds 25 μg / L, i.e., the environmental standard value or the red tide detection value, the total nitrogen discharge is reduced as much as possible. The correction of this correction amount (correction value) for the nutrient control target value is performed by the nutrient control target value setting unit 3 based on the correction policy (correction result) described above.

[0056]

[0057] As shown in Table 8, when both the total nitrogen concentration and the chlorophyll a concentration exceed the second constraint value, both policies aim to "reduce total nitrogen emissions as much as possible," thus reducing the control target value for total nitrogen emissions. However, the indicated values ​​may differ. For example, if the measured total nitrogen concentration X is 0.28 mg-N / L (nitrogen equivalent concentration), referring to the second constraint value (0.27 mg-N / L (nitrogen equivalent concentration)) shown in Table 6, the difference Z for total nitrogen concentration becomes 0.01 mg-N / L (nitrogen equivalent concentration). Similarly, if the measured chlorophyll a concentration X is 40 μg / L, referring to the second constraint value (25 μg / L) shown in Table 6, the difference Z for chlorophyll a concentration becomes 15 μg / L. Therefore, as shown in Table 8, the correction value for total nitrogen emissions related to total nitrogen concentration is -500 kg-N / day (nitrogen equivalent mass), while the correction value for total nitrogen emissions related to chlorophyll a concentration is -2000 kg-N / day. In this case, prioritizing environmental protection, the nutrient control target value setting unit 3 adopts a safer direction, i.e., a smaller value of -2000 kg-N / day.

[0058] Thus, in this embodiment, by considering adjusting the target value of nutrients to increase them for economic value, and at the same time adjusting the target value of nutrients to reduce them in order to suppress environmental damage, it is possible to implement control that balances economic and environmental considerations. The first and second constraint values ​​in this embodiment are items that indicate the appropriate range for balancing environmental value and economic value. For example, in the case of total nitrogen concentration in this embodiment, if it exceeds the second constraint value, environmental value will be impaired, and if it falls below the first constraint value, marine ecosystems will be damaged, which may result in a decrease in economic and social value such as a decline in marine life, a decrease in biodiversity, a decrease in fish catches, a decrease in blue carbon sequestration, and a decrease in the amount of blue carbon credits created.

[0059] In this embodiment, total nitrogen concentration was chosen as the nutrient management item in the managed water area 8, but ammonia nitrogen concentration, nitrate nitrogen concentration, nitrite nitrogen concentration, organic nitrogen concentration, total phosphorus concentration, phosphate phosphorus concentration, organic phosphorus concentration, etc., or a combination of several of these may be used. Any of these can be used to suitably control nutrients at point PB in the managed water area 8. It is preferable that these management items have a first constraint value and a second constraint value arbitrarily determined considering economic and environmental value. In this embodiment, chlorophyll a concentration was chosen as the nutrient management item related to red tide, i.e., in the managed water area 8, but it is also possible to use phytoplankton cell density, chlorophyll concentration, pheo pigment concentration, fluorescence intensity, plant pigment concentration, seawater color value, reciprocal of transparency, dissolved oxygen saturation, pH, etc., or a combination of several of these may be used. Any of these can be used to suitably control nutrients at point PB in the managed water area 8. In this case, it is preferable that these management items have a second constraint value. This reduces environmental damage. Both of the above are management items related to eutrophication, and multiple items may be combined as in this embodiment.

[0060] Regarding the frequency of correction based on measured values ​​of the management items in this embodiment, as with the first embodiment, since the target is ecosystem growth, short-term frequencies such as hourly or daily may be used. However, it is preferable to monitor the average trend at medium- to long-term frequencies such as weekly, monthly, seasonal, or yearly, and reflect this in the correction. Doing so will yield a long-term growth suppression effect. From this viewpoint, it is more preferable that the frequency of correction of the control target value by the nutrient control target value correction unit 7 be, for example, at most once a month.

[0061] In this embodiment, as in the first embodiment, it is preferable to simultaneously display the measured values ​​from the control item measurement unit 5 and the control target values ​​for nutrients on the display screen. In this case, the nutrient items for which the control target values ​​for nutrients are corrected may be distinguished so that the items to be increased or decreased can be visually confirmed. Also, in this embodiment, the first constraint value and the second constraint value were considered simultaneously, but from the viewpoint of suppressing environmental damage, only the second constraint value may be considered.

[0062] In this embodiment, Table 8 shows only the correction calculation method when the correction policy for the control target value of nutrients is "reduction," but the same method can be used when it is "increase." That is, for example, by referring to Table 5, setting "difference Z = first constraint value - measured value X" and the conditions related thereto, and setting the correction value for the control target value of nutrients accordingly, the nutrient control target value setting unit 3 can perform the correction calculation when it is "increase."

[0063] Furthermore, in this embodiment as in the first embodiment, a table with predetermined numerical values ​​was used as the correction method, but a function format may also be used, or the results of a simulation that calculates the relationship between the measured value and the correction value of the control target value of nutrients may be used.

[0064] In this embodiment, the control item targeted by the nutrient control target value setting unit 3 is set to total nitrogen discharge, but it may also be set to ammonia nitrogen discharge, nitrate nitrogen discharge, nitrite nitrogen discharge, organic nitrogen discharge, total phosphorus discharge, phosphate phosphorus discharge, organic phosphorus discharge, or a combination of several of these. Also, in this embodiment, the discharge is set as the product of flow rate and concentration, but it may also be set to concentration or flow rate.

[0065] Nutrients can be broadly classified into nitrogen-based (total nitrogen, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, organic nitrogen) and phosphorus-based (total phosphorus, phosphate phosphorus, organic phosphorus). The discharge rate from water treatment plant 1 and the concentration measured after reaching the controlled water area 8 show a positive correlation for both nitrogen-based and phosphorus-based nutrients, suggesting that nitrogen-based and phosphorus-based nutrients are independent of each other. In this embodiment, the control item was total nitrogen discharge rate and the management items were total nitrogen concentration and nitrogen-based nutrients. However, if the control item were total phosphorus discharge rate, the management items would be phosphorus-based nutrients such as total phosphorus concentration and phosphate concentration.

[0066] On the other hand, phytoplankton concentration and chlorophyll a concentration, which are management parameters related to red tides, increase as a result of the release of both nitrogen-based and phosphorus-based nutrients, which the nutrients use. Therefore, if phytoplankton concentration or chlorophyll a concentration are selected as management parameters, then either nitrogen-based, phosphorus-based, or both of these may be selected as control parameters.

[0067] In this embodiment, the measurement location for the control item (the location where the control item measurement unit 5 is installed) is assumed to be one location, but there may be multiple locations or multiple depths. Since the growth conditions of marine ecosystems differ depending on the environment, the magnitudes of the first and second constraint values ​​may be varied by season, year, region, and depth. Here, Table 9 shows an example of the first constraint value (left) and second constraint value (right) when the control item is total nitrogen concentration. Specifically, Table 9 shows an example of the first constraint value (left) and second constraint value (right) for total nitrogen concentration at times T1, T2, and T3 at locations L, M, and N. When varying the magnitude of the first constraint value and / or second constraint value, the measured value of the control item may be the average of measured values ​​from multiple locations, a predetermined weighted average value, or a statistical method such as the most frequent constraint condition (for example, if the most frequent measured value is below the first constraint value, then it is considered below the first constraint value).

[0068]

[0069] Furthermore, in this embodiment, pre-specified values ​​were used for the first constraint value and the correction value, but these values ​​may also be predicted values ​​based on past performance data, measurement history, or simulation results related to seaweed bed cultivation. In that case, the difference between the first constraint value and the predicted value of the measurement item will arise due to changes in environmental conditions or differences in assumed coefficients, and the nutrient control target value setting unit 3 will correct the nutrient target value of the control item based on this.

[0070] In this embodiment, an inner bay is used as an example for the managed water area 8 (sea area), but any water area to which the effluent from the water treatment plant 1 reaches, such as lakes, bays, inner bays, inland seas, or open seas, is acceptable. In this embodiment, a method for correcting the nutrient discharge rate of one water treatment plant 1 has been described, but the nutrients of the entire watershed, including multiple water treatment plants 1, may also be targeted. In that case, the nutrient correction can be applied to the multiple water treatment plants 1 by distributing according to predetermined distribution ratios, distribution ratios according to treatment efficiency, or predetermined load acceptance order. Furthermore, the distribution to multiple series within each water treatment plant 1 can also be applied according to predetermined distribution ratios, distribution ratios according to treatment efficiency, or predetermined load acceptance order. The management items may be indicators related to organic matter such as BOD and COD, or indicators related to potassium.

[0071] The plant operation support system S according to the present invention has the configuration described above, and can supply an appropriate amount of nutrients to a specific point (for example, point PB) within the controlled water area 8. Furthermore, in a water treatment plant 1 that treats and discharges wastewater containing nutrients, and the discharged water flows into the controlled water area 8 (for example, the sea), the plant operation support system S makes the sea area to which the discharged water reaches clean and rich, and also reduces CO2 ２ This can help promote permanent ownership.

[0072] Although the plant operation support system S according to the present invention has been described in detail above with reference to embodiments, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add a configuration from another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with other configurations.

[0073] 1. Water treatment plant 2. Monitoring and control unit 3. Nutrient control target value setting unit 4. Management item constraint condition setting unit 5. Management item measurement unit 6. Managed water area environmental classification setting unit 7. Nutrient control target value correction unit 8. Managed water area

Claims

1. A plant operation support system comprising: a nutrient control target value setting unit that sets a control target value for nutrients discharged from one or more water treatment plants that discharge nutrients into a controlled water area; a control item constraint condition setting unit that sets constraint conditions for control items in the controlled water area; a control item measurement unit that measures control items in the controlled water area; a controlled water area environmental classification setting unit that sets points for correcting constraint conditions for control items in the controlled water area; and a nutrient control target value correction unit that calculates a correction result for the control target value based on the measured value measured by the control item measurement unit and the constraint conditions set by the control item constraint condition setting unit, wherein the nutrient control target value setting unit corrects the control target value based on the correction result.

2. The plant operation support system according to claim 1, characterized in that the frequency of correction of the control target value by the nutrient control target value correction unit is at most once a month.

3. The plant operation support system according to claim 1, characterized in that the management items in the managed water area have a first constraint value, the points set in the managed water area environmental classification setting unit have a correction value for the first constraint value corresponding to that point, the instruction for the control target value corresponding to that point is set to "maintain" when the measured value exceeds the first constraint value after correction by the correction value, the instruction for the control target value corresponding to that point is set to "increase" when the measured value falls below the first constraint value after correction by the correction value, and the instruction for the control target value is set to "maintain" when the instruction for the control target value at all points is "maintain", and to "increase" otherwise.

4. The plant operation support system according to claim 1, characterized in that the points set in the managed water area environmental classification setting unit are points where structures that serve as a foothold for seaweed bed growth exist and / or within the area of ​​influence thereof.

5. The plant operation support system according to claim 1, characterized in that the control item in the controlled water area has a second constraint value, and when the measured value exceeds the second constraint value, the instruction for the control target value corresponding to that location is set to "reduce", and when "reduce" is included in the instruction for the control target value at all locations, the instruction for the control target value is set to "reduce".

6. The plant operation support system according to claim 1, characterized in that the control item targeted by the nutrient control target value setting unit is one or more of the following: total nitrogen discharge, ammonia nitrogen discharge, nitrate nitrogen discharge, nitrite nitrogen discharge, organic nitrogen discharge, total phosphorus discharge, phosphate phosphorus discharge, and organic phosphorus discharge.

7. The plant operation support system according to claim 1, characterized in that the control items in the controlled water area are one or more of the following: total nitrogen concentration, ammonia nitrogen concentration, nitrate nitrogen concentration, nitrite nitrogen concentration, organic nitrogen concentration, total phosphorus concentration, phosphate phosphorus concentration, and organic phosphorus concentration.

8. The plant operation support system according to claim 7, characterized in that the management items in the management area have a first constraint value and a second constraint value.

9. The plant operation support system according to claim 1, characterized in that the management items in the managed water area are one or more of the following: distribution area of ​​the target ecosystem, absorption coefficient, wet weight per unit area, blue carbon retention rate, and blue carbon amount.

10. The plant operation support system according to claim 9, characterized in that the management items in the management area have a first constraint value.

11. The plant operation support system according to claim 1, characterized in that the management items in the managed water area are one or more of the following: phytoplankton concentration, chlorophyll concentration, chlorophyll a concentration, pheo pigment concentration, fluorescence intensity, plant pigment concentration, seawater color value, reciprocal of transparency, dissolved oxygen saturation, and pH.

12. The plant operation support system according to claim 11, characterized in that the management items in the management area have a second constraint value.

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