JP2006263588A - Water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment apparatus by which power consumption can be reduced while appropriately controlling electrolysis reaction without using high-priced measuring instrument, or the like. <P>SOLUTION: The water treatment apparatus 1 treats nitrogen compounds or phosphorus compounds in water to be treated and is provided with at least a pair of electrodes 22, 23 (electron pair 8) at least a part of which is immersed in the water to be treated, an ORP sensor 13 for detecting oxidation reduction potential (ORP) of the water to be treated and a controlling device 20 for controlling current supply to the electrodes. The controlling device 20 controls current supply to the electrodes 22, 23 based on degree of change of oxidation reduction potential of the water to be treated detected by the ORP sensor 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In particular, the present invention relates to a water treatment apparatus for treating water to be treated containing nitrogen compounds and phosphorus compounds as eutrophication substances.

  Conventionally, it is well known that nitrogen compounds exist as one of the causes of eutrophication of rivers and lakes. In addition, this nitrogen compound is present in a large amount in domestic household wastewater and factory wastewater, but it is difficult to purify and no effective measures can be taken. In general, biological treatment is performed. First, it is performed in two steps, a nitrification step for converting ammonia nitrogen into nitrate nitrogen and a denitrification step for converting nitrate nitrogen into nitrogen gas. Two reaction vessels are required, and the processing time is slow, so that there is a problem that the processing efficiency is lowered.

  In addition, in the biological treatment as described above, a large-capacity anaerobic tank is required to hold nitrifying bacteria and denitrifying bacteria, resulting in a problem that the construction cost increases and the installation area of the apparatus increases. Furthermore, the nitrifying bacteria and denitrifying bacteria are significantly affected by the ambient temperature environment and other components contained in the water to be treated. In particular, in winter, when the temperature is low, the activity of these bacteria is reduced, resulting in a problem that the denitrification action is reduced and the treatment efficiency becomes unstable.

  Therefore, in order to solve the above technical problem, in the conventional electrolysis method of water to be treated, for example, platinum is used for the anode, and current is passed through the water to be treated to produce ammonia, nitrite nitrogen, nitrate nitrogen. To nitrogen gas (see, for example, Patent Document 1).

At this time, when the nitrogen compound of the water to be treated is actually removed in the water treatment apparatus, the treatment of the water to be treated is terminated by performing the electrolytic treatment only for a predetermined time. For this reason, when the concentration of the nitrogen compound in the water to be treated fluctuates, that is, when a nitrogen compound exceeding the assumed concentration is contained, the electrolytic treatment will end during the treatment, which is assumed. When the concentration is less than the required concentration, the electrolysis process is performed wastefully and more power than necessary is consumed.
Japanese Patent Laid-Open No. 54-16844

  Therefore, in order to avoid the termination of the electrolytic treatment in the middle of the treatment as described above and the inconvenience of performing unnecessary electrolytic treatment, the concentration of the nitrogen compound in the water to be treated is detected by a total nitrogen concentration measuring device, etc. Controlling the reaction in the water treatment device based on the output can be mentioned. However, since a sensor such as a total nitrogen concentration measuring device is expensive, there is a problem that the cost of the water treatment device itself increases.

  Therefore, the present invention was made to solve the conventional technical problems, and it is possible to reduce the power consumption while appropriately controlling the electrolytic reaction without using an expensive measuring instrument or the like. A water treatment apparatus is provided.

  The water treatment apparatus of the present invention treats eutrophication substances in the water to be treated, and detects at least a pair of electrodes at least partially immersed in the water to be treated and fluctuations in the quality of the water to be treated. And a control means for controlling energization to the electrode, and the control means controls the energization to the electrode based on the detection of the water quality detection means.

  The water treatment device of the invention of claim 2 treats a nitrogen compound or a phosphorus compound in the water to be treated, and at least a pair of electrodes at least partially immersed in the water to be treated, and oxidation of the water to be treated ORP detection means for detecting the reduction potential and control means for controlling energization to the electrode, and the control means applies to the electrode based on the degree of change in the oxidation-reduction potential of the water to be treated detected by the ORP detection means. It is characterized by controlling energization.

  In the water treatment apparatus according to the third aspect of the invention, the control means determines that the electrolysis is finished when the degree of increase in the oxidation-reduction potential of the water to be treated has decreased and then the degree of change has decreased. It is characterized by cutting off.

  The water treatment device of the invention of claim 4 includes a pH detection means for detecting the pH of the water to be treated, and the control means, when the pH of the water to be treated detected by the pH detection means has changed from a drop to an increase, or Then, after the degree of increase in the oxidation-reduction potential of the water to be treated detected by the ORP detection means increases, when the degree of change decreases, it is determined that the electrolysis is finished, and the power supply to the electrode is cut off.

  The water treatment device of the invention of claim 5 comprises pH detection means for detecting the pH of the water to be treated, and the control means is such that the pH of the water to be treated detected by the pH detection means has changed from falling to rising, and Then, after the degree of increase in the oxidation-reduction potential of the water to be treated detected by the ORP detection means increases, when the degree of change decreases, it is determined that the electrolysis is finished, and the power supply to the electrode is cut off.

  According to the present invention, in a water treatment apparatus for treating a eutrophic substance in water to be treated, at least a pair of electrodes that are at least partially immersed in the water to be treated, and a water quality that detects fluctuations in the quality of the water to be treated. A detection means and a control means for controlling energization to the electrode, and the control means controls the energization to the electrode based on the detection of the water quality detection means, so that the state of the water quality of the water to be treated is treated. Accordingly, it is possible to accurately determine the reaction end time.

  As a result, the treatment in the treated water ends in the middle, resulting in inconvenience that the eutrophication substance remains in the treated water after treatment, and wasteful power is consumed by performing electrolysis more than necessary. Can be avoided.

  According to the invention of claim 2, the nitrogen compound or phosphorus compound in the water to be treated is treated, and at least a pair of electrodes at least partially immersed in the water to be treated, and the redox potential of the water to be treated ORP detecting means for detecting the current and control means for controlling the energization to the electrode, and the control means energizes the electrode based on the degree of change in the oxidation-reduction potential of the water to be treated detected by the ORP detecting means. By controlling, it is possible to accurately determine the reaction end time according to the concentration of nitrogen compound in the water to be treated without using an expensive sensor such as a total nitrogen concentration measuring device.

  As a result, the treatment of the nitrogen compound in the water to be treated ends in the middle, so that the inconvenience that the nitrogen compound remains in the water to be treated after treatment, and unnecessary electric power is generated by performing electrolysis more than necessary. It is possible to avoid the inconvenience consumed.

  According to the third aspect of the present invention, the control means determines that the electrolysis is finished when the degree of increase in the oxidation-reduction potential of the water to be treated decreases and then decreases the degree of change, and cuts off the power supply to the electrode. As a result, it becomes possible to determine the reaction end time more precisely and to save power accurately.

  According to the invention of claim 4, the pH detecting means for detecting the pH of the water to be treated is provided, and the control means is a case where the pH of the water to be treated detected by the pH detecting means has changed from rising to rising, or ORP. After the degree of increase in the oxidation-reduction potential of the water to be detected detected by the detection means increases, it is judged that the electrolysis is finished when the degree of change decreases, and the power supply to the electrode is cut off. This makes it possible to determine the reaction end time and to save power accurately.

  According to the invention of claim 5, the pH detecting means for detecting the pH of the water to be treated is provided, and the control means has the pH of the water to be treated detected by the pH detecting means changed from a drop to an increase, and the ORP. After the degree of increase in the oxidation-reduction potential of the water to be detected detected by the detection means increases, it is judged that the electrolysis is finished when the degree of change decreases, and the power supply to the electrode is cut off. This makes it possible to determine the reaction end time and to save power accurately.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view showing an outline of a water treatment apparatus 1 of the present invention. A water treatment apparatus 1 includes a wastewater tank 2 that contains wastewater discharged from a home or a factory, and a treatment tank 3 that constitutes a treatment chamber 4 that has a wastewater inlet and outlet 5 as untreated water to be treated. And a chloride ion supply tank 16. The treated water once stored in the drainage tank 2 is introduced into the treatment tank 3 through the pump 6 and the inlet. An electrode pair 8 is provided so that at least a part thereof is immersed in the water to be treated in the treatment tank 3, and power supply to the electrode pair 8 is performed by a power source 9 connected to a control device 20 described later. Is called. The treatment tank 3 is provided with a water level sensor 10, and the pump 6 is operated and controlled based on the output of the water level sensor 10 to control the water level in the treatment chamber 4.

  The treatment tank 3 is supplied with a solution containing saline or hypochlorous acid from a chloride ion supply tank 16 via a pump 15 and an inflow port (not shown).

  Further, the water to be treated in the treatment tank 3 is sent to the ORP sensor 13 through the outlet 5, the pump 11, and the electromagnetic on-off valve 12. The ORP sensor 13 detects the oxidation-reduction potential of the water to be treated, and the detected oxidation-reduction potential is output to the control device 20. The treated water that has passed through the ORP sensor 13 is then sent to the pH sensor 14 and sent again to the treatment tank 3. The pH sensor 14 detects the pH of the water to be treated, and the detected pH value is output to the control device 20. The electromagnetic on-off valve 12 is a three-way valve, and the water to be treated sent from the treatment tank 3 via the outlet 5 is controlled to the outside or the next treatment facility by being controlled by the control device 20. It can be discharged.

  FIG. 2 is a control block diagram of the water treatment apparatus 1 in the present embodiment. The control device 20 provided in the water treatment device 1 is configured by a general-purpose microcomputer, and controls the operation of the entire water treatment device 1. A water level sensor 10, an ORP sensor 13, and a pH sensor 14 are connected to the input side of the control device 20. On the output side, a power source 9 for supplying power to the electrode pair 8, pumps 6, 11, 15 and an electromagnetic valve 12 are connected and controlled based on the detection output of each sensor.

With the above configuration, water to be treated containing nitrogen compounds such as nitrate ions and nitrite ions is stored in the treatment tank 3, the power supply 9 is turned on by the control device 20, and a potential is applied to the electrode pair 8. The electrode pair 8 includes an electrode 22 constituting an anode and an electrode 23 constituting a cathode as shown in FIG. Moreover, in the to-be-processed water in the processing tank 3, the balance of the following reaction A and B is materialized by adding salt solution (sodium chloride).
Reaction A H ₂ O → H ⁺ + OH ⁻
Reaction B NaCl → Na ⁺ + Cl ⁻

Further, in the vicinity of the electrode 22 constituting the anode, as shown in reactions C to E, oxygen gas is generated by electrolysis of water, chloride ions become chlorine gas, and a part of the chlorine gas is hydrated next. Produces chlorous acid.
Reaction C 2 H ₂ O → O ₂ ↑ + 4H ⁺ + 4e ⁻
Reaction D 2Cl ⁻ → Cl ₂ ↑ + 2e ⁻
Reaction E Cl ₂ + H ₂ O → H ⁺ + Cl ⁻ + HClO

In the vicinity of the electrode 23 constituting the cathode, as shown in reactions F and G, hydrogen gas is generated by electrolysis of water, and sodium ions generated at the electrode 22 constituting the anode react with hydroxide ions. This produces sodium hydroxide. Thereby, in the vicinity of the electrode 23 constituting the cathode, sodium hydroxide is generated and the water to be treated becomes alkaline.
Reaction F 2H ₂ O + 2e ⁻ → H ₂ ↑ + 2OH ⁻
Reaction G Na ⁺ + OH ⁻ → NaOH

Further, nitrate ions in the for-treatment water stored in the treatment tank are reduced to nitrite ions on the surface of the electrode 23 constituting the cathode (reaction H). Further, nitrite ions are reduced to ammonia (ammonium ions) by supplying electrons on the electrode 23 side constituting the cathode (reaction I).
Reaction H NO ₃ ⁻ + H ₂ O + 2e ⁻ → NO ₂ ⁻ + 2OH ⁻
Reaction I NO ₂ ⁻ + 5H ₂ O + 6e ⁻ → NH ₃ (aq) + 7OH ⁻

The hypochlorous acid produced as described above reacts with ammonia (ammonium ions) produced in the water to be treated in the reaction I, and after undergoing a plurality of chemical changes, is converted into nitrogen gas (reaction J ).
Reaction J NH ₃ + HClO → NH ₂ Cl + H ₂ O
NH ₂ Cl + HClO → NHCl ₂ + H ₂ O
NH ₂ Cl + NHCl ₂ → N ₂ ↑ + 3HCl

  This makes it possible to efficiently treat nitrate ions, nitrite ions, ammonia, and the like as nitrogen compounds in the water to be treated in the same treatment tank 3. Therefore, nitrogen compounds can be efficiently removed from the water to be treated containing nitrogen compounds discharged from ordinary households and factories, and the nitrogen compound treatment capacity is improved.

In the series of electrolytic reactions as described above, if chloride ions exist in the treatment tank 3 at an early stage, nitrite ions generated by reducing nitrate ions at the electrode 23 constituting the cathode constitute the anode. When moving to the electrode 22 side, an oxidation reaction occurs at the electrode 22 constituting the anode, and nitrite ions are oxidized to nitrate ions (reaction K). That is, the reverse reaction of reaction H occurs.
Reaction K NO ₂ ⁻ + H ₂ O → NO ₃ ⁻ + 2H ⁺ + 2e ⁻

  Therefore, in this example, the compound containing sodium chloride ions (sodium chloride) is added to the treatment tank 3 after a predetermined time has elapsed since the start of electrolysis. In addition, delaying the addition of the compound containing chloride ions in this way is easy to oxidize to hypochlorous acid such as chromium, lead, molybdenum, vanadium, etc., particularly in the water to be treated stored in the treatment tank 3. This is effective when an element that forms an oxide is contained. Oxidation of such elements with hypochlorous acid has a much faster reaction rate than the oxidation of ammonia in reaction J with hypochlorous acid, so that the nitrite ions generated in reaction H are the reaction H to J. This is because it is oxidized to nitrate ions by the reverse reaction of reaction H before being consumed in reaction I, which is the rate-limiting reaction. Further, since the oxide of such an element is reduced on the electrode 23 constituting the cathode, oxidation / reduction of the element occurs cyclically in the treatment tank 3, and the element in the treated water is in a very small amount. This is because hypochlorous acid is consumed by the element.

  Next, with reference to FIG. 4 thru | or FIG. 6, the process completion judgment of the nitrogen compound in the said to-be-processed water is demonstrated. In the treatment tank 3, the nitrate ions in the water to be treated are reduced to nitrogen gas sequentially through nitrite ions and ammonia in accordance with the chemical reactions of the above reactions A to K. In this case, as the treatment of the nitrogen compound in the water to be treated and finally ammonia proceeds, the oxidation-reduction potential (ORP) due to the amount of hypochlorous acid accumulated in the water to be treated changes. Further, during the treatment reaction as described above, the pH changes due to the decrease in the amount of ammonia accompanying the treatment and the production of sodium hydroxide. Thereby, in a present Example, the progress degree of the removal reaction of a nitrogen compound is estimated based on ORP and pH of the to-be-processed water in the processing tank 3, and the electric power supply to the electrode pair 8 is performed based on the said estimation. Control.

  FIG. 4 shows an example of the relationship between the electrolysis time in the treatment tank 3 and the ORP and pH of the water to be treated when nitrogen compounds (nitrate ions and nitrite ions) are removed by the electrolytic reaction of the water treatment apparatus 1.

FIG. 4 shows an example in which the removal of ammonia as nitrogen oxides in the treatment tank 3 is completed when the electrolysis time is about 40 minutes (2400 seconds). 4, the ORP of the water to be treated in the treatment tank 3 increases as the treatment time becomes longer, and the degree of change in the ORP increases after the ORP once drops. Decrease. This is because ORP rises due to accumulation of hypochlorous acid produced in the water to be treated and chloroamine (NH ₂ Cl) produced by the reaction between ammonia and hypochlorous acid (reaction J). Is due to. Further, when the treatment of the nitrogen compound is completed or approaches the end, the ORP overshoots, and then the degree of change in the ORP is reduced by eliminating the chloroamine or ammonia that reacts with hypochlorous acid.

  Further, the pH of the water to be treated in the treatment tank 3 decreases once as the treatment time becomes longer, and rises after taking a minimum value. The decrease in pH until the minimum value is reached is based on the removal of ammonia nitrogen as nitrogen as shown in Reaction J. Then, after the removal of ammonia nitrogen is completed, the increase in pH after taking the minimum value is caused by electrolytic reaction, followed by strongly alkaline sodium hydroxide according to reaction G, and weakly acidic following according to reaction E. This is based on the production of chlorous acid.

  In this embodiment, the degree of progress of the ammonia nitrogen removal reaction is estimated from the degree of change in ORP of the water to be treated in the treatment tank 3 and the degree of pH reduction, and the electrode pair 8 is based on the degree of progress. The current value flowing between the electrode 22 constituting the anode and the electrode 23 constituting the cathode is controlled, and after the degree of increase of the ORP of the water to be treated in the treatment tank 3 is increased, it is once lowered, Thereafter, when the degree of change is reduced and the pH of the water to be treated in the treatment tank 3 takes a minimum value, it is estimated that the removal of ammonia nitrogen has been completed, and the power supplied to the electrode pair 8 To control.

  The control contents according to the present embodiment will be described below with reference to the flowcharts of FIGS. First, the control based on the change of the ORP according to FIG. 5 will be described. The control apparatus 20 measures ORP of the to-be-processed water in the processing tank 3 by ORP sensor 13 by S1, and memorize | stores the measured ORP value as ORPa. Next, in S2, the control device 20 measures the ORP value 5 seconds after the ORP is measured (S1 or S2) last time (after a predetermined time has elapsed), and stores the measured ORP value as ORPb. To do.

  In S3, the control device 20 calculates ORPc, which is the difference between ORPa and ORPb (ORPb−ORPa), and then stores the value stored as ORPb so far as ORPa. Here, the calculated ORPc is a change value of the ORP in the processing tank 3 for 5 seconds.

  Next, in S4, the control device 20 determines whether or not the value of the ORPc is +5 mV or more. If it is determined that the value is less than +5 mV, the control device 20 returns to S2. On the other hand, if it is determined that it is +5 mV or more, the process proceeds to S5, the electrolysis by the electrode pair 8 is terminated, and the process is terminated. Thereby, when the rate of change of ORP per unit time (5 seconds) exceeds a predetermined value (+5 mV), it can be determined that the treatment reaction of the water to be treated in the treatment tank 3 has been completed.

  Therefore, by determining the progress of the electrolytic reaction of the nitrogen compound in the water to be treated in the treatment tank 3 due to the change in the ORP, the nitrogen compound in the water to be treated can be treated accurately and necessary. Inconveniences that consume power can be avoided.

  On the other hand, the control based on the change in pH according to FIG. 6 will be described. The control device 20 measures the pH of the water to be treated in the treatment tank 3 with the pH sensor 14 in S10, and stores the measured pH value as pHa. Next, in S11, the control device 20 measures the pH value 5 seconds after the previous pH measurement (in S1 or S2) (after a predetermined time has elapsed), and stores the measured pH value as pHb. To do.

  In S12, the control device 20 calculates pHc, which is the difference between pHa and pHb (pHa−pHb), and then stores the value stored as pHa until then as pHb. Here, the calculated pHc is a change value of pH in the treatment tank 3 for 5 seconds.

  Next, in S13, the control device 20 determines whether or not the value of pHc is 0.01 or less. If it is determined that the value is 0.01 or less, the control device 20 proceeds to S14 and exceeds 0.01. If it is determined, the process proceeds to S17.

  In S14, after starting the internal timer, the control device 20 determines whether or not 30 seconds have elapsed since the start of the internal timer in S15. If it is determined that it has elapsed, the process proceeds to S16. In S16, the control device 20 ends the electrolysis by the electrode pair 8 and then ends the process.

  On the other hand, in S17, the control device 20 determines whether or not pHc is 0.1 or less. If it is determined that the pHc is 0.1 or less, the control device 20 proceeds to S18 and determines that it exceeds 0.1. If so, the process proceeds to S19. Further, in S19, the control device 20 determines whether or not pHc is 0.5 or less. If it is determined that the pHc is 0.5 or less, the process proceeds to S20 and exceeds 0.5. If determined, the process proceeds to S21.

  Then, the control device 20 sets the current value flowing between the electrode 22 constituting the anode and the electrode 23 constituting the cathode to 10A in S18, 20A in S20, 30A in S21, and then returns to S11. .

  By performing this treatment, the rate of increase in the pH of the water to be treated per unit time (5 seconds) in the treatment tank 3 is calculated, and the greater the rate of increase, the lower the degree of nitrogen compound removal in the water to be treated. As shown, the value of the current flowing between the electrodes of the electrode pair 8 is increased. And when the said raise value is below a predetermined value (0.01), it electrolyzes only for predetermined time (30 second), and complete | finishes electrolysis.

  In this example, both the rate of change of ORP and the rate of increase in pH are adopted as materials for determining the reaction end timing, and when the determination is made to end the electrolysis process, whichever comes first, control is performed. The apparatus 20 shall end the electrolytic treatment.

  This makes it possible to determine the reaction end time according to the concentration of the nitrogen compound in the water to be treated that is actually the object of treatment without using an expensive sensor such as a total nitrogen concentration meter. Therefore, avoiding the inconvenience of nitrogen compounds remaining in the treated water after treatment and the inconvenience of wasted power consumption by performing electrolysis more than necessary. Will be able to.

  In this example, as described above, both the rate of change in ORP and the rate of increase in pH are adopted as materials for determining the reaction end time, so that it is possible to accurately determine the end of the treatment of the nitrogen compound. Thus, it is possible to further avoid the disadvantage that the nitrogen compound remains in the treated water after treatment and the disadvantage that unnecessary power is consumed by performing electrolysis more than necessary.

  In this example, both the rate of change of ORP and the rate of increase of pH are adopted, but the reaction end time may be judged from only the rate of change of ORP or only the rate of increase of pH. To do.

  In particular, even when the reaction end time is determined only from the change rate of the ORP, the change in the ORP is, as is apparent from FIG. Since it changes significantly, a more accurate judgment can be made.

  In addition, although the water treatment apparatus 1 in a present Example demonstrated as what removes the nitrogen compound in the waste liquid which flowed out from a household or a factory, in addition to this, a nitrogen compound is removed from rain water containing a nitrogen compound etc. However, it can also be used for watering plants.

  In the said Example, although it described that the rate of change of ORP or pH was used about judgment of the reaction end time in the electrolysis of the to-be-processed water containing a nitrogen compound, it contains not only this but a phosphorus compound. The rate of change of ORP may be used for determining the reaction end time in the electrolytic treatment of water to be treated. Hereinafter, it describes about the case of the to-be-processed water containing the said phosphorus compound.

  That is, water to be treated containing a phosphorus compound such as phosphate ions is stored in the treatment tank 3, the power supply 9 is turned on by the control device 20, and a potential is applied to the electrode pair 8. The electrode pair 8 includes an electrode 30 constituting an anode and an electrode 31 constituting a cathode as shown in FIG. It is assumed that at least the electrode 30 constituting the anode is made of an iron material.

Therefore, when electricity is applied between the electrodes 30 and 31, iron (II) ions are eluted from the electrode 30 constituting the anode into the water to be treated, and at the electrode 31 constituting the cathode, water is electrolyzed and hydrogen gas is generated. appear. The eluted iron (II) ions are oxidized to iron (III) ions in the water to be treated (reaction L). The generated iron (III) ions coagulate and precipitate with phosphate ions in the water to be treated by a dephosphorylation reaction as shown in reaction M to produce iron phosphate that is sparingly soluble in water.
Reaction L Fe → Fe ²⁺ + 2e ⁻
2H ₂ O + 2e ⁻ → H ₂ ↑ + 2OH ⁻
Fe ²⁺ (+ O ₂ ) → Fe ³⁺
Reaction M Fe ³⁺ + PO ₄ ^3- → FePO ₄ ↓

  Thereby, the phosphate ion as a phosphorus compound contained in to-be-treated water can be subjected to precipitation treatment as iron phosphate.

  As described above, in the treatment tank 3, according to the chemical reaction of the reaction L and the reaction M, phosphate ions in the water to be treated are treated as iron phosphate that is hardly soluble in water. In this case, when the treatment of phosphate ions in the water to be treated proceeds, the oxidation-reduction potential (ORP) decreases from the potential value before the electrolytic treatment. Thereby, in this Example, the progress degree of the removal reaction of a phosphorus compound is estimated based on ORP of the to-be-processed water in the processing tank 3, and the electric power supply to the electrode pair 8 is controlled based on the said estimation. .

  FIG. 8 shows an example of the relationship between the amount of iron dissolved in the treatment tank 3 and the ORP of the water to be treated when the phosphorus compound (phosphate ion) is removed by the electrolytic reaction of the water treatment apparatus 1.

  FIG. 8 shows an example in which removal of phosphate ions as phosphides in the treatment tank 3 is completed when the amount of dissolved iron is about 2.7 mmol / L. Then, as will be considered from FIG. 8, the ORP of the water to be treated in the treatment tank 3 is about 45 mV at the time when the phosphate ions are almost treated, that is, the iron dissolution amount is about 1. At about 8 mmol / L, it drops to about −250 mV, and when the phosphate ions are almost completely processed, that is, when the amount of dissolved iron is about 2.7 mmol / L, the water to be treated in the treatment tank 3 is treated. The ORP is reduced to about -300 mV.

  Thereby, also in the electrolytic treatment of the phosphorus compound, it is possible to determine the reaction end time of the phosphorus compound based on the degree of change in the ORP of the water to be treated.

  Therefore, it is possible to accurately treat the phosphorus compound according to the concentration of the phosphorus compound in the water to be treated without dissolving iron more than necessary. Thereby, useless melting of iron can be avoided and the life of the iron electrode can be extended.

  In each of the above embodiments, in the treatment of water to be treated containing nitrogen compounds, phosphorus compounds, etc., using an ORP sensor or pH sensor that detects the oxidation-reduction potential, nitrogen compounds, phosphorus compounds, etc. in the water to be treated The progress of the treatment of the treatment object is judged and the reaction end time is judged, but in addition to this, the treated water containing eutrophication substances including biological substances as treated water As a means to detect the water quality in the water to be treated, it is possible to determine the progress of treatment of the treatment object by using dissolved oxygen concentration detection means, conductivity detection means, turbidity detection means, etc. Thus, the reaction end time may be determined. That is, since the dissolved oxygen concentration of the water to be treated changes according to the progress of the treatment of the eutrophication substance in the water to be treated, the reaction end time of the treatment can be determined based on this. Since the conductivity of the water to be treated changes according to the progress of the treatment of the eutrophication substance in the water to be treated, it is possible to determine the reaction end time of the treatment based on this. Since the turbidity of the water to be treated changes according to the progress of the treatment of the eutrophication substance in the water to be treated, the reaction end time of the treatment can be determined based on this.

It is explanatory drawing which shows the outline | summary of a water treatment apparatus. It is an electrical block diagram of the control apparatus of a water treatment apparatus. It is a figure which shows typically the chemical reaction considered to occur when it supplies with electricity to an electrode pair in the processing tank of FIG. It is a figure which shows an example of the relationship between the electrolysis time in the processing tank at the time of a nitrogen compound being removed by the electrolytic reaction of the water treatment apparatus of FIG. It is a flowchart figure of the control content of the control apparatus in the water treatment apparatus in FIG. It is a flowchart figure of the control content of the control apparatus in the water treatment apparatus in FIG. It is a figure which shows typically the chemical reaction considered to occur when it supplies with electricity to an electrode pair in the processing tank in another Example. It is a figure which shows an example of the relationship of the amount of iron melt | dissolution in the processing tank when the phosphorus compound is removed by the electrolytic reaction of the water treatment apparatus in the Example of FIG. 7, and ORP of to-be-processed water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water treatment apparatus 2 Drain tank 3 Processing tank 4 Processing chamber 5 Outlet 6 Pump 8 Electrode pair 9 Power supply 10 Water level sensor 11 Pump 12 Electromagnetic switching valve 13 ORP sensor 14 pH sensor 15 Pump 16 Chloride ion supply tank 20 Control device 22 23, 30, 31 electrodes

Claims (5)

A water treatment device for treating eutrophication substances in water to be treated,
At least a pair of electrodes at least partially immersed in the water to be treated;
Water quality detection means for detecting fluctuations in the quality of the treated water;
Control means for controlling energization to the electrode,
The control means controls the energization to the electrodes based on the detection of the water quality detection means. A water treatment device for treating nitrogen compounds or phosphorus compounds in water to be treated,
At least a pair of electrodes at least partially immersed in the water to be treated;
ORP detection means for detecting the oxidation-reduction potential of the treated water;
Control means for controlling energization to the electrode,
The control means controls the energization to the electrodes based on the degree of change in the oxidation-reduction potential of the water to be treated detected by the ORP detection means.   The control means determines that the electrolysis is terminated when the degree of increase in the oxidation-reduction potential of the water to be treated decreases and then decreases the degree of change, and cuts off the power supply to the electrode. Item 2. A water treatment apparatus according to item 2. PH detecting means for detecting the pH of the water to be treated is provided,
The control means increases when the pH of the treated water detected by the pH detecting means changes from a drop to an increase, or the degree of increase in the redox potential of the treated water detected by the ORP detecting means increases. Then, when the degree of change decreases, it is determined that the electrolysis is finished, and the current supply to the electrode is cut off. PH detecting means for detecting the pH of the water to be treated is provided,
In the control means, the pH of the water to be treated detected by the pH detection means has changed from a drop to an increase, and the degree of increase in the oxidation-reduction potential of the water to be treated detected by the ORP detection means is increased. Then, when the degree of change decreases, it is determined that the electrolysis is finished, and the current supply to the electrode is cut off.

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