JP2002263668A - Advanced water purification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an advanced water purification method which takes advantage of the merits of BAC treatment and GAC treatment by performing flow change of both of the treatments in correspondence to the quality of raw water. SOLUTION: The advanced water cleaning method of making highly cleaned water by a water quality sensor for measuring the index of the organic matter of the raw water, an ozone treating process step for subjecting the raw water to ozone treatment and a biologically active carbon treating process step or granular active carbon treating process step for the raw water subjected to the ozone treatment is provided with a system switching controller for switching the biologically active carbon treating process step and the granular active carbon treating process step according to the water quality load by the measured value of the water quality sensor and therefore the organic matter remaining in the active carbon treating water can be regulated to a specified value or below and the amount of the trihalomethane formed by post chlorine treatment is suppressed. Since the biological assimilation organic matter remaining in the clean water is suppressed to a low concentration, the clean water having the stable water quality can be supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly purified water treatment method for converting raw water into highly purified water, and more particularly to a highly purified water treatment method for obtaining highly purified water by appropriately switching control between a biological activated carbon treatment step and a granular activated carbon treatment step.

[0002]

2. Description of the Related Art Ozone treatment, granular activated carbon (GAC) treatment, and biological activated carbon (BAC) have recently been developed in response to the deterioration of raw water quality and interest in "safer and more delicious water".
Advanced water treatment combined with treatment has begun to be introduced. Raw water to which such advanced water purification treatment is introduced / applied is generally river water or lake (dam) water that has been contaminated (eutrophication).

[0003] The purpose of ozone treatment for high-purity water purification is to decompose (remove) odor components, reduce trihalomethane precursors, remove iron and manganese that have been oxidized and removed by pre-chlorination, and remove hard-to-decompose organic substances. The modification to the easily decomposable organic substance improves the removal rate of the organic substance including the trihalomethane precursor in the BAC treatment.

[0004] The purpose of the activated carbon treatment is to adsorb and remove organic substances including trihalomethane precursors and odor components, and to remove organic oxides such as aldehydes and ketones that may be generated by the ozone treatment. The installation is required after ozone treatment under the guidance of the government.

The GAC treatment and the BAC treatment each have advantages and disadvantages. When used as the BAC treatment, microorganisms (bacteria) adhering to the surface of the activated carbon maintain the performance of removing organic substances within a range of 20 to 40%, and the activated carbon is prevented. Although the life is obtained for about 2 to 3 years, the organic matter removal rate is inferior to that of the GAC treatment. However, nitric acid bacteria and nitrite bacteria that nitrify ammonia nitrogen on the surface of activated carbon also adhere and grow, so that a low concentration of ammonia nitrogen can be removed to some extent. In addition, micro-animals that prey on microorganisms (e.g., metazoans and crustaceans) may breed,
In order to control the propagation and leakage from the C treatment, appropriate backwash control of the activated carbon layer is indispensable.

On the other hand, in the GAC treatment, the activated carbon life is about half a year when there is residual chlorine, but the organic substance removal rate is 70 to 90% or more until immediately before the breakthrough, and the organic substance adsorption performance is higher than that of the BAC treatment. Are better. There is no concern about breeding or leakage of small animals.

FIG. 6 is a typical process flow chart of a conventional advanced water purification treatment combining an ozone treatment and a BAC treatment. The landing well 1 is installed to smooth the fluctuation of the raw water level and water quantity and to grasp the raw water quantity, and various sensors such as an oil film sensor and a toxic substance detection sensor are installed to monitor the quality of the raw water. Sometimes.

The coagulation / precipitation treatment step 2 involves flocculating and suspending suspended and dissolved substances in raw water by adding a coagulant (polyaluminum chloride, sulfate band, etc.). The sand filtration step 3 captures and filters the flocs that could not be settled in the coagulation / precipitation step 2. The ozone treatment step 4 and the BAC treatment step 5 are used for the above-described purposes, respectively, and remove organic substances, iron, manganese, and the like.

In the post-chlorination step 6, a chlorine agent for disinfection (sodium hypochlorite, liquid chlorine, etc.) is injected and BAC
The treated water and the chlorinating agent are brought into contact with and mixed with each other, the ripening of the reaction between the BAC treated water and the chlorinating agent in the distribution reservoir 7 and the adjustment of the residual chlorine concentration are performed, and the resulting water is supplied as purified water. When the concentration of ammonia nitrogen in the raw water is high, a treatment step (not shown) for biological contact oxidation may be provided between the landing well 1 and the coagulation / precipitation treatment step 2.

[0010]

Since the BAC treatment step 5 utilizes the action of adsorbing activated carbon and the action of metabolism of microorganisms, it is easily affected by the quality and temperature of the water to be treated. Organic matter (TOC) removal rate is 20
It is limited to about 40%. In addition, when the water temperature dropped, such as in winter, the ammonia nitrogen removal rate also dropped. In addition, the TOC removal rate in the BAC treatment step 5 may be reduced due to the presence of any substance (toxic substance) that inhibits biological activity, but this is a rare event. Further, although it differs depending on the quality of raw water and water purification treatment conditions, the removal rates of organic substances in the coagulation / precipitation treatment step 2, the BAC treatment step 5, and the like are grasped as empirical values.

Here, the TOC concentration in the raw water is set to Tr, and the TOC removal rate in the sand filtration step 3 for the raw water (normally 30 to 4).
If the TOC removal rate of the BAC treatment step 5 relative to the ozone treatment step 4 is Rb (the ozone treatment step 4 has almost no TOC removal function), the TOC concentration of the BAC treated water (post-chlorination treatment) TOC concentration before
Tp is assumed by the following equation (1.1).

Tp = Tr * (1-Rs) * (1-Rb) (1.1) The TOC concentration Tr of the raw water is set to 5 mg / when the water quality is deteriorated.
L, the TOC concentration removal rate Rs in the sand filtration step 3 was 30%, and the TOC removal rate Rb in the BAC treatment step 5 with respect to the ozone treatment step 4 was 2% when the biological activity was reduced.
Assuming 0%, substituting each value into the above equation (1.1),
The TOC concentration Tp of the BAC treated water is calculated by the following equation (1.2).

Tp = 5 * (1-0.3) * (1-0.2) = 2.8 mg / L (1.2) The value of Tp is the TOC of the river water level in the middle basin.
It corresponds to a concentration (2-3 mg / L). Usually, most of the TOC component contained in river water is composed of humic acid, fulvic acid, and the like, and can be a precursor of trihalomethane (trihalomethane generating ability).

Here, the production amount of trihalomethane per 1 mg / L of TOC concentration was calculated as Rthm (μg-THMFP /
mg-TOC), from equation (1.1), the amount of trihalomethane Tthm (μ
g / L) is assumed as in the following equation (1.3).

Tthm = Tr * (1-Rs) * (1-Rb) * Rthm (1.3) Water temperature, pH, chlorine injection rate (residual chlorine concentration), residence time (contact time with chlorine), coexistence Although it varies depending on the conditions of substances, etc., TOC which generally contains humic acid or fulvic acid as a main component
It is known that about 20 to 40 μg / L of trihalomethane is generated from a concentration of 1 mg / L,
Rthm = 40 μg− in equations (1.2) and (1.3).
By substituting THM FP / mg-TOC, the amount of trihalomethane generated from raw water having a TOC concentration Tr = 5 mg / L is assumed as in the following equation (1.4).

Tthm = 5 * (1-0.3) * (1-0.2) [mg / L] * 40 [μg-THMFP / mg-TOC] = 112 μg / L (1.4) As described above, when the water quality deteriorates, it is very likely that the total trihalomethane will exceed the standard value of tap water quality of 100 μg / L (0.1 mg / L) even in the advanced water purification treatment using ozone and biological activated carbon treatment. Was.

Further, when the water quality deteriorates at the time of drought, or when the biological activity decreases at the time of winter, the organic matter concentration (TOC) remaining in the BAC treated water becomes relatively high, and the ammonia nitrogen May not be completely removed, so that the chlorine injection rate in the subsequent post-chlorination step 6 may increase.

If ammonia nitrogen remains in the BAC-treated water, the ammonia nitrogen is removed by the pre-discontinuous point chlorination, so that chlorine consumed in addition to disinfection and sterilization (maintaining residual chlorine concentration) is not used. The amount increased and chlorine also reacted with organic substances, causing an increase in chlorine injection rate.

The theoretical amount of reaction between chlorine and ammoniacal nitrogen is 1: 7.6, but it is also consumed by other coexisting substances. Therefore, the actual chlorine injection rate is 1% of the amount of ammoniacal nitrogen.
In most cases, it is required to be 0 times or more. As a result,
The contact amount (reaction amount) between the remaining organic matter and the chlorine for disinfection increased, and the generation amount of harmful trihalomethane and organic chlorine compounds increased.

On the other hand, in the ozone treatment, when the water quality is deteriorated at the time of drought or the like, the concentration of inorganic substances such as iron and manganese tends to increase in addition to the concentration of organic substances. The amount of ozone for oxidizing and removing manganese and the like also increased, causing an increase in the ozone injection rate.

When the number of substances to be removed in the ozone treatment step 4 increases, the competitive reaction of coexisting substances becomes complicated,
Optimal ozone injection control becomes difficult, and the ozone injection rate may be excessive or insufficient.

The ozone injection control has few problems when the quality of the raw water (water to be treated) is stable and relatively good, but when the quality of the raw water fluctuates or deteriorates, the ozone inflow rate becomes too short or too high.
There are the following problems.

When the ozone injection rate is insufficient When the organic substance concentration is low even when the ozone injection rate is insufficient,
In the subsequent BAC treatment step 5, removal and reduction of odor components and trihalomethane precursors are possible to some extent. However, since the biodegradability of the organic matter is not so improved, the load on the BAC treatment step 5 increases, and if an odor component or an organic matter (trihalomethane precursor) exceeding the permissible amount of the BAC treatment flows, the treatment cannot be completed. May remain in the clean water.

Further, iron ions (Fe ²⁺ , Fe ³⁺ ) and manganese ions (Mn ²⁺ ) which have conventionally been removed by discontinuous point pre-chlorination are oxidized by ozone treatment and BA
If the ozone injection rate is insufficient, iron ions and manganese ions are not completely oxidized and flow out into the BAC-treated water. It may be oxidized to (MnO ₂ ) and develop a chromaticity of about 230 to 300 times the manganese concentration.

When the Ozone Injection Rate is Appropriate When the ozone injection rate is properly performed, the component decomposition of organic substances is improved to some extent, and the load on the BAC treatment is somewhat reduced as compared with the above case. However, when the amount of the organic substance in the raw water increases, such as when the concentration of the organic substance exceeds the allowable amount of the BAC treatment, the odor component and the organic substance may remain in the purified water in the same manner as described above.

On the other hand, iron and manganese are oxidized and precipitated as hydroxide and manganese as insoluble manganese dioxide when the injection rate of ozone is properly performed in the ozone treatment step 4; Captured in process step 5.

The divalent manganese ion is represented by the following (2.1)
As shown in the equations (2.2) and (2.2), 4
It is oxidized to a valence and becomes insoluble manganese dioxide. Mn ⁺² + O ₃ + H ₂ O → Mn ⁺⁴ + O ₂ COH ⁻ (2.1) Mn ⁺⁴ + 4OH ⁻ → MnO ₂ ↓ + H ₂ O (2.2) Next, the oxidation reaction of iron is described below (2. Equations 3) and (2.4) are shown. Divalent iron ions undergo ozone oxidation, become trivalent, and hydrate, aggregate, and precipitate. Fe ⁺² + O ₃ + H ₂ O → Fe ⁺³ + O ₂ +2 (OH ⁻ ) (2.3) Fe ⁺³ + 3H ₂ O → Fe (OH) ₃ ↓ + 3H ⁺ (2.4) However, organic substances and iron. Since manganese mutually affects the ozone injection rate, it may be difficult to control the ozone injection rate to an appropriate amount when water quality deteriorates.

Excessive Ozone Injection Rate When the ozone injection rate is excessive, the dissolved ozone concentration of the ozonated water increases, which may damage BAC microorganisms and accelerate the consumption of activated carbon. In this case, BA
As the processing function of C deteriorates, the odor components and organic substances may not be completely removed and may flow out into the purified water when the allowable amount of BAC processing is exceeded, such as an increase in the concentration of organic substances in raw water. There is.

Further, manganese ions are once oxidized to insoluble manganese dioxide by ozone treatment. As shown in the following formula (2.5), soluble manganese permanganate ions are dissolved by excessive oxidation of ozone. (MnO ₄ ⁻ ) and colored pink.

[0030] The permanganate ion is reduced by the BAC treatment and returns to manganese dioxide. However, it is not the original treatment function of the BAC, and the permanganate ion itself is a strong oxidizing agent, damaging the microorganisms of the BAC, and further reducing the BAC treatment. The function was sometimes reduced.

When iron and manganese remain in the purified water,
Efficient removal is necessary because it causes off-flavors such as gold odor, red water, and black water, and coloring problems. In the water quality standard, iron is set to 0.3 mg / L or less, and manganese is set to 0.05 mg / L or less, respectively. In addition, in the comfortable water quality item for the purpose of further improving the water quality, manganese is 0.0
The target value is 1 mg / L or less.

Further, the generated amount is uneconomic due to the excessive ozone injection rate, and the load on the ozone decomposition catalyst and the activated carbon in the waste ozone treatment device (not shown) increases due to the increase in the amount of waste ozone. The running cost for ozone treatment may increase.

Further, the organic matter remaining in the purified water that has not been completely removed in the BAC treatment step 5 has a disinfection / sterilizing effect while residual chlorine is present, so that there is no danger that microorganisms such as bacteria will propagate. If the water stays in a high temperature environment such as summer or in a long-term pipe, residual chlorine is lost, and the organic matter remaining in the purified water is bio-utilizable organic matter (AOC), which is a nutrient source for microorganisms. There was a concern that bacteria and the like would propagate in the receiving tank.

The present invention has been made in view of the above circumstances, and provides an advanced water purification treatment method in which the flow of BAC treatment and GAC treatment is changed according to the quality of raw water, and the advantages of each treatment are utilized. The purpose is to do so.

Further, in the present invention, from the viewpoint of preventing excessive injection of ozone when water quality is deteriorated, the oxidation treatment of iron and manganese is performed by medium chlorine treatment during GAC treatment, and ammonia nitrogen cannot be removed by GAC treatment. The purpose of this study is to provide an advanced water purification method for a wide range of raw water quality by installing a honeycomb tube (filler) at the landing well to give the biological oxidation treatment effect and removing ammonia nitrogen. Is what you do.

[0036]

According to a first aspect of the present invention, there is provided an advanced water purification method comprising: a water quality sensor for measuring an index of an organic matter in raw water; and an ozone treatment step for ozonating the raw water. In an advanced water purification method for converting ozone-treated raw water into a highly purified water through a biological activated carbon treatment step or a granular activated carbon treatment step, the biological activated carbon treatment step and the granular activated carbon treatment according to a water quality load measured by the water quality sensor. A system switching control device that switches between the processes is provided. According to the first aspect, the amount of organic substances remaining in the activated carbon treated water can be reduced to a certain value or less, and the amount of trihalomethane generated by the post-chlorination can be suppressed. Furthermore, since the bio-assimilating organic matter (AOC) remaining in the purified water is suppressed to a lower concentration than in the conventional treatment, there is no concern about breeding of bacteria and the like in the stagnant distribution pipe, and it is possible to supply purified water with stable water quality. .

[0037] According to a second aspect of the present invention, there is provided an advanced water purification method, wherein a water quality sensor for measuring an index of organic matter in the raw water, an ozone processing step for ozonizing the raw water, a biological activated carbon processing step or a granular activated carbon processing for the ozonized raw water. In an advanced water purification method for performing advanced water purification through a treatment process, the system includes a system switching control device that switches between a biological activated carbon treatment process and a granular activated carbon treatment process according to a water quality load based on a measured value of the water quality sensor, and is switched to the granular activated carbon treatment. During this period, the medium chlorine is supplied from the medium chlorine injection device to the ozone treatment step, and the dissolved oxygen is supplied to the biological activated carbon layer.

According to the second aspect, in addition to the effect of the first aspect, a decrease in the biological activity of the BAC layer can be minimized, and the state almost the same as before the suspension can be maintained during the suspension of the BAC treatment. Also,
With the combined use of the medium chlorination treatment, it is possible to remove an unstable element of the ozone injection control due to the deterioration of the water quality and to maintain and control the ozone injection rate in an appropriate range.

Therefore, the running cost can be reduced due to excessive generation of ozone, the load on GAC treatment can be reduced due to the high dissolved ozone concentration, and the outflow of iron and manganese into purified water due to insufficient ozone injection can be prevented.

According to a third aspect of the present invention, there is provided the advanced water purification method according to the second aspect, wherein the filler for biological contact filtration, the ammonia nitrogen sensor and the air diffuser installed in the landing well are provided. And providing the biological contact filtration function to the landing well by blowing air to the air diffuser.

According to the third aspect, in addition to the effect of the second aspect, the ammonia nitrogen concentration in the water to be treated is always 0.1%.
It can be less than mg / L, and can effectively act on the oxidative removal of iron and manganese with a smaller chlorine injection rate. For this reason, the amount of trihalomethane generated by the medium chlorination is further suppressed.

According to a fourth aspect of the present invention, there is provided the advanced water purification method according to the second or third aspect.
During the treatment in the granular activated carbon treatment process, the waste ozone gas discharged from the ozone treatment process is rendered harmless by the waste ozone treatment device, and then the surface back is performed by the surface backing device via the treatment gas switching device. Dissolved oxygen is supplied to the circulating water in the activated carbon treatment step.

According to claim 4, claims 2 and 3
In addition to the effect of the above, sufficient dissolved oxygen can be supplied to the microorganisms in the BAC layer even during the suspension of the BAC treatment, so that the activity of the organism is maintained for a long time. In addition, by using the exhausted ozone-treated gas for the surface back, it is not necessary to newly install a compressor or a blower, and the installation cost and the power cost can be reduced.

According to a fifth aspect of the present invention, there is provided the advanced water purification method according to any one of the first to fourth aspects, wherein the ozone water injection device is provided below the biological activated carbon layer in the biological activated carbon treatment step. It is characterized by suppressing the propagation and leakage of metazoans by injecting ozone-contact water from.

According to the fifth aspect, in addition to the effects of the first to fourth aspects, metazoans leaking from the BAC treatment step can be significantly suppressed. In addition, since the backwashing cycle can be extended by about two days as compared with the conventional advanced treatment, it can contribute to reducing the abrasion of activated carbon, stabilizing the microbial layer, etc., thereby obtaining more stable water purification and running costs in BAC treatment. Can be greatly reduced.

[0046]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process flow diagram of the advanced water purification method of the first embodiment of the present invention. As shown in the figure, the advanced water purification apparatus according to the present embodiment includes a landing well 1, a coagulation / precipitation processing step 2, a sand filtration processing step 3,
Ozone treatment step 4, BAC treatment step 5, and this BAC
The GAC treatment step 8, the post-chlorination treatment step 6, and the reservoir 7 are connected in parallel to the treatment step 5, and the water quality sensor 9 installed in the landing well 1 and the BAC treatment step 5 A BAC control valve 10 provided at the preceding stage;
GAC control valve 11 provided before AC processing step 8
A drain valve 12 for discharging the drain in the BAC processing step 5, a drain valve 13 for discharging the drain in the GAC processing step 8, and a system switching control device 14.

Next, the operation of the present embodiment will be described. Note that the same components as those in the conventional example of FIG. 6 are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, the water quality sensor 9 installed in the landing well 1 measures the organic matter (TOC) concentration of the raw water flowing into the landing well 1 online.
Is being entered. Although a total organic carbon concentration meter (TOC meter) is used for the water quality sensor 9, any one that can measure an index of an organic substance can be substituted. A trihalomethane precursor concentration meter using a fluorescent sensor, a potassium permanganate consumption meter,
An ultraviolet absorption photometer or the like can be used.

The BAC control valve 10 controls the flow rate of the ozonated water flowing into the BAC processing step 5, and outputs an output signal Vb from the system switching controller 14.
1, the opening degree and the opening / closing are controlled. Also, GA
The C control valve 11 controls the flow rate of the ozonized water flowing into the GAC processing step 8, and the opening and the opening and closing are controlled based on the opening and closing signal Vg 1 from the system switching control device 14. The opening and closing of the drain valve 12 and the drain valve 13 are also controlled based on the opening and closing signals Vb2 and Vg2 from the system switching control device 14, respectively.

In the system switching control device 14, the landing well 1
From the TOC concentration T1 in the raw water flowing into the BAC control valve 10 and the GAC control valve 11 to control the opening and opening and closing of the BAC processing step 5 and the GAC processing step 8 to control the activated carbon processing step. The effect is
It is as shown below.

Normally, when the water quality is stable, the TOC concentration T1 in the raw water is less than 5 mg / L, and the activated carbon treatment after the ozone treatment step 4 in the present embodiment is performed in the BAC treatment step 5 as an initial state. Is specified.

In this embodiment, the system switching control device 1
Although the TOC concentration of 4 mg / L is used as a criterion for the determination in step 4, the actual switching of the control mode is performed according to T
6-hour moving average value Ta at the measured value T1 of the OC concentration
v6, the lower point Td of the TOC concentration, and the upper point Tu, Td = 3.5 mg / L, Tu = 4 mg / L
L is set.

In the system switching control device 14, the T
The OC concentration T1 is recorded, and when the moving average value Tav6 for 6 hours (continuous processing continuation time) becomes a value equal to or more than Tu (4 mg / L), the processing steps from the BAC processing step 5 to the GAC processing step 8 waiting. The opening degree and the opening / closing control of the BAC control valve 10 and the GAC control valve 11 are performed so as to make the change. In the activated carbon treatment in the GAC treatment step 8 shifted from the standby state, even if the measured value of the TOC concentration T1 in the raw water is temporarily lower than Td (3.5 mg / L),
If the condition of d (3.5 mg / L) ≦ Tav6 is satisfied, the process is continued, and when Tav6 <Td (3.5 mg / L), the process is switched to the BAC processing step 5.

As described above, the 6-hour moving average value Tav6 of the measured value T1 of the TOC concentration is used as a criterion,
OC concentration lower point Td = 3.5 mg / L, upper point Tu =
The reason why the 0.5 mg / L width dead zone is set between 4 mg / L and 4 mg / L is to prevent frequent switching of processing steps near the determination reference density.

The control conditions are summarized as follows. Tu ≦ Tav6, → Switch from the BAC processing step to the GAC processing step and execute. Td ≦ Tav6 <Tu, → dead zone, continue the current activated carbon treatment process. Td> Tav6, →
Switch from GAC processing to BAC processing and execute. Based on experience, these setting values were set to 3.5 mg / Tu.
It is understood that the range of Tu−Tu = 0.5 to 1 mg / L is desirable.

The system switching control device 14 switches from the BAC processing step 5 to the GAC processing step 8,
At the time of switching from the C treatment step 8 to the BAC treatment step 5, the opening degree is gradually increased from the control valve of the activated carbon treatment step to start the treatment so that the water purification treatment is not interrupted even temporarily, and Then, the control valve in the activated carbon treatment step, which is on standby, is gradually closed to perform control so as to be fully closed. Further, in the activated carbon treatment step which shifts to the standby state, the drain valve is quickly opened to drain water, thereby preventing contamination of the activated carbon layer due to stagnation in the system.

For example, when switching from the BAC processing step 5 to the GAC processing step 8, the system switching controller 14 outputs an open / close signal Vg1 so as to open the GAC control valve 11 which has been in a fully closed state. At the same time as the valve 11 is fully opened, the BAC control valve 10 is gradually closed to control the valve to be in a fully closed state.

When the system switching controller 14 confirms that the GAC control valve 11 is fully closed, the drain valve 12
The open / close signal Vb2 is output so as to open the drain valve 12, and the treated water remaining in the BAC processing step 5 is discharged from the drain valve 12. This prevents contamination in the BAC processing step 5 due to anaerobicization in the BAC layer and stagnation in the system.
In the switching from the GAC processing step 8 to the BAC processing step 5, the drainage in the GAC processing step 8 is performed by the same operation.

Here, in this embodiment, the amount of trihalomethane Tthm generated in the purified water in the post-chlorination treatment step 6
Assuming (μg / L), the case of BAC processing (TthmB) and the case of GAC processing (TthmG) are compared under the following conditions according to equation (1.3) shown in the conventional example.

(Comparative conditions) Moving average value of TOC concentration in raw water Tav6 = 4 mg /
L ・ TOC removal rate Rs = 30% in the sand filtration process 3 for raw water ・ TOC in the GAC process 5 for the ozone treatment 4
Removal rate Rg = 20% ・ TOC of GAC treatment step 8 with respect to ozone treatment step 4
Removal rate Rg = 70% Trihalomethane production per unit TOC Rthm =
In the case of 40 μg-THM FP / mg-TOC BAC treatment, TthmB = 90 μg / L In the case of GAC treatment, TthmG = 33 μg / L, and in the case of BAC treatment, the water quality reference value (100 μg)
/ L) is no longer sufficient, and it is acceptable to exceed the water quality reference value immediately, but by switching to GAC processing according to the water quality load as in the present embodiment, it is sufficient for the water quality reference value. Water purification treatment that can afford is realized.

The treatment of ammoniacal nitrogen during the transition to the GAC treatment step 8 is removal by a conventional discontinuous point chlorination method (breakpoint method). As described above, in the present embodiment, by selecting the water purification treatment step that incorporates the advantages of the BAC treatment and the GAC treatment, the organic matter remaining in the activated carbon treated water can be reduced to a certain value or less. The amount of trihalomethane generated could be suppressed.

Further, even if residual chlorine is lost, the amount of bio-utilizing organic matter (AOC) remaining in the purified water is suppressed to a lower concentration than in the conventional treatment, and this may cause the propagation of bacteria and the like in the stagnant distribution pipe. Concerns disappeared and purified water with stable water quality could be supplied in addition to the effect of suppressing the production of trihalomethane.

FIG. 2 is a process flow chart of the advanced water purification method according to the second embodiment of the present invention. As shown in the figure, the advanced water purification apparatus of the present embodiment includes a landing well 1,
Coagulation / precipitation treatment step 2, sand filtration treatment step 3, ozone treatment step 4, BAC treatment step 5, and post-chlorination treatment step 6.
A water reservoir 7, a GAC treatment step 8, a water quality sensor 9 installed in the landing well 1, a BAC control valve 10
The configuration including the GAC control valve 11, the drain valve 12, the drain valve 13, and the system switching control device 14 is the same as that of the first embodiment in FIG. This embodiment further includes a middle chlorine injection device 15 and a post chlorine injection device 1.
6, a circulation line 17, a circulation pump 18, and a BAC circulation valve 19 are additionally provided.

Next, the operation of the present embodiment will be described. In the present embodiment, when switching to the GAC processing step 8 in the first embodiment of FIG. 1, in order to minimize the decrease in the biological activity of the BAC layer during the idle period of the BAC processing step 5, the circulation line 17 is connected. Using the circulation pump 18, B
While supplying dissolved oxygen to the AC layer, the GAC processing step 8
While the mode is switched to, the medium chlorine treatment is performed by the medium chlorine injection device 15 in order to reduce the load of the ozone treatment step 4.

Further, the system switching control device 14 adds to the control of the first embodiment shown in FIG.
And overall control of chlorine injection in the post-chlorine injection device 16 is added.

The BA in the system switching control device 14
The criterion for switching from the C processing step 5 to the GAC processing step 8 or for switching from the GAC processing step 8 to the BAC processing step 5 is the same as in the first embodiment. However, since the control of each valve in the BAC processing step 5 is different, the operation is also different.

This is shown by an example of switching from the BAC processing step 5 to the GAC processing step 8. In the system switching control device 14, the open / close signal Vg1 is output so as to open the GAC control valve 11 which has been in the fully closed state. Then, at the same time as the GAC control valve 11 is fully opened, the opening / closing signal Vb3 is output so as to gradually close the BAC circulation valve 19, and control is performed to bring the BAC circulation valve 19 into the fully closed state. When the fully closed state of the BAC circulation valve 19 is confirmed, the BAC control valve 10 is gradually closed to make the fully closed state and the circulation pump 18 is started,
The circulation line 17 is brought into a water-permeable state.

Further, when the process is completely shifted to the GAC processing step 8, the system switching control device 14 calculates a medium chlorine injection rate C1 for performing medium chlorination for oxidizing and removing iron and manganese. Chlorine is injected from the chlorine injection device 15 into the preceding stage of the sand filtration process 3 to form an oxide (solid).
The resulting iron and manganese are captured in the sand filtration step 3.

Further, the system switching control device 14 controls the medium chlorine injection rate C1 in the medium chlorine injection device 15 and the post-chlorine injection rate C2 in the post-chlorine injection device 16 as a whole.
Comprehensively manage chlorine injection volume and residual chlorine concentration.

Generally, the medium chlorine treatment is performed after the coagulation / precipitation treatment step 2. Since suspended substances and some soluble organic substances have been removed, the chlorine injection rate can be reduced as compared with the pre-chlorination, and the amount of trihalomethane generated is greatly reduced. In fact, a larger amount of trihalomethane is produced.

In the medium chlorination, iron and manganese are oxidized. Complete removal of ammonia nitrogen,
Chlorine injection in which residual chlorine is converted from bound chlorine (chloramine) to free chlorine is performed by a conventional discontinuous point chlorination method (breakpoint method) in the post-chlorination step 6.

In this embodiment, when the water quality is deteriorated, the process is switched to the GAC treatment step 8 in which the activated carbon adsorption performance is high. Therefore, the trihalomethane produced by the medium chlorination treatment and the organic matter remaining after the ozone treatment step 4 are transferred to the GAC treatment step 8. Is absorbed. Further, since the organic matter is largely removed, the amount of trihalomethane generated after the post-chlorination step 6 is also greatly suppressed, and the concentration of trihalomethane in the purified water can be reduced to the same level as in the conventional advanced treatment.

The oxidation of iron and manganese in the ozone treatment step 4 is performed by the medium chlorine treatment, and is captured by sand filtration. For this reason, the ozone injection control factor in the ozone treatment step 4 decreases, and the accuracy of ozone injection control increases. This solves the problem of ozone injection control that occurred when water quality deteriorated as shown in the conventional example,
Stable ozone treatment can be realized.

On the other hand, in the switching from the GAC processing step 8 to the BAC processing step 5, the medium chlorine injection in the medium chlorine injection device 15 is first stopped (C1 = 0 mg / L), and then the residual chlorine is contained in the BAC processing step 5. During the replacement time (1 hour) for preventing the inflow of sand filter water, the GAC treatment step 8 is continued,
Thereafter, the valves are controlled by the system switching control device 14 so as to proceed to the BAC processing step 5.

As described above, this embodiment adds the effects of the first embodiment and minimizes the decrease in the biological activity of the BAC layer in the BAC processing step 5 even during the transition to the GAC processing step 8, Shift to BAC processing step 5 again (return)
In this case, the rise processing characteristics can be maintained in substantially the same state as before the suspension. Further, by using the medium chlorination treatment together, it is possible to remove an unstable element of the ozone injection control due to the deterioration of the water quality and to maintain and control the ozone injection rate in an appropriate range.

For this reason, it is possible to suppress an increase in the running cost (electricity cost, waste ozone treatment cost, etc.) of the ozone equipment due to excessive generation of ozone, prevent oxidation of manganese dioxide to permanganate ion by excessive oxidation of ozone, It is possible to reduce the load on the GAC treatment due to the concentration of ions and high dissolved ozone, and to prevent iron and manganese from flowing into purified water due to insufficient ozone injection. In addition, deterioration of purified water quality due to these factors can be prevented. As a result, according to the present embodiment, it was possible to always supply purified water with stable water quality in the advanced water purification treatment.

FIG. 3 is a process flow diagram of the advanced water purification method according to the third embodiment of the present invention. The same components as those in the second embodiment in FIG. As shown in the figure, this embodiment is different from the second embodiment of FIG.
A filler 21 for biological contact filtration, a blower 22, and an air diffuser 23, which are installed inside, are added.

Next, the operation of the present embodiment will be described. In this embodiment, when the BAC processing step 5 is switched to the GAC processing step 8 as shown in the second embodiment of FIG. During the period, air is diffused from the bottom of the landing well 1 in which the filler 21 is installed, and ammonia nitrogen is removed by biological oxidation.

BAC in system switching control device 14
Switching from processing step 5 to GAC processing step 8 and GAC
The criterion for switching from the processing step 8 to the BAC processing step 5 and the overall control of the medium chlorine injection device 15 and the post chlorine injection device 16 are the same as in the second embodiment.
Since the control of each valve in the GAC processing step 8 is the same, a detailed description therefor is omitted.

In this embodiment, the ammonia nitrogen concentration of the raw water flowing into the landing well 1 is measured online using the ammonia nitrogen sensor 20, and the measured value N
1 is input to the system switching control device 14. A filler 21 with nitrifying bacteria attached thereto is installed in the landing well 1, and is characterized by a high ability to remove ammonia nitrogen when the nitrifying bacteria are activated.

When the process is switched from the BAC processing step 5 to the GAC processing step 8, if the concentration of ammoniacal nitrogen is high, there is a concern that the amount of trihalomethane generated due to the increase rate of the chlorine injection rate may increase.

In the present embodiment, when the ammonia nitrogen concentration N1 is 0.1 mg / L or more during the transition to the GAC processing step 8, the system switching control device 14 sends the air from the air supply device 22 to the air diffusion device in the landing well 1. The control signal A1 is output to the air supply device 22 so as to send the pressurized air to the air supply device. The dissolved oxygen concentration in the landing well 1 is always kept close to the saturation concentration, and the nitrifying bacteria attached to the filler 21 are activated to remove the ammonia nitrogen concentration in the raw water by 90% or more.

When the ammoniacal nitrogen concentration N1 is 0.1 mg /
In the case of less than L, the air diffusion to the landing well 1 is reduced because the chlorine injection rate does not increase so much even by the conventional discontinuous point chlorination method (breakpoint method) and the energy cost in the air supply device 22 is saved. Paused.

For surface water such as river water and lake water, several mg
Since dissolved oxygen of the order of / L is contained, nitrifying bacteria are not killed even if air diffusion to the landing well 1 is stopped. Also, if there is ammonia nitrogen concentration in raw water,
The activity of nitrifying bacteria is kept to a minimum. In recent years, there has been no case in which the concentration of ammonia nitrogen in the surface water system exceeds 1 mg / L due to the restoration and maintenance of sewerage and the like, and the maximum value of the ammonia nitrogen concentration in the present embodiment is 0.82 mg.
/ L.

As described above, this embodiment is in addition to the effect of the second embodiment, and the ammonia nitrogen concentration in the water to be treated before chlorination is always kept at 0 even during the transition to the GAC treatment step 8. 0.1 mg / L, the amount of chlorine consumed by ammoniacal nitrogen during the medium chlorination is reduced,
It works effectively for oxidative removal of iron and manganese with a smaller chlorine injection rate. For this reason, the amount of trihalomethane generated by the middle chlorination treatment was suppressed as compared with the second embodiment, and as a result, purified water with more stable water quality could be supplied.

FIG. 4 is a process flow chart of an advanced water purification method according to a fourth embodiment of the present invention. The same components as those in the third embodiment in FIG. As shown in the figure, the present embodiment is different from the third embodiment of FIG.
5, a backing device 26, and a backing line 27 are added.

Next, the operation of the present embodiment will be described. In the present embodiment, the criteria for switching from the BAC processing step 5 to the GAC processing step 8 and switching from the GAC processing step 8 to the BAC processing step 5 in the system switching control device 14, The overall control is the same as in the second embodiment of FIG. 2 and the third embodiment of FIG. BAC processing step 5 and GAC
Since the control of each valve in the processing step 8 is the same, a detailed description thereof will be omitted.

In the present embodiment, when the process is switched to the GAC treatment step 8, there is no treatment step having an action of removing ammoniacal nitrogen. The control relating to the air diffusion from the bottom of 1 and the removal of ammonia nitrogen by the biological oxidation action is the same as that of the third embodiment in FIG.

In the second embodiment shown in FIG. 2 and the third embodiment shown in FIG. 3, when the BAC processing step 5 is switched to the GAC processing step 8, the biological activity of the BAC layer during the idle period of the BAC processing step 5 is reduced. In order to minimize the reduction of the BAC, the circulation line 17 and the circulation pump 18 are used
Dissolved oxygen was being supplied to the bed. But with this method,
The location of gas-liquid contact between the circulating water flowing through the circulation line 17 and the air is limited, and the dissolved oxygen concentration decreases in summer or the like when the oxygen solubility decreases, and the maintenance of the activity of microorganisms (bacteria) in the BAC layer is prolonged. Sometimes did not last for a period.

In the present embodiment, the ozone gas discharged from the ozone treatment step 4 is detoxified by the ozone treatment device 24, and the back gas is switched by the surface back device 26 via the process gas switching device 25. To supply dissolved oxygen to the circulating water flowing through the circulation line 17.

The processing gas switching device 25 switches whether the processing gas from the exhausted ozone processing device 24 is opened to the atmosphere or guided to the surface back line 27. The processing gas switching device 25 is controlled by a control signal A 2 from the system switching control device 14. I have. That is, the processing gas from the exhaust ozone treatment device 24 is transferred to the surface back line 2 in conjunction with the activation of the circulation pump 18.
7, the line is switched to the atmosphere opening at the same time when the circulation pump 18 is stopped.

[0091] In the exhaust ozone treatment device 24, exhaust ozone gas concentration 1 to 2 g / m ³ (injection ozone concentration 20 g / m ^3,
Exhaust gas with an ozone absorption efficiency of 90 to 95%) is treated. A heated manganese-based catalyst is used as an ozone decomposing agent, and the exhausted ozone gas returns to oxygen again after decomposition.

When the ozone concentration of 20 g / m ³ is converted into a concentration of mol / m ³ , the following formula is obtained from the molecular formula of ozone: O ₃ MW (molecular weight): 48. (20 [g] / 48 [g / mol]) / [m ³ ] = 0.417 mol / m ³ (3.1) Since 2 mol of ozone molecules are generated from 3 mol of oxygen molecules (3O ₂ → 2O ₃ ), the oxygen molecules used to generate 20 g / m ³ of ozone are: 0.417 / m ³ * 3/2 = 0.625 mol / m ³ (3.2)

On the other hand, all gases existing in 1 m ³ (1000 L) of air are regarded as ideal gases, and the number of moles is calculated.
(2.4 ° C., 101.32 kPa), which is 1000 [L] /22.4 [L / mol] = 44.64 mol / m ³ (3.3).

The volume ratio of oxygen in the air is 20.
95% of the calculation of the mol of oxygen present in the air of 1 m ³ by Bun'atsunohousoku ^{Dalton, 44.64 [mol / m 3]} * 0.2095 = 9.35mol / m 3 ... (3 .4).

From the above equations (3.2) and (3.4), 20
The ratio of oxygen molecules used to generate g / m ³ of ozone is 6.7% of the total oxygen amount.

0.625 [mol / m ³ ] /9.35 [mol / m ³ ] * 100 = 6.7% (3.5) About 10% of unreacted ozone is contained in the exhausted ozone gas.
If the amount is subtracted to return to oxygen again by the waste ozone treatment, about 6% of oxygen will be lost. If this is recalculated as the oxygen gas concentration in the newly treated exhaust gas, the oxygen concentration becomes about 20%.

(9.35-9.35 * 0.06) / (44.64-9.35 * 0.06) * 100 = 19.9% (3.6) Therefore, the treated exhaust gas is It can be seen that there is no problem with the oxygen concentration even when used for the backing.

The surface backing device 26 is installed on the suction side of the circulation pump 18. The pressure of the processing gas discharged from the exhaust ozone processing apparatus 25 is atmospheric pressure + 500 to 600
Since it is about mmAq, it can be seen that a surface backing with a water depth of about 30 to 40 cm can be sufficiently performed.

For reference, 600 mmAq is set to the absolute pressure M
When converted to Pa units, 1 atm = 0.101325 MPa = 1.03323 *
Since it is 10 ⁴ mmAq, (0.101325 + 600 / 1.03323 * 1
0 ⁴ ) = 0.1594 MPa (absolute pressure).

The backing device 26 is provided on the suction side of the circulating pump 18 so that the backing can be performed even if the exhaust pressure of the processing gas described above is slightly reduced.

As described above, the present embodiment employs the second
In the same manner as in the third embodiment and the third embodiment, it is possible to supply purified water with stable water quality. In addition to these effects, even during the transition to the GAC processing step 8, the BAC layer in the BAC processing step 5 is formed. Since sufficient dissolved oxygen can be supplied to the microorganisms, the activity of the living organism can be maintained for a long period of time, and the rising treatment characteristics when the process returns (returns) to the BAC treatment step 5 are faster than those of the second and third embodiments. I was able to do it. In addition, by using the exhausted ozone-treated gas for the surface back, it is not necessary to newly install a compressor or a blower, and the installation cost and the power cost can be reduced.

FIG. 5 is a process flow chart of an advanced water purification treatment method according to a fifth embodiment of the present invention. The same components as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. As shown in the figure, the present embodiment is different from the first embodiment in that an ozone water bypass pipe 28 and an ozone water injection device 29 are provided.
And an infusion pump 30 is added.

In the present embodiment, the ozone bypass pipe 28 is inserted into the contact portion of the ozone reaction layer (not shown) constituting the ozone treatment step 4, and the ozone contact pipe having a relatively high dissolved ozone concentration immediately after the ozone contact. Water can be collected.

The ozone water bypass pipe 28 is connected to an ozone water injection device 29 via an injection pump 30. The ozone water injecting device 29 is a component of the BAC
It is installed below the AC layer (not shown) and injects ozone contact water into the BAC layer to remove micro-animals (metamorphous organisms) by the strong sterilizing power of ozone.
To control breeding and leakage. The BAC tank that constitutes the BAC processing step 5 performs the processing by a downward flow.

The injection of ozone contact water from the ozone water injection device 29 is performed during the processing in the BAC processing step 5, and the control is performed by starting the injection pump 30 based on the control signal P1 from the system switching control 14. And stop. That is, the infusion pump 30 is stopped in conjunction with switching from the BAC processing step 5 to the GAC processing step 8, and conversely, the infusion pump 30 is activated in conjunction with switching from the GAC processing step 8 to the BAC processing step 5. Is controlled by the system switching control 14.

It should be noted that BA in system switching control device 14
Switching from C processing step 5 to GAC processing step 8 and GA
The criterion for switching from the C processing step 8 to the BAC processing step 5 and the overall control of the medium chlorine injection device 15 and the post chlorine injection device 16 can be implemented in the same manner as in the above embodiment. The control of each valve is the same as that of the above embodiment, so that the detailed description is omitted.

In the conventional advanced treatment, the washing (backwashing) of the BAC layer, which is a combination of empty washing and water washing, is performed about once every three days in consideration of the breeding cycle of metazoans. . On the other hand, excessive backwashing may cause abrasion of activated carbon and adversely affect microorganisms that remove organic substances.

In the present embodiment, the ozone contact water is constantly supplied from the ozone water injection device 29 during the treatment in the BAC treatment step 5 in consideration of metazoans descending from the upper part of the BAC layer. Therefore, metazoans can be efficiently removed. In addition, since the BAC tank is a downward flow treatment, the ozone contact water injected from the ozone water injection device 29 has no adverse effect on microorganisms that are often present above the BAC layer. For this reason, the backwashing cycle can be extended by about two days as compared with the conventional advanced treatment. However, since the clogging of the BAC layer is not different from the conventional advanced treatment, it is impossible to control the rise of the filtration height and the regular backwashing of the activated carbon layer.

As described above, according to the present embodiment, in addition to the effects of the first embodiment, metazoic organisms leaking from the BAC treatment step 5 can be significantly suppressed. In addition, since the backwashing cycle can be extended by about two days as compared with the conventional advanced treatment, it can contribute to reducing the abrasion of activated carbon, stabilizing the microbial layer, etc., thereby obtaining more stable water purification and running costs in BAC treatment. Was significantly reduced.

[0110]

As described above, according to the present invention,
Organic matter remaining in the activated carbon treated water can be reduced to a certain value or less,
The amount of trihalomethane generated by post-chlorination can be suppressed. In addition, since the bio-utilizing organic matter remaining in the purified water is suppressed to a low concentration, there is no concern about the breeding of bacteria and the like in the stagnant water distribution pipe, and further, the unstable element of the ozone injection control due to the deterioration of the water quality is removed, and the ozone injection is performed. It is possible to prevent the outflow of iron and manganese into the purified water due to shortage, and to supply purified water of stable water quality.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of an advanced water purification method according to a first embodiment of the present invention.

FIG. 2 is a process flow chart of an advanced water purification treatment method according to a second embodiment of the present invention.

FIG. 3 is a process flow diagram of an advanced water purification method according to a third embodiment of the present invention.

FIG. 4 is a process flow chart of an advanced water purification method according to a fourth embodiment of the present invention.

FIG. 5 is a process flow chart of an advanced water purification method according to a fifth embodiment of the present invention.

FIG. 6 is a process flow diagram of a conventional advanced water purification treatment method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Landing well, 2 ... Agglomeration / precipitation processing step, 3 ... Sand filtration processing step, 4 ... Ozone processing step, 5 ... BAC processing step, 6 ...
Post-chlorination process, 7: Reservoir, 8: GAC process, 9
... water quality sensor, 10 ... BAC control valve, 11 ... GA
C control valve, 12: drain valve, 13: drain valve, 14: system switching control device, 15: medium chlorine injection device,
16: Post chlorine injection device, 17: Circulation line, 18: Circulation pump, 19: BAC circulation valve, 20: Ammonia nitrogen sensor, 21: Filler, 22: Blower, 23 ...
A diffuser device, 24 an exhaust ozone treatment device, 25 a processing gas switching device, 26 a surface backing device, 27 a surface backing line, 28 an ozone water bypass pipe, 29 an ozone water injection device, and 30 an injection pump.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shioko Miyajima 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu Works Co., Ltd. F term (reference) 4D003 AA01 AB11 BA02 CA02 CA03 CA10 EA01 EA14 EA25 4D024 AA01 AB11 BA02 BB01 BC01 CA01 DB03 DB21 DB23 4D050 AA03 AB55 BB02 BB04 CA06 CA15 CA16 CA17

Claims (5)

[Claims] 1. A water quality sensor for measuring an index of organic matter in raw water, an ozone treatment step for ozonating the raw water,
In an advanced water purification method for converting ozone-treated raw water to highly purified water through a biological activated carbon treatment step or a granular activated carbon treatment step, the biological activated carbon treatment step and the granular activated carbon treatment step according to a water quality load measured by the water quality sensor. An advanced water purification treatment method, comprising a system switching control device for switching between water and water. 2. A water quality sensor for measuring an index of organic matter in raw water, an ozone treatment step for ozonating the raw water,
In an advanced water purification method for converting ozone-treated raw water to highly purified water through a biological activated carbon treatment step or a granular activated carbon treatment step, the biological activated carbon treatment step and the granular activated carbon treatment step are switched according to the water quality load based on the measured value of the water quality sensor. A high-purity water purification system comprising a system switching control device, wherein medium chlorine flows into the ozonation process from a medium chlorine injection device and dissolved oxygen is supplied to the biological activated carbon layer during switching to granular activated carbon treatment. Processing method. 3. A biological contact filtration function, comprising a filler for biological contact filtration installed in the landing well, an ammonia nitrogen sensor and an air diffuser, and sending air to the diffuser to provide a biological contact filtration function to the water arrival well. The advanced water purification treatment method according to claim 2, wherein 4. While the treatment is continued in the granular activated carbon treatment process, the exhausted ozone gas discharged from the ozone treatment process is rendered harmless by the exhausted ozone treatment device, and then the surface is switched by the surface backing device via the treatment gas switching device. The advanced water purification method according to claim 2 or 3, wherein a backing is performed to supply dissolved oxygen to circulating water in the biological activated carbon treatment step. 5. The method according to claim 1, wherein in the biological activated carbon treatment step, the propagation and leakage of metazoans are suppressed by injecting ozone contact water from an ozone water injection device provided below the biological activated carbon layer. The method of any one of claims 4 to 5.