JPH04197498A - Water purifying treatment - Google Patents

Abstract

PURPOSE:To perform water purifying treatment with high accuracy by facilitating the treatment of raw water by supplying sodium sulfite to raw water as an electron donor and also supplying sodium bicarbonate thereto as an inorg. carbon source to perform the desulfurization and denitrification treatment of raw water. CONSTITUTION:Na2CO3 is supplied to raw water to be treated as an electron donor and NaHCO3 is supplied thereto as an inorg. carbon source and the desulfurization and denitrification treatment of the raw water is performed in a desulfurization and denitrification tank 1 and a nitrification tank 2. A flocculant (e.g. PAC) is injected in and mixed with this raw water subjected to desulfurization and denitrification treatment in a quick mixing basin 5 and sludge is flocculated and settled in a flocculation and sedimentation basin 6 and chlorine is injected in the raw water to sterilize the raw water. As a result, the treatment of raw water is facilitated and water purifying treatment can be performed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field The present invention relates to a water purification treatment method, and in particular to a water purification method that enables total nitrogen removal by making it possible to remove nitrate ions, which are difficult to remove with existing water purification treatments. The present invention relates to a water purification treatment method and a water purification treatment device.

B0 Summary of the Invention The present invention provides a water purification method in which sludge from raw water to be treated is subjected to coagulation sedimentation and coagulation sedimentation treatment. Performs water purification treatment.

C0 Conventional technology [Conventional technology, C-1] Currently, the commonly used water purification treatment method uses a flocculant to remove turbidity and sterilizes with chlorine. In this method, ammonia (NHs) contained in tap water reacts with chlorine and is oxidized to nitrogen and chloramines, but nitrate ions (NO3) cannot be removed.

The regulatory value for nitrate nitrogen in drinking water is 10mg/ff,
Fortunately, there are no cases in Japan of exceeding the regulation value. However, the health effects of nitrate ions are being debated, and there are moves to tighten regulations.

The total nitrogen removal method in the sewage treatment field is biological nitrification and
Although the denitrification method has been put into practical use, it is generally difficult to apply this method to water purification treatment. Methods for removing nitrate ions in water purification include reverse osmosis and ion exchange, but both have high processing costs, and although small-scale treatment equipment has been put into practical use, it is difficult to use them for general water purification. is difficult to apply.

[Conventional technology, C-21 There is a research report on a nitrification/sulfur denitrification system for the purpose of total nitrogen removal in sewage treatment (About biological denitrification by various denitrifying bacteria. 14th Sewerage Research Presentation .19
77, Sho Hashimoto, Kenji Furuyo).

Mr. Hashimoto et al. studied sulfur denitrification and found that the denitrification reaction rate by sulfur denitrifying bacteria using sodium thiosulfate as an electron donor was comparable to the denitrification reaction rate by ordinary denitrifying bacteria using organic matter as an electron donor. reported. Furthermore, the reaction rate of denitrification reactions using reduced sulfur compounds such as calcium sulfide and sulfur as electron donors is lower than when sodium thiosulfate is used. Since calcium sulfide has the drawbacks of odor and toxicity, and sodium thiosulfate has the drawbacks of high reagent costs, it has been reported that sulfur, which is inexpensive and non-toxic, is suitable as an electron donor in sulfur denitrification reactions.

There are physicochemical treatment methods such as reverse osmosis and sulfur exchange to remove total nitrogen in water purification treatment, but because these treatment costs are high, small-scale equipment has been put into practical use, but - boat fishing etc. Application to water purification treatment is difficult.

[Prior art, C-3] The biological activated carbon treatment method, which is a type of advanced water purification treatment, has the ability to nitrify ammonia in addition to the function of activated carbon that removes color and odor by attaching microorganisms to granular activated carbon. You will be given the ability to

Granular activated carbon can become biologically activated carbon if the water does not contain residual chlorine, so it is likely to be introduced in the future in combination with ozone treatment. In the biological activated carbon method, the ammonia contained in the tap water is nitrified, so it is possible to reduce the consumption of chlorine, but it is impossible to remove NO3- ions, and the total nitrogen concentration of the treated water is lower than the biological activated carbon method. higher than if no treatment was performed.

D6 Problem to be solved by the invention [Problem, D-1] In the above-mentioned prior art C-1, the biological nitrification/denitrification method has been put into practical use as the nitrogen removal method for sewage wastewater, and the physicochemical method is not popular due to its high cost.

Biological nitrification and denitrification methods consist of a nitrification process that oxidizes ammonia to nitrite and nitric acid under aerobic conditions, and a denitrification process that generates nitrogen from nitrite and nitric acid under anaerobic conditions. The former is due to the action of autotrophic nitrifying bacteria, while the latter is due to the action of heterotrophic denitrifying bacteria, so an organic carbon source is usually required. Organic matter in sewage and wastewater is used as an organic carbon source, but it is also common practice to supply methanol or the like to increase the denitrification rate.

The reason why normal biological nitrification and denitrification treatment cannot be applied in water purification treatment is considered to be due to the following reasons (la) to (1c).

(1a) Water supply raw water has a relatively high dissolved oxygen concentration, and it is difficult to create anaerobic conditions where denitrification reactions occur.

(1b) Since tap water has a relatively low concentration of organic matter and a high composition ratio of persistent organic matter that has already undergone biodegradation, it lacks the organic carbon source necessary for the denitrification reaction. Means for supplying organic substances such as methanol are economically disadvantageous and cannot be applied to the bottom for hygienic reasons.

(1c) The growth rate of nitrifying bacteria is HRT in a normal aeration tank.
When the (hydrological residence time) is shortened, bacterial cells flow out,
Since it is difficult to maintain a sufficient bacterial cell concentration, nitrification does not proceed sufficiently. Further, when the temperature decreases, the nitrification property decreases, and ammonia and intermediate nitrite ions (NOx-) remain.

Among these, (1c) is treated with biological activated carbon.

Methods to increase the nitrification rate by immobilizing nitrifying bacteria, such as fixed-bed biological oxidation treatment, have been put into practical use, and by reducing ammonia, there is an economical effect of reducing the amount of chlorine injection, and the reduction of carcinogenic trihalomethanes. The sanitary effect of reducing the amount produced was observed.

However, when only nitrification is performed in water purification treatment, nitrate ions and total nitrogen will increase by the amount of ammonia nitrified compared to existing water purification methods that do not perform nitrification.

An increase in nitrate ion concentration is not desirable. According to recent research reports, organic halogenated nitro chemicals or organic nitro chemicals, which are highly carcinogenic, are produced by chlorine treatment from organic substances and nitrate ions. It is also known that drinking water with a high concentration of nitrate ions can cause blood disorders in infants. It is also said that nitrate ions are reduced to nitrite by oral bacteria, increasing the risk of cancer.

As mentioned above, in water purification treatment, it is recognized that it is necessary to remove total nitrogen, especially nitrate ions, but in normal biological nitrification and denitrification treatment methods, for reasons (1a) and (1b'),
Cannot remove nitrate ions.

[Problem, D-2] In conventional technology C-2, it is highly unlikely that a biological denitrification treatment method using ordinary organic matter as an electron donor would be applied in water purification treatment. On the other hand, are there any examples in which biological sulfur denitrification treatment methods using reduced sulfur compounds as electron donors have been applied to water purification treatment? However, judging from the research reports to date, among the reducing sulfur compounds, only NatSOs has the potential to be used for water purification when used alone. This is due to the following reasons.

Since raw water from tap water originally has a high dissolved oxygen concentration, it is necessary to reduce the dissolved oxygen concentration to zero in order to cause a denitrification reaction, and NatSO3, NaS, and Cps have the effect of lowering the dissolved oxygen concentration. However, NaS and CaS cannot be used because they are toxic. NagS Os is excellent as an electron donor for sulfur denitrification reactions, but it is relatively safe and has a weak ability to reduce dissolved oxygen concentration, so it is not used for academic purposes in cases where the dissolved oxygen concentration is originally low, such as in sewage. Although it is effective, it is not effective when used alone for water purification treatment.

However, when N a t S 'Os is used alone as an electron donor in the sulfur denitrification reaction, the oxidation number of the sulfur atom is 4, which is high, so the amount of chemical injection as a sulfur atom becomes high, and ultimately The disadvantage is that the concentration of So, ``-'' increases. SO4''- is not toxic, but
If there is a large amount of calcium, it will cause permanent hardness and cause scale formation, so the concentration of SO4''- should be kept as low as possible.

[Problem, D-31 In conventional technology C-3, in the biological nitrification/sulfur denitrification treatment method that can be applied to water purification treatment, the nitrifying bacteria and sulfur denitrifying bacteria that play the main role in total nitrogen removal are non-aggregating. Since these bacteria are difficult to separate by sedimentation, it is not easy to maintain the number of bacterial cells. If microorganisms do not settle in the sedimentation basin, they must be treated in the existing water purification process, so leakage of microorganisms must be avoided as much as possible. Furthermore, if excessive amounts of NatsOs, Na, S, and O are injected, the amount of chlorine consumed in the existing water purification process will increase, so it is necessary to inject just the right amount.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to facilitate the treatment of raw water by removing nitrate ions through sulfur denitrification treatment before the sedimentation treatment of the raw water to be treated. The purpose of the present invention is to provide a high-precision water purification method.

81 Means and Effects for Solving the Problems In order to achieve the above objects, the present invention has the following first to third aspects.
take the following measures.

(E-1, First Means) In order to solve problem D-1, sodium sulfite is supplied as an electron donor to the raw water to be treated, and sodium bicarbonate is supplied as an inorganic carbon source to improve the raw water. Sulfur denitrification treatment is performed, a coagulant is injected and mixed into the sulfur denitrified raw water to coagulate and precipitate the sludge, and then nitrate is injected into the raw water for nitrification treatment.

In nature, in addition to polytrophic denitrifying bacteria that require organic matter as an electron donor for denitrification reactions, there are also S''-, s', and s.

Using reduced sulfur compounds such as o, "-, s, o, "-, sos"- as electron donors in the denitrification reaction, so, "-
Thobacillus denitritica can grow using the energy generated when it oxidizes to
ns (sulfur denitrifying bacteria) are present. Sulfur denitrifying bacteria convert NO3 into N during the oxidation of reduced sulfur compounds to 804'-
However, in the presence of oxygen, oxygen is preferentially used, so the denitrification reaction is 0. This occurs only under so-called anoxic environmental conditions where NO3- is present and NO3- is present, and the optimum pH for growth is in the neutral range of 6 to 8. Sulfur denitrifying bacteria are autotrophic bacteria that denitrify CO, HCO3-.

It grows using inorganic carbon such as CO3 as a carbon source. If the denitrification reaction of sulfur denitrifying bacteria, which uses low-cost reduced sulfur compounds as electron donors, can be applied to wastewater treatment, denitrification will be possible at an extremely low cost, and denitrification of secondary nitrification treated water and lack of electron donors can be achieved. Since the denitrification capacity of denitrification tanks can be improved, biological nitrogen removal methods can be expected to become more widespread, and will play a major role in preventing water pollution. However, there is little knowledge regarding practical applications such as denitrification reaction conditions and optimal growth conditions for sulfur denitrifying bacteria, and this is currently still in the laboratory experiment stage, and there are no examples of its application.

The present inventor is concerned with a method for removing nitrate ions, which are difficult to remove at low cost in water purification treatment, by using sulfur denitrifying bacteria. It is highly safe and can reduce processing costs. We also invented a method for calculating the injection rate of chemicals used in this method from water quality factors.

(E-2, second means) In order to solve problem D-2, Na
After injecting tS O or Na2S2Os to lower the dissolved oxygen concentration, the raw water is injected with Na t S t
Sulfur denitrification treatment is performed by supplying O8 as an electron donor.

We previously proposed a system that combines nitrification and sulfur denitrification systems with existing water purification treatment systems to provide turbidity and sterilization functions as well as total nitrogen removal ability. Na as a donor
aS Os (sodium sulfite) was used. N
atSOs has a high ability to reduce the dissolved oxygen concentration in raw water, but it is not suitable as an electron donor for sulfur denitrification reactions, and its oxidation number is high at 44, making it uneconomical due to the high chemical injection rate. .

On the other hand, Na2S2Os (sodium thiosulfate) has a low ability to reduce the dissolved oxygen concentration, but it can be used as an electron donor for the sulfur denitrification reaction because the oxidation number of the sulfur atom is 42, and N
Since it is lower than aySO3, the chemical injection rate can be reduced. It is also known that the denitrification reaction is fast.

Therefore, we devised a biological sulfur denitrification system that uses both in combination to take advantage of their strengths.

(E-3, Third Means) In order to solve problem D-3, the raw water to be treated was passed through nitrifying bacteria-immobilized activated carbon to nitrify the ammonia in the raw water, and this ammonia was nitrified. NhtSO3 in raw water
After reducing the dissolved oxygen concentration by supplying NatS
Treat by injecting t, o a and NaHCO.

In normal biological activated carbon treatment equipment, the nitrifying bacteria are attached and immobilized on the granular activated carbon, which prevents the nitrifying bacteria from flowing out.
It is relatively easy to maintain the number of nitrifying bacteria. Sulfur denitrifying bacteria are also thought to be relatively easy to immobilize on activated carbon, but among the microorganisms immobilized on activated carbon, sulfur-yellow denitrifying bacteria are the dominant species, and sulfur denitrification reactions may occur. It is necessary to meet the following conditions.

■There is no dissolved oxygen.

■N01- ions and trace amounts of NH4'' ions are present.

■Reduced sulfur compounds exist that are electron donors for sulfur denitrification reactions.

■Inorganic carbon sources exist.

Taking the above conditions into consideration, we invented a total nitrogen removal biological polluted charcoal treatment system that can be applied to water purification treatment.

F. EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 8.

CF-1, First Embodiment] Fig. 1 shows a water purification treatment apparatus according to an embodiment of the present invention, where l is a sulfur denitrification tank, 2 is a nitrification tank, 4 is a settling tank, 5 is a rapid mixing tank, and 6 7 is a coagulation sedimentation tank, and 7 is a sand filtration tank.

In the apparatus shown in FIG. 1, raw water enters the sulfur denitrification tank 1 after being injected with a sodium sulfite solution and a sodium bicarbonate solution, and undergoes denitrification by sulfur denitrifying bacteria. Next, the raw water enters the nitrification tank 2, where it is aerated, and the ammonia in the raw water is nitrified by the action of nitrifying bacteria. The interior of the nitrification tank 2 is a fixed bed in which nitrifying bacteria are immobilized, thereby preventing the nitrifying bacteria from leaking out. A part of the nitrification liquid from the nitrification tank 2 is returned to the sulfur denitrification tank 1 by the circulation pump 8, and NO3-, NO
t- is subjected to denitrification, N, (nitrogen gas) or partially N
, 0 (nitrous oxide gas) into the atmosphere. Water flowing into the settling tank 4 from the nitrification tank 2 is separated into solid and liquid and divided into sludge and supernatant water. Sludge containing microorganisms is stored in a sulfur denitrification tank.
However, if excess sludge is generated due to growth of microorganisms or an increase in the temperature of raw water, the excess sludge will be discharged. The supernatant water in the sedimentation tank 4 is transferred to the rapid mixing tank 5. Coagulation sedimentation pond 6. Water is supplied and distributed after being subjected to turbidity removal treatment through coagulation and sedimentation using a coagulant such as PAC and sterilization treatment through chlorine injection in an existing water purification treatment system comprising a sand filter 7 and the like.

Figure 2 shows another example of a water purification device, which combines a nitrification/sulfur denitrification system with an existing water purification system.

In the apparatus shown in FIG. 2, raw water enters a nitrification tank 2, and ammonia in the raw water is nitrified by the action of nitrifying bacteria under aerobic conditions. The nitrification tank 2 is a biological activated carbon treatment tank or a fixed bed type biological oxidation treatment tank, and does not necessarily need to be aerated.

The nitrifying liquid flowing out from the nitrifying tank 2 is injected with a sodium sulfite solution and a sodium bicarbonate solution, and then enters the sulfur denitrifying tank 1, where it is subjected to denitrification by sulfur denitrifying bacteria, and N O3'', N in the nitrifying liquid is Ot- is N or partially N
, O, into the atmosphere. The dissolved oxygen in the water flowing out from the sulfur denitrification tank 1 has decreased due to the addition of sodium sulfite solution, so by aeration in the re-aeration tank 3, the excess SOs is oxidized to so, and the dissolved oxygen concentration is reduced. In the case shown in Fig. 1, the nitrification tank 2 also plays the role of a reaeration tank, so a reaeration tank is not installed.

The water flowing out from the reaeration tank enters the sedimentation tank 4, where it is separated into solid and liquid and divided into sludge and supernatant water. Sludge containing microorganisms is returned to the nitrification tank 2, but if excess sludge is generated due to proliferation of microorganisms or an increase in the temperature of raw water, the excess sludge is discharged.

The supernatant water in the sedimentation tank 4 is subjected to turbidity and sterilization treatment in an existing water purification system, similar to that shown in FIG. 1, before being supplied and distributed.

Next, for the so-called advanced water purification treatment system, which adds an ozone activated carbon treatment system to the existing water treatment system,
Figures 3 and 4 show a system that has total nitrogen removal ability by combining nitrification and sulfur denitrification systems. Figure 3 shows a system that combines a circulating nitrification/sulfur denitrification system, an ozone-activated carbon system, and an existing system.
Figure 4 shows a system that combines a nitrification/sulfur denitrification system, an ozone-activated carbon system, and an existing system.

The one in Figure 3 has a circulating nitrification/sulfur denitrification system and the existing system parts are the same as those in Figure 1, but an ozone-activated carbon system is inserted between the former two, and the color and odor are It has the ability to remove. In addition, in Figure 4, the nitrification/sulfur denitrification system and the existing system are the same as in Figure 2, and an ozone-activated carbon system is inserted between the former two, which has the effect of removing color and odor. has been granted. In FIGS. 3 and 4, 9 is an ozone reaction tank, and IO is an activated carbon adsorption tank.

In the sulfur denitrification reaction, as mentioned above, 5l-9S'
, 5yOs"-, 5-Os"-, S'Os"-, and other reduced sulfur compounds are supplied as electron donors. Among the reduced sulfur compounds, sodium sulfite was selected as one suitable for water purification treatment, but this This is due to the following reasons.

(2) SO3'- produced by dissolving sodium sulfite has the function of lowering the dissolved oxygen concentration, so it is easy to create an anoxic state in which denitrification occurs. Sulfuric acid such as sodium sulfide has a similar effect, but is expensive.

■If reduced sulfur compounds remain after sulfur denitrification treatment, they will react with chlorine and ozone, so the amount of chlorine and ozone injected must be increased.

S Os''- is easily oxidized to so,''- by just aeration and does not react with chlorine or ozone.

■In terms of drug prices, S is the cheapest and has an oxidation number of 0.
It is economical because the amount of chemicals injected is small, but it is inconvenient to handle because it is poorly soluble in water. NatSO
In No. 3, the oxidation number of the S atom is 4, which is the highest among the reduced sulfur compounds, and requires a large amount of chemical injection, but the chemical price is relatively low.

(2) The denitrification rate varies depending on the type of reduced sulfur compound supplied as an electron contributor, and S*Oa"- has the highest denitrification rate, but Na*StOs is not cheap.

Sulfur denitrification reactions require an inorganic carbon source along with reduced sulfur compounds. Inorganic carbon sources include COt, HC
There are Os"-, COs"-, etc., but sodium bicarbonate was selected for the following reasons.

■CO2 dissolves in water and becomes positive (N a tS
Os is alkaline when dissolved in water), and S is convenient in terms of pH adjustment, but the dissolution operation is complicated.

There are chemicals such as NatCOs and CaCOs, but NλtCOs is strongly alkaline and is not convenient from the viewpoint of pH adjustment.

CaCOs has low solubility and is inconvenient to handle.

Further, an increase in Ca''' ions is undesirable because it causes schooling.

■N a HCOs is weakly alkaline and dissolves well in water, making it suitable for ease of p)I adjustment and handling.

The nitrifying solution that flows into the denitrification tank is usually acidic, so even if alkaline chemicals are injected, it still has some buffering capacity. In some cases, it may become necessary to inject acid, and acid injection equipment must be installed.

Sulfur denitrifying and nitrifying bacteria, which play a central role in the nitrification/sulfur denitrification system, are ubiquitous bacteria. As the number increases, it becomes possible to apply it to water purification treatment. Sulfur denitrifying bacteria are acclimated using raw tap water supplemented with nitrate ions, reducing ionic compounds, and inorganic carbon sources. Regarding nitrifying bacteria, it is assumed that they are the same type of nitrifying bacteria that are the dominant species in nitrification/denitrification systems that use organic matter such as methanol as an electron donor, so river water added with ammonia and NaHCOs is supplied. Get used to it.

Since sulfur denitrifying bacteria do not have a flocculating property, increasing the HRT causes them to flow out and reduce the number of bacterial cells.An alternative method of entrapping and immobilizing the acclimatized bacteria to pellet them and supplying them to the sulfur denitrifying tank is also considered.

Na! The sulfur denitrification reaction using S 2 O3 as an electron donor can be expressed as a chemical formula (1).

6 S 03"-+2 N O3→6SOt"-10Nt
...(1) On the other hand, the stoichiometric equation taking into account the bacterial cell production is expressed by equation (2).

3.759SO,”-+N03+Q,337CO,40
,0851CO,-+0.085NH,' →0.08
5CsHtOtN+ 0,5Nt+ 3.759SO,
Mushroom - (2) According to the formula (1), N01- ion 1
It is thought that 3 moles of SO1'-ions are required per mole, but since equation (1) does not take into account the consumption of the inorganic carbon source, equation (2) is closer to reality. As is clear from equation (2), in addition to SOs''-, NH4', CO*, HCO3, and H'' are required to denitrify No3-.

NH," exists in the raw water or nitrifying solution, so there is no need to replenish it unless the nitrifying solution is completely nitrified. Regarding H0 ions, the H° ions in the raw water or nitrifying solution are consumed. , since the pH increases, it is necessary to replenish acid if the pH rises above the optimum pH of 6 to 8, but this is usually not necessary.

3.759 5031- for 1 mol of NOs
moles are required. NO3-N (nitrate nitrogen) 1m9-N
/1. 4.429 m9/6 (0°0
NatSOs for 714 m mole/12)
is 33 in terms of 0.268 m mole/L solid weight
．． 8m9/Q is required.

NatSOs reacts with dissolved oxygen as shown in equation (3).

2SOs"-+ot→2SO,"-...(3) That is,
Dissolved oxygen 1 mV15h a, N at SOs
O.

0625 m mole/, solid equivalent 7.88 m9/C
consume.

The sulfur denitrification reaction occurs after dissolved oxygen reaches zero, so N at S is used to reduce the dissolved oxygen in raw water to zero.
Os must be added.

Therefore, the injection rate of Nλt S Os is expressed by equation (4).

NatSO3 solid injection rate = raw water N03N [ya9-N
/(lkoX33.8[s9#]
+I water-dissolved acid 1 [ms+-0#koX7.88-(4)N
a @ S Os is usually used as a solution, so N
The volume injection rate of the atsOs solution is determined by the purity of the NatSOs solid as P [%] and the concentration of the Na2SO3 solution as C [wt%].
Letting the specific gravity be d, it is expressed by equation (5).

NatSOJ * Sho λ rate = NatSOJ body injection rate [m
9/12] X 100/P[%kof(1/Qko
x 1/dx 100/C [weight $]
- (5) Nλt S Os solution injection amount is calculated by multiplying equation (5) by the flow rate.

On the other hand, the required amount of inorganic carbon source is NO, -N, 1m5-N
/Q, COt is 0.0240m 5ole(G
o, weight as 1.056m9/Q, alkalinity conversion 2
, 4 m9/Q), HCO3 is 0.006 m
5tole(HCO3-0.366m9/ as weight)
12, the alkalinity conversion is 0.6 m9/(2), and in total, the alkalinity conversion is 3 m9/Q, N a
In terms of HCOs solid weight, 2.52 m9/12g a
is necessary. Since natural alkalinity normally exists in tap water, the NaHcOs injection rate is expressed by equation (6).

NaHCO, solid injection rate = (No, -N [m9#!]
X3- Fluidity) Xo, 84 [s9/e]
...(6) If it is normal tap water, (NOs N [m 9/12] x 3
- alkalinity) becomes negative, so it is thought that there is no need to inject NaHCOs, but Fig. 1.

When sulfur denitrification is performed after nitrification, as in the case of nitrification tank 2 shown in FIG. 2, alkalinity may become insufficient and must be replenished. Therefore, in a circulating nitrification/sulfur denitrification system such as sulfur denitrification tank 1 in Figures 1 and 2, the water to be sulfur denitrified is more alkaline than in a nitrification/sulfur denitrification system such as nitrification tank 2. The advantage of the circulating nitrification/sulfur denitrification system is that the water quality suitable for sulfur denitrification is easy to obtain due to the high NH and NH ion concentrations. Also, as is clear from the stoichiometric equation (2), the sulfur denitrification reaction requires H ions.
and Na, SO, since the solution is alkaline, p
H tends to increase. Since the nitrification reaction is a reaction that lowers the pH, it is easier to maintain the pH in the neutral range of 6 to 8, which is the optimum pH for sulfur denitrification, by carrying out the sulfur denitrification reaction after the nitrification reaction.

As described above, when comparing the circulating nitrification/sulfur denitrification system and the nitrification/sulfur denitrification system, there are advantages and disadvantages, and it is difficult to say which one is better.

Figure 5 shows the sulfur denitrification chemical injection control system.
is NO, - concentration meter, 12 is alkalinity meter, 13 is dissolved oxygen concentration meter, 14 is pH meter, 15 is work station,
16 is an operation panel, 17 is a calculation device, 18 is a printer,
19 is a display (CRT), 20 is a NatSOs injector,
21 is a N a HCO3 injector, 22 is an acid injector, 23
is a flow meter.

Water quality was measured for sulfur denitrification treated raw water using N03 concentration meter 1 (measurable by ion electrode method), alkalinity meter 2, dissolved oxygen concentration meter 3, and from the measured values, Nats
The injection rates of Os and N a HCOs are determined by the injection rate determination formula. If the water quality does not fluctuate significantly, the injection rate may be fixed, but if the water quality fluctuates significantly, automatic control is preferable. For automatic control, NO3
N from the measured values of ion concentration, alkalinity, and dissolved oxygen concentration
a Calculate the injection rate of 1SO3 and NaHCOa, perform feedforward control, and adjust the pH of the sulfur denitrification tank to p
Measurement is performed using an H meter 4, and acid injection control is performed using feedback control.

No. - Densitometer 11. Alkalinity liver 12. Dissolved acidity meter 13. The pH meter 14 constitutes a water quality measuring device, and an electrical signal sent from this water quality measuring device enters the workstation 5 and is displayed on the printer 18 and CRT 19. On the other hand, it also enters the arithmetic unit 17 and calculates the drug injection rate. Electrical signals related to drug injection rate are sent to workstation 1.
5, the information is displayed on the printer 18 and CRT 19, and a person operates the operation panel 16 to command the drug injection rate. The electrical signal for the chemical injection rate command is returned to the workstation 15, where the chemical injection rate is calculated in the arithmetic unit 17 based on the electrical signal from the flowmeter 23, and the electrical signal for the chemical injection rate is sent from the workstation 15 to the NatSOs injection. device 20
and is sent to the N a HCOs injection device 21 . 2
pH fluctuated as a result of chemical injection at 0.21
is measured by the pH meter 14, and if the measured pH value deviates from the optimum pH range, the acid injection amount is calculated in the calculation unit 17, and the electric signal of the acid injection amount is sent to the workstation 15.
A signal is sent to the acid injection device 22, and acid injection is performed.

Therefore, the following water purification treatment method and apparatus can be obtained from the first embodiment of the present invention.

Configuration of a total nitrogen removal side sterilization treatment system that combines a circulating nitrification/sulfur denitrification treatment system or a nitrification/sulfur denitrification treatment system and an existing water purification system.

A total nitrogen removal, deodorization, decolorization, clarification, and sterilization treatment system that combines a circulating nitrification/sulfur denitrification treatment system or a nitrification/sulfur denitrification treatment system, an ozone activated carbon treatment system, and an existing water purification system.

Among the above-mentioned treatment systems, especially in sulfur denitrification treatment, the denitrification reaction is normally carried out using organic matter as an electron donor by supplying sodium sulfite as an electron donor and sodium bicarbonate as an inorganic carbon source. A treatment method and a treatment system configuration that are characterized by the ability to cause denitrification reactions even in unattainable raw water.

After sulfur denitrification, a nitrification/sulfur denitrification system is configured with a re-aeration tank to decompose excess reagent and increase dissolved oxygen concentration.

Acclimatization method for sulfur denitrification treatment system and treatment system using comprehensively immobilized sulfur denitrification bacteria.

Method for determining the injection rate of chemicals such as sodium sulfite and sodium bicarbonate in a sulfur denitrification treatment system and N03-
Chemical injection rate determination formula using water quality factors such as N, alkalinity, and dissolved oxygen concentration, and chemical injection amount determination formula using flow rate.

Automatic control method in sulfur denitrification treatment, No. -meter.

Configuration of automatic chemical injection control system for sulfur denitrification using alkalinity, dissolved concentration meter, pH meter, flow meter, etc.

According to the water purification method of the first embodiment, the following advantages can be obtained.

(IA) In water purification treatment where normal biological nitrification and denitrification treatment cannot be applied, biological nitrification and denitrification treatment, which is cheaper in treatment cost than physicochemical methods, can be applied, making it possible to remove total nitrogen. Ta.

(IB) Since ammonia is removed, the amount of chlorine injection in existing water purification processes can be reduced. If the amount of chlorine injection is reduced, the amount of carcinogenic trihalomethanes produced can be reduced.

In the (IC) powder method, the number of NO,- ions decreases, while the number of So,"- ions increases; however, so,
”- is safer than NO,-, so the sanitary safety is relatively high.

(ID) Labor savings can be achieved by enabling automatic control to determine the chemical injection rate necessary for sulfur denitrification using automatically measurable water quality factors.

(IE) Nitrification and sulfur denitrification systems are originally applied to sewage treatment, and chemical injection control systems for sulfur denitrification treatment can also be applied to sewage treatment.

CF-2, Second Embodiment] FIG. 6 shows a water purification treatment method and water purification treatment apparatus according to a second embodiment of the present invention, in which 20 is a Na, S03 injection machine, 21 is a Na HCOs injection machine, and 24 is Na2S2O
It is an injection machine.

In FIG. 6, raw water is converted into N2LtSOs in the NatSOs mixing tank 24 before the sulfur denitrification tank 1.
NatS Os is injected and mixed from the injector 20, and the dissolved acidity concentration is reduced by the reaction of equation (7).

2so, "-+0.→2SO,"-... (7) Next, it flows into the sulfur denitrification tank l, and NatS, 0. Na, S, 03 from the injection device 24 and the Na HCOs injection device 21
and N a HCOs are injected, and due to the denitrification reaction by sulfur denitrifying bacteria, N01− in the raw water is reduced to nitrogen, and S,0? - is oxidized to so,'-.

The stoichiometric formula for the sulfur denitrification reaction using Na, S, and 03 as electron donors is expressed by equation (8).

0.844 S+03”-+ F2O3-+0.347
COt+ 0.0865 HCO3-+0.865
Ni1. ″+0.434 H*0→0.0865CsH
JJ+0.5Nt"1.689SO4"-+0.697
H''-(8) (7), Na calculated using formula (8),
The chemical injection rate formula for So and Na2S2Os is (9),
It is expressed as (10).

NatSOs solid injection rate = UIHH concentration [ts9・
o/(l) X'1.88- (9) [119/1
21 NalStOs solid pressure λ rate = i tree NOs N
[m9・N/Qco X9.35・ (10) [s12/
12] NOs N 1m9/Q is 4.4 as NOa-
2 m9/(1= 0.0714 m 5ole/12
, the required number of moles of St's''- for 1 mol of NO3- is 0.844 mol, and the molecular weight of NapS,03 is 15 g, so N a * S
t Oa is 0.0714x O,844x 15g=
9.53 m9/Q is required.

NO3'', DO are measured and using equations (9) and (10), N a t S Os and N a t S t O
If 3 is injected, biological sulfur denitrification is possible.

In the second embodiment, the following water purification method and water purification apparatus cannot be obtained. In other words, N in biological nitrification and sulfur denitrification systems applicable to water purification
A configuration of a sulfur denitrification system that reduces the dissolved oxygen concentration in raw water by a y S Os and supplies Na2S2Os as an electron donor.

Nats Os and Na*5 in this system
Method for determining chemical rate such as t03 and chemical injection rate formula using water quality factors such as NOs − and dissolved acidity concentration.

Further, according to the water purification method of the second embodiment, the following advantages can be obtained.

(2A) In water purification treatment where normal biological nitrification and denitrification treatment cannot be applied, biological nitrification and denitrification treatment, which is cheaper in treatment cost than physicochemical methods, can be applied, making it possible to remove total nitrogen. Ta.

(2B) Since ammonia is removed by nitrification treatment, the amount of chlorine injection in existing water purification processes can be reduced. If the amount of chlorine injection is reduced, the amount of carcinogenic trihalomethanes produced can be reduced.

(2C) In this system, when Na*S03 and Nats to s are used together, the injection rate of chemicals that convert sulfur atoms can be reduced compared to when Na1SOs is used alone, and the S04 that is finally generated! - It has the effect of reducing the amount of ions.

(2D) Nitrification/sulfur denitrification systems are originally applied to sewage treatment, and the sulfur denitrification chemical injection control system of the present invention can also be applied to sewage treatment.

(F-3, Third Example) FIG. 7 shows a biological nitrification/sulfur denitrification system for water purification in the water purification apparatus according to this example, and 24 is a Nat.
SOs mixer, 25 is NatS*Os injection machine.

In this example, as shown in FIG.
8 alone or with Na1SOs and N ats +
When used in combination with 03, it reduces the dissolved oxygen concentration and uses it as an electron donor in the sulfur denitrification reaction, promoting the denitrification reaction by sulfur denitrifying bacteria. It has the advantage that it can be applied to water purification processes where reactions cannot be applied.

FIG. 8 shows a total nitrogen removal biological activated carbon treatment system for water purification in the water purification treatment apparatus according to this embodiment, where 26 is a nitrifying bacteria-immobilized activated carbon tower, 27 is a sulfur-denitrifying bacteria-immobilized activated carbon tower, and 28 is an aeration system. It's a tank.

In Fig. 8, raw water to be treated, such as tap water, coagulated sedimentation water, and ozonated water, first flows into the nitrifying bacteria-immobilized activated carbon tower 26, which is the same as a normal biological activated carbon treatment device, and ammonia is nitrified by the action of the nitrifying bacteria. Ru. Next, in the NatSO3 mixing tank 24, Nat is injected from the NatSOs injection machine 20.
An appropriate amount of SOs is injected according to the formula (l l) to bring the dissolved oxygen concentration to zero.

2 S Q,”-+ ot-2S O,”-...(1
1) Next, Na*5yOs injector 25 and NaHC,0
° NatSt03 and NaHCO3 are injected from the injector 21. In addition, normal tap water contains sufficient natural alkalinity as an inorganic carbon source, so
There is no need to inject N a HCO3.

Next, it flows into the sulfur denitrification bacteria immobilized activated carbon tower 27, and the 5ho
A sulfur denitrification reaction occurs using s''- as an electron donor.

The stoichiometric formula for the sulfur dechambering reaction is expressed by equation (12).

0.8445t03”-+ No,-+ 0.347
COx + 0.0865 HCO3 + 0.865 N
B,"+0.434)1.0→0.Q865C5H,
OJ+0.5N! +1.689SO,”+0.697H
"・-(12) The chemical injection rate formulas for Na*S Os and NaHCO3 calculated using the formulas (11) and (12) are expressed by (3) and (4).

NatSO3! Body pressure λ rate = UIHHIf [a+y・O
/Q] x7.8g-(13) [Set 9/e] NatS, Os1 body i person rate = I tree NO, -N [I
Ig-N/Q co x9.35-(14) [s9#! ] In the sulfur denitrifying bacteria immobilized activated carbon tower 27, NO3− is
, S, 0-- becomes S04'-, but then the aeration tank 28
All of the excess SOs"- and a portion of the 5tOs"- are oxidized and further increases the dissolved oxygen concentration before entering the existing clarification and sterilization system or sterilization system.

Excess N at S t Os reacts with chlorine as shown in equation (15) and is oxidized to so,''-.

NaHCO3+ 4CQt + 5HtO-2NaCI
2+ 2H*SO4+ 6HC(1-(15)) Total nitrogen removal is possible without adversely affecting the existing water purification process as above.

Furthermore, according to the water purification method and apparatus of the third embodiment, the following can be roughly obtained.

A total nitrogen removal treatment method for water purification that combines a nitrifying bacteria-immobilized activated carbon tower filled with granular activated carbon immobilized nitrifying bacteria and a sulfur denitrifying bacteria-immobilized activated carbon tower filled with granular activated carbon that immobilized sulfur denitrifying bacteria, and System unit configuration.

In order to impart denitrification ability to the sulfur denitrifying bacteria-immobilized activated carbon tower, NatS03 is injected into the effluent water of the nitrifying bacteria-immobilized activated carbon tower to reduce the dissolved oxygen concentration, and then the electrons of the sulfur denitrification reaction are Nat S 103 as donor.

A sulfur denitrification treatment method for water purification treatment and a configuration of a system device, which comprises a system for injecting N a HCOa as an inorganic carbon source and an aeration tank for increasing dissolved oxygen concentration after a sulfur denitrification reaction.

The above-mentioned total nitrogen removal method and system device configuration for secondary treated water of a sewage activated sludge treatment system.

Furthermore, according to the water purification method of the third embodiment, the following advantages can be obtained.

(3A) By immobilizing non-aggregating sulfur denitrifying bacteria on activated carbon, it is possible to prevent bacteria from flowing out even when the water flow rate is increased, making it easy to maintain the number of bacterial cells.

(3B) Ammonia is removed by nitrification, so
The amount of chlorine injection can be reduced. It can also reduce the amount of trihalomethane that is harmful to health.

Although this system increases sulfate ions in the treated water, sulfate ions are hygienically harmless, and nitrate ions, which are harmful to health, can be removed.

(3C) In water purification treatment where normal biological nitrification and denitrification treatment cannot be applied, biological nitrification and denitrification treatment, which is cheaper in treatment cost than physicochemical methods, can be applied, making it possible to remove total nitrogen.

(3D) This treatment system can also be applied to secondary treated water of a sewage activated sludge treatment system, and can remove total nitrogen from sewage.

G8 Effects of the Invention The present invention is as described above. According to the second and third inventions, since sodium sulfite is supplied to raw water as an electron donor and an inorganic carbon source is supplied to carry out sulfur denitrification treatment, carcinogenic toxic substances are reliably removed. It can be removed, improving safety and saving labor.

According to the fourth invention, the dissolved oxygen concentration in raw water is reduced by N a I S Os in a biological nitrification sulfur denitrification system applicable to water purification treatment, and N a
Since the sulfur denitrification treatment is carried out by supplying Oa as an electron donor, a water purification treatment method that is low in treatment cost and can effectively remove toxic substances can be obtained.

Fifth. According to the sixth invention, raw water is passed through nitrifying bacteria-immobilized activated carbon to nitrify ammonia, and after the ammonia has been nitrified, Na and SO are supplied to the raw water to lower dissolved oxygen. , O, and N a HCOs
Since the treatment is carried out by injecting water, it is possible to maintain the number of bacterial cells, reduce the treatment cost, and obtain an effective water purification treatment method that can remove total nitrogen and easily remove toxic substances.

[Brief explanation of the drawing]

Figures 1 to 5 relate to the water purification treatment method according to the first embodiment of the present invention, Figure 1 is a block diagram of a system that combines circulating nitrification and denitrification with an existing system, and Figure 2 is a total nitrogen removal system. Figure 3 is a block diagram of a system that combines cyclic nitrification and sulfur denitrification, ozone - activated carbon and an existing system, Figure 4 is a block diagram of a system that combines nitrification and sulfur denitrification, and ozone - Fig. 5 is a block diagram of a system combining activated carbon and an existing system, Fig. 5 is a block diagram of a sulfur denitrification chemical injection control system, and Fig. 6 relates to a water purification method according to a second embodiment of the present invention. The block diagrams of the treatment system, FIGS. 7 and 8, relate to the water purification treatment method according to the third embodiment of the present invention, and FIG.
Block diagram of sulfur denitrification system, FIG. 8 is a block diagram of total nitrogen removal biological activated carbon treatment system. ■... Sulfur denitrification tank, 2... Nitrification tank, 3... Reaeration tank, 4... Sedimentation tank, 5... Rapid mixing tank, 6... Coagulation sedimentation tank, 7... Sand filter pond, 8...Circulation pump, 9
...Ozone reaction tank, IO...Activated carbon adsorption tank, 11.
・・NO, -densitometer, 12・alkalinity liver, 13・
...Dissolved oxygen meter, 14...pH meter, 15...Work station, 16--Operation panel, 17--Arithmetic unit, 18--Printer, 19-CRT, 2O-Na
, SO, injection device, 2l-NaHcO3 injection device, 22
... Acid injection device, 23 ... Flow meter, 24 ... Na
tSOs mixing tank, 25-NatS, 03 injection device, 26
... Nitrifying bacteria immobilized activated carbon tower, 27... Sulfur denitrification bacteria immobilized activated carbon tower, 28... Aeration tank. (Combination of circulating nitrification/sulfur denitrification and existing systems) 4.
... Shen RFa 8... wII Pon 7th 5th
Figure (Sulfur denitrification agent injection control system) 23...air Figure 6 25-Na2S203a person 1tct Figure 8 28...@Kixing April 4, 1991

Claims (6)

[Claims] (1) Supply sodium sulfite as an electron donor and sodium bicarbonate as an inorganic carbon source to the raw water to be treated, perform sulfur denitrification treatment on the raw water, and coagulate into the sulfur denitrified raw water. 1. A water purification treatment method, which comprises injecting and mixing an agent to coagulate and precipitate sludge, and then injecting nitrate into the raw water for nitrification treatment. (2) Sulfur denitrification treatment is performed on the raw water by supplying sodium sulfite and sodium bicarbonate as electron donors and sodium bicarbonate as an inorganic carbon source to the raw water to be treated. A water purification method characterized by subjecting raw water to an ozone reaction and removing activated carbon, and then injecting nitrate for treatment. (3) Calculate the injection rate of sodium sulfite and sodium bicarbonate to be injected into the raw water to be treated based on water quality factors consisting of nitrate concentration, alkali concentration and dissolved oxygen concentration, and perform feedback control to remove sulfur. A water purification method characterized by measuring the pH value of raw water after nitrogenization and controlling acid injection by feedback control. (4) Na_2SO_3 or Na_2 in the raw water to be treated
A water purification treatment method characterized in that after injecting S_2O_3 to lower the dissolved oxygen concentration, Na_2S_2O_3 is supplied to the raw water as an electron donor to perform sulfur denitrification treatment. (5) The raw water to be treated is passed through nitrifying bacteria-immobilized activated carbon to nitrify the ammonia in the raw water, and after the ammonia has been nitrified, Na_2SO_3 is supplied to the raw water to reduce the dissolved oxygen concentration, Na_2S_2O_3 and N
A water purification treatment method characterized by treatment by injecting aHCO_3. (6) In claim 5, using a water quality factor consisting of NO_3 or dissolved oxygen concentration, Na_2SO_3 or Na
A water purification treatment method characterized by determining an injection rate of _2S_2O_3.