JP2002221518A - Water quality monitor and controller for water treatment process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently maintain concentration of nitrogen or phosphor in treatment water by rapidly grasping accurate alkalinity and properly controlling an injected flocculant amount in a water treatment process. SOLUTION: Treated liquid such as mixed liquid, inflow sewage 13 or the treatment water 16 is directly led into a biological reaction tank 1, the true alkalinity is found by an alkalinity measurement device 41, the flocculant injection amount is found by a calculation device 50 by use of the found alkalinity value, and a controller 55 is controlled on the basis of the result. The alkalinity measurement device 41 has a titration device 411 measuring an acid consumption amount on the basis of a pH set value from a pH setting circuit 412, a calculation circuit 413 finding temporary alkalinity from the acid consumption amount, and a calculation circuit 414 finding the true alkalinity on the basis of the temporary alkalinity and the pH set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the monitoring of water quality of municipal sewage, industrial effluent, river water, lake water or dam lake water, and biological treatment or physical treatment of organic substances, nitrogen and phosphorus dissolved in these waters. In the water treatment process that removes by chemical coagulation, especially when biological or organic or inorganic substances are suspended, the exact alkalinity can be grasped. The present invention relates to a water quality monitoring method and a control method for adjusting a coagulant to be injected for the purpose of (1) and maintaining nitrogen and phosphorus concentrations in treated water at target values.

[0002]

2. Description of the Related Art In a sewage treatment plant, domestic wastewater and industrial wastewater are treated by the reaction of a complex microorganism group called activated sludge. Sewage contains nitrogen and phosphorus in addition to organic matter. Nitrogen is mainly NH4-N, and phosphorus is orthophosphoric acid (hereinafter PO).
4-P) flows into the sewage treatment plant. If the water is released without removing these nitrogen and phosphorus, eutrophication proceeds in the discharge water area, and the water quality is further deteriorated due to abnormal reproduction of algae and the like.
Therefore, a sewage treatment plant is required to have an advanced treatment capable of removing nitrogen and phosphorus in addition to organic matter.

[0003] Activated sludge contains organic matter-decomposing bacteria, nitrifying bacteria, denitrifying bacteria, phosphorus-accumulating bacteria, and the like. In advanced treatment, the metabolic function of these microorganisms is effectively exerted to remove organic matter, nitrogen, and phosphorus. Remove. Advanced treatment requires two or more reaction tanks, an anaerobic tank and an aerobic tank, and there are various treatment methods depending on the combination of the reaction tanks. As a typical method,
Anaerobic-anoxic-aerobic method (A2O method), Anaerobic-aerobic method (AO
Method), anaerobic-aerobic-anoxic-re-aeration method (AOAO method or two-stage anaerobic-aerobic method), anoxic-aerobic method (activated sludge or nitrification liquid circulation modified method), and the like. The A2O and AOAO methods can be expected to improve the removal rate of nitrogen and phosphorus, the activated sludge circulation method can improve the nitrogen removal rate, and the AO method can improve the phosphorus removal rate. As described above, there are various types of advanced treatment, but the principle of removing nitrogen, phosphorus, and organic substances is common.

[0004] Nitrogen flows in as ammoniacal nitrogen NH4-N, and is subjected to nitrification reaction of formula (1) in an aerobic tank to produce nitrate nitrogen NO3.
-N, and NO3-N is removed in a two-stage reaction in which nitrogen gas is obtained by the denitrification reaction of the formula (2) in the anaerobic tank. A2O
Method and activated sludge circulation method, NH4-N in NO2
The nitrification reaction to oxidize to -N is advanced, and the nitrification reaction liquid is circulated to the anoxic tank in the preceding stage to perform a denitrification reaction for reducing NO3-N to N2 or the like with an organic substance to remove nitrogen. In the AOAO method, NO3-N generated in the first aerobic tank is reduced to N2 or the like in the subsequent anoxic tank to remove nitrogen.

[0005] The nitrification reaction is NH4-N → NO2-N → NO3-
N, the denitrification reaction is said to follow the reaction form via nitrous acid (NO2-N) in the order of NO3-N → NO2-N → N2,
In the formulas (1) and (2), these reaction routes are omitted.

NH4 ++ 2O2 → NO3− + 2H ++ H2O (1) 2NO3− + 5 (H2) → N2 ↑ + 2OH− + 4H2O (2) In the nitrification reaction of the formula (1), if an alkali component is present,
It reacts with the generated hydrogen ions to lower the alkalinity. When the alkalinity is 1 mg / L NH4-N is nitrified,
Decrease by 7.14 mg / L. Conversely, in the denitrification reaction of the formula (2), hydroxyl ions are generated, and when 1 mg of NO3-N is removed, the alkalinity increases by 3.57 mg.

[0007] On the other hand, phosphorus is removed by utilizing the excess sludge intake function of activated sludge (phosphorus accumulating bacteria). Phosphorus-accumulating bacteria once release intracellular phosphorus under anaerobic conditions,
When the released bacteria are brought into an aerobic state, phosphorus is more likely to be taken into cells than released.

[0008] In the A2O method, the AO method and the AOAO method, by disposing the anaerobic tank in the first stage and the aerobic tank in the second stage, it is possible to biologically remove the phosphorus in the inflowing sewage. The function of excess phosphorus ingestion of activated sludge varies depending on the quality of inflow sewage water, plant operating conditions, or the management state of activated sludge, and may cause poor discharge or poor intake to increase the phosphorus concentration in treated water. For this reason, the sewage treatment plant uses a method of injecting a flocculant and removing it physically and chemically.

As the coagulant, an aluminum or iron-based metal salt or slaked lime is used. Phosphorus in the solution is orthophosphoric acid
It exists in the form of PO4-P and condensed phosphoric acid, and forms a sparingly soluble salt upon injection of a flocculant. Further, the flocculant also reacts with an alkaline component such as bicarbonate HCO3. The reaction formula when an aluminum-based flocculant is used is represented by formulas (3) and (4).

[0010] Al3 ++ PO43- → AlPO4 ↓ (3) Al3 ++ 3HCO3-- → Al (OH) 3 ↓ + 3CO2 (4) The hydroxide formed by the formula (4) becomes a floc and further removes phosphorus by adsorption. (Literature 1: Tsuneo Murata, edited by "Advanced Sewage Treatment Technology", Science and Engineering Books, 1992).

As described above, in the advanced sewage treatment, the alkalinity is an important factor as a monitoring index of the progress of the nitrification / denitrification reaction, a judgment index for operation management, and an operation index for the coagulant injection amount. Alkalinity is the amount of acid required to neutralize alkali components, such as carbonates, bicarbonates and hydroxides, contained in water to a predetermined pH, by the corresponding concentration of calcium carbonate. It is a representation.

The alkalinity includes M alkalinity at which the pH at the neutralization point is 4.8 (also called total alkalinity) and pH 8.3 at the neutralization point.
There are two types of P alkalinity. Influent sewage pH ranges from 6.8 to 8.3, effluent pH
Ranges from 6.3 to 7.7. For this reason, in sewage treatment plants,
P alkalinity cannot be measured, and M alkalinity with a neutralization point pH of 4.8 is targeted. The measurement of M alkalinity is a predetermined amount
A sample of (La mL) is titrated with an acid using a pH meter until the pH becomes 4.8, and the amount of acid (Da mL) required for the titration is determined, and calculated by equation (5).

M alkalinity (mgCaCO 3 / L) = 1000 · Da · F · Kc / La (5) Here, F is a factor of the acid used, and Kc is a calcium carbonate equivalent value of 1 mL of the acid (Reference 2; Japan Sewage Works Association, "Sewage test method-Volume 1", 1997 edition, P120-122). Since then
M alkalinity is simply referred to as alkalinity.

A device for automatically measuring alkalinity has been put to practical use for purified water. If the test sample to be titrated contains a turbid substance from which an alkaline component elutes or a solid component that interferes with measurement, a pretreatment operation for separating and removing these suspended substances in advance is required. As means for separation and removal, a centrifugal separation method and a method using a filter paper are known (Reference 3; Japan Water Works Association "Water supply test method", 1993 edition, p. 58).

In a sewage treatment plant, when alkalinity is measured for a sample containing activated sludge, centrifugation is performed.
It is stated that the supernatant is used as a liquid to be titrated (Reference 2; P293, P300).

Furthermore, the centrifugal separation method and the method using filter paper have a problem that the removal rate of suspended substances is low and the measurement accuracy is reduced. A water quality monitoring method (Japanese Patent Laid-Open No. 5-212399) has been proposed.

Regarding sewage treatment control using alkalinity as an operation management index, a method of adjusting and controlling the amount of organic carbon source injected into a denitrification tank based on the total alkalinity change in a nitrification tank (JP-A-56-53795) JP-A-9-38), a nitrification reaction state is determined by calculating an amount of nitrified nitrogen from an alkalinity change amount of a nitrification tank, and a factor affecting nitrification is adjusted (Japanese Patent Laid-Open No. 9-38)
No. 682).

[0018]

SUMMARY OF THE INVENTION The above-mentioned JP-A-5-21
The alkalinity measurement method of No. 2399 determines the effect of digested sludge on acid-alkali titration, and based on the result that solid-liquid separation means is indispensable (Japanese Patent Laid-Open No. 5-253600), the solid-liquid separation performance is higher than that of other prior arts. The ultrafiltration apparatus, which is superior in the above, is adopted as the pretreatment means.

The ultrafiltration apparatus generally uses a membrane having a pore size of 20 to 0.2 μm, and performs solid-liquid separation under pressure or under reduced pressure. On the membrane surface on the side of the liquid to be filtered, the amount of suspended substances attached increases with the filtration time and the filtration performance decreases, so that a membrane cleaning means for removing the attached matter is required. In addition, the performance of the filtration membrane deteriorates due to deterioration and damage or clogging of the pores that are not improved even after backwashing.Therefore, check and monitor the filtration flow rate, the concentration of suspended solids in the filtrate, and the pressure loss. Need to be replaced.

JP-A-56-53795 and JP-A-9-38682 for the purpose of operation control are also provided with activated sludge separating means such as membrane filtration, centrifugal separation, or gravity sedimentation. A method is used in which the alkalinity of the supernatant is measured by a titration method. In these methods, since a solid-liquid separation unit is provided in addition to the alkalinity meter, equipment and operation costs are increased, and further, maintenance and inspection work is required, and the work load of the operation manager is increased. In addition, since the reaction proceeds even during the pretreatment, the water quality changes. The alkalinity is a water quality that is particularly liable to change, regardless of whether the liquid to be filtered is in an aerobic state or an anaerobic state, because it is affected by both nitrification and denitrification reactions.

In view of the above-mentioned state of the prior art, the object of the present invention is to eliminate the need for installing a pretreatment means for solid-liquid separation of activated sludge, and to directly titrate even a mixed liquid containing activated sludge to reduce the alkalinity. An object of the present invention is to provide a simple water quality monitoring device capable of promptly measuring with high accuracy and a control device for a water treatment plant using the water quality monitoring method.

[0022]

A water quality monitoring apparatus according to the present invention which achieves the above object has a pH setting circuit for setting a pH of 4.8 as a reference value and inputting a pH set value higher than the pH reference value, Introducing a sample to be titrated, the pH of the sample to be titrated
A titrator for neutralizing with an acid so as to have a pH set value output from the H setting circuit, an acid consumption measuring circuit for measuring the amount of acid consumed for neutralization by the titrator, and the acid consumption measurement value A provisional alkalinity calculating circuit for obtaining a provisional value of the alkalinity at the pH set value, and an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value at the pH set value, and the alkalinity prediction coefficient and the An alkalinity calculation circuit for calculating the alkalinity at the pH reference value from the provisional alkalinity is provided, and the calculated alkalinity value is output as the true alkalinity of the test water to be titrated.

The water quality monitoring device of the present invention has a pH of 4.8.
Is a reference value, a pH setting circuit for inputting a pH set value higher than the pH reference value, and a predetermined amount of the test water to be titrated is introduced, and the pH of the test water to be titrated is the pH output from the pH setting circuit.
A titrator for neutralizing with an acid so as to be a set value, an acid consumption measuring circuit for measuring an amount of acid consumed for neutralization by the titrator, and an acid consumption amount of the pH reference value at the pH set value. An acid consumption prediction coefficient to be predicted, an acid consumption calculation circuit for calculating an acid consumption of the pH reference value from the acid consumption prediction coefficient and the acid consumption measurement value at the pH set value; An alkalinity calculation circuit for calculating alkalinity from the consumption calculation value is provided, and the alkalinity calculation value is output as the true alkalinity of the test water to be titrated.

In the above-mentioned present invention, the test water to be titrated is suspended by the inflow sewage or activated sludge in the sewage treatment process in which organic matter, nitrogen and phosphorus in inflow sewage such as domestic wastewater and industrial wastewater are removed by activated sludge. It is a mixed liquid of activated sludge which becomes turbid or a supernatant obtained by solid-liquid separation of the activated sludge of the mixed liquid.

Further, the water quality monitoring apparatus of the present invention has a pH setting circuit for inputting a pH reference value of 4.8 and a predetermined amount of test water to be titrated, and the pH of the test water to be titrated is set to the pH setting circuit. A titrator for neutralizing with an acid so as to have a pH reference value output from the apparatus, an acid consumption measuring circuit for measuring an amount of acid consumed for neutralization by the titrator, and an activated sludge concentration in the test water to be titrated. Sludge concentration measurement circuit to measure pH and pH reference value of 4.8
The amount of acid consumed by the activated sludge per unit weight beforehand is set in advance, and the amount of acid consumed by the activated sludge obtained by integrating the sludge concentration from the sludge concentration measuring circuit is determined by the acid consumption of the acid consumption measuring circuit. An acid consumption correction circuit for calculating an acid consumption correction value by subtracting from the measured amount value; and an alkalinity calculation circuit for calculating alkalinity based on the acid consumption correction value. It is characterized in that the titration sample is output as a true alkalinity in a state not containing activated sludge.

Alternatively, a water tank comprising a reaction tank for removing pollutants in the water to be treated by a biological reaction, and a sedimentation tank for sedimenting suspended substances in the effluent of the reaction tank and using the supernatant as treated water. In the water quality monitoring device of the treatment process, pH 4.8
A pH setting circuit for inputting as a set value and a predetermined amount of a test water to be titrated are introduced, and a titration for neutralizing with an acid so that the pH of the test water to be titrated becomes the pH set value output from the pH setting circuit. A device, an acid consumption measuring circuit for measuring the amount of acid consumed for neutralization in the titrator, and the pH value from the acid consumption measurement value.
A first arithmetic circuit for calculating the alkalinity at a set value, a means for measuring the biological concentration of the test water to be titrated, and an alkali which has increased in organisms until the pH of the test water to be titrated reaches the pH set value. The alkalinity correction coefficient for correcting the degree is input, and the titration test water at the pH set value from the alkalinity correction coefficient, the alkalinity calculation value of the first calculation circuit, and the biological concentration measurement value includes living organisms. A second arithmetic circuit for calculating the alkalinity in the absence state, wherein the second arithmetic value is output as the true alkalinity of the test water to be titrated.

The control device for the water treatment process of the present invention comprises a reaction tank for removing or suspending pollutants in the water to be treated by a biological reaction and / or a physicochemical reaction by adding a flocculant, and an effluent of the reaction tank. In a water treatment process provided with a sedimentation basin in which suspended substances in the sediment are settled and the supernatant liquid is treated water, a reference pH value as a reference and a higher p value than the reference pH value
H set value, and an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value with the pH set value, introducing a predetermined amount of titration test water from the water to be treated, and adjusting the pH of the titration test water Neutralize with an acid so as to reach the pH set value, measure the amount of acid consumed by the neutralization, and calculate the p from the measured value of the acid consumption.
A provisional value of the alkalinity at the H set value is obtained, and an alkalinity measuring device for calculating the alkalinity at the pH reference value from the provisional value of the alkalinity and the alkalinity prediction coefficient is provided. Is used to adjust the amount of operation affecting the reaction of the water treatment process.

A biological reactor for removing pollutants in the water to be treated by a biological reaction, a sedimentation pond for sedimenting suspended substances in the effluent of the biological reactor and treating the supernatant as treated water, In a water treatment process including a coagulant injection facility between the biological reaction tank or the sedimentation tank or the biological reaction tank and the sedimentation tank, a reference pH reference value, and a pH set value higher than the pH reference value, and Setting an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value with the pH set value;
A predetermined amount of titration test water is introduced from the water to be treated, neutralized with an acid so that the pH of the titration test water becomes the pH set value, and the amount of acid consumed in the neutralization is measured. Obtain a provisional value of alkalinity at the pH set value from the measured value of acid consumption,
An alkalinity measuring device for calculating the alkalinity at the pH reference value from the provisional value of the alkalinity and the alkalinity prediction coefficient, and a phosphorus concentration meter for measuring the phosphorus concentration of the water to be treated, wherein the alkalinity measuring device The injection amount from the coagulant injection equipment is adjusted using the calculated value of the above and the measurement value of the phosphorus concentration meter.

Alternatively, a pH reference value as a reference, a pH set value higher than the reference value, and the pH set value
A setting circuit for setting an alkalinity prediction coefficient for predicting the alkalinity of a reference value, and measuring an acid consumption amount with a predetermined amount of water to be treated as the pH setting value, and calculating the acid consumption amount and the alkalinity prediction coefficient from the acid consumption amount and the alkalinity prediction coefficient. A first arithmetic circuit for calculating the alkalinity at the pH reference value, a coagulant is injected into the water to be treated so as to have a predetermined concentration, and a predetermined amount of a liquid into which the coagulant is injected is set as the pH set value. A second arithmetic circuit for measuring an acid consumption amount and calculating an alkalinity at the pH reference value from the acid consumption amount and the alkalinity prediction coefficient, wherein two alkalinities by the first and second arithmetic circuits are provided; And calculating the phosphorus concentration of the water to be treated based on the coagulant injection concentration, determining the phosphorus release or intake state of the activated sludge from the phosphorus concentration, and adjusting the manipulated variable affecting the release or intake response. And

Further, in a water treatment process having a mixing pond, a floc forming pond, and a sedimentation pond, wherein a coagulant is injected into the mixing pond or raw water flowing into the mixing pond, a pH reference value as a reference, and the reference value A higher pH set point and the p
Setting an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value with the H set value, measuring an acid consumption amount with a predetermined amount of the water to be treated before injecting the flocculant as the pH set value, An alkalinity measuring device for calculating the alkalinity at the pH reference value from the consumption and the alkalinity prediction coefficient is provided, and the calculated alkalinity and the suspended substance concentration and / or the pH and / or the water temperature in the water to be treated are provided. The injection amount of the coagulant is adjusted by using the measured value of (1) to calculate the coagulant injection amount.

The operation of the present invention will be described. The present invention relates to (1) a pH in which the pH-alkalinity characteristics of the activated sludge mixed liquid and the clarified liquid obtained by separating the activated sludge of the mixed liquid are the same.
A range exists, and the provisional alkalinity of the activated sludge mixture obtained in this pH range and the true alkalinity of the clarified solution (pH = 4.
8) correlates and can be formulated. (2) This pH range is not affected by changes in activated sludge concentration or alkalinity. (3)
The alkalinity of the activated sludge mixture obtained at pH = 4.8 was higher than that of the clarified liquid, and the change was proportional to the activated sludge concentration. Less than,
The pH-alkaline property of the present invention and the effect of the activated sludge concentration on this property will be described.

FIG. 3 shows the relationship between acid consumption and pH change characteristics when the activated sludge concentration is changed.
Activated sludge concentration (hereinafter referred to as MLSS) can be measured in four steps by allowing the activated sludge mixed liquid sampled from the biological reaction tank of the actual sewage treatment plant to stand to precipitate sludge and changing the amount of the supernatant liquid to be discarded. Was changed to. Therefore, the alkalinity is almost the same under all conditions, and only the MLSS is different.

The relationship between the amount of acid added and the pH was determined by preparing three samples of the activated sludge mixture, the supernatant of this mixture centrifuged, and the filtrate of 0.45 μm filter paper for each sludge concentration. . The pH tends to be higher when centrifugation and filtration with filter paper are performed, but the acid consumption at the end point at which the pH reaches 4.8 was consistent. As shown in equation (5), the alkalinity is proportional to the amount of acid consumed. Therefore, the alkalinities of the centrifuged supernatant and the filtrate are the same, indicating that the pretreatment has no effect on the alkalinity. Was. In the case of an activated sludge mixture, the acid consumption at the end point of pH 4.8 increases as the sludge concentration increases, affecting the alkalinity. PH matching
Region exists. It has been found that this pH range is in the range of 6.5 to 5.5, and tends to narrow as the sludge concentration increases.

FIG. 4 shows the result of FIG. 3 converted into alkalinity.
The alkalinity at the pH = 4.8 of the supernatant was set to a true value, and the alkalinity obtained at each pH was set as a provisional value, and an alkalinity ratio (= provisional value / true value) was determined to show the relationship with the pH. is there. As for the alkalinity ratio, when the pH was around 6.0, the mixture, the supernatant and the filtrate showed almost the same value, and were not affected by the sludge concentration.

FIG. 5 shows a sample of activated sludge mixed from an anaerobic tank, an anoxic tank and an aerobic tank of a plant operated by the A2O method, and the acid addition amount and pH characteristics were determined. This is the result of the arrangement. These samples have almost constant sludge concentration and differ in alkalinity. Also in this result, the alkalinity ratio at pH around 6.0 showed the same value in all the samples, and it was found that the alkalinity ratio was not affected.

FIG. 6 shows the relationship between the provisional value of alkalinity and the true value at three points in the pH range of 6.5 to 5.5. The relationship between the two can be approximated by a straight line, and the slope becomes gentler and closer to 1 as the pH becomes lower. This slope is defined as a ratio of the provisional value to the true value, and is defined as an alkalinity prediction coefficient Ke for predicting the true value from the provisional value. Thus, a linear approximation formula is obtained for each pH, and the relationship between the alkalinity prediction coefficient Ke and the correlation coefficient for pH is shown in FIG.

In FIG. 7, when the pH is in the range of 5.5 to 6.2, the correlation coefficient is 0.95 or more, and the true value can be predicted from the provisional value with high accuracy. This range is referred to as a pH optimum range. Note that the optimum value exists near pH = 5.8 at which the correlation coefficient becomes almost 1. p
H and the alkalinity prediction coefficient Ke have an exponential correlation,
In the optimal range, it can be expressed by a linear expression.

From the above experimental findings, there is a pH optimum range for predicting alkalinity that is not affected by the activated sludge concentration or alkalinity. By determining the provisional alkalinity of the activated sludge mixed solution within this range, clarification is performed. The true alkalinity of the solution (pH = 4.8) can be predicted. Since the alkalinity of the supernatant and the filtrate at the pH of 4.8 is the same, these are collectively called a clarified solution, and the true alkalinity may be obtained from the supernatant or the filtrate. The prediction formula has been formulated based on the results of FIG.

FIG. 7 shows that the alkalinity prediction coefficient Ke in the optimum range is a pH set value for provisional alkalinity measurement.
Assuming that pHs, it can be obtained by equation (6). Furthermore, pH =
The alkalinity true value ALi of 4.8 is obtained by the product of the prediction coefficient Ke and the provisional value ALs as in equation (7). Here, a and b are constants, which are 0.89 and 3.86 according to the empirical formula.

Ke = a · pHs−b (6) ALi = Ke · ALs (7) By the way, the relations of the equations (6) and (7) are not limited to the activated sludge mixed liquid, but also the supernatant liquid and the filtrate. Or to river water. Since the relationship shown in FIG. 7 was obtained including the supernatant and the filtrate, it means that a sludge separation liquid and a liquid originally containing no sludge can be satisfied.

The above alkalinity monitoring method can be realized by combining an alkalinity meter already in practical use for water supply and the like with a small-capacity computing unit. The pH titration target value of the alkalinity meter is changed from 4.8 to the range of 5.5 to 6.2, and the output alkalinity is set as a provisional value by the arithmetic unit using the formulas (6) and (7).
The calculation of the expression is executed to output the alkalinity true value ALi.

According to the alkalinity monitoring method of the present invention, it is not necessary to provide a pretreatment means for solid-liquid separation of activated sludge, and a mixed solution containing activated sludge is directly titrated.
There is no change in water quality and alkalinity can be measured with high accuracy. Since there is no pretreatment means, no new equipment and operating costs are required, and no maintenance and inspection work is required. In addition, to increase the pH titration target value, it is possible to reduce the acid consumption required for titration,
It is economical. Further, since the target value of the pH titration is set to 5.5 or more, the titration treatment liquid does not need to be neutralized and can be discharged.

FIG. 8 shows the titration end point value (pH =
It is the result of comparing the alkalinity of the sludge mixed solution and the centrifuged supernatant in 4.8). The alkalinity of the sludge mixture with respect to the supernatant increased in proportion to the sludge concentration MLSS. This means that the alkalinity ALf of the sludge mixture obtained at pH = 4.8
Is corrected by the sludge concentration Sm, the alkalinity ALi of the supernatant is determined. The prediction equation is shown in equation (8).

ALi = ALf−Ks · Sm (8) where Ks is an alkalinity correction coefficient. In addition, when the water quality in the sludge mixed solution after the titration was measured, the concentrations of organic substances, nitrogen, and phosphorus were increased, and it was expected that they were eluted from the sludge or oxidatively decomposed. The added acid is also consumed in the sludge, and as a result, it can be determined that the alkalinity has increased. According to this monitoring method, the acid consumption increases,
There is no need to provide a pretreatment means for solid-liquid separation of activated sludge.

The coagulant injected for the purpose of removing phosphorus is also consumed by the alkali component, and the consumption ratio is affected by the ratio between the phosphorus concentration Pi and the alkalinity ALi before the injection (for details, see Japanese Patent Application No. 11-110,1992). 210244). Based on this experimental knowledge, the coagulant injection concentration Ca that makes the phosphorus concentration Pi less than or equal to the target value Pm can be calculated by equation (9). ηp is the phosphorus removal coefficient, (6)
Using the alkalinity ALi obtained by the equation and the equation (7), (1
0) can be calculated. Here, Ap and Bp are coefficients.

Ca = (Pi−Pm) / ηp (9) ηp = A _p · (Pi / ALi) ^Bp (10) The coagulant injection concentration uses the alkalinity ALi directly measured without the sludge separation pretreatment operation. Therefore, an accurate value required for the liquid to be treated can be obtained. The required concentration of the coagulant can be calculated by multiplying the injection concentration Ca by the amount of the coagulant per unit volume of the liquid to be treated and the flow rate of the liquid to be treated.

Obtaining alkalinity by directly measuring the activated sludge mixture in an aerobic tank, an anaerobic tank, or an anoxic tank is as follows:
It is possible to accurately grasp the state of the nitrification reaction or denitrification reaction that is proceeding in the original microorganism reaction tank. The amount of nitrified or denitrified nitrogen is the alkalinity calculated by the equations (6) and (7).
It can be calculated from the amount of change in AL in each reaction tank. The nitrification amount SN is
The amount of alkalinity change ΔALn in the aerobic tank and the amount of denitrification DN are calculated from the amount of alkalinity change ΔALd in the anaerobic tank or anoxic tank,
Prediction can be made with high accuracy by the equations (11) and (12).

SN = ΔALn / Kn (11) DN = ΔALd / Kd (12) where Kn is the alkalinity change amount per unit nitrification amount, and Kd is the alkalinity change amount per unit denitrification amount. 3.57 is given. The nitrification amount SN and the denitrification amount DN calculated by the equations (11) and (12) are calculated based on the concentration. By grasping the total nitrogen concentration at an arbitrary place in the plant, the nitrification rate and the denitrification rate can be predicted, the suitability of factors affecting the nitrification reaction and the denitrification reaction can be determined, and the plant can be appropriately adjusted and managed.

As described above, according to the water quality monitoring and control method of the present invention, the plant can be monitored and controlled by using the correct alkalinity of the mixed liquid to be treated. Thus, there is an effect that high quality treated water can be stably provided.

[0050]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described in detail with reference to the drawings. Note that the same reference numerals are given to the same components throughout the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a sewage treatment facility using an anaerobic-anoxic-aerobic method (A2O method). A flocculant control device for controlling the phosphorus concentration of treated water to a target value or less is provided. ing. Example 1 The sewage treatment equipment of the first embodiment is a biological reaction tank 1 composed of an anaerobic tank 1A, an oxygen-free tank 1B, and an aerobic tank 1C, a final sedimentation tank 2, an underwater stirrer 5, a sludge return facility 7, a sludge discharge facility 8, and a blower. 9, a circulation facility 10, a flocculant storage tank 11, and a flocculant injection facility 12.

Inflow sewage including municipal sewage, industrial effluent, and rainwater flows into the biological reaction tank 1 after coarse sediment is first removed in a sedimentation basin (not shown). Upstream anaerobic tank 1A
And the sludge return equipment 7 from the final sedimentation basin 2
A return sludge 14 containing a high concentration of activated sludge is supplied via the. The inflow sewage 13 and the returned sludge 14 are mixed with an underwater stirrer 5
A. Stir and mix. In the anaerobic tank 1A in the anaerobic state, the activated sludge hydrolyzes the polyphosphoric acid accumulated in the cells and releases it into the liquid as orthophosphate PO4-P. During this phosphorus release, the activated sludge adsorbs organic matter and accumulates in the cells.

NOx-N is contained in the inflow sewage 13 and return sludge 14.
(Generic term for NO3-N and NO2-N)
The denitrification reaction of the formula (2) proceeds. For this reason, anaerobic tank 1A
In this case, the phosphorus concentration increases and the concentration of organic substances and NOx-N decreases. The mixed solution in the anaerobic tank 1A is led to the oxygen-free tank 1B via the partition 4A. In the oxygen-free tank 1B, the mixed liquid of the aerobic tank 1C, which is recirculated as the circulating liquid 18 by the circulation equipment 10, and the anaerobic tank 1
The mixed solution of A is stirred and mixed by the underwater stirrer 5B.
The circulating fluid 18 containing dissolved oxygen flows in, but the oxygen-free tank 1B
Is almost free of oxygen, and the NOx-N contained in the circulating fluid 18 is removed from the anaerobic tank 1A,
Alternatively, the denitrification reaction of the formula (2) mainly proceeds using the organic matter in which the activated sludge has accumulated in the cells. Therefore, in the oxygen-free tank 1B, NOx-N and organic matter decrease, and alkalinity increases.

The liquid mixture in the oxygen-free tank 1B is led to the aerobic tank 1C via the partition 4B. A diffuser 6 is provided at the bottom of the aerobic tank 1C.
Is installed, and injects air 18 from the blower 9,
The mixed liquid is stirred and an activated sludge oxygen source is supplied. In the aerobic tank 1C in the aerobic state, the activated sludge oxidizes and decomposes the accumulated organic matter and the organic matter in the mixed solution into water and carbon dioxide gas. Further, the nitrification reaction of the formula (1) for oxidizing NH 4 —N to NOx—N proceeds.

Further, PO4-P in the mixed solution is taken into cells as polyphosphoric acid. This intake is usually in the anaerobic tank 1
Since the amount was released by A (overdose), phosphorus was reduced and removed in the entire process. Therefore, in the aerobic tank 1C, organic matter, PO4-P, NH4-N and alkalinity decrease, and NOx-N increases. Since a part of the mixed solution at the outlet of the aerobic tank 1C is used as the circulating fluid 18, the circulating fluid 18 contains almost no organic matter or phosphorus and contains NOx-N.

The effluent 15 from the aerobic tank 1C is led to the final sedimentation basin 2, where the activated sludge in the mixture is settled by gravity. The supernatant is disinfected and sterilized as treated water 16 and then discharged into rivers and oceans. The precipitated activated sludge has a high concentration, and is mostly returned to the anaerobic tank 1A of the biological reaction tank 1 as returned sludge 14 by the sludge return equipment 7. In the biological reaction tank 1, specific microorganisms proliferate in response to the reaction and increase the concentration of activated sludge. However, sludge corresponding to the proliferated portion is discharged as excess sludge 17 out of the process system through the sludge discharge facility 8. . The amount of phosphorus retained by the discharged sludge corresponds to the amount of phosphorus removed in the entire process.

As described above, in the process of biologically removing nitrogen and phosphorus, the release and denitrification of phosphorus in the anaerobic tank 1A and the anaerobic tank 1B, and the excessive intake of phosphorus and nitrification in the aerobic tank 1C, respectively. Appropriate maintenance is required to fully demonstrate the functions. These activated sludge treatment functions vary depending on the quality of inflow sewage, plant operating conditions, or activated sludge management conditions, and gradually or suddenly cause defective removal.

The deterioration of the phosphorus release / uptake state lowers the phosphorus removal rate of the whole process, and the phosphorus concentration of the treated water 16 may be higher than that of the inflow sewage 13 in some cases. In such a case, a method of physicochemically removing phosphorus by injecting a flocculant is also used. The sewage treatment equipment of the present embodiment includes a flocculant storage tank 11 and a flocculant injection equipment 12, and maintains the phosphorus concentration of the treated water 16 at a target value Pm or less based on the alkalinity and the phosphorus concentration before the flocculant injection. So that the coagulant injection equipment 12
Control. The water quality monitoring device of the present invention is applied to the measurement of the alkalinity.

In the aerobic tank 1C, an alkalinity measuring device 41 and a phosphorus concentration meter 42 capable of measuring the alkalinity and the phosphorus concentration of the mixed liquid in which activated sludge is present are installed. These measuring instruments are placed close to each other so as to be able to measure the water quality of almost the same mixed liquid, and are installed at a position where the measured water quality does not greatly change until the coagulant is injected. In Figure 1, aerobic tank 1
It is installed at the outlet of C.

The coagulant from the coagulant injection equipment 12 is injected into the reaction tank effluent 15 between the biological reaction tank 1 and the final sedimentation tank 2. With such a positional relationship between water quality measurement and coagulant injection, accurate alkalinity and phosphorus concentration can be measured without being affected by coagulant injection. The positional relationship between the two is based on the premise that the injected flocculant does not affect the water quality measurement position, the upstream and downstream portions of the effluent 15, the effluent 15 and the final sedimentation basin 2, the aerobic tank 1C and the final sedimentation basin 2 Alternatively, if it is an aerobic tank 1C separated by a partition, the upstream part and the downstream part thereof may be used.

FIG. 2 shows a configuration example of the alkalinity measuring device 41. A predetermined amount (for example, 100 mL) of the mixed liquid of the aerobic tank 1C is sent to the titrator 411 as a titration test water. In the titrator 411, the pH set value pHs for provisional alkalinity measurement input from the pH setting circuit 412 is set as the end point, and the acid consumption Da necessary for the pH of the predetermined amount La to indicate the pHs is measured. The pHs are set in the range of 6.2 to 5.5, and the treatment liquid (titration water) after the titration is discharged, and a new test water for titration is introduced to measure the acid consumption Da. Provisional alkalinity calculation circuit 413
Then, the provisional alkalinity ALs is calculated by the equation (13). Here, Kc is an alkalinity conversion coefficient per unit volume of the acid used for the titration.

ALs = 1000 · Kc · Da / La (13) The alkalinity calculation circuit 414 calculates the true alkalinity ALi ending at pH = 4.8 of the test water to be titrated by the equations (6) and (7). Calculate. The arithmetic expression is input in advance, and the pH setting circuit 4
PH setting value pHs from 12 and provisional alkalinity calculation circuit 4
Based on the input value of the provisional alkalinity ALs from No. 13, the alkalinity ALi is output.

The phosphorus concentration meter 42 is a concentration meter using an ion filter for selectively transferring phosphate ions from the mixed solution, and directly measures and outputs the phosphorus concentration Pi of the mixed solution in the aerobic tank 1C.

In the arithmetic unit 50, first, the phosphorus concentration Pi of the mixed solution in the aerobic tank 1C and the alkalinity AL
i is input, and the phosphorus removal coefficient ηp, which is the amount of phosphorus removed per unit metal contained in the coagulant injected in the downstream part, is calculated by equation (10). When the coagulant is polyaluminum chloride (PAC), the coefficient Ap of the equation (10) is 0.5 to 1.0, Bp
Is set in the range of 0.1 to 0.5.

The determination circuit 52 obtains a deviation εp (= Pi−Pm) between the phosphorus concentration Pi and a pre-input phosphorus concentration target value Pm of the treated water 16 after the coagulant injection, and determines whether or not the coagulant injection is necessary. judge. The judgment is that injection is unnecessary when εp ≦ 0, and εp> 0
In this case, injection is required.

The coagulant amount calculation circuit 53 calculates the coagulant injection amount based on the judgment of the judgment circuit 53. When it is determined that injection is necessary, first, (Pi−Pm) in equation (9) is set to εp, and the metal-concentrated injection concentration Ca is calculated using the phosphorus removal coefficient ηp from the removal coefficient calculation circuit 51. Next, the injection concentration
The metal injection amount Ma is obtained from Ca and the flow rate of the water to be treated, and the coagulant injection amount Ga including the metal injection amount Ma is calculated from equation (14).

Ma = Ca · (Qi + Qr), Ga = Ma / Cm (14) Although the flow rate of the water to be treated differs depending on the treatment method and the injection position of the flocculant, in the case of FIG. 1, the inflow sewage flow rate Qi and the return sludge flow rate Qr Is the sum of These flow rates are measured by flow meters 31 and 32,
The signal is output to the arithmetic circuit 53. Metal concentration in coagulant
Since Cm differs depending on the type of coagulant and dissolution conditions, the amount of metal Ma
It is necessary to convert to a coagulant amount Ga containing

The adjusting device 55 operates the coagulant injection equipment 12 so that the measured value of the flow meter 34 becomes the calculated value Ga, and adjusts the coagulant amount to the effluent 15. Note that the deviation εp ≦ 0
In the case of (1), it is determined that the phosphorus concentration of the treated water 16 satisfies the target value, and the injection of the flocculant is stopped according to the instruction that injection is unnecessary. By this intermittent operation, the injection of an extra coagulant is suppressed, the operating cost is reduced, and the adverse effect of the coagulant on the activated sludge is avoided.

According to the present embodiment, no pretreatment means is required for solid-liquid separation of activated sludge, equipment and operating costs can be reduced, and monitoring and control work such as cleaning and replacement of parts is also unnecessary. it can. In addition, since the activated sludge mixture is directly measured, monitoring and control based on accurate measurement values can be provided.

(Embodiment 2) FIG. 9 is a configuration diagram of a sewage treatment facility using the A2O method. The difference from the configuration of FIG. 1 lies in the method of measuring and calculating the true alkalinity ALi of the alkalinity measuring device 41. MLSS meter 44 is installed in aerobic tank 1C,
The SS concentration Sm is measured and output to the alkalinity measuring device 41.

FIG. 10 shows the configuration of the alkalinity measuring device 41. The pH setting circuit 412 outputs the set value pHs to the titrator 411 as 4.8. In the titrator 411, pH = 4.8
The acid consumption Da ending at is determined. The mixed liquid alkalinity calculation circuit 413 calculates the alkalinity ALf of the mixed liquid at pH = 4.8 according to the equation (15).

ALf = 1000 · Kc · Da / La (15) The alkalinity calculation circuit 414 obtains the true alkalinity ALi in which the increase in the MLSS concentration Sm is corrected according to the equation (8).

The removal coefficient calculation circuit 51, the judgment circuit 52, the coagulant amount calculation circuit 53, the adjusting device 55, and the metal injection amount M
a, the coagulant injection amount Ga, and the operation method of the coagulant injection equipment 12 are the same as those in the first embodiment.

The method of the second embodiment requires more acid for the titration than that of the first embodiment, but can be applied without modifying an existing alkalinity meter used in a water purification plant or the like.

(Embodiment 3) In Embodiments 1 and 2,
Although the true alkalinity ALi was obtained using the alkalinity prediction coefficient Ke and the alkalinity correction coefficient Ks, the alkalinity can be calculated after obtaining the true acid consumption.

FIG. 11 is different from the first embodiment in the method of obtaining the alkalinity ALi in the alkalinity measuring device 41. p
The H setting circuit 412 gives the set value pHs in the range of 5.5 to 6.2, and the titrator 411 provides the acid consumption D with the set value pHs as the end point.
Measure a. The acid consumption calculating circuit 415 calculates the acid consumption Di at pH = 4.8 by the equation (16). Ke ′ is an acid consumption prediction coefficient, which can be expressed by equation (17) similar to equation (6) since alkalinity and acid consumption are in a proportional relationship.

Di = Ke ′ · Da (16) Ke ′ = a ′ · pHs−b ′ (17) ALi = 1000 · Kc · Di / La (18) where a ′ and b ′ are constants and titration The value differs from the value of the expression (6) depending on the kind and concentration of the acid used for the above. Alkalinity calculation circuit 416
Calculates the alkalinity ALi at pH = 4.8 by equation (18).

FIG. 12 is different from the second embodiment in the method of calculating the alkalinity ALi in the alkalinity measuring device 41. The acid consumption correction circuit 415 determines the pH of the mixed solution containing the activated sludge.
The consumption of sludge with the acid consumption Da at = 4.8 is corrected, and the acid consumption Di in the case of the supernatant is calculated by the equation (19).

Di = Da−Ks ′ · Sm (19) Here, Ks ′ is an acid consumption correction coefficient, and is affected by the type and concentration of the acid used for titration. The alkalinity calculation circuit 416 calculates the alkalinity ALi of the supernatant at pH = 4.8 and outputs the calculated alkalinity ALi according to equation (18) in the same manner as in FIG.

Even when the alkalinity calculation method of the third embodiment is used, the same results as in the first and second embodiments can be obtained, and the coagulant can be appropriately controlled.

(Embodiment 4) FIG. 13 shows a sewage treatment facility based on the A2O method. Using the alkalinity measuring device of Embodiment 1, the amount of generation and removal of Nox-N in the process is accurately detected and detected. The nitrification reaction and the denitrification reaction are properly managed based on the information.

For this purpose, the anaerobic tank 1A, the anaerobic tank 1B,
Alkalinity measuring device 4 for mixture of effluent 15
1A, 41B and 41C are installed, respectively, and a TN meter for measuring the total nitrogen (hereinafter referred to as TN) concentration TNe of the supernatant of the final sedimentation basin 2 or the treated water 16 is provided. The alkalinity measuring devices 41A, 41B, and 41C measure the anaerobic tank alkalinity ALa, the anaerobic tank alkalinity ALn, and the aerobic tank effluent alkalinity ALo by the same measurement and calculation method as in FIG.

The flow meters 31, 32, 33, 35, 3
6 is the inflow sewage volume Qi, the returned sludge volume Qr, and the circulating fluid volume Q, respectively.
j, the amount of excess sludge Qe and the amount of air Qg are measured. The dissolved oxygen (hereinafter referred to as DO) concentration meter 43 and the ML are provided in the aerobic tank 1C.
An SS meter 44 is installed to measure the DO concentration Do and the MLSS concentration Sm, and a sludge concentration meter 42 is installed on the returned sludge 14 to return the sludge concentration.
Measure Sr. These measured values are output and stored in the data storage device 57.

The arithmetic unit 60 determines the state of the nitrification reaction or the denitrification reaction, and calculates and outputs an appropriate operation amount. First,
The nitrification amount calculation circuit 61 calculates a deviation ΔALn between the alkalinity of the oxygen-free tank ALn and the alkalinity of the effluent of the aerobic tank ALO, and calculates the nitrification amount SN in the aerobic tank 1C by the equation (11). The denitrification amount calculation circuit 62 calculates the alkalinity change amount ΔALd of the oxygen-free tank 1B by the equation (20), and further calculates the denitrification amount DN by the equation (12).
Is calculated.

ΔALd = ALn − ((ALa (Qi + Qr) + ALo · Qj) / (Qi + Qr + Qj)) (20) FIG. 14 shows the Nox-N change of the anoxic tank and the aerobic tank when the actual sewage is treated by the A2O method. It is a relationship between the amount and the alkalinity change amount. The relationship between the two is linear in both the anoxic tank and the aerobic tank, and the nitrification amount and the denitrification amount can be obtained from the change in alkalinity with the slopes of these as Kn and Kd.

The determination circuit 63 determines the quality of nitrogen removal, and if the removal is defective, selectively determines the factor and the amount of operation. The method is shown in FIG. The quality of the nitrogen removal is determined to be good if the TN concentration TNe of the supernatant of the final sedimentation basin 2 or the treated water 16 is lower than the target value TNm (s10).
1). When TNm <TNe, the operation amount is selected based on the progress of the nitrification reaction and the denitrification reaction. Measurement value TNe of TN meter 46
Is the total concentration of NH4-N, Nox-N, and organic nitrogen.

The concentration of organic nitrogen in the treated water after the activated sludge treatment is very small, and the nitrification reaction state can be diagnosed based on the nitrification amount SN based on the measured value TNe and the alkalinity change amount. In the nitrification reaction, if the deviation between the TN concentration TNe and the nitrification amount SN is smaller than the target deviation αn, it is judged that the nitrification is good, and if (Tne−SN)> αn, the residual NH4—N is large and it is judged that the nitrification is poor ( s10
2).

The denitrification reaction is carried out using the No.
The deviation βn is the target deviation between the x-N amount SNj and the denitrification amount DN.
If it is smaller, it is diagnosed that denitrification is good, and if (SNj−DN)> βn, it is diagnosed that it is not good for denitrification (s103, s104). Bring in
The Nox-N amount SNj (concentration reference) is calculated by equation (21).

SNj = SN · Qj / (Qi + Qr + Qj) (21) Based on these diagnostic results, if both (1) the nitrification and denitrification reactions are good, the circulating fluid volume is increased, and (2) the nitrification reaction is good. However, if the denitrification reaction is poor, the amount of sludge will increase,
(3) The nitrification reaction is poor, but if the denitrification reaction is good, the amount of circulating liquid or air or sludge increases, (4)
If both the nitrification and the denitrification reactions are not satisfactory, an operation selection such as an increase in the amount of air or sludge is performed.

In the control target value setting circuit 64, the judgment circuit 6
The target value of the operation amount is set based on the operation selection of 3. For the target value, upper and lower limits are set for each manipulated variable, and within the range, a constant ratio method in which the current value is increased or decreased by 5% or 10%, and a fixed amount in which a constant amount or a constant concentration is added to or subtracted from the current value. Set by method. The target value may be the air amount or DO concentration if the operation amount is the air amount, the return sludge flow amount or the excess sludge flow amount, the MLSS concentration, the sludge residence time (SRT, A-SRT), or the circulating liquid amount if the operation amount is the sludge amount. For example, the circulating liquid amount or the ratio of the circulating liquid amount to the inflow sewage flow rate can be targeted.

The adjusting device 55 is based on the operation amount selected by the judgment circuit 63 and the setting circuit 64, the new target value, and the current value of the data storage device 57, and the sludge return equipment 7 or the sludge discharge equipment 8, Alternatively, the blower 9 or the circulation equipment 10 is adjusted. In addition, the display device 56 displays the calculation results of the nitrification amount and the denitrification amount in the calculation device 60, the status of the nitrification reaction and the denitrification reaction, the selected operation amount and its target value, and the like, so as to display the target to the driver. Present the plant status.

The supernatant or treated water 16 of the final sedimentation basin 2
If the TN concentration TNe of the control value satisfies the target value TNm, the determination circuit 63 maintains the current manipulated variable or returns a control target value setting circuit to return the previously selected target value of the manipulated variable to the value before selection. Instruct 64.

According to the fourth embodiment, the amount of nitrification and the amount of denitrification can be predicted by a simple and highly reliable alkalinity measuring device without using an expensive NH4-N meter or NOx-N meter which requires a large maintenance burden. Therefore, the reliability of monitoring control can be improved.

(Example 5) FIG. 16 shows a sewage treatment system using the A2O method. The phosphorus concentration is determined from the measured alkalinity, and the phosphorus release and intake states of the anaerobic tank and the aerobic tank are predicted to determine the phosphorus removal reaction. It is properly managed. The alkalinity measuring devices 41A 'and 41C' provided with the pretreatment device 418 are installed in the anaerobic tank 1A and the reaction tank effluent 15, and the alkalinity AL before the pretreatment is set.
Measure 1 and alkalinity AL2 after pretreatment.

FIG. 17 shows a configuration example of the alkalinity measuring devices 41A 'and 41C'. In the pretreatment device 418, the stirring tank 418A
A predetermined amount of the anaerobic tank 1A mixture or the reaction tank effluent 15
Then, a predetermined amount of coagulant is mixed and stirred from the coagulant storage tank 418B via the coagulant injection device 418C. Stirring tank 418A
In this case, the coagulant is consumed by reacting with the phosphorus concentration and the alkalinity of the inflowing mixture, and the alkalinity and the phosphorus concentration in the solution decrease. The breakdown of coagulant consumption at this time varies depending on the phosphorus concentration and alkalinity before the coagulant injection. Water sampling switch 418D
Is to switch the titration test water sent to the titrator 411,
The mixed solution of the reaction tank not subjected to the pretreatment and the coagulant treatment solution after the pretreatment are alternately switched and fed. The functions and calculation contents of the titrator 411, the pH setting circuit 412, the provisional alkalinity calculation circuit 413, and the alkalinity calculation circuit 414 are the same as those in FIG. 2, except that the alkalinity AL1 of the reaction mixture and the coagulant treatment liquid. Outputs alkalinity AL2.

In the arithmetic unit 70, first, in the phosphorus concentration calculating circuit 71, based on the experimental finding that the reduction in alkalinity accompanying the coagulant injection is affected by the phosphorus concentration and alkalinity before the coagulant injection. , (22) is used to calculate the phosphorus concentration Cp.

Cp = AL1 ((Ka− (AL1-AL2) / Ca) / Aa) ^{1 / Ba} (22) where Ca is the coagulant injection concentration in the stirring tank 418A.
(In terms of metal), Ka, Aa, and Ba are constants. When the flocculant is PAC, it is set in the range of Ka = 2 to 3, Aa = 0.5 to 1.0, and Ba = 0.1 to 0.5.

The output values AL1, AL2 of the alkalinity measuring device 41A '
Thus, the phosphorus concentration Cpa of the reaction tank effluent is calculated from the phosphorus concentration Cpa of the anaerobic tank mixture and the output values AL1 and AL2 of the measuring device 41C ′.

The determination circuit 72 determines the quality of the phosphorus removal (s201). If the removal is defective, the factor and the operation amount are selected and determined. FIG. 18 shows a determination example. The quality of the phosphorus removal is determined to be good if the phosphorus concentration Cpo of the reaction tank effluent 15 is lower than the target value Pm. On the other hand, when Cpo> Pm, the operation amount for improving the function is determined and selected in accordance with the state of the phosphorus release and the intake function.

In the phosphorus release state, if Cpa is higher than the set value αp, it is determined that the release is good, and if Cpa <αp, it is determined that the release is poor (s
202). Phosphorus intake is determined to be good if Cpo is lower than the set value βp, and poor if Cpo> βp (s20).
3, s204).

Based on these diagnostic results, (1) the amount of air or sludge is changed if the release and intake are good, and (2) the amount of air or sludge is good if the release is good, but the intake is poor. Change the amount or add a flocculant,
(3) If the discharge is poor, but the intake is good, change the amount of sludge. (4) If both the release and the intake are poor, change the sludge amount or add an aggregating agent.

The control target value setting circuit 73 sets the target value of the operation amount based on the operation selection of the determination circuit 72 in the same manner as in the fourth embodiment. The adjusting device 55 controls the sludge return equipment 7 based on the operation amount selected by the determination circuit 72 and the setting circuit 73, the new target value, and the current value of the data storage device 57.
Alternatively, the sludge discharge equipment 8, the blower 9, or the coagulant injection equipment 12 is adjusted. The display device 56
Displays the phosphorus concentration calculation result, the phosphorus release / intake state, the selected manipulated variable and its target value, etc., and presents the plant situation to the driver.

According to the fifth embodiment, since the phosphorus release and the intake concentration can be predicted from the alkalinity measurement value without using an expensive and heavy maintenance PO4-P meter, a simple and highly reliable monitoring control can be performed. Can be provided.

(Example 6) FIG. 19 shows that the nitrification amount or the phosphorus concentration was determined from the measured alkalinity value, and the NH4-N meter and the Nox-N
This is a configuration example for diagnosing normal / abnormal of the meter or the PO4-P meter. Alkalinity measuring device 41A 'and PO4-P meter 42 in anaerobic tank 1A
A, alkalinity measuring device 41B 'and NH4-N total 4 in anoxic tank 1B
7A and Nox-N total 48A, PO4-P total 42B and NH4-N in aerobic tank 1C
A totality 47B, a Nox-N total 48B, and an alkalinity measuring device 41C 'are provided in the reaction tank effluent 15. Alkalinity measuring device 41A ', 41
B 'and 41C' use the method shown in FIG. All of these measured values are stored in the data storage device 57 and output to the arithmetic device 80 as appropriate.

In the nitrification amount calculation circuit 61, the amount of nitrification, that is, the nitrification concentration SN in the aerobic tank 1C is calculated from the equation (11) using the alkalinity AL1 of the alkalinity measuring devices 41B 'and 41C' before the coagulant is injected. Calculate. The phosphorus concentration calculation circuit 71 calculates the phosphorus concentration of each reaction tank in the same manner as in the fifth embodiment. In the comparison circuit 81, the change amount ΔNH of the NH4-N totals 47A and 47B and the Nox-N
The amount of change ΔNO and the nitrification concentration SN of the total 48A and 48B are compared. Further, the calculated value of the phosphorus concentration from the phosphorus concentration
-Compare the output values of the P total 42A and 42B.

In the judgment circuit 82, if the deviation of ΔNH-SN and ΔNO-SN is less than a predetermined value, the NH4-N totals 47A and 47B and the Nox-N total 48
A and 48B are determined to be normal, and if they are equal to or greater than a predetermined value, it is determined to be abnormal. The PO4-P meters 42A and 42B also determine that the deviation between the output value and the calculated phosphorus concentration is normal if it is equal to or less than a predetermined value, and that it is abnormal if the deviation is equal to or more than the predetermined value. NH4-N Total 47A, 47B, Nox-N Total 48
A and 48B evaluate the denitrification state based on the denitrification amount in the denitrification amount calculation circuit 62 in the same manner as in the fourth embodiment, and if it is complete denitrification, the Nox-N meter 48B is directly measured with the nitrification concentration SN. Diagnose. Further, if the denitrification is poor, the Nox-N total 48B can determine an abnormality based on whether or not the output value is equal to or higher than the nitrification concentration SN.

The results of these comparisons and judgments can be displayed on the display device 56. Although not shown in the Examples, NH4-N
When the operation management for nitrification, denitrification, phosphorus release and ingestion is performed with a meter, Nox-N meter, or PO4-P meter, the operation amount is not changed by the meter that has been determined to be abnormal, and operation is only performed during normal times. Apply to management.

Although the above embodiment has been described with reference to the sewage treatment equipment of the A2O method, the AO method, the AOAO method, the modified nitrification liquid circulation method, the standard activated sludge method, and the step method AOAO in which the inflowing sewage is divided and introduced. Law, etc. Although the alkalinity measuring device is installed in the biological reaction tank, it can be applied to inflow sewage, treated water, and returned sludge. In addition, by measuring a mixture of sludge concentration equipment and digestion equipment for processing excess sludge, it is possible to adjust factors affecting sludge concentration and digestion.

(Embodiment 7) FIG. 20 shows an example of the configuration of a water purification treatment system, which is provided with a flocculant and a chemical injection control device for controlling turbid components and alkaline components of sedimentation supernatant water (treated water) to target values. I have. The water purification treatment equipment removes minute turbid particles suspended in the inflow raw water 131 by coagulating and sedimenting with a coagulant, and includes a landing well 101, a mixing pond 102, a floc forming pond 103, a sedimentation pond 104, and a coagulant storage tank 11. , A coagulant injection facility 12, chemical storage tanks 111A and 111B, and a chemical injection facility 112.

The inflow raw water 131 taken from rivers and lakes is subjected to removal of sediment and contaminants by a sand basin (not shown).
It flows into the landing well 101. In the landing well 101, the water is mixed with other raw water or return water from the downstream equipment, so that the water quality can be stabilized. In the mixing pond 102, the acid or alkali agent from the chemical storage tank 111A and the coagulant from the coagulant storage tank 11 are injected and mixed and diffused by the stirrer 106. The floc forming pond 103 rotates the stirrer 107 gently to turn the fine turbid particles into coarse aggregates (hereinafter, referred to as flocs) by the action of the flocculant, and to settle easily. In the sedimentation basin 104, coarse flocs are removed by sedimentation to form a supernatant. The supernatant liquid is filtered through sand and sterilized, and
Becomes

Hereinafter, the configuration and operation of the coagulant injection control device and the chemical injection control device realized by the arithmetic unit 90 will be described. A water quality measuring device 142 is installed in the landing well 101 to measure turbidity, pH, and water temperature, and these measured values TUi, pHi, Ti
Is input to the data storage device 57. The same alkalinity measuring device 4 as in the first embodiment is applied to the landing well 101 or the landing well effluent.
1 is set, and the operation value ALi is input to the storage device 57. The storage device 57 is supplied with the inflow raw water amount, the coagulant injection amount, and the chemical injection amount from the flow meters 141, 143, and 144.

In the arithmetic unit 90, the chemical injection concentration calculating circuit 92 first determines whether the alkalinity calculation value ALi is within a predetermined alkalinity setting range. Ask for. In the chemical injection amount calculation circuit 94, when the calculated value ALi is equal to or less than the set range, an alkaline agent is injected, and when the calculated value ALi is equal to or more than the set range, an acid is determined to be injected.
The chemical injection amount is calculated by the product of the minimum injection concentration and the inflowing raw water amount. The coagulant injection concentration calculation circuit 91 calculates the injection concentration Ca using a preset injection model: f (TUi, pHi, Ti, ALi). The coagulant injection amount calculation circuit 93 calculates the coagulant injection amount from the product of the injection concentration Ca and the inflowing raw water amount.

The adjusting device 55 adjusts the coagulant injection equipment 12 and the chemical injection equipment 112 according to the coagulant injection amount and the chemical injection amount output from the arithmetic unit 90. The chemical injection equipment 112 operates the switching device 113 based on the determination result of the alkali agent or acid injection to adjust the amount of the chemical injected from the alkali agent storage tank 111A or the acid storage tank 111B.

According to this embodiment, in the water purification treatment, even if microorganisms that affect the measurement of alkalinity flow into the raw water that has been withdrawn, the alkalinity can be accurately measured, and a highly reliable coagulant or chemical injection control can be performed. realizable. Further, the amount of acid consumed for alkalinity measurement can be reduced, and the operating cost can be reduced.

[0115]

According to the method for monitoring alkalinity of the present invention,
There is no need to install a pretreatment means for solid-liquid separation of activated sludge, and even a mixed solution containing activated sludge is directly titrated,
There is no change in water quality and alkalinity can be measured with high accuracy. Since there is no pretreatment means, no new equipment and operating costs are required, and no maintenance and inspection work is required. In addition, to increase the pH titration target value, it is possible to reduce the acid consumption required for titration,
It is economical. Further, since the target value of the pH titration is set to 5.5 or more, the titration treatment liquid does not need to be neutralized and can be discharged.

Further, according to the control of the water treatment process of the present invention, the plant can be monitored and controlled by using the correct alkalinity of the mixture to be treated, and the nitrification amount, the denitrification amount, and the phosphorus concentration can be controlled. Since it can be grasped, an appropriate plant operation management can be performed without using an expensive water quality measuring instrument, so that there is an effect that high quality treated water can be stably provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an alkalinity measuring device according to the first embodiment.

FIG. 3 is a graph showing an example of test results of an acid addition amount and pH characteristics.

FIG. 4 is a graph showing an example of test results of alkalinity ratio and pH characteristics.

FIG. 5 is a graph showing another example of test results of alkalinity ratio and pH characteristics.

FIG. 6 is a graph showing an example of test results of alkalinity and true alkalinity at various pHs.

FIG. 7 is a graph showing an example of a test result illustrating a pH set value for predicting alkalinity.

FIG. 8 is a graph showing an example of test results of MLSS and alkalinity characteristics.

FIG. 9 is a configuration diagram of a sewage treatment facility including a flocculant control device according to a second embodiment.

FIG. 10 is a configuration diagram of an alkalinity measuring device according to a second embodiment.

FIG. 11 is a configuration diagram of an alkalinity measuring device according to a third embodiment.

FIG. 12 is a configuration diagram showing another example of the alkalinity measuring device according to the third embodiment.

FIG. 13 is a configuration diagram of a sewage treatment facility including a nitrogen removal control device according to a fourth embodiment.

FIG. 14 is a graph showing an example of test results of Nox-N and alkalinity change characteristics.

FIG. 15 is a configuration diagram illustrating an example of a nitrogen removal determination method according to a fourth embodiment.

FIG. 16 is a configuration diagram of a sewage treatment facility including a phosphorus removal control device according to a fifth embodiment.

FIG. 17 is a configuration diagram of an alkalinity measuring device according to a fifth embodiment.

FIG. 18 is a configuration diagram illustrating an example of a phosphorus removal determination method according to a fifth embodiment.

FIG. 19 is a configuration diagram of a sewage treatment facility including a measuring instrument diagnostic device according to a sixth embodiment.

FIG. 20 is a configuration diagram of a water purification treatment facility including a flocculant and a chemical control device according to a seventh embodiment.

[Explanation of symbols]

1. Biological reaction tank, 1A: Anaerobic tank, 1B: Anoxic tank, 1C
... Aerobic tank, 2 ... Final sedimentation basin, 5 ... Underwater stirrer, 7 ... Sludge return equipment, 8 ... Sludge discharge equipment, 9 ... Blower, 10 ... Circulation equipment, 11 ... Coagulant storage tank, 12 ... Coagulant injection Equipment, 3
1, 32, 33, 34, 35, 36 ... flow meter, 41, 4
1 ': alkalinity measuring device, 411: titration device, 412
... pH setting circuit, 413 ... Temporary alkalinity calculation circuit, 4
14, 416: alkalinity calculation circuit, 415: acid consumption calculation circuit, 417: acid consumption correction circuit, 418: pretreatment device, 42: phosphorus concentration meter, 43: DO meter, 44: MLSS meter,
45: Sludge concentration meter, 46: TN meter, 47: NH4-N meter, 48
... Nox-N meter, 50, 60, 70, 80, 90 ... arithmetic unit, 55 ... adjusting unit, 56 ... display unit, 57 ... data storage unit, 101 ... landing well, 102 ... mixing pond, 103 ... floc Formation pond, 104: sedimentation pond, 111: chemical storage tank, 1
12 ... chemical injection equipment, 142 ... water quality measuring instrument.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/52 C02F 1/52 E 1/66 510 1/66 510K 530 530L 530P 540 540J 540Z 3/30 ZAB 3/30 ZABC G01N 31/16 G01N 31/16 A (72) Inventor Tsuyoshi Takemoto 7-2-1, Omika-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Electric Power and Electric Development Laboratory (72) Inventor En Ichiro, France 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Power and Electricity Research Laboratory, Hitachi, Ltd. (72) Inventor Fumichi Kimura 5-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Information Control System Division F term (reference) 2G042 AA01 BB03 CA02 CB03 DA02 FA01 GA05 4D015 BA21 BB05 CA02 CA14 EA16 EA19 EA32 FA01 FA16 4D040 BB32 BB72 BB91 4D062 BA21 BB05 CA02 CA14 EA16 EA19 EA32 FA01 FA16

Claims (10)

[Claims] 1. A pH setting circuit for inputting a pH set value higher than the pH reference value with a pH of 4.8 as a pH reference value, and introducing a predetermined amount of test water for titration, wherein the pH of the test water for titration is adjusted. The pH
A titrator for neutralizing with acid so as to have a pH set value output from the setting circuit, an acid consumption measuring circuit for measuring the amount of acid consumed for neutralization by the titrator, and A provisional alkalinity calculating circuit for obtaining a provisional value of alkalinity at the pH set value, and an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value based on the pH set value, wherein the alkalinity prediction coefficient and the provisional A water quality monitoring device, comprising: an alkalinity calculating circuit for calculating the alkalinity at the pH reference value from the alkalinity, and outputting the calculated alkalinity value as the true alkalinity of the test water to be titrated. 2. A pH setting circuit for inputting a pH set value higher than the pH reference value with a pH of 4.8 as a pH reference value, and introducing a predetermined amount of test sample water to be measured. The pH
A titrator for neutralizing with an acid so as to have a pH set value output from a setting circuit, an acid consumption measuring circuit for measuring an amount of acid consumed for neutralization by the titrator,
An acid consumption prediction coefficient for predicting the acid consumption of the H reference value is input, and an acid for calculating the acid consumption of the pH reference value from the acid consumption prediction coefficient and the acid consumption measurement value at the pH set value. Water consumption, comprising: a consumption calculation circuit; and an alkalinity calculation circuit for calculating alkalinity from the acid consumption calculation value, wherein the alkalinity calculation value is output as the true alkalinity of the test water to be titrated. Monitoring device. 3. The influent sewage of the sewage treatment process according to claim 1 or 2, wherein the test water to be titrated is an organic waste, a domestic wastewater, an industrial effluent, or the like, and the organic matter, nitrogen, and phosphorus in the influent sewage are removed by activated sludge. A water quality monitoring device, which is an activated sludge mixture in which activated sludge is suspended, or a supernatant liquid obtained by solid-liquid separation of the activated sludge of the mixed solution. 4. The water quality monitoring device according to claim 1, wherein the pH set value is set in a range of 5.5 to 6.2. 5. A water comprising a reaction tank for removing pollutants in the water to be treated by a biological reaction, and a sedimentation pond for sedimenting suspended substances in the effluent of the reaction tank and using the supernatant as treated water. A pH setting circuit for inputting pH 4.8 as a pH set value in the water quality monitoring device of the treatment process;
Introducing a predetermined amount of the test water for titration, a titrator for neutralizing with acid so that the pH of the test water for titration becomes the pH set value output from the pH setting circuit, and neutralization with the titrator. An acid consumption measuring circuit for measuring the amount of consumed acid; and
An arithmetic circuit, a means for measuring the biological concentration of the test water for titration, and an alkalinity correction coefficient for correcting the alkalinity increased by the organism until the pH of the test water for titration reaches the pH set value. Input, the alkalinity correction coefficient and the first
A second arithmetic circuit for calculating the alkalinity of the test sample at the pH set value in a state that does not include living organisms, from the alkalinity arithmetic value of the arithmetic circuit and the measured value of the biological concentration, 2. The water quality monitoring device according to claim 2, wherein the calculated alkalinity value is output as a true alkalinity of the test water for titration. 6. A reaction tank for removing or suspending pollutants in water to be treated by a biological reaction and / or a physicochemical reaction by adding a flocculant, and suspending substances in an effluent of the reaction tank by sedimentation. In a water treatment process provided with a sedimentation basin using the supernatant as treated water, a pH reference value as a reference, a pH set value higher than the pH reference value, and an alkalinity of the pH reference value at the pH set value. Set the alkalinity prediction coefficient to be predicted, introduce a predetermined amount of titration test water from the water to be treated, neutralize with acid so that the pH of the titration test water becomes the pH set value, and neutralize with the acid. The consumed acid consumption is measured, and a provisional value of the alkalinity at the pH set value is obtained from the measured value of the acid consumption, and the alkalinity at the pH reference value is calculated from the provisional value of the alkalinity and the alkalinity prediction coefficient. Alkalinity measuring device that calculates A control device for a water treatment process, wherein an operation amount affecting a reaction of the water treatment process is adjusted using a calculation value of the alkalinity measurement device. 7. A biological reaction tank for removing pollutants in water to be treated by a biological reaction, a sedimentation pond for sedimenting suspended substances in an effluent of the biological reaction tank and using the supernatant as treated water, In a water treatment process including a coagulant injection facility between the biological reaction tank or the sedimentation tank or the biological reaction tank and the sedimentation tank, a reference pH reference value, a pH set value higher than the pH reference value, and An alkalinity prediction coefficient for estimating the alkalinity of the pH reference value is set at the pH set value, a predetermined amount of titration test water is introduced from the water to be treated, and the pH of the titration test water is equal to the pH set value. Neutralize with acid so as to measure the amount of acid consumed by the neutralization, determine the provisional value of the alkalinity at the pH set value from the measured value of the acid consumption, and the provisional value of the alkalinity From the alkalinity prediction coefficient, the An alkalinity measuring device that calculates the degree of luster,
Providing a phosphorus concentration meter for measuring the phosphorus concentration of the water to be treated, using the calculated value of the alkalinity measuring device and the measured value of the phosphorus concentration meter, to adjust the injection amount from the coagulant injection equipment. Control device for water treatment process. 8. A reaction tank for removing or suspending pollutants in the water to be treated by a biological reaction and a physicochemical reaction by the addition of a flocculant, and the suspended matter in the effluent of the reaction tank is settled and the supernatant is removed. In a water treatment process provided with a sedimentation tank using liquid as treated water, a pH reference value as a reference, a pH set value higher than the reference value, and an alkali for predicting the alkalinity of the pH reference value with the pH set value A setting circuit for setting an acidity prediction coefficient, measuring an acid consumption amount with a predetermined amount of water to be treated as the pH set value, and calculating the p from the acid consumption amount and the alkalinity prediction coefficient.
A first arithmetic circuit for calculating the alkalinity at the H reference value; and an acid which injects a coagulant into the water to be treated so as to have a predetermined concentration, and sets a predetermined amount of the liquid into which the coagulant is injected as the pH set value. A second arithmetic circuit for measuring consumption and calculating the alkalinity at the pH reference value from the acid consumption and the alkalinity prediction coefficient is provided, and two alkalinities by the first and second arithmetic circuits are provided. Calculating the phosphorus concentration of the water to be treated based on the coagulant injection concentration, determining the phosphorus release or intake state of the activated sludge from the phosphorus concentration, and adjusting the operation amount affecting the release or intake response. Water treatment process control device. 9. A water treatment process comprising a mixing pond, a floc forming pond, and a sedimentation pond, wherein a pH reference value as a reference in a water treatment process in which a coagulant is injected into the mixing pond or raw water flowing into the mixing pond; A higher pH set value, and an alkalinity prediction coefficient for predicting the alkalinity of the pH reference value at the pH set value, and an acid having the water to be treated as the pH set value before injecting a predetermined amount of coagulant. Provide an alkalinity measuring device that measures consumption, calculates the alkalinity at the pH reference value from the acid consumption and the alkalinity prediction coefficient, and calculates the alkalinity and the suspended solids concentration in the water to be treated. And / or controlling the injection of the flocculant by using a measured value of the pH and / or the water temperature to adjust the injection of the flocculant. 10. The control device for a water treatment process according to claim 6, wherein the pH reference value is set in a range of 4.8, and the pH set value is set in a range of 5.5 to 6.2.