JP2010029771A - Method for estimating water quality and biological treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water quality estimating method which enables the estimation of the BOD of treated water with high accuracy, thereby improving the treatment efficiency of a biological treatment method. <P>SOLUTION: In the water quality estimating method for estimating the water quality of treated water obtained after biological treatment of water to be treated containing organic components and nitrogen components by calculation based on one of the activated sludge models of IWA, ASM1, ASM2, ASM2d, and ASM3, the concentration of ammonia nitrogen in the treated water is estimated by the calculation, and the amount of biochemical oxygen, demand of the treated water, is estimated from the estimated ammonia nitrogen concentration. In the biological treatment method for carrying out the biological treatment while estimating the water quality of biologically treated water by the calculation based on the activated sludge models of IWA, the process for estimating the ammonia nitrogen concentration in the treated water by the calculation, and the process for calculating the amount of biochemical oxygen, demand of the treated water, from the estimated ammonia nitrogen concentration are carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water quality prediction method and a biological treatment method, and more specifically, a water quality prediction method for predicting the water quality of treated water after biological treatment of water to be treated containing an organic component and a nitrogen component, and an organic component And a biological treatment method for carrying out the biological treatment while predicting the quality of the treated water after the treated water containing a nitrogen component has been biologically treated.

  Conventionally, biological water treatment has been performed to remove substances to be treated such as organic components, nitrogen components and phosphorus components contained in water to be treated (treated water) such as factory wastewater by the action of bacteria. In general, this biological treatment is carried out under control so that nitrogen and phosphorus contained in the treated water discharged out of the system after the treatment have a predetermined concentration or less. Moreover, about an organic component, it manages by the value of a biochemical oxygen demand (BOD) etc., and is controlled so that BOD of treated water will become below a predetermined value.

In recent years, in such biological treatment, it has been carried out to predict the quality of treated water by simulating the decomposition behavior of substances to be treated by bacteria, and this simulation adjusts various conditions of biological treatment to improve treatment efficiency. Attempts have been made to improve.
This simulation is performed by calculation using variables such as the concentration of bacteria in the aquarium where biological treatment is performed and the substance to be processed, and such calculation is proposed by IWA (International Water Association). Active sludge models such as ASM1, ASM2, ASM2d, and ASM3 are widely used.
For example, the following Patent Document 1 describes that a simulation based on this activated sludge model is performed.

The activated sludge model proposed by IWA is set to perform calculations using parameters such as reaction kinetic constants in addition to the above variables. In addition, it is easy to adjust the value of this parameter or improve the model, and it is excellent in versatility and can be expected to have high prediction accuracy.
However, this activated sludge model of IWA is not constructed so as to be able to directly predict the BOD of treated water, and as an organic component handling, it is an easily decomposable organic substance (S _S ) with COD _Cr as a unit. Or slow-decomposable organic substances (X _S ) are only set.
Moreover, the easily decomposable organic substance (S _S ) in these cases often results in hardly remaining in the treated water in any case, even when various setting values are changed for calculation. organic material (X _S), since handled as a solid component, so that the result is uniquely determined substantially by the solid-liquid separation characteristic by the hard sedimentation tank to strictly predict the residual amount of treated water by the ASM .
For this reason, in the IWA activated sludge model, it has been practically difficult to predict the BOD of treated water directly or indirectly.

  Therefore, in the conventional water quality prediction method using the activated sludge model of IWA, it is difficult to accurately predict the BOD value of the treated water, and the treated water is predicted while predicting the water quality using the activated sludge model of IWA. However, the conventional biological treatment method for biologically treating the material has a problem that it is difficult to sufficiently improve the treatment efficiency.

JP 2000-107796 A

  This invention is made | formed in view of the said problem, and provides the water quality prediction method which can estimate the value of BOD of treated water with high precision, and makes it a subject to aim at the improvement of the treatment efficiency in a biological treatment method. .

  As a result of intensive studies to solve the above problems, the present inventors have found that in the treated water after biological treatment, the amount of ammonia nitrogen in the treated water and the BOD value have a relatively good linear relationship. As a result, the present invention was completed.

  That is, according to the present invention relating to the water quality prediction method, the quality of the treated water after the treated water containing the organic component and the nitrogen component is biologically treated is determined according to ASM1, ASM2, ASM2d, and ASM3, which are IWA activated sludge models. A water quality prediction method for predicting by performing an operation based on any of the above, predicting the ammonia nitrogen concentration of the treated water by the operation, and biochemical oxygen of the treated water based on the value of the ammonia nitrogen concentration It is characterized by predicting the required amount.

  In addition, the present invention relating to the biological treatment method is characterized in that the quality of treated water after the treated water containing organic components and nitrogen components is biologically treated is the activated water sludge model ASM1, ASM2, ASM2d, and ASM3. A biological treatment method that performs the biological treatment while performing and predicting a calculation based on any one of the steps, and predicting the ammoniacal nitrogen concentration of the treated water by the calculation and the value of the ammoniacal nitrogen concentration And the step of calculating the value of the biochemical oxygen demand of the treated water.

Since the BOD value in the treated water has a relatively good correlation with the amount of ammonia nitrogen, the calculation based on the activated sludge model of IWA is performed to determine the ammonia nitrogen concentration of the treated water. By obtaining the predicted value, the value of BOD in the treated water can also be predicted.
Therefore, according to the present invention, the BOD value of the treated water can be accurately predicted, and the treatment efficiency in the biological treatment method can be improved by controlling the operating conditions based on the prediction result.

First, a case where a biological treatment process is performed on water to be treated that contains an organic substance and a nitrogen component such as ammoniacal nitrogen as a treatment target substance, and the quality of the treated water discharged after the biological treatment is predicted. The water quality prediction method and biological treatment method of this embodiment will be described as an example.
FIG. 1 is a schematic block diagram showing a biological treatment facility in which the quality of treated water is predicted by the water quality prediction method of the present embodiment. As shown in FIG. It has an aerobic tank 2 in which water is introduced and biological treatment is carried out under an aerobic condition, and a settling tank 3 into which water in the tank of the aerobic tank 2 flows and precipitates.
The aerobic tank 2 contains sludge containing organic matter-decomposing bacteria, nitrifying bacteria, etc., and a gas containing oxygen is diffused into the tank in order to carry out removal of organic components by the organic matter-decomposing bacteria. An air diffuser (not shown) is provided for bringing the water in the tank to a predetermined dissolved oxygen concentration.
The sludge contained in the aerobic tank 2 contains nitrifying bacteria as described above, so ammonia nitrogen contained in the water to be treated is nitrite nitrogen or nitrate nitrogen. Oxidized.

  Examples of organic matter-degrading bacteria contained in the sludge include Bacillus subtilis, and nitrifying bacteria include ammonia-oxidizing bacteria such as nitrosomonas, nitrosococcus, nitrosospira, and nitrosolobas, nitrobacter, nitro Nitrite-oxidizing bacteria such as Coccus and Nitrospira can be mentioned.

Further, in the biological treatment facility 1, the treated water inflow path 10 for allowing the treated water to flow into the aerobic tank 2 and the water in the aerobic tank 2 are discharged from the aerobic tank 2 and settled. A biological treatment liquid flow path 20 that flows into the tank 3 and a supernatant liquid discharge path 30 through which the supernatant liquid is discharged from the settling tank 3 are provided.
Furthermore, in the biological treatment facility 1, the sludge settled in the settling tank 3 is extracted from the bottom of the tank and a part thereof is returned to the aerobic tank 2, and the remaining sludge is surplus. An excess sludge discharge path 60 for discharging the sludge out of the system is provided.

In the biological treatment method of the present embodiment, biological treatment (decomposition and removal of organic components) is performed as follows.
First, treated water is caused to flow into the aerobic tank 2 through the treated water inflow path 10, and the air in the tank of the aerobic tank 2 is diffused by the air diffuser so that it is covered by the organic matter-decomposing bacteria. In addition to oxidizing the organic components contained in the treated water, among the nitrogen components contained in the water to be treated by ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, ammonia nitrogen and organic nitrogen can be converted to nitrite nitrogen and Oxidize to nitrate nitrogen.

By continuously inflowing the water to be treated into the aerobic tank 2, the in-vessel water (biological treatment liquid) in the aerobic tank 2 overflows and the precipitation tank 3 passes through the biological treatment liquid distribution path 20. The sludge in the biological treatment liquid is precipitated and separated.
Part of the sludge that has been separated by settling is withdrawn from the bottom of the settling tank 3 as sludge, a part of the sludge is returned to the aerobic tank 2 through the return sludge distribution channel 50 as the return sludge, and the remaining sludge as excess sludge Discharge from the discharge path 60 to the outside of the system.
At the same time, the supernatant liquid is discharged out of the system through the supernatant liquid discharge path 30.

In the present embodiment, the water quality prediction is performed using the supernatant liquid discharged from the sedimentation tank 3 as treated water that requires management of the BOD value.
In this water quality prediction, the status of biological treatment is modeled by a model published so far by IWA (International Water Association), for example, ASM1, ASM2, ASM2d, ASM3, etc., and calculation is performed based on this simulation model Then, the step of predicting the ammoniacal nitrogen concentration contained in the treated water (supernatant liquid) is performed, and the step of predicting the BOD value of the treated water based on the ammoniacal nitrogen concentration is performed.
Here, the BOD value of the treated water is predicted based on the ammonia nitrogen concentration because the BOD value in the treated water has a relatively good correlation with the amount of ammonia nitrogen. This is because there is a correlation between the BOD oxidation treatment and the ammoniacal nitrogen oxidation treatment under aerobic conditions, and the concentration remaining without these treatments. It was a matter that I found out that I could get it.

At this time, as to how to predict the BOD value with respect to the predicted value of the ammoniacal nitrogen concentration, at least several points, for example, about 10 points or more and 20 points or less about the water quality of the treated water in advance. And a function based on the data is set.
That is, a function is set from data obtained by collecting several points or more about the BOD and ammonia nitrogen concentration values of the treated water in advance. It can be obtained by calculation based on the predicted value of nitrogen concentration and its function.
For example, the BOD and ammonia nitrogen concentration values of this treated water are measured, the orthogonal coordinates are set with the X axis as the ammonia nitrogen concentration value and the Y axis as the BOD value, and the measured data is plotted linearly. A point cloud that rises to the right is formed.
Therefore, by setting an approximate straight line or a function for drawing an approximate curve from these data by the least square method or the like, for example, the ammonia nitrogen concentration value is set to “S _NH4 ” and the BOD value is set to “ X _BOD ”is set in advance as a function that _satisfies X _BOD = f (S _NH4 ). Thereafter, the process of predicting the ammonia nitrogen concentration is calculated based on the IWA activated sludge model. The step of calculating the BOD value by substituting the predicted value of the ammoniacal nitrogen concentration into the previous function and calculating the value of X _BOD can be performed.

Note that the biological treatment liquid flowing down from the aerobic tank 2 to the settling tank 3 is set as treated water without predicting the supernatant liquid discharged from the settling tank 3, and the BOD value of the treated water is predicted. In this case, the same method can be adopted.
That is, data on the ammonia nitrogen concentration and BOD value contained in the biological treatment liquid are collected in advance, a function based on the data is set, and the ammonia nitrogen concentration is calculated by calculation based on the activated sludge model of IWA. By predicting this value and substituting this predicted value into the function, a highly accurate predicted value of BOD can be calculated as in the case of the supernatant.

In the conventional biological treatment method, since it was difficult to accurately predict the BOD value, the treatment time (average) in the aerobic tank was set so that the BOD value of the treated water did not exceed a predetermined value. (Residence time = tank volume ÷ average inflow of water to be treated per unit time)) was given more than necessary.
In the biological treatment method of the present embodiment, the biological treatment can be performed while predicting the BOD value with higher accuracy than in the past, and thus, for example, the water treatment amount per unit time can be reduced to the conventional amount. Compared with the biological treatment method, it can be increased and the treatment efficiency can be improved.
In addition, since the operation can be performed while accurately predicting the BOD of the treated water, the amount of power required for air diffusion can be minimized by appropriately controlling the amount of air diffused.

  In the present embodiment, the water quality prediction method and the biological treatment method of the present invention are described based on the above examples, but the present invention is not limited to the above examples. As long as the effects of the present invention are not significantly impaired, it is possible to replace or add conventionally known configurations to the above examples in the water quality prediction method and the biological treatment method.

  For example, in the above-described embodiment, a mode in which biological treatment is performed mainly using an organic component as a processing target substance is illustrated, but for example, a processing target substance mainly including a nitrogen component as illustrated in FIG. 2 is used. Such cases are also within the intended scope of the present invention.

The biological treatment facility 1x shown in FIG. 2 includes a denitrification tank 4x in which sludge containing denitrifying bacteria such as Shademonas, Micrococcus, Paracoccus, Alkalinegenes, Achromobacter and the like and sludge containing the nitrifying bacteria are contained. The nitrification tank 5x is housed in the biological treatment facility 1x in order of the denitrification tank 4x, the nitrification tank 5x, the denitrification tank 4x, and the nitrification tank 5x from the upstream side of the treatment. There are stands.
A settling tank 3x is provided on the rear side of the tank in which this biological nitrification / denitrification treatment is carried out, and a part of the sludge that has been separated from the settling tank 3x passes through the return sludge flow path 50x. Regarding points that are returned to the denitrification tank of the eyes, the remainder is discharged as excess sludge from the excess sludge discharge path 60x, and the supernatant liquid is discharged outside the system through the supernatant liquid discharge path 30x. It is the same as the biological treatment facility 1 described in 1. above.
Also in such a biological treatment facility 1x, the BOD value of the supernatant liquid discharged out of the system through the supernatant liquid discharge path 30x can be predicted based on the predicted value of the ammoniacal nitrogen concentration by ASM, About the quality of water, it is the same as that of the case of the biological treatment equipment 1 demonstrated previously also about the point which can be accurately estimated by the method of collecting about 10-20 points data and setting the function based on the data concerned. .

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Investigation of correlation between ammoniacal nitrogen concentration and BOD)
Measurements were made on the quality of the discharged water from sewage treatment plants where biological removal of organic matter has been carried out.
The sampling time was changed and sampling of treated water was performed 14 times in total, and ammonia nitrogen concentration and BOD were measured, respectively.
Each measuring method is as follows.

(Ammonia nitrogen concentration measurement method)
The ammoniacal nitrogen of each sample was measured by the indophenol blue absorptiometry described in JIS K0102 (1998) 42.1 and 42.2.

(BOD measurement method)
Moreover, BOD of each sample was measured by the seeding dilution described in JIS K0102 (1998) 21 and 32.3. When measuring BOD here, the value of BOD may change under the influence of residual ammoniacal nitrogen due to the action of nitrifying bacteria. BOD was measured by the method of suppressing nitrification described in this analysis method to eliminate the influence of residual ammoniacal nitrogen.

FIG. 3 shows a graph of the obtained results.
Thus, it can be seen that there is a linear correlation between the values of BOD and ammoniacal nitrogen concentration.
When the BOD value is “X” and the ammoniacal nitrogen concentration value is “Y”, an approximate expression of “Y = 3.68X + 2.56” can be established between them. You can see from

Next, FIG. 4 is a graph showing a prediction result obtained by predicting the ammonia nitrogen concentration of the discharged water discharged from the sewage treatment plant based on ASM3 and an actual measurement result of the ammonia nitrogen concentration of the discharged water.
As shown in the figure, it can be seen that the ammonia nitrogen concentration of the discharged water is predicted with relatively high accuracy.

A graph showing the result of substituting the ammonia nitrogen concentration value of the effluent water into the above equation “Y” to obtain the BOD value (the above equation “X”) and the actual measurement result of the BOD of the effluent water is shown in FIG. As shown in FIG.
From this figure, it can be seen that the BOD value of the discharged water can be predicted with relatively high accuracy by predicting the BOD value based on the ammonia nitrogen concentration value.

Incidentally, the result of having predicted the value of the easily decomposable organic substance (S _S ) in the discharged water based on ASM3 is shown in FIG.
It can also be seen from FIG. 6 that ASM3 can obtain only the result that almost no readily decomposable organic substance (S _S ) remains.

  That is, according to the present invention, it can be understood that the BOD value of the treated water can be predicted with high accuracy, and as a result, the treatment efficiency in the biological treatment method can be improved.

The block diagram which shows the biological treatment equipment in which the biological treatment of one Embodiment is implemented. The block diagram which shows the biological treatment equipment in which the biological treatment of other embodiment is implemented. The graph which shows the correlation of ammonia nitrogen concentration of treated water and BOD. The graph which shows the prediction result of ammonia nitrogen concentration of the discharge water (treated water) discharged | emitted from a sewage treatment plant. The graph which shows the result of having performed prediction of BOD based on the prediction result of ammoniacal nitrogen concentration shown in FIG. The graph which shows the easily decomposable organic substance residual amount by the calculation based on ASM.

Explanation of symbols

1, 1x: biological treatment equipment, 2: aerobic tank, 3, 3x: sedimentation tank, 4x: denitrification tank, 5x: nitrification tank, 10, 10x: treated water inflow path, 20: biological treatment liquid distribution path, 30 : Supernatant discharge route, 50, 50x: Return sludge distribution route, 60, 60x: Excess sludge discharge route

Claims (2)

Predicting the quality of treated water after biological treatment of water to be treated containing organic components and nitrogen components by performing calculations based on any of ASM1, ASM2, ASM2d, and ASM3, which are IWA activated sludge models A water quality prediction method,
A method for predicting water quality by predicting the ammoniacal nitrogen concentration of treated water by the calculation and predicting the value of biochemical oxygen demand of treated water based on the value of the ammoniacal nitrogen concentration. The quality of treated water after biological treatment of treated water containing organic components and nitrogen components is predicted by performing an operation based on one of ASM1, ASM2, ASM2d, and ASM3, which are IWA activated sludge models. A biological treatment method for carrying out the biological treatment,
The step of predicting the ammonia nitrogen concentration of the treated water by the calculation and the step of calculating the biochemical oxygen demand value of the treated water based on the value of the ammonia nitrogen concentration are performed. Biological treatment method.

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