KR101922228B1 - Method of Compensation for In-Situ Coagulant Input to Control Phosphate Concentration and Device thereof - Google Patents

Abstract

According to the phosphorus removal method of the present invention, the concentration of phosphorus in the influent water and the phosphorus concentration in the treated water are alternately measured in order to predict the change in the concentration of phosphorus in the influent water changing in real time, A phosphorus concentration correcting method and an apparatus for accurately controlling the concentration of phosphorus in the field so that phosphorus concentration can be controlled more precisely.

Description

TECHNICAL FIELD [0001] The present invention relates to a coagulant feed flow rate correction method and apparatus,

The present invention relates to a coagulant input flow correction method and apparatus that reflects on-the-spot conditions for controlling phosphorus concentration in the monitoring of influent water quality.

In general, the method of performing additional flocculation after the biological treatment of sewage and wastewater is carried out by administering a coagulant such as polychlorinated aluminum (PAC) to a waterway or a sedimentation bed and allowing the coagulant to be mixed with sewage and wastewater, Chemical treatment method.

Such a chemical treatment method is currently carried out by comparing the efficiency and the cost of the coagulant to each other, selecting the coagulant after the field test, the coagulant dosing facility, the storage facility and the stirring facility.

However, the input of coagulant is usually done manually, and even if the input is automated, there is no system that can automatically dispense the appropriate amount of coagulant according to the real-time change of phosphorus concentration in sewage.

In Korean Patent No. 10-1301598, the dissolved concentration of the sample wastewater is measured by a coagulant Jar test, and the concentration of the coagulant is determined and the dissolved concentration after the addition, stirring, and precipitation is measured. At this time, the amount of phosphorus per 1 ppm of the added flocculant is calculated by Jar test, and it means (amount of phosphorus removed) / (concentration of flocculant added). The Jar test is a type of sampling test.

Herein, the amount of phosphorus per 1ppm of coagulant is used as a factor determining the coagulant input concentration according to the target of removal of dissolved phosphorus, considering the characteristics of sewage and the characteristics of coagulant in use such as sulfur and pH. The coagulant input concentration is (amount of phosphorus to be removed) / (phosphorous content per 1ppm of flocculant), and is in ppm unit based on the mass of the flocculant being fed.

In recent years, it is necessary to check on whether the phosphorus concentration control is proper, so that more accurate phosphorus concentration can be removed. Therefore, it is necessary to control the situation in the field by reflecting the situation in the field on the field The needs of people are increasing.

Korean Patent No. 10-1301598

The present invention solves the problems of the prior art. In order to predict the change in the concentration of phosphorus in the inflow water changing in real time and to determine the amount of the flocculant, the phosphorus concentration of the influent water and the phosphorus concentration of the treated water are alternately measured And a method of correcting phosphorus concentration, which allows the phosphorus concentration control to reflect the situation of the site more precisely by data of the flocculant removal efficiency in the field in consideration of the flow rate of the flocculating agent.

The present invention relates to a method for controlling the concentration of phosphorus in an influent of a water treatment plant, comprising the steps of: measuring the concentration of influent water; Predicting a concentration of influent water after a predetermined time; Calculating a coagulant input flow rate by the following equations (1) to (4); Injecting a flocculant input flow rate into the influent; Measuring the concentration of the treated water; Calculating in situ application flocculant efficiency from the flocculant field efficiency; A field correction step of comparing the concentration of the treated water with the concentration of the discharge target and comparing the immediately preceding value of the concentration of the treated water with the concentration of the treated water to correct the flocculant input flow rate; The concentration of the coagulant added to the flocculant is determined by the flow rate correction method.

[Equation 1]

Coagulant input flow rate (ml / min) = Coagulant input concentration (ppm) x Sewage inflow flow (ton / hour) / 60 x Safety factor x Correction factor /

&Quot; (2) "

Coagulant field efficiency = (influent concentration - concentration as treated water) / coagulant input concentration (ppm),

&Quot; (3) "

Effective Coagulant Efficiency at Site = (Effective Coagulant Efficiency x Site Weight + Coagulant Efficiency) / (Weight + 1)

&Quot; (4) "

Coagulant input concentration (ppm) = (concentration in the influent water - concentration as the target of discharge) / Coagulant efficiency in the field

According to the phosphorus removal method of the present invention, the input amount of the flocculant is determined in consideration of the change in phosphorus concentration of the inflow water and the treated water changing in real time, and as a result of data recording, it is confirmed that the phosphorus removal efficiency of the flocculant varies with the phosphorus concentration of the influent water Respectively.

In addition, there was a difference in the removal efficiency of the coagulant on the spot due to unknown factors, such as the flow meter error and the deterioration of the coagulant pump performance, compared with the coagulant removal efficiency measured by the actual Jar test. Thus, by cross-measuring the phosphorus concentration of the influent and treated water at the site and analyzing the efficiency and trend of the coagulant, the improved coagulant loading from the field coagulant efficiency is determined, enabling more accurate and effective removal of phosphorus.

Fig. 1 shows changes in phosphorus concentration and phosphorus removal efficiency measured in the field.
Figure 2 is a flow chart of a method for calculating and correcting coagulant efficiency in the field.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would unnecessarily obscure the gist of the present invention.

In order to discharge the phosphorus contained in the influent water flowing into the sewage treatment plant and to discharge the sewage water to the sewage treatment plant as a treated water, a part of the influent water is sampled to measure the phosphorus concentration. Then, the phosphorus concentration of the sewage is controlled by injecting the coagulant at a predetermined flow rate in accordance with the target concentration of the treated water. At this time, if the amount of the coagulant is determined based on the phosphorus concentration sampled from the influent, the process proceeds without recognizing the specific situation that may occur in the field. For example, sudden process operating conditions may change, or the inlet phosphorus concentration may be lower than expected or the phosphorus removal rate expected due to the change in the properties of the flocculant. In addition, the performance of the hardware such as the error of the flowmeter and the performance of the pump is deteriorated.

In order to reflect unforeseeable or unpredictable conditions at such sites, it is necessary to measure the concentration of the treated water from the flocculant input, as well as the influent concentration, from time to time, and to incorporate both results into the coagulant input calculation. The flocculant input amount calculation method described below can be applied to the wastewater treatment system.

Figure 1 shows the change in phosphorus concentration and the phosphorus removal efficiency measured in the field. The change in the concentration of the influent does not mean that the concentration of phosphorus is maintained within a certain range in each measurement, but suddenly, the concentration suddenly rises and then falls again. In addition, although the concentration of the treated water is kept at a relatively low level of less than a certain ppm and the concentration of the influent water is not high, there is an interval in which the concentration of the influent water is irregularly peaked although the cause thereof is unknown. Of course, this is just one example of concentration changes as influent and treated water, and in practice there will be more field variables.

Therefore, it is necessary to periodically measure not only the influent concentration but also the treated water concentration, and the difference between the concentration of the treated water and the target treatment water concentration should be automatically corrected to the flocculant input flow rate.

In Figure 1, the " flocculant site efficiency " and " field coagulant efficiency " &Quot; Coagulant site efficiency " is the efficiency of the coagulant calculated from the in-situ measurements of the phosphorus concentration of influent and treated water. In other words, the amount of coagulant injected varies depending on the concentration of influent water, which shows how effective the coagulant is in removing phosphorus concentration. The reason for putting the flocculant into the sewage is to keep the phosphorus concentration of the treated water below a certain standard. Therefore, if the concentration of the treated water sufficiently satisfies the phosphorus concentration standard, it is cost-effective to reduce the amount of the flocculant to be added.

Further, considering that the treatment time delay due to the chemical reaction of the flocculant occurs, it is also not preferable that the flocculant input amount changes rapidly with the change in the concentration of the influent water. Therefore, it is desirable to control the amount of coagulant input so that the average coagulant efficiency can be maintained without significantly changing the coagulant field efficiency.

The application of this is "Field Coagulant Efficiency". That is, the field-applied flocculant efficiency is the weighted value of the on-site flocculant efficiency measured immediately before, using the current field coagulant efficacy and the immediately measured field coagulant efficiency. This weight can be adjusted by the user, and the equation for this can be expressed by Equation (3).

&Quot; (3) "

Current on-site application flocculant efficiency (t) = (on-site flocculant efficiency (t-1) x weight + flocculant field efficiency) / (weight + 1).

The effluent efficiency of the current applied flocculant is expressed as (t), and the efficiency of the field coagulant measured immediately before is expressed as (t-1). In Equation (3), if the weight is 9, then the field application coagulant efficiency (t) = (field application coagulant efficiency immediately before (t-1) x 9 + coagulant field efficiency) / 10.

FIG. 2 illustrates a method for calculating the flocculant efficiency at such a site and correcting the coagulant input flow rate. The concrete method is as follows.

First, the concentration of the influent water is measured to predict the phosphorus concentration (S10).

The method of predicting the phosphorus concentration is to estimate the phosphorus concentration (PT) flowing in accordance with the change of the values of P1, P2, and P3 by sequentially measuring three times (P1, P2, P3) (S20).

The first step for predicting the phosphorus concentration is a step of measuring the phosphorus concentration contained in the influent water three times at a time interval selected from the range of 10 to 30 minutes with the phosphorus concentration measuring instrument installed before the coagulant administration point, The measured phosphorus concentration values are sequentially determined as P1, P2 and P3 values. Measuring the phosphorus concentration in the influent water three times in succession is intended to determine what trend the phosphorus concentration in the influent water varies with. The values of P1, P2, and P3 measured at this stage are used to predict the phosphorus concentration PT after a certain time has elapsed from P3 (e.g., 15 minutes in Fig. 1) via the following steps b) and c) .

If it is determined that the value of (P2 - P3) is larger than the decrease limit value, that is, if the latest measured value P3 is abnormally decreased compared to the previous measured value P2, if the value of (P2 - P3) is less than or equal to the decreasing limit, and (c) the step (c) Step to execute the step.

The reduction limit is an empirical value obtained from the field test of the phosphorus concentration of the influent for a certain period of time considering the characteristics of the site and the measurement period of the phosphorus concentration measuring device, Means the limit value. Therefore, the value of (P2 - P3) above is larger than the decrease limit, which means that there is a high possibility that an error has occurred in the measured value.

Therefore, the concentration of the flocculant added is not changed according to the decrease in the phosphorus concentration, but is set to be the same as the concentration of the flocculant immediately before the flooding, thereby preventing the outflow of the phosphorus due to the measurement error.

On the other hand, when the value of (P2 - P3) is smaller than or equal to the decrease limit, it is necessary to change the coagulant input concentration, so the subsequent step c) is performed. Step c) is a step of comparing the values of P3 and P2 to obtain PTs in the following cases (i) to (iv).

(I) if P3 is greater than or equal to P2 and (P3 - P2) is greater than or equal to (P2 - P1), that is, if the current influent concentration increases (P3> = P2) - P 2) is greater than or equal to the previous phosphorus concentration change value (P 2 - P 1), it is determined that the phosphorus concentration is steeply increasing and the phosphorus phosphorus concentration included in the influent to be influenced after the measurement interval from the P 3 measurement point The expected concentration PT is calculated by PT = P3 + (P3 - P2) + (P3 - P2) - (P2 - P1)

(P3 - P2) - (P2 - P1)) of the phosphorus concentration change amount by adding the latest concentration increase value (P3 - P2) to the latest measured value P3, It is calculated to reflect the rapidly increasing trend of phosphorus concentration.

That is, in the above case, the graph of the phosphorus concentration change value composed of P1, P2 and P3 may be, for example, the following form.

In the case of (A), PT is calculated by adding the value of (P3 - P2) to P3 and adding again the value of ((P3 - P2) - (P2 - P1)). At this time, the value of (P2 - P1) becomes a positive value.

In the case of (B), the value of (P3 - P2) is added to P3 and the value of ((P3 - P2) - (P2 - P1)) is added again to calculate PT. At this time, the value of (P2 - P1) becomes a negative value, and the value of PT becomes larger as compared with the case of (A) above. This is because, in the case of (B), the phosphorus concentration increasing tendency is confirmed to be further strengthened in the case of (A).

(Ii) If P3 is greater than or equal to P2 and (P3 - P2) is less than the value of (P2 - P1), that is, if the current influent concentration increases (P3> = P2) - P 2) is smaller than the previous phosphorus concentration change value (P 2 - P 1), the current phosphorus concentration is rising, but is included in the influent water to be introduced after the same time as the measurement interval from the P 3 measurement point, The expected concentration PT of phosphorus is calculated by PT = P3 + (P3 - P2)

In the above equation, the phosphorus concentration predicted value PT is calculated by adding the latest increase value (P3 - P2) to the latest measured value P3 so that the gentle phosphorus concentration increase is sufficiently reflected.

(Iii) If P3 is smaller than P2 and P3 - P2 is greater than or equal to (P2 - P1), that is, if the current influent concentration is decreasing (P3 <P2) - P 2) is greater than or equal to the previous phosphorus concentration change value (P 2 - P 1), it is determined that the decrease in the current phosphorus concentration is gradual and may be gradually increased. The expected concentration PT of phosphorus in the incoming influent is calculated by PT = P3 + (P3 - P2) - (P2 - P1).

In this formula, the phosphorus concentration prediction value PT is calculated by adding the calculated value ((P3 - P2) - (P2 - P1)) of the phosphorus concentration change amount to the latest measured value P3, It is calculated considering the possibility of changing to one rising trend.

(Iv) If P3 is smaller than P2 and P3 - P2 is smaller than (P2 - P1), that is, if the current influent concentration is decreasing (P3 <P2) Of the phosphorus contained in the influent to be introduced after the same time as the measurement interval from the P3 measurement point is judged to be abruptly decreasing when the phosphorus concentration is lower than the previous phosphorus concentration change value (P2 - P1) Is calculated by PT = P3.

In the above equation, the phosphorus concentration predicted value PT is calculated such that the phosphorus concentration is gradually decreased, but the PT value is at least equal to the P3 measured value in consideration of an increase in phosphorus concentration which may be present in only one phosphorus concentration.

The step c) is a step for predicting the concentration PT as an influent to be introduced after the same time interval as the measurement interval applied when measuring P1, P2 and P3 from the P3 measurement time point.

Thereafter, step (S30) of calculating the coagulant input concentration by the following equations (1) to (4) according to the predicted influent phosphorus concentration (PT) and step (S40) of calculating the coagulant input flow rate. The unit of all concentrations used is ppm.

[Equation 1]

Coagulant input flow rate (ml / min) = Coagulant input concentration (ppm) x Sewage inflow flow (ton / hour) / 60 x Safety factor x Correction factor /

Here, the safety factor is a value set so that the operator can increase or decrease the flow rate of the coagulant depending on the characteristic of wastewater treatment. The correction coefficient is used to correct the coagulant input flow rate according to the difference between the concentration, Lt; / RTI &gt;

&Quot; (2) &quot;

Coagulant field efficiency = (concentration of influent water - concentration of treated water) / concentration of coagulant,

&Quot; (3) &quot;

Field Coagulant Efficiency = (Site Coagulant Efficiency (t-1) x Weight + Coagulant Efficiency (t)) / (Weight + 1)

&Quot; (4) &quot;

Coagulant input concentration = (concentration in the influent water - concentration as the target of discharge) / field coagulant efficiency

Injecting the flocculant input flow rate into the inflow water (S50);

Measuring the concentration of the treated water after the flocculant is added to the influent water (S60);

(S80) of calculating the field efficiency of the flocculant of the formula (2) (S70) and calculating the field application flocculant efficiency of the formula (3);

Coagulant In-situ efficiency means the coagulant removal efficiency of a field, which is calculated on a fixed time basis, and means the concentration (ppm) of phosphorus removed by 1ppm of the coagulant.

Here, the efficiency of the field application flocculant shows the tendency of efficiency change of the flocculant in the field, which is calculated in a predetermined time unit as shown in FIG. 2, and this value is used as the flocculant removal efficiency value in the calculation of the actual flocculant input concentration. In FIG. 2, the field efficiency of the flocculant means the flocculant efficiency calculated by the existing analytical method applied in the field based on the concentration of influent water. The field coagulant efficiency is similar to the flocculant field efficiency, but the amplitude of the applied flocculant efficiency is reduced as the concentration of influent and the concentration of treated water are applied to the flocculant application efficiency.

(S80) of calculating the field application flocculant efficiency of the formula (3); Thereafter, the concentration of the treated water is compared with the concentration of the discharging target (S90), and the concentration (t-1) as the treated water and the concentration (t) An on-site calibration step of the coagulant input flow rate to correct the flow rate; . S100, S120 and S130 are carried out when the concentration (t) as the treatment water is smaller than the concentration as the discharge target, and the concentration (t) as the treatment water is equal to or greater than the concentration as the discharge target, If Equation (6) of S120 is performed, the concentration (t) as the treatment water is equal to or greater than the concentration of the effluent target , And if the concentration (t) as the treatment water is smaller than the concentration (t-1) as the immediately preceding treatment water, the following equation (7) in S130 is performed.

Here, t, t-1, and t + 1 are time-based distinctions, t is a current value, t-1 is a previous time value, and t + 1 is a predicted value after a certain time.

Further, when the concentration of the treated water is less than the concentration as the discharge target, the correction coefficient of the above-mentioned formula (1) is calculated by the following formula (5).

&Quot; (5) &quot;

The correction coefficient t = the correction coefficient immediately before the value t-1 + (the concentration of the treated water t-the concentration of the discharge target) + (the concentration of the treated water t- 1))) / Field Coagulant Efficiency x Second Factor Value,

When the concentration of the treated water is equal to or higher than the concentration of the discharge target and the concentration t of the treated water is not less than the immediately preceding value (t-1) of the concentration of the treated water, the correction coefficient of the formula (1) 6].

&Quot; (6) &quot;

(T-1) + (concentration as treated water - concentration as treated water (t-1)) / on-site application coagulant efficiency / coagulant input concentration x first factor value, At this time, the first factor value corresponding to the case where the concentration as the process water is equal to or higher than the target value is greater than or equal to the second factor value corresponding to the case where the concentration as the process water is less than the target value.

When the concentration of the treated water is equal to or higher than the concentration of the discharge target and the concentration t of the treated water is less than the immediately preceding concentration (t-1) of the concentration of the treated water, the correction coefficient of the formula (1) 7].

&Quot; (7) &quot;

Correction factor (t) = value immediately before correction factor (t-1) + (concentration in treated water (t) - concentration in treated water (t-1))

The first factor value and the second factor value are based on 1.0 unless otherwise determined by the user.

Claims (6)

Measuring the concentration of influent water;
Predicting the concentration of the influent water after a predetermined time;
Calculating a coagulant input flow rate by the following equations (1) to (4);
Injecting the flocculant input flow rate into the inflow water;
Measuring the concentration of the treated water;
Calculating in situ application flocculant efficiency from the flocculant field efficiency;
A field correction step of comparing the concentration of the treated water with the concentration of the discharged water and comparing the immediately preceding value of the concentration of the treated water with the concentration of the treated water to correct the flocculant input flow rate; A method for calibrating the amount of flocculant input through field application.

[Equation 1]
Coagulant input flow rate (ml / min) = Coagulant input concentration (ppm) x Sewage inflow flow (ton / hour) / 60 x Safety factor x Correction factor /
&Quot; (2) &quot;
Coagulant field efficiency = (concentration of influent water - concentration of treated water) / concentration of coagulant,
&Quot; (3) &quot;
Effective Coagulant Efficiency in Field = (Effective Coagulant Efficiency x Site Weight + Coagulant Efficiency) / (Weight + 1)
&Quot; (4) &quot;
Coagulant input concentration = (concentration in the influent water - concentration as the target of discharge) / field coagulant efficiency The method according to claim 1,
Wherein the correction coefficient of the equation (1) is calculated by the following formula (5) if the concentration of the treated water is smaller than the concentration of the discharge target.
&Quot; (5) &quot;
Correction factor t = correction factor t-1 + (concentration of treated water t-concentration of discharged water) + (concentration of treated water t-concentration of treated water t- Field Coagulant Efficiency x Second Factor Value 3. The method of claim 2,
If the concentration as the treated water is equal to or greater than the concentration as the discharge target and the concentration as the treated water is equal to or greater than the immediately preceding value of the concentration as the treated water, the correction coefficient of the above formula (1) Wherein the flow rate of the coagulant is calculated by the method of claim 1.
&Quot; (6) &quot;
Correction factor (t) = Correction coefficient immediately preceding value (t-1) + ((concentration before treatment) 1 Factor value The method of claim 3,
Wherein the first factor value is greater than or equal to the second factor value. The method according to claim 1,
If the concentration as the treated water is equal to or greater than the concentration as the discharge target and the concentration as the treated water is smaller than the immediately preceding value of the concentration as the treated water, the correction coefficient of the above formula (1) Wherein the amount of the coagulant is greater than the amount of the flocculant.
&Quot; (7) &quot;
Correction factor (t) = Correction factor immediately preceding value (t-1) + ((concentration before treatment) A wastewater treatment system to which a coagulant input flow correction method is applied through the field application of any one of claims 1 to 5.

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