JPH01218692A - Operation control method in activated sludge method - Google Patents

Abstract

PURPOSE:To control an operating condition on the basis of the concn. and activity of sludge, by calculating the concn. and activity of sludge in an aeration tank on the basis of an estimated model using the measured value from a sensor. CONSTITUTION:The ammoniacal liquor generated in a coke oven is stored in an ammoniacal liquor tank and subsequently guided to an ammonical liquor still to be distilled therein and ammonia is removed to a COG main pipe while the residual water is introduced into a raw water tank while the pH thereof is adjusted by sulfuric acid. Raw water is guided to an activated sludge neutralizing tank to be subjected to neutralizing treatment along with slaked lime. Further, said raw water is sent to an aeration tank and a precipitation tank while sludge is separated into the section returned to the aeration tank and the other section discharged out of the system. The supernatant liquid is guided to a flocculation/sedimentation/neutralization tank to separate a precipitate. In this process, the inflow amount, COD, NH3, SCN, pH, DO and temp. of raw water are inputted to be processed and controlled online.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention <Industrial Application Field> The present invention relates to an operational management method in a wastewater treatment method using an activated sludge method.

(Conventional method) In the conventional activated sludge method, urban domestic wastewater or industrial wastewater is processed through an activated sludge neutralization tank, aeration tank, and settling tank, followed by slaked lime, iron chloride, and a polymer flocculant. is added to remove organic substances as precipitates, and then sand,
The activated sludge method is discharged into the river via an activated carbon tower, but the most important thing in the activated sludge method is to monitor whether the amount of COD in the supernatant liquid in the settling tank after the aeration tank is within regulatory limits. It is fine if the situation is normal, but if it tends to increase, measure the amount of raw water introduced into the treatment equipment, the analysis value, the pH in the aeration tank, etc., and take various measures when abnormalities occur. The general operating method is to take measures to immediately change operating conditions based on the countermeasures, and then measure the amount of COD in the supernatant liquid in the settling tank to confirm the effectiveness.

(Problems to be Solved by the Invention) Wastewater treatment using the activated sludge method effectively utilizes sludge bacteria in water without using any drugs to remove organic matter that consumes large amounts of dissolved oxygen present in wastewater. The process involves removing these and returning the treated water to rivers or seawater, so the reaction requires atmospheric oxygen or active bacterial activity, so long aeration treatments and sedimentation are not required. Due to the fact that a large storage tank is required for formation, once the smooth growth of sludge bacteria is disrupted, it may take one to two months to restore normal conditions, which is a major problem in terms of pollution control. This has become a problem.

The present invention was created in response to the current situation, and uses measurement values from continuously available sensors to obtain guidelines for continuing stable operations using a predictive estimation model, and based on this, The purpose is to provide a way to control conditions.

"Structure of the Invention" (Means for Solving the Problems) In order to achieve the above-mentioned purpose, the present inventors have developed a method for predicting and estimating sludge in an aeration tank using a predictive estimation model formula using measurements from continuously available sensors. The sludge concentration is calculated, the activity of the sludge is calculated from the sludge concentration, and the amount of raw water flowing into the sludge treatment equipment, the amount of sludge, the amount of excess sludge extracted, or a combination thereof is controlled. We propose an operational management method for the activated sludge method.

(Function) Ammonium water generated in a coke oven at a steelworks is usually first stored in an ammonium tank along with miscellaneous water in the system, and then guided by a pump to an ammonium still, where it is distilled to produce 1,000 bottles of ammonia. The remaining water is returned to the pipe, and the PL+ is adjusted using sulfuric acid, etc., and then introduced into the raw water tank. This raw water is led to the activated sludge neutralization tank, which is the first step in the wastewater treatment facility, and is neutralized with slaked lime or phosphoric acid (this step may be omitted in some cases). The liquid is then transferred to an aeration tank, where oxygen is supplied and the liquid is stirred.

The sludge is then sent to a settling tank, where the organic matter is decomposed to form microbial cells, which become flocculated sludge and settle. The sludge produced here is divided into sludge that is returned to the aeration tank and sludge that is discharged outside the system. Here, the supernatant liquid is led to the coagulation-sedimentation neutralization tank in the next step, where slaked lime, iron chloride, and a polymer flocculant are added to form flocs, separated from the sediment, and finally sand or activated carbon. The water is discharged into the river via an adsorption tower, but the problem in the present invention is from the raw water tank to the step of obtaining the supernatant after the settling tank (see Figure 3).

In this activated sludge treatment process, the things that can be entered into the online digital calculator include the amount of raw water inflow, COD in the raw water, NH3, SCN, as well as pH, D○, and temperature. MLSS can be measured. Regarding the supernatant liquid after the settling tank, the same measurement values as those for the analysis and measurement of the raw water can be obtained.

Next, the second predictive estimation model, which is a feature of the present invention, will be described. It is preferable to use coefficients depending on the processing equipment so that the results calculated using these formulas match the actual measured values.

The basic formula of the predictive estimation model of the present invention is established as follows.

MLSS=f (C, F, S, μ, t) [In the formula, MLSS: sludge concentration, C: concentration, F: flow rate, S.

Inflow, outflow SS, μ: growth rate, t: time, V: volume of tank] This M L S S '114 degree can be determined by expressing it in kg/m3. (t,:?% sludge negative load kg/kg/day), a: sludge conversion rate, b: self-oxidation rate,
R: sludge return ratio] In the present invention, MLSS contains COD bacteria, SCN bacteria, NO
Since the calculation is performed assuming the total of three bacterial groups, C
0D-Load = f(C, F, MLSS.

■) It can be expressed as: 5CN-Load.

Similarly, NH3-Load % is f(C, F, MLSS
, V).

Next, the ammonium water treatment amount in m3/H is f, and the ammonium water C in g/m3 is
If OD concentration is CcoD, COD sludge load L CO
D can be expressed as , so the sludge concentration is 5a-2
4°a COD' r, COD 24
°a scy 'L 5cst(μcoo 10b C0
D) (1+R) t(μSCN + b 5C
N) (1+R) Dissolved oxygen consumption rate in this Sa (
ppm/H) r R (A, B, C; coefficient) (dt
: Time change, dRo : Dissolved oxygen change, dL : Load change), which is Acon ・1/24 ・L
coo + ASCN ・1/24 ・LSCN+A
N H3・1/24・LNH3+ 5a (Bcon+
BSCM + BNI-13) + C・1/24・LNo.
Corresponds to z. The optimal range for this calculated rR varies depending on the chemical composition of the wastewater to be treated, the amount of treatment per unit time, and the type of bacterial group. In cases where the treatment equipment is for wastewater containing NH3 and the main purpose is to remove COD without expecting complete decomposition of NH3, it is preferable that rR be in the range of 30≦r≦60; below 30, the decomposition of COD is insufficient. On the other hand, if it exceeds 60, it will be oxidized to NH, and converted to NO2, impairing the activity of sludge bacteria. The rR can be controlled by adjusting any one or a combination of the amount of raw water flowing into the aeration tank from the raw water tank, the amount of sludge, and the amount of excess sludge extracted.

Next, the removal efficiency of each component can be determined by the following formula.

(KCOD: COD removal rate constant), so SCN, NH3 will be calculated in the same manner below.

(2) From the calculation, it is confirmed whether the removal efficiency of each component has achieved a predetermined target value. If the specified value is not met, it is necessary to take measures to control the Sa concentration so that it falls within the control value. Specific methods for controlling this concentration include increasing or decreasing the inflow of raw water, increasing or decreasing the amount of sludge, or controlling the amount of excess sludge removed, or by combining these methods.Other methods include adjusting by pH and temperature. You can also take that into consideration. The main thing is decomposition of COD, and N
In the activated sludge method, which does not require oxidation of H3, η
COD≧0.90, ηSCN≧0.95, η9. +3≦
The control limit is around 0.05. The example in the next section illustrates this example.

(Example) 1. Example where operation was smooth and there was no need to change management conditions a) Composition of raw water COD: 5000rtg/f! ,,SCN: 1
00mg#! , NH3: 1000■/l, b) Raw water inflow m: 30 m3/Hc)
Sa: 5000mg/j2 (obtained from the basic formula of the prediction estimation model) d) rR: 40 (same as above) e) Actual measurement value of supernatant analysis: SCN 3■/ρ In this example, dissolved oxygen consumption rate rH Since the temperature was 40 degrees and within the control limit of 30 to 6 degrees mentioned above in the present invention, no particular changes were made to the operating conditions.

2. An example where the analytical value of the supernatant liquid reached the regulation value limit and the operating conditions were changed by the method of the present invention a) Composition of raw water COD: 7000■/β, SCN: 100㎵/j2
゜NH3:1000■/! , b) Raw water inflow: 40 m3/Hc) Sa
: 10000mg/A (according to Example 1)d
) rR: 20 (above) e) Supernatant analysis actual value: SCN 30 ppm In this example,
rR was below the lower control limit of 30, and COD decomposition was insufficient, so we changed the operation to reduce the amount of raw water flowing in (scN was intentionally raised by 1 degree for the purpose of the experiment). example).

FIG. 1 shows the amount of raw water taken in for 26 hours before and after this example, in which the amount of inflow was controlled because the analysis value of the clear solution approached the limit value.

Figure 2 shows approximately 6 liters of water due to the regulation of the amount of raw water inflow shown in the previous figure.
This shows that the SCN amount in the supernatant liquid (treated water) returned to the normal content after a period of time, and also shows the fluctuation in the SCN amount before and after 26 hours.

"Effects of the Invention" As explained in detail above, when operating the activated sludge method using the method of the present invention, the concentration of sludge can be constantly measured and the activity of sludge can be predicted from that value. Since it is possible to control the optimal flow of raw water, appropriate operational management can be carried out before operational conditions deteriorate, and by making the most of the activity of sludge bacteria, complete decomposition of organic matter can be achieved. .

[Brief explanation of the drawing]

The drawings show an example of the operational management of the activated sludge method according to the present invention. Fig. 1 shows the control status of the amount of raw water flowing into the treatment equipment, and Fig. 2 shows the control status of the amount of raw water flowing into the treatment equipment, and Fig. 2 shows the control status of the amount of raw water flowing into the treatment equipment. This shows the fluctuation in the amount of SCN in the treated water. FIG. 3 shows the flow of the main part of the activated sludge method used in the present invention. Patent applicant Nippon Kokan Co., Ltd. Inventor Tomo Kato Betsuma
Tsuka 1) Hagane Nidou
Susumu Matsumura1go1
P11

Claims (1)

[Claims] The sludge concentration in the aeration tank is calculated from a predictive estimation model formula using measured values from continuously available sensors, and the sludge activity is calculated from the sludge concentration, and the amount of raw water flowing into the sludge treatment equipment is calculated. An operational management method in an activated sludge method, characterized by controlling the amount of sludge, the amount of excess sludge extracted, or a combination thereof.