JPS5938840B2 - Sludge dewatering control method and manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method and a control device for dewatering organic sludge, and particularly to a control method and control device for dewatering sewage sludge whose properties change by adding a cationic flocculant. It is.

A cationic organic polymer flocculant is added to organic sludge such as sewage sludge and raw sludge to form flocs, which are mechanically dehydrated using a dehydrator such as a centrifugal dehydrator, belt press type dehydrator, or filter press. In actual treatment sites, the sludge properties are constantly and drastically changing, and the dewatering effect is also constantly changing accordingly.

Conventionally, processing was carried out under constant conditions despite such changes.

Therefore, if the relationship between sludge properties and dewatering effect can be grasped in some way, dewatering treatment can be carried out under optimal conditions and the treatment effect can be increased.

The purpose of this invention is to propose a sludge dewatering treatment management method that can meet the above demands, and includes the following two inventions.

(1) In a method of adding a flocculant to organic sludge for dewatering, the viscosity of sludge at a predetermined concentration or a value correlated with this is measured, an index of sludge properties is determined from that value, and based on that, A sludge dewatering control method comprising determining a cationic group or addition rate of a cationic organic polymer flocculant suitable for sludge dehydration, or a sludge dewatering amount per unit time.

(2) A plurality of flocculant storage means for storing cationic organic flocculants of different cation groups, a flocculant injection means for injecting the cationic organic flocculant into sludge, and an SS concentration measuring device for measuring the SS concentration of sludge. and Sv of sludge at a given concentration
A sludge dewatering control system that includes an SV measuring device that measures SV, and a control means that calculates and controls the cation group of a cationic organic flocculant to be added from the SS concentration signal and Sv value multiplied signal obtained by those measuring devices. Device.

In the present invention, when organic sludge such as sewage sludge or raw sludge is mechanically dehydrated using a cationic organic polymer flocculant as an aid using a centrifugal dehydrator, belt press type dehydrator, etc., the sludge slurry is Measure the viscosity or a value that correlates with it, select a cationic organic polymer flocculant suitable for sludge dehydration from that value, and calculate the water content of the dehydrated cake using an actual machine at a predetermined addition amount. Make predictions possible.

Furthermore, the following on-site management is possible.

That is, by measuring the sludge slurry viscosity or sludge, or a value having a correlation therewith, (1) the optimum cation group of the cationic organic polymer flocculant used as a dewatering aid can be predicted.

(2) The necessary addition rate of the cationic organic polymer flocculant that can maintain the SS recovery rate at a predetermined level or higher can be determined.

■ Determine the sludge load or flow rate that can be dewatered.

0 It is possible to predict and save the amount of heavy oil expected to be required when incinerating a dehydrated cake based on the predicted cake moisture content.

This enables a series of on-site management such as

A value that has a correlation with viscosity is, for example, 5KI of sludge at a predetermined concentration (volume per unit weight of SS when sludge is adjusted to a predetermined SS concentration and then allowed to stand for a predetermined time).

Measurement items that determine sludge properties include slurry viscosity and SEI.
A slurry viscosity measured by adjusting the consistency between % and 30% is desirable.

That is, the slurry viscosity value of sludge is greatly influenced by its SS concentration.

Therefore, the viscosity value measured by adjusting the SS concentration to a constant concentration between 1 and 6% is easy to measure and accurately indicates the properties of the sludge.

The SS concentration can be measured based on JIS KO10210, 2, but it can also be measured using a known measuring device using ultrasound or a phototube.

A method for measuring viscosity is, for example, as follows.

Centrifuge at 3000 rpm for about 10 minutes to take a certain amount of the principle, and discard the supernatant water to obtain thickened mud.

After thoroughly kneading the concentrated mud, a certain amount was taken into a crucible, the wet weight was measured, and the dry weight was determined by drying at 105°C overnight.
The SS concentration (A%) of the thickened mud is determined from these values.

Next, thicken mud for 300m/! Accurately collect an appropriate amount in a beaker, add strained water or industrial water (CXIII), and mix thoroughly to prepare a slurry with a constant SS concentration.

For example, when preparing a 4% SS slurry, the final amount of water (Xml) to be added is determined by the following formula.

W

For example, the measured value on the scale at 30 rpm and rotor boiling 2 (
If the sludge slurry viscosity (displayed value) is C, then the sludge slurry viscosity (
SS4% preparation) is 10c (cps).

Next, the SEI is preferably an SEI measured by adjusting the SS concentration to a constant concentration between 0.1 and 1.0, particularly 0.5.
Recommended degree is desirable.

SEI is the volume percentage of the settling part when the sludge is adjusted to a predetermined SS concentration and then left to stand for a predetermined time, that is, the value obtained by dividing sv by the SS concentration, Sv S E I = -X 10' [ml It is expressed as /fri.

S Note that the method of determining this SEI is similar to the SVI in the activated sludge treatment method for wastewater.

The volume percentage of the precipitated portion when the mixed liquid (MLSS) in the SVI+r aeration tank is allowed to stand still for 30 minutes, that is, 5v3
o divided by the MLSS concentration, usually Sv■
−SV×104 [7721/v] L S S Both SVI and SEI have in common that they indicate the volume occupied by sludge with a dry weight of 11.

However, while SVI directly measures the mixed liquid in the aeration tank, SEI measures sludge at a specified SS.
Measure after adjusting the concentration.

In other words, dewatered sludge is usually already concentrated in a settling tank, etc., so even if you measure SV without adjusting the SS concentration, the degree of change in the measured value depending on the sludge properties is small, and the so-called sensitivity is low. On the other hand, SEI measures the SS concentration after adjusting it to a predetermined concentration as mentioned above, so it has high sensitivity, allows accurate understanding of sludge properties, and is a convenient index for controlling the setting of optimal conditions for sludge dewatering. Become.

Figure 1 shows the relationship between slurry viscosity (cps) when prepared to 884% and SEI when prepared to SS 0.5% for raw sludge and sewage sludge (digested sludge and raw sludge) at treatment plants in various places. As is clear from FIG. 1, the relationship between the slurry viscosity value and the SEI value is a nearly linear relationship, so it can be seen that it is sufficient to measure either one of them.

Therefore, the explanation regarding slurry viscosity will be continued from now on.

In the present invention, a cationic organic polymer compound is added to organic sludge to form flocs, but the cationic organic polymer flocculant that can be used in the present invention is an aminoalkyl (meth)acrylate homopolymer or Examples include copolymers of acrylamide or other monomers, Mannich modified products of polyacrylamide, Hofmann decomposition products of polyacrylamide, polyamide polyamines, polyvinylimidacillin, polyethylene imine, polydialkyl diallyl quaternary ammonium salts, and chitosan.

Figure 2 shows a copolymer of a quaternized product of dimethylamine ethyl methacrylate with methyl chloride and acrylamide (the cationic degree was adjusted by adjusting the molar ratio of the quaternized product) as a polymer flocculant to sewage sludge. This is a graph showing the slurry viscosity and cake moisture content of SS4'% preparation when added under optimal conditions and dehydrated with a centrifugal dehydrator. From this graph, the moisture content of the dehydrated cake can be predicted from the viscosity of the sludge, and this is incinerated. It is also possible to predict the amount of heavy oil required for this purpose.

Further, the relationship between the slurry viscosity and the physical property value (cation degree) of the optimum cationic organic polymer flocculant used as the dehydration aid is as shown in FIG.

FIG. 3 is a graph showing the 884% prepared slurry viscosity and the optimum cation degree (mol % of the quaternized product) of the polymer flocculant when tested in an actual machine under the same conditions as the test in FIG. 2.

Therefore, when sludge fluctuates, by using the slurry viscosity as an index, it is possible to select a polymer flocculant with the optimal cation degree from this graph, which can prevent deterioration of the recovery rate due to sludge fluctuations and stabilize the cake water content. It becomes possible.

When performing dehydration using a polymer flocculant with a certain cationic degree, the slurry viscosity and SS in centrifugal dehydration
The relationship between the required addition rate of the cationic organic polymer flocculant and the recovery rate of 95 or more is shown in FIG.

In Figure 4, the horizontal axis is the viscosity of 4% SS slurry, the vertical axis is the added cation ratio (colloid equivalent value with respect to SS) on the left, and the right side is the relationship between 15 mol of quaternized dimethylamine ethyl methacrylate with methyl chloride and 85 mol of acrylamide. The addition rate of the copolymer (relative to SS%) is taken.

From FIG. 4, the amount of polymer flocculant added can be adjusted using the sludge slurry viscosity as an index, and the amount of chemical injection can be controlled.

Similarly, a graph of the sludge load (or sludge flow rate) that can be treated when the slurry viscosity of the sludge and the amount of added polymer flocculant used are constant. ) can be determined.

In the present invention, the optimal cationization rate, required addition rate, or sludge load amount of the added flocculant is determined from these graphs, and dewatering treatment is performed under such treatment conditions.

These processing conditions may be employed individually or in combination.

Once the dehydration treatment conditions are determined, for example, in order to adjust the cationic degree to meet those conditions, among the multiple flocculants with different cationic degrees prepared in advance, the one that best matches the determined cationic degree is selected. It is sufficient to select a flocculant with a similar degree of cation and inject it into the sludge.

The degree of cation may be adjusted by mixing two or more flocculants having different degrees of cation.

Further, the amount of flocculant added and the amount of mud supplied can be adjusted, for example, by adjusting the cri output of each pump and the opening degree of the valve.

Note that the processing conditions may be set in stages, such as using a flocculant with a certain degree of cation when the measured value of the index is within a certain range.

The viscosity or SEI, which serves as an index, may be determined by using the measured value as it is and determining the processing conditions from Figures 2 to 4, but other related numerical values may be calculated from the measured value and the processing conditions may be determined based on that value. may be determined.

For example, when processing is performed by an automated device, if the graphs have a linear relationship, the processing becomes extremely easy, but as stated above,
It would be extremely preferable if numerical values that have a linear relationship could be selected by processing the fixed value with other values.

FIG. 5 is a graph showing the relationship between the ratio of SEI and SS concentration and the optimum degree of cation (molti) of the polymer flocculant, and it can be seen that the relationship between the two is linear.

Therefore, by measuring the sludge viscosity or SEI and also measuring the SS concentration and finding the ratio of the two, the optimum cation degree can be determined by proportional calculation.

As is clear from the above explanation, in the present invention, the relationship between the sludge properties and the dewatering effect of the cationic organic flocculant can be understood by measuring the viscosity of the sludge or a value such as II that has a correlation with the viscosity. For example, sludge dewatering operation at a sewage treatment plant can be performed under suitable conditions.

That is, it is possible to selectively use a flocculant with a better dewatering effect, it is possible to prevent the amount of flocculant from being added in excess of the required amount, or it is possible to lower the water content of dehydrated sludge.

Particularly preferably, measuring devices such as sludge viscosity and SEI, which are indicators of sludge properties, can be automated, and control devices such as signal converters, arithmetic units, marking devices, comparators, etc. can be automated based on the measured values. It is possible to automate chemical injection pumps, sludge supply pumps, valve opening and closing, etc. using equipment U, and dewatering process management such as flocculant selection and sludge supply can be automated.

Therefore, the complicated maintenance and management of sludge treatment can be performed with less manpower and under optimal conditions, which has extremely high practical value.

FIG. 6 is a system diagram showing a sludge dewatering apparatus according to an embodiment of the present invention, in which 1 is a sludge storage tank, 2 is a sludge supply pump, 3 is a reaction tank, and 4 is a dewatering machine. The sludge flows and is dehydrated.

Reference numeral 5 denotes a sample collection regulator, which introduces a portion of sludge from the sludge feed pump 2, measures the SS concentration in the SS concentration measuring device 6, and determines whether the value is suitable for SEI measurement. , if appropriate, measure Sv with an Sv measuring device 7.

If it is inappropriate, the dilution ratio is determined, dilution water is introduced from the water supply pipe 5a, and the SS concentration is adjusted to 0.5%.

5b is a mud drainage pipe.

The sludge with adjusted SS concentration was measured with Sv meter I after 30 minutes.
Measure v.

8 is a control device which, in addition to the above-mentioned steps, calculates SEI and SE I /S S from the Sv value, determines the optimum cation degree, addition rate, and slurry supply rate from the results, and displays the results. The control signal is displayed on the device 9 and sent to the slurry pump 2 and other devices.

The reaction tank 3 has a flocculant storage means, for example, a flocculant tank 10.1.
From 2.14, the flocculant injection pumps 11, 13,
The flocculant is injected through the flocculant tank 15, and each flocculant tank 10, 12.14 stores flocculants having different degrees of cation.

Therefore, by selecting the flocculant having the optimum cation degree from among the flocculants in each flocculant tank 10, 12, and 14, or by adjusting the mixing ratio of each flocculant, it is possible to inject the flocculant having the optimum cation degree.

This control! This can be done by controlling the injection volume of each injection pump 11, 13.15 using a control signal from the 1m device 8, thereby maintaining the injected flocculant at the optimum cation degree and adding it at the required addition rate. can.

The sludge load amount is controlled by controlling the sludge feed pump 2 based on a signal from the control device 8.

Furthermore, the moisture content of the cake can be predicted from the slurry supply rate, and from this it is possible to predict the amount of heavy oil required for incineration, which is calculated by the control device 8 and displayed on the display device 9.

In Fig. 6, coagulant injection pumps 11, 13, and 15 are provided in coagulant tanks 10, 12, and 14, respectively, but one coagulant pump is used between the pump and each coagulant tank. Of course, it is also possible to control the provided valve and inject the flocculant with the optimum degree of cation.

Next, the present invention will be explained in more detail with reference to Examples.

Example I In the A sewage treatment plant, a polymer flocculant C0 made of a copolymer of dimethylamine ethyl methacrylate quaternized with methyl chloride and acrylamide was used as a dehydration aid in the dewatering process, and the solids of sludge were The flocculant is added at a constant addition rate per SS in response to changes in concentration, and dewatering is performed using a centrifugal dehydrator.

Slurry viscosity on April 1st was 150eps,
Use polymer flocculant C1, addition rate 1.0 to 1.2
The SS recovery rate and cake moisture content (for SS section) were as shown in Table 1.

On April 2nd, the polymer flocculant C1 was used as before, and the addition rate was 1.
When the treatment was performed at 0 (relative to SS%), the dehydration treatment worsened and the cake moisture content increased from 75.0 to 78.

When the slurry viscosity was measured, it was found to have increased to 320 cpsl.

This indicates that stable dewatering cannot be achieved even if the amount of flocculant added is varied depending on the solid content concentration of the sludge and maintained at a constant flocculant addition rate per SS.

Therefore, based on the knowledge obtained from Figure 3, the applied chemical was changed to C2, which has a high cationic degree of the same copolymer, and was similarly dehydrated at an addition rate of 1.0 to 1.2 (relative to SS'%). As a result, the moisture content of the cake changed from 78.0% to 76.0-7.
It decreased to 6.5%, and the SS recovery rate also improved.

Also, based on the knowledge obtained from the whistle diagram 4, the applied chemical was changed to C1 again and the SS was increased to 1.6% of the maximum chemical injection amount. It became clear that the cake moisture content decreased and the SS recovery rate also improved compared to the case of .

In this way, it is possible to determine the optimum degree of cation of the applied polymer flocculant using the sludge slurry viscosity as an index, and it is also possible to determine the necessary addition rate of the applied polymer flocculant using the slurry viscosity as an index. became clear.

Since then, C1 has been used at sewage treatment plant A, and good results have been obtained with a constant chemical injection amount (1% of SS), but on April 10
By the end of the day, it was no longer possible to treat the situation with that amount of medicine.

When we measured the slurry viscosity of the sludge, it was found to be 400c.
It was found that there was an increase in psl.

So, the sludge flow rate in the trench now is 5rr? Temporarily 3t from /h
When lowered by y//hf, the SS recovery rate improved,
It was also observed that the moisture content of the cake was slightly improved.

The above results are summarized in Table 1.

Example 2 In sewage treatment plant B, dehydration is carried out in a centrifugal dehydrator using flocculant C3, which is a copolymer of acrylamide and a quaternized product of dimethylaminoethyl methacrylate with methyl chloride.

Since this treatment plant has only one chemical dissolution tank, only one type of applicable chemical can be used.

On May 1st, the treatment shown in Table 2 (addition rate 2
, 35 sections), the cake moisture content was 80.0 sections, and the SS recovery rate was 9.
It was 5.0%.

Note that at an addition rate of 1.80%, the SS recovery rate was less than 80%, making treatment impossible.

The 5EI (preparation at SS 0.5, 30 minutes) of this sludge was 84.

When I measured the 5EI (SS 0.5cm, 30 minutes) on May 3rd, it had dropped to 44, so even if the injection amount was reduced by 1.3%f to SS, the recovery rate was 88 and the recovery rate was 96. -0%,
It was confirmed that an excellent cake moisture content of 76.5% could be obtained.

Furthermore, when the SEI was measured by 4H in May, it had risen to 70.

At this time, the chemical injection amount was 1.3 ql of SS, and the SS recovery rate was poor at less than 80 ql, so when the chemical injection amount was increased to 831.9% of SS, the SS recovery rate increased to over 95%, and the cake contained water. The rate was 78.5%.

The above results are summarized and shown in Table-2.

From these results, it has become clear that by measuring the SEI of sludge, it is possible to check the required addition amount of a certain applied polymer flocculant, and furthermore, it is possible to predict the moisture content of the cake.

Example 3 Using the treatment equipment shown in Figure 6, a flocculant with varying cationic degree consisting of a copolymer of dimethylamine ethyl methacrylate quaternized with methyl chloride and acrylamide was applied to the SEI/SS of sludge shown in Table 3. Table 3 shows the results of addition in response to changes in .

In the above examples, a copolymer of methyl chloride quaternized dimethylaminoethyl methacrylate and acrylamide is used as a flocculant, but other cationic organic polymer flocculants can also be used.

In addition, slurry viscosity, S
In addition to EI and SEI/SS, other numerical values derived by calculation from these numerical values may be employed.

Further, as a management method using these indicators, control can be performed using a relational diagram, but it is not necessary to use a relational diagram; for example, it is also possible to perform direct computer control from the relational expressions between the two.

As described above, according to the present invention, by measuring the viscosity of sludge or a value having a correlation thereto, the cationic polymer flocculant necessary to maintain the SS recovery rate at a predetermined level or higher is determined based on the value. Determine the optimum cation degree, minimum addition amount, maximum sludge flow rate, etc., and perform dewatering under conditions according to these.
The SS recovery rate can be controlled to a predetermined level or higher.

Therefore, processing can be performed efficiently under optimal conditions, and processing costs can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between slurry viscosity and SEI, Figure 2 is a graph showing the relationship between slurry viscosity and cake water content, and Figure 3 is a graph showing the relationship between slurry viscosity and the optimum cation degree of the polymer flocculant. , Figure 4 is a graph showing the relationship between slurry viscosity and added cation rate, Figure 5 is SE I /S
FIG. 6 is a graph showing the relationship between the S concentration and the optimum cation degree of the polymer flocculant, and FIG. 6 is a system diagram showing a sludge dewatering apparatus according to an embodiment of the present invention. 1 is a sludge storage tank, 2 is a sludge pump, 3 is a reaction tank, 4 is a dehydrator, 5 is a sampling regulator, 6 is an SS concentration measuring device, 7 is an S
v measuring device, 8 is a control device, 9 is a display device, '10, 12
．． 14 is a flocculant tank, and 11° 13.15 is an injection pump.

Claims (1)

[Claims] 1. In a method of dewatering organic sludge by adding a flocculant, the viscosity of the sludge at a predetermined concentration or a value correlated therewith is measured, and an index of sludge properties is determined from the value. sludge dewatering control characterized by determining the cationic degree or addition rate of a cationic organic polymer flocculant suitable for dewatering sludge, and the amount of sludge dewatered per unit time of sludge, based on the obtained cationic polymer flocculant. Method. 2 The correlated value is the 5E of sludge at a given concentration.
1. The method for controlling sludge dewatering according to claim 1, wherein the sludge is adjusted to a predetermined SS concentration and then left to stand for a predetermined time, the volume per SS unit weight SV. 3. A method for controlling sludge dewatering according to claim 1, wherein the indicator is a viscosity measurement value or an SEI measurement value itself. 4. A method for controlling sludge dewatering according to claim 1 or 2, wherein the index is the ratio of the viscosity measurement value or SEI measurement value to the SS concentration measurement value. 5 a plurality of flocculant storage means for storing cationic organic flocculants having different degrees of cation, a flocculant injection means for injecting the cationic organic flocculant into the sludge, and an SS concentration measuring device for measuring the SS concentration of the sludge; The cationic degree of the cationic organic flocculant to be added is calculated and controlled based on the Svv measuring device that measures the Sv of sludge at a predetermined concentration, and the SS concentration signal and Sv value multiplication signal obtained by these measuring devices. A sludge dewatering control device comprising: a control means for controlling sludge dewatering; 6. The sludge dewatering control device according to claim 5, wherein the control means calculates the SEI/SSO value and calculates the optimum cation degree from the value.