JPS59183899A - Method for controlling addition ratio of ionic organic high-molecular flocculant - Google Patents

Abstract

PURPOSE:To lower the total cost of sludge treatment by reducing the cost of a chemical agent, by controlling the addition ratio of an ionic org. high-molecular flocculant so as to adjust the colloid charge amount in a liquid after said flocculant is added to sludge to 0meq/l. CONSTITUTION:In adding an ionic org. high-molecular flocculant to sludge, the addition ratio of said flocculant is controlled so as to adjust the colloid charge amount after addition to 0meq/l, the amount to be added of the flocculant may be adjusted or the flow amount of sludge may be adjusted if there is no problem in a dehydrating process. The aforementioned method is useful as a method for controlling the addition ratio of the flocculant capable of sufficiently corresponding to the variation of sludge quality and oncn. and not only promotes the automation and labor saving of sludge treatment but also can reduce the cost of a chemical agent as compared with a conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the flocculant addition rate in sludge dewatering treatment using an ionic organic polymer flocculant.

In recent years, ionic organic polymer flocculants have been widely used in place of inorganic flocculants for sludge dewatering treatment, but these flocculants have a preferable addition rate range for dewatering treatment, and are not limited to under-addition. Excessive addition must also be avoided, and the chemical addition rate must always be kept within an appropriate range using a certain method, which is a hassle in terms of maintenance and management.

In view of the current situation, the present invention provides a method for controlling the addition rate of an ionic organic polymer flocculant that can sufficiently cope with fluctuations in quality and concentration of sludge, overcomes the above-mentioned drawbacks, reduces chemical costs, and
The aim is to make it possible to significantly reduce labor costs through automation, and to reduce the overall cost of sludge treatment.

The present invention is a method of dewatering sludge by adding and mixing an ionic organic polymer flocculant to sludge, and the method involves controlling the flocculant addition rate so that the amount of colloid charge in the liquid after adding the flocculant becomes Omeq/t. It is characterized by

The present invention was achieved by studying the relationship between the addition rate of an ionic organic polymer flocculant and the flocculating and dewatering properties of sludge, paying attention to changes in the amount of colloid charge in the liquid. The relationship between the flocculant addition rate and the amount of colloid charge in the liquid was determined for organic sludge A.
An example of a combination of cationic organic polymer flocculants is schematically shown in FIG. 1. That is, in the region where the coagulant addition rate is extremely low, the colloid charge amount is negative and 1
1. Approaches zero as the loading of the septic agent increases,
It becomes zero at point a (addition rate A). After that, after continuing to be zero for a certain period, when it exceeds point b (addition rate B), it becomes positive +
[', the added flocculant remains in the liquid, and the amount of colloid charge increases as the addition rate increases. On the other hand, when the flocculating property of sludge to which a flocculant has been added is determined by the thickness of the flocculates, there is a very thick value near point b, and in particular around the addition rate that slightly exceeds point b, and furthermore, near the maximum value. The performance of dehydrators such as belt presses is maximized.

This kind of relationship is basically maintained even if the sludge, flocculant dewatering method, etc. change, so if the colloid charge amount is controlled at a value exceeding the + b point, changes in the quality and concentration of the sludge can be avoided. This means that the dehydrator can be kept in its best condition without being affected. Therefore, it is possible to stably obtain dehydrated aggregates having an extremely large aggregate diameter, and to obtain advantages such as a reduction in cake moisture content and a large throughput. However, depending on the disposal method, such as when disposing of dehydrated cake in a landfill, it is not necessarily necessary to maintain the highest dewatering performance. Rather, it is necessary to add a flocculant to the extent that labor savings can be maintained by automating the dewatering and disposal processes. It is often desirable to find a way to reduce drug costs by reducing drug rates. From such a point of view,
When the relationship shown in FIG. 1 was further investigated, it was found that the above condition for sludge dewatering is that the amount of colloid charge is zero.

The second study investigated the same relationship as in Figure 1 by changing the type of dehydration machine.
It is a diagram. It can be seen that in all models, the dehydration properties are best near the addition rate slightly exceeding point b, but the degree of dehydration deterioration when the addition rate is reduced is different. In centrifuges, screw presses, etc., the degree of
In belt press, screen sun drying, etc., some improvement in dehydration was observed, as long as the amount of colloidal charge was at least zero. Further, by changing the molecular weight and ionic strength of the flocculant, the relative diameter of the flocs can be changed, and the degree of deterioration in the performance of the dehydrator can be alleviated. In addition, depending on the sludge, as shown in Figure 3, there are some sludges in which the width of the addition rate (a = b) in which the amount of colloid charge is zero is small, and in this case, a normal dehydrator can be used satisfactorily with the present invention. . The above findings differ only in sign even when an anionic organic polymer flocculant is used.

The present invention is characterized by controlling the flocculant addition rate so that the amount of colloid charge after the flocculant is added is zero, and a specific method for this is to adjust the amount of flocculant added. Alternatively, if there is no problem with the dewatering process, the sludge flow rate may be adjusted. 1. Even in the case of a dehydration method in which two types of ionic flocculants are sequentially added, it is important not only to control the addition rate of the second flocculant, but also to control the addition rate of the first flocculant. The invention can be used. In this case, since the optimum addition rate must be determined by a combination of two types, the time and effort that conventionally required numerous preliminary experiments is greatly alleviated. Since the waste of the second coagulant partner is eliminated, the effect of reducing chemical costs is also significant.

As described above, the present invention is a control method after the addition of flocculant that can sufficiently cope with fluctuations in the quality and concentration of sludge, which not only promotes automation and labor saving in sludge treatment but also improves the efficiency of conventional methods. It has the advantage of further reducing drug costs.

Some examples will be described below.

Example 1 Liang sewage treatment plant mixed raw sludge was dehydrated using a cationic organic polymer flocculant in a centrifuge. In the present invention, the amount of colloid charge in the centrifuged liquid is automatically measured, and the flow rate of the chemical injection bonder is automatically controlled to obtain a predetermined addition rate and amount of colloid charge. In the conventional method, the sludge concentration was measured only at the start of operation, and the chemical injection bonding flow rate was fixed so that the addition rate would not deteriorate dewatering performance due to concentration fluctuations, which had been determined empirically.

The results are shown in Table 1.

Table 1 Here, Sludge concentration 2.0-3.0 Sludge pH, 6.5-6.8 *Addition rate A 1.2chi1/B*1.5" Coagulant: Evagrowth C-164 (Ebara Infilco) company product name)
, (weak cation system) *These are A and B in FIG. 1 described above.

This sludge has the addition rates A and B of 1.2° and 1.5, respectively.
The percentage of coagulant added that makes the digoloid charge amount zero is small. In addition, the sludge concentration fluctuates, and the sludge load 1
．． If the content drops below 2%, the dewatering performance will deteriorate significantly and the centrifugal dehydrator will no longer be able to operate, so in the conventional method, the addition rate is set on the safe side.

According to the present invention, both the addition rate and the water content can be significantly reduced compared to the conventional method.

Example 2 Sludge generated at a certain human waste treatment plant is dehydrated using a belt press type dehydrator using a cationic flocculant. The addition rate A of this treatment plant sludge is 1.0%, and the addition rate B is 2.5.
It was t16. Since this treatment plant has such qualitative variations in sludge, the conventional method was to operate at a safe addition rate as in Example 1. The results are shown in Table 2.

Table 2 Here, sludge concentration 2.0-2.1 flocculant Evagrowth C104G (trade name of Ebara Infilco) (Strong thione) Example 3 At a certain water treatment plant, an anionic organic polymer flocculant was added to the sludge. The water was dehydrated using an inclined screen and then dried in the sun. Because the quality and concentration of sludge fluctuates due to weather and other factors, conventional methods add a large amount of flocculant to form strong flocs for dewatering. In the method of the present invention, the amount of colloid charge in the screen separation liquid was automatically measured and the chemical injection pump was controlled. Table 3 shows the results.

Table 3 Sludge concentration 3-5.5%, H6.5 Addition rate A O, 0.2% 1/B '0.03 Coagulant Evagrowth A-152 (Ebara Infilco Co., Ltd. product name)
(Weak Anion) According to the present invention, dehydration performance equivalent to that of the conventional method is achieved at a lower flocculant addition rate.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the addition rate of the ionic organic polymer flocculant and the amount of colloid charge in the liquid. FIG. 2, like FIG. 1, shows the relationship between the addition rate of the ionic organic polymer flocculant and the amount of colloid charge in the liquid, obtained by changing the type of dehydration machine. FIG. 3 shows the relationship between the addition rate of the flocculant and the amount of colloid charge in the liquid when the type of sludge was changed. Agent Patent Attorney Tadashi Shiozaki Hiroka 1 Figure 2 e Cdf: mattrko4ii1-+LI-i;

Claims (1)

[Claims] A method for dewatering sludge by adding and mixing an ionic organic polymer flocculant to sludge, characterized by controlling the flocculant addition rate so that the amount of colloid charge in the liquid after adding the flocculant becomes Omeq/L. Method for controlling the addition rate of ionic organic polymer flocculants.