KR20060010851A - Water-conetntreducing technology for dehydrated cake by multi-chemical treatments - Google Patents

Abstract

The present invention relates to a technology for reducing dehydration cake moisture content through a multi-step chemical treatment, and more particularly, to a water content reduction technology by multiple input of a single coagulant, and a water content reduction technology and application method by multiple inputs using multiple coagulation and flocculant. will be.

Coagulation, Condensation, Cake, Water Content, Wastewater Treatment

Description

Water-conetntreducing technology for dehydrated cake by multi-chemical treatments}

1 is a graph showing a result of comparing the flocculation efficiency according to the charging of the flocculant.

2 is a graph showing the results of experiments of the correlation between the molecular weight and the aggregation efficiency.

3 shows the floc formation mechanism of a multiple flocculation system.

Figure 4 is a graph showing the results of comparing the cohesive performance according to the input ratio of the coagulant.

5 is a graph showing the correlation between the PAC dose and the filtration rate.

6 is a graph showing the floc formation process according to the flocculation reaction time.

7 is a graph showing the floc formation process according to the coagulation reaction time of the coagulant.

The present invention is a dehydration cake moisture content reduction technology through a multi-step chemical treatment is characterized in that the pre-treatment and the dehydration efficiency degradation by the residual viscosity between the floc, which is a characteristic of the polymer coagulant and the dehydration efficiency by the generation of the gap between the floc in the floc formation It is to improve the performance of the flocculation dehydration process to reduce the water content by improving the dehydration efficiency through multi-stage flocculation.

In the prior art, in the case of wastewater treatment, studies on alumina by two-component flocculants of Yu and Somasundaran [1] and pretreatment of iron salts or cationic surfactants by Chitikela and Dentel [2] have been carried out. Investigation on the Effects of Cationic and Anionic Polymer Coagulants for Improvement of Sedimentation Efficiency of Dredged Sludges of Bohm and Kulicke [3], and Cationic and Nonionic Polymer Coagulants of CHLee and JCLiu [4] Researches such as evaluation of the impact on sludge dewatering have been conducted. In addition, in the case of Kurita, various types of research have been made, including a patent (Japan Patent No.4-59100) for an assembly and concentration system using an iron salt and an amphoteric polymer flocculant.

[1] Xiang Yu and P. Somasundaran, "Enhanced flocculation with double flocculants", Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 81, 13 December 1993, Pages 17-23

[2] Chitikela S. and Dentel S., "Dual chemical condition-ing and dewatering of anaerobically digested biosolids: laboratory evaluations." Wat. Environ. Res. 70, 1062- 1069, 1998

[3] Bohm N. and Kulicke W. M., "Optimization of the use of polyelectrolytes for dewatering industrial sludge of various origins". Colloid Polym. Sci. 275, 73-81, 1997

[4] C.H.Lee and J.C.Liu, "Enhanced sludge dewatering by dual polyelectrolytes conditioning", Water research, 34, 18, 4430-4436, 2000.

As described above, the conventional techniques are not intended to improve the flocculation efficiency by the single flocculant and to improve the efficiency of the change of the flocculation system. It is difficult to apply the generalized coagulation treatment in terms of improvement.

In addition, in the case of Kurita's patent, a technique using iron salt as an inorganic coagulant and an amphoteric coagulant as a coagulant, this technology also adds partial cationic and anionic properties in accordance with the combination ratio to cope with the size of the flocks. Since it is an application technology suitable for sludge, it is difficult to apply it universally, and it is difficult to put into practical use in consideration of the amount of sludge generated in the actual site because the input amount of the inorganic system is applied in excess of 2%.

Therefore, the inventor of the present invention has been researched to solve the above problems, and as a result, multiply the coagulant currently used in each treatment plant without additional input of other drugs to increase the cohesive efficiency even with a small amount of use, in particular, It has been found that the treatment cost can be reduced by improving the water content of the dehydrated cake. In addition, in the case of high-sludge sludge, the amount of flocculant is excessive, and the method of improving the dehydration efficiency due to the viscosity of the flocculant itself and the remaining flocculant between flocs is also applied. The present invention has been completed by a study on the improvement of the cohesive efficiency by using parallel.

Therefore, an object of the present invention is to provide a water content reduction technique and application method of the dewatered cake using a multi-aggregation system using a single flocculant as described above, and the present invention will be described in detail below.

The present invention is a method for maximizing the efficiency of the flocculation process by the cross-linking action between the suspended contaminants and the flocculant by the charging of the flocculant, each sludge treatment process characteristics such as influent wastewater properties, pretreatment process, digestibility and concentration rate The composition and coagulation characteristics are different by each other.In each wastewater treatment process, the flocculation sedimentation and organic components of organic and inorganic components are decomposed and removed, resulting in a difference in the surface charge of the sludge. The proper charge of the flocculant used in the forming process also has a big difference, but the invention relates to a technique for increasing the efficiency by using the multiple drug system and multiple coagulation system.

As the first detailed technology, the cohesive efficiency improvement technology by the multistage injection of a single coagulant, the configuration of the detailed invention is as follows.

Most of the raw sludge is strongly cationic, and in the case of digested sludge, most of the cationicity is applied. As shown in FIG. 1, it shows another dehydration efficiency according to the efficiency of charge neutralization and crosslinking action with suspended pollutants between coagulants having different charges, as shown in the comparison of the coagulation efficiency according to the charge of the coagulant. In the case of, the cationicity shows the optimum coagulation efficiency at 20 mol% and 60 mol%, because the proper charge necessary for the formation of the ring for coarsening in coagulation theory is formed in this region.

Figure 2 shows the results of experiments on the correlation between the molecular weight and the flocculation efficiency by applying the product of different molecular weight among the cationic 20 mol% flocculant evaluated by the appropriate charge, the input amount at different molecular weights, unlike the effect of the charge It shows different cohesive behavior with change.

The selection technology of the flocculant according to the charge and the molecular weight is a conventionally commercialized technology, but a multistage flocculation system using a single flocculant is not a conventional technique. The approximate mechanism of the multiaggregation system of FIG. 3 is proposed in the present invention. The efficiency is shown by the schematic diagram.

As shown in FIG. 3, in the case of a single flocculation system, a flocculation process of coagulation by flocculant injection or a multi-aggregation system is performed at the initial stage of formation of a pin floc. By changing the system, such as using a multi-stage flocculation tank, the first formed floc is dismantled to remove the gap and free water between the flocs as much as possible, and to induce a second reaction that maximizes the intensity while keeping the size of the floc small. The same coagulant is added to the flocculation through the cross-linking of the flocs to maximize the discharge of the pore water or free water contained in the flocks in the existing single flocculation system, and to improve the consolidation efficiency by forming the flocculation flocculation efficiency Improve the dewatering efficiency by using multiple flocculation system to minimize residual flocculant By a technique for reducing the water content of the cake.

The most important part of the present technology is shown in Figure 4 the application results for the coagulation performance of the representative input ratio by the control of the first and the second or more input ratio in the multi-coagulant dosing method.

In the present invention, the high molecular weight flocculant exhibited the best dehydration efficiency in the preliminary experiments in order to compare the results of the single flocculation using the same flocculant and the result of applying the multiple flocculation system and to determine the effect of molecular weight. The experiment was compared using.

The amount of flocculant in the first and second doses was adjusted based on 25%, and the dose was controlled. The control was tested under the same conditions for other flocculation reactions.

As a result, as shown in FIG. 4, the best performance was obtained in the ratio of 75: 25, and the dehydration efficiency was determined in the order of 25: 75> 50: 50> 100: 0> 0: 100.

This result is the result of the coarsening process for dehydration after increasing the consolidation and the strength of the floc during disassembly by generating the primary floc with the initial 75% dose as shown in the above mechanism. In this case, the initial floc is formed in a very fine shape, but the separation effect of free water is excellent in this process, but in the case of floc pore water, it remains in some flocks during the coarsening process, which is the second input, and the efficiency is decreased.

In the case of inputting with the primary input amount of 100% by single input, after the coagulated flocculation is coarse, the floc is disassembled and the flocc is smaller than the size suitable for dehydration, and the efficiency is lowered. In the case of adding as%, the flocculated floc became coarse but the flocculation effect of the flocculant was not reduced and the dehydration efficiency was lowered.

Compared with the high molecular weight flocculant, it can be seen that the result of the two-stage addition resulted in a dehydration efficiency improvement of about 20%.

Therefore, in the present invention, it is preferable that the primary coagulant input amount is 60 to 80%, and the secondary coagulant input amount is 20 to 40%, and the efficiency is most excellent. Is a technique in which a flocculant is added.

In addition to the two-stage input, when the multistage input is applied, the primary input amount is 50 to 70%, the input amount of each stage is about 10%, and the final input amount is 10 to 15%. to be.

In general aggregation theory, when the molecular weight is large, the ring formation process for coarsening is slow, and the overall aggregation reaction rate is slow. In addition, even in the case of a slight overload, the residual viscosity is increased due to the overlapping of the polymer as the coagulant on the surface of the suspended pollutant. As a result, the dehydration efficiency is drastically lowered and, on the contrary, in the case of low molecular weight, in contrast to this phenomenon, it has a fast flocculation reaction rate and a wide range of appropriate flocculant input, but there is a small number of rings between the flocculant and the suspended contaminants which act as a coarsening between flocks. It is known to exhibit disadvantages in indicating floc strength.

In addition, the turbidity of the treated water is lower as the coagulation performance is excellent, and it is known that the fine floc adheres to all the flocs due to the residual viscosity in the excessive injection of the high molecular weight flocculant, thereby showing the optimum haze removal efficiency.

However, this experiment can be applied to the dehydration process of sludge that will contain most of the organic components regardless of the molecular weight and ionicity of the flocculant.

The second technique of the present invention is a technique for improving cohesion efficiency by multistage injection of a multi-drug system, and the configuration of the detailed invention is as follows.

Generally, the coagulant is used for the first chemical treatment. In the dehydration process, since most of the dehydrating coagulant is cationic, it is not applied on the background of the theoretical background that the efficiency of the coagulant with the same charge decreases in parallel. It is a reality. However, the present invention aims to develop an application technology for improving the dehydration efficiency of high-density sludge, in particular through the multi-stage treatment of such coagulant.

As a result of evaluating the applicability of the inorganic coagulant and the organic coagulant used in the coagulation reaction as a dehydration pretreatment agent, the high molecular weight coagulant and the high molecular weight coagulant and the low molecular weight coagulant PAC (polyaluminum chloride) The treatment efficiency was the best. The parallel processing efficiency is shown in FIG.

The parallel treatment efficiency was about 30% higher than that of the flocculant at 160 to 1200 mg / L, when the flocculant was applied at only 160 mg / L to 200 mg / L.

The rapid decrease in dehydration efficiency in the region of 200 mg / L PAC is caused by the neutralization of flocculation effect due to the complete neutralization of the charge of flocculant and coagulant and suspension contaminants. However, in the case of parallel treatment, the amount of PAC, which is a coagulant, is more than 1000 mg / L as compared to the case of the addition of a single flocculant, which makes it difficult to apply.

By applying the multi-stage process proposed in the present invention, the efficiency can be improved. In the case of the coagulation reaction, unlike the coagulation reaction, the charge neutralization process due to the high charge of the low molecular weight coagulant is the most important performance factor. Since the processing efficiency is lowered, the input amount is excessive.

However, in the multistage flocculation process, the coagulant may be applied as a pretreatment to the front end of the pump conveyed from the sludge supply storage tank such as the concentration tank and the digestion tank, so that the multistage flocculation and flocculation process can be applied without installing the flocculation or the flocculation reaction tank separately. The efficiency was improved by about 20-30% compared with the simultaneous injection.

After the coagulation treatment, the efficiency of single coagulation and the coagulation without coagulation are similar, but in terms of economics, the coagulation is more economical, but it is more economical, but compared with other coagulation processes in the case of multistage coagulation after sludge improvement by precoagulation. Initial dehydration is improved by about 20%. In addition, the turbidity of the treated water is improved by about 50% or more, which indicates that the fine suspended solids, which are not removed by the flocculation process, form a fine floc by coagulation, and also the charge repulsion between the coagulant and the flocculant and the coarsening ring formation. The interaction shows that the dewatering efficiency is greatly improved.

In addition, such multi-stage or multi-splitting dosing, as shown in Figures 6 and 7, the appropriate reaction time of the coagulant takes about 1 minute or more on a laboratory basis, and in the case of the coagulant, it is about 10 seconds to induce such a proper reaction time. This is to exclude mutual competition by simultaneous input and to induce complementary action.

In the present invention, the coagulant represented by the polyDADMAC coagulant was used, and the present invention does not limit the type of coagulant used in the pretreatment. In each case, aluminum, iron salt, etc. may be applied as inorganic, and polyamine as organic. Both of the system or the poly-dead film system can be applied. It is also possible to apply a coagulant-only multi-drug system according to their parallel use.

In addition, the flocculant can be applied irrespective of the charged amount and the molecular weight, and in some cases, the multistage injection effect is also possible by applying the anionic flocculant, so that the flocculant can be applied regardless of the type of flocculant. It is not limited to specific types such as water, water or water-in-oil.

In addition, in the present invention, a method using a specific apparatus (agitation stirrer, instantaneous reactor, line mixer, etc.) or applying a multistage reactor for the application of the flocculation system and a method of multi-splitting the sludge feed pipe without applying the same And the present invention does not define this method because it can be applied without being limited to the reaction apparatus or the input method of the condensation and flocculation, such as a method of adding to the front of the sludge transfer pump to replace it.

The dewatering efficiency of the cake was dramatically improved by the multistage flocculation system of the present invention and the process of pretreatment followed by flocculation.

Claims (5)

A method for reducing the moisture content of a dewatered cake, characterized in that the flocculant is a single flocculant and the flocculation step is performed in multiple stages in the process of improving the moisture content of the dehydrated cake by applying a flocculant. The method of claim 1, wherein the multistage flocculation step is a two-stage flocculation step, wherein the primary coagulant content is 60 to 80% and the secondary coagulant content is 20 to 40%. . According to claim 1, wherein the multi-stage flocculation step is a three-step or more flocculation step, the first coagulant input amount is 50 to 70%, the second and subsequent coagulant input amount is about 10% and the final input amount is 10 to 15% And low-speed stirring to reduce the moisture content of the dehydrated cake. A method for reducing the moisture content of a dewatered cake, characterized in that sludge is improved by using inorganic and organic coagulants as a pretreatment agent, and a coagulant is applied by single or multistage flocculation. The dewatering cake of claim 4, wherein the inorganic coagulant is an aluminum or iron salt coagulant, and the organic coagulant is a polyamine and a polydead film coagulant, and a polymer coagulant having a crosslinking degree of 0% or more and 50% or less is used as a coagulant. How to reduce moisture content of

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