KR102051106B1 - Apparatus and method for dewatering sewage sludge - Google Patents

Abstract

The present invention is to sewage sludge and flocculation sludge by improving the dehydration and sedimentation of the sewage sludge by mixing and stirring the sewage sludge and flocculation sludge, and the sewage sludge treatment apparatus and method that can reduce the treatment cost of sewage sludge The sewage sludge treatment apparatus according to the present invention comprises a flocculation tank for providing flocculation sludge while providing a space in which flocculation reaction between sewage and flocculant proceeds; Sedimentation tank separating raw water into supernatant and sewage sludge; A sludge mixing tank for mixing and stirring agglomerated sludge and sewage sludge to produce mixed sludge; A sludge concentration tank in which coagulated sludge and sewage sludge are mixed and precipitated mixed sludge naturally to concentrate mixed sludge; And a sludge dewatering tank for dehydrating water contained in the mixed sludge in a state in which the mixed sludge concentrated from the sludge thickening tank is supplied.

Description

Apparatus and method for dewatering sewage sludge}

The present invention relates to a sewage sludge treatment apparatus and method, and more specifically, to sewage sludge and flocculation sludge by effectively treating sewage sludge and flocculation sludge by mixing and stirring sewage sludge and flocculation sludge. It relates to a sewage sludge treatment apparatus and method that can reduce the treatment cost of.

The amount of sewage flowing into public sewage treatment facilities is continuously increasing, and the amount of sewage sludge, the final product of sewage treatment, is also increasing. Sewage sludge has a large change in properties and inflows according to regions and seasons, and it is difficult to dehydrate and concentrate due to high organic matter content and water content.

The treatment of sewage sludge is concentrated, digested, and dehydrated. The sewage sludge dehydration process is generally carried out in the form of reducing the water content of the sludge through injection of dehydrating drugs such as inorganic coagulants and organic polymer coagulants. Thus, as a considerable amount of dehydration medicine is required for dewatering sewage sludge, sewage sludge treatment costs are increasing every year.

In addition, due to the regulation of total phosphorus of sewage effluents, there are many cases in which a wastewater treatment for the purpose of removing phosphorus from sewage effluents is additionally added. Accordingly, the treatment and disposal of agglomerated sludge generated in large quantities is a big problem.

 Han, G. S., Kim, G. H., Jang, S. Y., Ahn, B. S., Lee, G. S., Lee, J. G., Choi, Y. J., Kwon, H. G., Jeon, T. S. (2015). Reduction of sludge dewatering chemicals and improvement of water content, The Office Of Waterworks Seoul Metropolitan Government, pp. 864-889.  Lee, C. H., Ahn, K. H., Song, S. K. (2010). Dewatering characteristics for physico-chemical properties with sewage sludge, KSBB Journal, 25 (1), 41-46.  Karr, P. R., & Keinath, T. M. (1978). Influence of particle size on sludge dewaterability, J. Water Pollut. Con. F., 1911-1930.

The present invention has been made in order to solve the above problems, by mixing and stirring sewage sludge and flocculation sludge to improve the dehydration and sedimentation of the sewage sludge and to effectively treat the sewage sludge and flocculation sludge and the treatment of sewage sludge It is an object of the present invention to provide a sewage sludge treatment apparatus and method that can reduce costs.

Sewage sludge treatment apparatus according to the present invention for achieving the above object provides a space in which the flocculation reaction of sewage and flocculant proceeds, and a flocculation tank for producing flocculation sludge; Sedimentation tank separating raw water into supernatant and sewage sludge; A sludge mixing tank for mixing and stirring agglomerated sludge and sewage sludge to produce mixed sludge; A sludge concentration tank in which coagulated sludge and sewage sludge are mixed and precipitated mixed sludge naturally to concentrate mixed sludge; And a sludge dewatering tank for dehydrating water contained in the mixed sludge in a state in which the mixed sludge concentrated from the sludge thickening tank is supplied.

Sewage sludge and flocculated sludge may be mixed in a volume ratio of 3: 1 to 1: 1.

The flocculating sludge is a sewage flocculating sludge generated in a sewage treatment process or a purified flocculating sludge generated in a water treatment process.

The coagulant is an inorganic coagulant or an organic polymer coagulant.

Sewage sludge treatment method according to the present invention comprises the steps of preparing agglomerated sludge and sewage sludge, respectively; Mixing and stirring agglomerated sludge and sewage sludge into a sludge mixing tank; Condensing the mixed sludge by sedimenting the mixed sludge and the sewage sludge in a sludge thickening tank; And conveying the mixed sludge concentrated in the sludge thickening tank to a sludge dewatering tank, and dehydrating the mixed sludge in the sludge dewatering tank, wherein the flocculating sludge is produced by the coagulation reaction between the flocculant and the sewage sludge. Is characterized in that the sludge generated as a by-product in the final stage of the biological sewage treatment process.

Sewage sludge treatment apparatus and method according to the present invention has the following effects.

In the dewatering treatment of sewage sludge, by mixing and stirring the flocculating sludge containing the coagulant component with the sewage sludge, it is possible to improve the dehydration and sedimentation of the sewage sludge, thereby effectively treating the sewage sludge and the sewage sludge. The cost of dehydration can be reduced.

1 is a block diagram of a sewage sludge treatment apparatus according to an embodiment of the present invention.
2 is a flow chart for explaining the sewage sludge treatment method according to an embodiment of the present invention.
Figure 3a is a filter time (CST) results according to the inorganic coagulant injection amount, Figure 3b is a reference diagram showing the SRF results according to the inorganic coagulant injection amount.
Figure 4a shows the water content of the sludge according to the inorganic coagulant injection amount, Figure 4b is a reference diagram showing the SV ₃₀ of the sludge according to the inorganic coagulant injection amount.
5 is a reference diagram showing the TS, VS and VS / TS of the sludge after the flocculation experiment according to the inorganic coagulant injection amount.
Figure 6a is a result of the filtration time (CST) according to the mixing ratio of sewage sludge and flocculation sludge, Figure 6b is a reference diagram showing the SRF results according to the mixing ratio of sewage sludge and flocculation sludge.
Figure 7a shows the water content of the mixed sludge according to the mixing ratio of sewage sludge and flocculated sludge, Figure 7b is a reference diagram showing the SV ₃₀ of the mixed sludge according to the mixing ratio of sewage sludge and flocculated sludge.
8 is a reference diagram showing the TS, VS and VS / TS of the mixed sludge after proceeding the flocculation experiment according to the mixing ratio of sewage sludge and flocculated sludge.

The present invention proposes a technique for improving the dehydration and sedimentation of sewage sludge, thereby reducing the treatment cost of sewage sludge.

In order to improve the dehydration and sedimentation of sewage sludge, the present invention proposes a technique for introducing flocculated sludge into sewage sludge. The mixing and stirring of sewage sludge and flocculated sludge can improve the dehydration and sedimentation of sewage sludge, thereby minimizing the dehydration chemicals required for the dewatering process of sewage sludge.

As used herein, "sewage sludge" refers to the final product of the sewage treatment process, and "aggregated sludge" refers to sludge generated in the flocculation process of the sewage treatment process. In addition, the term "sewage treatment process" in the present invention means a process for removing nitrogen and phosphorus contained in the sewage by biologically treating sewage, and a general sewage treatment process capable of removing nitrogen and phosphorus is' Sewage treatment process.

On the other hand, the present invention, as described above using the flocculation sludge, the 'sewage treatment process' of the present invention is required to generate flocculation sludge. Agglomerated sludge is produced by the coagulation reaction between the flocculant and the sewage, and can aggregate the phosphorus (P) contained in the sewage through this coagulation process. The flocculant used in the flocculation process for phosphorus removal is an inorganic flocculant or an organic polymer flocculant. Inorganic coagulants include aluminum (alum) containing aluminum, poly-aluminium chloride (PAC) or iron salts containing iron (ferric chloride, ferric sulfate, ferrous sulfate). The organic polymer coagulant may be used, and cationic, anionic, nonionic polymer coagulant, or the like may be used. The inorganic coagulant is cationic as aluminum (Al) or iron (Fe) is included and can adsorb phosphorus in sewage through such positive charge. The organic polymer coagulant may be cationic, anionic or amphoteric, depending on the material.

The present invention proposes to improve the dehydration and sedimentation properties of sewage sludge by injecting agglomerated sludge into sewage sludge, which utilizes a flocculant component contained in the flocculated sludge. The coagulant component contained in the coagulant sludge has cationic, anionic or amphoteric properties as described above, and when the coagulant sludge containing the coagulant component is mixed and stirred in the sewage sludge, static electricity on the surface of the sewage sludge particles is discharged. By neutralizing to reduce the repulsion between particles, cross-linking between the particles can increase the dehydration and sedimentation of sewage sludge.

Hereinafter, a sewage sludge treatment apparatus and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to Figure 1, the sewage sludge treatment apparatus according to an embodiment of the present invention is a flocculation tank 110, sedimentation tank 120, sludge mixing tank 130, sludge thickening tank 140 and sludge dewatering tank 150 It is made to include.

The flocculation tank 110 provides a space in which the flocculation reaction between sewage and flocculant proceeds. Phosphorus (P) component contained in the sewage is combined with the flocculant to form flocculation sludge, the flocculation sludge is precipitated in the lower portion of the flocculation tank (110). The coagulant is an inorganic coagulant or an organic polymer coagulant, and the inorganic coagulant includes aluminum salt containing aluminum, iron salt containing poly aluminum chloride (PAC) iron (ferric chloride, sulfuric acid agent). Ferric sulfate, ferrous sulfate), and the like, and the organic polymer coagulant may be cationic, anionic, nonionic polymer coagulant, or the like. As described above, although the flocculation tank 110 is specified as a reaction tank in which the flocculation reaction of the sewage flocculent proceeds, that is, a flocculation tank of the sewage treatment apparatus, the flocculation tank of the purified water treatment apparatus may be used. In other words, the coagulated sludge applied to the present invention can be used not only sewage coagulated sludge generated in the sewage treatment process but also purified coagulated sludge generated in the water treatment process.

The sedimentation tank 120 is provided at the final stage of the sewage treatment device serves to separate the raw water flowing into the sedimentation tank 120 into the supernatant and sewage sludge. Various reaction tanks for biological water treatment may be provided in addition to the flocculation tank 110 and the precipitation tank 120.

The sludge mixing tank 130 serves to mix and stir the flocculating sludge of the flocculation tank 110 and the sewage sludge of the precipitation tank 120 to produce a mixed sludge, and the sludge thickening tank 140 is a sludge mixing tank 130. ) To supply mixed sludge mixed with coagulated sludge and sewage sludge to concentrate the sludge by naturally settling the mixed sludge. Here, the coagulation sludge of the coagulation tank 110 and the sewage sludge of the settling tank 120 are respectively drawn and supplied to the sludge mixing tank 130.

As the flocculating sludge contains coagulant components, when coagulated sludge and sewage sludge are mixed and stirred, the flocculant component of the flocculating sludge neutralizes static electricity on the surface of the sewage sludge particles, thereby reducing the repulsive force between particles and causing crosslinking between particles. This can increase the dehydration and sedimentation of sewage sludge.

The sludge dewatering tank 150 serves to dehydrate water contained in the mixed sludge in a state in which the mixed sludge concentrated from the sludge thickening tank 140 is supplied. Dewatering of the mixed sludge can be carried out using a press, centrifugation, or the like.

Operation of the sewage sludge treatment apparatus according to an embodiment of the present invention, that is, the sewage sludge treatment method according to an embodiment of the present invention are as follows.

Referring to Figure 2, agglomerated sludge and sewage sludge are prepared respectively (S201).

The flocculant sludge is produced by a flocculation reaction between a flocculant and sewage or a flocculant and a purified water, and includes a flocculant component. The flocculant sludge may be obtained from the flocculation tank 110 in which the flocculation reaction proceeds, and the flocculant component included in the flocculation sludge is an inorganic flocculant or an organic polymer flocculant component. As the inorganic coagulant, aluminum salts (alum aluminum sulfate), polyaluminum chloride (PAC), iron salts containing iron (ferric chloride, ferric sulfate, ferrous sulfate) and the like may be used. The organic polymer coagulant may be cationic, anionic, nonionic polymer coagulant, or the like. As described above, the flocculation sludge means sewage flocculation sludge generated in the sewage treatment process or purified water flocculation sludge generated in the water treatment process.

The sewage sludge means sludge generated as a by-product in the final stage of the biological sewage treatment process, in one embodiment may be specified as sludge settled in the sedimentation tank 120 of the sewage treatment apparatus.

Agglomerated sludge and sewage sludge are prepared, respectively, agglomerated sludge and sewage sludge are introduced into the sludge mixing tank 130 and mixed and stirred (S202). Subsequently, agglomerated sludge and sewage sludge are mixed and agitated mixed sludge is naturally precipitated in the sludge thickening tank 140 (S203). At this time, when the flocculating sludge contains the coagulant component, when the flocculating sludge and the sewage sludge are mixed and stirred, the flocculant component of the flocculating sludge neutralizes the static electricity on the surface of the sewage sludge particles, thereby reducing the interparticle repulsion force. Cross-linking of the sewage sludge can increase the dehydration and sedimentation.

Then, the mixed sludge sedimented in the sludge thickening tank 140 is transferred to the sludge dewatering tank 150, and the mixed sludge is dewatered in the sludge dewatering tank 150 (S204). Dewatering of the mixed sludge can be carried out using a press, centrifugation, or the like. As described above, as the flocculating sludge and sewage sludge are mixed and agitated, the dewatering and sedimentation efficiency are improved by the flocculating agent component of the flocculating sludge, thereby improving the dewatering and sedimentation efficiency in the sludge dewatering tank 150.

Experimental Example 1 Treatment of Sewage Sludge Using Coagulant and Coagulant Sludge

The experiment was conducted using sewage sludge collected from the secondary sedimentation battery of Y sewage treatment plant in Gyeonggi-do. A PAC (poly-aluminum chloride, [ Al 2 (OH) n Cl 6-n] m, 17% as Al 2 O 3, Jin environment, Korea) for evaluating the coagulation characteristic of the sewage sludge in accordance with the coagulant dosage Al ^{3 +} in a concentration based on the injection with 0, 5, 10, 15, 20, 25 mg Al / L was carried out for comparison. PAC is useful in treating high concentration of raw water because it is excellent in electric neutralization ability and OH crosslinking action for suspended solids in water.

In addition, the applicability of the flocculating sludge was evaluated. In order to secure the flocculation sludge, a continuous experiment using a flocculation sedimentation tank was conducted on the secondary treated water of the sewage treatment plant. As the flocculation process was applied to remove the sewage from the sewage water, an inorganic coagulant was injected based on the total phosphorus concentration of the sewage secondary treated water. The total phosphorus concentration in the sewage secondary treatment water was 1.04 mgP / L, and PAC was injected at an Al: P mol concentration ratio as the inorganic coagulant. Experiments to secure flocculated sludge were carried out for 13 hours of continuous operation and secured about 8L of flocculated sludge. Sewage sludge and flocculation sludge were mixed in a ratio of 9: 1, 6: 1, 3: 1, 2: 1, and 1: 1 based on the volume ratio.

Experimental Example 2 Analysis of Sewage Sludge, Coagulated Sludge and Improved Sewage Sludge

The sewage sludge used in Experimental Example 1, coagulated sludge and sewage sludge improved by flocculant or flocculant sludge were analyzed.

In order to compare the characteristics of sewage sludge and flocculated sludge, items such as MLSS, MLVSS, SV ₃₀ , VS, TS, and SRF were measured. In addition, the sewage sludge improved by flocculant or flocculant sludge was compared with the basic characteristics, sedimentation and dehydration, respectively. TS, VS, and water content of each sample were analyzed for basic characteristics and turbidity of SV ₃₀ , SVI, and concentrated filtrate was measured for sedimentation evaluation. CST analysis was carried out using Triton Electronics Type 319 CST analyzer to evaluate the dehydration of sludge. Capillary suction time (CST) is derived from the time it takes for a well-known filtration amount to be absorbed from the suspended solids by capillary suction pressure generated from standard CST filter paper. (Im, 2002). Using the time derived through the CST experiment, the SRF, which represents the resistance value (m / kg) for filtration, was calculated using the following equation (1).

(Equation 1)

A: filter paper size (mm ² )

Pt: Filtration pressure (Pa)

b: Gradient of the multi-CST line divided by the amount of filtrate in the ring, respectively (s / cm ⁶ )

C ₁ : Mass of solid sludge to liquid volume in sludge (g / cm ³ )

μ: Filtration rate (cp)

Experimental Example 3 Comparison of Characteristics of Sewage Sludge and Aggregate Sludge

The characteristics of sewage sludge and flocculated sludge used in Experimental Example 1 are shown in Table 1 below.

MLSS of sewage sludge was 8450mg / L, MLVSS was 7400mg / L, which was higher than that of agglomerated sludge with MLSS of 2450mg / L and MLVSS of 1300mg / L. The MLVSS / MLSS ratio of the sewage sludge is about 0.876, which is higher than that of the flocculating sludge with a ratio of 0.531. The injection of inorganic coagulant and the flocculation sludge with low organic content are expected to affect the treatment characteristics of the sewage sludge. . Sludge dehydration has been reported to decrease with increasing sludge concentration (Lee et al., 2010), but dewatering efficiency is correlated with floc size and morphology, sedimentation rate and specific surface area (Karr et al., 1978; Bruus et al., 1993). Sewage sludge and flocculated sludge were compared through the following sludge characteristics analysis.

<Characteristics of Sewage Sludge and Coagulated Sludge> factor unit Sewage Sludge Coagulated Sludge MLSS (mg / L) 8450 2450 MLVSS (mg / L) 7400 1300 SV30 (%) 95 90 Residual Turbidity (NTU) 98.7 45.6 VS / TS (%) 84.4 33.9 SVI - 11.2 36.7 SRF (m / kg) 5.6 E + 11 1.15 E + 12

Analysis of total solids (TS) and volatile solids (VS) in the sludge showed that the volatile solids content (VS / TS) in the total solids of sewage sludge was more than two times higher than that of the coagulated sludge. Increasing the proportion of volatile solids (VS) in sewage sludge is known to lower the density per unit volume of sludge, thereby reducing the concentration and dehydration. Therefore, the dehydration of sewage sludge is expected to be lower than that of flocculant sludge.

Accordingly, specific filtration resistance (SRF) was measured for sludge dehydration evaluation. SRF refers to the resistance due to the solid layer accumulated as the filtration occurs, the higher the SRF value means poor dehydration. The SRF value of the flocculated sludge was about 2 times higher than that of sewage sludge, indicating that the dewatering property was poor compared to the sewage sludge. This is in contrast to the sludge concentration and VS / TS results expected. The MLSS content and VS content of sewage sludge are higher than those of flocculant sludge, but the dehydration and sedimentation properties are affected by the type of sludge floc. The poor dehydration of flocculated sludge compared to sewage sludge, even at low VS content, is due to coagulation sludge properties of volatiles (organic substances) and flocculants in raw water. Because there is.

As a result of sludge sedimentation evaluation, SV ₃₀ of sewage sludge and flocculant sludge were high as 95 and 90%, respectively, and SVI values were 11.2 and 36.7, respectively. The SVI value representing the sludge settling rate is known to be an appropriate value from 50 to 150, but all of the values are less than 50, and the sludge settling properties were judged to be somewhat poor. As a result, the turbidity of the sludge filtrate is somewhat higher, and as a result, it is understood that treatment such as improvement using chemicals is required for the disposal of sewage sludge and flocculated sludge.

Experimental Example 4: Coagulation Characteristics of Sewage Sludge by Application of Inorganic Coagulant

The flocculation characteristics of sewage sludge according to the amount of inorganic coagulant injected were evaluated. PAC was used as the inorganic coagulant to investigate the effects of varying the injection volume. The injection amount of PAC was expressed based on Al ³⁺ , and the coagulation experiment was performed by injecting up to 25 mg / L. The experimental method is as described in Experimental Example 1.

Figure 3a is the result of the filtration time (CST) according to the inorganic coagulant injection amount, Figure 3b shows the SRF results according to the inorganic coagulant injection amount. Referring to FIG. 3A, the CST of the sewage sludge not injected with the inorganic coagulant was measured at about 234 sec, and the CST gradually decreased as the amount of the inorganic coagulant was increased. When an inorganic coagulant was injected at a maximum of 25 mg / L, it was measured with a short CST of about 137 sec and was judged to have a significant effect on improving dehydration. This is believed to be the result of inorganic coagulant porosizing the dehydrated cake and affecting the moisture structure.

In addition, the SRF value of the sewage sludge derived through the CST experiment was found to be about 5.6 x 10 ¹¹ m / kg, as shown in Figure 3b and when the inorganic coagulant is injected up to 25 mg / L, about 2.28 x It confirmed that the result is lowered to 10 ¹¹ m / kg. As the coagulant injection amount increased, the sedimentation rate was increased, and the results of the CST and SRF confirmed that the injection of the inorganic coagulant is effective in improving the dehydration of sewage sludge.

Figure 4a shows the water content of the sludge according to the amount of inorganic coagulant injection, Figure 4b shows the SV ₃₀ of the sludge according to the amount of inorganic coagulant injection. 4A and 4B, the water content of the sewage sludge was lowered up to about 84% by injecting the inorganic coagulant at about 99%, and the SV _{30 was} also lowered by 95% up to 44% by the injection of the inorganic coagulant. It is thought to have a significant effect on improving water content and sedimentation.

In addition, the turbidity of the filtrate after the mixed concentration of sewage sludge was high to about 98.7 NTU level before the injection of the inorganic coagulant.However, as the amount of the inorganic coagulant was increased to 5, 10, 15, 20, 25 mg / L, about 67, 54 , 46, 44, and 36 NTU. This is due to ion exchange with divalent cations (Ca ²⁺ , Mg ^2+, etc.) that make up Al ³⁺ sludge floc, which is the trivalent cation of PAC injected with inorganic coagulant, to increase flocculation and decrease water content in the cake. It is because of the result.

Figure 5 shows the sludge TS, VS and VS / TS after the flocculation experiment according to the inorganic coagulant injection amount. Referring to FIG. 5, the initial TS of sewage sludge was about 9950 kg / m ³ , and VS was about 8400 kg / m ³ , and the TS was about 14,150 kg / m ³ when the inorganic coagulant was injected at a maximum of 25 mg / L. , VS increased to about 10,700 kg / m ³ . As the amount of inorganic coagulant injection increases and TS and VS gradually increase, the sludge flocculates and the floc size increases.

Experimental Example 5: Coagulation Characteristics of Sewage Sludge by Application of Coagulated Sludge

Through the experimental method of Experimental Example 1 and the experimental results of Experimental Example 4, the flocculation characteristics of sewage sludge using the inorganic coagulant was confirmed. In Experimental Example 5, to reduce the use of the inorganic coagulant and to use the coagulant sludge as an alternative material, the possibility of coagulant sludge as a substitute material was examined. The experimental method is as described in Experimental Example 1.

Figure 6a is the result of the filtration time (CST) according to the mixing ratio of sewage sludge and flocculation sludge, Figure 6b shows the SRF results according to the mixing ratio of sewage sludge and flocculation sludge. Referring to FIG. 6A, when the sewage sludge and the flocculated sludge were mixed at a volume ratio of 9: 1, the CST was measured at about 182 sec, which is a result of injecting 10 mg / L of an inorganic coagulant (about 202 sec, see Experimental Example 4). Shorter results confirmed significant improvement. In addition, when the volume ratio is 1: 1, the CST is 101 sec, which is very low, and it is superior to the result of injecting the inorganic coagulant at the maximum injection amount (25 mg / L) in Experimental Example 4 (about 137 sec). .

This is believed that metal hydrates such as aluminum hydroxide in the coagulated sludge neutralize the static electricity on the surface of sewage sludge particles, resulting in increased flocs, and thus the precipitation rate is improved.

Next, referring to Figure 6b, SRF is the result of injecting 10 mg / L of inorganic coagulant at about 3.5 x 10 ¹¹ m / kg when the volume ratio of sewage sludge and flocculation sludge is 9: 1 (see Experimental Example 4) Appeared smaller. Then, when the mixing ratio was increased to 6: 1, 3: 1, 2: 1 by increasing the flocculation sludge ratio, the SRF value was about 3.0 x 10 ¹¹ m / kg, and it was confirmed that the decrease due to the increase of flocculation sludge ratio was insufficient. However, when mixed in a 1: 1 volume ratio, the SRF value was reduced by about 68% to 1.8 x 10 ¹¹ m / kg, which resulted in better dehydration than when the inorganic coagulant was injected at 25 mg / L.

Water content and SV ₃₀ of the mixed sludge were analyzed to evaluate the dehydration and sedimentation of the mixed sludge according to the mixing ratio of sewage sludge and flocculated sludge. Figure 7a shows the water content of the mixed sludge according to the mixing ratio of sewage sludge and flocculated sludge, Figure 7b shows the SV ₃₀ of the mixed sludge according to the mixing ratio of sewage sludge and flocculated sludge.

Referring to FIG. 7A, the water content of the mixed sludge was lowered to about 96% at the 9: 1 mixing ratio and about 80% at the 1: 1 mixing ratio. The decrease in water content of the mixed sludge in the 9: 1 volume ratio mixing was somewhat insignificant, but the increase of the mixing volume ratio of the flocculated sludge resulted in the injection of 25 mg / L of inorganic coagulant in the 2: 1 and 1: 1 mixing experiments (approximately 84% , Experimental Example 4) was confirmed to improve the results. This is a result of the additional floc formation and floc size increase due to the mixing of sewage sludge and flocculated sludge. As the floc size increases, the dewatering property of the sludge is improved. In addition, referring to FIG. 7B, SV ₃₀ was reduced to about 32% when mixed at an initial ratio of 95% to 1: 1, and it was confirmed that the increase in floc size improved not only dehydration but also sedimentation rate.

Figure 8 shows the TS, VS and VS / TS of the mixed sludge after the flocculation experiment according to the mixing ratio of sewage sludge and flocculation sludge. Referring to FIG. 8, as the mixing ratio of sewage sludge and flocculated sludge increased, TS and VS increased by 59% and 53%, respectively, thereby increasing the size of the sludge floc. In addition, since the VS content of the flocculated sludge is smaller than that of the sewage sludge, the VS / TS was reduced to about 81% through mixing. The turbidity of the sewage sludge filtrate before mixing was about 99 NTU, and the turbidity of the coagulated sludge filtrate was about 46 NTU, but the turbidity of the filtrate after mixing was reduced to about 16 NTU at 1: 1 ratio. Through this, it was confirmed that the mixing with the flocculating sludge without the addition of the flocculant is effective in improving the sewage sludge as well as the water quality of the sludge filtrate.

Based on the above experimental results, it can be seen that the optimum mixing ratio (volume ratio basis) of sewage sludge and flocculated sludge for treating sewage sludge is 3: 1 to 1: 1. That is, when the sewage sludge of 1 to 3 times compared to the flocculation sludge is mixed, it can be seen that the characteristics of the filtration time (CST), SRF characteristics, moisture content and SV ₃₀ of the mixed sludge is improved.

110: flocculation tank 120: precipitation tank
130: sludge mixing tank 140: sludge thickening tank
150: sludge dewatering tank

Claims (8)

A flocculation tank which provides a space in which the flocculation reaction between sewage and flocculant proceeds and generates flocculation sludge;
Sedimentation tank separating raw water into supernatant and sewage sludge;
A sludge mixing tank for mixing and stirring agglomerated sludge and sewage sludge to produce mixed sludge;
A sludge concentration tank in which coagulated sludge and sewage sludge are mixed and precipitated mixed sludge naturally to concentrate mixed sludge; And
And a sludge dewatering tank for dehydrating water contained in the mixed sludge in a state in which the mixed sludge concentrated from the sludge thickening tank is supplied.
Sewage sludge and flocculated sludge are mixed in a volume ratio of 3: 1 to 1: 1,
The flocculant is an inorganic coagulant or an organic polymer coagulant,
The flocculant component of the flocculating sludge neutralizes static electricity on the surface of the sewage sludge particles, thereby reducing the repulsion force between particles, and increasing the dehydration and sedimentation of the sewage sludge by crosslinking between particles.
delete The sewage sludge treatment apparatus according to claim 1, wherein the flocculation sludge is sewage flocculation sludge generated in a sewage treatment step or purified water flocculation sludge generated in a water treatment step.
delete Preparing agglomerated sludge and sewage sludge, respectively;
Mixing and stirring agglomerated sludge and sewage sludge into a sludge mixing tank;
Condensing the mixed sludge by sedimenting the mixed sludge and the sewage sludge in a sludge thickening tank;
And transporting the mixed sludge concentrated in the sludge concentration tank to a sludge dewatering tank, and dehydrating the mixed sludge in the sludge dewatering tank.
The flocculated sludge is produced by flocculation of flocculant and sewage, and the sewage sludge is sludge generated as a by-product in the final stage of the biological sewage treatment process.
Sewage sludge and flocculated sludge are mixed in a volume ratio of 3: 1 to 1: 1,
The flocculant is an inorganic coagulant or an organic polymer coagulant,
The flocculant component of the flocculating sludge neutralizes static electricity on the surface of the sewage sludge particles to reduce the repulsive force between particles, and increases the dehydration and sedimentation of the sewage sludge by crosslinking between particles.
delete The sewage sludge treatment method according to claim 5, wherein the flocculation sludge is sewage flocculation sludge generated in a sewage treatment step or purified water flocculation sludge generated in a water treatment step.
delete

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