KR101973986B1 - Method of preparation for coagulant and treating method of water/wastewater using the same - Google Patents

Abstract

According to the present invention, provided are a preparation method of coagulant for water treatment and a water treatment method using the same. The preparation method of coagulant for water treatment comprises: a step of preparing reactant by reacting 50 parts by weight of aluminum hydroxide (Al(OH)_3) and 100 parts by weight of sulfuric acid (H_2SO_4) (for 5 to 7 hours at the temperature of 140 to 200°C by exothermic reaction of sulfuric acid); a step of preparing Alum by adding 200 parts by weight of dilution water to the reactant; and a step of preparing coagulant by adding 20 to 50 parts by weight of the iron salt compound as the additive to the prepared Alum wherein the coagulant contains 4.5 to 7.5 wt% of aluminum oxide (Al_2O_3) and 0.5 to 1.0 wt% of Fe. The coagulant (aluminum sulfate) prepared according to the preparation method of the present invention maintains excellent cohesive performance and exhibits excellent stability such as no precipitation of solid phase during long term storage. In addition, the coagulant reduces the volume of sludge generated in drinking water and wastewater treatment, prevents the reduction of residual aluminum and coloration, shows smooth cohesion ability even in high turbidity, and is effective in removing algae. In particular, the coagulant has an excellent effect of removing organic substances and phosphorus and thus, has excellent coagulant properties to prevent eutrophication such as green algae.

Description

Preparation method of flocculant for water treatment and water treatment method using same {Method of preparation for coagulant and treating method of water / wastewater using the same}

The present invention relates to a method for producing a flocculant for water and sewage and wastewater treatment, and more particularly, to a method for producing flocculant for water treatment and a method for treating water and sewage and wastewater using the same.

Aluminum sulfate (also referred to as 'Alum') was the most commonly used inorganic coagulant in flocculation facilities, which are physical and chemical treatment facilities installed at various water treatment sites for water purification and wastewater treatment. The monomolecular Al is mainly dominated. On the other hand, polyaluminum chloride (hereinafter referred to as “PAC”) contains high molecular weight Al and shows a somewhat better cohesive efficiency than Alum, and is used in various water treatment sites. However, PAC has a disadvantage in that the price is higher than that of Alum, and precipitates are generated due to the storage period, which causes many difficulties in maintenance. In addition, in the case of hydrochloric acid, which is one of the raw materials, it is often difficult to supply smoothly depending on the source of supply, and thus there is a disruption in production. In addition, due to the increased use of flocculant due to the strengthening of water quality standards for phosphorus in treated water at various water treatment sites of sewage and wastewater treatment, the burden of maintenance costs is very high, and the burden of economic burden is increasing. Therefore, while the use of Alum, which is economical, has no difficulty in supplying, and is easy to maintain, is increasing, development of Alum's new coagulant having excellent cohesive efficiency is needed.

Phosphorus to be treated at each of these water treatment sites may be removed in the form absorbed by microorganisms in the biological treatment process, but due to its low solubility, it is easy to process by generating precipitates in water, thereby causing flocculation and chemicals in the chemical treatment process. In addition, the use of inorganic coagulant is essential because it needs to be removed in the form of physically bonded sediment. In recent years, low base PAC of aluminum-based inorganic coagulant, which is commonly used in water treatment sites, is widely used for the treatment of phosphorus (P). There is still a burden on the market, and on the other hand, the difficulties caused by the smooth supply of raw materials still remain. Therefore, it is economical and improves the removal efficiency of particulate matter and the removal efficiency of soluble materials such as organic matter and phosphate, reduces the residual aluminum after the flocculation treatment, and secures the stability of the new flocculant and flocculant which can escape the limit of flocculation pH. There may be a need for the development of new flocculants.

As a prior art related to a water treatment agent for removing phosphorus in sewage and wastewater treatment, for example, Korean Patent Publication No. 10-1159236 discloses a method for preparing a low-basicity polyaluminum chloride flocculant and a water treatment method using the same. In this patent, low-basicity PAC is commercialized through a two-step manufacturing process. Such aluminum-based flocculants have a small limit (pH 5.5-8.0) of the width of the flocculation pH, and a countermeasure against residual aluminum after the flocculation treatment is necessary. In addition, Korean Patent Publication No. 10-1640368 discloses a method for preparing a coagulant for maintaining a low base, and a water treatment method using the same. In this patent, the basicity of 40 to 45% is maintained in preparing a low base for a coagulant. PAC is also commercialized by using a low salt base using a metal compound of iron salt as a base regulator to maintain a basicity of 30% or less in PAC. The PAC flocculant which maintains the low basicity prepared by adding ferric chloride as a base regulator may have a precipitate depending on the amount of ferric chloride added, which requires a careful attention to the amount of additives. In addition, the patented technology of the water treatment agent for phosphorus treatment discloses a coagulant composition for water treatment containing zirconium in aluminum-based inorganic coagulant and a water treatment method using the same in Korea Patent Publication No. 10-1016392. Korean Patent Publication No. 2001-0094714 discloses calcium type artificial zeolites, soluble aluminum-based or iron salt-based compounds, natural or synthetic polymer coagulants, carbonate granules of alkali metals, and calcium compounds, carbonates of alkaline earth metals, titanium dioxide and powdered activated carbon. Disclosed is a water treatment composition composed of two or more functional preparations selected from the group consisting of nitrogen and phosphorus in sewage / wastewater.

Therefore, in the present invention, the most widely used for water treatment, using an inorganic coagulant Alum that can secure economical efficiency and using a metal compound of iron salt as an additive to develop a new coagulant to maintain a better flocculation efficiency than conventional PAC. The iron salt coagulant is an inorganic coagulant having a wide range of coagulation pH (pH 4.0-11.0), excellent sedimentation properties of coagulum, excellent organic matter removal efficiency and coagulation even at low temperature in winter. The stability of the material is ensured according to the amount of flocculant added in Alum and iron salt, and the synergistic effect is induced in consideration of the characteristics of aluminum and iron salt. It was confirmed that the flocculation efficiency of the suspended solids or suspended particles as a particulate material can be improved and completed the present invention.

1. Domestic Patent No. 10-1159236 1. Domestic Patent No. 10-1640368 1. Domestic Patent No. 10-1016392 1. Domestic Patent No. 10-221977 1. Domestic Patent No. 10-1280550 1. Domestic Patent No. 10-1661179 1. Domestic Patent No. 10-1842094 1. Domestic Patent No. 10-1119623

The present invention to secure the stability of the material according to the addition amount of the Alum and iron salt in order to solve the problems of the prior art, and induces synergistic effect in consideration of the characteristics of aluminum and iron salts of the sludge volume during drinking water treatment In the reduction, the reduction of residual aluminum, the prevention of coloration and the treatment of sewage and wastewater, in particular, the method of preparing a flocculant for water treatment to prevent eutrophication of green algae and the like by removing organic substances and phosphorus, and treatment of purified water and sewage using The purpose is to provide a method.

As a solution of the method for producing a flocculant, which is the object of the present invention, 100 parts by weight of sulfuric acid (H ₂ SO ₄ ) having a concentration of 25 to 35% using an iron salt flocculant as an additive and a hydroxide having a concentration of 40 to 68% of aluminum oxide 50 parts by weight of aluminum (Al (OH) ₃ ) was added to 200 parts by weight of dilution water based on 100 parts by weight of the reactant prepared by reacting at a temperature of 140 to 200 ° C. for 5 to 7 hours to prepare Alum, and to the prepared Alum. The coagulant prepared by adding 20 to 50 parts by weight of iron sulfate as an additive contains aluminum oxide (Al ₂ O ₃ ) content of 4.5 to 7.5 wt%, Fe content of 0.5 to 1.0 wt%.

The flocculant (aluminum sulfate) maintaining the Al ₂ O ₃ content of 4.5 to 7.5% by weight and the Fe content of 0.5 to 1.0% by weight is 50 parts by weight of aluminum hydroxide (Al (OH) ₃ ) and sulfuric acid ( H ₂ SO ₄ ) 100 parts by weight of the reaction (reacted for 5 to 7 hours at a temperature of 140 ~ 200 ℃ by exothermic reaction of sulfuric acid) to 200 parts by weight of dilution water to the reactant prepared to prepare an Alum, It is made up by adding 20-50 parts by weight of ferric sulfate as an additive to 300 parts by weight of Alum.

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In the present invention, the Al ₂ O ₃ content and the Fe content of the flocculant (aluminum sulfate) are determined by the Korean Industrial Standard KS M 1411 or the standard, standard and labeling standard of the water treatment agent (Ministry of Environment Notice 2017-190). Can be obtained by

The coagulant represented by the formula (1) prepared in the present invention (aluminum sulfate) is economical, excellent cohesive performance is maintained, and exhibits excellent stability, such as precipitation of a solid phase during a long storage period.

The flocculant (aluminum sulfate) prepared according to the production method of the present invention maintains excellent cohesive performance and exhibits excellent stability such as no precipitation of solid phase during long term storage.

In addition, it reduces the volume of sludge generated in drinking water and wastewater treatment, prevents the reduction of residual aluminum and coloring, and shows cohesive ability even in high turbidity and removes algae. In particular, it has an excellent effect of removing organic substances and phosphorus and has excellent flocculant properties to prevent eutrophication of green algae and the like.

As the additive used in the present invention, iron salt compounds such as ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate and iron polysulfate may be used. Preferably, ferric sulfate is used. good. In addition, any aluminum-based inorganic coagulant such as polyaluminum chloride may be used in place of Alum.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the following Examples do not limit the present invention.

<Example 1>

(a) Preparation of Coagulant (Aluminum Sulfate) (Sample 1)

A reactant prepared by reacting 13% by weight of aluminum hydroxide (Al (OH) ₃ ) and 24% by weight of sulfuric acid (H ₂ SO ₄ ) (reaction for 5 to 7 hours at a temperature of 140 to 200 ° C. by exothermic reaction of sulfuric acid). 63 wt% of dilution water was added thereto to prepare Alum, and 10 wt% of ferric sulfate was added as an additive to 90 wt% of the prepared Alum to finally prepare 100 kg of aluminum sulfate coagulant. Al ₂ O ₃ content in the prepared flocculant (aluminum sulfate) was 7.5% by weight, Fe content was 1.0% by weight, and Al ₂ O ₃ content was the standard, specification and labeling of 2017-190 water treatment agent. Based on the analysis, the Fe content was analyzed using the DR-2700 equipment of HACH.

<Test Example 1>

In order to ensure the stability of the coagulant (aluminum sulfate) prepared in <Example 1> freeze generation, sediment generation, state and freezing after long-term storage for 6 months at -20 ℃, room temperature 20 ℃ and 50 ℃ high temperature, respectively The results for the stability of the product by measuring whether or not is shown in Table 1 below.

<Reliability Review> Item Example 1 Temperature Minus 20 ℃ 20 ℃ 50 ℃ January February In March April In May June January February In March April In May June January February In March April In May June Freezing × × × × × × × × × × × × × × × × × × Sediment formation × × × × × × × × × × × × × × × × × × condition □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ ○: Occurrence, ×: No occurrence, □: Stable, △: Unstable

<Test Example 2>

In order to examine the flocculation characteristics of the flocculant (aluminum sulfate) prepared in <Example 1>, the sedimentation basin effluent was treated by biological treatment in a sewage treatment plant before being introduced into the disinfection tank (water quality conditions [Table 2]). The coagulation test was conducted using Jar-test, and the coagulation test apparatus was performed using Jar-tester (Phipps & Bird Co., Ltd.). The water quality analysis in the coagulation test was performed by COD, turbidity, TP and PO ₄ -P. The method was performed by Standard methods (AWWA, 2005) and Water Pollution Process Test (Ministry of Environment). Analytical methods and instruments used for water quality analysis are shown in Table 3.

In the flocculation experiment, the flocculant used in the flocculation experiment (aluminum sulfate) and polyaluminum chloride (PAC, Al ₂ O ₃ content 10%, basicity 40%) and aluminum sulfate (commonly used in water treatment sites) are commonly used. Alum, Al ₂ O ₃ content of 8%), low basicity PAC (10% Al ₂ O ₃ content, 20% basicity) using the coagulation characteristics of the flocculant according to the injection amount of each flocculant, and the results It is shown in [Table 4] below.

<Water quality conditions of the final sedimentation effluent from sewage treatment plant> Item pH Turbidity (NTU) COD (mg / L) UV ₂₅₄ (cm ^-1 ) TP (mg / L) PO ₄ -P (mg / L) Water quality 7.13 2.02 9.28 0.110 2.31 1.98

<Water analysis method and device> Item unit Analytical Methods and Instruments Jar-test - Jar-tester (Phipps & Bird, Model 7790-500) pH - pH Meter (Mettler Delta 345) Turbidity NTU Tubidity meter (HACH, 2100P) COD mg / L Environmental Pollution Process Test (Water Quality) UV ₂₅₄ cm ^-1 UV Spectrophotometer (UV-1201, Shimadzu) TP, PO ₄ -P mg / L Environmental Pollution Process Test (Water Quality)

<Agglomeration Experiment Result According to Coagulant Injection> Flocculant Injection amount (mg / L) COD (mg / L) UV ₂₅₄ (cm ^-1 ) Turbidity (NTU) TP (mg / L) PO ₄ -P (mg / L) Aluminum aluminum sulfate (Example 1)
(Sample 1) 30 8.90 0.076 0.51 0.24 0.06 50 8.00 0.064 0.31 0.06 0.02 100 7.73 0.056 0.22 0.02 0.01 Polychlorinated
aluminum
(PAC) 30 8.89 0.078 0.53 0.43 0.06 50 8.10 0.065 0.33 0.09 0.03 100 7.57 0.057 0.23 0.04 0.01 Low baseline PAC 30 8.87 0.078 0.53 0.41 0.06 50 8.10 0.065 0.33 0.07 0.03 100 7.57 0.057 0.22 0.03 0.01 Sulfuric acid
aluminum
(Alum) 30 9.10 0.079 0.65 0.32 0.12 50 8.45 0.072 0.51 0.10 0.06 100 8.04 0.068 0.43 0.08 0.04

As shown in the flocculation efficiency according to the flocculant injection amount of each flocculant used in the flocculation experiment of [Table 4], in the case of the flocculent (iron aluminum sulfate) according to the present invention, the PAC and the low base are also included in the PAC and aluminum sulfate (Alum). Compared with the low Al ₂ O ₃ content, it shows excellent cohesive efficiency, and in particular, shows excellent effects on the removal of organic matter and the removal of phosphorus and phosphate phosphorus in water.

Claims (6)

100 parts by weight of sulfuric acid (H ₂ SO ₄ ) having a concentration of 25 to 35% and 50 parts by weight of aluminum hydroxide (Al (OH) ₃ ) having a concentration of 40 to 68% at a temperature of 140 to 200 ° C. for 5 to 7 hours. Alum was prepared by adding 200 parts by weight of dilution water to the reactant prepared by adding 20 to 50 parts by weight of the iron salt compound as an additive to the prepared Alum as a final coagulant,
The flocculant is aluminum aluminum (Al ₂ O ₃ ) content of 4.5 to 7.5% by weight, Fe content 0.5 to 1.0% by weight of the manufacturing method of the aluminum sulfate salt coagulant. delete delete delete The method according to claim 1,
The iron salt compound as an additive is a method for producing an aluminum iron salt coagulant, characterized in that any one of the iron salt compounds of ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate and iron polysulfate. delete