JPH0215243B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for coagulating organic wastewater,
In particular, it relates to an effective method for removing COD components and chromaticity components from wastewater. Organic wastewater such as human waste, sewage, pulp wastewater, food factory wastewater, etc. is usually purified by biological treatment or coagulation-sedimentation treatment. However, biological treatment methods reduce COD in wastewater.
Removal of components and chromaticity components is not sufficient. In general, pulp wastewater has a higher COD value than BOD, and this COD component is difficult to remove. For example, activated sludge treatment can remove over 90% of BOD components, but only about 50% of COD components. Therefore, in conjunction with the recent tightening of regulations on the total amount of COD, an effective method for removing COD components and chromaticity components is desired. Conventional methods for removing COD components and chromaticity components include:
There are agglomeration treatment methods, oxidation methods using oxidizing agents, adsorption methods using activated carbon, etc., but the aggregation treatment method is common. Inorganic coagulants and polymer coagulants are generally used for coagulation treatment of organic wastewater. For the purpose of removing SS components (or turbidity components) and color components in wastewater, organic coagulants such as polyethyleneimine, polyalkylene polyamines, and dicyandiamide formalin condensates are used instead of inorganic coagulants. However, for the purpose of removing COD components, conventional organic coagulants cannot remove COD as well as inorganic coagulants. However, in general, large amounts of inorganic coagulants such as aluminum sulfate must be added to remove COD components, and the sludge generated after treatment contains aluminum hydroxide, making it difficult to dehydrate and thus difficult to dispose of. It is. The present invention was made to solve the above problems, and an object of the present invention is to provide a method for coagulating organic wastewater that is excellent in removing COD components, particularly soluble COD components and chromaticity components. That is, the present invention adds melamine 1 to organic wastewater (excluding polyvinyl alcohol-containing water and starch-containing water).
It is obtained by reacting 1.8 to 2.5 moles of formaldehyde to 1 mole of melamine, and by adding an acid colloid solution of methylolmelamine in which 1.8 to 2.5 moles of formaldehyde are bound to 1 mole of melamine.
This is a coagulation treatment method for organic wastewater characterized by removing COD components. Methylolmelamine used in the present invention is melamine bound to formaldehyde,
In the present invention, 1.8 to 2.5 moles of formaldehyde are bonded to 1 mole of melamine by reacting 1.8 to 2.5 moles of formaldehyde with 1 mole of melamine. If the amount of formaldehyde is less than 1.8 mol per mol of melamine, the coagulation effect will not be sufficient when made into an acid colloid solution, and conversely, if the amount of formaldehyde exceeds 2.5 mol per mol of melamine, the coagulation effect will be insufficient when made into an acid colloid solution. Since the amount of free formaldehyde increases, COD cannot be reduced. Methylolmelamine can be produced by reacting melamine with a predetermined amount of formaldehyde, and an example is shown below for reference. Add 1 mole of melamine and 2 moles of paraformaldehyde as formaldehyde to 200 ml of distilled water, adjust the pH to 10, and then heat to 70°C to dissolve. After dissolution, the reaction was maintained at 70°C for another 5 minutes, and then the mixture was left at room temperature to gradually cool and precipitate crystals. The crystals are washed with methanol and then dried under reduced pressure to obtain methylolmelamine powder. Formalin may be used instead of paraformaldehyde. In order to obtain methylolmelamine in which 1.8 to 2.5 moles of formaldehyde are bound to 1 mole of melamine, the charging ratio of melamine and formaldehyde and pH may be adjusted as appropriate. The methylolmelamine thus obtained does not dissolve in water, but dissolves in an acid solution in a colloidal state. As the acid, in addition to mineral acids such as hydrochloric acid and nitric acid, formic acid, acetic acid, lactic acid, etc. may be used, but hydrochloric acid is preferred since a stable colloidal solution can be obtained. Hydrochloric acid is methylolmelamine 1
It is usually about 1 mol per mol. A large amount of free formaldehyde is present in this acid colloidal solution of methylolmelamine at the initial stage of preparation of the colloidal solution, but when it is left to mature at room temperature after preparation, the amount of free formaldehyde decreases.
Ripening can also be accelerated by heating. In the case of room temperature aging, it takes 5 days to 3 months, and in the case of heat aging, it takes about 2 to 3 hours at 50°C. The amount of the acid colloid solution to be added varies depending on the type of wastewater and the treatment target, and is appropriately determined by a jar test. The acid colloid solution may be used by being added to wastewater alone, but it may also be used in combination with an inorganic coagulant such as aluminum sulfate or ferric chloride, or in combination with an organic coagulant. As the organic coagulant, polyalkylene polyamines represented by polyethyleneimine, water-soluble dicyandiamide-formaldehyde condensates, polydimethyldiallylammonium salts, epihalohydrin-amine condensates, cationized starch, cationized guar gum, etc. can be used. When an inorganic coagulant and an organic coagulant are used together, it is preferable to add an acid colloid solution at the same time as or after the addition of these agents. It is not preferable to add the acid colloid solution first because it may act on the COD component, which can be removed by an inorganic coagulant or an organic coagulant. After the acid colloid solution is added to coagulate the COD component, an organic polymer flocculant is added to form a floc, which is preferably separated into solid and liquid. Known organic polymer flocculants can be used, but
Among them, acrylamide-based ones are preferable, such as polyacrylamide, polymethacrylamide, polyacrylamide or a partial hydrolyzate of polymethacrylamide, acrylamide or methacrylamide and other vinyl monomers such as acrylic ester, acrylonitrile, dialkylamino. Examples include copolymers with ethyl methacrylate or its quaternized product. According to the present invention, organic wastewater (excluding polyvinyl alcohol-containing water and starch-containing water)
Formaldehyde per mole of melamine
It is obtained by reacting 1.8 to 2.5 mol,
Formaldehyde is 1.8 to 1 mole of melamine
Since an acid colloid solution of 2.5 moles of methylolmelamine is added, COD components in wastewater can be removed, and turbidity and color can also be reduced. Hereinafter, the effects of the present invention will be clarified by examples using acid colloid liquids obtained in the following production examples. Example of producing acid colloid liquid: 63 g (0.5 mol) of melamine and 30 g of paraformaldehyde (as formaldehyde) in 93 ml of distilled water.
1.0 mol) was added, the pH was adjusted to 10.0 with NaOH, and the mixture was heated to 70°C to dissolve the melamine. 70 more
After reacting at °C for 5 minutes, the mixture was left at room temperature and gradually cooled to precipitate methylolated melamine crystals. This precipitate was collected on a Buchner funnel, washed with methanol, and then dried under reduced pressure. Elemental analysis of this dried methylolated melamine revealed that the ratio of melamine to formaldehyde was 1:2.19. 10g (0.05mol) of this methylolated melamine
It was added to 100 ml of 1.8% hydrochloric acid solution and stirred to obtain an acid colloid solution. When used in each of the following examples, the mixture was further left to mature at room temperature for 12 days. Example 1 Paper manufacturing factory wastewater (PH7.7, turbidity 195 degrees,
Take 500 ml of COD _Mo (96 mg/) in a beaker, add 100 to 400 mg of the acid colloid solution of the above production example as methylolated melamine, stir for 1 minute at 150 rpm using a stirrer, and then add the polyacrylamide hydrolyzate. 1 mg/ml was added and rapidly stirred at 150 rpm for 1 minute, then slowly stirred at 50 rpm for 2 minutes, and left to stand for 10 minutes to measure the COD and turbidity of the supernatant. The results are shown in Table 1. For comparison, Table 1 also shows a case in which 200 to 800 mg of liquid sulfuric acid was added as a product instead of acid colloid. In addition, in the case of liquid sulfuric acid band, after addition
Stir at 150 rpm for 1 minute, adjust the pH to 6.5, and then
After stirring at 150 rpm for 1 minute and adding the polyacrylamide hydrolyzate, the same procedure was performed.

【table】

[Table] cannot be lowered any further.
The limit value.
In the case of acid colloid treatment, COD decreased as the addition amount increased up to 200mg/, but when the addition amount was 200 or more and 400mg/, COD _Mo decreased to 30mg/
There was no difference. In addition, in the case of liquid sulfuric acid band treatment, as the amount of addition increases up to 600mg/
Although COD decreased, COD _Mo remained unchanged at 65 mg/ when the addition amount was 600 or more and 800 mg/. Example 2 Activated sludge treated water (PH
7.0, turbidity 46 degrees, chromaticity 630 degrees, COD _Mo 60 mg/) was treated in the same manner as in Example 1. The results are shown in Table 2.

[Table] Example 3 Activated sludge treated water from human waste (PH8.4, chromaticity 467 degrees,
COD _Mo (122 mg/) was treated in the same manner as in Example 1. The results are shown in Table 3. In addition, cases in which liquid sulfuric acid and acid colloid are used together (simultaneous addition) are also described.

[Table] Example 4 General wastewater from a pulp and paper factory (PH6.0, turbidity 45 degrees,
The same process as in Example 1 was performed for a sample having a chromaticity of 862 degrees and a COD _Mo content of 159 mg/). The results are shown in Table 4. In addition, cases in which polyethyleneimine was added instead of acid colloid, and cases in which polyethyleneimine and acid colloid were used together (simultaneous addition) are also described.

【table】

[Table] As can be seen from Tables 1 to 4, COD can be reduced by adding an acid colloid solution to wastewater. Example 5 Melamine and paraformaldehyde were added to distilled water under the conditions shown in Table 5, the pH was adjusted to 10.0 with NaOH, and the mixture was heated to 70°C to dissolve the melamine. Furthermore, after reacting at 70°C for 5 minutes, the mixture was left at room temperature and gradually cooled to precipitate methylolated melamine crystals. However, since the samples A and B in Table 5 did not precipitate crystals when left at room temperature, they were concentrated under reduced pressure at 35° C. to precipitate crystals. This precipitate was collected on a Buchner funnel, washed with methanol, and then dried under reduced pressure. As a result of elemental analysis of this dried methylolated melamine, the number of moles of formaldehyde bonded to 1 mole of melamine was as shown in Table 5.

【table】

[Table] Add 10 g of this methylolated melamine to 100 g of hydrochloric acid solution.
ml and heated at 50°C for 2 hours to obtain an acid colloid solution. At this time, the molar ratio of hydrochloric acid and methylolated melamine is HCl:methylolated melamine = 0.8:
It was set to 1. Next, wastewater from a paper manufacturing factory (PH7.9, turbidity 825 degrees)
Place 500ml of COD _Mo (226mg/) in a beaker, and add the acid colloid solution prepared from methylolated melamine shown in Table 5 as methylolated melamine.
Add 100-400mg/150rpm using a stirrer
After stirring for 2 minutes at
After standing for 10 minutes, the COD _Mo and turbidity of the supernatant were measured. The results are shown in Table 6. For comparison, liquid sulfate was used as a product instead of acid colloid.
Table 6 also shows the case where 100 to 600 mg/addition was made. In addition, in the case of liquid sulfuric acid band, it was treated in the same manner as in Example 1.

【table】

[Table] From this, it can be seen that when the molar ratio is outside the range of 1.8 to 2.5, the amount of residual COD increases rapidly.

Claims (1)

[Claims] 1 Melamine 1 is added to organic wastewater (excluding polyvinyl alcohol-containing water and starch-containing water).
It is obtained by reacting 1.8 to 2.5 moles of formaldehyde to 1 mole of melamine, and by adding an acid colloid solution of methylolmelamine in which 1.8 to 2.5 moles of formaldehyde are bound to 1 mole of melamine.
A method for coagulating organic wastewater, characterized by removing COD components.