JPH0438475B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to the treatment of alcohol distillation waste liquid,
In particular, the present invention relates to a method for removing chromaticity and COD components remaining after the waste liquid is subjected to biological treatment such as methane fermentation and activated sludge. (Conventional technology) In alcohol manufacturing factories that extract alcohol from raw materials such as molasses and sugarcane sugar, high-density
Black-brown distillation waste containing BOD and COD is discharged. When treating this waste liquid, for example, there is a method of decomposing the BOD component through methane fermentation treatment, recovering energy as CH ₄ gas, and then mixing and diluting it with other factory wastewater and performing biological treatment using activated sludge or the like. (Problem to be solved by the invention) However, in the alcohol distillation process, dark brown color components (called melanoidin-based organic substances) are generated, and these components cannot be removed by the above treatment. It remains in the effluent. This chromaticity component not only causes color pollution of rivers, but also causes organic pollution because it is a COD substance. Therefore, in order to treat alcohol distillation waste liquid to a water quality that can be discharged, it is necessary to apply equipment such as activated carbon or membrane separation, which is expensive to operate, and from an economic point of view it is considered unprocessable wastewater. ing.
In light of the above, it is of great significance to find an economical method for treating alcohol distillation waste. Therefore, an object of the present invention is to provide a treatment method that can efficiently remove the blackish-brown chromaticity and COD components remaining in the alcohol distillation waste liquid. (Means for Solving the Problems) The present invention utilizes coagulation-sedimentation technology, which is a relatively inexpensive treatment, without applying expensive equipment such as activated carbon or membrane separation, to improve the chromaticity and It removes COD components. That is, the method for treating alcohol distillation waste liquid according to the present invention includes the first step of subjecting the alcohol distillation waste liquid to anaerobic biological treatment and further aerobic biological treatment, and adding and mixing the obtained treated liquid with an inorganic flocculant under acidic conditions. The second step is characterized by comprising a third step of adding an alkali and a polymer flocculant to the liquid mixture obtained in the second step and performing solid-liquid separation. Next, each step in the method of the present invention will be explained in detail. First step: In the first step, the alcohol distillation waste liquid discharged from the distillation process is first introduced into a methane fermentation tank, and the BOD in the waste liquid is decomposed into CH ₄ gas, which flows out as a desorbed liquid. This methane fermentation desorbed liquid is mixed with diluted wastewater from other systems in a combined tank, subjected to aerobic treatment in an activated sludge tank, etc., and after further decomposition and removal of BOD components, it flows out to the flocculation process. Second step: In the second step, the treatment liquid is adjusted to be acidic using a mineral acid, such as sulfuric acid or hydrochloric acid, and then an inorganic flocculant is added and mixed. Examples of the inorganic flocculant include aluminum sulfate, ferric sulfate, and ferric chloride. In this step, the blackish-brown chromatic component in the treatment solution reacts with the injected inorganic coagulant, and precipitates as fine SS. The flocculating properties of inorganic flocculants vary significantly depending on the pH. Figure 1 shows the changes in the chromaticity and COD components of supernatant water when aluminum sulfate is used as a flocculant and the amount added and pH are changed.
As a result, the chromaticity and COD removal rate improve from PH4.5, and remain constant below PH4. That is, P.H.
Chromaticity and COD coagulation are noticeable below 4,
It is recognized that it is largely dependent on pH. Furthermore, at a pH of 2 or less, most of the chromaticity components in the processing solution precipitate as SS, and the carbon dioxide gas generated at this time causes the SS to float. Therefore, SS can be floated and separated in advance at this stage. Figure 2 shows the results of measuring the chromaticity and COD concentration of the separated water thus obtained. From this result, by injecting H ₂ SO ₄ into the test water and lowering the reaction pH to 2 or less, approximately 2000 mg of floatable SS was precipitated, and the chromaticity (expressed as Lovibond color) in the separated water was reduced.
It can be seen that COD can be treated to 100 or less and COD to 500mg/or less. The sample water used in the above experiments and the following examples had the following water quality. PH 8.0 SS 210mg / COD _Mo 2750mg / COD _Cr 4510mg / BOD 42mg / M-Alkalinity 1050mg / Color 370 When an inorganic flocculant is added to the treated water that has been subjected to flotation separation in advance, it remains in the treated liquid. The chromaticity component reacts with the inorganic flocculant and newly precipitates as thin SS. Third step: In this step, an alkaline agent such as sodium hydroxide is added to bring the pH to around neutral, which can be discharged, and a polymer flocculant is added to coarsen the fine flocs. As the polymer flocculant, any commonly used nonionic or anionic polymer flocculant can be used. When carrying out this process, after the second process, the PH
If floc formation is performed and solid-liquid separation is performed as it is at 4, there will be problems with corrosion of equipment components due to low pH, and the pH of the treated water after solid-liquid separation will be the standard discharge standard of 5.8 to 8.6. There remain problems such as an increase in SS due to precipitation of soluble metals due to adjustment to Furthermore, even if solid-liquid separation is performed at PH4, a solid-liquid separation tank will be additionally required to remove SS generated during neutralization. Furthermore, if you try to adjust the PH to the effluent water quality pH directly with alkali after coagulation at PH4, the chromaticity and chromaticity of the treated water will change even if you add a polymer flocculant after adjusting the PH.
COD can get worse. This means that the coagulated chromaticity components are redissolved. In such a case, a suitable treatment can be achieved by first adding a polymer flocculant to form a floc after the second step and then adding an alkali to adjust the pH. Note that chromaticity treatment can sometimes be performed stably by adding a small amount of a nonionic or anionic polymer flocculant as a supplement when adjusting the pH with an alkali. As mentioned above, the mechanism by which the coagulated chromaticity components do not re-dissolve by adjusting the pH after forming coarse flocs with a polymer flocculant cannot be clearly explained, but by pre-flocculating the flocs, the alkali added At the same time, it is presumed that the metal hydroxides precipitated by neutralization with alkali are captured on the surface of the floc, making it less susceptible to the effects of alkali. (Example) Next, the present invention will be explained in detail based on an example.
The present invention is not limited to this. Example 1 Sulfuric acid was added to test water having the above water quality to adjust the pH.
4, then mix sulfuric acid sodium chloride in various addition amounts, and use sodium hydroxide to adjust the pH to allow for discharge.
Adjusted to 6-7. Then, 20% of Himoroku PN-161 (trademark), a nonionic polymer flocculant, was applied.
mg/mg was added to coarsen the floc, and solid-liquid separation was performed by sedimentation. Color, COD concentration, and generated SS of the obtained treated water
is shown in Figure 3. For comparison, the results of the conventional method, which was treated in the same manner except that sulfuric acid was not used, are shown in broken lines in FIG. As is clear from Fig. 3, in the method of the present invention, the chromaticity of the treated water (expressed as Lovibond color) is 30, COD 100, and
mg/, whereas in the conventional method, sulfuric acid
It can be seen that unless 3000mg/or more is injected, the treated water quality cannot be obtained at the same level as the method of the present invention, and the amount of SS generated increases. In other words, by employing the method of the present invention, the amount of flocculant used in flocculation treatment can be significantly reduced, and the generated
It can be seen that the SS amount can be reduced and the COD chromaticity processing effect is also excellent. Example 2 Test water having the above water quality was treated by adding sulfuric acid.
The pH was adjusted to 2, and flotation separation was performed using the generated carbon dioxide gas. As can be seen from Figure 2, the buoyancy SS is approximately
2000mg/precipitation, chromaticity in separated water is less than 100,
COD was less than 500mg/. Various amounts of sulfuric acid salt were added to the separated water, and the subsequent steps of adding an alkali agent and a polymer flocculant were carried out in the same manner as in Example 1. The results are shown in Figure 4. Also, for comparison, the results of treating the same sample water by conventional coagulation-sedimentation, that is, a combination treatment of an inorganic flocculant and a polymer flocculant, are shown by a broken line in Figure 4, but the method of the present invention Ban soil injection amount 500mg/
In contrast, conventional coagulation and sedimentation treatment uses sulfuric acid.
Even if 2000mg/injected, the chromaticity of the treated water is more than 100,
COD was over 500mg/. In addition, the amount of SS generated by coagulation and precipitation in this case is as high as 5000mg/
This causes problems in sludge treatment. That is, it can be seen that by applying the method of the present invention, the amount of flocculant used in the treatment and the amount of SS generated can be significantly reduced, and a treatment effect with excellent COD and chromaticity can be achieved. Example 3 (1) Aluminum sulfate was added to the above sample water.
After setting the pH to 4 and carrying out the reaction,
Add 20mg/-161 to form coarse flocs. Then add sodium hydroxide to pH
After setting the value to 6.5, solid-liquid separation was performed. (2) The treatment was carried out in the same manner as in (1) except that ferric chloride was used instead of the aluminum sulfate. The quality of the treated water obtained in (1) and (2) above was measured. The results are shown in Table 1 below.

[Table] As is clear from this result, it is possible to reduce chromaticity and COD components by 90% or more by the coagulation-precipitation treatment according to the present invention. Figure 5 shows the relationship between pH and chromaticity of supernatant water when aluminum sulfate is added as curve A. After setting the pH to 4 with aluminum sulfate, the pH was increased with sodium hydroxide. Curve B shows the relationship between pH and chromaticity of supernatant water in this case. After aluminum sulfate was added to adjust the pH to 4, a nonionic polymer flocculant was added to form a floc, and then NaOH was added. Curve C shows the relationship between the chromaticity of supernatant water and PH when the PH is increased. (Effects of the Invention) As described above, by employing the method of the present invention after methane fermentation and aerobic biological treatment of alcohol distillation waste liquid, it is possible to efficiently remove the blackish brown chromaticity and COD remaining in the waste liquid. can.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between PH and dye and COD _Mo concentrations when aluminum sulfate is used alone as a flocculant. Figure 2 is a graph showing the PH of the sample water and flotation separation before addition of the inorganic flocculant. A graph showing the relationship between the chromaticity of water and the COD concentration.
A graph showing the relationship between the COD concentration. Figure 4 is a graph showing the relationship between the amount of sulfuric acid sodium chloride added and the chromaticity and COD concentration of the treated water in Example 2. Figure 5 is a graph showing the relationship between the sulfuric acid chloride concentration and the chromaticity of the treated water in Example 3. It is a graph diagram showing the relationship between the amount of addition, chromaticity of treated water, and COD concentration.

Claims (1)

[Claims] 1. A first step of subjecting the alcohol distillation waste liquid to anaerobic biological treatment and further aerobic biological treatment; a second step of adding and mixing the obtained treated liquid with an inorganic flocculant under acidic conditions; A method for treating alcohol distillation waste liquid, comprising a third step of adding an alkali and a polymer flocculant to the mixed liquid obtained in the step and performing solid-liquid separation. 2. In the second step, flotation separation is carried out under strongly acidic conditions before adding the inorganic flocculant.
Treatment method described in section. 3. The treatment method according to claim 1, wherein in the third step, a nonionic polymer flocculant is added to the mixed liquid to form a floc, and then an alkali is added to the mixture until it reaches neutrality. 4. In the third step, after adding a nonionic polymer flocculant to the mixed solution to form a floc, alkali is added to the mixture until it reaches neutrality, and then a nonionic or anionic polymer flocculant is added. A treatment method according to claim 1.