JP2000015007A - Flocculating method and flocculant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform solid-liquid separation of drainage difficult to be treated. SOLUTION: After the prescribed amount of a flocculant auxiliary consisting of lime and cement is added to liquid to be treated and the mixture is agitated, an acid salt solution of aluminum is added. Thereby, solid-liquid separation is easily performed even in liquid difficult to be treated and also water quality of drainage after treatment is enhanced than heretofore. Further, the above- mentioned auxiliary and the acid salt solution of aluminum are added to water to form floc and this floc together with water content is added to liquid to be treated and agitation is performed. Thereafter, treatment for separating water content and solid material is performed. Thereby, even when solid-liquid separation is not enabled in the above-mentioned method, solid-liquid separation is easily enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coagulation method, and more particularly, to a coagulation method using an inorganic drug.

[0002]

2. Description of the Related Art Fine suspended substances called SS, which are contained in large amounts in dyeing drainage, civil engineering drainage, sewage, or industrial wastewater, become suspended in water and are disposed of in rivers and seas, causing pollution. . Therefore, recently, the above-mentioned civil engineering waste liquid and the like are discarded after being treated so that the suspended matter and dissolved substances in the water are below the standard concentration, but the time and cost required for the treatment become enormous. I have.

[0003] For example, it is very difficult to remove dissolved pigment from wastewater from a dyeing factory. At present, the wastewater is temporarily stored in a water storage tank and decolorized by activated carbon and bio-treatment.
D and COD are treated and drained so as to be below the reference value.

The waste water from a paper mill contains fine powder of titanium oxide or fine powder of pulp fiber, which is widely used for smoothing the paper surface. In order to remove these fine powders, they are once stored in a water storage tank, and an organic or inorganic coagulant is added to coagulate and precipitate, and then drained.

[0005] In the sewage treatment, as in the above, raw water is once stored in a vast water tank, coagulated and precipitated with an organic or inorganic coagulant, and then drained.

[0006] Further, in the treatment of civil engineering wastewater, it is pending to reduce the concentration of iron contained in the treated wastewater.

Various coagulants have been developed for the coagulation treatment. For example, inorganic salts include aluminum salts (aluminum sulfate, aluminum hydroxide, ammonium alum, potassium alum, sodium aluminate, polyaluminum chloride) and iron salts (ferrous chloride, ferric chloride, ferrous sulfate, ferrous sulfate). In the organic system, low molecular salts, surfactants, natural or synthetic high molecular substances, and the like have been developed and used.

Further, the applicant of the present application proposed in Japanese Patent Publication No. 08-018016 a coagulant comprising a soluble aluminum salt and an alkali metal salt and a third substance for reducing the direct contact density between the above-mentioned agent and the agent. And it has a great effect.

[0009]

Although various flocculants have been developed and used as described above, it is difficult to perform solid-liquid separation of dyeing wastewater, papermaking wastewater, and the like. In addition, sewage treatment requires an enormous settling tank and the treatment time is enormous at present.
Furthermore, when a large amount of the organic flocculant is used, the cost increases and the above-mentioned difficulty of the solid-liquid separation increases.

In particular, sludge containing bentonite discharged from a civil engineering site, surplus concentrated sludge generated in the final step of sewage treatment, and the like cannot be further separated at present even if the sludge is directly separated by a stretching separator. It is a difficult-to-treat waste liquid.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and exhibits a rapid coagulation effect using only an inorganic agent. It is an object of the present invention to provide an inexpensive aggregating method and an aggregating agent capable of treating a liquid.

[0012]

The present invention employs the following means to achieve the above object. That is, a predetermined amount of a coagulation aid composed of lime and cement is added to the liquid to be treated, and after stirring, an acid salt solution of aluminum is added. Further, gypsum can be added as needed.

The amount of lime constituting the coagulation aid is 10 to 90% by weight of the aid. If a coagulation rate is not expected, lime 100% may be used, but adding a small amount of cement (Portland cement) can enhance the coagulation effect. The amount of lime added is controlled by 1
0% by weight. If the addition amount is lower than this, a sufficient effect cannot be obtained.

[0014] The addition amount of cement must be 10 to 90% by weight. Increasing the amount of cement increases the sedimentation rate of flocs generated in the liquid to be treated, but it is necessary to distribute the amount of lime not to less than 10%.
Gypsum can be used instead of or in addition to the lime. When gypsum is used in addition to lime, the coagulation rate can be further increased.

The above coagulation aid is added to the liquid to be treated in an amount of 0.01 to 1%.
After adding and stirring by weight, an acid salt solution of aluminum is added to the liquid to be treated in an amount of 0.01 to 1% by weight. Here, the addition amount of the acidic salt solution of aluminum is based on a commercial product having a concentration of about 30% when aluminum sulfate is used.
The addition amount varies depending on the pH of the liquid to be treated, but it is preferable to add an amount that makes the PH after treatment neutral. However,
The acid salt of aluminum used here is not only provided with the function of adjusting pH, but is an element necessary for causing the above-mentioned auxiliary to react. As a result, the solid content of the liquid to be treated including seabed sludge and river sludge, papermaking wastewater, and the like settles in 30 seconds to 1 minute. The same effect can be obtained by using polyaluminum chloride, aluminum chloride, ferrous sulfate or the like instead of aluminum sulfate.

Further, a predetermined amount of a coagulation aid consisting of lime and cement is added to the liquid to be treated, and after stirring, sodium silicate is added, followed by the addition of an acid salt solution of calcium chloride or aluminum to form the same. The effect can be obtained.

In this case, the components and distribution of the auxiliaries are the same as described above. Sodium silicate (35% -4
0%) is preferably added to the liquid to be treated in an amount of 0.01 to 1% by weight. The upper limit of the amount of sodium silicate (commercially available product having a concentration of about 35%) is not particularly limited, but if it is too large, floc is not formed, and the entire sludge is solidified with gelled sodium silicate, which is not consistent with the purpose of the present application. . The lower limit of sodium silicate may be 0 when an acidic salt of aluminum is used later, but when calcium chloride is used, the lower limit is about 0.01% by weight based on the liquid to be treated. Here, since the solid substance is taken into the gel body as the sodium silicate gels, the amount of sodium silicate cannot be further reduced.

The amount of the calcium chloride is not particularly limited, but is preferably about twice as much as the sodium silicate.

As described above, surplus concentrated sludge finally generated by drainage and sewage treatment from civil engineering work sites including bentonite cannot further separate water and solids (hereinafter referred to as solid-liquid separation). It is. However, when the floc generated by adding the above-mentioned auxiliary agent and aluminum acid salt to water is added to the wastewater containing the bentonite, excess concentrated sludge and stirred, further solid-liquid separation by a centrifuge is performed. It becomes possible. At this time, the type of sludge used to form the flocks is not limited.

[0020]

[Example] (Example 1) Treatment of sewage in Aktori Sewage Treatment Plant in Tottori City (tester: Regional Environment Planning Office, Faculty of Agriculture, Tottori University).

To 500 ml of raw water, 2 g of the auxiliaries of the present invention (lime 4, cement 4, gypsum 2) and 2 g of an aqueous solution of aluminum sulfate (concentration: 30%) were added to form flocs. Here, 0.8 g of fly ash is added to enhance the coagulation effect. After floc formation, the results obtained by agglomerating using a coagulant disclosed in Japanese Patent Publication No. 08-018016 of the present applicant and filtering through filter paper are shown in Table 1. The above-mentioned special fair 08
The flocculant described in -018016 is a flocculant containing lime, aluminum sulfate and sodium carbonate as main components.

[0022]

[Table 1]

The coagulation and precipitation is completed in about 30 seconds to 1 minute.
From Table 1, it can be noted that both TP (residual phosphorus) and TN (residual nitrogen) are remarkably improved and the pH is close to neutral.

(Example 2) Treatment of secondary treated water in the domestic wastewater treatment facility of Miura housing complex in Tottori city (tester: Regional Environment Planning Office, Faculty of Agriculture, Tottori University).

Treatment 1: 2 g of auxiliary agent of the present invention (lime 4, cement 4, gypsum 2) and sodium silicate 2 to raw water 11
g and 2 g of an aqueous solution of aluminum sulfate (concentration: 30%) were added to form flocs, which were filtered through filter paper.

Treatment 2: Use 0.2 g of raw water 11 with the coagulant of Japanese Patent Publication No. 08-018016 filed by the present applicant.

In the treatments 1 and 2, about 0.5 g of fly ash was added in order to enhance the coagulation effect.

[0028]

[Table 2]

The same effect was obtained when 4 g of calcium chloride was used instead of the above aluminum sulfate.

(Example 3) Dehydration of sludge with respect to the dredged sludge of the Milky Way flowing in Himeji City, Hyogo Prefecture.

First, the procedure is as follows.

An appropriate amount of the assistant of the present invention and aluminum silicate (1 g of assistant and 1 g of aluminum sulfate with respect to 11) are added to water to form flocs by the above procedure.

The floc formed as described above is added to the container containing the sludge together with water, followed by stirring.

Is filtered.

The result was that the amount of dewatering of the raw water was around 24%, while the amount of the above treatment was 70%.

Instead of the above, an appropriate amount of sodium silicate and calcium chloride is added to water (1 g of sodium silicate and 2 g of calcium chloride with respect to 11) to form flocs, and the flocs are added to the liquid to be treated. Also achieved the same effect.

(Example 4) Treatment of wastewater from the Obayashi Corporation Kyoto construction site (tester: Hyogo Analysis Center Co., Ltd.).

To the raw water 11, 2 g of the auxiliaries of the present invention (lime 4, cement 4, gypsum 2) was added, and various aluminate carbonates were further added to form flocs, and treated water filtered through filter paper. The concentration of iron contained was compared between four types (Comparative Examples 1 to 4) and four types of treated water (Examples 1 to 4) in which aluminum sulfate was added by the method of the present invention in the same treatment. The drugs used and their abbreviations, and
The processing method of each of the comparative examples and examples is as follows. Drugs and their abbreviations POK: Coagulant for Japanese Patent Publication No. 08-018016 filed by the applicant of the present application BK: Polyacrylic acid organic coagulant, MCA: Calcium sulfate CS: Coagulant for lime 5, cement 5, KC: Aluminum sulphate Comparative example 1: Raw water + POK 0.4g + BK 2.0g 2: Raw water + MCA 0.2g + POK 0.4g + BK 2.0g 3: Raw water + POK 0.2g + BK 1.0g 4: Raw water + MCA 0.2g + POK 0.4g + BK 2.0g Example 1: Raw water + CS 0.3g + KC 0.36g + BK2.0g 2: Raw water + MCA0.2g + CS0.3g + KC0.36g + BK2.
0g 3: Raw water + CS 0.15g + KC 0.18g + BK 1.0g 4: Raw water + MCA 0.1g + CS 0.15g + KC 0.18g + BK
1.0g

[0039]

[Table 3]

As shown in Table 3, when the treatment was carried out using the assistant of the present invention, the iron concentration in the wastewater decreased in any case. However, as shown in Examples 1 to 4, the iron concentration was increased when aluminum sulfate was added. It decreases significantly.

(Example 5) For wastewater containing iron,
A series of treatment methods using sodium hydroxide, polyaluminum chloride and a polymer flocculant have been conventionally known.
Using this conventional processing method and the CS and BK, the K
The change in iron content, the wastewater treatment speed, and the treatment cost per unit volume were compared between the treatment method using polyaluminum chloride instead of C.

[0042]

[Table 4]

As shown in Table 4, the method of the present invention is excellent in all of the degree of decrease in the iron content, the wastewater treatment speed, and the treatment cost. When the iron content exceeds 5 PPM, the red color of the treated water becomes remarkable.

[0044]

As described above, according to the present invention, while using only the inorganic agent, the coagulation rate is excellent and the liquid after solid-liquid separation becomes neutral, so that the pH adjustment is not required at all. Furthermore, the floc formed in the above process can be used for solid-liquid separation of bentonite-containing wastewater, surplus concentrated sludge, etc., and the treatment of difficult-to-treat liquids, which was conventionally impossible, can be performed at low cost.

Claims (6)

[Claims] 1. A coagulation method comprising adding a predetermined amount of a coagulation aid composed of lime and cement to a liquid to be treated, stirring and then adding an acidic salt solution of aluminum. 2. A method wherein a predetermined amount of a coagulation aid composed of lime and cement is added to the liquid to be treated, stirred, an aqueous solution of sodium silicate is added, and an acid salt solution of aluminum or calcium chloride is further added. Aggregation method. 3. The coagulation method according to claim 1, wherein gypsum is added to the coagulation aid as needed. 4. The coagulation method according to claim 1, wherein the distribution of the coagulation aid is 10 to 90% by weight of lime and 10 to 90% by weight of cement. 5. A process in which water is subjected to the treatment according to claim 1 to form flocs, and the flocs are added to the liquid to be treated together with the water, and after stirring, the water and solids are separated. Agglomeration method, wherein the coagulation method is used. 6. A flocculant comprising lime, cement, and an acid salt powder of aluminum.