JP2008043904A - Flocculating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flocculating method which enables the quick flocculation of every pollutant such as a very poisonous substance, for example, PCB, arsenic and the like, treats a treatment-difficult liquid, and is low in cost. <P>SOLUTION: A main flocculant which primarily comprises water glass and sea water is applied to a liquid to be treated. The main flocculant can be used alone, but the use of a preparatory flocculant at a prior stage increases the effect of the main flocculant. When water glass is added to sea water, the water glass is gelificated by the stimulus of calcium ion in the sea water. So, a gel, which is obtained by adding water glass of 30-100 g, preferably 50-80 g, to sea water of 1,000 cc, is preliminarily prepared as the main flocculant. The preparatory flocculant can be a flocculant consisting of aluminium sulfate and sodium carbonate or a flocculant consisting of water glass and calcium chloride. When organic substances are contained, the preparatory flocculant can be calcium chloride. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for aggregating suspended substances in polluted water, and more particularly to a method for aggregating PCBs.

  Extremely toxic substances such as polychlorinated biphenyl (PCB), arsenic, and chromium hexadide contained in plating wastewater are not allowed to leak to the outside, causing soil pollution and river water pollution. However, there is no cheap and effective method for recovering the highly toxic substances leaked to the outside unfortunately, and the only proven process is the high-temperature process at Kaneka Chemical's Takasago Factory. However, this method is large and expensive, and only the accumulated PCB is incinerated. It is not a method that can recover PCB that has flowed out to the surface or river. For example, many power transformers using biphenyl chloride as a coolant remain. In March 2006, there was an incident in Tottori Prefecture where a utility pole collapsed due to a landslide and was damaged, and a PCB filled inside the transformer leaked out. Thus, the incineration method described above is not a method that can be applied to cases where it is necessary to suppress further seepage and outflow of PCB that has flowed out to the ground surface or rivers.

  Taking extremely toxic substances as an example, fine suspended solids (SS) contained in large quantities in dyeing wastewater, civil engineering wastewater, sewage, or factory wastewater are suspended in water and discarded in rivers and oceans, causing pollution. Yes. Therefore, recently, the above-mentioned civil engineering waste liquid and the like are disposed of after being treated so that the suspended matters and dissolved substances in the water are below the standard concentration. However, the time and cost required for the treatment are enormous.

  For example, it is very difficult to remove dissolved pigment from wastewater from dyeing factories. At present, wastewater is temporarily stored in a water tank and decolorized by activated carbon and biotreatment, and BOD and COD are below standard values. So that it is treated and drained.

  The wastewater from the paper mill contains titanium oxide fine particles or pulp fiber fine particles which are widely used to smooth the paper surface. In order to remove these fine particles, an organic or inorganic flocculant is once stored in a water storage tank, and after agglomeration and precipitation, the water is drained.

  In sewage treatment, an organic flocculant is added to the liquid to be treated, and it is retained in a large-capacity sedimentation tank for a long time to precipitate suspended substances. If necessary, activated carbon treatment and biotreatment are added to SS, BOD, COD. After processing so that the value is equal to or less than a predetermined value, the value is discarded.

  In the treatment of civil engineering wastewater, it is a concern to reduce the concentration of iron contained in the wastewater after treatment.

  In addition, sludge discharged when dredging the seabed and rivers has a very high moisture content, and enormous amount of cement is required to solidify as it is. In view of this, sludge is introduced into a large-capacity sedimentation tank, and an organic flocculant is added to perform precipitation treatment, followed by solidification treatment.

  For this reason, a huge sedimentation tank is required, the processing apparatus becomes large, a large installation area is required, processing time is long, and the cost is high.

  Various flocculants have been developed for use in the flocculant treatment. For example, in inorganic systems, aluminum salts (aluminum sulfate, aluminum hydroxide, ammonium alum, potash alum, sodium aluminate, polyaluminum chloride), iron salts (ferrous chloride, ferric chloride, ferrous sulfate, sulfuric acid In the organic system, low molecular salts, surfactants, natural or synthetic polymer substances, etc. are being developed and used.

  Furthermore, the present applicant proposed in Patent Document 1 a flocculant comprising a soluble aluminum salt, an alkali metal salt, and a third substance for reducing the direct contact density of both agents, and achieved a great effect. ing.

Various flocculants have been developed and used as described above. However, it is difficult to perform solid-liquid separation of the above-mentioned highly toxic contaminants such as PCB and arsenic, as well as dyeing wastewater and papermaking wastewater. In addition, a sewage treatment requires a huge sedimentation tank and the treatment time is enormous. Further, when a large amount of the organic flocculant is used, the cost increases and the difficulty of the solid-liquid separation increases.
Japanese Examined Patent Publication No. 8-18016

  The present invention has been made in view of the above-described conventional circumstances, and exhibits a rapid agglomeration effect on all pollutants including highly toxic substances such as PCB and arsenic, and can process difficult-to-treat liquids. And it aims at providing a cheap aggregation method.

  In order to achieve the above object, the present invention is characterized in that a main flocculant mainly composed of water glass and seawater is added to the liquid to be treated. According to this method, it is possible to treat all kinds of polluted water, not limited to the case of containing a virulent poison such as polychlorinated biphenyl or arsenic.

  As the main flocculant, a main flocculant mainly composed of water glass and seawater is used. This main flocculant can be used alone. When water glass is added to seawater, the water glass gels under the stimulation of calcium ions in the seawater. Accordingly, a state in which 30 to 100 g of water glass, preferably 50 to 80 g, is added to gel with respect to 1000 cc of seawater and gelled is prepared in advance as a main flocculant.

  Even if only the main flocculant is added, there is an effect, but it is more effective if a preliminary flocculant described below is used in the previous stage.

  The preliminary flocculant may be a flocculant composed of aluminum sulfate and sodium carbonate (see, for example, Patent Document 1), or may be a flocculant composed of water glass and calcium chloride. This preliminary flocculant is added to the liquid to be treated prior to the addition of the main flocculant. As a result, SS and organic matter form large flocs and almost settle.

  The addition amount of the pre-flocculating agent varies depending on the amount of the flocculating agent. When the preaggregating agent is aluminum sulfate and sodium carbonate, the ratio of the aluminum sulfate and sodium carbonate is about 2 to 3 to 3: 2. When the preaggregating agent is water glass and calcium chloride, the water glass is about 1 to 5 g / l and the calcium chloride is 1 to 5 g / l.

  In addition, when an organic substance is included in the liquid to be treated, it is effective to use calcium chloride as a preliminary flocculant.

  Next, after the preliminary flocculant is added as described above, the main flocculant prepared as described above is further added. As a result, the flocs of the suspended matter formed by the preliminary flocculant become larger and settle. The amount of gelled water glass added at this time also varies depending on the amount of contaminants and cannot be determined in general.

  After forming a large floc with an inorganic flocculant as described above, it is preferable to further use an organic flocculant that has been conventionally used in order to enhance the effect of the present invention. As the organic flocculant, any of polyacrylamide-based cations, anions, and nonionic organic flocculants can be used.

  By the above, there exists an effect which can aggregate not only highly toxic substances, such as PCB in polluted water, heavy metal, or simple SS but total nitrogen, total phosphorus, etc.

  Embodiments of the present invention will be described based on examples.

  The treated liquid used here was river water and groundwater from Tottori Prefecture, where the power pole was collapsed due to earth and sand and the transformer on the pole was damaged and the PCB that had been filled leaked (March 4, 2006) , Reported in Nihonkai Shimbun).

  The concentration of water glass used in the following is 29.03% silicon dioxide, 9.40% sodium oxide, 7 to 8% aqueous solution of aluminum sulfate, 12% aqueous solution of sodium carbonate, and powder of calcium sulfate. The organic flocculant is a 1% aqueous solution of any of polyacrylamide-based cations, anions and nonions.

Test method A:
First, when water glass is mixed into seawater, the water glass gels due to the influence of alkali ions in seawater. Therefore, 80 g of water glass is mixed into 1000 cc of seawater to be gelled, and a main flocculant in which the gelled sodium silicate is precipitated in a particle state is prepared. In addition, 6 g of calcium sulfate is mixed in this seawater.

  On the other hand, when contaminated water is mixed with metal salts (eg, aluminum sulfate, iron chloride, etc.) and alkalis (eg, sodium carbonate), it is known that SS, organic matter, etc. will flocate simultaneously with the product during the neutralization reaction. ing. Therefore, 3 g of sodium carbonate and 2 g of aluminum sulfate (hereinafter referred to as a first preliminary flocculant) are put into a 1000 cc liquid to be treated to form a floc, and then 15 g of the main flocculant is mixed into the liquid. Thereafter, 4 g of a polyacrylamide organic flocculant (concentration around 1%) is added.

Test method B:
The preparation of the main flocculant is the same as Test Method A. It is the same as Test Method A that 6 g of calcium sulfate is mixed.

On the other hand, when water glass and calcium chloride are added to the polluted water, the water glass gels and at the same time, SS, organic substances, etc. contained in the liquid to be treated are floculated and settled. Therefore, first, 3 g of water glass and 3 g of calcium chloride (hereinafter referred to as a second preaggregating agent) are put into a 1000 cc liquid to be treated. Next, 4 g of the above main flocculant is charged into the liquid to be treated. Further, 4 g of the organic flocculant is added.
(I) Pre-test Test method
pH: Factory drainage test method JIS K 0102 12.1 Glass electrode method Polychlorinated biphenyl (PCB): Conforms to Annex 3 of Circular 59 dated December 28, 1971 Sample (before test) PCB concentration 430mg / l
3. Test results (Examination in charge: Tottori Prefecture)

※１ 試験品容器にラベルされていた文字を示す。
※２ ND：定量下限値である0.0005mg/L未満であることを示す。

* 1 Indicates the characters that are labeled on the test product container.
* 2 ND: Indicates that it is less than the lower limit of quantification of 0.0005 mg / L.

  4). Lower limit of quantification

As a result of the preliminary test, both the test methods A and B for the agglutination test showed good results for the lower limit of quantification (0.0005 mg / l) for PCB, but test method B showed better SS improvement. Therefore, the following test method B is used.
(II) This test About the test result of river water and groundwater (3 cases in total) (Hereinafter, test method B is used for the coagulation test)
1. Test method Method defined in 2005 public water area and groundwater quality measurement plan Sample (before test), sample at the same point for numbers 1 and 2 in the following (Table 3), PCB concentration before treatment 430 mg / l
3. Test results (Examination in charge: Tottori Prefecture)

※１ ND：報告下限値である0.0005mg/L未満であることを示す。

* 1 ND: Indicates that it is less than the reporting lower limit of 0.0005 mg / L.

  4). Standard value, etc.

※２ 水質汚濁に係る環境基準について（昭和46年12月28日付環告59号）による環境基準。

* 2 Environmental standards based on environmental standards for water pollution (announcement No. 59 dated December 28, 1971).

(III) PCB removal from earth and sand As a result of the above-described test, it was confirmed that the present invention is effective even for PCBs having a high concentration as described above. That is, no PCB is detected after the processing. Based on this, PCB removal was carried out at the points indicating the pre-removal concentrations of (1) to (10) below in the PCB-contaminated area of the Katsube River. In the implementation method, first, earth and sand containing a large amount of moisture at a target point was accumulated in one place, and the following plant was constructed and processed.

  That is, as shown in FIG. 1, the muddy water containing the sediment to be treated accumulated in the reservoir 100 is pumped up through a pipe 30 having a predetermined diameter, and the preliminary coagulant water glass, calcium chloride, and the main coagulant seawater. The organic flocculant is sequentially added. In the pipe 30, the negative pressure of the flow of earth and sand is used, and each of the aggregating agents and the like is naturally drawn through the bubbles 34a to 34d using the negative pressure. Of course, each valve 10a-10d can adjust the addition amount of each chemical | medical agent by adjusting the degree of opening and closing. Moreover, since the earth and sand flowing through the pipe 30 are forced to become turbulent by the weir structures 20a to 20d, they are well mixed with the preliminary coagulant or the main coagulant. The weir structures 20a to 20d are not the essence of the present invention and will not be described in detail.

  As described above, the earth and sand mixed with the flocculant is transferred to the sedimentation tank 40, but again here, it is separated from solids and moisture in an early time (for example, within 10 minutes), and the supernatant liquid is as shown in the following table. In this state, the PCB cannot be detected. In addition, in FIG. 1, the drained water (without storing for a long time) drained in the three sedimentation tanks 41a-41c is drained.

  The results in the above plant are as follows. That is, no PCB was detected in the waste water (0.0005 mg / l or less), and ss was 4 mg or less.

1 Test method Verification method for drainage standards established by the Minister of the Environment based on the provisions of the ministerial ordinance that establishes drainage standards (announcement No. 64, September 30, 1974)
2 Test results (Examination: Tottori Prefecture)
Test collection date March 10, 2006

※１ 報告下限値である0.0005mg/L未満であることを示す。

* 1 Indicates that it is less than the reporting lower limit of 0.0005 mg / L.

  3 Report lower limit

  Moreover, about the earth and sand which added the processing agent as mentioned above and precipitated PCB, when PCB was measured after spin-drying | dehydrating, it became as follows (Table 7). That is, the PCB content of the earth and sand after the removal was an acceptable standard value of 10 mg or less, and PCB elution was not observed.

(IV) Removal of substances other than PCB In addition to the above, an experiment was conducted in which the main flocculant was added to the sludge (Table 8) of the pond of Kashima Shrine in Amida-cho, Takasago City. It can be understood that the present invention shows a great effect not only for the PCB of the above embodiment but also for removal of heavy metals such as nitrogen, phosphorus and iron.

  Add 3g of calcium chloride and 5g of sodium hypochlorite to 1L of the liquid to be treated. By adding calcium chloride, organic substances such as starch, light white and fat coagulate and precipitate. Moreover, sterilization and bleaching can be performed by adding sodium hypochlorite. 5 g of the main flocculant is added to the liquid to be treated in this state, and then 5 g of the organic flocculant is added. As a result, the results shown in (Table 9) were obtained. Comparing these two tables, it can be seen that there is a marked improvement in total nitrogen, total phosphorus, and iron.

  As described above, the present invention is extremely effective for removing highly toxic substances such as PCB and arsenic and removing heavy metals such as nitrogen, phosphorus and iron.

The figure which shows the structure of the apparatus used for this invention

Explanation of symbols

10a, 10b, 10c, 10d Valve 20a, 20b, 20c, 20d Weir structure 30 Pipe 34a, 34b, 34c, 34d Bubble 40 Settling tank 100 Reservoir

Claims (5)

  A coagulation method comprising adding a main coagulant mainly composed of water glass and seawater to a liquid to be treated.   The aggregating method according to claim 1, wherein a preliminary aggregating agent is added before the addition of the main aggregating agent.   The agglomeration method according to claim 2, wherein the preliminary aggregating agent comprises aluminum sulfate and sodium carbonate.   The aggregating method according to claim 2, wherein the preliminary aggregating agent comprises water glass and calcium chloride. The aggregation method according to claim 1, wherein the liquid to be treated is polluted water containing polychlorinated biphenyl.

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