JP2008142683A - Water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved technique for enhancing water treatment efficiency in a present treatment apparatus by neither installing a new treatment apparatus nor converting to a treatment system in the present water treatment. <P>SOLUTION: Alginic acid or alginate adding treatment is applied to a water treatment process to biologically treat a hardly treatable turbidity substance by naturally generating and growing microorganisms or biological membranes formed thereby in a subsequently treatment route. By this constitution, the reducing efficiency of the turbid substance in water can be enhanced using an existing water treatment system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water treatment method for reducing pollutants in water by microorganisms that naturally occur and grow in a water treatment process.

  Usually, organic pollutants in water are coagulated and settled and then treated by biological treatment methods such as activated sludge. However, water, especially wastewater, often contains difficult-to-process organic substances that are difficult to be decomposed by microorganisms, but these cannot be removed by general biological treatment such as the activated sludge method. Moreover, when the salt concentration of waste water is high or a heavy metal is contained in water, since the action of microorganisms is suppressed or inhibited, it is known that general biological treatments such as the activated sludge method do not function well. For this reason, it is normal for factories that discharge them to have no biological treatment, and in order to further treat these wastewaters, advanced treatment such as activated carbon adsorption, oxidative decomposition, and membrane separation is required. It becomes. However, the cost of any advanced processing is a problem. For this reason, it is said that there are not a few cases where it is diluted and discharged.

  The waste water containing difficult-to-process organic substances includes, for example, a resist waste liquid discharged from a printed circuit board factory, and the resist waste liquid includes a development waste liquid and a stripping waste liquid. All of these waste liquids are alkaline and contain a large amount of COD components mainly composed of a resist which is an alkali-soluble resin. As a method for treating the resist waste liquid, there is a method in which sulfuric acid, hydrochloric acid, or the like is added to the waste liquid to make it acidic, and the COD component containing the resist, which is a resin, as a main component is insolubilized and removed. However, the treatment liquid contains an organic component that cannot be removed by this method. However, this organic component has a low biodegradability, a high salt concentration, and a heavy metal. For this reason, it cannot be removed by biological treatment at a later stage, for example, by mixing with general waste water. Since biological treatment cannot be performed in this way, a method of reusing and recycling reused development waste liquid or stripping waste liquid containing a water-soluble photoresist to be discharged separately is disclosed (Patent Document 1). . Also in this document, because it is difficult to decompose biologically, it requires dilution water that is several tens of times the amount of waste liquid, a large tank is required for biological treatment, etc., and The processing cost is enormous.

  Examples of such cases are found in many places such as a plating factory and a machine metal factory, in addition to a printed circuit board factory. Even in these factories, wastewater standards such as COD, nitrogen, phosphorus, and heavy metals are complied with for the time being, but the current situation is that they operate in a state of margin. For this reason, the actual situation is that it is not possible to cope with the increase in the amount added to the wastewater treatment system, such as an increase in production volume and the manufacture of new products. Installation of a new processing device and conversion to an efficient processing system is not impossible because it is economically impossible and the processing system cannot be stopped during construction. For this reason, innovative processing technology is important, but there is a strong demand for improved technology, such as how to increase efficiency with current processing equipment.

  In addition, even when a biological treatment device is provided in the latter stage as in a pulp factory, coloring components caused by the non-biodegradable lignin contained in the bleaching effluent are difficult to remove by biological treatment. It is required to remove as much as possible. The improvement in treatment efficiency in the first stage is not limited to pulp factories, but can be applied to chemical factories that contain non-biodegradable and harmful chemical substances in general.

Refractory organic pollutants include not only those contained in factory effluents, but also humic substances, which are natural difficult-to-treat pollutants that are problematic in water purification treatment. Even if it is not possible, if the processing efficiency can be increased even slightly from the current level, the load of chlorination after that can be reduced.
Japanese Examined Patent Publication No. 6-15078

  An object of the present invention is to provide a technique for increasing the reduction efficiency of pollutants in water using an existing water treatment system by microorganisms that naturally occur and grow in the water treatment process.

  The inventors of the present invention have intensively studied to solve the above problems, and as a result, have found the following matters and have completed the present invention.

  By subjecting the water treatment to the addition of alginic acid or alginate, pollutants in the water are reduced by the naturally occurring and growing microorganisms in the subsequent treatment route. That is, by performing an operation of adding alginic acid or alginate, contaminant components in water such as COD can be further removed by a biofilm (microorganism membrane) that naturally occurs and grows in the water treatment channel.

  Conventionally, it has been considered that biological treatment cannot be performed with wastewater containing components that suppress biological treatment or inhibit the action of microorganisms, and it has not been known to allow generation of microorganisms at a later stage. By applying the alginic acid treatment according to the present invention, microorganisms can be generated at a later stage, and polluted components in the wastewater can be removed.

  Thus, the removal efficiency of the pollutant component contained in water can be improved without changing the water treatment system, and the present invention has been completed.

  That is, according to the present invention, the following techniques are provided.

(1) A water treatment method characterized in that alginic acid or alginate is added to the water to be treated to reduce pollutants in the water by naturally occurring and growing microorganisms in the subsequent treatment route.

(2) The water treatment method according to (1), wherein in the water treatment, after addition of alginic acid or alginate, the alginic acid is insolubilized and contaminants contained in the water are precipitated and separated.

(3) The water according to (1) or (2), wherein in the water treatment, the pH of the water is adjusted to 1 to 3 to insolubilize alginic acid, and the pollutant components contained in the water are precipitated and separated. Processing method.

(4) Any of the above (1) to (3), wherein in the water treatment, polyhydric metal ions are present in the water to insolubilize alginic acid and precipitate and separate pollutants contained in the water. Water treatment method.

(5) The water treatment method according to any one of (1) to (4), wherein the polyvalent metal ion is one of iron ions, aluminum ions, calcium ions, or a plurality thereof.

(6) Any one of (1) to (5) above, wherein the pollutant component reduced in (1) is any one of COD component, nitrogen, phosphorus, heavy metal, or a plurality thereof. Water treatment method

(7) In the water treatment, the part that functions to reduce pollutants in water by microorganisms that naturally occur and grow after the insolubilization treatment of alginic acid is the part that precipitates and separates pollutant components in the water treatment system. The water treatment method according to any one of (1) to (6) above.

  By adding alginic acid or alginate, microorganisms naturally occur and grow later, and COD components, nitrogen, phosphorus, heavy metals, etc. that could not be reduced can be reduced. That is, it is possible to increase the removal efficiency of polluted components contained in water, which has been impossible until now, without newly providing a biological treatment tank or changing the current water treatment system.

  Hereinafter, the present invention will be described in detail.

  What is to be treated in the present invention is difficult-to-treat pollutants such as COD components in water, nitrogen, phosphorus, and heavy metals that cannot be removed only by coagulation sedimentation treatment or neutralization treatment.

  In the present invention, first, alginic acid or alginic acid salt is added to waste water containing difficult-to-process organic substances.

  The alginic acid or alginic acid salt is not particularly limited as long as it promotes the generation of a biofilm at a later stage.

  The alginate is not particularly limited, but sodium alginate is preferably used in view of operability and availability.

  In the present invention, it is not particularly limited which step in the water treatment step to which alginic acid or alginate is added.

  Alginic acid or alginate may be added after coagulation sedimentation treatment or neutralization treatment, after which alginic acid treatment may be carried out, or alginate treatment may be carried out directly without coagulation precipitation treatment or neutralization treatment. An optimum method may be adopted as appropriate in consideration of the density and processability.

  The addition of alginic acid or alginate can also be performed in the solid-liquid separation step, but it can be expected to remove aggregates produced by alginic acid in the solid-liquid separation tank before the solid-liquid separation tank, In addition, the production of biofilm can be expected in the solid-liquid separation tank, which is preferable.

  In the present invention, by continuing the addition treatment of alginic acid or alginate for a certain period of time, in the subsequent treatment route, microorganisms naturally occur and grow to form a biofilm, and biological treatment for difficult-to-treat pollutants proceeds. , Resulting in improved processing efficiency.

  In the present invention, the effect can be expected only by adding a treatment with alginic acid or alginate. Or, it takes in, and further improvement in processing efficiency is expected.

  As a method for insolubilizing alginic acid, wastewater containing difficult-to-treat contaminants may be acidified or a polyvalent metal ion may be added.

  As a method for insolubilizing alginic acid, when making wastewater containing difficult-to-treat pollutant components acidic, the pH of the wastewater is adjusted to 1 to 5, preferably 1 to 4, and more preferably pH is adjusted to 1 to 3. preferable.

  In order to adjust to pH 1-3, an acid or an alkali is added. These concentrations are not limited as long as the pH of the wastewater can be adjusted to the above range, and can be adjusted as appropriate.

  As the acid, hydrochloric acid, sulfuric acid, nitric acid and the like are used. As the alkali, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, magnesium hydroxide or the like is used.

  In the present invention, the pH of the waste water may be adjusted to 1 to 3 or less, and an aqueous solution of sodium alginate may be added and stirred or mixed, or an aqueous solution of sodium alginate may be added and stirred and mixed, The pH may be adjusted to 1 to 3, and is not particularly limited.

  Sodium alginate is insolubilized at pH 1 to 3, and at that time, by taking in COD components in water, an efficient removal action is achieved.

  The sodium alginate to be added may be in any state as long as the object of the present invention can be achieved, but it is preferably added to the water to be treated as an aqueous solution. The concentration is not particularly limited, but considering operability, it is 0.02 to 10% by mass, more preferably 0.1 to 5% by mass.

  In the present invention, the amount of sodium alginate added depends on the concentration of organic matter in the liquid to be treated, but is preferably 0.1 to 200 mg / L, more preferably 1 to 100 mg / L, per 100 mg / L of dissolved TOC. More preferably, it is 10-50 mg / L.

  As another method for insolubilizing alginic acid, a polyvalent metal ion may be present together with alginic acid.

  In the present invention, as a method for causing polyvalent metal ions to be present together with alginic acid, the polyvalent metal salt may be added after the addition of alginic acid, or the alginic acid may be added after the addition of the polyvalent metal salt. Further, when there is sufficient polyvalent metal ion to insolubilize alginic acid in the waste water, it is not necessary to add it.

  Multivalent metal salts include iron salts, aluminum salts, calcium salts and the like.

  Iron salts include iron compounds such as ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, polyferric chloride, and polyferric sulfate.

  Aluminum salts include aluminum compounds such as aluminum sulfate, aluminum chloride, polyaluminum chloride and sodium aluminate.

  Calcium salts include calcium compounds such as calcium chloride and calcium hydroxide.

  In the present invention, the amount of polyvalent metal salt added depends on the concentration of the organic substance in the liquid to be treated, but is preferably 0.1 to 500 mg / L, more preferably 0.2 to 100 mg / L per dissolved TOC. 200 mg / L, more preferably 1 to 100 mg / L.

  Next, an alkali is added to the liquid to be treated, and when the polyvalent metal salt is an iron salt, the pH is adjusted to 7 to 12, preferably 8 to 11, and in the case of an aluminum salt, The pH is adjusted to a range of 5 to 10, preferably 6 to 8. In the case of calcium salt, the pH is adjusted to a range of 7 to 12, preferably 8 to 11, so that the metal in the solution is insolubilized and precipitated. Is generated. Thereafter, a flocculant is added as necessary.

  As the alkali, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, magnesium hydroxide or the like is used as an aqueous solution or suspension.

  In the present invention, a flocculant may be used in combination. The flocculant in this case is used for floc aggregation, such as calcium chloride, bis (dihydrogen phosphate) calcium, ferrous chloride, ferric chloride, sulfuric acid In addition to inorganic flocculants such as ferrous sulfate, ferric sulfate, ferrous polysulfate, polyferric sulfate, aluminum sulfate, polyaluminum chloride, etc., cationized modified polyacrylamide, polydimethylaminoethyl ester of polyacrylic acid , Cationic organic flocculants such as polymethacrylic acid dimethylaminoethyl ester, polyethyleneimine and chitosan, nonionic organic flocculants such as polyacrylamide, polyacrylic acid, copolymers of acrylamide and acrylic acid and / or salts thereof Anionic organic flocculants such as are included. For example, in the case of a polymer flocculant, the amount added to the water to be treated is preferably 0.1 to 50 ppm, more preferably 0.2 to 20 ppm, and still more preferably 1 to 10 ppm.

  In the present invention, by performing the addition treatment of alginic acid or alginate, microorganisms are naturally generated and grown in the subsequent treatment tank, and a biofilm is formed to enable biological treatment.

  In the present invention, although environmental conditions are not particularly limited for naturally occurring and grown microorganisms to form a biofilm, it usually takes 1 to 2 weeks. It is possible to speed up biofilm formation by adjusting the water temperature, nutrient salts, etc. as necessary.

  In the present invention, although microorganisms capable of removing difficult-to-treat pollutant components are not specified, it is considered that a complex microorganism group that requires the presence of alginic acid is involved.

  In the present invention, the mechanism capable of removing difficult-to-treat pollutant components is unknown, but it is considered that degradation by microorganisms and adsorption to a biofilm are involved in a complex manner.

  Next, the present invention will be described in more detail with reference to examples.

  The electroless nickel plating rinse water of factory A contains difficult-to-process organic substances, and its treatment is very difficult, and the treatment water concentration can be reduced to a TOC of about 50 to 100 mg / L and a phosphorus concentration of about 23 mg / L or less. There wasn't. A 0.25% aqueous solution of sodium alginate was added and stirred so that the concentration of alginic acid in the waste water was 2 mg / L, and the pH was adjusted to about 3 by adding sulfuric acid. , Concentration 37.5%) was added at 0.5 mL / L. Next, when calcium hydroxide suspension was added to adjust the pH to about 10, a precipitate containing heavy metal ions was produced. A biofilm (microorganism film) was naturally generated and grew in the treated water flow path above the settling tank. When the TOC and phosphorus concentration of the treated water were measured, the TOC was about 30 mg / L and the phosphorus concentration was about 3 mg / L.

  The general waste water containing the difficult-to-process organic resist of the factory B was very difficult to process and could not be reduced to a TOC of about 33 mg / L or less. This general waste water was treated by adding sodium alginate. The processing steps are as follows.

  Add a 0.25% aqueous solution of sodium alginate so that the concentration of alginic acid in the waste water is 1 mg / L, adjust the pH with sulfuric acid (pH 3), and ferric chloride solution (industrial, concentration 37.5%) Was added at 0.1 mL / L, and then the pH was adjusted with an aqueous sodium hydroxide solution (pH 10). A precipitate containing heavy metal ions was produced. Solid-liquid separation is performed in a sedimentation tank (thickener), and the separated water becomes treated water.

  About 3 days after the addition of alginic acid, the TOC of treated water begins to decrease, and about 2 weeks later, an algal biofilm (microorganism membrane) naturally develops and grows in the treated water flow path at the top of the sedimentation tank (thickener). (The TOC of the treated water was about 17 mg / L). After about 4 weeks, the treated water TOC further decreased to about 9 mg / L.

  When this algal biofilm (microbial film) was removed, the TOC increased.

  That is, the addition of sodium alginate decreased the TOC, and the algae-like biofilm (microorganism membrane) generated by the addition of sodium alginate further reduced the TOC.

  A mixed liquid in which acid waste liquid and alkaline waste liquid of C paper mill were mixed at a ratio of 5: 1 was prepared (pH 7, TOC 545 mg / L), and a treatment experiment was performed. 1 g (hydrated state) of the biofilm collected in Example 1 was added to 100 mL of the liquid to be treated and stirred at room temperature under aerobic conditions. When the TOC concentration of the solution was measured after 6 days, it was reduced to 437 mg / L.

  Drainage from the copper plating plant is very difficult to process. pH 7.5, TOC 94 mg / L. To this wastewater, a 0.25% aqueous solution of sodium alginate was added and stirred so that the concentration of alginic acid in the wastewater was 1 mg / L, and sulfuric acid was added to adjust the pH to about 3. Next, a calcium hydroxide suspension (concentration 5%) was added to adjust the pH to 9. 1 mL / L of a 0.1% aqueous solution of anionic polymer flocculant AP120C (manufactured by Daianitrix) was added to form a precipitate. A biofilm (microorganism film) was naturally generated and grew in the treated water flow path above the settling tank. The TOC of treated water was measured and found to be 38 mg / L.

Effluent from the E printed circuit board factory is very difficult to process. TOC is 83 mg / L. To this wastewater, a 0.25% aqueous solution of sodium alginate was added and stirred so that the concentration of alginic acid in the wastewater was 1.5 mg / L, and sulfuric acid was added to adjust the pH to about 3. Next, 10 mg / L of aluminum sulfate aqueous solution (concentration 8% as Al ₂ O ₃ ) was added as Al, and then the pH was adjusted to 7 with aqueous sodium hydroxide solution. 1 mL / L of a 0.1% aqueous solution of anionic polymer flocculant AP120C (manufactured by Daianitrix) was added to form a precipitate. A biofilm (microorganism film) was naturally generated and grew in the treated water flow path above the settling tank. The TOC of treated water was measured and found to be 29 mg / L.

Claims (7)

  A water treatment method comprising adding alginic acid or alginate to water to be treated, and reducing pollutants in water by a naturally occurring / growing microorganism in a subsequent treatment route.   The water treatment method according to claim 1, wherein the alginic acid or the alginate is added to insolubilize the alginic acid and the pollutant contained in the water is precipitated and separated.   The water treatment method according to claim 1 or 2, wherein the pH of the water to be treated is adjusted to 1 to 3, insoluble alginic acid, and alginic acid and contaminants contained in water are precipitated and separated.   The water according to any one of claims 1 to 3, wherein polyvalent metal ions are present in the water to be treated to insolubilize alginic acid and precipitate and separate alginic acid and contaminants contained in water. Processing method.   The water treatment method according to claim 4, wherein the polyvalent metal ion is one of iron ions, aluminum ions, calcium ions, or a plurality thereof.   The water treatment method according to any one of claims 1 to 5, wherein the pollutant component is a COD component, nitrogen, phosphorus, heavy metal, or a plurality thereof.   The place which fulfills the function of reducing pollutants in water by the microorganisms that naturally occur and grow after insolubilization treatment of alginic acid is a place that precipitates and separates pollutant components in the water treatment system. The water treatment method according to claim 6.