JP6826926B2 - Wastewater treatment method - Google Patents

Description

The present invention relates to a wastewater treatment method for separating and recovering pollutants and the like from factory wastewater and the like containing pollutants or pollutants (hereinafter referred to as pollutants and the like) and removing them.

Conventionally, as shown in FIG. 14, the wastewater treatment system 1 includes a raw water tank 2 for storing wastewater D1. The wastewater D1 of the raw water tank 2 is transferred to the granulation tank 3, a flocculant is charged from the chemical feeder 4, and the mixture is stirred and mixed. The mixed solution D2 of the granulation tank 3 is transferred to the agglutinating tank 5, and the agglomerate D3 is precipitated in the mixed solution D2. The supernatant liquid C1 of the coagulation tank 5 is received by the discharge tank 6 and discharged, while the coagulation D3 is extracted by the pump P and dehydrated by a squeezing machine 7 such as a filter press or a belt press to reduce the volume. The dehydrated sludge D4 is stored in the mud storage tank 9 and disposed of, while the filtered water C2 by the squeezing machine 7 is stored in the filtered water tank 8 and reused or discharged after confirming its properties. The flocculant coagulates and precipitates pollutants in wastewater. As this flocculant, a sulfuric acid band, ferrous sulfate, polyaluminum chloride, clay mineral, polymer compound and the like are used. When the pollutant in the wastewater is a heavy metal or the like, a method of adding a pollutant adsorbent together with a flocculant has also been proposed (see Patent Documents 1 and 2).
Further, as shown in FIG. 15, when the agglomerate D3 floats and separates on the liquid surface of the mixed liquid D2 due to the specific gravity in the coagulation tank 5, it floats due to the bubbles released from the air diffuser tube 5a connected to the blower 5c. Separated, scraped with a skimmer 5b, and dehydrated sludge D4 with a squeezer 7.

Japanese Unexamined Patent Publication No. 09-001131 Japanese Unexamined Patent Publication No. 2013-083616

In the above-mentioned conventional method, there are cases where sufficient installation space for the squeezer cannot be secured for dewatering agglomerates associated with wastewater treatment in small-scale civil engineering work, groundwater pollution countermeasure work, radioactive decontamination work, etc. Also, because of the high cost, it is not a method that is commensurate with the scale of construction. As an alternative to this dehydration, self-weight squeezing, air-drying, sun-drying, etc., in which agglomerates are packed in a flexible container bag for filtration and hung, are performed, but it takes days to dry and is generated by wastewater treatment at the site. A simple dewatering method for coagulated sludge is desired.
Therefore, the present invention provides a wastewater treatment method for easily separating and recovering residual water contained in coagulated sludge generated in wastewater treatment without requiring special equipment.

In order to solve the above problems, the present invention comprises a coagulation step of mixing a wastewater treatment agent with wastewater D1 containing a pollutant or the like and aggregating the pollutant or the like with the wastewater treatment agent, and a coagulation D3 from the mixed solution D2. A wastewater treatment method including a solid-liquid separation step of separation and a dehydration step of reducing the residual water content of the separated agglomerates D3 to generate dehydrated sludge D4 is adopted. The wastewater treatment agent contains a temperature-responsive polymer material, and the mixed solution D2 mixed with the waste water is placed on the high temperature side of the temperature-responsive polymer material at the lower limit critical solution temperature or at a low temperature of the upper limit critical solution temperature. By adjusting the temperature to the side, the hydrophobicity of the temperature-responsive polymer is strengthened, and the agglomeration of pollutants or pollutants is promoted by the wastewater treatment agent.

In the present invention, the hydrophobicity of the temperature-responsive polymer can be strengthened by simple temperature adjustment, pollutants and the like can be aggregated in the wastewater treatment agent containing the temperature-responsive polymer, and the dehydration and volume reduction of the aggregated sludge can be promoted. It has the effect that pollutants and the like can be easily removed from wastewater in a short time without requiring a large-scale dehydration facility.

It is a schematic block diagram of the wastewater treatment system which concerns on 1st Embodiment of this invention. It is a schematic block diagram of the equipment which performs the agglutination process of the wastewater treatment system which concerns on 1st Embodiment. It is a schematic block diagram of the equipment which performs the dehydration process of the wastewater treatment system which concerns on 1st Embodiment. It is explanatory drawing of the chemical structure of the wastewater treatment agent used in the coagulation step and the dehydration step of the wastewater treatment system which concerns on this invention. It is a time chart which shows the heating state of a dehydration process. It is a graph which shows the time change of the sedimentation volume of agglomerates in a tabletop test. It is a graph which shows the time change of the sedimentation volume of agglutinating sludge when a periodic temperature change is applied in a dehydration step. It is a schematic block diagram of the wastewater treatment system which concerns on 2nd Embodiment. It is explanatory drawing of other wastewater treatment agents. It is explanatory drawing of the other wastewater treatment agent. It is a schematic block diagram of the wastewater treatment system which concerns on 3rd Embodiment. It is a schematic block diagram of the equipment which performs the solid-liquid separation process of the wastewater treatment system which concerns on 3rd Embodiment. It is a schematic block diagram of the equipment which performs the dehydration process of the wastewater treatment system which concerns on 4th Embodiment. It is a schematic block diagram of the conventional wastewater treatment system. It is a schematic block diagram of another conventional wastewater treatment system.

Embodiments of the present invention will be described with reference to the drawings. In the following, the same components as those in the conventional case will be designated by the same reference numerals, and the description thereof will be omitted.
In FIG. 1, the wastewater treatment system 10 according to the first embodiment includes an aggregation promoting means 11 and a dehydration promoting means 12.
As shown in FIG. 2, the aggregation promoting means 11 includes a heat exchanger 13 mounted on the outer periphery of the granulation tank 3. The heat exchanger 13 is connected to the heat source 14. In the granulation tank 3, the wastewater D1 is transferred from the raw water tank 2, the wastewater treatment agent is charged from the chemical supply machine 4, and the mixed liquid D2 is sent to the coagulation tank 5. The wastewater treatment agent contains a temperature-responsive polymer material, and when it is heated to raise the temperature or dissipate heat to lower the temperature, it strengthens hydrophobicity and self-shrinks to separate pollutants and the like as agglomerates. , The details will be described later. The heat exchanger 13 is a means for heating or dissipating heat from the mixed solution D2 according to the type of the temperature-responsive polymer material. If the heat exchanger 13 is a heating means, in addition to an electric heater such as a silicon rubber heater, hot water from a solar water heater, exhaust heat from a boiler in a nearby factory, or the like can be used as the heat source 14. Further, if the heat exchanger 13 is the heat radiating means, a cooling device that circulates cold water can be applied.

As shown in FIGS. 1 and 3, the dehydration promoting means 12 includes a heat exchanger 16 mounted on the outer periphery of a transfer path 15 on the way of transferring the agglomerate D3 from the agglutinating tank 5 to the squeezing machine 7. The heat exchanger 16 is connected to the heat source 17. The heat exchanger 16 is a means for heating or dissipating heat from the agglomerates D3 according to the type of the temperature-responsive polymer material, in the same manner as the heat exchanger 13 described above.

Due to a specific molecular structure, the temperature-responsive polymer material applied to wastewater treatment agents becomes hydrophobic in water at a high temperature side with a predetermined lower critical solution temperature (hereinafter referred to as LCST) as a boundary. It has the property of becoming stronger and hydrophilicity on the low temperature side, and the hydrophobicity becomes stronger on the low temperature side and the hydrophilicity becomes stronger on the high temperature side at the upper critical solution temperature (hereinafter referred to as UCST). Some of them have characteristics, and they reversibly show the behavior of phase transition in which the solubility in water differs depending on the temperature. Specific examples of the temperature-responsive polymer material include poly N-isopropylacrylamide (PNIPAM). PNIPAM is a high-molecular compound at LCST of 32 ° C. On the high temperature side, the isopropyl group, which is the hydrophobic part of the side chain, strengthens the hydrophobic bonds in and between the molecules, causing a dehydration reaction, and is insoluble in separation from water. Since the amide bond of the hydrophilic part of the side chain and the water molecule are bonded on the low temperature side, a hydration reaction in which the water molecule strongly adheres around the side chain occurs, and the side chain exhibits water solubility. Utilizing this temperature responsiveness for the treatment of wastewater D1, PNIPAM takes in pollutants and the like which are hydrophobic substances of wastewater D1 on the high temperature side, dehydrates and shrinks, and aggregates. LCST can be freely changed depending on the copolymerization composition of the polymer compound, and the phase transition can be controlled in a narrow temperature range before and after. Since PNIPAM strongly depends on the molecular structure of the polymer chain, the hydrophobic monomer and NIPAM, which is a monomer of PNIPAM, are copolymerized to form a hydrophobic copolymer, which makes it possible to lower the temperature and to make it hydrophilic. By copolymerizing the monomer and NIPAM to form a hydrophilic copolymer, each of them can be shifted to the high temperature side.

When precipitating pollutants, the wastewater treatment agent may be only a temperature-responsive polymer material, but on the surface thereof, an inorganic material containing silica or alumina as a main component such as zeolite or layered clay mineral is used as a base material. It may be produced by chemically coating a temperature-responsive polymer material. In particular, if a material that adsorbs harmful substances (hazardous heavy metals such as radioactive cesium, arsenic, and lead), organic compounds that cause coloring of wastewater, oils, etc. is used as the base material of the wastewater treatment agent, it is more effective for wastewater treatment. Is the target.

When the waste water treatment agent is produced by coating an inorganic base material with PNIPAM, for example, mesoporous silica is used as the base material and allyltriethoxysilane (silane coupling agent) is used as the coating base material, as shown in FIG. When used, the ethoxy group (-OC2H5) at the end of the silane coupling agent is easily hydrolyzed to a hydroxyl group (-OH), and this hydroxyl group and the hydroxyl group on the surface of the substrate are dehydrated and condensed. The functional groups of the silane coupling agent can be covalently bonded on the solid surface. That is, by adding a coated base material to the surface of the base material and using it as a scaffold, a temperature-responsive polymer chain is extended and developed on the scaffold. Here, since the mesoporous silica has a large number of micropores on the surface capable of adsorbing pollutants and the like, the wastewater treatment agent can function not only as a coagulant but also as an adsorbent.
As shown in FIG. 9, the magnetic wastewater treatment agent is made of a magnetic material such as magnetite or a mineral material (zeolite, layered clay mineral, etc. with a magnetic material such as magnetite added) as a base material, and the surface thereof is first coated. It is manufactured by chemically coating a temperature-responsive polymer material in the same manner as above.
Further, as shown in FIG. 10, a wastewater treatment agent in which a mineral material such as zeolite is used as a base material, a magnetic material such as magnetite is added, and a silane coupling agent is used to coat the surface with PNIPAM to impart magnetism. Can be manufactured. In particular, since there are many fine pores capable of adsorbing pollutants and the like on the surface of zeolite, the wastewater treatment agent functions not only as a coagulant but also as an adsorbent.

In the wastewater treatment system 10, in the granulation tank 3, the mixed liquid D2 in which the wastewater D1 is mixed with the wastewater treatment agent is heated or dissipated by the heat exchanger 13 of the aggregation promoting means 11. When the mixed solution D2 is heated above LCST or dissipated below UCST, the intramolecular and intermolecular hydrophobic bonds of the temperature-responsive polymer material of the wastewater treatment agent are strengthened, and the wastewater treatment agent adsorbing pollutants and the like Aggregation is promoted to produce highly agglomerated D3, which is insoluble and separated from water. The agglomerate D3 is pumped out in the coagulation tank 5 and transferred to the squeezer 7. The agglomerates D3 are heated or dissipated by the heat exchanger 16 of the dehydration promoting means 12 in the transfer path 15 on the way from the agglutinating tank 5 to the squeezing machine 7. At this time, as shown in FIG. 5, the residual water of the agglomerate D3 is effectively dehydrated by periodically heating or dissipating heat of the agglomerate D3 and alternately repeating high temperature and low temperature with LCST or UCST as a boundary. Can be done

In order to clarify the agglutination effect of the wastewater treatment agent used in the agglutination promoting means 11, the graph of FIG. 6 shows the result of a comparative test on the time change of the sedimentation volume of the agglomerate D3 depending on the presence or absence of a temperature change. From this graph, it can be seen that by using the wastewater treatment agent according to the present invention, the sedimentation volume of the agglomerate D3 is reduced by the temperature change, and the degree of cohesion is increased.

Regarding the dehydration promoting means 12, 25 mL of turbid water containing 40,000 mg / L of Manko soil having a particle size of 75 μm or less was prepared as a test piece, and the dehydration property was compared from the change in the sedimentation volume of the sludge aggregated under the following conditions. The test was performed.
Specimen 1: Add PNIPAM at a ratio of 600 mg / L (600 ppm) to turbid water.
Stand for 10 minutes in an environment of 50 ° C (LCST or higher) → Stand for 10 minutes at 20 ° C (LCST or lower) →
Stand for 10 minutes in an environment of 50 ° C (LCST or higher) → Stand for 10 minutes at 20 ° C (LCST or lower).
Specimen 2: Add PNIPAM at a ratio of 100 mg / L (100 ppm) to turbid water.
Stand for 10 minutes in an environment of 50 ° C (LCST or higher) → Stand for 10 minutes at 20 ° C (LCST or lower) →
Stand for 10 minutes in an environment of 50 ° C (LCST or higher) → Stand for 10 minutes at 20 ° C (LCST or lower).
The test results are shown in FIG.
1) The change in sedimentation volume of Specimen 1 changes from 3.1 mL (10 minutes later) → 2.4 mL (20 minutes later) → 2.2 mL (30 minutes later) → 2.1 mL (40 minutes later), and is due to coagulation sedimentation alone. Comparing the sedimentation volume of 3.1 mL after 10 minutes with the sedimentation volume of 2.1 mL after 40 minutes at the completion of the second cycle of the temperature change cycle, the volume was reduced to 67.7% of the former.
2) The change in sedimentation volume of Specimen 2 changes from 3.1 mL (10 minutes later) → 2.6 mL (20 minutes later) → 2.4 mL (30 minutes later) → 2.3 mL (40 minutes later), and is due to coagulation sedimentation alone. Comparing the sedimentation volume of 3.1 mL after 10 minutes with the sedimentation volume of 2.3 mL after 40 minutes at the completion of the second cycle of the temperature change cycle, the volume was reduced to 74.1% of the former.
3) From the above, it is clear that the periodic temperature change contributes to the volume reduction of the sludge that has coagulated and settled, and the case where the amount of chemical (wastewater treatment agent) added is 600 mg / L is higher than the case where 100 mg / L is added. It was found that the dehydration efficiency of the more sedimented coagulated sludge was high.

The second embodiment is shown in FIG. In the coagulation tank 5 of the wastewater treatment system 18 shown in the figure, a magnetic wastewater treatment agent is used to heat or dissipate the mixed solution D2 in the heat exchanger 13 of the coagulation promoting means 11, and suspend or dissipate in the coagulation tank 5. The floating aggregate D3 is magnetically attracted by the magnet portion 5e. The drum casing 5d that houses the magnet portion 5e fixed at a predetermined position is rotated, and the aggregate D3 is scraped off by the skimmer 5b at a position away from the magnet portion 5e and stored in the magnetic deposit separation tank 19. In the transfer path 15 on the way from the magnetic deposit separation tank 19 to the press 7, the agglomerates D3 are periodically heated or dissipated by the heat exchanger 16 of the dehydration promoting means 12 to increase the degree of cohesion.

As shown in FIG. 9, the magnetic wastewater treatment agent is made of a magnetic material such as magnetite or a mineral material (zeolite, layered clay mineral, etc. with a magnetic material such as magnetite added) as a base material, and the surface thereof is first coated. It is manufactured by chemically coating a temperature-responsive polymer material in the same manner as above.
Further, as shown in FIG. 10, a wastewater treatment agent in which a mineral material such as zeolite is used as a base material, a magnetic material such as magnetite is added, and a silane coupling agent is used to coat the surface with PNIPAM to impart magnetism. Can be manufactured. In particular, since there are many fine pores capable of adsorbing pollutants and the like on the surface of zeolite, the wastewater treatment agent functions not only as a coagulant but also as an adsorbent.

A third embodiment is shown in FIG. In the waste water treatment system 20 shown in the figure, the mixed liquid D2 using the magnetized waste water treatment agent is sent to the circulation tank 21 in the solid-liquid separation step and circulated in the magnetic collector 22 to utilize the high-gradient magnetic separation method. The agglomerates D3 to which magnetism is imparted by magnetism or the like are magnetically collected in the magnetic separation tank 19. The magnetron 22 is provided on a magnetic collector tube 23 that constitutes a long flow path in the vertical direction, a magnetic filter 24 that fits in the magnetic collector tube 23 so as to be movable in the longitudinal direction, and an outer periphery of the magnetic collector tube 23. It includes a pair of magnets 25 having S poles and N poles arranged opposite to each other. The magnet 25 may be a permanent magnet or an electromagnet. As shown in FIG. 12, the magnetic collector 22 magnetizes the magnetized portion 23a on which the magnet 25 is arranged on the outer periphery of the upper portion of the magnetic collecting tube 23, and magnetizes the magnetic filter 24 when the magnetic filter 24 is located on the magnetically attached portion 23a at the lower portion. It is provided with a detachable portion 23b for moving the captured agglomerate D3 together with the magnetic filter 24 and separating it from the magnetic field region to demagnetize it, and separating it from the magnetic filter 24 by a cleaning fluid such as water or air. A water inlet D1 mixed with a magnetic wastewater treatment agent and a water inlet 23c for taking in a cleaning fluid are above the desorption portion 23b, and a water outlet for discharging treated water is above the magnetic attachment portion 23a. The 23d is provided with a mud drain port 23e for discharging the agglomerate D3 at the lower part of the detachable portion 23b. The magnetic filter 24 is composed of ferromagnetic thin wires, magnetizes the agglomerates generated in the waste water D1 passing through the magnetic field at the corresponding position of the magnet 25 in the magnetic collecting tube 23, and magnetic force between the agglomerated particles having magnetism. By combining with, it is agglomerated and the particle size is expanded to generate agglomerates D3, which are magnetically adsorbed.

The magnetic filter 24 on which the agglomerate D3 is adsorbed is moved to the desorption portion 23b and radiated or heated on the low temperature side with LCST as the boundary or on the high temperature side with UCST as the boundary with a heat exchanger (not shown). As a result, the water solubility is increased, the agglomerates D3 are washed away from the magnetic filter 24, discharged from the mud drain port 23e, and then transferred to the squeezing machine 7 to carry out the dehydration step.

The squeezing machine 7 in each of the above embodiments shall be used as needed, and contributes to the improvement of the dehydration ability.

Another example of a temperature responsive polymer material is polyvinyl methyl ether (PVME). PVME has an oxyethylene chain in the side chain and exhibits a highly sensitive responsiveness that shows a phase transition in an aqueous solution with a temperature difference of only 1 ° C. Furthermore, crystalline vinyl ethers with long-chain alkyl groups and fluorine-containing vinyl ethers with fluoroalkyl groups have a predetermined UCST that exhibits hydrophilicity on the high temperature side and hydrophobicity on the low temperature side in many organic solvents. Is shown with high sensitivity. These phase transition temperatures can be freely controlled by the copolymerization composition of the polymer as described above.

A fourth embodiment is shown in FIG. The flexible container bag 27 for filtration of the wastewater treatment system shown in the figure is provided with a dehydration promoting means 26 instead of the squeezing machine 7. The flexible container bag 27 for filtration accommodates and suspends the agglomerates D3 sent from the magnetic deposit separation tank 19, and dehydrates them by self-weight pressing. The dehydration promoting means 26 includes a heat exchanger 28 mounted on the outer periphery of the filtering flexible container bag 27. The heat exchanger 28 is connected to the heat source 29. The heat exchanger 28 is a means for heating or dissipating heat of the agglomerate D3 according to the type of the temperature-responsive polymer material, substantially like the heat exchanger 13 described above. The filtered water C2 of the filtering flexible container bag 27 is stored in the filtered water tank 8 and reused or discharged.

1 Waste water treatment system 2 Raw water tank 3 Granulation tank 4 Chemical supply machine 5 Coagulation tank 5a Air diffuser 5b Skimmer 5c Blower 5d Magnet drum casing 5e Magnet part 6 Discharge tank 7 Squeezer 8 Filter water tank 9 Mud storage tank 10 Waste water treatment system 11 Coagulation promoting means 12 Dehydration promoting means 13 Heat exchanger 14 Heat source 15 Transfer path 16 Heat exchanger 17 Heat source 18 Waste water treatment system 19 Magnetic deposit separation tank 20 Waste water treatment system 21 Circulation tank 22 Magnetic collector 23 Magnetic collector tube 23a Magnetized portion 23b Detachable part 23c Water inlet 23d Water outlet 23e Mud drain 24 Magnetic filter 25 Magnet 26 Dehydration promoting means 27 Flecon bag for filtration 28 Heat exchanger 29 Heat source C1 Superfluous liquid C2 Filtered water C3 supernatant liquid D1 Waste water D2 Mixed liquid D3 Aggregates D4 dehydrated sludge

Claims (6)

A coagulation step in which a wastewater treatment agent is mixed with wastewater containing pollutants or pollutants and the pollutants and the like are aggregated into the wastewater treatment agent.
A solid-liquid separation step that separates agglomerates from this mixture,
In a wastewater treatment method including a dehydration step of reducing residual water content of separated aggregates to generate aggregated sludge.
The wastewater treatment agent contains a temperature-responsive polymer material, and the mixed solution mixed with the waste water is mixed with the temperature-responsive polymer material on the high temperature side of the lower limit critical solution temperature or the low temperature of the upper limit critical solution temperature. By adjusting the temperature to the side, the hydrophobicity of the temperature-responsive polymer is strengthened, and the agglomeration of pollutants or pollutants is promoted by the wastewater treatment agent .
In the dehydration step, the agglomerates are intermittently heated or dissipated a plurality of times so as to alternately shift the agglomerated sludge to the high temperature side and the low temperature side with the lower limit critical solution temperature or the upper limit critical solution temperature as a boundary. Wastewater treatment method. The wastewater treatment method according to claim 1, wherein the wastewater treatment agent is a base material having a property of adsorbing a specific harmful substance and / or a magnetic base material coated with a temperature-responsive polymer material. .. The wastewater treatment method according to claim 1 or 2 , wherein the agglomerates are heated or dissipated by an electric heater or a heat exchanger in the agglutination step and / or the dehydration step . The wastewater treatment method according to any one of claims 1 to 3, wherein the solid-liquid separation step separates agglomerates adhering to the magnetically imparted wastewater treatment agent by magnetic adsorption . By adjusting the temperature of the magnetically adsorbed aggregate to the low temperature side with the lower limit critical solution temperature of the temperature-responsive polymer material as the boundary or the high temperature side with the upper limit critical solution temperature as the boundary, the degree of aggregation is lowered and the aggregate The waste water treatment method according to claim 4 , wherein the magnetic adsorption is weakened by dissociating the water. The wastewater treatment method according to any one of claims 1 to 5 , wherein the agglomerates are further squeezed and dehydrated .