JPH01288391A - Method and apparatus for treatment of waste water - Google Patents

Abstract

PURPOSE:To reduce treatment cost, by using a soluble electrode as an anode while using a solar cell as a power supply to apply electrolytic treatment to waste water. CONSTITUTION:In a waste water treatment apparatus consisting of a solar cell 1 and an electrolytic cell 7, six pairs of electrodes 12, 12A are provided in an electrolytic cell 7 and a separation tank 10 for separating the floc formed in the electrolytic cell 7 is connected to the electrolytic cell 7. A waste water storage tank 5 stores waste water temporarily and also has functions for adjusting pH and the concn. of an electrolyte, and a stirrer 8 and an air bubble generator 9 promote the electrolytic treatment in the electrolytic cell 7 and prevent the surface contamination of the electrodes. When a DC current is supplied to the electrodes, nascent colloidal anodic metal hydroxide is formed from anodes and heavy metal hydroxide is floated and precipitated as floc along with anodic metal hydroxide colloid to be separated from waste water. By this method, a heavy metal can be effectively separated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for treating wastewater, and in particular to a method for effectively removing heavy metals and oil from wastewater using hydroxides of electrode metals eluted from molten electrodes. The present invention relates to a method and device for treating wastewater that can be removed.

[Conventional technology]

In recent years, the discharge of pollutants into the environment has been strictly restricted by the Environmental Pollution Control Act, etc., and when discharging pollutants, certain measures are taken to satisfy such standards.

Conventionally, methods for treating wastewater containing heavy metals include adsorption treatment using activated carbon, ion exchange resins, or chelate resins, ion flotation in which heavy metals are separated by flotation in the coexistence of specific ions, and heavy metals using coagulants. A coagulation-sedimentation method in which heavy metals are coagulated and precipitated, and an electrolysis method in which heavy metals are precipitated by electrolysis of wastewater are known.

On the other hand, methods for treating oil-containing wastewater include an adsorption method in which oil is adsorbed onto an adsorbent and separated, a flocculation method in which oil is flocculated using a flocculant, an electrolysis method in which oil is flocculated electrically, a bubble flotation method, and a gravity method. Also known are an incineration method in which floating oil is incinerated using a coalescer or the like, and a membrane separation method in which oil and water are separated using a permeable membrane.

[Problem to be solved by the invention]

The conventional heavy metal-containing wastewater treatment methods and oil-containing wastewater treatment methods described above both have high processing costs, and the problem of secondary treatment, such as how to further treat the collected heavy metals and oil, must be resolved. It won't happen.

The present invention eliminates such conventional drawbacks and provides a wastewater treatment method that can inexpensively and effectively remove heavy metals and oil from wastewater, and a wastewater treatment device that is extremely compact and easy to operate. The purpose is to

[Means to solve the problem]

The wastewater treatment method of the present invention that achieves the above object uses a soluble electrode at least as an anode, and electrolytically treats wastewater using a solar cell as a power source.

Further, the wastewater treatment device of the present invention is characterized by comprising a solar cell and at least one electrolytic cell using the solar cell as a power source and having at least an anode as a soluble electrode.

FIG. 1 shows one embodiment of the wastewater treatment apparatus of the present invention, which is composed of a solar cell 1 and an electrolytic cell 7, and the electrolytic cell 7 is provided with six pairs of electrodes 12.12A.

The solar cell 1 further includes an overcharge and overdischarge prevention control device 2, a thin battery 3, a constant current generator 4, and a polarity exchange device 11.

The solar cell 1 is a power source for all the electric power of the wastewater treatment device of the present invention, and an appropriate number of solar modules that are currently commercially available at about 1,000 yen per watt are used in combination. can do.

The overcharge and overdischarge prevention control device 2 is a protection device for the storage battery 3, and when charging the storage battery 3 with the solar cell 1, in order to prevent overcharging (for example, when the voltage reaches 13V, the controller operates and automatically stops charging. ),
It is also used to prevent over-discharge when power is supplied from the storage battery 3 to each device (for example, power supply is automatically stopped when the battery reaches 11.2 cm).

The storage batteries 3 are generally 12V or 24V, and the number of batteries installed varies depending on the amount of wastewater treated by the apparatus of the present invention and the concentration of heavy metals and oil in the wastewater, as well as the specified voltage and battery capacity of the storage battery.

The electric power necessary for operating the device of the present invention other than during solar irradiation is provided by this storage battery.

The constant current generator 4 performs electrolytic treatment of wastewater.
A device for supplying a constant current to a soluble electrode.

Furthermore, if a device for converting AC power into constant current exists, a constant current generating device with a converter is used.

The polarity changing device 11 is used to prevent contamination of the electrodes and to equalize the consumption of the electrodes when soluble electrodes are used for both the anode and the cathode. According to this device, it is possible to alternately convert the polarities of + and - in arbitrary seconds or minutes.

A plurality of electrolytic tanks 7 may be provided, and a wastewater storage tank 5 may also be provided.
, liquid feed pump 6, and stirring t8 as a drainage flow device
8 and a bubble generator 9 are provided.

Furthermore, a separation tank 10 for separating aggregates formed in the electrolytic tank 7 is connected to the electrolytic tank 7.

The electrodes 12 are generally plate-shaped, at least one pair of electrodes are used, and at least a soluble electrode is used as an anode.

As the soluble electrode, it is preferable to use an electrode made of aluminum or iron, which tends to form colloidal hydroxide. The cathode is not particularly limited, and like the anode, a soluble electrode may be used, or an insoluble electrode may be used.

Ferrite, carbon, etc. are used as the insoluble electrode.

The wastewater storage tank 5 has the function of adjusting pH and electrolyte concentration in addition to temporarily storing wastewater, and the agitator 8 and the bubble generator 9 promote the electrolytic treatment in the electrolytic tank 7.
The purpose is to prevent contamination of the electrode surface.

The aggregate separation tank 10 is a device for separating aggregates formed in the electrolytic cell by flotation, sedimentation, or filtration.

FIG. 2 shows another embodiment of the device of the invention, which is a simplified version of the device shown in FIG. 1, and is composed of a solar cell 1, an electrolytic cell 7, and a pair of electrodes 12,128.

[Effect]

As described above, in the present invention, a soluble electrode is used at least as an anode. Accordingly, nascent colloidal anode metal hydroxide is formed from the anode upon application of direct current.

Then, the heavy metal ions in the wastewater combine with OH ions near the alkaline cathode to become heavy metal hydroxides, which are occluded in the colloidal anode metal hydroxide formed at the anode. It floats or precipitates together with metal hydroxide colloid as an aggregate (co-precipitation effect) and is separated from the wastewater.

In addition, in the case of oil-containing wastewater, especially in the case of emulsified oil wastewater, the nascent hydroxide colloid formed from the anode metal as described above changes the hydrophilic group of the surfactant in the wastewater into a poorly soluble one, and As the surfactant disappears, the micelles are destroyed and the oil coagulates, resulting in rapid oil-water separation.

〔Example〕

Example 1 Heavy metal-containing wastewater was treated using the wastewater treatment apparatus shown in FIG.

The solar cell used was a 7.3 watt module, the electrolytic cell was a cylindrical glass container with a diameter of 10 cm and a height of 25 cm, and the electrodes were a pair of aluminum rods with a diameter of 8 mm and a length of 25 cm. The electrode spacing was 1 cm.

Further, as the heavy metal-containing wastewater, 1 liter of a solution adjusted to a heavy metal ion concentration of 1100 pp was used.

The electrolysis conditions are as follows.

Current 0.5±0. IA Temperature: 21-23°C Time: 15 minutes In addition, an atomic absorption spectrophotometer was used to measure the heavy metal ion concentration.

The results of the electrolytic treatment are shown in Table 1 below.

From Table 1, it is clear that each heavy metal ion can be sufficiently removed.

Table 1 Heavy metal ions Initial concentration (ppm) Removal rate (χ) Trivalent chromium 100 98.3 Zinc
99.4 copper
98.8 Tin 97.
4 Lead 96.1
Example 2 Oil-containing wastewater was treated using the same wastewater treatment equipment as in Example 1.

As wastewater, JIS Class 1 No. 1 water-soluble cutting oil (7)
1,000ppm solution and 500% as electrolyte.
ppm sodium chloride was added.

The electrolysis conditions are as follows.

Current 0.4±0.05A Temperature　　21.5~22.5℃ Time 10 minutes The electrolytic treatment results are shown in Table 2.

As is clear from Table 2, it is clear that in all cases, not only the oil but also the activator were sufficiently treated in a short period of time.

Table 2 Emulsified oil Initial concentration (ppm) Removal rate (χ) Water-soluble cutting oil 1000 98.6〃700
99.2 〃50099.5 Example 3 Emulsified oil wastewater was treated using a part of the wastewater treatment apparatus shown in FIG.

As a power source, a directly connected 12V storage battery and a directly connected 7,
A 3W module solar cell was used.

The electrolytic cell was square, and the drainage capacity was 71 and 1111.

The electrodes were made of aluminum and arranged in 6 and 10 pairs with a spacing of 5 mm. Note that the same waste water as in Example 2 was used.

The experimental conditions are as follows.

Experiment number Power source Discharge amount Current (A) Voltage (V) I
N battery 7110~412±0.12 Solar cell 7β0.5±0.117±23 〃1
160.3 Soil 0.05 17±2 The results of the electrolytic treatment are shown in Figure 3.

In addition, in Fig. 3, 10- is the experiment number 1, and -・- is 2.
and -x- indicate 3, respectively.

From FIG. 3, it can be seen that the removal rate increases as the electrolytic treatment time progresses.

Note that the emulsified oil wastewater concentration was measured by the TOC method.

Example 4 Emulsified oil wastewater was treated using the wastewater treatment apparatus shown in FIG.

The same waste water as in Example 2 was used.

However, the electrolytic treatment was carried out using an electrolytic tank having a drainage capacity of 7N and 11/2, arranged in series.

That is, waste water was injected into both electrolytic cells, a constant current of 2 A was applied to each for 15 minutes, and then the liquid was continuously passed through the electrolytic cells at a flow rate of 601/hour.

The solar cell used was a 42 Watt module.

The continuous processing conditions are as follows.

Electrolytic cell drainage capacity Current Voltage Flow rate 1st 7Z
2A 1.7V 60A'/h 2nd 1112A
The 1.4V 6072/h results are shown in FIG.

As is clear from this figure, it is clear that according to the treatment method of the present invention, sufficiently satisfactory results can be obtained even in continuous treatment of emulsified oil wastewater.

〔Effect of the invention〕

Since the present invention is configured as described above, it can produce the following effects.

In the present invention, since a soluble electrode is used at least as an anode, nascent colloidal hydroxide of soluble electrode metal is formed as wastewater is electrolyzed, and this colloid is mixed with similarly formed heavy metal hydroxide at the cathode. It absorbs oxides and floats or precipitates together, making it possible to remove heavy metals from wastewater.

In addition, in oil-containing wastewater, colloids in the nascent stage destroy micelles of emulsified oil, coagulate oil, and quickly separate oil and water.

That is, according to the present invention, heavy metals and oil in wastewater can be effectively removed.

Furthermore, since the wastewater is simply electrolyzed, it is easy to operate.

Furthermore, in the present invention, since the solar energy, which is said to be unrequired, is used as a power source, the energy cost is extremely low compared to the conventional system even when the initial cost is added.

Furthermore, running costs are also extremely low.

Electric power obtained from solar cells can be used not only for electrolysis but also for liquid transport pumps, stirrer motors, or bubble generators, so it has the advantage that conventional electric power is not substantially required.

[Brief explanation of the drawing]

1st y! J is a schematic diagram showing an embodiment of the wastewater treatment device of the present invention, FIG. 2 is a schematic diagram showing another embodiment, and FIGS. 3 and 4 are relationships between treatment time and removal rate in the treatment of emulsified wastewater. FIG. 1-Solar cell, 3-Storage battery, 7-Electrolytic cell, 8.9...
Drain fluid flow device, 10-agglomerate separation tank, 12.12A-electrode. Figure 2 12 12A Removal rate (%)

Claims (1)

[Scope of Claims] 1. A method for treating wastewater, which comprises using a soluble electrode as at least an anode and electrolytically treating wastewater containing heavy metals and/or oil-containing wastewater using a solar cell as a power source. 2. The method for treating wastewater according to claim 1, wherein the soluble electrode is an aluminum or iron electrode. 3. A wastewater treatment device comprising a solar cell and at least one electrolytic cell using the solar cell as a power source and having at least an anode as a soluble electrode. 4. The wastewater treatment apparatus according to claim 3, wherein the electrolytic cell is provided with a wastewater flow means and a separation tank for aggregates formed in the electrolytic cell. 5. The wastewater treatment apparatus according to claim 4, wherein the wastewater flowing means is an agitator. 6. Claim 4, wherein the waste water flowing means is a bubble generator.
The wastewater treatment equipment described. 7. The wastewater treatment device according to claim 3, further comprising an overcharge and overdischarge prevention control device, a storage battery, a constant current generator, and a polarity switching device.