JP2002282867A - Wastewater treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently removing heavy metals contained in wastewater produced by washing a waste material such as incineration ash and the like. SOLUTION: This wastewater treating method characteristically comprises a step of adding a sulfurating agent to the wastewater produced by washing the waste material to precipitate the metals contained in the wastewater, a step of solid-liquid separating the liquid thus obtained, a step of removing calcium from the liquid obtained by the solid-liquid separation, a step of precipitating calcium and sulfate radical from the liquid by a sulfuric acid removing treatment, if necessary, and a step of precipitating chlorides from the liquid by adjusting the temperature of the liquid obtained by the solid-liquid separation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method for effectively separating salts contained in wastewater.

[0002]

2. Description of the Related Art Dust discharged from garbage incineration facilities and sewage sludge incineration facilities, and various industrial wastes, and various dusts discharged from cement kilns and high-temperature treatment processes, together with chlorine, contain several percent of copper, It contains heavy metals such as lead and zinc. If these wastes are directly disposed of in landfills, heavy metals such as lead will elute and cause environmental pollution. Therefore, these metals should be separated and removed as much as possible. Is required.

[0003]

2. Description of the Related Art Conventionally, the following treatment methods have been known as methods for removing heavy metals from waste such as incinerated ash. First, waste such as incineration ash is washed with water to elute water-soluble metal components.
While lead and zinc are precipitated and filtered to separate and recover heavy metals, calcium carbonate or sodium carbonate is introduced into the filtrate to precipitate calcium carbonate, which is filtered to remove calcium, and the filtrate is filtered. The sulfate is removed by electrodialysis, and the liquid is further introduced into a crystallization tank to precipitate sodium chloride, potassium chloride, and the like remaining in the liquid, thereby performing solid-liquid separation.

[0004]

However, in such a method of adding a chelating agent to waste water for washing to precipitate heavy metals, the cost of the chelating treatment is high, and furthermore, since the chelating treatment is performed first, In some cases, the precipitation of heavy metals may be insufficient due to the influence of calcium ions and the like existing in the water. Further, although the salt concentration is increased by electrodialysis, there is a problem that calcium remaining in the solution adheres to the dialysis membrane and the dialysis effect is greatly reduced. The present invention solves such a problem in the conventional wastewater treatment method, and provides a treatment method that is excellent in the effect of separating and removing heavy metals while having a simple treatment process, and that is excellent in the effect of recovering salt. is there.

[0005]

According to the present invention, there is provided a method for treating wastewater having the following constitution. (1) A sulphating agent is added to waste water obtained by washing the waste with water to precipitate metals in the liquid, and the solid-liquid separated liquid is decalcified to precipitate calcium and sulfate groups in the liquid.
A method for treating wastewater, further comprising adjusting the liquid temperature of a liquid subjected to solid-liquid separation to precipitate and separate chlorides in the liquid. (2) Desulfurization treatment together with decalcification treatment
(1) Wastewater treatment method. (3) The wastewater treatment method according to the above (1) or (2), wherein sodium bisulfide or hydrogen sulfide is used as a sulfidizing agent, carbonate is used as a decalcifying agent, and a barium compound is used as a desulfating agent. (4) After the calcium removal treatment or the desulfurization treatment, the liquid temperature after the solid-liquid separation is adjusted to 60 ° C. to 80 ° C., and the filtrate is concentrated to precipitate sodium chloride remaining in the liquid. Is adjusted to the normal temperature range to precipitate potassium chloride.
(1) Wastewater treatment method. (5) The wastewater treatment according to (1) above, wherein sodium hydrosulfide is added to the wastewater obtained by washing the wastewater to precipitate copper, lead and zinc in the liquid as sulfide, and the precipitate is separated by solid-liquid separation and recovered. Method. (6) Sodium hydrosulfide is added to the wastewater obtained by washing the waste with water to precipitate copper, lead, and zinc in the liquid as sulfide, and separated by solid-liquid recovery. The wastewater treatment method according to the above (1), wherein the wastewater is recovered and used as a cement raw material.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on embodiments. FIG. 1 shows an outline of the processing method of the present invention. As shown in the figure, in the treatment method of the present invention, a metal in the liquid is precipitated by adding a sulfide agent to the wastewater obtained by washing the waste with water, and the liquid fraction obtained by solid-liquid separation is subjected to decalcification treatment and desulfurization treatment. Precipitate the calcium and sulfate groups in the liquid, further adjust the liquid temperature of the solid-liquid separated liquid and concentrate it.
A wastewater treatment method characterized in that chloride in a liquid is precipitated and separated.

[0007] In the treatment method of the present invention, the wastes include a wide range of dusts discharged from garbage incineration facilities and sewage sludge incineration facilities, various industrial wastes, and dusts discharged from cement kilns and high-temperature treatment processes. Can be processed. These wastes are washed with water to elute water-soluble metal components into the liquid. In the water washing treatment, it is preferable that the washing wastewater is repeatedly circulated a plurality of times to increase the concentration of the metal component in the liquid.

[0008] A sulphidating agent is added to the waste water obtained by washing the waste with water to precipitate metals in the liquid. Sodium hydrosulfide or hydrogen sulfide can be used as the sulfiding agent. By adding these sulfurizing agents to the wastewater, copper, lead, zinc and the like in the liquid become sulfides and precipitate. After the formation of the precipitate, the precipitate is collected by solid-liquid separation. This sulfide precipitate can be reused as it is as a smelting raw material. The addition amount of sodium hydrosulfide is preferably 1 to 1.2 equivalents in terms of sulfur relative to the amount of metal in the liquid.

Next, the liquid from which the sulfide precipitate has been separated is subjected to a decalcification treatment to remove calcium and a sulfuric acid component (sulfate group) from the liquid. A carbonate such as sodium carbonate can be used as a decalcifying agent. When sodium carbonate is added, the calcium content in the liquid turns into calcium carbonate and precipitates. Although carbon dioxide gas may be blown as a decalcifying agent, sodium carbonate is more effective in forming a precipitate. In addition, for those containing sulfate ions in the liquid, desulfurization treatment is performed together with decalcification treatment. As the desulfurizing agent, for example, a barium compound such as barium chloride can be used. When barium chloride is added, the sulfate ions in the liquid react with barium chloride to cause precipitation of barium sulfate. Sodium carbonate and barium chloride may be added simultaneously or separately. The calcium content and the sulfuric acid component contained in the liquid are precipitated by the decalcification treatment and the desulfurization treatment, and are separated from the liquid by solid-liquid separation. If lead remains in the liquid, when sodium carbonate is added, this lead also turns into lead carbonate and precipitates, so that it can be separated into solid and liquid and removed from the liquid at the same time.

After the above-mentioned calcium removal treatment and desulfurization treatment, the liquid component subjected to solid-liquid separation is led to a crystallization tank, and the liquid temperature is adjusted to precipitate chloride remaining in the liquid. Specifically, for example, the filtrate is concentrated by adjusting the liquid temperature to 60 ° C. to 80 ° C., and sodium chloride remaining in the liquid is precipitated. Further, by adjusting the liquid temperature to a normal temperature range, preferably 30 ° C. or lower, potassium chloride remaining in the liquid is precipitated.

[0011] The wastewater treatment method of the present invention, as described above,
Sodium hydrosulfide is added to the wastewater that has been washed with water to precipitate copper, lead, and zinc in the liquid as sulfide, and separated by solid-liquid separation and collected. Since it is mainly used, an embodiment in which this is collected and used as a cement raw material can be included. The washed cake can be used as it is. In addition, it is preferable to dry, pulverize, and use. If necessary, the water-washed cake is acid leached to elute the remaining copper and zinc components into the liquid, and this is precipitated and separated, and the solid content of the acid leached slurry is alkali leached to remove the remaining copper and zinc components. The method may include a treatment step of eluting the lead component to be precipitated and separating it by precipitation, and a treatment step of recovering calcium content from the solid content of the alkali leaching slurry and using it as a cement raw material.

[0012]

EXAMPLE Incineration ash was processed according to the processing steps shown in FIG. First, 500 kg of incinerated ash was repeatedly washed with 100 liters of water three times and dehydrated. Table 1 shows the concentrations of metal components and the like contained in 50 liters of the washing wastewater. Next, 3.3 kg of sodium carbonate and 19.2 g of barium chloride were added to the washing waste water, and the mixture was stirred for about 15 minutes to form a precipitate. This was subjected to solid-liquid separation, and the concentration of metal components and the like contained in the filtrate was measured. The results are shown in Table 1. Next, the filtrate was introduced into a crystallization tank, and concentrated under reduced pressure while maintaining the liquid temperature at 80 ° C. to precipitate sodium chloride, and further, the liquid temperature was lowered to room temperature to precipitate potassium chloride. separated. Table 1 shows the concentrations of metal components and the like contained in the liquid after crystallization. As a control, the concentrations of metal components and the like contained in the liquid after electrodialysis by the conventional treatment method are shown in comparison with Table 1.

[0013] As shown in the results of Table 1, those treated by the method of the present invention have much less chloride ions and alkali metal elements than those treated by the conventional method. In addition, the remaining amounts of sulfate ions, nitrate nitrogen, ammonia nitrogen, and carbonate ions are greatly reduced. In addition, in the treatment results of the present invention shown in Table 1, the residual amount of lead is slightly high, but this is caused by adding a chelating agent after the decalcification treatment and desulfation treatment and before the crystallization step. The concentration of lead therein can be reduced to <0.1 ppm or less. Incidentally, the purity of the sodium chloride recovered by the crystallization treatment was 95.1% (containing 1.04% of KCl on an outer basis), and the purity of potassium chloride was 92.0% (containing 1.5% of NaCl on an outer basis). there were.

[0014]

[Table 1]

[0015]

According to the treatment method of the present invention, salts contained in wastewater obtained by washing waste such as incineration ash are effectively separated and removed, and high-quality salts (NaCl, KCl, etc.) are recovered. be able to. In addition, heavy metals can be efficiently removed. Moreover, the processing method is simple and the processing effect is excellent.

[Brief description of the drawings]

FIG. 1 is a process chart showing a processing method of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaya Ida 2-4-2 Daisaku, Sakura-shi, Chiba Pref. Inside the Central Research Institute of Pacific Cement Co., Ltd. (72) Keiichi Miura 2-4-2 Daisaku, Sakura-shi, Chiba Taiheiyo Cement Co., Ltd. Central Research Laboratory (72) Inventor Toyoshige Okamoto 3-1-1 Nishikanda, Chiyoda-ku, Tokyo Taiheiyo Cement Co., Ltd. F-term (reference) 4D038 AA08 AB59 AB68 AB69 AB74 AB80 AB81

Claims (6)

[Claims] 1. A sulphating agent is added to waste water obtained by washing wastes to precipitate metals in the liquid, and the solid-liquid separated liquid is decalcified to precipitate calcium and sulfate groups in the liquid. A method for treating wastewater, further comprising adjusting a liquid temperature of a liquid subjected to solid-liquid separation to precipitate and separate chlorides in the liquid. 2. The wastewater treatment method according to claim 1, wherein the desulfurization treatment is performed together with the calcium removal treatment. 3. The wastewater treatment method according to claim 1, wherein sodium sulfide or hydrogen sulfide is used as the sulfurizing agent, carbonate is used as the decalcifying agent, and a barium compound is used as the desulfating agent. 4. After the calcium removal treatment or the desulfurization treatment, the liquid temperature after solid-liquid separation is adjusted to 60 ° C. to 80 ° C., and the filtrate is concentrated to precipitate sodium chloride remaining in the liquid. The wastewater treatment method according to claim 1, wherein the liquid temperature is adjusted to a normal temperature range to precipitate potassium chloride. 5. The wastewater according to claim 1, wherein sodium hydrosulfide is added to the wastewater obtained by washing the waste with water to precipitate copper, lead and zinc in the liquid as sulfide, and the precipitate is recovered by solid-liquid separation. Processing method. 6. Sodium hydrosulfide is added to waste water obtained by washing the waste with water to precipitate copper, lead, and zinc in the liquid as sulfide, and solid-liquid separation is performed. The wastewater treatment method according to claim 1, wherein the solid content is recovered and used as a cement raw material.