TWI602784B - A regeneration method for high-hardness wastewater containing heavy metal - Google Patents

Description

Method for regenerating high hardness wastewater containing heavy metals

The present invention relates to a method for regenerating wastewater, and more particularly to a method for treating and regenerating high hardness wastewater containing heavy metals.

At present, although the utilization rate of ash generated by waste incineration is nearly 52%, the harmful elements such as heavy metals, soluble salts and organic substances contained in the ash can not be completely treated, which is the obstacle to the effective reuse of ash.

For this reason, the use of a water washing process to ensure the quality of the ash treatment is the current stage of the reaction, so that the harmful elements in the ash can be dissolved after washing with water. For example, the Patent No. 201013123 of the Republic of China discloses a treatment method for the harmless treatment of heavy metal incineration fly ash, in which the prepared extractant of clean water, weak alkali liquor and medium concentration acid liquid is added to the harmful fly ash, fully The mixture is mixed with fly ash slurry and impregnated and extracted; the extracted fly ash slurry is dehydrated to separate the fly ash from the waste liquid, and the waste liquid is treated in the wastewater treatment plant; the fly ash after the rinsing can be further dried and pulverized In order to achieve the purpose of harmlessness, and the pulverized fly ash becomes a recyclable substance.

Although the above-mentioned ash obtained by the water washing process can dissolve harmful elements therein, and the ash becomes a recyclable substance, the ash contains SiO ₂ , Al ₂ O ₃ , CaO, NaCl, KCl, MgO, CaSO. _4. Harmful substances such as CaCO ₃ and CaClOH will produce other substances due to the cooperation of water washing and discharge with the waste liquid generated by the washing process. Even after the ash is washed with water, it is possible to wash out harmful organic substances such as polycyclic aromatic hydrocarbons, chlorobenzene, chlorophenol, and dioxin/fusane adsorbed on the surface, and remain in the waste liquid.

In this way, the waste liquid discharged through the above is provided with a large amount of substances such as calcium, magnesium and composite salts thereof which are easy to improve the hardness of the water, and heavy metals and organic substances dissolved/washed from the ash residue, so that the waste liquid is discharged into the wastewater treatment. After the plant, it is easy to block the wastewater treatment system due to the calcium, magnesium and its composite salts, which causes the waste liquid to be incompletely treated, and traces of heavy metals and organic matter remain therein. Therefore, if the waste liquid is not properly disposed before being sent to the wastewater treatment plant, it is not only impossible to improve the treatment efficiency of the waste liquid, but also relatively increase the maintenance cost due to the damage of the waste water treatment system.

In view of the above reasons, it is indeed necessary to develop a method for treating high-hardness wastewater containing heavy metals and regenerating it to apply to the waste liquid from which ash is washed by water, thereby solving various problems as described above.

The main object of the present invention is to improve the above disadvantages to provide a method for regenerating a high-hardness wastewater containing heavy metals, which is capable of improving the waste liquid for treating ash slag washing, recycling the waste liquid for recycling, and reducing waste water pollution.

The second object of the present invention is to provide a method for regenerating high-hardness wastewater containing heavy metals, which is capable of softening the waste liquid washed by ash and removing heavy metals and organic substances in the waste liquid, thereby improving the quality of wastewater treatment and reducing equipment maintenance. The cost.

In order to achieve the foregoing object, the method for regenerating a heavy metal-containing high hardness wastewater of the present invention comprises: a water softening step of mixing a compound containing an inorganic anion in a high hardness wastewater containing heavy metals to dissolve the compound in the high hardness wastewater, Producing a calcium-containing compound by reacting the compound with calcium ions in the high-hardness wastewater, and recovering the calcium-containing compound, thereby obtaining one a soft metal removal step of adsorbing and removing heavy metals contained in the soft water by an adsorbent; and a de-neutralization step of mixing an oxidant in the soft water for removing heavy metals to decompose the soft water by the oxidant The organic matter contained therein is obtained by regenerating purified water; wherein, prior to the water softening step, the high-hardness wastewater containing heavy metals is preliminarily treated with sodium hydroxide to adjust the high-hardness wastewater containing heavy metals to be high. The base wastewater reacts sodium hydroxide with a portion of the calcium ions in the high hardness wastewater to form a calcium-containing compound. The inorganic anion-containing compound is gaseous carbon dioxide having a purity of 99.9%, and the gaseous carbon dioxide is ventilated at 01 to 20 mL/ Min. .

In the water softening step, the inorganic anion-containing compound is dissolved in the high-hardness wastewater to produce an anion-containing acid radical and free in the high-hardness wastewater to permeate the anion-bearing acid and high-hardness wastewater. The calcium ion reacts to form a calcium-containing compound.

Wherein the inorganic anion-containing compound is any compound derived from F ^- , Cl ^- , Br ^- , I ^- , NO ^{3 -} , PO ₄ ^3- , SO ₄ ^2- or CO ₃ ^2- .

In the de-neutralization step, the regenerated purified water is heated by a heat source, and the regenerated purified water is forced to be distilled under high temperature to regain clean water without impurities. Among them, the heat source can be derived from the waste heat generated by the on-line boiler of the ash incineration process.

Alternatively, in the decontamination regeneration step, the regenerated purified water is discharged into a wastewater treatment plant to re-obtain clean water without impurities after being decontaminated by the wastewater treatment plant.

Among them, the adsorbent material is powder activated carbon, granular activated carbon, fibrous activated carbon, regenerated activated carbon, clay or ion exchange resin.

Wherein, the oxidizing agent is ozone, potassium permanganate or a photocatalyst.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The invention is used for treating waste water produced by a water washing process of fly ash and bottom slag (so-called ash ash slag) after waste incineration, and the waste water is contaminated with harmful elements such as heavy metals, soluble salts and organic substances, and The content of calcium, magnesium, and composite salts thereof causes high hardness of the wastewater. Therefore, the wastewater is referred to as "high-hardness wastewater containing heavy metals" in the following section.

Referring to FIG. 1 , which is a preferred embodiment of the present invention, the heavy metal-containing high hardness wastewater regeneration method includes a water softening step S1, a heavy metal removal step S2, and a decontamination regeneration step S3.

The water softening step S1 is a method of mixing a compound containing an inorganic anion in a high-hardness wastewater containing heavy metals, and dissolving the compound in the high-hardness wastewater to react with the calcium ions in the high-hardness wastewater to form a calcium-containing compound. The calcium-containing compound is recovered to obtain a soft water. Wherein, the inorganic anion may be any one of F ^- , Cl ^- , Br ^- , I ^- , NO ^{3 -} , PO ₄ ^3- , SO ₄ ^2- or CO ₃ ^2- , and the inorganic anions may be derivatized as Various inorganic anion-containing compounds such as CO ₂ , NO ₂ , and SO ₂ are known to those having ordinary knowledge in the art, and the above description can be made without any discretion.

For example, in this embodiment, the carbon dioxide is selectively introduced into the high-hardness wastewater containing heavy metals, and when the carbon dioxide is dissolved in the high-hardness wastewater, the calcium ions in the high-hardness wastewater are passed through the chemical formula. The reaction is described to produce calcium carbonate and calcium hydroxide.

Ca ²⁺ _(aq) +CO _2(g) →CaCO _3(s) +Ca(OH) _2(s) [Chemical Formula 1]

Alternatively, in the water softening step S1, the inorganic anion-containing compound may be forced to dissolve in the high-hardness wastewater to produce an anion-containing acid radical and freed in the high-hardness wastewater to permeate the anion-bearing acid radical [ For example, carbonate or sulfate is reacted with calcium ions in high-hardness wastewater to carry out the reaction as described in [Chemical Formula 2] to form calcium carbonate.

Ca ²⁺ _(aq) +CO ₃ ^2- /SO ₄ ^2- _(g) →CaCO _3(s) /CaSO _4(s) [Chemical Formula 2]

Thereby, the calcium-containing compound such as calcium carbonate or calcium hydroxide produced by the water softening step S1 can be precipitated and recovered, and selected to be reused in the washing tower of the ash treatment procedure as the acid gas neutralizing agent. At the same time, the hardness of the high-hardness wastewater can be further reduced by solid/liquid separation, and the soft water is obtained. At this time, impurities such as heavy metals and organic substances remain in the soft water, so that the heavy metal removal step S2 and the de-waste regeneration are continued. Processing of step S3.

It is to be noted that the amount of the inorganic anion-containing compound to be added is necessary to correspond to the treatment amount of the high-hardness wastewater, and it is preferable to select a compound having a higher purity. Specifically, as shown in the present embodiment, gaseous carbon dioxide having a purity of 99.9% is selected, and the aeration amount thereof is controlled to be 0.1 to 20 mL/min. However, the conditions described herein are only used as proof of subsequent experiments (see the drawings for further details), and those having ordinary knowledge in the field can be processed according to the concept of the present invention. Equipment, compound concentration, appropriate adjustment of the ventilation during mixing, in order to force the compound to fully react with calcium ions in the wastewater to form calcium-containing compounds [the type of calcium-containing compound is determined by the inorganic anion-containing reaction with calcium ions The compound can be used without limitation and will not be described.

Referring to FIG. 1 again, the present invention may further select the heavy metal removal step S2 after the water softening step S1 to treat the high hardness wastewater. After softening, completely eliminate the threat of heavy metals.

The heavy metal removing step S2 adsorbs and removes heavy metals contained in the soft water by an adsorbent. The adsorbent material may be generally adsorbent materials such as various activated carbons (such as powder, granular, fibrous, recyclable, etc.), clay, or ion exchange resins. For example, in this embodiment, activated carbon having a better adsorption capacity for low-polarity compounds and metal ions is selected as an adsorption material, thereby forcing heavy metal ions to remain in the pores of the activated carbon, as shown in [Chemical Formula 3]. The reaction is adsorbed on the surface of the activated carbon, whereby the heavy metal in the soft water is effectively removed.

C _(s) +M ²⁺ _(aq) =CM _(s) [Chemical Formula 3]

According to the above, as shown in FIG. 1 , the present invention may further select the de-heterogeneous regeneration step S3 after the heavy metal removal step S2 to remain after the water softening step S1 and the heavy metal removal step S2. Treatment with organic matter (eg polycyclic aromatic hydrocarbons, chlorobenzene, chlorophenol, and dioxin/fusane) to reduce the threat of organic matter, and reuse the water for reuse in ash treatment In the program.

The de-heterogeneous regeneration step S3 is to mix an oxidizing agent in the soft water (ie, the above-mentioned raw water) for removing heavy metals to decompose the organic matter contained in the soft water by the oxidizing agent. The oxidizing agent may be an oxide such as a dichromate solution, a permanganate solution or an ozone gas, or may be a catalytic homogeneous or heterogeneous catalyst film. For example, in the present embodiment, the ozone gas having a relatively high oxidative decomposition efficiency is selected to rapidly oxidize the organic substance by performing an oxidation reaction between the active oxygen and the organic substance in the water to be produced as described in [Chemical Formula 4]. break down.

CxHyOzNsClr+[O]→R-OH+R-COOH+R-CHO R-OH+R-COOH+R-CHO+[O]→CO ₂ +H ₂ O+Cl ^- +NO _2(s) [Chemical Formula 4]

In this way, after the heavy metal removal step S2 and the de-heterogeneization regeneration step S3, a regenerated purified water containing no heavy metals and organic substances can be obtained, and the regenerated purified water is remarkably low-hardness regenerated due to the decrease of the calcium ion content therein. Purified water, so as to achieve the purpose of purification of ash washing wastewater.

In particular, in order to further ensure that the wastewater can be recirculated and reused after purification, the present invention can be selected in the decontamination regeneration step S3, and then the reclaimed purified water is discharged into a wastewater treatment plant to pass through the wastewater treatment plant. After the second decontamination, the clean water without impurities is regained; or, in the decontamination regeneration step S3, the regenerated purified water may be heated by a heat source to force the regenerated purified water to be distilled under high temperature. Get clean water free of impurities. Wherein, the heat source can be derived from the waste heat generated by the on-line boiler of the ash incineration process to take advantage of energy reuse. Moreover, after this treatment, the clean water containing no impurities can be recycled and reused in the ash treatment process to achieve the effect of zero waste water pollution while improving the quality of the wastewater treatment.

In order to prove that the present invention can perfectly treat the wastewater for ash washing, and recycle the effluent treatment process with recycled effluent, the present invention performs the following experiment with carbon dioxide with different venting time, and observes the softening of the high hardness wastewater from the calcium content. situation.

In this embodiment, the wastewater after washing the ash residue (that is, the high-hardness wastewater containing the heavy metal mentioned above) is recovered and the pH value is detected; then, after adjusting the pH value with sodium hydroxide, the pH is 0.1. Aeration of ~20 mL/min is fed into the wastewater. In this way, calcium is sampled every five minutes. Changes in concentration are recorded in Figures 2A and 2B.

It can be seen from the results of FIG. 2A that after adjusting the wastewater to a low base, medium base, and high base wastewater solution by sodium hydroxide, the calcium content in each wastewater solution is significantly reduced; however, After 5 minutes of carbon dioxide, the calcium content in the low base wastewater solution was only slightly reduced by 1.08%, but the calcium content in the high base wastewater solution was significantly reduced by 20.24%, but the calcium content in the medium base wastewater solution increased by 16.73. %. Thereby, after the initial reaction of sodium hydroxide with calcium ions in the wastewater, the ruthenium can help to enhance the effect of the subsequent carbon dioxide softening wastewater, and proves that the present invention can effectively reduce the hardness of the wastewater and recover the calcium ions contained therein.

Through the above, it was found that after the initial action of sodium hydroxide, the subsequent treatment efficiency of carbon dioxide can be improved, as shown in FIG. 2B. Among them, the a shown in the figure is the calcium content in each wastewater adjusted by sodium hydroxide; the b shown in the figure is the calcium content in each wastewater after passing short-time carbon dioxide; The c is the calcium content in each wastewater after a long period of carbon dioxide is introduced. From the results of Fig. 2B, it can be seen that not only the sodium content in the wastewater can be reduced by using sodium hydroxide, but also the time for introducing carbon dioxide increases, and the calcium content in each wastewater is relatively reduced by 91.5% or more.

According to the experimental results, it is known that the carbon dioxide in the waste water can be effectively reduced by the carbon dioxide, and the reaction equation of the heavy metal removal step S2 and the de-nego-regeneration step S3 is combined to prove that the present invention can effectively treat the waste water of the ash washing water for regeneration. The wastewater is recycled for use to reduce the pollution of wastewater. It should be noted that, before carrying out the water softening step S1 of the present invention, the high-hardness wastewater containing heavy metals may be further treated with sodium hydroxide to make the sodium hydroxide first and some calcium ions in the high hardness wastewater. The reaction produces a calcium-containing compound, thereby increasing the efficiency of carbon dioxide action in the subsequent water softening step S1.

In summary, the main feature of the method for regenerating high-hardness wastewater containing heavy metals of the present invention is that the carbon dioxide is fully reacted with calcium ions in the high-hardness wastewater, which not only can effectively soften the hardness of the wastewater, but also can produce the calcium-containing compound produced by the reaction. It will be recycled and reused. In addition, the heavy metals and organic matter in the softened wastewater will be removed to improve the quality of wastewater treatment and generate clean water for recirculation in the ash treatment process. In this way, the method for regenerating the high-hardness wastewater containing heavy metals of the present invention can not only reduce the pollution of the wastewater discharged from the online washing ash and slag, but also achieve the effect of improving the quality of the wastewater treatment; and even avoid the blockage of a large amount of substances entrained in the wastewater. The wastewater treatment system causes damage to the wastewater treatment system, thereby further reducing the cost of equipment maintenance.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

〔this invention〕

S1‧‧‧ water softening step

S2‧‧‧ Heavy metal removal steps

S3‧‧‧De-regeneration step

Figure 1: Schematic diagram of the process of the present invention.

2A-2B: Schematic diagram of experimental data of the present invention.

S1‧‧‧ water softening step

S2‧‧‧ Heavy metal removal steps

S3‧‧‧De-regeneration step

Claims (8)

A method for regenerating a high hardness wastewater containing heavy metals, comprising: a water softening step of mixing a compound containing an inorganic anion in a high hardness wastewater containing heavy metals to dissolve the compound in the high hardness wastewater to permeate the compound and the high hardness Calcium ions in the wastewater react to form a calcium-containing compound, and the calcium-containing compound is recovered to obtain a soft water; a heavy metal removal step absorbs and removes the heavy metal contained in the soft water by an adsorbent; a heterogeneous regeneration step of mixing an oxidizing agent in the soft water for removing heavy metals to decompose the organic matter contained in the soft water by the oxidizing agent to obtain a regenerated purified water; wherein, prior to the water softening step, sodium hydroxide is used. The high-hardness wastewater containing heavy metals is subjected to preliminary treatment to adjust the high-hardness wastewater containing heavy metals to high base wastewater, and reacts sodium hydroxide with a part of calcium ions in the high-hardness wastewater to form a calcium-containing compound, which contains inorganic The anion compound is gaseous carbon dioxide having a purity of 99.9%, and the gaseous carbon dioxide is ventilated at 0.1 to 20 mL/min. The method for regenerating a high-hardness wastewater containing heavy metals according to claim 1, wherein in the water softening step, the inorganic anion-containing compound is dissolved in the high-hardness wastewater to produce an anion-free acid radical and free In the high-hardness wastewater, the acid ions passing through the anion are reacted with calcium ions in the high-hardness wastewater to form a calcium-containing compound. The method for regenerating a high-hardness wastewater containing heavy metals according to claim 1 or 2, wherein the inorganic anion-containing compound is composed of F ^- , Cl ^- , Br ^- , I ^- , NO ^3- , PO ₄ ^{3 -} Any compound derived from SO ₄ ^2- or CO ₃ ^2- . The method for regenerating a high-hardness wastewater containing heavy metals according to claim 1 or 2, wherein in the decontamination step, the regenerated purified water is heated by a heat source to force the regenerated purified water to be distilled under high temperature. Get clean water free of impurities. The method for regenerating a high-hardness wastewater containing heavy metals as described in claim 4, wherein the heat source is derived from waste heat generated by an on-line boiler of the ash incineration process. For the method for regenerating high-hardness wastewater containing heavy metals as described in claim 1 or 2, in the de-neutralization step, the regenerated purified water is discharged into a wastewater treatment plant to be treated twice by the wastewater treatment plant. After removing the impurities, regain clean water without impurities. The method for regenerating a high-hardness wastewater containing heavy metals according to claim 1 or 2, wherein the adsorbent is powder activated carbon, granular activated carbon, fibrous activated carbon, regenerated activated carbon, clay or ion exchange. Resin. The method for regenerating a high-hardness wastewater containing heavy metals according to claim 1 or 2, wherein the oxidizing agent is a dichromate solution, a permanganate solution, an ozone gas, and a catalytic homogeneous catalyst film. Or a catalytic heterogeneous catalyst film.