A method for disinfecting wastewater using pyrite in combination with sodium hypochlorite

Abstract

This invention discloses a method for wastewater disinfection using pyrite in synergy with sodium hypochlorite, belonging to the field of wastewater disinfection technology. Specifically, it includes: adjusting the pH of the wastewater to obtain pH-adjusted wastewater; adding pyrite powder to the pH-adjusted wastewater and mixing it evenly to obtain a pyrite-wastewater system; then adding sodium hypochlorite to the pyrite-wastewater system to obtain a mixed system, and continuing to stir the mixed system for disinfection; after the disinfection reaction is completed, the reaction system is subjected to solid-liquid separation to obtain pyrite residue and disinfected effluent. This invention achieves efficient, broad-spectrum, and safe disinfection through the synergistic effect of the natural mineral pyrite and sodium hypochlorite, reducing the amount of sodium hypochlorite used, enhancing the disinfection effect, broadening the bactericidal spectrum, and effectively inhibiting the formation of carcinogenic disinfection byproducts. The method of this invention is simple to operate, has high disinfection efficiency, produces few byproducts, and has low operating costs, showing broad application prospects in the field of wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater disinfection technology, specifically a method for disinfecting wastewater using pyrite in combination with sodium hypochlorite. Background Technology

[0002] Currently, even after biochemical treatment, industrial wastewater still retains a large amount of fecal coliforms, pathogenic bacteria, and other microbial pollutants, as well as small amounts of recalcitrant organic matter and suspended solids. Sodium hypochlorite disinfection remains the mainstream technology for wastewater disinfection in wastewater treatment plants. Although simple to operate and low in cost, it still has significant shortcomings: First, when used alone, the available chlorine in sodium hypochlorite is easily consumed by organic matter and reducing substances in the wastewater, resulting in poor disinfection effects. To ensure compliance, the dosage of sodium hypochlorite must be increased, which not only drives up the cost of the reagent but may also produce chlorinated disinfection byproducts. Second, for industrial wastewater with high fecal coliform counts, sodium hypochlorite disinfection alone is insufficient to rapidly reduce the bacterial count to below 1000 CFU / L, has poor effectiveness against stubborn pathogens, and the residual chlorine retention is unstable, easily leading to secondary pollution or disinfection failure in subsequent discharges. Furthermore, it is highly pH dependent.

[0003] Therefore, it is of great significance to develop a wastewater disinfection method for sewage treatment plants that can both ensure disinfection effectiveness and control the generation of byproducts. Summary of the Invention

[0004] To address the problems of existing sodium hypochlorite disinfection technologies, such as high disinfection dosage, high operating costs, large amounts of byproducts, poor inactivation effect on stubborn pathogens such as Cryptosporidium and adenovirus, and disinfection efficiency significantly limited by the pH value of the water, the present invention aims to provide a method for wastewater disinfection using pyrite in synergy with sodium hypochlorite, specifically including the following steps: (1) Adjust the pH of the wastewater to obtain the pH-adjusted wastewater.

[0005] (2) Pyrite is crushed and sieved to obtain pyrite powder; pyrite powder is added to the wastewater after pH adjustment and stirred evenly to obtain pyrite-wastewater system; sodium hypochlorite is then added to the pyrite-wastewater system to obtain a mixed system, and the mixed system is further stirred for disinfection.

[0006] (3) After the disinfection reaction is completed, the reaction system is separated into solid and liquid to obtain pyrite residue and disinfected effluent.

[0007] Preferably, in step (1) of the present invention, adjusting the pH of the wastewater specifically means adjusting the pH of the wastewater to 6.0-7.5.

[0008] Preferably, the particle size of the pyrite powder in step (2) of the present invention is 100-200 mesh (the pyrite powder of the present invention is screened by a double-layer sieve, passing through a 100-mesh sieve and being retained in a 200-mesh sieve, and the portion with a particle size of 100-200 mesh is taken).

[0009] Preferably, the concentration of pyrite powder in the pyrite-wastewater system in step (2) of the present invention is 300-400 mg / L.

[0010] Preferably, the concentration of sodium hypochlorite in the mixed system in step (2) of the present invention is 15-30 mg / L, calculated as available chlorine.

[0011] Preferably, the conditions for uniform mixing in step (2) of the present invention are: stirring for 10-15 minutes at a speed of 150-200 r / min.

[0012] Preferably, the conditions for continuing stirring for sterilization in step (2) of the present invention are: stirring for 20-30 minutes at a speed of 150-200 r / min.

[0013] The solid-liquid separation in step (3) of the present invention is carried out by conventional methods. Preferably, the solid-liquid separation method of the present invention is static sedimentation or plate and frame filtration.

[0014] Mechanism of the invention: (1) Step-by-step addition and activation enhancement: Pyrite is added first to ensure its full dispersion, and then sodium hypochlorite is added to avoid local loss of oxidant and improve the utilization rate of effective chlorine; redox reaction occurs at the pyrite interface to generate The cycle continuously catalyzes sodium hypochlorite to produce highly active oxide species, significantly improving the disinfection rate and sterilization depth.

[0015] (2) Suppression of by-product sources: The iron ions dissolved from pyrite hydrolyze to form ferric hydroxide colloids, which adsorb organic matter and suspended matter in wastewater, reducing the combination reaction of organic matter and chlorine, and reducing the amount of chlorinated disinfection by-products such as chloroform by 50%-60%.

[0016] (3) The core reaction consists of the following three steps: ① Cyclic activation and adsorption purification: ② Pyrite activates sodium hypochlorite to form highly reactive oxide species: ③ pH buffering mechanism: Oxidation and Hydrolysis consumption This creates a dynamic acid-base balance, buffering pH fluctuations in wastewater and ensuring the system can stably generate wastewater within a pH range of 6.0-7.5. And HClO.

[0017] This invention provides a method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite, which has the following beneficial effects: (1) The present invention utilizes the synergistic effect of natural mineral pyrite and sodium hypochlorite to achieve a highly efficient, broad-spectrum, and safe disinfection method, which can reduce the amount of sodium hypochlorite used, enhance the disinfection effect, broaden the bactericidal spectrum, and effectively inhibit the generation of carcinogenic disinfection byproducts.

[0018] (2) The raw material of this invention is low-cost natural pyrite, while reducing the amount of sodium hypochlorite added. Under the same disinfection effect, the synergistic system can reduce the effective chlorine dosage of sodium hypochlorite by 20%-30%, directly reducing the consumption of expensive disinfectants. It can also directly utilize existing disinfection tanks, stirring devices, sedimentation tanks / filtration equipment without increasing infrastructure investment and energy consumption. The operation and management are simple, and the overall treatment cost is reduced by 20%-25%.

[0019] (3) This invention uses pyrite and sodium hypochlorite in synergy. The active species generated during the disinfection process have high redox potentials and can directly mineralize organic matter. It contains inorganic ions, and its inactivation rate against fecal coliforms and Cryptosporidium exceeds 98%, which is significantly higher than that of sodium hypochlorite alone for disinfection.

[0020] (4) The disinfection byproducts generated by the present invention are significantly reduced, and the amount of chlorinated disinfection byproducts generated is reduced by 50%-60% compared with traditional methods.

[0021] (5) The present invention has a wide pH range and can operate stably in the pH range of 6.0-7.5, covering the pH conditions of most wastewater. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In the embodiments and comparative examples of this invention, the wastewater from the wastewater treatment plant treated had an ammonia nitrogen concentration of 8 mg / L, a COD concentration of 45 mg / L, and a fecal coliform concentration of [missing information]. The wastewater to be disinfected was obtained from the CFU / L.

[0024] Example 1 A method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite, specifically including the following steps: (1) Use 5% hydrochloric acid or 10% sodium hydroxide solution to adjust the pH of the wastewater to 7.0 to obtain the pH adjusted wastewater.

[0025] (2) Pyrite is crushed and sieved, and the 100-200 mesh portion is taken to obtain pyrite powder; pyrite powder is added to the wastewater after pH adjustment, and the stirrer is turned on for stirring and disinfection. First, the stirring is carried out at a speed of 180 r / min for 12 min to achieve full contact between pyrite and wastewater, and a pyrite-wastewater system is obtained (the concentration of pyrite powder is 350 mg / L); then sodium hypochlorite is added to the pyrite-wastewater system to obtain a mixed system (the concentration of sodium hypochlorite is 20 mg / L based on available chlorine), and the mixed system is stirred at a speed of 180 r / min for 25 min for disinfection.

[0026] (3) After the disinfection reaction is completed, the reaction system is filtered by plate and frame filter (filtration pressure 0.1-0.2MPa) to separate and remove the residue in the system and obtain the disinfected effluent.

[0027] The fecal coliform count in the effluent was determined using a membrane filtration method, and the chloroform content was determined using headspace gas chromatography. The results showed that the fecal coliform count was... CFU / L (fecal coliform removal rate 99.24%), chloroform generation 9.5. The COD removal rate is 30%, which meets the wastewater disinfection and discharge requirements of the sewage treatment plant.

[0028] Example 2 A method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite, specifically including the following steps: (1) Use 5% hydrochloric acid or 10% sodium hydroxide solution to adjust the pH of the wastewater to 6.0 to obtain the pH adjusted wastewater.

[0029] (2) Pyrite is crushed and sieved, and the 100-200 mesh portion is taken to obtain pyrite powder; pyrite powder is added to the wastewater after pH adjustment, and the stirrer is turned on for stirring and disinfection. First, the stirring is carried out for 10 minutes at a speed of 150 r / min to achieve full contact between pyrite and wastewater, and a pyrite-wastewater system is obtained (the concentration of pyrite powder is 400 mg / L); then sodium hypochlorite is added to the pyrite-wastewater system to obtain a mixed system (the concentration of sodium hypochlorite is 30 mg / L based on available chlorine). The mixed system is then stirred for 30 minutes at a speed of 150 r / min for disinfection.

[0030] (3) After the disinfection reaction is completed, the reaction system is filtered by plate and frame filter (filtration pressure 0.1-0.2MPa) to separate and remove the residue in the system and obtain the disinfected effluent.

[0031] The fecal coliform count in the effluent was determined using a membrane filtration method, and the chloroform content was determined using headspace gas chromatography. The results were as follows: fecal coliform count was 3.1 × 10² CFU / L (fecal coliform removal rate was 99.38%), and chloroform formation was 10.2%. The COD removal rate is 30%, which meets the wastewater disinfection and discharge requirements of the sewage treatment plant.

[0032] Example 3 A method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite, specifically including the following steps: (1) Use 5% hydrochloric acid or 10% sodium hydroxide solution to adjust the pH of the wastewater to 6.0 to obtain the pH adjusted wastewater.

[0033] (2) Pyrite is crushed and sieved, and the 100-200 mesh portion is taken to obtain pyrite powder; pyrite powder is added to the wastewater after pH adjustment, and the stirrer is turned on for stirring and disinfection. First, the stirring is carried out at a speed of 200 r / min for 15 min to achieve full contact between pyrite and wastewater, and a pyrite-wastewater system is obtained (the concentration of pyrite powder is 300 mg / L); then sodium hypochlorite is added to the pyrite-wastewater system to obtain a mixed system (the concentration of sodium hypochlorite is 15 mg / L based on available chlorine). The mixed system is then stirred at a speed of 200 r / min for 20 min for disinfection.

[0034] (3) After the disinfection reaction is completed, the reaction system is filtered by plate and frame filter (filtration pressure 0.1-0.2MPa) to separate and remove the residue in the system and obtain the disinfected effluent.

[0035] The fecal coliform count in the effluent was determined using a membrane filtration method, and the chloroform content was determined using headspace gas chromatography. The results showed that the fecal coliform count was 6.9 × 10⁻⁶. 2 CFU / L (fecal coliform removal rate 98.62%), chloroform generation 8.9. The COD removal rate is 25%, which meets the wastewater disinfection and discharge requirements of sewage treatment plants.

[0036] Comparative Example 1 A method for disinfecting wastewater using sodium hypochlorite specifically includes the following steps: (1) Use 5% hydrochloric acid or 10% sodium hydroxide solution to adjust the pH of the wastewater to pH = 7 to obtain the pH adjusted wastewater.

[0037] (2) Add sodium hypochlorite to the wastewater after pH adjustment to obtain a mixed system (the concentration of sodium hypochlorite is 20 mg / L based on available chlorine). Continue to stir the mixed system at a speed of 180 r / min for 25 min for disinfection.

[0038] (3) After the disinfection reaction is completed, the reaction system is filtered by plate and frame filter (filtration pressure 0.1-0.2MPa) to separate and remove the residue in the system and obtain the disinfected effluent.

[0039] The fecal coliform count in the effluent was determined using a membrane filtration method, and the chloroform content was determined using headspace gas chromatography. The results showed that the fecal coliform count was... CFU / L The amount of chloroform produced was 22.7. COD removal rate <5%.

[0040] This invention achieves low-cost disinfection of wastewater treatment plant effluent through the synergistic effect of pyrite and sodium hypochlorite. Pyrite is widely available and inexpensive, and can form a synergistic oxidation system with oxidants. Sodium hypochlorite, after dissolving in water, reacts directly with the reducing agent pyrite to generate a large number of hydroxyl radicals with an oxidation potential higher than that of hypochlorous acid, as well as ferric iron. The hydroxyl radicals non-selectively attack the cell membranes, enzymes, and genetic material of microorganisms, exhibiting extremely high killing efficiency, and are particularly effective against "stubborn" pathogens such as Cryptosporidium and adenovirus. The ferric iron forms ferric hydroxide colloidal precipitate, adsorbing some organic matter and impurities, reducing the consumption of available chlorine by organic matter. Furthermore, the generated ferric iron can further react with S(II) in pyrite. The components react to generate ferrous iron, which continuously activates sodium hypochlorite, thereby enhancing the disinfection effect on industrial wastewater. The method of this invention is simple to operate, has high disinfection efficiency, produces few byproducts, and has low operating costs, making it a promising candidate for wastewater treatment.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite, characterized in that, Specifically, the following steps are included: (1) Adjust the pH of the wastewater to obtain the pH-adjusted wastewater; (2) Pyrite is crushed and sieved to obtain pyrite powder; pyrite powder is added to the wastewater after pH adjustment and stirred to mix evenly to obtain pyrite-wastewater system; sodium hypochlorite is then added to the pyrite-wastewater system to obtain a mixed system, and the mixed system is further stirred for disinfection; (3) After the disinfection reaction is completed, the reaction system is separated into solid and liquid to obtain pyrite residue and disinfected effluent.

2. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The adjustment of wastewater pH in step (1) specifically refers to adjusting the wastewater pH to 6.0-7.

5.

3. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The pyrite powder in step (2) has a particle size of 100-200 mesh.

4. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The concentration of pyrite powder in the pyrite-wastewater system described in step (2) is 300-400 mg / L.

5. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The concentration of sodium hypochlorite in the mixed system described in step (2) is 15-30 mg / L, calculated as available chlorine.

6. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The conditions for uniform mixing in step (2) are: stirring for 10-15 minutes at a speed of 150-200 r / min.

7. The method for disinfecting wastewater using pyrite in conjunction with sodium hypochlorite according to claim 1, characterized in that, The conditions for continuing to stir for sterilization in step (2) are: stirring for 20-30 minutes at a speed of 150-200 r / min.

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