Treatment method of fly ash washing high-salinity wastewater

Abstract

The invention relates to the technical field of fly ash treatment, in particular to a treatment method of fly ash washing high-salinity wastewater, which comprises the following steps: A) stirring and mixing the fly ash washing high-salinity wastewater and a flocculating agent for flocculation; adjusting the pH (Potential of Hydrogen) value of the supernate to 8.5 to 9.5; b) stirring and mixing the treated wastewater with sodium sulfide and a flocculating agent for removing heavy substances, and then carrying out solid-liquid separation; c) stirring and mixing the wastewater subjected to solid-liquid separation with sodium sulfate for primary calcium removal and solid-liquid separation; d) stirring and mixing the wastewater treated in the step C), sodium carbonate and a flocculating agent for secondary calcium removal and solid-liquid separation; e) filtering the wastewater treated in the step D), mixing with an oxidizing agent, and performing ultrafiltration; and F) adjusting the pH value of the ultra-filtered wastewater to 6.5-7.5, filtering with activated carbon, and carrying out nanofiltration to obtain a purified water body. The treatment method provided by the invention can realize efficient treatment of the fly ash washing high-salinity wastewater, and is simple to operate, relatively low in energy consumption and relatively low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of fly ash treatment, and in particular to a method for treating high-salt wastewater from fly ash washing. Background Art

[0002] In modern industrial production, fly ash refers to solid waste generated during the combustion process, usually from the combustion process of materials such as coal, biomass or garbage. Fly ash washing refers to the water washing of fly ash produced after the incineration of waste to extract soluble salts and other valuable components. The wastewater after fly ash washing is usually high-salt wastewater, containing a large amount of high-concentration salt substances, including chlorides, sulfates, sodium ions, etc. Traditional methods for treating water-washed wastewater mainly include leaching, crystallization and membrane technology. However, traditional methods have problems such as incomplete solid-liquid separation and high solution treatment costs, making it difficult to achieve efficient treatment and recycling of high-salt wastewater.

[0003] Existing treatment methods mainly include nanofiltration salt separation, conventional ultrafiltration + nanofiltration and electrochemical methods. However, these methods have certain limitations: although nanofiltration salt separation can achieve ion separation and purification of salt solutions, the nanofiltration membrane is easily blocked in a high-salt environment, resulting in unstable operation; although conventional ultrafiltration + nanofiltration can improve the efficiency of solid-liquid separation, the cleaning frequency is high and the operating cost is relatively high; although the electrochemical method can achieve efficient separation, it has high energy consumption, complex operation and high cost. These problems limit the further application and promotion of existing treatment methods, and it is necessary to seek a new treatment method to solve these problems. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for treating high-salt wastewater from fly ash washing, which can achieve efficient treatment of high-salt wastewater from fly ash washing, and has simple operation, low energy consumption and low cost.

[0005] The present invention provides a method for treating high-salt wastewater from fly ash washing, comprising the following steps:

[0006] A) mixing the fly ash washing high-salt wastewater with a flocculant to perform flocculation; adjusting the pH value of the supernatant after flocculation to 8.5-9.5;

[0007] B) mixing the wastewater treated in step A) with sodium sulfide and a flocculant, removing weight, and then separating the solid from the liquid;

[0008] C) mixing the wastewater after solid-liquid separation in step B) with sodium sulfate, performing primary decalcification, and then performing solid-liquid separation;

[0009] D) mixing the wastewater after solid-liquid separation in step C), sodium carbonate and a flocculant, performing secondary decalcification, and then performing solid-liquid separation;

[0010] E) filtering the wastewater after solid-liquid separation in step D), and then mixing it with an oxidant for ultrafiltration;

[0011] F) adjusting the pH value of the wastewater after ultrafiltration to 6.5-7.5, filtering with activated carbon, and then performing nanofiltration to obtain purified water.

[0012] Preferably, in step A), in the fly ash washing high-salt wastewater, Ca 2+ The content is 35000~45000mg / L, Pb 2+ The content is 100~270mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 1000~1400mg / L, CO3 2- The content is 0-10 mg / L, the particulate matter content is 100-500 mg / L, the COD content is 1000-4000 mg / L; the pH value is 8.5-9.5.

[0013] Preferably, in step A), the flocculant is polyacrylamide;

[0014] The mass ratio of the fly ash washing high-salt wastewater to the flocculant is 1000000:2-10.

[0015] Preferably, in step A), the reagent for adjusting the pH value of the supernatant after flocculation is a hydrochloric acid solution with a mass concentration of 29% to 31%.

[0016] Preferably, in step B), the flocculant is polyacrylamide;

[0017] The mass ratio of the treated wastewater, sodium sulfide and flocculant in step A) is 1000000:580-1565:2-10.

[0018] Preferably, in step C), the mass ratio of the wastewater after solid-liquid separation in step B) to sodium sulfate is 1000:425-546.

[0019] Preferably, in step D), the flocculant is polyacrylamide;

[0020] The mass ratio of the wastewater after solid-liquid separation in step C), sodium carbonate and flocculant is 100000:600-800:2-10.

[0021] Preferably, in step E), the oxidant is ozone or hydrogen peroxide;

[0022] The mass ratio of the filtered wastewater to the oxidant is 100:100-425.

[0023] Preferably, in step E), the ultrafiltration uses a ceramic ultrafiltration membrane; the main material of the ceramic ultrafiltration membrane is Al2O3, the flux is 150-500LMH, and the pore size is 30nm.

[0024] Preferably, in step F), the reagent for adjusting the pH value of the wastewater after ultrafiltration is a hydrochloric acid solution with a mass concentration of 29% to 31%;

[0025] The nanofiltration membrane adopts the Durafoul nanofiltration membrane series, which is made of composite polyamide material.

[0026] The invention provides a method for treating high-salt wastewater from fly ash washing, comprising the following steps: A) stirring and mixing the high-salt wastewater from fly ash washing with a flocculant to perform flocculation; adjusting the pH value of the supernatant after the flocculation to 8.5-9.5; B) stirring and mixing the wastewater treated in step A) with sodium sulfide and a flocculant to perform weight removal, and then performing solid-liquid separation; C) stirring and mixing the wastewater after the solid-liquid separation in step B) with sodium sulfate to perform primary calcium removal, and then performing solid-liquid separation; D) stirring and mixing the wastewater after the solid-liquid separation in step C), sodium carbonate and a flocculant to perform secondary calcium removal, and then performing solid-liquid separation; E) filtering the wastewater after the solid-liquid separation in step D), and then mixing with an oxidant to perform ultrafiltration; F) adjusting the pH value of the wastewater after the ultrafiltration to 6.5-7.5, filtering with activated carbon, and then performing nanofiltration to obtain a purified water body. The treatment method provided by the present invention can achieve efficient treatment of high-salt wastewater from fly ash washing, can run stably, and has simple operation, low energy consumption and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A process flow chart for treating high-salt wastewater from fly ash washing provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention provides a method for treating high-salt wastewater from fly ash washing, comprising the following steps:

[0030] A) mixing the fly ash washing high-salt wastewater with a flocculant to perform flocculation; adjusting the pH value of the supernatant after flocculation to 8.5-9.5;

[0031] B) mixing the wastewater treated in step A) with sodium sulfide and a flocculant, removing weight, and then separating the solid from the liquid;

[0032] C) mixing the wastewater after solid-liquid separation in step B) with sodium sulfate, performing primary decalcification, and then performing solid-liquid separation;

[0033] D) mixing the wastewater after solid-liquid separation in step C), sodium carbonate and a flocculant, performing secondary decalcification, and then performing solid-liquid separation;

[0034] E) filtering the wastewater after solid-liquid separation in step D), and then mixing it with an oxidant for ultrafiltration;

[0035] F) adjusting the pH value of the wastewater after ultrafiltration to 6.5-7.5, filtering with activated carbon, and then performing nanofiltration to obtain purified water.

[0036] Figure 1 A process flow chart for treating high-salt wastewater from fly ash washing provided in one embodiment of the present invention.

[0037] In step A):

[0038] The fly ash washing high-salt wastewater is stirred and mixed with a flocculant to perform flocculation; and the pH value of the supernatant after flocculation is adjusted to 8.5-9.5.

[0039] In certain embodiments of the present invention, the fly ash washing high-salinity wastewater contains Ca 2+ The content is 35000~45000mg / L, Pb 2+ The content is 100~270mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 1000~1400mg / L, CO3 2- The content is 0-10 mg / L, the particulate matter content is 100-500 mg / L, the COD content is 1000-4000 mg / L; the pH value is 8.5-9.5.

[0040] Specifically, in the fly ash washing high-salt wastewater, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 250mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 1200mg / L, CO3 2- The content is 0mg / L, the particulate matter content is 200mg / L, the COD content is 2000mg / L; the pH value is 9.5.

[0041] In certain embodiments of the present invention, the flocculant is polyacrylamide (PAM).

[0042] The mass ratio of the fly ash washing high-salt wastewater to the flocculant is 1000000:2-10, such as 1000000:8-10, specifically 1000000:10.

[0043] The flocculation can be performed in a raw water collection tank.

[0044] In certain embodiments of the present invention, in the supernatant after flocculation, Ca 2+ The content is 35000~45000mg / L, Pb 2+ The content is 100~270mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 1000~1400mg / L, CO3 2- The content is 0-10mg / L, the particulate matter content is 0-200mg / L, and the COD content is 1000-4000mg / L.

[0045] Specifically, in the supernatant after flocculation, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 250mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 1200mg / L, CO3 2- The content is 0mg / L, the particulate matter content is 100mg / L, and the COD content is 2000mg / L.

[0046] After flocculation, the supernatant was separated.

[0047] In certain embodiments of the present invention, the reagent for adjusting the pH value of the supernatant after flocculation is a hydrochloric acid solution with a mass concentration of 29% to 31%, such as 31%.

[0048] In the present invention, the pH value of the supernatant after flocculation is adjusted to 8.5-9.5 to precipitate most of the Pb in the wastewater. 2+ Specifically, the pH value of the supernatant after flocculation is adjusted to 9.

[0049] In step B):

[0050] The wastewater treated in step A) is stirred and mixed with sodium sulfide and a flocculant to remove weight, and then the solid and liquid are separated.

[0051] In certain embodiments of the present invention, the flocculant is polyacrylamide (PAM).

[0052] In certain embodiments of the present invention, the mass ratio of the wastewater treated in step A), sodium sulfide and flocculant is 1000000:580-1565:2-10, such as 1000000:1300-1565:8-10, specifically 1000000:1449:10.

[0053] In the present invention, sodium sulfide is added to remove the remaining Pb in the wastewater. 2+ The de-weighting is carried out in a de-weighting tank.

[0054] In certain embodiments of the present invention, the solid-liquid separation method is centrifugation, and specifically centrifugation can be performed using a horizontal screw centrifuge.

[0055] In certain embodiments of the present invention, in the wastewater after solid-liquid separation, Ca 2+ The content is 35000~45000mg / L, Pb 2+ The content is 0~100mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 1000~1400mg / L.

[0056] In certain embodiments, in the wastewater after solid-liquid separation, Pb 2+ The content is 0-10mg / L.

[0057] Specifically, in the wastewater after solid-liquid separation, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 1200mg / L.

[0058] In step C):

[0059] The wastewater after solid-liquid separation in step B) is stirred and mixed with sodium sulfate to perform primary calcium removal, and then solid-liquid separation is performed.

[0060] In certain embodiments of the present invention, the mass ratio of the wastewater after solid-liquid separation in step B) to sodium sulfate is 1000:425-546, such as 1000:494. Sodium sulfate is added to remove most of the Ca in the wastewater. 2+ .

[0061] The primary decalcification is carried out in a primary decalcification reaction tank.

[0062] In certain embodiments of the present invention, the solid-liquid separation method is filter pressing, and specifically a plate and frame filter press can be used.

[0063] In certain embodiments of the present invention, in the wastewater after solid-liquid separation, Ca 2+ The content is 200~1000mg / L, Pb 2+ The content is 0~100mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 4000~8000mg / L.

[0064] Specifically, in the wastewater after solid-liquid separation, Ca 2+ The content is 600mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 6000mg / L.

[0065] In step D):

[0066] The wastewater after solid-liquid separation in step C), sodium carbonate and flocculant are stirred and mixed, and secondary calcium removal is performed, followed by solid-liquid separation.

[0067] In certain embodiments of the present invention, the flocculant is polyacrylamide (PAM).

[0068] In certain embodiments of the present invention, the mass ratio of the wastewater after solid-liquid separation in step C), sodium carbonate and flocculant is 100000:600-800:2-10, such as 100000:709:10. The role of adding sodium carbonate is to remove the remaining Ca in the wastewater. 2+ .

[0069] The secondary decalcification is carried out in a secondary decalcification reaction tank.

[0070] In certain embodiments of the present invention, the solid-liquid separation method is filter pressing, and specifically a plate and frame filter press can be used.

[0071] In certain embodiments of the present invention, in the wastewater after solid-liquid separation, Ca 2+ The content is 0~200mg / L, Pb 2+ The content is 0~100mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 4000~8000mg / L, CO3 2- The content of water is 0-500mg / L, and the content of particulate matter is 0-200mg / L.

[0072] Specifically, in the wastewater after solid-liquid separation, Ca 2+The content is 100mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 6000mg / L, CO3 2- The content of is 300mg / L and the content of particulate matter is 200mg / L.

[0073] In step E):

[0074] The wastewater after solid-liquid separation in step D) is filtered and then mixed with an oxidant for ultrafiltration.

[0075] The filtration is used to remove larger particles and foreign matter to ensure the stable operation of the ceramic ultrafiltration membrane. The filtration is performed in a multi-media filter.

[0076] In certain embodiments of the present invention, the content of particulate matter in the filtered wastewater is 0-100 mg / L. Specifically, the content of particulate matter in the filtered wastewater is 30 mg / L.

[0077] In some embodiments of the present invention, the oxidant is ozone or hydrogen peroxide. The mass ratio of the filtered wastewater to the oxidant is 100:100-425, such as 100:425. The oxidant is used to reduce the COD content and remove the residual PAM in the solution to ensure the stable operation of the ceramic ultrafiltration membrane and the nanofiltration membrane.

[0078] In certain embodiments of the present invention, the ultrafiltration uses a ceramic ultrafiltration membrane. The main material of the ceramic ultrafiltration membrane is Al2O3, the flux is 150-500LMH, and the pore size is 30nm. After ultrafiltration, the fly ash removal rate with a particle size of 1-100μm in the wastewater is close to 100%. In this step, the ceramic ultrafiltration membrane is used for further solid-liquid separation to ensure the normal operation of subsequent nanofiltration. In the present invention, the ceramic ultrafiltration membrane can operate stably in a high-particle, high-oxidizing environment, reduce the cleaning frequency, and improve the operating stability.

[0079] In certain embodiments of the present invention, the particle content in the wastewater after ultrafiltration is 0-10 mg / L, such as 0.5-1.5 mg / L. Specifically, the particle content in the wastewater after ultrafiltration is 1 mg / L.

[0080] In step F):

[0081] The pH value of the wastewater after ultrafiltration is adjusted to 6.5-7.5, and then filtered with activated carbon and then nanofiltered to obtain purified water.

[0082] In certain embodiments of the present invention, the reagent for adjusting the pH value of the wastewater after ultrafiltration is a hydrochloric acid solution with a mass concentration of 29% to 31%, such as 31%. Specifically, the pH value of the wastewater after ultrafiltration is adjusted to 7. After adjusting the pH value, the CO3 2- Converted to HCO3 - .

[0083] In certain embodiments of the present invention, Pb 2+ The content of Pb in the wastewater after activated carbon filtration is 0-10 mg / L, such as 0-5 mg / L. 2+ The content is 1mg / L.

[0084] In certain embodiments of the present invention, the nanofiltration membrane adopts Durafoul nanofiltration membrane series (Veolia). Compared with other series, Durafoul nanofiltration membrane elements have lower flow rate and higher desalination rate. The material is TMF material, and the average MgSO4 retention rate is 98.5%. Nanofiltration technology separates divalent ions from monovalent ions in the solution through a special nanofiltration membrane. The purpose of this step is to avoid severe scaling and high energy consumption during the evaporation of the solution, and to reduce the impurity content in the solution.

[0085] In certain embodiments of the present invention, in the purified water, Ca 2+ The content is 0~10mg / L, Pb 2+ The content is 0mg / L, NO3 - The content is 0~100mg / L, SO4 2- The content is 100~500mg / L, CO3 2- The content is 0-30mg / L, the particulate matter content is 0mg / L, and the COD content is 10-25mg / L.

[0086] Specifically, in the purified water, Ca 2+ The content is 5mg / L, Pb 2+ The content is 0mg / L, NO3 - The content is 80mg / L, SO4 2- The content is 300mg / L, CO3 2- The content is 15mg / L, the particulate matter content is 0mg / L, and the COD content is 15mg / L.

[0087] The present invention has no particular limitation on the two raw materials used above, and they can be commonly available on the market.

[0088] In order to further illustrate the present invention, a method for treating high-salt wastewater from fly ash washing provided by the present invention is described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0089] Example 1

[0090] In the high-salinity wastewater of fly ash washing, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 250mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 1200mg / L, CO3 2- The content is 0mg / L, the particulate matter content is 200mg / L, the COD content is 2000mg / L; the pH value is 9.5.

[0091] The method for treating high-salt wastewater from fly ash washing includes the following steps:

[0092] 1) The fly ash washing high-salt wastewater and the flocculant (PAM) are stirred and mixed in a raw water collection tank, wherein the mass ratio of the fly ash washing high-salt wastewater to the flocculant is 1000000:10, and flocculation is performed;

[0093] In the supernatant after flocculation, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 250mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 1200mg / L, CO3 2- The content is 0mg / L, the particulate matter content is 100mg / L, and the COD content is 2000mg / L;

[0094] After flocculation, the supernatant was separated; and the pH value of the supernatant was adjusted to 9 using a hydrochloric acid solution with a mass concentration of 31%;

[0095] 2) stirring and mixing the wastewater treated in step 1), sodium sulfide and flocculant (PAM) in a deweighting tank to remove weight, wherein the mass ratio of the wastewater treated in step 1), sodium sulfide and flocculant (PAM) is 1000000:1449:10;

[0096] The water after deweighting is centrifuged in a horizontal screw centrifuge;

[0097] In the wastewater after centrifugation, Ca 2+ The content is 40666 mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO42- The content is 1200mg / L;

[0098] 3) stirring and mixing the wastewater after centrifugation in step 2) with sodium sulfate in a primary decalcification reaction tank to perform primary decalcification; the mass ratio of the wastewater after centrifugation in step 2) to sodium sulfate is 1000:494;

[0099] The wastewater after primary decalcification is filtered through a plate and frame filter press;

[0100] In the wastewater after the filter press, Ca 2+ The content is 600mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 6000mg / L;

[0101] 4) stirring and mixing the wastewater after the filter press in step 3), sodium carbonate and flocculant (PAM) in a secondary decalcification reaction tank to perform secondary decalcification; the mass ratio of the wastewater after centrifugation in step 3), sodium carbonate and flocculant (PAM) is 100000:709:10;

[0102] The wastewater after secondary decalcification is filtered through a plate and frame filter press;

[0103] In the wastewater after the filter press, Ca 2+ The content is 100mg / L, Pb 2+ The content is 10mg / L, NO3 - The content is 1600mg / L, SO4 2- The content is 6000mg / L, CO3 2- The content of is 300mg / L, and the content of particulate matter is 200mg / L;

[0104] 5) filtering the wastewater after the filter press in step 4) in a multi-media filter; the particulate matter content in the filtered wastewater is 30 mg / L;

[0105] The filtered wastewater is mixed with an oxidant (hydrogen peroxide) at a mass ratio of 100:425, and then ultrafiltration is performed; the ultrafiltration uses a ceramic ultrafiltration membrane; the main material of the ceramic ultrafiltration membrane is Al2O3, the flux is 150-500LMH, and the pore size is 30nm; the particle content in the wastewater after ultrafiltration is 1mg / L;

[0106] 6) Using a 31% hydrochloric acid solution to adjust the pH value of the ultrafiltered wastewater to 7, and then filtering it with activated carbon; in the wastewater filtered with activated carbon, Pb 2+ The content is 1mg / L;

[0107] Then nanofiltration is performed to obtain purified water;

[0108] The nanofiltration membrane adopts Durafoul nanofiltration membrane series (Veolia), made of TMF material;

[0109] In the purified water, Ca 2+ The content is 5mg / L, Pb 2+ The content is 0mg / L, NO3 - The content is 80mg / L, SO4 2- The content is 300mg / L, CO3 2- The content is 15mg / L, the particulate matter content is 0mg / L, and the COD content is 15mg / L.

[0110] It can be calculated that the treatment method of the present invention can reduce the Ca 2+ The removal rate is 99%, Pb 2+ The removal rate of NO3 is 96%. - The removal rate is 95%, SO4 2- The removal rate of argon is 75%, the removal rate of particulate matter is 99%, and the removal rate of COD is 99%.

[0111] Comparative Example 1

[0112] The difference from Example 1 is:

[0113] Swap the order of step 2) and step 3):

[0114] 2) stirring and mixing the wastewater treated in step 1) with sodium sulfate in a primary decalcification reaction tank to perform primary decalcification; the mass ratio of the wastewater treated in step 1) to sodium sulfate is 1000:494;

[0115] The wastewater after primary decalcification is filtered through a plate and frame filter press;

[0116] 3) stirring and mixing the wastewater treated in step 2), sodium sulfide and flocculant (PAM) in a deweighting tank to remove weight, wherein the mass ratio of the wastewater treated in step 2), sodium sulfide and flocculant (PAM) is 1000000:1449:10;

[0117] The deweighted water is centrifuged in a horizontal screw centrifuge.

[0118] It can be calculated that the treatment method of the present invention can reduce the Ca 2+ The removal rate is 90%, Pb 2+ The removal rate is 90%, NO3 - The removal rate is 95%, SO4 2-The removal rate of argon is 60%, the removal rate of particulate matter is 95%, and the removal rate of COD is 95%.

[0119] Comparative Example 2

[0120] The difference from Example 1 is:

[0121] Swap the order of step 3) and step 4):

[0122] 3) stirring and mixing the wastewater treated in step 2), sodium carbonate and flocculant (PAM) in a primary decalcification reaction tank to perform primary decalcification; the mass ratio of the wastewater treated in step 2), sodium carbonate and flocculant (PAM) is 100000:709:10;

[0123] The wastewater after primary decalcification is filtered through a plate and frame filter press;

[0124] 4) stirring and mixing the wastewater treated in step 3) with sodium sulfate in a secondary decalcification reaction tank to perform secondary decalcification; the mass ratio of the wastewater treated in step 3) to sodium sulfate is 1000:494;

[0125] The wastewater after secondary decalcification is filtered through a plate and frame filter press.

[0126] It can be calculated that the treatment method of the present invention can reduce the Ca 2+ The removal rate of Pb is 95%. 2+ The removal rate of NO3 is 96%. - The removal rate is 95%, SO4 2- The removal rate of argon is 70%, the removal rate of particulate matter is 97%, and the removal rate of COD is 97%.

[0127] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating fly ash washing high-salt wastewater, comprising the following steps: A) mixing the fly ash washing high-salt wastewater with a flocculant to perform flocculation; adjusting the pH value of the supernatant after flocculation to 8.5-9.5; B) mixing the wastewater treated in step A) with sodium sulfide and a flocculant, removing weight, and then separating the solid from the liquid; C) mixing the wastewater after solid-liquid separation in step B) with sodium sulfate, performing primary decalcification, and then performing solid-liquid separation; D) mixing the wastewater after solid-liquid separation in step C), sodium carbonate and a flocculant, performing secondary decalcification, and then performing solid-liquid separation; E) filtering the wastewater after solid-liquid separation in step D), and then mixing it with an oxidant for ultrafiltration; F) adjusting the pH value of the wastewater after ultrafiltration to 6.5-7.5, filtering with activated carbon, and then performing nanofiltration to obtain purified water.

2. The processing method according to claim 1, characterized in that: In step A), the fly ash washing high-salinity wastewater contains Ca 2+ The content is 35000~45000mg / L, Pb 2+ The content is 100~270mg / L, NO3 - The content is 1400~1800mg / L, SO4 2- The content is 1000~1400mg / L, CO3 2- The content is 0-10 mg / L, the particulate matter content is 100-500 mg / L, the COD content is 1000-4000 mg / L; the pH value is 8.5-9.

5.

3. The processing method according to claim 1, characterized in that: In step A), the flocculant is polyacrylamide; The mass ratio of the fly ash washing high-salt wastewater to the flocculant is 1000000:2-10.

4. The processing method according to claim 1, characterized in that: In step A), the reagent for adjusting the pH value of the supernatant after flocculation is a hydrochloric acid solution with a mass concentration of 29% to 31%.

5. The processing method according to claim 1, characterized in that: In step B), the flocculant is polyacrylamide; The mass ratio of the treated wastewater, sodium sulfide and flocculant in step A) is 1000000:580-1565:2-10.

6. The processing method according to claim 1, characterized in that: In step C), the mass ratio of the wastewater after solid-liquid separation in step B) to sodium sulfate is 1000:425-546.

7. The processing method according to claim 1, characterized in that: In step D), the flocculant is polyacrylamide; The mass ratio of the wastewater after solid-liquid separation in step C), sodium carbonate and flocculant is 100000:600-800:2-10.

8. The processing method according to claim 1, characterized in that: In step E), the oxidant is ozone or hydrogen peroxide; The mass ratio of the filtered wastewater to the oxidant is 100:100-425.

9. The processing method according to claim 1, characterized in that: In step E), the ultrafiltration uses a ceramic ultrafiltration membrane; the main material of the ceramic ultrafiltration membrane is Al2O3, the flux is 150-500LMH, and the pore size is 30nm.

10. The processing method according to claim 1, characterized in that: In step F), the reagent for adjusting the pH value of the wastewater after ultrafiltration is a hydrochloric acid solution with a mass concentration of 29% to 31%; The nanofiltration membrane adopts the Durafoul nanofiltration membrane series, which is made of composite polyamide material.

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