Wastewater reuse treatment method

Abstract

The invention discloses a wastewater reuse treatment method. The method comprises the following steps: S1, mixing wastewater, a biological agent, alkali and a flocculant I, and carrying out solid-liquid separation to obtain supernate I and bottom slag I; s2, concentrating the supernatant I to obtain produced water I and produced water II; s3, mixing the produced water II, the modified bottom slag I and a flocculating agent II, performing crystallization treatment, and performing solid-liquid separation to obtain supernate II and bottom slag II. The method comprises the following steps: concentrating supernate I, concentrating salt which takes sulfate radicals as main components in the wastewater into produced water II, and then crystallizing to separate salt which takes calcium sulfate as main components from the wastewater in the form of crystallized products. The method does not involve agent consumption of a dual-alkali method in a traditional pretreatment-membrane-evaporation process and energy consumption of evaporation and concentration, the treatment cost is low, and the open circuit efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a wastewater reuse treatment method. Background Art

[0002] In the typical mining, smelting, and processing of non-ferrous metals, a large amount of heavy metal wastewater will be generated. In addition, due to the conversion of sulfur in sulfide ores in the non-ferrous metal industry, a large amount of sulfate ions coexist in the wastewater, forming sulfate system heavy metal wastewater. The conventional treatment requirement for this type of wastewater is the deep removal of heavy metals, and sulfidation, neutralization, flocculation and other processes are often used. Among them, neutralization treatment is the lowest cost and the most frequently used. The neutralizer used for neutralization is usually calcium carbonate and calcium hydroxide. The introduction of calcium ions in the neutralizer will increase the saturation of calcium sulfate in the wastewater. Wastewater containing saturated calcium sulfate will scale and cause blockage of pipelines and equipment during discharge and reuse, especially in reuse occasions with special requirements for scaling problems and salt content, such as cooling water, circulating water, process water, etc. The reuse of wastewater containing salt, sulfate ions, and calcium will affect equipment performance and process indicators.

[0003] If it is necessary to completely remove the salt, sulfate and other components in the wastewater, the conventional process is the pretreatment-membrane-evaporation combined process. Through pretreatment, the components that affect the membrane operation are removed, such as the double alkali method to remove calcium and magnesium ions in the wastewater, and the flocculation method to remove fluoride ions in the wastewater. The pretreated effluent enters the membrane concentration process, and the generated fresh water is reused as recycled water. The salt in the wastewater basically enters the membrane concentrated water, and then the salt is removed from the wastewater system in the form of crystals through evaporation and other methods. The double alkali method of this treatment process consumes a large amount of reagents, and the hot steam and electricity consumption during the evaporation process are large. Although the anions and cations are completely removed, there are problems such as a long process flow, a large amount of reagents, and high operating costs.

[0004] Therefore, it is necessary to develop a heavy metal wastewater reuse treatment method with simple process, low treatment cost and open circuit efficiency that meets usage requirements. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention provides a heavy metal wastewater reuse treatment method, which has a simple process, low treatment cost, and an open circuit efficiency that meets the use requirements.

[0006] According to a first aspect of the present invention, a method for recycling heavy metal wastewater is provided, comprising the following steps:

[0007] S1, mixing wastewater, biological agent, alkali and flocculant I, and performing solid-liquid separation to obtain supernatant I and bottom residue I;

[0008] S2, concentrating the supernatant I to obtain produced water I and produced water II;

[0009] S3, mixing the produced water II, the modified bottom residue I and the flocculant II, performing crystallization treatment, and performing solid-liquid separation to obtain a supernatant II and bottom residue II;

[0010] The raw materials of the biological preparation include bacterial liquid obtained by culturing chemoautotrophic bacteria; and iron salt or ferrous salt;

[0011] The modified bottom slag I is prepared by the following method:

[0012] (1) filtering the bottom residue I to obtain filter press bottom residue I; mixing and stirring the filter press bottom residue I, limestone powder, sawdust and sulfuric acid; obtaining a precursor;

[0013] (2) The precursor is granulated, calcined, cooled and crushed to obtain modified bottom slag I.

[0014] The wastewater reuse treatment method according to the embodiment of the present invention has at least the following beneficial effects:

[0015] The present invention firstly mixes wastewater, biological agent, alkali and flocculant to perform weight removal treatment to obtain supernatant I and bottom residue I, concentrates the supernatant I to obtain produced water I and produced water II, and crystallizes the produced water II and the modified bottom residue I to obtain supernatant II.

[0016] The present invention adopts a concentration treatment method for the supernatant I, concentrates the salts in the wastewater with sulfate as the main component into the produced water II, and then separates the salts mainly composed of calcium sulfate from the wastewater in the form of crystallized products through crystallization treatment. The present invention does not involve the consumption of reagents of the double alkali method in the traditional pretreatment-membrane-evaporation process and the energy consumption of evaporation concentration, and has low processing cost.

[0017] Further, the present invention modifies the bottom slag I of the biological agent weight removal treatment with limestone powder, sawdust, and sulfuric acid, on the one hand, to achieve the reuse of the system of the bottom slag for weight removal of solid wastewater, and on the other hand, through modification, the efficiency of the crystallization treatment is promoted. In the modification process, the bottom slag I and limestone powder form a large amount of active iron, calcium and other metal ions under the regulation of sulfuric acid, and after mixing with sawdust and sintering and pulverizing, the modified bottom slag I formed has the characteristics of multi-group, multi-porosity, high specific surface area, etc. In the subsequent crystallization process, the active groups such as iron, calcium, and sulfate on the surface can efficiently form adsorption on ions such as calcium ions and sulfate ions in the wastewater, destroy the charge balance between ions in the micro-region, form a chain induction effect, and significantly improve the solid-liquid open circuit efficiency of the salt in the crystallization process.

[0018] According to a preferred embodiment of the present invention, the substances in the wastewater described in the present invention include sulfate and heavy metal ions.

[0019] According to a preferred embodiment of the present invention, the mass ratio of the filter press bottom residue I, limestone powder, sawdust and sulfuric acid is (6-10):(2-3):(1-3):1.

[0020] According to a preferred embodiment of the present invention, the hydrogen ion concentration in the sulfuric acid is 10 -3 ~10 -5 mol / L.

[0021] According to a preferred embodiment of the present invention, the biological agent is prepared by the following method:

[0022] a. Cultivating the chemoautotrophic bacteria in a 9K medium supplemented with FeSO4·7H2O to obtain a bacterial solution;

[0023] b. Stirring the bacterial solution obtained by culturing in step a with a salt containing iron or ferrous salt to obtain a biological preparation.

[0024] According to a preferred embodiment of the present invention, the chemoautotrophic bacteria include Thiobacillus ferrooxidans or Thiobacillus thiooxidans.

[0025] According to a preferred embodiment of the present invention, the dosage of the biological agent is 0.1-2.4 g / L.

[0026] According to a preferred embodiment of the present invention, the alkali includes at least one of calcium hydroxide and sodium hydroxide.

[0027] According to a preferred embodiment of the present invention, the flocculant I and the flocculant II are independently selected from at least one of PAM, polyaluminium chloride and polyferric chloride.

[0028] According to a preferred embodiment of the present invention, the concentration of the alkali is 0.5-5 g / L.

[0029] According to a preferred embodiment of the present invention, the addition amount of flocculant II and flocculant II is independently selected from 1 to 50 g / m 3 .

[0030] According to a preferred embodiment of the present invention, in step S2, the concentration treatment includes at least one of reverse osmosis concentration, electrodialysis concentration and thermal concentration.

[0031] According to a preferred embodiment of the present invention, the particle size of the pulverized product is 1.7 μm to 30 μm.

[0032] According to a preferred embodiment of the present invention, the calcination temperature is 400°C to 900°C.

[0033] According to a preferred embodiment of the present invention, the calcination time is 15 to 60 minutes.

[0034] According to a preferred embodiment of the present invention, in step (1), the stirring speed is 2000-5000 r / min; and the stirring time is 30-60 min.

[0035] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0037] Figure 1 This is a processing flow chart of Example 1 of the present invention;

[0038] Figure 2 1 is a processing effect diagram of Example 1 of the present invention;

[0039] Figure 3 This is a processing effect diagram of Example 2 of the present invention;

[0040] Figure 4 It is a processing effect diagram of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0041] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0042] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0043] The raw materials used in the embodiments and comparative examples of the present invention are as follows:

[0044] Biological preparation: prepared according to Example 1 of patent CN 104478160 A.

[0045] Alkali: milk of lime; commercially available.

[0046] Flocculant: PAM; commercially available.

[0047] The calculation formula for the open circuit rate is: (inlet water concentration - outlet water concentration) / inlet water concentration*100%.

[0048] TDS test: Leizhi DZS-706F multi-parameter analyzer.

[0049] The ion concentration of each substance was determined by ion chromatography.

[0050] Example 1

[0051] This example provides a wastewater reuse treatment method; the unit treatment cost is about 6.2 yuan / m 3 , the processing flow diagram is as follows Figure 1 As shown, the steps are as follows:

[0052] S1, a lead-zinc mine industrial wastewater, in the de-weighting treatment reaction tank, add 0.5g / L biological agent, 1.1g / L calcium hydroxide, 3g / m 3 PAM, performing a weight removal treatment to obtain a supernatant I and a bottom residue I;

[0053] S2, the supernatant I is subjected to reverse osmosis concentration treatment, the reverse osmosis water inlet pressure is 1.4MPa, and the water production rate is 75%, to obtain produced water I and produced water II;

[0054] S3, in the crystallization reaction tank, add the modified bottom slag 1,3g / m 3 PAM and produced water II are crystallized; solid-liquid separation is performed to obtain supernatant II and bottom residue II.

[0055] The modification treatment method of bottom slag I is as follows: the filter press bottom slag I, limestone powder, sawdust and dilute sulfuric acid are mixed in a mass ratio of 7:2:1:1, and the concentration of the dilute sulfuric acid is 10 -4 mol / L, after stirring, granulation, roasting, cooling and crushing, the stirring speed is 3000r / min, the stirring time is 30min, the roasting temperature is 800℃, the roasting time is 30min, and the particle size of the crushed product is ≤13μm.

[0056] The produced water I is directly used as recycled water, and the supernatant II is returned to the degravity treatment reaction tank.

[0057] The ion concentrations of wastewater and treated reuse water are shown in Figure 2 ;from Figure 2 It can be seen that the TDS of the wastewater (raw water) is as high as 3930 mg / L; the TDS content of the produced water I is 182 mg / L, the calcium ion concentration is lower than 10 mg / L, the sulfate ion concentration is lower than 50 mg / L, and the open circuit rate is 99%, which can meet the "Water Quality Standard for Recycled Water for Circulating Cooling Water" (HG / T3923-2007) and can be used as a reuse water with higher water quality requirements such as equipment cooling water.

[0058] Example 2

[0059] This example provides a wastewater reuse treatment method; the unit treatment cost is about 6.0 yuan / m 3 , the steps are as follows:

[0060] S1, a lead-zinc mine industrial wastewater, in the de-weighting treatment reaction tank, add 0.5g / L biological agent, 1.15g / L sodium hydroxide, 40g / m 3 Polyaluminium chloride is subjected to a weight removal treatment to obtain a supernatant I and a bottom slag I;

[0061] S2, the supernatant I is subjected to reverse osmosis concentration treatment, the reverse osmosis water inlet pressure is 1.25MPa, and the water production rate is 77%, to obtain produced water I and produced water II;

[0062] S3, in the crystallization reaction tank, add the modified bottom slag I, 50g / m 3 Polyferric chloride is subjected to crystallization treatment; and solid-liquid separation is performed to obtain supernatant II and bottom residue II.

[0063] The modification treatment method of bottom slag I is as follows: the filter press bottom slag I, limestone powder, sawdust and dilute sulfuric acid are mixed in a mass ratio of 7:2:1:1, and the concentration of the dilute sulfuric acid is 10 -4 mol / L, after stirring, granulation, roasting, cooling and crushing. Among them, the stirring speed is 3000r / min, the stirring time is 30min, the roasting temperature is 800℃, the roasting time is 30min, and the crushed product particle size is ≤13μm.

[0064] The produced water I and the supernatant II are combined and used as recycled water. The ion concentrations of the wastewater and the treated recycled water are shown in Figure 3 The TDS content of the recycled water is 1832 mg / L, the calcium ion open circuit rate is 75%, and the sulfate ion open circuit rate is 77%, which can meet the reuse needs of circulating water, flushing water and other water quality requirements with low requirements.

[0065] Comparative Example

[0066] This example provides a wastewater reuse treatment method; the steps are as follows:

[0067] S1, a lead-zinc mine industrial wastewater, in the de-weighting treatment reaction tank, add 0.5g / L biological agent, 1.15g / L lime milk, 3g / m 3 PAM, performing a weight removal treatment to obtain a supernatant I and a bottom residue I;

[0068] S2, the supernatant I is subjected to reverse osmosis concentration treatment, the reverse osmosis water inlet pressure is 1.25MPa, and the water production rate is 77%, to obtain produced water I and produced water II;

[0069] S3, in the crystallization reaction tank, add II; and add 3g / m 3PAM, crystallization treatment is performed; solid-liquid separation is performed to obtain supernatant II and bottom residue II.

[0070] The produced water I and the supernatant II are combined to obtain the recycled water. The ion concentrations of the original wastewater and the treated recycled water are shown in Figure 4 ;from Figure 4 It can be seen that the TDS content of the combined recycled water is 3472 mg / L, the calcium ion open circuit rate is only 28%, and the sulfate ion open circuit rate is only 22%. Compared with Example 2, the treatment effect is significantly poorer and cannot be used for recycled water.

[0071] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A wastewater reuse treatment method, characterized in that: The steps include: S1, mixing wastewater, biological agent, alkali and flocculant I, and performing solid-liquid separation to obtain supernatant I and bottom residue I; S2, concentrating the supernatant I to obtain produced water I and produced water II; S3, mixing the produced water II, the modified bottom residue I and the flocculant II, performing crystallization treatment, and performing solid-liquid separation to obtain a supernatant II and bottom residue II; The raw materials of the biological preparation include bacterial liquid obtained by culturing chemoautotrophic bacteria; and iron salt or ferrous salt; The modified bottom slag I is prepared by the following method: (1) filtering the bottom residue I to obtain filter press bottom residue I; mixing and stirring the filter press bottom residue I, limestone powder, sawdust and sulfuric acid; obtaining a precursor; (2) The precursor is granulated, calcined, cooled and crushed to obtain modified bottom slag I.

2. The wastewater reuse treatment method according to claim 1, characterized in that: The mass ratio of the filter press bottom residue I, limestone powder, sawdust and sulfuric acid is (6-10):(2-3):(1-3):

1.

3. The wastewater reuse treatment method according to claim 1, characterized in that: The hydrogen ion concentration in the sulfuric acid is 10 -3 ~10 -5 mol / L.

4. The wastewater reuse treatment method according to claim 1, characterized in that: The biological preparation is prepared by the following method: a. Cultivating the chemoautotrophic bacteria in a 9K medium supplemented with FeSO4·7H2O to obtain a bacterial solution; b. The bacterial solution obtained by culturing in step a is reacted with ferrous salt or ferrous salt by stirring to obtain a biological agent.

5. The wastewater reuse treatment method according to claim 1, characterized in that: The feeding amount of the biological agent is 0.1-2.4 g / L.

6. The wastewater reuse treatment method according to claim 1, characterized in that: The alkali includes at least one of calcium hydroxide and sodium hydroxide.

7. The wastewater reuse treatment method according to claim 1, characterized in that: The flocculant I and flocculant II are independently selected from at least one of polyacrylamide, polyaluminium chloride or polyferric sulfate.

8. The wastewater reuse treatment method according to claim 1, characterized in that: In step S2, the concentration treatment includes at least one of reverse osmosis concentration, electrodialysis concentration and thermal concentration.

9. The wastewater reuse treatment method according to claim 1, characterized in that: The particle size of the pulverized product is 1.7 μm to 30 μm.

10. The wastewater reuse treatment method according to claim 1, characterized in that: The calcination temperature is 400°C to 900°C.

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