CN108409042A - It is a kind of using qualified discharge as the organic-inorganic heavy metal production wastewater treatment method of core - Google Patents

Abstract

The invention discloses a method for treating organic and inorganic heavy metal production wastewater with standard discharge as the core. The steps of the method are as follows: the copper and nickel wastewater is chemically precipitated in a sequencing batch mixed reaction sedimentation tank, and the effluent enters an intermediate water tank; the chromium-containing wastewater is sequentially The effluent enters the intermediate water tank after passing through the chromium breaking tank and the sequencing batch mixed reaction sedimentation tank; the organic wastewater enters the intermediate water tank after passing through the micro-electrolysis-Fenton reaction tank and the inclined plate sedimentation tank in turn; the three streams of wastewater enter the AO-MBR reactor, and the effluent enters the Out of the pool and then discharged up to standard. The present invention uses micro-electrolysis-Fenton combination to pretreat organic-inorganic heavy metal production wastewater, strengthens the removal of complexed heavy metals and improves the biodegradability of wastewater, and uses the AO-MBR process with strong impact resistance to deeply carry out organic-inorganic composite pollutants Treatment, this process can meet the technical needs of organic and inorganic heavy metal production wastewater treatment in the electroplating industrial park, and ensure that the treated effluent can meet the discharge standards stably.

Description

A treatment method for organic and inorganic heavy metal production wastewater with standard discharge as the core

technical field

The invention belongs to the technical field of sewage treatment, and relates to a standard-reaching treatment method for organic-inorganic compound-polluted heavy metal production wastewater in electroplating industrial parks, and in particular to a method for improving the removal of organic complex heavy metals and refractory organic matter in wastewater, so that the quality of effluent reaches the discharge standard processing method.

Background technique

With the rapid development of my country's economy, the basic processing and manufacturing industry has also developed rapidly. A large number of cities and towns have established surface treatment industrial parks, and some industrial parks produce wastewater that is directly discharged after treatment. Electroplating wastewater is not only complex in composition, but also varies greatly with different plating types. Typical pollutants in wastewater include heavy metal ions such as chromium, copper, nickel, cadmium, and zinc, as well as organic substances such as mineral oil, lipids, and surfactants. , Most of these pollutants are toxic, and some belong to "three harmful" substances, which are extremely harmful to human health and the environment. For heavy metals in electroplating wastewater, chemical precipitation is generally used in the park to form insoluble compounds to precipitate and remove them. This method needs to consume a large amount of chemicals and the generated sediment will produce a large amount of sludge with low density, which will bring problems to the subsequent sludge dewatering and disposal; in addition, due to the presence of complexing agents in the electroplating wastewater, the precipitation method is difficult. Effectively remove complex heavy metals. For the organic matter in the electroplating wastewater, when the park uses the activated sludge method to treat the wastewater, the biodegradability of the wastewater is poor, and the presence of complexed heavy metals will cause stress to the microorganisms, resulting in poor treatment effect of the biochemical unit and unstable system performance, making it difficult to discharge the effluent. standard.

In view of the above problems, it is cost-effective and necessary for the treatment of electroplating wastewater in the park to decomplex complex heavy metals and take appropriate pretreatment for refractory organics to improve their biodegradability when treating electroplating wastewater. On the one hand, it is necessary to add complexed heavy metal removal units at the organic-inorganic mixed wastewater, which not only improves the removal of heavy metals but also relieves the stress of complexed heavy metals on subsequent biochemical treatment units. On the other hand, it is necessary to increase the pretreatment process before the biochemical unit, improve the biodegradability of wastewater, reduce the impact on the biochemical unit, and enhance the stability of the system.

Contents of the invention

In order to solve the above problems, the present invention provides a method for treating organic and inorganic heavy metal production wastewater with the core of discharge up to standard. The present invention adopts the "micro-electrolysis-Fenton (Fenton)-precipitation-anoxic/aerobic membrane bioreactor (A/O membrane bioreactor)" combination process to treat organic-inorganic compound pollution electroplating industrial park sewage, so that the effluent Meet the emission requirements in Table 2 of the "Electroplating Pollutant Discharge Standard" (GB21900-2008).

The purpose of the present invention is achieved through the following technical solutions:

A method for treating organic-inorganic heavy metal production wastewater centering on standard discharge, comprising the following steps:

1. After the copper and nickel wastewater is chemically precipitated in the sequencing batch mixed reaction sedimentation tank, the effluent enters the intermediate water tank. The operating conditions are:

1) Adjust the pH of copper and nickel wastewater to 9.5~10.5;

2) Stir and react for 30~40 minutes;

3) At the same time, add flocculant polyacrylamide and polyaluminum chloride to assist precipitation, settling for 30 to 40 minutes, control the dosage of polyacrylamide to 2~3mg/L, and the dosage of polyaluminum chloride to 20~30mg/L L;

4) Add acid to adjust pH to neutral;

5) Discharge the settled sludge and supernatant, dehydrate the sludge and transport it outside, and discharge the supernatant to the intermediate water tank.

2. The chromium-containing wastewater passes through the chromium-breaking tank and the sequencing batch mixed reaction sedimentation tank in turn, and then the effluent enters the intermediate water tank. The operating conditions are:

1) Add sulfuric acid to the chromium-containing wastewater to adjust the pH to 2.0~3.0;

2) Add sodium metabisulfite to the redox potential of 200~300mV, react for 30~40 minutes, until the wastewater turns from yellow to light green, and the reduction of chromium is completed;

3) Add alkali to adjust the pH to 9.5~10.5, and at the same time add flocculant polyacrylamide and polyaluminum chloride to assist in precipitation, settling for 30~40 minutes, control the dosage of polyacrylamide to 2~3mg/L, and polymerize chloride The dosage of aluminum is 20~30mg/L;

4) Add acid to adjust pH to neutral;

5) Discharge the settled sludge and supernatant, dehydrate the sludge and transport it outside, and discharge the supernatant to the intermediate water tank.

3. The organic wastewater enters the intermediate water tank after passing through the micro-electrolysis-Fenton reaction tank and the inclined plate sedimentation tank in sequence, in which:

1) The micro-electrolytic cell adopts iron-carbon micro-electrolysis, and the operating conditions of the micro-electrolysis reaction are as follows:

The mass ratio of iron to carbon is 1~2:1, the aeration rate is 0.2~0.5 m ³ /h, the reaction time is 30~60 min, and the initial pH is 2~4;

2) The operating conditions of the Fenton reaction are as follows: the molar ratio of H ₂ O ₂ and Fe ²⁺ dosage is 2~3:1, the reaction time is 30~60min, and the initial pH value is 2~4;

3) Add acid to adjust the pH to be neutral and enter the sedimentation tank, and the settled water is discharged to the intermediate water tank.

4. The three strands of waste water are gathered in the middle water tank and then enter the anoxic/aerobic membrane bioreactor (AO-MBR reactor for short), and the effluent enters the effluent pool and then discharges up to the standard, of which:

The AO-MBR reactor is composed of anoxic zone and aerobic zone, and the aerobic zone selects membrane module filtration as the water outlet method; the hydraulic retention time is 6-10 h, and the hydraulic retention time of the anoxic zone is 1-3 h. The aerobic hydraulic retention time is 4~8 h; the sludge concentration in the reaction tank is maintained at 3000~4000 mg/L, and the dissolved oxygen in the anoxic zone and aerobic zone is kept at 0.2~0.5 mg/L and 2.0~4.0 mg/L respectively ; The sludge age in the aerobic zone is 40-60 days, and the internal reflux ratio is 100-300%; the membrane module adopts hollow fiber membrane, the average pore size is 0.1-0.3 μm, and the critical pressure is 20-40 kPa. 6~10 min: 1~3 min.

The present invention has the following advantages:

1. The present invention proposes a combination process of "micro-electrolysis-Fenton-precipitation-A/O membrane bioreactor", and adopts the idea of three-stage strengthening to realize the removal of organic-inorganic composite pollutants. First, the complexed heavy metals are decomplexed by micro-electrolysis, and metal oxides are formed and precipitated. At the same time, the flocs generated during the micro-electrolysis process can also absorb some organic matter; then, the hydroxyl radicals released by the Fenton reaction are used to treat the refractory organic matter in the wastewater. Carry out oxidative decomposition and mineralize part of the organic matter, thereby losing the complexation ability and improving the biodegradability of the wastewater, and at the same time reducing the presence of complexed heavy metals; finally, the wastewater is further removed under the combined action of AO-MBR biochemistry and membrane filtration organic matter and heavy metals.

2. The present invention is characterized by using micro-electrolysis-Fenton combination to pretreat organic and inorganic heavy metal production wastewater, strengthening the removal of complexed heavy metals and improving the biodegradability of wastewater, and using the AO-MBR process with strong impact resistance to treat organic and inorganic heavy metals. Advanced treatment of complex pollutants, this process can meet the technical needs of organic and inorganic heavy metal production wastewater treatment in electroplating industrial parks, and ensure that the treated effluent can meet the discharge standards stably.

Description of drawings

Figure 1 is a process flow diagram of the organic-inorganic complex pollution electroplating wastewater treatment process in the surface treatment industrial park.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the present invention. within the scope of protection.

The present invention provides a method for treating organic-inorganic heavy metal production wastewater with standard discharge as the core. The method adopts the method of classified collection and classified treatment of production wastewater in electroplating parks, as shown in Figure 1, and the specific steps are as follows:

1. The copper and nickel wastewater is chemically precipitated to remove most of the heavy metals through the sequencing batch mixed reaction sedimentation tank, and the effluent enters the intermediate water tank.

2. Chromium-containing wastewater Due to the existence of hexavalent chromium, it needs to be reduced to trivalent chromium in the chromium breaking tank first, and then enters the sequencing batch mixed reaction sedimentation tank for chemical precipitation to remove most of the heavy metals, and the effluent enters the intermediate water tank.

3. Organic wastewater contains a large amount of complex heavy metals and refractory organic matter. The wastewater first enters the micro-electrolysis-Fenton pool for treatment, and then enters the inclined plate sedimentation tank to remove the sediment and then enters the intermediate water tank.

The micro-electrolysis method is based on the principle of electrochemical corrosion of metal materials, and forms a deformation of the electroflocculation of the primary battery between the iron and carbon particles in the wastewater. The micro-electrolysis process includes many functions such as adsorption, coagulation, sweeping, co-precipitation, and electrochemical redox. The micro-electrolysis cell in the present invention adopts iron-carbon micro-electrolysis, and iron filings are used as an anode to rapidly dissolve and release Fe ²⁺ under the action of micro-electrolysis, and Fe ²⁺ is oxidized to Fe ³⁺ and Fe ³⁺ under the action of dissolved oxygen in water. Under acidic conditions, the complexed heavy metals can be replaced to become free, and the free heavy metals can form metal oxides under the reduction of iron filings, and finally the flocculation of Fe(OH) ₂ and Fe(OH) ₃ produced in the reaction Precipitated by adsorption. In addition, part of the complexing agent is oxidized and decomposed due to micro-electrolysis, and the macromolecular chain is decomposed into small molecular organic matter or completely decomposed, and the complexing agent loses its complexing ability. The complexed heavy metals in the effluent of the micro-electrolytic cell are significantly reduced, and the biodegradability of the wastewater is also improved. Hydroxyl radicals will be released after adding Fenton's reagent (H ₂ O ₂ and Fe ²⁺ mixture) to the effluent from micro-electrolysis. The strong oxidative properties of hydroxyl radicals can oxidize and decompose refractory organic matter in wastewater and mineralize part of the organic matter. While removing organic pollutants, it can also significantly improve the biodegradability of wastewater. The Fe(OH) ₂ and Fe(OH) ₃ produced simultaneously in this process have flocculation adsorption, which can remove heavy metals by adsorption and precipitation. There is a large amount of Fe ²⁺ in the effluent of micro-electrolysis. The feature of the present invention is that the combination of micro-electrolysis and Fenton can directly add H ₂ O ₂ to the effluent of micro-electrolysis to cause Fenton reaction and save the dosage of medicine. The combined process can achieve good results in treating refractory organics while ensuring the removal rate of complexed heavy metals.

4. Three streams of waste water are gathered in the middle water tank and then enter the AO-MBR reactor. The AO-MBR reactor is composed of anoxic zone and aerobic zone. The volume ratio of the second zone is 1:3, separated by a partition wall, wherein: The anoxic pool has a water level balance water tank and a mixer, and the aerobic pool has a membrane module, a membrane suction pump and an aeration pan. The activated sludge in the AO tank completes the decomposition of organic pollutants and can adsorb and fix heavy metals in the influent. The ammonia nitrogen in the influent is oxidized to nitrate under the action of ammonia oxidizing bacteria and nitrifying bacteria in the aerobic zone, and a sludge pump is set in the aerobic zone to draw the nitrifying liquid back to the anoxic zone, where the denitrifying bacteria carry out denitrification The effect is to complete the denitrification. The activated sludge method in the AO pool belongs to a mature process. The feature of the present invention is that membrane module filtration is selected as the water outlet method, and the outlet water enters the outlet pool and then discharges up to the standard. On the one hand, membrane filtration retains some pollutants. On the other hand, this method effectively solves the problem of sludge flocculation and flotation caused by toxic pollutants in wastewater. It is especially suitable for the treatment of toxic sewage such as electroplating wastewater.

In the above method, the optimized operating conditions of the micro-electrolysis reaction are as follows: the mass ratio of iron to carbon is 1:1, the optimal aeration rate is 0.2 m ³ /h, the optimal reaction time is 30 min, and the optimal initial pH is 3.

In the above method, the optimized operating conditions of the Fenton reaction are as follows: the molar ratio of the optimal dosage of H ₂ O ₂ and Fe ²⁺ is 2.5:1, the optimal reaction time is 30 min, and the optimal initial pH value is 3 .

In the above method, the parameters of the AO-MBR reactor are as follows: the hydraulic retention time is 8 h, of which the hydraulic retention time in the anoxic zone is 2 h, and the aerobic hydraulic retention time is 6 h. The sludge concentration in the reaction tank was maintained at about 3500 mg/L, and the dissolved oxygen in the anoxic zone and aerobic zone were kept in the range of 0.2-0.5 mg/L and 2.0-4.0 mg/L, respectively. The sludge age in the aerobic pool is 45 days (that is, the weight ratio of aerobic sludge to daily sludge discharge is 45), and the internal return ratio is 200%. The membrane module adopts a hollow fiber membrane with an average pore size of 0.2 μm and a critical pressure of 30 kPa. The time ratio between pumping and pausing of the membrane module is 8 min:2 min.

In order to test the application effect of the "micro-electrolysis-Fenton-precipitation-AO-MBR" combined process of the present invention, an engineering application was carried out in an electroplating enterprise, and the treated wastewater was organic wastewater, chromium-containing wastewater and copper-nickel wastewater, and the process operation parameters were in accordance with the above The process and optimized parameters are operated. The quality of the discharged water after treatment is below 35 mg/L for COD, below 0.6 mg/L for total chromium, below 0.2 mg/L for total nickel, and below 0.3 mg/L for total copper. Stably meet the requirements of electroplating wastewater discharge standards.

Claims (10)

1. a method for treating organic-inorganic heavy metal production wastewater with up-to-standard discharge as the core, characterized in that the method steps are as follows: 1. After the copper and nickel wastewater is chemically precipitated in the sequencing batch mixed reaction sedimentation tank, the effluent enters the intermediate water tank; 2. The chromium-containing wastewater passes through the chromium-breaking tank and the sequencing batch mixed reaction sedimentation tank in turn, and then the effluent enters the intermediate water tank; 3. The organic wastewater enters the intermediate water tank after passing through the micro-electrolysis-Fenton reaction tank and the inclined plate sedimentation tank in sequence; 4. The three streams of waste water are gathered in the middle water tank and then enter the AO-MBR reactor, and the effluent enters the effluent pool and is discharged up to the standard. 2. the method for treating organic-inorganic heavy metal production wastewater based on up-to-standard discharge according to claim 1, characterized in that the operating conditions of said step 1 are as follows: 1) Adjust the pH of copper and nickel wastewater to 9.5~10.5; 2) Stir and react for 30~40 minutes; 3) At the same time, add flocculant polyacrylamide and polyaluminum chloride to assist precipitation, and precipitate for 30 to 40 minutes; 4) Add acid to adjust pH to neutral; 5) Discharge the settled sludge and supernatant, dehydrate the sludge and transport it outside, and discharge the supernatant to the intermediate water tank. 3. The organic-inorganic heavy metal production wastewater treatment method centered on up-to-standard discharge according to claim 2, characterized in that the dosage of polyacrylamide is 2 to 3 mg/L, and the dosage of polyaluminum chloride is 20 ~30mg/L. 4. The organic-inorganic heavy metal production wastewater treatment method based on up-to-standard discharge as the core according to claim 1, characterized in that the operating conditions of the step 2 are as follows: 1) Add sulfuric acid to the chromium-containing wastewater to adjust the pH to 2.0~3.0; 2) Add sodium metabisulfite to the redox potential of 200~300mV, react for 30~40 minutes, until the wastewater turns from yellow to light green, and the reduction of chromium is completed; 3) Add alkali to adjust the pH to 9.5~10.5, and at the same time add flocculant polyacrylamide and polyaluminum chloride to assist precipitation, and precipitate for 30~40 minutes; 4) Add acid to adjust pH to neutral; 5) Discharge the settled sludge and supernatant, dehydrate the sludge and transport it outside, and discharge the supernatant to the intermediate water tank. 5. The organic-inorganic heavy metal production wastewater treatment method centered on up-to-standard discharge according to claim 4, characterized in that the dosage of polyacrylamide is 2 to 3 mg/L, and the dosage of polyaluminum chloride is 20 ~30mg/L. 6. the organic-inorganic heavy metal production wastewater treatment method based on up-to-standard discharge as the core according to claim 1 is characterized in that in said step 3, the micro-electrolytic cell adopts iron-carbon micro-electrolysis, and the operating conditions of the micro-electrolysis reaction are as follows: iron The carbon mass ratio is 1~2:1, the aeration rate is 0.2~0.5 m ³ /h, the reaction time is 30~60min, and the initial pH is 2~4; the Fenton reaction operating conditions are as follows: H ₂ O ₂ and Fe ^{2 +} The molar ratio of dosage is 2~3:1, the reaction time is 30~60 min, and the initial pH value is 2~4. 7. The method for treating organic-inorganic heavy metal production wastewater based on up-to-standard discharge according to claim 4, characterized in that the optimized operating conditions of the micro-electrolysis reaction are as follows: the mass ratio of iron to carbon is 1:1, and the optimum exposure The gas volume is 0.2m ³ /h, the optimal reaction time is 30 min, and the optimal initial pH is 3; the operating conditions after the optimization of the Fenton reaction are as follows: the molar ratio of the optimal dosage of H ₂ O ₂ and Fe ²⁺ is 2.5:1, the optimal reaction time is 30 min, and the optimal initial pH value is 3. 8. The organic-inorganic heavy metal production wastewater treatment method centering on standard discharge according to claim 1, characterized in that in said step 4, the AO-MBR reactor is composed of anoxic zone and aerobic zone, and the anoxic zone The volume ratio to the aerobic zone is 1:3, and the aerobic zone chooses membrane module filtration as the water outlet method. 9. The organic-inorganic heavy metal production wastewater treatment method centered on up-to-standard discharge according to claim 7, characterized in that the hydraulic retention time in the AO-MBR reactor is 6 to 10 h, wherein the hydraulic retention time in the anoxic zone The aerobic hydraulic retention time is 4-8 h; the sludge concentration in the reactor is maintained at 3000-4000 mg/L, and the dissolved oxygen in the anoxic zone and aerobic zone is kept at 0.2-0.5 mg/L and 2.0~4.0 mg/L; the sludge age in the aerobic zone is 40~60 days, and the internal reflux ratio is 100~300%; the membrane modules are hollow fiber membranes with an average pore size of 0.1~0.3 μm and a critical pressure of 20~40 kPa. The time ratio of pumping and pausing of the membrane module is 6-10 min:1-3 min. 10. The organic-inorganic heavy metal production wastewater treatment method based on up-to-standard discharge as the core according to claim 8, characterized in that the hydraulic retention time is 8 h, wherein the hydraulic retention time in the anoxic zone is 2 h, and the aerobic hydraulic retention time is 2 h. The time is 6 hours; the sludge concentration in the reactor is maintained at 3500 mg/L; the sludge age in the aerobic tank is 45 days, the internal reflux ratio is 200%; the average pore size is 0.2 μm, the critical pressure is 30 kPa, and the The time ratio is 8 min:2 min.