CN111573969A - A combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater - Google Patents

Abstract

The invention relates to a combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater. The wastewater is sequentially treated by a conditioning tank, a primary filtering unit, an oxidation unit, a biodegradation unit and a post-filtering unit, and then discharged up to the standard, directly reused or processed through a deep reuse after processing. The invention organically combines heterogeneous catalytic oxidation technology and biological technology, and the two types of treatment technologies complement each other. For the refractory high-concentration COD-containing chromium-containing electroplating and cleaning organic wastewater, high-concentration COD, low ammonia nitrogen, total phosphorus, hexavalent chromium, etc. Synergistic removal of heavy metals and other pollutants. This kind of refractory wastewater is regulated by heterogeneous catalytic oxidation to create an advantageous environment for the subsequent biological treatment of specific bacterial species, so as to complete the detoxification of hexavalent chromium and the removal of organic pollutants at the same time. There is no need to add chemicals in the whole process of the treatment process, and it does not increase the ion concentration in the wastewater, and finally achieves standard discharge or reuse as supplementary water for enterprise production, and realizes wastewater purification or resource utilization.

Description

A combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater

technical field

The invention relates to the technical field of industrial wastewater purification and treatment, in particular to a combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater.

Background technique

Metal chromium has the advantages of high hardness, low friction coefficient and good chemical stability. It is widely used as protective and decorative coatings, and occupies a high proportion in the electroplating industry. The electroplating cleaning wastewater produced by the enterprise is mainly the mixed water of cleaning and degreasing wastewater, rinsing wastewater, passivation wastewater, etc. in the pretreatment process of the parts to be plated. The ammonia nitrogen concentration is low, the pH value is mostly strong alkaline, and there are many inorganic salt components, including the heavy metal ion chromium. The toxicity of chromium is related to its valence. The toxicity of hexavalent chromium is significantly higher than that of trivalent chromium. Due to the characteristics of pollutants, a considerable part of the chromium ions contained in the electroplating cleaning wastewater produced by enterprises is hexavalent chromium, which has a high It is toxic and has poor biochemical properties, and belongs to a kind of industrial organic wastewater that is difficult to treat.

In recent years, the research on wastewater biotechnology treatment methods using microorganisms to enrich and metabolize heavy metals has gradually emerged. Because of its economical, efficient, and no secondary pollution, it is considered to be a pollution control method with great development potential. However, limited by the conditions of the organism itself, specific bacterial species usually have specific requirements on the pollutant concentration, pH value, dissolved oxygen, temperature and other indicators of wastewater. Due to the high toxicity of electroplating cleaning wastewater, high COD concentration, and high refractory components, traditional biological treatment processes are almost unsuitable. At least, it is necessary to consider reducing the toxicity of this type of electroplating wastewater, that is, it is necessary to reduce hexavalent chromium to trivalent first. Chromium, and then form a precipitate to achieve the separation of pollutants. Such treatment technologies are currently common reduction treatment technologies such as sulfite method, ferrous sulfate-lime method, and electrolytic reduction method, as well as physicochemical treatment technologies such as electrodialysis, reverse osmosis, ion exchange, activated carbon adsorption, and flocculation. There are generally problems such as large consumption of energy and chemicals, high investment and operating costs, and a large amount of chromium-containing waste that needs to be treated separately, and the concentration of chromium ions in electroplating cleaning wastewater is not within the applicable concentration range of the above-mentioned treatment technology. Technical and economic indicators will be bad too.

Therefore, it is still necessary to find an efficient and low-cost method for targeted purification treatment of high-concentration COD-containing chromium-containing electroplating cleaning wastewater produced by electroplating enterprises.

SUMMARY OF THE INVENTION

The invention provides a combined biological treatment method for high-concentration COD-chromium-containing electroplating cleaning wastewater, which organically combines heterogeneous catalytic oxidation technology and biological technology; Synergistic removal of COD, low ammonia nitrogen, total phosphorus, hexavalent chromium and other heavy metals and other pollutants. This kind of refractory wastewater is regulated by heterogeneous catalytic oxidation to create a favorable environment for the subsequent biological treatment of specific bacterial species, so as to complete the detoxification of hexavalent chromium and the removal of organic pollutants at the same time. The whole process of the treatment process does not require external addition of chemicals, does not increase the ion concentration in the wastewater, and finally achieves standard discharge or reuse as supplementary water for enterprise production to achieve wastewater purification or resource utilization.

In order to achieve the above object, the present invention adopts the following technical solutions to realize:

A combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater, wherein the COD concentration in the electroplating cleaning wastewater is greater than or equal to 2000 mg/L, and the hexavalent chromium concentration is less than or equal to 10 mg/L; the treatment method comprises the following steps:

(1) The waste water is first sent to the regulating tank for homogenization;

(2) The effluent of the conditioning tank is sent to the primary filtration unit to remove large particles of insoluble impurities in the wastewater;

(3) The effluent of the primary filtration unit is sent to the oxidation unit; the oxidation unit adopts heterogeneous catalytic oxidation, and under the action of normal temperature and pressure and a catalyst, the complex organic pollutants in the wastewater are chain-severed, and the efficiency of the wastewater is improved at the same time. Biochemical properties, while adjusting the properties of wastewater to meet the requirements of subsequent processes;

(4) The effluent of the oxidation unit is sent to the biodegradation unit; the large carbon chain organic matter obtained by the preliminary degradation of the oxidation unit in the wastewater is further degraded into small carbon chain and single carbon chain organic matter, and finally converted into water, carbon dioxide and other small molecular inorganic substances ; The biochemical reactions of oxidation and reduction in the biodegradation unit occur alternately and repeatedly, and the hexavalent chromium contained in the wastewater is reduced to the precipitate of trivalent chromium, which is deposited at the bottom of the biodegradation unit and discharged regularly;

(5) The effluent of the biodegradation unit is sent to the post-filtration unit to remove excess impurities in the wastewater, and then discharged up to the standard, directly reused or reused after advanced treatment.

The filter medium in the primary filter unit is one or more combinations of porous filter medium, granular filter medium, and alloy screen; the porous filter medium is ceramic or nylon, and the filter pore size is 30-50 μm; the granular filter medium It is one or both of manganese sand or quartz sand.

In the heterogeneous catalytic oxidation process in the oxidation unit, the catalyst adopts one or more of oxides of platinum, lead, nickel and copper, and is sintered at high temperature into a network or granular structure; the oxidant is selected from air or ozone .

The biodegradation unit is a full-process anaerobic biodegradation process, including two process sections, a hydrolysis acidification section and an anaerobic digestion section; in the hydrolysis acidification section, the large carbon chain organic matter contained in the wastewater is converted into small carbon chain organic matter. Hydrocarbons, there are a variety of organic acids in the product; in an acidic environment, hexavalent chromium in wastewater is used as an electron acceptor, and biological bacteria use small carbon chain molecules as electron donors to achieve the reduction of hexavalent chromium to trivalent chromium In the anaerobic biological section, relying on the metabolism of anaerobic biological bacteria, in a weak alkaline environment, the low-valent chromium ions generated by the hydrolysis and acidification section are combined with OH- in the wastewater to form low-valent chromium precipitates, Gradually separated from wastewater; at the same time, small carbon chain organic pollutants rely on the metabolism of biological bacteria, and finally converted into water, carbon dioxide and other inorganic substances; at the same time, ammonia nitrogen and total phosphorus are also removed.

The low-valent chromium precipitate is collected separately and used as a raw material for metal chromium smelting.

The filter medium in the post-filter unit is one or more of quartz sand, anthracite, activated carbon, magnetite, manganese sand, ceramsite, and porous ceramics, and the particle size of the filter medium is 0.5-5 mm.

Compared with the prior art, the beneficial effects of the present invention are:

1) The present invention adopts a "combined biotechnology treatment method" to treat high-concentration COD chromium-containing electroplating cleaning wastewater with specific pollutant characteristics in a targeted manner, which can overcome the toxicity tolerance of anaerobic bacteria in conventional biochemical treatment to hexavalent chromium. At the same time, it can also solve the problem that the existing anaerobic treatment of chromium-containing wastewater has low treatment efficiency for low-concentration hexavalent chromium, and has a single function and cannot remove organic pollutants at the same time. The optimized combination of the process flow, the chain scission of the refractory organic matter through the chemical oxidation section, to improve the biodegradability of the wastewater, and to adjust the properties of the wastewater at the same time, to create favorable environmental conditions for the growth of specific bacterial species in the subsequent biological treatment, so as to pass through the biodegradation unit. The synergistic effect of hydrolysis acidification and anaerobic process section can complete the detoxification of hexavalent chromium and the removal of organic pollutants at the same time. The organic combination of the two processes enables the wastewater with high toxicity, high concentration of refractory pollutants and poor biodegradability to be efficiently and stably purified.

2) In the whole process of the wastewater treatment process, there is no need to add acid, alkali or other chemicals externally, and the ion concentration in the wastewater treatment process is not increased, so the conductivity before and after wastewater treatment will not increase, and the treated effluent can meet the requirements of electroplating. Standard for cleaning and reuse water in production.

3) There is no solid waste discharge in the process of heterogeneous catalytic oxidation, and the biochemical reaction process of biological bacteria in the biodegradation unit produces only a small amount of biological sludge metabolized by biological bacteria, and low-valent metal chromium precipitates; low-cost Metal chromium precipitates are discharged together with biological sludge as waste in the wastewater treatment process. Because this waste contains biological sludge and metallic chromium, it can be used as a raw material for resource recycling and achieve zero emission of pollutants.

4) In the biological treatment process of high-concentration COD-containing chromium-containing electroplating cleaning wastewater, the biochemical reaction of each stage of biological bacteria is completed under anoxic conditions, so after the hexavalent chromium contained in the wastewater is reduced to trivalent chromium, it will not. It is oxidized to hexavalent chromium again, so as to completely eliminate the hexavalent chromium in the wastewater and ensure the stable and reliable treatment effect.

5) Compared with the conventional chemical method to eliminate hexavalent chromium ions in wastewater, the present invention has the advantages of non-toxic, harmless and waste-free; The advantages of less and less emissions.

6) The method of the present invention has the advantages of good process stability, strong impact resistance, concise process, simple operation, high efficiency, low cost, and no secondary pollution, and is suitable for popularization and application.

Description of drawings

1 is a process flow diagram of a combined biological treatment method for high-concentration COD-containing chromium-containing electroplating cleaning wastewater according to the present invention.

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings:

As shown in Figure 1, a combined biological treatment method of high-concentration COD-containing chromium-containing electroplating cleaning wastewater according to the present invention, the COD concentration in the electroplating cleaning wastewater is ≥ 2000mg/L, and the hexavalent chromium concentration is ≤ 10mg/L; The method includes the following steps:

(1) The waste water is first sent to the regulating tank for homogenization;

(2) The effluent of the conditioning tank is sent to the primary filtration unit to remove large particles of insoluble impurities in the wastewater;

(3) The effluent of the primary filtration unit is sent to the oxidation unit; the oxidation unit adopts heterogeneous catalytic oxidation, and under the action of normal temperature and pressure and a catalyst, the complex organic pollutants in the wastewater are chain-severed, and the efficiency of the wastewater is improved at the same time. Biochemical properties, while adjusting the properties of wastewater to meet the requirements of subsequent processes;

(4) The effluent of the oxidation unit is sent to the biodegradation unit; the large carbon chain organic matter obtained by the preliminary degradation of the oxidation unit in the wastewater is further degraded into small carbon chain and single carbon chain organic matter, and finally converted into water, carbon dioxide and other small molecular inorganic substances ; The biochemical reactions of oxidation and reduction in the biodegradation unit occur alternately and repeatedly, and the hexavalent chromium contained in the wastewater is reduced to the precipitate of trivalent chromium, which is deposited at the bottom of the biodegradation unit and discharged regularly;

(5) The effluent of the biodegradation unit is sent to the post-filtration unit to remove excess impurities in the wastewater, and then discharged up to the standard, directly reused or reused after advanced treatment.

The filter medium in the primary filter unit is one or more combinations of porous filter medium, granular filter medium, and alloy screen; the porous filter medium is ceramic or nylon, and the filter pore size is 30-50 μm; the granular filter medium It is one or both of manganese sand or quartz sand.

In the heterogeneous catalytic oxidation process in the oxidation unit, the catalyst adopts one or more of oxides of platinum, lead, nickel and copper, and is sintered at high temperature into a network or granular structure; the oxidant is selected from air or ozone .

The biodegradation unit is a full-process anaerobic biodegradation process, including two process sections, a hydrolysis acidification section and an anaerobic digestion section; in the hydrolysis acidification section, the large carbon chain organic matter contained in the wastewater is converted into small carbon chain organic matter. Hydrocarbons, there are various organic acids in the product; in an acidic environment, hexavalent chromium in wastewater is used as electron acceptor, and biological bacteria use small carbon chain molecules as electron donors to achieve the reduction of hexavalent chromium to trivalent chromium In the anaerobic biological section, relying on the metabolism of anaerobic biological bacteria, in a weak alkaline environment, the low-valent chromium ions generated by the hydrolysis and acidification section are combined with OH- in the wastewater to form low-valent chromium precipitates, It is gradually separated from the wastewater; at the same time, the small carbon chain organic pollutants rely on the metabolism of biological bacteria, and are finally converted into water, carbon dioxide and other inorganic substances; at the same time, ammonia nitrogen and total phosphorus are also removed.

The low-valent chromium precipitate is collected separately and used as a raw material for metal chromium smelting.

The filter medium in the post-filter unit is one or more of quartz sand, anthracite, activated carbon, magnetite, manganese sand, ceramsite, and porous ceramics, and the particle size of the filter medium is 0.5-5 mm.

The following examples are implemented on the premise of the technical solutions of the present invention, and provide detailed embodiments and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

【Example】

In this embodiment, a high-concentration COD-containing chromium-containing electroplating cleaning wastewater is the cleaning wastewater generated by cleaning and degreasing the surface of the roll to be plated in a certain enterprise. The total phosphorus was 53.9mg/L, the hexavalent chromium was 0.96mg/L, the total chromium was 1.77mg/L, and the pH value was 9.73. At the same time, the wastewater contained a large amount of iron ions.

The wastewater is first sent to the conditioning tank for homogenization, and then sent to the primary filtration unit to remove large particles of insoluble impurities in the wastewater. The filter medium in the primary filter unit is aluminosilicate ceramics, and the filter pore size is 30 μm. During the filtration operation, the filtration rate remains unchanged, and the waste water quickly passes through the filter layer.

The effluent from the primary filter unit is sent to the oxidation unit. The solid fillers made of nylon 66, PE, pebbles, clay particles and other non-metallic materials are arranged inside the oxidation unit. The catalyst is an alloy oxide of platinum, lead, nickel and copper. Oxygen in the oxidant. Under the environmental conditions of normal temperature and pressure, the wastewater is fully contacted and reacted with oxygen, and the large carbon chain of the oil molecule is broken, forming organic carbon chains of different sizes.

The wastewater after chain scission enters the subsequent biodegradation unit, and the carbon chain of the organic matter in the wastewater is further degraded until H ₂ O and CO ₂ are finally formed. After the wastewater passes through the hydrolysis and acidification section and the anaerobic nitrification section in sequence, the effluent is sent to the post-filtration unit.

The post-filtration unit is used to remove excess impurities in the wastewater. The filter media select manganese sand with a particle size of 0.5-4mm, quartz sand with a particle size of 0.5-1.2mm, activated carbon with a particle size of 0.8-1.8mm, manganese sand, quartz sand Sand and activated carbon are laid sequentially from bottom to top.

In this embodiment, the treated effluent COD≤30mg/L, ammonia nitrogen≤2mg/L, total phosphorus≤1mg/L, hexavalent chromium≤0.02mg/L, total chromium≤0.03mg/L, pH value of 7.80, satisfying The water quality standard for reused water can be reused as supplementary water for cleaning tanks.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (6)

1. A combined biological treatment method of high-concentration COD chromium-containing electroplating cleaning wastewater is characterized in that the COD concentration in the electroplating cleaning wastewater is more than or equal to 2000mg/L, and the concentration of hexavalent chromium is less than or equal to 10 mg/L; the processing method comprises the following steps:

(1) firstly, feeding the wastewater into a regulating tank, and homogenizing;

(2) the effluent of the regulating reservoir is sent into a primary filtering unit to remove large-particle insoluble impurities in the wastewater;

(3) the effluent of the primary filtering unit is sent into an oxidizing unit; the oxidation unit adopts heterogeneous catalytic oxidation, carries out chain scission on complex organic pollutants in the wastewater under the action of a catalyst at normal temperature and normal pressure, improves the biodegradability of the wastewater, and simultaneously adjusts the property of the wastewater to ensure that the wastewater meets the requirements of the subsequent process;

(4) the effluent of the oxidation unit is sent to a biodegradation unit; the large carbon chain organic matter obtained by the preliminary degradation of the wastewater through the oxidation unit is further degraded into small carbon chain and single carbon chain organic matter, and finally converted into water, carbon dioxide and other small molecular inorganic matters; the biochemical reactions of oxidation and reduction in the biodegradation unit are alternately and repeatedly carried out, hexavalent chromium contained in the wastewater is reduced into precipitate of trivalent chromium, the precipitate is deposited at the bottom of the biodegradation unit, and the precipitate is periodically discharged;

(5) and (3) sending the effluent of the biodegradation unit into a post-filtering unit, removing redundant impurities in the wastewater, and then discharging the wastewater after reaching the standard and directly recycling the wastewater or recycling the wastewater after advanced treatment.

2. The combined biological treatment method for the high-concentration COD chromium-containing electroplating cleaning wastewater according to claim 1, characterized in that the filter medium in the primary filter unit is one or more of porous filter medium, granular filter medium and alloy screen; wherein the porous filter medium is ceramic or nylon, and the filter aperture is 30-50 μm; the granular filter medium is one or two of manganese sand or quartz sand.

3. The combined biological treatment method for the high-concentration COD chromium-containing electroplating cleaning wastewater according to claim 1, characterized in that in the heterogeneous catalytic oxidation process in the oxidation unit, the catalyst adopts one or more oxides of platinum, lead, nickel and copper, and is sintered into a net-shaped or granular structure at high temperature; the oxidant is air or ozone.

4. The combined biological treatment method for the high-concentration COD chromium-containing electroplating cleaning wastewater according to claim 1, characterized in that the biodegradation unit is a full-flow anaerobic biodegradation process comprising 2 process sections of a hydrolytic acidification section and an anaerobic digestion section;

in the hydrolysis acidification section, large carbon chain organic matters contained in the wastewater are converted into small carbon chain hydrocarbon compounds, and a plurality of organic acids are contained in the products; in an acidic environment, hexavalent chromium in the wastewater is used as an electron acceptor, and the biological strain takes small carbon chain molecules as an electron donor to reduce the hexavalent chromium into trivalent chromium;

in the anaerobic biological section, low-valence chromium ions generated by the reaction of the hydrolytic acidification section are combined with OH < - > in the wastewater in a weak alkali environment by means of metabolism of anaerobic biological strains to form low-valence chromium precipitates which are gradually separated from the wastewater; meanwhile, the small carbon chain organic pollutants are metabolized by the biological strains and finally converted into water, carbon dioxide and other inorganic substances; ammonia nitrogen and total phosphorus are also removed.

5. The combined biological treatment method of high concentration COD chromium containing electroplating cleaning waste water according to claim 4, characterized in that the low valence state chromium precipitate is collected separately and used as metallic chromium smelting raw material.

6. The combined biological treatment method of high concentration COD chromium containing electroplating cleaning wastewater according to claim 1, characterized in that the filtering medium in the post-filtering unit is one or more of quartz sand, anthracite, activated carbon, magnetite, manganese sand, ceramsite and porous ceramic, and the particle size of the filtering medium is 0.5-5 mm.

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