A green treatment process for contaminated sludge

Abstract

This invention relates to a green resource utilization process for contaminated sludge, comprising: river dredging sludge, lake and reservoir dredging sludge, culvert dredging sludge, and various types of sludge. After passing through a screen, the contaminated sludge is transported to a heavy metal release treatment facility. Following release treatment, it is transported to a Fenton process to treat organic pollutants, then to an activated particle filter to remove heavy metals. The remaining sludge is flocculated, and the flotation scum and sediment are collected and transported to a CO2 carbonization process. Finally, it is transported to a mechanical dewatering process. The resulting solids are used as improved soil for resource utilization, and the dewatered filtrate is used as reclaimed water through ion exchange.

Description

Technical Field

[0001] This invention relates to a green resource utilization process for contaminated sludge, and more particularly to a green treatment process for contaminated sludge. Background Technology

[0002] Polluted sludge mainly originates from the dredging of rivers, lakes, reservoirs, and culverts. This sludge contains large amounts of heavy metals, persistent organic pollutants, nitrogen, phosphorus, and other pollutants, which can cause serious environmental pollution if not properly treated. Existing sludge treatment systems primarily focus on solidifying pollutants within the sludge and sealing it underground after treatment. This poses a risk of pollutant redistribution and also prevents the recycling of the sludge, wasting land and soil resources.

[0003] The main development goal of sludge treatment is to achieve both green treatment of polluted sludge and resource utilization of sludge. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a green treatment process for contaminated sludge. To this end, this invention adopts the following technical solution:

[0005] A green treatment process for contaminated sludge, comprising: river dredging sludge, lake / reservoir dredging sludge, and culvert dredging sludge; characterized in that the green treatment process includes the following treatment steps:

[0006] The contaminated sludge, after passing through a screen, is transported to a heavy metal release treatment facility. The contaminated sludge after heavy metal release treatment is then transported to the Fenton process to treat organic pollutants, and then to an activated particle filter to remove heavy metals. After heavy metal removal, the sludge is flocculated, and the flotation scum and sediment are collected and transported to a CO2 carbonization process for treatment, and then to a mechanical dewatering process to produce slag. The slag can be used as a resource for soil improvement.

[0007] Furthermore, the contaminated sludge is transported to a heavy metal release unit for heavy metal release treatment. The heavy metal release unit adds one or more combinations of inorganic and organic acids, such as ethylenediaminetetraacetic acid, citric acid, and hydrochloric acid, at a concentration of 0.005%–0.05%, and adjusts the pH of the contaminated sludge to 3–6. The heavy metal release unit also adds large-radius cation salts such as Ca, Mn, and Fe at a concentration of 0.01%–0.05%.

[0008] Furthermore, the sludge produced by the heavy metal release unit is transported to the Fenton unit for processing;

[0009] Furthermore, the sludge produced by the Fenton unit is transported to the activated granular filtration unit. The activated granular filtration unit comprises one or more combinations of filter materials such as granular activated carbon, zeolite, and pebbles with multi-sized particle sizes.

[0010] Furthermore, according to claim 1, the green treatment process for contaminated sludge is characterized in that the sludge produced by the filtration unit is transported to the flocculation unit. The air flotation scum and sediment are transported to the CO2 carbonization unit. The CO2 carbonization unit is characterized in that alkaline silicate waste such as fly ash and fly ash are added at a ratio of 0-10%. The CO2 carbonization unit pressurizes CO2 at a pressure of 5-20 bar.

[0011] Furthermore, the residue produced by the CO2 carbonization unit is conveyed to the mechanical dewatering unit. The mechanical dewatering unit can be one or more combinations of plate and frame dewatering, centrifugal dewatering, and screw dewatering.

[0012] Furthermore, the water produced by mechanical dehydration is transported to an ion exchange unit, which uses a hydrogen ion exchange membrane to generate reclaimed water that is reused in a heavy metal release unit to adjust the pH.

[0013] Furthermore, the residue produced by mechanical dehydration is then dried using methods such as natural air drying and oven drying to form improved soil. The improved soil has a moisture content of less than 30%, and 0.05% to 0.1% calcium phosphate is added to it.

[0014] The green treatment process for contaminated sludge of the present invention has many advantages:

[0015] 1. The polluted sludge undergoes heavy metal release, Fenton, and activated particle filtration to thoroughly remove heavy metals and persistent organic matter, improving the safety of sludge resource utilization; the Ca, Mn, and Fe used in the sludge release process can enhance the sludge flocculation performance.

[0016] 2. Utilizing multi-size active particles, it can effectively separate sludge and pollutants in water, and also has a trapping effect on clay particles, reducing the difficulty of subsequent flocculation and dewatering.

[0017] 3. The scum and sediment produced by flocculation of polluted sludge are carbonized by CO2. Elements such as Ca and Fe in the sludge react with CO2, causing CO2 to be mineralized and fixed in the sludge. This improves the mechanical strength and dewatering performance of the sludge, while fixing and reducing CO2 emissions, thus achieving carbon neutrality.

[0018] 4. After mechanical dehydration, the water produced can be recycled through ion exchange and used to adjust pH during the heavy metal release stage or other stages requiring conditioning, thus realizing the recycling of water.

[0019] 5. The slag produced by mechanical dewatering does not contain heavy metals or persistent organic matter. The nitrogen and phosphorus retained therein can be used as nutrients to supply plant growth, and the alkaline carbonates contained in the improved soil can be used as soil conditioners for acidic soils, thus realizing the clean and resource-based utilization of polluted sludge. Attached Figure Description

[0020] Figure 1 This is a green treatment process for polluted sludge. Detailed Implementation

[0021] The present invention will be further described in detail below through embodiments, so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “have,” “include,” and “include” used in the text do not preclude the presence or addition of one or more other elements or combinations thereof.

[0023] Example 1: Green treatment of dredged sludge from a river.

[0024] The parameters of the dredged sludge are as follows: pH 7.10, water content 90.4%, solid content 9.6%, total organic carbon 1.75%, and heavy metal content: 203 mg / kg Cu, 605 mg / kg Zn, 156 mg / kg Pb, and 1.6 mg / kg Cd.

[0025] The dredged sludge, after being screened to remove debris, is transported to the heavy metal release unit. Ethylenediaminetetraacetic acid (EDTA), citric acid, and hydrochloric acid are added at a mass ratio of 1:5:1, with a dosage of 0.5%, adjusting the sludge pH to 4.0 and a retention time of 60 minutes. After release, the heavy metal content in the sludge is reduced to: 88 mg / kg Cu, 266 mg / kg Zn, 98 mg / kg Pb, and 0.8 mg / kg Cd. The released sludge is then transported to the Fenton unit, where hydrogen peroxide is added at 0.15%, reducing the total organic carbon in the effluent to 1.13%. After treatment in the Fenton unit, the sludge undergoes activated particle filtration, reducing the slurry solids content to 6.8%. The filtered sludge is then transported to the flocculation unit, where PFC is added at a dosage of 0.5 g / L. Sediment is obtained through sedimentation, and the effluent from the flocculation unit is then sent to the flotation unit, where the surface loading rate is 5.0 m³. 3 / (m 2•h), residence time 20min; the scum from the air flotation unit and the sediment are transported together to the CO2 carbonization unit, pressure 10bar, residence time 6h, the carbon sequestration of the sludge is 1.58gCO2 / 100g dry weight sludge. The sludge is dewatered by a plate and frame filter press, the effluent pH is 6.9, the filter cake moisture content is 73.4%, and after natural air drying, improved soil is obtained with pH 7.2, total organic carbon 1.05%, and heavy metal content: 79mg / kgCu, 201mg / kgZn, 88mg / kgPb, 0.6mg / kgCd, all of which meet the agricultural land soil pollution risk control standards.

[0026] Example 2

[0027] Based on Example 1, 0.01% CaO was added to the heavy metal release unit. After release, the heavy metal content in the sludge decreased to 80 mg / kg Cu, 243 mg / kg Zn, 88 mg / kg Pb, and 0.7 mg / kg Cd. The final improved soil had a pH of 7.4, and the heavy metal content decreased to 68 mg / kg Cu, 185 mg / kg Zn, 75 mg / kg Pb, and 0.5 mg / kg Cd.

[0028] Example 3

[0029] Based on Example 1, ozone-assisted mineralization was added to the Fenton unit, reducing the total organic carbon content in the sludge to 0.77% after release. The final improved soil had a total organic carbon content of 0.68%. The heavy metal content all met the standards for risk management of agricultural land soil pollution.

[0030] Example 4

[0031] Based on Example 1, 2% fly ash was added to the CO2 carbonization unit, resulting in a carbon sequestration rate of 2.35g CO2 / 100g dry weight sludge. After plate and frame filtration, the filter residue had a moisture content of 69.8%. The final improved soil pH was 7.8, and the heavy metal content met the standards for risk management of agricultural land soil pollution.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A green treatment process for contaminated sludge, wherein the contaminated sludge comprises: The dredging of riverbeds and silt, lake and reservoir silt, and culvert silt; characterized in that the green treatment process includes the following treatment steps: The contaminated sludge, after passing through a screen, is transported to a heavy metal release treatment facility. The contaminated sludge after heavy metal release treatment is then transported to the Fenton process to treat organic pollutants, and then to an activated particle filter to remove heavy metals. The sludge after heavy metal removal is then transported to a flocculation unit for sedimentation to obtain sludge. The effluent from the flocculation unit is then transported to an air flotation unit to collect the air flotation sludge and sludge, which is then transported to a CO2 carbonization process for treatment, and then to a mechanical dewatering process to produce slag. The slag can be used as a resource for soil amendment. The heavy metal release treatment includes the following steps: adding acid at a ratio of 0.005% to 0.05% to adjust the pH of the polluted sludge to 3 to 6; adding large-radius cation salts at a ratio of 0.01% to 0.05%, wherein the large-radius cation salts include Ca salts, Mn salts, and Fe salts; and the acid is selected from one or more organic and inorganic acids, including ethylenediaminetetraacetic acid, citric acid, and hydrochloric acid.

2. The green treatment process for contaminated sludge according to claim 1, characterized in that... The activated particle filtration removes heavy metals and includes one or more combinations of filter materials with multiple particle sizes, such as granular activated carbon, zeolite, and pebbles.

3. The green treatment process for contaminated sludge according to claim 1, characterized in that... The air flotation scum and sediment are transported to the CO2 carbonization process for treatment. In the CO2 carbonization process, silicate waste is added at a ratio not exceeding 10%. The silicate waste includes fly ash and fly ash. In the CO2 carbonization process, CO2 is pressurized at a pressure of 5 to 20 bar.

4. The green treatment process for contaminated sludge according to claim 1, characterized in that... The slag after CO2 carbonization is transported to a mechanical dewatering unit, which is one or more combinations of plate and frame dewatering, centrifugal dewatering, and screw dewatering.

5. The green treatment process for contaminated sludge according to claim 1, characterized in that... The water produced by mechanical dehydration is transported to the ion exchange unit, which uses a hydrogen ion exchange membrane to generate reclaimed water that is reused in the heavy metal release unit to adjust the pH.

6. The green treatment process for contaminated sludge according to claim 1, characterized in that... The material residue produced by mechanical dehydration is dried to form improved soil; the drying methods include natural air drying and oven drying; the moisture content of the improved soil is less than 30%, and 0.05% to 0.1% calcium phosphate is added to the improved soil.

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