A method and application for removing perchlorate pollution in water using agricultural waste

Abstract

The present invention discloses a method and application for removing perchlorate contamination from water bodies using agricultural waste. This method uses activated sludge and agricultural waste, or activated sludge, vegetable oil, and agricultural waste, to treat perchlorate-contaminated water bodies, using at least one of static and dynamic treatment methods. This method has the following advantages: waste recycling, turning waste into valuable resources; low cost and simple process; bioremediation without secondary pollution; and simultaneous achievement of multiple benefits, achieving multiple goals at once. Therefore, this method has broad application prospects in the treatment of perchlorate-contaminated water bodies.

Description

Technical Field

[0001] The present invention belongs to the field of agricultural solid waste treatment and comprehensive utilization, as well as the technical field of pollutant bioremediation, and particularly relates to a method for removing perchlorate pollution in water bodies by utilizing agricultural waste and its application. Background Art

[0002] Strong oxidizing agent perchlorate (ClO4 - ) is an endocrine disruptor that is highly toxic to humans and animals. ClO4 is highly water-soluble, has low adsorption and high mobility and diffusion. - It can enter farmland through agricultural irrigation water, posing a huge threat to agricultural ecosystems and human health. - It is chemically inert in aqueous solution and does not react with most reducing ions when the concentration is less than 10% (w / w). Therefore, conventional treatment technologies such as coagulation, filtration, adsorption, and adding reducing agents cannot effectively remove ClO4. - The remediation technology of polluted water bodies can be divided into two categories: non-biological remediation and biological remediation. The former mainly includes anion exchange and adsorbent adsorption, chemical reduction, electrochemical reduction, membrane filtration and electrodialysis. This type of technology has made great progress in the laboratory research stage. Its remediation principles and technical characteristics are relatively clear. However, the biggest disadvantage of non-biological remediation technology is that it is expensive and difficult to promote and apply. Biological remediation technology has attracted more and more attention due to its unique advantages such as low cost, no secondary pollution, and large-scale application. It is one of the most promising remediation technologies. Current research has proved that ClO4 can be degraded in nature. - Microorganisms are present almost everywhere, but they can only be used in pollution control practices after being enriched and properly regulated. Due to the low cost of microbial reduction degradation remediation technology, it is currently the most promising ClO4 - Pollution remediation technology. But ClO4 - Microbial degradation requires appropriate electron donors (organic, inorganic) and carbon sources. Summary of the Invention

[0003] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a method for removing perchlorate pollution in water bodies by utilizing agricultural waste.

[0004] Another object of the present invention is to provide an application of the above method for removing perchlorate pollution in water bodies by utilizing agricultural waste.

[0005] The object of the present invention is achieved through the following technical solution: a method for removing perchlorate pollution in water bodies by using agricultural waste, comprising the following steps: treating water bodies containing perchlorate with activated sludge and agricultural waste, or activated sludge, vegetable oil and agricultural waste.

[0006] The processing is preferably one of the following methods:

[0007] (1) Static treatment: adding water containing perchlorate to activated sludge and agricultural waste, or activated sludge, vegetable oil and agricultural waste, and allowing to stand for treatment to obtain treated water;

[0008] (2) Dynamic processing combined with static processing:

[0009] A. Construction of a biofiltration column: Using river sand as a support, activated sludge acclimated with perchlorate and agricultural waste, or activated sludge acclimated with perchlorate, vegetable oil, and agricultural waste, to form a biofiltration column;

[0010] B. Adding a nutrient solution to the biofiltration column and incubating in the dark to enrich the microorganisms in the activated sludge; then adding water containing perchlorate and incubating in the dark to further enrich and culture the perchlorate-degrading bacteria, thereby obtaining a biofiltration column enriched with perchlorate-degrading bacteria;

[0011] C. Passing the perchlorate-containing water through the biological filtration column obtained in step A or the biological filtration column enriched with perchlorate-degrading bacteria obtained in step B to obtain a filtrate;

[0012] D. adding the obtained filtrate to activated sludge and agricultural waste, or activated sludge, vegetable oil and agricultural waste, and allowing the mixture to stand for treatment to obtain treated water.

[0013] The agricultural waste in embodiment (1) is a rice by-product, preferably at least one of rice straw and rice husk.

[0014] The vegetable oil in embodiment (1) is preferably at least one of peanut oil, soybean oil and corn oil.

[0015] The activated sludge in the embodiment (1) is preferably activated sludge acclimated with perchlorate.

[0016] The activated sludge acclimated with perchlorate is obtained by culturing with perchlorate solutions having increasing contents; preferably, the activated sludge is prepared by the following steps: adding 50 mL of nutrient solution to every 300-500 mL of activated sludge, then adding deionized water to 900 mL, stirring evenly, and culturing for 7 days; starting from the 8th day, adding 1 mL of contaminated solution every other day; starting from the 14th day, adding 2 mL of contaminated solution every other day; and starting from the 20th day, adding 4 mL of contaminated solution every day; after each addition, discarding the supernatant, adding 50 mL of nutrient solution and deionized water to 900 mL, stirring for a certain period of time every day to mix evenly; continuously increasing the perchlorate concentration in the nutrient solution until the added perchlorate ions can be completely degraded within 24 hours, thereby obtaining the activated sludge acclimated with perchlorate; wherein the nutrient solution is a glucose solution with a concentration of 35-45 g / L; the contaminating solution is a ClO4 solution with a concentration of 80-120 mg / L - of perchlorate solution.

[0017] The nutrient solution is preferably a glucose solution with a concentration of 40g / L.

[0018] The contaminated liquid preferably has a concentration of 100 mg / L ClO4 - of perchlorate solution.

[0019] The agricultural waste, the vegetable oil and the activated sludge in method (1) are mixed in a ratio of 50-80 g: 20 mL: 20 mL.

[0020] The standing treatment in the method (1) is standing at room temperature for more than 8 days; more preferably, standing for more than 30 days.

[0021] The room temperature is 15-40°C; more preferably 20-40°C; most preferably 25-35°C.

[0022] The river sand described in step A of method (2) is preferably clean river sand that has passed through a 2 mm sieve.

[0023] The agricultural waste in step A of method (2) is rice byproduct, preferably at least one of rice straw and rice husk.

[0024] The vegetable oil described in step A of method (2) is preferably at least one of peanut oil, soybean oil and corn oil.

[0025] The activated sludge acclimated with perchlorate in step A of method (2) is obtained by culturing with perchlorate solutions having increasing contents; preferably, the activated sludge is prepared by the following steps: adding 50 mL of nutrient solution to every 300-500 mL of activated sludge, then adding deionized water to 900 mL, stirring evenly, and culturing for 7 days; starting from the 8th day, adding 1 mL of contaminated solution every other day; starting from the 14th day, adding 2 mL of contaminated solution every other day; starting from the 20th day, adding 4 mL of contaminated solution every day; each time the supernatant is poured out, 50 mL of nutrient solution and deionized water are added to 900 mL, and stirring is given for a certain period of time every day to mix evenly; the perchlorate concentration in the nutrient solution is continuously increased until the added perchlorate ions can be completely degraded within 24 hours, thereby obtaining the activated sludge acclimated with perchlorate; wherein the nutrient solution is a glucose solution with a concentration of 35-45 g / L; the contaminating solution is a ClO4 solution with a concentration of 80-120 mg / L - of perchlorate solution.

[0026] The nutrient solution is preferably a glucose solution with a concentration of 40g / L.

[0027] The contaminated liquid preferably has a concentration of 100 mg / L ClO4 - of perchlorate solution.

[0028] Method (2) The agricultural waste, the vegetable oil and the activated sludge described in step A are mixed in a ratio of 30-40 g: 20 mL: 20 mL.

[0029] The nutrient solution described in step B of method (2) is preferably glucose solution; more preferably, it is a glucose solution with a concentration of 35 to 45 g / L; and most preferably, it is a glucose solution with a concentration of 40 g / L.

[0030] The conditions for culturing in dark with the addition of nutrient solution in step B of method (2) are preferably culturing at 20-30° C. for 60-90 h; more preferably culturing at 25° C. for 72 h.

[0031] The conditions for culturing in the dark with water containing perchlorate in step B of method (2) are preferably 20-30° C. for 100-150 h; more preferably 25° C. for 120 h.

[0032] Method (2) ClO4 in the water containing perchlorate in step B - The concentration is 140-160 mg / L; preferably 150 mg / L.

[0033] Method (2) The agricultural waste, the vegetable oil and the activated sludge in step D are mixed in a ratio of 50-80 g: 20 mL: 20 mL.

[0034] The time for the static treatment described in step D of method (2) is preferably greater than 48 hours.

[0035] The above method of removing perchlorate pollution in water bodies by utilizing agricultural waste is applied in water treatment to remove perchlorate pollution in water bodies.

[0036] The present invention has the following advantages and effects compared to the prior art:

[0037] Agricultural waste, such as rice by-products, mainly includes rice straw and husks. They are rich in cellulose, lignin, and silicon dioxide, but have low fat and protein contents. Their main chemical components are C, H, O, K, Si, Cl, S, Ca, etc. The nutrients and trace elements in the leachate of rice by-products can provide the necessary elements for the growth of microorganisms. According to research, rice straw leachate mainly contains macroelements required for microbial growth, such as calcium, potassium, magnesium, sodium, silicon, and phosphorus, which can promote the growth of microorganisms; at the same time, rice straw leachate also contains trace elements such as barium and zinc, which are also indispensable for the growth and reproduction of microorganisms; while the content of toxic and harmful substances such as copper, cadmium, lead, and chromium that are toxic to microorganisms is relatively low. Husk cells are rich in organic components such as crude protein, crude fiber, lignin, and chitin. Their cell walls contain functional groups such as hydroxyl, carboxyl, and amino groups that can bind to heavy metal ions, and have a good adsorption effect on heavy metal ions. Therefore, the present invention has the following advantages:

[0038] (1) Utilize waste and turn it into treasure;

[0039] (2) Low cost and simple process;

[0040] (3) Bioremediation, no secondary pollution;

[0041] (4) Achieve multiple functions at the same time, killing two birds with one stone. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 ClO4 in a system constructed with rice husk as a biofilm carrier - Graph of changes over time.

[0043] Figure 2 is ClO4 in the system at different temperatures - Graph of changes over time.

[0044] Figure 3 It is the ClO4 in the filtrate after being treated by the rice husk filter column. - Graph of changes over time.

[0045] Figure 4 This is a diagram of the dynamic test device.

[0046] Figure 5It is the ClO4 in the sewage after passing through various types of biological filter columns - Content diagram.

[0047] Figure 6 This is a graph showing the removal rates of perchlorate by various types of biological filtration columns.

[0048] Figure 5 and Figure 6 Among them, S is the river sand group, C is the rice straw group, C+Y is the rice straw + vegetable oil group, G is the rice husk group, and G+Y is the rice husk + vegetable oil group. DETAILED DESCRIPTION

[0049] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0050] Example 1: Removal of ClO4 from water using rice husk as a biofilm carrier - Static test

[0051] (1) Experimental process: 6 circular fermentation tanks (22 cm in diameter and 55 cm in height) were prepared and divided into two groups, with three replicates in each group. In the first group, 80 g of rice husk, 20 mL of vegetable oil, and 20 mL of activated sludge (activated sludge was obtained from Guangzhou Lijiao Wastewater Treatment Plant, the same below) were added to each tank in sequence. Finally, 6 L of ClO4 was added to each tank. - A 150 mg / L artificially prepared contaminated solution was added; a second set of fermenters received only 6 L of the same contaminated solution. The fermenters were covered and allowed to stand at room temperature. The perchlorate concentration in each fermenter was measured on days 1, 2, 4, 6, 8, 16, 32, 48, 56, and 72.

[0052] (2) Detection of perchlorate content: After sampling on the same day, the sample liquid should be processed and the content should be detected immediately (if the content cannot be determined on the same day, the sample should be stored in a -20℃ refrigerator). When measuring, 1 mL of each sample liquid should be taken, and after passing through a C18 solid phase extraction cartridge, it should be directly measured using an ICS900 ion chromatograph. The results are as follows: Figure 1 shown.

[0053] (3) Analysis of results: The test results showed that the perchlorate content in the solution remained unchanged for the first 6 days, but began to decrease from the 8th day. By the 16th day, the perchlorate content had decreased by 22.1%. Thereafter, the perchlorate content in the system continued to decrease. By the 72nd day, the perchlorate content had decreased by 98.3%. This indicates that the "husk + vegetable oil + activated sludge" system constructed with husk as the biofilm carrier in this experiment has a significant degradation effect on perchlorate in sewage, and perchlorate can be degraded by more than 98% within 72 days. The perchlorate content in the control group without the addition of husk, vegetable oil and activated sludge did not change, indicating that under natural conditions, perchlorate in general water bodies is difficult to degrade.

[0054] Example 2: Effect of temperature on the removal of ClO4 from water using rice husk as a biofilm carrier - Static impact test

[0055] (1) Acclimation of microorganisms in activated sludge: Take a 1000mL beaker, pour about 400mL of activated sludge, add 50mL of nutrient solution (using a glucose solution with a concentration of 40g / L), and then add deionized water to 900mL, stir evenly, and culture for 7 days. Starting from the 8th day, add 1mL of contaminated solution (with a concentration of 100mg / L ClO4) every other day. - ); starting on the 14th day, add 2 mL of contaminated solution every other day; starting on the 20th day, add 4 mL of contaminated solution daily. After each addition, discard the supernatant and add 50 mL of nutrient solution and deionized water to a volume of 900 mL. Stir for a period of time each day to ensure uniform mixing. Continue increasing the perchlorate concentration in the nutrient solution in this manner until the added perchlorate ions are completely degraded within 24 hours.

[0056] (2) Experimental process: Prepare 9 barrels (20 cm in diameter and 25 cm in height), add 50 g rice husk, 20 mL vegetable oil, 20 mL acclimated activated sludge, 2 L of ClO4 - The wastewater was 150mg / L and the bucket was covered. It was divided into three groups, with three replicates in each group. The first group was placed in a 25℃ constant temperature box, the second group was placed in a 35℃ constant temperature box, and the third group was placed in a 45℃ constant temperature box. The experiment lasted for 1 month, during which samples were collected every two days to test the concentration of perchlorate. The results are as follows Figure 2 shown.

[0057] (3) Result analysis: Under the three temperature conditions, the perchlorate in the system did not degrade in the first four days. From the sixth day, the perchlorate began to degrade at a temperature of 35°C, and no ClO4 was detected on the 18th day. - From the 10th day, perchlorate began to degrade at 25℃, and no ClO4 could be detected on the 22nd day. - However, perchlorate degradation at 45°C remained unaffected during the experimental period. This suggests that under these experimental conditions, the degradation rate of perchlorate at 25°C was slightly lower than that at 35°C. Perchlorate-degrading bacteria grew fastest at 35°C, but could not survive at 45°C.

[0058] Example 3: Biofiltration column constructed with rice husk as main filler for ClO4 removal in water - Dynamic removal test

[0059] (1) Acclimation of activated sludge: The sludge used in this part of the experiment was acclimated for one month (see Example 2 for the specific method). Before use, the supernatant of the sludge that was stirred and then naturally clarified was tested. Only the sludge that did not detect perchlorate was used in this experiment.

[0060] (2) Experimental procedure: Prepare 6 plastic cylinders with a diameter of 8 cm and a height of 25 cm. After washing, add 200 g of clean river sand (passed through a 2 mm sieve) to each column as a support. Divide into two groups, with three replicates in each group. Add 30 g of rice husk, 20 mL of vegetable oil, and 20 mL of acclimated activated sludge to the first group of sand columns. No substance is added to the second group. Add ClO4 to both groups of columns. - Sewage with a concentration of 150 mg / L was added from the top of the permeation column and flowed out from the bottom. The flow rate was controlled at about 1 mL / min. The perchlorate concentration in the filtrate after passing through the column was sampled and analyzed on the 1st, 3rd, 5th, 7th, 9th, 15th, 19th, 23rd, 27th, and 32nd day of the experiment. The results are as follows: Figure 3 shown.

[0061] (3) Result analysis: The results of this experimental study found that the removal rate of perchlorate by the filter column was low in the first few days, with 12.0% and 21.9% on the first and second days respectively, and 44.6% on the fourth day. The average removal rate thereafter was basically between 40-55%, while the removal rate of the control group (only river sand) was 0, indicating that the filter column has a certain removal effect on perchlorate, but further optimization of conditions is needed to achieve the best effect.

[0062] Example 4: Effects of different types of biofiltration columns on ClO4 in water - Dynamic removal comparison test

[0063] (1) Experimental process:

[0064] Take 15 plastic cylinders with the same specifications as above. Set up the following experimental groups: a filter column containing only 200g of clean river sand (passed through a 2mm sieve) is group S; a biological filter column with 200g of clean river sand (passed through a 2mm sieve) as a support, 20mL of acclimated activated sludge (same as Example 3) and 30g of straw is group C; a biological filter column with 200g of clean river sand (passed through a 2mm sieve) as a support, 20mL of acclimated activated sludge, 20mL of vegetable oil and 30g of straw is group C+ Group Y; Group G, a biological filtration column using 200 g of clean river sand (passed through a 2 mm sieve) as a support, 20 mL of domesticated activated sludge and 30 g of rice husk; Group G+Y, a biological filtration column using 200 g of clean river sand (passed through a 2 mm sieve) as a support, 20 mL of domesticated activated sludge, 20 mL of vegetable oil and 30 g of rice husk. Each group had 3 replicates, and different types of biological filtration columns were constructed to compare their removal effects on perchlorate in sewage.

[0065] Add culture medium (glucose solution with a concentration of 40g / L) to each biofiltration column and culture in the dark at 25℃ for 3 days to enrich the microorganisms in the activated sludge. On the 4th day, add a certain amount of ClO4 with a concentration of 150mg / L to each group. - The solution was cultured at 25°C in the dark for 5 days to further enrich and culture perchlorate-degrading bacteria.

[0066] Add ClO4 at a concentration of 150 mg / L to the enriched and acclimated biofilter column - The sewage solution is added from the upper end of the permeation column at a rate of 3 mL / min and flows out from the lower end (device such as Figure 4 The perchlorate and its degradation products in the effluent of each treatment group were collected and analyzed on the 1st, 5th, 10th, 20th and 30th day of the experiment.

[0067] (2) Experimental results

[0068] Research results ( Figure 5 ) showed that the perchlorate content in the water flowing through each treatment group was significantly lower than that in the control group (Group S: composed of sand columns and activated sludge), indicating that rice byproducts can serve as a carbon source and biofilm support for perchlorate-degrading bacteria. Data from the first day showed that perchlorate levels in each treatment group were high, exceeding 100 mg / L. On the fifth day, perchlorate levels ranged from 80 to 100 mg / L. Starting from the tenth day, perchlorate levels in each treatment group decreased rapidly, and by the 20th day, concentrations had stabilized, indicating that perchlorate-degrading bacteria in the activated sludge still need time to enrich and grow before achieving optimal degradation.

[0069] Comparative analysis of perchlorate levels across treatment groups revealed that rice straw and rice straw + vegetable oil contained significantly lower levels than rice husk and rice husk + vegetable oil, suggesting that rice straw is more suitable as a culture medium for perchlorate-degrading bacteria than rice husk. However, the addition of vegetable oil had no significant effect on perchlorate levels, suggesting that vegetable oil does not play a significant role in this process.

[0070] If the perchlorate concentration of the influent is regarded as 100%, the removal rate of perchlorate in the sewage by each type of column after passing through the biological filter column can be calculated ( Figure 6 The results showed that on the first day, perchlorate removal rates in each treatment group were low, ranging from 25-30%. After the tenth day, perchlorate removal rates in groups C and C+Y reached over 80%, with a maximum of 91.35%. Groups G and G+Y also achieved removal rates exceeding 50%, with a maximum of 68.99%. These results provide a theoretical basis for the effective utilization of crops such as rice straw and husks, as well as for the bioremediation of perchlorate.

[0071] Example 5: ClO4 in the filtrate - Purification treatment test

[0072] To a circular fermentation tank (22 cm in diameter and 55 cm in height), 80 g of rice husk (or straw), 20 mL of vegetable oil, and 20 mL of fully acclimated sludge supernatant were added in sequence. The filtrates from each biofiltration column in Example 4 were collected and placed in the fermentation tank for static purification. Samples were taken and tested at different times. The results showed that no perchlorate was detected in the filtrates from all treatment groups after 48 hours of treatment.

[0073] The vegetable oil used in the above embodiment is peanut oil, the husks are not processed in any way, and the rice straw is cut into small pieces of about 2-5 mm in length.

[0074] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for removing perchlorate pollution in water using agricultural waste, characterized in that The steps include: A. Construction of a biofiltration column: Using river sand as a support, activated sludge acclimated with perchlorate and agricultural waste, or activated sludge acclimated with perchlorate, vegetable oil, and agricultural waste, to form a biofiltration column; B. Adding a nutrient solution to the biofiltration column and incubating in the dark to enrich the microorganisms in the activated sludge; then adding water containing perchlorate and incubating in the dark to further enrich and culture the perchlorate-degrading bacteria, thereby obtaining a biofiltration column enriched with perchlorate-degrading bacteria; C. Passing the perchlorate-containing water through the biofiltration column enriched with the perchlorate-degrading bacteria obtained in step B to obtain a filtrate; D. adding the obtained filtrate to activated sludge and agricultural waste, or activated sludge, vegetable oil and agricultural waste, and allowing to stand for treatment to obtain treated water; The agricultural waste is rice straw; The vegetable oil is at least one of peanut oil, soybean oil and corn oil; The river sand described in step A is clean river sand that has passed a 2 mm sieve; The nutrient solution described in step B is glucose solution.

2. The method for removing perchlorate pollution in water by utilizing agricultural waste according to claim 1, characterized in that: The nutrient solution described in step B is a glucose solution with a concentration of 35 to 45 g / L.

3. The method for removing perchlorate pollution in water by utilizing agricultural waste according to claim 1, characterized in that: The agricultural waste, the vegetable oil and the activated sludge described in step A are mixed in a ratio of 30-40 g: 20 mL: 20 mL; The agricultural waste, the vegetable oil and the activated sludge in step D are mixed in a ratio of 50-80 g: 20 mL: 20 mL.

4. The method for removing perchlorate pollution in water by utilizing agricultural waste according to claim 1, characterized in that: The conditions for adding nutrient solution and culturing in the dark in step B are culturing at 20-30° C. for 60-90 hours; The conditions for culturing in the dark by adding water containing perchlorate in step B are culturing at 20-30° C. for 100-150 hours; ClO4 in the water containing perchlorate described in step B - The concentration is 140-160 mg / L; The time for the static treatment described in step D is greater than 48 hours.

5. The method for removing perchlorate pollution in water by utilizing agricultural waste according to any one of claims 1 to 4, characterized in that: The activated sludge acclimated with perchlorate is prepared by the following steps: adding 50 mL of nutrient solution to every 300-500 mL of activated sludge, then adding deionized water to 900 mL, stirring evenly, and culturing for 7 days; starting from the 8th day, adding 1 mL of contaminated solution every other day; starting from the 14th day, adding 2 mL of contaminated solution every other day; starting from the 20th day, adding 4 mL of contaminated solution every day; after each addition, discarding the supernatant, adding 50 mL of nutrient solution and deionized water to 900 mL, stirring for a certain period of time every day to mix evenly; continuously increasing the perchlorate concentration in the nutrient solution until the added perchlorate ions can be completely degraded within 24 hours, thereby obtaining the activated sludge acclimated with perchlorate; wherein the nutrient solution is a glucose solution with a concentration of 35-45 g / L; the contaminating solution is a ClO4 solution with a concentration of 80-120 mg / L - of perchlorate solution.

6. Use of the method for removing perchlorate pollution in water bodies by utilizing agricultural wastes as claimed in any one of claims 1 to 5 in water treatment.

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