Method for enhancing the ability of duckweed to treat sewage

Abstract

The present application belongs to the field of sewage treatment, and particularly relates to a method for enhancing the sewage treatment capacity of duckweed. The specific technical scheme is as follows: a method for improving the sewage treatment capacity of duckweed, which combines the use of duckweed and Klebsiella sp. to treat sewage. The present application provides a new method for comprehensively improving the sewage treatment capacity of duckweed, which can significantly improve the removal rate of various pollutants in sewage by duckweed, inhibit the rapid proliferation of duckweed, avoid the secondary pollution of water bodies caused by the too fast growth of duckweed, reduce the risk of COD pollution caused by the decay of duckweed, and also reduce the labor cost caused by salvaging duckweed. The method of the present application does not need to add aeration equipment, aeration tank and the like, has a wide application range, and can be used for ecological restoration in multiple fields, such as livestock and poultry breeding wastewater, aquaculture wastewater, eutrophication and the like.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, and specifically relates to a method for enhancing the wastewater treatment capacity of duckweed. Background Technology

[0002] Duckweed is a common aquatic floating plant with rapid asexual reproduction and strong adaptability to the environment. It can effectively remove nitrogen, phosphorus, nutrients, heavy metals, and other pollutants from water and is widely used in the treatment of polluted water bodies. However, current technology shows that duckweed is only effective in removing nitrogen and phosphorus from water, and its effect on removing chemical oxygen demand (COD) is relatively poor. Furthermore, when using duckweed to treat wastewater, its rapid growth and reproduction mean that if mature duckweed is not harvested in time, its decay will further aggravate COD pollution.

[0003] Currently, methods for enhancing duckweed's ability to treat pollutants include aeration enhancement, artificial packing enhancement, and microbial agent enhancement. Among these, aeration enhancement not only increases wastewater treatment costs but also requires a larger land area. Studies have shown that using artificial packing to enhance duckweed only significantly improves nitrogen removal; it does not significantly promote the removal of other pollutants. Existing research has also explored methods that couple functional bacteria to duckweed roots to improve its removal capacity for specific pollutants (p-tert-butylphenol) in wastewater treatment plant effluent. However, this method only achieves a COD removal rate of 23.81% and an almost zero ammonia nitrogen removal rate.

[0004] In summary, there is currently no comprehensive method to enhance duckweed's ability to treat various pollutants, especially COD. Developing a method that can comprehensively improve duckweed's wastewater treatment capacity would have enormous research value and application potential. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enhancing the ability of duckweed to treat wastewater, especially to increase the ability of duckweed to treat COD in wastewater.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a method for improving the sewage treatment capacity of duckweed, which combines duckweed and Klebsiella sp. to treat sewage.

[0007] Preferably, the Klebsiella pneumoniae was deposited at the China General Microbiological Culture Collection Center on September 18, 2017, with accession number CGMCC NO.14619.

[0008] Preferably, the Klebsiella pneumoniae is domesticated before being used to treat wastewater. The domestication method is as follows: Klebsiella pneumoniae is introduced into wastewater, and the COD concentration in the wastewater is gradually increased. After the effluent from each stage of wastewater treatment is stable, the COD concentration is increased. The COD concentration of the wastewater is gradually increased to be equivalent to or higher than the COD concentration of the wastewater to be treated. After the Klebsiella pneumoniae can stably treat wastewater with a COD concentration equivalent to or higher than that of the wastewater to be treated, the domesticated microbial agent is obtained.

[0009] Preferably, the Klebsiella pneumoniae and materials that facilitate the attachment of Klebsiella pneumoniae are added to the sewage for acclimation.

[0010] Preferably, the material that facilitates the attachment of Klebsiella pneumoniae is any one or more combinations of multifaceted hollow spheres, fiber-filled suspension spheres, and K3 filler.

[0011] Preferably, the material that facilitates the attachment of Klebsiella pneumoniae is a fiber-filled suspension ball.

[0012] Accordingly, a method for improving the ability of duckweed to treat COD in water is carried out using the above-mentioned method.

[0013] Accordingly, a method for improving the nitrogen removal efficiency of water bodies by duckweed is carried out using the above-mentioned method.

[0014] Accordingly, a method for improving the phosphorus removal efficiency of duckweed in water is carried out using the above-mentioned method.

[0015] Correspondingly, a method for inhibiting the growth or reproduction of duckweed, or reducing the growth or reproduction activity of duckweed, or reducing the yield of duckweed, is carried out using the above-mentioned method.

[0016] The present invention has the following beneficial effects: The present invention provides a new method that can comprehensively improve the sewage treatment capacity of duckweed, which can significantly improve the removal rate of various pollutants in sewage by duckweed, the COD removal rate can be increased by more than 50%, and the removal rates of ammonia nitrogen, total nitrogen and total phosphorus are also significantly improved.

[0017] Meanwhile, the method of the present invention can also inhibit the rapid proliferation of duckweed, avoid secondary pollution of water caused by the rapid growth of duckweed, reduce the risk of COD pollution after duckweed decays, and also reduce the labor costs incurred due to duckweed harvesting.

[0018] The method of this invention does not require additional aeration equipment or aeration tanks, and has a wide range of applications. It can be used for ecological restoration in many fields, such as livestock and poultry breeding wastewater, aquaculture wastewater, and eutrophication. Attached Figure Description

[0019] Figure 1Schematic diagram of the COD treatment effect of different microbial agents-artificial fillers on wastewater;

[0020] Figure 2 This is a schematic diagram illustrating the impact of microorganisms on duckweed growth. Detailed Implementation

[0021] This invention provides a method to enhance the wastewater treatment capacity of duckweed, specifically by using duckweed and Klebsiella sp. in combination to treat wastewater. A preferred embodiment is Klebsiella sp. BFX-01, which was deposited on September 18, 2017, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC NO.14619; derived from patent CN201711116739.9.

[0022] A more preferred method is to first culture Klebsiella pneumoniae to a viable bacterial concentration ≥ 1 × 10⁻⁶. 9 After obtaining the microbial agent (CFU / mL), it is combined with duckweed to treat wastewater. A more preferred method is to add the microbial agent to the wastewater and gradually increase the COD concentration / content in the wastewater. After each stage of wastewater treatment, the COD is significantly reduced and the effluent is stable, the COD concentration is further increased. The wastewater COD concentration is gradually increased to be equivalent to or higher than the COD concentration of the wastewater to be treated. After the microbial agent can stably treat the wastewater, the COD in the wastewater is significantly reduced, and the effluent is stable, the acclimated microbial agent is obtained.

[0023] A more preferred approach is to conveniently obtain the acclimatized microbial agent by adding it along with filler materials, substrates, and other materials that facilitate microbial attachment, growth, and biofilm formation into the wastewater for microbial acclimatization. After acclimatization, the material with the acclimatized microbial agent attached can be removed. An even more preferred approach is to add the acclimatized microbial agent into a wastewater treatment system already inoculated with duckweed, forming a combined microbial-duckweed wastewater treatment system.

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. All obtained data are average values ​​obtained after at least three repetitions, and each repetition yields valid data.

[0025] Example 1: The Impact of Artificial Packing Material on Wastewater Treatment Efficiency

[0026] 1. Combination of microbial inoculants and artificial fillers. BFX-01 strain was cultured in LB medium at 30℃ and 160 rpm for 48 h to obtain microbial inoculants. These inoculants were then simultaneously added to domestic sewage along with multifaceted hollow spheres, suspended spheres (fiber-filled), and K3 fillers. The mass ratio of carbon, nitrogen, and phosphorus in the domestic sewage was adjusted to 100:5:1 (C:N:P = 100:5:1) by adding glucose, ammonium chloride, and potassium dihydrogen phosphate, resulting in an initial CODcr concentration of 300 mg / L. Dissolved oxygen concentration was controlled between 2 and 3 mg / L through aeration. The same domestic sewage was replaced every 24 h, and the COD content was measured. In this embodiment, potassium dichromate was used as the oxidant for COD measurement, i.e., the dichromate index (CODcr). After the effluent stabilized, the CODcr concentration in the domestic sewage was gradually increased to 400 mg / L and then 600 mg / L. After the CODcr content in the final effluent of domestic sewage stabilized, the artificial packing material with attached microbial agents was removed, thus obtaining the microbial agent-artificial packing material. Three replicates were set up for each group, and the results were averaged. The effects of using different artificial packing materials on the sewage treatment effect are shown in Table 1.

[0027] Table 1 Comparison of Wastewater Treatment Effects of Different Microbial Agents and Artificial Packers

[0028] COD Microorganisms - Multifaceted Hollow Spheres Microbial-suspension spheres (fiber-filled) Microbial-K3 Water ingress 300mg / L 300mg / L 300mg / L Out of water 130.25 mg / L 115.36 mg / L 135.14 mg / L Water ingress 400mg / L 400mg / L 400mg / L Out of water 173.48 mg / L 157.66 mg / L 175.63 mg / L Water ingress 600mg / L 600mg / L 600mg / L Out of water 261.07 mg / L 236.36 mg / L 265.45 mg / L

[0029] 2. Combination of duckweed, microbial inoculants, and artificial fillers. In this step, the wastewater originated from a residential community in Chengdu, Sichuan Province, with ammonia nitrogen concentrations of 27.31–31.91 mg / L, total nitrogen concentrations of 31.65–36.25 mg / L, total phosphorus concentrations of 2.63–3.92 mg / L, and CODcr concentrations of 193.44–211.2 mg / L. The duckweed used was *Lemna minor*, and the inoculum size was 240 g / m³. -2 The wastewater treatment system measures 34×27×35cm, with a total wastewater volume of 24L. Various acclimated microbial agent-artificial filler combinations were obtained using the method described in step 1. Microbial agent-hollow spheres, microbial agent-suspended spheres (fiber-filled), and microbial agent-K3 were placed into the wastewater treatment system inoculated with *Lysimachia christinae*, with a filler filling rate of 50% (v / v). These were designated as the *Lysimachia christinae* + hollow sphere group, the *Lysimachia christinae* + suspended sphere group (fiber-filled), and the *Lysimachia christinae* + K3 group, respectively. The control group was inoculated only with *Lysimachia christinae* and no microbial agent-artificial filler was added; all other conditions were the same, and this group was designated as the *Lysimachia christinae* group. A sequential batch treatment was used, meaning that after inoculation, the wastewater, inoculum, and filler were kept in the treatment system for a specific period. The operation of the wastewater treatment system was examined over 10 days. Wastewater samples were taken daily after treatment to determine the CODcr treatment effect of different microbial agent-artificial filler combinations on domestic wastewater. Each group had three replicates, and the average value was taken. The results are as follows: Figure 1As shown.

[0030] The results showed that the addition of microbial inoculant-artificial filler significantly improved the CODcr removal efficiency in domestic sewage. Within 7 days, the CODcr removal rates of duckweed + suspended balls (fiber-filled), duckweed + multi-faceted hollow balls, and duckweed + K3 reached 95.20%, 79.53%, and 67.15%, respectively. The duckweed + suspended balls (fiber-filled) group showed the highest CODcr removal rate and was chosen for subsequent examples.

[0031] Example 2: Demonstration of the effect of duckweed + suspended balls (fiber filling) in wastewater treatment

[0032] 1. Following the method in step 1 of Example 1, obtain the acclimatized microbial inoculant-suspension balls (fiber-filled); following the method in step 2 of Example 1, establish a wastewater treatment system. Add the acclimatized microbial inoculant-suspension balls (fiber-filled) to the inoculated duckweed (240 g·m³). -2 In a wastewater treatment system, one group was used as the experimental group. Simultaneously, a wastewater treatment system inoculated only with duckweed was set up, with all other conditions identical, serving as the control group. Sequencing batch reactor (SBR) treatment was used, and hydraulic retention time was controlled to set up groups for 2 days, 3 days, and 4 days. Measurements were taken continuously for 21 days to determine the concentrations of CODcr, ammonia nitrogen, total nitrogen, and total phosphorus in the influent and effluent of both the experimental and control groups. The average removal rate of each pollutant was calculated. Each group was replicated three times, and the average value was taken. The results are shown in Tables 2 and 3. Table 2 shows the measured values ​​of the influent and effluent for each group at different time points, and Table 3 shows the pollutant removal rates for each group.

[0033] Table 2 Comparison of Wastewater Treatment Results

[0034]

[0035] Table 3. Comparison of Wastewater Treatment Results (Removal Rate)

[0036]

[0037] When the hydraulic retention time was 4 days, the experimental group achieved an average CODcr removal rate of 80.72% for domestic sewage, which was 45.49% higher than that of the control group. The average removal rates for ammonia nitrogen, total nitrogen, and total phosphorus reached 73%, 64%, and 60%, respectively, which were at least 18.46%, 13.83%, and 10.62% higher than those of the control group.

[0038] 2. Take duckweed harvested weekly under different hydraulic retention conditions in step 1 of this embodiment, as well as duckweed from the final domestic sewage treatment system, and determine the dry weight of the duckweed. Duckweed is harvested twice a week to maintain the fresh weight of duckweed in the sewage treatment system at approximately 20g. Method for determining the dry weight of duckweed: Rinse the harvested fresh duckweed with pure water, spread it evenly on absorbent paper for 5 minutes, filter out the free water, and then place it in an oven at 60℃ for 48 hours. After cooling to room temperature, weigh it using a 0.01g balance and record the weight as the dry weight of the duckweed. Three replicates are set for each group, and the average value is taken. Experimental results are as follows: Figure 2 As shown in the figure. The results showed that the dry weight of duckweed in the experimental groups was lower than that in the control group at all hydraulic retention times. The dry weight of duckweed in the experimental groups with hydraulic retention times of 2 days, 3 days, and 4 days reached 62.62 g·m³. -2 65.78 g·m -2 and 67.12 g·m -2 Compared with the control group, the percentages were reduced by 8.8%, 3.5%, and 3.0%, respectively. This demonstrates that the microbial inoculant provided by this invention can effectively improve the treatment capacity of duckweed wastewater while controlling duckweed production and preventing rapid and massive proliferation of duckweed.

[0039] When Klebsiella pneumoniae BFX-01 was replaced with five other Klebsiella pneumoniae from different sources, and the same experiment as in Example 2 was performed under the same conditions, it was not possible to simultaneously obtain the effects of improving the sewage treatment capacity of duckweed and inhibiting the growth of duckweed.

[0040] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, substitutions, or variations made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for improving the wastewater treatment capacity of duckweed, characterized in that: Wastewater was treated by combining duckweed and Klebsiella sp. The duckweed was purple-backed duckweed, and the Klebsiella sp. was deposited at the China General Microbiological Culture Collection Center on September 18, 2017, with accession number CGMCC NO.14619.

2. The method according to claim 1, characterized in that: The Klebsiella pneumoniae is domesticated before being used to treat wastewater; the domestication method is as follows: The Klebsiella pneumoniae was introduced into the wastewater, and the COD concentration in the wastewater was gradually increased. After the effluent from each stage of wastewater treatment stabilized, the COD concentration was increased. The COD concentration of the wastewater was gradually increased to be equivalent to or higher than that of the wastewater to be treated. After the Klebsiella pneumoniae could stably treat wastewater with a COD concentration equivalent to or higher than that of the wastewater to be treated, the acclimatized microbial agent was obtained.

3. The method according to claim 2, characterized in that: The Klebsiella pneumoniae, along with materials that facilitate its attachment, were added to the wastewater for acclimation.

4. The method according to claim 3, characterized in that: The material that facilitates the attachment of Klebsiella pneumoniae is any one or more combinations of multifaceted hollow spheres, fiber-filled suspension spheres, and K3 filler.

5. The method according to claim 4, characterized in that: The material that facilitates the attachment of Klebsiella pneumoniae is a fiber-filled suspension ball.

6. A method for improving the ability of duckweed to treat COD in water, characterized in that: The method described in any one of claims 1 to 5 shall be used.

7. A method for improving the ability of duckweed to remove nitrogen from water, characterized in that: The method described in any one of claims 1 to 5 shall be used.

8. A method for improving the ability of duckweed to remove phosphorus from water, characterized in that: The method described in any one of claims 1 to 5 shall be used.

9. A method for inhibiting the growth or reproduction of duckweed, or reducing the growth or reproductive activity of duckweed, or reducing the yield of duckweed, characterized in that: The method described in any one of claims 1 to 5 shall be used.

Images