Method for treating acidic organic wastewater by using mixed algae and application thereof

Abstract

The invention discloses a method for treating acidic organic wastewater by using mixed algae. The method comprises the following steps: (1) inoculating and culturing filamentous algae in the acidic organic wastewater; (2) culturing the filamentous algae in the acidic organic wastewater for 6 days, and then adding streptozotoci or / and Widdersonia with the same algae cell concentration to carry out cooperative treatment or gradient treatment on the acidic organic wastewater; (3) fishing algal biomass in the wastewater after the co-treatment or gradient treatment is performed for 6 days; and (4) detecting parameters of the acidic organic wastewater, and judging whether cooperative treatment or cascade treatment needs to be carried out again according to the detected parameters. The obtained algae biomass is used as feed. The method has the innovation points that filamentous algae and high-stain-resistance streptazone algae or / and high-nutrient-value widmannella are subjected to mixed culture in the acidic organic wastewater by adopting a synergistic treatment or gradient treatment mode, so that high-yield algae biomass is obtained while the acidic organic wastewater is treated; an efficient, stable, economical and feasible microalgae wastewater treatment system is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating acidic organic wastewater by utilizing mixed algae and application thereof. Background Art

[0002] Acidic organic wastewater is a type of wastewater that pollutes aquatic life and has significant negative impacts on water, soil, ecosystems and human health. Traditional chemical and physical methods of adding alkali to treat acidic organic wastewater have the disadvantages of complex steps, high energy consumption, high cost, unstable effects, and waste of recyclable resources.

[0003] In recent years, microalgae wastewater treatment technology has attracted much attention due to its potential for both pollutant removal and biomass resource utilization, but existing research still faces multiple bottlenecks: 1. The tolerance and pollutant removal efficiency of a single algae species in a complex acidic environment are limited, and pH adjustment is required for the treatment of acidic organic wastewater; 2. High value-added microalgae (such as unicellular algae) are difficult to apply on a large scale due to the high harvesting cost; 3. Microalgae biomass after wastewater treatment is mostly limited to the value conversion path and fails to give full play to its nutritional function advantages. Therefore, how to build an efficient, stable and economically feasible microalgae wastewater treatment system and realize the high-value utilization of microalgae biomass has become a key issue that needs to be broken through in this field. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention invents a method for treating acidic organic wastewater using mixed algae and its application.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A method for treating acidic organic wastewater using mixed algae and its application, comprising the following steps: (1) Inoculate and culture filamentous algae in acidic organic wastewater at an algae cell concentration of OD750 = 0.5-1; (2) After 6 days of cultivation of filamentous algae in acidic organic wastewater, Desmodesmus or / and Weimerella are added at the same algal cell concentration to perform synergistic or cascade treatment of the acidic organic wastewater; (3) After 6 days of coordinated or cascade treatment of acidic organic wastewater, algae biomass in the wastewater is removed; (4) Detect the parameters of acidic organic wastewater and determine whether the acidic organic wastewater needs to be treated again in a coordinated or cascaded manner based on the detected parameters.

[0006] The innovation of the present invention is to use a coordinated treatment or cascade treatment method to mix filamentous algae with highly pollution-tolerant single-celled Desmodium and / or highly nutritious single-celled Wei'sonia to treat the acidic organic wastewater, thereby obtaining high-yield algae biomass while treating the acidic organic wastewater, thereby realizing an efficient, stable and economically feasible microalgae wastewater treatment system.

[0007] Further, the co-treatment is that after the filamentous algae are cultured in acidic organic wastewater for 6 days, Ulothrix zonata or / and Westella botryoides are directly added for continuous culture.

[0008] Further, the stepwise treatment is that after the filamentous algae are cultured in acidic organic wastewater for 6 days, the filamentous algal biomass is fished out and then Ulothrix zonata or / and Westella botryoides are added for continuous culture.

[0009] Further, the COD of the acidic organic wastewater is 3000 - 5000 mg / L. In previous experiments, microalgae showed high tolerance within this concentration range and had good growth conditions, breaking through the traditional limitation that ordinary microalgae are intolerant to high concentrations of COD. This concentration range has high representativeness and application value in actual wastewater treatment.

[0010] Further, the pH of the acidic organic wastewater is 4 - 5.

[0011] Further, the growth conditions of the algae in the acidic organic wastewater include aeration with compressed air enriched with 1 - 2% carbon dioxide, the culture temperature is maintained at 25 ± 1°C, and continuous illumination is carried out under a light intensity of 300 μmol / (m²·s). The mixed algae can grow normally under suitable external culture conditions.

[0012] Further, the filamentous algae is Tribonema sp. GXU - A10, with the Latin name Tribonema sp. GXU - A10, preservation date: January 6, 2023, preservation unit: China Center for Type Culture Collection, preservation number: CCTCC M 2023047. Its morphological characteristics make it more convenient in the harvesting process, which can effectively reduce the harvesting cost and improve economic benefits. Secondly, Tribonema sp. GXU - A10 has strong pollution tolerance and can grow stably in a relatively harsh wastewater environment, ensuring the stability of the treatment effect. In addition, considering that large algae may entangle some macromolecular pollutants during the culture process, the preliminary culture of Tribonema sp. can effectively remove this part of pollutants and lighten the burden on subsequent treatment links.

[0013] Further, the parameters for detecting the acidic organic wastewater include the pH value, organic matter, nitrogen, and phosphorus content of the wastewater. Through the above parameters, the purification effect of the acidic organic wastewater can be intuitively understood.

[0014] Further, the acidic organic wastewater is molasses alcohol wastewater, which is a typical representative of wastewater.

[0015] The application of the algal biomass obtained by the present invention as feed can be used as aquaculture feed.

[0016] The advantages of the present invention are as follows: By culturing different algae, Tribonema and Desmodesmus or / and Westiellopsis are co-cultured in acidic organic wastewater, and their synergistic effect is utilized to enhance the treatment effect of acidic organic wastewater. This treatment method can make full use of the complementarity between different microalgae, improve the wastewater treatment efficiency, achieve the treatment of acidic organic wastewater, and at the same time obtain high-yield algal biomass; the application of algal biomass as feed realizes the high-value utilization of microalgae products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a three-dimensional fluorescence effect comparison diagram before and after the treatment of acidic organic wastewater by different algae alone and in combination in the present invention; Figure 2 is a comparison of the algal biomass obtained by treating different algae alone, in combination, and in a cascading manner in the present invention Figure 1 ; Figure 3 is a comparison of the algal biomass obtained by treating different algae alone, in combination, and in a cascading manner in the present invention Figure 2 ; Figure 4 is a comparison of the algal biomass obtained by treating different algae alone, in combination, and in a cascading manner in the present invention Figure 3 ; Figure 5 is a microscopic image of Nile red fluorescence staining during the treatment of wastewater by different algae alone, in combination, and in a cascading manner in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below with reference to the accompanying drawings: In the embodiment of the present invention, the Tribonema GXU-A10, with the Latin name Tribonema sp. GXU-A10, preservation date: January 6, 2023, preservation unit: China Center for Type Culture Collection, preservation number: CCTCC M 2023047, can be found in the literature "Dual application of Tribonema sp. GXU-A10 for purifying molassesvinasse and promoting the growth and health of Oreochromis niloticus [J]. Algal Research, 2023, 76,103298". The Desmodesmus GXU-A4, with the Latin name Desmodesmus sp. GXU-A4 was deposited at the China Center for Type Culture Collection in Wuhan, China on December 17, 2021, with the deposit number CCTCC M 20211641, and can be found in the literature "Potential application of a newly isolated microalga Desmodesmus sp. GXU-A4 for recycling Molasses vinasse[J]. Chemosphere, 2023,(328),138616". Westiellopsis stellata, with the Latin name Vischeria stellata SAG 887-2, was purchased from the Algae Culture Collection of the University of Göttingen in Germany (SAG), can be found in the algal species library (https: / / www.uni-goettingen.de / en / 45175.html), was preserved in BG-11 medium, and the algal species was aseptically cultured and the aseptic algal species was preserved in the Laboratory of Environmental Microbial Resources and Utilization, College of Life Science and Technology, Guangxi University, with the deposit number GXU-A13. Example 1

[0019] A method for treating acidic organic wastewater using mixed algae, comprising the following steps: (1) Tribonema was inoculated and cultured in acidic organic wastewater with a COD of 3000 - 5000 mg / L and a pH of 4 - 5 at an algal cell concentration of OD750 = 0.5 - 1; (2) After Tribonema was cultured in acidic organic wastewater for 6 days, Stichococcus with high pollution tolerance or / and Westiellopsis with high nutritional value were added at the same algal cell concentration to co-treat the acidic organic wastewater; (3) After co-treating the acidic organic wastewater for 6 days, the algal biomass in the wastewater was fished out to obtain mixed algal biomass; (4) The parameters of the acidic organic wastewater were detected, and it was judged whether the acidic organic wastewater needed to be co-treated again according to the detected parameters; the parameters included the pH value, organic matter, nitrogen and phosphorus content of the wastewater. Example 2

[0020] A method for treating acidic organic wastewater using mixed algae, comprising the following steps: (1) Tribonema was inoculated and cultured in acidic organic wastewater with a COD of 3000 - 5000 mg / L and a pH of 4 - 5 at an algal cell concentration of OD750 = 0.5 - 1; (2) After Tribonema was cultured in acidic organic wastewater for 6 days, the Tribonema biomass was fished out, and then Stichococcus with high pollution tolerance or / and Westiellopsis with high nutritional value were added at the same algal cell concentration to perform cascade treatment on the acidic organic wastewater; (3) After 6 days of cascade treatment of acidic organic wastewater, the algal biomass in the wastewater was fished out to obtain algal biomass; (4) Detect the parameters of the acidic organic wastewater, and judge whether the acidic organic wastewater needs to be subjected to cascade treatment again according to the detected parameters; the parameters include the pH value of the wastewater, the contents of organic matter, nitrogen and phosphorus.

[0021] The co-treatment is to first cultivate filamentous algae in acidic organic wastewater for 6 days and then add Ulothrix zonata or / and Westella botryoides to cultivate for 6 days; in the co-treatment, filamentous algae, Ulothrix zonata and Westella botryoides can act on pollutants such as organic matter, nitrogen and phosphorus in the wastewater together, and convert them into harmless substances through mechanisms such as adsorption and degradation. At the same time, the interaction between mixed microalgae can also promote the growth and metabolism of each other, further improving the treatment effect. There are also multiple advantages that the coexistence of multiple microalgae can reduce the environmental sensitivity of a single species and improve the stability of the system, and by optimizing the combination of filamentous algae and other small-volume microalgae, the cost of wastewater treatment can be reduced.

[0022] The cascade treatment is to first cultivate filamentous algae in acidic organic wastewater for 6 days and then fish out the filamentous algae in the wastewater, and then add Ulothrix zonata or / and Westella botryoides to cultivate for 6 days, that is, different types of microalgae are used for treatment in each stage to achieve the purpose of gradually removing pollutants. During the cascade treatment process, the wastewater first enters the first treatment stage, and filamentous algae are used to remove some pollutants. Using its morphological advantages, some macromolecular substances can be entangled; then, the wastewater enters the second treatment stage, and another single-celled microalgae with pollution tolerance or / and high value is used to further remove the remaining pollutants. Pollutants are gradually removed through multiple treatment stages to improve the treatment effect. At the same time, the growth of microalgae in each stage brings high-value biomass to maximize resource utilization, and the treatment difficulty and cost of each stage can also be reduced.

[0023] In the embodiment of the present invention, the growth conditions of algae in acidic organic wastewater include aeration with compressed air enriched with 1-2% carbon dioxide, the cultivation temperature is maintained at 25±1°C, and continuous illumination is carried out under a light intensity of 300 μmol / (m²·s), and it is necessary to ensure that the algae can grow normally. The acidic organic wastewater is molasses alcohol wastewater, which is a typical representative in wastewater.

[0024] In order to highlight the innovation of the method of this application, in the experimental comparison of acidic organic wastewater, three methods of single-algae treatment, co-treatment and cascade treatment are compared with each other. The single-algae treatment is to treat acidic organic wastewater with a single type of algae. After 6 days of cultivation, the same amount of algae will be added to the acidic organic wastewater; except for the different algae treatment methods, the other cultivation conditions of the three treatment methods are the same.

[0025] Such as Figure 1As shown in the figure, regions I and II where the excitation wavelength (Ex) is below 380 nm and the emission wavelength (Em) is below 250 nm represent a class of aromatic proteins, tryptophan-like substances, and tyrosine-like organic substances; region III with Ex < 250 nm and Em > 380 nm represents the fulvic acid family; region IV with 250 < Ex < 400 nm and Em < 380 nm represents a class of soluble microbial by-products; region V with Ex > 250 nm and Em > 380 nm represents the humic acid family; all samples were diluted 10 times before measurement. In the figure, A10 represents the treatment with Tribonema aequale alone, A4 represents the treatment with Ulothrix zonata alone, and A13 represents the treatment with Westiellopsis prolifica alone; A10 + A4 represents the co-treatment of Tribonema aequale and Ulothrix zonata, A10 + A13 represents the co-treatment of Tribonema aequale and Westiellopsis prolifica, and A10 + A4 + A13 represents the co-treatment of Tribonema aequale, Ulothrix zonata, and Westiellopsis prolifica; A10 - A4 represents the stepwise treatment of Tribonema aequale and Ulothrix zonata, A10 - A13 represents the stepwise treatment of Tribonema aequale and unicellular Westiellopsis prolifica, and A10 - A4 - A13 represents the stepwise treatment of Tribonema aequale, Ulothrix zonata, and Westiellopsis prolifica.

[0026] After the co-treatment or stepwise treatment of acidic organic wastewater, the peak intensity of the wastewater fluorescence spectrum decreased significantly, confirming its high purification ability. Different algal strains showed specificity in the removal of characteristic pollutants: A4 had an advantage in removing soluble microbial by-products, A10 showed the best removal effect on humic acid substances, and A13 had a specific removal ability for aromatic proteins, tryptophan-like, and tyrosine-like organic substances. Through experimental comparison, the co-treatment system of A10 + A4 + A13 and the stepwise treatment of A10 - 13 had the best comprehensive purification effect. This treatment effect was the complementary effect of the metabolic pathways of multiple algal species, achieving full coverage of the organic matter degradation pathways. Specifically, the cultivation of filamentous algae in the early stage improved the biocompatibility in acidic organic wastewater, enabling the subsequent addition of high-value sensitive algal strains to enhance their biological activity. The present invention confirms that constructing a co-treatment or stepwise treatment system of multiple algal species can break through the functional limitations of single algal species and provide a new strategy for the advanced treatment and resource utilization of wastewater.

[0027] Figures 2 - 4 The figure is a comparison chart of the algal biomass obtained after different treatments of acidic organic wastewater. It can be seen from the figure that after cultivation, the biomass of A4 alone in acidic organic wastewater is 1.30 g / L, the biomass of the co-treatment of A4 and A10 is 3.28 g / L, and the biomass of the stepwise treatment of A4 and A10 is 1.55 g / L.

[0028] The biomass of A13 alone is 1.40 g / L, the biomass of the co-treatment of A13 and A10 is 2.62 g / L, and the biomass of the stepwise treatment of A13 and A10 is 2.15 g / L.

[0029] The biomass of A10 treated alone is 1.48 g / L, the biomass of A10 treated in cooperation with A10 is 2.41 g / L, the biomass of A10 treated in cooperation with A4 and A13 is 2.85 g / L, and the biomass of the cascade treatment of A10 in mixed culture with A4 and A13 is 1.41 g / L.

[0030] Therefore, experimental comparison shows that the maximum algal biomass is obtained by the cooperative treatment of acidic organic wastewater.

[0031] Figure 5 The change in the Nile red fluorescence intensity during the cultivation of algae in each group is shown. The fluorescence intensity of A10 and A13 is the strongest in the later stage of cultivation, indicating that they accumulate oil during the growth process. It can be observed that the wastewater is basically full of algae. The single-celled Westella tends to attach to the filamentous algae, and the Schroederia tends to accumulate near the filamentous algae. This shows that the treatment method of using filamentous algae in cooperation with small-cell algae is more conducive to the harvesting of algae and reduces the actual application cost.

[0032] The algal biomass obtained after the treatment of acidic organic wastewater in this embodiment can be used as feed. Feeding with algal feed can enhance the immunity and antioxidant capacity of fish, comprehensively improve the growth performance of fish, and contribute to the improvement of the economic benefits of aquaculture.

[0033] The present invention innovatively proposes an integrated solution centered on "directional combination of functional algal species - synergistic optimization of treatment processes - high-value closed-loop utilization of products". First, filamentous algae (such as Tribonema) are screened as carriers to construct a mixed algal system, and their natural flocculation characteristics are used to achieve low-cost harvesting; by introducing Schroederia with outstanding pollution tolerance (such as Schroederia ostenfeldii) to strengthen the heavy metal tolerance and sulfate reduction ability, and coupling with highly nutritious acid-tolerant unicellular algae (such as Westella botryoides) to improve the biomass quality. Secondly, the effects of three modes of single treatment, cooperative treatment and cascade treatment on the pollutant removal kinetics and algal population stability are systematically compared. Finally, the obtained eutrophic algal powder is directionally developed into a functional aquatic feed to construct a circular economy chain of "wastewater purification - resource recovery - feed value addition".

[0034] Although the specific implementation modes of the present invention have been described and illustrated in detail above, it should be pointed out that we can make various changes and modifications to the above implementation modes, but these do not deviate from the spirit of the present invention and the scope recorded in the appended claims.

Claims

1. A method for treating acidic organic wastewater using mixed algae, characterized in that: The steps include: (1) Inoculate and culture filamentous algae in acidic organic wastewater at an algae cell concentration of OD750 = 0.5-1; (2) After 6 days of cultivation of filamentous algae in acidic organic wastewater, Desmodesmus or / and Weimerella are added at the same algal cell concentration to perform synergistic or cascade treatment of the acidic organic wastewater; (3) After 6 days of coordinated or cascade treatment of acidic organic wastewater, algae biomass in the wastewater is removed; (4) Detect the parameters of acidic organic wastewater and determine whether the acidic organic wastewater needs to be treated again in a coordinated or cascaded manner based on the detected parameters.

2. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The synergistic treatment is that after the filamentous algae are cultured in the acidic organic wastewater for 6 days, Desmodesmus and / or Weimerella are directly added to continue the culture.

3. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The cascade treatment is to culture the filamentous algae in the acidic organic wastewater for 6 days, remove the filamentous algae biomass, and then add Desmodesmus and / or Weimerella to continue the culture.

4. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The COD of the acidic organic wastewater is 3000-5000 mg / L.

5. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The pH of the acidic organic wastewater is 4-5.

6. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The growth conditions of algae in acidic organic wastewater include aeration with compressed air enriched with 1-2% carbon dioxide, culture temperature maintained at 25±1℃ and continuous illumination at a light intensity of 300μmol / (m²·s).

7. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The parameters for detecting acidic organic wastewater include pH value, organic matter, nitrogen and phosphorus content of the wastewater.

8. The method for treating acidic organic wastewater using mixed algae according to claim 1, characterized in that: The acidic organic wastewater is molasses alcohol wastewater.

9. Use of the algal biomass according to claim 1 as feed.

Images