An aerobic granular sludge based on functional flora-microalgae-pyrite composite system for strengthening synergy and a preparation method thereof

Abstract

The present application relates to sewage biological treatment technical field, provide a kind of based on function bacteria group-microalgae-pyrite composite system enhanced synergistic aerobic granular sludge and its preparation method.Characteristics are that the method is composed of four steps of pyrite pretreatment, bacteria-algae synergistic acclimation inoculation, aerobic granular sludge induction formation and mature stable aerobic granular sludge.The present application constructs the trinity system of "pyrite-function bacteria group-microalgae", and makes three form physical-chemical-biochemical synergistic network.The aerobic granular sludge prepared by function bacteria group-microalgae-pyrite composite system enhanced synergistic, when deep treatment mariculture tail water, not only has higher COD, TN and TP removal efficiency, good anti-impact resistance and load capacity, but also can regularly harvest microalgae in system as aquatic feed additive, realize "pollutant→resource" transformation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biological treatment of mariculture effluent, and particularly relates to an aerobic granular sludge based on functional flora-microalgae-pyrite composite system for enhanced synergy and a preparation method thereof. BACKGROUND

[0002] With the popularization of intensive and high-density breeding modes, the water environment pollution is aggravated while the output of aquatic products is significantly improved. Effluent treatment is a key link to ensure the ecological sustainability and environmental protection of aquaculture. The traditional method for treating effluent is conventional physical and chemical method. Although these methods have rapid effects, they have problems such as being only suitable for small-scale water areas, high cost and easy to cause secondary pollution. Compared with the traditional method, the biological treatment technology is more and more concerned due to its environmental friendliness and low economic cost. Among them, the bacteria-algae symbiotic system has become one of the research hotspots.

[0003] The bacteria-algae symbiotic sludge technology (Microalgal-bacterial Aggregates, referred to as MABA) is based on the activated sludge method and adds microalgae. The extracellular polymeric substance (EPS) secreted by bacteria adheres the microalgae to the surface of the bacteria aggregates, and is commonly used in a sequencing batch reactor (SBR). The bacteria-algae symbiotic aerobic granular sludge is a kind of MABA technology, which is usually formed by the self-aggregation of microorganisms based on the aerobic granular sludge as seed sludge. The bacteria-algae symbiotic aerobic granular sludge has a highly specialized community and strong resistance to organic / toxicity shock load, and can efficiently remove COD, ammonia nitrogen and the like, and is suitable for water treatment with high load and high standard discharge such as high-density mariculture effluent. However, the MABA technology has the problems that the bacteria-algae floc has weak ability to resist hydraulic shock load, and the bacteria-algae in the floc is easily separated under high hydraulic disturbance; the bacteria-algae symbiotic aerobic granular sludge strictly depends on an aerobic environment, and has weak functions of phosphorus removal and anaerobic denitrification; the activated sludge has a dark color, which hinders the absorption of light energy by microalgae, resulting in low treatment efficiency of the reactor.

[0004] Previous studies have shown that pyrite (FeS2) is a typical sulfide mineral. Its surface can not only slightly dissolve in water to release Fe 2+ and reduced sulfide, but also can efficiently adsorb various pollutants. Therefore, introducing pyrite into the bacteria-algae symbiotic aerobic granular sludge system can help to play the advantages of chemical and biological synergies through the three core functions of chemical substance release, physical structure regulation and microbial metabolism synergy, and strengthen the “high efficiency and high controllability” of the bacteria-algae symbiotic aerobic granular sludge in wastewater treatment. SUMMARY

[0005] To solve the above technical problems, the present application provides an aerobic granular sludge based on a functional flora-microalgae-pyrite composite system for enhanced synergy and a preparation method thereof. The present application is different from the traditional "bacteria-algae simple mixing" mode, and a "pyrite (carrier / nutrient slow-release)-functional flora (degradation)-microalgae (oxygen production / carbon fixation)" trinity system is constructed, so that the three form a physicochemical-biochemical synergistic network. The aerobic granular sludge prepared by the functional flora-microalgae-pyrite composite system for enhanced synergy has not only high COD, TN and TP removal efficiency and good impact resistance and load capacity when used for deep treatment of seawater breeding tail water, but also can periodically harvest the microalgae in the system as aquatic feed additives, realizing the transformation of "pollutants to resources".

[0006] The first object of the present application is to provide a preparation method of an aerobic granular sludge based on a functional flora-microalgae-pyrite composite system for enhanced synergy, comprising the following steps:

[0007] (1) Pretreatment of pyrite: soak pyrite particles in an acid solution, stir to remove impurities; adjust the pyrite to pH 7.0-7.5 using an alkaline adjusting agent to avoid acid damage to bacteria and algae, and wash with a detergent to obtain pretreated pyrite particles;

[0008] (2) Bacteria-algae co-domestication inoculation: select a salt-tolerant microalgae for inoculation, place it in a light incubator for culture and activation, and expand the culture to obtain an algal liquid; take the activated sludge from a seawater breeding tail water sedimentation tank, take the lower sludge after standing and settling, seal it and aerate it with oxygen, control the dissolved oxygen DO at 2-5 mg / L, and add simulated seawater breeding tail water to obtain bacteria sludge [here, the bacteria sludge refers to a muddy aggregate with certain humidity and density formed by mixing microorganisms (bacteria, fungi, actinomycetes, etc.) and activated sludge]; inoculate the bacteria sludge with the algal liquid and add the pretreated pyrite particles obtained in step (1) to obtain a functional flora-microalgae-pyrite composite; then perform bacteria-algae co-domestication;

[0009] (3) Induction of aerobic granular sludge: inoculate the mixed solution of the "functional flora-microalgae-pyrite composite" after domestication in step (2) into an SBR reactor provided with a light source, and operate under light conditions;

[0010] (4) Maturation and stabilization of aerobic granular sludge: extend the operation cycle to 30-60 days, gradually increase the influent load, and detect the particle size, strength and pollutant removal rate of the granules every week; the yellow aerobic granular sludge in the SBR reactor begins to turn green and adheres to the pyrite particles to obtain the aerobic granular sludge.

[0011] In some embodiments of the present application, in step (1), the original particle size of the pyrite particles is 5.0-7.0 mm, and then the particles are ground and sieved, with a sieve size of 20-400 mesh, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400 mesh, or any interval value between any two numerical values.

[0012] The concentration of the acid solution is 0.2-1 mol / L.

[0013] The acid is selected from one or more of sulfuric acid, hydrochloric acid, and nitric acid; further, the dilute sulfuric acid is 0.5-1 mol / L, the dilute hydrochloric acid is 0.5-1 mol / L, and the dilute nitric acid is 0.2-0.5 mol / L.

[0014] The solid-liquid ratio of the acid solution to the sieved pyrite particles is (1:4)-(1:6) g / mL.

[0015] The stirring time is 2-4 hours.

[0016] The alkaline adjusting agent includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate; the concentration of the alkaline adjusting agent is 0.05-0.2 mol / L.

[0017] The washing agent includes deionized water or filtered seawater, and the washing is performed at least three times.

[0018] In some embodiments of the present application, the seawater aquaculture tail water is tail water from a pond or a factory farming workshop, which contains natural nitrifying bacteria and heterotrophic degrading bacteria, such as Nitrosomonas, Pseudomonas, etc.

[0019] In some embodiments of the present application, in step (2), the salt-tolerant microalgae include one or more of Chlorella vulgaris, Dunaliella salina, and Navicula marina.

[0020] After the salt-tolerant microalgae are expanded and cultured, the OD680 value of the algal liquid is stabilized at 0.8-1.2, and the algal density is 1×10 6 -5×10 6 cells / mL, which can be used for subsequent inoculation;

[0021] The light culture and activation conditions are as follows: light / dark ratio (10:14)-(14:10), light intensity 2000-4000 xl, and static culture for 18-36 h.

[0022] In some embodiments of the present application, in step (2), the time for standing and precipitating is 20-40 minutes.

[0023] The MLSS of the lower layer sludge is 3-5 g / L.

[0024] The aeration intensity is 1.5-2.0 L / (L·min).

[0025] In some embodiments of the present application, in step (2), the COD of the simulated mariculture tail water is 50-150 mg / L, the TN is 30-50 mg / L, the TP is 5-10 mg / L, and the salinity is 20-30‰.

[0026] In some embodiments of the present application, in step (2), the MLSS of the bacterial sludge is 3-5 g / L.

[0027] The volume ratio of the bacterial sludge to the algal liquid is (2:1)-(4:1).

[0028] The dosage of the pyrite particles is 5wt%-10wt% of the dry weight of the mixed liquid of the bacterial sludge and the algal liquid, about 0.2-0.3 g / L.

[0029] In some embodiments of the present application, in step (2), after the COD in the reaction liquid increases to 200 mg / L and the TN increases to 60 mg / L after the bacterial-algal cooperative domestication, if the COD removal rate in the reactor is ≥80%, the NH4 + removal rate is ≥70%, and the microscopic examination shows that the bacteria and algae are attached to the surface of the pyrite, it indicates that the algae have adapted to the high-salt environment and can utilize the Fe 2+ / SO4 2- .

[0030] In some embodiments of the present application, in step (2), the period of cooperative domestication of the functional bacterial flora-microalgae-pyrite complex is 10-15 days, and 30-70% of the simulated mariculture tail water is replaced every day to gradually increase the pollutant concentration.

[0031] In some embodiments of the present application, in step (3), the initial MLSS of the mixed liquid of the domesticated “functional bacterial flora-microalgae-pyrite complex” is controlled to be 3-4 g / L, and the concentration of the pyrite is 0.5-1.5 g / L.

[0032] The light condition is that the light-dark ratio is (10:14)-(14:10), the light intensity is 2000-4000 xl, and the standing culture is performed for 18-36 h.

[0033] In some embodiments of the present application, in step (4), the influent load includes a COD load and an NH4 + -N load, the COD load is from 1.0 kg / (m3 • d) up to 2.5 kg / (m 3 • d), NH4 + - the N load is increased from 0.15 kg / (m 3 • d) to 0.4 kg / (m 3 • d);

[0034] When the particle size of the granules is 1.0-2.0 mm, the granules are not broken when blown with a straw, the COD removal rate is ≥85%, the TN removal rate is ≥80%, the TP removal rate is ≥85%, and the above values are stable for 10 consecutive days, then the high-efficiency aerobic granular sludge is mature;

[0035] When the granules are broken under impact load (such as the sudden increase of influent COD to more than 500 mg / L), the aeration intensity is reduced to 0.8-1.5 L / (L·min), and the load is temporarily suspended until the granules recover, and then adjusted;

[0036] Since the pyrite will be slowly oxidized and consumed during the operation of the SBR reactor, in order to maintain the "nutrient release" function, the pyrite content is regularly detected every 5-10 days, and if it is lower than 0.5 g / L, 0.1-0.2 g / L is added;

[0037] The ratio of SVI5 to SVI30 of the aerobic granular sludge is above 0.85.

[0038] A second object of the present application is to provide an aerobic granular sludge based on a functional flora-microalgae-pyrite composite system for enhanced synergy, which is prepared by the above preparation method. The aerobic granular sludge presents a core-shell-like structure, with pyrite particles as the core to form an internal anaerobic region, and an intermediate layer and an outer layer successively wrapped on the surface of the core, the intermediate layer comprising denitrifying functional bacteria, and the outer layer comprising microalgae and aerobic functional bacteria; wherein the pyrite particles and the intermediate layer, and the intermediate layer and the outer layer are connected and aggregated by the extracellular polymeric substance of microorganisms.

[0039] The aerobic granular sludge obtained by the present application presents a core-shell-like layered structure:

[0040] (1) Structure layering and core component:

[0041] Core region (anaerobic region):

[0042] The core is a relatively closed space, which is mainly the microenvironment formed by the aggregation of pyrite particles. Pyrite as the core, on the one hand, can form the basis of internal anaerobic due to its own physical structure, and on the other hand, it can slowly release Fe 2+ and SO4 2-and so on, provide special nutrients and reaction conditions for surrounding microorganisms, and drive anaerobic-related metabolic processes, such as some anaerobic microorganisms can utilize Fe 2+ and so on to carry out metabolism.

[0043] Intermediate region (anoxic zone):

[0044] The outer side of the core (anaerobic zone) is the region where functional bacteria (such as denitrifying bacteria) are mainly distributed. The dissolved oxygen concentration here is between aerobic and anaerobic, providing a suitable environment for anoxic metabolic processes (such as denitrification). Functional bacteria, core pyrite, and outer aerobic zone microalgae, functional bacteria, and other microorganisms are connected and adhered by microbial secretions (such as extracellular polymeric substances, EPS). EPS acts like "biological glue", promoting aggregation between microorganisms and between microorganisms and pyrite.

[0045] Outer region (aerobic zone):

[0046] The outermost side is the main habitat of microalgae and aerobic functional bacteria (such as nitrifying bacteria, heterotrophic degrading bacteria, etc.). Microalgae produce oxygen through photosynthesis, providing sufficient dissolved oxygen for the metabolism of aerobic functional bacteria; at the same time, aerobic functional bacteria degrade organic matter and other pollutants, producing substances (such as carbon dioxide, nitrogen-containing and phosphorus-containing compounds, etc.) that can provide raw materials for the growth of microalgae. Microalgae, aerobic functional bacteria, and microorganisms in the intermediate anoxic zone rely on secretions such as EPS to achieve connection and aggregation, together forming the structure of the aerobic zone.

[0047] (2) Material connection method:

[0048] Microorganisms (functional bacteria, microalgae) and pyrite, as well as microorganisms among each other, are mainly connected through extracellular polymeric substances (EPS). Microorganisms secrete EPS during the metabolic process, which contains polysaccharides, proteins and other components, has adhesion, can make microorganisms adhere to the surface of pyrite, and can also allow different microorganisms to aggregate with each other, eventually forming this layered composite. EPS can also help maintain the structural stability of the composite, which is beneficial to its role in the water treatment system.

[0049] In the present invention, in the treatment of seawater aquaculture effluent based on the functional bacteria-microalgae-pyrite composite system, the settling time of the SBR reactor is shortened (5 min) and pyrite is used as a carrier to strengthen the formation of granular sludge. On the one hand, it significantly promotes the synthesis of extracellular polysaccharides (EPS) by functional bacteria (such as salt-tolerant nitrifying bacteria and heterotrophic degrading bacteria), and the porous surface of pyrite can anchor EPS, making it act as a "structural link" to enhance the aggregation ability between bacteria-microalgae-carrier, and reduce the loss rate of flocculent sludge; on the other hand, it improves the cell surface hydrophobicity (CSH) and microbial metabolic activity (such as dehydrogenase activity is increased by 25%-40%), combined with the slow release of Fe 2+The activation of the bacterial population enzymatic reaction provides double protection for the densification of the efficient aerobic granular sludge and the resistance to high salt impact, and speeds up the granulation process.

[0050] Secondly, after adding salt-tolerant microalgae (such as chlorella and cladophora) to the composite system, pyrite can act as a "synergistic carrier" for bacteria-algae symbiosis, promoting the stable closed loop of "photosynthetic oxygen production-aerobic degradation-nutrient cycling": microalgae rely on the surface of pyrite for attachment and growth, and assimilate CO2, nitrogen and phosphorus pollutants (such as NH4 + -N, PO4 3- -P) in the seawater culture tail water through photosynthesis, and the released O2 directly supplies the functional bacteria in the aerobic granular sludge, driving the oxidation of organic matter (such as COD) and the nitrification of ammonia nitrogen; and the CO2 produced in the bacterial degradation process can provide a carbon source for the photosynthesis of microalgae in real time, while the SO4 2- released by pyrite oxidation provides essential elements for the synthesis of photosynthetic pigments (chlorophyll a) by microalgae, further consolidating the symbiotic balance of "bacteria-algae-pyrite", and improving the stability of the system against salt load.

[0051] In addition, when the functional bacteria-microalgae-pyrite composite system driven by the aerobic granular sludge system reaches a steady state (granular size 1.0-2.5 mm, SVI≤75 mL / g, suitable for seawater salinity 30-35‰), it can achieve deep removal of conventional pollutants (COD, TN, TP) in seawater culture tail water: a "multi-level functional synergistic network" is formed in the system: functional bacteria (such as pseudomonas and nitrifying spirochetes) rely on pyrite carriers to efficiently degrade easily / degraded organic matter and complete ammonia nitrogen nitrification and denitrification; fungi (such as aspergillus) participate in the bond-breaking decomposition of complex new pollutants; protozoa optimize the bacterial community structure by predating on free bacteria, reducing the risk of sludge bulking; and microalgae remove residual nitrogen and phosphorus and part of new pollutants through adsorption and assimilation, while the Fe 2+ on the surface of pyrite can adsorb TP and heavy metals (such as Cu 2+ ) through complexation, ultimately achieving standard purification of seawater culture tail water (meeting the requirements of DB33 / 1384-2024 for coastal discharge).

[0052] The present application utilizes FeS2, a typical pyrite mineral, which can slightly dissolve in water to release Fe 2+ and reduced sulfide, and can efficiently adsorb a variety of pollutants. Therefore, the coupling of the bacteria-algae symbiotic aerobic granular sludge technology and the advantageous characteristics of pyrite to construct an efficient aerobic granular sludge for the enhanced and synergistic treatment of seawater culture tail water based on a functional bacteria-microalgae-pyrite composite system helps to achieve "physical-chemical and biochemical synergistic effect" and overcome the technical difficulties in traditional bacteria-algae symbiotic aerobic granular sludge systems.

[0053] The present application takes pyrite as a trinity carrier of "nutrient slow-release agent-structure stabilizer-microenvironment regulator", constructs an aerobic granular sludge preparation method based on functional flora-microalgae-pyrite composite system, establishes a synergistic network of "bacteria (metabolic degradation)-algae (oxygen production and carbon sequestration)-sludge (granular loading)", helps to realize "physical-chemical and biochemical synergistic effect", overcomes the bottleneck of traditional bacteria-algae symbiotic sludge technology, solves the core pain points of "poor stability, weak high salt tolerance, and incomplete nitrogen and phosphorus removal" of bacteria-algae symbiotic aerobic granular sludge in mariculture effluent treatment, promotes the transformation of mariculture effluent treatment to a green and circular economy model, and shows application potential in mariculture effluent treatment technology.

[0054] The above technical scheme of the present application has the following advantages compared with the prior art:

[0055] (1) Pyrite as the core carrier of bacteria-algae symbiotic aerobic granular sludge provides an attachment surface for functional flora and microalgae, which is conducive to the attachment and growth of microorganisms, and can also release Fe 2+ , SO4 2- and other nutrients through slow oxidation to promote the metabolic activity of bacteria and algae to synthesize more EPS, meeting the requirement of enhancing the stability of sludge structure.

[0056] (2) Pyrite can serve as a "synergistic carrier" for bacteria-algae symbiosis, promoting a stable closed loop of "photosynthetic oxygen production-aerobic degradation-nutrient cycling", and further improving the removal efficiency of nutrients such as nitrogen and phosphorus.

[0057] (3) The pyrite in the functional flora-microalgae-pyrite composite system has certain chemical activity, and the Fe 2+ on its surface can have a certain removal effect on some refractory pollutants such as antibiotics and perfluorinated compounds through redox reaction and adsorption, thereby widening the range of pollutants removed.

[0058] (4) The mariculture effluent has high salinity, and the functional flora in the composite system can better adapt to the high-salt environment after domestication, while the presence of pyrite can adjust the microenvironment inside the granules, reduce the stress of high salt on microorganisms, and enable the composite system to maintain high microbial activity in the high-salt environment of mariculture effluent, have stronger buffering capacity and adaptability, and ensure the stability of mariculture effluent treatment effect. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings, wherein,

[0060] Figure 1A schematic diagram of the aerobic granular sludge structure based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0061] Figure 2 A COD change and degradation rate diagram of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0062] Figure 3 A TN change and degradation rate diagram of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0063] Figure 4 A TP change and degradation rate diagram of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0064] Figure 5 A structure diagram of the preparation method of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0065] Figure 6 A flowchart of the preparation method of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0066] Figure 7 A reactor operation diagram of the preparation method of the aerobic granular sludge based on the functional flora-microalgae-pyrite composite system for strengthening and synergizing provided by the embodiment of the present application.

[0067] In the figure: 1, water inlet bucket; 2, water inlet peristaltic pump; 3, time control switch; 4, aeration pump; 5, rotor flowmeter; 6, water inlet; 7, aeration ring; 8, stirring paddle; 9, water outlet; 10, sampling port; 11, constant temperature heating rod; 12, stirrer; 13, water outlet peristaltic pump; 14, water outlet bucket; 15, reaction dish. DETAILED DESCRIPTION

[0068] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0069] The reactor used in the present application comprises a reaction dish, which is provided with aeration structure, water inlet structure, stirring structure, heating structure and water outlet structure.

[0070] The aeration structure comprises an aeration pump 4 arranged outside the reaction vessel, a rotor flow meter 5 and an aeration ring 7 connected in sequence with the aeration pump 4, the rotor flow meter 5 is arranged on the outer wall of the reaction vessel and connected with the aeration ring 7, the aeration ring 7 is arranged on the bottom wall of the internal cavity of the reaction vessel, and the aeration pump 4 is connected with the time control switch 3;

[0071] The water inlet structure comprises a water inlet bucket 1 and a water inlet peristaltic pump 2 connected in sequence, the water inlet peristaltic pump 2 is further connected to the time control switch 3, the bottom of the reaction vessel is provided with a water inlet 6, one end of a water inlet pipe extends into the internal cavity of the reaction vessel through the water inlet 6, and the other end of the water inlet pipe is connected to the water inlet peristaltic pump 2;

[0072] The stirring structure comprises a stirrer 12 arranged on the top of the reaction vessel and a stirring paddle 8, the stirrer 12 is connected to the time control switch 3, one end of the stirring paddle 8 is connected to the stirrer 12, and the other end of the stirring paddle 8 extends into the bottom of the internal cavity of the reaction vessel from the top of the reaction vessel;

[0073] The heating structure comprises a constant-temperature heating rod 11 arranged on the inner side wall of the reaction vessel;

[0074] The water outlet structure comprises a water outlet bucket 14 and a water outlet peristaltic pump 13, the water outlet peristaltic pump 13 is further connected to the time control switch 3, the side wall of the reaction vessel is provided with a water outlet 9, one end of a water outlet pipe extends into the internal cavity of the reaction vessel through the water outlet 9, and the other end of the water outlet pipe is connected to the water outlet peristaltic pump 13; the side wall of the reaction vessel above the water outlet 9 is further provided with a sampling port 10.

[0075] Embodiment 1

[0076] The embodiment provides a method for preparing aerobic granular sludge based on a functional flora-microalgae-pyrite composite system, and the method is specifically as follows:

[0077] 1. Pretreatment of pyrite: use a grinder to crush and mill pyrite particles with a particle size of 5.0-7.0 mm, screen the milled powder through a 200-mesh screen, and collect the pyrite particles after screening; use 0.75 mol / L dilute sulfuric acid (H2SO4) to soak the pyrite particles at a solid-liquid ratio of 1:5 (g:mL), and stir for 3 hours at room temperature to remove carbonates, oxides and other impurities on the surface of the pyrite particles, and at the same time, generate Fe 2+ ions through slight oxidation; use 0.1 mol / L sodium hydroxide (NaOH) to adjust the pH of the pyrite after acid washing to 7.0 to avoid damage to the bacteria and algae, and then repeatedly wash with deionized water or filtered seawater for 3 times to avoid introducing foreign bacteria until the supernatant is free of SO4 2-Residual, at this time with BaCl2 solution detection, no white precipitate, finally 60 ℃ vacuum drying 2 hours for standby.

[0078] 2, select salt-tolerant microalgae Chlorella vulgaris (order from Chinese Academy of Sciences Freshwater Algae Culture Collection website: https: / / algae.ihb.ac.cn / Membership / PasswordModify.aspx), inoculated into BG11 medium, placed in a light incubator, and cultured for 24 h until the algal liquid was uniformly green. Then the activated algal liquid was inoculated into the expanded culture bottle containing BG11 medium at a ratio of 1:10, and cultured under the same conditions for 3 days until the OD680 value of the algal liquid was stable at 0.8-1.2, at which time the algal density was about 1×10 6 -5×10 6 cells / mL, which can be used for inoculation.

[0079] 3, take the activated sludge of mariculture tail water sedimentation tank, which contains natural nitrifying bacteria and heterotrophic degrading bacteria, and take the lower sludge after standing and precipitating for 30 minutes, at which time the MLSS of the sludge is 4 g / L;

[0080] 4, take 500 mL triangular flask, seal and pass through the aeration head, control the DO at 3 mg / L, add simulated mariculture tail water (COD=50-150 mg / L, TN=30-50 mg / L, TP=5-10 mg / L, salinity 20-30‰), inoculate according to the volume ratio of bacteria sludge (MLSS=4 g / L) to algal liquid 3:1, and add the pretreated pyrite obtained in step 1, the dosage of pyrite is 6% of the dry weight of bacteria-algal mixed liquid, the dosage of this time is about 1.2 g / L, the acclimation period of the bacteria-microalgae-pyrite complex is 10-15 days, 50% of the simulated tail water is replaced every day, and the pollutant concentration is gradually increased until the COD increases to 200 mg / L and the TN increases to 60 mg / L, at which time the COD removal rate is ≥80% and the TN removal rate is ≥70%; when the COD removal rate is ≥80% and the NH4 + removal rate is ≥70%, it indicates that the bacteria-algae have adapted to the high-salt environment and can utilize the Fe 2+ / SO4 2- released by pyrite, microscopic examination shows that bacteria and algae are attached to the surface of pyrite, and finally "bacteria-algae-pyrite mixed liquid" is obtained.

[0081] 5. The "bacteria-algae-pyrite mixed solution" after acclimation in step 4 is inoculated into the SBR reactor, an external light source LED lamp is provided on the basis thereof, and is wound around the reactor, with a light-dark ratio of 12:12, an illumination intensity of 3000xl, and the same as when the halophilic microalgae Chlorella vulgaris is expanded. The initial MLSS is controlled to be 3 g / L, the pyrite concentration [the pyrite concentration refers to the mass of pyrite contained in the mixed solution (including the mixed system of functional bacteria group, microalgae, pyrite, and mariculture tail water, and all components) in a unit volume in the SBR reactor, and the unit is g / L] is maintained to be 1.0 g / L, and if pyrite loss occurs during the operation of the reactor, 0.1 g / L is added every 3 days.

[0082] The SBR reactor is operated with a cycle of 6h, and the operation process of each cycle is as follows: water feeding for 5 min, aeration for 345 min, the aeration amount is 2.0 L / min, and the dissolved oxygen is adjusted to be in the range of 3 mg / L, sedimentation for 5 min, and drainage for 5 min, and the volume exchange rate is 52%. After 15 days of operation, the initial granules are formed, the particle size is 0.5-1.0 mm, the settling velocity is ≥15 m / h, and the SVI (sludge volume index) is ≤80 mL / g. Since the chlorophyll of the algae is green, the surface of the granules is smooth, and therefore "green dense granules" can be observed under a microscope. Subsequently, the operation cycle is extended to 45 days, and the water feeding load is gradually increased, and the particle size, strength, and pollutant removal rate of the granules are detected every week. When the particle size of the granules is 1.0-2.0 mm, the granules are lightly blown with a pipette, and the COD removal rate is ≥85%, the TN removal rate is ≥80%, the TP removal rate is ≥85%, and the granules are stable for 10 consecutive days, which indicates that the granules are mature.

[0083] The pyrite is slowly oxidized and consumed during the operation of the SBR, and since the "nutrient slow-release" function needs to be maintained, the pyrite content is regularly detected every 7 days, and if it is lower than 0.5 g / L, 0.1 g / L is added. At the same time, impact load (such as sudden increase of the water feeding COD to more than 500 mg / L) should be avoided, and if the granules are broken, the aeration intensity can be reduced to 1.2 L / (L·min), and the load can be adjusted again after the granules are restored.

[0084] After the construction and stable operation of the seawater mariculture tail water deep treatment high-efficiency aerobic granular sludge system based on the functional bacteria group-microalgae-pyrite composite system, the simulated seawater mariculture tail water (COD=240 mg / L, TN=40 mg / L, TP=8 mg / L) is added, and the degradation performance of the conventional pollutants (COD, TN, and TP) and the physicochemical properties of the sludge are monitored.

[0085] The data show that under the operation of this method, the sludge settling performance is significantly improved, the SVI is below 28 mL / g, the ratio of SVI5 to SVI30 of the sludge is above 0.85, and the removal efficiencies of COD, TN and TP are 95%, 80% and 90%, respectively. The method can ensure long-term stable operation of the system, and the data graphs of the related experiments are shown in the accompanying drawings Figures 2-4 ; the mechanical strength is high, and the breakage rate is 5%-10% when blowing with a straw.

[0086] Comparative Example 1

[0087] The preparation method of the aerobic granular sludge of the present comparative example is basically the same as that of Example 1, except that no pyrite is added in step 4.

[0088] In the present comparative example, the granulation time is significantly longer than that required in Example 1 (even after running for 60-70 days, the particle size can only reach 0.8-1.3 mm, and the mechanical strength is significantly reduced, with a breakage rate of 25%-35% when blowing with a straw), the sludge settling performance is poor, the SVI is higher than 80 mL / g, and the ratio of SVI5 to SVI30 of the sludge is below 0.85, and the removal efficiencies of COD, TN and TP are reduced, being 94%, 75% and 85%, respectively. The above results show that the pyrite plays the triple roles of “carrier anchoring core”, “nutrient ion supply source” and “environmental buffer” in the composite system, and its absence leads to slow formation of aerobic granular sludge, loose structure, and reduced removal rates of COD, TN and TP compared with Example 1, proving that the pyrite is a key component to ensure efficient and stable operation of the composite system.

[0089] Comparative Example 2

[0090] The preparation method of the aerobic granular sludge of the present comparative example is basically the same as that of Example 1, except that no salt-tolerant microalgae Chlorella vulgaris is added in step 2.

[0091] In the present comparative example, the granulation time is obviously longer than that required in Example 1 (even running for 60-80 days, the particle size can only reach 0.8-1.2 mm, and the particle strength is significantly reduced, with a breakage rate of 30%-40% when blown with a straw), the sludge has poor settling properties, the SVI is less than 80 mL / g, and the ratio of SVI5 to SVI30 is below 0.75, the removal efficiencies of COD, TN and TP are reduced, being 75%, 55% and 65% respectively. The above results show that the salt-tolerant microalgae assumes the three roles of "oxygen supplier", "pollutant direct absorber" and "particle agglomeration promoter" in the composite system, and its absence leads to slow formation of aerobic granular sludge, poor stability, reduced removal rates of COD, TN and TP compared with the example, and significantly reduced system impact resistance and operating economy, further proving that microalgae is a key component for the technology to achieve deep treatment of seawater aquaculture tail water.

[0092] Obviously, the above examples are merely examples for the sake of clarity, and are not limiting of the embodiments. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergistic effect, characterized in that, Includes the following steps: (1) Pretreatment of pyrite: Pyrite particles are soaked in acid solution and stirred to remove impurities; pyrite is adjusted to pH 7.0-7.5 using an alkaline regulator and washed with detergent to obtain pretreated pyrite particles; (2) Co-cultivation of bacteria and algae: Salt-tolerant microalgae were selected for inoculation, placed in a light incubator for cultivation and activation, and the culture was expanded to obtain algal solution; activated sludge from the sedimentation tank of seawater aquaculture tailwater was taken, and after static sedimentation, the lower layer of sludge was taken, sealed and aerated to purify oxygen, and dissolved oxygen (DO) was controlled at 2-5 mg / L. Simulated seawater aquaculture tailwater was added to obtain bacterial sludge; bacterial sludge and algal solution were mixed and inoculated, and pyrite particles obtained in step (1) were added to obtain functional bacterial community-microalgae-pyrite complex; then, co-cultivation of bacteria and algae was carried out; the co-cultivation cycle of functional bacterial community-microalgae-pyrite complex was 10-15 days, and 30-70% of simulated seawater aquaculture tailwater was replaced every day to gradually increase the concentration of pollutants; (3) Aerobic granular sludge induction formation: The mixture of "functional bacteria-microalgae-pyrite complex" after domestication in step (2) is inoculated into an SBR reactor equipped with a light source and operated under light conditions; (4) Aerobic granular sludge matures and stabilizes: Extend the operating cycle to 30-60 days, gradually increase the influent load, and test the particle size, strength and pollutant removal rate weekly; the yellow aerobic granular sludge in the SBR reactor begins to turn green and attaches to the pyrite particles, thus obtaining the aerobic granular sludge.

2. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (1), the original particle size of the pyrite particles is 5.0~7.0 mm, and then they are ground and sieved with a screen of 20~400 mesh. The concentration of the acid solution is 0.2-1 mol / L; The acid is selected from one or more of sulfuric acid, hydrochloric acid, and nitric acid; The solid-liquid ratio of the acid solution to the sieved pyrite particles is (1:4) to (1:6) g / mL; The stirring time is 2-4 hours; The alkalinity regulator includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate; the concentration of the alkalinity regulator is 0.05~0.2 mol / L; Detergents include deionized water or filtered seawater, and washing should be performed at least three times.

3. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (2), the salt-tolerant microalgae include Chlorella vulgaris. Chlorella vulgaris Dunaliella salina Dunaliella salina and Marine Navicula Navicula marina One or more of the following; After large-scale cultivation, the OD680 value of the salt-tolerant microalgae solution stabilized at 0.8-1.2, and the algal density was 1×10⁻⁶. 6 -5×10 6 When the concentration is cells / mL, it is used for subsequent inoculation; Conditions for light culture and activation: light-dark ratio of (10:14) to (14:10), light intensity of 2000 to 4000 lx, and static culture for 18 to 36 h.

4. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (2), the settling time is 20-40 minutes; The MLSS of the lower sludge layer is 3-5 g / L; The aeration intensity is 0.1-0.

5. .

5. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (2), the COD of the simulated seawater aquaculture tailwater is 50-150 mg / L, TN is 30-50 mg / L, TP is 5-10 mg / L, and salinity is 20-30‰.

6. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (2), the MLSS of the fungal sludge is 3~5 g / L; The volume ratio of bacterial sludge to algal solution is (2:1) to (4:1); the dosage of pyrite particles is 5wt%-10wt% of the dry weight of the mixture of bacterial sludge and algal solution. After the synergistic acclimatization of bacteria and algae, if the COD in the reaction solution rises to 200 mg / L and TN rises to 60 mg / L, and the COD removal rate in the reactor is ≥80%, and NH4+ is ≥60%, then... + If the removal rate is ≥70% and microscopic examination reveals that algae and bacteria are attached to the surface of pyrite, it indicates that the algae have adapted to the high-salt environment and can utilize the Fe released from the pyrite. 2+ SO4 2- .

7. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (3), the initial MLSS of the mixture of "functional microbial community-microalgae-pyrite complex" after domestication is controlled to be 3-4 g / L, and the concentration of pyrite is 0.5-1.5 g / L; Light conditions: The light-dark ratio was (10:14) to (14:10), the light intensity was 2000 to 4000 lx, and the culture was static for 18 to 36 hours.

8. The method for preparing aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergy, as described in claim 1, is characterized in that... In step (4), the influent load includes COD load and NH4 load. + -N load, the COD load is from 1.0 Rise to 2.5 NH4 + -N load from 0.15 Rise to 0.4 ; When the particle size reaches 1.0-2.0 mm, the particles do not break when gently blown with a pipette, and the COD removal rate is ≥85%, TN removal rate is ≥80%, and TP removal rate is ≥85%, and the above values ​​are stable for 10 consecutive days, it indicates that the high-efficiency aerobic granular sludge is mature. When impact loads occur and particles break, reduce the aeration intensity to 0.8~1.

5. And suspend increasing the load until the particles recover before making adjustments; Since pyrite is slowly oxidized and consumed during the operation of the SBR reactor, in order to maintain the "nutrient slow release" function, the pyrite content is tested regularly every 5 to 10 days. If it is lower than 0.5 g / L, 0.1 to 0.2 g / L is added. The SVI5 to SVI30 ratio of the aerobic granular sludge is above 0.

85.

9. An aerobic granular sludge based on a functional microbial community-microalgae-pyrite composite system with enhanced synergistic effects, characterized in that, The aerobic granular sludge is prepared by any one of claims 1 to 8 using a method for enhancing synergy of functional microbial community-microalgae-pyrite composite system; the aerobic granular sludge exhibits a core-shell structure, with pyrite particles as the core, forming an internal anaerobic region, and an intermediate layer and an outer layer sequentially wrapping the surface of the core, the intermediate layer including denitrifying functional bacteria, and the outer layer including microalgae and aerobic functional bacteria; wherein, the pyrite particles and the intermediate layer, as well as the intermediate layer and the outer layer, are connected and aggregated by extracellular polymers of microorganisms.

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