A biological phosphorus removal method and device based on photosynthetic bacteria light regulation

Abstract

This invention discloses a biological phosphorus removal method and device based on photosynthetic bacteria light regulation, belonging to the field of wastewater biological treatment and resource utilization technology. This invention constructs a synergistic regulation mechanism of "phosphorus uptake under light and phosphorus release in darkness," utilizing the photoresponsive characteristics of photosynthetic bacteria to replace traditional aeration for energy supply, achieving stable phosphorus removal under low-energy / no-aeration conditions; it overcomes the application limitations of single strains and single morphologies, adapting to multiple forms of photosynthetic bacteria, including suspended and fixed states (including immobilized particles, biofilms, etc.), improving the adaptability to various process scenarios; it integrates online monitoring and intelligent control to achieve precise regulation of phosphorus metabolism rhythm, ensuring the stability and repeatability of phosphorus removal effects; and it opens up pathways for phosphorus removal and resource utilization, realizing phosphorus resource recovery and high-value utilization of photosynthetic bacterial biomass, improving the overall efficiency of the process.

Description

Technical Field

[0001] This invention belongs to the field of wastewater biological treatment and resource utilization technology, specifically relating to a biological phosphorus removal method and device based on light regulation of photosynthetic bacteria. Background Technology

[0002] Phosphorus is a key limiting nutrient element in eutrophication and algal blooms, and its efficient removal is crucial for water environment management. Existing phosphorus removal technologies are mainly divided into two systems: chemical phosphorus removal and enhanced biological phosphorus removal (EBPR), each with significant technical limitations. Chemical phosphorus removal: This method involves adding metallic reagents such as iron, aluminum, and calcium salts to convert phosphates into insoluble phosphate precipitates, achieving solid-liquid separation. While this process offers high phosphorus removal efficiency and rapid start-up, it suffers from drawbacks such as high reagent consumption, high sludge production, and high operating costs. Furthermore, the subsequent disposal of chemical sludge poses a risk of secondary pollution and fails to achieve phosphorus resource recovery. Enhanced biological phosphorus removal (EBPR): This process relies on the physiological characteristics of polyphosphate-accumulating organisms (PAOs) under alternating anaerobic-aerobic / anoxic conditions to remove phosphorus. While this process requires no chemical additives, it is highly dependent on aeration for oxygen supply. Furthermore, under conditions of high salinity, high temperature, insufficient carbon sources, or shock loads on water quality, the activity of PAOs is easily inhibited, leading to a significant decrease in system stability and making it difficult to meet the development needs of low-carbon wastewater treatment.

[0003] In recent years, significant breakthroughs have been achieved in the application research of photosynthetic bacteria (PSB) in the field of phosphorus removal. Studies have confirmed that under anaerobic / low dissolved oxygen (DO≤2.0 mg / L) light conditions, photosynthetic bacteria can generate ATP and reducing power (NADH) through photosynthetic electron transport, providing an energy basis for active phosphorus uptake and intracellular polyphosphate (Poly-P) accumulation; under light-dark switching conditions, their phosphorus metabolism exhibits a significant periodic characteristic of "light-directed phosphorus uptake - dark-metabolic phosphorus release".

[0004] However, to date, phosphorus removal technology using photosynthetic bacteria remains at the level of strain screening, single-factor condition verification, and phenomenon observation, and has not yet formed a mature engineering technology solution. Existing research lacks four core shortcomings: precise coordinated control of the light and dark phases, adaptive design of multi-form (suspended and stationary) photosynthetic bacteria, real-time feedback regulation of online phosphorus signals, and integrated process integration of phosphorus removal and resource recovery. These shortcomings prevent the engineering implementation of deep phosphorus removal in municipal wastewater, low-carbon process upgrades, and high-concentration phosphorus removal from industrial wastewater.

[0005] Therefore, there is an urgent need to provide a complete, precisely controlled, stable, and scale-up biological phosphorus removal method and device using photosynthetic bacteria under light regulation, so as to overcome the technical limitations of traditional phosphorus removal processes and achieve the dual goals of low-carbon wastewater treatment and phosphorus resource recovery. Summary of the Invention

[0006] Technical problems addressed: Addressing the shortcomings of existing chemical phosphorus removal methods, such as high chemical consumption and large sludge production, as well as the high energy consumption and poor adaptability of enhanced biological phosphorus removal due to reliance on aeration, this invention provides a biological phosphorus removal method and device based on photosynthetic bacteria light regulation. It constructs a synergistic regulation mechanism of "phosphorus uptake under light and phosphorus release in darkness," utilizing the photoresponsive characteristics of photosynthetic bacteria to replace traditional aeration for energy supply, achieving stable phosphorus removal under low-energy / no-aeration conditions. It overcomes the application limitations of single strains and single morphologies, adapting to both suspended and fixed (including immobilized particles and biofilms) photosynthetic bacteria, improving process adaptability. It integrates online monitoring and intelligent control to achieve precise regulation of phosphorus metabolism rhythms, ensuring the stability and repeatability of phosphorus removal effects. It opens up pathways for phosphorus removal and resource recovery, realizing phosphorus resource recovery and high-value utilization of photosynthetic bacterial biomass, improving the overall efficiency of the process.

[0007] Technical solution: In a first aspect, the present invention provides a biological phosphorus removal method based on light regulation by photosynthetic bacteria, comprising the following steps: S1. Inoculation and Culture Procedures: Photosynthetic bacteria (purple non-sulfur photosynthetic bacteria, preferably Rhodopseudomonas palustris) Rhodopseudomonas palustris The bacteria are inoculated into the photobioreactor in both suspended and fixed forms (including immobilized particles, biofilms, etc.), which can be flexibly selected according to the treatment scenario. Phosphorus-containing wastewater is introduced into the reactor to control the reaction system in an anaerobic or low dissolved oxygen (DO≤2.0 mg / L) environment, which is achieved by nitrogen bubbling or sealed anaerobic methods, providing basic conditions for the growth of photosynthetic bacteria and phosphorus metabolism. During the cultivation process, the system temperature was controlled at 25–35℃, and the pH of the phosphorus-containing wastewater was controlled at 6.0–8.5, which is suitable for the optimal growth and metabolic range of photosynthetic bacteria.

[0008] S2, Photosynthetic Phosphorus Uptake Step: The photosynthetic phase is the core stage for phosphorus uptake and intracellular polyphosphate (Poly-P) accumulation. Precise light regulation drives photosynthetic bacteria to efficiently uptake phosphorus. Light source selection: Natural light and / or artificial light are used. The artificial light is visible to near-infrared light, with the wavelength range controlled at 650-900 nm (preferably 700-880 nm). This wavelength range is highly matched with the absorption peak of photosynthetic pigments in photosynthetic bacteria, resulting in the highest light energy conversion efficiency. Lighting parameters: Light intensity controlled at 50–250 W / m 2 The duration of the light phase is 20–180 min, which can be flexibly adjusted according to the phosphorus concentration of wastewater, water quality fluctuations, and strain morphology. Metabolic effects: Under light conditions, photosynthetic bacteria actively take up orthophosphate (PO4) from wastewater using ATP and reducing power generated by photosynthesis.3- It is stored in large quantities in the form of Poly-P within the cell, thus achieving a rapid reduction in soluble phosphorus.

[0009] S3. Effluent control steps: Supernatant discharge: At the end of the illumination stage, when the orthophosphate concentration in the reactor drops to the target value (≤1.0 mg / L) and the rate of change is stable, the supernatant is discharged; this effluent is low-phosphorus treated water and can be directly discharged or reused.

[0010] S4. Dark Phosphorus Release Step (Core Step in Phosphorus Recovery): Stop the light exposure and transfer the photosynthetic bacteria solution rich in polyphosphate to a dark environment for 20–180 min; control the temperature at 25–35℃ and the pH at 6.0–8.5; utilize the active phosphorus excretion characteristics of photosynthetic bacteria under dark conditions to decompose the polyphosphate stored in the cells into orthophosphate and release it into the liquid phase to obtain a high-concentration phosphorus recovery solution.

[0011] S5. Cyclic operation steps: Repeat steps S2 to S4, selecting either batch or continuous operation mode based on processing requirements: Sequential batch operation mode: The entire process is completed in the following order in a single cycle: water inlet → phosphorus uptake under light → phosphorus release in darkness (side flow enrichment, recovery of high concentration phosphorus solution, and reflux of dephosphater cells) → supernatant discharge → sludge discharge (optional); The multi-cycle continuous operation mode is suitable for small and medium-sized wastewater treatment or deep phosphorus removal scenarios. Through the series or parallel design of "photosynthetic phosphorus absorption unit" and "dark phosphorus release unit", it realizes continuous wastewater feeding and continuous phosphorus removal: wastewater continuously enters the photosynthetic phosphorus absorption unit, where photosynthetic bacteria actively absorb phosphorus; a portion of the phosphorus-rich bacterial solution is periodically diverted to the dark phosphorus release unit (independent dark environment) for phosphorus release and recovery, and the dephosphorized bacteria are returned to the reactor; the treated low-phosphorus effluent is continuously discharged; it is suitable for large-scale municipal sewage or industrial wastewater treatment scenarios.

[0012] Secondly, the present invention provides a biological phosphorus removal method based on photosynthetic bacteria light regulation, comprising the following steps: S1. Inoculation and Culture Procedures: Photosynthetic bacteria (purple non-sulfur photosynthetic bacteria, preferably Rhodopseudomonas palustris) Rhodopseudomonas palustris The bacteria are inoculated into the photobioreactor in both suspended and fixed forms (including immobilized particles, biofilms, etc.), which can be flexibly selected according to the treatment scenario. Phosphorus-containing wastewater is introduced into the reactor to control the reaction system in an anaerobic or low dissolved oxygen (DO≤2.0 mg / L) environment, which is achieved by nitrogen bubbling or sealed anaerobic methods, providing basic conditions for the growth of photosynthetic bacteria and phosphorus metabolism. During the cultivation process, the system temperature was controlled at 25–35℃, and the pH of the phosphorus-containing wastewater was controlled at 6.0–8.5, which is suitable for the optimal growth and metabolic range of photosynthetic bacteria.

[0013] S2, Photosynthetic Phosphorus Uptake Step: The photosynthetic phase is the core stage for phosphorus uptake and intracellular polyphosphate (Poly-P) accumulation. Precise light regulation drives photosynthetic bacteria to efficiently uptake phosphorus. Light source selection: Natural light and / or artificial light are used. The artificial light is visible to near-infrared light, with the wavelength range controlled at 650-900 nm (preferably 700-880 nm). This wavelength range is highly matched with the absorption peak of photosynthetic pigments in photosynthetic bacteria, resulting in the highest light energy conversion efficiency. Lighting parameters: Light intensity controlled at 50–250 W / m 2 The duration of the light phase is 20–180 min, which can be flexibly adjusted according to the phosphorus concentration of wastewater, water quality fluctuations, and strain morphology. Metabolic effects: Under light conditions, photosynthetic bacteria actively take up orthophosphate (PO4) from wastewater using ATP and reducing power generated by photosynthesis. 3- It is stored in large quantities in the form of Poly-P within the cell, thus achieving a rapid reduction in soluble phosphorus.

[0014] S3, Dark Phosphorus Release Step: Stop the light exposure and transfer the photosynthetic bacteria solution rich in polyphosphate to a dark environment for 20–180 min; control the temperature at 25–35℃ and the pH at 6.0–8.5; utilize the active phosphorus release characteristics of photosynthetic bacteria under dark conditions to decompose the polyphosphate stored in the cells into orthophosphate and release it into the liquid phase to obtain a high-concentration phosphorus recovery solution.

[0015] S4. Assisted phosphorus removal step: After the dark phosphorus release step is completed, when there is too much photosynthetic bacterial biomass in the reactor, the bacterial solution rich in polyphosphate is diverted to an independent side-flow enrichment unit for phosphorus release under completely dark and stirred conditions; after phosphorus release is completed, a high-concentration phosphorus recovery solution is obtained by precipitation or centrifugation, and the dephosphorized bacterial cells are returned to the reactor for recycling. The preferred method for phosphorus recovery is the side-flow enrichment method: the phosphorus-rich bacterial solution is diverted to an independent side-flow enrichment unit (complete darkness, no light), and stirring is maintained to allow the bacteria to fully release phosphorus; after phosphorus release is completed, a high-concentration phosphorus solution (tens to hundreds of mg / L) is obtained by precipitation or centrifugation, which can be directly used for struvite crystallization or acid leaching recovery; the dephosphorized bacteria are returned to the reactor for recycling. This step enables the transfer of phosphorus from the solid phase (bacterial cells) to the liquid phase, obtaining a high-concentration phosphorus recovery solution, which is the core link of the present invention for phosphorus net removal and resource utilization. Phosphorus-rich sludge discharge (optional): When there is excessive photosynthetic bacterial biomass in the reactor, some phosphorus-rich sludge is discharged, and phosphorus is further recovered by methods such as acid leaching and struvite crystallization, as a supplementary approach to phosphorus recovery.

[0016] S5. Cyclic operation steps: Repeat steps S2 to S4, selecting either batch or continuous operation mode based on processing requirements: Sequential batch operation mode: The entire process is completed in the following order in a single cycle: water inlet → phosphorus uptake under light → phosphorus release in darkness (side flow enrichment, recovery of high concentration phosphorus solution, and reflux of dephosphater cells) → supernatant discharge → sludge discharge (optional); The multi-cycle continuous operation mode is suitable for small and medium-sized wastewater treatment or deep phosphorus removal scenarios. Through the series or parallel design of "photosynthetic phosphorus absorption unit" and "dark phosphorus release unit", it realizes continuous wastewater feeding and continuous phosphorus removal: wastewater continuously enters the photosynthetic phosphorus absorption unit, where photosynthetic bacteria actively absorb phosphorus; a portion of the phosphorus-rich bacterial solution is periodically diverted to the dark phosphorus release unit (independent dark environment) for phosphorus release and recovery, and the dephosphorized bacteria are returned to the reactor; the treated low-phosphorus effluent is continuously discharged; it is suitable for large-scale municipal sewage or industrial wastewater treatment scenarios.

[0017] Thirdly, the present invention provides a biological phosphorus removal device based on photosynthetic bacteria light regulation, comprising: Photobioreactor, used to house photosynthetic bacteria and treat phosphorus-containing wastewater; The light source assembly, connected to the photobioreactor, provides illumination in the wavelength range of 650–900 nm, with the light intensity controlled at 50–250 W / m². 2 ; The inlet and outlet units are respectively connected to the photobioreactor and are used for inlet water and outlet of low phosphorus supernatant; A sludge discharge unit and / or a side-flow enrichment unit, which is independent of the photobioreactor and is in a completely dark environment, for receiving phosphorus-rich bacterial solutions and realizing phosphorus recovery; The online monitoring unit is used to monitor orthophosphate concentration, dissolved oxygen, pH, temperature and light parameters in real time. The control unit is electrically connected to the light source assembly, water inlet unit, water outlet unit, sludge removal unit, and online monitoring unit, respectively, and is used to automatically control the operation of each unit to achieve periodic regulation of "phosphorus absorption under light and phosphorus release in darkness".

[0018] Beneficial effects: (1) Low carbon and energy saving, significantly reduced carbon footprint: This invention uses light energy to replace part or all of the aeration energy supply in the traditional enhanced biological phosphorus removal process, which can achieve phosphorus removal under anaerobic or low dissolved oxygen conditions, which is conducive to reducing process energy consumption and operating carbon footprint. (2) High efficiency in phosphorus uptake and excellent single-cycle phosphorus removal performance: During a single light-dark cycle, the dissolved phosphorus decreased by 7.43 mg / L during the light period, and the removal rate reached 65.5%, indicating that the light phase can significantly promote the uptake of orthophosphate. (3) High-value phosphorus storage with outstanding intracellular Poly-P accumulation efficiency: Under light conditions, the peak value of intracellular Poly-P reached 13.42±0.52% of the cell dry weight, indicating that this method can effectively achieve bio-storage of phosphorus; (4) Stable and controllable, with strong repeatability in multi-cycle operation: In the immobilized sequencing batch reactor, the process of the present invention can reproduce the periodic adsorption-release process of phosphorus in 5 consecutive cycles, with a net removal of up to 7.5 mg / L, indicating that the present invention has certain operational stability and engineering application potential. (5) Economical and efficient, with significant cost advantages throughout the entire process: at 100,000 m 3 In the context of a wastewater treatment plant, the annual cost of the process of this invention is approximately US$8.05 per person per year, which is significantly lower than the traditional biological phosphorus removal route of US$15.67 per person per year and the chemical phosphorus removal route of US$21.71 per person per year. This indicates that the present invention has a cost advantage in terms of aeration reduction and sludge treatment burden reduction. (6) Resource integration, achieving both phosphorus recovery and high-value utilization of biomass: This invention can not only be used for deep phosphorus removal from municipal wastewater, but also can be coupled with phosphorus-rich side-flow separation, phosphorus recovery units, etc., to form a process path for phosphorus removal and resource utilization. This method can achieve periodic and repeatable operation under the conditions of phosphorus absorption by light and phosphorus release in darkness. Unlike traditional phosphorus removal by polyphosphate-accumulating bacteria, which mainly relies on the discharge of residual sludge to remove phosphorus, this invention can obtain a high-concentration phosphorus solution and / or phosphorus-rich biomass removal through side-flow enrichment and dark phosphorus release, thereby achieving phosphorus resource recovery and making the process path more flexible. At the same time, photosynthetic bacterial biomass is rich in protein, pigments and other active components, and has the potential to be further utilized as feed, fertilizer, water purification functional materials or other high-value-added biomass products, thus helping to improve the overall economic benefits of the process. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the light-controlled biological phosphorus removal method of the present invention; Figure 2 Image of photosynthetic bacteria embedded in sodium alginate; Figure 3 The graph shows the changes in orthophosphate and organic matter concentrations in an immobilized photosynthetic bacteria sequencing batch reactor under a light-dark cycle. Figure 4 A comparative chart of the techno-economic analysis of different phosphorus removal routes; Figure 5 This is a schematic diagram of the phosphorus removal device of the present invention. Detailed Implementation

[0020] The present invention will be described in detail below with reference to specific embodiments: Example 1: Batch Light-Dark Switching Phosphorus Metabolism Verification Experiment This embodiment is used to verify the regulatory effect of light on the directionality of phosphorus metabolism in photosynthetic bacteria. Figure 1 This is a schematic diagram of the process flow of the method of the present invention. This embodiment follows... Figure 1 The core logic shown (phosphorus absorption under light → phosphorus release in darkness) is simplified and verified to confirm the on / off effect of light on phosphorus metabolism. The specific steps are as follows: Strains and culture media: Selection Rhodopseudomonas palustris (Bio-52488) was used as the type strain. The strain was pre-cultured in Van Niel's Yeast Broth to the logarithmic phase before being used in experiments. The culture temperature was 30 °C and the shaking condition was 120 rpm.

[0021] A batch reactor was constructed using 150 mL serum bottles, with a working volume of 50 mL, simulating the operating environment of a small-scale photobioreactor. The influent was prepared using a KH₂PO₄ / K₂HPO₄ buffer system, controlling the total phosphorus concentration at 20 mg / L and adjusting the pH to 7.0±0.2. Sodium acetate / acetic acid was used as the carbon source, controlling the COD concentration at 2000 mg / L, ensuring a COD:P ratio of 100:1 to meet the carbon-to-phosphorus ratio required for photosynthetic bacteria metabolism and provide the energy basis for phosphorus uptake.

[0022] Two parallel experiments were set up: a light-to-dark switching group and a dark-to-light switching group, to comprehensively verify the regulatory effect of light on phosphorus metabolism. Light was provided by a 40 W artificial light source, and the irradiance was controlled at 150 W / m². 2 During the reaction, samples were taken every 20 minutes. After being filtered through a 0.45 μm filter membrane, the samples were used to determine the orthophosphate concentration and monitor the dynamic changes in phosphorus concentration.

[0023] The results showed that during the light phase, the concentration of soluble orthophosphate in the system exhibited a significant decreasing trend, demonstrating a significant active phosphorus uptake effect, consistent with the description of "promoting orthophosphate uptake during the light phase" in the invention's technical solution. Upon entering the dark phase, the polyphosphate (Poly-P) stored intracellularly by photosynthetic bacteria decomposed and was released into the liquid phase as orthophosphate, leading to a certain degree of recovery in the concentration of soluble phosphorus in the system, confirming the technical characteristic of "phosphorus release in the dark." These results are consistent with... Figure 1 The process flow shown is perfectly aligned with the stage division of "phosphorus uptake under light → phosphorus release in darkness," confirming that light can serve as a key switch to regulate the direction and magnitude of phosphorus uptake by photosynthetic bacteria, providing core theoretical support for subsequent process control.

[0024] Example 2: Phosphorus removal using a sequencing batch reactor with immobilized photosynthetic bacteria An immobilized photosynthetic bacteria were used to construct a sequencing batch reactor (SBR) to verify the phased phosphorus uptake capacity, cycle operation stability, and engineering application potential of the method of this invention, as detailed below: Preparation of immobilized photosynthetic bacteria: Immobilized photosynthetic bacteria particles were prepared using the sodium alginate-CaCl2 cross-linking method. The specific steps are as follows: Bio-52488 bacterial culture pre-cultured to the logarithmic growth phase was centrifuged to collect the bacterial cells. The cells were thoroughly mixed with a 3% (w / v) sodium alginate solution. The mixture was then added dropwise to a 10% (w / v) CaCl2 solution using a syringe at a uniform rate. The mixture was allowed to stand and solidify to form immobilized particles (e.g., ...). Figure 2 As shown in the figure, wash three times with sterile water to remove residual CaCl2 on the surface, and set aside for later use.

[0025] SBR Reactor Setup and Operating Parameters: A sequencing batch reactor (SBR) was constructed using 150 mL serum bottles. The reactor working volume was 50 mL, and the operating temperature was kept constant at 30℃. The specific process for each operating cycle is as follows: (1) Influent: Add the prepared phosphorus-containing wastewater to the reactor. The influent parameters are the same as in Example 1: total phosphorus concentration 20 mg / L, pH 7.0±0.2, COD concentration 2000 mg / L, COD:P=100:1; (2) Anaerobic environment construction: Nitrogen gas was bubbled into the reactor for 5 min to remove dissolved oxygen in the system and establish an anaerobic environment (dissolved oxygen concentration ≤ 0.5 mg / L). (3) Photoluminescence phosphorus absorption stage: Turn on magnetic stirring (120 rpm) and provide light (irradiance 150 W / m²). 2 This process, lasting 60 minutes, promotes the uptake of orthophosphate by photosynthetic bacteria and the accumulation of Poly-P intracellularly. (4) Dark phosphorus release stage: turn off the light source, keep the magnetic stirring (120 rpm) for 60 min, so that the Poly-P stored in the photosynthetic bacteria cells decomposes and is released into the liquid phase in the form of orthophosphate, and is recovered by side flow; (5) Drainage and circulation: At the end of the dark phase, the supernatant in the reactor is discharged and the next operating cycle begins, thus achieving the circulating operation requirement in the invention.

[0026] The SBR reactor was run continuously for 5 cycles, with 1 mL sample taken every 20 min to evaluate the phase response of phosphorus metabolism and the repeatability of the operation.

[0027] The results are as follows Figure 3As shown, within a single light-dark cycle, the concentration of soluble orthophosphate in the system decreased by 7.43 mg / L during the light phase, achieving a phosphorus removal rate of 65.5%. The peak intracellular Poly-P content of photosynthetic bacteria reached 13.42 ± 0.52% of the cell dry weight, indicating that this method can effectively promote intracellular phosphorus storage. Over five consecutive operating cycles, the system consistently exhibited a cyclical adsorption-release characteristic of "phosphorus uptake under light - phosphorus release under darkness," with a maximum net phosphorus removal of 7.5 mg / L in a single cycle, demonstrating good operational stability and confirming the promising engineering application potential of this method in immobilized SBR systems.

[0028] Figure 4 This is a techno-economic comparison chart of the process of this invention with traditional chemical phosphorus removal and traditional biological phosphorus removal (EBPR) routes. Based on the operating parameters of the immobilized SBR system in Example 2 (influent COD 2000 mg / L, total phosphorus 20 mg / L, COD:P = 100:1, light intensity 150 W / m², light and dark cycles 60 min each), combined with a 100,000 m³... 3 A techno-economic analysis was conducted on a wastewater treatment plant of 400,000 PE population (serving a total population of 400,000). The results show that the total annual cost of the process described in this invention is approximately US$8.05 per person per year, significantly lower than the US$15.67 per person per year of traditional biological phosphorus removal and the US$21.71 per person per year of chemical phosphorus removal. Specifically, the lighting energy cost of the process is only US$1.97 per person per year, eliminating the need for aeration. Furthermore, the recyclable biomass from phosphorus-rich photosynthetic bacteria (e.g., for protein extraction, pigment extraction, or as a feed additive) generates an additional benefit of approximately US$684.38 per person per year, further enhancing the process's economic viability. This comparative result is as follows: Figure 4 As shown, this invention has significant comprehensive cost advantages in terms of reducing aeration energy consumption, reducing sludge treatment burden, and biomass resource utilization.

[0029] Example 3: Continuous Flow / Parallel Dual-Unit Phosphorus Removal Device like Figure 5 As shown, a biological phosphorus removal device based on photosynthetic bacteria light regulation includes: Photobioreactor, used to house photosynthetic bacteria and treat phosphorus-containing wastewater; The light source assembly, connected to the photobioreactor, provides illumination in the wavelength range of 650–900 nm, with the light intensity controlled at 150 W / m². 2 ; The inlet and outlet units are respectively connected to the photobioreactor and are used for inlet water and outlet of low phosphorus supernatant; A sludge discharge unit and / or a side-flow enrichment unit, which is independent of the photobioreactor and is in a completely dark environment, for receiving phosphorus-rich bacterial solutions and realizing phosphorus recovery; The online monitoring unit is used to monitor orthophosphate concentration, dissolved oxygen, pH, temperature and light parameters in real time. The control unit is electrically connected to the light source assembly, water inlet unit, water outlet unit, sludge discharge unit, side flow enrichment unit, and online monitoring unit, respectively, and is used to automatically control the operation of each unit to achieve periodic regulation of "phosphorus absorption under light and phosphorus release in darkness".

[0030] The dephosphorized bacteria can be returned to the photo-phosphorus uptake unit for recycling, maintaining the biomass within the reactor. This device is suitable for deep phosphorus removal in municipal wastewater, deep treatment of reclaimed water, and phosphorus removal in industrial wastewater. It can efficiently recover phosphorus resources while reducing the phosphorus concentration in the effluent.

[0031] Comparative Example 1 The experimental conditions were exactly the same as in Example 2, including the influent composition (total phosphorus 20 mg / L, pH 7.0±0.2, COD 2000 mg / L, COD:P=100:1), operating temperature (30℃), stirring parameters (magnetic stirring at 120 rpm), and the same total running time (120 min). The only difference was that the light stage was cancelled and the entire process was run in darkness to eliminate the interference of light factors and verify the necessity of light.

[0032] Orthophosphate was determined using the ammonium molybdate colorimetric method; total phosphorus was determined using the digestion-ammonium molybdate method; intracellular Poly-P was determined using the solid-state method. 31 Analysis was performed using P NMR (nuclear magnetic resonance) or staining characterization methods. Sample centrifugation, filtration, sampling intervals, and quantification methods were performed according to conventional phosphorus analysis methods.

[0033] Under complete darkness, the system did not exhibit the significant staged phosphorus uptake response seen in Example 2, and the soluble phosphorus concentration did not decrease significantly. Simultaneously, the intracellular Poly-P accumulation in photosynthetic bacteria was far lower than in Example 2, failing to reach the high accumulation level of over 13% of cell dry weight. Due to the lack of light for phosphorus uptake, there was insufficient intracellular Poly-P for subsequent phosphorus release in the dark, thus preventing net phosphorus removal. These results clearly demonstrate that the light stage is a key technical condition for achieving efficient phosphorus removal and promoting a large accumulation of intracellular Poly-P in this invention; without light, the expected phosphorus removal effect cannot be achieved.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biological phosphorus removal method based on light regulation by photosynthetic bacteria, characterized in that, Includes the following steps: S1. Inoculation and Cultivation Steps: Inoculate photosynthetic bacteria into the photobioreactor, introduce phosphorus-containing wastewater into the reactor, control the dissolved oxygen concentration of the reaction system to be ≤2.0 mg / L, the reaction system temperature to be 25-35℃, and the pH of the phosphorus-containing wastewater to be 6.0-8.

5. S2. Photochemical phosphorus absorption step: The inside of the reactor is treated with light, with the light intensity controlled at 50–250 W / m². 2 The duration of light exposure is 20–180 min, which drives photosynthetic bacteria to actively take up orthophosphate in wastewater and accumulate it in the form of polyphosphate in the cell. S3. Effluent control steps: At the end of the light exposure stage, when the concentration of orthophosphate in the reactor is ≤1.0 mg / L and the rate of change is stable, the supernatant is discharged as low-phosphorus treated water. S4. Dark phosphorus release step: Stop the light exposure and transfer the photosynthetic bacteria solution rich in polyphosphate to a dark environment for 20–180 min; control the temperature at 25–35℃ and the pH at 6.0–8.5; utilize the active phosphorus release characteristics of photosynthetic bacteria under dark conditions to decompose the polyphosphate stored in the cells into orthophosphate and release it into the liquid phase to obtain a high-concentration phosphorus recovery solution. S5. Cyclic operation steps: Repeat steps S2 to S4, selecting either sequential batch or continuous operation mode, until phosphorus removal is completed.

2. A biological phosphorus removal method based on light regulation by photosynthetic bacteria, characterized in that, Includes the following steps: S1. Inoculation and Cultivation Steps: Inoculate photosynthetic bacteria into the photobioreactor, introduce phosphorus-containing wastewater into the reactor, control the dissolved oxygen concentration of the reaction system to be ≤2.0 mg / L, the reaction system temperature to be 25-35℃, and the pH of the phosphorus-containing wastewater to be 6.0-8.

5. S2. Photochemical phosphorus absorption step: The inside of the reactor is treated with light, with the light intensity controlled at 50–250 W / m². 2 The duration of light exposure is 20–180 min, which drives photosynthetic bacteria to actively take up orthophosphate in wastewater and accumulate it in the form of polyphosphate in the cell. S3, Dark phosphorus release step: Stop the light exposure and transfer the photosynthetic bacteria solution rich in polyphosphate to a dark environment for 20-180 min; control the temperature at 25-35℃ and the pH at 6.0-8.5; utilize the active phosphorus release characteristics of photosynthetic bacteria under dark conditions to decompose the polyphosphate stored in the cells into orthophosphate and release it into the liquid phase to obtain a high-concentration phosphorus recovery solution. S4. Assisted phosphorus removal step: After the dark phosphorus release step is completed, when there is too much photosynthetic bacterial biomass in the reactor, the bacterial solution rich in polyphosphate is diverted to an independent side-flow enrichment unit for phosphorus release under completely dark and stirred conditions. After phosphorus release is completed, a high-concentration phosphorus recovery solution is obtained by precipitation or centrifugation, and the dephosphorized bacterial cells are returned to the reactor for recycling. S5. Cyclic operation steps: Repeat steps S2 to S4, selecting either sequential batch or continuous operation mode, until phosphorus removal is completed.

3. A biological phosphorus removal method based on photosynthetic bacteria light regulation according to claim 1 or 2, characterized in that: The photosynthetic bacteria are purple non-sulfur photosynthetic bacteria, preferably Rhodopseudomonas palustris; the photosynthetic bacteria include both suspended and fixed states.

4. A biological phosphorus removal method based on photosynthetic bacteria light regulation according to claim 1 or 2, characterized in that: The light source is natural light and / or artificial light, wherein the wavelength of the artificial light is 650–900 nm, preferably 700–880 nm.

5. The biological phosphorus removal method based on photosynthetic bacteria light regulation according to claim 2, characterized in that, In step S4, photosynthetic bacteria can be further processed using acid leaching or struvite crystallization to recover phosphorus.

6. A biological phosphorus removal device based on photosynthetic bacteria light regulation, characterized in that, include: Photobioreactor, used to house photosynthetic bacteria and treat phosphorus-containing wastewater; The light source assembly, connected to the photobioreactor, provides illumination in the wavelength range of 650–900 nm, with the light intensity controlled at 50–250 W / m². 2 ; The inlet and outlet units are respectively connected to the photobioreactor and are used for inlet water and outlet of low phosphorus supernatant; A sludge discharge unit and / or a side-flow enrichment unit, which is independent of the photobioreactor and is in a completely dark environment, for receiving phosphorus-rich bacterial solutions and realizing phosphorus recovery; The online monitoring unit is used to monitor orthophosphate concentration, dissolved oxygen, pH, temperature and light parameters in real time. The control unit is electrically connected to the light source assembly, water inlet unit, water outlet unit, sludge removal unit, and online monitoring unit, respectively, and is used to automatically control the operation of each unit to achieve periodic regulation of "phosphorus absorption under light and phosphorus release in darkness".

Images