A method for enhancing the operation of a biofilm reactor using extracellular polymeric substances

Abstract

A method for enhancing the operation of a biofilm reactor using extracellular polymers involves adding SLB-EPS (soluble extracellular polymer SB-EPS and loosely bound extracellular polymer LB-EPS) and tightly bound EPS (TB-EPS) extracted from waste activated sludge to the biofilm reactor during both the start-up and operation phases. The different amounts of PS and PN components in the EPS promote the initial and stable adhesion of negatively charged microorganisms to the carrier surface, achieving rapid start-up and long-term efficient and stable operation of the biofilm reactor. Simultaneously, it realizes the resource utilization of waste sludge, reduces sludge disposal costs, integrates wastewater treatment plants into the circular economy concept, and responds to the carbon neutrality principle. This invention is applicable to different types of biofilm reactors and packing materials, has a wide range of applications, and has significant potential for widespread application.

Description

Technical Field

[0001] This invention relates to a method for enhancing the operation of a biofilm reactor using extracellular polymers, belonging to the field of wastewater treatment technology. Background Technology

[0002] Excess sludge is a major byproduct of wastewater treatment using the activated sludge process. It primarily exists as activated sludge flocs, formed by the binding of active microorganisms and extracellular polymeric substances (EPS), with EPS accounting for 60%–80% of the total sludge volume. EPS is a product secreted during microbial metabolism and plays important roles in maintaining the stable structure of organisms, retaining moisture, protecting cells from damage, and storing excess carbon. Based on the degree of binding between organic matter and the cellular phase, sludge EPS can be classified into soluble (S-EPS), loosely bound (LB-EPS), and tightly bound (TB-EPS). Furthermore, EPS mainly comprises proteins (PN) and polysaccharides (PS), and its content is influenced by various factors such as temperature, pH, and the source of the sludge.

[0003] Biofilm reactors are widely used in wastewater treatment plants, but they generally suffer from slow biofilm formation rates and difficulty in controlling biofilm thickness over long-term operation, leading to poor and unstable treatment effects. Extensive literature review and preliminary experimental verification show that the composition and content of EPS (extracellular polymeric substances) in biofilm reactors not only affect the biofilm formation efficiency of the packing material but also influence biofilm properties such as adsorption performance, pollutant mass transfer, and microbial metabolic activity. This is mainly due to the interaction between PN (phosphoric acid) and PS (polysaccharide) in EPS, which influences the electrostatic repulsion between cells, thereby affecting cell attraction, attachment, aggregation behavior, and microbial cell attachment on the packing surface. Furthermore, the specific functional group structures, hydrophilic / hydrophobic properties, and spatial network structures of PN and PS affect the stability of the biofilm structure. Current research utilizes PN or PS-based substances (such as rhamnose, sodium alginate, and cysteine) to promote biofilm formation and start-up operation in biofilm reactors, but these methods are costly and have limited effectiveness.

[0004] In view of the above situation, the present invention provides a method for enhancing the operation of a biofilm reactor by adding EPS of different components extracted from waste activated sludge to the biofilm reactor. Summary of the Invention

[0005] This invention provides a method for enhancing the operation of a biofilm reactor using extracellular polymers.

[0006] The technical solution of this invention is as follows:

[0007] A method for enhancing the operation of a biofilm reactor using extracellular polymeric substances (EPS) involves adding EPS with different component contents extracted from waste activated sludge to the biofilm reactor during the biofilm formation start-up and operation stages. Specifically, during the biofilm formation start-up stage, EPS mainly composed of S-EPS and LB-EPS (SLB-EPS for short) is pumped in once. The amount of EPS added accounts for 8% to 15% of the biofilm reactor's influent volume, and the SLB-EPS concentration in the biofilm reactor is 20 mg / gss to 80 mg / gss. SLB-EPS accounts for more than 65% of the total EPS, and the PN / PS ratio is 0.5 to 2.0. When the pollutant removal efficiency in the biofilm reactor reaches 50%, the biofilm reactor enters the operation stage, where EPS mainly composed of TB-EPS is pumped in once. The amount of EPS added accounts for 10% to 18% of the biofilm reactor's influent volume, and the TB-EPS concentration in the biofilm reactor is 100 mg / gss to 250 mg / gss. mg / gss, TB-EPS accounts for more than 70% of the total EPS, and the PN / PS ratio is 4.0~8.5.

[0008] The EPS is derived from the waste activated sludge in the sludge storage tank of the sewage treatment plant. The sludge storage tank is equipped with a matching stirring paddle and temperature control device, and its sludge concentration ranges from 6000 to 15000 mg / L.

[0009] The SLB-EPS is extracted from waste activated sludge using a mild heating method. Specifically, the temperature of the temperature control device is adjusted by the EPS extraction automatic control system to maintain the temperature in the sludge storage tank at 50-60°C. After stirring for 30-40 minutes, the sludge mixture is pumped to a downstream hydrocyclone separator. Through centrifugation in the hydrocyclone separator, the SLB-EPS solution is separated from the sludge and stored in an SLB-EPS storage tank. The sludge that has settled after centrifugation is recycled back to the sludge storage tank for further TB-EPS extraction.

[0010] The TB-EPS is extracted from the returned activated sludge using either the cation exchange resin method or the sodium citrate method. Specifically, the EPS extraction automatic control system is adjusted, and an appropriate amount of cation exchange resin or sodium citrate is added to the sludge storage tank. After stirring for 40-50 minutes, the mixture is pumped to a hydrocyclone separator. The TB-EPS solution is then centrifuged to separate from the sludge and stored in a TB-EPS storage tank. The remaining sludge is discharged to the sludge treatment system for disposal.

[0011] In addition, the biofilm reactor can be an aerobic, anoxic, or anaerobic environment, in the form of a fixed bed or a moving bed, and the filling material is a conventional commercially available material with a filling ratio of 30% to 60% and an inoculated sludge concentration of 2000 to 5000 mg / L.

[0012] The key features of this invention are: SLB-EPS and TB-EPS extracted from waste activated sludge are added separately to the biofilm reactor during the biofilm formation and operation stages. The different amounts of PS and PN components in the EPS promote the initial and stable adhesion of negatively charged microorganisms to the carrier surface, particularly targeting slow-growing, biofilm-promoting microorganisms such as nitrifying bacteria and methanogens. The EPS extraction method used maximizes extraction efficiency and preserves cell activity and integrity without damaging or altering the properties and structure of the extract. Different amounts of EPS components also enhance the biofilm reactor's resistance to shocks, protecting it from adverse environments such as long-term oligotrophic conditions, low temperatures, high load shocks, and toxic substances. The EPS originates from waste activated sludge from various wastewater treatment plants, reducing sludge production and disposal costs. It is applicable to various types of biofilm reactors and packing materials, offering a wide range of applications.

[0013] The beneficial effects of this invention are as follows: Utilizing EPS (expanded polystyrene) with varying component contents extracted from waste activated sludge provides shape and structural support for the formation and maturation of the biofilm in the biofilm reactor. Compared to traditional biofilm reactors with attached membrane operation, the biofilm reactor's start-up time can be effectively shortened by 40-60%, while the efficient and stable operation time can be extended by more than 1.5 times, effectively reducing sludge volume. This invention achieves rapid biofilm formation and start-up, as well as long-term efficient and stable operation of the biofilm reactor, while simultaneously realizing the resource utilization of waste sludge, reducing sludge disposal costs, integrating wastewater treatment plants into the concept of a circular economy, responding to the carbon neutrality principle, and possessing significant potential for widespread application. Attached Figure Description

[0014] Figure 1 A schematic diagram of an enhanced biofilm reactor operation.

[0015] Attached Figure

[0016] 1-Biofilm reactor; 2-Packing material; 3-Inlet pipe; 4-Outlet pipe; 5-SLB-EPS feed pump; 6-TB-EPS feed pump; 7-TB-EPS storage tank; 8-SLB-EPS storage tank; 9-Cyclone separator; 10-Sludge storage tank; 11-Agitator; 12-Temperature control device; 13-EPS extraction automatic control system; 14-Sludge return pump; 15-Excess sludge treatment system. Implementation

[0017] The invention will be further described below with reference to the accompanying drawings and examples:

[0018] Establish such as Figure 1 A method for enhancing the operation of a biofilm reactor is shown below:

[0019] EPS with different component contents extracted from waste activated sludge was added to the biofilm reactor 1 during the biofilm formation start-up and operation stages. Specifically: During the biofilm formation start-up stage, SLB-EPS feed pump 5 was started, pumping in EPS, primarily SLB-EPS, in a single batch. The amount of EPS added accounted for 8%~15% of the effective volume of biofilm reactor 1, with a concentration of 20 mg / gss~80 mg / gss. SLB-EPS accounted for more than 65% of the total EPS, and the PN / PS ratio was 0.5~2.0. When the pollutant removal efficiency in biofilm reactor 1 reached 50%, and biofilm reactor 1 entered the operation stage, SLB-EPS feed pump 5 was shut off, and TB-EPS feed pump 6 was started, pumping in EPS, primarily TB-EPS, in a single batch. The amount of EPS added accounted for 10%~18% of the effective volume of biofilm reactor 1, with a concentration of 200 mg / gss~250 mg / gss. mg / gss, TB-EPS accounts for more than 70% of the total EPS, and the PN / PS ratio is 4.0~8.5.

[0020] The EPS is derived from the waste activated sludge in the sludge storage tank 10 of the sewage treatment plant. The sludge storage tank 10 is equipped with a matching stirring paddle 11 and a temperature control device 12, and its sludge concentration ranges from 6000 to 15000 mg / L.

[0021] The extraction method of SLB-EPS is a mild heating method, specifically: by adjusting the EPS extraction automatic control system 13 and the temperature control device 12, the temperature in the sludge storage tank 10 is adjusted to 50~60℃. After stirring for 30~40 minutes, the sludge mixture is pumped to the downstream hydrocyclone 9. Through the centrifugation of the hydrocyclone 9, the SLB-EPS solution is separated from the sludge and stored in the SLB-EPS storage tank 8. The sludge that has settled after centrifugation is circulated back to the sludge storage tank 10 by the sludge return pump 14 for further extraction of TB-EPS.

[0022] The extraction method of TB-EPS is either the cation exchange resin method or the sodium citrate method. Specifically, the EPS extraction automatic control system 13 is adjusted, an appropriate amount of cation exchange resin or sodium citrate is added to the sludge storage tank 10, and after stirring for 40 to 50 minutes, it is pumped to the hydrocyclone separator 9. After the TB-EPS solution and sludge are separated by centrifugation, it is stored in the TB-EPS storage tank 7, and the remaining sludge is discharged to the sludge treatment system 15 for disposal.

[0023] The biofilm reactor 1 can be an aerobic, anoxic, or anaerobic environment, in the form of a fixed bed or a moving bed. The packing material 2 is a conventional commercially available packing material with a filling ratio of 30% to 60%, and the inoculum sludge concentration is 2000 to 5000 mg / L. The positions of the inlet pipe 3 and the outlet pipe 4 can be adjusted according to specific circumstances. Example

[0024] Using the method of this invention, SLB-EPS and TB-EPS extracted from sludge in a sludge storage tank (sludge concentration of 6000 mg / L) of a municipal wastewater treatment plant in a certain region are added in a single batch to the biofilm formation start-up and operation stages of an aerobic moving bed biofilm reactor fed with municipal wastewater. The SLB-EPS extraction temperature is 50°C, and the TB-EPS extraction method is the cation exchange resin method. The addition volumes of SLB-EPS and TB-EPS account for 8% and 10% of the effective volume of the reactor, respectively. The aerobic moving bed biofilm reactor is filled with 30% MBBR packing material, and the inoculated sludge is sludge from the plant's sludge storage tank with an inoculated sludge concentration of 2000 mg / L. During the experiment, the contents of SLB-EPS and TB-EPS, the PN / PS ratio of SLB-EPS, the PN / PS ratio of TB-EPS, the time required for successful biofilm formation and start-up of the reactor, the time for efficient and stable operation (the pollutant removal efficiency reaches its maximum and remains almost constant), and the removal efficiency of pollutants COD and TN when the aerobic moving bed biofilm reactor was monitored and recorded during the biofilm formation start-up and operation phases. The specific data are shown in Table 1 below.

[0025] Table 1. Start-up and operation data of the aerobic moving bed biofilm reactor in Example 1.

[0026]

[0027] Comparative Example 1

[0028] The same aerobic moving bed biofilm reactor as in Example 1 was used. The type, amount, inoculated sludge and sludge concentration, and influent water quality and quantity of the packing material in the aerobic moving bed biofilm reactor were the same as those in Example 1. However, SLB-EPS and TB-EPS were not added separately during the biofilm formation start-up and operation phases of the aerobic moving bed biofilm reactor. Instead, the same volume of municipal wastewater as SLB-EPS was added during the biofilm formation start-up phase as in Example 1, and the same volume of municipal wastewater as TB-EPS was added during the operation phase as in Example 1. During the experiment, the contents of SLB-EPS and TB-EPS, the PN / PS ratio of SLB-EPS, the PN / PS ratio of TB-EPS, the time required for successful biofilm formation and start-up of the reactor, the time for efficient and stable operation (when the pollutant removal efficiency reaches its maximum and remains almost constant), and the removal efficiency of pollutants COD and ammonia nitrogen during the stable operation phase of the aerobic moving bed biofilm reactor were monitored and recorded. The specific data are shown in Table 2 below.

[0029] Table 2. Start-up and operation data of the aerobic moving bed biofilm reactor in Comparative Example 1.

[0030]

[0031] Comparative Example 2

[0032] The same aerobic moving bed biofilm reactor as in Example 1 was used. The type, amount, inoculated sludge and sludge concentration, and influent water quality and quantity of the packing material in the aerobic moving bed biofilm reactor were the same as those in Example 1. However, during the biofilm formation and start-up phase of the aerobic moving bed biofilm reactor, SLB-EPS was not added. Instead, the same volume of influent as that added in Example 1 was used. During the operation phase, the same amount of TB-EPS as in Example 1 was added. The source and extraction method of TB-EPS were the same as those in Example 1. During the experiment, the contents of SLB-EPS and TB-EPS, the PN / PS ratio of SLB-EPS, the PN / PS ratio of TB-EPS, the time required for successful biofilm formation and start-up of the reactor, the time for efficient and stable operation (the pollutant removal efficiency reaches its maximum and remains almost constant) and the removal efficiency of pollutants COD and ammonia nitrogen during the stable operation phase of the aerobic moving bed biofilm reactor were monitored and recorded. The specific data are shown in Table 3 below.

[0033] Table 3. Start-up and operation data of the aerobic moving bed biofilm reactor in Comparative Example 2.

[0034] Example

[0035] Using the method of this invention, SLB-EPS and TB-EPS extracted from sludge in a sludge storage tank (sludge concentration of 15000 mg / L) of a wastewater treatment plant in a chemical plant are added in a single batch to the biofilm formation start-up and operation stages of an anaerobic fixed-bed biofilm reactor fed with simulated chemical wastewater. The SLB-EPS extraction temperature is 60°C, and the TB-EPS extraction method is the sodium citrate method. The addition volumes of SLB-EPS and TB-EPS account for 15% and 18% of the effective volume of the reactor, respectively. The anaerobic fixed-bed biofilm reactor is filled with 60% elastic three-dimensional packing material and inoculated with sludge from the chemical plant's sludge storage tank at a concentration of 15000 mg / L. During the experiment, the contents of SLB-EPS and TB-EPS, the PN / PS ratio of SLB-EPS, the PN / PS ratio of TB-EPS, the time required for successful biofilm formation and start-up of the anaerobic fixed-bed biofilm reactor, the time for efficient and stable operation (the pollutant removal efficiency reaches its maximum and remains almost constant), and the removal efficiency of pollutant COD when the reactor is stable were monitored and recorded during the biofilm formation start-up and operation phases. The specific data are shown in Table 4 below.

[0036] Table 4. Start-up and operation data of the anaerobic biofilm reactor in Example 2

[0037]

[0038] Comparative Example 3

[0039] The same anaerobic fixed-bed biofilm reactor as in Example 2 was used. The type and quantity of packing material, the inoculated sludge and its concentration, and the influent water quality and quantity were the same as in Example 2. However, during the biofilm formation and start-up phase, the same amount of TB-EPS as in Example 2 was added, and during the operation phase, the same amount of SLB-EPS as in Example 2 was added. The extraction methods for SLB-EPS and TB-EPS were the same as those in Example 2. During the experiment, the contents of SLB-EPS and TB-EPS, the PN / PS ratio of SLB-EPS, the PN / PS ratio of TB-EPS, the time required for successful biofilm formation and start-up of the reactor, the time for efficient and stable operation (the pollutant removal efficiency reaches its maximum and remains almost constant), and the COD removal efficiency of pollutants when the reactor is stable were monitored during the biofilm formation start-up and operation phases of the anaerobic fixed bed biofilm reactor. The specific data are shown in Table 5 below.

[0040] Table 5. Start-up and operation data of the anaerobic biofilm reactor in Comparative Example 3.

[0041]

[0042] Comparing the biofilm formation start-up time, efficient and stable operation time, and pollutant removal efficiency of Examples 1-2 and Comparative Examples 1-3, it can be seen that the method of enhancing the operation of biofilm reactors using extracellular polymeric substances (EPS) provided by this invention effectively shortens the biofilm formation start-up time and extends the efficient and stable operation time. It is applicable to different types of biofilm reactors and packing materials, and has a wide range of applications. In addition, EPS is derived from waste activated sludge from various wastewater treatment plants, reducing sludge production and disposal costs, responding to the concept of carbon neutrality, and has great potential for widespread application.

Claims

1. A method for enhancing the operation of a biofilm reactor using extracellular polymers, characterized in that, The operation method is divided into a membrane formation initiation stage and an operation stage: When the biofilm reactor (1) is in the biofilm formation start-up stage, a single pump is used to introduce extracellular polymeric EPS, which mainly includes soluble extracellular polymeric S-EPS and loosely bound extracellular polymeric LB-EPS. S-EPS and LB-EPS are referred to as SLB-EPS. The SLB-EPS accounts for more than 65% of the total EPS. The EPS mainly consists of protein PN and polysaccharide PS, with a PN / PS ratio of 0.5 to 2.

0. The amount of EPS added accounts for 8% to 15% of the influent of the biofilm reactor, and the concentration of SLB-EPS in the biofilm reactor (1) is 20 mg / gss to 80 mg / gss. When the pollutant removal efficiency in the biofilm reactor (1) reaches 50%, the biofilm reactor (1) enters the operation stage. EPS mainly consisting of tightly bound extracellular polymeric substances (TB-EPS) is pumped in at one time. The TB-EPS accounts for more than 70% of the total EPS. The amount of EPS added accounts for 10% to 18% of the influent volume of the biofilm reactor. The concentration of TB-EPS in the biofilm reactor (1) is 100 mg / gss to 250 mg / gss, and the PN / PS ratio is 4.0 to 8.

5. The EPS originates from the waste activated sludge in the sludge storage tank (10) of the sewage treatment plant; The biofilm reactor (1) is an aerobic, anoxic, or anaerobic environment, in the form of a fixed bed or a moving bed, and the biofilm reactor (1) is filled with packing material (2).

2. The method as described in claim 1, characterized in that, The sludge storage tank (10) is equipped with a matching stirring paddle (11), a temperature control device (12) and an EPS extraction automatic control system (13). The sludge concentration range of the sludge storage tank (10) is 6000~15000mg / L.

3. The method as described in claim 2, characterized in that, SLB-EPS is extracted from waste activated sludge using a mild heating method. Specifically, the temperature in the sludge storage tank (10) is 50-60°C by regulating the EPS extraction automatic control system (13) and the temperature control device (12). After stirring for 30-40 minutes, the sludge mixture is pumped to the downstream hydrocyclone (9). The SLB-EPS solution is separated from the sludge by centrifugation in the hydrocyclone (9) and stored in the SLB-EPS storage tank (8). The sludge that has been precipitated after centrifugation is recycled back to the sludge storage tank (10) by the sludge return pump (14) for further extraction of SLB-EPS.

4. The method as described in claim 3, characterized in that, TB-EPS is extracted from the returned sludge. The extraction method is either the cation exchange resin method or the sodium citrate method. Specifically, the EPS extraction automatic control system (13) is adjusted, and an appropriate amount of cation exchange resin or sodium citrate is added to the sludge storage tank (10). After stirring for 40 to 50 minutes, the mixture is pumped to the hydrocyclone separator (9). After the TB-EPS solution is separated from the sludge by centrifugation, it is stored in the TB-EPS storage tank (7). The remaining sludge is discharged to the sludge treatment system (15) for disposal.

5. The method as described in claim 1, characterized in that, The filling ratio of the packing material (2) in the biofilm reactor (1) is 30%~60%, and the concentration of inoculated sludge is 2000~5000mg / L.

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