Baffled biological nest / fluidized bed coupled nitrogen and carbon removal reactor and enhanced nitrification method

Abstract

The invention discloses a baffled biological nest / fluidized bed coupled nitrogen and carbon removal reactor and an enhanced nitrification method, and belongs to the technical field of sewage treatment.The reactor is improved on the basis of a traditional baffled anaerobic reactor, the proportion of an aerobic chamber to an anaerobic chamber is adjusted to be 1: 2 or 1: 3, and the aerobic chamber is communicated with the anaerobic chamber; a fluidized bed taking loofah sponge slices as a carrier is arranged in the aerobic chamber, full fluidization of the carrier and sewage is realized through a gas-cement mixer, and a biological nest is arranged in the anaerobic chamber; meanwhile, sufficient fluidization of sludge and a carrier in the aerobic chamber is realized through the gas-cement mixer, so that blockage and a dead zone are avoided, and the stability and the denitrification efficiency of the system are improved.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically a baffled biological nest / fluidized bed coupled denitrification and carbon removal reactor and enhanced nitrification method. Background Technology

[0002] In the field of municipal wastewater treatment, activated sludge processes, represented by A / O, A² / O, and their derivatives, have long held a dominant position. These processes achieve efficient simultaneous removal of organic matter, nitrogen, and phosphorus through precise control of anaerobic, anoxic, and aerobic environments. They are technologically mature, operate stably, and are a reliable choice to meet current high-standard discharge regulations. However, their core reliance on aerobic biodegradation processes, which depend on aeration and oxygen supply, is essentially a high-energy-consuming model of "exchanging energy (electricity) for removal." This results in high operating costs and the generation of large amounts of residual sludge requiring further treatment, making wastewater treatment plants "energy centers" and "cost centers" in cities.

[0003] Against this backdrop, the value of anaerobic biological treatment processes has been re-examined and enhanced. Its revolutionary significance lies in transforming organic matter in wastewater from "energy-consuming pollutants" into "recoverable energy carriers (biogas)." Anaerobic processes require no aeration, produce extremely low sludge yields, and directly achieve net energy output and sludge reduction from the source of the treatment process, perfectly aligning with the urgent need for wastewater treatment plants to transform into "energy plants" and "resource plants" under the "dual-carbon" strategy.

[0004] Among numerous anaerobic processes, the baffled reactor (ABR) stands out for its unique structure, demonstrating significant advantages in upgrading the applicability of municipal wastewater treatment. Compared to traditional UASB or EGSB reactors, which require high concentrations and excellent sedimentation performance, the ABR, through its multi-chamber series-connected plug-flow structure, achieves spatial partitioning for microbial functions such as hydrolysis acidification and methanogenesis. This makes the ABR more adaptable and buffering towards the complex organic matter, fluctuating water quality, and lower temperatures commonly found in municipal wastewater, resulting in more stable and reliable operation. Its modular design, free of complex internal components, also reduces the difficulty and cost of construction and maintenance.

[0005] A baffle-flow anaerobic bioreactor is a process for efficiently removing organic pollutants from anaerobic wastewater. It uses internal vertical baffles to divide the reactor into several reaction chambers connected in series. Wastewater flows up and down along the baffles within the reactor, ensuring thorough contact with the anaerobic sludge in each chamber. Its core concept combines the advantages of traditional completely mixed reactors with plug-flow reactors. Wastewater enters the first reaction chamber from one end of the reactor. Guided by the baffles, the water flows into the lower (or upper) part of one reaction chamber, mixes with the high concentration of anaerobic sludge, and then flows out from the upper (or lower) part into the next reaction chamber. Each reaction chamber is a relatively independent micro-ecosystem. As the water flows forward, the concentration and composition of organic matter, as well as the population and activity of microorganisms, exhibit a clear gradient distribution: the initial reaction chamber has a high concentration of organic matter, dominated by hydrolytic fermentation bacteria and acid-producing bacteria, undergoing rapid hydrolysis and acidification processes, resulting in a potentially lower pH value; the middle and later reaction chambers have a lower concentration of organic matter, dominated by hydrogen-producing and acetic acid-producing bacteria and, most importantly, methanogenic bacteria, converting volatile fatty acids into methane and carbon dioxide, resulting in a near-neutral pH value. The upper space of each reaction chamber functions as a three-phase separator. The biogas produced rises to the top and is collected; the treated water overflows into the next reaction chamber; the activated sludge settles and remains in the reaction chamber; and the effluent, after being treated in the last reaction chamber, is discharged from the effluent weir.

[0006] Although ABRs offer structural advantages such as phase separation and multi-stage buffering, their core principles still adhere to the fundamental principles of anaerobic biological treatment. These principles, when faced with the typical requirements of treating low-concentration municipal wastewater, constitute a fundamental technical weakness. Firstly, their production efficiency is low, limiting their "energy-generating" value for low-concentration municipal wastewater.

[0007] The production capacity (methane output) of anaerobic digestion directly depends on the total amount and biodegradability of organic matter in the influent. Typical municipal wastewater has a low COD concentration (usually 200-500 mg / L), and a significant portion of it consists of recalcitrant, inert organic matter. This means that even if an ABR (Anaerobic Batch Reactor) achieves a COD removal rate of 60%-80%, the actual amount of biogas it can produce is far lower than that produced by high-concentration industrial wastewater. Collecting, purifying, and utilizing such a low amount of biogas often presents significant challenges in terms of system complexity and economic viability, potentially leading to a situation where "production does not cover investment," making it difficult to realize the economies of scale of its role as an "energy plant" in municipal wastewater treatment. Secondly, the extremely low cell yield results in a lack of nutrient removal capacity, which is one of the most critical shortcomings of anaerobic processes (including ABR) in treating municipal wastewater. The cell yield of anaerobic metabolism is extremely low, typically only 1 / 5 to 1 / 10 of that of aerobic processes. This means that large amounts of nitrogen (NH4⁺-N) and phosphorus (PO4³⁻-P) in the wastewater need to be assimilated and absorbed into the cells of microorganisms before they can be removed. The extremely low biomass growth in anaerobic processes results in negligible ability to remove nutrients through anabolism. Furthermore, it cannot provide sufficient organic carbon sources for subsequent nitrogen removal: mainstream nitrogen removal processes (such as A² / O) require ample readily biodegradable carbon sources (such as volatile fatty acids, VFAs) for denitrification. While ABRs can produce some VFAs, their extremely low sludge production means that they convert the vast majority of influent COD into biogas (CH4 / CO2) rather than using it for new cell synthesis. This leaves very little bioavailable carbon (BOD) in the effluent, severely limiting the efficiency of subsequent deep nitrogen removal and typically requiring the addition of additional carbon sources (such as methanol or sodium acetate), increasing operating costs and complexity. Finally, it completely lacks nitrification capabilities and cannot initiate a nitrogen conversion cycle.

[0008] This is determined by the nature of the anaerobic environment. Nitrification is the key step in converting ammonia nitrogen (NH4⁺-N) into nitrate (NO3⁻-N), and it is completed by strictly aerobic autotrophic nitrifying bacteria. In the strictly anaerobic environment of an ABR (Acoustic Batch Reactor), nitrification occurs at zero; the ammonia nitrogen concentration remains essentially unchanged after passing through the ABR, and may even increase slightly due to the ammonification of organic nitrogen. Denitrification also cannot occur. Although denitrification takes place under anoxic conditions, it requires nitrate (NO3⁻-N) as an electron acceptor. Due to the absence of the preceding nitrification step, nitrate is not present inside the ABR, therefore denitrification is impossible. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention provides a baffled biological nest / fluidized bed coupled denitrification and decarbonization reactor and an enhanced nitrification method. By adjusting the ratio of anaerobic and aerobic chambers and using loofah sponge as a carrier to construct a fluidized bed, efficient nitrification and denitrification are achieved, thereby improving the overall denitrification and decarbonization performance of the system.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A baffled bio-nest / fluidized bed coupled denitrification and decarbonization reactor includes anaerobic chambers and aerobic chambers connected in series. The aerobic chambers are characterized by a ratio of 1:2 or 1:3 to anaerobic chambers. The aerobic chambers are equipped with a fluidized bed using loofah slices as a carrier, and the carrier and wastewater are fully fluidized through an air-cement mixer. The anaerobic chambers are equipped with bio-nests.

[0011] Preferably, in the above technical solution, the loofah slices are used as biological carriers after being cut, cleaned, and pretreated by soaking in a weak alkali.

[0012] Preferably, in the above technical solution, the aerobic chamber is provided with a perforated partition for retaining the loofah slices and preventing them from being lost with the water flow.

[0013] Preferably, in the above technical solution, the gas-cement mixer is located at the bottom of the aerobic chamber to achieve three-phase mixing and circulation of gas, water and sludge, thereby avoiding sludge deposition and carrier caking.

[0014] Preferably, in the above technical solution, the aerobic chamber and the anaerobic chamber are baffled structures with built-in vertical baffles, forming a multi-stage series plug-flow reaction unit.

[0015] Preferably, in the above technical solution, each chamber is provided with a baffle plate, and the baffle plate is provided with a bending structure, the bending structure and the baffle plate forming a 120-150° angle; the bending structure in the anaerobic chamber faces the biological nest; the bending structure in the aerobic chamber faces the baffle of the same chamber; all bending structures have the same orientation.

[0016] Preferably, in the above technical solution, the reactor cavity is divided into four chambers by three baffles, namely chamber I, chamber IV, chamber III, and chamber II. Chamber I is an anaerobic chamber, and chambers IV, III, and II are aerobic chambers. Each chamber is equipped with a guide plate. Chamber I is provided with an inlet and a return outlet located at both ends of the guide plate, and the return outlet and the biological nest are located on the same side of the guide plate. Chamber II is provided with a return inlet for receiving water from the return outlet to the return inlet in Chamber II.

[0017] Preferably, in the above technical solution, three biological nests are arranged in the I chamber; the biological nests are teardrop-shaped; the biological nests are composed of basalt fibers, and the three biological nests are arranged at equal intervals.

[0018] This invention also provides an enhanced nitrification method using a baffled biological nest / fluidized bed coupled denitrification and decarbonization reactor. The enhanced digestion using the aforementioned denitrification and decarbonization reactor includes the following steps: S1, wastewater sequentially enters the anaerobic chamber for anaerobic digestion of organic matter; S2 then enters the aerobic chamber, where nitrification occurs under the action of nitrifying bacteria enriched on the loofah carrier; S3, the nitrified liquid is returned to the front end of the anaerobic chamber, mixed with the raw water, and then denitrification is completed; S4, the final treated water is discharged from the anaerobic chamber.

[0019] Preferably, in the above technical solution, the hydraulic retention time of the aerobic chamber is 2-3 times that of the anaerobic chamber.

[0020] Preferably, in the above technical solution, the biofilm attached to the loofah carrier is periodically partially renewed by hydraulic rinsing to maintain biological activity.

[0021] The present invention provides a baffled biological nest / fluidized bed coupled denitrification and decarbonization reactor and an enhanced nitrification method, which has the following advantages compared with the prior art: The present invention relates to a baffled biological nest / fluidized bed coupled denitrification and carbon removal reactor and enhanced nitrification method, which introduces slices of loofah sponge as a carrier for the aerobic chamber, transforming the aerobic chamber into a fluidized bed. The loofah sponge is used to enrich nitrifying bacteria and is blocked by the perforated baffle during the flow process, so it will not flow out of the aerobic chamber. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the loofah slice of the present invention.

[0023] Figure 2 This is a schematic diagram of the denitrification and decarbonization reactor of the present invention.

[0024] Explanation of the labels in the diagram: 1. Inlet; 2. Return outlet; 3. Return inlet; 4. Loofah slices; 5. Aerated cement mixer; 6. Perforated baffle; 7. Slot; 8. Biological nest; 9. Drain; 10. Guide plate; 11. Baffle. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] like Figure 1 and Figure 2As shown, the baffled biological nest / fluidized bed coupled denitrification and decarbonization reactor of the present invention includes one anaerobic chamber I and two aerobic chambers II, III, and IV, with an anaerobic chamber to aerobic chamber ratio of 1:3. The aerobic chambers are filled with pretreated loofah slices 4 as fluidized bed carriers, and an aerated cement mixer 5 is provided at the bottom to achieve carrier fluidization. The aerobic and anaerobic chambers have a baffled structure, formed by guide plates 10 and baffles 11, allowing wastewater to flow sequentially through each chamber to complete the anaerobic digestion, nitrification, and denitrification processes. The aerobic chambers are equipped with perforated baffles 6 to prevent carrier loss. Slots 7 are provided at the top of the baffles 11 and corresponding locations on the guide plates 10, and the perforated baffles 6 are fixedly installed in the slots 7. A biological nest 8 is provided inside the anaerobic chamber I.

[0027] Municipal wastewater flows in through inlet 1 into chamber I, where it undergoes anaerobic digestion. It then flows through return outlet 2 and return inlet 3 into chambers II, III, and IV for nitrification. Finally, the nitrified liquid flows from the cover of chamber IV into the guide section of chamber I, mixing thoroughly with the influent. Denitrification also occurs simultaneously in chamber I, and the wastewater exits through outlet 9 of chamber I. The aerated cement mixer 5 acts as a mixing and plug flow mechanism, ensuring no sludge dead zones exist in chambers II, III, and IV. It also ensures that the loofah slices 4 form a circulating flow within the chambers, driving them to function as a fluidized bed. This reactor combines the advantages of a traditional completely mixed reactor with a plug flow reactor.

[0028] The core advantages of loofah sponge as a biological carrier lie in its intricate fiber network, which provides a huge specific surface area and interconnected pores. This facilitates: providing ample attachment space for slow-growing microorganisms such as nitrifying bacteria, leading to the formation of high-biomass biofilms; reducing mass transfer resistance through its open network structure, which promotes the diffusion of substances such as oxygen, ammonia nitrogen, nitrite, and nitrate, crucial for aerobic nitrification; and reducing the likelihood of complete clogging compared to some dense packing materials. Furthermore, dry loofah sponge has a very low density, but after absorbing water, its density is slightly greater than or close to that of water. Under moderate water flow and aerodynamic stirring, fluidization is easily achieved with relatively low energy consumption. The fluidized state ensures sufficient contact between the carrier and wastewater, avoiding dead zones, and promotes the shedding of aged biofilm through friction, maintaining biofilm activity.

[0029] The enhanced nitrification method using the baffled biological nest / fluidized bed coupled denitrification and carbon removal reactor of this invention employs the above-mentioned reactor for enhanced digestion, and the specific steps are as follows: Step S1, sludge inoculation: Clean the equipment, add carrier and inoculate sludge.

[0030] First, all chambers of the reactor are rinsed with clean water to remove construction residues. Pretreated loofah slices are added to the aerobic chamber, filling it to 30% of its volume. Then, aerobic activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant is added to the aerobic chamber at an inoculum concentration of 3000-4000 mg / L. Anaerobic granular sludge is inoculated into the anaerobic chamber at an inoculum concentration of 5000-6000 mg / L.

[0031] Step S2, Biofilm Initiation and Low-Load Operation: Low-load water intake is adopted to promote the attachment of microorganisms on the carrier surface.

[0032] Start the influent system, controlling the influent COD at 150-200 mg / L and ammonia nitrogen at 30-40 mg / L, with a hydraulic retention time of 12-16 hours. Turn on the aerobic chamber air-cement mixer, maintaining an air-to-water ratio of 5:1 and a dissolved oxygen concentration of 2-3 mg / L. This stage lasts 10-15 days, monitoring the effluent COD and ammonia nitrogen daily. Once the removal rate stabilizes above 60%, proceed to the next stage.

[0033] Step S3, hydraulic regulation and biofilm thickening: Gradually increase the influent load and hydraulic shear to promote a denser biofilm structure.

[0034] Gradually increase the influent COD to 250-300 mg / L and ammonia nitrogen to 40-50 mg / L, while shortening the hydraulic retention time to 8-10 hours. Adjust the strength of the aerated cement mixer to increase the shear force of the water flow, promoting the renewal and thickening of the biofilm on the surface of the loofah carrier. This stage lasts for 15-20 days until a uniform, dense, yellowish-brown biofilm forms on the surface of the aerobic chamber carrier.

[0035] Step S4, Biofilm maturation and nitrification performance enhancement: Further optimize operating parameters to increase the proportion and activity of nitrifying bacteria.

[0036] Maintain influent COD at 300-350 mg / L and ammonia nitrogen at 50-60 mg / L, with dissolved oxygen in the aerobic chamber controlled at 3-4 mg / L, and a hydraulic retention time (HRT) stabilized at 8 hours. Regularly monitor effluent nitrate concentration; if nitrification efficiency is below 80%, appropriately extend the HRT in the aerobic section or increase aeration intensity. This stage should last 10-15 days until the system's ammonia nitrogen removal rate stabilizes above 85%, and the nitrification liquor recirculation denitrification efficiency is significant.

[0037] Step S5, Stable Operation and Performance Maintenance: Long-term operation under optimized parameters to achieve stable nitrogen and carbon removal.

[0038] After the reactor enters the stable operation phase, daily monitoring of influent and effluent COD, ammonia nitrogen, nitrate, and total nitrogen is conducted. Quarterly sampling inspections of the loofah carrier are performed; if excessive biofilm thickness or blockage is found, hydraulic flushing can be initiated by temporarily increasing the air-to-water ratio. 5-10% fresh loofah slices can be added annually to maintain carrier activity and system stability.

[0039] The above embodiments are merely preferred examples of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A denitrification and decarbonization reactor coupled with a baffled biological nest and a fluidized bed, characterized in that, The reactor comprises an anaerobic chamber and an aerobic chamber connected in series, characterized in that the number ratio of the aerobic chamber to the anaerobic chamber is 1:2 or 1:3; a fluidized bed with gourd sponge slices as carriers is arranged in the aerobic chamber, and the carriers and sewage are fully fluidized by a gas-water-cement mixer, and the anaerobic chamber is provided with biological nests.

2. The baffling bio-nest / fluidized bed coupled denitrification and decarbonization reactor according to claim 1, characterized in that, The gourd sponge slices are pretreated by cutting, cleaning and weak alkali soaking, and then used as biological carriers.

3. The baffling bio-nest / fluidized bed coupled denitrification and decarbonization reactor according to claim 1, characterized in that, The aerobic chamber is provided with a perforated baffle.

4. The baffling bio-nest / fluidized bed coupled denitrification and decarbonization reactor according to claim 1, characterized in that, The gas-water-cement mixer is arranged at the bottom of the aerobic chamber to realize three-phase mixing and circulation of gas, water and cement.

5. The short-cut basalt fiber-based sewage aerobic granular sludge cultivation method according to claim 1, characterized in that, The aerobic chamber and the anaerobic chamber are of a baffling structure, and are provided with vertical baffles to form multiple push-flow reaction units connected in series.

6. The short-cut basalt fiber-based sewage aerobic granular sludge cultivation method according to claim 5, characterized in that, Each chamber is provided with a guide plate, and the guide plate is provided with a bending structure, and a bending angle of 120-150° is formed between the bending structure and the baffle; the bending structure in the anaerobic chamber faces the biological nest; the bending structure in the aerobic chamber faces the baffle in the same chamber; and the directions of all the bending structures are consistent.

7. The short-cut basalt fiber-based sewage aerobic granular sludge cultivation method according to claim 6, characterized in that, The inner cavity of the reactor is divided into four chambers, namely, chamber I, chamber IV, chamber III and chamber II, in sequence, chamber I is an anaerobic chamber, chamber IV, chamber III and chamber II are aerobic chambers, a guide plate is arranged in each chamber, a water inlet and a backflow outlet are arranged at both ends of the guide plate in chamber I, the backflow outlet is located at the same side of the guide plate as the biological nest, chamber II is provided with a backflow inlet for connecting the water in the backflow outlet to chamber II.

8. A kind of baffling biological nest / fluidized bed coupling denitrification and decarbonization reactor enhanced nitrification method, it is characterized in being, The denitrification and decarbonization reactor of any one of claims 1 to 7 is used for enhanced digestion, S1, sewage is sequentially introduced into the anaerobic chamber for anaerobic digestion of organic matter; S2, then introduced into the aerobic chamber for nitrification reaction under the action of nitrobacteria enriched on the gourd sponge carriers; S3, the nitrification liquid is backflowed to the front end of the anaerobic chamber, mixed with raw water, and then denitrification is completed; S4, the final treated water is discharged from the anaerobic chamber.

9. The enhanced nitrification process of the baffling bio-nest / fluidized bed coupled denitrification and decarbonization reactor according to claim 8, characterized in that, The hydraulic retention time of the aerobic chamber is 2-3 times that of the anaerobic chamber.

10. The enhanced nitrification process of the baffling bio-nest / fluidized bed coupled denitrification and decarbonization reactor according to claim 8, characterized in that, The biofilm attached to the gourd sponge carriers is periodically scoured by water.

Images