Energy and resource recycling-oriented sewage treatment system and process operation method

Abstract

The present application relates to a kind of energy, resource recycling-oriented sewage treatment system and process operation method, belong to sewage treatment field.The sewage treatment system includes chemical strengthening pretreatment unit, enhanced nitrification unit, oxygen-consuming unit and sulfur autotrophic denitrification unit, strengthening pretreatment unit includes the mechanical mixing pool and strengthening primary sedimentation tank connected in sequence, and primary sludge enters sludge treatment unit and carries out phosphorus recovery and anaerobic digestion and heat power cogeneration capacity;Enhanced nitrification unit is moving bed membrane bioreactor;Oxygen-consuming unit is oxygen-consuming tank, and the sludge discharge port in the bottom of oxygen-consuming tank is connected with sludge treatment unit and sludge reflux pump;Sulfur autotrophic denitrification unit includes sulfur autotrophic vibrating membrane bioreactor.The sewage treatment system and process operation method of the present application are simple, easy to operate, and easy to realize unattended;It can be in energy, resource efficient recycling, ensure that effluent quality meets the standard while, realize short process low carbon operation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and specifically to a wastewater treatment system and process operation method for energy and resource recovery. Background Technology

[0002] The decarbonization and resource and energy recovery of urban wastewater treatment plants are inevitable trends in their development and essential requirements for high-quality economic and social development. Currently, the carbon-to-nitrogen ratio of influent wastewater at Chinese wastewater treatment plants is generally low, but effluent standards are constantly improving, leading to a high dependence on external carbon sources and high chemical consumption. Recommended treatment processes are mostly long-process processes such as modified Bardenpho, which have high energy consumption and complex operation and management. Furthermore, the organic matter content of residual sludge is low, resulting in low methanogenesis efficiency in anaerobic digestion and low energy and resource recovery rates. Therefore, there is an urgent need to transform wastewater treatment concepts and models, and to construct low-carbon, short-process wastewater treatment systems oriented towards energy and resource recovery.

[0003] In response to the demands for low-carbon, resource-efficient, and energy-efficient wastewater treatment plants, technologies shifting from secondary biological oxidation removal of organic matter to primary treatment non-oxidative carbon source recovery have received increasing research and attention. The high-load activated sludge process combined with mainstream anaerobic ammonia oxidation (ANAO) has become the preferred short-process wastewater treatment model for future wastewater treatment plants worldwide. However, the high-load activated sludge process still requires aeration energy and mineralizes some influent carbon sources, resulting in energy consumption at the expense of other energy sources. Mainstream ANAO technology for municipal wastewater remains difficult to implement, and effluent total nitrogen levels often fail to meet standards. Furthermore, this process is ineffective at phosphorus removal. Therefore, it is necessary to construct more efficient and feasible short-process wastewater treatment technologies to truly transform and develop wastewater treatment plants.

[0004] Chemically enhanced primary treatment offers advantages such as a short process flow, stable operation, no organic matter loss, retention of dissolved organic matter to drive downstream denitrification, and carbon-phosphorus co-conversion. However, it is generally considered to have high chemical consumption and produces phosphorus-deficient wastewater with extremely low carbon-to-nitrogen ratios, which may be detrimental to the stable operation of the biological treatment process. Therefore, there are few practical cases of its use for upstream carbon source concentration and conversion. Designing reasonable process operating parameters and combining it with downstream biological treatment processes to form a process coupling is expected to give it new application vitality. Sulfate autotrophic denitrification technology is currently the most widely researched and applied autotrophic nitrogen removal technology. It has advantages such as cheap and readily available elemental sulfur, stable reaction, and high nitrogen removal load. However, this process consumes a lot of alkalinity, generally requiring external reagents for supplementation. Moreover, existing sulfur autotrophic denitrification processes are generally in the form of fixed packed beds, which have high initial packing costs, are prone to clogging in long-term operation, and are prone to elemental sulfur stripping and biofilm shedding during backwashing, leading to effluent quality deterioration. Therefore, there are no cases of its application as the mainstream nitrogen removal process in the secondary biological treatment stage of municipal wastewater treatment.

[0005] To promote the low-carbon and resource- and energy-efficient transformation of wastewater treatment plants and to drive the transformation of wastewater treatment processes towards shorter processes, this invention aims to establish a novel short-flow wastewater treatment system based on chemically enhanced primary treatment and sulfur autotrophic denitrification technology. Based on novel and reasonable operation methods and parameter design, it achieves organic combination of processes, complementary unit functions, and optimal overall operation. Summary of the Invention

[0006] To achieve synergistic pollution reduction and carbon reduction in wastewater treatment, and to effectively shorten the process flow, save land area, reduce operating costs, and reduce carbon emissions from wastewater treatment while ensuring stable effluent discharge that meets standards, this invention develops a short-process wastewater treatment system and its operation method that combines a chemically enhanced primary treatment unit, a moving bed biofilm reactor, and a vibrating membrane sulfur autotrophic bioreactor. This treatment system has a small footprint, a short process flow, and is easy to modularize and equip, facilitating intelligent implementation. It also boasts high treatment efficiency and can enhance the simultaneous recovery of energy and resources from wastewater, achieving carbon reduction and carbon sequestration during the wastewater treatment process.

[0007] This invention provides a wastewater treatment system for energy and resource recovery, which includes a chemically enhanced primary treatment unit, a simultaneous nitrification and denitrification unit, and a high-load autotrophic denitrification unit.

[0008] Furthermore, the chemically enhanced primary treatment unit includes a mechanical mixing tank and an enhanced primary sedimentation tank connected in sequence.

[0009] Furthermore, the simultaneous nitrification and denitrification unit consists of a moving bed biofilm reactor and a deaerator connected in sequence.

[0010] Furthermore, the high-load autotrophic denitrification unit is a vibrating membrane sulfur autotrophic bioreactor.

[0011] Furthermore, the enhanced primary sedimentation tank in the chemically enhanced primary treatment unit is connected to the moving bed biofilm reactor in the simultaneous nitrification and denitrification unit.

[0012] Furthermore, the deaerator in the simultaneous nitrification-denitrification unit is connected to a high-load autotrophic denitrification unit.

[0013] Furthermore, the mechanical mixing tank is equipped with inlet and outlet ports. The mechanical mixing tank is fed by water from the top and discharged from the bottom. The inlet is equipped with a stainless steel mesh plate with a hole diameter of 2mm to 5mm to prevent inorganic particles such as fibers and gravel from entering.

[0014] Furthermore, the primary sedimentation tank is equipped with inlet and outlet ports and sludge discharge port. The primary sedimentation tank is inlet from the middle, outlet from the top weir, and sludge discharge port at the bottom is used to discharge and recycle the primary sedimented sludge.

[0015] Furthermore, the moving bed biofilm reactor is equipped with inlet and outlet ports, with water entering from the bottom and exiting from the top. Both inlet and outlet ports are equipped with stainless steel screens with a pore size of 0.5 to 2.0 cm. The stainless steel screen at the outlet port adopts a three-dimensional columnar structure to prevent the packing material from accumulating at the outlet port.

[0016] Furthermore, the deaeration tank is equipped with inlet and outlet, sludge return port and sludge discharge port. The deaeration tank is fed into the water from the bottom and discharged from the top weir. An overpass valve is installed before the water inlet. The water inlet is equipped with a water distributor. The sludge return port is used to return the sludge water to the inlet end of the moving bed biofilm reactor. The sludge discharge port is used to discharge the excess sludge.

[0017] Furthermore, the vibrating membrane sulfur autotrophic bioreactor is equipped with inlet and outlet, backwash water inlet and bottom internal circulation port. The vibrating membrane sulfur autotrophic bioreactor is fed into the water from the top and the membrane draws water out. The effluent is used as backwash water for membrane backwashing. The internal circulation port returns the bottom sludge and sulfur powder to the top inlet.

[0018] This invention provides an application of a wastewater treatment system for energy and resource recovery in the fields of environmental protection and wastewater treatment.

[0019] This invention provides a process operation method for the above-mentioned wastewater treatment system oriented towards energy and resource recovery, the steps of which are as follows:

[0020] (1) The wastewater is fed into a mechanical mixing tank, then flocculant is added, and then the mixture is stirred to react and obtain a mixed liquid;

[0021] (2) The mixture obtained in step (1) is transported into the enhanced primary sedimentation tank for sedimentation to obtain the effluent from the enhanced primary sedimentation tank. The sludge rich in organic matter and phosphorus is used for anaerobic digestion to produce methane, and the digestion liquid is used to recover phosphorus.

[0022] (3) The effluent from the enhanced primary sedimentation tank in step (2) is transported into the moving bed biofilm reactor for simultaneous nitrification and denitrification treatment to obtain the effluent from the moving bed biofilm reactor.

[0023] (4) The effluent from the moving bed biofilm reactor obtained in step (3) is transported into the deoxygenation tank for deoxygenation treatment. The settled sludge is returned to the inlet of the moving bed biofilm reactor, and the effluent from the deoxygenation tank is then processed in the next step.

[0024] (5) The deaerated water obtained in step (4) is transported into a vibrating membrane sulfur autotrophic bioreactor for retention treatment. During this period, sulfur powder is added as an electron donor for the denitrification reaction, and sodium bicarbonate is added to supplement alkalinity. Finally, effluent that meets the discharge standards is obtained.

[0025] Furthermore, in step (1), the wastewater is urban domestic sewage, rural sewage, and industrial wastewater with a low carbon-to-nitrogen ratio and no toxic or harmful substances.

[0026] Furthermore, in step (1), the organic matter and phosphorus in the wastewater are concentrated in the sludge, which can be used for anaerobic digestion to produce methane for energy recovery, thus simultaneously realizing phosphorus resource recovery.

[0027] Furthermore, in step (1), the flocculant is one or a mixture of two of polyaluminum chloride and polyferric chloride.

[0028] Furthermore, the effective content of polyaluminum chloride and polyferric chloride in step (1) is 8-15%.

[0029] Furthermore, the dosage of polyaluminum chloride is 5–10 mg Al / L.

[0030] Furthermore, the dosage of polyferric chloride is 10–20 mg Fe / L.

[0031] Specifically, the dosage of polyaluminum chloride in step (1) can be 8 mg Al / L.

[0032] Furthermore, in step (1), the stirring rate of the mechanical mixing tank is 20-50 r / min.

[0033] Furthermore, the reaction time in the mechanical mixing tank in step (1) is 20 to 40 minutes.

[0034] Furthermore, in step (2), the surface loading of the primary sedimentation tank is enhanced to 1-2 m. 3 / (m 2 ·h).

[0035] Furthermore, in step (2), the sedimentation time in the primary sedimentation tank is enhanced to be 0.5 to 1.5 hours.

[0036] Furthermore, in step (3), the moving bed biofilm reactor is divided into 2 to 3 compartments.

[0037] Furthermore, in step (3), the moving bed biofilm reactor is filled with a material with an effective specific surface area of ​​700–800 m². 2 / m 3 K3 type suspended carrier packing.

[0038] Furthermore, in step (3), the filling rate of the moving bed biofilm reactor is 30-50%.

[0039] Preferably, the filling rate of the moving bed biofilm reactor in step (3) is 40%.

[0040] Furthermore, in step (3), the effective specific surface area per ton of water in the moving bed biofilm reactor is 2300–3800 m². 2 / m 3 .

[0041] Furthermore, in step (3), the dissolved oxygen concentration in the moving bed biofilm reactor is controlled to be 1.5–2.5 mg / L.

[0042] Preferably, the dissolved oxygen concentration in the moving bed biofilm reactor in step (3) is controlled at 1.5 mg / L.

[0043] Furthermore, in step (3), the total suspended solids concentration in the moving bed biofilm reactor is controlled to be 300–600 mg / L.

[0044] Furthermore, in step (3), the residence time of the effluent from the primary sedimentation tank in the moving bed biofilm reactor is 4 to 5 hours.

[0045] Furthermore, the surface loading of the deaerator in step (4) is 1–2 m³. 3 / (m 2 ·h).

[0046] Furthermore, in step (4), the angle of the inclined tube assembly of the deaerator is 60°.

[0047] Furthermore, in step (4), the effluent from the moving bed biofilm reactor has a residence time of 1 to 2 hours in the deaeration tank.

[0048] Furthermore, in step (4), the sludge recirculation ratio is 50%.

[0049] Furthermore, in step (5), the vibrating membrane assembly of the vibrating membrane sulfur autotrophic bioreactor is submerged.

[0050] Furthermore, in step (5), the pore size of the microfiltration membrane in the vibrating membrane sulfur autotrophic bioreactor is 0.05–0.15 μm.

[0051] Furthermore, in step (5), the reciprocating motion rate of the membrane in the vibrating membrane autotrophic bioreactor is 40-60 r / min, and the amplitude is 1-5 cm.

[0052] Furthermore, in step (5), the sulfur powder used in the vibrating membrane sulfur autotrophic bioreactor has a particle size of 50–500 nm.

[0053] Furthermore, in step (5), the vibrating membrane sulfur autotrophic bioreactor adopts intermittent internal circulation operation, with an internal circulation frequency of 1 to 2 times / 3h.

[0054] Furthermore, in step (5), the effluent flux of the vibrating membrane sulfur autotrophic bioreactor is 10–20 L / (m³). 2 ·h).

[0055] Furthermore, in step (5), the dissolved oxygen concentration in the vibrating membrane sulfur autotrophic bioreactor is controlled below 0.2 mg / L.

[0056] Furthermore, in step (5), the total suspended solids concentration in the vibrating membrane sulfur autotrophic bioreactor increases in a gradient from top to bottom, with the total suspended solids concentration ranging from 3000 to 5000 mg MLSS / L.

[0057] Furthermore, in step (5), the mass of sulfur powder added to the vibrating membrane sulfur autotrophic bioreactor is 2 to 3 times the equivalent of nitrate nitrogen removal in the deoxygenation tank effluent.

[0058] Furthermore, in step (5), the mass of sodium bicarbonate added to the vibrating membrane sulfur autotrophic bioreactor should be 2 to 3 times the equivalent of nitrate nitrogen removal in the deoxygenation tank effluent. If the actual final treated effluent pH value is 6 to 9, no additional sodium bicarbonate needs to be added.

[0059] Furthermore, in step (5), the residence time of the deaerated water in the vibrating membrane sulfur autotrophic bioreactor is 1 to 2 hours.

[0060] The main innovation of this invention is as follows:

[0061] 1) This invention is the first to propose a short-process wastewater treatment system combining chemically enhanced primary treatment, a moving bed biofilm reactor, and a vibrating membrane autotrophic bioreactor. Functionally, these processes correspond to carbon-phosphorus co-direction / simultaneous nitrification-denitrification / autotrophic denitrification, respectively, achieving efficient recovery and utilization of organic matter and phosphorus, and efficient nitrogen removal. Each process unit in this invention is functionally complete and independent, requires a small footprint, is easily modularized, and is interconnected and complementary. Specifically, the chemically enhanced pretreatment produces wastewater with low organic matter concentration and an extremely low carbon-to-nitrogen ratio. The organic matter is mainly dissolved organic matter, which reduces the aeration energy consumption required by the moving bed biofilm reactor, facilitating its low dissolved oxygen operation. The extremely low carbon-to-nitrogen ratio promotes the enrichment of nitrifying bacteria, and the dissolved organic matter promotes rapid heterotrophic denitrification, thus creating conditions for simultaneous nitrification and denitrification in the moving bed biofilm reactor. The low dissolved oxygen operation of the moving bed biofilm reactor reduces the deoxygenation burden on the deaerator, creating space for autotrophic denitrification in the vibrating membrane reactor. The moving bed biofilm reactor provides a stable anoxic environment, and the simultaneous heterotrophic denitrification rapidly converts dissolved organic matter into inorganic carbon sources and alkalinity, providing reaction substrates for sulfur autotrophic denitrification in the vibrating membrane tank and reducing alkalinity addition. The vibrating membrane sulfur autotrophic bioreactor uses high specific surface area sulfur powder as an electron donor and makes full use of influent nitrate nitrogen, alkalinity and inorganic carbon sources as substrates to carry out high-load sulfur autotrophic denitrification reaction, achieving efficient nitrogen removal. After membrane interception and screening, high-quality effluent is produced, which can stably meet the quasi-IV or quasi-III water discharge standards.

[0062] 2) This invention differs from the widely proposed carbon diversion model, which involves redirecting the influent carbon source to the sidestream for anaerobic fermentation and then adding the resulting high-quality carbon source to the biochemical stage to enhance heterotrophic denitrification. This invention focuses on constructing a novel wastewater treatment system that is energy-neutral and operates with low carbon emissions. The carbon source is shifted from chemically enhanced primary treatment to the primary sludge, increasing the organic matter content of the discharged sludge and improving the anaerobic digestion capacity efficiency. The resulting wastewater with extremely low C / N ratio enters the secondary biochemical stage. Currently, the heterotrophic denitrification used in wastewater treatment plants relies on the influent carbon source level and is not suitable for treating wastewater with extremely low C / N ratios. Adding an external carbon source would significantly increase operating costs and lead to additional carbon emissions. This invention is the first to propose combining a moving bed biofilm reactor with a sulfur-powder-driven vibrating membrane sulfur autotrophic bioreactor to achieve a denitrification process that combines simultaneous nitrification / denitrification with high-load sulfur autotrophic denitrification, constructing a short-process, high-efficiency nitrogen control model centered on autotrophic microorganisms.

[0063] 3) In response to the special wastewater characteristics of phosphorus deficiency, extremely low carbon-nitrogen ratio, low organic matter concentration and mainly dissolved components after the upstream carbon source shift, and taking into account the influent requirements of low dissolved oxygen and sufficient alkalinity for downstream sulfur autotrophic denitrification, this invention innovatively adopts a moving bed biofilm reactor operation mode with low dissolved oxygen, low reflux, high packing ratio, low suspended sludge concentration and no sludge discharge. While operating with low energy consumption, it achieves high enrichment of autotrophic functional bacteria and low sludge production; simultaneous nitrification and denitrification are stable and alkalinity is effectively replenished.

[0064] 4) Addressing the problems of high initial investment costs, easy caking, biofilm detachment after backwashing, bacterial loss, and poor effluent quality associated with existing fixed-bed sulfur autotrophic denitrification processes, which are difficult to apply to municipal wastewater treatment, this paper innovatively designs and employs a vibrating membrane sulfur autotrophic bioreactor using powdered elemental sulfur fluidization. Sulfur powder, with its larger specific surface area, serves as an electron donor and a microcarrier for sulfur autotrophic denitrifying bacteria, achieving rapid autotrophic denitrification with low dosage. This improves reactor space utilization efficiency. The vibrating membrane bioreactor eliminates the need for aeration, providing an anaerobic environment for sulfur autotrophic denitrification while preventing the loss of sulfur powder and suspended sludge, ensuring clear effluent with excellent water quality. An innovative combination of internal circulation and reciprocating motion of the membrane module enhances mass transfer within the membrane tank, facilitating rapid and efficient denitrification. Using a suspended sludge concentration of 3000–5000 mg MLSS / L, the hydrolytic microorganisms accelerate the dissolution of sulfur powder on the surface, promoting the retention and enrichment of sulfur autotrophic denitrifying bacteria on the elemental sulfur surface, thus forming a biofilm.

[0065] Compared with the prior art, the present invention has the following advantages:

[0066] (1) The organic matter content of the residual sludge in existing wastewater treatment plants is only about 30%, resulting in low anaerobic digestion efficiency for methanogenesis. Phosphate is stored in polyphosphate-accumulating bacteria cells, and recovery generally involves methods such as hot water hydrolysis and acid hydrolysis to release phosphorus from the sludge, followed by chemical precipitation and recovery, which is quite complex. In contrast, the primary sludge obtained by this invention has a high organic matter content and is chemical sludge, making it easier to anaerobically digest and produce methanogens compared to biological sludge, resulting in higher energy efficiency. Phosphorus in the primary sludge is enriched in the form of metallic salt sludge, which can be directly recovered by adjusting pH and other methods compared to biological sludge, without the need for secondary chemical addition, resulting in higher phosphorus recovery efficiency.

[0067] (2) Municipal wastewater in my country typically exhibits a low carbon-to-nitrogen ratio, and wastewater treatment plants often face problems such as insufficient influent carbon sources, low denitrification efficiency, and difficulty in meeting total nitrogen standards. To address this issue, existing wastewater treatment plants add large amounts of carbon sources, leading to a significant increase in operating costs. Furthermore, the added carbon sources are mostly fossil-based, and their consumption results in additional greenhouse gas emissions. On the other hand, under increasingly stringent emission standards, newly built wastewater treatment plants are often recommended to adopt modified Bardenpho and other long-process technologies, with biological treatment time exceeding 20 hours. Under the same or better effluent quality conditions, compared to the treatment processes of existing and newly built wastewater treatment plants, the short-process wastewater treatment system constructed in this invention is more conducive to the retention and enrichment of autotrophic microorganisms, primarily using autotrophic denitrification, requiring no external carbon sources, and resulting in lower operating costs. The wastewater treatment system constructed in this invention has a biological treatment time of only 4.5–8.5 hours and a total retention time of 5.5–10 hours, which can significantly shorten the wastewater treatment process, improve operating efficiency, and reduce the carbon footprint during construction and carbon emissions during operation.

[0068] (3) Existing wastewater treatment plants use single-sludge systems for their biological treatment stages. The removal of carbon, nitrogen, and phosphorus is mutually influential and restrictive. By setting different operating conditions for different process stages to change the dominant functional bacteria in the activated sludge, problems such as conflicting sludge ages of different functional bacteria and competition for carbon sources arise. This makes it difficult to efficiently enrich functional bacteria, and the operation and management are complex. The level of operation and management significantly affects the wastewater treatment efficiency. Compared with the current single-sludge system treatment mode of wastewater treatment plants, this invention decouples the removal processes of carbon, nitrogen, and phosphorus. The primary treatment stage, which is chemically enhanced, completes the co-conversion of carbon and phosphorus, removing more than 90% of phosphorus and more than 50% of organic matter, which mainly exists in the form of particles and colloids. The secondary biological treatment stage is a dual-sludge system. Nitrifying functional bacteria are enriched in the moving bed biofilm reactor, while the dissolved organic matter in the wastewater is used for rapid heterotrophic denitrification. Sulfotrophic denitrifying bacteria are enriched in the vibrating membrane sulfur autotrophic bioreactor to complete the final denitrification. Each functional unit is complementary but the processes are relatively independent. Functional microbial communities are enriched in the corresponding units, which can simplify the sewage treatment process, realize the modularization of the sewage treatment process, reduce the difficulty of operation and management, and help realize intelligentization. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the process system of the present invention. Detailed Implementation

[0070] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0071] Example 1

[0072] like Figure 1 A wastewater treatment system for energy and resource recovery is proposed. The system includes a chemically enhanced primary treatment unit, a simultaneous nitrification and denitrification unit, and a high-load autotrophic denitrification unit connected in sequence. The chemically enhanced primary treatment unit includes a mechanically mixed tank and an enhanced primary sedimentation tank connected in sequence. The simultaneous nitrification and denitrification unit is a moving bed biofilm reactor and a deaerator. The high-load autotrophic denitrification unit is a vibrating membrane sulfur autotrophic bioreactor.

[0073] The mechanical mixing tank is equipped with inlet and outlet ports, with water entering from the top and exiting from the bottom. The inlet is fitted with a stainless steel mesh plate with a mesh size of 2mm to 5mm to prevent inorganic particles such as fibers and gravel from entering. The enhanced primary sedimentation tank is equipped with inlet, outlet, and sludge discharge port, with water entering from the middle and exiting through a weir at the top. The bottom sludge discharge port is used to discharge and recycle the primary sedimented sludge. The moving bed biofilm reactor is equipped with inlet and outlet ports, with water entering from the bottom and exiting from the top. Both inlet and outlet ports are fitted with stainless steel screens with a mesh size of 0.5 to 2.0cm. The stainless steel screen at the outlet has a three-dimensional columnar structure to prevent the packing material from being impacted. The outlet is clogged; the deaeration tank is equipped with inlet and outlet, sludge return port and sludge discharge port. The deaeration tank is filled with water from the bottom and discharged from the top weir. An overpass valve is installed before the water inlet. The water inlet is equipped with a water distributor. The sludge return port is used to return the mud and water to the inlet end of the moving bed biofilm reactor. The sludge discharge port is used to discharge the excess sludge; the vibrating membrane sulfur autotrophic bioreactor is equipped with inlet and outlet, backwash water inlet and bottom internal circulation port. The vibrating membrane sulfur autotrophic bioreactor is filled with water from the top and discharged from the membrane. The discharged water is used as backwash water for membrane backwashing. The internal circulation port returns the bottom sludge and sulfur powder to the top inlet end.

[0074] Example 2

[0075] Using the above system, a wastewater treatment process operation method oriented towards energy and resource recovery includes the following steps:

[0076] (1) The wastewater had a COD concentration of 376.3 mg / L, a TN concentration of 51.6 mg / L, a TP concentration of 3.7 mg / L, a wastewater temperature of 23.4℃, and a pH of 7.5. The wastewater entered a mechanical mixing tank with a stirring rate of 30 r / min. Polyaluminum chloride with an effective content of 10% was added to a concentration of 8 mg Al / L. The mixture was reacted in the mechanical mixing tank for 0.5 h to obtain a mixed liquid.

[0077] (2) The mixture obtained in step (1) is transported into a flow path with a surface loading of 1.2m. 3 / (m 2 The vertical flow enhanced primary sedimentation tank (h) was used for sedimentation for 1 hour;

[0078] (3) The effluent from the primary sedimentation tank is introduced into a moving bed biofilm reactor. The moving bed biofilm reactor is divided into two compartments, both with an effective specific surface area of ​​800 m². 2 / m 3 The K3 type suspended carrier packing material has a filling rate of 40% and an effective specific surface area of ​​3070 m² per ton of water. 2 / m 3 The dissolved oxygen concentration in the reactor was controlled at 1.5 mg / L, the total suspended solids concentration at 375 mg / L, and the wastewater retention time in the reactor was 4.5 h.

[0079] (4) The surface loading of the effluent from the moving bed biofilm reactor is 1.5 m. 3 / (m 2 •h), an aeration tank with an inclined tube assembly angle of 60° and a retention time of 1.2h, with sludge returned to the inlet of the moving bed biofilm reactor at a return ratio of 50%;

[0080] (5) The effluent from the deaeration tank enters the vibrating membrane sulfur autotrophic bioreactor. The membrane module in the reactor is set to submerged type. The vibrating membrane sulfur autotrophic bioreactor adopts intermittent internal circulation operation with an internal circulation frequency of 2 times / 3h. It uses a 0.1μm microfiltration membrane with a membrane movement speed of 50r / min, an amplitude of 3cm, and an effluent flux of 15L / (m³). 2 In the continuously operating reactor, the dissolved oxygen concentration was controlled below 0.2 mg / L. The total suspended solids (TSS) concentration increased gradually from top to bottom, with 3500 mg / L in the middle and 4180 mg / L in the bottom. Sulfur powder was added as an electron donor for the denitrification reaction, and sodium bicarbonate was added to supplement alkalinity. The mass of both sulfur powder and sodium bicarbonate added was 2.5 times the target nitrate nitrogen removal equivalent. The wastewater retention time in the reactor was 1.8 h.

[0081] Table 1. Treatment status of the short-process wastewater treatment system

[0082]

[0083]

[0084] The effluent from each stage of the equipment was tested, as shown in Table 1. The effluent from the enhanced primary sedimentation tank in step (2) was tested and found to have a COD concentration of 82.3 mg / L, which is 78.1% lower than the influent from the mechanical mixing tank; a TP concentration of 0.29 mg / L, which is 92.2% lower than the influent from the mechanical mixing tank; a TN concentration of 42 mg / L; a COD / TN ratio of 7.3 to 2.0; and a pH value of 7.5 to 7.0.

[0085] In step (4), the influent and effluent of the moving bed biofilm reactor were tested. It was found that the ammonia nitrogen in the influent decreased from 40.6 mg / L to 0.62 mg / L, nitrate nitrogen increased to 35.2 mg / L, and nitrite nitrogen increased to 0.22 mg / L. The nitrogen in the effluent of the moving bed biofilm reactor was mainly nitrate nitrogen. Simultaneous nitrification and denitrification occurred in the moving bed biofilm reactor, removing 8.3 mg / L of total nitrogen, contributing 19.8% to the denitrification. At the same time, the pH value increased from 7.0 to 7.2, and alkalinity was replenished.

[0086] In step (5), sulfur autotrophic denitrification in the vibrating membrane sulfur autotrophic bioreactor removed 29.6 mg / L of total nitrogen, contributing 70.5% to nitrogen removal. The final effluent concentration of the short-process wastewater treatment system was 25.3 mg / L COD, 0.01 mg / L TP, and 4.1 mg / L TN. Compared with the wastewater influent of the mechanical mixing tank, the COD removal rate was 93.3%, the total phosphorus removal rate was 99.9%, and the TN removal rate was 92.1%, with a total retention time of 9 h.

[0087] Comparative Example 1

[0088] This comparative example uses similar influent water quality conditions and the same effluent water quality standard (Class A standard of the "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants" (GB18918-2002)). It follows the combined treatment process recommended in the "Technical Guidelines for Upgrading Urban Wastewater Treatment Plants in Taihu Lake Area, Jiangsu Province (DB32 / 1072) (2018 Trial Version)". The specific steps are: coarse screen and influent pump station + fine screen and high-efficiency grit chamber + combined pre-anoxic AAO / AO biological treatment tank (i.e., pre-anoxic / anaerobic / anoxic / aerobic / anoxic / aerobic) + denitrification filter + high-efficiency dissolved air flotation tank + contact disinfection tank. Pollutant removal mainly occurs in the secondary biological treatment stage, i.e., in the combined pre-anoxic AAO / AO biological treatment tank, with a total retention time of 21 hours. Sludge-water separation takes place in the secondary sedimentation tank, with a sedimentation time of 6.3 hours. To enhance nitrogen and phosphorus removal, a denitrification filter and a high-efficiency dissolved air flotation tank are installed after the biological treatment stage, each with a hydraulic retention time of 0.5 hours.

[0089] Table 2. Treatment status of recommended processes in newly built wastewater treatment plants

[0090]

[0091] The actual influent and effluent water quality during operation is shown in Table 2. Compared with Example 2, this comparative example shows that, under the same treatment capacity, the short-process sewage treatment system constructed by the present invention has a shorter process flow, and the hydraulic retention time is only 30% to 50% of the existing recommended process. At the same time, it does not require a complex reflux system, is easy to operate and manage, and has lower energy and chemical consumption. It can also achieve simultaneous recovery of energy and resources.

[0092] Comparative Example 2

[0093] This comparative example is the comparative example of Example 2, except that the amount of coagulant added in step (1) was adjusted to 2 mg Al / L and 20 mg Al / L respectively, while other operations and parameters remained unchanged. The results are as follows:

[0094] Table 3 Comparison of system operation under different coagulant dosages

[0095]

[0096] Table 3 shows that when the dosage of coagulant in the mechanical mixing tank is too low, the removal efficiency of COD, TP, and TN deteriorates significantly. This is because a low dosage reduces the effectiveness of the chemically enhanced primary treatment, resulting in insufficient carbon-phosphorus diversion efficiency. This leads to a significant increase in the volumetric load of pollutants in the downstream moving bed biofilm reactor, preventing sufficient organic matter mineralization and ammonia nitrification. Phosphorus absorbed in the aerobic stage is then anaerobically released in the downstream vibrating membrane autotrophic bioreactor, ultimately making it difficult to meet the removal standards for COD, TN, and TP. Conversely, when the coagulant dosage is too high, TN and NH4+ removal efficiency also decreases. + The poor removal of -N is due to the low organic load in the influent of the moving bed biofilm reactor (MBBR). The MBBR is dominated by fine, dispersed autotrophic nitrifying sludge, and under phosphorus-free conditions, the activity of nitrifying bacteria is limited, leading to a gradual deterioration in nitrification capacity and ultimately resulting in low NH4+ removal. + -N and TN exceed the standard. Therefore, for the equipment and usage method designed in this invention, the dosage of chemical agents in the mechanical mixing tank should not be too high or too low. Taking aluminum salt as an example, for municipal sewage, the preferred dosage is 5 to 10 mg Al / L.

[0097] Comparative Example 3

[0098] This comparative example is the same as Example 2, except that the filling rate of the moving bed biofilm reactor packing in step (3) was adjusted to 10%, while other operations and parameters remained unchanged. The results are as follows:

[0099] Table 4 Comparison of system operation under different packing ratios

[0100]

[0101]

[0102] Table 4 shows that when the packing rate of the moving bed biofilm reactor decreases to 10%, the removal efficiency of COD, TP, and TN significantly deteriorates. This is mainly because the reduced biomass within the moving bed biofilm reactor leads to a corresponding decrease in the consumption and removal capacity of dissolved oxygen, organic matter, and ammonia nitrogen, resulting in increased dissolved oxygen levels. This, in turn, disrupts the anoxic environment required for sulfur autotrophic denitrification in the downstream vibrating membrane tank, causing an overall decrease in TN removal capacity. Generally, when the packing rate is between 10% and 30%, a mixed suspension sludge-biofilm operation is used to increase biomass. However, in the process flow of this invention, the hydraulic retention time of the moving bed biofilm reactor is relatively short, making sludge easily lost. The high sludge concentration will burden the downstream process and increase the frequency of sludge discharge. If the packing rate is increased to 60%, the moving bed biofilm reactor will be difficult to operate with low carbon emissions, requiring higher energy consumption to achieve packing fluidization. Therefore, for the equipment and method designed in this invention, if the packing material in the moving bed biofilm reactor is too high or too low, it will have a direct negative impact on the overall pollutant removal and the operation of downstream processes. The preferred packing material ratio is 40%.

[0103] Comparative Example 4

[0104] This comparative example is the same as Example 2, except that the dissolved oxygen in the moving bed biofilm reactor in step (3) was adjusted to 4 mg / L, while other operations and parameters remained unchanged. The results are as follows:

[0105] Table 5 Comparison of system operation under different dissolved oxygen concentrations

[0106]

[0107] The data in Table 5 show that when the dissolved oxygen level in the moving bed biofilm reactor is set to around 4 mg / L, the removal efficiency of COD and TN significantly deteriorates. This is mainly because the higher dissolved oxygen level in the effluent from the moving bed biofilm reactor disrupts the anoxic environment of the downstream vibrating membrane sulfur autotrophic bioreactor, thus inhibiting the sulfur autotrophic denitrification process. As a result, some dissolved oxygen will replace NO3. --N, acting as an electron acceptor, reacts with elemental sulfur, leading to poorer denitrification and increased total nitrogen (TN) in the effluent. Simultaneously, higher dissolved oxygen levels within the moving bed biofilm reactor inhibit simultaneous nitrification and denitrification, increasing the sulfur autotrophic denitrification load and resulting in additional sulfur powder and alkalinity consumption. Furthermore, at low organic matter concentrations, higher dissolved oxygen levels stimulate heterotrophic bacteria in the vibrating membrane tank, accelerating their endogenous respiration and releasing intracellular substances, thus increasing effluent organic matter. Higher dissolved oxygen levels also lead to higher operating energy consumption and increased carbon emissions during operation. When the dissolved oxygen concentration in the moving bed biofilm reactor falls below 0.5 mg / L, TN removal efficiency also deteriorates, resulting in higher effluent NH4 levels. + The -N concentration is mainly due to the fact that when dissolved oxygen is set low, the metabolic activity of ammonia-oxidizing bacteria is inhibited, and the nitrification process is limited. Therefore, for the equipment and method designed in this invention, the dissolved oxygen in the moving bed biofilm reactor should not be too high or too low, and the preferred dissolved oxygen concentration is 1.5 mg / L.

[0108] Comparative Example 5

[0109] This comparative example is the same as Example 2, except that the total suspended solids concentration in the vibrating membrane sulfur autotrophic bioreactor in step (5) was adjusted to 1000 mg / L, while other operations and parameters remained unchanged. The results are as follows:

[0110] Table 6 Comparison of system operation of the vibratory milling autotrophic bioreactor under different suspended solids concentrations.

[0111]

[0112] The data in Table 6 show that when the total suspended solids concentration in the vibrating membrane sulfur autotrophic bioreactor is set to around 1000 mg / L, the TN removal efficiency will significantly decrease, resulting in a large amount of NO3 residue in the effluent. - -N. This is mainly because at low suspended solids concentrations, the abundance and total amount of sulfur autotrophic bacteria are both low. Since sulfur powder is added on demand, sulfur autotrophic bacteria have difficulty rapidly retaining and accumulating on the surface of small amounts of sulfur powder, making it difficult to complete the denitrification process in a short residence time. Furthermore, when the total suspended solids concentration in the membrane tank is too high, it will cause serious membrane fouling problems, restricting the system's water production. Therefore, for the equipment and usage method designed in this invention, the total suspended solids concentration in the vibrating membrane sulfur autotrophic bioreactor should not be too high or too low; preferably, the total suspended solids concentration is 3300–3700 mg / L.

[0113] Comparative Example 6

[0114] This comparative example is the comparative example of Example 2, except that the vibrating membrane sulfur autotrophic bioreactor in step (5) is adjusted to the general vibrating membrane bioreactor operation mode without internal circulation. Other operations and parameters remain unchanged. The results are as follows:

[0115] Table 7 Comparison of system operation under different internal circulation rates in the vibratory milling autotrophic bioreactor

[0116]

[0117] The data in Table 7 show that when the vibrating membrane autotrophic bioreactor has no internal circulation, the TN removal efficiency will significantly deteriorate, resulting in high concentrations of NO3 residue in the effluent. - -N. This is mainly due to the specific gravity of sulfur powder being approximately 2.07 g / cm³. 3 The sediment, with a density significantly higher than that of sludge, easily settles within the membrane tank, hindering effective mass transfer. When the bottom sediment is circulated internally to the upper part of the membrane tank, the mass transfer process within the reactor is enhanced by the reciprocating motion of the membrane modules, allowing for successful sulfur autotrophic denitrification. However, excessively high internal circulation rates significantly increase operating energy consumption and may lead to localized short-circuiting, resulting in a further deterioration in treatment efficiency. Therefore, for the equipment and method designed in this invention, setting the internal circulation frequency in the vibrating membrane sulfur autotrophic bioreactor to 1-2 times / 3 hours, with the single circulation volume determined by the sediment level in the sedimentation zone, allows for efficient denitrification of the reactor under low-energy operation.

[0118] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A process operation method for a wastewater treatment system oriented towards energy and resource recovery, characterized in that, The wastewater treatment system includes a chemically enhanced primary treatment unit, a simultaneous nitrification and denitrification unit, and a high-load autotrophic denitrification unit. The chemically enhanced primary treatment unit includes a mechanical mixing tank and an enhanced primary sedimentation tank connected in sequence. The simultaneous nitrification and denitrification unit consists of a moving bed biofilm reactor and a deoxygenation tank connected in sequence. The high-load autotrophic denitrification unit is a vibrating membrane sulfur autotrophic bioreactor. The enhanced primary sedimentation tank in the chemically enhanced primary treatment unit is connected to the moving bed biofilm reactor in the synchronous nitrification and denitrification unit. The deaeration tank in the synchronous nitrification-denitrification unit is connected to the high-load autotrophic denitrification unit; The steps of the process operation method are as follows: (1) Wastewater is fed into a mechanical mixing tank, then flocculant is added, followed by stirring to obtain a mixed liquid; the dosage of the reagent in the mechanical mixing tank should not be too high or too low. If the dosage of the reagent in the mechanical mixing tank is too low, the volumetric load of pollutants in the downstream moving bed biofilm reactor will increase significantly, and organic matter mineralization and ammonia nitrogen nitrification will not be fully completed. After the aerobic section absorbs phosphorus, it will be anaerobically released in the downstream vibrating membrane sulfur autotrophic bioreactor, resulting in the final COD, TN, and TP removal effects being difficult to meet the standards; if the dosage of the reagent is too high, the organic load in the influent of the moving bed biofilm reactor will be low, and the MBBR will be mainly composed of fine and dispersed autotrophic nitrifying sludge. Under phosphorus-free conditions, the activity of nitrifying bacteria will be limited, and the nitrification capacity will gradually deteriorate, resulting in the final NH4 + -N and TN exceeded the standard; (2) The mixture obtained in step (1) is transported into the enhanced primary sedimentation tank for sedimentation to obtain the effluent from the enhanced primary sedimentation tank. The sludge rich in organic matter and phosphorus is used for anaerobic digestion to produce methanogens, and the digestion liquid is used to recover phosphorus. (3) The effluent from the enhanced primary sedimentation tank in step (2) is transported into the moving bed biofilm reactor for simultaneous nitrification and denitrification treatment to obtain the effluent from the moving bed biofilm reactor; (4) The effluent from the moving bed biofilm reactor obtained in step (3) is transported into the deoxygenation tank for deoxygenation treatment. The settled sludge is returned to the inlet of the moving bed biofilm reactor, and the effluent from the deoxygenation tank is then processed in the next step. (5) The deaerated water obtained in step (4) is transported into a vibrating membrane sulfur autotrophic bioreactor for retention treatment. The total suspended solids concentration in the vibrating membrane sulfur autotrophic bioreactor increases in a gradient from top to bottom. The total suspended solids concentration is 3000~5000 mg MLSS / L. During this period, sulfur powder is added as an electron donor for the denitrification reaction, and sodium bicarbonate is added to supplement alkalinity. Finally, effluent that meets the discharge standards is obtained. The vibrating membrane sulfur autotrophic bioreactor is equipped with an inlet and outlet, a backwash water inlet and a bottom internal circulation port. The vibrating membrane sulfur autotrophic bioreactor is fed into the water from the top and the membrane draws water out. The effluent is used as backwash water for membrane backwashing. The internal circulation port returns the bottom sludge and sulfur powder to the top inlet. The vibrating membrane sulfur autotrophic bioreactor adopts intermittent internal circulation operation, with an internal circulation frequency of 1~2 times / 3 hours; The combination of internal circulation and reciprocating motion of membrane modules enhances mass transfer within the membrane pool.

2. The process operation method according to claim 1, characterized in that, The mechanical mixing tank is equipped with inlet and outlet ports, with water entering from the top and exiting from the bottom. The inlet port is equipped with a stainless steel mesh plate with a mesh size of 2 mm to 5 mm to prevent the entry of fibers, gravel, and inorganic particles. The enhanced primary sedimentation tank is equipped with inlet, outlet, and sludge discharge port, with water entering from the middle and exiting through a weir at the top. The bottom sludge discharge port is used to discharge and recycle the primary sedimented sludge. The moving bed biofilm reactor is equipped with inlet and outlet ports, with water entering from the bottom and exiting from the top. Both inlet and outlet ports are equipped with stainless steel screens with a mesh size of 0.5 to 2.0 cm. The stainless steel screen at the outlet has a three-dimensional columnar structure to prevent the packing material from accumulating at the outlet.

3. The process operation method according to claim 1, characterized in that, The deaeration tank is equipped with an inlet and outlet, a sludge return outlet, and a sludge discharge outlet. Water enters the deaeration tank from the bottom and exits through a weir at the top. An overpass valve is installed before the water enters the tank. The inlet is equipped with a water distributor. The sludge return outlet is used to return the sludge water to the inlet end of the moving bed biofilm reactor. The sludge discharge outlet is used to discharge the remaining sludge.

4. The process operation method according to claim 1, characterized in that, In step (1), the wastewater is urban domestic sewage, rural sewage, and industrial wastewater with a low carbon-to-nitrogen ratio and no toxic or harmful substances.

5. The process operation method according to claim 1, characterized in that, In step (3), the packing rate of the moving bed biofilm reactor is 30-50%.

6. The process operation method according to claim 1, characterized in that, In step (3), the dissolved oxygen concentration in the moving bed biofilm reactor is controlled to be 1.5~2.5 mg / L.

Images