Rapid forming device and method for anaerobic ammonia oxidation granular sludge

Abstract

The invention provides a double-threshold (SI, Ca / P) closed-loop device and a double-threshold (SI, Ca / P) closed-loop method taking a hydroxyapatite (HAP) skeletonization window as a core, aiming at rapid prototyping of anammox granular sludge in a high ammonia nitrogen sewage treatment process. The device comprises an SBR (sequencing batch reactor), an online DO / pH / TDS (dissolved oxygen / pH / total dissolved solids) and Ca / P feeding and linkage controller, is matched with a coaxial double-ring microporous injection component to realize short pulse (lagging for 2-10 seconds) of'first calcium and then phosphorus', and is provided with a replaceable sacrificial nucleation cylinder to capture Ca-P microcrystals and reduce scale. The controller adjusts Ca and P pulses and SBR phase time in a linkage mode according to DO, pH, TDS and a manually-input target window (SI = 0.2-0.6, Ca / P = 1.4-1.8); when TDS / pH exceeds a limit value or an excessive mineralization symptom (for example, the HAP peak area in XRD is greater than 15%) occurs, Ca is automatically reduced, and hunger time is prolonged. OCT / FBRM can be selectively accessed, mu t / void ratio or chord length distribution is used as auxiliary triggering, and integration of structure-chemistry-operation is achieved. According to the scheme, anammox granulation is stably and efficiently achieved, an HAP nucleation-growth window is used as a main target, the volume fraction of particles with the particle size larger than or equal to 0.5 mm and larger than or equal to 80% can be obtained within 2-4 weeks, the strength and settleability are remarkably improved, and over-mineralization embrittlement is avoided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and particularly relates to optimization of anammox process, in particular, an apparatus and method based on an upflow anaerobic sludge bed (UASB) reactor for rapid formation of anammox granular sludge for high ammonia-nitrogen industrial wastewater. BACKGROUND

[0002] Anammox directly converts ammonia-nitrogen into nitrogen gas with nitrite as the electron acceptor, which has the advantages of low energy consumption, less carbon source demand, and low sludge yield compared with traditional nitrification-denitrification, and has been valued in the treatment of high ammonia-nitrogen wastewater (such as landfill leachate and some industrial wastewater). Engineering practice shows that the formation and stability of anammox granular sludge (particle size ≥0.5 mm) is the key to realize high volumetric loading, good settling property and impact resistance.

[0003] The existing strategies for accelerating granulation include: starvation-banquet selection pressure under SBR conditions, moderate shear, selective sludge discharge, addition of divalent cations (Ca²⁺ / Mg²⁺) to enhance extracellular polymer (EPS) crosslinking, control of nitrite inhibition, stratification or multi-point water inlet to improve substrate penetration, etc. However, there is no clear and definite operation procedure that can effectively accelerate the granulation process of anammox. These means usually have certain effect, but when combined, they also face typical problems: 1. The "calcium / magnesium addition" lacks chemical nucleation window constraints, and is prone to produce disordered precipitation in the bulk phase or excessive crystallization on the particle surface, resulting in particle shell brittleness, pore plugging, and limited mass transfer; 2. Without online calculation and control of HAP saturation index and other chemical nucleation indicators, the addition of Ca and P is mostly performed in an empirical concentration or single threshold (mg / L) manner, which is difficult to balance the "densification speed" and "reaction-diffusion balance"; 3. Controlling NO2⁻ only by a single-point concentration threshold ignores the coupling of particle structure-chemical environment, resulting in "inhibition-recovery-reinhibition" fluctuations; 4. There is a lack of closed-loop linkage of structure characterization and chemical target value, making it difficult to reproduce rapid and controllable granulation under different sludge sources, influent composition and hydraulic conditions.

[0004] Therefore, there is an urgent need for a closed-loop control method and device that takes the HAP nucleation-growth window as the core, organically couples chemical driving (Ca / P, SI) with operation driving (pulse feeding, selective sludge discharge, phase-time adjustment), and optional structure signals (OCT / FBRM), to shorten the formation period, improve the mechanical and settling properties of the particles, and at the same time avoid the brittleness and mass transfer deterioration caused by over-mineralization. SUMMARY

[0005] The present application aims to solve the problems of lack of HAP chemical window constraint, rough Ca / P addition, excessive mineralization or insufficient densification of particles, and mismatch between mass transfer and reaction in the existing anammox granulation process, and proposes a rapid forming technology taking HAP saturation index and Ca / P molar ratio as double control quantities, so that the particles are densified in a controllable skeletonization window, the strength and mass transfer are considered, and the replicability and operation stability are improved.

[0006] To achieve the above-mentioned purpose, the present application provides the following device and method.

[0007] (I) Device A HAP skeletonization window-based anammox granular sludge rapid forming device, comprising: 1. SBR reactor main body; 2. Saturation index calculation module, which calculates HAP saturation index SI (preferably according to SI = log 10 (IAP / Ksp) or equivalent function, IAP is ion activity product, Ksp is HAP solubility product, and activity is corrected by ion strength) by using test data; 4. Ca addition unit and P addition unit, supporting two feeding modes of continuous and short pulse; 5. Linkage controller, connected with the monitoring and adding unit signal, configured to take SI and Ca / P molar ratio as double control quantities, maintain SI at 0.2-0.6, and maintain Ca / P at 1.4-1.8; when SI or Ca / P is low, execute short pulse co-injection of Ca and P and / or shorten the precipitation time; when SI or Ca / P is high, reduce Ca addition and prolong the starvation phase; 6. Optional structure characterization module: OCT (output optical attenuation coefficient μ t , porosity, shell thickness / core radius) or FBRM (output chord length distribution CLD, D10 / D50 / D90, Span), whose signal is used as an auxiliary trigger of the chemical window; 7. Optional process optimization unit: stratification / multi-point water inlet to maintain the vertical NO2⁻ gradient ratio (upper / lower) 1.2-1.8.

[0008] (II) Method A method for realizing rapid particle forming by using the above-mentioned device, comprising: S1) inoculate flocculent sludge and start the basic cycle of SBR; S2) test Ca²⁺, PO4³⁻, pH, temperature and calculate SI, and calculate the Ca / P molar ratio after water inlet / addition; S3) Dual-threshold closed-loop control with target window of SI=0.2-0.6, Ca / P=1.4-1.8: - When SI or Ca / P is too low: execute short pulse co-dosing of Ca and P (5-30 mg / L each, ion basis, pulse ≤20 min) and shorten the precipitation time; - When SI or Ca / P is too high: reduce Ca dosage by 20-50% and extend the starvation phase by 20-60 min; S4) When over-mineralization signs appear (e.g. HAP peak area ratio in XRD >15%, ash content significantly increased, OCT void ratio ≤35%, etc.), adjust Ca / P to 1.4-1.6 and reduce the pulse frequency; S5) Optionally switch to maintenance mode using structural thresholds of OCT / FBRM (e.g. D50≥0.45-0.60 mm and Span≤1.2 or μ t =0.8-1.3 mm⁻¹); S6) When the volume fraction of particles with particle size ≥0.5 mm is ≥80%, fix SI=0.25-0.5, Ca / P=1.4-1.6, and maintain long-term stability through selective sludge discharge and layered water feeding.

[0009] Compared with the prior art, the present application has the following beneficial effects: 1. Closed-loop control with chemical window as the core: using HAP saturation index + Ca / P molar ratio as the interlocking master control quantity, upgrading "Ca dosage / P dosage" from empirical concentration scheduling to nucleation-growth window control; 2. Avoiding over-mineralization and embrittlement: triggering actions such as "reducing Ca + extending starvation phase" when SI or Ca / P is out of range, effectively inhibiting over-crystallization of the shell and maintaining porosity and mass transfer; 3. Faster and replicable granulation: in the preferred embodiment, a molding rate of ≥80% (particle size ≥0.5 mm) can be achieved in 2-4 weeks, with stable settling and impact resistance performance; 4. Integration of structure-chemistry-operation: optionally introducing structural parameters (μ t , void ratio, D50 / Span) of OCT / FBRM as auxiliary triggers to match control actions with the real densification progress of particles; 5. Parameter expression for engineering: using SI, Ca / P, gradient ratio, etc. to replace single-point concentration thresholds, making it easier to reproduce across water quality and sources; 6. Improved process robustness: maintaining vertical NO2⁻ gradient ratio through layered water feeding and selective sludge discharge, reducing the frequency of NO2⁻ inhibition events, and balancing load and stability; 7. Strong scalability: compatible with existing SBR / mainstream or side-stream Anammox start-up processes, modular deployment of devices and algorithms, easy to scale up and upgrade.

[0010] The above is a summary of the technical field, background and content of the invention; further features, parameter intervals and trigger logic of the invention are described in the foregoing summary and draft claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Figure 1 is a structural schematic diagram of the anammox granular sludge rapid forming device based on the HAP skeleton window of the present application; it includes an SBR reactor main body (1), a water inlet bucket (2), a peristaltic pump (2.1), a DO / pH / TDS sensor (3), a Ca and P feeding unit and a linkage controller (4), a Ca feeding unit (4.1), a P feeding unit (4.2), a peristaltic pump (4.3), a water outlet bucket (5), and a stirring paddle (6).

[0012] Figure 2 Figure 2 is a structural schematic diagram of the Ca and P dosing unit in the device of the present application. DETAILED DESCRIPTION

[0013] Example 1: Device construction, the main body is a glass SBR reactor with an effective volume of 10 L, equipped with a hydraulic stirrer (rotating speed 15 rpm).

[0014] The online monitoring module includes a pH electrode, a temperature probe, and a conductivity meter.

[0015] The saturation index calculation module has a built-in Ksp(HAP) correction database to correct the activity coefficient according to temperature and ionic strength.

[0016] The Ca dosing unit is a peristaltic pump connected to a 0.5 mol / L CaCl2 storage tank, and the P dosing unit is a peristaltic pump connected to a 0.5 mol / L NaH2PO4 storage tank.

[0017] The linkage controller is a PLC, with preset SI=0.2-0.6, Ca / P=1.4-1.8 control range.

[0018] Example 2: Method flow 1. Inoculation and start-up: inoculate flocculent anammox sludge (3000 mg VSS / L), run for 6 h (influent-reaction-settling-drainage).

[0019] 2. Record Ca²⁺, PO₄³⁻, pH, temperature, and conductivity every 5 minutes; calculate SI and Ca / P in real time.

[0020] 3. Closed-loop control: When SI < 0.2 or Ca / P < 1.4, simultaneously pulse-add 20 mg / L each of Ca²⁺ and PO₄³⁻ for 10 min, and shorten the precipitation phase by 15 min. When SI > 0.6 or Ca / P > 1.8, reduce Ca dosage by 30% and prolong the starvation phase by 40 min. When the HAP peak area detected by XRD is >15%, adjust the Ca / P ratio to 1.5 and reduce the pulse frequency.

[0021] 4. Optional structural feedback: Use OCT for weekly scans, if μ t >1.3 mm⁻¹ or porosity <35% → Initiate overmineralization protection, reduce Ca addition and prolong the starved phase.

[0022] 5. Results: Within 21 days, D50 increased from 0.18 mm to 0.55 mm, the proportion of particles with a diameter ≥0.5 mm reached 83%, the settling rate increased by 25%, and the molding cycle was shortened by about 50% compared with the control group.

Claims

1. An anammox granular sludge rapid prototyping device based on a hydroxyapatite (HAP) skeletal window, comprising an SBR reactor body (1), an inlet tank (2), DO / pH / TDS sensors (3), Ca and P feeding units, and a linkage controller (4); the device is equipped with a coaxial double-ring microporous injection assembly (the inner ring is a Ca channel and the outer ring is a P channel) to achieve short pulse co-injection of "calcium first, then phosphorus", and a replaceable sacrificial nucleation tube is set in the return branch to preferentially capture Ca–P microcrystals; the linkage controller only receives DO, pH, TDS signals and manually entered target window parameters (HAP saturation index SI and Ca / P molar ratio), and outputs pulse feeding commands for Ca and P and duration corrections for the SBR phase, without connecting to an online ion concentration analyzer; it can optionally connect to an OCT or FBRM as an auxiliary trigger signal for control actions.

2. The apparatus as described in claim 1, characterized in that: The injection assembly creates a phase difference δt of 2–10 s between the Ca pulse and the P pulse, with a micropore diameter of 0.2–0.8 mm and an outlet axis angle of 20–45° with the horizontal plane.

3. The apparatus as described in claim 1, characterized in that: The Ca and P feeding unit is equipped with a diaphragm-type micro-pulse valve and a pulsation damping chamber at the front end to form short pulses. The duration of a single pulse is ≤20 min, the duty cycle is 10–40%, and the volume of a single pulse per orifice is 0.1–2.0 mL.

4. The apparatus as described in claim 1, characterized in that: The reactor is equipped with a stepped adjustable slit weir at the top, with the slit width adjustable in increments of 0.5–1.0 mm, for selective sludge discharge based on particle size threshold.

5. The apparatus as described in claim 1, characterized in that: The linkage controller is set to TDS / pH safety linkage. When ΔTDS / Δt > 150 mg·L⁻¹·10 min⁻¹ or pH > 8.0, it will automatically reduce the Ca pulse by 20–50% and extend the starvation phase by 20–60 min.

6. A method for rapid prototyping of anammox granular sludge based on a HAP-based skeletalized window, implemented on the apparatus of any one of claims 1–5, comprising: Ca and P were measured offline, and SI and Ca / P were calculated. The target window values ​​of SI = 0.2–0.6 and Ca / P = 1.4–1.8 were manually entered into the controller. During the SBR cycle, coaxial dual-ring injection was used to achieve short pulse co-injection of calcium first and then phosphorus. When SI or Ca / P was low, the pulse frequency was increased and / or the precipitation phase was shortened. When SI or Ca / P was high, the Ca pulse was reduced and the starved phase was prolonged. At the same time, a slit-type effluent weir was used to select the particle size threshold.

7. The method as described in claim 6, characterized in that: The single Ca and P pulse doses were 5–30 mg·L⁻¹ (in ions), with a phase difference δt of 3–6 s. When the HAP peak area ratio in XRD was >15% or the ash content increased by ≥10–25% from the baseline, it was determined to be overmineralized and the following actions were taken: Ca / P ratio was adjusted to 1.4–1.6, Ca pulse was reduced by 20–50%, and the starvation phase was extended by 20–60 min.

8. The method as described in claim 6 or 7, characterized in that: When the volume fraction of particles with a diameter ≥0.5 mm is ≥80%, the maintenance mode is entered, SI is fixed at 0.25–0.5, Ca / P is fixed at 1.4–1.6, and the pulse frequency is reduced by 30–60%.

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