Sludge quality-divided reflux type aerobic-anoxic sulfur autotrophic activated sludge denitrification process

Abstract

The invention relates to the technical field of water treatment, and discloses a sludge quality-divided reflux type aerobic-anoxic sulfur autotrophic activated sludge denitrification process. The process comprises the following steps: wastewater enters a sectional type aerobic tank, the wastewater enters the sectional type aerobic tank, organic matters are removed in a strengthened manner in a first section of aerobic tank, part of ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen, and nitrification is strengthened in a second section of aerobic tank, so that the ammonia nitrogen is deeply removed; effluent of the sectional type aerobic tank enters an anoxic tank and is completely mixed with sulfur particles and activated sludge for sulfur autotrophic denitrification; effluent of the anoxic tank enters a secondary sedimentation tank for sedimentation, supernate is discharged, and bottom mud enters a hydrocyclone to be divided into heavy sludge and light sludge; the heavy sludge flows back to the front end of the anoxic tank, the light sludge flows back to the front end of the sectional aerobic tank, and the remaining sludge is discharged. According to the invention, sulfur autotrophic denitrification is deeply integrated into an activated sludge system, so that high-efficiency nitrogen removal without carbon source and internal reflux is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to a sludge separation and reflux type aerobic-anoxic sulfur autotrophic activated sludge denitrification process. Background Art

[0002] In the field of wastewater denitrification technology, the mainstream processes currently used include traditional A / O biological denitrification and sulfur autotrophic denitrification technology. However, these processes all have different drawbacks, which have limited their promotion and use and resulted in unsatisfactory wastewater treatment results. Among them:

[0003] Traditional A / O biological denitrification processes primarily rely on heterotrophic denitrifying bacteria, using organic matter as electron donors, to reduce nitrate nitrogen to nitrogen gas. This process suffers from the following technical bottlenecks: ① Limited by carbon source competition, when the influent carbon-nitrogen ratio (C / N) is low, additional carbon sources (such as methanol, glucose, and sodium acetate) must be added, leading to increased operating costs and the risk of secondary pollution. ② The process relies on an internal recirculation system to return nitrate nitrogen generated in the aerobic zone to the anoxic zone for denitrification. To achieve a high total nitrogen removal rate, a very large internal recirculation ratio (typically 200%-400%) is theoretically required, resulting in increased equipment investment and operating energy consumption. ③ The denitrification rate of a single-stage A / O process has a clear technical upper limit. While increasing the internal recirculation ratio improves the theoretical denitrification rate, it also leads to multiple constraints, such as increased dissolved oxygen in the anoxic zone, imbalanced carbon source competition, and shortened actual residence time, limiting the denitrification rate to around 80%. In the treatment scenarios of low carbon-nitrogen ratio wastewater (such as industrial wastewater and deep treatment of urban sewage), the contradiction between the denitrification efficiency and economy of the traditional A / O process is particularly prominent.

[0004] Sulfur autotrophic denitrification technology uses reduced sulfur (elemental sulfur, sulfide, etc.) as an electron donor to drive the reduction of nitrate nitrogen to nitrogen gas via sulfur autotrophic denitrifying bacteria. In recent years, sulfur autotrophic denitrification technology has shown great potential for treating low-carbon-nitrogen ratio wastewater due to its advantages, such as the lack of an external carbon source and high reaction stability. However, this technology still has the following key defects, which have limited its promotion and use: ① Inherent defects of the packed bed model: the mainstream process adopts a fixed bed of granular sulfur fillers, and its porous structure easily causes packing compaction and clogging caused by excessive proliferation of microbial biofilms, forcing the system to be frequently backwashed and aggravating packing wear, resulting in a high sulfur loss rate in long-term operation; in addition, sulfur is a consumable filler, and changes in the fixed bed load lead to flow disorder and uneven hydraulic distribution, aggravating device losses; and sulfur is hydrophobic, and the nitrogen produced by denitrification is easy to carry sulfur particles with the water and discharge, resulting in ineffective sulfur loss and secondary pollution of the effluent; ② Ecological competitive disadvantages of sulfur autotrophic bacteria: when mixed with activated sludge, sulfur autotrophic denitrifying bacteria have a slow growth rate and a long generation cycle, which makes them difficult to grow in a mixed culture system dominated by heterotrophic bacteria. ③ Insufficient integration and compatibility with the activated sludge process: In engineering practices coupled with the traditional activated sludge process (A / O process), the sulfur autotrophic denitrification fixed bed is often placed at the rear end of the anoxic section or at the effluent end of the secondary sedimentation tank for independent operation. As a post-auxiliary denitrification treatment facility, sulfur autotrophic denitrification has not yet broken away from the process limitations of the fixed bed reactor. In the sulfur autotrophic process of the activated sludge process, sulfur relies on quantitative and precise addition, and it is difficult to achieve efficient separation from the activated sludge. Sulfur particles are discharged with the residual sludge or effluent, causing sulfur loss and secondary pollution, making operation and maintenance difficult. In the presence of an organic carbon source, sulfate-reducing bacteria will reduce sulfate to hydrogen sulfide, leading to equipment corrosion, odor and safety risks. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, one of the objectives of the present invention is to provide a sludge separation and reflow type aerobic-anoxic sulfur autotrophic activated sludge denitrification process.

[0006] The second object of the present invention is to provide a wastewater treatment system for a sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process, comprising the following steps:

[0009] S1. Wastewater enters the segmented aerobic tank. First, in the first aerobic tank, organic matter is enhanced and part of the ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen. Then, in the second aerobic tank, nitrification is enhanced to deeply remove ammonia nitrogen.

[0010] S2, the effluent from the segmented aerobic tank enters the anoxic tank and is completely mixed with sulfur particles and activated sludge to carry out sulfur autotrophic denitrification;

[0011] S3. The effluent from the anoxic tank enters the secondary sedimentation tank for sedimentation, the supernatant is discharged, and the bottom sludge enters the cyclone to be separated into heavy sludge and light sludge; the heavy sludge is returned to the front end of the anoxic tank, and the light sludge is returned to the front end of the segmented aerobic tank, and the remainder is discharged as residual sludge.

[0012] In some embodiments of the present invention, in step S1, the dissolved oxygen content in the first aerobic tank is 1.5-2.0 mg / L; the hydraulic retention time is 5-25 h; and the sludge load is ≤0.2 kg BOD5 / (MLSS·d).

[0013] In some embodiments of the present invention, in step S1, the pH of the water in the first aerobic tank is 6.5-8.5.

[0014] In some embodiments of the present invention, in step S1, the dissolved oxygen content in the second aerobic tank is 2.0-3.0 mg / L; and the hydraulic retention time is 5-15 h.

[0015] In some embodiments of the present invention, in step S1, the pH of the water in the second aerobic tank is 7.0-8.5.

[0016] In some embodiments of the present invention, in step S2, in the anoxic tank, the sulfur particle concentration is 2-20 g / L wastewater; the activated sludge concentration is 2-5 g / L wastewater; and the hydraulic retention time is 4-10 h.

[0017] In some embodiments of the present invention, in step S2, the pH of the water in the anoxic tank is 7.0-8.5.

[0018] In some embodiments of the present invention, in step S2, the particle size of the sulfur particles is 0.05-0.5 mm, and the water immersion time is ≤5 s.

[0019] In some embodiments of the present invention, in step S3, the surface hydraulic load of the secondary sedimentation tank is 2.5-3.2m 3 / (m 2 ·h).

[0020] In some embodiments of the present invention, in step S3, the separation standard of the cyclone is: sulfur content of heavy sludge> 5wt%, density> 1.05g / cm 3 ; Light sludge sulfur content ≤ 5wt%, density ≤ 1.05g / cm 3 .

[0021] In some embodiments of the present invention, in step S3, the return ratio of the heavy sludge is 100%; the return ratio of the light sludge is 70%-90%.

[0022] In some embodiments of the present invention, step S3 further includes monitoring the total sulfur content of the sludge. When the total sulfur content is ≤2000 mg / kg, sulfur particles are added to be synchronously returned to the front end of the anoxic tank together with the heavy sludge.

[0023] In some embodiments of the present invention, in step S3, the monitoring frequency of the total sulfur content of the sludge is 1 / 2 hydraulic retention time of the secondary sedimentation tank; sulfur granules are added when the total sulfur content is ≤2000 mg / kg after 3-4 consecutive monitorings.

[0024] In some embodiments of the present invention, in step S3, the method for calculating the amount of sulfur particles added is:

[0025] During one hydraulic retention time, the mass of sulfur particles added Ms (kg) = Cs × V 缺氧池 Where Cs is the preferred sulfur particle concentration in the anoxic pool (20 g / L), V 缺氧池 is the effective volume of the anoxic pool (m 3 ).

[0026] The basic principles of the present invention are described as follows:

[0027] The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process provided by the present invention deeply integrates sulfur autotrophic denitrification into the activated sludge system, and controls sulfur distribution through segmented aerobic tank enhanced nitrification + anoxic tank sulfur-sludge symbiotic denitrification + cyclone separation and reflux, thereby achieving efficient denitrification without a carbon source and internal reflux. Specifically:

[0028] 1) In the first aerobic tank, aerobic and facultative heterotrophic bacteria degrade organic pollutants (COD) through aerobic respiration. This metabolic process involves the mineralization of organic matter (decomposition into CO2 and H2O) and microbial assimilation and proliferation (synthesis of new cellular material). Essentially, it involves the transfer of electrons from organic matter to oxygen. The core function of the first aerobic tank is to remove organic pollutants. By controlling hydraulic retention time, sludge concentration, and dissolved oxygen concentration, the system maintains a low sludge load (F / M ≤ 0.2 kg BOD5 / (kg MLSS·d)). Compared to activated sludge systems operating under high organic loads, heterotrophic bacteria in low organic load environments experience a slowed growth phase or endogenous respiration due to carbon source limitation. This leads to a decrease in the abundance of copiotrophs due to carbon source limitation, while oligotrophs, due to their efficient resource utilization, become the dominant population. They derive energy from a higher proportion of organic matter catabolism, resulting in a decrease in anabolism (assimilation). This macroscopic manifestation is a high mineralization rate of organic pollutants in the effluent and a low sludge growth rate. In the first aerobic tank, the dissolved oxygen concentration remains stable at 1.5-2.0 mg / L. The supply rate of oxygen molecules, the final electron acceptor, is limited by liquid-phase diffusion, forming a radial oxygen concentration gradient within the activated sludge flocs: an aerobic outer layer and an anoxic inner layer. In the outer aerobic environment, using oxygen as an electron acceptor, nitrite-forming bacteria convert ammonia nitrogen into nitrite nitrogen, and nitrifying bacteria, in turn, convert nitrite nitrogen into nitrate nitrogen. In the inner anoxic environment, denitrifying bacteria convert nitrite nitrogen and nitrate nitrogen into nitrogen gas. This aerobic-anoxic microenvironment of the flocs fosters localized simultaneous nitrification and denitrification (SND). However, in an environment characterized by relatively abundant biodegradable organic matter, the competitive advantage of heterotrophic bacteria weakens the niche advantage of autotrophic nitrite-forming bacteria and nitrifying bacteria, resulting in relatively weak simultaneous nitrification and denitrification.

[0029] In the second aerobic tank, the dissolved oxygen content is increased to 2.0-3.0 mg / L, with the core function of enhancing nitrification. Nitrosating and nitrifying bacteria are obligate aerobic, autotrophic microorganisms with lower growth and oxygen uptake rates than heterotrophic microorganisms. To ensure that dissolved oxygen penetrates both inside and outside the activated sludge flocs and guarantees adequate oxygen supply for the nitrification process, the dissolved oxygen concentration in the second aerobic tank is increased. This aims to overcome oxygen mass transfer resistance and ensure that nitrifying bacteria deep in the flocs have sufficient electron acceptors. The content of readily biodegradable organic matter does not directly affect autotrophic nitrosating and nitrifying bacteria. Instead, it promotes the rapid growth of heterotrophic microorganisms, which compete for dissolved oxygen, competing for or even occupying the ecological niches of slower-growing nitrosating and nitrifying bacteria, ultimately affecting the progress of the nitrification process. Organic pollutants are deeply decomposed by the activated sludge in the first aerobic tank, and the residual concentration of biodegradable organic matter is at a low level (BOD5 / TN≤2). The low organic substrate environment inhibits the proliferation of heterotrophic bacteria, ensuring that nitrite bacteria and nitrifying bacteria occupy the dominant ecological niche, and realizing the efficient conversion of ammonia nitrogen to nitrate.

[0030] 2) The anoxic tank uses elemental sulfur autotrophic denitrification technology, with denitrification as its core function. Sulfur autotrophic denitrifying bacteria (such as Thiobacillus) are facultative anaerobic, obligate autotrophic microorganisms that can oxidize elemental sulfur to sulfate under both aerobic and anaerobic conditions. Under anoxic conditions, they perform autotrophic denitrification using nitrate and nitrite as electron acceptors, reducing nitrate and nitrite to nitrogen gas to achieve nitrogen removal. The chemical reaction equation is as follows:

[0031]

[0032] The present invention uses small-particle sulfur with a hydrophilic surface as a sulfur source for autotrophic denitrification. Its particle size range (0.05-0.5mm) is highly matched with conventional activated sludge flocs (0.02-0.2mm). The two are physically mixed to form a unique sulfur-activated sludge symbiotic bacterial floc structure. The small-particle sulfur has a large specific surface area, providing a densely attached carrier interface for sulfur autotrophic denitrifying bacteria, thereby increasing the effective biofilm area per unit volume by 2-3 orders of magnitude. The sulfur particles in the floc serve as the skeleton core, fixing the sulfur autotrophic bacteria group through electrostatic adsorption and extracellular polymer bridging, while the activated sludge wraps the periphery to form a dynamic protective layer. This structure gives the floc a dual characteristic: on the one hand, because the sulfur density is much higher than that of the activated sludge, a density gradient is formed from the inside to the outside, which significantly optimizes the sedimentation performance of the mixed liquor (sludge settling ratio SV30 = 8%-20%, sludge volume index SVI <30-40mL / g), supporting the surface hydraulic load of the secondary sedimentation tank to be increased to 2.5-3.2m 3 / (m 2 h), which is higher than the surface hydraulic load of the secondary sedimentation tank using conventional activated sludge or biofilm methods; on the other hand, the overall apparent density of the flocculent group is maintained at 1.05-1.10 g / cm 3 interval, so that it can still be fully mixed with the wastewater under the action of mechanical stirring or plug flow, greatly enhancing the liquid-solid mass transfer efficiency of sulfur-microorganism interface and nitrate nitrogen.

[0033] Sulfur autotrophic denitrifiers, as obligate chemoautotrophs, express sulfur dioxygenase and sulfite oxidase on their cell membranes, forming a unique sulfur metabolic pathway that enables the directional transfer of electrons from elemental sulfur to nitrate nitrogen. This type of bacterial community is tightly colonized on the surface of the sulfur carrier, forming a physical spatial isolation from the free heterotrophic bacteria and nitrifying bacteria flowing into the segmented aerobic tank. Moreover, the heterotrophic bacteria rely on organic carbon sources, and the nitrifying bacteria are obligately aerobic, which circumvents niche competition at the kinetic level. The resulting microbial functional zoning enables efficient synergy at the spatial and metabolic levels between oligotrophic heterotrophic bacteria (first aerobic tank), autotrophic nitrifying bacteria (second aerobic tank), and sulfur autotrophic denitrifying bacteria (anoxic section), increasing both nitrification and denitrification loads. Thanks to the slower proliferation rate of the functional bacterial community, the amount of excess sludge is significantly reduced.

[0034] 3) In the secondary sedimentation tank, the supernatant is discharged and the sediment sludge enters the cyclone for quality separation. The heavy sludge is sulfur and activated sludge containing sulfur particles (sulfur content > 5wt%, density > 1.05g / cm 3 ), full return to the anoxic tank can maintain the sulfur concentration, sulfur autotrophic bacteria concentration and activity, so that the sulfur loss rate is reduced to less than 5%; light sludge is activated sludge that does not contain or contains very small amounts of sulfur particles (sulfur content ≤ 5wt%, density ≤ 1.05g / cm 3 ), part of the water is returned to the aerobic pool to ensure the niche advantage of nitrifying bacteria.

[0035] A second aspect of the present invention provides a wastewater treatment system for the sludge separation and return aerobic-anoxic sulfur autotrophic activated sludge denitrification process described in the first aspect of the present invention. Along the water flow direction, the wastewater treatment system includes: a segmented aerobic tank, an anoxic tank, a secondary sedimentation tank, a cyclone separation unit and a sludge return unit;

[0036] Wherein, the segmented aerobic tank includes a first-stage aerobic tank and a second-stage aerobic tank; the secondary sedimentation tank includes a bottom mud total sulfur content monitoring unit and a sulfur automatic dosing unit.

[0037] In some embodiments of the present invention, a dissolved oxygen control unit, a pH monitor and a sludge load controller are provided in the first-stage aerobic tank.

[0038] In some embodiments of the present invention, a dissolved oxygen control unit and a pH monitor are provided in the second-stage aerobic tank.

[0039] In some embodiments of the present invention, the anoxic tank is provided with a stirring device, a sulfur addition port and a pH monitor.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1) The sludge separation and reflow aerobic-anoxic sulfur autotrophic activated sludge denitrification process provided by the present invention utilizes segmented aerobic tanks, with the first aerobic tank enhancing COD removal and converting part of the ammonia nitrogen into nitrite nitrogen and nitrate nitrogen through nitrification. The second aerobic tank then enhances nitrification and deeply removes ammonia nitrogen. No internal recirculation system or external carbon source is required. By controlling the hydraulic retention time, sludge concentration, and dissolved oxygen concentration, the system maintains low sludge load operation, which reduces the abundance of eutrophic microorganisms, reduces the anabolism of oligotrophic microorganisms, slows the sludge proliferation rate, and reduces the excess sludge production by 30% compared to conventional A / O activated sludge denitrification processes.

[0042] 2) The present invention integrates sulfur autotrophic denitrification into an activated sludge process, which can directly utilize existing AO tanks for transformation, achieving high sludge concentration and ultra-high denitrification load, significantly improving resistance to water quality shocks;

[0043] 3) The present invention abandons the fixed bed and prefabricated packing design, eliminating the problems of packing blockage, frequent backwashing, and complicated feeding operations. By adding micron-grade hydrophilic sulfur and completely mixing it with the activated sludge, the single sulfur dosage is reduced by more than 90% compared with the fixed bed packing, and the one-time investment is reduced by 60%;

[0044] 4) The present invention achieves sludge separation and return by introducing a cyclone. The heavy sludge is returned to the anoxic tank, which can maintain the sulfur concentration, the concentration and activity of sulfur autotrophic bacteria, and reduce the sulfur loss rate to less than 5%. The light sludge is returned to the aerobic tank to ensure the ecological niche advantage of nitrifying bacteria. The supporting sulfur content online monitoring and automatic dosing system realizes precise addition on demand, greatly improving the effective utilization rate of sulfur, simplifying the sulfur replenishment operation, and significantly reducing the difficulty and cost of operation and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process of the present invention;

[0046] Figure 2 The change of nitrate nitrogen concentration in the inlet and outlet water of the anoxic tank during the acclimation process of Example 1;

[0047] Figure 3 This is a microscopic photograph of the sulfur-sludge symbiotic structure sulfur autotrophic activated sludge micelles domesticated in Example 1;

[0048] Figure 4 The water quality index changes of each process section of the tanning wastewater in Example 2;

[0049] Figure 5 The water quality index changes of each process section of the pesticide wastewater in Example 3;

[0050] Figure 6 The water quality index changes of each process section of slaughterhouse wastewater in Example 4;

[0051] Figure 7 The water quality index changes of each process section of the landfill leachate in Example 5;

[0052] Figure 8 The sedimentation performance changes of the sulfur autotrophic denitrification activated sludge in Example 6;

[0053] Figure 9 The sedimentation performance change of sulfur autotrophic denitrification activated sludge in Example 7;

[0054] Figure 10This is a morphological comparison of the sludge samples in Example 8. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below by way of specific examples. Unless otherwise specified, the raw materials, reagents, or devices used in the examples are all commercially available or can be obtained by conventional methods. Unless otherwise specified, all experiments or testing methods are conventional methods in the art.

[0056] Figure 1 This is a schematic diagram of the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process of the present invention, Figure 1 It can be seen that in this process, wastewater flows through the segmented aerobic tank, anoxic tank and secondary sedimentation tank in sequence, the supernatant of the secondary sedimentation tank is discharged, and the bottom sludge enters the cyclone to be divided into heavy sludge and light sludge. The light sludge is returned to the front end of the segmented aerobic tank, and the heavy sludge is returned to the front end of the anoxic tank. During the process, the total sulfur content of the bottom sludge of the secondary sedimentation tank is monitored, and sulfur is added to the heavy sludge return pipe at a constant rate in real time through the automatic sulfur dosing system, so that it is synchronized with the heavy sludge and returned to the front end of the anoxic tank. The sulfur dosing process does not rely on feedback regulation. It automatically waits after the dosing is completed, and the remaining sludge is discharged as residual sludge. The following will be combined with Figure 1 The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process in the embodiment is described as follows:

[0057] Example 1

[0058] This example demonstrates the acclimation process of the sulfur autotrophic denitrification activated sludge in the anoxic tank in the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0059] Add the wastewater treatment plant tail water that meets the standards into the anoxic tank, inoculate 5000mg / L of activated sludge from the original biochemical system that is operating normally, and add 2-20g / L of small-particle sulfur with a hydrophilic surface (water infiltration time ≤ 5s) and a particle size of 0.05-0.5mm:

[0060] In the first stage, 20 mg / L of nitrate nitrogen was added to the wastewater, and sodium bicarbonate was added to make the pH of the wastewater 7.0-8.5. The wastewater was stirred intermittently, and the mixture was allowed to stand for 50 minutes after each stirring for 10 minutes. The cycle was continued for 10 hours until the nitrate nitrogen in the effluent was less than 1.0 mg / L, and then the process was switched to the second stage.

[0061] In the second stage, 40 mg / L of nitrate nitrogen was added to the wastewater, and sodium bicarbonate was added to make the pH of the wastewater 7.0-8.5. The wastewater was stirred intermittently, and the mixture was allowed to stand for 50 minutes after each stirring for 10 minutes. The cycle was continued for 10 hours until the nitrate nitrogen in the effluent was less than 1.0 mg / L, and then the process was switched to the third stage.

[0062] In the third stage, 40 mg / L of nitrate nitrogen was added to the wastewater, and sodium bicarbonate was added to make the pH of the wastewater 7.0-8.5. The wastewater was stirred intermittently, and the mixture was allowed to stand for 50 minutes after each stirring for 10 minutes. The cycle was continued for 5 hours until the nitrate nitrogen in the effluent was less than 1.0 mg / L, and then the process was switched to the fourth stage.

[0063] In the fourth stage, 50 mg / L of nitrate nitrogen is added to the wastewater, and sodium bicarbonate is added to make the pH of the wastewater 7.0-8.5. The mixture is stirred continuously for 5 hours. The cycle is continued until the nitrate nitrogen in the effluent is less than 1.0 mg / L, and then the process is switched to the fifth stage.

[0064] In the fifth stage, 50 mg / L of nitrate nitrogen was added to the wastewater, and sodium bicarbonate was added to make the pH of the wastewater 7.0-8.5. The process was stirred continuously for 2.5 hours and circulated until the nitrate nitrogen in the effluent was less than 1.0 mg / L, and the acclimation was completed.

[0065] The acclimatization time of the sulfur autotrophic denitrification activated sludge in the anoxic tank of this embodiment is 35 days. Figure 2 The nitrate nitrogen concentration changes of the inlet and outlet water of the anoxic tank during the acclimation process of Example 1 are as follows: Figure 2 It can be seen that from the first to the fifth stage of acclimation, the nitrate nitrogen load increased from 20 mg / L to 50 mg / L, and the nitrate nitrogen in the effluent decreased from the initial greater than 15 mg / L to less than 1.0 mg / L. In the fourth and fifth stages, continuous stirring was carried out, the nitrate nitrogen concentration in the effluent dropped sharply, and the denitrification rate increased sharply, indicating that sulfur-autotrophic activated sludge with a sulfur-sludge symbiotic structure was formed.

[0066] Figure 3 This is a microscopic photograph of the sulfur-sludge symbiotic structure sulfur autotrophic activated sludge micelles domesticated in Example 1, wherein: Figure 3 (a), (b), (c), (d), (e), and (f) are microscope photos of sulfur autotrophic activated sludge flocs in different fields of view. Figure 3 It can be seen that sulfur-autotrophic activated sludge with a sulfur-sludge symbiotic structure is formed.

[0067] Example 2

[0068] This example uses tanning wastewater as an example to verify the treatment effects in the segmented aerobic tank and anoxic tank in the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0069] The wastewater was taken from the effluent of the primary sedimentation tank of a leather wastewater comprehensive treatment plant in Shijiazhuang, Hebei Province. The COD of the wastewater was 148 mg / L, the total nitrogen concentration was 41.2 mg / L, the ammonia nitrogen concentration was 34.5 mg / L, and the nitrate nitrogen concentration was 4.0 mg / L.

[0070] S11. The wastewater enters the first aerobic tank of the segmented aerobic tank, where the activated sludge concentration is 2000 mg / L. The dissolved oxygen concentration is controlled at 1.5-1.8 mg / L by adjusting the aeration intensity, and aeration is continued for 7 hours. The wastewater then enters the second aerobic tank, where the dissolved oxygen concentration is controlled at 2.7-3.0 mg / L, and aeration is continued for 4 hours.

[0071] S21. The effluent from the segmented aerobic tank enters the anoxic tank, which is inoculated with 2000 mg / L of the sulfur autotrophic activated sludge domesticated in Example 1 and 5 g / L of hydrophilic small sulfur particles with a particle size of 0.2-0.5 mm and a water infiltration time of ≤5 s. The mechanical stirring device is started to completely mix the wastewater, sulfur particles and sulfur autotrophic activated sludge. The system is operated continuously for 4 hours, and the dissolved oxygen concentration is monitored at 0.15-0.25 mg / L.

[0072] Figure 4 The water quality index changes of each process section of the tanning wastewater in Example 2 are as follows: Figure 4 It can be seen that the COD of the effluent from the segmented aerobic pool is 42.5 mg / L, the ammonia nitrogen concentration is 0.8 mg / L, the nitrate nitrogen concentration is 36.1 mg / L, the COD removal rate is 71%, the sludge load is 0.12 kg BOD5 / (kgMLSS·d), and the nitrification rate is 98%; the COD of the effluent from the anoxic pool is 38.2 mg / L, the total nitrogen concentration is 1.8 mg / L, the ammonia nitrogen concentration is 0.7 mg / L, the nitrate nitrogen concentration is 0.3 mg / L, the denitrification rate is 99%, and the denitrification load is 0.21 kg NO3-N / (m 3 ·d).

[0073] Example 3

[0074] This example uses pesticide wastewater as an example to verify the treatment effects in the segmented aerobic tank and anoxic tank in the sludge separation and reflow aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0075] The wastewater comes from a pesticide chemical company in Changde, Hunan. The COD of the wastewater is 141 mg / L, the total nitrogen concentration is 36.1 mg / L, the ammonia nitrogen concentration is 35.0 mg / L, and the nitrate nitrogen concentration is 1.0 mg / L.

[0076] S11. The wastewater enters the first aerobic tank of the segmented aerobic tank, where the activated sludge concentration is 2000 mg / L. The dissolved oxygen concentration is controlled at 1.6-2.0 mg / L by adjusting the aeration intensity, and aeration is continued for 5 hours. The wastewater then enters the second aerobic tank, where the dissolved oxygen concentration is controlled at 2.4-2.8 mg / L, and aeration is continued for 5 hours.

[0077] S21. The effluent from the segmented aerobic tank enters the anoxic tank, which is inoculated with 2000 mg / L of the sulfur autotrophic activated sludge domesticated in Example 1 and 5 g / L of hydrophilic small sulfur particles with a particle size of 0.05-0.2 mm and a water infiltration time of ≤5 s. The mechanical stirring device is started to completely mix the wastewater, sulfur particles and sulfur autotrophic activated sludge. The system is operated continuously for 4 hours, and the dissolved oxygen concentration is monitored at 0.2-0.3 mg / L.

[0078] Figure 5 The water quality index changes of each process section of the pesticide wastewater in Example 3 are as follows: Figure 5 It can be seen that the COD of the effluent from the segmented aerobic pool is 101 mg / L, the ammonia nitrogen concentration is 1.3 mg / L, the nitrate nitrogen concentration is 29.5 mg / L, the COD removal rate is 28%, the sludge load is 0.05 kg BOD5 / (kgMLSS·d), and the nitrification rate is 96.6%; the COD of the effluent from the anoxic pool is 99.6 mg / L, the total nitrogen concentration is 1.6 mg / L, the ammonia nitrogen concentration is 1.2 mg / L, the nitrate nitrogen concentration is 0.1 mg / L, the denitrification rate is 99.7%, and the denitrification load is 0.18 kg NO3-N / (m 3 ·d).

[0079] Example 4

[0080] This example uses slaughterhouse wastewater as an example to verify the treatment effects of the segmented aerobic and anoxic tanks in the sludge separation and reflow aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0081] The wastewater is the effluent from the regulating pond of a slaughterhouse wastewater comprehensive treatment plant in Zibo, Shandong Province. The COD of the wastewater is 422 mg / L, the total nitrogen concentration is 87.6 mg / L, the ammonia nitrogen concentration is 81.7 mg / L, and the nitrate nitrogen concentration is 3.6 mg / L.

[0082] S11. The wastewater enters the first aerobic tank of the segmented aerobic tank, where the activated sludge concentration is 4000 mg / L. The dissolved oxygen concentration is controlled at 1.5-2.0 mg / L by adjusting the aeration intensity, and aeration is continued for 12 hours. The wastewater then enters the second aerobic tank, where the dissolved oxygen concentration is controlled at 2.7-3.0 mg / L, and aeration is continued for 11 hours.

[0083] S21. The effluent from the segmented aerobic tank enters the anoxic tank, which is inoculated with 4000 mg / L of the sulfur autotrophic activated sludge domesticated in Example 1 and 5 g / L of hydrophilic small sulfur particles with a particle size of 0.1-0.4 mm and a water infiltration time of ≤5 s. The mechanical stirring device is started to completely mix the wastewater, sulfur particles and sulfur autotrophic activated sludge. The system is operated continuously for 6 hours, and the dissolved oxygen concentration is monitored at 0.1-0.2 mg / L.

[0084] Figure 6The water quality index changes of each process section of slaughterhouse wastewater in Example 4 are as follows: Figure 6 It can be seen that the COD of the effluent from the segmented aerobic pool is 135 mg / L, the ammonia nitrogen concentration is 49.3 mg / L, the nitrate nitrogen concentration is 34.9 mg / L, the COD removal rate is 68%, the sludge load is 0.07 kg BOD5 / (kgMLSS·d), and the nitrification rate is 95%; the COD of the effluent from the anoxic pool is 142 mg / L, the total nitrogen concentration is 4.7 mg / L, the ammonia nitrogen concentration is 3.7 mg / L, the nitrate nitrogen concentration is 0.2 mg / L, the denitrification rate is 99.7%, and the denitrification load is 0.33 kg NO3-N / (m 3 ·d).

[0085] Example 5

[0086] This example uses landfill leachate as an example to verify the treatment effects in the segmented aerobic and anoxic tanks in the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0087] The wastewater is leachate from a landfill in Heyuan, Guangdong. The COD of the wastewater is 928 mg / L, the total nitrogen concentration is 374 mg / L, the ammonia nitrogen concentration is 357 mg / L, and the nitrate nitrogen concentration is 2.4 mg / L.

[0088] S11. The wastewater enters the first aerobic tank of the segmented aerobic tank, where the activated sludge concentration is 5000 mg / L. The dissolved oxygen concentration is controlled at 1.8-2.0 mg / L by adjusting the aeration intensity, and aeration is continued for 20 hours. The wastewater then enters the second aerobic tank, where the dissolved oxygen concentration is controlled at 2.7-3.0 mg / L, and aeration is continued for 16 hours.

[0089] S21. The effluent from the segmented aerobic tank enters the anoxic tank, which is inoculated with 5000 mg / L of the sulfur autotrophic activated sludge domesticated in Example 1 and 5 g / L of hydrophilic small sulfur particles with a particle size of 0.1-0.4 mm and a water infiltration time of ≤5 s. The mechanical stirring device is started to completely mix the wastewater, sulfur particles and sulfur autotrophic activated sludge. The system is operated continuously for 10 hours, and the dissolved oxygen concentration is monitored at 0.1-0.2 mg / L.

[0090] Figure 7 The water quality index changes of each process section of the landfill leachate in Example 5 are as follows: Figure 7It can be seen that the COD of the effluent from the segmented aerobic pool is 151 mg / L, the ammonia nitrogen concentration is 4.7 mg / L, the nitrate nitrogen concentration is 236 mg / L, the COD removal rate is 84%, the sludge load is 0.10 kg BOD5 / (kgMLSS·d), and the nitrification rate is 98.6%; the COD of the effluent from the anoxic pool is 168 mg / L, the total nitrogen concentration is 19.3 mg / L, the ammonia nitrogen concentration is 4.5 mg / L, the nitrate nitrogen concentration is 0.6 mg / L, the denitrification rate is 99.7%, and the denitrification load is 0.56 kg NO3-N / (m 3 ·d).

[0091] Example 6

[0092] This example verifies the evolution of the settling performance of the sulfur autotrophic denitrification sludge in the anoxic tank in the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0093] 5000 mg / L of activated sludge and 10 g / L of hydrophilic small-particle sulfur with a water infiltration time of ≤5 s and a particle size of 0.05-0.5 mm were added to the anoxic tank. The sulfur autotrophic denitrification sludge was acclimated and operated continuously according to the acclimation method in Example 1.

[0094] Figure 8 is the sedimentation performance change of sulfur autotrophic denitrification activated sludge in Example 6, Figure 8 It can be seen that as the process progresses, the sulfur autotrophic denitrifying bacteria are enriched on the surface of sulfur particles, and form a "sulfur core-biofilm" composite structure through the adhesion of extracellular polymers. This complex is due to the high density of sulfur (2.07g / cm 3 ) and the densification of bacterial flocs, and its apparent density is significantly higher than that of ordinary activated sludge flocs (1.02-1.05g / cm 3 As the operation time increases, the amount of sulfur entrained by the complex continues to increase, and the sludge density rises, which is ultimately reflected in an increase in settling velocity and a decrease in the sludge settling ratio (SV30) and sludge volume index (SVI), indicating an improvement in settling performance.

[0095] Example 7

[0096] This example verifies the evolution of the settling performance of the sulfur autotrophic denitrification sludge in the anoxic tank in the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0097] 2500 mg / L of activated sludge and 10 g / L of hydrophilic small-particle sulfur with a water soaking time of ≤5 s and a particle size of 0.05-0.5 mm were added to the anoxic tank. The sulfur autotrophic denitrification sludge was acclimated and operated continuously according to the acclimation method in Example 1.

[0098] Figure 9is the sedimentation performance change of sulfur autotrophic denitrification activated sludge in Example 7, Figure 9 It can be seen that as the operation time increases, the amount of sulfur entrained by the complex continues to increase, the sludge density increases, the sedimentation rate increases, and the sludge settling ratio (SV30) and sludge volume index (SVI) decrease, indicating an improvement in the sedimentation performance. However, compared with the activated sludge of 5000 mg / L in Example 6, the SV30 under the same conditions decreases slowly, indicating that a high sludge concentration is more conducive to the stability of the symbiotic structure.

[0099] Example 8

[0100] This example verifies the regulatory effect of cyclone separation on sludge properties in a sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process:

[0101] The wastewater is leachate from a landfill in Heyuan, Guangdong. The COD of the wastewater is 928 mg / L, the total nitrogen concentration is 374 mg / L, the ammonia nitrogen concentration is 357 mg / L, and the nitrate nitrogen concentration is 2.4 mg / L.

[0102] S11. The wastewater enters the first aerobic tank of the segmented aerobic tank, where the activated sludge concentration is 5000 mg / L. The dissolved oxygen concentration is controlled at 1.8-2.0 mg / L by adjusting the aeration intensity, and aeration is continued for 20 hours. The wastewater then enters the second aerobic tank, where the dissolved oxygen concentration is controlled at 2.7-3.0 mg / L, and aeration is continued for 16 hours.

[0103] S21. The effluent from the segmented aerobic tank enters the anoxic tank, which is inoculated with 5000 mg / L of the sulfur autotrophic activated sludge acclimated in Example 1 and 5 g / L of hydrophilic small sulfur particles with a particle size of 0.1-0.4 mm and a water infiltration time of ≤5 s. A mechanical stirring device is started to completely mix the wastewater, sulfur particles, and sulfur autotrophic activated sludge. The system is operated continuously for 10 hours, and the dissolved oxygen concentration is monitored at 0.1-0.2 mg / L.

[0104] S31, the effluent from the anoxic tank enters the secondary sedimentation tank for sedimentation, the supernatant is discharged, and the bottom sludge enters the cyclone to be divided into heavy sludge (sulfur content> 5wt%, density> 1.05g / cm 3 ) and light sludge (sulfur content ≤ 5wt%, density ≤ 1.05g / cm 3 ), the remainder is discharged as excess sludge. Take the secondary sedimentation tank sludge, light sludge, and the density of 1.1g / cm 3 , 1.5g / cm 3 and 1.9 g / cm 3 The heavy sludge samples were compared.

[0105] Figure 10 This is a morphological comparison of the sludge samples in Example 8, wherein: Figure 10(a) is a photo of the bottom mud of the secondary sedimentation tank. Figure 10 (b) is a photo of light sludge. Figure 10 (c) is the density 1.1 g / cm 3 Photos of heavy sludge, Figure 10 (d) is the density 1.5g / cm 3 Photos of heavy sludge, Figure 10 (e) is the density of 1.9 g / cm 3 Photo of heavy sludge from Figure 10 It can be seen that the bottom mud of the secondary sedimentation tank is gray-yellow mixed in color, loose in shape, and has poor sedimentation because the sulfur and sludge are not completely separated. After cyclone separation, the light sludge is gray-brown and flocculent, with no visible sulfur particles; the density is 1.1g / cm 3 Heavy sludge contains a small amount of sulfur particles with a density of 1.5g / cm 3 The heavy sludge showed sulfur accumulation with a density of 1.9g / cm 3 The sulfur particles in the heavy sludge are densely adhered, indicating that the present invention can distinguish heavy sludge from light sludge through cyclone separation, and can enrich sulfur in the heavy sludge. Full reflow to the anoxic tank is beneficial to maintaining the sulfur concentration, sulfur autotrophic bacteria concentration and activity, and the method is highly feasible.

Claims

1. A sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process, characterized in that: The following steps are involved: S1, wastewater enters the staged aerobic tank, first in the first stage aerobic tank to strengthen the removal of organic matter, and convert part of the ammonia nitrogen into nitrite nitrogen and nitrate nitrogen, then in the second stage aerobic tank to strengthen nitrification and deeply remove ammonia nitrogen; S2, the effluent from the segmented aerobic tank enters the anoxic tank and is completely mixed with sulfur particles and activated sludge to carry out sulfur autotrophic denitrification; S3. The effluent from the anoxic tank enters the secondary sedimentation tank for sedimentation, the supernatant is discharged, and the bottom sludge enters the cyclone to be separated into heavy sludge and light sludge; the heavy sludge is returned to the front end of the anoxic tank, and the light sludge is returned to the front end of the segmented aerobic tank, and the remainder is discharged as residual sludge.

2. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: In step S1, the dissolved oxygen content in the first aerobic tank is 1.5-2.0 mg / L; the hydraulic retention time is 5-25 hours; Sludge load ≤0.2kg BOD5 / (MLSS·d).

3. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: In step S1, the dissolved oxygen content in the second aerobic tank is 2.0-3.0 mg / L; and the hydraulic retention time is 5-15 hours.

4. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: In step S2, in the anoxic tank, the concentration of sulfur particles is 2-20 g / L wastewater; the concentration of activated sludge is 2-5 g / L wastewater; The hydraulic retention time is 4-10h.

5. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 4, characterized in that: In step S2, the particle size of the sulfur particles is 0.05-0.5 mm, and the water immersion time is ≤5 s.

6. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: In step S3, the surface hydraulic load of the secondary sedimentation tank is 2.5-3.2m 3 / (m 2 ·h).

7. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: In step S3, the cyclone separation standard is: heavy sludge sulfur content> 5wt%, density> 1.05g / cm 3 ; Light sludge sulfur content ≤ 5wt%, density ≤ 1.05g / cm 3 .

8. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 7, characterized in that: In step S3, the reflow ratio of the heavy sludge is 100%; The reflux ratio of the light sludge is 70%-90%.

9. The sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to claim 1, characterized in that: Step S3 also includes monitoring the total sulfur content of the sludge. When the total sulfur content is ≤2000 mg / kg, sulfur particles are added to synchronously flow back to the front end of the anoxic tank with the heavy sludge.

10. A wastewater treatment system for the sludge separation and reflux aerobic-anoxic sulfur autotrophic activated sludge denitrification process according to any one of claims 1 to 9, characterized in that: Along the water flow direction, the wastewater treatment system includes: a segmented aerobic tank, an anoxic tank, a secondary sedimentation tank, a cyclone separation unit and a sludge return unit; Wherein, the segmented aerobic tank includes a first-stage aerobic tank and a second-stage aerobic tank; the secondary sedimentation tank includes a bottom mud total sulfur content monitoring unit and a sulfur automatic dosing unit.

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