Biological Fluidized Bed Process with High Concentration Powder Carriers Used for Treatment of Municipal Wastewater

Abstract

The invention relates to a new biological fluidized bed process with high concentration powder carriers used for the treatment of municipal wastewater, which is a fluidized bed system based on the principle of sewage biochemical treatment, by adding a compound powder carrier to the biochemical tank, and forming a high concentration mixture after mixing and microbial attachment; the sludge mixture after the reaction is concentrated and separated, and then enters the compound powder carrier cyclone separation and recovery system, which can separate most of the compound powder carrier from the discharged excess sludge, and then return to the biochemical tank for recycling. The highly integrated municipal wastewater treatment process proposed in the invention has high treatment efficiency, small occupation area, low operation energy consumption, and can realize the doubling of sewage treatment capacity and the improvement of effluent water quality without adding additional occupancy.

Claims

1. A high concentration powder carrier bio-fluidized bed (HPB) process for the treatment of municipal wastewater, comprising a HPB biochemical tank, a cyclone separation and recovery system, a high-efficient clarification tank, a filter tank and a disinfection tank, which are successively connected, wherein the process comprises the following steps: (1) flowing the wastewater through a coarse screen and a lifting pump, lifting to a fine screen and a grit chamber, and then entering the HPB biochemical tank; (2) dividing the HPB biochemical tank successively into an anaerobic zone, an anoxic zone, an aerobic zone and a concentrated separation zone along the flow direction of the wastewater, adding a compound powder carrier into the anaerobic zone, the anoxic zone and the aerobic zone respectively, and then forming a high concentration mixture in respective zones by agitating, mixing, and attachment of microorganism; (3) transporting the final mixture of the aerobic zone into the concentrated separation zone and concentrating and separating, wherein a concentrated sludge at the bottom part returns back to the anaerobic zone, other concentrated sludge as excess sludge is transported to a compound powder carrier cyclone separation and recovery system, and a supernatant from the concentrated separation zone is discharged and successively flows through the high-efficient clarification tank, the filter tank and the disinfection tank so as to accomplish the purification of the wastewater; (4) separating the compound powder carrier by the compound powder carrier cyclone separation and recovery system using a hydrocyclone; (5) adding the separated compound powder carrier to the HPB biochemical tank again; (6) dehydrating the residual part of the excess sludge from which the compound powder carrier is separated by cyclone separation, for a subsequent treatment, wherein the compound powder carrier is composed of a base carrier of larger equivalent particle size and an inorganic alternative carbon source ultrafine powder, wherein the equivalent particle size of the base carrier is 10-100 microns, the equivalent particle size of the inorganic alternative carbon source ultrafine powder is less than 1 micron.

2. The process according to claim 1, wherein the anaerobic zone, the anoxic zone, the aerobic zone and the concentrated separation zone are all divided into several independent cells, each of which is separately controlled the water inflow and outflow by a water channel and a sluice valves, and is interconnected each other and equipped with a bypass valve.

3. The process according to claim 2, wherein the HPB biochemical tank is equipped with a feeder, which is used to add the compound powder carrier to each of the cells in the anaerobic zone, the anoxic zone and the aerobic zone.

4. The process according to claim 3, wherein each of the cells in the anaerobic zone, the anoxic zone and the aerobic zone is equipped with a stirring device, which is used for stirring the mixture in the corresponding cell.

5. The process according to claim 2, wherein each of the cells in the concentrated separation zone is equipped with a concentrated machine, each of which is used to concentrate and separate a corresponding mixture.

6. The process according to claim 1, wherein the base carrier comprises diatomite, attapulgite, perlite or zeolite.

7. The process according to claim 1, wherein the inorganic alternative carbon source ultrafine powder is refined pyrite ultrafine powder.

8. The process according to claim 4, wherein at least one stirring device is an impeller agitator.

9. The process according to claim 8, wherein an impeller of the impeller agitator is located in the bottom of the corresponding cell.

10. The process according to claim 9, wherein each of the cells is a square with length of 2-15 m, the water depth is 5-8.5 m, the outer edge linear velocity of the impeller is 1-2 m/s, and the impeller stirring power per unit volume of water is 3-6 W/m.sup.3.

11. The process according to claim 4, wherein the gate valve, the stirring device, the compound powder carrier cyclone separation and recovery system and the feeder are controlled and coordinated by a centralized control system.

Description

DESCRIPTION OF THE EMBODIMENTS

[0033] The following describes the present invention in detail with reference to FIG. 1 and FIG. 2. The schematic embodiments and descriptions of the present invention herein are used to explain the present invention, but are not intended to limit the present invention.

[0034] The present invention provides a new biological fluidized bed process with high concentration powder carriers used for the treatment of municipal wastewater, wherein the process comprises the following: the wastewater flows through a coarse screen (channel system) and a lifting pump firstly, then lifts to a fine screen and a grit chamber, and then enters a HPB biochemical tank. The HPB biochemical tank includes four functional zones, i.e., an anaerobic zone, an anoxic zone, anoxic zone and a concentrated zone (A.sup.2/O/C for short). A compound powder carrier is added in the anaerobic zone, the anoxic zone and the aerobic zone, respectively and stirred and mixed, with attachment of microorganisms, into a high concentration mixture. The mixture of the aerobic zone will flow into the concentrated separation zone and be concentrated and separated. The portion of concentrated sludge runs back into the anaerobic zone to maintain the sludge concentration of biochemical tank. The supernatant in the concentrated separation zone is discharged and passed through a high-efficient clarification tank, a filter tank and a disinfection tank successively for wastewater purification, reaching the discharge standard or reuse. Other concentrated sludge is transported through a compound powder carrier cyclonic separation and recovery system. The compound powder carrier could be separated from the compound powder carrier cyclonic separation and recovery system. The separated compound powder carrier will be re-added to the HPB biochemical tank to realize the recycle of the compound powder carrier.

[0035] All gate valves, the stirring device, the concentrate reflux pump, the internal reflux pump, the compound powder carrier cyclone separation and recovery system, the feeder and the aeration equipment in the entire HPB biological treatment system are precisely controlled and coordinated by the special centralized control system, which highly elevates the smart level of the whole compound powder carrier fluidized bed system, furthermore reduces the operation cost and improves the wastewater treatment efficiency.

[0036] Specifically, the anaerobic zone, the anoxic zone, the aerobic zone and the concentrated separation zone in the present invention are divided into several independent cells, each of the cells is set to independent water inflow and outflow through runner and gate valves and is successively interconnected each other. Each cell is controlled by gate valves for independent water inflow and outflow and is equipped with a bypass valve, which can be shut down for checking or maintaining, without affecting the normal continuous operation of the system. On the one hand, it strengthens the uniform mixing reaction of each unit, and on the other hand, it is used for uninterrupted water maintenance and overhaul. The runner may be a pipeline or a channel, and the following uses a pipeline as an example for description: when the cell is operated normally, the gate valves of the inlet and outlet pipelines are opened at the same time, and the bypass valve is closed; during the maintenance or overhaul of the cell, the inlet and outlet pipelines are closed at the same time, and the bypass valve will be opened, and then the wastewater and the mixture can directly bypass the cell and directly enter into the subsequent cells. After the maintenance/overhaul of the cell, the valves of the inlet and outlet pipelines will be opened, while the bypass valve is closed to restore the normal inflow and outflow of water.

[0037] The HPB biochemical tank is successively divided into an anaerobic zone, an anoxic zone, an aerobic zone and a concentrated separation zone along the flow direction of the wastewater. While the wastewater enters the HPB biochemical tank, it is necessary to gradually add an appropriate amount of compound powder carriers which have the characteristics of small particle size, excellent suspension and dispersion, large specific surface area and strong affinity for microorganisms, and mix them with the activated sludge in the tank, so as to increase the concentration of the sludge mixture in the tank, and provide more carriers for the growth of the attached microorganisms, thereby increasing the biodiversity in the activated sludge, and realizing high-efficient removal of pollutants in the wastewater. To this end, a feeder is used to add the compound powder carrier to any of the cells in the anaerobic zone, the anoxic zone and the aerobic zone, which is beneficial to the growth of nitrifying bacteria and denitrifying bacteria, so that the system has an ability of deep removal of phosphorus and nitrogen in wastewater biological treatment.

[0038] In order to avoid the sedimentation of compound powder carriers and make full use of the function of the activated sludge in the HPB biochemical tank, all cells are equipped with a stirring device, by which the activated sludge in the mixture of the biochemical tank is stirred to being fully suspended and mixed, and the convective mass transfer and dissolved oxygen utilization rate may be improved. The stirring device is preferably an impeller agitator, and an impeller of each impeller agitator is preferably located in the bottom of the corresponding cell. Due to the fact that the sedimentation always occurs at the bottom of the tank, only a lower stirring power needs to be input at the bottom rather than agitating all water in the tank to effectively prevent sedimentation. According to “Norm for design of outdoor wastewater engineering” (GB50014-2021), the sedimentation of the mixture is prevented with a minimum linear velocity of 0.6 m/s. Increasing the linear velocity can enlarge the disturbance, prevent the deposition of the compound powder carrier and improve the utilization rate of dissolved oxygen, but it will increase the energy consumption. Preferably, to achieve this equilibrium between the disturbance and the energy consumption, each cell is designed as a square with a side length of 2˜15 m, the water depth is 5˜8.5 m, the outer edge linear velocity of the impeller is 1˜2 m/s, and the stirring power per unit volume of water is 3˜6 W/m.sup.3. According to the formula recommended in “Water Supply and Drainage Design Manual”, the stirring power is related to the area of the paddle board or impeller. When the section size of the cell is 10 m×10 m and the water depth is 5.5 m, the water volume is 550 m.sup.3, the actual output power of the bottom hyperboloid mixer is 2.7 kw, and the input power per unit volume of water is 4.91 W/m.sup.3. Furthermore, it is demonstrated from the simulation tests that when the cell is a square with a side length of 2˜15 m, and the water depth is 5˜8.5 m, the linear velocity of outer edge of the impeller is 1˜2m/s, and the stirring power per unit volume of water is 4˜6W/m.sup.3, the dissolved oxygen utilization rate can be increased by 20% ˜30%.

[0039] In general, the aeration and dissolving-oxygen process from the tank bottom is one that only micro-bubbles in the bottom rises to the surface of water, wherein the exchange rate of the dissolved oxygen in water is related to the linear rise rate of micro-bubbles, and the efficiency of dissolving oxygen is limited. After mechanical stirring, the micro-bubbles can rise along the vertical swirling field formed by the agitator, whereby the ascent path and hydraulic retention time are extended, and the dissolving-oxygen efficiency is improved. In the simulation tests, it is shown that the dissolving-oxygen efficiency in the spiral ascending process of the micro-bubbles in water can be increased by at least 20%˜30% or more.

[0040] A concentrated separation zone is disposed on the end of the HPB biochemical tank. Each of the cells in the concentrated separation zone is equipped with a concentrated machine for the concentration and separation of the mixture in the biological treatment tank, and the concentrate will run back from the inlet of the front anaerobic zone into the anaerobic zone so as to maintain stability of mixture concentration and biological removal efficiency of phosphorus, with the concentrated sludge at the bottom part entering the cyclone separation and recovery system, while avoiding the burden of high-concentration mixture on the subsequent high-efficient clarification tank. The preferred manner is to recycle most of the concentrate and to pass the minor part as the excess sludge through the compound powder carrier cyclonic separation and recovery system, and to discharge and dehydrate the residue for the next treatment after recovery of the compound powder carrier. The concentrated and separated supernatant as the effluent enters the subsequent high-efficiency clarification tank to further remove a small amount of residual suspended solids (SS) in water and to control the total phosphorus, and then pass through the filter tank and the disinfection tank to be purified. The purified water may be discharged or reused reaching the discharge standard.

[0041] The HPB process in the present invention is a highly integrated process of municipal wastewater treatment, with only one-time lifting in the treatment process. In addition, it has small occupation area, low operating energy consumption and a daily treatment capacity of more than 10000 m.sup.3/d. As an embodiment of the present invention, the design parameters of the HPB biochemical tank can be that as follows: the plane view of each cell is a square with length of 2 m<L<15 m; the water depth of the cells is 5 m<h<8.5m; the total hydraulic retention time HRT is about 10˜13h; total variation coefficient Kz is about 1.5˜2.0. Taking the treatment capacity of 10000m.sup.3/d for an example, the HPB biochemical tank is designed in 12 cells, wherein the size of each cell is 8.7 m×8.7 m, the effective water depth is 5.5 m, and the retention time is 12 h. The design of the tank type is shown in

[0042] FIG. 2 in detail. The wastewater enters the HPB biochemical tank through pipelines or channels, and successively flows through the anaerobic zone (2 cells), the anoxic zone (1 cell), the aerobic region (6 cells), and the concentrated separation zone (3 cells) in vertical S-shape direction. The HPB biochemical tank in the embodiment has an external dimension of 27 m×27 m, followed by a high-efficient clarification tank with the surface loading rate of 6m.sup.3/(m.sup.2.Math.h), a filter tank with a hydraulic loading of 15m.sup.3/(m.sup.2.Math.h), and a disinfection tank in order, and finally reusing or discharge after metering.

[0043] The invention also adopts a recovery process of compound powder carrier, and realizes accurate automatic control, thereby making the process system more energy saving and efficient. The control system can control gate valves and feeders according to the amount of municipal wastewater entering the system, which can not only accurately control the amount of the added compound powder carriers, but also control the treatment time of each cell, and thus greatly improving the treatment efficiency and saving the treatment cost. The compound powder carrier cyclone separation and recovery system uses an optimized high precision cyclone separator to recycle the compound powder carrier.

[0044] Specially, the compound powder carrier in the present invention is formed by compounding the base carrier and the inorganic alternative carbon source ultra-fine powder, wherein the ultra-fine powder as the alternative carbon source has a small diameter. However, the base carrier to be attached by microbial growing is a particle with a relatively larger diameter. Since the ultra-fine powder “alternative carbon source” particles have large difference on both volume and weight from that of the base carrier particles, the fine “alternative carbon source” particles are firmly absorbed on the surface of carrier particles based on an absorption advantage of the carrier particles for example big volume, great weight and large surface energy with respect to “alternative carbon source” particles. With this kind of asymmetric adsorption on the mass and surface, it is difficult for the “alternative carbon source” particles to overcome the repulsion energy peak and re-desorb it back into the water, thereby ensuring that the compound powder carriers together with the “alternative carbon source” and the attached biofilm are completely separated from the excess sludge, and return to the biochemical pool for carrier recycling and functional microbial screening. The aging biofilm debris peeled off from the compound powder carriers, the organic matter belonging to the proliferation part of activated sludge in suspension growth in the concentrated solution, the small part of the smaller carrier debris, and the microbial degraded ash have a smaller specific gravity, which has a large difference in specific gravity from the compound powder carriers. Using this difference in specific gravity, a cyclone separator can be used to separate them by controlling an appropriate swirling speed, and thus achieving the compound powder carriers with high recycling value and attached with microorganisms and ultra-fine powder “alternative carbon source”. The compound powder carrier cyclonic separation and recovery system not only improves the utilization rate of the compound powder carriers, but also reduces the processing cost.

[0045] Specifically, the compound powder carrier is composed of a large equivalent particle size base carrier and an inorganic alternative carbon source ultrafine powder. The equivalent particle size of the base carrier is 10-100 microns, the base carrier comprises diatomite, attapulgite, perlite or zeolite, and the equivalent particle size of the inorganic alternative carbon source ultra-fine powder is less than 1 micron. The nano-sized inorganic alternative carbon source ultra-fine powders were closely adsorbed on the base carrier in advance by use of the large surface energy of the base carrier and wet stirring method.

[0046] Furthermore, the inorganic alternative carbon source ultra-fine powder proposed in the invention mainly refers to the refined pyrite ultra-fine powder, which is mainly composed of ultrafine inorganic functional powder material with particle size below 1 micron by wet grinding. The ultra-fine powder contains negative divalent sulfur, which can provide electron donors for wastewater denitrification. Denitrification is enhanced by sulfur autotrophic denitrification, so that additional organic carbon sources are not necessary and the addition of methanol, sodium acetate, glucose and other organic carbon sources in the low carbon to nitrogen ratio wastewater treatment process is avoided, thus playing the role of carbon source substitution.

[0047] The implementations above are only for the purpose of illustrating the present invention, and are not intended to limit the present invention. Those ordinary skilled in the relevant art may make various changes and modifications, without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention.