CN101973679B - Distributed sewage treatment and regeneration technology - Google Patents

Abstract

A decentralized urban sewage treatment and regeneration process suitable for small towns belongs to the technical field of water pollution treatment. The process includes the following steps: urban sewage is first hydrolyzed and acidified, and then enters the aerated biological fluidized bed through the submersible sewage pump, removes organic matter and undergoes denitrification treatment through its anoxic section, and then enters the sedimentation tank for mud-water separation; the sedimentation tank The effluent goes through the quick sand filter to remove suspended solids, and then enters the buffer tank; the water from the buffer tank is further purified by artificial soil infiltration, and then enters the clear water tank through the collection pipe. The sewage treatment method has a simple process, stable effluent quality, and the water quality meets the urban sewage recycling-urban miscellaneous water quality standard (GB/T 18920-2002).

Description

A decentralized sewage treatment and regeneration process

technical field

The invention belongs to the technical field of water pollution treatment, and in particular relates to a decentralized sewage treatment and regeneration process suitable for small and medium-sized towns.

Background technique

Sewage treatment can be divided into centralized sewage treatment and decentralized sewage treatment. Distributed treatment refers to the establishment of a small sewage treatment system integrating pretreatment, secondary treatment and advanced treatment to treat sewage. Distributed treatment began to attract people's attention and research at the end of the last century, and now it has become a new concept of domestic sewage treatment at home and abroad. With the development of my country's national economy and the acceleration of urbanization, as well as the continuous improvement of environmental quality requirements, decentralized processing has a very broad space for development in our country.

Compared with centralized sewage treatment, decentralized treatment has unique advantages. First of all, the small scale of decentralized treatment is conducive to the demonstration application of the latest treatment technology, rapid technological update, and promotion of technological innovation; secondly, in many areas of our country, the economic level of small and medium-sized towns does not have the ability to build large-scale centralized sewage treatment plants and corresponding Distributed treatment facilities should be the first choice for the conditions of sewage facilities; third, decentralized treatment devices have low energy consumption and save treatment costs; third, decentralized treatment can effectively reduce the spread of harmful substances and provide opportunities for sewage recycling. Replenish and conserve local groundwater to minimize the environmental impact of sewage treatment.

The current conventional technologies for decentralized sewage treatment include:

(1) Anaerobic-aerobic biological treatment technology, combining anaerobic and aerobic biological treatment technology, can achieve the purpose of removing not only organic matter but also phosphorus and nitrogen-containing substances, reducing energy consumption and sludge volume.

(2) Membrane bioreactor technology, which is a process that combines biological treatment and membrane separation. Because the membrane has the characteristics of high-efficiency separation, the effluent water quality is good, and the water quality required for reuse can be directly achieved. In the bioreactor High concentrations of biomass were maintained and loads increased.

(3) Natural purification. When the geographical and climatic conditions are suitable and the land is available, natural purification systems such as artificial wetlands, land infiltration, and oxidation ponds are used to treat sewage, which has the characteristics of stable treatment effects, low investment, and simple management. Land treatment is the best choice for urban suburbs as well as decentralized treatment technology in rural areas.

In the aerobic biological treatment technology of sewage, the mass transfer conditions between sewage, microorganisms and oxygen are the key factors to determine the efficiency of the reactor. Compared with the traditional biological treatment method, the aerobic biological fluidized bed has high biomass, high organic load, and short hydraulic retention time, so the equipment volume can be greatly reduced, saving floor space and infrastructure costs; it does not exist in the activated sludge process. The problem of sludge bulking or bed blockage in the biological filter is stable, and the biological fluidized bed also has a high impact load resistance. The above characteristics make the biological fluidized bed suitable for the requirements of the decentralized treatment of urban sewage. Processing technology.

Artificial soil infiltration is an ecological treatment technology for urban sewage formed by combining ecological principles and engineering methods. By artificially constructing a soil system, the sewage is infiltrated through the system under certain hydraulic conditions. , chemical, biological mechanisms, and self-regulating ecological mechanisms, intercepting, adsorbing, and degrading pollutants in water, fully degrading and absorbing biodegradable organic substances in sewage, and realizing the ecological system engineering of harmless and resourceful sewage.

With the help of the above-mentioned various treatment mechanisms, artificial soil infiltration has good sewage treatment effect, and at the same time has the function of self-ecological adjustment, has a certain buffer capacity for incoming water quality and water volume, stable and reliable operation status, simple operation and management, and low construction and operation maintenance costs. Inexpensive and widely applicable.

Contents of the invention

The invention combines an aerated biological fluidized bed with artificial soil infiltration, and proposes a decentralized sewage treatment and regeneration process suitable for small towns.

Process of the present invention realizes through following steps:

(1) The sewage first enters the hydrolytic acidification tank, and the residence time is controlled at 2.5 to 3.0 hours; after the sewage is hydrolyzed and acidified, it is sucked into the aerated biological fluidized bed by the submersible sewage pump; the aerated biological fluidized bed is divided into anoxic zone and In the aerobic zone, the sewage is denitrified by the anoxic zone; the sewage flows out of the aerated biological fluidized bed and enters the sedimentation tank for mud-water separation;

(2) The sludge from the sedimentation tank flows back into the aerated biological fluidized bed, and the effluent from the sedimentation tank enters the rapid sand filter to remove suspended particles in the water; the effluent from the rapid sand filter enters the buffer tank;

(3) An artificial soil infiltration tank is arranged on one side of the buffer tank, the depth of the artificial soil infiltration tank is ≥ 5m, the soil depth is ≥ 1m, and the side near the water is set as a slope, and the angle between the slope and the bottom surface of the buffer tank Greater than 0° and not greater than 45°; a collection pipe is installed at the bottom of the artificial soil infiltration tank, and the outlet water of the collection pipe enters the clear water pool; the filtration speed of the artificial soil infiltration tank is ≤5m/day, and the hydraulic retention time is ≥7 days .

The volume ratio of the anoxic zone to the aerobic zone of the aerated biological fluidized bed is 1:3, and the hydraulic retention time is 3 to 6 hours; the aerobic zone is filled with hollow columnar three-dimensional hollow packing, and the DO is controlled at 3 to 5 mg/L , The sludge reflux ratio is 200%; the concentration of the carrier-attached sludge is maintained at 700mg/L-900mg/L.

The particle size range of the sand filling in the fast sand filter is 0.5-1.0 mm, and the flow rate is controlled at 3-5 m/h.

The soil particle size of the artificial soil infiltration tank ranges from 0.075 to 0.5mm, empty the water in the buffer tank and the artificial soil infiltration tank every 8 to 12 days, remove the silt at the bottom of the buffer tank, and turn over to dry the artificial soil infiltration For the sand layer on the surface of the pool, the depth of turning over and drying should be ≥0.5m to promote reoxygenation of the sand layer.

The beneficial effects of the present invention are:

(1) Urban sewage is first pretreated by hydrolysis and acidification, which can not only effectively remove COD, BOD ₅ and SS, but also effectively increase BOD ₅ /COD, which is beneficial to subsequent biological treatment.

(2) The submersible sewage pump feeds the pretreated domestic sewage into the bottom of the aerated biological fluidized bed, fully mixes with the air entering from the air distributor at the bottom of the fluidized bed, and drives the carrier carrying the biofilm upward to form a fluidized state . The filler in the biological fluidized bed has a large specific surface area, which can effectively degrade and remove organic matter.

(3) The effluent of the aerated biological fluidized bed enters the sedimentation tank for mud-water separation, and part of the nitrifying liquid flows back into the anoxic zone of the biological fluidized bed, and the returning nitrifying liquid is reduced to nitrogen under the action of denitrifying bacteria to realize denitrification. The supernatant of the sedimentation tank enters the rapid sand filter to remove suspended particles in the water.

(4) The effluent from the quick sand filter flows into the buffer tank by itself and passes through the artificial soil infiltration tank. The soil infiltration tank has a long residence time, which can effectively remove some refractory organic matter and pathogenic microorganisms, and the effluent meets the urban miscellaneous water standard for urban sewage recycling.

(5) It has the advantages of low land occupation, less investment, low operating cost and good treatment effect, meets the actual needs of small and medium-sized towns, and is easy to popularize and use.

Description of drawings

Fig. 1 is a process flow diagram of the present invention;

Figure 2 is a schematic cross-sectional view of the buffer tank and the artificial soil infiltration tank.

Labels in the figure:

1-hydrolytic acidification tank; 2-submersible sewage pump; 3-aerated biological fluidized bed; 4-sedimentation tank; 5-rapid sand filter;

6-buffer tank; 7-artificial soil infiltration tank; 8-collection pipe; 9-clear water tank.

Detailed ways

The present invention provides a decentralized sewage treatment and regeneration process, which will be further described below in conjunction with the accompanying drawings and specific implementation methods.

As shown in Figure 1 and Figure 2, technique of the present invention mainly is the following steps:

(1) The sewage first enters the hydrolytic acidification tank 1, and the residence time is controlled at 2.5 to 3.0 hours; after the sewage is hydrolyzed and acidified, it is sucked into the aerated biological fluidized bed 3 by the submersible sewage pump 2; the aerated biological fluidized bed 3 is divided into The anoxic zone and the aerobic zone, denitrification treatment is performed on the sewage in the anoxic zone; the volume ratio of the anoxic zone to the aerobic zone of the aerated biological fluidized bed 3 is 1:3, and the hydraulic retention time is 3 to 6 hours. The DO in the aerobic zone is controlled at 3-5mg/L, and the sludge reflux ratio is 200%; the concentration of the sludge attached to the carrier is maintained at 700mg/L-900mg/L; the sewage flows out from the aerated biological fluidized bed 3 and enters the sedimentation tank 4 for further processing. mud and water separation;

(2) The sludge in the sedimentation tank 4 is returned to the aerated biological fluidized bed 3, and the effluent of the sedimentation tank 4 enters the fast sand filter 5 to remove suspended particles in the water; the sand filling particle size range of the fast sand filter is 0.5 ～1.0mm, the flow rate is controlled at 3～5m/h; the effluent from the quick sand filter 5 enters the buffer tank 6;

(3) An artificial soil infiltration tank 7 is arranged on one side of the buffer tank 6. The depth of the artificial soil infiltration tank 7 is ≥ 5m, the soil depth is ≥ 1m, and the soil particle size range is 0.075-0.5mm. It is a slope, and the angle between the slope and the bottom surface of the buffer pool 6 is greater than 0° and not more than 45°; a collection pipe 8 is set at the bottom of the artificial soil infiltration pond 7, and the outlet water of the collection pipe 8 enters the clear water pool 9; The filtration rate of the soil infiltration tank 7 is ≤5m/day, and the hydraulic retention time is ≥7 days;

(4) Empty the water in the buffer tank 6 and the artificial soil infiltration tank 7 every 10 days, remove the silt at the bottom of the buffer tank 6, turn over the artificial soil infiltration tank 7 surface sand layers, and turn over and air the depth ≥ 0.5m, with Improve sand re-oxygenation.

The following examples use urban sewage treatment plant sewage and industrial wastewater to test the aerated biological fluidized bed proposed by this process. On the basis of the test, an actual sewage treatment project is established. The design treatment capacity is 30m ³ /h, and the effluent meets the urban Sewage Reuse-Urban Miscellaneous Water Quality Standards (GB/T 18920-2002).

Example 1: Pilot test of Beijing Beixiaohe Sewage Plant

The effluent from the primary sedimentation tank of Beijing Beixiaohe Sewage Plant is used as the raw water. The COD _Cr in the water is 200-450mg/L, the BOD ₅ is 150-250mg/L, the SS is 200-400mg/L, and the ammonia nitrogen concentration is 70-90mg/L. . Using the fluidized bed process proposed in the present invention, COD _Cr ≤70mg/L in the effluent, BOD ₅ ≤20mg/L, SS ≤70mg/L, ammonia nitrogen ≤15mg/L, and the pH of the influent and effluent are both 6~ 9 range.

The test found that the fluidized bed process in this process has the ability to operate at low temperature, the nitrification activity at 5°C is about 60% of that at 18°C, and the optimal hydraulic retention time is 6h. The test also observed the micro-morphological structure of the sludge in the fluidized bed. There are many types of bacteria in the sludge, and the bacteria are closely arranged, mainly Brevibacteria. In addition, cocci, mycelium, longbacteria and protozoa can be observed. Electron microscopy found that bell worms and isopods were the main microorganisms in the sludge.

Embodiment 2: industrial wastewater pilot test

Sugar beet sugar wastewater, COD _Cr is 1000-5000mg/L, BOD ₅ is 500-3000mg/L, SS is 200-1500mg/L, pH 3.5-7.5. Using the fluidized bed process in this process, the fluidized bed is started by the natural film-hanging method. After the start-up, the hydraulic retention time is 6h, and the volume load is 5.625kgCOD/m ³ -d. The COD of the effluent of the aerobic fluidized bed is stable at about 350mg/L.

Embodiment 3: Sewage treatment project in actual operation

Tsinghua University Institute of Nuclear Research, the nature of sewage is domestic sewage and experimental wastewater, the design water volume is 30m ³ /h, the influent water quality is DOC 5-7mg/L, UV254 is 15-20m ^-1 , total phosphorus 4-5mg/L, ammonia nitrogen 28~30mg/L, NO ₃ -N 3~7mg/L. The technology proposed by the invention is used for treatment, and the aerated biological fluidized bed is filled with a new type of columnar hollow filler, with a specific surface area of 1040m ² /m ³ and a steam-water ratio of 12.75:1. Effluent turbidity<1, DOC<3mg/L, UV254 10~11m ^-1 , TP<0.05mg/L, ammonia nitrogen 2~5mg/L, NO ₃ -N 3~5mg/L. The effluent meets the GB/T 18920-2002 water quality standard and can be used for urban miscellaneous purposes.

Claims (4)

1. a decentralized type sewage is handled and reclaiming process, it is characterized in that this technology comprises the steps:

(1) sewage at first gets into hydrolysis acidification pool, and the residence time was controlled at 2.5～3.0 hours; After the sewage hydrolyzing acidifying, get into the aeration and biological fluidized-bed through the submersible sewage pump suction; The aeration and biological fluidized-bed is divided into oxygen-starved area and aerobic zone, by the oxygen-starved area sewage is carried out denitrogenation processing; Sewage flows out back entering settling tank from the aeration and biological fluidized-bed and carries out mud-water separation;

(2) mud of settling tank is back in the aeration and biological fluidized-bed, and the water outlet of settling tank gets into rapid sand filter, removes the suspended particle in the water; The water outlet of rapid sand filter gets into Buffer Pool;

(3) arrange the artificial soil diffusion cell in a side of Buffer Pool, the depth>=5m of this artificial soil diffusion cell, depth of soil>=1m leans on water one side to be set to the slope, and the bottom surface angle of said slope and Buffer Pool is greater than 0 ° and be not more than 45 °; Bottom in the artificial soil diffusion cell is provided with collection tube, and the water outlet of collection tube gets into clean water basin; Filtration velocity≤5m/ days of said artificial soil diffusion cell, hydraulic detention time>=7 day.

2. a kind of decentralized type sewage according to claim 1 is handled and reclaiming process; It is characterized in that the oxygen-starved area of said aeration and biological fluidized-bed and the volumetric ratio of aerobic zone are 1: 3, hydraulic detention time is 3～6h; Aerobic zone DO is controlled at 3～5mg/L, return sludge ratio 200%; Carrier adheres to sludge concentration and maintains 700mg/L～900mg/L.

3. a kind of decentralized type sewage according to claim 1 is handled and reclaiming process, it is characterized in that the back-up sand particle size range of said rapid sand filter is 0.5～1.0mm, and flow rate control is at 3～5m/h.

4. a kind of decentralized type sewage according to claim 1 is handled and reclaiming process; It is characterized in that the soil particle diameter scope of said artificial soil diffusion cell is 0.075～0.5mm, every at a distance from 8～12 days with the water emptying in Buffer Pool and the artificial soil diffusion cell; Remove the Buffer Pool bottom sludge; Turn over top layer, the artificial soil diffusion cell layer of sand that dries in the air, turn over the degree of depth >=0.5m that dries in the air, to promote the layer of sand reoxygenation.

Images