CN1182049C - Biological aerated filter with double-layer filter material - Google Patents

Abstract

The present invention discloses a double-layer filter material aeration biological filter belonging to sewage treatment. Two kinds of filter materials with different grain sizes are filled in the same equipment, and an intermediate discharge device is arranged at the juncture of two layers of filter materials. The wall of an intermediate discharge branch pipe of the intermediate discharge device is provided with a water flowing hole. Sludge, etc. is discharged from the intermediate discharge branch pipe in small backflushing, and gas and water are utilized to carry out alternating flushing in large backflushing and small backflushing. The double-layer filter material aeration biological filter has good effect when used for treating the low concentration domestic sewage. The double-layer filter material aeration biological filter can reduce the running resistance in a decarbonizing area and can make biomass in a nitrifying area accumulated to enhance the nitrifying efficiency. The water consumption for backflushing and the resistance loss for backflushing can be reduced, and the time for the effluent water quality to reach stability after the backflushing can be shortened. Compared with the prior art, the double-layer filter material aeration biological filter has the advantages that the decarbonizing function and the nitrifying function can be simultaneously realized in the same biological filter pool. More than 80% of organic substances can be removed, and the ammonia nitrogen removal rate can reach 95%. The double-layer filter material aeration biological filter is a better practical device with simple system and little investment in the current device for treating the low concentration domestic sewage.

Description

Biological aerated filter with double-layer filter material

technical field

The invention belongs to a sewage treatment device, in particular to a double-layer filter material aerated biological filter for treating low-concentration domestic sewage.

Background technique

Biological aerated filter (BAF) is a sewage treatment process that emerged in the late 1980s and early 1990s. It was initially used as a tertiary treatment, and later developed into a direct secondary treatment. It uses rough and porous granular filter material. Biofilm grows on the surface of the filter material, and aeration is provided at the bottom of the pool. When the sewage flows through the filter bed, the pollutants are first filtered and adsorbed, and then oxidized and decomposed by the microorganisms on the surface of the filter material. Its biggest feature is that it integrates biological oxidation and interception of suspended solids, saves subsequent sedimentation tanks, has the advantages of large volume load, short hydraulic retention time, low infrastructure investment, and high effluent quality. The patented product BIOFOR process of Deliman Company in France generally uses 3-5mm ceramsite as the filter material and is divided into two levels; A method of incomplete backwashing of biological aerated filter was proposed for the first time in "Pilot Test Study on Treatment of Domestic Sewage".

But these have disadvantages, mainly manifested in:

(1) Use filter materials of the same particle size range. Then, if the particle size is too small, it is easy to clog, and if the particle size is too large, the external specific surface area of the filter material will be small, the biomass will be small, and the treatment efficiency will be low. It is difficult to balance the two.

(2) The running cycle is short. Due to the short age and rapid growth of heterotrophic bacteria sludge, the water head loss in the filter layer near the water inlet increases rapidly, requiring frequent backwashing. If the backwashing water distribution is uneven, the phenomenon of filter material sticking is easy to occur, and finally It will cause the quality of the effluent from the filter to deteriorate, the resistance will increase, and the filter has to be shut down for maintenance.

(3) BIOFOR is not easy to backwash. The backwashing intensity is high, the backwashing water consumption is large (up to 40%), the backwashing time is long, and the recovery time after backwashing is long (> 2h).

(4) It is not conducive to completing the decarburization and nitrification functions at the same time. If the removal of organic matter and ammonia nitrogen is completed in one equipment, it will affect the growth of nitrifying bacteria due to the rapid growth of heterotrophic bacteria and the need for frequent backwashing. If the decarburization and nitrification functions are completed in two series-connected BAFs, since the removal of organic matter is completed in a very short area, the height of the decarburization section is very low at a normal flow rate of 4-6m/h, resulting in Waste of equipment; if increasing the load by increasing the filtration rate, it will increase the power loss and shorten the backwash cycle, which is also uneconomical.

Contents of the invention

The purpose of the present invention is to provide a double-layer filter material aerated biological filter. Composed of pipes and water outlets, it is characterized in that: a device is filled with double-layer filter materials, one layer of filter material has a coarse particle size, and the other layer of filter material has a fine particle size; filter materials of different particle sizes are used to simultaneously realize Decarbonization and nitrification functions; and at the junction of the upper filter material layer 1 and the lower filter material layer 2, install the middle discharge pipe 7, and open small holes on the wall of the middle discharge pipe branch to discharge the sludge from backwashing ; The upper and lower layers of the double-layer biological aerated filter can adopt different backwashing methods.

The heights of the loaded coarse and fine filter materials are respectively thick on the top and thin on the bottom, or equal or opposite. The lower filter material layer 2 is a filter material with a coarse particle size of 4-6 mm, which is used to improve the dirt-holding capacity of the filter tank and prolong the cycle running time of the filter tank; the upper filter material layer 1 is filled with filter material with a fine particle size of 1-3 mm. It is used to increase the specific surface area of the filter material, thereby increasing the biomass of attached nitrifying bacteria and improving the removal rate of ammonia nitrogen.

The two layers of filter materials can be the same filter material or different types of filter materials with similar densities, and their shapes can be regular filter materials or irregular filter materials.

The backwash method adopts alternating large and small backwashes, and a large backwash is performed after every 5-7 small backwashes, and a small backwash is performed before each large backwash. The backwashing process is as follows: compressed air enters from the air inlet 4 during backwashing, and is evenly distributed through the backwashing air distribution device 13, and clean water enters from the backwashing water inlet 8. The backwash sludge is discharged from the middle discharge pipe 7 during small backwash, and is discharged from the upper drain 6 located on the upper part of the double-layer filter material aerated biological filter during large backwash. When the water surface loss of the filter reaches a height of 1-2m , combined with compressed air and clean water for backwashing, the backwashed water is clear water and can be put into operation.

The beneficial effect of the present invention is that the present invention can not only reduce the running resistance in the decarburization zone, but also accumulate the biomass in the nitrification zone and improve the nitrification efficiency; in addition, it can also reduce backwash water consumption and backwash resistance loss, and shorten the time after backwash. The time until the effluent quality reaches stability. Compared with prior art, the advantage that the present invention has is:

(1) It can simultaneously realize decarburization and nitrification functions in one BAF, and has a high removal rate for organic matter and ammonia nitrogen. The removal rate of COD (chemical oxygen demand) is over 80%, and the removal rate of ammonia nitrogen can reach 95%.

(2) The running and backwashing resistance is small, the running cycle is long, and the backwashing water consumption is low. The running resistance generally does not exceed 2m. A small backwash is required only after 24 hours, and a large backwash is only required after 5-7 cycles. The self-water consumption of backwash is within 10%.

(3) It takes a short time to restore the normal operation state after small backwashing, within 2 hours.

(4) The gas-water ratio is low, only 2:1-6:1, and the operating cost is low.

(5) Compared with the two-stage BAF, the occupied area is small, the system is simple, and the investment is small.

Description of drawings

Figure 1 is a schematic diagram of the structure of a double-layer filter material aeration filter.

Detailed ways

Figure 1 shows a schematic diagram of the structure of a double-layer filter material aeration filter. The double-layer biological aerated filter is mainly composed of the upper filter material layer 1, the lower filter material layer 2, the supporting layer 11, the porous plate water distribution device 12, the process aeration device 10, and the backwash air distribution device 13. Located at the junction of the upper filter material layer 1 and the lower filter material layer 2, the middle row pipe 7 is installed, and holes 14 are opened on the wall of the branch pipe of the middle row pipe 7, which is convenient for the upper and lower of the double-layer filter material aerated biological filter The two layers can adopt different backwashing methods and are used to drain the sludge during small backwashing. Fill the filter material with a coarse particle size of 4-6mm in the lower layer to improve the dirt-holding capacity of the filter and prolong the cycle time of the filter; fill the filter material with a fine particle size of 1-3mm in the upper layer to increase the filter material The specific surface area, thereby increasing the biomass of nitrifying bacteria and improving the removal rate of ammonia nitrogen. During operation, the sewage enters from the water inlet 9, passes through the water inlet distribution device 12, passes through the supporting layer 11, and passes through the lower filter material layer 2 and the upper filter material layer 1 to remove suspended solids, COD, BOD ₅ (biochemical oxygen demand) and After ammonia nitrogen, it is discharged from the water outlet 5, and the compressed air enters from the 3 at the same time, and is aerated through the process aeration device 10 to provide oxygen for the growth of microorganisms; during backwashing, the compressed air enters from the air inlet 4, and is evenly distributed through the backwashing air distribution device 13 Distribution, clear water enters from the backwash water inlet 8. During small backwashing, the backwash sludge is discharged from the middle discharge pipe 7, and during large backwashing, it is discharged from the upper drain (6) located on the upper part of the double-layer filter material biological aerated filter. Generally, ^a small backwash is performed every 24 hours. The process is to first close the water outlet 5, open the middle discharge pipe 7, and empty the upper part of the water. Rinse for 2-4 minutes, then perform air-water co-washing with water at (8-12) L/m ² .s for 3-6 minutes, rinse with water of the same strength and put it into operation. After 5 to 7 cycles, there is another big backwash, and the process is basically the same as the small backwash. When the water head loss of the filter reaches a certain height (generally about 1-2m), backwash with compressed air and clean water, and the backwashed water can be put into operation after it is clear water.

Enumerate two embodiments again below and further illustrate the present invention:

Example 1:

Treatment of low-concentration domestic sewage (COD concentration is 100-250mg/l): the particle size of the lower filter material is 4-6mm, the density is (1800-2200) kg/m ³ , and the height is 1-1.5m; the upper filter material The density is 2-3mm, the density is (1800-2200) kg/m ³ , and the height is 2-3m. The operating water flow rate is 2-3m/h, and the water-gas ratio is 1:3~1:6. This process adopts the method of alternating large and small backwashes for backwashing, and a large backwash is performed after about 5-7 small backwashes. Both large and small backwashing adopt air-water combined backwashing method. The removal rate of suspended solids is about 80%, the removal rate of COD is about 80%, and the removal rate of ammonia nitrogen is 80-95%.

Example 2:

Treatment of extremely low-concentration domestic sewage (COD concentration <100mg/l): the particle size of the lower filter material is 3-5mm, the density is (1800-2200) kg/m ³ , and the height is 1-1.5m; the upper filter material is 1 -3mm, the density is (1800~2200)kg/m ³ , and the height is 2~3m. The operating water flow rate is 3-6m/h, and the water-gas ratio is 1:2-1:4. This process adopts the method of alternating large and small backwashes for backwashing, and after about 5-7 small backwashes, a large backwash is performed. Both large and small backwashing adopt air-water combined backwashing method. The removal rate of suspended solids is about 80%, the removal rate of COD is about 80%, and the removal rate of ammonia nitrogen is 80-95%.

Claims (4)

1. A double-layer filter material aerated biological filter, said biological filter is mainly composed of water inlet distribution device, support layer, double filter material layer, process aeration device, backwash air distribution device, middle discharge pipe, outlet The nozzle composition is characterized in that: a device is filled with double-layer filter materials, one layer of filter material has a coarse particle size, and the other layer of filter material has a fine particle size; filter materials of different particle sizes are used to realize decarburization and nitrification at the same time function; and at the junction of the upper filter material layer (1) and the lower filter material layer (2), install the middle row pipe (7), and open small holes on the wall of the middle row pipe (7) for discharging Backwashed sludge; the upper and lower layers of the double-layer biological aerated filter can adopt different backwashing methods. 2. The double-layer filter material biological aerated filter according to claim 1 is characterized in that: the heights of the thick and thin two-layer filter material of the filling are respectively upper thick, lower thin, or equal, or on the contrary, the lower filter material Layer (2) is a filter material with a coarse particle size of 4-6mm, which is used to improve the dirt-holding capacity of the filter and prolong the cycle running time of the filter; the upper filter material layer (1) is filled with filter material with a fine particle size of 1-3mm , used to increase the specific surface area of the filter material, thereby increasing the attached nitrifying bacteria biomass and improving the removal rate of ammonia nitrogen. 3. according to the described double-layer filter material biological aerated filter of claim 1, it is characterized in that: described two-layer filter material can be same kind of filter material, also can be the different kind of filter material of similar density, and its shape is both It can be a regular filter material or an irregular filter material. 4. according to the described double-layer filter material aerated biological filter of claim 1, it is characterized in that: described backwash mode adopts big and small backwash alternately, carry out one big backwash after every 5-7 small backwashes, Small backwashing is performed before each big backwashing, and the backwashing process is as follows: compressed air enters from the air inlet (4) during backwashing, and is evenly distributed through the backwashing air distribution device (13), and clean water flows from the backwashing water inlet ( 8) Enter, the backwash sludge is discharged from the middle discharge pipe (7) during small backwash, and discharged from the upper drain (6) located on the upper part of the double-layer filter material aerated biological filter during large backwash, when the filter After the water surface loss reaches a height of 1-2m, use compressed air and clean water for backwashing, and the backwashed water can be put into operation after it is clarified water.