CN101698552B - Method for treating domestic sewage with reinforced capillary infiltration trench system - Google Patents

Abstract

The invention discloses a method for treating domestic sewage by an enhanced capillary infiltration ditch system. The domestic sewage first enters a hydrolysis acidification tank for pretreatment, and the pretreated effluent enters successively from the soil layer, the sandy soil layer, the artificial soil layer and the aquifer The formed enhanced capillary infiltration ditch is processed, and the effluent is collected and discharged; wherein both the soil layer and the artificial soil layer of the enhanced capillary infiltration ditch are inoculated with earthworms. The enhanced capillary infiltration ditch system of the present invention has strong impact load resistance, greatly increases the daily sewage treatment volume, and the removal efficiency of COD _cr , ammonia nitrogen and total phosphorus reaches over 90%. Under the current water quality conditions of village and town sewage inflow, the effluent can meet the requirements of "GB8978-1996 National Sewage Discharge Standard".

Description

The Method of Strengthening Capillary Infiltration Ditch System to Treat Domestic Sewage

technical field

The invention belongs to the field of domestic sewage treatment in rural areas, and in particular relates to an enhanced capillary infiltration ditch system and a method for treating domestic sewage by using it.

Background technique

Rural areas across the country produce more than 8 billion tons of domestic sewage every year, seriously polluting the living environment in rural areas. Water bodies such as rivers and lakes in most rural areas are generally polluted, eutrophication is becoming more and more serious, and pollution incidents frequently break out. The safety of drinking water quality is seriously threatened, directly endangering the health of farmers, seriously affecting the environmental sanitation in rural areas, and easily leading to the occurrence and spread of some epidemic diseases. It is estimated that the annual economic loss caused by rural environmental problems has exceeded 100 billion yuan, and the rural environment and ecological conditions in my country are worrying. At present, there is a big difficulty in the treatment of rural domestic sewage, that is, the capital investment and operating costs are relatively large, and the rural economic strength and technical strength are difficult to meet the technical requirements of conventional urban domestic sewage treatment plants.

Therefore, the rural domestic sewage treatment technology must have the characteristics of low investment, high treatment efficiency, low operating cost, and simple management. The current capillary infiltration ditch technology consists of surface soil layer, sandy soil layer, artificial soil layer and aquifer layer from top to bottom; plants are planted on the surface soil layer, and in the surface soil layer and artificial soil layer There are surface water distribution pipes and deep water distribution pipes connected with the hydrolytic acidification tank or septic tank respectively, and the water distribution pipes are surrounded by bluestones wrapped with geotextiles; the drainage pipes connected with the drainage tank are arranged in the aquifer; The principle of pulling out the wind comes from the pulling out of the wind pipe for natural forced ventilation. The hydraulic load is high, and the removal efficiency of COD, BOD ₅ , TP, NH ₃ -N, TN in domestic sewage is high, and the effluent can reach the national comprehensive sewage discharge standard, but the water flow speed of the infiltration ditch is slow, and the daily treatment capacity is small. This limits the widespread application of this technique.

Contents of the invention

The purpose of the present invention is to improve and strengthen the existing capillary infiltration ditch system, so as to provide a method for treating domestic sewage with an enhanced capillary infiltration ditch system with higher treatment efficiency, more stable operation and stronger processing capacity.

Another object of the present invention is to provide an enhanced capillary infiltration trench system.

The purpose of the present invention can be achieved through the following measures:

A method for treating domestic sewage with an enhanced capillary infiltration ditch system. The domestic sewage first enters a hydrolysis acidification tank for pretreatment, and the pretreated water enters an enhanced sewage treatment system consisting of soil layer, sandy soil layer, artificial soil layer and water-conducting layer in sequence. The capillary infiltration ditch is treated, and the effluent is collected and discharged; wherein, both the soil layer and the artificial soil layer of the enhanced capillary infiltration ditch are inoculated with earthworms.

The method of the present invention is carried out in an enhanced capillary infiltration ditch system, which system is composed of a hydrolytic acidification tank and an enhanced capillary infiltration ditch, the water outlet of the hydrolytic acidification tank is connected to the soil in the enhanced capillary infiltration ditch The layer communicates with the water inlet of the water distribution pipe laid in the artificial soil layer; earthworms are arranged in both the soil layer and the artificial soil layer of the enhanced capillary infiltration ditch.

The present invention first adopts hydrolytic acidification tank according to local conditions (also can adopt a kind of septic tank-hydrolytic acidification tank) as the pretreatment technology of front, forms combined process with capillary infiltration ditch; Secondly, in the surface layer soil of capillary infiltration ditch Add earthworms to the layer and artificial soil layer, and use earthworms to swallow organic matter, improve soil aeration and water permeability, and strengthen the removal of organic matter and nitrogen and phosphorus in water through the synergistic effect with microorganisms.

Using the hydrolytic acidification tank as the pretreatment device of the sewage capillary infiltration system can provide the follow-up system with low pollutant concentration and high biodegradability influent. The BOD ₅ of the effluent is 30-80mg/L, and the COD _Cr is about 50-150mg/L. At the same time, the parasite eggs and pathogenic microorganisms in the feces are killed by biological antagonism in the anaerobic environment, and the feces in the sewage have also been harmlessly treated to a certain extent. The hydrolytic acidification tank is a buried tank with a water inlet, a water outlet and an inspection port. The structure is shown in Figure 1. The hydrolytic acidification tank is equipped with a brick-concrete structure baffle to prevent short flow. The outlet water passes through the submersible electric pump, flows through the surface water distribution pipe and the deep water distribution pipe and enters the capillary infiltration ditch. The volume of the hydrolytic acidification tank is determined according to the amount of treated water and the retention time.

Enhanced capillary percolation ditch, composed of various fillers. From top to bottom, there are soil layer, sand layer, artificial soil layer and aquifer layer (each layer adopts conventional thickness). Among them, the water distribution pipes are laid in the surface soil layer and the artificial soil layer. The water distribution pipes are PVC water distribution pipes with double rows of holes. The diameter of the water distribution holes is 4-5mm, the hole spacing is 45-55mm, and the buried depth is 15-20cm. Lawn plants are planted on the surface, and the plants absorb a large amount of nitrogen and phosphorus substances through the action of the root system, which is an important way for sewage purification. At the same time, the growth of plants has greatly changed the environmental conditions of sewage treatment. Because the plant root system goes deep into the soil, it not only improves the hydraulic infiltration rate of the soil, but also helps to create a good microenvironment of the plant root zone, which is conducive to the degradation of pollutants by microorganisms. The sandy soil layer is mainly fine sand with a particle size not greater than 2mm. Due to the huge specific surface area, a large number of microorganisms are gathered, which can adsorb and degrade pollutants. At the same time, the large permeability coefficient of fine sand can ensure normal hydraulic load. Below the sandy soil layer is an artificial soil layer, which is prepared by mixing soil with sawdust and/or rice husk (that is, the ratio of soil to wood fiber) in a ratio of 2.5 to 3.5:1. This kind of soil rich in organic matter is beneficial to the activities of earthworms with strong metabolism, and at the same time the activity of various bacteria and microorganisms is also strengthened. This layer plays a major role in the removal of organic matter and nitrogen and phosphorus. The bottom layer is the water-conducting layer, which is filled with pebbles and supported and filtered by the pebble layer. The drainage pipe laid in the aquifer, the water filtered by the pebbles flows into the drainage pipe. The sewage after advanced treatment is discharged through the drainage system, thereby increasing the sewage treatment capacity of the system. The drainage pipe adopts corrugated aqueduct, and the pipe material is 4″, PVC pipe material; considering the drainage efficiency, the pipe network should not be too thin. The distance between the aqueduct is 0.6-0.8m, and the isolation layer composed of pebbles around the water collection pipe can prevent artificial The soil in the soil layer clogs the water collection pipe and affects the drainage.

The key of this technology lies in the addition of earthworms. Earthworms like warm, moist and quiet environments. In the soil, burrows live in the upper layer of the soil within a depth of 15-20 cm, and the lower the layer, the less it is, which is mainly determined by the feeding habits of earthworms. In fact, almost all earthworms are involved in the degradation of organic matter in the environment. During their life activities, they devour a large amount of organic debris and mix them with the soil. function for decomposition and transformation. In addition, earthworms also promote the transformation of carbon and nitrogen in the soil through themselves and their impact on the soil microbial community. Their roles include direct and occasional cannibalism, loosening, competition and potential symbiosis. The surface soil of the enhanced capillary infiltration ditch soil layer and the artificial soil layer of the artificial soil layer must be put in a certain number and type of earthworms, and the density of inoculated earthworms is 8g-12g (earthworms)/(L filler). The earthworms inoculated in the soil layer are Daping No. 2 earthworms, and the depth of feeding is 5 to 8 cm (from the upper surface of the soil layer); counting from the upper surface of the soil layer).

Through research, it is found that in the enhanced capillary infiltration ditch system, earthworms can cooperate with microorganisms to promote the transformation and mineralization of C, N, and P. At the same time, the movement of earthworms forms more gaps and speeds up the water flow. Therefore, the enhanced capillary infiltration ditch with earthworms has higher removal efficiency for COD, BOD ₅ , TP, NH ₃ -N, and TN in domestic sewage, and the daily treatment capacity is enhanced. This fully utilizes the self-regulation mechanism of the terrestrial ecosystem of the soil-microbe-animal-plant system and the comprehensive purification function of pollutants to treat sewage, which improves the water quality to varying degrees and realizes the recycling and harmlessness of sewage. .

After the implementation of the appeal technical plan, the enhanced capillary infiltration ditch system has a strong impact load resistance capacity, and the daily sewage treatment volume has been greatly increased. The removal efficiency of COD _cr , ammonia nitrogen and total phosphorus can reach over 90%. Under the current water quality conditions of village and town sewage inflow, the effluent can meet the requirements of "GB8978-1996 National Sewage Discharge Standard".

Description of drawings

Figure 1 is a schematic diagram of the structure of the hydrolytic acidification tank.

Among them: 1 is the water inlet pipe; 2 is the inspection port; 3 is the baffle; 4 is the outlet of the surface soil distribution pipe; 5 is the outlet of the water distribution pipe for artificial soil distribution; 6 is the submersible pump.

Figure 2 is a schematic diagram of an enhanced capillary percolation ditch.

Among them: 7 is the surface soil; 8 is the sand layer; 9 is the artificial soil layer; 10 is the drainage pipe of the aquifer; 11 is the aquifer; 12 is the surface soil water distribution pipe; 13 is the deep soil (artificial soil) Water distribution pipe; 14 is the earthworm that adds.

Detailed ways

Example 1: Enhanced capillary infiltration ditch system with a daily processing capacity of 15 tons

Design treatment water volume: Q=15t/d.

The structure of the hydrolytic acidification tank is shown in Figure 1, with a length of 5 meters, a width of 3 meters, an effective depth of 1.5m, a super height of 0.2m, and a total depth of 1.7m. 20mm thick. The water inlet pipe is embedded at a height of 35cm from the bottom of the pool wall, and is downward at an angle of 25° with the pool wall. The outlet water enters the water distribution pipe in the surface soil layer of the enhanced capillary infiltration ditch and the water distribution pipe in the artificial soil layer through the submersible electric pump. The structure of the enhanced capillary infiltration ditch is shown in Figure 2, covering an area of 20m ² , and the pool structure adopts brick-concrete structure:

The processing unit has a total volume of 15m ³ and a surface area of 18m ² . The length is 6m, the width is 3m, and the height is 1m (the effective height is 0.9m). The depth of the surface soil is 25cm, the depth of the sandy soil is 15cm, the artificial soil is 40cm (the mass ratio of soil to sawdust is 3:1), and the depth of the aquifer is 10cm. Among them, the depth of water distribution pipes is 15cm in the surface soil, the depth of water distribution pipes in the artificial soil layer is 20cm, and the drainage pipes (ie drainage pipes) are laid in the aquifer layer. The aperture of the water distribution pipe is about 5mm, and the hole spacing is about 50mm; the aperture of the aqueduct pipe is 8mm, and the spacing is about 0.7m; the pipe materials of the water distribution pipe and the aqueduct are all PVC materials. Put Daping No. 2 earthworms in the surface soil at a depth of 8-10cm and a density of 8g (earthworms)/(L filler); put the William Ringworm in the artificial soil with a depth of 15-20cm and a density of 12g (earthworms)/(L filler). (L packing).

Under the condition of an ambient temperature of 28°C, the sewage from villages and towns is introduced into the enhanced capillary infiltration ditch system, and pretreated in the hydrolytic acidification tank first. The BOD ₅ of the pretreated water is 30-80mg/L, and the COD _Cr is about 50-150mg/L.

The pretreated effluent enters the above-mentioned capillary infiltration ditch without adding earthworms for treatment, and the treated water is finally discharged from the aqueduct in the aquifer. The treatment effect is shown in Table 1:

Table 1 Treatment of sewage by conventional capillary infiltration ditch

Monitoring items Influent (mg/L) Effluent (mg/L) Removal rate (100%) CODcr 70 19.6 71.96% TN 16.7 3.25 80.56% NH ₃ -N 15.3 1.86 87.79% TP 1.26 0.082 93.49%

The pretreated effluent enters the above-mentioned enhanced capillary infiltration ditch where earthworms are added for treatment, and the treated water is finally discharged from the aqueduct in the aquifer. The treatment effect is shown in Table 2:

Table 2 Enhanced capillary infiltration ditch treatment of sewage

Monitoring items Influent (mg/L) Effluent (mg/L) Removal rate (100%) CODcr 70 12.2 82.86% TN 16.7 2.05 87.72% NH ₃ -N 15.3 1.18 92.28% TP 1.26 0.052 95.87%

The enhanced capillary infiltration ditch with earthworms has a higher removal rate and stronger stability for organic matter, TN, NH ₃ -N and TP, and the removal rates reached 82.86%, 87.72%, 92.28% and 95.87%, respectively. %, which is a substantial improvement on the original technology. Among them, the addition of earthworms had the greatest effect on the removal of organic matter, and the removal rate of CODcr increased by 11%, but had little effect on the removal of TP.

Claims (9)

1. reinforced capillary infiltration trench system; It is characterized in that this system is made up of hydrolysis acidification pool and reinforced capillary diafiltration ditch; Said reinforced capillary diafiltration ditch is followed successively by pedosphere, sand layer, artificial soil horizon and water guide layer from top to bottom, and the water-in of the water distributor of laying among pedosphere in the water outlet of said hydrolysis acidification pool and the said reinforced capillary diafiltration ditch and the artificial soil horizon communicates; Wherein in the pedosphere of reinforced capillary diafiltration ditch and artificial soil horizon, be equipped with earthworm; Manual work among the said artificial soil horizon join soil by soil and wood chip and/or rice husk according to 2.5～3.5: 1 mixed; Said water guide layer is filled by pebbles, and in said water guide layer, lays water shoot.

2. reinforced capillary infiltration trench system according to claim 1, the density that it is characterized in that the earthworm among pedosphere and the artificial soil horizon are 8g～12g (earthworm)/L (filler).

3. reinforced capillary infiltration trench system according to claim 1 is characterized in that the input degree of depth of earthworm in the pedosphere is 5～8cm, and the input degree of depth of earthworm is 15～20cm among the artificial soil horizon.

4. method of using the said treating domestic sewage with reinforced capillary infiltration trench system of claim 1; It is characterized in that sewage is introduced into hydrolysis acidification pool and carries out pre-treatment; The pre-treatment water outlet gets into the reinforced capillary diafiltration ditch that is made up of pedosphere, sand layer, artificial soil horizon and water guide layer successively and handles, and collects water outlet and discharge; Wherein in the pedosphere of said reinforced capillary diafiltration ditch and artificial soil horizon, all inoculate earthworm; Manual work among the said artificial soil horizon join soil by soil and wood chip and/or rice husk according to 2.5～3.5: 1 mixed.

5. the method for treating domestic sewage with reinforced capillary infiltration trench system according to claim 4, the density of the earthworm that it is characterized in that inoculating among said pedosphere and the artificial soil horizon is 8g～12g (earthworm)/L (filler).

6. according to the method for claim 4 or 5 described treating domestic sewage with reinforced capillary infiltration trench system, it is characterized in that the earthworm of said pedosphere inoculation is big flat No. 2 earthworms, the input degree of depth is 5～8cm.

7. according to the method for claim 4 or 5 described treating domestic sewage with reinforced capillary infiltration trench system, it is characterized in that the earthworm that inoculates among the said artificial soil horizon encircles a mao earthworm for William, the input degree of depth is 15～20cm.

8. the method for treating domestic sewage with reinforced capillary infiltration trench system according to claim 4; It is characterized in that the water distributor of laying among pedosphere and the artificial soil horizon is the PVC water distributor in double hole; The water distributing pore diameter is 4～5mm, and pitch of holes is 45～55mm, the depth of burying 15～20cm.

9. the method for treating domestic sewage with reinforced capillary infiltration trench system according to claim 4 is characterized in that the water shoot of laying in the water guide layer adopts the PVC corrugated drain pipe, and the spacing of water shoot is 0.6～0.8m.

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