CN101973637B - River channel purification system for processing rural domestic sewage - Google Patents

Abstract

The invention discloses a river channel purification system for processing rural domestic sewage, belonging to the field of rural sewage processing. The system is characterized in that a processing unit is established by utilizing a waste river channel or a swale near-natural type channel; a plant grid sedimentation unit, an artificial biomimetic material contact oxidation unit, a vertical current artificial wetland unit and a floating plant unit are successively arranged from top to bottom according to the direction of water flow; and the rural domestic sewage is processed successively through the four processing units so as to finally achieve the purpose of improving water quality. The system has the advantages that the removing rates of CODcr, SS, NH3-N, TN and TP of the domestic sewage entering the system respectively reach 77.1%, 84.1%, 70%, 68% and 58.8% through the application of the invention; the effect of reducing the pollution load and improving the water quality is realized; and the system provides the guarantee to the improvement of the water environment quality in a downstream river.

Description

A river purification system for treating domestic sewage in rural areas

technical field

The invention relates to a rural water pollution control system. Specifically, the present invention is a river purification system for treating domestic sewage in rural areas.

Background technique

According to estimates, the rural areas of the country produce about 8 billion tons of domestic sewage every year, and 96% of the villages do not have drainage channels and sewage treatment systems. Domestic sewage is discharged randomly, which seriously pollutes the rural ecological environment and directly threatens the health and well-being of the broad masses of farmers. Rural economic development.

Rural domestic sewage is mainly toilet flushing sewage, laundry, rice washing, vegetable washing, and bathing wastewater. Sewage is mainly domestic waste and human excrement, generally does not contain toxic substances, often contains nitrogen, phosphorus and other nutrients, as well as a large number of bacteria, viruses and parasite eggs. The water quality and quantity of domestic sewage in different rural areas vary greatly due to living habits, lifestyles, economic levels, etc., and the sewage has the following characteristics and problems: (1) The distribution of sewage is scattered, involving a wide range, strong randomness, and prevention and control are very difficult. The collection system is not perfect, the discharge is extensive, and there is basically no sewage treatment facility; (2) the water consumption standard in rural areas is low, the sewage flow rate is small and the coefficient of variation is large (3.5-5.0); (3) the sewage composition is complex, but various pollutants The concentration is low, and the biodegradability of sewage is strong.

Due to the scattered sources of domestic pollution in rural areas, it is not easy to concentrate, the awareness of environmental protection of village and town residents is poor, and the economic level is relatively backward, and there are also great difficulties in governance. Therefore, it is necessary to develop and invest in low-cost, low-cost operation, guaranteed treatment effect, and convenient management and maintenance. sewage system. At present, some foreign countries have accumulated a lot of experience in the research and application of rural domestic sewage treatment technology. my country should learn from foreign experience and combine it with local agriculture to explore and improve various rural domestic sewage treatment processes to form sewage reuse. The eco-agricultural model of reuse and reuse realizes the harmlessness and resource utilization of sewage.

(1) Australia's "FILTER" sewage treatment system is a "sewage reuse system combining filtration, land treatment and underground pipe drainage". Underground pipes collect and discharge it. On the one hand, the system can meet the water and nutrient requirements of crops, and at the same time reduce the content of nitrogen, phosphorus and other elements in sewage to meet the sewage discharge standards. Its characteristic is that the filtered sewage is collected into the underground underground pipe drainage system, and a water pump is provided to control the underground water level above the underground drainage pipe and the discharge of treated sewage. The "FILTER" system has a good treatment effect on domestic sewage, and its operating cost is low. It is especially suitable for areas with rich land resources, where crops can be rotated and fallow, or areas where grass is mainly planted. The disadvantage is that after long-term irrigation with sewage, the pathogens in the sewage may enter the soil and pollute the crops; limited by the growing season of the crops, the sewage treatment system will not work if the crops are not irrigated in the non-growing seasons; For the treatment of domestic sewage, it is necessary to build a pumping station to control the displacement, and the cost is higher, and it is difficult to popularize and apply.

(2) Japan Rural Sewage Treatment Association has studied a series of sewage treatment equipment suitable for application in rural towns. Fifteen different types of sewage treatment devices in the JARUS model have been designed, mainly using a combination of physical, chemical and biological measures, and achieved good results. The 15 different types of processing units can be divided into two categories. One type uses the biofilm method, and the sewage passes through a filter layer made of plastic with microorganisms attached to it. After passing through the biofilm, the biological oxygen consumption in the sewage can be reduced to below 20mg/L, the suspended solids can be reduced to below 50mg/L, and the total nitrogen content can be below 20mg/L. The other is the plankton method, through the oxidation of microorganisms floating in the sewage, BOD can be reduced to 10-20mg/L, SS can be reduced to 15-50mg/L, COD can be reduced to below 15mg/L, and TN can be reduced to Below 10-15mg/L, TP drops below 1-3mg/L. Theoretical research and practical application of biofilm abroad have a history of several decades. The biofilm method requires simple equipment, low energy consumption, low cost and maintenance costs, and high efficiency in sewage treatment. It is a direction for future development.

(3) The artificial wetland treatment system is generally composed of artificial substrates (mostly gravel) and marsh plants (reeds, cattails, rushes, hemp, etc.) growing on them, which is a unique "soil-plant-microbe" The ecosystem uses the joint action of various plants, animals, microorganisms and soil to filter and absorb pollutants in sewage step by step to achieve the purpose of purifying sewage. This technology has been widely used in countries such as Europe, North America, Australia and New Zealand. Its disadvantage is that it requires a lot of land, and it needs to solve the problem of sufficient oxygen supply in soil and water and the influence of temperature and plant growth season. the

(4) The earthworm ecological filter is designed based on the functions of earthworms to improve soil ventilation and water permeability and promote the decomposition and transformation of organic matter. A new concept of sewage treatment process that reduces the cost of excess sludge treatment and disposal. The ecological filter treatment system integrates the primary settling tank, aeration tank, secondary settling tank, sludge return facility and oxygen supply facility, which greatly simplifies the sewage treatment process; the operation and management are simple and convenient, and can withstand strong impact loads ; The treatment system basically does not discharge excess sludge, and its sludge yield is significantly lower than that of ordinary activated sludge method; through the movement of earthworms to dredge and swallow proliferating microorganisms, it solves the clogging problem encountered by traditional biological filters. the

(5) Capillary soil infiltration treatment system is especially suitable for areas with incomplete sewage pipe network, and it is a practical technology for treating scattered sewage. The sewage transported to the infiltration field is first distributed to each infiltration ditch through the water distribution pipe. The sewage in the infiltration ditch is redistributed through the gravel layer, and rises to the root zone of the plant under the action of the soil capillary. Chemistry, biochemical action of microorganisms and absorption and utilization of plants are processed and purified. The system is stable and reliable in operation, strong in impact load resistance, and has a high removal rate of BOD ₅ , nitrogen, and phosphorus; easy maintenance, low infrastructure investment, and low operating costs; the entire system is underground, will not emit odor, and the ground lawn can also Beautify the environment; the removal rate of E. coli is high; the storage and transportation of sewage are carried out underground, with less heat loss, and can still maintain a certain temperature in winter, maintain basic biochemical reactions, and ensure a more stable removal effect. However, its removal effect on total nitrogen is not significant; it occupies a large area; it may pollute groundwater. However, since the living habits of earthworms are significantly affected by temperature, they will hibernate or aestivate when the temperature is lower or higher than a certain temperature, so the treatment effect is not very satisfactory when the earthworms hibernate or aestivate, and the filler of the filter is prone to blockage.

Biological and ecological treatment technology is the main method often used in small town sewage treatment at home and abroad. The use of biological treatment technologies such as activated sludge and biofilm has problems such as high construction and operation costs, complex denitrification process, and the treatment effect is difficult to meet the national surface water discharge standards; ecological treatment technologies such as artificial wetlands, oxidation ponds, and soil infiltration The effect of nitrogen and phosphorus removal is good, but there are disadvantages such as large area, foul smell, and easy blockage. Therefore, in order to realize the complementary advantages of biological and ecological treatment technologies, it is very necessary to develop and utilize enhanced pretreatment-constructed wetland combination technology.

Now there are anaerobic reactor-constructed wetland combination process, biological method-constructed wetland combination process, biological oxidation tank-constructed wetland combination process, sand rate sedimentation tank-constructed wetland combination and other processes. These process combinations are mainly for strengthening pretreatment , and combined with the high efficiency of artificial wetland ecological treatment, to a certain extent, it solves the problems of land occupation, stench, and blockage. There is almost no pipe network collection system in the rural areas of our country. The residential areas are relatively scattered, the economic level is low, and the rural farmland resources are tight. However, the river network is densely covered, especially in front of and behind the houses in the village. There are many abandoned river ditches, pits and ponds. Therefore, it is of practical significance to choose abandoned river courses and ponds to receive and treat domestic sewage according to local conditions, and to develop new rural domestic sewage treatment technologies with simple equipment, easy management, and low investment and operation costs. The research idea of the present invention is to strengthen pretreatment, adopt contact oxidizing organisms with less energy consumption, and add ecologically enhanced purification units to improve water quality, accept and treat rural sewage in abandoned river courses, develop simple equipment, easy management, and low operating costs sewage treatment technology.

Contents of the invention

1. The technical problem to be solved by the invention: the purpose of the invention is to provide a river purification system for treating domestic sewage in rural areas. Utilize abandoned river courses and use plant fences to intercept rural domestic sewage. The sewage is purified through artificial bionic material contact oxidation tanks, vertical flow constructed wetlands and floating plants to strengthen purification, which can solve the pollution problem of rural domestic sewage and effectively remove organic matter and nitrogen in sewage. and phosphorus and other pollutants.

2. Technical solution

The principle of the present invention is as follows: according to the characteristics of the original river channel, through appropriate transformation, plant large-scale aquatic plants (reeds, cattails, wicker, etc.) Intercept objects, sediment, etc., so that part of the suspended matter settles down. After settling, the sewage enters the contact oxidation tank. This unit uses a high-performance contact filter material - biological rope. The contact between the sewage and the biological rope makes the microorganisms attach to the biological rope to form a biofilm. The microorganisms attached to the surface of the biological rope make the The organic matter in the wastewater is oxidized and decomposed to achieve water purification. Near the center of the biological rope, due to the reduction of dissolved oxygen, such microorganisms can consume nitrate nitrogen in the water, thereby achieving the effect of denitrification. Then the sewage enters the vertical flow artificial wetland unit. Due to the transfer and release of oxygen by plant roots in the wetland system, aerobic, anoxic, and anaerobic states appear in the surrounding environment in turn, ensuring that the nitrogen and phosphorus in the wastewater can not only pass through Plants and microorganisms absorb them as nutrients, and can also remove them through nitrification and denitrification. Finally, the wetland system replaces the filler or harvests the planted plants to remove the pollutants. Finally, the use of floating plants to further improve water quality can reduce the nutrient salt in the water, improve the ecological environment quality of the river, and achieve the effect of enhanced purification.

The present invention is achieved through the following technical solutions:

A river purification system for treating domestic sewage in rural areas. The river water flow rate in the river is slow (<1m/s), and the treatment unit is constructed by using abandoned river or low-lying near-natural river, and plant grid settlement units are arranged in sequence from top to bottom according to the direction of water flow. , contact oxidation unit, vertical flow constructed wetland unit and phytoplankton unit.

(1) Plant grid settlement unit

The plant grid settlement unit mainly uses physical settlement, adsorption, and biological absorption and microbial degradation. Plant large-scale aquatic plants (reeds, cattails, wicker, etc.) in the repaired river channel, and build plant grids, which intercept large floating objects and sediment in domestic sewage or surface runoff, and make part of the suspended matter After settling down, nitrogen, phosphorus and other organic pollutants in surface runoff can be removed.

(2) Artificial biomimetic material contact oxidation unit

The unit uses high-performance contact filter material - biological rope, biological rope is a new type of contact oxidation material, the main chemical fiber materials used are: the most hydrophilic chemical fiber - polypropylene fiber , vinylon and nylon, which can maintain a stable structure even if a large number of microorganisms are attached, and polyvinylidene chloride, which has the best elastic recovery effect. The biological rope can stably maintain microorganisms with slow proliferation, such as nitrifying bacteria and denitrifying bacteria. At the same time, the peeling off of attached microorganisms is continuous rather than concentrated, and the phenomenon of effluent water quality will not be affected by biofilm shedding. Utilizing the high-efficiency food chain attached to the biological rope can also reduce the amount of excess sludge. The advantages of biological contact oxidation: easy operation and management, microorganisms with slow proliferation can be kept in a high concentration state, reduce the amount of excess sludge, and eliminate the phenomenon of activated sludge swelling and foaming.

The biological rope is in the shape of a rope, and the upper and lower ends of the biological rope are fixed on the frame (bamboo or steel pipe). , placed in the channel. The contact between the sewage and the biological rope makes the microorganisms adhere to the biological rope to form a biofilm, and the microorganisms attached to the surface of the biological rope make the organic matter in the wastewater oxidized and decomposed to achieve water purification. Near the center of the biological rope, due to the reduction of dissolved oxygen, such microorganisms can consume nitrate nitrogen in the water, thereby achieving the effect of denitrification.

(3) Vertical flow constructed wetland unit

The treatment of wastewater by constructed wetlands integrates the three functions of physics, chemistry and biology. The vertical flow constructed wetland is mainly composed of three parts: substrate, plants and water distribution system. At present, the substrates available for constructed wetland systems mainly include soil, gravel, gravel, coal, fine sand, coarse sand, cinder, porous media (LECA), wollastonite, and industrial waste. On the one hand, the matrix provides a medium for the growth of plants and microorganisms, and on the other hand, it directly removes pollutants through sedimentation, filtration, and adsorption. The plants used in the vertical flow constructed wetland mainly include cattail, wild rice stem, reed, andrographis, rushes, water onion, canna, etc. This kind of microenvironment transports oxygen to the root zone, forming a special rhizosphere micro-ecological environment. This micro-ecological environment has a strong ability to purify wastewater.

After the wetland system matures, the surface of the filler and the root system of the plant will form a biofilm due to the growth of a large number of microorganisms. When the sewage flows through the biofilm, a large amount of SS is blocked and intercepted by the filler and plant roots, and the organic pollutants are removed through the absorption, assimilation and dissimilation of the biofilm. In the wetland system, due to the transfer and release of oxygen by plant roots, the surrounding environment appears aerobic, anoxic, and anaerobic in sequence, ensuring that nitrogen and phosphorus in wastewater can not only be absorbed by plants and microorganisms as nutrients, but also can be absorbed by plants and microorganisms. It is removed through nitrification and denitrification, and finally the wetland system replaces the filler or harvests the planted plants to remove the pollutants.

(4) Floating plant purification unit

Floating plants are plants suspended on the water or only leaves floating on the water surface. Using them to purify water quality can not only further absorb nutrients in the water, greatly improve the transparency of the water body, but also effectively improve the water quality indicators, especially for algae. Very good inhibitory effect, to achieve the effect of strengthening purification.

3. Beneficial effect

The invention provides a river purification system for treating domestic sewage in rural areas. The test results show that the removal rates of COD _cr , SS, NH ₄ -N, TN, and TP can reach 77.1%, 84.1%, 70%, and 68%, respectively. 58.8%. Through the comprehensive application of the above technologies, the contents of COD _cr , TSS, NH ₄ -N, TN, and TP can reach the first-level standard of pollutant discharge standards for urban sewage treatment plants, which can effectively improve the quality of sewage water and contribute to downstream water bodies. Reduce pollution load pressure.

Description of drawings

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

Figure 2 is a schematic diagram of the channel layout, in which 1. water inlet 2. plant grid 3. contact oxidation biological rope 4. water inlet pipe 5. retaining wall 6. filling matrix 7. connecting pipe 8. wetland plants 9. water collection pipe 10. floating water Plant 11. Water outlet 12. River water surface 13. River bottom;

Fig. 3 is a schematic diagram of the immobilization of biological ropes in the contact oxidation unit. Among them 3. Contact oxidation biological rope 14. Fixed bracket

Figure 4 is a cross-sectional view of the constructed wetland sinkhole, in which 1. water inlet 5. retaining wall 8. wetland plants (cattail, canna, etc.) 11. water outlet 15. mellow soil 16. gravel 17. slag 18. pebbles;

Figure 5 is a cross-sectional view of the constructed wetland upward pool, in which 1. water inlet 5. retaining wall 8. wetland plants (cattail, canna, etc.) 11. water outlet 15. mellow soil 16. crushed stone 17. slag 18. pebbles.

Detailed ways

Further illustrate the present invention below in conjunction with accompanying drawing

Taking a river channel in northern Jiangsu as an example, the experimental research was carried out. The flow rate of this channel is about 0.1 m/s ~0.3 m/s, and the pollutants received are mainly organic matter, nitrogen, phosphorus and suspended solids, etc., which is a typical domestic pollution type channel. A domestic sewage purification system was built in the river, using plant grid settlement (plant grid settlement unit), artificial bionic material contact oxidation tank (contact oxidation unit), vertical flow artificial wetland (vertical flow artificial wetland unit) and floating water plants (floating water plant Purification unit) consists of four processing units in series (see Figure 1), the core technology - artificial bionic material contact oxidation technology and vertical flow constructed wetland technology, using bionic materials to absorb and degrade microorganisms, degrade organic matter, vertical flow constructed wetland to remove nitrogen and phosphorus, etc. Pollutants, without aeration device, can greatly reduce the energy consumption of sewage biological treatment.

The river channel for the implementation of the project is about 1000m long, 8m wide at the top, 2m wide at the effective water surface, and 0.8m deep. The project starts from about 500m away from the discharge source of domestic pollution, and successively set up 100m of plant grid settlement units, 10m of contact oxidation pond units, 40m of vertical flow artificial wetland units, and 50m of floating water plant purification units, totaling 200m, with an effective floor area of about 400m ² . The structure covers an area of 100m ² . The water treatment volume of the whole system is about 285-450m ³ /d, and the hydraulic retention time is 17h-28h. The project layout and structure are shown in Figure 2, Figure 3, Figure 4, and Figure 5, and the details are as follows:

(1) The system unit is 2m wide and 200m long, with 1 water inflow from the front of the plant grid unit and 11 water outflow from the floating plant purification unit.

(2) Vegetation grid settlement unit: repair the river channel, the effective water surface 12 is about 2m wide, and the water depth is 0.8m. Emergent plant reeds are planted on the river bottom 13 at a density of 10-15cm at intervals, and the plant grid 2 is about 100m long. It plays the role of intercepting and settling the particles and sediment in the water flow.

(3) Contact oxidation unit: take the height of the upstream water surface as the horizontal line, dig down to a depth of 0.5m, trim and harden, and build a trapezoidal canal with a length of 10m, an upper width of 2m, a lower width of 1.5m, and a depth of 1.5m. The contact oxidation biological rope 3 is selected and placed in the trapezoidal ditch, the biological rope is PP+K-45, the material is polypropylene+vinylon, the specific surface area is 1.6m ² /m, and the specific gravity is 1.24. The biological rope is in the shape of a rope, and the upper and lower ends of the biological rope are fixed on the frame 14, and the setting standard is 10cm in vertical and horizontal intervals. Therefore, the installation amount of the frame biological rope of 1 cubic meter is 100m. The contact oxidation unit uses about 2000m of biological rope, which is 20 cubic meters. The contact between the sewage and the biological rope makes the microorganisms adhere to the biological rope to form a biofilm, and the microorganisms attached to the surface of the biological rope make the organic matter in the wastewater oxidized and decomposed to achieve water purification.

(4) Vertical flow constructed wetland unit: The vertical flow constructed wetland is composed of a downflow pool and an upflow pool in series. The volume of each pool is 2m×1.5m×0.8m. The middle filling matrix is 6, and the bottom of the middle partition wall of the two pools is connected by a connecting pipe 7. The water distribution adopts the water inlet pipe 4 to evenly enter the water, and the water collection pipe 9 to discharge the water. This system has a total of 10 single pools in series. The bottom of the descending tank is a drainage layer, and the filler is pebbles 18 with a thickness of 100 mm and a particle size of 40-80 mm; the middle part is filled with slag 17 with a thickness of 300 mm, and the slag is blast furnace slag with a particle size of 30-50 mm. Hard, the particle size can be graded, the pH value of its aqueous solution is neutral, and it has a good adsorption effect on pollutants, especially fast and good adsorption efficiency on phosphorus; the upper and middle parts use 100mm gravel 16, mainly Limestone with a particle size of 10-30mm, this part can prevent water gushing in the wetland and maintain the stability of the wetland; the upper part is covered with 100mm mellow soil 15, and wetland plants 8 cattails, water onions, cannas, etc. are planted. The filling of the upflow pool is the same as that of the downflow pool, and the direction of water in and out is opposite.

(5) Floating plant purification unit: the unit area of floating plant 11 is about 100m ² . By selecting four kinds of plants, water hyacinth, water peanut, water water chestnut, and water chestnut, for indoor small-scale experiments, the test proves that the local dominant species of water peanut has the best treatment effect on nitrogen and phosphorus, so water peanut is chosen to be planted. In the downstream of the vertical flow artificial wetland, a water peanut plant belt with a length of 50m and a width covering the entire river surface is planted to absorb nutrients in the water body, improve the transparency of the water body, and achieve the effect of enhanced purification.

Through the implementation of the experimental project, the concentration of COD _cr , SS, NH ₄ -N, TN, TP and other pollutants in the system effluent decreased significantly, and the water quality was significantly improved. The removal rates of COD _cr , SS, NH ₄ -N, TN, TP were respectively Up to 77.1%, 84.1%, 70%, 68%, 58.8%.

Table 1 Monitoring data of water quality in and out of the system after project implementation (mg/L)

Sample serial number pH COD _cr SS NH ₃ -N TN TP flooded 8.13 123 69 23.4 27.3 2.85 out of water 7.77 28.2 11 7.02 8.7 1.18

Claims (4)

1. A river purification system for treating domestic sewage in rural areas. The river water flow rate in the river is less than 1m/s. It is characterized in that it utilizes abandoned river courses or low-lying land near natural river courses to construct treatment units, and arranges plant fences sequentially from top to bottom according to the flow direction. Sedimentation unit, contact oxidation unit, vertical flow constructed wetland unit and floating plant purification unit. 2. A river purification system for treating rural domestic sewage according to claim 1, characterized in that the plant grid is built by planting large aquatic plants reed, cattail or wicker in the plant grid settlement unit. 3. A river purification system for treating domestic sewage in rural areas according to claim 2, characterized in that a bionic material biological rope is fixed in the contact oxidation unit. 4. A river purification system for treating rural domestic sewage according to claim 3, characterized in that the matrix of the vertical flow constructed wetland unit is cobblestone, slag, crushed stone, and mellow soil from bottom to top, and the wetland plants are reeds, For cattail or canna, the water distribution method is to distribute water evenly at multiple points.

Images