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    Artificial wetland sewage treatment system

    来源:本站  最后更新:2017-06-08 17:12:07  作者:中农天陆  浏览:514次

    First, the introduction of artificial wetlands
      Wetlands are natural or artificial, regular or temporary swamps, wetlands, peatlands or watersheds, with or stationary or flowing, or fresh water, brackish water or salt water. Whether artificial or natural, wetlands have their very strong ecological functions, with the same characteristics of its surface perennial or often covered with water or filled with water, is between the land and water between the transition zone, which grows a lot of water , Water and submerged plants. These plants can be in their tissues to absorb metal and some harmful substances, many plants can also participate in the detoxification process, the absorption of pollutants, metabolism, decomposition, to achieve water purification. Wetlands are often referred to as "natural sewage processors" and this "natural sewage processor" requires little or no fossil fuels and chemicals.

     

     

      The natural wetland is a complex ecosystem in the water and land facies, while the Constructed Wetland is a wetland system that is designed and constructed by sewage and man-made. The range of pollutants is extensive, including organic matter, nitrogen (N ), Phosphorus (P), suspended solids (SS), trace elements, pathogens, etc., the purification mechanism is very complex, combined with the physical, chemical and biological effects of three, the supply of wetland decontamination required oxygen; Plant roots and fill the surface of the growth of biofilm purification, the retention of filler bed and plant absorption of nutrients, and to achieve the purification of water.
    Second, the development of artificial wetland status quo
      Artificial wetlands developed in the 1970s and 1980s, and various wetlands have been used around the world to handle a large number of different wastewater. Artificial wetlands are used to treat coal waste water, biological sludge, storm runoff, dairy products processing wastewater.
      The constructed wetland is constructed and controlled by a marshland similar to the marshes. The sewage and the sludge are controlled to the artificial wetlands where the sewage and the sludge flow in a certain direction. Soil, artificial medium, plant, microbial physical, chemical, biological triple synergies, sewage, sludge treatment of a technology. Its mechanism of action includes adsorption, retention, filtration, redox, precipitation, microbial decomposition, transformation, plant shelter, residue accumulation, transpiration water and nutrient uptake and the role of various animals. It is a comprehensive ecosystem, which applies the principles of species symbiosis, material recycling principle, structure and function coordination in the ecosystem, and fully exploits the potential of resources to prevent the environment from promoting the virtuous circle of pollutants in wastewater. Pollution, access to sewage treatment and the best benefits of resources.
      The area of ​​artificial wetlands may, as the case may be, be located in the suburbs or near the effluent from the sewage treatment plant. Some artificial wetlands are pretreatment, in those who do not have the construction of sewage treatment plants in urban and rural areas to build artificial wetlands, the sewage discharged into the use of the plant to deal with it, and then discharged into the natural water system to protect the water ; And some wetlands are reinforced, the construction of artificial wetlands near the sewage treatment plant, the sewage treatment plant to deal with the introduction of water, and then through the strengthening of artificial wetlands to improve its water quality, and then discharged into the natural water system, as its supplementary water.
    Third, the classification of artificial wetlands
      Artificial wetland sewage treatment technology after years of development and research, according to the wetland in the form of the main plant will be divided into artificial wetlands: phytoplankton system, water plant system, submerged plant system. The submerged plant system is still in the laboratory research stage, the main application areas are primary processing and secondary treatment after the fine treatment. Phytoplankton is mainly used for the removal of N, P and to improve the efficiency of traditional stabilization ponds. At present the general refers to the artificial wetland system refers to the water plant system.

     

     

      Domestic and foreign scholars from the point of view of engineering design, according to the system of different water or water flow in the system will be different flow of artificial wetland processing system is divided into the following types: 1, surface wetland treatment system; 2, System; 3, vertical flow wetland processing system.
      1. Surface FlowConstructed Wetland (Surface FlowConstructed Wetland)
      Is a kind of sewage from the surface of the wet flow of rectangular structures, simple structure, low cost of the project; but because the sewage flow in the filler surface, easy to breed mosquitoes, the surrounding environment will have a negative impact, and its processing efficiency is low. Sewage flows from the surface of the wetland, as shown in Figure 1. The waste water is purified during the flow. Water depth of 0.3 to 0.5 meters in general, the flow was pushed forward. Sewage from the entrance to a certain speed slowly flowing through the wetland surface, part of the sewage or evaporate or penetrate the ground. The near water surface is an aerobic zone, the deeper part and the bottom is usually an anaerobic biota. The source of oxygen in surface flow artificial wetlands is mainly due to the surface diffusion of water bodies, the transmission of plant roots and the photosynthesis of plants. However, due to the transmission capacity is very limited, so most of the artificial wetland using subsurface wetland system.

     

     

      2. Subsurface Constructed FlowWetland
      Sewage in the filler gap between the seepage, can make full use of filler surface and plant roots on the biofilm and other effects of sewage treatment, water quality is good. As the horizontal surface in the cover soil or fine sand layer below, better health conditions, it is widely used. Submerged wetlands are usually composed of two wetlands in series, the processing unit in parallel. Compared with the surface flow artificial wetland, the hydraulic load of the horizontal subsurface constructed wetland is large, and the removal efficiency is obvious for BOD, COD, TSS, TP, TN, algae and petroleum. Subsurface flow wetlands are generally designed to have a certain bottom slope, the aspect ratio is greater than 3 and longer than 20 m of the structure, the sewage process is longer, is conducive to the occurrence of nitrification and denitrification, nitrogen removal effect is better. Or square structures, the short process of sewage, denitrification is weak, and the engineering requirements are higher. As the vertical flow wetland can easily use engineering means to improve the system of oxygen supply situation, improve the uniformity of water distribution, to create a more conducive to nitrification and denitrification occurred in the system environment, it is more and more attention.

     

     

      3. Vertical Flow Constructed Wetland, where sewage flows in the vertical direction
      Oxygen supply capacity is strong, nitrification more fully, covers an area of smaller, can achieve a large hydraulic load long-term operation. The nitrification capacity of vertical subsurface flow constructed wetland is higher than that of horizontal subsurface constructed wetland, and it has better treatment effect for wastewater with higher ammonia content. Vertical flow wetlands are generally designed to be about 1 m round or square structures as shown in Figure 2, the sewage process is short, denitrification is weak, and engineering requirements are higher. As the vertical flow wetland can be easily used to improve the system to improve the system of oxygen supply conditions, improve water distribution uniformity, and create a more conducive to nitrification and denitrification occurred in the system environment. Vertical wetlands of the shortcomings of the sewage for the handling of organic matter is insufficient, the control is relatively complex, the phenomenon of breeding mosquitoes in summer.

     

     

    Fourth, the artificial wetland sewage treatment system process
      The constructed wetland sewage treatment system consists of a pretreatment unit and an artificial wetland unit. Through reasonable design can BOD5, SS, nutrients, protozoa, metal ions and other substances to achieve secondary and advanced treatment level. The purpose of the pretreatment is to reduce the suspended matter in the sewage, prevent the wetland packing, ensure the stability of the constructed wetland ecosystem, and increase the wetland life and processing capacity. Its facilities include grille, grit chamber, sedimentation tank, stable pond and so on. Artificial wetland system The general process flow is: sewage → grille → grit chamber → sedimentation tank → stable pond → artificial wetland → water.
      Removal of organic matter by artificial wetlands: artificial wetlands have strong ability to deal with organic matter. Insoluble organic matter through the precipitation of wetlands, filtration can be quickly shut down from the wastewater, the use of microorganisms; soluble organic matter can be microbial adsorption and microbial metabolic process is removed. The ultimate fate of most organic matter in wastewater is the conversion of heterotrophic microorganisms into microbial cells and CO2 and H2O.
      Removal of Nitrogen from Constructed Wetlands: Nitrogen removal in wastewater is mainly removed by plant uptake and nitrification and denitrification of microorganisms, in which plant uptake only removes a small portion of nitrogen from the wastewater, and the removal of nitrogen in the effluent is mainly through nitrification of microorganisms. Nitrification to complete. Artificial wetlands have a stronger nitrogen handling capacity than conventional activated sludge treatment systems (which can not normally complete denitrification), saving a lot of infrastructure and operating costs over A / A / O systems.
      Removal of Phosphorus from Constructed Wetlands: Removal of Phosphorus from Constructed Wetlands is the result of three aspects: plant uptake, microbial removal and physical and chemical action. Inorganic phosphorus in wastewater can be transformed into plant ATP, DNA and RNA by plant uptake and assimilation, and removed by plant harvesting. Physical and chemical effects include the adsorption of phosphorus on the filler and the chemical reaction of the filler with the phosphate ion. The removal of phosphorus by microorganisms includes their normal assimilation of phosphorus (incorporation of phosphorus into its molecular composition) and over-accumulation of phosphorus. Among them, the physical and chemical effects of the filler for the removal of phosphorus the largest contribution.

     

     

    Five, artificial wetland plant selection:
      Artificial wetland plants have the ability to decompose and transform organic matter and other substances, as well as all photosynthetic autotrophic organisms. Plants through the absorption of assimilation, can directly absorb the available nutrients from the sewage, such as water in the nitrogen and phosphorus. Ammonium salts, nitrates and phosphates in water can be absorbed by the plant by this action, and finally through the harvest and leave the water. The roots of plants can adsorb and enrich heavy metals and toxic and hazardous substances. Plant roots and leaves have absorbed the role of heavy metals, in which the root of the strongest absorption capacity. In different plant species, submerged plants have a strong ability to adsorb. Root-intensive and intertwined plants can also play a role in blocking the adsorption of solid particles. Plants provide greater surface area for microbial adsorption growth. The roots of plants are places where microbes are important habitat, attach and multiply. The literature shows that the number of microorganisms in the rhizosphere of plants is much greater than that of non-rhizosphere microorganisms, and microbes can play an important role in the degradation of pollutants in water. Plants can also provide oxygen for the body of water, increase the activity of water.
      Artificial wetlands are not very rich in natural wetlands, but there are many types of flora and fauna grown in water fields such as paddy fields, ponds and lakes. For example, plants in paddy fields are different from seasons and paddy fields. Before the spring plowing, in the paddy field in the growth of Pescar, wild flowers and the like, in the dry season there are lotus grass, wild chrysanthemum and other growth, in the wet season there are fields, six grass and other development. There are many wet plants in the paddy field weeds, as well as aquatic plants such as water beans, algae, water hyacinth, indicating that paddy fields are diverse wetlands, aquatic plants. In addition, animals in paddy fields are diverse. Lobster to spend a lifetime in the paddy fields, frogs, dragonflies and so on to lay eggs in paddy fields, and is the larvae of the living space, heron birds like waterfowl to feed in paddy fields. There are fields in the field of freshwater fish, snail and other survival, as well as living in the leaf of the semi-winged insects and so on. These animals have herbivorous animals, but also carnivorous animals, paddy fields in a variety of biological composition of the complex food chain. Similarly, in the ponds and lakes also grow a large number of aquatic plants and a variety of fish, shrimp, crab, mussels and other animals and microorganisms, for birds, fish to provide rich food and good survival and reproduction space , Plays an important role in the conservation of species and the conservation of species diversity.
    Six, the main advantages of artificial wetlands
      Low cost of energy consumption, easy maintenance: artificial wetlands do not use a large number of artificial structures and mechanical and electrical equipment, without aeration, dosing and return sludge, and no excess sludge generated, which can greatly save investment and operating costs. As for the maintenance of technology, artificial wetlands basically do not need mechanical and electrical equipment, so the maintenance is only clean up channels and management of crops, the general staff can afford, only individual professionals regularly check.
    Nitrogen and phosphorus removal effect is good, the pathogen microbial removal rate is high: artificial wetland is a low input, high efficiency nitrogen and phosphorus removal process, without special disinfection can be removed from the source of microbial large, treated water can be discharged directly into the lake, Reservoirs or rivers, can also be used for flushing, car washing, irrigation, greening and industrial reuse.
      Can be combined with the construction of water landscape: artificial wetlands can be used as part of the waterfront landscape, along the river and lake embankment construction, can be small, in situ use, some wet plants (such as banana, Iris, etc.) itself has Good landscape effect.

     

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