At present, the treatment and maintenance methods of river eutrophication at home and abroad can be roughly classified into physical method, chemical method, bio-ecological method and so on.
1, the sewage
Pollution interception is an effective way to harness rivers. At present, all polluted rivers in China are caused by foreign pollutants far beyond the purification capacity of lakes, which leads to the deterioration of water quality and ecological destruction. Pollution control is widely recognized as an effective measure.
But the river sewage engineering, wide range, including a large number of pipe laying, sewage plant construction, personnel movements, surrounding the river ecological restoration, factories and enterprises pollution control, etc., the large engineering investment, long construction period and complicated project, make the department in charge of many rivers in a certain period of time cannot afford, but progress is slow, and the current sewage work more reflect one river management measures for the relevant department in charge of our strengths, often combined with other management methods.
Due to perennial natural deposition, a large amount of silt has accumulated in the bottom of the river, which is rich in considerable nutrient salts. The removal of sediment from river body can reduce nutrient salts accumulated in surface sediment and potential internal pollution sources, which is a direct and effective measure to reduce endogenous pollution. In the construction of the project, to close the mechanical working face, the silt to safe disposal, to prevent secondary pollution. However, the water quality can only be temporarily improved after dredging. With the input of pollution, the river quickly silted up again, and the project was large and the investment cost was high.
The successful example of river desilting is rarely reported. At present, developed countries such as Japan are carrying out detailed and thorough demonstration on whether the desilting is done and the thickness of the desilting.
3, aeration reoxygenation
River water with serious pollution is in anoxic (or anaerobic) state because the oxygen consumption is higher than the natural reoxygenation. Artificial oxygenation (a process called river aeration reoxygenation) to a river in anoxic (or anaerobic) state can enhance the river's self-purification ability, improve water quality, and improve or restore the river's ecological environment. Therefore, aeration reoxygenation in a river in anoxic (or anaerobic) state can supplement the excess dissolved oxygen in the river, enhance the self-purification ability of the water body, and help to speed up the restoration of the river to the normal water ecosystem in the state of black and smelly, poor sense sense, etc.
Because of river aeration reoxygenation engineering good effects and relatively low investment and operation cost, as some developed countries such as America, Germany, England, Portugal, Australia and moderately developed countries and regions such as South Korea, Hong Kong, China, in small and medium pollution water and harbor and river water pollution control in the frequently used methods.
4. Change water to flush dilute
By means of engineering, water is diverted to dilute the polluted water body, so as to reduce the pollution load of water body in a short time, improve the living environment of aquatic animals and aquatic plants, and improve the self-purification ability of rivers. However, the total amount of pollution did not decrease after the water was changed and diluted. In fact, it was the transfer of pollutants. If the external pollution persisted, it would soon return to the original pollution level and waste high-quality water resources.
Through water dilution, the dominant bacteria in the river can be transformed from green algae to large aquatic plants, which greatly improves the water quality of the river. However, dilution of diversion water will lead to changes in the ecological system of exchange water body, which will also have a certain negative impact.
2. Chemical method
1. Add coagulant
The direct addition of "coagulant" in the river has a quick effect, but the drug dose is difficult to grasp, the pollutant deposition on the river bottom damages the bottom biological environment, and there is the possibility of secondary release of pollution.
2. Apply algae remover
Remove algae and nitrogen from water, but not phosphorus; The biological toxicity of chemical algicide is harmful to the growth of fish and other organisms.
The chemical method is to add the corresponding chemical agents according to the pollution characteristics of the river and remove the pollution substances forcibly. By adding aluminum salt to a river in the United States, the phosphorus in the river dropped from 65 mug /L to 30 mug /L. This method is simple to operate, but high cost, easy to cause secondary pollution.
Bio-ecological restoration technology
At present, the natural water body ecological restoration technology at home and abroad includes aquatic plant technology, biological enhancement technology, microbial preparation technology, artificial floating island technology and so on. Among them, the first two are mainly aquatic vegetation restoration technology and biological efficiency enhancement technology, which are generally used as the main technology of river management and are relatively mature in application. Artificial floating island technology is generally used as auxiliary technology.
Ecological restoration measures have the characteristics of in-situ purification of water quality, restoration of aquatic ecological structure in water bodies, low operating cost and increase of self-purification ability of water bodies. In natural unpolluted water, ecosystems are complex. There are a lot of bacteria in the bottom of water, on the surface of particulate matter and on the surface of revetment. Protozoa in water also feed on fungi. Protozoan predation can accelerate the renewal of biofilm. After the aging bacteria are preyed on, the growth space is provided for the growth of new bacteria, making the whole bacteria in a more active state. At the same time, protozoa are the food for metazoan animals, while benthic creatures such as spiral lions and some fish feed on metazoan animals such as rotifers. The plants growing in water not only provide oxygen for the water, but also provide adhesion space for the growth of bacteria and micro-animals. The complex environment composed of water bottom and plants also provides different habitats for various organisms. The whole ecosystem itself has a certain direction of material flow and energy flow, in the system, between organisms promote or restrict each other, maintain the overall function and vitality.
The self-purification function of natural water body mainly depends on the ecosystem in the water body. This self-purification ability is very great. Without human intervention, all organic substances in the natural water body can be decomposed, and the nutrient balance in the water body can be automatically adjusted. To a certain extent, the increase of organic substances and inorganic salts in the water can improve the density of organisms in the water, meanwhile, the material flow and energy flow in the system will also increase correspondingly, and the ability of purifying pollutants in the water will also be improved. However, once the carrying capacity of the system is exceeded, some links of the water ecosystem will be destroyed or lose its function, and the loss of the function of the ecosystem will react on the self-purification ability of the water body. The weakening of the self-purification ability of water also accelerates the collapse of the ecosystem. In a vicious cycle, water gradually loses its ability to purify itself.
The restoration of the ecological structure of the water body can restore the self-purification ability of the water body, achieve self-purification of the water body through the self-purification function of the water body, and achieve the sound and coordinated development of the water body and the aquatic ecosystem. In water bodies where water quality has deteriorated, it is difficult to quickly restore the ecological structure of water bodies by relying entirely on spontaneous restoration and simple physical restoration. Under the condition of artificial participation, a systematic and comprehensive restoration of the ecological structure of the water body can achieve the benign and coordinated development of the water body ecosystem.
1. Aquatic plant technology
Aquatic plants is an important part of the river ecosystem, and has significant environmental ecological function, using the method of aquatic organisms grow aquatic plants, plant growth through transfer of water pollution loads in the system and its developed root system for microbial growth breeding sites, to break down the water for plants absorb pollutants, has certain absorption purification, clarify the function of the water quality, inhibit the algae.
Artificially create certain conditions, the use of suitable for river water environment of aquatic plants and its corresponding symbiotic environment, to construct water characteristics of aquatic plant community, can effectively reduce the concentration of suspended solids, improve the water transparency and dissolved oxygen, to provide a good living environment to other creatures, to improve the biodiversity of the aquatic ecosystem.
2. Biosynergy technology
Biological technology will increase microbial through certain technical means (such as the use of carrier materials, embedding material or reasonable control hydraulic conditions, etc.), make the growth of microbial fixation, improve the microbial number inside the bioreactor, thus conducive to the solid-liquid separation after reaction, nitrogen removal and remove high concentrations of organic matter, and is hard to biodegradable materials, improve system capacity and adaptability of biological synergistic technology based on the recovery, strengthen the microbial communities to purify the water. Microbial community is the basic biological component of water ecosystem, which is not only the "scavenger" of water body, degrading pollutants, creating a healthy water environment for other aquatic organisms, but also an important link of biological chain, maintaining normal material circulation.
Microorganisms (fungi, algae, protozoan animals, etc.) are the main force in the natural purification of water bodies. The polluted water quality of rivers is deteriorated, which is also due to the pollution that exceeds the digestibility of microorganisms. The decline of water quality leads to the gradual extinction of some biological species (including microorganisms) without living environment, and the change of aquatic biological structure in turn also contributes to the trend of water environment deterioration, such a vicious circle leads to the degradation of water ecosystem. By creating the space for the growth of microorganisms, the biosynergy technology amplifies the microbial biomass by hundreds or tens of thousands of times, greatly enhancing the natural purification capacity of water bodies, amplifying the digestion capacity of pollution, and cutting off the vicious circle. It can not only reflect the obvious improvement of water quality, but also promote the benign development cycle of water ecosystem.
Indigenous microbial biological synergistic technology in training and development as the priority, these microbes due to water environment suitable for the originally with the height of the vitality and the ability of sustainable development, there is neither may be produced by adding the microbial biological invasion, or because of microbial death to repeated dosing, and no chemical biological hazards; Water purification is based on the spontaneous nutrient consumption of microorganisms without the huge energy consumption or complex operation management requirements caused by mechanical cleaning.
Biosynergy technology relies on the ability of microorganisms to purify water body naturally, and closely combines the improvement of water ecosystem and mutual promotion of development. Therefore, it is a long-term and ecological river management measure.
At present, the most mature biological efficiency enhancement technology at home and abroad is biological nest efficiency enhancement technology, which takes biological nest as the core, synchronously purifies water quality and establishes ecological water body management and maintenance system of water body ecosystem. Biological nest is a new and highly efficient ecological carrier, it is a blend of subjects such as material science, microbiology and water ecology, USES the food grade raw material, through the patent weaving technology, the high specific surface area, high load, is the most advanced at home and abroad, the most effective method for ecological restoration of fundamentally solve the problem of water body purification environmental protection product.
3. Microbial preparation technology
The strains with high efficiency were selected and made into microbial compound preparation to treat polluted water. The process is based on the enzymatic reaction and USES the special protein with catalytic function produced by the organism as the catalyst to purify sewage, decompose silt and eliminate odor.
The main advantage of microbial preparation technology is that it can rapidly increase the concentration of microorganisms in the contaminated media and is expected to improve the biodegradation rate of pollutants in a short time. Its disadvantage is that in order to maintain a good water improvement effect, continuous addition is needed according to the change of water body, which can be used as an auxiliary measure in the process of water body ecological restoration. Microbiological preparation technology is suitable for closing slow-flow water body and can be used before algae bloom, which can make up for the disadvantage that microbiological preparation usually takes longer to take effect.
4. Artificial floating island technology
Ecological floating bed technology is the principle of management of water environment and ecological restoration through the plant in the process of growth of water absorption of nitrogen, phosphorus and other plant essential elements in use, and its roots and floating bed matrix on the adsorption of suspended solids in water, the concentration of harmful substances in water body, at the same time, plant roots can release a large number of secretion of the degradation of organic matter, so as to accelerate the decomposition of organic pollutants, as the improvement of some water quality indicators, especially the increase of dissolved oxygen, create conditions for aerobic microbial multiply, again through the microbes to further decomposition of organic pollutants and nutrients, improve water quality further, Ultimately through the harvest plant form, accumulation of nitrogen, phosphorus and other nutrients and adsorbed on the surface of the plants and root, pollutants move out water, make the pollutants in water are greatly reduced, the water quality improved, so that higher survival and reproduction of aquatic creatures in the ecological environment conditions, provide may eventually repair water ecosystem.
The planting methods of artificial floating island include floating growth, fixed growth of polystyrene foam board, artificial matrix filled with woven bag, and bamboo as floating object. Plants planted directly floating cannot stand upright; Plants with fixed growth of polystyrene foam board can have good dispersion, but the foam board is easy to break. After improving the mechanical properties of the foam board, it can be directly used in the implementation of projects, and can also reduce the possibility of causing landscape pollution to a certain extent. Artificial matrix filled with woven bag can be used for planting plants. Plants can grow upright in the matrix, and roots can be fully distributed in the matrix to a large extent, or in water bodies to a certain extent. However, the existence of matrix limits the effective contact area between plant roots and water bodies. Other fixation methods also have the characteristics of allowing the plant root system to stretch in the water, which can provide support for the growth of microorganisms in the water.
The matrix filler in the artificial floating island can also provide the carrier for the growth of microorganisms and increase the effective carrier area. Matrix fillers increase the density of fillers per unit volume and reduce the exchange and circulation of water in the spatial network of plant roots. Artificial floating islands adopt the way of plant floating and growing, which can make the technology applicable to water bodies of different depths. The change of water level will not affect the artificial floating islands.
At present, bio-ecological technology is the main technology of river management at home and abroad.
The establishment of river water ecosystem is the foundation of long-term maintenance of water quality. This plan mainly adopts biological nest enhancement technology for river management and ecological restoration, supplemented by ecological floating bed and aeration technology (improve dissolved oxygen concentration of water body).
In addition, in the early stage of treatment, environmental microorganisms were added to improve the black and smelly condition of the water bottom. After a period of treatment, water quality and transparency are improved. Benthic organisms (snails and shellfish) and fish with strong pollution resistance are added, and aquatic plants are planted to enhance the self-purification ability of water body and the integrity of the ecological chain.