First, biological control law. Cyanobacteria are the food of freshwater fish, and we can control algae by throwing such fry to prevent algae from erupting. Cyanobacteria itself is the food of freshwater fish, and every 1 kg of silver carp can "kill" 40-50 kg of cyanobacteria. From releasing fry to fishing ashore, a silver carp can eat about 60 kilograms of cyanobacteria. It is estimated that about 280 million silver carp fry worth 654.38 billion yuan can effectively control the occurrence of cyanobacteria in Taihu Lake. However, if the water bloom is seriously polluted and fish cannot grow and form a large population, it is difficult to control the large-scale outbreak of cyanobacteria.
Second, the biological floating bed method. Using plants and other organisms that adsorb algae to control nutrients in water and inhibit algae overgrowth, thus establishing an ecological balance system. Artificial planting of aquatic plants such as canna, water hyacinth and Eclipta prostrata on artificial floating bed can not only absorb nitrogen, phosphorus and other pollution factors in water, but also inhibit the growth of cyanobacteria.
Third, the mechanical fishing method. This is the most primitive and traditional method, that is, the algae are fished out together by manpower, which is adopted in Wuxi Shuiyuankou. In order to improve the speed, someone also invented an automatic metal film filter. During the slow running of the power boat, all the cyanobacteria are salvaged by the metal film, and the salvage speed is thousands of times that of manual operation. In the process of fishing, the functions of flocculation, sedimentation, air flotation, pushing flow and algae collection are added. The advantage is that it is completely salvaged, but the disadvantage is that it is still difficult to control large areas of cyanobacteria.
Fourth, chemical methods. It is to kill with chemicals, usually copper sulfate. Copper sulfate is also often used to control early marine red tides with good results. However, the metamorphosis of copper ions on biological larvae is teratogenic and causes serious shedding of bait algae. At the same time, copper sulfate is toxic and can destroy the normal ecosystem of water, so chemical algae removal should be cautious.
Fifth, microbial bacteria remove algae. Beneficial strains in activated sludge were screened and separated, and high-density bacterial powder was obtained after spray drying, and then it was attached to patented filler through industrial production to form an efficient treatment system. Some experiments in Shanghai show that the water body is dark black before river regulation, and the water body is seriously eutrophic, and there is no water for vivid plant growth. After 12 days of treatment, the water quality of Xiachangpu River was obviously improved, and the water body was clear and odorless.
Sixth, strong magnetic field is used to kill algae. The results showed that the number of algae in the water decreased from 500,000 to 50,000/ml under the action of a high-intensity magnetic water processor with a magnetic field intensity of 3,700 gauss, and cyanobacteria were basically eliminated. The dissolved oxygen and transparency of water increased from 2.40 mg/L and 40 cm to 7.20 mg/L and 75 cm respectively, and the water quality was obviously improved. The disadvantage of this method is its high cost and inability to deal with a wide range of cyanobacteria.
Seventh, engineering dredging method. That is to say, fresh water, such as Yangtze River water, is introduced, and cyanobacteria and smelly lake water are washed into the ocean with a lot of water. The characteristic is that cyanobacteria can be controlled in a large area, but the disadvantage is that it is not fundamentally controlled, but the pollution is transferred to other places. Not suitable for large-scale promotion.
It should be said that the above treatment methods are at the end of treatment, and they are the "last resort" to treat the symptoms instead of the root cause. The failure of pollution control in Dianchi Lake cost 4.8 billion yuan, which shows that the artificial control measures are very limited. Although the beggar-thy-neighbor approach is adopted to divert the Yangtze River water to Taihu Lake or Chaohu Lake, it can temporarily alleviate the pollution, but only transfer the pollution to the offshore, from cyanobacteria to brown algae, from water bloom to red tide, and finally the pollution becomes more and more serious without treatment. The scientific control measure is to make great determination and take strong measures to cut off the pollution sources such as industrial and domestic sewage and farmland nitrogen and phosphorus, so as to make the water flow. After the pollution source is interrupted, natural selection should be respected, ecological self-repair should be implemented, and only necessary manual control measures should be supplemented.