1 Physical methods Clearance of dredging in clear ponds is generally performed during the production season, such as winter or early spring. Most of the water is drained first, and then the water is used to dig ponds to remove silt. This method is low-cost and adaptable, but it requires a source of water and a large wasteland or shoal to discharge mud to allow it to settle. Production practice proves that: the thickness of bottom mud of oysters, cockroaches and tilapia ponds is 20-40 cm; the bottom sludge of grasses, cocks and squid pools is 0-15 cm. Therefore, in order to maintain good water quality, 10 to 20 cm dark black sediment should be removed every 1 to 2 years. The bottom of the pool undergoes freezing and sun exposure to promote the decomposition of organic matter and eliminate pathogens and other harmful organisms. In the meantime, ponds can also be trimmed and reinforced, plugged leaks, gates repaired and weeds removed.
Production sometimes requires dredging without draining the pool water. Currently used dredging machinery can be roughly divided into two types: ship-type dredging machines and submersible dredging machines. The main working parts of the ship-type dredger are all installed on the ship. Only the suction head sinks underwater, and the sludge at the bottom of the tank can be cleared during the breeding period. The continuous suction operation is continuous; the entire working part of the submerged dredging machine dive into the bottom of the tank. , While walking on the surface of the mud, suction operation is performed. However, since the whole machine is operating underwater, the waterproof seal of the power machine is required to be high, and the maintenance technology is difficult, and the user himself is inconvenient for maintenance and repair.
In addition to dredging, often stirring the bottom of the pond to loosen the mud at the bottom of the pond and mixing the pool underwater can also promote the decomposition of organic matter at the bottom of the pond and re-release the nutrients deposited in the bottom mud to restore nutrients in the pond. The balanced distribution of upper and lower water layers promotes the growth and reproduction of plankton, which can prevent the aging of the bottom of the pool. Aeration of aerators can also improve the bottom environment and slow down the blackening process. The physical type of bottom modifier mainly composed of zeolite powder, charcoal and other adsorbent substances can absorb a large amount of ammonia and other harmful substances in the water, depositing the bottom of the pool, but it will cause rapid increase of ammonia and other harmful substances in the sediment. Bottom odor, and thus cannot fundamentally solve the problem.
2 Chemical method Chemical method is the most commonly used lime clear pond. After the lime reacts with water, a chemical reaction takes place, releasing a large amount of heat energy, neutralizing various organic acids in the sludge, and changing the acidic environment, so that it can play a role in harm sterilization, fertilization, and improving the quality of the bottom and water. Clear pond or clear pond with water. Water clear ponds are generally in ponds with low total alkalinity, total hardness, and low pH. In the pool waters and sediments, where the calcium concentration is high and the alkalinity is high, no lime is necessary. In poorly organic ponds Lime alone should not be used alone, otherwise it will exacerbate the decomposition of organic matter, so that less organic matter accumulates, pond fertility is further reduced, and recovery is more difficult.
In addition to lime, chemical composite modifiers can also be used. For example, the white granular â€œbottom water quality improverâ€ whose main component is calcium peroxide is added into the water to rapidly increase oxygen, promote nitrification, reduce the content of ammonia nitrogen, nitrite, and sulfide in water, and can also supplement biological growth facilities. Calcium is required, and the substrate is loose and air-permeable, which promotes the complete decomposition of organic matter. At present, a new type of nitrite ion remover, a nitrite chelating agent (BRT) and its salts, has the functions of degrading nitrite nitrogen and ammonia nitrogen in the water of the pool, chelating the organic matter in the pool water, eliminating pool water and containing in the bottom of the pool. Heavy metal ion pollution can be used as a pond soil improver, sediment improver, and substrate activator. In production, it is recommended to use 0.1-0.3g/m3.
3 Biological methods can also achieve remarkable results by using organisms to repair the bottom of the culture pond and reduce the accumulation of organic matter in the sediment. It has been reported that in the aging and polluted shrimp ponds, benthic organisms such as nereis are transplanted and cultivated into dominant populations, which can consume large amounts of residual baits, excrement, and other biological corpses and organic debris in shrimp ponds, slowing down the organic matter at the bottom of shrimp ponds. accumulation. In addition, the sandworm camp burrowing life, its bristly constantly shifting feasible into a small water circulation, can increase the dissolved oxygen in the substrate.
Microbial agents such as photosynthetic bacteria and complex probiotics can also improve the quality of pond sediment. Because photosynthetic bacteria can reproduce in the rich bottom of light, organic matter and hydrogen sulfide, and use these substances to build their own, which itself is preyed by other animals, constitute an important part of the material circulation and food chain in culture ponds, so photosynthetic bacteria Closed culture ponds that have serious or poor water quality and cannot replace water can play a significant role. The compound microbial sediment modifier can exert the synergistic effect of each strain and timely eliminate and eliminate the hidden troubles such as baits, excrements, dead animals and dead bodies, etc., which can not only improve the quality of sediment and water, but also control the pathogens. The spread of microorganisms and their diseases spreads.
4 Other methods Silt deposition rate is directly related to feeding and management measures such as fertilization and feeding. In production, we must strive to see water and fertilize, and avoid overdosing; in accordance with the principle of ecological complementarity, we should rationally mix and raise the fish; the amount of feed should be flexibly controlled according to the seasons, climate, growth, and changes in the water environment; add food attractants and promote Long agents, etc., enhance the appetite of aquatic animals, promote the absorption and conversion of feed nutrients, reduce the bait coefficient, and reduce the pollution of excrement on the sediment and water quality; prevent the growth of aquatic grasses (especially filamentous algae), and remove them excessively in time. The dead plants deteriorated with antiseptic rotting; conditionally, the iron slag (typically 1.5kg/m2) was splashed into the blackened area to delay the blackening process and reduce the damage.
In addition, aquaculture and crop rotation may be considered if the dry pool period is longer. In this way, the sludge can be fully dried out, and the root system developed in terrestrial crops can make the soil fully in contact with the air, which is conducive to the mineralization of organic matter and the absorption of nutrients in the sludge to better improve the bottom of the pool. The economic value of the crop itself can be obtained. In addition, the growing green crops and grasses can also be used as ponds for good green manure and fish feed.
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