The main pollutants in aquaculture come from the bottom sludge, which mainly consists of feed residues and fish and shrimp feces.The main requirement for treating aquaculture wastewater is to reduce the organic matter content in the wastewater and separate the sludge settled at the bottom of the aquaculture tank into solid and liquid. Aquaculture wastewater is mainly treated by activated sludge process.

Aquaculture effluentThe main pollutants in are ammonia nitrogen, nitrite, organic pollutants, phosphorus, and fouling organisms. Research has confirmed that during the breeding process, only 1/4 to 1/2 of the phosphorus and nitrogen that enter the breeding water as feed can be absorbed and utilized by the breeding animals, while the rest is dissolved in the water. The breeding variety, feed type, feeding method, and management level all affect the water quality of aquaculture effluent. Inappropriate feeding can cause serious pollution exceeding the standard in aquaculture water bodies. If the aquaculture effluent is not treated in a timely and effective manner, it will pollute the surrounding water environment after discharge, leading to a series of fish diseases and ecological problems.

Eel aquaculture wastewater treatment process diagram

Introduction to equipment and processes used in processing

Cyclone desander:

Cyclone desanderIt is based on the principles of centrifugal settling and density difference. When the water flow enters the equipment tangentially from the inlet of the desander under a certain pressure, strong rotational motion is generated. Due to the different densities of sand and water, the low-density clear water rises under the action of centrifugal force, centripetal buoyancy, and fluid drag force, and is discharged through the overflow outlet. The high-density sand is discharged through the bottom sand discharge outlet, thus achieving the purpose of desanding. Within a certain range and conditions, the higher the inlet pressure of the sand remover, the higher the sand removal rate, and multiple units can be used in parallel.

Fiber turntableFilter cloth filter:

Fiber turntableFilter cloth filterComposed of a series of vertically installed, rotatable filter discs, the discs are mounted on the central drum. Each turntable consists of two semi-circular fan blades. Install a mesh stainless steel filter cloth membrane on the component, and the average pore size of the filter cloth can be selected from 5 μ m-200 μ m according to the actual requirements of the customer. The incoming water flows through a free fall and enters the filtering turntable from the central drum, passing through and filtering from the inside out. The filtered liquid then flows out from the outlet of the structure.

Solid substances in the inflow are intercepted by the filter cloth and deposited on it. As the filtration time increases, the liquid level of the central drum rises. When the preset maximum liquid level is reached, the turntable begins to slowly rotate, and the backwash water pump extracts filtered water through the flushing nozzle to flush the solid substances deposited on the filter cloth.

Dissolved Air Flotation (DAF) Unit：

Dissolved Air Flotation (DAF) UnitMainly used for solid-liquid or liquid-liquid separation. By using a gas dissolution and release system to produce a large number of fine bubbles in water, they adhere to solid or liquid particles in wastewater with a density close to that of water, resulting in a state where the overall density is lower than that of water, and rely on buoyancy to rise to the water surface, thereby achieving solid-liquid or liquid-liquid separation.

Plate and frame filter press:

Plate and frame filter pressIt is an intermittent solid-liquid separation equipment, which is composed of filter plates and filter frames arranged to form filter chambers. Under the pressure of the feeding pump, the feed liquid is sent into each filter chamber, and the solid and liquid are separated through the filtering medium. Widely used in chemical, dye, petroleum, ceramic, pharmaceutical, sugar, food, starch, maltose, paint, metallurgy, and sewage treatment in various industries. It has the advantages of good separation effect, wide range of applications, simple operation, and low investment, especially for the separation of viscous fine materials, which has incomparable superiority.

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In recent years, China's aquaculture industry has developed rapidly. If a large amount of aquaculture wastewater cannot be scientifically and effectively treated, it will cause huge environmental problems and ultimately affect the healthy development of the aquaculture industry. Common physical, chemical, and biological treatment technologies have their own advantages and limitations in the treatment of aquaculture wastewater, and should be selected according to the actual situation. Biological treatment technology, as a hot topic in current aquaculture wastewater treatment, can effectively improve the comprehensive treatment efficiency of wastewater, save water resources, and prevent secondary pollution. The combined application of physical, chemical, and biological treatment technologies can achieve more ideal results. Continuously improving and innovating existing wastewater treatment technologies is of great significance for achieving healthy, green, and sustainable development of the aquaculture industry.