1 physical treatment method
1) filtration method
Since most of the remaining residual bait in the aquaculture wastewater and aquaculture biological excreta, etc. exist in the form of large particles in the form of suspended state, the removal of the physical filtration method is the most rapid and economical method. Commonly used filtration equipment are mechanical filters, pressure filters, sand filters and so on. In the actual treatment works, mechanical filter (microfilter) is more applications, better filtration effect. Zeolite filter has both filtration and adsorption functions, not only can remove suspended solids, but also can effectively remove heavy metals, ammonia and nitrogen and other dissolved pollutants through adsorption.
12) Foam separation method
Foam separation according to the principle of surface adsorption, the use of aerated bubbles formed in the liquid phase as a carrier for the separation of solutes or particles in the liquid phase, so it is also known as foam adsorption separation. The principle is to pass air into the treated water, so that the surface-active substances in the water are sucked by the tiny bubbles and float up to the surface of the water with the bubbles to form foam, and then separate the foam on the surface of the water, so as to achieve the purpose of removing the dissolved and suspended pollutants in the wastewater. As the foam separation technology not only can be protein and other organic matter in the mineralization of ammonia and other toxic substances have been removed before, to avoid the accumulation of toxic substances in the water body, and can provide the necessary dissolved oxygen to the breeding water, the maintenance of the ecological environment of the breeding water body has a good role.
Foam separation is based on the principle of adsorption, to the liquid containing surface-active substances in the bubble, so that the surface-active substances within the liquid gathered in the gas-liquid interface (the surface of the bubble) on the surface of the liquid body above the formation of a foam layer, the foam layer and the main body of the liquid phase is separated, you can achieve the concentration of the surface-active substances (in the foam layer) and purification of the main body of the liquid phase of the purpose. The concentrated substance can be a surface-active substance or a substance that can be complexed with the surface-active substance, but they must have the ability to complex or chelate with a certain type of surface-active substance.
2 Chemical treatment method
1) Ozone treatment method
Sea water factory farming wastewater exists in the aquaculture biological excreta and other suspended matter, as well as ammonia and nitrogen, biodegradable organic matter and other substances, and there are also difficult to biodegradable organic matter. Therefore, the use of ozone, hydrogen peroxide, chlorine dioxide, bleach solution and other chemical oxidants oxidation, oxidative decomposition of difficult biodegradable dissolved organic matter is the main means of deep treatment of aquaculture wastewater. Therefore, the use of O3/UV process can both improve the treatment efficiency and reduce the amount of ozone. Purification of lake water with O3/UV technology can achieve the purpose of water purification and water body oxygenation.
The purification principle of ozone lies in its redox potential of 2.07 V in water, higher than chlorine (1.36 V) and chlorine dioxide (1.5 V). It can destroy and decompose the cell wall of the cell (membrane), rapid diffusion penetration into the cell, thus killing pathogenic bacteria. Ozone in the water decomposition of intermediate substances hydroxyl radical (?OH), has a strong oxidizing properties, can decompose the general oxidant difficult to decompose organic matter. Therefore, the ozone treatment of wastewater, not only can quickly eliminate bacteria, viruses and ammonia and other harmful substances, but also increase the dissolved oxygen in the water, so as to achieve the purpose of purification of aquaculture wastewater.
2) Electrochemical method
Electrochemistry is the study of the interrelationship between electricity and chemical reaction science. Electricity and chemical reaction interaction can be completed through the battery, can also be realized using high-voltage electrostatic discharge, both collectively referred to as electrochemistry, the latter is a branch of electrochemistry, called discharge chemistry. In the treatment of aquaculture wastewater, the results of the study on the removal of dissolved nitrite and ammonia nitrogen in water by electrochemical method showed that the time and energy consumption for the complete removal of nitrite decreased with the increase of the conductivity, and the least energy was consumed when the input current was maximum 2A, and pH had almost no effect relative to the input current and the conductivity; the removal of nitrite was favored in the acidic condition, and the removal of ammonia was favored in the alkaline condition. Under acidic conditions, it is favorable for nitrite removal, and under alkaline conditions, it is favorable for ammonia removal, and the rate of ammonia removal is lower than the rate of nitrite removal.
3 Biological treatment method
1) Activated sludge method
Activated sludge method is the main biological treatment of wastewater with activated sludge as the main method. Activated sludge is a sludge-like floc formed after a certain period of time due to aerobic microbial reproduction by continuous air intake into the wastewater. It is inhabited by microorganisms mainly in the form of bacterial colloids, which have a strong ability to adsorb and oxidize organic matter.
The typical activated sludge process consists of an aeration tank, a sedimentation tank, a sludge return system and a residual sludge removal system.
The effluent and return activated sludge enter the aeration tank together to form a mixture. Compressed air sent from the air compressor station, through the air diffusion device laid at the bottom of the aeration tank, in the form of small bubbles into the sewage, the purpose is to increase the dissolved oxygen content in the sewage, but also to make the mixture in the state of violent agitation, the shape of the suspended state. Dissolved oxygen, activated sludge and sewage mixed with each other, full contact, so that the activated sludge reaction can be carried out normally.
In the first stage, the organic pollutants in the sewage are adsorbed by the activated sludge particles on the surface of the bacterial colloid, which is due to its huge specific surface area and polysaccharides viscous substances. At the same time, some large molecules of organic matter are decomposed into small molecules of organic matter under the action of bacterial extracellular enzymes.
The second stage, microorganisms in the oxygen-rich conditions, absorb these organic materials, and oxidative decomposition, the formation of carbon dioxide and water, part of the supply of their own proliferation. The result of the activated sludge reaction, the sewage organic pollutants are degraded and removed, the activated sludge itself is able to reproduce and grow, and the sewage is purified and treated.
After the activated sludge purification effect of the mixture into the secondary sedimentation tank, the mixture of suspended activated sludge and other solids in the precipitation here and the water separation, the clarified sewage as treated water discharged from the system. The settled and concentrated sludge is discharged from the bottom of the settling tank, most of which is returned to the aeration tank as inoculated sludge to ensure the concentration of suspended solids and microorganisms in the aeration tank; the proliferating microorganisms are discharged from the system and are called the "residual sludge". In fact, pollutants are largely transferred from the effluent to this residual sludge.
2) Biofilm method
Biofilm method is a type of aerobic biological treatment of wastewater alongside the activated sludge method. It is a stationary membrane method, which is an artificialization and enhancement of soil self-purification; it mainly removes dissolved and colloidal organic pollutants from wastewater. See more related technical documents.
The biofilm method is a method of organic wastewater treatment that utilizes microorganisms (i.e., biofilms) attached to and growing on the surface of certain solids. Biofilm is a highly dense ecosystem of aerobic bacteria, anaerobic bacteria, parthenogenic bacteria, fungi, protozoa, and algae, etc., and the solid medium to which it is attached is called the filter media or carrier. Biofilm from the filter media outward can be divided into celebratory layer, aerobic layer, attached water layer, movement water layer. The principle of the biofilm method is that the biofilm first adsorbs the organic matter in the attached water layer, which is decomposed by the aerobic bacteria in the aerobic layer, and then enters the anaerobic layer for anaerobic decomposition, and the flowing water layer flushes out the aging biofilm in order to grow a new biofilm, and so on in order to achieve the purpose of purifying the wastewater. Biofilm method has the following characteristics: (1) strong adaptability to changes in water quantity, water quality and water temperature; (2) good treatment effect and good nitrification function; (3) small amount of sludge (about 3/4 of the activated sludge method) and easy to separate the solid-liquid; (4) power cost savings.