Aquaculture wastewater biological treatment technology
1 China's aquaculture industry ranks first in the world, but its environmental protection measures lag behind Some coastal cities have many harbor areas, vast shallow beaches and rich marine life resources. At present, the mode of farming has been changed from the previous extensive and semi-intensive cultivation to intensive cultivation. However, the one-sided pursuit of economic benefits, over-breeding of aquaculture, and single breed of aquaculture have destroyed the balance of the natural ecological system in aquaculture water and seriously polluted itself. In addition, as the industrial waste water, domestic sewage disorder chaos, resulting in exogenous pollution of aquaculture water is also increasingly serious, frequent occurrence of aquaculture diseases. Currently, farmers use broad-spectrum antibiotics to control the occurrence of disease, but this is only a temporary solution because the use of antibiotics is not only highly residual, increases the resistance of bacteria, but also destroys the normal biological flora in aquaculture waters Balance, resulting in a vicious circle. 2 aquaculture wastewater characteristics Aquaculture wastewater main pollutants are ammonia nitrogen, nitrite, organic pollutants, phosphorus and fouling organisms. At present, some researches on fouling organisms in harbor and traditional cage aquaculture areas have been carried out in our country. Different from industrial and domestic sewage, aquatic fish sewage is a kind of low-concentration organic sewage with simple pollutant composition. The BOD generally does not exceed 80mg / L. However, aquatic organisms have higher requirements on water quality. Ammonia nitrogen and hydrogen sulfide are the most common harmful substances in the water of seedling raising. The concentration of ammonia nitrogen and hydrogen sulfide in water body gradually increases with the growth of seedling. Ammonia nitrogen is a waste of aquatic organisms, but also the remnants of bait, faeces and animal and plant dead bodies and other nitrogen-containing organic matter decomposition of the final product. Hydrogen sulfide is due to the sulfur-containing organic matter in hypoxic conditions, formed by the decomposition of anaerobic bacteria. Water quality and the bottom of the corrupt nature of the induced Vibrio and other pathogenic bacteria in large numbers, leading to disease; more due to ecosystem destruction and stocking density caused by the ecological imbalance caused by a combination of factors, aquatic resistance Reduce the force, resulting in more susceptible to pathogenic bacteria. 3 aquaculture wastewater treatment process Many domestic and foreign aquaculture wastewater treatment methods have been developed, including the physical, chemical and biofilm methods, salt-tolerant plant treatment, wetland treatment, sedimentation-shellfish filtration-algae adsorption comprehensive treatment. In addition, there are specific methods for the treatment of suspended particulates. 3.1 physical processing method According to the physical and chemical properties of pollutants in water bodies and bodies of water, aeration, filtration, sedimentation, adsorption and air flotation are adopted to purify water and remove suspended substances or harmful gases in water. 3.2 chemical treatment method Use chemical reactions to treat contaminants or suspended particles in water. Including flocculation, neutralization, complexation, redox, disinfection and other methods. 3.3 Biological methods The use of microorganisms and autotrophic plants (such as green algae, higher aquatic plants) to improve water quality helps to prevent the deterioration of water quality caused by the accumulation of bait and metabolites. 3.3.1 activated sludge method Activated sludge activated sludge by bacteria, protozoa and other components, common yeast, mold, Paramecium and so on. The law has a long history of application, principles, methods and technology have matured, applied to farming water treatment, nitrogen and phosphorus removal effect is better, but the law of large land, resulting in the sludge if not handled well will produce secondary Pollution, and high operating costs. The existing biological method, activated sludge method only in the case of low salinity has a more ideal effect, not suitable for the treatment of mariculture wastewater. 3.3.2 biofilm method Biofilm method with high efficiency, easy operation and so on. Different biofilm carrier, attached to the carrier on the growth of different microorganisms, the treatment of aquaculture wastewater is also different. At present, the use of UV disinfection, ozone generator, protein separator and biofilter 4 parts of the biofilm processing aquaculture system. Commonly used biological filters have submerged biological filter bed, trickling biological filter bed, biological turntable and so on. However, the biofilm method has some shortcomings such as weak impact resistance, easy to be contaminated, can not be reused many times, and has long running time, which can not be widely applied to the treatment of breeding sewage. Therefore, some researchers based on this to improve the study. For example, Wan Hong et al proposed a sequencing batch biofilm reactor with a combination of fillers as a carrier for treating aquaculture wastewater. Li et al. Also designed a composite membrane bioreactor (MBR) unit with powdered activated carbon (PAC) After activated sludge was acclimated, the sewage was treated by this device. Continuous operation for 100 days, membrane effluent COD was always stable below 25mg / L, NH3-N removal rate could reach more than 99%. PAC provided a good carrier for the adsorption growth of nitrifying bacteria and allowed it to breed well, thereby improving the ammonia nitrogen removal rate of the membrane bioreactor. He Jie et al. Screened bacteria were attached to sand, activated carbon and zeolite On the carrier, treatment of aquaculture wastewater, studies have shown that the biofilter of these three carriers on the aquaculture wastewater ammonia removal rate is similar. ] 3.3.3 Constructed wetlands Taking the landscape water body as the object of treatment, a multi-level artificial ecosystem for plant-floor floating bed eco-box-plantation floating bed eco-box-constructed wetland-submerged plant ecological box was constructed. Various species of plants, fish, snail, shrimp and the like were introduced into the system , And the system is operated in a circular flow mode, the average hydraulic retention time of the system is 2d, and the simulated landscape water 4.2d is exchanged once by the system. The results showed that the mean value of DO was 4.93 mg / L, NH4 + -N was 0.673 mg / L, TN was 17.303 mg / L and TP was 0.703 mg after the system reached stable operation. / L, COD average of 20.967mg / L. 3.3.4 Large algae Family Board Games,Strategy Board Games,Party Board Games,Adults Strategy Board Games NINGBO PAPER GAMES KINGDOM CO.,LTD , https://www.papergameskingdom.com