with the continuous development of aquaculture industry, a large number of aquaculture wastewater is discharged, which causes serious water pollution and brings a series of environmental protection problems. aquaculture pollution has become the third major source of pollution after industrial pollution and domestic pollution, and one of the main causes of water pollution in china. if the pollution from these farms can not be handled in time, it will cause great harm to the environment, resulting in the deterioration of the ecological environment, the decline of the quality of aquatic products and endangering human health.
during a visit to some farms, it was found that the water environment would deteriorate rapidly due to various reasons. the harmful substances such as residual bait and feces remained in the aquaculture pond. the algae were unstable, ammonia nitrogen and nitrite content increased, and the water surface was full of foam and slow feeding. excessive ammonia nitrogen in water has a great influence on the catalysis of enzymes and the stability of cell membranes in shrimp, and destroys the excretion system and osmotic balance, resulting in excessive activity or convulsion, loss of balance and lack of vitality of shrimp. high concentration of nitrite can oxidize ferrous hemoglobin (blue) protein in fish and shrimp blood into ferrous hemoglobin (blue) protein, which can not carry oxygen, inhibit the oxygen carrying capacity of blood, resulting in hypoxia, low feeding capacity and even death of fish and shrimp.
the current aquaculture mode is still the aquaculture mode in the 1970s (water intake aquaculture pond drainage). with the continuous expansion of the scale of aquaculture, the number of aquaculture is also increasing, leading to a large number of feeding and animal excrement in the water body accumulated for a long time, not only polluted the water in the aquaculture pond, but also seriously affected the nutrient level of nearby waters with the discharge. the untreated aquaculture wastewater contains a lot of organic pollutants, suspended substances and nutrients such as nitrogen and phosphorus. direct discharge into nearby waters may not only lead to eutrophication, but also cause the gradual death of aquatic organisms sensitive to organic pollutants. in serious cases, the water body will be black and smelly, resulting in persistent organic pollution.
however, compared with other pollution, aquaculture wastewater can be recycled, and some treatment technologies of aquaculture wastewater pollution have emerged as the times require. most industrial aquaculture in foreign countries use biological rotating disc, biological contact tank, biological filter, mechanical filter device to extract pollutants from aquaculture wastewater. with the continuous development of aquaculture sewage treatment technology is also constantly improving and improving. at present, there are two main types of ecological restoration technologies for aquaculture ponds:
1. in-situ remediation technology, also known as three-dimensional remediation, is mainly used to plant plants in the upper layer of the water body, to put shellfish and other aquatic animals in the lower layer of the water body, to promote the multi-level utilization of nutrients in the pond, and so on. it is generally applied to the soil pond of the symbiotic aquaculture mode.
2. ectopic remediation technology, also known as plane remediation, mainly discharges aquaculture wastewater from ponds. firstly, it filters feces, baits and other impurities in water through physical filtration equipment. then, it is treated by microbial bacterial agent to decompose harmful substances such as ammonia nitrogen and nitrite dissolved in water. finally, it discharges water into rivers to achieve zero pollution or after sterilization. re-pumping into aquaculture ponds to achieve zero emissions and realize the recycling of aquaculture water.
zero-pollution and zero-emission circular aquaculture mode can control from the source, which can play a very good role in environmental restoration. but the cost must be considered in the actual production. laboratories are used to treat aquaculture wastewater, only considering the treatment effect. in production, the use cost of aquaculture wastewater treatment should be considered. the harmless treatment of aquaculture wastewater can not avoid generating additional economic costs and occupying land resources. sewage treatment equipment also has some shortcomings, such as large investment, high energy consumption, high operating costs, and need to be managed by specialized technicians. therefore, we should not only consider the technical advantages of a treatment method, but also consider the investment, daily operating costs and operation convenience of this method.
on may 31, 2017, the state council issued the opinions of the general office of the state council on accelerating the resource utilization of livestock and poultry breeding wastes. in addition to self-construction and joint establishment of sewage treatment equipment, the state council can also introduce third-party treatment, establish polluter payment, professional corporate governance and government-led pollution control. in view of the attention and regulation of environmental protection in domestic industries this year, it is believed that the pollution prevention and control regulations in aquaculture will be promulgated soon.
under the environment protection policy, how will the aquaculture model develop in order to form an eco-aquaculture economy suitable for production development and environmental carrying capacity? this requires more exploration to integrate laboratory and aquaculture farm.
source: polaris water treatment network
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