Economic and water purification efficiency gain type mariculture tail water treatment system and method

Abstract

The invention discloses an economic and water purification efficiency gaining type mariculture tail water treatment system and method.The system comprises a sedimentation tank, a biological purification tank and an ecological purification tank which are sequentially connected, salt-tolerant floating plant biological floating beds are arranged on the water surfaces of the sedimentation tank and the biological purification tank, oysters are bred below the salt-tolerant floating plant biological floating beds in the biological purification tank in a hanging mode, and the ecological purification tank is connected with the sedimentation tank. Algae seedlings are cultured in the ecological purification pond in a hanging manner. According to the invention, purification of tail water can be realized in a limited purification space by fully utilizing physical sedimentation in the sedimentation tank, nitrogen and phosphorus absorption, shading and heat insulation of floating plants, microbial mineralization and conversion of eutrophic substances in the physicochemical treatment tank, a filtering effect of functional organisms, an absorption effect of macroalgae in the biological purification tank and the like in a step-by-step and multi-layer manner.

Description

Technical Field

[0001] The invention relates to aquaculture tail water treatment system and method, and in particular to an economic and water purification efficiency gain type seawater aquaculture tail water treatment system and method. Background Art

[0002] Pond aquaculture is the main fishery production method in my country's inland and coastal tidal flats. With the reduction of wild fishery resources and the emergence of marine pollution, pond aquaculture has become the most stable and safest way to meet people's consumption needs for various aquatic products. However, with the development of the intensive trend of pond aquaculture, the pollution of aquaculture tail water has attracted more and more attention from all walks of life. The effective treatment of aquaculture tail water is not only related to the ecological safety of the water body in the surrounding areas of the aquaculture pond area, but also to the health and sustainable development of the aquaculture industry itself.

[0003] At present, with the improvement of relevant laws and regulations, tailwater discharge and treatment have become one of the main factors restricting aquaculture. Although there are many technical routes for tailwater treatment in China, from the perspective of economy and operation and maintenance, the ecological treatment of the pond dam model has the most application prospects. However, this type of treatment model has the problems of high land cost and insufficient treatment efficiency. For this reason, some people, based on the concept of resource reuse, propose to select functional organisms such as fish, shellfish, and algae with certain economic value to increase the treatment efficiency of the system while increasing income and reducing costs. However, they also face the problems of excessive fluctuations in the physical and chemical factors of the water body, resulting in high mortality rates of fish and shellfish, and low water transparency that cannot meet the algae's demand for light and the selected algae. The growth cycle is short, the economic value is low, and the suitable temperature and salinity range is narrow. In addition, data show that the settleable part of the main pollution indicators such as COD, nitrogen, and phosphorus in the newly discharged tailwater of the high-level pond accounts for 13.40%, 34.85%, and 50.46% respectively. If the removal of large-size particles can be achieved in the sedimentation stage, the treatment load of subsequent links can be greatly reduced, thereby improving the water quality of terminal drainage. Therefore, optimization of sedimentation design parameters, regulation of physical and chemical factors such as water temperature within the system, removal of suspended particles and improvement of transparency, as well as screening and cultivation management of excellent tool algae are the key to making up for the above-mentioned technical shortcomings. Summary of the invention

[0004] One of the purposes of the present invention is to provide an economical and water purification efficiency-enhanced marine aquaculture tailwater treatment system.

[0005] Specifically, the economic and water purification efficiency gain type seawater aquaculture tailwater treatment system provided by the present invention includes a sedimentation tank, a biological purification tank and an ecological purification tank connected in sequence, and a salt-tolerant floating plant biological floating bed is arranged on the water surface of the sedimentation tank and the biological purification tank. Oysters are suspended under the salt-tolerant floating plant biological floating bed in the biological purification tank, and algae seedlings are suspended in the ecological purification tank.

[0006] The coverage rate of the salt-tolerant floating plant biological floating bed set in the sedimentation tank is above 60%, so as to achieve the requirement of controlling the surface temperature of the water body within 35° C. Preferably, the coverage rate of the salt-tolerant floating plant biological floating bed set in the sedimentation tank is above 90%.

[0007] The sedimentation tank is provided with an overflow hole, which is a "∫" structure, with its water inlet 0.5 meters below the water surface and the water outlet above the water surface.

[0008] The coverage rate of the salt-tolerant floating plant biological floating bed set in the biological purification pool is above 40% to achieve the effect of properly regulating the water temperature.

[0009] The salt-tolerant floating plant is the seahorse tooth.

[0010] An oxygenation device is installed at the bottom of the biological purification tank.

[0011] The density of oysters suspended on rafts is 120 to 150 per m 2 , oyster specifications are above 20g / piece.

[0012] The density of algae seedlings in the ecological purification pool is 30 plants / m 2 The single plant specification is 15-20g / plant, and the breeding water depth is 20-80cm above the water surface.

[0013] The algae seedlings are selected from red ling seaweed. Red ling seaweed is a large algae that grows all year round. Its lower limit of tolerance to salinity is 13‰ and its upper limit of tolerance to temperature is 37℃. It can completely cover the aquaculture cycle and overcome the problems of large fluctuations in water salinity in the rainy season and easy decay of algae in high temperature periods.

[0014] The second object of the present invention is to provide an economical and water purification efficiency-enhanced method for treating marine aquaculture tail water.

[0015] Specifically, the economic and water purification efficiency gain type seawater aquaculture tail water treatment method provided by the present invention, the seawater aquaculture tail water enters the sedimentation tank, the biological purification tank and the ecological purification tank for treatment in sequence, wherein the water surface of the sedimentation tank and the biological purification tank is provided with a salt-tolerant floating plant biological floating bed, oysters are suspended under the salt-tolerant floating plant biological floating bed in the biological purification tank, and algae seedlings are suspended in the ecological purification tank.

[0016] The coverage rate of the salt-tolerant floating plant biological floating bed set in the sedimentation tank is above 60%, so as to achieve the requirement of controlling the surface temperature of the water body within 35° C. Preferably, the coverage rate of the salt-tolerant floating plant biological floating bed set in the sedimentation tank is above 90%.

[0017] The sedimentation tank is provided with an overflow hole, which is a "∫" structure, with its water inlet 0.5 meters below the water surface and the water outlet above the water surface.

[0018] Furthermore, the hydraulic retention time of marine aquaculture tail water in the pond should be controlled at more than 24 hours. After 24 hours of static sedimentation, indicators such as COD, total nitrogen and total phosphorus in the middle and upper tail water tend to be stable. Therefore, the design of the sedimentation tank should be based on the flow rate during the drainage cycle of the aquaculture pond, that is, its volume must ensure that the hydraulic retention time of the tail water in the sedimentation tank is more than 24 hours, that is, its design standard should be based on volume rather than area.

[0019] The coverage rate of the biological floating bed of salt-tolerant floating plants in the biological purification pool is above 40% to achieve the function of properly regulating the water temperature. The salt-tolerant floating plants are seahorses.

[0020] An oxygenation device is installed at the bottom of the biological purification tank to control the dissolved oxygen in the water to no less than 4.0 mg / L.

[0021] Furthermore, the hydraulic retention time of marine aquaculture tail water in the pond needs to be more than 12 hours to ensure that the transparency of the water body reaches more than 1 meter when flowing out of the pond.

[0022] The density of oysters suspended on rafts is 120 to 150 per m 2 , oyster specifications are above 20g / piece.

[0023] The density of algae seedlings in the ecological purification pool is 30 plants / m 2 The single plant specification is 15-20g / plant, and the breeding water depth is 20-80cm above the water surface.

[0024] Choose red ling algae seedlings.

[0025] Beneficial effects of the present invention:

[0026] The present invention provides a solution for treating tail water from aquaculture in seawater ponds, which effectively solves the problems of unclear design standards for sedimentation tanks, high water temperature, low survival rate of shellfish in purified water, and lack of excellent tool algae. It ultimately greatly improves the working efficiency of the treatment system, reduces land occupation, and significantly increases economic output, thereby achieving a balance between economic and ecological benefits.

[0027] The present invention is based on the traditional pond and dam treatment model, and focuses on solving the technical points such as the regulation of physical and chemical conditions in sedimentation tanks, the removal of suspended particles and the improvement of transparency in biological purification tanks, and the cultivation and management of large algae in ecological purification tanks. The regulation of physical and chemical factors in sedimentation tanks is achieved by selecting the salt-tolerant floating plant Hippocampus to construct a floating bed on the water surface, and utilizing its characteristics of absorbing nitrogen and phosphorus and shading and heat insulation. By adjusting its coverage rate, the water temperature and microalgae biomass of the water body are maintained at an appropriate level to ensure the requirements of functional organisms for feeding and living water temperature in the next treatment link. The removal of suspended particles and the improvement of transparency in biological purification tanks are aimed at achieving sufficient purification of microalgae and suspended particles by optimizing the matching relationship between the hydraulic load of tailwater, the oxygenation intensity and the amount of functional organisms such as oysters and scallops, and significantly improving the transparency of the water body while achieving the removal of microalgae and particles in the tailwater. The technical key points of the cultivation and management of large algae in ecological purification ponds are to design appropriate hanging culture methods to ensure that the red ling seaweed, a large algae with a long growth period, strong adaptability to salinity and temperature fluctuations, high economic value and great development potential, can deeply absorb soluble nitrogen, phosphorus and other eutrophic substances in the water, and ultimately achieve full purification of the aquaculture effluent.

[0028] The present invention can effectively integrate the above three technical links to fully utilize the physical sedimentation in the sedimentation tank, the nitrogen and phosphorus absorption and light-shielding and heat-insulating of floating plants, the microbial mineralization and transformation of nutrient-rich substances in the physical and chemical treatment tank, the filtering effect of functional organisms such as filter-feeding shellfish, and the absorption effect of large algae such as red winged algae in the biological purification tank to purify the tail water step by step and at multiple levels in a limited purification space. This model greatly improves the treatment efficiency of the pool dam water purification system. The use of filter-feeding shellfish biological filtration can effectively avoid the problems of filter material blockage and pollutant re-release in physical filtration. At the same time, the timely fishing and harvesting of functional organisms such as shellfish and red winged algae can also achieve the effect of increasing production and income, subsidizing the cost of tail water treatment, and resource utilization of pollutants in tail water to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the marine aquaculture tailwater treatment system.

[0030] Figure 2 This is a schematic diagram of the red ling vegetable cultivation frame;

[0031] 51 fixing frame, 52 plastic mesh, 53 algae seedlings.

[0032] Figure 3 The floating bed coverage rate regulates water temperature.

[0033] Figure 4 This shows the growth of red lily under different salinities.

[0034] Figure 5 This shows the growth of red lingcai under different temperatures.

[0035] Figure 6 This is the changing trend of total nitrogen in the sedimentation tank.

[0036] Figure 7 This is the changing trend of total phosphorus in the sedimentation tank.

[0037] Figure 8 COD change trend in the sedimentation tank. DETAILED DESCRIPTION

[0038] The present invention is further described below through the following specific implementation modes, but the content of the present invention is not limited thereto at all.

[0039] The marine aquaculture tailwater treatment system comprises a sedimentation tank 1, a biological purification tank 2 and an ecological purification tank 3 which are connected in sequence. The volume ratio of the sedimentation tank 1, the biological purification tank 2 and the ecological purification tank 3 can be set to 55:20:35.

[0040] The volume of the sedimentation tank 1 should be determined based on the flow rate during the drainage cycle of the aquaculture pond, and its volume is required to ensure that the hydraulic retention time of the tail water in the sedimentation tank 1 is more than 24 hours, that is, its design standard should be based on volume rather than area. An overflow hole 4 is set on the upper part of the side wall of the sedimentation tank 1 on the side connected to the biological purification tank 2. It is a "∫" structure, with its water inlet 0.5 meters below the water surface and the water outlet above the water surface.

[0041] After 24 hours of static sedimentation, the COD, total nitrogen and total phosphorus in the middle and upper tailwater of the aquaculture pond drainage tended to be stable.

[0042] A seahorse tooth biological floating bed 7 is set on the surface of the sedimentation tank 1. Experiments have shown that when the coverage rate of the floating bed is 0%, 30%, 60% and 90%, respectively, its regulating effect on water temperature gradually increases, and the peak water temperatures are 38.28℃, 36.24℃, 35.18℃, and 33.19℃, respectively. When the floating bed covers 30%, 60% and 90%, the peak water temperature decreases by 5.35%, 8.11% and 13.30%, respectively. Among them, the floating bed coverage rate is 90%, which ensures that the water temperature is always below 35℃ all day (see Figure 2 ). The water temperature data at different coverage rates at different time points are shown in the following table. Statistical analysis shows that different floating bed coverage rates and detection time have significant effects on water temperature.

[0043] Table 1 Water temperature at different coverage rates at different time points

[0044]

[0045] Note: Different capital letters represent significant differences in water temperature at different time points with the same coverage (P<0.05); different lowercase letters represent significant differences in water temperature at different coverages at the same time (P<0.05).

[0046] Therefore, the seahorse tooth biological floating bed 7 covers more than 90% of the water surface of the sedimentation tank. In addition to enhancing the absorption of soluble nitrogen and phosphorus, it can stabilize the upper temperature of the water body below 32°C during the high temperature period, thereby ensuring the water temperature requirements of the water-purifying shellfish (Omi oysters) in the biological purification pool treatment link, thereby solving the main cause of shellfish death, which is the summer survival.

[0047] The water depth of the biological purification pool 2 is not less than 1.5 meters. A seahorse tooth biological floating bed 7 is set on the water surface. A hanging cage 6 is set under the floating bed. The density of hanging oysters with a specification of 20g or more is 120 to 150 pieces / m 2 . An aerator is installed at the bottom of the pool to oxygenate the pool water and ensure that the dissolved oxygen is not less than 4.0 mg / L. The seahorse tooth biological floating bed 7 laid on the surface of the pool has a coverage rate of about 40% to achieve the effect of properly regulating the water temperature. The hydraulic retention time in the pool must be controlled to be more than 12 hours to ensure the removal of suspended particles in the water body and the transparency of the water outflow from the pool reaches more than 1m. After the oysters grow to commercial specifications, they are harvested and sold to generate income, and then replenished with shellfish seedlings to ensure the water purification efficiency of the purification pool.

[0048] In the ecological purification pool 3, red wing algae 53 is cultivated by cultivation frames 5. Red wing algae is a large algae that grows all year round. Its lower limit of tolerance to salinity is 13‰ and its upper limit of tolerance to temperature is 37℃, which can completely cover the aquaculture cycle. At the same time, it can overcome the problems of large fluctuations in water salinity in the rainy season and easy decay of algae in high temperature periods. The algae seedlings are suspended in the water in a special cultivation frame and arranged throughout the pool. The density of the algae seedlings is 30 plants / m 2 The single plant size is 15-20g / plant, and the culture depth is 20-80cm above the water surface. When the red winged vegetable grows in large quantities, it can be harvested at an appropriate time and can be used as abalone and other shellfish feed or sent to factories to extract carrageenan and other products to achieve economic benefits. Figure 2 As shown, the culture frame 5 includes a rectangular frame 51 , which is fixed with two upper and lower plastic nets 52 , and the red wing algae seedlings are fixed between the two plastic nets 52 .

[0049] Solieria (formerly known as Pacific Solieria) belongs to the genus Solieria, family Solieriaceae, order Gigartinales, Rhodophyta. It grows on shells or gravels on the mud bottom of mid-tidal to low-tidal zones or clear ponds. It is mainly distributed in Guangdong and Hainan provinces in China. Solieria species resources have very high economic and ecological value and can be used as food, raw materials for extracting carrageenan and phycoerythrin, abalone feed, green aquaculture, and aquaculture tailwater treatment tool. As a tool for aquaculture effluent treatment, it has several advantages: 1) strong water purification ability, excellent nitrogen and phosphorus removal effect on eutrophic water bodies; 2) fast growth and long growth cycle, in general months, the fresh weight can increase by 0.2kg / day per square meter; 3) simple breeding model, low cost, easy to promote, high efficiency of expansion; 4) good processing characteristics and great economic potential, can be developed into special meal pre-prepared dishes, functional beverage additives or as high-quality raw materials for phycobiliprotein and carrageenan extraction. It is estimated that under the premise of completing relevant technology research and development and industrial layout, the medium- and long-term unit annual output value of red lingcai can reach 15,000 to 20,000 yuan / mu. In addition, relevant salinity and temperature adaptability tests have shown that the suitable salinity range for red lingcai is 15‰ to 35‰ ( Figure 4 ), can grow well at water temperatures between 17°C and 33°C ( Figure 5 ), can withstand temperatures as high as 40°C, is suitable for a wide range of salinity and temperature, and is fully adapted to the large fluctuations in salinity and temperature in tailwater treatment ponds and canals.

[0050] Experiment on the adaptability of red lingonberry to salinity

[0051] The relative growth rate was analyzed based on the state of the algae fourteen days after the experiment. When the salinity was 10‰, there were no new branches and buds in the algae, the overall color of the algae became lighter, some tissues of the algae were soft and rotten, and the osmotic pressure was unbalanced. Due to the hollow characteristics of the algae of the red ling seaweed, seawater may have infiltrated the interior, and the initial experimental algae amount was about 1.4g, which led to a high numerical value of the experimental result and a certain experimental error. When the salinity was 15‰, new buds sprouted from the algae. The salinity may be low, and the osmotic pressure effect occurred, and the cells absorbed external water, resulting in a high relative growth rate. When the salinity was 20‰-30‰, the color of the algae was normal, and there were many branches and buds. The branches and buds of the algae at 20‰ salinity were dense but small. The branches and buds of the algae at 25‰ and 30‰ salinities were thicker and longer than those at 20‰, but the new branches and buds of the algae at 30‰ were sparser. When the salinity was 35‰, the growth was slower than that at 15‰-30‰, and the new branches and buds were thinner and shorter. Based on this experiment, the salinity range that the red ling seaweed can adapt to is 15‰-35‰, and the salinity of 25‰ is the most suitable ( Figure 4 ).

[0052] Experiment on temperature adaptability of red lingcai

[0053] Select healthy and non-rotten complete red ling seaweed of about 1g, carefully remove foreign matter on the seaweed, record the actual initial weight of the seaweed, and place it in a 1L plastic bottle in a constant temperature incubator for culture. The culture conditions are: light 5000Lx, salinity 25, L:D=12h:12h, set 6 temperature gradients (10℃, 15℃, 20℃, 25℃, 30℃ and 35℃), and set 3 parallel experiments in each group. The sterilized seawater was changed once a day, and the weight of the seaweed was measured and its various physiological indicators were tested for seven days of culture, and the changes in physiological indicators of the seaweed under different temperature stress were compared. The results showed that the red ling seaweed showed small branches at 10℃, and the weight of the seaweed decreased during the experiment; the morphology of the seaweed remained basically unchanged at 15℃, and the weight increased slightly; there were different degrees of growth at 20℃, 25℃, 30℃ and 35℃, among which the growth was the fastest at 30℃, and the average daily relative growth rate could reach about 5%. This experiment shows that the lowest water temperature that red lingcai can adapt to is around 15℃, the most suitable water temperature for growth is around 30℃, and the high temperature it can tolerate is above 35℃.

[0054] Experiment on sedimentation characteristics of aquaculture tail water

[0055] The water samples collected from sedimentation tank 1 were tested for tailwater settling efficiency.

[0056] The main pollution indicators of the upper water body of the tailwater of the high-position aquaculture pond were measured after different static times. The results showed that total nitrogen, total phosphorus and chemical oxygen demand (COD) all decreased significantly over time (P<0.05). Among them, the final decrease of total nitrogen after 48 hours of static was about 34.85%, but its decrease rate dropped sharply after 12 hours ( Figure 6 ); the total phosphorus decreased by 47.74% in the 6th hour, and there was no significant decrease thereafter ( Figure 7 ); The final decrease of COD was 13.40%, and its decrease rate also dropped significantly after 12 hours ( Figure 8 ). From the above data, it can be seen that sedimentation treatment has a relatively outstanding treatment effect on total phosphorus, COD and total nitrogen, and the reduction range after 48 hours of standing can reach 34.85% to 47.74%. However, from the perspective of optimizing the actual treatment efficiency, the optimal standing time should be 12 hours, at which time the reduction range of the above three major pollutants can reach between 27.10% and 48.92%.

[0057] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. An economic and water purification efficiency gain type marine aquaculture tailwater treatment system, comprising a sedimentation tank, a biological purification tank and an ecological purification tank connected in sequence, characterized in that: A salt-tolerant floating plant biological floating bed is arranged on the water surface of the sedimentation tank and the biological purification tank, oysters are cultured under the salt-tolerant floating plant biological floating bed in the biological purification tank, and algae seedlings are cultured in the ecological purification tank.

2. The economic and water purification efficiency gain type marine aquaculture tailwater treatment system according to claim 1 is characterized in that: The coverage rate of the salt-tolerant floating plant biological floating bed arranged in the sedimentation tank is above 60%.

3. The economic and water purification efficiency gain type marine aquaculture tailwater treatment system according to claim 1 is characterized in that: The coverage rate of the salt-tolerant floating plant biological floating bed arranged in the sedimentation tank is above 90%.

4. The economic and water purification efficiency gain type marine aquaculture tailwater treatment system according to claim 1 is characterized in that: The sedimentation tank is provided with an overflow hole, which is a "∫" structure, with its water inlet being 0.5 meters below the water surface and the water outlet being located above the water surface.

5. The economic and water purification efficiency gain type marine aquaculture tailwater treatment system according to claim 1 is characterized in that: The coverage rate of the salt-tolerant floating plant biological floating bed in the biological purification pool is above 40%; an oxygenation device is arranged at the bottom of the biological purification pool; the density of the suspended oysters is 120 to 150 oysters / m 2 The oyster size is 20g / piece or more; the density of algae seedlings in the ecological purification pool is 30 plants / m 2 The single plant specification is 15-20g / plant, and the breeding water depth is 20-80cm above the water surface.

6. The economic and water purification efficiency gain type marine aquaculture tailwater treatment system according to claim 1 is characterized in that: The salt-tolerant floating plant is seahorse teeth, and the algae seedlings are red lingonberry.

7. An economic and water purification efficiency gain type marine aquaculture tail water treatment method, the marine aquaculture tail water enters the sedimentation tank, biological purification tank and ecological purification tank for treatment in sequence, and its characteristics are: A salt-tolerant floating plant biological floating bed is arranged on the water surface of the sedimentation tank and the biological purification tank, oysters are cultured under the salt-tolerant floating plant biological floating bed in the biological purification tank, and algae seedlings are cultured in the ecological purification tank.

8. The economic and water purification efficiency gain type marine aquaculture tail water treatment method according to claim 7 is characterized by: The coverage rate of the salt-tolerant floating plant biological floating bed arranged in the sedimentation tank is above 60%; the sedimentation tank is provided with an overflow hole, which is a "∫" structure, with its water inlet 0.5 meters below the water surface and the water outlet located above the water surface.

9. The economic and water purification efficiency gain type marine aquaculture tail water treatment method according to claim 7 is characterized by: The hydraulic retention time of the seawater aquaculture tail water in the sedimentation tank should be controlled to be more than 24 hours.

10. The economic and water purification efficiency gain type marine aquaculture tail water treatment method according to claim 7 is characterized by: The coverage rate of the salt-tolerant floating plant biological floating bed in the biological purification pool is above 40%; an oxygenation device is arranged at the bottom of the biological purification pool to control the dissolved oxygen in the water to be no less than 4.0 mg / L; the hydraulic retention time of the seawater aquaculture tail water in the biological purification pool must be above 12 hours; the density of the suspended oysters is 120 to 150 oysters / m 2 The oyster size is 20g / piece or more; the density of algae seedlings in the ecological purification pool is 30 plants / m 2 The single plant specification is 15-20g / plant, and the breeding water depth is 20-80cm above the water surface.

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