A system for treating aquaculture wastewater

Abstract

This invention discloses a livestock wastewater treatment system. The livestock wastewater sequentially passes through a screen, sedimentation tank, wastewater recovery device, and anaerobic system before entering an ecological treatment system. The ecological treatment system is a treatment pond planted with water celery. The water in the treatment pond is mixed with the wastewater treated by the anaerobic system and then recycled. The volume ratio of wastewater entering the treatment pond to circulating water is 1:(5~30). The water celery in the treatment pond is planted at a spacing of 15~50cm and a planting density of 3~6kg / m². 2 The water in the treatment tank meets the following conditions: the water temperature is at least 5℃, the pH is 6.5~8.5, the ammonia nitrogen concentration is less than or equal to 300mg / L, and the COD is less than or equal to 1500mg / L; the treatment tank is supplemented with wastewater treated by the anaerobic system to ensure that the water in the treatment tank meets the above conditions.

Description

Technical Field

[0001] This invention relates to the field of aquaculture wastewater treatment technology, and specifically to an aquaculture wastewater treatment system. Background Technology

[0002] The discharge of wastewater from livestock and poultry farming is enormous and causes severe pollution. In 2010, the emissions of COD and ammonia nitrogen from livestock and poultry farming in my country were approximately three times and two times the emissions from industrial sources, respectively, accounting for 45% and 25% of the total pollutant emissions nationwide. Untreated discharge leads to excessive levels of heavy metals in the soil, pollutes the soil environment, and threatens the quality and safety of agricultural products. Manure contains parasite eggs and pathogens, which, once they enter water sources, can cause the spread of waterborne diseases, seriously threatening drinking water safety. The volatilization of nitrogenous and sulfurous substances in manure creates foul odors, severely polluting the atmosphere and harming human health. Current technologies for treating aquaculture wastewater typically involve separating the solids and liquids. This separated wastewater often exhibits high levels of COD, NH3-N, TP, and SS, making it extremely difficult to treat. Existing technologies generally employ traditional biological processes for this purpose, but pretreatment is necessary. This involves using various compounds to lower the wastewater's various indicators, ensuring that it doesn't negatively impact the microorganisms within the biological system upon entry, thus preventing mass mortality and ultimately affecting treatment efficiency. Furthermore, the control of these traditional biological systems is highly complex and difficult to manage in practice, easily causing adverse effects on the microorganisms and compromising treatment effectiveness. For example, patent CN116022967A provides a high COD livestock and poultry breeding wastewater treatment process. Although this patent can treat high-concentration COD wastewater, it can be seen from its technical solution that the patent still treats wastewater through multi-stage biological treatment tanks and sedimentation tanks, and further degrades COD, NH3-N, TP and SS through packing. The overall treatment system is very complex, and many parameters need to be adjusted in actual operation. Moreover, the large number of biological treatment tanks used makes the adjustment of them even more demanding. Summary of the Invention

[0003] In view of the above-mentioned shortcomings of the existing technology, the purpose of the present invention is to provide an aquaculture wastewater treatment system to solve the problems of the existing technology in treating aquaculture wastewater, which has high requirements for the wastewater entering the biochemical system, and the traditional biochemical system is very complicated to control and is very easy to have an adverse effect on the microorganisms in the biochemical tank.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A livestock wastewater treatment system comprises a system in which livestock wastewater sequentially passes through a screen, a sedimentation tank, a wastewater recovery device, and an anaerobic system before entering an ecological treatment system. The ecological treatment system is a treatment tank planted with water celery. The water in the treatment tank is mixed with the wastewater treated by the anaerobic system and then recycled. The volume ratio of wastewater entering the treatment tank to circulating water is 1:(5~30). The water celery in the treatment tank is planted at a spacing of 15~50cm and a planting density of 3~6kg / m². 2 ;

[0006] The influent to the treatment tank meets the following conditions: the water temperature is at least 5°C, the pH is 6.5~8.5, the ammonia nitrogen concentration is less than 500 mg / L, and the COD is less than or equal to 1800 mg / L.

[0007] The effluent from the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 100 mg / L, and COD less than or equal to 200 mg / L.

[0008] Preferably, the system also includes a fermentation system, wherein the solid obtained after the aquaculture wastewater is treated by a wastewater recycling device enters the fermentation system for fermentation and maturation.

[0009] Preferably, the wastewater recovery device includes an influent flow meter and a sludge concentration meter, and the dosage is automatically controlled by a dosing pump to allow the obtained solids to enter the fermentation system. Specifically, the control program is set to use the influent flow meter and sludge concentration meter to detect the influent flow rate and effluent concentration, and promptly feeds the detected data back to the control program. The control program then controls the dosing pump to adjust the dosage in real time, ensuring that the effluent concentration meets the influent requirements of the treatment tank.

[0010] Preferably, in the wastewater recovery device, the dosing concentration is 100~500ppm, so that the moisture content of the sludge is 80%~90%.

[0011] Preferably, when the height of water celery in the treatment tank is less than 18cm, the influent of the treatment tank meets the following requirements: ammonia nitrogen concentration less than or equal to 100mg / L and COD less than or equal to 500mg / L; the effluent of the treatment tank meets the following requirements: ammonia nitrogen concentration less than or equal to 30 mg / L and COD less than or equal to 150mg / L.

[0012] Preferably, when the height of the water celery in the treatment tank is higher than 18cm, the influent of the treatment tank meets the following requirements: ammonia nitrogen concentration less than or equal to 500mg / L and COD less than or equal to 1800mg / L; the effluent of the treatment tank meets the following requirements: ammonia nitrogen concentration less than or equal to 60mg / L and COD less than or equal to 150mg / L.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention, by combining water celery cultivation with wastewater treatment, unexpectedly discovered that the water celery in the treatment pond not only degrades wastewater but also provides some resistance to high-concentration wastewater. This significantly reduces the requirements for wastewater entering the treatment pond, thereby simplifying the operation of the entire wastewater treatment system, shortening the treatment process, and making operation more convenient. At the same time, it also significantly reduces treatment costs, and the water celery in the treatment pond can generate economic benefits. Thus, by combining it with livestock and poultry farming, it integrates pollution control and resource utilization, achieving resource utilization and increasing economic returns. Attached Figure Description

[0015] Figure 1 This is a flowchart of the aquaculture wastewater treatment system described in this invention. Detailed Implementation

[0016] This invention will describe the technical solutions of the embodiments of the invention clearly and completely. Obviously, the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on this invention are within the scope of protection of this invention.

[0017] Unless otherwise specified in the specific context, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined. The term "and / or" as used herein is inclusive; for example, "A and / or B" means either only A, or only B, or both A and B.

[0018] I. A wastewater treatment system for aquaculture

[0019] In this invention, such as Figure 1 As shown, the aquaculture wastewater sequentially passes through a screen, sedimentation tank, wastewater recovery device, and anaerobic system before entering the ecological treatment system. The ecological treatment system is a treatment tank planted with water celery. The water in the treatment tank is mixed with the wastewater treated by the anaerobic system and then recycled, with a wastewater-to-recycled water volume ratio of 1:(5~30). The water celery in the treatment tank is planted at a spacing of 15~50cm, with a planting density of 3~6kg / m². 2 .

[0020] The influent to the treatment tank meets the following conditions: the water temperature is at least 5°C, the pH is 6.5~8.5, the ammonia nitrogen concentration is less than 500 mg / L, and the COD is less than or equal to 1800 mg / L.

[0021] The effluent from the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 100 mg / L, and COD less than or equal to 200 mg / L.

[0022] In practice, water celery is cultivated hydroponically in the treatment tank, specifically via a floating bed. The sedimentation tank, equipped with a screen, provides initial filtration of the aquaculture wastewater. After filtration, the wastewater enters a wastewater recovery device for solid-liquid separation, primarily treating most of the manure residue. The treated wastewater then enters an anaerobic system, a biological treatment tank containing anaerobic microorganisms for further treatment. A fermentation system is also included; the solids from the wastewater recovery process are fermented and matured, with the resulting product used as fertilizer for other aquaculture operations. The sedimentation tank and anaerobic system can be designed using existing conventional techniques. The wastewater recovery device uses an influent flow meter and sludge concentration meter, and controls the dosage via a dosing pump to regulate the moisture content of the sludge, ensuring the treated solids are properly fermented. In the wastewater recovery device, the concentration of the added chemicals is 100-500 ppm, resulting in a sludge moisture content of 80%-90%. The added chemicals are flocculants and coagulants.

[0023] In some embodiments, the planting density of water celery can be considered as the amount of water celery seedlings used. The amount of water celery seedlings used in the treatment tank can be adjusted according to the season and planting method. The planting density is 3~6 kg / m². 2 It can be 3kg / m 2 4kg / m 2 5kg / m 2 6kg / m 2 And so on, as well as all ranges and subranges between the above values. If water celery is planted on a floating bed using stem or creeping stem planting methods, the seedling rate is preferably 5 kg / m² in spring and summer. 2 The preferred value for autumn and winter is 2.5 kg / m³. 2 If seedling planting is chosen, the optimal seed quantity for spring and summer is 3 kg / m². 2 The optimal weight for autumn and winter is 2kg / m³. 2 Regardless of the method used, the seedlings must be planted evenly on the floating bed and completely submerged in water, avoiding overlapping, tipping, or extending beyond the floating bed. This improves the survival rate of the water celery, allowing the treatment pond to treat wastewater more quickly. The amount of seedlings used also affects the treatment effect. Too few seedlings result in insufficient water celery in the pond, prolonging treatment time; too many seedlings lead to overcrowding, increasing competition and hindering growth. During the peak growth period, this can cause widespread death of water celery, further reducing the treatment effect.

[0024] In some embodiments, when the height of the water celery in the treatment tank is less than 18 cm, the growth state of the water celery in the treatment tank can be considered as the seedling stage. The parameters of the water in the treatment tank need to be adjusted so that the wastewater entering the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 100 mg / L and COD less than or equal to 500 mg / L, thus enabling the water celery to healthily pass through the seedling stage and enter the vigorous growth stage. During the seedling stage, the effluent from the treatment tank can achieve: ammonia nitrogen concentration less than or equal to 30 mg / L and COD less than or equal to 150 mg / L. When the height of the water celery in the treatment tank is greater than 18 cm, the height can reach 18-22 cm, or even greater than 22 cm. At this time, the water celery in the treatment tank can be considered to have entered the vigorous growth stage. At this time, the parameter requirements for the influent and the water in the treatment tank can be reduced so that the wastewater entering the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 500 mg / L and COD less than or equal to 1800 mg / L. During the vigorous growth period, the effluent from the treatment tank can achieve the following: COD less than or equal to 150 mg / L, and ammonia nitrogen concentration less than or equal to 60 mg / L. Furthermore, during the growth of water celery, the water in the treatment tank can be monitored to ensure it does not exceed the parameter range described in this invention, allowing for timely replenishment of wastewater and thus accelerating the wastewater treatment speed of the tank.

[0025] II. Examples and Comparative Examples

[0026] A pig farm with 100 pigs produces 2.5m³ of wastewater. 3 / d, adopting the conventional sedimentation tank anaerobic system design in existing technology, the wastewater recovery device is set with a dosing concentration of 300ppm, and the moisture content of the manure sludge discharged after treatment by the wastewater recovery device is designed to be 85%, combining water celery planting with livestock and poultry breeding. After treatment through identical sedimentation tanks, wastewater recovery devices, and anaerobic systems, the resulting wastewater is discharged to the treatment tanks of the examples and comparative examples for degradation treatment, and after meeting the degradation standards, it is discharged for recycling. The treatment tanks of the examples and comparative examples are independent of each other and do not affect each other. The treatment tanks used in the examples and comparative examples are both 0.5 acres in area, with 250m³ of water arranged in them. 2 Floating beds are used for plant cultivation. If no more than 30% of the planted area of ​​the plants in the treatment tank withers, the plants are considered to be in a normal growth state; if more than 30% of the planted area of ​​the plants in the treatment tank withers, the plants are considered to have growth problems and are unable to grow normally in the wastewater and treat the wastewater.

[0027] Example 1:

[0028] In this embodiment, the planting density of water celery is 3 kg / m². 2(The planting density refers to the amount of water celery seedlings used.) The seedlings are evenly planted on the floating bed. Subsequently, the wastewater treated by the anaerobic system is discharged into the treatment tank of this embodiment for further treatment. Based on the nutrient requirements during the seedling and vigorous growth stages, the concentration of nutrients entering the treatment tank is adjusted through a circulating water system. The growth height of the water celery in the treatment tank is measured. When the average height of the water celery planted in areas less than 50% is less than 18cm, it is in the seedling stage. The amount of wastewater entering the treatment tank is adjusted through the circulating water system to ensure that the ammonia nitrogen concentration in the treatment tank is 30-300 mg / L and the COD is less than or equal to 1500 mg / L. When the average height of the water celery planted in areas greater than 50% is more than 18cm, it is in the vigorous growth stage. At this time, the requirements for the wastewater parameters entering the treatment tank can be reduced, ensuring that the influent parameters meet the requirements of ammonia nitrogen less than 300 mg / L and COD less than or equal to 1500 mg / L.

[0029] The wastewater parameters entering the treatment tank in this embodiment are:

[0030] When the water celery is in the seedling stage, the influent parameters are COD 389 mg / L and ammonia nitrogen concentration 47 mg / L; at this time, within 10 days, the effluent parameters of the treatment tank are reduced to COD 104 mg / L and ammonia nitrogen concentration is reduced to 15 mg / L.

[0031] When water celery enters its vigorous growth period, the influent parameters are adjusted to COD of 1472 mg / L and ammonia nitrogen concentration of 289 mg / L. At this time, the effluent from the treatment tank can reach COD of 132 mg / L and ammonia nitrogen concentration of 59 mg / L within 20 days.

[0032] Example 2:

[0033] An improvement was made based on Example 1, the difference being that the planting density of water celery in the treatment tank was different; in this example, the amount of water celery seedlings used was 4 kg / m². 2 .

[0034] In Example 2, the water celery in the treatment tank did not show any growth problems, and similarly:

[0035] When the water celery is in the seedling stage, the influent parameters are COD of 489 mg / L and ammonia nitrogen concentration of 58 mg / L. At this time, within 10 days, the effluent from the treatment tank is reduced to COD of 114 mg / L and ammonia nitrogen concentration is reduced to 25 mg / L.

[0036] When the water celery enters its vigorous growth period, the influent parameters are adjusted to COD of 1497 mg / L and ammonia nitrogen concentration of 290 mg / L. At this time, within 20 days, the effluent from the treatment tank can reach COD of 102 mg / L and ammonia nitrogen concentration of 47 mg / L.

[0037] Example 3:

[0038] An improvement was made based on Example 1, the difference being that the planting density of water celery in the treatment tank was different; in this example, the amount of water celery seedlings used was 6 kg / m². 2 .

[0039] In Example 3, the water celery in the treatment tank did not show any growth problems. Similarly:

[0040] When the water celery is in the seedling stage, the influent parameters are COD of 494 mg / L and ammonia nitrogen concentration of 55 mg / L. At this time, within 10 days, the effluent from the treatment tank is reduced to COD of 91 mg / L and ammonia nitrogen concentration is reduced to 14 mg / L.

[0041] When water celery enters its vigorous growth period, the influent parameters are adjusted to COD of 1500 mg / L and ammonia nitrogen concentration of 295 mg / L. At this time, within 20 days, the effluent from the treatment tank can reach COD of 84 mg / L and ammonia nitrogen concentration of 31 mg / L.

[0042] Comparative Example 1:

[0043] An improvement was made to Example 1, the difference being that the planting density of water celery in the treatment tank was lower, and the amount of water celery seedlings used was 1 kg / m². 2 .

[0044] In this comparative example, the water celery in the treatment tank did not show any growth problems. However, due to the low planting density, the degradation rate of wastewater by the water celery in the treatment tank remained very slow even after it entered its vigorous growth period. Specifically:

[0045] When water celery is in the seedling stage, the influent parameters are COD 481 mg / L and ammonia nitrogen concentration 54 mg / L. At this time, it will take 15 days to reduce the effluent from the treatment tank to COD 134 mg / L and ammonia nitrogen concentration to 61 mg / L.

[0046] When the water celery entered its vigorous growth period, the influent parameters were adjusted to a COD of 1217 mg / L and an ammonia nitrogen concentration of 261 mg / L. At this point, it took 30 days for the effluent from the treatment tank to reach a COD of 345 mg / L and an ammonia nitrogen concentration of 76 mg / L. This shows that the degradation rate was far lower than in the previous example.

[0047] Comparative Example 2:

[0048] An improvement was made to Example 1, the difference being that the planting density of water celery in the treatment tank was higher, and the amount of water celery seedlings used was 10 kg / m². 2 .

[0049] In this comparative example, the water celery in the treatment tank experienced growth problems after entering its vigorous growth period, with over 50% of the planted area in the treatment tank withering. Specifically:

[0050] When the water celery is in the seedling stage, the influent parameters are COD of 491 mg / L and ammonia nitrogen concentration of 58 mg / L. At this time, the effluent from the treatment tank can be reduced to COD of 94 mg / L and ammonia nitrogen concentration of 16 mg / L within 10 days. The overall degradation rate is not much different from that in Example 3.

[0051] However, once the water celery entered its vigorous growth phase, a large area of ​​it withered in the treatment pond, reaching 65%, significantly reducing the wastewater treatment rate. At this point, the influent parameters were adjusted to a COD of 1500 mg / L and an ammonia nitrogen concentration of 291 mg / L. After 45 days, the effluent quality still only achieved a COD of 345 mg / L and an ammonia nitrogen concentration of 124 mg / L. During these 45 days of water quality measurements, it was also observed that while the degradation rate slightly increased after the water celery entered its vigorous growth phase, it significantly decreased as the withered area increased after growth problems occurred. The degradation rate only stopped decreasing once the withered area ceased to increase. This indicates that the planting density of water celery should not be too high during treatment.

[0052] Comparative Example 3:

[0053] An improvement was made based on Example 1, the difference being that instead of water celery, other plants with wastewater degradation effects, such as water hyacinth, were planted in the treatment tank, with the planting density being exactly the same as in Example 1.

[0054] In this comparative example, the wastewater entering Example 1 also enters the same treatment tank for treatment.

[0055] When water hyacinth is in the seedling stage, the influent parameters are the same as in Example 1, but it takes 15 days to reduce the parameters of the effluent from the treatment tank to COD of 130 mg / L and ammonia nitrogen concentration to 26 mg / L. This shows that water hyacinth has a slow wastewater treatment speed.

[0056] However, when the water hyacinth reached its peak growth period, the wastewater from the peak growth period of the water celery in Example 1 was discharged into the treatment pond. The water hyacinth exhibited significant growth problems; over 40% of the planted area of ​​water hyacinth withered, and the treatment effect on the wastewater was significantly reduced. After 20 days, the effluent from the treatment pond only achieved a COD of 345 mg / L and an ammonia nitrogen concentration of only 98 mg / L.

[0057] Example 4:

[0058] An improvement was made based on Example 1. The difference is that the anaerobic system was affected by the wastewater discharged from the wastewater recovery device, which reduced the treatment effect of the anaerobic system. As a result, wastewater with parameters of COD of 1781 mg / L and ammonia nitrogen concentration of 421 mg / L was discharged into the treatment tank for treatment. At this time, the water celery in the treatment tank was already in the vigorous growth period.

[0059] In this embodiment, after the high-concentration wastewater entered the treatment tank, the growth of water celery was not affected throughout the entire treatment process. At the same time, within 30 days, the COD of the effluent from the treatment tank was reduced to 130 mg / L and the ammonia nitrogen concentration was 96 mg / L, proving that the treatment tank of the present invention can withstand the impact of high-concentration wastewater and degrade it in a relatively short period of time.

[0060] Comparative Example 4:

[0061] An improvement was made based on Example 4, the difference being that the wastewater discharged from the anaerobic system was introduced into the treatment tank for treatment, in which water hyacinth was planted and kept in a healthy and vigorous growth period.

[0062] In this comparative example, the wastewater entering the treatment tank was the same wastewater that entered the treatment tank of Example 4. After this high-concentration wastewater entered the treatment tank, more than 47% of the water hyacinth plants withered, indicating that the plant could not withstand the impact of high-concentration wastewater. Furthermore, after 30 days, the parameters of the effluent from the treatment tank only reached COD of 407 mg / L and ammonia nitrogen concentration of 176 mg / L. It can be seen that the plant's treatment effect on high-concentration wastewater is poor, and the parameters of the wastewater in the treatment tank are still high, which also proves that the plant cannot complete the degradation of it in a short period of time.

[0063] During the treatment process described in the above embodiments, the water in the treatment tank, after the concentrations of COD and ammonia nitrogen have been reduced, can be reused for livestock and poultry farming; or, it can be mixed with wastewater treated by the anaerobic system and then recycled back into the treatment tank. The manure residue treated by the wastewater recycling device enters the fermentation system for fermentation and maturation, and can be sold as fertilizer or used to cultivate water celery for use in other treatment tanks.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. An aquaculture wastewater treatment system, characterized by, The aquaculture wastewater passes sequentially through a screen, sedimentation tank, wastewater recovery device, and anaerobic system before entering the ecological treatment system. The ecological treatment system is a treatment tank planted with water celery. The water in the treatment tank is mixed with the wastewater treated by the anaerobic system and then recycled, with a wastewater-to-recycle water volume ratio of 1:(5~30). The water celery in the treatment tank is planted at a spacing of 15~50cm and a planting density of 3~6kg / m². 2 ; Wherein, the seedling planting method is selected, and the seedling dosage is 3 kg / m 2 ; When the height of the water celery in the treatment tank is less than 18cm, the wastewater entering the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 100mg / L and greater than or equal to 47mg / L, and COD less than or equal to 500mg / L and greater than or equal to 389mg / L. After 10 days of treatment, the effluent from the treatment tank can achieve: ammonia nitrogen concentration less than or equal to 30mg / L and COD less than or equal to 150mg / L. When the height of the water celery in the treatment tank is greater than 18cm, the wastewater entering the treatment tank meets the following conditions: ammonia nitrogen concentration less than or equal to 500mg / L and greater than or equal to 289mg / L, and COD less than or equal to 1800mg / L and greater than or equal to 1472mg / L. After 20 days of treatment, the effluent from the treatment tank can achieve: COD less than or equal to 150mg / L and ammonia nitrogen concentration less than or equal to 60mg / L.

2. The aquaculture wastewater treatment system of claim 1, wherein, It also includes a fermentation system, in which the solids obtained after the aquaculture wastewater is treated by a wastewater recycling device are fermented and matured.

3. The aquaculture wastewater treatment system of claim 2, wherein, The wastewater recovery device includes an influent flow meter and a sludge concentration meter. The dosage is automatically controlled by a dosing pump so that the obtained solids enter the fermentation system. The wastewater recovery device controls the moisture content of the sludge to be between 80% and 90%.

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