A method for treating aquaculture wastewater using aquatic plants

Abstract

The present invention relates to a method for treating wastewater from a farm using aquatic plants, belonging to the field of sewage treatment. The present invention uses Myriophyllum verticillatum to treat the wastewater from the farm. Myriophyllum verticillatum seeds are selected and cultured with digested sludge as the culture medium to obtain Myriophyllum verticillatum seedlings. The Myriophyllum verticillatum seedlings are sprinkled into the pig farm sewage to grow, and the growth cycle is 2 to 3 months. Myriophyllum verticillatum grows well in the wastewater. After the sewage is treated by the method of the present invention, the water body is clear and the odor disappears. The removal rates of the main pollutants COD, TN, TP, and NH3-N are above 80%.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and particularly relates to a method for treating aquaculture wastewater by using aquatic plants. Background Art

[0002] Submerged plants refer to aquatic plants that maintain their survival entirely below the water surface, including Hydrilla, Vallisneria, Myriophyllum, Ceratophyllum, Chara coronata, etc. They are usually fixed to the underwater sediment by roots, root hairs or thalli, and their leaves also grow underwater. Submerged plant roots are usually underdeveloped, and the epidermal cells of the plant body do not have a cutin or wax layer, which can directly absorb water, oxygen and nutrients. They are widely used in water purification in fields such as river regulation and aquaculture wastewater treatment, and have important practical significance for improving the water ecological environment.

[0003] In recent years, large-scale pig farming has developed rapidly, and the concentrated discharge of aquaculture wastewater has caused very prominent environmental problems. Research shows that at least 6 - 7 hm 2 of land is required to absorb the manure water of a 10,000 - head pig farm. When treating sewage with aquatic plants propagated by traditional methods, the expected effect is often not achieved. Moreover, the aquatic plants propagated by traditional propagation methods often have a high usage cost and cannot well adapt to growing in sewage. Therefore, there is an urgent need to develop a method for efficiently treating wastewater by using aquatic plants. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for treating aquaculture wastewater by using aquatic plants, and the specific scheme is as follows:

[0005] A method for treating aquaculture wastewater by using aquatic plants, which selects Myriophyllum seeds and cultivates them with digested sludge as a culture medium to obtain Myriophyllum seedlings, and then sprinkles the Myriophyllum seedlings into the aquaculture sewage to grow, with a growth cycle of 2 - 3 months.

[0006] Furthermore, the method for cultivating Myriophyllum seeds with digested sludge as a culture medium in the present invention is:

[0007] (1) Soak Myriophyllum seeds in a 3% - 5% hydrogen peroxide solution for 5 - 10 minutes, fish them out and soak them in clear water for 1 - 3 minutes, drain the clear water and use it for sowing and seedling raising; spread the treated seeds on a tray, cover them with 5 - 6 mm thick fine sand, add 1 - 1.5 cm deep clear water, and place them in a constant temperature incubator for light cultivation;

[0008] (2) Use digested sludge as the culture medium, reduce the water content of the sludge to 40%-50%, and evenly spread the Myriophyllum verticillatum seeds in the culture container filled with digested sludge. The seeding density of the Myriophyllum verticillatum seeds is 300-350 seeds / m 2 ; when the Myriophyllum verticillatum seedlings grow to 0.5-1 cm, adjust the water depth to 5-6 cm and cover with a plastic film; when the seedlings grow to 8-10 cm, increase the water depth to 15-20 cm, culture for 40-50 days, and obtain Myriophyllum verticillatum seedlings when the seedling height grows to 15-20 cm.

[0009] Furthermore, the organic matter content of the digested sludge culture medium is 20%-25%, the total nitrogen is 1.5%-2%, the total phosphorus is 1.5%-2%, the total potassium is 0.8%-1%, and the total nutrient content (N+P 2 O 5 +K 2 O) is greater than 4%, the pH is 6-9, and the salt content is less than 0.2%.

[0010] Furthermore, the planting density of the Myriophyllum verticillatum seedlings in the wastewater is 16-20 plants / m 2 .

[0011] The COD concentration of the sewage treated by the present invention is 100-1000 mg / L, the TN concentration is 200-1000 mg / L, the TP concentration is 10-50 mg / L, and the NH 3 -N concentration is 100-500 mg / L.

[0012] Preferably, the COD concentration of the sewage treated is 100-800 mg / L, the TN concentration is 200-800 mg / L, the TP concentration is 10-40 mg / L, and the NH 3 -N concentration is 100-400 mg / L.

[0013] Preferably, the COD concentration of the sewage treated is 300-600 mg / L, the TN concentration is 300-600 mg / L, the TP concentration is 20-30 mg / L, and the NH 3 -N concentration is 200-300 mg / L.

[0014] Preferably, the COD concentration of the sewage treated is 600 mg / L, the TN concentration is 600 mg / L, the TP concentration is 30 mg / L, and the NH 3 -N concentration is 300 mg / L.

[0015] Furthermore, when the Myriophyllum verticillatum in the wastewater grows to 50 cm-60 cm, it is harvested and used for covering orchards and bare ground surfaces.

[0016] The present invention achieves beneficial effects compared with the prior art in that:

[0017] The method for rapidly propagating Myriophyllum verticillatum seeds of the present invention can reproduce commercial seedlings of Myriophyllum verticillatum at low cost, rapidly and in large quantities; at the same time, it can make full use of the nutrients in the aquaculture wastewater as much as possible, not only reducing the treatment cost but also purifying the water quality, achieving a win-win goal. The present invention uses sludge to cultivate Myriophyllum verticillatum seedlings to further enhance the ability of Myriophyllum verticillatum to purify wastewater. The bottom mud is the basis for the growth of Myriophyllum verticillatum and also the main source of its growth nutrients, which has a great impact on the growth and development and community construction of Myriophyllum verticillatum. Increasing the organic matter can stimulate the growth of Myriophyllum verticillatum. The Myriophyllum verticillatum seedlings cultivated with the bottom mud can well adapt to the sewage environment, effectively reduce the concentration of water body nutrients, create a microecological environment for rhizosphere microorganisms, and achieve denitrification through ammonification-nitrification-denitrification. Through experimental verification, it is found that the cultivated Myriophyllum verticillatum grows well in the wastewater. After the experiment, the water body is clear and the odor disappears. The removal rates of the main pollutants COD, TN, TP, and NH 3 -N are above 80%, and the water body basically meets the "Pollutant Discharge Standard for Livestock and Poultry Industries" (GB18596-2001). Description of the Drawings

[0018] Figure 1 Average rooting rate of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0019] Figure 2 Average number of rooting cuttings of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0020] Figure 3 Average plant height of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0021] Figure 4 Average dry weight per plant of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0022] Figure 5 Average removal rate of wastewater COD of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0023] Figure 6 Average removal rate of wastewater TN of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0024] Figure 7 Average removal rate of wastewater TP of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0025] Figure 8 Average removal rate of wastewater NH 3 -N of Myriophyllum verticillatum seedlings cultivated with different substrates after growing in the wastewater pool for 60 days;

[0026] Figure 9 Average Cu removal rate of Myriophyllum spicatum seedlings cultured in different substrates after growing in the wastewater pond for 60 days;

[0027] Figure 10 Average Zn removal rate of Myriophyllum spicatum seedlings cultured in different substrates after growing in the wastewater pond for 60 days. Specific implementation manners

[0028] The present invention will be described in detail below with reference to specific embodiments. The embodiments are only used to understand the present invention and do not limit the scope of the present invention.

[0029] Example 1

[0030] Growth study of different aquatic plants in the wastewater storage pond

[0031] By comparing the growth conditions of three different types of aquatic plants, Myriophyllum spicatum, Oenanthe javanica, and Acorus tatarinowii, the seedlings of the three plants were cultivated in the wastewater storage pond at a depth of 5 - 10 cm. The planting densities of different aquatic plants are shown in Table 1, and the growth period is 60 days. The wastewater concentration in the wastewater storage pond is COD 500 - 600 mg / L, TN 550 - 600 mg / L, TP 25 - 30 mg / L, NH 3 -N 400 - 500 mg / L.

[0032] Table 1 Selection and planting density of aquatic plants

[0033]

[0034] The test results are shown in Table 2. It can be seen that the biomass of Myriophyllum spicatum increased by 5 times after growing for 60 days; the biomass of Oenanthe javanica increased by 2 - 3 times; 2 / 3 of the seedlings of Acorus tatarinowii died and were not suitable for growing in water. Therefore, Myriophyllum spicatum seedlings were selected for wastewater cultivation.

[0035] Table 2 Analysis of the growth of three aquatic plants

[0036]

[0037] Example 2

[0038] Study on the propagation of Myriophyllum spicatum seedlings using different substrates

[0039] Test grouping:

[0040] Test group 1: Concentrated sludge, which is the product from the discharge outlet of the solid - liquid separator for the pig house effluent, with a water content of more than 99%;

[0041] Experimental group 2: Digestive sludge, which is the excess sludge discharged from the SBR treatment process of pig breeding wastewater; most of the pathogenic bacteria and other harmful microorganisms are killed during the digestion process, and the water content is about 95%;

[0042] Experimental group 3: Natural pond sludge, which is taken from the bottom of the lotus pond where lotus roots are planted, with a water depth of 0.4 - 0.6 m. After being dug out with a spade, 5% quicklime is added and mixed evenly, then spread out evenly on an open ground and exposed to the sun for 3 - 5 days to kill pathogenic microorganisms. After collection, it is pulverized, and 3% - 5% river sand can be added appropriately and mixed evenly to improve the porosity of the pond sludge and ensure the air permeability of plant roots;

[0043] Experimental group 4: Humus soil, purchased from a local humus soil manufacturer, mainly used for improving soil for greening planting, and widely used for seedling raising and flower gardening cultivation.

[0044] Cultivation method of Myriophyllum verticillatum seedlings:

[0045] 1. Soak Myriophyllum verticillatum seeds in 3% hydrogen peroxide solution for 5 minutes to kill harmful germs on the seed surface and soften the seed coat at the same time. After fishing out, soak in clean water for 1 minute, drain the clean water and use it for sowing and seedling raising, and the emergence rate can reach over 95% at most; Spread the treated seeds flat on a tray, cover with 5 mm thick fine sand, and add 1 cm deep clean water, then place it in a constant temperature incubator for light cultivation;

[0046] 2. Adjust the water content of the 4 kinds of culture substrates to 50% and load them into a white foam incubator with length × width × height (50 cm × 40 cm × 40 cm), with a height of 20 cm and a flat surface. Evenly spread Myriophyllum verticillatum seeds, 300 - 350 seeds / m 2 , when the seedlings are 0.5 - 1 cm, at the corresponding water level mark of the incubator, the water surface depth is 5 - 6 cm. After the water volume loss, replenish the water volume according to the mark position until the water level reaches the mark position, and cover with a plastic film; When the seedlings grow to 8 - 10 cm, increase the water depth to 15 cm and cultivate for 40 days, then they can be transferred to the wastewater storage tank (effluent from the three - stage oxidation pond) for sewage treatment.

[0047] Table 3 Component content table of different types of culture substrates

[0048]

[0049] According to the above - mentioned cultivation method of Myriophyllum verticillatum seedlings, control the water temperature at 22 - 25 °C. After 40 days, measure the growth situation of Myriophyllum verticillatum, including indicators such as plant height, dry weight per plant, leaf color value, and crown width, etc. The specific results are shown in Table 4.

[0050] Table 4 Growth table of Myriophyllum verticillatum cultivated with different types of substrates for 40 days

[0051] Species Plant height (cm) Dry weight per plant (g) Leaf color value Crown width (cm) Thickened sludge 12.3 0.152 25.4 8.9-11.3 Digested sludge 16.7 0.267 33.6 12.3-14.5 Natural pond sludge 13.1 0.178 27.5 9.6-12.4 Humus soil 14.5 0.214 29.3 10.2-12.7

[0052] Test results:

[0053] By analyzing the organic matter content, total nutrient content, pH value and total salt content of four substrate materials, namely concentrated sludge, digested sludge, natural pond sludge and humus soil, it is found that the component content and ratio of digested sludge are appropriate and suitable for the cultivation of Myriophyllum verticillatum seedlings. The test results show that as a culture medium, the organic matter content of digested sludge is 20%-25%, total nitrogen is 1.5%-2%, total phosphorus is 1.5%-2%, total potassium is 0.8%-1%, and the total nutrient content (N+P 2 O 5 +K 2 O) is greater than 4%, pH value is 6-9, and total salt content is less than 0.2% are the best culture conditions, which are beneficial to the growth and development of Myriophyllum verticillatum seedlings.

[0054] After 40 days, the plant height, single-plant biomass, leaf color value and crown width of Myriophyllum verticillatum seedlings cultured with digested sludge reached the highest values, indicating that this substrate provided a suitable habitat condition for the breeding of Myriophyllum verticillatum seedlings.

[0055] Engineering application research on cultivating Myriophyllum verticillatum seedlings with different substrates in Example 3

[0056] Select a wastewater storage pond of a pig farm in Anhui. This wastewater pond is a temporary storage pond for the effluent of the oxidation pond. The external discharged wastewater is used for the test. The test is divided into 4 groups, with 3 replicates in each group:

[0057] Test group 1: Myriophyllum verticillatum seedlings obtained by culturing with concentrated sludge;

[0058] Test group 2: Myriophyllum verticillatum seedlings obtained by culturing with digested sludge;

[0059] Test group 3: Myriophyllum verticillatum seedlings obtained by culturing with natural pond sludge, which are obtained by naturally growing Myriophyllum verticillatum seeds in natural ponds and wetlands;

[0060] Test group 4: Myriophyllum verticillatum seedlings obtained by culturing with humus soil.

[0061] To ensure the comparability of test results, seedlings with basically the same height, single-plant biomass, leaf color value and crown width under 4 culture substrate conditions were selected and transferred to the storage pond for cultivation.

[0062] The seedlings were transplanted in May 2021, and the planting density was 16-20 plants / m 2 , and the seedlings were transplanted before 9:00 or after 16:00 to prevent the roots from being burned by high temperature and causing the death of the seedlings. The treatment period was 2 months. During the test process, the growth of Myriophyllum verticillatum was measured, and the water quality of the wastewater storage pond was measured 2 months later.

[0063] During the growth process of Myriophyllum verticillatum, when it reaches 50 cm, harvest it appropriately to prevent decay from entering the water body; regularly remove weeds on the water surface and pay attention to observing whether Myriophyllum verticillatum is infested by pests. Once discovered, spray insecticides as soon as possible; to better promote the growth of Myriophyllum verticillatum, under the condition that the water surface is covered by Myriophyllum verticillatum, appropriately use aeration devices to increase the oxygen content in the water body to prevent the water quality from turning black and emitting a stench. After harvesting, Myriophyllum verticillatum can be used for covering orchards and bare ground surfaces.

[0064] Myriophyllum verticillatum seedlings cultivated with four substrates, namely concentrated sludge, digested sludge, natural pond sludge, and humus soil, were cultivated in a wastewater storage pond. Among them, the rooting rate, average number of rooting cuttings per single plant, plant height, and dry weight of the seedlings bred from digested sludge all reached the maximum values. At the same time, the removal efficiencies of COD, TN, TP, NH 3 -N, Cu, and Zn were the highest, indicating that Myriophyllum verticillatum cultivated with this substrate has higher environmental adaptability in engineering applications.

[0065] The test results are shown in Table Figures 1 - 10 as follows. Among them, Myriophyllum verticillatum cultivated with digested sludge grew best in the wastewater pond. After the test ended, the water body was clear and the odor disappeared. The removal rates of the main pollutants COD, TN, TP, and NH 3 -N were above 80%, and the water body basically met the "Pollutant Discharge Standard for Livestock and Poultry Breeding Industries" (GB18596 - 2001).

[0066] Example 4

[0067] Study on the treatment of sewage with different concentrations using Myriophyllum verticillatum seedlings obtained by cultivating with digested sludge

[0068] Test method: Under the conditions of good ventilation and sufficient sunlight outdoors, a white foam cultivation box with a length × width × height of (50 cm × 40 × 40 cm) was selected as the cultivation container. A 10 - cm - thick layer of sieved digested sludge was evenly laid at the bottom of the cultivation box. The cultivated Myriophyllum verticillatum seedlings were planted in the cultivation box, and the evaporation loss was supplemented with distilled water every 2 days to keep the volume of the cultivation solution unchanged (the transpiration loss of water was small during the test process and was ignored when calculating the pollutant removal).

[0069] Selection of sewage conditions: Five sewage concentration treatments were set up, as shown in Table 5 specifically.

[0070] Table 5 Treatment conditions of different sewage concentrations

[0071] Treatment COD (mg / L) TN (mg / L) TP (mg / L) <![CDATA[NH 3 -N (mg / L)]]> T1 100 200 10 100 T2 300 300 20 200 T3 600 600 30 300 T4 800 800 40 400 T5 1000 1000 50 500

[0072] The specific results are shown in Table 5 - 6. From the test results, it can be seen that when the sewage COD concentration is 100 - 1000 mg / L, TN concentration is 200 - 1000 mg / L, TP concentration is 10 - 50 mg / L, and NH 3Within the range of 100 - 500 mg / L of -N concentration, the method of the present invention can well reduce the COD concentration, TN concentration, TP concentration, and NH 3 -N concentration of the sewage. When the sewage concentration is COD 600 mg / L, TN 600 mg / L, TP 30 mg / L, and NH 3 -N 300 mg / L, the treatment method of the present invention has the best effect, and the removal rates of COD, TN, TP, and NH 3 -N all reach over 80%.

[0073] Table 6 Analysis table of Myriophyllum aquaticum purifying sewage with different concentrations

[0074]

[0075]

[0076] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for treating wastewater from a farm using aquatic plants, characterized in that, Myriophyllum verticillatum seeds are selected and cultured with digested sludge as a culture medium to obtain Myriophyllum verticillatum seedlings, and the Myriophyllum verticillatum seedlings are sprinkled into the farm wastewater to grow, with a growth cycle of 2 to 3 months; The method for culturing Myriophyllum verticillatum seeds with digested sludge as a culture medium is as follows: (1) Soak Myriophyllum verticillatum seeds in a 3%-5% hydrogen peroxide solution for 5-10 minutes, fish them out and soak them in clear water for 1-3 minutes, drain the clear water and use it for sowing and seedling raising; lay the treated seeds flat on a tray, cover them with 5-6 mm thick fine sand, and add 1-1.5 cm deep clear water, and place them in a constant temperature incubator for light culture; (2)Use digested sludge as a culture medium, reduce the water content of the sludge to 40%-50%, and evenly sprinkle the watermilfoil seeds in the culture container filled with digested sludge. The sowing density of the watermilfoil seeds is 300-350 seeds / m 2 ; When the watermilfoil seedlings grow to 0.5-1 cm, adjust the water depth to 5-6 cm and cover with a plastic film; When the seedlings grow to 8-10 cm, increase the water depth to 15-20 cm, culture for 40-50 days, and obtain watermilfoil seedlings when the seedling height grows to 15-20 cm; The organic matter content of the digested sludge is 20%-25%, total nitrogen is 1.5%-2%, total phosphorus is 1.5%-2%, total potassium is 0.8%-1%, and the total nutrient content N 2 O 5 +K 2 O is greater than 4%, pH is 6-9, and the salt content is less than 0.2%; The planting density of the Myriophyllum verticillatum seedlings in the wastewater is 16 - 20 plants / m 2 ; The COD concentration of the wastewater from the farm is 100 - 1000 mg / L, the TN concentration is 200 - 1000 mg / L, the TP concentration is 10 - 50 mg / L, and the NH 3 -N concentration is 100 - 500 mg / L.

2. The method for treating farm wastewater according to claim 1, characterized in that, The COD concentration of the wastewater from the farm is 100 - 800 mg / L, the TN concentration is 200 - 800 mg / L, the TP concentration is 10 - 40 mg / L, and the NH 3 -N concentration is 100 - 400 mg / L.

3. The method for treating farm wastewater according to claim 2, characterized in that, The COD concentration of the wastewater from the farm is 300 - 600 mg / L, the TN concentration is 300 - 600 mg / L, the TP concentration is 20 - 30 mg / L, and the NH 3 -N concentration is 200 - 300 mg / L.

4. The method for treating farm wastewater according to claim 3, characterized in that, The COD concentration of the wastewater from the farm is 600 mg / L, the TN concentration is 600 mg / L, the TP concentration is 30 mg / L, and the NH 3 -N concentration is 300 mg / L.

5. The method for treating farm wastewater according to claim 1, characterized in that, When the Myriophyllum verticillatum grows to 50-60 cm, it is harvested and used for covering orchards and bare ground surfaces.

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