A precious fish pet micro-nano ecological algae trapping formula, algae trapping device and algae control method thereof

Abstract

The application is a kind of micro-nano ecological algae trapping formula, algae trapping device and algae control method for precious fish pets, belonging to the field of water ecological management technology. In view of the problems of water pollution or uncertain effect of the existing algae bloom treatment measures, the micro-nano ecological algae trapping formula comprises 50-70% diatomite, 0-30% red clay and 0-30% PAC, preferably 70% diatomite and 30% red clay are used to prepare the micro-nano ecological algae trapping device. When used, the micro-nano ecological algae trapping device is diluted with water and uniformly sprayed on the surface of the water body. Through light induction, algae bodies are aggregated and floated. The micro-nano ecological algae trapping device is used to quickly capture suspended matters such as blue-green algae in the water body through the bridging net trapping effect, so as to realize algae-water separation and restore the water quality to be clear in a short time. The micro-nano ecological algae trapping device has the characteristics of simple use method, rapid effect and no toxic and side effects, and can be used for a long time in the daily management of the landscape water body of the precious fish pet breeding, courtyard or hotel.

Description

Technical Field

[0001] This invention relates to the field of water ecological management technology, and in particular to a micro-nano ecological algae-catching formula, algae-catching device and algae control method for precious pet fish. Background Technology

[0002] In some high-end pet fish, such as koi and goldfish, as well as landscape water bodies in courtyards and hotels, eutrophication easily occurs in enclosed ponds due to increased daily feeding and the continuous influx of uneaten food and fish waste. In highly alkaline and high-nitrogen, low-phosphorus aquaculture waters, cyanobacterial blooms are more likely to occur. These blooms form a blue-green film on the water surface, or turn ponds and landscape water bodies blue-green, primarily due to the rapid proliferation of cyanobacteria (mainly Microcystis) in the water, accompanied by turbidity and a significant decrease in overall visibility. These blooms are more common during the high-temperature season from June to August each year, easily leading to rapid disease and mortality in fish and causing significant challenges in the daily management of landscape water bodies.

[0003] Currently, the main methods used to control cyanobacterial blooms in surface water bodies can be categorized into engineering methods, physical methods, chemical methods, and biological methods. Engineering methods include sediment dredging, artificial reoxygenation, and ecological water regulation; physical methods include filtration, flotation, mechanical methods, clay removal, and ultrasonic control; chemical methods primarily utilize algaecides; and biological methods include algae suppression using aquatic higher plants, algae control using aquatic animals, and algae control using microorganisms. The existing technologies mentioned above have significant drawbacks for the treatment of water bodies in courtyard landscapes. Engineering methods are costly to construct and are more suitable for large rivers and lakes. For landscape water bodies, engineering construction is neither feasible nor necessary. Physical methods, which alter the physical properties of water flow, are relatively simple to implement for courtyard water bodies, and some methods are used in the daily management of courtyard water bodies. However, their long-term effectiveness is poor, and they cannot completely solve the problem. They also have limitations in use for water bodies used to raise valuable fish. Chemical methods, such as algaecides, are mainly composed of chemical drugs and are toxic to fish and shrimp, easily affecting water quality and lacking universal applicability, so they are rarely used. Biological methods, including the use of aquatic plants, animals, and microorganisms to control algae, suffer from slow effectiveness, uncertain results, and limitations imposed by environmental conditions, resulting in low public acceptance.

[0004] Therefore, there is an urgent need to develop a formula and method for algae removal and water purification that has a wider range of applications, such as aquaculture water bodies, landscape water bodies, and courtyard ponds, and that has no toxic side effects on fish. This is of great significance for the effective management of aquatic ecosystems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a micro-nano ecological algae-catching formula, algae trap, and algae control method for raising valuable pet fish. This micro-nano ecological algae-catching formula uses non-chemical reagents, posing no harm to koi or goldfish and having no adverse effects on water quality. Simultaneously, utilizing the micro-nano ecological algae trap, combined with the light-induced algae aggregation and buoyancy effect, it quickly captures suspended matter such as blue-green algae floating in the water, purifying algal blooms and restoring the ecological landscape of the water body in a short time. This effectively solves the problems of algal blooms and greening of water in the water bodies of valuable pet fish (such as koi or goldfish) farms, courtyards, or hotel landscape water bodies.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention discloses a micro-nano ecological algae-catching formula for precious fish pets, which includes the following components by mass fraction: 50% to 70% diatomaceous earth, 0% to 30% red clay, 0% to 30% PAC, and 0% to 10% pregelatinized starch.

[0008] A further preferred embodiment of the above technical solution is: the micro-nano ecological algae-trapping formula includes the following components by mass fraction: 70% diatomaceous earth and 30% red clay.

[0009] As a further preferred embodiment of the above scheme: the physicochemical properties of diatomaceous earth are as follows: diatom content ≥80%, pH 6-8, moisture content ≤10%, and bulk density ≤0.4g / cm³. 3 The red clay has a water content of 50%–60%, a porosity of 1.4–1.7, a saturation of ≥85%, and a liquid limit of ≥50%.

[0010] Secondly, the present invention discloses a micro-nano ecological algae trap for precious fish pets, which is prepared by the micro-nano ecological algae trap formula for precious fish pets described in any of the above claims.

[0011] As a further preferred embodiment of the above scheme: the specific surface area of ​​the micro-nano ecological algae trap is >55m². 2 / g, pore volume >0.90cm³ 3 / g.

[0012] Thirdly, this invention discloses a method for controlling algae in a micro-nano ecological algae trap for valuable pet fish, comprising the following steps:

[0013] (1) Take the micro-nano ecological algae trap and dilute it with water according to the ratio to form an algae removal stock solution;

[0014] (2) Sprinkle the algae removal solution evenly on the surface of the water. The algae removal solution causes the algae in the water to quickly gather and form algae flocs and float to the surface. After being exposed to sunlight, due to photocatalysis, the algae cells are induced to produce microbubbles, which accelerates the floating and rising of the algae flocs.

[0015] (3) Drive the algae flocs that float to the surface through the drain outlet or use a dip net to assist in retrieval.

[0016] Based on the above technical solution, in step (1), the mass ratio of the micro-nano ecological algae trap to water is 1 / 3 to 1 / 5. After being stirred and mixed thoroughly, it forms an algae removal stock solution, which is then evenly sprayed onto the water body. The water body can be mechanically turned upside down and stirred to accelerate the contact between the micro-nano ecological algae trap and algae cells in different water layers.

[0017] Based on the above technical solution, further, in step (2), more than 95% of the algal flocs float to the surface of the water, thus achieving algae-water separation.

[0018] Based on the above technical solution, further, the overall algae removal and water purification time of steps (1) to (3) does not exceed 4 hours.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The micro-nano ecological algae trap of this invention uses non-chemical reagents. The principle of algae trapping is the light-induced algal aggregation and buoyancy effect. Combined with the bridging and netting effect of the micro-nano ecological algae trap, it quickly captures suspended matter such as blue-green algae floating in the water. Under the biochemical stress reaction of the algae, a large number of microbubbles are formed, which further causes the algal flocs to float to the surface, making them easy to collect and remove. It can achieve algae-water separation in a short time, control algal blooms, and restore the ecological landscape of the water body. It is loved by many owners of precious fish and pets and is a product for daily management and long-term use of landscape water bodies in precious fish and pet breeding, courtyards, or hotels.

[0021] 2. The micro-nano ecological algae trap of the present invention uses diatomaceous earth as the base material. By adding specific modifiers, it significantly improves the removal effect of algal blooms. At the same time, the micro-nano ecological algae trap is simple to use, fast, effective and non-toxic. It will not harm koi or goldfish, nor will it have an adverse effect on water quality. It provides a brand-new solution to the problems of low stocking density and high water change costs of valuable pet fish, and also provides important scientific basis for its widespread application in the field of water treatment.

[0022] 3. Using the micro-nano ecological algae trap of this invention to treat algal blooms takes about 4 hours, with long-lasting effects. Using it once a year in summer can ensure that the water does not need to be changed or that there is no green water all year round, reducing the user's water production and replacement costs. In the process of efficiently removing suspended algae from the water, it significantly reduces the chemical oxygen demand and dissolved biological oxygen demand of the aquaculture water, improves the survival rate of aquatic products, and greatly increases the breeding density of valuable pet fish. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0024] Figure 1 The present invention provides a micro-nano ecological algae trap prepared using formula A, wherein: a is the outer packaging of the micro-nano ecological algae trap, b is the internal product of the micro-nano ecological algae trap, and c is the micro-nano ecological algae trap sealed in a transparent plastic bag.

[0025] Figure 2 The algae-catching effect of formula A of the present invention after being added to the experimental water body is shown, wherein: a is a top view of the experimental water body after being treated with formula A, and b is a side view of the experimental water body after being treated with formula A.

[0026] Figure 3 The algae-catching effect of formula B of the present invention after being added to the experimental water body is shown in the figure. In the figure: a is a top view of the experimental water body after being treated with formula B, and b is a side view of the experimental water body after being treated with formula B.

[0027] Figure 4 The algae-catching effect of formula C of the present invention after being added to the experimental water body is shown in the figure. In the figure: a is a top view of the experimental water body after being treated with formula C, and b is a side view of the experimental water body after being treated with formula C.

[0028] Figure 5 This invention describes the algae-catching process and effect in an ornamental koi breeding pond in Example 2, wherein: a) before treatment, the koi breeding pond is overrun with blue-green algae and the water has high turbidity; b) the micro-nano ecological algae catcher of Example 2 is evenly sprinkled into the pond; c) the algae in the pond clump together and float on the water surface, providing food for the koi; d) after the algae clumps are removed, the water is clear and the fish are visible.

[0029] Figure 6 This is an example of the algae removal process and effect on the goldfish breeding water in Minhou County in Embodiment 3 of the present invention, wherein: a) is a picture of severe green algae bloom in the goldfish breeding pond before treatment; b) is a picture of the micro-nano ecological algae trap diluted according to the ratio; c) after the algae removal stock solution is evenly sprinkled, the green algae float to the surface and clump together, accompanied by a large number of microbubbles; d) after skimming off the high concentration of algae clumps, the breeding water is restored to clearness and fish can be seen.

[0030] Figure 7 This is an EDS elemental analysis diagram of the algae flocs formed by the micro-nano ecological algae trap in Example 4 of the present invention;

[0031] Figure 8 This is a graph showing the elemental composition of algae flocs formed by the micro-nano ecological algae trap in Example 4 of the present invention.

[0032] Figure 9 This is a microscopic morphology observation image of the algae flocs formed by the micro-nano ecological algae trap in Example 4 of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0034] Reference Figure 1 This invention provides a micro-nano ecological algae-catching formula, algae trap, and algae control method for expensive pet fish, as detailed below:

[0035] (1) A micro-nano ecological algae-catching formula for precious fish pets, the micro-nano ecological algae-catching formula includes the following components by mass fraction: 50% to 70% diatomaceous earth, 0% to 30% red clay, 0% to 30% PAC, depending on the algae density of the water body, 0% to 10% pregelatinized starch (food grade) can be selectively added to improve the algae-catching effect, wherein PAC refers to polyaluminum chloride, PAC (PolyAluminium Chloride) is a highly efficient water-soluble inorganic polymeric water purification flocculant.

[0036] Specifically, the micro-nano ecological algae-trapping formula of the present invention is independently developed, and the following three formulas are preferred: Formula A: 70% diatomaceous earth and 30% red clay; Formula B: 70% diatomaceous earth, 15% red clay and 15% PAC; Formula C: 70% diatomaceous earth and 30% PAC.

[0037] More preferably, the micro-nano ecological algae-trapping formula comprises the following components by mass fraction: 70% diatomaceous earth and 30% red clay.

[0038] In this invention, the physicochemical properties of diatomaceous earth are as follows: diatom content ≥80%, pH 6-8, moisture content ≤10%, and bulk density ≤0.4 g / cm³. 3 The red clay has a water content of 50%–60%, a porosity of 1.4–1.7, a saturation of ≥85%, and a liquid limit of ≥50%.

[0039] (2) A micro-nano ecological algae trap for valuable fish pets, prepared from the above-mentioned micro-nano ecological algae trapping formula, includes the following preparation process: testing the selected raw materials, mixing and stirring the raw materials in the optimal ratio, then sieving, removing impurities, drying, and packaging the mixed raw materials, and finally conducting a quality inspection on the finished product. Testing shows that the specific surface area of ​​the micro-nano ecological algae trap prepared by this invention is >55 m². 2 / g, pore volume >0.90cm³ 3 / g.

[0040] (3) A method for controlling algae in a micro-nano ecological algae trap for expensive fish pets, comprising the following steps:

[0041] Dilute the micro-nano ecological algae trap with water in a certain proportion, where the mass ratio of the micro-nano ecological algae trap to water is 1 / 3 to 1 / 5. After stirring and mixing thoroughly, an algae removal stock solution is formed. Sprinkle it evenly into the water body. You can mechanically turn the water up and down to stir it, which will accelerate the contact between the micro-nano ecological algae trap and algae cells in different water layers.

[0042] The algae-removing solution is evenly sprayed onto the surface of the water. The solution causes algae in the water to quickly aggregate and form algal flocs that float to the surface. When exposed to sunlight, the algal cells produce microbubbles due to photocatalysis. A large number of microbubbles appear during the process of taking effect, which accelerates the floating and rising of the algal flocs.

[0043] Algae flocs that float to the surface through the drain outlet can be removed with a dip net as needed, restoring the water to its original clarity.

[0044] Using the algae control method of this invention, more than 95% of the algae flocs formed float to the surface of the water, and the retrieval effect is better than other water purification materials that settle to the bottom of the pond. When used in full sunlight or under midday sun, the algae and water separation effect is better, and microbubbles are generated more abundantly and quickly. The overall algae removal and water purification time can be controlled within 4 hours.

[0045] The micro-nano ecological algae trapping formula, micro-nano ecological algae trapping device and algae control method proposed in this invention have the function of water purification and algae removal in various precious fish and pet breeding water bodies, architectural landscaping, parks, hotels, courtyard ponds, etc., and will not have a toxic effect on the fish being raised.

[0046] Currently, the micro-nano ecological algae trap of this invention is available in two packaging specifications: bags and drums, including 100g / bag, 200g / bag, 1KG / drum, 5KG / drum, and 10KG / drum. Other forms of sealed packaging conforming to the relevant provisions of NY / T1108 can also be used according to user requirements or order agreements. Figure 1 a, Figure 1 b, Figure 1As shown in Figure c, the packaging consists of two layers: a rectangular transparent plastic bag and a storage container. The storage container has an external packaging design. This micro-nano ecological algae trap is not recommended for use with other similar products and should be stored in a dry, ventilated, and dark environment, avoiding moisture, heat, and freezing. During storage, attention should be paid to moisture prevention, dust prevention, and insect prevention. Under the specified transportation and storage conditions, and provided the packaging is intact and unopened, the shelf life of this product is 3 years.

[0047] Example 1:

[0048] Equal amounts of formulations A, B, and C of this invention were taken, diluted with water in a uniform ratio, and then added to experimental water of the same turbidity for a comparative experiment. The aggregation of bacteria and algae in the experimental water, as well as the turbidity and transparency of the experimental water, were observed. The results are shown below:

[0049] like Figures 2-4 As shown, formula A has the best algae removal effect and the lowest water turbidity, formula C has the second best algae removal effect, and formula B has the worst algae removal effect, resulting in visibly turbid water. Figure 2 a, Figure 2 As can be clearly seen in section b, almost all the algae flocs in the experimental water body with added formula A floated on the surface. Figure 3 a, Figure 3 The experimental water body with added formula B, as shown in Figure b, remained turbid, indicating poor results. Figure 4 a, Figure 4 The addition of ingredient b to the experimental water body of formula C had a water purification effect, but the flocculated material was deposited at the bottom of the water body.

[0050] The experimental results above show that Formula A has the most obvious algae-catching effect, the lowest cost, and does not require the addition of chemical components. Furthermore, the effect of diatomaceous earth is better than that of PAC, and it can be used as a new type of water purification component to replace PAC. It has the advantages of being more environmentally friendly and more convenient for removing flocculation.

[0051] Example 2:

[0052] Based on the research results of Example 1 above, this example uses Formula A (70% diatomaceous earth and 30% red clay) with the best algae-catching effect as the product raw material to make a micro-nano ecological algae trap, which is used in the treatment of ornamental koi breeding ponds with high turbidity and excessive growth of blue-green algae to carry out a pilot application of algae capture experiment.

[0053] According to the operating instructions in the product manual, the micro-nano ecological algae trap was diluted according to the specified ratio to form an algae-removing solution, which was then evenly spread on the water surface. Observations showed that the solution dissolved rapidly in the water, effectively adsorbing and trapping blue-green algae, causing algal cells to aggregate and form algal flocs, accompanied by numerous microbubbles rising to the surface. This process, due to enhanced photocatalytic activity, allowed the large number of accumulated algae to photosynthesize, significantly increasing the dissolved oxygen concentration in the water. Further observation revealed that the formed algal flocs not only became a food source for koi, but the remainder could be naturally discharged through the drainage system or collected from the water's edge through manual intervention (such as using a dip net), ultimately achieving a significant improvement in water quality. Figure 5 From middle a to Figure 5 As shown in Figure d, after treatment, the water in the aquaculture pond was odorless, the turbidity was significantly lower than before treatment, and the water color and transparency were restored. The entire treatment process took approximately 4 hours, with long-lasting effects, ensuring that algae blooms would not recur within a year. It achieved the expected goal of controlling blue-green algae, efficiently removing suspended algae from the water, significantly reducing the chemical oxygen demand (COD) and dissolved biological oxygen demand (BOD) of the aquaculture water, and greatly increasing the stocking density of valuable pet fish.

[0054] Example 3:

[0055] Using Formula A (70% diatomaceous earth and 30% red clay) as the raw material, which has the best algae-catching effect, a micro-nano ecological algae trap was made. The efficiency of this micro-nano ecological algae trap in removing easily proliferating bacteria and algae in the breeding water of the precious pet fish, Minhou goldfish, was evaluated. This solved a series of practical problems in aquaculture, such as extremely low stocking density, high water change costs, and poor economic benefits.

[0056] like Figure 6 As shown, in practical application, first observe the water color and then take a sample to observe the density of bacteria and algae. Dilute the micro-nano ecological algae trap with water according to the instructions to prepare an algae-removing solution. Evenly sprinkle the solution onto the water surface. The components of the solution quickly enter the water, and the captured bacteria and algae begin to float to the surface at a visible rate, with their concentration continuously increasing. Extremely fine microbubbles can be observed constantly rising to the surface. Then, the algae flocs attract goldfish to feed. Uneaten algae flocs can be naturally discharged through the drainage system or removed using a dip net from dead corners of the water surface, ultimately achieving a significant improvement in water quality. Figure 6 As shown in Figure d, after treatment, the aquaculture water had no odor, the turbidity was significantly lower than before treatment, and the water color and transparency were restored to crystal clear. This result demonstrates that the treatment efficiency of diatomaceous earth is significantly improved by adding a specific modifier (red clay in this invention), and it can be used to replace traditional biological or chemical algaecides, providing a scientific basis for the widespread application of diatomaceous earth in the field of water treatment.

[0057] Example 4:

[0058] Based on the research results of Examples 1-3 above, this example further analyzes the physicochemical properties and microstructure of algal flocs formed by the micro-nano ecological algae trap in pilot applications.

[0059] Morphological observation using scanning electron microscopy and elemental analysis using EDS revealed that the algal flocs formed by the micro-nano ecological algae trap of this invention are mainly composed of elements such as carbon (C), nitrogen (N), and oxygen (O). Figures 7-9 As shown.

[0060] Specifically, the normalized mass percentages of C and N elements are 21.71% and 3.15%, respectively, indicating that the algae control method of the micro-nano ecological algae trap of this invention can not only effectively adsorb and remove bacteria and algae in aquaculture wastewater, but also has a significant adsorption and purification effect on common high concentrations of carbon and nitrogen elements in water. The normalized mass percentage of O element is as high as 48.07%, which not only reflects the oxygen content of the water itself, but also includes the oxygen released during algal cell photosynthesis, providing empirical support for the continuous floating of algal flocs on the water surface due to their high oxygen content. In addition, the normalized mass percentages of aluminum (Al) and silicon (Si) elements are 18.51% and 8.56%, respectively. These components mainly come from trace elements contained in diatomaceous earth or red clay. Apart from these, no other heavy metal elements or other toxic components were found, indicating that the micro-nano ecological algae trap of this invention meets environmental protection requirements and will not pollute the water environment during the algae removal process.

[0061] The microstructure of algal flocs is as follows Figure 9 As shown, the micro-nano morphology of a large number of adsorbed algal cells can be clearly seen. Figure 9 The micro-nano ecological algae trap demonstrates its superior specific surface area and pore volume characteristics. The high porosity provides a wide range of adsorption sites for algae, thereby promoting the formation of algal flocs, effectively enhancing the adsorption function of algal cells in algal bloom water, and efficiently achieving algae-water separation.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A micro-nano ecological algae-catching formula for expensive pet fish, characterized in that, This micro-nano ecological algae-trapping formula includes the following components by mass fraction: 50-70% diatomaceous earth, 0-30% red clay, 0-30% PAC, and 0-10% pregelatinized starch.

2. The micro-nano ecological algae-catching formula for precious pet fish according to claim 1, characterized in that, This micro-nano ecological algae-trapping formula includes the following ingredients: 70% diatomaceous earth and 30% red clay.

3. The micro-nano ecological algae-catching formula for precious fish pets according to claim 1 or 2, characterized in that, The physicochemical properties of diatomaceous earth are as follows: diatom content ≥80%, pH 6–8, moisture content ≤10%, and bulk density ≤0.4 g / cm³. 3 The red clay has a water content of 50%–60%, a porosity of 1.4–1.7, a saturation of ≥85%, and a liquid limit of ≥50%.

4. A micro-nano ecological algae trap for expensive fish pets, characterized in that, The micro-nano ecological algae trap is prepared from a micro-nano ecological algae trapping formula for a precious fish pet as described in any one of claims 1-3.

5. The micro-nano ecological algae trap for valuable pet fish according to claim 4, characterized in that, The specific surface area of ​​this micro-nano ecological algae trap is >55m². 2 / g, pore volume >0.90cm³ 3 / g.

6. The method for controlling algae in a micro-nano ecological algae trap for valuable pet fish according to claim 5, characterized in that, Includes the following steps: (1) Take the micro-nano ecological algae trap and dilute it with water according to the ratio to form an algae removal stock solution; (2) Sprinkle the algae removal solution evenly on the surface of the water. The algae removal solution causes the algae in the water to quickly gather and form algae flocs that float to the surface. After being exposed to sunlight, the photocatalytic effect induces the algae cells to produce microbubbles, which accelerates the floating and rising of the algae flocs. (3) Drive the algae flocs that float to the surface through the drain outlet or use a dip net to assist in retrieval.

7. The method for controlling algae in a micro-nano ecological algae trap for valuable pet fish according to claim 6, characterized in that, In step (1), the mass ratio of the micro-nano ecological algae trap to water is 1 / 3 to 1 / 5. After being thoroughly mixed by stirring, it is evenly sprinkled into the water body. The water body can be mechanically turned up and down to accelerate the contact between the micro-nano ecological algae trap and algal cells in different water layers.

8. The method for controlling algae in a micro-nano ecological algae trap for valuable pet fish according to claim 6, characterized in that, In step (2), more than 95% of the algal flocs float to the surface of the water, achieving algae-water separation.

9. The method for controlling algae in a micro-nano ecological algae trap for valuable pet fish according to claim 6, characterized in that, The total time for algae removal and water purification from step (1) to step (3) shall not exceed 4 hours.

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