Wastewater treatment carriers

Abstract

To provide a wastewater treatment carrier which can be manufactured at a low cost and can shorten a start-up time.SOLUTION: A wastewater treatment carrier is formed into a foam structure from a thermoplastic resin containing a fermented product of kelp made from soup stock residue and a specific gravity adjusting filler. The wastewater treatment carrier preferably contains 5 to 10 pts.wt of fermented product of kelp made from the soup stock residue per 100 pts.wt in total of the thermoplastic resin and the specific gravity adjusting filler. The wastewater treatment carrier preferably has a specific gravity of 1.00 to 1.05.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sewage treatment carrier (material for attaching microorganisms) used in septic tanks for biologically treating wastewater such as domestic wastewater, industrial wastewater, and sewage such as water for cultivating fish and shellfish. [Background technology]

[0002] Conventionally, a biological wastewater treatment method is known in which a carrier is floated in an aeration tank and microorganisms attached to the carrier are brought into contact with the wastewater to purify the wastewater (for example, Patent Document 1, etc.). As a carrier for wastewater treatment, a foam structure made of a thermoplastic resin is widely known, and a thermoplastic resin containing an inorganic material such as calcium carbonate for the purpose of improving hydrophilicity and adjusting specific gravity is also known (Patent Documents 1 to 3). In addition, since a sewage treatment carrier containing these inorganic materials in a thermoplastic resin requires a long start-up time until it exerts a predetermined treatment capacity, a thermoplastic resin containing nutrients for microorganisms for the purpose of shortening the start-up time is also known (Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 55-24955 [Patent Document 2] Japanese Patent Application Publication No. 56-89897 [Patent Document 3] Japanese Patent Application Publication No. 57-30596 [Patent Document 4] JP 2003-245682 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional sewage treatment carriers that incorporate microbial nutrients into thermoplastic resins use phosphates or polyphosphates as nutrients, but the costs of these chemicals are high, making the sewage treatment carriers themselves expensive. In particular, large land-based aquaculture facilities and wastewater treatment facilities use large amounts of sewage treatment carriers, so there is a demand for suppressing increases in unit prices. In addition, conventional sewage treatment carriers generally require a long start-up time before they can demonstrate their sewage treatment capacity.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, a primary object of the present invention is to provide a carrier for wastewater treatment which can be produced at low cost and in which the start-up time can be shortened. [Means for solving the problem]

[0006] In order to achieve the above object, a sewage treatment carrier according to one embodiment of the present invention is formed into a foam structure from a thermoplastic resin containing fermented kelp from soup stock residue and a filler for adjusting specific gravity.

[0007] It is preferable that the thermoplastic resin is polypropylene, the gravity-adjusting filler is talc, and the fermented kelp stock residue is contained in an amount of 5 to 10 parts by weight per 100 parts by weight of the total of the thermoplastic resin and the gravity-adjusting filler.

[0008] The sewage treatment carrier preferably has a specific gravity of 1.00 to 1.05. Effect of the Invention

[0009] According to the present invention, by fermenting kelp waste, which is discarded in large quantities, and mixing it with a thermoplastic resin to form a foamed structure, it is possible to obtain a carrier for wastewater treatment that can be manufactured at low cost and has a short start-up time. [Brief description of the drawings]

[0010] [Figure 1] 1 is a photograph showing the appearance of one embodiment of a sewage treatment carrier according to the present invention. [Diagram 2]1 is a photograph showing the flowability test results of an example of the present invention. [Diagram 3] 1 is a photograph showing the flowability test results of a comparative example. [Figure 4] 1 shows the results of a water absorption measurement test for an embodiment of the present invention and a comparative example. [Diagram 5] 4 is a photograph showing test results regarding water compatibility of an embodiment of the present invention. [Figure 6] 13 is a photograph showing test results regarding water compatibility of a comparative example. [Figure 7] 1A and 1B are micrographs of an example of the present invention, showing the fermented kelp stock residue product before and after dissolution. [Figure 8] 1 is a graph showing the results of measuring changes in COD concentration using an experimental tank for an example of the present invention and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] BEST MODE FOR CARRYING OUT THE DISCLOSURE An embodiment of a wastewater treatment carrier according to the present invention will be described below with reference to Figs.

[0012] The wastewater treatment carrier according to the present invention is formed into a foam structure from a thermoplastic resin containing a fermented product of kelp made from soup stock residue and a filler for adjusting specific gravity.

[0013] The kelp waste can be the waste that is discharged after making soup stock from kelp in food factories, restaurants, etc. By using kelp waste that would have been discarded in the past, it is possible to reduce costs by receiving payment as a waste collection fee or disposal fee instead of purchasing kelp waste. The fermented kelp waste can be obtained by subjecting kelp waste to the well-known composting method used in producing compost, i.e., aerobic fermentation by aerobic bacteria. Although the fermentation process takes time (for example, several months), it costs almost nothing, so the fermented kelp waste (compost) can be produced at low cost.

[0014] As the thermoplastic resin, polypropylene can be suitably used, but other thermoplastic resins such as polyethylene can also be used.

[0015] Talc is preferably used as the specific gravity adjusting filler, but calcium carbonate, diatomaceous earth, zeolite, slaked lime, bentonite, etc. can also be used. The amount of the specific gravity adjusting filler is adjusted so that the sewage treatment carrier is close to the specific gravity of the sewage to be treated. For example, when the treatment target is used for filtering the breeding water of freshwater fish, the amount of the specific gravity adjusting filler can be adjusted so that the specific gravity of the sewage treatment carrier is 1.00 to 1.02, and when the treatment target is used for filtering the breeding water of saltwater fish, the amount of the specific gravity adjusting filler can be adjusted so that the specific gravity of the sewage treatment carrier is 1.02 to 1.05. For example, when the thermoplastic resin is polypropylene and the specific gravity adjusting filler is talc, the specific gravity can be adjusted to the desired specific gravity by adding 15 to 25 parts by weight of talc to 80 parts by weight of polypropylene.

[0016] The fermented kelp used in the bottling is preferably blended in an amount of 5 to 10 parts by weight per 100 parts by weight of the total of the thermoplastic resin and the specific gravity adjusting filler. If the blending amount of the fermented kelp used in the bottling exceeds 10 parts by weight per 100 parts by weight of the total of the thermoplastic resin and the specific gravity adjusting filler, molding becomes difficult, and if it is less than 5 parts by weight, the desired effect of shortening the start-up time cannot be obtained.

[0017] In order to make the sewage treatment carrier into a foamed structure, a thermoplastic resin, a specific gravity adjusting filler, and a fermented product of kelp from soup stock residue are mixed in predetermined amounts and molded using a known foam molding method. There are two types of foam molding: chemical foaming and physical foaming. In chemical foaming, a foaming agent is mixed in the manufacturing process of the sewage treatment carrier. Any foaming agent that is compatible with the thermoplastic resin, such as azodicarbonamide or sodium bicarbonate, can be used as the foaming agent, and the amount added can be set according to the desired expansion ratio. FIG. 1 is a photograph of the sewage treatment carrier according to the present invention. The shape of the sewage treatment carrier is not limited to the illustrated example, and other shapes can also be used.

[0018] Next, the present invention will be described in more detail with reference to examples and comparative examples of the sewage treatment carrier according to the present invention, but the present invention is not limited to these examples.

[0019] As an example, 80 parts by weight of polypropylene, 20 parts by weight of talc, 5 parts by weight of fermented kelp from soup stock residue, and 0.5 parts by weight of azodicarbonamide (Dainichiseika Color & Chemicals Mfg. Co., Ltd., product name "DAIBLOW AC2040(L)", "DAIBLOW" is a registered trademark) were mixed and used with an extrusion molding machine to produce a sewage treatment carrier consisting of a cylindrical foam structure as shown in Figure 1. The sewage treatment carrier was molded to an outer diameter of approximately 15 mm, length of approximately 15 mm, and thickness of approximately 2 mm. The specific gravity of the obtained example sewage treatment carrier was 1.02.

[0020] As a comparative example, 80% by weight of polypropylene, 20% by weight of talc, and 0.5 parts by weight of azodicarbonamide were mixed and an extrusion molding machine was used to produce a sewage treatment carrier having a foam structure with the same dimensions and shape as the example. The specific gravity of the obtained comparative sewage treatment carrier was approximately 1.02.

[0021] In the above examples and comparative examples, talc was used under the trade name of Junsei Chemical Co., Ltd. (product number 43117Jis_J-1), and the specific gravity was measured by the underwater displacement method.

[0022] A comparison test of fluidity was carried out using the above-mentioned Examples and Comparative Examples. As a method of the fluidity test, two tanks were prepared, each of which was filled with fresh water and aerated, and 200 sewage treatment carriers of the Example were placed in one tank, and 200 sewage treatment carriers of the Comparative Example were placed in the other tank, and the state was observed after 12 hours and 24 hours, respectively. After 12 hours, the sewage treatment carrier of the Comparative Example was hardly flowing, and when the aeration was stopped, it floated on the water surface. On the other hand, in the Example, after 12 hours, about 2 / 3 of the total was flowing, and even when the aeration was stopped, it sank below the water surface, and the fermented kelp from the soup stock dissolved from the sewage treatment carrier, causing the water to become turbid. After 24 hours, only about 1 / 3 of the sewage treatment carrier of the Comparative Example was flowing, while the entire sewage treatment carrier of the Example was flowing. FIG. 2 shows the state after 24 hours of the Example, and FIG. 3 shows the state after 24 hours of the Comparative Example.

[0023] In addition, a comparative test on water absorption was conducted using the above-mentioned Examples and Comparative Examples. As a test method, 75 sewage treatment carriers (total of 50 g) from each of the Examples and Comparative Examples were submerged in water, and after a predetermined time, they were removed from the water and their masses were measured to measure the water absorption. The measurement results are shown in Figure 4. As a result of the water absorption test, it was found that the sewage treatment carriers of the Examples had approximately 1.5 times the water absorption capacity of the sewage treatment carriers of the Comparative Examples.

[0024] Furthermore, the sewage treatment carriers of the Example and Comparative Example were each placed in a water tank with no water flow, and a comparison test was conducted on the water compatibility test. In the water compatibility test, the sewage treatment carrier of the Example gradually sank in 10 days and completely sank in 3 weeks, while the sewage treatment carrier of the Comparative Example did not sink even after 2 months. Figure 5 shows the state of the Example after 2 months, and Figure 6 shows the state of the Comparative Example after 2 months. In the Example, the fermented kelp from soup stock was dissolved in the water on the second day, and the water turned light brown.

[0025] It is considered that the sewage treatment carriers of the Examples have higher water absorption rates and better water affinity than the Comparative Examples, and therefore can quickly obtain fluidity.

[0026] As can be seen from the above comparative tests, the sewage treatment carriers of the Examples have higher water absorption rates, better compatibility with water, and superior fluidity in water compared to the sewage treatment carriers of the Comparative Examples.

[0027] Figure 7 shows electron microscope photographs of the wastewater treatment carrier of the embodiment taken at a magnification of about 40 times, where Figure 7(a) shows the carrier before being placed in water and Figure 7(b) shows the carrier one week after being placed in water. Figure 7(b) shows that the pores have expanded compared to Figure 7(a) as a result of the elution of fermented kelp from soup stock residue.

[0028] By fluidizing the sewage treatment carrier in water, the carrier comes into contact with the treated water more frequently, and can exert its filtering ability. Therefore, the embodiment can shorten the sewage treatment period by obtaining fluidity earlier than the comparative example. Furthermore, the fermented kelp from soup stock residue contains high concentrations of nutrients that are easily metabolized and utilized by microorganisms, and when these are dissolved in water, they become a nutrient source (food) for filtering bacteria (aerobic bacteria), promoting the growth of aerobic bacteria and increasing the sewage treatment ability.

[0029] Using a sewage purification experimental tank equipped with an aeration tank (volume 4 liters) and a sedimentation tank (volume 2 liters), 200 pieces of each of the sewage treatment carriers of the above-mentioned Example and Comparative Example were put into the aeration tank of each sewage purification experimental tank, artificial sewage (COD concentration 200 mg / liter) was flowed into the aeration tank at 4 liters / day, and the COD concentration of the treated water (water flowing out from the sedimentation tank) was measured every two days. The daily change in COD concentration is shown in the graph of FIG. 8. From the graph of FIG. 8, it can be seen that the COD concentration of the water treated with the sewage treatment carrier of the Example is significantly lower than that of the water treated with the sewage treatment carrier of the Comparative Example from the second day after the start of the inflow of artificial sewage. Therefore, by using the sewage treatment carrier of the Example, the effect of speeding up the start-up of the sewage treatment facility can be obtained compared to the conventional sewage treatment carrier of the Comparative Example.

[0030] The present invention should not be construed as being limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

Claims

1. A sewage treatment carrier formed into a foam structure from a thermoplastic resin containing fermented kelp from soup stock residue and a filler for adjusting specific gravity.

2. The sewage treatment carrier according to claim 1, wherein the thermoplastic resin is polypropylene, the specific gravity adjusting filler is talc, and the fermented kelp from soup stock residue is contained in an amount of 5 to 10 parts by weight per 100 parts by weight of the total of the thermoplastic resin and the specific gravity adjusting filler.

3. The sewage treatment carrier according to claim 1, having a specific gravity of 1.00 to 1.05.

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