Wastewater treatment system

Abstract

To provide a wastewater treatment system that requires simple equipment, has a short treatment time, low equipment costs and operation costs, and can sufficiently reduce coloration of treated wastewater. [Solution] A wastewater treatment system that separates and purifies wastewater from washing discharged from livestock barns, comprising a treated water tank 120 into which the supernatant components of the wastewater are introduced by a supernatant transfer unit 121, a first filtration tank 130 into which the supernatant components of the treated water tank 120 are introduced by a first treated water transfer unit 131, a second filtration tank 140 into which liquid components that have passed through the first filtration tank 130 are introduced by a second treated water transfer unit 141, and a decolorization treatment tank 160 into which liquid components that have passed through the second filtration tank 140 are introduced by a decolorization treatment water transfer unit 161.

Description

[Technical Field]

[0001] This invention relates to a wastewater treatment system for separating and purifying wastewater discharged from livestock barns. [Background technology]

[0002] The wastewater discharged from livestock barns has a strong odor, is polluted, discolored, and has a high BOD value. When processing these materials, one could consider separating them into solid and liquid wastewater, adding dilution water to the wastewater, and then discharging it or allowing it to infiltrate the ground. However, it was difficult to produce purified water that could be discharged without causing environmental pollution. Furthermore, methods to reduce BOD values ​​in order to minimize environmental impact include treating wastewater in aeration tanks that contain microorganisms that process organic matter.

[0003] For example, in a wastewater treatment system known from Patent Document 1, etc., the system includes a raw water tank for temporarily storing parlor wastewater, a screen for removing coarse solids contained in the parlor wastewater, a storage tank for storing the parlor wastewater from which the coarse solids have been removed, a first sedimentation tank for separating and settling the parlor wastewater, an aeration tank containing microorganisms that process the organic matter contained in the parlor wastewater and aerates the water, and a second sedimentation tank for separating and settling the treated parlor wastewater. In this system, the liquid components separated from the solids are purified by microorganisms in the aeration tank. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-87968 [Patent Document 2] Japanese Patent Publication No. 2023-161382 [Overview of the project] [Problems that the invention aims to solve]

[0005] In known wastewater treatment systems, it is possible to reduce BOD values ​​by sufficiently decomposing organic matter in the aeration tank. However, treating large volumes of wastewater requires a large installation area, takes a long time to process, and incurs high equipment costs such as pumps for aeration, as well as high operating costs.

[0006] To solve these problems and provide a wastewater treatment system that uses simple equipment, has a short processing time, low equipment and operating costs, and can sufficiently reduce the BOD value of the treated wastewater, the present inventors have invented the wastewater treatment system shown in Patent Document 2. In one embodiment of the wastewater treatment system described in Patent Document 2, treated water can be obtained in which BOD (biochemical oxygen demand), COD (chemical oxygen demand), SS (suspended solids), and phosphorus all fall below the general wastewater standards set by the Ministry of the Environment based on the Water Pollution Control Law. This treated water can be reused as washing water for the parlor inside the cowshed, or it can be discharged as is. However, because porous wood chips called "Merton Chips" (registered trademark) are used as the filter material for the first and second filtration tanks, there was a problem in that a yellowish-brown color remained in the treated water. If treated water containing this kind of discoloration were reused as cleaning water for the cowshed's parlor, there was a risk that the color would transfer to the parlor and accelerate soiling. Furthermore, if the water were discharged as is, it could lead to local residents and others mistakenly believing that untreated water was being released, potentially hindering the discharge process.

[0007] This invention was made based on the above circumstances, and aims to provide a wastewater treatment system that can use simple equipment, has a short processing time, low equipment and operating costs, and can sufficiently reduce the discoloration of the wastewater after treatment. [Means for solving the problem]

[0008] The present invention relates to a wastewater treatment system for separating and purifying wastewater discharged from a livestock barn, comprising: a treatment tank into which the supernatant component of the wastewater is introduced by a supernatant transfer unit; a first filtration tank into which the supernatant component of the treatment tank is introduced by a first treated water transfer unit; a second filtration tank into which the liquid component that has passed through the first filtration tank is introduced by a second treated water transfer unit; and a decolorization treatment tank into which the liquid component that has passed through the second filtration tank is introduced by a decolorization treatment water transfer unit. The first and second filtration tanks have porous wood chips as a filter material, and the decolorization treatment tank has one or more decolorization treatment layers, and of the decolorization treatment layers, the first decolorization treatment layer into which the liquid component is first introduced by the decolorization treatment water transfer unit contains rice husk activated carbon as a decolorization treatment material. This solves the aforementioned problem. [Effects of the Invention]

[0009] According to the wastewater treatment system of the invention described in claim 1, the liquid components of the wastewater can be purified as it passes continuously through the first and second filtration tanks, thereby reducing equipment costs such as pump equipment for aeration and operating costs. Furthermore, by having a treatment tank into which the supernatant components of the wastewater are introduced by a supernatant transfer unit, even if solid-liquid separation treatment is performed intermittently upstream of the treatment tank, the supernatant components of the wastewater can be stored in the treatment tank and continuously sent to the first and second filtration tanks as a buffer. This allows the first and second filtration tanks to be kept in continuous operation at all times, enabling efficient use of the equipment. Furthermore, by having a decolorization treatment tank into which the liquid components that have passed through the second filtration tank are introduced by a decolorization treatment water transfer unit, the discoloration of the wastewater after treatment can be reduced. Furthermore, since the liquid components that have passed through the second filtration tank are introduced into the decolorization treatment tank by the decolorization treatment water transfer unit, the treated water, in which SS (suspended solids) and other substances have been sufficiently reduced, can be efficiently decolorized, and the operating costs of the decolorization treatment tank can also be reduced. Furthermore, by having one or more decolorization treatment layers in the decolorization treatment tank, the discoloration of the wastewater after treatment can be further reduced. Furthermore, by including rice husk activated carbon as a decolorizing agent, decolorization can be performed using inexpensive and readily available materials.

[0010] According to the configuration described in claim 2, by having a plurality of raw water tanks and a sludge tank into which the precipitated components of the raw water tanks are introduced by the first sludge transfer unit, it becomes possible to introduce the drainage into another raw water tank while introducing the drainage into one raw water tank and allowing it to settle for a predetermined time, and to continuously introduce the drainage while sufficiently performing solid-liquid separation by precipitation, thereby improving the treatment efficiency.

[0011] Claim 3 According to the configuration described in, the decolorization treatment layer is provided on a support member having through holes By doing so, for each decolorization treatment layer, adjustment and replacement of the decolorization treatment material can be performed.

Brief Description of the Drawings

[0012] [Figure 1] Schematic configuration diagram of the wastewater treatment system according to an embodiment of the present invention. [Figure 2] Plan view explanatory diagram of the wastewater treatment system according to an embodiment of the present invention. [Figure 3] Appearance view of the treated water of the wastewater treatment system according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0013] As shown in FIGS. 1 and 2, a wastewater treatment system 100 according to an embodiment of the present invention has a plurality of raw water tanks 110 into which the drainage of the washing wastewater discharged from the livestock house is introduced by a drainage introduction unit 111, a treatment agent is added and stirred by a stirring unit 112, and then precipitation separation is performed, a treatment water tank 120 into which the supernatant components of the raw water tanks 110 are introduced by a supernatant transfer unit 121, a first filtration tank 130 into which the supernatant components of the treatment water tank 120 are introduced by a first treated water transfer unit 131, a second filtration tank 140 into which the liquid components passing through the first filtration tank 130 are introduced by a second treated water transfer unit 141, and a decolorization treatment tank 160 into which the liquid components passing through the second filtration tank 140 are introduced by a decolorized treated water transfer unit 161. Further, it has a sludge tank 150 into which the precipitated components of the plurality of raw water tanks 110 are introduced by a sludge transfer unit 151.

[0014] The sludge tank 150 is located below the bottom of the raw water tank 110 and the treated water tank 120. In this embodiment, the raw water tank 110, the treated water tank 120, the first filtration tank 130, and the second filtration tank 140 are separated by partition walls rising from the floor, and the sludge tank 150 is located below the floor as an underground conduit. A sludge bin 115 containing solid matter, which is a sedimentary component, is provided at the bottom of the raw water tank 110, and the sludge transfer unit 151 is configured to transfer the sludge accumulated in the sludge bin 115 to the sludge tank 150.

[0015] The first filtration tank 130 and the second filtration tank 140 are filled with a filter material made of porous wood chips, and the liquid components introduced from the first treated water transfer unit and the second treated water transfer unit are showered onto the upper surface of the filter material, allowing them to permeate evenly. Furthermore, bottom pipes 135 and 145, which are made of pipe members with numerous inlet holes on their sides, are arranged at the bottom of the first filtration tank 130 and the second filtration tank 140, respectively, and are configured to efficiently recover the liquid components that have passed through the filter material. In this embodiment, two raw water tanks 110 are provided, but three or more tanks may be used. Furthermore, the first filtration tank 130 is divided into two sections, and its total capacity is twice that of the second filtration tank 140. However, the volume ratio can be appropriately set according to the passage rate of each liquid component. Furthermore, it is desirable to install blower piping at an intermediate height in the first filtration tank 130 and the second filtration tank 140 to prevent clogging by small amounts of solid matter and to maintain the activity of microorganisms.

[0016] As shown in Figure 1, the decolorization tank 160 has a decolorization treatment layer 162 consisting of a total of three layers: a first decolorization treatment layer 162a provided on a first support member 163a, a second decolorization treatment layer 162b provided on a second support member 163b, and a third decolorization treatment layer 162c provided on a third support member 163c. The decolorization treatment layer 162 is filled with a decolorization treatment material made of porous activated carbon, and the liquid component introduced from the decolorization treatment water transfer unit 161 is configured to penetrate evenly by showering the upper surface of the decolorization treatment material in the first decolorization treatment layer 162a. Here, since each decolorization treatment layer 162 is provided on a support member 163, the amount of decolorization treatment material to be filled can be adjusted according to the flow rate of the liquid component introduced into the decolorization treatment tank 160, and the decolorization treatment material can be replaced individually for each decolorization treatment layer 162, thereby reducing equipment costs and operating costs. Furthermore, a bottom pipe 165, consisting of a pipe member with numerous inlet holes on its sides, is positioned at the bottom of the decolorization treatment tank 160, and is configured to efficiently recover the liquid components that have passed through the decolorization treatment layer 162. In this embodiment, one decolorization treatment tank 160 is provided, but two or more tanks may be provided.

[0017] The following describes the specific treatment flow when treating wastewater discharged from the cowshed parlor (the place where milk is extracted) using the wastewater treatment system 100 configured as described above. The capacities of each tank are as follows: Raw water tank ···Approx. 35m 3 *2 1st filtration tank ···Approx. 40m 3 *2 2nd filtration tank ·Approx. 40m 3 Treatment tank ··approximately 90m 3 Furthermore, "Merton Chips" (registered trademark) were used as the filter material for the first filtration tank 130 and the second filtration tank 140.

[0018] First, the wastewater from the cowshed parlor is pumped into one of the raw water tanks 110 by a pump installed in the wastewater introduction unit 111 until it reaches 30 tons. When 30 tons of wastewater are introduced into one of the raw water tanks 110, the electric ball valve connected to that raw water tank 110 is closed, and the electric ball valve connected to the other raw water tank 110 is opened. Next, the treatment agent is added to one of the raw water tanks 110 while stirring it with the stirring unit 112. In this embodiment, ferric polysulfate solution, caustic soda solution, and polymer flocculation accelerator (Z-Floc C-101) were used as treatment agents. Using a metering pump (not shown), 45 L of ferric polysulfate is injected over 2 minutes, followed by 20 L of caustic soda solution over 2 minutes, and finally, 450 L of polymer flocculation accelerator is injected over 3 minutes. Once the chemicals are injected into the raw water tank 110, the metering pump's piping also closes the electric ball valve connected to one of the raw water tanks 110, and opens the electric ball valve connected to the other raw water tank 110.

[0019] After stirring for another 2 minutes, the stirring unit 112 is temporarily stopped, and after stirring in reverse for 1 minute, the stirring unit 112 is stopped and left to stand for 30 minutes to 1 hour. Next, the pump of the supernatant transfer unit 121 operates to transfer the supernatant components to the treatment tank 120, and the pump of the sludge transfer unit 151 operates to transfer the settled components to the sludge tank 150. At this time, the pump of the sludge transfer unit 151 repeats an intermittent operation of 10 seconds of operation followed by 20 seconds of rest until the pump of the supernatant transfer unit 121 stops operating. Subsequently, the sludge remaining at the bottom of the raw water tank 110 is transferred to the sludge tank 150 by operating the stirring motor for approximately 20 seconds, followed by continuously operating the pump of the sludge transfer unit 151. By performing the above process alternately in the two raw water tanks 110, a predetermined amount of liquid is always stored in the treated water tank 120, making it possible to efficiently carry out subsequent continuous processing.

[0020] The liquid components stored in the treated water tank 120 are transferred to the first filtration tank 130 by the pump of the first treated water transfer unit 131. At this time, it is desirable to draw water from 500 mm above the bottom of the treatment tank 120 so that any small amount of residual solid components do not mix with the sludge that settles at the bottom of the treatment tank 120. Also, as maintenance about twice a year, it is desirable to transfer the sludge deposited at the bottom of the treatment water tank 120 to the sludge tank 150. The liquid component that has passed through the first filtration tank 130 is transferred to the second filtration tank 140 by the pump of the second treated water transfer unit 141. The liquid component discharged from the second filtration tank 140 has a significantly reduced BOD value. Further, the liquid component that has passed through the second filtration tank 140 is transferred to the decolorization treatment tank 160 by the pump of the decolorized treated water transfer unit 161. The treated water discharged from the decolorization treatment tank 160 has a sufficiently reduced color, and it is possible to reuse the water as the washing water for the in-barn parlour, or it can also be discharged as it is.

[0021] The results of the treatment in this embodiment are shown below.

Table 1

[0022] As can be seen from the above table, by passing through the first filtration tank 130, all of BOD (biochemical oxygen demand), COD (chemical oxygen demand), SS (suspended solids), and phosphorus are reduced to values below the general wastewater standards set by the Ministry of the Environment based on the Water Pollution Control Law. By passing through the second filtration tank 140, SS and phosphorus are further reduced.

[0023] The specific treatment flow when treating the wastewater discharged from the in-barn parlour (the place where milk is taken out) with the wastewater treatment system 100 configured as described above will be explained. The capacity of each tank is as follows. Raw water tank ·· approximately 35m 3 *2 First filtration tank ·· approximately 40m 3 *2 Second filtration tank ·· approximately 40m 3 Treatment water tank ·· approximately 90m 3 Decolorization treatment tank ·· approximately 40m 3 Furthermore, rice husk activated carbon was used as the decolorizing material for the first decolorizing layer 162a, rice husk activated carbon processed into 8mm diameter pellets was used as the decolorizing material for the second decolorizing layer 162b, and activated carbon made from food waste was used as the decolorizing material for the third decolorizing layer 162c. Furthermore, a perforated metal plate with numerous through holes, each 1 mm in diameter, was used as the support member 163.

[0024] The liquid components that have passed through the second filtration tank 140 are transferred to the decolorization treatment tank 160 by the pump of the decolorization treatment water transfer unit 161. At this time, the treated water discharged from the second filtration tank 140 has a significantly reduced SS value, which prevents clogging of the decolorization treatment layer 162, allows for efficient decolorization in a short time, and reduces operating costs. Furthermore, the frequency of replacing the decolorizing treatment material can be reduced, thereby lowering equipment costs.

[0025] The liquid components, which are transferred to the decolorization tank 160 and showered onto the upper surface of the first decolorization layer 162a, pass through the first decolorization layer 162a and are decolorized by the decolorization agent, and then pass through the through holes provided in the first support member 163a and are introduced onto the upper surface of the second decolorization layer 162b. The liquid component introduced to the upper surface of the second decolorization layer 162b passes through the second decolorization layer 162b, is decolorized by the decolorization agent, and then passes through the through hole provided in the second support member 163b and is introduced to the upper surface of the third decolorization layer 162c. The liquid component introduced onto the upper surface of the third decolorization layer 162c passes through the third decolorization layer 162c, is decolorized by the decolorization agent, and then passes through the through-hole provided in the third support member 163c and is introduced into the bottom piping 165. The treated water discharged from the decolorization tank 160 has had its coloring sufficiently reduced, and can be reused as washing water in the cowshed parlor, or it can be discharged as is.

[0026] Figure 3 shows photographs of the wastewater treated in this embodiment after passing through the first filtration tank 130, the second filtration tank 140, and the decolorization treatment tank 160. As can be seen in Figure 3, passing through the decolorization tank 160 significantly reduces the yellowish-brown discoloration that remained in the treated water after passing through the second treatment tank 140.

[0027] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design modifications can be made without departing from the present invention as described in the claims. The wastewater treatment system according to the present invention has a decolorization treatment layer 162 consisting of a total of three layers, but the number of layers in the decolorization treatment layer 162 is not limited to three, and may consist of one to two layers or four or more layers. Furthermore, in the embodiment described above, the first decolorization layer 162a, the second decolorization layer 162b, and the third decolorization layer 162c all have the same volume, but the mounting position of the support member 163 may be changed to appropriately alter the volume of the decolorization layer 162. Furthermore, in the above-described embodiment, rice husk activated carbon is used as the decolorizing material for the first decolorizing layer 162a, rice husk activated carbon processed into 8 mm diameter pellets is used as the decolorizing material for the second decolorizing layer 162b, and activated carbon made from food waste is used as the decolorizing material for the third decolorizing layer 162c. However, the order of the decolorizing layers through which the wastewater to be decolorized passes may be changed, and different types of activated carbon may be used as decolorizing materials. [Explanation of symbols]

[0028] 100 ··· Wastewater treatment system 110 ··· Raw water tank 111 ··· Drainage Inlet Unit 112 ··· Stirring Unit 115 ··· Sludge manhole 120 ··· Treatment tank 121 ··· Supernatant Transfer Unit 130... 1st filtration tank 131 ··· First treated water transfer unit 135 ... bottom piping 140... 2nd filtration tank 145 ... bottom piping 141 ··· Second treated water transfer unit 150 ··· Sludge tank 151 ··· Sludge transfer unit 160 ··· Decolorization treatment tank 161 ··· Decolorized water transfer unit 162 ··· Decolorized layer 162a ··· First decolorization layer 162b ··· Second decolorization layer 162c ··· Third decolorization layer 163 ··· Support member 163a ··· First support member 163b ··· Second support member 163c ··· Third support member 165 ... bottom piping

Claims

1. A wastewater treatment system that separates and purifies wastewater discharged from livestock barns, A treatment tank into which the supernatant components of wastewater are introduced by a supernatant transfer unit, The supernatant components of the aforementioned treated water tank are introduced into a first filtration tank by a first treated water transfer unit, The liquid components that have passed through the first filtration tank are introduced into a second filtration tank by a second treated water transfer unit, The system includes a decolorization treatment tank into which the liquid components that have passed through the second filtration tank are introduced by a decolorization treatment water transfer unit, The first and second filtration tanks have porous wood fragments as a filter material. The decolorization treatment tank has one or more decolorization treatment layers, A wastewater treatment system characterized in that, among the decolorization treatment layers, the first decolorization treatment layer into which the liquid component is first introduced by the decolorization treatment water transfer unit contains rice husk activated carbon as a decolorization treatment material.

2. The wastewater treatment system comprises multiple raw water tanks into which wastewater is introduced and sedimentation and separation are performed, The system includes a sludge tank into which the settled components of the raw water tank are introduced by a sludge transfer unit, The wastewater treatment system according to claim 1, characterized in that the first filtration tank and the second filtration tank have the same filter material.

3. The wastewater treatment system according to claim 1, characterized in that the decolorization treatment layer is provided on a plate-shaped support member having through holes.

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