Treatment method of fermentation wastewater

Abstract

The invention discloses a treatment method of fermentation wastewater. The fermentation wastewater is wastewater generated after fermentation treatment of kitchen garbage, and the treatment method comprises the following steps: adding trichoderma harzianum into the fermentation wastewater for fermentation culture until a thallus wall-hanging phenomenon occurs, then adding green algae, carrying out fermentation culture for 5-8 days, then carrying out solid-liquid separation, adding a flocculating agent into liquid obtained after solid-liquid separation for sedimentation, and finally, carrying out solid-liquid separation to obtain the fermentation wastewater. And adding activated carbon, stirring, and centrifuging after stirring to obtain a supernatant which is purified water capable of being directly discharged from a sewer. According to the treatment method of the fermentation wastewater, purified water which can be directly discharged from a sewer can be obtained at a lower cost.

Description

[0001] This application is a divisional application of the patent application number 2025112474933 filed on September 3, 2025. Technical Field

[0002] This invention relates to a method for treating fermentation wastewater, and particularly to a method for producing oils from fermentation wastewater. Background Technology

[0003] Fermentation wastewater, especially the wastewater produced after fermenting kitchen waste to produce lactic acid, is a high-concentration organic wastewater with a high COD content. The main indicators exceeding the standards include COD (chemical oxygen demand), TN (total nitrogen), TP (total phosphorus), ammonia nitrogen, and BOD (biochemical oxygen demand). If it is directly discharged into the external environment, it will seriously cause eutrophication of water bodies and pollute the environment.

[0004] There are reports on the treatment and reuse of fermentation wastewater. For example, patent CN105417844A discloses a method for treating fermentation wastewater, including the following steps: centrifuging the fermentation wastewater to separate it into a clear liquid and a concentrated liquid, wherein the biomass concentration of the concentrated liquid is greater than that of the clear liquid; sending the concentrated liquid to a drying tower for atomization drying to obtain dry powder, which can be used as biological feed or raw material for biological feed; sending the clear liquid to a wastewater treatment system, where the pH is adjusted to neutral and then discharged after biochemical treatment. However, in this method, the clear liquid still contains high levels of COD, TN, TP, ammonia nitrogen, and BOD, requiring further biochemical treatment in the wastewater treatment system. Although there are also solutions using bacteria to treat fermentation wastewater, the cost of traditional bacterial treatment of fermentation wastewater is usually high.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method for treating fermentation wastewater, which can produce oil while treating fermentation wastewater, thereby reducing the cost of fermentation wastewater treatment.

[0007] The present invention adopts the following technical solution: A method for treating fermentation wastewater includes: adding filamentous fungi and green algae to the fermentation wastewater generated after fermenting kitchen waste for fermentation culture, followed by solid-liquid separation, and extracting oil from the separated solid.

[0008] In a preferred embodiment, the filamentous fungus includes Trichoderma harzianum.

[0009] In a preferred embodiment, the green algae includes one or more combinations selected from Chlorella vulgaris, Chlamydomonas, Haematococcus pluvialis, filamentous algae, Alternaria obliqueiformis, and Trichoderma.

[0010] In a preferred embodiment, the amount of the filamentous fungus added is 0.5 × 10⁻⁶. 7 ~1.5×10 7 The number of filamentous fungi added is 0.5 × 10⁻⁶ per mL. 7 cells / mL, 0.6×10 7 cells / mL, 0.7×10 7 cells / mL, 0.8×10 7 cells / mL, 0.9×10 7 cells / mL, 1.0×10 7 cells / mL, 1.1×10 7 cells / mL, 1.2×10 7 cells / mL, 1.3×10 7 cells / mL, 1.4 × 10 7 cells / mL or 1.5 × 10⁻⁶ 7 / mL. In a more preferred embodiment, the amount of filamentous fungi added is 0.8 × 10⁻⁶. 7 cells / mL ~1.2×10 7 / mL. In a more preferred embodiment, the amount of filamentous fungi added is 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 / mL. In a specific and preferred embodiment, the amount of filamentous fungi added is 1×10 7 per mL.

[0011] In a preferred embodiment, the amount of green algae added is 0.5 × 10⁻⁶. 7 ~1.5×10 7 The concentration of green algae added can be 0.5 × 10⁻⁶ cells / mL. 7 cells / mL, 0.6×10 7 cells / mL, 0.7×10 7 cells / mL, 0.8×10 7 cells / mL, 0.9×10 7 cells / mL, 1.0×10 7 cells / mL, 1.1×10 7 cells / mL, 1.2×10 7 cells / mL, 1.3×10 7 cells / mL, 1.4 × 10 7 cells / mL or 1.5 × 10⁻⁶ 7 / mL. In a more preferred embodiment, the amount of green algae added is 0.8 × 10⁻⁶. 7 cells / mL ~1.2×10 7 / mL. In a more preferred embodiment, the amount of green algae added is 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 / mL. In a specific and preferred embodiment, and in a more preferred embodiment, the amount of green algae added is 1×10 7 per mL.

[0012] In a preferred embodiment, the fermentation is carried out under shaking conditions without the addition of carbon dioxide. This avoids the need for equipment to inject carbon dioxide into the shaking flasks, reducing the cost of both carbon dioxide and the equipment used for injecting it.

[0013] In a preferred embodiment, filamentous fungi are first added to a fermentation container containing fermentation wastewater. After observing the presence of fungal cells adhering to the walls, green algae are added, and fermentation continues. Furthermore, no additional carbon dioxide is added to the fermentation container.

[0014] In a preferred embodiment, the fermentation culture time is 4 to 10 days. The fermentation culture time can be, for example, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, or 10 days. In a more preferred embodiment, the fermentation culture time is 5 to 8 days. In a specific and preferred embodiment, the fermentation culture time is 5 days.

[0015] In a preferred embodiment, the separated solid is first freeze-dried, ground into powder, and extracted with an organic solvent to obtain oil; after the separated liquid is settled by adding a flocculant, powdered activated carbon is added and stirred; the supernatant after separation is clean water that can be directly discharged into the sewer. In a more preferred embodiment, the ground powder can be purified by extraction with a chloroform-methanol mixture, wherein the weight / volume ratio of the powder to the chloroform-methanol mixture is 1:(5~8), more preferably 1:(5.5~6.5). The volume ratio of chloroform to methanol is (1~3):1. In a more preferred embodiment, the flocculant can be alumina, and the activated carbon is added at a rate of 1g~5g per 100mL of supernatant, more preferably 1g~2g per 100mL of supernatant.

[0016] In a preferred embodiment, the processing method is implemented as follows: Trichoderma harzianum was added to a shake flask containing fermentation wastewater at a concentration of 0.5 × 10⁻⁶. 7 ~1.5×10 7 Cells / mL, pre-cultured at 25~35℃ and shaking speed of 80~120rpm; After observing bacterial cells adhering to the walls of the shake flask, Chlorella or Chlamydomonas was added at a rate of 0.5 × 10⁻⁶. 7 ~1.5×10 7 cells / mL; Maintain a temperature of 25-35℃ and a shaking speed of 80-120 rpm, and continue fermentation for 4-10 days with a light-12-hour light / dark cycle. During the fermentation process, no additional carbon dioxide is introduced into the shake flask.

[0017] In a more preferred embodiment, the fermentation broth in the shake flask after fermentation culture is centrifuged, the centrifuged solid is freeze-dried and ground into powder; the powder and chloroform-methanol mixture are mixed at a weight / volume ratio of 1:(5~8), and extracted at a temperature of 25~35°C and a shaking speed of 80~120 rpm; then centrifuged, the chloroform phase at the bottom is removed, and the oil is obtained by vortexing or blowing.

[0018] In a more preferred embodiment, aluminum chloride flocculant is added to the supernatant after centrifugation. After sedimentation, the supernatant is collected, and activated carbon is added at a rate of 1.5 g per 100 mL of supernatant. The mixture is stirred at 50-60°C and then centrifuged. The resulting purified water is suitable for direct discharge into the sewer system. Furthermore, the purified water after centrifugation is subjected to quality control using an ultrafiltration membrane and a vacuum filtration device. Because the final treated water has undergone the aforementioned biological treatment, membrane clogging time is significantly delayed, thereby reducing losses in the ultrafiltration device. The inventors have not encountered membrane clogging in numerous experiments.

[0019] The present invention adopts the above solution and has the following advantages: This invention proposes a method for treating fermentation wastewater. It utilizes the symbiotic relationship between filamentous fungi and green algae, using fermentation wastewater as the basis for co-cultivation of filamentous fungi and green algae. This method can achieve oil production while treating fermentation wastewater, and can extract oils such as oleic acid, linoleic acid, and palmitic acid from the solids after wastewater treatment. This offsets part of the cost of fermentation wastewater treatment, thereby reducing the overall cost of fermentation wastewater treatment.

[0020] In a further embodiment, the waste liquid after the solids are separated can be transformed into purified water that meets the standards for direct discharge into sewers through simple treatment (such as activated carbon adsorption). Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a photograph of the original water sample of the fermentation wastewater used in Example 1.

[0023] Figure 2 The image shows the bacterial cells adhering to the walls of the three shake flasks in Example 1, before the addition of green algae.

[0024] Figure 3 The image shows photos of the biologically treated fermentation wastewater from the three shake flasks in Example 1.

[0025] Figure 4 The image shows the biomass in the fermentation broth after biological treatment in the three shake flasks in Example 1.

[0026] Figure 5 This is a photograph of the microbial solid residue from Example 1.

[0027] Figure 6 This is a photograph of the oil product from Example 1.

[0028] Figure 7 This is a photograph of the purified water after the final treatment in Example 1.

[0029] Figure 8a This is a microscope image of the fermentation broth after biological treatment in Comparative Example 1.

[0030] Figure 8b This is a microscope image of the fermentation broth after biological treatment in Example 2. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more readily understood by those skilled in the art. It should be noted that the description of these embodiments is for the purpose of aiding understanding the present invention, but does not constitute a limitation thereof.

[0032] This embodiment directly utilizes the fermentation wastewater generated from the fermentation production process (kitchen waste fermentation treatment) of our company (Suzhou Xinghuan Biotechnology Co., Ltd.) to co-culture filamentous fungi and green algae. The solid portion of the fermentation liquid after biological treatment produces algal oil, while the liquid portion, after simple treatment, meets discharge standards and can be directly discharged into the sewer. Furthermore, the inventors discovered a symbiotic relationship between the filamentous fungi *Trichoderma harzianum* and green algae (especially *Chlorella vulgaris* and *Chlamydomonas*). Co-culturing these two fungi significantly increases the biomass of both fungi and algae, resulting in increased oil production.

[0033] In a specific implementation, filamentous fungi—Trichoderma harzianum—are mixed with algae (such as Chlorella or Chlamydomonas) in a one-step fermentation process. The fermentation is carried out in shake flasks for 5 days without the addition of carbon dioxide. The resulting algal residue produces biomass oil, the quality of which is provided by the third-party testing agency, PONY Testing. After biological treatment, the pollution indicators in the fermentation wastewater are significantly reduced, allowing for easier flocculation and activated carbon adsorption, followed by ultrafiltration to obtain clean water, with a significantly delayed membrane clogging time.

[0034] In some embodiments, a method for producing oil from fermentation wastewater is provided, comprising: adding filamentous fungi and green algae to the fermentation wastewater for fermentation culture, followed by solid-liquid separation, and extracting oil from the separated solid. The filamentous fungi include *Trichoderma harzianum*, and the green algae include one or more combinations selected from *Chlorella vulgaris*, *Chlamydomonas*, *Haematococcus pluvialis*, filamentous algae, *Pterocarya oblata*, and *Trichoderma*, preferably *Chlorella vulgaris* and / or *Chlamydomonas*. The amount of filamentous fungi added is 0.5 × 10⁻⁶. 7 ~1.5×10 7 Cells / mL, preferably 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 The concentration of green algae added was 0.5 × 10⁻⁶ cells / mL. 7 ~1.5×10 7 Cells / mL, preferably 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 Cells / mL. More specifically, the pre-culture inoculum size is 5% fungi v / v + 5% algae v / v.

[0035] Specifically, *Trichoderma harzianum* was added to a shake flask containing fermentation wastewater at a concentration of 0.5 × 10⁻⁶. 7 ~1.5×10 7 Pre-culture was carried out at a concentration of 10 cells / mL, with a temperature of 25-35℃ and a shaking speed of 80-120 rpm. After observing the appearance of bacterial cells adhering to the walls of the shake flask, Chlorella or Chlamydomonas was added at a concentration of 0.5 × 10⁻⁶. 7 ~1.5×10 7 The concentration of 10 cells / mL was maintained at 25-35℃ and a shaking speed of 80-120 rpm. The light exposure was alternating between 12 hours of light and 12 hours of darkness, and fermentation was continued for 4-10 days. During the fermentation process, no additional carbon dioxide was introduced into the shake flask. After fermentation, the fermentation broth in the shake flask was centrifuged, and the solid was freeze-dried and ground into powder. The powder was mixed with a chloroform-methanol mixture at a weight / volume ratio of 1:(5-8), and extracted at 25-35℃ and a shaking speed of 80-120 rpm. Then, the mixture was centrifuged, and the chloroform phase at the bottom was removed and evaporated or dried to obtain the oil.

[0036] In other embodiments, a complete treatment method for fermentation wastewater is provided, comprising: adding filamentous fungi and green algae to the fermentation wastewater for fermentation culture, followed by solid-liquid separation, centrifuging the supernatant for flocculation and / or adsorption treatment, and finally centrifuging to obtain purified water that meets sewer discharge standards. The filamentous fungi include *Trichoderma harzianum*, and the green algae include one or more combinations selected from *Chlorella vulgaris*, *Chlamydomonas*, *Haematococcus pluvialis*, filamentous algae, *Phyllostachys pubescens*, and *Trichoderma*, preferably *Chlorella vulgaris* and / or *Chlamydomonas*. The amount of filamentous fungi added is 0.5 × 10⁻⁶. 7 ~1.5×10 7 Cells / mL, preferably 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 The concentration of green algae added was 0.5 × 10⁻⁶ cells / mL. 7 ~1.5×10 7 Cells / mL, preferably 0.9 × 10⁻⁶. 7 cells / mL ~1.2×10 7 Cells / mL. More specifically, the pre-culture inoculum size is 5% fungi v / v + 5% algae v / v.

[0037] Specifically, aluminum chloride flocculant is added to the supernatant after centrifugation. After sedimentation, the supernatant is collected, and activated carbon is added at a rate of 1.5g per 100mL of supernatant. The mixture is stirred at 50-60℃ and then centrifuged. The resulting water is clean and can be directly discharged into the sewer system. The solids from sedimentation and centrifugation are still treated as hazardous waste, but compared to conventional treatment methods that require the removal of large volumes of hazardous waste, removing only the activated carbon and flocculated solids significantly reduces costs.

[0038] Furthermore, the purified water after centrifugation is subjected to quality control using an ultrafiltration membrane and a vacuum filtration device. Since the final treated water has already undergone the aforementioned biological treatment, membrane clogging time is significantly delayed, thereby reducing losses in the ultrafiltration device. The inventors have not encountered membrane clogging in numerous experiments.

[0039] Example 1 Original water sample: Fermentation wastewater generated during the fermentation production process of Suzhou Xinghuan Biotechnology Co., Ltd., such as... Figure 1 As shown in Table 1 below, the pollution data for the original water samples were tested and provided by the Industrial Water Center of Tsinghua Suzhou Environmental Innovation Research Institute.

[0040] Table 1

[0041] Biological treatment: Without any other pretreatment steps, take three equal portions of fermentation wastewater and add them to three shake flasks, preparing a fermentation scale of 500ml. Simultaneously add *Trichoderma harzianum* (1×10⁻⁶). 7 Fermentation was carried out at 30°C with a volume of 1 / ml and a pre-culture volume of 25ml, using a shaking speed of 90 rpm, until the following results appeared: Figure 2 The bacterial cell adhesion phenomenon shown was observed when adding common Chlorella vulgaris or Chlamydomonas reinhardtii (1×10⁻⁶). 7 (Number of cells / ml, pre-culture volume 25ml), culture time 5 days, light cycle 12h light / 12h dark alternation, temperature 30°C, shaking speed 90rpm. Only ordinary shake flasks are used; no additional nitrogen dioxide is added.

[0042] See wastewater after biological treatment Figure 3 Microscopic examination revealed a significant increase in the biomass of algae and bacteria in the fermentation broth. (See [reference]) Figure 4 The indicators of the biologically treated water samples from the three shake flasks are shown in Table 2 below. Among them, water sample 1 is the water sample after final treatment of shake flask No. 1 (with Chlorella vulgaris added), and water samples 2 and 3 are the water samples after final treatment of shake flasks No. 2 and No. 3 (with Chlamydomonas reinhardtii added), respectively.

[0043] Table 2

[0044] The fermentation broth was centrifuged at 12,000 rpm to separate the solid and liquid components.

[0045] Solid processing: The separated solids are freeze-dried to obtain the following: Figure 5 The microbial solids are shown. The three shake flasks yielded 3.62 g, 3.76 g, and 3.55 g of lyophilized product, respectively. The lyophilized product was then ground into powder and extracted with a 1:6 (w / v) mixture of algal powder and chloroform-methanol (2:1). The reaction vessel temperature was 30°C, and the stirring speed was 100 rpm for 1 hour. The mixture was then centrifuged at 5000 rpm for 10 min at room temperature. The lower chloroform phase was collected, and the upper organic phase was discarded. The product was then evaporated / blown dry to obtain 0.78 g, 0.86 g, and 0.82 g of the corresponding oils.

[0046] See the appearance of the obtained oil. Figure 6 The collected oils were tested by a third-party company, PONY, and the test results are shown in Table 3 below.

[0047] Table 3

[0048] Butyric acid, hexanoic acid, undecanoic acid, lauric acid, myristic acid, myristic acid, pentadecanoic acid, pentadecanoic acid-enoic acid, heptadecanoic acid, heptadecanoic acid-enoic acid, linolenic acid, and arachidic acid were not detected.

[0049] Liquid treatment: Collect the separated liquid and add 0.1% (w / w) polyaluminum chloride flocculant. After sedimentation, adsorb the supernatant, then add 1.5% (w / v) powdered activated carbon to the supernatant and treat with a magnetic stirrer at 55 degrees Celsius for 45 minutes. Centrifuge at 12000 rpm to obtain the following purified water that can be directly discharged into the sewer system, such as... Figure 7 As shown.

[0050] The testing indicators for the treated purified water are shown in Table 4 below.

[0051] Table 4

[0052] The fully treated water meets the standards for direct discharge into the sewer system.

[0053] Example 2 Example 2 uses the same treatment method as Example 1, the only difference being that the pH in the shake flask was not controlled during the fermentation culture process in Example 2, and the microorganisms added in the biological treatment were Trichoderma harzianum and Chlorella.

[0054] Comparative Example 1 Comparative Example 1 used the same treatment method as Example 1, except that the pH in the shake flask was not controlled during the fermentation culture of the comparative example, and the microorganisms added in the biological treatment were Aspergillus niger and Chlorella.

[0055] The detection indicators of the water samples after biological treatment in Example 2 and Comparative Example 1 are shown in Table 5 below.

[0056] Table 5

[0057] Figure 8a Microscopic images of the fermentation broth after biological treatment in Comparative Example 1 are shown. Figure 8b A microscope image of the fermentation broth after biological treatment in Example 2 is shown. Figure 8a and Figure 8b The comparison of the growth states of different bacterial species in symbiosis with Chlorella shows that... Figure 8b The abundance of algae in the middle reaches of the sea results in a higher oil yield.

[0058] As indicated in this specification and claims, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0059] It can be further understood that in this disclosure, "multiple" refers to two or more, and other quantifiers are similar.

[0060] It is further understood that the terms "first," "second," etc., are used to describe various types of information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another, and do not indicate a specific order or degree of importance. In fact, the expressions "first," "second," etc., are completely interchangeable. For example, without departing from the scope of this disclosure, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention, and are preferred embodiments. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention.

Claims

1. A method for treating fermentation wastewater, wherein the fermentation wastewater is wastewater generated after fermenting kitchen waste, characterized in that, The treatment method includes: adding Trichoderma harzianum to the fermentation wastewater for fermentation culture until the bacterial cells adhere to the wall, then adding green algae and fermenting for 5-8 days, followed by solid-liquid separation, adding flocculant to the liquid after solid-liquid separation for sedimentation, adding activated carbon, stirring, centrifuging, and the supernatant from centrifugation is clean water that can be directly discharged into the sewer.

2. The method for treating fermentation wastewater according to claim 1, characterized in that, After adding green algae, the light exposure time is alternated between 12 hours of light and 12 hours of darkness.

3. The method for treating fermentation wastewater according to claim 1 or 2, characterized in that, The green algae include one or more combinations selected from Chlorella vulgaris, Chlamydomonas, Haematococcus pluvialis, filamentous algae, Alternaria obliqueiformis, and Trichoderma.

4. The method for treating fermentation wastewater according to claim 1, characterized in that, The amount of the filamentous fungus added was 0.5 × 10⁻⁶. 7 ~1.5×10 7 per mL.

5. The method for treating fermentation wastewater according to claim 1, characterized in that, The amount of Trichoderma harzianum added was 0.5 × 10⁻⁶. 7 ~1.5×10 7 per mL.

6. The method for treating fermentation wastewater according to claim 1, characterized in that, The fermentation culture is carried out under shake culture conditions without the addition of carbon dioxide.

7. The method for treating fermentation wastewater according to claim 1, characterized in that, The separated solids are first freeze-dried, ground into powder, and extracted with organic solvents to obtain oils; and / or, the purified water after centrifugation is subjected to quality control using an ultrafiltration membrane and a vacuum filtration device.

8. The method for treating fermentation wastewater according to claim 1, characterized in that, The specific implementation of the processing method is as follows: Trichoderma harzianum was added to a shake flask containing fermentation wastewater at a concentration of 0.5 × 10⁻⁶. 7 ~1.5×10 7 Cells / mL, pre-cultured at 25~35℃ and shaking speed of 80~120rpm; After observing bacterial cells adhering to the walls of the shake flask, Chlorella or Chlamydomonas was added at a rate of 0.5 × 10⁻⁶. 7 ~1.5×10 7 cells / mL; Maintain a temperature of 25-35℃ and a shaking speed of 80-120 rpm, and continue fermentation for 4-10 days with a light-12-hour light / dark cycle. During the fermentation process, no additional carbon dioxide is introduced into the shake flask.

9. The method for treating fermentation wastewater according to claim 8, characterized in that, After fermentation, the fermentation broth in the shake flask is centrifuged, the centrifuged solid is freeze-dried and ground into powder; the powder and chloroform-methanol mixture are mixed at a weight / volume ratio of 1: (5~8), and extracted at a temperature of 25~35℃ and a shaking speed of 80~120rpm; then centrifuged, the chloroform phase at the bottom is removed, and the oil is obtained by rotary drying or blow-drying.

10. The method for treating fermentation wastewater according to claim 9, characterized in that, Aluminum chloride flocculant was added to the supernatant after centrifugation. After sedimentation, the supernatant was collected, and activated carbon was added at a rate of 1.5g per 100mL of supernatant. The mixture was stirred at 50~60℃ and then centrifuged. The resulting purified water was suitable for direct discharge into the sewer system.

Images