Wastewater treatment method and system

Abstract

A method and system for treating wastewater is provided. [Solution] The present disclosure provides a method for treating wastewater, the method including the steps of: (a) providing wastewater containing fine plastics; (b) forming a coagulate in the wastewater using iron ions; (c) separating a supernatant liquid and the coagulate from the wastewater; (d) aging the coagulate; and (e) heat treating the coagulate, and also provides a system capable of realizing the method.

Description

[Technical field]

[0001] The present disclosure relates to methods and systems for treating wastewater. [Background technology]

[0002] Wastewater is water that contains liquid or solid pollutants and cannot be used as is. In a broad sense, wastewater includes all types of wastewater, including domestic sewage, laundry wastewater, industrial wastewater, agricultural and livestock wastewater, etc.

[0003] Wastewater treatment is a process to remove pollutants or harmful substances contained in wastewater, thereby eliminating the adverse effects on rivers and oceans into which wastewater flows. Wastewater treatment methods include physical treatments such as screening, filtration, sedimentation, distillation, evaporation, and magnetic separation, and chemical treatments such as neutralization, oxidation-reduction, decomposition, coagulation, adsorption, flotation, extraction, ion exchange, stripping, and combustion / incineration. There are also aerobic biological treatments such as activated sludge, trickling filter bed, oxidation pond, rotating plate, and contact oxidation, and anaerobic biological treatments such as digestion (methane fermentation) and septic tanks.

[0004] Plastics are used for many purposes due to their light weight, durability and low cost, but when they find their way into water systems, they break down to form microplastics, defined as plastic pieces less than 5mm in size.

[0005] Hydrophobic plastics, which are hydrocarbon-based polymeric compounds, have high adsorption properties for persistent organic pollutants, which are highly hydrophobic. The smaller the size of the plastic, the greater the surface area, which enhances the adsorption properties. In addition, chemicals such as plasticizers, flame retardants, and antioxidants are used in the plastic manufacturing process to improve ease of processing and functionality. Therefore, during the process of decomposing or disposing of plastics, these chemicals may be released directly into the environment and act as toxic substances to marine life.

[0006] Microplastics are so small that they cannot be filtered by sewage treatment plants and are dumped into the ocean, where marine organisms mistake the microplastics containing adsorptive pollutants for food and ingest them, which can cause disturbance to the marine ecosystem. The ingestion of microplastics can cause problems for marine organisms, such as physical injury, changes in feeding behavior, and reduced growth and reproductive ability. Furthermore, all organisms may be exposed to the dangers of microplastics through the food chain. Today, it is important not only to minimize the generation of microplastics, but also to reduce the flow of microplastics that have already been generated into rivers and the ocean.

[0007] Meanwhile, iron oxide is used in many industrial fields. For example, iron oxide is used as a color pigment in ceramics, building materials, plastics, surface coatings and paper, acts as a base for various catalysts or carrier materials, and can absorb or adsorb pollutants. Magnetic iron oxide is used in magnetic storage media, toners, ferrofluids or medical applications, for example as a contrast agent for magnetic resonance tomography. In many of these applications, the particle size of iron oxide particles plays an important role. Therefore, the production of controlled particle sizes is very important. However, it is complicated to produce good quality micronized iron oxide with limited particle size on an industrial scale. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2021-0086149 Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure seeks to provide methods and systems for treating wastewater. [Means for solving the problem]

[0010] A first aspect of the present disclosure is a method for treating wastewater, which may include the steps of: (a) providing wastewater containing microplastics; (b) forming a coagulate in the wastewater using iron ions; (c) separating a supernatant and the coagulate from the wastewater; (d) aging the coagulate; and (e) heat treating the coagulate.

[0011] According to one embodiment, step (b) may comprise positioning an electrode comprising iron within the wastewater and supplying electricity to the electrode.

[0012] According to one embodiment, the pH of the wastewater after step (b) may be above 8.5.

[0013] According to one embodiment, the method may further comprise a step of further purifying the separated supernatant.

[0014] According to one embodiment, step (e) may be carried out at a temperature of 400-1000°C.

[0015] According to one embodiment, the method may further comprise recovering the iron oxide from the heat-treated agglomerate.

[0016] According to one embodiment, the recovered iron oxide may include Fe3O4, γ-Fe2O3, α-Fe2O3, or combinations thereof.

[0017] A second aspect of the present disclosure is a wastewater treatment system that may include a flocculation unit that uses iron ions to form a flocculate in incoming wastewater, a separation unit that separates the wastewater into a flocculate and a supernatant liquid, an aging unit that ages the flocculate, and a heat treatment unit that heat-treats the flocculate.

[0018] According to one embodiment, the coagulation unit is an electro-coagulation device comprising an anode and a cathode, the anode may comprise iron. Effect of the Invention

[0019] The present disclosure provides a method and system that can remove microplastics from wastewater containing microplastics while obtaining pure iron oxide nanoparticles. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic process flow diagram of a wastewater treatment method according to one embodiment. [Diagram 2] 1 shows the results of XRD analysis in Experimental Example 1. [Diagram 3] 1 shows the results of TEM analysis in Experimental Example 1. [Figure 4] 1 shows the results of XRD analysis in Experimental Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The objects, advantages, and features of the present disclosure will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings, but the present disclosure is not necessarily limited thereto. Note that, in describing the present disclosure, if it is determined that a specific description of related publicly known techniques may unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted.

[0022] Wastewater Treatment Methods The present disclosure provides a method for treating wastewater. Figure 1 is a schematic process flow diagram of the wastewater treatment method according to one embodiment of the present disclosure. Hereinafter, the wastewater treatment method of the present disclosure will be described with reference to Figure 1.

[0023] The wastewater to be treated in the present disclosure may contain fine plastics. The fine plastics can be removed from the wastewater by using the wastewater treatment method of the present disclosure. Preferably, by using the wastewater treatment method of the present disclosure, not only the fine plastics but also other contaminants such as organic matter that may be present in the wastewater can be removed from the wastewater.

[0024] The disclosed method can include forming floccules in the provided wastewater using iron ions, the floccules containing fine plastics in the wastewater.

[0025] In the present disclosure, electro-coagulation can be used to form flocculants. Electro-coagulation is a technique that supplies electricity to wastewater to destabilize suspended, emulsified, and insoluble particles of pollutants. When an electrode is placed in the wastewater and electricity is supplied, an electrochemical reaction occurs in which the soluble anode electrode is oxidized to generate metal cations. The metal cations convect and diffuse due to the electric field and concentration gradient, and electrically bond with the pollutants to neutralize them, forming flocculants.

[0026] Such an electrocoagulation method has the advantage that the device is simple and easy to operate. In addition, the sludge generated is mainly composed of metal hydroxides, which easily settles, is easy to dehydrate, and generates a small amount of sludge. In addition, flocs formed by electrocoagulation tend to be larger in size, have a lower water content, and are more stable against acidity than chemically coagulated flocs. In addition, treated water after electrocoagulation has a lower TDS (total dissolved solids) content than chemically coagulated water, so the cost of treatment for reuse is lower. In addition, unlike chemical coagulation that requires a coagulant, electrocoagulation does not use chemicals, so there is no need to neutralize chemicals and no secondary treatment is required.

[0027] Therefore, the wastewater treatment method of the present disclosure includes the steps of placing electrodes in the wastewater and supplying electricity to the electrodes in order to supply iron ions to the wastewater, i.e., to form flocculants in the wastewater. The electrodes include an anode and a cathode. A soluble electrode is used as the anode. In the present disclosure, the anode includes iron. When electricity is supplied to the electrode, the iron of the anode is oxidized, and iron ions can be supplied to the wastewater. The anode can be an electrode made of iron or coated with iron.

[0028] When an iron electrode is used as the anode, an iron, aluminum, or stainless steel electrode can be used as the cathode. The electrode that can be used as the cathode is not limited thereto, and any known insoluble electrode can be used as the cathode as long as it does not interfere with the achievement of the object of the present disclosure.

[0029] Such electrocoagulation may be performed at room temperature. The time for supplying electricity to the electrodes may vary depending on the metal content of the electrodes, the amount of wastewater, the pH of the wastewater, etc. Exemplarily, the step of supplying electricity to the electrodes may be performed for about 10 minutes to about 3 hours. Preferably, the step may be performed for about 20 minutes to about 2 hours. If the step is performed for less than 10 minutes, the oxidation of the metal at the anode may not proceed sufficiently, so that the coagulation is not sufficiently formed, and as a result, the fine plastics may not be sufficiently removed. On the other hand, if the step is performed for more than 3 hours, the metal of the anode may be excessively oxidized, so that the metal electrode used as the anode may need to be replaced too frequently.

[0030] Furthermore, the step of supplying electricity to the electrodes may be performed simultaneously with the step of stirring the wastewater. Stirring during the electric coagulation reaction can improve the flow in the reactor and increase the contact possibility between the metal cations and the hydroxyl groups, thereby increasing the coagulation efficiency, and as a result, the removal rate of fine plastics can be improved.

[0031] In one embodiment of the present disclosure, the step of supplying electricity to the electrodes may be carried out until the pH of the wastewater is greater than about 8.5. Preferably, said step may be carried out until the pH of the wastewater is greater than about 9, more preferably greater than about 9.5.

[0032] Therefore, the pH of the wastewater in which the coagulation is formed may be more than about 8.5, preferably about 9 or more, more preferably about 9.5 or more. If the pH of the wastewater is 8.5 or less, there is a risk that magnetite (Fe3O4) will not be produced in the subsequent process. In addition, from the viewpoint of improving the conversion rate of magnetite, the pH of the wastewater is preferably 9.5 or more.

[0033] After iron ions are supplied into the wastewater, a flocculant is formed after a certain time has elapsed. The iron ions supplied into the wastewater may react with water and oxygen and exist mostly in the form of iron hydroxide and / or iron oxide. Thus, in some embodiments of the present disclosure, the flocculant may include iron hydroxide and fine plastics. In some of these embodiments, the flocculant may further include a small amount of iron oxide. Here, a small amount of iron oxide may be understood as an amount of iron oxide that is less than the amount of iron hydroxide.

[0034] When an iron electrode is used as an anode, electricity is supplied to the iron electrode to supply iron cations in the wastewater. The iron cations react with water and oxygen and are present in the wastewater mostly in the form of iron hydroxides such as Fe(OH)2. Iron cations may also be present in the wastewater in small amounts in the form of iron oxides such as FeO, Fe2O3, and Fe3O4.

[0035] The wastewater treatment method of the present disclosure includes a step of separating a supernatant and a flocculate from the wastewater. In one embodiment of the present disclosure, the separated flocculate can include a precipitate and a suspended solid. Therefore, the separation step can be performed in a manner that separates the precipitate and the suspended solid in the wastewater from the supernatant.

[0036] The wastewater in which the aggregates have formed can be left for a certain period of time after the stirring is stopped. In one embodiment of the present disclosure, the wastewater can be left for about 3 hours to about 48 hours. Preferably, the wastewater can be left for about 5 hours to about 36 hours, preferably about 6 hours to about 24 hours, more preferably about 10 hours to about 18 hours. If the wastewater is left for less than the above-mentioned time, a layer between the precipitate and the supernatant liquid is not sufficiently formed, which may cause a problem of poor separation efficiency. On the other hand, if the wastewater is left for more than the above-mentioned time, there is a problem that the total process time increases and the amount of wastewater treated can be reduced.

[0037] The precipitate and the float thus formed can be separated from the supernatant by known methods, and the precipitate and the float are not treated separately and can be mixed and introduced into the subsequent step.

[0038] One embodiment of the wastewater treatment method of the present disclosure may further include a step of further purifying the supernatant liquid separated from the flocculants. The supernatant liquid separated due to the difference in specific gravity from the flocculants may contain small amounts of contaminants such as residual organic matter and ions. These contaminants can be removed by further purification before the supernatant liquid is discharged into rivers and / or oceans. The method of further purification is not particularly limited as long as it is possible to remove remaining contaminants, and secondary electric coagulation can be performed as necessary. Furthermore, the further purification may include neutralizing the pH of the supernatant liquid.

[0039] According to an embodiment of the present disclosure, the supernatant liquid separated from the flocculate may have a microplastic removal rate of about 90% or more, preferably about 95% or more, and more preferably about 99% or more, before further purification. The removal rate is calculated by dividing the difference between the number of microplastics in the wastewater containing microplastics initially provided and the number of microplastics in the supernatant liquid by the number of microplastics in the wastewater. Here, the number of microplastics may mean the number of microplastics per 1 L of the water. Also, exemplarily, the number of microplastics may be measured by Image FT-IR analysis, but is not limited thereto. The particle size of the microplastics measured here is based on 20 μm or more. The wastewater treatment method of the present disclosure includes a step of aging the separated flocculate. The aging step may convert at least a portion of the iron hydroxide (Fe(OH)2) into magnetite (Fe3O4). According to an embodiment of the present disclosure, the aging step may be performed at room temperature and may be performed for about 12 hours or more. Preferably, the aging step may be performed for 18 hours or more, preferably 24 hours or more. For example, the aging step may be performed for about 24 hours to about 48 hours, about 24 hours to about 36 hours, or about 24 hours to about 30 hours. If the aging time is less than 12 hours, a problem may occur in which magnetite (Fe3O4) is not produced. From the viewpoint of improving the conversion rate to magnetite, the aging time is preferably about 24 hours or more.

[0040] The pH of the flocculant during aging may be greater than about 8.5, preferably about 9 or more, more preferably about 9.5 or more. If the pH of the wastewater is 8.5 or less, a problem may occur in which magnetite (Fe3O4) is not produced during the aging stage. From the viewpoint of improving the conversion rate to magnetite, the pH of the flocculant is preferably about 9.5 or more.

[0041] In order to prevent oxidation of the substances in the agglomerate due to contact with the outside air, the aging step of the agglomerate is preferably carried out in a sealed state. The sealing of the agglomerate can be carried out by a known means. There is no particular limitation as long as it does not hinder the achievement of the object of the present disclosure.

[0042] The wastewater treatment method of the present disclosure may further include a step of dehydrating and pulverizing the aged aggregate. The aggregate may be dehydrated and pulverized to form a powder. The dehydration method of the present disclosure is not particularly limited, and a known sludge dehydration method may be used. For example, centrifugation, pressurized dehydration, drying, evaporation, heating, etc. may be used. The pulverization means of the present disclosure is also not particularly limited. By pulverizing the aggregate by dehydrating and pulverizing, the efficiency of the subsequent heat treatment step can be increased.

[0043] The wastewater treatment method of the present disclosure includes a step of heat treating the pulverized agglomerate. The pulverized agglomerate may include fine plastics, iron hydroxide, and iron oxide. The agglomerate may further include other contaminants such as organic matter.

[0044] The heat treatment step can burn and remove fine plastics and other contaminants from the agglomerates, convert the iron hydroxide in the agglomerates to iron oxide, and in some cases, the iron oxide may change its crystal form.

[0045] According to some embodiments of the present disclosure, the heat treatment step may be performed at a temperature of about 400 to about 1000° C. for about 1 to about 6 hours. The heat treatment step can provide iron oxide nanoparticles, including magnetite (Fe3O4), maghemite (γ-Fe2O3), or hematite (α-Fe2O3) nanoparticles. Preferably, the heat treatment step can provide magnetite (Fe3O4), maghemite (γ-Fe2O3), or hematite (α-Fe2O3) nanoparticles.

[0046] By controlling the temperature of the heat treatment step, iron oxide of a specific crystal form can be produced. Thus, the heat treatment temperature may vary within the above range depending on the crystal form of the iron oxide to be finally obtained. For example, in one embodiment, the heat treatment temperature may be about 400° C. or more and less than about 700° C. In another embodiment, the heat treatment temperature may be about 700° C. or more and less than about 1000° C. If the heat treatment temperature is less than about 400° C., there is a risk that fine plastics in the aggregates may not be completely removed.

[0047] When the aggregates are heat-treated at a temperature between about 400°C and 700°C, maghemite (γ-Fe2O3) nanoparticles can be predominantly produced. When the aggregates are heat-treated at a temperature between about 700°C and 1000°C, hematite (α-Fe2O3) nanoparticles can be predominantly produced. Here, the expression "predominantly produced" means that about 90% or more of the total iron oxide can be produced in a specific crystal form.

[0048] According to one embodiment of the present disclosure, the heat treatment step may be carried out in an air or nitrogen atmosphere.

[0049] An embodiment of the wastewater treatment method of the present disclosure may further include a step of recovering iron oxide from the heat-treated agglomerate. By the above-mentioned heat treatment step, fine plastics are removed, and iron oxide nanoparticles with high purity can be obtained. The recovered iron oxide may include magnetite (Fe3O4), maghemite (γ-Fe2O3), hematite (α-Fe2O3), or a combination thereof. Preferably, the recovered iron oxide may be magnetite (Fe3O4), maghemite (γ-Fe2O3), hematite (α-Fe2O3), or a combination thereof. In one embodiment of the present disclosure, the size of the iron oxide nanoparticles may be about 1 to 200 nm, preferably about 10 to 100 nm.

[0050] The iron oxide nanoparticles obtained by the method of the present disclosure can be utilized in a variety of fields.

[0051] Wastewater Treatment System The present disclosure provides a wastewater treatment system. The system is capable of realizing the wastewater treatment method described above. Hereinafter, descriptions of contents common to the contents described above regarding the wastewater treatment method may be omitted. Furthermore, unless otherwise specified, the technical features related to the wastewater treatment method described above can be similarly applied to the system of the present disclosure.

[0052] The system includes a coalescing unit, a separating unit, an aging unit and a heat treatment unit. In the present disclosure, the term "unit" does not mean only a single device, but can be used as a term including both a single device and multiple devices.

[0053] The flocculation unit uses iron ions to form flocculants in wastewater flowing into the flocculation unit. The wastewater is wastewater containing fine plastics. The flocculants include iron hydroxide or iron oxide generated from fine plastics and iron ions. In one embodiment of the present disclosure, the flocculation unit may be an electric flocculation device. The electric flocculation device includes electrodes, the electrodes including an anode and a cathode. Specifically, the electric flocculation device may include electrodes located inside where the wastewater flows in. In some embodiments of the present disclosure, the flocculation unit may further include a stirring device. The flocculation unit includes an inlet through which the wastewater can flow in and an outlet through which the wastewater having formed flocculants therein can flow out.

[0054] The separation unit separates the wastewater into flocculants and a supernatant liquid. The flocculants include sediment and float. The separation unit may include known means for separating the flocculants from the supernatant liquid. For example, the separation unit may include a settling tank. To remove float, the separation unit may include, for example, a skimmer. The separation unit also includes an inlet that communicates with the outlet of the flocculation unit. The separation unit also includes a supernatant liquid outlet through which the supernatant liquid can be discharged, and a flocculated stream outlet through which the flocculated material can flow out.

[0055] In one embodiment of the present disclosure, the system can include an additional purification unit. The additional purification unit includes an inlet that communicates with the supernatant outlet of the separation unit and includes an outlet. The additional purification unit further purifies the supernatant separated from the coagulate in the separation unit. Any known means capable of further purifying the supernatant can be included in the additional purification unit. The additionally purified supernatant flowing out through the outlet of the additional purification unit can be discharged into a river or ocean, or recycled as industrial water, etc.

[0056] The system of the present disclosure may further include a dewatering unit and a grinding unit. The dewatering unit removes water from the flocculants separated from the supernatant liquid. The dewatering unit includes an inlet that communicates with the flocculant flow outlet of the separation unit and an outlet for discharging the dewatered flocculants.

[0057] The grinding unit grinds the agglomerates, the grinding unit includes an inlet in communication with the outlet of the dewatering unit, and an outlet through which the ground agglomerates flow.

[0058] In this disclosure, the dehydration unit and the grinding unit are described as separate units for the purpose of functional division, but according to one embodiment of the present disclosure, the dehydration unit and the grinding unit may be a single piece of equipment, in which case the outlet of the dehydration unit and the inlet of the grinding unit may not be necessary.

[0059] The heat treatment unit heat-treats the crushed agglomerates. The heat treatment unit includes an agglomerate flow inlet communicating with the outlet of the crushing unit and an outlet for discharging the heat-treated agglomerates. In the heat treatment unit, fine plastics in the agglomerates are removed and iron oxide is produced. According to one embodiment of the present disclosure, the heat treatment unit may further include a gas inlet. The atmosphere in the unit may be controlled to a desired gas atmosphere via the gas inlet.

[0060] Preferred examples are presented below to aid in understanding the present disclosure. However, the following examples are provided merely to facilitate understanding of the present disclosure, and the present disclosure is not limited thereto.

[0061] Working Example Regarding the wastewater treatment method, a laboratory-scale experiment was carried out as follows.

[0062] Experimental example 1. (1) Sludge production Wastewater from a waste plastic recycling process with a suspended solids content of approximately 39 mg / L was supplied to a 500 mL reactor. An electrode was immersed in the reactor. An iron electrode was used as the anode, and a stainless steel electrode was used as the cathode. Approximately 6 mA / cm was applied to the electrode. 2 A current of 10 ...

[0063] (2) XRD and TEM analysis 1) The produced sludge was placed in a bottle, the lid was closed and aged for about 24 hours. It was then dried in an oven at 80°C to remove any residues. Then, XRD and TEM analysis of a part of the sludge was carried out, and the results are shown in Figures 2 and 3 (Aging / pH 9.5 (where pH 9.5 means that the pH of the sludge is 9.5 or higher).

[0064] 2) The sludge produced in the above manner was not aged, and after removing the residue, an XRD analysis was performed, the results of which are also shown in Figure 2 (No Aging / pH 9.5).

[0065] 3) The same wastewater was also subjected to electrocoagulation until the pH of the wastewater reached about 8.5, and the resulting sludge was then aged for about 24 hours. The residues were then removed by drying. The resulting sludge was subjected to XRD analysis, and the results are shown in Figure 2 (Aging / pH 8.5).

[0066] 2 and 3, it can be seen that magnetite (Fe3O4) nanoparticles are generated in the sludge only when the sludge is aged for 24 hours or more and has a pH of 9.5 or more.

[0067] (3) Analysis of microplastic removal rate The number of microplastic particles per 1L of wastewater and the separated supernatant from the waste plastic recycling process used in "(1) Sludge production" was measured. An Image FT-IR instrument was used for the measurement, and the measurement results are shown in Table 1 below.

[0068] [Table 1]

[0069] As shown in Table 1, it is possible to achieve a microplastic removal rate of about 99% without additional purification of the separated supernatant.

[0070] Experimental example 2. 0.2 g of sludge obtained in the same manner as in Experimental Example 1 (2)-1) was placed in a crucible and loaded into a furnace. After purging the inside of the furnace with N2, the temperature of the furnace was raised to about 500°C and about 800°C, respectively, and heat treatment was performed for about 4 hours, after which XRD analysis was performed on the product. The results are shown in Figure 3 (500, 800-sludge). From the XRD analysis results, it was confirmed that magnetic maghemite (γ-Fe2O3) was produced when heat treatment was performed at about 500°C, and non-magnetic hematite (α-Fe2O3) was produced when heat treatment was performed at about 800°C. This is thought to be due to the conversion of iron hydroxide and magnetite in the sludge into these, respectively.

[0071] Any mere variations or modifications of the present disclosure should fall within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be made clear by the appended claims.

Claims

1. A method for treating wastewater, comprising the steps of: (a) providing wastewater containing microplastics; (b) forming a flocculate in the wastewater using iron ions; (c) separating the supernatant and the flocculate from the wastewater; (d) aging the agglomerate; (e) subjecting the agglomerate to heat treatment.

2. Step (b) includes positioning an iron-containing electrode in the wastewater; and providing electricity to the electrodes.

3. 2. The method of claim 1, wherein the pH of the wastewater after step (b) is greater than 8.

5.

4. 2. The method for treating wastewater according to claim 1, further comprising the step of further purifying the separated supernatant liquid.

5. 2. The method of claim 1, wherein step (e) is carried out at a temperature of 400 to 1000°C.

6. 10. The method of claim 1, further comprising recovering iron oxide from the heat-treated agglomerate.

7. The recovered iron oxide is Fe ３ O ４ , γ-Fe ２ O ３ , α-Fe ２ O ３ or a combination thereof.

8. 1. A wastewater treatment system comprising: a flocculation unit that uses iron ions to form flocs in the incoming wastewater; a separation unit for separating the wastewater into a flocculate and a supernatant; an aging unit for aging the agglomerate; a heat treatment unit for heat treating the agglomerate.

9. 10. The wastewater treatment system of claim 8, wherein the flocculation unit is an electro-coagulation device comprising an anode and a cathode, the anode electrode comprising iron.

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