KR20070011720A - Process for treating refractory wastewater using zero-valent iron treatment and biodegradation - Google Patents

Abstract

A method for treating indegradable wastewater by a zero-valent iron process and a biological process is provided to purify even wastewater containing recalcitrant contaminants by combining a physicochemical wastewater treatment process with a biological wastewater treatment process. In a wastewater treatment process for changing toxic compounds in wastewater into non-toxic compounds, a method for treating refractory wastewater by a zero-valent iron process(1) and a biological process comprises: a pretreatment process of pretreating wastewater by containing zero-valent iron as an active component in wastewater; a biological oxidation process(2) for secondly degrading the pretreated wastewater; and a solid-liquid separation process(3) of separating solid and liquid from wastewater by settling the degraded wastewater. The pretreatment process is performed by adding any one or more of sand, gravel and pyrite to wastewater according to characteristics of a removal target and wastewater. The biological oxidation process is selected from activated sludge, trickling filter, rotating biological contactor, other aerobic biological treatment, or anaerobic biological treatment processes.

Description

Non-degradable wastewater treatment method using zero-ferrous iron process and biological process. {PROCESS FOR TREATING REFRACTORY WASTEWATER USING ZERO-VALENT IRON TREATMENT AND BIODEGRADATION}

1 is a schematic view showing a hardly degradable wastewater treatment method using a zero-ferrous iron process and a biological process according to the present invention.

FIG. 2 is a graph showing the reduction of acrolein and formation of propionaldehyde as a product thereof in a batch pretreatment process including a valent metal.

Figure 3 is a graph showing the BOD results in the respiratory system experiments of iodine added wastewater.

Figure 4 is a graph showing the BOD results of wastewater containing acrolein and wastewater containing propylaldehyde.

5 is a photograph observing the physical chromaticity change in the wastewater.

6 and 7 are graphs showing the results of UV-VIS screening measurement of the wastewater before and after the ferrous iron treatment.

8 and 9 show the results of HPLC screening of the wastewater before and after the ferric iron treatment.

10 is a graph showing the results of the BOD measurement of the wastewater before and after the zero-iron treatment.

FIG. 11 is a graph showing biodegradation performance and iodine toxicity of wastewater before and after ferrous iron treatment.

12 is a graph showing the results of BOD measurement of wastewater injected with 25 mg / L and 50 mg / L of acrolein and propylaldehyde.

FIG. 13 is a graph showing the results of BOD measurement before and after the ferric iron treatment of wastewater adjusted to pH 4.4 and pH 5.7, respectively.

14 is a graph showing the batch anaerobic biodegradation performance before and after the wastewater is treated with zero iron as gas as an index.

15 is a graph showing the batch anaerobic biodegradation performance before and after the wastewater is treated with zero iron, with gas composition, in particular methane.

* Explanation of symbols for main parts of drawing *

1: Iron iron process 2: Biological oxidation process

3: solid and liquid separation process

The present invention relates to a wastewater treatment method, in particular, by combining a physicochemical wastewater treatment method and a biological wastewater treatment method, it is possible to purify wastewater containing pollutants that are not easy to decompose, and to process the biological iron and biological The present invention relates to a hardly degradable wastewater treatment method using a process.

Wastewater treatment methods to remove harmful substances or pollutants in wastewater discharged from factories and establishments include solid and liquid separation, physicochemical treatment, biological treatment, and heat treatment, depending on the type and content of wastewater.

Solid-liquid separation method aims to separate and recover the suspended matter in the wastewater, and the sedimentation separation by gravity is the most widely used because of the low processing cost and easy operation and management. However, this method is not preferable to be used in the case where the sedimentation separation efficiency of the suspended solids depends on the area of the sedimentation tank, and the filtration area of the treatment apparatus is limited, and another filtration process must be adopted.

Physical and chemical treatment methods include neutralization, pH adjustment, oxidation and reduction, extraction, adsorption, ion exchange, electrodialysis, and treatment with reverse osmosis membranes. Such a method has a problem in that the treatment cost is high and the stability is not high due to the need for a separate by-product treatment by adding a flocculant or a flocculent aid for neutralization, pH adjustment, oxidation, reduction, and the like.

Processes consisting only of existing biological treatment processes, such as activated sludge processes, are not suitable for the treatment of wastewater containing toxic or hardly decomposable substances, which makes them difficult to apply to wastewater treatment containing such substances. For example, nitroaromatic, azoaromatic, and chloroaromatic compounds are widely used and commonly found in industry and sewage, most of these aromatic compounds are peroxides and are subject to aerobic decomposition. For resistance reasons, conventional aerobic biological treatments are often not suitable for wastewater containing these organic substances.

The heat treatment method is to prevent the discharge of waste water by evaporating water, such as when the environmental conditions of the discharge area are not good, but it is widely used in the treatment of sludge generated by the waste water treatment, but the applicable range is limited. The disadvantage is that the processing cost is high.

The present invention has been made to solve the above problems, by combining a chemical pretreatment process and a biological treatment process, to convert the non-degradable contaminants into biodegradable substances by a chemical pretreatment process consisting of a zero iron column, Subsequent biological treatment process allows the secondary treatment of wastewater containing contaminants with improved biodegradability by the pretreatment process, effectively improving the biodegradability of hardly degradable contaminants that were not easily degraded by the existing activated sludge process. The present invention provides a hardly degradable wastewater treatment method using a zero iron and biological process.

Another object of the present invention is to solve the problem of stability due to the conventional toxic chemicals by using a column containing zero iron as a chemical treatment material, and easy-to-operate non-degradable wastewater treatment method using a non-ferrous iron process and a biological process In providing.

Another object of the present invention is not only to produce toxic by-products, but also inexpensive compared to carbon adsorption and chemical or biological oxidation processes, due to the rapid removal of the compound, the residence time is short, the pollution load is small, and the continuous flow Minimal maintenance is required during the process and the service life is long.

The non-degradable wastewater treatment method using the zero-ferrous iron process and the biological process according to the present invention for achieving the above object, in the wastewater treatment process for changing the toxic compounds in the wastewater to non-toxic, containing the iron as an active component It consists of a pretreatment step, a biological oxidation step of secondary decomposition of the pretreated wastewater, and a separation step by precipitation.

In addition, the pretreatment process is characterized in that any one or more of sand, gravel, pyrite (pyrite) is added according to the treatment target and the characteristics of the waste water.

In addition, the biological oxidation process is characterized in that any one of activated sludge, trickling filter (rotating filter), rotating biological contactor (rotating biological contactor), other aerobic biological treatment process, or anaerobic biological treatment process.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

1 is a schematic view showing a hardly decomposable wastewater treatment method using a zero-ferrous iron process and a biological process according to the present invention,

The wastewater is pretreated by a pretreatment step (1) with a column containing zero constituents, the active constituents, which is pretreated by a biochemical oxidation process (2) and then precipitated in a settling tank (3). After the separation process (3) by the final treatment.

The pretreatment process (1) may include ductile iron, and may further include sand, gravel, pyrite as a secondary component. Such ancillary components may be added depending on the nature of the wastewater or the treatment target to remove dissolved oxygen and suspended particles, minimize head loss and clogging, and neutralize pH. Wastewater containing toxic contaminants enters the bottom of the metal column and as the wastewater flows upwards through the column, the toxic substances are rapidly reduced. For example, iodine is reduced to the corresponding non-toxic iodide, while acrolein is readily reduced to biodegradable aldehydes. Wastewater effluent containing the reduced product and by-products such as Fe ²⁺ flows out of the top of the column and flows by gravity into a biochemical oxidation process involving aerobic bacteria. An air vent valve is present at the top of the column to allow the exhaust of hydrogen gas from the anaerobic pretreatment process.

The biological oxidation process (2) is a method of treating wastewater using microorganisms. Commonly used biological oxidation processes are classified into suspension and fixation methods depending on the type of microorganism and wastewater contact. As shown in the active pollution method, the suspended suspension method is mixed with microorganisms and wastewater, and the microorganisms are separated into treated water and microorganisms in a suspended state, and the microorganisms are returned to wastewater treatment. The sedimentation method includes a spraying method, a rotating disk method, an immersion furnace method, and a fluidized bed method, all of which have a fixed support for attaching microorganisms, so that only wastewater passes around the fixing microorganism. However, as the microorganism multiplies, the adherent biofilm is peeled off and should be removed from the sedimentation basin. This method is also classified by the microbial population used, but nitrifying bacteria (aerobic bacteria), which oxidize ammonia to promote nitriding reactions, and denitrification bacteria (nitrous and nitric acid, which are produced by nitrifying bacteria, are reduced to nitrogen gas using organic substances). Bacteria) are utilized. In general, microorganisms which oxidatively decompose organic matter are of various kinds such as bacteria, yeasts, and fungi and cannot be specified. On the other hand, in anaerobic treatment using anaerobic microorganisms, acid-producing bacteria that decompose organic matter into lower fatty acids, acetic acid produced by acid-producing bacteria, and bacteria that produce methane using carbon dioxide and hydrogen are used. This treatment is prevalent for the digestion of sludge and for the treatment of rich organic wastewater, but also for low concentration organic wastewater.

The biological oxidation process 2 according to the present invention employs any of the above methods, such as activated sludge or trickling filter, rotating biological contactor and anaerobic biotreatment. It can be one of them. The reduced products of the effluent from the pretreatment process (1) are oxidized by aerobic or anaerobic bacteria in the biological oxidation process (2). At the same time, the iron ions produced in the pretreatment step 1 are oxidized to form insoluble iron hydroxide. Using a pH adjuster, the pH is constantly checked and sulfuric acid is added whenever necessary to maintain sub-neutral levels. The wastewater treated by the biological oxidation process 2 is discharged to enter the separation process 3.

The effluent is introduced into the storage tank by gravity for separation process 3, and suspended solids such as biomass and iron hydroxide precipitates are separated from the effluent by precipitation.

In order to find out the effects of the present invention, the non-degradable wastewater treatment method using the iron and iron process of the present invention was performed as follows.

Experimental Example 1

Experimental Example 1 is an experimental performance result in the laboratory for the hardly degradable wastewater treatment method using the present invention of the iron-iron process and biological process.

1. Experiment Method

Experiments were run in batch reactors to demonstrate biodegradation enhancement of iodine and acrolein containing wastewater as a result of iron pretreatment. The wrought iron used was Master Builders iron (Aurora, OH) and the measuring surface area was 1.28 ± 0.06 m ² / g.

Batch reduction experiments were performed in an anaerobic glove box using an 8 mL borosilicate vial containing 2.5 g of 5 mL aqueous solution. The vials are placed horizontally on a shelf and mixed in an orbital mixer at a speed of 100 rpm. All batch reduction experiments were conducted at room temperature (21 ± 1 ° C.). The same glass bottle is installed in each experimental step, one of the glass bottles is taken at each sampling time, and the supernatant is vacuum filtered through a glass fiber filter to be applied to the analysis of the initial composition and the reduced test product.

2. Respiratory System Analysis

In order to compare the biodegradation of non-treated wastewater with zero-treatment wastewater, respiratory experiments were performed with a BOD device (Hach). The device monitors changes in the partial pressure of oxygen caused by microbial respiration and automatically calculates BOD values. Zero-iron wastewater was exposed to air for approximately 2 hours, minimizing the oxygen demand from oxidation of residual iron ions during respiratory assays.

BOD vessels (600 mL) containing toxic contaminants and ferrous iron reduction products were prepared according to Standard Methods (APHA, 1992) and incubated in unacclimated culture (5 mL). Add nitric acid and pH buffer solution to BOD nutrient solution. Emptys that were not incubated were prepared the same as the samples, but without the test chemicals. Respiratory analysis was run at 20 ° C. for 120 hours.

3. Experimental Results

Batch Anaerobic Reduction Experiment

FIG. 2 is a graph showing the reduction of acrolein and the formation of propionaldehyde as a product thereof in a batch pretreatment process including ferrous iron.

Within 90 minutes, the concentration of acrolein in aqueous solution decreased to an undetectable level in the presence of 1 g of flake iron. A rapid decrease in acrolein coincides with an increase in the aqueous phase concentration of propionaldehyde, indicating that iron and iron quickly transform toxic contaminants into readily biodegradable byproducts.

The results of the experiment of biodegradation are shown in FIGS. 3 and 4.

The iron reduction of iodine is particularly fast. Iodine in a 5 mL aqueous solution is reduced to iodine ions within 1 minute in the presence of 1 g of ferrous iron.

Figure 3 is a graph showing the BOD results in the respiratory system experiments of iodine added wastewater.

This is the biochemical oxygen demand (BOD) data of the respiratory system test of wastewater showing a sharp rise in iodine, and reducing iodine with zero iron results in a rapid rise in BOD.

Figure 4 is a graph showing the BOD results of wastewater containing acrolein and wastewater containing propylaldehyde.

It can be seen that an aqueous solution containing propylaldehyde, a reduction product of acrolein, shows a much higher BOD than an aqueous solution containing acrolein. Acrolein does not undergo aerobic bioreactions.

4. Analysis of Experiment Results

Ferrous iron, such as Fe ⁰ , quickly reduces the toxicity of wastewater, including halogens and other oxidized components, and transforms other molecules into products that are better mineralized by bacteria in biological treatment processes such as activated sludge. In batch anaerobic reduction experiments, toxic components such as iodine and acrolein are treated with flake iron, producing non-toxic products. The data from the respiratory system experiments demonstrate that toxic acrolein can be aerobic biodegradable after ferrous iron pretreatment, as the aqueous solution of iron-treated acrolein exhibits a much higher BOD than that containing untreated acrolein.

This invention is characterized by combining a reduction process, a ferrous iron treatment and an oxidation process, and aerobic biodegradation. Recently, zero iron is used in permeable reactive barriers (PRBs) to improve groundwater contaminated with many kinds of pollutants. Biological oxidation, on the other hand, is a universal and cost-effective approach to removing biodegradable chemicals from wastewater. In the treatment system proposed in FIG. 1, the toxic constituents of the waste water are first transformed into non-toxic molecules by iron, which biodegrades the waste water into non-toxic results such as carbon dioxide and water.

Based on the experimental results as described above, the following experiment was performed to find the applicability of the above process to the actual wastewater.

Experimental Example 2

< Wastewater Selection>

1. Experiment Overview

Young's iron technology has been proven to be particularly effective for improving biodegradation of hardly decomposable materials such as nitrate and azoaromatic compounds. However, this study suggests a screening evaluation technique for selecting wastewaters that can be applied to Young-Chul Technology because it is difficult to easily find out the wastewaters with these target substances in industrial wastewater in Korea or to identify which substances exist in the wastewater. It was. In other words, wastewater screening evaluation refers to a technique that explores the potential of zero-iron application technology for black box wastewater.

2. Experimental method

Wastewater screening techniques are a combination of physicochemical and biological assessments. Physicochemical evaluation primarily examines the change in absorbance by scanning the UV-VIS spectra and tracks changes in organic properties through HPLC analysis to check for the presence of obvious physicochemical changes before and after ferrous iron treatment. Wastewater that has passed a series of physicochemical screening assessments is selected as a target wastewater by biological assessment to determine the applicability of zero-ferrous iron technology.

In the experiment, 11 types of industrial wastewater from nine wastewater treatment plants were collected. In order to minimize the reduction reactions that may occur during the transport of the sample, only half of the 2 liter vessel was filled.

3. Experimental Results

Table 1 shows the pH values, which are the type and characteristics of the wastewater.

number Type of wastewater pH One Chemical system 4.45 2 Chemical System (EPA) 12.23 3 Chemical System (Iodine) 8.78 4 Chemical system 8.71 5 UV protectants 2.05 6 Mixed (chemical / household) 9.4 7 Biochemistry (Pharmaceutical) 7.5 8 Electronic Engineering (Inorganic) 2.56 9 Electronic Engineering (Organic) 8.15 10 Electronic Engineering (Inorganic) 1.46 11 Electronic Engineering (Organic) 8.84 12 Fiber 7.4

Table 2 summarizes the changes in pH, chemical oxygen demand (COD), and total organic carbon (TOC) before and after the ferrous iron treatment.

 Type of wastewater pH TOC COD Before processing After processing Before processing After processing Before processing After processing One 3.82 6.52 2080 1949 4650 4525 2 4.83 7 29092 29492 87600 80000 3 3.69 6.26 147 154 435 600 4 3.71 6.19 136 115 185 385 5 4.25 4.77 4084 3986 11450 10900 6 3.89 5.92 2633 1648 4325 4300 7 3.67 5.80 16140 18422 61675 63100 8 2.64 6.44 ND ND 20 40 9 2.36 7.06 421 371 1340 1225 10 2.86 5.29 ND ND 475 1050 11 3.57 5.30 1520 1422 4460 4560 12 3.87 6.29 100 21 495 140

Neutral or higher pH samples were subjected to acidification with 1 M hydrochloric acid prior to the batch reduction test. In all samples except sample 5, a sharp increase in pH due to corrosion of iron was observed during the reaction time of 3 hours. Wastewater number 5 was probably considered to have a high acidity, indicating no significant change in pH before and after treatment. The total organic carbon (TOC) and chemical oxygen demand (COD) concentrations did not change significantly before and after the ferrous iron treatment, but in some wastewaters (3, 4, 7, and 10), the chemical oxygen demand (COD) COD) concentration was confirmed to increase. This is probably due to the reason that the oxidation state of the sample was lowered through the reduction of the ferrous iron, and the data proved that the ferrous reduction reaction proceeded relatively well.

5 is a photograph observing the physical chromaticity change in some wastewater.

In particular, in the case of wastewater No. 6 and wastewater No. 5 which had high color of raw water itself, clear color change was found after zero-iron treatment. In the case of wastewater No. 5, it is reported that some dye is present in the wastewater, and in addition to color removal, it is expected to improve biodegradation performance of dye component through zero iron treatment.

6 and 7 are graphs showing the results of UV-VIS screening measurement of the wastewater before and after the zero-iron treatment.

Seven of the eleven wastewaters (Nos. 1, 2, 5, 6, 7, 10, and 11) show a clear change in absorbance in the UV region, especially 200-300 nm after ferrous iron treatment. It was. The relevant UV region was also used as an important data for selection of analytical wavelength band in future high performance liquid chromatography (HPLC) screening evaluation. The screening evaluation technique using UV-VIS can be used relatively simply in a short time and was considered a very suitable technique for primary screening evaluation.

As a result of the UV-VIS screening evaluation, the material change was clearly observed in the 200-300 nm wavelength region, so the detection wavelength condition of 254 nm was adopted in the HPLC screening evaluation equipped with the UV detector. This was the same condition as a typical detection wavelength that is frequently used for organic material analysis using HPLC.

8 and 9 show the results of HPLC screening of the wastewater before and after the ferric iron treatment.

 Samples 8 and 9 dropped from the primary screening (UV-VIS) were excluded from the analysis. As a result, it can be seen that the organic composition of wastewater in Nos. 2, 3, 4, 5, and 6 was clearly changed before and after the ferric iron treatment. In particular, sample 5 was evaluated as the most applicable sample since the change was most pronounced after the removal of color iron in addition to color removal.

4. Target Selection

The analysis using the UV-VIS spectrum is evaluated by the change of organic material in the UV region and the presence or absence of chromaticity change in the visible region, and the change of properties of the major organic substances in the wastewater before and after the ferrous iron treatment through HPLC analysis. Based on the experimental results of the laboratory that measured the BOD and on-site survey data such as the inclusion of iodine and EPA, wastewater No. 2, No. 3 and No. 5 were first selected as the target wastewater.

< Biodegradation Performance and Biotoxicity Evaluation>

The biodegradation performance was evaluated for the selected wastewater through physicochemical screening evaluation. In addition to the above screening evaluation, the effect of zero iron on biotoxicity evaluation and toxicant removal was evaluated based on the investigation of toxic substances in the treatment plant. Toxic substances of interest in the treatment plant were iodine in wastewater 3 and ethyl propyl acrolein (EPA) in wastewater 2, and in existing treatment plants, activated carbon (waste 3) ) And incineration process (waste 2). Therefore, if it is possible to remove the biotoxicity through the treatment of iron and iron, it is considered that the iron reduction process proposed in this study can be a good alternative to the existing treatment process that requires expensive maintenance cost.

FIG. 10 is a graph showing the results of BOD measurement of wastewater before and after ferrous iron treatment, and shows the results of preferentially performing biodegradation performance on wastewater 5 and 6 according to the screening evaluation results described above.

Biodegradation performance was evaluated by BOD concentration using Hark's BODTrak instrument. Similar results to the HPLC screening results showed that the wastewater from wastewater # 5 was more pronounced than the wastewater from wastewater # 6. In the case of wastewater no. 5, there was a clear inhibition when zero iron treatment was not performed, whereas much of the inhibition phenomenon was improved after zero iron treatment. On the other hand, in the case of wastewater No. 6, the biodegradability of the wastewater itself was high, and the effect of improving the biodegradation performance by the treatment of zero iron was insignificant.

FIG. 11 is a graph showing biodegradation performance and iodine toxicity of wastewater before and after ferric iron treatment.

This study focuses on how zero ferric iron can reduce iodine's biotoxicity against wastewater No. 3 containing iodine. However, iodine in wastewater 3 used in the experiment was present at a concentration low enough to degrade biotoxicity due to degradation during prolonged transportation. Therefore, in this study, toxicological evaluation experiments were conducted by separately injecting iodine at different concentrations (0, 1.5, 30, 60 mg / l) into the wastewater.

The biotoxicity of each iodine concentration and the biodegradation performance of the wastewater were compared with the BOD values. Referring to FIG. 11 (a), it was confirmed that the biodegradation performance of the hardly decomposable substance was significantly improved when the non-ferrous iron treatment was performed on wastewater No. 3 without a separate iodine injection. On the other hand, as shown in (b), (c), (d) of Figure 11, the concentration of iodine and the toxic effect was proportional, the increase in concentration was closely related to the period of inhibition of microbial activity in the BOD experiment . That is, for example, a high concentration of iodine injection of about 60 mg / l showed a relatively long retention time of about 1.5 days or more. However, over time, iodine oxidizes the organic matter in the wastewater, and self-disappears, and finally BOD showed a level similar to that after the ferric iron treatment. It is not clear whether these results are due to chemical oxidation by iodine or whether the microorganisms that were inhibited after the iodine toxicity disappeared in the water revived to decompose the oxidized organic products due to iodine. Even if iodine causes biological inhibition in the short term, it is expected that biological inhibition will continue to occur in the continuous injection process. If some technical supplementation is made, it is expected that the zero-ferrous iron treatment process can be utilized as a technology to guarantee good treatment performance while replacing the activated carbon process which currently requires expensive maintenance costs.

12 is a graph showing the results of measuring the BOD of wastewater injected with 25 mg / L and 50 mg / L of acrolein and propylaldehyde.

Ethyl Propyl Acrolein (EPA), present in wastewater No. 2, is a toxic chemical compound of the acrolein class and is clearly a biologically toxic substance. Acrolein is a representative biological inhibitor included in both the US toxic chemical list and the Korean toxic release inventory (TRI). Acrolein is converted to propylaldehyde through ferric iron reduction at pH 3, which is an acidic condition. In this study, biodegradability of these two chemicals was evaluated. In the biodegradation performance evaluation experiment, BOD was measured by injecting two compounds at 25 and 50 mg / l, respectively, and the results are presented graphically.

Irrespective of the injection concentration, all of the acrolein showed clear biotoxic properties, while the ductaldehyde, ductaldehyde reduction product, showed a significantly higher level of biodegradation with biotoxins removed. In the 25 mg / L injection experiment, acrolein showed BOD of 0 mg / mL, while propyl aldehyde showed 23 mg / L of BOD. In other words, the obvious reduction of biological toxic substances through the reduction of ferric iron can be converted to non-toxic substances, rather the result shows high biodegradation characteristics.

FIG. 13 is a graph showing the results of BOD measurement before and after iron-iron treatment of wastewater in which wastewater No. 2 was adjusted to pH 4.4 and pH 5.7, respectively.

No significant improvement in biodegradation performance was observed in wastewater # 2. This is because wastewater No. 2 is a very high concentration (87,000 mg COD / l) organic wastewater, which requires excessive dilution in BOD experiments. Therefore, the toxic effect of Ethylpropyl Acrolein (EPA) is also considerably diluted. However, after adjusting the pH to 4.4, the ferric iron treatment showed the highest biodegradation characteristics. Based on the results of this experiment, it is determined that wastewater No. 2 is capable of aerobic treatment through many dilution after zero-iron treatment, but considering the small amount of wastewater generated and high concentration of wastewater, anaerobic organisms after zero-iron treatment It has been suggested that treatment is more effective.

14 is a graph showing the batch anaerobic biodegradation performance before and after the wastewater is treated with zero iron as gas as an index.

15 is a graph showing the batch anaerobic biodegradation performance before and after the wastewater is treated with zero iron, with gas composition, in particular methane.

Before and after the zero-ferrous iron treatment, wastewater No. 2 was injected into a serum bottle and inoculated with anaerobic digester sludge. The initial chemical oxygen demand (COD) was 14500 and 14000 mg / L, respectively, before and after the ferrous iron treatment. Anaerobic biodegradation performance of both samples was evaluated as good, but the gas generation amount and gaseous methane content of the sample were analyzed after the ferric iron treatment. This is believed to be the result of the ferrous iron pretreatment technology, which lowers the redox potential of the sample to improve the anaerobic biodegradability, and also reduces the biodegradation inhibitor such as ethylpropyl acrolein (EPA). Based on the results of this study, the applicability of zero-iron technology to wastewater No. 2 or similar high-concentration organic wastewater can be reviewed positively.The anaerobic biodegradation tank process through zero-treatment pretreatment is similar to the conventional incineration process. It is evaluated as an efficient new process that can replace expensive processes.

While specific structures for realizing the invention have been shown and described, various modifications and rearrangements are possible without departing from the spirit and scope of the invention, and the spirit and scope of the invention are not limited to the specific forms set forth and described herein. It is obvious to the person skilled in the art. The examples are representative only and are given by way of example only, and the invention is not limited thereto.

As described above, according to the present invention, the non-degradable wastewater treatment method using the zero-ferrous iron process and the biological process, combining the reduction process, iron-iron treatment and oxidation process, conventional aerobic or anaerobic biological decomposition process, pre-treatment of the hard-decomposable compound in the waste water Can be transformed into highly biodegradable material and can be finally decomposed in a biological oxidation process.

In addition, the non-degradable wastewater treatment method using the present invention, such as a ferrous iron process and a biological process is very flexible, it can be applied to the individual treatment process or to modify the existing biological treatment facilities. Since azo-, nitro- and chloro- compounds are generally found in many industrial compounds, iron technology (iron-based treatment) is used to manufacture and process fibers and dyes, pesticides (insecticides and herbicides), pharmaceuticals and ammunition. It can be used for wastewater treatment across industries, including.

In addition, according to the present invention, ductile iron and aerobic activated sludge method, as well as the two advantages of the metal treatment and aerobic biological treatment process, the combination can produce the following additional synergistic effect.

(1) The scrap metal is easily obtained as industrial waste, and is relatively inexpensive. The proposed metal column has a long service life and requires little maintenance or regeneration in an inert process. Corrosion of noble metals does not produce toxic by-products and, therefore, is rarely harmful to the environment.

(2) The reduction products formed in the metal pretreatment column, however, are related to the environment. This potential problem is solved by the subsequent oxidation of the reduction product to a non-toxic result by the subsequent biodegradation process.

(3) Although biological oxidation processes can minimize degradable components with high efficiency, they are inefficient in treating wastewater containing toxic and prohibited components. This drawback can be overcome by the use of a strong reducing agent which quickly transforms the noble metals and these compounds into non-toxic molecules.

(4) Compared with the conventional biological treatment process, this invention can reduce the size of the bioreactor required, thus reducing the treatment cost or increasing the treatment efficiency.

(5) Compared with carbon adsorption, the present invention is a destructive process and therefore does not require additional treatment and will also eliminate the concern of secondary contamination.

(6) Fe ²⁺ formed in the iron column is eventually Fe ³⁺ oxidized (Al ³⁺ if zero valence aluminum is used). The cations of these metals are flocculants that can promote the removal of residual solids.

Claims (3)

 In the wastewater treatment process for changing the toxic compounds in the wastewater to non-toxic, A pretreatment step containing iron as an active component; A biological oxidation process for secondaryly decomposing the pretreated wastewater; And Separation Process by Precipitation Non-degradable wastewater treatment method using a duct iron process and a biological process, characterized in that consisting of.  The method of claim 1, wherein the pretreatment process comprises one or more of sand, gravel, and pyrite depending on the object to be treated and the characteristics of the wastewater.  The method of claim 1 or 2, wherein the biological oxidation process is any one of activated sludge, trickling filter, rotating biological contactor, other aerobic biological treatment process or anaerobic biological treatment process. Refractory wastewater treatment method using a zero-ferrous iron process and a biological process, characterized in that.

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