KR20060087058A - Food waste leachate treatment method - Google Patents

Abstract

The present invention is to treat the high-density food waste degreasing solution in the form of thick porridge, which removes foreign substances through crushing and screening process from food waste, by combining chemical and biological methods, to directly meet the effluent water quality standards in wastewater treatment plants, or to treat sewage treatment plants. Is a method of transporting after pretreatment with good properties and low concentration to avoid overload.

Food Waste, Desorption, Sewage Treatment Plant, Wastewater Treatment Plant, High Concentration, Purification

Description

Food waste leachate treatment method

1 is a process chart illustrating a method of treating food waste stripping liquid.

The present invention is a method for purifying food waste detachment solution in which there is an extremely high concentration of contaminants. Due to the large amount of biodegradable substances, food waste desorption liquids have an acidic acidity of about 5 ~ 4.5 due to active acid-fermenting microorganisms. It is a state. These food waste stripping solutions are in a very difficult state in which ultra high concentrations of contaminants such as BOD of about 10 to 60,000 ppm and COD of about 6 to 40,000 ppm T-N are about 6 to 4,000 ppm are present. The present invention is a series of processes for treating such difficult contaminants with a treatment efficiency of 95 to 98%.

Food waste desorption liquid contains various substances, shows very high concentrations of BOD (10-60,000 ppm) and COD (5-30,000 ppm), and various substances that interfere with microbial growth exist. The technique is very difficult to purify the food waste stripping solution.

Due to the above reasons, most of the domestic food processing plants are currently dumping the desorption liquid in the ocean, and in some cases, anaerobic treatment method using hydrolysis-acid fermentation-methane fermentation using anaerobic microorganisms in order to reduce the pollution concentration, As it takes much more than 15 days and needs to be stored for a long time, large scale facility is indispensable, and operating conditions are difficult, and as a fundamental problem, the efficiency of the removal of the desorption liquid passed through the anaerobic process is about 55-65. As a result, almost all treatment facilities have problems in operation, and local governments are discontinuing operation and seeking measures.

After the problem of anaerobic treatment was identified, the decompression evaporation method was installed and operated in several facilities as an alternative to the new desorption solution. However, this method requires enormous energy costs for evaporation. Due to the large amount of small volatile substances present in the desorption liquid, the amount of evaporation / concentration with water is 70-80%, resulting in satisfactory results such as BOD and COD values of 10,000 ppm or more.

As another alternative, there is a method of treating food by supplying it to a carbon source during advanced treatment for nitrogen removal from a sewage treatment plant after acid fermentation. In order to adopt this method, the operating conditions are difficult because the proper acid fermentation time and the input ratio must be correct. When this method is adopted, the discharge concentration is often higher than the calculated wastewater contamination concentration. There is a limit to the application because there are constraints to be a sewage treatment plant.

The present invention is a method derived to solve the above-mentioned conventional problems, economical to solve the purpose of purifying the food waste detachment liquid in which contaminants exist in a very high concentration to 95-98% BOD and COD, 90% or less TN It is to provide a purification device to achieve.

Another object of the present invention is to provide a method for maximally reducing the inhibitory factor in the biological treatment of the latter stage through the chemical treatment. The latter biological treatment method includes both a wastewater treatment plant for direct treatment of the desorption liquid and a treatment method by transfer to a sewage treatment plant.

The present invention is a method for purifying food waste desorption solution in which there is an extremely high concentration of contaminants, the composition of which is adjusted to pH 5 ~ 6 of the food waste desorption solution, which has been subjected to a known crushing and screening process, to a polymer flocculant according to the concentration of the desorption solution. 200 ~ 1000ppm to agglomerate the particulate matter, and proceed with the dehydration process to separate the solid and liquid using a press. Through this process, about 70 ~ 80% of liquid is generated according to the inflow waste characteristics. At this time, it is important to determine the injection amount according to the appropriate pH and the concentration of the desorption solution.

As such, the dehydrated liquid is transferred to a floating reactor in a natural flow manner so as to remove the SS substances that cannot be removed during the dehydration process. At the bottom of the flotation tank, a micro-pores diffuser is installed to blow and remove the floating airborne substances in the liquid, and a scum removal facility is installed at the top. In addition, the sludge precipitated at the bottom of the flotation reaction tank is passed through the decanter of the centrifugal force specific gravity method to remove the precipitated material by specific gravity method. The above process removes about 60 ~ 70% of the coagulated BOD and about 85 ~ 90% of SS material.

The pH of the decontaminated liquid is maintained at an acidic level of about 5-4. To this acidic solution, add alkaline substances (caustic soda, quicklime, slaked lime, activated silicic acid, etc.) until the pH reaches 7 ~ 7.5 and slowly stir to neutralize the acidic contaminants and the injected alkaline substances. Substances that could not be removed in the acidic zone are neutralized and precipitated and removed as precipitates. At this time, in order to accelerate the sedimentation effect, a small amount of precipitated sludge may be returned to the initial reactor (0.5-10%), increase the flocculation and coagulation rates, and reduce the amount of alkaline substances introduced.

Through this reaction, the air is blown back to the liquid from which the contaminants are first removed to remove the injuries. The purpose of this process is to remove SS, the suspended particulate matter, which has not been precipitated before proceeding to the next stage, and has a residence time of 2 to 6 hours. Most of the SS materials that are difficult to settle in this process are removed, and colloidal and molecular material materials make up the most amount. The treated water is converted to a slightly yellowish liquid with almost no suspended matter.

Multivalent metallic substances (e.g., Fe, Co, Ni, Mn, Cu, Zn, Al, etc.) salts are added to the liquid from which the floating matter is removed to induce reaction with contaminants such as colloidal and molecular material substances in the liquid. Generate. At this time, the concentration range varies depending on the concentration of contaminants, but injected a range of about 0.3 ~ 1.5% by weight. In addition, the sludge transport (0.5 ~ 10%) to maximize the precipitation efficiency.

Fine air is blown into the liquid from which the precipitate is removed to remove residual particulate matter, and then the pH is induced to neutral.

After that, after checking the ammonia nitrogen value, if the value is higher than the desired level, activated carbon and bentonite were added to the liquid to ion exchange ammonia nitrogen to reduce the removed nitrogen value to the desired level and then transferred to the biological treatment facility. This is because excessive nitrogen concentrations reduce the efficiency of biological treatment facilities.

The biological treatment facility in the latter stage is maintained with aeration that injects micro air from 12 hours to 1 day in a biological reactor with 1,500 to 5,000 ppm of microorganisms and 15 to 30 degrees of water temperature depending on the load of contaminants. The appropriate DO (dissolved oxygen) value of the biological reactor is adjusted in the range of 2 to 5 mg / L according to the conditions of the influent load and the target food waste removing solution. The liquid which dwelled for a predetermined time in the biological reaction tank is suspended and precipitated and separated by a well-known method, and the supernatant is drained by being discharged.

The concentration of supernatant supernatant can be processed and transported below the concentration that the sewage treatment plant can handle. (Some sewage treatment plants have BOD 1,000 ~ 3,000mg / L and CODmn 1,000 ~ 3,000mg / L. Treated water at the wastewater treatment plant and discharged directly into the water system, so the treated water must be treated with BOD 10mg / L, COD 40mg / L, SS 10mg / L, TN 20mg / L. After the addition of salts of the metallic material is added to precipitate, the flotation is separated in the flotation reaction tank, the biological treatment is added for 12 hours to 1 day to discharge the treated water to meet the above water quality standards.

As described above, the present invention treats food desorption liquid which had to be treated simply by ocean dumping as described above, thereby lowering the concentration of contaminants to a low concentration so as not to overload the sewage treatment plant, and of course, the wastewater can be combined with wastewater. It was possible to reduce the concentration of contaminants to the extent that they could be treated directly in the treatment plant and discharged directly into the water system. This process should be chemically treated, but refrain from using the components that may be toxic to the microorganisms at the end, and minimize the components that can interfere with the microbial process by removing harmful substances in advance through the flotation separation process. By doing this, it was possible to invent a method that can treat the concentration of the final contaminant to a very low concentration.

In the present invention, the dehydration cake of food desorption liquid obtained as a by-product can be used as a compost raw material because no heavy metal or other harmful chemicals are injected.

Claims (3)

(1) After adjusting the food waste desorption solution in which ultra high concentration of contaminants exist to pH 5 ~ 6, add 200 ~ 1000ppm of polymer coagulant according to the concentration of the desorption liquid to agglomerate the particulate matter, and separate the solids and liquid using a press. Making a step; (2) blowing air bubbles into the dehydrated liquid to float and remove the floating material in the liquid; (3) Slowly stir with an alkaline substance (caustic soda, quicklime, hydrated lime, activated silicic acid, etc.) until the pH reaches 7-7.5 to a solution that shows the acidity of pH 5 ~ 4 from which contaminants are removed. At this time, in order to accelerate the sedimentation effect, a portion of the small amount of precipitated sludge is returned to the initial reactor (0.5 ~ 10%); (4) Blow the fine air into the liquid from which the contaminants were first removed to remove the injuries, Inject the salt of the polyvalent metal material (e.g. Fe, Co, Ni, Mn, Cu, Zn, Al, etc.) in the weight ratio to 0.3 ~ 1.5% by weight to react with contaminants in the liquid. Inducing to generate and remove a precipitate, in which a portion of the small amount of precipitated sludge is returned to the initial reactor (0.5 to 10%) to accelerate the precipitation effect; (5) blowing the fine air into the liquid from which the precipitate is removed to remove residual particulate matter and induce the pH to neutral; (6) adding activated carbon and bentonite to react with ammonia nitrogen to reduce the nitrogen value to a desired level; (7) In the presence of aerobic microorganisms, depending on the degree of influx load of contaminants, aeration is carried out for 12 hours to 1 day. The method according to claim 1, wherein the steps (4) to (7) are repeated to discharge the discharged water after satisfying the direct discharge water quality standard. The method of claim 1, wherein in the steps (2), (4), and (5), fine air is blown to remove suspended solids and components which may adversely affect the biological treatment of the latter stage.

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