KR100510166B1 - Combined treatment method with chemical coagulation and biological process for high-strength organic wastewater - Google Patents

Abstract

The present invention is a process for biologically removing organic matter after performing solid-liquid separation of livestock wastewater having a large change in the solids concentration in the wastewater according to the breeding form, biochemical oxygen demand (biochemical oxygen demand) 150 Provides a method to simultaneously satisfy <= mg / L and suspended solids <150 mg / L.

The present invention continuously maintains the concentration of suspended solids between 500-100,000 mg / L in livestock wastewater through a chemical solid-liquid separator in which ferric sulfate is added as an inorganic coagulant using pH in the reactor as a reaction factor. It can be removed below to maintain stable performance of the subsequent biological organics removal process, as well as to significantly reduce the organic residence time by the solids can significantly shorten the hydraulic residence time. In addition, through the chemical solid-liquid separator, it is possible to stably maintain the water quality of the biologically treated water through the complete separation of the suspended solids in the treated water and removal of the polymer organic matter and color. In addition, anoxic selectors with a hydraulic retention time of 1-24 hours can be placed in front of the aerobic bioreactor to maintain stable microbial activity.

Description

Combined treatment method with chemical coagulation and biological process for high-strength organic wastewater}

The present invention relates to a method for treating wastewater containing a high concentration of suspended solids, such as swine wastewater, and more specifically, it is possible to treat wastewater more simply and economically than the conventional technology, and in particular, the cheapest and most effective sulfuric acid in Korea. It is composed of chemical coagulation process that automated reaction pH as fertilizer with ferrous iron as a coagulant, and solid-liquid separation and biological treatment process at the rear stage by using filter press. It is about.

Swine wastewater is largely divided into high concentration wastewater from slurry type piglet and low concentration wastewater from scraper type piglet, and the concentration of contaminants in the wastewater varies greatly depending on the type of house and cleaning method. Biological treatment of wastewater can lead to frequent operational failures and poor water quality. In particular, high concentrations of suspended solids in swine wastewater are difficult to maintain if the bioreactor is introduced into the bioreactor without proper pretreatment.

In the case of livestock wastewater, the effluent standard of the livestock wastewater public treatment plant and the water quality standard for the individual treatment facility (implemented on January 1, 2000) are different as shown in Table 1 below. Development of advanced treatment technology to remove phosphorus and residual COD _Mn [Korea Patent Publication No. 0142723 (High concentration wastewater treatment method using membrane separation); Japanese Patent Application No. 10-0386224 (Livestock Wastewater Treatment System); 2001-0036777 (circulation treatment method and system for livestock wastewater using soil microorganisms); Japanese Patent No. 0151928 (Manure and Organic Wastewater Treatment Method); Japanese Patent Application No. 10-0303765 (Livestock Wastewater Advanced Treatment Apparatus and Method); Japanese Patent Application No. 10-0342667 (Method for removing nitrogen and phosphorus in advanced livestock wastewater or manure in liquid corrosion method); 10-0355880 (Method and Apparatus for Purifying Livestock Wastewater), as well as the difficulty of maintenance due to the complexity of the process, as well as other areas of the target area where the farm size is relatively small due to the high initial investment cost. At farm scales in regulated areas, it is almost impossible to apply these technologies.

On the other hand, Korea Patent Publication No. 10-0341467 (high concentration wastewater purification method by chemical adsorption reaction using hydrolysis and ionization tendency of metal salts) is a livestock wastewater treatment technology by solid-liquid separation by agglomeration and ammonia degassing in high concentration wastewater. Although it was applicable in the case of low concentration between low molecular weight organic matters, it was difficult to remove organic matters effectively when low molecular weight organic matters such as volatile fatty acids were present in high concentrations during solid-liquid separation by chemical coagulation.

Treatment Plant Mode Individual treatment plant Public treatment plant Farm scale Permitted Area Regulated Area area Specific area Other Area Specific area Other Area BOD ₅ (mg / L) 50 150 150 350 30 COD _Mn (mg / L) - - - - 50 SS (mg / L) 50 150 150 350 30 Coliform group (dog / 100mL) - - - - 3,000 TN (mg / L) 260 - - - 60 TP (mg / L) 50 - - - 8

The present invention aims to solve the above problems, and the present invention aims to efficiently treat high concentration organic wastewater such as livestock wastewater.

In order to achieve the above object, the high concentration organic wastewater treatment method combining the chemical coagulation and biological process according to the present invention, in the method for treating high concentration organic wastewater, such as livestock wastewater, the waste water at 1,000 to 3,000 rpm A first step of reacting the wastewater into the reactor containing the wastewater until the pH of the wastewater reaches 3.5 or more and less than 5.0; A second step of adjusting the pH of the treated water by adding an alkaline agent to the treated water treated in the first step; A third step of forming a floc under low-speed mixing conditions by introducing a polymer flocculant into the treated water after the second step and solid-liquid separation of the formed floc; And a fourth step of treating the treated water separated from the solid-liquid separated through the third step by an aerobic biological process using activated sludge, wherein the aerobic biological process of the fourth step is performed in a floc forming bacteria selection process by an anaerobic selector. To improve sludge settling properties, and the activated sludge of the aerobic biological process is returned to the oxygen-free selector.

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The method according to the present invention described above, when the concentration of the inorganic solids of the treated water treated through the method exceeds 3%, reprocessing the treated water through the first to third steps It features.

The method according to the present invention is characterized in that before performing the fourth step, phosphate is added to the treated water.

Hereinafter, the present invention will be described in detail.

(1) First step: ferric sulfate treatment

The present inventors have found that ferric chloride (Ferric chloride, FeCl ₃ ), polyaluminium chloride, alum (Alum, Aluminum sulfate, Al ₂ ) for the separation of solids in the wastewater, which is recognized as the biggest problem in the treatment of swine wastewater. Although flocculation tests were carried out using various inorganic coagulants such as (SO ₄ ) ₃ ) and ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), a batch experiment was performed to determine the optimum amount of inorganic coagulant injection. It is difficult not only to satisfy the optimal conditions for swine wastewater changing from time to time, but also to accommodate the change of wastewater phase according to the pig farm, and the treatment cost per ton due to the amount of chemicals added in large quantities. There was a difficulty to rise sharply. Therefore, in the present invention, ferric sulfate was selected as the cheapest inorganic coagulant with excellent flocculation separation ability, and the optimum chemical amount was 3.0-5.5 when the wastewater pH was rapidly mixed under high-speed mixing conditions using the reaction characteristics between the wastewater and the flocculant. Add an inorganic coagulant until the reaction is about 2 hours.

If ferric sulphate is added until the pH of the wastewater is lower than 3.0, there is no big difference in performance, but the economic efficiency is drastically reduced due to the increase of sludge generation and the increase of chemical cost due to the addition of excess ferric sulphate. When ferric sulphate is added so that the pH of the wastewater is higher than 5.5, the concentration of iron ions, which play the role of inorganic coagulant in the solution, is significantly lower than the concentration of oil and minerals in the wastewater. The dewatering capacity of the sludge was then lowered to increase the concentration of suspended solids in the treated water. The preferred pH range is therefore 3.0 to 5.5. Especially preferred is until the pH is between 3.5 and 5.0.

It is preferable that the rotation speed at the time of the said mixing is 1,000-3,000 rpm. If the rotational speed is less than 1,000rpm, the mixing effect of the livestock wastewater in which the solids and the solution are mixed in the slurry state is insignificant, and the flocculation reaction does not occur efficiently.If the rotational speed exceeds 3,000rpm, not only waste of energy but also mechanical resistance This increases, resulting in premature replacement of the blades of the rotating shaft during long term operation. Thus, the preferred range of revolutions during the flocculation reaction is from 1,000 to 3000 rpm.

(2) second step: pH adjustment

By adding ferric sulfate in the first step, an alkaline agent such as NaOH is introduced into the reactor into raw water having a pH of 3.0 to 5.5, thereby increasing the pH in the reactor to 7.0 to 8.0. If the pH was less than 7.0, the iron concentration remaining after the condensation reaction was increased, the iron concentration in the treated water was increased, and the strength of the floc was also weakened. When the pH exceeds 8.0, the amount of alkaline agents such as NaOH is rapidly increased to increase the cost. Thus, the preferred pH range after the condensation reaction is between 7 and 8.

(3) step 3: floc forming and solid-liquid separation

In the second step, the raw water of which pH is adjusted is condensed by adding an anionic polymer coagulant under low speed mixing conditions, and then solid-liquid separation is performed as a filter press.

It is preferable that the rotation speed at the time of the said mixing is 100-500 rpm. If it is less than 100rpm, the condensation efficiency falls, and if it exceeds 500rpm, the condensed floc is broken and the dewatering efficiency decreases. Thus, the preferred slow stirring speed is between 100 and 300 rpm.

(4) biological treatment process

After solid-liquid separation of swine wastewater by the inorganic coagulant as described above, organic matter and nitrogen remaining in the wastewater are mostly composed of low molecular weight organic matter composed of volatile fatty acids and dissolved ammonia nitrogen, The increase (1-5%) resulted in severe microbial losses when treated with conventional activated sludge processes. Therefore, in the method according to the present invention, the hydraulic residence time is set to be an oxygen-free selector 20 within 1 hour to 24 hours to convey the sludge of the settling tank 23 to the oxygen-free selector 20. This greatly improves the sedimentation and flocculation of the sludge. The anaerobic selector 20 is located in front of the aerobic tank 21 and the activated sludge of the aerobic tank is returned to the anaerobic selector and mixed with the influent. The oxygen-free selector is composed of floating microorganisms and agitation facility returned from the sedimentation basin at the next stage. The anaerobic selector grows only the floc-forming microorganisms and kills filamentous bacteria by providing an environment suitable for the growth of the floc-forming microorganisms. This improves the settling properties of the sludge.

(5) post-treatment process

When the turbidity of the initial run-off water in the step (4) is high or the concentration of inorganic matter after chemical treatment exceeds 3%, the biologically treated water is coagulated and precipitated with ferric sulfate to remove the polymer organic matter, turbidity and color in the treated water. It's a step.

The aerobic biological treatment process including an oxygen free selector ensures stable water quality with excellent sedimentation when it is acclimatized, but due to the high concentration of minerals in the initial wastewater, large amounts of bubbles in the aeration tank and deterioration of sedimentation may occur. Initially, the treated water is chemically agglomerated in the same manner as described in the above (1) to (3) to remove the polymer organic matter, chromaticity-inducing substance, turbidity, and suspended solids.

In particular, if the concentration of inorganic matter in the treated water after the chemical treatment exceeds 3%, the suspended solids and turbidity in the treated water increases with serious foaming in the reactor. Therefore, chemical post-treatment by this step is essential to ensure stable water quality.

Hereinafter, the Example of this invention is described. However, the following examples are only preferred examples of the present invention for the purpose of understanding the present invention, and the present invention is not limited by these examples.

<Example>

In order to evaluate the wastewater treatment system according to the present invention, first, sludge type swine wastewater containing a high concentration of solids was applied.

The following analysis method was used for the following examples.

. pH: pH meter (glass electrode method, Corning 120, TOA HM71)

.SS (floating solids): Total amount of suspended solids dried for 2 hours in a drying oven at 103-105 ° C. using a GF / C filter.

.TDS (Total Dissolved Solids): Total amount of dissolved solids where the GF / C filter filtrate was dried at 180 ° C. until water completely evaporated.

.FDS (Inorganic Dissolved Solids): The amount of dissolved solids remaining after burning the total amount of dissolved solids for 15-20 minutes in an electric furnace at 550 ± 50 ° C.

BOD ₅ : Determination of BOD after 5 days

CODcr: Titration K ₂ Cr ₂ O ₇ Closed reflux

NH ₄ ⁺ -N: Distillation and titration (Nonorganic Kjeldahl Method)

.PO ₄ ^3- -P (Total Phosphorus Content): Stannous Chloride Method (λ = 690 nm)

<Example 1>

Slurry pig wastewater with a chemical oxygen demand of 42,000 mg / L, a biological oxygen demand of 30,600 mg / L, a suspended solids content of 23,000 mg / L, total nitrogen of 2,200 mg / L and a total phosphorus of about 1,000 mg / L was prepared by the method described above. In a 50L chemical reactor made of stainless steel, 11% ferric sulfate was added and rapidly mixed at 1,500 rpm for 2 hours. 35% NaOH was added to adjust the pH of the reaction to 7.3. While reducing, an A601P of Yiyang Chemical was added as an anionic polymer flocculant. The floc formed reactants were subjected to solid-liquid separation using a solid-liquid separator such as a filter press. The results are shown in Table 2 below.

     Item (mg / L) Sample Type SS BOD ₅ COD _Cr T-N T-P Wastewater 23,000 30,563 44,200 2,220 1,017 Reaction pH 2.5 63 10,632 18,421 1,693 0.2 Reaction pH 3.0 64 10,545 18,770 1,670 0.2 Reaction pH 3.5 3 10,345 15,363 1,541 0.2 Reaction pH 4.5 2 10,815 15,560 1,590 0.2 Reaction pH 5.0 20 11,012 17,945 1,617 0.1 Reaction pH 5.5 25 11,475 18,530 1,680 0.1 Reaction pH 6.0 1,200 17,200 24,380 1,720 52.6

As shown in the experimental results, when ferric sulfate was added until the pH in the reactor reached 5.5, the removal rate of the suspended solids was more than 99.7%, but when sludge was injected only until the pH in the reactor reached 6.0, The water content rapidly deteriorated, and the concentration of suspended solids in the treated water also increased. The removal rate of chemical oxygen demand in the chemical coagulation process was dependent on the content of suspended solids and macromolecular organic matter in the livestock wastewater, and the remaining organic matter was mostly volatile fatty acids. On the other hand, when ferric sulfate was added until the pH in the reactor was 2.5, there was no significant difference in performance compared to the case where the ferric sulfate was injected until the pH was 3.5, and the treatment efficiency was lowered.

<Example 2>

50L of slurry-type pig wastewater made of stainless steel with chemical oxygen demand of 42,000 mg / L, biological oxygen demand of 30,600 mg / L, suspended solids content of 23,000 mg / L, total nitrogen of 2,200 mg / L and total phosphorus of about 1,000 mg / L 11% ferric sulfate was added until the reaction pH was 4.5 in the chemical reaction tank of the reaction mixture and rapidly mixed at 1,500 rpm for 2 hours, and then the reaction product was adjusted to 7.3 by addition of 35% NaOH and stirred at 300 rpm. The anionic polymer flocculant was administered while slowing down. The floc formed reactants were subjected to solid-liquid separation using a solid-liquid separator such as a filter press. The solid-liquid separated chemically treated water used as influent for subsequent biological treatment systems added a certain amount of phosphate phosphorus to prevent degradation of microbial activity due to phosphorus deficiency. An effective volume 6-liter acrylic reactor with 0.5 liters of anoxic selector and 5.5 liters of aerobic reactor was fabricated, and the wastewater after solid-liquid separation was introduced into the organic material load of 1.4 kg COD / m ³ · day at 22.5 ℃. Drive. In the beginning of operation, the influent specified above was used, but in the latter part of the experiment, experiments were made on pig wastewater having a concentration approximately twice that of the influent under the same operating conditions.

Comparative Example 1

As a biological reactor, the experiment was performed in the same manner as in Example 2, except that a 6 liter acrylic reactor without an oxygen free selector was used.

As a result of the experiment, the bioreactor without anoxic selector was greatly deteriorated in sludge settling and the sludge was intensified. Less than 70 mg / L, SS 50 mg / L could be maintained continuously. At this time, the concentration of inorganic solids in the effluent was 2.0-2.5%.

That is, in the biological treatment process after the chemical treatment of high concentration livestock wastewater, there was no oxygen selector as in Comparative Example 1, the normal operation was impossible due to severe microorganisms loss due to settling deterioration. On the other hand, when there is an oxygen-free selector as in Example 2, it was possible to secure a stable treated water quality after a certain period of compliance.

<Example 3>

In this embodiment, when the concentration of inorganic matter in the treated water exceeds 3%, the treated water is subjected to the post-treatment of the chemical flocculation according to the first to third steps of the method according to the present invention. The wastewater treatment efficiency of the case was compared. the results are as follow.

Inorganic concentration of treated water 3% or less Mineral concentration in treated water 3-5% Before the post-treatment of step (5) After the post-treatment of step (5) BOD ₅ (mg / L) 70 or less 500-1,000 100 or less SS (mg / L) 50 or less 1,000-2,000 50 or less COD _Cr (mg / L) 1,000 or less 2,000-3,000 1,000 or less

As shown in the table above, when the concentration of inorganic matter in the treated water is 3% or less, good water quality is shown without post-treatment of chemical flocculation, whereas when the concentration of inorganic matter in the treated water is 3-5%, It was found that post-treatment is essential. That is, when the concentration of minerals in the treated water exceeds 3%, the generation of severe bubbles and turbidity in the treated water increased. Subsequent chemical treatments were essential at this time, and even though the concentration of minerals in the wastewater increased to 5%, subsequent chemical treatments continued to stabilize biochemical oxygen demands of less than 100 mg / L and suspended solids of 50 mg / L. Water quality could be secured.

By using the high concentration organic wastewater treatment method combining the chemical coagulation and biological process according to the present invention, the livestock wastewater of various characteristics discharged from small and medium-sized farms has a biochemical oxygen demand and a concentration of suspended solids of 150 mg / L or less. Can be processed stably. The use of inexpensive inorganic coagulant greatly reduces the load of organic material flowing into the rear stage bioreactor due to the solid-liquid separation by chemical treatment, thereby greatly reducing the treatment cost per ton. In addition, the concentration of inorganic matter during chemical treatment, which is determined by the chemical oxygen demand of the raw wastewater and the concentration of the suspended solids, can represent an excellent biochemical oxygen demand and the removal rate of the suspended solids without further treatment. Subsequent chemical aggregation up to -5% ensures stable water quality of less than 100 mg / L of biochemical oxygen demand and less than 50 mg / L of suspended solids. According to the present invention, in the case of swine wastewater having a chemical oxygen demand of 50,000 mg / L or less, including about 20,000 mg / L of suspended solids, it is possible to exhibit excellent and continuous removal of contaminants without subsequent chemical coagulation treatment.

1 is a view schematically showing the configuration of a livestock wastewater treatment method according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: chemical reactor 11: stirrer

12: pH meter 13: ferric sulfate

14: sodium hydroxide 15: anionic polymer coagulant

16: filter press 17: reservoir

18: Sludge generated during chemical treatment 20: Oxygen-free selector

21: Aerobic Biological Reactor 22: Recirculation Pump

23: sedimentation tank 24: excess sludge during biological treatment

25: biologically treated water

Claims (6)

In the method of treating high concentration organic wastewater, such as livestock wastewater, A first step of reacting the wastewater with ferric sulfate at 1,000 to 3,000 rpm in a reactor containing the wastewater until the pH of the wastewater reaches 3.5 or more and less than 5.0; A second step of adjusting the pH of the treated water by adding an alkaline agent to the treated water treated in the first step; A third step of forming a floc under low-speed mixing conditions by introducing a polymer flocculant into the treated water after the second step and solid-liquid separation of the formed floc; And And a fourth step of treating the treated water separated through the third step by an aerobic biological process using activated sludge. The aerobic biological process of the fourth step is aided by a floc forming bacteria screening process by an anoxic selector to improve sludge settling, and the activated sludge of the aerobic biological process is returned to the anoxic selector. High concentration organic wastewater treatment method combining biological process. delete delete delete The method of claim 1, wherein when the concentration of inorganic solids in the treated water treated by the method exceeds 3%, the treated water is reprocessed through the first to third steps. High concentration organic wastewater treatment method combining chemical coagulation and biological process. The method of claim 1, wherein phosphate is added to the treated water before performing the fourth step.