KR100503134B1 - A wastewater treatment methods - Google Patents

Abstract

Conventionally, there have been wastewater treatment methods using various methods, but all of them have problems of uneconomical problems and a problem of not simultaneously treating denitrification and color of wastewater.

In order to solve this problem, the wastewater is introduced into the bottom of the reaction tank filled with a gravel layer and a mixture of sulfur and calcium carbonate (S ⁰ + CaCO 3) while having a large amount of ammonia nitrogen or when there is a coloring problem. Intermittent aeration maintains aerobic and anoxic conditions. Under aerobic conditions, ammonia nitrogen is nitrated with nitrate nitrogen and nitrite nitrogen, and decolorized by a sulfation reaction under aerobic conditions.

In anoxic conditions, denitrification of nitrate nitrogen or nitrite nitrogen with nitrogen gas is carried out by a sulfation reaction under anoxic conditions, and in the case of large amounts of nitrate nitrogen or nitrite nitrogen, sulfuric acid is maintained without an aeration without maintaining aeration. It is characterized in that the wastewater is purified by a method of removing the nitrogen component and color by performing denitrification of nitrate nitrogen or nitrite nitrogen with nitrogen gas by the oxidation reaction.

Description

Wastewater Treatment Methods {A WASTEWATER TREATMENT METHODS}

The present invention relates to a wastewater treatment method, and more particularly, to a wastewater treatment method for denitrification and decolorization of wastewater having a low C / N ratio using a sulfation reaction.

Conventionally, there are many techniques regarding the purification of waste water.

First, the conventional technology related to nitrogen removal will be described, and then the conventional technology related to decolorization will be described.

Looking at the prior art with respect to nitrogen removal as follows.

In general, as the most widely used method for removing nitrogen contained in wastewater, biological nitrogen removal by nitrification and denitrification using heterotrophic microorganisms is known.

This is a process in which ammonia nitrogen (NH ₄ ⁺ -N) is converted to nitrite nitrogen (NO ₂ ^-- N) or nitrate nitrogen (NO ₃ ^-- N) by autotrophic microorganisms. When oxidized to nitrosomonas, Nitrosococcus, Nitrosobacillus, etc., microorganisms are involved. When oxidized from nitrous nitrogen to nitrate nitrogen, Nitrobacter and Nitrosocystis are involved.

However, the rate of proliferation of autotrophic microorganisms is much slower than that of heterotrophs, and the microbial growth rate is low.

Nitrosomonas and Nitrobacter produced 0.15 mg-cell / mg-NH ₄ ⁺ -N, 0.02mg-cell / mg-NO ₂ ^-- N, and oxygen consumption was 3.22mg-O ₂ / mg-NH ₄ ⁺ -N , 1.11mg-O ₂ / mg-NO ₂ ^-- N, and the decrease in alkalinity are 7.14mg -Alkalinity / mg-NH ₄ ⁺ -N.

In other words, the nitrification reaction requires oxygen, and a large amount of nitrification bacteria must be secured and maintained in the reaction tank.

In addition, a large amount of alkalinity is also required, so a pH buffering action is required to control the decreasing pH.

Temperature, BOD / TKN ratio, and ammonia nitrogen concentration also affect nitrification.

Denitrification is carried out in the presence of dissolved oxygen (DO) in the presence of nitrate nitrogen or nitrite nitrogen (Anoxic condition), Pseudomonas, It refers to a process in which nitrate nitrogen or nitrite nitrogen is converted to nitrogen gas (N ₂ ) by heterotrophic organisms such as Bacillus and Micrococcus.

Denitrification consists of the conversion of nitrate nitrogen to nitrite nitrogen and the conversion of nitrite nitrogen to N2 gas via NO and NO ₂ .

Denitrification produces an alkalinity of about 2.3 to 3.0 mg as CaCO ₃ / mg-N.

In a system that simultaneously performs nitrification and denitrification, the alkalinity lowered in nitrification can be increased to some extent.

However, conventional denitrification using heterotrophic microorganisms requires an organic carbon source as an electron donor.

    At present, the most common nitrogen removal method is circulating nitrification and denitrification using suspended activated sludge.

This method consists of an anaerobic tank and an aerobic tank. By circulating the waste water, denitrification in the anoxic tank and nitrification occur in the aerobic tank.

However, this method requires a separate installation of the reaction tank, so a large installation site is required and the aerobic capacity must be increased.

In order to obtain stable treated water with a small reaction tank volume, a method of filling activated sludge or a carrier immobilized with nitrifying or denitrifying bacteria is also used instead of suspending activated sludge. However, there is a disadvantage that the carrier cost is high.

As a method of nitrifying and denitrifying in a single bath, there is a batch activated sludge process (SBR process).

This process is a variation of the activated sludge method, and five processes of [inflow-reaction-precipitation-discharge-atmosphere] are sequentially performed in one reactor, and in the precipitation process, aeration is stopped to form an oxygen-free tank to perform denitrification.

This process has the advantage of a simple device, easy maintenance and low installation and operating costs.

However, scum is easy to accumulate in the reactor and a discharge device of supernatant is required.

Table 1 shows the principle, advantages, and disadvantages of the device developed as a nitrogen-removing device for a single reaction tank with the aim of packaging as a batch activated sludge method (SBR).

In any of the above-described methods, when the nitrogen concentration is high and the organic matter concentration is low, that is, the C / N ratio is low, the waste water requires a lot of energy to supply the oxygen required for nitrification and an electron donor must be added for the denitrification. .

The most commonly used is methanol.

However, in the case of methanol addition, it is difficult to control the proper amount of addition and methanol should not remain in the treated water due to the toxicity of methanol itself.

The amount requires more than three times the amount of nitrogen to be treated and the maintenance costs cannot be ignored.

A new technique that supplements the above disadvantages is the denitrification using sulfur.

Denitrification with NO ₂ sulfur is a sulfated microorganisms represented by Thiobacillus denitrificans as the final ^receptor-a, burnout reaction occurs while using the NO, N ₂ O ^-, NO _3.

The final product of sulfur in NO x removal reaction is ^{_{SO 4 2- O 2, NO 2}} -, NO 3 -, NO, N 2 O is used, but as the final hydrogen acceptor of sulfation, as the final hydrogen acceptor NO ₂ ^- or NO ₃ ^- more preferred O ₂ because the sulfur denitrification without the O ₂ present nO ₂ ^- can be expected only in the presence of an oxygen-free state ^- or nO _3.

T. denitrificans is absolute CO _2, HCO ₃ by chemical autotrophic microorganisms ^- to grow using the arms of carbon, CO ₃ ^2-, etc. as a carbon source.

The sulfation of the _{^{T. denitrificans S 0, S 2 -}} , S 2 O 3 2-, S 4 O 6 2-, SO 3 2- is a high denitrification efficiencies are low oxidation state sulfur compounds so used as a hydrogen donor.

Comparison of the cost of the sulfur compounds in drug costs per electronic equivalent as a hydrogen acceptor in a sulfur denitrification reaction by the T. denitrificans has been reported that S ⁰ is the most cost-effective hydrogen donor (Bisogni, JJr & Driscoll, CT Jr.: Denitrification using thiosulfate and sulfide, J. Environ. Eng. Div. Proc. ASCE, Vol. 103, p. 593-604 (1977).

S ⁰ has the advantages of abundant resources, low price, easy storage, good handling, no toxicity, etc., but it does not dissolve easily in water.

And denitrifying microorganisms are known to be difficult to accumulate microorganisms and solid-liquid separation because they are not cohesive.

There is also a problem that SO ₄ ^2- , the final product of the sulfation reaction, lowers the pH.

    As the desulfurization technology using sulfur in Korea, biofilm filtration sewage treatment technology using coagulation sedimentation and granularity of FineProtec Co., Ltd., and advanced alkalinity wastewater treatment technology using desulfurization process of Hyundai Heavy Industries Co., Ltd. There is SPAD method of same name industry.

These processes are similar in terms of using sulfur but are different.

In the case of FINEPROTEC Co., Ltd., the wastewater flows into the down-current into an oxygen-free reaction tank filled with a granular state (S ⁰ ), and a fixed amount is provided with a fixed amount pump to replenish some of the alkali consumed during the denitrification reaction. Thick sodium carbonate (Na ₂ CO ³ ) is used to mix the treated water of the biofilm filtration (nitrification tank) into the line conveyed to the granular denitrification tank in a line mixing manner. It is said to be put in operation.

In the case of Hyundai Heavy Industries Co., Ltd., the wastewater is introduced into the denitrification tank filled with the granular state (S ⁰ ) to the Up-Current, and the alkaline material filling tank is used to replenish some of the alkali consumed during the denitrification reaction. It is said to fill carbonate-based alkalinity materials, including limestone, shells, oyster shells, eggshells, dolomite, magnesium carbonate, etc., and the eluted alkalinity materials are fed into the denitrification tank with a metering pump.

The denitrification process of FineProtec Co., Ltd. and Hyundai Heavy Industries Co., Ltd. injects alkalinity materials from the outside. In the case of Dongmyung Industrial Co., Ltd. It is a method to use autotrophic and heterotrophic denitrification at the same time by adding methanol to the contact tank.

This method using sulfur is also shown in Japanese Patent Application Laid-open No. Hei 4-9119, which is a technique for simultaneously removing nitrogen and phosphorus in wastewater, and desulfurization is performed by adding sulfur to the existing aerobic-anaerobic activated sludge process.

The above-mentioned denitrification methods deteriorate alkalinity in denitrification of the conventional denitrification method, and especially in the case of wastewater containing high concentration of nitrate nitrogen and low alkalinity, the pH is lowered so that denitrification does not proceed anymore. A method of adding an alkalinity substance, adding a small amount of methanol, or filling with sulfur in a reactor is adopted.

However, since only sulfur is present inside the reactor when the alkali material or methanol is added from the outside, it is difficult to retain the denitrifying bacteria during the initial application, and when the alkalinity is low, the denitrification is not possible and the pH is lowered as the amount of SO ₄ ^2- is increased. There is a disadvantage that denitrification no longer proceeds.

In particular, when the concentration of nitrate nitrogen or nitrite nitrogen is high, denitrification is difficult.

And when the ratio of the alkalinity added and sulfur content is not correct, Ca ²⁺ in the alkalinity material reacts with SO ₄ ^2- generated by oxidizing sulfur to form gypsum (CaSO ₄ ), which sinks to the bottom and hardens the inflow. There is a problem.

Next, a description will be given of a conventional technology related to decolorization.

Techniques related to decolorization of wastewater include ion exchange treatment, oxidative decomposition, ultraviolet irradiation, and hydrogen peroxide-added ultraviolet irradiation.

Recently, decolorization treatment using activated carbon adsorption or ozone injection has also been carried out.

However, these methods have a problem in that the cost of chemicals is high and the power cost is high.

In order to solve this problem, there is a soil adsorption method which has a low treatment cost, but there are disadvantages of soil closure and difficulty in exchanging soil after use.

In the case of the membrane filtration method as a technique for removing the original color of the drink, when the color concentration of the raw water is high, there is a problem that the membrane is filtered or added to the activated carbon treatment after the flocculant is added.

The present invention is to solve the problems of the prior art described above, the present invention has the following features.

Wastewater with a low C / N ratio containing nitrous and nitrous nitrogen, that is, organic matter was removed during the treatment of wastewater or wastewater, which was originally low in organic matter and relatively high in nitrogen (especially nitrate or nitrous nitrogen). Nitrogen is discharged with little removal, for example, livestock wastewater that has undergone anaerobic processes, chemical plant wastewater, plating wastewater, landfill leachate, agricultural drainage, aquaculture plant wastewater, composting plant wastewater, groundwater contaminated with nitrate nitrogen, etc. Nitrogen removal is melon and at the same time to provide a method for color removal of waste water.

This is based on the fact that sulfite ions (SO ₃ ^2- ) generated in the sulfation reaction pathway have reducibility, and the reducing power is used for bleaching. Made it possible.

In order to implement the wastewater treatment method of the present invention, a configuration of an apparatus will be described with reference to FIG. 1, and the wastewater treatment method of the present invention using such a device will be described with reference to Examples. It should be noted that the present invention is not limited to the embodiments described below.

First, a device for implementing the method of the present invention will be described.

A waste water inlet pipe 3 and a pump 4 are formed at the lower end of the reaction tank 10 having a predetermined size so that the waste water can be introduced from the lower portion of the reaction tank 10, and the reaction tank 10 is inside the reaction tank 10. After installing the steel mesh 9 at regular intervals at the bottom 11, a gravel layer 1 is formed on the top of the steel mesh 9, and a mixture of sulfur and calcium carbonate is formed on the top of the gravel layer 1 ( S ⁰ + CaCO _3: SC constitutes the pellet) layer 2: a mixture of sulfur and calcium carbonate stacking the pellet SC) (S ⁰ + CaCO _3.

In addition, a gas discharge port 8 and a treated water discharge port 7 are formed at an upper end of the reaction tank.

In order to supply air according to the type of wastewater, the air inlet pipe 5 is installed at the lower end of the reactor 10 so that the air can be supplied by the blower 6.

The wastewater treatment apparatus of the present invention supplies the wastewater through the operation of the pump (4) through the wastewater inlet pipe (3) through the bottom of the reaction tank (10).

This waste water is first purified while passing through a gravel layer 1 stacked on top of the steel mesh 9 and secondly while passing through a mixture of sulfur and calcium carbonate (S ⁰ + CaCO ₃ : SC pellet) layer (2). Will be.

At this time, the air containing N ₂ generated by the chemical reaction between the waste water and the mixture of sulfur and calcium carbonate is discharged through the gas outlet 8, and the purified treated water is discharged through the outlet 7.

In this case, when air is required according to the type of waste water, air is supplied to the inside of the reaction tank 10 through the air inlet pipe 5 by a method of blowing air to the blower 6.

In view of the wastewater treatment apparatus of the present invention will be described in detail the present invention by the embodiment carried out below.

Example 1

Livestock wastewater after anaerobic treatment

The raw water to be treated was swine wastewater after anaerobic treatment using the UASB method.

As a breeding source, activated sludge (MLSS: 6,000 mg / L) of the livestock wastewater treatment facility was collected and introduced for 8 hours in an upward flow type upwardly from the bottom of the reactor 10 through the wastewater inflow pipe 3.

After adapting for 20 days in this state, the experiment was performed.

Swine wastewater after anaerobic treatment was operated by intermittent aeration because of high ammonia nitrogen (NH ₄ -N) concentration, which requires nitrification, denitrification, and decolorization.

Raw water phase is shown in Table 1.

Table 1. Raw water phase (swine wastewater after anaerobic treatment)

pH (-) Color (U) TOC (mg / L) T-P (mg / L) PO4-P Range 7.3 to 7.7 96.5-1423 258-354 92.6 to 138.9 Average - 1201 323.1 112.4 T-N (mg / L) NH ₄ -N (mg / L) NO ₃ -N (mg / L) NO ₂ -N (mg / L) SO ₄ -S (mg / L) Range 228.6 ~ 434.7 213.8 to 330.1 5.5 to 5.6 ND * 17.3-39.0 Average 314.5 276.9 5.5 ND * 23.7

* ND: Not detected

The change in pH in the effluent phase after treatment is shown in FIG. 2.

And the removal efficiency of the color of TN, NH ₄ ⁺ -N, TP, PO ₄ ^2- -P, TOC, and the waste water is shown in Table 2.

Table 2. Treatment efficiency after application of the present invention to swine wastewater after anaerobic treatment (HRT: 8 hr)

Color removal rate T-N removal rate NH ₄ -N removal rate T-P removal rate PO ₄ -P removal rate TOC removal rate 62.73% 54.31% 61.38% 68.22% 64.13% 78.20%

As a result of intermittent aeration with 8 hours of HRT, as shown in Table 2, more than 50% of TN, NH ₄ ⁺ -N, TP, PO ₄ ^2- -P, TOC, and wastewater were removed.

At this time, HRT was operated for 12 hours to increase the removal efficiency. As shown in Table 3, the removal efficiency was over 70%.

Table 3. Treatment efficiency after application of the present invention to swine wastewater after anaerobic treatment (HRT: 12 hr)

Color removal rate T-N removal rate NH ₄ -N removal rate T-P removal rate PO ₄ -P removal rate TOC removal rate 70.64% 73.58% 71.53% 80.14% 76.42% 72.72%

Example 2

Chemical Plant Wastewater

In the case of wastewater discharged from the chemical plant, the wastewater discharged from the chemical plant is supplied in an upflow manner upward from the bottom of the reactor 10 through the wastewater inlet pipe 3 in the same manner as in Example 1 above. Since there is almost no coloring problem, it was operated under anoxic conditions for the purpose of nitrogen removal only.

After acclimation for 2 days after the sludge planting, the results of operating in HRT 12 hours are shown in Table 4.

Table 4. Treatment efficiency after application of the present invention to chemical plant wastewater (HRT: 12 hr)

Time (days) pH T-N (ppm) T-N (%) NH ₄ -N (ppm) NH ₄ -N (%) enemy 7.4 132 - 40.22 - 2.5 7.2 42 68.18 17.67 56.07 3.5 7.2 39 70.45 16.32 59.42 4.5 7.2 36 72.73 16.78 58.28 5.5 7.3 35 73.48 13.98 65.24

The pH was almost unchanged from neutral and the removal rate of TN was about 70%.

NH ₄ ⁺ -N also increased the removal efficiency over time.

In general, denitrification using sulfur causes only denitrification and little nitrification (ammonia nitrogen removal).

However, in the case of the present invention, as shown in Table 3, the removal of ammonia occurs in anoxic conditions as well as in intermittent aeration conditions (ammonia removal rate: about 70%) as shown in Table 4.

This is because conditions such as pH in the reaction tank are not only for desulfurization denitrification bacteria but also conditions for nitrifying bacteria and the like.

That is, the present invention can be said to be a breakthrough method that is very advantageous for nitrification (removal of ammonia nitrogen) as well as denitrification (removal of nitrate nitrogen and nitrite nitrogen).

In addition, from the above results, it is considered that if the acclimation period of the seedling sludge (about 2 days in Table 4) is longer (about 2 weeks), the removal efficiency may be increased.

Example 3

Semiconductor production plant wastewater

In the case of semiconductor production factory waste water, the concentration of TN inflow raw water to be treated, and accounts for most of the NO ₃ -N ⁺ to about 450ppm, CODCr concentration was about 800mg / L.

After supplying and adapting wastewater to be treated for 2 days in the same manner as in Example 1 described above, HRT was operated for 24 hours for 10 days.

As a result, as shown in FIG. 3, T-N and CODCr decreased as time passed, and the removal rate was more than 90% after 10 days.

4, the pH of the influent was 6.8 to 7.2, but the treated water after the sulphate denitrification tank of the present invention slightly increased to 7.5 to 8.0.

In general, in the case of the denitrification reaction, it is known that the pH is lowered with time, so that the denitrification performance is lowered or denitrification is no longer performed.

However, as shown in FIG. 4 and FIG. 2, the present invention not only solves this problem but also raises the pH.

This is because the amount of SO ₄ ^2- ions, Ca ²⁺ ions, and CO ₃ ^- ions eluted due to the characteristics of the mixture of sulfur and calcium carbonate (S ⁰ + CaCO ₃ : SC pellet) as a filling carrier is balanced. It is feed.

Example 4

end. Plating wastewater (plating wastewater flowing into the integrated wastewater treatment plant)

The wastewater flowing into the integrated wastewater treatment plant of the Plating Corporation has high nitrogen concentration and fluctuations in concentration and quantity due to nitric acid used by each company in the metal acid treatment process. The wastewater was supplied in the same manner as in Example 1 and operated for 12 hours in HRT, and as shown in Table 5, the nitrogen removal efficiency was about 56.87%.

In the case of CODCr, approximately 48.78% were removed. From this result,

If the HRT is longer (approximately 12 hours) and the fluorinated denitrification bacteria have a longer period of adaptation to the actual wastewater, the addition of this process to the existing wastewater treatment process will enable stable nitrogen and organics removal.

Table 5. Treatment result of the present invention of plating wastewater (HRT: 6 hr)

Item Emission allowance standard Influent Runoff % Removal pH 5.8-8.6 6.8 7.7 - CODCr 130 164 84 48.78 T-N 60 211 91 56.87 NH ₃ -N - 3.2 9.06 - NO ₂ -N - 11.24 0 100 NO ₃ -N - 164.95 22.89 86.12 PO ₄ -P - 0.27 0.55 - T-P 8 1.34 1.06 20.90

I. Plating wastewater (wastewater after plating process generated during metal processing)

In the process of metal processing, the wastewater of the place where the plating process is taken is supplied in the same manner as in Example 1, and then the result of operation for 4 hours (HRT) is shown in Table 6 below.

The operation resulted in high treatment efficiency for the removal of total nitrogen and heavy metals, and the water quality after the treatment achieved stable regulatory standards.

Since the plant is chromium (Cr) plated, T-Cr was also analyzed, and the removal rate was about 65%.

In other words, it showed the possibility of removing heavy metals.

Table 6. Post-Application Treatment Results of Plating Process Effluent from Metal Processing Plant (HRT: 4 hr)

pH TN NH ₃ -N NO ₂ -N NO ₃ -N Influent 8.4 98.2 3.5 3.5 81.0 Runoff 8.0 46.6 12.4 3.9 30.3 % Removal - 53.0 - - 62.6 CODCr T-P PO ₄ -P SO ₄ Cr Influent 38.0 0.3 0.0 609.5 1.77 Runoff 20.0 0.1 0.0 687.3 0.62 % Removal 47.4 54.0 - - 65

As described above, the present invention enables simultaneous denitrification by nitrite oxidation, sulfur denitrification, and desulfation by nitrous acid from a single reactor, and desulfurization and decolorization by sulphation. It is very economical to solve the difficult problems of nitrogen and color at the same time by using simple materials such as sulfur and calcium carbonate, which are relatively inexpensive and easy to handle.

In particular, the present invention is suitable for the removal of nitrogen and color of the wastewater, which is difficult to use heterotrophic denitrification because of high nitrogen concentration or color and low C / N ratio. In other words, wastewater or wastewater that is organically removed but little nitrogen is removed from the wastewater or wastewater treatment process, which has a low organic matter concentration and relatively high nitrogen concentration (especially nitrate or nitrite nitrogen). It is obvious that this invention is a very useful invention that provides a method for removing nitrogen from coarse animal wastewater, chemical plant wastewater, plating wastewater, landfill leachate, agricultural drainage, fish farm wastewater, and groundwater contaminated with nitrate nitrogen. .

1 is a cross-sectional configuration diagram schematically showing an apparatus for implementing the method of the present invention;

2 is a graph showing a change in pH obtained in Example 1 of the present invention,

Figure 3 is a graph showing the change in total nitrogen (TN) and ammonia nitrogen (NH ₄ ⁺ -N) obtained in Example 3 of the present invention,

Figure 4 is a graph showing the change in pH obtained in Example 3 of the present invention.

<Explanation of symbols for main parts of drawing>

1: gravel layer 2: a mixture of sulfur and calcium carbonate (S ⁰ + CaCO ₃ ) layer

3: inlet line 4: pump

5: air inlet pipe 6: blower

7: gas outlet 8: gas outlet

9: steel mesh 10: reactor

Claims (5)

The wastewater to be treated is introduced into the upflow type, which moves from the lower part of the reaction tank filled with the gravel layer and the mixture of sulfur and calcium carbonate (S ⁰ + CaCO3) to the upper part, and the sulfated denitrification bacteria dominates in the reaction tank. In the wastewater treatment method, characterized in that to remove the If the waste water contains ammonia nitrogen, or if there is a coloring problem, the aeration and anoxic conditions are maintained by intermittent aeration, but under aerobic conditions, the ammonia nitrogen is nitrated with nitrate nitrogen or nitrite nitrogen by a sulfation reaction. Decolorization, waste water treatment method characterized in that the denitrification and decolorization at the same time by nitrogen gasification of nitrate nitrogen or nitrite nitrogen by the sulfation reaction under anoxic conditions. delete The method of claim 1, When the wastewater contains a lot of nitrate nitrogen or nitrite nitrogen, it is not aerated and maintained in anoxic conditions, and denitrification of nitrate nitrogen or nitrite nitrogen with nitrogen gas is carried out by a sulfation reaction under anoxic conditions. Wastewater treatment method characterized in that to remove. delete delete