KR100453484B1 - Method of wasetwater treatment - Google Patents

Abstract

The present invention relates to a method for treating wastewater having a high concentration of solids (SS) and organic matter and containing high concentrations of nitrogen and phosphorus, which are difficult to be treated by general chemical and biological treatment methods. It relates to a new continuous wastewater treatment method that can remove nitrogen, phosphorus and in the chemical unit process crystallize high purity nitrogen and phosphorus to recover by-products available as fertilizer.

Its composition consists of a solid-liquid separation process for separating solids in wastewater; and a struvite crystallization process for removing nitrogen and phosphorus from dissolved solids separated in solid-liquid separation process; and the supernatant water from the struvite crystallization process in a two-stage intermittent aeration tank. Characterized in that the intermittent aeration process for nitrification and denitrification.

The advantage of this wastewater treatment method, which is a continuous treatment process with a suitable combination of physical, chemical and biological treatments, is easy to treat wastewater containing high concentrations of solids and nutrients. Suitable. In addition, it is possible to remove most of the solids of the target wastewater from the solid-liquid separator by using flocculation, which is a chemical operation, and to remove toxic substances introduced at the same time.

Description

Method of wasetwater treatment

The present invention relates to a wastewater treatment method, and more particularly, to effectively remove high concentrations of organic matter and solids as a pretreatment to facilitate subsequent struvite crystallization reactions and biological treatments, and to eutrophication in rivers and lakes, etc. It can effectively treat nutrients (nitrogen and phosphorus) in the wastewater that is a problem as a causative agent, and wastewater that has been technically made of high purity crystals of nitrogen and phosphorus using physicochemical properties to make it available as fertilizer. It relates to a treatment method.

In general, wastewater containing very high concentrations of organic matter and high concentrations of nutrients (especially livestock wastewater discharged in the form of slurries) is difficult to be treated by physical, chemical, and biological treatment alone. For the economical practical treatment device has not been developed yet.

Nutrients contained in the wastewater are inorganic elements, but they flow into rivers, coastal seas, lakes (lakes and reservoirs), and promote algae growth to cause eutrophication.

When the nutrients contained in the wastewater enter the coastal seas, they cause red tide, and if the rots decay at the bottom of the water and cause bad smells, they promote water pollution. The material to be removed before it is introduced.

At the same time, technologies that can efficiently treat wastewater containing high concentrations of organic matter and high concentrations of nutrients (especially slaughtered livestock wastewater) are currently insignificant and are currently used to remove nitrogen and phosphorus from water. As far as technology can be divided into physical, chemical and biological methods.

First of all, physical methods include ammonia degassing, ion exchange using selective adsorption, precipitation of phosphorus using slaked lime and flocculant, and struvite formation of precipitation of nitrogen and phosphorus simultaneously. It is used.

Struvite is a method in which Mg: N: P is crystallized in a molar ratio of 1: 1: 1 under alkaline conditions so that nitrogen and phosphorus are precipitated and removed at the same time. No. 2002-5521.

The Korean Patent Publication No. 2002-5521 discloses struvite by sequentially injecting agglomeration sources such as magnesium or phosphorus into livestock manure and industrial wastewater containing high concentrations of nitrogen in a predetermined order or by injecting the agglomeration sources into two or more times. A method for treating high concentration nitrogen wastewater using struvite precipitation which improves the crystallization efficiency and reduces the amount of flocculation source is disclosed, and the flocculation source and alkali mixing tank for struvite precipitation, struvite crystal reaction, precipitation tank, etc. Disclosed is a nitrogen wastewater treatment apparatus using struvite sedimentation in which a reactor can be packaged into one apparatus and continuously treated.

However, when a large amount of solids is contained in the above method, there is a problem that the purity of the struvite crystallization is reduced. Therefore, there is a limit to using crystals directly as a fertilizer.

On the other hand, in the biological treatment method, in the case of nitrogen, ammonia nitrogen and organic nitrogen in the dissolved state are nitrified (ie, Nitrosomonas & Nitrobacter ) under aerobic conditions (ie, ammonia is transformed into nitrate form), and nitrate is denitrified. Oxidized bacteria (ie, Pseudomonas, Paracoccus denitrifiers) are used as electron acceptors instead of oxygen under anoxic conditions, converted to nitrogen gas and released into the atmosphere (denitrification) and removed.

For phosphorus, wastewater is alternately maintained under anaerobic and aerobic conditions, releasing phosphorus from phosphorus-removing microorganisms (ie, Acinetobacter ) under anaerobic conditions, and in subsequent aerobic conditions, causing the microorganism to overdose phosphorus, Phosphorus in the wastewater is removed by a gentle removal.

The degree to which the microorganism ingests phosphorus excessively in the aerobic condition depends on the amount and type of organic matter introduced into the anaerobic condition. In particular, in the case of maintaining a pure anaerobic state and a large amount of organic acid salts such as acetate in pure anaerobic condition The amount of phosphorus released is enhanced, and the intake of phosphorus is enhanced in subsequent aerobic conditions, thereby increasing the throughput.

Therefore, the biological nitrogen and phosphorus removal process is appropriately arranged anaerobic-aerobic-anaerobic-aerobic reactors in accordance with the characteristics of each reactor to induce organic oxidation and nitrification reaction and microorganism intake of phosphorus in the aerobic reactor, and in anaerobic and anoxic reactor Nitrate nitrogen is converted into nitrogen gas to induce denitrification and phosphorus release into the atmosphere.

Currently, Bardenpho, A2 / O, A / O, UTC and VIP have been developed as wastewater treatment processes widely used as nutrient control methods based on biological treatment principles, all of which are developed by applying the above principles. It's been a process. Although these technologies are already widely used in developed countries, such as sewage treatment plants, in Korea, some sewage treatment plants have attempted to convert them from the existing standard activated sludge process to such processes. to be.

In particular, in the case of wastewater containing high concentrations of organic matter and nitrogen and phosphorus, such as livestock wastewater, the above processes are used. However, most treatment facilities are arranged in such a manner that various processes are cluttered and combined to satisfy legal discharge standards. Even if the existing developed process is used effectively, the concentration of ammonia nitrogen is high due to the nature of the waste water, which requires a long hydraulic residence time for nitrification, which causes a lot of land area.

Therefore, the present invention is to treat wastewater containing high concentration of solids and nitrogen and phosphorus at the same time and to improve the struvite crystallization purity to solve the conventional problems in the treatment of nutrients wastewater treatment method that can utilize the crystals as a fertilizer The purpose is to provide.

1 is a schematic diagram of a device for implementing the method of the present invention.

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

1: solid-liquid separator

2: crystallization reactor

3: first aeration tank

4: second aeration tank

5: terminal sedimentation basin

6: crystal reservoir

Wastewater treatment method according to the present invention for achieving the above object is a method for treating wastewater containing a high concentration of solids, solid-liquid separation process for separating the solids in the waste water; and the dissolved dissolved in the solid-liquid separation process Struvite crystallization to remove nitrogen and phosphorus in water; And an intermittent aeration process for nitrifying and denitrifying the supernatant water from the struvite crystallization process in a two-stage intermittent aeration tank.

That is, in the method of the present invention, solids and organics are solid-liquid separated in a solid-liquid separator using a flocculant, and high concentrations of nitrogen and phosphorus are mostly removed through subsequent struvite crystallization (3 minutes of crystallization + 30 minutes of precipitation).

The struvite crystallization process is highly pure because the organic matter is almost completely removed from the solid-liquid separator. Residual organics and nutrients are then removed during subsequent biological treatment, and most of the organics are removed from the solid-liquid separator at the front end, so that they are easily removed due to the low load in the biological treatment process.

In particular, since nitrogen is mostly removed in the preceding struvite crystallization process, nitrification and denitrification are smoothly performed without being subjected to free ammonia toxicity in subsequent biological processes.

The harmonious combination of solid-liquid separation, struvite crystallization, and biological processes is a technical feature of the present invention, which solves the problems of conventional high concentration nitrogen-containing wastewater treatment (degradation of crystallization efficiency) through this method, thereby removing organic matter, nitrogen, and phosphorus. At the same time, it can be processed quickly and completely, and at the same time, it can crystallize nitrogen and phosphorus in wastewater and use it as a high-purity fertilizer.

The method of the present invention can be carried out using a known urea apparatus, Figure 1 schematically shows an example, as shown, solid-liquid separator (1), crystallization reaction tank (2), crystal storage tank (6) ), Two-stage intermittent aeration tanks 3 and 4, and a terminal needle battery 5.

The solid-liquid separator (1) is a device for the separation of solids and dissolved substances whose properties have been changed so that the solid-liquid separation occurs properly by mixing a coagulant of an appropriate concentration in the influent. Most solids (organic matter) contained in the waste water are Removed.

At this time, if the solid concentration is too high, the solid-liquid separator 1 may not be properly treated, so the solid-liquid separated wastewater is returned (10), mixed with a coagulant of an appropriate concentration, and then a condensate may be made and processed.

By removing the solids through the solid-liquid separator 1, it is possible to increase the purity of the struvite crystal produced in the subsequent struvite crystallization process.

The struvite crystallization tank 2 precipitates and removes nitrogen and phosphorus using a struvite crystallization reaction. The struvite crystallization is carried out in a molar ratio of magnesium, ammonia nitrogen, and phosphorus at 1: 1: 1, and stirred under alkaline conditions (pH 8-12).

If the magnesium source is expensive, it is possible to use seawater and concentrated seawater (salt water), which has already been confirmed.

In the crystallization reaction, ammonia nitrogen and phosphorus of the wastewater can be selectively crystallized, and the purity of crystals becomes very high if only ammonia nitrogen and phosphorus are present in the solid-liquid separator.

In this case, a portion of the crystal may be circulated to the crystallization reactor in the crystal reservoir 6 to increase the crystallization efficiency (60).

The struvite crystals produced by the struvite crystallization reaction are mainly magnesium, ammonia nitrogen, and phosphorus and have high purity, which is very effective when used as fertilizer in farms and the like.

After struvite crystallization, residual organics and nutrients are removed by alternating aeration and non-aeration processes in subsequent two-step intermittent aeration tanks 3 and 4.

Since solids are removed through solid-liquid separation in the solid-liquid separator 1, there is an advantage that the organic load is less during biological treatment, and thus the hydraulic retention time (HRT) can be reduced. In addition, since most of the nitrogen is removed through the struvite crystallization process, ammonia toxicity can be avoided during the subsequent biological treatment, and thus smooth nitrogen removal is achieved.

The two-stage intermittent aeration reactor consists of a first intermittent aeration tank (3) and a second intermittent aeration tank (4), each reaction tank is a predetermined time aeration and non-aeration process alternately.

That is, when the first intermittent aeration tank 3 is in the aerated state, the second intermittent aeration tank 4 maintains aeration when the first intermittent aeration tank 3 is in the non-aeration state.

This is to advance the denitrification in the aeration state nitrification and non-aeration state, wastewater treatment apparatus and method using the two-stage intermittent aeration tank is disclosed in detail in Korean Patent Laid-Open No. 1999-46813.

The biologically treated wastewater from the two-stage intermittent aeration tanks 3 and 4 flows into the terminal sedimentation cell 5 and is separated into activated sludge and effluent and the treatment is completed.

Hereinafter, the operation of the wastewater purification process of the present invention will be described in detail once again.

As shown in Figure 1, the apparatus for performing the waste water purification process of the present invention is a solid-liquid separator (1), crystallization reaction tank (2), intermittent aeration reactor (3, 4), sedimentation tank (5) and crystal storage tank (6) It consists of).

Each reactor is connected to each other, and the two-stage intermittent aeration tanks (3 and 4) are biological treatment processes, and the solid-liquid separator (1), crystallization tank (2) and precipitation tank (5), and the crystal reservoir (6) are physical and chemical treatment processes. to be.

Solids in the wastewater introduced into the solid-liquid separator 1 are separated, and wastewater having a low concentration of solids is continuously removed from the ammonia nitrogen and phosphorus in the struvite crystallization process, thereby facilitating residual organic matter and nitrogen treatment in subsequent biological processes. do.

Here, a flocculant is injected into the wastewater flowing into the solid-liquid separator 1 to promote the separation of solids in the wastewater. Coagulants vary in type and amount depending on the wastewater and are readily available commercially.

The supernatant from which the solid-liquid separation is carried out in the solid-liquid separator (1) is transferred to the struvite crystallization reactor (2), and the supernatant after the crystallization reaction is continuously introduced into the intermittent aeration process (3, 4). Is transferred to the crystal reservoir 6.

At this time, in order to increase the nitrogen removal efficiency, a portion of the crystal may be introduced into the struvite crystallization reaction tank 2 for treatment.

In the two-stage intermittent aeration process, the biologically treated wastewater is introduced into the terminal sedimentation cell (6), and the liquid is separated into effluent and activated sludge from the terminal sedimentation cell to purify the wastewater.

Solids precipitated in the sedimentation tank (5) during the process are removed from the process as some excess sludge, sludge and sedimented waste water is transferred to the intermittent aeration reactor (3, 4) (50) and aeration and non-aeration proceeds as organic matter Nitric oxidation during oxidation and aeration (NH4 + -N → NO2--N → NO3--N) and denitrification during non-aeration (NO3--N → NO2--N → N2 (gas)). Removed from water in the form of nitrogen gas.

The advantage of this wastewater treatment method, which is a continuous treatment process with a suitable combination of physical, chemical and biological treatments, is easy to treat wastewater containing high concentrations of solids and nutrients. Suitable.

In addition, it is possible to remove most of the solids of the target wastewater from the solid-liquid separator by using flocculation, which is a chemical operation, and to remove toxic substances introduced at the same time.

In addition, since most of the organic matter is removed from the solid-liquid separator, there is an advantage in reducing the organic load in the subsequent biological treatment and it is possible to increase the purity of the crystal obtained through the struvite crystallization device.

In the struvite crystallization process, nutrients such as nitrogen and phosphorus can be almost completely removed, and the struvite crystals produced through the crystallization process contain a large amount of nitrogen and phosphorus contained in the fertilizer 3 element, which is used as a high-purity fertilizer. There is an advantage to commercialization.

An especially important advantage is that in the subsequent biological treatment process, Nitrosomonas can perform nitrification smoothly without the toxic effects of free ammonia because nitrogen is almost completely removed through the crystallization process at the front end. The present invention can be effectively used in industrial wastewater and livestock wastewater in the form of a slurry, which is difficult to treat nutrients.

Claims (2)

As a method for treating wastewater containing a high concentration of solids, Solid-liquid separation process for separating solids in the wastewater; Struvite crystallization to remove nitrogen and phosphorus in the dissolved solution separated in the solid-liquid separation process; And And an intermittent aeration process for nitrifying and denitrifying the supernatant water from the struvite crystallization process in a two-stage intermittent aeration tank. The wastewater treatment method according to claim 1, wherein a portion of the crystal is introduced into the struvite crystallization reactor from the crystal reservoir to increase the nitrogen removal efficiency.