KR20010065008A - A treatment method of leachates discharged from landfill by using reverse osmosis system and evaporation method - Google Patents

Abstract

PURPOSE: A landfill leachate treatment method using a reverse osmosis system and an evaporation process is provided, which can treat leachate to be discharged directly into river or to be reused by pretreatment using an impregnation-type separation membrane bioreactor before reverse osmosis treatment followed by evaporation treatment. CONSTITUTION: The method comprises as follows: (i) feed leachate into a bioreactor (2) in which separation membrane is impregnated in aeration tank and feed air to the reactor for growing microorganism to microorganism floc and for removing the grown floc of microorganism to yield pre-treated water; (ii) pass the pre-treated water through a reverse osmosis system (8), discharge passed water, and then feed highly concentrated water containing dissolved ionic impurities to an evaporator(9); and (iii) evaporate the concentrated water at the evaporator (9), discharge pure water together with the passed water from the reverse osmosis system (8), and then solidify the residue.

Description

Landfill leachate treatment method using reverse osmosis system and evaporative concentration method {A TREATMENT METHOD OF LEACHATES DISCHARGED FROM LANDFILL BY USING REVERSE OSMOSIS SYSTEM AND EVAPORATION METHOD}

The present invention relates to a landfill leachate treatment method using a reverse osmosis system and an evaporation concentration method, and more specifically, the leachate generated in the landfill is pretreated with an immersion membrane bioreactor and then concentrated through a reverse osmosis system. Finally, the present invention relates to an improved process for effectively treating leachate by evaporation.

Currently, general leachate treatment adopts anaerobic or aerobic biological treatment. However, due to the high concentration of hardly decomposable substances and salts in the leachate generated in the landfill, there is a limitation in treating only the biological treatment method, so most leachate effluents are not treated within the legal standards.

Therefore, some landfills have introduced advanced treatment facilities such as activated carbon adsorption and Fenton oxidation.In this case, while the removal efficiency of organic matters is good, the discharge of dissolved ionic impurities such as ammonia nitrogen contained in leachate is allowed. It cannot be processed within the standard value.

In view of this, in recent years, attempts have been made to introduce a separation membrane method using a reverse osmosis membrane. In this case, it is also found that there are many problems due to the high facility investment and operating costs and the problems caused by the deep membrane fouling of the reverse osmosis membrane.

Conventional techniques for such a leachate treatment method include "reduced steam extraction, manure using live evaporative compression method, livestock wastewater, industrial waste leachate treatment technology (Korean Patent Publication No. 94-10031)," leachate generated from garbage landfill Treatment Technology (Korean Patent Publication No. 94-6146), "Method of Treating Landfill Leachate by Reverse Osmosis Method (Korean Patent Publication No. 97-10662)", "Method of Treating Leachate in Landfill (Japanese Patent Laid-Open No. 7-116639) "," Leachate Treatment Facility (WP 9-225452), "Lessage Treatment Facility (Japanese Patent Application Laid-Open No. 10-5792), etc.) of the final waste disposal site, but these are mostly strengthened as a method using chemical treatment technology. It is not easy to meet the leachate treatment standards.

Republic of Korea Patent Publication No. 94-6146 uses the reverse osmosis system as in the present invention, but there is a difference using a fine filter and an ultrafiltration system as a pretreatment process. This method is very good in the treated water quality, but there is a problem that the contamination of the membrane is intensified when the dissolved organic matter present in the leachate is high concentration, and there is no way to treat the high concentration concentrated water generated in the reverse osmosis system, especially Since it requires a lot of land, there is a disadvantage that the facility investment cost increases.

Accordingly, an object of the present invention is to provide a method capable of effectively treating contaminants present in leachate even when dissolved ionic impurities are present in high concentration in leachate.

Another object of the present invention is to provide a method for effectively treating the concentrated concentrated water discharged when treating the leachate using a reverse osmosis system.

1 is a schematic diagram of a landfill leachate treatment process using the reverse osmosis system and the evaporative concentration method of the present invention.

Figure 2 is a graph showing the amount of water treatment according to the operation time when the membrane of the backwashable type (A) and the general type (B) is immersed in the aeration tank in the pretreatment process of the present invention.

* Brief description of the main symbols in the drawings *

1 ... raw water pump 2 ... bioreactor

3 ... air blower 4 ... suction pump

5 ... Immersion type membrane 6 ... Pretreatment bath

7 ... high pressure pump 8 ... reverse osmosis system

9 ... evaporator

According to the invention,

Charging the leachate into an immersion membrane bioreactor in which the membrane is immersed in the aeration tank and supplying air to obtain pretreated water from which microbial flocs and fine particulate matter grown in the reactor are removed;

Passing the pretreated water through a reverse osmosis system to discharge permeated water and sending the concentrated water containing the dissolved ionic impurities to an evaporator; And

The landfill leachate treatment method using the reverse osmosis system and the evaporation concentration method comprising the step of evaporating the concentrated water to evaporate pure water to be discharged together with the permeate discharged from the reverse osmosis system and to solidify the evaporation residue. Is provided.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, as shown in the process schematic of the present invention of Figure 1 by treating the leachate using a backwashable immersion membrane bioreactor, reverse osmosis system and evaporative concentration method to dissolve the ionic impurities contained in the leachate with high efficiency It can be handled.

That is, when only the bioreactor is applied to the leachate treatment, the contamination of the membrane is intensified, and the efficiency of treating the leachate cannot be improved. Also, when only the reverse osmosis system is applied, the concentrated water generated in the leachate can be treated. There is no problem.

However, according to the method of the present invention, the leachate is subjected to a pretreatment process through an immersion membrane bioreactor, and then treated primarily with a reverse osmosis system, and the leachate concentrated water generated is evaporated and concentrated secondarily to dissolve the high concentration present in the leachate. It is possible to effectively treat all the concentrated concentrated water discharged from ionic impurities or reverse osmosis system. In the present invention, aeration, reverse osmosis system and evaporative concentration are carried out in a general manner.

In the present invention, as the leachate flowing into the bioreactor 2, leachate generated by rainwater or groundwater is used when the waste which can be decomposed such as food waste is buried in a conventional landfill.

When air is blown into the bioreactor 2, the organic matter is removed by metabolism by using the organic matter in the inflow leachate and oxygen supplied microorganisms, thereby reducing membrane contamination.

The hydraulic retention time in the biological reactor is on the order of 1-10 days and the microbial concentration (MLSS) is maintained at 10,000-15,000 mg / l.

The microbial flocs and fine particulate matter grown through the pretreatment step are removed by the immersion membrane 5 having a pore diameter of 0.01-0.2 μm, and then only the pretreatment water is transferred to the pretreatment tank 6.

The membrane used in the bioreactor 2 is not limited thereto, but does not require a separate sedimentation basin or an external circulation membrane system and facility, and maintains the concentration of microorganisms at a high concentration to improve the treatment efficiency of the leachate. It is preferable to use an immersion type membrane which is structured so as to immerse the membrane directly in the bioreactor (aeration tank) used in the present invention.

Further, the immersion type membrane is suppressed by the contact with the air bubbles generated in the diffuser of the blower during operation, but if the operation time is over a certain time, the membrane contamination is inevitably proceeds to increase the operating pressure or treatment Since the amount is reduced, the immersion type separation membrane used in the present invention is not limited thereto, but it is preferable to use a backwashable type separation membrane capable of backwashing the immersion type separation membrane using water or air.

The suction pump used at this time serves to discharge the treated water by the suction force. In addition, by discharging the treated water to the outside of the bioreactor by the suction pump in this way, the concentration of microorganisms in the reactor is maintained, resulting in the efficiency of decomposition of organic matter by the microorganisms.

The reverse osmosis system serves to remove dissolved ionic impurities in the leachate. When the pretreated water is supplied to the reverse osmosis system 8, total nitrogens remaining without being treated in the pretreatment process as shown in FIG. ), Most of the dissolved ionic impurities, including ammonia nitrogen and total dissolved solids. When the leachate pretreated water is treated with a reverse osmosis system, 50-80% of the permeate can be discharged or recycled as it is because most impurities are removed and maintain a constant water quality.

Meanwhile, the remainder 20-50% is charged into the evaporator 9 and concentrated by evaporation, pure water is evaporated and the cooling water is treated together with the permeated water discharged from the reverse osmosis system and the high concentration residue is solidified and discharged in the form of cake. Will be.

That is, the pretreated water obtained by treating the leachate with a backwashable immersion membrane bioreactor then removes dissolved ionic impurities in the leachate using a reverse osmosis system. The dissolved ionic impurities contain a large amount of ammonia nitrogen, total nitrogen, and dissolved solids, and the remaining high concentration concentrated water including them can be effectively treated by evaporative concentration. By treating the leachate with a backwashable immersion membrane bioreactor and a reverse osmosis system as described above, it can be discharged or recycled as it is while maintaining a constant water quality, and the remaining high concentration water can be significantly improved by using an evaporative concentration method. It is discharged to the treated water and the remainder can be safely treated as solids.

Hereinafter, embodiments of the present invention will be described in detail. The following examples are intended to illustrate the invention and are not intended to limit the invention thereto.

<Example>

In each of the following examples, the leachate was simulated using leachate generated in a landfill in an amount of 100 liters.

Example 1

This embodiment is to find the effect of improving the water quality of the pre-treated water when the leachate is pretreated using a backwashable immersion membrane bioreactor.

The bioreactor 2 used in the present embodiment is a 150-l transparent acrylic material, and the membrane is formed by directly immersing two hollow fiber modules (made by Mitsumi-shi Rayon, Japan) made of polyethylene with a pore diameter of 0.1 μm in the bioreactor. Used as.

One of them was made to be automatically backwashed and operated while repeating driving and backwashing in the form of 30 minutes driving-2 minutes backwashing (A), while the other one was operating in 30 minutes driving-2 minutes stopping without backwashing ( B) The amount of treatment of these two submerged membranes was also investigated. Figure 2 shows a graph comparing the treated water amount (permeate amount) of the two types of immersion type separation membrane.

Air was aerated in the bioreactor with air blower 3 at a rate of 5 l / min. The leachate capacity in the bioreactor was kept 100 l by raw water pump 1 in conjunction with the level sensor. In addition, the residence time of the bioreactor was operated in the range of 5-10 days, the microbial concentration (MISS) was maintained at 10,000-15,000mg / l.

The pretreated water was stored in the pre-treatment tank 6 by operating the suction pump 4, wherein the operating pressure ranged from -200 to -500 mmHg at reduced pressure, and the flow rate was in the range of 10 to 20 l / day.

Table 1 shows the results of analyzing the water quality of the pretreated water obtained by such a method.

Raw Leachate (mg / ℓ) Backwashable Immersion Membrane Treated Water (mg / ℓ) SS ^* (mg / L) 750 3 COD (mg / L) 3,400 35 BOD ₅ (mg / L) 4,900 18 NH ₃ -N ^** (mg / L) 3,170 720 T-N (mg / L) 3,850 2,090 TDS ^*** (mg / L) 6,260 5,870

^* Suspended solids (SS): suspended solids content

^** NH ₃ -N: ammonia nitrogen content

^*** Total dissolved solids (TDS): Total dissolved solids content

As can be seen in Table 1 above, by pretreating the leachate using a bioreactor in which the membrane is immersed, it is possible to treat the suspended solids and a considerable amount of ammonia nitrogen in the leachate.

On the other hand, when the general immersion type membrane is used, the water quality is improved similarly to the case where the backwashable immersion type membrane is used, but the backwashable type membrane is backwashable because it suppresses membrane contamination due to its cleaning effect and improves the throughput. It can be seen that it is preferable to use a separator (see Fig. 2).

Example 2

This embodiment is to find the effect of removing the dissolved ionic impurities using a reverse osmosis system.

The pretreated water obtained in Example 1 was fed to a reverse osmosis system 8. The reverse osmosis module used here is a BW-2540 product of the American Film Tech.

The inflow into the reverse osmosis system was 15 L / min and the treated water was operated at 1 L / min, where the operating pressure of the reverse osmosis system was in the range of 20-25 kg / cm3.

In order to determine the removal efficiency of dissolved ionic impurities, the change in water quality of the permeate was measured and the results are shown in Table 2 below.

Reverse Osmosis System Permeate (mg / ℓ) SS (mg / l) 0 COD (mg / L) 10.1 BOD ₅ (mg / L) 4.9 NH ₃ -N (mg / L) 4.8 T-N (mg / L) 7.6 TDS (mg / l) 5.2

^* SS: suspended solids content

^** NH ₃ -N: ammonia nitrogen content

^*** TDS: Total dissolved solids content

As can be seen from Table 2, it is confirmed that the removal efficiency of dissolved ionic impurities including total nitrogen, ammonia nitrogen and total dissolved solids is reliably improved when passing the pretreated water from which floating organic matters are removed through the reverse osmosis system. Can be.

Example 3

This embodiment is to find the effect of improving the water quality of the cooling water discharged when the concentrated concentrated residual water of the high concentration untreated in the reverse osmosis system.

13.5 L / min of the concentrated water discharged after passing through the reverse osmosis system of Example 2 was introduced into the pretreatment tank 6 to maintain the system recovery at 66.7%, and the remaining 0.5 L / min was introduced into the evaporator 9. The vapor generated by the evaporation concentration was cooled down and discharged with the permeate discharged from the reverse osmosis system, and the evaporation residue was intermittently discharged. The water quality of the cooled cooling water after double evaporation concentration was measured and shown in Table 3 below.

Evaporative Concentrated Cooling Water (mg / l) SS (mg / l) 0.5 COD (mg / L) 17.3 BOD ₅ (mg / L) 6.4 NH ₃ -N (mg / L) 5.2 T-N (mg / L) 8.3 TDS (mg / l) 4.9

^* SS: suspended solids content

^** NH ₃ -N: ammonia nitrogen content

^*** TDS: Total dissolved solids content

As can be seen in Table 3, the cooling water obtained by evaporating the concentrated water discharged from the reverse osmosis system showed a water quality almost similar to that of the permeate water described in Table 2. Therefore, these cooling water can be discharged or recycled together with the permeate.

The leachate generated from the landfill by the method of the present invention is pretreated with an immersion membrane bioreactor and then treated with a reverse osmosis system, and the concentrated water discharged is secondly evaporated to concentrate or discharge a large amount of leachate as it is. It is possible to improve the water quality to the extent possible, and the concentrated water remaining in the reverse osmosis system is also discharged into the cooling water with the remarkably improved water quality, and the remainder is discharged in the form of cake to effectively and safely treat the landfill leachate.

Claims (3)

Charging the leachate into an immersion membrane bioreactor in which the membrane is immersed in the aeration tank and supplying air to obtain pretreated water from which microbial flocs and fine particulate matter grown in the reactor are removed; Passing the pretreated water through a reverse osmosis system to discharge permeated water and sending the concentrated water containing the dissolved ionic impurities to an evaporator; And Landfill leachate treatment method using a reverse osmosis system and an evaporative condensation method comprising the step of evaporating the concentrated water to evaporate pure water to be discharged with the permeate discharged from the reverse osmosis system and the evaporation residue is solidified. The method of claim 1, wherein the membrane is a leachate treatment method characterized in that the use of a backwashable membrane. The method of claim 1, wherein the dissolved ionic impurities include total nitogen, ammonia nitrogen, and total dissolved solids.