KR20010076873A - Organic and nitrogen compound removal methods from landfill leachate using an anaerobic-aerobic-anoxic system - Google Patents

Abstract

PURPOSE: A removal method of high concentration organic matter and nitrogen in leachate using anaerobic-aerobic-anoxic system is provided, which can remove biologically high concentration organic matter and nitrogen contained in leachate without any pretreatment, remove organic matter and nitrogen contained in livestock wastewater, remove organic matter by conversion of methane and also remove nitrogen at the same time by an anaerobic tank. CONSTITUTION: The system comprises the followings: (i) a vertical anaerobic reactor (R1) in which methane converting and denitrification are carried out simultaneously at the first time of landfill and only denitrification is carried out at the last time of landfill; (ii) an aerobic tank (R2) for nitrification; (iii) a settling tank (C1); (iv) an anoxic tank (R3) for post denitrification; (v) a deaeration tank (R4) for removing denitrified gas; and (vi) a settling tank (C2) for separating solid liquid.

Description

ORGANIC AND NITROGEN COMPOUND REMOVAL METHODS FROM LANDFILL LEACHATE USING AN ANAEROBIC-AEROBIC-ANOXIC SYSTEM}

The present invention relates to a new method of removing leachate containing a high concentration of organic matter and nitrogen components using an anaerobic tank (filtered bed) method, an aerobic tank (activated sludge) method, and an anaerobic tank (after denitrification tank).

The characteristics of the leachate include high concentrations of organic substances and nitrogen in the early stages of landfilling. When the years of landfilling are over 3-5 years, the concentration of organic substances in the leachate decreases rapidly and the nitrogen content decreases not much. In addition, leachate contains many hardly decomposable substances.

Therefore, after the coagulation treatment using a chemical flocculant as a method for treating the leachate in the design of the landfill site, it is introduced into the anaerobic tank to remove 70% or more of the organic matter, and then enters the aerobic tank in the long-term aeration tank to finish the organic matter removal. Advanced oxidation methods such as Fenton oxidation are also used to remove hardly decomposable substances.

Conventional methods such as pretreatment of leachate have less than 20% efficiency of flocculation and leachate generated at the early stage of landfill contain high concentration of organic material, so anaerobic tank is required but leachate generated after landfill is stabilized As there is almost no decomposable organic matter, the anaerobic tank becomes obsolete.

In addition, despite the conventional method, HRT in anaerobic tanks can be up to 10-15 days or 30 days, it is difficult to remove high concentrations of nitrogen in the leachate. The disadvantage is that it can also be provided.

On the other hand, the method adopted in the present invention is composed of an anaerobic tank, an aerobic tank, and a post-denitrification tank. In the anaerobic tank, not only organic matters are removed by simple methane conversion but also nitrified in the aerobic tank can be returned to the anaerobic tank to simultaneously perform denitrification to remove nitrogen components. have.

In the process of the present invention, since the microorganisms of the anaerobic tank, the aerobic tank, and the denitrification tank are maintained independently, methane-producing bacteria and denitrifying bacteria are maintained as the dominant species in the anaerobic tank, and the aerobic tank is the nitrifying bacteria and the denitrifying bacteria in the post-denitrification tank. It has the advantage of having higher processing capacity.

In addition, even if methane conversion does not occur even after the landfill is stabilized and the organic matter is reduced, it may serve as a denitrification tank, thereby solving the problem of anaerobic silencing of the anaerobic tank generated after the landfill is stabilized.

In particular, as social expectations for the water environment have increased, it is necessary to remove nutrients that cause eutrophication as well as to remove existing organic matter.

In addition, in view of the fact that the problem of securing the site of the increasingly difficult treatment plant acts as a strong motive for reducing the scale of the treatment process, the present invention can simultaneously obtain organic matter removal and nitrogen content removal with HRT within 7 days.

In particular, the advantage of this process is that after the anaerobic tank-aerobic tank is placed behind an anoxic tank to perform post-denitrification, the inflow leachate properties exceed NH ₄ ⁺ -N 1,500 mg / l. It should be operated at the return rate of. This not only makes it difficult to maintain the anaerobic condition of the anaerobic tank, but also overcomes the burden of operating costs of the pump for return, driving at a return rate of 300%, and satisfying the water quality standards with an anaerobic residence time of 3 hours for post-denitrification. .

Taken together, the process proposed by the present invention has sufficient advantages as an alternative to the low cost, high efficiency leaching treatment.

In the present invention, it is possible to remove nutrients such as organic matter and nitrogen components through a biological treatment method consisting of anaerobic tank, aerobic tank and anoxic tank, and organic matter removal and denitrification are performed at the same time in a single anaerobic tank. It is intended to provide a leachate treatment method that can overcome the problem of process (eg anaerobic tank) uselessness and reduce the size of the process to solve the site securing problem.

1 is a complete system consisting of an anaerobic tank and an aerobic tank, anoxic tank showing an embodiment of the present invention

☞ Explanation of symbols used in the main part of the drawing ☜

R1: Filling anaerobic tank R2: Aerobic tank for nitrification

R3: Anaerobic tank for post denitrification R4: Aeration tank for degassing

B1: Air supply blower to exhalation tank B2: Degassing tank air supply blower

P1: Leachate Inflow Pump P2: Anaerobic Tank Internal Circulation Pump

P3: aerobic sludge return pump P4: denitrification return pump to anaerobic tank

P5: Oxygen-free sludge conveying pump P6: External carbon source supply pump

C1: aeration tank effluent solid-liquid sedimentation tank C2: final solid-liquid sedimentation tank

T1: External carbon source storage tank G1: Anaerobic outflow gas flow meter

1 illustrates an entire system consisting of an anaerobic tank, an aerobic tank, and an anaerobic tank showing an embodiment of the present invention, and various types of carriers may be used to fill a carrier in a volume ratio of 70% in an anaerobic reactor.

Leachate from P1 to the bottom of the anaerobic reactor undergoes organics removal through methane conversion with return water returned to anaerobic tank through P4 for denitrification in sedimentation tank C1. In addition, denitrification of the nitrate nitrogen contained in the return water occurs, and additional organic matter removal occurs due to the organic matter required for denitrification.

Organics not removed in the anaerobic reactor are removed in the aerobic reactor and ammonia nitrogen is converted to nitrate in the aerobic reactor.

In addition, the solids contained in the leachate have the effect of being partially absorbed or reduced through hydrolysis in the anaerobic tank filling. In order to prevent clogging of the packed phase in this process, the circulation rate is maintained at 1m / hr or more by circulating from 5 to 10 times the raw water flow rate through P2 from the top of the anaerobic tank to the bottom of the anaerobic tank. Normal operation of the anaerobic tank can be quickly determined by checking the gas generation and characteristics using the gas meter G1.

On the other hand, in order to maintain the microbial amount of the aerobic reaction tank, sludge is returned to the first stage of the aerobic tank R2 through P3 at the lower end of the precipitation tank 3.

Air blower B1 is used to supply oxygen, which is the energy source of the aerobic microorganisms.

Treated water, which has undergone anaerobic and aerobic sedimentation tanks, removes the nitrate nitrogen present in the anaerobic bath R3 through microbial denitrification due to the limitation of T-N removal with a 300% return rate. The depleted carbon source in anoxic tank R3 is supplied from an external carbon source storage tank T1 via an external carbon source feed pump P6.

The effluent from the anaerobic tank R3 is mixed with the microorganisms and the denitrification gas so that it is aerated for 15 minutes in the degassing tank R4. The air needed for degassing is supplied via air blower B2.

The sludge is conveyed through the sludge conveying pump P5 in order to maintain the microbial mass of the anoxic tank R3 and to separate the solids and the liquid phase in the settling tank C2 before finally flowing out.

Example

The anaerobic reactor was operated with a hydraulic retention time of 2 days to obtain the following results.

Filling in the anaerobic tank was 70% of the reactor volume using a commercially available carrier.

When leachate inflow COD _Cr was 25,960mg / l and volume load was 13kg / ㎥ · d, anaerobic effluent outflow was 3020mg / L and COD _Cr removal efficiency was 84%. The result of COD _Mn in Korea was 55% removal efficiency with 780mg / L of anaerobic effluent when the influent was 1740mg / l and the volume load was 0.48kg / ㎥.d.

COD _Mn removal efficiency is lower than COD _Cr removal efficiency because COD _Cr- induced organic material is converted into COD _Mn- induced organic material in anaerobic tank.

The result of BOD ₅ , the biological oxygen demand, was introduced at 11655 mg / L, and the effluent from the anaerobic tank was 1135 mg / L, resulting in 90% removal efficiency.

The maximum organic matter removal rate in the anaerobic tank obtained 16 kg / ㎥ · d.

In addition, the result of nitrate removal, which is another purpose in the anaerobic tank, was 100% because the nitrate concentration in the return water was almost 0 in the denitrification tank at 450 mg / L.

Since the nitrate nitrogen concentration flowing into the anoxic tank is 450mg / l, supplying glucose, methanol, acetate, etc. as a carbon source to obtain 90% denitrification efficiency can satisfy the water quality standards.

In addition, the amount and composition of the gas produced in the anaerobic tank was 0.5L / kg COD _Cr · d, and the components were composed of CH ₄ 65-75%, CO ₂ 20-30%, and N ₂ 2-5%.

Given that the fraction of CH ₄ of biogas from anaerobic digestion tanks is 70%, the biogas from leachate and methane conversion can be used as energy.

The role of the aerobic tank is to remove organic material that has not been removed from the anaerobic tank and to nitrate ammonium nitrogen with nitrates.

The COD _Cr to the aerobic tank was 3020 mg / L and the final effluent was 836 mg / l, resulting in 97% overall removal efficiency of the anaerobic-aerobic system.

COD _Mn was introduced at 780 mg / L and finally at 350 mg / L, resulting in 80% total removal efficiency.

BOD ₅ was introduced at 1135 mg / L and was not detected in the final runoff, resulting in a total removal efficiency of 100%.

Nitrification, the most important role of the aerobic tank, achieved 97% nitrification with an inflow concentration of 1655 mg / L (680 mg / L aerobic influent) and an outflow concentration of 20 mg / L or less. The nitrification rate per volume at this time was 0.75 kg / m <3> * d. This result is twice as much nitrification as compared with 0.3-0.4 kg / m 3 · d in the general activated sludge process.

Finally, the availability of the anaerobic tank as a denitrification tank was evaluated when the landfill stabilized leachate was treated using the anaerobic-aerobic system.

The landfill stabilized leachate showed COD _Cr 2112mg / L, BOD5 320mg / L, and ammonia nitrogen 1589mg / L.

In the same way, the hydraulic retention time of the anaerobic tank was operated for 2 days, the aerobic tank for 4 days, and organic matters were lacking during denitrification.

The nitrification efficiency in the aerobic tank was 97% at 1589mg / L (1589mg / L), and the concentration of effluent was less than 20mg / L.

In the anaerobic tank (now acting as a denitrification tank), the denitrification efficiency was 70% when glucose was supplied as an external carbon source and 90% when methanol was supplied.

As described above, the present invention is used to treat leachate using an anaerobic-aerobic-anaerobic system.

First, it is possible to maintain a high concentration of microorganisms by filling the media in the anaerobic tank, so that it is possible to remove the high concentration organic matter in the leachate

Second, related facilities can be reduced by simultaneously performing denitrification as well as organic matter removal by methane conversion in the anaerobic tank.

Third, by returning a part of the effluent for the denitrification in the anaerobic tank, the dilution effect in the anaerobic tank decreases the concentration of ammonia nitrogen to a concentration that does not affect the nitrification in the aerobic tank, thereby increasing the nitrification efficiency.

Fourth, by removing the organic matter sufficiently from the anaerobic tank and performing nitrification in the aerobic tank to increase the fraction of nitrifying bacteria in the microorganism in the aerobic tank to increase the nitrification

Fifth, the removal of nutrients, which was difficult to carry out in the existing treatment process, was made possible by maximizing the removal efficiency by making it easy to maintain a single microorganism per process.

Sixth, by performing methane conversion and denitrification at the same time in a single anaerobic reactor, the use of anaerobic tank can be overcome in the latter stage of landfill due to the characteristics of leachate, so that the system can be used stably during landfill or after landfill completion and economical efficiency is achieved. can do.

The organic and nitrogen removal method of the leachate using the anaerobic-aerobic-anoxic system of the present invention as described above was able to maximize the nitrification efficiency in the aerobic tank by simultaneously performing methane conversion and denitrification in the anaerobic tank. It can be maintained to maximize efficiency, and above all, the system can be used stably and continuously even after the initial landfill or stabilization.

In addition, it is possible to obtain economic efficiency because organic matter and nitrogen components can be removed without pretreatment such as chemical flocculation treatment, which is applied when treating wastewater containing high concentrations of organic substances and nitrogen components.

Therefore, the organic and nitrogen removal method of the leachate using the anaerobic-aerobic-oxygen-free system of the present invention can be expected several advantages and economic effects, such as the following.

First, since high concentrations of organic matter and nitrogen contained in leachate generated from urban waste landfills where food waste is mainly used can be removed biologically without pretreatment, it can be used as a leachate treatment process of large-scale and medium-sized urban landfills.

Second, in addition to leachate, wastewater containing high concentrations of organic matter and nitrogen at the same time as livestock wastewater can be applied as a process to remove nitrogen.

Third, since it is possible to perform denitrification as well as organic matter removal by methane conversion in a single anaerobic reactor, it is possible to use a continuous anaerobic reactor.

Claims (1)

In constructing the anaerobic-aerobic-anaerobic system, The pump P1 supplying leachate and methane conversion and denitrification can be carried out simultaneously in the early stage of landfill and denitrification only in the late stage of landfill, so that the gas volume and composition for the stable and continuously available anaerobic reactor R1 and anaerobic reactor R1 can be checked. The meter G1 consists of four stages, which can be replaced stably at high loads and can expect high nitrification efficiency, an aerobic tank R2, a sedimentation tank C1 to separate microbial solids and treated water, and to prevent clogging in filling in anaerobic tanks. Anaerobic tank internal circulation pump P2 to provide sufficient ascent rate, return pump P4 for denitrification in anaerobic tank, sludge return pump P3 to maintain microbial volume in aerobic reactor, blower B1 for supplying oxygen to aerobic microbes as energy source, Anaerobic bath R to remove residual nitrate nitrogen due to limit of return rate 3, degassing tank R4 to remove denitrification gas, settling tank C2 for solid-liquid separation of final effluent, sludge return pump P5 for microorganism maintenance of anoxic tank R3, external carbon source storage tank for supplying external carbon source for denitrification reaction in anoxic tank R3 Treatment apparatus for organic matter and nitrogen removal of leachate by anaerobic-aerobic-oxygen system characterized by consisting of T1 and external carbon supply pump P6