CN117843127A - A microbial coupled ozone advanced oxidation integrated device and method for treating landfill leachate - Google Patents

Abstract

The invention relates to the technical field of sewage treatment, in particular to a microorganism coupling ozone advanced oxidation integrated device for garbage leachate treatment and a method thereof. The microorganism coupling ozone advanced oxidation integrated device for garbage leachate treatment comprises a biological film reactor, wherein the top of the biological film reactor is provided with a water inlet, the top of the biological film reactor is connected with a circulating water pump through a first pipeline, and a sampling port/water outlet is arranged on the first pipeline; the circulating water pump is connected with the bottom of the biomembrane reactor; the bottom of the biomembrane reactor is provided with an air inlet which is connected with an ozone generator, the ozone generator is connected with an oxygen tank, and a gas flowmeter is arranged between the ozone generator and the oxygen tank; the top of the biomembrane reactor is provided with an air outlet which is connected with an ozone analyzer. The invention can improve the removal efficiency of nitrogen and micro pollutants, simultaneously integrates two treatment units, reduces the production and treatment of residual sludge, and saves the construction and operation cost.

Description

A microbial coupled ozone advanced oxidation integrated device and method for treating landfill leachate

Technical Field

The present invention relates to the technical field of sewage treatment, and in particular to a microbial coupled ozone advanced oxidation integrated device and method for treating landfill leachate.

Background technique

Landfill leachate contains high concentrations of organic matter and ammonia nitrogen, as well as various emerging micropollutants, which can have toxic effects on ecosystems and humans even at low concentrations. Due to the complexity of wastewater components, the treatment of landfill leachate requires a combination of physical, biological and chemical methods.

Biological treatment methods based on conventional nitrification and denitrification are widely used to remove ammonia nitrogen and degradable organic matter from wastewater. In this process, ammonia nitrogen is converted into nitrates through nitrification under aerobic conditions, and nitrates are reduced to nitrogen gas and removed from the water through denitrification under anaerobic conditions. Low-cost and efficient nitrification and denitrification biofilm reactors have been widely studied for the removal of ammonia nitrogen from high-strength wastewater. In a single biofilm reactor, nitrification and denitrification (SND) can be achieved simultaneously. Due to the oxygen diffusion limitation inside the biofilm, there is an oxygen concentration gradient in the biofilm reactor. Therefore, heterotrophic denitrifying bacteria are dominant inside the biofilm, while nitrifying bacteria dominate on the surface of the biofilm, so that nitrification and denitrification occur simultaneously in the same reactor.

Although biofilm treatment has high efficiency and low cost in removing nitrogen from wastewater, the landfill leachate after biological treatment still contains a large amount of non-biodegradable organic matter, such as humic acid substances and emerging micropollutants. Therefore, in order to meet the increasingly stringent sewage discharge standards and reduce the threat of wastewater to the environment and human health, it is necessary to further treat the wastewater after biodegradation. Ozone is a strong oxidant, and ozone advanced oxidation technology can effectively oxidize and remove residual humic acid organic matter and emerging micropollutants. Therefore, the most common method for treating landfill leachate is to combine biological treatment and ozone treatment units. Since ozone has a certain bactericidal effect, in order to avoid the potential negative impact of ozone on microorganisms, sewage treatment plants generally set up two independent treatment units. Previous studies have shown that water treatment microorganisms are tolerant to O ₃ and oxidative free radicals. However, these studies were conducted through short batch tests on synthetic wastewater, lacking the use of real wastewater for reactor development and long-term test operation.

Summary of the invention

One of the purposes of the present invention is to provide an integrated microbial-coupled ozone advanced oxidation device for treating landfill leachate, which integrates biodegradation and ozone oxidation processes and can effectively remove nitrogen and micropollutants in landfill leachate; the device integrates two treatment units into one, reduces the production and treatment of excess sludge, and saves construction and operating costs; and the device can operate stably for a long time.

The microbial coupled ozone advanced oxidation integrated device for treating landfill leachate of the present invention adopts the following technical scheme:

A microorganism-coupled ozone advanced oxidation integrated device for treating landfill leachate comprises a biofilm reactor, wherein a water inlet is provided on one side of the top of the biofilm reactor, and the other side of the top of the biofilm reactor is connected to a circulating water pump through a first pipe, and the first pipe is provided with a sampling port/water outlet; the circulating water pump is connected to the bottom of the biofilm reactor through a second pipe; an air inlet is provided at the bottom of the biofilm reactor, and the air inlet is connected to an ozone generator, and the ozone generator is connected to an oxygen tank, and a gas flow meter is provided between the ozone generator and the oxygen tank; an air outlet is also provided on the top of the biofilm reactor, and the air outlet is connected to an ozone analyzer.

Preferably, an aeration diffuser is provided at the bottom of the biofilm reactor, and the aeration diffuser is connected to the air inlet.

The second object of the present invention is to provide a microbial coupled ozone advanced oxidation treatment method for landfill leachate treatment, which can increase the mass transfer efficiency of ozone by 30% to 45% and the oxidation efficiency of organic matter by 20% to 40%. Compared with the traditional nitrification and denitrification process, the present invention can increase the removal efficiency of nitrogen, COD and micropollutants by 40%, 30% and 40 to 80% respectively.

The microbial coupled ozone advanced oxidation treatment method for landfill leachate treatment of the present invention adopts the following technical scheme:

A microbial coupled oxidation method for treating landfill leachate comprises the following steps:

S1, adding carriers to the biofilm reactor, inoculating sludge, and introducing landfill leachate sewage;

S2, start the circulating water pump to start the microbial degradation process;

S3. After the biodegradation process is completed, a small amount of water sample is taken from the sampling port for subsequent testing;

S4, connecting the aeration diffuser at the bottom of the biofilm reactor to the ozone generator, passing ozone gas into the biofilm reactor, and aerating for ozone treatment;

S5. After the ozone treatment is completed, a small amount of water sample is taken from the sampling port for testing, the treated part of the leachate is discharged from the outlet, untreated landfill leachate is added, the treated leachate is exchanged with the original leachate, and steps S2-S4 are repeated.

Preferably, in step S1, the carrier is at least one of expanded clay mineral particles and volcanic rocks, and the particle size of the expanded clay mineral particles and volcanic rocks is 5 to 20 mm.

Preferably, in step S1, the sludge is activated sludge with a volume index of 80-90 mL/g, the inoculation concentration of the activated sludge is 1-5 g/L, and the suspended solids concentration of the mixed liquor in the activated sludge is 2000-5000 mg/L.

Preferably, in step S1, the pollutants in the landfill leachate include ammonia nitrogen, humic acid organic matter and micro-pollutants, and the micro-pollutants include pesticides, antibiotics, hormones and plasticizers.

Further preferably, in step S4, the concentration of the ozone gas is 1-60 mg/L, the dosage of the ozone gas is increased from 0.01 g O ₃ /gCOD to 1 g O ₃ /gCOD, and the ozone treatment time is 15-60 min.

More preferably, in step S5, the exchange rate between the treated leachate and the original leachate is 50-95%.

More preferably, in steps S2-S3, the time for microorganisms to degrade wastewater is 24 to 72 hours.

Beneficial Effects

In the mixed filled biofilm reactor, the mineral carrier provides attachment sites and rich mineral elements (such as calcium, magnesium, iron, etc.) for the growth of microorganisms to promote the growth of microorganisms and the formation of biofilms. The biofilm can improve the ability of microorganisms to resist the stress of ozone oxidation through the quorum sensing effect. The present invention uses a filled ozone bubble column to increase the mass transfer efficiency of ozone by 30-45% and the oxidation efficiency of organic matter by 20-40%. Compared with the traditional nitrification and denitrification process, the ozone intermittent aeration biofilm reactor can increase the removal efficiency of nitrogen, COD and micropollutants by 40%, 30% and 40-80% respectively. At the same time, it integrates two treatment units into one, reduces the production and treatment of excess sludge, and saves construction and operation costs.

The present invention utilizes clay mineral carriers to synergistically stimulate the activity of microorganisms and the catalytic oxidation performance of ozone, strengthens the tolerance of microorganisms in the coupling system to ozone, realizes advanced oxidation and biodegradation of pollutants in garbage infiltration in the same reactor, and improves its removal performance and system stability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a microbial coupled ozone advanced oxidation integrated device for treating landfill leachate in Example 1 of the present invention;

Reference numerals: 1, biofilm reactor; 2, aeration diffuser; 3, O ₃ generator; 4, O ₃ analyzer; 5, oxygen tank; 6, gas flow meter; 7, sampling port/water outlet; 8, circulating water pump; 9, air inlet; 10, air outlet; 11, water inlet; 12, clay mineral particles; 13, activated sludge; 14, O ₃ bubbles; 15, tail gas;

FIG2 is a flow chart of a treatment method for landfill leachate treatment by microbial coupling with ozone advanced oxidation in Example 2 of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

Example 1

A microorganism-coupled ozone advanced oxidation integrated device for treating landfill leachate, as shown in FIG1 , includes a biofilm reactor 1, a water inlet 11 is provided on one side of the top of the biofilm reactor 1, and the water inlet 11 is used to introduce sewage from the sewage treatment tank into the biofilm reactor 1; the other side of the top of the biofilm reactor 1 is connected to a circulating water pump 8 through a first pipeline, and a sampling port/water outlet 7 is provided on the first pipeline, and the sampling port/water outlet 7 can conveniently collect biodegraded and ozone-oxidized sewage for testing and analyzing residual nitrogen and micro-pollutants in the sewage; the circulating water pump 8 is connected to the bottom of the biofilm reactor 1 through a second pipeline; the circulating water pump 8 is connected to the bottom and top of the biofilm reactor 1, and is used to promote water circulation inside the biofilm reactor 1 to ensure uniform water quality in the reactor. When it is necessary to discharge the treated sewage in the biofilm reactor 1, the connection between the reactor and the circulating water pump 8 can be unplugged to discharge the treated sewage from the pipeline.

An air inlet 9 is provided at the bottom of the biofilm reactor 1, and the air inlet 9 is connected to the ozone generator 3, and the ozone generator 3 is connected to the oxygen tank 5. A gas flow meter 6 is provided between the ozone generator 3 and the oxygen tank 5, and the oxygen tank 5 can provide oxygen to the ozone generator 3 for generating ozone; an aeration diffuser 2 is provided at the bottom of the biofilm reactor 1, and the aeration diffuser 2 is connected to the air inlet 9. The aeration diffuser 2 can be connected to an air pump, and can provide sufficient oxygen when aerobic conditions are required in the biodegradation stage. The aeration diffuser 2 can also be connected to the ozone generator 3 to provide ozone for the reactor in the coupling stage of biodegradation and ozone advanced oxidation.

The top of the biofilm reactor 1 is also provided with an air outlet 10, which is connected to an ozone analyzer 4. The top of the biofilm reactor 1 is connected to the ozone analyzer 4, and the concentration of ozone can be tested by the ozone analyzer 4. The air inlet 9 is also provided with an ozone analyzer for testing the concentration of ozone in the inlet and outlet air, so as to calculate the amount of ozone consumption.

The 3.5L biofilm reactor 1 with a height-to-diameter ratio of 10:1 is a sealable container for simultaneous nitrification and denitrification and coupling of microbial degradation with ozone advanced oxidation to treat sewage. The biofilm reactor 1 is equipped with a carrier (clay mineral particles 12), which provides attachment sites and mineral elements to promote the growth of microorganisms and the formation of biofilms. It also contains ion exchange sites that can adsorb nitrates produced during nitrification and improve denitrification efficiency. In the process of coupling biodegradation with ozone advanced oxidation, the porous mineral carrier can provide a shelter for microorganisms to protect them from excessive ozone exposure.

During specific implementation, clay mineral particles 12 and activated sludge 13 are arranged in the biofilm reactor 1, the oxygen tank 5, the ozone generator 3 and the aeration diffuser 2 are turned on, O ₃ enters the biofilm reactor 1 from the air inlet 9 and forms a large number of O ₃ bubbles 14 in the biofilm reactor 1, and is discharged from the gas outlet 10 as tail gas 15 after ozone oxidation.

The device has a simple composition and can be used to treat landfill leachate. It can simultaneously realize microbial nitrification and denitrification in one reactor, as well as microbial degradation coupled with ozone advanced oxidation to remove micropollutants, greatly saving floor space and facility costs. The biofilm reactor 1 is connected to a circulating water pump 8, which is beneficial to promoting water circulation inside the reactor and ensuring the uniformity of water quality.

Example 2

A treatment method for landfill leachate by microbial coupling with ozone advanced oxidation, as shown in FIG2 , comprises the following steps:

S1. Using the biofilm reactor in Example 1, adding a carrier to the biofilm reactor, inoculating sludge, and then introducing landfill leachate sewage; the carrier is at least one of expanded clay mineral particles and volcanic rocks, and the particle size of the expanded clay mineral particles and volcanic rocks is 5 to 20 mm; the sludge is activated sludge with a volume index of 80 to 90 mL/g, the inoculation concentration of the activated sludge is 1 to 5 g/L, and the suspended solid concentration of the mixed liquor in the activated sludge is 2000 to 5000 mg/L; the pollutants in the landfill leachate include ammonia nitrogen, humic acid organic matter and micropollutants, and the micropollutants include pesticides, antibiotics, hormones and plasticizers;

S2, start the circulating water pump to start the microbial degradation process. The time for microbial degradation of sewage is 24 to 72 hours;

S3. After the biodegradation process is completed, a small amount of water sample is taken from the sampling port for testing;

S4. Connect the aeration diffuser at the bottom of the reactor to the ozone generator, pass ozone gas into the reactor, and perform ozone treatment after aeration; the concentration of ozone gas is 1-60 mg/L, the dosage of ozone gas increases from 0.01 g O ₃ /gCOD to 1 g O ₃ /gCOD, and the ozone treatment time is 15-60 min.

S5. After the ozone treatment is completed, a small amount of water sample is taken from the sampling port for testing, the treated part of the leachate is discharged from the outlet, untreated landfill leachate is added, the treated leachate is exchanged with the original leachate, and steps S2-S4 are repeated. The exchange rate between the treated leachate and the original leachate is 50-95%.

When the concentration of dissolved oxygen in the wastewater in the biofilm reactor does not reach the required concentration in the simultaneous nitrification and denitrification (SND) microbial denitrification process, in the biodegradation step S2, the aeration diffusion device is connected to an air pump for aeration treatment to make the concentration of dissolved oxygen reach the required concentration to activate the nitrification ability of the microorganisms. The preferred dissolved oxygen concentration is 7 to 10 mg/L.

Blockage caused by excessive biofilm growth can adversely affect the performance of the reactor after long-term operation, especially when the influent organic matter load is high. Injecting a low dose of ozone gas into the reactor can inhibit extracellular polymers (EPS) and reduce sludge production, which is beneficial to prevent blockage of the bioreactor. In this example, the reactor maintained good performance after 150 days of stable operation without clogging problems. This is because the injection of ozone gas in the microbial coupling ozone advanced oxidation stage can control the accumulation of biomass and prevent excessive sludge.

At appropriate ozone dosage, in situ ozone oxidation has no significant negative impact on nitrification and enhances denitrification. This is because ozone oxidation can break down recalcitrant organic compounds into small, biodegradable fragments that serve as carbon sources in the denitrification process.

At the end of each cycle, a portion of the treated sewage is exchanged with the original leachate, and more biodegradable sewage and activated sludge are retained in the reactor, which greatly reduces the loss of activated sludge. The remaining biodegradable leachate can also be used for denitrification in the next cycle. The preferred sewage exchange rate is 80-95%, and the best sewage exchange rate is 90%.

Example 3

A method for treating landfill leachate by microbial coupling with ozone advanced oxidation comprises the following steps:

Expanded clay mineral (ECA) was filled into a 3.5L cylindrical glass reactor to construct an ECA-filled biofilm reactor (EBC). The reactor was inoculated with activated sludge from an aerobic reactor tank of a landfill wastewater treatment plant. The mixed liquor suspended solids (MLSS) of the inoculated sludge was 3000mg/L. The reactor was operated at room temperature (20±2°C). The reactor was operated for 150 days and can be divided into two stages, namely (i) the biofilm reactor startup stage with only biodegradation and (ii) the biodegradation coupled with ozone advanced oxidation stage.

(i) Biofilm reactor startup phase

The reactor was a biofilm reactor and treated 1L of landfill leachate. After 48h of treatment, 90% (0.9L) of the treated leachate was exchanged with fresh original leachate, and the hydraulic retention time (HRT) was equal to 2.22d. From this treated leachate, 30mL was taken to measure the residual concentration of pollutants. The nitrogen loading rate (NLR) increased from 30g N/(m ³ ·d) to 76g N/(m ³ ·d). The start-up period was 60 days and could be divided into 3 stages. During the first 12 days (stage A), an air pump was connected to the aeration diffuser to continuously inject air from the bottom of the reactor in order to provide enough dissolved oxygen (DO) in the leachate to activate nitrification. From the 12th day (stage B), the air pump was removed and aeration was stopped to keep the DO low to achieve simultaneous nitrification and denitrification processes.

(ii) Biodegradation coupled with ozone advanced oxidation stage

After the biofilm reactor was successfully started, the aeration diffuser at the bottom of the reactor was connected to the ozone generator. The ozone gas analyzer can measure the ozone concentration in the inlet and exhaust gas. After 1L of landfill leachate was biodegraded for 48h, ozone gas was aerated through the biofilm reactor at a gas flow rate of 200mL/min for 30min. After ozone treatment, 0.9L of treated leachate was exchanged with the original leachate to start a new biodegradation and ozone treatment cycle. At the end of each biodegradation and ozone oxidation cycle, 30mL of treated leachate water samples were taken to test the concentrations of _NH4 ⁺ -N ammonia nitrogen, _NO2 ^-- N nitrite nitrogen, _NO3 ^-- N nitrate nitrogen, and six emerging micropollutants. Among them, the six emerging pollutants are atrazine (ATZ), chloramine (ALA), diuron (DIR), bisphenol A (BPA), carbamazepine (CBZ) and 17α-ethinyl estradiol (EE2). In order to study the effect of ozone dosage on system performance, the ozone concentration at the air inlet was adjusted (1-40 mg/L), and the ozone dosage was gradually increased from 0.01 g O ₃ /gCOD to 0.4 g O ₃ /gCOD during 60-150 days.

The concentrations of NH ₄ ⁺ -N, NO ₂ ^- -N and NO ₃ ^- -N in the landfill leachate used in the present invention are respectively in the range of 100-250 mg/L, 0-2.5 mg/L and 0-80 mg/L. The COD varies between 550-700 mg/L, and the conductivity varies between 5.0-10.2 mS/cm. The initial concentrations of the six micropollutants are 0.2-220 μg/L.

Example 2: In stage A, oxygen is continuously introduced into the reactor, and the reactor is operated for 12 days. Repeated sampling tests show that the concentrations of dissolved oxygen in the inlet and outlet water are both high (>7 mg/L), which allows for sufficient nitrification, but inhibits the occurrence of denitrification. Therefore, in stage B, oxygen is stopped from being introduced into the reactor, and the reactor is operated for 12 days. Repeated sampling shows that the dissolved oxygen content in the inlet water is high, and the dissolved oxygen content in the outlet water is low, which enables simultaneous nitrification and denitrification. Therefore, the treatment of sewage in the present invention does not require additional oxygen, and the dissolved oxygen contained in the sewage itself is sufficient for biodegradation. However, if the dissolved oxygen content in other treated sewage is low, the aeration diffuser needs to be connected to the air pump to aerate and oxygenate the sewage.

According to the method of Example 2, the expanded clay mineral particles are suitable as the filling material of the biofilm reactor. After 60 days of operation, the simultaneous nitrification and denitrification process (SND) was stably achieved, the nitrogen removal efficiency reached 75%, and the total nitrogen removal efficiency (NRR) exceeded 30g N/(m ³ ·d).

Since the landfill leachate used in this implementation case contains a large amount of non-biodegradable organic compounds, only about 30% of COD is degraded by microorganisms. The biodegradation efficiency of different micropollutants is different, and BPA has the highest removal efficiency (98%), followed by EE2 (94%), ALA (90%), DIR (82%), ATZ (56%) and CBZ (22%). Using this integrated reactor, increasing the O ₃ dosage to 0.4 g O ₃ /g COD can completely remove the micropollutants (ALA and CBZ) that are most difficult to degrade ozone, and increase the total denitrification efficiency and COD removal efficiency to 85% and 60%, respectively.

In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims (9)

1. The microorganism coupling ozone advanced oxidation integrated device for garbage leachate treatment is characterized by comprising a biological film reactor, wherein one side of the top of the biological film reactor is provided with a water inlet, the other side of the top of the biological film reactor is connected with a circulating water pump through a first pipeline, and a sampling port/water outlet is arranged on the first pipeline; the circulating water pump is connected with the bottom of the biomembrane reactor through a second pipeline; the bottom of the biomembrane reactor is provided with an air inlet which is connected with an ozone generator, the ozone generator is connected with an oxygen tank, and a gas flowmeter is arranged between the ozone generator and the oxygen tank; the top of the biomembrane reactor is also provided with an air outlet which is connected with an ozone analyzer.

2. The microorganism-coupled ozone advanced oxidation integrated device for landfill leachate treatment according to claim 1, wherein an aeration diffuser is arranged at the inner bottom of the biofilm reactor, and the aeration diffuser is connected with an air inlet.

3. A method of treatment for the microbial coupled ozone advanced oxidation of landfill leachate treatment according to claim 1, comprising the steps of:

s1, adding a carrier into a biomembrane reactor, inoculating sludge, and introducing landfill leachate sewage;

s2, starting a circulating water pump, and starting a microbial degradation process;

s3, after the biodegradation process is finished, a small amount of water sample is taken from a sampling port for subsequent detection;

s4, connecting an aeration diffuser at the bottom of the biological film reactor to an ozone generator, introducing ozone gas into the biological film reactor, and performing ozone treatment by aeration;

s5, after ozone treatment is finished, a small amount of water sample is taken from a sampling port to be detected, a part of treated percolate is discharged from a water outlet, untreated garbage percolate is added, the treated percolate and the percolate stock solution are exchanged, and the steps S2-S4 are repeated.

4. The method for treating landfill leachate according to claim 3, wherein in the step S1, the carrier is at least one of swelling clay mineral particles and vesuvianite, and the particle size of the swelling clay mineral particles and the vesuvianite is 5-20 mm.

5. A method for the treatment of landfill leachate according to claim 3, wherein in step S1, the sludge is activated sludge with a volume index of 80-90 mL/g, the inoculation concentration of the activated sludge is 1-5 g/L, and the suspension solid concentration of the mixed solution in the activated sludge is 2000-5000 mg/L.

6. A method for the treatment of landfill leachate according to claim 3, wherein in step S1, the pollutants in the landfill leachate comprise ammonia nitrogen, humic organic matters and micro-pollutants, and the micro-pollutants comprise pesticides, antibiotics, hormones and plasticizers.

7. The method for advanced oxidation by microorganism-coupled ozone for garbage leachate treatment according to any one of claims 3 to 6, wherein in step S4, the concentration of the ozone gas is 1 to 60mg/L, and the dosage of the ozone gas is from 0.01 to 0.01g O ₃ Increase of/gCOD to 1g O ₃ The ozone treatment time is 15-60 min.

8. The method for the treatment of landfill leachate according to claim 7, wherein the exchange rate of the treated leachate with the original leachate is 50 to 95% in the step S5.

9. The method for advanced oxidation by coupling microorganisms to ozone for garbage leachate treatment according to claim 7, wherein the time for degrading the sewage by microorganisms is 24-72 h in the steps S2-S3.