KR20080019975A - Wastewater treatment apparatus using hybrid bio-electrochemical sequencing batch reactor combined a biological reactor and an electrode system - Google Patents

Abstract

A wastewater treatment apparatus using a hybrid bio-electrochemical biofilm sequencing batch reactor is provided, and a wastewater treatment method for removing organic matters and nitrogen using the wastewater treatment apparatus is provided. A wastewater treatment apparatus(100) comprises: a wastewater tank(10); an intake pump(20) for introducing raw water from the wastewater tank; a hybrid bio-electrochemical biofilm sequencing batch reactor(30) including a cylindrical body(31), an agitator(32) installed at the upper part inside the body to circulate the raw water, an electrode system(33) which is installed at the lower part inside the body and has a titanium electrode and a carbon electrode used as an anode and a stainless steel used as a cathode, and a biological activation tank(34) installed at the middle part inside the body; a recycling pump for circulating the raw water; a discharge pump(50) for discharging wastewater treated through the reactor; a ventilator(60) for flowing air into the reactor; and an air diffuser(70) for circulating the air flowing into the reactor through the ventilator.

Description

Wastewater Treatment Apparatus using Hybrid Bio--Electrochemical Sequencing Batch Reactor combined a biological reactor and an Electrode System}

Figure 1 shows a schematic diagram of a wastewater treatment apparatus using a hybrid bio-electrochemical biofilm continuous batch reactor combined with a biological activation tank and an electrode system according to the present invention.

Figure 2 shows a layout view of the electrode used in the present invention.

3 shows a flowchart of the operating mode of the reactor according to the invention.

4 is a graph showing a change in the concentration of MLSS in the wastewater treatment apparatus according to the present invention.

5 is a graph showing a change in nitrogen concentration of the influent and effluent in the wastewater treatment apparatus according to the present invention.

6 is COD _Cr in the wastewater treatment apparatus according to the present invention. It is a graph showing the change in concentration.

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

10: wastewater tank 20: inflow pump

30: reactor 31: body

32: stirrer 33: electrode system

34: biologically active tank 40: recycling pump

50: outflow pump 60: ventilator

70: diffuser 100: wastewater treatment device

Field of invention

The present invention is a waste water tank; An inflow pump for introducing raw water from the waste water tank; Cylindrical body; A stirrer installed at an upper end of the body to circulate the raw water; An electrode system installed at a lower end of the body and using titanium and carbon electrodes as an anode and using stainless steel as a cathode; And a hybrid bio-electrochemical biofilm continuous batch reactor comprising a biologically activated tank installed in the middle portion of the body. A recycling pump for circulating the raw water; An outflow pump for discharging the treated water through the reactor; A ventilator for introducing air into the reactor; And it relates to a wastewater treatment apparatus comprising an acid pipe for circulating the air introduced through the ventilator.

Background of the Invention

Recently, the nutrient nutrients in domestic streams and lakes, which are becoming more serious, are repeatedly circulated every year without removing nutrients. Not only nutrients generated from point sources, but also small scale barns, which take up a large portion as nonpoint sources, are urgent to treat nitrogen and phosphorus. Among various processes proposed for advanced treatment of wastewater, rivers, and lakes, biological treatment methods are being studied with great interest, and in particular, studies using microbial membranes or immobilizing microorganisms to increase the amount of microorganisms are made. ought. In connection with biofilm processes immobilized with these microorganisms, new continuous processes combining treatment conditions, such as anaerobic-aerobic or anaerobic-aerobic, are being actively studied. However, these processes may be suitable for the advanced treatment of wastewater, but are present in low concentrations such as rivers and lakes, but suffer from difficulties due to not enough organic matters to be applied to nitrogen or phosphorus removal which have a great effect on algae generation. Typical nitrogen removal processes such as A / O or A2 / O require a lot of time and cost, including spatially continuous anoxic bath (denitrification) and aerobic bath (nitrification). In treating appeals and rivers with low concentrations of biodegradable organics, denitrification essentially requires a carbon source as an electron donor. For this reason, autotrophic denitrification has attracted much attention in recent years because of the need for external carbon sources (methanol, ethanol, acetic acid, etc.) and the production of less excess sludge. Currently, autotrophic denitrification is likely to be used for this process. Hydrogen-soluble denitrification microorganisms (Hydrogentrophic) uses carbon dioxide in the water as a carbon source, nitrate is converted to nitrite to remove nitrogen with nitrogen gas using hydrogen gas oxidation in water. The process has the greatest advantage that hydrogen gas is not naturally a harmful contaminant and does not need to be overdosed to make an excellent reactant with low solubility of hydrogen in water. However, low concentrations of hydrogen gas in water are insoluble or can be controlled by autotrophic denitrification at a rate of conversion of gas from liquid gas to liquid gas. Therefore, a large volume biological reactor is required to increase the contact time to achieve complete denitrification. The explosive nature of hydrogen gas in the natural state may cause a safety problem during the operation of the reactor, the disadvantage is that the operating cost and initial cost is higher than the heterotrophic denitrification.

Accordingly, the present inventors have made diligent efforts to solve the shortcomings of the prior art. As a result, the present invention is equipped with a biological activator and an electrode system in a continuous batch reactor to remove organic matter and nitrogen, and to remove algae The present invention was completed by confirming that removal was possible.

The main object of the present invention is to provide a wastewater treatment apparatus using a hybrid bio-electrochemical biofilm continuous batch reactor.

Still another object of the present invention is to provide a method for treating wastewater, which comprises removing organic matter and nitrogen using the wastewater treatment apparatus.

In order to achieve the above object, the present invention is a waste water tank; An inflow pump for introducing raw water from the waste water tank; Cylindrical body; A stirrer installed at an upper end of the body to circulate the raw water; An electrode system installed at a lower end of the body and using titanium and carbon electrodes as an anode and using stainless steel as a cathode; And a hybrid bio-electrochemical biofilm continuous batch reactor comprising a biologically activated tank installed in the middle portion of the body. A recycling pump for circulating the raw water; An outflow pump for discharging the treated water through the reactor; A ventilator for introducing air into the reactor; And it provides a wastewater treatment apparatus using a hybrid type bio-electrochemical biofilm continuous batch reactor combined with a biological active tank and an electrode system comprising a diffuser circulating the air flowing through the ventilator.

In the present invention, the reactor may be selected from the group consisting of A / O process, A / O modification process, A / O / A / O process.

In the present invention, the biologically active tank may be characterized in that the rope-type biofilm media is used as a fix-bed, and the microorganisms are fixed and operated on a carrier.

The present invention also provides a method for treating wastewater, which comprises removing organic matter and nitrogen using the wastewater treatment apparatus.

Hereinafter, the present invention will be described in detail.

Wastewater treatment device 100 using a hybrid type bio-electrochemical biofilm continuous batch reactor combined with a biological activation tank and an electrode system according to the present invention is a wastewater tank (10); An inflow pump 20 for introducing raw water from the waste water tank; Cylindrical body 31; An agitator 32 installed at an upper end of the body to circulate the raw water; An electrode system (33) installed at the lower end of the body and using titanium and carbon electrodes as the anode and using stainless steel as the cathode; And a hybrid bio-electrochemical biofilm continuous batch reactor (30) comprising a biologically active tank (34) installed in the middle portion of the body; A recycling pump 40 circulating the raw water; Outflow pump 50 for discharging the treated water through the reactor; A ventilator 60 for introducing air into the reactor; And an diffuser 70 for circulating air introduced through the ventilator.

Raw water is introduced into the wastewater treatment device from the wastewater tank using the inflow pump, and discharged the treated water treated through the wastewater treatment device through the outflow pump, and further provided with the recycling pump to circulate the raw water. And the circulation of the raw water improves the mixed state in the wastewater treatment apparatus.

In the electrode system installed in the reactor according to the present invention, a pair of electrodes is used to make oxygen gas (anode) in the nitrification stage, and the other pair of electrodes is carbon dioxide than oxygen when carbon is used as the anode at the electrode of the reactor. Since it is formed first, it is used to generate hydrogen gas (cathode) in an anoxic denitrification step. The anode of the electrode system may use a titanium electrode and a carbon electrode, and the cathode of the electrode system may use stainless steel. In addition, a biological activation tank is installed in the middle of the reactor according to the present invention, and the biological activation tank uses a rope-type biofilm media as a fix-bed, and provides a carrier capable of forming a biofilm in the reactor to attach to the carrier. By using adherent microorganisms to grow, it promotes oxidation, nitrification and denitrification of organic matter. As described above, the microorganism is fixed to the carrier and operated. In addition, the lower end of the reactor is further provided with an immersion type thermostat to maintain the temperature in the reactor 25 ~ 30 ℃.

Next, looking at the operation of the wastewater treatment apparatus using a hybrid bio-electrochemical biofilm continuous batch reactor combined with a biological active tank and an electrode system according to the present invention, it consists of a cycle of inflow, anaerobic, aerobic tank, precipitation and outflow. The biofilm media and electrode system may be installed in the wastewater treatment apparatus to remove organic matter and nitrogen, and oxygen and hydrogen generated in the electrode system may be directly used as electron donors and electron acceptors used for oxidation, nitrification and denitrification of organic matter.

Denitrification using hydrogen-soluble denitrifying microorganisms (hydrogentrophic) is performed using the wastewater treatment apparatus according to the present invention to remove nitrogen present with low concentrations of organic matter, to remove lakes and river water algae, and to include lake water or river water. Injured algae are removed. In addition, algae present in rivers and lakes are allowed to float and be removed by bubbles generated from the electrodes, and hydrogen is made up of small bubbles in the reactor, so that hydrogen is dissolved to a degree that can be readily used for biological reactions. It can be made by the generation of bubbles of hydrogen gas having a diameter of 20 ~ 40um in water. It is known that oxygen is incidentally generated at the surface of the anode when the anode material is suitable. The bio-electrochemical biofilm continuous batch reactor using several pairs of electrode systems is used for nitrification and hydrogen-soluble denitrification microorganisms. Denitrification using hydrogentrophic is performed simultaneously.

The process of the reactor installed in the wastewater treatment apparatus according to the present invention may be selected from the group consisting of an A / O process, an A / O transformation process and an A / O / A / O process.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and the scope of the present invention will not be construed as being limited by these examples.

Example  1: fabrication of experimental equipment

(1) Construction of wastewater treatment system using hybrid bio-electrochemical biofilm continuous batch reactor combined with biological activation tank and electrode system

Bio-Electrochemical Biofilm Sequencing Batch Reactor (BESBR) was manufactured on a lab-scale, and the reactor was made of acryl having a cylindrical shape, as shown in FIG. 1. The prototype reactor produced a total volume of 21L and an operating volume of 19L.

The experimental device was configured with a biologically activated tank having fixed-bed media attached to the middle portion (8.4L) of the reactor, and the reactor was divided into upper and lower portions in the remaining operating volume (10.6 L) except for the biologically active tank. On the top of the reactor was installed a stirrer, diffuser, lever-sensor and online sensor measuring device.

At the bottom of the reactor, as shown in Figure 2, two pairs of electrodes (metal-metal, carbon electrode-metal) were installed. In addition, the electrode was tested several times to select the titanium electrode and the carbon electrode having the best performance, and the selected 12 titanium anode positive electrode (aerobic bath) and 6 carbon anode positive electrode (anoxic bath) were selected. Was installed with the other 20 stainless steel cathode negative electrodes. The size of each electrode is 30 (height) x 50 (width) x 0.5 (thickness), and the effective area of the anode is 15 cm 2 and the effective area of the cathode is 30 cm 2. One pair of electrodes is used to make oxygen gas (anode) in the nitrification step, and the other pair of electrodes is hydrogen gas in the anoxic denitrification step because carbon dioxide is formed before oxygen when carbon is used as anode in the electrode of the reactor. It was used to generate (cathode).

In addition, a biologically active tank was installed in the middle of the reactor according to the present invention, and the biologically active tank was used as a fix-bed of a rope-shaped media in the form of a biofilm. Y-shaped media consists of numerous multi-filaments and mono-filaments of nylon condensed filamentous (BCF) and used Hyosung BC ^PLUS products in Seoul, Korea. The media used in the experiments had a surface area per unit length of 1 m2 / m, a width of 30 to 40 mm, and a void fraction of 95%. Since Y-shaped BCF media is a form in which microorganisms are stably maintained, the attached microorganisms are not easily affected by airflow and water circulation in the reactor. 28 media ropes (length: 220 mm) were attached to the stainless steel structure and installed in the middle of the reactor. The total surface area of the reactor media was 6.2 m2.

Raw water was introduced directly into the bio-electrochemical biofilm continuous batch reactor using a metering pump, and the treated effluent was discharged to the outside. The circulation was applied to improve the mixing in the reactor and consequently was recycled at a flow rate of 65 ml / min during the run. The air supply in the conventional continuous operation mode and the bioelectrochemical operation mode was maintained at 2 L / min. Wastewater treatment apparatus according to the present invention automatically adjusted the driving cycle time by the electrical control device.

3 is a flow chart of the operation mode of the bio-electrochemical biofilm continuous batch reactor according to the present invention, and as shown in FIG. 3, it is a schematic diagram of one operation of a conventional batch batch reactor (Sequenct Batch Reactor). . Feeding, anoxic, aoxic, sedimentation and draw phases were achieved during one cycle. The anoxic tank and the aerobic tank were changed according to HRT, and the other reaction time was kept constant. The outflow volume ratio was 0.11 relative to the operating volume and 2 liters of raw water was introduced into the reactor during each cycle cycle. The temperature of the reactor was maintained at 25 to 30 ° C. using an immersion type hot water heater at the bottom portion.

In order to form a biofilm, seeding was carried out using a return activated sludge of the Kyungan sewage treatment plant, and the reactor was operated for one week by using artificial wastewater to stabilize biomass and form biofilm in the reactor. The initial biomass concentration is 5500 mg MLSS / L, and the composition of artificial wastewater is Glucose, 100 mg COD _Cr / l; (NH ₄ ) ₂ SO ₄ , 75 mg N / l; Glutamate, 0.15 g / l; NaCl, 0.015 g / l; CaCl ₂ H ₂ O, 0.006 g / l; _{MgSO 4 .7H 2 O, 0.0051 g} / l; and pH buffer solution (solution B) (KH ₂ PO ₄ , 0.0021 g / l; K ₂ HPO ₄ , 0.009 g / l; Na ₂ CO ₃ , 0.09 g / l; NaHCO ₃ , 0.09 g / l).

(2) Characteristics of influent wastewater

The influent wastewater was collected from the influent of the treatment system in Icheon-si sewage treatment plant in Gyeonggi-do and stored in 4 ℃ refrigerator until it was used for the experiment. The influent into the wastewater treatment apparatus according to the present invention was used by diluting the collected wastewater 10 times with tap water. Influent properties are shown in [Table 1].

Influent Characteristics Items Average value Minimum value Maximum value Unit pH 8.38 8.02 8.5 - Alkalinity 1243 830 1545 mg / L SCOD _Cr 875 467 1500 mg / L TCODD _Cr 1274 876 2140 mg / L NH ₄ ⁺ -N 255 130 378 mg / L NO _x ^-- N 1.2 0 2.0 mg / L

Example  2: test result

(1) change of microbial concentration

Figure 4 shows a graph showing the change in MLSS concentration in the bio-electrochemical biofilm continuous batch reactor according to the present invention, the dissolved solids concentration during the batch operation for biofilm formation was the first 4 days, 5500 mg It rapidly decreased from / l to about 3000 mg / l. This has the advantage that the large surface area and the yarn-shaped BC ^PLUS media (generally about 7 times more than the conventional media used in actual process) can quickly attach and maintain a large amount of biomass to the carrier. During the next three days, little change in the MLSS concentration in the reactor was observed, which successfully attached the biomass immobilized on the carrier at maximum capacity after one week. The dissolved biomass at day 7 was completely removed from the reactor's MLSS concentration, and for the next 17 days (until day 25), the MLSS concentration remained low (10 ± 2 mg / l). After two weeks of reactor operation, the concentration of MLSS slowly increased to 70 mg / l, presumably due to the accumulation of insoluble hardly degradable particles and the dissolved growth microorganisms in the reactor. After 60 days of operation, the rate of increase in MLSS concentration was higher than in the previous period and a final about 3000 mg / L MLSS concentration was observed during the last period of operation.

(2) change of nitrogen and organic matter

5 is a graph showing a change in nitrogen concentration of the influent and the effluent in the bio-electrochemical biofilm continuous batch reactor according to the present invention, the nitrification process can be observed from the beginning of the experiment. This can be explained by the reduction of NH ₄ ⁺ -N and NO _X ^-- N concentrations during microbial planting, with approximately 80% of NH ₄ ⁺ -N being nitrified in 6 days of operation. Inhibition of nitrification by accumulation of nitrite nitrogen (NO ₂ ^-- N) was observed during the first four days of operation. It was not found after two days. The concentration of nitrate nitrogen (NO ₃ ^-- N) steadily increased during the batch run period and showed about 72 mg N / l corresponding to the NH ₄ ⁺ -N concentration of the initial artificial wastewater on day 6 of the run. This indicates that ammonium oxidivzing bacteria (AOB; nitrite oxidizing bacteria (NOB)) have been fully acclimated to the reactor. On the eighth day of operation, starting with continuous operation, diluting the wastewater into the reactor, and between 8 and 17 days of operation, the reactor was operated with 9.5 days of HRT, resulting in a very high nitrification rate and Low ammonia nitrogen concentrations and similar removal rates of influent NH ₄ ⁺ -N concentrations and nitrate nitrogen concentrations were observed. This shows that the nitrifiers did not have an impact load on the dilute wastewater properties. The nitrification efficiency remained constant at 99.5% for the next week after the HRT was reduced by 2 times (4.25 HRT at 9.5 days HRT). On the 17th day of operation, the total inorganic nitrogen load increased from 0.04 kg N / m3 / d to 0.07 kg N / m3 / d, indicating that the nitrifying activity of nitrifying bacteria by biofilm was not affected by the reduction of HRT. Also, almost no nitrite nitrogen concentrations in the effluent occurred, indicating that ammonia nitrogen was completely oxidized to nitrate nitrogen during the first 16 days of continuous operation. At 24 days of operation, new wastewater was collected, containing higher ammonia nitrogen (2 times) than the previous wastewater, and the TIN load increased to 0.16 kg N / m3 / d. Two days after the replacement of the new influent, the ammonia nitrogen in the effluent increased to 50 mg / l, but gradually decreased, maintaining a low concentration of ammonia nitrogen (2 mg / l) at 90 days of operation. Nitrification efficiency of% was achieved, indicating that the activity of the ammonia oxidizing bacteria of the biofilm is fast with increasing TIN load. In the case of NO _x ^-- N during the operation period, the concentration of nitrate nitrogen suddenly decreased to about 5 mg / l one week after the new influent changeover (27-40 days of reactor operation), consequently approximately 16 mg during the next week. / l was maintained. However, nitrite nitrogen in the effluent was accumulated at 30 days of reactor operation and showed 100 mgNO ₂ ^-- N / l. This is because the efficiency of nitrification did not change during the period mentioned, and incomplete nitrification (a form in which ammonia nitrogen was converted only to nitrite nitrogen) occurred in the reactor.

Biological nitrification involves the continuous oxidation of ammonia nitrogen through nitrite nitrogen to nitrate nitrogen using AOB and NOB nitrifying bacteria, respectively. Nitrous acid nitrogen oxides are generally known to be affected by free ammonia nitrogen (0.1-10 mg N / l) and the limitation of dissolved oxygen concentration, HNO ₂ (0.22 to 0.8 mg N / l), which is ammonium oxidation. Different oxygen saturation factors (0.16 mg / l and 0.54 mg / l, respectively) are required for nitrous acid and nitrite oxidation. Therefore, low dissolved oxygen can occur with limited acyl acid nitrogen oxidation. Incomplete nitrification in the biofilm between 27 and 41 days is largely due to the limitation of dissolved oxygen. In addition, an increase in TCOD loading during this period results in a rapid increase in heterotrophic bacteria in the outer layer of the biofilm and a decrease in DO concentration in the inner layer of the biofilm in which the autotrophic nitrifier is located. The pH is neutral and it can be assumed that the average HNO ₃ concentration is low, and it can be concluded that HNO ₃ does not correspond to the accumulation of nitrite. Between 41 and 97 days, nitrites in the effluent mostly accumulate at concentrations below 10 mg / L, whereas nitrate concentrations gradually increase and are always about 100 mg / L. This makes it possible to restore water or activity equilibrium between AOB and NOB in the reactor system. Attention should be paid to the accumulation data of ammonium and nitrite due to the failure of the aeration device on day 99. Failure of the aeration device caused low DO concentration in the reactor. After maintaining the aeration rate, the trends for ammonium, nitrite and nitrate remained the same. On day 111, the previously used operating mode of the reactor was changed to a bioelectrochemical continuous batch method, and the application density flows were 15 A / m 2 and an aerobic tank 7.5 A / m 2, respectively. When the nitrification rate is the same as before, the nitrate concentration in the effluent is reduced to about 50 mg / L. Denitrification appears to be affected by using electrodes in the reactor. This suggests that nitrates can be reduced and autotrophically reduced to nitric acid using the H ₂ gas produced at the anode when hydrogen soluble hydrogenotrophic microorganisms are present in the reactor.

Figure 6 shows a graph showing the change in the COD _Cr concentration of the bio-electrochemical biofilm continuous batch reactor according to the present invention, which is about 90% removal of the biodegradable organic matter contained in the influent to the end of the experiment The efficiency was shown, and the TCOD _cr loading was calculated to be about 1.15 kg / m 3 / d. COD _{cr of} runoff It is considered that the value of the component corresponds to the hardly degradable organic matter contained in the livestock wastewater.

The specific parts of the present invention have been described in detail above, and for those skilled in the art, these specific descriptions are merely preferred embodiments, and the scope of the present invention is not limited thereto. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described in detail above, the present invention has the effect of easy operation and maintenance by installing a bio-electrochemical biofilm continuous batch reactor including a biologically active tank and an electrode system in the wastewater treatment apparatus, Hydrogen consisting of bubbles is generated and sufficiently dissolved, so that it can be more easily used for biological reactions. In addition, oxygen and hydrogen generated in the electrode system are directly used as electron donors and electron acceptors used for oxidizing, nitrifying and denitrifying organic substances, thereby removing organic substances and nitrogen.

Claims (4)

Waste water tank; An inflow pump for introducing raw water from the waste water tank; Cylindrical body; A stirrer installed at an upper end of the body to circulate the raw water; An electrode system installed at a lower end of the body and using titanium and carbon electrodes as an anode and using stainless steel as a cathode; And a hybrid bio-electrochemical biofilm continuous batch reactor comprising a biologically activated tank installed in the middle portion of the body. A recycling pump for circulating the raw water; An outflow pump for discharging the treated water through the reactor; A ventilator for introducing air into the reactor; And Wastewater treatment apparatus using a hybrid type bio-electrochemical biofilm continuous batch reactor combined with a biological activation tank and an electrode system including an acid pipe for circulating the air flowing through the ventilator. The wastewater treatment apparatus of claim 1, wherein the reactor process is selected from the group consisting of an A / O process, an A / O transformation process, and an A / O / A / O process. The wastewater treatment apparatus according to claim 1, wherein the biologically activated tank is operated by fixing microorganisms to a carrier using a rope-type biofilm media. A method for treating wastewater, comprising removing organic matter and nitrogen using the wastewater treatment apparatus of any one of claims 1 to 3.

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