CN1903752A

CN1903752A - Method of nitrosation electrochemical back nitrosation full autotrophic deammoniacal nitrogen and its reactor

Info

Publication number: CN1903752A
Application number: CNA2005100855443A
Authority: CN
Inventors: 王海燕; 周岳溪; 蒋进元
Original assignee: Chinese Research Academy of Environmental Sciences
Current assignee: Chinese Research Academy of Environmental Sciences
Priority date: 2005-07-28
Filing date: 2005-07-28
Publication date: 2007-01-31
Anticipated expiration: 2025-07-28
Also published as: CN100491274C

Abstract

The present invention provides a new method for treating amino-nitrogen waste water with low carbon-nitrogen ratio, namely nitrosation electrochemical denitrosation full-autotrophic amino-nitrogen-removing new method. It is characterized by that the biological nitrosation and electrochemical denitrosation two processes are combined together. Said invention also provides a reactor for removing amino-nitrogen from amino-nitrogen waste water with low carbon-nitrogen ratio, it includes biological nitrosation device and electrochemical denitrosation device, both are series-connected together. Under the complete autotrophic condition above 98% of amino-nitrogen can be converted into non-toxic harmful nitrogen gas.

Description

Nitrosation electrochemical denitrosation full-autotrophic ammonia nitrogen removal method and reactor

Technical Field

The invention relates to a method and a reactor for removing ammonia nitrogen in low-carbon-nitrogen-ratio ammonia nitrogen sewage, in particular to a method and a reactor for removing ammonia nitrogen in low-carbon-nitrogen-ratio ammonia nitrogen sewage by combining a biological nitrosation process and an electrochemical denitrosation process, and realizing a completely autotrophic denitrification process.

Background

Conventional biological denitrification typically involves oxidizing ammonia nitrogen to NO₃ ^-Nitration and NO reduction of₃ ^-Reduction to N₂Two stages of denitrification; but the aeration energy consumption in the nitrification stage is high, and the alkalinity is consumed; an organic carbon source is needed in the denitrification stage; for low carbon nitrogen ratio wastewater such as coking wastewater, petrochemical wastewater, landfill leachate, chemical fertilizer and the like, carbon sources such as methanol and the like are required to be added. In order to solve the problem of adding a carbon source, nitrite type biological denitrification is developed, namely, the oxidation of ammonia nitrogen is controlled in a nitrous acid stage by controlling the reaction operating conditions, and then nitrous acid is further converted into nitrogen, namely NH₄ ⁺→NO₂ ^-→N₂(ii) a The nitrite type biological denitrification occupies small area, saves investment and has O₂Low consumption of power, carbon source and alkali; however, a certain amount of organic carbon source is also added. The deep research shows that the nitrite pathway denitrification can be realized by biological full autotrophy without organic carbon source, namely, nitrification section NH₄ ⁺Is partially oxidized to NO₂ ^-Then remaining NH₄ ⁺And NO produced₂ ^-And then denitrogenated in the form of anammox, i.e. Such as the common SHARON-ANAMMOX suspension system (Single reactor system for High rate Ammonia removal over nitrile-Anaerobic Ammonium Oxidation, SHARON-ANAMMOX for short), but the Anaerobic Ammonia Oxidation conditions are harsh and slow to start (>2 months). The method for producing hydrogen and elemental sulfur by electrolysis provides a nutrient source for the autotrophic denitritizing process, and is a clean and effective method. Specifically, a carbon electrode is used as an anode, metals such as iron or aluminum and the like are used as a cathode to prepare a facultative electrolytic reactor, hydrogen is provided for a biological denitritification process after water passes through the reactor and is electrified, a mode of adding conductive (carbon) and non-conductive filler (sulfur) between electrodes is adopted, pH adjustment is facilitated, current efficiency and denitritification capacity can be greatly improved, compared with anaerobic ammonia oxidation, the condition is easy to control and start, the effluent quality is good, and the recycling standard can be reached.

Disclosure of Invention

The purpose of the invention is: overcomes the defects of the existing biological full-autotrophic nitrite type denitrification, comprehensively utilizes the advantages of biological nitrosation and electrochemical denitrosation, and establishes a novel method and a reactor for treating the low-carbon-nitrogen-ratio ammonia nitrogen wastewater, which are high-efficiency recyclable wastewater.

The method of the invention comprises the following steps: combining two processes of biological nitrosation and electrochemical denitrosation, and enabling the biological nitrosation section and the electrochemical denitrosation section to work in a series mode: 95% NH in raw water₄ ⁺Conversion of-N to NO in the nitrosation stage₂ ^-After N, the nitrogen enters an electrochemical denitritification section which provides a nutrient source by electrolyzing hydrogen and sulfur to remove the generated NO₂ ^-N and small amounts of organic matter in the raw water.

Drawings

The basic configuration of the reactor of the invention is shown in the attached drawing. The reactor adopts a mode of connecting two sections of reactors in series from left to right (figure 1) or up and down (figure 2), when the reactors are connected in series from top to bottom, the water flow adopts an upflow type, and the nitrosation section of the reactor is arranged below and the electrochemical denitrosation section is arranged above.

The nitrosation/electrochemical denitrosation reactor 1 is composed of a biological nitrosation reactor 2 and an electrochemical denitrosation reactor 3, and the volume ratio of the two parts 2 to 3 is 1: 1-1: 6. The biological nitrosation section 2 when the reactors are connected in series at the left and right is equivalent to an internal immersion type membrane bioreactor, hollow fiber membranes 5 such as polyvinylidene fluoride and polyether sulfone are taken as membrane components, preferably a polyvinylidene fluoride membrane component, and a SBR or CSTR reactor form is adopted, and stirring is carried out by a stirring device 4. When the reactors are connected in series, the nitrosation section 2 of the reactor is equivalent to a fixed bed biofilm reactor, solid particles 21 with the particle size of 1.0-5.0 mm are used as filling media, such as anthracite, activated carbon, quartz sand, zeolite and the like, and the quartz sand and the zeolite are preferably selected. The anode 12 of the electrochemical denitritization section 3 can adoptgraphite, carbon fiber, metallic nickel, titanium-ruthenium and other materials, and graphite is preferred; the cathode 13 may be made of stainless steel, iron, aluminum, graphite, carbon fiber, metallic nickel, titanium-ruthenium, etc., preferably stainless steel. The cathode and anode electrodes are arranged in parallel or concentric circles, the distance between the electrodes is 1.5-6cm, and short circuit can be prevented by insulating the electrodes in the reactor. The anode and cathode are connected to the negative and positive poles of a dc power supply 9 by

leads

10 and 11, respectively. Carbon-sulfur mixed particles (volume ratio 1: 1-5: 1)19 with the particle size of 2.0-20.0 mm can be filled between the electrodes as a filling medium.

Containing NH₄ ⁺The water 8 to be treated enters the reactor 2 through the constant flow pump 7 and the water inlet valve 16 (or 22). The water treated in reactor 2 is discharged by pump 15 through valve 17 into reactor 3 (or rises from reactor 2 into reactor 3). Meanwhile, an aeration device 6 is arranged at the bottom of the nitrosation section 2, and an aeration pump 20 is used for DO supply. When the fixed bed is back flushed, the required water is provided through the back flushing water valve 18 (or 23).

Detailed Description

The reactor system of the present invention operates as follows: firstly, the bacteria are inoculated and cultured, in the stage, the nitrosation section is inoculated by aerobic sludge, and the electrochemical section is inoculated by anoxic pond sludge. Two stages are respectively cultured when the two stages are connected in series, the nitrosation stage maintains lower DO, and a proper amount of NaHCO is added₃Buffer adjusting pH to 7.5-8.3, and adding NH₄ ⁺Adding appropriate amount of phosphorus as inlet water, and gradually adding NH₄ ⁺The nitrosation rate reaches 95% in about 30 days; electrochemical section to gradually increase NO in the feed water₂ ^-And culturing with proper amount of methanol, wherein the ratio of organic carbon to nitrite nitrogen is C: N (mg/mg) ═ 3, and the pH of the system is maintained at neutral by phosphate buffering. After about 14 days, a layered biofilm was observed on the reactor packing and cathode surfaces, and the voltage (0.5-5V) and current density (0.001-0.09 mA/cm) were gradually increased by turning on the power supply 9²Cathode area) while reducing methanol to 0. After about 7

days

1 and 2 were connected in series and subsequently fed with water in the manner shown in FIG. 1: the water inlet valve 16 is firstly opened, then the constant flow pump 7 is started, and the treated water 24 enters the reactor 2 upwards through the pump 15 and the valve 17 and is finally discharged from the water outlet 14 in an overflowing way. 1 and 2 are connected in series up and down, aerobic sludge and anoxic sludge are mixed and inoculated, and water is fed according to the mode of the attached figure 2: the water inlet valve 22 is firstly opened, then the constant flow pump 7 is started, and the quilt is closedThe treated water 8 enters the

reactors

2 and 3 in sequence and is finally discharged through the overflow of the water outlet 14. By NH₄ ⁺、NaHCO₃Adding appropriate amount of phosphorus as water, adjusting pH to about 7.8, and turning on power supply 9 to gradually increase voltage (0.5-5V) and current density (0.001-0.09 mA/cm)²Cathode area), gradually increasing feed water NH₄ ⁺By adjusting DO, the filler obviously forms a film after about 30 days, and the effluent NH₄ ⁺Remove more than 95% of NO without NO₂ ^-Obvious accumulation indicates successful domestication. In the culture and operation process, an aeration device 6 is arranged at the bottom of the nitrosation section 2, and an aeration pump 20 is used for DO supply. When the reactor needs back flushing, the constant flow pump 7 (or 15) is stopped, the water inlet valves 16 and 17 (or 22) are closed, the back flushing valve 18 (or 23) is opened, and back flushing is carried out for 1-5 min. After the backwash is completed, valve 18 (or 23) is closed and the system is restarted.

The invention is characterized in that:

1. the biological nitrosation and the electrochemical denitrosation are comprehensively applied, and the autotrophic treatment is completely realized;

2. the proportion of the two sections can be adjusted according to the condition of the treated water, so as to meet the water outlet requirement;

3. organic carbon sources are not required to be added in the whole reaction process;

4. the low DO mode is adopted, so that the energy consumption is low;

5. the electrochemical denitritification treatment efficiency is high, and the effluent quality is good;

6. the effluent can reach the reuse standard of the domestic miscellaneous water.

Example (b):

7. example 1 nitrosation stage Using a rectangular plexiglass column as reactor (80L volume), a curtain polyvinylidene fluoride membrane module, 1m membrane area²Maximum flux of membrane 10L/m²H. The anode of the electrochemical denitritification section adopts a graphite plate (with the thickness of 1cm), the height of the electrode is 30cm, and the distance between the electrodes is 2.5 cm. Adding a sulfur simple substance with the particle size of 4-20 mm and the particle size of 4mm into a cathode reactorAnthracite carbon is used as a filling medium (the volume ratio is 1: 1), and the anthracite carbon and the filling medium are uniformly mixed and filled, and the effective volume is 40L. The feed water is prepared from tap water NH₄ ⁺A concentration of-N of30-200 mg/L, adding a proper amount of phosphorus source, and using NaHCO₃Adjusting the pH of the inlet water. The denitration treatment was carried out under the following conditions:

nitrosation stage:

DO：0.5～1.0mg/L

pH：7.5～8.3

MLSS：1000～3000mg/L

electrochemical denitritification stage:

anode: graphite plate 400mm long, 300mm high and 10mm thick

Cathode: stainless steel plate 400mm long, 300mm high and 1mm thick

Electrode spacing: 2.5cm

Current density: 0.0001-0.0018mA/cm²

Voltage:<5V

Current efficiency: 160 to 200 percent

Total Hydraulic Retention Time (HRT): 24-48 h

Maximum NH₄ ⁺-N load: 0.629kgNH₄ ⁺-N/(m³·d)

Temperature: 30 deg.C

The water quality after treatment is shown in Table 1.

TABLE 1 Water quality after treatment of example 1

8. Example 2 the nitrosation stage used a plexiglass cylinder as reactor (volume 5L), a fixed bed membrane bioreactor, and quartz sand with an average particle size of 5.0mm as packing medium. The anode of the electrochemical denitritization section adopts a graphite rod (the diameter is 3.70cm), the electrode height is 40cm, the electrode distance is 5.0cm, a sulfur simple substance with the particle size of 4-5 mm and anthracite carbon with the particle size of 4-5 mm are added into a reactor as filling media (the volume ratio is 1: 1), the sulfur simple substance and the anthracite carbon are uniformly mixed and filled, and the effective volume is 8L. The feed water is prepared from tap water NH₄ ⁺The concentration of-N is 30-300 mg/L, and a proper amount of phosphorus source is added. Under the following conditionsAnd (3) denitration treatment:

nitrosation stage:

DO：0.5～1.0mg/L

pH：7.5～8.3

biomass: 7.8 to 10.0mg-VSS/g

Electrochemical denitritification stage:

anode: graphite rod with diameter of 3.70cm and electrode height of 40cm

Cathode: stainless steel cylinder with inner diameter of 13.7cm and height of 40cm

The electrode spacing was 5.0cm

Current intensity: 0.0001-0.0025mA/cm²

Voltage:<5V

Current efficiency: 200 to 240 percent

Total Hydraulic Retention Time (HRT): 12 to 24 hours

Maximum NH₄ ⁺-N load: 0.668kgNH₄ ⁺-N/(m³·d)

Temperature: 30 deg.C

The water quality after treatment is shown in Table 2.

Table 2 water quality after treatment of example 2

Claims

1. A method for removing ammonia nitrogen in ammonia nitrogen wastewater with low carbon-nitrogen ratio is characterized in that biological nitrosation and electrochemical denitrosation are combined.

2. The method of claim 1, wherein biological nitrosation is conducted by retaining ammonia oxidizing bacteria oxidizing ammonia nitrogen at a lower Dissolved Oxygen (DO) concentration.

3. The method of claim 1, wherein the electrochemical denitritification is performed by sulfur-carbon mixed complex three-dimensional electrode biofilm denitritification.

4. A process according to claim 2, wherein the biological nitrosation is carried out at a temperature of 25 to 30 ℃ and a pH of 7.5 to 8.3.

5. The process of claim 3, wherein the electrochemical denitritification is carried out in a sulfur-carbon mixed complex three-dimensional electrode electrolyzer using graphite, carbon rods, carbon fibers or carbon-substitutable metallic nickel, titanium-ruthenium, etc. as anode and stainless steel, iron, aluminum, graphite, carbon fibers, metallic nickel, titanium-ruthenium, etc. as cathode. And carbon and sulfur fillers (volume ratio is 1: 1-5: 1) are added between the electrodes.

6. A reactor for removing ammonia nitrogen in ammonia nitrogen wastewater with low carbon-nitrogen ratio is characterized by comprising a nitrosation device and an electrochemical denitrosation device which are connected in series.

7. A reactor according to claim 6, wherein the biological nitrosation device is upstream (lower) and the electrochemical denitrosation device is downstream (upper).

8. The reactor according to claim 6, wherein the biological nitrosation device adopts a membrane bioreactor, and the membrane material is hollow fiber membrane material such as polyvinylidene fluoride and polyether sulfone; or a fixed bed biomembrane reactor is adopted, the filler is anthracite, activated carbon, quartz sand, zeolite and the like, and the quartz sand, the zeolite and the like are preferred.

9. The reactor of claim 6, wherein the anode of the electrochemical denitritification device is made of graphite, carbon rods, carbon fibers or metal nickel, titanium-ruthenium and the like which can replace carbon, the cathode is made of stainless steel, iron, aluminum, graphite, carbon fibers, nickel, titanium or titanium-ruthenium, and carbon and sulfur mixed fillers (volume ratio is 1: 1-5: 1) are filled between electrodes.