CN1689989A - Nitrogen Removal Process of High Concentration Ammonia Nitrogen Wastewater - Google Patents

Abstract

The invention is a denitrification process for high-concentration ammonia nitrogen wastewater. Its system consists of three units: nitrosation biofilm reactor, anaerobic ammonium oxidation biofilm reactor and land treatment. In the nitrosation biofilm reactor, part of NH ₄ -N in the wastewater is oxidized to NO ₂ -N; then in the anaerobic ammonium oxidation biofilm reactor, microorganisms use NH ₄ -N as The electron donor reduces nitrite, uses nitrite as the electron acceptor to oxidize NH ₄ -N, converts ammonia nitrogen and nitrite nitrogen into N ₂ , and achieves the purpose of simultaneously removing two kinds of nitrogen; anammox reactor The effluent enters the land treatment unit, and the suspended solid particles and dissolved components in the wastewater are removed through the capillary infiltration of the soil, microbial degradation, soil particle filtration, ion exchange, adsorption and precipitation, and the organic matter and nitrogen in it are transformed. The invention can complete nitrogen removal under the condition of low carbon-to-nitrogen ratio, has low energy consumption, and makes waste water meet discharge requirements.

Description

Nitrogen Removal Process of High Concentration Ammonia Nitrogen Wastewater

technical field

The invention relates to the technical field of environmental protection, and belongs to a denitrification process for treating high-concentration ammonia nitrogen wastewater by using a bioreactor.

Background technique

High-concentration ammonia-nitrogen wastewater is difficult to treat and has serious environmental hazards, such as landfill leachate, sludge supernatant and some chemical industrial wastewater. The main water quality characteristics are: high ammonia nitrogen concentration and low carbon-nitrogen ratio (C/N). At present, the main technologies for treating nitrogen-containing wastewater at home and abroad include biological treatment and physical and chemical treatment. Although physical and chemical treatment technology has a good treatment effect, it is expensive, energy-consuming, and prone to secondary pollution. Biological treatment technology is economical and simple, etc. advantages and are widely used.

Traditional biological denitrification includes two steps of biological aerobic nitrification and denitrification: ① Under aerobic conditions, ammonia nitrogen is converted into nitrate nitrogen through two reactions of nitrosation and complete nitrification. The reaction formula is as follows:

It can be known from the above formula that for complete nitration of 1mg NH ₄ ⁺ -N, 4.57mg of oxygen and 7.14mg of alkali (calculated as CaCO ₃ ) are required.

②Under anoxic conditions, denitrifying bacteria use organic matters as electron donors, and nitrate nitrogen (NO ₃ ^- -N) and nitrite nitrogen (NO ₂ ^- -N) are reduced to nitrogen (N ₂ ). The reaction formula is as follows:

It can be known from the above formula that 1.71 mg and 2.86 mg of organic matter (CODc _r ) are required to convert 1 mg of NO ₂ ^- -N or NO ₃ ^- -N into N ₂ , respectively.

The traditional biological denitrification process flow is shown in Figure 2.

The application of traditional biological denitrification technology to treat wastewater with high ammonia nitrogen and low carbon-to-nitrogen ratio (C/N) has the following main problems:

(1) Excessively high ammonia nitrogen increases energy consumption, and 4.57g of oxygen is required for complete nitrification of 1g of ammonia nitrogen;

(2) The denitrification process requires sufficient organic carbon sources as electron donors to ensure the denitrification rate. For wastewater with high ammonia nitrogen and low carbon-to-nitrogen ratio (C/N), it is difficult to denitrify effectively, resulting in low denitrification efficiency, and adding an external carbon source not only increases the treatment cost, but also easily causes secondary pollution;

(3) In order to neutralize the acidity produced by the nitrification process, it is necessary to add alkali to neutralize it, which increases the operating cost.

(4) The technological process is complicated, and the return of sludge and mixed liquid increases the power cost.

At present, biological fluidized bed is mostly used for anaerobic ammonium oxidation reactor at home and abroad, which has the following main disadvantages:

(1) It is necessary to set up a carrier stripping device and carry out carrier reflux, which complicates the operation.

(2) A large reflux ratio is required to suspend and fluidize the carrier, which increases energy consumption.

Contents of the invention

Considering the water quality and quantity characteristics of high ammonia nitrogen wastewater, as well as the typical problems faced by the current treatment technology, a single treatment method cannot meet its treatment requirements, and an optimized combination of different methods is required to effectively treat it. The purpose of the present invention is to use the denitrification principle of anaerobic ammonium oxidation, combine nitrification-anammox technology with land treatment, and propose an economical denitrification that can not only efficiently and stably denitrify, but also save energy. Reasonable new process for biological denitrification of high ammonia nitrogen wastewater.

In order to achieve the above object, the technical solution of the present invention is to provide a denitrification process for high-concentration ammonia nitrogen wastewater. The system is composed of three units: nitrosation biofilm reactor, anammox biofilm reactor and land treatment. The processing unit includes two parts: soil infiltration ditch and subsurface flow wetland, which includes the following steps:

(1) High-concentration ammonia-nitrogen wastewater enters the nitrosation biofilm reactor from the bottom, flows upward, and removes most of the easily biodegradable organic matter in the wastewater through the water distribution device, aeration device, and biofilm reaction zone, and performs nitrosation reaction. After part of the ammonia nitrogen is converted into nitrite (NO ₂ -N), it overflows from the upper connecting pipe;

(2) The wastewater treated in the first step enters the anammox biofilm reactor from the bottom through the connecting pipe, flows upward, passes through the water distribution device and the biofilm reaction zone, and the remaining ammonia nitrogen (NH ₄ -N ) and the generated nitrite (NO ₂ -N) undergo anaerobic ammonium oxidation denitrification reaction, and overflow from the upper connecting pipe; the gas generated in the anammox biofilm reactor is discharged from the upper part of the reactor;

(3) The wastewater treated in the second step flows into the soil infiltration ditch water distribution pipe of the land treatment unit through the connecting pipe, enters the soil infiltration ditch through the water distribution pipe, diffuses and infiltrates into the surrounding soil, and filters the gravel layer, soil After the sedimentation, filtration, adsorption and decomposition of the layer, it enters the water collection pipe at the bottom;

(4) Wastewater flows into the subsurface wetland water distribution pipe of the land treatment unit through the water collection pipe, and the wastewater flows into the bottom layer of the subsurface wetland through the water distribution pipe, and passes through the sedimentation, filtration, adsorption and decomposition of the gravel layer, filler layer, and soil layer from bottom to top , the particulate matter and odor in the wastewater are effectively removed, the chroma is greatly reduced, and the effluent meets the discharge requirements;

(5) The dischargeable water overflows the ground, collects in the outlet weir, and is discharged into nature through the outlet of the outlet weir.

In the denitrification process of high-concentration ammonia-nitrogen wastewater, part of the wastewater treated in the second step is pumped into the anammox biofilm reactor from the bottom by the circulation pump through the circulation pipe, and the circulating water and the influent water are mixed into the reaction The device can reduce the concentration of ammonia nitrogen and nitrite nitrogen in the influent and reduce its inhibitory effect on microorganisms.

The denitrification process of high-concentration ammonia-nitrogen wastewater, in the first step, the reaction water temperature of the nitrification biofilm reactor is 33-34°C, the hydraulic retention time is 2.0-2.1d, and the dissolved oxygen DO: 0.8-1.0mg /L, pH: 8.0-8.2.

The denitrification process of high-concentration ammonia-nitrogen wastewater, in the second step, the reaction water temperature of the anammox biofilm reactor is 30-31°C, the hydraulic retention time is 4.0-4.2d, and the pH: 7.9-8.1 .

The denitrification process of the high-concentration ammonia-nitrogen wastewater, the nitrosation biofilm reactor, adopts a fixed bed biofilm reactor; it is composed of two parts: a biofilm reaction zone and a solid-liquid separation zone, and the biofilm reaction zone is installed Filling, the top is expanded to slow down the rising velocity, the aeration gas is collected in the central tube, and the outer periphery of the tube is a solid-liquid separation area; the upper side of the reactor is equipped with a connecting pipe; the aeration pipe, aeration device and water distribution device are installed At the bottom of the reactor; one side of the bottom of the reactor is connected with a waste water inlet pipe, and the aeration pipe is drawn out from the other side.

The denitrification process of the high-concentration ammonia-nitrogen wastewater, the anaerobic ammonium oxidation biofilm reactor adopts a fixed bed biofilm reactor; it is composed of two parts: a biofilm reaction zone and a solid-liquid separation zone, and the biofilm reaction zone Packing is installed inside, and the top is expanded to slow down the rising flow rate. The outer periphery of the central cylinder is a solid-liquid separation area; the upper side of the reactor is equipped with a connecting pipe and a circulation pipe; The lower end of the connecting pipe of the reactor is connected, and the outlet of the lower end of the connecting pipe of the nitrosative biofilm reactor is connected to the bottom side of the reactor, and the circulating pump makes the effluent of the reactor enter the reactor for internal circulation; bottom of the container.

The denitrification process of the high-concentration ammonia-nitrogen wastewater, the soil infiltration ditch, the upper part is a soil layer, the middle part is a filter gravel layer, the bottom is a water collection pipe, and the water distribution pipe is placed on the upper part of the filter gravel layer; the soil infiltration ditch The method of alternating dry and wet operation is used to keep the soil alternately aerobic and anoxic, so as to achieve the purpose of aerobic nitrification and anoxic denitrification.

In the denitrification process of high-concentration ammonia-nitrogen wastewater, the subsurface flow wetland has a soil layer in the upper part, a filler layer in the middle, and a gravel layer in the bottom, and the water distribution pipe is placed in the gravel layer at the bottom.

The denitrification principle of the nitrification-anammox technology adopted in the present invention is: about 50% of the ammonia nitrogen in the waste water is oxidized to nitrite nitrogen, that is, the nitrification process only proceeds to the nitrification stage, and the microorganisms are denitrified under anaerobic conditions. Under this condition, the remaining 50% of ammonia nitrogen is used as the electron donor, and nitrite nitrogen is used as the electron acceptor to convert ammonia nitrogen and nitrite nitrogen into nitrogen gas. The anammox technology does not need to add organic carbon sources. The reaction formula is as follows:

Compared with the traditional nitrification-denitrification biological nitrogen removal technology, this biological nitrogen removal technology has the following advantages:

(1) The nitrification reaction only proceeds to the nitrosation stage, and only about 50% of the ammonia nitrogen is oxidized to nitrite nitrogen, which reduces the energy consumption of aeration. Only 0.75 mol of oxygen is needed to remove 1 mol of NH ₄ ⁺ , saving 62.5% of energy consumption. .

(2) Save 100% denitrification organic carbon source.

(3) Since only 50% of ammonia nitrogen is oxidized to nitrite nitrogen, the amount of acid production is greatly reduced, and only 1 mol of H ⁺ is produced for every 1 mol of NH ₄ ⁺ removed, which can save considerable neutralization reagents.

Nitrosation and anammox reactor in the present invention all adopt fixed-bed biofilm reactor, have following main features:

(1) The microorganisms are diverse, the food chain of the organism is long, and the microorganisms that can survive for a long time for generations.

(2) There is no need for sludge backflow and fluidization, and the chief mate reduces energy consumption; there is no need to set up a separate sedimentation tank, which simplifies operation.

(3) Shock load resistance, strong adaptability to changes in water quality and water quantity.

In the present invention, the land treatment system is placed after the anaerobic ammonium oxidation reactor, so that the whole process has the advantages of good treatment effect, large buffer capacity, low investment, low operating cost and convenient management. Moreover, the technological process is simple, no sludge return and mixed liquid return are required, and energy consumption is low.

The new denitrification process of the present invention has the following advantages:

(1) The denitrification efficiency is high, and there is no need to add organic carbon sources.

(2) It not only removes refractory organic matter, but also has the functions of decolorization and deodorization.

(3) The technological process is simple and the operation is convenient.

(4) Reduce power costs, chemical costs and management costs, and reduce operating costs.

(5) Less infrastructure investment.

(6) Using land treatment as an ecological technology can not only deal with pollutants, but also beautify the environment.

Both the soil infiltration ditch and the subsurface wetland are placed underground, on which flowers and crops can be planted, pavilions and other landscapes can be built according to different needs.

Description of drawings

The process flow diagram of the denitrification process of Fig. 1 high concentration ammonia nitrogen wastewater of the present invention;

Fig. 2 Traditional biological denitrification process flow chart.

Detailed ways

Process flow of the present invention is shown in Fig. 1. Both nitrosation and anammox biofilm reactors use fixed-bed biofilm reactors, and fixed packing is installed in nitrosation biofilm reactor 1 and anammox biofilm reactor 2. The land treatment unit consists of two devices, the soil infiltration ditch 3 and the subsurface flow wetland 4, which can be constructed according to the site topography and land use conditions.

The waste water flows into the nitrosation biofilm reactor 1 from the bottom, and the water is evenly distributed in the reactor 1 through the water distribution device 5, and the air is supplied to the reactor 1 by the air supply facility through the aeration pipe and the aeration device 6, so as to provide biological benefits. Oxygen required for the oxygen reaction, waste water and air bubbles flow from bottom to top, contact with the biofilm grown on the filler in the biofilm reaction zone 7, and the mixed solution of biodegraded waste water and suspended sludge enters the solid-liquid separation zone 8, The sludge flocculates and settles, and enters the biofilm reaction zone 7, the clarified water flows out from the upper connecting pipe 22 of the reactor 1, and flows into the anammox biofilm reactor 2, and the influent water flows from bottom to top through the water distribution device 9, Metabolized and degraded by the biofilm growing on the filler in the biofilm reaction zone 10, the mud-water mixture is separated in the solid-liquid separation zone 11, and the outlet water of the reactor 2 is internally circulated through the circulation pipe 24 and the circulation pump 12, and the circulating water is mixed with the influent water Entering the reactor 2, it can reduce the concentration of ammonia nitrogen and nitrite nitrogen in the influent, and reduce its inhibitory effect on microorganisms. The outlet water passes through the water seal to ensure that the air does not enter the reactor 2, the gas generated by the biological reaction is collected from the top of the reactor 2 and discharged, the outlet water flows out from the upper connecting pipe 23 of the reactor 2, and flows into the water distribution pipe in the soil infiltration ditch 3 13. Infiltration, infiltration and diffusion into the soil layer 15 through the filter gravel layer 14 around the water distribution pipe 13, degradation of the biofilm on the gravel layer 14, filtration of the soil layer, adsorption, biological metabolism, and absorption of surface crops, etc. The waste water is further purified and collected by the perforated water collection pipe 16 at the bottom, and then flows into the water distribution pipe 17 of the subsurface wetland 4 . The soil infiltration ditch 3 adopts the mode of alternating dry and wet operation to keep the soil alternately aerobic and anoxic. The incoming water of the subsurface wetland 4 flows upward through the water distribution pipe 17 and the gravel layer 18 around the pipe and enters the filler layer 19, and discarded building materials (such as masonry, etc.) and other materials can be used as fillers for the subsurface wetland 4. Pollutants in the wastewater are further removed from the wastewater through utilization of the biofilm on the filler layer 19 , filtration and biodegradation of the surface soil 20 , and absorption by crops, and the purified effluent is collected by the outlet weir 21 and then discharged.

Example 1

Please refer to attached picture 1.

Landfill leachate is used as the source of wastewater treatment. The entire technological process has been running continuously and stably for nearly four months. The conditions for stable operation and the treatment effect of the entire process are as follows:

Nitrosation biofilm reactor: water temperature 33-34°C, hydraulic retention time 2.0-2.1d, dissolved oxygen DO: 0.8-1.0mg/L, pH: 8.0-8.2.

Anaerobic ammonia oxidation biofilm reactor: water temperature 30-31 ℃, hydraulic retention time 4.0-4.2d, pH: 7.9-8.1.

Influent concentration of NH ₄ -N: 736.77mg/L, effluent concentration: 58.17mg/L, removal rate: 92.11%; TN influent concentration: 767.18mg/L, effluent concentration: 68.61mg/L, removal rate: 91.06%; CODcr influent concentration: 951.50mg/L, effluent concentration: 160.98mg/L, removal rate: 83.08%.

Claims (7)

1. The utility model provides a denitrogenation technology of high concentration ammonia nitrogen waste water, the system comprises nitrosation biofilm reactor, anaerobic ammonia oxidation biofilm reactor and three units of land treatment, and the land treatment unit includes two parts of soil infiltration ditch and underground underflow wetland, characterized by: comprises the following steps:

(1) high-concentration ammonia nitrogen wastewater enters a nitrosation biofilm reactor from the bottom and flows upwards, most of easily biodegradable organic matters in the wastewater are removed through a water distribution device, an aeration device and a biofilm reaction zone, nitrosation reaction is carried out, and part of ammonia nitrogen is converted into Nitrite (NO)₂-N) after, overflow from the upper connecting tube;

(2) the wastewater treated in the first step enters an anaerobic ammonia oxidation biomembrane reactor from the bottom through a connecting pipe, flows upwards, passes through a water distribution device and a biomembrane reaction zone, and residual ammonia Nitrogen (NH) in the wastewater₄-N) with Nitrite (NO) formed₂N) overflowing from the upper connecting pipe after anaerobic ammoxidation denitrification reaction; gas generated in the anaerobic ammonia oxidation biofilm reactor is discharged from the upper part of the reactor;

(3) the wastewater treated in the second step flows into a water distributor of a soil infiltration ditch of the land treatment unit through a connecting pipe, enters the soil infiltration ditch through the water distributor, diffuses and permeates to the surrounding soil, and enters a water collecting pipe at the bottom after being precipitated, filtered, adsorbed and decomposed by a gravel filtering layer and a soil layer;

(4) the wastewater flows into the subsurface flow wetland water distribution pipe of the land treatment unit through the water collection pipe, flows into the bottom layer of the subsurface flow wetland through the water distribution pipe, and is subjected to precipitation, filtration, adsorption and decomposition from bottom to top through the gravel layer, the packing layer and the soil layer, so that particulate matters and odor in the wastewater are effectively removed, the chromaticity is greatly reduced, and the effluent meets the discharge requirement;

(5) the water which can be discharged overflows the ground, is collected in the water outlet weir and is discharged into the nature through the outlet of the water outlet weir.

2. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: and pumping part of the wastewater treated in the second step into an anaerobic ammonia oxidation biomembrane reactor from the bottom by a circulating pump through a circulating pipe, mixing the circulating water with the inlet water, and feeding the mixture into the reactor to reduce the concentration of ammonia nitrogen and nitrite nitrogen in the inlet water and reduce the inhibition effect of the mixture on microorganisms.

3. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: in the first step, the reaction water temperature of the nitrosation biofilm reactor is 33-34 ℃, the hydraulic retention time is 2.0-2.1 d, and the dissolved oxygen DO: 0.8-1.0 mg/L, pH: 8.0 to 8.2.

4. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: in the second step, the reaction water temperature of the anaerobic ammonia oxidation biofilm reactor is 30-31 ℃, the hydraulic retention time is 4.0-4.2 d, and the pH value is as follows: 7.9 to 8.1.

5. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: the nitrosation biomembrane reactor adopts a fixed bed biomembrane reactor; the device consists of a biomembrane reaction zone and a solid-liquid separation zone, wherein the biomembrane reaction zone is internally provided with a filler, the top of the biomembrane reaction zone is expanded to slow the ascending flow velocity, the aerated gas is collected in a central cylinder, and the solid-liquid separation zone is arranged at the periphery outside the tube; one side of the upper part of the reactor is provided with a connecting pipe; the aeration pipe, the aeration device and the water distribution device are arranged at the bottom in the reactor; one side of the bottom of the reactor is connected with a wastewater inlet pipe, and an aeration pipe is led out from the other side.

6. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: the anaerobic ammonia oxidation biomembrane reactor adopts a fixed bed biomembrane reactor; the device consists of a biomembrane reaction zone and a solid-liquid separation zone, wherein the biomembrane reaction zone is internally provided with a filler, the top of the biomembrane reaction zone is expanded to slow down the ascending flow velocity, and the solid-liquid separation zone is arranged at the periphery of a central cylinder; one side of the upper part of the reactor is provided with a connecting pipe and a circulating pipe;the circulating pump is arranged in the circulating pipe, the lower end of the circulating pipe is communicated with the lower end of a connecting pipe of the nitrosation biofilm reactor, the outlet of the lower end of the connecting pipe of the nitrosation biofilm reactor is connected to one side of the bottom of the reactor, and the circulating pump enables the effluent of the reactor to enter the reactor again for internal circulation; the water distribution device is arranged at the bottom in the reactor.

7. The denitrification process of the high-concentration ammonia nitrogen wastewater as set forth in claim 1, which is characterized in that: the upper part of the soil infiltration ditch is a soil layer, the middle part of the soil infiltration ditch is a filtering gravel layer, the bottom of the soil infiltration ditch is a water collecting pipe, and the water distributing pipe is arranged on the upper part of the filtering gravel layer; the soil infiltration ditch adopts a dry-wet alternate operation mode to ensure that the soil alternately keeps aerobic and anoxic so as to achieve the aims of aerobic nitrification and anoxic denitrification.

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