Method for efficiently treating nitrogen-containing wastewater based on combination of dissimilatory reduction of nitrate into ammonium and denitrification coupled anaerobic ammonia oxidation
Technical Field
The invention relates to a method for treating nitrogen-containing wastewater based on ammonium-combined denitrification-coupled anaerobic ammonia oxidation through nitrate dissimilatory reduction, and belongs to the technical field of wastewater microbial treatment.
Background
Some industrial wastewater contains high-concentration nitrate nitrogen and nitrite nitrogen and contains a large amount of organic matters, and is high-pollution wastewater which is strictly forbidden by the nation and is directly discharged. High-concentration nitrate nitrogen wastewater directly flows into rivers and lakes to pollute surface water and underground water, so that aquatic animals and plants die and even die, and if surrounding residents adopt the surface water or the underground water polluted by nitrate and nitrite as domestic water, the body health is seriously harmed, and the rapid and harmonious development of local economy is influenced.
The traditional sewage denitrification process can convert nitrate nitrogen into nitrogen to perform denitrification, and the reaction formula is as follows:
(ii) a However, denitrification is suitable for the condition of low C/N, but some industrial wastewater contains a large amount of organic matters, and the conventional denitrification process causes the treated wastewater to containThere are a large number of organic substances. Nitrate dissimilation to ammonium (DNRA) is a process for converting nitrate nitrogen into ammonium through nitrite nitrogen, and the reaction process is
. The DNRA procedure is more advantageous in cases where the C/N is high.
Because the denitrification and the nitrate isomerization are different in applicable C/N conditions, the denitrification and the nitrate isomerization can not be combined together to treat the nitrogen-containing wastewater, and if the denitrification and the nitrate isomerization are combined together, the denitrification and the nitrate isomerization are mutually inhibited, so that the single treatment effect is greatly weakened.
The anaerobic ammonia oxidizing bacteria take nitrite nitrogen as an electron acceptor, and ammonia nitrogen is directly converted into nitrogen. The reaction formula is as follows:
if the denitrification, the nitrate catabolism and the anaerobic ammonia oxidation are coupled, the mutual inhibition of the denitrification and the nitrate catabolism into ammonium is avoided, so that the DNRA bacteria, the denitrifying bacteria and the anaerobic ammonia oxidation bacteria respectively exert respective advantages in the same environment, and the denitrification efficiency and the organic matter utilization rate can be greatly improved, therefore, how to avoid the mutual inhibition of the denitrification and the nitrate catabolism into ammonium and ensure that the DNRA bacteria, the denitrifying bacteria and the anaerobic ammonia oxidation bacteria respectively exert respective advantages in the same environment is a great problem at present.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for treating nitrogen-containing wastewater based on ammonium combination denitrification coupling anaerobic ammonia oxidation reduction of nitrate dissimilation. The method of the invention simultaneously generates combined denitrification processes of denitrification, anaerobic ammonium oxidation and DNRA at the later stage of the process of enrichment culture of DNRA, greatly improves the low COD and low-temperature tolerance of the anaerobic ammonium oxidation bacteria, enables the DNRA bacteria, the denitrifying bacteria and the anaerobic ammonium oxidation bacteria to respectively exert respective advantages in the same environment, and can greatly improve the denitrification efficiency and the organic matter utilization rate.
Description of terms:
nitrate is dissimilated and reduced into ammonium (DNRA), namely DNRA bacteria use organic matters as electron donors and NO3 -Is an electron acceptor, is subjected to NO2 -Finally converted into NH4 +The reaction formula is CH3COOH + NO3 -+ 2H+ →2CO2 + NH4 + + H2O。
Non-woven fabric membrane: the membrane made of non-woven fabrics can make microorganisms attached, and the transmembrane pressure (TMP) is small.
The technical scheme of the invention is as follows:
a method for treating nitrogen-containing wastewater based on ammonium nitrate dissimilatory reduction combined with denitrification coupling anaerobic ammonia oxidation comprises the following steps:
(1) adding aerobic activated sludge into an anaerobic membrane bioreactor;
(2) introducing wastewater to be treated into the anaerobic membrane bioreactor through two paths of inlet water to realize the synchronous enrichment step of DNRA bacteria, denitrifying bacteria and anaerobic ammonium oxidation bacteria;
(3) the nitrate dissimilation reduction is successfully started to be ammonium, combined with denitrification coupling anaerobic ammonia oxidation, and the nitrogen in the sewage is removed.
According to the invention, preferably, in the step (1), the aerobic activated sludge is uniformly stirred and then is added into the reaction zone of the anaerobic membrane bioreactor.
According to the invention, preferably, the aerobic activated sludge is sludge discharged from an aerobic section of a domestic sewage treatment plant, and the impurities of leaves, waste paper and waste plastics in the sludge are removed through filtering and screening, wherein the water content of the aerobic activated sludge is more than or equal to 98 wt%.
According to the invention, the anaerobic membrane bioreactor is preferably an immersed anaerobic membrane bioreactor, the top of the anaerobic membrane bioreactor is provided with two water inlets, the membrane is a non-woven fabric membrane, and the membrane flux is 80-150L/m2H; the membrane bracket is a polymethyl methacrylate bracket.
Preferably, in the step (2), one path of water is communicated with the inorganic wastewater, the other path of water is communicated with the organic wastewater, and the organic wastewater and the inorganic wastewater are separately communicated into the anaerobic membrane bioreactor.
Preferably, in the step (2), the inflow flow rate of the inorganic wastewater is the same as that of the organic wastewater, and the inflow flow rate is controlled so that the hydraulic retention time of the sewage to be treated in the anaerobic membrane bioreactor is 30-40 hours.
According to the invention, in the step (2), the flow rate of the feed water is controlled so that the C/N of the wastewater fed into the reactor is 6-12:1, and most preferably, the C/N of the wastewater is 10: 1.
Further preferably, the water inlet flow rates of the inorganic wastewater and the organic wastewater are both 70-80 mL/h; most preferably, the flow rate of the inorganic wastewater and the organic wastewater is 78 mL/h.
According to the invention, in the step (2), the sludge concentration after the inorganic wastewater and the organic wastewater are introduced is 1500-2500 mg/L; most preferably, the sludge concentration after the inorganic wastewater and the organic wastewater are introduced is 2000 mg/L.
Preferably, in step (2), the temperature and the pH are adjusted to maintain the temperature at 20 to 25 ℃ and the pH at 7.0 to 7.2; and simultaneously, aerating nitrogen, and maintaining an anaerobic environment to synchronously enrich DNRA bacteria, denitrifying bacteria and anaerobic ammonium oxidation bacteria.
Further preferably, in the step (2), the pH is adjusted to 7.1 by using 0.5mol/L hydrochloric acid while maintaining the temperature at 22 to 24 ℃.
Preferably, the air guide pipe and the water outlet pipe of the anaerobic membrane bioreactor are both provided with water seals for isolating oxygen to maintain an anaerobic environment, nitrogen is introduced into the anaerobic membrane bioreactor every 6 hours for 20-30 minutes to maintain the anaerobic environment, and the aeration intensity is 2-5 mL/(L.min).
Preferably, mechanical stirring is carried out after the wastewater to be treated is introduced in the step (2) so as to uniformly mix the matrix in the reactor.
Preferably, the sludge DNRA, denitrification and anaerobic ammonia oxidation coupling reaction is successfully started after the anaerobic membrane bioreactor in the step (3) runs for 204 days after 160 days, so that the nitrogen in the sewage is efficiently removed.
Preferably, the organic wastewater is organic wastewater generated in beer and paper making processes, and the inorganic wastewater is high-nitrate-nitrogen wastewater generated in a coal-to-ethylene-glycol production process.
The invention unexpectedly discovers that organic wastewater and inorganic wastewater are separately introduced into an anaerobic membrane bioreactor, the inflow flow rates of the inorganic wastewater and the organic wastewater are the same, the mutual inhibition of denitrification and nitrate isomerization into ammonium in the same environment is avoided, and the combined denitrification process of denitrification, anaerobic ammonium oxidation and DNRA is simultaneously generated at the later stage of the process of enrichment culture of DNRA, so that the low COD and low-temperature tolerance of the anaerobic ammonium oxidation bacteria are greatly improved, the DNRA bacteria, the denitrifying bacteria and the anaerobic ammonium oxidation bacteria respectively play respective advantages in the same environment, and the denitrification efficiency and the organic matter utilization rate are greatly improved.
The invention has the following advantages:
1. the method of the invention simultaneously generates combined denitrification processes of denitrification, anaerobic ammonium oxidation and DNRA at the later stage of the process of enriching and culturing DNRA, greatly improves the low COD and low-temperature tolerance of the anaerobic ammonium oxidation bacteria, as shown in figures 1 and 2, and as can be seen from figure 2, the organic wastewater and the inorganic wastewater of the invention are separately introduced into the anaerobic membrane bioreactor, so that the anaerobic ammonium oxidation bacteria amx, the denitrifying bacteria nirS, nirK and the DNRA bacteria nrfA can be enriched in the same environment, and particularly, the DNRA bacteria nrfA copy enrichment is obvious.
2. The anaerobic membrane bioreactor can quickly enrich DNRA bacteria, is simple to operate, does not generate additional products, and is economical and efficient;
3. the method has mild operation conditions, can be carried out under normal pressure, and does not need specific conditions; and no toxic and harmful substances are generated, and the method is safe and harmless to the environment.
4. On one hand, the invention utilizes the non-woven fabric membrane effect of the anaerobic membrane bioreactor, the transmembrane pressure (TMP) is small, a microorganism attachment point is provided, and the enrichment of DNRA bacteria, denitrifying bacteria and anaerobic ammonium oxidation bacteria is accelerated; on the other hand, nitrate reducing bacteria with higher enrichment degree increase the load impact resistance of the reactor, so that the reactor is more suitable for the nitrogen-containing sewage treatment task with complicated and variable water quality in practical application.
Drawings
FIG. 1 is a graph showing the variation of the concentration of nitrogen in the inlet and outlet water in the method for treating nitrogen-containing wastewater according to the present invention.
FIG. 2 is a bar graph showing the change in copy number of the functional genes of the nitrate-reducing bacteria (anammox bacteria amx, denitrifying bacteria nirS, nirK and DNRA bacteria nrfA) in the reactor of the method for treating nitrogen-containing wastewater of the present invention.
Detailed Description
The present invention will now be described in detail by way of examples with reference to the accompanying drawings. It should be noted that the examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, as many insubstantial modifications and variations of the invention may be made by those skilled in the art in light of the above teachings.
In the examples, all the chemicals used were purchased from chemical reagents of national drug group, ltd, and were all analytical grade. The peristaltic pump is purchased from Zenglang constant flow pump, Inc., and has the model number of BT 100-2J.
The membrane bioreactor and the membrane bracket are made of polymethyl methacrylate materials, and the membrane materials are non-woven fabrics.
The high-purity nitrogen used for aeration is purchased from special gas of Jinan De Yangtze province, Co., Ltd, and the specification is 99.999%.
Example 1
A method for treating nitrogen-containing wastewater based on ammonium nitrate dissimilatory reduction combined with denitrification coupling anaerobic ammonia oxidation comprises the following steps:
(1) stirring the aerobic activated sludge uniformly and adding the aerobic activated sludge into a reaction zone of an anaerobic membrane bioreactor; the aerobic activated sludge is obtained by filtering and screening sludge discharged from an aerobic section of a domestic sewage treatment plant and removing leaves, waste paper and waste plastic impurities in the sludge, wherein the water content of the aerobic activated sludge is more than or equal to 98 wt%; the anaerobic membrane bioreactor is an immersed anaerobic membrane bioreactor, the membrane is a non-woven fabric membrane, and the membrane flux is 120L/m2H; the membrane bracket is a polymethyl methacrylate bracket; anaerobic membrane bioreactorThe top of the water inlet is provided with two water inlets;
(2) two paths of water inflow are carried out from two water inlets at the top of the anaerobic membrane bioreactor, wherein one path of water inflow is communicated with inorganic wastewater, the other path of water inflow is communicated with organic wastewater, and the organic wastewater and the inorganic wastewater are separately introduced into the anaerobic membrane bioreactor; the water inflow velocity of the inorganic wastewater and the water inflow velocity of the organic wastewater are the same, the water inflow velocity of the inorganic wastewater and the water inflow velocity of the organic wastewater are both controlled to be 78mL/h, the total water inflow velocity is 156mL/h, the hydraulic retention time of the sewage to be treated in the anaerobic membrane bioreactor is 38 hours, the C/N of the wastewater is 10:1, a constant-temperature circulating water bath device is adopted to maintain the internal temperature of the anaerobic membrane bioreactor at 23 ℃, nitrogen is introduced into the anaerobic membrane bioreactor for aeration for 20 minutes every 6 hours, the aeration intensity is 5 mL/(L.min), preferably, before the inorganic wastewater and the organic wastewater are introduced, the nitrogen aeration is also carried out on the wastewater to be treated for 30 minutes, and the aeration intensity is 5 mL/(L.min) so as to maintain the. Adjusting the pH to 7.1 with 0.5M HCl; the sludge concentration after the inorganic wastewater and the organic wastewater are introduced is 2000 mg/L. The mechanical stirring makes the matrix in the reactor mix evenly.
(3) Keeping the flow rate of the two paths of inlet water of the anaerobic membrane bioreactor the same, and continuously feeding water. The water outlet is controlled by a liquid level controller, and the water is discharged about every 4 h. The anaerobic membrane bioreactor successfully enriches DNRA bacteria after 137 days of operation, successfully realizes denitrification, anaerobic ammonia oxidation and DNRA combined denitrification reaction and stably operates 204 days of operation, realizes the removal of nitrogen in sewage, has no large fluctuation in nitrogen removal effect, and has a total nitrogen removal rate of about 97%.
Application example:
introducing synthetic wastewater into the method of the embodiment, treating the wastewater, controlling continuous flow inflow by using a peristaltic pump, controlling hydraulic retention time to be 38 hours, controlling outflow by using the peristaltic pump, and controlling the flow rate of each inflow of the reactor to be 78 mL/h; the artificial synthetic wastewater comprises the following specific components in percentage by mass: 1.003 g NaNO3/L,1.999 g KH2PO4/L,40 mg NaOH/L,197 mg MgSO4·7H2O/L,44.32 mg CaCl2/L,39.92 mg FeSO4·7H2O/L,40.48 mg MnCl2·4H2O/L, 10 mg yeast extract, 4mL trace elements/L. The specific components of the trace elements are 50000 mg EDTA/L and 2.20 g ZnSO4·7H2O /L,1.61 g CoCl2·6H2O /L,1.57 g CuSO4· 5H2O /L, 1.10 g (NH4)6Mo7O24·4H2O/L, pH adjusted to about 6.0 with KOH. The feed water of the B strand is 48.09 g of NaCH3COO·3H2O/L。
Measuring the nitrogen concentration once every 3 days, and accordingly evaluating the running state of the reactor, the enrichment degree of DNRA bacteria and the combined denitrification starting effect; and (3) taking sludge samples at the beginning and the end to perform q-PCR analysis once, and evaluating the abundance changes of the anammox bacteria, the denitrifying bacteria and the DNRA bacteria.
In the experimental example of the invention, the anaerobic membrane bioreactor successfully enriches DNRA bacteria after 137 days of operation, successfully realizes denitrification, anaerobic ammonium oxidation and DNRA combined denitrification reaction at 204 days and stably operates, and the q-PCR result of the anaerobic ammonium oxidation bacteria in the sludge of the reactor is 1.45 multiplied by 1012The q-PCR result of copies/g wet slab, denitrifying bacteria was 5.67X 1011 The q-PCR result of copies/g wet slab, DNRA bacteria was 5.85X 1011The number of the anaerobic ammonium oxidation bacteria is increased by 3.06 times compared with the inoculated sludge, the number of the denitrifying bacteria is increased by one order of magnitude, and the number of the DNRA bacteria is increased by two orders of magnitude.
Example 2
The method for treating nitrogen-containing wastewater based on nitrate dissimilatory reduction to ammonium combined with denitrification coupled with anaerobic ammonia oxidation as described in example 1 is different in that:
step (2), the inflow flow rates of inorganic wastewater and organic wastewater are the same, the inflow flow rates of the inorganic wastewater and the organic wastewater are controlled to be 75mL/h, the total inflow flow rate is 150mL/h, the hydraulic retention time of the sewage to be treated in the anaerobic membrane bioreactor is 40 hours, the C/N of the wastewater is 10:1, a constant-temperature circulating water bath device is adopted to maintain the internal temperature of the anaerobic membrane bioreactor at 22 ℃, nitrogen is introduced into the anaerobic membrane bioreactor every 6 hours for aeration for 20 minutes, the aeration intensity is 5 mL/(L.min), preferably, the inorganic wastewater and the organic wastewater are subjected to nitrogen aeration for 30 minutes before introduction, the aeration intensity is 5 mL/(L.min) to maintain the anaerobic environment, and the pH is adjusted to be 7.05 by adopting 0.5M HCl; the sludge concentration after the inorganic wastewater and the organic wastewater are introduced is 1800 mg/L. The mechanical stirring makes the matrix in the reactor mix evenly.
Comparative example 1
A method for treating nitrogen-containing wastewater is carried out according to the method and the conditions of example 1, with the only difference that: and mixing the inorganic wastewater and the organic wastewater, and feeding water at the flow rate of 156 mL/h.
Comparative application Experimental example:
introducing synthetic wastewater into the method of the comparative example, treating the wastewater, controlling continuous flow inflow by using a peristaltic pump, controlling the hydraulic retention time to be 38 hours, controlling outflow by using the peristaltic pump, and controlling the flow rate of each inflow of the reactor to be 156 mL/h; the artificial synthetic wastewater comprises the following specific components in a path A: 1.003 g NaNO3/L,1.999 g KH2PO4/L,40 mg NaOH/L,197 mg MgSO4·7H2O/L,44.32 mg CaCl2/L,39.92 mg FeSO4·7H2O/L,40.48 mg MnCl2·4H2O/L, 10 mg yeast extract, 4mL trace elements/L. The specific components of the trace elements are 50000 mg EDTA/L and 2.20 g ZnSO4·7H2O /L,1.61 g CoCl2·6H2O /L,1.57 g CuSO4· 5H2O /L, 1.10 g (NH4)6Mo7O24·4H2O/L, pH adjusted to about 6.0 with KOH. The water inflow of the path B is 48.09 g NaCH3COO·3H2O/L。
After 137 days of operation, the enrichment degree of NRA bacteria in the reactor is tested, sludge samples are taken at the beginning and the end to perform q-PCR analysis once, and the abundance changes of the anaerobic ammonium oxidation bacteria, the denitrifying bacteria and the DNRA bacteria are evaluated according to the q-PCR analysis.
Tests show that nitrate nitrogen can not be detected in the inlet water, the denitrifying bacteria nirS and nirK in the reactor are few, and DNRA bacteria nrfA can not be detected. DNRA bacteria, denitrifying bacteria and anaerobic ammonium oxidation bacteria cannot be synchronously enriched in the same environment.