A method for accelerating short-cut nitrification start-up through sludge pretreatment

Abstract

This invention relates to the field of environmental protection and wastewater treatment technology, specifically disclosing a method for accelerating short-cut nitrification start-up through sludge pretreatment. The method includes: (1) pretreating activated sludge in a biological reactor for 1-20 days in the presence of low-ammonia-nitrogen water to obtain starved sludge; wherein the ammonia-nitrogen concentration of the low-ammonia-nitrogen water is 0-10 mg / L; and controlling the dissolved oxygen concentration of the pretreatment to 0-4 mg / L; (2) contacting the ammonia-nitrogen wastewater with the starved sludge for short-cut nitrification to obtain effluent. This invention provides a method for accelerating short-cut nitrification start-up through sludge pretreatment. By using starvation coupled with oxygen-limiting regulation, it can achieve rapid start-up and steady-state maintenance of short-cut nitrification, and has advantages such as high ammonia oxidation rate and high nitrite accumulation rate, maintaining the activity of ammonia-oxidizing bacteria (AOB) during short-cut nitrification.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and wastewater treatment technology, specifically to a method for accelerating short-cut nitrification start-up through sludge pretreatment. Background Technology

[0002] With increasing restrictions on nitrogen emissions and growing demands for carbon reduction, traditional nitrification and denitrification processes are facing bottlenecks. Short-cut nitrification is a low-carbon wastewater denitrification technology, often combined with other biological denitrification processes. The short-cut nitrification / anaerobic ammonium oxidation process, in particular, reduces oxygen supply and sludge production, and requires no carbon source, thus reducing carbon emissions and operating costs. To achieve this highly efficient and energy-saving denitrification, controlling the short-cut nitrification process to provide nitrite to these biological denitrification processes is essential. However, due to competition from nitrite-oxidizing bacteria (NOBs), maintaining stable short-cut nitrification over the long term is often difficult. Therefore, the key to achieving stable short-cut nitrification is the long-term stable control of NOB.

[0003] Generally, strategies for suppressing NOB can be divided into two categories: one is process control, such as controlling temperature, dissolved oxygen (DO), free ammonia, free nitrite and intermittent aeration; the other is sludge pretreatment, such as adding NOB inhibitors, ultrasound, ultraviolet light and starvation (no ammonia supply).

[0004] Therefore, it is of great significance to provide a method that can rapidly initiate short-cut nitrification while maintaining the activity of ammonia-oxidizing bacteria (AOB) and simultaneously achieve long-term stable suppression of NOB during short-cut nitrification. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in the existing technology of inhibiting NOB in short-cut nitrification through sludge pretreatment, such as long start-up time and simultaneous inhibition of AOB activity while achieving long-term stable inhibition of NOB.

[0006] To achieve the above objectives, the present invention provides a method for accelerating short-cut nitrification start-up through sludge pretreatment, the method comprising:

[0007] (1) In the presence of low ammonia nitrogen water, activated sludge is pretreated in a biological reactor for 1-20 days to obtain starved sludge; wherein the ammonia nitrogen concentration of the low ammonia nitrogen water is 0-10 mg / L; and the dissolved oxygen concentration of the pretreatment is controlled to be 0-4 mg / L.

[0008] (2) The ammonia nitrogen wastewater is contacted with the starved sludge for short-cut nitrification to obtain effluent.

[0009] The principles of this invention include:

[0010] Under the stress of hunger, AOB and NOB are suppressed to varying degrees, with AOB being able to [restrict / control] through [other mechanisms]. hao and amo The rapid response of AOB (Aerobic Biological Organisms) achieves the goal of resisting starvation. Simultaneously, considering that starvation damages microorganisms, leading to cell death and lysis releasing organic matter, and that the organic nitrogen in this matter can be converted into substrates for AOB survival, while NOB lacks a corresponding mechanism to resist the damage caused by starvation, thus achieving short-cut nitrification. Lower DO concentrations have varying degrees of inhibitory effects on both AOB and NOB; employing a starvation-coupled DO approach to inhibit NOB, thereby achieving short-cut nitrification.

[0011] Compared with existing technologies, the method provided by this invention has at least the following advantages:

[0012] (1) Using the method of the present invention, a nitrite accumulation rate of over 90% can be achieved in a short time, thereby enabling rapid start-up of short-cut nitrification;

[0013] (2) Compared with other sludge pretreatment methods, the present invention does not require the use of special instruments and reagents, and is simple to operate, saves energy and electricity consumption, has a high fault tolerance rate, and can save manpower and material resources;

[0014] (3) The method provided by the present invention has a wide range of applications. It is not only applicable to the research process of batch short-cut nitrification in the laboratory, but also applicable to the research and development of denitrification process for domestic sewage such as municipal sewage treatment plants. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the pretreatment apparatus in a preferred embodiment of the present invention;

[0016] Figure 2 This is a trend chart of nitrate nitrogen, nitrite nitrogen, and NAR in the pretreated effluent of a preferred embodiment of the present invention;

[0017] Figure 3 This is a graph showing the changing trends of effluent ammonia removal rate (ARE) and NAR in a preferred embodiment of the present invention;

[0018] Figure 4 This is a trend graph showing the variation of ARE and NAR in the effluent of a preferred embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures

[0020] 1. Inlet pump; 2. Inlet overflow tank;

[0021] 3. Continuous automatic pH monitor; 4. Automatic DO monitor;

[0022] 5. Stirrer; 6. Acid and alkali storage tank;

[0023] 7. Aeration pipe; 8. Membrane bioreactor;

[0024] 9. Water pump; 10. Pre-treated effluent;

[0025] 11. Hunger and sludge. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] As mentioned above, this invention provides a method for accelerating short-cut nitrification start-up through sludge pretreatment, the method comprising:

[0028] (1) In the presence of low ammonia nitrogen water, activated sludge is pretreated in a biological reactor for 1-20 days to obtain starved sludge; wherein the ammonia nitrogen concentration of the low ammonia nitrogen water is 0-10 mg / L; and the dissolved oxygen concentration of the pretreatment is controlled to be 0-4 mg / L.

[0029] (2) The ammonia nitrogen wastewater is contacted with the starved sludge for short-cut nitrification to obtain effluent.

[0030] It should be noted that the present invention does not have specific requirements for the source of the low ammonia nitrogen water, and it can be, but is not limited to, domestic sewage and rainwater, as well as other low-salt, low-ammonia wastewater.

[0031] According to a preferred embodiment, in step (1), the pretreatment time is 8-12 days. Studies have found that in this preferred case, NOB activity can be inhibited while AOB activity can be better maintained.

[0032] In a preferred embodiment, in step (1), the preprocessing includes a first stage and a second stage, and

[0033] The first stage lasts 1-4 days, with a hydraulic residence time of 10-14 hours; the second stage lasts 5-12 days, with a hydraulic residence time of 5-7 hours.

[0034] In a preferred embodiment, in step (1), the concentration of the pretreated sludge is controlled at 3-8 g / L.

[0035] In a preferred embodiment, in step (1), the pretreatment temperature is 15-30°C and the pH is 7.0-9.0.

[0036] In a preferred embodiment, in step (1), the pretreatment is carried out under stirring conditions and the rotation speed is 150-500 rpm.

[0037] Preferably, an automatic DO monitor is installed in the bioreactor to monitor the dissolved oxygen in the pretreatment.

[0038] Preferably, the dissolved oxygen in the pretreatment is controlled by providing an aeration pipe at the bottom of the bioreactor unit.

[0039] Preferably, in step (1), the pH of the pretreatment is adjusted by adding acid and / or alkali solutions, and

[0040] The acid solution is a hydrochloric acid solution with a concentration of 2-10 wt%, and the alkali solution is a sodium bicarbonate solution with a concentration of 2-10 wt%.

[0041] Preferably, an inlet overflow tank is provided upstream of the bioreactor unit in accordance with the direction of liquid phase flow to prevent sewage from overflowing.

[0042] In a preferred embodiment, in step (1), the bioreactor unit is at least one of a sequencing batch reactor, a moving bed biofilm reactor, an aerated biofilter, and a membrane bioreactor.

[0043] The following combination Figure 1 A preferred embodiment is provided, comprising:

[0044] (1) Low ammonia nitrogen water with an ammonia nitrogen concentration of 0-10 mg / L is introduced into the inlet overflow tank 2 by the inlet pump 1, and then enters the membrane bioreactor 8 of the biological reaction unit through the one-way flow valve to pretreat the activated sludge, thereby obtaining starved sludge 11 and pretreated effluent 10. The pretreated effluent 10 is then drawn out by the effluent pump 9.

[0045] The preprocessing includes a first stage and a second stage, and

[0046] The first stage lasts 1-4 days, and the hydraulic residence time in the first stage is 10-14 hours; the second stage lasts 5-12 days, and the hydraulic residence time in the second stage is 5-7 hours.

[0047] A continuous automatic pH monitor 3 is installed in the membrane bioreactor 8 to monitor the pH during the pretreatment.

[0048] An acid-base storage tank 6 is provided in the membrane bioreactor 8 to add acid and / or alkali solutions to adjust the pH of the pretreatment to 7.0-9.0;

[0049] An automatic DO monitor 4 is installed in the membrane bioreactor 8 to monitor the dissolved oxygen in the pretreatment process;

[0050] A stirrer 5 is installed in the membrane bioreactor 8 within the bioreactor unit and the stirring is performed at a speed of 150-500 rpm.

[0051] An aeration pipe 7 is installed at the bottom of the bioreactor 8 to control the dissolved oxygen in the pretreatment to be 0-4 mg / L;

[0052] (2) The ammonia nitrogen wastewater is contacted with the starved sludge for short-cut nitrification to obtain effluent.

[0053] In a preferred embodiment, the short-range nitration time in step (2) is 1-17 days.

[0054] In a preferred embodiment, in step (2), the sludge concentration of the short-cut nitrification is 1-8 g / L, the pH is 7.0-9.0, and the dissolved oxygen is 0-4 mg / L.

[0055] Preferably, in step (2), the hydraulic retention time of the ammonia nitrogen wastewater in the short-cut nitrification process is 1-24 h.

[0056] It should be noted that the present invention does not impose any requirements on the reactor for the short-cut nitrification, and conventional techniques in the art can be used. For example, it can be carried out in an aerobic bioreactor.

[0057] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0058] Low ammonia nitrogen water:

[0059] Low ammonia nitrogen water I: ammonia nitrogen concentration is 2.0 ± 1.0 mg / L;

[0060] Low ammonia nitrogen water II: ammonia nitrogen concentration is 50±2 mg / L;

[0061] Ammonia nitrogen wastewater: This is domestic sewage, with an ammonia nitrogen concentration of 50±2 mg / L;

[0062] Acid solution: a 5 wt% hydrochloric acid solution;

[0063] Alkaline solution: a 2 wt% sodium bicarbonate solution.

[0064] Example 1

[0065] This embodiment illustrates that the sludge pretreatment method for accelerating short-cut nitrification start-up provided by the present invention is performed according to the following steps:

[0066] (1) Adopt Figure 1 The apparatus shown introduces low-ammonia nitrogen water (low-ammonia nitrogen water I) into the low-ammonia nitrogen water overflow tank 2 via low-ammonia nitrogen water pump 1, and then into the membrane bioreactor 8 of the bioreactor unit through a one-way flow valve to pretreat the activated sludge for 20 days (including the first stage of 1-4 days with a hydraulic retention time of 12 h; the second stage of 5-20 days with a hydraulic retention time of 6 h), resulting in starved sludge 11 and pretreated effluent 10, which is then drawn out by effluent pump 9.

[0067] The membrane bioreactor 8 is equipped with a continuous automatic pH monitor 3 to monitor the pH during the pretreatment.

[0068] An acid-base storage tank 6 is provided in the membrane bioreactor 8 to add acid and / or alkali solutions to adjust the pH of the pretreatment to 7.0 ± 0.5;

[0069] An automatic DO monitor 4 is installed in the membrane bioreactor 8 to monitor the dissolved oxygen in the pretreatment process;

[0070] A stirrer 5 is installed in the membrane bioreactor 8 within the bioreactor unit and the stirring is performed at a speed of 250 rpm.

[0071] An aeration pipe 7 is installed at the bottom of the bioreactor 8 to control the dissolved oxygen in the pretreatment to be 1-2 mg / L;

[0072] The concentration of the pretreated sludge was controlled at 4±0.5 g / L, and the temperature was controlled at 27.0±0.5℃.

[0073] (2) The ammonia nitrogen wastewater and the starved sludge were contacted in an aerobic bioreactor for short-cut nitrification for 17 days to obtain effluent;

[0074] The sludge concentration of the short-cut nitrification is 4±0.5 g / L, the pH is 7.0±0.5, the dissolved oxygen is 1-2 mg / L, and the hydraulic retention time of the ammonia nitrogen wastewater in the short-cut nitrification process is 6 h.

[0075] Monitor and record the nitrate nitrogen, nitrite nitrogen, and NAR in the pretreated effluent daily for 20 days. The results are as follows: Figure 2 As shown in the figure, NAR gradually increases, eventually reaching 60%;

[0076] Monitor and record the daily NAR and ARE of the effluent during short-cut nitrification for 17 days, and the results are as follows: Figure 3 As shown, the highest NAR during short-cut nitrification is 94%, which meets the requirement (90%) for short-cut nitrification startup.

[0077] Example 2

[0078] This embodiment uses a method similar to that of Embodiment 1, except that the first stage of pretreatment in step (1) lasts for 1-4 days, and the second stage lasts for 5-12 days;

[0079] Monitoring of NAR and ARE in daily effluent from short-cut nitrification over 17 days, results are as follows: Figure 4 As shown in the figure, the highest NAR is 94%, which meets the requirement for short-range nitrification start-up (90%).

[0080] and Figure 4 The ARE in the sample can reach up to 69%, indicating that the AOB activity is high in the short-cut nitrification process.

[0081] Comparative Example 1

[0082] This comparative example was conducted using a method similar to that of Example 1. The difference was that in step (1), the low ammonia nitrogen water was low ammonia nitrogen water II. The results showed that the NAR of the pretreated effluent from the bioreactor unit of this comparative example was 54% after 20 days of pretreatment, which was 6% lower than that in Example 1.

[0083] Furthermore, in the later stages of short-cut nitrification, the NAR was only 15% at most, which could not meet the requirement of 90% for short-cut nitrification startup.

[0084] Comparative Example 2

[0085] This comparative example was carried out using a method similar to that of Example 1. The difference was that in step (1), the dissolved oxygen in the pretreatment was controlled to be 4-5 mg / L. The results showed that the NAR of the pretreated effluent of the bioreactor unit in this comparative example was 55% after 20 days of pretreatment, which was 5% lower than that in Example 1.

[0086] Furthermore, in the later stages of short-cut nitrification, the NAR was only 11% at most, which could not meet the requirement of 90% for short-cut nitrification startup.

[0087] Comparative Example 3

[0088] This comparative example was conducted using a method similar to that of Example 1. The difference was that in step (1), the low ammonia nitrogen water was low ammonia nitrogen water II, and the dissolved oxygen in the pretreatment was controlled to be 4-5 mg / L. The results showed that the NAR of the pretreated effluent of the bioreactor unit in this comparative example was 48% after 20 days of pretreatment, which was 12% lower than that in Example 1.

[0089] Furthermore, in the later stages of short-cut nitrification, the NAR was only 14% at most, which could not meet the requirement of 90% for short-cut nitrification startup.

[0090] The results above show that the method for accelerating short-cut nitrification start-up through sludge pretreatment provided by this invention can achieve rapid start-up and steady-state maintenance of short-cut nitrification by starvation coupled with low DO regulation. It also has the advantages of good ammonia oxidation rate and higher nitrite accumulation rate, and can maintain the activity of ammonia oxidizing bacteria (AOB) in short-cut nitrification.

[0091] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for accelerating short-cut nitrification start-up through sludge pretreatment, characterized in that, The method includes: (1) In the presence of low ammonia nitrogen water, activated sludge is pretreated in a biological reactor for 1-20 days to obtain starved sludge; wherein the ammonia nitrogen concentration of the low ammonia nitrogen water is 0-10 mg / L; and the dissolved oxygen concentration of the pretreatment is controlled to be 0-4 mg / L; the pretreatment includes a first stage and a second stage, wherein the first stage lasts for 1-4 days and the hydraulic retention time is 10-14 h in the first stage; the second stage lasts for 5-12 days and the hydraulic retention time is 5-7 h in the second stage; The pretreatment temperature is 15-30℃, and the pH is 7.0-9.0; The ammonia nitrogen concentration of the low ammonia nitrogen water and the dissolved oxygen concentration of the pretreated water are both not 0 mg / L; (2) The ammonia nitrogen wastewater is contacted with the starved sludge for short-cut nitrification to obtain effluent.

2. The method according to claim 1, characterized in that, In step (1), the pretreatment time is 8-12 days.

3. The method according to claim 1 or 2, characterized in that, In step (1), the concentration of the pretreated sludge is controlled at 3-8 g / L.

4. The method according to claim 1 or 2, characterized in that, In step (1), the pretreatment is carried out under stirring conditions and the rotation speed is 150-500 pm.

5. The method according to claim 1 or 2, characterized in that, In step (1), the pH of the pretreatment is adjusted by adding acid and / or alkali solutions, and The acid solution is a hydrochloric acid solution with a concentration of 2-10 wt%, and the alkali solution is a sodium bicarbonate solution with a concentration of 2-10 wt%.

6. The method according to claim 1 or 2, characterized in that, In step (1), the bioreactor unit adopts at least one of the following: sequencing batch reactor, moving bed biofilm reactor, aerated biofilter, and membrane bioreactor.

7. The method according to claim 1 or 2, characterized in that, In step (2).

8. The method according to claim 1 or 2, characterized in that, In step (2), the hydraulic retention time of the ammonia nitrogen wastewater in the short-cut nitrification process is 1-24h.

Images