CN118359353A - Synchronous denitrification and dephosphorization method and device for low-carbon sewage - Google Patents
Synchronous denitrification and dephosphorization method and device for low-carbon sewage Download PDFInfo
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Abstract
The invention discloses a synchronous denitrification and dephosphorization method and device for low-carbon sewage, and belongs to the technical field of sewage treatment. Comprising the following steps: introducing a part of low-carbon sewage and excess sludge into a primary sludge fermentation reactor for anaerobic fermentation to obtain fermentation liquor; introducing the fermentation liquor and the other part of low-carbon sewage into a nitrogen and phosphorus removal reactor for nitrogen and phosphorus removal treatment, and synchronously performing nitrogen and phosphorus removal on the low-carbon sewage in the nitrogen and phosphorus removal reactor. The invention is applied to the aspect of synchronous denitrification and dephosphorization of low-carbon sewage, solves the problems of high production cost and poor denitrification and dephosphorization effect caused by a carbon source in the existing synchronous denitrification and dephosphorization process of low-carbon sewage, can effectively improve the utilization rate of the carbon source of the original sewage, reduces the problem of increased cost caused by the additional carbon source, and simultaneously ensures the synchronous denitrification and dephosphorization effect.
Description
Technical Field
The invention belongs to the technical field of sewage treatment, and particularly relates to a synchronous denitrification and dephosphorization method and device for low-carbon sewage.
Background
In the traditional denitrification process of a sewage treatment plant, ammoniated microorganisms are decomposed and converted into NH 4 + -N by utilizing organic nitrogen compounds under aerobic/anaerobic conditions; nitrosating bacteria and nitrifying bacteria are converted into nitrite (NO 2 - -N) and nitrate (NO 3 - -N) under aerobic conditions by ammonia nitrogen; the denitrifying bacteria uses organic matters as electron donors to reduce the nitric acid nitrogen into nitrogen, and the theoretical value of COD (chemical oxygen demand) consumption required for reducing 1 g nitric acid nitrogen into nitrogen is 2.87 g; in the dephosphorization process, the phosphorus accumulating bacteria still need to take easily degradable carbon sources such as acetic acid, propionic acid, formic acid and the like as a phosphorus release matrix so as to improve the release rate of phosphorus. The competition of the sewage synchronous denitrification and dephosphorization process in the aspect of carbon sources is remarkable, the further improvement of the nitrogen and phosphorus removal rate is limited, and the sewage synchronous denitrification and dephosphorization process is particularly embodied in the low-carbon sewage synchronous deep denitrification and dephosphorization process.
In addition, as the sewage discharge standard is gradually improved, the bottleneck of standard improvement and transformation of the urban sewage treatment plant still lies in that the carbon source of the inlet water is insufficient, so that the requirements of denitrification and dephosphorization are difficult to meet. In recent years, sewage plants increase C/N and C/P by adding easily available high-quality carbon sources, such as glucose, methanol, acetic acid, propionic acid and other additional carbon sources, to sewage, and the mode improves the removal effect of nitrogen and phosphorus in the sewage, but the investment specific gravity is the largest, so that the operation cost of the sewage treatment plant is greatly increased. The primary sedimentation tank unit of the sewage treatment plant removes partial nondegradable granular pollutants in the inlet water by utilizing the natural sedimentation effect of the granular pollutants so as to reduce the load of the subsequent biological treatment unit, but a large amount of carbon sources in the sewage are removed simultaneously when the granular matters are settled, so that the difficulty of subsequent biological denitrification and dephosphorization is increased.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to solve the technical problems of high production cost and poor denitrification and dephosphorization effects caused by a carbon source in the existing low-carbon sewage synchronous denitrification and dephosphorization process, and provides the low-carbon sewage synchronous denitrification and dephosphorization method and device which can effectively improve the utilization rate of the carbon source of the original sewage, reduce the problem of increased cost caused by the additional carbon source and simultaneously ensure the synchronous denitrification and dephosphorization effects.
In order to solve the technical problems, the invention adopts the following technical scheme:
The invention provides a method for synchronously removing nitrogen and phosphorus from low-carbon sewage, which comprises the following steps: introducing a part of low-carbon sewage and excess sludge into a primary sludge fermentation reactor for anaerobic fermentation to obtain fermentation liquor; introducing the fermentation liquor and the other part of low-carbon sewage into a nitrogen and phosphorus removal reactor for nitrogen and phosphorus removal treatment, and synchronously performing nitrogen and phosphorus removal on the low-carbon sewage in the nitrogen and phosphorus removal reactor;
The flow rate of the residual sludge introduced into the primary sludge fermentation reactor is 4-6% of the inflow water flow rate of the low-carbon sewage introduced into the primary sludge fermentation reactor, and the sludge concentration in the primary sludge fermentation reactor is 8000-10000 mg/L;
The hydraulic retention time in the primary sludge fermentation reactor is regulated to be 1.7-2.0 h, the sludge retention time is regulated to be 3-4 d, and the anaerobic fermentation process in the primary sludge fermentation reactor is controlled to reach the hydrolysis acidification stage to obtain the fermentation liquor.
Preferably, a part of the low-carbon sewage and the residual sludge are introduced into a primary sludge fermentation reactor for anaerobic fermentation until:
The mass concentration of the soluble organic matters of the sludge fermentation liquor is improved by 10-30% relative to the mass concentration of SCOD of the low-carbon sewage; and the mass concentration of volatile fatty acid of the sludge fermentation broth is improved by 15-40% relative to the mass concentration of VFA of the low-carbon sewage; and when the ratio of the soluble organic matters to the total nitrogen of the sludge fermentation liquor is improved by 15-35% relative to the SCOD/TN of the low-carbon sewage, obtaining the fermentation liquor, and introducing the fermentation liquor and the other part of the low-carbon sewage into a denitrification and dephosphorization reactor for denitrification and dephosphorization treatment.
Preferably, the physicochemical properties of the excess sludge are as follows: ph=7.8±0.1, suspended solids concentration ss=7000±500 mg/L, volatile suspended matter vss=5500±100 mg/L, scod=40±5 mg/L, total organic matter tcod=8500±500 mg/L, zymophyte relative abundance ratio not less than 20%.
Preferably, the relative abundance of the zymophytes in the sludge in the primary sludge fermentation reactor is 10-20%, and the relative abundance of the zymophytes in the upper sludge is 15-25%.
Preferably, the low-carbon sewage and the residual sludge are uniformly stirred in the primary sludge fermentation reactor, sludge anaerobic fermentation is carried out for 3-4 d, and when the SCOD value of the sludge fermentation liquid reaches more than 95% of the maximum fermentation potential, stirring is stopped and precipitation is started for 30-60 min, so that the fermentation liquid is obtained.
Preferably, the denitrification phosphorus accumulating bacteria and the phosphorus accumulating bacteria are inoculated in the denitrification phosphorus accumulating reactor, and the abundance ratio of the denitrification phosphorus accumulating bacteria to the phosphorus accumulating bacteria is 30-60%.
Preferably, the fermentation liquor and the other part of low-carbon sewage are introduced into a denitrification and dephosphorization reactor, after anaerobic stirring is carried out for 1-3 h, oxygen limiting aeration is carried out for 2.5-4.5 h, the concentration of dissolved oxygen is controlled to be 0.8-1.2 mg/L, and finally stirring and precipitation are stopped for 0.5-1.5 h.
Preferably, the sludge mixed solution is discharged from the denitrification and dephosphorization reactor 5-10 min before stopping aeration stirring, the suspension activated sludge concentration in the denitrification and dephosphorization reactor is maintained to be 4000-6000 mg/L, and the sludge residence time is 12-16 d.
The invention also provides a device for the low-carbon sewage synchronous denitrification and dephosphorization method according to any technical scheme, which comprises the primary sludge fermentation reactor, the denitrification and dephosphorization reactor, a low-carbon sewage raw water tank, a residual sludge storage tank, a fermentation liquor storage tank and a water outlet tank; the outlet of the low-carbon sewage raw water tank is connected with the primary sludge fermentation reactor and one inlet of the nitrogen and phosphorus removal reactor, the outlet of the residual sludge storage tank is connected with the other inlet of the primary sludge fermentation reactor, the inlet of the fermentation liquor storage tank is connected with the outlet of the primary sludge fermentation reactor, the outlet of the fermentation liquor storage tank is connected with the other inlet of the nitrogen and phosphorus removal reactor, and the inlet of the water outlet tank is connected with the outlet of the nitrogen and phosphorus removal reactor.
Preferably, the device also comprises an aeration component connected with the denitrification and dephosphorization reactor and a stirring component arranged in the primary sludge fermentation reactor and the denitrification and dephosphorization reactor.
Compared with the prior art, the invention has the beneficial effects that:
The invention provides a synchronous denitrification and dephosphorization method for low-carbon sewage, which utilizes residual sludge to reflux to strengthen primary sludge fermentation, in a primary sludge fermentation reactor under anaerobic condition, firstly, primary sludge utilizes facultative anaerobic bacteria and obligate anaerobic bacteria extracellular enzymes to decompose solid organic matters in the sludge into simple organic matters mainly natural high molecular compounds, and then the simple organic matters are converted into fatty acids and alcohols such as acetic acid, propionic acid, acid and the like through anaerobic fermentation and oxidation under the action of acidogenic bacteria, and organic matter intermediate products are used as electron donor and acceptor to convert complex organic matters into high-quality carbon sources which are easy to use; meanwhile, the reflux of the surplus sludge is beneficial to improving the proportion and activity of the phosphorus removal flora of the primary sludge, can further improve the storage efficiency of carbon sources PHAs in the sludge, has the advantages of low sludge yield, reduced recycling of the surplus sludge and stable operation, and can solve the problem that the effluent carbon source of the traditional primary sedimentation tank is difficult to meet the requirement of subsequent biological nitrogen and phosphorus removal.
Drawings
FIG. 1 is a schematic diagram of a synchronous denitrification and dephosphorization device for low-carbon sewage provided by an embodiment of the invention;
In the above figures: 1. a raw water tank; 2. a surplus sludge storage tank; 3. a primary sludge fermentation reactor; 4. a fermentation liquor storage tank; 5. a denitrification and dephosphorization reactor; 6. and a water outlet tank.
Detailed Description
The following detailed description of the technical solutions in the specific embodiments of the present invention will be given with reference to the accompanying drawings. It is apparent that the described embodiments are only some specific implementations, but not all implementations, of the general technical solution of the present invention. All other embodiments, which are obtained by those skilled in the art based on the general inventive concept, fall within the scope of the present invention.
The invention provides a method for synchronously removing nitrogen and phosphorus from low-carbon sewage, which comprises the following steps: introducing a part of low-carbon sewage and excess sludge into a primary sludge fermentation reactor 3 for anaerobic fermentation to obtain fermentation liquor; introducing the fermentation liquor and the other part of low-carbon sewage into a nitrogen and phosphorus removal reactor 5 for nitrogen and phosphorus removal treatment, and synchronously performing nitrogen and phosphorus removal on the low-carbon sewage in the nitrogen and phosphorus removal reactor 5;
The flow rate of the excess sludge introduced into the primary sludge fermentation reactor 3 is 4-6% of the inflow water flow rate of the low-carbon sewage introduced into the primary sludge fermentation reactor 3, and the sludge concentration in the primary sludge fermentation reactor 3 is 8000-10000 mg/L;
The hydraulic retention time in the primary sludge fermentation reactor 3 is regulated to be 1.7-2.0 h, the sludge retention time is regulated to be 3-4 d, and the anaerobic fermentation process in the primary sludge fermentation reactor 3 is controlled to reach the hydrolysis acidification stage to obtain the fermentation liquor.
The traditional activated sludge process is mainly adopted by most urban sewage treatment plants in China, along with the annual increase of urban domestic sewage discharge, the sewage discharge standard is increasingly improved, the carbon nitrogen ratio (C/N) of the urban domestic sewage is generally less than 4, the treatment efficiency of the traditional nitrification and denitrification process is greatly limited due to the lack of a carbon source, more easily-utilized high-quality alternative carbon sources (such as methanol and the like) are required to be added, and the carbon discharge and the running cost of the sewage treatment plants are also greatly improved. In addition, the production of surplus sludge and solid waste is estimated to be about 4000 ten thousand tons each year in China, and the treatment and reutilization of sludge face a great challenge. In the method for synchronously denitrifying and dephosphorizing the low-carbon sewage, the residual sludge is utilized to reflux to strengthen the primary sludge fermentation, in a primary sludge fermentation reactor 3 under anaerobic condition, the primary sludge is firstly decomposed into simple organic matters by utilizing facultative anaerobic bacteria and exoenzyme of obligate anaerobic bacteria, wherein solid organic matters in the sludge are mainly natural high molecular compounds, and then the simple organic matters are converted into acetic acid, propionic acid, fatty acid such as acid, alcohols and the like through anaerobic fermentation and oxidation under the action of acidogenic bacteria, and organic matter intermediate products are used as electron donors to convert complex organic matters into easy-to-use high-quality carbon sources; meanwhile, the reflux of the surplus sludge is beneficial to improving the proportion and activity of the phosphorus removal flora of the primary sludge, can further improve the storage efficiency of carbon sources PHAs in the sludge, has the advantages of low sludge yield, reduced recycling of the surplus sludge and stable operation, and can solve the problem that the effluent carbon source of the traditional primary sedimentation tank is difficult to meet the requirement of subsequent biological nitrogen and phosphorus removal.
The invention improves the activity of the primary sludge, improves the acid production performance of the primary sludge fermentation and greatly improves the denitrification and dephosphorization of sewage by refluxing a certain proportion of secondary sedimentation tank surplus sludge to the primary sedimentation sludge fermentation reactor 3 (replacing the traditional primary sedimentation tank) compared with a primary sedimentation sludge system because the number and the composition of the active microorganisms in the surplus sludge are different. Specifically, low-carbon domestic sewage and a certain proportion of residual activated sludge enter a sludge fermentation SBR 1 (namely a primary sludge fermentation reactor 3) for inoculating primary sludge, and the sludge is subjected to anaerobic stirring to convert the difficultly biodegradable organic matters in the sludge into easily biodegradable organic matters; then, the sludge fermentation liquor mixture containing ammonia nitrogen, phosphate, acetic acid and the like enters a fermentation liquor storage tank 4 and enters a nitrogen and phosphorus removal SBR 2 (namely a nitrogen and phosphorus removal reactor 5) together with the low-carbon domestic sewage; the denitrification and dephosphorization SBR 2 operates in an anaerobic-limited oxygen mode, organic matters in sewage and fermentation liquor can be simultaneously utilized by phosphorus accumulating bacteria (PAOs) and polysaccharide bacteria (GAOs) to be stored as an internal carbon source in the form of poly-beta-hydroxyalkanoate (PHA), NH 4 + -N in sewage is NO 3 - -N by Ammonia Oxidizing Bacteria (AOB) and nitrite Nitrogen Oxidizing Bacteria (NOB) in an oxygen limiting stage, the PAOs complete aerobic and denitrification phosphorus absorption, the GAOs carry out denitrification and denitrification, and effluent enters the effluent water tank 6. The method connects primary sludge fermentation and synchronous nitrification and denitrification dephosphorization (SNDPR) technology in series, and residual sludge reflux can strengthen the primary sludge to be used in-situ fermentation and resource utilization, and is beneficial to primary stabilization and reduction of sludge; in addition, through regulating and controlling the water inlet proportion of the primary sludge fermentation liquor and the domestic sewage, the water inlet carbon-nitrogen ratio and the carbon-phosphorus ratio can be improved, the nitrogen and phosphorus removal rate of the SNDPR technology is further improved, the addition of a zero carbon source is realized, and the problem that the water outlet carbon source of the traditional primary sedimentation tank is difficult to meet the requirement of subsequent biological nitrogen and phosphorus removal is solved.
According to the technical scheme, the hydraulic retention time in the primary sludge fermentation reactor 3 is limited to be 1.7-2.0 h, the sludge retention time is 3-4 d, so that the anaerobic fermentation process in the primary sludge fermentation reactor 3 can be ensured to go to the hydrolysis acidification stage instead of going to the methanogenesis stage (a large amount of volatile fatty acids VFAs are generated in the hydrolysis acidification stage), namely, a large amount of refractory organic matters in the primary sludge fermentation reactor 3 are ensured to be degraded into a high-quality carbon source which is easy to utilize through in-situ fermentation as much as possible, the conversion rate of the high-quality carbon source is improved, and the high-quality carbon source loss and the cost waste caused by over fermentation are avoided. It should be noted that, in order to ensure that the anaerobic fermentation process in the primary sludge fermentation reactor 3 goes to the hydrolytic acidification stage and not to the methanogenesis stage, not only is the HRT (hydraulic retention time) regulated to be 1.7-2.0 h and the bottom SRT (sludge retention time) regulated to be 3-4 d, but also the flow rate of the residual sludge introduced into the primary sludge fermentation reactor 3 and the sludge concentration in the primary sludge fermentation reactor 3 defined by the technical scheme of the invention are required, because the flow rate of the residual sludge introduced into the primary sludge fermentation reactor 3 directly influences the amount of refractory organic matters introduced into the primary sludge fermentation reactor 3, but also the quantity and composition of active microorganisms introduced into the primary sludge fermentation reactor 3, which have important influences on the anaerobic fermentation process in the primary sludge fermentation reactor 3, thereby influencing the amount and composition of high-quality carbon sources in the obtained fermentation broth and further influencing the subsequent denitrification and dephosphorization effects.
In a preferred embodiment, a portion of the low carbon sewage and excess sludge is fed into the primary sludge fermentation reactor 3 for anaerobic fermentation to:
The mass concentration of soluble organic matters (SCOD) of the sludge fermentation liquor is improved by 10-30% relative to the mass concentration of SCOD of the low-carbon sewage; and the Volatile Fatty Acid (VFA) mass concentration of the sludge fermentation broth is increased by 15-40% relative to the VFA mass concentration of the low carbon wastewater; and when the ratio (SCOD/TN) of the soluble organic matters and the total nitrogen of the sludge fermentation broth is increased by 15-35% relative to the SCOD/TN of the low-carbon sewage, obtaining the fermentation broth, and introducing the fermentation broth and the other part of the low-carbon sewage into a denitrification and dephosphorization reactor 5 for denitrification and dephosphorization treatment.
According to the technical scheme, the physicochemical index of the sludge fermentation liquid in the primary sludge fermentation reactor 3 is used as the completion index for limiting the sludge fermentation acid production in the primary sludge fermentation reactor 3, so that the control and adjustment of the sludge fermentation in the primary sludge fermentation reactor 3 are facilitated, the physicochemical index of the fermentation liquid fed into the denitrification and dephosphorization reactor 5 is further ensured to meet the requirement of synchronous denitrification and dephosphorization, and the denitrification and dephosphorization effect is improved.
In a preferred embodiment, the physicochemical properties of the excess sludge are as follows: ph=7.8±0.1, suspended solids concentration ss=7000±500 mg/L, volatile suspended matter vss=5500±100 mg/L, scod=40±5 mg/L, total organic matter tcod=8500±500 mg/L, zymophyte relative abundance ratio not less than 20%. The technical scheme further limits the physicochemical properties of the excess sludge, further ensures that physicochemical indexes of fermentation liquor obtained by fermentation in the primary sludge fermentation reactor 3 meet the requirement of synchronous denitrification and dephosphorization, remains relatively stable, and ensures the denitrification and dephosphorization effects.
In a preferred embodiment, the relative abundance of the fermenting bacteria of the sludge in the primary sludge fermentation reactor 3 is 10-20% and the relative abundance of the fermenting bacteria of the upper sludge is 15-25%. The abundance ratio of zymophyte in the excess sludge which is introduced into the primary sludge fermentation reactor 3 is more than 19.2 percent, and the abundance ratio of zymophyte at the level is first four, namely, the mycofamily (0.1073), the microfilament genus (0.039), the trichomonas genus (0.0211) and the lactic acid coccus genus (0.0108).
In a preferred embodiment, the low-carbon sewage and the residual sludge are uniformly stirred in the primary sludge fermentation reactor 3, sludge anaerobic fermentation is carried out for 3-4 d, and when the SCOD value of the sludge fermentation liquid reaches more than 95% of the maximum fermentation potential, stirring is stopped and precipitation is started for 30-60 min, so that the fermentation liquid is obtained.
Further, the wastewater of the primary sedimentation tank for active fermentation is a sludge mixed solution with the sludge concentration of about 3000-4000 mg/L, and the sludge concentration at the water outlet weir position of the primary sedimentation tank (primary sedimentation sludge fermentation reactor 3) is controlled to be within 500 mg/L in consideration that the denitrification and dephosphorization performance and the microbial community structure can be influenced by the wastewater entering the subsequent A2O biochemical tank.
In a preferred embodiment, the denitrification phosphorus accumulating bacteria and phosphorus accumulating bacteria are inoculated in the denitrification phosphorus accumulating reactor 5, and the abundance ratio of the denitrification phosphorus accumulating bacteria to the phosphorus accumulating bacteria is 30-60%. The technical scheme specifically limits the abundance ratio of denitrifying phosphorus accumulating bacteria to phosphorus accumulating bacteria, and it can be understood that the abundance ratio can be any point value within 35%, 40%, 45%, 50%, 55% and the range thereof.
In a preferred embodiment, the fermentation liquor and the other part of low-carbon sewage are introduced into the denitrification and dephosphorization reactor 5, after anaerobic stirring for 1-3 h, oxygen limiting aeration is carried out for 2.5-4.5-h, the concentration of dissolved oxygen is controlled to be 0.8-1.2 mg/L, and finally stirring and precipitation are stopped for 0.5-1.5 h. Further, the sludge mixed solution is discharged from the denitrification and dephosphorization reactor 5 at 5-10 min before stopping aeration stirring, the suspension activated sludge concentration in the denitrification and dephosphorization reactor 5 is maintained to be 4000-6000 mg/L, and the sludge residence time is 12-16 d. In the nitrogen and phosphorus removal SBR 2 of the present invention, nitrogen and phosphorus removal (nitrogen and phosphorus removal using an organic carbon source in fermentation supernatant liquid produced by SBR 1) is performed, and the nitrogen and phosphorus removal reactor does not include a fermentation process. Compared with the traditional denitrification and dephosphorization process, the anaerobic fermentation of the invention generates a large amount of short chain fatty acid SCFAs which are high-quality carbon sources of a biological denitrification and dephosphorization system, the denitrification and dephosphorization efficiency of the sludge fermentation broth used as the carbon source and added with SBR (F-SBR) is higher than that of the sludge fermentation broth used as the carbon source and added with SBR (A-SBR) and the short-range nitrification and denitrification and dephosphorization phenomena of the F-SBR are obvious compared with those of the A-SBR, because humic acid in the fermentation broth inhibits NOB activity in the F-SBR system, and fewer GAOs, more PAOs and DPAOs in the F-SBR system are the reasons of denitrification and dephosphorization in the anoxic section.
According to the process for realizing the synchronous denitrification and dephosphorization of the low-carbon sewage by the residual sludge reflux reinforced primary sludge fermentation, the residual sludge of the biochemical tank with the concentration of 10 g/L is subjected to reflux reinforced primary sludge fermentation according to the economic reflux ratio of 4-6% in an inert environment so as to utilize the solidified carbon source which should be abandoned in the primary sludge, and high-quality available carbon sources (volatile fatty acid VFAs) are generated by conversion and are used for subsequent biological denitrification and dephosphorization, so that the carbon source structure of the low C/N of the inflow water is improved, the sludge is reduced, the carbon emission is reduced, and the recycling of the sludge energy resource is realized.
The method for synchronously removing nitrogen and phosphorus from the low-carbon sewage comprises the following steps:
1) The key technologies of primary sludge fermentation, surplus sludge recycling, synchronous nitrification, denitrification, dephosphorization and the like are organically combined, so that the organic internal carbon source in the sludge is utilized to the maximum extent, the utilization rate of raw water carbon sources is improved, the addition of external carbon sources for biological treatment of sewage is reduced, the problem that the carbon source discharged from the traditional primary sedimentation tank is difficult to meet the requirement of subsequent biological denitrification and dephosphorization is solved, and a combined system with low energy consumption, low cost and integrated denitrification and dephosphorization is realized;
2) In the modern process of China, mud water treatment is increasingly emphasized, the change of sewage purification and sludge treatment is positively promoted on the basis of the existing sewage treatment, the resource utilization efficiency is improved, the sludge is greatly developed and utilized, the economic benefit and the environmental benefit win one of the effective measures are realized, the innovation provides a novel primary sedimentation sludge in-situ fermentation process, the efficient in-situ fermentation acid production and reduction of primary sedimentation tank sludge can be realized, and meanwhile, the macromolecular organic matters which are difficult to degrade in sewage can be hydrolyzed into the easily degradable organic matters, so that the technology can optimize the carbon source structure and carbon-nitrogen ratio of the primary sedimentation water, improve the sludge activity and denitrification and dephosphorization capability of a subsequent biochemical tank, realize zero carbon source addition, reduce the treatment cost of the subsequent residual sludge, save the running cost and provide theoretical basis and technical support for the carbon source development and the primary sedimentation sludge reduction of a primary sedimentation system of a domestic sewage treatment plant;
3) The technical scheme of the invention can effectively solve the problems of water resource shortage, imperfect sewage treatment process and sludge treatment technology, large energy consumption and the like in China, realize energy-saving and consumption-reducing advanced treatment and sludge reduction of the zero-carbon-source added town sewage, has particularly obvious advantages in low carbon-nitrogen-ratio town sewage treatment, effectively solves the problem of secondary pollution of sludge to ecological environment, effectively reduces the energy resource consumption in the sewage treatment process, accelerates the promotion of the quick implementation of the environmental protection target of double carbon in the sewage treatment industry in China, and has obvious benefits.
In conclusion, the method for realizing synchronous denitrification and dephosphorization of low-carbon sewage by the residual sludge reflux reinforced primary sludge fermentation can provide technical support for the efficient treatment of town sewage with zero carbon source addition, energy conservation and consumption reduction, and can effectively improve the carbon source utilization rate of raw sewage by constructing an active primary sedimentation system and an in-situ carbon source development technology, thereby realizing the effects of zero carbon source addition and denitrification and dephosphorization of a subsequent biochemical pond.
Another aspect of the present invention provides a device for the method for simultaneous denitrification and dephosphorization of low-carbon sewage according to any one of the above-mentioned aspects, comprising the primary sludge fermentation reactor 3, the denitrification and dephosphorization reactor 5, the low-carbon sewage raw water tank 1, the residual sludge storage tank 2, the fermentation liquor storage tank 4, and the effluent water tank 6; the outlet of the low-carbon sewage raw water tank 1 is connected with the primary sludge fermentation reactor 3 and one inlet of the denitrification and dephosphorization reactor 5, the outlet of the residual sludge storage tank 2 is connected with the other inlet of the primary sludge fermentation reactor 3, the inlet of the fermentation liquor storage tank 4 is connected with the outlet of the primary sludge fermentation reactor 3, the outlet of the fermentation liquor storage tank 4 is connected with the other inlet of the denitrification and dephosphorization reactor 5, and the inlet of the water outlet tank 6 is connected with the outlet of the denitrification and dephosphorization reactor 5. In a preferred embodiment, the device also comprises an aeration component connected with the denitrification and dephosphorization reactor 5 and a stirring component arranged in the primary sludge fermentation reactor 3 and the denitrification and dephosphorization reactor 5.
The invention provides a method and a device for realizing synchronous denitrification and dephosphorization of low-carbon sewage by using residual sludge to reflux and strengthen primary sludge fermentation, and provides a device and a method for treating municipal sewage by saving energy and reducing consumption by combining key process technologies such as co-fermentation acid production, synchronous nitrification and denitrification dephosphorization of residual sludge and primary sludge of a sewage treatment plant, namely, sewage inflow water and partial residual sludge reflux enter a primary sludge reactor (primary sludge fermentation reactor 3), difficultly biodegradable organic matters in the sludge are converted into easily biodegradable organic matters through anaerobic fermentation, then sludge fermentation liquor enters a fermentation liquor water tank, and enters denitrification and dephosphorization SBR 2 together with domestic sewage inflow water, and finally sewage denitrification and dephosphorization is realized by taking fermentation liquor as a supplementary carbon source. According to the method, the anaerobic fermentation of the residual sludge reflux primary sedimentation sludge and the synchronous nitrification and denitrification dephosphorization process are connected in series, and the residual sludge reflux can strengthen the in-situ fermentation acid production of the primary sedimentation sludge, so that the recycling and sludge reduction of the residual sludge are facilitated, the utilization rate of raw water carbon sources is improved, the addition of external carbon sources in sewage biological treatment is reduced, and the problem that the carbon sources in the effluent of the traditional primary sedimentation tank are difficult to meet the requirements of subsequent biological denitrification and dephosphorization is solved.
The device specifically comprises a domestic low-carbon sewage raw water tank 1, a residual sludge storage tank 2, a primary sludge fermentation reactor 3 (sludge fermentation SBR 1), a fermentation liquor storage tank 4, a denitrification and dephosphorization reactor 5 (denitrification and dephosphorization SBR 2) and a water outlet tank 6; wherein, the domestic low-carbon sewage raw water tank 1 is connected with the primary sludge fermentation reactor 3 through the water inlet pump I; the living low-carbon sewage raw water tank 1 is connected with the denitrification and dephosphorization reactor 5 through a water inlet pump II; the excess sludge storage tank 2 is connected with the primary sludge fermentation reactor 3 through a sludge inlet pump; the primary sludge fermentation reactor 3 is connected with a fermentation liquor storage tank 4 through a drainage electric valve I; the fermentation liquor water storage tank 4 is connected with a denitrification and dephosphorization reactor 5 through a water inlet pump III; the denitrification and dephosphorization reactor 5 is connected with a water outlet tank 6 through an electric drainage valve II; the primary sludge fermentation reactor 3 is internally provided with a centralized controller I, a stirring component I, a water inlet pump I, a sludge inlet pump, a drainage electric valve I and a sampling port I; the denitrification and dephosphorization reactor 5 is internally provided with a water inlet pump II, a water inlet pump III, a stirring assembly II, a centralized controller, an aeration assembly, a drainage electric valve II and a sampling port II;
The sewage and sludge treatment process in the device comprises the following steps: municipal domestic sewage is sent into the primary sludge fermentation reactor 3 from the domestic sewage raw water tank 1 through a water inlet pump, and the excess sludge of the sewage treatment plant is sent into the primary sludge fermentation reactor 3 from the excess sludge storage tank 2 through a sludge inlet pump; in the primary sludge fermentation reactor 3, facultative anaerobes and obligate anaerobes utilize the anaerobic fermentation of difficultly biodegradable organic matters (starch, protein, fat and the like) in the sludge to convert into readily biodegradable organic matters (fatty acids, alcohols and the like such as acetic acid, propionic acid and the like) and simultaneously release ammonia nitrogen and phosphate, and in the process, the primary sludge fermentation reactor 3 always maintains an anaerobic stirring state; after the primary sludge fermentation reactor 3 finishes fermentation, the sludge fermentation liquor is discharged into a fermentation liquor storage tank 4 through a drainage electric valve; the urban domestic sewage raw water tank 1 is pumped into the denitrification and dephosphorization reactor 5, and sludge fermentation liquor containing easily biodegradable organic matters is pumped into the denitrification and dephosphorization reactor 5 from the fermentation liquor storage tank 4; in the denitrification and dephosphorization reactor 5, denitrification and dephosphorization are completed in a period of operation in an anaerobic-limited oxygen mode.
The starting and operating steps of the device are as follows:
1) And (3) starting a system:
Adding primary sludge of a sewage treatment plant of the Qingdao into a primary sludge fermentation reactor 3, so that the concentration of the primary sludge in the reactor after inoculation reaches 8000-12000 mg/L; the inoculation sludge for the test of the denitrification and dephosphorization reactor 5 is taken from a secondary sedimentation tank of an A2/O reactor of a certain laboratory, the abundance ratio of denitrifying phosphorus accumulating bacteria (DPAOs) and phosphorus accumulating bacteria (PAOs) in the inoculation sludge is about 30-60%, and the concentration of the activated sludge in the reactor after inoculation reaches 4000-6000 mg/L;
2) The runtime adjustment operation is as follows:
municipal domestic sewage is put into a domestic sewage raw water tank 1, and excess sludge of a sewage treatment plant is put into an excess sludge storage tank 2;
Domestic sewage is pumped into the primary sludge fermentation reactor 3 through a water inlet pump, and residual sludge is pumped into the primary sludge fermentation reactor 3 from the residual sludge storage tank 2 through the sludge inlet pump according to the water inlet flow of 5-10%;
The primary sludge fermentation reactor 3 starts a stirring device I to uniformly mix the sludge in the reactor, anaerobic fermentation is carried out on the sludge for 2 to 6 d, and when the SCOD value reaches more than 95 percent of the maximum fermentation potential, stirring is stopped to start precipitation for 30 to 60 min; the sludge fermentation liquor enters a fermentation liquor storage tank 4 through a drainage electric valve I, and the reactor is idle for 20-40 min to enter the next operation period;
starting a water inlet pump II to pump domestic sewage into the denitrification and dephosphorization reactor 5, and starting a water inlet pump III to pump sludge fermentation liquor into the denitrification and dephosphorization reactor 5;
The denitrification and dephosphorization reactor 5 starts a stirring device to uniformly mix the reactor, anaerobic stirring is carried out for 1-3 h, then oxygen limiting aeration is carried out for 2.5-4.5 h, an aeration pump is used for adjusting a rotor flowmeter to control air aeration to enable the concentration of dissolved oxygen to be 0.8-1.2 mg/L, finally stirring and precipitation are stopped for 0.5-1.5 h, supernatant is discharged into a water outlet tank 6 through an electric drain valve, and the reactor is idle for 60-90 min and then the next cycle is carried out;
In addition, when the denitrification and dephosphorization reactor 5 is operated, the sludge mixed solution 100-300 mL is discharged from 5-10 min before stopping aeration stirring to maintain the concentration of suspended activated sludge in the range of 4000-6000 mg/L and the corresponding sludge age (SRT is maintained at 12-16 d).
In order to more clearly and in detail describe the method and the device for synchronous denitrification and dephosphorization of low-carbon sewage provided by the embodiment of the invention, the following description will be made with reference to specific embodiments.
Example 1
As shown in fig. 1, the device comprises a domestic low-carbon sewage raw water tank 1, a residual sludge storage tank 2, a primary sludge fermentation reactor 3 (sludge fermentation SBR 1), a fermentation liquor storage tank 4, a nitrogen and phosphorus removal reactor 5 (nitrogen and phosphorus removal SBR 2) and a water outlet tank 6; wherein, the domestic low-carbon sewage raw water tank 1 is connected with the primary sludge fermentation reactor 3 through the water inlet pump I; the living low-carbon sewage raw water tank 1 is connected with the denitrification and dephosphorization reactor 5 through a water inlet pump II; the excess sludge storage tank 2 is connected with the primary sludge fermentation reactor 3 through a sludge inlet pump; the primary sludge fermentation reactor 3 is connected with a fermentation liquor storage tank 4 through a drainage electric valve I; the fermentation liquor water storage tank 4 is connected with a denitrification and dephosphorization reactor 5 through a water inlet pump III; the denitrification and dephosphorization reactor 5 is connected with a water outlet tank 6 through an electric drainage valve II; the primary sludge fermentation reactor 3 is internally provided with a centralized controller I, a stirring component I, a water inlet pump I, a sludge inlet pump, a drainage electric valve I and a sampling port I; the denitrification and dephosphorization reactor 5 is internally provided with a water inlet pump II, a water inlet pump III, a stirring assembly II, a centralized controller, an aeration assembly, a drainage electric valve II and a sampling port II.
In the test process, the primary sludge fermentation reactor 3 and the denitrification and dephosphorization reactor 5 used in the test are made of organic glass, the effective volume of the primary sludge fermentation reactor 3 is 3L, a stirring component and a centralized controller are arranged, a plurality of layers of tinfoil are wrapped on the surface of the reactor, the sealing place is sealed by rubber, so that an internal anaerobic microenvironment is created, the effective volume of the denitrification and dephosphorization reactor 5 is 10L, and an aeration pump, a stirring component and the centralized controller are arranged; the primary sludge of a sewage treatment plant in Qingdao city and the biochemical sludge of a secondary sedimentation tank in a laboratory are inoculated in a test, and the sewage inflow water quality of the sewage treatment plant in Qingdao city is simulated.
The specific operation process for sludge fermentation and wastewater treatment by using the device is as follows:
1) And (3) starting a system:
adding primary sludge of a sewage treatment plant into a primary sludge fermentation reactor 3, so that the sludge concentration in the reactor after inoculation reaches about 10000 mg/L;
Inoculating sludge for the test of the denitrification and dephosphorization reactor 5 is taken from a secondary sedimentation tank of an A2/O reactor of a certain laboratory, and the concentration of activated sludge in the reactor after inoculation reaches 4000 mg/L;
adding the surplus sludge of the sewage treatment plant into a surplus sludge storage tank 2 to ensure that the concentration of the surplus sludge is about 15000 mg/L;
the domestic sewage is added into a raw water tank 1 of the domestic sewage, and the water quality is 80 mg/L COD, 35 mg/L NH 4 +-N、2 mg/L PO4 3- -P, 0.1% of trace elements 1 and 0.1% of trace elements 2;
2) The runtime adjustment operation is as follows:
municipal domestic sewage is put into a domestic sewage raw water tank 1, and excess sludge of a sewage treatment plant is put into an excess sludge storage tank 2;
domestic sewage is pumped into the primary sludge fermentation reactor 3 through a water inlet pump, and residual sludge is pumped into the primary sludge fermentation reactor 3 from the residual sludge storage tank 2 through the sludge inlet pump according to the water inlet flow of 7%;
the primary sludge fermentation reactor 3 starts a stirring component I to uniformly mix the inside of the reactor, carries out anaerobic sludge fermentation 3d, and stops stirring to start 60 min precipitation when the SCOD value reaches more than 95% of the maximum fermentation potential; the sludge fermentation liquor is discharged into a fermentation liquor storage tank 4 through a drainage electric valve I, and the reactor is idle for 30min to enter the next operation period;
starting a water inlet pump II to pump domestic sewage into the denitrification and dephosphorization reactor 5, and starting a water inlet pump III to pump sludge fermentation liquor into the denitrification and dephosphorization reactor 5;
the denitrification and dephosphorization reactor 5 starts a stirring device to uniformly mix the reactor, anaerobic stirring is carried out for 2.5 h, then oxygen limiting aeration is carried out for 3.5 h, an aeration pump is used for adjusting a rotor flowmeter to control air aeration to enable the concentration of dissolved oxygen to be 0.8-1.2 mg/L, finally stirring and precipitation are stopped for 1 h, supernatant is discharged into a water outlet tank 6 through an electric drain valve, and the reactor is idle for 60 min and then carries out the next period;
In addition, when the denitrification and dephosphorization reactor 5 is operated, the appropriate sludge mixed solution is discharged 5-10 min before stopping aeration agitation to maintain the suspended activated sludge concentration within 4000 mg/L and the corresponding sludge age (SRT is maintained at 15 d).
The test results show that: after the operation is stable, the concentration of SCOD and VFAs in the primary sludge fermentation reactor 3 is continuously increased, the maximum release amount of the VFAs is 160 mg/L, and the SCOD/NH 4 + -N is increased from original 2.3 to 4.3, so that the increase of 86.6 percent is achieved;
The COD concentration of the effluent of the denitrification and dephosphorization reactor 5 is 22-45 mg/L, the NH 4 + -N concentration is less than 3 mg/L, the NO 2 - -N concentration is less than 2 mg/L, the NO 3 - -N concentration is less than 8 mg/L, and the PO 4 3- -P concentration is less than 0.5 mg/L.
Claims (10)
1. The method for synchronously denitrifying and dephosphorizing the low-carbon sewage is characterized by comprising the following steps: introducing a part of low-carbon sewage and excess sludge into a primary sludge fermentation reactor for anaerobic fermentation to obtain fermentation liquor; introducing the fermentation liquor and the other part of low-carbon sewage into a nitrogen and phosphorus removal reactor for nitrogen and phosphorus removal treatment, and synchronously performing nitrogen and phosphorus removal on the low-carbon sewage in the nitrogen and phosphorus removal reactor;
The flow rate of the residual sludge introduced into the primary sludge fermentation reactor is 4-6% of the inflow water flow rate of the low-carbon sewage introduced into the primary sludge fermentation reactor, and the sludge concentration in the primary sludge fermentation reactor is 8000-10000 mg/L;
The hydraulic retention time in the primary sludge fermentation reactor is regulated to be 1.7-2.0 h, the sludge retention time is regulated to be 3-4 d, and the anaerobic fermentation process in the primary sludge fermentation reactor is controlled to reach the hydrolysis acidification stage to obtain the fermentation liquor.
2. The method for simultaneous denitrification and dephosphorization of low carbon sewage according to claim 1, wherein a part of low carbon sewage and residual sludge are fed into a primary sludge fermentation reactor for anaerobic fermentation until:
The mass concentration of the soluble organic matters of the sludge fermentation liquor is improved by 10-30% relative to the mass concentration of SCOD of the low-carbon sewage; and the mass concentration of volatile fatty acid of the sludge fermentation broth is improved by 15-40% relative to the mass concentration of VFA of the low-carbon sewage; and when the ratio of the soluble organic matters to the total nitrogen of the sludge fermentation liquor is improved by 15-35% relative to the SCOD/TN of the low-carbon sewage, obtaining the fermentation liquor, and introducing the fermentation liquor and the other part of the low-carbon sewage into a denitrification and dephosphorization reactor for denitrification and dephosphorization treatment.
3. The method for simultaneous denitrification and dephosphorization of low carbon sewage according to claim 1, wherein the physicochemical properties of the excess sludge are as follows: ph=7.8±0.1, suspended solids concentration ss=7000±500 mg/L, volatile suspended matter vss=5500±100 mg/L, scod=40±5 mg/L, total organic matter tcod=8500±500 mg/L, zymophyte relative abundance ratio not less than 20%.
4. A method for simultaneous denitrification and dephosphorization of low carbon wastewater according to claim 3 wherein said relative abundance of said fermentation bacteria in said primary sludge fermentation reactor is 10-20% and said relative abundance of said fermentation bacteria in said upper sludge is 15-25%.
5. The method for simultaneous denitrification and dephosphorization of low carbon sewage according to claim 1, wherein the low carbon sewage and the surplus sludge are uniformly stirred in the primary sludge fermentation reactor, anaerobic sludge fermentation is carried out for 3-4 d, and when the SCOD value of the sludge fermentation liquid reaches more than 95% of the maximum fermentation potential, stirring is stopped and precipitation is started for 30-60 min, so as to obtain the fermentation liquid.
6. The method for synchronous denitrification and dephosphorization of low-carbon sewage according to claim 1, wherein the denitrification and dephosphorization reactor is connected with denitrifying phosphorus bacteria and phosphorus bacteria, and the abundance ratio of the denitrifying phosphorus bacteria and the phosphorus bacteria is 30-60%.
7. The method for simultaneous denitrification and dephosphorization of low-carbon sewage according to claim 1, wherein the fermentation broth and the other part of low-carbon sewage are introduced into a denitrification and dephosphorization reactor, after anaerobic stirring for 1-3 h, oxygen limiting aeration is carried out for 2.5-4.5 h, the concentration of dissolved oxygen is controlled to be 0.8-1.2 mg/L, and finally stirring and precipitation are stopped for 0.5-1.5 h.
8. The method for simultaneous denitrification and dephosphorization of low carbon sewage according to claim 7, wherein the sludge mixed solution is discharged 5-10 min before stopping aeration and stirring in the denitrification and dephosphorization reactor, and the suspension activated sludge concentration in the denitrification and dephosphorization reactor is maintained to be 4000-6000 mg/L, and the sludge retention time is 12-16 d.
9. An apparatus for the synchronous denitrification and dephosphorization method for low carbon sewage according to any one of claims 1 to 8, comprising the primary sludge fermentation reactor, the denitrification and dephosphorization reactor, a low carbon sewage raw water tank, a residual sludge storage tank, a fermentation liquor storage tank and a water outlet tank; the outlet of the low-carbon sewage raw water tank is connected with the primary sludge fermentation reactor and one inlet of the nitrogen and phosphorus removal reactor, the outlet of the residual sludge storage tank is connected with the other inlet of the primary sludge fermentation reactor, the inlet of the fermentation liquor storage tank is connected with the outlet of the primary sludge fermentation reactor, the outlet of the fermentation liquor storage tank is connected with the other inlet of the nitrogen and phosphorus removal reactor, and the inlet of the water outlet tank is connected with the outlet of the nitrogen and phosphorus removal reactor.
10. The apparatus of claim 9, further comprising an aeration assembly coupled to the nitrogen and phosphorus removal reactor and a stirring assembly disposed within the primary sludge fermentation reactor and the nitrogen and phosphorus removal reactor.
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