Device and Method for Enhancing Nitrogen and Phosphorus Removal Based on Multistage AO Partial Denitrification Coupled with Anammox in Combination with Sludge Hydrolytic Acidification

Abstract

A device and method for enhancing nitrogen and phosphorus removal based on a multistage AO partial denitrification coupled with Anammox process in combination with a sludge hydrolytic acidification mixture belong to the technical field of active sludge method wastewater treatment. A system includes a water tank, a water pump, a biochemical reaction zone, a hydrolytic acidification tank and other devices. A multistage AO step-feed pipeline is used to inject raw water into the reaction zone in a segmented manner, guaranteeing efficient utilization of organic matter in the raw water; biofilm carriers are added into an anaerobic zone and anoxic zones to enrich anammox bacteria, and nitrite nitrogen produced by partial denitrification provides a substrate for the anammox bacteria to realize autotrophic nitrogen removal; a nitrification and phosphorus accumulating bacteria aerobic phosphorus uptake are performed in aerobic zones; and part of excess sludge in a secondary sedimentation tank enters the hydrolytic acidification tank to convert macromolecular organic matter into low molecular weight organic matter, a hydrolytic acidification mixture and the excess sludge in the secondary sedimentation tank synchronously flow back to the anaerobic zone, and as a high-quality carbon source, the low molecular weight organic matter can promote partial denitrification. The system provides a novel method for efficient and energy-saving treatment of municipal wastewater.

Claims

1. A method for enhancing nitrogen and phosphorus removal based on a multistage AO partial denitrification coupled with Anammox process in combination with a sludge hydrolytic acidification mixture, applying the following device that: raw water in a raw water tank enters a biochemical reaction zone from an anaerobic zone, a second anoxic zone and a third anoxic zone via a feed pump and a step-feed pipeline; the biochemical reaction zone is formed by sequentially connecting the anaerobic zone, a first anoxic zone, a first aerobic zone, the second anoxic zone, a second aerobic zone, the third anoxic zone and a third aerobic zone; each branch water inlet pipeline in the step-feed pipeline is provided with a water inlet valve; a biofilm carrier is added into and a submersible mixer is mounted in each of the three anoxic zones; the three aerobic zones are each provided with an aeration device, and an aeration head is connected with a rotor flow meter, an air valve and an air compressor via an aeration pipeline; the third aerobic zone is provided with an overflow weir, a pipeline of the overflow weir is connected with a secondary sedimentation tank center pipe via a secondary sedimentation tank water inlet pipe and a secondary sedimentation tank water inlet valve, and a water outlet of a secondary sedimentation tank is connected with a water outlet pipe; active sludge in the secondary sedimentation tank is injected into a sludge hydrolytic acidification tank through a sludge pump and a sludge pipeline, a sludge hydrolytic acidification product enters a sludge backflow header pipe through a sludge pump and a sludge pipeline, the sludge hydrolytic acidification mixture and excess sludge in the secondary sedimentation tank flow back into the anaerobic zone through a sludge backflow pump and the sludge backflow header pipe, and the excess sludge in the secondary sedimentation tank is discharged to a sludge treatment system through a sludge discharging pipeline.

2. The method for enhancing nitrogen and phosphorus removal based on the multistage AO partial denitrification coupled with Anammox process in combination with the sludge hydrolytic acidification mixture of claim 1, wherein, the biofilm carrier with a specific surface area being 400-500 m.sup.2/m.sup.3 and a filling ratio being 20%-40% are added into the anaerobic zone and the anoxic zones to provide a condition for attachment of anammox bacteria.

3. A method for enhancing nitrogen and phosphorus removal based on a multistage AO partial denitrification coupled with Anammox process in combination with a sludge hydrolytic acidification mixture, comprising the following steps: adding excess sludge in a secondary sedimentation tank of a municipal WWTPs into a biochemical reaction zone as seed sludge, a ratio of water inlet volumes of an anaerobic zone to a second anoxic zone to a third anoxic zone being 4:3:3; controlling a reflux ratio of the excess sludge to a sludge hydrolytic acidification mixed liquid to be 100%-150%, the sludge and the sludge hydrolytic acidification liquid synchronously flowing back to the anaerobic zone, and maintaining mixed liquid suspended solids (MLSS) in a reactor to be 4000-5000 mg/L; at a start stage of a hydrolytic acidification tank, adding a carbon source into a raw water tank, controlling a raw water C/N ratio to be 3-5, and stopping adding the carbon source after starting of the sludge hydrolytic acidification tank is completed; by monitoring dissolved oxygen (DO) of an aerobic segment through a real-time monitoring system, controlling DO of a first aerobic zone to be 1-1.5 mg/L, and controlling DO of a second aerobic zone and a third aerobic zone to be 2-3 mg/L; adjusting hydraulic retention time (HRT) of each segment by controlling flow of each segment of a system so as to maintain the HRT of the biochemical reaction zone at 12-14 h and HRT anaerobic zone: HRT anoxic zone: HRT aerobic zone=1:3:3; by controlling a direct sludge discharging amount of the excess sludge in the secondary sedimentation tank, maintaining sludge retention time in the biochemical reaction zone to be 13-15 days; and controlling a submersible mixing speed to make the biofilm carrier and active sludge in the anaerobic zone and the anoxic zone mix evenly and fully contact.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic structural diagram of a system for enhancing nitrogen and phosphorus removal based on municipal wastewater continuous flow step-feed denitrification part anaerobic ammonia oxidation coupled with sludge hydrolytic acidification of this application.

[0020] In FIG. 1: 1raw water tank; 2feed pump; 3anaerobic zone; 4first anoxic zone; 5first aerobic zone; 6second anoxic zone; 7second aerobic zone; 8third anoxic zone; 9third aerobic zone; 10sedimentation tank; 11sludge hydrolytic acidification tank; 12step-feed pipeline; 13submersible mixer; 14water inlet valve; 15secondary sedimentation tank water inlet valve; 16secondary sedimentation tank water inlet pipe; 17water outlet pipe; 18secondary sedimentation tank center pipe; 19air compressor; 20sludge backflow header pipe; 21aeration pipeline; 22aeration device; 23rotor flow meter; 24sludge backflow pump; 25air valve; 26sludge pipeline; 27sludge pump; 28sludge pump; 29sludge pipeline.

DETAILED DESCRIPTION

[0021] In combination with FIG. 1, implementations of this application are specifically described.

[0022] 1) Raw water enters an anaerobic zone (3), a second anoxic zone (6) and a third anoxic zone (8) respectively via a feed pump (2) from a raw water tank (1), output water treated through a biochemical reaction zone flows out from a third aerobic zone (9) and flows into a secondary sedimentation tank (10) through a secondary sedimentation tank water inlet pipe (15) and a secondary sedimentation tank center pipe (18), a supernatant in the secondary sedimentation tank is discharged as output water, part of excess sludge at the bottom of the secondary sedimentation tank enters a hydrolytic acidification tank (11) via a sludge pipeline (29), a mixture in the hydrolytic acidification tank and part of the excess sludge in the secondary sedimentation tank flow back into the anaerobic zone together via a sludge backflow header pipe (20), and the rest of the excess sludge in the secondary sedimentation tank is discharged to a sludge treatment system through a sludge discharging pipeline (30).

[0023] 2) In a multistage AO step-feed system, the raw water enters the anaerobic zone (3), the second anoxic zone (6) and the third anoxic zone (8) in a segmented manner, thereby guaranteeing a stable carbon source of the anaerobic zone and the anoxic zones.

[0024] 3) Phosphorus accumulating bacteria in the anaerobic zone (3) take volatile fatty acids (VFA) from a raw water and active sludge hydrolytic acidification mixture to synthesize PHAs and release phosphorus.

[0025] 4) Nitrification liquid from aerobic zones flows back to take nitrate nitrogen into the anaerobic zone (3), the second anoxic zone (6) and the third anoxic zone (8), and denitrifying bacteria utilize organic matter as electron donors to perform a partial denitrification process so as to provide a substrate, nitrite nitrogen, for anammox bacteria, thereby realizing coupling of partial denitrification and the Anammox.

[0026] 5) Biofilm carriers are added into the anaerobic zone and the anoxic zones and evenly mix and fully contact active sludge through submersible mixers (13), the biofilm carriers provide an attachment condition for enrichment and proliferation of the anammox bacteria, and the anammox bacteria realize autotrophic nitrogen removal with ammonia nitrogen in the raw water and the nitrite nitrogen produced in the partial denitrification process as substrates.

[0027] 6) The aerobic zones can finally oxidize the ammonia nitrogen in the raw water into nitrate nitrogen under the action of nitrifying bacteria, the phosphorus accumulating bacteria in the aerobic zones can perform an aerobic phosphorus uptake process with own PHAs as electron donors and oxygen as electron acceptors, and part of phosphorus-rich sludge is discharged out of the system from the secondary sedimentation tank so as to realize removal of phosphorus in wastewater.

[0028] 7) Part of the excess sludge enters the hydrolytic acidification tank via a sludge pipeline and is subjected to hydrolytic acidification under an anaerobic condition to convert macromolecular organic matter into low molecular weight organic matter, the hydrolytic acidification mixture and part of the excess sludge in the secondary sedimentation tank flow back into the anaerobic zone together, and while a stable sludge concentration in the system is guaranteed, the low molecular weight organic matter, as a high-quality carbon source, further promotes the partial denitrification process.

[0029] Specific Steps:

[0030] excess sludge in a secondary sedimentation tank of a municipal WWTPs is added into a biochemical reaction zone as seed sludge, raw water enters an anaerobic zone, a second anoxic zone and a third anoxic zone of a reactor after flowing through a step-feed pipeline through a feed pump, and a ratio of water inlet volumes of the three segments is controlled to be 4:3:3; the reflux ratio of the excess sludge to a sludge hydrolytic acidification mixed liquid is controlled to be 100%-150%, the sludge and the sludge hydrolytic acidification liquid synchronously flow back to the anaerobic zone, and mixed liquid suspended solids (MLSS) in the reactor is maintained to be 4000-5000 mg/L; when a sludge hydrolytic acidification effect in a hydrolytic acidification tank at an initial stage is not obvious, a carbon source is added into a raw water tank to make a raw water C/N ratio be 3-5, and adding of the carbon source is stopped after starting of the sludge hydrolytic acidification tank is completed; by monitoring dissolved oxygen (DO) of an aerobic segment through a real-time monitoring system, DO of a first aerobic zone is controlled to be 1-1.5 mg/L, and DO of a second aerobic zone and a third aerobic zone is controlled to be 2-3 mg/L; hydraulic retention time (HRT) of each segment is adjusted by controlling flow of each segment of a system so as to maintain the HRT of the biochemical reaction zone at 12-14 h and HRT anaerobic zone: HRT anoxic zone: HRT aerobic zone=1:3:3; by controlling a direct sludge discharging amount of the excess sludge in the secondary sedimentation tank, sludge retention time in the biochemical reaction zone is maintained to be 13-15 days; and a submersible mixing speed is controlled to make the biofilm carriers and active sludge in the anaerobic zone and the anoxic zones mix evenly and fully contact.

[0031] The device and method for enhancing nitrogen and phosphorus removal based on the multistage AO partial denitrification coupled with Anammox process in combination with the sludge hydrolytic acidification mixture take a multistage AO step-feed mode as a process carrier, a process of coupling partial denitrification with the Anammox is realized therein, and advantages of the two are combined. In addition, hydrolytic acidification of part of the excess sludge in the secondary sedimentation tank provides a high-quality micromolecular carbon source for the partial denitrification process in the biochemical reaction zone, which solves the problem of sludge treatment of the municipal WWTPs to a certain extent while promoting the partial denitrification. In summary, the device and method for enhancing nitrogen and phosphorus removal based on the multistage AO partial denitrification coupled with Anammox process in combination with the sludge hydrolytic acidification mixture have the potential to realize efficient and energy-saving treatment of municipal wastewater.