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CN-121974494-A - Wastewater treatment system and method based on sulfur recovery and denitrification

CN121974494ACN 121974494 ACN121974494 ACN 121974494ACN-121974494-A

Abstract

The invention discloses a wastewater treatment system and method based on sulfur recovery and denitrification, and belongs to the technical field of wastewater biological treatment. The system comprises an anaerobic reactor, a hypoxia reactor, a primary precipitator, an aerobic-anoxic reactor and a secondary precipitator which are communicated in sequence. The method comprises the steps of enabling wastewater to enter an anaerobic reactor for sulfate reduction, enabling anaerobic effluent to enter a low-oxygen reactor for oxidation of sulfide into elemental sulfur, enabling sulfur-containing sludge separated by a primary precipitator to enter an anoxic section of an aerobic-anoxic reactor after wall breaking, and reducing nitrate nitrogen into nitrogen by using elemental sulfur and an organic carbon source in the sludge as electron donors of sulfur autotrophic denitrification and heterotrophic denitrification respectively. The invention realizes the directional conversion and recycling recovery of sulfur element by the process of anaerobic sulfur production, low oxygen sulfur fixation and oxygen deficiency sulfur, reduces the requirement for additional carbon source, and has the advantages of high denitrification efficiency, low sludge yield and low treatment cost.

Inventors

  • YU JUN
  • BIAN XINGYU
  • CHEN ZHIHONG
  • GAO LEI
  • JIN LIJIAN

Assignees

  • 山东省环科院股份有限公司

Dates

Publication Date
20260505
Application Date
20260409

Claims (7)

  1. 1. A wastewater treatment system based on sulfur recovery and denitrification is characterized by comprising an anaerobic reactor, a low-oxygen reactor, a primary precipitator, an aerobic-anoxic reactor and a secondary precipitator which are sequentially communicated, wherein the anaerobic reactor, the primary precipitator and the secondary precipitator are all provided with sludge discharge pipes; The anaerobic reactor is internally enriched with sulfate reducing bacteria, the water inlet end of the anaerobic reactor is communicated with the water inlet pipeline, the water outlet end of the anaerobic reactor is communicated with the water inlet end of the low-oxygen reactor, and the top exhaust end of the anaerobic reactor is communicated with the air inlet end of the desulfurization scrubber; the low-oxygen reactor is internally enriched with sulfur oxidizing bacteria, and the water outlet end of the low-oxygen reactor is communicated with the water inlet end of the primary precipitator; The supernatant fluid water outlet end of the first-stage precipitator is communicated with the aerobic section water inlet end of the aerobic-anoxic reactor, the precipitated sulfur-containing activated sludge is divided into two parts, the first part of sulfur-containing activated sludge flows back to the anoxic reactor, and the second part of sulfur-containing activated sludge is communicated with the sludge inlet of the anoxic section of the aerobic-anoxic reactor after being treated by the sludge wall breaking device; the aerobic-anoxic reactor comprises an aerobic section and an anoxic section which are sequentially connected in series, wherein an aeration device is arranged in the aerobic section, a mixing and stirring device is arranged in the anoxic section, and the anoxic section is also provided with a mud inlet communicated with a mud discharge pipe of the primary precipitator; The water inlet end of the secondary precipitator is communicated with the water outlet end of the anoxic section of the aerobic-anoxic reactor, and the bottom of the secondary precipitator is provided with a sludge return pipe communicated with the aerobic section of the aerobic-anoxic reactor.
  2. 2. The wastewater treatment system of claim 1, wherein the anaerobic reactor controls a sulfate volumetric load of 1-3 kg SO 4 2- /m 3 -d.
  3. 3. The wastewater treatment system of claim 1, wherein the hypoxia reactor controls sulfide volume load to between 0.5 and 1.5 kg S 2- /m 3 -d.
  4. 4. A wastewater treatment method based on sulfur recovery and denitrification, characterized in that the system of any one of claims 1-3 is adopted, comprising the following steps: (1) The sulfate reduction stage, namely, the wastewater enters an anaerobic reactor, sulfate radical in the wastewater is reduced into sulfide by sulfate reducing bacteria, and the anaerobic effluent containing the sulfide is obtained; (2) A sulfide oxidation stage, namely, anaerobic effluent enters a low-oxygen reactor, is mixed with a first part of sulfur-containing activated sludge which flows back by a primary precipitator, and utilizes sulfur oxidizing bacteria to oxidize sulfide into elemental sulfur; (3) The first stage of mud-water separation, namely, the effluent of the low-oxygen reactor enters a first stage of precipitator to carry out mud-water separation, and the supernatant fluid after precipitation enters an aerobic section of an aerobic-anoxic reactor; (4) Mixing supernatant fluid from the first-stage precipitator with return sludge from the second-stage precipitator, entering an aerobic section, oxidizing ammonia nitrogen into nitrate nitrogen, then entering an anoxic section, mixing the anoxic section with sulfur-containing sludge from the first-stage precipitator, and reducing the nitrate nitrogen into nitrogen by using elemental sulfur and an organic carbon source in the sludge as electron donors of sulfur autotrophic denitrification and heterotrophic denitrification respectively; (5) In the secondary mud-water separation stage, effluent from the anoxic stage enters a secondary precipitator for solid-liquid separation, supernatant of the secondary precipitator is discharged after reaching standards, and sludge of the secondary precipitator flows back to the aerobic stage to maintain the mud age of the system; (6) And the residual sludge treatment stage comprises the steps of carrying out dehydration treatment on residual sludge generated by the anaerobic reactor and the secondary precipitator and carrying out outward treatment on the residual sludge, and recovering elemental sulfur from the residual sludge containing elemental sulfur generated by the primary precipitator after dehydration and drying treatment.
  5. 5. The method for treating wastewater according to claim 4, wherein in the step (3), the amount of the sulfur-containing sludge entering the anoxic zone is calculated as follows: (1) When the effluent has no control requirement on SO 4 2- : Wherein Q is sulfur-containing sludge reflux quantity per unit kg/d, C 0 is waste water COD concentration per unit mg/L entering an aerobic-anoxic reactor, C e is waste water COD concentration per unit mg/L entering the aerobic-anoxic reactor, N 0 is waste water total nitrogen concentration per unit mg/L entering the aerobic-anoxic reactor, N e is waste water total nitrogen concentration per unit mg/L entering the aerobic-anoxic reactor, Q is waste water treatment capacity, and m 3 /d;X a is elemental sulfur ratio in sulfur-containing sludge; (2) When the effluent has control requirements on SO 4 2- : wherein Q is the reflux amount of sulfur-containing sludge, the unit is kg/d, S a is the concentration control unit of SO 4 2- , the unit is mg/L, Q is the wastewater treatment amount, and the unit is m 3 /d;X a is the elemental sulfur ratio in the sulfur-containing sludge, and the unit is percent.
  6. 6. The method for treating wastewater according to claim 4, wherein in the step (1), the pH in the anaerobic reactor is controlled to be 6.5 to 7.5.
  7. 7. The method for treating wastewater according to claim 4, wherein in the step (2), the dissolved oxygen concentration in the low-oxygen reactor is controlled to be 0 to 0.5 mg/L.

Description

Wastewater treatment system and method based on sulfur recovery and denitrification Technical Field The invention belongs to the technical field of biological wastewater treatment, and particularly relates to a wastewater treatment system and method based on sulfur recovery and denitrification. Background Industrial wastewater produced in the industries of pharmacy, chemical industry, printing and dyeing and the like usually contains high-concentration pollutants such as Chemical Oxygen Demand (COD), total Nitrogen (TN), sulfate (SO 42-) and the like, and if the wastewater is directly discharged without proper treatment, serious harm is caused to the water body environment. How to realize the synergistic removal of carbon, nitrogen and sulfur multi-pollutants economically and efficiently and realize the effective recovery of sulfur resources at the same time is always a technical difficulty in the field of industrial wastewater treatment. The traditional treatment process mostly adopts a mode of combining a physical and chemical method with a biochemical method. For sulfate, chemical precipitation (such as lime addition to produce calcium sulfate) or membrane separation is often adopted for removal, but the physicochemical methods have the problems of large dosage of the medicament, high running cost, large production of a large amount of salt-containing chemical sludge and other secondary pollution. The removal of COD and total nitrogen is usually carried out in independent biochemical units, and if the carbon nitrogen ratio of the wastewater is insufficient, external carbon sources such as methanol, sodium acetate and the like are additionally added. The treatment mode causes the problems of lengthy process flow, low total nitrogen removal rate, high power consumption and serious carbon source waste, when the traditional nitrification and denitrification process is adopted, the organic carbon source which can be originally used as an electron donor in the wastewater is consumed in a large amount in an aerobic section, and the external carbon source is required to be relied on in the denitrification stage, so that the double dilemma of resource waste and cost increase is formed. Although the A/O process solves the problem of waste of organic carbon sources to a certain extent, the internal reflux increases power consumption and limits the total nitrogen removal rate. More importantly, the sulfate in the wastewater is hardly utilized effectively in this process, but rather becomes a contaminant requiring additional treatment. In recent years, biological treatment technology based on sulfur autotrophic denitrification becomes a research hot spot in the field of synchronous denitrification and sulfur removal because of the advantages of no need of additional carbon source, low sludge yield and the like. In the prior art, as CN117819712A discloses a deep denitrification device based on sulfur autotrophic denitrification, autotrophic denitrification is realized by arranging an elemental sulfur filler layer, and CN111777179B relates to a sulfur autotrophic denitrification filter and application thereof, and the stable operation of a system is maintained by intercepting elemental sulfur. The common characteristics of the technology are that sulfate reduction, sulfide oxidation, sulfur autotrophic denitrification and other processes are dispersed in different units to operate, the sulfur autotrophic denitrification unit usually exists in a form of an independent filter tank, and the sulfur autotrophic denitrification unit depends on externally added elemental sulfur (such as sulfur particles) as an electron donor. Although the technologies break through in specific links, the limitation of unit fracture and one-way material flow is not eliminated, namely, sulfate in raw water is not converted into available resources, sulfur-containing sludge is only regarded as waste, and organic cooperation is lacking among carbon, nitrogen and sulfur removal processes. Of note, in the process of oxidizing sulfides to elemental sulfur, elemental sulfur typically attaches to the surface of the sludge to form sulfur-containing sludge. The prior art generally treats such sludge as conventional excess sludge, failing to recognize its dual resource attributes of being enriched in both "elemental sulfur" and "adsorptive internal carbon source". In fact, the sulfur-containing sludge can be used as an electron donor for sulfur autotrophic denitrification and also can be used as a supplementary carbon source for heterotrophic denitrification, and has the potential of becoming an 'endogenous electron donor library'. However, no technical scheme is known at present for combining the attribute with the system integrated design to realize in-situ recycling of sulfur resources and cascade utilization of carbon sources. In summary, when the existing industrial wastewater treatment technology is applied to complex water quality with coexisting