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CN-121990726-A - Method for treating high COD and high ammonia nitrogen wastewater

CN121990726ACN 121990726 ACN121990726 ACN 121990726ACN-121990726-A

Abstract

The application relates to the technical field of wastewater treatment, in particular to a method for treating high COD and high ammonia nitrogen wastewater, which comprises the steps of S1, introducing wastewater into a double-electrode chamber-mixing chamber three-section electrochemical reactor, adopting a titanium-based PbO 2 anode and an IrO 2 anode to form an oxidation potential gradient for selective oxidation, S2, enabling effluent to pass through a short-cut nitrification reactor, then enabling the effluent to pass through an anaerobic ammonia oxidation-denitrification coupling reactor for denitrification, S3, removing residual organic matters through a biological membrane reactor, controlling the effluent COD to be less than 100 mg/L, S4, adopting a membrane distillation device to pre-concentrate by utilizing a low-grade heat source, and S5, treating concentrated solution by an MVR evaporation crystallization system to produce solid salt and treated water. The process realizes the organic unification of high-efficiency conversion, autotrophic denitrification, zero wastewater discharge and resource recovery of refractory organic matters through the combination of electrochemical oxidation, short-cut nitrification, anaerobic ammonia oxidation, biomembrane, membrane distillation and MVR, and has the advantages of high treatment efficiency, low operation cost, low energy consumption and strong system stability.

Inventors

  • CHEN HAIMAO
  • LI XIANGLIN

Assignees

  • 广东春和景明环保科技有限公司

Dates

Publication Date
20260508
Application Date
20260327

Claims (10)

  1. 1. The method for treating the high COD and high ammonia nitrogen wastewater is characterized by comprising the following preparation steps: S1, introducing high COD and high ammonia nitrogen wastewater into a double-electrode chamber-mixing chamber three-section electrochemical reactor, controlling a first electrode chamber to adopt a titanium-based PbO 2 anode, controlling a second electrode chamber to adopt a titanium-based IrO 2 anode, and carrying out selective oxidation under the condition of oxidation potential gradient to convert refractory organic matters into biodegradable matters, so that the B/C ratio of effluent is increased to more than 0.3; S2, sequentially introducing the water discharged from the step S1 into a short-cut nitrification reactor and an anaerobic ammonia oxidation-denitrification coupling reactor, realizing short-cut nitrification by controlling dissolved oxygen and pH, oxidizing ammonia nitrogen into nitrite nitrogen partially, and then realizing total nitrogen removal under anaerobic conditions through the synergistic effect of anaerobic ammonia oxidation bacteria and denitrification bacteria; A short-cut nitrification stage, namely under the conditions of 0.8-1.0 mg/L, pH, 7.8-8.0 of dissolved oxygen and 25-35 ℃, nitrite oxidizing bacteria are cooperatively inhibited by free ammonia and free nitrous acid, so that 50% of NH 4 + -N is oxidized into NO 2 - -N by the ammonia oxidizing bacteria, and the accumulation rate of the nitrous acid is more than 90%; The anaerobic ammonia oxidation-denitrification section is characterized in that short-cut nitrification effluent is deoxidized and enters an anaerobic ammonia oxidation-denitrification reactor, ammonia nitrogen and nitrite nitrogen are converted into nitrogen through the synergistic effect of anaerobic ammonia oxidation bacteria and denitrifying bacteria in granular sludge under the conditions that the temperature is 28-30℃, pH, the hydraulic retention time is 24 hours and the COD/NO 2 - -N=2.0, and the residual COD is utilized to carry out denitrification; S3, introducing the effluent from the step S2 into a biomembrane reactor, removing residual organic matters and suspended matters, and controlling the COD (chemical oxygen demand) of the effluent to be less than 100 mg/L; s4, introducing the effluent from the step S3 into a membrane distillation device, and pre-concentrating the wastewater by using a low-grade heat source to obtain concentrated solution and output distilled water; s5, enabling the concentrated solution in the step S4 to enter a mechanical vapor recompression evaporation crystallization system, and performing evaporation crystallization at the evaporation temperature of 75-85 ℃ and the compressor pressure ratio of 1.5-2.5 to produce solid salt and treated water.
  2. 2. The method for treating wastewater with high COD and high ammonia nitrogen as claimed in claim 1, wherein the dual-electrode chamber-mixing chamber three-stage electrochemical reactor in the step S1 is composed of a first electrode chamber, a mixing chamber and a second electrode chamber which are connected in series, the first electrode chamber is provided with a titanium-based PbO 2 anode and a first cathode, the second electrode chamber is provided with a titanium-based IrO 2 anode and a second cathode, the mixing chamber is provided with a mechanical stirring device, the wastewater sequentially flows through the first electrode chamber, the mixing chamber and the second electrode chamber to form an oxidation potential gradient, and the potential of the first electrode chamber is higher than that of the second electrode chamber.
  3. 3. The method for treating high COD and high ammonia nitrogen wastewater according to claim 1, wherein in the step S1, the gradient oxidation reaction is carried out under the conditions of current density of 15-25 mA/cm 2 , pH of 3.5-5.0 and polar plate spacing of 15-20 mm for 2-4 hours.
  4. 4. The method for treating wastewater with high COD and high ammonia nitrogen as claimed in claim 1, wherein the current density in the step S1 is feedback-regulated according to the concentration of the inflow COD, the current density is controlled to be 15-20 mA/cm 2 when the inflow COD is 5000-10000 mg/L, and the current density is controlled to be 20-25 mA/cm 2 when the inflow COD is 10000-20000 mg/L.
  5. 5. The method for treating wastewater with high COD and high ammonia nitrogen as claimed in claim 1, wherein the anaerobic ammoxidation-denitrification section in the step S2 adopts an up-flow anaerobic sludge bed reactor, the particle size of anaerobic ammoxidation granular sludge in the reactor is 2-4 mm, the sludge concentration is 8000-12000mg/L, and the up-flow speed is controlled to be 0.5-1.0 m/h so as to maintain the stability of the granular sludge bed.
  6. 6. The method for treating wastewater with high COD and high ammonia nitrogen as claimed in claim 1, wherein the step S2 controls the short-range nitrification process by monitoring the pH and the dissolved oxygen in real time, and the aeration is stopped when the pH is more than 8.0.
  7. 7. The method for treating high COD and high ammonia nitrogen wastewater according to claim 1, wherein the biofilm reactor in the step S3 is a moving bed biofilm reactor or a biological aerated filter, polyurethane sponge filler or ceramsite is adopted, dissolved oxygen is controlled to be 3-4 mg/L, hydraulic retention time is controlled to be 4-6 hours, and volume load is 1.5-2.5 kgCOD/(m 3 . D).
  8. 8. The method for treating high COD and high ammonia nitrogen wastewater according to claim 1, wherein in the step S4, the membrane distillation device adopts vacuum membrane distillation or air gap membrane distillation, the membrane material is a hydrophobic PTFE hollow fiber membrane, the hot side temperature is 60-80 ℃, the cold side temperature is 20-30 ℃, the membrane flux is 5-15L/(m 2 . H), and the retention rate is not less than 99.9%.
  9. 9. The method for treating high COD and high ammonia nitrogen wastewater according to claim 1, wherein the method further comprises a nanofiltration salt separation step before the step S5, wherein the concentrated solution obtained in the step S4 is separated by a nanofiltration membrane, the sulfate ion interception rate is equal to or greater than 98%, the chloride ion interception rate is equal to or less than 20%, a sodium sulfate-rich side and a sodium chloride-rich side are respectively obtained, and the concentrated solution is respectively fed into different MVR evaporators for salt separation crystallization.
  10. 10. The method for treating high-COD and high-ammonia nitrogen wastewater according to claim 1, wherein the heat source of the membrane distillation system in the step S4 is from condensate water waste heat generated by the MVR evaporation crystallization system in the step S5, so that the energy cascade utilization in the system is realized, and distilled water is produced as supplementing water of the MVR evaporation crystallization system, so that the water resource is recycled.

Description

Method for treating high COD and high ammonia nitrogen wastewater Technical Field The application relates to the technical field of wastewater treatment, in particular to a method for treating high-COD and high-ammonia nitrogen wastewater. Background Along with the acceleration of the industrialization progress, the discharge amount of high-concentration organic wastewater generated in industries such as chemical industry, pharmacy, printing and dyeing, landfill leachate and the like is increased year by year. The waste water has the characteristics of high Chemical Oxygen Demand (COD), high ammonia nitrogen concentration, hard-degradation organic matters, accumulation of salt and the like, and causes serious pollution to environmental water. Therefore, developing high-efficiency, economical and stable high-COD and high-ammonia nitrogen wastewater treatment technology has become an important research direction in the field of water treatment. Currently, a process route combining a biochemical method and a physicochemical method is mainly adopted for treating the wastewater. In the aspect of biochemical treatment, the activated sludge method and the biomembrane method are widely applied because of the mature technology and relatively low running cost. However, when the traditional activated sludge method is used for treating high-concentration organic wastewater, the problems of sludge expansion, sedimentation performance deterioration and the like are caused by over-high organic load, and for refractory organic matters, microorganisms are difficult to directly utilize due to poor biodegradability, and the removal efficiency is generally less than 30%. Although the biomembrane method has certain impact load resistance, the method also has the bottleneck that nitrifying bacteria are inhibited under the conditions of low removal rate of refractory organic matters and high ammonia nitrogen. In the aspect of physical and chemical treatment, the coagulating sedimentation and filtration process can effectively remove suspended matters, colloid substances and partial macromolecular organic matters in the wastewater, but has almost no removal capability on soluble micromolecular organic matters and ammonia nitrogen. Advanced oxidation technologies such as Fenton oxidation and ozone oxidation can degrade part of refractory organic matters, but have the problems of high medicament consumption, high operation cost, possibility of secondary pollution and the like. In recent years, with the increasing strictness of industrial wastewater discharge standards and the increasing demand for wastewater reuse, the evaporation concentration technology is widely applied to wastewater zero discharge treatment. However, the conventional evaporation concentration process faces a challenge of significantly increasing energy consumption, especially when treating salt-containing wastewater, the steam consumption per ton of evaporated water can reach 0.3-0.4 ton, and the operation cost is high. Meanwhile, the problem of membrane pollution in the membrane treatment process is increasingly serious due to salt accumulation, and the problems of rapid flux reduction, frequent cleaning and shortened membrane service life seriously affect the stability and economy of a treatment system. The prior art has the problem of high carbon source addition cost when treating high COD and high ammonia nitrogen wastewater. The traditional denitrification process requires adding external carbon sources such as methanol, sodium acetate and the like to meet the requirement of denitrifying bacteria on electron donors. For the high ammonia nitrogen wastewater with unbalanced C/N ratio, the carbon source adding cost can account for 40% -60% of the whole operation cost, and excessive adding is easy to cause out-of-standard COD of the effluent and unbalanced nutrient substances in the system. In addition, pretreatment steps (such as iron-carbon micro-electrolysis, hydrolytic acidification and the like) aiming at refractory organic matters tend to increase the complexity and the occupied area of the process flow, and the overall energy consumption and the investment cost are further increased. In view of the above, the existing high-COD and high-ammonia nitrogen wastewater treatment technologies still have obvious shortcomings in the aspects of treatment efficiency, running cost, system stability and the like, and development of a novel treatment technology capable of cooperatively removing refractory organics, high-efficiency denitrification, low energy consumption and low running cost is needed to realize economic and efficient treatment of the wastewater. Disclosure of Invention The application provides a method for treating high-COD and high-ammonia-nitrogen wastewater, which aims to solve the problems that the existing high-COD and high-ammonia-nitrogen wastewater treatment technology still has obvious defects in the aspects of treatment efficiency, running c