Search

CN-121978041-A - Accurate measurement and calculation full mixed flow A2Method for O process external reflux ratio

CN121978041ACN 121978041 ACN121978041 ACN 121978041ACN-121978041-A

Abstract

The invention provides a method for accurately measuring and calculating the external reflux ratio of a full mixed flow A 2 O process, and relates to the technical field of sewage treatment. The method is based on an ammonia nitrogen conservation principle of an anaerobic tank and comprises the following steps of roughly estimating an external reflux ratio and calculating hydraulic retention time of the anaerobic tank, continuously sampling inflow and external reflux sludge in the complete hydraulic retention time, collecting samples in the anaerobic tank at the starting time and the ending time, testing the concentration of relevant ammonia nitrogen, calculating the external reflux ratio by using a derived formula, and improving the calculation accuracy by iterative optimization. The method solves the problems of experience-dependent estimation, low accuracy and poor adaptability in the prior art, has the advantages of high measuring accuracy, full theoretical basis, simplicity and convenience in operation and strong adaptability, can meet different accuracy requirements through iteration according to actual working conditions, is suitable for regulating and controlling the external reflux ratio of various full mixed flow A 2 O processes, and is beneficial to improving the operation stability and treatment effect of the processes.

Inventors

  • CHEN YANLIN
  • LI CHENG
  • JIAO YANG
  • ZHANG JUN
  • PENG MENGWEN
  • WANG FEI

Assignees

  • 中国长江三峡集团有限公司
  • 长江生态环保集团有限公司

Dates

Publication Date
20260505
Application Date
20260123

Claims (10)

  1. 1. The method for precisely measuring and calculating the external reflux ratio of the full mixed flow A 2 O process is characterized by comprising the following steps of: (1) According to a design drawing of a fully mixed flow A 2 O process, roughly estimating an external reflux ratio R 0 , and calculating hydraulic retention time HRT 0 of an anaerobic tank based on R 0 , wherein the hydraulic retention time HRT 0 meets the formula V=HRT.Q (1+R), V is anaerobic Chi Rongji, Q is water inflow, and R is the external reflux ratio; (2) Continuously sampling the inflow water and the external reflux sludge of the anaerobic tank in one complete HRT 0 of the anaerobic tank; (3) Collecting mixed samples in an anaerobic tank at the time T=0 and the time T=HRT 0 respectively; (4) Respectively testing the ammonia nitrogen concentration a of the inlet water, the ammonia nitrogen concentration b of the external reflux and the ammonia nitrogen concentration C t of the anaerobic tank when T=0 and the ammonia nitrogen concentration C 0 、T=HRT 0 of the anaerobic tank when the samples are collected in the steps (2) and (3); (5) Based on the principle of conservation of ammonia nitrogen in the anaerobic tank, the external reflux ratio R 1 is calculated by using the following formula: ; (6) Reckoning hydraulic retention time HRT 1 of the anaerobic tank according to R 1 calculated in the step (5), and repeating the steps (2) - (5) to obtain an external reflux ratio R 2 ; (7) And (3) repeating the step (6) by using R n (n is more than or equal to 2) according to the measurement accuracy requirement to perform iterative calculation, so as to obtain the external reflux ratio R n+1 with higher accuracy.
  2. 2. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein in the step (2), the continuous sampling frequency is once every 10-30 minutes, the single sampling amount is 50-100mL, and the samples are refrigerated and stored in an environment of 0-4 ℃ after sampling.
  3. 3. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein in the step (7), the iteration number is 1-3, and when the iteration is up to R 2 , the accuracy requirement of conventional sewage process regulation is met.
  4. 4. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein the measuring and calculating process is based on the following assumed conditions: The method is characterized in that 1, the anaerobic tank is in a complete mixing state, namely the ammonia nitrogen concentration of effluent liquid of the anaerobic tank is equal to that of mixed liquid in the tank; Assuming that 2 the ammonia nitrogen in the anaerobic tank is only physically mixed, the biotransformation does not occur due to the metabolism of the activated sludge.
  5. 5. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein in the step (4), the ammonia nitrogen concentration is tested by adopting a Nahner reagent spectrophotometry or a salicylic acid-hypochlorite spectrophotometry, and the testing precision is less than or equal to 0.01mg/L.
  6. 6. The method for precisely measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein in the step (1), the value range of the roughly estimated external reflux ratio R 0 is 0.5-2.0.
  7. 7. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1 is characterized in that in the step (2), a water inlet sampling point is arranged at a position 1-3m away from a water inlet pipeline of an anaerobic tank, an external reflux sludge sampling point is arranged at a position 0.5-2m away from an inlet of the anaerobic tank, and in the step (3), a sampling point in the anaerobic tank is arranged in the middle of the anaerobic tank, and the sampling depth is 1/2-2/3 of the depth of the tank.
  8. 8. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein the formula in the step (5) is derived based on a material balance differential equation, and the material balance differential equation is: ; Wherein, the Is that Ammonia nitrogen concentration in the anaerobic tank at any time, Is the external reflux flow.
  9. 9. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, wherein in the step (1), the anaerobic tank volume V is calculated by dimensioning a design drawing, and the water inflow Q is obtained by monitoring a pipeline flowmeter in real time.
  10. 10. The method for accurately measuring and calculating the external reflux ratio of the full mixed flow A 2 O process according to claim 1, which is characterized in that the method is suitable for the full mixed flow A 2 O process with the COD concentration of inflow water of 100-800mg/L and the ammonia nitrogen concentration of inflow water of 5-50 mg/L.

Description

Method for accurately measuring and calculating external reflux ratio of full mixed flow A 2 O process Technical Field The invention relates to the technical field of municipal wastewater treatment, in particular to a method for accurately measuring and calculating the external reflux ratio of a full mixed flow A 2 O process. Background In the field of sewage treatment, the full mixed flow A 2 O technology is widely applied to town sewage and industrial wastewater treatment engineering due to the synchronous denitrification and dephosphorization function. The external reflux ratio is used as a core operation parameter of the process, directly influences the sludge concentration distribution, the substrate degradation efficiency and the denitrification and dephosphorization effect of an anaerobic tank, an anoxic tank and an aerobic tank, and is critical to the stable operation of the process. At present, the external reflux ratio measuring and calculating method commonly used in the industry mainly comprises the steps of experience estimation of operators, and lacks scientific theoretical basis and accurate calculation support. Because the quality (such as ammonia nitrogen and COD concentration) and the quantity of water of the inflow water can fluctuate along with time, and the process design parameters (such as the volume of an anaerobic tank and the inflow water flow) of different sewage treatment plants are different, the external reflux ratio obtained through empirical estimation tends to deviate greatly, and is difficult to adapt to complex and changeable operation conditions, so that the process treatment effect is unstable, and even the problems of out-of-standard water quality, energy waste and the like occur. Disclosure of Invention The invention aims to solve the technical problems that the existing total mixed flow A 2 O process external reflux ratio measuring and calculating method depends on experience estimation, lacks scientific basis, has large measuring and calculating deviation and is difficult to adapt to different water quality and working condition changes. In order to achieve the above purpose, the present invention adopts the following technical scheme: the method for precisely measuring and calculating the external reflux ratio of the full mixed flow A 2 O process comprises the following steps of: The core principle is as follows: The measuring and calculating method is based on the principle of conservation of ammonia nitrogen in the anaerobic tank, wherein the total ammonia nitrogen in the anaerobic tank is basically not changed due to the metabolism of activated sludge, and the total ammonia nitrogen at the outlet is equal to the sum of the total ammonia nitrogen in the inlet and the total ammonia nitrogen brought by the external reflux sludge. Meanwhile, a material balance differential equation is established by combining a complete mixing assumption (effluent concentration=concentration in a pool) and a no biotransformation assumption (only physical mixing), an external reflux ratio calculation formula is obtained through mathematical deduction, and then the measuring and calculating precision is improved through iterative optimization. Parameter definition: 1. the ammonia nitrogen concentration of the inlet water is a (unit is mg/L), namely the ammonia nitrogen mass concentration of the inlet water of the anaerobic tank; 2. B (unit: mg/L) is the ammonia nitrogen mass concentration in the external reflux sludge; 3. the water inflow rate is Q (unit: m 3/h), namely the sewage flow rate entering the anaerobic tank; 4. RQ (unit: m 3/h), wherein R is the external reflux ratio (dimensionless); 5. total inflow flow rate q+rq=q (1+r) (unit: m 3/h); 6. HRT (unit: h) of hydraulic retention time of the anaerobic tank, calculated based on total inflow of the anaerobic tank, satisfying V=HRT.Q (1+R), wherein V is anaerobic Chi Rongji (unit: m 3); Ammonia nitrogen concentration in the anaerobic tank at 7.t is C (t) (unit: mg/L), when initial condition t=0, C (0) =c 0, and when t=hrt, C (t) =c t. The measuring and calculating steps are as follows: 1. Roughly estimating the external reflux ratio and calculating the HRT, namely acquiring the volume V of the anaerobic tank according to a design drawing of the full mixed flow A 2 O process, acquiring the inflow Q through a pipeline flowmeter, roughly estimating the external reflux ratio R 0 (the value range is 0.5-2.0), and calculating the hydraulic retention time HRT 0 of the anaerobic tank according to the formula V=HRT.Q (1+R). 2. And continuously sampling, namely continuously sampling the inflow water and the external reflux sludge of the anaerobic tank in one complete HRT 0 of the anaerobic tank. The water inlet sampling point is arranged at the position, 1-3m away from the tank body, of the water inlet pipeline of the anaerobic tank, the outer reflux sludge sampling point is arranged at the position, 0.5-2m away from the inlet of the anaerob