Integrated Detection Technology Of COD And BOD Based On Unconventional Quantitative Basis

In the context of increasingly serious water pollution,effective water quality testing must be carried out in order to achieve scientific and accurate treatment of polluted water bodies and protection of unpolluted water resources.It can comprehensively master the situation of water pollution so as to provide basis and guidance for water resources protection.At present,the conventional detection indicators used to indicate the degree of organic pollution in water bodies mainly include chemical oxygen demand（COD）and biochemical oxygen demand（BOD）.Therefore,this paper discusses an integrated measurement technology of COD and BOD based on previous studies.The determination process of BOD was investigated by aeration of activated sludge to degrade organic pollutants.The single factor of control variable and response surface experiment method were used to optimize the technological conditions affecting the determination of BOD.The best conditions were obtained:reaction time was 273.68min,the amount of activated sludge was 8.72 m L,and the initial p H value was 7.18.According to the correlation experimental analysis under the optimal conditions,BOD_ΔCOD has a good linear relationship with BOD₅,the correlation coefficient R² is0.996,and the linear range up to 500 mg/L.Sludge ceramsite for biological fillers was prepared using dehydrated sludge,fly ash and clay as materials in order to establish a membrane biodegradation system for integrated detection.Firstly,the preparation process of ceramsite was preliminarily determined by orthogonal experiment with the compressive strength and specific surface area as the detection indicators.At the same time,the significant influencing factors were found out:ratio of raw materials,ratio of additive and sintering temperature.Then the influence trend of significant factors on ceramsite performance was investigated.Finally,the optimal process parameters was concluded as follows:raw material ratio of 1:3,additive ratio of 60%,preheating temperature of 350℃,preheating time of 10 min,sintering temperature of 900℃,sintering time of 10 min.The Scanning Electron Microscopy（SEM）analysis of the sludge ceramsite showed that the surface of the ceramsite was rough,the microporous structure was rich,and the specific surface area was large（5.782 m2/g）,which was convenient for microorganisms to accumulate and form biofilm on it.The prepared sludge ceramsite was used as the biological filler for the biofilm culturing experiment.After running for 24 days,the COD removal rate of the reactor effluent reached 90%,and the biofilm formed.A Ti/α/β-Pb O₂ electrode used as working electrode was prepared by electrodeposition method,and COD determination experiment was carried out in three-electrode system.According to the SEM image,theβ-Pb O₂ crystals were evenly distributed on the titanium substrate after electrodeposition.The X-Ray Diffraction（XRD）spectrum showed that the active layer of the electrode was mainlyβ-Pb O₂crystals,and no substrate exposure occurred.In the single-factor experiment,the influence of common experimental parameters such as electrolysis time and working voltage on its analytical performance was studied.The optimal electrolysis time and working voltage were 100 s and 1.45V（vs Saturated Calomel Electrode）respectively.Under the optimized conditions,the linear range of COD in electrochemical determination was 10-150 mg/L and the detection limit was 1.54 mg/L.Correlation experiments showed that the method has a high degree of consistency with the potassium dichromate method and can be used for the determination of COD.An integrated determination system of COD and BOD was established by combining the above biofilm reaction system and electrochemical determination of COD system.This method quantifies BOD value by the change of COD before and after biodegradation of a given water sample.Then,the principle of the system is introduced in detail.The comprehensive analysis shows that it has the advantages of environmental friendliness,less consumption of chemical reagent,and simple operation,which provides a new idea for the field of water quality detection.