| With the high increase of the population and industry development, water source shortage is becoming more and more serious. Petrochemical industries demand a large amount of water during refining process, and a large amount of industrial sewage with various pollutants was drained from this source. This drain has been seriously contaminated the environment, to harm human health and influence the sustainable development of economy. Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) are the most important pollution index for water environmental monitoring. The method of determining COD with potassium dichromate under acid medium is noted as CODCr, this is the most common method at present. China has enacted a national standard GB11914-1989based on the relatively international standard. BOD5is a dilution inoculation method, its detection time is5days and the demand of experimental temperature is very strict, so it is inconvenience for actual real-time detection. This study attempt to explore the interconnectedness between COD and BOD in the same sewage, and to calculate the BOD value through the detected COD value. Through analysis of COD and BOD data for a petrochemical corporation in Northeast zone, we summarize a linear relationship between COD and BOD values using Least Square Method. The linear relationship is BOD=0.1076COD+0.8068, and the significant difference was also checked, that is r=0.7725> r0.01. So the linear relationship between the COD and BOD in the petrochemical sewage is significant. In addition, the linear accuracy was described with Surplus Standard Difference. Furthermore, the BOD range was evaluated, and95.4%of the experimental data are between BOD=0.1076COD+0.8068+1.829and BOD=0.1076COD+0.8068-1.829, and the100%of the experimental data are between the two lines BOD=0.1076COD+0.8068+2.7447and BOD=0.1076COD+0.8068-2.7447. Therefore, BOD can be calculated according to the above-mentioned linear relationship when the COD value is know. |
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