Investigation of BOD and COD values of waste waters that have certain organic matters

The ratio of BOD and COD values which are indicate the pollution level of domestic and industrial wastewater, is given as 0,4-0,8. Although this is valid for domestic wastewater, it is usually not valid for industrial wastewater, because some of the organic matters can not degrade biochemically. Also some of them can have toxic effects on the microorganisms, that are responsible for the biochemical reaction. In this study, dependence of ratio of BOD5/COD to the functional group in the organic matter is investigated. For this purpose; BOD and COD values of the synthetic wastewaters, prepeared using acetaldehyde, formaldehyde, n- buthanol, acetic acid, aniline, phenol and o- nitro phenol solutions are determined. BOD measurements are carried out in different milieus that have both rich and poor number of microorganisms in the unit volume. In these analysis, the BOD values of solutions that contain formaldehyde, aniline, phenol and o- nitro phenol are determined as zero. Consequently their BOD5/COD ratios are also calculated as zero. This shows that these organic matters have toxic effects on the microorganisms that are responsible for the biochemical reaction. Ratio of BOD5/COD is not only dependent to the pollution in the wastewater, it is also dependent to the number of microorganisms in the unit volume. This argument is established from the measurements of BOD and COD values which are determined continually from the same water for 15 days. Besides, the relationship between pH and BOD value is searched. For survival and reproduction of microorganisms, it is found that the appropriate pH range are 8- 10.Keywords : BOD5/COD ratio, pH, number of microorganisms in the unit volume, acetaldehyde, formaldehyde, n- buthanol, acetic acid, aniline, phenol and o- nitro phenol.