ULTRAVIOLET SPECTROPHOTOMETRY AS AN INDEX PARAMETER FOR ESTIMATING THE BIOCHEMICAL OXYGEN DEMAND OF DOMESTIC WASTEWATER

摘要

The relationship between ultraviolet absorbance at 280 run (UV_(280)) and the 5-day Biochemical Oxygen Demand (BOD_5) test was evaluated using wastewater samples collected during March - December 1998 from the Fort Meade wastewater treatment plant (Maryland, U.S.A.). Three types of samples were collected: raw influent wastewater, primary effluent, and the effluent from the nitrification settling basin. A regression of BOD_5 on UV_(280) was obtained using half of the data, with the other half of the data used to test application of the equation. The presence of NO_3 and NO_2, did not interfere with the BOD_5/UV relationship. However, the relative fraction of organic compounds that absorb at UV_(280) and are biodegradable did appear to decrease across the treatment plant, thereby reducing the strength of the association between BOD_5 and UV_(280) further along the treatment train. Interestingly, the exclusion of solids > 1 μm from the BOD_5 test did not strengthen the association between BOD_5 and UV_(280). These results suggest that simple UV absorbance measurements may be a useful analytical tool for wastewater treatment personnel, allowing them to quickly monitor for changes in the BOD_5 during the treatment process and to quickly estimate the BOD_5 when determining what dilutions to use in the standard BOD_5 test. However, such relationships are likely to be wastewater and treatment plant specific and variable with time and treatment.