A rapid determination method of chemical oxygen demand in printing and dyeing wastewater using ultraviolet spectroscopy.

A rapid method to determine chemical oxygen demand (COD) in printing and dyeing wastewater using ultraviolet (UV) spectroscopy was developed in this study. The UV method has several advantages compared to the chemical method, such as shortened analysis time, convenience, no requirement of expensive and toxic reagents, and good reproducibility. It was established that the magnitude of COD and, to a certain extent, pH and suspended solids of the sample have effects on the accuracy and precision of the method. The results showed the fitting range of COD(Cr) (COD determined by the dichromate method) was 0 to 360 mg/L(-1) And the pH ranged from 2.45 to 9.22. If the UV(365) (UV absorbance at 365 nm) is measured and is subtracted from UV(254) (UV absorbance at 254 nm), then the effects of suspended solids was eliminated. A control experiment of COD(Cr) determination using the rapid method and the standard dichromate method was carried out, which validated the former.