ULTRAVIOLET DISINFECTION OF MARGINAL EFFLUENTS - DETERMINING ULTRAVIOLET ABSORBENCY AND SUBSEQUENT ESTIMATION OF ULTRAVIOLET INTENSITY

The ultraviolet (UV) absorbance characteristics of effluents with a wi de range of water quality were measured using direct and integrating s phere spectroscopy. The point source summation (PSS) method was used t o estimate the effect of three UV absorbance measurement techniques (f iltered direct, unfiltered direct, and unfiltered integrating sphere) on estimation of UV intensity in a UV reactor. Intensity values estima ted from the PSS model were compared with direct intensity measurement s made with a chemical actinometer. Use of the integrating sphere meth od for measuring the UV absorbance of the bulk wastewater was validate d experimentally with UV absorbance coefficients derived from chemical actinometry. Absorbance coefficient values derived from direct spectr oscopy were significantly different from the actinometrically derived absorbance coefficients. Particulates in waste-water both absorbed and scattered UV light, decreasing the overall available UV radiation for disinfection. As compared to the integrating sphere method, use of ei ther filtered or unfiltered direct absorbance to determine the UV inte nsify with the PSS model provided an overestimate or underestimate of UV intensity, respectively. No significant differences were observed b etween the chemical actinometry and point source summation methods of estimating UV intensity after accounting for experimental differences.