Abstract: 5910 A. Introduction

1. Applications

Because some organic compounds commonly found in water and wastewater (e.g., lignin, tannin, humic substances, and various aromatic compounds) strongly absorb ultraviolet (UV) radiation, UV absorption is a useful surrogate measure of such constituents in fresh waters,^1–3 salt waters,^4–6 and wastewater.^7,8 Strong correlations may exist between UV absorption and organic carbon content, color, and precursors of trihalomethanes (THMs) and other disinfection byproducts.^9,10 UV absorption also has been used to monitor industrial wastewater effluents¹¹ and to evaluate the effectiveness of coagulation,¹⁰ carbon adsorption,^12–14 and other water treatment processes that remove organics.^10,15 Specific absorption (the ratio of UV absorption to organic carbon concentration) has been used to characterize natural organic matter.^10,16–18 Some regulatory programs include specific ultraviolet absorbance (SUVA)—a ratio of UV absorption to dissolved organic carbon concentration—to help control disinfection byproducts.