Effluent Organic Matter Is Similar to Microbially Derived Natural Organic Matter

This comprehensive study of effluent organic matter, using geochemical techniques, finds that effluent organic matter is similar to microbially derived natural organic matter. It is found that the characteristics of the effluent organic matter are similar, regardless of the treatment plant. Effluent discharges of treated municipal wastewater represent an important source of organic matter to aquatic ecosystems. However, there has been little examination of anthropogenic sources of organic matter, such as in wastewater effluent. Thus it is unknown how effluent organic matter (EfOM) contributes to ecosystem processes in streams that receive wastewater effluent discharges. In this study, researchers at the University of Connecticut isolated EfOM from five municipal wastewater treatment plants in the state, using DAX8 (hydrophobic fraction) and XAD4 (transphilic fraction) resins. Isolate recoveries ranged from 18 to 42 percent of the total organic carbon for DAX8 resin, and from 6 to 12 percent for XAD4 resin. Isolated EfOM was characterised by traditional organic geochemistry techniques. Weight-averaged molecular weights of extracted EfOM by size exclusion chromatography were 450–670 daltons, with higher weights observed for the hydrophobic fractions than the transphilic fractions. Fluorescence characterisation showed both humic- and fulvic-like fluorescence, as well as tryptophan- and tyrosine-like fluorescence (the latter is not commonly observed for terrestrial organic matter). Fluorescence indices were between 1.5 and 1.9, with lower values observed for hydrophobic EfOM fractions than for transphilic fractions. Specific ultraviolet absorbance was measured between 0.8 and 3.0 L/mg/m, with higher values for the hydrophobic EfOM fractions. Together these results indicate that isolated EfOM is similar in characteristics to microbially derived organic matter from natural aquatic systems. Little variation in EfOM characteristics was observed between the five wastewater treatment plants, suggesting that the characteristics of EfOM are similar, regardless of the treatment plant design. Source: workingwithwater.filtsep.com