AWWA WQTC65752

The Lowry and Bradford assays are appropriate for untreated or poorly treated wastewaters, but are not sensitive enough for low protein concentrations such as found in reclaimed waters or drinking waters. A biomedical assay, NanoOrange® (Molecular Probes Inc., Oregon) which has been used to measure protein content in cells, is very sensitive, but exhibited interferences from salts in water, especially from divalent ions. As such it is of limited use for bulk drinking water samples, but could be used on samples after dialysis pretreatment. For natural organic matter (NOM) isolates and cloud samples, the NanoOrange® method could be used without concern for salts. The colloidal fraction of natural organic matter (NOM) exhibited the highest protein content based upon the NanoOrange® reagent. Includes 7 references, tables, figures.