Effluent organic matter (EfOM) characterization by simultaneous measurement of proteins and humic matter

• Simultaneous measurement of proteins and humic acids in wastewater.
• Interference of carbohydrates.
• Comparison with Lowry method.
• Correlation between calculated and measured organic carbon.

This work developed a method, based on the Lowry method and Frølund modification, for the simultaneous determination of proteins and humic matter in wastewater effluent samples at low concentrations. The method was based on simultaneous spectrophotometric measurements of proteins and humic matter at 750 nm in the absence and presence of CuSO4, which is responsible for increasing the absorbance only in the presence of to proteins. Statistical analysis through ANOVA showed that the response surface of the method fit the experimental measurements at significance level lower than 0.05, indicating satisfactory fit. The quantification limits of the proposed method were 0.5–30 mg/l for proteins and 2–30 mg/l for humic matter. The presence of carbohydrates did not interfere with the analysis of proteins and humic matter at carbohydrate concentrations below 35–40 mg/l. The Lowry method overestimated the concentration of the proteins because of the presence of humic substances. A carbon balance indicated that the analytical method developed could provide a satisfactory distribution of the main organic constituents in wastewater and effluents.

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