Identification of wastewater dissolved organic carbon characteristics in reclaimed wastewater and recharged groundwater

Abstract

Nonvolatile dissolved organic carbon (DOC) in reclaimed wastewaters and groundwater was characterized and indicators of wastewater origin were identified. Over 50% of the DOC in activated carbon and reverse osmosis effluents was classified as hydrophilic, and no humic acid was isolated. In groundwater partially recharged by the reclaimed wastewaters, only 16% of the DOC was hydrophilic, 50% of the DOC was fulvic acid, and humic acid was recovered. The H:C ratios of the isolated fulvic acids were higher in the wastewaters and recharged groundwater than in deep well water not affected by recharge. N:C ratios in the wastewater and recharged groundwater fulvic and humic acid fractions were also higher than in the deep well water. The 1 H NMR spectra of the effluent and recharged groundwater fulvic acid fractions exhibited a characteristic fingerprint pattern, indicating a correlation between origin and spectral appearance. Gas chromatography‐mass spectrometry analysis confirmed the presence of specific trace organic compounds, including EDTA and alkylphenol polyethoxylate residues, in the wastewaters and recharged groundwater.