Bioavailability and characterization of dissolved organic nitrogen and dissolved organic phosphorus in wastewater effluents

• Published in: The Science of the total environment Vol. 511; pp. 47 - 53
• Main Authors: Qin, Chao, Liu, Haizhou, Liu, Lei, Smith, Scott, Sedlak, David L., Gu, April Z.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2015
• Subjects: Algae; anion exchange resins; Bioavailability; carbon nitrogen ratio; deoxynivalenol; Dissolution; dissolved organic matter; Dissolved organic nitrogen; Dissolved organic phosphorus; DON; Dopants; Effluents; Environmental Monitoring; Eutrophication; factor analysis; fluorescence; Fluorescence spectroscopy; Hydrophilic; hydrophilicity; Hydrophobic fractionation; hydrophobicity; Nitrogen - analysis; Nitrogen - chemistry; phosphorus; Phosphorus - analysis; Phosphorus - chemistry; Plants (organisms); Resins; Waste Disposal, Fluid; Waste water; Waste Water - chemistry; wastewater; Wastewater effluent; Wastewater treatment; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Fluorescence spectroscopy; Hydrophobic fractionation; DON; Hydrophilic; Dissolved organic nitrogen; Wastewater effluent; Bioavailability; Dissolved organic phosphorus; Eutrophication
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.11.005

There is still a great knowledge gap in the understanding of characteristics and bioavailability of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in wastewater effluents, which surmise implications related to both discharge regulation and treatment practice. In this study, we simultaneously investigated the characteristics and bioavailability of both DON and DOP, with separated hydrophilic versus hydrophobic fractions, in highly-treated wastewater effluents for the first time. The tertiary effluents from two wastewater treatment plants were separated into two fractions by XAD-8 resin coupled with anion exchange resin based on the hydrophobicity. Results showed that the majority of DON was present in hydrophilic forms while more DOP existed in hydrophobic forms. Hydrophilic DON contributed to 64.0%–72.2% of whole DON, while hydrophobic DOP accounted for 61.4%–80.7% of total DOP for the two plants evaluated. The effluents and their fractions were then subject to bioavailability assay based on 14-day algae growth. The results indicated that majority (~73–75%) of the effluent DOP, particularly the hydrophobic fraction with lower C/P ratio was more likely to be bioavailable for algal growth. The bioavailable fraction of DON varied widely (28%–61%) for the two plants studied and the hydrophilic fraction with lower C/N ratio seemed to exhibit higher bioavailability than the hydrophobic portion. The differences in bioavailable DON and DOP distributions of effluents from those two plants could be attributed to different receiving effluent compositions and wastewater treatment processes. In addition, fluorescence excitation–emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) were used to characterize the dissolved organic matter (DOM) in wastewater effluent, which provided insights into the nature of organic matter in wastewater samples with different characteristics and originating sources. [Display omitted] •The bioavailability of DON/DOP in wastewater effluents were examined.•The majority of DON was hydrophilic while more DOP existed in hydrophobic forms.•Hydrophobic fraction of effluent DOP was more likely to be bioavailable for algae.•Hydrophilic fraction of effluent DON seemed to exhibit higher bioavailability.•Fluorescence spectroscopy analysis provided insights of DOM in wastewater effluents.