Removal Characteristics of Dissolved Organic Nitrogen and Its Bioavailable Portion in a Postdenitrifying Biofilter: Effect of the C/N Ratio

Abstract

Addition of external carbon sources to postdenitrification biofilters (DNFs) is frequently used in municipal wastewater treatment plants to enhance dissolved inorganic nitrogen removal. However, little is known about its influence on the removal of dissolved organic nitrogen (DON). This study investigated the effect of the carbon-to-nitrogen (C/N) ratio (3, 4, 5, and 6) on the removal characteristics of DON and bioavailable DON (ABDON) in the pilot-scale DNFs treating real secondary effluent. Results showed that DNFs effluent DON accounted for 31.2-39.8% of the effluent total nitrogen. The maximum effluent DON and ABDON concentrations both occurred in DNF operated at a C/N ratio of 3. There was no significant difference in effluent DON concentrations in DNFs at C/N ratios of 4, 5, and 6; however, effluent ABDON and DON bioavailability significantly decreased with C/N ratios (p < 0.05, t-test). According to the chemical composition analysis, effluent DON at high C/N ratios tends to contain less % molecular weight < 1 kDa nitrogenous organic compounds and proteins/amino sugars-like nitrogenous organic formulas, which is likely responsible for its low bioavailability. Overall, this study indicates the benefit of a high C/N ratio during the DNF process in terms of controlling the DON forms that readily stimulate algal growth.

Algae Biofilm Reduces Microbe-Derived Dissolved Organic Nitrogen Discharges: Performance and Mechanisms

“…Given the absence of DON in the synthetic wastewater, all of the effluent DON from AB 1 and AS reactors was mDON. The concentration (1.20 ± 0.36 mg•L −1 , Figure 1b) of mDON derived from AS was consistent with those reported in previous studies, 24,44 indicating the universal limitation of AS-based denitrification processes in minimizing mDON formation. In contrast, AB 1 reactors produced mDON in a significantly (Tukey HSD's p < 0.05) lower concentration (0.21 ± 0.16 mg• L −1 ).…”

“…70 Thus, cyanobacteria-dominated AB may be practically more suitable than chlorophytedominated AB for DON control in wastewater treatment. Particularly for the treatment of low C/N ratio wastewater, which readily causes the overproduction of mDON when using the conventional denitrification process, 24 cyanobacteriadominated AB could have growth advantages over other ABs. 53 Nevertheless, validation based on the direct comparison between the cyanobacteria-and eukaryotic microalgaedominant AB processes is required.…”

“…Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) has been widely used for the molecular characterization of dissolved organic matter. ,, Coupling the high-throughput sequencing technologies, the mDON molecular compositions, microbial communities, and their relationships can be explored. Furthermore, recent advances in computational algorithms allow the precise metabolic reconstruction of metagenome-assembled genomes (MAGs) .…”

Molecular characterization of dissolved organic nitrogen during anoxic/oxic and anammox processes using ESI FT–ICR MS

“…The nitrogen in the wastewater discharged from municipal water resource recovery facility leads to eutrophication of aquatic environments (Hu et al, 2018). Thus, many methods have been considered for improving nitrogen removal.…”

Characteristics of Dissolved Organic Nitrogen in the Sediments of Six Water Sources in Taihu Lake, China

“…Lin et al [6] researched six lakes, including Poyang Lake, and Dongting Lake in Hunan and Jiangxi Provinces, China, and reported that the DON content varied from 17.18 mg/kg to 292.31 mg/kg (mean content, 134.45 mg/kg), comprising 51.86% TDN and 7.14% total nitrogen (TN) across the six lakes; in addition, the distribution of DON was closely related to pollution levels in each lake. The sources of DON are extensive, including sediment, organic matter in the soil, microbial and biological organic debris, and their metabolites [7], besides, the effluent discharged from wastewater treatment plants is also an important source of anthropogenic DON loading to surface waters [8,9], with extremely complex composition [10] that can be bioavailable to aquatic plant species and toxic risk [11].…”