Dissolved Organic Nitrogen Bioavailability Research Articles

Effect of external carbon source type on effluent dissolved organic nitrogen characteristics in postdenitrifying moving bed biofilm reactors: Chemical molecular and microbial insights

Despite the higher potential for eutrophication of dissolved organic nitrogen (DON) than dissolved inorganic nitrogen, the influence of the types of external carbon sources on DON remains largely unknown. This study investigated the effect of external carbon source type (acetate, glucose, methanol, and ethanol) on effluent DON characteristics in postdenitrifying moving bed biofilm reactors (MBBRs) from chemical molecular and microbial insights. The results showed that the effluent DON concentration in postdenitrifying MBBRs fed different carbon source types followed the order of ethanol > glucose > methanol > acetate. Interestingly, the acetate-fed postdenitrifying MBBR effluent DON contained a less labile molecular composition (5.03%), indicating that these effluent DON are not prone to stimulate algae production in receiving waters. Principal component analysis demonstrated that the produced DON instead of removed and/or resisted DON during the denitrification process mainly contributed to the differences in DON molecular composition and bioavailability in effluent. The key microbes, including Proteobacteria, Chloroflexi, etc. and amino acid metabolism were potentially responsible for the produced DON. Overall, this study demonstrated that MBBRs used for postdenitrification could be optimized to minimize eutrophication effects by accounting for optimal carbon sources and that acetate is recommended as the preferred external carbon source in wastewater treatment using postdenitrifying MBBRs.

Quantitative study on the structure-bioavailability relationship of dissolved organic nitrogen in wastewater treatment plant effluent.

This study systematically investigated the relationship between the structure properties and biological characteristics of dissolved organic nitrogen (DON) in the effluents from municipal wastewater treatment plants. Ultrafiltration, Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV) spectroscopy, and excitation-emission matrix (EEM) fluorescence spectroscopy were used to characterize the structure of organic matters in the effluent samples, and the bioavailability of DON was determined by algal/bacterial-based bioassay. The quantitative analysis of EEM spectra conducted by fluorescence regional integration method showed that the organic portion of all samples was mainly consistent with fulvic acid and protein. Combined with the bioassay results, a positive correlation between the DON bioavailability and the protein content (sum of region I and region II) (r = 0.80, P < 0.02) and soluble microbial byproduct-like materials (region IV) (r = 0.76, P < 0.03) were observed. Nevertheless, the humic substances content represented by the region III and V would negatively affect the DON bioavailability. High humification degree (high HIX value) (r = - 0.77, P < 0.03) was related to low bioavailability. Furthermore, according to UV spectroscopy results, strong aromaticity (high UV254 values) (r = - 0.78, P < 0.03) suggested low DON bioavailability. One protein-like component (C3) and two humic-like components (C1 and C2) were identified via fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC), and component C3 values were positively correlated to the BAN/DON ratio (r = 0.74, P < 0.03). The ultrafiltration showed that the low molecular weight DON (< 3kDa) accounted for 30-73% of the total DON, and no notable relationship was observed for DON molecular weight and its bioavailability.

Effects of organic nitrogen components from terrestrial input on the phytoplankton community in Jiaozhou Bay

Dissolved organic nitrogen (DON) from terrestrial input exacerbates eutrophication and induces harmful algal blooms. We investigated the effects of hydrophilic (Hic) and low molecular weight (LMW) DON on the phytoplankton community in Jiaozhou Bay during autumn (October 2017) and spring (May 2018). Our results showed DON additions significantly increased algal growth while decreasing community biodiversity and provide a competitive advantage for Skeletonema costatum. These situations were further intensified by increasing temperature in autumn. Additionally, Hic DON had a higher bioavailability than LMW DON. Based on emission-excitation matrix spectra, we identified protein-like components as the main components of Hic DON whereas humus-like components were the principal components of LMW. Correlation analysis confirmed a positive correlation between DON bioavailability and protein-like components. Therefore, our results indicate DON from terrestrial input disrupts the structural stability of the phytoplankton community and increases the risk of harmful algal blooms, which in turn threaten coastal ecosystems.

Characteristics of dissolved organic nitrogen in effluent from a biological nitrogen removal process using sludge alkaline fermentation liquid as an external carbon source

The addition of sludge alkaline fermentation liquid (SAFL) to biological nutrient removal (BNR) processes has been widely shown to reduce the dissolved inorganic nitrogen (DIN) in the effluent. However, knowledge regarding the effect of using SAFL in a BNR as an additional carbon source on the characteristics of dissolved organic nitrogen (DON) in the effluent is limited. This study investigated the effect of SAFL addition on effluent DON features and microbial community dynamics in a BNR process treating municipal wastewater. The performance of SAFL was compared with other two reactors (i.e., without an external carbon source and with the addition of sodium acetate). The results showed that the addition of SAFL can significantly reduce effluent DON (p < 0.05). The effluent DON was slightly higher with SAFL than with sodium acetate, but the bioavailable DON of the two reactors was similar (1.06 ± 0.11 vs 1.04 ± 0.12 mg/L, respectively, p > 0.05). The SAFL addition led to a decreased percentage of low molecular weight DON (p < 0.05) as well as an increased ratio of fulvic-like and humic-like substances to proteins-like substances. Moreover, the SAFL addition resulted in a lower percentage of substances resembling proteins/amino sugars and a higher percentage of lignin-like molecules than sodium acetate. These features accounted for the low DON bioavailability. The SAFL promoted the increased abundance of Bacteroidetes, Chloroflexi, Comamonadaceae and Rhodocyclaceae, which could be associated with the decreased effluent DON and its bioavailability. This study indicates that using SAFL as a BNR carbon source not only improves the removal of DIN but also reduces effluent DON and specifically DON bioavailability. These results facilitate the acquisition of comprehensive knowledge regarding the use of SAFL as an alternative external carbon source in the BNR process.

Spatiotemporal Urea Distribution, Sources, and Indication of DON Bioavailability in Zhanjiang Bay, China

In marine environments, urea is an important component of the biogeochemical cycle of nitrogen. The autochthonous and allochthonous sources (rivers, aquaculture, waste water input, etc.) of urea play a key role in urea cycles in adjacent coastal waters. Because urea is a specific marker to trace the sewage fluxes in coastal waters, we investigated urea associated with terrestrial source input and coastal water in Zhanjiang Bay (ZJB) during the time from November 2018 to July 2019, and the spatiotemporal urea distribution and the bioavailability of dissolved organic nitrogen (DON) based on urea concentration in the ZJB were explored. The results showed that the urea enrichment in coastal water was mainly due to discharge from urban sewage systems, rivers, and coastal aquaculture. The concentration of urea ranged from 1.14 to 5.53 μmol·L−1, and its mean value was 3.13 ± 1.02 μmol·L−1 in the ZJB. The urea concentration showed a significantly different seasonal variation in the ZJB (p &lt; 0.05), and the highest and lowest concentrations were found in November 2018 and April 2019, respectively. Its high value appeared in the north and northeast of the ZJB, which were polluted by coastal aquaculture and agriculture fertilizer utilization. The range of urea concentration of terrestrial source inputs in the ZJB was 1.31–10.29 μmol·L−1, and the average urea concentration reached 3.22 ± 0.82 μmol·L−1. Moreover, the total urea flux surrounding the ZJB was 2905 tons·year−1. The seasonal terrestrial source of urea flux contributions had significant seasonal variation in wet, normal, and dry seasons (p &lt; 0.05). The ZJB was subjected to a large flux of urea by estuaries and sewage outlet discharges. The seasonal urea concentration in all stations (&gt;1 μmol·L−1) indicated that urea in the ZJB may have a bioavailable DON source. As a bioavailable nitrogen source, the ability of terrestrial source-derived urea to increase eutrophication should not be ignored in ZJB.

Land-based dissolved organic nitrogen dynamics and bioavailability in Jiaozhou Bay, China

Dissolved organic matter (DOM) samples from forestry, livestock breeding, urban domestic and agricultural sources around Jiaozhou Bay were incubated in seawater to examine DOM dynamics and bioavailability, which is the availability of DOM to degradation by microbes. The fluorescence signals of protein- and humic-like compounds were used as a proxy for bioavailable and refractory materials, respectively, whereas the evolution of SUVA254, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations were used to discuss bioavailability. The high bioavailability DON sources were from livestock breeding and urban domestic sources, with no significant difference, followed by agricultural and forestry sources, with respective degradation rate constants of 0.36 ± 0.01 (mean ± SD) d−1, 0.32 ± 0.03 d−1, 0.22 ± 0.04 d−1, and 0.18 ± 0.01 d−1, and with bioavailable DON (BDON%) representing 70% ± 10%, 67% ± 7%, 62% ± 8% and 37% ± 12% of the total DON, respectively. The turnover times of BDON were 3–6 days, far less than the flushing time of Jiaozhou Bay. Approximately 66% of land-based DON may contribute to DIN by microbial re-mineralization in Jiaozhou Bay, with the main sources being urban domestic, agricultural and livestock breeding. DON seemed to exhibit higher bioavailability than DOC. The temporal evolution of fluorophores and optical indices revealed that bioavailable DOM from livestock breeding and urban domestic sources was high. Spectroscopic properties indicated that the degree of humification of the organic molecules changed significantly for DON from livestock breeding and urban domestic sources, followed by agricultural sources, and forestry sources were the lowest. SUVA254 values and HIX were negatively correlated with DON bioavailability, which can be used as a refractory index and for predicting bioavailable DON.

Effect of Solids Retention Time on Effluent Dissolved Organic Nitrogen in the Activated Sludge Process: Studies on Bioavailability, Fluorescent Components, and Molecular Characteristics.

Wastewater-derived dissolved organic nitrogen (DON) should be minimized by municipal wastewater treatment plants (MWWTPs) to reduce its potential impact on receiving waters. Solids retention time (SRT) is a key control parameter for the activated sludge (AS) process; however, knowledge of its impact on effluent DON is limited. This study investigated the effect of SRT on the bioavailability, fluorescent components, and molecular characteristics of effluent DON in the AS process. Four lab-scale AS reactors were operated in parallel at different SRTs (5, 13, 26, and 40 days) for treatment of primary treated wastewater collected from an MWWTP. Results showed the positive effect of prolonged SRT on DON removal. AS reactors during longer SRTs, however, cannot sequester the bioavailable DON (ABDON) and occasionally contribute to greater amounts of ABDON in the effluents. Consequently, effluent DON bioavailability increased with SRT ( R2 = 0.619, p < 0.05, ANOVA). Analysis of effluent DON fluorescent components and molecular characteristics indicated that the high effluent DON bioavailability observed at long SRTs is contributed by the production of microbially derived nitrogenous organics. The results presented herein indicate that operating an AS process with a longer SRT cannot control the DON forms that readily stimulate algal growth.

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

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.

Algal activity of dissolved organic nitrogen (DON) in the sediments of Lake Taihu, Eastern China

Understanding the contents and reactivity of dissolved organic nitrogen (DON) is important for illustrating its productivity contribution in aquatic ecosystem. The primary objective of this study was to investigate the characteristics and algal activity of DON in the sediments of Lake Taihu. A series of experiments were carried out to evaluate the algal bioavailability of DON fractions in the sediments of Lake Taihu, Eastern China. DON extracted in the lake sediments was separated into hydrophilic and hydrophobic forms by DAX-8 resin, and ammonia nitrogen in raw sample and hydrophilic fraction was removed by cation exchange resin. 77.42–109.18% DON recovery rates were obtained after DON fractionation at ZSW and DPG stations. The hydrophilic DON was the main DON form contributing 62.74–76.33% of total DON concentrations. Selenastrum capricornutum was incubated for 15 days with different nitrogen forms (raw sample, hydrophilic and hydrophobic fractions). Approximately 33.69–79.23% DON of the three fractions was available for algal uptake in the incubation. The order of DON bioavailability was ranked as follows: raw sample > hydrophilic fraction > hydrophobic fraction, indicating that hydrophilic fractions and raw samples exhibited higher DON bioavailability for algae. Parallel factor analysis resulted in identification of tryptophan-like proteins, tyrosine-like proteins and humic acid (HA)-like substances during the incubation periods. During the growth phase, the relative fluorescent intensities of tryptophan-like proteins, tyrosine-like substance and HA-like substance accumulated greatly with 24.84–26.38, 27.82–62.73 and 0–28.92%, respectively.

Algal uptake of dissolved organic nitrogen in wastewater treatment plants

The algal uptake of dissolved organic nitrogen (DON) in the anaerobic–anoxic–oxic (A2O) process was investigated in this study. Anaerobic, aerobic and effluent DON samples from two wastewater treatment plants (WWTPs) were separated into hydrophilic and hydrophobic fractions using a DAX-8 resin coupled with an anion exchange resin and a nanofiltration (NF) pretreatment. Hydrophilic DON accounted for 66.66%–88.74% of the entire DON for the two plants evaluated. After a 15-day incubation, 16.95%–91.75% DON was bioavailable for algal growth, and untreated samples exhibited higher DON bioavailability, with 52.83% DON average uptake rates, compared with the hydrophilic and hydrophobic fractions (45.53% and 44.40%, respectively) because the pretreatment caused the inorganic salt to be resistant to algae. Anaerobic untreated samples, hydrophilic fractions and hydrophobic fractions showed higher DON reduction rates and higher biomass accumulation compared with the other DON fractions due to the decomposition of resistant organics by anaerobic and anoxic bacteria. DON in aerobic and effluent samples of plant A was more bioavailable than that of plant B with usages of 27.49%–55.26% DON. DON bioavailability in the anaerobic–anoxic–oxic process decreased in the following order: anaerobic>effluent>aerobic. The DON contents were reduced after anaerobic treatment in the two plants. The EEM-PARAFAC model identified three DON components, including two humic acid-like substances and one protein-like substance in plant A and two protein-like substances and one humic acid-like substance in plant B.

Effect of coagulation on dissolved organic nitrogen (DON) bioavailability in municipal wastewater effluents

Bioavailable dissolved organic nitrogen (ABDON) can support algal growth and consume oxygen in surface waters. In this study, the variations of ABDON and DON bioavailability in municipal wastewater effluents after coagulation were evaluated by algal bioassay. Surprisingly, the bioavailability of DON increased from 45 to 81% (mean 62%) to 50 to 96% (mean 79%) after coagulation and the concentration of ABDON were not significantly different before and after coagulation (p>0.05, t-test). Correlations of carbon characteristics of DON, specific DON compounds, different fractions of DON, and DON bioavailability were assessed. Spearman’s correlation analysis showed DON bioavailability correlated strongly with hydrophobicity-based DON fractions (r=0.67, p<0.01 and r=−0.60, p<0.05 for hydrophilic and hydrophobic fraction, respectively). Fluorescence excitation-emission matrix (EEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed that proteinaceous materials mainly exist in the hydrophilic fraction, improving the bioavailability of hydrophilic DON. Meanwhile, coagulation preferentially removed the hydrophobic DON, 75±6% of which was non-bioavailable. It was, therefore, the removal of hydrophobic DON that led to the increase of the bioavailability of DON in effluents after coagulation. Further, coagulation pH has been shown to have little effect on the removal of ABDON. These results indicated that coagulation is ineffective at sequestering the DON forms that most readily pose algal growth stimulation problems.

Influence of dissolved organic nitrogen on surface waters

Summary The aim of this study was to determine the susceptibility of dissolved organic nitrogen (DON) contained in biologically treated wastewater disposed from municipal wastewater treatment plants (WWTPs) to biodegradability and bioavailability in a water environment. Additionally an evaluation was performed of the participation of this organic nitrogen fraction, including bioavailable DON (bDON), in the nitrogen balance for the Baltic Sea. Based on the samples of secondary effluent taken from two large municipal WWTPs located in Northern Poland DON bioavailability and biodegradability tests were carried out. It was concluded that DON concentration in the tested samples was on average from 1.5 to 2.0 g N m−3. This fraction constituted as much as 50% of organic nitrogen and 15–18% of total nitrogen contained in treated wastewater. The participation of biodegradable DON (brDON) in activated sludge tests was on average 24–35%. In the bioavailability tests Selenastrum capricornutum were able to use from 19 to 26% of DON, however taking into account the results of the control test, these values are reduced to 3–4%. On the other hand, taking into account the combined effect of bacteria and algae it was possible to reduce the DON concentration by nearly 40%. The estimated annual bDON load introduced to Baltic Sea waters from Poland through disposal of treated biological wastewater in 2010 reached up to 1.7 thousand tons of N year−1.

Dissolved organic nitrogen bioavailability indicated by amino acids during a diatom to dinoflagellate bloom succession in the Changjiang River estuary and its adjacent shelf

This study investigates the bioavailability and potential nutritional role of dissolved organic nitrogen (DON) in the development and progression of a large-scale dinoflagellate bloom that occurred in the Changjiang River estuary and its adjacent shelf (CJREAS) in the East China Sea (ECS). Three cruises were conducted during the late spring and early summer following the bloom progression, i.e., the termination phase of the diatom bloom, and the initiation/growth and peak phases of the dinoflagellate bloom. Concentrations of dissolved organic carbon (DOC), DON, dissolved inorganic nitrogen (DIN), dissolved free amino acids (DFAA) and dissolved combined amino acids (DCAA) were measured. The degradation index (DI), based on the relative abundance of total dissolved amino acids (TDAA) and amino acids yields was applied to indicate the diagenetic alteration of dissolved organic matter (DOM). During the succession from a diatom to dinoflagellate bloom, a decrease in DON co-occurred with a decrease in DIN. Concentrations of DFAA and DCAA also clearly decreased. The yields of DFAA and the DCAA and DI values decreased concomitantly with an increase in the DOC/DON, indicating that bioavailability of DON was relatively higher during the end stage of the diatom bloom than during the peak of the dinoflagellate bloom. These results indicated that DON may provide a significant portion of the total N demand throughout the duration of the large-scale dinoflagellate bloom under conditions of low DIN availability in the CJREAS.

Bioavailability and Characteristics of Dissolved Organic Nutrients in Wastewater Effluents

Excessive phosphorus (P) is considered to be the primary cause for eutrophication in fresh waterbodies and, the increasingly stringent discharge limits have pushed wastewater facilities to achieve extremely low effluent total phosphorus (TP) levels (e.g., 10-50 μg/L). Pushing the P removal to the level of limit of technology has drawn significant attention from both regulatory agencies and wastewater utilities to the removal and bioavailability of various wastewater derived phosphorus fractions such as non-reactive phosphorus (NRP) and dissolved organic phosphorus (DOP). As more advanced treatment processes have been applied to nearly completely eliminate the soluble reactive P (sRP, i.e., ortho-P), these P fractions (NRP and DOP) contribute an increasingly larger percentage and often become the dominant P fractions in the final effluents. For utilities, the concern arises from the substantial capital cost that is required to research and implement more advanced treatment technologies beyond the current practices in order to remove these P fractions. On the regulatory side, current watershed protection plans (e.g., total maximum daily loads (TMDLs)) use TP for setting limits without considering the possibility that those different P fractions may differ in their bioavailability and therefore their potential to cause eutrophication. Bioavailable P (BAP) is defined as the sum of immediately available P and the P that can transform into an available form by naturally occurring physical, chemical, and biological processes. Although rarely analyzed in routine monitoring, effluents from municipal treatment plants contain various P forms, all of which may have different availabilities to algae and other primary producers. In addition, the bioavailability of different P fraction depends on the different sources of wastewater as well as the method and incubation length of the bioassay used. Currently, little information is available about the bioavailability of various P fractions in various wastewater effluents. Particularly, there is limited information on the bioavailability of wastewater derived DOP to eutrophying phytoplankton in receiving waters. Therefore, it is critical to further identify DOP components and their bioavailability. This study investigated and assessed: • The bioavailability of various P fractions, particularly dissolved P fractions (DOP), in advanced wastewater effluents. • The nature and composition of effluent DOP and its association with effluent dissolved organic nitrogen (DON). • The link and correlation of wastewater characteristics and treatment process with bioavailable effluent DOP. Tertiary effluents from the selected representative wastewater treatment plants were collected and subjected to a detailed and comprehensive analysis for wastewater characterization, phosphorus fractions analysis, and bioavailability assays. Standard methods were employed for the phosphorus fractionation and speciation analysis. Wastewater effluent fingerprinting was performed using fluorescence spectrum and parallel factor (PARAFAC) analysis to gain insights into the nature and characteristics of the effluent organic nitrogen and phosphorus. The bioavailability of P fractions in effluents were assessed using both chemical enzymatic assays and algal bioassays. For selected effluents, simultaneous DOP and DON bioavailability assays were performed to elucidate the differential availability of wastewater effluent-derived organic nitrogen and phosphorus and their association with hydrophilic versus hydrophobic fractions. The results provided: • Information on the bioavailability of different P fractions, particularly the dissolved P fractions, in effluents from a range of advanced treatment processes/technologies. • Revealed the nature of dissolved organic phosphorus in highly treated wastewater effluents via fluorescence spectrum analysis and C/N and C/P ratio evaluations. • Elucidated the correlation between bioavailable effluent DOP and DON with different water fractions (hydrophilic versus hydrophobic), as well as with wastewater sources (humic substances versus proteinaceous matters). • Identified the potentially bioavailable P fractions in effluent and suggested possible mechanisms for their effective removal. This title belongs to WERF Research Report Series ISBN: 9781780405568 (eBook)

Effect of High Flow Events on In-Stream Dissolved Organic Nitrogen Concentration

Dissolved organic nitrogen (DON) can comprise a large and biologically important fraction of total dissolved N in surface water. Biotic and abiotic processes result in heterogeneous DON concentrations and bioavailability in soils, and as hydrologic connectivity expands and flow paths change in watersheds, novel sources of DON can be mobilized and transported to surface water. Although the relationship between in-stream DOC concentration and stream discharge has previously been examined in the literature, up to now there has not been a synthesis examining how DON concentrations, loads, and composition change during transitions from base flow to pulse flow conditions. We present a meta-analysis examining the effect of high flow on DON concentration ([DON]). The ratio of mean pulse flow [DON] to mean base flow [DON] (P:B) was calculated for individual events and averaged (geometric) within and then across sites to generate an overall effect size. For 47 sites (78 events), mean P:B was 1.58, which was significantly different from unity. This moderate increase in DON concentration contributed to over a more than 10-fold average increase in the rate of DON yield from base flow to high flow. The response of [DON] to high flow was significant in catchments where individual storm events or snowmelt runoff events were responsible for elevated flows, whereas the response was not significant in catchments where high discharge resulted from a mixture of upstream snowmelt and rain events. Additionally, an examination of DOC:DON ratios during high flow indicates that multiple sources of DON may be mobilized during high flow. Finally, current models of annual DON export may be improved by including a positive relationship between discharge and DON.

Bioavailability of Dissolved Organic Nitrogen in Treated Effluents

The research objective was to assess dissolved organic nitrogen (DON) bioavailability in wastewater effluents from a pilot-scale nitrification plant and a laboratory-scale total nitrogen (TN) removal plant. The DON bioavailability was assessed using a 14-day bioassay protocol containing bacterial and algal inocula. Nitrogen species, dissolved organic carbon, chlorophyll a, and biomass (as total suspended solids and culturable cell counts) concentrations were measured to assess DON bioavailability. The results showed an increase in algal chlorophyll a concentration, with a concurrent increase in algal biomass over time; increased bacterial counts and a decrease in DON concentration over time; and increased carbon-to-nitrogen ratio at the end of the 14-day bioassay, indicating effluent DON bioavailability to algae and bacteria. Approximately 18 to 61% of the initial DON in low-total-nitrogen wastewater effluent (TN = 4 to 5 mg/L) sample was bioavailable. The results show that bacteria and algae uptake and release DON during their growth.

BIOAVAILABILITY OF DISSOLVED ORGANIC NITROGEN IN TREATED EFFLUENTS

The research objective was to assess dissolved organic nitrogen (DON) bioavailability in wastewater effluents from a pilot-scale nitrification plant and a laboratory-scale total nitrogen (TN) removal plant. The DON bioavailability was assessed using a 14-day bioassay protocol containing bacterial and algal inocula. Nitrogen species, dissolved organic carbon, chlorophyll a, and biomass (as total suspended solids and culturable cell counts) concentrations were measured to assess DON bioavailability. The results showed an increase in algal chlorophyll a concentration, with a concurrent increase in algal biomass over time; increased bacterial counts and a decrease in DON concentration over time; and increased carbon-to-nitrogen ratio at the end of the 14-day bioassay, indicating effluent DON bioavailability to algae and bacteria. Approximately 18 to 61% of the initial DON in low-total-nitrogen wastewater effluent (TN = 4 to 5 mg/L) sample was bioavailable. The results show that bacteria and algae uptake and release DON during their growth.

Bioavailability of dissolved organic nitrogen and carbon from nine rivers in the eastern United States

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 43:277-287 (2006) - doi:10.3354/ame043277 Bioavailability of dissolved organic nitrogen and carbon from nine rivers in the eastern United States Tracy N. Wiegner1,5,*, Sybil P. Seitzinger2, Patricia M. Glibert3, Deborah A. Bronk4,6 1Institute of Marine and Coastal Sciences, and 2NOAA CMER Program, Institute of Marine and Coastal Sciences, Rutgers, The State University of New Jersey, 71 Dudley Road, New Brunswick, New Jersey 08901-8521, USA 3Horn Point Laboratory, University of Maryland Center for Environmental Science, PO Box 755, Cambridge, Maryland 21613, USA 4Department of Marine Sciences, University of Georgia, 220 Marine Sciences Building, Athens, Georgia 30602-3636, USA 5Present address: Marine Science Department, University of Hawaii at Hilo, 200 W. Kawili Street, Hilo, Hawaii 96720, USA 6Present address: College of William and Mary/VIMS, Department of Physical Sciences, Route 1208, Greate Road, Gloucester Point, Virginia 23062, USA *Email: wiegner@hawaii.edu ABSTRACT: Dissolved organic nitrogen (DON) and carbon (DOC) often dominate the dissolved nitrogen and organic carbon fluxes from rivers, yet they are not considered to affect coastal water quality because of their assumed refractory nature. The objective of this study was to quantify DON and DOC bioavailability to bacteria in 9 rivers on the east coast of the United States during a 6 d dark bioassay experiment. Water was collected from the freshwater portion of a forest stream in New Jersey (Forest 17a), and from the Bass (New Jersey), Delaware (New Jersey), Hudson (New York), Altamaha (Georgia), Savannah (Georgia), Pocomoke (Maryland), Choptank (Maryland), and Peconic (New York) Rivers during base-flow conditions. DON concentrations ranged from 1 to 35 µM and comprised 8 to 94% of the total dissolved nitrogen (TDN) in these rivers. Bioassay results indicate that 23% (±4) of the DON (2 ± 1 µM) was bioavailable in all the rivers except the Bass and Pocomoke, where no DON consumption was measured. Of the TDN consumed by bacteria, DON comprised 43% (±6), demonstrating that DON is an important nitrogen source for bacteria. In contrast, only 4% (±1) of DOC (12 ± 3 µM), was bioavailable in the 9 rivers. Percent-wise, 8 times more DON was consumed relative to DOC in 6 of the rivers, demonstrating that DON cycles faster than DOC. Overall, our study demonstrates that DON is an important part of the TDN pool that needs to be incorporated into coastal nitrogen loading budgets because it is bioavailable on the order of days. KEY WORDS: Bacteria · Bioavailability · DON · DOC · Rivers Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 43, No. 3. Online publication date: July 19, 2006 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2006 Inter-Research.

SUMMER INPUTS OF RIVERINE NUTRIENTS TO THE BALTIC SEA: BIOAVAILABILITY AND EUTROPHICATION RELEVANCE

Most nitrogen and phosphorus transported by world rivers to the oceans is associated with dissolved organic matter. However, organic matter as a potential source of N and P has hitherto been largely neglected in studies of coastal microbial food webs. We examined 50 rivers, draining a major part of the Baltic Sea watershed, with respect to summer concentrations, chemical composition, and biological availability of N and P. The broad spectrum of rivers studied enabled us to assess whether the input of terrigenous organic matter can be an important nutrient source, at various levels of anthropogenic loading of inorganic N and P. Concentrations of total N and P ranged from 9 to 220 μmol/L and from 0.14 to 5.56 μmol/L, respectively, with the highest concentrations in the southern part of the Baltic Sea drainage area and in several rivers on the Finnish western coast. Urea and dissolved combined amino acids (DCAA) each constituted 4–20% of dissolved organic nitrogen (DON), while dissolved free amino acids (DFAA) made up <3% of DON. The contribution of urea and amino acids to the DON pool was inversely correlated with DON concentration. Bacterial regrowth bioassays in selected rivers demonstrated that ∼30% of DON and ∼75% of dissolved organic phosphorus (DOP) was potentially available to the indigenous bacterial assemblage of the Baltic Sea, and hence susceptible to mineralization within the pelagic food web. Our study is among the first to demonstrate that bacterioplankton are able to utilize a major part of DON and DOP from a broad spectrum of natural waters. The C:N ratio, absorbance spectra, and fluorescence properties of the organic matter suggest that the observed high bioavailability of DON and DOP was due to a large contribution of organic matter from riverine primary production compared to the humic matter derived from terrestrial vascular plants. In addition, algal and bacterial cells dominated the transport of particulate organic material, further enhancing productivity of coastal waters. No correlations were found between DON bioavailability and the fraction of DON bound in urea and amino acids, indicating a utilization of other N compounds (e.g., amides) by the bacteria. We estimate that the input of summer riverine N to the Baltic Sea consists of 48% dissolved inorganic N, 41% DON, and 11% particulate N. Corresponding values for phosphorus are 46%, 18%, and 36% of dissolved inorganic P, DOP, and particulate P, respectively. During the thermal summer stratification, when freshwater inputs are trapped in the surface layer, rivers contribute ∼30% of N and ∼5% of P needed to support the export production (plankton sedimenting out of the photic layer) in the Baltic Sea. The high availability to bacteria suggests that DOP is a major stimulator of pelagic productivity in the P-limited northern part of the Baltic Sea. Based on reported concentrations in other areas, we suggest that the global contribution of riverine organic N and P to the primary production of coastal waters is comparable to the contribution of inorganic nutrients.

Bioavailability of DON from natural and anthropogenic sources to estuarine plankton

Utilization of dissolved organic nitrogen (DON) from natural (forests) and anthropogenic (animal pastures, urban/suburban storm water runoff) sources (three sites per source) by estuarine plankton communities was examined in spring, summer, and fall. The proportion of DON utilized ranged from 0 to 73%. Overall, urban/suburban storm water runoff had a higher proportion of bioavailable DON (59% ± 11) compared to agricultural pastures (30% 14) and forests (23% ± 19). DON bioavailability varied seasonally; however, the seasonal pattern differed for the three sources. Bacterial production increased linearly with the amount of DON utilized across all sources and seasons; the rate of increase was approximately five times greater per micromole of N as DON used relative to dissolved inorganic N (DIN) used. Although phytoplankton production generally increased with DON addition, the increased production was not correlated with the amount of DON utilized, suggesting that a variable portion of dissolved organic matter (DOM)‐N was directly or indirectly available to the phytoplankton. This indicates that phytoplankton production is not a good measure of the amount of bioavailable DON, and measurements of the amount of bioavailable DON based on bacterial responses alone might not reflect N available to phytoplankton. Preliminary seasonal budgets of bioavailable N (DIN plus bioavailable DON) as a function of land use suggest that ~80% of the total dissolved N (TDN) from urban/suburban runoff is bioavailable, whereas a lower proportion (20–60%) of TDN is bioavailable from forests and pastures. N budgets for aquatic ecosystems based on only DIN loading underestimate bioavailable N loading, whereas total N or TDN budgets overestimate bioavailable N inputs.