Article pubs.acs.org/est
Overlapping Photodegradable and Biodegradable Organic Nitrogen in Wastewater Effluents Halis Simsek,† Tanush Wadhawan,‡ and Eakalak Khan*,‡ †
Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, North Dakota 58108, United States Department of Civil Engineering, North Dakota State University, Fargo, North Dakota 58108, United States
‡
S Supporting Information *
ABSTRACT: Photochemical degradation of dissolved organic nitrogen (DON) in final effluent of trickling filter and activated sludge wastewater treatment plants (WWTPs) was studied. Inorganic N, mostly nitrite, was produced from the photodegradation of DON for samples from both WWTPs. Photodegradable DON (PDON), biodegradable DON (BDON), and overlapping photodegradable− biodegradable DON (OPBDON) were determined. BDON was associated with PDON as well as non-PDON. BDON and PDON concentrations in the final effluent samples were 4.71 and 4.62 mg N/L for the trickling filter plant and 3.95 and 3.73 mg N/L for the activated sludge plant, indicating that photodegradation is as important as biodegradation in the mineralization of effluent DON in receiving waters. OPBDON, which is more problematic in the water environment because it can be mineralized by light or bacteria or both, was 3.68 and 2.64 mg N/L (57% and 43% of total DON) in the final effluent samples from the trickling filter and activated sludge plants, respectively. The DON fraction that is resistant to biodegradation and photodegradation was 10% to 20% of total DON.
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artificial light (DEST Heraus solar simulator, 860 W/m2 for the 200−3000 nm wavelength range normalized to absorption coefficient at 350 nm) for different exposure times from 4.8 to 72 h. Ammonium was photochemically released from all exposed samples regardless of the light source (natural versus artificial). They concluded that exposure time and initial concentration of humic substances affect the photodegradation efficiency of DON and photodegradable DON (PDON) is up to 20% of the total DON in coastal waters. Bronk et al.1 investigated photodegradation of effluent organic nitrogen (EON) from two enhanced nutrient removal WWTPs. Grab samples of the effluent were collected prior to ultraviolet (UV) disinfection at the two WWTPs and were named as EON4 and EON5. The samples were exposed to natural sunlight for 0 (control), 9, and 33 h. Significant photoproduction of NH4+ and DPA was observed from both EON4 and EON5 samples, but NO2− release was observed only in EON4 samples. Biodegradable DON (BDON) is a portion of DON that can be mineralized (ammonified) by an acclimated mixed bacterial culture.11 Khan et al.12 developed a procedure for measuring BDON in wastewater that is analogous to the biochemical oxygen demand (BOD) method. Wastewater effluent DON is
INTRODUCTION Wastewater treatment plants (WWTPs) discharge effluents that normally contain significant amounts of dissolved organic nitrogen (DON) into surface waters. Because of its complexity, effluent DON may not be instantaneously bioavailable to some or all bacterial, algal, and phytoplankton species in the aquatic environment. However, photodegradation of DON in WWTP effluent provides biologically available nitrogen-rich labile compounds which could contribute to eutrophication in receiving waters.1 Photochemical reactions increase the lability of organic material in marine and freshwater ecosystems by converting recalcitrant compounds into reactive materials and, ultimately, these photoreactive organic compounds increase bioavailable N in the aquatic environment.2 Photochemical release of lower molecular weight components and uncharacterized labile compounds causes undesirable conditions in aquatic systems by affecting bacterial growth, bacterial nutrient demand, bacterial biomass, and respiration rates in the water body.1,3,4 Exposure to sunlight or artificial light causes DON to release NH4+, NO2−, urea and amino acids, dissolved primary amines (DPA), humic-associated nitrogen species, and unidentified organic nitrogen complexes.1,3−10 Bushaw et al.5 studied the photochemical conversion of DON in humic substances from an estuary into biologically available components. Humic substances are biologically refractory, high-molecular-mass components; however, exposure to sunlight causes humic substances to release nitrogenous compounds. They experimented with natural sunlight and © XXXX American Chemical Society
Received: January 9, 2013 Revised: May 28, 2013 Accepted: May 31, 2013
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made up of 27−80% BDON.11,13−15 BDON after being converted to ammonia can lead to oxygen consumption and support eutrophication. Ammonia biologically produced from DON ammonification can serve as a preferred nitrogen source for bacterial and algal growth. Studies have shown substantially more DON reduction and chlorophyll a production when wastewater effluent is incubated with acclimated bacteria and the algal species Selenastrum capriconutum.13,14,16,17 Less BDON in treated wastewater is therefore desirable to minimize its negative impact on receiving water quality. There has been very limited information on BDON removal by WWTPs. Simsek et al.11 reported 72% BDON removal by a two-stage trickling filter WWTP. There has been no study to thoroughly investigate the relationship between BDON and PDON. It is not known whether the photodegradable portion of DON is BDON and/ or non-BDON (NBDON). PDON and BDON could overlap, and the overlapping portion of DON is more problematic in the water environment due to the greater probability to be decomposed (by both photodegradation and biodegradation) to ammonia and/or nitrite (and eventually nitrate) which could support eutrophication. This common portion of DON should be minimized by WWTPs to reduce the potential impact of effluent DON on receiving waters. Quantifying this portion of DON in wastewater effluent is the first step toward that goal. To the best of our knowledge, only one study has been conducted on the photodegradation of wastewater derived DON to determine photolabile compounds released from DON by light exposure.1 The study did not determine the extent to which any portion of PDON was also biodegradable. This paper presents an experimental study that was conducted to understand the relationship between PDON and BDON in wastewater effluent. Final effluents from two-stage trickling filter and activated sludge combined with moving bed bioreactor (MBBR) WWTPs were studied.
UV−visible spectra of the samples are shown in the Supporting Information (Figure SI-1). Absorbance was observed mainly in the UV range, and the spectra for the two WWTPs were similar. Sample Preparation. All samples from both WWTPs were filtered through a 0.2 μm pore-size hydrophilic polyethersulfone membrane filter (Pall Co., Port Washington, NY, USA). The filtered samples were autoclaved for 15 min to remove any remaining bacteria. Light exposure was started immediately after the samples were filtered and autoclaved. An experiment was performed to address the effects of autoclaving on DON and its photoreactivity in the samples. Results shown in Figure SI-2 in the Supporting Information indicate that autoclaving reduces DON very minimally (1.4 to 6.6%). Table SI-1 in the Supporting Information shows that the chemical constituents of autoclaved samples kept in the dark for 6 days were stable (very limited changes in DON or other nitrogen species were observed). This suggests that autoclaving did not affect the photoreactivity of the samples. Inocula Collection and Preparation. Bacteria for BDON determination were collected from the Fargo and Moorhead WWTPs and used to inoculate respective samples from these plants. Wastewater influent was used as a bacterial inoculum for the Fargo WWTP samples. The Fargo WWTP recycles settled solids from intermediate and final clarifiers, and hence, the wastewater influent contains a representation of mixed bacterial culture in the treatment facility. For the samples from the Moorhead WWTP, mixed liquor suspended solids (2,500 mg suspended solids/L) were diluted 10-fold by distilled deionized water and used as a bacterial inoculum. Experiments conducted with mixed liquor suspended solids (MLSS) and wastewater influent inocula produced consistent results in a previous study.11 The MLSS and wastewater influent samples were collected fresh before every experiment. Experimental Setup and Operation. UV light experiments were conducted using 400 mL of samples from each treatment plant in 500 mL quartz beakers, which were used to allow the majority of UV to penetrate. The quartz beakers were covered with parafilm and aluminum foil to prevent any evaporation. All quartz beakers were placed on an orbital shaker (80 rpm) during light irradiation, and the shaker was turned off automatically when the UV light was off for a dark period. All the experiments were conducted at room temperature (20 °C). Two UV lamps (306 nm peak and 15 W each, radiation intensity at a distance of 1 m of 0.5 W/m2 for each lamp, Universal Light Source Inc., San Francisco, CA) were attached to clamp holders in parallel along the two sides of the beakers. A similar type of UV light (peak intensity of 306 nm) was used to study photodegradation of DON in seawater samples by Xie et al.18 In addition, a peak intensity of 300 nm has been used in a previous study on overlapping photodegradable and biodegradable organic carbon in lake and river waters.19 The UV lamps were placed about 30 cm from the samples. The spectrum range of the UV light was 281 to 355 nm. Information on relative energy and radiation intensity at different wavelengths is provided in the Supporting Information (Figure SI-3). The light intensity, which was provided by the lamp manufacturer, was measured using a digital radiometer (G&R Laboratories, Model 100, Santa Clara, CA, USA). The samples were filtered through a 0.22 μm pore-size filter resulting in nonturbid and colorless filtrates, which facilitated UV light penetration with little or no attenuation. In addition, quartz beakers were used to minimize light attenuation. Light attenuation was not a major concern in this study, and a detailed explanation has been included in Detailed Information SI-1 (Supporting Information).
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EXPERIMENTAL SECTION Sample Source and Characteristics and Plant Description. Approximately 1.5 L samples of final effluent (grab samples) were collected from two different WWTPs: the City of Fargo WWTP (Fargo, ND, USA) and the City of Moorhead WWTP (Moorhead, MN, USA). Samples were collected at 2 to 3 week intervals on six different occasions during the winter months (November to March). Fecal coliform numbers are not regulated during the winter months at either plant; therefore, chlorination and dechlorination were not performed during the sampling period. These two plants were selected because of the differences in the processes and similarities in the nature of the wastewater characteristics. The two plants are located in the same metropolitan area. The Fargo WWTP has an average flow of 57,000 m3/day with a peak pumping capacity of 110,000 m3/day. It primarily treats the wastewater for BOD and ammonia through the two-stage trickling filter process, which consists of BOD and nitrification trickling filters. The Moorhead WWTP has an average flow of 15,000 m3/ day with a peak pumping capacity of 38,000 m3/day. The plant treats the wastewater for BOD and ammonia through high purity oxygen activated sludge (HPO-AS) and MBBR. Both plants have to comply with the discharge limits for BOD and ammonia but are not regulated for any total nitrogen or total phosphorus limits. The average pH of the samples from the Fargo and Moorhead WWTPs was 7.30 and 8.25, respectively. Dissolved organic carbon (DOC) in the samples from Fargo and Moorhead WWTPs averaged 16.87 mg/L and 15.22 mg C/L, respectively. The B
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(dark) treatment was conducted at 20 °C using 400 mL of each sample in 500 mL amber bottles. The control was treated in the same manner as the light treatment with the exception that it was kept in the dark for the entire experiment. After 3 days of UV light exposure, DON in the sample was determined (DONf(UV, 3 days)) and consequently PDONUV, 3 days was calculated using eq 3. The subscript UV, 3 days denotes 3 days (10 h/day) of UV light exposure.
The light exposure was 10 h per day for 3 or 6 consecutive days. Samples were kept in the dark for the remaining 14 h in a day. This light exposure pattern was selected to simulate the day and night conditions that the wastewater sample is exposed to in receiving waters. The 3 and 6 days of light exposure were selected to allow sufficient time for degradation of organic nitrogen in the samples. Light exposure time in previous studies varied from 6 h to 19 days.1,4,5,20 Light exposure of more than 6 days (7, 9, and 12 days) was conducted at the beginning of the study, and the DON degradation results were only marginally different from the 6-day exposure results. DON and BDON Determinations. Thirty milliliters of the filtered and autoclaved sample was used to measure dissolved ammonia N (DNH3−N), dissolved nitrite N (DNO2−N), dissolved nitrate N (DNO3−N), and TDN, and the results were used to calculate DON before incubation [initial DON (DONi)] according to eq 1. The detailed procedure for BDON determination was described in a previous study.11 Briefly, 170 or 200 mL of the filtered sample was mixed with 1.7 or 2 mL of the inoculum, respectively, in a 250 mL amber bottle. The mixture was aerated by thorough shaking and incubated in the dark at 20 °C for 28 days before determining DON [final DON (DONf)]. The BDON procedure relies on the change of DON in the sample before and after incubation. Pre- and postincubation DON was determined in the same manner using eq 1, and BDON was calculated using eq 2. During the incubation period, the solution in the bottle was manually shaken to aerate at least once every day to maintain aerobic conditions. A control (sample b) was prepared by adding the inoculum to distilled deionized water and treating it the same way as the sample (DONbi and DONbf).
PDONUV,3 or 6 days = (DONi − DONf(UV,3 or 6 days)) − [(DONi − DONf(UV,3 or 6 days))]control
Before the UV light exposure, BDONi was determined as described in the preceding subsection. After 3 days of UV light exposure, 170 mL of sample was used for final BDON measurement (BDONf(UV, 3 days)). It should be noted that DONi in the BDONf(UV, 3 days) measurement is DON after the light exposure. Six-day UV light experiments were conducted by extending the light exposure for 3 more days after the 3-day UV light experiments. PDONUV, 6 days calculation was based on eq 3. It should be noted that BDONi was the same for the 3-day and 6-day experiments. Overlapping photodegradable−biodegradable DON (OPBDON) values for 3 or 6 days of UV light exposure (OPBDONUV, 3 or 6 days) were determined using eq 4: OPBDONUV,3 or 6 days = (BDONi − BDONf(UV, 3 or 6 days)) (4)
Four possible scenarios exist for the calculation of OPBDON. (1) BDONf = 0 (all of the BDONi is associated with PDON), OPBDON = BDONi This scenario is applicable when BDONi is completely photodegraded to inorganic N (no BDON is left after the light exposure). (2) BDONf = BDONi (all of BDONi is associated with nonPDON (NPDON)), OPBDON = 0 This case occurs when BDONi is completely resistant to photodegradation (BDON level is not affected by the light exposure). (3) BDONf > BDONi, OPBDON cannot be determined. This case is possible only if NBDONi gets photodegraded into BDON. Under this case, there are two possibilities. If NBDONi is photodegraded into BDON and BDONi is not converted into inorganic N at all, OPBDON does not exist (OPBDON = 0). If NBDONi is photodegraded into BDON more than BDONi that is photolytically mineralized into inorganic N, OPBDON exists. Regardless, these two possibilities are not distinguishable experimentally, and as a result, OPBDON cannot be determined. (4) BDONf < BDONi and BDONf ≠ 0 (BDONi is associated with both PDON and NPDON), OPBDON = (BDONi − BDONf) This scenario occurs only when a portion of BDONi is photodegraded to inorganic N and/or NBDON but the conversion of BDONi to NBDON is not likely. As stated in scenario 3, it is possible that NBDONi is converted to BDON and/or directly to inorganic N. BDON photolytically produced from NBDONi can be further photodegraded to inorganic N. As a result, quantifying the exact phototransformation between BDON and NBDON is not feasible. To estimate OPBDON, an assumption that photoproduced BDON from NBDONi is further photodegraded to inorganic N is required.
DONi or f = TDN − (DNH3−N) − (DNO2 −N) − (DNO3−N) BDON = (DONi − DONf ) − (DONbi − DONbf )
(3)
(1) (2)
PDON and OPBDON Determinations. The procedure for determining PDON is summarized in Figure 1. The control
Figure 1. Schematic diagram of the PDON procedure. C
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Inorganic Nitrogen Species and TDN. During the course of experiments, no major changes in nitrate concentration were observed after 3 and 6 days of light exposure for samples from both plants (Figure SI-4 in the Supporting Information). Nitrate concentration before and after light exposure varied between 30.65 and 31.23 mg N/L in the samples from the Fargo plant. The corresponding values for the Moorhead plant samples were 23.76 to 24.02 mg N/L. These narrow variations in nitrate levels before and after light exposures are evidence that nitrification did not occur or was not substantial during the light irradiation. Other researchers also did not observe any major changes on nitrate concentration during simulated or natural solar irradiations.6,8,23 Following BDON incubation, nitrate concentrations increased, as expected, in all samples due to nitrification. Initial nitrite concentrations in all the samples from both plants were less than 0.5 mg N/L and gradually increased through 3 and 6 days of UV light exposure (Figure 2a). Nitrite increases were from the photodegradation of DON. Kieber et al.9 observed nitrite production from photodegradation of humic substances isolated from coastal waters by 6 h of sunlight exposure. In their samples, nitrite increases varied between 40% and 118%. They concluded that the initial nitrite concentration and irradiation time positively correlated with the photoproduction of nitrite. Following BDON incubation, nitrite concentrations were low in samples from both plants (150 nm. When the spiked concentration was higher than 150 nM, NO2− decreased to less than 150 nM.9 Overlapping Photodegradable−Biodegradable Dissolved Organic Nitrogen. From the BDON and PDON data collected, it is possible to determine whether PDON and BDON are overlapping (OPBDON). As discussed above in the Experimental Section, four different scenarios for OPBDON calculations exist. Only the fourth scenario (BDONi is associated with both PDON and NPDON) was observed in this study. In this scenario, a portion of PDON is OPBDON, and OPBDON = BDONi − BDONf (Figure 6). This calculation of OPBDON is valid when complete photodegradation of NBDONi to BDON and further into inorganic N is assumed. A total dissolved nitrogen balance before and after the UV light exposure was observed in this study (Table SI-2 in the Supporting Information). The amounts of nitrite produced in the samples shown in Table SI-2 (Supporting Information) were greater than the BDON decrease due to light exposure. That means that the nitrite produced must also be from source(s) other than BDONi. The amounts of NBDON reduction during the light exposure were very close to the unaccountable nitrite increases. Nitrite could come from ammonia; however, increases in ammonia were observed after the light exposure (Table SI-2 in the Supporting Information). Hence, the above assumption is valid as the changes in NBDON before and after the light exposure were approximately equal to the increase of nitrite (after compensating for BDON decreases) for the samples from both treatment plants.
Figure 5. (a) PDON for 3 or 6 days of light exposure and (b) PDON as a percentage of initial DON for samples from the Fargo and Moorhead WWTPs.
samples for both plants are presented in Figure 5b. The results are similar between the two WWTPs. DON photodegradability of the samples were quite high (50% to 70%), which is not desirable from the receiving water quality standpoint. PDON concentrations were 4.62 and 3.73 mg N/L for the Fargo and Moorhead WWTPs, respectively. About 0.45 and 0.53 mg/L of PDON were converted to DNH3−N for the Fargo and Moorhead samples, respectively, while the rest was transformed to DNO2−N. Application of UV as a disinfectant in WWTPs is increasingly more common due to the germicidal characteristics of light at wavelengths 220 and 320 nm.25 This study indicates that UV could produce PDON in wastewater effluent. However, Sattayatewa et al.26 observed no change in effluent DON during the operation of two WWTPs that used UV for disinfection. This might be due to insufficient UV dose and contact time in their study. Several studies have reported release of NH4+ from DON upon exposure to light.1,7,8,18,20,24,27,28 Bronk et al.1 reported photomineralization of effluent organic nitrogen to NH4+ and NO2−; however, NO2− was observed only in low concentrations in one of the two samples studied. Higher NO2− formation was observed in this study. The difference in type and magnitude of inorganic N production could be due to different DON characteristics and light source. For example, effluent samples in the study of Bronk et al.1 were from TN removal treatment plants and therefore went through different type and extent of biological treatment compared to the samples used in this study, which were not from TN removal plants. Koopmans and Bronk6 exposed surface water and surficial groundwater to sunlight. Photoproduction of NH4+ was observed only in surface water samples, which have more DON and DIN (77−97% of TDN was DON). Nitrogen in surficial groundwater samples was dominated by DIN (80% of TDN was DIN).6 The results suggest that the composition of N affects the photoproduction of DIN from DON. Jeff et al.27 used DON concentration and pH to predict the degree of photoammonification in 7 lake samples. Only 0.18− 0.3% of the DON pool in their samples was converted to NH4+. F
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DON that can be degraded strictly by light (PDON associated with NBDON), and DON that can be degraded only biologically (BDON associated with NPDON) exists. As described above, overlapping between NPDON and NBDON (NPDON∩NBDON portion in Figure 6), which is DON that is recalcitrant to both photodegradation and biodegradation, can be identified. This recalcitrant DON fraction in the samples is important because it will likely remain in the receiving waters for a very long period unless it is subject to chemical reactions. The fraction goes through biological treatment processes and additional photodegradation and biodegradation treatment (PDON and BDON tests) and should be considered when setting regulatory N limits (DON that is not degradable or is very hard to degrade does exist). Environmental Relevance. Photochemical production of nitrite from DON was observed after exposing the samples to UV light. Nitrite in the water environment is eventually nitrified to NO3− by nitrite oxidizing bacteria. Nitrate is an alternative source of nitrogen for algal growth and is well-known for causing eutrophication in waters. High NO2− can bind to the hemoglobin of aquatic organisms and cause death while high NO3− can result in a public health problem when present in drinking water sources.29 Nitrite in the water environment can photochemically react with dimethylamine to undergo a nitrosation reaction to form N-nitrosodimethylamine (NDMA).30 NDMA is a probable human carcinogen, even when present at nanogram per liter levels.31 Ayanaba and Alexander32 reported high rates of formation of NDMA in lake water containing dimethylamine and high nitrite. Other organics such as fulvic acid also catalyze nitrosation of nitrite to form NDMA.32 Results showed that BDON and PDON were overlapping, and BDON was associated with both PDON and NPDON. The absolute and relative magnitudes of PDON in the samples make photomineralization more relevant. A fraction of DON that is very or truly resistant to biodegradation and photodegradation was identified in the samples. This study provides useful information to enhance the understanding of photodegradation of wastewater-derived effluent DON. It elucidates that light promotes eutrophication through not only photosynthesis but also photoproduction of essential nutrients. This study reports a major portion of effluent DON is susceptible to both biodegradation and photodegradation in receiving water. It is essential to treat wastewater effluent for OPBDON before it is discharged. OPBDON can be removed by decreasing the concentration of BDON and/or PDON. Promoting TN removal in WWTPs through nutrient removal processes has been proven to reduce effluent DON and BDON. Also, the use of advanced oxidation for disinfection (such as ozone and/or UV with long contact time) instead of chlorination may help reduce the amounts of PDON and OPBDON in the effluent. Aerobic ponds as a form of tertiary treatment can also help remove OPBDON. Aerobic ponds are shallow ponds that allow photodegradation (PDON reduction) to occur, while the growth of microorganisms in the ponds will remove both DON and BDON. To further understand the role of photodegradation in eutrophication potential, a future study on algae or phytoplankton growth in photodegraded wastewater samples is recommended. Chemical compositions of different fractions of DON such as PDON and BDON in the final effluent and receiving water should be investigated to gain a more complete picture on their evolution through treatment and natural systems.
Figure 6. OPBDON for 6 days of light exposure for samples from the Fargo and Moorhead WWTPs.
The bar plots in Figure 6 are based on the following equations that are made up of terms that can be linearly added. DON = PDON + NPDON
(5)
DON = BDON + NBDON
(6)
BDON = (BDONi − BDONf ) + BDONf
(7)
Note that OPBDON = BDONi − BDONf. Substituting 7 in 6 and equating it to 5 result in: (BDONi − BDONf ) + BDONf + NBDON = DON = PDON + NPDON
(8)
BDONf can be calculated by rearranging 8: BDONf = DON − NBDON − (BDONi − BDONf ) = PDON + NPDON − NBDON − (BDONi − BDONf )
(9)
For the determination of NPDON∩NBDON (the portion of DON that is not photodegradable and biodegradable), NPDON (DON left after light exposure) is subtracted by BDONf (DON left after light exposure that is biodegradable). The data in Figure 6 are based on 6 days of light exposure (PDONUV, 6 days and BDONUV, 6 days). The magnitudes and fractions of OPBDON in the samples from both WWTPs are substantial. In the samples from both plants, PDON is associated with both BDON and NBDON. BDON determined in the effluent samples is the portion of DON that was not photodegraded during the UV exposure. Hence, the amount left is NPDON. BDON in light-exposed samples is associated with NPDON. Vähätalo and Zepp8 found a similar result when they applied pretreatment to seawater samples prior to UV light exposure to remove the biologically labile portion of DON. They observed photoproduction of NH4+ in pretreated samples, indicating that PDON could be associated with NBDON. The overlapping between PDON and BDON has not been reported previously. Obernosterer and Benner19 conducted a study to determine overlapping DOC using a high-pressure xenon UV lamp (300 nm) as a light source on lake water samples. They found about 15% of DOC was overlapping (susceptible to both bio- and photomineralization). Both light and availability of microorganisms are critical for the mineralization of DON in the final effluent. There is a fraction of G
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(14) Sattayatewa, C.; Pagilla, K.; Pitt, P.; Selock, K.; Bruton, T. Organic nitrogen transformations in a 4-stage Bardenpho nitrogen removal plant and bioavailability/ biodegradability of effluent DON. Water Res. 2009, 43 (18), 4507−4516. (15) Liu, H.; Jeong, J.; Gray, H.; Smith, S.; Sedlak, D. L. Algal uptake of hydrophobic and hydrophilic dissolved organic nitrogen in effluent from biological nutrient removal municipal wastewater treatment systems. Environ. Sci. Technol. 2012, 46 (2), 713−721. (16) Pehlivanoglu, E.; Sedlak, D. L. Bioavailability of wastewaterderived organic nitrogen to the alga Selenastrum capricornutum. Water Res. 2004, 38 (14−15), 3189−3196. (17) United States Environmental Protection Agency. Method 1003.0 in Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, 4th ed.; U.S. EPA: Washington DC, 2002. (18) Xie, H.; Bélanger, S.; Song, G.; Benner, R.; Taalba, A.; Blais, M.; Tremblay, J.-E.; Babin, M. Photoproduction of ammonium in the southeastern Beaufort Sea and its biogeochemical implications. Biogeosciences 2012, 9 (8), 3047−3061. (19) Obernosterer, I.; Benner, R. Competition between biological and photochemical processes in the mineralization of dissolved organic carbon. Limnol. Oceanogr. 2004, 49, 117−124. (20) Vähätalo, A. V.; Järvinen, M. Photochemically produced bioavailable nitrogen from biologically recalcitrant dissolved organic matter stimulates the production of nitrogen-limited microbial food web in the Baltic Sea. Limnol. Oceanogr. 2007, 52, 132−143. (21) Sattayatewa, C.; Pagilla, K. Nitrogen Species Measurement in Low Total Nitrogen Effluents. In Proceedings of the Water Environment Federation 81st Annual Technical Exhibition & Conference; Water Environment Federation, WEF: Chicago, IL, 2008; pp 3775−3788. (22) APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater; American Public Health Association: Washington, DC, 2005. (23) Buffam, I.; McGlathery, K. J. Effect of ultraviolet light on dissolved nitrogen transformations in coastal lagoon water. Limnol. Oceanogr. 2003, 48, 723−734. (24) Aarnos, H.; Ylöstalo, P.; Vähätalo, A. V. Seasonal phototransformation of dissolved organic matter to ammonium, dissolved inorganic carbon, and labile substrates supporting bacterial biomass across the Baltic Sea. J. Geophys. Res. Biogeosci. 2012, 117 (G1); DOI:10.1029/2010JG001633. (25) Tchobanoglous, G.; Burton, F. L.; Stensel, H. D. Wastewater Engineering: Treatment and Reuse, 4th ed.; McGraw-Hill: New York, 2003. (26) Sattayatewa, C.; Pagilla, K.; Sharp, R.; Pitt, P. Fate of organic nitrogen in four biological nutrient removal wastewater treatment plants. Water Environ. Res. 2010, 82, 2306−2315. (27) Jeff, S.; Hunter, K.; Vandergucht, D.; Hudson, J. Photochemical mineralization of dissolved organic nitrogen to ammonia in prairie lakes. Hydrobiologia 2012, 693, 71−80. (28) Wang, W.; Tarr, M. A.; Bianchi, T. S.; Engelhaupt, E. Ammonia photoproduction from aquatic humic and colloidal matter. Aquat. Geochem. 2000, 6, 275−292. (29) Lewis, W. M.; Morris, D. P. Toxicity of nitrite to fish: A review. Trans. Am. Fish. Soc. 1986, 115, 183−195. (30) Ohta, T.; Suzuki, J.; Iwano, Y.; Suzuki, S. Photochemical nitrosation of dimethylamine in aqueous solution containing nitrite. Chemosphere 1982, 11 (8), 797−801. (31) Weerasooriya, S. V. R.; Dissanayake, C. B. The enhanced formation of N-nitrosamines in fulvic acid mediated environment. Toxicol. Environ. Chem. 1989, 25, 57−62. (32) Ayanaba, A.; Alexander, M. Transformations of methylamines and formation of a hazardous product, dimethylnitrosamine, in samples of treated sewage and lake water. J. Environ. Qual. 1974, 3 (1), 83−89.
ASSOCIATED CONTENT
S Supporting Information *
Additional information as noted in the text (discussion on light attenuation, figures, and tables). This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*Phone: 701-231-7717; fax: 701-231-6185; e-mail: eakalak.
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS Funding for this research was partially provided by the North Dakota Water Resources Research Institute. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the North Dakota Water Resources Research Institute.
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REFERENCES
(1) Bronk, D.; Roberts, Q. N.; Sanderson, M. P.; Canuel, E. A.; Hatcher, P. G.; Mesfioui, R.; Filippino, K. C.; Mulholland, M. R.; Love, N. G. Effluent organic nitrogen (EON): Bioavailability and photochemical and salinity-mediated release. Environ. Sci. Technol. 2010, 44 (15), 5830−5835. (2) Wetzel, R. G.; Hatcher, P. G.; Bianchi, T. S. Natural photolysis by irradiance of recalcitrant dissolved organic matter to simple substrates for rapid bacterial metabolism. Limnol. Oceanogr. 1995, 40 (8), 1369− 1380. (3) Moran, M. A.; Zepp, R. G. Role of photoreactions in the formation of biologically labile compounds from dissolved organic matter. Limnol. Oceanogr. 1997, 42, 1307−1316. (4) Bushaw-Newton, K. L.; Moran, M. A. Photochemical formation of biologically available nitrogen from dissolved humic substances in coastal marine systems. Aquat. Microb. Ecol. 1999, 18, 285−292. (5) Bushaw, K. L.; Zepp, R. G.; Tarr, M. A.; Schulz-Jander, D.; Bourbonniere, R. A.; Hodson, R. E.; Miller, W. L.; Bronk, D. A.; Moran, M. A. Photochemical release of biologically labile nitrogen from dissolved organic matter. Nature 1996, 381, 404−407. (6) Koopmans, D. J.; Bronk, D. A. Photochemical production of inorganic nitrogen from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwater. Aquat. Microb. Ecol. 2002, 26, 295−304. (7) Lomas, M. W.; Rumbley, C. J.; Glibert, P. M. Ammonium release by nitrogen sufficient diatoms in response to rapid increases in irradiance. J. Plankton Res. 2000, 22, 2351−2366. (8) Vähätalo, A. V.; Zepp, R. G. Photochemical mineralization of dissolved organic nitrogen to ammonium in the Baltic Sea. Environ. Sci. Technol. 2005, 39, 6985−6992. (9) Kieber, R. J.; Li, A.; Seaton, P. J. Production of nitrite from the photodegradation of dissolved organic matter in natural waters. Environ. Sci. Technol. 1999, 33, 993−998. (10) Coffin, R. B. Bacterial uptake of dissolved free and combined amino acids in estuarine waters. Limnol. Oceanogr. 1989, 34, 531−542. (11) Simsek, H.; Kasi, M.; Wadhawan, T.; Bye, C.; Blonigen, M.; Khan, E. Fate of dissolved organic nitrogen in two stage trickling filter process. Water Res. 2012, 46 (16), 5115−5526. (12) Khan, E.; Awobamise, M.; Jones, K.; Murthy, S. Method development for measuring biodegradable dissolved organic nitrogen in treated wastewater. Water Environ. Res. 2009, 81 (8), 779−787. (13) Urgun-Demirtas, M.; Sattayatewa, C.; Pagilla, K. Bioavailability of dissolved organic nitrogen in treated effluents. Water Environ. Res. 2008, 80 (5), 397−406. H
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