Low Ammonium Concentrations Research Articles

Accounting for Non-Detects: Application to Satellite Ammonia Observations

Presented is a methodology to explicitly identify and account for cloud-free satellite measurements below a sensor’s measurement detection level. These low signals can often be found in satellite observations of minor atmospheric species with weak spectral signals (e.g., ammonia (NH3)). Not accounting for these non-detects can high-bias averaged measurements in locations that exhibit conditions below the detection limit of the sensor. The approach taken here is to utilize the information content from the satellite signal to explicitly identify non-detects and then account for them with a consistent approach. The methodology is applied to the CrIS Fast Physical Retrieval (CFPR) ammonia product and results in a more realistic averaged dataset under conditions where there are a significant number of non-detects. These results show that in larger emission source regions (i.e., surface values > 7.5 ppbv) the non-detects occur less than 5% of the time and have a relatively small impact (decreases by less than 5%) on the gridded averaged values (e.g., annual ammonia source regions). However, in regions that have low ammonia concentration amounts (i.e., surface values < 1 ppbv) the fraction of non-detects can be greater than 70%, and accounting for these values can decrease annual gridded averaged values by over 50% and make the distributions closer to what is expected based on surface station observations.

Biotechnological product potential of Auxenochlorella protothecoides including biologically active compounds (BACs) under nitrogen stress conditions.

Nitrogen stress can influence microalgae's growth characteristics, and microalgae grown in nitrogen-deficient conditions may produce higher or lower levels of biotechnological products as a result of metabolic changes. In photoautotrophic and heterotrophic cultures, nitrogen limitation has been proven effective in promoting lipid accumulation. In spite of this, no study has demonstrated a significant correlation between lipid content and other biotechnological products such as bioactive compounds (BACs).This research examines a strategy for lipid accumulation as well as the potential production of BACs with antibacterial properties in parallel with that strategy. This concept involved the treatment of the microalga Auxenochlorella protothecoides with low and high concentrations of ammonium (NH4+). This particular experiment reached a maximum lipid content of 59.5% using a 0.8 mM NH4+ concentration, resulting in the yellowing of the chlorophyll levels. Agar diffusion assays were conducted to determine the antibacterial activity of different extracts derived from the biomass when stressed with different levels of nitrogen.Algal extracts prepared by a variety of solvents showed different levels of antibacterial activity against representative strains of both gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria. Among the extracts tested, 500mg/L ethyl acetate extract had the greatest antibacterial activity against Escherichia coli. In order to identify the components responsible for the extract's antibacterial activity, fatty acid methyl ester (FAME) analysis was performed. It has been suggested that the lipid fraction may be a valuable indicator of these activities since some lipid components are known to possess antimicrobial properties. In this regard, it was found that the amount of polyunsaturated fatty acid (PUFA) significantly decreased by 53.4% under the conditions with the highest antibacterial activity observed.

Plasma‐catalytic Ammonia Synthesis via Eley‐Rideal Reactions: A Kinetic Analysis

AbstractThe reaction mechanism of plasma‐catalytic ammonia synthesis is not fully understood. MgO supported Ru, Co, Pt, Pd, Cu and Ag catalysts are tested in a DBD plasma at temperature between room temperature and 500 °C and plasma power between 3.8 W and 6.4 W. The resulting ammonia production in the presence of a plasma and a catalyst can be distinguished into (1) temperature‐independent plasma‐based ammonia synthesis, and (2) temperature‐dependent plasma‐catalytic ammonia synthesis. Turn‐over‐frequencies (TOF) are calculated based on the rate of the second pathway and chemisorption data, measuring the number of active sites. Underestimation of TOFs caused by ammonia decomposition was minimized by using exclusively observations at low ammonia concentration. The kinetic results suggest that the Eley‐Rideal reaction between N radicals from the plasma with chemisorbed H atoms is the rate‐determining step for plasma‐catalytic ammonia synthesis on Ru/MgO, Co/MgO, Pt/MgO, Pd/MgO, and Cu/MgO, with apparent activation barriers in the range 18–24 kJ mol−1. In contrast, the apparent activation barrier on Ag/MgO is significant higher at 30 kJ mol−1, suggesting a shift in rate determining step. The low H coverage on Ag may induce a shift to a Langmuir‐Hinshelwood pathway, via adsorption of N radicals on the metal surface.

House ammonia exposure causes alterations in microbiota, transcriptome, and metabolome of rabbits.

Pollutant gas emissions in the current production system of the livestock industry have negative influences on environment as well as the health of farm staffs and animals. Although ammonia (NH3) is considered as the primary and harmful gas pollutant in the rabbit farm, less investigation has performed to determine the toxic effects of house ammonia exposure on rabbit in the commercial confined barn. In this study, we performed multi-omics analysis on rabbits exposed to high and low concentration of house ammonia under similar environmental conditions to unravel the alterations in nasal and colonic microbiota, pulmonary and colonic gene expression, and muscular metabolic profile. The results showed that house ammonia exposure notably affected microbial structure, composition, and functional capacity in both nasal and colon, which may impact on local immune responses and inflammatory processes. Transcriptome analysis indicated that genes related to cell death (MCL1, TMBIM6, HSPB1, and CD74) and immune response (CDC42, LAMTOR5, VAMP8, and CTSB) were differentially expressed in the lung, and colonic genes associated with redox state (CAT, SELENBP1, GLUD1, and ALDH1A1) were significantly up-regulated. Several key differentially abundant metabolites such as L-glutamic acid, L-glutamine, L-ornithine, oxoglutaric acid, and isocitric acid were identified in muscle metabolome, which could denote house ammonia exposure perturbed amino acids, nucleotides, and energy metabolism. In addition, the widespread and strong inter-system interplay were uncovered in the integrative correlation network, and central features were confirmed by in vitro experiments. Our findings disclose the comprehensive evidence for the deleterious effects of house ammonia exposure on rabbit and provide valuable information for understanding the underlying impairment mechanisms.

Effects of probiotics on growth, survival, and intestinal and liver morphometry of Gangetic mystus (Mystus cavasius)

The usage of probiotics proved advantageous in aquaculture due to its positive impact on fish growth, immune response and environment. This study was aimed to assess the effects of probiotics on growth, survival and histometry of intestine and liver in Gangetic mystus (Mystus cavasius) using two separate experiments for a period of 8 weeks (in aquaria) and 16 weeks (in earthen ponds). Three different probiotic treatments were incorporated i.e. commercial probiotic one; CP-1 (T1), commercial probiotic two; CP-2 (T2), Lab developed (Lab dev.) probiotic (T3) including a control. The results indicated that the probiotics usage especially Lab dev. probiotic (T3) significantly improved the growth parameters such as weight gain (g) and specific growth rate (SGR, %/day) as well as ensured better feed conversion efficiency. Zero mortality was observed in aquaria whereas probiotic application enhanced survivability in earthen ponds. Moreover, all probiotic treatment exhibited positive results for different histo-morphometric features of intestine and liver. Mucus secreting goblet cells and fattening of mucosal fold increased significantly with probiotic usage. The amount of regular shaped nucleus was maximum in T3 with least intra cellular distance between liver tissues in earthen ponds. The greatest value for hemoglobin with lowest glucose level was observed in T3 as well. Furthermore, probiotic ensured low concentration of ammonia during culture. Overall, it was anticipated that the application of probiotics in Gangetic mystus culture resulted positive effect on its growth, feed utilization, survivability, histo-morphometry, immunity and hematological parameters.

Deciphering the effect of temperature reduction on the biofilm in partial nitritation-anammox system: Insights from microbial community to metabolic pathways

The concept of partial nitritation-anammox (PN/A) process has been proposed for many years, however seasonal temperatures and low ammonia concentrations under mainstream conditions always challenge the application in practical engineering. Thus, we operated a PN/A moving bed biofilm reactor (PN/A-MBBR) for treating 50 mg-NH4/L wastewater at various temperatures of 35 °C, 25 °C, and 15 °C. The effect of temperature reduction on biofilm system was investigated from process performance, microbial community and activity, to metabolic pathways. The results showed that total nitrogen removal efficiency declined from 76.6 % to 48.6 % as the temperature was reduced from 35 °C to 15 °C, while nitrogen removal rate decreased to 0.28 kg-N/m3/d. Low temperature stimulated the secretion of polysaccharide in loosely bound-EPS and protein in tightly bound-EPS. Meanwhile, specific activity of anammox declined from 1.53 to 0.56 g-N/g-VSS/d, and the relative abundance of Candidatus Brocadia dropped from 20.1 % to 9.4 %. Temperature reduction had significant effect on the expression of functional genes (hzsA and hdh) for anammox reaction. Nitrification-denitrification process was enhanced during low temperatures and recovery phases. Biofilm system might respond to temperature reduction by the decline of substance transport and energy consumption, as well as the enhancement of biofilm formation and diversity of nitrogen removal pathways. The findings of this study provide a deep insight into the effect of temperature reduction on PN/A process, also promote the practical applications of mainstream PN/A in the future.

Influence of the Ammonia Concentration in Chemical Bath Deposition and Selenourea Concentration in Hydrothermal Process on the Properties of CdS and Sb2S3−ySey Thin Films and the Photovoltaic Performance of the Corresponding Solar Cells

To explore the feasibility of the flexible Sb2S3−ySey thin‐film solar cell fabrication using polyimide thin films as substrates, CdS thin films are prepared on SnO2:F conducting glass (FTO) substrates by decreasing the ammonia concentration of chemical bath deposition, and Sb2S3−ySey thin films are grown on the FTO/CdS substrate by changing the selenourea concentration of hydrothermal process. The influence of the ammonia and selenourea concentration on properties of CdS and Sb2S3−ySey is systematically investigated and solar cells with the architecture of FTO/CdS/Sb2S3−ySey/spiro‐OMeTAD/Au are fabricated. For CdS thin films on FTO substrate, the thickness decreases and roughness increases with the decrease of ammonia concentration in chemical bath deposition. The compact and full‐coverage CdS thin films with thickness of 50 ± 6 nm are successfully obtained using the low ammonia concentration (0.59 m). For Sb2S3−ySey thin films on FTO/CdS substrate, the Se:S:Sb atomic ratio and thickness increases with the increase of selenourea concentration in hydrothermal process. The optimal selenourea concentration is 6 mM. The solar cells with the 50 ± 6 nm thick CdS thin film and Sb2S2.10Se0.56 thin film achieve photoelectric conversion efficiency of 8.07%. The results can provide an efficient support for further applying polyimide thin films to fabricate flexible Sb2S3−ySey thin film solar cells.

Ionic liquid hybrid metal–organic frameworks for efficient adsorption and selective separation of ammonia at high temperature

Efficient adsorption and selective separation of ammonia at high temperature is a crucial and challenging issue. In this work, a series of stable ionic liquid hybrid materials have been developed by simple impregnation of ionic liquids into stable metal–organic framework Al-fum with 1D pores. The hybrid material [C2N][Zn3Cl7]@Al-fum-60% exhibited an exceptionally high uptake (9.9 mmol/g at 80 °C, 8.8 mmol/g at 100 °C) at high temperature, excellent uptake (9.8 mmol/g at 25.0 °C) at low ammonia concentration (100,000 ppm), and remarkable selective separation performance (selectivity factor is 25.1) of NH3 from NH3/CO2 mixture at high temperature. The NH3 uptake of [C2N][Zn3Cl7]@Al-fum-60% at 100 °C was higher than the capacity of most of typical porous NH3 adsorbents at room temperature. It is revealed that such superior NH3 capacity and selective separation performance are mainly attributed to coordination interactions of NH3 to Zn centre of the ionic liquids and the hydrogen bonding interactions of NH3 with Cl of the ionic liquids and NH3 with μ-OH of Al-fum.

The Effect of Functional Ceramsite in a Moving Bed Biofilm Reactor and Its Ammonium Nitrogen Adsorption Mechanism

For aquaculture wastewater with low ammonium nitrogen concentration, combining the carrier adsorption and biological nitrogen removal processes can maximize their respective advantages. Functional ceramsite that has excellent ammonium nitrogen adsorption performance and excellent biocompatibility was the key to the moving bed biofilm reactor (MBBR) adsorption—shortcut simultaneous nitrification and denitrification (shortcut SND) process. Our group prepared a high-strength lightweight ceramsite that met those requirements. In this study, we applied functional ceramsite in MBBR to cope with low-concentration ammonium aquaculture wastewater. The findings show that utilizing functional ceramsite as a filler was conducive to the adhesion of microorganisms. The biofilm has a minimal effect on the adsorption capacity of ceramsite due to the existence of pores on its surface. Our study further examined the NH4+-N adsorption mechanism of bio-ceramsite. The Freundlich adsorption isotherm model and the quasi-second-order kinetic model had better fitting effects on the NH4+-N adsorption process. The adsorption of bio-ceramsite to NH4+-N was an endothermic process that included physical and chemical adsorption. Furthermore, the results of adsorption thermodynamics suggested that bio-ceramsite has an affinity for the adsorption of NH4+-N. Consequently, this functional ceramsite can be a promising option for MBBR to improve nitrogen removal from aquaculture wastewater.

Assessment on Water Quality Parameter and Nutrients Level of Nyatuh River in Relations with Macrobrachium Rosenbergii Prawn Populations.

In order to determine the safety level of water parameters and nutrients in the natural environment of fish and freshwater prawn in Nyatuh River, Terengganu, Malaysia, it is necessary to conduct an assessment of water quality parameters. Due to its important, a study was conducted to assess the water quality parameter and nutrients contents from Nyatuh River of Setiu Terengganu in relations to the population of freshwater prawn, Macrobrachium rosenbergii caught along the Nyatuh River basin. Total of four expeditions and five stations at different tidal condition for the water quality parameter were assessed during the study. From the results achieved, the overall temperature varied between (26.56°C-29.30°C), dissolved oxygen, DO (3.59 mg/L-6.50 mg/L), pH (4.99-7.01), salinity (0.01ppt-4.22ppt), depth (2.71 m-5.54 m) while for ammonia (0.01 mg/L-0.24 mg/L), nitrite (0.01 mg/L-0.05 mg/L) and phosphate (0.01 mg/L-0.12 mg/L). While the number of prawns caught are 176, 160, 102 and 68 for Expeditions 1, 2, 4 and 3, respectively. Possibly, the heterogeneous number of prawns caught is a result of significant differences in water level depth during high tides and low tides, as well as a fluctuation in the ammonia concentration levels in each of the stations and expeditions. For statistical analysis, the temperature showed no significant difference between the expedition, stations and tidal. That is p = 0.280, p > 0.05 and F = 1.206, respectively. While dissolved oxygen, DO, showed no significant difference as well, that is p = 0.714, p > 0.05 and F = 0.737. However, the level of water depth was significantly different between expedition, station and tidal, that is p = 0.000, p < 0.05 and F = 3.120. Ammonia, on the other hand shows no significant difference between expedition, station and tidal, that is p = 0.476, p > 0.05 and F = 0.973. The same goes for nitrite and phosphate concentration. There was no significant difference between expedition, stations and tidal, that is p = 0.569, p > 0.05 and F = 0.879 and p = 0.247, p > 0.05, F = 1.255, respectively. In Expedition 1, the good water quality parameter and very low ammonia concentration resulted in a larger prawn population as compared to other expeditions. The distribution or mixture of prawns caught is heterogeneous at different stations due to the significant differences in water depth and also to the fluctuation in water quality due to varying ammonia levels. In conclusion, the water quality in Nyatuh River fluctuated across expeditions, stations, and tides, as well as significant differences in water level depths between high and low tides. Due to the rapid growth and importance of industrial and aquaculture operations along the river, extra attention should be devoted to avoid the impact of excessive pollutant in order to protect the ecosystem.

Response of granular anammox process under mainstream conditions to continuous and transient organic loads

Even small fluctuations in the amount of organic matter in wastewater significantly affect the structure and function of anammox microbial communities under mainstream conditions with low ammonium concentrations, because a high organic C/N ratio causes heterotrophic denitrifying bacteria to outcompete anammox bacteria. This paper presents a comprehensive investigation of the effects of different levels of continuous and transient organic loads on nitrogen removal and sludge characteristics in upflow granular anammox reactors under mainstream conditions. Continuous organic load at 30 mg chemical oxygen demand (COD)/L influent improved nitrogen removal efficiency without compromising anammox performance. However, exposure to higher levels of continuous organic load (≥60 mg COD/L) caused significant inhibition of anammox activity (complete inhibition at 150 mg COD/L). The performance degradation was accompanied by the destabilization of anammox granular sludge, with a decrease in tightly bound protein and increase in loosely bound polysaccharide contents in the sludge extracellular polymeric substances. Further, DNA sequencing analysis showed that heterotrophic denitrifying Rhodocyclaceae and Pseudomonadaceae bacteria collectively accounted for 36.8–61.3% of the total bacterial reads. These bacteria emerged and outcompeted anammox Ca. Brocadiaceae (accounting for less than 8.4% of the total reads) with increasing organic load, resulting in a significant decrease in anammox activity. Meanwhile, the inhibitory effect of transient organic load (one-day shock loading) was fully reversed within one day at both 150 and 300 mg COD/L shock levels, although the latter caused a sudden fall in anammox performance. The overall results suggest that loading an appropriately low amount of organic matter can provide a means to improve the nitrogen removal performance of anammox granular sludge without sacrificing anammox activity and granule stability under mainstream conditions.

Nitrogen Removal for Low Concentration Ammonium Wastewater by Adsorption, Shortcut Simultaneous Nitrification and Denitrification Process in MBBR

Excessive discharge of ammonia nitrogen wastewater from intensive aquaculture has worsened in recent years. Therefore, there is an urgent need to develop an effective and energy-saving denitrification technology. This study intends to adopt a moving bed biofilm reactor (MBBR) to remove ammonia nitrogen through the combination of adsorption and shortcut simultaneous nitrification and denitrification (SND). The research focuses on the operational parameters and regeneration mechanism of the MBBR adsorption-shortcut SND process. The optimal operating parameters in the adsorption stage were a hydraulic retention time of 8 h and an agitation rate of 120 r/min. For the shortcut SND stage, the ideal optimal parameters were two times alkalinity and dissolved oxygen (DO) 1.0 mg/L. Under optimal operating parameters conditions, the SND rate, TN removal rate, NH4+-N removal rate and nitrite accumulation rate were 89.1%, 84.0%, 94.3%, and 86.4%, respectively. The synergetic actions of ion exchange and microorganisms were the main driving force for regenerating ceramsite zeolite components. The synergistic inhibitory effect of high-concentration free ammonia and low-level DO on nitrite-oxidizing bacteria was the key to achieving stable and efficient NO2−-N accumulation. NO2−-N produced in shortcut nitrification entered the ceramsite through complex mass transfer, and denitrifying bacteria can reduce these NO2−-N to N2.

A developed system to extract specific responses of increment length in rice shoots under gradient changes in nitrogen concentration regimes.

Nitrogen (N) fertilization is one of the most crucial factors that contribute to increasing food production requiring the generation of rice cultivars with improved N use efficiency (NUE) to maintain yield during low N fertilizer application. To assay NUE extent, we developed a screening system to evaluate shoot growth of each rice cultivar under gradient changes in N concentrations. This system comprises a gradient hydroponic culture and growth visualization systems. The former allows gradient changes in ammonium concentrations, while the latter records the increment in shoot length of individual rice seedlings at given time periods using a fixed-point camera. We chose 69 cultivars including two controls (Oryza sativa L. cv. Nipponbare [WRC01] and Kasalath [WRC02]) from the World Rice Core Collection to investigate shoot growth responses under ammonium-sufficient, ammonium-limited, and low ammonium concentration gradients without transplanting stress. We observed three growth patterns in response to different ammonium concentrations. Subsequently, we selected three representative cultivars (Kasalath, WRC03, and WRC05) for the characteristic responses under the different ammonium environments. Distinct expression patterns of glutamine synthetase 1;2 (OsGS1;2) but OsGS1;1 were observed in response to varying ammonium concentration regimes, indicating that the expression patterns of OsGS1;2 may be a growth marker in terms of shoot growth when transitioning from ammonium-limited to low ammonium concentrations. This system with the level of OsGS1;2 allows us to screen for candidate cultivars that return high NUE in low N environments.

Dynamic and explainable fish mortality prediction under low-concentration ammonia nitrogen stress

Dynamic and explainable fish mortality prediction under low-concentration ammonia nitrogen stress

Simultaneous ammonia recovery and water reclamation from brackish aquaculture effluent via reactive vacuum membrane distillation

Due to the high volatility of ammonia and contemporaneous condensation of water and ammonia on permeate side, it remains a challenge to obtain a high concentration of ammonia or high-quality water using conventional vacuum membrane distillation (VMD). In this study, a reactive VMD (RVMD) with a two-stage downstream system was developed for simultaneous recovery of ammonia and water from brackish aquaculture effluent with dilute ammonia content. Notably, the RVMD system allowed for complete recovery of dilute ammonia in acid solution. Compared to a conventional VMD system, both the separation factor (SF) and concentration factor (CF) were intensified by 16 times within 2 h using the RVMD system. In the RVMD system, ammonia was first dissolved in acid solution without chilling using immersed trap tube; followed by water vapor condensation under chilling to obtain clean water. It was found that more diluted acid (0.0025 M of sulphuric acid or 0.005 M of phosphoric acid) could be applied to absorb the same amount of ammonia by using this system. Through this system, the recovered ammonia from brackish aquaculture effluent could be concentrated by 23 times (from 19.83 to 465 mg/L) with an SF of 148, while very low ammonia content (0.04 mg/L) was detected in the recovered water. These findings demonstrate that RVMD with a two-stage downstream system outperforms conventional VMD in concentrating ammonia and purifying water.

Pathways of N2O production by marine ammonia-oxidizing archaea determined from dual-isotope labeling

The ocean is a net source of the greenhouse gas and ozone-depleting substance, nitrous oxide (N2O), to the atmosphere. Most of that N2O is produced as a trace side product during ammonia oxidation, primarily by ammonia-oxidizing archaea (AOA), which numerically dominate the ammonia-oxidizing community in most marine environments. The pathways to N2O production and their kinetics, however, are not completely understood. Here, we use 15N and 18O isotopes to determine the kinetics of N2O production and trace the source of nitrogen (N) and oxygen (O) atoms in N2O produced by a model marine AOA species, Nitrosopumilus maritimus. We find that during ammonia oxidation, the apparent half saturation constants of nitrite and N2O production are comparable, suggesting that both processes are enzymatically controlled and tightly coupled at low ammonia concentrations. The constituent atoms in N2O are derived from ammonia, nitrite, O2, and H2O via multiple pathways. Ammonia is the primary source of N atoms in N2O, but its contribution varies with ammonia to nitrite ratio. The ratio of 45N2O to 46N2O (i.e., single or double labeled N) varies with substrate ratio, leading to widely varying isotopic signatures in the N2O pool. O2 is the primary source for O atoms. In addition to the previously demonstrated hybrid formation pathway, we found a substantial contribution by hydroxylamine oxidation, while nitrite reduction is an insignificant source of N2O. Our study highlights the power of dual 15N-18O isotope labeling to disentangle N2O production pathways in microbes, with implications for interpretation of pathways and regulation of marine N2O sources.

Adsorption of Low-Concentration Ammonia Nitrogen from Water on Alkali-Modified Coal Fly Ash: Characterization and Mechanism

The huge annual output of coal fly ash is harmful to the environment, but it is widely used because of its good adsorption potential. In this study, using coal fly ash as a raw material and sodium hydroxide as an activator, a novel adsorbent was synthesized at 300 °C and used to adsorb low concentrations of ammonia nitrogen from water. In this study, scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and a surface area and porosity analyzer were used to analyze the adsorbent’s physicochemical properties. The results showed that after alkali modification, the activity of the adsorbent had greatly enhanced. The impacts of solution pH, adsorbent dosage, adsorption time, and initial concentration of ammonia nitrogen on the adsorption capacity and removal efficiency were evaluated through a series of adsorption experiments. Moreover, the adsorption data were better fitted to the pseudo-second-order kinetic model and Langmuir model, indicating that the adsorption process was mainly chemical adsorption and monolayer uniform adsorption. As a result, the new adsorbent is inexpensive and effective, and it could be used to remove low-concentration ammonia nitrogen from water with a maximum removal efficiency of approximately 89%.

Integrated resource recovery from aerobic granular sludge plants

The study evaluated the combined phosphorus, nitrogen, methane, and extracellular polymeric substances (EPS) recovery from aerobic granular sludge (AGS) wastewater treatment plants. About 30% of sludge organics are recovered as EPS and 25–30% as methane (≈260 ml methane/g VS) by integrating alkaline anaerobic digestion (AD). It was shown that 20% of excess sludge total phosphorus (TP) ends in the EPS. Further, 20–30% ends in an acidic liquid waste stream (≈600 mg PO4-P/L), and 15% in the AD centrate (≈800 mg PO4-P/L) as ortho-phosphates in both streams and is recoverable via chemical precipitation. 30% of sludge total nitrogen (TN) is recovered as organic nitrogen in the EPS. Ammonium recovery from the alkaline high-temperature liquid stream is attractive, but it is not feasible for existing large-scale technologies because of low ammonium concentration. However, ammonium concentration in the AD centrate was calculated to be 2600 mg NH4-N/L and ≈20% of TN, making it feasible for recovery. The methodology used in this study consisted of three main steps. The first step was to develop a laboratory protocol mimicking demonstration-scale EPS extraction conditions. The second step was to establish mass balances over the EPS extraction process on laboratory and demonstration scales within a full-scale AGS WWTP. Finally, the feasibility of resource recovery was evaluated based on concentrations, loads, and integration of existing technologies for resource recovery.

In situ investigation of N deposit effects on polycyclic aromatic hydrocarbons (PAHs) photolysis in snow

As snow is an ideal scavenger of polycyclic aromatic hydrocarbons (PAHs) for both particulate- and gas-phase PAHs, a large amount of PAHs are accumulated in snowpacks. These PAHs could be released from seasonal snowpacks into environment over a short time during the snow melting period, causing a flush of contaminants. Understanding the fate of PAHs in snow therefore is important to evaluate the contaminant flush during snow melting. However, as an important natural process, PAH photolysis in snow is still unclear, especially in the context of global climate change. Therefore, photolysis of the 16 PAHs, which are listed as priority controlled pollutants by United States Environmental Protection Agency (US EPA), was investigated with N deposit in field in snow in this study. A mixture of the 16 US EPA priority PAHs and nitrate/ammonia were spiked into sealed quartzose bottles containing snow samples in field. The bottles were then exposed to solar radiation in field for 6 h. Experimental results showed that >50% of PAHs were lost during 6 h photolysis, mostly occurred in the first hour. Generally, HMW PAHs were photolyzed faster than LMW PAHs, though the photolysis rate did not strictly increase with molecular weight. Low concentrations of nitrate can enhance photolysis of Ant and Pyr, while photolysis of investigated PAHs was inhibited with nitrate concentration increasing. In contrast, both low and high concentration of ammonium can inhibit PAH photolysis. The inhibiting effect of both nitrate and ammonia on photolysis of HMW PAH is stronger than that of LMW PAHs, indicating direct photolysis of PAHs is the main pathway of PAH degradation in snow in situ. This study firstly showed the effect of N deposition on PAH photolysis in snow. Under current increasing N deposition in northeast China, this study implied that more PAHs in snow could be preserved during winter and released shortly during snowmelt, resulting in high ecological risk in spring.

Effects of probiotics on blood metabolites, enterocytes, growth, and carcass characteristics of broilers challenged with Salmonella Serovar Heidelberg

This study was aimed to evaluate the use of probiotics (B. amyloliquefaciens, B. subtilis, B. thuringiensis, and S. cerevisiae) both in the litter and diets of broiler chickens challenged with Salmonella Serovar Heidelberg (SH) on performance, carcass, and cut yield, relative liver and fat weight, blood biochemistry parameters, intestinal morphometry, caecal contamination by SH and litter quality. A total of 640 one-day-old male broiler chickens (Cobb 500) were randomly assigned to 5 treatments: NC - negative control feed (no antibiotics); PC - positive control feed (antibiotics); NCPF-NC + 1 kg ton−1 of probiotic in the feed; NCPL-NC + 20 g m−2 of probiotic in the litter; NCPFL-NC + 1 kg ton−1 of probiotic in the feed and application of 20 g m−2 of probiotic in the litter. Each treatment consisted of 8 replicated pens with 16 broiler chickens per pen. The poultry received bran feed and water ad libitum throughout the experimental period. Probiotic application to litter was performed 5 days before housing of chicks, later the litter was collected for evaluation of dry matter, pH, and ammonia. At 3 days of age, 4 chicks per experimental unit received a culture inoculum solution with SH (106 CFU chick−1). Data were submitted to analysis of variance and Tukey's test at 5% probability. In the initial phase (1 to 21 days), it was observed that poultry receiving the treatments PC (1.393), NCPF (1.396) and NCPFL (1.383) had better feed conversion rate results (P < 0.05). In the same period, the same treatments, PC (916), NCPF (865) and NCPFL (914) provided better weight gain results (P < 0.05). At the end of the experiment (42 days), the treatments NCPF (5.023) and NCPFL (5.005) showed lower feed intake (P < 0.05). In the same period, NCPF (1.564) and NCPFL (1.544) showed better feed conversion ratio results (P < 0.05). Probiotic was not influenced (P > 0.05) on the characteristics of carcass yield, cutting yields, relative liver weight, and fat. Probiotic was not influenced (P > 0.05) on the blood biochemistry and the cecum. Probiotic in the diets and litter promoted an improvement in litter quality at 28 days, with lower concentration of ammonia and lower humidity. In conclusion, probiotic improved growth performance, without altering intestinal morphometric, serum metabolites, liver, and kidney metabolites in poultry.