Low Ammonium Concentrations Research Articles

A sulfur-based cyclic denitrification filter for marine recirculating aquaculture systems

Nitrogen removal from saline wastewater is challenging due to adverse effects of salinity on biological processes. A novel sulfur-autotrophic cyclic denitrification filter (CDF) was tested for marine recirculating aquaculture systems (RAS) under varying conditions. Low ammonia, nitrite and sulfide concentrations were maintained at residence times between 4 and 12 h. After introduction of Poecilia sphenops, concentrations of NH4+-N, NO2−-N, NO3−-N were maintained below 1, 1, and 60 mg/L, respectively. Fish waste inputs to the CDF contributed to mixotrophic denitrification and low sulfate production. A mass balance showed that 7% of the feed nitrogen was assimilated by fish, 6% was removed by passive denitrification (e.g., in anoxic zones in filters), 60% in the CDF and 27% was discharged during sampling and solids removal. Daily fresh water addition was <2% of fish tank volumes. The results are promising as a low cost alternative for saline wastewater denitrification.

Ppb-Level of Ammonia Sensor on Reduced-Graphene Oxide Nanocomposite By the Supercritical Fluid Technique

Ammonia is an important indicator for the environment quality and agriculture safety applications. Besides, various medical reports have indicated that exhaled ammonia gas is considered to be a non-invasive biomarker of liver and kidney diseases. The exhaled ammonia gas concentration for healthy human is in the range of 200-2000 ppb [1], and for the environmental quality evaluation it should be lower than 50 ppb [2]. Due to the low concentration and the complicate sample gases, it is important to develop a highly sensitive and selective ammonia sensor. Several materials such as metal oxide, conducting polymer and carbon nanomaterials have been extensively examined for ammonia gas sensing. In this study, tungsten oxide and polyaniline was incorporated into easily functionalized reduced graphene in supercritical fluid to form a p-type nanocomposite. Metallic nanocatalyst was doped to enhance the sensitivity and selectivity. Ammonia was adsorbed onto the sensing membrane and then oxidized at room-temperature. Therefore, the resistance of sensing membrane increased with ammonia concentration. The sensor could detect the ammonia concentration in the range from 0 to 100 ppm at room temperature. The sensitivity was enhanced 4 times by the nanocatalyst, and the lower detection limit was 50 ppb. The effect of interference gases, including nitric oxide (NO), carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2) has been evaluated as well, and all the cross-talk was less than 10%. Furthermore, ammonia gas is highly water soluble, the sensing resistance could shift significantly with humidity, especially in higher humid atmosphere. In order to solve the problem, the electrode surface was designed to be more hydrophobic. After surface modification, the humidity effect decreased. The sensing mechanism of electrode and effect of humidity was also investigated. The experimental result suggested that the catalyst doped nanocomposite had high sensitivity, stability and selectivity for low concentration ammonia sensing at room temperature. A room temperature operated ppb-level ammonia sensor could be valuable solution for exhaled gas or environmental quality monitoring.[1] S. Abdulla, J. Dhakshinamoorthy, V. Mohan, D. V. Ponnuvelu, V. K. Kallidaikuruchi, L. M. Thalakkotil, B. Pullithadathil. J. Breath Res. 13 (2019) 046005; doi: https://doi.org/10.1088/1752-7163/ab278b[2] M. Insaustia, R. Timmis, R. Kinnersley , M. C. Rufino. Sci. Total Environ. (2019) 135124； doi: https://doi.org/10.1016/j.scitotenv.2019.135124.

Poly[2,5-bis(3-tetradecylthiophen-2-yl) thieno [3,2-b] thiophene] Organic Polymer Based-Interdigitated Channel Enabled Thin Film Transistor for Detection of Selective Low ppm Ammonia Sensing at 25°C

In the present work, we have developed a solution-processable poly (2,5-bis (3-tetradecylthiophen 2yl) thieno(3,2b) thiophene) (PBTTT-C14) based organic thin film transistor, for possible selective sensing the toxic ammonia (NH3) gas at 25°C. This thin-film transistor based sensor makes use of PBTTT-C14 polymer as an organic channel that exhibits highly responsive (>61%) behavior at different levels of ammonia concentrations, even in presence of a mixture of ethanol and butanol gases in a humid environment. The notable changes are observed in the transistor parameters including channel mobility, threshold voltage and the on-off ratio. Interdigitated channels obtained using shadow masking technique enables the device to respond to a low ammonia concentration (<10 ppm). Better sensing capabilities with a detection limit of 2 ppm, the response time of 30 sec and recovery time of 40 sec of exposed ammonia, butanol and ethanol gases have been recorded. The mechanism of sensing has been explained for a better understanding of electrostatic and chemical interaction between gases and PBTTT-C14 semiconductor. Electrical characterizations of the device for the sensing were carried-out in the ambient condition. The device performance has been tested in humid environmental conditions. The fabricated device exhibited enormous potential for ammonia sensing for real-life applications.

Electrochemical oxidation of ammonia (NH4+/NH3) ON synthesized nickel-cobalt oxide catalyst

Ni–C and Co/Ni–C electro-catalysts were prepared using solvothermal reaction method and used to oxidize ammonia in aqueous solution. Ni and Co were consistently dispersed in carbon generating spherical and porous structure (pore size~ 20–50 nm). The sphericity and porosity of the electro-catalysts increased by increasing the percentage of Co in the composite. The XRD pattern confirmed the formation of Co/Ni–C composite with a reasonable presence of metal hydroxide (Ni(OH)2 & Co(OH)2). The addition of Co to Ni–C enhanced ammonia oxidation reaction (AOR) by decreasing the oxidation peaks in the range of 0.23–0.56 V, increasing the reversible production of metal-hydroxides and generating power (Pgen) to sustain the reaction. The reported Pgen were 0.55, 0.85, 1.1 and 0.0.93 mW/cm2 for Ni–C, Co10/Ni–C, Co20/Ni–C and Co40/Ni–C. A concentration of Co higher than 40% decreased cell potential (Vcell) and reduced the percentage removal of ammonia (%REAmm). A %REAmm of 97 and 99% were achieved by Ni–C and Co20/Ni–C, respectively. The mechanism of AOR follows direct electron transfer at low initial ammonia concentrations and changed to oxidation mechanism at higher concentrations. AOR is more effective at alkaline and high temperature with a high possible chance to be used as fuel in electrochemical cell to generate electricity as well as treating wastewater contaminated with ammonia.

Synergistic effects of co-trace elements on anaerobic co-digestion of food waste and sewage sludge at high organic load.

Trace elements play an indispensable role in stabilizing the performance of anaerobic co-digestion (Co-AD) of food waste (FW) and sewage sludge (SS) at greater organic load (OL). The results of high organic-loaded reactors showed that the stability of the system failed due to the buildup of volatile fatty acid (VFA) and ammonia. At the OL of 6.5g/L, the stability of the system failed due to the buildup of propionic acid. The optimum dosage of Fe (5000mg/L), Ni (200mg/L), Zn (320mg/L), and Mo (2.2mg/L) was experimentally determined and added to reduce the inhibition condition. Consequently, the propionic acid concentration, which was above 1500mg/L reduced to under 500mg/L during Co-AD. Hence, higher biogas production, and biodegradability of 236 ± 23mL/g VS, and 41.75%, respectively, were obtained. Increasing OL (9.5g/L), the stability of the system was hindered due to only the buildup of ammonia (up to 188 ± 6 NH3-Nmg/L). Therefore, the trace elements of Cu (250mg/L) and Co (3mg/L) were experimentally determined and added into the Co-AD to diminish ammonia accumulation and process instability. The experimental results showed that at OL of 14g/L, biogas production, low ammonia concentration and biodegradability of 332 ± 21mL/g VS, and 70 NH3-Nmg/L, and 57.89%, respectively, were achieved. However, the performance and stability of the system failed at the higher OL due to the more increased ammonia and VFA concentration, and the greater dosages of trace elements did not enhance the process stability.

Water quality, nutrients, and stable isotopic signatures of particulates and vegetation in a mangrove ecosystem exposed to past anthropogenic perturbations

Water quality in mangrove estuaries within Caroni Swamp, Trinidad is impaired by a combination of recent increases in nitrogen loads and lingering effects of a series of reclamation efforts that reduced tidal exchanges and fostered low oxygen and high ammonium concentrations, conditions that are relatively unusual for estuaries. Concentrations of available nitrogen diminish down-estuary, with an overall within-estuary interception of about 25% of total dissolved nitrogen. Caroni Swamp remains a productive mangrove environment, and a tourist attraction, in spite of failed and continuing reclamation efforts and increased N loads, a demonstration of remarkable resilience. Developing ecosystem-based management to support that resilience will benefit from improved understanding of processes involved in nitrogen retention and losses, consideration of the consequences in intensifying land use on contributing watersheds and plans to ease tidal water exchanges and diminish extent of shallow and stagnant areas.

Nitrogen preference and genetic variation of cotton genotypes for nitrogen use efficiency.

Although nitrogen (N) availability is a major determinant of cotton production, little is known about the importance of plants' preference for ammonium versus nitrate for better growth and nitrogen use efficiency (NUE). We aimed to assess the growth, physiology, and NUE of contrasting N-efficient cotton genotypes (Z-1017, N-efficient and GD-89, N-inefficient) supplied with low and high concentrations of ammonium- and nitrate-N. The results revealed that ammonium fed plants showed poor root growth, lower dry biomass, N content, leaf chlorophyll and gas exchange than those under nitrate irrespective of the concentration. However, the highest N uptake and utilization efficiency were obtained with nitrate fed plants, which also resulted in the highest dry biomass, N content, leaf chlorophyll and gas exchange as well as root growth. The results further confirmed that N-efficient (Z-1017) genotype performed better under both N sources, showing more flexibility to contrasting N condition by increasing growth and NUE in either source of N. Moreover, multivariate analysis showed a strong relationship of root morphological traits with N utilization efficiency, suggesting the physiological importance of roots over shoots in response to low nitrate concentration. Thus, it was confirmed that nitrate-N is superior to ammonium-N and the use of nitrate and N-efficient genotype is the best option for optimum cotton growth and NUE. Further, field evaluation is required to confirm the hypothesis that nitrate is a preferred N source for better cotton production and NUE. © 2020 Society of Chemical Industry.

Nitrifier adaptation to low energy flux controls inventory of reduced nitrogen in the dark ocean

Ammonia oxidation to nitrite and its subsequent oxidation to nitrate provides energy to the two populations of nitrifying chemoautotrophs in the energy-starved dark ocean, driving a coupling between reduced inorganic nitrogen (N) pools and production of new organic carbon (C) in the dark ocean. However, the relationship between the flux of new C production and the fluxes of N of the two steps of oxidation remains unclear. Here, we show that, despite orders-of-magnitude difference in cell abundances between ammonia oxidizers and nitrite oxidizers, the two populations sustain similar bulk N-oxidation rates throughout the deep waters with similarly high affinities for ammonia and nitrite under increasing substrate limitation, thus maintaining overall homeostasis in the oceanic nitrification pathway. Our observations confirm the theoretical predictions of a redox-informed ecosystem model. Using balances from this model, we suggest that consistently low ammonia and nitrite concentrations are maintained when the two populations have similarly high substrate affinities and their loss rates are proportional to their maximum growth rates. The stoichiometric relations between the fluxes of C and N indicate a threefold to fourfold higher C-fixation efficiency per mole of N oxidized by ammonia oxidizers compared to nitrite oxidizers due to nearly identical apparent energetic requirements for C fixation of the two populations. We estimate that the rate of chemoautotrophic C fixation amounts to ∼1 × 1013 to ∼2 × 1013 mol of C per year globally through the flux of ∼1 × 1014 to ∼2 × 1014 mol of N per year of the two steps of oxidation throughout the dark ocean.

Preparation of modified Chinese medical stone and its performance on the removal of low-concentration ammonium from water

The ammonium ion occurrence in excess consequences in the adverse effects on the ecosystem, and human health. The experiment was conducted using the Chinese medical stone to remove ammonium ion from the water. The Chinese medical stone was modified by citric acid monohydrate and designed to identify the ammonium ion uptake capacity by the MMS and focused on evaluating the adsorption and kinetics isotherm, modifier’s concentration, contact time and initial concentration effects on MMS performance. The modification process was well-appointed by mixing and shaking at 180 rpm; at 60 °C; for eighth, at mixing ratio 1:20 of the UMMS with 0.2 mol concentration of citric acid monohydrate solution. The optimum adsorption performance was determined using Beaker sequence batch test method. The SEM micrographs; BET and FTIR of UMMS and MMS tests have undertaken and evaluated. The result showed that the maximum adsorption amount of MMS to ammonium ions was 5.38 mg/g at 50 mg/L ammonium ion concentration by the experiment, and the qe max was 3.5 mg/g from Langmuir equation. The ammonium adsorption by the MMS had fitted for both the Langmuir isotherm and the Freundlich isotherm models and also adapted to the kinetic parameter pseudo-second-order model shows a superior expectation of the sorption kinetics.

Electrochemical Gas Sensor Integrated with Vanadium Monoxide Nanowires for Monitoring Low Concentrations of Ammonia Emission

An electrochemical sensor for the detection of extremely low concentration of ammonia (1 part per billion, ppb) was fabricated by integrating vanadium monoxide (VOx; x = 0.8–1.2) nanowires on the platinum electrodes. The nanowire-based sensor responds at room temperature non-linearly to a staircase sequence of ammonia from 1 ppb to 100 ppb. The rise and fall time of the nanowire sensor was found to be 10 s and 9 s, respectively. While the immobilization of VO nanowires increased the electrochemical surface area, the defect rich and ionic nature of the VO surface (V2+O2−) facilitated the chemical interaction and adsorption of polar ammonia molecules as evident in the room temperature response of the VO@Pt amperometric electrochemical sensor. The availability of metal centered d-electrons and the semiconductor nature of vanadium monoxide lowered the interfacial resistance of the nanowire-modified sensor enabling the lower detection limit of ammonia. The sensor seems to respond to CH4, H2S and C3H6 as well although the NH3 response is nearly six-fold compared to these common interfering compounds. The results pave the way for a low-cost alternative paper-based sensor to monitor ammonia emissions primarily from confined animal feeding operations (CAFOs).

Abundance and activity of ammonia oxidizing archaea and bacteria in bulk water and biofilm in water supply systems practicing chlorination and chloramination: Full and laboratory scale investigations.

The abundance and nitrification activity of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) in bulk water and biofilm in chloraminated and chlorinated water supply systems were investigated. The abundance of AOB varied between cold and warm periods while that was the case for AOA only in biofilm. Lower ammonia concentrations favored the abundance of AOA over AOB. AOA and AOB were found more in distal zones of the distribution system (DS). Higher numbers of AOA and AOB were observed in DS associated with chloramination compared to those associated with chlorination. Significant positive correlations between ammonia-N in bulk water and AOA indicate a possibility of involvement of AOA in nitrification in DS. A separate laboratory-based experiment simulating DS condition was conducted to understand the effects of chlorine and chloramine dosages and temperature on AOA and AOB. AOA were inhibited less than AOB in the presence of lower concentrations of chlorine and chloramine (1.5 and 2.0mg/L chlorine; 0.05-0.1 and 0.3-0.4mg/L chloramine) while both of them were not detected at higher dosages (2.5mg/L chlorine and 1.5-1.6mg/L chloramine). At a low temperature (10-12°C), chloramine and chlorine provided similar inhibition trends in which AOB were inhibited more than AOA. At a high temperature (25°C), chloramine was less inhibitory to AOA and AOB than chlorine.

Low-Concentration Ammonia Gas Sensors Manufactured Using the CMOS-MEMS Technique.

This study describes the fabrication of an ammonia gas sensor (AGS) using a complementary metal oxide semiconductor (CMOS)–microelectromechanical system (MEMS) technique. The structure of the AGS features interdigitated electrodes (IDEs) and a sensing material on a silicon substrate. The IDEs are the stacked aluminum layers that are made using the CMOS process. The sensing material; polypyrrole/reduced graphene oxide (PPy/RGO), is synthesized using the oxidation–reduction method; and the material is characterized using an electron spectroscope for chemical analysis (ESCA), a scanning electron microscope (SEM), and high-resolution X-ray diffraction (XRD). After the CMOS process; the AGS needs post-processing to etch an oxide layer and to deposit the sensing material. The resistance of the AGS changes when it is exposed to ammonia. A non-inverting amplifier circuit converts the resistance of the AGS into a voltage signal. The AGS operates at room temperature. Experiments show that the AGS response is 4.5% at a concentration of 1 ppm NH3; and it exhibits good repeatability. The lowest concentration that the AGS can detect is 0.1 ppm NH3

Highly sensitive OFET-based gas sensors using fluorinated naphthalenediimide semiconductor films

Naphthalene diimide bearing fluorinated alkyl side chains (FNDI) was synthesized and characterized by NMR spectroscopy. FNDI demonstrated good semiconductor characteristics and was used to fabricate gas sensors based on organic field-effect transistors (OFETs). The designed sensor devices exhibited fast response to low concentrations (1 ppm and less) of ammonia and some aliphatic amines. The revealed high sensitivity of the sensors in combination with the group-selectivity (with respect to amines) and good operational stability makes promising their practical application for food (e.g. fish) quality control or for medical diagnostics.

Hydrochemical differentiation of selected reservoirs in Carpathian Mts. and Eastern European Lowland

The aim of the analysis was to compare physicochemical parameters and chemical composition of two groups of artificial reservoirs, mountain and lowland ones, characterised by different parameters and functions. Three mountain artificial reservoirs (Klimkówka, Dobczyce, Czorsztyn) located in the Upper Vistula basin (Carpathian Mountains in Poland) and three lowland reservoirs (Ivankovo, Verhnevolzhskoye, Vyshnevolotzkoye) located in the Upper Volga basin (Eastern European Lowland in Russia) were selected for the study. Data for the summer season in 2009-2013 were used in the analysis. Mountain reservoirs display high water concentrations of sulphates, chlorides and biogenic nitrates, and lower concentrations of ammonium and oxygen indicator in relation to lowland reservoirs. Similar concentrations of phosphates were noticed in both the mountain and the lowland reservoirs. The hydrochemical differentiation between the individual mountain reservoirs was small, and statistically significant differences only occurred for SEC. Greater differentiation of the hydrochemical parameters was found among the lowland reservoirs. Statistically significant differences were demonstrated with regard to SEC, Cl- and NO3-.

Successful enrichment of low-abundant comammox Nitrospira from nitrifying granules under ammonia-limited conditions.

In artificial engineered systems, nitrification is a key reaction that accounts for the removal of biological nitrogen. Recently, a single microbe capable of oxidizing ammonia to nitrate, known as a complete ammonia oxidizer (comammox), has been discovered. Although the abundance and diversity of comammox Nitrospira in engineered systems have been identified through molecular-based approaches, the enrichment and isolation of comammox Nitrospira remains a challenge. Therefore, the aim of this study was to enrich comammox Nitrospira from nitrifying granules, which were used to increase the efficiency of biological nitrogen removal in wastewater treatment plants. We sought to accomplish this through the use of a fixed-bed continuous feeding bioreactor. Fluorescence in situ hybridization, 16S rRNA gene amplicon sequencing and qPCR of functional genes were utilized to monitor the growth of nitrifiers including comammox Nitrospira. Cloning of comammox amoA genes identified amoA phylogeny of enriched comammox Nitrospira. This work is an example demonstrating that continuous supply of low ammonium concentrations alongside biomass carriers is effective in cultivating comammox Nitrospira from engineered systems.

Community metagenomic assembly reveals microbes that contribute to the vertical stratification of nitrogen cycling in an aquaculture pond

The identities and functional capacities of the microbial populations within surface water (SW), bottom water (BW), surface sediment (SS) and deep sediment (DS) samples from a typical grass carp (Ctenopharyngodon idellus) culturing pond in central China were explored using metagenomics. In total, the community structure and microbial processes of the water columns was distinct from that of the SS and DS layers. Alphaproteobacteria, Actinobacteria, Cyanobacteria and Planctomycetes were abundant in the water, while Deltaproteobacteria, Gammaproteobacteria, Euryarchaeota (Archaea) and Nitrospirae were more abundant in the sediment (P < .05). The functional potential and microorganisms responsible for the N nutrient cycles were also reconstructed in silico. The high functional potential for N assimilation, protein synthesis and cell proliferation in pond water should be responsible for low ammonia concentration detected. Ammonia oxidation functional genes were present in very low abundances, and were mostly detected in the water columns and related to Nitrosomonas (100%). Denitrification were observed mostly in SS and the main taxon involved was Rhodocyclales. The potential for N fixation (nif genes) and dissimilatory nitrate reduction to ammonium was also observed mostly in sediment, which is a disadvantage for ammonia reduction in the pond ecosystem. Overall, these results offer a more detailed perspective on the microbial functional ecology of the aquaculture pond.

Experimental substantiation of new criteria for silage quality evaluation

Purpose. To substantiate new criteria for evaluation of corn silage quality with bio-preservatives. Methods. Zootechnical method to determine feed digestibility in animal experiments. It is incorporated in amphorae of 1.8 tons of corn silage mass of the beginning of wax ripeness. The first amphora was without preservative, the second was with bio preservative No. 1 and the third one was with bio preservative No. 2. The silo of 3 amphorae according to the standard was evaluated. In all 3 amphorae, the silo was of good quality, but the digestibility of dry matter in the balance experiments on the rams was different. Results. The most commonly accepted criteria for evaluating silo quality are its pH value and the solids content. The high quality silo has a pH of water extract in the range of 3.6—3.9. Such pH values are created by the high content of lactic acid and low ammonia content. Under these conditions, the nutrient retention in the silage feed is the highest compared to other acidity parameters. Thus, under pH higher than 4.4 and dry matter content of 30 %, the fermentation in the silo process takes place by the proteolytic type and, as a result, butyric acid, amines and ammonia, not lactic acid, are formed. Due to the fact that butyric acid is much weaker than lactic acid and thus has a low preservative capacity, the silo is of poor quality. Therefore, high levels of ammonia, amines and butyric acid cause poor quality of the silo. High quality silo contains up to 20 % free acids (2/3 – lactic acid and 1/3 acetic acid). Our research has shown that silage packed with bio-preservatives based on lactic and propionic acid bacteria has a higher digestibility of nutrients than the same starting mass (raw material), which is ensiled without a bio-preservative. Lactic acid bacteria synthesize B vitamins (B1, B2, B5 and B7) and essential amino acids, and propionic bacteria further synthesize vitamin B12, forming mucus and giving the silage a specific, pleasant taste, providing better feed for animals, e.g. cows, substances, which is a consequence of the higher productive action of the feed. Digestibility of dry matter of silage, which was incorporated without a biological preservative, was at the rate of 53.9 %, and it was 8.8 % higher with bio-preservative No. 1. Studies conducted with an air-dry matter of 3 silos to obtain a suspension have provided the basis for evaluating bacterial preservatives for their ability to stimulate the growth of microbial protein in the silage. Conclusions. On the basis of the conducted researches new criteria for evaluation of corn silage quality were experimentally substantiated. Indicators of high-quality silage, namely, pH, total acidity, lactic, content of acetic and butyric acids and ammonia, include the digestibility of dry matter in animals, and the determination of bacterial protein as an important factor in the influence of lactic and propionic acid bacteria of bio-preservatives on the biological value of feed protein, which is a criterion for evaluating biological preservatives for the ability to stimulate bacterial protein gain in silage.

Degradation of ammonia from gas stream by advanced oxidation processes

The reduction of ammonia emissions from air was experimentally investigated by advanced oxidation processes (AOPs) utilizing the combination of ultraviolet irradiation with ozone. The influence of operating conditions such as initial ammonia concentration and flow rate of gas on the reduction of ammonia concentration was investigated in homemade photochemical unit. The conversion of ammonia decreased with increasing initial concentration of ammonia and with increasing flow rate of air (decreasing retention time). The highest conversion of ammonia (97%) was achieved under lower initial concentration of ammonia (30 ppm) and lower flow rate of air (28 m3/h). The energy per order was evaluated for the advanced oxidation process too. The energy consumption was about 0.037 kWh/m3/order for the 97% ammonia conversion at 30 ppm of initial ammonia concentration and 28 m3/h flow rate of air. Based on the results, the advanced oxidation process combining the UV irradiation and ozone was effective for mitigation of ammonia concentration and presents a promising technology for the reduction of odor emissions from livestock buildings. Moreover, the AOPs are suitable for application for high flow rate of air, especially for ammonia abatement from livestock buildings, where very high efficiency is expected.

Effects of dietary crude protein levels on ammonia emission, litter and manure composition, N losses, and water intake in broiler breeders

This study determined the effects of different dietary crude protein (CP) levels on ammonia emission (NH3), litter and manure composition, nitrogen (N) losses, and water intake in broiler breeders. A total of 480 females and 64 males (Ross 308) 20 wk of age were randomly allotted to 2 dietary treatments with 8 replicates of 30 females and 4 males per replicate. Birds were fed either high CP (CPh) or low CP diets (CPl) supplemented with free amino acids (AA). Both diets consisted of 3 sub-diets; 1 for each phase of the laying period. Diets were formulated to be iso-caloric and calculated CP content of the CPl diets was 15 g/kg lower than the CPh diets (Breeder 1 (23 to 34 wk): 135 vs. 150, Breeder 2 (35 to 46 wk): 125 vs. 140 and Breeder 3 (47 to 60 wk of age): 115 vs. 130 g/kg, respectively). Pens consisted of an elevated slatted floor (25% of the floor surface) and a litter floor. Water and feed intake were recorded daily. Litter (floor) and manure (below slatted floor) composition and ammonia concentration were measured at 34, 44, and 54 wk of age. Ammonia concentration was measured using a flux chamber on top of the litter or manure. Estimated N losses were calculated. Dietary protein level did not affect water intake and dry matter (DM) content of the litter or manure. Compared to birds fed the CPh diets, the litter and manure samples of broiler breeders fed the CPl had 8% lower total-N and 13% lower ammonia-N content resulting in a 9% lower ammonia concentration, 9% lower ammonia emission, and 11% lower total-N losses. In conclusion, this study shows that reducing CP level in the diet of broiler breeders reduces ammonia emission and total N-losses from litter and manure.

Efficient poultry manure management: anaerobic digestion with short hydraulic retention time to achieve high methane production

The efficient treatment or appropriate final disposal of poultry manure (PM) to avoid serious environmental impacts is a great challenge. In this work, the optimization of a 2-stage anaerobic digestion system (ADS) for PM was studied with the aim of reaching a maximal methane yield with a short hydraulic retention time (HRT). Three activities were performed: The first activity, ADS 1, consisted of evaluating the effect of the substrate concentration and the HRT on the process, with a constant organic loading rate (OLR) of 3.66 ± 0.21 gVS L−1 d−1. The second activity, ADS 2, consisted of decreasing the HRT from 9.09 to 2.74 d with a constant substrate concentration. In the third activity, ADS 3, the substrate concentration was increased from 10.09 ± 1.41 to 35.25 ± 6.20 gVS L−1 with an average HRT of 4.66 ± 0.11 d.Maximal methane yields of 0.22, 0.21, and 0.22 LCH4 gVS−1 were reached for ADS 1, ADS 2, and ADS 3, respectively, at a low HRT (3.38 to 4.66 d) and high free ammonia concentration (between 323.05 ± 56.48 and 460.93 ± 135.40 mgN-NH3 L−1). These methane yields correspond to the production of 40.36 and 42.28 cubic meters of methane per ton of PM, respectively, and a laying hen produces between 47.45 and 54.75 kg of PM per year in Chile.Finally, this is the first study of the separate and combined effects of OLR, HRT and substrate concentration on the anaerobic digestion of PM. The results demonstrate the technical feasibility of the two-stage ADS treatment of PM with a short HRT; the system tolerates variations in the total ammonia nitrogen concentration of PM throughout the year and achieves a high methane yield when the correct operational conditions are selected.