Total Ammonia Concentration Research Articles

Effect of concentrate level on feeding behavior and rumen and blood parameters in dairy goats: Relationships between behavioral and physiological parameters and effect of between-animal variability

This work aimed first to compare 2 diets differing in their percentage of concentrate [low (LO): 30% concentrate vs. High (HI): 60% concentrate] by measuring simultaneously feeding behavior, rumen parameters, blood and plasma parameters, and milk yield and composition in 8 mid-lactation goats. The second aim was to study the interrelationships between these variables and to analyze the between-animal variability to better understand the between-animal differences in acidosis susceptibility. All of the animals received the 2 diets ad libitum as total mixed ration according to a crossover design of two 4-wk periods. Mean daily DMI was similar between the 2 diets but the variability was higher for the HI than for the LO diet. Goats produced more milk when fed the HI diet compared with the LO diet but with a lower fat:protein ratio (0.81 vs. 0.99). They ate more rapidly the HI than the LO diet but stopped eating sooner after the afternoon feed allowance, and spent less time chewing. The increase in concentrate percentage modified rumen parameters: the pH and acetate:propionate ratio decreased and total VFA, ammonia, and soluble carbohydrate concentrations increased. Hematocrit, plasma NEFA, and blood K and Ca concentrations decreased but glycemia and uremia increased. Other parameters were not modified: milk fat content, blood pH, and bicarbonate and Na concentrations. A large between-animal variability was detected for all the measured parameters, especially for feeding behavior, with important consequences on rumen and blood parameters. This work confirmed the effects of a high percentage of concentrate on feeding behavior, rumen and blood parameters, and milk production, and some known relationships such as the positive link between rumen pH and chewing index. It also pointed out other relationships between parameters seldom measured at the same time, such as rumen redox potential or blood pH and chewing index, or the negative link between blood and rumen pH. When the animals spent a lot of time chewing, they probably produced a lot of saliva that buffered the rumen pH and prevented them from suffering from subacute ruminal acidosis. However, they used part of their blood bicarbonates reserve, which might have induced metabolic acidosis, as rumen and blood pH were inversely related. This could explain why some animals suffer from acidosis and others do not in a herd receiving the same diet, and why some animals seem to suffer more from subacute ruminal acidosis and others from metabolic acidosis.

Comparison of the water quality of the surface microlayer and subsurface water in the Guangzhou segment of the Pearl River, China

The water quality in the surface microlayer (SML) and subsurface water (SSW) in the Guangzhou segment of Pearl River, a eutrophic urban river section in China, were analyzed. The spatial and temporal dynamics of nutrient concentrations, heavy metals and bacteria were examined from two sampling sites in monthly samples throughout 2010. The mean concentrations of total nitrogen, ammonia, nitrate and nitrite were higher than 7.0 mg/L, 3.1 mg/L, 1.1 mg/L and 0.3 mg/L, while total phosphorus and orthophosphate were 0.5 mg/L and 0.1 mg/L, respectively. These results indicated that the water quality was rich in minerals and eutrophic. The mean concentrations of Mn and Fe were higher than 0.013 mg/L; and Ni, Cr and Pb were higher than 0.001 mg/L. The mean concentrations were in the order of Mn >Fe > Ni > Pb > Cr. The concentrations of heavy metals in the Guangzhou segment were lower than the limit of the surface water quality standards in China and the World Health Organization (WHO), but higher than the median values in the world’s freshwater. The density of bacteria ranged from 3.30×105 to 5.23×106 cells/mL, and the amount of cultivable heterotrophic bacteria ranged from 1.30×103 to 1.89×106 cfu/mL. Fecal coliform levels were beyond the V class of China water quality standard. The SML was enriched in nutrients, heavy metals and bacteria, with the maximum enrichment factor of 3.84 for nutrients, 8.00 for heavy metals, and 3.04 for bacteria, suggesting that the water quality of the SML of the Guangzhou segment of the Pearl River was more serious than in the SSW.

An anaerobic dynamic membrane bioreactor (AnDMBR) for landfill leachate treatment: Performance and microbial community identification

In this study, a pilot-scale anaerobic dynamic membrane bioreactor was operated for 142days for treating landfill leachate. Under stable operation, average COD removal efficiency of 62.2% was achieved when the reactor was fed with the raw leachate containing total ammonium concentration above 3000mg/L and COD above 13,000mg/L. The methane content in the biogas was in the range of 70-90%, and the average methane yield was 0.34L/g CODremoved at the organic loading rate of 4.87kg COD/(m(3)d). Pyrosequencing analyses indicated that during the operation the archaeal community was relatively stable while obvious changes took place in the bacterial community. Alkaliphilus, Petrimonas, Fastidiosipila and vadinBC27 were the abundant fermentation bacteria in bacterial communities. Moreover, phylum TM6 gradually became the most dominant bacterial community and reached the highest relative abundance of 32.9% as the operation elapsed. In archaeal communities, genus Methanosarcina was identified as the dominant methanogen.

Dissolution mechanism and solubility of hemimorphite in NH3-(NH4)2SO4-H2O system at 298.15 K

The dissolution mechanism of hemimorphite in NH3-(NH4)2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. The results show that hemimorphite is soluble in NH3-(NH4)2SO4-H2O system and its residue exists in the form of an amorphous SiO2 layer on the hemimorphite surface. The XPS data also indicate that the Si 2p3/2 and O 1s spectra of the hemimorphite are broadened and shift to higher binding energies and their binding energies are closer to silica with an increase of total ammonia and time. Solubility of hemimorphite in NH3-(NH4)2SO4-H2O system was measured by means of isothermal solution method at 298.15 K based on the study of the dissolution mechanism of hemimorphite. The results show that the solubility of zinc in solution increases firstly and then decreases with the increase of c T(NH3) (total ammonia concentration) at different NH3/NH4 + ratios. The solubility of silicon in solution decreases from 0.0334 mol/kg in c T(NH3)=4.1245 mol/kg NH3-(NH4)2SO4-H2O solution to 0.0046 mol/kg in c T(NH3)=7.6035 mol/kg NH3-(NH4)2SO4-H2O solution.

Ration formulations containing reduced-fat dried distillers grains with solubles and their effect on lactation performance, rumen fermentation, and intestinal flow of microbial nitrogen in Holstein cows

Sixteen multiparous lactating Holstein cows were used in 2 experiments to evaluate the effects of reduced-fat dried distillers grains with solubles (RFDG) on milk production, rumen fermentation, intestinal microbial N flow, and total-tract nutrient digestibility. In experiment 1, RFDG was fed at 0, 10, 20, or 30% of diet dry matter (DM) to 12 noncannulated Holstein cows (mean ± standard deviation: 89±11d in milk and 674±68.2kg of body weight) to determine effects on milk production. In experiment 2, the same diets were fed to 4 ruminally and duodenally cannulated Holstein cows (mean ± standard deviation: 112±41d in milk; 590±61.14kg of body weight) to evaluate the effects on rumen fermentation, intestinal flow of microbial N, and total-tract nutrient digestibility. In both experiments, cows were randomly assigned to 4×4 Latin squares over 21-d periods. Treatments (DM basis) were (1) control (0% RFDG), (2) 10% RFDG, (3) 20% RFDG, and (4) 30% RFDG. Feed intake and milk yield were recorded daily. In both experiments, milk samples were collected on d 19 to 21 of each period for analysis of milk components. In experiment 2, ruminal pH was measured; samples of rumen fluid, duodenal digesta, and feces were collected on d 18 to 21. Microbial N was estimated by using purines and DNA as microbial markers. Milk yield was not affected by treatment and averaged 34.0±1.29kg/d and 31.4±2.81kg/d in experiments 1 and 2, respectively. Percentage of milk protein tended to increase in experiment 1; estimates were 3.08, 3.18, 3.15, and 3.19±0.06% when RFDG increased from 0 to 30% in the diets. However, milk protein concentration was not affected in experiment 2 and averaged 3.02±0.07%. Percentage of milk fat was not affected and averaged 3.66±0.05% and 3.25±0.14% in experiments 1 and 2, respectively. Total ruminal volatile fatty acids and ammonia concentrations were not affected by treatment and averaged 135.18±6.45mM and 18.66±2.32mg/dL, respectively. Intestinal microbial N flow was not affected by treatment; however, purines yielded higher estimates of flow compared with DNA markers. When averaged across treatments, intestinal flow of microbial N was 303 and 218±18g of N/d, using purines and DNA as the markers. Dry matter, organic matter, neutral detergent fiber, and nonfiber carbohydrate digestibility tended to increase with increasing inclusion of RFDG. Results from these experiments indicate that dairy rations can be formulated to include up to 30% RFDG while maintaining lactation performance, volatile fatty acids concentration, and intestinal supply of microbial N.

Pretreating Stored Human Urine for Solar Evaporation by Low-Technology Ammonia Stripping

In order to avoid the loss of ammonia during solar drying of stored urine, low-tech stripping is suggested as a pretreatment process for ammonia recovery. The mass transfer of ammonia from stored urine with an initial pH of about 9 was tested in a simple closed vessel operated at 72°C, 74°C and 85°C. The specific urine/gas interface was 16.97 m-1. For ammonia absorption, a beaker with sulfuric acid was positioned in the gas phase of the container. After keeping the stored urine for 73 h at 85°C, the concentration of free ammonia (NH3) was reduced by more than 99%, and the pH of the stored urine decreased to 6.4 due to ammonia volatilization. Total ammonia (NH3+ NH4+) concentration was reduced by only 83% in the same period. At lower temperatures, the process was slower. Required treatment time can be reduced when specific gas/liquid interface is increased. Because it is known that water can be heated in solar boxes to temperatures above 90°C, this simple stripping apparatus is feasible to be operated with solar energy in remote areas with suitable climatic conditions where no electric power is available. As the area demand for solar “low-tech stripping” is less than 1 m2 per capita, this process can be looked at as a suitable pretreatment of stored urine prior to solar evaporation.

Competition for Ammonia Influences the Structure of Chemotrophic Communities in Geothermal Springs

Source waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon "Candidatus Nitrosocaldus yellowstonii" and the putatively nitrogen-fixing (diazotrophic) bacterium Thermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2 fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increased amoA transcript levels while it suppressed rates of acetylene reduction and decreased nifH transcript levels. Sequencing of amplified nifH and amoA transcripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2 fixation are closely affiliated with Ca. Nitrosocaldus yellowstonii and T. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such as Ca. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs.

The dominant acetate degradation pathway/methanogenic composition in full-scale anaerobic digesters operating under different ammonia levels

Ammonia is a major environmental factor influencing biomethanation in full-scale anaerobic digesters. In this study, the effect of different ammonia levels on methanogenic pathways and methanogenic community composition of full-scale biogas plants was investigated. Eight full-scale digesters operating under different ammonia levels were sampled, and the residual biogas production was followed in fed-batch reactors. Acetate, labelled in the methyl group, was used to determine the methanogenic pathway by following the 14CH4 and 14CO2 production. Fluorescence in situ hybridisation was used to determine the methanogenic communities’ composition. Results obtained clearly demonstrated that syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis was the dominant pathway in all digesters with high ammonia levels (2.8–4.57 g NH4 +-N L−1), while acetoclastic methanogenic pathway dominated at low ammonia (<1.21 g NH4 +-N L−1). Thermophilic Methanomicrobiales spp. and mesophilic Methanobacteriales spp. were the most abundant methanogens at free ammonia concentrations above 0.44 g NH3-N L−1 and total ammonia concentrations above 2.8 g NH4 +-N L−1, respectively. Meanwhile, in anaerobic digesters with low ammonia (<1.21 g NH4 +-N L−1) and free ammonia (<0.07 g NH3-N L−1) levels, mesophilic and thermophilic Methanosaetaceae spp. were the most abundant methanogens.

Promotion of cashmere growth by sulfur supplements in cashmere goats

This study was conducted to investigate effects of inorganic and organic sulfur supplements on cashmere growth and their differences. Thirty-six six-month-old female Liaoning cashmere goats with a body weight of approximately 25 kg and good health were randomly assigned to three treatments: control, ZnSO4 and HMBi (2-hydroxy-4-(methylthio) butyric acid isopropyl ester). The three groups were fed a basal diet, a ZnSO4 diet (supplemented with 0.63% ZnSO4.H2O) and an HMBi diet (supplemented with 1.27% HMBi), respectively. Blood and cashmere samples were collected at the end of the three-month experimental period. The plasma concentrations of total protein, urea nitrogen, ammonia and amino acids; the cashmere content of amino acids and sulfur contents; the cashmere growth rates; and the diameter of the cashmere fibres were determined. The results indicated that dietary supplementation with ZnSO4 or HMBi can decrease the plasma urea nitrogen concentration and increase concentrations of total protein and methionine in plasma. In addition, the two types of sulfur supplements appeared to increase the methionine, cysteine and sulfur contents in cashmere fibres. Furthermore, the supplements can accelerate cashmere growth, with no significant effect on cashmere fineness. The promotion of cashmere growth probably stems from the improvement in the protein metabolic balance, sulfur retention and sulfur-containing amino acids synthesis in cashmere goats following the ZnSO4 or HMBi supplementation. In general, the ZnSO4 supplement promotes greater cashmere growth than the HMBi supplement under the experimental conditions.

Thermodynamic study on phosphorus removal from tungstate solution via magnesium salt precipitation method

The thermodynamic equilibrium diagrams of Mg2+−PO43−−NH4+−H2O system at 298 K were established based on the thermodynamic calculation. From the diagram, the thermodynamic conditions for removing phosphorus from the tungstate solution by magnesium salt precipitation were obtained. The results show that when the concentration of total magnesium increases from 0.01 mol/L to 1.0 mol/L, the optimal pH for the phosphorus removal by magnesium phosphate decreases from 9.8 to 8.8. The residual concentration of total phosphorus almost keeps the level of 4.0×10−6 mol/L in the system. MgHPO4, Mg3(PO4)2 and the mixture of Mg3(PO4)2 and Mg(OH)2 are stabilized in these system, respectively. However, increasing the total concentration of magnesium has little effect on phosphorus removal by magnesium ammonium phosphate, while it is helpful for phosphorus removal by increasing the total ammonia concentration. The calculated results demonstrate that the residual concentration of total phosphorus can decrease to 5.0×10−7 mol/L as the total concentration of ammonia reaches 5.0 mol/L and the optimal pH value is 9–10. Finally, verification experiments were conducted with home-made ammonium tungstate solution containing 50 g/L WO3 and 13 g/L P. The results show that when the dosage of MgCl2 is 1.1 times of the theoretical amount, the optimum pH for removing phosphorus is 9.5, which matches with the results of the theoretical calculation exactly.

Ammonia transport across the skin of adult rainbow trout (Oncorhynchus mykiss) exposed to high environmental ammonia (HEA)

Recent molecular evidence points towards a capacity for ammonia transport across the skin of adult rainbow trout. A series of in vivo and in vitro experiments were conducted to understand the role of cutaneous ammonia excretion (J amm) under control conditions and after 12-h pre-exposure to high environmental ammonia (HEA; 2 mmol/l NH4HCO3). Divided chamber experiments with bladder-catheterized, rectally ligated fish under light anesthesia were performed to separate cutaneous J amm from branchial, renal, and intestinal J amm. Under control conditions, cutaneous J amm accounted for 4.5 % of total J amm in vivo. In fish pre-exposed to HEA, plasma total ammonia concentration increased 20-fold to approximately 1,000 μmol/l, branchial J amm increased 1.5- to 2.7-fold, and urinary J amm increased about 7-fold. Urinary J amm still accounted for less than 2 % of total J amm. Cutaneous J amm increased 4-fold yet amounted to only 5.7 % of total J amm in these fish. Genes (Rhcg1, Rhcg2, Rhbg, NHE-2, v-type H(+)-ATPase) known to be involved in ammonia excretion at the gills of trout were all expressed at the mRNA level in the skin, but their expression did not increase with HEA pre-exposure. In vitro analyses using [(14)C] methylamine (MA), an ammonia analog which is transported by Rh proteins, demonstrated that MA permeability in isolated skin sections was higher in HEA pre-exposed fish than in control fish. The addition of basolateral ammonia (1,000 μmol/l) to this system abolished this increase in permeability, suggesting ammonia competition with MA for Rh-mediated transport across the skin of HEA pre-exposed trout; this did not occur in skin sections from control trout. Moreover, in vitro J amm by the skin of fish which had been pre-exposed to HEA was also higher than in control fish in the absence of basolateral ammonia, pointing towards a possible cutaneous ammonia loading in response to HEA. In vitro MA permeability was reduced upon the addition of amiloride (10(-4) mol/l), but not phenamil (10(-5) mol/l) suggesting a role for a Na/H-exchanger (NHE) in cutaneous ammonia transport, as has been previously described in the skin of larval fish. Overall, it appears that under control conditions and in response to HEA pre-exposure, the skin makes only a very minor contribution to total J amm, but the observed increases in cutaneous J amm in vivo and in cutaneous J amm and MA permeability in vitro demonstrate the capacity for ammonia transport in the skin of adult trout. It remains unclear if this capacity may become significant under certain environmental challenges or if it is merely a remnant of cutaneous transport capacity from early life stages in these fish.

Comparative performance of mesophilic and thermophilic anaerobic digestion for high-solid sewage sludge

In local cities, many small sewage and waste treatment facilities are operated independently. To encourage processing by anaerobic digestion at a centralized sewage treatment plant (STP), high-solid sewage sludge is helpful because it reduces the energy and cost required for transporting the sludge from other STPs. Mesophilic and thermophilic anaerobic digestion of sewage sludge at total solids concentrations (TS) of 7.5% and 10% were evaluated using laboratory-scale continuous reactors. Under the mesophilic condition, sewage sludge of 10% TS was successfully treated. Under the thermophilic condition, sewage sludge of 7.5% TS was not successfully treated when the total ammonia concentration was over 2000 mg N/L. Batch experiments showed that it takes a few weeks for the methane fermentation activity to recover after being inhibited. The effectiveness of adding easily biodegradable organic matter was confirmed. These results show that high-solid sewage sludge is suitable for small facilities by controlling the operating conditions.

An in vitro analysis of intestinal ammonia handling in fasted and fed freshwater rainbow trout (Oncorhynchus mykiss)

Ammonia transport and metabolism were investigated in the intestinal tract of freshwater rainbow trout which had been either fasted for 7 days, or fasted then fed a satiating meal of commercial trout pellets. In vivo, total ammonia concentrations (T amm) in the chyme were approximately 1 mmol L(-1) across the entire intestine at 24 h after the meal. Highest chyme pH and P NH3 values occurred in the posterior intestine. In vitro gut sac experiments examined ammonia handling with mucosal (Jmamm) and serosal (Js amm) fluxes under conditions of fasting and feeding, with either background (control ≤ 0.013 mmol L(-1)) or high luminal ammonia concentrations (HLA = 1 mmol L(-1)), the latter mimicking those seen in chyme in vivo. Feeding status (fasted or fed) appeared to influence ammonia handling by each individual section. The anterior intestine exhibited the greatest Jm amm and Js amm values under fasted control conditions, but these differences tended to disappear under typical post-feeding conditions when total endogenous ammonia production (Jt amm = Js amm - Jm amm, signs considered) was greatly elevated in all intestinal sections. Under fasted conditions, glutamate dehydrogenase (GDH) and glutaminase (GLN) activities were equal across all sections, but the ammonia-trapping enzyme glutamine synthetase (GS) exhibited highest activity in the posterior intestine, in contradiction to previous literature. Feeding clearly stimulated the total rate of endogenous ammonia production (Jt amm), even in the absence of a high luminal ammonia load. This was accompanied by an increase in GDH activity of the anterior intestine, which was also the site of the largest Jt amm. In all sections, during HLA exposure, either alone or in combination with feeding, there were much larger increases in endogenous Jt amm, most of which was effluxed to the serosal solution. This is interpreted as a response to avoid potential cytotoxicity due to overburdened detoxification mechanisms in the face of elevated mucosal ammonia. Thus T amm of the intestinal tissue remained relatively constant regardless of feeding status and exposure to HLA. Ammonia production by the gut may explain up to 18 % of whole-body ammonia excretion in vivo under fasting conditions, and 47 % after feeding, of which more than half originates from endogenous production rather than from absorption from the lumen.

Influence of Backwashing Time on Iron, Manganese, Ammonia and Turbidity Removal Using a Pilot-Scale Biological Filter

Backwashing time is one of the most critical operational parameters for biological filter. In order to investigate the effect of backwashing time on iron, manganese, ammonia and turbidity removal, three backwashing time (5 min, 4 min and 3 min) were adopted. Results showed that the average concentration of total iron, manganese and ammonia in effluent was 0.025 mg/L, 0.007 mg/L, and 0.022 mg/L; 0.012 mg/L, 0.001 mg/L and 0.017 mg/L; 0.013 mg/L, 0.000 mg/L and 0.016 mg/L, respectively, which illustrated varying backwashing time had little influence on the removal efficiency of them. The turbidity in effluent was 0.28 NTU, 0.38 NTU, 0.57 NTU, respectively. The shorter backwashing time, the higher turbidity in effluent. Turbidity was almost completely removed in 0~0.4m of the media. After backwashing, the turbidity in effluent was decreased to less than 1 NTU in 40 min, droped to less than 0.5 NTU in 90 min.

Improvement of separation efficiency of Cu(II) and Ni(II) in ammoniacal solutions by antagonistic effect of Aliquat336 on LIX84I

Abstracts The extraction and separation of copper and nickel in ammoniacal chloride media were studied using the mixed extractants containing of LIX84I and Aliquat336. The separation efficiency of Cu/Ni has been discussed under different concentration ratios of LIX84I and Aliquat336, aqueous pH values, concentrations of total ammonia and chloride in aqueous phase. The results indicate that the addition of Aliquat336 into LIX84I induces an antagonistic effect on the extraction reaction, especially for nickel. Nonetheless, an evident improvement of separation efficiency of copper over nickel can be found under the low concentration ratio of Aliquat336. The efficient separation of Cu/Ni also can be achieved by adjusting the aqueous pH and the concentration of ammonia and chloride. At the pH range of 7–11, the separation efficiency for the mixed extractant system is superior to that for LIX84I system. The low concentrations of chloride and ammonia in the aqueous phase are favorable to the extraction and separation of Cu/Ni.

Sanitation ability of anaerobic digestion performed at different temperature on sewage sludge

A small amount of ammonia is used in full-scale plants to partially sanitize sewage sludge, thereby allowing successive biological processes to enable the high biological stability of the organic matter. Nevertheless, ammonia and methane are both produced during the anaerobic digestion (AD) of sludge. This paper describes the evaluation of a lab-scale study on the ability of anaerobic process to sanitize sewage sludge and produce biogas, thus avoiding the addition of ammonia to sanitize sludge.According to both previous work and a state of the art full-scale plant, ammonia was added to a mixture of sewage sludge at a rate so that the pH values after stirring were 8.5, 9 and 9.5. This procedure determined an ammonia addition lower than that generally indicated in the literature. The same sludge was also subjected to an AD process for 60days under psychrophilic, mesophilic and thermophilic conditions. The levels of fecal coliform, Salmonella spp. helmints ova, pH, total N, ammonia fractions and biogas production were measured at different times during each process.The results obtained suggested that sludge sanitation can be achieved using an AD process; however, the addition of a small amount of ammonia was not effective in sludge sanitation because the buffer ability of the sludge reduced the pH and thus caused ammonia toxicity.Mesophilic and thermophilic AD sanitized better than psychrophilic AD did, but the total free ammonia concentration under the thermophilic condition inhibited biogas production. The mesophilic condition, however, allowed for both sludge sanitation and significant biogas production.

PH dynamics in sewers and its modeling

pH variation in sewers has a significant effect on hydrogen sulfide production and emissions, and hence its accurate prediction is critical for the optimization of mitigation strategies. In this study, the nature and dynamics of pH variation in a sewer system is examined. Three sewer systems collecting domestic wastewater were monitored, with pH in all cases showing large diurnal variations. pH in fresh sewage in all three cases had a very similar trend with maximum pH in the range of 8.5–8.7. pH variation in fresh sewage followed the same pattern as the sewage flow rate, suggesting that sewage pH is influenced by household water use. Nitrogen content of the wastewater was found to be the most influential factor causing pH variation in fresh sewage, with the total ammonium concentration variation well correlated with the pH variation. A methodology for predicting pH variation in sewers is developed and calibration protocols proposed. The methodology, which is based on the concept of charge balance, was validated using titration curves and field pH data. Measurement of the total ammonium concentration in fresh sewage was found necessary and adequate for the calibration of the charge balance-based pH model.

LANDFILL LEACHATE TREATMENT IN JET-LOOP MEMBRANE BIOREACTOR OPERATED UNDER DIFFERENT ORGANIC LOADING RATES

Since treatment of landfill leachate is quite complicated, there is a need to develop a system that is capable of providing high treatment efficiencies. In this study, the treatment performance of a jet - loop membrane bioreactor (JLMB) operated at different organic loading rates was investigated by observing the changes in Chemical Oxygen Demand (COD), Total Kjehldahl Nitrogen (TKN) and Total Ammonia (NH 3 ) concentrations. The same COD removal rates (83%) were observed at all the studied loading rates, and it should be noted that the biodegradable part of the leachate was removed completely. It was also observed that the NH 4 - N / TKN ratios, which were found to be approximately 0.9, did not change throughout the study. However, further treatment technologies, such as reverse osmosis, nanofiltration or ion - exchange, should be employed for the complete removal of inert COD and NH 3 in order to meet related discharge limits.

Protein replacement by digestible fibre in the diet of growing rabbits. 1: Impact on digestive balance, nitrogen excretion and microbial activity

The effects of protein replacement by digestible fibre fractions “DgF” (hemicelluloses+water-insoluble pectins) on the digestive physiology of the weaned rabbit were analysed by comparing four diets with a linear increase of the digestible fibre:crude protein ratio “DgFP” (1.01, 1.16, 1.34 and 1.55 for DgFP1 to DgFP4 groups, respectively), without changes of poorly digestible fibre levels (acid detergent fibre=190g/kg). 12 male rabbits were allotted to each of the four diets at weaning (32 days), housed in metabolism cages up to 71 days of age, and fed freely one of the four diets. Faecal and urine excretion were individually measured from 43 to 47 days of age, and from 63 and 67 days. At 71 days of age, the caecal contents of DgFP1 and DgFP4 groups were sampled to assess microbial activity (pH, volatile fatty acids concentration, etc.).The organic matter digestibility was similar for the four diets, but decreased by 2 units (0.65–0.63, P<0.001) with age (from 45 to 65 days) and without interaction with diet effect. As the intake of DgF increased by 20% from DgFP1 to DgFP4, the digestion of fibres increased (+9 and +15 units for NDF and hemicelluloses respectively, P<0.05). A diet by age interaction (P<0.05) was detected for crude protein (CP) digestion and retention: a 8% decrease in the digestibility of CP was observed between DgFP1 and DgFP4 for 7 weeks old rabbits, while for 9 weeks old rabbits this decrease reached 15%. While the faecal excretion of nitrogen remained unaffected by the diet, a 60% decrease in urinary nitrogen excretion was observed between DgFP1 and DgFP4 (P<0.001). The quantity of nitrogen excreted via the urine exceeded that of faeces for the DgFP1 group, but was 50% lower via urine than via the faecal route in the DgFP4 group. The nitrogen retention coefficient increased linearly (P<0.001) from DPF1 to DgFP4 (P<0.001), both in the post-weaning period (+5 units) or in the finishing period (+7 units). The ratio of retained nitrogen to digestible nitrogen increased linearly (P<0.001) between DgFP1 and DgFP4, and decreased substantially with age (−23 to −40% according to the diet). Although the caecal pH seemed to be lower (P=0.12) in the DgFP4 group, the total VFA and ammonia concentrations were similar between DgFP1 and DgFP4. High dietary DgFP ratios are thus recommended to reduce nitrogen output in urine; particularly at the end of the growing period when a reduced protein supply also decreases faecal nitrogen excretion.

English

The research was accomplished in order to study the efficiency of natural zeolite to prevent acute toxicity of ammonia on&nbsp;Huso huso.&nbsp;The study was performed using Water static method for 96 h. Fish with average weight 46 &plusmn; 5 g and total length 22 &plusmn; 4 cm were exposed to four different concentrations (15, 30, 50, 75 mg L-1) of ammonia salt. A group of fish was considered as control. Under stable condition, the lethal concentration of&nbsp;ionized&nbsp;ammonia was 50 mg L-1&nbsp;during 96 h. In the lethal concentration of total ammonia, different amounts of 5, 10, 15 g L-1&nbsp;granulated clinoptilolite zeolite were used.&nbsp;Results indicate significant differences between treatments and also with control (p&nbsp;&lt; 0.05). With increasing clinoptilolite zeolite in each treatment, the survival rate of fish also increased significantly (p&nbsp;&lt; 0.05).&nbsp;In lethal concentration of ammonia, the use of 15 g L-1&nbsp;zeolite could prevent the mortality rate. Histopathological findings showed that major lesions were hemorrhage, hyperemia, hyperplasia, epithelial cells necrosis, degenerated tubules of kidney, expansion of Bowman&#39;s capsule and hepatocytes necrosis. &nbsp; Key words:&nbsp;Ammonia, histopathological, lethal concentration, zeolilte,&nbsp;Huso huso.