Simultaneous organic matter removal and nitrification of an inert self-supporting immersed media to upgrade aerated lagoons.

A pilot study was performed to evaluate the potential of an inert self-supported immersed fixed film media to upgrade aerated lagoons. Simultaneous organic matter removal and nitrification was assessed under different loading rates and temperatures (near 0 °C) using 12 laboratory-scale reactors operated in parallel. Test results showed that both the temperature and the load have an influence on organic matter effluent concentrations. Effluent quality seemed related to the observed biofilm thickness. Thicker biofilm is believed to have contributed to biomass detachment and increased particulate organic matter concentrations in the effluent. Simultaneous organic removal and nitrification was obtained at loads above 5 g CBOD5/m2·d. The highest nitrification rate at 0.4 °C was obtained for the smallest load, which showed a nitrification limitation close to freezing point.

Grit particle characterization: influence of sample pretreatment and sieving method.

Grit causes problems in water resource recovery facilities (WRRFs): clogging pipes, damaging pumps, and reducing the active volume of aeration tanks and anaerobic digesters by grit accumulation. Grit chambers are built to remove these particles. However, no standardized methodology exists to characterize grit particles for grit chamber design and operation despite the large observed variability in grit composition. Therefore, this paper proposes a combination and adaptation of existing methods to sample and characterize grit particles in view of proper grit chamber design and its modelling to ultimately optimize the efficiency of this important WRRF unit process. Characteristics evaluated included particle size distribution from sieving after different sample pretreatments, organic/inorganic fractions, and density.

Understanding the contribution of biofilm in an integrated fixed-film-activated sludge system (IFAS) designed for nitrogen removal.

The objective of this study is to improve knowledge on the integrated fixed-film-activated sludge (IFAS) system designed for nitrogen removal. Biofilm growth and its contribution to nitrification were monitored under various operating conditions in a semi-industrial pilot-scale plant. Nitrification rates were observed in biofilms developed on free-floating media and in activated sludge operated under a low sludge retention time (4 days) and at an ammonia loading rate of 45-70 gNH4-N/kgMLVSS/d. Operational conditions, i.e. oxygen concentration, redox potential, suspended solids concentration, ammonium and nitrates, were monitored continuously in the reactors. High removal efficiencies were observed for carbon and ammonium at high-loading rate. The contribution of biofilm to nitrification was determined as 40-70% of total NOx-N production under the operating conditions tested. Optimal conditions to optimize process compacity were determined. The tested configuration responds especially well to winter and summer nitrification conditions. These results help provide a deeper understanding of how autotrophic biomass evolves through environmental and operational conditions in IFAS systems.

A calibration protocol of a one-dimensional moving bed bioreactor (MBBR) dynamic model for nitrogen removal.

This work suggests a procedure to correctly calibrate the parameters of a one-dimensional MBBR dynamic model in nitrification treatment. The study deals with the MBBR configuration with two reactors in series, one for carbon treatment and the other for nitrogen treatment. Because of the influence of the first reactor on the second one, the approach needs a specific calibration strategy. Firstly, a comparison between measured values and simulated ones obtained with default parameters has been carried out. Simulated values of filtered COD, NH(4)-N and dissolved oxygen are underestimated and nitrates are overestimated compared with observed data. Thus, nitrifying rate and oxygen transfer into the biofilm are overvalued. Secondly, a sensitivity analysis was carried out for parameters and for COD fractionation. It revealed three classes of sensitive parameters: physical, diffusional and kinetic. Then a calibration protocol of the MBBR dynamic model was proposed. It was successfully tested on data recorded at a pilot-scale plant and a calibrated set of values was obtained for four parameters: the maximum biofilm thickness, the detachment rate, the maximum autotrophic growth rate and the oxygen transfer rate.

Characterization of the potential impact of retention tank emptying on wastewater primary treatment: a new element for CSO management.

Theoretical studies have shown that discharges from retention tanks could have a negative impact on the WWTP's (Wastewater Treatment Plant) effluent. Characterization of such discharges is necessary to better understand these impacts. This study aims at: (1) characterizing water quality during emptying of a tank; and (2) characterizing the temporal variation of settling velocities of the waters released to the WWTP. Two full-scale sampling campaigns (18 rain events) have been realized in Quebec City and laboratory analyses have shown a wide variability of total suspended solids (TSS) and Chemical Oxygen Demand (COD) concentrations in the water released from the tank. Suspended solids seem to settle quickly because they are only found in large amounts during the first 15 min of pumping to the WWTP. These solids are hypothesized to come from the pumping in which solids remained after a previous event. When these solids are evacuated, low TSS containing waters are pumped from the retention tank. A second concentration peak occurs at the end of the emptying period when the tank is cleaned with wash water. Finally, settling velocity studies allowed characterizing combined sewer wastewaters by separating three main fractions of pollutants which correspond to the beginning, middle and end of emptying. In most cases, it is noticed that particle settling velocities increase as the pollutant load increases.

Modelling using rRNA-structured biomass models.

Models currently used have been developed to describe the storage response in the activated sludge process. In these models the distribution of the substrate flux between growth and storage is an empirical function. rRNA-structured biomass models are proposed to describe the metabolic status of cells in view of predicting the growth response (dmicro/dt) of cells in activated sludge process. The autocatalytic reaction rate of the synthesis of the PSS component (rRNA) can provide a mechanistic explanation for the growth response and the growth lag phase. The proposed models were able to describe and predict properly the growth response of the biomass in various types of reactor. Such models could be more widely applicable by using intrinsic model parameters. This would be a key improvement for as it would lead to improved models for design.

Effect of algal incorporation on growth, survival and carcass composition of rainbow trout (Oncorhynchus mykiss) fry.

A nutritional assay has been conducted with rainbow trout fry (Oncorhynchus mykiss) using a biomass of photosynthetic micro-organisms. The algal biomass was incorporated in the feed at increasing levels (12.5%, 25% and 50%) in order to verify the effects on survival (%), growth (length and mass) and carcass quality of the fish (skin color, water, protein and lipid content). Two commercial feeds (CF, as sold, and 0% A, reprocessed without algae) have been used as controls. After eight weeks at 10 degrees C, the growth has been significantly reduced in fish fed the feeds containing 25% and 50% algae diets (P<0.01). Moreover, an incorporation of algae higher than 12.5% in the feed led to a increase of water content (CF versus other diets; P<0.01) and TL (CF versus 50% A; P<0.01) (wet basis) content of carcasses. Survival was 100% in all treatment groups. Under the experimental conditions used, the results obtained show that a maximum of 12.5% of algal biomass can be incorporated in the feed for rainbow trout fry (O. mykiss) without negative consequences on growth and body content in lipids and energy of fish.

Aeration effect on the efficiency of swine manure treatment in a trickling filter packed with organic materials.

Effect of aeration rate on the removal of organic matter and nitrogen and on the formation of NH3, N2O and N2 was studied for an extensive biofiltration system packed with an organic media, which was used to treat pig manure. The results show high removal of BOD5 and TSS (99 and > or = 98%), independently of the four aeration rate tested (3.4-34 m3/m2 x h). Aeration rate > or = 4.4 m/h resulted in high ammonia stripping during start-up (> or = 1.0 kg NH3-N/m3 of swine manure treated), while using 3.4 m/h only 0.3 kg NH3-N/m3 were stripped. Complete nitrification was achieved after day 100 of operation, except in the biofilter with the lowest aeration rate. Simultaneous denitrification established in all the biofilters. Applying an aeration rate of 9.4 m/h up to 1.2 kg nitrogen was removed in the form of N2 for each m3 of swine manure treated. Contrary to the expectations, N2 formation and release increased with the aeration rate. This particular behaviour seems to be related to the punctual accumulation of water layers inside the biofilters, caused by the air force flowing in the opposite direction to the water flux. N2O production was quite similar in all biofilters (between 0.25-0.36 kg N2O-N/m3 of swine manure treated).

Toward an operational dynamic model for tertiary nitrification by submerged biofiltration.

This work deals with the methodology put in place to fit and validate the parameters of a biofiltration model (BAF) in tertiary nitrification treatment and dynamic conditions. For an average loading rate of 0.65 kg NH4-N/m(3) media/d, different time loading rates are applied inside a filtration-backwash run using a semi-industrial pilot. Comparisons between predicted and observed values on the NH4-N, NO3-N and TSS in treated water and the total head loss deltaP are carried out firstly using default values of BAF parameters. Model predictions overestimate values measured but trends are well reproduced. A sensitivity analysis is carried out and the hierarchy of BAF parameters has been set up classifying them into strong and low influence on the effluent concentrations. Among parameters revealing the strongest influence are those of the filtration module and the mean density of biofilm for the TSS effluent and the total AP, the specific autotrophic growth rate, the maximum biofilm thickness and the reduction coefficient of diffusivity in the biofilm for the NH4-N, NO3-N effluent. Finally, this classification leads to setting a calibration procedure, thanks to specific experimental tests directly measuring some BAF parameters.

Long chain fatty acids (LCFA) evolution for inhibition forecasting during anaerobic treatment of lipid-rich wastes: Case of milk-fed veal slaughterhouse waste.

A detailed study of a solid slaughterhouse waste (SHW) anaerobic treatment is presented. The waste used in this study is rich in lipids and proteins residue. Long chain fatty acids (LCFA), coming from the hydrolysis of lipids were inhibitory to anaerobic processes at different degrees. Acetogenesis and methanogenesis processes were mainly affected by inhibition whereas disintegration and hydrolysis processes did not seem to be affected by high LCFA concentrations. Nevertheless, because of the high energy content, this kind of waste is very suitable for anaerobic digestion but strict control of operating conditions is required to prevent inhibition. For that, two inhibition indicators were identified in this study. Those two indicators, LCFA dynamics and LCFA/VSbiomass ratio proved to be useful to predict and to estimate the process inhibition degree.

Comparison of existing models to simulate anaerobic digestion of lipid-rich waste.

Models for anaerobic digestion of lipid-rich waste taking inhibition into account were reviewed and, if necessary, adjusted to the ADM1 model framework in order to compare them. Experimental data from anaerobic digestion of slaughterhouse waste at an organic loading rate (OLR) ranging from 0.3 to 1.9kgVSm-3d-1 were used to compare and evaluate models. Experimental data obtained at low OLRs were accurately modeled whatever the model thereby validating the stoichiometric parameters used and influent fractionation. However, at higher OLRs, although inhibition parameters were optimized to reduce differences between experimental and simulated data, no model was able to accurately simulate accumulation of substrates and intermediates, mainly due to the wrong simulation of pH. A simulation using pH based on experimental data showed that acetogenesis and methanogenesis were the most sensitive steps to LCFA inhibition and enabled identification of the inhibition parameters of both steps.

Identification of cdc2cAt: a new cyclin-dependent kinase expressed in Arabidopsis thaliana flowers.

In the present paper, the isolation of a third cyclin-dependent kinase gene and its cognate cDNA from Arabidopsis thaliana is described. Whereas other characterised cdc2 genes are ubiquitously expressed in Arabidopsis, expression of cdc2cAt is restricted to flowers. This gene, named cdc2cAt, differs from the two previously reported cdc2 genes in its organisation. Comparison with other cdc2 genes suggests that the deduced protein belongs to a new family of CDC2-like proteins related to the human CHED protein kinase.

Distribution and Activity of the Plasma Membrane H+-ATPase in Mimosa pudica L. in Relation to Ionic Fluxes and Leaf Movements.

Plasma membrane H+-ATPase was immunolocalized in several cell types of the sensitive plant Mimosa pudica L., and transmembrane potentials were measured on cortical cells. In comparison with the nonspecialized cortical cells of the petiole or stem, the proton pump was highly expressed in motor cells. These immunological data are in close agreement with electrophysiological data, because the active component of the transmembrane potential was low in the nonspecialized cortical cells and high in motor cells. Therefore, motor cells contain the plasma membrane H+-ATPase required to mediate the ionic fluxes that are involved in circadian leaf movements and that are necessary to recover the turgor potential that is considerably affected by the large K+ and Cl- efflux associated with seismonastic movement. With the exception of sieve tubes, the phloem also had a high density of H+-ATPase. This suggests that the recovery of the transmembrane ionic gradients (K+ and Cl-), which is affected by various stimuli, is more energized by the companion and parenchyma cells than by the sieve elements. In addition, at the phloem/cortex interface collocytes displayed the required properties for lateral transduction of the action potential toward the pulvinal motor cells.

Increased Expression of Vacuolar Aquaporin and H+-ATPase Related to Motor Cell Function in Mimosa pudica L.

Mature motor cells of Mimosa pudica that exhibit large and rapid turgor variations in response to external stimuli are characterized by two distinct types of vacuoles, one containing large amounts of tannins (tannin vacuole) and one without tannins (colloidal or aqueous vacuole). In these highly specialized cells we measured the abundance of two tonoplast proteins, a putative water-channel protein (aquaporin belonging to the [gamma]-TIPs [tonoplast intrinsic proteins]) and the catalytic A-subunit of H+-ATPase, using either high-pressure freezing or chemical fixation and immunolocalization. [gamma]-TIP aquaporin was detected almost exclusively in the tonoplast of the colloidal vacuole, and the H+-ATPase was also mainly localized in the membrane of the same vacuole. Cortex cells of young pulvini cannot change shape rapidly. Development of the pulvinus into a motor organ was accompanied by a more than 3-fold increase per length unit of membrane in the abundance of both aquaporin and H+-ATPase cross-reacting protein. These results indicate that facilitated water fluxes across the vacuolar membrane and energization of the vacuole play a central role in these motor cells.

Control of Vascular Sap pH by the Vessel-Associated Cells in Woody Species (Physiological and Immunological Studies).

In Robinia wood, the vessel-associated cells form a continuous sleeve around the vessels. Variations in pH of the solution perfused through the vessels during the annual cycle and the opposing effects of carbonyl cyanide-m-chlorophenylhydrazone and fusicoccin on this pH value indicate that some living cells of the wood are involved in the control of vascular sap pH and that this control fluctuates with the seasons. The immunolocalization of the plasma membrane HT+-ATPase in Robinia wood was studied by the immunogold-silver-staining technique using an antibody raised against a conserved stretch of the cytoplasmic domain of the H+-ATPase. The immunostaining is much stronger in vessel-associated cells than in other living cell types (ray and axial parenchyma elements) of the secondary xylem. Our data show an efficient involvement of this cell type in the control of vascular sap pH.

Immunolocalization of the Plasma Membrane H+ -ATPase in Minor Veins of Vicia faba in Relation to Phloem Loading.

The immunolocalization of the plasma membrane H+ -ATPase, which generates a proton motive force energizing the uptake of inorganic and organic solutes, was studied by electron microscopy. The cells studied were in minor veins of Vicia faba L. exporting leaves, where photosynthates are supposed to be absorbed from the apoplast by phloem transfer cells. Immunologically detectable H+ -ATPase varied among the different cell types and was considerably denser in the transfer cells than in the other cell types, particularly in the sieve tube. Moreover, the distribution of the H+ -ATPase was not homogeneous in transfer cells, that pump being more concentrated in the region adjacent to the bundle sheath, phloem parenchyma, and xylem vessels than along the smooth part of the wall bordering the sieve tube. These results show that the plasma membrane infoldings of transfer cells possess the proton-pumping machinery required to energize an efficient uptake of photosynthates from the phloem apoplast and an efficient retrieval of nitrogenous compounds from the vascular sap.

Nitrogen elimination mechanisms in an organic media aerated biofilter treating pig manure.

Biofilters using organic media are known to procure efficient treatment for different types of wastewater, but the nitrogen removal pathways implied are still not well understood. In this study, a lab-scale aerated biofilter using peat and treating pig manure was operated for 180 days, in order to quantify the nitrogen transformations occurring in it. It was shown that stripping was important during the start-up, until nitrification took place. Simultaneous nitrification and denitrification, proved by N2 production, became the principal mechanism after some time. The production of N2O did not seem to come only from heterotrophic denitrification, but also from chemodenitrification and autotrophic denitrification. It has also been found that part of the influent nitrogen was retained in the system during the first 150 days, due to filtration, sorption and assimilation. During the last periods of operation, the nitrogen previously retained has been used by microorganisms, leading to an excessive N2 discharge.

Contrasting behavior of tetracene and perylene in collision-induced dissociation: a theoretical interpretation.

Dimethyl ether chemical ionization mass spectrometry of polycyclic aromatic hydrocarbons (PAHs) leads to [M + 13](+) and [M + 45](+) ions. The process leading to these ions is sensitive to the proton affinity of the PAH. Collision-induced dissociation observations on [M + 45](+) ion also show that tetracene has a peculiar reactivity in comparison with perylene, despite the similar physico-chemical properties of these two molecules. Ab initio calculations were used to establish a potential energy profile for the mechanistic pathway of [M + 13](+) and [M + 45](+) formation. [M + 45](+) ions result from the addition of CH(3)-O-CH(2)(+) to PAHs. A 1,2-hydride transfer followed by a 1,4-proton transfer and a loss of methanol subsequently lead to the formation of [M + 13](+) ions. For tetracene, the 1,2-hydride transfer does not occur, as it would lead to a thermodynamically unstable non-planar ion.

Sensitivity and specificity of antigen-capture ELISAs for diagnosis of Trypanosoma congolense and Trypanosoma vivax infections in cattle.

Sensitivity and specificity of the FAO/IAEA antigen-ELISA kits for diagnosis of bovine trypanosomosis were investigated using sera from experimental cattle infected by tsetse challenge with cloned populations of Trypanosoma congolense (three populations) or T. vivax (one population). The kits are based on monoclonal antibodies that recognise internal antigens of tsetse-transmitted trypanosomes. Ten cattle were infected with each trypanosome population for at least 60 days, and in combination with uninfected cohorts (n = 16) were used in a double-blind study design. Sensitivity and specificity of the tests depended on the choice of positive-negative thresholds expressed as percent positivity with respect to the median OD of four replicates of the strong positive reference serum provided with the kit. In general, while overall specificities were high, sensitivities of the antigen-ELISAs were poor. For example, at a cut-off of 5% positivity, the sensitivities of the antigen-ELISAs were 11% for samples (n = 1162) from T. congolense infected cattle (n = 30), and 24% for samples (n = 283) from T. vivax infected cattle (n = 10). The corresponding specificity values were 95% and 79%, respectively. At a cut-off of 2.5% positivity sensitivity for T. congolense was 25%, and for T. vivax 35%; corresponding specificity values were 85% and 63% respectively. There were no values of the positive-negative threshold at which both sensitivity and specificity were satisfactory. Restricting the analyses to samples taken more than 2 weeks after tsetse challenge did little to improve sensitivity estimates. Trypanosome species specificities of the antigen-ELISAs were also poor. Sensitivity and species specificity of the antigen-ELISA for Trypanosoma brucei infections were not investigated. In contrast to the antigen-ELISA, the sensitivity of the buffy-coat technique when applied to the same experimental animals was fairly high at 67% for T. congolense infections and 60% for T. vivax infections. For samples taken more than 2 weeks after tsetse challenge, high sensitivity estimates of 96% for T. congolense and 76% for T. vivax infections were obtained.

Dimethyl sulfoxide intrauterine therapy in the mare: effects upon endometrial histological features and biopsy classification.

The effects upon equine endometrial histological features produced by 10 to 30% concentrations of dimethyl sulfoxide (DMSO) in sterile saline were compared with the effects of sterile saline (0.9% NaCl) alone as an intrauterine infusion therapy in 16 barren mares. No harmful histological changes were noted (P>0.05) as a result of the therapy. Thirty percent intrauterine DMSO therapy produced a significant (P<0.01) improvement (i.e., reduction of chronic inflammatory cell infiltrates and reduction of periglandular fibrosis) in endometrial biopsy classification in 18 of the 27 barren mares evaluated; whereas only 2 of 18 barren mares improved following intrauterine saline treatment in the control group. In subsequent breeding trials, the pregnancy rates following intrauterine therapy were no different between DMSO-treated mares and saline-treated control mares (P>0.05); however, there was a trend toward a higher pregnancy rate following DMSO therapy. The inability to control for sire variability in the breeding trials may have contributed toward the result that no significant difference could be demonstrated in the pregnancy rates between treated and control mares.