Comparison of Two Mathematical Models for Greenhouse Gas Emission from Membrane Bioreactors

In this study two mathematical models (Model I and Model II), able to predict the nitrous oxide (N2O) and carbon dioxide (CO2) emission from an University Cape Town (UCT) \u2013 membrane bioreactor (MBR) plant, have been compared. Model I considers the N2O production only during the denitrification. Model II takes into account the two ammonia-oxidizing bacteria (AOB) formation pathways for N2O. Both models were calibrated adopting real data. Results highlight that Model II had a better capability of reproducing the measured data especially in terms of N2O model outputs. Indeed, the average efficiency related to the N2O model outputs was equal to 0.3 and 0.38 for Model I and Model II respectively

Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background: Hydrogen peroxide is a common reactive oxygen intermediate generated by variousforms of oxidative stress. Aims: The aim of this study was to investigate the DNA damage capacity ofH2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50 μM for5 min, 30 min, 40 min, 1 h or 24 h in parallel. The extent of DNA damage was assessed by the cometassay. Results: Compared to the control, DNA damage by 25 μM and 50 μM H2O2 increasedsignificantly with increasing incubation time up to 1 h, but it was not increased at 24 h. Conclusions:Our Findings confirm that H2O2 is a typical DNA damage inducing agent and thus is a good modelsystem to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantlywith H2O2 concentration and time of incubation but later decreased likely due to DNA repairmechanisms and antioxidant enzyme

Traitement de l'eau usée

National audienceLes stations d’épuration sont construites en aval des villes et traitent les eaux « usées » produites lors des activités domestiques (toilettes, salles de bains, cuisines…) avant de les rejeter vers le milieu récepteur de surface. Elles éliminent la pollution carbonée, mais aussi les pollutions azotée et phosphorée générées par le métabolisme humain (urine, matières fécales). Ces installations jouent un rôle indispensable pour protéger la ressource en eau et la vie dans les milieux aquatiques

The effect of phytase in pig diet and solid/liquid separation of pig slurry on phosphorus, calcium, and magnesium fractionation

International audienceIn some intensive animal production areas, the accumulation of nutrient surpluses (N, P, etc.) from livestock effluents has led to severe pollution problems (water, air, soil). The control of this potential pollutant load requires the development of processing methods to remove the excess nutrients. In France, biological treatment based on aeration (nitrification/denitrification)is the most widespread technology on farms. This treatment must now be adapted to include phosphorus removal as well as nitrogen removal. For this purpose, the characteristics of pig slurry from different farms (with or without phytase in pig diets) were studied through phosphorus, magnesium, and calcium fractionation including ortho−P, organic dissolved P, precipitated P, biomass P, and residual P. Moreover, the influence of mechanical separation (press auger and centrifugation)was studied. In raw slurry, 4% to 10% of phosphorus was soluble, 60% to 85% was precipitated, and 3% to 20% was phosphorus linked to the biomass. The total phosphorus concentration decreased slightly when diets with phytase were used (12%). Without phytase, around 20% of total phosphorus was "residual" (i.e., in a very insoluble form, probably as calcium phytate). Up to 50% of this form remained after the separation step. No residual phosphorus was found with phytase in the diet. Both separators studied (press auger and centrifugation) did not affect the concentration of soluble compounds in the separated slurry. When the TSS concentration in the raw slurry was high (>3.5%), the abatement of the TSS concentration was similar with centrifugation or press auger. In contrast, centrifugation and press auger decreased the total phosphorus concentration in the effluent by up to 50% and 15%, respectively. Most of the phosphorus removed by centrifugation is precipitated phosphorus. The difference between the amount and the quality of the phosphorus present in the effluents for each type separator should be considered in proposing a relevant dephosphorization strategy for pig slurry

The effect of phytase in pig diet and solid/liquid separation of pig slurry on phosphorus, calcium, and magnesium fractionation

International audienceIn some intensive animal production areas, the accumulation of nutrient surpluses (N, P, etc.) from livestock effluents has led to severe pollution problems (water, air, soil). The control of this potential pollutant load requires the development of processing methods to remove the excess nutrients. In France, biological treatment based on aeration (nitrification/denitrification)is the most widespread technology on farms. This treatment must now be adapted to include phosphorus removal as well as nitrogen removal. For this purpose, the characteristics of pig slurry from different farms (with or without phytase in pig diets) were studied through phosphorus, magnesium, and calcium fractionation including ortho−P, organic dissolved P, precipitated P, biomass P, and residual P. Moreover, the influence of mechanical separation (press auger and centrifugation)was studied. In raw slurry, 4% to 10% of phosphorus was soluble, 60% to 85% was precipitated, and 3% to 20% was phosphorus linked to the biomass. The total phosphorus concentration decreased slightly when diets with phytase were used (12%). Without phytase, around 20% of total phosphorus was "residual" (i.e., in a very insoluble form, probably as calcium phytate). Up to 50% of this form remained after the separation step. No residual phosphorus was found with phytase in the diet. Both separators studied (press auger and centrifugation) did not affect the concentration of soluble compounds in the separated slurry. When the TSS concentration in the raw slurry was high (>3.5%), the abatement of the TSS concentration was similar with centrifugation or press auger. In contrast, centrifugation and press auger decreased the total phosphorus concentration in the effluent by up to 50% and 15%, respectively. Most of the phosphorus removed by centrifugation is precipitated phosphorus. The difference between the amount and the quality of the phosphorus present in the effluents for each type separator should be considered in proposing a relevant dephosphorization strategy for pig slurry

Dépense énergétique des bioréacteurs à membranes pour le traitement des eaux résiduaires urbaines

National audienceRappel de l'intérêt des bioréacteurs à membrane (BAM) pour le traitement des eaux usées urbaines. Origine des coûts énergétiques et résultats obtenus sur installations vraie grandeur. Analyse des paramètres sur lesquels agir pour réduire les coûts. Perspectives d'évolution du procédé pour réduire les coûts énergétiques

Modélisation dynamique des procédés biologiques de traitement des eaux

National audienceLes procédés biologiques à biomasse en suspension, du type des boues activées, sont largement appliqués pour le traitement des eaux usées urbaines ou industrielles. Généralement, ces procédés sont dimensionnés sur la base d'équations de bilans « matières » établis à partir de l'hypothèse d'un régime permanent. Pourtant ces systèmes subissent continuellement des perturbations. En particulier, ils sont soumis à des variations importantes de charge en polluant(débit et concentration) à différentes échelles temporelles : journalières, hebdomadaires, annuelles, traduisant les fluctuations de l'activité humaine. De plus, ces procédés d'épuration sont gérés par des opérations parfois discontinues(aération séquencée, purge de boues, alimentation par bâchée, etc....). Par conséquent, même si des régimes pseudo-stationnaires peuvent être atteints, l'analyse dynamique des procédés biologiques d'épuration est incontournable pour appréhender le fonctionnement réel des unités et pour optimiser les paramètres de dimensionnement : volume et agencement des bassins, gestion de l'aération, extraction des boues, rôle tampon du clarificateur. Ceci est d'autant plus important que les configurations et les géométries des bassins biologiques se sont profondément diversifiées et complexifiées afin d'intégrer l'élimination des nutriments. L'objectif de cet article est d'une part de présenter les bases scientifiques de ces outils et, d'autre part, de proposer des méthodologies d'utilisation pour l'ingénieur

Influence of pH and biological metabolism on dissolved phosphorus during biological treatment of piggery wastewater

International audienceIn areas with intensive animal farming, phosphorus from livestock waste contributes to the eutrophication of surface water. To increase the phosphorus recycling potential, mineral phosphorus products have to be obtained not only from the liquid but also from the solid phase of piggery wastewater needing new physicochemical processes to be investigated. Discarding phosphorus from organic matter by a previous solubilisation of phosphorus improves the potential recycling yield. In this aim, evolution of dissolved phosphorus was studied during a simplified sequencing batch reactor process. Two slurries were tested in a sequencing batch reactor pilot plant to see if the biological phosphorus metabolism could be used to obtain a phosphorusenriched effluent suitable for chemically recycling phosphorus. Dissolved phosphorus, calcium, magnesium and intracellular carbon storage as polyhydroxybutyrate were measured. When available carbon was sufficient both biological and chemical mechanisms were involved in phosphorus evolution. Dissolved P concentration was increased by up to seven fold by the biological treatment. However, the precipitation/dissolution of phosphate driven by the pH was dominant to explain the changes during one treatment cycle. Higher dissolved phosphorus concentration was obtained at the end of the acidification step due to nitrification. This result was discussed in the perspective to develop alternative strategies to obtain an enriched effluent suitable for a sidestream phosphorus recycling process

A two pathway model for N2O emissions by ammonium oxidizing bacteria supported by the NO/N2O variation

International audienceIn this work, a new model for nitritation combining two N2O emission pathways was confronted with both NO and N2O measurements during nitrification. The model was calibrated with batch experiments and validated with long-term data collected in a sequencing batch reactor (SBR). A good prediction of the evolution of N2O emissions for a varying level of nitrite was demonstrated. The NO/N30/11/22O ratio was shown to vary during nitritation depending on the nitrite level. None of the models based on a single pathway could describe this variation of the NO/N2O ratio. In contrast, the 2 pathway model was capable of describing the trends observed for the NO/N2O ratio and gave better predictions of N2O emission factors. The model confirmed that the decrease of the NO/N2O ratio can be explained by an increase of the ND pathway to the detriment of the NN pathway. The ND pathway was systematically the predominant pathway during nitritation. The combined effect 2 of nitrite (or free nitrous acid) and dissolved oxygen (DO) on the contribution of each pathway was in agreement with practical observations and the literature