Treatment of low strength sewage with high suspended organic matter content in an anaerobic sequencing batch reactor and modeling application

In this work, an anaerobic sequencing batch reactor (ASBR) was operated for 8 months to treat low strength sewage with high suspended organic matter content. Three phases of operation with increasing organic loading rates (OLR) were performed: 0.4 kg COD/m³ x d (phase I), 0 .8 kg COD/m³ x d (phase II) and 1.2 kg COD/m³ x d (phase III). Adequate stability parameters (pH, total alkalinity) were obtained through all three experimental phases. During phases I and II, the removal efficiencies of organic matter (expressed as total chemical oxygen demand (COD) and total suspended solids ranged between 50-60%. However, these values decreased to 15-25% in phase III. In addition, a non-complex model, including hydrolysis, acidogenesis and methanogenesis, was applied to predict the reactor behavior

A methodology for coupling DGGE and mathematical modelling : application in bio-hydrogen production

Molecular biology techniques provide valuable information in terms of microbial dynamic and evolution. DGGE analysis is one of the most popular methods, which has been used in bioprocess assessment. A novel procedure that combines common experimental measurements, DGGE and image analysis is presented as a new methodology for preliminary assessment. In this study, the methodology was applied as an example to the start up of a hydrogen bioreactor, in order to have a preliminary estimation of the actual concentration of the different microbial species. The obtained results are used for determining the kinetic parameter by using a simple mathematical model focusing on species dynamic

A methodology for a quantitative interpretation of DGGE with the help of mathematical modelling: application in bio-hydrogen production

Molecular biology techniques provide valuable insights in the investigation of microbial dynamics and evolution. Denaturing gradient gel electrophoresis (DGGE) analysis is one of the most popular methods which have been used in bioprocess assessment. Most of the anaerobic digestion models consider several microbial populations as state variables. However, the difficulty to measure individual species concentrations may cause inaccurate model predictions. The integration of microbial data and ecosystem modelling is currently a challenging issue for improved system control. A novel procedure that combines common experimental measurements, DGGE, and image analysis is presented in this study in order to provide a preliminary estimation of the actual concentration of the dominant bacterial ribotypes in a bioreactor, for further use as variable in mathematical modelling of the bioprocess. This approach was applied during the start-up of a continuous anaerobic bioreactor for hydrogen production. The experimental concentration data were used for determining the kinetic parameters of each species, by using a multi-species chemostat-model. The model was able to reproduce the global trend of substrate and biomass concentrations during the reactor start-up, and predicted in an acceptable way the evolution of each ribotype concentration, depicting properly specific ribotype selection and extinction

Modeling the Odor Generation in WWTP: An Integrated Approach Review

International audienceNuisance odors generation from waste and wastewater treatment plants are a cause of public discomfort and complaints. This situation impairs the air quality and represents a growing social and public health problem, especially in developing countries. Several modeling approaches have been developed and successfully implemented in the frame of a wastewater treatment plant for both the biological treatment and physicochemical processes. The mathematical modeling of the odor generation process is still considered a quite complex issue, mainly due to the fact that olfactory nuisance can be caused by many different chemical compounds and the perception of odors is influenced by subjective thresholds. Moreover, the impact of odor sources on air quality is highly conditioned by complex atmospheric dispersion processes. This review presents a critical state-of-art and assessment where information related to odor emissions impact studies as well as modeling applications are compiled and discussed

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Anaerobic co-digestion of sewage sludge and grease trap: Assessment of enzyme addition

International audienceAnaerobic co-digestion of grease trap and sewage sludge from a wastewater treatment plant is evaluated.Enzyme-lipase application, both addition and dosage, are evaluated by fitting the methane productionof biochemical potential tests with the first order model. The enzyme addition effect, at 2, 5 and 10% ofgrease trap (%GT VSFED−1) and the enzymes doses, between 0.25 and 1.67% (v/v), without and with greasetrap presence were studied. Grease trap addition showed a negative effect on the waste biodegradability,which was completely overcome by the addition of lipase. Enzyme addition improved notably themethane production for all grease trap fractions studied. In regards to the dosage, the best result wasachieved between 0.33 and 0.83% (v/v) of enzyme. The co-digestion of sewage sludge and grease trapmay be a feasible process by using lipases due to the saving in operational costs and the increase in thebiogas productio

Optimal Control of Landfills

International audienc

Anaerobic biodegradability of fish remains: experimental investigation and parameter estimation

The generation of organic waste associated with aquaculture fish processing has increased significantly in recent decades. The objective of this study is to evaluate the anaerobic biodegradabilityof several fish processingfractions, aswell aswatertreatment sludge,fortilapia and sturgeon species cultured in recirculated aquaculture systems. After substrate characterization, the ultimate biodegradability and the hydrolytic rate were estimated by fitting a first-order kinetic model with the biogas production profiles. In general, the first-order model was able to reproduce the biogas profiles properly with a high correlation coefficient. In the case of tilapia, the skin/fin, viscera, head and flesh presented a high level of biodegradability, above 310 mLCH4 gCOD1, whereas the head and bones showed a low hydrolytic rate. For sturgeon, the results for all fractions were quite similar in terms of both parameters, although viscera presented the lowest values. Both the substrate characterization and the kinetic analysis of the anaerobic degradation may be used as design criteria for implementing anaerobic digestion in a recirculating aquaculture system

Dynamical modelling and optimal control of landfills

Version preprint https://hal.inria.fr/hal-01087946International audienceWe propose a simple model of landfill and study a minimal time control problem where the re-circulation leachate is the manipulated variable. We propose a scheme to construct the optimal strategy by dividing the state space into three subsets $\mathcal{E}_0$, $\mathcal{Z}_{1}$ and the complementary. On $\mathcal{E}_0$ and $\mathcal{Z}_{1}$, the optimal control is constant until reaching target, while it can exhibit a singular arc outside these two subsets. Moreover, the singular arc could have a {\em barrier}.In this case, we prove the existence of a switching curve that passes through a point of {\em prior saturation} under the assumption that the set $\mathcal{E}_0$ intersects the singular arc.Numerical computations allow then to determine the switching curve and depict the optimal synthesis

Improvement of anaerobic digestion of swine slurry by steam explosion and chemical pretreatment application. Assessment based on kinetic analysis

International audienceSwine slurry is generated in large quantities and anaerobic digestion may represent an appropriate process to both treat and revalue this waste as an energy source. Pretreatment processes aim to increase the anaerobic biodegradability of a specific waste. In this study, steam explosion and weak thermal-alkali pretreatments are evaluated. The first series of Biochemical potential (BMP) test is set to establish the best substrate/inoculum ratio conditions, and then other tests are carried out to assess the impact of these pretreatments on the methane potential and maximum production rate by using the modified Gompertz equation. The S/I ratio exerts an influence on the BMP results and the optimum ratio was found to be between 0.1–0.25 gVSs gVSI−1. Steam explosion leads to an improvement of both the methane potential and the maximum production rate at the highest severity conditions. Weak alkali thermal pretreatment improved the maximum production rate but affected negatively the methane potential of the substrate