MODELLING OF BACTERIAL SULPHATE REDUCTION IN ANAEROBIC PONDS : KINETIC INVESTIGATIONS

peer reviewedaudience: researcher, professional, student, popularization, otherThe aim of the study was first to develop a simple and practical model of anaerobic digestion including sulphate-reduction in anaerobic ponds. The basic microbiology of our model consists of three steps, namely, acidogenesis, methanogenesis, and sulphate reduction. This model includes multiple reaction stoichiometry and substrate utilization kinetics. The second aim was to determine some kinetic parameters associated with this model. The values of these parameters for sulfidogenic bacteria are used in the anaerobic pond model to describe the sulphate reduction processes and to evaluate the risk of odour generation

Green 4 Indoor - Wallonia Présentation AG SPHERES 18/12/2023

Présentation des résultats de recherche du projet G4i-W sur l'étude d'impacts en milieu intérieur des murs verts et sur la réutilisation des eaux grisesGreen 4 Indoor Walloni

Development of a SBR bench-scale to optimize the partial nitrification process in landfill laechate treatment and its possible application in Vietnam.

Landfill leachate treatment is a major issue in many developing countries including Vietnam. Leachates are characterised by very high nitrogen concentrations, especially ammonium, needing an appropriate treatment technology. Conventional treatment technology has some drawbacks: mostly its high costs and problems to meet discharged standards requirements. This study applies a more recent approach for nitrogen removal, which is known as partial nitrification, by using a sequencing batch reactor (Bernet et al., 2005) technique. For the first step, the experiments were done with Belgian leachates. Based on mathematical models derived from generally accepted ASM Model, specific growth rates of biomass (μ(T)) found is 0.48 (d-1), 0.39 (d-1), 1.56 (d-1) and 0.82 (d-1) for ammonium nitrifiers, nitrite nitrifiers, nitrite denitrifiers and nitrate denitrifiers respectively. Concentration of the active part of these four kinds of bacteria is estimated of 22.3 mg/L, 12.4 mg/L, 464 mg/L and 12.3 mg/L. Maintaining dissolved Oxygen concentrations in the range 0.8 to 2.1 mgO2/L, with typical value around 1.5 mg/L, the system yields nitrite accumulation (preliminary step of partial nitrification/denitrification). SBR cycle was changed from 4 hours/4 hours of aeration/mixing in turn to 5 hours/3 hours and then 6 hours/2 hours. The last cycle has shown the best partial nitrification capacity of the SBR (a nitrite accumulation of 89 %) but not yet yielding a 50/50 ratio of ammonium/nitrite at the end of nitrification process. However, a well managed SHARON process will be processed in the next step of the study to obtain higher nitrogen removal efficiency and the expected ammonium/nitrite ratio. It has also been shown that free ammoniac concentration affects the nitrite/(nitrite + nitrate) ratio at the end of aeration phase

Modeling of partial nitrification and denitrification in an SBR for leachate treatment without carbon addition

A process of partial nitrification and denitrification in a sequencing batch reactor (SBR) treating leachate was simulated by applying a modified version of activated sludge model no. 3 (ASM3), named ASM3_2step. This model modifies the ASM3 model by separating nitrification and denitrification into two steps with nitrite as an intermediate substrate. Three periods, including long term period, steady state and cycle evolution, were used for calibration. Three main processes were observed, including biomass production, nitrification (focusing on nitrite accumulation) and denitrification. The kinetic and stoichiometric parameters (μA\_NH, YA\_NH, YA_NO2, YH_O2, b A, KA\_NH), were determined from biokinetic and respirometry tests. Some of the default values of kinetic and stoichiometric parameters available in the ASM3 model and in the literature were kept constant, while some others were adjusted step by step until observed state variables fit with experimental data. The maximum specific growth rate of nitrite oxidizing bacteria (0.108 day−1) (simulated by the model) and that of ammonium oxidizing bacteria (0.61 day−1) (from biokinetic tests) are the parameters which have the highest influence on the nitrite accumulation, even more than oxygen supply intensity or Kla value. Other important parameters were KAO\_NH and KAO_NO2, calibrated at the values of 1.37 and 1.59 mg O2/L, respectively. The modified model and values of the kinetic and stoichiometric parameters obtained from the modeling process will be used for optimization of the partial nitrification in the next stud

Advancing Methodologies for Investigating PM_2.5 Removal Using Green Wall System

Combustion processes are the primary source of fine particulate matter in indoor air. Since the 1970s, plants have been extensively studied for their potential to reduce indoor air pollution. Leaves can retain particles on their surfaces, influenced by factors such as wax content and the presence of hairs. This study introduces an innovative experimental approach using metal oxide particles in an office-like environment to evaluate the depolluting effect of plant walls. Two plant walls were installed in a controlled room, housing three plant species: Aglaonema commutatum ‘Silver Bay’, Dracaena fragrans, and Epipremnum aureum. Metal oxide particles were introduced via a compressed air blower positioned between the two walls. The concentration of these particles was monitored using PM2.5 sensors, and the deposition of iron (Fe) on the leaves was quantified through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This novel methodology effectively demonstrated the utility of both real-time sensors and ICP-MS in quantifying airborne particle concentrations and leaf deposition, respectively. The results revealed that Dracaena fragrans had a 44% higher Fe particle retention rate compared to the control (wallpaper). However, further validation through methodological replication is necessary to confirm the reproducibility of these findings

A process to reduce the cost of leachates treatment

The cost of leachate treatment can be reduced by an appropriate selection of the unit operations needed. Moreover in some cases other liquid residues (waste) can be used as reactants to reduce the operating costs. The biological part of the system is based on a SBR process whose operating parameters are fitted on data collected on site. A sophisticated control scheme depending on the specific characteristics of the leachates is used to optimize the treatmen

Comparaison des systèmes d’agitation par diffuseur d’air et roue à aube dans un chenal algal à haut rendement

La technique d'épuration des eaux usées par chenal algal à haut rendement se distingue du lagunage traditionnel par un temps de séjour plus court, une faible profondeur, et une agitation mécanique constante. Cette agitation peut se faire soit par un jet d’eau, une roue à aube, ou encore un diffuseur d’air (air lift).Une comparaison du comportement hydrodynamique entre deux systèmes d’agitation les plus souvent utilisés pour des installations de traitement des eaux usées de type chenal algal à haut rendement (diffuseur d’air et roue à aube) est proposée. La puissance énergétique consommée par ces deux systèmes d’agitation est comparée par rapport à des vitesses de circulation de l’effluent usuellement rencontrées dans ce type de filière de traitement des eaux usées. Les performances épuratoires relatives des deux systèmes sont aussi analysées.Les résultats obtenus ont montré qu’en matière de consommation énergétique, le diffuseur d’air semble trois à cinq fois plus économique que la roue à aube. Cet avantage est confirmé aussi sur le plan des performances épuratoires puisqu’on a observé une meilleure élimination de l’azote total (NTK) et du phosphore en utilisant le système de diffusion d’air.Les résultats de ce travail montrent qu’un bon fonctionnement du chenal algal peut être obtenu en utilisant le diffuseur d’air comme système d’agitation.The purification technique of wastewater by High Rate Algal Ponds (HRAP) is distinguished from the traditional lagoon by a shorter residence time, a shallow depth and constant mechanical agitation. This agitation can be done by a water jet, a paddle wheel, or an air lift. A comparison of the hydrodynamic behaviour of the two agitation systems most often used for wastewater treatment systems similar to High Rate Algal Ponds (air lift and paddle wheel) was undertaken. Power energy consumed by these two agitation systems is compared for typical effluent circulation rates usually encountered in this type of wastewater treatment process. The purification performances for both agitation systems are also analyzed.The results showed that energy consumption using the air lift is about 3 to 5 times less costly than the paddle wheel. This advantage is also confirmed in terms of treatment efficiency since better removal of nitrogen and phosphorus using the air lift system is observed. This study shows that good functioning of the High Rate Algal Ponds can be obtained using the air lift as the agitation system