Eric Dumont

Aerial pollutants in swine buildings: a review of their characterization and methods to reduce them.

The swine industry follows a large increase of meat production since the 1950s causing the development of bigger swine buildings which involves a raise of pollutants emissions. Due to recent anthropological pressures concerning the animal welfare, the limitation of neighborhood disturbances and atmospheric pollutions limitations, the livestock farming has to adapt their management methods to reduce or treat the aerial pollutants emissions. Through the diversity of livestock barns configurations, their climatic location, their size, and their management, we thus propose hereafter a critical review of the characterizations of these aerial pollutants. This is realized by distinguishing both solids and gaseous emissions and by referencing the measurements methods mainly used to analyze and quantify airborne particles, odorants, and gaseous compounds in the atmosphere of swine buildings. The origins of these pollutants are focused and the sturdiest techniques for concentration measurements are highlighted. Finally, we discuss pollutants abatement techniques criticizing their implementation in swine buildings and emphasizing the use of biological ways such as biofiltration for gases and odors treatment.

Wood bark as packing material in a biofilter used for air treatment.

Biotechnology has been applied to find green and low cost environmental processes. In the waste gas treatments (odours and volatile organic compounds VOC) one of the main biological systems used is biofilters. This technology works at normal operating conditions of temperature and pressure, and therefore it is relatively cheap with high efficiencies when the waste gas is characterized by high flow and low pollutant concentration. The aim of this work is to use wood barks (Pinus) as packing material in the biofilter. For this purpose, the influence of various parameters such as residence time of the gas and pollutant loads on removal efficiencies was studied for a biofilter pilot unit. Ethanol, methyl ethyl ketone, dichloromethane and toluene were used as pollutant compounds, because they are representative of both volatile organic compounds. Packing material stability and good biodegradation performances were found.

Steady- and transient-state H2S biofiltration using expanded schist as packing material.

The performances of three laboratory-scale biofilters (BF1, BF2, BF3) packed with expanded schist for H(2)S removal were studied at different empty bed residence times (EBRT=35, 24 and 16s) in terms of elimination capacity (EC) and removal efficiency (RE). BF1 and BF2 were filled with expanded schist while BF3 was filled with both expanded schist and a nutritional material (UP20; 12% vol). BF1 and BF3 were inoculated with activated sludge, whereas BF2 was not inoculated. A maximum EC of 42 g m(-3) h(-1) was recorded for BF3 at EBRT=35 s demonstrating the ability of schist to treat high H(2)S loading rates, and the ability of UP20 to improve H(2)S removal. Michaelis-Menten and Haldane models were fitted to the experimental elimination capacities while biofilter responses to transient-state conditions in terms of removal efficiency during shock load events were also evaluated for BF1 and BF3.

Biofiltration of high concentration of H2S in waste air under extreme acidic conditions

Removal of high concentrations of hydrogen sulfide using a biofilter packed with expanded schist under extreme acidic conditions was performed. The impact of various parameters such as H2S concentration, pH changes and sulfate accumulation on the performances of the process was evaluated. Elimination efficiency decreased when the pH was lower than 1 and the sulfate accumulation was more than 12 mg S-SO4(2-)/g dry media, due to a continuous overloading by high H2S concentrations. The influence of these parameters on the degradation of H2S was clearly underlined, showing the need for their control, performed through an increase of watering flow rate. A maximum elimination capacity (ECmax) of 24.7 g m(-3) h(-1) was recorded. As a result, expanded schist represents an interesting packing material to remove high H2S concentration up to 360 ppmv with low pressure drops. In addition, experimental data were fitted using both Michaelis-Menten and Haldane models, showing that the Haldane model described more accurately experimental data since the inhibitory effect of H2S was taken into account.

Activated Sludge Acclimation for Hydrophobic VOC Removal in a Two-Phase Partitioning Reactor

The effect of activated sludge acclimation on the biodegradation of toluene and dimethyldisulphide (DMDS) in the presence of a non-aqueous phase liquid, polydimethylsiloxane (PDMS), in a two-phase partitioning bioreactor was characterized. The influence of the presence of PDMS, at a ratio of 25% (v/v), and acclimation of activated sludge on two hydrophobic VOC biodegradation was studied. Activated sludge were acclimated to each VOC and in the presence of the non-aqueous phase liquid, namely in the emulsion of PDMS in water. Using acclimated cells, 97.9% and 108.7% improvement of the mean biodegradation rates were recorded for toluene and DMDS, respectively, if compared to the values recorded in the absence of acclimation. While and in agreement with the lower solubility in water of DMDS if compared to toluene, a most significant effect of PDMS addition on the rate of DMDS removal was recorded, 87.0% and 153.6% for toluene and DMDS, respectively. In addition and if both biomass acclimation and PDMS addition were considered, overall improvements of the removal rates were 204% and 338% for toluene and DMDS.

Biofiltration using peat and a nutritional synthetic packing material: influence of the packing configuration on H2S removal

This study aims to evaluate the feasibility of using a nutritional synthetic material (UP20) combined with fibrous peat as a packing material in treating H2S (up to 280 ppmv). Three identical laboratory-scale biofilters with different packing material configurations (peat only; peat+UP20 in a mixture; peat+UP20 in two layers) were used to determine the biofilter performances. The superficial velocity of the polluted gas on each biofilter was 65 m/h (gas flow rate 0.5 Nm3/h) corresponding to an empty bed residence time=57 s. Variations in elimination capacity, removal efficiency, temperature and pH were tracked during 111 d. A removal efficiency of 100% was obtained for loading rates up to 6 g/m3/h for the biofilter filled with 100% peat, and up to 10 g/m3/h for both biofilters using peat complemented with UP20. For higher loading rates (up to 25.5 g/m3/h), the configuration of peat-UP20 in a mixture provided the best removal efficiencies (around 80% compared to 65% for the configuration of peat-UP20 in two layers and 60% for peat only). Microbial characterization highlighted that peat is able to provide sulfide-oxidizing bacteria. Through kinetic analysis (Ottengraf and Michaelis-Menten models were applied), it appeared that the configuration peat-UP20 in two layers (80/20 v/v) did not show significant improvement compared with peat alone. Although the configuration of peat-UP20 in a mixture (80/20 v/v) offered a real advantage in improving H2S treatment, it was shown that this benefit was related to the bed configuration rather than the nutritional properties of UP20.

Efficiency of biological activator formulated material (BAFM) for volatile organic compounds removal--preliminary batch culture tests with activated sludge.

During biological degradation, such as biofiltration of air loaded with volatile organic compounds, the pollutant is passed through a bed packed with a solid medium acting as a biofilm support. To improve microorganism nutritional equilibrium and hence to enhance the purification capacities, a Biological Activator Formulated Material (BAFM) was developed, which is a mixture of solid nutrients dissolving slowly in a liquid phase. This solid was previously validated on mineral pollutants: ammonia and hydrogen sulphide. To evaluate the efficiency of such a material for biodegradation of some organic compounds, a simple experiment using an activated sludge batch reactor was carried out. The pollutants (sodium benzoate, phenol, p-nitrophenol and 2-4-dichlorophenol) were in the concentration range 100 to 1200 mg L−1. The positive impact of the formulated material was shown. The improvement of the degradation rates was in the range 10–30%. This was the consequence of the low dissolution of the nutrients incorporated during material formulation, followed by their consumption by the biomass, as shown for urea used as a nitrogen source. Owing to its twofold interest (mechanical resistance and nutritional supplementation), the Biological Activator Formulated Material seems to be a promising material. Its addition to organic or inorganic supports should be investigated to confirm its relevance for implementation in biofilters.

Characterization techniques of packing material colonization in gas biofiltration processesThis article is one of a selection of papers published in this Special Issue on Biological Air Treatment.

Biological air treatment is largely used for the decontamination of large air streams with low pollutant concentrations. As a result of microbial metabolism, the pollutants are degraded into carbon dioxide and water or converted into cell biomass. Three main research domains have emerged within the field of biofiltration: filter bed development, process optimization, and microbiological studies (community, nutrients, …). The objective of this paper is to focus on the microbial activities in air biofiltration processes. The nutrient contribution and the packing material effects are described. Special attention is paid to the description of techniques for the characterization and identification of the microbial population.

Performance evaluation of a slow-release packing material-embedded functional microorganisms for biofiltration

ABSTRACT A composite packing material (CM-5) was prepared in this study, mainly consisting of compost with functional microorganisms, calcium carbonate (CaCO3), perlite, cement and plant fiber. To get stronger compressive strength, mass ratios of these components were optimized based on single factor experiments, and finally adding amounts of perlite, cement, plant fiber, CaCO3, compost and binder at 18%, 18%, 7%, 13%, 17% and 27%, respectively. According to the optimum proportion, CM-5 was extruded in cylindrical shape (12 mm in diameter and 20 mm in length) with a bulk density of 470 kg m−3, a moisture retention capacity of 49% and the microbial counts of × 105 CFU g−1 of packing material. The cumulative release rates of total organic carbon (TOC) and total nitrogen (TN) from CM-5 were 3.1% and 6.5%, respectively, after 19 times extraction in distilled water. To evaluate the H2S removal capacity, CM-5 was compared with an organic (corncob) and an inorganic (ceramsite) packing material in three biofilters. The results showed that CM-5 had higher H2S removal capacity compared with corncob and ceramsite. CM-5 could avoid the large fluctuation of pH value and pressure drop during the operation. The maximum H2S removal capacity of CM-5 was 12.9 g m−3 h−1 and the removal efficiency could maintain over 95.4% when the inlet H2S loading rate was lower than 11.3 g m−3 h−1 without any addition of nutrients and pH buffer substances. Besides, only 2–3 days were needed for the recovery of biofiltration performance after about two weeks of idle period.

Quantification of the NH3 Adsorption on Dusts and its Consequences on the Design of Systems for the Removal of Aerial Pollutants in Piggeries

Through the framework of the aerial pollutants removal from the atmosphere of piggeries using a biofilter, this paper focuses on the effect of the presence of dust on the design of the biofilter. Simultaneous measurements (dust size distribution, dust concentration and NH3 concentrations) are carried out in the casing of the piggery air extraction.