Influence of packing material on the biofiltration of butyric acid: A comparative study from a physico-chemical, olfactometric and microbiological perspective

Simultaneous biofiltration of H2S, NH3, and toluene using compost made of chicken manure and sugarcane bagasse as packing material

Offensive odors from wastewater treatment plants (WWTP) are caused by volatile inorganic compounds such as hydrogen sulfide and ammonia and volatile organic compounds (VOCs), such as toluene. To treat these pollutants, biofiltration is an effective and economical technology used worldwide due to its low investment and environmental impact. In this work, a laboratory-scale prototype biofilter unit for the simultaneous biofiltration of hydrogen sulfide, ammonia, and toluene was evaluated by simulating the emission concentrations of the El Salitre WWTP Bogotá, Colombia, using a compost of chicken manure and sugarcane bagasse as packing material for the biofilter. The prototype biofilter unit was set to an operation flow rate of 0.089 m3/h, an empty bed residence time (EBRT) of 60 s, and a volume of 0.007 m3 (6.6 L). The maximum removal efficiency were 96.9 ± 1.2% for H2S, at a loading rate of 4.7 g/m3 h and a concentration of 79.1 mg/m3, 68 ± 2% for NH3, at a loading rate of 1.2 g/m3 h and a concentration of 2.0 mg/m3, and 71.5 ± 4.0% for toluene, at a loading rate of 1.32 g/m3 h and a concentration of 2.3 mg/m3. The removal efficiency of the three compounds decreased when the toluene concentration was increased above 40 mg/m3. However, a recovery of the system was observed after reducing the toluene concentration and after 7 days of inactivity, indicating an inhibitory effect of toluene. These results demonstrate the potential use of the prototype biofilter unit for odor treatment in a WWTP.

Biofiltration of n-butyl acetate with three packing material mixtures, with and without biochar

Two cost-effective packing materials were used for n-butyl acetate removal in lab-scale biofilters, namely waste spruce root wood chips and biochar obtained as a byproduct from a wood gasifier. Three biofilters packed with spruce root wood chips: without biochar (SRWC), a similar one with 10% of biochar (SRWC-B) and that with 10% of biochar impregnated with a nitrogen fertilizer (SRWC-IB) showed similar yet differing maximum elimination capacities of 206 ± 27, 275 ± 21 and 294 ± 20 g m-3 h-1, respectively, enabling high pollutant removal efficiency (>95% at moderate loads) and stable performance. The original biochar adsorption capacity was high (208 ± 6 mgtoluene g-1), but near 70% of it was lost after a 300-day biofilter operation. By contrast, the exposed impregnated biochar drastically increased its adsorption capacity in 300 days (149 ± 7 vs. 17 ± 5 mgtoluene g-1). Colony forming unit (CFU) and microscopic analyses revealed significant packing material colonization by microorganisms and grazing fauna in all three biofilters with an acceptable pressure drop, up to 1020 Pa m-1, at the end of biofilter operation. Despite a higher price (14 vs. 123 €m-3), the application of the best performing SRWC-IB packing can reduce the total investment costs by 9% due to biofilter volume reduction.

Application of different packing media for the biofiltration of gaseous effluents from waste composting

A pilot-scale experiment was implemented in a waste bioreactor with an inner capacity of 1 m3 in order to simulate a real-scale composting process. The waste underwent composting conditions that are typical of the initial bio-oxidation phase, characterised by a high production of volatile organic compounds (VOCs), hydrogen sulphide (H2S) and odorants. The waste bioreactor was fed with an intermittent airflow rate of 6 Nm3/h. The target of this study was to investigate the air treatment performance of three biofilters with the same size, but filled with different filtering media: (1) wood chips, (2) a two-layer combination of lava rock (50%) and peat (50%), and (3) peat only. The analyses on air samples taken upstream and downstream of the biofilters showed that the combination of lava rock and peat presents the best performance in terms of mean removal efficiency of odour (96%), total VOCs (95%) and H2S (77%) concentrations. Wood chips showed the worst abatement performance, with respective mean removal efficiencies of 90%, 88% and 62%. From the results obtained, it is possible to conclude that the combination of lava rock and peat can be considered as a promising choice for air pollution control in waste composting facilities.

Odors Emitted from Biological Waste and Wastewater Treatment Plants: A Mini-Review

In recent decades, a new generation of waste treatment plants based on biological treatments (mainly anaerobic digestion and/or composting) has arisen all over the world. These plants have been progressively substituted for incineration facilities and landfills. Although these plants have evident benefits in terms of their environmental impact and higher recovery of material and energy, the release into atmosphere of malodorous compounds and its mitigation is one of the main challenges that these plants face. In this review, the methodology to determine odors, the main causes of having undesirable gaseous emissions, and the characterization of odors are reviewed. Finally, another important topic of odor abatement technologies is treated, especially those related to biological low-impact processes. In conclusion, odor control is the main challenge for a sustainable implementation of modern waste treatment plants.

A review on biofiltration techniques: Recent advancements in the removal of volatile organic compounds and heavy metals in the treatment of polluted water

Good quality of water determines the healthy life of living beings on this earth. The cleanliness of water was interrupted by the pollutants emerging out of several human activities. Industrialization, urbanization, heavy population, and improper disposal of wastes are found to be the major reasons for the contamination of water. Globally, the inclusion of volatile organic compounds (VOCs) and heavy metals released by manufacturing industries, pharmaceuticals, and petrochemical processes have created environmental issues. The toxic nature of these pollutants has led researchers, scientists, and industries to exhibit concern towards the complete eradication of them. In this scenario, the development of wastewater treatment methodologies at low cost and in an eco-friendly way had gained importance at the international level. Recently, bio-based technologies were considered for environmental remedies. Biofiltration based works have shown a significant result for the removal of volatile organic compounds and heavy metals in the treatment of wastewater. This was done with several biological sources such as bacteria, fungi, algae, plants, yeasts, etc. The biofiltration technique is cost-effective, simple, biocompatible, sustainable, and eco-friendly compared to conventional techniques. This review article provides deep insight into biofiltration technologies engaged in the removal of volatile organic compounds and heavy metals in the wastewater treatment process.