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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 m 3 /h, an empty bed residence time (EBRT) of 60 s, and a volume of 0.007 m 3 (6.6 L). The maximum removal efficiency were 96.9 ± 1.2% for H 2 S, at a loading rate of 4.7 g/m 3 h and a concentration of 79.1 mg/m 3 , 68 ± 2% for NH 3 , at a loading rate of 1.2 g/m3 h and a concentration of 2.0 mg/m 3 , and 71.5 ± 4.0% for toluene, at a loading rate of 1.32 g/m 3  h and a concentration of 2.3 mg/m 3 . The removal efficiency of the three compounds decreased when the toluene concentration was increased above 40 mg/m 3 . 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., (© 2024. The Author(s).)

Cadmium (Cd) presence and bioavailability in soils is a serious concern for cocoa producers. Cocoa plants can bioaccumulate Cd that can reach humans through the food chain, thus posing a threat to human health, as Cd is a highly toxic metal. Currently, microbiologically induced carbonate precipitation (MICP) by the ureolytic path has been proposed as an effective technique for Cd remediation. In this work, the Cd remediation potential and Cd resistance of two ureolytic bacteria, Serratia sp. strains 4.1a and 5b, were evaluated. The growth of both Serratia strains was inhibited at 4 mM Cd(II) in the culture medium, which is far higher than the Cd content that can be found in the soils targeted for remediation. Regarding removal efficiency, for an initial concentration of 0.15 mM Cd(II) in liquid medium, the maximum removal percentages for Serratia sp. 4.1.a and 5b were 99.3% and 99.57%, respectively. Their precipitates produced during Cd removal were identified as calcite by X-ray diffraction. Energy dispersive X-ray spectroscopy analysis showed that a portion of Cd was immobilized in this matrix. Finally, the presence of a partial gene from the czc operon, involved in Cd resistance, was observed in Serratia sp. 5b. The expression of this gene was found to be unaffected by the presence of Cd(II), and upregulated in the presence of urea. This work is one of the few to report the use of bacterial strains of the Serratia genus for Cd remediation by MICP, and apparently the first one to report differential expression of a Cd resistance gene due to the presence of urea., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Biofiltration offers an efficient and economical alternative for the elimination of offensive odors caused by hydrogen sulfide, ammonia, and volatile organic compounds. Considering that packing materials affect the performance and represent the main installation cost, the purpose of this work was to evaluate the biofiltration of H 2 S and NH 3 comparing three composted mixtures made from chicken manure and lignocellulosic residues (pruning waste, sugarcane bagasse, and rice husk) used as packing material. A range of gas concentrations similar to those of a municipal WWTP was used in the biofiltration of a contaminated stream performed on a laboratory scale. The results indicate that at low concentrations of H 2 S (6-36 ppm) and NH 3 (0-1 ppm), the three biofilters showed 100% removal efficiency. Now, at the maximum levels of gas concentrations of H 2 S (250 ppm) and NH 3 (19 ppm) while the removal efficiency of H 2 S remained higher than 90% in all cases, the removal efficiency of NH 3 remained higher than 90% only in the sugarcane bagasse biofilter. Compost mixtures with sugarcane bagasse and rice husk are highly reliable as packing material for biofiltration at high concentration of H 2 S. Specifically, the sugarcane bagasse mixture had the highest removal efficiency (99% H 2 S and 95% NH 3 ) and the highest elimination capacity (15 g H 2 S/m 3 h and 0.6 g NH 3 /m 3 h), making it a better option for the elimination of both gases. These results represent a contribution to the construction of a low-price elimination system of offensive odors in WTTPs and other industries.