Identification of sulfur-oxidizing bacteria from fishponds and their performance to remove hydrogen sulfide under aquarium conditions.

Hydrogen sulfide is a highly toxic gas that causes many economic losses in aquaculture ponds. The application of sulfur-oxidizing bacteria (SOB) to remove hydrogen sulfide is an eco-friendly approach. This study aimed to isolate and identify the most efficient SOBs from the sediment of warm-water fish farms. Enrichment and isolation were performed in three different culture media (Starkey, Postgate, and H-3) based on both mineral and organic carbon. Overall, 27 isolates (14 autotrophic and 13 heterotrophic isolates) were purified based on colony and cell morphology differences. Initial screening was performed based on pH decrease. For final screening, the isolates were assessed based on their efficacy in thiosulfate oxidation and the sulfate production on Starkey liquid medium. Among isolated strains, 3 strains of Iran 2 (FH-13), Iran 3 (FH-21), and Iran 1 (FH-14) that belonged to Thiobacillus thioparus species (identified by 16s rRNA) showed the highest ability in thiosulfate oxidation (413.21, 1362.50, and 4188.03 mg/L for 14 days) and the highest sulfate production (3350, 2075, and 1600 mg/L). In the final phase, the performance of these strains under aquarium conditions showed that Iran 1 and Iran 2 had the highest ability in sulfur oxidation. In conclusion, Iran 1 and 2 strains can be used as effective SOB to remove hydrogen sulfide in fish farms. It is very important to evaluate strains in an appropriate strategy using a combination of different criteria to ensure optimal performance of SOB in farm conditions.

High-Rate Sulfate Removal Coupled to Elemental Sulfur Production in Mining Process Waters Based on Membrane-Biofilm Technology.

It is anticipated that copper mining output will significantly increase over the next 20 years because of the more intensive use of copper in electricity-related technologies such as for transport and clean power generation, leading to a significant increase in the impacts on water resources if stricter regulations and as a result cleaner mining and processing technologies are not implemented. A key concern of discarded copper production process water is sulfate. In this study we aim to transform sulfate into sulfur in real mining process water. For that, we operate a sequential 2-step membrane biofilm reactor (MBfR) system. We coupled a hydrogenotrophic MBfR (H2-MBfR) for sulfate reduction to an oxidizing MBfR (O2-MBfR) for oxidation of sulfide to elemental sulfur. A key process improvement of the H2-MBfR was online pH control, which led to stable high-rate sulfate removal not limited by biomass accumulation and with H2 supply that was on demand. The H2-MBfR easily adapted to increasing sulfate loads, but the O2-MBfR was difficult to adjust to the varying H2-MBfR outputs, requiring better coupling control. The H2-MBfR achieved high average volumetric sulfate reduction performances of 1.7-3.74 g S/m3-d at 92-97% efficiencies, comparable to current high-rate technologies, but without requiring gas recycling and recompression and by minimizing the H2 off-gassing risk. On the other hand, the O2-MBfR reached average volumetric sulfur production rates of 0.7-2.66 g S/m3-d at efficiencies of 48-78%. The O2-MBfR needs further optimization by automatizing the gas feed, evaluating the controlled removal of excess biomass and S0 particles accumulating in the biofilm, and achieving better coupling control between both reactors. Finally, an economic/sustainability evaluation shows that MBfR technology can benefit from the green production of H2 and O2 at operating costs which compare favorably with membrane filtration, without generating residual streams, and with the recovery of valuable elemental sulfur.

Thermoplasmatales and sulfur-oxidizing bacteria dominate the microbial community at the surface water of a CO2-rich hydrothermal spring located in Tenorio Volcano National Park, Costa Rica.

Here we report the chemical and microbial characterization of the surface water of a CO2-rich hydrothermal vent known in Costa Rica as Borbollones, located at Tenorio Volcano National Park. The Borbollones showed a temperature surrounding 60 °C, a pH of 2.4 and the gas released has a composition of ~ 97% CO2, ~ 0.07% H2S, ~ 2.3% N2 and ~ 0.12% CH4. Other chemical species such as sulfate and iron were found at high levels with respect to typical fresh water bodies. Analysis by 16S rRNA gene metabarcoding revealed that in Borbollones predominates an archaeon from the order Thermoplasmatales and one bacterium from the genus Sulfurimonas. Other sulfur- (genera Thiomonas, Acidithiobacillus, Sulfuriferula, and Sulfuricurvum) and iron-oxidizing bacteria (genera Sideroxydans, Gallionella, and Ferrovum) were identified. Our results show that CO2-influenced surface water of Borbollones contains microorganisms that are usually found in acid rock drainage environments or sulfur-rich hydrothermal vents. To our knowledge, this is the first microbiological characterization of a CO2-dominated hydrothermal spring from Central America and expands our understanding of those extreme ecosystems.

Bacterial communities involved in sulfur transformations in wastewater treatment plants.

The main sulfate-reducing (SRB) and sulfur-oxidizing bacteria (SOB) in six wastewater treatment plants (WWTPs) located at southern Brazil were described based on high-throughput sequencing of the 16S rDNA. Specific taxa of SRB and SOB were correlated with some abiotic factors, such as the source of the wastewater, oxygen content, sample type, and physical chemical attributes of these WWTPs. When the 22 families of SRB and SOB were clustered together, the samples presented a striking distribution, demonstrating grouping patterns according to the sample type. For SOB, the most abundant families were Spirochaetaceae, Chromatiaceae, Helicobacteriaceae, Rhodospirillaceae, and Neisseriaceae, whereas, for SRB, were Syntrophaceae, Desulfobacteraceae, Nitrospiraceae, and Desulfovibriaceae. The structure and composition of the major families related to the sulfur cycle were also influenced by six chemical attributes (sulfur, potassium, zinc, manganese, phosphorus, and nitrogen). Sulfur was the chemical attribute that most influenced the variation of bacterial communities in the WWTPs (λ = 0.14, p = 0.008). The OTUs affiliated to Syntrophus showed the highest response to the increase of total sulfur. All these findings can contribute to improve the understanding in relation to the sulfur-oxidizing and sulfate-reducing communities in WWTPs aiming to reduce H2S emissions.