We found well-preserved, rocky artefacts that had been buried in the healing mud (fango) for more than 1,500 years at the Roman archaeological site at Varaždinske Toplice. This Roman pool with fango sediments and artefacts is fed from hot sulphidic springs. The fango exhibited nearly neutral pH, a high level of organic C, an elevated concentration of heavy metals and a high total microbial biomass, greater than 10(8) cells per gram of dry weight. The dominant microbes, assessed by molecular profiling (denaturing gradient gel electrophoresis), were affiliated with Thiobacillus, Sulfuricurvum, Polaromonas, and Bdellovibrio. Polymerase chain reaction screening for microbial functional guilds revealed the presence of sulphur oxidizers and methanogens but no sulphate reducers. The dominance of four Proteobacterial classes (α-, β-, δ- and ε-Proteobacteria) was confirmed by fluorescence in situ hybridisation; Actinobacteria were less abundant. Cultivable bacteria represented up to 23.4 % of the total bacterial counts when cultivation media was enriched with fango. These bacteria represented the genera Acinetobacter, Aeromonas, Arthrobacter, Comamonas, Ewingella, Flavobacterium, Pseudomonas, Rahnella and Staphylococcus. This study showed that the heterogeneous nature of fango at neutral pH created various microniches, which largely supported microbial life based on sulphur-driven, autotrophic denitrification.
This study assesses the total suspended solids (TSS) retention capacity of different organic filter media for two potential applications: (i) a polishing unit for package treatment plants and (ii) a pretreatment for blackwater from low-flushing toilets. The results showed that the peat filter media used can be significantly improved in terms of structural stability and TSS removal capacity by mixing it with sawdust. Most of the TSS accumulated in the upper part of the filter material, and filter thickness exceeding 15 cm had no statistically significant effect (P < 0.1) on the TSS treatment performance. The experimental system reached a TSS reduction of 60-70% for blackwater and 80-90% for simulated effluent peaks from a package treatment plant. The main challenge of a full-scale application of an organic filter is the issue of clogging, especially when treating concentrated blackwater. However, this work indicates that a clogged filter media can be regenerated by mixing the uppermost filter layer without significant loss of filter performance regarding TSS. More research is needed to develop an appropriate mechanical unit for automatic filter media regeneration.
Air and water habitats in the Great Cavern of Santo Tomás were investigated using cultivable indicator microbial groups. In addition, cave pools were sampled to evaluate the biomass and diversity of aquatic meiofauna. In the climatically dynamic entrance part named Cueva de las Antorchas, concentrations of total cultivable airborne bacteria ranged from 2 to 15 CFU/20 cm 2 /20 min, and of airborne yeasts and moulds from 2 to 23 CFU/20 cm 2 /20 min. Different pools fed by constant percolation water or occasional underground floods were sampled. Microbial indicators of water habitats (total bacteria, coliforms, Escherichia coli, Enterobacteriaceae) showed that microbial load very likely depended on the sampling position in the vertical transection of the cave system and closeness to the entrance. During the underground flow of Santo Tomás Stream through the cave system, the concentration of isolates typical for E. coli was reduced from 56 CFU/ml at the ponor in Valle de Santo Tomás to a concentration below the detection limit at the spring in Valle de Quemado. In some cave pools, apart from microorganisms, aquatic fauna contribute highly to the total biomass. Investigation for aquatic meiofauna diversity in cave pools revealed relative high abundances of copepods and ostracods.
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