Fate of mercury in a terrestial biological lab process using Polypogon monspeliensis and Cyperus odoratus.

Mercury has been extracted in Queretaro, Mexico since the 1960s. The mining wastes were open-air disposal and these mercury wastes have polluted the zone. The aim of this research was to evaluate mercury's fate in lab scale terrestrial reactors considering the following mercury species: soluble, interchangeable, strongly bound, organic, and residual ones. Soils were sampled in two former mines of Pinal de Amoles, Queretaro, Mexico (N 20° 58' to 21° 21' and West 99° 26' to 99° 43') with initial mercury concentrations were 424 ± 29 and 433 ± 12 mg kg-1 for "La Lorena" and "San Jose" former mines, respectively. Two vegetal species Polypogon monspeliensis and Cyperus odoratus were used and 20 reactors were constructed for the lab process. Total mercury was removed to 49-79% from both soils. Mercury elemental, exchangeable, and organic species had the most removal or exchange in the process. Metal uptake, by the plants, was of 5-6% for P. monspeliensis and 5-15% for C. odoratus. Also, mercury fate was estimated to the atmosphere to be 3.3-4.5 mg m-2 h-1 for both soils.

Tylosin effect on methanogenesis in an anaerobic biomass from swine wastewater treatment.

The effect of different concentrations of tylosin on methane production was investigated: first methanogenesis in a biomass without contact with the antibiotic, and later the ability of the sludge to adapt to increasing concentrations of tylosin. Results showed that, for biomass that had no contact with the antibiotic, the presence of tylosin inhibits the generation of methane even at concentrations as small as 0.01 mg L(-1), and samples at concentrations above 0.5 mg L(-1) produced practically no methane, whereas, in the digesters acclimated in the presence of tylosin at a concentration of 0.01 to 0.065 mg L(-1), methanogenesis is not inhibited in the presence of antibiotic and the generation of methane is improved. This behaviour suggests the microorganisms have developed not only resistance to the antibiotic but also an ability to metabolize it.

Performance of a biofilter system with agave fiber filter media for municipal wastewater treatment.

Agave plants grow in semi-arid regions and are used for mescal production. However, agave fiber by-products are considered waste materials. Thus, we tested agave fiber as a filter media and biofilm material carrier for removing pollutants from municipal wastewater. Three laboratory-scale biofiltration reactors were used in two trials with five hydraulic loading rates (HLRs = 0.27, 0.54, 0.80, 1.07 and 1.34 m(3) m(-2) d(-1)). One series was conducted using mechanical aeration (0.62 m(3) m(-2) h(-1)). To prevent compaction, decreasing pressure and clogging of the filter media, 4, 8 and 12 internal divisions were evaluated in the biofilter column. After 17 months of continuous operation at an HLR of 0.80 m(3) m(-2) d(-1), the removal efficiencies of the aerated biofilters were 92.0% biochemical oxygen demand, 79.7% chemical oxygen demand, 98.0% helminth eggs, 99.9% fecal coliforms and 91.9% total suspended solids. Statistical analysis showed that the chosen operational parameters significantly influenced the removal efficiencies of the biofilters. The effluent quality obtained under these conditions complied with the Mexican and US EPA standards for agricultural irrigation and green spaces, except for coliforms, which is why the effluents must be disinfected. Thus, agave fiber is a favorable choice for use as a packing material in biofiltration processes.

Occurrence of tylosin in swine wastewater in Mexico.

This study determined a tylosin concentration in swine wastewater located in a Mexican pig farm, during different stages of the pigs' growth. The detection of antibiotics in swine wastewater is complex due to its high concentration of solids. Analytical method was developed for detection of tylosin in swine wastewater and swine slurry. Average recoveries of tylosin in the liquid and solid phase were greater than 51 and 44%, respectively, with a greater total recovery of 95%. The results indicated the presence of tylosin in swine wastewater and slurry at concentrations greater than the ones reported in the literature. In grab samples of swine wastewater, the tylosin detected showed concentrations of 56, 72 and 8.6 µg L(-1), in breeding-gestation, nursery pigs, and grow-finishing area, respectively. In composite samples, the concentration of tylosin was 11.8 µg L(-1) for the breeding-gestation area and 2.4 µg L(-1) for the grow-finishing area. For slurry, the concentration of tylosin was 20.6 and 17.8 µg L(-1), for the breeding-gestation and grow-finishing area, respectively. This study presents the detection of a high concentration of tylosin in breeding-gestation and nursery pigs. Traces of tylosin in wastewater from grow-finishing stage were found although the animals were not receiving antibiotics.