María Elena Fernández Martínez

Distribution of free-living amoebae in a treatment system of textile industrial wastewater

Free-living amoebae have been found in soil, air and a variety of aquatic environments, but few studies have been conducted on industrial wastewater and none on wastewater from the textile industry. The aim of this study was to determine the presence and distribution of free-living amoebae in a biological treatment system that treats textile industrial wastewater. Samples were taken from input, aeration tank, sedimentation tank and output. Samples were centrifuged at 1200g for 15min, the sediment was seeded on non-nutritive agar with Enterobacter aerogenes (NNE) and the plates were incubated at 30 and 37°C. Free-living amoebae were present in all stages of the treatment system. The highest number of amoebic isolates was found in the aeration tank and no seasonal distribution was observed during the year. A total of 14 amoeba genera were isolated: Acanthamoeba, Echinamoeba, Korotnevella, Mayorella, Naegleria, Platyamoeba, Saccamoeba, Stachyamoeba, Thecamoeba, Vahlkampfia, Vannella, Vermamoeba, Vexillifera and Willaertia. The most frequently found amoebae were Acanthamoeba and Vermamoeba which were found in all treatment system stages. The constant presence and diversity of free-living amoebae in the treatment system were important findings due to the characteristics of the wastewater from the textile plant in terms of the residue content from colorants, fixers, carriers, surfactants, etc., used in fabric dyeing and finishing processes. The factors that determined the presence and distribution of amoebae in the activated sludge system were their capacity to form cysts, which allowed them to resist adverse conditions; food availability; an average temperature of 27-33°C; dissolved oxygen in average concentrations above 2mg/L, and pH in a range of 5.9-7.1.

Microbiological and Physicochemical Quality of Well Water Used as a Source of Public Supply

The sources of microbial and chemical contamination of groundwater are numerous and have severe implications for public health. The objective was to determine the microbiological and physicochemical quality of wells in the west and east of the Cuautla-Yautepec aquifer in Mexico. Wells showed bacteriological contamination in at least one sampling. Coliform values were lower than the maximum permissible limit indicated in the Mexican Ecological Criteria of Water Quality (1000 colony forming unit (CFU)/100 ml of fecal coliforms) for supply sources. The number of isolated amoebae was low, but these were present all year round. Amoebae were found in 71.7% of the samples and belonged to 13 genera. The most frequent amoeba, Hartmannella, occurring in 44% of the samples, has been associated with eye and brain infection, but its role as a cause of infection has not been confirmed. A gradient was observed for dissolved solids according to altitude; the concentrations of dissolved solids increased in wells with lower altitudes. Total hardness values were above 180 mg/L CaCO3, therefore the water is considered very hard, and both carbonate and non-carbonate hardness was detected. The average values of physicochemical parameters were below the maximum permissible limits indicated in the Mexican official norm.