Impact of pre-treatments on nitrifying bacterial community analysis from wastewater using fluorescent in situ hybridization and confocal scanning laser microscopy
Journal of General and Applied Microbiology
Centre for Water and Wastewater Technology, Department of Biotechnology and Food Technology, Faculty of Applied Sciences, Durban University of Technology, Durban, South Africa
Fluorescent in situ hybridization (FISH) and confocal scanning laser microscopy (CSLM) are the key techniques used to investigate bacterial community structure at wastewater treatment plants. An optimum nitrifying bacterial population is necessary for nitrification, which plays a significant ecological role in regulating the overall quality of water. Nitrifying bacteria mainly appear as dense aggregates within activated sludge flocs. The impacts of five different pre-treatment meth-ods (physical, chemical, enzymatic and combinations) on floc dispersion from two different wastewater treatment plants were determined. The effect of pre-treatment on the enumeration of the nitrifying bacterial population was also investigated. This study on floc dispersion using CSLM images showed sonication was the superior method for all the samples tested, irrespec-tive of the sludge type. For samples from industrial wastewater plants, an optimized sonication level of 8 W for 8 min could reduce the floc size to 10 μm, whereas for domestic wastewater samples, the floc size was reduced to 10 μm at 8 W for 5 min. The maximum number of nitrifying bacterial cells was observed at this optimized level for different samples. A decrease in the num-ber of cells was observed beyond this optimized level for both the plants. The results presented here highlight the importance of optimizing pre-treatment methods for different types of waste-water for accurate bacterial community analysis using FISH-CSLM.
activated sludge; article; confocal laser microscopy; controlled study; environmental impact; flocculation; fluorescence in situ hybridization; microbial community; microbial population dynamics; nitrification; nonhuman; process optimization; ultrasound; waste water treatment plant; water quality; Bacteria; Bacterial Adhesion; Ecosystem; Flocculation; Image Processing, Computer-Assisted; In Situ Hybridization, Fluorescence; Microscopy, Confocal; Muramidase; Nitrates; Polyethylene Glycols; Sewage; Sonication; Waste Disposal, Fluid; Water Purification; Bacteria (microorganisms); Ziziphus mauritiana