Comparison of Conventional Multiple Tube Fermentation Technique with A-1 Medium in the Assessment of the Microbial Quality of Wastewater Treatment Plant Sludge

Despite the obvious benefits of sludge or biosolids in land application as a soil conditioner and fertilizer, there are concerns about its potential hazards. There is a great concern in the world about the disposal of biosolids due to the numerous pathogenic microorganisms, and chemicals, such as heavy metals, present in it. Therefore, microbiological monitoring of sludge by wastewater utilities is essential to assess the efficiency of treatment plants and the land application of sludge.

In this study the A-1 medium was compared with the conventional multiple tube fermentation technique (MTF) for the microbial evaluation of wastewater treatment plant sludge. In this research, 30 biosolids samples were taken from north and south Wastewater Treatment Plants of Isfahan. After measuring the ambient and sample temperature, the samples were transported to the laboratory. Fecal coliforms were analyzed by two methods. Total solids (TS) and volatile solids (VS) were also measured.

The number of fecal coliforms in all samples of the north and south wastewater sludge treatment was higher than the class A and B of biosolids standards. Enumeration of fecal coliforms averaged 3.25E+14 and 2.1E+14 MPN/g by the MTF and A-1, respectively and this difference was statistically significant

In conclusion, A-1 medium technique can be used as an alternative approach to the MTF method for microbial monitoring of biosolids with less labor and detecting of fecal coliforms in a shorter amount of time.