Search

The use of treated municipal wastewater residues (biosolids) as fertilizers is an attractive, inexpensive option for growers and farmers. Various regulatory bodies typically employ indicator organisms (fecal coliforms, E. coli and Salmonella) to assess the adequacy and efficiency of the wastewater treatment process in reducing pathogen loads in the final product. Molecular detection approaches can offer some advantages over culture-based methods as they can simultaneously detect a wider microbial species range, including non-cultivable microorganisms. However, they cannot directly assess the viability of the pathogens. Here, we used bacterial enumeration methods together with molecular methods including qPCR, 16S rRNA and cpn60 gene amplicon sequencing and shotgun metagenomic sequencing to compare pre- and post-treatment biosolids from two Canadian wastewater treatment plants (WWTPs). Our results show that an anaerobic digestion WWTP was unsuccessful at reducing the live indicator organism load (coliforms, generic E. coli and Salmonella) below acceptable regulatory criteria, while biosolids from a dewatering/pelletization WWTP met these criteria. DNA from other pathogens was detected by the molecular methods, but these species were considered less abundant. Clostridium DNA increased significantly following anaerobic digestion treatments. In addition to pathogen DNA, genes related to virulence and antibiotic resistance were identified in treated biosolids. Shotgun metagenomics revealed the widest range of pathogen DNA and, among the approaches used here, was the only approach that could access functional gene information in treated biosolids. Overall, our results highlight the potential usefulness of amplicon sequencing and shotgun metagenomics as complementary screening methods that could be used in parallel with culture-based methods, although more detailed comparisons across a wider range of sites would be needed. [ABSTRACT FROM AUTHOR]

Patterns of microbial fatty acids (MFAs) from activated sludge samples were analyzed over one year's operation at the Hamilton Woodward municipal wastewater treatment plant in Canada. The objective was to examine community structure dynamics and to consider the potential for interrelationships between the population dynamics and treatment performance. With the exception of a higher than normal solids discharge on one day, the treatment plant operations were otherwise stable during the year. As such, wastewater temperature appeared to be the dominant influence on the observed dynamics of the MFA community structure. MFA monitoring and analysis was demonstrated as a practical diagnostic tool in community structure trend monitoring. While the findings did suggest potential for full-scale treatment process monitoring, further development is required. Advancement in technique and greater insight for the data interpretation will be made with historical data from continued case studies. In future studies, selective sub-sampling of biomass fractions (settling and dispersed fauna), evolution in the compositional analysis methods, and, ideally, complementary genotypic and classical microscopic analyses on select samples are recommended. [ABSTRACT FROM AUTHOR]