Metagenomic Insights in Activated Biomass Treating Industrial Wastewater at Different DO Levels.

Dissolved oxygen (DO) is an imperative parameter of the activated sludge process (ASP) for wastewater bioremediation. The effect of DO on microbial communities and corresponding metabolic functions in wastewater bioremediation was investigated using next-generation analysis techniques in this study. Illumina-based whole genome sequencing was applied to analyze the composition of the microbial community along with their functional diversity in activated sludge systems operating at three different DO levels. Activated biomass was collected from lab-scale reactors maintained at 1, 2, and 4 mg/L DO levels. Metagenomes were sequenced on an Illumina platform and analyzed using various tools. Results revealed that Proteobacteria phylum and Pseudomonas, Nitrobacter, Thauera, and Alicyclipilus genera were abundant in all reactor samples. Despite distinct DO levels, the microbial communities were conserved and consisted of a common population forming the core group governing the metabolic functions. However, higher diversity was observed at functional level indicating that microbes evolve and adapt to serve their role in a typical ASP. Metabolic pathway related to benzoate dominated at 1 mg/L DO level, while pathways for degradation of aromatic compounds like phenol, toluene, and biphenyl via central metabolic pathway were found dominating at 4 mg/L DO level. Pathways corresponding to homogentisate, naphthalene, cresol, and salicylate degradation enriched at 2 mg/L DO level.

Comparative metagenomics demonstrating different degradative capacity of activated biomass treating hydrocarbon contaminated wastewater.

This study demonstrates the diverse degradative capacity of activated biomass, when exposed to different levels of total dissolved solids (TDS) using a comparative metagenomics approach. The biomass was collected at two time points to examine seasonal variations. Four metagenomes were sequenced on Illumina Miseq platform and analysed using MG-RAST. STAMP tool was used to analyse statistically significant differences amongst different attributes of metagenomes. Metabolic pathways related to degradation of aromatics via the central and peripheral pathways were found to be dominant in low TDS metagenome, while pathways corresponding to central carbohydrate metabolism, nitrogen, organic acids were predominant in high TDS sample. Seasonal variation was seen to affect catabolic gene abundance as well as diversity of the microbial community. Degradation of model compounds using activated sludge demonstrated efficient utilisation of single aromatic ring compounds in both samples but cyclic compounds were not efficiently utilised by biomass exposed to high TDS.

Shifts in microbial community in response to dissolved oxygen levels in activated sludge.

This study evaluates the degradative efficiency of activated biomass collected from a Common Effluent Treatment Plant (CETP) under three different dissolved oxygen (DO) levels, 1, 2 and 4mgl(-1). The change in bacterial diversity with reference to DO levels was also analyzed. Results demonstrate that degradative efficiency was the highest, when the reactor was maintained at 4mgl(-1) DO, but amplicon library analysis showed a greater diversity of bacteria in the reactor maintained at 2mgl(-1) DO. Bacteria belonging to the order Desulfuromonadales, Entomoplasmatales, Pasteurellales, Thermales and Chloroflexales have only been detected in this reactor. Ammonia and nitrate levels in all three reactors indicated efficient nitrification process. Results of this study offer new insights into understanding the performance of activated biomass vis-à-vis microbial diversity and degradative efficiency with reference to DO. This information would be useful in improving the efficiency of any wastewater treatment plant.