Increased Detection of Desulfobacterota in Wastewater Treatment Plant Effluent via Composite Sampling Versus Grab Sampling

Municipal wastewater surveillance is essential for public health monitoring and preventing environmental contamination. Analysing treatment plant influents offers insights into population exposure to chemicals and microbes, while effluent and activated sludge reflect treatment efficiency and the quality of substances released into the environment. Our study, which compared grab and 24-hour composite bacterial sampling methods using next-generation sequencing of the 16S V4 region, offers practical insights. We collected samples from influent, activated sludge from the activated sludge process, and effluent wastewater on eight dates in 2017-2018 at wastewater treatment plants in Pirkanmaa, Finland. The results showed distinct bacterial compositions across sample types, with composite effluent samples revealing significantly higher Desulfobacterota abundance than the grab sample, thereby highlighting its higher resolution for effluent sampling.