Citation:

Tiwari, A., A. Hokajärvi, J. SantoDomingo, M. Elk, B. Jayaprakash, H. Ryu, S. Siponen, A. Vepsäläinen, A. Kauppinen, O. Puurunen, A. Artimo, N. Perkola, T. Huttula, I. Miettinen, AND T. Pitkänen. Bacterial diversity and predicted enzymatic function in a multipurpose surface water system – from wastewater effluent discharges to drinking water production. Environmental Microbiome. BioMed Central Ltd, London, Uk, 16:11, (2021). https://doi.org/10.1186/s40793-021-00379-w

Impact/Purpose:

The maintenance of decent quality and quantity of raw waters used for drinking water production is a challenge in many cities in the world. Mostly, surface waters such as rivers and lakes nearby the cities fulfill the demand of raw water. However, discharges of treated municipal and industrial effluents as anthropogenic sources of pollution often pose a threat to the quality of river water. Despite the highly developed wastewater treatment techniques, all pollutants are not sufficiently removed. Occasionally, raw sewage from combined sewer overflows may also contaminate river water. In addition, diffuse sources of pollution like runoff from agricultural land and forest areas and also urban flow during heavy rains and snow melt may deteriorate river water quality. Overall, the protection of raw water quality from multiple sources of pollution is a critical task for maintaining environmental health. Instead of using surface waters, groundwater can be a good source of high quality raw water for drinking water production. However, the high drinking water demand of many cities may require the use of artificial groundwater recharge (AGR). Bacterial communities have incredible roles in biogeochemical cycles and in freshwater ecosystems. For example, bacteria may contribute to degradation of pollutants. In an aquatic ecosystem, bacterial communities can be affected by various ecological factors like temperature and light conditions, UV radiation, pH, concentration of available oxygen, nitrogen, phosphorous and metal ions, interactions with the other biological communities (e.g., predators or phages of bacteria), and land-use patterns of catchment area. While being often ultimately different between geographical locations, many of the ecological factors vary even at a single location between the seasons of the year, affecting for instance the rate of photosynthesis and ecosystem productivity. Still, due to unidirectional flow of water, ecological factors within a river ecosystem can be almost unique. The recent studies of bacterial communities in water are often based on high-throughput amplicon sequencing of 16S rRNA gene. This technology has been used to study, for example, bacterial community of drinking water systems and aquatic ecosystems, especially in river water. While the 16S rRNA amplicon library analysis can provide information on presence of potential health related bacteria, the same sequences can also be used to predict the enzymatic function of bacterial communities in aquatic ecosystems by using an PICRUSt algorithm. The functional diversity can be different than taxonomic diversity, as many bacterial taxa may perform the same biological function within an ecosystem. The bacteria introduced from pollutant sources may shape both taxonomic and functional diversity of the recipient water. Herein, we studied bacterial community structure and function at river ecosystem, its major point sources of contaminants, to the drinking water production with AGR process, a path rarely followed all the way before.

Description:

Seasonal and temporal variation in bacterial communities, their predicted function and potential health related bacteria (PHRB) from a Nordic river, its major point sources of pollution and drinking water production process with artificial groundwater recharge (AGR) was studied with 16S ribosomal RNA genes based high-throughput sequencing. A total of 243 water samples were collected during four seasons (winter, spring, summer and autumn) in two consecutive years to enable sufficient biological replicates for comparing how bacterial diversity, taxonomy, predicted enzymatic function and the reads counts of PHRB changes over time and place. The reduction of PHRB in production well demonstrated AGR as one of best options of raw water for drinking water production. The possible seasonal change of bacterial diversity, community structure, predicted function and PHRB in surface water may imply that the ratio of FIB and pathogens may vary on different seasons. The change in bacterial community and taxonomic variation in different sample groups highlight the importance of effective treatment of municipal sewage and industrial effluent for protecting the microbial quality of surface water. This study widen knowledge of bacterial communities' behavior, fate, transport and change in different pollution scenarios.

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