Bacterial diversity and predicted enzymatic function in a multipurpose surface water system – from wastewater effluent discharges to drinking water production

• Published in: Environmental microbiome Vol. 16; no. 1; pp. 1 - 11
• Main Authors: Tiwari, Ananda, Hokajärvi, Anna-Maria, Domingo, Jorge Santo, Elk, Michael, Jayaprakash, Balamuralikrishna, Ryu, Hodon, Siponen, Sallamaari, Vepsäläinen, Asko, Kauppinen, Ari, Puurunen, Osmo, Artimo, Aki, Perkola, Noora, Huttula, Timo, Miettinen, Ilkka T., Pitkänen, Tarja
• Format: Journal Article
• Language: English
• Published: London BioMed Central 22-05-2021; BMC
• Subjects: 16S rRNA amplicon sequencing; Aquatic ecosystems; Aquifers; Bacteria; Bacterial communities; Contamination; Drinking water; Effluents; Environmental protection; Groundwater; Groundwater recharge; Industrial effluents; Industrial wastewater; Laboratories; Lakes; Mine wastes; Pollutants; Pollution sources; Precipitation; Predicted biological function; Raw water; Relative abundance; River ecology; Rivers; rRNA 16S; Runoff; Seasonal effects; Sewage; Sewage effluent; Species richness; Surface water; Taxonomy; Wastewater discharges; Wastewater treatment; Water analysis; Water quality; Water sampling; Water treatment; Watershed management; Watersheds; United States > US; Germany; Finland
• ISSN: 2524-6372; 2524-6372
• DOI: 10.1186/s40793-021-00379-w

Abstract
Background
Rivers and lakes are used for multiple purposes such as for drinking water (DW) production, recreation, and as recipients of wastewater from various sources. The deterioration of surface water quality with wastewater is well-known, but less is known about the bacterial community dynamics in the affected surface waters. Understanding the bacterial community characteristics —from the source of contamination, through the watershed to the DW production process—may help safeguard human health and the environment.
Results
The spatial and seasonal dynamics of bacterial communities, their predicted functions, and potential health-related bacterial (PHRB) reads within the Kokemäenjoki River watershed in southwest Finland were analyzed with the 16S rRNA-gene amplicon sequencing method. Water samples were collected from various sampling points of the watershed, from its major pollution sources (sewage influent and effluent, industrial effluent, mine runoff) and different stages of the DW treatment process (pre-treatment, groundwater observation well, DW production well) by using the river water as raw water with an artificial groundwater recharge (AGR).
The beta-diversity analysis revealed that bacterial communities were highly varied among sample groups (R = 0.92,
p
 <  0.001, ANOSIM). The species richness and evenness indices were highest in surface water (Chao1; 920 ± 10) among sample groups and gradually decreased during the DW treatment process (DW production well; Chao1: 320 ± 20). Although the phylum
Proteobacteria
was omnipresent, its relative abundance was higher in sewage and industrial effluents (66–80%) than in surface water (55%). Phyla
Firmicutes
and
Fusobacteria
were only detected in sewage samples.
Actinobacteria
was more abundant in the surface water (≥13%) than in other groups (≤3%).
Acidobacteria
was more abundant in the DW treatment process (≥13%) than in others (≤2%). In total, the share of PHRB reads was higher in sewage and surface water than in the DW treatment samples. The seasonal effect in bacterial communities was observed only on surface water samples, with the lowest diversity during summer.
Conclusions
The low bacterial diversity and absence of PHRB read in the DW samples indicate AGR can produce biologically stable and microbiologically safe drinking water. Furthermore, the significantly different bacterial communities at the pollution sources compared to surface water and DW samples highlight the importance of effective wastewater treatment for protecting the environment and human health.