Ultraviolet disinfection impacts the microbial community composition and function of treated wastewater effluent and the receiving urban river
- Published
- Accepted
- Subject Areas
- Microbiology, Freshwater Biology, Environmental Impacts
- Keywords
- wastewater treatment, ultraviolet disinfection, stormwater, microbial community, 16S rRNA sequencing
- Copyright
- © 2019 Kauser et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2019. Ultraviolet disinfection impacts the microbial community composition and function of treated wastewater effluent and the receiving urban river. PeerJ Preprints 7:e27605v1 https://doi.org/10.7287/peerj.preprints.27605v1
Abstract
Background. In the United States, an estimated 14,748 wastewater treatment plants (WWTPs) provide wastewater collection, treatment, and disposal service to more than 230 million people. The quality of treated wastewater is often assessed by the presence or absence of fecal indicator bacteria. UV disinfection of wastewater is a common final treatment step used by many wastewater treatment plants in order to reduce fecal coliform bacteria and other pathogens; however, its potential impacts on the total effluent bacterial community are seemingly varied. This is especially important given that urban wastewater treatment plants (WWTPs) typically return treated effluent to coastal and riverine environments and thus are a major source of microorganisms, genes, and chemical compounds to these systems. Following rainfall, stormflow conditions can result in substantial increases to effluent flow into these systems.
Methods. Here, we conducted a lab-scale UV disinfection on WWTP effluent using UV dosage of 100 mJ/cm2 and monitored the active microbiome in UV-treated effluent and untreated effluent over the course of 48h post-exposure using 16S rRNA sequencing. In addition, we simulated stormflow conditions with effluent UV-treated and untreated effluent additions to river water and compared the microbial communities to those in baseflow river water. We also tracked the functional profiles of genes involved in tetracycline resistance (tetW) and nitrification (amoA) in these microcosms using qPCR.
Results. We showed that while some organisms, such as members of the Bacteroidetes, are inhibited by UV disinfection and overall diversity of the microbial community decreases following treatment, many organisms not only survive, but remain active. These include common WWTP-derived organisms such as Comamonadaceae and Pseudomonas. When combined with river water to mimic stormflow conditions, these organisms can persist in the environment and potentially enhance microbial functions such as nitrification and antibiotic resistance.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
Taxonomic distribution of OTUs at the family level
Relative abundance refers to percentage of the OTUs attributed to each family with respect to all OTUs from each sample, including those that were unclassified. Only families represented by a total of >0.1% of OTUs across all samples are shown. The five sample types are separated vertically by treatment (top two are effluent only and bottom three are river water or river with added effluent) and horizontally by time point.
Taxonomic distribution of OTUs at the genus level
Relative abundance refers to percentage of the OTUs attributed to each genus with respect to all OTUs from each sample, including those that were unclassified. Only genera represented by a total of >0.1% of OTUs across all samples are shown. The five sample types are separated vertically by treatment (top two are effluent only and bottom three are river water or river with added effluent) and horizontally by time point.
Predicted functional metagenomic pathways in effluent samples, as identified by PICRUSt and STAMP analyses
Functions are shown at hierarchical level 3 based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology (KO) database. Welch'st-test was used to calculate variance between untreated vs. UV-treated effluent samples, all time points combined. TheP-values and 95% confidence intervals for the total variance of the two groups areindicated for each function.
Differential abundances of specific taxa based on sample type and time (DeSeq)
Phylogenetic assignment is given to the deepest possible level up to family. BaseMean is the mean of normalized counts for all samples; padj is the Benjamini–Hochberg adjusted P value.
Differential abundance of sewage indicator bacteria in untreated and UV-treated effluent (DESeq)
Mean of normalized counts at each time point are shown; padj is the Benjamini–Hochberg adjusted P value.