Impact of treated wastewater for irrigation on soil microbial communities

Authors: Ibekwe, Abasiofiok - Mark; GONZALEZ-RUBIO, ALBERTO - University Of California - Cooperative Extension Service; Suarez, Donald

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2017
Publication Date: 10/18/2017
Citation: Ibekwe, A.M., Gonzalez-Rubio, A., Suarez, D.L. 2017. Impact of treated wastewater for irrigation on soil microbial communities. Science of the Total Environment. 622:1603-1610. https://doi.org/10.1016/j.scitotenv.2017.10.039.

Interpretive Summary: The current fresh water use for irrigation in arid and semiarid lands is not sustainable, as use exceeds replenishment and demand for water continues to increase. Therefore, treated wastewater for irrigation has been suggested as an alternative for fresh water because of the increasing scarcity of fresh water in arid and semiarid regions of the world. However, significant barriers exist to widespread adoption of treated wastewater due to some potential contaminants that may have adverse effects on the environment and public health. In this study, we investigated the abundance and diversity of different bacterial communities in treated waste water in comparison to fresh water using advance DNA methods. Our data showed that sequences of nitrifying bacteria, nitrogen-fixing bacteria, carbon degraders, denitrifying bacteria, potential pathogens, and fecal indicator bacteria were more abundant in treated waste water than synthetic fresh water. The results of this research will be used by water quality managers from different water districts, researchers, international water management institute, EPA, and other local agencies that are involved in irrigation management in southwestern United States and other semi-arid regions of the world.

Technical Abstract: The use of treated wastewater (TWW) for irrigation has been suggested as an alternative to use of fresh water because of the increasing scarcity of fresh water in arid and semiarid regions of the world. However, significant barriers exist to widespread adoption due to some potential contaminants that may have adverse effects on soil quality. In this study, we investigated the abundance and diversity of bacterial communities and the presence of potential pathogenic bacterial sequences in TWW in comparison to synthetic fresh water (SFW) using pyrosequencing. The results were analyzed using UniFrac coupled with principal coordinate analysis (PCoA) to compare diversity and abundance of different bacterial groups in TWW irrigated soils to soils treated with SFW. Shannon diversity index values (H') suggest that microbial diversity was not significantly different (P < 0.086) between soils with TWW and SFW. Pyrosequencing detected sequences of 17 bacterial phyla with Proteobacteria (32.1%) followed by Firmicutes (26.5%) and Actinobacteria (14.3%). Most of the sequences associated with nitrifying bacteria, nitrogen-fixing bacteria, carbon degraders, denitrifying bacteria, potential pathogens, and fecal indicator bacteria were more abundant in TWW than in SFW. Therefore, TWW effluent may contain bacteria that may be very active in many soil functions as well as some potential pathogens.