Increasing reclaimed wastewater is viewed as water resource for beneficial reuse. This beneficial reuse is particularly vital for sustainable biomass production for the biofuel and green chemical industries. Biomass production is increased with irrigation, but this is not realistic in water-limited areas. Irrigation with reclaimed wastewater offers a potential solution and has the added benefit of removing residual pollutants from the reclaimed water. To assess sustainability of water reuse for irrigation, the impact of residual wastewater contaminants on the soil microbial community must be understood. We compared soil microbial communities at long-term biomass-production groves irrigated with reclaimed wastewater to unirrigated control plots. Community composition was examined via 16S rRNA Illumina sequencing. Batch testing was conducted to compare microbial degradation of select residual contaminants associated with reclaimed wastewater. Bacterial and archaeal biomass were quantified via droplet digital PCR. Principal component analysis showed differences between irrigated and non-irrigated communities at two sites, and several OTUs of the Acidobacteria and Proteobacteria were correlated with soil organic carbon and organic contaminant degradation. The underlying cause for the observed differences could not be resolved between exposure to reclaimed wastewater or increased watering, as control plots were unirrigated. To address this, we constructed controlled testing systems that allowed for manipulation of both water and nutrient loading rates. Ongoing work will further elucidate the impact of irrigation on soil microbial communities, thus increasing the prevalence of wastewater reuse for biomass production and contributing to the growth of the circular economy.
