Abstract
The effluents of wastewater treatment plants (WWTPs) represent a complex mixture of nutrients and toxic substances, thus, the potential exists for the effluents to significantly impact the biochemical characteristics and bacterial communities of the receiving water. We examined spatial and seasonal patterns, and the impact of effluents on microbial biomass, bacterial community structure, and metabolic diversity on a fourth-order stream. We took triplicate sediment samples at five different locations along a 5000m transect over three sampling periods. We quantified bacterial community structure as community-level physiological profiles and microbial biomass with phospholipid phosphate analysis. Our findings highlight the worrisome impacts of effluents on microbial biomass and bacterial metabolic diversity on the receiving water. Microbial biomass was significantly higher at the WWTP outfall compared to upstream and downstream sites and correlated positively with sediment physicochemical parameters. Furthermore, our data revealed significant spatial differences in bacterial community structure in the context of WWTP impact. High nutrient availability (lower carbon/nitrogen ratios) at the outfall increased site-specific bacterial metabolic diversity in winter but decreased the same in fall. Seasonal changes in the sedimentary microbial biomass and bacterial carbon substrate utilization were evident regardless of the spatial variations or impacts of the wastewater effluents. Communities in fall showed more versatile substrate utilization patterns than the winter communities. These results suggest that WWTP effluents significantly increased microbial biomass and highlight its mixed effects on bacterial community structure and metabolic diversity. Also, our data underscore a close association between sedimentary physicochemical parameters and the associated microbial functional activities.
Highlights
Anthropogenic disturbances such as wastewater treatment plant effluents, irrigation with treated wastewater, heavy metals pollution, agricultural uses of antibiotics, pesticides, and fertilizers have considerable impacts on the biotic properties of natural aquatic ecosystems, especially microbial activity and processes (Englert et al 2013; Kunhikrishnan et al 2017), biomass (Wang et al 2007a), and community structure (Dang et al 2019; Guo et al 2019)
Communities in fall showed more versatile substrate utilization patterns than the winter communities. These results suggest that Wastewater treatment plant (WWTP) effluents significantly increased microbial biomass and highlight its mixed effects on bacterial community structure and metabolic diversity
The sedimentary microbial biomass and bacterial community structure of Big Walnut Creek (BWC) exhibited spatial variations associated with positioning from the WWTP outfall and a temporal pattern associated with seasonal differences
Summary
Anthropogenic disturbances such as wastewater treatment plant effluents, irrigation with treated wastewater, heavy metals pollution, agricultural uses of antibiotics, pesticides, and fertilizers have considerable impacts on the biotic properties of natural aquatic ecosystems, especially microbial activity and processes (Englert et al 2013; Kunhikrishnan et al 2017), biomass (Wang et al 2007a), and community structure (Dang et al 2019; Guo et al 2019). Progress in WWTP processes removes the majority of solid organic matter as well as nitrogen and phosphorus, biochemical parameters of effluents are in stark differences to that of the water in the receiving lotic system. Wakelin et al (2008) reported the effect of the WWTP effluents on microbiological characteristics for more than 1 km downstream
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