Effect of Wastewater Treatment Plant Effluent on Microbial Function and Community Structure in the Sediment of a Freshwater Stream with Variable Seasonal Flow

Abstract

We investigated the effects of wastewater treatment plant (WWTP) discharge on the ecology of bacterial communities in the sediment of a small, low-gradient stream in South Australia. The quantification of genes involved in the biogeochemical cycling of carbon and nitrogen was used to assess potential impacts on ecosystem functions. The effects of disturbance on bacterial community structure were assessed by PCRdenaturing gradient gel electrophoresis of 16S rRNA genes, and clone library analysis was used to phylogenetically characterize significant shifts. Significant (P < 0.05) shifts in bacterial community structures were associated with alteration of the sediment's physicochemical properties, particularly nutrient loading from the WWTP discharge. The effects were greatest at the sampling location 400 m downstream of the outfall where the stream flow is reduced. This highly affected stretch of sediment contained representatives of the gammaproteobacteria that were absent from less-disturbed sites, including Oceanospirillales and Methylococcaceae. 16S rRNA gene sequences from less-disturbed sites had representatives of the Caulobacteraceae, Sphingomonadaceae, and Nitrospirae which were not represented in samples from disturbed sediment. The diversity was lowest at the reference site; it increased with proximity to the WWTP outfall and declined toward highly disturbed (400 m downstream) sites (P < 0.05). The potential for biological transformations of N varied significantly with the stream sediment location (P < 0.05). The abundance of amoA, narG, and nifH genes increased with the distance downstream of the outfall. These processes are driven by N and C availability, as well as redox conditions. Together these data suggest cause and effect between nutrient loading into the creek, shift in bacterial communities through habitat change, and alteration of capacity for biogeochemical cycling of N.

Wastewater Treatment Effluent Reduces the Abundance and Diversity of Benthic Bacterial Communities in Urban and Suburban Rivers

“…Toxic compounds could also explain the observed increases in per-cell respiration rates, as previous studies indicated that respiration rates normalized by biomass increase for bacterial cells that are under stress (47). Toxic compounds in the effluent could also contribute to the decreases in bacterial diversity and species richness at the downstream sites, which conflicted with previously reported findings that demonstrated an increase in bacterial diversity downstream of a WWTP effluent input (9). Although quantification of toxic compounds in the effluents was beyond the scope of this study, future explorations of this topic are warranted.…”

“…Several previous studies have also examined the effects of WWTP effluent on bacterial populations within the water column (6)(7)(8), and some have demonstrated the ability of microorganisms contained in the effluent to persist in the water column of the receiving system (8). However, few studies have examined the potential effects of WWTP effluent on benthic microbial communities (9) despite the fact that bacterial numbers are generally much higher in freshwater sediment than in the overlying water (10) and despite the fact that benthic microbial communities are critical components of lotic ecosystems, as they contribute to organic matter decomposition, nutrient cycling, and bioremediation of a variety of pollutants. Several recent studies have presented evidence that WWTP effluent may impact the function and structure of sediment microbial communities.…”

“…For example, Lofton et al (11) previously reported a significant increase in denitrification rates in sediment samples collected downstream of a WWTP in Greensboro, NC. In addition, Wakelin et al (9) previously used denaturing gradient gel electrophoresis (DGGE) to demonstrate that effluent from a small WWTP altered the composition of sediment bacterial communities in a small rural stream in Australia. However, we are not aware of any study that has examined the effects of WWTP effluent on sediment microbial community function and structure in a highly urbanized habitat within a major city.…”

Effect of reclaimed water effluent on bacterial community structure in the Typha angustifolia L. rhizosphere soil of urbanized riverside wetland, China

“…Therefore, wetland plant rhizosphere microbial characteristics can sensitively reflect the status of plant and water quality, which are considered ideal indicators of aquatic ecosystems and have been extensively used to assess the degree of toxicity imposed by various pollutants. To the best of our knowledge, most studies have focused on the impacts of wastewater treatment plants (WWTPs) effluent on bacterial communities in the water column and sediment of receiving river (Wakelin et al, 2008;Drury et al, 2013). But few studies have investigated wetland plant rhizosphere bacteria community under reclaimed water disturbance condition.…”

Electricity Generation Coupled with Wastewater Treatment Using a Microbial Fuel Cell Composed of a Modified Cathode with a Ceramic Membrane and Cellulose Acetate Film

“…In wastewater treatment systems, aeration has typically been used to activate the biochemical oxidation of organic compounds, sulfide, ammonia, and nitrite [7,31,35,37], but it is a highly costly process. Wastewater treatment using an MFC may be a less energy-dependent but less efficient process than an aeration-dependent system.…”