The interactions between sediment microbial assemblages and submerged macrophytes in aquatic ecosystems can be potentially regulated by benthic macrofauna, and the regulation effect may be closely ...related to macrophyte species with distinct properties; however, little information on this is available. An aquarium experiment was designed to evaluate the role of snail
Bellamya aeruginosa
(Reeve) in regulating sediment bacterial communities associated with two common types of submerged macrophytes,
Ceratophyllum demersum
(L.) and
Hydrilla verticillata
(L. f.) Royle. The results showed that the effect of
B. aeruginosa
on sediment bacterial diversity and richness was plant species-specific; the presence of
B. aeruginosa
increased the bacterial diversity and richness in
C. demersum
systems while slightly decreased them in
H. verticillata
systems. Similar variations in the predicted microbial functions related to matter cycle in these systems were observed. Bacterial community composition patterns were also modified by
B. aeruginosa
; in its presence, the discrepancy between systems harbouring two different plants diminished, although the effect was limited. Application of the linear discriminant analysis effect size (LEfSe) method showed that the presence of
B. aeruginosa
resulted in appearance of significantly different bacterial taxa mainly in the
C. demersum
systems. Redundancy analysis showed that available phosphorus and NH
4
+
were significantly related to the observed variations in bacterial community compositions across the samples. Overall, a plant species-specific role of
B. aeruginosa
in modifying sediment bacterial communities and functions was found.
Summary
Biological approaches are considered promising and eco‐friendly strategies to remediate Hg contamination in soil. This study investigated the potential of two ‘green’ additives, ...Hg‐volatilizing bacteria (Pseudomonas sp. DC‐B1 and Bacillus sp. DC‐B2) and sawdust biochar, and their combination to reduce Hg(II) phytoavailability in soil and the effect of the additives on the soil bacterial community. The results showed that the Hg(II) contents in soils and lettuce shoots and roots were all reduced with these additives, achieving more declines of 12.3–27.4%, 24.8–57.8% and 2.0–48.6%, respectively, within 56 days of incubation compared to the control with no additive. The combination of DC‐B2 and 4% biochar performed best in reducing Hg(II) contents in lettuce shoots, achieving a decrease of 57.8% compared with the control. Pyrosequencing analysis showed that the overall bacterial community compositions in the soil samples were similar under different treatments, despite the fact that the relative abundance of dominant genera altered with the additives, suggesting a relatively weak impact of the additives on the soil microbial ecosystem. The low relative abundances of Pseudomonas and Bacillus, close to the background levels, at the end of the experiment indicated a small biological disturbance of the local microbial niche by the exogenous bacteria.
Hg‐volatilizing bacteria and biochar can reduce soil Hg bioavailability. Combination of bacteria DC‐B2 and 4% biochar performed best to lower Hg(II) bioavailability. Soil bacterial community structure was limitedly influenced by the additives.
•Bayesian nonparametric general regression was used for anammox optimization.•Working volume was identified as a neglected key process optimization variable.•Correlation among working volume-mixing ...intensity-nitrogen removal was established.•Input power-based anammox reactor design and operating conditions were derived.
Extensive studies on improving anammox performance have taken place for decades with particular focuses on its operational and environmental factors, but such parameter-based optimization is difficult, because of the sheer number of possible combinations and multidimensional arrays of these factors. Utilizing machine-learning algorithm and published anammox data, Bayesian nonparametric general regression (BNGR) was applied to identify the possible governing variable(s) from among 11 operating and environmental parameters: reactor type, mixing type, working volume, hydraulic retention time, temperature, influent pH, nitrite, ammonium, nitrate concentration, nitrogen loading rate, and organic concentration. The results showed that working volume is a key but oft-overlooked governing parameter. By integrating the BNGR findings with computational fluid dynamics simulation, which assessed mixing properties, it became feasible to conclude that working volume and mixing intensity co-regulated flow fields in reactors and had a significant influence on anammox performance. Furthermore, this study experimentally validated how mixing intensity affected performance, and specific input power (x), a parameter that conjugates both working volume and mixing intensity, was used to establish the relationship with ammonium removal rate (NH4+-N RR, y) y = 49.90x+1.97 (R2 = 0.94). With specific input power increased from 3.4 × 10−4 to 2.6 × 10−2 kW m−3, the ammonium removal rate exhibited a rise from 1.8 to 3.2 mg L−1h−1. Following, a relationship among input power-working volume-nitrogen removal rate was also established with a view to determining the design variables for anammox reactor. Consequently, the study highlighted the necessity to consider the working volume-mixing intensity correlation when optimizing the anammox process.
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A large quantity of surfactants (e.g., sodium dodecyl sulfate (SDS)) are discharged along with greywater especially during the COVID-19 pandemic, while information on the treatment of ...surfactant-containing greywater using eco-friendly constructed wetlands (CWs) and the impact of surfactants on CW systems has rarely been reported. In the present study, lab-scale CWs amended with a biochar substrate and operated in tidal flow (TF) mode were used to treat SDS-containing greywater. The results showed that the biochar-amended CWs removed NH4+-N significantly better (18.2–37.9%) than the gravel-only CWs (2.5–24.6%) but removed phosphorus (P) and COD less efficiently, and the feeding of SDS at 50 and 100 mg/L led to a notable decrease in N removal. TF not only notably improved the pollutant removal performance but also effectively eliminated SDS stress in the CWs (NH4+-N removal of 67.1–72.1%). Mean SDS removal efficiencies of 75.3–79.3% were obtained in the CWs. TF mode altered the microbial community structure and metabolic pattern and enhanced the abundance of functional bacteria related to N and P removal in the CWs. The bacterial community shifted considerably with SDS feeding, resulting in higher species diversity and more intensive co-occurrence network relationships. TF-CWs filled with composite substrates are highly feasible and promising for the treatment of SDS-containing greywater.
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•SDS-containing greywater was treated by constructed wetlands (CWs) with different setups.•SDS caused a dose-response reduction in nitrogen removal in flooded CWs.•Tidal flow (TF) mode notably enhanced CW treatment performance and eliminated SDS stress.•SDS feeding and TF enhanced microbial diversity and regulated community structure.•SDS feeding notably strengthened microbial interspecific interactions in the CWs.
Controlling nonpoint source pollution (NPSP) is very important for protecting the water environment, and surface-flow constructed wetlands (SFCWs) have been widely established to mitigate NPSP loads. ...In this study, the pollutant removal efficiencies, greenhouse gas (GHG) emissions, and chemical and microbial community properties of the sediment in a large-scale SFCW established beside a plateau lake (Qilu Lake) in southwestern China to treat agricultural runoff were evaluated over a year. The SFCW performed best in terms of nitrogen removal in autumn (average efficiency of 63.5% at influent concentrations of 9.3–35.4 mg L−1) and demonstrated comparable efficiency in other seasons (23.7–40.0%). The removal rates of total phosphorus (TP) and chemical oxygen demand (COD) were limited (18.6% and 12.4% at influent concentrations of 1.1 and 45.5 mg L−1 on average, respectively). The SFCW was a hotspot of CH4 emissions, with an average flux of 31.6 mg m−2·h−1; moreover, CH4 emissions contributed the most to the global warming potential (GWP) of the SFCW. Higher CH4 and N2O fluxes were detected in winter and in the front-end section of the SFCW with high pollutant concentrations, and plant presence increased CH4 emissions. Significant positive relationships between nutrient and heavy metal contents in the SFCW sediment were detected. The microbial community compositions were similar in autumn and winter, with Thiobacillus, Lysobacter, Acinetobacter and Pseudomonas dominating, and this distribution pattern was clearly distinct from those in spring and summer, with high proportions of Spirochaeta_2 and Denitratisoma. The microbial co-occurrence network in spring was more complex with stronger positive correlations than those in winter and autumn, while it was more stable in autumn with more keystone taxa. Optimization of the construction, operation and management of SFCWs treating NPSP in lake watersheds is necessary to promote their environmental benefits.
•Comprehensive environmental functions of a large-scale constructed wetland (CW) treating agricultural runoff were evaluated.•Moderate nitrogen removal was obtained, with the best efficiency in autumn, while COD and P removals were limited in the CW.•The CW was a hotspot of CH4 emissions and plant presence increased the CH4 emission flux.•A complex microbial co-occurrence network with strong cooperation was formed in spring, while the network was stable in autumn.•Suggestions for optimization of such CW systems were proposed.
Gravel-based subsurface-flow constructed wetlands (CWs) amended with a walnut shell (WS) substrate were established to treat synthetic acid mine drainage (AMD) in this study, and artificial domestic ...wastewater (DW) and plant litter broth (PLB) were supplemented to enhance the performance. The CW media rapidly reached adsorption saturation with respect to metals (except Fe and Cr) without an external carbon source, while the addition of DW and PLB stimulated sulfate reduction activity and achieved efficient biogenic metal removal, primarily by the formation of hydroxide and sulfide precipitates and concomitant co-precipitation. The WS-amended CWs performed notably better than the control systems, not only in sequestering more metals and rapidly establishing favourable environments for biogenic metal abatement but also in supporting better growth of plants and functional microbes. The external organic carbon input greatly shaped the bacterial community compositions in the CWs, with substantial increases in the proportions of core functional populations involved in AMD biotreatment. Cooperation among Cellulomonas, Propioniciclava and sulfate-reducing bacteria (SRB), dominated by Desulfobulbus and Desulfatirhabdium, was the primary biogenic mechanism of AMD remediation in the CWs. Cellulosic waste-amended CWs with DW and PLB addition offer a promising eco-technology for AMD remediation.
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•Constructed wetlands amended with walnut shells performed better than those with gravel in AMD remediation.•Domestic wastewater and plant litter broth efficiently enhanced the treatment effectiveness.•Precipitation as hydroxides/oxides and sulfides was the dominant mechanism of metal removal.•External carbon increases the functional population abundances greatly.•Synergy among Cellulomonas, Propioniciclava and SRB was responsible for AMD bioremediation.
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•Tidal operated biofilters were investigated to treat heavily polluted river water.•Inorganic materials are efficient in NH4+-N and P removal.•Fibrous carrier is preferable for NO3−-N ...and TN removal.•Higher abundance of denitrifiers developed in organic substrate-based systems.
In this study, biofilters (BFs) packed with inorganic (ceramsite and lava rock) and organic (fibrous carrier and biological ball) materials were applied in a tide-flow mode at three flooded/drained (F/D) time ratios (16/8 h, 12/12 h and 8/16 h) to treat heavily polluted river water. The results showed that higher ammonium and phosphorus removals were achieved with BFs filled with ceramsite (95–97% and 76–77%) and lava rock (87–92% and 84–94%), while fibrous carrier-packed BFs obtained better total nitrogen removal (37–44%). Moreover, the F/D time ratio of 16/8 h was slightly preferable for pollutant removal. High-throughput sequencing analysis illustrated that the relative abundance of potential denitrifiers that developed on organic media was much higher than those on inorganic substrates. The results indicated that the combination of inorganic materials and fibrous carriers as substrates could be an effective strategy for enhancing overall pollutant removal in BFs.
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•Biochar was superior to ceramsite for nutrient removal and microbial diversity.•Tidal flow enhanced nutrient removal over intermittent aeration.•Biochar media and intermittent ...aeration could reduce greenhouse gas emissions.•Operation mode shaped bacterial communities in CWs more than media type.•Microbial functions of different CW groups were predicted using Tax4Fun2.
Biochar-based subsurface-flow constructed wetlands (CWs) with intermittent aeration (IA) or tidal flow (TF) oxygen supply strategies were established to treat domestic wastewater. The results showed that biochar achieved higher nutrient removal and lower greenhouse gas (GHG) emissions than ceramsite while supporting more diverse bacterial communities and higher abundances of functional taxa. Both IA and TF effectively enhanced nutrient removal, though the latter was more efficient and practical, and aeration conditions greatly influenced nutrient removal efficiency. GHG emissions were decreased by IA but were slightly increased by TF. Both oxygen supply methods significantly shaped the biofilm microbial communities and influenced biodiversity and richness, with observably higher proportions of potential nitrifiers and denitrifiers present in aerated CWs. Overall, biochar-based CWs operated with oxygen supply strategies provide superior treatment of decentralized wastewater.
Biochar substrates and tidal flow (TF) and intermittent aeration (IA) operation modes have recently been applied to improve the treatment performance of constructed wetlands (CWs), but their roles in ...regulating greenhouse gas (GHG) emissions from CWs are still unclear. In this preliminary study, CO2, CH4 and N2O fluxes and associated microbial characteristics in four groups of subsurface-flow CWs, i.e., ceramsite CWs (C-CWs), biochar-amended CWs (B-CWs), intermittently aerated B-CWs (AB-CWs) and tide-flow B-CWs (TB-CWs), were comparatively investigated. The results showed that biochar amendment significantly mitigated CH4 and N2O fluxes from the CWs by supporting higher abundances of mcrA and nosZ genes and higher ratios of pmoA/mcrA and nosZ/(nirK + nirS), thus reducing global warming potential (GWP, a decrease of 55.8%), in addition to promoting total nitrogen (TN) removal by 41.3%, mainly by increasing the abundances and activities of nitrifiers and denitrifiers. The TF mode efficiently improved nitrogen removal, but it greatly increased GHG fluxes since large amounts of GHGs escaped from the empty CW matrix after water draining. IA abated GHG emissions from the CWs, mainly after aeration. TF and IA decreased the abundances of functional bacteria and archaea related to C and N transformation, except nitrifiers, and shaped the microbial community structures. The application of a biochar substrate and IA mode can facilitate the design and operation of CWs in a more ecologically sustainable way.
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•Biochar substrates and tidal flow and intermittent aeration effectively enhanced N removal in CWs.•Biochar mitigates GHG emissions by supporting higher ratios of pmoA/mcrA and nosZ/(nirK + nirS) in CWs.•Intermittent aeration reduced GHG emissions from CWs, mainly after aeration.•GHG emissions from tidal flow CWs largely increased after water draining.•Bacterial and archaeal communities in the CWs were comparatively characterized.
The deep purification of secondary effluent from wastewater treatment plants (WWTPs) is essential for protecting the receiving water environment. Recently, iron-carbon materials have attracted more ...and more attention for treating secondary effluent. In this study, lab-scale iron-carbon microelectrolysis constructed wetlands (Fe–C CWs) filled with iron scraps (ISs) and granular biochar were established to purify secondary effluent with C/N ratios of 0.5–5. Walnut shells or pyrite were amended as organic or inorganic electron donors to enhance nutrient removal and reduce iron consumption. The IS substrate substantially promoted nutrient removal when the C/N ratio ≤2 (20.3–36.5% for nitrogen and 10.4–21.8% for phosphorus) by supplying Fe2+/H2 for autotrophic denitrification and iron compounds for phosphorus sequestration. Walnut shell supplementation further strengthened nutrient removal, achieving excellent effluent water quality. Fe substrate consumption was alleviated by electron donor supplementation. The IS substrate decreased CO2 emissions while increasing CH4 and N2O fluxes of the biochar-based CWs, and pyrite addition mitigated the global warming potential (GWP) of the Fe–C CWs. When the C/N ratio changed from 5.0 to 0.5, the abundance of autotrophic denitrifiers and Fe cycle-related populations dominated by Dechloromonas, Ferritrophicum and Thiobacillus increased notably in ISs-amended CWs, and they were responsible for the efficient nitrogen removal. Fe–C CW supplemented with organic solid wastes presents high potential for advanced purification of low C/N nitrified effluent.
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•Autotrophic denitrification dominated in CWs filled with iron scraps (ISs) and biochar at COD/TN ≤ 2.•Walnut shell addition effectively enhanced nutrient removal in Fe–C CWs.•Fe substrate loss was mitigated by electron donor addition.•Pyrite addition reduced greenhouse gas emissions from Fe–C CWs.•IS amendment largely increased the abundance of autotrophic denitrifiers in CWs.
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