Triclosan disturbs nitrogen removal in constructed wetlands: Responses of microbial structure and functions.

This study investigated the influence of wetland types (vertical and tidal flow constructed wetlands [CWs] [VFCW and TFCW, respectively]) and concentrations of triclosan (TCS) on the removal of pollutants (TCS and nitrogen) and microbial characteristics. The efficiency of TCS removal was significantly higher with 5 µg/L TCS (Phase B) than with 30 µg/L (Phase C) in the two CWs. The efficiencies of removal of NH4+-N and NO3--N were significantly inhibited in Phase C. Compared with the VFCW, the TFCW removed more NH4+-N at the same concentration of TCS, whereas less NO3--N was removed, and it even accumulated. Saccharimondales, an important functional genus with the highest abundance and more node connections with other genera, had a sharp decrease in relative abundance as the increasing concentrations of TCS of the two CWs conformed with its relative abundance and significantly negatively correlated with the concentration of TCS. Differentiated Roseobacter_Clade_CHAB-I-5_Lineage and Sphaerotilus were enriched in the VFCW and TFCW, respectively. The abundance of enzymes that catalyzed nitritation was significantly inhibited by TCS, whereas nitrate reductase (EC 1.7.99.4) catalyzed both denitrification and dissimilatory nitrate reduction to ammonium (DNRA), and nitrite reductase (NADH) (EC 1.7.1.15) that catalyzed DNRA comprised a larger proportion in the two CWs. Simultaneously, the abundances of two enzymes were higher in the TFCW than in the VFCW. The network analysis indicated that the main genera were promoted more by TCS in the VFCW, while inhibited in the TFCW. Moreover, the concentrations of nitrogen (NH4+-N, NO3--N, and TN) significantly positively correlated with TCS-resistant bacteria, and negatively correlated with most nitrogen-transforming bacteria with species that varied between the VFCW and TFCW. The results of this study provide a reference for the molecular biological mechanism of the simultaneous removal of nitrogen and TCS in the CWs.

Overlying water fluoride concentrations influence dissolved organic matter composition and migration from pore water in sediment via bacterial mechanisms.

Fluoride (F-) is widespread in aquatic environments; however, it is not clear whether the fluctuation of F- concentrations in overlying lake water affects the composition and migration of dissolved organic matter (DOM) from sediment. A case study was presented in Sand Lake, China, and an experiment was conducted to analyze the influence of different F- concentrations in overlying water on DOM characteristics. Diffusion resulted in similarities in DOM components between overlying and pore waters, and bacterial activities and enzyme variation resulted in differences between them. Higher F- concentrations in overlying water resulted in a higher pH of pore water, which favored the enrichment of protein-like substances. Higher F- concentrations caused lower DOM concentrations and lower maximum fluorescence intensities (Fmax) of protein-like components in pore water. The F- concentrations had significantly negative correlations with Shannon indexes (P < 0.05). Thiobacillus influenced the migration of tyrosine-like substances by decreasing the pH of pore water. Trichococcus and Fusibacter altered the Fmax of protein-like, humic-like, and fulvic-like substances. The F- concentrations affected the DOM composition and migration due to the response of functional bacterial communities, which were positively correlated with the relative abundance of Thiobacillus and negatively correlated with the relative abundances of Trichococcus and Fusibacter. The high F- concentrations influenced the biosynthesis and degradation of protein-like substances by shifting the abundances of the relevant enzymes. The results of this study may provide ideas for investigating DOM cycling under the influence of F-, especially in lakes with fluctuations in F- concentrations.

Sustainable phosphorus recovery from wastewater and fertilizer production in microbial electrolysis cells using the biochar-based cathode.

Reducing the energy consumption and electrode cost for electrochemical recovery of phosphorus (P) from wastewater is crucial for the large-scale application. In this study, biochar electrodes were investigated as the low-cost cathode in a microbial electrolysis cell (MEC) and this P-enriched biochar electrode was directly retrieved as P fertilizer after wastewater treatment. The Fe2+ salt modified biochar significantly increased the electrochemical performance of MECs due to the improved electrical conductivity and cathodic activity. Compared to the pristine biochar cathode, the current density of the MEC increased from 16.8 ± 0.2 A/m3 to 20.7 ± 0.8 A/m3, and the P removal increased from 28.8% ± 1% to 62.4% ± 3.5%. The power consumption was 0.25 ± 0.01 kWh/kg P which was more than one order of magnitude lower than the previous report. It was also demonstrated that the P enriched biochar amended soil improved the Pakchoi cultivation.

Functional genera for efficient nitrogen removal under low C/N ratio influent at low temperatures in a two-stage tidal flow constructed wetland.

A two-stage tidal flow constructed wetland (referred to as TFCW-A and TFCW-B) was used to treat low chemical oxygen demand/total nitrogen (COD/TN or simply C/N) ratio influent at low temperatures (<15 °C). The influence of the flooding-resting time (A: 8 h-4 h, B: 4 h-8 h) and effluent recirculation on nitrogen removal and microbial community characteristics were explored. TFCW-B achieved optimal average nitrogen removal efficiency with effluent recirculation (96.05% ammonium nitrogen (NH4+-N); 78.43% TN) and led to nitrate nitrogen (NO3--N) accumulation due to the lack of a carbon source and longer resting time. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were inhibited at low temperatures. Except for nrfA, AOA, AOB, narG and nirS were separated by the flooding-resting time rather than by spatial position. Furthermore, the dominant genera in TFCW-A were Arthrobacter, Rhodobacter, Pseudomonas, and Solitalea, whereas prolonging resting time promoted the growth of Thauera and Zoogloea in TFCW-B. Spearman correlation analysis showed that Zoogloea and Rhodobacter had the strongest correlations with other genera. Moreover, the NH4+-N concentration was significantly positively influenced by Arthrobacter, Rhodobacter, Pseudomonas, and Solitalea but negatively influenced by Thauera and Zoogloea. There was no significant correlation between TN and the dominant genera. This study not only provides a practicable system for wastewater treatment with a low C/N ratio but also presents a theoretical basis for the regulation of microbial communities in nitrogen removal systems at low temperatures.

Long-term trends in water quality and influence of water recharge and climate on the water quality of brackish-water lakes: A case study of Shahu Lake.

This study aimed to assess the long-term fluctuations in water quality and the influence of Yellow River water recharge and climatic condition on the water environmental index of a typical brackish-water lake. This study investigated several surface water quality parameters and their relationships with the water quality index (WQI) and trophic status index (TSI) of Shahu Lake from 2011 to 2018. A health risk assessment was conducted, and the correlations among water recharge, climatic conditions, and the aforementioned elements were determined. Results show that the water quality in this lake went from good to moderate and back to good as reflected in the changes in its WQI values from 2011 to 2018. The relative water quality inferiority of this lake in 2015 and 2016 was attributed to the significant increase in its CODMn, TP, TN, NH3-N, and fluoride (F-) concentrations during these years. A combination of these parameters could rapidly predict water quality through a stepwise multiple linear regression. During the study period (except in the frozen season), Shahu Lake maintained a eutrophic status every month (especially in July) irrespective of the spatial changes resulting from low secchi depth and high TP. The limiting nutrient of Shahu Lake changed from phosphorus to both nitrogen and phosphorus, especially during summer, due to seasonal variations and exogenous inputs. The lake had an acceptable health risk level, and water recharge both had positive and negative effects on this lake as reflected in the significant decrease or increase in the concentrations of its principal parameters. This condition was also attributed to temperature and precipitation, which resulted in significant TSI variations. The findings of this study provide ways of estimating and forecasting water quality and trophic status and a basis for managing and improving similar brackish-water lakes.

Response Characteristics of Nitrifying Bacteria and Archaea Community Involved in Nitrogen Removal and Bioelectricity Generation in Integrated Tidal Flow Constructed Wetland-Microbial Fuel Cell.

This study explores nitrogen removal performance, bioelectricity generation, and the response of microbial community in two novel tidal flow constructed wetland-microbial fuel cells (TFCW-MFCs) when treating synthetic wastewater under two different chemical oxygen demand/total nitrogen (COD/TN, or simplified as C/N) ratios (10:1 and 5:1). The results showed that they achieved high and stable COD, NH4 +-N, and TN removal efficiencies. Besides, TN removal rate of TFCW-MFC was increased by 5-10% compared with that of traditional CW-MFC. Molecular biological analysis revealed that during the stabilization period, a low C/N ratio remarkably promoted diversities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in the cathode layer, whereas a high one enhanced the richness of nitrite-oxidizing bacteria (NOB) in each medium; the dominant genera in AOA, AOB, and NOB were Candidatus Nitrosotenuis, Nitrosomonas, and Nitrobacter. Moreover, a high C/N ratio facilitated the growth of Nitrosomonas, while it inhibited the growth of Candidatus Nitrosotenuis. The distribution of microbial community structures in NOB was separated by space rather than time or C/N ratio, except for Nitrobacter. This is caused by the differences of pH, dissolved oxygen (DO), and nitrogen concentration. The response of microbial community characteristics to nitrogen transformations and bioelectricity generation demonstrated that TN concentration is significantly negatively correlated with AOA-shannon, AOA-chao, 16S rRNA V4-V5-shannon, and 16S rRNA V4-V5-chao, particularly due to the crucial functions of Nitrosopumilus, Planctomyces, and Aquicella. Additionally, voltage output was primarily influenced by microorganisms in the genera of Nitrosopumilus, Nitrosospira, Altererythrobacter, Gemmata, and Aquicella. This study not only presents an applicable tool to treat high nitrogen-containing wastewater, but also provides a theoretical basis for the use of TFCW-MFC and the regulation of microbial community in nitrogen removal and electricity production.

Robust nitrate removal and bioenergy generation with elucidating functional microorganisms under carbon constraint in a novel multianode tidal constructed wetland coupled with microbial fuel cell.

This study investigated synthetic wastewater treatment under low inflow C/N ratio and characterized NO3--N-transforming and electricity-producing bacteria in a multi-anode tidal constructed wetland-microbial fuel cell (TFCW-MFC). The optimal concurrent average removal rates of NH4+-N and NO3--N were 73% and 78%, respectively, under a flood/rest/flood time of 4 h/2h/4h in "tide" mode accompanied by one recirculation. The lowest NO3--N concentration among all anodes was observed when the electrode gap was 45 cm. Similarly, the 45 cm anode exhibited selective enrichment of Variovorax and Azoarcus. Correction analysis showed that the high relative abundance of Azoarcus was crucial in enhancing NO3--N removal, and the internal resistance significantly decreased as the relative abundance of Acidovorax increased. These results suggest that NO3--N removal and bioelectricity generation can be promoted in a TFCW-MFC with limited carbon by improving the culture conditions for specific genera.

Field observation and simulation experiments on nutrient transformation during phytoplankton-derived particulate matter deposition.

Phytoplankton-derived particulate matter (PPM) is the active component of the solid particles in eutrophic shallow lakes. To date, understanding of the degradation characteristics of PPM and the effect of degradation products on nutrient cycling in water are limited. In this study, field observations and simulation experiments were carried out to elaborate the nutrient transformation during phytoplankton-derived particulate matter deposition in the cyanobacterial blooming area of Lake Taihu. Results showed that the deposition of the PPM was strongly facilitated by the cyanobacterial bloom and the sediment resuspension. The main variation characteristics of phosphorus (P) species in PPM are shown in the increase of Ortho-P and the decrease of biodegradable phosphorus (Poly-P, DNA-P) during the deposition of PPM. The degradation of the PPM resulted in the release of dissolved nitrogen (N) and P to the water body. The conversion of easily degradable particulate N and P in the PPM to ammonium nitrogen (NH3-N) and soluble reactive phosphorus were believed to be responsible for this phenomenon. The cycling of nutrients and the cyanobacterial bloom status might therefore be altered because of the deposition and degradation of PPM. More considerations should be given on this process in future works.

Spatiotemporal distribution and interaction of denitrifying functional genes in a novel DAS-NUA biofilter used for groundwater nitrate treatment.

A newly combined dewatered alum sludge (DAS) and neutralized used acid (NUA) biofilter has been constructed and investigated recently, aiming for improving nitrate (NO3--N) removal in simulated groundwater and exploring the spatiotemporal distribution of nirS and nosZ. The biofilter achieved 81.54% and 13.6 g N/ (m3 d) removal efficiency of NO3--N during the stabilization period. Spatiotemporal distributions of diversity and composition of nirS and nosZ varied approximately in two media with depths and time. Both DAS and NUA played important roles in attenuating nitrate because of predominant denitrifying genera functions, and the core differences were Rhodanobacter and Rhodobacter in DAS while Halomonas, Pseudogulbenkiania, and Cupriavidus in NUA. Acting as the strongly correlated genera, Magnetospirillum and Halomonas had a significantly positive or negative correlation with other dominant genera. Positive correlations existed among COD, TN, NO3--N, NO2--N, and both nirS and nosZ in the DAS filter, whereas the correlations were negative in the NUA filter. Particularly, the effluent concentration of NO3--N had a significantly negative correlation with the relative abundance of Rubrivivax and Pseudomonas. These results could be useful in adjusting the denitrification of nitrogen contaminants at the genetic level, especially in mitigating the influence of discharge of NO3--N on the process of groundwater restoration.

Spatial and Temporal Distribution of Particulate Phosphorus and Their Correlation with Environmental Factors in a Shallow Eutrophic Chinese Lake (Lake Taihu).

Spatial and seasonal variations of particulate phosphorus (PP) in a large shallow, eutrophic Lake Taihu with different ecotypes (including a phytoplankton-dominated zone, lake center zone, estuary zone and macrophyte-dominated zone) were investigated. The results showed that particulate organic phosphorus (POP) was the dominant form of PP (>88.0%). The concentration of POP showed higher levels in the bloom-sensitive northwestern zone (phytoplankton-dominated zone and estuary zone) during warm seasons, phytoplankton blooms and input of exogenous particulate matter were the main sources of POP in the lake water. Based on 31P nuclear magnetic resonance (31P NMR) analysis, orthophosphate (Ortho-P) was the dominant molecular species of PP and positively correlated with soluble reactive phosphorus (SRP) (p < 0.01). This suggested that the release of Ortho-P from suspended particulate matter (SPM) was the main source of SRP in the lake water. Pyrophosphate (Pyro-P), which is regarded as a highly labile species of P compounds, represented a large fraction of PP, and its significant positive correlations with chlorophyll a (Chl a), indicated that the concentration of Pyro-P could be used as an important indicator for the degree of eutrophication of Lake Taihu. These results proved that PP in lake water was a significant factor supporting lake eutrophication and must be controlled.

Nitrate removal, spatiotemporal communities of denitrifiers and the importance of their genetic potential for denitrification in novel denitrifying bioreactors.

Nitrate treatment performance and denitrification activity were compared between denitrifying biological filters (DNBFs) based on dewatered alum sludge (DAS) and neutralized used acid (NUA). The spatiotemporal distribution of denitrifying genes and the genetic potential associated with denitrification activity and nitrate removal in both DNBFs were also evaluated. The removal efficiency of NUA-DNBF increased by 8% compared with that of DAS-DNBF, and the former NUA-DNBF emitted higher amount of N2O. Analysis of abundance and composition profiles showed that denitrifying gene patterns varied more or less in two matrices with different depths at three sampling times. Burkholderiales, Rhodocyclales, and Rhizobiales were the most commonly detected in both media during stable periods. Denitrification was determined by the abundance of specific genes or their ratios as revealed by controlling factors. The enhanced nitrate removal could be due to increasing qnosZ or decreasing ∑qnir/qnosZ. Furthermore, NUA-DNBF solely reduced nitrate by increasing the denitrification enzyme activity.

Long-term moderate wind induced sediment resuspension meeting phosphorus demand of phytoplankton in the large shallow eutrophic Lake Taihu.

The objective of this study was to investigate the impact of sediment resuspension and phosphorus (P) release on phytoplankton growth under different kinds of wind-wave disturbance conditions in the large and shallow eutrophic Lake Taihu in China. Short-term strong wind (STSW) conditions, long-term moderate wind (LTMW) conditions, and static/calm conditions were investigated. To address this objective, we (1) monitored changes in surface water P composition during field-based sediment resuspension caused by STSW conditions in Lake Taihu, and also conducted (2) a series of laboratory-based sediment resuspension experiments to simulate LTMW and calm conditions. The results showed that under both strong and moderate wind-wave conditions, suspended solids (SS) and total phosphorus (TP) in the water column increased significantly, but total dissolved phosphorus (TDP) and soluble reactive phosphorus (SRP) remained low throughout the experiments, indicating that the P released from sediments mainly existed in particulate forms. In STSW conditions, alkaline phosphatase activity (APA) and enzymatically hydrolysable phosphorus (EHP) increased rapidly, with the peak value occurring following the peak value of wind speed for 1-2 days, and then rapidly decreased after the wind stopped. Under LTMW conditions, APA and EHP increased steadily, and by the end of the laboratory experiments, APA increased by 11 times and EHP increased by 5 times. Chlorophyll a (Chl-a) in LTMW conditions increased significantly, but remained low under STSW conditions, demonstrating that the former type of sediment P release promoted phytoplankton growth more effectively, and the latter type did not. Despite the fact that STSW conditions resulted in the release of more TP, TP settled to the bottom rapidly with SS after the wind stopped, and did not promote algal growth. Under LTMW conditions, suspended particulate P was hydrolyzed to SRP by phosphatase and promoted algae growth. Algal growth in turn secreted more phosphatase and accelerated particulate P regeneration, which may be the main mechanism of sediment bio-available P release that promotes phytoplankton growth in shallow lakes.

Effects of earthworms and substrate on diversity and abundance of denitrifying genes (nirS and nirK) and denitrifying rate during rural domestic wastewater treatment.

This study investigated the performance of an ecological filter (EF) and vermifiltration (VF) system, the effects of substrate and earthworms on the diversity and abundance of denitrifying genes coding for nitrite (nirS and nirK) reductases and on denitrifying rate, and the factors influencing denitrification. The majority of organic matter, ammonia nitrogen and total nitrogen from sewage was removed by the soil layer in both reactors, and their total removal efficiencies increased in VF compared with those in EF. Additionally, substrate in the reactors significantly influenced the Shannon diversity index and abundance of nirS and nirK, as well as the denitrifying rate. However, the earthworms only significantly influenced nirS diversity. Furthermore, evaluation of the factors controlling denitrification implied that increasing NH3-N availability, diversity and abundance of nirS and nirK or decreasing available NO3-N might be responsible for the enhanced denitrification activity obtained using VF for rural domestic wastewater treatment.

Accumulation and risk assessment of heavy metals in sediments and zoobenthos (Bellamya aeruginosa and Corbicula fluminea) from Lake Taihu.

Accumulation and risk assessment of metals in sediments and zoobenthos (Bellamya aeruginosa and Corbicula fluminea) from Lake Taihu were studied. Results showed that metal (Cr, Cd, Cu, Zn, Pb and Ni) concentrations in Lake Taihu varied greatly, and Cd in the Zhushan Bay showed higher bioavailability compared to the other metals studied. The spatial distribution of metals in B. aeruginosa and C. fluminea was similar to that in sediments. Zn and Cu exhibited the higher mean concentration in B. aeruginosa and C. fluminea, which was in good accordance with its higher content in surrounding sediment. Labile fractions (i.e., acid-soluble (F1), reducible (F2) and F1+F2) of Cu and Zn in sediments showed a significant positive correlation with them in B. aeruginosa (P<0.01); no correlation relationship was found for metals (Cd, Cr, Cu, Zn, Pb and Ni) between in the tissue of C. fluminea and in sediments. The results of ecological risk assessment showed that Zhushan Bay was seriously contaminated by metal Cd, as it made the main contribution of all the metals. Total target hazard quotients indicated that adults and children both had potential health risk through consuming C. fluminea. Hazard index values suggested that adults and children might experience adverse health effects through consuming B. aeruginosa and C. fluminea.

[Nitrogen Removal and the Characteristics of Denitrification Bacteria Using NUA-DAS Ecofilter].

A small-scale combined ecofilter was constructed using neutralized-used acid residue (NUA) and dewatered alum sludge (DAS), and the nitrogen removal for wastewater treatment and characteristics of denitrification bacteria using the NUA-DAS ecofilter were studied. After the system was stabilized, the average removal rates of COD, TN, NO3--N in the final effluents were 60%, 70% and 95%, respectively, and the range of NO3--N concentration in the effluents was only 0.02-0.55 mg·L-1. Furthermore, the richness and similarity of three types of functional genes (nirS, nirK and nosZ) for denitrification in different substrates during the operation period were analyzed using PCR-DGGE method. These results showed that the richness of all denitrification bacteria at NUA and DAS increased remarkably after operation for 30 and 60 days compared to that in fresh substrate, and the richness was basically the same for the same kind of gene at the identical substrate regardless of depth gradient and operation period. The richness of nirS, nirK and nosZ detected in the NUA and DAS followed the order of nosZ > nirK > nirS. It was also revealed that spatial location had an apparent influence on the community structure of denitrifying bacteria (nirS, nirK and nosZ) but operation time had no obvious effect. Finally, nirK might be the most suitable for the environment in the system, and the adaptive capacity of denitrification bacteria (nirS, nirK and nosZ) in NUA could be superior to that in DAS.

Impact of fly ash and phosphatic rock on metal stabilization and bioavailability during sewage sludge vermicomposting.

Sewage sludge (SS) was mixed with different proportions of fly ash (FA) and phosphoric rock (PR), as passivators, and earthworms, Eisenia fetida, were introduced to allow vermicomposting. The earthworm growth rates, reproduction rates, and metal (except Zn and Cd) concentrations were significantly higher in the vermireactors containing FA and PR than in the treatments without passivators. The total organic carbon (TOC) and total metal concentrations in the mixtures decreased, and the mixtures were brought to approximately pH 7 during vermicomposting. There were significant differences in the decreases in the metal bioavailability factors (BFs) between the passivator and control treatments, and adding 20% FA (for Cu and Zn) or 20% PR (for Pb, Cd, and As) to the vermicompost were the most effective treatments for mitigating metal toxicity. The BF appeared to be dependent on TOC in the all treatments, but was not closely dependent on pH in the different vermibeds.

Biostabilization enhancement of heavy metals during the vermiremediation of sewage sludge with passivant.

The present study revealed the effects of fly ash (FA) and phosphoric rock (PR) on stabilization of sewage sludge (SS) after vermicomposting for 60 days. The earthworms in all vermibeds showed significant increases in tissue metal; however, the bioconcentration factors (BCFs) of all investigated metals (except Zn) differed among treatments. Additionally, significant differences were observed in the final system weight and SS+Passivant weight reduction among treatments, but not in the percentage reduction of total system weight and organic matter (OM). pH decreased from the initial levels, eventually reaching neutrality. Significantly greater earthworm heavy metals content, growth and reproduction rates and BCFs were observed, while a decreased percentage of total heavy metals concentration and a proportional decrease of extractable metals (except Cu and Zn) were observed in treatments mixed with FA and PR. Furthermore, significant linear correlations between BCFs and a reduction in percentage concentration of total metals (Cu, Pb, Cd and As) were shown, as well as BCF-Cu and relative proportional changes in extractable Cu. These results indicate that vermicomposting with proportions of FA and PR is better for stabilization and remediation of SS in a short period of time.

Performance and mechanisms of a microbial-earthworm ecofilter for removing organic matter and nitrogen from synthetic domestic wastewater.

The performance of a microbial-earthworm ecofilter for the treatment of synthetic domestic wastewater is evaluated, and the mechanisms of organic matter and nitrogen transformation investigated. Vermifiltration efficiently reduced chemical oxygen demand (COD) and ammonia nitrogen (NH(3)-N) from the influent. A combination of soil with sawdust possessed higher porosity and specific surface area than other media, and this microporous structure together with wormcast surface greatly facilitated COD reduction at depths from 5 to 35 cm. Nitrogen variations in wastewater were influenced by soil properties, earthworm activities, and wormcast characteristics. Their interaction with added nitrogen determined soil nitrogen distribution. In addition, denaturing gradient gel electrophoresis (DGGE) profiles revealed a highly diverse community of ammonia-oxidizing bacteria (AOB) and Nitrospira in soil layers. There was a positive correlation between the Shannon biodiversity index for AOB and decreasing NH(3)-N concentration, indicating that dominant soil microbes played a major role in removing NH(3)-N and nitrogen conversion. In contrast to previous reports, identification of retrieved sequences of AOB species showed that most belonged to an uncertain AOB genus. This biofiltration system is a low cost, efficient alternative for decontaminating local domestic wastewater.

Enhancement of rural domestic sewage treatment performance, and assessment of microbial community diversity and structure using tower vermifiltration.

The performance of a novel three-stage vermifiltration (VF) system using the earthworm, Eisenia fetida, for rural domestic wastewater treatment was studied during a 131-day period. The average removal efficiencies of the tower VF planted with Penstemon campanulatus were as follows: chemical oxygen demand, 81.3%; ammonium, 98%; total nitrogen, 60.2%; total phosphorus, 98.4%; total nitrogen, mainly in the form of nitrate. Soils played an important role in removing the organic matter. The three-sectional design with increasing oxygen demand concentration in the effluents, and the distribution of certain oxides in the padding were likely beneficial for ammonium and phosphorus removal, respectively. The microbial community profiles revealed that band patterns varied more or less in various matrices of each stage at different sampling times, while the presence of earthworms intensified the bacterial diversity in soils. Retrieved sequences recovered from the media in VF primarily belonged to unknown bacterium and Bacilli of Firmicutes.