Vertical Flow Constructed Wetlands Research Articles

Influence of loading rates and feeding conditions on hybrid constructed wetlands integrated with microbial fuel cells

The present study had as objective to evaluate the influence of different operation conditions on two treatment systems composed of anerobic biofilter (AF) and hybrid constructed wetlands (CWs). Both treatment lines had as the first treatment stages an 1450 L AF unit and a CW designed as a Floating Treatment Wetland. Then, a pump directed half of the wastewater flow for each of the treatment lines. One of the lines was composed of a Vertical Flow CW incorporated with microbial fuel cells (CW-MFC), called Configuration 1 (C1), whereas the other line consisted of a Vertical Flow CW (VFCW) and a Horizontal Flow CW (HFCW), named Configuration 2 (C2). The treatment system was fed with wastewater generated in a university campus and monitored for 13 months, with three operation conditions tested: 3 pulses per day with 50 L each (20.5 L/m2day); 4 pulses with 75 L each (41 L/m2day) and 6 pulses with 75 L each (61.6 L/m2day). In addition, the potential bioenergy generated was monitored. For the last operation condition, C1 efficiently reduced BOD5 (88.7%) and turbidity (84.4%). On the other hand, for the nutrients the treatment efficiencies were lower, with 40.3% (TP) and 46.6% (N−NH3). Overall, similar results were obtained with the C2, with mean removal efficiencies of BOD5 (87.3%), turbidity (93.1%), and lower TP (10.4%) reduction. The treatment performance presented similar tendencies even with the changes in loading rates and in hydraulic retention times. Regarding the voltage monitoring, a peak of 687 mV was obtained considering a mean loading rate of 15.6 gCOD/m2day, whereas the maximum power density was 0.25 mW/m. Future research should focus on reducing the internal resistance of the CW system, thus increasing the bioelectricity generated and in treating wastewater with higher organic matter content.

Comparative study on the treatment of swine wastewater by VFCW-MFC and VFCW: Pollutants removal, electricity generation, microorganism community

Swine wastewater, characterized by high organic and nutrient content, poses significant environmental challenges. This study aims to compare the effectiveness of two treatment technologies, namely Vertical Flow Constructed Wetland-Microbial Fuel Cell (VFCW-MFC) and Vertical Flow Constructed Wetland (VFCW), in terms of pollutant removal, electricity generation, and microorganism community dynamics. The results showed that the average removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen, total nitrogen (TN), total phosphorus (TP) and sulfadiazine antibiotics (SDZ) by VFCW-MFC were as high as 94.15%, 95.01%, 42.24%, 97.16% and 82.88%, respectively, which were all higher than that by VFCW. Both VFCW-MFC and VFCW have good tolerance to SDZ. In addition, VFCW-MFC has excellent electrical performance, with output voltage, power density, coulombic efficiency and net energy recovery up to 443.59 mV, 51.2 mW/m3, 52.91% and 2.04 W/(g·s), respectively, during stable operation. Moreover, the microbial community diversity of VFCW-MFC was more abundant, and the species abundance distribution in cathode region was more rich and even than in anode region. At phylum level, the dominant microorganisms in VFCW-MFC included Proteobacteria, Bacteroidota, Firmicutes and Actinobacteriota, which showed good degradation effect on SDZ. Proteobacteria and Firmicutes are also involved in electricity production. Chloroflexi, Proteobacteria and Bacteroidota play a major role in nitrogen reduction.

Plasterboard sheet applied in vertical-flow constructed wetlands: Nutrients removal, microbial diversity, and mechanisms

Wetlands are an economically viable alternative for decentralized wastewater treatment. Plasterboard sheets (PS) are commonly used in civil construction; however, the waste generated could be an environmental concern. Thus, fragments of plasterboard sheets and modified PS were used as substrates in two sequencing-batch vertical-flow constructed wetlands (VFCW) of 28 L of the working volume to evaluate the carbonaceous, nitrogenous, and phosphorous matter removal from synthetic wastewater, combining sewage treatment and reuse of civil construction waste. The systems, planted with Eichhornia crassipes, were named CW-P (11.36 kg of PS fragments and 30 % porosity) and CW-MP (9.34 kg of modified PS fragments and 35 % porosity). The systems were evaluated under two different sampling conditions after 24 h (Phase I) and 48 h (Phase II) for 308 days. The PS was characterized using SEM, SED, and XRF analyses, and the bacterial community in the biofilm was evaluated in the systems. CW-MP achieved the highest COD removals (65 % and 70 %) in both phases. The results for TN and TAN were similar, with CW-P achieving higher efficiency in Phase I. In Phase II, there was no significant difference between CW-P and CW-MP. Regarding total phosphorus removal, CW-P was slightly better than C-MP, with removal efficiencies of 64 % in Phase I and 54 % in Phase II for both systems. The proposed systems could remove organic matter and phosphorus through different processes such as adsorption on the substrate, precipitation, plant uptake, and as a source of carbon and nutrients for microorganisms.

Manganese ore enhanced polycyclic aromatic hydrocarbons removal in constructed wetlands: Insights into the key removal mechanism and main driving factor

Substrates are vital to efficiently remove polycyclic aromatic hydrocarbons (PAHs) in constructed wetlands (CW). However, the critical role of the substrate in the system is still not fully understood due to the unclear PAHs removal mechanism and particularly the main driving factor affecting PAHs removal. In this study, four vertical-flow CWs with different typical substrate types (A: quartz sand, B: quartz sand + granular activated carbon, C: quartz sand + ceramsite, and D: quartz sand + manganese ore) were established to investigate the treatment performance and mechanism of CW systems. Satisfactory and stabilized PAHs removal was achieved in CW-D during the operation period of 120 days, which significantly increased the removal of PAHs by 23.80%–31.18% compared with control group. Microbial degradation was revealed to dominate PAHs removal in CWs, and the enhanced proportion of microbial degradation (21.12%-35.43%) in CW-D led to the higher PAHs removal compared with other CWs. Further analysis showed that altered extracellular polymeric substances and Mn cycle improved the electron transfer capacity, and strengthened the interaction between plants and microorganisms in CW-D. Microbial analysis showed that the abundance of key PAH-degrading microorganisms and microbial metabolic gene expression were enhanced in CW-D, which supported the increased microbial degradation of PAHs. Additionally, root length and microbial diversity were two driving factors affecting PAHs removal rather than specific surface area based on the structural equation modeling analysis. This study provides comprehensive insights into the key role of suitable substrates for PAHs removal as well as the related mechanism and driving factors of PAHs removal in CWs.

Performance of olive mill wastewater treatment using hybrid system combining sand filtration and vertical flow constructed wetlands

Olive mill wastewater (OMWW) is a main source of noxious and recalcitrant organic pollutants of significant concern in environmental engineering. For this purpose, the current study assessed the performance of system combining sand filtration and vertical flow constructed wetlands (VF-CWs) in reducing the organic load of OMWW. Sand filter system wed in this study is composed of 6 plastic columns of 0.50 m in diameter and 120 L of capacity. The irrigation of sand filter columns was assured by 50 % diluted OMWW at flow rate of 5 L/day. VF-CWs system consists of a 1 m3 tank filled with soil and gravel in the bottom and planted of Typha latifolia, Phragmites australis and Arundo donax aquatic plants. The irrigation of VF-CWs system was assured with treated OMWW with a flow rate of 20 L twice in the week. Obtained results showed that sand filtration achieved a high removal rate of 76.42, 75.12, 79.7 and 78.10 %, respectively, for total suspended solid (TSS), dissolved COD (chemical oxygen demand), total COD and phenolic compounds. The usage of the combination of sand filter and VF-CWS improved significantly the elimination efficiency of total COD up to 91.44 %, dissolved COD up to 77.09 % and phenolic compounds up to 79.47 %, but it did not report any performance in the removal of TSS. Despite the high performance of hybrid system (sand filter+VF-CWs) in reducing the organic pollution, final effluent concentrations remained below the permitted limits for discharge into a municipal sewer system.

Analysis of changes on substrates filling constructed wetland systems after landfill leachate treatment - FTIR study

A rapid and inexpensive method, Fourier transform infrared spectroscopy (FTIR), can be used to identify impurities and determine the functional groups responsible for the sorption of specific ions. The FTIR method has already been used in research. However, there is a lack of research on constructed wetland (CW) infill materials used to treat landfill leachate (LL). Therefore, the aim of this study was to verify the changes occurring in selected substrates (zeolite, expanded clay and bark) constituting vertical flow CW infill (VFCW) supplied with municipal LL. The principal component analysis carried out mainly showed differences in the results between the variants of the experiment with an infill of expanded clay and the others (for the values obtained at wave numbers in the range 1600-400 cm−1, in which most changes occurred). All peaks of the FTIR spectra of the pine bark filling the CW differ in location and intensity between the samples. In most cases, the stripes were elongated at exposure to 25% and 100% LL (compared to tap water). In all CW variants infill made of zeolite, peaks occurred at wave numbers within 1049-1012 cm−1, which were most likely caused by the presence of inorganic substances corresponding to clay minerals, and to silica. The FTIR spectra for zeolites, do not show large differences between the different infill samples used for LL treatment (100% LL and 25% LL). In all CW variants with expanded clay infill, peaks in the 1250-900 cm−1 wave number region, possibly indicating the presence of polysaccharides and phosphodiesters. FTIR spectroscopy has proven to be a very useful tool for rapid grade assessment determination of changes occurring on selected substrates and the identification of contaminants that remained after treatment in VFCWs fed with LL.

Hybrid constructed wetlands amended with zeolite/biochar for enhanced landfill leachate treatment

Landfill leachate contains high concentrations of ammonia and recalcitrant organic compounds, which can interfere with wastewater treatment processes. Hybrid constructed wetlands (CWs), consisting of Vertical Flow (VF) CWs followed by Horizontal Flow (HF) CWs, are low cost technologies for onsite leachate treatment. This study investigated the potential of low-cost adsorbent materials, a natural zeolite mineral (clinoptilolite) and biochar, to enhance leachate treatment in hybrid CWs. Two mesocosm hybrid CWs were set up at a Florida (US) landfill. In the Adsorbent-CW 10% (v/v) of zeolite was added to the VF-CW to enhance nitrification and 13% (v/v) biochar was added to the HF-CW to increase microbial activity and plant growth. A Control-CW contained only gravel. Both systems were planted with cattails (Typha latifolia) and cordgrass (Spartina alterniflora) and operated at varying hydraulic loading rates for ~2 years. A HF-CW containing wood chips (Woodchip-CW) was added downstream of the Adsorbent-CW during the final 6-months of operation to enhance denitrification. Results showed that zeolite addition to the VF-CW significantly increased nitrification rates by 16–93% due to cycles of ammonium adsorption and bioregeneration under intermittent loading conditions. Biochar addition increased removal of organic matter (21–26% to 29–44%) and color (1–18% to 7–49%), and improved wetland plant growth and nitrogen removal due to enhanced plant growth and rhizosphere microbial activity. Addition of the Woodchip-CW reduced nitrate accumulation, resulting in total nitrogen removals of up to 79%.

Application of vetiver grass (Vetiveria Zizanioides L.) for organic matter removal from contaminated surface water

This study presents the vertical flow constructed wetlands (VFCWs) as a green solution for organic matter removal in contaminated surface water – a case study in Vietnam. The experiments were conducted with hydraulic loading rates (HLRs) of 500 mL/m2/min (T1), 1000 mL/m2/min (T2), and 1500 mL/m2/min (T3) using Vetiver grass (V) and Control (C). The findings indicated that Vetiver grass (Vetiveria Zizanioides L.) based-VFCWs model achieves a removal efficiency of 90 % for biochemical oxygen demand (BOD5) and >80 % for chemical oxygen demand (COD). This could explain the significant contribution of aquatic plants to the VFCWs based on vertical flow characteristics. Analysis of variance showed that HLRs significantly influence the treatment efficiency of BOD5 and COD (P < 0.05). Furthermore, the quality of treated water meets standards for reuse for irrigation in agriculture. It provides an essential understanding to enhance organic removal in VFCWs and expand their applications for wastewater treatment.

Comparative Study on the Performances of Modified Vertical Flow–Constructed Wetlands for the Treatment of Domestic Wastewater

The present case study evaluates the treatment efficiency (R%) of vertical flow constructed wetlands (VFCW) with different design considerations for the efficient treatment of domestic wastewater. Four modified VFCW’s were constructed at the pilot scale to study their overall performance with domestic wastewater as the source. Since traditional VFCWs are responsible for increases in nitrates, this study also focuses on the removal of nitrates. These different VFCW’s were termed two stage (TS), two stage-charcoal (TSC), mixed flow (MF), and double stage (DS) VFCWs. The inlet chemical oxygen demand (COD), NH3-N, NO3-N, NO2-N, TN, total organic carbon (TOC), and ortho-P ranged from 300–900, 30–50, 25–50, 30–40, 15–50, 30–120 and 10–15 mg/L, respectively, with a pH around 7 and high total coliforms (T-C). The MFCW and DS-VFCW were found to be the most effective in treating almost all the parameters with the highest R% (>90). The TS-VFCW showed better treatment of carbon rather than nitrogen compounds (like NO3-N). The TSC-VFCW showed better treatment when the system was new, as decreases in R% were observed over time. Statistical analysis with one and paired-sample T-tests were conducted to support similar findings with significance values <0.05. The findings from both tests showed that DS-VFCW was the better system compared to the other two for COD, TOC, NO2-N, and ortho-P showing p=0.000; whereas, MFCW was the better system to treat pollutants like TN and NO3-N. The MFCW and DS-VFCW were both shown to effectively treat NH3-N and T-C.

Life cycle cost assessment and economic analysis of a decentralized wastewater treatment to achieve water sustainability within the framework of circular economy

Research background: The increasing water demand together with an unceasing production of wastewater worldwide has resulted in a situation where the scarcity and pollution of water resources are jeopardizing and depleting such a vital asset. Purpose of the article: In this context, Nature Based Solutions (NBS) such as Vertical Flow Constructed Wetlands (VFCWs) are key because of their capacity of channelling a waste into a resource. However, and notwithstanding their essential role, their financial benefits too often go unnoticed because of missing research that study them from an economic perspective and this article has covered this existing gap. The objective of this research is to analyse the economic consequences of using VFCW against its traditional alternative through a comprehensive economic assessment. Methods: After doing a Life Cycle Assessment (LCA), a combination of two approaches has been carried out. This research has developed a holistic approach where a Life Cycle Cost Assessment (LCCA) based on a Cost Benefit Analysis (CBA) along with an economic evaluation of cleaning environmental costs have been calculated for two different scenarios. For this monetary analysis, the environmental externalities derived from the use of cleaning the pollution caused by a public water supply and sewerage system and the VFCW have been quantified. Findings &amp; value added: Results conclude that VFCW apart of being a cost-effective and profitable alternative for an investor, it has also valuable benefits for the society in general because of its meaningful and positive externalities and the high removal cost of the environmental pollutants of the traditional water supply and sewage system both contributing directly to the achievement of Sustainable Development Goals (SDGs). Furthermore, 4/5 environmental impacts derived from the use of traditional alternative pollute more than twice as much as the VFCW does. Lastly, the cleaning costs difference between both alternatives is 1,984,335?.

Effectiveness of the tropical plants Rhynchospora corymbosa and Coix lacryma-jobi in vertical flow constructed wetlands for municipal primary sewage effluent treatment

The performance of two tropical plants, Rhynchospora corymbosa L. (RC) and Coix lacryma-jobi, L (CL) in treatment of primary sewage effluent in lab-scale vertical-flow constructed wetlands (VFCW) along with no plant control wetland was investigated. A batch-flow VFCWs were operated under batch fill and drain hydraulic loading system with hydraulic retention times (HRT) of 0.5, 1, and 2 days and fill rate of 8 L/day. Removal of solids, organics, nutrients, and pathogens were monitored. The volumetric contaminant removal rates were best described by 1st order kinetics except for ammonia and phosphate, which was best described by Stover-Kincannon kinetics. Influent TSS, PO4 3−, COD, BOD5, and total coliform concentration were low but high in NH4 + concentration. CL was better in nutrient removal as HRT increases compared to RC. RC was more efficient at TSS, turbidity, and organics removal. Pathogen removal was independent of plant type but HRT. Solids and organic removal were lower in CL planted CWs due to preferential flow paths created by their bulky root. CL planted CWs removed more nutrients followed by RC planted CWs and then no-plant control CWs. The results of these tests demonstrate that both CL and RC are suitable for the treatment of municipal wastewater in VFCW system.

Behavior of Per- and polyfluoroalkyl substances (PFAS) in Pilot-Scale vertical flow constructed wetlands treating landfill leachate

This study investigated the behavior of per- and polyfluoroalkyl substances (PFAS) in multiple pilot-scale vertical flow constructed wetlands (VFCW) treating landfill leachate. Eight pilot-scale VFCW columns planted with Typha latifolia or Scirpus Californicus were fed untreated municipal solid waste (MSW) landfill leachate that was diluted with potable water at a 1:10 ratio (1 part leachate to 10 parts total) at a fixed daily hydraulic loading rate of 0.525 m d-1. Ninety-two PFAS were examined and 18 PFAS were detected at quantifiable concentrations (7 precursor species and 11 terminal species). The average concentration of Σ92 PFAS in the influent was 3,100 ng L-1, which corresponded with minimal reduction in the effluents from the four VFCW (decreases ranged from 1% to 12% on average for Σ18 PFAS); however, precursors 6:3 FTCA, 7:3 FTCA, N-MeFOSAA, and N-EtFOSAA concentrations decreased significantly in the VFCW effluents, and significant decreases in the concentrations of these PFAA-precursors were concurrent with a significant increase in concentrations of five PFAAs (PFBA, PFNA, PFBS, PFOS, and PFOSI). This trend indicates that from a regulatory perspective, standalone VFCWs are likely to produce an apparent PFAS increase, which may also be true for many other leachate treatment processes incorporating aerobic biological treatment. Additional treatment to address PFAS should be integrated prior to the use of any system, including VFCWs, for the treatment of constituents of concern in MSW landfill leachate.

Pathogen Treatment in Single and Two-Stage Vertical Flow Wetland as a Potential Sanitation Technology for Rural India

Vertical flow-constructed wetlands (VFCW) are well-established, cost-effective, and sustainable options for wastewater treatment. Along with organic matter removal, wetlands are helpful in the removal of microbial pathogens. This study focuses on understanding the bacterial pathogen removal efficacy of three different design types of VFCWs and understands the best designs for the efficient removal of pathogens in a tropical climate. The three wetlands studied for removal efficiency were (a) two-stage vertical flow constructed wetland (TSVFCW), (b) Single-stage vertical flow constructed wetland (SSVFCW), and (c) single-stage saturated vertical flow constructed wetland (SSSVFCW). Results revealed that all three types of wetlands were effective in removing pathogenic bacteria. Still, TSVFCW was found to be more efficient in pathogen removal (Total Coliforms, Shigella spp., Salmonella spp., Pseudomonas spp., Vibrio spp., Enterococcus faecalis) 7.04 ± 0.17, 6.53 ± 0.08, 4.0 ± 0.42, 7.67 ± 0.08, 5.73 ± 0.70 and10 5.23 ± 0.96 Log10 reductions respectively compared to SSVFCW (5.28 ± 0.18, 5.18 ± 0.09, 3.74 ± 0.74, 6.98 ± 0.01, 3.97 ±0.32, 4.74 ± 1.08 Log10 reductions respectively) and SSSVFCW (4.48 ± 0.46, 4.83 ± 0.15, 2.74 ± 0.44, 6.71 ± 0.03, 4.31 ± 0.49, 5.03 ± 1.20 Log10 decreases respectively). For abiotic factors (Chemical oxygen demand, total Kjeldahl nitrogen, and phosphorus) also TSVFW shows better efficiency (45 ± 8.7, 24.7±4.5 and 3.1, ± 0.2 g.m-2, respectively) than SSVFCW (12 ± 1.3, 7.6 ± 0.4 and 1.8 ± 0.2 g.m-2 respectively) and SSVFCW (6.3 ± 1.1, 7.7 ± 0.1 and 1.2 ± 0.1 g.m-2 respectively). However, the removal efficiency of both single-stage wetlands was comparable.

Study on Effectiveness of Intervention of a Vertical Flow Constructed Wetland in between Septic Tank and Soak Pit for the Treatment of Septic Tank Effluent

Septage comprises the solid and liquid constituents of any primary treatment system, including a Septic Tank. In this study, the wastewater collected from a septic tank is passed through a partially converted anaerobic filter, and a vertical flow constructed wetland (VFCW) before being sent to a soak pit. The main objective of this case study was to check the effectiveness of incorporating a VFCW between a septic tank and a soak pit to bring down the consequences created due to effluent seepage from soak pits to the groundwater. Conventionally, the effluent gets directly passed to soak pits after primary onsite treatment in the septic tank. The soak pit walls made of porous materials allow the gradual seepage of final effluent into the ground, polluting the groundwater reserves. We analyzed the septic tank effluent from 60 households wherein the effluent was let off into the soak pits. The various parameters analyzed with their averages were 393.83 ± 293.41 mg.L-1 for COD, 151.48 ± 94.37 mg.L-1 for BOD, 30.81 ± 13.05 mg.L-1 for NO3-, 23.35 ± 13.54 mg.L-1 for PO43-, 7.35 ± 0.31 for pH, 184.05 ± 163.20 mg.L-1 for TSS, 3.05 x 107± 2.04 x 108 CFU.100mL-1 for TC. Therefore, it is certain that the final effluent being sent into soak pits after primary treatment does not meet the Central Pollution Control Board (CPCB) discharge standards. In this case study, we were able to obtain final effluent values after VFCW treatment as 55.72 mg.L-1 for COD, 12.12 mg.L-1 for BOD, 10.2 mg.L-1 for NO3-, 3.74 mg.L-1 for PO43-, 7.41 for pH, 8.37 mg.L-1 for TSS, 379.27 mg.L-1 for TS and 51.9 CFU.100mL-1 for TC. With this case study, we were able to resolve this impediment by bringing down the values of all the parameters considered while analyzing under the limits of discharge standards set by CPCB. The removal efficiency of COD, BOD, NO3-, PO43-, pH, TSS, and TC after wetland was found to be 89.46%, 88.051, 63.484, 44.37%, 3.41%, 98.47%, 97.71%, 97.19% respectively. The study has proven that with the introduction of another decentralized treatment system between a septic tank and soak pit, it is safe to dispose of the effluent into soak pits, thereby reducing the chances of groundwater pollution considerably.

Plant and microbial communities responded to copper and/or tetracyclines in mycorrhizal enhanced vertical flow constructed wetlands microcosms with Canna indica L.

Arbuscular mycorrhizal fungi (AMF) play a significant role in pollutants removal in constructed wetlands (CWs). However, the purification effects of AMF on combined copper (Cu) and tetracycline (TC) pollution in CWs remains unknown. This study investigated the growth, physiological characteristics and AMF colonization of Canna indica L. living in vertical flow CWs (VFCWs) treated for Cu and/or TC pollution, the purification effects of AMF enhanced VFCWs on Cu and TC, and the microbial community structures. The results showed that (1) Cu and TC inhibited plant growth and decreased AMF colonization; (2) the removal rates of TC and Cu by VFCWs were 99.13–99.80% and 93.17–99.64%, respectively; (3) the growth, Cu and TC uptakes of C. indica and Cu removal rates were enhanced by AMF inoculation; (4) TC and Cu stresses reduced and AMF inoculation increased bacterial operational taxonomic units (OTUs) in the VFCWs, Proteobacteria, Bacteroidetes, Firmicutes and Acidobacteria were the dominant bacteria, and AMF inoculation decreased the relative abundance of Novosphingobium and Cupriavidus. Therefore, AMF could enhance the pollutants purification in VFCWs by promoting plant growth and altering the microbial community structures.

Degradation of fluoroquinolones in rural domestic wastewater by vertical flow constructed wetlands and ecological risks assessment

Fluoroquinolones (FQs) are new environmental pollutants in rural domestic wastewater and vertical flow constructed wetlands (VFCWs) are widely used to treat rural domestic wastewater. However, studies on degradation products of FQs by VFCWs and ecological risks assessment have been very limited so far. The degradation of FQs by VFCWs under different hydraulic loads was investigated in this study. The results showed all VFCWs had high removal efficiencies of FQs under either high hydraulic load (above 80%) or low hydraulic load (above 95%). Only one degradation product of FQs was detected and the ecotoxicity declined significantly under low hydraulic load. Six degradation products of FQs were detected and the ecotoxicity had also been reduced in general under high hydraulic load. Cytochrome P450 and enzymes with acetyl transfer activity were directly related to the degradation of FQs. The most dominant ARGs in this experiment was qnrD and the relative abundance of qnrD in effluent of device-A, device-B, device-C and device-D were 93.0%, 94.4%, 85.6% and 89.0% lower than that in influent. Flavobacterium, Microbacterium, Dechloromonas, etc. were the key microorganisms for biological removal of FQs by VFCWs.

Effect of Loading Frequency on Ammonia-Nitrogen Removal Kinetics in Early-Stage Pilot-Scale Vertical Flow Constructed Wetlands Treating Landfill Leachate

This study measured the effects of loading frequency and plant species on the removal of ammonia-nitrogen (NH3-N) in a vertical flow constructed wetland (VFCW). Eight pilot-scale VFCW columns were constructed for this experiment; half of the columns were planted with Typha latifolia and the other half Scirpus californicus. To test the effect of loading frequency, half of the columns for each plant species were fed diluted leachate over the course of 24 h, and the other half were fed diluted leachate over the course of 8 h. This study was conducted in the early stages of plant and biofilm development within the system. Removal of chemical oxygen demand (COD) was observed but inconsistent, as was denitrification. Average NH3-N removal efficiencies in the various configurations ranged from 39.4 to 55.1%, and all configurations experienced peak removal efficiencies at a 1:20 dilution of leachate. Columns planted with T. latifolia and fed over 24 h performed significantly better than those planted with S. Californicus; this effect was not observed for columns fed over 8 h. Of the four configurations, columns planted with T. latifolia and fed over the course of 24 h performed best. The mechanisms responsible for this deserve further study.

Synergistic removal of sulfamethoxazole and dimethyl phthalate by five constructed wetland substrates

Frequent detection and joint toxicity of sulfonamides (SAs) and phthalate acid esters (PAEs) in water environment have caused serious health and safety problems that can be reduced by vertical flow constructed wetland (VFCW). However, it remains unclear what kind of substrate used in VFCW can synergistically remove SAs and PAEs. In this study, it was determined if biochar, zeolite, vermiculite, peat and sand synergistically removed sulfamethoxazole (SMX) and dimethyl phthalate (DMP) as representatives of SAs and PAEs by using batch and column experiments. The batch experiments showed that pseudo-second-order and intraparticle diffusion kinetics and Freundlich isotherm could better describe the synergistic adsorption of SMX and DMP on each substrate. SMX promoted hydrophobic interaction between DMP and each substrate so that low concentration DMP almost was adsorbed completely at neutral pH. Both neutral and alkaline pH conditions were favorable for synergistic adsorption of SMX and DMP on each substrate. The column experiments showed that removal of SMX or DMP in VFCW by substrate adsorption alone was limited with run time increasing, but SMX and DMP were effectively removed with run time increasing when loaded with simulated wastewater, SMX and DMP. The VFCW not only removed 94.7% SMX and 91.8% DMP after running 50 d, but also improved total nitrogen removal. In conclusion, these results strongly suggest that biochar, zeolite, vermiculite, peat and sand filled in VFCW can synergistically remove SMX and DMP.

Effect of organophosphate esters on microbial community and proteomics in constructed wetlands and its removal mechanism

Organophosphorus esters (OPEs) may cause potential risks to human health and ecological environment safety when they enter water. In this study, A lab-scale vertical flow constructed wetlands (VFCWs) exposed to dichlorvos (DDVP) was carried out to reveal removal effect and mechanism of DDVP in VFCWs. The findings indicated CWs can remove DDVP with 94%–95% average removal efficiency in long-term operation. Besides, soluble phosphate (SRP) and total phosphorus (TP) were removed by VFCWs with 48.60%–64.10% average removal efficiency, and the addition of DDVP enhanced the effect of CWs on nitrogen removal. High-throughput sequencing demonstrated that Massiilia (2.67%–18.06%), Denitratisoma (2.07%–3.80%) and SM1A02 (2.85%–4.67%) played an important role in the removal process of DDVP in VFCWs. Proteomics of plant root showed that A0A3B6ARQ4 (increased 29.53 times) and LOC_Os11g38050.1 protein (decreased 0.001 times) responsed more sensitive to OPEs which suggested DDVP enhancesenhancing plants energy production and hydrolyase synthesis, thereby promoting it hydrolysis. Therefore, the use of VFCWs to treat organic phosphate wastewater has future prospects.

Enhancement of organics and nutrient removal and microbial mechanism in vertical flow constructed wetland under a static magnetic field

Low and unstable pollutant removal is regarded as the bottleneck problem in constructed wetlands (CWs) for wastewater treatment. This study investigated the effect of static magnetic field (MF) on enhancing the purification efficiency and microbial mechanism in vertical flow CW systems for treating domestic wastewater. The results showed that MF-CWs outperformed control systems in terms of treatment performance, with average removal efficiencies of COD, NH4+-N, TN, and TP reaching 92.58%, 73.58%, 72.53%, and 95.83%, respectively. The change of malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) activity indicated that MF application was beneficial for plant health. Additionally, higher ammonia monooxygenase (AMO) activity in MF-CWs suggested the removal of NH4+-N was facilitated. The high-throughput sequencing results demonstrated that MF application could enrich the functional bacteria such as Patescibacteria phylum, mainly, including Gammaproteobacteria, Betaproteobacteria, and Alphaproteobacteria, which further accelerated pollutants transformation. These findings would be beneficial in understanding pollutant removal processes and their mechanism in CWs with MF application.