Vertical Flow Constructed Wetlands Research Articles

Comparison of Canna indica and Acorus calamus for surfactant removal in biochar augmented constructed wetlands

Surfactants get discharged indiscriminately in wastewater which increased several fold during COVID-19, raising environmental concerns. In this study, two locally available plant species Canna indica and Acorus calamus were compared for the sodium dodecyl sulfate (SDS, − a chemical surfactant) removal in vertical flow constructed wetlands (VFCWs) augmented with biochar. The dose-response relationship was studied for 144 days in four phases by varying the SDS concentration at 10, 25, 50, and 100 ppm in wastewater. The mean SDS removal efficiencies varied from 85 % - 98 % during the different phases. The results suggested that planted artificial wetlands acted more stable than unplanted ones, although the removal efficiencies of the planted and unplanted were found similar (97.9 % - 98.4 %) in phase 4. Further, GC–MS analysis confirmed C2 products formed during SDS degradation indicating mineralization of SDS. The bioconcentration factor (BCF) and translocation factor (TF) studies revealed no accumulation of SDS in the roots of both plants as BCF (root) < 1 whereas, the aerial part of C. indica showed bioaccumulation of SDS with BCF (aerial) values nearly 1. TF for SDS was >1 in the case of both plants, among which translocation of SDS in C. indica with biochar amendment (TF = 17.8) was found to be highest. TF values indicated that biochar may have supported the uptake and translocation of SDS in C. indica whereas biochar has not supported the pollutant transfer in A. calamus. In terms of plant health, C. indica showed better growth and higher biomass increase than the A. calamus. The results implicate that C. indica with biochar-amended CW systems has great potential and can be recommended for efficient removal and uptake of SDS.

Olive mill wastewater treatment using vertical flow constructed wetlands (VFCWs)

The study explores a synergistic two-phase system to treat olive mill wastewater (OMW), comprising a multilayer adsorbent filter (pretreatment) and a vertical flow constructed wetland (VFCW). The pretreatment phase includes layers of commercial granular activated carbon (CGAC) and volcanic tuff (VT), while the VFCW phase consists of planted tank with Phragmites australis reeds and unplanted tanks. Initially, municipal wastewater is introduced into the VFCW to establish the required microbial community. Then, pre-treated OMW is passed through the VFCW. The removal rates of various pollutants were assessed. The planted VFCW showed superior removal efficiencies, averaging 97.82% for total chemical oxygen demand (CODT), 92.78% for dissolved oxygen demand (CODd), 99.61% for total phenolic compounds (TPC), 98.94% for total nitrogen (TN), 96.96% for ammonium, and 95.83% for nitrate. In contrast, the unplanted VFCW displayed lower removal efficiencies, averaging 91.47% for CODT, 77.82% for CODd, 98.53% for TPC, 97.51% for TN, 92.04% for ammonium, and 90.82% for nitrate. These findings highlight the significant potential of VFCWs, which offer an integrated approach to OMW treatment by incorporating physical, chemical, and biological mechanisms within a single treatment system.Graphical

Enhancing Greywater Treatment: High-Efficiency Constructed Wetlands with Seashell and Ceramic Brick Substrates

Constructed wetland (CW) systems have been recognized as a sustainable technology for wastewater treatment that can be easily integrated into the local natural environment, offering both low cost and high efficiency. In this study, synthetic greywater was treated using a vertical subsurface flow CW operated in batch mode with 7-day cycles across two phases, operated in parallel: I, non-vegetated, and II, vegetated, with Echinodorus subalatus. The mixed filter bed was composed of seashells, ceramic brick fragments, and sand. No statistically significant differences (p &gt; 0.05) were observed between the non-vegetated and vegetated phases for most parameters. The removal efficiencies of organic matter, anionic surfactants, and total phosphorus in the non-vegetated versus vegetated phases were (91.0 ± 3.8)% versus (94.0 ± 1.1)%; (71.9 ± 14.1)% versus (60.0 ± 9.5)%; and (35.2 ± 4.6)% versus (40.2 ± 15.5)%, respectively. Phosphorus removal exceeded values reported in the literature for both phases, primarily due to the calcium present in the seashells, which increased the electrical conductivity and hardness of the effluent compared to the influent. The macrophyte exhibited leaf desiccation, possibly due to contact with greywater and its young age (30 days), which may have negatively impacted the system’s performance during the vegetated phase.

Enhanced textile wastewater remediation in Phragmites karka-based vertical flow constructed wetlands using Phragmites-derived biochar

Vertical flow-constructed wetlands (VFCWs) are treatment systems that can be used for the phytoremediation of highly polluted textile wastewater. Using plant-derived biochar to simultaneously improve the contaminant removal performance of CWs and sustainable utilization of harvested plant biomass is an interesting proposition. The present study explored the phytoremediation potential of Phragmites karka and verified the impact of using P. karka-derived biochar as a substrate in VFCWs for the treatment of textile wastewater. For this, three types of VFCWs were designed; (i) non-vegetated (VFCW), (ii) vegetated with P. karka (VFCW–P), and (iii) vegetated with P. karka and amended with P. karka-derived biochar (VFCW-BP) and semi-batch experiments were conducted. The investigation confirmed that wetlands using biochar as substrate were more efficient than other wetlands in pollutant load reduction. The maximum pollutant removal efficiencies were recorded for VFCW-BP vis-à-vis COD (83.61%), color (77.87%), chloride (73.22%), calcium (73.52%), sodium (67.18%), and potassium (75.72%) after five days. Furthermore, biochar addition enhanced the growth conditions for wetland plants by alleviating osmotic and oxidative stresses and hence helped them to perform better while removing pollutants. The maximum reduction of various pollutant parameters was reached within 72 h, after which remediation efficiency was slowed down. The study suggests that VFCW with biochar amendment is a useful strategy for textile wastewater treatment. Because the experimental design satisfies the needs for low-cost wastewater treatment, it may find widespread applications.

Nutrient removal efficacy and microbial dynamics in constructed wetlands using Fe(III)-mineral substrates for low carbon-nitrogen ratio sewage treatment.

This study evaluated the roles of two common sources of Fe(III)-minerals-volcanic rock (VR) and synthetic banded iron formations from waste iron tailings (BIF-W)-in vertical flow-constructed wetlands (VFCWs). The evaluation was conducted in the absence of critical environmental factors, including Fe(II), Fe(III), and soil organic matter (SOM), using metagenomic analysis and integrated correlation networks to predict nitrogen removal pathways. Our findings revealed that Fe(III)-minerals enhanced metabolic activities and cellular processes related to carbohydrate decomposition, thereby increasing the average COD removal rates by 10.7% for VR and 5.90% for BIF-W. Notably, VR improved nitrogen removal by 1.70% and 5.40% compared to BIF-W and the control, respectively. Fe(III)-mineral amendment in bioreactors also improved the retention of denitrification and nitrification bacteria (phylum Proteobacteria) and anammox bacteria (phylum Planctomycetes), with increases of 3.60% and 3.20% using VR compared to BIF-W. Metagenomic functional predictionindicated that the nitrogen removal mechanisms in VFCWs with low C/N ratios involve simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD). Network-based analyses and correlation pathways further suggest that the advantages of Fe(III)-minerals are manifested in the enhancement of denitrification microorganisms. Microbial communities may be activated by the functional dissolution of Fe(III)-minerals, which improves the stability of SOM or the conversion of Fe(III)/Fe(II). This study provides new insights into the functional roles of Fe(III)-minerals in VFCWs at the microbial community level, and provides a foundation for developing Fe-based SNAD enhancement technologies.

Optimized ammonium-nitrate ratios in constructed wetlands for simultaneously efficient nitrogen removal and greenhouse gas reduction

Constructed wetlands (CWs) are increasingly employed for treating secondary tailwater treatment from wastewater treatment plants (WWTPs), addressing the challenges of nitrogen removal and greenhouse gas (GHG) emission reduction. This study explores the potential for enhancing nitrogen removal while reducing GHG emissions in vertical flow CWs by optimizing the influent ammonium-nitrate ratio in real tailwater scenarios. Six different influent ammonium-nitrate ratios (0:15, 1:20, 1:10, 1:5, 1:2, 1:1) were investigated and the results indicate that an ammonium-nitrate ratio of 1:5 achieves the highest total nitrogen (TN) removal efficiency of 77.50 ± 2.40 %, with the effluent concentrations below 4 mg/L. Conversely, a ratio of 1:10 minimized N2O emissions (0.027 mg/(m2⋅h)), representing just 0.054 ‰ of influent TN. Additionally, it was observed that increasing the ammonium-nitrate ratio influences microbial selectivity within the system. Moreover, a life cycle assessment further indicates that a 1:5 ratio poses the lowest potential environmental impact. These insights guide the design optimization of CWs for enhanced nitrogen removal and GHG mitigation, providing valuable strategies for tailwater management from WWTPs.

Effect of plant species on wastewater treatment performance of a subsurface vertical-flow constructed wetland with step-feeding at low temperature

To improve the treatment performance of constructed wetlands under low-temperature conditions, this study investigated the effects of plant species on wastewater treatment performance at low temperature and the associated microbiological characteristics in a subsurface vertical-flow constructed wetland (VFCW) with step-feeding. The results showed that the redox microenvironment in the VFCW filter with step-feeding could be restored and optimized by planting appropriate species that can tolerate low temperature, ensuring a high nitrification performance for the system. Correspondingly, the abundance and activity of three functional microbes (namely nitrifiers, denitrifiers, and anammox bacteria) increased to different degrees in the system, eventually ensuring ideal nitrogen removal by the VFCW. Compared with the VFCW planted with Phragmites australis and Acorus gramineus, the operation performance of the VFCW planted with Iris wilsonii could be recovered at low temperature, and its chemical oxygen demand, total phosphorus, total nitrogen, and ammonium nitrate removal rates could respectively reach 95.7%, 99.2%, 93.0%, and 94.4%, respectively. Moreover, nitrogen removal in the system relied on the nitrification/denitrification and partial denitrification - anaerobic ammonium oxidation processes. Nitrosomonas, Nitrospira, Thauera, and Candidatus Brocadia were the four dominant bacterial genera in the filter layer.

Evaluation of the pollutant removal efficiency of swine wastewater through two configurations of hybrid wetlands with tropical ornamental plants

The pig farming industry in Mexico is an important economic activity that is growing significantly, generating large volumes of wastewater that negatively affect water bodies and human health. The lack of adequate treatment systems exacerbates this problem. Hybrid constructed wetlands that combine Vertical Flow Constructed Wetlands (VF-CWs) and Horizontal Flow Constructed Wetlands (HF-CWs) offer an economical and effective treatment using natural processes. The objective was to evaluate the removal of contaminants from pig farm wastewater using two configurations of hybrid systems with ornamental plants. Two configurations were established: System I: VF-CWs + HF-CWs and System II: HF-CWs + VF-CWs. The VF-CWs were planted with Canna hybrids and the HF-CWs with Heliconia latispatha. The results indicated higher removal efficiencies of organic matter, nitrogen, and phosphorus in System I (BOD5: 72.99 %, COD: 71.41 %, TN: 79 %, NH4+: 84.31 %, NO3-: 74.29 %, TP: 59.54 %, FC: 99.88 %) compared to System II (BOD5: 66.80 %, COD: 67.01 %, TN: 77.90 %, NH4+: 82.31 %, NO3-: 70.48 %, TP: 55.81 %, FC: 99.89 %), regarding FC, the same results were obtained in both systems. Both plant species showed vigorous development, although the growth of Heliconia latispatha was more notable. In conclusion, the results suggest that the VF-CWs + HF-CWs configuration in hybrid wetlands could be a suitable option for treating this type of effluent.

Potential of phragmites australis in vertical flow constructed wetland for heavy metals removal from urban wastewater

ABSTRACT Constructed wetlands (CWs) have emerged as effective biotechnological solutions for wastewater treatment in recent decades. While plants are recognized components of these systems, their specific role in nutrient and heavy metal (HM) uptake warrants further investigation. This study assesses the efficacy of a vertical flow constructed wetland (VFCW) unit planted with Phragmites australis in treating HM-laden wastewater. Through standard methods, wastewater samples from inlet and outlet were analyzed for HMs (Cd, Zn, Pb, Cu), alongside plant and sediment samples. Planted CWs demonstrated remarkable removal efficiencies: 89.34% for Cd, 76.27% for Zn, 68.14% for Cu, and 66.42% for Pb, surpassing unplanted systems (18.27% to 33.16% removal). Notably, P. australis exhibited strategic pollutant absorption, with highest HM concentrations below-ground. Though above-ground HM accumulation was relatively minor, it exceeded soil concentrations. Analysis of accumulation factors confirmed roots and rhizomes as primary bio-accumulators, with transfer factor values (Cd > Pb > Zn > Cu) indicating efficient uptake. These findings underscore the pivotal role of P. australis in enhancing HM removal within VFCW systems, emphasizing the importance of plant-based strategies in HM remediation. Recommendations include further exploration of plant-assisted methods to optimize HM treatment in CWs.

Nutrient removal in floating and vertical flow constructed wetlands using aluminium dross: An innovative approach to mitigate eutrophication

On global scale, eutrophication is one of the most prevalent environmental threats to water quality, primarily caused by elevated concentration of nutrients in wastewater. This study utilizes aluminum dross (AD), an industrial waste, to create a value-added material by improving its operational feasibility and application for removing phosphate and ammonium from water. The operational challenges of AD such as its powdered nature and effective operation under only extreme pH conditions were addressed by immobilizing in calcium alginate to form calcium alginate aluminium dross (Ca-Alg-Al dross) beads. These Ca-Alg-Al dross beads were further tested for phosphate and ammonium removal from natural wastewater in two different aqueous environment systems: (i) vertical flow constructed wetlands (VF-CWs) followed by Ca-Alg-Al dross beads fixed bed system and (ii) Ca-Alg-Al dross beads mounted floating constructed wetlands (FCW) for remediating polluted lentic ecosystems. Our results show maximum phosphate and ammonium removal of 85 ± 0.41 % and 93.44 %, respectively, in VF-CWs followed by Ca-Alg-Al dross beads fixed bed system. The Ca-Alg-Al dross beads mounted FCW system achieved maximum phosphate removal of 79.18 ± 8.56 % and ammonium removal of 65.45 ± 21.04 %. Furthermore, the treated water from the FCW system was assessed for its potential to inhibit algal growth by artificially inoculating treated water with natural algae to simulate eutrophic conditions. Interestingly, treated water from the FCW system was found capable of arresting the algal growth. Besides, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) spectroscopy confirmed the functional groups and surface properties and probable participation of multiple mechanisms including ion exchange, electrostatic attraction, and ligand complexation for phosphate and ammonium removal. Overall, these results offer a promising way to utilize AD for high-end applications in wastewater treatment.

CONSTRUCTED WETLANDS FOR NITROGEN REMOVAL AND SIMULTANEOUS REUSE OF DOMESTIC SEWAGE

This study evaluated the behavior of vertical flow constructed wetland (VFCW), planted with irrigated rice (Oryza sativa L.), specie BRS-GO Guará, and a vertical flow soil filter without plant (VFSF-CTR), as control, both on a reduced experimental scale. The objective was the removal and recovery of N from domestic sewage, using soil latossoil red-yellow (LRY) mixed with medium sand (modified LRY) as support medium. The operation of VFCW and VFSF-CTR for ten months and two rice crop cycles, used three different hydraulic loading rates - HLR (4.0, 8.0 and 15.0 cm/d); with three repetitions, totalizing eighteen experimental units. For the VFCW, the total Kjeldahl nitrogen (KTN) and N-NH4+ removal efficiencies, ranged from 86% to 95%; and, for VFSF-CTR, from 79 to 94%; with the rice crop favoring higher efficiencies in KTN removal, independent of HLR. Both systems showed tertiary treatment removal efficiency in a single stage; in addition, the variations in the removal efficiencies were minimal when operated with HLR of 15 cm/d. There was great accumulation of KTN and mineral N (N-NH4+ and N-NO3-) in soil, mainly in the 0-5 cm soil layer, which can be used for fertilization of other crops. There was also N immobilised in microbial biomass (MBN). This rapid fertilisation improved the soil quality in a short term (ten months of sewage application) and provided the production of grains and vegetable biomass for human and animal food. The VFCW presented good results, either operated with low or high hydraulic loads, showing larger operational flexibility.

Optimization of “sulfur–iron–nitrogen” cycle in constructed wetlands by adjusting siderite/sulfur (Fe/S) ratio

Sulfur-siderite autotrophic denitrification (SSAD) has been proved to solve the key problem of low nitrogen removal efficiency caused by the shortage of carbon source in constructed wetlands (CWs). In this study, five vertical flow constructed wetlands (VFCWs) were constructed with different Fe/S ratios (0/0, 0/1, 1/1, 2/1 and 1/2) to optimizing SSAD process, labeled S.0, S.1, S.2, S.3 and S.4. The results showed that the best NO3−-N and TN removal rates were achieved with a Fe/S ratio of 2:1 (S.3), which were 96.26 ± 1.40% and 93.63 ± 3.12%, respectively. The abundance of denitrification genes (nirS, nirK and nosZ) in S.3 was significantly increased. Illumina high-throughput sequencing analysis indicated that the abundance and diversity of microorganisms involved in the “Sulfur–Iron–Nitrogen” cycle were enriched in S.3. The current study provided that the “Sulfur–Iron–Nitrogen” cycle in CWs was optimized by adjusting Fe/S ratio, and more types of denitrifying bacteria could be enriched, thereby enhancing nitrogen removal.

A partial siphon operational strategy strengthens nitrogen removal performance in partially saturated vertical flow constructed wetlands

The carbon‒oxygen balance has always been problematic in constructed wetlands (CWs), putting pressure on stable and efficient nitrogen removal. In this study, a novel partial siphon operational strategy was developed to further optimize the carbon and oxygen distributions of a partially saturated vertical flow CW (SVFCW) to enhance nitrogen removal. The removal performances of the partial siphon SVFCW (S-SVFCW) were monitored and compared with those of the SVFCWs at different partial siphon depths (15 cm, 25 cm and 35 cm) in both the warm and cold seasons. The results showed that the partial siphon operating strategy significantly facilitated the removal of ammonia and total nitrogen (TN) in both the warm and cold seasons. When the partial siphon depth was 25 cm, the S-SVFCWs had the highest TN removal efficiency in both the warm (71%) and cold (56%) seasons, with an average improvement of 46% and 52%, respectively, compared with those of the SVFCWs. The oxidation‒reduction potential (ORP) results indicated that richer OPR environments and longer hydraulic detention times were obtained in the S-SVFCWs, which enriched the denitrification bacteria. Microbial analysis revealed greater nitrification and denitrification potentials in the unsaturated zone with enriched functional genes (e.g., amo_AOA, amo_AOB, nxrA and nirK), which are related to nitrification and denitrification processes. Moreover, the strengthening mechanism was the intensified oxygen supply and carbon utilization efficiency based on the cyclic nitrogen profile analysis. This study provides a novel partial siphon operational strategy for enhancing the nitrogen removal capacity of SVFCWs without additional energy or land requirements.

Analysis of ammonia-nitrogen removal kinetics by stage in pilot scale vertical flow wetlands treating landfill leachate in series

This study explored the effect stage number and plant type have on ammonia-nitrogen (NH3–N) removal kinetics in a two-stage pilot-scale vertical flow constructed wetland (VFCW) system treating landfill leachate. Half of the VFCW columns were planted with Typha latifolia and the other half Scirpus californicus, and half of the columns were loaded with municipal solid waste landfill leachate (diluted to 1 part leachate to 2 parts total) with the effluent from these columns was collected in two separate barrels. The remaining columns were loaded with the effluent collected from the first columns, creating a two-stage VFCW system with four unique pairs to be tested. The leachate used here experienced no prior pre-treatment, and average influent concentrations of NH3–N for the first- and second-stage VFCWs were 508 and 321 mg L−1, respectively— much higher than many other VFCW treatment systems. Some reduction in chemical oxygen demand was observed, as well as generation of nitrate and nitrite, evidence of nitrification. No apparent correlation between aboveground biomass and removal of NH3–N was observed. Overall removal efficiency of NH3–N through two stages of VFCWs was 53.7% for columns planted with T. latifolia and 58.3% for those planted with S. Californicus. Average NH3–N removal efficiencies for the first stage VFCWs were 32.7% and 34.3%, while those in the second stage were 31.3% and 36.5%; no significant difference was observed between the first and second stage, suggesting that stage number does not have a significant effect on the removal efficiency of NH3–N in the primary treatment of landfill leachate via VFCWs. However, average mass removal rates of NH3–N in the first stage were 166 and 175 mg L−1 d−1; the second stage was significantly lower at 99.4 and 112 mg L−1 d−1, indicating that the first stage removed more pollutants overall.

Synergistic Removal of Nitrogen and Phosphorus in Constructed Wetlands Enhanced by Sponge Iron

Insufficient denitrification and limited phosphorus uptake hinder nitrogen and phosphorus removal in constructed wetlands (CWs). Sponge iron is a promising material for the removal of phosphorus and nitrogen because of its strong reducing power, high electronegativity, and inexpensive cost. The influence of factors including initial solution pH, dosage, and the Fe/C ratio was investigated. A vertical flow CW with sponge iron (CW-I) was established, and a traditional gravel bed (CW-G) was used as a control group. The kinetic analysis demonstrated that for both nitrogen and phosphorus, pseudo-second-order kinetics were superior. The theoretical adsorption capacities of sponge iron for nitrate (NO3−-N) and phosphate (PO43−-P) were 1294.5 mg/kg and 583.6 mg/kg, respectively. Under different hydraulic retention times (HRT), CW-I had better total nitrogen (TN) and total phosphorus (TP) removal efficiencies (6.08–15.18% and 5.00–20.67%, respectively) than CW-G. The enhancing effect of sponge iron on nitrogen and phosphorus removal was best when HRT was 48 h. The increase in HRT improved not only the nitrogen and phosphorus removal effects of CWs but also the reduction capacity of iron and the phosphorus removal effect. The main mechanisms of synergistic nitrogen and phosphorus removal were chemical reduction, ion exchange, electrostatic adsorption, and precipitation formation.

New insights for simultaneous nutrient removal enhancement and greenhouse gas emissions reduction of constructed wetland by optimizing its redox environment through manganese oxide addition

Manganese oxide (MnOx) is receiving increased interest in the nutrient removal of constructed wetlands (CWs); however, its service effectiveness for simultaneous greenhouse gas (GHG) emissions reduction is still vague. In this study, three vertical flow CWs, i.e., volcanics (CCW), manganese sand uniformly mixing with volcanics (Mn-CW) and MnOx doped volcanics (MnV-CW), were constructed to investigate the underlying mechanisms of MnOx on nutrient removal enhancement and greenhouse gas (GHG) emissions reduction. The results showed that the MnOx doped volcanics optimized the oxidation–reduction potential surrounding the substrate (-164.0 ∼ +141.1 mv), and resulted in the lowest GHG emissions (CO2-equivalent) from MnV-CW, 16.8–36.5 % lower than that of Mn-CW and CCW. This was mainly ascribed to mitigation of N2O produced during the NO3−-N reduction process, according to results of 15N stable isotope labeling. Analysis of the microbial community structure revealed that due to the optimized redox conditions through chemical doping of MnOx on volcanics, the abundance of microbe involved in denitrification and Mn-oxidizing process in the MnV-CW was significantly increased at genus level, which led to a higher Mn cycling efficiency between biogenic MnOx and Mn2+, and enhanced denitrification efficiency and N2O emission reduction. This study would help to understand and provide a preferable reference for future applications for manganese-based CW.

Biochar from co-pyrolysis of biological sludge and sawdust in comparison with the conventional filling media of vertical-flow constructed wetlands for the treatment of domestic-textile wastewater.

A biochar from co-pyrolysis of a mixture of sawdust and biological sludge (70/30, w/w), providing a high environmental compatibility in terms of water leachable polycyclic aromatic hydrocarbons and inorganic elements, together with a remarkable surface area (389 m2/g), was integrated into laboratory-scale vertical-flow constructed wetlands (VF-CWs), planted with Phragmites australis and unplanted. Biochar-filled VF-CWs have been tested for 8 months for the refining of effluents from the tertiary clariflocculation stage of a wastewater treatment plant operating in a mixed domestic-industrial textile context, in comparison with systems filled with gravel. VF-CW influents and effluents were monitored for chemical oxygen demand (COD), nitrogen and phosphorus cycles, and absorbance values at 254 and 420 nm, the latter as rapid and reliable screening parameters of the removal of organic micropollutants containing aromatic moieties and/or chromophores. Biochar-based systems provided a statistically significant improvement in COD (Δ = 22%) and ammonia (Δ = 35%) removal, as well as in the reduction of UV-Vis absorbance values (Δ = 32-34% and Δ = 28% for 254 and 420 nm, respectively), compared to gravel-filled microcosms. The higher removal of organic was mainly attributed to the well-known adsorption properties of biochars, while for nitrogen the biological mechanisms seem to play a predominant role.

Application of New Filling Material Based on Combined Heat and Power Waste for Sewage Treatment in Constructed Wetlands.

The filling of constructed wetlands (CWs) affects the efficiency of sewage treatment and proper operation. Mineral aggregates are most often used as filling materials. Significant environmental burdens from mineral mining operations justify the search for waste fill. This study aimed to determine the possibility of increasing the efficiency of CW by using a Certyd aggregate as a new filling. Certyd is produced in the sintering process of coal ash, a waste from combined heat and power (CHP) plant operation. Comprehensive two-year studies were conducted using two real-scale subsurface vertical flow (SS VF) CWs supplied with domestic sewage. One bed was filled with a Certyd and the other was filled with appropriate fractions of a mineral aggregate. Both beds worked in parallel, and to compare their effectiveness, account seasonality was taken into account. The SS-VF Certyd-filled bed achieved an average efficiency of 88.0% for biological oxygen demand (BOD5), 80.2% for chemical oxygen demand (COD), 80.4% for suspended solids (SSs), 80.2 for ammonia nitrogen (N-NH4), 72.2% for total nitrogen (TN), and 55.3% for total phosphorus (TP), while the gravel-filled bed achieved 84.5%, 77.0%, 86.9%, 74.2%, 69.4%, and 57.8% for the whole research period, respectively. A higher effect of the removed unit load was achieved in the bed filled with Certyd (36.2 g BOD5 m-2 d-1, 50.0 g COD m-2 d-1, 5.88 g SS m-2 d-1, 7.1 g TN m-2 d-1, 7.9 g N-NH4 m-2 d-1, 0.79 g TP m-2 d-1) compared to the gravel-filled bed (34.7 g BOD5 m-2 d-1, 47.0 g COD, 6.35 g SS m-2 d-1, 6.9 g TN m-2 d-1, 7.3 g m-2 d-1 N-NH4, 0.83 g TP m-2 d-1).

Arbuscular mycorrhizal fungi enhanced the drinking water treatment residue-based vertical flow constructed wetlands on the purification of arsenic-containing wastewater

Arsenic (As) is a toxic metalloid that poses a potential risk to the environment and human health. In this study, drinking water treatment residue (DWTR) and ceramsite-based vertical flow constructed wetlands (VFCWs) were built to purify As-containing wastewater. As a method of bioaugmentation, arbuscular mycorrhizal fungi (AMF) was inoculated to Pteris vittata roots to enhance the As removal of the VFCWs. The results showed that the As removal rates reached 87.82–94.29% (DWTR) and 33.28–58.66% (ceramsite). DWTR and P. vittata contributed 64.33–72.07% and 7.57–29% to the removal of As, while AMF inoculation intensified the As accumulation effect of P. vittata. Proteobacteria, the main As3+ oxidizing bacteria in the aquatic systems, dominated the microbial community, occupying 72.41 ± 7.76%. AMF inoculation increased As-related functional genes abundance in DWTR-based wetlands and provided a reliable means of arsenic resistance in wetlands. These findings indicated that the DWTR-based VFCWs with AMF inoculated P. vittata had a great purification effect on As-containing wastewater, providing a theoretical basis for the application of DWTR and AMF for As removal in constructed wetlands.

Impact analysis of hydraulic loading rate and antibiotics on hybrid constructed wetland systems: Insight into the response to decontamination performance and environmental-associated microbiota

Hybrid constructed wetlands (HCWs) are a promising solution for water ecology and environmental treatment, not only for conventional types of water pollution but also for antibiotics. Among the critical parameters for wetlands, the hydraulic loading rate (HLR) is especially important given the challenges of antibiotics treatment and frequent extreme rainfall. To investigate the removal performance of different HLRs on nutrients and antibiotics, as well as the response of antibiotics to nutrient removal, and the impact of HLRs on microbial communities, new HCWs with vertical flow constructed wetlands (VFCWs) and floating constructed wetlands (FCWs) in series were built. The results of the study showed that: (1) HCWs are highly effective in removing chemical oxygen demand (COD), NH4+−N, NO2−−N, and total phosphorus (TP) at low HLR (L_HLR), with removal efficiencies as high as 97.8%, 99.6%, 100%, and 80.5%. However, high HLR (H_HLR) reduced their removal efficiencies; (2) The average removal efficiency of fluoroquinolones (FQs) under different HLRs was consistently high, at 99.9%, while the average removal efficiency of macrolides (MLs) was 96.3% (L_HLR) and 88.4% (H_HLR). The removal efficiency of sulfonamides (SAs) was susceptible to HLRs, and the removal of antibiotics occurred mainly in the rhizosphere zone of wetland; (3) High concentrations of antibiotics in HCWs were found to inhibit and poison plant growth and to reduce the removal efficiency of TP by 12%. However, they had a minor effect on the removal efficiency of carbon and nitrogen nutrients; (4) H_HLR altered the diversity and abundance of microbial communities in different compartments of the wetland and also reduced the relative abundance of Bacillus, Hydrogenophaga, Nakamurella, Denitratisoma and Acidovorax genera, which are involved in denitrification and phosphorus removal processes. This alteration in microbial communities was one of the main reasons for the reduced performance of nitrogen and phosphorus removal.