Vertical Subsurface Flow Research Articles

Numerical Approximation Tool Prediction on Potential Broad Application of Subsurface Vertical Flow Constructed Wetland (SSVF CW) Using Chromium and Arsenic Removal Efficiency Study on Pilot Scale

\noindent {\bf Abstract:} This study investigates the potential broad application of Subsurface Vertical Flow Constructed Wetlands (SSVF CWs) for heavy metal remediation, focusing on Chromium (Cr) and Arsenic (As) removal efficiency. A pilot-scale experimental setup was employed, utilizing a SSVF CW filled with 12 mm gravel and 2 mm coarse sand, planted with Phragmites Australis. The research, conducted over 366 days, aimed to develop a numerical approximation tool to predict the performance and applicability of SSVF CWs in various environmental conditions. The experimental system operated at a hydraulic loading rate of $98-111 \mathrm{~mm} / \mathrm{d}$ and a hydraulic retention time of 6 days. Results showed average removal efficiencies of $44.87 \pm 9.52 \%$ for Cr and $43.16 \pm 9.43 \%$ for As. A mass balance analysis revealed that substrate accumulation was the primary mechanism for heavy metal removal, accounting for $29 \%$ of Cr and $26 \%$ of As removal. Plant uptake contributed to $3.5-9.9 \%$ of Cr and $0.3-$ $8.8 \%$ of As removal. Based on these findings, a numerical model was developed to simulate SSVF CW performance under varying environmental and operational parameters. The model incorporated factors such as influent concentrations, hydraulic loading rates, substrate composition, and plant species. Validation against experimental data showed good agreement, with an $\mathrm{R}^{2}$ value of 0.89 . The numerical tool was then used to predict SSVF CW performance across a range of scenarios, indicating potential broad applications in industrial wastewater treatment, mine drainage remediation, and contaminated groundwater cleanup. This study provides valuable insights into the scalability and versatility of SSVF CWs for heavy metal removal, offering a sustainable and cost-effective solution for water treatment challenges.\\

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 > 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.

Treatment of domestic wastewater and extracellular polymeric substance accumulation in siphon-type composite vertical subsurface flow constructed wetland.

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3 --N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging.

Microplastic removal and risk assessment framework in a constructed wetland for the treatment of combined sewer overflows

Combined sewer overflows (CSOs) release a significant amount of pollutants, including microplastics (MPs), due to the discharge of untreated water into receiving water bodies. Constructed Wetlands (CWs) offer a promising strategy for CSO treatment and have recently attracted attention as a potential solution for MP mitigation. Nevertheless, limited research on MP dynamics within CSO events and MP removal performance in full-scale CW systems poses a barrier to this frontier of application. This research aims to address both these knowledge gaps, representing the first investigation of a multi-stage CSO-CW for MP removal. The study presents one year of seasonal data from the CSO-CW upstream of the WWTP in Carimate (Italy), evaluating the correlation of MP abundance with different water quality/quantity parameters and associated ecological risks. The results show a clear trend in MP abundance, which increases with rainfall intensity. The strong correlation between MP concentration, flow rate, and total suspended solids (TSS) validates the first flush phenomenon hypothesis and its impact on MP release during CSOs. Chemical characterization identifies acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), and polypropylene (PP) as predominant polymers. The first vertical subsurface flow (VF) stage showed removal rates ranging from 40 % to 77 %. However, the unexpected increase in MP concentrations after the second free water surface (FWS) stage suggests the stochasticity of CSO events and the different hydraulic characteristics of the CW units have diverse effects on MP retention. These data confirm filtration as the main retention mechanism for MP within CW systems. The MP ecological risk assessment indicates a high-risk category for most of the water samples, mainly related to the frequent presence of ABS fragments. The results contribute to the current understanding of MPs released by CSOs and provide insights into the performance of different treatment units within a large-scale CSO-CW system, suggesting the requirement for further attention.

Comparing the performance of microbial electrochemical assisted and aerated treatment wetlands in pilot-scale: Removal of major pollutants and organic micropollutants

The combination of treatment wetlands (TWs) with microbial electrochemical technologies (MET) is often studied in the lab to improve the performance and decrease the footprint of TWs. In this article we evaluated the long-term performance of four pilot-scale vertical sub-surface flow TWs for major pollutants' and organic micropollutants' removal from domestic wastewater. Three of them were filled with electroconductive material and operated under saturated (MET SAT), unsaturated (MET UNSAT) and unsaturated-saturated (MET HYBRID) conditions while the fourth one was a saturated intensified aerated system (AEW) filled with gravel. The MET-TWs achieved significant removals of COD (>78 %) with no clogging issues at the maximum applied OLR (249 g COD m−3 d−1) while under these loading conditions TSS removal exceeded 84 %. Among all electroactive TWs, UNSAT could remove 25 g NH4-N m−3 d−1 through nitrification when peak ammonium loading rate was applied; however this removal was significantly lower than AEW (35 g NH4-N m−3d−1). No important removal of P was observed in all systems with the exception of MET-SAT were precipitation reactions of P with iron occurred when anaerobic pretreated wastewater was used. The removal of the sum of studied organic micropollutants ranged between 70 ± 18 % (MET UNSAT) to 91 ± 4 % (AEW) and improved with feeding pulses increase. Moderate to high removal of specific microcontaminants was observed depending on the target compound, the studied system and the operational conditions. AEW and MET HYBRID systems complied with the limits set by EU for wastewater discharge to non-sensitive water bodies and for Class B water reuse. Scale-up calculations for a settlement of 500 PE showed that these systems require much less area per PE (0.51 m2 PE−1) comparing to conventional TWs while the operational cost was calculated to 0.07 € m−3 for the AEW and 0.02 € m−3 for the MET HYBRID.

The efficacy of integrated vermifiltration technology for treatment of food analysis laboratory wastewater

The macrophyte-assisted vermifiltration (MAVF) technology was applied for treatment of food analysis laboratory wastewater at Industrial Technology Institute (ITI), Sri Lanka for the first time. Three laboratory-scale sub-surface vertical flow units were established:1) without earthworms and plants (Control unit), 2) with earthworms (Eisenia fetida) (vermi-filtration unit (VF unit), 3) with both earthworms and macrophytes (Canna indica) (MAVF unit). Wastewater was fed batch-wise with a feeding rate of 10 mL/min and seven days hydraulic retention time (HRT) for eight consecutive batches. Physiochemical parameters, Chemical Oxygen Demand (COD), Total Phosphorus (TP), Total Nitrogen (TN), pH, of the influent and effluent of all three units were analyzed to investigate the treatment efficiencies. One-Way ANOVA was performed to evaluate the significant differences in treatment efficiencies. The mean COD removal efficiencies of the control unit, VF unit, and MAVF unit were 60.2 % ± 10.7, 71.6± 8.07 %, and 72.0 % ± 8.86, respectively. Average TN removal efficiencies of the control unit, VF unit, and MAVF unit were 8.05 % ± 5.75, 10.9±6.4 %, and 24.9 % ±12.84, respectively. Average TP removal efficiencies were 35.84 % ± 17.5, 35.84 % ± 17.5 %, and 40.0 % ±16.76, respectively. The COD removal displayed promising results, whereas the means for enhancing TP and TN removal should be further studied. The findings of this study sensitizes the testing laboratories to go green by adopting in-house cost effective laboratory wastewater treatment systems.

Performance of vertical and horizontal treatment wetlands planted with ornamental plants in Central Chile: comparative analysis of initial operation stage for effluent reuse in agriculture.

This study comparatively evaluated effluent reuse from two TWs-a horizontal subsurface flow (HF) and a vertical subsurface flow (VF)-used for rural wastewater treatment in Central Chile during the initial operation stage. The two TWs were planted with Zantedeschia aethiopica and were operated for 10months at a pilot scale. The water quality of the influent and effluents was measured and compared with reuse regulations. The results showed similarities in the behavior of the effluents from the two TWs, presenting differences only in the chemical oxygen demand (COD) and different forms of nitrogen, suggesting the necessity of complementary treatment stages or modifications to the operation. The effluents from the HF better fulfilled the reuse standards for irrigation, as the VF faced problems associated with its size. However, a complementary disinfection system is necessary to improve pathogen removal in the effluents coming from the two TWs, especially to be reused as irrigation water for crops. Finally, this work showed the potential for applying subsurface TWs for wastewater treatment in rural areas and reusing their effluents as irrigation water, practice that can contribute to reducing the pressure on water resources in Chile, and that can be used as an example for other countries facing similar problems.

Study Filter Materials for Vertical Subsurface Flow Constructed Wetland to Treat Wastewater from the Da Mai Noodle Handicraft Village in Bac Giang Province

Vertical subsurface flow-constructed wetlands (VSF CW) are evaluated in this research as a potentially effective and cost-efficient solution for treating wastewater from Da Mai noodle handicraft village in Bac Giang province. Due to the high pollution load in this type of wastewater, there are concerns about clogging and the stability of the technology. In this study, we explored different sizes of limestone and gravel for the five medium composition formulas in the VSF CW system. The experiments were conducted over a period of three months. We used ANOVA, one-sample T-test, and Pearson correlation analysis methods to evaluate the experimental results, with statistical significance set at 0.05. The results showed a linear correlation between medium size, hydraulic conductivity, and treatment efficiency (p < 0.05). Smaller medium sizes had higher pollutant removal efficiency but lower porosity and hydraulic conductivity. For the same sizes, limestone demonstrated higher treatment efficiency compared to gravel (p < 0.05). The Cp5 formula (comprising sand, 1×2 cm limestone, and 3×5 cm gravel) was selected as the best filter medium for VSF CW, achieving COD, TSS, TN, and TP removal efficiencies of 86.02 ± 1.71%, 81.15 ± 2.24%, 64.46 ± 2.23%, and 69.76 ± 2.68%, respectively. After three months of operation, the treated wastewater consistently met QCVN 40:2011/BTNMT Column B standards, and there were no significant differences in hydraulic conductivity (p > 0.05), indicating stable operation of the VSF CW.

Removal of metals and emergent contaminants from liquid digestates in constructed wetlands for agricultural reuse.

Given the increasing pressure on water bodies, it is imperative to explore sustainable methodologies for wastewater treatment and reuse. The simultaneous presence of multiples contaminants in complex wastewater, such as the liquid effluents from biogas plants, can compromise biological treatment effectiveness for reclaiming water. Vertical subsurface flow constructed wetlands were established as low-cost decentralized wastewater treatment technologies to treat the liquid fraction of digestate from municipal organic waste with metals, antibiotics, and antibiotic resistance genes, to allow its reuse in irrigation. Twelve lab-scale planted constructed wetlands were assembled with gravel, light expanded clay aggregate and sand, testing four different treating conditions (liquid digestate spiked with oxytetracycline, sulfadiazine, or ofloxacin, at 100 μg/ L, or without dosing) during 3 months. Physicochemical parameters (pH, chemical oxygen demand (COD), nutrients, metals, and antibiotics), the microbial communities dynamics (through 16S high-throughput sequencing) and antibiotic resistance genes removal (qPCR) were monitored in influents and effluents. Systems removed 85.8%-96.9% of organic matter (as COD), over 98.1% of ammonium and phosphate ions, and 69.3%-99.4% of nitrate and nitrite ions, with no significant differences between the presence or absence of antibiotics. Removal of Fe, Mn, Zn, Cu, Pb and Cr exceeded 82% in all treatment cycles. The treatment also removed oxytetracycline, sulfadiazine and ofloxacin over 99%, and decreased intl1, tetA, tetW, sul1 and qnrS gene copies. Nonetheless, after 3 months of ofloxacin dosing, qnrS gene started being detected. Removal processes relied on high HRT (14 days) and various mechanisms including sorption, biodegradation, and precipitation. Microbial community diversity in liquid digestate changed significantly after treatment in constructed wetlands with a decrease in the initial Firmicutes dominance, but with no clear effect of antibiotics on the microbial community structure. Removals above 85% and 94% were observed for Streptococcus and Clostridium, respectively. Results suggest that vertical subsurface flow constructed wetlands were a suitable technology for treating the liquid digestate to reuse it in irrigation agricultural systems, contributing to the circular bioeconomy concept. However, a more profound understanding of effective wastewater treatment strategies is needed to avoid antibiotic resistance genes dissemination.

Application of coconut shell activated carbon filter in vertical subsurface flow constructed wetland for enhanced multi-metal bioremediation and antioxidant response of Salvinia cucullate

Coconut shell activated carbon (CNSAC) was applied as a filter layer in hybrid vertical subsurface flow constructed wetland (H-VSSF-CW), in order to enhance the multi-metal removal efficiency of the constructed wetland (CW) and to reduce heavy metal accumulation on Salvinia cucullata. Treatment P + AC, (having CNSAC filter layer), showed 32, 21 and 34% more Cd, Cr, and Pb removal efficiency than treatment P (without CNSAC layer). CNSAC activated carbon adsorbed Cd and Pb and Cr by functional groups –NH, -NO2, -C-O, –OH and –CO, and significantly reduced Cd and Pb exposure to S. cucullate. Chromium adsorption by CNSAC filter layer was half (just 25% of total input) of the Cd and Pb. In treatment P, due to high Cd, Pb and Cr accumulation in S. cucullate, the antioxidant defense mechanism of the plant was collapsed and cell death was observed, which in turn has resulted reduced biomass gain (5% reduction). On the other hand, in treatment P + AC, an antioxidant defense mechanism was active in the form significantly (p ≤ 0.05) increased of SOD, CAT and proline content while reduced MDA, EL, %EB and soluble sugar. So, the application of CNSAC increased the heavy metal removal efficiency of H-VSSF-CW by adsorption of a considerable share of heavy metal and hence, reduced the heavy metal load/exposure to S. cucullate.

Removal of Heavy Metals and Bulk Organics towards Application in Modified Constructed Wetlands Using Activated Carbon and Zeolites

Constructed wetlands are a versatile technology for various treatment approaches, especially in emerging countries. The research aims to study and optimize the hybridizing process of a vertical subsurface flow constructed wetland with adsorption technology to provide energy-efficient and sustainable removal of heavy metals and bulk organics before their discharge into water bodies or water reuse for irrigation. This study focuses on the adsorption of selected heavy metals present in sewage from Kanpur, India, a cluster of tanning industries and other relevant industrial polluters, investigating the pollutant adsorption onto activated carbon and zeolites in batch and column tests. The results of the batch tests indicated high zeolite loading rates for lead (91.6 mg/g), chromium (60.8 mg/g) and copper (47.4 mg/g). In the column tests applying different adsorbent combinations and ratios, the average removal rates were as follows: 54.6% for cadmium, 14.1% for chromium, 52.4% for copper, 2.2% for iron, 29.2% for manganese, 26.6% for nickel, 35.2% for lead and 44.6% for zinc. The column tests conducted in preparation for field testing in pilot wetlands showed that shorter retention times and background bulk organic concentrations, as well as high ammonium concentrations, negatively affected heavy metal removal by reducing the adsorption and ion exchange capacity of the adsorbents.

Assessing lab-scale hybrid wetland performance for pollutant and pathogen removal from high organic loading septage

A laboratory-scale three-staged hybrid constructed wetland (CW) system was operated for the treatment of septage. The Hybrid-CW, covering an area of 1.92 m2, consisted of a sludge drying bed (SDB) of 0.41 m2, a vertical sub-surface flow bed (VSSF) of 0.58 m2, and a horizontal sub-surface flow bed (HSSF) of 0.93 m2. The SDB, VSSF and HSSF beds were operated at an average hydraulic loading rate (HLR) 22.2, 5.2 and 3.2 cm d−1. With an average organic loading rate (OLR) of 28.8 g d−1 the Hybrid-CW confirmed effective removal of BOD5, COD, TS, and TSS by 99.2 ± 0.3% and 99.4 ± 0.2%, 96.4 ± 0.8% and 86.9 ± 2.4%, respectively. The correlation between effluent TS and TSS concentrations with influent concentrations indicated a dependence of TS and TSS removal on influent concentration. Average total coliform count in influent and effluent was observed as 6.3 × 107 and 1.6 × 103 CFU L−1respectively. Average helminthes eggs count in the influent and effluent was recorded as 5 × 107 and 2 × 104 eggs L−1 respectively. With an inlet TS loading of 177.5 g d−1, the hybrid CW system attained 96.4% TS removal and 87% TSS removal. The sludge drying bed, operating with a remarkably high TS loading of 861.9 ± 77.1 g m−2 d−1, avoided clogging and achieved >90% removal rates for total coliform and helminthes eggs along with around 60% for TS and BOD. Furthermore, the system exhibited excellent removal rates of over 99% for both total coliform (TC) and helminthes eggs (HE). Treated septage meets the Indian wastewater discharge criteria for BOD, COD, TS and TN.

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).

Kinetic-hydrodynamic models considering climatic influence on the domestic sewage treatment by constructed wetlands in tropical country

Typical constructed wetlands (CW) sizing methods in tropical countries rarely considers climate parameters as evapotranspiration (EPT) and rainfall (Ra), even though high levels of EPT and Ra can change the pollutant removal kinetic and Wastewater hydrodynamic. This paper aims to evaluate the climatic influences (EPT and Ra) on fit of several kinetic-hydrodynamic models used to describe the sewage organic matter removal in a real scale vertical (VSSF-CW) and horizontal (HSSF-CW) subsurface flow constructed wetland. Sewage quality (Biochemical Oxygen Demand - BOD and Chemical Oxygen Demand - COD) and sewage flow rates data were applied of First Order, Grau-Second Order, Monod, Monod Multi and Stover-Kincannon kinetic models, combined with ideal continuous stirred-tank reactor (CSTR) and plug-flow reactor (PF) hydrodynamic models. Monod, Monod Multi and Stover-Kincannon models (in CSTR) were more able to represent organic matter removal in CWs. Models considering EPT and Ra were more adequate or with no statistical difference compared with conventional models (that don’t consider EPT and Ra), except for BOD in VSSF-CW.

Effect of varying retention times and feeding schemes on the performance of vertical constructed wetlands planted with vetiver grass in treating dairy wastewater in the Philippines

AbstractAdequate wastewater treatment from the dairy industry before disposal is still lacking in the Philippines, particularly in small‐scale sectors. This limitation is due to the high cost and expertise required from conventional wastewater treatment systems. One option is using constructed wetlands, a nature‐based solution with low cost, less specialized expertise and maintenance requirements and high wastewater treatment efficiency. To further evaluate the application of constructed wetlands in the Philippines, this paper studied the wastewater from the manufacturing processes of the Dairy Training Research Institute, University of the Philippines Los Baños (DTRI‐UPLB). It is a small dairy farm inside the University with economic constraints in using a conventional wastewater treatment system. The main aim of this study is to determine the effect of using vertical subsurface flow constructed wetlands (VSSFCW) planted with Vetiver grass (Chrysopogon zizanioides) in sand and gravel media to treat the DTRI‐UPLB effluent, using very low retention times (4 and 8 h), with daily and alternate days of wastewater feeding into the VSSFCW. The average removal efficiencies for total suspended solids (TSS), biological oxygen demand for (BOD5), total phosphorus (TP), and Total Kjeldahl Nitrogen (TKN) are 88.34%, 93.56%, 78.42%, and 94.63%, respectively. Moreover, alternate wastewater feeding provided a statistically significant increase in the performance of VSSFCW, while there is no statistical difference between the two retention times evaluated. Finally, it was observed that plant age significantly affects the performance of VSSFCW setup but should be explored further with longer operation times and additional nutrient uptake analysis.

Impact of Climate Conditions on Pollutant Concentrations in the Effluent from a One-Stage Constructed Wetland: A Case Study

This paper reports the results of an investigation into the influence of precipitation and air temperature on the efficiency of pollutant removal processes and effluent pollutant concentrations in a one-stage constructed wetland with subsurface vertical flow. We studied an on-site constructed wetland system that used Phragmites australis for the treatment of domestic wastewater. The system was located in central Europe, in the south-east of Poland, in a temperate climate zone with transitional features. Physico-chemical analyses of influent and effluent wastewater, as well as measurements of precipitation and air temperature were carried out in the years 2001–2010. It was shown that the pollutant removal efficiency of the treatment plant was significantly higher in the growing season than outside the growing season (the mean efficiency is usually a few percent higher but generally this parameter is highly varied). This indicated that temperature determined the efficiency of the wastewater treatment. We found that the amount of precipitation affected the concentration of pollutants in the effluent. The more rainfall there was, the lower the content of pollutants in the effluent from the treatment plant, which demonstrated that rainwater diluted the concentrations of pollutants in the treated wastewater—thus improving the efficiency of the wastewater treatment plant.

The Vertical Subsurface Flow Constructed Wetland (VSSFCW) Performance Using Typha angustifolia and Ipomoea aquatica for Tofu Wastewater BOD and COD Removal

Tofu is one of the most popular foods in Indonesia. in the production process, it produces quite a high BOD and COD which are around 5.000-10.000 mg/L and 7.000-14.000 mg/L in liquid waste effluent. Tofu wastewater effluent that exceeds the quality standard of soybean processing industry wastewater into river waters without prior treatment and reduction can certainly cause environmental damage. On the other hand, tofu wastewater made from soybeans with high nutritional content has the potential for sustainable use. Therefore, an effective, and sustainable wastewater treatment process to minimize environmental damage and increase the circular economy is needed. In situ wastewater treatment utilizing an equalization tank and a wetland with a Vertical Subsurface Flow Constructed Wetland (VSSFCW) type connected by a distribution tank using Typha angustifolia and Ipomoea aquatic plants were employed to treat tofu wastewater in order to reduce the organic matter inside wastewater measured by BOD and COD levels. The treatment plants were able to reduce approximately 68,53% of BOD levels and 70,29% of COD levels with Typha angustifolia as a phytoremediator and about 56,96% of BOD levels and 59,04% of COD levels with Ipomoea aquatica as a phytoremediator. Typha angustifolia has better resistance and adaptability than Ipomoea aquatica to tofu wastewater. A wetland-based system can potentially be developed considering the sustainability opportunities of using phytoremediator plants.

A survey on constructed wetland publications in the past three decades.

Decentralised wastewater treatment systems, such as constructed wetlands, are becoming increasingly popular these days because they are more economical and cost-effective than conventional plants. The primary objective of this review paper is to determine the number of studies that have been conducted on constructed wetlands, specifically 'free water surface flow constructed wetlands', 'horizontal subsurface flow constructed wetlands', 'vertical subsurface flow constructed wetlands', and 'hybrid constructed wetlands'. In addition, the paper examines the status of research publications on constructed wetlands by country, author, and journal. Based on the review, it has been found that although constructed wetland technology is economical and cost-effective, it is still not among the top 10 effluent treatment methods. Compared to other constructed wetland systems, 'hybrid constructed wetlands' have received minimal attention. Based on the search results, 4639 documents published between 1989 and 2021 have been extracted from the online edition of SCI-EXPANDED, Web of Science. The documents associated with constructed wetlands are divided into eight main document types. Articles and proceedings papers are the most common document type, accounting for 93% of all publications, followed by reviews (4%), meeting abstracts (1.3%), corrections (0.56%), editorial materials (0.38%), news items (0.2%), letters (0.04%), and book reviews (0.02%).

Constructed Wetlands as Nature-Based Solutions for Wastewater Treatment in the Hospitality Industry: A Review

The hospitality industry is increasing its awareness of how the integration of nature-based solutions can decrease its environmental impact while maintaining or increasing the service level of the sector. Constructed wetlands (CWs) constitute a promising sustainable solution for proper in situ domestic wastewater treatment. This literature review elucidates the status of CWs implementation in the hospitality industry to help foster the exchange of experiences in the field and deliver examples of approaches in different contexts to support future applications of this technology. Most of the studies reported in the literature were conducted in Europe, but studies emanating from Asia and South America are also available. The design of CWs, the horizontal and vertical subsurface flow CWs (HSFCW, VSFCW), and hybrid systems have been reported. The average removal efficiencies of the systems ranged from 83 to 95% for biochemical oxygen demand, 74 to 94% for chemical oxygen demand, 78 to 96% for total suspended solids, 75 to 85% for ammonium, 44 to 85% for ammonia, 50 to 73% for nitrate, 57 to 88% for total Kjeldahl nitrogen, 51 to 58% total nitrogen, and 66 to 99% for total phosphorus. The majority of the systems were implemented as decentralized treatment solutions using HSFCWs, with the second most common design being the hybrid CW systems in order to reduce area requirements, increase treatment efficiency, and prevent clogging. Overall, CWs are a promising sustainable solution which may support access to adequate sanitation worldwide as well as safe wastewater recycling and reuse, leading to more sustainable tourist destinations.

Subsurface flow constructed wetlands for treating of simulated cadmium ions-wastewater with presence of Canna indica and Typha domingensis

The presence of toxic cadmium ions in the wastewater resulted from industrial sector forms the critical issue for public health and ecosystem. This study determines the ability of four vertical subsurface flow constructed wetlands units in the treatment of simulated wastewater laden with cadmium ions. This was achieved through using sewage sludge byproduct as alternative for the traditional sand to be substrate for aforementioned units in order to satisfy the sustainable concepts; however, Canna indica and Typha domingensis can apply to enhance the cadmium removal. The performance of constructed wetlands has been evaluated through monitoring of the pH, dissolved oxygen (DO), temperature, and concentrations of cadmium (Cd) in the effluents for retention time (0.5–120 h) and metal concentration (5–40 mg/L). The results demonstrated that the Cd removal percentage was exceeded 82% beyond 5 days and for concentration of 5 mg/L; however, this percentage was decreased with smaller retention time and higher metal concentration. The Grau second-order kinetic model accurately simulated the measurements of effluent Cd concentrations as a function of retention times. The FT-IR analysis indicated the existence of certain functional groups capable of enhancing the Cd removal. The treated wastewater's pH, DO, temperature, total dissolved solids (TDS), and electrical conductivity (EC) all meet the requirements for irrigation water.