Overview of the state of the art of constructed wetlands for decentralized wastewater management in Brazil

A pilot scale of electrochemical integrated treatment technology and equipment driven by solar energy for decentralized domestic sewage treatment

Based on the natural air diffusion electrode (NADE) cathode, a solar-driven electrochemical integrated sewage treatment technology and equipment in a pilot scale was developed to treat dispersed rural wastewater. The non-aeration NADE had efficient and stable H2O2 production performance, maintaining the H2O2 output between 1474 and 1535 mg h-1 within 50 h with the current efficiency of 77.4%-80.6%. This electrochemical integrated wastewater treatment system was coupled with technologies such as dual-cathode electro-Fenton, peroxi-coagulation and photoelectro-Fenton, which effectively improved the conversion and utilization efficiency of H2O2. It integrated Fenton-like oxidation, electro-oxidation and UV/H2O2, as well as Fe(OH)3-dominated flocculation, which could effectively remove various pollutants in wastewater. The integrated sewage treatment equipment (500 L d-1) realized the effective treatment of a rural decentralized domestic sewage, achieving simultaneous removal of chemical oxygen demand (COD), NH3-N, total phosphorus (TP) and bacteria. Driven by solar energy, its application feasibility, superiority and stability have been proved, providing theoretical and technical support for the efficient and low-consumption treatment of dispersed organic wastewater.

Natural wetlands contribution on phosphorus removal in small northern communities in Canada

This study focuses on understanding the role of passive wastewater treatment (wastewater lagoon plus wetland) in reducing the phosphorus discharge levels in a northern small community in Manitoba, Canada. The facultative lagoon system of that small community treats domestic wastewater and seasonally discharges effluent into a wetland that connects to Lake Manitoba. This research assesses phosphorus removal efficiency through the natural wetland during the vegetation growing season. The average total phosphorus (TP) concentration reduction for the observed treatment area of 1.3 ha was more than 70%, achieving the desired TP discharge concentration below 1 mg/L. Data analysis showed that the main accumulation of TP occurred at the 21-40 cm soil depth, which indicates the potential of natural wetland treatment applications under cold continental climate conditions as an effluent polishing step to satisfy regulatory requirements for phosphorus reduction.

Removal of pharmaceuticals by vertical flow constructed wetland with different configurations: Effect of inlet load and biochar addition in the substrate

Pharmaceuticals (PCs) residues are considered an emerging threat to the environment due to their persistency, ecotoxicity and bioaccumulative nature. To study the PC (amoxicillin, AMX; caffeine, CF; ibuprofen, IBU) removal efficiency of vertical flow constructed wetland (VFCW), three setups of VFCWs were configured: SB (substrate matrix + biochar (BC)); SBP (substrate matrix + BC + plant); SP (substrate matrix + plant) and changes in effluent PC load was estimated at 24, 48, 72, 96, 120, 144 and 168 h intervals. SBP with an influent load of 1,000 μg L^-1 showed the maximum removals of 75.51% (AMX), 87.53% (CF), and 79.93% (IBU) significantly higher than that of SB and SP (p < 0.00). Results showed an inverse relationship between removal efficacy and influent PCs loading. The average removal (%) by VFCWS (of all studied setups) was in the order: 66.20 > 47.88 > 39.0 (IBU), 56.56 > 42.12 > 34.36 (AMX), and 74.13 > 64.0 > 52.07 (CF) with 1,000, 5,000 > 10,000 μg L^-1 influent load, respectively. The maximum removal of COD, NH₄⁺-N, and NO₃-N was recorded at 88.8%, 83.1%, and 64.9%, respectively in SBP, and their removal was hardly affected by influent PC concentration. In summary, planted VFCW spiked with BC could be a viable approach for the removal of PCs in wastewater. The impact of PC load on plant toxicity in VFCWs can be taken as a research problem for future work in this series.

Wastewater treatment using bamboos in constructed wetlands: experiences and future perspectives

Wastewater treatment using constructed wetlands (CWs) based on natural wetlands constitute a viable alternative with excellent cost and benefit, presenting themselves as efficient technologies in the secondary and tertiary treatment of wastewaters with low implementation, operation, and maintenance costs. The present study aims to evaluate the use of bamboo species, as an alternative to macrophytes, frequently used in CWs, through bibliometric analysis, besides to a review based on case studies. The maps generated by the VOSviewer software and by the analyses of the Web of Science and Scopus databases allowed for a review of typical concepts of CWs, in addition to revealing potential benefits of using bamboos in CWs, such as their hyperaccumulation capacity and bioproduct generation. Other promising aspects were identified, for example the use of bamboo charcoal as a substrate used in subsurface wetlands and the application of ornamental bamboo species for landscape improvements, among other observations. The efficiencies found in six case studies showed values between 89-99.7%, 47.6-99.7%, 58.3-99.9%, and 85.5-99.8% for BOD₅, COD, total nitrogen (TN), and total phosphorus (TP), respectively. Despite the promising results, the lack of studies using bamboos in CWs for the treatment of wastewaters limits an assertive statement about the use of this technology, requiring further research, focusing on the morphological functions of bamboos in this treatment with landscape integration and resources recovery.

In-depth performance study of an innovative decentralized multistage constructed wetland system treating real institutional wastewater

The performance of an innovative decentralized multistage constructed wetland (DMCW) treating institutional wastewater is studied covering three seasons. The DMCW system with Canna lily efficiently removed organics contaminants like COD and BOD, and nutrients from the wastewater, showing its dependency on meteorological factors. Overall the performance is maximum in summer and least in monsoon, with a COD removal of 85.6% in summer followed by 82.5% in winter and 61.2% in monsoon. Removal of TSS (67.7-85.5%), PO₄^3--P (52.1-64.4%), NH₄⁺-N (56.6-71.6%), NO₃^--N (47.3-63.4%) and NO₂^--N (62-75.4%) were achieved along with heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Hg and Pb. Removal of pathogens like Vibrio is >98%, E. coli 95%, Pseudomonas 99%, and Aeromonas 63% was observed. Mass removal rate of COD was maximum in summer (97.3 g/m²/d) followed by winter (78.7 g/m²/d) and monsoon (43.5 g/m²/d). Majority of organics removal during the treatment was highlighted through Gas Chromatography-Mass Spectrometry (GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed wastewater to be complex. The Canna lily accumulated various elements and oxides during the treatment with no stress on its health. The treated water quality is within the permissible limits and stands suitable for irrigational purposes. Better plant health and increased microbial diversity in the garden proves the suitability of treated water for irrigational activities. The results were validated using statistical tools like Mann-Whitney U test and principal component analysis.

Swine Wastewater Treatment in Constructed Wetland Systems: Hydraulic and Kinetic Modeling

The use of constructed wetland systems (CWS) is presented as an alternative for the treatment of effluents since these have reduced implementation costs and relative ease of operation. The present research was undertaken to evaluate to study the hydrodynamic and the fitting of first-order mathematical kinetic models for the removal of pollutants in CWS. Three CWS were built, using expanded clay as filter support: one cultivated with Polygonum punctatum (CWSw), another cultivated with Chrysopogon zizanioides (CWSV), and a control unit (CWSc). The actual retention time was 3.12 days in the CWSc, whereas, in the CWSw and CWSv, we observed values of 4.14 and 4.11 days, respectively. The dispersion values were high in all CWS. The values of chemical oxygen demand (COD) across the length of the CWS were used to fit the kinetic models that describe the first-order decay of organic matter over the CWS. The models that showed a better fit to the experimental data were the plug-flow with residual concentration, the continuous stirred tank reactor, and Shepherd’s models.

Constructed wetlands as a sustainable technology for wastewater treatment with emphasis on chromium-rich tannery wastewater

Water scarcity is a major threat to agriculture and humans due to over abstraction of groundwater, rapid urbanization and improper use in industrial processes. Industrial consumption of water is lower than the abstraction rate, which ultimately produces large amounts of wastewater such as from tannery industry containing high concentration of chromium (Cr). Chromium-contaminated tannery industry wastewater is used for irrigation of food crops, resulting in food safety and public health issues globally. In contrast to conventional treatment technologies, constructed wetlands (CWs) are considered as an eco-friendly technique to treat various types of wastewaters, although their application and potential have not been discussed and elaborated for Cr treatment of tannery wastewater. This review briefly describes Cr occurrence, distribution and speciation in aquatic ecosystems. The significance of wetland plant species, microorganisms, various bedding media and adsorbents have been discussed with a particular emphasis on the removal and detoxification of Cr in CWs. Also, the efficiency of various types of CWs is elaborated for advancing our understanding on Cr removal efficiency and Cr partitioning in various compartments of the CWs. The review covers important aspects to use CWs for treatment of Cr-rich tannery wastewater that are key to meet UN's Sustainable Development Goals.

Materials in constructed wetlands for wastewater remediation: A review

The wastewater treatment industry is constantly evolving to abate emerging contaminants and to meet stringent legislative requirements. The existing technologies need to be modified, or new innovative treatment techniques need to be developed to ensure environmental protection and secure sustainability in the future. Emphasis is mainly on nutrient recovery, energy-efficient systems, zero waste generation, and environmentally friendly techniques. Constructed wetlands (CWs) have evolved as natural, eco-friendly, economical, and low-maintenance alternatives for wastewater remediation. These wetlands employ several materials as adsorbents for the treatment, commonly known as media/substrate. This review paper presents an assessment of various materials that can be used as substrates in CWs for the efficient removal of organic and non-biodegradable pollutants in different types of wastewaters. The effect of pH, mineral composition, specific surface area, and porosity of various natural materials and agricultural and industrial wastes used as media in CWs for wastewater remediation was discussed. The study showed that different substrates like alum sludge, limestone, coal slags, rice husk, and sand had removal efficiency for chemical oxygen demand (COD): 71.8%-82%, total phosphorous (TP): 77%-80%, and total nitrogen (TN): 52%-82% for different types of wastewaters. It also highlights the challenges related to the long-term sustainability of these materials. PRACTITIONER POINTS: Physicochemical characteristics influence the removal efficiency of the materials Life of media is also important along with removal efficiency and cost The sustainability of materials is very crucial for the overall performance of the system.

Multistage Constructed Wetland in the Treatment of Greywater under Tropical Conditions: Performance, Operation, and Maintenance

Greywater (GW) can be separated in different fractions where the kitchen component might be included. Constructed wetland (CW) systems are commonly used for the onsite treatment of GW, and the fraction treated might impact the performance, operation, and maintenance. These aspects are still poorly explored in the literature and are of importance for a proper design and system sustainability. In this study, a multi-stage household-scale CW system composed of a horizontal flow (HF), followed by a vertical flow (VF) unit, was monitored over 1330 days, focusing on different GW fractions and hydraulic and organic loading rates. The biochemical oxygen demand (BOD) was ~50% lower without the kitchen sink component (GWL) in the system inlet, while no drop was observed in the chemical oxygen demand (COD). Treatment with the GWL component caused a sudden drop in the hydraulic loading rate applied at the HF-CW (~114 to 35 mm per day) and the VF-CW (~230 to 70 mm per day). Even when the HF-CW received ~90 gCOD m−2 per day (GW), the multistage system reached a COD removal of 90%. The lower BOD load when treating GWL avoids clogging and decreases the frequency of maintenance. These variables can be used for the optimal design and operation of a CW, contributing with empirical data to CW guidelines in Brazil, and could additionally be expanded for application in other countries with similar climates.

Coupling transformation of carbon, nitrogen and sulfur in a long-term operated full-scale constructed wetland

The coupling transformation of carbon, nitrogen and sulfur compounds has been studied in lab-scale and pilot-scale constructed wetlands (CWs), but few studies investigated full-scale CW. In this study, we used batch experiments to investigate the potentials of carbon, nitrogen and sulfur transformation in a long-term operated, full-scale horizontal subsurface flow wetland. The sediments collected from the HSFW were incubated for 48 h in the laboratory with supplying various dosages of carbon, nitrogen and sulfur compounds. The results showed that heterotrophic denitrification was the main pathway. At the same time, the sulfide (S^2-)-based autotrophic denitrification was also present. Increasing TOC concentration or NO₃^- concentration could promote heterotrophic denitrification but did not inhibit the sulfide-based autotrophic denitrification. In our experiment, the highest NO₃^- removal via autotrophic denitrification was 25.23% while that via heterotrophic denitrification was 73.66%, leading to the total NO₃^- removal of 98.89%. The results also demonstrated that NO₃^- rather than NO₂^- was the preferable electron acceptor for both heterotrophic and sulfide-based autotrophic denitrification in the CW. Increasing S^2- concentrations promote NO₃^- removal from 12.99% to 25.23% without organic carbon, but varying NO₃^- or NO₂^- has no effects. These results indicated that concentrations of S^2-, instead of NO₃^- or NO₂^-, was the limiting factor for sulfide-based autotrophic denitrification in the studied CW. The microbial community analysis and correlation analysis between the transformation of carbon, nitrogen and sulfur compounds and relative abundance of bacteria further confirmed that in the CW, the key pathways coupling transformation were heterotrophic denitrification and sulfide-based autotrophic denitrification. Overall, the current study will enhance understanding of carbon, nitrogen, and sulfur transformation in CW and support better design and treatment efficiency.

Boosting pharmaceutical removal through aeration in constructed wetlands

This work evaluated the removal efficiency of 13 wastewater-borne pharmaceuticals in a pilot constructed wetland (CW) operated under different aeration strategies (no aeration, intermittent and continuous). Aeration improved the removal of conventional wastewater parameters and the targeted micropollutants, compared to the non-aerated treatment. Reduction of chemical oxygen demand (COD) and total nitrogen (TN) was slightly higher applying intermittent aeration than applying continuous aeration, the opposite was observed for the investigated pharmaceuticals. Seven targeted compounds were found in influent wastewater, and five of them (acetaminophen, diclofenac, ketoprofen, bezafibrate and gemfibrozil) were efficiently removed (> 83%) in the aerated systems. The overall risk of the investigated samples against aquatic ecosystems was moderate, decreasing in the order influent > no aeration > intermittent aeration > continuous aeration, based on the hazard quotient approach. Lorazepam, diclofenac and ketoprofen were the pharmaceuticals that could contribute the most to this potential environmental impact of the CW effluents after discharge. To the authors' knowledge this is the first sound study on the removal and fate of ketoprofen, bezafibrate, and lorazepam in aerated CWs, and provides additional evidence on the removal and fate of acetaminophen, diclofenac, gemfibrozil, and carbamazepine in this type of bioremediation systems at pilot plant scale.

Pharmaceutical compound removal efficiency by a small constructed wetland located in south Brazil

The fate of pharmaceuticals during the treatment of effluents is of major concern since they are not completely degraded and because of their persistence and mobility in environment. Indeed, even at low concentrations, they represent a risk to aquatic life and human health. In this work, fourteen pharmaceuticals were monitored in a constructed wetland wastewater treatment plants (WWTP) assessed in both influent and effluent samples. The basic water quality parameters were evaluated, and the removal efficiency of pharmaceutical, potential for bioaccumulation, and the impact of WWTP were assessed using Polar Organic Chemical Integrative Sampler (POCIS) and biofilms. The pharmaceutical compounds were quantified by High Performance Liquid chromatography coupled to mass spectrometry. The sampling campaign was carried out during winter (July/2018) and summer (January/2019). The WWTP performed well regarding the removal of TSS, COD, and BOD₅ and succeeded to eliminate a significant part of the organic and inorganic pollution present in domestic wastewater but has low efficiency regarding the removal of pharmaceutical compounds. Biofilms were shown to interact with pharmaceuticals and were reported to play a role in their capture from water. The antibiotics were reported to display a high risk for aquatic organisms.

Constructed wetland for improved wastewater management and increased water use efficiency in resource scarce SAT villages: a case study from Kothapally village, in India

Evaluation a field-scale of constructed wetland (CW) for the treatment of rural wastewater (WW), in resource-scarce semi-arid tropic (SAT) villages, to provide improved wastewater management and increased water use efficiency, was the main objective of this study. A CW was commissioned in Kothapally village of Telangana to treat the wastewater generated from 100 households. The CW was vegetated with Typha latifolia and Canna indica. Average COD, sulfate and inorganic nitrogen removal efficiencies observed were 65%, 60% and 67% respectively, for the study period (one year). Removal efficiency for total coliform was consistently above 80%. The treated wastewater was stored in a farm pond and was utilized for irrigation in the nearby agricultural fields (0.6 ha). This perennial source of water, helped the nearby farmers to cultivate two additional crops, chickpea during rabi and sweetcorn during summer. The assured availability of water reduced their vulnerability to dry spells during the kharif by providing means for lifesaving irrigation. The biomass harvested from the constructed wetland was used as fodder for the livestock. A net additional income of Rs.70,000 (∼US$1,000) was realized by the farmers using the treated wastewater for cultivation. Similar constructed wetland-based wastewater management system can be scaled up across water scarce semi-arid tropics. Novelty statementField-scale performance evaluation of constructed wetland based wastewater treatment in a semi-arid tropic village is scarce in the literature. The work presented gives a feasibility assessment for this technology critical for its wide-scale application to augment rural wastewater management in resource poor villages.

Aquatic Macrophytes in Constructed Wetlands: A Fight against Water Pollution

There is growing concern among health institutions worldwide to supply clean water to their populations, especially to more vulnerable communities. Although sewage treatment systems can remove most contaminants, they are not efficient at removing certain substances that can be detected in significant quantities even after standard treatments. Considering the necessity of perfecting techniques that can remove waterborne contaminants, constructed wetland systems have emerged as an effective bioremediation solution for degrading and removing contaminants. In spite of their environmentally friendly appearance and efficiency in treating residual waters, one of the limiting factors to structure efficient artificial wetlands is the choice of plant species that can both tolerate and remove contaminants. For sometimes, the chosen plants composing a system were not shown to increase wetland performance and became a problem since the biomass produced must have appropriated destination. We provide here an overview of the use and role of aquatic macrophytes in constructed wetland systems. The ability of plants to remove metals, pharmaceutical products, pesticides, cyanotoxins and nanoparticles in constructed wetlands were compared with the removal efficiency of non-planted systems, aiming to evaluate the capacity of plants to increase the removal efficiency of the systems. Moreover, this review also focuses on the management and destination of the biomass produced through natural processes of water filtration. The use of macrophytes in constructed wetlands represents a promising technology, mainly due to their efficiency of removal and the cost advantages of their implantation. However, the choice of plant species composing constructed wetlands should not be only based on the plant removal capacity since the introduction of invasive species can become an ecological problem.

Implementation of a full-scale constructed wetland to treat greywater from tourism in Suluban Uluwatu Beach, Bali, Indonesia

This original research examines a full-scale subsurface Constructed Wetland (CW) system in Indonesia, where most CW research has been limited to laboratory scale experiments. The CW system was located in Bali and built in 2015 in a single series formation. This study aims to demonstrate the performance of the system in treating greywater and examine the nutrient content plants' above-ground biomass. The CW was arranged in linear sequence composed of one unplanted (CW1) and five planted treatments of Iris pseudacorus (CW2), Caladium bicolor (CW3), Rhoe discolor (CW4), Sansevieria trifasciata (CW5) and Heliconia psittacorum (CW6). There has been little research on Caladium bicolor, Rhoe discolor and Sansevieria trifasciata in a full-scale CW application. Our results showed fluctuating efficiency (%) in the reduction of Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), Oil and Grease (O&G), Nitrate and Phosphate. The highest removal efficiency for CW1, CW2, CW3, CW4, CW5, CW6 were O&G (63.63%), BOD (90.66%), Nitrate (83.55%), BOD (80%), BOD (82.88%) and Phosphate (89.93%) respectively. After the experimental period, S. trifasciata and H. psittacorum experienced a decrease in Total N concentration, while H. psittacorum experienced a decrease in phosphate in above-ground biomass. Species of R. discolor, C. bicolor and I. pseudacorus showed good performance in terms of their growth and development. Although high removal efficiency was observed at certain times, this study showed the negative removal efficiencies at times among parameters as a consequence of the low Hydraulic Retention Time (HRT) and high Hydraulic Loading Rate (HLR).

Construction waste as substrate in vertical subsuperficial constructed wetlands treating organic matter, ibuprofenhene, acetaminophen and ethinylestradiol from low-strength synthetic wastewater

This study aimed to evaluate the removal of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), total ammonia nitrogen (TAN), total phosphorus (TP), ibuprofen, acetaminophen and ethinylestradiol of synthetic effluent simulating low-strength sewage by sequencing-batch mode constructed wetlands (CWs). To verify the feasibility of using a floating macrophyte in CWs and compare different substrates, three CWs containing light expanded clay aggregates (CWL), expanded clay with porcelain tiles (CWLP) and bricks (CWB) were planted with Pistia stratiotes. The results showed that CWB achieved the highest removals of TKN (78%), TAN (70%) and TP (46%), and CWLP achieved the highest COD removal (75%). LECA favored the removal of ibuprofen (92%, p < 0.05) when compared to bricks (77%), probably by the combination of biodegradation and sorption in the systems. The highest acetaminophen removal (71% to 96%) was observed in CWL, probably via biodegradation, but no significant differences were found between the CWs (p > 0.05). Ethinylestradiol was removed 76% in CWLP and 73% in CWB, both differing statistically from CWL (p < 0.05), demonstrating that brick and the combination of clay with porcelain were better than just clay in this hormone removal. After 188 days of operation, P. stratiotes was able to uptake nitrogen and phosphorus of approximately 0.28 g and 0.25 g in CWL, 0.33 g and 0.21 g CWLP, and 0.22 g and 0.09 g in CWB of, respectively. Adsorption of nitrogen and phosphorus onto the substrates was 0.48 g and 6.84 g in CWL, 0.53 g and 5.69 g in CWLP, and 0.36 g and 10.18 g in CWB, respectively. The findings on this study suggest that adsorption was possible the main process for TP removal onto the evaluated substrates whereas microbial activity was the most probable mechanism for TN removal in the evaluated CW systems.

Constructed Wetlands in Latin America and the Caribbean: A Review of Experiences during the Last Decade

The review aims to report the state-of-the-art constructed wetlands (CW) in the Latin America and Caribbean (LAC) region not limited to national and local conditions. The aim is with a broader view, to bring updated and sufficient information, to facilitate the use of the CW technology in the different countries of LAC. Thus, 520 experiences extracted from the 169 reviewed documents in 20 countries were analyzed. According to the data, horizontal subsurface flow wetlands are the most reported CW in the region (62%), the second most common CW technology in the region is free water surface CW (17%), then vertical flow systems (9%), followed by intensified constructed wetlands (8%), and finally French systems (4%). The performance for nutrient removal is analyzed, finding that the mean of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorous (TP) removal efficiencies varies from 65% to 83%, 55% to 72%, and 30% to 84%, respectively. The results suggest a generally good performance for COD and TN removal, but a low performance for TP removal. Regarding plant species used for CWs, 114 different plant species were reported, being until now the most extensive report about plant species used in CWs in the LAC region.

Performance of Iris pseudacorus and Typha domingensis for furosemide removal in a hydroponic system

The potential of Iris pseudacorus and Typha domingensis to remove the pharmaceutical active compound (PhAC) Furosemide from a nutrient solution was assessed. Both plants were exposed to 2 mg L^-1 of furosemide during 21 days and the removal of furosemide was monitored. Vessels without furosemide were also implemented as control systems for plants development. Likewise, unplanted vessels with furosemide were employed to assess abiotic removal mechanisms. All vessels were covered with aluminum foil to avoid photodegradation of the compound. Both plants showed potential to remove Furosemide, attaining, at the end of the experiment, a removal of 42.0-66.9% and 40.5-57.8%, for Typha and Iris, respectively. The plants do not presented a visible negative stress response to the exposure to furosemide, having a positive growth rate at the end of the experiment. Biodegradation seems to play an important role in furosemide removal, being enhanced by the presence of the plants. The two macrophytes presented different removal behaviors, particularly in the first 48 h of contact time. FUR removal by Iris follows a pseudo-first order while by Typha is divide in different phases. These results indicate that different plants species seem to have different mechanisms to remove pollutants from water.HighlightsPhACs removal potential of Iris pseudacorus and Typha domingensis was assessed.Plants were exposed to 2 mg L^-1 of furosemide during 21 days.Both macrophytes showed good removal efficiencies.Biodegradation of furosemide seems to be the main removal mechanism.Plants demonstrated different removal behavior along the experiment.Removal mechanisms of plants seem to differ between species.

Multiphasic assessment of effects of design configuration on nutrient removal in storing multiple-pond constructed wetlands

As an important technology for purifying and recycling agricultural wastewater, storing multiple-pond constructed wetlands (SMCWs) are widely used in the treatment of non-point source pollution. However, the influences of design configuration (surface area, volume, flow path, aspect ratio, water depth, percent vegetation cover and planting pattern) on pollution mitigation in SMCWs are still underexplored. To improve the sustainability of constructed wetlands, the removal performances of four groups of SMCWs were assessed through multiphasic analyses. The maximum removal efficiencies of nitrogen and phosphorus were 63.7% and 64.0%, respectively. Higher mass removal rates per square meter (MRR) and mass removal rates per cubic meter (MRR_V) were observed in ecological floating treatment wetlands (EFTWs). Compared with RE, the interception performances of deep-water SMCWs were more clearly described by using MRR and MRR_V. EFTWs with good plant configurations (mixed planting, 60-80% plant cover) were recommended in deep-water SMCWs (water depth > 1.5 m).

Effects of graywater on the growth and survival of ornamental plants in nature-based systems

The current paper investigates the development of two ornamental plants, canna lily (Canna x generalis) and giant horsetail (Equisetum giganteum), at both bench and pilot scale. Combinations of gravel-filled mesocosm, planted and unplanted (control), irrigated with light greywater (GW_L) or tap water (W_T), were used. Both species were able to grow under the tested conditions with no indication of toxicity that could affect the development. Irrigation with GW_L, resulted in higher evapotranspiration (2.2 mm-2.8 mm) in canna lily than giant horsetail (1.7 mm-2.3 mm) in mesocosm system. When the plants were mature and the season was more humid and warmer, canna lily and giant horsetail irrigated with GW_L evapotranspirated 69.23% and 30.77%, respectively as compared to the unplanted GW_L-irrigated-mesocosm. Principal components and cluster analysis identified similarity between evapotranspiration (ET) and the characteristics of the plants. Both species can thus be used in constructed wetlands taking into consideration elements such as the space available, level of water and solar incidence so as to allow the full development of the plants. The roots of giant horsetail require high water availability. Low solar incidence is indicated for giant horsetail, and the opposite for canna lily, if flowering is desired.

Role of Wetland Plants and Use of Ornamental Flowering Plants in Constructed Wetlands for Wastewater Treatment: A Review

The vegetation in constructed wetlands (CWs) plays an important role in wastewater treatment. Popularly, the common emergent plants in CWs have been vegetation of natural wetlands. However, there are ornamental flowering plants that have some physiological characteristics similar to the plants of natural wetlands that can stimulate the removal of pollutants in wastewater treatments; such importance in CWs is described here. A literature survey of 87 CWs from 21 countries showed that the four most commonly used flowering ornamental vegetation genera were Canna, Iris, Heliconia and Zantedeschia. In terms of geographical location, Canna spp. is commonly found in Asia, Zantedeschia spp. is frequent in Mexico (a country in North America), Iris is most commonly used in Asia, Europe and North America, and species of the Heliconia genus are commonly used in Asia and parts of the Americas (Mexico, Central and South America). This review also compares the use of ornamental plants versus natural wetland plants and systems without plants for removing pollutants (organic matter, nitrogen, nitrogen and phosphorous compounds). The removal efficiency was similar between flowering ornamental and natural wetland plants. However, pollutant removal was better when using ornamental plants than in unplanted CWs. The use of ornamental flowering plants in CWs is an excellent option, and efforts should be made to increase the adoption of these system types and use them in domiciliary, rural and urban areas.

Risk-Yuck Factor Nexus in Reclaimed Wastewater for Irrigation: Comparing Farmers’ Attitudes and Public Perception

The successes and failures of water reuse schemes are shaped by complex interrelationships between technological, economic, and socio-political factors. However, it has long been recognized that the main challenges to more effective water management are largely social rather than technical. This article reviews the recent literature (2007–2017) to analyze driving factors associated with farmers’ concerns and public perception of reclaimed wastewater for irrigation. The aim of the paper is to synthetize how both environmental and health risks and the yuck factor could be addressed in order to promote mutual understanding between farmers and the public. Results show: (1) how farmers and the public perceive environmental and health risks in a similar way, (2) how the yuck factor is more noticeable for the public than farmers, and (3) how constructed wetlands, reclaimed water exchange consortiums, product certification, and direct site visits to water reuse infrastructure could be promoted in order to foster understanding between farmers and the public. The article concludes by providing key research questions for managers and public authorities relating to how to focus on the study of technical and social issues related to water reuse.

Performance of different substrates in constructed wetlands planted with E. crassipes treating low-strength sewage under subtropical conditions

The present study aimed to assess removal potential of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), total ammonia nitrogen (TAN), total phosphorus (TP) and acetylsalicylic acid (ASA) in synthetic wastewater simulating low-strength sewage by sequencing-batch mode constructed wetlands (CWs). Six CWs with three substrates (gravel, light expanded clay and clay bricks) and one CW of each substrate was planted with E. crassipes to verify the feasibility of using a floating macrophyte in CWs and verify the best optimized substrate. Results showed that the presence of E. crassipes enhanced the removal of COD for systems with gravel, increasing the removal efficiency from 37% in the unplanted system (CW_G-U) to 60% in the planted system (CW_G-P). The vegetated CW with clay bricks (CW_B-P) presented the best performance for both TKN and TAN removal, with maximum removal efficiencies of 68% and 35%, respectively. Phosphorus was observed to be efficiently removed in systems with clay bricks, both planted (CW_B-U) and unplanted (CW_B-P), with mean removal efficiencies of 82% and 87%, respectively, probably via adsorption. It was also observed that after 296days of operation, no desorption or increase on phosphorus in effluent samples were observed, thus indicating that the material was not yet saturated and phosphorus probably presents a strong binding to the media. ASA removal efficiency varied from 34% to 92% in CWs, probably due to plant uptake through roots and microbial biodegradation. Plant direct uptake varied from 4 to 74% of the total nitrogen and from 26 to 71% of the total phosphorus removed in CW_G-P, CW_C-P and CW_B-P. E. crassipes was able to uptake up to 4.19g of phosphorus in CW_C-P and 11.84g of nitrogen in CW_B-P. The findings on this study suggest that E. crassipes could be used in CWs and clay bricks could significantly enhance phosphorus removal capacity in CWs.

Enhanced Nutrients Removal Using Reeds Straw as Carbon Source in a Laboratory Scale Constructed Wetland

The low carbon/nitrogen (C/N) ratio and high nitrate content characteristics of agricultural runoff restricted the nitrogen removal in constructed wetlands (CWs). To resolve such problems, the economically- and easily-obtained Phragmites Australis (reeds) litters were applied and packed in the surface layer of a surface flow CW as external carbon sources. The results demonstrated that the introduction of the reeds straw increased the C concentration as a result of their decomposition during the CW operation, which will help the denitrification in the ensuing operation of an entire 148 days. The total nitrogen (TN) and Chemical Oxygen Demand (COD) () in the effluent reached the peak level of 63.2 mg/L and 83 mg/L at the fourth and the second day, respectively. Subsequently, the pollutants in the CW that were filled with straw decreased rapidly and achieved a stable removal after 13 days of operation. Moreover, the present study showed that the N removal efficiency increased with the increase of the hydraulic retention time (HRT). Under the HRT of four days, the CW presented 74.1 ± 6%, 87.4 ± 6% and 56.0 ± 6% removal for TN, NO₃^-, and TP, respectively.

Constructed wetlands and solar-driven disinfection technologies for sustainable wastewater treatment and reclamation in rural India: SWINGS project

SWINGS was a cooperation project between the European Union and India, aiming at implementing state of the art low-cost technologies for the treatment and reuse of domestic wastewater in rural areas of India. The largest wastewater treatment plant consists of a high-rate anaerobic system, followed by vertical and horizontal subsurface flow constructed wetlands with a treatment area of around 1,900 m² and a final step consisting of solar-driven anodic oxidation (AO) and ultraviolet (UV) disinfection units allowing direct reuse of the treated water. The implementation and operation of two pilot plants in north (Aligarh Muslim University, AMU) and central India (Indira Gandhi National Tribal University, IGNTU) are shown in this study. The overall performance of AMU pilot plant during the first 7 months of operation showed organic matter removal efficiencies of 87% total suspended solids, 95% 5-day biological oxygen demand (BOD₅) and 90% chemical oxygen demand, while Kjeldahl nitrogen removal reached 89%. The UV disinfection unit produces water for irrigation and toilet flushing with pathogenic indicator bacteria well below WHO guidelines. On the other hand, the AO disinfection unit implemented at IGNTU and operated for almost a year has been shown to produce an effluent of sufficient quality to be reused by the local population for agriculture and irrigation.