Types Of Constructed Wetlands Research Articles

Greenhouse gases emissions and carbon budget estimation in horizontal subsurface flow constructed wetlands with different plant species

Constructed wetlands (CWs) are pivotal for wastewater treatment due to their high efficiency and numerous advantages. The impact of plant species and diversity on greenhouse gas (GHG) emissions from CWs requires a more comprehensive evaluation. Moreover, controversial perspectives persist about whether CWs function as carbon sinks or sources. In this study, horizontal subsurface flow (HSSF) CWs vegetated with Cyperus alternifolius, Typhae latifolia, Acorus calamus, and the mixture of these three species were constructed to evaluate pollutant removal efficiencies and GHG emissions, and estimate carbon budgets. Polyculture CWs can stably remove COD (86.79 %), NH4+-N (97.41 %), NO3−-N (98.55 %), and TP (98.48 %). They also mitigated global warming potential (GWP) by suppressing N2O emissions compared with monoculture CWs. The highest abundance of the Pseudogulbenkiania genus, crucial for denitrification, was observed in polyculture CWs, indicating that denitrification dominated in nitrogen removal. While the highest nosZ copy numbers were observed in CWs vegetated with Cyperus alternifolius, suggesting its facilitation of denitrification-related microbes. Selecting Cyperus alternifolius to increase species diversity is proposed for simultaneously maintaining the water purification capacity and reducing GHG emissions. Carbon budget estimations revealed that all four types of HSSF CWs were carbon sinks after six months of operation, with carbon accumulation capacity of 4.90 ± 1.50 (Cyperus alternifolius), 3.31 ± 2.01 (Typhae latifola), 1.78 ± 1.30 (Acorus calamus), and 2.12 ± 0.88 (polyculture) kg C/m2/yr. This study implies that under these operation conditions, CWs function as carbon sinks rather than sources, aligning with carbon peak and neutrality objectives and presenting significant potential for carbon reduction efforts.

Promoting Aquatic Health in Constructed Wetlands: Removal of Pathogens and Nitrogen

Due to urbanization and population growth, freshwater resources have become a long-term concern for most developing countries. With the growth of population, the demand for fresh water is increasing and the requirement for sewage treatment is also increasing. In recent years, the demand for sewage recycling has increased sharply. Constructed wetlands (CWs) are an effective sewage treatment system with low energy consumption, minimal maintenance requirements, and a low operation cost, which will meet the current demand for the removal of nutrients and pathogens. The application of CWs in sewage treatment has attracted more and more attention because it is also a nature-based solution (NbS). These systems are capable of removing not only nitrogen (N) and phosphorus (P), but also pathogen indicators, such as fecal coliform and Escherichia coli. The presence of these indicators also suggests the influx of other pathogens into aquatic systems, thereby threatening aquatic ecological health. However, research on the removal of pathogens in CWs is relatively scare and their removal mechanisms are not fully understood. Despite their widespread application, the role of plants in CWs, particularly in the specific mechanism of pathogens and nitrogen removal, remains largely unknown. This article will help us to better understand this technology and provide help for our further research. In this paper, the coupled denitrification mechanism between microorganisms and plants in the process of nitrogen transformation was discussed. Plants affect nitrogen transformation microorganisms by releasing oxygen and secretions from their roots and provide substrates for bioremediation. The removal effects of different types of CWs on pathogen and nitrogen species were also summarized. Overall, the removal effect of subsurface flow wetlands outperforms that of surface flow wetlands, with multi-stage wetland systems being the most effective. The main factors affecting the removal of pathogens and nitrogen species in CWs include plants, substrates, operating parameters, UV radiation, temperature, water composition, and pH. Finally, the research frontiers on the removal of pathogens in CWs were prospected.

The comparison between different types of constructed wetlands for biochemical oxygen demand removal efficiency

This research shows efficiency of constructed wetlands (CWs) to purify waste water in the case of Biochemical Oxygen Demand (BOD). CWs such as surface flow (SF), subsurface flow (SSF), and hybrid (HYB) systems have been compared to provide an analysis about which system has better performance for BOD removal efficiency. Data were collected from different scientific articles and from all over the world. Meta-analysis technique was employed to aggregate data from scientific sources, facilitating hypothesis testing, and comparisons between different types of CWs. All the systems of CWs show satisfactory removal efficiency. HYB systems are shown to be the most efficient. One-way analysis of variance (ANOVA) has been applied to analyze differences between respective CWs using R software. It shows that there is a statistically significant difference between different types of CWs. Post-hoc Tukey?s Honestly Significant Different (HSD) analysis demonstrates a statistically significant difference between SF and HYB systems in the case of BOD removal efficiency. Also, Post-hoc Tukey?s HSD shows statistically significant difference between SSF and SF CWs. On the other hand, Post-hoc Tukey?s HSD does not show statistically significant difference between HYB and SSF CWs. The significant reduction rates for BOD removal efficiency, demonstrates that CWs can be used to diminish this kind of pollution.

Opposite response of constructed wetland performance in nitrogen and phosphorus removal to short and long terms of operation

Constructed wetlands (CWs) have been widely used for treating polluted water since the 1950s, with applications in over 50 countries worldwide. Most studies investigating the pollutant removal efficiency of these wetlands have focused on differences among wetland designs, operation strategies, and environmental conditions. However, there still remains a gap in understanding the variation in wetland pollutant removal efficiency over different time scales. Therefore, the main aim of the study is to address this gap by conducting a global meta-analysis to estimate the variation in nitrogen (N) and phosphorus (P) removal by wetland in short- and long-term pollutant treatment. The findings of this study indicated that the total efficiencies of N and P removal increased during short-term wetland operation but decreased during long-term operation. However, for surface flow CWs specifically, the efficiencies of N and P removal increased during short-term operation and remained stable during long-term operation. Moreover, the study discovered that wetland N removal efficiency was influenced by seasons, with an increase in spring and summer and a decrease in autumn and winter. Conversely, there was no significant seasonal effect on P removal efficiency. Additionally, high hydraulic load impaired wetland N and P removal efficiency during long-term operation. This study offers a critical review of the role of wetlands in wastewater treatment and provides valuable reference data for the design and selection of CWs types during wastewater treatment in the aspect of sustainability.

Microbiota and genetic potential for reducing nitrous oxide emissions by biochar in constructed wetlands

The denitrification process in constructed wetlands (CWs) is responsible for most of the nitrous oxide (N2O) emissions, which is an undesired impact on the ecology of sewage treatment systems. This study compared three types of CWs filled with gravel (CW-B), gravel mixed with natural pyrite (CW-BF), or biochar (CW-BC) to investigate their impact on microbiota and genetic potential for N2O generation during denitrification under varying chemical oxygen demand (COD) to nitrate (NO3−-N) ratios. The results showed that natural pyrite and biochar were superior in enhancing COD (90.6–91.2 %) and NO3−-N removal (90.0–93.5 %) in CWs with a COD/NO3−-N ratio of 9. The accumulation of NO2−-N during the denitrification process was the primary cause of N2O emission, with the fluxes ranging from 95.6–472.0 μg/(m2·h) in CW-B, 92.9–400 μg/(m2·h) in CW-BF, and 54.0–293.3 μg/(m2·h) in CW-BC. The addition of biochar significantly reduced N2O emissions during denitrification, while natural pyrite had a lesser inhibitory effect on N2O emissions. The three types of substrates also influenced the structure of microbiota in the biofilm, with natural pyrite enriched nitrogen transformation microorganisms, especially for denitrifiers. Notably, biochar significantly enhanced the abundance of nosZ and the ratio of nosZ/(norB + norC), which are critical factors in reducing N2O emissions from CWs. Overall, the results suggest that the biochar-induced changes in microbiota and genetic potential during denitrification play a significant role in preventing N2O production in CWs, especially when treating sewage with a relatively high COD/NO3−-N ratio.

A REVIEW ON PHYTOREMEDIATION POTENTIAL OF CANNA SPECIES FOR WASTEWATER TREATMENT

Globally, contamination of water is a serious environmental issue which necessitates continuous attention and remediation. The demand for good quality water is increasing so it becomes essential to promote the cost effective and sustainable wastewater treatment technologies like phytoremediation by using constructed wetlands (CWs). This review focused to investigate the phytoremediation efficiency of Canna species for the treatment of wastewater originated from different sources, by using different type of CWs around the world. It includes 33 research studies reported in the literature, for the phytoremediation of wastewater. Canna species performed well under different experimental conditions and recommended for the remediation of water and wastewater.

Fifteen-year analysis of constructed wetland clogging: A critical review

Clogging has attracted increasing attention as one of the key problems affecting the development and application of constructed wetland (CW) technology. However, there is a lack of systematic research on the evolution history, hot spots, frontiers and direction classification of CW clogging, lack of research papers on how to effectively solve clogging, and some mixed use in methods and concepts. To bridge these research gaps, this systematic and in-depth review was conducted using published references and analyses and the visualization software CiteSpace based on 15 years of literature research. Keyword cluster and reference co-cited analyses were conducted. Hotspot directions and cutting-edge development trends of CW clogging fields were obtained. Some methods discussed in this review could not only be used to monitor but also evaluate CW clogging. The boundaries and usage of monitoring and evaluation have not been studied before, which can lead to potential inconsistencies in classification standards in the future. Therefore, the differences and definitions are based on comprehensive and in-depth analyses and considerations. The existing literature is classified based on three aspects: mechanism, monitoring and evaluation, and solutions. Specific analyses and assessments were also conducted on the progress and cutting-edge development trends in these three directions. • “CiteSpace” is used to conduct a comprehensive study on clogging occurs in constructed wetland (CW). • Knowledge structure, historical evolution, and cutting-edge trends of CW clogging are revealed based on a 15-year analysis. • Wastewater treatment, solids accumulation, and flow, etc., are the hotspots of CW clogging research in recent years. • The mechanism, monitoring and evaluation, and solutions to solve CW clogging was discussed, respectively. • A new type of promising modular CW is proposed for the first time, which can effectively solve the clogging problem.

Various Types of Constructed Wetland for Wastewater Treatment-A Review

As per the World Health Organization 80% of wastewater is released to the environment without satisfactory treatment. Constructed Wetlands (CWs) are one of the natural wastewater (WW) treatment methods. CWs have been recommended as a low technology, low maintenance, low operation cost, and green technology wastewater treatment system. Many types of CWs are currently in use. This paper studies these different types based on the climate, area, base materials, temperature, contaminant removal efficiency, removal mechanism and physicochemical analysis of various wastewater parameters. It is found that wetlands are successful in removing organic matter–Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD) and suspended solids and nutrients–total Nitrogen (TN) and total Phosphorus (TP). CWs need to be studied as a promising solution not only for effective treatment of wastewater but also as an economical method to improve the fertility of soil. Further, the paper discusses the scope of future research in CW to further improve the wastewater treatment technology.

Wastewater Pretreatment Methods for Constructed Wetland: A Review

The constructed wetland (CW) performance depends on constructed wetland, bed media, and vegetation variations. This study represents a descriptive review of wastewater methods for wetland construction. The wastewater generation includes dairy waste, textile waste, piggery waste, petrochemical waste, tannery waste, etc. This review summarizes constructed wetlands variations, including vegetation, efficiency removal, maintenance, and construction cost. The fundamental definition of CW is that it is an eco-friendly technique to remove the pollutants from the wastewater and is mostly used by petroleum refineries, municipalities, the drainage system of agriculture and so on. Earlier, multiple innovations in the microbiology field eventually correlated with wastewater contaminants removal techniques. This review provides a brief review of the CW key aspects, like the CW types, challenges, opportunities, applications, materials, the recent advances. It also covers the current-technical advancement evaluation report and frames the unsolved CW problems. The terminology on the performance metric demonstrates that the CW community is growing rapidly. This manuscript has also mentioned an outline of the future trends and research proposals.

Particularities of Fungicides and Factors Affecting Their Fate and Removal Efficacy: A Review

Systemic fungicide use has increased over the last decades, despite the susceptibility of resistance development and the side effects to human health and the environment. Although herbicides and insecticides are detected more frequently in environmental samples, there are many fungicides that have the ability to enter water bodies due to their physicochemical properties and their increasing use. Key factors affecting fungicide fate in the environment have been discussed, including the non-target effects of fungicides. For instance, fungicides are associated with the steep decline in bumblebee populations. Secondary actions of certain fungicides on plants have also been reported recently. In addition, the use of alternative eco-friendly disease management approaches has been described. Constructed Wetlands (CWs) comprise an environmentally friendly, low cost, and efficient fungicide remediation technique. Fungicide removal within CWs is dependent on plant uptake and metabolism, absorption in porous media and soil, hydrolysis, photodegradation, and biodegradation. Factors related to the efficacy of CWs on the removal of fungicides, such as the type of CW, plant species, and the physicochemical parameters of fungicides, are also discussed in this paper. There are low-environmental-risk fungicides, phytohormones and other compounds, which could improve the removal performance of CW vegetation. In addition, specific parameters such as the multiple modes of action of fungicides, side effects on substrate microbial communities and endophytes, and plant physiological response were also studied. Prospects and challenges for future research are suggested under the prism of reducing the risk related to fungicides and enhancing CW performance.

Microbial Communities and Nitrogen Transformation in Constructed Wetlands Treating Stormwater Runoff

Microbial communities play a vital role in nitrogen (N) removal in constructed wetlands (CWs). However, the lack of studies on microbial characteristics of wetland systems designed to treat stormwater demonstrates the importance of comprehensive investigation on microbial response to wetland fluctuations. Moreover, the observed inconsistency in N removal, and detected links between microbial shifts and wetland water level fluctuations is an area of research interest perculiar to stormwater applications. This study surveyed nearly 150 publications to provide a summary and evaluation of N removal efficiency in different types of CWs where microbial communities and their behavior have been correlated to regulating factors. Factors such as flow regime, plants, and physico-chemical properties (e.g., temperature, dissolved oxygen, pH, and nitrogen concentration) were found to significantly influence microbial diversity and composition. Although many studies have analyzed microbial N removal, a majority conducted their studies in bioretention systems. Accordingly, some of the microbial pathways in CWs designed for stormwater treatment have not been investigated. As such, it is suggested that pathways, such as dissimilatory nitrate reduction to ammonium (DNRA) and comammox activity and their changes over dry-wet cycles in stormwater constructed wetlands be investigated. This information could assist engineers to take advantage of the presence of other N transforming communities which could improve microbial diversity within wetland systems. Moreover, it is recommended to track microbial functional genes and their changes over wetland water fluctuation to develop an ecosystem with conditions favorable for microbial pathways with higher N removal potential. In conclusion, the findings of the current literature review reinforce the importance of stormwater runoff treatment and the implementation of new design strategies that are able to enhance microbial activity and diversity leading to a better treatment outcome.

The Historical Development of Constructed Wetlands for Wastewater Treatment

Constructed wetlands (CWs) for wastewater treatment are engineered systems that are designed and operated in order to use all natural processes involved in the removal of pollutants from wastewaters. CWs are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment. The basic classification is based on the presence/absence of wastewater on the wetland surface. The subsurface flow of CWs can be classified according to the direction of the flow to horizontal and vertical. The combination of various types of CWs is called hybrid CW. The CWs technology began in the 1950s in Germany, but the major extension across the world occurred during the 1990s and early 2000s. The early CWs in Germany were designed as hybrid CWs; however, during the 1970s and 1980s, horizontal subsurface flow CWs were mostly designed. The stricter limits for nitrogen, and especially ammonia, applied in Europe during the 1990s, brought more attention to vertical subsurface flow and hybrid systems. Constructed wetlands have been used to treat various types of wastewater, including sewage, industrial and agricultural wastewaters, various drainage and runoff waters and landfill leachate. Recently, more attention has also been paid to constructed treatment wetlands as part of a circular economy in the urban environments: it is clear that CWs are a good fit for the new concept of sponge cities.

Potential Use of Constructed Wetland Systems for Rural Sanitation and Wastewater Reuse in Agriculture in the Moroccan Context

Located in a semi-arid to arid region, Morocco is confronting increasing water scarcity challenges. In the circular economy paradigm, the reuse of treated wastewater in agriculture is currently considered a possible solution to mitigate water shortage and pollution problems. In recent years, Morocco has made significative progress in urban wastewater treatment under the National Wastewater Program (PNA). However, rural sanitation has undergone significant delays. Therefore, an alternative technology for wastewater treatment and reuse in rural areas is investigated in this review, considering the region’s economic, social, and regulatory characteristics. Constructed wetlands (CWs) are a simple, sustainable, and cost-effective technology that has yet to be fully explored in Morocco. CWs, indeed, appear to be suitable for the treatment and reuse of wastewater in remote rural areas if they can produce effluent that meets the standards of agricultural irrigation. In this review, 29 studies covering 16 countries and different types of wastewater were collected and studied to assess the treatment efficiency of different types of CWs under different design and operational parameters, as well as their potential application in agricultural reuse. The results demonstrated that the removal efficiency of conventional contamination such as organic matter and suspended solids is generally high. CWs also demonstrated a remarkable capacity to remove heavy metals and emerging contaminants such as pharmaceuticals, care products, etc. The removal of microbial contamination, on the other hand, is challenging, and does not satisfy the standards all the time. However, it can be improved using hybrid constructed wetlands or by adding polishing treatment. In addition, several studies reported that CWs managed to produce effluent that met the requirements of wastewater reuse in agriculture of different countries or organisations including Morocco.

A Review on Constructed Treatment Wetlands for Removal of Pollutants in the Agricultural Runoff

Constructed wetland (CW) is a popular sustainable best management practice for treating different wastewaters. While there are many articles on the removal of pollutants from different wastewaters, a comprehensive and critical review on the removal of pollutants other than nutrients that occur in agricultural field runoff and wastewater from animal facilities, including pesticides, insecticides, veterinary medicine, and antimicrobial-resistant genes are currently unavailable. Consequently, this paper summarized recent findings on the occurrence of such pollutants in the agricultural runoff water, their removal by different wetlands (surface flow, subsurface horizontal flow, subsurface vertical flow, and hybrid), and removal mechanisms, and analyzed the factors that affect the removal. The information is then used to highlight the current research gaps and needs for resilient and sustainable treatment systems. Factors, including contaminant property, aeration, type, and design of CWs, hydraulic parameters, substrate medium, and vegetation, impact the removal performance of the CWs. Hydraulic loading of 10–30 cm/d and hydraulic retention of 6–8 days were found to be optimal for the removal of agricultural pollutants from wetlands. The pollutants in agricultural wastewater, excluding nutrients and sediment, and their treatment utilizing different nature-based solutions, such as wetlands, are understudied, implying the need for more of such studies. This study reinforced the notion that wetlands are effective for treating agricultural wastewater (removal > 90%) but several research questions remain unanswered. More long-term research in the actual field utilizing environmentally relevant concentrations to seek actual impacts of weather, plants, substrates, hydrology, and other design parameters, such as aeration and layout of wetland cells on the removal of pollutants, are needed.

Recent advances on the removal of phosphorus in aquatic plant-based systems

Phosphorus (P) is a vital nutrient for the ecosystems and its excess in wastewater streams leads to some environmental issues such as extensive algae growth (eutrophication). Phytoremediation is a green technology that is based on the combined actions of plants and their associated microbial groups to remove and transfer the toxic compounds in surface water, groundwater and soil. Aquatic plants are widely used for the remediation of contaminated rivers, eutrophic lakes, and other water bodies. In the past three decades, free-floating, submerged, emergent macrophytes and microalgae species have been used for P removal in aquatic plant-based systems such as constructed wetlands (CWs). This paper reviews the recent studies on the potential of aquatic plants such as free-floating, submerged, and emergent plants, and also microalgae for removal of P in different types of wastewaters. Several parameters such as plant species, hydraulic retention time, temperature, type of CWs, effluent concentration, and seasonal changes have effects on P removal. Based on the findings, some of the species such as Azolla and water hyacinth had the highest uptake ability up to 90% while algae species such as Chlorella showed about 70% of P removal. In addition, the mixed culture of aquatic plants can increase P removal if the interaction of the species is considered before cultivation in CWs. • The potential of different aquatic plants on phosphorous (P) removal is reviewed. • Azolla and water hyacinth had the highest P removal ability. • The algae are sensitive to the low P effluent concentration and the removal is quite low. • Submerged and emergent plants showed different removal patterns in P removal. • The recovered P can be used in beneficial applications such as biofertilizers.

Wastewater Treatment Using Constructed Wetland: Current Trends and Future Potential

Constructed wetlands (CW) is an environmentally friendly technique for removing pollutants from wastewater and has been applied to municipal wastewater, petroleum refinery wastewater, agriculture drainage, acid mine drainage, etc. The past decade has seen a remarkable number of innovations in the exponentially growing field of microbiology. This manuscript covers a critical review of key aspects of CW, such as various types of CW, the contaminants and their removal mechanisms, degradation pathways, challenges and opportunities, materials, applications, and theory with a focus on recent advances in the last three decades. In addition, an attempt has been taken to project future advances in the field of CW and facilitate these advances by framing key unsolved problems in CW. Guidelines are prepared for the fast-growing CW field through the standardization of key design aspects. This review covers the evaluation of the current state-of-the-art of CW technology and provides definitions and performance metric nomenclature in an effort to unify the fast-growing CW community. It also contains an outlook on the emerging trends in CW and proposes future research and development directions.

Effects of selection and compiling strategy of substrates in column-type vertical-flow constructed wetlands on the treatment of synthetic landfill leachate containing bisphenol A.

A constructed wetland (CW) is a low-cost, eco-friendly, easy-to-maintain, and widely applicable technology for treating various pollutants in the waste landfill leachate. This study determined the effects of the selection and compiling strategy of substrates used in CWs on the treatment performance of a synthetic leachate containing bisphenol A (BPA) as a representative recalcitrant pollutant. We operated five types of lab-scale vertical-flow CWs using only gravel (CW1), a sandwich of gravel with activated carbon (CW2) or brick crumbs (CW3), and two-stage hybrid CWs using gravel in one column and activated carbon (CW4) or brick crumbs (CW5) in another to treat synthetic leachate containing BPA in a 7-d sequential batch mode for 5 weeks. CWs using activated carbon (CW2 and CW4) effectively removed ammonium nitrogen (NH4-N) (99-100%), chemical oxygen demand (COD) (93-100%), and BPA (100%), indicating that the high adsorption capacity of activated carbon was the main mechanism involved in their removal. CW5 also exhibited higher pollutant removal efficiencies (NH4-N: 94-99%, COD: 89-98%, BPA: 89-100%) than single-column CWs (CW1 and CW3) (NH4-N: 76-100%, COD: 84-100%, BPA: 51-100%). This indicates the importance of the compiling strategy along with the selection of an appropriate substrate to improve the pollutant removal capability of CWs.

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.

Efficiency and plant indication of nitrogen and phosphorus removal in constructed wetlands: A field-scale study in a frost-free area

Frost-free areas have suitable climate for wetland plant growth and constructed wetlands (CW) technology. Information on the quantification of plant biomass and uptake efficiency in field-scale CWs is limited in these climates. The removal efficiency of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and total suspended solids (TSS) in wastewater from sewage plants, domestic sewage, and an industrial park in 15 rural and urban CWs in Guangdong Province, China, with an average temperature of 30 °C was evaluated. The effects of influent concentration, hydraulic load, the wastewater's physicochemical properties, operating conditions, and plant uptake were analysed. The mean removal rates were 40.0%, 45.2%, 41.1%, and 71.7% for TN, TP, COD, and TSS, respectively, which were higher than the removal load of the field-scale CWs in temperate regions. Removal loads of TN, TP, COD, and TSS were highest in CWs that have been operating for 5–6 years, treating wastewater volumes of over 1 m3/m2·d. The removal efficiency was mainly related to the inflow concentration and less affected by the type of CWs. Nutrient accumulation trends were primarily linked to influent concentrations (TN: r2 = 0.89, P = 0.007; TP: r2 = 0.96, P = 0.001) and plant biomass (TN: r2 = 0.96, P = 0.001; TP: r2 = 0.92, P = 0.004). Plant biomass contributed 2%–29% and 2%–70%, respectively, to removing N and P in CWs. The average uptake concentration of N and P in aboveground plant organs (15.66 ± 4.44 mg N/g, 2.15 ± 1.18 mg P/g) was generally higher than that of other temperate plants. A strong relationship between TN and TP in the biomass was also observed; however, the relationship is only restricted by the influent TP concentration. Arundo donax is well-adapted for nutrient accumulation and adaptation and is an ideal wetland plant to purify wastewater in frost-free climates.

Performance of horizontal flow constructed wetland for secondary treatment of domestic wastewater in a remote tribal area of Central India

The purification of the primary treated domestic sewage was performed in the present study through the horizontal sub-surface flow constructed wetland (CW) of 10 × 3.5 m dimension. The study was performed using three setups of CW 1 (Unplanted CW), CW 2 (CW planted with macrophyte Typha latifolia), and CW 3 (CW planted with two species of macrophyte T. latifolia and Commelina benghalensis). The purification experiments were performed by converting one type of CW into the other form sequentially, i.e., CW 1 was built first and after the experiments, it was converted into CW 2 and then CW 3. The CW was filled with a layer of coarse and fine gravel of 70 cm depth as filter media in 1:2 ratio. Each set of wetland was operated for 3 months (12 wk) during which the treatment performance of wetlands for basic physicochemical parameters was evaluated. The CW was operated in continuous mode at an average hydraulic loading rate of 250 L h− 1 and the treated effluent was analysed twice every week at four different sampling points having hydraulic retention times (HRT) of 12, 24, 36 and 48 h for important sewage quality parameters All the three setups of CW were able to clean the primary treated sewage significantly. Among the three sets of wetlands used, CW 3 was the best performer removing 79, 77, 79, 79, and 78% of biochemical oxygen demand, chemical oxygen demand, nitrate, ammonia, and phosphate respectively in 48 h HRT. Among the three sets of wetlands, the CW 3 removed the highest percent of total coliforms, fecal coliforms, and E. coli as 64, 61 and 52% respectively.