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Horizontal Sub-Surface Flow and Hybrid Constructed Wetlands Systems for Wastewater Treatment

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Abstract

The first experiments using wetland macrophytes for wastewater treatment were carried by out by Käthe Seidel in Germany in early 1950s. The horizontal sub-surface flow constructed wetlands (HF CWs) were initiated by Seidel in the early 1960s and improved by Reinhold Kickuth under the name Root Zone Method in late 1960s and early 1970s and spread throughout Europe in 1980s and 1990s. However, cohesive soils proposed by Kickuth got clogged very quickly because of low hydraulic permeability and were replaced by more porous media such as gravel in late 1980s in the United Kingdom and this design feature is still used. In fact, the use of porous media with high hydraulic conductivity was originally proposed by Seidel. HF CWs provide high removal of organics and suspended solids but removal of nutrients is low. Removal of nitrogen is limited by anoxic/anaerobic conditions in filtration beds which do not allow for ammonia nitrification. Phosphorus removal is restricted by the use of filter materials (pea gravel, crushed rock) with low sorption capacity. Various types of constructed wetlands may be combined in order to achieve higher treatment effect, especially for nitrogen. However, hybrid systems are comprised most frequently of vertical flow (VF) and HF systems arranged in a staged manner. HF systems cannot provide nitrification because of their limited oxygen transfer capacity. VF systems, on the other hand, do provide a good conditions for nitrification but no denitrification occurs in these systems. In hybrid systems (also sometimes called combined systems) the advantages of the HF and VF systems can be combined to complement processes in each system to produce an effluent low in BOD, which is fully nitrified and partly denitrified and hence has a much lower total-N outflow concentrations.

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... Meanwhile, HFCWs have shown slightly lower removal efficiency of phosphorus and careful consideration for media selection should be taken into account to ensure better removal efficiency [10]. Effective pretreatment of wastewater is deemed necessary in the case of HFWCs due to the potential accumulation of leading solids, which may result in bed clogging [21]. ...
... VFCWs are very effective in treating organics and suspended solids due to the oxidation reduction environment as well as the flow distribution [18]. Contrary to HFCWs, VFCWs are a good option in case of limited land availability [10] and normally preferred in cases of domestic and industrial wastewaters, where they provide enough and reasonable treatment for organic, nitrogen, phosphorus, pathogen removal and solids due to the microbial activity as well as the oxidation reduction environment they provide [9,15,21,26]. One of the design considerations in the case of VFCWs is the proper selection of wetland media where to avoid clogging. ...
... Extra attention should be paid towards proper media selection as well as pre-treatment processes to ensure even distribution of the wastewater across the wetland surface whilst carefully selecting the optimum hydraulic loading rate. The hydraulic loading rate is defined as the rate at which wastewater is being discharged to the CW treatment system, expressed in depth (or volume) of water per unit area per unit time [21,28,29]. Moreover, another drawback of the VCW compared to the HCW is the heterogenous nature of the influent over the bed, which results in various treatment efficiencies compared to the HWC [30]. ...
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Article
There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.
... In Vermont (USA), Lee et al. (2010) used an integrated system to treat DWW, obtaining a BOD 5 removal rate of 89.0%. As stated by Kadlec et al. (2000) and Vymazal (2005), the main removal processes of BOD 5 and COD in the HSSFs CW are anaerobic degradation, filtration and sedimentation, which depend on the activities of plants, microorganisms and substrates and their interaction. However, the high performance of this system is related to the type of DWW pretreatment, size of the CW, organic loading rate of BOD 5 and presence of monocultures or polycultures in the CW, for example. ...
... However, the findings were consistent with those obtained by Mantovi et al. (2003) and Gorra et al. (2014) in Italy, which were in the range of 40-50.0%. Vymazal (2005) states that the most important removal mechanism of N in an HSSFs is nitrification/denitrification. However, the same author affirms that oxygenation of the rhizosphere is often insufficient and, therefore, incomplete nitrification leads to limited N removal. ...
... The Arundo donax-unit showed higher patogen removal than the Cyperus alternifolius-unit in all samples. As well explained in previous studies (Kadlec et al., 2000;Vymazal, 2005;El-Khateeb et al., 2009;Wu et al., 2016), the high E. coli, TC, FC and FS removal rates in the HSSFs CW can be explained by considering the combination of physical, chemical and biological processes carried out by the plants, nematodes, viruses, bacteria and the effect of high oxygen levels in the root area. ...
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Constructed wetland systems provide the ideal solution for small and medium dairy farms as they can be built close to the farm and are easy to manage and use. However, their perfomance is significantly affected by vegetation activity during the year. The aims of the present study were to assess the treatment of dairy wastewater (DWW) by a horizontal subsurface flow system (HSSFs) and the effect of plants in the removal efficiency (RE) of BOD5, COD, total N (TN) and total P (TP), in Sicily (Italy). The HSSFs treated 6/7 m³ per day of wastewater produced by a small dairy farm subsequent to biological treatment. The system included two units which were separately planted with Arundo donax L. and Cyperus alternifolius L. During a three-year study, the main chemical and microbiological characteristics were determined as well as pollutant RE. Plant growth analysis was carried out and biomass production was determined. All DWW parameters showed significant differences between inlet and outlet. In particular, for BOD5 and COD, average RE values were 77.8% and 61.6%, respectively. Arundo donax produced greater biomass than Cyperus alternifolius for both above- (4240.3 g m²/year) and below-ground (6996.3 g m²/year) plant parts. A seasonal variation in RE of BOD5, COD, TN and TP was recorded due to plant growth rates. Our findings highlight that the contribution of plants in pollutant RE tends to vary seasonally.
... Also, the higher operational and maintenance cost limits the use of ozonation and ultraviolet disinfection for pathogen removals (Metcalf and Eddy 1991). The CW is better known to eliminate these constraints with its suitable combination of a physical, chemical and biological factor for pathogen removal (Vymazal 2005). The pathogen treatment in wetland systems relies on sedimentation, natural die-off, temperature, oxidation, predation and UV radiation (Vymazal 2005;Alufasi et al. 2017). ...
... The CW is better known to eliminate these constraints with its suitable combination of a physical, chemical and biological factor for pathogen removal (Vymazal 2005). The pathogen treatment in wetland systems relies on sedimentation, natural die-off, temperature, oxidation, predation and UV radiation (Vymazal 2005;Alufasi et al. 2017). The pathogen removal is most often required when dealing with domestic wastewater. ...
... The inactive pathogens are easy to treat (Weber and Legge 2008). Some bacteria are facultative or anaerobic and thus the presence of oxygen creates unfavourable conditions for these organisms (Vymazal 2005). Song et al. (2008) investigated the efficiency to remove pathogen by the construal wetland and found out that the system effectively removes E. Coli, fecal and total coliforms. ...
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Chapter
Ground water is the water that fills the natural open spaces in soil and rock underground. It is stored in the underground geological water system called an aquifer. An aquifer is any geological material that is filled with water and yields useful quantities of ground water to a well or spring. Both consolidated and unconsolidated geological materials are important as aquifers. Sedimentary rocks are the most important consolidated materials (bedrock), because they tend to have the highest porosities and permeability. Although most bedrock aquifers are within sedimentary rock, in some areas igneous or metamorphic rock can be important as aquifers (David et al. 1997). Sand and gravel aquifers are unconsolidated materials.
... The choice of treatment system configuration using CWs depends primarily on the nature of the water being treated, geographic location, cost, land availability and treatment objective (Horner et al. 2011). For Hammam discharge, the hybrid system combining VF and HF CWs is the best solution for organic matter and nitrogen removal, which allows a higher treatment effect to be achieved using the advantages of each system individually (Vymazal 2005). Generally, VF CWs are followed by HF CWs (Vymazal 2005;Kadlec & Wallace 2009), the configuration adopted here. ...
... For Hammam discharge, the hybrid system combining VF and HF CWs is the best solution for organic matter and nitrogen removal, which allows a higher treatment effect to be achieved using the advantages of each system individually (Vymazal 2005). Generally, VF CWs are followed by HF CWs (Vymazal 2005;Kadlec & Wallace 2009), the configuration adopted here. Because of the constraint of needing rest periods for the VF CWs, three VF CWs in parallel ensure a continuous operation of the overall system, such that each bed operates for 2 days and rests for 4 days, as well as good system flexibility. ...
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Article
Hammams or public baths continue to consume substantial quantities of drinking water up to 120 m3/day and discharge equivalent quantities of greywater. These Hammams thus become an important source of this greywater which can be easily treated using constructed wetlands (CWs). In this context, the present study proposes to practitioners a general method for sizing subsurface flow (SSF) CWs for the treatment of greywater discharged from Hammams. It is oriented to simple applications such as irrigation, car washing and toilet flushing. Due to the complexity of quantifying the evapotranspiration (ET) of the treated water at the CWs, a practical and flexible method is presented here to calculate ET. In the end, a case study of a Moroccan Hammam has been treated and discussed. It provides the designers of SSF CWs with a concrete example of the application of the proposed methodology.
... Constructed Wetlands also known as Root-Zone system is or Bio-Filter Reed Bed system or Treatment Wetland system or Phytotechnology or Phytoremediation system (Brix et al., 2002). The horizontal sub-surface flow constructed wetlands (HF CWs) were commence by Seidel in the early 1960s and enhanced by Reinhold Kickuth underneath the name Root Zone Method in late 1960s and near the beginning 1970s and spread throughout Europe in 1980s and 1990s (Vymazal, 2005). ...
... (BOD mg/L) Before Treatment (Inlet) The use of wetlands in water pollution control is a cost effective treatment option that is widely used around the world (Vymazal, 2006;Kadlec and Wallace, 2009). Constructed wetlands have been found to be able to remove various pollutants and nutrients from polluted waters, and they are also cost-effective, robust and capable of operating with minimal maintenance or supervision (Brix et.al., 2007;Vymazal, 2005). Since then there have been several treatment wetlands developed in the various provinces for domestic wastes (Pries, 1994). ...
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Article
Nowadays, natural wastewater treatment technologies have gained more significance. Root zone treatment technology for domestic sewage wastewater treatment has been proven to be an effective and sustainable alternative to various conventional wastewater technologies. Increasing urbanisation and human activities exploit and affect the quality and quantity of the water resources; this has been resulted in pollution of fresh water bodies. Due to increased use of water and thus release of domestic sewage. Treatment of domestic sewage is necessary to ensure that the receiving water into which the effluent is finally discharged is not significantly polluted. During 2015, the estimated sewage generation in India was 61754 MLD as against the developed sewage treatment capacity of 22963 MLD. Because of the hiatus in sewage treatment capacity, about 38791 MLD of untreated sewage (62% of the total sewage) is discharged directly into nearby water bodies (CPCB 2016). As still we had not developed a planned strategy for waste water treatment completely. Constructed wetlands have been developed for domestic sewage treatment. This technique exploits the natural ability of the reeds to transfer large quantities of oxygen from the atmosphere to its root zone. Where a variety of bacteria in the soil effect biological removal of pollutants. The objective of this study is to install a pilot-scale Root zone treatment system to treat domestic sewage using an aquatic macrophyte Phragmites Australis. In the present investigation, water samples were collected seasonally for two years and treated with a Root zone treatment system; both influent and effluent samples were taken for BOD analysis. The maximum BOD reduction was found to be 72.83 % in the winter season, and the minimum BOD reduction was found to be 59.66 % in the summer season.
... In fact, untreated sewage and agricultural runoff continue to be a worldwide problem. Constructed wetlands are increasingly receiving attention for wastewater treatment including sewage, industrial and agricultural wastewaters and landfill leachate (Vymazal, 2005;Vymazal, 2010). ...
... Constructed wetlands (CWs) are efficient in removing organics through microbial degradation and settling of colloidal particles. In addition, pollution is removed under more controlled conditions to produce an acceptable quality of water for either reuse or discharge (Vymazal, 2005;Saeed & Sun, 2012;Mehta et al., 2015). CWs systems have very low operation and maintenance costs, and they have a strong potential for application in a small community. ...
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Article
This work investigates the possibility of using constructed wetland system for the management of municipal wastewaters with reuse strategies for the irrigation of landscapes in Ouled Djellal city of Biskra, Algeria. The design of this system was based on the characteristics (volume and physico-chemical properties) of wastewaters and the urban plan of the studied city. Results showed that studied effluent is easily biodegradable with COD/BOD5 of 1.84 (< 3), BOD5 (325-365 mg/L), COD (620-644 mg/L) and TSS (120-250mg/l). The peak of raw wastewater flow was found to be 32.4 m 3 /h, which was used for the calculation of drip network for the landscape irrigation. The selected variant for the configuration of the CW system is HF-VF-HF, which occupies an area of 11.580 m 2 and will reduce significantly the water pollution. The treated wastewater will be reused for the irrigation of landscapes via the dimensioned drip network. Results of this study showed that the proposed design for the system (treatment and reuse) would be effective in reducing pollution in the urban environment by ensuring possibility of the reuse of the treated water for irrigation. This gives also a great opportunity for using this strategy in small neighborhoods in other cities.
... Hybrid CWs with the combination of FSF-CWs have also gained interest (Vymazal, 2005). The combination of oxidation pond as a pre-treatment with a series of two surface flow wetlands was reported for water quality improvement in Taiwan (Yeh and Wu, 2009). ...
... The combination of various CWs can be exploited to achieve better treatment performance. VF-HF hybrid systems take advantage of both individual systems to achieve low BOD and nitrogen content in effluent through the complete nitrification and partial denitrification of wastewater (Vymazal, 2005). ...
Chapter
Once abundant, water has become a limited natural resource with its tremendously growing consumption. The utilization of clean water and disposal of untreated wastewater back to the water bodies has shrunk the accessibility of clean water to humans. In order to maintain the integrity of water bodies, the discharge of properly treated water is imperative. Existing centralized treatment systems are cost-intensive and, therefore, not much suitable to address growing treatment demand. The constructed wetland (CW) has emerged as a low-cost, green, robust, versatile, and simple treatment system that is economically and ecological more effective. This chapter describes the CWs as an effective alternative to the centralized traditional treatment systems, their origin, and spread, different designs and modes of operations, their treatment efficacy, reusability potential of treated effluent, innovations and integrations made to improve the treatment quality, current status and futuristic approaches needed to make it more robust treatment system. The chapter majorly focuses on the potential of CWs and their coupling with other technologies to reclaim high-quality treated water fit for various reusability purposes.
... Constructed wetlands or treatment wetlands have emerged as one such sustainable, environmentally friendly, real-world efficient treatment technique for pollutant removal from wastewater around the globe. Constructed wetlands (CWs) are a dedicated setup designed and manufactured to deploy natural operations of wetlands effectively in terms of their vegetational, edaphic, and microbial community in a more controlled way for wastewater treatment (Hammer, 1989;Vymazal, 2005). ...
... Constructed wetlands classification basically depends upon types of macrophytes as well as on water flow regime. Constructed wetlands are classified on the basis of various design parameters, among which three principal areas are hydrology (open water-surface flow and subsurface flow), type of vegetational growth (emergent, submerged, free-floating), and flow direction or path (horizontal and vertical) (Vymazal, 2005;Stefanakis et al., 2014;Srivastava et al., 2019) (Fig. 21.3). ...
Chapter
Water is indeed one of the most important matter, providing functionality to life forms and makes this planet habitable. Humans did not imagine their life without water. Ever-growing anthropogenic stress due to extensive urbanization and industrialization leads to the fatal impact of emerging water crisis in today's world. Along with economic shifts, extensive resource-intensive consumptions have increased the freshwater withdrawals for different sectors by six or seven times since 1900s. With less or almost no water recovery after end use from various sources like- wastewater along with unsustainable urbanization makes the situation even worse. Wetlands play a crucial role in regulating the global climate and are natural biofilters for pollutant removal, nutrient absorption, and efficient detoxification of many toxic and harmful chemicals into non-toxic forms. They are considered as one of the most productive ecosystems, acknowledged by the United Nations to achieve SDG-6 (clean water and sanitation). Constructed wetlands based on various physiochemical and biological characteristics of natural one could be used as an alternative in modern urban areas to combat the water crisis. In this chapter, we highlight the ongoing problems related to water scarcity and crisis in temporal and spatial terms, and attempt to put forward the role and importance of natural and constructed wetlands in maintaining a sustainable aqueous environment in urban localities.
... In the absence of oxygen, the oxidation of organic matter occurs through electron receptors other than O 2 , such as NO 3 − , Mn 2 + , Fe 3 + , SO 4 −2 or even organic matter itself, but with a slower rate. Although slower, the largest portion of organic matter degradation in CWs occurs due to the action of microorganisms that act precisely at low concentrations or absence of oxygen (Philippi and Sezerino 2004;Vymazal 2005). ...
... The VFAs are produced from complex organic compounds by fermentation, which has in its own organic matter the electron acceptor of the process (United States Environmental Protection Agency 1988; Vymazal 2005). Fermentation is a two-step process: acidogenesis and acetogenesis. ...
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Article
Constructed wetlands (CWs) are ecosystems artificially designed to mimic natural wetland systems for the treatment of effluents. Its adoption can be given both at a decentralized level and as an economic alternative for a variety of pollution controls: agricultural, industrial, mines and urban drainage effluents. Although a CW has larger area requirements than conventional energy-intensive treatment technologies, they have several advantages: lower costs; energy savings; fewer operating and maintenance requirements; enable wild habitat and natural leisure areas; and allow the use of solar energy. Thus, the treatment of effluents through CWs is highly promising. This review aims to encompass the current literature and state-of-the-art on CWs applied on domestic wastewater in decentralized systems, explaining with visual examples their constructions, processes and modalities.
... Nowadays, a new low capital cost, less maintenance cost, and eco-friendly constructed wetland (CWs) is becoming popular for the municipal wastewater treatment (Abidi et al., 2009;Vymazal & Masa, 2003;Molle et al., 2008;Kouki et al., 2009;Brix0 & Arias, 2005;Zhang et al., 2014). Constructed wetlands (CWs) are the new artificially engineered system that remove the pollutants load from various types of wastewater (Masi et al., 2002;Brix & Arias, 2005;Vymazal, 2005;Kouki et al., 2009;Dotro et al., 2015). It has been found to effectively remove pollutants like organic and inorganic contamination, nutrients, and pathogens as well as transmitted virus in wastewater bodies and pathogens (Lesage, 2006(Lesage, & 2007Keffala & Ghrabi, 2005;Tanner et al., 2012;Haiming et al., 2013;Dotro et al., 2015). ...
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Article
The utilization of hybrid-constructed wetland systems has recently expanded due to more rigorous municipal wastewater discharge and also complex wastewaters treated in hybrid-constructed wetlands (HCWs). A lab-scale two-stage experimental setup of vertical flow followed by horizontal flow hybrid-constructed wetland (VFHCW-HFHCW) configuration was built. First-stage vertical flow hybrid-constructed wetland reactor with the surface area was 1963.49 cm² and second-stage horizontal flow hybrid-constructed wetland reactor with the surface area was 2025 cm². The HCW unit was planted with two type plants: Calibanus hookeri and Canna indica (Cannaceae). Influent Municipal wastewater flow rate 112.32 l/day, hydraulic loading rate (HLR) 0.55 m/day, and hydraulic retention time of 1 day. The efficiency was evaluated in municipal wastewater quality improvement and physico-chemical analysis in our laboratory. The removal rate after the second-stage horizontal flow of BOD3 at 27 °C, COD, TSS, TP, NH3-N, and NO3-N reached 92.75%, 89.90%, 85.45%, 88.83%, 99.09%, and 96.05%, respectively. The results shown after both stage hybrid-constructed wetland VFHCW-HFHCW, treated effluent of Municipal wastewater produced high-quality effluent which may be reused in gardening, agriculture, and flushing in toilet purpose according to Bureau of Indian Standards (BIS) code for practices. However, in the future, hybrid-constructed wetlands could be standards design criteria developing and enhancing the performance standards and economic meets both to make more popular technology of the hybrid-constructed wetland (HCW).
... Heavy metals are usually found in industrial wastewater and mine drainages. However insignificant quantities may be detected in municipal wastewaters (Vymazal, 2005). The main heavy metals associated with wastewater and produced by mines and industries are chromium, iron, mercury, copper, lead, cadmium and zinc (Thullen et al., 2005). ...
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Article
Constructed wetlands are artificial wastewater treatment systems consisting of shallow ponds or channels which have been planted with aquatic plants, and which rely upon natural microbial, biological, physical and chemical processes to treat wastewater. They typically have impervious clay or synthetic liners, and engineered structures to control the flow direction, liquid detention time and water level. Depending on the type of system, they may or may not contain an inert porous media such as rock, gravel or sand. Constructed wetlands have been used to treat a variety of wastewaters including urban runoff; municipal, industrial, agricultural and acid mine drainage. In this regard’s an attempted has been made to reduce the heavy metal present in waste water
... Ces systèmes sont utilisés pour atteindre une plus grande efficacité de traitement qu'une simple ZHA. Les configurations qui sont davantage valorisées sont celles combinant des ZHA-VS et ZHA-HS(Vymazal, 2005 ;Vymazal et Kröpfelová, 2015). ...
Thesis
Malgré la réglementation, la pollution anthropique (azote, phosphore, éléments-traces métalliques (ETM), produits pharmaceutiques, coliformes fécaux, etc.) liée aux rejets urbains (stations de traitement des eaux urbaines (STEU) et rejets urbains par temps de pluie (RUTP)) n'est pas négligeable car elle fragilise les écosystèmes aquatiques et peut nuire à la santé humaine. Pour améliorer cette situation, la quantité de polluants se trouvant dans les eaux usées traitées ou de ruissellement urbain doit être amoindrie. Les zones humides sont des merveilles de la nature et sont souvent qualifiées de rein de la Terre du fait de leurs facultés à filtrer les polluants ; elles seraient donc de bonnes candidates pour épurer ces eaux urbaines. Malheureusement, elles sont en fort déclin depuis quelques siècles (13 % des zones humides du 17ème siècle persistaient au début du 21ème siècle). C'est pourquoi en 2011 est né le projet AZHUREV (Aménagement d'une Zone Humide à Reims pour l'Épuration et le Vivant). Ce projet a permis la construction d'une zone humide artificielle (ZHA) ou zone de rejet végétalisée (ZRV) de grande taille (6 ha) (mise en eau en 2017) à la sortie de la STEU du Grand Reims (capacité de 470000 équivalents habitants). Elle est composée de trois bassins de 2 ha alimentés en parallèle, par une partie des effluents de la STEU (10 %), ou des RUTP (25 %) lors d'événements pluvieux, pour améliorer la qualité de ces eaux avant leur rejet dans l'environnement. Initialement ce qui différenciait ces bassins étaient la quantité et le type de végétaux émergés plantés (Phragmites australis, Glyceria maxima, Scirpus lacustris). Dorénavant ce n'est plus le cas car la proportion de végétaux plantés a drastiquement diminué, P. australis étant la seule espèce toujours présente, au profit d'espèces opportunistes (submergées ou flottantes). Ces bassins ont la capacité de réduire la concentration de nombreux composés via différents processus tels que l'oxydation/réduction (azote, ETM), la précipitation/coprécipitation avec les carbonates et le sulfure d'hydrogène (ETM), la biodégradation (produits pharmaceutiques), la photolyse (produits pharmaceutiques, coliformes fécaux) l'adsorption sur les sédiments (ETM et produits pharmaceutiques) ou encore l'assimilation des végétaux (azote et phosphore). La plupart de ces mécanismes sont dépendants à la fois des bactéries et des végétaux aquatiques. De ce fait la capacité d'épuration des bassins est supérieure en été grâce aux températures élevées et aux jours plus longs. L'activité bactérienne a un effet direct sur les polluants et les genres bactériens retrouvés à la sortie de la ZRV font partie du cycle de l'azote, du soufre et du carbone. L'effet des végétaux est quant à lui indirect en promouvant le développement bactérien (source de carbone et d'énergie, support pour le biofilm) et en apportant de la matière organique dans les sédiments lors de la sénescence (site d'adsorption pour les polluants). Ces végétaux sont aussi une source de nourriture, une zone d'habitat et/ou de nidification pour de nombreux animaux sauvages qu'ils soient considérés comme « nuisibles » (rat musqué ou ragondin) ou non (cygne, foulque, canard, grèbe, grenouille, libellule, demoiselle, gammare, limnée, etc.). L'intérêt environnemental de cette ZRV est double, car elle améliore la qualité des eaux urbaines avant leur rejet dans le milieu récepteur tout en fournissant le gîte et le couvert pour de nombreuses espèces animales dépendantes de ce type de milieu. L'interconnexion des multiples variables mesurées a été retranscrite sous la forme d'un modèle conceptuel. Ces résultats sont encourageants pour une éventuelle extension de la ZRV.
... A solution to mitigate pesticide pollution from vineyard runoff water is detention ponds (DPs) (e.g., Maillard et al., 2011;Maillard and Imfeld 2014;Liu et al., 2019;Malyan et al., 2021). DPs are engineered systems designed to use nature-based solutions such as adsorption followed by sedimentation, physicochemical and microbial degradation and plant uptake (Vymazal 2005), depending on the hydraulic residence time (HRT) and thus water inputs. The adsorption of pesticides on solid substrates depends on the physicochemical properties of the pesticides, i.e. water solubility, octanol/water partition coefficient (K ow ) and half-life (Landry et al., 2004;De Wilde et al., 2009;Kom arek et al., 2010;Passeport et al., 2011). ...
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Detention ponds (DPs) are used to reduce the pesticide inputs from runoff to surface water. This study aimed to assess the role of the sorption process in the mitigation of a DP made up of four successive units and built at the outlet of a vineyard catchment in Champagne (France) to treat runoff waters. Sorption kinetics and isotherms were studied for four pesticides with contrasting properties, cyazofamid (CYA), fludioxonil (FLX), fluopicolide (FLP) and oryzalin (ORY), in the presence of copper in sediments and four emergent macrophyte roots and rhizomes sampled in the DP units 2 (photodegradation) and 3 (phytoremediation). The adsorption equilibrium time (from 24 to 96 h) was less than the hydraulic residence times in the two units (6 and 18 days on average) between November 2016 and November 2017. Sorption equilibrium could then be reached in situ in 85 % of cases. The Kd coefficients of the four pesticides were overall greater in plant roots (14–6742 L kg⁻¹) than in sediments (6–163 L kg⁻¹) because of their affinity for organic matter and the molecular and porous structure of the plant matrices. Typha latifolia and Iris pseudacorus exhibited greater Kd coefficients than Mentha aquatica and Phragmites australis, probably due to their greater specific surface area. The pesticide adsorption capacity in sediments and in T. latifolia and I. pseudacorus roots (ORY ≥ FLX > CYA > FLP) was linked to their Kow. The estimated total annual amounts of the four pesticides adsorbed in situ were determined to be 1236 mg for unit 2 and 1570 mg for unit 3. The four plants improved the removal efficiency of the unit 3 by 33%. Thus, the establishment of suitable and effective plants should be promoted to optimize sorption processes and DP efficiency in reducing water pollution.
... Regarding FS which are indicators of faecal contamination of water [68], the results obtained in HCW showed that the concentrations of FS oscillate between [(0.39 ± 0.044) × 10 7 ] and [(0.55 ± 0.0027) × 10 7 ], during the first eight days of treatment, then decreased to its minimum on day 10 where we noticed a total removal. The same removal rate was observed for the Ref; this indicates that bacterial removal efficiency is primarily influenced by the long HRT that exposes bacteria to unfavourable conditions [69]. ...
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Article
The objective of this work was to evaluate the performance of a laboratory-scale Hybrid Constructed Wetland (HCW) planted with different macrophytes, at different hydraulic retention times (HRT), for physicochemical parameters improvement and bacterial enteric pathogens removal, in industrial wastewater. The results revealed that treatment efficiency of HCW planted with Phragmites Australis and Lemna Minor was kept on increasing with the increase in hydraulic retention time. Maximum efficiency of HCW was observed with a 12-day HRT, that is, 82.6, .90.9, 78.3, 92.1, 80.2, 93.5, 99.6, 99.3, and 100% reduction from the zero-time value for, TSS, BOD 5 , COD TKN, OP, TC, FC, MF, and FS, respectively. Interestingly, we found a strong negative relationship between pH and the majority of microbiological parameters which demonstrates its role in the phytoremediation process, especially in terms of mesophilic flora and faecal coliform removal. ARTICLE HISTORY
... Previous studies highlighted that the salt content of wastewater has no significant impact on the function of the reeds [16,17]. Furthermore, an impervious layer of soil is recommended when wastewater is fed via various pathways and/or directions [18]. In a few studies, a modeling approach is also applied for evaluating the growth of crops, the amount of water given or absorbed, water movement, nitrogen dynamics, and types of pesticides used for agriculture [19]. ...
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Rapid urbanization has led to the exploitation of water quality and quantity. Urban growth and its activities result in the pollution of freshwater by generating different types of waste. Root Zone Technology (RZT) has successfully been adopted and employed in several countries to promote sustainable development. RZT paves the way for the incorporation of automated dynamics into an artificial soil ecosystem. This study’s primary goal was to develop a water treatment process for industrial effluents naturally and effectively using RZT. The technology adopts layers of coarse and fine aggregates, charcoal, sand, and planted filter beds consisting of compost media to treat effluents; the system is easily installed, low-maintenance, and has low operational costs. Selected plants achieved a result of 50–80% pollutant removal. RZT reduces the characteristics of effluents, such as chemical oxygen demand, biochemical oxygen demand, pH, color, TSS, TDS, BOD, COD, etc., by a more significant amount. Further studies of more plant species should be performed to improve this technology. Soil tests will also be an excellent option for understanding the concepts of reed absorption mechanisms. In addition, incorporating modeling in agricultural systems will be beneficial for future studies.
... desteklenerek, bitkilerin veya bitki ürünlerinin kirli ortamları temizleme, yenileme ve stabilize etme yetenekleri sayesinde, atıkların- Bahsi geçen yapay sulak alan tiplerinin haricinde, her iki sistemin birlikte kullanıldığı, tek bir sistem yardımıyla giderilemeyen kirleticilerin uzaklaştırılması için her iki sistemin avantajlarından yararlanıldığı "Hibrit Sistemler" de bulunmaktadır (USEPA, 1995;Othman, 2007;Vymazal, 2005;Aydın Temel, 2016). ...
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Green Infrastructures
... Genel bir tanımla yeşil altyapı, gri altyapıya destek olarak doğal ve Bahsi geçen yapay sulak alan tiplerinin haricinde, her iki sistemin birlikte kullanıldığı, tek bir sistem yardımıyla giderilemeyen kirleticilerin uzaklaştırılması için her iki sistemin avantajlarından yararlanıldığı "Hibrit Sistemler" de bulunmaktadır (USEPA, 1995;Othman, 2007;Vymazal, 2005;Aydın Temel, 2016 ...
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Chapter
Yeşil Altyapı Kitabı- 5. Bölüm Green Infrastructure Book Chapter 5
... Genel bir tanımla yeşil altyapı, gri altyapıya destek olarak doğal ve Bahsi geçen yapay sulak alan tiplerinin haricinde, her iki sistemin birlikte kullanıldığı, tek bir sistem yardımıyla giderilemeyen kirleticilerin uzaklaştırılması için her iki sistemin avantajlarından yararlanıldığı "Hibrit Sistemler" de bulunmaktadır (USEPA, 1995;Othman, 2007;Vymazal, 2005;Aydın Temel, 2016 ...
... Low treatment, operating and maintenance costs, sludge-free operations, fewer labor needs, effective removal of organic and inorganic contaminants, and the capacity to handle influent load changes are some of the advantages of CW technology. These are engineered systems that use natural processes (nitrification, denitrification, adsorption/absorption, microbial degradation, ammonification, precipitation, nutrient/pollutant uptake etc.) involving wetland vegetation, filter material, and associated microbial assemblages to help with wastewater treatment (Vymazal, 2005). Horizontal, vertical, and hybrid systems are the most extensively used CW designs owing to their long-term efficacy in removing contaminants from wastewater (Rousseau et al., 2004;Sharma et al., 2011Sharma et al., , 2013Sharma et al., , 2018. ...
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Article
The current research intends to assess the impact of shorter hydraulic retention time (HRTs) and different sized filter material on the pollutant removal performance of two pilot-scale vertical sub-surface flow constructed wetlands (VSSF CW) to treat dairy wastewater. Two CWs (CW-1 & CW-2) were filled with 10 mm and 20 mm gravels, respectively, planted with Arundo donax, and operated at three different HRTs for treating dairy farm wastewater viz. 6, 12, and 24 h. Over three months, the effluent was tested for TSS, BOD5, TP, and NH4–N removal using standard procedures at regular intervals. Average concentrations of TSS, BOD5, TP, and NH4–N at the final outlets CW-1 and CW-2 were recorded in the range of; TSS: 44.7–118.7 mg L⁻¹, BOD5: 8.1–33.9 mg L⁻¹, TP: 13.7–22.2 mg L⁻¹and NH4–N: 9.1–11.4 mg L⁻¹, respectively. The highest removal of TSS (81.2%), BOD5 (90.2%), TP (65.1%), and NH4–N (82.5%) from wastewater was seen after a 12 h HRT, whereas maximum DO rise (579.0%) was reported after a 6 h HRT in 20 mm gravel-filled CW units. Short HRTs of 6, 12, and 24 h were found to be effective in removing all pollutants from wastewater and maintaining a constant treatment throughout the evaluation period. Results suggest that VSSF CW systems can be operated efficiently under short HRTs while still effectively removing contaminants from dairy wastewater.
... While flowing, the wastewater is acted upon by anaerobic, anoxic and aerobic (present near rhizomes and roots and add oxygen to the substrate) zones. "Hybrid constructed wetlands" constitute of different variety of wetlands combined for greater efficiency of treatment [60,61]. For example, Horizontal flow constructed wetlands have low or no oxygen in the filtration beds and thus there is low nitrification. ...
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Chapter
Owing to the importance of water and increasing water crises, wastewater analysis has become extremely important. For water to be usable, there are certain physical, chemical and biological criteria which need to be fulfilled, such as the concentration of elements for drinking as well as for agricultural purposes. Quality of water is affected by natural and human interferences and the major factor is pollution created by human. The wastewater from the population if handled and treated with care should be able to promote the sustainable use of water and make the water available for our upcoming generations. Countries are stressing on water management and have certain specifications for the water being potable. The water–energy nexus describes the relationship between water and energy wherein wastewater can act as a reservoir of renewable energy leading a way towards sustainability. This chapter elaborates the energy–water nexus, strategies towards wastewater remediation and the technological interventions in wastewater application for irrigation.KeywordsPollutionRemediationSustainabilityWastewater managementWater–Energy Nexus
... CWs in both experiments showed a reduction of TP concentration in all effluents, where the average TP removal efficiencies ranged between 87 and 94% (Table 5). Vymazal (2005) reported that the removal of phosphorus is usually low in constructed wetlands and does not exceed 50% when dealing with municipal sewage. But in the current study, the mean removal efficiencies of TP exceeded this rate for all planted CWs and even for the unplanted ones. ...
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Article
The objective of present study was to assess the water quality parameters in two experiments, comprising six configurations of pilot-scale vertical subsurface flow constructed wetlands (VSFCWs) by the comparison of the removal efficiency of organic matter and nutrient pollutants from water in arid region. Effluent treatments were studied in 5-month experiment under different operational conditions including (1) substrate type: sand (S) (experiment 1) or fine gravel (G) (experiment 2) and (2) agronomic species: Phragmites australis (Ph) or Typha latifolia (Ty). This experiment demonstrated that the vegetated wetlands were more efficient than non-planted (Np) ones in terms of removal of TSS, COD, NO3-N, and TKN from wastewater in the first experiment and more efficient for all water quality parameters except for TSS and BOD5 in the second experiment. For a given species, the efficiency of both experiments was generally higher with Ph–S than Ph-G and with Ty-S than Ty-G. Regarding unplanted CWs, Np-S performed better than Np-G for all of the tested water quality parameters except TSS. The wetland efficiency indicated that CWs planted with P. australis contributed greatly to the removal of COD, NO3-N, and TKN in the first experiment, and NO3-N, NH4-N, PO4³-P, and TP in the second experiment, whereas CWs planted with T. latifolia provided the highest removal only with TSS for the first experiment, and COD and TKN for the second experiment. The highest efficiency of unplanted setups (Np-S) was for BOD5, NH4-N, PO4³-P, and TP, while with Np-G was only for TSS and BOD5. In general, the first experiment is better than the second in removal efficiency for most of the tested parameters. Therefore, the use of sand substrate was more suitable than gravel for wastewater treatment in VSSFCW. As well as, P. australis performed better than T. latifolia for most of the studied parameters.
... Therefore, a hybrid wetland system offers high treatment efficiency for wastewater treatment (Xiong et al. 2011;Zhang et al. 2014). The hybrid system generates a low BOD 5 effluent that is completely nitrified through the vertical filter stage and slightly denitrified through the horizontal filter stage, thus reducing the intensity of overall nitrogen outflow (Vymazal 2005b). Zhang et al. (2014) expressed that the hybrid system effectively removes TSS, BOD 5 , COD, and NH 4 -N at an efficiency of 93.8%, 84.1%, 85.7%, and 80.1% respectively. ...
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Article
Constructed wetland (CW) systems have proven to be one of the panaceas to the water crisis that can contribute to environmental protection and human health security. Considering the popularity of CW in wastewater treatment, its broader application , especially for remediation of contaminants of emerging concerns in the real-world scenario, is limited. Therefore, to promote real-world applications as well as further research and development in CW, detailed scope of CWs for remediation of wastewater, including contaminants of emerging concern, was critically reviewed. In addition, construction and components, design, and interaction of different biotic communities of a CW in wastewater treatment were analyzed and compiled in a consolidated form. The consolidated information on know-how of the CW technology along with future scope presented in the review would be instrumental for holistic and sustainable treatment of wastewater at larger scales.
... Greywater treatment is achieved by soil filtration in reeds bed systems, which reduce the organic load of the greywater considerably (Avila et al., 2014), in addition to decreasing the concentration of fecal coliforms (Pelissari et al., 2016). If properly designed, these systems could produce a clear and odourless effluent (Vymazal, 2005). ...
Chapter
Distillery wastewater (spent wash) is one of the highly polluted wastewater generated from alcohol distilleries. In India, there are around 319 distilleries, producing about 40 thousand million litres of wastewater annually (Pant and Adholeya, 2007). Ministry of Environment, Forestry and Climate Change (MOEF & CC) has categorised alcohol distilleries among the top positions in the “Red Category Industry” list (Tewari et al., 2007). A huge amount of high strength wastewater is generated by this industry every day as a spent wash, spent lees and fermenter sludge. Approximately 8-15 L of the spent wash is generated for every 1 L of alcohol produced by a conventional distillery industry (Sankaran et al., 2014). Distillery wastewater is recalcitrant in nature having a dark brown colour with high organic (biological oxygen demand and chemical oxygen demand) and inorganic (sulphates, potassium, phosphates, and nitrogen) load (Sankaran and Premlatha, 2018). Melanoidins present in the distillery wastewater imparts a brown colour to this wastewater and are formed due to Maillard amino carbonyl condensation reaction. Due to the antioxidant properties of melanoidins, these compounds are typically not degraded by micro-organisms present in the wastewater treatment process and are also toxic to those micro-organisms. This resistant nature of melanoidins makes a clear route for their entrance into the environment even after various stages of treatments (Singh et al., 2018). When such a high strength untreated or partially treated distillery wastewater enters into the environment, it leads to serious environmental threats such as eutrophication of water bodies and loss of soil fertility (Chowdhary et al., 2018).
... This development has produced many wastewater treatment designs, including integrating WSPs and constructed wetlands (CWs). CWs are engineered wastewater treatment systems that encompass a plurality of treatment modules, including biological, chemical, and physical processes, similar to those occurring in natural wetlands (Vymazal 2005). CWs that are positioned at the final stage of a treatment system operate (polishing) more efficiently and deliver other beneficial outcomes such as enhanced biodiversity (Kihila et al. 2014). ...
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Article
This study assessed the social knowledge, attitude, and perceptions (KAPs) on wastewater treatment, the technologies involved, and its reuse across different wastewater treatment areas in four regions of Tanzania. We used both quantitative and qualitative data collection methods in a household-level questionnaire (n=327) with structured and semi-structured questions, which involved face-to-face interviews and observation. Our results show that social KAPs surrounding wastewater treatment and reuse were sufficient based on KAP scores achieved from asked questions. However, the general knowledge on treatment technologies, processes, and reuse risks was still low. Of the respondents, over 50% approved using treated wastewater in various applications, while the majority (93%) were reluctant if the application involved direct contact with the water. Furthermore, over 90% of interviewees did not know the technologies used to treat wastewater and the potential health risks associated with its use (59%). Multivariate analysis of variance revealed significant differences (P<0.05) in the KAPs on treated wastewater across different studied demographic variables, i.e., age, sex, and education level. Therefore, we recommend that more effort be spent on providing public education about the potential of wastewater treatment and existing technologies in order to facilitate their adoption for the community's and environment's benefit.
... There are also species placed in wetlands that are more specific, depending on the climate of the area in which they are located. Regarding the type of wetland used, the most studied systems are subsurface flow wetlands [15,16]. This is because the water surface remains under the gravel and odors and mosquito-related problems disappear. ...
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Article
The treatment of wastewater from small towns supposes problems of economic efficiency, leading to very high environmental costs in areas with low population density. Constructed wetlands (CW) seems to be the more suitable solution for this kind of situation, but further investigations are needed regarding their efficiency under different climatic conditions. This work presents the results concerning urban wastewater treatment by means of two different constructed wetlands using macrophytes: horizontal subsurface flow (HSSF) and free water surface (FWS). The systems are located in a Mediterranean continental climate area and are fed by a by-pass at the entrance of a wastewater treatment plant. A four-year sampling campaign at the outlet of the CW allowed verifying their relative effectiveness in removing pollutants in the different seasons of the year. BOD5, COD, and TSS were significantly removed (with average reductions of 55%, 60%, and 57%, respectively) by these natural phytodepuration systems, with HSSF being more efficient during plants’ dormancy than FWS, but the concentrations of nutrients indicated that cumulative effects occur in CW with the need of adequate annual maintenance. It was found that the main factors controlling the efficiency of such systems throughout the year are the period of vegetative development, the presence/absence of a solid substrate, and the pollutant load of the wastewater inlet.
... However, aeration does not have a significant effect on phosphates, and nitrates retained in the presence of high dissolved oxygen. Nitrification -denitrification is generally recognised as the primary process for the removal of total nitrogen in wetlands (Vymazal, 2005). Insufficient oxygen availability in horizontal subsurface flow leads to delays in the nitrification process as well as the degradation of organic substances (Noorvee, Põldvere & Mander, 2007). ...
... (Saeed et al., 2012;Serrano et al., 2011;Vymazal, 2005). ...
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In the last few decades, nutrient-rich wastewater has become a worldwide problem due to exponentially increased anthropogenic activities causing eutrophication or algal blooms in waters and affect the water bodies with their biological and chemical activities. Physico-chemical techniques have shown promising results, while operational cost, hefty sludge generation, and energy requirement are the major drawbacks. On the other hand, biological processes are cost-effective and efficient, although they are associated with design complexity and extensive monitoring. Among biological techniques, constructed wetland (CW) is an economical, efficient, and green technique for nutrient removal comprising of inherent mechanisms, such as microbial degradation, rhizofiltration, phytodegradation, sorption, etc. This major highlight of the present study is to apprise and critically analyze the ideal conditions and system insights to enhance the nutrient removal efficiency of CW. Macrophytes play a vital role in CW and its planting practices, namely monoculture and polyculture, also influence the removal efficiency of the CW. In the present study, an in-depth analysis reflected that polyculture exhibits better treatment for TN and TP compared to monoculture practices. The observed optimum conditions for nutrient removal in CW were polyculture in combination with higher temperature (23ºC-29 º C), artificial aeration, advanced substrate, and bioaugmentation. The review emphasized the process and design criticality of CWs in removing nutrients from various types of wastewater, which may be instrumental for water research and field applications.
... This study revealed that Cr reduction from contaminated water in VF-CWs vegetated with L. fusca and B. mutica was attributed to their extensive plant root growth, which served as an active zone for inorganic contaminants sequestration by microbial population. Wetland plant species having extensive root growth in Cr-contaminated water are more active in removing contaminants, as observed in earlier studies [40][41][42][43]. In the CWs, the extensive root system of wetland plant species enhances the oxygen transfer efficiency, which increases the contribution of microbial biomass towards contaminant degradation and treatment [7,44]. ...
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Article
Water scarcity is one of the key global challenges affecting food safety, food security, and human health. Constructed wetlands (CWs) provide a sustainable tool to remediate wastewater. Here we explored the potential of vertical flow-CWs (VF-CWs) vegetated with ten indigenous wetland plant species to treat chromium (Cr)-contaminated water. The wetland plants were vegetated to develop VF-CWs to treat Cr-contaminated water in a batch mode. Results revealed that the Cr removal potential of VF-CWs vegetated with different wetland plants ranged from 47% to 92% at low (15 mg L−1 ) Cr levels and 36% to 92% at high (30 mg L−1) Cr levels, with the maximum (92%) Cr removal exhibited by VF-CWs vegetated with Leptochloa fusca. Hexavalent Cr (Cr(VI)) was reduced to trivalent Cr (Cr(III)) in treated water (96–99 %) of all VF-CWs. All the wetland plants accumulated Cr in the shoot (1.9–34 mg kg−1 dry weight (DW)), although Cr content was higher in the roots (74–698 mg kg−1 DW) than in the shoots. Brachiaria mutica showed the highest Cr accumulation in the roots and shoots (698 and 45 mg kg−1 DW, respectively), followed by Leptochloa fusca. The high Cr level significantly (p < 0.05) decreased the stress tolerance index (STI) percentage of the plant species. Our data provide strong evidence to support the application of VF-CWs vegetated with different indigenous wetland plants as a sustainable Cr-contaminated water treatment technology such as tannery wastewater.
... These heavy metals (e.g., Pb, Ni, Cd and Cr) entre into the various food chains, posing a health risk to living beings (Dickin et al., 2016;Kumar et al., 2020;. Skin illnesses, asthma, cancer, dehydration, respiratory issues, cardiovascular and excretory systems and human growth retardation have been listed as major problems concerning the high concentration of heavy metals in freshwater and potable water (Ansari et al., 2020;Dutta et al., 2021;Kumar, Jigyasu, et al., 2021;Vymazal, 2005). Some metals (e.g., Fe, Cu, Zn and Mn) are important micronutrients for living organisms, despite producing toxic effects at higher concentrations (Kabata-Pendias, 2011;Ventura et al., 2021). ...
Article
Heavy metal removal by constructed wetland (CWs) is becoming the most efficient and greener technology around the world where plants are used in phytoremediation to degrade, stabilize, and remove contaminants from soils, water, and waste. The design of CWs for successful phytoremediation in heavy metals contaminated wastewater should not affect the local environment. By‐product generation is another crucial part of phytoremediation's success. In the study, phytoremediation plants (Canna indica and Acorus calamus) biomass has been successfully used in the manufacture of 70 fly‐ash bricks. Further, these bricks are used for CWs to see the efficiency in removing heavy metals pollution. Results found that high rate of Cu (96 %), Zn (95 %), (Fe 93), and Cr (91 %) removal from Canna indica and Acorus calamus were found as compared to the Typha latifoliya, Myriophylhum aquaticum, Ludwigina palustris, Eichhornia crassipes, Schoenoplectus californicus, Cyperus papyrus, and Phragmites australis reported by others global researchers which indicates C. indica is the high potential for heavy metal removal and can be strongly used for industrial wastewater. The use of ornamental plants for phytoremediation of contaminated sewage wastewater would also change the landscape of the aquatic environment. This study summarises viable avenues in the method of using phytoremediation plant biomass for environmental protection and sustainable environmental management.
... The NTS's adaptability is another big problem facing NTS designers and operators. Disordered vegetation growth, nuisance control (e.g., insect vectors, nuisance animals), slow treatment rates, wastewater exposure and fast macrophyte growth rate pose a concern for NTSs [79][80][81]. Lack of awareness about tropical wetland ecology and species and lack of local knowledge about design and management along with the prevalence of mixed domestic/industrial wastewaters pose problems for embracing NTSs [38,82]. Routine maintenance of vegetation is another difficult task for the owner-manager of NTSs in tropical regions [83]. ...
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Article
This review article attempts to analyse the social issues that impact the performance of natural treatment systems (NTSs). An NTS is a decentralised wastewater treatment system found to be appropriate in developing countries due to its affordability and lower technicity. However, if socio-economic and institutional issues of community are ignored then NTSs may turn out to be unsuitable for developing countries. The article also takes a critical view on the extant literature which ignores the social cost of NTSs. The social cost of NTSs may be high as a decentralised system requires the engagement of various governmental agencies, research institutes and the community. The cost of engagement may make NTSs a socio-economically unattractive proposition. The article discusses the variables to be considered for the social cost-benefit analysis. It also discusses the implications of social cost-benefit analysis for appreciating the incentives and net benefits for collective actions at the community level. Social cost-benefit analysis can help overcome the initial difficulty of high financial cost and usher sustainability.
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Article
Sewage treatment through constructed wetland is an ecofriendly and sustainable approach proven effective worldwide. Constructed wetland with appropriate species is capable of eliminating all pollutants in sewage, except pathogen removal. An additional polishing treatment is required to eliminate pathogen. Optimization of HLR in CWS was executed by applying first order kinetics. Nanocomposite clay filter with economically viable materials was synthesized and disinfection ability was evaluated. A novel approach integrating constructed wetland system tailed by nanocomposite clay filter was designed. Control was setup with constructed wetland system devoid of plants integrated with clay filter devoid of nanoparticles. The constructed wetland system devoid of plants was used as plants play a vital role in the removal of pollutants. The quality of the influent for (n=20) BOD, COD, TKN, TP, TSS, TDS, SO 4 , Cl, lead and iron were 248, 345, 26, 4.8, 350, 450, 50, 48, 0.2, 5 mg/L respectively. The quality of effluent in the control was 145, 225, 18, 3.8, 185, 345, 31, 30, 0.6, 2 mg/L for BOD,COD, TKN, TP, TSS, TDS, SO 4 , Cl, lead and iron respectively. While in the test, 10, 30, 2, 1, 30, 128, 13, 12, BDL, BDL mg/L for BOD, COD, TKN, TP,TSS, TDS, SO 4 , Cl, lead and iron respectively. The inlet concentration of T.C, F.C and E.coli were 42.1x10 ⁶ -6.3x10 ⁸ , 4.9x10 ⁵ -14.4x10 ⁶ and 7.8x10 ³ -3.8x10 ⁵ respectively. The pathogen reduction in log removal for test and control units were 5.4 and 1.1 for T.C, 4.4 and 1.2 for F.C and 3 and 1 for E.coli . Thus it is a clean green initiative combating the limitations of disinfection surpassing the existing barriers.
Chapter
This chapter explains the significance of the removal of selected categories of organic contaminants (polycyclic aromatic hydrocarbons, petroleum hydrocarbons, azo dyes, chlorinated solvents, pharmaceuticals, personal care products, steroidal hormones, and pesticides) and inorganic contaminants (nutrients, metal(loid)s, and radioactive compounds) from the wastewater while synthesizing the available knowledge on the sources of these types of contaminants in water resources and the environment as well as the societal challenges related to their discharge. The available wastewater treatment technologies (physicochemical and bioremediation techniques) for these types of contaminants are described in this chapter with the detail description of bioremediation techniques (microbial remediation (microbes (e.g., bacteria)), mycoremediation (fungi), phycoremediation (algae), and phytoremediation (plants)). The concept of constructed wetlands, which is a phytoremediation technique, is discussed for the treatment of wastewater containing the selected categories of organic and inorganic contaminants. Finally, the main findings, key insights, and specific conclusions are summarized.KeywordsBioremediationBiodegradationOrganic contaminantsInorganic contaminantsConstructed wetland
Article
Both the tailings and associated leachates should be characterised to predict contaminant levels and identify suitable remediation strategies for appropriate closure planning of tailings management facilities (TMFs). Tailings and associated drainage waters from a modern Pb/Zn site were characterised to determine contaminants of possible concern for discharge. The potential for constructed wetlands to provide suitable treatment of tailings waters was assessed over a 10 month period. Tailings were slightly alkaline (pH 8.3), with high net neutralising capacity (578 kg CaCO3/t), very high level of neutralising carbonate minerals (ca. 60%), and low sulphide content (< 5%). Metal content was Zn (2430 mg/kg), Pb (1900 mg/kg), As (620 mg/kg), Sb (80 mg/kg), Ni (50 mg/kg), and Cr (30 mg/kg). The pH dependent leaching demonstrated the potential for higher amounts of metals to be released under acidic conditions (pH < 5), although this would be most unlikely given the very high NP/AP ratio. Drainage waters were net neutral (pH 7.7) but exceedance of surface water directive levels was observed for sulphate, Sb, and Zn. Constructed wetland treatment demonstrated effective Zn and Sb to achieve limit values. Sulphate levels remained high and exceeded the 250 mg/L limit values. Mn values in the wetland effluent exceeded influent levels. Further evaluation of the constructed wetland treatment option is warranted to achieve sufficient treatment of the neutral pH discharge to levels suitable for discharge.
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Article
This study aimed to investigate the performance of the French Type Constructed Wetlands (FTCW) at a pilot scale level in real field conditions for sewage treatment in India. The pilot plant consisted of hybrid wetlands in two stages, vertical and horizontal sub-surface flow types. The first stage comprised three compartments, vegetated with three different native plants (phragmites australis, canna indica, and sagittaria), operated in parallel, and sequentially loaded. Each VSSF bed of 12.25m2 was fed with raw sewage directly for 3.5 days followed by twice the time resting period. The second stage consisted of one bed of an area of 45m2, planted with canna indica. The filter media used in stage 1 was a dual type (gravel and coarse sand) in three layers. The first stage was designed for the loadings of 33.75gBOD/m2d and 14.1 gNH4-N/m2d with the flexibility to operate at a variable hydraulic loading rate (HLR). Two years of monitoring data after the steady-state condition show variable performances at different hydraulic loading rates. Removal efficiencies of COD, BOD5, TSS, TN, and TP of the hybrid system at HLR of 0.4m/day were 87.1%, 87.3%, 84.6%, 67.93%, and 69.32% respectively. Doubling the HLR, the efficiency of the system decreased marginally for the same parameters. Out of the three vegetation, the bed planted with phragmites has shown the highest removal efficiency. The study has demonstrated that FTCW can be a suitable proposition as one of the potential methods for sewage treatment in India and similar regions.
Thesis
The problem of wastewater sanitation in Algeria is a subject that remains an issue, despite the many initiatives undertaken to date. Because of its position at the heart of a fragile ecosystem and a galloping demography, the sebkhas serve as receptors for huge domestic effluents. This promotes the salinization of these biotopes then during floods, the wadis flow inland, dragging raw sewage, contaminating this landlocked environment, as is the case of the sebkha of the city of Naâma. The improvement of knowledge in the field of wastewater treatment has strongly contributed to the design of new wastewater treatment systems inspired by natural processes, called "planted macrophyte filters", is a process that uses natural self-purification techniques and contributes to the protection of the environment in order to preserve conventional water resources. The main objective of this work is to create an eco-technical purification system and to test the potential of the absorbing and purifying power of certain macrophytes (Phragmites australis, Typha latifolia, Lemna minor Tamarix africana, Nerium oleander, Juncus sp) by improving their efficiency combined with an alluvial substrate against organic pollution and, on the other hand, to propose it as an environmental bio-monitor of water pollution in an arid climate. The experiments were carried out in the field, where a settling tank receives domestic wastewater from the Naâma agglomeration (FPR, FPM) and that of Mécheria (Baquet 1 and Baquet 2). The results obtained from this study were very encouraging and show that Phragmites australis, Typha latifolia and Lemna minor are probably to be the most cost-effective in terms of removing all pollutants from domestic wastewater. Thus, we can observe a perfect adequacy of this system to the objectives of carbonaceous matter degradation, TSS retention and nitrification which were primarily targeted according to the aridity conditions. Reductions in COD and BOD5 are very high and even greater than those obtained with a mechanized activated sludge treatment plant. Optimum yields reach 93.5 and 95.7% for the first and second pilot for biological oxygen demand (BOD5) and 90 and 96.5% for chemical oxygen demand (COD) respectively. The reduction in suspended solids (SS) is 96.8% for the first pilot and 97.8% for the second pilot. The total nitrogen abatement efficiency is between 48 and 50% depending on hydraulic residence time, the phosphorus abatements are on average 65.3 and 72%. The system allows significant reductions in bacteria; maximum removal of total coliforms and faecal coliforms in the effluent is on average 93 to 99 % CFU/100 ml, as well as streptococcal removal in the order of 50 to 99 %. A significant difference in the reduction of organic and bacteriological pollution was observed between the control and the macrophyte filters, as well as a correlation between purification efficiency and the presence of the plant, its biomass and residence time.
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Chapter
No Brasil, grande parte dos mananciais apresenta algum tipo de poluição, afetando tanto qualitativamente como quantitativamente a disponibilidade de água para consumo humano. A expansão do mercado de produtos farmacêuticos e a difusão do seu uso pela sociedade corroboram com a intensificação desse problema ambiental, através do descarte inadequado de medicamentos que atingem as águas superficiais. Nesse contexto, a Filtração em Margem (FM) surge como uma tecnologia bastante promissora, pois se apresenta como um pré tratamento para reter e eliminar estes compostos, facilitando e diminuindo o custo do tratamento das águas de abastecimento público. O presente artigo descreve os fundamentos do processo de Filtração em Margem e apresenta um estudo de caso realizado às margens do rio Beberibe no estado de Pernambuco, abrangendo a investigação de resíduos farmacêuticos e analisando as potencialidades do processo de FM na redução destes.
Chapter
Bioelectrochemical systems (BESs) are a type of new bioengineered systems or technologies that has integrated microorganisms with the electrochemical-based processes to achieve improved or better redox metabolism. Generally, BESs involves processes where electrical power is generated due to oxidation of organic matter present in waste. Here, the chemical energy in waste is converted to electrical energy by means of catalytic reactions (electron transfer) carried out by microbes. Such systems where organic matter is converted to electrical energy are called as Microbial Fuel Cells (MFCs). Similarly, other system where hydrogen or by-products like peroxide or caustic are produced, are called as Microbial Electrolysis Cells (MECs). BESs have been recently characterized for their ability to recover value added products like nutrients, metals etc. from waste and removal or degradation of recalcitrant compounds. Another microbial-based system that is used in wastewater treatment is constructed wetland (CW). CWs are the simulated or engineered form of natural wetlands designed to optimize the conditions of natural wetlands. This system consists of an impermeabilized hole, filled with a filter or support media like gravels and sand and planted with rooted macrophytes. The MFCs require redox conditions to be implemented for their functioning, while CWs have naturally occurring redox conditions. Therefore, this chapter aims to discuss about the functioning of BESs and CWs as independent system and as merged system CW-BES, their possible applications and their performance evaluation in comparison to other technologies.
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Conference Paper
The aim of this paper was to determine the water quality and ecological status of the Drina River at the sector of the flow through Banja Koviljača according to selected physico-chemical and microbiological parameters. The ecological status was determined as weak in 2013, during 2014, 2015 and 2016 as moderate, while in 2017 it was good. The number of total coliform bacteria indicated a good ecological status. According to SWQI water quality can be rated as good to very good. Based on all analyzed parameters during the five-year monitoring, a positive linear trend of Drina River water quality was assessed at the sector of the flow through Banja Koviljača. Also, when it comes to ecological status, the results indicate a positive trend. KEY WORDS: SWQI, water quality, ecological status, Drina River, Banja Koviljača
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Chapter
As the population grows, water consumption increases and a large amount of wastewater is generated. The release of untreated wastewater into the aquatic systems is the reason for dilapidated conditions of the water bodies. Intercepting and treating wastewater before it meets the water bodies shall be prioritized in order to protect them, not even in urban but also in rural locations. Constructed wetlands (CW) are emerging and gaining popularity in recent times as a technological option for wastewater treatment. CWs are progressively being applied across the countries for treating variety of wastewaters and it is being looked as an alternative to the conventional wastewater treatment plants. The locally available components and simple design make it decentralized and sustainable choice for wastewater treatment. CWs are based on the principles of ecological engineering; they mimic the natural wetlands processes. The assemblage of soil, substrate, vegetation, microorganisms work cohesively in an engineered system to give desired output of wastewater cleansing. Varied experimental material and designs have been tested for treating sewage, but the common group of components are water, filter media, vegetation, microorganisms, and liners. The major classes of CW are horizontal and vertical flow CWs. The choice of vertical or horizontal type of treatment units depends on the type of wastewater, desired quality of treatment, and availability of land. The degree of treatment depends on the vegetation material, size of the system, retention period, organic loads, and surface loading. This chapter is a compilation on the design aspects of CWs, their operations details, site selection criteria, treatment mechanisms, and advantages and drawbacks.
Chapter
The water crisis and its scarcity have pushed countries, especially the energy-rich countries, during the large part of the year, to exploit resources that are not sufficiently replaced. Also, waste water from agricultural and residential areas contains high levels of nutrients and if this water is not treated, it could contaminate surface water and groundwater systems, thereby restricting the availability of water for other uses (Sarafraz et al., 2009).
Article
Low-polluted waters treated by traditional constructed wetlands were usually difficult especially because of restricted available land use. A hybrid constructed wetlands (CWs) could be applied to remediate low-polluted rivers, which can realize steps complementary to each other that exploit the specific advantages of the individual systems and achieve higher treatment effects. The hybrid CWs covering a total area of 99647m², was developed to treat the polluted Bagong River, one of tributary to the Yellow River, have been in operation since the end of 2020. This paper introduced the specific construction method of the hybrid CWs, and the water quality of the river could be improved 1–2 grades after flowing through the CWs (according to the Chinese standard GB3838-2002). The treatment capacity was designed to be 65,000 m³·d⁻¹, and the obtained results showed a satisfactory pollutant removal capacity of the hybrid system, with mean removal rates of 57.00%, 20.00%, 48.00%, and 29.00% for ammonia nitrogen, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD), respectively. Meanwhile, >12 species of aquatic birds were attracted to inhabited in the hybrid CWs. The results of correlation analysis concluded that temperature and plant growth were the dominant factors affecting the removal of pollutants in the hybrid CWs system, and the porous concrete as substrate also has obvious phosphorus removal effect. The results showed that the system had relatively stable impact resistance and good ecological benefits under different influent loads, and can better improve water quality and biodiversity. Thus, the hybrid CWs would be a promising and feasible treatment method for low-polluted waters, as adapted to the local context.
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Thesis
The biosphere is undergoing an environmental crisis caused by our energy-intensive economic model. Understanding the regulation and exchange processes of global ecosystems is the key challenge to improve our resilience and reduce our impact on the Earth. The aim of this thesis is to assess the dynamic role of wetland ecosystems in the global nitrogen cycle. The Soil Denitrification Model (SDM) was developed using soil moisture and temperature satellite Earth Observations. The model was validated at local scale with laboratory measurements, then upscale global scale. Identification of hot moments and hot spots in natural wetlands. Southeast Asia and Oceania was identified as the main hot spot. The hot moments varied by region and by typology. May was the hot moment for freshwater marshes and complex wetlands. While brackish wetlands are active all year long and flooded forest, have their peak in December and January. Quantitative estimation of denitrification was estimated at 169.32± 18.31 TgN (N2O-N +N2-N).yr-1 and evolution of denitrification in the last 8 year was analysed and linked to global climate anomalies.
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Le développement d'urbanisation conjugué à la croissance démographique engendre l'augmentation des besoins en eau qui se traduit par l'utilisation excessive des ressources en eau et par la production et le rejet d'un important volume d'eau dans l'environnement. Les résultats de cette étude prouvent que la phytoépuration par C. nigritanus et H. diplandra se présente comme une alternative très éfficace pour le traitement des eaux usées domestiques à N'sele. Les abattements les plus élevés sont ceux de MES avec 87% et 76% respectivement pour les EUE avec C. nigritanus et H. diplandra. Mots clés-Traitement, eaux usées, microphytostation, Chrysopogon nigritanus Benth., Hyparrhenia diplandra (Hack.) Stapf, N'sele et Kinshasa. Abstract : The development of urbanization combined with population growth generates an increase in water needs which results in the excessive use of water ressources and the production and discharge of a large volume of water into the environment. The results of this study prove that phytopurification by C. nigritanus And H. diplandra is a very effective alternative for the treatment of wastewater in N'sele. The highest reductions are those of MES with 87% and 76% respectively for the EUE with C. nigritanus and H. diplandra.
Thesis
The biosphere is undergoing an environmental crisis caused by our energy-intensive economic model. Understanding the regulation and exchange processes of global ecosystems is the key challenge to improve our resilience and reduce our impact on the Earth. The aim of this thesis is to assess the dynamic role of wetland ecosystems in the global nitrogen cycle. The Soil Denitrification Model (SDM) was developed using soil moisture and temperature satellite Earth Observations. The model was validated at local scale with laboratory measurements, then upscale global scale. Identification of hot moments and hot spots in natural wetlands. Southeast Asia and Oceania was identified as the main hot spot. The hot moments varied by region and by typology. May was the hot moment for freshwater marshes and complex wetlands. While brackish wetlands are active all year long and flooded forest, have their peak in December and January. Quantitative estimation of denitrification was estimated at 169.32± 18.31 TgN (N2O-N +N2-N).yr-1 and evolution of denitrification in the last 8 year was analysed and linked to global climate anomalies.
Chapter
Sanitary landfilling is the major method of disposal of municipal solid waste (MSW) in developing countries. The disposal of MSW in landfills generates a large amount of highly toxic leachate, which has high potential hazards for the public, flora, fauna health and ecosystems. Advanced leachate treatment systems using biological and chemical treatment methods are recently implemented in developed countries, but high investment and operating costs restricted their application in most of the developing countries. To overcome this problem, an alternative sustainable treatment technology such as phytoremediation could be beneficial. The constructed wetland treatment system is an economical alternative for leachate treatment using local resources and is an energy-efficient technology. These green systems utilize anaerobic and aerobic reactions to break down, immobilize, or incorporate organic substances and other contaminants from polluted effluent. This chapter highlights the recent advances in the treatment of landfill leachates using constructed wetlands.
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Conference Paper
Quadrature spatial modulation (QSM) activates one or two transmit antennas at a time, and uses extra modulation spatial dimension to improve the overall throughput of spatial modulation (SM) scheme. Most contributions, thus far, have only addressed aspects of QSM for point-to-point communication systems. In this paper, the behaviour of QSM in the multiple access/user (MU) scenario, is characterised. A Maximum-likelihood (ML) receiver for the new MU-QSM system is proposed and its performance was observed in the presence of perfect channel state information (CSI). Results showed that; compared to the existing forms of MU-MIMO systems, MU-QSM achieves lower error rates and offers an improved overall spectral efficiency as well as capacity.
Article
Solving the problem of rural sewage is considered an essential task in China's rural revitalization strategy. Based on the yearbook data of sewage treatment in rural areas between 2014 and 2019, although the rate of sewage treatment in rural areas of China showed an upward trend, it was still below 35%, mainly due to the lack of suitable sewage treatment technologies. Here, we discuss the multi-soil-layering (MSL) system, which is an emerging technology suitable for rural sewage treatment. It was deemed to overcome the shortcomings of current biological and ecological treatment technologies, such as complex operation, large area, and high operating costs. We used system dynamics to evaluate the advancing and limiting factors of MSL application for rural sewage treatment from the social, environmental, and economic dimensions. The results illustrated a complete causal loop diagram in which essential variables and relationships were concentrated in the technology, operation and maintenance, and satisfaction of farmers. The efficiency of MSL is the key variable affecting the final decision of the MSL application. Overall, using MSL to treat rural sewage could be an option to improve the rural environment in China. However, the scientific technological model for MSL should be further explored. This review provides guidance on how to promote MSL systems in rural areas.
Chapter
The world we are living in is slowly getting urbanized. The world’s urban population which accounts for 55% today will rise to 66% by 2050 (World Urbanization Prospects: the 2014 Revision UN) (United Nations 2014). This increasing influx of the population into the cities has increased the stress in the water demand, as most of the cities are already facing severe water crisis (Hanjra and Qureshi 2010; Jury and Vaux 2007). Even if the water demand is met, it will create an additional challenge to treat wastewater generated, which accounts for almost 80% of water supplied. The latest report by United Nations World Water Assessment Programme (WWAP) (2017) highlighted that the 80% of the wastewater generated in the entire world is disposed without treatment, directly into the water bodies or open drainage and this figure is 95% in some poor countries. Disposal of this untreated wastewater in the lake, river, and stream will lead to unprecedented deterioration of health of these water bodies (Edokpayi et al. 2017; Lee et al. 2016; Khan and Ansari 2005). Untreated wastewaters have a very high concentration of nutrients, possibly heavy metals, emerging contaminants, suspended solids and pathogens, which alter the physical, chemical and biological properties of water, and thereby affect natural properties of water bodies, and biological life that thrive in it (Khan and Ansari 2005). Eutrophication, also known as an algal bloom, is one of the worst ramifications of excessive nutrient loading in water bodies due to discharge of nutrient-rich (nitrogen and phosphorus) wastewater in it (US EPA 1999; Khan and Ansari 2005).
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Article
For several years, the CEMAGREF has been interested in the study of treatment plants adapted to rural areas. In this field, “macrophyte beds”, as a new procedure in water treatment, has been closely followed. This treatment plant is made up of a series of watertight tubes filled with gravel and rooted with aquatic plants. Since autumn of 1982, this plant has been treating the wastewater of a rehabilitation center which functions according to a scholastic calendar. Receiving loading of 28 population equivalents, the plant must be able to cope with loading variations reaching a factor of 6. The total planted surface is 63 m2, thus 2.5 m2 per population equivalent. The different series of measurements taken during an annual plant cycle show that:–the abatement of the organic loading (COD, BOD5) reaches 85% to 90%;–the elimination rate of total nitrogen is near 50%;–the phosphorus is mineralised but is not retained by the treatment. The samplings of effluent discharge, taken several times over a three year study period, showed that the once satisfactory discharge had degraded. The origin of this degradation should be looked into. The first results (as described above) will be completed by those obtained during a study which is being conducted on a larger scale (500 population equivalent). This plant was put into use in September 1985 and receives a loading of domestic wastewater from an urban neighborhood. The research project has as its aim to optimize both the economic and operational aspects of the treatment plant to answer the real needs of small rural communities.
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Article
Three different multistage constructed wetland plants for wineries wastewater treatment, located in central Italy, have been monitored and designed by the IRIDRA Ltd engineering firm. The three treatment systems are: 1) Casa Vinicola Luigi Cecchi & Sons (Siena): single stage horizontal subsurface flow system (SFS-h) followed by a Free Water System (FWS); 2) Azienda Vitivinicola "Tenuta dell'Ornellaia" (Leghorn): vertical flow constructed wet land (SFS-v) as a first stage followed by a second SFS -h stage with recirculation to the first stage and then by a single FWS; 3) Azienda Agricola La Croce (Siena): a single stage SFS-h constructed wetland. This paper presents the principal design specifications, a description of the plant operations and the analyses of influent and effluent characteristics (pH, COD, BOD5, TN, TP, TSS). The comparison of the performances of these three different plants is of the great interest, given that they have been designed with different layouts and are set in the same geographical region in Italy, where the wine industry represents a very important economic sector. The mean COD concentration in the three plants, after a primary anaerobic treatment and equalization, is in the range of 1000 -4000 mgO2/l, while pH varies from 4.8 to 6.9. The preliminary data indicates that constructed wetlands have great potential for treatment of this kind of wastewaters: so far, the BOD5 and COD removal as high as 92-98% and 87-98% have been achieved, respectively. Suspended solids (TSS) were removed with up to 70-90% efficiency, neutralization of the pH in the effluents contributed to the increase from 6.5 to 7.5, total nitrogen (TN) removal was 50 -90% and total phosphorus (TP) 20-60%.
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Article
Several European countries have produced guidelines for the construction of subsurface flow constructed wetland systems. No consensus has however been reached because the discharge requirements vary from country to country. The guidelines cannot be directly transferred to Denmark because of very stringent outlet requirements. In order to improve the knowledge on nitrification capacity of vertical flow systems and the potential to remove phosphorus in constructed wetlands, a number of studies were conducted in a five-year old constructed wetland system with a horizontal subsurface flow bed and a vertical flow bed, serving two small communities in Denmark. The experiments evaluated the nitrification activity in vertical flow systems as a function of area mass loading rate, loading frequency and temperature of treated, but not nitrified, effluent. The constructed wetland system used as basis for the experiments was, however, poorly suited for these experiments because of the restricted bed depth and other on-site problems with system design and wastewater composition. It was therefore not possible to establish the relationship between area loading rate and nitrification activity. However, the studies do indicate that frequent pulse loadings increase the nitrification rate. Furthermore, nitrification occurred even at 2degreesC. Thus, a pulse loaded vertical bed can sustain some nitrification activity even at very low water temperatures. The studies also documented that recycling of nitrified effluent water to the sedimentation tank increases the removal of total-nitrogen because of denitrification. It is concluded that constructed wetland systems with vertical non-saturated flow will be able to fulfil the most stringent treatment requirements imposed for on-site treatment of domestic sewage in rural areas. However, design and area demand is not yet fully established, and more work is needed to refine the removal process for phosphorus. A set of provisional guidelines for the design and construction of vertical flow systems is presented.
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Article
The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands. The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing. (C) 1997 IAWQ.
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Article
Macrophytes have several intrinsic properties that makes them an indispensable component of constructed wetlands. The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects brought about by the presence of the plants. The macrophytes stabilise the surface of the beds, provide good conditions for pbysical filtration, prevent vertical flow systems from clogging, insulate against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the design of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte-mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.
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Article
The present paper describes the theoretical basis of wastewater treatment in the rhizosphere of wetland plants, the so-called “root-zone method”, along with the first working experiences from eight treatment plants in Denmark. Mechanically treated wastewater is led horizontally through the rhizosphere of wetland plants. During the passage of the wastewater through the rhizosphere, the wastewater is cleaned by microbiological degradation and by physical/chemical processes. The wetland plants supply oxygen to the heterotrophic microorganisms in the rhizosphere and stabilize the hydraulic conductivity of the soil. Nitrogen is removed by denitrification and phosphorus and heavy metals are bound in the soil. The first working experiences from Denmark show, that as far as BOD is concerned root-zone treatment plants are very nearly up to conventional secondary treatment standards already from the first growing season (removal efficiency: 51-95%). For the nutrients nitrogen and phosphorus the results vary (total-N removal: 10-88%; total-P removal: 11-94%). The removal efficiencies depended mainly on the composition of the soils and the degree of surface runoff in each treatment plant. It is concluded that root-zone treatment plants seem to be a viable alternative to conventional wastewater treatment technology, especially suitable for single households and small to medium sized communities. There is, however, still very little information on the removal processes for nitrogen (denitrification), on the effect of soil type and on the required surface area to load ratio
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Article
Up to the present time documentation for the functioning of the root-zone method is almost exclusively based on data from the Othfresen plant in Western Germany, a 22.5 ha large wetland, which since 1974 has received municipal wastewater. The present paper describes the working experiences from Othfresen, and evaluates the applicability of the data from Othfresen as basis for the scientific documentation of the root-zone method in general. It is concluded that the data from Othfresen are useless in the documentation of the root-zone method for the following reasons: (a) The loaded area has not until 1985 been well-defined, (b) the soil in the treatment plant is very atypical (old mine debris), (c) a major proportion of the wastewater does not penetrate the soil, but distributes on the surface as overland flow, (d) the quality of the water in the “defined” outlet, i.e. a well consisting of a PVC-tube, has no relation to the treatment of wastewater in the area, and (e) the true effluent to the recipient is of varying quality, especially as far as nitrogen is concerned. It is therefore necessary to await results from well-controlled experimental treatment plants before the functioning and the applicability of the root-zone method can be properly evaluated.
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Article
This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD> 75%), P (> 90%) and total and ammonia N (40–80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3–6 years of monitoring. Iron-rich sand from Bsh and Bs, horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.
Article
A greenhouse experiment was conducted at Tennessee Valley Authority, Alabama, USA, in the summer of 1993 to investigate ammonium and nitrate removal processes in constructed wetlands. Microcosm wetlands cells were used in the study and consisted of plastic containers with 0.4 × 0.35 m2 surface area and 0.5 m depth. Two separate experiments were conducted. One experiment analyzed NH4-N removal and the other analyzed NO3-N removal. Nutrient solutions containing approximately 48 mg/l NH4-N or NO3-N were added in a batch mode to the wetland microcosms and the solution chemistry was analyzed with time. Treatments consisted of unplanted cells or cells planted with canarygrass (Phalaris arundinacea), reed (Phragmites communis), bulrush (Scirpus atrovirens georgianus) or typha (Typha latifolia). Another treatment consisted of added nutrient solutions containing or not containing C at 112 mg/l. In the NH4-N removal experiment, the rate of NH4-N removal occurred in the order: reed > canarygrass = bulrush > typha ≫ unplanted in wetland cells with and without C. The order of NH4-N removal was believed to be associated with the density of root biomass in the gravel. The greater the root biomass, the greater the chance for plant N uptake or nitrification mediated by O2 transport to the rhizosphere. In the NO3-N experiment, the rate of NO3-N removal occurred in the order: reed = canarygrass > typha = bulrush > unplanted cells. Labelled K15NO3 was used to trace the NO3-N removal process. By measuring the 15N in the plant biomass, the quantity of NO3-N removed via plant uptake was delineated from combined removal processes of denitrification and immobilization. In the treatments with C, 55 to 70% of the NO3-N was removed via denitrification and immobilzation. For bulrush, reed and typha, the quantity of NO3-N removed via denitrification and immobilization without added C was reduced to 14 to 30%. However, NO3-N removal via denitrification and immobilization remained high at 72% of added NO3-N in canarygrass cells due to high concentrations of organic C released from the canarygrass roots (15-20 mg/l C) that apparently did not limit denitrification or immobilization.
Article
This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD> 75%), P (> 90%) and total and ammonia N (40-80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3-6 years of monitoring. Iron-rich sand from Bsh and Bs horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.
Article
The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands. The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.
Article
Constructed wetlands proved to be an effective and low-cost technology to control environmental pollution. The introduction of such low-tech systems is supported by the Slovenian Government. The aim of our research project was to intensify the reduction of nutrients (nitrogen compounds mainly) prior to discharging the effluents into the rivers, a contribution to the common target of the global environmental policy. The construction of the integrated system was completed in Autumn 1993 to treat domestic sewage for 10 PE. The system consists of three interconnected beds with vertical and horizontal flows. The vertical flow at the first stage is intermittent, while the horizontal one is continuous. The system is flexible due to mode of operation and the quality of the influent. Ten analyses were made during the initial months of operation. In bed B nitrification was taking place and the reduction of all other parameters but NO3-N was documented. In bed A denitrification was on in spite of intermittent vertical flow. Since the reed stand was scarce, recultivation was needed. The system showed its characteristics more clearly when more concentrated domestic wastewater was led in. Further investigation should reveal further details on proper media, surface area, and flow sequence selection. Reduction of some parameters was as follows: NH3-N 97.5%, NO3-N 74.5%, org-N 84.8%, P-tot 97.1% and COD 94.4%.
Article
Constructed wetlands with horizontal sub-surface flow (HSF CWs) usually provide high removal of BOD5. Organic compounds are degraded by both aerobic and anaerobic bacteria in the rhizosphere of vegetated beds. The results from the Czech HSF CWs showed an average treatment efficiency of 86.6% with an average effluent BOD5 concentration of 13.2 mg 1−1. The BOD5 loading of vegetated beds of HSF CWs varied between 2.6 and 99.6 kg ha−1 d−1 with an average of 33.5 kg ha−1 d−1. The results also indicated that the removal of BOD5 is not temperature dependent and is steady throughout the year.
Chapter
The success of the two sewage treatment systems based on aquatic plants at Oaklands Park in Gloucestershire has attracted the attention of the industry and the media. The industry has been impressed by the performance of the two systems; the media and the public are drawn to the concept of a sewage treatment system being an attractive community amenity. The incorporation of FLOWFORMS to impart rhythmical, pulsating movement into the heart of the treatment “organisms” also creates further interest. The philosophy of these two systems - that the responsibility for cleansing wastewater rests with the community - has inspired a number of other (dedicated) communities to work with similar landscaped sewage treatment systems.
Chapter
It is not easy to find a solution which allows good management of sludge at reasonable costs for small wastewater treatment plants using the activated sludge process in extended aeration, which are common in France. Normal sludge drying beds are very expensive in terms of operational costs, their use is more and more being abandoned in favour of direct agricultural use of the liquid sludge. However, this solution, although satisfactory, cannot be chosen in all cases and often requires the construction of large storage tanks at high costs. A literature survey had shown that planting reeds on drying beds with sufficiently high free boards could be an interesting solution which combines both low investment and operational costs. A trial has been started in summer 1989 in France, using three experimental beds of 20 m2 each. Two beds are designed in the traditional way, one of them is planted and the other one is an unplanted control bed. The third bed is also planted, but Bioterra blocks are used for drainage and aeration from below. In six months the planted beds have received about 15 kg of dry matter m–2 and the control bed has received 6.5 kg of dry matter m–2 during the three and a half winter months.
Article
The paper reviews the different options for the combination of vertical- and horizontal-flow beds used in hybrid reed bed/wetland systems. The design and performance of these systems are briefly described. The importance of the oxygen transfer capacity of the different arrangements to their performance and their size is discussed. Alternative methods for denitrification are briefly described.
Article
The Tennessee Valley Authority is demonstrating use of constructed wetlands for municipal wastewater treatment with three full-scale small community sewage systems. Project objectives include determining permit compliance ability, evaluating basic design and operational factors, evaluating cost effectiveness, investigating process variables to further optimize design and operation factors, and conducting technology transfer activities. Results of the initial 11 to 20 months of data reveal that all constructed wetland cells are very effective in reducing suspended solids, biochemical oxygen demand, and fecal coliforms. Nitrification appears to be limited by dissolved oxygen. Phosphorus removal is variable. Gravel cells generally provide slightly better effluent quality than surface flow cells. Clogging in the inlet areas of gravel cells has been a major problem with the existing design and treatment performance. Vegetation species that have rhizomes appear to be a much better choice than other types based on quicker cell coverage. Vegetation should generally be allowed a period of establishment (one growing season if practicable) prior to sustained pollutant loading.
Article
This paper briefly describes experiences of a research project in Southern Germany about wastewater treatment with a reed-bed system called “Planted Soil Filter”, beginning 1985 and ending 1990, with tests in full-scale with a pilot-plant, half-technical and laboratory scale. Used soils: alkaline coarse-grained, alkaline fine-grained, acid coarse-grained, acid fine-grained. Used plants: common reed (Phragmites australis), bulrush (Schoenoplectus lacustris), cattail (Typha latifolia), sweet flag (Acorus calamus), yellow flag (Iris pseudacorus).
Article
The paper reviews the different options for the combination of vertical- and horizontal-flow beds used in hybrid reed bed/wetland systems. The design and performance of these systems are briefly described. The importance of the oxygen transfer capacity of the different arrangements to their performance and their size is discussed. Alternative methods for denitrification are briefly described.
Article
Methane emissions were measured during mid-smaller in four pilot-scale constructed wetlands that had treated dairy farm wastewaters for a period of 2 yr. Measurements were made at up and downstream sites in wetlands receiving low and high wastewater loadings (~26 and 45 mm d-1), both in the presence of wetland vegetation (Schoenoplectus validus). An automated flux chamber (enclosure area 0.25 m2) and gas circulation system, and associated sampling and chromatographic analysis system, were used to make measurements directly in the field. Median emissions ranged between 48 and 482 mg CH4 m-2 d-1, without discernible diurnal patterns. Upstream sites, closest to wastewater inflows, generally showed significantly higher (P < 0.05) emissions than downstream sites in the same wetland. Unvegetated sites tended to show higher emission rates than corresponding vegetated sites, with highest rates recorded at the highest loaded unvegetated site. Redox potentials in the surface 100 mm of the substratum at upstream sites, with and without vegetation, showed consistently more oxidized conditions in the presence of plants. This suggests that plant root-zone oxidation was acting to suppress methanogenesis and/or enhance methane oxidation in the vegetated wetlands. Emissions from the vegetated constructed wetlands were comparable with those reported for natural wetlands and inorganically fertilized rice paddies. Methane emissions were estimated to account for around 2 to 4% of wastewater C loadings to the vegetated wetlands and 7 to 8% of loadings to the unvegetated systems during the period of measurement.
Article
The present study consists of assessing the efficiency of a macrophyte (Phragmites australis) system in wastewater purification in an arid climate. The experimental system is made up of three beds differing in length (30, 40 and 50 m) and implanted with Phragmites australis. Wastewater inflow through these beds is horizontal with a flow of 10 l.s⁻¹. Retention time varies between 1 and 4 h. The frequency of irrigation is weekly. The studied parameters are: the organic load (COD and TSS), nutrients (total Kjeldhal nitrogen: TKN and total phosphorus: TP) and the parasitical load (helminth eggs). Water, soil and plants are the three components of the experimental system we analyzed.
Article
Constructed wetlands with horizontal sub-surface flow (HSF CWs) usually provide high removal of BOD5. Organic compounds are degraded by both aerobic and anaerobic bacteria in the rhizosphere of vegetated beds. The results from the Czech HSF CWs showed an average treatment efficiency of 86.6% with an average effluent BOD5 concentration of 13.2 mg l−1. The BOD5 loading of vegetated beds of HSF CWs varied between 2.6 and 99.6 kg ha−1 d−1 with an average of 33.5 kg ha−1 d−1. The results also indicated that the removal of BOD5 is not temperature dependent and is steady throughout the year.
Article
The in- and efflux of metabolic gases through the soil-atmosphere interface and through the hollow culms of reed (Phragmites australis) in a soil-based constructed reed bed with lateral sub-surface water flow was quantified. The total flux of gaseous oxygen into the bed substrate was 5.86 g m-2day-1 of which 2.08 g m-2 day-1 was through the hollow culms of standing-dead culms of P. australis. The respiratory oxygen consumption of roots and rhizomes almost perfectly balanced the oxygen influx through the culms leaving only 0.02 g O2 m-2day-1 to be released to the surrounding soil. The macrophyte-induced rhizosphere oxygenation was therefore of no quantitative importance for aerobic BOD degradation and microbial nitrification. The major drawbacks of the design are the lack of ability of the reeds to develop a sufficiently high hydraulic conductivity of the soil and to transfer oxygen into the substrate. Subapical regions of white young roots of P. australis, Glyceria maxima, Typha latifolia and Iris pseudacorus released oxygen, whereas no release was detected from old roots and rhizomes Studies on the potential diffusive oxygen transfer capacity of reeds showed that at 15° C the respiratory oxygen demand of the root-system would balance the diffusive transport capacity for root lengths of approx. 60 cm. The oxidation in constructed reed beds can be significantly improved by changes in the design and loading regime. In a vertical flow system consisting of several beds laid out in parallel with intermittent water loading, the oxygen transfer from the atmosphere to the bed substrate would be 30 to 150 g m-2day-1 depending on substrate texture.
Article
Constructed wetlands proved to be an effective and low-cost technology to control environmental pollution. The introduction of such low-tech systems is supported by the Slovenian Government. The aim of our research project was to intensify the reduction of nutrients (nitrogen compounds mainly) prior to discharging the effluents into the rivers, a contribution to the common target of the global environmental policy. The construction of the integrated system was completed in Autumn 1993 to treat domestic sewage for 10 PE. The system consists of three interconnected beds with vertical and horizontal flows. The vertical flow at the first stage is intermittent, while the horizontal one is continuous. The system is flexible due to mode of operation and the quality of the influent. Ten analyses were made during the initial months of operation. In bed B nitrification was taking place and the reduction of all other parameters but NO3−N was documented. In bed A denitrification was on in spite of intermittent vertical flow. Since the reed stand was scarce, recultivation was needed. The system showed its characteristics more clearly when more concentrated domestic wastewater was led in. Further investigation should reveal further details on proper media, surface area, and flow sequence selection. Reduction of some parameters was as follows: NH3−N 97.5%, NO3−N 74.5%, org-N 84.8%, P-tot 97.1% and COD 94.4%.