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Horizontal subsurface flow constructed wetland. 

Horizontal subsurface flow constructed wetland. 

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Conventional secondary and tertiary wastewater treatment methods include activated sludge, trickling filters, slow sand filtration, chlorination, ozonation and UV radiation. Chlorination being the most widely used pathogen disinfection method is presently under scrutiny as chlorination can produce carcinogenic trihalomethanes when natural organic m...

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... distribution system and, in comparison to chlorination, both technologies require an increase in energy usage. Cost and maintenance have limited the use of UV and ozonation (Kadlec and Knight, 1996). Low energy non chemical methods of pathogen treatment have been used when receiving waters are non potable or disinfection requirements relaxed. Wetlands have been shown to reduce pathogen counts to varying degrees (Vymazal, 2005). Constructed Wetlands have low capital and operating costs making them popular in remote areas and developing countries. The wetland concept has become an attractive cost-effective wastewater treatment alternative compared to conventional or tertiary treatment processes (Morsy, 2007). The natural ability of wetland ecosystems to improve water quality has been recognized since the 1970s (Knight et al. , 1999). The main idea behind a constructed wetland used for water treatment is to try and reproduce a wetland ecosystem with the expectation that the contaminated water will be treated as it passes through this artificial wetland system. Constructed wetlands have been used to treat a number of different contaminated waters including organic farm waste (Cronk, 1996), food processing waste (Burgoon et al. , 1999), human wastewater (Decamp and Warren, 2000), and acid mine drainage (Mitsch and Wise, 1998). There are three general types of constructed wetland systems; free surface water (FSW), horizontal subsurface flow (HSSF), and vertical flow (VF) constructed wetlands. FSW CWs are built by first digging a trench with a slight incline (~1o) from inlet to outlet to allow gravity movement of the water. This trench is then lined with an impermeable polymer, or low a permeability soil such as densely packed clay. This lined trench is then filled with the desired bed media. Bed media is most often selected based on desired flow patterns, nutrient and mechanical support for the chosen plant types, and as a nutrient source required for some biologically-mediated treatment processes. In some geographical locations the native soil may have a permeability low enough such that no liner is required. In this case the trench can simply be dug and filled with the desired bed media. Common media include peat, gravel, sand, soil and compost. FWS constructed wetlands contain standing water on the surface of the treatment system and can be fed from either below ground or above ground (Figure1). HSSF CWs are similar in construction to FSW CWs, but are typically fed from below ground and are designed so the maximum flow rate will not allow surface water formation on top of the HSSF CW (Figure ...

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... Given the size of land, the aspect ratio of the shallow wetland basins was designed to be 1:5. Trenches were dug to a depth of about 0.60 m to enable the root to extend with a slight incline (~1°) from inlet to outlet to allow gravity movement of the water (Weber & Legge, 2008). The trench was then lined with an impermeable polymer or water proof membrane to prevent seepage. ...
... The study recorded removal efficiencies for total coliform between 44% and 50%. This is slightly lower than observations made by authors such as Weber and Legge (2008), and Kadlec (2009) where coliform removal ranged between 65% and 99%. observed that the the removal efficiency of pathogenic organisms in free water surface flow constructed wetlands were a little lower compared with subsurface flow constructed wetlands. ...
... Others produce tannic and gallic acids (anti-bacterial substances), which according to Kinnear et al. (2008), are responsible for antimicrobial activity, though other compounds may probably be involved as well. Weber and Legge (2008) state that plant type is among the latent variables that influence the removal efficiencies. This could be seen in Table 3 where different plants recorded different removal efficiencies for total coliform. ...
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Although the role of plants in wetland ecosystems is largely known, not many native plant species have been used in constructed wetlands, especially in sub-Saharan Africa to treat oilfield wastewater, an emerging contaminant of considerable concern to both academics and policy makers owing to its deleterious effects on aquatic organisms and human health. This study assessed the contaminant removal efficiencies of three indigenous wetland plants (Typha latifolia, Ruellia simplex and Alternanthera philoxeroides) in a small-field-scale free water surface flow constructed wetland to polish effluent treated in a conventional oily wastewater treatment plant. Statistical significant differences in removal efficiencies were recorded between the planted wetlands and the unplanted wetland for all parameters examined, with the exception of total phosphorus. The results also showed that the removal efficiencies for oil and grease, biochemical oxygen demand, chemical oxygen demand and total dissolved solids were highest in wetland planted with Alternanthera philoxeroides followed by Typha latifolia planted wetland. Whereas the removal of nitrate and total phosphorus were highest in wetland planted with Typha latifolia, the removal of coliform bacteria was highest in Ruellia simplex planted wetland. The study showed that free water surface flow constructed wetland has the potential to improve quality of effluent treated with conventional oily wastewater treatment plant. The study is very significant because it has extensive practical application in the oil and gas industry in terms of improving the contaminant removal efficiency and thereby limiting adverse environmental and human health impacts. Also, wetland treatment systems are nature-based solution to environmental problems because they are built on sound ecological principles and for that matter they are sustainable in terms of the capital cost involved, energy consumption and technological requirement.
... It is found out that decreased temperatures outside will inactivate pathogens. 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). ...
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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.
... Cell death is the major factor in coliform removal; other factors such as filtration, adsorption, and sedimentation play a role in coliform removal. Oxidation, predation, inactivation of cells, temperature, and water chemistry also significantly influence the pathogen removal in constructed wetlands (Weber & Legge 2008;Vymazal 2011;Makvana & Sharma 2013;Karimi et al. 2014;Wu et al. 2016). The coliform group of bacteria was reduced in higher order and the effluent would still have a high potential for containing pathogens, and would need to be disinfected before discharge. ...
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To find the effect of Hydraulic Retention Time (HRT) and seasons on the performance of horizontal subsurface flow constructed wetland (HSSF CW) in treating rural wastewater, a pilot scale unit 2.5 m × 0.4 m × 0.3 m size bed planted with Typha latifolia and Phragmites australis was operated for a 12-month duration. During the study 2, 4, 6, 8, and 10 days of HRT were maintained in winter, summer, and rainy seasons. The removal efficiency obtained ranged from 62.09 to 87.23% for Chemical Oxygen Demand, 69.58% to 93.32% for Biochemical Oxygen Demand5 (BOD), 31.55% to 59.89% for Ammonia Nitrogen (NH4-N), 15.18% to 52.90% for Total Kjeldahl Nitrogen (TKN), 21.02% to 50.21% for Phosphate Phosphorus (PO43− P), 19.82% to 48.23% for Total phosphorus (TP), 74.93% to 93.10% for Faecal Coliform (FC) and 69.93% to 90.23% Total Coliform (TC). Overall, results showed that the performance of the unit was good. For statistical analysis two way ANOVA test followed by Tukey's test was used with a 95% level of significance. It was observed that the removal efficiency of the pollutants was increased with an increase in HRT. HRT of 6 days was found as adequate for significant removal of organic matter (COD and BOD). Seasonal removal efficiencies followed the order of summer > rainy > winter for all the parameters, but the difference was not statistically significant. HIGHLIGHTS Sporadic study in the study area.; Helps in the prevention of pollution.; Low cost treatment solution for the rural areas.; Helps to optimize the design of treatment unit.;
... This screening process can occur not only in the wetland system media but also through the plant root structure. [15] In Vymazal (2008) explained that the wetland system offers a combination of physical, chemical and biological factors that are suitable for eliminating pathogenic organisms. Physical factors include filtration mechanisms, exposure to ultraviolet radiation and sedimentation. ...
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The Indonesian Ministry of Environment in 2014 released study results that 60-70% of rivers in Indonesia have been polluted by domestic wastewater, which is not treated properly. Improper and inadequate wastewater treatment not only pollutes water resources and damages ecosystems, but can also pose a significant public health risk. The development of spontaneous settlements in urban kampong makes the environmental quality within the settlements getting worse and many people consider that the area of urban kampong is not habitable. The efforts to treat wastewater before being discharged into water bodies are very important. The study of "vertical constructed wetland" model using water plants which are also ornamental plants can be considered as an alternative system for household wastewater treatment in kampong settlements. The objective of the research is to develop an alternative model of wastewater treatment that can overcome the obstacles of implementing a wastewater treatment system in terms of cost and availability land. The result shows that the removal efficiency of BOD, phosphate and total coliform are 71.64%, 50,92% and 99.67% respectively. Since the research is still being conducted on a laboratory scale, the further study must be developed with real case studies in low income community settlements in Kampung Kota. Additionally this research can give suggestions to local government an alternative policy to implement domestic waste water treatment plan in a densely populated settlement along the riverbank in the city.
... The removal of pathogens comprises one of the most important factors in terms of reclamation. Many authors have reported removal rates for pathogens in constructed wetlands of as high as 99.99% [51]. This study revealed a removal efficiency of 99.5% at the outlet, with similar results in the stabilization pond for Escherichia coli, i.e., 95.4%, for intestinal enterococci, 95.7%, and 99.4% and 97.8% for the thermotolerant coliforms. ...
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Agriculture is being negatively affected by the decrease in precipitation that has been observed over the last few years. Even in the Czech Republic, farmers are being urged to irrigate their fields despite the fact that sources of water for irrigation are rapidly being depleted. This problem might be partially solved via the reuse of treated wastewater in certain agricultural sectors. However, the public perception of the reuse of wastewater remains negative primarily due to unknown risks to the environment and public health. To overcome this barrier, a semi-operated irrigation field was established at Kostelec nad Ohří in the Central Bohemian region of the Czech Republic and planted with common garden crops such as tomatoes (Lycopersicon esculentum), potatoes (Solanum tuberosum) and lettuces (Lactuca sativa L.) irrigated with two different water sources, i.e., treated wastewater from a local nature-based treatment system, a hybrid constructed wetland (HCW), and local fresh water from well. The HCW was put into operation in 2017 and was reconstructed in 2018 and includes both horizontal and vertical flow beds; the trial irrigation field was added in the same year. The reconstruction of the facility significantly enhanced the removal efficiency with respect to all monitored parameters, e.g., biochemical oxygen demand (BOD5), chemical oxygen demand (COD), N–NH4⁺, total N and the suspended solids (TSS), except for total P. The HCW also ensured the significant removal of several observed pathogenic microorganisms (E. coli, intestinal enterococci and thermotolerant coliforms). During the 2018 and 2019 growing seasons, we observed the significantly enhanced growth of the crops irrigated with wastewater from the HCW due to the fertilizing effect. The risks associated with the contamination of crops irrigated with treated water are not negligible and it is necessary to pay sufficient attention to them, especially when introducing irrigation with wastewater into practice.
... The contribution of wetlands to reducing pathogen counts has been well demonstrated (Rogers, 1983;Weber and Legge, 2008). A wide variety of processes are involved in a wetland's removal and inactivation of pathogens in water, including sedimentation, natural die-off, inactivation or death related to temperature, oxidation, predation, inactivation or death related to unfavourable water chemistry, biofilm interaction, mechanical filtration, exposure to substances (e.g. from root secretions) which are toxic to the pathogens and UV radiation (Rogers, 1983;Weber and Legge, 2008). ...
... The contribution of wetlands to reducing pathogen counts has been well demonstrated (Rogers, 1983;Weber and Legge, 2008). A wide variety of processes are involved in a wetland's removal and inactivation of pathogens in water, including sedimentation, natural die-off, inactivation or death related to temperature, oxidation, predation, inactivation or death related to unfavourable water chemistry, biofilm interaction, mechanical filtration, exposure to substances (e.g. from root secretions) which are toxic to the pathogens and UV radiation (Rogers, 1983;Weber and Legge, 2008). The importance of riparian areas in providing this service has also been well documented, together with the primary factors affecting performance (Macfarlane and Bredin, 2016a). ...
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A rapid assessment technique, termed WET-EcoServices, was developed 10 years ago to help assess the ecosystem services that individual wetland hydrogeomorphic units supply. The technique requires the assessor to consider and score a suite of indicators (e.g., hydraulic roughness of the vegetation) which are then used to rate the ability of the wetland to provide 16 different ecosystem services. WET-EcoServices has become well entrenched in the South African context, with wetland specialists routinely using the technique to inform development planning, whilst it has also been used extensively in the wetland rehabilitation context. The technique has recently been revised, including the following key changes: (i) the technique is now more explicit in terms of distinguishing both ecosystem services’ supply and the demand for all ecosystem services assessed; (ii) the technique has been expanded to include non-wetland riparian areas; (iii) several of the indicators have been refined or replaced with indicators more relevant or appropriate for informing the rating of the ecosystem service or for which information is more readily available at a national level; and (iv) the algorithms used to integrate scores for the relevant indicators have been comprehensively refined so as to better account for the relative importance of the respective indicators. The aim of this paper is to present an overview of Version 2 of the technique and its underlying approach and then to demonstrate its application to 6 selected cases representing contrasting contexts, with a particular focus on the graphical representation of ecosystem service supply and demand for each case. Some of the key emphases and approaches applied by WET-EcoServices are then discussed in relation to other published techniques widely used for assessing wetland ecosystem services. After reflecting on some key limitations of WET-EcoServices, the paper concludes with recommendations on the technique’s potential contributions to operationalizing key broad imperatives of government.
... There have been several studies published on microbial water quality improvement using wetland systems (Vymazal, 2005;Wu et al., 2016). Pathogen treatment relies on complex mechanisms of multiple chemical (oxidation, UV radiation, exposure to plant biocides, unfavourable water chemistry, adsorption to organic matter and biofilm), physical (sedimentation, adsorption and filtration), and biological (predation, biolytic processes, antibiosis, natural die-off) factors, which often act in combination (Stefanakis & Akratos, 2016;Weber & Legge, 2008). The effectiveness of these treatment mechanisms is dependent on a synergistic effect of natural (environmental) and technical (design, operation and maintenance) features, which affect the various microbial pathogens differently. ...
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Natural swimming pools are outdoor swimming pools with biological water treatment. They are separated form natural waters and sealed off from the groundwater. They are divided into bathing and treatment areas and must meet defined quality requirement, especially in the case of pools open to the public.
... There have been several studies published on microbial water quality improvement using wetland systems (Vymazal, 2005;Wu et al., 2016). Pathogen treatment relies on complex mechanisms of multiple chemical (oxidation, UV radiation, exposure to plant biocides, unfavourable water chemistry, adsorption to organic matter and biofilm), physical (sedimentation, adsorption and filtration), and biological (predation, biolytic processes, antibiosis, natural die-off) factors, which often act in combination (Stefanakis & Akratos, 2016;Weber & Legge, 2008). The effectiveness of these treatment mechanisms is dependent on a synergistic effect of natural (environmental) and technical (design, operation and maintenance) features, which affect the various microbial pathogens differently. ...
... There have been several studies published on microbial water quality improvement using wetland systems (Vymazal, 2005;Wu et al., 2016). Pathogen treatment relies on complex mechanisms of multiple chemical (oxidation, UV radiation, exposure to plant biocides, unfavourable water chemistry, adsorption to organic matter and biofilm), physical (sedimentation, adsorption and filtration), and biological (predation, biolytic processes, antibiosis, natural die-off) factors, which often act in combination (Stefanakis & Akratos, 2016;Weber & Legge, 2008). The effectiveness of these treatment mechanisms is dependent on a synergistic effect of natural (environmental) and technical (design, operation and maintenance) features, which affect the various microbial pathogens differently. ...
... While, some previous works have reported that vegetation did not play a significant role in the reduction of bacteria (Torrens et al., 2009;Headley et al., 2013). Other factors such as hydraulic retention time (HRT), (HLR) of wastewater and natural die off may play a role in removal of bacteria in VF-CW 2 and HF-CW 2 beds as has been proposed by some authors (Wand et al., 2007;Weber and Legge, 2008). ...
Article
Factors affecting the removal of opportunistic pathogens were evaluated in a hybrid constructed wetland (CW2) treating rural wastewater. The correlations between the bacterial population and the environmental variables showed that bacteria discharge was the result of abiotic factors change such as temperature (T), electrical conductivity (EC), dissolved oxygen (DO), organic matter and nutrient availability, as well as biotic factors like antagonism and competition with the native microbial community. However, the contribution of each factor depends on bacteria nature, on the influence of wetland design, availability of oxygen, season, presence of plant, and wastewater composition. Higher removals rates of biochemical oxygen demand BOD5 (94.64 ± 3.92 %), chemical oxygen demand COD (90.91 ± 6.81%), total suspended solids TSS (98.05 ± 1.18%), nitrogen (total Kjeldahl nitrogen TKN (81.78 ± 11.01%), ammonia nitrogen NH4+ (92.17 ± 6.56 %), orthophosphate PO43‐ (79.73 ± 10.41%) and bacteria (>98 %) were observed in CW2.