Subsurface flow constructed wetland with plants reduced organic and heavy metal con- centrations by more than 85%. E.sexangulare removed organics and heavy metals better than S. globulosus. The higher removal efficiency for E. sexangulare was probably due to a better oxygen transfer as it had a larger leaf surface area. A higher dosage of heavy metals did not change the removal efficiency of the reactors. S. globulosus removed solids more efficiently than E. sexangulare which was probably due to better roots devel- opment to intercept the particles.
Based on the above results and discussions, it can be summarized that HSSF system has higher removal efficiency compared to VSSF system for the removal of heavy metals. The higher removal of HSSF system was due to the higher HRT value for this system, which also indicates the importance of HRT that affects the removal efficiency of heavy metals in the constructed wetland system. Also, it’s so obvious that by comparing the planted and control system, both systems were achieved high percentage of heavy metals removal at the end of treatment. The greater heavy metals removal in the control system maybe was due to clogging of the substrate in the soil media. So it can be concluded that, reduction of heavy metals concentration in the planted and control system were most likely due to chemical precipitation and sorption on sediment, and aided by the macrophytes. This is also shows the shorter treatment period is required in achieving optimum removal for planted system as compared to unplanted system. However, for a longer treatment period there were only slender differences in the effluent concentration of pollutants between the planted and control system. To further enhance the result obtained in this study, the following areas of investigation are recommended: (1) degradation by microorganism is among the important mechanisms in the removal of pollutants. However, this study does not quantify the development of microorganism within the wetland reactor. If the microorganism formation and development within the reactor could be measured, it surely will enhance the findings in this study and (2) further studies should vary the flow rates, retention time, types of plant and size of constructed wetlands system in order to determine the efficient of pollutants removal.
Though several studies have investigated the kinematics of pollutant removal, most have concentrated on one line studies concerning flow hydraulics of constructed wetlands and applying different hydraulic models [15, 32]. However, the kinetic model has to be assisted by a hydraulic model to achieve an optimum model-based design . Even with abundance of well documented models currently available, one major problem often preventing their optimal use is the extensive work required for data preparation, numeric grid design and graphical presentation of the output results [9, 30, 34]. However, HYDRUS/CW2D is designed to create, manipulate and display large data files. The model also facilitates interactive data management. Interestingly, more recently, first stage anaerobic up-flow and the remaining stages tidal flow with effluent recirculation operation strategy has proved to be an effective approach to promote the capacity of the CW for high-strength wastewater treatment .
For more than two decades, countries have used con- structed wetlands to improve the quality of contaminated water and wastewaters [2-4]. Constructed wetlands have successfully been used for environmental pollution con- trol despite the fact that it was initially designed for use in domestic wastewater . A constructed wetland sys- tem has the positive characteristics of a natural wetland and it duplicates the physical, chemical and biological processes in the natural system . Constructed wetlands are artificial wastewater systems consisting of shallow ponds or channels which have been planted with aquatic plants and which act as biofilters through natural micro- bial, biological, physical and chemical processes to treat wastewater .
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One of the leading pollutants of surface and underground water resources is the effluent from meat processing industry. Pollution load from slaughterhouses has become an issue of considerable public and scientific concern in the light of evidence of their extreme toxicity to human health and biological ecosystems [1- 2]. To ensure sustainable use of the environment and by extension, future users of this essential elements of nature, treatment of slaughterhouse wastewater prior to discharge has becomes imperative. CWs have is used for environmental pollution control although its initial focus was domestic wastewater treatment . CWs are engineered systems designed to mimic and use ecological processes found in natural wetland ecosystems to remove pollutants from wastewater. They are a versatile and cost effective technology suitable for removing several pollutants from different wastewater. Macrophytes are an integral part of CWs, as they play important roles in the removal of pollutants from wastewater. Results have shown performance differences according to macrophyte species in the system, with some species yielding higher removal efficiencies. Key consideration for species suitability include ability to flourish under local climatic conditions, ecological acceptability, extensive root systems, ability to withstand hydraulic and pollutant shock loads, rapid establishment and propagation, and high pollutant removal capacity, either through direct assimilation and storage, or by enhancement of microbial transformations such as nitrification . Lack of these knowledge leads to the failure and poor survival of plants in CWs . There are studies on CWs performance in Nigeria with different plant species and for different wastewater . However, no studies have investigated macrophyte performance for secondary treatment of high strength slaughterhouse wastewater in Nigeria. The aim of this study was to evaluate the growth and performance of three available macrophyte species for secondary treatment of high strength slaughterhouse wastewater.
Our study was focused on a HSSF-CW in the Beijing Wildlife Rescue and Rehabilitation Center, Beijing, China (Latitude: 40˚6'14.40ʺ N, Longitude: 116°42'35.71ʺ E) (Fig. 1). The annual average temperature at the study site is 11.5 °C. The average temperatures in January and July are 4.9 and 25.7 °C, respectively, and the minimum temperature in July is 19.1 °C from 2012 to 2013. The average annual rainfall is 625 mm from 2012 to 2013. The wetland consists of three treatment cells (Table 1), and its purpose is to improve the water quality of the artificial lake in the site. Gravel is the principal media; there are two layers, one 20 cm deep that comprises gravels with a diameter of between 15 and 30 mm and the other 50 cm deep comprised of finer gravels with diameters of between 5 and 15 mm from bottom to top. The average water depths in the three treatment cells are 0.3, 0.1, and 0.1 m. Plants in the upper media, planted at a density of two plants per centiare, show vigorous growth. The plant species are mainly tectorum Lythrum, salicaria Iris, and congesta Eleocharis, with densities of 30, 50, and 60 stem/m 2 , respectively. Birds, such as Ardea alba, Anas platyrhynchos, and Anatidae, are
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Abstract- The objective of the present study was to assess the simultaneous removal of physiochemical parameters in moderate strength wastewater using a lab scale horizontal subsurface flow constructed wetland (HFCW) with natural zeolite as a substrate. In this study, high-density polyethylene tanks (0.36 m 2 ) were planted with phragmites australis and scirpus maritimus and received 0.012 m 3 /d to 0.08 m 3 /d of synthetic wastewater corresponding to a HLR of 0.035 to 0.243 m/d and a COD loading rate of 0.0148 kg COD (m 2 .d) -1 to 0.026 kg COD (m 2 .d) -1 . The HFCW was subjected to three hydraulic retention times (HRT) for 4, 3 and 2 days respectively. Averaged data reported coincided with the plant age (4 to 55 weeks) and covered the entire cold season and early part of the hot season. Based on the 55 weeks of operation, the HFCW unit with zeolite achieved significantly higher removal for COD (85 to 88%), TN (54 to 96%), NH 4 -N (50 to 99%) and TSS (91 to
constructed wetland using magnetic technology is a relatively new idea in Malaysia and the potential of magnets has not yet been discovered. Increasing research and knowledge of wetland have led to the trend to construct wetlands enhanced with magnetic field that obviously duplicate the environmental friendly benefit to the ecosystem. Therefore, this study was carried out to study the effectiveness of a magnetic field to leachate treatment using subsurface flow constructed wetland (SSF) planted with Limnocharis flava.
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The average COD removal efficiency for wetland systems with and without electrolysis integration is 72% and 73% respectively. It is found that there is no significant effect on between COD removal in both the systems. The COD removal mechanism can be explained as settleable organics are rapidly removed in wetland systems under quiescent conditions by deposition and filtration. Attached and suspended microbial growth is responsible for removal of soluble organics. Organic compounds are degraded both aerobically and anaerobically. The oxygen required for aerobic degradation is supplied directly by diffusion or oxygen leakage from the macrophyte roots into the rizhosphere. Uptake of organic matter by the macrophytes is negligible compared to biological degradation . In a tidal flow constructed wetland system, due to the higher efficiency of oxygen transfer to the wetland bed, aerobic degradation will pre-dominate the anaerobic degradation. Aerobic degradation of soluble organic matter is governed by the aerobic heterotrophic bacteria according to the following reaction,
without plant was 15% - 48.51%. The comparison of COD between the outlets of the aeration tank, SCW-MLF vertical flow with Vetiveria Zizanioides unit and MLF without plant is shown in Figure 6. On the first week, the effluent concentration in each unit, for both COD and BOD parameters, was almost the same. However, the difference was significant after that period. Treatment efficiency on SCW-MLF vertical flow with Vetiveria Zizanioides increased linearly with the plant growth. The higher the growth of the plant as well as its leaves and roots, the higher the plant’s ability to absorb organic materials. Furthermore, the deeper and spread out the roots were, the more the microorganism around the roots. Therefore, it increases the removal efficiency of SCW-MLF vertical flow with Vetiveria zizanioides. Hence, SCW-MLF is affected by medium, the roots of Vetiveria zizanioides as well as the microorganism living in both media, while the MLF unit is affected only by the medium and microorganism living in it. This phenomenon explains why microorganism capacity in MLF unit was less effective compared to SCW-MLF with Vetiveria Zizanioides unit. The result was similar to the analysis of Darajeh et al. (2014) on oil palm. According to the research, Vetiveria zizanioides removed COD on a low concentration of Palm Oil Mill Effluent (POME) by 94% and 39% at high concentration . Also, Vetiveria zizanioides removed BOD by 90% at a minimum concentration of POME and 60% at maximum concentration, while control set (without plant) only removed 15% of BOD.
The sources of wastewater can be either from the industrial or non-industrial area. The major source of pollution comes from the non-industrial parts and the waste produced by human contributes the largest part of the non-industrial pollution. If it cannot be well handled, many problems will arise including epidemics. Hence, pollution level should be maintained at a very low level or at least controllable. Wastewater with human sources can be efﬁciently treated by oxidation pond. In addition, wetland system can effectively control industrial wastewater; for instance, the wastewater discharging from construction sites. Currently, there are several mathematical models available for simulating oxidation pond process where some important parameters are considered such as bacteria (cleansing agent), pollutants and dissolved oxygen (DO). However, previous results did not provide good approximation on the required parameters. Moreover, stability analysis was rarely considered for constructed wetland models. However, the steady-state and bifurcation analyses are usually crucial in determining the reliability of the models that is under study. Thus, dynamic mathematical models are developed in this study to allow the simulation and prediction of wastewater treatment process for both oxidation pond and CW case studies. Furthermore, the nonlinear system of ordinary differential equations (ODE) using multiple substrate limiting factors with interactive reactions and partial differential equations (PDE) using advection-diffusion-reaction equations are implemented for CW and oxidation pond, respectively.
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In artificial wetlands, soluble organic compounds are biodegraded by aerobic processes where oxygen is supplied directly from the atmosphere by diffusion and mainly through the process of photosynthesis, into the water column . Microorganisms that are attached to the support medium in subsurface flow systems are those that biodegrade the soluble organic compounds , the degradation rate being 10 times faster than that of the anaerobic processes . On the other hand, aerobic processes are the main mechanism to reduce soluble BOD, and the elimination of particulate BOD occurs rapidly by sedimentation and particle filtration in the spaces between gravel and roots .
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which macrophytes affect water treatment in constructed wetlands are under debate. Evapotranspiration is one of the most important roles of plants. Constructed wetlands receive water through inflows and precipitation, and lose water to outflows, evaporation and transpiration, i.e., evapotranspiration (ET). The evapotranspiration of plants has a close relation to the water budget in the constructed wetlands and influences the HRT and purification process . Plants have a critical role in determining the dynamics of water loss, mainly through ET. There have been many studies concerning the ET of constructed wetlands, and these studies demonstrate that the ET of emergent macrophytes is a significant process in constructed wetlands [13-15]. For example, ET from a constructed wetland in Morocco planted with Arundo donax was 40mm/d and 60mm/d with Phragmites australis, compared to 7mm/d in an unplanted HSF .
Treatment efficiency was measured against the primary objective for which Liege St Wetland was constructed: to remove nutrients during low flow periods (Syrinx 2004). The other objectives, to provide flood storage capacity during high flows and to increase local habitat and amenity value, were not directly addressed though both were considered when evaluating the outcomes of the study. In addition, treatment efficiency of contaminant removal (metals, BOD and DOC) was also considered. Using available information and data collected through a series of supplementary investigations, changes to system components were assessed and the parameters involved in these changes were identified. Applying an active adaptive management approach, an experimental trial was then conducted to evaluate proposed modifications to the system design to improve macrophyte cover.
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Jennifer A. Schaafsma, et.al.,(1999), has studied results suggest that while reductions are large, further removal is necessary to meet design requirements. This may be possible through the addition of another anaerobic wetland cell downstream of the system or recirculation of wastewater through the wetland cells to promote denitrification and uptake of nutrients by plants. Jaiprakash kushwaha,et al (2002), they work on various technologies for the treatment of dairy Wastewaters at Poompavai , Uttarakhand , India 2002. Erin Smith et.al.(2007), has studided two small-scale constructed wetlands (100 m2) of differing operational depth (wetland 1: 0.15 m shallow zone depth and wetland 2: managed water level) were designed to treat agricultural wastewater at the Bio-Environmental Engineering Center of the Nova Scotia Agricultural College. Coulibalyet al.,(2008), emphasis on constructed wetland planted with Amaranthus hybridus was developed for domestic wastewater treatment. Two beds planted with yang A. Hybridus plants and one with unplanted bed were used to perform the experiment. M. Tsalkatidouet. al ( 2008), worked on the Combined stabilization ponds– constructed wetland system. In a pre-existing wastewater treatment pilot plant consisting of three interconnected waste stabilization ponds. Oneţ Cristian(2010), worked on the characteristics of the untreated wastewater produced by food industry. Fang CUI et. al (2011), worked on Constructed Wetland as an alternative solution to Maintain Urban Landscape Lake Water Quality, and concluded that the SFS constructed wetland is better than the FWS wetland. Ramprasad. C (2012), worked on waste water treatment using lab scale reed bed system using Phragmitis australis, chennai . The waste water generated from the quarters, school hostel and college hostels in our university campus were collected and analyzed.
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The comparison study of nitrogen at the same conditions of vertical distribution. Remove the path of vertical flow wetland nitrogen mainly for nitrification denitrification reaction [7-8]. Study on vertical flow constructed wetland using zeolite and ceramic filler, Lythrum salicaria as nitrogen vertical system of wetland plants to the distribution of concentration and proportion, in order to explore the effective depth of filler, effect of DO concentration on the reaction of microbial nitrification and denitrification. Improve the nitrogen removal efficiency and investment economy, the more efficient removal of sewage nitrogen has practical significance is worthy of popularization.
The plant was chosen on the basis of requirement of plants, their role, desired properties like local availability, deep root penetration and high tolerance to pollutants. The plant species used was Canna Indica. The wetland plant species, Canna Indica, was selected due to its high tolerance to pore clogging, its large biomass, and high removal of N and P. Canna Indica brought from a local nursery was planted in the pilot scale VFCW model.
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Most of the studies on SSF had used T. latifolia as an emergent plant alone or combined with others. T. latifolia (broad leaf cattail) is one of Cattail typical varities besides Typha angustifolia (narrow-leaf cattail). M.E Kaseva (2003) reported on the performances of a subsurface horizontal flow (SSHF) constructed wetland pilot plant to treat domestic wastewater which was discharged from the student’s hostel. The study was carried out at hydraulic retention time of 1.99 days and found that COD removal rate is 60.7 %. The study also indicated that pH increased from the influent to the effluent, probably due to nature of the substrate material (limestone) used in SSF fortunately the changes was within the recommended range (4.0< pH< 9.5). The increase in DO was accompanied with the decrease in temperature.
Studies at three different hydraulic retention times of 4 days, 6 day and 8 days were carried out. This study was carried out to determine the performance of the constructed wetland in the removal of COD, Ammonia nitrogen and phosphate and the effect of varying HRT. Wastewater was fed into the three systems in which one was controlled and other two were planted. The study was carried out for each HRT in all three systems till stable values were obtained and the performance of planted and unplanted system was compared. The results obtained in the performance of the systems for the removal of concern parameters COD, ammonia nitrogen and phosphate at HRT 4 days, 6days and 8days were shown Fig 5 to Fig 7 respectively.
Page | 124 Constructed wetlands were first developed in 1960. These systems have been modified until the current advanced technology was obtained & have been effectively used for the treatment of domestic waste; compared to high-cost conventional mechanical treatment systems, constructed wetland technology is cheaper, more easily operated, more efficient to maintain. Moreover, minimal or no fossil fuel is required, no chemicals are necessary as well as it is a green technology. Implementing low cost technology systems like constructed wetlands can also be a proper solution for treatment of different types of wastewater in India. However, there have been hardly few constructed wetland applications in India until 2013; also research has been initiated for a few laboratory scale experimental studies on constructed wetlands .