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Wetland System (wetland + system)
Selected AbstractsThe performance of constructed wetlands for, wastewater treatment: a case study of Splash wetland in Nairobi KenyaHYDROLOGICAL PROCESSES, Issue 17 2001Daniel Muasya Nzengy'a Abstract The performance of a constructed wetland for wastewater treatment was examined for four months (December 1995 to March 1996). The study area, hereby referred to as the Splash wetland, is approximately 0·5 ha, and is located in the southern part of Nairobi city. Splash wetland continuously receives domestic sewage from two busy restaurants. Treated wastewater is recycled for re-use for various purposes in the restaurants. Both wet and dry season data were analysed with a view of determining the impact of seasonal variation on the system performance. The physical and chemical properties of water were measured at a common intake and at series of seven other points established along the wetland gradient and at the outlet where the water is collected and pumped for re-use at the restaurants. The physico-chemical characteristics of the wastewater changed significantly as the wastewater flowed through the respective wetland cells. A comparison of wastewater influent versus the effluent from the wetland revealed the system's apparent success in water treatment, especially in pH modification, removal of suspended solids, organic load and nutrients mean influent pH = 5·7 ± 0·5, mean effluent pH 7·7 ± 0·3; mean influent BOD5 = 1603·0 ± 397·6 mg/l, mean effluent BOD5 = 15·1 ± 2·5 mg/l; mean influent COD = 3749·8 ± 206·8 mg/l, mean effluent COD = 95·6 ± 7·2 mg/l; mean influent TSS = 195·4 ± 58·7 mg/l, mean effluent TSS = 4·7 ± 1·9 mg/l. As the wastewater flowed through the wetland system dissolved free and saline ammonia, NH4+, decreased from 14·6 ± 4·1 mg/l to undetectable levels at the outlet. Dissolved oxygen increased progressively through the wetland system. Analysis of the data available did not reveal temporal variation in the system's performance. However, significant spatial variation was evident as the wetland removed most of the common pollutants and considerably improved the quality of the water, making it safe for re-use at the restaurants. Copyright © 2001 John Wiley & Sons, Ltd. [source] A MODEL TO ENHANCE WETLAND DESIGN AND OPTIMIZE NONPOINT SOURCE POLLUTION CONTROL,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2002Erik R. Lee ABSTRACT: A dynamic, compartmental, simulation model (WETLAND) was developed for the design and evaluation of constructed wetlands to optimize nonpoint source (NPS) pollution control. The model simulates the hydrologic, nitrogen, carbon, dissolved oxygen (DO), bacteria, vegetative, phosphorous, and sediment cycles of a wetland system. Written in Fortran 77, the WETLAND models both free-water surface (FWS) and subsurface flow (SSF) wetlands, and is designed in a modular manner that gives the user the flexibility to decide which cycles and processes to model. WETLAND differs from many existing wetland models in that the interactions between the different nutrient cycles are modeled, minimizing the number of assumptions concerning wetland processes. It also directly links microbial growth and death to the consumption and transformations of nutrients in the wetland system. The WETLAND model is intended to be utilized with an existing NPS hydro-logic simulation model, such as ANSWERS or BASINS, but also may be used in situations where measured input data to the wetland are available. The model was calibrated and validated using limited data from a FWS wetland located at Benton, Kentucky. The WETLAND predictions were not statistically different from measured values for of five-day biochemical oxygen demand (BOD5), suspended sediment, nitrogen, and phosphorous. Effluent DO predictions were not always consistent with measured concentrations. A sensitivity analysis indicated the most significant input parameters to the model were those that directly affected bacterial growth and DO uptake and movement. The model was used to design a hypothetical constructed wetland in a subwatershed of the Nomini Creek watershed, located in Virginia. Two-year simulations were completed for five separate wetland designs. Predicted percent reductions in BOD5 (4 to 45 percent), total suspended solids (85 to 100 percent), total nitrogen (42 to 56 percent), and total phosphorous (38 to 57 percent) were similar to levels reported by previous research. [source] Temporal changes to spatially stratified waterbird communities of the Coorong, South Australia: implications for the management of heterogenous wetlandsANIMAL CONSERVATION, Issue 5 2009D. C. Paton Abstract The Coorong, South Australia, is a globally significant wetland system, listed in the Ramsar Convention under a number of different criteria, including its importance to waterbird populations. Based on annual waterbird censuses conducted between 2000 and 2007, spatiotemporal analyses revealed that significant differences in waterbird community structure exist along the length of the Coorong. This spatial diversity in community structure was also found to be temporally consistent over this 8-year period. The abundance of the most numerically dominant bird species, such as red-necked stint Calidris ruficollis and grey teal Anas gracilis, explained much of this spatial variation. However, comparisons between data collected for the Coorong south lagoon in 1985 and 2000,2007 show that dramatic changes in these waterbird communities have occurred over longer periods of time, with 23 of the 27 most common species having declined in this period by at least 30%. The Coorong still regularly supports globally important populations (>1% of global population) of nine waterbird taxa, including three Palearctic shorebirds, confirming its Ramsar status. The functional links between the overutilized Murray-Darling basin river system and the Coorong are discussed. [source] Hillslope-swamp interactions and flow pathways in a hypermaritime rainforest, British ColumbiaHYDROLOGICAL PROCESSES, Issue 15 2003D. F. Fitzgerald Abstract The process of water delivery to a headwater stream in a hypermaritime rainforest was examined using a variety of physical techniques and tracing with dissolved organic carbon (DOC) and the stable isotopes of water. Headwater swamps, often the major discharge zones for water draining off steep forest slopes, strongly affect the physical and chemical character of streamflow in the region. The headwater swamp selected for detailed investigation was sustained by relatively constant groundwater input from the steep colluvial slopes that maintained the water table above the ground surface. During significant storm events the water table rose quickly and the swamp expanded to engulf marginal pools that developed rapidly on the adjacent ground surfaces. The corresponding release of surface water directly to the stream typically comprised up to 95% of total stream discharge. The proportion of groundwater seepage to the stream by matrix flow (<1%) and via macropore-fed springs (up to 73%) increased during the recession period, but could not be sustained over the longer term. In more protracted drying periods, deep groundwater contributions to the stream were routed first to the headwater swamp. Dissolved organic carbon (DOC) in the stream, measured daily or more frequently during storm events, was found to be directly proportional to discharge, owing to the domination of DOC-rich headwater-swamp water sources. Although ,18O and ,2H composition of rainwater, groundwater and stream flow were found to be similar, deuterium excess (d ,2H , 8,18O) of water components was often found to be distinct, and suggested short water residence times of roughly 12 days for one event. Overall, observations of a typical headwater swamp reveal that the groundwater regime is dominated by rapid infiltration and short, emergent flow paths. With a relatively short turnover time, potential disturbances to the system by harvesting of upslope areas can be expected to occur rapidly. Forest managers can mitigate some of the harmful effects of logging operations by respecting the integrity of headwater wetland systems. The nature and magnitude of such perturbations will require further study. Copyright © 2003 John Wiley & Sons, Ltd. [source] Can management practices in rice fields contribute to amphibian conservation in southern Brazilian wetlands?AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010Iberę Farina Machado Abstract 1.Rice field expansion is one of the activities associated with the disappearance of 90% of the wetlands in southern Brazil. Worldwide, rice agriculture has been recognized as having considerable potential value for many aquatic species. Nevertheless, management practices in such systems must be ameliorated and better investigated. 2.This study evaluated the potential role of rice fields as refugia for amphibians, and whether different hydrologic management practices after rice cultivation could contribute to wetland amphibian conservation in southern Brazil. 3.Six collections were made in six rice fields with different management practices after cultivation (three dry and three flooded) and three natural wetlands. The amphibians were sampled through six random 15-min visual transects per collection in each rice field and the natural wetlands. 4.In total, 2139 anuran individuals were observed in rice fields (798) and Reserva Lake (1341), comprising 12 anuran species distributed among five anuran families. Anuran richness and abundance varied over the rice cultivating cycle, and they were higher in the growing phases than in the fallow phases. The mean anuran richness and abundance was higher in Reserva Lake than in flooded and dry rice fields. 5.The different management practices adopted after the harvesting period (presence or lack of surface water) did not influence the anuran richness and abundance. It did, however, influence species composition. 6.The difference in species composition between the management practices adopted is an interesting result in terms of biodiversity conservation. Rice producers could maintain part of their agricultural land flooded during the fallow phase as a strategy to preserve a higher diversity of anurans. These results should be taken into consideration in wetland conservation plans in southern Brazil; however, the percentage of each agricultural land that should be kept flooded should be decided by Brazilian agricultural and conservation policies. Such a strategy would reconcile agricultural/economic needs with the conservation of biodiversity in southern Brazil, where more than 90% of wetland systems have already been lost. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||