Hydraulic & Design Parameters in Full-Scale Constructed Wetland & Treatment Units: Six Case Studies

The efficiency of pond and constructed wetland (CW) treatment systems, is influenced by the internal hydrodynamics and mixing interactions between water and aquatic vegetation. In order to contribute to current knowledge of how emergent real vegetation affects solute mixing, and on what the shape and size effects are on the mixing characteristics, an understanding and quantification of those physical processes and interactions was evaluated. This paper presents results from tracer tests conducted during 2015-2016 in six full-scale systems in the UK under different flow regimes, operational depths, shapes and sizes, and in-/outlet configurations. The aim is to quantify the hydraulic performance and mixing characteristics of the treatment units, and to investigate the effect of size and shape on the mixing processes. Relative comparison of outlet configuration, inflow conditions, and internal features between the six different treatment units showed variations in residence times of up to a factor of 3. A key outcome of this study, demonstrated that the width is a more important dimension for the efficiency of the unit compared to the depth. Results underlined the importance of investigating hydrodynamics and physics of flow in full-size units to enhance treatment efficiency and predictions of water quality models

The value of wetlands for water quality improvement: an example from the St. Johns River watershed, Florida

Wetlands provide many valuable ecosystem functions such as sediment and nutrient retention, high biological productivity and biodiversity, flood control, and opportunities to recreate. Despite their importance, estimating the value of wetlands is difficult as the worth of these functions and services is not easily quantified. The overall objective of this study was to estimate the value of freshwater wetlands in the Saint Johns River (SJR) watershed, Florida based on their ability to remove nutrients, namely nitrogen (N) and phosphorus (P). We used a combination of literature review, geospatial analysis of land cover, and regression analysis to determine the total wetland area in the SJR watershed and the rates of nitrogen and phosphorus burial in the wetlands. We then estimated the economic value of these wetlands based on the replacement cost of nutrient removal by wastewater treatment plants. Nitrogen burial rates ranged from 27 g/m2/year to a background rate of 6.56 g/m2/year, and phosphorus burial rates range from 1.31 g/m2/year to a background of 0.11 g/m2/year. Using these rates, we calculate wetlands of the SJR catchment remove 79,873 MT of nitrogen annually just from burial in the soil, with a replacement cost of between $240 million to$150 billion per year. The amount of phosphorus buried yearly is more than 2400 MT with an annual replacement cost of $17 to$497 million. Though they are based on limited data and include a variety of watershed-scale research limitations, these findings highlight the significant potential value of conserving functional wetlands based solely on their nutrient retention functions. If we were to consider the benefits associated with other wetland functions such as flood control, biological productivity, and biodiversity in addition to their ability to retain nutrients, the value of the SJR wetlands would be even greater

Fish farming water quality and environmental concerns in Argentina: a Regional approach

In spite of the steady increase in fish farming in Argentina, studies on water quality are scarce. Eight fish farms from two different regions in the northeast and east of Argentina were studied to explore source and effluent water quality. Ammonium (NH4), nitrate (NO3-), and nitrite (NO2-) levels were measured. High nitrate concentrations in water source were observed in the eastern region farms. An increase in NH4-, NO3-, and NO2- in effluent water was determined in most of the sampled farms. Heavy metals (i.e.,cadmium, chromium, copper, iron, manganese, nickel, and zinc) and arsenic concentrations were analyzed. Heavy metal concentrations were below the detection limit in the northern region. However, As was detected in the water source of five farms and was over the recommended limit (100 lgl-1) for aquaculture in one. An increase in Mn and Zn concentrations in effluent water was observed in two farms. The lack of treatment of the effluent water in these farms leads to an increase of nutrients and heavy metal concentrations in the surrounding areas. Environmental effects of fish-farming practices in Argentina are discussedFil: Schenone, Nahuel Francisco. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Vackova, Lenka. Institute Of Chemical Technology Prague; República ChecaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin

The contribution of Potamogeton crispus to the phosphorus budget of an urban shallow lake: Lake Monger, Western Australia

© 2015, The Japanese Society of Limnology. Lake Monger (Perth, Western Australia) is a highly eutrophic lake, characterised by very low species richness of macrophytes with the dominance of Potamogeton crispus. Mesocosm experiments were performed using water and plants collected from the lake to determine the effects of vegetation decay on the phosphorus (P) con centrations in the overlying waters. After 2 weeks of experimental incubation of mesocosms with and without re-oxygenation, P concentrations in the water column were significantly higher, showing a quite similar effect of P. crispus on the phosphorus release in different mesocosms. The results of our study provide clear evidence that the P concentrations in overlying waters mainly depend upon the plant P content and developmental stage. Although many sources contribute to the nutrient load of Lake Monger, macrophyte harvesting, prior to its senescence, might constitute a significant in-lake measure for reducing the internal P load