Vymazal J.,Czech University of Life Sciences |
Ecological Engineering | Year: 2015
Hybrid constructed wetlands (HCWs) are very efficient in removal of total nitrogen. So far hybrid-constructed wetlands have been composed of various combinations of wetland units but most common combination is vertical flow-horizontal flow system. Also, multistage HCWs have recently been used. The present study describes the use of three-stage HCWs for treatment of municipal sewage. The system consists of saturated vertical flow, free-drain vertical and horizontal flow units in series. The experimental system with a total surface area of 10.1m2 has been operated for 19 months between March 2009 and October 2010. The results proved that multistage hybrid constructed wetland was able to remove efficiently organics, suspended solids and nitrogen. The overall removal efficiency amounted to 92.5%, 83.8%, 96.0%, 88.8% and 79.9% for BOD5, COD, TSS, NH4-N and TN, respectively. The aerobic vertical flow stage provided high degree of nitrification (removal rate of 4.17g NH4-Nm-2d-1) while remaining anaerobic stages (first and third) provided suitable conditions for denitrification (removal rates of 0.83g N-NO3m-2d-1 and 0.47g N-NO3m-2d-1, respectively). The outflow NH4-N concentrations were below 5mgl-1 throughout the monitored period including winter period when the air temperature dropped below -20°C. Plant biomass sequestered 28% and 26% of phosphorus and nitrogen inflow load, respectively. © 2015 Elsevier B.V.
Vymazal J.,ENKI |
Vymazal J.,Czech University of Life Sciences
Ecological Engineering | Year: 2011
Constructed wetlands with horizontal sub-surface flow (HF CWs) have been in use in the Czech Republic since 1989. Evaluation of the long-term performance of horizontal sub-surface flow constructed wetlands in the Czech Republic indicates that removal of organics and suspended solids is very effective; efficiencies are steady throughout the year and are not affected by season and also by the length of operation. The results from systems treating wastewaters from combined sewer systems clearly indicate that HF CWs can very effectively cope with low inflow concentrations of organics and can provide effluent BOD5 concentrations less than 5mgl-1. Phosphorus removal is seasonally steady but low as Czech constructed wetlands do not use special filtration media with high sorption capacity. This is not a problem, because in the Czech Republic, there is currently no discharge limit for phosphorus for wastewater treatment plants up to 2000 person equivalents (PE). Removal of ammonia-N is limited by lack of dissolved oxygen in filtration beds caused by permanent saturation. The removal of ammonia-N is steady over the life of operation but is affected by season but the decrease in ammonia removal efficiency during winter is not large. © 2009 Elsevier B.V.
Cizkova H.,University of South Bohemia |
Kvet J.,University of South Bohemia |
Comin F.A.,CSIC - Pyrenean Institute of Ecology |
Laiho R.,University of Helsinki |
And 2 more authors.
Aquatic Sciences | Year: 2013
The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other. © 2011 Springer Basel AG.
Bila J.,Czech Technical University |
Jura J.,Czech Technical University |
Pokorny J.,ENKI |
Bukovsky I.,Czech Technical University
Ecological Modelling | Year: 2011
This paper proposes three qualitative models that were applied for modeling of Small Water Cycle violation in ecosystem of Trebon region, South Bohemia. SWC refers to the behavior of the local ecosystem (e.g., the Trebon region), in which the volume of water that comes into the ecosystem is evaporated and falls back into this system. SWC is characterized by early morning dues and frequent small rain precipitation. In the Trebon Biosphere Reserve characterized by wetlands, forests and agriculture land, the evaporated water rises quickly inside the zone and does not have time to recondense before it is transported outside the ecosystem to the distant mountains, where it condenses spontaneously in the rising air streams. The essential pre-model for developing our qualitative models is the database model implemented in the MS SQL environment. The data in this model were collected for last five years and contain information about SWC violation and about the landscape stability development. The database system is used for standard reports, for correlating digital and graphic runs from associated meteorological stations, and for computing the evapotranspiration at the points where the stations are located and also at approximate inter-points. In parallel, and in addition to this standard use of the database model, the data was applied in the development of qualitative models (state model, model for the detection of unexpected situations and matroid model). This transformation and compression of the data was done with help of experienced experts and with the help of special mathematical operations. Qualitative models introduced in this paper overcome experience with quantitative models namely in these items: (1) They provide compression of information contained in large volumes of numerical data. (2) On the contrary of individual quantitative modeling qualitative models enable to describe the function and properties of the whole ecosystem. (3) Conclusions from qualitative models are in many cases better than are the generalizations of results from quantitative models. The first goal of the paper is to model situations associated with violations of the Small Water Cycle (SWC) in this ecosystem, and to contribute to acceptable solutions. The second goal of the paper is to investigate temporary models for the stability of the landscape development and to propose qualitative models for software support for integrated environmental modeling. © 2011 Elsevier B.V.
Communications of the ACM | Year: 2010
The competition among cloud providers may drive prices downward, but at what cost? © 2010 ACM.