Fractionation, Biodegradability and Particle-Size Distribution of Organic Matter in Horizontal Subsurface-Flow Constructed Wetlands
ABSTRACT In order to analyse the fate of organic matter and particles along the length of horizontal subsurface-flow constructed wetlands,
two pilot wetlands were monitored in terms of BOD5, COD and their fractions, TOC and particle counts in various sampling campaigns. Anaerobic biodegradability properties of
the effluent organic matter were also measured by means of a methane-production test. The most abundant particles in the influent,
at intermediate points along the length of the wetlands, and in the effluent were those comprised in the range of 0.7 to 2m.
Most of the particles (close to 80%) were removed within the first quarter of the wetland length. Most organic matter was
also removed within the first quarter (50% and 80% in terms of TOC and COD, respectively). Further organic matter removal
along the rest of the length of the wetland only accounted for a 0–10% of the total removal. The organic matter of the effluents
is difficult to biodegrade under anaerobic conditions, but it is readily biodegradable under aerobic conditions.
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ABSTRACT: A Finite Element Analysis (FEA) model is used to explore the relationship between clogging and hydraulics that occurs in Horizontal Subsurface Flow Treatment Wetlands (HSSF TWs) in the United Kingdom (UK). Clogging is assumed to be caused by particle transport and an existing single collector efficiency model is implemented to describe this behaviour. The flow model was validated against HSSF TW survey results obtained from the literature. The model successfully simulated the influence of overland flow on hydrodynamics, and the interaction between vertical flow through the low permeability surface layer and the horizontal flow of the saturated water table. The clogging model described the development of clogging within the system but under-predicted the extent of clogging which occurred over 15 years. This is because important clogging mechanisms were not considered by the model, such as biomass growth and vegetation establishment. The model showed the usefulness of FEA for linking hydraulic and clogging phenomenon in HSSF TWs and could be extended to include treatment processes. KeywordsClogging-Horizontal subsurface flow-Modelling-Suspended solids-Hydraulics01/1970: pages 85-101;
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ABSTRACT: A technical overview of the prioritization and transport in the advanced digital television system (ADTV) is provided. ADTV incorporates an efficient MPEG-compatible compression algorithm at its central core, with application-specific data prioritization and transport features added as separable layers. The compression process is based on a 1440×960 HDTV format, producing a selectable bit-rate in the region of 15-20 Mb/s. The data prioritization layer of ADTV achieves robust delivery over an appropriate two-tier modem by separating compressed video data into high- and standard-priority bit-streams with appropriate bit-rates. These prioritized data are then formatted into fixed-length cells with appropriate data-link-level and service-specific adaptation-level headersIEEE Transactions on Consumer Electronics 09/1992; · 1.09 Impact Factor