Size fractionation of COD in urban wastewater from a combined sewer system

The objective of this work was to determine the partitioning of the pollutant load in urban wastewater in order to improve the conventional sewage treatment. In addition to settling tests, physical fractionation of COD in the degritted influent of Roma-Nord sewage treatment plant was performed via s...

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Bibliographic Details
Published in:Water science and technology 2004-01, Vol.50 (12), p.79-86
Main Authors: Marani, D, Renzi, V, Ramadori, R, Braguglia, C M
Format: Article
Language:English
Subjects:
Biodegradability
Biodegradation
Biological treatment
Chemical Fractionation
Colloids
Combined sewers
Filtration
Fractionation
Lime
Oxygen - analysis
Oxygen - chemistry
Particle Size
Pollution load
Pore size
Porosity
Sewage - analysis
Sewage - chemistry
Sewage - microbiology
Sewage disposal
Sewage treatment plants
Sewer systems
Sieves
Waste Disposal, Fluid - methods
Wastewater treatment
Wastewater treatment plants
Water Pollutants - isolation & purification
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Summary:The objective of this work was to determine the partitioning of the pollutant load in urban wastewater in order to improve the conventional sewage treatment. In addition to settling tests, physical fractionation of COD in the degritted influent of Roma-Nord sewage treatment plant was performed via sequential filtration through sieves and membrane filters of the following pore size: 150-100-50-25-1-0.2 microm, and 100 kD (about 0.02 microm). Biodegradability studies were also performed on the different size fractions. Size fractionation showed that COD in Roma-Nord sewage is predominantly associated with settleable and supracolloidal (> 1 microm) particles, each size range including about 40% of total COD. Biodegradability tests indicated that the large fraction of COD associated with supracolloidal particles, which are not removed in the primary treatment, is characterised by slow degradability. This suggests that removal of these particles prior to biological treatment may greatly improve the overall treatment scheme. Preliminary pilot plant coagulation tests with lime at pH 9 showed that lime-enhanced primary treatment may increase COD removal efficiencies from typical 30-35% up to 65-70%, by inducing almost complete removal of the COD fraction associated with supracolloidal particles.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2004.0698