Nitrogen removal in fixed-bed submerged biofilters without backwashing

The paper reports the findings of four years of pilot-scale research on nitrogen removal in fixed-bed biofilters fed on real raw municipal wastewater. The plant was made of two fixed-bed biofilm reactors in series with an intermediate settling tank from which excess biomass from the first stage was...

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Bibliographic Details
Published in:Water science and technology 1999, Vol.40 (4-5), p.145-152
Main Authors: Canziani, R., Vismara, R., Basilico, D., Zinni, L.
Format: Article
Language:English
Subjects:
Applied sciences
Biofilm processes
Biofilms
Biological and medical sciences
Biological filter beds
Biological treatment of waters
Biotechnology
Carbon
Chemical oxygen demand
Denitrification
Environment and pollution
Exact sciences and technology
Fundamental and applied biological sciences. Psychology
Hydrolysis
Industrial applications and implications. Economical aspects
Industrial wastes
Nitrates
Nitrification
nitrogen removal
Other wastewaters
Pollution
Temperature
Wastewaters
Water treatment and pollution
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Summary:The paper reports the findings of four years of pilot-scale research on nitrogen removal in fixed-bed biofilters fed on real raw municipal wastewater. The plant was made of two fixed-bed biofilm reactors in series with an intermediate settling tank from which excess biomass from the first stage was discharged. The first filter was used for carbon removal either with oxygen or nitrates. The second filter was used for nitrification. The average nitrification rate at 20°C was 0.84 gNH4+-N m−2d−1 with 5 mg I−1 dissolved oxygen in the bulk liquid. Temperature dependence was calculated (rn = rn.20° 1,05T−20). The influent organic load strongly affected ammonia oxidation. If the organic loading exceeded 2.5 gCOD m−2 d−1 nitrification rate was reduced by 50%. Denitrification was performed by recycling nitrates back from the second filter and by using sewage itself as carbon source. Denitrification rate showed to be strongly dependent on temperature (rd = rd.20° 1.11T−20) and on the recycle rate. Hydrolysis of the colloidal COD fraction showed a similar dependence on both temperature and recycle rate. Therefore, it has been concluded that the hydrolysis of finely dispersed COD particles can be the limiting step of denitrification in the biofilter when real sewage is used as carbon source.
ISSN:0273-1223
1996-9732
DOI:10.1016/S0273-1223(99)00496-5