3.2. Performance of FLFW as a carbon source for the denitrification
process
3.2.1. Effect of initial COD/N ratios on the denitrification process
Fig. 3 illustrates the transformation of NO2
-N, NO3
-N and COD
in the denitrification process at different initial COD/N ratios when
using FLFW as the carbon source. Incomplete denitrification often
occurs when the carbon is limiting and is characterized by a large
fraction of residual nitrate and a slight nitrite accumulation at the
end of the process. Such a relationship was clearly indicated when
the COD/N ratio was 2, and the accumulation value of nitrite (i.e.,
12% of the total influent nitrate) in the effluent when the COD/N
ratio was up to 4, though a value lower than 2 mg NO3
-N/L was
obtained in the treated effluent after 3 h of reaction. At COD/N
ratios up to 6 and 8, the nitrite accumulation substantially
increased to a value of 9.5 mg/L and 12.2 mg/L, respectively, at
60 min with complete denitrification (N quantities in the effluent
was less than 1 mg/L), which indicated that denitrification was
limited by the carbon amount rather than the carbon availability.
The maximum nitrite accumulation occurred 10 min earlier with
3.2. Performance of FLFW as a carbon source for the denitrificationprocess3.2.1. Effect of initial COD/N ratios on the denitrification processFig. 3 illustrates the transformation of NO2-N, NO3-N and CODin the denitrification process at different initial COD/N ratios whenusing FLFW as the carbon source. Incomplete denitrification oftenoccurs when the carbon is limiting and is characterized by a largefraction of residual nitrate and a slight nitrite accumulation at theend of the process. Such a relationship was clearly indicated whenthe COD/N ratio was 2, and the accumulation value of nitrite (i.e.,12% of the total influent nitrate) in the effluent when the COD/Nratio was up to 4, though a value lower than 2 mg NO3-N/L wasobtained in the treated effluent after 3 h of reaction. At COD/Nratios up to 6 and 8, the nitrite accumulation substantiallyincreased to a value of 9.5 mg/L and 12.2 mg/L, respectively, at60 min with complete denitrification (N quantities in the effluentwas less than 1 mg/L), which indicated that denitrification waslimited by the carbon amount rather than the carbon availability.The maximum nitrite accumulation occurred 10 min earlier with
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