1 research outputs found
Removal Characteristics of Dissolved Organic Nitrogen and Its Bioavailable Portion in a Postdenitrifying Biofilter: Effect of the C/N Ratio
Addition of external carbon sources
to postdenitrification biofilters
(DNFs) is frequently used in municipal wastewater treatment plants
to enhance dissolved inorganic nitrogen removal. However, little is
known about its influence on the removal of dissolved organic nitrogen
(DON). This study investigated the effect of the carbon-to-nitrogen
(C/N) ratio (3, 4, 5, and 6) on the removal characteristics of DON
and bioavailable DON (ABDON) in the pilot-scale DNFs treating real
secondary effluent. Results showed that DNFs effluent DON accounted
for 31.2–39.8% of the effluent total nitrogen. The maximum
effluent DON and ABDON concentrations both occurred in DNF operated
at a C/N ratio of 3. There was no significant difference in effluent
DON concentrations in DNFs at C/N ratios of 4, 5, and 6; however,
effluent ABDON and DON bioavailability significantly decreased with
C/N ratios (<i>p</i> < 0.05, <i>t</i>-test).
According to the chemical composition analysis, effluent DON at high
C/N ratios tends to contain less % molecular weight < 1 kDa nitrogenous
organic compounds and proteins/amino sugars-like nitrogenous organic
formulas, which is likely responsible for its low bioavailability.
Overall, this study indicates the benefit of a high C/N ratio during
the DNF process in terms of controlling the DON forms that readily
stimulate algal growth