Nitrogen removal using biodegradable polymers as carbon source and biofilm carriers in a moving bed biofilm reactor

Biodegradable polymer (PCL) was used as both solid carbon source and biofilm carriers to remove nitrogen from wastewater with a low C/N ratio by simultaneous nitrification and denitrification (SND) in a moving bed biofilm reactor. The experimental results showed that the average TN removal efficiency was 74.6% at hydraulic retention time of 18.5 h. PCL was available both for microbial attachment and for carbon source. The consumed PCL amount for removing per gram of TN was calculated to be 1.27 g PCL g−1 N. From the batch tests, 96.3% of nitrogen was removed via SND for the biofilm biomass attached to PCL, compared to 52.0% for the suspended sludge with addition of glucose. This indicated that PCL is an effective solid carbon source for simultaneous nitrification and denitrification since it was degraded much slower than soluble substrate which can be rapidly oxidized to CO2 within the early stage of aeration, instead of providing reducing power for denitrification.