Biological denitrification using starch/polycaprolactone blends as carbon source and biofilm support

A novel kind of biodegradable polymer, cross-linked starch/polycaprolactone (PCL) blends was prepared, characterized and applied for biological denitrification. The results showed that the blends could be used as carbon source and biofilm carrier for denitrifying bacteria attachment. The temperature had a significant influence on denitrification rate, and the temperature constant was determined to be 0.0151 between 15 and 30 degrees C in batch tests. The continuous fixed-bed experiments indicated that the average removal efficiency of NO3 was 92.51% at 25 degrees C, while it was only 68.69% at 15 degrees C. The formation of NH3-N was observed at both 15 and 25 degrees C, but it kept below 1.0 mg/L. The excess release of dissolved organic compound was much lower at 15 degrees C compared with that at 25 degrees C. The scanning electron microscope results confirmed that both cross-linked starch and PCL could be utilized by denitrifying bacteria as carbon source for nitrate removal.