Biological denitrification using cross-linked starch/PCL blends as solid carbon source and biofilm carrier.

A novel kind of cross-linked starch/polycaprolactone (SPCL11) was prepared and used as carbon source and biofilm attachment carrier for denitrifying bacteria. The results showed that the average denitrification rate was 0.027 mg NO₃-N/(g·h) in batch tests. The continuous fixed-bed experiments indicated that more than 90% NO₃-N was removed, the denitrification rate reached 26.86 mg NO₃-N/(L·h), and NO₂-N concentration was below 0.16 mg/L. The formation of NH₄-N was observed, but usually below 1.0 mg/L. Rapid biodegradation of starch on the surfaces of SPCL11 granules could cause an initial excess release of dissolved organic compound (DOC), and shortening HRT from 2h to 1h can result in sharp decrease of DOC.