Denitrification of nitrate-contaminated groundwater in columns packed with PHBV and ceramsites for application as a permeable reactive barrier

Groundwater contamination via nitrate leaching has been observed in many countries. The denitrification performance of a poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV)–ceramsite-based reactive barrier system was evaluated in continuous upflow bioreactors. Artificial groundwater spiked with nitrate (44.75–57.25 mg NO₃⁻-N/L) was tested under different hydraulic retention times (HRT; 5.2 h and 2.6 h). The continuous experiment for 35 days showed that more than 95% NO₃⁻-N was removed. The maximum denitrification rate was determined to be 241 mg NO₃⁻-N/(L· d), and NO₂⁻-N concentration was below 0.1 mg/L in the effluent at the substrate:ceramsite mass ratio of 1:40. Rapid biodegradation of PHBV granules caused an initial excess release of dissolved organic compound (DOC), and shortening HRT from 5.2 h to 2.6 h can result in a sharp decrease of DOC. The minimum DOC concentrations were determined to be 20–33 mg/L in the effluent when the HRT was set at 2.6 h. So the PHBV granules may be a suitable solid-phase carbon source for enhancing denitrification in nitrate-contaminated groundwater.