Slowly released carbon source from composite materials system for removing nitrate pollution in groundwater

Chemoheterotrophic denitrification technologies using biopolymers as a solid carbon source and biofilm carriers have been widely trialed to remove nitrate from groundwater. Here, we use a polyhydroxyalkanoates (PHA) and cellulose blend as a slowly released carbon material, the performance of which was detected through static and dynamic experiments. In the static experiment, the carbon released from the straw, cob and bagasse was 66.95, 40.12 and 40.65 mg L-1, respectively. Results show that the straw possessed higher carbon content than the others. In the dynamic experiments, the PHA/cellulose blend exhibited excellent nitrate removal efficiency and less adverse effects in nitrite accumulation during stable operation. The nitrate nitrogen removal rate reduced from 99.80% to 73.13% as nitrate loading increased from 40 to 60 mg L-1. The microbial structure of a permeable reactive barrier (PRB) system was revealed by high-throughput sequencing analysis. Azospira, Rhizomicrobium and Acidovorax were found to be the predominant species in the PHA system after the system had stabilized. Our results highlight that the PHA/cellulose blend is an economically attractive carbon source with good denitrification performance.