Effective control of the carbon release of starch/polyvinyl alcohol based on a polyamide coating in solid-phase denitrification†
Inspired by the controlled release technique of microcapsules, a novel carbon source using starch/polyvinyl alcohol (PVA) as the active material and a polyamide layer (PAL) as the shell coating on the surface of the carbon source was prepared and used for denitrification. Compared to the pure starch/PVA, the PAL-coated carbon source showed a lower chemical oxygen demand (COD) concentration (20 mg L−1) in effluent with excellent removal rate of NO3−-N exceeding 95% when the mass ratio of starch to PVA was 3 : 1. The high content of starch in the composite carbon source contributed to a decrease of denitrification cost. The carbon balance result indicated that the carbon release of the PAL-coated carbon source was mainly caused by microbial action (72.9%). Besides, little difference of microbial community was observed between pure starch/PVA and PAL-starch/PVA supported systems and the vast majority of biofilm species belonged to the six major phyla Proteobacteria, Bacteroidetes, Firmicutes, Planctomycetes, Chloroflexi and Actinobacteria, and Thauera and Zoogloea were the major genera which were denitrifying bacteria. In all, these results demonstrated that the PAL played a vital role in controlling COD in effluent without degrading the denitrification efficiency, as well as changing the structure of the microbial community, which paves a new way to fabricate a novel solid carbon source with low cost and excellent denitrification performance.