Effect of weight ratios of PHBV/PLA polymer blends on nitrate removal efficiency and microbial community during solid-phase denitrification

This study investigates the effect of weight ratios of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/poly (lactic acid) (PHBV/PLA) polymers blends on the denitrification performance and microbial community in fixed-bed reactors. Nitrate removal efficiency was enhanced with the increasing weight ratio of PHBV/PLA polymers, while the total organic carbon in the effluent increased. Meanwhile, there was an obvious negative correlation between PHBV/PLA weight ratio and the effluent pH. Moreover, fluorescence excitation-emission matrix spectra (EEM) indicated that the effluents from all reactors mainly contained soluble microbial by-product-like substances and Fourier transform infrared spectra (FTIR) analysis indicated that there were compounds containing hydroxyl groups generated through hydrolysis. The weight-averaged molecular weight (Mw) of the degradation products in the effluent were distributed into high, intermediates and low Mw and the proportion of low-molecular-weight substances consisting principally of acetic acid correlated positively with to the nitrate removal efficiencies. Illumina-sequencing indicated that weight ratios did partly affect the microbial diversity, while the dominant genus of denitrifying bacteria in both biofilms of PHBV/PLA blends mainly included Dechloromonas, Desulfovibrio, and Flavobacterium.