[Effect of denitrifying biofilm development on the surface configuration and chemical composition of PBS polymer]

PBS, a new kind of biodegradable polymers (BDPs), can be used as carbon source and biofilm carrier to remove nitrate from drinking water source. The effect of denitrification on the surface configuration and chemical composition of PBS was analyzed by using IR spectrum and SEM observation. The results showed that PBS could be only decomposed under attack of microbial enzymes and provided the carbon source for biomass. Influent nitrate concentration (53 mg x L- 1) can be reduced to less than 10 mg x L(-1) within 12 h. The IR spectrum showed that under development of denitrifying biofilm, absorption band at 2 925 cm(-1),2 850 cm(-1), 3200 cm(-1) -3410 cm-1 became weak, which suggested that the content of methyl or hydroxyl group in PBS decreased slightly, and the other functional groups were not influenced apparently. The main monomer gradients of PBS, such as starch and ethylene, could all be utilized as carbon source by denitrifiers. The SEM observation indicated that the cavity could be formed on the PBS granular surface, which increased the area for denitrifiers to attach. The formation of the cavity structure on the PBS surface was beneficial to further development of compact biofilm, which can protect denitrifiers.