Effect of nano-ZnO particles on nitrification of SBR activated sludge and its mechanism

Abstract

Nano-ZnO particles were prepared by hydrothermal method with zinc acetate as zinc raw material. The lattice structure, microstructure and spectral properties of the samples were analyzed by XRD, SEM and FT-IR. The effect of nano-ZnO particles on nitrification of activated sludge was studied by sequencing batch reactor (SBR). The results showed that the synthesized nano-ZnO particles were standard wurtzite structure, with high crystallinity, good dispersion, granular shape and particle size between 25 - 45 nm. With the increase of the amount of nano-ZnO particles, the concentration of Zn2+ in SBR solution increased gradually. The morphological changed of activated sludge before and after adsorption of nano-ZnO particles showed that the surface of granular sludge was relatively smooth before adsorption, and there were many convex spots on the surface after adsorption. The nano-ZnO particles were unevenly distributed on the surface of sludge. With the increase of the amount of nano-ZnO particles, the nitrification inhibition of nitrous granular sludge increased gradually. When the addition amount of nano-ZnO particles was 50 mg/L, at 270 min, the minimum removal rate of NH+4, -N by granular sludge was 52.35%, and the minimum generation amount of NO2- -N and NO3- -N were 98. 5 and 11.9 mg/L, which decreased by 38.93% and 42.79% respectively compared with that without nano-ZnO particles.