纳米零价铁对升流式颗粒污泥床反硝化性能的影响

为探究连续流条件下,纳米零价铁(nZVI)对反硝化颗粒污泥(DGS)性能的影响,本文利用升流式污泥床(USB),系统考察了反应器脱氮效能、污泥形态和反硝化特性随进水nZVI浓度的变化规律.结果表明,当nZVI5 mg·L~(-1)时,反应器脱氮效能与对照期(nZVI=0 mg·L~(-1))相差很小,DGS活性略微增大.当nZVI浓度在5~10 mg·L~(-1)时,DGS对nZVI的生物抑制作用表现出一定适应性,污泥浓度和颗粒粒径仍保持增长趋势,但泥相中总铁含量明显增大,DGS活性开始降低.当nZVI浓度增至30 mg·L~(-1)时,反应器对COD和NO-3-N的去除率分别降至对照期的23.3%和20.3%.DGS因吸附大量nZVI而呈黑色,颗粒粒径减小,污泥表面短杆菌等微生物密度明显降低.停止投加nZVI后,污泥浓度与DGS活性的持续上升,使得反应器脱氮效能在20 d内基本恢复至对照期的水平.异养菌在颗粒表面的快速增殖是实现上述目标的主要原因.

Effects of Nanoscale Zero-valent Iron (nZVI) on Denitrifying Performance of an Upflow Granular Sludge Bed Reactor

In order to examine the effects of nanoscale zero-valent iron (nZVI) on the performance of denitrifying granular sludge (DGS) in a continuous flow model, the variations of nitrogen removal efficiency in the reactor, sludge morphology, and denitrifying characteristics at different influent nZVI concentrations were investigated in an upflow sludge bed (USB). The results showed that nZVI concentrations lower than 5 mg·L^-1 did not influence the nitrogen removal performance of the reactor significantly, and the activity of DGS was improved slightly. When the influent nZVI concentration was in the range of 5 to 10 mg·L^-1, the DGS could adapt to the biological inhibition of nZVI partially, with the increase of sludge concentration and grain size. However, the higher total iron contents in the sludge resulted in the lower denitrifying activity of the DGS. The removal efficiencies of COD and NO₃^--N in the reactor decreased to 23.3% and 20.3%, respectively, at the influent nZVI concentration of 30 mg·L^-1. Moreover, the DGS was a dark color and of a smaller grain size because of the adsorption of a large amount of nZVI, while the microbe density, such as that of the bacillus species, on the granule surface decreased significantly. In the recovery phase, the nitrogen removal performance of the reactor could almost reach its initial level at nZVI=0 mg·L^-1 during an operation of 20 days due to the fast growth of heterotrophic microbes on the surface of the DGS.