光照强度对光能自养生物膜去除低污染水体中硝态氮的影响研究

The effect of light intensity on removal efficiency of nitrate in low-polluted water treated by phototrophic biofilm

低污染水体存在C/N较低的特征,往往导致水体自净过程中反硝化碳源的不足。提出采用光能自养生物膜去除低污染水体中的硝态氮,研究不同光照强度对光能自养生物膜脱氮能力的影响,并验证了生物膜自行产生的胞外聚合物(EPS)及溶解性微生物产物(SMP)中多糖能否成为反硝化的碳源。结果表明,采用光能自养生物膜去除低污染水体中硝态氮具有良好的效果,光照强度的提高可以有效促进硝态氮的去除,在光暗比为12∶12、水力停留时间为72h时,1 500、3 000、4 500lx光照强度下系统的硝酸盐去除率分别为37.1%、56.7%、62.5%,且随着光照强度增加硝酸盐去除速率逐渐提高;光照强度的增加可促进光能自养生物膜系统的EPS、SMP中多糖的产生,且光暗交替时EPS、SMP中多糖浓度呈"锯齿形"变化,在有光照时浓度明显上升,而在无光照时浓度下降;光能自养生物膜系统的EPS、SMP中的多糖可作为碳源被反硝化菌利用,而且在无外加碳源条件下,SMP中多糖对碳源的贡献大于EPS中的多糖。

The characteristics of low C/N ratio in less-polluted water results in the lack of carbon source for denitrification in the self-purification process of natural water. The phototrophic biofilm was applied to removal the nitrate in less-polluted water, the effect of light intensity on nitrogen removal capacity was investigated. Besides, the feasibility of denitrifying bacteria utilizing polysaccharide of soluble microbial products （SMP） and extracellular polymers （EPS） as carbon sources was studied. The study indicates that phototrophic biofilm has positive effect on the removal of NOx-N from less-polluted water and high light intensity enhances the removal efficiency of nitrate nitrogen. After 72 h of hydraulic retention time （HRT） with 1 500,3 000,4 500 lx of light intensity and 12 ： 12 of dark/light ratio, the removal efficiency of NO3^- -N could reach 37.1%, 56.7 %, 62.5 V0 respectively. Higher light intensity promoted the production of polysaccharide in SMP and EPS. The content of polysaccharide changing in zigzag shape under the condi- tion of alternating light and dark, they showed a obviously increase under illumination and sharply decreased in the dark. Polysaccharide of both SMP and EPS can be used as carbon sources for denitrification with polysaccharide of SMP having more contribution.