基于15N质量平衡法研究养殖消化废水中氨氮的去除机理

Mechanisms of ammonium removal from digested piggery wastewater by Oedogonium sp.assessed via isotope mass balance analysis

为避免养猪场消化废水对环境造成的污染,利用微藻去除消化废水中营养物质的二次处理方法受到了广泛关注。采用15N质量平衡法研究了鞘藻去除氨氮的主要机理,重点研究了鞘藻生长与氨氮去除的关系以及氨氮去除的主要途径。经高压灭菌后的消化废水在鞘藻培养期的氨氮去除率为96.2%,鞘藻特定生长率为0.04~0.15;稀释后的原消化废水氨氮的去除率为94.1%,鞘藻特定生长率为-0.14~0.13。通过曝气的汽提效应对氨的去除有显著的促进作用,尤其在高pH值试验条件下更有利于脱氨。15N同位素质量平衡分析表明,原始消化废水中存在的细菌对氨氮的去除影响小,在鞘藻培养期去除原消化废水中氨氮的主要途径是鞘藻的吸收和气体的损失,分别占总氮量的40.97%和32.59%。氨氮的去除与主要影响因素间的回归和通径分析表明,要提高氨氮去除率,需要提高鞘藻Chl-a含量和DO浓度,同时限制或保持pH值在弱碱性状态。

Nutrient removal from digested piggery wastewater(DPW)using microalgae is of increasing interest as a secondary treatment prior to discharge to avoid environmental contamination.In this study,we investigated the main mechanisms involved in ammonium removal from DPW by Oedogonium sp.using the15N mass balance approach with a focus on the relationship between algal growth and ammonium removal and the dominant ammonium removal pathway.We noted 96.2%ammonium removal and 0.04~0.15 specific growth rate of Oedogonium sp.in the diluted autoclaved DPW during the incubation period and 94.1%ammonium removal and-0.14~0.13 specific growth rate in the diluted raw DPW.Aeration provided a significant benefit to ammonium removal via the stripping effect,which was favored by the high pH in the experimental conditions.Isotope mass balance analysis indicated that bacteria present in the initial DPW had little effect on ammonium removal in the experiment.Algal uptake and gaseous loss were the dominant pathways for NH4—N removal from the diluted DPW using Oedogonium sp.cultures and accounted for 40.97%and 32.59%of the total 15N amount,respectively.Regression and path analyses between NH4—N removal and its main influencing factors indicated that to improve NH4—N removal efficiency,the levels of Oedogonium sp.and dissolved oxygen(DO)should be increased under weakly alkaline conditions.