蓝藻对太湖底泥反硝化过程的影响和机理分析

Effect and mechanism of algae bloom on the denitrification processes in the sediments of Lake Taihu

通过模拟实验,研究了因自然或人工沉降的太湖蓝藻在厌氧条件下作为碳源对底泥微生物反硝化脱氮的促进作用.通过对底泥总氮、化合态氮素、挥发性脂肪酸(VFAs)、COD、电位和pH等指标的监测,发现藻体中大量的生物可降解碳素在厌氧消解后产生挥发性脂肪酸等一些可供反硝化菌直接利用的小分子物质,2×藻组VFAs含量可达2232.96μl/L,1×藻组可达1263.36μl/L,最高可达42.1%,为对照组(无添加蓝藻)的2.43倍,从而促进了硝态氮和亚硝态氮还原成N2和N2O的过程,提高氮素的去除率.但底泥中沉降蓝藻需要一定的降解时间,前4天添加冷冻干蓝藻粉的处理组COD降解率较低,电位处于正值,体系中产生硝态氮,随后COD持续降低,添加2×藻组COD最大去除率为42.08%,1×藻组为32.93%,对照组仅为14.46%,表明藻细胞中的碳素已开始被利用.本研究表明沉降蓝藻细胞能够为底泥中的反硝化过程提供可利用碳源,并深入揭示了沉降蓝藻作为碳源促进底泥反硝化过程的机理和对底泥中C、N的影响,为在湖泊治理中降低氮素的内源污染提供了新的科学依据.

Denitrifieation in anaerobic lake bottom sediments and leachate providing carbon source via flocculated algae were simu- lated in the laborato~,. TN, ammonium, nitrite, nitrate, volatile fatty acids （VFAs）, COD, electric potential and pH were ana- lyzed to confirm that the denitrification in sediments was truly promoted by small molecular compounds such as VFAs which were reduced from the plentiful biodegradable carbon in algae. The maximum VFAs content in 2 × algae system and l x algae system were 2232.96 and 1263.36 μl/L, respectively. The maximum TN removal ratio was about 42.1% , nearly 2.43 times of the con- trol. The carbon of flocculated algae is available for heterotrophic microbes but needs some time to be transformed. A sustaining COD reduction rate showed in all the added algae systems after low COD reduction rate, positive electric potential and increasing nitrate had last in them for about 4 days. The maximum COD reduction rate of 2 x algae system, 1 x algae system and the control was 42.08% , 32.93% and 14.46% , respectively. The degradation of algae generated VFAs can be directly used by denitrifying bacteria to facilitate denitrification process. The effect that flocculated algae cell as carbon source can promote sediment denitrifying process was verified, and the influence of flocculated algae on C and N of sediments was analyzed. The study could provide techni- cal basis for reducing the internal nitrogen in sediments of eutrophic lakes.