污水氮浓度对粉绿狐尾藻去氮能力的影响

粉绿狐尾藻是构建人工湿地的重要植物,对污水具有较强的净化作用,但有关其去氮能力及其与污水氮浓度的关系尚不清楚.本试验采用人工模拟盆栽试验,设2、5、10、20、100、200、400 mg·L~(-1)共7个氮水平,研究污水氮浓度对粉绿狐尾藻去氮能力的影响.结果表明,氮浓度不高于20 mg·L~(-1)时,前3周粉绿狐尾藻以20 mg·L~(-1)生长最好,处理1周水体总氮和氨氮的去除率接近100%,而硝态氮浓度低、变化不大;粉绿狐尾藻氮含量因氮浓度变化不大但部位间有"上高下低"趋势,且粉绿狐尾藻还利用了底泥氮.氮浓度100~400 mg·L~(-1)时,4~5周以氮浓度200 mg·L~(-1)粉绿狐尾藻生长最好;处理5周总氮去除率依次为76.5%、71.5%和48.1%,氨氮去除率依次为99.6%、99.3%和60.2%;各处理硝态氮去除率约为50%且处理间差异不大;粉绿狐尾藻氮含量随氮浓度而升高,但部位间差异小、呈均匀分布;粉绿狐尾藻积累氮、底泥固定氮分别占水体去除氮的27.9%~48.4%和12.2%~24.4%.因此,粉绿狐尾藻去氮能力受污水氮浓度的显著影响,去除氨氮率显著高于硝态氮;氮浓度还影响粉绿狐尾藻对氮的吸收积累和分配机制,值得深入研究.

Effect of Wastewater Nitrogen Concentrations on Nitrogen Removal Ability of Myriophyllum aquaticum

Myriophyllum aquaticum, which is an important plant for constructed wetlands, has powerful purification ability for wastewater, however, the relationship between nitrogen removal ability of Myriophyllum aquaticum and wastewater nitrogen concentrations is still unclear. In this study, pot culture experiment was conducted to investigate the effect of wastewater nitrogen levels on nitrogen removal ability of Myriophyllum aquaticum. 7 nitrogen levels were set up as following:2, 5, 10, 20, 100, 200, 400 mg·L^-1. The results showed that when the wastewater nitrogen concentration was not higher than 20 mg·L^-1, Myriophyllum aquaticum with 20 mg·L^-1 of nitrogen concentration grew best in the first 3 weeks; the removal rates of total and ammonia nitrogen were nearly 100% after one week, while the nitrate nitrogen concentrations were very low and varied little; the nitrogen contents of Myriophyllum aquaticum had no significant change, the upper part nitrogen content was higher than the underneath, Myriophyllum aquaticum could also remove nitrogen from the sediment. When wastewater nitrogen concentrations were 100-400 mg·L^-1, Myriophyllum aquaticum with 200 mg·L^-1 of nitrogen concentration grew best from 4th to 5th week; the removal rates of total nitrogen were 76.5%, 71.5% and 48.1% in the three treatments, and the removal rates of ammonia nitrogen were 99.6%, 99.3% and 60.2% respectively, while the removal rates of nitrate nitrogen were all about 50% and there was no significant difference among treatments; the nitrogen contents of Myriophyllum aquaticum increased with nitrogen levels, but the difference between upper part and underneath was not remarkable, showing uniform distribution; nitrogen accumulations by Myriophyllum aquaticum and sediment accounted for 27.9%-48.4% and 12.2%-24.4% of total nitrogen loss in wastewater. Therefore, the nitrogen removal ability of Myriophyllum aquaticum should be inhibited by higher wastewater nitrogen level, the ammonia nitrogen removal rate was significantly higher than nitrate, the mechanism of Myriophyllum aquaticum nitrogen accumulation and distribution should also be affected by wastewater nitrogen level, and further research is needed.