污水厂尾水占主导溪流养分滞留潜力及影响因素

Potential and influencing factors of nutrient retention in a headwater stream predominated by wastewater treatment plant effluent

为了解污水厂尾水排入对小河流养分滞留的影响,选择南淝河流域二十埠河上游污水厂尾水占主导的磨店小溪流为对象,根据野外示踪试验和模型模拟结果,利用养分螺旋指标定量评估溪流NH_4^+-N、NO_3^--N和SRP滞留潜力,识别主要影响因素.结果表明,NH_4^+-N和SRP的主流区一阶吸收系数(λ)较暂态存储区(λ_s)高1个数量级,而且两者的λ或λ_s数值大小颇为接近.Sw-NH_4、Sw-SRP和Sw-NO_3平均值分别为12.71,14.09,7.48km,均远高于溪流总长度,意味着溪流已不具备氮磷养分的去除能力.NH_4^+-N和SRP吸收长度高于NO_3^--N,但其吸收速度却较NO_3^--N低,表明NO_3^--N滞留潜力相对较高.与该溪流上已有研究的比较,未发现污水厂尾水排入对溪流养分滞留带来明显的不利影响.回归分析表明,水文条件是影响溪流氮磷滞留的重要因素,虽然Vf-SRP、U-SRP都与暂态存储显著相关(P<0.05),但NH_4^+-N、NO_3^--N吸收指标与其关系并不显著.

To investigate the effects of wastewater treatment plant effluent on nutrient retention in streams, a case study in Modian Creek, which is a typical first-order stream of Ershibu River in Nanfei River basin and predominated by wastewater treatment plant effluent, was conducted. Potentials of ammonium nitrogen （NH4＋-N）, nitrate nitrogen （NO3--N） and soluble reactive phosphorus （SRP） retention were evaluated quantitatively by nutrient spiraling metrics and its influencing factors were identified by means of regression analysis based on tracer experiments and modeling of models. Results showed that the first-order uptake coefficients of NH4＋-N and SRP in the main channel （λ） were an order of magnitude higher than those in the transient storage zone （λs）, while the values of λ-NH4＋-N and λs-NH4＋-N were similar to λ-SRP and λs-SRP values, respectively. The mean values of Sw-NH4, Sw-SRP and Sw-NO3 were significantly larger than the whole length of Modian Creek, suggesting that the studied stream had no any ability to retain or remove nitrogen and phosphorus. Since the uptake lengths of both NH4＋-N and SRP were longer than that of NO3--N, but their uptake velocities were all lower than that of NO3--N, indicating that NO3--N retention potential was greater than those of NH4＋-N and SRP. Moreover, significantly adverse impacts of wastewater treatment plant effluent on nitrogen and phosphorus retention were not found through comparison with the published literature of nutrient spiraling studies in the studied stream. Regression analysis suggested that hydrological condition was key drivers influencing nutrient retention in the Modian Creek. Transient storage was significantly correlated with Vf-SRP and U-SRP （both P〈0.05）, but was independent on NH4＋-N and NO3--N.