城市污水氮污染排放特征及来源探讨——以北京市海淀区为例

污水处理厂是城市重要的氮移除系统,同时也是潜在的氮污染源.研究城市污水处理过程中的点源氮污染物排放特征及其潜在可能性来源,有助于理解城市化过程中污染性氮素的循环过程.本文选择北京市城市化程度较高的海淀区,对服务此区域的污水处理厂进行为期1年的定点采样,分析区域污水处理过程中氮污染排放规律,并探讨其可能来源.研究结果表明,研究区城市污水中氮浓度具有显著的月变化特征,城市污水TN浓度呈现缓慢增长后递减趋势,变化范围在34.975~59.987 mg·L-1之间;从四季整体来看,TN在中午11:00—13:00和傍晚18:00—21:00浓度值较高.城市污水氮污染物主要以NH+4-N形态存在,而排河尾水中以NO-3-N形态为主.月均每人导致的污水氮污染排放量为0.95kg,峰值出现在12月;污水处理过程中氮污染排放率在寒冷季较高;更为先进的污水处理技术有助于减少处理过程中产生的氮污染排放.寒冷季是1年中控制污水氮污染排放的重要时期.稳定氮同位素溯源方法初步表明,城市污水氮来源呈现季节差异,春、夏、冬季潜在来源包括生活黑水及大气降雨,而当年秋季主要来源是生活黑水.从源头上提高生活黑水的资源化率,有助于城市污水氮污染排放的实际削减.

Analysis of nitrogen pollutant emissions by urban sewage with initial nitrogen source apportionment:A case study of Haidian district in Beijing City

As the important disposal system in urban ecosystem, wastewater treatment plant is gradually recognized as the potential source of nitrogen pollution. The analysis of the characteristics and the potential nitrogen sources of point-source nitrogen pollution emissions during wastewater treatment, may contribute to the understanding of nitrogen pollutant cycling process during urbanization. Haidian district, with a high level of urbanization in Beijing city, was selected as a case study, and the characteristics of nitrogen pollutions emissions during the sewage disposal process and the possible sources were evaluated, based on one year point sampling in the wastewater treatment plant in this region. The results show that the nitrogen concentrations of urban sewage presented obvious differences monthly. TN concentrations presented decreasing trend after the slight growth, ranging from 34.975~59.987 mg·L^-1. Within a day, the TN concentrations in raw sewage overall were higher in the periods of the 11:00-13:00 and 18:00-21:00 across seasons. NH₄⁺-N was the main nitrogen pollutant in untreated urban sewage, and NO₃^--N was the dominant nitrogen species in the discharged effluent after treatment. The nitrogen environmental emission rate of sewage treatment was higher in cold season, peaking in December. The average amount of personal emission approximately was 0.95 kg per month. More advanced treatment technology could contribute to the reduction of nitrogen environmental emissions. The cold seasons was supposed as the key period for nitrogen pollution control in this region. The results of stable nitrogen isotope tracer analysis indicate that the potential sources of nitrogen in sewage may include residential black water and rainfall, and the residential black water was the dominant nitrogen source in autumn that year. The recycling of residential black water from the source may contribute to the reduction of nitrogen environmental emissions in the process of wastewater disposal.