北运河上游合流制管网溢流污染特性研究

Characteristics of the combined sewer overflows pollution in the upper North Canal of Beijing

以北运河沙河水库周边合流制管网为研究对象,选取浊度为主要指示指标,通过监测典型溢流排口,考察了2019年4次合流制管网溢流污染物的变化过程,研究了降雨事件之间的干旱天数和降雨强度对溢流污染的影响,并分析浊度和典型污染物之间的相关性.结果表明,汛期降雨强度较大、历时较长,是溢流事件发生的主要时期.当单场次累积降雨量达到15 mm和单场次平均降雨强度达到1.4 mm·h^-1时,溢流开始发生.其中,4月24日(第一次溢流)和汛期7月22日(干旱天数为23 d,降雨强度最强)的初期溢流污染最为严重,这两次溢流污水中TN、TP、TCOD都与浊度显著相关(p<0.01);5月26日(非汛期典型降雨)的溢流污染物与浊度相关性不显著(p>0.05),污染负荷较低.这说明北运河上游沙河水库周边合流制管网溢流污染主要受降雨强度和干旱天数的影响.因此,以年总溢流污染负荷为控制目标时,应优先控制年度初次溢流和主汛期初次溢流的初期溢流污染.

A study was carried out to investigate the combined sewer overflows(CSOs) pollution at the upper North Canal, and turbidity was selected as the main indicator for CSOs pollution. Through investigating changes of CSOs pollutants during 4 rainfall events in 2019, the effect of dry days and rainfall intensity on CSOs pollution was analyzed, as well as the correlation between turbidity and typical pollutants in this study. Results suggested that the CSOs mainly occurred in the rain season due to the higher rainfall intensity and longer rainfall duration. The CSOs occurred at the accumulated precipitation over 15 mm and the average intensity up to 1.4 mm·h^-1. The heavier polluted initial CSOs occurred at the first overflow on Apr. 24 and the overflow on July 22 due to the intensive rainfall after 23 days rain free period. During these two CSOs events, concentrations of TN, TP, and TCOD significantly correlated with the turbidity(p<0.01). However, there is no significant correlation(p>0.05) observed between concentrations of TN, TP, and TCOD and turbidity due to low pollutants loading of the CSOs occurred on May 26. In a word, the CSOs pollution was mainly affected by rainfall intensity and rain free period in the upper North Canal, Beijing. Therefore, it is of great importance to control the initial overflow pollutants of both the first CSOs in the year and the first CSOs in the main flood season, with aiming to control annual CSOs pollution loading.