原水输水渠道中粉末活性炭吸附污染物的模拟研究

Modeling of pollutants adsorbed by powdered activated carbon in raw water aqueduct

在原水输水管渠中投加粉末活性炭,对污染原水进行预处理,已经成为水源地突发污染事故条件下的应急处理技术手段。本文提出了原水输水渠道中粉末活性炭动态沉降条件下,粉末活性炭—污染物耦合数学模型,以水源地硝基苯浓度超标为例(分别超标2、5和10倍),模拟了粉炭对硝基苯的吸附净化效果。得出基本结论为:粉炭吸附污染物的效果既与水流条件(实际水流剪应力或供水水量)有关,也与输水渠道的断面水深有关。在相同的粉炭投加浓度条件下,水流剪应力越低,断面水深越低,污染物吸附平衡浓度就越高。当水源地水质严重超标时(超标5–10倍),应将增加粉末活性炭投加量作为解决方案;而当水源地水质超标不明显时(超标2倍),可在合理调控供水水量和粉炭投加量的条件下,达到供水水质要求。该研究建立的数学模型,对突发污染事故条件下城市应急供水,具有借鉴意义。

Use of powdered activated carbon （PAC） in raw water supply networks under emergency response and recovery conditions, has proved to be a promising method for the removal of water pollutants. This study was developed a coupled PAC-pollutant removal model to assess PAC adsorption to pollutants in raw water aqueduct, under dynamic PAC deposition to the aqueduct due to low water flow. With the scenario of nitrobenzene concentration exceeding approximate 2, 5, and 10 times of drinking water standard as an example, the nitrobenzene adsorbed to PAC within the raw water aqueduct is assessed. It was concluded that nitrobenzene removal within the aqueduct is related to the water flowing pattern （i.e., actual fluid shear, or actual water supply）, as well as aqueduct depth, that is, the lower the actual fluid shear and the lower the aqueduct depth, the higher the steady nitrobenzene concentration. For the scenario of nitrobenzene seriously exceeding drinking water standard （i.e., approximately exceeding 5 or 10 times drinking water standard）, the increase of PAC dose should be the priority option. However, for the scenario of nitrobenzene level exceeding approximate 2 times of drinking water use standard, the increase of actual fluid shear, instead of solely increasing PAC dose, could be the option; therefore, a balance between water supply flow and initial PAC dose could be operated to ensure drinking water safety. Generally, the developed mathematical model provides insights into city＇s emergency water supply aroused by sudden drinking water pollution incidents.