西北地区某市地下水供水管网黄水产生原因分析与控制技术中试研究

Cause analysis and control technology pilot study of yellow water in a groundwater water supply network in a city in northwest China

随着供水管道使用年限的增加,管网逐渐老化,管网化学稳定性问题日益突出。为解决西北地区某市高碱度地下水供水管网黄水问题,保障用水安全,开展了黄水产生原因分析与控制技术中试研究。一方面,监测黄水形成过程中水质特点和规律,对铸铁管腐蚀管垢成分进行分析,探明黄水形成原因。另一方面,搭建管网中试系统,研究了余氯、碱度、缓蚀剂对管网铁释放的影响。结果表明:黄水形成存在周期性规律,形成原因为水力冲刷增强导致管垢中的铁释放到水体中,水体存在一定的腐蚀性也会影响铁释放。管垢主要成分为Fe3O4和α-FeOOH,但不同管垢层形貌特征及化学组成存在差异。建议该地区管网余氯浓度控制在0.4 mg/L左右,余氯较高或较低均会促进铁释放。综合考虑效果和经济性,应对突发性黄水问题时,建议优先采用0.5 mg/L(以P计)的三聚磷酸钠作为缓蚀剂投加控制黄水现象。每吨水需增加药剂成本约为0.018元。

With the increase of the service life of water supply pipe,the pipe network is gradually aging,and the problem of chemical stability of pipe network is increasingly prominent.In order to solve the yellow water problem in a water supply network with high alkalinity groundwater in a city of northwest China and ensure the safety of water use,the cause of yellow water was analyzed and a pilot scale study of the yellow water control technology was carried out.On the one hand,the water quality characteristics and rules of the formation of yellow water were monitored,the corrosion pipe scale composition of cast iron pipe was analyzed,and the cause of the formation of yellow water was explored.On the other hand,the pilot pipe network system was built,and the effect of residual chlorine,alkalinity,and corrosion inhibitor on the iron release was studied by the pilot system.The results showed that:The formation of yellow water was periodic,it was the enhancement of hydraulic erosion led to the release of iron from the corrosion scale,and the corrodibility of water could also affect iron release.The main components of the corrosion scale were Fe_3O_4 andα-FeOOH,but the morphological characteristics and chemical composition of different corrosion scale layers varied.It is suggested that the residual chlorine in the pipe network should be controlled at about 0.4 mg/L,raising or lowering residual chlorine concentration would promote the iron release.When dealing with the sudden yellow water problem,and considering the control efficiency and economy comprehensively,it is suggested to use 0.5 mg/L(as P)tripolyphosphate preferentially as the corrosion inhibitor to control the yellow water phenomenon of the pipe network.The extra cost for water treatment per ton is about 0.018 yuan.