针对丹江口水库水源调入北方某受水区城市后对管网水质可能造成的影响,开展了初步的模拟管网中试研究。从北方某受水区城市的实际管网中挖取了历史通水水源不同的4个地点的无内衬铸铁管并运输至丹江口中试基地,搭建了4套管网模拟系统,并在水源切换为丹江口水源水后对模拟管网进、出水水质进行了6个月的连续跟踪监测。中试结果表明:丹江口水库水的拉森指数在0.5左右,低于该北方受水城市的地表水但高于其地下水,具有微弱的腐蚀性。水源切换后,原通地下水的管道铁释放量最高,呈现“黄水”现象,切换75d后逐渐达到稳定,“黄水”现象消失;而原通地表水为主的3套管道系统只在水源切换初期铁释放量较高,约30d后铁释放趋于稳定并一直维持在较低的水平。管网水的铁释放量与出水浊度存在明显的正相关性。水源切换后伴随总铁释放量的增加,管网出水的pH值、总碱度、总硬度、溶解氧浓度明显降低。不同管道对水源切换响应的差异与其内壁的管垢特征不同有关,长期通地下水的管道内部管垢较薄且无明显分层特征,而长期通地表水的管垢较厚且多呈瘤状分布,具有明显的分层特征。
A pilot-scale test was performed to evaluate the possible effects of using source water from Danjiangkou Reservoir on the water quality in the drinking water distribution system in a northern China city. Four simulated water distribution systems were established using unlined cast iron pipes from four different sites of the existing water distribution system. Continuous monitoring was conducted for six months to investigate the water quality changes after the source water switch. The results showed that the Larson ratio of Danjiangkou Reservoir water was around 0.5, lower than that of the municipal surface water, but higher than that of the municipal ground water of the northern city. The Danjiangkou Reservoir water was slightly corrosive. After the source water switch, the iron pipe transporting groundwater underwent a long period (75 d) of high iron release with significant "red water" phenomenon, while the other three pipes transporting surface water had much lower iron releases except during the initial 30 d of the source water switch. There was a significant positive relationship between the iron release and effluent turbidity. Compared with the influent quality parameters, the effluent pH, dissolved oxygen, alkalinity and hardness were decreased with the iron release in the simulated water distribution systems. The different iron release responses of four simulated water distribution systems were dependent on the characteristics of corrosion scales formed under different water source conditions. Corrosion scales on pipes transporting groundwater were relatively thin and had no layered structure, while the corrosion scales on pipes transporting surface water were rather thick, mainly in tubercle form, and had layered structure.