广东某水厂自来水煮沸结垢成因分析及解决方案

Cause Analysis and Solution Schemes of Scale Formation in Boiled Tap Water of a WTP in Guangdong

针对广东省A水厂愈加频繁的自来水煮沸结垢投诉问题,需要系统探究其成因及解决方案。研究采用X射线衍射能谱(XRD)和扫描电镜电子能谱(SEM-EDS)分析A水厂水垢样品的成分。采用雷兹纳稳定指数(RSI)分析了近10年A水厂出厂水加热煮沸的结垢趋势,应用卡方检验统计模型探究RSI<6与频繁出现投诉月份之间的关联性,通过皮尔逊相关性分析法筛选出对RSI数值具有显著影响的水质参数。统计分析历年水质指标数值,反演水质参数发生的变化及结垢成因。研究表明:A水厂出厂水煮沸产生的垢样主要成分为碳酸钙。结垢趋势预测显示,出厂水RSI(80℃)指数月均值由2014年—2020年的6.11降低至2021年—2023年的5.78,显示出更强的结垢趋势。RSI(80℃)<6的月份与频繁的居民投诉之间具有极显著关联性(χ^(2)=34.90,p=3.498×10^(-9))。结垢问题的加剧与pH、总硬度、总碱度的变化呈极显著负相关(r<-0.8,p≤0.01)。历年枯水期总硬度、总碱度的同时上升导致了偶发的结垢问题;而2021年初以来,氯消毒剂的更换和西江流量减少引起的原水水质变化共同导致了出厂水pH的上升,引发频繁的结垢问题。对此,A水厂应以科学引导民众为主、工艺调节为辅,同时可将RSI(80℃)用于结垢趋势的监测和预测。

In response to the increasingly frequent complaints about boiled tap water scaling against water treatment plant(WTP)A in Guangdong Province,a systematic research into its causes and solutions is necessary.The composition of scale samples from WTP A was analyzed by X-ray dffraction(XRD)and scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS).An analysis based on Reznor stability index(RSI)was conducted on the scaling tendency of boiled tap water in the past ten years from WTP A.Chi-square test was applied to explore the correlation between"RSI<6"and months with frequent complaints.Pearson correlation analysis was conducted to identify water quality parameters that significantly affected RSI value,The changes of water quality parameters and causes of scaling were coupled with statistical methods through the analysis of the water quality indexes of the past years.The majority component of the scale samples produced by boiling the water from WTP A was calcium carbonate.The prediction of scaling tendency showed that the monthly average value of RSI(80℃)index of the treated water decreased from 6.11(20142020)to 5.78(20212023),indicating a stronger scaling tendency.The predicted results of monthly RSI(80℃)values less than 6 were highly consistent with frequent complaints of residents on boiled tap water scaling problems in recent years(χ^(2)=34.90,p=3.498×10^(-9)).A highly negative correlation was found between the intensification of scaling problems and changes in pH,total hardness and total alkalinity(r<-0.8,p≤0.01).In previous years,the scaling phenomenon occasionally occurred due to the simultaneous increase in total hardness and total alkalinity during the dry period.However,since the beginning of 2021,the replacement of disinfection and the flux reduction of source water increased the pH value of the treated water,leading to the much more frequent scaling.To solve this problem,scientific guidance for the population should be prioritized,with process adjustments implemented as a secondary measure.Additionally,RSI(80℃)can be utilized to predict the scaling tendency of boiled tap water timely.