灰口铸铁管输配淡化海水铁释放控制

Controlling iron release of desalinated seawater transmitted in existing grey cast iron pipe

以灰口铸铁管管段为研究对象,运用管段反应器,研究淡化海水在市政管网输配过程中,灰口铸铁管内壁铁释放现象及探讨如何控制铁释放。研究结果表明:管龄约10 a的灰口铸铁管内壁管垢的主要组成物质为Fe_3O_4,α-FeO(OH)和γ-FeO(OH);采用投加磷酸盐、调整自来水与淡化海水的混掺比及增加硬度的方式控制输配淡化海水过程中的铁释放,其中1 mg/L的磷酸钠对管段内壁铁释放表现出一定的抑制作用,总铁质量浓度平均降低20%,磷酸氢二钠抑制铁释放效果最好;将自来水与淡化海水混掺后进入灰口铸铁管,对于减缓管段铁释放具有一定作用,并且淡化海水比例越低,总铁质量浓度越小;当水中硬度为200 mg/L和300 mg/L时,总铁质量浓度分别减少43%和50%左右;三因素对灰口铸铁管反应器铁释放减缓作用的影响程度从大到小依次为混掺比、硬度、磷酸氢二钠。

Taking the gray cast iron pipe section as the research object,the iron release from the grey cast iron pipe wall and controlling iron release during the transmission of desalinated seawater in municipal distribution system were studied by using the grey cast iron pipe section reactors.The results indicate that the main compositions of the scale in grey cast iron pipe(pipe age of approximately10years)are Fe3O4,α-FeO(OH)andγ-FeO(OH).The iron release is controlled by adding phosphate chemical,adjusting the mixing ratio of finished water and desalinated seawater and increasing hardness,and the addition of1mg/L phosphate is effective in inhibiting iron release with average total iron concentration decreasing by20%,and Na2HPO4shows the best efficiency.Mixing finished water and desalinated seawater in gray cast iron pipe section can reduce iron release,and the total iron concentration decreases with the decrease of ratio of desalinated seawater.The addition of200mg/L and300mg/L hardness in desalinated seawater results in total iron reduction by around43%and50%,respectively.The influence of three factors on inhibiting iron release in cast iron pipe section reactors is mixing ratio,hardness and Na2HPO4.